Early-life disruption of amphibian microbiota decreases later-life resistance to parasites.

PubMed

Knutie, Sarah A; Wilkinson, Christina L; Kohl, Kevin D; Rohr, Jason R

2017-07-20

Changes in the early-life microbiota of hosts might affect infectious disease risk throughout life, if such disruptions during formative times alter immune system development. Here, we test whether an early-life disruption of host-associated microbiota affects later-life resistance to infections by manipulating the microbiota of tadpoles and challenging them with parasitic gut worms as adults. We find that tadpole bacterial diversity is negatively correlated with parasite establishment in adult frogs: adult frogs that had reduced bacterial diversity as tadpoles have three times more worms than adults without their microbiota manipulated as tadpoles. In contrast, adult bacterial diversity during parasite exposure is not correlated with parasite establishment in adult frogs. Thus, in this experimental setup, an early-life disruption of the microbiota has lasting reductions on host resistance to infections, which is possibly mediated by its effects on immune system development. Our results support the idea that preventing early-life disruption of host-associated microbiota might confer protection against diseases later in life.Early-life microbiota alterations can affect infection susceptibility later in life, in animal models. Here, Knutie et al. show that manipulating the microbiota of tadpoles leads to increased susceptibility to parasitic infection in adult frogs, in the absence of substantial changes in the adults' microbiota.

Effect of the Specific Toxin in Helminthosporium victoriae on Host Cell Membranes 1

PubMed Central

Samaddar, K. R.; Scheffer, R. P.

1968-01-01

Helminthosporium victoriae toxin, which affects only hosts of the toxin-producing fungus, causes loss of electrolytes from roots, leaves, and coleoptiles of treated plants. Root hair cells lost the ability to plasmolyze after 20 minutes exposure to toxin in solution; comparable resistant cells retained plasmolytic ability during 3 hours exposure. Toxin stopped uptake of exogenous amino acids and Pi by susceptible but not by resistant tissue. Incorporation of 32P into organic-P and 14C-amino acids into protein was blocked in susceptible but not in resistant tissue. Apparent free space increased in susceptible but not in resistant roots. The increase was evident within 30 minutes, and reached 80% free space after 2 hours exposure to toxin. When cell wall-free protoplasts were exposed to 0.16 μg toxin/ml, protoplasmic streaming stopped and all plasma membranes of susceptible protoplasts broke within 1 hour. Resistant protoplasts were not affected significantly. Data support the hypothesis of a primary lesion of toxin in the plasma membrane. Effects on synthesis could result from lack of transport of exogenous solutes to sites of synthesis. It is possible that all other observed effects of toxin are secondary to membrane damage. PMID:16656731

Energy conserving thermoregulatory patterns and lower disease severity in a bat resistant to the impacts of white-nose syndrome.

PubMed

Moore, Marianne S; Field, Kenneth A; Behr, Melissa J; Turner, Gregory G; Furze, Morgan E; Stern, Daniel W F; Allegra, Paul R; Bouboulis, Sarah A; Musante, Chelsey D; Vodzak, Megan E; Biron, Matthew E; Meierhofer, Melissa B; Frick, Winifred F; Foster, Jeffrey T; Howell, Daryl; Kath, Joseph A; Kurta, Allen; Nordquist, Gerda; Johnson, Joseph S; Lilley, Thomas M; Barrett, Benjamin W; Reeder, DeeAnn M

2018-01-01

The devastating bat fungal disease, white-nose syndrome (WNS), does not appear to affect all species equally. To experimentally determine susceptibility differences between species, we exposed hibernating naïve little brown myotis (Myotis lucifugus) and big brown bats (Eptesicus fuscus) to the fungus that causes WNS, Pseudogymnoascus destructans (Pd). After hibernating under identical conditions, Pd lesions were significantly more prevalent and more severe in little brown myotis. This species difference in pathology correlates with susceptibility to WNS in the wild and suggests that survival is related to different host physiological responses. We observed another fungal infection, associated with neutrophilic inflammation, that was equally present in all bats. This suggests that both species are capable of generating a response to cold tolerant fungi and that Pd may have evolved mechanisms for evading host responses that are effective in at least some bat species. These host-pathogen interactions are likely mediated not just by host physiological responses, but also by host behavior. Pd-exposed big brown bats, the less affected species, spent more time in torpor than did control animals, while little brown myotis did not exhibit this change. This differential thermoregulatory response to Pd infection by big brown bat hosts may allow for a more effective (or less pathological) immune response to tissue invasion.

Mining a differential sialotranscriptome of Rhipicephalus microplus guides antigen discovery to formulate a vaccine that reduces tick infestations.

PubMed

Maruyama, Sandra R; Garcia, Gustavo R; Teixeira, Felipe R; Brandão, Lucinda G; Anderson, Jennifer M; Ribeiro, José M C; Valenzuela, Jesus G; Horackova, Jana; Veríssimo, Cecília J; Katiki, Luciana M; Banin, Tamy M; Zangirolamo, Amanda F; Gardinassi, Luiz G; Ferreira, Beatriz R; de Miranda-Santos, Isabel K F

2017-04-26

Ticks cause massive damage to livestock and vaccines are one sustainable substitute for the acaricides currently heavily used to control infestations. To guide antigen discovery for a vaccine that targets the gamut of parasitic strategies mediated by tick saliva and enables immunological memory, we exploited a transcriptome constructed from salivary glands from all stages of Rhipicephalus microplus ticks feeding on genetically tick-resistant and susceptible bovines. Different levels of host anti-tick immunity affected gene expression in tick salivary glands; we thus selected four proteins encoded by genes weakly expressed in ticks attempting to feed on resistant hosts or otherwise abundantly expressed in ticks fed on susceptible hosts; these sialoproteins mediate four functions of parasitism deployed by male ticks and that do not induce antibodies in naturally infected, susceptible bovines. We then evaluated in tick-susceptible heifers an alum-adjuvanted vaccine formulated with recombinant proteins. Parasite performance (i.e. weight and numbers of females finishing their parasitic cycle) and titres of antigen-specific antibodies were significantly reduced or increased, respectively, in vaccinated versus control heifers, conferring an efficacy of 73.2%; two of the antigens were strong immunogens, rich in predicted T-cell epitopes and challenge infestations boosted antibody responses against them. Mining sialotranscriptomes guided by the immunity of tick-resistant hosts selected important targets and infestations boosted immune memory against salivary antigens.

Feeding guild of non-host community members affects host-foraging efficiency of a parasitic wasp.

PubMed

De Rijk, Marjolein; Yang, Daowei; Engel, Bas; Dicke, Marcel; Poelman, Erik H

2016-06-01

Interactions between predator and prey, or parasitoid and host, are shaped by trait- and density-mediated processes involving other community members. Parasitoids that lay their eggs in herbivorous insects locate their hosts through infochemicals such as herbivore-induced plant volatiles (HIPVs) and host-produced kairomones. Hosts are frequently accompanied by non-host herbivores that are unsuitable for the parasitoid. These non-hosts may interfere with host location primarily through trait-mediated processes, by their own infochemicals, and their induction of the emission of plant volatiles. Although it is known that single non-hosts can interfere with parasitoid host location, it is still unknown whether the observed effects are due to species specific characteristics or to the feeding habits of the non-host herbivores. Here we addressed whether the feeding guild of non-host herbivores differentially affects foraging of the parasitoid Cotesia glomerata for its common host, caterpillars of Pieris brassicae feeding on Brassica oleracea plants. We used different phloem-feeding and leaf-chewing non-hosts to study their effects on host location by the parasitoid when searching for host-infested plants based on HIPVs and when searching for hosts on the plant using infochemicals. To evaluate the ultimate effect of these two phases in host location, we studied parasitism efficiency of parasitoids in small plant communities under field-tent conditions. We show that leaf-chewing non-hosts primarily affected host location through trait-mediated effects via plant volatiles, whereas phloem-feeding non-hosts exerted trait-mediated effects by affecting foraging efficiency of the parasitoid on the plant. These trait-mediated effects resulted in associational susceptibility of hosts in environments with phloem feeders and associational resistance in environments with non-host leaf chewers.

Within-host competitive interactions as a mechanism for the maintenance of parasite diversity

PubMed Central

Bashey, Farrah

2015-01-01

Variation among parasite strains can affect the progression of disease or the effectiveness of treatment. What maintains parasite diversity? Here I argue that competition among parasites within the host is a major cause of variation among parasites. The competitive environment within the host can vary depending on the parasite genotypes present. For example, parasite strategies that target specific competitors, such as bacteriocins, are dependent on the presence and susceptibility of those competitors for success. Accordingly, which parasite traits are favoured by within-host selection can vary from host to host. Given the fluctuating fitness landscape across hosts, genotype by genotype (G×G) interactions among parasites should be prevalent. Moreover, selection should vary in a frequency-dependent manner, as attacking genotypes select for resistance and genotypes producing public goods select for cheaters. I review competitive coexistence theory with regard to parasites and highlight a few key examples where within-host competition promotes diversity. Finally, I discuss how within-host competition affects host health and our ability to successfully treat infectious diseases. PMID:26150667

Air Pollution and Epigenetics: Effects on SP-A and Innate Host Defense in the Lung

PubMed Central

Silveyra, Patricia; Floros, Joanna

2013-01-01

Summary An appropriate immune and inflammatory response is key to defend against harmful agents present in the environment such as pathogens, allergens, and inhaled pollutants, including ozone and particulate matter. Air pollution is a serious public health concern worldwide, and cumulative evidence revealed that air pollutants contribute to epigenetic variation in several genes, and this in turn can contribute to disease susceptibility. Several groups of experts have recently reviewed findings on epigenetics and air pollution [1–6]. Surfactant proteins play a central role in pulmonary host defense by mediating pathogen clearance, modulating allergic responses and facilitating the resolution of lung inflammation. Recent evidence indicates that surfactant proteins are subject to epigenetic regulation under hypoxia and other conditions. Oxidative stress caused by ozone, and exposure to particulate matter have been shown to affect the expression of surfactant protein A (SP-A), an important lung host defense molecule, as well as alter its functions. In this review, we discuss recent findings in the fields of epigenetics and air pollution effects on innate immunity, with focus on SP-A, and the human SP-A variants in particular. Their function may be differentially affected by pollutants and specifically by ozone-induced oxidative stress, and this in turn may differentially affect susceptibility to lung disease. PMID:22553125

Infection's Sweet Tooth: How Glycans Mediate Infection and Disease Susceptibility.

PubMed

Taylor, Steven L; McGuckin, Michael A; Wesselingh, Steve; Rogers, Geraint B

2018-02-01

Glycans form a highly variable constituent of our mucosal surfaces and profoundly affect our susceptibility to infection and disease. The diversity and importance of these surface glycans can be seen in individuals who lack a functional copy of the fucosyltransferase gene, FUT2. Representing around one-fifth of the population, these individuals have an altered susceptibility to many bacterial and viral infections and diseases. The mediation of host-pathogen interactions by mucosal glycans, such as those added by FUT2, is poorly understood. We highlight, with specific examples, important mechanisms by which host glycans influence infection dynamics, including by: acting as pathogen receptors (or receptor-decoys), promoting microbial stability, altering the physical characteristics of mucus, and acting as immunological markers. We argue that the effect glycans have on infection dynamics has profound implications for many aspects of healthcare and policy, including clinical management, outbreak control, and vaccination policy. Copyright © 2017 Elsevier Ltd. All rights reserved.

Molecular Neuro-Pathomechanism of Neurocysticercosis: How Host Genetic Factors Influence Disease Susceptibility.

PubMed

Arora, Naina; Tripathi, Shweta; Sao, Reshma; Mondal, Prosenjit; Mishra, Amit; Prasad, Amit

2018-02-01

Neurocysticercosis (NCC) is one of the most neglected tropical diseases among widely endemic neurological diseases. It is caused by cysticerci of Taenia solium. The clinical symptom for the outcome of infection and progression of disease is pleomorphic and its neuro-pathomechanism is still illusive. Identification of host genetic factors and their association with disease susceptibility is one of the most important areas of research towards personalized medicine in the era of omics. Several genes and their allelic variations had been identified to be associated with various neurological disorders; however, the information for parasitic diseases affecting the central nervous system is very limited. Both Th1 and Th2 arms of the immune system are reported to be active at different stages of T. solium infection in the brain. Recently, several papers had been published, where the role of host genetic makeup with NCC had been explored. Increased frequency of HLA-A28, HLA-B63, HLA-B58, TLR 4 Asp299Gly, sICAM-1 gene K469E, GSTM1, and GSTT1 were found to be associated with increased risk of NCC occurrence, while HLA-DQW2 and HLA-A11 were shown to be providing protection from disease. In this review, we have summarized these findings and analyzed the influence of host genetic polymorphism on the susceptibility/resistance of host to NCC.

Discovery of a lentivirus susceptibility gene in sheep

USDA-ARS?s Scientific Manuscript database

Ovine lentivirus targets the host immune system and causes persistent retroviral infections affecting millions of sheep worldwide. In primates, lentivirus resistance is attributed to mutant virus coreceptors that are not expressed. In sheep, some animals are resistant to lentivirus infection despit...

Murine respiratory mycoplasmosis (MRM) in C57BL/6N and C3H/HeN mice: strain differences in early host responses and exacerbation by nitrogen dioxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, R.F.

1987-01-01

The studies reported here used genetic differences in susceptibility of C57BL/6N and C3H/HeN mice and exacerbation of the disease by nitrogen dioxide (NO/sub 2/) as tools in assessing the role of early host responses in the pathogenesis of MRM. The two strains did not differ in susceptibility to infection, but C3H/HeN mice were more susceptible to and had increased severity of lung lesions 14 days after intranasal inoculation as determined by 50% biological endpoints and morphometric analysis of tissues. Exposure to NO/sub 2/ for 4 hours prior to exposure to infectious aerosols exacerbated murine respiratory mycoplasmosis (MRM) by 7 daysmore » after exposure in both mouse strains. NO/sub 2/ appeared to affect host lung defense mechanisms responsible for limiting mycoplasmal growth in the lungs. The NO/sub 2/ exposure concentration required for this effect varied with the genetic background of the host, the dose of mycoplasmas administered, and the endpoint measured. Pulmonary clearance of radiolabeled M. pulmonis was determined in both mouse strains, and in C57BL/6N mice exposed to NO/sub 2/.« less

Macrobiota — helminths as active participants and partners of the microbiota in host intestinal homeostasis

PubMed Central

Gause, William C; Maizels, Rick M

2016-01-01

Important insights have recently been gained in our understanding of the intricate relationship in the intestinal milieu between the vertebrate host mucosal immune response, commensal bacteria, and helminths. Helminths are metazoan worms (macrobiota) and trigger immune responses that include potent regulatory components capable of controlling harmful inflammation, protecting barrier function and mitigating tissue damage. They can secrete a variety of products that directly affect immune regulatory function but they also have the capacity to influence the composition of microbiota, which can also then impact immune function. Conversely, changes in microbiota can affect susceptibility to helminth infection, indicating that crosstalk between these two disparate groups of endobiota can play an essential role in host intestinal immune function and homeostasis. PMID:27116368

Grapevine Pathogenic Microorganisms: Understanding Infection Strategies and Host Response Scenarios

PubMed Central

Armijo, Grace; Schlechter, Rudolf; Agurto, Mario; Muñoz, Daniela; Nuñez, Constanza; Arce-Johnson, Patricio

2016-01-01

Grapevine (Vitis vinifera L.) is one of the most important fruit crop worldwide. Commercial cultivars are greatly affected by a large number of pathogenic microorganisms that cause diseases during pre- and/or post-harvest periods, affecting production, processing and export, along with fruit quality. Among the potential threats, we can find bacteria, fungi, oomycete, or viruses with different life cycles, infection mechanisms and evasion strategies. While plant–pathogen interactions are cycles of resistance and susceptibility, resistance traits from natural resources are selected and may be used for breeding purposes and for a sustainable agriculture. In this context, here we summarize some of the most important diseases affecting V. vinifera together with their causal agents. The aim of this work is to bring a comprehensive review of the infection strategies deployed by significant types of pathogens while understanding the host response in both resistance and susceptibility scenarios. New approaches being used to uncover grapevine status during biotic stresses and scientific-based procedures needed to control plant diseases and crop protection are also addressed. PMID:27066032

PrPC Governs Susceptibility to Prion Strains in Bank Vole, While Other Host Factors Modulate Strain Features

PubMed Central

Espinosa, J. C.; Nonno, R.; Di Bari, M.; Aguilar-Calvo, P.; Pirisinu, L.; Fernández-Borges, N.; Vanni, I.; Vaccari, G.; Marín-Moreno, A.; Frassanito, P.; Lorenzo, P.; Agrimi, U.

2016-01-01

ABSTRACT Bank vole is a rodent species that shows differential susceptibility to the experimental transmission of different prion strains. In this work, the transmission features of a panel of diverse prions with distinct origins were assayed both in bank vole expressing methionine at codon 109 (Bv109M) and in transgenic mice expressing physiological levels of bank vole PrPC (the BvPrP-Tg407 mouse line). This work is the first systematic comparison of the transmission features of a collection of prion isolates, representing a panel of diverse prion strains, in a transgenic-mouse model and in its natural counterpart. The results showed very similar transmission properties in both the natural species and the transgenic-mouse model, demonstrating the key role of the PrP amino acid sequence in prion transmission susceptibility. However, differences in the PrPSc types propagated by Bv109M and BvPrP-Tg407 suggest that host factors other than PrPC modulate prion strain features. IMPORTANCE The differential susceptibility of bank voles to prion strains can be modeled in transgenic mice, suggesting that this selective susceptibility is controlled by the vole PrP sequence alone rather than by other species-specific factors. Differences in the phenotypes observed after prion transmissions in bank voles and in the transgenic mice suggest that host factors other than the PrPC sequence may affect the selection of the substrain replicating in the animal model. PMID:27654300

Effects of phenotypic plasticity on pathogen transmission in the field in a Lepidoptera-NPV system.

PubMed

Reeson, A F; Wilson, K; Cory, J S; Hankard, P; Weeks, J M; Goulson, D; Hails, R S

2000-08-01

In models of insect-pathogen interactions, the transmission parameter (ν) is the term that describes the efficiency with which pathogens are transmitted between hosts. There are two components to the transmission parameter, namely the rate at which the host encounters pathogens (contact rate) and the rate at which contact between host and pathogen results in infection (host susceptibility). Here it is shown that in larvae of Spodoptera exempta (Lepidoptera: Noctuidae), in which rearing density triggers the expression of one of two alternative phenotypes, the high-density morph is associated with an increase in larval activity. This response is likely to result in an increase in the contact rate between hosts and pathogens. Rearing density is also known to affect susceptibility of S. exempta to pathogens, with the high-density morph showing increased resistance to a baculovirus. In order to determine whether density-dependent differences observed in the laboratory might affect transmission in the wild, a field trial was carried out to estimate the transmission parameter for S. exempta and its nuclear polyhedrosis virus (NPV). The transmission parameter was found to be significantly higher among larvae reared in isolation than among those reared in crowds. Models of insect-pathogen interactions, in which the transmission parameter is assumed to be constant, will therefore not fully describe the S. exempta-NPV system. The finding that crowding can influence transmission in this way has major implications for both the long-term population dynamics and the invasion dynamics of insect-pathogen systems.

Herbivory by Thrips tabaci

Treesearch

Deborah M. Kendall

1991-01-01

Herbivory by Thrips tabaci (Lindeman) affects both the bulb yield and phytohormone balance in its major host plant, the onion (Alium cepa L.). Seasonal changes in the susceptibility of onion yield to T. tabaci feeding were examined during the three growth stages of onion; prebulbing, bulbing and sizing (Kendall...

Mismatch between herbivore behavior and demographics contributes to scale-dependence of host susceptibility in two pine species

Treesearch

Tiina Ylioja; Daniel H. Slone; Matthew P. Ayres

2005-01-01

The impacts on forests of tree-killing bark beetles can depend on the species composition of potential host trees. Host susceptibility might be an intrinsic property of tree species, or it might depend on spatial patterning of alternative host species. We compared the susceptibility of loblolly pine (Pinus taeda) and Virginia pine (P. ...

Macrobiota - helminths as active participants and partners of the microbiota in host intestinal homeostasis.

PubMed

Gause, William C; Maizels, Rick M

2016-08-01

Important insights have recently been gained in our understanding of the intricate relationship in the intestinal milieu between the vertebrate host mucosal immune response, commensal bacteria, and helminths. Helminths are metazoan worms (macrobiota) and trigger immune responses that include potent regulatory components capable of controlling harmful inflammation, protecting barrier function and mitigating tissue damage. They can secrete a variety of products that directly affect immune regulatory function but they also have the capacity to influence the composition of microbiota, which can also then impact immune function. Conversely, changes in microbiota can affect susceptibility to helminth infection, indicating that crosstalk between these two disparate groups of endobiota can play an essential role in host intestinal immune function and homeostasis. Copyright © 2016. Published by Elsevier Ltd.

Synergy in spreading processes: from exploitative to explorative foraging strategies.

PubMed

Pérez-Reche, Francisco J; Ludlam, Jonathan J; Taraskin, Sergei N; Gilligan, Christopher A

2011-05-27

An epidemiological model which incorporates synergistic effects that allow the infectivity and/or susceptibility of hosts to be dependent on the number of infected neighbors is proposed. Constructive synergy induces an exploitative behavior which results in a rapid invasion that infects a large number of hosts. Interfering synergy leads to a slower and sparser explorative foraging strategy that traverses larger distances by infecting fewer hosts. The model can be mapped to a dynamical bond percolation with spatial correlations that affect the mechanism of spread but do not influence the critical behavior of epidemics. © 2011 American Physical Society

Regulation of the host immune system by helminth parasites.

PubMed

Maizels, Rick M; McSorley, Henry J

2016-09-01

Helminth parasite infections are associated with a battery of immunomodulatory mechanisms that affect all facets of the host immune response to ensure their persistence within the host. This broad-spectrum modulation of host immunity has intended and unintended consequences, both advantageous and disadvantageous. Thus the host can benefit from suppression of collateral damage during parasite infection and from reduced allergic, autoimmune, and inflammatory reactions. However, helminth infection can also be detrimental in reducing vaccine responses, increasing susceptibility to coinfection and potentially reducing tumor immunosurveillance. In this review we will summarize the panoply of immunomodulatory mechanisms used by helminths, their potential utility in human disease, and prospective areas of future research. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Climate of seed source affects susceptibility of coastal Douglas-fir to foliage diseases

Treesearch

Nicholas P. Wilhelmi; David C. Shaw; Constance A. Harrington; John Bradley St. Clair; Lisa M. Ganio

2017-01-01

Seed-source movement trials using common garden experiments are needed to understand climate, tree (host), and pathogen interactions. Douglas-fir (Pseudotsuga menziesii var menziesii) is an important tree species native to western North America influenced by the foliar fungi Phaeocryptopus gaeumannii, a biotroph and causal...

Host Genetic Background Strongly Affects Pulmonary microRNA Expression before and during Influenza A Virus Infection.

PubMed

Preusse, Matthias; Schughart, Klaus; Pessler, Frank

2017-01-01

Expression of host microRNAs (miRNAs) changes markedly during influenza A virus (IAV) infection of natural and adaptive hosts, but their role in genetically determined host susceptibility to IAV infection has not been explored. We, therefore, compared pulmonary miRNA expression during IAV infection in two inbred mouse strains with differential susceptibility to IAV infection. miRNA expression profiles were determined in lungs of the more susceptible strain DBA/2J and the less susceptible strain C57BL/6J within 120 h post infection (hpi) with IAV (H1N1) PR8. Even the miRNomes of uninfected lungs differed substantially between the two strains. After a period of relative quiescence, major miRNome reprogramming was detected in both strains by 48 hpi and increased through 120 hpi. Distinct groups of miRNAs regulated by IAV infection could be defined: (1) miRNAs ( n  = 39) whose expression correlated with hemagglutinin (HA) mRNA expression and represented the general response to IAV infection independent of host genetic background; (2) miRNAs ( n  = 20) whose expression correlated with HA mRNA expression but differed between the two strains; and (3) remarkably, miR-147-3p, miR-208b-3p, miR-3096a-5p, miR-3069b-3p, and the miR-467 family, whose abundance even in uninfected lungs differentiated nearly perfectly (area under the ROC curve > 0.99) between the two strains throughout the time course, suggesting a particularly strong association with the differential susceptibility of the two mouse strains. Expression of subsets of miRNAs correlated significantly with peripheral blood granulocyte and monocyte numbers, particularly in DBA/2J mice; miR-223-3p, miR-142-3p, and miR-20b-5p correlated most positively with these cell types in both mouse strains. Higher abundance of antiapoptotic (e.g., miR-467 family) and lower abundance of proapoptotic miRNAs (e.g., miR-34 family) and those regulating the PI3K-Akt pathway (e.g., miR-31-5p) were associated with the more susceptible DBA/2J strain. Substantial differences in pulmonary miRNA expression between the two differentially susceptible mouse strains were evident even before infection, but evolved further throughout infection and could in part be attributed to differences in peripheral blood leukocyte populations. Thus, pulmonary miRNA expression both before and during IAV infection is in part determined genetically and contributes to susceptibility to IAV infection in this murine host, and likely in humans.

SLC11A1 polymorphisms and host susceptibility to cutaneous leishmaniasis in Pakistan.

PubMed

Sophie, Mariam; Hameed, Abdul; Muneer, Akhtar; Samdani, Azam J; Saleem, Saima; Azhar, Abid

2017-01-07

The vector-borne cutaneous leishmaniasis (CL) is endemic in several regions of Pakistan mainly affecting poor populations. Host genetic factors, particularly SLC11A1 (solute carrier transmembrane protein) within macrophages, play a crucial role in disease pathology and susceptibility. Association of SLC11A1 with cutaneous leishmaniasis, a neglected tropical disease, is not well established. Inconsistencies have been observed within different populations worldwide with respect to genetic susceptibility. This study was designed to investigate genetic variation(s) in SLC11A1 and to assess possible association with cutaneous leishmaniasis in Pakistan. Eight polymorphisms (rs2276631, rs3731864, rs2290708, rs2695342, rs201565523, rs17215556, rs17235409, rs17235416) were genotyped across SLC11A1 in 274 patients and 119 healthy controls. Six polymorphisms were studied by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and sequencing. Two single nucleotide polymorphisms were analyzed with newly designed semi-nested PCR assays. Case-control analysis showed no association between selected polymorphisms in SLC11A1 and cutaneous leishmaniasis. No significant difference was observed in the distribution of alleles between leishmaniasis patients and healthy individuals. Strong pairwise linkage disequilibrium was observed between rs2276631 and rs2290708 (r 2  = 64); and rs17235409 and rs17235416 (r 2  = 78). This study shows that genetic variations in the candidate gene SLC11A1 do not affect susceptibility to cutaneous leishmaniasis in the sample population from Pakistan.

PrPC Governs Susceptibility to Prion Strains in Bank Vole, While Other Host Factors Modulate Strain Features.

PubMed

Espinosa, J C; Nonno, R; Di Bari, M; Aguilar-Calvo, P; Pirisinu, L; Fernández-Borges, N; Vanni, I; Vaccari, G; Marín-Moreno, A; Frassanito, P; Lorenzo, P; Agrimi, U; Torres, J M

2016-12-01

Bank vole is a rodent species that shows differential susceptibility to the experimental transmission of different prion strains. In this work, the transmission features of a panel of diverse prions with distinct origins were assayed both in bank vole expressing methionine at codon 109 (Bv109M) and in transgenic mice expressing physiological levels of bank vole PrP C (the BvPrP-Tg407 mouse line). This work is the first systematic comparison of the transmission features of a collection of prion isolates, representing a panel of diverse prion strains, in a transgenic-mouse model and in its natural counterpart. The results showed very similar transmission properties in both the natural species and the transgenic-mouse model, demonstrating the key role of the PrP amino acid sequence in prion transmission susceptibility. However, differences in the PrP Sc types propagated by Bv109M and BvPrP-Tg407 suggest that host factors other than PrP C modulate prion strain features. The differential susceptibility of bank voles to prion strains can be modeled in transgenic mice, suggesting that this selective susceptibility is controlled by the vole PrP sequence alone rather than by other species-specific factors. Differences in the phenotypes observed after prion transmissions in bank voles and in the transgenic mice suggest that host factors other than the PrP C sequence may affect the selection of the substrain replicating in the animal model. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Contrasting amino acid profiles among permissive and non-permissive hosts of Candidatus Liberibacter asiaticus, putative causal agent of Huanglongbing

PubMed Central

Alabi, Olufemi J.; Simpson, Catherine R.; Jifon, John L.

2017-01-01

Huanglongbing is a devastating disease of citrus. In this study, a comprehensive profile of phloem sap amino acids (AA) in four permissive host plants of Candidatus Liberibacter asiaticus (CLas) and three non-permissive Rutaceae plants was conducted to gain a better understanding of host factors that may promote or suppress the bacterium. The AA profiles of Diaphorina citri nymphs and adults were similarly analyzed. A total of 38 unique AAs were detected in phloem sap of the various plants and D. citri samples, with phloem sap of young shoots containing more AAs and at higher concentrations than their mature counterparts. All AAs detected in phloem sap of non-permissive plants were also present in CLas -permissive hosts plus additional AAs in the latter class of plants. However, the relative composition of 18 commonly shared AAs varied between CLas -permissive hosts and non-permissive plants. Multivariate analysis with a partial least square discriminant methodology revealed a total of 12 AAs as major factors affecting CLas host status, of which seven were positively related to CLas tolerance/resistance and five positively associated with CLas susceptibility. Most of the AAs positively associated with CLas susceptibility were predominantly of the glutamate family, notably stressed-induced AAs such as arginine, GABA and proline. In contrast, AAs positively correlated with CLas tolerance/resistance were mainly of the serine family. Further analysis revealed that whereas the relative proportions of AAs positively associated with CLas susceptibility did not vary with host developmental stages, those associated with CLas tolerance/resistance increased with flush shoot maturity. Significantly, the proline-to-glycine ratio was determined to be an important discriminating factor for CLas permissivity with higher values characteristic of CLas -permissive hosts. This ratio could be exploited as a biomarker in HLB-resistance breeding programs. PMID:29236706

The other white-nose syndrome transcriptome: Tolerant and susceptible hosts respond differently to the pathogen Pseudogymnoascus destructans.

PubMed

Davy, Christina M; Donaldson, Michael E; Willis, Craig K R; Saville, Barry J; McGuire, Liam P; Mayberry, Heather; Wilcox, Alana; Wibbelt, Gudrun; Misra, Vikram; Bollinger, Trent; Kyle, Christopher J

2017-09-01

Mitigation of emerging infectious diseases that threaten global biodiversity requires an understanding of critical host and pathogen responses to infection. For multihost pathogens where pathogen virulence or host susceptibility is variable, host-pathogen interactions in tolerant species may identify potential avenues for adaptive evolution in recently exposed, susceptible hosts. For example, the fungus Pseudogymnoascus destructans causes white-nose syndrome (WNS) in hibernating bats and is responsible for catastrophic declines in some species in North America, where it was recently introduced. Bats in Europe and Asia, where the pathogen is endemic, are only mildly affected. Different environmental conditions among Nearctic and Palearctic hibernacula have been proposed as an explanation for variable disease outcomes, but this hypothesis has not been experimentally tested. We report the first controlled, experimental investigation of response to P. destructans in a tolerant, European species of bat (the greater mouse-eared bat, Myotis myotis ). We compared body condition, disease outcomes and gene expression in control (sham-exposed) and exposed M. myotis that hibernated under controlled environmental conditions following treatment. Tolerant M. myotis experienced extremely limited fungal growth and did not exhibit symptoms of WNS. However, we detected no differential expression of genes associated with immune response in exposed bats, indicating that immune response does not drive tolerance of P. destructans in late hibernation. Variable responses to P. destructans among bat species cannot be attributed solely to environmental or ecological factors. Instead, our results implicate coevolution with the pathogen, and highlight the dynamic nature of the "white-nose syndrome transcriptome." Interspecific variation in response to exposure by the host (and possibly pathogen) emphasizes the importance of context in studies of the bat-WNS system, and robust characterization of genetic responses to exposure in various hosts and the pathogen should precede any attempts to use particular bat species as generalizable "model hosts."

Host Phenology and Leaf Effects on Susceptibility of California Bay Laurel to Phytophthora ramorum.

PubMed

Johnston, Steven F; Cohen, Michael F; Torok, Tamas; Meentemeyer, Ross K; Rank, Nathan E

2016-01-01

Spread of the plant pathogen Phytophthora ramorum, causal agent of the forest disease sudden oak death, is driven by a few competent hosts that support spore production from foliar lesions. The relationship between traits of a principal foliar host, California bay laurel (Umbellularia californica), and susceptibility to P. ramorum infection were investigated with multiple P. ramorum isolates and leaves collected from multiple trees in leaf-droplet assays. We examined whether susceptibility varies with season, leaf age, or inoculum position. Bay laurel susceptibility was highest during spring and summer and lowest in winter. Older leaves (>1 year) were more susceptible than younger ones (8 to 11 months). Susceptibility was greater at leaf tips and edges than the middle of the leaf. Leaf surfaces wiped with 70% ethanol were more susceptible to P. ramorum infection than untreated leaf surfaces. Our results indicate that seasonal changes in susceptibility of U. californica significantly influence P. ramorum infection levels. Thus, in addition to environmental variables such as temperature and moisture, variability in host plant susceptibility contributes to disease establishment of P. ramorum.

Philometra floridensis (Nematoda: Philometridae) damages ovarian tissue without reducing host (Sciaenops ocellatus) fecundity.

PubMed

Bakenhaster, Micah D; Lowerre-Barbieri, Susan; Kiryu, Yasunari; Walters, Sarah; Fajer-Avila, Emma J

2014-04-03

The parasitic nematode Philometra floridensis infects the ovary of its only host, the economically important fish species Sciaenops ocellatus, but the factors influencing host susceptibility and potential pathogenic effects are unknown. Here we report new information on these topics from evaluations of infected and uninfected hosts collected from the northeastern Gulf of Mexico. Fish length and age were evaluated vis-à-vis nematode prevalence to check for ontogenetic differences in host susceptibility. To evaluate health and reproductive consequences of infection, we looked for effects in Fulton's condition factor (K) and batch fecundity estimates (BF), and we evaluated ovarian tissue histologically to check for oocyte atresia and other host responses. We observed localized pathological changes in fish ovarian tissue associated with female nematodes, including leucocytic exudates, granulomatous inflammation, and Langhans-type multinucleated giant cells; the hosts, however, appeared to maintain high fecundity and actually exhibited, on average, better health index scores and higher relative fecundity than did uninfected fish. These differences are likely explained by the parasite's tendency to disproportionately infect the largest, actively spawning fish and by the localization of pathogenic changes, which could have masked effects that otherwise would have been reflected in mass-based health indicators. Although we did not detect negative effects on measures of overall health or reproductive output, further research is needed to better elucidate the relationship between these parasites and other factors affecting host reproductive potential, such as egg quality.

Immunological Response to Single Pathogen Challenge with Agents of the Bovine Respiratory Disease Complex: An RNA-Sequence Analysis of the Bronchial Lymph Node Transcriptome.

PubMed

Tizioto, Polyana C; Kim, JaeWoo; Seabury, Christopher M; Schnabel, Robert D; Gershwin, Laurel J; Van Eenennaam, Alison L; Toaff-Rosenstein, Rachel; Neibergs, Holly L; Taylor, Jeremy F

2015-01-01

Susceptibility to bovine respiratory disease (BRD) is multi-factorial and is influenced by stress in conjunction with infection by both bacterial and viral pathogens. While vaccination is broadly used in an effort to prevent BRD, it is far from being fully protective and cases diagnosed from a combination of observed clinical signs without any attempt at identifying the causal pathogens are usually treated with antibiotics. Dairy and beef cattle losses from BRD are profound worldwide and genetic studies have now been initiated to elucidate host loci which underlie susceptibility with the objective of enabling molecular breeding to reduce disease prevalence. In this study, we employed RNA sequencing to examine the bronchial lymph node transcriptomes of controls and beef cattle which had individually been experimentally challenged with bovine respiratory syncytial virus, infectious bovine rhinotracheitis, bovine viral diarrhea virus, Pasteurella multocida, Mannheimia haemolytica or Mycoplasma bovis to identify the genes that are involved in the bovine immune response to infection. We found that 142 differentially expressed genes were located in previously described quantitative trait locus regions associated with risk of BRD. Mutations affecting the expression or amino acid composition of these genes may affect disease susceptibility and could be incorporated into molecular breeding programs. Genes involved in innate immunity were generally found to be differentially expressed between the control and pathogen-challenged animals suggesting that variation in these genes may lead to a heritability of susceptibility that is pathogen independent. However, we also found pathogen-specific expression profiles which suggest that host genetic variation for BRD susceptibility is pathogen dependent.

An epidemiological model of internet worms with hierarchical dispersal and spatial clustering of hosts.

PubMed

Hiebeler, David E; Audibert, Andrew; Strubell, Emma; Michaud, Isaac J

2017-04-07

Beginning in 2001, many instances of malicious software known as Internet worms have been using biological strategies such as hierarchical dispersal to seek out and spread to new susceptible hosts more efficiently. We measured the distribution of potentially susceptible hosts in the space of Internet addresses to determine their clustering. We have used the results to construct a full-size simulated Internet with 2 32 hosts with mean and variance of susceptible hosts chosen to match our measurements at multiple spatial scales. Epidemiological simulations of outbreaks among the roughly 2.8×10 6 susceptible hosts on this full-sized network show that local preference scanning greatly increases the chances for an infected host to locate and infect other susceptible hosts by a factor of as much as several hundred. However, once deploying this strategy, the overall success of a worm is relatively insensitive to the details of its dispersal strategy over a wide range of parameters. In addition, although using localized interactions may allow malicious software to spread more rapidly or to more hosts on average, it can also lead to increased variability in infection levels among replicate simulations. Using such dispersal strategies may therefore be a high risk, high reward strategy for the authors of such software. Copyright © 2017 Elsevier Ltd. All rights reserved.

Postnatal Infections and Immunology Affecting Chronic Lung Disease of Prematurity.

PubMed

Pryhuber, Gloria S

2015-12-01

Premature infants suffer significant respiratory morbidity during infancy with long-term negative consequences on health, quality of life, and health care costs. Enhanced susceptibility to a variety of infections and inflammation play a large role in early and prolonged lung disease following premature birth, although the mechanisms of susceptibility and immune dysregulation are active areas of research. This article reviews aspects of host-pathogen interactions and immune responses that are altered by preterm birth and that impact chronic respiratory morbidity in these children. Copyright © 2015 Elsevier Inc. All rights reserved.

Intraspecific variation in a generalist herbivore accounts for differential induction and impact of host plant defences

PubMed Central

Kant, Merijn R; Sabelis, Maurice W; Haring, Michel A; Schuurink, Robert C

2007-01-01

Plants and herbivores are thought to be engaged in a coevolutionary arms race: rising frequencies of plants with anti-herbivore defences exert pressure on herbivores to resist or circumvent these defences and vice versa. Owing to its frequency-dependent character, the arms race hypothesis predicts that herbivores exhibit genetic variation for traits that determine how they deal with the defences of a given host plant phenotype. Here, we show the existence of distinct variation within a single herbivore species, the spider mite Tetranychus urticae, in traits that lead to resistance or susceptibility to jasmonate (JA)-dependent defences of a host plant but also in traits responsible for induction or repression of JA defences. We characterized three distinct lines of T. urticae that differentially induced JA-related defence genes and metabolites while feeding on tomato plants (Solanum lycopersicum). These lines were also differently affected by induced JA defences. The first line, which induced JA-dependent tomato defences, was susceptible to those defences; the second line also induced JA defences but was resistant to them; and the third, although susceptible to JA defences, repressed induction. We hypothesize that such intraspecific variation is common among herbivores living in environments with a diversity of plants that impose diverse selection pressure. PMID:18055390

Allelic Variation in the Toll-Like Receptor Adaptor Protein Ticam2 Contributes to SARS-Coronavirus Pathogenesis in Mice.

PubMed

Gralinski, Lisa E; Menachery, Vineet D; Morgan, Andrew P; Totura, Allison L; Beall, Anne; Kocher, Jacob; Plante, Jessica; Harrison-Shostak, D Corinne; Schäfer, Alexandra; Pardo-Manuel de Villena, Fernando; Ferris, Martin T; Baric, Ralph S

2017-06-07

Host genetic variation is known to contribute to differential pathogenesis following infection. Mouse models allow direct assessment of host genetic factors responsible for susceptibility to Severe Acute Respiratory Syndrome coronavirus (SARS-CoV). Based on an assessment of early stage lines from the Collaborative Cross mouse multi-parent population, we identified two lines showing highly divergent susceptibilities to SARS-CoV: the resistant CC003/Unc and the susceptible CC053/Unc. We generated 264 F2 mice between these strains, and infected them with SARS-CoV. Weight loss, pulmonary hemorrhage, and viral load were all highly correlated disease phenotypes. We identified a quantitative trait locus of major effect on chromosome 18 (27.1-58.6 Mb) which affected weight loss, viral titer and hemorrhage. Additionally, each of these three phenotypes had distinct quantitative trait loci [Chr 9 (weight loss), Chrs 7 and 12 (virus titer), and Chr 15 (hemorrhage)]. We identified Ticam2 , an adaptor protein in the TLR signaling pathways, as a candidate driving differential disease at the Chr 18 locus. Ticam2 -/- mice were highly susceptible to SARS-CoV infection, exhibiting increased weight loss and more pulmonary hemorrhage than control mice. These results indicate a critical role for Ticam2 in SARS-CoV disease, and highlight the importance of host genetic variation in disease responses. Copyright © 2017 Gralinski et al.

Allelic Variation in the Toll-Like Receptor Adaptor Protein Ticam2 Contributes to SARS-Coronavirus Pathogenesis in Mice

PubMed Central

Gralinski, Lisa E.; Menachery, Vineet D.; Morgan, Andrew P.; Totura, Allison L.; Beall, Anne; Kocher, Jacob; Plante, Jessica; Harrison-Shostak, D. Corinne; Schäfer, Alexandra; Pardo-Manuel de Villena, Fernando; Ferris, Martin T.; Baric, Ralph S.

2017-01-01

Host genetic variation is known to contribute to differential pathogenesis following infection. Mouse models allow direct assessment of host genetic factors responsible for susceptibility to Severe Acute Respiratory Syndrome coronavirus (SARS-CoV). Based on an assessment of early stage lines from the Collaborative Cross mouse multi-parent population, we identified two lines showing highly divergent susceptibilities to SARS-CoV: the resistant CC003/Unc and the susceptible CC053/Unc. We generated 264 F2 mice between these strains, and infected them with SARS-CoV. Weight loss, pulmonary hemorrhage, and viral load were all highly correlated disease phenotypes. We identified a quantitative trait locus of major effect on chromosome 18 (27.1–58.6 Mb) which affected weight loss, viral titer and hemorrhage. Additionally, each of these three phenotypes had distinct quantitative trait loci [Chr 9 (weight loss), Chrs 7 and 12 (virus titer), and Chr 15 (hemorrhage)]. We identified Ticam2, an adaptor protein in the TLR signaling pathways, as a candidate driving differential disease at the Chr 18 locus. Ticam2−/− mice were highly susceptible to SARS-CoV infection, exhibiting increased weight loss and more pulmonary hemorrhage than control mice. These results indicate a critical role for Ticam2 in SARS-CoV disease, and highlight the importance of host genetic variation in disease responses. PMID:28592648

Periodontal diseases.

PubMed

Kinane, Denis F; Stathopoulou, Panagiota G; Papapanou, Panos N

2017-06-22

Periodontal diseases comprise a wide range of inflammatory conditions that affect the supporting structures of the teeth (the gingiva, bone and periodontal ligament), which could lead to tooth loss and contribute to systemic inflammation. Chronic periodontitis predominantly affects adults, but aggressive periodontitis may occasionally occur in children. Periodontal disease initiation and propagation is through a dysbiosis of the commensal oral microbiota (dental plaque), which then interacts with the immune defences of the host, leading to inflammation and disease. This pathophysiological situation persists through bouts of activity and quiescence, until the affected tooth is extracted or the microbial biofilm is therapeutically removed and the inflammation subsides. The severity of the periodontal disease depends on environmental and host risk factors, both modifiable (for example, smoking) and non-modifiable (for example, genetic susceptibility). Prevention is achieved with daily self-performed oral hygiene and professional removal of the microbial biofilm on a quarterly or bi-annual basis. New treatment modalities that are actively explored include antimicrobial therapy, host modulation therapy, laser therapy and tissue engineering for tissue repair and regeneration.

Human genetic variation in VAC14 regulates Salmonella invasion and typhoid fever through modulation of cholesterol.

PubMed

Alvarez, Monica I; Glover, Luke C; Luo, Peter; Wang, Liuyang; Theusch, Elizabeth; Oehlers, Stefan H; Walton, Eric M; Tram, Trinh Thi Bich; Kuang, Yu-Lin; Rotter, Jerome I; McClean, Colleen M; Chinh, Nguyen Tran; Medina, Marisa W; Tobin, David M; Dunstan, Sarah J; Ko, Dennis C

2017-09-12

Risk, severity, and outcome of infection depend on the interplay of pathogen virulence and host susceptibility. Systematic identification of genetic susceptibility to infection is being undertaken through genome-wide association studies, but how to expeditiously move from genetic differences to functional mechanisms is unclear. Here, we use genetic association of molecular, cellular, and human disease traits and experimental validation to demonstrate that genetic variation affects expression of VAC14, a phosphoinositide-regulating protein, to influence susceptibility to Salmonella enterica serovar Typhi ( S Typhi) infection. Decreased VAC14 expression increased plasma membrane cholesterol, facilitating Salmonella docking and invasion. This increased susceptibility at the cellular level manifests as increased susceptibility to typhoid fever in a Vietnamese population. Furthermore, treating zebrafish with a cholesterol-lowering agent, ezetimibe, reduced susceptibility to S Typhi. Thus, coupling multiple genetic association studies with mechanistic dissection revealed how VAC14 regulates Salmonella invasion and typhoid fever susceptibility and may open doors to new prophylactic/therapeutic approaches.

Human genetic variation in VAC14 regulates Salmonella invasion and typhoid fever through modulation of cholesterol

PubMed Central

Alvarez, Monica I.; Glover, Luke C.; Luo, Peter; Wang, Liuyang; Theusch, Elizabeth; Oehlers, Stefan H.; Walton, Eric M.; Tram, Trinh Thi Bich; Kuang, Yu-Lin; Rotter, Jerome I.; McClean, Colleen M.; Chinh, Nguyen Tran; Medina, Marisa W.; Dunstan, Sarah J.

2017-01-01

Risk, severity, and outcome of infection depend on the interplay of pathogen virulence and host susceptibility. Systematic identification of genetic susceptibility to infection is being undertaken through genome-wide association studies, but how to expeditiously move from genetic differences to functional mechanisms is unclear. Here, we use genetic association of molecular, cellular, and human disease traits and experimental validation to demonstrate that genetic variation affects expression of VAC14, a phosphoinositide-regulating protein, to influence susceptibility to Salmonella enterica serovar Typhi (S. Typhi) infection. Decreased VAC14 expression increased plasma membrane cholesterol, facilitating Salmonella docking and invasion. This increased susceptibility at the cellular level manifests as increased susceptibility to typhoid fever in a Vietnamese population. Furthermore, treating zebrafish with a cholesterol-lowering agent, ezetimibe, reduced susceptibility to S. Typhi. Thus, coupling multiple genetic association studies with mechanistic dissection revealed how VAC14 regulates Salmonella invasion and typhoid fever susceptibility and may open doors to new prophylactic/therapeutic approaches. PMID:28827342

A Game of Russian Roulette for a Generalist Dinoflagellate Parasitoid: Host Susceptibility Is the Key to Success

PubMed Central

Alacid, Elisabet; Park, Myung G.; Turon, Marta; Petrou, Katherina; Garcés, Esther

2016-01-01

Marine microbial interactions involving eukaryotes and their parasites play an important role in shaping the structure of phytoplankton communities. These interactions may alter population densities of the main host, which in turn may have consequences for the other concurrent species. The effect generalist parasitoids exert on a community is strongly dependent on the degree of host specificity. Parvilucifera sinerae is a generalist parasitoid able to infect a wide range of dinoflagellates, including toxic-bloom-forming species. A density-dependent chemical cue has been identified as the trigger for the activation of the infective stage. Together these traits make Parvilucifera-dinoflagellate hosts a good model to investigate the degree of specificity of a generalist parasitoid, and the potential effects that it could have at the community level. Here, we present for the first time, the strategy by which a generalist dinoflagellate parasitoid seeks out its host and determine whether it exhibits host preferences, highlighting key factors in determining infection. Our results demonstrate that in its infective stage, P. sinerae is able to sense potential hosts, but does not actively select among them. Instead, the parasitoids contact the host at random, governed by the encounter probability rate and once encountered, the chance to penetrate inside the host cell and develop the infection strongly depends on the degree of host susceptibility. As such, their strategy for persistence is more of a game of Russian roulette, where the chance of survival is dependent on the susceptibility of the host. Our study identifies P. sinerae as a potential key player in community ecology, where in mixed dinoflagellate communities consisting of hosts that are highly susceptible to infection, parasitoid preferences may mediate coexistence between host species, reducing the dominance of the superior competitor. Alternatively, it may increase competition, leading to species exclusion. If, however, highly susceptible hosts are absent from the community, the parasitoid population could suffer a dilution effect maintaining a lower parasitoid density. Therefore, both host community structure and host susceptibility will determine infectivity in the field. PMID:27252688

Ants avoid superinfections by performing risk-adjusted sanitary care.

PubMed

Konrad, Matthias; Pull, Christopher D; Metzler, Sina; Seif, Katharina; Naderlinger, Elisabeth; Grasse, Anna V; Cremer, Sylvia

2018-03-13

Being cared for when sick is a benefit of sociality that can reduce disease and improve survival of group members. However, individuals providing care risk contracting infectious diseases themselves. If they contract a low pathogen dose, they may develop low-level infections that do not cause disease but still affect host immunity by either decreasing or increasing the host's vulnerability to subsequent infections. Caring for contagious individuals can thus significantly alter the future disease susceptibility of caregivers. Using ants and their fungal pathogens as a model system, we tested if the altered disease susceptibility of experienced caregivers, in turn, affects their expression of sanitary care behavior. We found that low-level infections contracted during sanitary care had protective or neutral effects on secondary exposure to the same (homologous) pathogen but consistently caused high mortality on superinfection with a different (heterologous) pathogen. In response to this risk, the ants selectively adjusted the expression of their sanitary care. Specifically, the ants performed less grooming and more antimicrobial disinfection when caring for nestmates contaminated with heterologous pathogens compared with homologous ones. By modulating the components of sanitary care in this way the ants acquired less infectious particles of the heterologous pathogens, resulting in reduced superinfection. The performance of risk-adjusted sanitary care reveals the remarkable capacity of ants to react to changes in their disease susceptibility, according to their own infection history and to flexibly adjust collective care to individual risk.

Bacterial Lipopolysaccharide Destabilizes Influenza Viruses.

PubMed

Bandoro, Christopher; Runstadler, Jonathan A

2017-01-01

Depending on the specific viral pathogen, commensal bacteria can promote or reduce the severity of viral infection and disease progression in their hosts. Influenza A virus (IAV) has a broad host range, comprises many subtypes, and utilizes different routes of transmission, including the fecal-oral route in wild birds. It has been previously demonstrated that commensal bacteria can interact with the host's immune system to protect against IAV pathogenesis. However, it is unclear whether bacteria and their products may be interacting directly with IAV to impact virion stability. Herein we show that gastrointestinal (GI) tract bacterial isolates in an in vitro system significantly reduce the stability of IAV. Moreover, bacterial lipopolysaccharide (LPS), found on the exterior surfaces of bacteria, was sufficient to significantly decrease the stability of both human and avian viral strains in a temperature-dependent manner, including at the relevant temperatures of their respective hosts and the external aquatic habitat. The subtype and host origin of the viruses were shown to affect the extent to which IAV was susceptible to LPS. Furthermore, using a receptor binding assay and transmission electron microscopy, we observed that LPS binds to and alters the morphology of influenza virions, suggesting that direct interaction with the viral surface contributes to the observed antiviral effect of LPS on influenza. IMPORTANCE Influenza A virus (IAV), transmitted primarily via the fecal-oral route in wild birds, encounters high concentrations of bacteria and their products. Understanding the extent to which bacteria affect the infectivity of IAV will lead to a broader understanding of viral ecology in reservoir hosts and may lead to insights for the development of therapeutics in respiratory infection. Herein we show that bacteria and lipopolysaccharide (LPS) interact with and destabilize influenza virions. Moreover, we show that LPS reduces the long-term persistence and freeze-thaw stability of IAV, which is important information for modeling the movement and emergence of novel strains from animal hosts. Our results, demonstrating that the subtype and host origin of a virus also influence its susceptibility to LPS, raise key questions about the fitness of viruses in reservoir hosts, their potential to transmit to humans, and the importance of bacterial-viral interactions in viral ecology.

Dual RNA-Sequencing of Eucalyptus nitens during Phytophthora cinnamomi Challenge Reveals Pathogen and Host Factors Influencing Compatibility

PubMed Central

Meyer, Febé E.; Shuey, Louise S.; Naidoo, Sitha; Mamni, Thandekile; Berger, Dave K.; Myburg, Alexander A.; van den Berg, Noëlani; Naidoo, Sanushka

2016-01-01

Damage caused by Phytophthora cinnamomi Rands remains an important concern on forest tree species. The pathogen causes root and collar rot, stem cankers, and dieback of various economically important Eucalyptus spp. In South Africa, susceptible cold tolerant Eucalyptus plantations have been affected by various Phytophthora spp. with P. cinnamomi considered one of the most virulent. The molecular basis of this compatible interaction is poorly understood. In this study, susceptible Eucalyptus nitens plants were stem inoculated with P. cinnamomi and tissue was harvested five days post inoculation. Dual RNA-sequencing, a technique which allows the concurrent detection of both pathogen and host transcripts during infection, was performed. Approximately 1% of the reads mapped to the draft genome of P. cinnamomi while 78% of the reads mapped to the Eucalyptus grandis genome. The highest expressed P. cinnamomi gene in planta was a putative crinkler effector (CRN1). Phylogenetic analysis indicated the high similarity of this P. cinnamomi CRN1 to that of Phytophthora infestans. Some CRN effectors are known to target host nuclei to suppress defense. In the host, over 1400 genes were significantly differentially expressed in comparison to mock inoculated trees, including suites of pathogenesis related (PR) genes. In particular, a PR-9 peroxidase gene with a high similarity to a Carica papaya PR-9 ortholog previously shown to be suppressed upon infection by Phytophthora palmivora was down-regulated two-fold. This PR-9 gene may represent a cross-species effector target during P. cinnamomi infection. This study identified pathogenicity factors, potential manipulation targets, and attempted host defense mechanisms activated by E. nitens that contributed to the susceptible outcome of the interaction. PMID:26973660

Host pathogen interactions in Helicobacter pylori related gastric cancer

PubMed Central

Chmiela, Magdalena; Karwowska, Zuzanna; Gonciarz, Weronika; Allushi, Bujana; Stączek, Paweł

2017-01-01

Helicobacter pylori (H. pylori), discovered in 1982, is a microaerophilic, spiral-shaped gram-negative bacterium that is able to colonize the human stomach. Nearly half of the world's population is infected by this pathogen. Its ability to induce gastritis, peptic ulcers, gastric cancer and mucosa-associated lymphoid tissue lymphoma has been confirmed. The susceptibility of an individual to these clinical outcomes is multifactorial and depends on H. pylori virulence, environmental factors, the genetic susceptibility of the host and the reactivity of the host immune system. Despite the host immune response, H. pylori infection can be difficult to eradicate. H. pylori is categorized as a group I carcinogen since this bacterium is responsible for the highest rate of cancer-related deaths worldwide. Early detection of cancer can be lifesaving. The 5-year survival rate for gastric cancer patients diagnosed in the early stages is nearly 90%. Gastric cancer is asymptomatic in the early stages but always progresses over time and begins to cause symptoms when untreated. In 97% of stomach cancer cases, cancer cells metastasize to other organs. H. pylori infection is responsible for nearly 60% of the intestinal-type gastric cancer cases but also influences the development of diffuse gastric cancer. The host genetic susceptibility depends on polymorphisms of genes involved in H. pylori-related inflammation and the cytokine response of gastric epithelial and immune cells. H. pylori strains differ in their ability to induce a deleterious inflammatory response. H. pylori-driven cytokines accelerate the inflammatory response and promote malignancy. Chronic H. pylori infection induces genetic instability in gastric epithelial cells and affects the DNA damage repair systems. Therefore, H. pylori infection should always be considered a pro-cancerous factor. PMID:28321154

Host pathogen interactions in Helicobacter pylori related gastric cancer.

PubMed

Chmiela, Magdalena; Karwowska, Zuzanna; Gonciarz, Weronika; Allushi, Bujana; Stączek, Paweł

2017-03-07

Helicobacter pylori ( H. pylori ), discovered in 1982, is a microaerophilic, spiral-shaped gram-negative bacterium that is able to colonize the human stomach. Nearly half of the world's population is infected by this pathogen. Its ability to induce gastritis, peptic ulcers, gastric cancer and mucosa-associated lymphoid tissue lymphoma has been confirmed. The susceptibility of an individual to these clinical outcomes is multifactorial and depends on H. pylori virulence, environmental factors, the genetic susceptibility of the host and the reactivity of the host immune system. Despite the host immune response, H. pylori infection can be difficult to eradicate. H. pylori is categorized as a group I carcinogen since this bacterium is responsible for the highest rate of cancer-related deaths worldwide. Early detection of cancer can be lifesaving. The 5-year survival rate for gastric cancer patients diagnosed in the early stages is nearly 90%. Gastric cancer is asymptomatic in the early stages but always progresses over time and begins to cause symptoms when untreated. In 97% of stomach cancer cases, cancer cells metastasize to other organs. H. pylori infection is responsible for nearly 60% of the intestinal-type gastric cancer cases but also influences the development of diffuse gastric cancer. The host genetic susceptibility depends on polymorphisms of genes involved in H. pylori -related inflammation and the cytokine response of gastric epithelial and immune cells. H. pylori strains differ in their ability to induce a deleterious inflammatory response. H. pylori -driven cytokines accelerate the inflammatory response and promote malignancy. Chronic H. pylori infection induces genetic instability in gastric epithelial cells and affects the DNA damage repair systems. Therefore, H. pylori infection should always be considered a pro-cancerous factor.

Comparison of Rift Valley fever virus and MP-12 replication in domestic livestock and North American wildlife cell lines.

USDA-ARS?s Scientific Manuscript database

Rift Valley fever virus (RVFV) is a mosquito-transmitted pathogen that primarily affects livestock, but can also cause mild to fatal disease in humans. Currently, there is no approved vaccine for use in the United States if it were introduced. Domestic goats, sheep and cattle are susceptible hosts ...

Biomarkers of susceptibility: State of the art and implications for occupational exposure to engineered nanomaterials

PubMed Central

Iavicoli, Ivo; Leso, Veruscka; Schulte, Paul A.

2016-01-01

Rapid advances and applications in nanotechnology are expected to result in increasing occupational exposure to nano-sized materials whose health impacts are still not completely understood. Scientific efforts are required to identify hazards from nanomaterials and define risks and precautionary management strategies for exposed workers. In this scenario, the definition of susceptible populations, which may be at increased risk of adverse effects may be important for risk assessment and management. The aim of this review is to critically examine available literature to provide a comprehensive overview on susceptibility aspects potentially affecting heterogeneous responses to nanomaterials workplace exposure. Genetic, genotoxic and epigenetic alterations induced by nanomaterials in experimental studies were assessed with respect to their possible function as determinants of susceptibility. Additionally, the role of host factors, i.e. age, gender, and pathological conditions, potentially affecting nanomaterial toxicokinetic and health impacts, were also analysed. Overall, this review provides useful information to obtain insights into the nanomaterial mode of action in order to identify potentially sensitive, specific susceptibility biomarkers to be validated in occupational settings and addressed in risk assessment processes. The findings of this review are also important to guide future research into a deeper characterization of nanomaterial susceptibility in order to define adequate risk communication strategies. Ultimately, identification and use of susceptibility factors in workplace settings has both scientific and ethical issues that need addressing. PMID:26724381

Effects of chytridiomycosis on hematopoietic tissue in the spleen, kidney and bone marrow in three diverse amphibian species.

PubMed

Brannelly, Laura A; Webb, Rebecca J; Skerratt, Lee F; Berger, Lee

2016-10-01

One of the major causes of amphibian population decline is the deadly fungal pathogen Batrachochytrium dendrobatidis, Bd Research on pathogenesis and host immunity aims to inform development of targeted conservation interventions. Studies examining global host immune responses as well as effects on lymphocytes in vitro suggest that Bd infection causes immunosuppression. However, it is unknown which hematopoietic tissues are affected and if these effects differ among host species. We investigated the effect of experimental Bd infection on three diverse amphibian species by quantifying the amount of hematopoietic tissue in the spleen, bone marrow and kidney. Upon Bd infection, hematopoietic tissue in the kidney tended to be depleted, while the spleen appeared unaffected. The bone marrow in highly susceptible species was depleted, whereas an increase in hematopoietic tissue was observed in the more resistant species. Our study demonstrates that species and hematopoietic tissues behave differently in response to Bd infection, and may be related to the species' susceptibility to infection. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Novel disease susceptibility factors for fungal necrotrophic pathogens in Arabidopsis.

PubMed

Dobón, Albor; Canet, Juan Vicente; García-Andrade, Javier; Angulo, Carlos; Neumetzler, Lutz; Persson, Staffan; Vera, Pablo

2015-04-01

Host cells use an intricate signaling system to respond to invasions by pathogenic microorganisms. Although several signaling components of disease resistance against necrotrophic fungal pathogens have been identified, our understanding for how molecular components and host processes contribute to plant disease susceptibility is rather sparse. Here, we identified four transcription factors (TFs) from Arabidopsis that limit pathogen spread. Arabidopsis mutants defective in any of these TFs displayed increased disease susceptibility to Botrytis cinerea and Plectosphaerella cucumerina, and a general activation of non-immune host processes that contribute to plant disease susceptibility. Transcriptome analyses revealed that the mutants share a common transcriptional signature of 77 up-regulated genes. We characterized several of the up-regulated genes that encode peptides with a secretion signal, which we named PROVIR (for provirulence) factors. Forward and reverse genetic analyses revealed that many of the PROVIRs are important for disease susceptibility of the host to fungal necrotrophs. The TFs and PROVIRs identified in our work thus represent novel genetic determinants for plant disease susceptibility to necrotrophic fungal pathogens.

Susceptibility to Ticks and Lyme Disease Spirochetes Is Not Affected in Mice Coinfected with Nematodes.

PubMed

Maaz, Denny; Rausch, Sebastian; Richter, Dania; Krücken, Jürgen; Kühl, Anja A; Demeler, Janina; Blümke, Julia; Matuschka, Franz-Rainer; von Samson-Himmelstjerna, Georg; Hartmann, Susanne

2016-05-01

Small rodents serve as reservoir hosts for tick-borne pathogens, such as the spirochetes causing Lyme disease. Whether natural coinfections with other macroparasites alter the success of tick feeding, antitick immunity, and the host's reservoir competence for tick-borne pathogens remains to be determined. In a parasitological survey of wild mice in Berlin, Germany, approximately 40% of Ixodes ricinus-infested animals simultaneously harbored a nematode of the genus Heligmosomoides We therefore aimed to analyze the immunological impact of the nematode/tick coinfection as well as its effect on the tick-borne pathogen Borrelia afzelii Hosts experimentally coinfected with Heligmosomoides polygyrus and larval/nymphal I. ricinus ticks developed substantially stronger systemic type 2 T helper cell (Th2) responses, on the basis of the levels of GATA-3 and interleukin-13 expression, than mice infected with a single pathogen. During repeated larval infestations, however, anti-tick Th2 reactivity and an observed partial immunity to tick feeding were unaffected by concurrent nematode infections. Importantly, the strong systemic Th2 immune response in coinfected mice did not affect susceptibility to tick-borne B. afzelii An observed trend for decreased local and systemic Th1 reactivity against B. afzelii in coinfected mice did not result in a higher spirochete burden, nor did it facilitate bacterial dissemination or induce signs of immunopathology. Hence, this study indicates that strong systemic Th2 responses in nematode/tick-coinfected house mice do not affect the success of tick feeding and the control of the causative agent of Lyme disease. Copyright © 2016 Maaz et al.

The Differential Expression of Immune Genes between Water Buffalo and Yellow Cattle Determines Species-Specific Susceptibility to Schistosoma japonicum Infection

PubMed Central

Yang, Jianmei; Fu, Zhiqiang; Hong, Yang; Wu, Haiwei; Jin, Yamei; Zhu, Chuangang; Li, Hao; Lu, Ke; Shi, Yaojun; Yuan, Chunxiu; Cheng, Guofeng; Feng, Xingang; Liu, Jinming; Lin, Jiaojiao

2015-01-01

Water buffalo are less susceptible to Schistosoma japonicum infection than yellow cattle. The factors that affect such differences in susceptibility remain unknown. A Bos taurus genome-wide gene chip was used to analyze gene expression profiles in the peripheral blood of water buffalo and yellow cattle pre- and post-infection with S. japonicum. This study showed that most of the identified differentially expressed genes(DEGs) between water buffalo and yellow cattle pre- and post-infection were involved in immune-related processes, and the expression level of immune genes was lower in water buffalo. The unique DEGs (390) in yellow cattle were mainly associated with inflammation pathways, while the unique DEGs (2,114) in water buffalo were mainly associated with immune-related factors. The 83 common DEGs may be the essential response genes during S. japonicum infection, the highest two gene ontology (GO) functions were associated with the regulation of fibrinolysis. The pathway enrichment analysis showed that the DEGs constituted similar immune-related pathways pre- and post-infection between the two hosts. This first analysis of the transcriptional profiles of natural hosts has enabled us to gain new insights into the mechanisms that govern their susceptibility or resistance to S. japonicum infections. PMID:26125181

Risk of Human Papillomavirus Infection in Cancer-Prone Individuals: What We Know

PubMed Central

Khoury, Ruby; Sauter, Sharon; Butsch Kovacic, Melinda; Nelson, Adam S.; Myers, Kasiani C.; Mehta, Parinda A.; Davies, Stella M.; Wells, Susanne I.

2018-01-01

Human papillomavirus (HPV) infections cause a significant proportion of cancers worldwide, predominantly squamous cell carcinomas (SCC) of the mucosas and skin. High-risk HPV types are associated with SCCs of the anogenital and oropharyngeal tract. HPV oncogene activities and the biology of SCCs have been intensely studied in laboratory models and humans. What remains largely unknown are host tissue and immune-related factors that determine an individual’s susceptibility to infection and/or carcinogenesis. Such susceptibility factors could serve to identify those at greatest risk and spark individually tailored HPV and SCC prevention efforts. Fanconi anemia (FA) is an inherited DNA repair disorder that is in part characterized by extreme susceptibility to SCCs. An increased prevalence of HPV has been reported in affected individuals, and molecular and functional connections between FA, SCC, and HPV were established in laboratory models. However, the presence of HPV in some human FA tumors is controversial, and the extent of the etiological connections remains to be established. Herein, we discuss cellular, immunological, and phenotypic features of FA, placed into the context of HPV pathogenesis. The goal is to highlight this orphan disease as a unique model system to uncover host genetic and molecular HPV features, as well as SCC susceptibility factors. PMID:29361695

Early gut colonizers shape parasite susceptibility and microbiota composition in honey bee workers

PubMed Central

Schwarz, Ryan S.; Moran, Nancy A.; Evans, Jay D.

2016-01-01

Microbial symbionts living within animal guts are largely composed of resident bacterial species, forming communities that often provide benefits to the host. Gut microbiomes of adult honey bees (Apis mellifera) include core residents such as the betaproteobacterium Snodgrassella alvi, alongside transient parasites such as the protozoan Lotmaria passim. To test how these species affect microbiome composition and host physiology, we administered S. alvi and/or L. passim inocula to newly emerged worker bees from four genetic backgrounds (GH) and reared them in normal (within hives) or stressed (protein-deficient, asocial) conditions. Microbiota acquired by normal bees were abundant but quantitatively differed across treatments, indicating treatment-associated dysbiosis. Pretreatment with S. alvi made normal bees more susceptible to L. passim and altered developmental and detoxification gene expression. Stressed bees were more susceptible to L. passim and were depauperate in core microbiota, yet supplementation with S. alvi did not alter this susceptibility. Microbiomes were generally more variable by GH in stressed bees, which also showed opposing and comparatively reduced modulation of gene expression responses to treatments compared with normal bees. These data provide experimental support for a link between altered gut microbiota and increased parasite and pathogen prevalence, as observed from honey bee colony collapse disorder. PMID:27482088

Family-based linkage and association mapping reveals novel genes affecting Plum pox virus infection in Arabidopsis thaliana.

PubMed

Pagny, Gaëlle; Paulstephenraj, Pauline S; Poque, Sylvain; Sicard, Ophélie; Cosson, Patrick; Eyquard, Jean-Philippe; Caballero, Mélodie; Chague, Aurélie; Gourdon, Germain; Negrel, Lise; Candresse, Thierry; Mariette, Stéphanie; Decroocq, Véronique

2012-11-01

Sharka is a devastating viral disease caused by the Plum pox virus (PPV) in stone fruit trees and few sources of resistance are known in its natural hosts. Since any knowledge gained from Arabidopsis on plant virus susceptibility factors is likely to be transferable to crop species, Arabidopsis's natural variation was searched for host factors essential for PPV infection. To locate regions of the genome associated with susceptibility to PPV, linkage analysis was performed on six biparental populations as well as on multiparental lines. To refine quantitative trait locus (QTL) mapping, a genome-wide association analysis was carried out using 147 Arabidopsis accessions. Evidence was found for linkage on chromosomes 1, 3 and 5 with restriction of PPV long-distance movement. The most relevant signals occurred within a region at the bottom of chromosome 3, which comprises seven RTM3-like TRAF domain-containing genes. Since the resistance mechanism analyzed here is recessive and the rtm3 knockout mutant is susceptible to PPV infection, it suggests that other gene(s) present in the small identified region encompassing RTM3 are necessary for PPV long-distance movement. In consequence, we report here the occurrence of host factor(s) that are indispensable for virus long-distance movement. © 2012 INRA. New Phytologist © 2012 New Phytologist Trust.

Host-seeking strategies of mosquito disease vectors.

PubMed

Day, Jonathan F

2005-12-01

Disease transmission by arthropods normally requires at least 2 host contacts. During the first, a pathogen (nematode, protozoan, or virus) is acquired along with the blood from an infected vertebrate host. The pathogen penetrates the vector's midgut and infects a variety of tissues, where replication may occur during an extrinsic incubation period lasting 3-30, days depending on vector and parasite physiology and ambient temperature. Following salivary-gland infection, the pathogen is usually transmitted to additional susceptible vertebrate hosts during future probing or blood feeding. The host-seeking strategies used by arthropod vectors can, in part, affect the efficiency of disease transmission. Vector abundance, seasonal distribution, habitat and host preference, and susceptibility to infection are all important components of disease-transmission cycles. Examples of 3 mosquito vectors of human disease are presented here to highlight the diversity of host seeking and to show how specific behaviors may influence disease-transmission cycles. In the African tropics, Anopheles gambiae s.s. is an efficient vector of human malaria due to its remarkably focused preference for human blood. Aedes aegypti is the main vector of dengue viruses in the New and Old World tropics and subtropics. This mosquito has evolved a domestic lifestyle and shares human habitations throughout much of its range. It prospers in settings where humans are its main source of blood. In south Florida, Culex nigripalpus is the major vector of St. Louis encephalitis (SLE) and West Nile (WN) viruses. This mosquito is opportunistic and blood feeds on virtually any available vertebrate host. It serves as an arboviral vector, in part, due to its ability to produce large populations in a short period of time. These 3 host-seeking and blood-feeding strategies make the specialist, as well as the opportunist, equally dangerous disease vectors.

Does interspecies hybridization affect the host specificity of parasites in cyprinid fish?

PubMed

Simková, Andrea; Dávidová, Martina; Papoušek, Ivo; Vetešník, Lukáš

2013-04-12

Host specificity varies among parasite species. Some parasites are strictly host-specific, others show a specificity for congeneric or non-congeneric phylogenetically related host species, whilst some others are non-specific (generalists). Two cyprinids, Cyprinus carpio and Carassius gibelio, plus their respective hybrids were investigated for metazoan parasites. The aim of this study was to analyze whether interspecies hybridization affects host specificity. The different degrees of host specificity within a phylogenetic framework were taken into consideration (i.e. strict specialist, intermediate specialist, and intermediate generalist). Fish were collected during harvesting the pond and identified using meristic traits and molecular markers. Metazoan parasite species were collected. Host specificity of parasites was determined using the following classification: strict specialist, intermediate specialist, intermediate generalist and generalist. Parasite species richness was compared between parental species and their hybrids. The effect of host species on abundance of parasites differing in host specificity was tested. Hybrids harbored more different parasite species but their total parasite abundance was lower in comparison with parental species. Interspecies hybridization affected the host specificity of ecto- and endoparasites. Parasite species exhibiting different degrees of host specificity for C. carpio and C. gibelio were also present in hybrids. The abundance of strict specialists of C. carpio was significantly higher in parental species than in hybrids. Intermediate generalists parasitizing C. carpio and C. gibelio as two phylogenetically closely related host species preferentially infected C. gibelio when compared to C. carpio, based on prevalence and maximum intensity of infection. Hybrids were less infected by intermediate generalists when compared to C. gibelio. This finding does not support strict co-adaptation between host and parasite genotypes resulting in narrow host specificity, and showed that hybrid genotypes are susceptible to parasites exhibiting host specificity. The immune mechanisms specific to parental species might represent potential mechanisms explaining the low abundance of parasites in C. gibelio x C. carpio hybrids.

Non-thermal plasma treatment diminishes fungal viability and up-regulates resistance genes in a plant host.

PubMed

Panngom, Kamonporn; Lee, Sang Hark; Park, Dae Hoon; Sim, Geon Bo; Kim, Yong Hee; Uhm, Han Sup; Park, Gyungsoon; Choi, Eun Ha

2014-01-01

Reactive oxygen and nitrogen species can have either harmful or beneficial effects on biological systems depending on the dose administered and the species of organism exposed, suggesting that application of reactive species can possibly produce contradictory effects in disease control, pathogen inactivation and activation of host resistance. A novel technology known as atmospheric-pressure non-thermal plasma represents a means of generating various reactive species that adversely affect pathogens (inactivation) while simultaneously up-regulating host defense genes. The anti-microbial efficacy of this technology was tested on the plant fungal pathogen Fusarium oxysporum f.sp. lycopersici and its susceptible host plant species Solanum lycopercicum. Germination of fungal spores suspended in saline was decreased over time after exposed to argon (Ar) plasma for 10 min. Although the majority of treated spores exhibited necrotic death, apoptosis was also observed along with the up-regulation of apoptosis related genes. Increases in the levels of peroxynitrite and nitrite in saline following plasma treatment may have been responsible for the observed spore death. In addition, increased transcription of pathogenesis related (PR) genes was observed in the roots of the susceptible tomato cultivar (S. lycopercicum) after exposure to the same Ar plasma dose used in fungal inactivation. These data suggest that atmospheric-pressure non-thermal plasma can be efficiently used to control plant fungal diseases by inactivating fungal pathogens and up-regulating mechanisms of host resistance.

Host susceptibility of citrus cultivars to Queensland fruit fly (Diptera: Tephritidae).

PubMed

Lloyd, A C; Hamacek, E L; Smith, D; Kopittke, R A; Gu, H

2013-04-01

Citrus crops are considered to be relatively poor hosts for Queensland fruit fly, Bactrocera tryoni (Froggatt), as for other tephritid species. Australian citrus growers and crop consultants have reported observable differences in susceptibility of different citrus cultivars under commercial growing conditions. In this study we conducted laboratory tests and field surveys to determine susceptibility to B. tryoni of six citrus cultivars [(Eureka lemon (Citrus limon (L.) Osbeck); Navel and Valencia oranges (C. sinensis (L.) Osbeck); and Imperial, Ellendale, and Murcott mandarins (C. reticulata Blanco). The host susceptibility of these citrus cultivars was quantified by a Host Susceptibility Index, which is defined as the number of adult flies produced per gram of fruit infested at a calculated rate of one egg per gram of fruit. The HSI was ranked as Murcott (0.083) > Imperial (0.052) > Navel (0.026) - Ellendale (0.020) > Valencia (0.008) > Eureka (yellow) (0.002) > Eureka (green) (0). Results of the laboratory study were in agreement with the level of field infestation in the four citrus cultivars (Eureka lemon, Imperial, Ellendale, and Murcott mandarins) that were surveyed from commercial orchards under baiting treatments against fruit flies in the Central Burnett district of Queensland. Field surveys of citrus hosts from the habitats not subject to fruit fly management showed that the numbers of fruit flies produced per gram of fruit were much lower, compared with the more susceptible noncitrus hosts, such as guava (Psidium guajava L.), cherry guava (P. littorale Raddi), mulberry (Morus nigra L.), loquat (Eriobotrya japonica (Thunb.) Lindl.), and pear (Pyrus communis L.). Therefore, the major citrus crops commercially cultivated in Australia have a relatively low susceptibility to B. tryoni, with Eureka lemons being a particularly poor host for this tephritid fruit fly.

A potential target gene for the host-directed therapy of mycobacterial infection in murine macrophages

PubMed Central

Bao, Zhang; Chen, Ran; Zhang, Pei; Lu, Shan; Chen, Xing; Yao, Yake; Jin, Xiaozheng; Sun, Yilan; Zhou, Jianying

2016-01-01

Mycobacterium tuberculosis (MTB), one of the major bacterial pathogens for lethal infectious diseases, is capable of surviving within the phagosomes of host alveolar macrophages; therefore, host genetic variations may alter the susceptibility to MTB. In this study, to identify host genes exploited by MTB during infection, genes were non-selectively inactivated using lentivirus-based antisense RNA methods in RAW264.7 macrophages, and the cells that survived virulent MTB infection were then screened. Following DNA sequencing of the surviving cell clones, 26 host genes affecting susceptibility to MTB were identified and their pathways were analyzed by bioinformatics analysis. In total, 9 of these genes were confirmed as positive regulators of collagen α-5(IV) chain (Col4a5) expression, a gene encoding a type IV collagen subunit present on the cell surface. The knockdown of Col4a5 consistently suppressed intracellular mycobacterial viability, promoting the survival of RAW264.7 macrophages following mycobacterial infection. Furthermore, Col4a5 deficiency lowered the pH levels of intracellular vesicles, including endosomes, lysosomes and phagosomes in the RAW264.7 cells. Finally, the knockdown of Col4a5 post-translationally increased microsomal vacuolar-type H+-ATPase activity in macrophages, leading to the acidification of intracellular vesicles. Our findings reveal a novel role for Col4a5 in the regulation of macrophage responses to mycobacterial infection and identify Col4a5 as a potential target for the host-directed anti-mycobacterial therapy. PMID:27432120

Bacterial Lipopolysaccharide Destabilizes Influenza Viruses

PubMed Central

2017-01-01

ABSTRACT Depending on the specific viral pathogen, commensal bacteria can promote or reduce the severity of viral infection and disease progression in their hosts. Influenza A virus (IAV) has a broad host range, comprises many subtypes, and utilizes different routes of transmission, including the fecal-oral route in wild birds. It has been previously demonstrated that commensal bacteria can interact with the host’s immune system to protect against IAV pathogenesis. However, it is unclear whether bacteria and their products may be interacting directly with IAV to impact virion stability. Herein we show that gastrointestinal (GI) tract bacterial isolates in an in vitro system significantly reduce the stability of IAV. Moreover, bacterial lipopolysaccharide (LPS), found on the exterior surfaces of bacteria, was sufficient to significantly decrease the stability of both human and avian viral strains in a temperature-dependent manner, including at the relevant temperatures of their respective hosts and the external aquatic habitat. The subtype and host origin of the viruses were shown to affect the extent to which IAV was susceptible to LPS. Furthermore, using a receptor binding assay and transmission electron microscopy, we observed that LPS binds to and alters the morphology of influenza virions, suggesting that direct interaction with the viral surface contributes to the observed antiviral effect of LPS on influenza. IMPORTANCE Influenza A virus (IAV), transmitted primarily via the fecal-oral route in wild birds, encounters high concentrations of bacteria and their products. Understanding the extent to which bacteria affect the infectivity of IAV will lead to a broader understanding of viral ecology in reservoir hosts and may lead to insights for the development of therapeutics in respiratory infection. Herein we show that bacteria and lipopolysaccharide (LPS) interact with and destabilize influenza virions. Moreover, we show that LPS reduces the long-term persistence and freeze-thaw stability of IAV, which is important information for modeling the movement and emergence of novel strains from animal hosts. Our results, demonstrating that the subtype and host origin of a virus also influence its susceptibility to LPS, raise key questions about the fitness of viruses in reservoir hosts, their potential to transmit to humans, and the importance of bacterial-viral interactions in viral ecology. PMID:29034326

Host instar susceptibility and selection and interspecific competition of three introduced parasitoids of the mealybug Paracoccus marginatus (Hemiptera: Pseudococccidae)

USDA-ARS?s Scientific Manuscript database

Acerophagus papayae, Anagyrus loecki, and Pseudleptomastix mexicana, three introduced parasitoids of Paracoccus marginatus were investigated for host stage susceptibility and sex ratio, host stage suitability, and interspecific competition. All three parasitoid species were able to develop and emer...

Analysis of molecular variability among the isolated of Verticillium dahliae from diverse host species based on florescene-based amplified fragment length polymorphism.

USDA-ARS?s Scientific Manuscript database

Verticillium dahliae is a soil borne fungus and the primary causal agent of Verticillium wilt, which affects many crops worldwide. Many crops grown in the Salinas Valley (SV) of California, including strawberry and lettuce (Lactuca sativa), are susceptible to V. dahliae and severe outbreaks are comm...

Interacting parasites

USGS Publications Warehouse

Lafferty, Kevin D.

2010-01-01

Parasitism is the most popular life-style on Earth, and many vertebrates host more than one kind of parasite at a time. A common assumption is that parasite species rarely interact, because they often exploit different tissues in a host, and this use of discrete resources limits competition (1). On page 243 of this issue, however, Telfer et al. (2) provide a convincing case of a highly interactive parasite community in voles, and show how infection with one parasite can affect susceptibility to others. If some human parasites are equally interactive, our current, disease-by-disease approach to modeling and treating infectious diseases is inadequate (3).

Novel Disease Susceptibility Factors for Fungal Necrotrophic Pathogens in Arabidopsis

PubMed Central

García-Andrade, Javier; Angulo, Carlos; Neumetzler, Lutz; Persson, Staffan; Vera, Pablo

2015-01-01

Host cells use an intricate signaling system to respond to invasions by pathogenic microorganisms. Although several signaling components of disease resistance against necrotrophic fungal pathogens have been identified, our understanding for how molecular components and host processes contribute to plant disease susceptibility is rather sparse. Here, we identified four transcription factors (TFs) from Arabidopsis that limit pathogen spread. Arabidopsis mutants defective in any of these TFs displayed increased disease susceptibility to Botrytis cinerea and Plectosphaerella cucumerina, and a general activation of non-immune host processes that contribute to plant disease susceptibility. Transcriptome analyses revealed that the mutants share a common transcriptional signature of 77 up-regulated genes. We characterized several of the up-regulated genes that encode peptides with a secretion signal, which we named PROVIR (for provirulence) factors. Forward and reverse genetic analyses revealed that many of the PROVIRs are important for disease susceptibility of the host to fungal necrotrophs. The TFs and PROVIRs identified in our work thus represent novel genetic determinants for plant disease susceptibility to necrotrophic fungal pathogens. PMID:25830627

Innate Resistance and Susceptibility to Norovirus Infection

DOE PAGES

Nordgren, Johan; Sharma, Sumit; Kambhampati, Anita; ...

2016-04-26

The notion that certain individuals appear more or less susceptible to infections or to specific microbes is not new, but, until recently, it was assumed that clinical outcome of an infection was mainly owing to virulence factors of the microorganism. Relatively little attention has been given to host genetic factors involved in innate or adaptive immunity or expression of pathogen receptors. A remarkable example of susceptibility dependence is the strong Mendelian trait resistance to the most common noroviruses among individuals with a nonsense mutation in chromosome 19. Norovirus is recognized as the leading cause of gastroenteritis worldwide, affecting children andmore » adults alike. Noroviruses are highly contagious and genetically diverse RNA viruses, but not all individuals are susceptible to infection to the same norovirus genotypes. Presence of histo-blood group antigens (HBGAs) on gut epithelial surfaces is essential for susceptibility to many norovirus genotypes. The synthesis of these HBGAs, specifically of the ABH and Lewis families, requires the use of several fucosyl and glycosyltransferases encoded by the FUT2, FUT3, and ABH genes. Polymorphisms in these genes vary considerably depending on ethnicity, with a homozygous nonsense mutation (individuals called non-secretors) in the FUT2 gene occurring in approximately 5%–50% of different populations worldwide. Secretor status also affects gut microbiota composition, including HBGA-expressing bacteria and bacteria inducing fucosylation in the gut. These could be intermediary factors that govern norovirus susceptibility.« less

Innate Resistance and Susceptibility to Norovirus Infection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nordgren, Johan; Sharma, Sumit; Kambhampati, Anita

The notion that certain individuals appear more or less susceptible to infections or to specific microbes is not new, but, until recently, it was assumed that clinical outcome of an infection was mainly owing to virulence factors of the microorganism. Relatively little attention has been given to host genetic factors involved in innate or adaptive immunity or expression of pathogen receptors. A remarkable example of susceptibility dependence is the strong Mendelian trait resistance to the most common noroviruses among individuals with a nonsense mutation in chromosome 19. Norovirus is recognized as the leading cause of gastroenteritis worldwide, affecting children andmore » adults alike. Noroviruses are highly contagious and genetically diverse RNA viruses, but not all individuals are susceptible to infection to the same norovirus genotypes. Presence of histo-blood group antigens (HBGAs) on gut epithelial surfaces is essential for susceptibility to many norovirus genotypes. The synthesis of these HBGAs, specifically of the ABH and Lewis families, requires the use of several fucosyl and glycosyltransferases encoded by the FUT2, FUT3, and ABH genes. Polymorphisms in these genes vary considerably depending on ethnicity, with a homozygous nonsense mutation (individuals called non-secretors) in the FUT2 gene occurring in approximately 5%–50% of different populations worldwide. Secretor status also affects gut microbiota composition, including HBGA-expressing bacteria and bacteria inducing fucosylation in the gut. These could be intermediary factors that govern norovirus susceptibility.« less

Interactions among two strains of Tubifex tubifex (Oligochaeta: Tubificidae) and Myxobolus cerebralis (Myxozoa)

USGS Publications Warehouse

Steinbach, Elwell L.C.; Kerans, B.L.; Rasmussen, C.; Winton, J.R.

2006-01-01

Host-parasite interactions influence host population growth, host evolution and parasite success. We examined the interactions among Myxobolus cerebralis, the parasite that causes salmonid whirling disease, and resistant and susceptible strains of the oligochaete host Tubifex tubifex. Strains of T. tubifex with diverse genotypes often coexist in nature and have variable susceptibilities to M. cerebralis infection. Further, parasite proliferation differs by several orders of magnitude among T. tubifex strains. We examined total biomass produced by individual T. tubifex, including progeny production and adult growth, parasite proliferation and prevalence of infection using 2 strains of T. tubifex at 2 myxospore doses in a response-surface experimental design. Total biomass production per individual oligochaete and progeny biomass produced by an individual adult oligochaete were density-dependent for both resistant and susceptible individuals and the effects did not change with the addition of myxospores. However, both resistant and susceptible adults had highest growth when exposed to M. cerebralis. The presence of resistant oligochaetes in mixed cultures did not reduce the infection prevalence or parasite proliferation in susceptible individuals. In natural aquatic communities, resistant strains of T. tubifex may not reduce the effects of M. cerebralis on the salmonid host, particularly if sufficient numbers of susceptible T. tubifex are present. ?? Inter-Research 2006.

Antibiotic exposure perturbs the gut microbiota and elevates mortality in honeybees

PubMed Central

Shaffer, Zack; Moran, Nancy A.

2017-01-01

Gut microbiomes play crucial roles in animal health, and shifts in the gut microbial community structure can have detrimental impacts on hosts. Studies with vertebrate models and human subjects suggest that antibiotic treatments greatly perturb the native gut community, thereby facilitating proliferation of pathogens. In fact, persistent infections following antibiotic treatment are a major medical issue. In apiculture, antibiotics are frequently used to prevent bacterial infections of larval bees, but the impact of antibiotic-induced dysbiosis (microbial imbalance) on bee health and susceptibility to disease has not been fully elucidated. Here, we evaluated the effects of antibiotic exposure on the size and composition of honeybee gut communities. We monitored the survivorship of bees following antibiotic treatment in order to determine if dysbiosis of the gut microbiome impacts honeybee health, and we performed experiments to determine whether antibiotic exposure increases susceptibility to infection by opportunistic pathogens. Our results show that antibiotic treatment can have persistent effects on both the size and composition of the honeybee gut microbiome. Antibiotic exposure resulted in decreased survivorship, both in the hive and in laboratory experiments in which bees were exposed to opportunistic bacterial pathogens. Together, these results suggest that dysbiosis resulting from antibiotic exposure affects bee health, in part due to increased susceptibility to ubiquitous opportunistic pathogens. Not only do our results highlight the importance of the gut microbiome in honeybee health, but they also provide insights into how antibiotic treatment affects microbial communities and host health. PMID:28291793

Parasite and nutrient enrichment effects on Daphnia interspecific competition.

PubMed

Decaestecker, Ellen; Verreydt, Dino; De Meester, Luc; Declerck, Steven A J

2015-05-01

Increased productivity due to nutrient enrichment is hypothesized to affect density-dependent processes, such as transmission success of horizontally transmitting parasites. Changes in nutrient availability can also modify the stoichiometry and condition of individual hosts, which may affect their susceptibility for parasites as well as the growth conditions for parasites within the host. Consequently, if not balanced by increased host immuno-competence or life history responses, changes in the magnitude of parasite effects with increasing nutrient availability are expected. If these parasite effects are host-species specific, this may lead to shifts in the host community structure. We here used the Daphnia- parasite model system to study the effect of nutrient enrichment on parasite-mediated competition in experimental mesocosms. In the absence of parasites, D. magna was competitively dominant to D. pulex at both low and high nutrient levels. Introduction of parasites resulted in infections of D. magna, but not of D. pulex and, as such, reversed the competitive hierarchy between these two species. Nutrient addition resulted in an increased prevalence and infection intensity of some of the parasites on D. magna. However, there was no evidence that high nutrient levels enhanced negative effects of parasites on the hosts. Costs associated with parasite infections may have been compensated by better growth conditions for D. magna in the presence of high nutrient levels.

The vaginal microbiota, host defence and reproductive physiology

PubMed Central

Smith, Steven B

2016-01-01

Abstract The interaction between the human host and the vaginal microbiota is highly dynamic. Major changes in the vaginal physiology and microbiota over a woman's lifetime are largely shaped by transitional periods such as puberty, menopause and pregnancy, while daily fluctuations in microbial composition observed through culture‐independent studies are more likely to be the results of daily life activities and behaviours. The vaginal microbiota of reproductive‐aged women is largely made up of at least five different community state types. Four of these community state types are dominated by lactic‐acid producing Lactobacillus spp. while the fifth is commonly composed of anaerobes and strict anaerobes and is sometimes associated with vaginal symptoms. The production of lactic acid has been associated with contributing to the overall health of the vagina due to its direct and indirect effects on pathogens and host defence. Some species associated with non‐Lactobacillus vaginal microbiota may trigger immune responses as well as degrade the host mucosa, processes that ultimately increase susceptibility to infections and contribute to negative reproductive outcomes such as infertility and preterm birth. Further studies are needed to better understand the functional underpinnings of how the vaginal microbiota affect host physiology but also how host physiology affects the vaginal microbiota. Understanding this fine‐tuned interaction is key to maintaining women's reproductive health. PMID:27373840

The genetic architecture of susceptibility to parasites.

PubMed

Wilfert, Lena; Schmid-Hempel, Paul

2008-06-30

The antagonistic co-evolution of hosts and their parasites is considered to be a potential driving force in maintaining host genetic variation including sexual reproduction and recombination. The examination of this hypothesis calls for information about the genetic basis of host-parasite interactions - such as how many genes are involved, how big an effect these genes have and whether there is epistasis between loci. We here examine the genetic architecture of quantitative resistance in animal and plant hosts by concatenating published studies that have identified quantitative trait loci (QTL) for host resistance in animals and plants. Collectively, these studies show that host resistance is affected by few loci. We particularly show that additional epistatic interactions, especially between loci on different chromosomes, explain a majority of the effects. Furthermore, we find that when experiments are repeated using different host or parasite genotypes under otherwise identical conditions, the underlying genetic architecture of host resistance can vary dramatically - that is, involves different QTLs and epistatic interactions. QTLs and epistatic loci vary much less when host and parasite types remain the same but experiments are repeated in different environments. This pattern of variability of the genetic architecture is predicted by strong interactions between genotypes and corroborates the prevalence of varying host-parasite combinations over varying environmental conditions. Moreover, epistasis is a major determinant of phenotypic variance for host resistance. Because epistasis seems to occur predominantly between, rather than within, chromosomes, segregation and chromosome number rather than recombination via cross-over should be the major elements affecting adaptive change in host resistance.

Mismatch between herbivore behavior and demographics contributes to scale-dependence of host susceptibility in two pine species

USGS Publications Warehouse

Ylioja, T.; Slone, D.H.; Ayres, M.P.

2005-01-01

The impacts on forests of tree-killing bark beetles can depend on the species composition of potential host trees. Host susceptibility might be an intrinsic property of tree species, or it might depend on spatial patterning of alternative host species. We compared the susceptibility of loblolly pine (Pinus taeda) and Virginia pine (P. virginiana) to southern pine beetle (Dendroctonus frontalis) at two hierarchical levels of geographic scale: within beetle infestations in heterospecific stands (extent ranging from 0.28 to 0.65 ha), and across a forest landscape (extent 72,500 ha) that was dominated by monospecific stands. In the former, beetles preferentially attacked Virginia pine (tree mortality = 65-100% in Virginia pine versus 0-66% in loblolly pine), but in the latter, loblolly stands were more susceptible than Virginia stands. This hierarchical transition in host susceptibility was predicted from knowledge of (1) a behavioral preference of beetles for attacking loblolly versus Virginia pine, (2) a negative correlation between preference and performance, and (3) a mismatch in the domain of scale between demographics and host selection by individuals. There is value for forest management in understanding the processes that can produce hierarchical transitions in ecological patterns. Copyright ?? 2005 by the Society of American Foresters.

Host phenology and leaf effects on susceptibility of California bay laurel to Phytophthora ramorum

Treesearch

Steven F. Johnston; Michael F. Cohen; Tamas Torok; Ross K. Meentemeyer; Nathan E. Rank

2016-01-01

Spread of the plant pathogen Phytophthora ramorum, causal agent of the forest disease sudden oak death, is driven by a few competent hosts that support spore production from foliar lesions. The relationship between traits of a principal foliar host, California bay laurel (Umbellularia californica), and susceptibility to

The thermal mismatch hypothesis explains host susceptibility to an emerging infectious disease.

PubMed

Cohen, Jeremy M; Venesky, Matthew D; Sauer, Erin L; Civitello, David J; McMahon, Taegan A; Roznik, Elizabeth A; Rohr, Jason R

2017-02-01

Parasites typically have broader thermal limits than hosts, so large performance gaps between pathogens and their cold- and warm-adapted hosts should occur at relatively warm and cold temperatures, respectively. We tested this thermal mismatch hypothesis by quantifying the temperature-dependent susceptibility of cold- and warm-adapted amphibian species to the fungal pathogen Batrachochytrium dendrobatidis (Bd) using laboratory experiments and field prevalence estimates from 15 410 individuals in 598 populations. In both the laboratory and field, we found that the greatest susceptibility of cold- and warm-adapted hosts occurred at relatively warm and cool temperatures, respectively, providing support for the thermal mismatch hypothesis. Our results suggest that as climate change shifts hosts away from their optimal temperatures, the probability of increased host susceptibility to infectious disease might increase, but the effect will depend on the host species and the direction of the climate shift. Our findings help explain the tremendous variation in species responses to Bd across climates and spatial, temporal and species-level variation in disease outbreaks associated with extreme weather events that are becoming more common with climate change. © 2017 John Wiley & Sons Ltd/CNRS.

Effects of rodent community diversity and composition on prevalence of an endemic bacterial pathogen - Bartonella

USGS Publications Warehouse

Bai, Y.; Kosoy, M.Y.; Calisher, C.H.; Cully, J.F.; Collinge, S.K.

2009-01-01

By studying Bartonella prevalence in rodent communities from 23 geographic sites in the western United States and one site in northern Mexico, the present study focused on the effects of rodent community diversity (measured by richness and Shannon index) and composition on prevalence of Bartonella infections. The analysis showed negative correlations of Bartonella prevalence with rodent richness and Shannon index. Further, Bartonella prevalence varied among rodent genera/species. Three models were applied to explain the observations. (1) Within-species/genus transmission: Bartonella strains usually are host-specific and adding non-host species would decrease Bartonella prevalence in its principal host through reduction of host contact (encounter reduction); (2) Frequency-dependence: Adding hosts would decrease the proportion of all infected individuals in the community, resulting in a reduction in the number of contacts between susceptible and infected individuals that usually leads to transmission (transmission reduction); and (3) Dominant species effect: Dominant species, if not susceptible to Bartonellae, can constrain the abundance of susceptible hosts (susceptible host regulation). These mechanisms work in concert; and the level of Bartonella prevalence is an outcome of regulation of all of these mechanisms on the entire system.

Biomarkers of susceptibility: State of the art and implications for occupational exposure to engineered nanomaterials.

PubMed

Iavicoli, Ivo; Leso, Veruscka; Schulte, Paul A

2016-05-15

Rapid advances and applications in nanotechnology are expected to result in increasing occupational exposure to nano-sized materials whose health impacts are still not completely understood. Scientific efforts are required to identify hazards from nanomaterials and define risks and precautionary management strategies for exposed workers. In this scenario, the definition of susceptible populations, which may be at increased risk of adverse effects may be important for risk assessment and management. The aim of this review is to critically examine available literature to provide a comprehensive overview on susceptibility aspects potentially affecting heterogeneous responses to nanomaterials workplace exposure. Genetic, genotoxic and epigenetic alterations induced by nanomaterials in experimental studies were assessed with respect to their possible function as determinants of susceptibility. Additionally, the role of host factors, i.e. age, gender, and pathological conditions, potentially affecting nanomaterial toxicokinetic and health impacts, were also analysed. Overall, this review provides useful information to obtain insights into the nanomaterial mode of action in order to identify potentially sensitive, specific susceptibility biomarkers to be validated in occupational settings and addressed in risk assessment processes. The findings of this review are also important to guide future research into a deeper characterization of nanomaterial susceptibility in order to define adequate risk communication strategies. Ultimately, identification and use of susceptibility factors in workplace settings has both scientific and ethical issues that need addressing. Copyright © 2015 Elsevier Inc. All rights reserved.

Biomarkers of susceptibility: State of the art and implications for occupational exposure to engineered nanomaterials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iavicoli, Ivo, E-mail: ivo.iavicoli@unina.it

Rapid advances and applications in nanotechnology are expected to result in increasing occupational exposure to nano-sized materials whose health impacts are still not completely understood. Scientific efforts are required to identify hazards from nanomaterials and define risks and precautionary management strategies for exposed workers. In this scenario, the definition of susceptible populations, which may be at increased risk of adverse effects may be important for risk assessment and management. The aim of this review is to critically examine available literature to provide a comprehensive overview on susceptibility aspects potentially affecting heterogeneous responses to nanomaterials workplace exposure. Genetic, genotoxic and epigeneticmore » alterations induced by nanomaterials in experimental studies were assessed with respect to their possible function as determinants of susceptibility. Additionally, the role of host factors, i.e. age, gender, and pathological conditions, potentially affecting nanomaterial toxicokinetic and health impacts, were also analysed. Overall, this review provides useful information to obtain insights into the nanomaterial mode of action in order to identify potentially sensitive, specific susceptibility biomarkers to be validated in occupational settings and addressed in risk assessment processes. The findings of this review are also important to guide future research into a deeper characterization of nanomaterial susceptibility in order to define adequate risk communication strategies. Ultimately, identification and use of susceptibility factors in workplace settings has both scientific and ethical issues that need addressing. - Highlights: • To define susceptible populations is important for risk assessment and management; • Genetic susceptibility may influence the individual response to nanomaterial exposure; • Susceptibility factors in workplace settings have both scientific and ethical issues.« less

CARD9 impacts colitis by altering gut microbiota metabolism of tryptophan into aryl hydrocarbon receptor ligands.

PubMed

Lamas, Bruno; Richard, Mathias L; Leducq, Valentin; Pham, Hang-Phuong; Michel, Marie-Laure; Da Costa, Gregory; Bridonneau, Chantal; Jegou, Sarah; Hoffmann, Thomas W; Natividad, Jane M; Brot, Loic; Taleb, Soraya; Couturier-Maillard, Aurélie; Nion-Larmurier, Isabelle; Merabtene, Fatiha; Seksik, Philippe; Bourrier, Anne; Cosnes, Jacques; Ryffel, Bernhard; Beaugerie, Laurent; Launay, Jean-Marie; Langella, Philippe; Xavier, Ramnik J; Sokol, Harry

2016-06-01

Complex interactions between the host and the gut microbiota govern intestinal homeostasis but remain poorly understood. Here we reveal a relationship between gut microbiota and caspase recruitment domain family member 9 (CARD9), a susceptibility gene for inflammatory bowel disease (IBD) that functions in the immune response against microorganisms. CARD9 promotes recovery from colitis by promoting interleukin (IL)-22 production, and Card9(-/-) mice are more susceptible to colitis. The microbiota is altered in Card9(-/-) mice, and transfer of the microbiota from Card9(-/-) to wild-type, germ-free recipients increases their susceptibility to colitis. The microbiota from Card9(-/-) mice fails to metabolize tryptophan into metabolites that act as aryl hydrocarbon receptor (AHR) ligands. Intestinal inflammation is attenuated after inoculation of mice with three Lactobacillus strains capable of metabolizing tryptophan or by treatment with an AHR agonist. Reduced production of AHR ligands is also observed in the microbiota from individuals with IBD, particularly in those with CARD9 risk alleles associated with IBD. Our findings reveal that host genes affect the composition and function of the gut microbiota, altering the production of microbial metabolites and intestinal inflammation.

Relationships between host viremia and vector susceptibility for arboviruses.

PubMed

Lord, Cynthia C; Rutledge, C Roxanne; Tabachnick, Walter J

2006-05-01

Using a threshold model where a minimum level of host viremia is necessary to infect vectors affects our assessment of the relative importance of different host species in the transmission and spread of these pathogens. Other models may be more accurate descriptions of the relationship between host viremia and vector infection. Under the threshold model, the intensity and duration of the viremia above the threshold level is critical in determining the potential numbers of infected mosquitoes. A probabilistic model relating host viremia to the probability distribution of virions in the mosquito bloodmeal shows that the threshold model will underestimate the significance of hosts with low viremias. A probabilistic model that includes avian mortality shows that the maximum number of mosquitoes is infected by feeding on hosts whose viremia peaks just below the lethal level. The relationship between host viremia and vector infection is complex, and there is little experimental information to determine the most accurate model for different arthropod-vector-host systems. Until there is more information, the ability to distinguish the relative importance of different hosts in infecting vectors will remain problematic. Relying on assumptions with little support may result in erroneous conclusions about the importance of different hosts.

Relationships Between Host Viremia and Vector Susceptibility for Arboviruses

PubMed Central

Lord, Cynthia C.; Rutledge, C. Roxanne; Tabachnick, Walter J.

2010-01-01

Using a threshold model where a minimum level of host viremia is necessary to infect vectors affects our assessment of the relative importance of different host species in the transmission and spread of these pathogens. Other models may be more accurate descriptions of the relationship between host viremia and vector infection. Under the threshold model, the intensity and duration of the viremia above the threshold level is critical in determining the potential numbers of infected mosquitoes. A probabilistic model relating host viremia to the probability distribution of virions in the mosquito bloodmeal shows that the threshold model will underestimate the significance of hosts with low viremias. A probabilistic model that includes avian mortality shows that the maximum number of mosquitoes is infected by feeding on hosts whose viremia peaks just below the lethal level. The relationship between host viremia and vector infection is complex, and there is little experimental information to determine the most accurate model for different arthropod–vector–host systems. Until there is more information, the ability to distinguish the relative importance of different hosts in infecting vectors will remain problematic. Relying on assumptions with little support may result in erroneous conclusions about the importance of different hosts. PMID:16739425

Burkholderia cenocepacia Lipopolysaccharide Modification and Flagellin Glycosylation Affect Virulence but Not Innate Immune Recognition in Plants

PubMed Central

Khodai-Kalaki, Maryam; Andrade, Angel; Fathy Mohamed, Yasmine

2015-01-01

ABSTRACT Burkholderia cenocepacia causes opportunistic infections in plants, insects, animals, and humans, suggesting that “virulence” depends on the host and its innate susceptibility to infection. We hypothesized that modifications in key bacterial molecules recognized by the innate immune system modulate host responses to B. cenocepacia. Indeed, modification of lipopolysaccharide (LPS) with 4-amino-4-deoxy-l-arabinose and flagellin glycosylation attenuates B. cenocepacia infection in Arabidopsis thaliana and Galleria mellonella insect larvae. However, B. cenocepacia LPS and flagellin triggered rapid bursts of nitric oxide and reactive oxygen species in A. thaliana leading to activation of the PR-1 defense gene. These responses were drastically reduced in plants with fls2 (flagellin FLS2 host receptor kinase), Atnoa1 (nitric oxide-associated protein 1), and dnd1-1 (reduced production of nitric oxide) null mutations. Together, our results indicate that LPS modification and flagellin glycosylation do not affect recognition by plant receptors but are required for bacteria to establish overt infection. PMID:26045541

The effect of water contamination and host-related factors on ectoparasite load in an insectivorous bat.

PubMed

Korine, Carmi; Pilosof, Shai; Gross, Amit; Morales-Malacara, Juan B; Krasnov, Boris R

2017-09-01

We examined the effects of sex, age, and reproductive state of the insectivorous bat Pipistrellus kuhlii on the abundance and prevalence of arthropod ectoparasites (Macronyssidae and Cimicidae) in habitats with either sewage-polluted or natural bodies of water, in the Negev Desert, Israel. We chose water pollution as an environmental factor because of the importance of water availability in desert environments, particularly for P. kuhlii, which needs to drink on a daily basis. We predicted that parasite infestation rates would be affected by both environment and demographic cohort of the host. We found that female bats in the polluted site harbored significantly more mites than female bats in the natural site and that juveniles in the polluted site harbored significantly more cimicid individuals than juveniles in the natural site. We further found that age and sex (host-related factors) affected ectoparasite prevalence and intensity (i.e., the abundance of parasites) in the polluted site. Our results may suggest that the interaction between host-related and environment-related factors affected parasite infestations, with females and young bats being more susceptible to ectoparasites when foraging over polluted water. This effect may be particularly important for bats that must drink or forage above water for other wildlife that depend on drinking water for survival.

Mapping of SnTox3-Snn3 as a major determinant of field susceptibility to Septoria nodorum leaf blotch in the SHA3/CBRD x Naxos population

USDA-ARS?s Scientific Manuscript database

Parastagonospora nodorum is a necrotrophic pathogen of wheat, causing Septoria nodorum blotch (SNB) affecting both the leaf and glume. P. nodorum is the major leaf blotch pathogen on spring wheat in Norway. Resistance to the disease is quantitative, but several host-specific interactions between nec...

High temperature and temperature variation undermine future disease susceptibility in a population of the invasive garden ant Lasius neglectus.

PubMed

Pamminger, Tobias; Steier, Thomas; Tragust, Simon

2016-06-01

Environmental temperature and temperature variation can have strong effects on the outcome of host-parasite interactions. Whilst such effects have been reported for different host systems, long-term consequences of pre-infection temperatures on host susceptibility and immunity remain understudied. Here, we show that experiencing both a biologically relevant increase in temperature and temperature variation undermines future disease susceptibility of the invasive garden ant Lasius neglectus when challenged with a pathogen under a constant temperature regime. In light of the economic and ecological importance of many social insects, our results emphasise the necessity to take the hosts' temperature history into account when studying host-parasite interactions under both natural and laboratory conditions, especially in the face of global change.

High temperature and temperature variation undermine future disease susceptibility in a population of the invasive garden ant Lasius neglectus

NASA Astrophysics Data System (ADS)

Pamminger, Tobias; Steier, Thomas; Tragust, Simon

2016-06-01

Environmental temperature and temperature variation can have strong effects on the outcome of host-parasite interactions. Whilst such effects have been reported for different host systems, long-term consequences of pre-infection temperatures on host susceptibility and immunity remain understudied. Here, we show that experiencing both a biologically relevant increase in temperature and temperature variation undermines future disease susceptibility of the invasive garden ant Lasius neglectus when challenged with a pathogen under a constant temperature regime. In light of the economic and ecological importance of many social insects, our results emphasise the necessity to take the hosts' temperature history into account when studying host-parasite interactions under both natural and laboratory conditions, especially in the face of global change.

Immune and biochemical responses in skin differ between bovine hosts genetically susceptible and resistant to the cattle tick Rhipicephalus microplus.

PubMed

Franzin, Alessandra Mara; Maruyama, Sandra Regina; Garcia, Gustavo Rocha; Oliveira, Rosane Pereira; Ribeiro, José Marcos Chaves; Bishop, Richard; Maia, Antônio Augusto Mendes; Moré, Daniela Dantas; Ferreira, Beatriz Rossetti; Santos, Isabel Kinney Ferreira de Miranda

2017-01-31

Ticks attach to and penetrate their hosts' skin and inactivate multiple components of host responses in order to acquire a blood meal. Infestation loads with the cattle tick, Rhipicephalus microplus, are heritable: some breeds carry high loads of reproductively successful ticks, whereas in others, few ticks feed and reproduce efficiently. In order to elucidate the mechanisms that result in the different outcomes of infestations with cattle ticks, we examined global gene expression and inflammation induced by tick bites in skins from one resistant and one susceptible breed of cattle that underwent primary infestations with larvae and nymphs of R. microplus. We also examined the expression profiles of genes encoding secreted tick proteins that mediate parasitism in larvae and nymphs feeding on these breeds. Functional analyses of differentially expressed genes in the skin suggest that allergic contact-like dermatitis develops with ensuing production of IL-6, CXCL-8 and CCL-2 and is sustained by HMGB1, ISG15 and PKR, leading to expression of pro-inflammatory chemokines and cytokines that recruit granulocytes and T lymphocytes. Importantly, this response is delayed in susceptible hosts. Histopathological analyses of infested skins showed inflammatory reactions surrounding tick cement cones that enable attachment in both breeds, but in genetically tick-resistant bovines they destabilized the cone. The transcription data provided insights into tick-mediated activation of basophils, which have previously been shown to be a key to host resistance in model systems. Skin from tick-susceptible bovines expressed more transcripts encoding enzymes that detoxify tissues. Interestingly, these enzymes also produce volatile odoriferous compounds and, accordingly, skin rubbings from tick-susceptible bovines attracted significantly more tick larvae than rubbings from resistant hosts. Moreover, transcripts encoding secreted modulatory molecules by the tick were significantly more abundant in larval and in nymphal salivary glands from ticks feeding on susceptible bovines. Compared with tick-susceptible hosts, genes encoding enzymes producing volatile compounds exhibit significantly lower expression in resistant hosts, which may render them less attractive to larvae; resistant hosts expose ticks to an earlier inflammatory response, which in ticks is associated with significantly lower expression of genes encoding salivary proteins that suppress host immunity, inflammation and coagulation.

Where are the horses? With the sheep or cows? Uncertain host location, vector-feeding preferences and the risk of African horse sickness transmission in Great Britain

PubMed Central

Lo Iacono, Giovanni; Robin, Charlotte A.; Newton, J. Richard; Gubbins, Simon; Wood, James L. N.

2013-01-01

Understanding the influence of non-susceptible hosts on vector-borne disease transmission is an important epidemiological problem. However, investigation of its impact can be complicated by uncertainty in the location of the hosts. Estimating the risk of transmission of African horse sickness (AHS) in Great Britain (GB), a virus transmitted by Culicoides biting midges, provides an insightful example because: (i) the patterns of risk are expected to be influenced by the presence of non-susceptible vertebrate hosts (cattle and sheep) and (ii) incomplete information on the spatial distribution of horses is available because the GB National Equine Database records owner, rather than horse, locations. Here, we combine land-use data with available horse owner distributions and, using a Bayesian approach, infer a realistic distribution for the location of horses. We estimate the risk of an outbreak of AHS in GB, using the basic reproduction number (R0), and demonstrate that mapping owner addresses as a proxy for horse location significantly underestimates the risk. We clarify the role of non-susceptible vertebrate hosts by showing that the risk of disease in the presence of many hosts (susceptible and non-susceptible) can be ultimately reduced to two fundamental factors: first, the abundance of vectors and how this depends on host density, and, second, the differential feeding preference of vectors among animal species. PMID:23594817

A missing dimension in measures of vaccination impacts

USGS Publications Warehouse

Gomes, M. Gabriela M.; Lipsitch, Marc; Wargo, Andrew R.; Kurath, Gael; Rebelo, Carlota; Medley, Graham F.; Coutinho, Antonio

2013-01-01

Immunological protection, acquired from either natural infection or vaccination, varies among hosts, reflecting underlying biological variation and affecting population-level protection. Owing to the nature of resistance mechanisms, distributions of susceptibility and protection entangle with pathogen dose in a way that can be decoupled by adequately representing the dose dimension. Any infectious processes must depend in some fashion on dose, and empirical evidence exists for an effect of exposure dose on the probability of transmission to mumps-vaccinated hosts [1], the case-fatality ratio of measles [2], and the probability of infection and, given infection, of symptoms in cholera [3]. Extreme distributions of vaccine protection have been termed leaky (partially protects all hosts) and all-or-nothing (totally protects a proportion of hosts) [4]. These distributions can be distinguished in vaccine field trials from the time dependence of infections [5]. Frailty mixing models have also been proposed to estimate the distribution of protection from time to event data [6], [7], although the results are not comparable across regions unless there is explicit control for baseline transmission [8]. Distributions of host susceptibility and acquired protection can be estimated from dose-response data generated under controlled experimental conditions [9]–[11] and natural settings [12], [13]. These distributions can guide research on mechanisms of protection, as well as enable model validity across the entire range of transmission intensities. We argue for a shift to a dose-dimension paradigm in infectious disease science and community health.

Non-Thermal Plasma Treatment Diminishes Fungal Viability and Up-Regulates Resistance Genes in a Plant Host

PubMed Central

Panngom, Kamonporn; Lee, Sang Hark; Park, Dae Hoon; Sim, Geon Bo; Kim, Yong Hee; Uhm, Han Sup; Park, Gyungsoon; Choi, Eun Ha

2014-01-01

Reactive oxygen and nitrogen species can have either harmful or beneficial effects on biological systems depending on the dose administered and the species of organism exposed, suggesting that application of reactive species can possibly produce contradictory effects in disease control, pathogen inactivation and activation of host resistance. A novel technology known as atmospheric-pressure non-thermal plasma represents a means of generating various reactive species that adversely affect pathogens (inactivation) while simultaneously up-regulating host defense genes. The anti-microbial efficacy of this technology was tested on the plant fungal pathogen Fusarium oxysporum f.sp. lycopersici and its susceptible host plant species Solanum lycopercicum. Germination of fungal spores suspended in saline was decreased over time after exposed to argon (Ar) plasma for 10 min. Although the majority of treated spores exhibited necrotic death, apoptosis was also observed along with the up-regulation of apoptosis related genes. Increases in the levels of peroxynitrite and nitrite in saline following plasma treatment may have been responsible for the observed spore death. In addition, increased transcription of pathogenesis related (PR) genes was observed in the roots of the susceptible tomato cultivar (S. lycopercicum) after exposure to the same Ar plasma dose used in fungal inactivation. These data suggest that atmospheric-pressure non-thermal plasma can be efficiently used to control plant fungal diseases by inactivating fungal pathogens and up-regulating mechanisms of host resistance. PMID:24911947

Female Gnathia marleyi (Isopoda: Gnathiidae) feeding on more susceptible fish hosts produce larger but not more offspring.

PubMed

Coile, A M; Welicky, R L; Sikkel, P C

2014-10-01

The reproductive success of female Gnathia marleyi (Crustacea: Isopoda) was examined among individuals from eight species belonging to five families of common Caribbean reef fishes of St. John, US Virgin Islands that differ in susceptibility to G. marleyi infestation. Fish were placed in cages during times of peak gnathiid activity. Gnathiids were recovered from host fishes and reared to adulthood in the laboratory. Ovigerous females were then placed in individual containers until offspring were released. Measures of reproductive success used were the number of hatched zuphea 1 larvae that emerged from the brood pouch, "brood size," and the average total length of newly emerged zuphea larvae, "average z-length." Among the five host fish families tested, females that fed on the two families most susceptible to gnathiid infestation (Haemulidae and Lutjanidae) produced longer larvae than those feeding on the three less susceptible host families. However, there was no significant difference in the number of viable offspring produced. To our knowledge, this is the first study to examine the relationship between the source of the blood meal and any measure of reproductive success in female gnathiid isopods. These findings open the door to future research on potential differences in host blood quality and defense mechanisms that may cause variations in susceptibility to gnathiid among different host fishes.

Recommendations for Optimizing Tuberculosis Treatment: Therapeutic Drug Monitoring, Pharmacogenetics, and Nutritional Status Considerations

PubMed Central

Choi, Rihwa; Jeong, Byeong-Ho

2017-01-01

Although tuberculosis is largely a curable disease, it remains a major cause of morbidity and mortality worldwide. Although the standard 6-month treatment regimen is highly effective for drug-susceptible tuberculosis, the use of multiple drugs over long periods of time can cause frequent adverse drug reactions. In addition, some patients with drug-susceptible tuberculosis do not respond adequately to treatment and develop treatment failure and drug resistance. Response to tuberculosis treatment could be affected by multiple factors associated with the host-pathogen interaction including genetic factors and the nutritional status of the host. These factors should be considered for effective tuberculosis control. Therefore, therapeutic drug monitoring (TDM), which is individualized drug dosing guided by serum drug concentrations during treatment, and pharmacogenetics-based personalized dosing guidelines of anti-tuberculosis drugs could reduce the incidence of adverse drug reactions and increase the likelihood of successful treatment outcomes. Moreover, assessment and management of comorbid conditions including nutritional status could improve anti-tuberculosis treatment response. PMID:28028995

Host-Microbiome Cross-talk in Oral Mucositis

PubMed Central

Vasconcelos, R.M.; Sanfilippo, N.; Paster, B.J.; Kerr, A.R.; Li, Y.; Ramalho, L.; Queiroz, E.L.; Smith, B.; Sonis, S.T.; Corby, P.M.

2016-01-01

Oral mucositis (OM) is among the most common, painful, and debilitating toxicities of cancer regimen–related treatment, resulting in the formation of ulcers, which are susceptible to increased colonization of microorganisms. Novel discoveries in OM have focused on understanding the host-microbial interactions, because current pathways have shown that major virulence factors from microorganisms have the potential to contribute to the development of OM and may even prolong the existence of already established ulcerations, affecting tissue healing. Additional comprehensive and disciplined clinical investigation is needed to carefully characterize the relationship between the clinical trajectory of OM, the local levels of inflammatory changes (both clinical and molecular), and the ebb and flow of the oral microbiota. Answering such questions will increase our knowledge of the mechanisms engaged by the oral immune system in response to mucositis, facilitating their translation into novel therapeutic approaches. In doing so, directed clinical strategies can be developed that specifically target those times and tissues that are most susceptible to intervention. PMID:27053118

Recommendations for Optimizing Tuberculosis Treatment: Therapeutic Drug Monitoring, Pharmacogenetics, and Nutritional Status Considerations.

PubMed

Choi, Rihwa; Jeong, Byeong Ho; Koh, Won Jung; Lee, Soo Youn

2017-03-01

Although tuberculosis is largely a curable disease, it remains a major cause of morbidity and mortality worldwide. Although the standard 6-month treatment regimen is highly effective for drug-susceptible tuberculosis, the use of multiple drugs over long periods of time can cause frequent adverse drug reactions. In addition, some patients with drug-susceptible tuberculosis do not respond adequately to treatment and develop treatment failure and drug resistance. Response to tuberculosis treatment could be affected by multiple factors associated with the host-pathogen interaction including genetic factors and the nutritional status of the host. These factors should be considered for effective tuberculosis control. Therefore, therapeutic drug monitoring (TDM), which is individualized drug dosing guided by serum drug concentrations during treatment, and pharmacogenetics-based personalized dosing guidelines of anti-tuberculosis drugs could reduce the incidence of adverse drug reactions and increase the likelihood of successful treatment outcomes. Moreover, assessment and management of comorbid conditions including nutritional status could improve anti-tuberculosis treatment response.

Brown dog tick, Rhipicephalus sanguineus sensu lato, infestation ofsusceptible dog hosts is reduced by slow release of semiochemicalsfrom a less susceptible host

USDA-ARS?s Scientific Manuscript database

Domestic dog breeds are hosts for the tick Rhipicephalus sanguineus sensu lato, but infestation levels vary among breeds. Beagles are less susceptible to tick infestations than English cocker spaniels due to enhanced production of 2-hexanone and benzaldehyde that act as tick repellents. We report th...

Predators, environment and host characteristics influence the probability of infection by an invasive castrating parasite.

PubMed

Gehman, Alyssa-Lois M; Grabowski, Jonathan H; Hughes, A Randall; Kimbro, David L; Piehler, Michael F; Byers, James E

2017-01-01

Not all hosts, communities or environments are equally hospitable for parasites. Direct and indirect interactions between parasites and their predators, competitors and the environment can influence variability in host exposure, susceptibility and subsequent infection, and these influences may vary across spatial scales. To determine the relative influences of abiotic, biotic and host characteristics on probability of infection across both local and estuary scales, we surveyed the oyster reef-dwelling mud crab Eurypanopeus depressus and its parasite Loxothylacus panopaei, an invasive castrating rhizocephalan, in a hierarchical design across >900 km of the southeastern USA. We quantified the density of hosts, predators of the parasite and host, the host's oyster reef habitat, and environmental variables that might affect the parasite either directly or indirectly on oyster reefs within 10 estuaries throughout this biogeographic range. Our analyses revealed that both between and within estuary-scale variation and host characteristics influenced L. panopaei prevalence. Several additional biotic and abiotic factors were positive predictors of infection, including predator abundance and the depth of water inundation over reefs at high tide. We demonstrate that in addition to host characteristics, biotic and abiotic community-level variables both serve as large-scale indicators of parasite dynamics.

The effects of inbreeding on disease susceptibility: Gyrodactylus turnbulli infection of guppies, Poecilia reticulata.

PubMed

Smallbone, Willow; van Oosterhout, Cock; Cable, Jo

2016-08-01

Inbreeding can threaten population persistence by reducing disease resistance through the accelerated loss of gene diversity (i.e. heterozygosity). Such inbreeding depression can affect many different fitness-related traits, including survival, reproductive success, and parasite susceptibility. Empirically quantifying the effects of inbreeding on parasite resistance is therefore important for ex-situ conservation of vertebrates. The present study evaluates the disease susceptibility of individuals bred under three different breeding regimes (inbred, crossed with full siblings; control, randomly crossed mating; and fully outbred). Specifically, we examined the relationship between inbreeding coefficient (F-coefficient) and susceptibility to Gyrodactylus turnbulli infection in a live bearing vertebrate, the guppy Poecilia reticulata. Host-breeding regime significantly affected the trajectories of parasite population growth on individual fish. Inbred fish showed significantly higher mean parasite intensity than fish from the control and outbred breeding regimes, and in addition, inbred fish were slower in purging their gyrodactylid infections. We discuss the role of inbreeding on the various arms of the immune system, and argue that the increased disease susceptibility of inbred individuals could contribute to the extinction vortex. This is one of the first studies to quantify the effects of inbreeding and breeding regime on disease susceptibility in a captive bred vertebrate of wild origin, and it highlights the risks faced by small (captive-bred) populations when exposed to their native parasites. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Track of fluid paleocirculation in dolomite host rock at regional scale by the Anisotropy of Magnetic Susceptibility (AMS): An example from Aptian carbonates of La Florida, Northern Spain

NASA Astrophysics Data System (ADS)

Essalhi, Mourad; Sizaret, Stanislas; Barbanson, Luc; Chen, Yan; Branquet, Yannick; Panis, Dominique; Camps, Pierre; Rochette, Pierre; Canals, Angels

2009-01-01

The present study aims to apply the AMS method (Anisotropy of Magnetic Susceptibility) at a regional scale to track the fluid circulation direction that has produced an iron metasomatism within pre-existing dolomite host rock. The Urgonian formations hosting the Zn-Pb mineralizations in La Florida (Cantabria, northern Spain) have been taken as target for this purpose. Sampling was carried out, in addition to ferroan dolomite host rock enclosing the Zn-Pb mineralizations, in dolomite host rock and limestone to make the comparison possible between magnetic signals from mineralized rocks, where fluid circulation occurred, and their surrounding formations. AMS study was coupled with petrofabric analysis carried out by texture goniometry, Scanning Electron Microscopy (SEM) observations and also Shape Preferred Orientation (SPO) statistics. SEM observations of ferroan dolomite host rock illustrate both bright and dark grey ribbons corresponding respectively to Fe enriched and pure dolomites. SPO statistics applied on four images from ferroan dolomite host rock give a well-defined orientation of ribbons related to the intermediate axis of magnetic susceptibility K2. For AMS data, two magnetic fabrics are observed. The first one is observed in ferroan dolomite host rock and characterized by a prolate ellipsoid of magnetic susceptibility with a vertical magnetic lineation. The magnetic susceptibility carrier is Fe-rich dolomite. These features are probably acquired during metasomatic fluid circulations. In Fe-rich dolomite host rock, ‹ c› axes are vertical. As a rule, (0001) planes (i.e. planes perpendicular to ‹ c› axes) are isotropic with respect to crystallographic properties. So, the magnetic anisotropy measured in this plane should reflect crystallographic modification due to fluid circulation. This is confirmed by the texture observed using the SEM. Consequently, AMS results show a dominant NE-SW elongation interpreted as the global circulation direction and a NW-SE secondary elongation that we have considered as sinuosities of the fluid trajectory. The second type of magnetic fabric is essentially observed in the limestone and characterized by an oblate form of the ellipsoid of magnetic susceptibility, a horizontal magnetic foliation and mixed magnetic susceptibility carriers. It is interpreted as a sedimentary fabric.

Environmental Assessment for Aerial Application of Pesticide for Gypsy Moth Control, Andrews Air Force Base, Maryland

DTIC Science & Technology

2008-04-01

spray alternatives, one ground-based spray alternative and one non- insecticide alternative were considered but eliminated from detailed study because...One application would not be effective in reducing gypsy moth populations and protecting host tree foliage. The ground-based insecticide ...present in the affected area, are not susceptible to these EPA-approved insecticides , as long as there applied according to the label. Dimilin

Altering host resistance to infections through microbial transplantation.

PubMed

Willing, Benjamin P; Vacharaksa, Anjalee; Croxen, Matthew; Thanachayanont, Teerawat; Finlay, B Brett

2011-01-01

Host resistance to bacterial infections is thought to be dictated by host genetic factors. Infections by the natural murine enteric pathogen Citrobacter rodentium (used as a model of human enteropathogenic and enterohaemorrhagic E. coli infections) vary between mice strains, from mild self-resolving colonization in NIH Swiss mice to lethality in C3H/HeJ mice. However, no clear genetic component had been shown to be responsible for the differences observed with C. rodentium infections. Because the intestinal microbiota is important in regulating resistance to infection, and microbial composition is dependent on host genotype, it was tested whether variations in microbial composition between mouse strains contributed to differences in "host" susceptibility by transferring the microbiota of resistant mice to lethally susceptible mice prior to infection. Successful transfer of the microbiota from resistant to susceptible mice resulted in delayed pathogen colonization and mortality. Delayed mortality was associated with increased IL-22 mediated innate defense including antimicrobial peptides Reg3γ and Reg3β, and immunono-neutralization of IL-22 abrogated the beneficial effect of microbiota transfer. Conversely, depletion of the native microbiota in resistant mice by antibiotics and transfer of the susceptible mouse microbiota resulted in reduced innate defenses and greater pathology upon infection. This work demonstrates the importance of the microbiota and how it regulates mucosal immunity, providing an important factor in susceptibility to enteric infection. Transfer of resistance through microbial transplantation (bacteriotherapy) provides additional mechanisms to alter "host" resistance, and a novel means to alter enteric infection and to study host-pathogen interactions.

The vaginal microbiota, host defence and reproductive physiology.

PubMed

Smith, Steven B; Ravel, Jacques

2017-01-15

The interaction between the human host and the vaginal microbiota is highly dynamic. Major changes in the vaginal physiology and microbiota over a woman's lifetime are largely shaped by transitional periods such as puberty, menopause and pregnancy, while daily fluctuations in microbial composition observed through culture-independent studies are more likely to be the results of daily life activities and behaviours. The vaginal microbiota of reproductive-aged women is largely made up of at least five different community state types. Four of these community state types are dominated by lactic-acid producing Lactobacillus spp. while the fifth is commonly composed of anaerobes and strict anaerobes and is sometimes associated with vaginal symptoms. The production of lactic acid has been associated with contributing to the overall health of the vagina due to its direct and indirect effects on pathogens and host defence. Some species associated with non-Lactobacillus vaginal microbiota may trigger immune responses as well as degrade the host mucosa, processes that ultimately increase susceptibility to infections and contribute to negative reproductive outcomes such as infertility and preterm birth. Further studies are needed to better understand the functional underpinnings of how the vaginal microbiota affect host physiology but also how host physiology affects the vaginal microbiota. Understanding this fine-tuned interaction is key to maintaining women's reproductive health. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

Chytridiomycosis of Marine Diatoms-The Role of Stress Physiology and Resistance in Parasite-Host Recognition and Accumulation of Defense Molecules.

PubMed

Scholz, Bettina; Küpper, Frithjof C; Vyverman, Wim; Ólafsson, Halldór G; Karsten, Ulf

2017-01-25

Little is known about the role of chemotaxis in the location and attachment of chytrid zoospores to potential diatom hosts. Hypothesizing that environmental stress parameters affect parasite-host recognition, four chytrid-diatom tandem cultures ( Chytridium sp./ Navicula sp., Rhizophydium type I/ Nitzschia sp., Rhizophydium type IIa/ Rhizosolenia sp., Rhizophydium type IIb/ Chaetoceros sp.) were used to test the chemotaxis of chytrid zoospores and the presence of potential defense molecules in a non-contact-co-culturing approach. As potential triggers in the chemotaxis experiments, standards of eight carbohydrates, six amino acids, five fatty acids, and three compounds known as compatible solutes were used in individual and mixed solutions, respectively. In all tested cases, the whole-cell extracts of the light-stressed (continuous light exposure combined with 6 h UV radiation) hosts attracted the highest numbers of zoospores (86%), followed by the combined carbohydrate standard solution (76%), while all other compounds acted as weak triggers only. The results of the phytochemical screening, using biomass and supernatant extracts of susceptible and resistant host-diatom cultures, indicated in most of the tested extracts the presence of polyunsaturated fatty acids, phenols, and aldehydes, whereas the bioactivity screenings showed that the zoospores of the chytrid parasites were only significantly affected by the ethanolic supernatant extract of the resistant hosts.

The Vascular Pathogen Verticillium longisporum Does Not Affect Water Relations and Plant Responses to Drought Stress of Its Host, Brassica napus.

PubMed

Lopisso, Daniel Teshome; Knüfer, Jessica; Koopmann, Birger; von Tiedemann, Andreas

2017-04-01

Verticillium longisporum is a host-specific vascular pathogen of oilseed rape (Brassica napus L.) that causes economic crop losses by impairing plant growth and inducing premature senescence. This study investigates whether plant damage through Verticillium stem striping is due to impaired plant water relations, whether V. longisporum affects responses of a susceptible B. napus variety to drought stress, and whether drought stress, in turn, affects plant responses to V. longisporum. Two-factorial experiments on a susceptible cultivar of B. napus infected or noninfected with V. longisporum and exposed to three watering levels (30, 60, and 100% field capacity) revealed that drought stress and V. longisporum impaired plant growth by entirely different mechanisms. Although both stresses similarly affected plant growth parameters (plant height, hypocotyl diameter, and shoot and root dry matter), infection of B. napus with V. longisporum did not affect any drought-related physiological or molecular genetic plant parameters, including transpiration rate, stomatal conductance, photosynthesis rate, water use efficiency, relative leaf water content, leaf proline content, or the expression of drought-responsive genes. Thus, this study provides comprehensive physiological and molecular genetic evidence explaining the lack of wilt symptoms in B. napus infected with V. longisporum. Likewise, drought tolerance of B. napus was unaffected by V. longisporum, as was the level of disease by drought conditions, thus excluding a concerted action of both stresses in the field. Although it is evident that drought and vascular infection with V. longisporum impair plant growth by different mechanisms, it remains to be determined by which other factors V. longisporum causes crop loss.

Biology, host instar suitability and susceptibility, and interspecific competition of three introduced parasitoids of Paracoccus marginatus (Hemiptera: Pseudococcidae)

USDA-ARS?s Scientific Manuscript database

Biology, host stage suitability and susceptibility, and interspecific competition of three previously introduced parasitoids (Acerophagus papayae, Anagyrus loecki, and Pseudleptomastix mexicana) (Hymenoptera: Encyrtidae) of Paracoccus marginatus were studied in the laboratory. Compared to P. mexica...

Resistance rather than tolerance explains survival of savannah honeybees (Apis mellifera scutellata) to infestation by the parasitic mite Varroa destructor.

PubMed

Strauss, Ursula; Dietemann, Vincent; Human, Hannelie; Crewe, Robin M; Pirk, Christian W W

2016-03-01

Varroa destructor is considered the most damaging parasite affecting honeybees (Apis mellifera L.). However, some honeybee populations such as the savannah honeybee (Apis mellifera scutellata) can survive mite infestation without treatment. It is unclear if survival is due to resistance mechanisms decreasing parasite reproduction or to tolerance mechanisms decreasing the detrimental effects of mites on the host. This study investigates both aspects by quantifying the reproductive output of V. destructor and its physiological costs at the individual host level. Costs measured were not consistently lower when compared with susceptible honeybee populations, indicating a lack of tolerance. In contrast, reproduction of V. destructor mites was distinctly lower than in susceptible populations. There was higher proportion of infertile individuals and the reproductive success of fertile mites was lower than measured to date, even in surviving populations. Our results suggest that survival of savannah honeybees is based on resistance rather than tolerance to this parasite. We identified traits that may be useful for breeding programmes aimed at increasing the survival of susceptible populations. African honeybees may have benefited from a lack of human interference, allowing natural selection to shape a population of honeybees that is more resistant to Varroa mite infestation.

Immunology of Cryptococcal Infections: Developing a Rational Approach to Patient Therapy

PubMed Central

Elsegeiny, Waleed; Marr, Kieren A.; Williamson, Peter R.

2018-01-01

Cryptococcal meningoencephalitis is responsible for upwards of 15% of HIV-related deaths worldwide and is currently the most common cause of non-viral meningitis in the US, affecting both previously healthy and people with immune suppression caused by cancer chemotherapy, transplantation, and biologic therapies. Despite a continued 30–50% attributable mortality, recommended therapeutic strategies have remained largely unchanged since the 1950s. Recent murine models and human studies examining the role of the immune system in both susceptibility to the infection as well as host damage have begun to influence patient care decisions. The Damage Framework Response, originally proposed in 1999, was recently used to discuss dichotomous etiologies of host damage in cryptococcal disease. These include patients suffering microbiological damage with low host immunity (especially those immunosuppressed with HIV) and those having low (live) microbiological burden but high immune-mediated damage (HIV-related immune reconstitution syndrome and non-HIV-related postinfectious inflammatory response syndrome). Cryptococcal disease in previously healthy hosts, albeit rare, has been known for a long time. Immunophenotyping and dendritic cell-T cell signaling studies on cerebral spinal fluid of these rare patients reveal immune capacity for recognition and T-cell activation pathways including increased levels of HLA-DR and CD56. However, despite effective T-cell signals, brain biopsy and autopsy specimens demonstrated an M2 alternative macrophage polarization and poor phagocytosis of fungal cells. These studies expand the paradigm for cryptococcal disease susceptibility to include a prominent role for immune-mediated damage and suggest a need for careful individual consideration of immune activation during therapy of cryptococcal disease in diverse hosts. PMID:29670625

Immunology of Cryptococcal Infections: Developing a Rational Approach to Patient Therapy.

PubMed

Elsegeiny, Waleed; Marr, Kieren A; Williamson, Peter R

2018-01-01

Cryptococcal meningoencephalitis is responsible for upwards of 15% of HIV-related deaths worldwide and is currently the most common cause of non-viral meningitis in the US, affecting both previously healthy and people with immune suppression caused by cancer chemotherapy, transplantation, and biologic therapies. Despite a continued 30-50% attributable mortality, recommended therapeutic strategies have remained largely unchanged since the 1950s. Recent murine models and human studies examining the role of the immune system in both susceptibility to the infection as well as host damage have begun to influence patient care decisions. The Damage Framework Response, originally proposed in 1999, was recently used to discuss dichotomous etiologies of host damage in cryptococcal disease. These include patients suffering microbiological damage with low host immunity (especially those immunosuppressed with HIV) and those having low (live) microbiological burden but high immune-mediated damage (HIV-related immune reconstitution syndrome and non-HIV-related postinfectious inflammatory response syndrome). Cryptococcal disease in previously healthy hosts, albeit rare, has been known for a long time. Immunophenotyping and dendritic cell-T cell signaling studies on cerebral spinal fluid of these rare patients reveal immune capacity for recognition and T-cell activation pathways including increased levels of HLA-DR and CD56. However, despite effective T-cell signals, brain biopsy and autopsy specimens demonstrated an M2 alternative macrophage polarization and poor phagocytosis of fungal cells. These studies expand the paradigm for cryptococcal disease susceptibility to include a prominent role for immune-mediated damage and suggest a need for careful individual consideration of immune activation during therapy of cryptococcal disease in diverse hosts.

Parasite-mediated selection drives an immunogenetic trade-off in plains zebras (Equus quagga)

PubMed Central

Kamath, Pauline L.; Turner, Wendy C.; Küsters, Martina; Getz, Wayne M.

2014-01-01

Pathogen evasion of the host immune system is a key force driving extreme polymorphism in genes of the major histocompatibility complex (MHC). Although this gene family is well characterized in structure and function, there is still much debate surrounding the mechanisms by which MHC diversity is selectively maintained. Many studies have investigated relationships between MHC variation and specific pathogens, and have found mixed support for and against the hypotheses of heterozygote advantage, frequency-dependent or fluctuating selection. Few, however, have focused on the selective effects of multiple parasite types on host immunogenetic patterns. Here, we examined relationships between variation in the equine MHC gene, ELA-DRA, and both gastrointestinal (GI) and ectoparasitism in plains zebras (Equus quagga). Specific alleles present at opposing population frequencies had antagonistic effects, with rare alleles associated with increased GI parasitism and common alleles with increased tick burdens. These results support a frequency-dependent mechanism, but are also consistent with fluctuating selection. Maladaptive GI parasite ‘susceptibility alleles’ were reduced in frequency, suggesting that these parasites may play a greater selective role at this locus. Heterozygote advantage, in terms of allele mutational divergence, also predicted decreased GI parasite burden in genotypes with a common allele. We conclude that an immunogenetic trade-off affects resistance/susceptibility to parasites in this system. Because GI and ectoparasites do not directly interact within hosts, our results uniquely show that antagonistic parasite interactions can be indirectly modulated through the host immune system. This study highlights the importance of investigating the role of multiple parasites in shaping patterns of host immunogenetic variation. PMID:24718761

Parasite-mediated selection drives an immunogenetic tradeoff in plains zebra (Equus quagga)

USGS Publications Warehouse

Kamath, Pauline L.; Turner, Wendy C.; Küsters, Martina; Getz, Wayne M.

2014-01-01

Pathogen evasion of the host immune system is a key force driving extreme polymorphism in genes of the major histocompatibility complex (MHC). Although this gene family is well characterized in structure and function, there is still much debate surrounding the mechanisms by which MHC diversity is selectively maintained. Many studies have investigated relationships between MHC variation and specific pathogens, and have found mixed support for and against the hypotheses of heterozygote advantage, frequency-dependent or fluctuating selection. Few, however, have focused on the selective effects of multiple parasite types on host immunogenetic patterns. Here, we examined relationships between variation in the equine MHC gene, ELA-DRA, and both gastrointestinal (GI) and ectoparasitism in plains zebras (Equus quagga). Specific alleles present at opposing population frequencies had antagonistic effects, with rare alleles associated with increased GI parasitism and common alleles with increased tick burdens. These results support a frequency-dependent mechanism, but are also consistent with fluctuating selection. Maladaptive GI parasite ‘susceptibility alleles’ were reduced in frequency, suggesting that these parasites may play a greater selective role at this locus. Heterozygote advantage, in terms of allele mutational divergence, also predicted decreased GI parasite burden in genotypes with a common allele. We conclude that an immunogenetic trade-off affects resistance/susceptibility to parasites in this system. Because GI and ectoparasites do not directly interact within hosts, our results uniquely show that antagonistic parasite interactions can be indirectly modulated through the host immune system. This study highlights the importance of investigating the role of multiple parasites in shaping patterns of host immunogenetic variation.

Unidentified Plasmodium species in Australian black swans (Cygnus atratus) hatched and raised in North America.

PubMed

Grim, K Christiana; McCutchan, Thomas; Sullivan, Margery; Cranfield, Michael R

2008-06-01

A pair of Australian black swans (Cygnus atratus) with origins in Wakefield, Virginia, USA, was admitted to the quarantine area at the Baltimore Zoo for general health assessments before housing in the collections. During the quarantine period, no clinical signs of disease were manifest; however, upon examination of a blood smear, intraerythrocytic parasites were detected and initially determined to be Haemoproteus species. Diagnostic polymerase chain reaction (PCR) and sequencing results, however, indicated that the parasites were within the genus Plasmodium. Subclinical infections with Plasmodium species in birds may affect collection management, and transmission from refractory hosts to susceptible hosts should be considered when multispecies exhibits are used. In addition, changes in the dynamics of host-vector-parasite interactions might have significant impacts on wild or domesticated populations of birds.

Climate warming and disease risks for terrestrial and marine biota

USGS Publications Warehouse

Harvell, C.D.; Mitchell, C.E.; Ward, J.R.; Altizer, S.; Dobson, A.P.; Ostfeld, R.S.; Samuel, M.D.

2002-01-01

Infectious diseases can cause rapid population declines or species extinctions. Many pathogens of terrestrial and marine taxa are sensitive to temperature, rainfall, and humidity, creating synergisms that could affect biodiversity. Climate warming can increase pathogen development and survival rates, disease transmission, and host susceptibility. Although most host-parasite systems are predicted to experience more frequent or severe disease impacts with warming, a subset of pathogens might decline with warming, releasing hosts from disease. Recently, changes in El Niño–Southern Oscillation events have had a detectable influence on marine and terrestrial pathogens, including coral diseases, oyster pathogens, crop pathogens, Rift Valley fever, and human cholera. To improve our ability to predict epidemics in wild populations, it will be necessary to separate the independent and interactive effects of multiple climate drivers on disease impact.

Climate Warming and Disease Risks for Terrestrial and Marine Biota

NASA Astrophysics Data System (ADS)

Harvell, C. Drew; Mitchell, Charles E.; Ward, Jessica R.; Altizer, Sonia; Dobson, Andrew P.; Ostfeld, Richard S.; Samuel, Michael D.

2002-06-01

Infectious diseases can cause rapid population declines or species extinctions. Many pathogens of terrestrial and marine taxa are sensitive to temperature, rainfall, and humidity, creating synergisms that could affect biodiversity. Climate warming can increase pathogen development and survival rates, disease transmission, and host susceptibility. Although most host-parasite systems are predicted to experience more frequent or severe disease impacts with warming, a subset of pathogens might decline with warming, releasing hosts from disease. Recently, changes in El Niño-Southern Oscillation events have had a detectable influence on marine and terrestrial pathogens, including coral diseases, oyster pathogens, crop pathogens, Rift Valley fever, and human cholera. To improve our ability to predict epidemics in wild populations, it will be necessary to separate the independent and interactive effects of multiple climate drivers on disease impact.

Modulating effects of plasma containing anti-malarial antibodies on in vitro anti-malarial drug susceptibility in Plasmodium falciparum.

PubMed

Monatrakul, Preeyaporn; Mungthin, Mathirut; Dondorp, Arjen M; Krudsood, Srivicha; Udomsangpetch, Rachanee; Wilairatana, Polrat; White, Nicholas J; Chotivanich, Kesinee

2010-11-16

The efficacy of anti-malarial drugs is determined by the level of parasite susceptibility, anti-malarial drug bioavailability and pharmacokinetics, and host factors including immunity. Host immunity improves the in vivo therapeutic efficacy of anti-malarial drugs, but the mechanism and magnitude of this effect has not been characterized. This study characterized the effects of 'immune' plasma to Plasmodium falciparumon the in vitro susceptibility of P. falciparum to anti-malarial drugs. Titres of antibodies against blood stage antigens (mainly the ring-infected erythrocyte surface antigen [RESA]) were measured in plasma samples obtained from Thai patients with acute falciparum malaria. 'Immune' plasma was selected and its effects on in vitro parasite growth and multiplication of the Thai P. falciparum laboratory strain TM267 were assessed by light microscopy. The in vitro susceptibility to quinine and artesunate was then determined in the presence and absence of 'immune' plasma using the 3H-hypoxanthine uptake inhibition method. Drug susceptibility was expressed as the concentrations causing 50% and 90% inhibition (IC50 and IC90), of 3H-hypoxanthine uptake. Incubation with 'immune' plasma reduced parasite maturation and decreased parasite multiplication in a dose dependent manner. 3H-hypoxanthine incorporation after incubation with 'immune' plasma was decreased significantly compared to controls (median [range]; 181.5 [0 to 3,269] cpm versus 1,222.5 [388 to 5,932] cpm) (p= 0.001). As a result 'immune' plasma reduced apparent susceptibility to quinine substantially; median (range) IC50 6.4 (0.5 to 23.8) ng/ml versus 221.5 (174.4 to 250.4) ng/ml (p = 0.02), and also had a borderline effect on artesunate susceptibility; IC50 0.2 (0.02 to 0.3) ng/ml versus 0.8 (0.2 to 2.3) ng/ml (p = 0.08). Effects were greatest at low concentrations, changing the shape of the concentration-effect relationship. IC90 values were not significantly affected; median (range) IC90 448.0 (65 to > 500) ng/ml versus 368.8 (261 to 501) ng/ml for quinine (p > 0.05) and 17.0 (0.1 to 29.5) ng/ml versus 7.6 (2.3 to 19.5) ng/ml for artesunate (p = 0.4). 'Immune' plasma containing anti-malarial antibodies inhibits parasite development and multiplication and increases apparent in vitro anti-malarial drug susceptibility of P. falciparum. The IC90 was much less affected than the IC50 measurement.

Airway protease/antiprotease imbalance in atopic asthmatics contributes to increased influenza A virus cleavage and replication

EPA Science Inventory

Asthmatics are more susceptible to influenza infections, yet mechanisms mediating this enhanced susceptibility are unknown. Influenza virus hemagglutinin (HA) protein binds to sialic add residues on the host cells. HA requires cleavage to allow fusion of the viral HA with host ce...

An experimental conflict of interest between parasites reveals the mechanism of host manipulation.

PubMed

Hafer, Nina; Milinski, Manfred

2016-01-01

Parasites can increase their host's predation susceptibility. It is a long-standing puzzle, whether this is caused by host manipulation, an evolved strategy of the parasite, or by side effects due to, for example, the parasite consuming energy from its host thereby changing the host's trade-off between avoiding predation and foraging toward foraging. Here, we use sequential infection of three-spined sticklebacks with the cestode Schistocephalus solidus so that parasites have a conflict of interest over the direction of host manipulation. With true manipulation, the not yet infective parasite should reduce rather than enhance risk taking because predation would be fatal for its fitness; if host behavior is changed by a side effect, the 2 parasites would add their increase of predation risk because both drain energy. Our results support the latter hypothesis. In an additional experiment, we tested both infected and uninfected fish either starved or satiated. True host manipulation should act independently of the fish's hunger status and continue when energy drain is balanced through satiation. Starvation and satiation affect the risk averseness of infected sticklebacks similarly to that of uninfected starved and satiated ones. Increased energy drain rather than active host manipulation dominates behavioral changes of S. solidus -infected sticklebacks.

Asynchrony in host and parasite phenology may decrease disease risk in livestock under climate warming: Nematodirus battus in lambs as a case study.

PubMed

Gethings, Owen J; Rose, Hannah; Mitchell, Siân; Van Dijk, Jan; Morgan, Eric R

2015-09-01

Mismatch in the phenology of trophically linked species as a result of climate warming has been shown to have far-reaching effects on animal communities, but implications for disease have so far received limited attention. This paper presents evidence suggestive of phenological asynchrony in a host-parasite system arising from climate change, with impacts on transmission. Diagnostic laboratory data on outbreaks of infection with the pathogenic nematode Nematodirus battus in sheep flocks in the UK were used to validate region-specific models of the effect of spring temperature on parasite transmission. The hatching of parasite eggs to produce infective larvae is driven by temperature, while the availability of susceptible hosts depends on lambing date, which is relatively insensitive to inter-annual variation in spring temperature. In southern areas and in warmer years, earlier emergence of infective larvae in spring was predicted, with decline through mortality before peak availability of susceptible lambs. Data confirmed model predictions, with fewer outbreaks recorded in those years and regions. Overlap between larval peaks and lamb availability was not reduced in northern areas, which experienced no decreases in the number of reported outbreaks. Results suggest that phenological asynchrony arising from climate warming may affect parasite transmission, with non-linear but predictable impacts on disease burden. Improved understanding of complex responses of host-parasite systems to climate change can contribute to effective adaptation of parasite control strategies.

Diet, microbes, and host genetics: the perfect storm in inflammatory bowel diseases.

PubMed

Leone, Vanessa; Chang, Eugene B; Devkota, Suzanne

2013-03-01

The incidence of inflammatory bowel diseases (IBD), as well as other inflammatory conditions, has dramatically increased over the past half century. While many studies have shown that IBD exhibits a genetic component via genome-wide association studies, genetic drift alone cannot account for this increase, and other factors, such as those found in the environment must play a role, suggesting a "multiple hit" phenomenon that precipitates disease. One major environmental factor, dietary intake, has shifted to a high fat, high carbohydrate Western-type diet in developing nations, nearly in direct correlation with the increasing incidence of IBD. Recent evidence suggests that specific changes in dietary intake have led to a shift in the composite human gut microbiota, resulting in the emergence of pathobionts that can thrive under specific conditions. In the genetically susceptible host, the emerging pathobionts can lead to increasing incidence and severity of IBD and other inflammatory disorders. Since the gut microbiota is plastic and responds to dietary modulations, the use of probiotics, prebiotics, and/or dietary alterations are all intriguing complementary therapeutic approaches to alleviate IBD symptoms. However, the interactions are complex and it is unlikely that a one-size-fits all approach can be utilized across all populations affected by IBD. Exploration into and thoroughly understanding the interactions between host and microbes, primarily in the genetically susceptible host, will help define strategies that can be tailored to an individual as we move towards an era of personalized medicine to treat IBD.

Effects of life-history traits on parasitism in a monogamous mammal, the eastern rock sengi ( Elephantulus myurus)

NASA Astrophysics Data System (ADS)

Lutermann, Heike; Medger, Katarina; Horak, Ivan G.

2012-02-01

The distribution of parasites is often characterised by substantial aggregation with a small proportion of hosts harbouring the majority of parasites. This pattern can be generated by abiotic and biotic factors that affect hosts and determine host exposure and susceptibility to parasites. Climate factors can change a host's investment in life-history traits (e.g. growth, reproduction) generating temporal patterns of parasite aggregation. Similarly, host age may affect such investment. Furthermore, sex-biased parasitism is common among vertebrates and has been linked to sexual dimorphism in morphology, behaviour and physiology. Studies exploring sex-biased parasitism have been almost exclusively conducted on polygynous species where dimorphic traits are often correlated. We investigated the effects of season and life-history traits on tick loads of the monogamous eastern rock sengi ( Elephantulus myurus). We found larger tick burdens during the non-breeding season possibly as a result of energetic constraints and/or climate effects on the tick. Reproductive investment resulted in increased larval abundance for females but not males and may be linked to sex-specific life-history strategies. The costs of reproduction could also explain the observed age effect with yearling individuals harbouring lower larval burdens than adults. Although adult males had the greatest larval tick loads, host sex appears to play a minor role in generating the observed parasite heterogeneities. Our study suggests that reproductive investment plays a major role for parasite patterns in the study species.

Vector specificity of Trypanosoma catostomi and its infectivity to freshwater fishes.

PubMed

Jones, S R; Woo, P T

1992-02-01

Trypanosoma catostomi was found in 36.2% of 558 white suckers (Catostomus commersoni) from Ontario, Canada. The abundance of Actinobdella inequiannulata was 35% (68 leeches/197 suckers examined for leeches). The susceptibility of 3 species of leeches (Hemiclepsis marginata, Desserobdella phalera, and A. inequiannulata) and 7 species of fishes (C. commersoni, Amia calva, Anguilla rostrata, Ictalurus nebulosus, Oncorhynchus mykiss, Perca flavescens, and Esox lucius) to infection with T. catostomi was examined. Metatrypanosomes were found in the crop and proboscis sheath of 13 of 21 A. inequiannulata and in the crop of 10 of 12 H. marginata and 1 of 21 D. phalera. Only flagellates from A. inequiannulata were infective to C. commersoni. Cultured T. catostomi infected C. commersoni and A. calva but not any other fish species. Laboratory-reared C. commersoni were more susceptible than wild-caught specimens. Cultured Trypanosoma phaleri did not infect its natural host, A. calva. Host specificity should be established experimentally before a specific diagnosis is made. Cultures may be useful in simulating factors that affect development in the vector.

Virus Infection of Plants Alters Pollinator Preference: A Payback for Susceptible Hosts?

PubMed Central

Davey, Matthew P.; Bruce, Toby J. A.; Caulfield, John C.; Furzer, Oliver J.; Reed, Alison; Robinson, Sophie I.; Miller, Elizabeth; Davis, Christopher N.; Pickett, John A.; Whitney, Heather M.; Glover, Beverley J.; Carr, John P.

2016-01-01

Plant volatiles play important roles in attraction of certain pollinators and in host location by herbivorous insects. Virus infection induces changes in plant volatile emission profiles, and this can make plants more attractive to insect herbivores, such as aphids, that act as viral vectors. However, it is unknown if virus-induced alterations in volatile production affect plant-pollinator interactions. We found that volatiles emitted by cucumber mosaic virus (CMV)-infected tomato (Solanum lycopersicum) and Arabidopsis thaliana plants altered the foraging behaviour of bumblebees (Bombus terrestris). Virus-induced quantitative and qualitative changes in blends of volatile organic compounds emitted by tomato plants were identified by gas chromatography-coupled mass spectrometry. Experiments with a CMV mutant unable to express the 2b RNA silencing suppressor protein and with Arabidopsis silencing mutants implicate microRNAs in regulating emission of pollinator-perceivable volatiles. In tomato, CMV infection made plants emit volatiles attractive to bumblebees. Bumblebees pollinate tomato by ‘buzzing’ (sonicating) the flowers, which releases pollen and enhances self-fertilization and seed production as well as pollen export. Without buzz-pollination, CMV infection decreased seed yield, but when flowers of mock-inoculated and CMV-infected plants were buzz-pollinated, the increased seed yield for CMV-infected plants was similar to that for mock-inoculated plants. Increased pollinator preference can potentially increase plant reproductive success in two ways: i) as female parents, by increasing the probability that ovules are fertilized; ii) as male parents, by increasing pollen export. Mathematical modeling suggested that over a wide range of conditions in the wild, these increases to the number of offspring of infected susceptible plants resulting from increased pollinator preference could outweigh underlying strong selection pressures favoring pathogen resistance, allowing genes for disease susceptibility to persist in plant populations. We speculate that enhanced pollinator service for infected individuals in wild plant populations might provide mutual benefits to the virus and its susceptible hosts. PMID:27513727

Brown dog tick, Rhipicephalus sanguineus sensu lato, infestation of susceptible dog hosts is reduced by slow release of semiochemicals from a less susceptible host.

PubMed

de Oliveira Filho, Jaires Gomes; Ferreira, Lorena Lopes; Sarria, André Lucio Franceschini; Pickett, John A; Birkett, Michael A; Mascarin, Gabriel Moura; de León, Adalberto A Pérez; Borges, Lígia Miranda Ferreira

2017-01-01

Domestic dog breeds are hosts for the brown dog tick, Rhipicephalus sanguineus sensu lato, but infestation levels vary among breeds. Beagles are less susceptible to tick infestations than English cocker spaniels due to enhanced production of 2-hexanone and benzaldehyde that act as volatile tick repellents. We report the use of prototype slow-release formulations of these compounds to reduce the burden of R. sanguineus s. l. on English cocker spaniel dogs. Twelve dogs were randomly assigned to two groups with six dogs each. The treated group received collars with slow-release formulations of the compounds attached, while the control group received collars with clean formulations attached. Five environmental infestations were performed, with the number of ticks (at all stages) on the dogs being counted twice a day for 45days. The counts on the number of tick stages found per dog were individually fitted to linear mixed effects models with repeated measures and normal distribution for errors. The mean tick infestation in the treated group was significantly lower than in the control group. For larvae and nymphs, a decrease in tick infestation was observed at the fifth count, and for adults, lower average counts were observed in all counts. The compounds did not interfere with the distribution of the ticks on the body of the dogs, as a similar percentage of ticks was found on the anterior half of the dogs (54.5% for the control group and 56.2% for the treated group). The biological and reproductive parameters of the ticks were not affected by the repellents. This study highlights for the first time the potential use of a novel allomone (repellent)-based formulation for reduction of tick infestation on susceptible dogs. Copyright © 2016 Elsevier GmbH. All rights reserved.

Early-Life Food Nutrition, Microbiota Maturation and Immune Development Shape Life-Long Health.

PubMed

Zhou, Xiaoli; Du, Lina; Shi, Ronghua; Chen, Zhidong; Zhou, Yiming; Li, Zongjie

2018-06-06

The current knowledge about early-life nutrition and environmental factors that affect the interaction between the symbiotic microbiota and the host immune system has demonstrated novel regulatory target for treating allergic diseases, autoimmune disorders and metabolic syndrome. Various kinds of food nutrients (such as dietary fiber, starch, polyphenols and proteins) can provide energy resources for both intestinal microbiota and the host. The indigestible food components are fermented by the indigenous gut microbiota to produce diverse metabolites, including short-chain fatty acids, bile acids and trimethylamine-N-oxide, which can regulate the host metabolized physiology, immunity homeostasis and health state. Therefore it is commonly believed early-life perturbation of the microbial community structure and the dietary nutrition interference on the child mucosal immunity contribute to the whole life susceptibility to chronic diseases. In all, the combined interrelationship between food ingredients nutrition, intestinal microbiota configurations and host system immunity provides new therapeutic targets to treat various kinds of pathogenic inflammations and chronic diseases.

Mycobacterium leprae–host-cell interactions and genetic determinants in leprosy: an overview

PubMed Central

Pinheiro, Roberta Olmo; de Souza Salles, Jorgenilce; Sarno, Euzenir Nunes; Sampaio, Elizabeth Pereira

2011-01-01

Leprosy, also known as Hansen’s disease, is a chronic infectious disease caused by Mycobacterium leprae in which susceptibility to the mycobacteria and its clinical manifestations are attributed to the host immune response. Even though leprosy prevalence has decreased dramatically, the high number of new cases indicates active transmission. Owing to its singular features, M. leprae infection is an attractive model for investigating the regulation of human immune responses to pathogen-induced disease. Leprosy is one of the most common causes of nontraumatic peripheral neuropathy worldwide. The proportion of patients with disabilities is affected by the type of leprosy and delay in diagnosis. This article briefly reviews the clinical features as well as the immunopathological mechanisms related to the establishment of the different polar forms of leprosy, the mechanisms related to M. leprae–host cell interactions and prophylaxis and diagnosis of this complex disease. Host genetic factors are summarized and the impact of the development of interventions that prevent, reverse or limit leprosy-related nerve impairments are discussed. PMID:21366421

Correlating Phytophthora ramorum infection rate and lesion expansion in tanoak

Treesearch

Katherine Hayden; Heather Rickard; Matteo Garbelotto

2008-01-01

To date, resistance to Phytophthora ramorum in its most susceptible hosts has most commonly been quantified by lesion growth, after wounding or non-wounding inoculations via mycelia or high concentrations of zoospores. However, even highly susceptible hosts may not always become infected when they are exposed to a pathogen under ecologically...

Anthropogenic drivers of gypsy moth spread

Treesearch

Kevin M. Bigsby; Patrick C. Tobin; Erin O. Sills

2011-01-01

The gypsy moth, Lymantria dispar (L.), is a polyphagous defoliator introduced to Medford, Massachusetts in 1869. It has spread to over 860,000 km2 in North America, but this still only represents 1/4 of its susceptible host range in the United States. To delay defoliation in the remaining susceptible host range, the government...

Effect of the irrigation regime on the susceptibility of pepper and tomato to post-harvest proliferation of Salmonella enterica.

PubMed

Marvasi, Massimiliano; George, Andrée S; Giurcanu, Mihai C; Hochmuth, George J; Noel, Jason T; Teplitski, Max

2015-04-01

Raw produce is increasingly recognized as a vehicle of human gastroenteritis. Non-typhoidal Salmonella, pathogenic Escherichia coli, and other human pathogens have been isolated from fruits and vegetables in the field and in the marketplace, which led to the hypothesis that these microbes can use plants as alternate hosts. However, environmental and physiological factors that facilitate persistence of these bacteria in the crop production environment and make produce more vulnerable to post-harvest contamination have not been fully delineated. This study tested the effect of irrigation regimes on the susceptibility of peppers and tomatoes to post-harvest proliferation of Salmonella. The experiments were carried out over three experimental seasons in two locations using seven strains of Salmonella. The irrigation regime per se did not affect susceptibility of tomatoes and peppers to post-harvest proliferation of Salmonella; however, in some of the seasons, irrigation regime-dependent differences were observed. Red peppers and tomatoes were more conducive to proliferation of Salmonella than green fruit in all seasons. Inter-seasonal differences were the strongest factors affecting proliferation of Salmonella in peppers. Copyright © 2014 Elsevier Ltd. All rights reserved.

Ecosystem consequences of fish parasites

USGS Publications Warehouse

Lafferty, Kevin D.

2008-01-01

In most aquatic ecosystems, fishes are hosts to parasites and, sometimes, these parasites can affect fish biology. Some of the most dramatic cases occur when fishes are intermediate hosts for larval parasites. For example, fishes in southern California estuaries are host to many parasites. The most common of these parasites, Euhaplorchis californiensis, infects the brain of the killifish Fundulus parvipinnis and alters its behaviour, making the fish 10–30 times more susceptible to predation by the birds that serve as its definitive host. Parasites like E. californiensis are embedded in food webs because they require trophic transmission. In the Carpinteria Salt Marsh estuarine food web, parasites dominate the links and comprise substantial amount of biomass. Adding parasites to food webs alters important network statistics such as connectance and nestedness. Furthermore, some free-living stages of parasites are food items for free-living species. For instance, fishes feed on trematode cercariae. Being embedded in food webs makes parasites sensitive to changes in the environment. In particular, fishing and environmental disturbance, by reducing fish populations, may reduce parasite populations. Indirect evidence suggests a decrease in parasites in commercially fished species over the past three decades. In addition, environmental degradation can affect fish parasites. For these reasons, parasites in fishes may serve as indicators of environmental impacts.

Fundamental properties of cooperative contagion processes

NASA Astrophysics Data System (ADS)

Chen, Li; Ghanbarnejad, Fakhteh; Brockmann, Dirk

2017-10-01

We investigate the effects of cooperativity between contagion processes that spread and persist in a host population. We propose and analyze a dynamical model in which individuals that are affected by one transmissible agent A exhibit a higher than baseline propensity of being affected by a second agent B and vice versa. The model is a natural extension of the traditional susceptible-infected-susceptible model used for modeling single contagion processes. We show that cooperativity changes the dynamics of the system considerably when cooperativity is strong. The system exhibits discontinuous phase transitions not observed in single agent contagion, multi-stability, a separation of the traditional epidemic threshold into different thresholds for inception and extinction as well as hysteresis. These properties are robust and are corroborated by stochastic simulations on lattices and generic network topologies. Finally, we investigate wave propagation and transients in a spatially extended version of the model and show that especially for intermediate values of baseline reproduction ratios the system is characterized by various types of wave-front speeds. The system can exhibit spatially heterogeneous stationary states for some parameters and negative front speeds (receding wave fronts). The two agent model can be employed as a starting point for more complex contagion processes, involving several interacting agents, a model framework particularly suitable for modeling the spread and dynamics of microbiological ecosystems in host populations.

Genetic resistance to rhabdovirus infection in teleost fish is paralleled to the derived cell resistance status.

PubMed

Verrier, Eloi R; Langevin, Christelle; Tohry, Corinne; Houel, Armel; Ducrocq, Vincent; Benmansour, Abdenour; Quillet, Edwige; Boudinot, Pierre

2012-01-01

Genetic factors of resistance and predisposition to viral diseases explain a significant part of the clinical variability observed within host populations. Predisposition to viral diseases has been associated to MHC haplotypes and T cell immunity, but a growing repertoire of innate/intrinsic factors are implicated in the genetic determinism of the host susceptibility to viruses. In a long-term study of the genetics of host resistance to fish rhabdoviruses, we produced a collection of double-haploid rainbow trout clones showing a wide range of susceptibility to Viral Hemorrhagic Septicemia Virus (VHSV) waterborne infection. The susceptibility of fibroblastic cell lines derived from these clonal fish was fully consistent with the susceptibility of the parental fish clones. The mechanisms determining the host resistance therefore did not associate with specific host immunity, but rather with innate or intrinsic factors. One cell line was resistant to rhabdovirus infection due to the combination of an early interferon IFN induction--that was not observed in the susceptible cells--and of yet unknown factors that hamper the first steps of the viral cycle. The implication of IFN was well consistent with the wide range of resistance of this genetic background to VSHV and IHNV, to the birnavirus IPNV and the orthomyxovirus ISAV. Another cell line was even more refractory to the VHSV infection through different antiviral mechanisms. This collection of clonal fish and isogenic cell lines provides an interesting model to analyze the relative contribution of antiviral pathways to the resistance to different viruses.

Dysregulation of retinoic acid receptor diminishes hepatocyte permissiveness to hepatitis B virus infection through modulation of sodium taurocholate cotransporting polypeptide (NTCP) expression.

PubMed

Tsukuda, Senko; Watashi, Koichi; Iwamoto, Masashi; Suzuki, Ryosuke; Aizaki, Hideki; Okada, Maiko; Sugiyama, Masaya; Kojima, Soichi; Tanaka, Yasuhito; Mizokami, Masashi; Li, Jisu; Tong, Shuping; Wakita, Takaji

2015-02-27

Sodium taurocholate cotransporting polypeptide (NTCP) is an entry receptor for hepatitis B virus (HBV) and is regarded as one of the determinants that confer HBV permissiveness to host cells. However, how host factors regulate the ability of NTCP to support HBV infection is largely unknown. We aimed to identify the host signaling that regulated NTCP expression and thereby permissiveness to HBV. Here, a cell-based chemical screening method identified that Ro41-5253 decreased host susceptibility to HBV infection. Pretreatment with Ro41-5253 inhibited the viral entry process without affecting HBV replication. Intriguingly, Ro41-5253 reduced expression of both NTCP mRNA and protein. We found that retinoic acid receptor (RAR) regulated the promoter activity of the human NTCP (hNTCP) gene and that Ro41-5253 repressed the hNTCP promoter by antagonizing RAR. RAR recruited to the hNTCP promoter region, and nucleotides -112 to -96 of the hNTCP was suggested to be critical for RAR-mediated transcriptional activation. HBV susceptibility was decreased in pharmacologically RAR-inactivated cells. CD2665 showed a stronger anti-HBV potential and disrupted the spread of HBV infection that was achieved by continuous reproduction of the whole HBV life cycle. In addition, this mechanism was significant for drug development, as antagonization of RAR blocked infection of multiple HBV genotypes and also a clinically relevant HBV mutant that was resistant to nucleoside analogs. Thus, RAR is crucial for regulating NTCP expression that determines permissiveness to HBV infection. This is the first demonstration showing host regulation of NTCP to support HBV infection. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Dysregulation of Retinoic Acid Receptor Diminishes Hepatocyte Permissiveness to Hepatitis B Virus Infection through Modulation of Sodium Taurocholate Cotransporting Polypeptide (NTCP) Expression*

PubMed Central

Tsukuda, Senko; Watashi, Koichi; Iwamoto, Masashi; Suzuki, Ryosuke; Aizaki, Hideki; Okada, Maiko; Sugiyama, Masaya; Kojima, Soichi; Tanaka, Yasuhito; Mizokami, Masashi; Li, Jisu; Tong, Shuping; Wakita, Takaji

2015-01-01

Sodium taurocholate cotransporting polypeptide (NTCP) is an entry receptor for hepatitis B virus (HBV) and is regarded as one of the determinants that confer HBV permissiveness to host cells. However, how host factors regulate the ability of NTCP to support HBV infection is largely unknown. We aimed to identify the host signaling that regulated NTCP expression and thereby permissiveness to HBV. Here, a cell-based chemical screening method identified that Ro41-5253 decreased host susceptibility to HBV infection. Pretreatment with Ro41-5253 inhibited the viral entry process without affecting HBV replication. Intriguingly, Ro41-5253 reduced expression of both NTCP mRNA and protein. We found that retinoic acid receptor (RAR) regulated the promoter activity of the human NTCP (hNTCP) gene and that Ro41-5253 repressed the hNTCP promoter by antagonizing RAR. RAR recruited to the hNTCP promoter region, and nucleotides −112 to −96 of the hNTCP was suggested to be critical for RAR-mediated transcriptional activation. HBV susceptibility was decreased in pharmacologically RAR-inactivated cells. CD2665 showed a stronger anti-HBV potential and disrupted the spread of HBV infection that was achieved by continuous reproduction of the whole HBV life cycle. In addition, this mechanism was significant for drug development, as antagonization of RAR blocked infection of multiple HBV genotypes and also a clinically relevant HBV mutant that was resistant to nucleoside analogs. Thus, RAR is crucial for regulating NTCP expression that determines permissiveness to HBV infection. This is the first demonstration showing host regulation of NTCP to support HBV infection. PMID:25550158

TGFβ Receptor 1: An Immune Susceptibility Gene in HPV-Associated Cancer

PubMed Central

Levovitz, Chaya; Chen, Dan; Ivansson, Emma; Gyllensten, Ulf; Finnigan, John P.; Alshawish, Sara; Zhang, Weijia; Schadt, Eric E.; Posner, Marshal R.; Genden, Eric M.; Boffetta, Paolo; Sikora, Andrew G.

2015-01-01

Only a minority of those exposed to human papillomavirus (HPV) develop HPV-related cervical and oropharyngeal cancer. Because host immunity affects infection and progression to cancer, we tested the hypothesis that genetic variation in immune-related genes is a determinant of susceptibility to oropharyngeal cancer and other HPV-associated cancers by performing a multitier integrative computational analysis with oropharyngeal cancer data from a head and neck cancer genome-wide association study (GWAS). Independent analyses, including single-gene, gene-interconnectivity, protein–protein interaction, gene expression, and pathway analysis, identified immune genes and pathways significantly associated with oropharyngeal cancer. TGFβR1, which intersected all tiers of analysis and thus selected for validation, replicated significantly in the head and neck cancer GWAS limited to HPV-seropositive cases and an independent cervical cancer GWAS. The TGFβR1 containing p38–MAPK pathway was significantly associated with oropharyngeal cancer and cervical cancer, and TGFβR1 was overexpressed in oropharyngeal cancer, cervical cancer, and HPV+ head and neck cancer tumors. These concordant analyses implicate TGFβR1 signaling as a process dysregulated across HPV-related cancers. This study demonstrates that genetic variation in immune-related genes is associated with susceptibility to oropharyngeal cancer and implicates TGFβR1/TGFβ signaling in the development of both oropharyngeal cancer and cervical cancer. Better understanding of the immunogenetic basis of susceptibility to HPV-associated cancers may provide insight into host/virus interactions and immune processes dysregulated in the minority of HPV-exposed individuals who progress to cancer. PMID:25273091

Humans as holobionts: implications for prevention and therapy.

PubMed

van de Guchte, Maarten; Blottière, Hervé M; Doré, Joël

2018-05-01

The human gut microbiota is increasingly recognized for its important or even decisive role in health. As it becomes clear that microbiota and host mutually affect and depend on each other in an intimate relationship, a holistic view of the gut microbiota-host association imposes itself. Ideally, a stable state of equilibrium, homeostasis, is maintained and serves health, but signs are that perturbation of this equilibrium beyond the limits of resilience can propel the system into an alternative stable state, a pre-disease state, more susceptible to the development of chronic diseases. The microbiota-host equilibrium of a large and growing proportion of individuals in Western society may represent such a pre-disease state and explain the explosive development of chronic diseases such as inflammatory bowel disease, obesity, and other inflammatory diseases. These diseases themselves represent other alternative stable states again and are therefore hard to cure. The holistic view of the microbiota-host association where feedback loops between microbiota and host are thought to maintain the system in a stable state-be it a healthy, pre-disease, or disease state-implies that integrated approaches, addressing host processes and microbiota, should be used to treat or prevent (pre-)disease.

Bemisia tabaci females from the Mediterranean (Q) species detect and avoid laying eggs in the presence of pyriproxyfen, a juvenile hormone analogue.

PubMed

Moshitzky, Pnina; Morin, Shai

2014-10-01

Pyriproxyfen, a juvenile hormone analogue, disrupts embryogenesis, metamorphosis and adult formation in Bemisia tabaci, but does not directly affect adult females. The effect of pyriproxyfen on egg-laying preference and performance of B. tabaci females and the influence of resistance to pyriproxyfen on these reproductive behaviours were studied. Choice experiments utilising cotton plants treated and not treated with pyriproxyfen revealed a significant preference for egg laying on non-treated plants both by resistant and susceptible females. No-choice assays indicated a reduction of ∼60% in the number of eggs laid on pyriproxyfen-treated plants by both resistant and susceptible females. The reduction in oviposition on treated plants was not accompanied with reduced expression of the vitellogenin gene or a delay in oocyte maturation, but significant accumulation of mature oocytes in the ovaries was observed, and could be reversed by transferring the females to non-treated plants. Pyriproxyfen caused reduced oviposition and enhanced mature oocyte accumulation in pyriproxyfen-resistant and pyriproxyfen-susceptible females. These findings can be explained by two alternative mechanisms: pyriproxyfen-regulated physiological arrest of oviposition, involving hormonal regulation of myotrophic factors, or the hierarchy-threshold behavioural theory of host choice, in which pyriproxyfen-treated plants are defined as low-quality hosts. Aspects of application are discussed. © 2013 Society of Chemical Industry.

Viral ancestors of antiviral systems.

PubMed

Villarreal, Luis P

2011-10-01

All life must survive their corresponding viruses. Thus antiviral systems are essential in all living organisms. Remnants of virus derived information are also found in all life forms but have historically been considered mostly as junk DNA. However, such virus derived information can strongly affect host susceptibility to viruses. In this review, I evaluate the role viruses have had in the origin and evolution of host antiviral systems. From Archaea through bacteria and from simple to complex eukaryotes I trace the viral components that became essential elements of antiviral immunity. I conclude with a reexamination of the 'Big Bang' theory for the emergence of the adaptive immune system in vertebrates by horizontal transfer and note how viruses could have and did provide crucial and coordinated features.

Viral Ancestors of Antiviral Systems

PubMed Central

Villarreal, Luis P.

2011-01-01

All life must survive their corresponding viruses. Thus antiviral systems are essential in all living organisms. Remnants of virus derived information are also found in all life forms but have historically been considered mostly as junk DNA. However, such virus derived information can strongly affect host susceptibility to viruses. In this review, I evaluate the role viruses have had in the origin and evolution of host antiviral systems. From Archaea through bacteria and from simple to complex eukaryotes I trace the viral components that became essential elements of antiviral immunity. I conclude with a reexamination of the ‘Big Bang’ theory for the emergence of the adaptive immune system in vertebrates by horizontal transfer and note how viruses could have and did provide crucial and coordinated features. PMID:22069523

Animal Viruses, Bacteria, and Cancer: A Brief Commentary

PubMed Central

Efird, Jimmy T.; Davies, Stephen W.; O’Neal, Wesley T.; Anderson, Ethan J.

2014-01-01

Animal viruses and bacteria are ubiquitous in the environment. However, little is known about their mode of transmission and etiologic role in human cancers, especially among high-risk groups (e.g., farmers, veterinarians, poultry plant workers, pet owners, and infants). Many factors may affect the survival, transmissibility, and carcinogenicity of these agents, depending on the animal-host environment, hygiene practices, climate, travel, herd immunity, and cultural differences in food consumption and preparation. Seasonal variations in immune function also may increase host susceptibility at certain times of the year. The lack of objective measures, inconsistent study designs, and sources of epidemiologic bias (e.g., residual confounding, recall bias, and non-randomized patient selection) are some of the factors that complicate a clear understanding of this subject. PMID:24592380

Molecular insights into Cassava brown streak virus susceptibility and resistance by profiling of the early host response.

PubMed

Anjanappa, Ravi B; Mehta, Devang; Okoniewski, Michal J; Szabelska-Berȩsewicz, Alicja; Gruissem, Wilhelm; Vanderschuren, Hervé

2018-02-01

Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV) are responsible for significant cassava yield losses in eastern sub-Saharan Africa. To study the possible mechanisms of plant resistance to CBSVs, we inoculated CBSV-susceptible and CBSV-resistant cassava varieties with a mixed infection of CBSVs using top-cleft grafting. Transcriptome profiling of the two cassava varieties was performed at the earliest time point of full infection (28 days after grafting) in the susceptible scions. The expression of genes encoding proteins in RNA silencing, salicylic acid pathways and callose deposition was altered in the susceptible cassava variety, but transcriptional changes were limited in the resistant variety. In total, the expression of 585 genes was altered in the resistant variety and 1292 in the susceptible variety. Transcriptional changes led to the activation of β-1,3-glucanase enzymatic activity and a reduction in callose deposition in the susceptible cassava variety. Time course analysis also showed that CBSV replication in susceptible cassava induced a strong up-regulation of RDR1, a gene previously reported to be a susceptibility factor in other potyvirus-host pathosystems. The differences in the transcriptional responses to CBSV infection indicated that susceptibility involves the restriction of callose deposition at plasmodesmata. Aniline blue staining of callose deposits also indicated that the resistant variety displays a moderate, but significant, increase in callose deposition at the plasmodesmata. Transcriptome data suggested that resistance does not involve typical antiviral defence responses (i.e. RNA silencing and salicylic acid). A meta-analysis of the current RNA-sequencing (RNA-seq) dataset and selected potyvirus-host and virus-cassava RNA-seq datasets revealed that the conservation of the host response across pathosystems is restricted to genes involved in developmental processes. © 2017 THE AUTHORS. MOLECULAR PLANT PATHOLOGY PUBLISHED BY BRITISH SOCIETY FOR PLANT PATHOLOGY AND JOHN WILEY & SONS LTD.

Gene Expression Profiling of the Local Cecal Response of Genetic Chicken Lines That Differ in Their Susceptibility to Campylobacter jejuni Colonization

PubMed Central

Kogut, Michael H.; Chiang, Hsin-I; Wang, Ying; Genovese, Kenneth J.; He, Haiqi; Zhou, Huaijun

2010-01-01

Campylobacter jejuni (C. jejuni) is one of the most common causes of human bacterial enteritis worldwide primarily due to contaminated poultry products. Previously, we found a significant difference in C. jejuni colonization in the ceca between two genetically distinct broiler lines (Line A (resistant) has less colony than line B (susceptible) on day 7 post inoculation). We hypothesize that different mechanisms between these two genetic lines may affect their ability to resist C. jejuni colonization in chickens. The molecular mechanisms of the local host response to C. jejuni colonization in chickens have not been well understood. In the present study, to profile the cecal gene expression in the response to C. jejuni colonization and to compare differences between two lines at the molecular level, RNA of ceca from two genetic lines of chickens (A and B) were applied to a chicken whole genome microarray for a pair-comparison between inoculated (I) and non-inoculated (N) chickens within each line and between lines. Our results demonstrated that metabolism process and insulin receptor signaling pathways are key contributors to the different response to C. jejuni colonization between lines A and B. With C. jejuni inoculation, lymphocyte activation and lymphoid organ development functions are important for line A host defenses, while cell differentiation, communication and signaling pathways are important for line B. Interestingly, circadian rhythm appears play a critical role in host response of the more resistant A line to C. jejuni colonization. A dramatic differential host response was observed between these two lines of chickens. The more susceptible line B chickens responded to C. jejuni inoculation with a dramatic up-regulation in lipid, glucose, and amino acid metabolism, which is undoubtedly for use in the response to the colonization with little or no change in immune host defenses. However, in more resistant line A birds the host defense responses were characterized by an up-regulation lymphocyte activation, probably by regulatory T cells and an increased expression of the NLR recognition receptor NALP1. To our knowledge, this is the first time each of these responses has been observed in the avian response to an intestinal bacterial pathogen. PMID:20676366

Spiroplasma and host immunity: activation of humoral immune responses increases endosymbiont load and susceptibility to certain Gram-negative bacterial pathogens in Drosophila melanogaster.

PubMed

Herren, Jeremy K; Lemaitre, Bruno

2011-09-01

Spiroplasma poulsonii and its relatives are facultative, vertically transmitted endosymbionts harboured by several Drosophila species. Their long-term survival requires not only evasion of host immunity, but also that Spiroplasma does not have a net detrimental effect on host fitness. These requirements provide the central framework for interactions between host and endosymbiont. We use Drosophila melaogaster as a model to unravel aspects of the mechanistic basis of endosymbiont-host immune interactions. Here we show that Spiroplasma does not activate an immune response in Drosophila and is not susceptible to either the cellular or humoral arms of the Drosophila immune system. We gain unexpected insight into host factors that can promote Spiroplasma growth by showing that activation of Toll and Imd immune pathways actually increases Sprioplasma titre. Spiroplasma-mediated protection is not observed for variety of fungal and bacterial pathogens and Spiroplasma actually increases susceptibility of Drosophila to certain Gram-negative pathogens. Finally, we show that the growth of endosymbiotic Spiroplasma is apparently self-regulated, as suggested by the unhindered proliferation of non-endosymbiotic Spiroplasma citri in fly haemolymph. © 2011 Blackwell Publishing Ltd.

The ectromelia virus SPI-2 protein causes lethal mousepox by preventing NK cell responses.

PubMed

Melo-Silva, Carolina R; Tscharke, David C; Lobigs, Mario; Koskinen, Aulikki; Wong, Yik Chun; Buller, R Mark; Müllbacher, Arno; Regner, Matthias

2011-11-01

Ectromelia virus (ECTV) is a natural pathogen of mice that causes mousepox, and many of its genes have been implicated in the modulation of host immune responses. Serine protease inhibitor 2 (SPI-2) is one of these putative ECTV host response modifier proteins. SPI-2 is conserved across orthopoxviruses, but results defining its mechanism of action and in vivo function are lacking or contradictory. We studied the role of SPI-2 in mousepox by deleting the SPI-2 gene or its serine protease inhibitor reactive site. We found that SPI-2 does not affect viral replication or cell-intrinsic apoptosis pathways, since mutant viruses replicate in vitro as efficiently as wild-type virus. However, in the absence of SPI-2 protein, ECTV is attenuated in mousepox-susceptible mice, resulting in lower viral loads in the liver, decreased spleen pathology, and substantially improved host survival. This attenuation correlates with more effective immune responses in the absence of SPI-2, including an earlier serum gamma interferon (IFN-γ) response, raised serum interleukin 18 (IL-18), increased numbers of granzyme B(+) CD8(+) T cells, and, most notably, increased numbers and activation of NK cells. Both virus attenuation and the improved immune responses associated with SPI-2 deletion from ECTV are lost when mice are depleted of NK cells. Consequently, SPI-2 renders mousepox lethal in susceptible strains by preventing protective NK cell defenses.

Genome-wide association study uncovers a novel QTL allele of AtS40-3 that affects the sex ratio of cyst nematodes in Arabidopsis.

PubMed

Anwer, Muhammad Arslan; Anjam, Muhammad Shahzad; Shah, Syed Jehangir; Hasan, M Shamim; Naz, Ali A; Grundler, Florian M W; Siddique, Shahid

2018-03-24

Plant-parasitic cyst nematodes are obligate sedentary parasites that infect the roots of a broad range of host plants. Cyst nematodes are sexually dimorphic, but differentiation into male or female is strongly influenced by interactions with the host environment. Female populations typically predominate under favorable conditions, whereas male populations predominate under adverse conditions. Here, we performed a genome-wide association study (GWAS) in an Arabidopsis diversity panel to identify host loci underlying variation in susceptibility to cyst nematode infection. Three different susceptibility parameters were examined, with the aim of providing insights into the infection process, the number of females and males present in the infected plant, and the female-to-male sex ratio. GWAS results suggested that variation in sex ratio is associated with a novel quantitative trait locus allele on chromosome 4. Subsequent candidate genes and functional analyses revealed that a senescence-associated transcription factor, AtS40-3, and PPR may act in combination to influence nematode sex ratio. A detailed molecular characterization revealed that variation in nematode sex ratio was due to the disturbed common promoter of AtS40-3 and PPR genes. Additionally, single nucleotide polymorphisms in the coding sequence of AtS40-3 might contribute to the natural variation in nematode sex ratio.

Diversity and geographical distribution of Flavobacterium psychrophilum isolates and their phages: patterns of susceptibility to phage infection and phage host range.

PubMed

Castillo, Daniel; Christiansen, Rói Hammershaimb; Espejo, Romilio; Middelboe, Mathias

2014-05-01

Flavobacterium psychrophilum is an important fish pathogen worldwide that causes cold water disease (CWD) or rainbow trout fry syndrome (RTFS). Phage therapy has been suggested as an alternative method for the control of this pathogen in aquaculture. However, effective use of bacteriophages in disease control requires detailed knowledge about the diversity and dynamics of host susceptibility to phage infection. For this reason, we examined the genetic diversity of 49 F. psychrophilum strains isolated in three different areas (Chile, Denmark, and USA) through direct genome restriction enzyme analysis (DGREA) and their susceptibility to 33 bacteriophages isolated in Chile and Denmark, thus covering large geographical (>12,000 km) and temporal (>60 years) scales of isolation. An additional 40 phage-resistant isolates obtained from culture experiments after exposure to specific phages were examined for changes in phage susceptibility against the 33 phages. The F. psychrophilum and phage populations isolated from Chile and Denmark clustered into geographically distinct groups with respect to DGREA profile and host range, respectively. However, cross infection between Chilean phage isolates and Danish host isolates and vice versa was observed. Development of resistance to certain bacteriophages led to susceptibility to other phages suggesting that "enhanced infection" is potentially an important cost of resistance in F. psychrophilum, possibly contributing to the observed co-existence of phage-sensitive F. psychrophilum strains and lytic phages across local and global scales. Overall, our results showed that despite the identification of local communities of phages and hosts, some key properties determining phage infection patterns seem to be globally distributed.

Genetic Resistance to Rhabdovirus Infection in Teleost Fish Is Paralleled to the Derived Cell Resistance Status

PubMed Central

Verrier, Eloi R.; Langevin, Christelle; Tohry, Corinne; Houel, Armel; Ducrocq, Vincent; Benmansour, Abdenour; Quillet, Edwige; Boudinot, Pierre

2012-01-01

Genetic factors of resistance and predisposition to viral diseases explain a significant part of the clinical variability observed within host populations. Predisposition to viral diseases has been associated to MHC haplotypes and T cell immunity, but a growing repertoire of innate/intrinsic factors are implicated in the genetic determinism of the host susceptibility to viruses. In a long-term study of the genetics of host resistance to fish rhabdoviruses, we produced a collection of double-haploid rainbow trout clones showing a wide range of susceptibility to Viral Hemorrhagic Septicemia Virus (VHSV) waterborne infection. The susceptibility of fibroblastic cell lines derived from these clonal fish was fully consistent with the susceptibility of the parental fish clones. The mechanisms determining the host resistance therefore did not associate with specific host immunity, but rather with innate or intrinsic factors. One cell line was resistant to rhabdovirus infection due to the combination of an early interferon IFN induction - that was not observed in the susceptible cells - and of yet unknown factors that hamper the first steps of the viral cycle. The implication of IFN was well consistent with the wide range of resistance of this genetic background to VSHV and IHNV, to the birnavirus IPNV and the orthomyxovirus ISAV. Another cell line was even more refractory to the VHSV infection through different antiviral mechanisms. This collection of clonal fish and isogenic cell lines provides an interesting model to analyze the relative contribution of antiviral pathways to the resistance to different viruses. PMID:22514610

Light quantity and photosystem function mediate host susceptibility to turnip mosaic virus via a salicylic acid-independent mechanism

USDA-ARS?s Scientific Manuscript database

Evidence going as far back as the early part of the 20th century suggests that both light and chloroplast function may play key roles in host susceptibility to viruses. Despite the long history of such work, confirmation of these phenomena and a determination of the underlying mechanisms remain elu...

An experimental conflict of interest between parasites reveals the mechanism of host manipulation

PubMed Central

Milinski, Manfred

2016-01-01

Parasites can increase their host’s predation susceptibility. It is a long-standing puzzle, whether this is caused by host manipulation, an evolved strategy of the parasite, or by side effects due to, for example, the parasite consuming energy from its host thereby changing the host’s trade-off between avoiding predation and foraging toward foraging. Here, we use sequential infection of three-spined sticklebacks with the cestode Schistocephalus solidus so that parasites have a conflict of interest over the direction of host manipulation. With true manipulation, the not yet infective parasite should reduce rather than enhance risk taking because predation would be fatal for its fitness; if host behavior is changed by a side effect, the 2 parasites would add their increase of predation risk because both drain energy. Our results support the latter hypothesis. In an additional experiment, we tested both infected and uninfected fish either starved or satiated. True host manipulation should act independently of the fish’s hunger status and continue when energy drain is balanced through satiation. Starvation and satiation affect the risk averseness of infected sticklebacks similarly to that of uninfected starved and satiated ones. Increased energy drain rather than active host manipulation dominates behavioral changes of S. solidus-infected sticklebacks. PMID:27004014

Aspergillosis and stem cell transplantation: An overview of experimental pathogenesis studies.

PubMed

Al-Bader, Nadia; Sheppard, Donald C

2016-11-16

Invasive aspergillosis is a life-threatening infection caused by the opportunistic filamentous fungus Aspergillus fumigatus. Patients undergoing haematopoietic stem cell transplant (HSCT) for the treatment of hematological malignancy are at particularly high risk of developing this fatal infection. The susceptibility of HSCT patients to infection with A. fumigatus is a consequence of a complex interplay of both fungal and host factors. Here we review our understanding of the host-pathogen interactions underlying the susceptibility of the immunocompromised host to infection with A. fumigatus with a focus on the experimental validation of fungal and host factors relevant to HSCT patients. These include fungal factors such as secondary metabolites, cell wall constituents, and metabolic adaptations that facilitate immune evasion and survival within the host microenvironment, as well as the innate and adaptive immune responses involved in host defense against A. fumigatus.

The host-pathogen interaction between wheat and yellow rust induces temporally coordinated waves of gene expression.

PubMed

Dobon, Albor; Bunting, Daniel C E; Cabrera-Quio, Luis Enrique; Uauy, Cristobal; Saunders, Diane G O

2016-05-20

Understanding how plants and pathogens modulate gene expression during the host-pathogen interaction is key to uncovering the molecular mechanisms that regulate disease progression. Recent advances in sequencing technologies have provided new opportunities to decode the complexity of such interactions. In this study, we used an RNA-based sequencing approach (RNA-seq) to assess the global expression profiles of the wheat yellow rust pathogen Puccinia striiformis f. sp. tritici (PST) and its host during infection. We performed a detailed RNA-seq time-course for a susceptible and a resistant wheat host infected with PST. This study (i) defined the global gene expression profiles for PST and its wheat host, (ii) substantially improved the gene models for PST, (iii) evaluated the utility of several programmes for quantification of global gene expression for PST and wheat, and (iv) identified clusters of differentially expressed genes in the host and pathogen. By focusing on components of the defence response in susceptible and resistant hosts, we were able to visualise the effect of PST infection on the expression of various defence components and host immune receptors. Our data showed sequential, temporally coordinated activation and suppression of expression of a suite of immune-response regulators that varied between compatible and incompatible interactions. These findings provide the framework for a better understanding of how PST causes disease and support the idea that PST can suppress the expression of defence components in wheat to successfully colonize a susceptible host.

Post-infectious immune suppression: a new paradigm of severe infections.

PubMed

Grimaldi, D; Llitjos, J F; Pène, F

2014-10-01

Infectious diseases remain a major public health issue in both developing and developed countries. For instance, there is still a high rate of morbidity and mortality due to seasonal influenza outbreaks and severe bacterial sepsis, despite major advances in their prevention and treatment. It is now clear that severe influenza and bacterial infections promote susceptibility for superinfections worsening the prognosis. Various immune defects acquired during severe infection may result in complex immunosuppression and may affect both innate and adaptive components. Some animal models of these common clinical situations have demonstrated the increased susceptibility of infected hosts to secondary infectious insult and allowed assessing the regulatory mechanisms. Such pathophysiological advances may help create new immunomodulatory therapeutics for infected patients exposed to severe secondary sepsis. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

In vitro encystment of Himasthla elongata cercariae (Digenea, Echinostomatidae) in the haemolymph of blue mussels Mytilus edulis as a tool for assessing cercarial infectivity and molluscan susceptibility.

PubMed

Levakin, I A; Losev, E A; Nikolaev, K E; Galaktionov, K V

2013-06-01

Infectivity of Himasthla elongata cercariae to mussels, their second intermediate hosts, and resistance by these hosts to infection were assessed on the basis of the cercariae's ability to encyst in mussel haemolymph in vitro. A series of experimental in vivo infections of mussels with batches of cercariae, each batch released from a different single infected mollusc and referred to as a clone (due to their shared genotype), demonstrated that the results of the in vitro tests corresponded to the actual indices of infectivity/susceptibility of the parasites and their hosts. Most cercarial clones had high infectivity, with a few clones having very high or, at the other extreme, very low infectivity. A similar pattern was revealed in mussel resistance to cercarial infection. Most of the molluscs tested were moderately susceptible to cercarial infection, but at each extreme a small fraction (less than 10%) displayed very high or very low susceptibility. It was shown that there were no totally compatible or totally incompatible 'cercaria clone/mussel' combinations. Results obtained are compared with the data on intra-population variability using the characters parasite infectivity/host compatibility for trematode/mollusc-first intermediate host associations. Results are made relevant to actual infection levels in mussel settlements at the White Sea.

Temperature and population density: interactional effects of environmental factors on phenotypic plasticity, immune defenses, and disease resistance in an insect pest.

PubMed

Silva, Farley W S; Elliot, Simon L

2016-06-01

Temperature and crowding are key environmental factors mediating the transmission and epizooty of infectious disease in ectotherm animals. The host physiology may be altered in a temperature-dependent manner and thus affects the pathogen development and course of diseases within an individual and host population, or the transmission rates (or infectivity) of pathogens shift linearly with the host population density. To our understanding, the knowledge of interactive and synergistic effects of temperature and population density on the host-pathogen system is limited. Here, we tested the interactional effects of these environmental factors on phenotypic plasticity, immune defenses, and disease resistance in the velvetbean caterpillar Anticarsia gemmatalis . Upon egg hatching, caterpillars were reared in thermostat-controlled chambers in a 2 × 4 factorial design: density (1 or 8 caterpillars/pot) and temperature (20, 24, 28, or 32°C). Of the immune defenses assessed, encapsulation response was directly affected by none of the environmental factors; capsule melanization increased with temperature in both lone- and group-reared caterpillars, although the lone-reared ones presented the most evident response, and hemocyte numbers decreased with temperature regardless of the population density. Temperature, but not population density, affected considerably the time from inoculation to death of velvetbean caterpillar. Thus, velvetbean caterpillars succumbed to Anticarsia gemmatalis multiple nucleopolyhedrovirus (AgMNPV) more quickly at higher temperatures than at lower temperatures. As hypothesized, temperature likely affected caterpillars' movement rates, and thus the contact between conspecifics, which in turn affected the phenotypic expression of group-reared caterpillars. Our results suggest that environmental factors, mainly temperature, strongly affect both the course of disease in velvetbean caterpillar population and its defenses against pathogens. As a soybean pest, velvetbean caterpillar may increase its damage on soybean fields under a scenario of global warming as caterpillars may reach the developmental resistance faster, and thus decrease their susceptibility to biological control by AgMNPV.

Effects of Spinosad, Imidacloprid, and Lambda-cyhalothrin on Survival, Parasitism, and Reproduction of the Aphid Parasitoid Aphidius colemani.

PubMed

D'Ávila, Vinicius A; Barbosa, Wagner F; Guedes, Raul N C; Cutler, G Christopher

2018-05-28

Insecticides can affect biological control by parasitoids. Here, we examined the lethal and sublethal effects of two conventional insecticides, imidacloprid and lambda-cyhalothrin, and a reduced-risk bioinsecticide, spinosad, on the aphid parasitoid Aphidius colemani Viereck (Hymenoptera: Braconidae). Concentration-mortality curves generated from insecticide residue bioassays found that wasps were nearly 20-fold more susceptible to spinosad than imidacloprid and lambda-cyhalothrin. Imidacloprid and lambda-cyhalothrin compromised adult parasitoid longevity, but not as dramatically as spinosad: concentrations >200 ng spinosad/cm2 reduced wasp longevity by half. Imidacloprid and lambda-cyhalothrin also compromised aphid parasitism by wasps. Although increasing imidacloprid concentrations led to increased host viability and reduced progeny production, lambda-cyhalothrin did not affect viability of parasitized hosts or parasitoid progeny production in a dose-dependent manner. Our results demonstrate that reduced risk bioinsecticide products like spinosad can be more toxic to biological control agents than certain conventional insecticides.

Development and infectious disease in hosts with complex life cycles.

PubMed

Searle, Catherine L; Xie, Gisselle Yang; Blaustein, Andrew R

2013-01-01

Metamorphosis is often characterized by profound changes in morphology and physiology that can affect the dynamics of species interactions. For example, the interaction between a pathogen and its host may differ depending on the life stage of the host or pathogen. One pathogen that infects hosts with complex life cycles is the emerging fungal pathogen of amphibians, Batrachochytrium dendrobatidis (Bd). We sought to determine how conditions at the larval stage can affect variation in development and patterns of Bd infection across amphibian life stages. We used outdoor experimental mesocosms to simulate natural pond habitats and manipulated the presence of Bd, the larval density, and the number of host species in larvae of two co-occurring amphibian species (Rana cascadae and Pseudacris regilla). We found that infection differed between species throughout development; P. regilla consistently had higher infection severity compared to R. cascadae. Additionally, while up to 100% of larvae were infected, only 18.2% of R. cascadae and 81.5% of P. regilla were infected after metamorphosis. This indicates that amphibians have the ability to recover from Bd infection as they undergo metamorphosis. Higher larval densities in P. regilla led to a shorter larval period, and individuals with a shorter larval period had lower infection severity. This led to a trend where P. regilla larvae reared at high densities tended to have lower infection prevalence after metamorphosis. We also found that exposure to Bd increased larval mortality and prolonged the larval period in P. regilla, indicating that P. regilla are susceptible to the negative effects of Bd as larvae. This study demonstrates that host density, species composition, and pathogen exposure may all interact to influence development and infection in hosts with complex life cycles.

Gut Dysbiosis in Animals Due to Environmental Chemical Exposures

PubMed Central

Rosenfeld, Cheryl S.

2017-01-01

The gut microbiome consists of over 103–104 microorganism inhabitants that together possess 150 times more genes that the human genome and thus should be considered an “organ” in of itself. Such communities of bacteria are in dynamic flux and susceptible to changes in host environment and body condition. In turn, gut microbiome disturbances can affect health status of the host. Gut dysbiosis might result in obesity, diabetes, gastrointestinal, immunological, and neurobehavioral disorders. Such host diseases can originate due to shifts in microbiota favoring more pathogenic species that produce various virulence factors, such as lipopolysaccharide. Bacterial virulence factors and metabolites may be transmitted to distal target sites, including the brain. Other potential mechanisms by which gut dysbiosis can affect the host include bacterial-produced metabolites, production of hormones and factors that mimic those produced by the host, and epimutations. All animals, including humans, are exposed daily to various environmental chemicals that can influence the gut microbiome. Exposure to such chemicals might lead to downstream systemic effects that occur secondary to gut microbiome disturbances. Increasing reports have shown that environmental chemical exposures can target both host and the resident gut microbiome. In this review, we will first consider the current knowledge of how endocrine disrupting chemicals (EDCs), heavy metals, air pollution, and nanoparticles can influence the gut microbiome. The second part of the review will consider how potential environmental chemical-induced gut microbiome changes might subsequently induce pathophysiological responses in the host, although definitive evidence for such effects is still lacking. By understanding how these chemicals result in gut dysbiosis, it may open up new remediation strategies in animals, including humans, exposed to such chemicals. PMID:28936425

Enhanced transcriptomic responses in the Pacific salmon louse Lepeophtheirus salmonis oncorhynchi to the non-native Atlantic Salmon Salmo salar suggests increased parasite fitness.

PubMed

Braden, Laura M; Sutherland, Ben J G; Koop, Ben F; Jones, Simon R M

2017-01-30

Outcomes of infections with the salmon louse Lepeophtheirus salmonis vary considerably among its natural hosts (Salmo, Oncorhynchus spp.). Host-parasite interactions range from weak to strong host responses accompanied by high to low parasite abundances, respectively. Parasite behavioral studies indicate that the louse prefers the host Atlantic Salmon (Salmo salar), which is characterized by a weak immune response, and that this results in enhanced parasite reproduction and growth rates. Furthermore, parasite-derived immunosuppressive molecules (e.g., proteases) have been detected at higher amounts in response to the mucus of Atlantic Salmon relative to Coho Salmon (Oncorhynchus kisutch). However, the host-specific responses of the salmon louse have not been well characterized in either of the genetically distinct sub-species that occur in the Atlantic and Pacific Oceans. We assessed and compared the transcriptomic feeding response of the Pacific salmon louse (L. salmonis oncorhynchi,) while parasitizing the highly susceptible Atlantic Salmon and Sockeye Salmon (Oncorhynchus nerka) or the more resistant Coho Salmon (Oncorhynchus kisutch) using a 38 K oligonucleotide microarray. The response of the louse was enhanced both in the number of overexpressed genes and in the magnitude of expression while feeding on the non-native Atlantic Salmon, compared to either Coho or Sockeye Salmon. For example, putative virulence factors (e.g., cathepsin L, trypsin, carboxypeptidase B), metabolic enzymes (e.g., cytochrome B, cytochrome C), protein synthesis enzymes (e.g., ribosomal protein P2, 60S ribosomal protein L7), and reproduction-related genes (e.g., estrogen sulfotransferase) were overexpressed in Atlantic-fed lice, indicating heightened parasite fitness with this host species. In contrast, responses in Coho- or Sockeye-fed lice were more similar to those of parasites deprived of a host. To test for host acclimation by the parasite, we performed a reciprocal host transfer experiment and determined that the exaggerated response to Atlantic Salmon was independent of the initial host species, confirming our conclusion that the Pacific salmon louse exhibits an enhanced response to Atlantic Salmon. This study characterized global transcriptomic responses of Pacific salmon lice during infection of susceptible and resistant hosts. Similar parasite responses during infection of Coho or Sockeye Salmon, despite differences in natural immunity to infection between these host species, indicate that host susceptibility status alone does not drive the parasite response. We identified an enhanced louse response after feeding on Atlantic Salmon, characterized by up-regulation of virulence factors, energy metabolism and reproductive-associated transcripts. In contrast, the responses of lice infecting Coho or Sockeye Salmon were weaker, with reduced expression of virulence factors. These observations indicate that the response of the louse is independent of host susceptibility and suggest that co-evolutionary host-parasite relationships may influence contemporary host-parasite interactions. This research improves our understanding of the susceptibility of Atlantic Salmon and may assist in the development of novel control measures against the salmon louse.

Grape Cultivar and Sap Culture Conditions Affect the Development of Xylella fastidiosa Phenotypes Associated with Pierce's Disease.

PubMed

Hao, Lingyun; Zaini, Paulo A; Hoch, Harvey C; Burr, Thomas J; Mowery, Patricia

2016-01-01

Xylella fastidiosa is a xylem-limited bacterium in plant hosts and causes Pierce's disease (PD) of grapevines, which differ in susceptibility according to the Vitis species (spp.). In this work we compared X. fastidiosa biofilm formation and population dynamics when cultured in xylem saps from PD-susceptible and -resistant Vitis spp. under different conditions. Behaviors in a closed-culture system were compared to those in different sap-renewal cultures that would more closely mimic the physicochemical environment encountered in planta. Significant differences in biofilm formation and growth in saps from PD-susceptible and -resistant spp. were only observed using sap renewal culture. Compared to saps from susceptible V. vinifera, those from PD-resistant V. aestivalis supported lower titers of X. fastidiosa and less biofilm and V. champinii suppressed both growth and biofilm formation, behaviors which are correlated with disease susceptibility. Furthermore, in microfluidic chambers X. fastidiosa formed thick mature biofilm with three-dimensional (3-D) structures, such as pillars and mounds, in saps from all susceptible spp. In contrast, only small aggregates of various shapes were formed in saps from four out of five of the resistant spp.; sap from the resistant spp. V. mustangensis was an exception in that it also supported thick lawns of biofilm but not the above described 3-D structures typically seen in a mature biofilm from the susceptible saps. Our findings provide not only critical technical information for future bioassays, but also suggest further understanding of PD susceptibility.

Toxoplasmosis and Polygenic Disease Susceptibility Genes: Extensive Toxoplasma gondii Host/Pathogen Interactome Enrichment in Nine Psychiatric or Neurological Disorders.

PubMed

Carter, C J

2013-01-01

Toxoplasma gondii is not only implicated in schizophrenia and related disorders, but also in Alzheimer's or Parkinson's disease, cancer, cardiac myopathies, and autoimmune disorders. During its life cycle, the pathogen interacts with ~3000 host genes or proteins. Susceptibility genes for multiple sclerosis, Alzheimer's disease, schizophrenia, bipolar disorder, depression, childhood obesity, Parkinson's disease, attention deficit hyperactivity disorder (P  from  8.01E - 05  (ADHD)  to  1.22E - 71) (multiple sclerosis), and autism (P = 0.013), but not anorexia or chronic fatigue are highly enriched in the human arm of this interactome and 18 (ADHD) to 33% (MS) of the susceptibility genes relate to it. The signalling pathways involved in the susceptibility gene/interactome overlaps are relatively specific and relevant to each disease suggesting a means whereby susceptibility genes could orient the attentions of a single pathogen towards disruption of the specific pathways that together contribute (positively or negatively) to the endophenotypes of different diseases. Conditional protein knockdown, orchestrated by T. gondii proteins or antibodies binding to those of the host (pathogen derived autoimmunity) and metabolite exchange, may contribute to this disruption. Susceptibility genes may thus be related to the causes and influencers of disease, rather than (and as well as) to the disease itself.

SELENIUM-DEFICIENCY MODIFIES INFLUENZA INFECTION OF DIFFERENTIATED HUMAN BRONCHIAL EPITHELIAL CELLS

EPA Science Inventory

The nutritional status of the host is important in the defense against invading pathogens. Many studies regarding the effects of host nutritional status on the immune response have demonstrated that suboptimal host nutrition results in impaired host immunity and increased suscept...

The infective cycle of Cabbage leaf curl virus (CaLCuV) is affected by CRUMPLED LEAF (CRL) gene in Arabidopsis thaliana

PubMed Central

Trejo-Saavedra, Diana L; Vielle-Calzada, Jean P; Rivera-Bustamante, Rafael F

2009-01-01

Background Geminiviruses are single-stranded DNA viruses that cause serious crop losses worldwide. Successful infection by these pathogens depends extensively on virus-host intermolecular interactions that allow them to express their gene products, to replicate their genomes and to move to adjacent cells and throughout the plant. Results To identify host genes that show an altered regulation in response to Cabbage leaf curl virus (CaLCuV) infection, a screening of transposant Arabidopsis thaliana lines was carried out. Several genes were identified to be virus responsive and one, Crumpled leaf (CRL) gene, was selected for further characterization. CRL was previously reported by Asano et al., (2004) to affect the morphogenesis of all plant organs and the division of plastids. We report here that CRL expression, during CaLCuV infection, shows a short but strong induction at an early stage (3-5 days post inoculation, dpi). To study the role of CRL in CaLCuV infection, CRL over-expressing and silenced transgenic plants were generated. We compared the replication, movement and infectivity of CaLCuV in transgenic and wild type plants. Conclusion Our results showed that CRL over-expressing plants showed an increased susceptibility to CaLCuV infection (as compared to wt plants) whereas CRL-silenced plants, on the contrary, presented a reduced susceptibility to viral infection. The possible role of CRL in the CaLCuV infection cycle is discussed. PMID:19840398

Intestinal Epithelial Toll-Like Receptor 4 Signaling Affects Epithelial Function and Colonic Microbiota and Promotes a Risk for Transmissible Colitis

PubMed Central

Dheer, Rishu; Santaolalla, Rebeca; Davies, Julie M.; Lang, Jessica K.; Phillips, Matthew C.; Pastorini, Cristhine; Vazquez-Pertejo, Maria T.

2016-01-01

Evidence obtained from gene knockout studies supports the role of Toll-like receptor 4 (TLR4) in intestinal inflammation and microbiota recognition. Increased epithelial TLR4 expression is observed in patients with inflammatory bowel disease. However, little is known of the effect of increased TLR4 signaling on intestinal homeostasis. Here, we examined the effect of increased TLR4 signaling on epithelial function and microbiota by using transgenic villin-TLR4 mice that overexpress TLR4 in the intestinal epithelium. Our results revealed that villin-TLR4 mice are characterized by increases in the density of mucosa-associated bacteria and bacterial translocation. Furthermore, increased epithelial TLR4 signaling was associated with an impaired epithelial barrier, altered expression of antimicrobial peptide genes, and altered epithelial cell differentiation. The composition of the colonic luminal and mucosa-associated microbiota differed between villin-TLR4 and wild-type (WT) littermates. Interestingly, WT mice cohoused with villin-TLR4 mice displayed greater susceptibility to acute colitis than singly housed WT mice did. The results of this study suggest that epithelial TLR4 expression shapes the microbiota and affects the functional properties of the epithelium. The changes in the microbiota induced by increased epithelial TLR4 signaling are transmissible and exacerbate dextran sodium sulfate-induced colitis. Together, our findings imply that host innate immune signaling can modulate intestinal bacteria and ultimately the host's susceptibility to colitis. PMID:26755160

A unifying theory for genetic epidemiological analysis of binary disease data

PubMed Central

2014-01-01

Background Genetic selection for host resistance offers a desirable complement to chemical treatment to control infectious disease in livestock. Quantitative genetics disease data frequently originate from field studies and are often binary. However, current methods to analyse binary disease data fail to take infection dynamics into account. Moreover, genetic analyses tend to focus on host susceptibility, ignoring potential variation in infectiousness, i.e. the ability of a host to transmit the infection. This stands in contrast to epidemiological studies, which reveal that variation in infectiousness plays an important role in the progression and severity of epidemics. In this study, we aim at filling this gap by deriving an expression for the probability of becoming infected that incorporates infection dynamics and is an explicit function of both host susceptibility and infectiousness. We then validate this expression according to epidemiological theory and by simulating epidemiological scenarios, and explore implications of integrating this expression into genetic analyses. Results Our simulations show that the derived expression is valid for a range of stochastic genetic-epidemiological scenarios. In the particular case of variation in susceptibility only, the expression can be incorporated into conventional quantitative genetic analyses using a complementary log-log link function (rather than probit or logit). Similarly, if there is moderate variation in both susceptibility and infectiousness, it is possible to use a logarithmic link function, combined with an indirect genetic effects model. However, in the presence of highly infectious individuals, i.e. super-spreaders, the use of any model that is linear in susceptibility and infectiousness causes biased estimates. Thus, in order to identify super-spreaders, novel analytical methods using our derived expression are required. Conclusions We have derived a genetic-epidemiological function for quantitative genetic analyses of binary infectious disease data, which, unlike current approaches, takes infection dynamics into account and allows for variation in host susceptibility and infectiousness. PMID:24552188

A unifying theory for genetic epidemiological analysis of binary disease data.

PubMed

Lipschutz-Powell, Debby; Woolliams, John A; Doeschl-Wilson, Andrea B

2014-02-19

Genetic selection for host resistance offers a desirable complement to chemical treatment to control infectious disease in livestock. Quantitative genetics disease data frequently originate from field studies and are often binary. However, current methods to analyse binary disease data fail to take infection dynamics into account. Moreover, genetic analyses tend to focus on host susceptibility, ignoring potential variation in infectiousness, i.e. the ability of a host to transmit the infection. This stands in contrast to epidemiological studies, which reveal that variation in infectiousness plays an important role in the progression and severity of epidemics. In this study, we aim at filling this gap by deriving an expression for the probability of becoming infected that incorporates infection dynamics and is an explicit function of both host susceptibility and infectiousness. We then validate this expression according to epidemiological theory and by simulating epidemiological scenarios, and explore implications of integrating this expression into genetic analyses. Our simulations show that the derived expression is valid for a range of stochastic genetic-epidemiological scenarios. In the particular case of variation in susceptibility only, the expression can be incorporated into conventional quantitative genetic analyses using a complementary log-log link function (rather than probit or logit). Similarly, if there is moderate variation in both susceptibility and infectiousness, it is possible to use a logarithmic link function, combined with an indirect genetic effects model. However, in the presence of highly infectious individuals, i.e. super-spreaders, the use of any model that is linear in susceptibility and infectiousness causes biased estimates. Thus, in order to identify super-spreaders, novel analytical methods using our derived expression are required. We have derived a genetic-epidemiological function for quantitative genetic analyses of binary infectious disease data, which, unlike current approaches, takes infection dynamics into account and allows for variation in host susceptibility and infectiousness.

Brachypodium distachyon as alternative model host system for the ergot fungus Claviceps purpurea.

PubMed

Kind, Sabine; Schurack, Selma; Hinsch, Janine; Tudzynski, Paul

2018-04-01

To investigate its susceptibility to ergot infection, we inoculated Brachypodium distachyon with Claviceps purpurea and compared the infection symptoms with those on rye (Secale cereale). We showed that, after inoculation of Brachypodium with Claviceps, the same disease symptoms occurred in comparable temporal and spatial patterns to those on rye. The infection rate of Claviceps on this host was reduced compared with rye, but the disease could be surveyed by fungal genomic DNA quantification. Mutants of Claviceps which were virulence attenuated on rye were also affected on Brachypodium. We were able to show that pathogenesis-related gene expression changed in a typical manner for biotrophic pathogen attack. Our results indicated that the Claviceps-Brachypodium interaction was dependent on salicylic acid, cytokinin and auxin. We consider Brachypodium to be a suitable and useful alternative host; the increased sensitivity compared with rye will be valuable for the identification of infection mechanisms. Future progess in understanding the Claviceps-plant interaction will be facilitated by the use of a well-characterized model host system. © 2017 BSPP AND JOHN WILEY & SONS LTD.

Host adaptation to viruses relies on few genes with different cross-resistance properties

PubMed Central

Martins, Nelson E.; Faria, Vítor G.; Nolte, Viola; Schlötterer, Christian; Teixeira, Luis; Sucena, Élio; Magalhães, Sara

2014-01-01

Host adaptation to one parasite may affect its response to others. However, the genetics of these direct and correlated responses remains poorly studied. The overlap between these responses is instrumental for the understanding of host evolution in multiparasite environments. We determined the genetic and phenotypic changes underlying adaptation of Drosophila melanogaster to Drosophila C virus (DCV). Within 20 generations, flies selected with DCV showed increased survival after DCV infection, but also after cricket paralysis virus (CrPV) and flock house virus (FHV) infection. Whole-genome sequencing identified two regions of significant differentiation among treatments, from which candidate genes were functionally tested with RNAi. Three genes were validated—pastrel, a known DCV-response gene, and two other loci, Ubc-E2H and CG8492. Knockdown of Ubc-E2H and pastrel also led to increased sensitivity to CrPV, whereas knockdown of CG8492 increased susceptibility to FHV infection. Therefore, Drosophila adaptation to DCV relies on few major genes, each with different cross-resistance properties, conferring host resistance to several parasites. PMID:24711428

Evaluating Weeds as Hosts of Tomato yellow leaf curl virus.

PubMed

Smith, Hugh A; Seijo, Teresa E; Vallad, Gary E; Peres, Natalia A; Druffel, Keri L

2015-08-01

Bemisia tabaci (Gennadius) biotype B transmits Tomato yellow leaf curl virus (TYLCV), which affects tomato production globally. Prompt destruction of virus reservoirs is a key component of virus management. Identification of weed hosts of TYLCV will be useful for reducing such reservoirs. The status of weeds as alternate hosts of TYLCV in Florida remains unclear. In greenhouse studies, B. tabaci adults from a colony reared on TYLCV-infected tomato were established in cages containing one of four weeds common to horticultural fields in central and south Florida. Cages containing tomato and cotton were also infested with viruliferous whiteflies as a positive control and negative control, respectively. Whitefly adults and plant tissue were tested periodically over 10 wk for the presence of TYLCV using PCR. After 10 wk, virus-susceptible tomato plants were placed in each cage to determine if whiteflies descended from the original adults were still infective. Results indicate that Bidens alba, Emilia fosbergii, and Raphanus raphanistrum are not hosts of TYLCV, and that Amaranthus retroflexus is a host. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Dynamics and profiles of a diffusive host-pathogen system with distinct dispersal rates

NASA Astrophysics Data System (ADS)

Wu, Yixiang; Zou, Xingfu

2018-04-01

In this paper, we investigate a diffusive host-pathogen model with heterogeneous parameters and distinct dispersal rates for the susceptible and infected hosts. We first prove that the solution of the model exists globally and the model system possesses a global attractor. We then identify the basic reproduction number R0 for the model and prove its threshold role: if R0 ≤ 1, the disease free equilibrium is globally asymptotically stable; if R0 > 1, the solution of the model is uniformly persistent and there exists a positive (pathogen persistent) steady state. Finally, we study the asymptotic profiles of the positive steady state as the dispersal rate of the susceptible or infected hosts approaches zero. Our result suggests that the infected hosts concentrate at certain points which can be characterized as the pathogen's most favoured sites when the mobility of the infected host is limited.

Experimental Infections of Wild Birds with West Nile Virus

PubMed Central

Pérez-Ramírez, Elisa; Llorente, Francisco; Jiménez-Clavero, Miguel Ángel

2014-01-01

Avian models of West Nile virus (WNV) disease have become pivotal in the study of infection pathogenesis and transmission, despite the intrinsic constraints that represents this type of experimental research that needs to be conducted in biosecurity level 3 (BSL3) facilities. This review summarizes the main achievements of WNV experimental research carried out in wild birds, highlighting advantages and limitations of this model. Viral and host factors that determine the infection outcome are analyzed in detail, as well as recent discoveries about avian immunity, viral transmission, and persistence achieved through experimental research. Studies of laboratory infections in the natural host will help to understand variations in susceptibility and reservoir competence among bird species, as well as in the epidemiological patterns found in different affected areas. PMID:24531334

Xanthomonas TAL effectors hijack host basal transcription factor IIA α and γ subunits for invasion.

PubMed

Ma, Ling; Wang, Qiang; Yuan, Meng; Zou, Tingting; Yin, Ping; Wang, Shiping

2018-02-05

The Xanthomonas genus includes Gram-negative plant-pathogenic bacteria, which infect a broad range of crops and wild plant species, cause symptoms with leaf blights, streaks, spots, stripes, necrosis, wilt, cankers and gummosis on leaves, stems and fruits in a wide variety of plants via injecting their effector proteins into the host cell during infection. Among these virulent effectors, transcription activator-like effectors (TALEs) interact with the γ subunit of host transcription factor IIA (TFIIAγ) to activate the transcription of host disease susceptibility genes. Functional TFIIA is a ternary complex comprising α, β and γ subunits. However, whether TALEs recruit TFIIAα, TFIIAβ, or both remains unknown. The underlying molecular mechanisms by which TALEs mediate host susceptibility gene activation require full elucidation. Here, we show that TALEs interact with the α+γ binary subcomplex but not the α+β+γ ternary complex of rice TFIIA (holo-OsTFIIA). The transcription factor binding (TFB) regions of TALEs, which are highly conserved in Xanthomonas species, have a dominant role in these interactions. Furthermore, the interaction between TALEs and the α+γ complex exhibits robust DNA binding activity in vitro. These results collectively demonstrate that TALE-carrying pathogens hijack the host basal transcription factors TFIIAα and TFIIAγ, but not TFIIAβ, to enhance host susceptibility during pathogen infection. The uncovered mechanism widens new insights on host-microbe interaction and provide an applicable strategy to breed high-resistance crop varieties. Copyright © 2018 Elsevier Inc. All rights reserved.

Reduced susceptibility of tomato stem to the necrotrophic fungus Botrytis cinerea is associated with a specific adjustment of fructose content in the host sugar pool

PubMed Central

Nicot, Philippe C.; Ripoll, Julie; Abro, Manzoor A.; Raimbault, Astrid K.; Lopez-Lauri, Félicie; Bertin, Nadia

2017-01-01

Background and aims Plant soluble sugars, as main components of primary metabolism, are thought to be implicated in defence against pathogenic fungi. However, the function of sucrose and hexoses remains unclear. This study aimed to identify robust patterns in the dynamics of soluble sugars in sink tissues of tomato plants during the course of infection by the necrotrophic fungus Botrytis cinerea. Distinct roles for glucose and fructose in defence against B. cinerea were hypothesized. Methods We examined sugar contents and defence hormonal markers in tomato stem tissues before and after infection by B. cinerea, in a range of abiotic environments created by various nitrogen and water supplies. Key Results Limited nitrogen or water supplies increased tomato stem susceptibility to B. cinerea. Glucose and fructose contents of tissues surrounding infection sites evolved differently after inoculation. The fructose content never decreased after inoculation with B. cinerea, while that of glucose showed either positive or negative variation, depending on the abiotic environment. An increase in the relative fructose content (defined as the proportion of fructose in the soluble sugar pool) was observed in the absence of glucose accumulation and was associated with lower susceptibility. A lower expression of the salicylic acid marker PR1a, and a lower repression of a jasmonate marker COI1 were associated with reduced susceptibility. Accordingly, COI1 expression was positively correlated with the relative fructose contents 7 d after infection. Conclusions Small variations of fructose content among the sugar pool are unlikely to affect intrinsic pathogen growth. Our results highlight distinct use of host glucose and fructose after infection by B. cinerea and suggest strongly that adjustment of the relative fructose content is required for enhanced plant defence. PMID:28065923

Oscillations in epidemic models with spread of awareness.

PubMed

Just, Winfried; Saldaña, Joan; Xin, Ying

2018-03-01

We study ODE models of epidemic spreading with a preventive behavioral response that is triggered by awareness of the infection. Previous studies of such models have mostly focused on the impact of the response on the initial growth of an outbreak and the existence and location of endemic equilibria. Here we study the question whether this type of response is sufficient to prevent future flare-ups from low endemic levels if awareness is assumed to decay over time. In the ODE context, such flare-ups would translate into sustained oscillations with significant amplitudes. Our results show that such oscillations are ruled out in Susceptible-Aware-Infectious-Susceptible models with a single compartment of aware hosts, but can occur if we consider two distinct compartments of aware hosts who differ in their willingness to alert other susceptible hosts.

Applications of biological control in resistant host-pathogen systems.

PubMed

White, Steven M; White, K A Jane

2005-09-01

Insect pest species can have devastating effects on crops. Control of these insect pests is usually achieved by using chemical insecticides. However, there has been much cause for concern with their overuse. Consequently, research has been carried out into alternative forms of control, in particular biological control methods. Recent laboratory studies have indicated that these natural forms of control can induce resistant strains of insect pest. In this paper we present a discrete-time host-pathogen model to describe the interaction between a host (insect species) that can develop a resistant strain and a pathogen (biological control) that can be externally applied to the system. For this model we use a single-state variable for the host population. We show that the proportion of resistance in the population impacts on the viability of the host population. Moreover, when the host population does persist, we explore the interaction between host susceptibility and host population levels. The different scenarios which arise are explained ecologically in terms of trade-offs in intrinsic growth rates, disease susceptibility and intraspecific host competition for the resistant subclass.

Die another day: molecular mechanisms of effector-triggered immunity elicited by type III secreted effector proteins

USDA-ARS?s Scientific Manuscript database

Bacterial pathogens inject type III secreted effector (T3SE) proteins into their hosts where they display dual roles depending on the host genotype. T3SEs promote bacterial virulence in susceptible hosts, and elicit immunity in resistant hosts. T3SEs are typically recognized when they modify a host ...

Influence of predation on community resilience to disease.

PubMed

Al-Shorbaji, Farah; Roche, Benjamin; Britton, Robert; Andreou, Demetra; Gozlan, Rodolphe

2017-09-01

Outbreaks of generalist pathogens are influenced by host community structure, including population density and species diversity. Within host communities predation can influence pathogen transmission rates, prevalence and impacts. However, the influence of predation on community resilience to outbreaks of generalist pathogens is not fully understood. The role of predation on host community resilience to disease was assessed using an epidemiological multi-host susceptible-exposed-infectious-recovered model. Sphaerothecum destruens, an emerging fungal-like generalist pathogen, was used as a model pathogen. Six cyprinid and salmonid fishes, including an asymptomatic carrier, were selected as model hosts that are known to be impacted by S. destruens, and they were used within a model host community. Pathogen release into the host community was via introduction of the asymptomatic carrier. Mortality from infection, pathogen incubation rate, and host recovery rate were set to a range of evidence-based values in each species and were varied in secondary consumers to predict top-down effects of infection on the resilience of a host community. Predation pressure within the fish community was varied to test its effects on infection prevalence and host survival in the community. Model predictions suggested that predation of the asymptomatic hosts by fishes in the host community was insufficient to eliminate S. destruens. Sphaerothecum destruens persisted in the community due to its rapid transmission from the asymptomatic host to susceptible host fishes. Following transmission, pathogen prevalence in the community was driven by transmission within and between susceptible host fishes, indicating low host community resilience. However, introducing low densities of a highly specific piscivorous fish into the community to pre-date asymptomatic hosts could limit pathogen prevalence in the host community, thus increasing resilience. The model predictions indicate that whilst resilience to this generalist pathogen in the host community was low, this could be increased using management interventions. The results suggest that this model has high utility for predicting community resilience to disease and thus can be applied to other generalist parasites to determine risks of disease emergence. © 2017 The Authors. Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.

Design of vaccination and fumigation on Host-Vector Model by input-output linearization method

NASA Astrophysics Data System (ADS)

Nugraha, Edwin Setiawan; Naiborhu, Janson; Nuraini, Nuning

2017-03-01

Here, we analyze the Host-Vector Model and proposed design of vaccination and fumigation to control infectious population by using feedback control especially input-output liniearization method. Host population is divided into three compartments: susceptible, infectious and recovery. Whereas the vector population is divided into two compartment such as susceptible and infectious. In this system, vaccination and fumigation treat as input factors and infectious population as output result. The objective of design is to stabilize of the output asymptotically tend to zero. We also present the examples to illustrate the design model.

Trace Fossil Evidence of Trematode-Bivalve Parasite-Host Interactions in Deep Time.

PubMed

Huntley, John Warren; De Baets, Kenneth

2015-01-01

Parasitism is one of the most pervasive phenomena amongst modern eukaryotic life and yet, relative to other biotic interactions, almost nothing is known about its history in deep time. Digenean trematodes (Platyhelminthes) are complex life cycle parasites, which have practically no body fossil record, but induce the growth of characteristic malformations in the shells of their bivalve hosts. These malformations are readily preserved in the fossil record, but, until recently, have largely been overlooked by students of the fossil record. In this review, we present the various malformations induced by trematodes in bivalves, evaluate their distribution through deep time in the phylogenetic and ecological contexts of their bivalve hosts and explore how various taphonomic processes have likely biased our understanding of trematodes in deep time. Trematodes are known to negatively affect their bivalve hosts in a number of ways including castration, modifying growth rates, causing immobilization and, in some cases, altering host behaviour making the host more susceptible to their own predators. Digeneans are expected to be significant agents of natural selection. To that end, we discuss how bivalves may have adapted to their parasites via heterochrony and suggest a practical methodology for testing such hypotheses in deep time. Copyright © 2015 Elsevier Ltd. All rights reserved.

Amphibian chytridiomycosis: a review with focus on fungus-host interactions.

PubMed

Van Rooij, Pascale; Martel, An; Haesebrouck, Freddy; Pasmans, Frank

2015-11-25

Amphibian declines and extinctions are emblematic for the current sixth mass extinction event. Infectious drivers of these declines include the recently emerged fungal pathogens Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans (Chytridiomycota). The skin disease caused by these fungi is named chytridiomycosis and affects the vital function of amphibian skin. Not all amphibians respond equally to infection and host responses might range from resistant, over tolerant to susceptible. The clinical outcome of infection is highly dependent on the amphibian host, the fungal virulence and environmental determinants. B. dendrobatidis infects the skin of a large range of anurans, urodeles and caecilians, whereas to date the host range of B. salamandrivorans seems limited to urodeles. So far, the epidemic of B. dendrobatidis is mainly limited to Australian, neotropical, South European and West American amphibians, while for B. salamandrivorans it is limited to European salamanders. Other striking differences between both fungi include gross pathology and thermal preferences. With this review we aim to provide the reader with a state-of-the art of host-pathogen interactions for both fungi, in which new data pertaining to the interaction of B. dendrobatidis and B. salamandrivorans with the host's skin are integrated. Furthermore, we pinpoint areas in which more detailed studies are necessary or which have not received the attention they merit.

Cloning and characterization of human immunodeficiency virus type 1 variants diminished in the ability to induce syncytium-independent cytolysis.

PubMed Central

Stevenson, M; Haggerty, S; Lamonica, C; Mann, A M; Meier, C; Wasiak, A

1990-01-01

The phenomenon of interference was exploited to isolate low-abundance noncytopathic human immunodeficiency virus type 1 (HIV-1) variants from a primary HIV-1 isolate from an asymptomatic HIV-1-seropositive hemophiliac. Successive rounds of virus infection of a cytolysis-susceptible CD4+ cell line and isolation of surviving cells resulted in selective amplification of an HIV-1 variant reduced in the ability to induce cytolysis. The presence of a PvuII polymorphism facilitated subsequent amplification and cloning of cytopathic and noncytopathic HIV-1 variants from the primary isolate. Cloned virus stocks from cytopathic and noncytopathic variants exhibited similar replication kinetics, infectivity, and syncytium induction in susceptible host cells. The noncytopathic HIV-1 variant was unable, however, to induce single-cell killing in susceptible host cells. Construction of viral hybrids in which regions of cytopathic and noncytopathic variants were exchanged indicated that determinants for the noncytopathic phenotype map to the envelope glycoprotein. Sequence analysis of the envelope coding regions indicated the absence of two highly conserved N-linked glycosylation sites in the noncytopathic HIV-1 variant, which accompanied differences in processing of precursor gp160 envelope glycoprotein. These results demonstrate that determinants for syncytium-independent single-cell killing are located within the envelope glycoprotein and suggest that single-cell killing is profoundly influenced by alterations in envelope sequence which affect posttranslational processing of HIV-1 envelope glycoprotein within the infected cell. Images PMID:1695254

A mechanism of transmission and factors affecting coral susceptibility to Halofolliculina sp. infection

NASA Astrophysics Data System (ADS)

Rodríguez, S.; Cróquer, A.; Guzmán, H. M.; Bastidas, C.

2009-03-01

Anecdotal evidence collected since 2004 suggests that infections caused by ciliates in the genus Halofolliculina may be related to coral mortality in more than 25 scleractinian species in the Caribbean. However, the relationship between the presence of ciliates and coral mortality has not yet been firmly established. Field and laboratory manipulations were used to test if ciliate infections harm corals, if ciliates are able to infect healthy colonies, and if coral susceptibility to ciliate infection depends on temperature, depth, distance to an infected colony, and the presence of injuries. Ciliate infections were always characterized by a visually detectable front of ciliates located on recently exposed coral skeletons. These infections altered the normal structure of the colony by causing tissue mortality (0.8 ± 0.95 cm month-1, mean ± SD) and by delaying or preventing recovery from injuries. Under laboratory conditions, ciliates transmitted directly and horizontally from infected to healthy hosts, and coral susceptibility to ciliate infections increased with the presence of injuries. After invasion, the ciliate population grew, rapidly and after 8 d, produced tissue mortality on 32% of newly infected hosts. Thus, our results support the existence of a new Caribbean coral syndrome that is associated with tissue mortality, is infectious, and transmits directly and horizontally. Even though the role of ciliates in the development of lesions on coral tissues remains unclear, their presence is by far the most conspicuous sign of this syndrome; thus, we propose to name this condition Caribbean ciliate infection (CCI).

The bacterial parasite Pasteuria ramosa is not killed if it fails to infect: implications for coevolution.

PubMed

King, Kayla C; Auld, Stuart K J R; Wilson, Philip J; James, Janna; Little, Tom J

2013-02-01

Strong selection on parasites, as well as on hosts, is crucial for fueling coevolutionary dynamics. Selection will be especially strong if parasites that encounter resistant hosts are destroyed and diluted from the local environment. We tested whether spores of the bacterial parasite Pasteuria ramosa were passed through the gut (the route of infection) of their host, Daphnia magna, and whether passaged spores remained viable for a "second chance" at infecting a new host. In particular, we tested if this viability (estimated via infectivity) depended on host genotype, whether or not the genotype was susceptible, and on initial parasite dose. Our results show that Pasteuria spores generally remain viable after passage through both susceptible and resistant Daphnia. Furthermore, these spores remained infectious even after being frozen for several weeks. If parasites can get a second chance at infecting hosts in the wild, selection for infection success in the first instance will be reduced. This could also weaken reciprocal selection on hosts and slow the coevolutionary process.

Innate immunity and genetic determinants of urinary tract infection susceptibility

PubMed Central

Godaly, Gabriela; Ambite, Ines; Svanborg, Catharina

2015-01-01

Purpose of review Urinary tract infections (UTIs) are common, dangerous and interesting. Susceptible individuals experience multiple, often clustered episodes, and in a subset of patients, infections progress to acute pyelonephritis (APN), sometimes accompanied by uro-sepsis. Others develop asymptomatic bacteriuria (ABU). Here, we review the molecular basis for these differences, with the intention to distinguish exaggerated host responses that drive disease from attenuated responses that favour protection and to highlight the genetic basis for these extremes, based on knock-out mice and clinical studies. Recent findings The susceptibility to UTI is controlled by specific innate immune signalling and by promoter polymorphisms and transcription factors that modulate the expression of genes controlling these pathways. Gene deletions that disturb innate immune activation either favour asymptomatic bacteriuria or create acute morbidity and disease. Promoter polymorphisms and transcription factor variants affecting those genes are associated with susceptibility in UTI-prone patients. Summary It is time to start using genetics in UTI-prone patients, to improve diagnosis and to assess the risk for chronic sequels such as renal malfunction, hypertension, spontaneous abortions, dialysis and transplantation. Furthermore, the majority of UTI patients do not need follow-up, but for lack of molecular markers, they are unnecessarily investigated. PMID:25539411

Toxoplasmosis and Polygenic Disease Susceptibility Genes: Extensive Toxoplasma gondii Host/Pathogen Interactome Enrichment in Nine Psychiatric or Neurological Disorders

PubMed Central

Carter, C. J.

2013-01-01

Toxoplasma gondii is not only implicated in schizophrenia and related disorders, but also in Alzheimer's or Parkinson's disease, cancer, cardiac myopathies, and autoimmune disorders. During its life cycle, the pathogen interacts with ~3000 host genes or proteins. Susceptibility genes for multiple sclerosis, Alzheimer's disease, schizophrenia, bipolar disorder, depression, childhood obesity, Parkinson's disease, attention deficit hyperactivity disorder (P  from  8.01E − 05  (ADHD)  to  1.22E − 71) (multiple sclerosis), and autism (P = 0.013), but not anorexia or chronic fatigue are highly enriched in the human arm of this interactome and 18 (ADHD) to 33% (MS) of the susceptibility genes relate to it. The signalling pathways involved in the susceptibility gene/interactome overlaps are relatively specific and relevant to each disease suggesting a means whereby susceptibility genes could orient the attentions of a single pathogen towards disruption of the specific pathways that together contribute (positively or negatively) to the endophenotypes of different diseases. Conditional protein knockdown, orchestrated by T. gondii proteins or antibodies binding to those of the host (pathogen derived autoimmunity) and metabolite exchange, may contribute to this disruption. Susceptibility genes may thus be related to the causes and influencers of disease, rather than (and as well as) to the disease itself. PMID:23533776

Is susceptibility to tuberculosis acquired or inherited?

PubMed

Schurr, E

2007-02-01

Tuberculosis is an ongoing major public health problem on a global scale. One of the striking features of the disease is that only an estimated 10% of immunocompetent persons infected by the causative pathogen Mycobacterium tuberculosis will develop clinical signs of disease. This well-established epidemiological observation has prompted an intense search for the factors that trigger advancement of infection to disease in the small proportion of susceptible individuals. Central to this search is the questions if tuberculosis patients are inherently susceptible to the disease or if disease development is promoted by specific environmental factors. It is known that genetic and non-genetic factors of both the bacterium and the host have impact on the host response to M. tuberculosis. Yet, little is known about the interaction of these different factors and the resulting impact on disease development. Recent work suggests that in addition to common host susceptibility genes a second group of susceptibility loci exists the action of which strongly depends on the individual's clinical and exposure history. The latter genes may have a very strong effect on promoting advancement from infection to disease only in specific epidemiological settings. These findings suggest that a more detailed knowledge of gene-environment interactions in tuberculosis is necessary to understand why a small proportion of individuals are susceptible to the disease whilst the majority of humans are naturally resistant to tuberculosis.

Molecules at the interface of Cryptococcus and the host that determine disease susceptibility.

PubMed

Wozniak, Karen L; Olszewski, Michal A; Wormley, Floyd L

2015-05-01

Cryptococcus neoformans and Cryptococcus gattii, the predominant etiological agents of cryptococcosis, are fungal pathogens that cause disease ranging from a mild pneumonia to life-threatening infections of the central nervous system (CNS). Resolution or exacerbation of Cryptococcus infection is determined following complex interactions of several host and pathogen derived factors. Alternatively, interactions between the host and pathogen may end in an impasse resulting in the establishment of a sub-clinical Cryptococcus infection. The current review addresses the delicate interaction between the host and Cryptococcus-derived molecules that determine resistance or susceptibility to infection. An emphasis will be placed on data highlighted at the recent 9th International Conference on Cryptococcus and Cryptococcosis (ICCC). Copyright © 2015. Published by Elsevier Inc.

A method to quantify infectious airborne pathogens at concentrations below the threshold of quantification by culture

PubMed Central

Cutler, Timothy D.; Wang, Chong; Hoff, Steven J.; Zimmerman, Jeffrey J.

2013-01-01

In aerobiology, dose-response studies are used to estimate the risk of infection to a susceptible host presented by exposure to a specific dose of an airborne pathogen. In the research setting, host- and pathogen-specific factors that affect the dose-response continuum can be accounted for by experimental design, but the requirement to precisely determine the dose of infectious pathogen to which the host was exposed is often challenging. By definition, quantification of viable airborne pathogens is based on the culture of micro-organisms, but some airborne pathogens are transmissible at concentrations below the threshold of quantification by culture. In this paper we present an approach to the calculation of exposure dose at microbiologically unquantifiable levels using an application of the “continuous-stirred tank reactor (CSTR) model” and the validation of this approach using rhodamine B dye as a surrogate for aerosolized microbial pathogens in a dynamic aerosol toroid (DAT). PMID:24082399

Vibrio vulnificus quorum-sensing molecule cyclo(Phe-Pro) inhibits RIG-I-mediated antiviral innate immunity.

PubMed

Lee, Wooseong; Lee, Seung-Hoon; Kim, Minwoo; Moon, Jae-Su; Kim, Geon-Woo; Jung, Hae-Gwang; Kim, In Hwang; Oh, Ji Eun; Jung, Hi Eun; Lee, Heung Kyu; Ku, Keun Bon; Ahn, Dae-Gyun; Kim, Seong-Jun; Kim, Kun-Soo; Oh, Jong-Won

2018-04-23

The recognition of pathogen-derived ligands by pattern recognition receptors activates the innate immune response, but the potential interaction of quorum-sensing (QS) signaling molecules with host anti-viral defenses remains largely unknown. Here we show that the Vibrio vulnificus QS molecule cyclo(Phe-Pro) (cFP) inhibits interferon (IFN)-β production by interfering with retinoic-acid-inducible gene-I (RIG-I) activation. Binding of cFP to the RIG-I 2CARD domain induces a conformational change in RIG-I, preventing the TRIM25-mediated ubiquitination to abrogate IFN production. cFP enhances susceptibility to hepatitis C virus (HCV), as well as Sendai and influenza viruses, each known to be sensed by RIG-I but did not affect the melanoma-differentiation-associated gene 5 (MDA5)-recognition of norovirus. Our results reveal an inter-kingdom network between bacteria, viruses and host that dysregulates host innate responses via a microbial quorum-sensing molecule modulating the response to viral infection.

Temporal trends of β-haemolytic streptococcal osteoarticular infections in western Norway.

PubMed

Oppegaard, Oddvar; Skrede, Steinar; Mylvaganam, Haima; Kittang, Bård Reiakvam

2016-10-04

Beta-haemolytic streptococci are important contributors to the global burden of osteoarticular infections (OAI). Knowledge on the disease traits specific for streptococcal OAI, however, remains scarce. We wished to explore temporal trends of OAI caused by Group A Streptococci (GAS), Group B Streptococci (GBS) and Group C and G Streptococci (GCGS), and furthermore, to describe the associated host and pathogen characteristics. All cases of microbiologically verified β-haemolytic streptococcal OAI in Health Region Bergen, Norway, in the period 1999-2013 were retrospectively identified. Clinical data were extracted from medical records. Microbial isolates were submitted to antibiotic susceptibility testing and molecular typing. A total of 24 GAS, 45 GBS and 42 GCGS acute OAI were identified. The cumulative incidence of GCGS OAI, but not GAS or GBS OAI, increased significantly from the first to the last 5-year period (IRR 5.7, p = 0.0003), with the annual incidence peaking at 1.9/100 000 in 2013. GAS OAI generally produced the most acute and severe clinical presentation, whereas GBS and GCGS predominantly affected the elderly, and were significantly associated with the presence of host risk factors of systemic and focal origin, respectively. We found a significantly increasing incidence of GCGS OAI, likely related to the presence of host susceptibility factors, including prosthetic material and pre-existing joint disease. With an increasing application of therapeutic and diagnostic bone and joint procedures, the rising trend of OAI caused by GCGS is likely to continue. Sustained epidemiological attentiveness to GCGS seems warranted.

Tick-Pathogen Interactions and Vector Competence: Identification of Molecular Drivers for Tick-Borne Diseases

PubMed Central

de la Fuente, José; Antunes, Sandra; Bonnet, Sarah; Cabezas-Cruz, Alejandro; Domingos, Ana G.; Estrada-Peña, Agustín; Johnson, Nicholas; Kocan, Katherine M.; Mansfield, Karen L.; Nijhof, Ard M.; Papa, Anna; Rudenko, Nataliia; Villar, Margarita; Alberdi, Pilar; Torina, Alessandra; Ayllón, Nieves; Vancova, Marie; Golovchenko, Maryna; Grubhoffer, Libor; Caracappa, Santo; Fooks, Anthony R.; Gortazar, Christian; Rego, Ryan O. M.

2017-01-01

Ticks and the pathogens they transmit constitute a growing burden for human and animal health worldwide. Vector competence is a component of vectorial capacity and depends on genetic determinants affecting the ability of a vector to transmit a pathogen. These determinants affect traits such as tick-host-pathogen and susceptibility to pathogen infection. Therefore, the elucidation of the mechanisms involved in tick-pathogen interactions that affect vector competence is essential for the identification of molecular drivers for tick-borne diseases. In this review, we provide a comprehensive overview of tick-pathogen molecular interactions for bacteria, viruses, and protozoa affecting human and animal health. Additionally, the impact of tick microbiome on these interactions was considered. Results show that different pathogens evolved similar strategies such as manipulation of the immune response to infect vectors and facilitate multiplication and transmission. Furthermore, some of these strategies may be used by pathogens to infect both tick and mammalian hosts. Identification of interactions that promote tick survival, spread, and pathogen transmission provides the opportunity to disrupt these interactions and lead to a reduction in tick burden and the prevalence of tick-borne diseases. Targeting some of the similar mechanisms used by the pathogens for infection and transmission by ticks may assist in development of preventative strategies against multiple tick-borne diseases. PMID:28439499

Vaccine Effects on Heterogeneity in Susceptibility and Implications for Population Health Management.

PubMed

Langwig, Kate E; Wargo, Andrew R; Jones, Darbi R; Viss, Jessie R; Rutan, Barbara J; Egan, Nicholas A; Sá-Guimarães, Pedro; Kim, Min Sun; Kurath, Gael; Gomes, M Gabriela M; Lipsitch, Marc

2017-11-21

Heterogeneity in host susceptibility is a key determinant of infectious disease dynamics but is rarely accounted for in assessment of disease control measures. Understanding how susceptibility is distributed in populations, and how control measures change this distribution, is integral to predicting the course of epidemics with and without interventions. Using multiple experimental and modeling approaches, we show that rainbow trout have relatively homogeneous susceptibility to infection with infectious hematopoietic necrosis virus and that vaccination increases heterogeneity in susceptibility in a nearly all-or-nothing fashion. In a simple transmission model with an R 0 of 2, the highly heterogeneous vaccine protection would cause a 35 percentage-point reduction in outbreak size over an intervention inducing homogenous protection at the same mean level. More broadly, these findings provide validation of methodology that can help to reduce biases in predictions of vaccine impact in natural settings and provide insight into how vaccination shapes population susceptibility. IMPORTANCE Differences among individuals influence transmission and spread of infectious diseases as well as the effectiveness of control measures. Control measures, such as vaccines, may provide leaky protection, protecting all hosts to an identical degree, or all-or-nothing protection, protecting some hosts completely while leaving others completely unprotected. This distinction can have a dramatic influence on disease dynamics, yet this distribution of protection is frequently unaccounted for in epidemiological models and estimates of vaccine efficacy. Here, we apply new methodology to experimentally examine host heterogeneity in susceptibility and mode of vaccine action as distinct components influencing disease outcome. Through multiple experiments and new modeling approaches, we show that the distribution of vaccine effects can be robustly estimated. These results offer new experimental and inferential methodology that can improve predictions of vaccine effectiveness and have broad applicability to human, wildlife, and ecosystem health. Copyright © 2017 Langwig et al.

Relative host body condition and food availability influence epidemic dynamics: a Poecilia reticulata-Gyrodactylus turnbulli host-parasite model.

PubMed

Tadiri, Christina P; Dargent, Felipe; Scott, Marilyn E

2013-03-01

Understanding disease transmission is important to species management and human health. Host body condition, nutrition and disease susceptibility interact in a complex manner, and while the individual effects of these variables are well known, our understanding of how they interact and translate to population dynamics is limited. Our objective was to determine whether host relative body condition influences epidemic dynamics, and how this relationship is affected by food availability. Poecilia reticulata (guppies) of roughly similar size were selected and assembled randomly into populations of 10 guppies assigned to 3 different food availability treatments, and the relative condition index (Kn) of each fish was calculated. We infected 1 individual per group ('source' fish) with Gyrodactyus turnbulli and counted parasites on each fish every other day for 10 days. Epidemic parameters for each population were analysed using generalized linear models. High host Kn-particularly that of the 'source' fish-exerted a positive effect on incidence, peak parasite burden, and the degree of parasite aggregation. Low food availability increased the strength of the associations with peak burden and aggregation. Our findings suggest that host Kn and food availability interact to influence epidemic dynamics, and that the condition of the individual that brings the parasite into the host population has a profound impact on the spread of infection.

Grape Cultivar and Sap Culture Conditions Affect the Development of Xylella fastidiosa Phenotypes Associated with Pierce's Disease

PubMed Central

Hoch, Harvey C.; Burr, Thomas J.; Mowery, Patricia

2016-01-01

Xylella fastidiosa is a xylem-limited bacterium in plant hosts and causes Pierce’s disease (PD) of grapevines, which differ in susceptibility according to the Vitis species (spp.). In this work we compared X. fastidiosa biofilm formation and population dynamics when cultured in xylem saps from PD-susceptible and -resistant Vitis spp. under different conditions. Behaviors in a closed-culture system were compared to those in different sap-renewal cultures that would more closely mimic the physicochemical environment encountered in planta. Significant differences in biofilm formation and growth in saps from PD-susceptible and -resistant spp. were only observed using sap renewal culture. Compared to saps from susceptible V. vinifera, those from PD-resistant V. aestivalis supported lower titers of X. fastidiosa and less biofilm and V. champinii suppressed both growth and biofilm formation, behaviors which are correlated with disease susceptibility. Furthermore, in microfluidic chambers X. fastidiosa formed thick mature biofilm with three-dimensional (3-D) structures, such as pillars and mounds, in saps from all susceptible spp. In contrast, only small aggregates of various shapes were formed in saps from four out of five of the resistant spp.; sap from the resistant spp. V. mustangensis was an exception in that it also supported thick lawns of biofilm but not the above described 3-D structures typically seen in a mature biofilm from the susceptible saps. Our findings provide not only critical technical information for future bioassays, but also suggest further understanding of PD susceptibility. PMID:27508296

Genetic susceptibility to Candida infections

PubMed Central

Smeekens, Sanne P; van de Veerdonk, Frank L; Kullberg, Bart Jan; Netea, Mihai G

2013-01-01

Candida spp. are medically important fungi causing severe mucosal and life-threatening invasive infections, especially in immunocompromised hosts. However, not all individuals at risk develop Candida infections, and it is believed that genetic variation plays an important role in host susceptibility. On the one hand, severe fungal infections are associated with monogenic primary immunodeficiencies such as defects in STAT1, STAT3 or CARD9, recently discovered as novel clinical entities. On the other hand, more common polymorphisms in genes of the immune system have also been associated with fungal infections such as recurrent vulvovaginal candidiasis and candidemia. The discovery of the genetic susceptibility to Candida infections can lead to a better understanding of the pathogenesis of the disease, as well as to the design of novel immunotherapeutic strategies. This review is part of the review series on host-pathogen interactions. See more reviews from this series. PMID:23629947

A fungal root symbiont modifies plant resistance to an insect herbivore.

PubMed

Borowicz, Victoria A

1997-11-01

Vesicular-arbuscular mycorrhizal (VAM) fungi are common root-colonizing symbionts that affect nutrient uptake by plants and can alter plant susceptibility to herbivores. I conducted a factorial experiment to test the hypotheses that colonization by VAM fungi (1) improves soybean (Glycine max) tolerance to grazing by folivorous Mexican bean beetle (Epilachna varivestis), and (2) indirectly affects herbivores by increasing host resistance. Soybean seedlings were inoculated with the VAM fungus Glomus etunicatum or VAM-free filtrate and fertilized with high-[P] or low-[P] fertilizer. After plants had grown for 7 weeks first-instar beetle larvae were placed on bagged leaves. Growth of soybean was little affected by grazing larvae, and no effects of treatments on tolerance of soybeans to herbivores were evident. Colonization by VAM fungus doubled the size of phosphorus-stressed plants but these plants were still half the size of plants given adequate phosphorus. High-[P] fertilizer increased levels of phosphorus and soluble carbohydrates, and decreased levels of soluble proteins in leaves of grazed plants. Colonization of grazed plants by VAM fungus had no significant effect on plant soluble carbohydrates, but increased concentration of phosphorus and decreased levels of proteins in phosphorus-stressed plants to concentrations similar to those of plants given adequate phosphorus. Mexican bean beetle mass at pupation, pupation rate, and survival to eclosion were greatest for beetles reared on phosphorus-stressed, VAM-colonized plants, refuting the hypothesis that VAM colonization improves host plant resistance. VAM colonization indirectly affected performance of Mexician bean beetle larvae by improving growth and nutrition of the host plant.

Persistence of canine distemper virus in the Greater Yellowstone ecosystem's carnivore community.

PubMed

Almberg, Emily S; Cross, Paul C; Smith, Douglas W

2010-10-01

Canine distemper virus (CDV) is an acute, highly immunizing pathogen that should require high densities and large populations of hosts for long-term persistence, yet CDV persists among terrestrial carnivores with small, patchily distributed groups. We used CDV in the Greater Yellowstone ecosystem's (GYE) wolves (Canis lupus) and coyotes (Canis latrans) as a case study for exploring how metapopulation structure, host demographics, and multi-host transmission affect the critical community size and spatial scale required for CDV persistence. We illustrate how host spatial connectivity and demographic turnover interact to affect both local epidemic dynamics, such as the length and variation in inter-epidemic periods, and pathogen persistence using stochastic, spatially explicit susceptible-exposed-infectious-recovered simulation models. Given the apparent absence of other known persistence mechanisms (e.g., a carrier or environmental state, densely populated host, chronic infection, or a vector), we suggest that CDV requires either large spatial scales or multi-host transmission for persistence. Current GYE wolf populations are probably too small to support endemic CDV. Coyotes are a plausible reservoir host, but CDV would still require 50000-100000 individuals for moderate persistence (> 50% over 10 years), which would equate to an area of 1-3 times the size of the GYE (60000-200000 km2). Coyotes, and carnivores in general, are not uniformly distributed; therefore, this is probably a gross underestimate of the spatial scale of CDV persistence. However, the presence of a second competent host species can greatly increase the probability of long-term CDV persistence at much smaller spatial scales. Although no management of CDV is currently recommended for the GYE, wolf managers in the region should expect periodic but unpredictable CDV-related population declines as often as every 2-5 years. Awareness and monitoring of such outbreaks will allow corresponding adjustments in management activities such as regulated public harvest, creating a smooth transition to state wolf management and conservation after > 30 years of being protected by the Endangered Species Act.

Molecular biology of viroid-host interactions and disease control strategies.

PubMed

Kovalskaya, Natalia; Hammond, Rosemarie W

2014-11-01

Viroids are single-stranded, covalently closed, circular, highly structured noncoding RNAs that cause disease in several economically important crop plants. They replicate autonomously and move systemically in host plants with the aid of the host machinery. In addition to symptomatic infections, viroids also cause latent infections where there is no visual evidence of infection in the host; however, transfer to a susceptible host can result in devastating disease. While there are non-hosts for viroids, no naturally occurring durable resistance has been observed in most host species. Current effective control methods for viroid diseases include detection and eradication, and cultural controls. In addition, heat or cold therapy combined with meristem tip culture has been shown to be effective for elimination of viroids for some viroid-host combinations. An understanding of viroid-host interactions, host susceptibility, and non-host resistance could provide guidance for the design of viroid-resistant plants. Efforts to engineer viroid resistance into host species have been underway for several years, and include the use of antisense RNA, antisense RNA plus ribozymes, a dsRNase, and siRNAs, among others. The results of those efforts and the challenges associated with creating viroid resistant plants are summarized in this review. Published by Elsevier Ireland Ltd.

Adaptation of tobacco etch potyvirus to a susceptible ecotype of Arabidopsis thaliana capacitates it for systemic infection of resistant ecotypes

PubMed Central

Lalić, Jasna; Agudelo-Romero, Patricia; Carrasco, Purificación; Elena, Santiago F.

2010-01-01

Viral pathogens continue to emerge among humans, domesticated animals and cultivated crops. The existence of genetic variance for resistance in the host population is crucial to the spread of an emerging virus. Models predict that rapid spread decreases with the frequency and diversity of resistance alleles in the host population. However, empirical tests of this hypothesis are scarce. Arabiodpsis thaliana—tobacco etch potyvirus (TEV) provides an experimentally suitable pathosystem to explore the interplay between genetic variation in host's susceptibility and virus diversity. Systemic infection of A. thaliana with TEV is controlled by three dominant loci, with different ecotypes varying in susceptibility depending on the genetic constitution at these three loci. Here, we show that the TEV adaptation to a susceptible ecotype allowed the virus to successfully infect, replicate and induce symptoms in ecotypes that were fully resistant to the ancestral virus. The value of these results is twofold. First, we showed that the existence of partially susceptible individuals allows for the emerging virus to bypass resistance alleles that the virus has never encountered. Second, the concept of resistance genes may only be valid for a well-defined viral genotype but not for polymorphic viral populations. PMID:20478894

Exploring the host transcriptome for mechanisms underlying protective immunity and resistance to nematode infections in ruminants.

PubMed

Li, Robert W; Choudhary, Ratan K; Capuco, Anthony V; Urban, Joseph F

2012-11-23

Nematode infections in ruminants are a major impediment to the profitable production of meat and dairy products, especially for small farms. Gastrointestinal parasitism not only negatively impacts weight gain and milk yield, but is also a major cause of mortality in small ruminants. The current parasite control strategy involves heavy use of anthelmintics that has resulted in the emergence of drug-resistant parasite strains. This, in addition to increasing consumer demand for animal products that are free of drug residues has stimulated development of alternative strategies, including selective breeding of parasite resistant ruminants. The development of protective immunity and manifestations of resistance to nematode infections relies upon the precise expression of the host genome that is often confounded by mechanisms simultaneously required to control multiple nematode species as well as ecto- and protozoan parasites, and microbial and viral pathogens. Understanding the molecular mechanisms underlying these processes represents a key step toward development of effective new parasite control strategies. Recent progress in characterizing the transcriptome of both hosts and parasites, utilizing high-throughput microarrays and RNA-seq technology, has led to the recognition of unique interactions and the identification of genes and biological pathways involved in the response to parasitism. Innovative use of the knowledge gained by these technologies should provide a basis for enhancing innate immunity while limiting the polarization of acquired immunity can negatively affect optimal responses to co-infection. Strategies for parasite control that use diet and vaccine/adjuvant combination could be evaluated by monitoring the host transcriptome for induction of appropriate mechanisms for imparting parasite resistance. Knowledge of different mechanisms of host immunity and the critical regulation of parasite development, physiology, and virulence can also selectively identify targets for parasite control. Comparative transcriptome analysis, in concert with genome-wide association (GWS) studies to identify quantitative trait loci (QTLs) affecting host resistance, represents a promising molecular technology to evaluate integrated control strategies that involve breed and environmental factors that contribute to parasite resistance and improved performance. Tailoring these factors to control parasitism without severely affecting production qualities, management efficiencies, and responses to pathogenic co-infection will remain a challenge. This review summarizes recent progress and limitations of understanding regulatory genetic networks and biological pathways that affect host resistance and susceptibility to nematode infection in ruminants. Published by Elsevier B.V.

Virus-induced gene silencing suggests (1,3;1,4)-β-glucanase is a susceptibility factor in the compatible russian wheat aphid-wheat interaction.

PubMed

Anderson, Victoria A; Haley, Scott D; Peairs, Frank B; van Eck, Leon; Leach, Jan E; Lapitan, Nora L V

2014-09-01

The Russian wheat aphid (RWA), Diuraphis noxia (Kurdjumov), is a significant insect pest of wheat (Triticum aestivum L.) and has a major economic impact worldwide, especially on winter wheat in the western United States. The continuing emergence of new RWA biotypes virulent to existing resistance genes reinforces the need for more durable resistance. Studies have indicated that resistance in previously susceptible plants can be produced by knock-down of susceptibility genes or other genes involved in host plant susceptibility. Therefore, investigation into genes involved in compatible RWA-wheat interactions could be a feasible approach to achieving durable RWA resistance. The objective of this study was to test whether silencing (1,3;1,4)-β-glucanase, previously observed to be highly induced in susceptible compared with resistant wheat during aphid infestation, would confer resistance to a susceptible wheat genotype. Barley stripe mosaic virus-mediated virus-induced gene silencing was employed to test whether (1,3;1,4)-β-glucanase is involved in the susceptible reaction of 'Gamtoos-S' (GS). Controlled infestation with U.S. biotype RWA2 was done to assess aphid reproduction and host symptom development. Aphids on (1,3;1,4)-β-glucanase-silenced plants reproduced less per day and had longer prenymphipositional periods than those on control GS plants. Furthermore, the (1,3;1,4)-β-glucanase-silenced plants exhibited less chlorosis and greater dry weight compared with GS. Aphid reproduction and host plant symptom development showed linear relationships with (1,3;1,4)-β-glucanase transcript levels. Our results suggest that (1,3;1,4)-β-glucanase is required for successful infestation by the RWA and may be a susceptibility factor that could be exploited as a potential target for RWA resistance breeding.

Glucosinolates from Host Plants Influence Growth of the Parasitic Plant Cuscuta gronovii and Its Susceptibility to Aphid Feeding1[OPEN

PubMed Central

2016-01-01

Parasitic plants acquire diverse secondary metabolites from their hosts, including defense compounds that target insect herbivores. However, the ecological implications of this phenomenon, including the potential enhancement of parasite defenses, remain largely unexplored. We studied the translocation of glucosinolates from the brassicaceous host plant Arabidopsis (Arabidopsis thaliana) into parasitic dodder vines (Convolvulaceae; Cuscuta gronovii) and its effects on the parasite itself and on dodder-aphid interactions. Aliphatic and indole glucosinolates reached concentrations in parasite tissues higher than those observed in corresponding host tissues. Dodder growth was enhanced on cyp79B2 cyp79B3 hosts (without indole glucosinolates) but inhibited on atr1D hosts (with elevated indole glucosinolates) relative to wild-type hosts, which responded to parasitism with localized elevation of indole and aliphatic glucosinolates. These findings implicate indole glucosinolates in defense against parasitic plants. Rates of settling and survival on dodder vines by pea aphids (Acyrthosiphon pisum) were reduced significantly when dodder parasitized glucosinolate-producing hosts (wild type and atr1D) compared with glucosinolate-free hosts (cyp79B2 cyp79B3 myb28 myb29). However, settling and survival of green peach aphids (Myzus persicae) were not affected. M. persicae population growth was actually reduced on dodder parasitizing glucosinolate-free hosts compared with wild-type or atr1D hosts, even though stems of the former contain less glucosinolates and more amino acids. Strikingly, this effect was reversed when the aphids fed directly upon Arabidopsis, which indicates an interactive effect of parasite and host genotype on M. persicae that stems from host effects on dodder. Thus, our findings indicate that glucosinolates may have both direct and indirect effects on dodder-feeding herbivores. PMID:27482077

Glucosinolates from Host Plants Influence Growth of the Parasitic Plant Cuscuta gronovii and Its Susceptibility to Aphid Feeding.

PubMed

Smith, Jason D; Woldemariam, Melkamu G; Mescher, Mark C; Jander, Georg; De Moraes, Consuelo M

2016-09-01

Parasitic plants acquire diverse secondary metabolites from their hosts, including defense compounds that target insect herbivores. However, the ecological implications of this phenomenon, including the potential enhancement of parasite defenses, remain largely unexplored. We studied the translocation of glucosinolates from the brassicaceous host plant Arabidopsis (Arabidopsis thaliana) into parasitic dodder vines (Convolvulaceae; Cuscuta gronovii) and its effects on the parasite itself and on dodder-aphid interactions. Aliphatic and indole glucosinolates reached concentrations in parasite tissues higher than those observed in corresponding host tissues. Dodder growth was enhanced on cyp79B2 cyp79B3 hosts (without indole glucosinolates) but inhibited on atr1D hosts (with elevated indole glucosinolates) relative to wild-type hosts, which responded to parasitism with localized elevation of indole and aliphatic glucosinolates. These findings implicate indole glucosinolates in defense against parasitic plants. Rates of settling and survival on dodder vines by pea aphids (Acyrthosiphon pisum) were reduced significantly when dodder parasitized glucosinolate-producing hosts (wild type and atr1D) compared with glucosinolate-free hosts (cyp79B2 cyp79B3 myb28 myb29). However, settling and survival of green peach aphids (Myzus persicae) were not affected. M. persicae population growth was actually reduced on dodder parasitizing glucosinolate-free hosts compared with wild-type or atr1D hosts, even though stems of the former contain less glucosinolates and more amino acids. Strikingly, this effect was reversed when the aphids fed directly upon Arabidopsis, which indicates an interactive effect of parasite and host genotype on M. persicae that stems from host effects on dodder. Thus, our findings indicate that glucosinolates may have both direct and indirect effects on dodder-feeding herbivores. © 2016 American Society of Plant Biologists. All rights reserved.

The genetic predisposition and the interplay of host genetics and gut microbiome in Crohn disease.

PubMed

Jianzhong, Hu

2014-12-01

Extensive genetic studies have identified more than 140 loci predisposing to Crohn disease (CD). Several major CD susceptibility genes have been shown to impair biological function with regard to immune response to recognizing and clearance of bacterial infection. Recent human microbiome studies suggest that the gut microbiome composition is differentiated in carriers of many risk variants of major CD susceptibility genes. This interplay between host genetics and its associated gut microbiome may play an essential role in the pathogenesis of CD. The ongoing microbiome research is aimed to investigate the detailed host genetics-microbiome interacting mechanism. Copyright © 2014 Elsevier Inc. All rights reserved.

[Validation of the modified algorithm for predicting host susceptibility to viruses taking into account susceptibility parameters of primary target cell cultures and natural immunity factors].

PubMed

Zhukov, V A; Shishkina, L N; Safatov, A S; Sergeev, A A; P'iankov, O V; Petrishchenko, V A; Zaĭtsev, B N; Toporkov, V S; Sergeev, A N; Nesvizhskiĭ, Iu V; Vorob'ev, A A

2010-01-01

The paper presents results of testing a modified algorithm for predicting virus ID50 values in a host of interest by extrapolation from a model host taking into account immune neutralizing factors and thermal inactivation of the virus. The method was tested for A/Aichi/2/68 influenza virus in SPF Wistar rats, SPF CD-1 mice and conventional ICR mice. Each species was used as a host of interest while the other two served as model hosts. Primary lung and trachea cells and secretory factors of the rats' airway epithelium were used to measure parameters needed for the purpose of prediction. Predicted ID50 values were not significantly different (p = 0.05) from those experimentally measured in vivo. The study was supported by ISTC/DARPA Agreement 450p.

Within-population covariation between sexual reproduction and susceptibility to local parasites.

PubMed

Gibson, Amanda K; Xu, Julie Y; Lively, Curtis M

2016-09-01

Evolutionary biology has yet to reconcile the ubiquity of sex with its costs relative to asexual reproduction. Here, we test the hypothesis that coevolving parasites maintain sex in their hosts. Specifically, we examined the distributions of sexual reproduction and susceptibility to local parasites within a single population of freshwater snails (Potamopyrgus antipodarum). Susceptibility to local trematode parasites (Microphallus sp.) is a relative measure of the strength of coevolutionary selection in this system. Thus, if coevolving parasites maintain sex, sexual snails should be common where susceptibility is high. We tested this prediction in a mixed population of sexual and asexual snails by measuring the susceptibility of snails from multiple sites in a lake. Consistent with the prediction, the frequency of sexual snails was tightly and positively correlated with susceptibility to local parasites. Strikingly, in just two years, asexual females increased in frequency at sites where susceptibility declined. We also found that the frequency of sexual females covaries more strongly with susceptibility than with the prevalence of Microphallus infection in the field. In linking susceptibility to the frequency of sexual hosts, our results directly implicate spatial variation in coevolutionary selection in driving the geographic mosaic of sex. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Columnaris disease in fish: a review with emphasis on bacterium-host interactions

PubMed Central

2013-01-01

Flavobacterium columnare (F. columnare) is the causative agent of columnaris disease. This bacterium affects both cultured and wild freshwater fish including many susceptible commercially important fish species. F. columnare infections may result in skin lesions, fin erosion and gill necrosis, with a high degree of mortality, leading to severe economic losses. Especially in the last decade, various research groups have performed studies aimed at elucidating the pathogenesis of columnaris disease, leading to significant progress in defining the complex interactions between the organism and its host. Despite these efforts, the pathogenesis of columnaris disease hitherto largely remains unclear, compromising the further development of efficient curative and preventive measures to combat this disease. Besides elaborating on the agent and the disease it causes, this review aims to summarize these pathogenesis data emphasizing the areas meriting further investigation. PMID:23617544

Parasitic plants of the genus Cuscuta and their interaction with susceptible and resistant host plants

PubMed Central

Kaiser, Bettina; Vogg, Gerd; Fürst, Ursula B.; Albert, Markus

2015-01-01

By comparison with plant–microbe interaction, little is known about the interaction of parasitic plants with their hosts. Plants of the genus Cuscuta belong to the family of Cuscutaceae and comprise about 200 species, all of which live as stem holoparasites on other plants. Cuscuta spp. possess no roots nor fully expanded leaves and the vegetative portion appears to be a stem only. The parasite winds around plants and penetrates the host stems via haustoria, forming direct connections to the vascular bundles of their hosts to withdraw water, carbohydrates, and other solutes. Besides susceptible hosts, a few plants exist that exhibit an active resistance against infestation by Cuscuta spp. For example, cultivated tomato (Solanum lycopersicum) fends off Cuscuta reflexa by means of a hypersensitive-type response occurring in the early penetration phase. This report on the plant–plant dialog between Cuscuta spp. and its host plants focuses on the incompatible interaction of C. reflexa with tomato. PMID:25699071

Parasitic plants of the genus Cuscuta and their interaction with susceptible and resistant host plants.

PubMed

Kaiser, Bettina; Vogg, Gerd; Fürst, Ursula B; Albert, Markus

2015-01-01

By comparison with plant-microbe interaction, little is known about the interaction of parasitic plants with their hosts. Plants of the genus Cuscuta belong to the family of Cuscutaceae and comprise about 200 species, all of which live as stem holoparasites on other plants. Cuscuta spp. possess no roots nor fully expanded leaves and the vegetative portion appears to be a stem only. The parasite winds around plants and penetrates the host stems via haustoria, forming direct connections to the vascular bundles of their hosts to withdraw water, carbohydrates, and other solutes. Besides susceptible hosts, a few plants exist that exhibit an active resistance against infestation by Cuscuta spp. For example, cultivated tomato (Solanum lycopersicum) fends off Cuscuta reflexa by means of a hypersensitive-type response occurring in the early penetration phase. This report on the plant-plant dialog between Cuscuta spp. and its host plants focuses on the incompatible interaction of C. reflexa with tomato.

Marek’s disease herpesvirus vaccines integrate into chicken host chromosomes yet lack a virus-host phenotype associated with oncogenic transformation

USDA-ARS?s Scientific Manuscript database

Marek's disease (MD) is a lymphotrophic and oncogenic disease of chickens that can lead to death in susceptible and unimmunized host birds. The causative pathogen, Marek's disease virus (MDV), a highly oncogenic alphaherpesvirus, integrates into host genome near the telomeres during viral latency an...

Evidence of host adaptation in Lawsonia intracellularis infections

PubMed Central

2012-01-01

Background Lawsonia intracellularis is the causative agent of proliferative enteropathy, an endemic disease in pigs and an emerging concern in horses. Enterocyte hyperplasia is a common lesion in every case but there are differences regarding clinical and pathological presentations among affected species. We hypothesize that host susceptibility to L. intracellularis infection depends on the species of origin of the bacterial isolate. The objective of this study was to evaluate the susceptibilities of pigs and horses to L. intracellularis infection using either a porcine or an equine isolate. Materials and methods Twelve foals and eighteen pigs were equally divided into three groups and infected with either a porcine or an equine isolate (109L. Intracellularis/challenged animal), and a saline solution (negative control group). The animals were monitored regarding clinical signs, average of daily weight gain, fecal shedding of the bacteria by PCR and humoral serological response. Results Foals infected with the equine isolate developed moderate to severe clinical signs and maintained a lower average of weight gain compared to control foals. Fecal quantitative PCR in equine isolate-infected foals revealed higher amounts of bacterial DNA associated with longer duration of shedding compared with porcine isolate-infected foals. All four foals infected with the equine isolate demonstrated higher IgG titers in the serum compared with porcine isolate-infected foals. In the pig trial, diarrhea and seroconversion were only observed in animals infected with the porcine isolate. Pathological changes typical of proliferative enteropathy were observed in the necropsied foal infected with equine isolate and in the two necropsied pigs infected with the porcine isolate. Conclusions Evident clinical signs, longer periods of bacterial shedding and stronger serologic immune responses were observed in animals infected with species-specific isolates. These results show that host susceptibility is driven by the origin of the isolated L. intracellularis strain. PMID:22715937

Environmental Variation Generates Environmental Opportunist Pathogen Outbreaks.

PubMed

Anttila, Jani; Kaitala, Veijo; Laakso, Jouni; Ruokolainen, Lasse

2015-01-01

Many socio-economically important pathogens persist and grow in the outside host environment and opportunistically invade host individuals. The environmental growth and opportunistic nature of these pathogens has received only little attention in epidemiology. Environmental reservoirs are, however, an important source of novel diseases. Thus, attempts to control these diseases require different approaches than in traditional epidemiology focusing on obligatory parasites. Conditions in the outside-host environment are prone to fluctuate over time. This variation is a potentially important driver of epidemiological dynamics and affect the evolution of novel diseases. Using a modelling approach combining the traditional SIRS models to environmental opportunist pathogens and environmental variability, we show that epidemiological dynamics of opportunist diseases are profoundly driven by the quality of environmental variability, such as the long-term predictability and magnitude of fluctuations. When comparing periodic and stochastic environmental factors, for a given variance, stochastic variation is more likely to cause outbreaks than periodic variation. This is due to the extreme values being further away from the mean. Moreover, the effects of variability depend on the underlying biology of the epidemiological system, and which part of the system is being affected. Variation in host susceptibility leads to more severe pathogen outbreaks than variation in pathogen growth rate in the environment. Positive correlation in variation on both targets can cancel the effect of variation altogether. Moreover, the severity of outbreaks is significantly reduced by increase in the duration of immunity. Uncovering these issues helps in understanding and controlling diseases caused by environmental pathogens.

Seasonal Patterns of Hormones, Macroparasites, and Microparasites in Wild African Ungulates: The Interplay among Stress, Reproduction, and Disease

PubMed Central

Cizauskas, Carrie A.; Turner, Wendy C.; Pitts, Neville; Getz, Wayne M.

2015-01-01

Sex hormones, reproductive status, and pathogen load all affect stress. Together with stress, these factors can modulate the immune system and affect disease incidence. Thus, it is important to concurrently measure these factors, along with their seasonal fluctuations, to better understand their complex interactions. Using steroid hormone metabolites from fecal samples, we examined seasonal correlations among zebra and springbok stress, reproduction, gastrointestinal (GI) parasite infections, and anthrax infection signatures in zebra and springbok in Etosha National Park (ENP), Namibia, and found strong seasonal effects. Infection intensities of all three GI macroparasites examined (strongyle helminths, Strongyloides helminths, and Eimeria coccidia) were highest in the wet season, concurrent with the timing of anthrax outbreaks. Parasites also declined with increased acquired immune responses. We found hormonal evidence that both mares and ewes are overwhelmingly seasonal breeders in ENP, and that reproductive hormones are correlated with immunosuppression and higher susceptibility to GI parasite infections. Stress hormones largely peak in the dry season, particularly in zebra, when parasite infection intensities are lowest, and are most strongly correlated with host mid-gestation rather than with parasite infection intensity. Given the evidence that GI parasites can cause host pathology, immunomodulation, and immunosuppression, their persistence in ENP hosts without inducing chronic stress responses supports the hypothesis that hosts are tolerant of their parasites. Such tolerance would help to explain the ubiquity of these organisms in ENP herbivores, even in the face of their potential immunomodulatory trade-offs with anti-anthrax immunity. PMID:25875647

Seasonal patterns of hormones, macroparasites, and microparasites in wild African ungulates: the interplay among stress, reproduction, and disease.

PubMed

Cizauskas, Carrie A; Turner, Wendy C; Pitts, Neville; Getz, Wayne M

2015-01-01

Sex hormones, reproductive status, and pathogen load all affect stress. Together with stress, these factors can modulate the immune system and affect disease incidence. Thus, it is important to concurrently measure these factors, along with their seasonal fluctuations, to better understand their complex interactions. Using steroid hormone metabolites from fecal samples, we examined seasonal correlations among zebra and springbok stress, reproduction, gastrointestinal (GI) parasite infections, and anthrax infection signatures in zebra and springbok in Etosha National Park (ENP), Namibia, and found strong seasonal effects. Infection intensities of all three GI macroparasites examined (strongyle helminths, Strongyloides helminths, and Eimeria coccidia) were highest in the wet season, concurrent with the timing of anthrax outbreaks. Parasites also declined with increased acquired immune responses. We found hormonal evidence that both mares and ewes are overwhelmingly seasonal breeders in ENP, and that reproductive hormones are correlated with immunosuppression and higher susceptibility to GI parasite infections. Stress hormones largely peak in the dry season, particularly in zebra, when parasite infection intensities are lowest, and are most strongly correlated with host mid-gestation rather than with parasite infection intensity. Given the evidence that GI parasites can cause host pathology, immunomodulation, and immunosuppression, their persistence in ENP hosts without inducing chronic stress responses supports the hypothesis that hosts are tolerant of their parasites. Such tolerance would help to explain the ubiquity of these organisms in ENP herbivores, even in the face of their potential immunomodulatory trade-offs with anti-anthrax immunity.

The rise and fall of infectious disease in a warmer world

USGS Publications Warehouse

Lafferty, Kevin D.; Mordecai, Erin A.

2016-01-01

Now-outdated estimates proposed that climate change should have increased the number of people at risk of malaria, yet malaria and several other infectious diseases have declined. Although some diseases have increased as the climate has warmed, evidence for widespread climate-driven disease expansion has not materialized, despite increased research attention. Biological responses to warming depend on the non-linear relationships between physiological performance and temperature, called the thermal response curve. This leads performance to rise and fall with temperature. Under climate change, host species and their associated parasites face extinction if they cannot either thermoregulate or adapt by shifting phenology or geographic range. Climate change might also affect disease transmission through increases or decreases in host susceptibility and infective stage (and vector) production, longevity, and pathology. Many other factors drive disease transmission, especially economics, and some change in time along with temperature, making it hard to distinguish whether temperature drives disease or just correlates with disease drivers. Although it is difficult to predict how climate change will affect infectious disease, an ecological approach can help meet the challenge.

Effects of road salt on larval amphibian susceptibility to parasitism through behavior and immunocompetence.

PubMed

Milotic, Dino; Milotic, Marin; Koprivnikar, Janet

2017-08-01

Large quantities of road salts are used for de-icing in temperate climates but often leach into aquatic ecosystems where they can cause harm to inhabitants, including reduced growth and survival. However, the implications of road salt exposure for aquatic animal susceptibility to pathogens and parasites have not yet been examined even though infectious diseases can significantly contribute to wildlife population declines. Through a field survey, we found a range of NaCl concentrations (50-560mg/L) in ponds known to contain larval amphibians, with lower levels found in sites close to gravel- rather than hard-surfaced roads. We then investigated how chronic exposure to environmentally-realistic levels of road salt (up to 1140mg/L) affected susceptibility to infection by trematode parasites (helminths) in larval stages of two amphibian species (Lithobates sylvaticus - wood frogs, and L. pipiens - northern leopard frogs) by considering effects on host anti-parasite behavior and white blood cell profiles. Wood frogs exposed to road salt had higher parasite loads, and also exhibited reduced anti-parasite behavior in these conditions. In contrast, infection intensity in northern leopard frogs had a non-monotonic response to road salts even though lymphocytes were only elevated at the highest concentration. Our results indicate the potential for chronic road salt exposure to affect larval amphibian susceptibility to pathogenic parasites through alterations of behavior and immunocompetence, with further studies needed at higher concentrations, as well as that of road salts on free-living parasite infectious stages. Copyright © 2017 Elsevier B.V. All rights reserved.

The bacterial parasite Pasteuria ramosa is not killed if it fails to infect: implications for coevolution

PubMed Central

King, Kayla C; Auld, Stuart K J R; Wilson, Philip J; James, Janna; Little, Tom J

2013-01-01

Strong selection on parasites, as well as on hosts, is crucial for fueling coevolutionary dynamics. Selection will be especially strong if parasites that encounter resistant hosts are destroyed and diluted from the local environment. We tested whether spores of the bacterial parasite Pasteuria ramosa were passed through the gut (the route of infection) of their host, Daphnia magna, and whether passaged spores remained viable for a “second chance” at infecting a new host. In particular, we tested if this viability (estimated via infectivity) depended on host genotype, whether or not the genotype was susceptible, and on initial parasite dose. Our results show that Pasteuria spores generally remain viable after passage through both susceptible and resistant Daphnia. Furthermore, these spores remained infectious even after being frozen for several weeks. If parasites can get a second chance at infecting hosts in the wild, selection for infection success in the first instance will be reduced. This could also weaken reciprocal selection on hosts and slow the coevolutionary process. PMID:23467806

Disentangling host, pathogen, and environmental determinants of a recently emerged wildlife disease: lessons from the first 15 years of amphibian chytridiomycosis research.

PubMed

James, Timothy Y; Toledo, L Felipe; Rödder, Dennis; da Silva Leite, Domingos; Belasen, Anat M; Betancourt-Román, Clarisse M; Jenkinson, Thomas S; Soto-Azat, Claudio; Lambertini, Carolina; Longo, Ana V; Ruggeri, Joice; Collins, James P; Burrowes, Patricia A; Lips, Karen R; Zamudio, Kelly R; Longcore, Joyce E

2015-09-01

The amphibian fungal disease chytridiomycosis, which affects species across all continents, recently emerged as one of the greatest threats to biodiversity. Yet, many aspects of the basic biology and epidemiology of the pathogen, Batrachochytrium dendrobatidis (Bd), are still unknown, such as when and from where did Bd emerge and what is its true ecological niche? Here, we review the ecology and evolution of Bd in the Americas and highlight controversies that make this disease so enigmatic. We explore factors associated with variance in severity of epizootics focusing on the disease triangle of host susceptibility, pathogen virulence, and environment. Reevaluating the causes of the panzootic is timely given the wealth of data on Bd prevalence across hosts and communities and the recent discoveries suggesting co-evolutionary potential of hosts and Bd. We generate a new species distribution model for Bd in the Americas based on over 30,000 records and suggest a novel future research agenda. Instead of focusing on pathogen "hot spots," we need to identify pathogen "cold spots" so that we can better understand what limits the pathogen's distribution. Finally, we introduce the concept of "the Ghost of Epizootics Past" to discuss expected patterns in postepizootic host communities.

Risk-based management of invading plant disease.

PubMed

Hyatt-Twynam, Samuel R; Parnell, Stephen; Stutt, Richard O J H; Gottwald, Tim R; Gilligan, Christopher A; Cunniffe, Nik J

2017-05-01

Effective control of plant disease remains a key challenge. Eradication attempts often involve removal of host plants within a certain radius of detection, targeting asymptomatic infection. Here we develop and test potentially more effective, epidemiologically motivated, control strategies, using a mathematical model previously fitted to the spread of citrus canker in Florida. We test risk-based control, which preferentially removes hosts expected to cause a high number of infections in the remaining host population. Removals then depend on past patterns of pathogen spread and host removal, which might be nontransparent to affected stakeholders. This motivates a variable radius strategy, which approximates risk-based control via removal radii that vary by location, but which are fixed in advance of any epidemic. Risk-based control outperforms variable radius control, which in turn outperforms constant radius removal. This result is robust to changes in disease spread parameters and initial patterns of susceptible host plants. However, efficiency degrades if epidemiological parameters are incorrectly characterised. Risk-based control including additional epidemiology can be used to improve disease management, but it requires good prior knowledge for optimal performance. This focuses attention on gaining maximal information from past epidemics, on understanding model transferability between locations and on adaptive management strategies that change over time. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Conditional Reduction of Predation Risk Associated with a Facultative Symbiont in an Insect

PubMed Central

Polin, Sarah; Le Gallic, Jean-François; Simon, Jean-Christophe; Tsuchida, Tsutomu; Outreman, Yannick

2015-01-01

Symbionts are widespread among eukaryotes and their impacts on the ecology and evolution of their hosts are meaningful. Most insects harbour obligate and facultative symbiotic bacteria that can influence their phenotype. In the pea aphid Acyrthosiphon pisum, an astounding symbiotic-mediated phenotype has been recently observed: when infected with the symbiotic bacteria Rickettsiella viridis, young red aphid larvae become greener at adulthood and even darker green when co-infected with Rickettsiella viridis and Hamiltonella defensa. As body colour affects the susceptibility towards natural enemies in aphids, the influence of the colour change due to these facultative symbionts on the host survival in presence of predators was tested. Our results suggested that the Rickettsiella viridis infection may impact positively host survival by reducing predation risk. Due to results from uninfected aphids (i.e., more green ones attacked), the main assumption is that this symbiotic infection would deter the predatory ladybird feeding by reducing the profitability of their hosts rather than decreasing host detection through body colour change. Aphids co-infected with Rickettsiella viridis and Hamiltonella defensa were, however, more exposed to predation suggesting an ecological cost associated with multiple infections. The underlying mechanisms and ecological consequences of these symbiotic effects are discussed. PMID:26618776

Relative Susceptibility of Quince, Pear, and Apple Cultivars to Fire Blight Following Greenhouse Inoculation

USDA-ARS?s Scientific Manuscript database

Fire blight caused by Erwinia amylovora (EA) is one of the most serious diseases of plants in the family Rosaceae, and Quince (Cydonia oblonga Mill.) is considered one of the most susceptible host genera. Apple (Malus sp.) and pear (Pyrus sp.) cultivars ranging from most susceptible to most resistan...

Apparent competition in canopy trees determined by pathogen transmission rather than susceptibility.

Treesearch

Richard Cobb; Ross Meentemeyer; David Rizzo

2010-01-01

Epidemiological theory predicts that asymmetric transmission, susceptibility, and mortality within a community will drive pathogen and disease dynamics. These epidemiological asymmetries can result in apparent competition, where a highly infectious host reduces the abundance of less infectious or more susceptible members in a community via a shared pathogen. We show...

Infections in immunocompromised patients. II. Established therapy and its limitations.

PubMed

Periti, P; Mazzei, T

1985-01-01

Diseases affecting host defense mechanisms include neutropenia, aplastic anemia, leukemia, lymphocytopenia (B- and T-lymphocyte abnormalities), deficiencies of complement, splenectomy, diabetes mellitus, renal failure, and autoimmune diseases. Immunocompromised patients face frequent life-threatening complications of infections, particularly when they are hospitalized and receiving cytotoxic myelosuppressive drugs. Oral antimicrobial agents affect the flora of the host's alimentary tract, enhancing colonization by resistant, potentially pathogenic, strains and species, especially in a hospital environment. Nalidixic acid, oxolinic acid, pipemidic acid, polymyxins, co-trimoxazole, polyene antibiotics, and framycetin, which preserve anaerobic colon flora, do not affect the host's colonization resistance and can be given in oral doses high enough to suppress and clear susceptible potential pathogens from the intestinal tract. Such prophylactic treatment permits patients to stay hospitalized in ward conditions. In the compromised host who has fever and suspected septicemia, a decision concerning treatment should be made within an hour of notification of the patient's condition. In acute stages of life-threatening infection, the principal aim of antimicrobial chemotherapy is to provide the most potent treatment; at this stage, the accompanying side effects are less important. An essential component of therapy should be an aminoglycoside paired with a beta-lactam antibiotic. Because the incidence of staphylococcal resistance to antibiotics is high, preliminary sensitivity-testing is essential when staphylococcal sepsis threatens the life of a compromised host. Despite aggressive antibiotic therapy, more than half of immunocompromised patients and patients with severe underlying diseases die when gram-negative bacteria invade their blood. In these patients, medical or surgical removal of the septic focus is a major part of management, but plasma or plasma fractions should be given to correct hypovolemia, and an agent such as dopamine should be administered if volume replacement fails to restore adequate blood pressure. A high dose of corticosteroids should have a beneficial effect, and, for neutropenic patients with gram-negative bacteremia or fever, transfusion with functional neutrophils improves survival.

CRISPR-based herd immunity can limit phage epidemics in bacterial populations

PubMed Central

Geyrhofer, Lukas; Barton, Nicholas H

2018-01-01

Herd immunity, a process in which resistant individuals limit the spread of a pathogen among susceptible hosts has been extensively studied in eukaryotes. Even though bacteria have evolved multiple immune systems against their phage pathogens, herd immunity in bacteria remains unexplored. Here we experimentally demonstrate that herd immunity arises during phage epidemics in structured and unstructured Escherichia coli populations consisting of differing frequencies of susceptible and resistant cells harboring CRISPR immunity. In addition, we develop a mathematical model that quantifies how herd immunity is affected by spatial population structure, bacterial growth rate, and phage replication rate. Using our model we infer a general epidemiological rule describing the relative speed of an epidemic in partially resistant spatially structured populations. Our experimental and theoretical findings indicate that herd immunity may be important in bacterial communities, allowing for stable coexistence of bacteria and their phages and the maintenance of polymorphism in bacterial immunity. PMID:29521625

Effects of antibiotic resistance (AR) and microbiota shifts on Campylobacter jejuni-mediated diseases.

PubMed

Brooks, Phillip T; Mansfield, Linda S

2017-12-01

Campylobacter jejuni is an important zoonotic pathogen recently designated a serious antimicrobial resistant (AR) threat. While most patients with C. jejuni experience hemorrhagic colitis, serious autoimmune conditions can follow including inflammatory bowel disease (IBD) and the acute neuropathy Guillain Barré Syndrome (GBS). This review examines inter-relationships among factors mediating C. jejuni diarrheal versus autoimmune disease especially AR C. jejuni and microbiome shifts. Because both susceptible and AR C. jejuni are acquired from animals or their products, we consider their role in harboring strains. Inter-relationships among factors mediating C. jejuni colonization, diarrheal and autoimmune disease include C. jejuni virulence factors and AR, the enteric microbiome, and host responses. Because AR C. jejuni have been suggested to affect the severity of disease, length of infections and propensity to develop GBS, it is important to understand how these interactions occur when strains are under selection by antimicrobials. More work is needed to elucidate host-pathogen interactions of AR C. jejuni compared with susceptible strains and how AR C. jejuni are maintained and evolve in animal reservoirs and the extent of transmission to humans. These knowledge gaps impair the development of effective strategies to prevent the emergence of AR C. jejuni in reservoir species and human populations.

Differential tolerances to ocean acidification by parasites that share the same host.

PubMed

MacLeod, C D; Poulin, R

2015-06-01

Ocean acidification is predicted to cause major changes in marine ecosystem structure and function over the next century, as species-specific tolerances to acidified seawater may alter previously stable relationships between coexisting organisms. Such differential tolerances could affect marine host-parasite associations, as either host or parasite may prove more susceptible to the stressors associated with ocean acidification. Despite their important role in many ecological processes, parasites have not been studied in the context of ocean acidification. We tested the effects of low pH seawater on the cercariae and, where possible, the metacercariae of four species of marine trematode parasite. Acidified seawater (pH 7.6 and 7.4, 12.5 °C) caused a 40-60% reduction in cercarial longevity and a 0-78% reduction in metacercarial survival. However, the reduction in longevity and survival varied distinctly between parasite taxa, indicating that the effects of reduced pH may be species-specific. These results suggest that ocean acidification has the potential to reduce the transmission success of many trematode species, decrease parasite abundance and alter the fundamental regulatory role of multi-host parasites in marine ecosystems. Copyright © 2015 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

Smallpox and live-virus vaccination in transplant recipients.

PubMed

Fishman, Jay A

2003-07-01

Recent bioterrorism raises the specter of reemergence of smallpox as a clinical entity. The mortality of variola major infection ('typical smallpox') was approximately 30% in past outbreaks. Programs for smallpox immunization for healthcare workers have been proposed. Atypical forms of smallpox presenting with flat or hemorrhagic skin lesions are most common in individuals with immune deficits with historic mortality approaching 100%. Smallpox vaccination, even after exposure, is highly effective. Smallpox vaccine contains a highly immunogenic live virus, vaccinia. Few data exist for the impact of variola or safety of vaccinia in immunocompromised hosts. Both disseminated infection by vaccinia and person-to-person spread after vaccination are uncommon. When it occurs, secondary vaccinia has usually affected individuals with pre-existing skin conditions (atopic dermatitis or eczema) or with other underlying immune deficits. Historically, disseminated vaccinia infection was uncommon but often fatal even in the absence of the most severe form of disease, "progressive vaccinia". Some responded to vaccinia immune globulin. Smallpox exposure would be likely to cause significant mortality among immunocompromised hosts. In the absence of documented smallpox exposures, immunocompromised hosts should not be vaccinated against smallpox. Planning for bioterrorist events must include consideration of uniquely susceptible hosts.

Identification of residues of SARS-CoV nsp1 that differentially affect inhibition of gene expression and antiviral signaling.

PubMed

Jauregui, Andrew R; Savalia, Dhruti; Lowry, Virginia K; Farrell, Cara M; Wathelet, Marc G

2013-01-01

An epidemic of Severe Acute Respiratory Syndrome (SARS) led to the identification of an associated coronavirus, SARS-CoV. This virus evades the host innate immune response in part through the expression of its non-structural protein (nsp) 1, which inhibits both host gene expression and virus- and interferon (IFN)-dependent signaling. Thus, nsp1 is a promising target for drugs, as inhibition of nsp1 would make SARS-CoV more susceptible to the host antiviral defenses. To gain a better understanding of nsp1 mode of action, we generated and analyzed 38 mutants of the SARS-CoV nsp1, targeting 62 solvent exposed residues out of the 180 amino acid protein. From this work, we identified six classes of mutants that abolished, attenuated or increased nsp1 inhibition of host gene expression and/or antiviral signaling. Each class of mutants clustered on SARS-CoV nsp1 surface and suggested nsp1 interacts with distinct host factors to exert its inhibitory activities. Identification of the nsp1 residues critical for its activities and the pathways involved in these activities should help in the design of drugs targeting nsp1. Significantly, several point mutants increased the inhibitory activity of nsp1, suggesting that coronaviruses could evolve a greater ability to evade the host response through mutations of such residues.

Reservoir-host amplification of disease impact in an endangered amphibian.

PubMed

Scheele, Ben C; Hunter, David A; Brannelly, Laura A; Skerratt, Lee F; Driscoll, Don A

2017-06-01

Emerging wildlife pathogens are an increasing threat to biodiversity. One of the most serious wildlife diseases is chytridiomycosis, caused by the fungal pathogen, Batrachochytrium dendrobatidis (Bd), which has been documented in over 500 amphibian species. Amphibians vary greatly in their susceptibility to Bd; some species tolerate infection, whereas others experience rapid mortality. Reservoir hosts-species that carry infection while maintaining high abundance but are rarely killed by disease-can increase extinction risk in highly susceptible, sympatric species. However, whether reservoir hosts amplify Bd in declining amphibian species has not been examined. We investigated the role of reservoir hosts in the decline of the threatened northern corroboree frog (Pseudophryne pengilleyi) in an amphibian community in southeastern Australia. In the laboratory, we characterized the response of a potential reservoir host, the (nondeclining) common eastern froglet (Crinia signifera), to Bd infection. In the field, we conducted frog abundance surveys and Bd sampling for both P. pengilleyi and C. signifera. We built multinomial logistic regression models to test whether Crinia signifera and environmental factors were associated with P. pengilleyi decline. C. signifera was a reservoir host for Bd. In the laboratory, many individuals maintained intense infections (>1000 zoospore equivalents) over 12 weeks without mortality, and 79% of individuals sampled in the wild also carried infections. The presence of C. signifera at a site was strongly associated with increased Bd prevalence in sympatric P. pengilleyi. Consistent with disease amplification by a reservoir host, P. pengilleyi declined at sites with high C. signifera abundance. Our results suggest that when reservoir hosts are present, population declines of susceptible species may continue long after the initial emergence of Bd, highlighting an urgent need to assess extinction risk in remnant populations of other declined amphibian species. © 2016 Society for Conservation Biology.

Resistance to rust fungi in Lolium perenne depends on within-species variation and performance of the host species in grasslands of different plant diversity.

PubMed

Roscher, Christiane; Schumacher, Jens; Foitzik, Oliver; Schulze, Ernst-Detlef

2007-08-01

The hypothesis that plant species diversity and genetic variation of the host species decrease the severity of plant diseases is supported by studies of agricultural systems, but experimental evidence from more complex systems is scarce. In an experiment with grassland communities of varying species richness (1, 2, 4, 8, 16, and 60 species) and functional group richness (1, 2, 3, and 4 functional groups), we used different cultivars of Lolium perenne (perennial ryegrass) to study effects of biodiversity and cultivar identity on the occurrence and severity of foliar fungal diseases caused by Puccinia coronata (crown rust) and P. graminis (stem rust). Cultivar monocultures of perennial ryegrass revealed strong differences in pathogen susceptibility among these cultivars. Disease intensity caused by both rust fungi decreased significantly with growing species richness of species mixtures. The response to the diversity gradient was related to the decreased density and size of the host individuals with increasing species richness. The occurrence of other grass species known to be possible hosts of the pathogens in the experimental mixtures did not promote disease intensity in L. perenne, indicating that there was a high host specificity of pathogen strains. Differences in pathogen susceptibility among perennial ryegrass cultivars persisted independent of diversity treatment, host density and host individual size, but resulted in a cultivar-specific pattern of changes in pathogen infestation across the species-richness gradient. Our study provided evidence that within-species variation in pathogen susceptibility and competitive interactions of the host species with the environment, as caused by species diversity treatments, are key determinants of the occurrence and severity of fungal diseases.

Mobilization of lipids and fortification of cell wall and cuticle are important in host defense against Hessian fly

PubMed Central

2013-01-01

Background Wheat – Hessian fly interaction follows a typical gene-for-gene model. Hessian fly larvae die in wheat plants carrying an effective resistance gene, or thrive in susceptible plants that carry no effective resistance gene. Results Gene sets affected by Hessian fly attack in resistant plants were found to be very different from those in susceptible plants. Differential expression of gene sets was associated with differential accumulation of intermediates in defense pathways. Our results indicated that resources were rapidly mobilized in resistant plants for defense, including extensive membrane remodeling and release of lipids, sugar catabolism, and amino acid transport and degradation. These resources were likely rapidly converted into defense molecules such as oxylipins; toxic proteins including cysteine proteases, inhibitors of digestive enzymes, and lectins; phenolics; and cell wall components. However, toxicity alone does not cause immediate lethality to Hessian fly larvae. Toxic defenses might slow down Hessian fly development and therefore give plants more time for other types of defense to become effective. Conclusion Our gene expression and metabolic profiling results suggested that remodeling and fortification of cell wall and cuticle by increased deposition of phenolics and enhanced cross-linking were likely to be crucial for insect mortality by depriving Hessian fly larvae of nutrients from host cells. The identification of a large number of genes that were differentially expressed at different time points during compatible and incompatible interactions also provided a foundation for further research on the molecular pathways that lead to wheat resistance and susceptibility to Hessian fly infestation. PMID:23800119

LTF and DEFB1 polymorphisms are associated with susceptibility toward chronic periodontitis development.

PubMed

Zupin, L; Robino, A; Navarra, C O; Pirastu, N; Di Lenarda, R; Gasparini, P; Crovella, S; Bevilacqua, L

2017-10-01

Chronic periodontitis is a common pathological condition that affects the supporting tissue of the teeth, leading to progressive alveolar bone destruction and teeth loss. The disease is caused by bacteria and derives from an altered host immune and inflammatory response, also involving different factors such as the oral hygiene, smoking, and genetic background. The innate immune response, the first line of host defense, could also play an important role in the susceptibility to chronic periodontitis. In this study, we evaluated the possible association between periodontal disease and seven genetic variations within DEFB1 and LTF genes, encoding for β-defensins 1 and lactoferrin (two members of oral innate immune system), in an Italian isolated population. DEFB1 5'UTR g. -52G>A (rs1799946), g. -44C>G (rs1800972), g. -20G>A (rs11362), 3'UTR c*5G>A (rs1047031), c*87A>G (rs1800971), LTF p.Ala29Thr (rs1126477), and p.Lys47Arg (rs1126478) single nucleotide polymorphisms (SNPs) were analyzed in 155 healthy individuals and 439 chronic periodontitis patients from North-East Italy. Significant associations were found between periodontitis and g. -20G>A (rs11362) and g. -44C>G (rs1800972) SNPs in DEFB1 gene as well as p.Ala29Thr (rs1126477) and p.Lys47Arg (rs1126478) SNPs in LTF gene. Our results suggest the involvement of DEFB1 and LTF genetic variations in the susceptibility toward development of periodontitis. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd. All rights reserved.

Thicker host tissues moderate light stress in a cnidarian endosymbiont.

PubMed

Dimond, James L; Holzman, Benjamin J; Bingham, Brian L

2012-07-01

The susceptibility of algal-cnidarian holobionts to environmental stress is dependent on attributes of both host and symbiont, but the role of the host is often unclear. We examined the influence of the host on symbiont light stress, comparing the photophysiology of the chlorophyte symbiont Elliptochloris marina in two species of sea anemones in the genus Anthopleura. After 3 months of acclimation in outdoor tanks, polyp photoprotective contraction behavior was similar between the two host species, but photochemical efficiency was 1.5 times higher in A. xanthogrammica than in A. elegantissima. Maximum relative electron transport rates, derived from rapid light curves, were 1.5 times higher in A. xanthogrammica than in A. elegantissima when symbionts were inside intact tissues, but were not significantly different between host species upon removal of outer (epidermis and mesoglea) tissue layers from symbiont-containing gastrodermal cells. Tissues of A. xanthogrammica were 1.8 times thicker than those of A. elegantissima, with outer tissue layers attenuating 1.6 times more light. We found no significant differences in light absorption properties per unit volume of tissue, confirming the direct effect of tissue thickness on light attenuation. The thicker tissues of A. xanthogrammica thus provide a favorable environment for E. marina - a relatively stress-susceptible symbiont - and may explain its higher prevalence and expanded range in A. xanthogrammica along the Pacific coast of North America. Our findings also support a photoprotective role for thicker host tissues in reef corals that has long been thought to influence variability in bleaching susceptibility among coral taxa.

Gypsy Moth Host Interactions: A Concept of Room and Board

Treesearch

William E.  Wallner

1983-01-01

The influence of host type and condition on the bioecology of gypsy moth are discussed from the viewpoint of room and board. Larval establishment was higher on preferred hosts; less than 5% migrated off them. Nonpreferred hosts lost 10-25% of larvae. Susceptibility of gypsy moth larvae to nucleopolyhedrosis virus increased following 1 or 2 years of defoliation....

Effects of Interactions among Heterodera glycines, Meloidogyne incognita, and Host Genotype on Soybean Yield and Nematode Population Densities

PubMed Central

Niblack, T. L.; Hussey, R. S.; Boerma, H. R.

1986-01-01

The effects of host genotype and initial nematode population densities (Pi) on yield of soybean and soil population densities of Heterodera glycines (Hg) race 3 and Meloidogyne incognita (Mi) race 3 were studied in a greenhouse and field microplots in 1983 and 1984. Centennial (resistant to Hg and Mi), Braxton (resistant to Mi, susceptible to Hg), and Coker 237 (susceptible to Hg and Mi) were planted in soil infested with 0, 31, or 124 eggs of Hg and Mi, individually and in all combinations, per 100 cm³ soil. Yield responses of the soybean cultivars to individual and combined infestations of Hg and Mi were primarily dependent on soybean resistance or susceptibility to each species separately. Yield of Centennial was stimulated or unaffected by nematode treatments, yield of Braxton was suppressed by Hg only, and yield suppressions caused by Hg and Mi were additive and dependent on Pi for Coker 237. Other plant responses to nematodes were also dependent on host resistance or susceptibility. Population densities of Mi second-stage juveniles (J2) in soil were related to Mi Pi and remained constant in the presence of Hg for all three cultivars. Population densities of Hg J2 on the two Hg-susceptible Cultivars, Braxton and Coker 237, were suppressed in the presence of Mi at low Hg Pi. PMID:19294208

Biocontrol Potential of Steinernema thermophilum and Its Symbiont Xenorhabdus indica Against Lepidopteran Pests: Virulence to Egg and Larval Stages.

PubMed

Kalia, Vinay; Sharma, Garima; Shapiro-Ilan, David I; Ganguly, Sudershan

2014-03-01

Under laboratory conditions, the biocontrol potential of Steinernema thermophilum was tested against eggs and larval stages of two important lepidopteran insect pests, Helicoverpa armigera and Spodoptera litura (polyphagous pests), as well as Galleria mellonella (used as a model host). In terms of host susceptibility of lepidopteran larvae to S. thermophilum, based on the LC50 36 hr after treatment, G. mellonella (LC50 = 16.28 IJ/larva) was found to be more susceptible than S. litura (LC50 = 85 IJ/larva), whereas neither host was found to be significantly different from H. armigera (LC50 = 54.68 IJ/larva). In addition to virulence to the larval stages, ovicidal activity up to 84% was observed at 200 IJ/50 and 100 eggs of H. armigera and S. litura, respectively. To our knowledge this is the first report of entomopathogenic nematode pathogenicity to lepidopteran eggs. Production of infective juvenile (IJ) nematodes/insect larva was also measured and found to be positively correlated with rate of IJ for H. armigera (r = 0.990), S. litura (r = 0.892), as well as G. mellonella (r = 0.834). Both Phase I and Phase II of symbiotic bacteria Xenorhabdus indica were tested separately against neonates of H. armigera and S. litura by feeding assays and found to be virulent to the target pests; phase variation did not affect the level of virulence. Thus S. thermophilum as well as the nematode's symbiotic bacteria applied separately have the potential to be developed as biocontrol agents for key lepidopteran pests.

Susceptibility against grey blight disease-causing fungus Pestalotiopsis sp. in tea (Camellia sinensis (L.) O. Kuntze) cultivars is influenced by anti-oxidative enzymes.

PubMed

Palanisamy, Senthilkumar; Mandal, Abul Kalam Azad

2014-01-01

Reactive oxygen species (ROS) production is the first level of response by a host during stress. Even though the ROS are toxic to cell, when present in a limited amount, they act as a signalling molecule for the expression of defence-related genes and later are scavenged by either enzymatic or non-enzymatic mechanisms of the host. The different anti-oxidative enzymes like glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APO), peroxidase (POD) and polyphenol oxidase (PPO) were estimated, and their activities were compared between infected and healthy leaves of the tolerant and susceptible cultivars of tea. The infected leaves of the susceptible cultivars registered higher amount of enzyme activity when compared with the tolerant cultivars. The study reveals that the more anti-oxidative enzymes, the more susceptible the cultivar will be.

MorTAL Kombat: the story of defense against TAL effectors through loss-of-susceptibility

PubMed Central

Hutin, Mathilde; Pérez-Quintero, Alvaro L.; Lopez, Camilo; Szurek, Boris

2015-01-01

Many plant-pathogenic xanthomonads rely on Transcription Activator-Like (TAL) effectors to colonize their host. This particular family of type III effectors functions as specific plant transcription factors via a programmable DNA-binding domain. Upon binding to the promoters of plant disease susceptibility genes in a sequence-specific manner, the expression of these host genes is induced. However, plants have evolved specific strategies to counter the action of TAL effectors and confer resistance. One mechanism is to avoid the binding of TAL effectors by mutations of their DNA binding sites, resulting in resistance by loss-of-susceptibility. This article reviews our current knowledge of the susceptibility hubs targeted by Xanthomonas TAL effectors, possible evolutionary scenarios for plants to combat the pathogen with loss-of-function alleles, and how this knowledge can be used overall to develop new pathogen-informed breeding strategies and improve crop resistance. PMID:26236326

MHC variation sculpts individualized microbial communities that control susceptibility to enteric infection

PubMed Central

Kubinak, Jason L.; Stephens, W. Zac; Soto, Ray; Petersen, Charisse; Chiaro, Tyson; Gogokhia, Lasha; Bell, Rickesha; Ajami, Nadim J.; Petrosino, Joseph F.; Morrison, Linda; Potts, Wayne K.; Jensen, Peter E.; O'Connell, Ryan M.; Round, June L.

2015-01-01

The presentation of protein antigens on the cell surface by major histocompatibility complex (MHC) molecules coordinates vertebrate adaptive immune responses, thereby mediating susceptibility to a variety of autoimmune and infectious diseases. The composition of symbiotic microbial communities (the microbiota) is influenced by host immunity and can have a profound impact on host physiology. Here we use an MHC congenic mouse model to test the hypothesis that genetic variation at MHC genes among individuals mediates susceptibility to disease by controlling microbiota composition. We find that MHC genotype significantly influences antibody responses against commensals in the gut, and that these responses are correlated with the establishment of unique microbial communities. Transplantation experiments in germfree mice indicate that MHC-mediated differences in microbiota composition are sufficient to explain susceptibility to enteric infection. Our findings indicate that MHC polymorphisms contribute to defining an individual's unique microbial fingerprint that influences health. PMID:26494419

[The susceptibility of different animal species to synanthropic and natural populations of Trichinella].

PubMed

Artemenko, Iu G; Artemenko, L P

1997-01-01

Pigs have been found to be highly susceptible to the synanthropic (domestic) population of Trichinella [correction of Trachina] and weakly susceptible to the natural (native) one. Fur-bearing animals (polar foxes and foxes) are more susceptible to the natural population of Trichinella [correction of Trachina], but minks are equally sensible to the two variants of T. spiralis. In the host's body, synanthropic Trichinella [correction of Trachinas] form capsules of lemon-like, less frequently, oval shape, but the native population do round capsules. There is larval adaptation when Trichinella [correction of Trachina] larvae enter the nonspecific host's body after their prepassage through the organism of domestic carnivorous animals (cats, dogs). The pig is successfully infected with T. spiralis nativa via the cat or dog; the infection rate is approximately close to that observed during control infection of pigs with synanthropic Trichinella [correction of Trachina].

IRES-mediated translation of foot-and-mouth disease virus (FMDV) in cultured cells derived from FMDV-susceptible and -insusceptible animals.

PubMed

Kanda, Takehiro; Ozawa, Makoto; Tsukiyama-Kohara, Kyoko

2016-03-31

Foot-and-mouth disease virus (FMDV) possess a positive sense, single stranded RNA genome. Internal ribosomal entry site (IRES) element exists within its 5' untranslated region (5'UTR) of the viral RNA. Translation of the viral RNA is initiated by internal entry of the 40S ribosome within the IRES element. This process is facilitated by cellular factors known as IRES trans-acting factors (ITAFs). Foot-and-mouth disease (FMD) is host-restricted disease for cloven-hoofed animals such as cattle and pigs, but the factors determining the host range have not been identified yet. Although, ITAFs are known to promote IRES-mediated translation, these findings were confirmed only in cells derived from FMDV-insusceptible animals so far. We evaluated and compared the IRES-mediated translation activities among cell lines derived from four different animal species using bicistronic luciferase reporter plasmid, which possesses an FMDV-IRES element between Renilla and Firefly luciferase genes. Furthermore, we analyzed the effect of the cellular factors on IRES-mediated translation by silencing the cellular factors using siRNA in both FMDV-susceptible and -insusceptible animal cells. Our data indicated that IRES-mediated translational activity was not linked to FMDV host range. ITAF45 promoted IRES-mediated translation in all cell lines, and the effects of poly-pyrimidine tract binding protein (PTB) and eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) were observed only in FMDV-susceptible cells. Thus, PTB and 4E-BP1 may influence the host range of FMDV. IRES-mediated translation activity of FMDV was not predictive of its host range. ITAF45 promoted IRES-mediated translation in all cells, and the effects of PTB and 4E-BP1 were observed only in FMDV-susceptible cells.

From perception to activation: the molecular-genetic and biochemical landscape of disease resistance signaling in plants.

PubMed

Knepper, Caleb; Day, Brad

2010-01-01

More than 60 years ago, H.H. Flor proposed the "Gene-for-Gene" hypothesis, which described the genetic relationship between host plants and pathogens. In the decades that followed Flor's seminal work, our understanding of the plant-pathogen interaction has evolved into a sophisticated model, detailing the molecular genetic and biochemical processes that control host-range, disease resistance signaling and susceptibility. The interaction between plants and microbes is an intimate exchange of signals that has evolved for millennia, resulting in the modification and adaptation of pathogen virulence strategies and host recognition elements. In total, plants have evolved mechanisms to combat the ever-changing landscape of biotic interactions bombarding their environment, while in parallel, plant pathogens have co-evolved mechanisms to sense and adapt to these changes. On average, the typical plant is susceptible to attack by dozens of microbial pathogens, yet in most cases, remains resistant to many of these challenges. The sum of research in our field has revealed that these interactions are regulated by multiple layers of intimately linked signaling networks. As an evolved model of Flor's initial observations, the current paradigm in host-pathogen interactions is that pathogen effector molecules, in large part, drive the recognition, activation and subsequent physiological responses in plants that give rise to resistance and susceptibility. In this Chapter, we will discuss our current understanding of the association between plants and microbial pathogens, detailing the pressures placed on both host and microbe to either maintain disease resistance, or induce susceptibility and disease. From recognition to transcriptional reprogramming, we will review current data and literature that has advanced the classical model of the Gene-for-Gene hypothesis to our current understanding of basal and effector triggered immunity.

Plasmodium Infections in Natural Populations of Anolis sagrei Reflect Tolerance Rather Than Susceptibility

PubMed Central

Bonneaud, Camille; Sepil, Irem; Wilfert, Lena; Calsbeek, Ryan

2017-01-01

Synopsis Parasites can represent formidable selection pressures for hosts, but the cost of infection is sometimes difficult to demonstrate in natural populations. While parasite exploitation strategies may, in some instances, actually inflict low costs on their hosts, the response of hosts to infection is also likely to determine whether or not these costs can be detected. Indeed, costs of infection may be obscured if infected individuals in the wild are those that are the most tolerant, rather than the most susceptible, to infection. Here we test this hypothesis in two natural populations of Anolis sagrei, one of the most common anole lizard of the Bahamas. Plasmodium parasites were detected in > 7% of individuals and belonged to two distinct clades: P. mexicanum and P. floriensis. Infected individuals displayed greater body condition than non-infected ones and we found no association between infection status, stamina, and survival to the end of the breeding season. Furthermore, we found no significant difference in the immuno-competence (measured as a response to phytohemagglutinin challenge) of infected versus non-infected individuals. Taken together, our results suggest that the infected individuals that are caught in the wild are those most able to withstand the cost of the infection and that susceptible, infected individuals have been removed from the population (i.e., through disease-induced mortality). This study highlights the need for caution when interpreting estimates of infection costs in natural populations, as costs may appear low either when parasites exploitation strategies truly inflict low costs on their hosts or when those costs are so high that susceptible hosts are removed from the population. PMID:28859403

Evolutionary tools for phytosanitary risk analysis: phylogenetic signal as a predictor of host range of plant pests and pathogens

PubMed Central

Gilbert, Gregory S; Magarey, Roger; Suiter, Karl; Webb, Campbell O

2012-01-01

Assessing risk from a novel pest or pathogen requires knowing which local plant species are susceptible. Empirical data on the local host range of novel pests are usually lacking, but we know that some pests are more likely to attack closely related plant species than species separated by greater evolutionary distance. We use the Global Pest and Disease Database, an internal database maintained by the United States Department of Agriculture Animal and Plant Health Inspection Service – Plant Protection and Quarantine Division (USDA APHIS-PPQ), to evaluate the strength of the phylogenetic signal in host range for nine major groups of plant pests and pathogens. Eight of nine groups showed significant phylogenetic signal in host range. Additionally, pests and pathogens with more known hosts attacked a phylogenetically broader range of hosts. This suggests that easily obtained data – the number of known hosts and the phylogenetic distance between known hosts and other species of interest – can be used to predict which plant species are likely to be susceptible to a particular pest. This can facilitate rapid assessment of risk from novel pests and pathogens when empirical host range data are not yet available and guide efficient collection of empirical data for risk evaluation. PMID:23346231

Evolutionary tools for phytosanitary risk analysis: phylogenetic signal as a predictor of host range of plant pests and pathogens.

PubMed

Gilbert, Gregory S; Magarey, Roger; Suiter, Karl; Webb, Campbell O

2012-12-01

Assessing risk from a novel pest or pathogen requires knowing which local plant species are susceptible. Empirical data on the local host range of novel pests are usually lacking, but we know that some pests are more likely to attack closely related plant species than species separated by greater evolutionary distance. We use the Global Pest and Disease Database, an internal database maintained by the United States Department of Agriculture Animal and Plant Health Inspection Service - Plant Protection and Quarantine Division (USDA APHIS-PPQ), to evaluate the strength of the phylogenetic signal in host range for nine major groups of plant pests and pathogens. Eight of nine groups showed significant phylogenetic signal in host range. Additionally, pests and pathogens with more known hosts attacked a phylogenetically broader range of hosts. This suggests that easily obtained data - the number of known hosts and the phylogenetic distance between known hosts and other species of interest - can be used to predict which plant species are likely to be susceptible to a particular pest. This can facilitate rapid assessment of risk from novel pests and pathogens when empirical host range data are not yet available and guide efficient collection of empirical data for risk evaluation.

QMRA for Drinking Water: 1. Revisiting the Mathematical Structure of Single-Hit Dose-Response Models.

PubMed

Nilsen, Vegard; Wyller, John

2016-01-01

Dose-response models are essential to quantitative microbial risk assessment (QMRA), providing a link between levels of human exposure to pathogens and the probability of negative health outcomes. In drinking water studies, the class of semi-mechanistic models known as single-hit models, such as the exponential and the exact beta-Poisson, has seen widespread use. In this work, an attempt is made to carefully develop the general mathematical single-hit framework while explicitly accounting for variation in (1) host susceptibility and (2) pathogen infectivity. This allows a precise interpretation of the so-called single-hit probability and precise identification of a set of statistical independence assumptions that are sufficient to arrive at single-hit models. Further analysis of the model framework is facilitated by formulating the single-hit models compactly using probability generating and moment generating functions. Among the more practically relevant conclusions drawn are: (1) for any dose distribution, variation in host susceptibility always reduces the single-hit risk compared to a constant host susceptibility (assuming equal mean susceptibilities), (2) the model-consistent representation of complete host immunity is formally demonstrated to be a simple scaling of the response, (3) the model-consistent expression for the total risk from repeated exposures deviates (gives lower risk) from the conventional expression used in applications, and (4) a model-consistent expression for the mean per-exposure dose that produces the correct total risk from repeated exposures is developed. © 2016 Society for Risk Analysis.

Rock magnetic and anisotropy of magnetic susceptibility(AMS) of earthquake affected soft sediments: Examples from Shillong and Latur (Deccan Trap), India.

NASA Astrophysics Data System (ADS)

Lakshmi, B. V., ,, Dr.; Gawali, Mr. Praveen B.; Deenadayalan, K., ,, Dr.; Ramesh, D. S., ,, Prof.

2017-04-01

Rock magnetic and anisotropy of magnetic susceptibility (AMS) of earthquake affected soft sediments: Examples from Shillong and Latur (Deccan Trap), India. B.V.Lakshmi, Praveen B.Gawali, K.Deenadayalan and D.S.Ramesh Indian Institute of Geomagnetism, plot 5, sector 18, Near Kalamboli Highway, New Panvel(W), Navi Mumbai 410218 Combined rock magnetism and anisotropy of magnetic susceptibility (AMS) studies on earthquake induced soft and non-soft sediments from Shillong and Latur, India have thrown up interesting results. The morphology of hysteresis loops, the pattern of isothermal remanent magnetization (IRM) acquisition, and temperature dependence of susceptibility indicate that titano-magnetite/magnetite is the main magnetic carrier in these sediments. We also analyzed the anisotropy of magnetic susceptibility (AMS) of liquefaction features within the seismically active Dauki fault, Shillong Plateau. We discovered that host sediments (non-liquefied), are characterized by an oblate AMS ellipsoid and liquefied sediment are characterized by a triaxial AMS ellipsoid, well grouped maximum susceptibility axis K1 (NNW-SSE trend). Field evidence and AMS analysis indicate that most of these features were emplaced by injection inferred to be due to seismically triggered fluidization. Anisotropy of magnetic susceptibility (AMS) of deformed and undeformed unconsolidated clay samples of Deccan Trap terrain from the 2000-year-old paleoearthquake site of Ther village, Maharashtra, India, was also studied. Such deposits are rare in the compact basaltic terrain because of which the results acquired are very important. The undeformed clay samples exhibit typical sedimentary fabric with an oblate AMS ellipsoid, whereas the deformed samples are tightly grouped in the inferred compression direction, probably effected by an earthquake, exhibiting prolate as well as oblate AMS ellipsoids. Rock magnetic and AMS methodology can help understand the behavior of different sediments to the regional deformational processes active in the Himalayan region, and possibly local deformational activities in the compact Deccan trap region. The accumulating stress and strain direction can be delineated to infer strike of the forces accumulating stresses. These studies can be used to build the chronology of past earthquakes.

Characterization of Arabidopsis Transcriptional Responses to Different Aphid Species Reveals Genes that Contribute to Host Susceptibility and Non-host Resistance

PubMed Central

Jaouannet, Maëlle; Morris, Jenny A.; Hedley, Peter E.; Bos, Jorunn I. B.

2015-01-01

Aphids are economically important pests that display exceptional variation in host range. The determinants of diverse aphid host ranges are not well understood, but it is likely that molecular interactions are involved. With significant progress being made towards understanding host responses upon aphid attack, the mechanisms underlying non-host resistance remain to be elucidated. Here, we investigated and compared Arabidopsis thaliana host and non-host responses to aphids at the transcriptional level using three different aphid species, Myzus persicae, Myzus cerasi and Rhopalosiphum pisum. Gene expression analyses revealed a high level of overlap in the overall gene expression changes during the host and non-host interactions with regards to the sets of genes differentially expressed and the direction of expression changes. Despite this overlap in transcriptional responses across interactions, there was a stronger repression of genes involved in metabolism and oxidative responses specifically during the host interaction with M. persicae. In addition, we identified a set of genes with opposite gene expression patterns during the host versus non-host interactions. Aphid performance assays on Arabidopsis mutants that were selected based on our transcriptome analyses identified novel genes contributing to host susceptibility, host defences during interactions with M. persicae as well to non-host resistance against R. padi. Understanding how plants respond to aphid species that differ in their ability to infest plant species, and identifying the genes and signaling pathways involved, is essential for the development of novel and durable aphid control in crop plants. PMID:25993686

Parasite transmission in social interacting hosts: Monogenean epidemics in guppies

USGS Publications Warehouse

Johnson, M.B.; Lafferty, K.D.; van, Oosterhout C.; Cable, J.

2011-01-01

Background: Infection incidence increases with the average number of contacts between susceptible and infected individuals. Contact rates are normally assumed to increase linearly with host density. However, social species seek out each other at low density and saturate their contact rates at high densities. Although predicting epidemic behaviour requires knowing how contact rates scale with host density, few empirical studies have investigated the effect of host density. Also, most theory assumes each host has an equal probability of transmitting parasites, even though individual parasite load and infection duration can vary. To our knowledge, the relative importance of characteristics of the primary infected host vs. the susceptible population has never been tested experimentally. Methodology/Principal Findings: Here, we examine epidemics using a common ectoparasite, Gyrodactylus turnbulli infecting its guppy host (Poecilia reticulata). Hosts were maintained at different densities (3, 6, 12 and 24 fish in 40 L aquaria), and we monitored gyrodactylids both at a population and individual host level. Although parasite population size increased with host density, the probability of an epidemic did not. Epidemics were more likely when the primary infected fish had a high mean intensity and duration of infection. Epidemics only occurred if the primary infected host experienced more than 23 worm days. Female guppies contracted infections sooner than males, probably because females have a higher propensity for shoaling. Conclusions/Significance: These findings suggest that in social hosts like guppies, the frequency of social contact largely governs disease epidemics independent of host density. ?? 2011 Johnson et al.

Parasite transmission in social interacting hosts: Monogenean epidemics in guppies

USGS Publications Warehouse

Johnson, Mirelle B.; Lafferty, Kevin D.; van Oosterhout, Cock; Cable, Joanne

2011-01-01

Background Infection incidence increases with the average number of contacts between susceptible and infected individuals. Contact rates are normally assumed to increase linearly with host density. However, social species seek out each other at low density and saturate their contact rates at high densities. Although predicting epidemic behaviour requires knowing how contact rates scale with host density, few empirical studies have investigated the effect of host density. Also, most theory assumes each host has an equal probability of transmitting parasites, even though individual parasite load and infection duration can vary. To our knowledge, the relative importance of characteristics of the primary infected host vs. the susceptible population has never been tested experimentally. Methodology/Principal Findings Here, we examine epidemics using a common ectoparasite, Gyrodactylus turnbulli infecting its guppy host (Poecilia reticulata). Hosts were maintained at different densities (3, 6, 12 and 24 fish in 40 L aquaria), and we monitored gyrodactylids both at a population and individual host level. Although parasite population size increased with host density, the probability of an epidemic did not. Epidemics were more likely when the primary infected fish had a high mean intensity and duration of infection. Epidemics only occurred if the primary infected host experienced more than 23 worm days. Female guppies contracted infections sooner than males, probably because females have a higher propensity for shoaling. Conclusions/Significance These findings suggest that in social hosts like guppies, the frequency of social contact largely governs disease epidemics independent of host density.

The bacterial skin microbiome in psoriatic arthritis, an unexplored link in pathogenesis: challenges and opportunities offered by recent technological advances.

PubMed

Castelino, Madhura; Eyre, Stephen; Upton, Mathew; Ho, Pauline; Barton, Anne

2014-05-01

The resident microbial community, harboured by humans in sites such as the skin and gastrointestinal tract, is enormous, representing a candidate environmental factor affecting susceptibility to complex diseases, where both genetic and environmental risk factors are important. The potential of microorganisms to influence the human immune system is considerable, given their ubiquity. The impact of the host-gene-microbe interaction on the maintenance of health and the development of disease has not yet been assessed robustly in chronic inflammatory conditions. PsA represents a model inflammatory disease to explore the role of the microbiome because skin involvement and overlap with IBD implicates both the skin and gastrointestinal tract as sources of microbial triggers for PsA. In parallel with genetic studies, characterization of the host microbiota may benefit our understanding of the microbial contribution to disease pathogenesis-knowledge that may eventually inform the development of novel therapeutics.

Animal models for influenza virus pathogenesis, transmission, and immunology

PubMed Central

Thangavel, Rajagowthamee R.; Bouvier, Nicole M.

2014-01-01

In humans, infection with an influenza A or B virus manifests typically as an acute and self-limited upper respiratory tract illness characterized by fever, cough, sore throat, and malaise. However, influenza can present along a broad spectrum of disease, ranging from sub-clinical or even asymptomatic infection to a severe primary viral pneumonia requiring advanced medical supportive care. Disease severity depends upon the virulence of the influenza virus strain and the immune competence and previous influenza exposures of the patient. Animal models are used in influenza research not only to elucidate the viral and host factors that affect influenza disease outcomes in and spread among susceptible hosts, but also to evaluate interventions designed to prevent or reduce influenza morbidity and mortality in man. This review will focus on the three animal models currently used most frequently in influenza virus research -- mice, ferrets, and guinea pigs -- and discuss the advantages and disadvantages of each. PMID:24709389

Differences in the number of hemocytes in the snail host Biomphalaria tenagophila, resistant and susceptible to Schistosoma mansoni infection.

PubMed

Oliveira, A L D; Levada, P M; Zanotti-Magalhaes, E M; Magalhães, L A; Ribeiro-Paes, J T

2010-12-21

The relationships between schistosomiasis and its intermediate host, mollusks of the genus Biomphalaria, have been a concern for decades. It is known that the vector mollusk shows different susceptibility against parasite infection, whose occurrence depends on the interaction between the forms of trematode larvae and the host defense cells. These cells are called amebocytes or hemocytes and are responsible for the recognition of foreign bodies and for phagocytosis and cytotoxic reactions. The defense cells mediate the modulation of the resistant and susceptible phenotypes of the mollusk. Two main types of hemocytes are found in the Biomphalaria hemolymph: the granulocytes and the hyalinocytes. We studied the variation in the number (kinetics) of hemocytes for 24 h after exposing the parasite to genetically selected and non-selected strains of Biomphalaria tenagophila, susceptible or not to infection by Schistosoma mansoni. The differences were analyzed referred to the variations in the number of hemocytes in mollusks susceptible or not to infection by S. mansoni. The hemolymph of the selected and non-selected snails was collected, and hemocytes were counted using a Neubauer chamber at six designated periods: 0 h (control, non-exposed individuals), 2 h, 6 h, 12 h, 18 h and, 24 h after parasite exposure. Samples of hemolymph of five selected mollusks and five non-selected mollusks were separately used at each counting time. There was a significant variation in the number of hemocytes between the strains, which indicates that defense cells have different behaviors in resistant and susceptible mollusks.

Weed hosts and relative weed and cover crop susceptibility to Rotylenchulus reniformis in the Mississippi Delta

USDA-ARS?s Scientific Manuscript database

The reniform nematode (Rotylenchulus reniformis) causes economic losses in cotton and soybean in the southeastern United States, and has the ability to reproduce on more than 300 plant species. Even when the host crop is protected through the use of nematicides or host plant resistance, the potentia...

Phomopsis and Sudden Oak Death: A Tale of Two Nursery Nuisances

Treesearch

Bruce D. Moltzan

2006-01-01

Tree nurseries, by their very nature, provide key components of the disease triangle (pathogen, host, and environment) simply by the widespread planting of susceptible host(s) grown under optimal conditions. Pathogens can severely impact the quality and quantity of seedling stock, making pest management a high priority in successful nursery practice. Careful...

RODENT MODELS OF SUSCEPTIBILITY: WHAT IS THEIR PLACE IN INHALATION TOXICOLOGY

EPA Science Inventory

Abstract: There is renewed interest in inhalation toxicology regarding "susceptibility" as associated with host variables, including genetics, age, diet, and disease. This interest derives from epidemiology that shows air pollution-related human mortality/morbidity, especially a...

Neurological syndromes driven by postinfectious processes or unrecognized persistent infections.

PubMed

Johnson, Tory P; Nath, Avindra

2018-06-01

The immune system serves a critical role in protecting the host against various pathogens. However, under circumstances, once triggered by the infectious process, it may be detrimental to the host. This may be as a result of nonspecific immune activation or due to a targeted immune response to a specific host antigen. In this opinion piece, we discuss the underlying mechanisms that lead to such an inflammatory or autoimmune syndrome affecting the nervous system. We examine these hypotheses in the context of recent emerging infections to provide mechanistic insight into the clinical manifestations and rationale for immunomodulatory therapy. Some pathogens endure longer than previously thought. Persistent infections may continue to drive immune responses resulting in chronic inflammation or development of autoimmune processes, resulting in damage to the nervous system. Patients with genetic susceptibilities in immune regulation may be particularly vulnerable to pathogen driven autoimmune responses. The presence of prolonged pathogens may result in chronic immune stimulations that drives immune-mediated neurologic complications. Understanding the burden and mechanisms of these processes is challenging but important.

Helminth parasites alter protection against Plasmodium infection.

PubMed

Salazar-Castañon, Víctor H; Legorreta-Herrera, Martha; Rodriguez-Sosa, Miriam

2014-01-01

More than one-third of the world's population is infected with one or more helminthic parasites. Helminth infections are prevalent throughout tropical and subtropical regions where malaria pathogens are transmitted. Malaria is the most widespread and deadliest parasitic disease. The severity of the disease is strongly related to parasite density and the host's immune responses. Furthermore, coinfections between both parasites occur frequently. However, little is known regarding how concomitant infection with helminths and Plasmodium affects the host's immune response. Helminthic infections are frequently massive, chronic, and strong inductors of a Th2-type response. This implies that infection by such parasites could alter the host's susceptibility to subsequent infections by Plasmodium. There are a number of reports on the interactions between helminths and Plasmodium; in some, the burden of Plasmodium parasites increased, but others reported a reduction in the parasite. This review focuses on explaining many of these discrepancies regarding helminth-Plasmodium coinfections in terms of the effects that helminths have on the immune system. In particular, it focuses on helminth-induced immunosuppression and the effects of cytokines controlling polarization toward the Th1 or Th2 arms of the immune response.

Phaeohyphomycoses, Emerging Opportunistic Diseases in Animals

PubMed Central

Seyedmousavi, S.; Guillot, J.

2013-01-01

Emerging fungal diseases due to black yeasts and relatives in domestic or wild animals and in invertebrates or cold- and warm-blooded vertebrates are continually being reported, either as novel pathogens or as familiar pathogens affecting new species of hosts. Different epidemiological situations can be distinguished, i.e., occurrence as single infections or as zoonoses, and infection may occur sporadically in otherwise healthy hosts. Such infections are found mostly in mammals but also in cold-blooded animals, are frequently subcutaneous or cerebral, and bear much similarity to human primary disorders. Infections of the nervous system are mostly fatal, and the source and route of infection are currently unknown. A third epidemiological situation corresponds to pseudoepidemics, i.e., infection of a large host population due to a common source. It is often observed and generally hypothesized that the susceptible animals are under stress, e.g., due to poor housing conditions of mammals or to a change of basins in the case of fishes. The descriptions in this article represent an overview of the more commonly reported and recurring black fungi and the corresponding diseases in different types of animals. PMID:23297257

Inulin and oligofructose in chronic inflammatory bowel disease.

PubMed

Leenen, Celine H M; Dieleman, Levinus A

2007-11-01

Crohn's disease and ulcerative colitis, also called chronic inflammatory bowel diseases (IBD), affect up to 500 per 100,000 persons in the Western world. Recent studies in the etiology of IBD suggest that these diseases are caused by a combination of genetic, environmental, and immunological factors. Results from humans and especially animal models of colitis reported by our group and others have indicated that these diseases result from a lack of tolerance to resident intestinal bacteria in genetically susceptible hosts. Probiotic bacteria have health-promoting effects for the host when ingested and have also shown efficacy in ulcerative colitis and refractory pouchitis. In light of the efficacy of providing probiotic bacteria to patients with IBD, there has been interest in the prophylactic and therapeutic potential of inulin, oligofructose, and other prebiotics for patients with or at risk of IBD. Prebiotics are nondigestible dietary oligosaccharides that affect the host by selectively stimulating growth, activity, or both of selective intestinal (probiotic) bacteria. Prebiotics are easy to administer and, in contrast to probiotic therapy, do not require administration of large amounts of (live) bacteria and are therefore easier to administer. Studies using prebiotics, especially beta-fructan oligosaccharides, for the treatment of chronic intestinal inflammation have shown benefit in animal models of colitis. Studies using these prebiotics alone or in combination with probiotics are emerging and have shown promise. These dietary therapies could lead to novel treatments for these chronic debilitating diseases.

Chronic bystander infections and immunity to unrelated antigens

PubMed Central

Stelekati, Erietta; Wherry, E. John

2012-01-01

Chronic infections with persistent pathogens such as helminths, mycobacteria, Plasmodium and hepatitis viruses affect more than a third of the human population and are associated with increased susceptibility to other pathogens as well as reduced vaccine efficacy. Although these observations suggest an impact of chronic infections in modulating immunity to unrelated antigens, little is known regarding the underlying mechanisms. Here, we summarize evidence of the most prevalent infections affecting immunity to unrelated pathogens and vaccines, and discuss potential mechanisms of how different bystander chronic infections might impact immune responses. We suggest that bystander chronic infections affect different stages of host responses and may impact transmission of other pathogens, recognition and innate immune responses, priming and differentiation of adaptive effector responses, as well as the development and maintenance of immunological memory. Further understanding of the immunological effects of co-infection should provide opportunities to enhance vaccine efficacy and control infectious diseases. PMID:23084915

Transcriptome profiling during a natural host-parasite interaction.

PubMed

McTaggart, Seanna J; Cézard, Timothée; Garbutt, Jennie S; Wilson, Phil J; Little, Tom J

2015-08-28

Infection outcome in some coevolving host-pathogens is characterised by host-pathogen genetic interactions, where particular host genotypes are susceptible only to a subset of pathogen genotypes. To identify candidate genes responsible for the infection status of the host, we exposed a Daphnia magna host genotype to two bacterial strains of Pasteuria ramosa, one of which results in infection, while the other does not. At three time points (four, eight and 12 h) post pathogen exposure, we sequenced the complete transcriptome of the hosts using RNA-Seq (Illumina). We observed a rapid and transient response to pathogen treatment. Specifically, at the four-hour time point, eight genes were differentially expressed. At the eight-hour time point, a single gene was differentially expressed in the resistant combination only, and no genes were differentially expressed at the 12-h time point. We found that pathogen-associated transcriptional activity is greatest soon after exposure. Genome-wide resistant combinations were more likely to show upregulation of genes, while susceptible combinations were more likely to be downregulated, relative to controls. Our results also provide several novel candidate genes that may play a pivotal role in determining infection outcomes.

Cell wall composition profiling of parasitic giant dodder (Cuscuta reflexa) and its hosts: a priori differences and induced changes.

PubMed

Johnsen, Hanne R; Striberny, Bernd; Olsen, Stian; Vidal-Melgosa, Silvia; Fangel, Jonatan U; Willats, William G T; Rose, Jocelyn K C; Krause, Kirsten

2015-08-01

Host plant penetration is the gateway to survival for holoparasitic Cuscuta and requires host cell wall degradation. Compositional differences of cell walls may explain why some hosts are amenable to such degradation while others can resist infection. Antibody-based techniques for comprehensive profiling of cell wall epitopes and cell wall-modifying enzymes were applied to several susceptible hosts and a resistant host of Cuscuta reflexa and to the parasite itself. Infected tissue of Pelargonium zonale contained high concentrations of de-esterified homogalacturonans in the cell walls, particularly adjacent to the parasite's haustoria. High pectinolytic activity in haustorial extracts and high expression levels of pectate lyase genes suggest that the parasite contributes directly to wall remodeling. Mannan and xylan concentrations were low in P. zonale and in five susceptible tomato introgression lines, but high in the resistant Solanum lycopersicum cv M82, and in C. reflexa itself. Knowledge of the composition of resistant host cell walls and the parasite's own cell walls is useful in developing strategies to prevent infection by parasitic plants. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Insecticide Resistance Mechanisms in the Green Peach Aphid Myzus persicae (Hemiptera: Aphididae) II: Costs and Benefits

PubMed Central

Silva, Andrea X.; Bacigalupe, Leonardo D.; Luna-Rudloff, Manuela; Figueroa, Christian C.

2012-01-01

Background Among herbivorous insects that have exploited agro-ecosystems, the peach-potato aphid, Myzus persicae, is recognized as one of the most important agricultural pests worldwide. Uses over 400 plant species and has evolved different insecticides resistance mechanisms. As M. persicae feeds upon a huge diversity of hosts, it has been exposed to a wide variety of plant allelochemicals, which probably have promoted a wide range of detoxification systems. Methodology/Principal Findings In this work we (i) evaluated whether insecticide resistance mutations (IRM) in M. persicae can give an advantage in terms of reproductive fitness when aphids face two hosts, pepper (Capsicum annuum) a suitable host and radish (Raphanus sativus) the unfavorable host and (ii) examined the transcriptional expression of six genes that are known to be up-regulated in response to insecticides. Our results show a significant interaction between host and IRM on the intrinsic rate of increase (rm). Susceptible genotypes (not carrying insensitivity mutations) had a higher rm on pepper, and the transcriptional levels of five genes increased on radish. The rm relationship was reversed on the unfavorable host; genotypes with multiple IRM exhibited higher rm, without altering the transcriptional levels of the studied genes. Genotypes with one IRM kept a similar rm on both hosts, but they increased the transcriptional levels of two genes. Conclusions/Significance Although we have studied only nine genotypes, overall our results are in agreement with the general idea that allelochemical detoxification systems could constitute a pre-adaptation for the development of insecticide resistance. Genotypes carrying IRM exhibited a higher rm than susceptible genotypes on radish, the more unfavorable host. Susceptible genotypes should be able to tolerate the defended host by up-regulating some metabolic genes that are also responding to insecticides. Hence, our results suggest that the trade-off among resistance mechanisms might be quite complex, with a multiplicity of costs and benefits depending on the environment. PMID:22685539

STAT2-dependent immune responses ensure host survival despite the presence of a potent viral antagonist.

PubMed

Le-Trilling, Vu Thuy Khanh; Wohlgemuth, Kerstin; Rückborn, Meike U; Jagnjic, Andreja; Maaßen, Fabienne; Timmer, Lejla; Katschinski, Benjamin; Trilling, Mirko

2018-05-09

Pathogen encounter induces interferons which signal via Janus kinases and STAT transcription factors to establish an antiviral state. However, host and pathogens are situated in a continuous arms race which shapes host evolution towards optimized immune responses and the pathogens towards enhanced immune evasive properties.Mouse cytomegalovirus (MCMV) counteracts interferon responses by pM27-mediated degradation of STAT2 which directly affects the signaling of type I as well as type III interferons. Using MCMV mutants lacking M27 and mice lacking STAT2, we studied the opposing relationship between antiviral activities and viral antagonism in a natural host-pathogen pair in vitro and in vivo In contrast to wt-MCMV, ΔM27-MCMV was efficiently cleared from all organs within a few days in BALB/c, C57BL/6, and 129 mice, highlighting the general importance of STAT2 antagonism for MCMV replication. Despite this effective and relevant STAT2 antagonism, wt and STAT2-deficient mice exhibited fundamentally different susceptibilities to MCMV infections. MCMV replication was increased in all assessed organs (e.g. liver, spleen, lungs, and salivary glands) of STAT2-deficient mice, resulting in mortality during the first week after infection.Taken together, our study reveals the importance of cytomegaloviral interferon antagonism for viral replication as well as a pivotal role of the remaining STAT2 activity for host survival. This mutual influence establishes a stable evolutionary stand-off situation with fatal consequences when the equilibrium is disturbed. IMPORTANCE The host limits viral replication by interferons which signal via STAT proteins. Several viruses evolved antagonists targeting STATs to antagonize IFNs (e.g. cytomegaloviruses, Zika virus, Dengue virus, and several paramyxoviruses). We analyzed infections of mouse CMV expressing or lacking the STAT2 antagonist pM27 in STAT2-deficient and control mice to evaluate their importance for host and virus in vitro and in vivo The inability to counteract STAT2 directly translates into exaggerated IFN susceptibility in vitro and pronounced attenuation in vivo Thus, the antiviral activity mediated by IFNs via STAT2-dependent signaling drove the development of a potent MCMV-encoded STAT2 antagonist which became indispensable for efficient virus replication and spread to organs required for dissemination. Despite this clear impact of viral STAT2 antagonism, the host critically required the remaining STAT2 activity to prevent overt disease and mortality upon MCMV infection. Our findings highlight a remarkably delicate balance between host and virus. Copyright © 2018 Le-Trilling et al.

Cattle Tick Rhipicephalus microplus-Host Interface: A Review of Resistant and Susceptible Host Responses

PubMed Central

Tabor, Ala E.; Ali, Abid; Rehman, Gauhar; Rocha Garcia, Gustavo; Zangirolamo, Amanda Fonseca; Malardo, Thiago; Jonsson, Nicholas N.

2017-01-01

Ticks are able to transmit tick-borne infectious agents to vertebrate hosts which cause major constraints to public and livestock health. The costs associated with mortality, relapse, treatments, and decreased production yields are economically significant. Ticks adapted to a hematophagous existence after the vertebrate hemostatic system evolved into a multi-layered defense system against foreign invasion (pathogens and ectoparasites), blood loss, and immune responses. Subsequently, ticks evolved by developing an ability to suppress the vertebrate host immune system with a devastating impact particularly for exotic and crossbred cattle. Host genetics defines the immune responsiveness against ticks and tick-borne pathogens. To gain an insight into the naturally acquired resistant and susceptible cattle breed against ticks, studies have been conducted comparing the incidence of tick infestation on bovine hosts from divergent genetic backgrounds. It is well-documented that purebred and crossbred Bos taurus indicus cattle are more resistant to ticks and tick-borne pathogens compared to purebred European Bos taurus taurus cattle. Genetic studies identifying Quantitative Trait Loci markers using microsatellites and SNPs have been inconsistent with very low percentages relating phenotypic variation with tick infestation. Several skin gene expression and immunological studies have been undertaken using different breeds, different samples (peripheral blood, skin with tick feeding), infestation protocols and geographic environments. Susceptible breeds were commonly found to be associated with the increased expression of toll like receptors, MHC Class II, calcium binding proteins, and complement factors with an increased presence of neutrophils in the skin following tick feeding. Resistant breeds had higher levels of T cells present in the skin prior to tick infestation and thus seem to respond to ticks more efficiently. The skin of resistant breeds also contained higher numbers of eosinophils, mast cells and basophils with up-regulated proteases, cathepsins, keratins, collagens and extracellular matrix proteins in response to feeding ticks. Here we review immunological and molecular determinants that explore the cattle tick Rhipicephalus microplus-host resistance phenomenon as well as contemplating new insights and future directions to study tick resistance and susceptibility, in order to facilitate interventions for tick control. PMID:29322033

Reduced susceptibility of tomato stem to the necrotrophic fungus Botrytis cinerea is associated with a specific adjustment of fructose content in the host sugar pool.

PubMed

Lecompte, François; Nicot, Philippe C; Ripoll, Julie; Abro, Manzoor A; Raimbault, Astrid K; Lopez-Lauri, Félicie; Bertin, Nadia

2017-03-01

Plant soluble sugars, as main components of primary metabolism, are thought to be implicated in defence against pathogenic fungi. However, the function of sucrose and hexoses remains unclear. This study aimed to identify robust patterns in the dynamics of soluble sugars in sink tissues of tomato plants during the course of infection by the necrotrophic fungus Botrytis cinerea . Distinct roles for glucose and fructose in defence against B. cinerea were hypothesized. We examined sugar contents and defence hormonal markers in tomato stem tissues before and after infection by B. cinerea , in a range of abiotic environments created by various nitrogen and water supplies. Limited nitrogen or water supplies increased tomato stem susceptibility to B. cinerea . Glucose and fructose contents of tissues surrounding infection sites evolved differently after inoculation. The fructose content never decreased after inoculation with B. cinerea , while that of glucose showed either positive or negative variation, depending on the abiotic environment. An increase in the relative fructose content (defined as the proportion of fructose in the soluble sugar pool) was observed in the absence of glucose accumulation and was associated with lower susceptibility. A lower expression of the salicylic acid marker PR1a , and a lower repression of a jasmonate marker COI1 were associated with reduced susceptibility. Accordingly, COI1 expression was positively correlated with the relative fructose contents 7 d after infection. Small variations of fructose content among the sugar pool are unlikely to affect intrinsic pathogen growth. Our results highlight distinct use of host glucose and fructose after infection by B. cinerea and suggest strongly that adjustment of the relative fructose content is required for enhanced plant defence. © The Author 2017. Published by Oxford University Press on behalf of the Annals of Botany Company.

Genome-wide association studies on HIV susceptibility, pathogenesis and pharmacogenomics

PubMed Central

2012-01-01

Susceptibility to HIV-1 and the clinical course after infection show a substantial heterogeneity between individuals. Part of this variability can be attributed to host genetic variation. Initial candidate gene studies have revealed interesting host factors that influence HIV infection, replication and pathogenesis. Recently, genome-wide association studies (GWAS) were utilized for unbiased searches at a genome-wide level to discover novel genetic factors and pathways involved in HIV-1 infection. This review gives an overview of findings from the GWAS performed on HIV infection, within different cohorts, with variable patient and phenotype selection. Furthermore, novel techniques and strategies in research that might contribute to the complete understanding of virus-host interactions and its role on the pathogenesis of HIV infection are discussed. PMID:22920050

Targeting the complex interactions between microbiota, host epithelial and immune cells in inflammatory bowel disease.

PubMed

Hirata, Yoshihiro; Ihara, Sozaburo; Koike, Kazuhiko

2016-11-01

Inflammatory bowel disease (IBD) is a chronic inflammatory intestinal disorder that includes two distinct disease categories: ulcerative colitis and Crohn's disease. Epidemiological, genetic, and experimental studies have revealed many important aspects of IBD. Genetic susceptibility, inappropriate immune responses, environmental changes, and intestinal microbiota are all associated with the development of IBD. However, the exact mechanisms of the disease and the interactions among these pathogenic factors are largely unknown. Here we introduce recent findings from experimental colitis models that investigated the interactions between host genetic susceptibility and gut microbiota. In addition, we discuss new strategies for the treatment of IBD, focusing on the complex interactions between microbiota and host epithelial and immune cells. Copyright © 2016 Elsevier Ltd. All rights reserved.

Viral Perturbations of Host Networks Reflect Disease Etiology

PubMed Central

Dricot, Amélie; Padi, Megha; Byrdsong, Danielle; Franchi, Rachel; Lee, Deok-Sun; Rozenblatt-Rosen, Orit; Mar, Jessica C.; Calderwood, Michael A.; Baldwin, Amy; Zhao, Bo; Santhanam, Balaji; Braun, Pascal; Simonis, Nicolas; Huh, Kyung-Won; Hellner, Karin; Grace, Miranda; Chen, Alyce; Rubio, Renee; Marto, Jarrod A.; Christakis, Nicholas A.; Kieff, Elliott; Roth, Frederick P.; Roecklein-Canfield, Jennifer; DeCaprio, James A.; Cusick, Michael E.; Quackenbush, John; Hill, David E.; Münger, Karl; Vidal, Marc; Barabási, Albert-László

2012-01-01

Many human diseases, arising from mutations of disease susceptibility genes (genetic diseases), are also associated with viral infections (virally implicated diseases), either in a directly causal manner or by indirect associations. Here we examine whether viral perturbations of host interactome may underlie such virally implicated disease relationships. Using as models two different human viruses, Epstein-Barr virus (EBV) and human papillomavirus (HPV), we find that host targets of viral proteins reside in network proximity to products of disease susceptibility genes. Expression changes in virally implicated disease tissues and comorbidity patterns cluster significantly in the network vicinity of viral targets. The topological proximity found between cellular targets of viral proteins and disease genes was exploited to uncover a novel pathway linking HPV to Fanconi anemia. PMID:22761553

Cancer: a missing link in ecosystem functioning?

PubMed

Vittecoq, Marion; Roche, Benjamin; Daoust, Simon P; Ducasse, Hugo; Missé, Dorothée; Abadie, Jérome; Labrut, Sophie; Renaud, François; Gauthier-Clerc, Michel; Thomas, Frédéric

2013-11-01

Cancer is a disease that affects the majority of metazoan species and, before directly causing host death, is likely to influence the competitive abilities of individuals, their susceptibility to pathogens, their vulnerability to predators, and their ability to disperse. Despite the potential importance of these ecological impacts, cancer is rarely incorporated into model ecosystems. We describe here the diversity of ways in which oncogenic phenomena, from precancerous lesions to generalized metastatic cancers, may affect ecological processes that govern biotic interactions. We argue that oncogenic phenomena, despite their complexity, can have significant and sometimes predictable ecological consequences. Our aim is to provide a new perspective on the ecological and evolutionary significance of cancer in wildlife, and to stimulate research on this topic. Copyright © 2013 Elsevier Ltd. All rights reserved.

Th2 and Th1 Responses: Clear and Hidden Sides of Immunity Against Intestinal Helminths.

PubMed

Cortés, Alba; Muñoz-Antoli, Carla; Esteban, J Guillermo; Toledo, Rafael

2017-09-01

Intestinal helminthiases affect millions of people worldwide, mainly in developing regions, where they cause a significant negative impact on human health and socioeconomic growth of affected populations. However, intestinal helminthiases are still among the most neglected tropical diseases. Protective immunity against intestinal helminths is associated with development of type 2 responses. Nevertheless, in some host-intestinal helminth combinations, local Th1 responses are initiated, inducing chronicity. The usage of helminth-mouse models is useful for elucidating the mechanisms behind the initiation of each type of response. Herein, the current knowledge on these topics is reviewed, paying particular attention to the earliest events of the immune cascade which eventually lead to either susceptibility or resistance to infection. Copyright © 2017 Elsevier Ltd. All rights reserved.

Transcriptional Basis of Drought-Induced Susceptibility to the Rice Blast Fungus Magnaporthe oryzae

PubMed Central

Bidzinski, Przemyslaw; Ballini, Elsa; Ducasse, Aurélie; Michel, Corinne; Zuluaga, Paola; Genga, Annamaria; Chiozzotto, Remo; Morel, Jean-Benoit

2016-01-01

Plants are often facing several stresses simultaneously. Understanding how they react and the way pathogens adapt to such combinational stresses is poorly documented. Here, we developed an experimental system mimicking field intermittent drought on rice followed by inoculation by the pathogenic fungus Magnaporthe oryzae. This experimental system triggers an enhancement of susceptibility that could be correlated with the dampening of several aspects of plant immunity, namely the oxidative burst and the transcription of several pathogenesis-related genes. Quite strikingly, the analysis of fungal transcription by RNASeq analysis under drought reveals that the fungus is greatly modifying its virulence program: genes coding for small secreted proteins were massively repressed in droughted plants compared to unstressed ones whereas genes coding for enzymes involved in degradation of cell-wall were induced. We also show that drought can lead to the partial breakdown of several major resistance genes by affecting R plant gene and/or pathogen effector expression. We propose a model where a yet unknown plant signal can trigger a change in the virulence program of the pathogen to adapt to a plant host that was affected by drought prior to infection. PMID:27833621

Environmental contaminant mixtures modulate in vitro influenza infection.

PubMed

Desforges, Jean-Pierre; Bandoro, Christopher; Shehata, Laila; Sonne, Christian; Dietz, Rune; Puryear, Wendy B; Runstadler, Jonathan A

2018-09-01

Environmental chemicals, particularly organochlorinated contaminants (OCs), are associated with a ranged of adverse health effects, including impairment of the immune system and antiviral immunity. Influenza A virus (IAV) is an infectious disease of major global public health concern and exposure to OCs can increase the susceptibility, morbidity, and mortality to disease. It is however unclear how pollutants are interacting and affecting the outcome of viral infections at the cellular level. In this study, we investigated the effects of a mixture of environmentally relevant OCs on IAV infectivity upon in vitro exposure in Madin Darby Canine Kidney (MDCK) cells and human lung epithelial cells (A549). Exposure to OCs reduced IAV infectivity in MDCK and A549 cells during both short (18-24h) and long-term (72h) infections at 0.05 and 0.5ppm, and effects were more pronounced in cells co-treated with OCs and IAV than pre-treated with OCs prior to IAV (p<0.001). Pre-treatment of host cells with OCs did not affect IAV cell surface attachment or entry. Visualization of IAV by transmission electron microscopy revealed increased envelope deformations and fewer intact virions during OC exposure. Taken together, our results suggest that disruption of IAV infection upon in vitro exposure to OCs was not due to host-cell effects influencing viral attachment and entry, but perhaps mediated by direct effects on viral particles or cellular processes involved in host-virus interactions. In vitro infectivity studies such as ours can shed light on the complex processes underlying host-pathogen-pollutant interactions. Copyright © 2018 Elsevier B.V. All rights reserved.

Reciprocal Hosts' Responses to Powdery Mildew Isolates Originating from Domesticated Wheats and Their Wild Progenitor.

PubMed

Ben-David, Roi; Dinoor, Amos; Peleg, Zvi; Fahima, Tzion

2018-01-01

The biotroph wheat powdery mildew, Blumeria graminis (DC.) E.O. Speer, f. sp. tritici Em. Marchal ( Bgt ), has undergone long and dynamic co-evolution with its hosts. In the last 10,000 years, processes involved in plant evolution under domestication, altered host-population structure. Recently both virulence and genomic profiling separated Bgt into two groups based on their origin from domestic host and from wild emmer wheat. While most studies focused on the Bgt pathogen, there is significant knowledge gaps in the role of wheat host diversity in this specification. This study aimed to fill this gap by exploring qualitatively and also quantitatively the disease response of diverse host panel to powdery mildew [105 domesticated wheat genotypes ( Triticum turgidum ssp. dicoccum, T. turgidum ssp. durum , and T. aestivum ) and 241 accessions of its direct progenitor, wild emmer wheat ( T. turgidum ssp. dicoccoides )]. A set of eight Bgt isolates, originally collected from domesticated and wild wheat was used for screening this wheat collection. The isolates from domesticated wheat elicited susceptible to moderate plant responses on domesticated wheat lines and high resistance on wild genotypes (51.7% of the tested lines were resistant). Isolates from wild emmer elicited reciprocal disease responses: high resistance of domesticated germplasm and high susceptibility of the wild material (their original host). Analysis of variance of the quantitative phenotypic responses showed a significant Isolates × Host species interaction [ P (F) < 0.0001] and further supported these findings. Furthermore, analysis of the range of disease severity values showed that when the group of host genotypes was inoculated with Bgt isolate from the reciprocal host, coefficient of variation was significantly higher than when inoculated with its own isolates. This trend was attributed to the role of major resistance genes in the latter scenario (high proportion of complete resistance). By testing the association between disease severity and geographical distance from the source of inoculum, we have found higher susceptibility in wild emmer close to the source. Both qualitative and quantitative assays showed a reciprocal resistance pattern in the wheat host and are well aligned with the recent findings of significant differentiation into wild-emmer and domesticated-wheat populations in the pathogen.

Effects of Peanut-Tobacco Rotations on Population Dynamics of Meloidogyne arenaria in Mixed Race Populations.

PubMed

Hirunsalee, A; Barker, K R; Beute, M K

1995-06-01

A 3-year microplot study was initiated to characterize the population dynamics, reproduction potential, and survivorship of single or mixed populations of Meloidogyne arenaria race 1 (Ma1) and race 2 (Ma2), as affected by crop rotations of peanut 'Florigiant' and M. incognita races 1 and 3-resistant 'McNair 373' and susceptible 'Coker 371-Gold' tobacco. Infection, reproduction, and root damage by Ma2 on peanut and by Ma1 on resistant tobacco were limited in the first year. Infection, reproduction, and root-damage potentials on susceptible tobacco were similar for Ma1 and Ma2. In the mixed (1:1) population, Ma1 was dominant on peanut and Ma2 was dominant on both tobacco cultivars. Crop rotation affected the population dynamics of different nematode races. For years 2 and 3, the low numbers of Ma1 and Ma2 from a previous-year poor host increased rapidly on suitable hosts. Ma1 had greater reproduction factors ([RF] = population density at harvest/population density at preplandng) than did Ma2 and Ma1 + Ma2 in second-year peanut plots following first-year resistant tobacco, and in third-year peanut plots following second-year tobacco. In mixed infestations, Ma1 predominated over Ma2 in previous-year peanut plots, whereas Ma2 predominated over Ma1 in previous-year tobacco plots. Moderate damage on resistant tobacco was induced by Ma1 in the second year. In the third year, moderate damage on peanut was associated with 'Ma2' from previous-year peanut plots. The resistant tobacco supported sufficient reproduction of Ma1 over 2 years to effect moderate damage and yield suppression to peanut in year 3.

Effects of Peanut-Tobacco Rotations on Population Dynamics of Meloidogyne arenaria in Mixed Race Populations

PubMed Central

Hirunsalee, Anan; Barker, K. R.; Beute, M. K.

1995-01-01

A 3-year microplot study was initiated to characterize the population dynamics, reproduction potential, and survivorship of single or mixed populations of Meloidogyne arenaria race 1 (Ma1) and race 2 (Ma2), as affected by crop rotations of peanut 'Florigiant' and M. incognita races 1 and 3-resistant 'McNair 373' and susceptible 'Coker 371-Gold' tobacco. Infection, reproduction, and root damage by Ma2 on peanut and by Ma1 on resistant tobacco were limited in the first year. Infection, reproduction, and root-damage potentials on susceptible tobacco were similar for Ma1 and Ma2. In the mixed (1:1) population, Ma1 was dominant on peanut and Ma2 was dominant on both tobacco cultivars. Crop rotation affected the population dynamics of different nematode races. For years 2 and 3, the low numbers of Ma1 and Ma2 from a previous-year poor host increased rapidly on suitable hosts. Ma1 had greater reproduction factors ([RF] = population density at harvest/population density at preplandng) than did Ma2 and Ma1 + Ma2 in second-year peanut plots following first-year resistant tobacco, and in third-year peanut plots following second-year tobacco. In mixed infestations, Ma1 predominated over Ma2 in previous-year peanut plots, whereas Ma2 predominated over Ma1 in previous-year tobacco plots. Moderate damage on resistant tobacco was induced by Ma1 in the second year. In the third year, moderate damage on peanut was associated with 'Ma2' from previous-year peanut plots. The resistant tobacco supported sufficient reproduction of Ma1 over 2 years to effect moderate damage and yield suppression to peanut in year 3. PMID:19277278

Medical hypothesis: xenoestrogens as preventable causes of breast cancer.

PubMed Central

Davis, D L; Bradlow, H L; Wolff, M; Woodruff, T; Hoel, D G; Anton-Culver, H

1993-01-01

Changes in documented risk factors for breast cancer and rates of screening cannot completely explain recent increases in incidence or mortality. Established risk factors for breast cancer, including genetics, account for at best 30% of cases. Most of these risk factors can be linked to total lifetime exposure to bioavailable estrogens. Experimental evidence reveals that compounds such as some chlorinated organics, polycyclic aromatic hydrocarbons (PAHs), triazine herbicides, and pharmaceuticals affect estrogen production and metabolism and thus function as xenoestrogens. Many of these xenoestrogenic compounds also experimentally induce mammary carcinogenesis. Recent epidemiologic studies have found that breast fat and serum lipids of women with breast cancer contain significantly elevated levels of some chlorinated organics compared with noncancer controls. As the proportion of inherited breast cancer in the population is small, most breast cancers are due to acquired mutations. Thus, the induction of breast cancer in the majority of cases stems from interactions between host factors, including genetics and environmental carcinogens. We hypothesize that substances such as xenoestrogens increase the risk of breast cancer by mechanisms which include interaction with breast-cancer susceptibility genes. A series of major epidemiologic studies need to be developed to evaluate this hypothesis, including studies of estrogen metabolism, the role of specific xenoestrogenic substances in breast cancer, and relevant genetic-environmental interactions. In addition, experimental studies are needed to evaluate biologic markers of suspect xenoestrogens and biologic markers of host susceptibility and identify pathways of estrogenicity that affect the development of breast cancer. If xenoestrogens do play a role in breast cancer, reductions in exposure will provide an opportunity for primary prevention of this growing disease.(ABSTRACT TRUNCATED AT 250 WORDS) Images p372-a Figure 1. PMID:8119245

Potential Association of IL1B Polymorphism With Iron Deficiency Risk in Childhood Helicobacter pylori Infection.

PubMed

Chen, Szu-Ta; Ni, Yen-Hsuan; Liu, Shing-Hwa

2018-02-01

Helicobacter pylori infection occurs predominantly in childhood. Host immune response gene polymorphism is reported to affect the susceptibility to H pylori infection and the outcome of H pylori-related gastric cancer. Not all H pylori-infected patients, however, exhibit iron deficiency (ID). The relationship between host genetic polymorphisms and ID mediated by H pylori infection is not well understood. Subjects (n = 644) from the general population of age 10 to 18 years were divided into 2 groups based on serology testing for anti-H pylori IgG: seropositive study group; and seronegative control group. Five single nucleotide polymorphisms (SNPs) in IL1B (rs1143627 and rs16944), IL8 (rs4073), IL10 (rs1800896), and ABO (rs505922), were genotyped and the iron status of the 2 groups was compared. The seroprevalence rate for H pylori was 10.7% in this study. Infected subjects were significantly older and had lower serum iron levels than uninfected subjects (P = 0.0195 and 0.0059, respectively). Multivariate analysis revealed a significantly higher frequency of the T allele of rs505922 (odds ratio [OR] = 6.128; P < 0.001) and lower frequency of the T allele of rs1143627 (OR = 0.846; P = 0.014) in seropositive subjects. Among 59 seropositive subjects, the T allele frequency of rs1143627 was significantly higher in those with ID (OR = 3.156; P = 0.043), compared with those without ID. ABO (rs505922) and IL1B (rs1143627) may affect H pylori infection susceptibility, and IL1B (rs1143627) may also influence ID risk in infected children.

Bacteria in the vaginal microbiome alter the innate immune response and barrier properties of the human vaginal epithelia in a species-specific manner.

PubMed

Doerflinger, Sylvie Y; Throop, Andrea L; Herbst-Kralovetz, Melissa M

2014-06-15

Bacterial vaginosis increases the susceptibility to sexually transmitted infections and negatively affects women's reproductive health. To investigate host-vaginal microbiota interactions and the impact on immune barrier function, we colonized 3-dimensional (3-D) human vaginal epithelial cells with 2 predominant species of vaginal microbiota (Lactobacillus iners and Lactobacillus crispatus) or 2 prevalent bacteria associated with bacterial vaginosis (Atopobium vaginae and Prevotella bivia). Colonization of 3-D vaginal epithelial cell aggregates with vaginal microbiota was observed with direct attachment to host cell surface with no cytotoxicity. A. vaginae infection yielded increased expression membrane-associated mucins and evoked a robust proinflammatory, immune response in 3-D vaginal epithelial cells (ie, expression of CCL20, hBD-2, interleukin 1β, interleukin 6, interleukin 8, and tumor necrosis factor α) that can negatively affect barrier function. However, P. bivia and L. crispatus did not significantly upregulate pattern-recognition receptor-signaling, mucin expression, antimicrobial peptides/defensins, or proinflammatory cytokines in 3-D vaginal epithelial cell aggregates. Notably, L. iners induced pattern-recognition receptor-signaling activity, but no change was observed in mucin expression or secretion of interleukin 6 and interleukin 8. We identified unique species-specific immune signatures from vaginal epithelial cells elicited by colonization with commensal and bacterial vaginosis-associated bacteria. A. vaginae elicited a signature that is consistent with significant disruption of immune barrier properties, potentially resulting in enhanced susceptibility to sexually transmitted infections during bacterial vaginosis. © The Author 2014. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Fire blight disease reactome: RNA-seq transcriptional profile of apple host plant defense responses to Erwinia amylovora pathogen infection.

PubMed

Kamber, Tim; Buchmann, Jan P; Pothier, Joël F; Smits, Theo H M; Wicker, Thomas; Duffy, Brion

2016-02-17

The molecular basis of resistance and susceptibility of host plants to fire blight, a major disease threat to pome fruit production globally, is largely unknown. RNA-sequencing data from challenged and mock-inoculated flowers were analyzed to assess the susceptible response of apple to the fire blight pathogen Erwinia amylovora. In presence of the pathogen 1,080 transcripts were differentially expressed at 48 h post inoculation. These included putative disease resistance, stress, pathogen related, general metabolic, and phytohormone related genes. Reads, mapped to regions on the apple genome where no genes were assigned, were used to identify potential novel genes and open reading frames. To identify transcripts specifically expressed in response to E. amylovora, RT-PCRs were conducted and compared to the expression patterns of the fire blight biocontrol agent Pantoea vagans strain C9-1, another apple pathogen Pseudomonas syringae pv. papulans, and mock inoculated apple flowers. This led to the identification of a peroxidase superfamily gene that was lower expressed in response to E. amylovora suggesting a potential role in the susceptibility response. Overall, this study provides the first transcriptional profile by RNA-seq of the host plant during fire blight disease and insights into the response of susceptible apple plants to E. amylovora.

Fire blight disease reactome: RNA-seq transcriptional profile of apple host plant defense responses to Erwinia amylovora pathogen infection

PubMed Central

Kamber, Tim; Buchmann, Jan P.; Pothier, Joël F.; Smits, Theo H. M.; Wicker, Thomas; Duffy, Brion

2016-01-01

The molecular basis of resistance and susceptibility of host plants to fire blight, a major disease threat to pome fruit production globally, is largely unknown. RNA-sequencing data from challenged and mock-inoculated flowers were analyzed to assess the susceptible response of apple to the fire blight pathogen Erwinia amylovora. In presence of the pathogen 1,080 transcripts were differentially expressed at 48 h post inoculation. These included putative disease resistance, stress, pathogen related, general metabolic, and phytohormone related genes. Reads, mapped to regions on the apple genome where no genes were assigned, were used to identify potential novel genes and open reading frames. To identify transcripts specifically expressed in response to E. amylovora, RT-PCRs were conducted and compared to the expression patterns of the fire blight biocontrol agent Pantoea vagans strain C9-1, another apple pathogen Pseudomonas syringae pv. papulans, and mock inoculated apple flowers. This led to the identification of a peroxidase superfamily gene that was lower expressed in response to E. amylovora suggesting a potential role in the susceptibility response. Overall, this study provides the first transcriptional profile by RNA-seq of the host plant during fire blight disease and insights into the response of susceptible apple plants to E. amylovora. PMID:26883568

Isolation and characterization of phytotoxins secreted by Phytophthora ramorum

Treesearch

Daniel K. Manter; Rick G. Kelsey; Joseph J. Karchesy

2006-01-01

Most Phythophthora species secrete a variety of small, hydrophilic proteins that induce a hypersensitive-like response to varying degrees in host and non-host plant species. Our research focuses on the potential role of these proteins in the biology and susceptibility of host species to sudden oak death (SOD). In this paper we reported on the...

Spatiotemporal model of barley and cereal yellow dwarf virus transmission dynamics with seasonality and plant competition

Treesearch

S.M. Moore; C.A. Manore; V.A. Bokil; E.T. Borer; P.R. Hosseini

2011-01-01

Many generalist pathogens are influenced by the spatial distributions and relative abundances of susceptible host species. The spatial structure of host populations can influence patterns of infection incidence (or disease outbreaks), and the effects of a generalist pathogen on host community dynamics in a spatially heterogeneous community may differ from predictions...

Life history and virulence are linked in the ectoparasitic salmon louse Lepeophtheirus salmonis.

PubMed

Mennerat, A; Hamre, L; Ebert, D; Nilsen, F; Dávidová, M; Skorping, A

2012-05-01

Models of virulence evolution for horizontally transmitted parasites often assume that transmission rate (the probability that an infected host infects a susceptible host) and virulence (the increase in host mortality due to infection) are positively correlated, because higher rates of production of propagules may cause more damages to the host. However, empirical support for this assumption is scant and limited to microparasites. To fill this gap, we explored the relationships between parasite life history and virulence in the salmon louse, Lepeophtheirus salmonis, a horizontally transmitted copepod ectoparasite on Atlantic salmon Salmo salar. In the laboratory, we infected juvenile salmon hosts with equal doses of infective L. salmonis larvae and monitored parasite age at first reproduction, parasite fecundity, area of damage caused on the skin of the host, and host weight and length gain. We found that earlier onset of parasite reproduction was associated with higher parasite fecundity. Moreover, higher parasite fecundity (a proxy for transmission rate, as infection probability increases with higher numbers of parasite larvae released to the water) was associated with lower host weight gain (correlated with lower survival in juvenile salmon), supporting the presence of a virulence-transmission trade-off. Our results are relevant in the context of increasing intensive farming, where frequent anti-parasite drug use and increased host density may have selected for faster production of parasite transmission stages, via earlier reproduction and increased early fecundity. Our study highlights that salmon lice, therefore, are a good model for studying how human activity may affect the evolution of parasite virulence. © 2012 The Authors. Journal of Evolutionary Biology © 2012 European Society For Evolutionary Biology.

Persistence of canine distemper virus in the Greater Yellowstone Ecosystem's carnivore community

USGS Publications Warehouse

Almberg, E.S.; Cross, P.C.; Smith, D.W.

2010-01-01

Canine distemper virus (CDV) is an acute, highly immunizing pathogen that should require high densities and large populations of hosts for long-term persistence, yet CDV persists among terrestrial carnivores with small, patchily distributed groups. We used CDV in the Greater Yellowstone ecosystem's (GYE) wolves (Canis lupus) and coyotes (Canis latrans) as a case study for exploring how metapopulation structure, host demographics, and multi-host transmission affect the critical community size and spatial scale required for CDV persistence. We illustrate how host spatial connectivity and demographic turnover interact to affect both local epidemic dynamics, such as the length and variation in inter-epidemic periods, and pathogen persistence using stochastic, spatially explicit susceptible-exposed-infectious-recovered simulation models. Given the apparent absence of other known persistence mechanisms (e.g., a carrier or environmental state, densely populated host, chronic infection, or a vector), we suggest that CDV requires either large spatial scales or multi-host transmission for persistence. Current GYE wolf populations are probably too small to support endemic CDV. Coyotes are a plausible reservoir host, but CDV would still require 50 000-100 000 individuals for moderate persistence (>50% over 10 years), which would equate to an area of 1-3 times the size of the GYE (60000-200000 km2). Coyotes, and carnivores in general, are not uniformly distributed; therefore, this is probably a gross underestimate of the spatial scale of CDV persistence. However, the presence of a second competent host species can greatly increase the probability of long-term CDV persistence at much smaller spatial scales. Although no management of CDV is currently recommended for the GYE, wolf managers in the region should expect periodic but unpredictable CDV-related population declines as often as every 2-5 years. Awareness and monitoring of such outbreaks will allow corresponding adjustments in management activities such as regulated public harvest, creating a smooth transition to state wolf management and conservation after >30 years of being protected by the Endangered Species Act. ?? 2010 by the Ecological Society of America.

Footprints of Directional Selection in Wild Atlantic Salmon Populations: Evidence for Parasite-Driven Evolution?

PubMed Central

Zueva, Ksenia J.; Lumme, Jaakko; Veselov, Alexey E.; Kent, Matthew P.; Lien, Sigbjørn; Primmer, Craig R.

2014-01-01

Mechanisms of host-parasite co-adaptation have long been of interest in evolutionary biology; however, determining the genetic basis of parasite resistance has been challenging. Current advances in genome technologies provide new opportunities for obtaining a genome-scale view of the action of parasite-driven natural selection in wild populations and thus facilitate the search for specific genomic regions underlying inter-population differences in pathogen response. European populations of Atlantic salmon (Salmo salar L.) exhibit natural variance in susceptibility levels to the ectoparasite Gyrodactylus salaris Malmberg 1957, ranging from resistance to extreme susceptibility, and are therefore a good model for studying the evolution of virulence and resistance. However, distinguishing the molecular signatures of genetic drift and environment-associated selection in small populations such as land-locked Atlantic salmon populations presents a challenge, specifically in the search for pathogen-driven selection. We used a novel genome-scan analysis approach that enabled us to i) identify signals of selection in salmon populations affected by varying levels of genetic drift and ii) separate potentially selected loci into the categories of pathogen (G. salaris)-driven selection and selection acting upon other environmental characteristics. A total of 4631 single nucleotide polymorphisms (SNPs) were screened in Atlantic salmon from 12 different northern European populations. We identified three genomic regions potentially affected by parasite-driven selection, as well as three regions presumably affected by salinity-driven directional selection. Functional annotation of candidate SNPs is consistent with the role of the detected genomic regions in immune defence and, implicitly, in osmoregulation. These results provide new insights into the genetic basis of pathogen susceptibility in Atlantic salmon and will enable future searches for the specific genes involved. PMID:24670947

Footprints of directional selection in wild Atlantic salmon populations: evidence for parasite-driven evolution?

PubMed

Zueva, Ksenia J; Lumme, Jaakko; Veselov, Alexey E; Kent, Matthew P; Lien, Sigbjørn; Primmer, Craig R

2014-01-01

Mechanisms of host-parasite co-adaptation have long been of interest in evolutionary biology; however, determining the genetic basis of parasite resistance has been challenging. Current advances in genome technologies provide new opportunities for obtaining a genome-scale view of the action of parasite-driven natural selection in wild populations and thus facilitate the search for specific genomic regions underlying inter-population differences in pathogen response. European populations of Atlantic salmon (Salmo salar L.) exhibit natural variance in susceptibility levels to the ectoparasite Gyrodactylus salaris Malmberg 1957, ranging from resistance to extreme susceptibility, and are therefore a good model for studying the evolution of virulence and resistance. However, distinguishing the molecular signatures of genetic drift and environment-associated selection in small populations such as land-locked Atlantic salmon populations presents a challenge, specifically in the search for pathogen-driven selection. We used a novel genome-scan analysis approach that enabled us to i) identify signals of selection in salmon populations affected by varying levels of genetic drift and ii) separate potentially selected loci into the categories of pathogen (G. salaris)-driven selection and selection acting upon other environmental characteristics. A total of 4631 single nucleotide polymorphisms (SNPs) were screened in Atlantic salmon from 12 different northern European populations. We identified three genomic regions potentially affected by parasite-driven selection, as well as three regions presumably affected by salinity-driven directional selection. Functional annotation of candidate SNPs is consistent with the role of the detected genomic regions in immune defence and, implicitly, in osmoregulation. These results provide new insights into the genetic basis of pathogen susceptibility in Atlantic salmon and will enable future searches for the specific genes involved.

Aberrant epithelial differentiation by cigarette smoke dysregulates respiratory host defence.

PubMed

Amatngalim, Gimano D; Schrumpf, Jasmijn A; Dishchekenian, Fernanda; Mertens, Tinne C J; Ninaber, Dennis K; van der Linden, Abraham C; Pilette, Charles; Taube, Christian; Hiemstra, Pieter S; van der Does, Anne M

2018-04-01

It is currently unknown how cigarette smoke-induced airway remodelling affects highly expressed respiratory epithelial defence proteins and thereby mucosal host defence.Localisation of a selected set of highly expressed respiratory epithelial host defence proteins was assessed in well-differentiated primary bronchial epithelial cell (PBEC) cultures. Next, PBEC were cultured at the air-liquid interface, and during differentiation for 2-3 weeks exposed daily to whole cigarette smoke. Gene expression, protein levels and epithelial cell markers were subsequently assessed. In addition, functional activities and persistence of the cigarette smoke-induced effects upon cessation were determined.Expression of the polymeric immunoglobulin receptor, secretory leukocyte protease inhibitor and long and short PLUNC (palate, lung and nasal epithelium clone protein) was restricted to luminal cells and exposure of differentiating PBECs to cigarette smoke resulted in a selective reduction of the expression of these luminal cell-restricted respiratory host defence proteins compared to controls. This reduced expression was a consequence of cigarette smoke-impaired end-stage differentiation of epithelial cells, and accompanied by a significant decreased transepithelial transport of IgA and bacterial killing.These findings shed new light on the importance of airway epithelial cell differentiation in respiratory host defence and could provide an additional explanation for the increased susceptibility of smokers and patients with chronic obstructive pulmonary disease to respiratory infections. Copyright ©ERS 2018.

Administration of ondansetron is associated with lethal outcome.

PubMed

Gener, Blanca; Burns, Jarrett M; Griffin, Susanne; Boyer, Edward W

2010-06-01

We report here the case of a child with a known muscular abnormality and susceptibility to malignant hyperthermia who abruptly died after receiving a therapeutic dose of ondansetron. Also, we discuss the pharmacodynamic relationship of ondansetron to malignant hyperthermia in a susceptible host.

Host susceptibility hypothesis for shell disease in American lobsters.

PubMed

Tlusty, Michael F; Smolowitz, Roxanna M; Halvorson, Harlyn O; DeVito, Simone E

2007-12-01

Epizootic shell disease (ESD) in American lobsters Homarus americanus is the bacterial degradation of the carapace resulting in extensive irregular, deep erosions. The disease is having a major impact on the health and mortality of some American lobster populations, and its effects are being transferred to the economics of the fishery. While the onset and progression of ESD in American lobsters is undoubtedly multifactorial, there is little understanding of the direct causality of this disease. The host susceptibility hypothesis developed here states that although numerous environmental and pathological factors may vary around a lobster, it is eventually the lobster's internal state that is permissive to or shields it from the final onset of the diseased state. To support the host susceptibility hypothesis, we conceptualized a model of shell disease onset and severity to allow further research on shell disease to progress from a structured model. The model states that shell disease onset will occur when the net cuticle degradation (bacterial degradation, decrease of host immune response to bacteria, natural wear, and resorption) is greater than the net deposition (growth, maintenance, and inflammatory response) of the shell. Furthermore, lesion severity depends on the extent to which cuticle degradation exceeds deposition. This model is consistent with natural observations of shell disease in American lobster.

Abrupt suspension of probiotics administration may increase host pathogen susceptibility by inducing gut dysbiosis

PubMed Central

Liu, Zhi; Liu, Wenshu; Ran, Chao; Hu, Jun; Zhou, Zhigang

2016-01-01

In this study, we investigated the risk associated with suspension of probiotics administration in tilapia, an animal model that may mimic immune-compromised conditions in humans. Tilapias were fed for 14 days using a probiotics-supplemented diet, followed by a three-day suspension of probiotics treatment and a subsequent challenge by Aeromonas hydrophila. Unexpectedly, the suspension of a probiotic strain Lactobacillus plantarum JCM1149 significantly triggered susceptibility of the host to A. hydrophila. We further observed that suspension of JCM1149 resulted in host gut microbiota dysbiosis and the subsequent disorder in the intestinal metabolites (bile acids, amino acids, and glucose) and damage in the intestinal epithelium, giving rise to a condition similar to antibiotics-induced gut dysbiosis, which collectively impaired tilapia’s gut health and resistance to pathogenic challenges. Additionally, we determined that JCM1149 adhered relatively poorly to tilapia intestinal mucosa and was rapidly released from the gastrointestinal tract (GIT) after suspension, with the rapid loss of probiotic strain probably being the direct cause of gut dysbiosis. Finally, three other probiotic Lactobacillus strains with low intestinal mucosa binding activity showed similar rapid loss phenotype following administration suspension, and induced higher host susceptibility to infection, indicating that the risk is a generic phenomenon in Lactobacillus. PMID:26983596

Correlations between Colonization of Onion Thrips and Leaf Reflectance Measures across Six Cabbage Varieties

PubMed Central

Bálint, János; Nagy, Balázs Vince; Fail, József

2013-01-01

The main purpose of this study was to reveal if the UV-A, and visible light reflection of leaves of white cabbage varieties is correlated to resistance against onion thrips. The antixenotic resistance (AR) against onion thrips and thrips damage differed between varieties Balashi, Bloktor, Riana – considered resistant – and Green Gem, Hurricane, Quisor – considered susceptible. The solar UV-A (340–400 nm) and visible (401–650 nm) light reflection of white cabbage leaves were recorded. Correlation between AR against onion thrips and reflection of leaves in UV-A and visible range of the studied white cabbage varieties were computed. According to the AR evaluation onion thrips density was always higher on susceptible than on resistant varieties. The UV-A light reflection of head forming leaves and the contrast between head and exterior leaves (H/E) was negatively correlated with onion thrips host preference at an early stage of cabbage head formation. The visible light reflection of both head forming and exterior leaves was also negatively correlated with onion thrips host preference. Susceptible varieties had greater damage ratings at harvest than resistant ones and positive correlations were observed between AR and damage. AR against onion thrips may be affected by differences in reflection of cabbage leaves at an early growth stage. It is suggested that more intensive reflection of leaves and/or higher contrast values between the reflectance intensity of head versus outer leaves made the resistant varieties less attractive to onion thrips. Our results reported here provide the first evidence of negative correlation between UV-A and visible reflection of leaves and AR of white cabbage against a dangerous insect pest, opening new perspectives for understanding the role of reflection by plant leaves in pest management. PMID:24040093

The genetic basis for variation in resistance to infection in the Drosophila melanogaster genetic reference panel

PubMed Central

Wang, Jonathan B.

2017-01-01

Individuals vary extensively in the way they respond to disease but the genetic basis of this variation is not fully understood. We found substantial individual variation in resistance and tolerance to the fungal pathogen Metarhizium anisopliae Ma549 using the Drosophila melanogaster Genetic Reference Panel (DGRP). In addition, we found that host defense to Ma549 was correlated with defense to the bacterium Pseudomonas aeruginosa Pa14, and several previously published DGRP phenotypes including oxidative stress sensitivity, starvation stress resistance, hemolymph glucose levels, and sleep indices. We identified polymorphisms associated with differences between lines in both their mean survival times and microenvironmental plasticity, suggesting that lines differ in their ability to adapt to variable pathogen exposures. The majority of polymorphisms increasing resistance to Ma549 were sex biased, located in non-coding regions, had moderately large effect and were rare, suggesting that there is a general cost to defense. Nevertheless, host defense was not negatively correlated with overall longevity and fecundity. In contrast to Ma549, minor alleles were concentrated in the most Pa14-susceptible as well as the most Pa14-resistant lines. A pathway based analysis revealed a network of Pa14 and Ma549-resistance genes that are functionally connected through processes that encompass phagocytosis and engulfment, cell mobility, intermediary metabolism, protein phosphorylation, axon guidance, response to DNA damage, and drug metabolism. Functional testing with insertional mutagenesis lines indicates that 12/13 candidate genes tested influence susceptibility to Ma549. Many candidate genes have homologs identified in studies of human disease, suggesting that genes affecting variation in susceptibility are conserved across species. PMID:28257468

Influence of body condition on influenza A virus infection in mallard ducks: Experimental infection data

USGS Publications Warehouse

Arsnoe, Dustin M.; Ip, Hon S.; Owen, Jennifer C.

2011-01-01

Migrating waterfowl are implicated in the global spread of influenza A viruses (IAVs), and mallards (Anas platyrhynchos) are considered a particularly important IAV reservoir. Prevalence of IAV infection in waterfowl peaks during autumn pre-migration staging and then declines as birds reach wintering areas. Migration is energetically costly and birds often experience declines in body condition that may suppress immune function. We assessed how body condition affects susceptibility to infection, viral shedding and antibody production in wild-caught and captive-bred juvenile mallards challenged with low pathogenic avian influenza virus (LPAIV) H5N9. Wild mallards (n = 30) were separated into three experimental groups; each manipulated through food availability to a different condition level (-20%, -10%, and normal ±5% original body condition), and captive-bred mallards (n = 10) were maintained at normal condition. We found that wild mallards in normal condition were more susceptible to LPAIV infection, shed higher peak viral loads and shed viral RNA more frequently compared to birds in poor condition. Antibody production did not differ according to condition. We found that wild mallards did not differ from captive-bred mallards in viral intensity and duration of infection, but they did exhibit lower antibody titers and greater variation in viral load. Our findings suggest that reduced body condition negatively influences waterfowl host competence to LPAIV infection. This observation is contradictory to the recently proposed condition-dependent hypothesis, according to which birds in reduced condition would be more susceptible to IAV infection. The mechanisms responsible for reducing host competency among birds in poor condition remain unknown. Our research indicates body condition may influence the maintenance and spread of LPAIV by migrating waterfowl.

Influence of body condition on influenza a virus infection in mallard ducks: Experimental infection data

USGS Publications Warehouse

Arsnoe, D.M.; Ip, Hon S.; Owen, J.C.

2011-01-01

Migrating waterfowl are implicated in the global spread of influenza A viruses (IAVs), and mallards (Anas platyrhynchos) are considered a particularly important IAV reservoir. Prevalence of IAV infection in waterfowl peaks during autumn pre-migration staging and then declines as birds reach wintering areas. Migration is energetically costly and birds often experience declines in body condition that may suppress immune function. We assessed how body condition affects susceptibility to infection, viral shedding and antibody production in wild-caught and captive-bred juvenile mallards challenged with low pathogenic avian influenza virus (LPAIV) H5N9. Wild mallards (n = 30) were separated into three experimental groups; each manipulated through food availability to a different condition level (-20%, -10%, and normal ??5% original body condition), and captive-bred mallards (n = 10) were maintained at normal condition. We found that wild mallards in normal condition were more susceptible to LPAIV infection, shed higher peak viral loads and shed viral RNA more frequently compared to birds in poor condition. Antibody production did not differ according to condition. We found that wild mallards did not differ from captive-bred mallards in viral intensity and duration of infection, but they did exhibit lower antibody titers and greater variation in viral load. Our findings suggest that reduced body condition negatively influences waterfowl host competence to LPAIV infection. This observation is contradictory to the recently proposed condition-dependent hypothesis, according to which birds in reduced condition would be more susceptible to IAV infection. The mechanisms responsible for reducing host competency among birds in poor condition remain unknown. Our research indicates body condition may influence the maintenance and spread of LPAIV by migrating waterfowl. ?? 2011 Arsnoe et al.

Reduced Carbohydrate Availability Enhances the Susceptibility of Arabidopsis toward Colletotrichum higginsianum1[W][OA

PubMed Central

Engelsdorf, Timo; Horst, Robin J.; Pröls, Reinhard; Pröschel, Marlene; Dietz, Franziska; Hückelhoven, Ralph; Voll, Lars M.

2013-01-01

Colletotrichum higginsianum is a hemibiotrophic ascomycete fungus that is adapted to Arabidopsis (Arabidopsis thaliana). After breaching the host surface, the fungus establishes an initial biotrophic phase in the penetrated epidermis cell, before necrotrophic growth is initiated upon further host colonization. We observed that partitioning of major leaf carbohydrates was shifted in favor of sucrose and at the expense of starch during necrotrophic fungal growth. Arabidopsis mutants with impaired starch turnover were more susceptible toward C. higginsianum infection, exhibiting a strong negative correlation between diurnal carbohydrate accumulation and fungal proliferation for the tested genotypes. By altering the length of the light phase and employing additional genotypes impaired in nocturnal carbon mobilization, we revealed that reduced availability of carbon enhances susceptibility in the investigated pathosystem. Systematic starvation experiments resulted in two important findings. First, we showed that carbohydrate supply by the host is dispensable during biotrophic growth of C. higginsianum, while carbon deficiency was most harmful to the host during the necrotrophic colonization phase. Compared with the wild type, the increases in the total salicylic acid pool and camalexin accumulation were reduced in starch-free mutants at late interaction stages, while an increased ratio of free to total salicylic acid did not convey elevated pathogenesis-related gene expression in starch-free mutants. These observations suggest that reduced carbon availability dampens induced defense responses. In contrast, starch-free mutants were more resistant toward the fungal biotroph Erysiphe cruciferarum, indicating that reduced carbohydrate availability influences susceptibility differently in the interaction with the investigated hemibiotrophic and biotrophic fungal pathogens. PMID:23487433

Modelling density-dependent resistance in insect-pathogen interactions.

PubMed

White, K A; Wilson, K

1999-10-01

We consider a mathematical model for a host-pathogen interaction where the host population is split into two categories: those susceptible to disease and those resistant to disease. Since the model was motivated by studies on insect populations, we consider a discrete-time model to reflect the discrete generations which are common among insect species. Whether an individual is born susceptible or resistant to disease depends on the local population levels at the start of each generation. In particular, we are interested in the case where the fraction of resistant individuals in the population increases as the total population increases. This may be seen as a positive feedback mechanism since disease is the only population control imposed upon the system. Moreover, it reflects recent experimental observations from noctuid moth-baculovirus interactions that pathogen resistance may increase with larval density. We find that the inclusion of a resistant class can stabilise unstable host-pathogen interactions but there is greatest regulation when the fraction born resistant is density independent. Nonetheless, inclusion of density dependence can still allow intrinsically unstable host-pathogen dynamics to be stabilised provided that this effect is sufficiently small. Moreover, inclusion of density-dependent resistance to disease allows the system to give rise to bistable dynamics in which the final outcome is dictated by the initial conditions for the model system. This has implications for the management of agricultural pests using biocontrol agents-in particular, it is suggested that the propensity for density-dependent resistance be determined prior to such a biocontrol attempt in order to be sure that this will result in the prevention of pest outbreaks, rather than their facilitation. Finally we consider how the cost of resistance to disease affects model outcomes and discover that when there is no cost to resistance, the model predicts stable periodic outbreaks of the insect population. The results are interpreted ecologically and future avenues for research to address the shortfalls in the present model system are discussed. Copyright 1999 Academic Press.

The immunoproteasome-specific inhibitor ONX 0914 reverses susceptibility to acute viral myocarditis.

PubMed

Althof, Nadine; Goetzke, Carl Christoph; Kespohl, Meike; Voss, Karolin; Heuser, Arnd; Pinkert, Sandra; Kaya, Ziya; Klingel, Karin; Beling, Antje

2018-02-01

Severe heart pathology upon virus infection is closely associated with the immunological equipment of the host. Since there is no specific treatment available, current research focuses on identifying new drug targets to positively modulate predisposing immune factors. Utilizing a murine model with high susceptibility to coxsackievirus B3-induced myocarditis, this study describes ONX 0914-an immunoproteasome-specific inhibitor-as highly protective during severe heart disease. Represented by reduced heart infiltration of monocytes/macrophages and diminished organ damage, ONX 0914 treatment reversed fulminant pathology. Virus-induced immune response features like overwhelming pro-inflammatory cytokine and chemokine production as well as a progressive loss of lymphocytes all being reminiscent of a sepsis-like disease course were prevented by ONX 0914. Although the viral burden was only minimally affected in highly susceptible mice, resulting maintenance of immune homeostasis improved the cardiac output, and saved animals from severe illness as well as high mortality. Altogether, this could make ONX 0914 a potent drug for the treatment of severe virus-mediated inflammation of the heart and might rank immunoproteasome inhibitors among drugs for preventing pathogen-induced immunopathology. © 2018 The Authors. Published under the terms of the CC BY 4.0 license.

Genetic susceptibility and periodontal disease: a retrospective study on a large italian sample.

PubMed

Tettamanti, L; Gaudio, R M; Iapichino, A; Mucchi, D; Tagliabue, A

2017-01-01

Periodontal disease (PD) is a multifactorial illness in which environment and host interact. The genetic component plays a key role in the onset of PD. In fact the genetic compound can modulate the inflammation of the mucous membranes and the loss of alveolar bone. The genetics of PD is not well understood. Previous studies suggest a strong association between PD occurrence and individual genetic profile. The role of genetic susceptibility could impact on the clinical manifestations of PD, and consequently on prevention and therapy. Genetic polymorphisms of VRD, IL6 and IL10 were investigated in Italian adults affected by PD. 571 cases classified according the criteria of the American Academy of Periodontology were included. All patients were Italian coming from three areas according to italian institute of statistics (ISTAT) (www.istat.it/it/archivio/regioni). The sample comprised 379 patients from North (66%), 152 from Central (26%) and 40 of South (8%). No significant differences were found among allele distribution. Chronic PD is a complex disease caused by a combination of genetic susceptibility, patients habits (oral hygiene, smoking, alcohol consumption) and oral pathogens. In our report no differences were detected among three Italian regions in allele distribution.

Whole Body Plethysmography Reveals Differential Ventilatory Responses to Ozone in Rat Models of Cardiovascular Disease

EPA Science Inventory

Increasingly, urban air pollution is recognized as an important determinant of cardiovascular disease. Host susceptibility to air pollution can vary due to genetic predisposition and underlying disease. To elucidate key factors of host ...

Insect Gut Symbiont Susceptibility to Host Antimicrobial Peptides Caused by Alteration of the Bacterial Cell Envelope*

PubMed Central

Kim, Jiyeun Kate; Son, Dae Woo; Kim, Chan-Hee; Cho, Jae Hyun; Marchetti, Roberta; Silipo, Alba; Sturiale, Luisa; Park, Ha Young; Huh, Ye Rang; Nakayama, Hiroshi; Fukatsu, Takema; Molinaro, Antonio; Lee, Bok Luel

2015-01-01

The molecular characterization of symbionts is pivotal for understanding the cross-talk between symbionts and hosts. In addition to valuable knowledge obtained from symbiont genomic studies, the biochemical characterization of symbionts is important to fully understand symbiotic interactions. The bean bug (Riptortus pedestris) has been recognized as a useful experimental insect gut symbiosis model system because of its cultivatable Burkholderia symbionts. This system is greatly advantageous because it allows the acquisition of a large quantity of homogeneous symbionts from the host midgut. Using these naïve gut symbionts, it is possible to directly compare in vivo symbiotic cells with in vitro cultured cells using biochemical approaches. With the goal of understanding molecular changes that occur in Burkholderia cells as they adapt to the Riptortus gut environment, we first elucidated that symbiotic Burkholderia cells are highly susceptible to purified Riptortus antimicrobial peptides. In search of the mechanisms of the increased immunosusceptibility of symbionts, we found striking differences in cell envelope structures between cultured and symbiotic Burkholderia cells. The bacterial lipopolysaccharide O antigen was absent from symbiotic cells examined by gel electrophoretic and mass spectrometric analyses, and their membranes were more sensitive to detergent lysis. These changes in the cell envelope were responsible for the increased susceptibility of the Burkholderia symbionts to host innate immunity. Our results suggest that the symbiotic interactions between the Riptortus host and Burkholderia gut symbionts induce bacterial cell envelope changes to achieve successful gut symbiosis. PMID:26116716

Host susceptibility to snake fungal disease is highly dispersed across phylogenetic and functional trait space

PubMed Central

Burbrink, Frank T.; Lorch, Jeffrey M.; Lips, Karen R.

2017-01-01

Emerging infectious diseases (EIDs) reduce host population sizes, cause extinction, disassemble communities, and have indirect negative effects on human well-being. Fungal EIDs have reduced population abundances in amphibians and bats across many species over large areas. The recent emergence of snake fungal disease (SFD) may have caused declines in some snake populations in the Eastern United States (EUS), which is home to a phylogenetically and ecologically diverse assembly of 98 taxa. SFD has been documented in only 23 naturally occuring species, although this is likely an underestimate of the number of susceptible taxa. Using several novel methods, including artificial neural networks, we combine phylogenetic and trait-based community estimates from all taxa in this region to show that SFD hosts are both phylogenetically and ecologically randomly dispersed. This might indicate that other species of snakes in the EUS could be currently infected or susceptible to SFD. Our models also indicate that information about key traits that enhance susceptiblity is lacking. Surveillance should consider that all snake species and habitats likely harbor this pathogen. PMID:29291245

Host susceptibility to snake fungal disease is highly dispersed across phylogenetic and functional trait space.

PubMed

Burbrink, Frank T; Lorch, Jeffrey M; Lips, Karen R

2017-12-01

Emerging infectious diseases (EIDs) reduce host population sizes, cause extinction, disassemble communities, and have indirect negative effects on human well-being. Fungal EIDs have reduced population abundances in amphibians and bats across many species over large areas. The recent emergence of snake fungal disease (SFD) may have caused declines in some snake populations in the Eastern United States (EUS), which is home to a phylogenetically and ecologically diverse assembly of 98 taxa. SFD has been documented in only 23 naturally occuring species, although this is likely an underestimate of the number of susceptible taxa. Using several novel methods, including artificial neural networks, we combine phylogenetic and trait-based community estimates from all taxa in this region to show that SFD hosts are both phylogenetically and ecologically randomly dispersed. This might indicate that other species of snakes in the EUS could be currently infected or susceptible to SFD. Our models also indicate that information about key traits that enhance susceptiblity is lacking. Surveillance should consider that all snake species and habitats likely harbor this pathogen.

Host susceptibility to snake fungal disease is highly dispersed across phylogenetic and functional trait space

USGS Publications Warehouse

Burbrink, Frank T.; Lorch, Jeffrey M.; Lips, Karen R.

2017-01-01

Emerging infectious diseases (EIDs) reduce host population sizes, cause extinction, disassemble communities, and have indirect negative effects on human well-being. Fungal EIDs have reduced population abundances in amphibians and bats across many species over large areas. The recent emergence of snake fungal disease (SFD) may have caused declines in some snake populations in the Eastern United States (EUS), which is home to a phylogenetically and ecologically diverse assembly of 98 taxa. SFD has been documented in only 23 naturally occuring species, although this is likely an underestimate of the number of susceptible taxa. Using several novel methods, including artificial neural networks, we combine phylogenetic and trait-based community estimates from all taxa in this region to show that SFD hosts are both phylogenetically and ecologically randomly dispersed. This might indicate that other species of snakes in the EUS could be currently infected or susceptible to SFD. Our models also indicate that information about key traits that enhance susceptiblity is lacking. Surveillance should consider that all snake species and habitats likely harbor this pathogen.

Comparative Analysis of Host Cell Entry of Ebola Virus From Sierra Leone, 2014, and Zaire, 1976.

PubMed

Hofmann-Winkler, Heike; Gnirß, Kerstin; Wrensch, Florian; Pöhlmann, Stefan

2015-10-01

The ongoing Ebola virus (EBOV) disease (EVD) epidemic in Western Africa is the largest EVD outbreak recorded to date and requires the rapid development and deployment of antiviral measures. The viral glycoprotein (GP) facilitates host cell entry and, jointly with cellular interaction partners, constitutes a potential target for antiviral intervention. However, it is unknown whether the GPs of the currently and previously circulating EBOVs use the same mechanisms for cellular entry and are thus susceptible to inhibition by the same antivirals and cellular defenses. Here, we show that the GPs of the EBOVs circulating in 1976 and 2014 transduce the same spectrum of target cells, use the same cellular factors for host cell entry, and are comparably susceptible to blockade by antiviral interferon-induced transmembrane proteins and neutralizing antibody KZ52. Thus, the viruses responsible for the ongoing EVD epidemic should be fully susceptible to established antiviral strategies targeting GP and cellular entry factors. © The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America.

The Type I Interferon Response Determines Differences in Choroid Plexus Susceptibility between Newborns and Adults in Herpes Simplex Virus Encephalitis.

PubMed

Wilcox, Douglas R; Folmsbee, Stephen S; Muller, William J; Longnecker, Richard

2016-04-12

Newborns are significantly more susceptible to severe viral encephalitis than adults, with differences in the host response to infection implicated as a major factor. However, the specific host signaling pathways responsible for differences in susceptibility and neurologic morbidity have remained unknown. In a murine model of HSV encephalitis, we demonstrated that the choroid plexus (CP) is susceptible to herpes simplex virus 1 (HSV-1) early in infection of the newborn but not the adult brain. We confirmed susceptibility of the CP to HSV infection in a human case of newborn HSV encephalitis. We investigated components of the type I interferon (IFN) response in the murine brain that might account for differences in cell susceptibility and found that newborns have a dampened interferon response and significantly lower basal levels of the alpha/beta interferon (IFN-α/β) receptor (IFNAR) than do adults. To test the contribution of IFNAR to restricting infection from the CP, we infected IFNAR knockout (KO) adult mice, which showed restored CP susceptibility to HSV-1 infection in the adult. Furthermore, reduced IFNAR levels did not account for differences we found in the basal levels of several other innate signaling proteins in the wild-type newborn and the adult, including protein kinase R (PKR), that suggested specific regulation of innate immunity in the developing brain. Viral targeting of the CP, a region of the brain that plays a critical role in neurodevelopment, provides a link between newborn susceptibility to HSV and long-term neurologic morbidity among survivors of newborn HSV encephalitis. Compared to adults, newborns are significantly more susceptible to severe disease following HSV infection. Over half of newborn HSV infections result in disseminated disease or encephalitis, with long-term neurologic morbidity in 2/3 of encephalitis survivors. We investigated differences in host cell susceptibility between newborns and adults that contribute to severe central nervous system disease in the newborn. We found that, unlike the adult brain, the newborn choroid plexus (CP) was susceptible early in HSV-1 infection. We demonstrated that IFN-α/β receptor levels are lower in the newborn brain than in the adult brain and that deletion of this receptor restores susceptibility of the CP in the adult brain. The CP serves as a barrier between the blood and the cerebrospinal fluid and plays a role in proper neurodevelopment. Susceptibility of the newborn choroid plexus to HSV-1 has important implications in viral spread to the brain and, also, in the neurologic morbidity following HSV encephalitis. Copyright © 2016 Wilcox et al.

DNA methylation differentially regulates cytokine secretion in gingival epithelia in response to bacterial challenges.

PubMed

Drury, Jeanie L; Chung, Whasun Oh

2015-03-01

Epigenetic modifications are changes in gene expression without altering DNA sequence. We previously reported that bacteria-specific innate immune responses are regulated by epigenetic modifications. Our hypothesis is that DNA methylation affects gingival cytokine secretion in response to bacterial stimulation. Gingival epithelial cells (GECs) were treated with DNMT-1 inhibitors prior to Porphyromonas gingivalis (Pg) or Fusobacterium nucleatum (Fn) exposure. Protein secretion was assessed using ELISA. Gene expression was quantified using qRT-PCR. The ability of bacteria to invade inhibitor pretreated GECs was assessed utilizing flow cytometry. Changes were compared to unstimulated GECs. GEC upregulation of IL-6 and CXCL1 by Pg or Fn stimulation was significantly diminished by inhibitor pretreatment. Pg stimulated IL-1α secretion and inhibitor pretreatment significantly enhanced this upregulation, while Fn alone or with inhibitor pretreatment had no effect on IL-1α expression. GEC upregulation of human beta-definsin-2 in response to Pg and Fn exposure was enhanced following the inhibitor pretreatment. GEC susceptibility to bacterial invasion was unaltered. These results suggest that DNA methylation differentially affects gingival cytokine secretion in response to Pg or Fn. Our data provide basis for better understanding of how epigenetic modifications, brought on by exposure to oral bacteria, will subsequently affect host susceptibility to oral diseases. © FEMS 2014. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Comparing Avocado, Swamp Bay, and Camphortree as Hosts of Raffaelea lauricola Using a Green Fluorescent Protein (GFP)-Labeled Strain of the Pathogen.

PubMed

Campbell, A S; Ploetz, R C; Rollins, J A

2017-01-01

Raffaelea lauricola, a fungal symbiont of the ambrosia beetle Xyleborus glabratus, causes laurel wilt in members of the Lauraceae plant family. North American species in the family, such as avocado (Persea americana) and swamp bay (P. palustris), are particularly susceptible to laurel wilt, whereas the Asian camphortree (Cinnamomum camphora) is relatively tolerant. To determine whether susceptibility is related to pathogen colonization, a green fluorescent protein-labeled strain of R. lauricola was generated and used to inoculate avocado, swamp bay, and camphortree. Trees were harvested 3, 10, and 30 days after inoculation (DAI), and disease severity was rated on a 1-to-10 scale. By 30 DAI, avocado and swamp bay developed significantly more severe disease than camphortree (mean severities of 6.8 and 5.5 versus 1.6, P < 0.003). The extent of xylem colonization was recorded as the percentage of lumena that were colonized by the pathogen. More xylem was colonized in avocado than camphortree (0.9% versus 0.1%, P < 0.03) but colonization in swamp bay (0.4%) did not differ significantly from either host. Although there were significant correlations between xylem colonization and laurel wilt severity in avocado (r = 0.74), swamp bay (r = 0.82), and camphortree (r = 0.87), even severely affected trees of all species were scarcely colonized by the pathogen.

White-Tailed Deer Susceptible to Scrapie by Natural Route of Infection

USDA-ARS?s Scientific Manuscript database

Interspecies transmission studies afford the opportunity to better understand the potential host range and origins of prion diseases. Previous experiments demonstrated that white-tailed deer are susceptible to sheep-derived scrapie by intracranial inoculation. The purpose of this study was to determ...

White-Tailed Deer Susceptible to Scrapie by Natural Route of Infection

USDA-ARS?s Scientific Manuscript database

Interspecies transmission studies afford the opportunity to better understand the potential host range and origins of prion diseases. Previous experiments demonstrated that white-tailed deer are susceptible to sheep-derived scrapie by intracranial inoculation. The purpose of an ongoing study is to...

Commensal Bacteroides species induce colitis in host-genotype-specific fashion in a mouse model of inflammatory bowel disease

PubMed Central

Bloom, Seth M.; Bijanki, Vinieth N.; Nava, Gerardo M.; Sun, Lulu; Malvin, Nicole P.; Donermeyer, David L.; Dunne, W. Michael; Allen, Paul M.; Stappenbeck, Thaddeus S.

2011-01-01

SUMMARY The intestinal microbiota is important for induction of inflammatory bowel disease (IBD). IBD is associated with complex shifts in microbiota composition, but it is unclear whether specific bacterial subsets induce IBD and, if so, whether their proportions in the microbiota are altered during disease. Here we fulfilled Koch’s postulates in host-genotype-specific fashion using a mouse model of IBD with human-relevant disease-susceptibility mutations. From screening experiments we isolated common commensal Bacteroides species, introduced them into antibiotic-pretreated mice, and quantitatively re-isolated them in culture. The bacteria colonized IBD-susceptible and non-susceptible mice equivalently, but induced disease exclusively in susceptible animals. Conversely, commensal Enterobacteriaceae were >100-fold enriched during spontaneous disease but an Enterobacteriaceae isolate failed to induce disease in antibiotic-pretreated mice despite robust colonization. We thus demonstrate that IBD-associated microbiota alterations do not necessarily reflect underlying disease etiology. These findings establish important experimental criteria and a conceptual framework for understanding microbial contributions to IBD. PMID:21575910

Recent advances in the understanding of Xanthomonas citri ssp. citri pathogenesis and citrus canker disease management.

PubMed

Ference, Christopher M; Gochez, Alberto M; Behlau, Franklin; Wang, Nian; Graham, James H; Jones, Jeffrey B

2018-06-01

Taxonomic status: Bacteria; Phylum Proteobacteria; Class Gammaproteobacteria; Order Xanthomonadales; Family Xanthomonadaceae; Genus Xanthomonas; Species Xanthomonas citri ssp. citri (Xcc). Host range: Compatible hosts vary in their susceptibility to citrus canker (CC), with grapefruit, lime and lemon being the most susceptible, sweet orange being moderately susceptible, and kumquat and calamondin being amongst the least susceptible. Microbiological properties: Xcc is a rod-shaped (1.5-2.0 × 0.5-0.75 µm), Gram-negative, aerobic bacterium with a single polar flagellum. The bacterium forms yellow colonies on culture media as a result of the production of xanthomonadin. Distribution: Present in South America, the British Virgin Islands, Africa, the Middle East, India, Asia and the South Pacific islands. Localized incidence in the USA, Argentina, Brazil, Bolivia, Uruguay, Senegal, Mali, Burkina Faso, Tanzania, Iran, Saudi Arabia, Yemen and Bangladesh. Widespread throughout Paraguay, Comoros, China, Japan, Malaysia and Vietnam. Eradicated from South Africa, Australia and New Zealand. Absent from Europe. © 2017 BSPP AND JOHN WILEY & SONS LTD.

Arabidopsis thaliana is a susceptible host plant for the holoparasite Cuscuta spec.

PubMed

Birschwilks, Mandy; Sauer, Norbert; Scheel, Dierk; Neumann, Stefanie

2007-10-01

Arabidopsis thaliana and Cuscuta spec. represent a compatible host-parasite combination. Cuscuta produces a haustorium that penetrates the host tissue. In early stages of development the searching hyphae on the tip of the haustorial cone are connected to the host tissue by interspecific plasmodesmata. Ten days after infection, translocation of the fluorescent dyes, Texas Red (TR) and 5,6-carboxyfluorescein (CF), demonstrates the existence of a continuous connection between xylem and phloem of the host and parasite. Cuscuta becomes the dominant sink in this host-parasite system. Transgenic Arabidopsis plants expressing genes encoding the green fluorescent protein (GFP; 27 kDa) or a GFP-ubiquitin fusion (36 kDa), respectively, under the companion cell (CC)-specific AtSUC2 promoter were used to monitor the transfer of these proteins from the host sieve elements to those of Cuscuta. Although GFP is transferred unimpedly to the parasite, the GFP-ubiquitin fusion could not be detected in Cuscuta. A translocation of the GFP-ubiquitin fusion protein was found to be restricted to the phloem of the host, although a functional symplastic pathway exists between the host and parasite, as demonstrated by the transport of CF. These results indicate a peripheral size exclusion limit (SEL) between 27 and 36 kDa for the symplastic connections between host and Cuscuta sieve elements. Forty-six accessions of A. thaliana covering the entire range of its genetic diversity, as well as Arabidopsis halleri, were found to be susceptible towards Cuscuta reflexa.

The infection rate of Daphnia magna by Pasteuria ramosa conforms with the mass-action principle.

PubMed

Regoes, R R; Hottinger, J W; Sygnarski, L; Ebert, D

2003-10-01

In simple epidemiological models that describe the interaction between hosts with their parasites, the infection process is commonly assumed to be governed by the law of mass action, i.e. it is assumed that the infection rate depends linearly on the densities of the host and the parasite. The mass-action assumption, however, can be problematic if certain aspects of the host-parasite interaction are very pronounced, such as spatial compartmentalization, host immunity which may protect from infection with low doses, or host heterogeneity with regard to susceptibility to infection. As deviations from a mass-action infection rate have consequences for the dynamics of the host-parasite system, it is important to test for the appropriateness of the mass-action assumption in a given host-parasite system. In this paper, we examine the relationship between the infection rate and the parasite inoculum for the water flee Daphnia magna and its bacterial parasite Pasteuria ramosa. We measured the fraction of infected hosts after exposure to 14 different doses of the parasite. We find that the observed relationship between the fraction of infected hosts and the parasite dose is largely consistent with an infection process governed by the mass-action principle. However, we have evidence for a subtle but significant deviation from a simple mass-action infection model, which can be explained either by some antagonistic effects of the parasite spores during the infection process, or by heterogeneity in the hosts' susceptibility with regard to infection.

Iron overload favors the elimination of Leishmania infantum from mouse tissues through interaction with reactive oxygen and nitrogen species.

PubMed

Vale-Costa, Sílvia; Gomes-Pereira, Sandra; Teixeira, Carlos Miguel; Rosa, Gustavo; Rodrigues, Pedro Nuno; Tomás, Ana; Appelberg, Rui; Gomes, Maria Salomé

2013-01-01

Iron plays a central role in host-parasite interactions, since both intervenients need iron for survival and growth, but are sensitive to iron-mediated toxicity. The host's iron overload is often associated with susceptibility to infection. However, it has been previously reported that iron overload prevented the growth of Leishmania major, an agent of cutaneous leishmaniasis, in BALB/c mice. In order to further clarify the impact of iron modulation on the growth of Leishmania in vivo, we studied the effects of iron supplementation or deprivation on the growth of L. infantum, the causative agent of Mediterranean visceral leishmaniasis, in the mouse model. We found that dietary iron deficiency did not affect the protozoan growth, whereas iron overload decreased its replication in the liver and spleen of a susceptible mouse strain. The fact that the iron-induced inhibitory effect could not be seen in mice deficient in NADPH dependent oxidase or nitric oxide synthase 2 suggests that iron eliminates L. infantum in vivo through the interaction with reactive oxygen and nitrogen species. Iron overload did not significantly alter the mouse adaptive immune response against L. infantum. Furthermore, the inhibitory action of iron towards L. infantum was also observed, in a dose dependent manner, in axenic cultures of promastigotes and amastigotes. Importantly, high iron concentrations were needed to achieve such effects. In conclusion, externally added iron synergizes with the host's oxidative mechanisms of defense in eliminating L. infantum from mouse tissues. Additionally, the direct toxicity of iron against Leishmania suggests a potential use of this metal as a therapeutic tool or the further exploration of iron anti-parasitic mechanisms for the design of new drugs.

The knottin-like Blufensin family regulates genes involved in nuclear import and the secretory pathway in barley-powdery mildew interactions

PubMed Central

Xu, Weihui; Meng, Yan; Surana, Priyanka; Fuerst, Greg; Nettleton, Dan; Wise, Roger P.

2015-01-01

Plants have evolved complex regulatory mechanisms to control a multi-layered defense response to microbial attack. Both temporal and spatial gene expression are tightly regulated in response to pathogen ingress, modulating both positive and negative control of defense. BLUFENSINs, small knottin-like peptides in barley, wheat, and rice, are highly induced by attack from fungal pathogens, in particular, the obligate biotrophic fungus, Blumeria graminis f. sp. hordei (Bgh), causal agent of barley powdery mildew. Previous research indicated that Blufensin1 (Bln1) functions as a negative regulator of basal defense mechanisms. In the current report, we show that BLN1 and BLN2 can both be secreted to the apoplast and Barley stripe mosaic virus (BSMV)-mediated overexpression of Bln2 increases susceptibility of barley to Bgh. Bimolecular fluorescence complementation (BiFC) assays signify that BLN1 and BLN2 can interact with each other, and with calmodulin. We then used BSMV-induced gene silencing to knock down Bln1, followed by Barley1 GeneChip transcriptome analysis, to identify additional host genes influenced by Bln1. Analysis of differential expression revealed a gene set enriched for those encoding proteins annotated to nuclear import and the secretory pathway, particularly Importin α1-b and Sec61 γ subunits. Further functional analysis of these two affected genes showed that when silenced, they also reduced susceptibility to Bgh. Taken together, we postulate that Bln1 is co-opted by Bgh to facilitate transport of disease-related host proteins or effectors, influencing the establishment of Bgh compatibility on its barley host. PMID:26089830

Influenza A Virus Infection Predisposes Hosts to Secondary Infection with Different Streptococcus pneumoniae Serotypes with Similar Outcome but Serotype-Specific Manifestation.

PubMed

Sharma-Chawla, Niharika; Sender, Vicky; Kershaw, Olivia; Gruber, Achim D; Volckmar, Julia; Henriques-Normark, Birgitta; Stegemann-Koniszewski, Sabine; Bruder, Dunja

2016-12-01

Influenza A virus (IAV) and Streptococcus pneumoniae are major causes of respiratory tract infections, particularly during coinfection. The synergism between these two pathogens is characterized by a complex network of dysregulated immune responses, some of which last until recovery following IAV infection. Despite the high serotype diversity of S. pneumoniae and the serotype replacement observed since the introduction of conjugate vaccines, little is known about pneumococcal strain dependency in the enhanced susceptibility to severe secondary S. pneumoniae infection following IAV infection. Thus, we studied how preinfection with IAV alters host susceptibility to different S. pneumoniae strains with various degrees of invasiveness using a highly invasive serotype 4 strain, an invasive serotype 7F strain, and a carrier serotype 19F strain. A murine model of pneumococcal coinfection during the acute phase of IAV infection showed a significantly increased degree of pneumonia and mortality for all tested pneumococcal strains at otherwise sublethal doses. The incidence and kinetics of systemic dissemination, however, remained bacterial strain dependent. Furthermore, we observed strain-specific alterations in the pulmonary levels of alveolar macrophages, neutrophils, and inflammatory mediators ultimately affecting immunopathology. During the recovery phase following IAV infection, bacterial growth in the lungs and systemic dissemination were enhanced in a strain-dependent manner. Altogether, this study shows that acute IAV infection predisposes the host to lethal S. pneumoniae infection irrespective of the pneumococcal serotype, while the long-lasting synergism between IAV and S. pneumoniae is bacterial strain dependent. These results hold implications for developing tailored therapeutic treatment regimens for dual infections during future IAV outbreaks. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

A stochastic model for transmission, extinction and outbreak of Escherichia coli O157:H7 in cattle as affected by ambient temperature and cleaning practices.

PubMed

Wang, Xueying; Gautam, Raju; Pinedo, Pablo J; Allen, Linda J S; Ivanek, Renata

2014-08-01

Many infectious agents transmitting through a contaminated environment are able to persist in the environment depending on the temperature and sanitation determined rates of their replication and clearance, respectively. There is a need to elucidate the effect of these factors on the infection transmission dynamics in terms of infection outbreaks and extinction while accounting for the random nature of the process. Also, it is important to distinguish between the true and apparent extinction, where the former means pathogen extinction in both the host and the environment while the latter means extinction only in the host population. This study proposes a stochastic-differential equation model as an approximation to a Markov jump process model, using Escherichia coli O157:H7 in cattle as a model system. In the model, the host population infection dynamics are described using the standard susceptible-infected-susceptible framework, and the E. coli O157:H7 population in the environment is represented by an additional variable. The backward Kolmogorov equations that determine the probability distribution and the expectation of the first passage time are provided in a general setting. The outbreak and apparent extinction of infection are investigated by numerically solving the Kolmogorov equations for the probability density function of the associated process and the expectation of the associated stopping time. The results provide insight into E. coli O157:H7 transmission and apparent extinction, and suggest ways for controlling the spread of infection in a cattle herd. Specifically, this study highlights the importance of ambient temperature and sanitation, especially during summer.

Climate forcing of an emerging pathogenic fungus across a montane multi-host community.

PubMed

Clare, Frances C; Halder, Julia B; Daniel, Olivia; Bielby, Jon; Semenov, Mikhail A; Jombart, Thibaut; Loyau, Adeline; Schmeller, Dirk S; Cunningham, Andrew A; Rowcliffe, Marcus; Garner, Trenton W J; Bosch, Jaime; Fisher, Matthew C

2016-12-05

Changes in the timings of seasonality as a result of anthropogenic climate change are predicted to occur over the coming decades. While this is expected to have widespread impacts on the dynamics of infectious disease through environmental forcing, empirical data are lacking. Here, we investigated whether seasonality, specifically the timing of spring ice-thaw, affected susceptibility to infection by the emerging pathogenic fungus Batrachochytrium dendrobatidis (Bd) across a montane community of amphibians that are suffering declines and extirpations as a consequence of this infection. We found a robust temporal association between the timing of the spring thaw and Bd infection in two host species, where we show that an early onset of spring forced high prevalences of infection. A third highly susceptible species (the midwife toad, Alytes obstetricans) maintained a high prevalence of infection independent of time of spring thaw. Our data show that perennially overwintering midwife toad larvae may act as a year-round reservoir of infection with variation in time of spring thaw determining the extent to which infection spills over into sympatric species. We used future temperature projections based on global climate models to demonstrate that the timing of spring thaw in this region will advance markedly by the 2050s, indicating that climate change will further force the severity of infection. Our findings on the effect of annual variability on multi-host infection dynamics show that the community-level impact of fungal infectious disease on biodiversity will need to be re-evaluated in the face of climate change.This article is part of the themed issue 'Tackling emerging fungal threats to animal health, food security and ecosystem resilience'. © 2016 The Authors.

Iron Overload Favors the Elimination of Leishmania infantum from Mouse Tissues through Interaction with Reactive Oxygen and Nitrogen Species

PubMed Central

Vale-Costa, Sílvia; Gomes-Pereira, Sandra; Teixeira, Carlos Miguel; Rosa, Gustavo; Rodrigues, Pedro Nuno; Tomás, Ana; Appelberg, Rui; Gomes, Maria Salomé

2013-01-01

Iron plays a central role in host-parasite interactions, since both intervenients need iron for survival and growth, but are sensitive to iron-mediated toxicity. The host's iron overload is often associated with susceptibility to infection. However, it has been previously reported that iron overload prevented the growth of Leishmania major, an agent of cutaneous leishmaniasis, in BALB/c mice. In order to further clarify the impact of iron modulation on the growth of Leishmania in vivo, we studied the effects of iron supplementation or deprivation on the growth of L. infantum, the causative agent of Mediterranean visceral leishmaniasis, in the mouse model. We found that dietary iron deficiency did not affect the protozoan growth, whereas iron overload decreased its replication in the liver and spleen of a susceptible mouse strain. The fact that the iron-induced inhibitory effect could not be seen in mice deficient in NADPH dependent oxidase or nitric oxide synthase 2 suggests that iron eliminates L. infantum in vivo through the interaction with reactive oxygen and nitrogen species. Iron overload did not significantly alter the mouse adaptive immune response against L. infantum. Furthermore, the inhibitory action of iron towards L. infantum was also observed, in a dose dependent manner, in axenic cultures of promastigotes and amastigotes. Importantly, high iron concentrations were needed to achieve such effects. In conclusion, externally added iron synergizes with the host's oxidative mechanisms of defense in eliminating L. infantum from mouse tissues. Additionally, the direct toxicity of iron against Leishmania suggests a potential use of this metal as a therapeutic tool or the further exploration of iron anti-parasitic mechanisms for the design of new drugs. PMID:23459556

A host basal transcription factor is a key component for infection of rice by TALE-carrying bacteria.

PubMed

Yuan, Meng; Ke, Yinggen; Huang, Renyan; Ma, Ling; Yang, Zeyu; Chu, Zhaohui; Xiao, Jinghua; Li, Xianghua; Wang, Shiping

2016-07-29

Transcription activator-like effectors (TALEs) are sequence-specific DNA binding proteins found in a range of plant pathogenic bacteria, where they play important roles in host-pathogen interactions. However, it has been unclear how TALEs, after they have been injected into the host cells, activate transcription of host genes required for infection success. Here, we show that the basal transcription factor IIA gamma subunit TFIIAγ5 from rice is a key component for infection by the TALE-carrying bacterium Xanthomonas oryzae pv. oryzae, the causal agent for bacterial blight. Direct interaction of several TALEs with TFIIAγ5 is required for activation of disease susceptibility genes. Conversely, reduced expression of the TFIIAγ5 host gene limits the induction of susceptibility genes and thus decreases bacterial blight symptoms. Suppression or mutation of TFIIAγ5 can also reduce bacterial streak, another devastating disease of rice caused by TALE-carrying X. oryzae pv. oryzicola. These results have important implications for formulating a widely applicable strategy with which to improve resistance of plants to TALE-carrying pathogens.

Central nervous system infection due to Cryptococcus gattii sensu lato in India: Analysis of clinical features, molecular profile and antifungal susceptibility.

PubMed

Lahiri Mukhopadhyay, Shayanki; Bahubali, Veenakumari H; Manjunath, Netravathi; Swaminathan, Aarthi; Maji, Sayani; Palaniappan, Marimuthu; Parthasarathy, Satishchandra; Chandrashekar, Nagarathna

2017-11-01

Cryptococcus gattii species complex has evolved as a pathogen in the last two decades causing infection among both immunocompetent and immunocompromised hosts. We aimed to analyse the clinical features of CNS infection caused by C. gattii sensu lato, molecular and antifungal susceptibility profile of this pathogen. Cases diagnosed to have CNS cryptococcosis were included in the study. Cryptococcus recovered from patient's specimen was identified by standard protocol. Species confirmation, mating type and molecular type determination were performed by PCR based methods. Antifungal susceptibility was tested in VITEK2C to amphotericin B, 5-flucytosine, fluconazole and voriconazole. Among 199 cases, 20 (10%) were due to C. gattii, comprising of 75% cryptococcal meningitis and 25% cryptococcoma cases. Young adult males were commonly affected. Headache and vomiting were prominent symptoms and 50% were immunocompromised. Among the isolates, 75%, 20% and 5% were C. tetragattii, C. gattii sensu stricto and C. bacillisporus respectively and all had mating type α. Four (20%) isolates of C. tetragattii and the only isolate of C. bacillisporus were resistant to fluconazole. The most common species isolated from south India is C. tetragattii. The study contributes to the epidemiology of C. gattii and reiterates the need for genotyping and antifungal susceptibility testing. © 2017 Blackwell Verlag GmbH.

Emerging prion disease drives host selection in a wildlife population

USGS Publications Warehouse

Robinson, Stacie J.; Samuel, Michael D.; Johnson, Chad J.; Adams, Marie; McKenzie, Debbie I.

2012-01-01

Infectious diseases are increasingly recognized as an important force driving population dynamics, conservation biology, and natural selection in wildlife populations. Infectious agents have been implicated in the decline of small or endangered populations and may act to constrain population size, distribution, growth rates, or migration patterns. Further, diseases may provide selective pressures that shape the genetic diversity of populations or species. Thus, understanding disease dynamics and selective pressures from pathogens is crucial to understanding population processes, managing wildlife diseases, and conserving biological diversity. There is ample evidence that variation in the prion protein gene (PRNP) impacts host susceptibility to prion diseases. Still, little is known about how genetic differences might influence natural selection within wildlife populations. Here we link genetic variation with differential susceptibility of white-tailed deer to chronic wasting disease (CWD), with implications for fitness and disease-driven genetic selection. We developed a single nucleotide polymorphism (SNP) assay to efficiently genotype deer at the locus of interest (in the 96th codon of the PRNP gene). Then, using a Bayesian modeling approach, we found that the more susceptible genotype had over four times greater risk of CWD infection; and, once infected, deer with the resistant genotype survived 49% longer (8.25 more months). We used these epidemiological parameters in a multi-stage population matrix model to evaluate relative fitness based on genotype-specific population growth rates. The differences in disease infection and mortality rates allowed genetically resistant deer to achieve higher population growth and obtain a long-term fitness advantage, which translated into a selection coefficient of over 1% favoring the CWD-resistant genotype. This selective pressure suggests that the resistant allele could become dominant in the population within an evolutionarily short time frame. Our work provides a rare example of a quantifiable disease-driven selection process in a wildlife population, demonstrating the potential for infectious diseases to alter host populations. This will have direct bearing on the epidemiology, dynamics, and future trends in CWD transmission and spread. Understanding genotype-specific epidemiology will improve predictive models and inform management strategies for CWD-affected cervid populations.

White-tailed Deer are Susceptible to Sheep Scrapie by Intracerebral Inoculation

USDA-ARS?s Scientific Manuscript database

Interspecies transmission studies afford the opportunity to better understand the potential host range and origins of prion diseases. The purpose of this experiment was to determine susceptibility of white-tailed deer to scrapie after intracerebral inoculation and to compare clinical signs and lesi...

First Record of Transversotrema Witenberg, 1944 (Digenea) from the Americas, with Comments on the Taxonomy of Transversotrema patialense (Soparkar, 1924) Crusz and Sathananthan, 1960, and an Updated List of Its Hosts and Geographic Distribution.

PubMed

Womble, Matthew R; Cox-Gardiner, Stephanie J; Cribb, Thomas H; Bullard, Stephen A

2015-12-01

Specimens of Transversotrema patialense (sensu lato) ( Soparkar, 1924 ) Crusz and Sathananthan, 1960 (Digenea: Transversotrematidae) infected the skin (epidermal spaces beneath scales near pectoral fins) of 4 of 126 (prevalence 3%; mean intensity 1.8) zebrafish ( Danio rerio (Hamilton, 1822) [Cypriniformes: Cyprinidae]) purchased in 2009 and cultured by a California (USA) fish supplier. These fish were sold as "laboratory-reared" and "specific pathogen free," purportedly raised in a recirculating aquaculture system that included zebrafish only. We herein describe the morphological features of this transversotrematid using light and scanning electron microscopy, provide a comprehensive list of hosts (snails and fishes) and geographic locality records for specimens reported as T. patialense, which is perhaps a species complex, and provide a brief historical synopsis of the taxonomic and life history research that has been conducted on this fluke. No species of Transversotrema previously had been reported from the Americas; however, this discovery is not surprising given that: (1) a suitable intermediate host (red-rimmed melania, Melanoides tuberculata (Müller, 1774) [Cerithioidea: Thiaridae]) has been established in California and elsewhere in North America, (2) the zebrafish is a susceptible definitive host, and (3) T. patialense reportedly matures on a broad ecological and phylogenetic spectrum of freshwater fishes. To our knowledge, this is the northern-most geographic locality record for a species of this genus. We suspect this case study represents an example of a parasite that may now be established in North America by the fortuitous co-occurrence of a susceptible, exotic snail host (the red-rimmed melania) and a susceptible, widely distributed, exotic fish host (the zebrafish).

Interaction Between Allergy and Middle Ear Infection.

PubMed

Oh, Jeong-Hoon; Kim, Woo Jin

2016-09-01

Recent studies have attempted to identify interactions among the causes of otitis media with effusion (OME). This review discusses the interaction between allergy and infection with regard to host and environmental factors in terms of the development of OME. Protection of the upper airway against microbial invasion requires active interaction between the defense mechanisms of the respiratory epithelium, including innate and adaptive immunity, and mechanical factors. The impairment of these defenses due to allergy and/or increased bacterial resistance may lead to increased susceptibility to infectious organisms in the respiratory tract and middle ear mucosa. Recent genetic studies have provided valuable information about the association of Toll-like receptor signaling variations with clinical phenotypes and the risk of infection in the middle ear. Among the causal factors of OME, allergy not only induces an inflammatory reaction in the middle ear cavity but also facilitates the invasion of infectious pathogens. There is also evidence that allergy can affect the susceptibility of patients to infection of the upper respiratory tract, including the middle ear cavity.

Susceptibility to an inoculum of infectious hypodermal and haematopoietic necrosis virus (IHHNV) in three batches of whiteleg shrimp Litopenaeus vannamei (Boone, 1931)

PubMed Central

Escobedo-Bonilla, César Marcial; Rangel, José Luis Ibarra

2014-01-01

Abstract The present study evaluated the susceptibility of three different batches of whiteleg shrimp Litopenaeus vannamei from Mexico to an inoculum of infectious hypodermal and haematopoietic necrosis virus (IHHNV). Each of the three shrimp batches came from a different hatchery. Because of their origin, it was possible that the genetic makeup of these batches was different among each other. The three batches tested showed differences in IHHNV susceptibility. Here, susceptibility is defined as the capacity of the host to become infected, and it can be measured by the infectivity titer. Susceptibility to IHHNV was observed in decreasing order in shrimp from batch 1 (hatchery from El Rosario, Sinaloa), batch 3 (hatchery from Nayarit) and batch 2 (hatchery from El Walamo, Sinaloa), respectively. The largest susceptibility difference between batches was 5012 times, and that between early and late juveniles from the same batch was 25 times. These results indicate that within a species, susceptibility to a pathogen such as IHHNV can have large differences. Susceptibility to pathogens is an important trait to consider before performing studies on pathogenesis. It may influence virological parameters such as speed of replication, pathogenicity and virus titer. In order to evaluate the potential use of IHHNV as a natural control agent against white spot syndrome virus (WSSV), it is necessary to know host susceptibility and the kinetics of IHHNV infection. These features can help to determine the conditions in which IHHNV could be used as antagonist in a WSSV infection. PMID:25561847

An Aphid Effector Targets Trafficking Protein VPS52 in a Host-Specific Manner to Promote Virulence1[OPEN

PubMed Central

2017-01-01

Plant- and animal-feeding insects secrete saliva inside their hosts, containing effectors, which may promote nutrient release and suppress immunity. Although for plant pathogenic microbes it is well established that effectors target host proteins to modulate host cell processes and promote disease, the host cell targets of herbivorous insects remain elusive. Here, we show that the existing plant pathogenic microbe effector paradigm can be extended to herbivorous insects in that effector-target interactions inside host cells modify critical host processes to promote plant susceptibility. We showed that the effector Mp1 from Myzus persicae associates with the host Vacuolar Protein Sorting Associated Protein52 (VPS52). Using natural variants, we provide a strong link between effector virulence activity and association with VPS52, and show that the association is highly specific to M. persicae-host interactions. Also, coexpression of Mp1, but not Mp1-like variants, specifically with host VPS52s resulted in effector relocalization to vesicle-like structures that associate with prevacuolar compartments. We show that high VPS52 levels negatively impact virulence, and that aphids are able to reduce VPS52 levels during infestation, indicating that VPS52 is an important virulence target. Our work is an important step forward in understanding, at the molecular level, how a major agricultural pest promotes susceptibility during infestation of crop plants. We give evidence that an herbivorous insect employs effectors that interact with host proteins as part of an effective virulence strategy, and that these effectors likely function in a species-specific manner. PMID:28100451

Insights on the injection mechanisms inferred from AMS fabrics of sand injectites in a turbiditic system, the exemple of Bevon area of the SE Basin (France).

NASA Astrophysics Data System (ADS)

Robion, Philippe; Mehl, Caroline

2016-04-01

We propose to investigate the set up mechanisms of sands injection in the case of dykes injected in host marls of Aptian-Albian age in the Vocontian basin (SE France). Several models have been proposed for a downward injection of the dyke in the Bevons area and we guess that AMS fabric investigations can be used to infer the flow direction. 144 drill cores distributed on 14 sites were sampled, among which 8 sites in the injectites and 6 sites in the host rocks. The studied dykes are generally of a few decimeters thick and are setting up in both in vertical or oblique position with respect to the subhorizontal bedding of the host rocks. There were sampled from one side to the other in order to track the flow direction by identification of imbricated fabric. Magnetic mineralogy, i.e. unblocking temperature inferred from IRM 3 axes demagnetization, indicates that the ferromagnetics s.l. mineralogy is dominated by an assemblage of magnetite (unblocking temperature Tub=580°C) and pyrrhotite (Tub=325°C). Magnetic susceptibility is low, typical for siliciclastic rocks, ranging from 4x10-5 up to 1.7x10-4 SI. Degree of magnetic anisotropy is likely representative of AMS measurements in sedimentary rocks with weak values, below than 5 %. In marly host rocks magnetic mineralogy is dominated by pyrrhotite associated with magnetite and both the magnetic susceptibility and degree of anisotropy are slightly lower than for injectites. Regarding magnetic fabric axes distribution, despite some dispersion, the results show that minimum axes of AMS (K3) are parallel to the dyke plane, and maximum axes (K1) are roughly in horizontal position. In marly host rocks, the magnetic fabric is related to tectonic shortening. We interpret that the host rocks have recorded the regional tectonic imprint while the magnetic fabric of the injectites are related to early sedimentary processes. The mechanism of set up proposed to explain the magnetic fabric in the Bevon injectites is a step-by-step process of filling the pre-existing fractures with highly fluidized sand and a compaction direction parallel to dyke plane. A late diagenetic cementation affecting the injectites network prevents any further deformation during tectonic inversion.

Utilization of human DC-SIGN and L-SIGN for entry and infection of host cells by the New World arenavirus, Junín virus

PubMed Central

Belouzard, Sandrine; Cordo, Sandra M.; Candurra, Nélida A.; Whittaker, Gary R.

2014-01-01

The target cell tropism of enveloped viruses is regulated by interactions between viral proteins and cellular receptors determining susceptibility at a host cell, tissue or species level. However, a number of additional cell-surface moieties can also bind viral envelope glycoproteins and could act as capture receptors, serving as attachment factors to concentrate virus particles on the cell surface, or to disseminate the virus infection to target organs or susceptible cells within the host. Here, we used Junín virus (JUNV) or JUNV glycoprotein complex (GPC)-pseudotyped particles to study their ability to be internalized by the human C-type lectins hDC- or hL-SIGN. Our results provide evidence that hDC- and hL-SIGN can mediate the entry of Junín virus into cells, and may play an important role in virus infection and dissemination in the host. PMID:24183720

Susceptibility to Phytophthora ramorum in California bay laurel, a key foliar host of sudden oak death

Treesearch

Brian L. Anacker; Nathan E. Rank; Daniel Hüberli; Matteo Garbelotto; Sarah Gordon; Rich Whitkus; Tami Harnik; Matthew Meshriy; Lori Miles; Ross K. Meentemeyer

2008-01-01

Sudden oak death, caused by the water mold Phytophthora ramorum, is a plant disease responsible for the death of hundreds of thousands of oak and tanoak trees. Some foliar hosts play a major role in the epidemiology of this disease. Upon infection by P. ramorum, these foliar hosts express non-fatal leaf lesions from which large...

Convergence in mycorrhizal fungal communities due to drought, plant competition, parasitism, and susceptibility to herbivory: consequences for fungi and host plants.

PubMed

Gehring, Catherine A; Mueller, Rebecca C; Haskins, Kristin E; Rubow, Tine K; Whitham, Thomas G

2014-01-01

Plants and mycorrhizal fungi influence each other's abundance, diversity, and distribution. How other biotic interactions affect the mycorrhizal symbiosis is less well understood. Likewise, we know little about the effects of climate change on the fungal component of the symbiosis or its function. We synthesized our long-term studies on the influence of plant parasites, insect herbivores, competing trees, and drought on the ectomycorrhizal fungal communities associated with a foundation tree species of the southwestern United States, pinyon pine (Pinus edulis), and described how these changes feed back to affect host plant performance. We found that drought and all three of the biotic interactions studied resulted in similar shifts in ectomycorrhizal fungal community composition, demonstrating a convergence of the community towards dominance by a few closely related fungal taxa. Ectomycorrhizal fungi responded similarly to each of these stressors resulting in a predictable trajectory of community disassembly, consistent with ecological theory. Although we predicted that the fungal communities associated with trees stressed by drought, herbivory, competition, and parasitism would be poor mutualists, we found the opposite pattern in field studies. Our results suggest that climate change and the increased importance of herbivores, competitors, and parasites that can be associated with it, may ultimately lead to reductions in ectomycorrhizal fungal diversity, but that the remaining fungal community may be beneficial to host trees under the current climate and the warmer, drier climate predicted for the future.

Shade tree spatial structure and pod production explain frosty pod rot intensity in cacao agroforests, Costa Rica.

PubMed

Gidoin, Cynthia; Avelino, Jacques; Deheuvels, Olivier; Cilas, Christian; Bieng, Marie Ange Ngo

2014-03-01

Vegetation composition and plant spatial structure affect disease intensity through resource and microclimatic variation effects. The aim of this study was to evaluate the independent effect and relative importance of host composition and plant spatial structure variables in explaining disease intensity at the plot scale. For that purpose, frosty pod rot intensity, a disease caused by Moniliophthora roreri on cacao pods, was monitored in 36 cacao agroforests in Costa Rica in order to assess the vegetation composition and spatial structure variables conducive to the disease. Hierarchical partitioning was used to identify the most causal factors. Firstly, pod production, cacao tree density and shade tree spatial structure had significant independent effects on disease intensity. In our case study, the amount of susceptible tissue was the most relevant host composition variable for explaining disease intensity by resource dilution. Indeed, cacao tree density probably affected disease intensity more by the creation of self-shading rather than by host dilution. Lastly, only regularly distributed forest trees, and not aggregated or randomly distributed forest trees, reduced disease intensity in comparison to plots with a low forest tree density. A regular spatial structure is probably crucial to the creation of moderate and uniform shade as recommended for frosty pod rot management. As pod production is an important service expected from these agroforests, shade tree spatial structure may be a lever for integrated management of frosty pod rot in cacao agroforests.

Field Susceptibility of Quince Hybrids to Fire Blight in Bulgaria

USDA-ARS?s Scientific Manuscript database

Spread of fire blight in Bulgaria during the last 20 years has nearly eliminated commercial production of pear and quince. Damage has increased in both nurseries and orchards, yet susceptible cultivars continue to be planted. Quince is the host most frequently attacked by Erwinia amylovora in Bulgar...

Eugregarines reduce susceptibility of the hide beetle, Dermestes maculatus, to apicomplexan pathogens and retard larval development

USDA-ARS?s Scientific Manuscript database

Eugregarines are abundant in a great diversity of invertebrates, and yet their relationships with their hosts are subject to controversy and confusion. We tested the effect of the eugregarine, Pyxinia crystalligera, on growth, development, and susceptibility to two Apicomplexa pathogens of the hide ...

Host genotype and hypersensitive reaction influence population levels of Xanthomonas campestris pv. vitians in lettuce

USDA-ARS?s Scientific Manuscript database

Population dynamics of Xanthomonas campestris pv. vitians spray inoculated on or infiltrated into lettuce leaves were monitored on cultivars that were well characterized for resistance or susceptibility to the pathogen. In general, population growth was greater for susceptible (Clemente, Salinas 88,...

Host-specific variation in infection by toxigenic fungi and contamination by mycotoxins in pearl millet and corn.

PubMed

Wilson, J P; Jurjevic, Z; Hanna, W W; Wilson, D M; Potter, T L; Coy, A E

2006-02-01

Pearl millet is widely consumed in regions of Africa and Asia, and is increasingly being grown as an alternative grain in drought-prone regions of the United States. Pearl millet and corn were grown in dryland conditions at Tifton, Georgia, USA and grains were compared for pre-harvest infection by potentially toxigenic fungi and contamination by mycotoxins. Corn hybrids Agripro 9909 and Pioneer 3146, and pearl millet Tifgrain 102 were grown in 2000 and 2001; pearl millet HGM 100 was included in the test in 2001. Hybrids were sown on multiple planting dates in each year to induce variation in flowering time. Host species differed in the frequency of isolation of potentially toxigenic fungal species in both years. Across years, corn hybrids were more prone to infection by Aspergillus flavus Link (maximum isolation frequency = 8.8%) and Fusarium moniliforme Sheldon sensu lato (maximum isolation frequency = 72.8%), with corresponding greater concentrations of aflatoxins (maximum concentration = 204.9 microg kg(-1)) and fumonisins (maximum concentration = 34,039 microg kg(-1)). Pearl millet was more prone to infection by F. semitectum Berk. & Ravenel (maximum isolation = 74.2%) and F. chlamydosporum Wollenweb & Reinking (maximum isolation = 33.0%), and contamination by moniliformin (maximum contamination = 92.1 microg kg(-1)). Beauvericin (maximum concentration = 414.6 microg kg(-1)) was present in both hosts. Planting date of corn affected aflatoxin and beauvericin contamination in 2000, and fumonisin concentration in 2001. The observed differences in mycotoxin contamination of the grains, which are likely due to host-specific differences in susceptibility to pre-harvest mycoflora, may affect food safety when the crops are grown under stress conditions.

Effects of Simulated Microgravity on a Host-Pathogen System

NASA Technical Reports Server (NTRS)

Gilbert, Rachel; Lo, Rachel; Bhattacharya, Sharmila

2017-01-01

While it has been shown that decades of astronauts and cosmonauts can suffer from illnesses both during and after spaceflight, the underlying causes are still poorly understood, due in part to the fact that there are so many variables to consider when investigating the human immune system in a complex environment. Invertebrates have become popular models for studying human disease because they are cheap, highly amenable to experimental manipulation, and have innate immune systems with a high genetic similarity to humans. Fruit flies (Drosophila melanogaster) have been shown to experience a dramatic shift in immune gene expression following spaceflight, but are still able to fight off infections when exposed to bacteria. However, the common bacterial pathogen Serratia marcescens was shown to become more lethal to fruit flies after being cultured in space, suggesting that not only do we need to consider host changes in susceptibility, but also changes in the pathogen itself after spaceflight conditions. Being able to simulate spaceflight conditions in a controlled environment on the ground gives us the ability to not only evaluate the effects of microgravity on the host immune system, but also how the microorganisms that cause immune disorders are being affected by these drastic environmental shifts. In this study, I use a ground-based simulated microgravity environment to examine the genetic changes associated with increased S. marcescens virulence in order to understand how microgravity is affecting this pathogen, as well as how these genetic changes influence and interact with the host immune system. This study will provide us with more directed approaches to studying the effects of spaceflight on human beings, with the ultimate goal of being able to counteract immune dysfunction in future space exploration.

Loss of compatibility might explain resistance of the Arabidopsis thaliana accession Te-0 to Golovinomyces cichoracearum.

PubMed

Fabro, Georgina; Alvarez, María Elena

2012-08-11

The establishment of compatibility between plants and pathogens requires compliance with various conditions, such as recognition of the right host, suppression of defence mechanisms, and maintenance of an environment allowing pathogen reproduction. To date, most of the plant factors required to sustain compatibility remain unknown, with the few best characterized being those interfering with defence responses. A suitable system to study host compatibility factors is the interaction between Arabidopsis thaliana and the powdery mildew (PM) Golovinomyces cichoracearum. As an obligate biotrophic pathogen, this fungus must establish compatibility in order to perpetuate. In turn, A. thaliana displays natural variation for susceptibility to this invader, with some accessions showing full susceptibility (Col-0), and others monogenic dominant resistance (Kas-1). Interestingly, Te-0, among other accessions, displays recessive partial resistance to this PM. In this study, we characterized the interaction of G. cichoracearum with Te-0 plants to investigate the basis of this plant resistance. We found that Te-0's incompatibility was not associated with hyper-activation of host inducible defences. Te-0 plants allowed germination of conidia and development of functional haustoria, but could not support the formation of mature conidiophores. Using a suppressive subtractive hybridization technique, we identified plant genes showing differential expression between resistant Te-0 and susceptible Col-0 plants at the fungal pre-conidiation stage. Te-0 resistance is likely caused by loss of host compatibility and not by stimulation of inducible defences. Conidiophores formation is the main constraint for completion of fungal life cycle in Te-0 plants. The system here described allowed the identification of genes proposed as markers for susceptibility to this PM.

Loss of compatibility might explain resistance of the Arabidopsis thaliana accession Te-0 to Golovinomyces cichoracearum

PubMed Central

2012-01-01

Background The establishment of compatibility between plants and pathogens requires compliance with various conditions, such as recognition of the right host, suppression of defence mechanisms, and maintenance of an environment allowing pathogen reproduction. To date, most of the plant factors required to sustain compatibility remain unknown, with the few best characterized being those interfering with defence responses. A suitable system to study host compatibility factors is the interaction between Arabidopsis thaliana and the powdery mildew (PM) Golovinomyces cichoracearum. As an obligate biotrophic pathogen, this fungus must establish compatibility in order to perpetuate. In turn, A. thaliana displays natural variation for susceptibility to this invader, with some accessions showing full susceptibility (Col-0), and others monogenic dominant resistance (Kas-1). Interestingly, Te-0, among other accessions, displays recessive partial resistance to this PM. Results In this study, we characterized the interaction of G. cichoracearum with Te-0 plants to investigate the basis of this plant resistance. We found that Te-0´s incompatibility was not associated with hyper-activation of host inducible defences. Te-0 plants allowed germination of conidia and development of functional haustoria, but could not support the formation of mature conidiophores. Using a suppressive subtractive hybridization technique, we identified plant genes showing differential expression between resistant Te-0 and susceptible Col-0 plants at the fungal pre-conidiation stage. Conclusions Te-0 resistance is likely caused by loss of host compatibility and not by stimulation of inducible defences. Conidiophores formation is the main constraint for completion of fungal life cycle in Te-0 plants. The system here described allowed the identification of genes proposed as markers for susceptibility to this PM. PMID:22883024

Fractional poisson--a simple dose-response model for human norovirus.

PubMed

Messner, Michael J; Berger, Philip; Nappier, Sharon P

2014-10-01

This study utilizes old and new Norovirus (NoV) human challenge data to model the dose-response relationship for human NoV infection. The combined data set is used to update estimates from a previously published beta-Poisson dose-response model that includes parameters for virus aggregation and for a beta-distribution that describes variable susceptibility among hosts. The quality of the beta-Poisson model is examined and a simpler model is proposed. The new model (fractional Poisson) characterizes hosts as either perfectly susceptible or perfectly immune, requiring a single parameter (the fraction of perfectly susceptible hosts) in place of the two-parameter beta-distribution. A second parameter is included to account for virus aggregation in the same fashion as it is added to the beta-Poisson model. Infection probability is simply the product of the probability of nonzero exposure (at least one virus or aggregate is ingested) and the fraction of susceptible hosts. The model is computationally simple and appears to be well suited to the data from the NoV human challenge studies. The model's deviance is similar to that of the beta-Poisson, but with one parameter, rather than two. As a result, the Akaike information criterion favors the fractional Poisson over the beta-Poisson model. At low, environmentally relevant exposure levels (<100), estimation error is small for the fractional Poisson model; however, caution is advised because no subjects were challenged at such a low dose. New low-dose data would be of great value to further clarify the NoV dose-response relationship and to support improved risk assessment for environmentally relevant exposures. © 2014 Society for Risk Analysis Published 2014. This article is a U.S. Government work and is in the public domain for the U.S.A.

Leptin Protects Host Cells from Entamoeba histolytica Cytotoxicity by a STAT3-Dependent Mechanism

PubMed Central

Verkerke, Hans P.; Paul, Shom N.; Mackey, Aaron J.; Petri, William A.

2012-01-01

The adipocytokine leptin links nutritional status to immune function. Leptin signaling protects from amebiasis, but the molecular mechanism is not understood. We developed an in vitro model of ameba-host cell interaction to test the hypothesis that leptin prevents ameba-induced apoptosis in host epithelial cells. We demonstrated that activation of mammalian leptin signaling increased cellular resistance to amebic cytotoxicity, including caspase-3 activation. Exogenous expression of the leptin receptor conferred resistance in susceptible cells, and leptin stimulation enhanced protection. A series of leptin receptor signaling mutants showed that resistance to amebic cytotoxicity was dependent on activation of STAT3 but not the Src homology-2 domain-containing tyrosine phosphatase (SHP-2) or STAT5. A common polymorphism in the leptin receptor (Q223R) that increases susceptibility to amebiasis in humans and mice was found to increase susceptibility to amebic cytotoxicity in single cells. The Q223R polymorphism also decreased leptin-dependent STAT3 activation by 21% relative to that of the wild-type (WT) receptor (P = 0.035), consistent with a central role of STAT3 signaling in protection. A subset of genes uniquely regulated by STAT3 in response to leptin was identified. Most notable were the TRIB1 and suppressor of cytokine signaling 3 (SOCS3) genes, which have opposing roles in the regulation of apoptosis. Overall apoptotic genes were highly enriched in this gene set (P < 1E−05), supporting the hypothesis that leptin regulation of host apoptotic genes via STAT3 is responsible for protection. This is the first demonstration of a mammalian signaling pathway that restricts amebic pathogenesis and represents an important advance in our mechanistic understanding of how leptin links nutrition and susceptibility to infection. PMID:22331430

Reciprocal Hosts' Responses to Powdery Mildew Isolates Originating from Domesticated Wheats and Their Wild Progenitor

PubMed Central

Ben-David, Roi; Dinoor, Amos; Peleg, Zvi; Fahima, Tzion

2018-01-01

The biotroph wheat powdery mildew, Blumeria graminis (DC.) E.O. Speer, f. sp. tritici Em. Marchal (Bgt), has undergone long and dynamic co-evolution with its hosts. In the last 10,000 years, processes involved in plant evolution under domestication, altered host-population structure. Recently both virulence and genomic profiling separated Bgt into two groups based on their origin from domestic host and from wild emmer wheat. While most studies focused on the Bgt pathogen, there is significant knowledge gaps in the role of wheat host diversity in this specification. This study aimed to fill this gap by exploring qualitatively and also quantitatively the disease response of diverse host panel to powdery mildew [105 domesticated wheat genotypes (Triticum turgidum ssp. dicoccum, T. turgidum ssp. durum, and T. aestivum) and 241 accessions of its direct progenitor, wild emmer wheat (T. turgidum ssp. dicoccoides)]. A set of eight Bgt isolates, originally collected from domesticated and wild wheat was used for screening this wheat collection. The isolates from domesticated wheat elicited susceptible to moderate plant responses on domesticated wheat lines and high resistance on wild genotypes (51.7% of the tested lines were resistant). Isolates from wild emmer elicited reciprocal disease responses: high resistance of domesticated germplasm and high susceptibility of the wild material (their original host). Analysis of variance of the quantitative phenotypic responses showed a significant Isolates × Host species interaction [P(F) < 0.0001] and further supported these findings. Furthermore, analysis of the range of disease severity values showed that when the group of host genotypes was inoculated with Bgt isolate from the reciprocal host, coefficient of variation was significantly higher than when inoculated with its own isolates. This trend was attributed to the role of major resistance genes in the latter scenario (high proportion of complete resistance). By testing the association between disease severity and geographical distance from the source of inoculum, we have found higher susceptibility in wild emmer close to the source. Both qualitative and quantitative assays showed a reciprocal resistance pattern in the wheat host and are well aligned with the recent findings of significant differentiation into wild-emmer and domesticated-wheat populations in the pathogen. PMID:29527213

Are hybrids between Atlantic salmon and brown trout suitable long-term hosts of Gyrodactylus salaris during winter?

PubMed

Knudsen, R; Henriksen, E H; Gjelland, K Ø; Hansen, H; Hendrichsen, D K; Kristoffersen, R; Olstad, K

2017-10-01

The monogenean parasite Gyrodactylus salaris poses serious threats to many Atlantic salmon populations and presents many conservation and management questions/foci and challenges. It is therefore critical to identify potential vectors for infection. To test whether hybrids of native Atlantic salmon (Salmo salar) × brown trout (Salmo trutta) are suitable as reservoir hosts for G. salaris during winter, infected hybrid parr were released into a natural subarctic brook in the autumn. Six months later, 23.9% of the pit-tagged fish were recaptured. During the experimental period, the hybrids had a sixfold increase in mean intensity of G. salaris, while the prevalence decreased from 81% to 35%. There was high interindividual hybrid variability in susceptibility to infections. The maximum infrapopulation growth rate (0.018 day -1 ) of G. salaris throughout the winter was comparable to earlier laboratory experiments at similar temperatures. The results confirm that infrapopulations of G. salaris may reproduce on a hybrid population for several generations at low water temperatures (~1 °C). Wild salmon-trout hybrids are undoubtedly susceptible to G. salaris and represent an important reservoir host for the parasite independent of other co-occurring susceptible hosts. Consequently, these hybrids may pose a serious risk for G. salaris transmission to nearby, uninfected rivers by migratory individuals. © 2017 John Wiley & Sons Ltd.

Intronic Deletions That Disrupt mRNA Splicing of the tva Receptor Gene Result in Decreased Susceptibility to Infection by Avian Sarcoma and Leukosis Virus Subgroup A

PubMed Central

Reinišová, Markéta; Plachý, Jiří; Trejbalová, Kateřina; Šenigl, Filip; Kučerová, Dana; Geryk, Josef; Svoboda, Jan

2012-01-01

The group of closely related avian sarcoma and leukosis viruses (ASLVs) evolved from a common ancestor into multiple subgroups, A to J, with differential host range among galliform species and chicken lines. These subgroups differ in variable parts of their envelope glycoproteins, the major determinants of virus interaction with specific receptor molecules. Three genetic loci, tva, tvb, and tvc, code for single membrane-spanning receptors from diverse protein families that confer susceptibility to the ASLV subgroups. The host range expansion of the ancestral virus might have been driven by gradual evolution of resistance in host cells, and the resistance alleles in all three receptor loci have been identified. Here, we characterized two alleles of the tva receptor gene with similar intronic deletions comprising the deduced branch-point signal within the first intron and leading to inefficient splicing of tva mRNA. As a result, we observed decreased susceptibility to subgroup A ASLV in vitro and in vivo. These alleles were independently found in a close-bred line of domestic chicken and Indian red jungle fowl (Gallus gallus murghi), suggesting that their prevalence might be much wider in outbred chicken breeds. We identified defective splicing to be a mechanism of resistance to ASLV and conclude that such a type of mutation could play an important role in virus-host coevolution. PMID:22171251

CRN13 candidate effectors from plant and animal eukaryotic pathogens are DNA-binding proteins which trigger host DNA damage response.

PubMed

Ramirez-Garcés, Diana; Camborde, Laurent; Pel, Michiel J C; Jauneau, Alain; Martinez, Yves; Néant, Isabelle; Leclerc, Catherine; Moreau, Marc; Dumas, Bernard; Gaulin, Elodie

2016-04-01

To successfully colonize their host, pathogens produce effectors that can interfere with host cellular processes. Here we investigated the function of CRN13 candidate effectors produced by plant pathogenic oomycetes and detected in the genome of the amphibian pathogenic chytrid fungus Batrachochytrium dendrobatidis (BdCRN13). When expressed in Nicotiana, AeCRN13, from the legume root pathogen Aphanomyces euteiches, increases the susceptibility of the leaves to the oomycete Phytophthora capsici. When transiently expressed in amphibians or plant cells, AeCRN13 and BdCRN13 localize to the cell nuclei, triggering aberrant cell development and eventually causing cell death. Using Förster resonance energy transfer experiments in plant cells, we showed that both CRN13s interact with nuclear DNA and trigger plant DNA damage response (DDR). Mutating key amino acid residues in a predicted HNH-like endonuclease motif abolished the interaction of AeCRN13 with DNA, the induction of DDR and the enhancement of Nicotiana susceptibility to P. capsici. Finally, H2AX phosphorylation, a marker of DNA damage, and enhanced expression of genes involved in the DDR were observed in A. euteiches-infected Medicago truncatula roots. These results show that CRN13 from plant and animal eukaryotic pathogens promotes host susceptibility by targeting nuclear DNA and inducing DDR. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

The effect of environmental heterogeneity on RPW8-mediated resistance to powdery mildews in Arabidopsis thaliana.

PubMed

Jorgensen, Tove H

2012-03-01

The biotic and abiotic environment of interacting hosts and parasites may vary considerably over small spatial and temporal scales. It is essential to understand how different environments affect host disease resistance because this determines frequency of disease and, importantly, heterogeneous environments can retard direct selection and potentially maintain genetic variation for resistance in natural populations. The effect of different temperatures and soil nutrient conditions on the outcome of infection by a pathogen was quantified in Arabidopsis thaliana. Expression levels of a gene conferring resistance to powdery mildews, RPW8, were compared with levels of disease to test a possible mechanism behind variation in resistance. Most host genotypes changed from susceptible to resistant across environments with the ranking of genotypes differing between treatments. Transcription levels of RPW8 increased after infection and varied between environments, but there was no tight association between transcription and resistance levels. There is a strong potential for a heterogeneous environment to change the resistance capacity of A. thaliana genotypes and hence the direction and magnitude of selection in the presence of the pathogen. Possible causative links between resistance gene expression and disease resistance are discussed in light of the present results on RPW8.

Helminth Parasites Alter Protection against Plasmodium Infection

PubMed Central

Salazar-Castañon, Víctor H.; Legorreta-Herrera, Martha

2014-01-01

More than one-third of the world's population is infected with one or more helminthic parasites. Helminth infections are prevalent throughout tropical and subtropical regions where malaria pathogens are transmitted. Malaria is the most widespread and deadliest parasitic disease. The severity of the disease is strongly related to parasite density and the host's immune responses. Furthermore, coinfections between both parasites occur frequently. However, little is known regarding how concomitant infection with helminths and Plasmodium affects the host's immune response. Helminthic infections are frequently massive, chronic, and strong inductors of a Th2-type response. This implies that infection by such parasites could alter the host's susceptibility to subsequent infections by Plasmodium. There are a number of reports on the interactions between helminths and Plasmodium; in some, the burden of Plasmodium parasites increased, but others reported a reduction in the parasite. This review focuses on explaining many of these discrepancies regarding helminth-Plasmodium coinfections in terms of the effects that helminths have on the immune system. In particular, it focuses on helminth-induced immunosuppression and the effects of cytokines controlling polarization toward the Th1 or Th2 arms of the immune response. PMID:25276830

Susceptibility of a North American Culex quinquefasciatus to Japanese encephalitis virus

USDA-ARS?s Scientific Manuscript database

Japanese encephalitis virus (JEV) is a flavivirus that is transmitted by Culex (Cx.) tritaeniorhynchus in tropical and subtropical regions of Asia. The endemic transmission cycle involves domestic pigs and avian species that serve as amplification hosts; humans are incidental hosts that cannot devel...

A Metronidazole-Resistant Isolate of Blastocystis spp. Is Susceptible to Nitric Oxide and Downregulates Intestinal Epithelial Inducible Nitric Oxide Synthase by a Novel Parasite Survival Mechanism ▿

PubMed Central

Mirza, Haris; Wu, Zhaona; Kidwai, Fahad; Tan, Kevin S. W.

2011-01-01

Blastocystis, one of the most common parasites colonizing the human intestine, is an extracellular, noninvasive, luminal protozoan with controversial pathogenesis. Blastocystis infections can be asymptomatic or cause intestinal symptoms of vomiting, diarrhea, and abdominal pain. Although chronic infections are frequently reported, Blastocystis infections have also been reported to be self-limiting in immunocompetent patients. Characterizing the host innate response to Blastocystis would lead to a better understanding of the parasite's pathogenesis. Intestinal epithelial cells produce nitric oxide (NO), primarily on the apical side, in order to target luminal pathogens. In this study, we show that NO production by intestinal cells may be a host defense mechanism against Blastocystis. Two clinically relevant isolates of Blastocystis, ST-7 (B) and ST-4 (WR-1), were found to be susceptible to a range of NO donors. ST-7 (B), a metronidazole-resistant isolate, was found to be more sensitive to nitrosative stress. Using the Caco-2 model of human intestinal epithelium, Blastocystis ST-7 (B) but not ST-4 (WR-1) exhibited dose-dependent inhibition of Caco-2 NO production, and this was associated with downregulation of inducible nitric oxide synthase (iNOS). Despite its higher susceptibility to NO, Blastocystis ST-7 (B) may have evolved unique strategies to evade this potential host defense by depressing host NO production. This is the first study to highlight a strain-to-strain variation in the ability of Blastocystis to evade the host antiparasitic NO response. PMID:21930763

Experimental parasite community ecology: intraspecific variation in a large tapeworm affects community assembly.

PubMed

Benesh, Daniel P; Kalbe, Martin

2016-07-01

Non-random species associations occur in naturally sampled parasite communities. The processes resulting in predictable community structure (e.g. particular host behaviours, cross-immunity, interspecific competition) could be affected by traits that vary within a parasite species, like growth or antigenicity. We experimentally infected three-spined sticklebacks with a large tapeworm (Schistocephalus solidus) that impacts the energy needs, foraging behaviour and immune reactions of its host. The tapeworms came from two populations, characterized by high or low growth in sticklebacks. Our goal was to evaluate how this parasite, and variation in its growth, affects the acquisition of other parasites. Fish infected with S. solidus were placed into cages in a lake to expose them to the natural parasite community. We also performed a laboratory experiment in which infected fish were exposed to a fixed dose of a common trematode parasite. In the field experiment, infection with S. solidus affected the abundance of four parasite species, relative to controls. For two of the four species, changes occurred only in fish harbouring the high-growth S. solidus; one species increased in abundance and the other decreased. These changes did not appear to be directly linked to S. solidus growth though. The parasite exhibiting elevated abundance was the same trematode used in the laboratory infection. In that experiment, we found a similar infection pattern, suggesting that S. solidus affects the physiological susceptibility of fish to this trematode. Associations between S. solidus and other parasites occur and vary in direction. However, some of these associations were contingent on the S. solidus population, suggesting that intraspecific variability can affect the assembly of parasite communities. © 2016 The Authors. Journal of Animal Ecology © 2016 British Ecological Society.

Decreasing stochasticity through enhanced seasonality in measles epidemics.

PubMed

Mantilla-Beniers, N B; Bjørnstad, O N; Grenfell, B T; Rohani, P

2010-05-06

Seasonal changes in the environment are known to be important drivers of population dynamics, giving rise to sustained population cycles. However, it is often difficult to measure the strength and shape of seasonal forces affecting populations. In recent years, statistical time-series methods have been applied to the incidence records of childhood infectious diseases in an attempt to estimate seasonal variation in transmission rates, as driven by the pattern of school terms. In turn, school-term forcing was used to show how susceptible influx rates affect the interepidemic period. In this paper, we document the response of measles dynamics to distinct shifts in the parameter regime using previously unexplored records of measles mortality from the early decades of the twentieth century. We describe temporal patterns of measles epidemics using spectral analysis techniques, and point out a marked decrease in birth rates over time. Changes in host demography alone do not, however, suffice to explain epidemiological transitions. By fitting the time-series susceptible-infected-recovered model to measles mortality data, we obtain estimates of seasonal transmission in different eras, and find that seasonality increased over time. This analysis supports theoretical work linking complex population dynamics and the balance between stochastic and deterministic forces as determined by the strength of seasonality.

Biology, Genetics, and Management of Ergot (Claviceps spp.) in Rye, Sorghum, and Pearl Millet

PubMed Central

Miedaner, Thomas; Geiger, Hartwig H.

2015-01-01

Ergot is a disease of cereals and grasses caused by fungi in the genus Claviceps. Of particular concern are Claviceps purpurea in temperate regions, C. africana in sorghum (worldwide), and C. fusiformis in pearl millet (Africa, Asia). The fungi infect young, usually unfertilized ovaries, replacing the seeds by dark mycelial masses known as sclerotia. The percentage of sclerotia in marketable grain is strictly regulated in many countries. In winter rye, ergot has been known in Europe since the early Middle Ages. The alkaloids produced by the fungus severely affect the health of humans and warm-blooded animals. In sorghum and pearl millet, ergot became a problem when growers adopted hybrid technology, which increased host susceptibility. Plant traits reducing ergot infection include immediate pollination of receptive stigmas, closed flowering (cleistogamy), and physiological resistance. Genetic, nonpollen-mediated variation in ergot susceptibility could be demonstrated in all three affected cereals. Fungicides have limited efficacy and application is weather dependent. Sorting out the sclerotia from the harvest by photocells is expensive and time consuming. In conclusion, molecular-based hybrid rye breeding could improve pollen fertility by introgressing effective restorer genes thus bringing down the ergot infection level to that of conventional population cultivars. A further reduction might be feasible in the future by selecting more resistant germplasm. PMID:25723323

Biology, genetics, and management of ergot (Claviceps spp.) in rye, sorghum, and pearl millet.

PubMed

Miedaner, Thomas; Geiger, Hartwig H

2015-02-25

Ergot is a disease of cereals and grasses caused by fungi in the genus Claviceps. Of particular concern are Claviceps purpurea in temperate regions, C. africana in sorghum (worldwide), and C. fusiformis in pearl millet (Africa, Asia). The fungi infect young, usually unfertilized ovaries, replacing the seeds by dark mycelial masses known as sclerotia. The percentage of sclerotia in marketable grain is strictly regulated in many countries. In winter rye, ergot has been known in Europe since the early Middle Ages. The alkaloids produced by the fungus severely affect the health of humans and warm-blooded animals. In sorghum and pearl millet, ergot became a problem when growers adopted hybrid technology, which increased host susceptibility. Plant traits reducing ergot infection include immediate pollination of receptive stigmas, closed flowering (cleistogamy), and physiological resistance. Genetic, nonpollen-mediated variation in ergot susceptibility could be demonstrated in all three affected cereals. Fungicides have limited efficacy and application is weather dependent. Sorting out the sclerotia from the harvest by photocells is expensive and time consuming. In conclusion, molecular-based hybrid rye breeding could improve pollen fertility by introgressing effective restorer genes thus bringing down the ergot infection level to that of conventional population cultivars. A further reduction might be feasible in the future by selecting more resistant germplasm.

Cheyletiella blakei, an Ectoparasite of Cats, as Cause of Cryptic Arthropod Infestations Affecting Humans

PubMed Central

Lane, Robert S.; Shachter, Sherry P.; Keh, Benjamin

1987-01-01

Cheyletiella blakei, an ectoparasitic mite of domestic cats, can cause an extremely annoying, persistent and pruritic dermatosis of obscure origin (cryptic infestation) in susceptible persons having close contact with infested cats. Although the prevalence of cheyletiellosis in humans and cats appears to be low, evidence of its occurrence in California is increasing. Cheyletiellosis is often underdiagnosed in both its natural host and in humans. The small size of the mite, lack of publicity about the disease, frequent absence of symptoms in infested cats and failure to recover the mite from humans contribute to its delayed recognition. When C blakei or other mites are suspected of being the cause of a dermatosis, medical entomologists may help to hasten the diagnosis by examining the patient's physical surroundings, potential vertebrate hosts and other sources for the presence of mites. After C blakei has been eliminated from cats with an appropriate pesticide, the disease in humans is self-limiting. PMID:3825118

Cheyletiella blakei, an ectoparasite of cats, as cause of cryptic arthropod infestations affecting humans.

PubMed

Keh, B; Lane, R S; Shachter, S P

1987-02-01

Cheyletiella blakei, an ectoparasitic mite of domestic cats, can cause an extremely annoying, persistent and pruritic dermatosis of obscure origin (cryptic infestation) in susceptible persons having close contact with infested cats. Although the prevalence of cheyletiellosis in humans and cats appears to be low, evidence of its occurrence in California is increasing. Cheyletiellosis is often underdiagnosed in both its natural host and in humans. The small size of the mite, lack of publicity about the disease, frequent absence of symptoms in infested cats and failure to recover the mite from humans contribute to its delayed recognition. When C blakei or other mites are suspected of being the cause of a dermatosis, medical entomologists may help to hasten the diagnosis by examining the patient's physical surroundings, potential vertebrate hosts and other sources for the presence of mites. After C blakei has been eliminated from cats with an appropriate pesticide, the disease in humans is self-limiting.

Cervicovaginal bacteria are a major modulator of host inflammatory responses in the female genital tract.

PubMed

Anahtar, Melis N; Byrne, Elizabeth H; Doherty, Kathleen E; Bowman, Brittany A; Yamamoto, Hidemi S; Soumillon, Magali; Padavattan, Nikita; Ismail, Nasreen; Moodley, Amber; Sabatini, Mary E; Ghebremichael, Musie S; Nusbaum, Chad; Huttenhower, Curtis; Virgin, Herbert W; Ndung'u, Thumbi; Dong, Krista L; Walker, Bruce D; Fichorova, Raina N; Kwon, Douglas S

2015-05-19

Colonization by Lactobacillus in the female genital tract is thought to be critical for maintaining genital health. However, little is known about how genital microbiota influence host immune function and modulate disease susceptibility. We studied a cohort of asymptomatic young South African women and found that the majority of participants had genital communities with low Lactobacillus abundance and high ecological diversity. High-diversity communities strongly correlated with genital pro-inflammatory cytokine concentrations in both cross-sectional and longitudinal analyses. Transcriptional profiling suggested that genital antigen-presenting cells sense gram-negative bacterial products in situ via Toll-like receptor 4 signaling, contributing to genital inflammation through activation of the NF-κB signaling pathway and recruitment of lymphocytes by chemokine production. Our study proposes a mechanism by which cervicovaginal microbiota impact genital inflammation and thereby might affect a woman's reproductive health, including her risk of acquiring HIV. Copyright © 2015 Elsevier Inc. All rights reserved.

Outbreak of Japanese encephalitis on the island of Saipan, 1990.

PubMed

Paul, W S; Moore, P S; Karabatsos, N; Flood, S P; Yamada, S; Jackson, T; Tsai, T F

1993-05-01

During October 1990, an outbreak of encephalitis occurred on Saipan. Although no virus was isolated, patients seroconverted to Japanese encephalitis (JE) virus, indicating the first known occurrence of JE on US territory since 1947. Ten cases occurred among a population of 40,000. The prevalence of antibody to JE virus among 234 lifelong Saipan residents surveyed after the outbreak was 4.2%. Age, household crowding, and lack of air conditioning were risk factors for infection. The seroprevalence in pigs, which are important amplifying hosts of JE virus, was 96% (n = 52). None of 288 stored serum specimens from lifelong Saipan residents sampled in 1984 were seropositive. These data suggest that JE virus was recently introduced onto Saipan and that peridomestic factors affected the risk of human infection. Transmission of JE virus probably ended with exhaustion of the supply of susceptible amplifying hosts. Surveillance for human cases and seroconversions in pigs during 1991 revealed no evidence of ongoing JE virus transmission.

Metabolism in Fungal Pathogenesis

PubMed Central

Ene, Iuliana V.; Brunke, Sascha; Brown, Alistair J.P.; Hube, Bernhard

2014-01-01

Fungal pathogens must assimilate local nutrients to establish an infection in their mammalian host. We focus on carbon, nitrogen, and micronutrient assimilation mechanisms, discussing how these influence host–fungus interactions during infection. We highlight several emerging trends based on the available data. First, the perturbation of carbon, nitrogen, or micronutrient assimilation attenuates fungal pathogenicity. Second, the contrasting evolutionary pressures exerted on facultative versus obligatory pathogens have led to contemporary pathogenic fungal species that display differing degrees of metabolic flexibility. The evolutionarily ancient metabolic pathways are conserved in most fungal pathogen, but interesting gaps exist in some species (e.g., Candida glabrata). Third, metabolic flexibility is generally essential for fungal pathogenicity, and in particular, for the adaptation to contrasting host microenvironments such as the gastrointestinal tract, mucosal surfaces, bloodstream, and internal organs. Fourth, this metabolic flexibility relies on complex regulatory networks, some of which are conserved across lineages, whereas others have undergone significant evolutionary rewiring. Fifth, metabolic adaptation affects fungal susceptibility to antifungal drugs and also presents exciting opportunities for the development of novel therapies. PMID:25190251

High frequency of Taenia pisiformis metacestodes and high sex-associated susceptibility to cysticercosis in naturally infected wild rabbits.

PubMed

Domínguez-Roldan, R; Pérez-Martínez, M; Rosetti, M F; Arias-Hernández, D; Bernal-Fernández, G; Flores-Pérez, F I; Hallal-Calleros, C

2018-05-10

Sexual dimorphism is a well-documented phenomenon observed at all levels of the animal kingdom, with the inclusion of both sexes in clinical trials and basic research becoming mandatory. Regarding parasitosis, in several animal species, the signs and virulence of the disease may change depending on the sex of the affected animal. In the cestodiasis caused by Taenia solium and Taenia crassiceps, females are more susceptible to experimental infection than males. Cysticercosis by Taenia pisiformis in rabbits has acquired relevance due to its economic impact, namely affecting welfare and production. In America, specifically in Mexico, there are no formal reports on the infection with T. pisiformis metacestodes in populations of wild rabbits, despite being the country with more endemic species (about 15 species), among them, the volcanoes rabbits or the endangered teporingo (Romerolagus diazi). In this study, 31 wild rabbits were obtained by hunters of some regions of Morelos state during several hunting seasons, and sex, physiological stage, and number of metacestodes were recorded. A high frequency of infection by T. pisiformis metacestodes (67.7%) was found. Also, a higher susceptibility to this infection was observed in does (80% infected) compared to bucks (40%), finding 84.2% of metacestodes (235 metacestodes) in does and 15.8% of metacestodes (44 metacestodes) in bucks. The percentage of infection was higher in lactating compared with pregnant and non-pregnant does, with metacestodes lodging mainly in the uterus. Increasing our knowledge regarding parasitic infections can help us better understand transmission circles as well as the parasite-host interaction of these increasingly at risk rabbit species.

Host Genetics and Environment Drive Divergent Responses of Two Resource Sharing Gall-Formers on Norway Spruce: A Common Garden Analysis.

PubMed

Axelsson, E Petter; Iason, Glenn R; Julkunen-Tiitto, Riitta; Whitham, Thomas G

2015-01-01

A central issue in the field of community genetics is the expectation that trait variation among genotypes play a defining role in structuring associated species and in forming community phenotypes. Quantifying the existence of such community phenotypes in two common garden environments also has important consequences for our understanding of gene-by-environment interactions at the community level. The existence of community phenotypes has not been evaluated in the crowns of boreal forest trees. In this study we address the influence of tree genetics on needle chemistry and genetic x environment interactions on two gall-inducing adelgid aphids (Adelges spp. and Sacchiphantes spp.) that share the same elongating bud/shoot niche. We examine the hypothesis that the canopies of different genotypes of Norway spruce (Picea abies L.) support different community phenotypes. Three patterns emerged. First, the two gallers show clear differences in their response to host genetics and environment. Whereas genetics significantly affected the abundance of Adelges spp. galls, Sacchiphantes spp. was predominately affected by the environment suggesting that the genetic influence is stronger in Adelges spp. Second, the among family variation in genetically controlled resistance was large, i.e. fullsib families differed as much as 10 fold in susceptibility towards Adelges spp. (0.57 to 6.2 galls/branch). Also, the distribution of chemical profiles was continuous, showing both overlap as well as examples of significant differences among fullsib families. Third, despite the predicted effects of host chemistry on galls, principal component analyses using 31 different phenolic substances showed only limited association with galls and a similarity test showed that trees with similar phenolic chemical characteristics, did not host more similar communities of gallers. Nonetheless, the large genetic variation in trait expression and clear differences in how community members respond to host genetics supports our hypothesis that the canopies of Norway spruce differ in their community phenotypes.

Sodium chloride inhibits the growth and infective capacity of the amphibian chytrid fungus and increases host survival rates.

PubMed

Stockwell, Michelle Pirrie; Clulow, John; Mahony, Michael Joseph

2012-01-01

The amphibian chytrid fungus Batrachochytrium dendrobatidis is a recently emerged pathogen that causes the infectious disease chytridiomycosis and has been implicated as a contributing factor in the global amphibian decline. Since its discovery, research has been focused on developing various methods of mitigating the impact of chytridiomycosis on amphibian hosts but little attention has been given to the role of antifungal agents that could be added to the host's environment. Sodium chloride is a known antifungal agent used routinely in the aquaculture industry and this study investigates its potential for use as a disease management tool in amphibian conservation. The effect of 0-5 ppt NaCl on the growth, motility and survival of the chytrid fungus when grown in culture media and its effect on the growth, infection load and survivorship of infected Peron's tree frogs (Litoria peronii) in captivity, was investigated. The results reveal that these concentrations do not negatively affect the survival of the host or the pathogen. However, concentrations greater than 3 ppt significantly reduced the growth and motility of the chytrid fungus compared to 0 ppt. Concentrations of 1-4 ppt NaCl were also associated with significantly lower host infection loads while infected hosts exposed to 3 and 4 ppt NaCl were found to have significantly higher survival rates. These results support the potential for NaCl to be used as an environmentally distributed antifungal agent for the prevention of chytridiomycosis in susceptible amphibian hosts. However, further research is required to identify any negative effects of salt exposure on both target and non-target organisms prior to implementation.

Sodium Chloride Inhibits the Growth and Infective Capacity of the Amphibian Chytrid Fungus and Increases Host Survival Rates

PubMed Central

Stockwell, Michelle Pirrie; Clulow, John; Mahony, Michael Joseph

2012-01-01

The amphibian chytrid fungus Batrachochytrium dendrobatidis is a recently emerged pathogen that causes the infectious disease chytridiomycosis and has been implicated as a contributing factor in the global amphibian decline. Since its discovery, research has been focused on developing various methods of mitigating the impact of chytridiomycosis on amphibian hosts but little attention has been given to the role of antifungal agents that could be added to the host's environment. Sodium chloride is a known antifungal agent used routinely in the aquaculture industry and this study investigates its potential for use as a disease management tool in amphibian conservation. The effect of 0–5 ppt NaCl on the growth, motility and survival of the chytrid fungus when grown in culture media and its effect on the growth, infection load and survivorship of infected Peron's tree frogs (Litoria peronii) in captivity, was investigated. The results reveal that these concentrations do not negatively affect the survival of the host or the pathogen. However, concentrations greater than 3 ppt significantly reduced the growth and motility of the chytrid fungus compared to 0 ppt. Concentrations of 1–4 ppt NaCl were also associated with significantly lower host infection loads while infected hosts exposed to 3 and 4 ppt NaCl were found to have significantly higher survival rates. These results support the potential for NaCl to be used as an environmentally distributed antifungal agent for the prevention of chytridiomycosis in susceptible amphibian hosts. However, further research is required to identify any negative effects of salt exposure on both target and non-target organisms prior to implementation. PMID:22590639

Extrahepatic exoerythrocytic forms of rodent malaria parasites at the site of inoculation: clearance after immunization, susceptibility to primaquine, and contribution to blood-stage infection.

PubMed

Voza, Tatiana; Miller, Jessica L; Kappe, Stefan H I; Sinnis, Photini

2012-06-01

Plasmodium sporozoites are inoculated into the skin of the mammalian host as infected mosquitoes probe for blood. A proportion of the inoculum enters the bloodstream and goes to the liver, where the sporozoites invade hepatocytes and develop into the next life cycle stage, the exoerythrocytic, or liver, stage. Here, we show that a small fraction of the inoculum remains in the skin and begins to develop into exoerythrocytic forms that can persist for days. Skin exoerythrocytic forms were observed for both Plasmodium berghei and Plasmodium yoelii, two different rodent malaria parasites, suggesting that development in the skin of the mammalian host may be a common property of plasmodia. Our studies demonstrate that skin exoerythrocytic stages are susceptible to destruction in immunized mice, suggesting that their aberrant location does not protect them from the host's adaptive immune response. However, in contrast to their hepatic counterparts, they are not susceptible to primaquine. We took advantage of their resistance to primaquine to test whether they could initiate a blood-stage infection directly from the inoculation site, and our data indicate that these stages are not able to initiate malaria infection.

Social apoptosis in honey bee superorganisms

PubMed Central

Page, Paul; Lin, Zheguang; Buawangpong, Ninat; Zheng, Huoqing; Hu, Fuliang; Neumann, Peter; Chantawannakul, Panuwan; Dietemann, Vincent

2016-01-01

Eusocial insect colonies form superorganisms, in which nestmates cooperate and use social immunity to combat parasites. However, social immunity may fail in case of emerging diseases. This is the case for the ectoparasitic mite Varroa destructor, which switched hosts from the Eastern honeybee, Apis cerana, to the Western honey bee, Apis mellifera, and currently is the greatest threat to A. mellifera apiculture globally. Here, we show that immature workers of the mite’s original host, A. cerana, are more susceptible to V. destructor infestations than those of its new host, thereby enabling more efficient social immunity and contributing to colony survival. This counterintuitive result shows that susceptible individuals can foster superorganism survival, offering empirical support to theoretical arguments about the adaptive value of worker suicide in social insects. Altruistic suicide of immature bees constitutes a social analogue of apoptosis, as it prevents the spread of infections by sacrificing parts of the whole organism, and unveils a novel form of transgenerational social immunity in honey bees. Taking into account the key role of susceptible immature bees in social immunity will improve breeding efforts to mitigate the unsustainably high colony losses of Western honey bees due to V. destructor infestations worldwide. PMID:27264643

Genetic resistance to smallpox: lessons from mousepox.

PubMed

Karupiah, Gunasegaran; Panchanathan, Vijay; Sakala, Isaac G; Chaudhri, Geeta

2007-01-01

There is increased interest in understanding protective immunity to smallpox for two principal reasons. First, it is the only disease that has been successfully eradicated using a live virus vaccine and, second, there exists a potential threat of intentional or unintentional release of variola virus, the causative agent of smallpox. Although mortality rates associated with smallpox were as high as 40%, a significant subset of those infected recovered. The basis of susceptibility or resistance, and the immune parameters associated with recovery, are still unknown. Animal models of poxvirus infections are being employed to understand what constitutes an effective host response. Ectromelia virus is closely related to variola virus and it causes a disease similar to smallpox in mice. This model is well established, resistant and susceptible strains of mice are defined and four genetic loci associated with resistance have been identified. Susceptibility to infec tion and disease severity is also influenced by virus immune evasion strategies. The outcome of infection is clearly dictated by several factors including host and viral genes, both of which influence the immune response. Here we present data on one virus-encoded immune modifier and its effect on the functions of two host genetic loci associ ated with resistance.

Trypanosoma cruzi subverts the sphingomyelinase-mediated plasma membrane repair pathway for cell invasion

PubMed Central

Fernandes, Maria Cecilia; Cortez, Mauro; Flannery, Andrew R.; Tam, Christina; Mortara, Renato A.

2011-01-01

Upon host cell contact, the protozoan parasite Trypanosoma cruzi triggers cytosolic Ca2+ transients that induce exocytosis of lysosomes, a process required for cell invasion. However, the exact mechanism by which lysosomal exocytosis mediates T. cruzi internalization remains unclear. We show that host cell entry by T. cruzi mimics a process of plasma membrane injury and repair that involves Ca2+-dependent exocytosis of lysosomes, delivery of acid sphingomyelinase (ASM) to the outer leaflet of the plasma membrane, and a rapid form of endocytosis that internalizes membrane lesions. Host cells incubated with T. cruzi trypomastigotes are transiently wounded, show increased levels of endocytosis, and become more susceptible to infection when injured with pore-forming toxins. Inhibition or depletion of lysosomal ASM, which blocks plasma membrane repair, markedly reduces the susceptibility of host cells to T. cruzi invasion. Notably, extracellular addition of sphingomyelinase stimulates host cell endocytosis, enhances T. cruzi invasion, and restores normal invasion levels in ASM-depleted cells. Ceramide, the product of sphingomyelin hydrolysis, is detected in newly formed parasitophorous vacuoles containing trypomastigotes but not in the few parasite-containing vacuoles formed in ASM-depleted cells. Thus, T. cruzi subverts the ASM-dependent ceramide-enriched endosomes that function in plasma membrane repair to infect host cells. PMID:21536739

Infection of host plants by Cucumber mosaic virus increases the susceptibility of Myzus persicae aphids to the parasitoid Aphidius colemani

PubMed Central

Mauck, Kerry E.; De Moraes, Consuelo M.; Mescher, Mark C.

2015-01-01

Plant viruses can profoundly alter the phenotypes of their host plants, with potentially far-reaching implications for ecology. Yet few studies have explored the indirect, host-mediated, effects of plant viruses on non-vector insects. We examined how infection of Cucurbita pepo plants by Cucumber mosaic virus (CMV) impacted the susceptibility of aphids (Myzus persicae) to attack by the parasitoid wasp Aphidius colemani. In semi-natural foraging assays, we observed higher rates of aphid parasitism on infected plants compared to healthy plants. Subsequent experiments revealed that this difference is not explained by different attack rates on plants differing in infection status, but rather by the fact that parasitoid larvae successfully complete their development more often when aphid hosts feed on infected plants. This suggests that the reduced nutritional quality of infected plants as host for aphids—documented in previous studies—compromises their ability to mount effective defenses against parasitism. Furthermore, our current findings indicate that the aphid diet during parasitoid development (rather than prior to wasp oviposition) is a key factor influencing resistance. These findings complement our previous work showing that CMV-induced changes in host plant chemistry alter patterns of aphid recruitment and dispersal in ways conducive to virus transmission. PMID:26043237

Genetic variation for maternal effects on parasite susceptibility.

PubMed

Stjernman, M; Little, T J

2011-11-01

The expression of infectious disease is increasingly recognized to be impacted by maternal effects, where the environmental conditions experienced by mothers alter resistance to infection in offspring, independent of heritability. Here, we studied how maternal effects (high or low food availability to mothers) mediated the resistance of the crustacean Daphnia magna to its bacterial parasite Pasteuria ramosa. We sought to disentangle maternal effects from the effects of host genetic background by studying how maternal effects varied across 24 host genotypes sampled from a natural population. Under low-food conditions, females produced offspring that were relatively resistant, but this maternal effect varied strikingly between host genotypes, i.e. there were genotype by maternal environment interactions. As infection with P. ramosa causes a substantial reduction in host fecundity, this maternal effect had a large effect on host fitness. Maternal effects were also shown to impact parasite fitness, both because they prevented the establishment of the parasites and because even when parasites did establish in the offspring of poorly fed mothers, and they tended to grow more slowly. These effects indicate that food stress in the maternal generation can greatly influence parasite susceptibility and thus perhaps the evolution and coevolution of host-parasite interactions. © 2011 The Authors. Journal of Evolutionary Biology © 2011 European Society For Evolutionary Biology.

Diversity and specificity in the interaction between Caenorhabditis elegans and the pathogen Serratia marcescens.

PubMed

Schulenburg, Hinrich; Ewbank, Jonathan J

2004-11-22

Co-evolutionary arms races between parasites and hosts are considered to be of immense importance in the evolution of living organisms, potentially leading to highly dynamic life-history changes. The outcome of such arms races is in many cases thought to be determined by frequency dependent selection, which relies on genetic variation in host susceptibility and parasite virulence, and also genotype-specific interactions between host and parasite. Empirical evidence for these two prerequisites is scarce, however, especially for invertebrate hosts. We addressed this topic by analysing the interaction between natural isolates of the soil nematode Caenorhabditis elegans and the pathogenic soil bacterium Serratia marcescens. Our analysis reveals the presence of i) significant variation in host susceptibility, ii) significant variation in pathogen virulence, and iii) significant strain- and genotype-specific interactions between the two species. The results obtained support the previous notion that highly specific interactions between parasites and animal hosts are generally widespread. At least for C. elegans, the high specificity is observed among isolates from the same population, such that it may provide a basis for and/or represent the outcome of co-evolutionary adaptations under natural conditions. Since both C. elegans and S. marcescens permit comprehensive molecular analyses, these two species provide a promising model system for inference of the molecular basis of such highly specific interactions, which are as yet unexplored in invertebrate hosts.

Diversity and specificity in the interaction between Caenorhabditis elegans and the pathogen Serratia marcescens

PubMed Central

Schulenburg, Hinrich; Ewbank, Jonathan J

2004-01-01

Background Co-evolutionary arms races between parasites and hosts are considered to be of immense importance in the evolution of living organisms, potentially leading to highly dynamic life-history changes. The outcome of such arms races is in many cases thought to be determined by frequency dependent selection, which relies on genetic variation in host susceptibility and parasite virulence, and also genotype-specific interactions between host and parasite. Empirical evidence for these two prerequisites is scarce, however, especially for invertebrate hosts. We addressed this topic by analysing the interaction between natural isolates of the soil nematode Caenorhabditis elegans and the pathogenic soil bacterium Serratia marcescens. Results Our analysis reveals the presence of i) significant variation in host susceptibility, ii) significant variation in pathogen virulence, and iii) significant strain- and genotype-specific interactions between the two species. Conclusions The results obtained support the previous notion that highly specific interactions between parasites and animal hosts are generally widespread. At least for C. elegans, the high specificity is observed among isolates from the same population, such that it may provide a basis for and/or represent the outcome of co-evolutionary adaptations under natural conditions. Since both C. elegans and S. marcescens permit comprehensive molecular analyses, these two species provide a promising model system for inference of the molecular basis of such highly specific interactions, which are as yet unexplored in invertebrate hosts. PMID:15555070

Host range expansion and increased damage potential of Euwallacea nr. fornicatus (Coleoptera: Curculionidae) in Florida

USDA-ARS?s Scientific Manuscript database

Ambrosia beetles in the Euwallacea nr. fornicatus complex (Coleoptera: Curculionidae) vector Fusarium spp. fungi pathogenic to susceptible hosts, including avocado. The Florida avocado production area in Miami-Dade County was surveyed for E. nr. fornicatus upon observations of initial damage in 2016...

Host boring preferences of the tea shot-hole borer Euwallacea fornicatus (Coleoptera: Curculionidae: Scolytinae)

USDA-ARS?s Scientific Manuscript database

The non-native shot-hole borer, Euwallacea nr. fornicatus Eichhoff (Coleoptera: Curculionidae: Scolytinae), was discovered in Florida’s avocado production area in Homestead in 2010. It is a highly polyphagous ambrosia beetle that carries Fusarium fungal symbionts. In susceptible host trees, the fung...

Susceptibility of sprouted oak acorns to Phytophthora ramorum zoospores

USDA-ARS?s Scientific Manuscript database

Phytophthora ramorum is a recently emerged pathogen, having established in Europe and several western U.S. states, including California and Oregon. It has a wide host range and is a threat to forest ecology and the nursery industry. In California, coast live oak (Quercus agrifolia) is a major host...

Alternate hosts of Blepharipa pratensis (Meigen)

Treesearch

Paul A. Godwin; Thomas M. Odell

1977-01-01

A current tactic for biological control of the gypsy moth, Lymantria dispar Linnaeus, is to release its parasites in forests susceptible to gypsy moth damage before the gypsy moth arrives. The basic assumption in these anticipatory releases is that the parasites can find and utilize native insects as hosts in the interim. Blepharipa...

Reversing the Resistance Phenotype of the Biomphalaria glabrata Snail Host Schistosoma mansoni Infection by Temperature Modulation

PubMed Central

Ittiprasert, Wannaporn; Knight, Matty

2012-01-01

Biomphalaria glabrata snails that display either resistant or susceptible phenotypes to the parasitic trematode, Schistosoma mansoni provide an invaluable resource towards elucidating the molecular basis of the snail-host/schistosome relationship. Previously, we showed that induction of stress genes either after heat-shock or parasite infection was a major feature distinguishing juvenile susceptible snails from their resistant counterparts. In order to examine this apparent association between heat stress and snail susceptibility, we investigated the effect of temperature modulation in the resistant snail stock, BS-90. Here, we show that, incubated for up to 4 hrs at 32°C prior to infection, these resistant snails became susceptible to infection, i.e. shedding cercariae at 5 weeks post exposure (PE) while unstressed resistant snails, as expected, remained resistant. This suggests that susceptibility to infection by this resistant snail phenotype is temperature-sensitive (ts). Additionally, resistant snails treated with the Hsp 90 specific inhibitor, geldanamycin (GA) after heat stress, were no longer susceptible to infection, retaining their resistant phenotype. Consistently, susceptible snail phenotypes treated with 100 mM GA before parasite exposure also remained uninfected. These results provide direct evidence for the induction of stress genes (heat shock proteins; Hsp 70, Hsp 90 and the reverse transcriptase [RT] domain of the nimbus non-LTR retrotransposon) in B. glabrata susceptibility to S. mansoni infection and characterize the resistant BS-90 snails as a temperature-sensitive phenotype. This study of reversing snail susceptibility phenotypes to S. mansoni provides an opportunity to directly track molecular pathway(s) that underlie the B. glabrata snail's ability to either sustain or destroy the S. mansoni parasite. PMID:22577362

Reversing the resistance phenotype of the Biomphalaria glabrata snail host Schistosoma mansoni infection by temperature modulation.

PubMed

Ittiprasert, Wannaporn; Knight, Matty

2012-01-01

Biomphalaria glabrata snails that display either resistant or susceptible phenotypes to the parasitic trematode, Schistosoma mansoni provide an invaluable resource towards elucidating the molecular basis of the snail-host/schistosome relationship. Previously, we showed that induction of stress genes either after heat-shock or parasite infection was a major feature distinguishing juvenile susceptible snails from their resistant counterparts. In order to examine this apparent association between heat stress and snail susceptibility, we investigated the effect of temperature modulation in the resistant snail stock, BS-90. Here, we show that, incubated for up to 4 hrs at 32°C prior to infection, these resistant snails became susceptible to infection, i.e. shedding cercariae at 5 weeks post exposure (PE) while unstressed resistant snails, as expected, remained resistant. This suggests that susceptibility to infection by this resistant snail phenotype is temperature-sensitive (ts). Additionally, resistant snails treated with the Hsp 90 specific inhibitor, geldanamycin (GA) after heat stress, were no longer susceptible to infection, retaining their resistant phenotype. Consistently, susceptible snail phenotypes treated with 100 mM GA before parasite exposure also remained uninfected. These results provide direct evidence for the induction of stress genes (heat shock proteins; Hsp 70, Hsp 90 and the reverse transcriptase [RT] domain of the nimbus non-LTR retrotransposon) in B. glabrata susceptibility to S. mansoni infection and characterize the resistant BS-90 snails as a temperature-sensitive phenotype. This study of reversing snail susceptibility phenotypes to S. mansoni provides an opportunity to directly track molecular pathway(s) that underlie the B. glabrata snail's ability to either sustain or destroy the S. mansoni parasite.

Arabidopsis Thaliana Ecotypes With Differential Susceptibility To The Bacterial Pathogen Xylella fastidiosa

USDA-ARS?s Scientific Manuscript database

Pierce’s disease of grapes and almond leaf scorch are devastating diseases caused by the bacterium Xylella fastidiosa (Xf). To date, progress in determining the mechanisms of host plant susceptibility, tolerance or resistance has been slow, due in large part to the long generation time and limited a...

Code-assisted discovery of TAL effector targets in bacterial leaf streak of rice reveals contrast with bacterial blight and a novel susceptibility gene

USDA-ARS?s Scientific Manuscript database

Transcription activator-like (TAL) effectors found in Xanthomonas spp. promote bacterial growth and plant susceptibility by binding specific DNA sequences or, effector-binding elements (EBEs), and inducing host gene expression. In this study, we have found substantially different transcriptional pro...

Variation in susceptibility of Umbellularia californica (Bay Laurel) to Phytophthora ramorum

Treesearch

Matthew Meshriy; Daniel Hüberli; Tamar Harnik; Lori Miles; Keefe Reuther; Matteo Garbelotto

2006-01-01

Bay laurel (Umbellularia californica) is an important foliar host in terms of spore production and transmission of disease. We designed a bioassay to screen for variation in susceptibility to Phytophthora ramorum among populations of bay laurel collected along the coast of California to southern Oregon and also from Yosemite....

Proteomics analysis reveals novel host molecular mechanisms associated with thermotherapy of ‘Ca. Liberibacter asiaticus’-infected citrus plants

USDA-ARS?s Scientific Manuscript database

Citrus huanglongbing (HLB) is the most devastating disease of citrus plants, and longer-term measures for controlling the disease via breeding or genetic engineering are hampered by the fact that all cultivated citrus species are susceptible to the disease. However, the degree of HLB susceptibility ...

Potential of host-plant resistance as an alternative control measure for sugarbeet root maggot

USDA-ARS?s Scientific Manuscript database

Sugarbeet (Beta vulgaris L.) Germplasm lines with sugarbeet root maggot (Tetanops myopaeformis von Röder) (SBRM) resistance have been available since 1996. Two resistant germplasm lines, F1015 and F1016, and a susceptible germplasm line, F1010, crossed with three susceptible CMS lines (L53cms, FC50...

PR10 expression in maize and its effect on host resistance against Aspergillus flavus infection and aflatoxin production

USDA-ARS?s Scientific Manuscript database

Maize (Zea mays L.) is a major crop susceptible to Aspergillus flavus infection and subsequent contamination with aflatoxins, the potent carcinogenic secondary metabolites of the fungus. Protein profiles of maize genotypes resistant and susceptible to A. flavus infection and/or aflatoxin contaminati...

Induced epidermal permeability modulates resistance and susceptibility of wheat seedlings to herbivory by Hessian fly larvae

PubMed Central

Williams, Christie E.; Nemacheck, Jill A.; Shukle, John T.; Subramanyam, Subhashree; Saltzmann, Kurt D.; Shukle, Richard H.

2011-01-01

Salivary secretions of neonate Hessian fly larvae initiate a two-way exchange of molecules with their wheat host. Changes in properties of the leaf surface allow larval effectors to enter the plant where they trigger plant processes leading to resistance and delivery of defence molecules, or susceptibility and delivery of nutrients. To increase understanding of the host plant's response, the timing and characteristics of the induced epidermal permeability were investigated. Resistant plant permeability was transient and limited in area, persisting just long enough to deliver defence molecules before gene expression and permeability reverted to pre-infestation levels. The abundance of transcripts for GDSL-motif lipase/hydrolase, thought to contribute to cuticle reorganization and increased permeability, followed the same temporal profile as permeability in resistant plants. In contrast, susceptible plants continued to increase in permeability over time until the entire crown of the plant became a nutrient sink. Permeability increased with higher infestation levels in susceptible but not in resistant plants. The ramifications of induced plant permeability on Hessian fly populations are discussed. PMID:21659664

The double edge to parasite escape: invasive host is less infected but more infectable.

PubMed

Keogh, Carolyn L; Miura, Osamu; Nishimura, Tomohiro; Byers, James E

2017-09-01

Nonnative species that escape their native-range parasites may benefit not only from reduced infection pathology, but also from relaxed selection on costly immune defenses, promoting reallocation of resources toward growth or reproduction. However, benefits accruing from a reduction in defense could come at the cost of increased infection susceptibility. We conducted common garden studies of the shore crab Hemigrapsus sanguineus from highly parasitized native (Japan) populations and largely parasite-free invasive (USA) populations to test for differences in susceptibility to infection by native-range rhizocephalan parasites, and to explore differences in host resource allocation. Nonnative individuals showed at least 1.8 times greater susceptibility to infection than their native counterparts, and had reduced standing metabolic rates, suggesting that less of their energy was spent on physiological self-maintenance. Our results support an indirect advantage to parasite escape via the relaxation of costly physiological defenses. However, this advantage comes at the cost of heightened susceptibility, a trade-off of parasite escape that is seldom considered. © 2017 by the Ecological Society of America.

An Aphid Effector Targets Trafficking Protein VPS52 in a Host-Specific Manner to Promote Virulence.

PubMed

Rodriguez, Patricia A; Escudero-Martinez, Carmen; Bos, Jorunn I B

2017-03-01

Plant- and animal-feeding insects secrete saliva inside their hosts, containing effectors, which may promote nutrient release and suppress immunity. Although for plant pathogenic microbes it is well established that effectors target host proteins to modulate host cell processes and promote disease, the host cell targets of herbivorous insects remain elusive. Here, we show that the existing plant pathogenic microbe effector paradigm can be extended to herbivorous insects in that effector-target interactions inside host cells modify critical host processes to promote plant susceptibility. We showed that the effector Mp1 from Myzus persicae associates with the host Vacuolar Protein Sorting Associated Protein52 (VPS52). Using natural variants, we provide a strong link between effector virulence activity and association with VPS52, and show that the association is highly specific to M persicae -host interactions. Also, coexpression of Mp1, but not Mp1-like variants, specifically with host VPS52s resulted in effector relocalization to vesicle-like structures that associate with prevacuolar compartments. We show that high VPS52 levels negatively impact virulence, and that aphids are able to reduce VPS52 levels during infestation, indicating that VPS52 is an important virulence target. Our work is an important step forward in understanding, at the molecular level, how a major agricultural pest promotes susceptibility during infestation of crop plants. We give evidence that an herbivorous insect employs effectors that interact with host proteins as part of an effective virulence strategy, and that these effectors likely function in a species-specific manner. © 2017 American Society of Plant Biologists. All Rights Reserved.

A host basal transcription factor is a key component for infection of rice by TALE-carrying bacteria

PubMed Central

Yuan, Meng; Ke, Yinggen; Huang, Renyan; Ma, Ling; Yang, Zeyu; Chu, Zhaohui; Xiao, Jinghua; Li, Xianghua; Wang, Shiping

2016-01-01

Transcription activator-like effectors (TALEs) are sequence-specific DNA binding proteins found in a range of plant pathogenic bacteria, where they play important roles in host-pathogen interactions. However, it has been unclear how TALEs, after they have been injected into the host cells, activate transcription of host genes required for infection success. Here, we show that the basal transcription factor IIA gamma subunit TFIIAγ5 from rice is a key component for infection by the TALE-carrying bacterium Xanthomonas oryzae pv. oryzae, the causal agent for bacterial blight. Direct interaction of several TALEs with TFIIAγ5 is required for activation of disease susceptibility genes. Conversely, reduced expression of the TFIIAγ5 host gene limits the induction of susceptibility genes and thus decreases bacterial blight symptoms. Suppression or mutation of TFIIAγ5 can also reduce bacterial streak, another devastating disease of rice caused by TALE-carrying X. oryzae pv. oryzicola. These results have important implications for formulating a widely applicable strategy with which to improve resistance of plants to TALE-carrying pathogens. DOI: http://dx.doi.org/10.7554/eLife.19605.001 PMID:27472897

Comparison of transcript profiles in different life stages of the nematode Globodera pallida under different host potato genotypes.

PubMed

Palomares-Rius, Juan E; Hedley, Pete E; Cock, Peter J A; Morris, Jenny A; Jones, John T; Vovlas, Nikos; Blok, Vivian

2012-12-01

The potato cyst nematodes (PCNs) Globodera pallida and Globodera rostochiensis are important parasites of potato. PCNs undergo complex biotrophic interactions with their hosts that involve gene expression changes in both the nematode and the host plant. The aim of this study was to determine key genes that are differentially expressed in Globodera pallida life cycle stages and during the initiation of the feeding site in susceptible and partially resistant potato genotypes. For this purpose, two microarray experiments were designed: (i) a comparison of eggs, infective second-stage juveniles (J2s) and sedentary parasitic-stage J2s (SJ2); (ii) a comparison of SJ2s at 8 days after inoculation (DAI) in the susceptible cultivar (Desirée) and two partially resistant lines. The results showed differential expression of G. pallida genes during the stages studied, including previously characterized effectors. In addition, a large number of genes changed their expression between SJ2s in the susceptible cultivar and those infecting partially resistant lines; the number of genes with modified expression was lower when the two partially resistant lines were compared. Moreover, a histopathological study was performed at several time points (7, 14 and 30 DAI) and showed the similarities between both partially resistant lines with a delay and degeneration in the formation of the syncytia in comparison with the susceptible cultivar. Females at 30 DAI in partially resistant lines showed a delay in their development in comparison with those in the susceptible cultivar. © 2012 THE AUTHORS. MOLECULAR PLANT PATHOLOGY © 2012 BSPP AND BLACKWELL PUBLISHING LTD.

Early Childhood Caries: A Review.

PubMed

Alazmah, Abdulfatah

2017-08-01

To review and update the current knowledge about early childhood caries (ECC) and its etiology, prevalence, risk factors, management, and preventive strategies. Early childhood caries is a disease affecting significantly both well-developed and industrial nations. The ECC can significantly affect the child's quality of life, as it may lead to infection, swelling, pain, and other symptoms. The ECC affects children after eruption of primary teeth until age of around 5 years. The ECC affects all parts of the tooth including the smooth surface. Upper anterior teeth and primary molars are usually affected. The lower anterior teeth are less likely affected. The risk factors for ECC are diet, bacteria, and host susceptibility. The additional factors, such as presence of enamel defect and the feeding practices also contribute to the initiation and progress of ECC. Dentists must focus on utilizing existing techniques to distinguish indications of right on time and propelled caries and give guidance on the best way to counteract and control caries in children. Approaches should be directed to preventive caries control strategies among children. Preventing and controlling the development of ECC among children is important to maintain effective eating, speech development, and formation of a positive self-image.

Effects of bonding with parents and home culture on intercultural adaptations and the moderating role of genes.

PubMed

Phua, Desiree Y; Meaney, Michael J; Khor, Chiea Chuen; Lau, Ivy Y M; Hong, Ying-Yi

2017-05-15

In the current age of globalization, living abroad is becoming an increasingly common and highly sought after experience. Sojourners' ability to adjust to a new culture can be affected by their existing attachments, internalized as intrapsychic environment, as well as their biological sensitivity to environment. This sensitivity can be partly attributed to one's genomic endowments. As such, this prospective study sought to examine the differential effects of early experiences with parents and affection for home culture on young adults' ability to adapt to a foreign culture (n=305, students who studied overseas for a semester) - specifically, the difficulties they experience - moderated by genetic susceptibility. An additional 258 students who did not travel overseas were included as a comparison group to demonstrate the uniqueness of intercultural adaptation. Current findings suggest that the maternal, paternal and cultural bondings or affections affect different aspects of intercultural adjustment. Maternal bonding affected sojourners' relationships with host nationals, while paternal bonding affected sojourners' adjustment to a new physical environment. Moreover, individuals' genetic predispositions significantly moderate these main effects regarding how much difficulty the sojourners experienced overseas. Copyright © 2017 Elsevier B.V. All rights reserved.

Toll-Like Receptor Responses to Peste des petits ruminants Virus in Goats and Water Buffalo

PubMed Central

Dhanasekaran, Sakthivel; Biswas, Moanaro; Vignesh, Ambothi R.; Ramya, R.; Raj, Gopal Dhinakar; Tirumurugaan, Krishnaswamy G.; Raja, Angamuthu; Kataria, Ranjit S.; Parida, Satya; Subbiah, Elankumaran

2014-01-01

Ovine rinderpest or goat plague is an economically important and contagious viral disease of sheep and goats, caused by the Peste des petits ruminants virus (PPRV). Differences in susceptibility to goat plague among different breeds and water buffalo exist. The host innate immune system discriminates between pathogen associated molecular patterns and self antigens through surveillance receptors known as Toll like receptors (TLR). We investigated the role of TLR and cytokines in differential susceptibility of goat breeds and water buffalo to PPRV. We examined the replication of PPRV in peripheral blood mononuclear cells (PBMC) of Indian domestic goats and water buffalo and demonstrated that the levels of TLR3 and TLR7 and downstream signalling molecules correlation with susceptibility vs resistance. Naturally susceptible goat breeds, Barbari and Tellichery, had dampened innate immune responses to PPRV and increased viral loads with lower basal expression levels of TLR 3/7. Upon stimulation of PBMC with synthetic TLR3 and TLR7 agonists or PPRV, the levels of proinflammatory cytokines were found to be significantly higher while immunosuppressive interleukin (IL) 10 levels were lower in PPRV resistant Kanni and Salem Black breeds and water buffalo at transcriptional level, correlating with reduced viralloads in infected PBMC. Water buffalo produced higher levels of interferon (IFN) α in comparison with goats at transcriptional and translational levels. Pre-treatment of Vero cells with human IFNα resulted in reduction of PPRV replication, confirming the role of IFNα in limiting PPRV replication. Treatment with IRS66, a TLR7 antagonist, resulted in the reduction of IFNα levels, with increased PPRV replication confirming the role of TLR7. Single nucleotide polymorphism analysis of TLR7 of these goat breeds did not show any marked nucleotide differences that might account for susceptibility vs resistance to PPRV. Analyzing other host genetic factors might provide further insights on susceptibility to PPRV and genetic polymorphisms in the host. PMID:25369126

Increased Abundance of M Cells in the Gut Epithelium Dramatically Enhances Oral Prion Disease Susceptibility

PubMed Central

Sehgal, Anuj; Rios, Daniel

2016-01-01

Many natural prion diseases of humans and animals are considered to be acquired through oral consumption of contaminated food or pasture. Determining the route by which prions establish host infection will identify the important factors that influence oral prion disease susceptibility and to which intervention strategies can be developed. After exposure, the early accumulation and replication of prions within small intestinal Peyer’s patches is essential for the efficient spread of disease to the brain. To replicate within Peyer’s patches, the prions must first cross the gut epithelium. M cells are specialised epithelial cells within the epithelia covering Peyer’s patches that transcytose particulate antigens and microorganisms. M cell-development is dependent upon RANKL-RANK-signalling, and mice in which RANK is deleted only in the gut epithelium completely lack M cells. In the specific absence of M cells in these mice, the accumulation of prions within Peyer’s patches and the spread of disease to the brain was blocked, demonstrating a critical role for M cells in the initial transfer of prions across the gut epithelium in order to establish host infection. Since pathogens, inflammatory stimuli and aging can modify M cell-density in the gut, these factors may also influence oral prion disease susceptibility. Mice were therefore treated with RANKL to enhance M cell density in the gut. We show that prion uptake from the gut lumen was enhanced in RANKL-treated mice, resulting in shortened survival times and increased disease susceptibility, equivalent to a 10-fold higher infectious titre of prions. Together these data demonstrate that M cells are the critical gatekeepers of oral prion infection, whose density in the gut epithelium directly limits or enhances disease susceptibility. Our data suggest that factors which alter M cell-density in the gut epithelium may be important risk factors which influence host susceptibility to orally acquired prion diseases. PMID:27973593

Increased Abundance of M Cells in the Gut Epithelium Dramatically Enhances Oral Prion Disease Susceptibility.

PubMed

Donaldson, David S; Sehgal, Anuj; Rios, Daniel; Williams, Ifor R; Mabbott, Neil A

2016-12-01

Many natural prion diseases of humans and animals are considered to be acquired through oral consumption of contaminated food or pasture. Determining the route by which prions establish host infection will identify the important factors that influence oral prion disease susceptibility and to which intervention strategies can be developed. After exposure, the early accumulation and replication of prions within small intestinal Peyer's patches is essential for the efficient spread of disease to the brain. To replicate within Peyer's patches, the prions must first cross the gut epithelium. M cells are specialised epithelial cells within the epithelia covering Peyer's patches that transcytose particulate antigens and microorganisms. M cell-development is dependent upon RANKL-RANK-signalling, and mice in which RANK is deleted only in the gut epithelium completely lack M cells. In the specific absence of M cells in these mice, the accumulation of prions within Peyer's patches and the spread of disease to the brain was blocked, demonstrating a critical role for M cells in the initial transfer of prions across the gut epithelium in order to establish host infection. Since pathogens, inflammatory stimuli and aging can modify M cell-density in the gut, these factors may also influence oral prion disease susceptibility. Mice were therefore treated with RANKL to enhance M cell density in the gut. We show that prion uptake from the gut lumen was enhanced in RANKL-treated mice, resulting in shortened survival times and increased disease susceptibility, equivalent to a 10-fold higher infectious titre of prions. Together these data demonstrate that M cells are the critical gatekeepers of oral prion infection, whose density in the gut epithelium directly limits or enhances disease susceptibility. Our data suggest that factors which alter M cell-density in the gut epithelium may be important risk factors which influence host susceptibility to orally acquired prion diseases.

Identification of novel host factors via conserved domain search: Cns1 cochaperone is a novel restriction factor of tombusvirus replication in yeast.

PubMed

Lin, Jing-Yi; Nagy, Peter D

2013-12-01

A large number of host-encoded proteins affect the replication of plus-stranded RNA viruses by acting as susceptibility factors. Many other cellular proteins are known to function as restriction factors of viral infections. Previous studies with tomato bushy stunt tombusvirus (TBSV) in a yeast model host have revealed the inhibitory function of TPR (tetratricopeptide repeat) domain-containing cyclophilins, which are members of the large family of host prolyl isomerases, in TBSV replication. In this paper, we tested additional TPR-containing yeast proteins in a cell-free TBSV replication assay and identified the Cns1p cochaperone for heat shock protein 70 (Hsp70) and Hsp90 chaperones as a strong inhibitor of TBSV replication. Cns1p interacted with the viral replication proteins and inhibited the assembly of the viral replicase complex and viral RNA synthesis in vitro. Overexpression of Cns1p inhibited TBSV replication in yeast. The use of a temperature-sensitive (TS) mutant of Cns1p in yeast revealed that at a semipermissive temperature, TS Cns1p could not inhibit TBSV replication. Interestingly, Cns1p and the TPR-containing Cpr7p cyclophilin have similar inhibitory functions during TBSV replication, although some of the details of their viral restriction mechanisms are different. Our observations indicate that TPR-containing cellular proteins could act as virus restriction factors.

Bleaching increases likelihood of disease on Acropora palmata (Lamarck) in Hawksnest Bay, St John, US Virgin Islands

USGS Publications Warehouse

Muller, E.M.; Rogers, Caroline S.; Spitzack, Anthony S.; van Woesik, R.

2007-01-01

Anomalously high water temperatures may enhance the likelihood of coral disease outbreaks by increasing the abundance or virulence of pathogens, or by increasing host susceptibility. This study tested the compromised-host hypothesis, and documented the relationship between disease and temperature, through monthly monitoring of Acropora palmata colonies from May 2004 to December 2006, in Hawksnest Bay, St John, US Virgin Islands (USVI). Disease prevalence and the rate of change in prevalence showed a positive linear relationship with water temperature and rate of change in water temperature, respectively, but only in 2005 during prolonged periods of elevated temperature. Both bleached and unbleached colonies showed a positive relationship between disease prevalence and temperature in 2005, but the average area of disease-associated mortality increased only for bleached corals, indicating host susceptibility, rather than temperature per se, influenced disease severity on A. palmata.

Bleaching increases likelihood of disease on Acropora palmata (Lamarck) in Hawksnest Bay, St John, US Virgin Islands

USGS Publications Warehouse

Muller, E.M.; Rogers, C.S.; Spitzack, Anthony S.; van Woesik, R.

2008-01-01

Anomalously high water temperatures may enhance the likelihood of coral disease outbreaks by increasing the abundance or virulence of pathogens, or by increasing host susceptibility. This study tested the compromised-host hypothesis, and documented the relationship between disease and temperature, through monthly monitoring of Acropora palmata colonies from May 2004 to December 2006, in Hawksnest Bay, St John, US Virgin Islands (USVI). Disease prevalence and the rate of change in prevalence showed a positive linear relationship with water temperature and rate of change in water temperature, respectively, but only in 2005 during prolonged periods of elevated temperature. Both bleached and unbleached colonies showed a positive relationship between disease prevalence and temperature in 2005, but the average area of disease-associated mortality increased only for bleached corals, indicating host susceptibility, rather than temperature per se, influenced disease severity on A. palmata. ?? 2007 Springer-Verlag.

The early interaction of Leishmania with macrophages and dendritic cells and its influence on the host immune response.

PubMed

Liu, Dong; Uzonna, Jude E

2012-01-01

The complicated interactions between Leishmania and the host antigen-presenting cells (APCs) have fundamental effects on the final outcome of the disease. Two major APCs, macrophages and dendritic cells (DCs), play critical roles in mediating resistance and susceptibility during Leishmania infection. Macrophages are the primary resident cell for Leishmania: they phagocytose and permit parasite proliferation. However, these cells are also the major effector cells to eliminate infection. The effective clearance of parasites by macrophages depends on activation of appropriate immune response, which is usually initiated by DCs. Here, we review the early interaction of APCs with Leishmania parasites and how these interactions profoundly impact on the ensuing adaptive immune response. We also discuss how the current knowledge will allow further refinement of our understanding of the interplay between Leishmania and its hosts that leads to resistance or susceptibility.

The early interaction of Leishmania with macrophages and dendritic cells and its influence on the host immune response

PubMed Central

Liu, Dong; Uzonna, Jude E.

2012-01-01

The complicated interactions between Leishmania and the host antigen-presenting cells (APCs) have fundamental effects on the final outcome of the disease. Two major APCs, macrophages and dendritic cells (DCs), play critical roles in mediating resistance and susceptibility during Leishmania infection. Macrophages are the primary resident cell for Leishmania: they phagocytose and permit parasite proliferation. However, these cells are also the major effector cells to eliminate infection. The effective clearance of parasites by macrophages depends on activation of appropriate immune response, which is usually initiated by DCs. Here, we review the early interaction of APCs with Leishmania parasites and how these interactions profoundly impact on the ensuing adaptive immune response. We also discuss how the current knowledge will allow further refinement of our understanding of the interplay between Leishmania and its hosts that leads to resistance or susceptibility. PMID:22919674

Endobiont Viruses Sensed by the Human Host – Beyond Conventional Antiparasitic Therapy

PubMed Central

Fichorova, Raina N.; Takagi, Yuko; Hayes, Gary R.; Goodman, Russell P.; Chepa-Lotrea, Xenia; Buck, Olivia R.; Murray, Ryan; Kula, Tomasz; Beach, David H.; Singh, Bibhuti N.; Nibert, Max L.

2012-01-01

Wide-spread protozoan parasites carry endosymbiotic dsRNA viruses with uncharted implications to the human host. Among them, Trichomonas vaginalis, a parasite adapted to the human genitourinary tract, infects globally ∼250 million each year rendering them more susceptible to devastating pregnancy complications (especially preterm birth), HIV infection and HPV-related cancer. While first-line antibiotic treatment (metronidazole) commonly kills the protozoan pathogen, it fails to improve reproductive outcome. We show that endosymbiotic Trichomonasvirus, highly prevalent in T. vaginalis clinical isolates, is sensed by the human epithelial cells via Toll-like receptor 3, triggering Interferon Regulating Factor -3, interferon type I and proinflammatory cascades previously implicated in preterm birth and HIV-1 susceptibility. Metronidazole treatment amplified these proinflammatory responses. Thus, a new paradigm targeting the protozoan viruses along with the protozoan host may prevent trichomoniasis-attributable inflammatory sequelae. PMID:23144878

Bleaching increases likelihood of disease on Acropora palmata (Lamarck) in Hawksnest Bay, St John, US Virgin Islands

NASA Astrophysics Data System (ADS)

Muller, E. M.; Rogers, C. S.; Spitzack, A. S.; van Woesik, R.

2008-03-01

Anomalously high water temperatures may enhance the likelihood of coral disease outbreaks by increasing the abundance or virulence of pathogens, or by increasing host susceptibility. This study tested the compromised-host hypothesis, and documented the relationship between disease and temperature, through monthly monitoring of Acropora palmata colonies from May 2004 to December 2006, in Hawksnest Bay, St John, US Virgin Islands (USVI). Disease prevalence and the rate of change in prevalence showed a positive linear relationship with water temperature and rate of change in water temperature, respectively, but only in 2005 during prolonged periods of elevated temperature. Both bleached and unbleached colonies showed a positive relationship between disease prevalence and temperature in 2005, but the average area of disease-associated mortality increased only for bleached corals, indicating host susceptibility, rather than temperature per se, influenced disease severity on A. palmata.

Epidemiological and evolutionary consequences of targeted vaccination.

PubMed

Williams, Paul D; Day, Troy

2008-01-01

Recent theory has examined the way in which vaccination strategies are expected to influence the evolution of parasite virulence. Most of this work has assumed that vaccination is imposed on a homogeneous host population. However, host populations are typically composed of different types of individuals, with each type responding differently to infection. Moreover, actual interventions often focus treatment on those hosts that are likely to suffer the most ill effects of a particular disease. Here we consider the epidemiological and evolutionary consequences of interventions that focus vaccination on individuals expressing the greatest susceptibility to infection and/or the greatest vulnerability to mortality once infected. Our results indicate that predictions are very sensitive to the nature and degree of heterogeneity in susceptibility and vulnerability. They further suggest that accounting for realistic kinds of heterogeneity when contemplating targeted treatment plans and policies might provide a new tool in the design of more effective virulence management strategies.

Blood Groups in Infection and Host Susceptibility

PubMed Central

2015-01-01

SUMMARY Blood group antigens represent polymorphic traits inherited among individuals and populations. At present, there are 34 recognized human blood groups and hundreds of individual blood group antigens and alleles. Differences in blood group antigen expression can increase or decrease host susceptibility to many infections. Blood groups can play a direct role in infection by serving as receptors and/or coreceptors for microorganisms, parasites, and viruses. In addition, many blood group antigens facilitate intracellular uptake, signal transduction, or adhesion through the organization of membrane microdomains. Several blood groups can modify the innate immune response to infection. Several distinct phenotypes associated with increased host resistance to malaria are overrepresented in populations living in areas where malaria is endemic, as a result of evolutionary pressures. Microorganisms can also stimulate antibodies against blood group antigens, including ABO, T, and Kell. Finally, there is a symbiotic relationship between blood group expression and maturation of the gastrointestinal microbiome. PMID:26085552

Immune and genetic gardening of the intestinal microbiome

PubMed Central

Jacobs, Jonathan P.; Braun, Jonathan

2014-01-01

The mucosal immune system – consisting of adaptive and innate immune cells as well as the epithelium – is profoundly influenced by its microbial environment. There is now growing evidence that the converse is also true, that the immune system shapes the composition of the intestinal microbiome. During conditions of health, this bidirectional interaction achieves a homeostasis in which inappropriate immune responses to nonpathogenic microbes are averted and immune activity suppresses blooms of potentially pathogenic microbes (pathobionts). Genetic alteration in immune/epithelial function can affect host gardening of the intestinal microbiome, contributing to the diversity of intestinal microbiota within a population and in some cases allowing for unfavorable microbial ecologies (dysbiosis) that confer disease susceptibility. PMID:24613921

Periodontology: past, present, perspectives.

PubMed

Slots, Jørgen

2013-06-01

Periodontitis is an infectious disease that affects the tooth-supporting tissues and exhibits a wide range of clinical, microbiological and immunological manifestations. The disease is associated with and is probably caused by a multifaceted dynamic interaction of specific infectious agents, host immune responses, harmful environmental exposure and genetic susceptibility factors. This volume of Periodontology 2000 covers key subdisciplines of periodontology, ranging from etiopathogeny to therapy, with emphasis on diagnosis, classification, epidemiology, risk factors, microbiology, immunology, systemic complications, anti-infective therapy, reparative treatment, self-care and affordability issues. Learned and unlearned concepts of periodontitis over the past 50 years have shaped our current understanding of the etiology of the disease and of clinical practice. © 2013 John Wiley & Sons A/S.

Effects of Nitrogen Fertilization on Potato Leafhopper (Hemiptera: Cicadellidae) and Maple Spider Mite (Acari: Tetranychidae) on Nursery-Grown Maples.

PubMed

Prado, Julia; Quesada, Carlos; Gosney, Michael; Mickelbart, Michael V; Sadof, Clifford

2015-06-01

Although leaf nitrogen (N) has been shown to increase the suitability of hosts to herbivorous arthropods, the responses of these pests to N fertilization on susceptible and resistant host plants are not well characterized. This study determined how different rates of N fertilization affected injury caused by the potato leafhopper (Empoasca fabae Harris) and the abundance of maple spider mite (Oligonychus aceris (Shimer)) on 'Red Sunset' red maple (Acer rubrum) and 'Autumn Blaze' Freeman maple (Acer×freemanii) during two years in Indiana. N fertilization increased leaf N concentration in both maple cultivars, albeit to a lesser extent during the second year of the study. Overall, Red Sunset maples were more susceptible to E. fabae injury than Autumn Blaze, whereas Autumn Blaze maples supported higher populations of O. aceris. Differences in populations of O. aceris were attributed to differences between communities of stigmaeid and phytoseiid mites on each cultivar. Injury caused by E. fabae increased with N fertilization in a dose-dependent manner in both cultivars. Although N fertilization increased the abundance of O. aceris on both maple cultivars, there was no difference between the 20 and 40 g rates. We suggest the capacity of N fertilization to increase O. aceris on maples could be limited at higher trophic levels by the community of predatory mites. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Barley disease susceptibility factor RACB acts in epidermal cell polarity and positioning of the nucleus

PubMed Central

Scheler, Björn; Schnepf, Vera; Galgenmüller, Carolina; Ranf, Stefanie; Hückelhoven, Ralph

2016-01-01

RHO GTPases are regulators of cell polarity and immunity in eukaryotes. In plants, RHO-like RAC/ROP GTPases are regulators of cell shaping, hormone responses, and responses to microbial pathogens. The barley (Hordeum vulgare L.) RAC/ROP protein RACB is required for full susceptibility to penetration by Blumeria graminis f.sp. hordei (Bgh), the barley powdery mildew fungus. Disease susceptibility factors often control host immune responses. Here we show that RACB does not interfere with early microbe-associated molecular pattern-triggered immune responses such as the oxidative burst or activation of mitogen-activated protein kinases. RACB also supports rather than restricts expression of defence-related genes in barley. Instead, silencing of RACB expression by RNAi leads to defects in cell polarity. In particular, initiation and maintenance of root hair growth and development of stomatal subsidiary cells by asymmetric cell division is affected by silencing expression of RACB. Nucleus migration is a common factor of developmental cell polarity and cell-autonomous interaction with Bgh. RACB is required for positioning of the nucleus near the site of attack from Bgh. We therefore suggest that Bgh profits from RACB’s function in cell polarity rather than from immunity-regulating functions of RACB. PMID:27056842

Barley disease susceptibility factor RACB acts in epidermal cell polarity and positioning of the nucleus.

PubMed

Scheler, Björn; Schnepf, Vera; Galgenmüller, Carolina; Ranf, Stefanie; Hückelhoven, Ralph

2016-05-01

RHO GTPases are regulators of cell polarity and immunity in eukaryotes. In plants, RHO-like RAC/ROP GTPases are regulators of cell shaping, hormone responses, and responses to microbial pathogens. The barley (Hordeum vulgare L.) RAC/ROP protein RACB is required for full susceptibility to penetration by Blumeria graminis f.sp. hordei (Bgh), the barley powdery mildew fungus. Disease susceptibility factors often control host immune responses. Here we show that RACB does not interfere with early microbe-associated molecular pattern-triggered immune responses such as the oxidative burst or activation of mitogen-activated protein kinases. RACB also supports rather than restricts expression of defence-related genes in barley. Instead, silencing of RACB expression by RNAi leads to defects in cell polarity. In particular, initiation and maintenance of root hair growth and development of stomatal subsidiary cells by asymmetric cell division is affected by silencing expression of RACB. Nucleus migration is a common factor of developmental cell polarity and cell-autonomous interaction with Bgh RACB is required for positioning of the nucleus near the site of attack from Bgh We therefore suggest that Bgh profits from RACB's function in cell polarity rather than from immunity-regulating functions of RACB. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Effect of Meloidogyne arenaria and Mulch Type on Okra in Microplot Experiments.

PubMed

Ritzinger, C H; McSorley, R; Gallaher, R N

1998-12-01

The effects of perennial peanut (Arachis glabrata) hay, an aged yard-waste compost (mainly woodchips), and a control treatment without amendment were determined on two population levels of root-knot (Melaidogyne arenaria) nematode over three consecutive years in field microplots. Okra (Hibiscus esculentus, susceptible to the root-knot nematode) and a rye (Secale cereale) cover crop (poor nematode host) were used in the summer and winter seasons, respectively. The organic amendment treatments affected plant growth parameters. In the first year, okra yields were greatest in peanut-amended plots. Yield differences with amendment treatment diminished in the second and third years. Okra plant height, total fruit weight, and fruit number were greater with the lower population level of the root-knot nematode. Residual levels of nutrients in soil were greater where root-knot nematode levels and damage were higher and plant growth was poor. Nutrient levels affected the growth of a subsequent rye cover crop.

The importance of appropriate initial bacterial colonization of the intestine in newborn, child and adult health

PubMed Central

Walker, W. Allan

2017-01-01

The fetus does not reside in a sterile intrauterine environment and is exposed to commensal bacteria from the maternal gut/blood stream which crosses the placenta and enters the amniotic fluid. This intestinal exposure to colonizing bacteria continues at birth and during the first year of life and has a profound influence on lifelong health. Why is this important? Intestinal crosstalk with colonizing bacteria in the developing intestine affects the infant’s adaptation to extrauterine life (immune homeostasis) and provides protection against disease expression (allergy, autoimmune disease, obesity, etc.) later in life. Colonizing intestinal bacteria are critical to the normal development of host defense. Disrupted colonization (dysbiosis) due to maternal dysbiosis, cesarean section delivery, use of perinatal antibiotics or premature delivery may adversely affect gut development of host defense and predispose to inflammation rather than homeostasis leading to increased susceptibility to disease later in life. Babies born by cesarean section have a higher incidence of allergy, type 1 diabetes and obesity. Infants given repeated antibiotic regimens during the first year of life are more likely to have asthma as adolescents. This research breakthrough helps to explain the shift in disease paradigms from infections to immune mediated in children from developed countries. This review will develop this research breakthrough. PMID:28426649

Identification of New World Quails Susceptible to Infection with Avian Leukosis Virus Subgroup J

PubMed Central

Plachý, Jiří; Reinišová, Markéta; Kučerová, Dana; Šenigl, Filip; Stepanets, Volodymyr; Hron, Tomáš; Trejbalová, Kateřina; Elleder, Daniel

2016-01-01

ABSTRACT The J subgroup of avian leukosis virus (ALV-J) infects domestic chickens, jungle fowl, and turkeys. This virus enters the host cell through a receptor encoded by the tvj locus and identified as Na+/H+ exchanger 1. The resistance to avian leukosis virus subgroup J in a great majority of galliform species has been explained by deletions or substitutions of the critical tryptophan 38 in the first extracellular loop of Na+/H+ exchanger 1. Because there are concerns of transspecies virus transmission, we studied natural polymorphisms and susceptibility/resistance in wild galliforms and found the presence of tryptophan 38 in four species of New World quails. The embryo fibroblasts of New World quails are susceptible to infection with avian leukosis virus subgroup J, and the cloned Na+/H+ exchanger 1 confers susceptibility on the otherwise resistant host. New World quails are also susceptible to new avian leukosis virus subgroup J variants but resistant to subgroups A and B and weakly susceptible to subgroups C and D of avian sarcoma/leukosis virus due to obvious defects of the respective receptors. Our results suggest that the avian leukosis virus subgroup J could be transmitted to New World quails and establish a natural reservoir of circulating virus with a potential for further evolution. IMPORTANCE Since its spread in broiler chickens in China and Southeast Asia in 2000, ALV-J remains a major enzootic challenge for the poultry industry. Although the virus diversifies rapidly in the poultry, its spillover and circulation in wild bird species has been prevented by the resistance of most species to ALV-J. It is, nevertheless, important to understand the evolution of the virus and its potential host range in wild birds. Because resistance to avian retroviruses is due particularly to receptor incompatibility, we studied Na+/H+ exchanger 1, the receptor for ALV-J. In New World quails, we found a receptor compatible with virus entry, and we confirmed the susceptibilities of four New World quail species in vitro. We propose that a prospective molecular epidemiology study be conducted to identify species with the potential to become reservoirs for ALV-J. PMID:27881654

Identification of genes differentially expressed during interaction of resistant and susceptible apple cultivars (Malus × domestica) with Erwinia amylovora

PubMed Central

2010-01-01

Background The necrogenic enterobacterium, Erwinia amylovora is the causal agent of the fire blight (FB) disease in many Rosaceaespecies, including apple and pear. During the infection process, the bacteria induce an oxidative stress response with kinetics similar to those induced in an incompatible bacteria-plant interaction. No resistance mechanism to E. amylovora in host plants has yet been characterized, recent work has identified some molecular events which occur in resistant and/or susceptible host interaction with E. amylovora: In order to understand the mechanisms that characterize responses to FB, differentially expressed genes were identified by cDNA-AFLP analysis in resistant and susceptible apple genotypes after inoculation with E. amylovora. Results cDNA were isolated from M.26 (susceptible) and G.41 (resistant) apple tissues collected 2 h and 48 h after challenge with a virulent E. amylovora strain or mock (buffer) inoculated. To identify differentially expressed transcripts, electrophoretic banding patterns were obtained from cDNAs. In the AFLP experiments, M.26 and G.41 showed different patterns of expression, including genes specifically induced, not induced, or repressed by E. amylovora. In total, 190 ESTs differentially expressed between M.26 and G.41 were identified using 42 pairs of AFLP primers. cDNA-AFLP analysis of global EST expression in a resistant and a susceptible apple genotype identified different major classes of genes. EST sequencing data showed that genes linked to resistance, encoding proteins involved in recognition, signaling, defense and apoptosis, were modulated by E. amylovora in its host plant. The expression time course of some of these ESTs selected via a bioinformatic analysis has been characterized. Conclusion These data are being used to develop hypotheses of resistance or susceptibility mechanisms in Malus to E. amylovora and provide an initial categorization of genes possibly involved in recognition events, early signaling responses the subsequent development of resistance or susceptibility. These data also provided potential candidates for improving apple resistance to fire blight either by marker-assisted selection or genetic engineering. PMID:20047654

Identification of New World Quails Susceptible to Infection with Avian Leukosis Virus Subgroup J.

PubMed

Plachý, Jiří; Reinišová, Markéta; Kučerová, Dana; Šenigl, Filip; Stepanets, Volodymyr; Hron, Tomáš; Trejbalová, Kateřina; Elleder, Daniel; Hejnar, Jiří

2017-02-01

The J subgroup of avian leukosis virus (ALV-J) infects domestic chickens, jungle fowl, and turkeys. This virus enters the host cell through a receptor encoded by the tvj locus and identified as Na + /H + exchanger 1. The resistance to avian leukosis virus subgroup J in a great majority of galliform species has been explained by deletions or substitutions of the critical tryptophan 38 in the first extracellular loop of Na + /H + exchanger 1. Because there are concerns of transspecies virus transmission, we studied natural polymorphisms and susceptibility/resistance in wild galliforms and found the presence of tryptophan 38 in four species of New World quails. The embryo fibroblasts of New World quails are susceptible to infection with avian leukosis virus subgroup J, and the cloned Na + /H + exchanger 1 confers susceptibility on the otherwise resistant host. New World quails are also susceptible to new avian leukosis virus subgroup J variants but resistant to subgroups A and B and weakly susceptible to subgroups C and D of avian sarcoma/leukosis virus due to obvious defects of the respective receptors. Our results suggest that the avian leukosis virus subgroup J could be transmitted to New World quails and establish a natural reservoir of circulating virus with a potential for further evolution. Since its spread in broiler chickens in China and Southeast Asia in 2000, ALV-J remains a major enzootic challenge for the poultry industry. Although the virus diversifies rapidly in the poultry, its spillover and circulation in wild bird species has been prevented by the resistance of most species to ALV-J. It is, nevertheless, important to understand the evolution of the virus and its potential host range in wild birds. Because resistance to avian retroviruses is due particularly to receptor incompatibility, we studied Na + /H + exchanger 1, the receptor for ALV-J. In New World quails, we found a receptor compatible with virus entry, and we confirmed the susceptibilities of four New World quail species in vitro We propose that a prospective molecular epidemiology study be conducted to identify species with the potential to become reservoirs for ALV-J. Copyright © 2017 American Society for Microbiology.

The Plant Actin Cytoskeleton Responds to Signals from Microbe-Associated Molecular Patterns

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henty-Ridilla, Jessica L.; Shimono, Masaki; Li, Jiejie

2013-04-04

Plants are constantly exposed to a large and diverse array of microbes; however, most plants are immune to the majority of potential invaders and susceptible to only a small subset of pathogens. The cytoskeleton comprises a dynamic intracellular framework that responds rapidly to biotic stresses and supports numerous fundamental cellular processes including vesicle trafficking, endocytosis and the spatial distribution of organelles and protein complexes. For years, the actin cytoskeleton has been assumed to play a role in plant innate immunity against fungi and oomycetes, based largely on static images and pharmacological studies. To date, however, there is little evidence thatmore » the host-cell actin cytoskeleton participates in responses to phytopathogenic bacteria. Here, we quantified the spatiotemporal changes in host-cell cytoskeletal architecture during the immune response to pathogenic and non-pathogenic strains of Pseudomonas syringae pv. tomato DC3000. Two distinct changes to host cytoskeletal arrays were observed that correspond to distinct phases of plant-bacterial interactions i.e. the perception of microbe-associated molecular patterns (MAMPs) during pattern-triggered immunity (PTI) and perturbations by effector proteins during effector-triggered susceptibility (ETS). We demonstrate that an immediate increase in actin filament abundance is a conserved and novel component of PTI. Notably, treatment of leaves with a MAMP peptide mimic was sufficient to elicit a rapid change in actin organization in epidermal cells, and this actin response required the host-cell MAMP receptor kinase complex, including FLS2, BAK1 and BIK1. Finally, we found that actin polymerization is necessary for the increase in actin filament density and that blocking this increase with the actin-disrupting drug latrunculin B leads to enhanced susceptibility of host plants to pathogenic and non-pathogenic bacteria.« less

Role of NETs in the difference in host susceptibility to Toxoplasma gondii between sheep and cattle.

PubMed

Yildiz, Kader; Gokpinar, Sami; Gazyagci, Aycan Nuriye; Babur, Cahit; Sursal, Neslihan; Azkur, Ahmet Kursat

2017-07-01

The main aim of this study was to compare extracellular traps (NETs) formation by polymorphonuclear neutrophils (PMNs) of cattle and sheep when exposed to T. gondii tachyzoites in vitro. The effects of parasite concentrations and different incubation periods on NETs development in cattle and sheep PMNs were studied. The effect of NET structures on host cell invasion by tachyzoites was also studied. This is the first report of NETs development by sheep and cattle PMNs against T. gondii in vitro. T. gondii-induced extracellular DNA production from PMNs was dependent on tachyzoite concentrations and incubation time in both sheep and cattle. Many nuclear and cytoplasmic changes were observed in sheep and cattle PMNs after exposure to T. gondii tachyzoites. The typical appearance of NETs, with MPO, NE and histone (H3) attached to extracellular DNA, was observed. Tachyzoites were entrapped within this structure. Myeloperoxidase (MPO) activity was higher in the cattle PMN-tachyzoite co-cultures than sheep. NETs structures released from sheep PMNs caused mechanical immobilisation of T. gondii tachyzoites, however, NET structures released from cattle PMNs may be lethal to tachyzoites. Bovine MPO may have a lethal effect on T. gondii tachyzoites in vitro during a 3h incubation. Besides other mechanisms that effect on host susceptibility to T. gondii in sheep and cattle, extracellular traps formation as a part of immunological reactions may be play a role in host susceptibility to T. gondii. Copyright © 2017 Elsevier B.V. All rights reserved.

Identification of five new hosts of Phytophthora ramorum in an infested forest in California

Treesearch

S. Rooney-Latham; C.L. Blomquist; A. Williams; E. Gunnison; T. Pastalka

2017-01-01

Phytophthora ramorum causes stem and bole cankers (sudden oak death) and foliar and twig dieback (ramorum blight) of susceptible plants. To date, more than 100 tree, shrub and herbaceous hosts of P. ramorum have been identified. In March 2015, plant samples were submitted to the CDFA Plant Pest Diagnostics...

Toward the molecular cloning of the Septoria nodorum blotch susceptibility gene Snn2 in wheat

USDA-ARS?s Scientific Manuscript database

Septoria nodorum blotch is a disease of wheat caused by the necrotrophic fungus Parastagonospora nodorum. In the wheat-P. nodorum pathosystem, recognition of pathogen-produced necrotrophic effectors (NEs) by dominant host genes leads to host cell death, which allows the pathogen to gain nutrients an...

Gene expression in the tanoak-Phytophthora ramorum interaction

Treesearch

Katherine J. Hayden; Matteo Garbelotto; Hardeep Fai; Brian Knaus; Richard Cronn; Jessica W. Wright

2012-01-01

Disease processes are dynamic, involving a suite of gene expression changes in both the host and the pathogen, all within a single tissue. As such, they lend themselves well to transcriptomic analysis. Here we focus on a generalist invasive pathogen (Phytophthora ramorum) and its most susceptible California Floristic Province native host, tanoak (...

Comparing root knot nematode (Meloidogyne spp.) effects on tomato (Solanum lycopersicum) and grapevine (Vitis spp.) metabolic profiles

USDA-ARS?s Scientific Manuscript database

Root knot nematodes (Meloidogyne spp., RKN) can negatively impact both herbaceous annual and woody perennial hosts. RKN infestations also may increase plant host susceptibility to other stresses such as those imposed by water deficits or various diseases. However, little is known about direct or ind...

Epifluorescence and stereomicroscopy of trichomes associated with resistant and susceptible host plant genotypes of the Asian citrus psyllid (Hemiptera: Liviidae)

USDA-ARS?s Scientific Manuscript database

Epifluorescence, light and stereo-microscopy were used to characterize foliar trichomes associated with young flush leaves and stems of six plant genotypes that are hosts of the Asian citrus psyllid, Diaphorina citri, vector of the economically important citrus greening disease. These genotypes incl...

Matrix stiffness modulates infection of endothelial cells by Listeria monocytogenes via expression of cell surface vimentin.

PubMed

Bastounis, Effie E; Yeh, Yi-Ting; Theriot, Julie A

2018-05-02

Extracellular matrix stiffness (ECM) is one of the many mechanical forces acting on mammalian adherent cells and an important determinant of cellular function. While the effect of ECM stiffness on many aspects of cellular behavior has been previously studied, how ECM stiffness might mediate susceptibility of host cells to infection by bacterial pathogens was hitherto unexplored. To address this open question, we manufactured hydrogels of varying physiologically-relevant stiffness and seeded human microvascular endothelial cells (HMEC-1) on them. We then infected HMEC-1 with the bacterial pathogen Listeria monocytogenes (Lm), and found that adhesion of Lm onto host cells increases monotonically with increasing matrix stiffness, an effect that requires the activity of focal adhesion kinase (FAK). We identified cell surface vimentin as a candidate surface receptor mediating stiffness-dependent adhesion of Lm to HMEC-1 and found that bacterial infection of these host cells is decreased when the amount of surface vimentin is reduced. Our results provide the first evidence that ECM stiffness can mediate the susceptibility of mammalian host cells to infection by a bacterial pathogen.

Effect of resistant and susceptible East European pears on development and mortality of the pear psylla, Cacopsylla pyricola (Forster)

USDA-ARS?s Scientific Manuscript database

The pear psylla (Cacopsylla spp.) is a major pest of European pear (Pyrus communis L.) in North America and Europe. In breeding resistant cultivars, a thorough understanding of the nature of host resistance and susceptibility is essential for designing efficient and accurate methods to identify res...

Susceptibility of larvae of nun moth, Lymantria monacha (Linnaeus 1758) (Lepidoptera), to the entomopathogenic fungus, Entomophaga maimaiga Humber, Shimazu and Soper (Entomophthorales) under laboratory and field conditions

Treesearch

Daniela Pilarska; Ann E. Hajek; Melody Keena; Andreas Linde; Manana Kereselidze; Georgi Georgiev; Margarita Georgieva; Plamen Mirchev; Danail Takov; Slavimira Draganova

2016-01-01

Susceptibility of Lymantria monacha larvae to Entomophaga maimaiga was investigated under laboratory and field conditions, using larvae of the natural host, Lymantria dispar, as positive controls. In laboratory bioassays, L. monacha and L. dispar were injected with...

Sapronosis: a distinctive type of infectious agent

USGS Publications Warehouse

Kuris, Armand M.; Lafferty, Kevin D.; Sokolow, Susanne H.

2014-01-01

Sapronotic disease agents have evolutionary and epidemiological properties unlike other infectious organisms. Their essential saprophagic existence prevents coevolution, and no host–parasite virulence trade-off can evolve. However, the host may evolve defenses. Models of pathogens show that sapronoses, lacking a threshold of transmission, cannot regulate host populations, although they can reduce host abundance and even extirpate their hosts. Immunocompromised hosts are relatively susceptible to sapronoses. Some particularly important sapronoses, such as cholera and anthrax, can sustain an epidemic in a host population. However, these microbes ultimately persist as saprophages. One-third of human infectious disease agents are sapronotic, including nearly all fungal diseases. Recognition that an infectious disease is sapronotic illuminates a need for effective environmental control strategies.

Time course and host responses to Escherichia coli urinary tract infection in genetically distinct mouse strains.

PubMed

Hopkins, W J; Gendron-Fitzpatrick, A; Balish, E; Uehling, D T

1998-06-01

Recurrent urinary tract infections (UTIs) are a significant clinical problem for many women; however, host susceptibility factors have not been completely defined. The mouse model of induced UTI provides an experimental environment in which to identify specific host characteristics that are important in initial bacterial colonization of the urinary tract and in resolution of an infection. This study examined initial susceptibility, bacterial clearance, and host defense mechanisms during induction and resolution of Escherichia coli UTIs in genetically distinct strains of mice. Of the ten inbred strains tested, six (BALB/c, C3H/HeN, C57BL/6, DBA.1, DBA.2, and AKR) showed progressive resolution of bladder infections over a 14-day period. A constant, low-level bladder infection was observed in SWR and SJL mice. High bladder infection levels persisted over the 14-day study period in C3H/HeJ and C3H/OuJ mice. Kidney infection levels generally correlated with bladder infection levels, especially in C3H/HeJ and C3H/OuJ mice, the two most susceptible strains, in which infections became more severe with time after challenge. The degree of inflammation in bladder and kidneys, as well as antibody-forming cell responses, positively correlated with infection intensity in all strains except C3H/HeJ, which had minimal inflammation despite high infection levels. These results demonstrate two important aspects of host defense against UTI. First, the innate immune response to an infection in the bladder or kidneys consists primarily of local inflammation, which is followed by an adaptive response characterized in part by an antibody response to the infecting bacteria. Second, a UTI will be spontaneously resolved in most cases; however, in mice with specific genetic backgrounds, a UTI can persist for an extended length of time. The latter result strongly suggests that the presence or absence of specific host genes will determine how effectively an E. coli UTI will be resolved.

Susceptibility of adult female Aedes aegypti (Diptera: Culicidae) to the entomopathogenic fungus Metarhizium anisopliae is modified following blood feeding.

PubMed

Paula, Adriano R; Carolino, Aline T; Silva, Carlos P; Samuels, Richard I

2011-05-26

The mosquito Aedes aegypti, vector of dengue fever, is a target for control by entomopathogenic fungi. Recent studies by our group have shown the susceptibility of adult A. aegypti to fungal infection by Metarhizium anisopliae. This fungus is currently being tested under field conditions. However, it is unknown whether blood-fed A. aegypti females are equally susceptible to infection by entomopathogenic fungi as sucrose fed females. Insect populations will be composed of females in a range of nutritional states. The fungus should be equally efficient at reducing survival of insects that rest on fungus impregnated surfaces following a blood meal as those coming into contact with fungi before host feeding. This could be an important factor when considering the behavior of A. aegypti females that can blood feed on multiple hosts over a short time period. Female A. aegypti of the Rockefeller strain and a wild strain were infected with two isolates of the entomopathogenic fungus M. anisopliae (LPP 133 and ESALQ 818) using an indirect contact bioassay at different times following blood feeding. Survival rates were monitored on a daily basis and one-way analysis of variance combined with Duncan's post-hoc test or Log-rank survival curve analysis were used for statistical comparisons of susceptibility to infection. Blood feeding rapidly reduced susceptibility to infection, determined by the difference in survival rates and survival curves, when females were exposed to either of the two M. anisopliae isolates. Following a time lag which probably coincided with digestion of the blood meal (96-120 h post-feeding), host susceptibility to infection returned to pre-blood fed (sucrose fed) levels. Reduced susceptibility of A. aegypti to fungi following a blood meal is of concern. Furthermore, engorged females seeking out intra-domicile resting places post-blood feeding, would be predicted to rest for prolonged periods on fungus impregnated black cloths, thus optimizing infection rates. It should be remembered that lowered susceptibility was only a temporary phenomenon and this may not necessarily occur when mosquitoes are infected with other fungal isolates. These results may have implications for field testing of entomopathogenic fungi by our group and further studies should be carried out to better understand the insect-fungus interaction.

Transcriptome dynamics of a susceptible wheat upon Fusarium head blight reveals that molecular responses to Fusarium graminearum infection fit over the grain development processes.

PubMed

Chetouhi, Cherif; Bonhomme, Ludovic; Lasserre-Zuber, Pauline; Cambon, Florence; Pelletier, Sandra; Renou, Jean-Pierre; Langin, Thierry

2016-03-01

In many plant/pathogen interactions, host susceptibility factors are key determinants of disease development promoting pathogen growth and spreading in plant tissues. In the Fusarium head blight (FHB) disease, the molecular basis of wheat susceptibility is still poorly understood while it could provide new insights into the understanding of the wheat/Fusarium graminearum (Fg) interaction and guide future breeding programs to produce cultivars with sustainable resistance. To identify the wheat grain candidate genes, a genome-wide gene expression profiling was performed in the French susceptible wheat cultivar, Recital. Gene-specific two-way ANOVA of about 40 K transcripts at five grain developmental stages identified 1309 differentially expressed genes. Out of these, 536 were impacted by the Fg effect alone. Most of these Fg-responsive genes belonged to biological and molecular functions related to biotic and abiotic stresses indicating the activation of common stress pathways during susceptibility response of wheat grain to FHB. This analysis revealed also 773 other genes displaying either specific Fg-responsive profiles along with grain development stages or synergistic adjustments with the grain development effect. These genes were involved in various molecular pathways including primary metabolism, cell death, and gene expression reprogramming. An increasingly complex host response was revealed, as was the impact of both Fg infection and grain ontogeny on the transcription of wheat genes. This analysis provides a wealth of candidate genes and pathways involved in susceptibility responses to FHB and depicts new clues to the understanding of the susceptibility determinism in plant/pathogen interactions.

Lattice Response Functions of Imperfect Crystals: Effects Due to a Local Change of Mass and Short-Range Interaction

NASA Astrophysics Data System (ADS)

Benedek, G.; Nardelli, G. F.

1967-03-01

Lattice response functions, such as the thermal conductivity and dielectric susceptibility of an imperfect crystal with rocksalt structure, are evaluated in terms of the irreducible T matrix accounting for the phonon scattering. It is shown that the effect of defects on thermal conductivity and dielectric susceptibility can be accounted for by expressions which have essentially the same structure. The T matrix for a defect which affects both the mass and the short-range interaction is analyzed according to the irreducible representations of the point group which pertains to the perturbation, and the resonance conditions for Γ1, Γ12, and Γ15 irreducible representations are considered in detail for any positive impurity in KBr crystals. Hardy's deformation-dipole (DD) model is employed for the description of the host-lattice dynamics. A comparison is made with simplified models, such as diatomic linear chains with nearest-neighbor interaction; it is shown that in polar crystals an effective-force constant has to be used in order to give a reliable description of the short-range interaction between the impurity and the host lattice. An attempt is made to define such effective force constants in the framework of the DD model. The numerical calculations concern positive monovalent impurities in KBr crystals. Γ1, Γ12, and Γ15 resonance frequencies are evaluated as a function of the change of mass and nearest-neighbor force constant. For KBr:Li+ and KBr:Ag+ we also evaluate the band shape of the absorption spectrum at infrared frequencies; good agreement is found between the theoretical prediction and the experimental data on KBr:Li+. It is shown that some structures actually observed in the spectrum are due to peaks in the projected density of states of the host lattice, and have nothing to do with resonance scattering. Good agreement is found between the impurity-host-lattice interaction as estimated from a priori calculations and as deduced by fitting the Γ15 resonance frequency to the experimental data. A simple explanation of the off-center position of small ions is also suggested. Finally, concentration and stress effects on the absorption coefficient are briefly discussed.

Differential Type I Interferon Signaling Is a Master Regulator of Susceptibility to Postinfluenza Bacterial Superinfection.

PubMed

Shepardson, Kelly M; Larson, Kyle; Morton, Rachelle V; Prigge, Justin R; Schmidt, Edward E; Huber, Victor C; Rynda-Apple, Agnieszka

2016-05-03

Bacterial superinfections are a primary cause of death during influenza pandemics and epidemics. Type I interferon (IFN) signaling contributes to increased susceptibility of mice to bacterial superinfection around day 7 post-influenza A virus (IAV) infection. Here we demonstrate that the reduced susceptibility to methicillin-resistant Staphylococcus aureus (MRSA) at day 3 post-IAV infection, which we previously reported was due to interleukin-13 (IL-13)/IFN-γ responses, is also dependent on type I IFN signaling and its subsequent requirement for protective IL-13 production. We found, through utilization of blocking antibodies, that reduced susceptibility to MRSA at day 3 post-IAV infection was IFN-β dependent, whereas the increased susceptibility at day 7 was IFN-α dependent. IFN-β signaling early in IAV infection was required for MRSA clearance, whereas IFN-α signaling late in infection was not, though it did mediate increased susceptibility to MRSA at that time. Type I IFN receptor (IFNAR) signaling in CD11c(+) and Ly6G(+) cells was required for the observed reduced susceptibility at day 3 post-IAV infection. Depletion of Ly6G(+) cells in mice in which IFNAR signaling was either blocked or deleted indicated that Ly6G(+) cells were responsible for the IFNAR signaling-dependent susceptibility to MRSA superinfection at day 7 post-IAV infection. Thus, during IAV infection, the temporal differences in type I IFN signaling increased bactericidal activity of both CD11c(+) and Ly6G(+) cells at day 3 and reduced effector function of Ly6G(+) cells at day 7. The temporal differential outcomes induced by IFN-β (day 3) and IFN-α (day 7) signaling through the same IFNAR resulted in differential susceptibility to MRSA at 3 and 7 days post-IAV infection. Approximately 114,000 hospitalizations and 40,000 annual deaths in the United States are associated with influenza A virus (IAV) infections. Frequently, these deaths are due to community-acquired Gram-positive bacterial species, many of which show increasing resistance to antibiotic therapy. Severe complications, including parapneumonic empyema and necrotizing pneumonia, can arise, depending on virulence factors expressed by either the virus or bacteria. Unfortunately, we are unable to control the expression of these virulence factors, making host responses a logical target for therapeutic interventions. Moreover, interactions between virus, host, and bacteria that exacerbate IAV-related morbidities and mortalities are largely unknown. Here, we show that type I interferon (IFN) expression can modulate susceptibility to methicillin-resistant Staphylococcus aureus (MRSA) infection, with IFN-β reducing host susceptibility to MRSA infection while IFN-α increases susceptibility. Our data indicate that treatments designed to augment IFN-β and/or inhibit IFN-α production around day 7 post-IAV infection could reduce susceptibility to deadly superinfections. Copyright © 2016 Shepardson et al.

Cryptococcus: from environmental saprophyte to global pathogen

PubMed Central

May, Robin C.; Stone, Neil R.H.; Wiesner, Darin L.; Bicanic, Tihana; Nielsen, Kirsten

2016-01-01

Cryptococcosis is a globally distributed invasive fungal infection that is caused by species within the genus Cryptococcus which presents substantial therapeutic challenges. Although natural human-to-human transmission has never been observed, recent work has identified multiple virulence mechanisms that enable cryptococci to infect, disseminate within and ultimately kill their human host. In this Review, we describe these recent discoveries that illustrate the intricacy of host-pathogen interactions and reveal new details about the host immune responses that either help to protect against disease or increase host susceptibility. In addition, we discuss how this improved understanding of both the host and the pathogen informs potential new avenues for therapeutic development. PMID:26685750

Cryptococcus: from environmental saprophyte to global pathogen.

PubMed

May, Robin C; Stone, Neil R H; Wiesner, Darin L; Bicanic, Tihana; Nielsen, Kirsten

2016-02-01

Cryptococcosis is a globally distributed invasive fungal infection that is caused by species within the genus Cryptococcus which presents substantial therapeutic challenges. Although natural human-to-human transmission has never been observed, recent work has identified multiple virulence mechanisms that enable cryptococci to infect, disseminate within and ultimately kill their human host. In this Review, we describe these recent discoveries that illustrate the intricacy of host-pathogen interactions and reveal new details about the host immune responses that either help to protect against disease or increase host susceptibility. In addition, we discuss how this improved understanding of both the host and the pathogen informs potential new avenues for therapeutic development.

Inhibition of OsSWEET11 function in mesophyll cells improves resistance of rice to sheath blight disease.

PubMed

Gao, Yue; Zhang, Chong; Han, Xiao; Wang, Zi Yuan; Ma, Lai; Yuan, De Peng; Wu, Jing Ni; Zhu, Xiao Feng; Liu, Jing Miao; Li, Dao Pin; Hu, Yi Bing; Xuan, Yuan Hu

2018-04-16

Pathogen-host interaction is a complicated process; pathogens mainly infect host plants to acquire nutrients, especially sugars. Rhizoctonia solani, the causative agent of sheath blight disease, is a major pathogen of rice. However, it is not known, as to how this pathogen obtains sugar from rice plants. In this study, we found that the rice sugar transporter, OsSWEET11 is involved in the pathogenesis of sheath blight disease. qRT-PCR and β-d-glucuronidase expression analyses showed that R. solani infection significantly enhanced OsSWEET11 expression in leaves among the clade III SWEET members. The analyses of transgenic plants revealed that Ossweet11 mutants were less susceptible, whereas plants overexpressing OsSWEET11 were more susceptible to sheath blight compared to wild-type controls, but the yield of OsSWEET11 mutants and overexpressors was reduced. SWEETs become active upon oligomerization. Split-ubiquitin yeast two-hybrid, bimolecular fluorescence complementation, and coimmunoprecipitation assays showed that mutated-OsSWEET11 interacted with normal OsSWEET11. In addition, expressing conserved residue mutated-AtSWEET1 inhibits normal AtSWEET1 activity. To analyze whether inhibition of OsSWEET11 function in mesophyll cells is related to defense against this disease, mutated- OsSWEET11 was expressed under the control of Rubisco promoter, which is specific for green tissues. The resistance of transgenic plants to sheath blight disease, but not other disease was improved, while yield production was not evidently affected. Overall, these results suggest that R. solani might acquire sugar from rice leaves by activating OsSWEET11 expression. The plants can be protected from infection by manipulating the expression of OsSWEET11 without affecting the crop yield. This article is protected by copyright. All rights reserved. © 2018 BSPP and John Wiley & Sons Ltd.

Microsatellite and mini-exon analysis of Mexican human DTU I Trypanosoma cruzi strains and their susceptibility to nifurtimox and benznidazole.

PubMed

Martínez, Ignacio; Nogueda, Benjamín; Martínez-Hernández, Fernando; Espinoza, Bertha

2013-03-01

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi, and it affects as many as 10 million people in North and South America, where it represents a major public health problem. T. cruzi is a parasite with high genetic diversity, and it has been grouped into 6 discrete typing units (DTUs), designated as T. cruzi I (TcI) to T. cruzi VI (TcVI). Mexican isolates from humans and from vector insects have been primarily found to be TcI, and these isolates are likely to be the strains that cause the clinical manifestations observed in Mexico. However, genetic characterization and drug susceptibility assays are limited in Mexican TcI strains. In this work, 24 Mexican T. cruzi strains, obtained primarily from humans, were studied with 7 locus microsatellites and mini-exon gene by PCR. Also, drug susceptibility was evaluated by growth and mobility assays. All of the human strains belonged to TcI, and they could be further grouped through microsatellite analysis into 2 subgroups (microsatellite genotypes 1 and 2), which were not related to the host clinical status or biological origin of the strain. Two strains, both from wild mammals, belonged to the TcII-TcVI groups; these strains and the CL Brener strain constituted microsatellite genotype 3. The number of alleles in each locus was lower than reported for South American strains, and a departure from the Hardy-Weinberg equilibrium was observed. The susceptibility of these strains to nifurtimox and benznidazole was heterogeneous. T. cruzi strains characterized as microsatellite genotypes 2 and 3 were significantly more susceptible to benznidazole than strains of microsatellite genotype 1. Only 1 Mexican strain resistant to both drugs was found in this study.

Human Genomic Loci Important in Common Infectious Diseases: Role of High-Throughput Sequencing and Genome-Wide Association Studies

PubMed Central

Sserwadda, Ivan; Amujal, Marion; Namatovu, Norah

2018-01-01

HIV/AIDS, tuberculosis (TB), and malaria are 3 major global public health threats that undermine development in many resource-poor settings. Recently, the notion that positive selection during epidemics or longer periods of exposure to common infectious diseases may have had a major effect in modifying the constitution of the human genome is being interrogated at a large scale in many populations around the world. This positive selection from infectious diseases increases power to detect associations in genome-wide association studies (GWASs). High-throughput sequencing (HTS) has transformed both the management of infectious diseases and continues to enable large-scale functional characterization of host resistance/susceptibility alleles and loci; a paradigm shift from single candidate gene studies. Application of genome sequencing technologies and genomics has enabled us to interrogate the host-pathogen interface for improving human health. Human populations are constantly locked in evolutionary arms races with pathogens; therefore, identification of common infectious disease-associated genomic variants/markers is important in therapeutic, vaccine development, and screening susceptible individuals in a population. This review describes a range of host-pathogen genomic loci that have been associated with disease susceptibility and resistant patterns in the era of HTS. We further highlight potential opportunities for these genetic markers. PMID:29755620

Differential gene expression of the honey bee Apis mellifera associated with Varroa destructor infection

PubMed Central

Navajas, M; Migeon, A; Alaux, C; Martin-Magniette, ML; Robinson, GE; Evans, JD; Cros-Arteil, S; Crauser, D; Le Conte, Y

2008-01-01

Background The parasitic mite, Varroa destructor, is the most serious pest of the western honey bee, Apis mellifera, and has caused the death of millions of colonies worldwide. This mite reproduces in brood cells and parasitizes immature and adult bees. We investigated whether Varroa infestation induces changes in Apis mellifera gene expression, and whether there are genotypic differences that affect gene expression relevant to the bee's tolerance, as first steps toward unravelling mechanisms of host response and differences in susceptibility to Varroa parasitism. Results We explored the transcriptional response to mite parasitism in two genetic stocks of A. mellifera which differ in susceptibility to Varroa, comparing parasitized and non-parasitized full-sister pupae from both stocks. Bee expression profiles were analyzed using microarrays derived from honey bee ESTs whose annotation has recently been enhanced by results from the honey bee genome sequence. We measured differences in gene expression in two colonies of Varroa-susceptible and two colonies of Varroa-tolerant bees. We identified a set of 148 genes with significantly different patterns of expression: 32 varied with the presence of Varroa, 116 varied with bee genotype, and 2 with both. Varroa parasitism caused changes in the expression of genes related to embryonic development, cell metabolism and immunity. Bees tolerant to Varroa were mainly characterized by differences in the expression of genes regulating neuronal development, neuronal sensitivity and olfaction. Differences in olfaction and sensitivity to stimuli are two parameters that could, at least in part, account for bee tolerance to Varroa; differences in olfaction may be related to increased grooming and hygienic behavior, important behaviors known to be involved in Varroa tolerance. Conclusion These results suggest that differences in behavior, rather than in the immune system, underlie Varroa tolerance in honey bees, and give an indication of the specific physiological changes found in parasitized bees. They provide a first step toward better understanding molecular pathways involved in this important host-parasite relationship. PMID:18578863

Differential gene expression of the honey bee Apis mellifera associated with Varroa destructor infection.

PubMed

Navajas, M; Migeon, A; Alaux, C; Martin-Magniette, Ml; Robinson, Ge; Evans, Jd; Cros-Arteil, S; Crauser, D; Le Conte, Y

2008-06-25

The parasitic mite, Varroa destructor, is the most serious pest of the western honey bee, Apis mellifera, and has caused the death of millions of colonies worldwide. This mite reproduces in brood cells and parasitizes immature and adult bees. We investigated whether Varroa infestation induces changes in Apis mellifera gene expression, and whether there are genotypic differences that affect gene expression relevant to the bee's tolerance, as first steps toward unravelling mechanisms of host response and differences in susceptibility to Varroa parasitism. We explored the transcriptional response to mite parasitism in two genetic stocks of A. mellifera which differ in susceptibility to Varroa, comparing parasitized and non-parasitized full-sister pupae from both stocks. Bee expression profiles were analyzed using microarrays derived from honey bee ESTs whose annotation has recently been enhanced by results from the honey bee genome sequence. We measured differences in gene expression in two colonies of Varroa-susceptible and two colonies of Varroa-tolerant bees. We identified a set of 148 genes with significantly different patterns of expression: 32 varied with the presence of Varroa, 116 varied with bee genotype, and 2 with both. Varroa parasitism caused changes in the expression of genes related to embryonic development, cell metabolism and immunity. Bees tolerant to Varroa were mainly characterized by differences in the expression of genes regulating neuronal development, neuronal sensitivity and olfaction. Differences in olfaction and sensitivity to stimuli are two parameters that could, at least in part, account for bee tolerance to Varroa; differences in olfaction may be related to increased grooming and hygienic behavior, important behaviors known to be involved in Varroa tolerance. These results suggest that differences in behavior, rather than in the immune system, underlie Varroa tolerance in honey bees, and give an indication of the specific physiological changes found in parasitized bees. They provide a first step toward better understanding molecular pathways involved in this important host-parasite relationship.

Peripartum Antibiotics Promote Gut Dysbiosis, Loss of Immune Tolerance, and Inflammatory Bowel Disease in Genetically Prone Offspring.

PubMed

Miyoshi, Jun; Bobe, Alexandria M; Miyoshi, Sawako; Huang, Yong; Hubert, Nathaniel; Delmont, Tom O; Eren, A Murat; Leone, Vanessa; Chang, Eugene B

2017-07-11

Factors affecting the developing neonatal gut microbiome and immune networks may increase the risk of developing complex immune disorders such as inflammatory bowel diseases (IBD). In particular, peripartum antibiotics have been suggested as risk factors for human IBD, although direct evidence is lacking. Therefore, we examined the temporal impact of the commonly used antibiotic cefoperazone on both maternal and offspring microbiota when administered to dams during the peripartum period in the IL-10-deficient murine colitis model. By rigorously controlling for cage, gender, generational, and murine pathobiont confounders, we observed that offspring from cefoperazone-exposed dams develop a persistent gut dysbiosis into adulthood associated with skewing of the host immune system and increased susceptibility to spontaneous and chemically dextran sodium sulfate (DSS)-induced colitis. Thus, early life exposure to antibiotic-induced maternal dysbiosis during a critical developmental window for gut microbial assemblage and immune programming elicits a lasting impact of increased IBD risk on genetically susceptible offspring. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Ecology and conservation biology of avian malaria.

PubMed

Lapointe, Dennis A; Atkinson, Carter T; Samuel, Michael D

2012-02-01

Avian malaria is a worldwide mosquito-borne disease caused by Plasmodium parasites. These parasites occur in many avian species but primarily affect passerine birds that have not evolved with the parasite. Host pathogenicity, fitness, and population impacts are poorly understood. In contrast to continental species, introduced avian malaria poses a substantial threat to naive birds on Hawaii, the Galapagos, and other archipelagoes. In Hawaii, transmission is maintained by susceptible native birds, competence and abundance of mosquitoes, and a disease reservoir of chronically infected native birds. Although vector habitat and avian communities determine the geographic distribution of disease, climate drives transmission patterns ranging from continuous high infection in warm lowland forests, seasonal infection in midelevation forests, and disease-free refugia in cool high-elevation forests. Global warming is expected to increase the occurrence, distribution, and intensity of avian malaria across this elevational gradient and threaten high-elevation refugia, which is the key to survival of many susceptible Hawaiian birds. Increased temperatures may have already increased global avian malaria prevalence and contributed to an emergence of disease in New Zealand. © 2012 New York Academy of Sciences.

Ecology and conservation biology of avian malaria

USGS Publications Warehouse

LaPointe, Dennis A.; Atkinson, Carter T.; Samuel, Michael D.

2012-01-01

Avian malaria is a worldwide mosquito-borne disease caused by Plasmodium parasites. These parasites occur in many avian species but primarily affect passerine birds that have not evolved with the parasite. Host pathogenicity, fitness, and population impacts are poorly understood. In contrast to continental species, introduced avian malaria poses a substantial threat to naive birds on Hawaii, the Galapagos, and other archipelagoes. In Hawaii, transmission is maintained by susceptible native birds, competence and abundance of mosquitoes, and a disease reservoir of chronically infected native birds. Although vector habitat and avian communities determine the geographic distribution of disease, climate drives transmission patterns ranging from continuous high infection in warm lowland forests, seasonal infection in midelevation forests, and disease-free refugia in cool high-elevation forests. Global warming is expected to increase the occurrence, distribution, and intensity of avian malaria across this elevational gradient and threaten high-elevation refugia, which is the key to survival of many susceptible Hawaiian birds. Increased temperatures may have already increased global avian malaria prevalence and contributed to an emergence of disease in New Zealand.

The effects of Phytophthora ramorum stem inoculation on aspects of tanoak physiology and xylem function in saplings and seedlings

Treesearch

Elizabeth Stamm

2012-01-01

Phytophthora ramorum, an oomycete plant pathogen, is the causal agent of sudden oak death, a serious disease of Fagaceous trees in California and Oregon over the last decade. Tanoak (Notholithocarpus densiflorus) is one of the most susceptible host species, but the cause of host mortality is poorly understood....

Alteration of a second putative fusion peptide of structural glycoprotein E2 of Classical Swine Fever Virus alters virus replication and virulence in swine

USDA-ARS?s Scientific Manuscript database

E2, the major envelope glycoprotein of Classical Swine Fever Virus (CSFV), is involved in several critical virus functions including cell attachment, host range susceptibility, and virulence in natural hosts. Functional structural analysis of E2 based on Wimley-White interfacial hydrophobicity dis...

Intraspecific variation in host susceptibility and climatic factors mediate epidemics of sudden oak death in western US forests

Treesearch

D. Huberli; K.J. Hayden; M. Calver; M. Garbelotto

2011-01-01

Umbellularia californica is one of the key infectious hosts of the exotic Phytophthora ramorum, which causes sudden oak death (SOD) in California and Oregon forests. This study provides a comprehensive analysis of the epidemiologically relevant parameters for SOD in California and southern Oregon, including potential differences between the two...

Integrated Pest Management Research Symposium: The Proceedings

Treesearch

Susan J. Branham; Robert C. Thatcher; [Editors

1985-01-01

Thirty-seven papers are presented that summarize the findings from research and development work conducted as a part of the Integrated Pest Management RD&A Program for Bark Beetles of Southern Pines during the 5-year period 1980-85. Presentations cover the areas of sampling and impact assessment, bark beetle biology and ecology, host susceptibility, host/pest...

Mountain pine beetle host selection behavior confirms high resistance in Great Basin bristlecone pine

Treesearch

Erika L. Eidson; Karen E. Mock; Barbara J. Bentz

2017-01-01

Over the last two decades, mountain pine beetle (Dendroctonus ponderosae) populations reached epidemic levels across much of western North America, including high elevations where cool temperatures previously limited mountain pine beetle persistence. Many high-elevation pine species are susceptible hosts and experienced high levels of mortality in recent outbreaks, but...

Modulation of nonessential amino acid biosynthetic pathways in virulent Hessian fly larvae (Mayetiola destructor), feeding on susceptible host wheat (Triticum aestivum)

USDA-ARS?s Scientific Manuscript database

Hessian fly (Mayetiola destructor), an obligate plant-parasitic gall midge, is an important dipteran pest of wheat (Triticum aestivum). The insect employs an effector-based feeding strategy to reprogram the host plant to be nutritionally beneficial for the developing larva by inducing formation of p...

Experimental transmission of Enteromyxum leei to freshwater fish.

PubMed

Diamant, A; Ram, S; Paperna, I

2006-10-17

The myxosporean Enteromyxum leei is known to infect a wide range of marine fish hosts. The objective of the present study was to determine whether freshwater fish species are also receptive hosts to this parasite. Seventeen species of freshwater fish were experimentally fed E. leei-infected gut tissue from donor gilthead sea bream Sparus aurata obtained from a commercial sea bream cage farm. Four of the tested species, tiger barb Puntius tetrazona, zebra danio Danio rerio, oscar Astronotus ocellatus and Mozambique tilapia Oreochromis mossambicus, were found to be susceptible with prevalences ranging from 53 to 90%. The course of infection and pathology was limited to the gut mucosa epithelium and was similar to that observed in marine hosts. Little is known of the differences in physiological conditions encountered by a parasite in the alimentary tract of freshwater vs. marine teleost hosts, but we assume that a similar osmotic environment is maintained in both. Parasite infectivity may be influenced by differences in the presence or absence of a true stomach, acidic gastric pH and digestive enzyme activity both in the stomach and intestine. Variability in susceptibility among species may also stem from differences in innate immunity. Dimensions of spores produced in the donor sea bream and recipient freshwater species are variable in size, as previously observed in other captive marine host species.

Effects of deterministic and random refuge in a prey-predator model with parasite infection.

PubMed

Mukhopadhyay, B; Bhattacharyya, R

2012-09-01

Most natural ecosystem populations suffer from various infectious diseases and the resulting host-pathogen dynamics is dependent on host's characteristics. On the other hand, empirical evidences show that for most host pathogen systems, a part of the host population always forms a refuge. To study the role of refuge on the host-pathogen interaction, we study a predator-prey-pathogen model where the susceptible and the infected prey can undergo refugia of constant size to evade predator attack. The stability aspects of the model system is investigated from a local and global perspective. The study reveals that the refuge sizes for the susceptible and the infected prey are the key parameters that control possible predator extinction as well as species co-existence. Next we perform a global study of the model system using Lyapunov functions and show the existence of a global attractor. Finally we perform a stochastic extension of the basic model to study the phenomenon of random refuge arising from various intrinsic, habitat-related and environmental factors. The stochastic model is analyzed for exponential mean square stability. Numerical study of the stochastic model shows that increasing the refuge rates has a stabilizing effect on the stochastic dynamics. Copyright © 2012 Elsevier Inc. All rights reserved.

Antioxidant responses to heat and light stress differ with habitat in a common reef coral

NASA Astrophysics Data System (ADS)

Hawkins, Thomas D.; Krueger, Thomas; Wilkinson, Shaun P.; Fisher, Paul L.; Davy, Simon K.

2015-12-01

Coral bleaching—the stress-induced collapse of the coral- Symbiodinium symbiosis—is a significant driver of worldwide coral reef degradation. Yet, not all corals are equally susceptible to bleaching, and we lack a clear understanding of the mechanisms underpinning their differential susceptibilities. Here, we focus on cellular redox regulation as a potential determinant of bleaching susceptibility in the reef coral Stylophora pistillata. Using slow heating (1 °C d-1) and altered irradiance, we induced bleaching in S. pistillata colonies sampled from two depths [5-8 m (shallow) and 15-18 m (deep)]. There was significant depth-dependent variability in the timing and extent of bleaching (loss of symbiont cells), as well as in host enzymatic antioxidant activity [specifically, superoxide dismutase and catalase (CAT)]. However, among the coral fragments that bleached, most did so without displaying any evidence of a host enzymatic antioxidant response. For example, both deep and shallow corals suffered significant symbiont loss at elevated temperature, but only deep colonies exposed to high temperature and high light displayed any up-regulation of host antioxidant enzyme activity (CAT). Surprisingly, this preceded the equivalent antioxidant responses of the symbiont, which raises questions about the source(s) of hydrogen peroxide in the symbiosis. Overall, changes in enzymatic antioxidant activity in the symbionts were driven primarily by irradiance rather than temperature, and responses were similar across depth groups. Taken together, our results suggest that in the absence of light stress, heating of 1 °C d-1 to 4 °C above ambient is not sufficient to induce a substantial oxidative challenge in S. pistillata. We provide some of the first evidence that regulation of coral enzymatic antioxidants can vary significantly depending on habitat, and, in terms of determining bleaching susceptibility, our results suggest a significant role for the host's differential regulation of cellular redox status.

Molecular typing and in vitro antifungal susceptibility of Cryptococcus spp from patients in Midwest Brazil.

PubMed

Favalessa, Olivia Cometti; de Paula, Daphine Ariadne Jesus; Dutra, Valeria; Nakazato, Luciano; Tadano, Tomoko; Lazera, Marcia dos Santos; Wanke, Bodo; Trilles, Luciana; Walderez Szeszs, Maria; Silva, Dayane; Hahn, Rosane Christine

2014-08-13

Cryptococcosis is a systemic fungal infection that affects humans and animals, mainly due to Cryptococcus neoformans and Cryptococcus gattii. Following the epidemic of acquired immunodeficiency syndrome (AIDS), fungal infections by C. neoformans have become more common among immunocompromised patients. Cryptococcus gattii has primarily been isolated as a primary pathogen in healthy hosts and occurs endemically in northern and northeastern Brazil. We to perform genotypic characterization and determine the in vitro susceptibility profile to antifungal drugs of the Cryptococcus species complex isolated from HIV-positive and HIV-negative patients attended at university hospitals in Cuiabá, MT, in the Midwestern region of Brazil. Micromorphological features, chemotyping with canavanine-glycine-bromothymol blue (CGB) agar and genotyping by URA5-RFLP were used to identify the species. The antifungal drugs tested were amphotericin B, fluconazole, flucytosine, itraconazole and voriconazole. Minimum inhibitory concentrations (MICs) were determined according to the CLSI methodology M27-A3. Analysis of samples yelded C. neoformans AFLP1/VNI (17/27, 63.0%) and C. gattii AFLP6/VGII (10/27, 37.0%). The MICs ranges for the antifungal drugs were: amphotericin B (0.5-1 mg/L), fluconazole (1-16 mg/L), flucytosine (1-16 mg/L), itraconazole (0.25-0.12 mg/L) and voriconazole (0.06-0.5 mg/L). Isolates of C. neoformans AFLP1/VNI were predominant in patients with HIV/AIDS, and C. gattii VGII in HIV-negative patients. The genotypes identified were susceptible to the antifungal drugs tested. It is worth emphasizing that AFLP6/VGII is a predominant genotype affecting HIV-negative individuals in Cuiabá. These findings serve as a guide concerning the molecular epidemiology of C. neoformans and C. gattii in the State of Mato Grosso.

Effect of environmental and seasonal factors on the susceptibility of different rhododendron species and hybrids to Phytophthora ramorum

Treesearch

Isabelle De Dobbelaere; Kurt Heungens; Martine Maes

2008-01-01

Although Rhododendron is the most important host of Phytophthora ramorum. in Europe, there is little scientific information about the susceptibility levels of different Rhododendron species and cultivars. Increasing this knowledge would help nurseries in the management of the disease and could be used by plant protection services to target their...

Comparative Susceptibility of Plants Native to the Appalachian Range of the United States to Inoculation With Phytophthora ramorum

Treesearch

R.G. Linderman; Patricia B. de Sá; E.A. Davis

2008-01-01

Phytophthora ramorum, cause of sudden oak death of trees or ramorum blight of other plant species, has many hosts. Some geographic regions, such as the Appalachian range of the eastern United States, are considered high risk of becoming infested with the pathogen because known susceptible plants occur there and climatic characteristics appear...

Long-term efficacy of diameter-limit cutting to reduce mountain pine beetle-caused tree mortality in a lodgepole pine forest

Treesearch

J. C. Vandygriff; E. Hansen; Barbara Bentz; K. K. Allen; G. D. Amman; L. A. Rasmussen

2015-01-01

Mountain pine beetle, Dendroctonus ponderosae Hopkins, is the most significant mortality agent in pine forests of western North America. Silvicultural treatments that reduce the number of susceptible host trees, alter age and size class distributions, and diversify species composition are considered viable, long-term options for reducing stand susceptibility...

Immunobiologic effects of cytokine gene transfer of the B16-BL6 melanoma.

PubMed

Strome, S E; Krauss, J C; Cameron, M J; Forslund, K; Shu, S; Chang, A E

1993-12-01

The genetic modification of tumors offers an approach to modulate the host immune response to relatively weak native tumor antigens. We examined the immunobiologic effects of various cytokine genes transferred into the poorly immunogenic B16-BL6 murine melanoma. Retroviral expression vectors containing cDNAs for interleukin 2, interleukin 4, interferon gamma, or a neomycin-resistant control were electroporated into a B16-BL6 tumor clone. Selected transfected clones were examined for in vitro cytokine secretion and in vivo tumorigenicity. When cells from individual clones were injected intradermally into syngeneic mice, the interleukin 4-secreting clone grew significantly slower than did the neomycin-resistant transfected control, while the growth of the interleukin 2- and interferon gamma-expressing clones was not affected. Despite minimal cytokine secretion by interferon gamma-transfected cells, these cells expressed upregulated major histocompatibility class I antigen and were more susceptible to lysis by allosensitized cytotoxic T lymphocytes compared with parental or neomycin-resistant transfected tumor targets. We observed diverse immunobiologic effects associated with cytokine gene transfer into the B16-BL6 melanoma. Interleukin 4 transfection of tumor resulted in decreased in vivo tumorigenicity that may be related to a host immune response. Further studies to evaluate the host T-cell response to these gene-modified tumors are being investigated.

Obesity: a chronic relapsing progressive disease process. A position statement of the World Obesity Federation.

PubMed

Bray, G A; Kim, K K; Wilding, J P H

2017-07-01

This paper considers the argument for obesity as a chronic relapsing disease process. Obesity is viewed from an epidemiological model, with an agent affecting the host and producing disease. Food is the primary agent, particularly foods that are high in energy density such as fat, or in sugar-sweetened beverages. An abundance of food, low physical activity and several other environmental factors interact with the genetic susceptibility of the host to produce positive energy balance. The majority of this excess energy is stored as fat in enlarged, and often more numerous fat cells, but some lipid may infiltrate other organs such as the liver (ectopic fat). The enlarged fat cells and ectopic fat produce and secrete a variety of metabolic, hormonal and inflammatory products that produce damage in organs such as the arteries, heart, liver, muscle and pancreas. The magnitude of the obesity and its adverse effects in individuals may relate to the virulence or toxicity of the environment and its interaction with the host. Thus, obesity fits the epidemiological model of a disease process except that the toxic or pathological agent is food rather than a microbe. Reversing obesity will prevent most of its detrimental effects. © 2017 World Obesity Federation.

The effect of environmental heterogeneity on RPW8-mediated resistance to powdery mildews in Arabidopsis thaliana

PubMed Central

Jorgensen, Tove H.

2012-01-01

Background and Aims The biotic and abiotic environment of interacting hosts and parasites may vary considerably over small spatial and temporal scales. It is essential to understand how different environments affect host disease resistance because this determines frequency of disease and, importantly, heterogeneous environments can retard direct selection and potentially maintain genetic variation for resistance in natural populations. Methods The effect of different temperatures and soil nutrient conditions on the outcome of infection by a pathogen was quantified in Arabidopsis thaliana. Expression levels of a gene conferring resistance to powdery mildews, RPW8, were compared with levels of disease to test a possible mechanism behind variation in resistance. Key Results Most host genotypes changed from susceptible to resistant across environments with the ranking of genotypes differing between treatments. Transcription levels of RPW8 increased after infection and varied between environments, but there was no tight association between transcription and resistance levels. Conclusions There is a strong potential for a heterogeneous environment to change the resistance capacity of A. thaliana genotypes and hence the direction and magnitude of selection in the presence of the pathogen. Possible causative links between resistance gene expression and disease resistance are discussed in light of the present results on RPW8. PMID:22234559

Genetic erosion in wild populations makes resistance to a pathogen more costly.

PubMed

Luquet, Emilien; Garner, Trenton W J; Léna, Jean-Paul; Bruel, Christophe; Joly, Pierre; Lengagne, Thierry; Grolet, Odile; Plénet, Sandrine

2012-06-01

Populations that have suffered from genetic erosion are expected to exhibit reduced average trait values or decreased variation in adaptive traits when experiencing periodic or emergent stressors such as infectious disease. Genetic erosion may consequentially modify the ability of a potential host population to cope with infectious disease emergence. We experimentally investigate this relationship between genetic variability and host response to exposure to an infectious agent both in terms of susceptibility to infection and indirect parasite-mediated responses that also impact fitness. We hypothesized that the deleterious consequences of exposure to the pathogen (Batrachochytrium dendrobatidis) would be more severe for tadpoles descended from European treefrog (Hyla arborea) populations lacking genetic variability. Although all exposed tadpoles lacked detectable infection, we detected this relationship for some indirect host responses, predominantly in genetically depleted animals, as well as an interaction between genetic variability and pathogen dose on life span during the postmetamorphic period. Lack of infection and a decreased mass and postmetamorphic life span in low genetic diversity tadpoles lead us to conclude that genetic erosion, while not affecting the ability to mount effective resistance strategies, also erodes the capacity to invest in resistance, increased tadpole growth rate, and metamorphosis relatively simultaneously. © 2012 The Author(s). Evolution © 2012 The Society for the Study of Evolution.

Human Immunodeficiency Virus Proteins Mimic Human T Cell Receptors Inducing Cross-Reactive Antibodies

PubMed Central

2017-01-01

Human immunodeficiency virus (HIV) hides from the immune system in part by mimicking host antigens, including human leukocyte antigens. It is demonstrated here that HIV also mimics the V-β-D-J-β of approximately seventy percent of about 600 randomly selected human T cell receptors (TCR). This degree of mimicry is greater than any other human pathogen, commensal or symbiotic organism studied. These data suggest that HIV may be evolving into a commensal organism just as simian immunodeficiency virus has done in some types of monkeys. The gp120 envelope protein, Nef protein and Pol protein are particularly similar to host TCR, camouflaging HIV from the immune system and creating serious barriers to the development of safe HIV vaccines. One consequence of HIV mimicry of host TCR is that antibodies against HIV proteins have a significant probability of recognizing the corresponding TCR as antigenic targets, explaining the widespread observation of lymphocytotoxic autoantibodies in acquired immunodeficiency syndrome (AIDS). Quantitative enzyme-linked immunoadsorption assays (ELISA) demonstrated that every HIV antibody tested recognized at least one of twelve TCR, and as many as seven, with a binding constant in the 10−8 to 10−9 m range. HIV immunity also affects microbiome tolerance in ways that correlate with susceptibility to specific opportunistic infections. PMID:28972547

Host genotype-specific therapies can optimize the inflammatory response to mycobacterial infections

PubMed Central

Tobin, David M.; Roca, Francisco J.; Oh, Sungwhan F.; McFarland, Ross; Vickery, Thad W.; Ray, John P.; Ko, Dennis C.; Zou, Yuxia; Bang, Nguyen D.; Chau, Tran T. H.; Vary, Jay C.; Hawn, Thomas R.; Dunstan, Sarah J.; Farrar, Jeremy J.; Thwaites, Guy E.; King, Mary-Claire; Serhan, Charles N.; Ramakrishnan, Lalita

2012-01-01

Summary Susceptibility to tuberculosis is historically ascribed to an inadequate immune response that fails to control infecting mycobacteria. In zebrafish, we find that susceptibility to Mycobacterium marinum can result from either inadequate or excessive acute inflammation. Modulation of the leukotriene A4 hydrolase (LTA4H) locus, which controls the balance of pro- and anti-inflammatory eicosanoids, reveals two distinct molecular routes to mycobacterial susceptibility converging on dysregulated TNF levels: inadequate inflammation caused by excess lipoxins and hyperinflammation driven by excess leukotriene B4. We identify therapies that specifically target each of these extremes. In humans, we identify a single nucleotide polymorphism in the LTA4H promoter that regulates its transcriptional activity. In tuberculous meningitis, the polymorphism is associated with inflammatory cell recruitment, patient survival and response to adjunctive anti-inflammatory therapy. Together, our findings suggest that host-directed therapies tailored to patient LTA4H genotypes may counter detrimental effects of either extreme of inflammation. PMID:22304914

Inhibitory activity of analogs of AM-toxin, a host-specific phytotoxin from the Alternaria alternata apple pathotype, on photosynthetic O2 evolution in apple leaves.

PubMed

Miyashita, Masahiro; Nakamori, Tomoko; Miyagawa, Hisashi; Akamatsu, Miki; Ueno, Tamio

2003-03-01

The effect of the host-specific phytotoxins, AM-toxins, on the photosynthetic activity of leaves from susceptible apple cultivars was investigated by using an oxygen electrode. The photosynthetic O2 evolution was inhibited by AM-toxin I in a host-specific manner. The inhibitory activity of several AM-toxin analogs against photosynthesis was also evaluated and the findings were correlated with their necrosis-inducing activity.

The Microbiome in Infectious Disease and Inflammation

PubMed Central

Honda, Kenya; Littman, Dan R.

2015-01-01

The mammalian alimentary tract harbors hundreds of species of commensal microorganisms (microbiota) that intimately interact with the host and provide it with genetic, metabolic, and immunological attributes. Recent reports have indicated that the microbiota composition and its collective genomes (microbiome) are major factors in predetermining the type and robustness of mucosal immune responses. In this review, we discuss the recent advances in our understanding of host-microbiota interactions and their effect on the health and disease susceptibility of the host. PMID:22224764

Rice Blast Fungus (Magnaporthe oryzae) Infects Arabidopsis via a Mechanism Distinct from That Required for the Infection of Rice1[W][OA

PubMed Central

Park, Ju-Young; Jin, Jianming; Lee, Yin-Won; Kang, Seogchan; Lee, Yong-Hwan

2009-01-01

Magnaporthe oryzae is a hemibiotrophic fungal pathogen that causes rice (Oryza sativa) blast. Although M. oryzae as a whole infects a wide variety of monocotyledonous hosts, no dicotyledonous plant has been reported as a host. We found that two rice pathogenic strains of M. oryzae, KJ201 and 70-15, interacted differentially with 16 ecotypes of Arabidopsis (Arabidopsis thaliana). Strain KJ201 infected all ecotypes with varying degrees of virulence, whereas strain 70-15 caused no symptoms in certain ecotypes. In highly susceptible ecotypes, small chlorotic lesions appeared on infected leaves within 3 d after inoculation and subsequently expanded across the affected leaves. The fungus produced spores in susceptible ecotypes but not in resistant ecotypes. Fungal cultures recovered from necrotic lesions caused the same symptoms in healthy plants, satisfying Koch's postulates. Histochemical analyses showed that infection by the fungus caused an accumulation of reactive oxygen species and eventual cell death. Similar to the infection process in rice, the fungus differentiated to form appressorium and directly penetrated the leaf surface in Arabidopsis. However, the pathogenic mechanism in Arabidopsis appears distinct from that in rice; three fungal genes essential for pathogenicity in rice played only limited roles in causing disease symptoms in Arabidopsis, and the fungus seems to colonize Arabidopsis as a necrotroph through the secretion of phytotoxic compounds, including 9,12-octadecadienoic acid. Expression of PR-1 and PDF1.2 was induced in response to infection by the fungus, suggesting the activation of salicylic acid- and jasmonic acid/ethylene-dependent signaling pathways. However, the roles of these signaling pathways in defense against M. oryzae remain unclear. In combination with the wealth of genetic and genomic resources available for M. oryzae, this newly established pathosystem allows comparison of the molecular and cellular mechanisms underlying pathogenesis and host defense in two well-studied model plants. PMID:18987215

Thymus transcriptome reveals novel pathways in response to avian pathogenic Escherichia coli infection

PubMed Central

Sun, H.; Liu, P.; Nolan, L. K.; Lamont, S. J.

2016-01-01

Avian pathogenic Escherichia coli (APEC) can cause significant morbidity in chickens. The thymus provides the essential environment for T cell development; however, the thymus transcriptome has not been examined for gene expression in response to APEC infection. An improved understanding of the host genomic response to APEC infection could inform future breeding programs for disease resistance and APEC control. We therefore analyzed the transcriptome of the thymus of birds challenged with APEC, contrasting susceptible and resistant phenotypes. Thousands of genes were differentially expressed in birds of the 5-day post infection (dpi) challenged-susceptible group vs. 5 dpi non-challenged, in 5 dpi challenged-susceptible vs. 5 dpi challenged-resistant birds, as well as in 5 dpi vs. one dpi challenged-susceptible birds. The Toll-like receptor signaling pathway was the major innate immune response for birds to respond to APEC infection. Moreover, lysosome and cell adhesion molecules pathways were common mechanisms for chicken response to APEC infection. The T-cell receptor signaling pathway, cell cycle, and p53 signaling pathways were significantly activated in resistant birds to resist APEC infection. These results provide a comprehensive assessment of global gene networks and biological functionalities of differentially expressed genes in the thymus under APEC infection. These findings provide novel insights into key molecular genetic mechanisms that differentiate host resistance from susceptibility in this primary lymphoid tissue, the thymus. PMID:27466434

Human susceptibility to legionnaires' disease.

PubMed

Berrington, William R; Hawn, Thomas R

2013-01-01

Legionella pneumophila is a facultative intracellular pathogen that is an important cause of pneumonia. Although host factors that may predispose to acquisition of Legionnaire's Disease (LD) include comorbid illnesses (e.g., diabetes, chronic lung disease), age, male sex, and smoking, many individuals have no identifiable risk factors. Some studies suggest that genetic factors may enhance susceptibility to LD. In this chapter we discuss current techniques and scientific methods to identify genetic susceptibility factors. These genetic studies provide insight into the human immune response to intracellular pathogens and may improve strategies for treatment and vaccine development.

The Relationship between Host Lifespan and Pathogen Reservoir Potential: An Analysis in the System Arabidopsis thaliana-Cucumber mosaic virus

PubMed Central

Hily, Jean Michel; García, Adrián; Moreno, Arancha; Plaza, María; Wilkinson, Mark D.; Fereres, Alberto; Fraile, Aurora; García-Arenal, Fernando

2014-01-01

Identification of the determinants of pathogen reservoir potential is central to understand disease emergence. It has been proposed that host lifespan is one such determinant: short-lived hosts will invest less in costly defenses against pathogens, so that they will be more susceptible to infection, more competent as sources of infection and/or will sustain larger vector populations, thus being effective reservoirs for the infection of long-lived hosts. This hypothesis is sustained by analyses of different hosts of multihost pathogens, but not of different genotypes of the same host species. Here we examined this hypothesis by comparing two genotypes of the plant Arabidopsis thaliana that differ largely both in life-span and in tolerance to its natural pathogen Cucumber mosaic virus (CMV). Experiments with the aphid vector Myzus persicae showed that both genotypes were similarly competent as sources for virus transmission, but the short-lived genotype was more susceptible to infection and was able to sustain larger vector populations. To explore how differences in defense against CMV and its vector relate to reservoir potential, we developed a model that was run for a set of experimentally-determined parameters, and for a realistic range of host plant and vector population densities. Model simulations showed that the less efficient defenses of the short-lived genotype resulted in higher reservoir potential, which in heterogeneous host populations may be balanced by the longer infectious period of the long-lived genotype. This balance was modulated by the demography of both host and vector populations, and by the genetic composition of the host population. Thus, within-species genetic diversity for lifespan and defenses against pathogens will result in polymorphisms for pathogen reservoir potential, which will condition within-population infection dynamics. These results are relevant for a better understanding of host-pathogen co-evolution, and of the dynamics of pathogen emergence. PMID:25375140

Host iron redistribution as a risk factor for incident tuberculosis in HIV infection: an 11-year retrospective cohort study

PubMed Central

2013-01-01

Background Identifying people at higher risk of developing tuberculosis with human immunodeficiency virus (HIV) infection may improve clinical management of co-infections. Iron influences tuberculosis (TB) pathogenesis, but understanding the exact mechanisms of how and timing of when iron is involved remains challenging since biological samples are rarely available from the disease susceptibility period due to the difficulty in predicting in who and when, if ever, TB will develop. The objective of this research was to determine how host iron status measured at HIV diagnosis and genotypes related to host iron metabolism were associated with incident TB. Methods Archived clinical data, plasma and DNA were analyzed from 1139 adult participants in a large HIV-1, HIV-2 and dual seroprevalent cohort based at the Medical Research Council Laboratories in The Gambia. Incident pulmonary and/or extrapulmonary TB diagnoses a minimum of 28 days after HIV diagnosis were independently re-confirmed using available evidence (n=152). Multiple host iron status biomarkers, Haptoglobin and solute carrier family 11, member 1 (SLC11A1) genotypes were modeled to characterize how indicators of host iron metabolism were associated with TB susceptibility. Results Hemoglobin (incidence rate ratio, IRR=0.88, 95% CI=0.79-0.98), plasma transferrin (IRR=0.53, 0.33-0.84) and ferritin (IRR=1.26, 1.05-1.51) were significantly associated with TB after adjusting for TB susceptibility factors. While genotype associations were not statistically significant, SLC11A1 associations replicated similar directions as reported in HIV-seronegative meta-analyses. Conclusions Evidence of host iron redistribution at HIV diagnosis was associated with incident TB, and genetic influences on iron homeostasis may be involved. Low hemoglobin was associated with subsequent diagnosis of TB, but when considered in combination with additional iron status biomarkers, the collective findings point to a mechanism whereby anemia and iron redistribution are likely due to viral and/or bacteria-driven processes and the host immune response to infection. As a result, iron supplementation may not be efficacious or safe under these circumstances. Clinical and nutritional management of HIV and Mycobacterium tuberculosis co-infected individuals, especially in regions where food insecurity and malnutrition co-exist, may be further improved when the iron-related TB risk factors identified here are better understood and managed to favor host rather than pathogen outcomes. PMID:23360117

Examination of immune parameters and host-resistance mechanisms in B6C3F1 mice following adult exposure to 2,3,7,8-tetrachlorodibenzo-'p'-dioxin

DOE Office of Scientific and Technical Information (OSTI.GOV)

House, R.V.; Lauer, L.D.; Murray, M.J.

1990-01-01

Adult female B6C3F1 mice were given a single IP dose of 0, 0.1, 1.0, or 10.0 micrograms/kg TCDD and examined for immune function and host resistance seven to ten days later. Exposure to TCDD resulted in a significant dose-related decrease in induction of both IgM and IgG antibody-forming cells. The suppression was noted for both T-dependent and T-independent antigens. TCDD at a dosage of 10 micrograms/kg was shown to suppress production of viral hemagglutinin. In contrast, TCDD exposure had no significant effect on natural killer cell function, production of interferon, or various parameters of macrophage function. Host resistance assessment revealedmore » a significant increase in susceptibility to fatal infection with influenza virus, but no significant alteration in susceptibility to infection with the bacterium Listeria monocytogenes.« less

The Course of Colonization of Two Different Vitis Genotypes by Plasmopara viticola Indicates Compatible and Incompatible Host-Pathogen Interactions.

PubMed

Unger, Sabine; Büche, Claudia; Boso, Susana; Kassemeyer, Hanns-Heinz

2007-07-01

ABSTRACT The course of colonization of leaf mesophyll by the causal agent of grapevine downy mildew, Plasmopara viticola, in a susceptible and a resistant grapevine genotype was examined in order to characterize the development of the pathogen in compatible and incompatible host-pathogen interactions. Within a few hours after inoculation, the pathogen was established in the susceptible Vitis vinifera cv. Müller-Thurgau and formed primary hyphae with a first haustorium. No further development occurred in the following 10 to 18 h. The next step, in which the hyphae grew and branched to colonize the intercellular space of the host tissue, was observed 1.5 days after inoculation. After 3 days, the intercostal fields were entirely filled with mycelium and sporulation was abundant under favorable environmental conditions. The first infection steps were essentially the same in the resistant V. rupestris. However, the invasive growth of P. viticola was delayed, and further development ceased before the intercostal fields were filled with mycelium.

Yeast casein kinase 2 governs morphology, biofilm formation, cell wall integrity, and host cell damage of Candida albicans.

PubMed

Jung, Sook-In; Rodriguez, Natalie; Irrizary, Jihyun; Liboro, Karl; Bogarin, Thania; Macias, Marlene; Eivers, Edward; Porter, Edith; Filler, Scott G; Park, Hyunsook

2017-01-01

The regulatory networks governing morphogenesis of a pleomorphic fungus, Candida albicans are extremely complex and remain to be completely elucidated. This study investigated the function of C. albicans yeast casein kinase 2 (CaYck2p). The yck2Δ/yck2Δ strain displayed constitutive pseudohyphae in both yeast and hyphal growth conditions, and formed enhanced biofilm under non-biofilm inducing condition. This finding was further supported by gene expression analysis of the yck2Δ/yck2Δ strain which showed significant upregulation of UME6, a key transcriptional regulator of hyphal transition and biofilm formation, and cell wall protein genes ALS3, HWP1, and SUN41, all of which are associated with morphogenesis and biofilm architecture. The yck2Δ/yck2Δ strain was hypersensitive to cell wall damaging agents and had increased compensatory chitin deposition in the cell wall accompanied by an upregulation of the expression of the chitin synthase genes, CHS2, CHS3, and CHS8. Absence of CaYck2p also affected fungal-host interaction; the yck2Δ/yck2Δ strain had significantly reduced ability to damage host cells. However, the yck2Δ/yck2Δ strain had wild-type susceptibility to cyclosporine and FK506, suggesting that CaYck2p functions independently from the Ca+/calcineurin pathway. Thus, in C. albicans, Yck2p is a multifunctional kinase that governs morphogenesis, biofilm formation, cell wall integrity, and host cell interactions.

Transmission or Within-Host Dynamics Driving Pulses of Zoonotic Viruses in Reservoir–Host Populations

PubMed Central

Plowright, Raina K.; Peel, Alison J.; Streicker, Daniel G.; Gilbert, Amy T.; McCallum, Hamish; Wood, James; Baker, Michelle L.; Restif, Olivier

2016-01-01

Progress in combatting zoonoses that emerge from wildlife is often constrained by limited knowledge of the biology of pathogens within reservoir hosts. We focus on the host–pathogen dynamics of four emerging viruses associated with bats: Hendra, Nipah, Ebola, and Marburg viruses. Spillover of bat infections to humans and domestic animals often coincides with pulses of viral excretion within bat populations, but the mechanisms driving such pulses are unclear. Three hypotheses dominate current research on these emerging bat infections. First, pulses of viral excretion could reflect seasonal epidemic cycles driven by natural variations in population densities and contact rates among hosts. If lifelong immunity follows recovery, viruses may disappear locally but persist globally through migration; in either case, new outbreaks occur once births replenish the susceptible pool. Second, epidemic cycles could be the result of waning immunity within bats, allowing local circulation of viruses through oscillating herd immunity. Third, pulses could be generated by episodic shedding from persistently infected bats through a combination of physiological and ecological factors. The three scenarios can yield similar patterns in epidemiological surveys, but strategies to predict or manage spillover risk resulting from each scenario will be different. We outline an agenda for research on viruses emerging from bats that would allow for differentiation among the scenarios and inform development of evidence-based interventions to limit threats to human and animal health. These concepts and methods are applicable to a wide range of pathogens that affect humans, domestic animals, and wildlife. PMID:27489944

Inverse gene-for-gene interactions contribute additively to tan spot susceptibility in wheat.

PubMed

Liu, Zhaohui; Zurn, Jason D; Kariyawasam, Gayan; Faris, Justin D; Shi, Gongjun; Hansen, Jana; Rasmussen, Jack B; Acevedo, Maricelis

2017-06-01

Tan spot susceptibility is conferred by multiple interactions of necrotrophic effector and host sensitivity genes. Tan spot of wheat, caused by Pyrenophora tritici-repentis, is an important disease in almost all wheat-growing areas of the world. The disease system is known to involve at least three fungal-produced necrotrophic effectors (NEs) that interact with the corresponding host sensitivity (S) genes in an inverse gene-for-gene manner to induce disease. However, it is unknown if the effects of these NE-S gene interactions contribute additively to the development of tan spot. In this work, we conducted disease evaluations using different races and quantitative trait loci (QTL) analysis in a wheat recombinant inbred line (RIL) population derived from a cross between two susceptible genotypes, LMPG-6 and PI 626573. The two parental lines each harbored a single known NE sensitivity gene with LMPG-6 having the Ptr ToxC sensitivity gene Tsc1 and PI 626573 having the Ptr ToxA sensitivity gene Tsn1. Transgressive segregation was observed in the population for all races. QTL mapping revealed that both loci (Tsn1 and Tsc1) were significantly associated with susceptibility to race 1 isolates, which produce both Ptr ToxA and Ptr ToxC, and the two genes contributed additively to tan spot susceptibility. For isolates of races 2 and 3, which produce only Ptr ToxA and Ptr ToxC, only Tsn1 and Tsc1 were associated with tan spot susceptibility, respectively. This work clearly demonstrates that tan spot susceptibility in this population is due primarily to two NE-S interactions. Breeders should remove both sensitivity genes from wheat lines to obtain high levels of tan spot resistance.

Dual RNA-seq of the plant pathogen phytophthora ramorum and its tanoak host

Treesearch

Katherine J. Hayden; Matteo Garbelotto; Brian J. Knaus; Richard C. Cronn; Hardeep Rai; Jessica W. Wright

2014-01-01

Emergent diseases are an ever-increasing threat to forests and forest ecosystems and necessitate the development of research tools for species that often may have few preexisting resources. We sequenced the mRNA expressed by the sudden oak death pathogen Phytophthora ramorum and its most susceptible forest host, tanoak, within the same tissue at two time points after...

An antibiotic-altered microbiota provides fuel for the enteric foe.

PubMed

Stiemsma, Leah T; Turvey, Stuart E; Finlay, Brett B

2014-01-01

Antibiotic therapies disrupt the intestinal microbiota and render the host susceptible to enteric infections. A recent report by Ng et al. explores the ability of two intestinal pathogens (Salmonella enterica serovar Typhimurium and Clostridium difficile) to use this disruption to their advantage and consume host carbohydrates that would otherwise be unavailable in the presence of a normal gut microbiota.

Antimicrobial susceptibility of Clostridium perfringens isolates of bovine, chicken, porcine, and turkey origin from Ontario.

PubMed

Slavić, Durđa; Boerlin, Patrick; Fabri, Marta; Klotins, Kim C; Zoethout, Jennifer K; Weir, Pat E; Bateman, Debbie

2011-04-01

Antimicrobial susceptibilities and toxin types were determined for 275 Clostridium perfringens isolates collected in Ontario in the spring of 2005. Minimal inhibitory concentrations (MICs) of C. perfringens isolates for 12 antimicrobials used in therapy, prophylaxis, and/or growth promotion of cattle (n = 40), swine (n = 75), turkeys (n = 50), and chickens (n = 100) were determined using the microbroth dilution method. Statistical analyses and MIC distributions showed reduced susceptibility to bacitracin, clindamycin, erythromycin, florfenicol, and tetracycline for some isolates. Reduced susceptibility to bacitracin was identified in chicken (64%) and turkey (60%) isolates. Swine isolates had predominantly reduced susceptibility to clindamycin (28%) and erythromycin (31%), whereas bovine isolates had reduced susceptibility to clindamycin (10%) and florfenicol (10%). Reduced susceptibility to tetracycline was spread across all species. No clear reduced susceptibility, but elevated MIC(50) for virginiamycin was found in chicken isolates in comparison with isolates from other species. Toxin typing revealed that C. perfringens type A is the dominant toxin type isolated in this study across all 4 host species.

Pathogen transmission at stage-structured infectious patches: Killers and vaccinators.

PubMed

Caraco, Thomas; Turner, Wendy C

2018-01-07

Spatial localization of an obligate-killing, free-living pathogen generates a landscape of patches where new infections occur. As an infectious patch ages, both pathogen exposure at the patch and the probability of lethal infection following exposure can decline. We model stage-structured infectious patches, where non-lethal exposure can naturally "vaccinate" susceptible hosts. We let the between-stage difference in pathogen transmission, and then the between-stage difference in patch virulence, increase independently of other parameters. Effects of increasing either between-stage difference (about a fixed mean) depend on the probability a patch transitions from the first to second stage, i.e., the chance that a killer patch becomes a vaccinator. For slower stage transition, greater between-stage differences decreased susceptibles, and increased both resistant-host and killer patch numbers. But our examples reveal that each effect can be reversed when between-stage transition occurs more rapidly. For sufficiently rapid stage transition, increased between-stage virulence differences can lead to pathogen extinction, and leave the host at disease-free equilibrium. The model's general significance lies in demonstrating how epidemiological variation among sites of environmentally transmitted disease can strongly govern host-parasite dynamics. Copyright © 2017 Elsevier Ltd. All rights reserved.

Deciphering the genetic control of gene expression following Mycobacterium leprae antigen stimulation.

PubMed

Manry, Jérémy; Nédélec, Yohann; Fava, Vinicius M; Cobat, Aurélie; Orlova, Marianna; Thuc, Nguyen Van; Thai, Vu Hong; Laval, Guillaume; Barreiro, Luis B; Schurr, Erwin

2017-08-01

Leprosy is a human infectious disease caused by Mycobacterium leprae. A strong host genetic contribution to leprosy susceptibility is well established. However, the modulation of the transcriptional response to infection and the mechanism(s) of disease control are poorly understood. To address this gap in knowledge of leprosy pathogenicity, we conducted a genome-wide search for expression quantitative trait loci (eQTL) that are associated with transcript variation before and after stimulation with M. leprae sonicate in whole blood cells. We show that M. leprae antigen stimulation mainly triggered the upregulation of immune related genes and that a substantial proportion of the differential gene expression is genetically controlled. Indeed, using stringent criteria, we identified 318 genes displaying cis-eQTL at an FDR of 0.01, including 66 genes displaying response-eQTL (reQTL), i.e. cis-eQTL that showed significant evidence for interaction with the M. leprae stimulus. Such reQTL correspond to regulatory variations that affect the interaction between human whole blood cells and M. leprae sonicate and, thus, likely between the human host and M. leprae bacilli. We found that reQTL were significantly enriched among binding sites of transcription factors that are activated in response to infection, and that they were enriched among single nucleotide polymorphisms (SNPs) associated with susceptibility to leprosy per se and Type-I Reaction, and seven of them have been targeted by recent positive selection. Our study suggested that natural selection shaped our genomic diversity to face pathogen exposure including M. leprae infection.

Dengue fever virus in Pakistan: effects of seasonal pattern and temperature change on distribution of vector and virus.

PubMed

Bostan, Nazish; Javed, Sundus; Nabgha-E-Amen; Eqani, Syed Ali Musstjab Akber Shah; Tahir, Faheem; Bokhari, Habib

2017-01-01

Dengue fever is regarded as one of the most prominent emerging arboviral infections in Pakistan since its first epidemic almost 2 decades ago. Interplay between potential vectors, susceptible host, and lax environmental conditions may promote the infection, leading to an epidemic. These factors may indeed have played a major role in the spread of the disease in the country, which was limited to Karachi till 2006. With recent natural disasters such as the earthquake in 2005 and flooding in 2010, 2011 and 2012, numbers of vector-borne diseases and outbreaks including dengue fever are on the rise in Pakistan. Therefore, it is a major concern for health sector workers and of utmost importance to have some understanding of the factors affecting disease outbreak for better risk assessment in the region. In the following report we review the climatic as well as host- and vector-associated factors involved in the outbreak of dengue epidemics in Pakistan and highlight high-risk zones in the country. Copyright © 2016 John Wiley & Sons, Ltd.

Macrophage migration inhibitory factor deficiency is associated with impaired killing of gram-negative bacteria by macrophages and increased susceptibility to Klebsiella pneumoniae sepsis.

PubMed

Roger, Thierry; Delaloye, Julie; Chanson, Anne-Laure; Giddey, Marlyse; Le Roy, Didier; Calandra, Thierry

2013-01-15

The cytokine macrophage migration inhibitory factor (MIF) is an important component of the early proinflammatory response of the innate immune system. However, the antimicrobial defense mechanisms mediated by MIF remain fairly mysterious. In the present study, we examined whether MIF controls bacterial uptake and clearance by professional phagocytes, using wild-type and MIF-deficient macrophages. MIF deficiency did not affect bacterial phagocytosis, but it strongly impaired the killing of gram-negative bacteria by macrophages and host defenses against gram-negative bacterial infection, as shown by increased mortality in a Klebsiella pneumonia model. Consistent with MIF's regulatory role of Toll-like 4 expression in macrophages, MIF-deficient cells stimulated with lipopolysaccharide or Escherichia coli exhibited reduced nuclear factor κB activity and tumor necrosis factor (TNF) production. Addition of recombinant MIF or TNF corrected the killing defect of MIF-deficient macrophages. Together, these data show that MIF is a key mediator of host responses against gram-negative bacteria, acting in part via a modulation of bacterial killing by macrophages.

CENTRAL NERVOUS SYSTEM INFECTION DURING IMMUNOSUPPRESSION

PubMed Central

Zunt, Joseph R.

2009-01-01

The central nervous system (CNS) is susceptible to bacterial, viral, and fungal infections. Suppression of the immune system by human immunodeficiency virus (HIV) infection or immunosuppressive therapy after transplantation increases susceptibility to CNS infection and modifies the presentation, diagnosis, and recommended treatment of various CNS infections. This chapter discusses how suppression of the host immune status modifies the presentation, diagnosis, and treatment of selected CNS infections. PMID:11754299

The role of Candida albicans AP-1 protein against host derived ROS in in vivo models of infection.

PubMed

Jain, Charu; Pastor, Kelly; Gonzalez, Arely Y; Lorenz, Michael C; Rao, Reeta P

2013-01-01

Candida albicans is a major fungal pathogen of humans, causing mucosal infections that are difficult to eliminate and systemic infections that are often lethal primarily due to defects in the host's innate status. Here we demonstrate the utility of Caenorhabditis elegans, a model host to study innate immunity, by exploring the role of reactive oxygen species (ROS) as a critical innate response against C. albicans infections. Much like a human host, the nematode's innate immune response is activated to produce ROS in response to fungal infection. We use the C. albicans cap1 mutant, which is susceptible to ROS, as a tool to dissect this physiological innate immune response and show that cap1 mutants fail to cause disease and death, except in bli-3 mutant worms that are unable to produce ROS because of a defective NADPH oxidase. We further validate the ROS-mediated host defense mechanism in mammalian phagocytes by demonstrating that chemical inhibition of the NADPH oxidase in cultured macrophages enables the otherwise susceptible cap1 mutant to resists ROS-mediated phagolysis. Loss of CAP1 confers minimal attenuation of virulence in a disseminated mouse model, suggesting that CAP1-independent mechanisms contribute to pathogen survival in vivo. Our findings underscore a central theme in the process of infection-the intricate balance between the virulence strategies employed by C. albicans and the host's innate immune system and validates C. elegans as a simple model host to dissect this balance at the molecular level.

Potential Information Loss Due to Categorization of Minimum Inhibitory Concentration Frequency Distributions.

PubMed

Mazloom, Reza; Jaberi-Douraki, Majid; Comer, Jeffrey R; Volkova, Victoriya

2018-01-01

A bacterial isolate's susceptibility to antimicrobial is expressed as the lowest drug concentration inhibiting its visible growth, termed minimum inhibitory concentration (MIC). The susceptibilities of isolates from a host population at a particular time vary, with isolates with specific MICs present at different frequencies. Currently, for either clinical or monitoring purposes, an isolate is most often categorized as Susceptible, Intermediate, or Resistant to the antimicrobial by comparing its MIC to a breakpoint value. Such data categorizations are known in statistics to cause information loss compared to analyzing the underlying frequency distributions. The U.S. National Antimicrobial Resistance Monitoring System (NARMS) includes foodborne bacteria at the food animal processing and retail product points. The breakpoints used to interpret the MIC values for foodborne bacteria are those relevant to clinical treatments by the antimicrobials in humans in whom the isolates were to cause infection. However, conceptually different objectives arise when inference is sought concerning changes in susceptibility/resistance across isolates of a bacterial species in host populations among different sampling points or times. For the NARMS 1996-2013 data for animal processing and retail, we determined the fraction of comparisons of susceptibility/resistance to 44 antimicrobial drugs of twelve classes of a bacterial species in a given animal host or product population where there was a significant change in the MIC frequency distributions between consecutive years or the two sampling points, while the categorization-based analyses concluded no change. The categorization-based analyses missed significant changes in 54% of the year-to-year comparisons and in 71% of the slaughter-to-retail within-year comparisons. Hence, analyses using the breakpoint-based categorizations of the MIC data may miss significant developments in the resistance distributions between the sampling points or times. Methods considering the MIC frequency distributions in their entirety may be superior for epidemiological analyses of resistance dynamics in populations.

Through Ageing, and Beyond: Gut Microbiota and Inflammatory Status in Seniors and Centenarians

PubMed Central

Biagi, Elena; Nylund, Lotta; Candela, Marco; Ostan, Rita; Bucci, Laura; Pini, Elisa; Nikkïla, Janne; Monti, Daniela; Satokari, Reetta; Franceschi, Claudio; Brigidi, Patrizia; De Vos, Willem

2010-01-01

Background Age-related physiological changes in the gastrointestinal tract, as well as modifications in lifestyle, nutritional behaviour, and functionality of the host immune system, inevitably affect the gut microbiota, resulting in a greater susceptibility to infections. Methodology/Principal Findings By using the Human Intestinal Tract Chip (HITChip) and quantitative PCR of 16S rRNA genes of Bacteria and Archaea, we explored the age-related differences in the gut microbiota composition among young adults, elderly, and centenarians, i.e subjects who reached the extreme limits of the human lifespan, living for over 100 years. We observed that the microbial composition and diversity of the gut ecosystem of young adults and seventy-years old people is highly similar but differs significantly from that of the centenarians. After 100 years of symbiotic association with the human host, the microbiota is characterized by a rearrangement in the Firmicutes population and an enrichment in facultative anaerobes, notably pathobionts. The presence of such a compromised microbiota in the centenarians is associated with an increased inflammatory status, also known as inflammageing, as determined by a range of peripheral blood inflammatory markers. This may be explained by a remodelling of the centenarians' microbiota, with a marked decrease in Faecalibacterium prauznitzii and relatives, symbiotic species with reported anti-inflammatory properties. As signature bacteria of the long life we identified specifically Eubacterium limosum and relatives that were more than ten-fold increased in the centenarians. Conclusions/Significance We provide evidence for the fact that the ageing process deeply affects the structure of the human gut microbiota, as well as its homeostasis with the host's immune system. Because of its crucial role in the host physiology and health status, age-related differences in the gut microbiota composition may be related to the progression of diseases and frailty in the elderly population. PMID:20498852

Diarrhea as a cause of mortality in a mouse model of infectious colitis

PubMed Central

Borenshtein, Diana; Fry, Rebecca C; Groff, Elizabeth B; Nambiar, Prashant R; Carey, Vincent J; Fox, James G; Schauer, David B

2008-01-01

Background Comparative characterization of genome-wide transcriptional changes during infection can help elucidate the mechanisms underlying host susceptibility. In this study, transcriptional profiling of the mouse colon was carried out in two cognate lines of mice that differ in their response to Citrobacter rodentium infection; susceptible inbred FVB/N and resistant outbred Swiss Webster mice. Gene expression in the distal colon was determined prior to infection, and at four and nine days post-inoculation using a whole mouse genome Affymetrix array. Results Computational analysis identified 462 probe sets more than 2-fold differentially expressed between uninoculated resistant and susceptible mice. In response to C. rodentium infection, 5,123 probe sets were differentially expressed in one or both lines of mice. Microarray data were validated by quantitative real-time RT-PCR for 35 selected genes and were found to have a 94% concordance rate. Transcripts represented by 1,547 probe sets were differentially expressed between susceptible and resistant mice regardless of infection status, a host effect. Genes associated with transport were over-represented to a greater extent than even immune response-related genes. Electrolyte analysis revealed reduction in serum levels of chloride and sodium in susceptible animals. Conclusion The results support the hypothesis that mortality in C. rodentium-infected susceptible mice is associated with impaired intestinal ion transport and development of fatal fluid loss and dehydration. These studies contribute to our understanding of the pathogenesis of C. rodentium and suggest novel strategies for the prevention and treatment of diarrhea associated with intestinal bacterial infections. PMID:18680595

Susceptibility of human and avian influenza viruses to human and chicken saliva.

PubMed

Limsuwat, Nattavatchara; Suptawiwat, Ornpreya; Boonarkart, Chompunuch; Puthavathana, Pilaipan; Auewarakul, Prasert; Wiriyarat, Witthawat

2014-05-01

Oral cavity can be an entry site of influenza virus and saliva is known to contain innate soluble anti-influenza factors. Influenza strains were shown to vary in their susceptibility to those antiviral factors. Whether the susceptibility to the saliva antiviral factors plays any role in the host species specificity of influenza viruses is not known. In this study, the antiviral activity of human and chicken saliva against human and the H5N1 avian influenza viruses were investigated by hemagglutination inhibition (HI) and neutralization (NT) assays. In comparison to human influenza viruses, H5N1 isolates showed reduced susceptibility to human saliva as measured by HI and NT assays. Interestingly, an H5N1 isolate that bind to both α2,3- and α2,6-linked sialic acid showed much higher HI titers with human saliva, suggesting that the susceptibility profile was linked to the receptor-binding preference and the presence of α2,6-linked sialic in human saliva. On the other hand, the H5N1 isolates showed increased HI titers but reduced NT titers to chicken saliva as compared to human influenza isolates. The human salivary antiviral components were characterized by testing the sensitivity to heat, receptor destroying enzyme (RDE), CaCl₂/EDTA dependence, and inhibition by mannan, and shown to be α- and γ-inhibitors. These data suggest that the H5N1 HPAI influenza virus had distinctive susceptibility patterns to human and chicken saliva, which may play some roles in its infectivity and transmissibility in these hosts. © 2013 Wiley Periodicals, Inc.

EXPERIMENTAL SUBCUTANEOUS CYSTICERCOSIS BY Taenia crassiceps IN BALB/c AND C57BL/6 MICE

PubMed Central

PEREIRA, Íria Márcia; LIMA, Sarah Buzaim; FREITAS, Aline de Araújo; VINAUD, Marina Clare; JUNIOR, Ruy de Souza LINO

2016-01-01

SUMMARY Human cysticercosis is one of the most severe parasitic infections affecting tissues. Experimental models are needed to understand the host-parasite dynamics involved throughout the course of the infection. The subcutaneous experimental model is the closest to what is observed in human cysticercosis that does not affect the central nervous system. The aim of this study was to evaluate macroscopically and microscopically the experimental subcutaneous cysticercosis caused by Taenia crassiceps cysticerci in BALB/c and C57BL/6 mice. Animals were inoculated in the dorsal subcutaneous region and macroscopic and microscopic aspects of the inflammatory process in the host-parasite interface were evaluated until 90 days after the inoculation (DAI). All the infected animals presented vesicles containing cysticerci in the inoculation site, which was translucent at 7 DAI and then remained opaque throughout the experimental days. The microscopic analysis showed granulation tissue in BALB/c mice since the acute phase of infection evolving to chronicity without cure, presenting 80% of larval stage cysticerci at 90 DAI. While C57BL/6 mice presented 67% of final stage cysticerci at 90 DAI, the parasites were surrounded by neutrophils evolving to the infection control. It is possible to conclude that the genetic features of susceptibility (BALB/c) or resistance (C57BL/6) were confirmed in an experimental subcutaneous model of cysticercosis. PMID:27410915

EXPERIMENTAL SUBCUTANEOUS CYSTICERCOSIS BY Taenia crassiceps IN BALB/c AND C57BL/6 MICE.

PubMed

Pereira, Íria Márcia; Lima, Sarah Buzaim; Freitas, Aline de Araújo; Vinaud, Marina Clare; Junior, Ruy de Souza Lino

2016-07-11

Human cysticercosis is one of the most severe parasitic infections affecting tissues. Experimental models are needed to understand the host-parasite dynamics involved throughout the course of the infection. The subcutaneous experimental model is the closest to what is observed in human cysticercosis that does not affect the central nervous system. The aim of this study was to evaluate macroscopically and microscopically the experimental subcutaneous cysticercosis caused by Taenia crassiceps cysticerci in BALB/c and C57BL/6 mice. Animals were inoculated in the dorsal subcutaneous region and macroscopic and microscopic aspects of the inflammatory process in the host-parasite interface were evaluated until 90 days after the inoculation (DAI). All the infected animals presented vesicles containing cysticerci in the inoculation site, which was translucent at 7 DAI and then remained opaque throughout the experimental days. The microscopic analysis showed granulation tissue in BALB/c mice since the acute phase of infection evolving to chronicity without cure, presenting 80% of larval stage cysticerci at 90 DAI. While C57BL/6 mice presented 67% of final stage cysticerci at 90 DAI, the parasites were surrounded by neutrophils evolving to the infection control. It is possible to conclude that the genetic features of susceptibility (BALB/c) or resistance (C57BL/6) were confirmed in an experimental subcutaneous model of cysticercosis.

Silicon influence on resistance induction against Bemisia tabaci biotype B (Genn.) (Hemiptera: Aleyrodidae) and on vegetative development in two soybean cultivars.

PubMed

Ferreira, R S; Moraes, J C; Antunes, C S

2011-01-01

The potential of populations of Bemisia tabaci (Genn.) to become resistant to insecticides has stimulated research into alternative tactics of integrated pest management such as the induction of host-plant resistance. Recent data have shown that silicon can increase the degree of resistance of host plants to insect pests. Therefore the aim of our work was to study the effects of silicon application on the vegetative development of soybean plants and on the induction of resistance to the silverleaf whitefly, B. tabaci biotype B. We performed choice and no-choice tests of oviposition preference on two soybean cultivars, IAC-19 (moderately resistant to B. tabaci biotype B) and MONSOY-8001 (susceptible), with and without application of silicon. Silicon did not affect silverleaf whitefly oviposition preferences, but caused significant mortality in nymphs. Thus, silicon increased the degree of resistance to silverleaf whitefly. Silicon decreased the production of phenolic compounds, but did not affect lignin production. However, when applied to cultivar IAC-19, it increased the production of non-protein organic nitrogen. Silicon had no effect on the vegetative development of soybean plants, but it increased the degree of resistance to the silverleaf whitefly. We conclude that silicon applications combined with cultivar IAC-19 can significantly decrease silverleaf whitefly populations, having a positive impact both on the soybean plant and on the environment.

Fatal disease and demographic Allee effect: population persistence and extinction.

PubMed

Friedman, Avner; Yakubu, Abdul-Aziz

2012-01-01

If a healthy stable host population at the disease-free equilibrium is subject to the Allee effect, can a small number of infected individuals with a fatal disease cause the host population to go extinct? That is, does the Allee effect matter at high densities? To answer this question, we use a susceptible-infected epidemic model to obtain model parameters that lead to host population persistence (with or without infected individuals) and to host extinction. We prove that the presence of an Allee effect in host demographics matters even at large population densities. We show that a small perturbation to the disease-free equilibrium can eventually lead to host population extinction. In addition, we prove that additional deaths due to a fatal infectious disease effectively increase the Allee threshold of the host population demographics.