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1

Altitudinal variation in haemosporidian parasite distribution in great tit populations  

PubMed Central

Background One of the major issues concerning disease ecology and conservation is knowledge of the factors that influence the distribution of parasites and consequently disease outbreaks. This study aimed to investigate avian haemosporidian composition and the distribution of these parasites in three altitudinally separated great tit (Parus major) populations in western Switzerland over a three-year period. The objectives were to determine the lineage diversity of parasites occuring across the study populations and to investigate whether altitudinal gradients govern the distribution of haemosporidian parasites by lineage. Methods In this study molecular approaches (PCR and sequencing) were used to detect avian blood parasites (Plasmodium sp., Haemoproteus sp. and Leucocytozoon sp.) in populations of adult great tits caught on their nests during three consecutive breeding seasons. Results High levels of parasite prevalence (88-96%) were found across all of the study populations with no significant altitude effect. Altitude did, however, govern the distribution of parasites belonging to different genera, with Plasmodium parasites being more prevalent at lower altitudes, Leucocytozoon parasites more at high altitude and Haemoproteus parasite prevalence increasing with altitude. A total of 27 haemosporidian parasite lineages were recorded across all study sites, with diversity showing a positive correlation to altitude. Parasites belonging to lineage SGS1 (P. relictum) and PARUS4 and PARUS19 (Leucocytozoon sp.) dominated lower altitudes. SW2 (P. polare) was the second most prevalent lineage of parasite detected overall and these parasites were responsible for 68% of infections at intermediate altitude, but were only documented at this one study site. Conclusions Avian haemosporidian parasites are not homogeneously distributed across host populations, but differ by altitude. This difference is most probably brought about by environmental factors influencing vector prevalence and distribution. The high occurrence of co-infection by different genera of parasites might have pronounced effects on host fitness and should consequently be investigated more rigorously. PMID:23648230

2013-01-01

2

Molecular characterization of haemosporidian parasites from kites of the genus Milvus (Aves: Accipitridae).  

PubMed

Despite the ecological significance and appeal of birds of prey, many aspects of their biology remain poorly known, including the diversity of parasites infecting them in the wild. We studied the diversity and prevalence of haemosporidian parasites infecting the two species of kites of the genus Milvus, aiming to describe the phylogenetic relationships among them and with other haemosporidians, as well as their distribution in the two host species. Black kites, Milvus migrans, harboured a more diverse community of parasites, including three haplotypes of each of the three genera Plasmodium, Haemoproteus and Leucocytozoon, which also occurred at a higher prevalence than in red kites. In red kites, Milvus milvus only three haplotypes of Leucocytozoon were found. Kite parasites were not closely related to one another nor were they kite-specific: their diversity spanned various branches of the haemosporidian phylogenetic tree, and their closest relatives were found in other species (including various avian orders), although some Leucocytozoon and Haemoproteus haplotypes clustered within apparently raptor-specific parasite clades. Remarkably, Plasmodium spp. and Haemoproteus spp. infected adult black kites only, an observation which supports the hypothesis that they are transmitted at the African wintering grounds, while Leucocytozoon spp. is putatively transmitted only in Europe. Intercontinental migration of the black kite might explain the divergence of parasite diversity between these two sister species. PMID:23376529

Pérez-Rodríguez, Antón; de la Puente, Javier; Onrubia, Alejandro; Pérez-Tris, Javier

2013-04-01

3

Different meal, same flavor: cospeciation and host switching of haemosporidian parasites in some non-passerine birds  

PubMed Central

Background Previous studies have shown that haemosporidian parasites (Haemoproteus (Parahaemoproteus) and Plasmodium) infecting passerine birds have an evolutionary history of host switching with little cospeciation, in particular at low taxonomic levels (e.g., below the family level), which is suggested as the main speciation mechanism of this group of parasites. Recent studies have characterized diverse clades of haemosporidian parasites (H. (Haemoproteus) and H. (Parahaemoproteus)) infecting non-passerine birds (e.g., Columbiformes, Pelecaniiformes). Here, we explore the cospeciation history of H. (Haemoproteus) and H. (Parahaemoproteus) parasites with their non-passerine hosts. Methods We sequenced the mtDNA cyt b gene of both haemosporidian parasites and their avian non-passerine hosts. We built Bayesian phylogenetic hypotheses and created concensus phylograms that were subsequently used to conduct cospeciation analyses. We used both a global cospeciation test, PACo, and an event-cost algorithm implemented in CoRe-PA. Results The global test suggests that H. (Haemoproteus) and H. (Parahaemoproteus) parasites have a diversification history dominated by cospeciation events particularly at the family level. Host-parasite links from the PACo analysis show that host switching events are common within families (i.e., among genera and among species within genera), and occasionally across different orders (e.g., Columbiformes to Pelecaniiformes). Event-cost analyses show that haemosporidian coevolutionary history is dominated by host switching and some codivergence, but with duplication events also present. Genetic lineages unique to raptor species (e.g., FALC11) commonly switch between Falconiformes and Strigiformes. Conclusions Our results corroborate previous findings that have detected a global cospeciation signal at the family taxonomic level, and they also support a history of frequent switching closer to the tips of the host phylogeny, which seems to be the main diversification mechanism of haemosporidians. Such dynamic host-parasite associations are relevant to the epidemiology of emerging diseases because low parasite host specificity is a prerequisite for the emergence of novel diseases. The evidence on host distributions suggests that haemosporidian parasites have the potential to rapidly develop novel host-associations. This pattern has also been recorded in fish-monogenean interactions, suggesting a general diversification mechanism for parasites when host choice is not restricted by ecological barriers. PMID:24957563

2014-01-01

4

SPATIAL VARIATION OF HAEMOSPORIDIAN PARASITE INFECTION IN AFRICAN RAINFOREST BIRD SPECIES  

E-print Network

., as well as the number of individuals with co-infections, varied significantly among the sites infected with Haemoproteus spp. were found only at 1 site. Furthermore, for both bird speciesSPATIAL VARIATION OF HAEMOSPORIDIAN PARASITE INFECTION IN AFRICAN RAINFOREST BIRD SPECIES Claire

Sehgal, Ravinder

5

Prevalence and Lineage Diversity of Avian Haemosporidians from Three Distinct Cerrado Habitats in Brazil  

Microsoft Academic Search

Habitat alteration can disrupt host–parasite interactions and lead to the emergence of new diseases in wild populations. The cerrado habitat of Brazil is being fragmented and degraded rapidly by agriculture and urbanization. We screened 676 wild birds from three habitats (intact cerrado, disturbed cerrado and transition area Amazonian rainforest-cerrado) for the presence of haemosporidian parasites (Plasmodium and Haemoproteus) to determine

Nayara O. Belo; Renato T. Pinheiro; Elivânia S. Reis; Robert E. Ricklefs; Érika M. Braga; Sharon Gursky-Doyen

2011-01-01

6

Multiple lineages of Avian malaria parasites (Plasmodium) in the Galapagos Islands and evidence for arrival via migratory birds.  

PubMed

Haemosporidian parasites in the genus Plasmodium were recently detected through molecular screening in the Galapagos Penguin (Spheniscus mendiculus). We summarized results of an archipelago-wide screen of 3726 endemic birds representing 22 species for Plasmodium spp. through a combination of molecular and microscopy techniques. Three additional Plasmodium lineages were present in Galapagos. Lineage A-infected penguins, Yellow Warblers (Setophaga petechia aureola), and one Medium Ground Finch (Geospiza fortis) and was detected at multiple sites in multiple years [corrected]. The other 3 lineages were each detected at one site and at one time; apparently, they were transient infections of parasites not established on the archipelago. No gametocytes were found in blood smears of infected individuals; thus, endemic Galapagos birds may be dead-end hosts for these Plasmodium lineages. Determining when and how parasites and pathogens arrive in Galapagos is key to developing conservation strategies to prevent and mitigate the effects of introduced diseases. To assess the potential for Plasmodium parasites to arrive via migratory birds, we analyzed blood samples from 438 North American breeding Bobolinks (Dolichonyx oryzivorus), the only songbird that regularly migrates through Galapagos. Two of the ephemeral Plasmodium lineages (B and C) found in Galapagos birds matched parasite sequences from Bobolinks. Although this is not confirmation that Bobolinks are responsible for introducing these lineages, evidence points to higher potential arrival rates of avian pathogens than previously thought. Linajes Múltiples de Parásitos de Malaria Aviar (Plasmodium) en las Islas Galápagos y Evidencia de su Arribo por Medio de Aves Migratorias. PMID:24033638

Levin, I I; Zwiers, P; Deem, S L; Geest, E A; Higashiguchi, J M; Iezhova, T A; Jiménez-Uzcátegui, G; Kim, D H; Morton, J P; Perlut, N G; Renfrew, R B; Sari, E H R; Valkiunas, G; Parker, P G

2013-12-01

7

Description of the first cryptic avian malaria parasite, Plasmodium homocircumflexum n. sp., with experimental data on its virulence and development in avian hosts and mosquitoes.  

PubMed

For over 100years studies on avian haemosporidian parasite species have relied on similarities in their morphology to establish a species concept. Some exceptional cases have also included information about the life cycle and sporogonic development. More than 50 avian Plasmodium spp. have now been described. However, PCR-based studies show a much broader diversity of haemosporidian parasites, indicating the possible existence of a diverse group of cryptic species. In the present study, using both similarity and phylogenetic species definition concepts, we believe that we report the first characterised cryptic speciation case of an avian Plasmodium parasite. We used sequence information on the mitochondrial cytochrome b gene and constructed phylogenies of identified Plasmodium spp. to define their position in the phylogenetic tree. After analysis of blood stages, the morphology of the parasite was shown to be identical to Plasmodium circumflexum. However, the geographic distribution of the new parasite, the phylogenetic information, as well as patterns of development of infection, indicate that this parasite differs from P. circumflexum. Plasmodium homocircumflexum n. sp. was described based on information about genetic differences from described lineages, phylogenetic position and biological characters. This parasite develops parasitemia in experimentally infected birds - the domestic canary Serinus canaria domestica, siskin Carduelis spinus and crossbill Loxia curvirostra. Anaemia caused by high parasitemia, as well as cerebral paralysis caused by exoerythrocytic stages in the brain, are the main reasons for mortality. Exoerythrocytic stages also form in other organs (heart, kidneys, liver, lungs, spleen, intestines and pectoral muscles). DNA amplification was unsuccessful from faecal samples of heavily infected birds. The sporogonic development initiates, but is abortive, at the oocyst stage in two common European mosquito species, Culex pipiens pipiens (forms pipiens and molestus) and Aedes vexans. Vectors of this Plasmodium sp. remain unknown. PMID:25449950

Palinauskas, Vaidas; Žiegyt?, Rita; Ilg?nas, Mikas; Iezhova, Tatjana A; Bernotien?, Rasa; Bolshakov, Casimir; Valki?nas, Gediminas

2015-01-01

8

Genome sequence of the human malaria parasite Plasmodium falciparum  

E-print Network

Genome sequence of the human malaria parasite Plasmodium falciparum Malcolm J. Gardner1 , Neil Hall ........................................................................................................................................................................................................................... The parasite Plasmodium falciparum is responsible for hundreds of millions of cases of malaria, and kills more of this intracellular parasite encodes fewer enzymes and transporters, but a large proportion of genes are devoted

Arnold, Jonathan

9

Translational control in Plasmodium and toxoplasma parasites.  

PubMed

The life cycles of apicomplexan parasites such as Plasmodium spp. and Toxoplasma gondii are complex, consisting of proliferative and latent stages within multiple hosts. Dramatic transformations take place during the cycles, and they demand precise control of gene expression at all levels, including translation. This review focuses on the mechanisms that regulate translational control in Plasmodium and Toxoplasma, with a particular emphasis on the phosphorylation of the ? subunit of eukaryotic translation initiation factor 2 (eIF2?). Phosphorylation of eIF2? (eIF2??P) is a conserved mechanism that eukaryotic cells use to repress global protein synthesis while enhancing gene-specific translation of a subset of mRNAs. Elevated levels of eIF2??P have been observed during latent stages in both Toxoplasma and Plasmodium, indicating that translational control plays a role in maintaining dormancy. Parasite-specific eIF2? kinases and phosphatases are also required for proper developmental transitions and adaptation to cellular stresses encountered during the life cycle. Identification of small-molecule inhibitors of apicomplexan eIF2? kinases may selectively interfere with parasite translational control and lead to the development of new therapies to treat malaria and toxoplasmosis. PMID:23243065

Zhang, Min; Joyce, Bradley R; Sullivan, William J; Nussenzweig, Victor

2013-02-01

10

Prevalence and Lineage Diversity of Avian Haemosporidians from Three Distinct Cerrado Habitats in Brazil  

PubMed Central

Habitat alteration can disrupt host–parasite interactions and lead to the emergence of new diseases in wild populations. The cerrado habitat of Brazil is being fragmented and degraded rapidly by agriculture and urbanization. We screened 676 wild birds from three habitats (intact cerrado, disturbed cerrado and transition area Amazonian rainforest-cerrado) for the presence of haemosporidian parasites (Plasmodium and Haemoproteus) to determine whether different habitats were associated with differences in the prevalence and diversity of infectious diseases in natural populations. Twenty one mitochondrial lineages, including 11 from Plasmodium and 10 from Haemoproteus were identified. Neither prevalence nor diversity of infections by Plasmodium spp. or Haemoproteus spp. differed significantly among the three habitats. However, 15 of the parasite lineages had not been previously described and might be restricted to these habitats or to the region. Six haemosporidian lineages previously known from other regions, particularly the Caribbean Basin, comprised 50–80% of the infections in each of the samples, indicating a regional relationship between parasite distribution and abundance. PMID:21408114

Belo, Nayara O.; Pinheiro, Renato T.; Reis, Elivânia S.; Ricklefs, Robert E.; Braga, Érika M.

2011-01-01

11

Avian haemosporidian persistence and co-infection in great tits at the individual level  

PubMed Central

Background Many studies have tracked the distribution and persistence of avian haemosporidian communities across space and time at the population level, but few studies have investigated these aspects of infection at the individual level over time. Important aspects of parasite infection at the individual level can be missed if only trends at the population level are studied. This study aimed to determine how persistent Haemosporida are in great tit individuals recaptured over several years, whether parasitaemia differed by parasite lineage (mitochondrial cytochrome b haplotype) and how co-infection (i.e. concurrent infection with multiple genera of parasites) affects parasitaemia and body mass. Methods Parasite prevalence was determined by polymerase chain reaction (PCR), quantitative PCR were used to assess parasitaemia and sequencing was employed to determine the identity of the lineages using the MalAvi database. Results Haemosporidian prevalence was high over sampled years with 98% of 55 recaptured individuals showing infection in at least one year of capture. Eighty-two percent of all positive individuals suffered co-infection, with an overall haemosporidian lineage diversity of seventeen. Plasmodium and Haemoproteus parasites were found to be highly persistent, with lineages from these genera consistently found in individuals across years and with no differences in individual parasitaemia being recorded at subsequent captures. Conversely, Leucocytozoon parasites showed higher turnover with regard to lineage changes or transitions in infection status (infected vs non-infected) across years. Parasitaemia was found to be lineage specific and there was no relationship between Plasmodium parasitaemia or host body condition and the presence of Leucocytozoon parasites. Conclusions The findings of this study suggest that different genera of haemosporidian parasites interact differently with their host and other co-infecting parasites, influencing parasite persistence most likely through inter-parasite competition or host-parasite immune interactions. Even-though co-infections do not seem to result in increased virulence (higher parasitaemia or poorer host body condition), further investigation into infection potential of these parasites, both individually and as co-infections, is necessary. PMID:23360530

2013-01-01

12

Central carbon metabolism of Plasmodium parasites  

PubMed Central

The central role of metabolic perturbation to the pathology of malaria, the promise of antimetabolites as antimalarial drugs and a basic scientific interest in understanding this fascinating example of highly divergent microbial metabolism has spurred a major and concerted research effort towards elucidating the metabolic network of the Plasmodium parasites. Central carbon metabolism, broadly comprising the flow of carbon from nutrients into biomass, has been a particular focus due to clear and early indications that it plays an essential role in this network. Decades of painstaking efforts have significantly clarified our understanding of these pathways of carbon flux, and this foundational knowledge, coupled with the advent of advanced analytical technologies, have set the stage for the development of a holistic, network-level model of plasmodial carbon metabolism. In this review we summarize the current state of knowledge regarding central carbon metabolism and suggest future avenues of research. We focus primarily on the blood stages of Plasmodium falciparum, the most lethal of the human malaria parasites, but also integrate results from simian, avian and rodent models of malaria that were a major focus of early investigations into plasmodial metabolism. PMID:20849882

Olszewski, Kellen L.; Llinás, Manuel

2010-01-01

13

Quantifying the biophysical characteristics of Plasmodium-falciparum-parasitized  

E-print Network

Quantifying the biophysical characteristics of Plasmodium-falciparum-parasitized red blood cells to endothelial cells (cytoadherence). The dynamics of Pf-parasitized RBCs is studied by three the wall, and intermittent flipping. The parasite inside the RBC is modeled explicitly in order to capture

Suresh, Subra

14

Avian Plasmodium in Culex and Ochlerotatus Mosquitoes from Southern Spain: Effects of Season and Host-Feeding Source on Parasite Dynamics  

PubMed Central

Haemosporidians, a group of vector-borne parasites that include Plasmodium, infect vertebrates including birds. Although mosquitoes are crucial elements in the transmission of avian malaria parasites, little is known of their ecology as vectors. We examined the presence of Plasmodium and Haemoproteus lineages in five mosquito species belonging to the genera Culex and Ochlerotatus to test for the effect of vector species, season and host-feeding source on the transmission dynamics of these pathogens. We analyzed 166 blood-fed individually and 5,579 unfed mosquitoes (grouped in 197 pools) from a locality in southern Spain. In all, 15 Plasmodium and two Haemoproteus lineages were identified on the basis of a fragment of 478 bp of the mitochondrial cytochrome b gene. Infection prevalence of blood parasites in unfed mosquitoes varied between species (range: 0–3.2%) and seasons. The feeding source was identified in 91 mosquitoes where 78% were identified as bird. We found that i) several Plasmodium lineages are shared among different Culex species and one Plasmodium lineage is shared between Culex and Ochlerotatus genera; ii) mosquitoes harboured Haemoproteus parasites; iii) pools of unfed females of mostly ornithophilic Culex species had a higher Plasmodium prevalence than the only mammophylic Culex species studied. However, the mammophylic Ochlerotatus caspius had in pool samples the greatest Plasmodium prevalence. This relative high prevalence may be determined by inter-specific differences in vector survival, susceptibility to infection but also the possibility that this species feeds on birds more frequently than previously thought. Finally, iv) infection rate of mosquitoes varies between seasons and reaches its maximum prevalence during autumn and minimum prevalence in spring. PMID:23823127

Ferraguti, Martina; Martínez-de la Puente, Josué; Muñoz, Joaquín; Roiz, David; Ruiz, Santiago; Soriguer, Ramón; Figuerola, Jordi

2013-01-01

15

Avian Plasmodium in Culex and Ochlerotatus Mosquitoes from Southern Spain: Effects of Season and Host-Feeding Source on Parasite Dynamics.  

PubMed

Haemosporidians, a group of vector-borne parasites that include Plasmodium, infect vertebrates including birds. Although mosquitoes are crucial elements in the transmission of avian malaria parasites, little is known of their ecology as vectors. We examined the presence of Plasmodium and Haemoproteus lineages in five mosquito species belonging to the genera Culex and Ochlerotatus to test for the effect of vector species, season and host-feeding source on the transmission dynamics of these pathogens. We analyzed 166 blood-fed individually and 5,579 unfed mosquitoes (grouped in 197 pools) from a locality in southern Spain. In all, 15 Plasmodium and two Haemoproteus lineages were identified on the basis of a fragment of 478 bp of the mitochondrial cytochrome b gene. Infection prevalence of blood parasites in unfed mosquitoes varied between species (range: 0-3.2%) and seasons. The feeding source was identified in 91 mosquitoes where 78% were identified as bird. We found that i) several Plasmodium lineages are shared among different Culex species and one Plasmodium lineage is shared between Culex and Ochlerotatus genera; ii) mosquitoes harboured Haemoproteus parasites; iii) pools of unfed females of mostly ornithophilic Culex species had a higher Plasmodium prevalence than the only mammophylic Culex species studied. However, the mammophylic Ochlerotatus caspius had in pool samples the greatest Plasmodium prevalence. This relative high prevalence may be determined by inter-specific differences in vector survival, susceptibility to infection but also the possibility that this species feeds on birds more frequently than previously thought. Finally, iv) infection rate of mosquitoes varies between seasons and reaches its maximum prevalence during autumn and minimum prevalence in spring. PMID:23823127

Ferraguti, Martina; Martínez-de la Puente, Josué; Muñoz, Joaquín; Roiz, David; Ruiz, Santiago; Soriguer, Ramón; Figuerola, Jordi

2013-01-01

16

Presence of Plasmodium and Haemoproteus in breeding prothonotary warblers (Protonotaria citrea: Parulidae): temporal and spatial trends in infection prevalence.  

PubMed

Prothonotary warbler (Protonotaria citrea) has shown a long-term decline in abundance in the United States. As a long-range migrant, these warblers are exposed to parasites in both tropical and temperate regions. The focus of this study was to use molecular techniques to examine the temporal prevalence patterns of heamosopridian parasites Plasmodium and Haemoproteus in breeding prothonotary warblers. The prevalence (presence or absence) of Plasmodium and Haemoproteus species was assayed using primer sets for the cytochrome b gene of the mitochondrial DNA. Blood samples were obtained from 187 adult prothonotary warblers collected at 3 central Virginia, U.S.A., breeding sites. The relationship between haemosporidian parasite infections and reproductive success also was examined. We found that 71% of captured prothonotary warblers were infected with haemosporidian parasites, specifically, with 36% prevalence for Haemoproteus spp. and 44% prevalence for Plasmodium spp., during the 2008 breeding season; for both parasites, prevalence increased throughout the season. We found significant variation in haemosporidian parasite prevalence across the breeding season that was strongly site specific. Conversely, we found no significant effects of haemosporidian parasite infections on the reproductive success of prothonotary warblers. This is in sharp contrast to recent reports suggesting considerable effects of these parasites on the reproductive success of wild birds. PMID:21790366

Grillo, Elena L; Fithian, Robert C; Cross, Heather; Wallace, Catherine; Viverette, Catherine; Reilly, Robert; Mayer, D C Ghislaine

2012-02-01

17

On the study of the transmission networks of blood parasites from SW Spain: diversity of avian haemosporidians in the biting midge Culicoides circumscriptus and wild birds  

PubMed Central

Background Blood-sucking flying insects play a key role in the transmission of pathogens of vector-borne diseases. However, at least for the case of avian malaria parasites, the vast majority of studies focus on the interaction between parasites and vertebrate hosts, but there is a lack of information regarding the interaction between the parasites and the insect vectors. Here, we identified the presence of malaria and malaria-like parasite lineages harbored by the potential vector Culicoides circumscriptus (Kieffer). Also, we identified some nodes of the transmission network connecting parasite lineages, potential insect vectors and avian hosts by comparing Haemoproteus and Plasmodium lineages isolated from insects with those infecting wild birds in this and previous studies. Methods Using a molecular approach, we analysed the presence of blood parasites in a total of 97 biting midges trapped in the Doñana National Park (SW Spain) and surrounding areas. Also, 123 blood samples from 11 bird species were analyzed for the presence of blood parasite infections. Blood parasites Haemoproteus and Plasmodium were identified by amplification of a 478 bp fragment of the mitochondrial cytochrome b gen. Results Thirteen biting midges harboured blood parasites including six Haemoproteus and two Plasmodium lineages, supporting the potential role of these insects on parasite transmission. Moreover, ten (8.1%) birds carried blood parasites. Seven Plasmodium and one Haemoproteus lineages were isolated from birds. Overall, six new Haemoproteus lineages were described in this study. Also, we identified the transmission networks of some blood parasites. Two Haemoproteus lineages, hCIRCUM03 and GAGLA03, were identical to those isolated from Corvus monedula in southern Spain and Garrulus glandarius in Bulgaria, respectively. Furthermore, the new Haemoproteus lineage hCIRCUM05 showed a 99% similarity with a lineage found infecting captive penguins in Japan. Conclusions The comparison of the parasite lineages isolated in this study with those previously found infecting birds allowed us to identify some potential nodes in the transmission network of avian blood parasite lineages. These results highlight the complexity of the transmission networks of blood parasites in the wild that may involve a high diversity of susceptible birds and insect vectors. PMID:23856348

2013-01-01

18

Comparative genomics of the neglected human malaria parasite Plasmodium vivax  

Microsoft Academic Search

The human malaria parasite Plasmodium vivax is responsible for 25-40% of the ~515 million annual cases of malaria worldwide. Although seldom fatal, the parasite elicits severe and incapacitating clinical symptoms and often causes relapses months after a primary infection has cleared. Despite its importance as a major human pathogen, P. vivax is little studied because it cannot be propagated continuously

Jane M. Carlton; John H. Adams; Joana C. Silva; Shelby L. Bidwell; Hernan Lorenzi; Elisabet Caler; Jonathan Crabtree; Samuel V. Angiuoli; Emilio F. Merino; Paolo Amedeo; Qin Cheng; Richard M. R. Coulson; Brendan S. Crabb; Hernando A. del Portillo; Kobby Essien; Tamara V. Feldblyum; Carmen Fernandez-Becerra; Paul R. Gilson; Amy H. Gueye; Xiang Guo; Taco W. A. Kooij; Michael Korsinczky; Esmeralda V.-S. Meyer; Vish Nene; Ian Paulsen; Owen White; Stuart A. Ralph; Qinghu Ren; Tobias J. Sargeant; Christian J. Stoeckert; Steven A. Sullivan; Marcio M. Yamamoto; Stephen L. Hoffman; Jennifer R. Wortman; Malcolm J. Gardner; Mary R. Galinski; John W. Barnwell; Claire M. Fraser-Liggett

2008-01-01

19

Protein targeting to destinations of the secretory pathway in the malaria parasite Plasmodium falciparum  

E-print Network

Protein targeting to destinations of the secretory pathway in the malaria parasite Plasmodium pathway in the malaria parasite Plasmodium falciparum has many unique aspects in terms of protein destinations and trafficking mechanisms. Recently, several exciting insights into protein trafficking within

McFadden, Geoff

20

Edinburgh Research Explorer Plasmodium falciparum-like parasites infecting wild apes in  

E-print Network

Edinburgh Research Explorer Plasmodium falciparum-like parasites infecting wild apes in southern, Peeters, M, Sharp, PM, Bushman, FD & Hahn, BH 2013, 'Plasmodium falciparum-like parasites infecting wild claim. Download date: 28. Jun. 2014 #12;Plasmodium falciparum-like parasites infecting wild apes

Hall, Christopher

21

Molecular epidemiology of the emerging human malaria parasitePlasmodium knowlesi”  

PubMed Central

Malaria is the most important parasitic disease with global concern. Plasmodium knowlesi recently has emerged from its natural simian host as a significant cause of human malaria, particularly in Malaysian Borneo. Therefore, it has been added as the fifth human Plasmodium specie which is widely distributed in Southeast Asia. Recent developments of new molecular tools enhanced our understanding about the key features of this malaria parasite. Here, we review some of the ways in which molecular approaches might be used for epidemiology of P. knowlesi and finally lead to an efficient control of malaria. PMID:24754022

Hakimi, Hassan; Kawai, Satoru; Kawazu, Shin-ichiro

2014-01-01

22

Life history of a malaria parasite (Plasmodium mexicanum): independent traits  

E-print Network

Life history of a malaria parasite (Plasmodium mexicanum): independent traits and basis infections in the life-history traits which de¢ne its blood-dwelling stages. Such variation in life histories¡ects producing the variation.We studied 11 life-history traits in 120 induced infections of P. mexicanum in its

Schall, Joseph J.

23

A regulatable transgene expression system for cultured Plasmodium falciparum parasites  

Microsoft Academic Search

BACKGROUND: The ability to transfect and create transgenic cultured malaria parasites has transformed the study of Plasmodium falciparum over the last decade. With the completion of the annotated genome sequence, the process of gene discovery now routinely includes gene knockouts, over-expression and complementation analysis. However, while this technology has proven extremely valuable, significant limitations exist. In particular, P. falciparum DNA

Christian Epp; Dima Raskolnikov; Kirk W Deitsch

2008-01-01

24

Origin of the human malaria parasite Plasmodium falciparum in gorillas  

PubMed Central

Plasmodium falciparum is the most prevalent and lethal of the malaria parasites infecting humans, yet the origin and evolutionary history of this important pathogen remain controversial. Here, we developed a novel polymerase chain reaction based single genome amplification strategy to identify and characterize Plasmodium spp. DNA sequences in fecal samples of wild-living apes. Among nearly 3,000 specimens collected from field sites throughout central Africa, we found Plasmodium infection in chimpanzees (Pan troglodytes) and western gorillas (Gorilla gorilla), but not in eastern gorillas (Gorilla beringei) or bonobos (Pan paniscus). Ape plasmodial infections were highly prevalent, widely distributed, and almost always comprised of mixed parasite species. Analysis of more than 1,100 mitochondrial, apicoplast and nuclear gene sequences from chimpanzees and gorillas revealed that 99% grouped within one of six host-specific lineages representing distinct Plasmodium species within the subgenus Laverania. One of these from western gorillas was comprised of parasites that were nearly identical to P. falciparum. In phylogenetic analyses of full-length mitochondrial sequences, human P. falciparum formed a monophyletic lineage within the gorilla parasite radiation. These findings indicate that P. falciparum is of gorilla and not of chimpanzee, bonobo or ancient human origin. PMID:20864995

Liu, Weimin; Li, Yingying; Learn, Gerald H.; Rudicell, Rebecca S.; Robertson, Joel D.; Keele, Brandon F.; Ndjango, Jean-Bosco N.; Sanz, Crickette M.; Morgan, David B.; Locatelli, Sabrina; Gonder, Mary K.; Kranzusch, Philip J.; Walsh, Peter D.; Delaporte, Eric; Mpoudi-Ngole, Eitel; Georgiev, Alexander V.; Muller, Martin N.; Shaw, George M.; Peeters, Martine; Sharp, Paul M.; Rayner, Julian C.; Hahn, Beatrice H.

2010-01-01

25

The genome of the simian and human malaria parasite Plasmodium knowlesi  

Microsoft Academic Search

Plasmodium knowlesi is an intracellular malaria parasite whose natural vertebrate host is Macaca fascicularis (the `kra' monkey); however, it is now increasingly recognized as a significant cause of human malaria, particularly in southeast Asia. Plasmodium knowlesi was the first malaria parasite species in which antigenic variation was demonstrated, and it has a close phylogenetic relationship to Plasmodium vivax, the second

A. Pain; U. Böhme; A. E. Berry; K. Mungall; R. D. Finn; A. P. Jackson; T. Mourier; J. Mistry; E. M. Pasini; M. A. Aslett; S. Balasubrammaniam; K. Borgwardt; K. Brooks; C. Carret; T. J. Carver; I. Cherevach; T. Chillingworth; T. G. Clark; M. R. Galinski; N. Hall; D. Harper; D. Harris; H. Hauser; A. Ivens; C. S. Janssen; T. Keane; N. Larke; S. Lapp; M. Marti; S. Moule; I. M. Meyer; D. Ormond; N. Peters; M. Sanders; S. Sanders; T. J. Sargeant; M. Simmonds; F. Smith; R. Squares; S. Thurston; A. R. Tivey; D. Walker; B. White; E. Zuiderwijk; C. Churcher; M. A. Quail; A. F. Cowman; C. M. R. Turner; M. A. Rajandream; C. H. M. Kocken; A. W. Thomas; C. I. Newbold; B. G. Barrell; M. Berriman

2008-01-01

26

Tetraethylthiuram disulfide (Antabuse) inhibits the human malaria parasite Plasmodium falciparum.  

PubMed Central

Plasmodium falciparum in culture grows optimally at 3% oxygen. Oxygen levels down to 0.5% still support growth, but anaerobic conditions do not. These findings, and the absence of the Krebs cycle in Plasmodium, suggested that in this organism oxygen may not function in electron transport but rather may act through metalloprotein oxygenases. Tetraethylthiuram disulfide (Antabuse, disulfiram) and its reduction product diethyldithiocarbamate inhibit many metalloprotein oxygenases and have a lipid/H2O partition coefficient and high binding constant for metal ions, favoring selective toxicity to the malaria parasite. These compounds exhibited active antimalarial effects in vitro in concentrations down to 0.1 microgram/ml, the lowest level tested. Tetraethylthiuram disulfide at a level as low as 1 microgram/ml inhibited parasite glycolysis with no effect on glycolysis of normal erythrocytes. Erythrocytes pretreated with this drug at 10 microgram/ml did not support growth of the parasite. PMID:388434

Scheibel, L W; Adler, A; Trager, W

1979-01-01

27

African origin of the malaria parasite Plasmodium vivax  

PubMed Central

Plasmodium vivax is the leading cause of human malaria in Asia and Latin America but is absent from most of central Africa due to the near fixation of a mutation that inhibits the expression of its receptor, the Duffy antigen, on human erythrocytes. The emergence of this protective allele is not understood because P. vivax is believed to have originated in Asia. Here we show, using a non-invasive approach, that wild chimpanzees and gorillas throughout central Africa are endemically infected with parasites that are closely related to human P. vivax. Sequence analyses reveal that ape parasites lack host specificity and are much more diverse than human parasites, which form a monophyletic lineage within the ape parasite radiation. These findings indicate that human P. vivax is of African origin and likely selected for the Duffy-negative mutation. All extant human P. vivax parasites are derived from a single ancestor that escaped out of Africa. PMID:24557500

Liu, Weimin; Li, Yingying; Shaw, Katharina S.; Learn, Gerald H.; Plenderleith, Lindsey J.; Malenke, Jordan A.; Sundararaman, Sesh A.; Ramirez, Miguel A.; Crystal, Patricia A.; Smith, Andrew G.; Bibollet-Ruche, Frederic; Ayouba, Ahidjo; Locatelli, Sabrina; Esteban, Amandine; Mouacha, Fatima; Guichet, Emilande; Butel, Christelle; Ahuka-Mundeke, Steve; Inogwabini, Bila-Isia; Ndjango, Jean-Bosco N.; Speede, Sheri; Sanz, Crickette M.; Morgan, David B.; Gonder, Mary K.; Kranzusch, Philip J.; Walsh, Peter D.; Georgiev, Alexander V.; Muller, Martin N.; Piel, Alex K.; Stewart, Fiona A.; Wilson, Michael L.; Pusey, Anne E.; Cui, Liwang; Wang, Zenglei; Färnert, Anna; Sutherland, Colin J.; Nolder, Debbie; Hart, John A.; Hart, Terese B.; Bertolani, Paco; Gillis, Amethyst; LeBreton, Matthew; Tafon, Babila; Kiyang, John; Djoko, Cyrille F.; Schneider, Bradley S.; Wolfe, Nathan D.; Mpoudi-Ngole, Eitel; Delaporte, Eric; Carter, Richard; Culleton, Richard L.; Shaw, George M.; Rayner, Julian C.; Peeters, Martine; Hahn, Beatrice H.; Sharp, Paul M.

2014-01-01

28

Traffic pathways of Plasmodium vivax antigens during intraerythrocytic parasite development.  

PubMed

We investigated the secretory traffic of a Plasmodium vivax antigen (Pv-148) synthesised by the parasite during the blood cycle, exported into the host cell cytosol and then transported to the surface membrane of the infected erythrocyte. Studies of the ultrastructure of erythrocytes infected with P. vivax showed that intracellular schizogony is accompanied by the generation of parasite-induced membrane profiles in the erythrocyte cytoplasm. These structures are detectable soon after the parasite invades the erythrocyte and develop an elaborate organisation, leading to a tubovesicular membrane (TVM) network, in erythrocytes infected with mature trophozoites. Interestingly, the clefts formed stacked, flattened cisternae resembling a classical Golgi apparatus. The TVM network stained with the fluorescent Golgi marker Bodipy-ceramide. Specific immunolabelling showed that Pv-148 was transferred from the parasite to the erythrocyte surface membrane via the clefts and the TVM network. These findings suggest that the TVM network is part of the secretory pathways involved in parasite protein transport across the Plasmodium-infected erythrocyte and that Pv- 148 may represent a marker that links the parasite with the host cell cytoplasm and, in turn, with the extracellular milieu. PMID:11954911

Bracho, Carmen; Dunia, Irene; De, La Rosa Mercedes; Benedetti, Ennio-Lucio; Perez, Hilda A

2002-03-01

29

High prevalence of haemosporidian parasites infection in southern grey shrike Lanius meridionalis (Laniidae, Aves) from agricultural areas  

Microsoft Academic Search

We present the first data on prevalence of haematozoa in Southern grey shrikes Lanius meridionalis (Temminck) in agricultural areas of western Spain. A fragment of the mitochondrial cytochrome b gene of the parasite was amplified, using a nested PCR assay from blood sample. Of the 81 shrikes analysed, 65.4% showed infection with Haemoproteus (Kruse, 1890) while neither Leucocytozoon (Berestneff, 1904)

P. Casanueva; M. Fernández; M. Ángeles Rojo; F. Campos

2012-01-01

30

The genome of the simian and human malaria parasite Plasmodium knowlesi  

E-print Network

LETTERS The genome of the simian and human malaria parasite Plasmodium knowlesi A. Pain1 *, U. Bo is an intracellular malaria parasite whose natural vertebrate host is Macaca fascicularis (the `kra' monkey); however,2 . Plasmodium knowlesi was the first malaria parasite species in which antigenic variation was demonstrated3

Cai, Long

31

Detection and molecular characterization of avian Plasmodium from mosquitoes in central Turkey.  

PubMed

Assessing vector-parasite relationship is important in understanding the emergence of vector-borne diseases and the evolution of parasite diversity. This study investigates avian Plasmodium parasites in mosquitoes collected from Kayseri province in Central Anatolian, Turkey and determines the haemosporidian parasite lineages from these mosquito species. A total of 6153 female mosquitos from 6 species were collected from 46 sites during June-August of 2008 and 2009. Each mosquito's head-thorax and abdomen were separated, categorized with respect to species and collection area and pooled for DNA extraction. A total of 1198 genomic DNA pools (599 thorax-head, 599 abdomen) were constituted of which 128 pools (59 thorax-head, 69 abdomen) were positive for avian haemosporidian parasites (Plasmodium and Haemoproteus) by Nested-PCR analysis. Culex pipens, Aedes vexans, Culex theileri and Culiseta annulata were positive with minimum infection rates (MIRs) of 16.22 and 18.15, 4.72 and 5.98, 5.18 and 10.36, 10.64 and 10.64 in their thorax-head and abdomen parts, respectively. No avian haemosporidian DNA was detected from Culex hortensis and Anopheles maculipennis. Phylogenetic analyses of the partial cytb gene of avian haemosporidian mt-DNA from 13 positive pools revealed that 11 lineages in four phylogenic groups were Plasmodium and the other two were Haemoproteus. Our results suggest that Cx. pipiens could probably be the major vector of avian Plasmodium in Central Turkey. This is the first report of molecular detection and characterization of avian Plasmodium lineages from mosquitoes in Turkey. PMID:22455723

Inci, A; Yildirim, A; Njabo, K Y; Duzlu, O; Biskin, Z; Ciloglu, A

2012-08-13

32

Genome sequence of the human malaria parasite Plasmodium falciparum  

Microsoft Academic Search

The parasite Plasmodium falciparum is responsible for hundreds of millions of cases of malaria, and kills more than one million African children annually. Here we report an analysis of the genome sequence of P. falciparum clone 3D7. The 23-megabase nuclear genome consists of 14 chromosomes, encodes about 5,300 genes, and is the most (A + T)-rich genome sequenced to date.

Malcolm J. Gardner; Neil Hall; Eula Fung; Owen White; Matthew Berriman; Richard W. Hyman; Jane M. Carlton; Arnab Pain; Sharen Bowman; Ian T. Paulsen; Keith James; Kim Rutherford; Steven L. Salzberg; Alister Craig; Sue Kyes; Man-Suen Chan; Vishvanath Nene; Shamira J. Shallom; Bernard Suh; Jeremy Peterson; Sam Angiuoli; Mihaela Pertea; Jonathan Allen; Jeremy Selengut; Daniel Haft; Michael W. Mather; Akhil B. Vaidya; Alan H. Fairlamb; Martin J. Fraunholz; David S. Roos; Stuart A. Ralph; Geoffrey I. McFadden; Leda M. Cummings; G. Mani Subramanian; Chris Mungall; J. Craig Venter; Daniel J. Carucci; Stephen L. Hoffman; Chris Newbold; Ronald W. Davis; Claire M. Fraser; Bart Barrell

2002-01-01

33

The malaria parasite Plasmodium vivax exhibits greater genetic diversity than Plasmodium falciparum  

PubMed Central

We sequenced and annotated the genomes of four Plasmodium vivax strains collected from disparate geographical locations, tripling the number of genome sequences available for this understudied parasite and providing the first genome-wide perspective of global variability within this species. We observe approximately twice as much SNP diversity among these isolates as we do among a comparable collection of isolates of Plasmodium falciparum, a malaria parasite that causes higher mortality. This indicates a distinct history of global colonization and/or a more stable demographic history for P. vivax than P. falciparum, which is thought to have undergone a recent population bottleneck. The SNP diversity, as well as additional microsatellite and gene family variability, suggests the capacity for greater functional variation within the global population of P. vivax. These findings warrant a deeper survey of variation in P. vivax to equip disease interventions targeting the distinctive biology of this neglected but major pathogen. PMID:22863733

Neafsey, Daniel E.; Galinsky, Kevin; Jiang, Rays H. Y.; Young, Lauren; Sykes, Sean M.; Saif, Sakina; Gujja, Sharvari; Goldberg, Jonathan M.; Young, Sarah; Zeng, Qiandong; Chapman, Sinéad B.; Dash, Aditya P.; Anvikar, Anupkumar R.; Sutton, Patrick L.; Birren, Bruce W.; Escalante, Ananias A.; Barnwell, John W.; Carlton, Jane M.

2012-01-01

34

ADP-ribosyltransferase in Plasmodium (malaria parasites).  

PubMed Central

The nuclei of Plasmodium yoelii nigeriensis contain an enzyme, ADP-ribosyltransferase, that will incorporate the ADP-ribose moiety of NAD+ into acid-insoluble product. The time, pH and temperature optima of this incorporation are 30 min, 8.5 and 25 degrees C respectively. Maximum stimulation of the enzyme activity is obtained with 1.0 mM-dithiothreitol or 2.0 mM-2-mercaptoethanol. Ca2+ and Mg2+ ions at optimum concentrations of 5 mM and 10 mM respectively stimulated the activity of the enzyme by 21% and 91%. The enzyme activity is, however, inhibited by 24% in the presence of 10 mM-MnSO4. The substrate, NAD+, exhibits an apparent Km of 500 microM, and the activity of the enzyme is inhibited by four chemical classes of inhibitors: nicotinamides, methylxanthines, thymidine and aromatic amides. The inhibitors are effective in the following increasing order: nicotinamide less than 3-aminobenzamide less than thymidine less than 5-methylnicotinamide less than theophylline less than m-methoxybenzamide less than theobromine. The enzyme activity is also inhibited by some DNA-binding anti-malarial drugs. PMID:6307262

Okolie, E E; Onyezili, N I

1983-01-01

35

Microfluidic biomechanical assay for red blood cells parasitized by Plasmodium falciparum  

E-print Network

Microfluidic biomechanical assay for red blood cells parasitized by Plasmodium falciparum Quan Guo December 2011 DOI: 10.1039/c2lc20857a Red blood cells parasitized by Plasmodium falciparum can and simplified analysis, we developed a microfluidic device to measure red blood cell deformability using

Ma, Hongshen

36

Hostile Takeover by Plasmodium: Reorganization of Parasite and Host Cell Membranes during Liver Stage  

E-print Network

Hostile Takeover by Plasmodium: Reorganization of Parasite and Host Cell Membranes during Liver, called merosomes, which are delivered directly into liver sinusoids. However, it was unclear whether by Plasmodium: Reorganization of Parasite and Host Cell Membranes during Liver Stage Egress. PLoS Pathog 7(9): e

Arnold, Jonathan

37

GEOGRAPHIC GENETIC DIFFERENTIATION OF A MALARIA PARASITE, PLASMODIUM MEXICANUM, AND ITS LIZARD HOST, SCELOPORUS OCCIDENTALIS  

E-print Network

GEOGRAPHIC GENETIC DIFFERENTIATION OF A MALARIA PARASITE, PLASMODIUM MEXICANUM, AND ITS LIZARD HOST parasite Plasmodium mexicanum, and its lizard host, Sceloporus occidentalis, at 8 sites in northern California, with the use of variable microsatellite markers for both species. These lizards are small

Schall, Joseph J.

38

Growth-inhibitory effect of a fucoidan from brown seaweed Undaria pinnatifida on Plasmodium parasites  

Microsoft Academic Search

The present study was undertaken to investigate the inhibitory effects of fucoidan, a sulfated polysaccharide isolated from\\u000a the edible brown seaweed Undaria pinnatifida, on the growth of Plasmodium parasites. In order to assess the anti-malarial activity of fucoidan, growth inhibition activities were evaluated using cultured\\u000a Plasmodium falciparum parasites in vitro and on Plasmodium berghei-infected mice in vivo. Fucoidan significantly inhibited

Jun-Hu Chen; Jung-Dae Lim; Eun-Hwa Sohn; Yong-Soon Choi; Eun-Taek Han

2009-01-01

39

Targeting NAD+ Metabolism in the Human Malaria Parasite Plasmodium falciparum  

PubMed Central

Nicotinamide adenine dinucleotide (NAD+) is an essential metabolite utilized as a redox cofactor and enzyme substrate in numerous cellular processes. Elevated NAD+ levels have been observed in red blood cells infected with the malaria parasite Plasmodium falciparum, but little is known regarding how the parasite generates NAD+. Here, we employed a mass spectrometry-based metabolomic approach to confirm that P. falciparum lacks the ability to synthesize NAD+ de novo and is reliant on the uptake of exogenous niacin. We characterized several enzymes in the NAD+ pathway and demonstrate cytoplasmic localization for all except the parasite nicotinamidase, which concentrates in the nucleus. One of these enzymes, the P. falciparum nicotinate mononucleotide adenylyltransferase (PfNMNAT), is essential for NAD+ metabolism and is highly diverged from the human homolog, but genetically similar to bacterial NMNATs. Our results demonstrate the enzymatic activity of PfNMNAT in vitro and demonstrate its ability to genetically complement the closely related Escherichia coli NMNAT. Due to the similarity of PfNMNAT to the bacterial enzyme, we tested a panel of previously identified bacterial NMNAT inhibitors and synthesized and screened twenty new derivatives, which demonstrate a range of potency against live parasite culture. These results highlight the importance of the parasite NAD+ metabolic pathway and provide both novel therapeutic targets and promising lead antimalarial compounds. PMID:24747974

O'Hara, Jessica K.; Kerwin, Lewis J.; Cobbold, Simon A.; Tai, Jonathan; Bedell, Thomas A.; Reider, Paul J.; Llinás, Manuel

2014-01-01

40

Blood-stage Plasmodium infection induces CD8 T lymphocytes to parasite-expressed antigens,  

E-print Network

Blood-stage Plasmodium infection induces CD8 T lymphocytes to parasite-expressed antigens, largely the blood stage of Plasmodium infection, there is mounting evidence that they are principal mediators in response to blood-stage infection. To resolve this and to define the cellular requirements for such priming

Arnold, Jonathan

41

Age of the last common ancestor of extant Plasmodium parasite lineages.  

PubMed

Parasites of the genus Plasmodium infect all classes of amniotes (mammals, birds and reptiles) and display host specificity in their infections. It is therefore generally believed that Plasmodium parasites co-evolved intimately with their hosts. Here, we report that based on an evolutionary analysis using 22 genes in the nuclear genome, extant lineages of Plasmodium parasites originated roughly in the Oligocene epoch after the emergence of their hosts. This timing on the age of the common ancestor of extant Plasmodium parasites suggest the importance of host switches and lends support to the evolutionary scenario of a "malaria big bang" that was proposed based on the evolutionary analysis using the mitochondrial genome. PMID:22555021

Hayakawa, Toshiyuki; Tachibana, Shin-Ichiro; Hikosaka, Kenji; Arisue, Nobuko; Matsui, Atsushi; Horii, Toshihiro; Tanabe, Kazuyuki

2012-07-01

42

Investigations into aspects of central metabolism in the human malaria parasite Plasmodium falciparum.  

E-print Network

??AbstractThe University of ManchesterMartin Read Doctor of PhilosophyInvestigations into aspects of central metabolism in the human malaria parasite Plasmodium falciparum. 2011. This thesis combines four… (more)

Read, Martin

2012-01-01

43

Ecole doctorale Sciences Chimiques et Biologiques pour la Sant Titre Modlisation intgre du mtabolisme des lipides chez Plasmodium, parasite causal  

E-print Network

métabolisme des lipides chez Plasmodium, parasite causal du paludisme. Title Systems biology modelling of lipid metabolism in the malaria parasite Plasmodium. Directeur de thèse : M. Ovidiu RADULESCU - Tel : 04 Plasmodium est d'un intérêt certain car il paraît essentiel à la survie de ce parasite et est l'objet d

Radulescu, Ovidiu

44

Gametocyte sex ratio in single-clone infections of the malaria parasite Plasmodium mexicanum  

E-print Network

Gametocyte sex ratio in single-clone infections of the malaria parasite Plasmodium mexicanum A 12 July 2010) SUMMARY Sex ratio theory predicts that malaria parasites should bias gametocyte system later in the infection. Recent experimental studies reveal genetic variation for gametocyte sex

Schall, Joseph J.

45

Evolution of the Multi-Domain Structures of Virulence Genes in the Human Malaria Parasite, Plasmodium  

E-print Network

Evolution of the Multi-Domain Structures of Virulence Genes in the Human Malaria Parasite. falciparum malaria. Citation: Buckee CO, Recker M (2012) Evolution of the Multi-Domain Structures of Virulence Genes in the Human Malaria Parasite, Plasmodium falciparum. PLoS Comput Biol 8(4): e1002451. doi

Arnold, Jonathan

46

Anthracene-Polyamine Conjugates Inhibit In Vitro Proliferation of Intraerythrocytic Plasmodium falciparum Parasites  

PubMed Central

Anthracene-polyamine conjugates inhibit the in vitro proliferation of the intraerythrocytic human malaria parasite Plasmodium falciparum, with 50% inhibitory concentrations (IC50s) in the nM to ?M range. The compounds are taken up into the intraerythrocytic parasite, where they arrest the parasite cell cycle. Both the anthracene and polyamine components of the conjugates play a role in their antiplasmodial effect. PMID:23545535

Niemand, Jandeli; Burger, Pieter; Verlinden, Bianca K.; Reader, Janette; Joubert, Annie M.; Kaiser, Annette; Louw, Abraham I.; Kirk, Kiaran; Phanstiel, Otto

2013-01-01

47

Plasmodium gallinaceum:Differential Killing of Some Mosquito Stages of the Parasite by Insect Defensin  

Microsoft Academic Search

Shahabuddin, M., Fields, I., Bulet, P., Hoffmann, J. A., and Miller, L. H. 1998.Plasmodium gallinaceum:Differential killing of some mosquito stages of the parasite by insect defensin.Experimental Parasitology89, 103–112. We examined several insect antimicrobial peptides to study their effect onPlasmodium gallinaceumzygotes, ookinetes, oocysts, and sporozoites. Only two insect defensins—Aeschna cyanea(dragon fly) andPhormia terranovae(flesh fly)—had a profound toxic effect on the oocysts

Mohammed Shahabuddin; Iesha Fields; Philippe Bulet; Jules A. Hoffmann; Louis H. Miller

1998-01-01

48

The genome of the simian and human malaria parasite Plasmodium knowlesi  

PubMed Central

Plasmodium knowlesi is an intracellular malaria parasite whose natural vertebrate host is Macaca fascicularis (the ‘kra’ monkey); however, it is now increasingly recognized as a significant cause of human malaria, particularly in southeast Asia1,2. Plasmodium knowlesi was the first malaria parasite species in which antigenic variation was demonstrated3, and it has a close phylogenetic relationship to Plasmodium vivax?4, the second most important species of human malaria parasite (reviewed in ref. 4). Despite their relatedness, there are important phenotypic differences between them, such as host blood cell preference, absence of a dormant liver stage or ‘hypnozoite’ in P. knowlesi, and length of the asexual cycle (reviewed in ref. 4). Here we present an analysis of the P. knowlesi (H strain, Pk1(A+) clone5) nuclear genome sequence. This is the first monkey malaria parasite genome to be described, and it provides an opportunity for comparison with the recently completed P. vivax genome4 and other sequenced Plasmodium genomes6-8. In contrast to other Plasmodium genomes, putative variant antigen families are dispersed throughout the genome and are associated with intrachromosomal telomere repeats. One of these families, the KIRs9, contains sequences that collectively match over one-half of the host CD99 extracellular domain, which may represent an unusual form of molecular mimicry. PMID:18843368

Pain, A.; Böhme, U.; Berry, A. E.; Mungall, K.; Finn, R. D.; Jackson, A. P.; Mourier, T.; Mistry, J.; Pasini, E. M.; Aslett, M. A.; Balasubrammaniam, S.; Borgwardt, K.; Brooks, K.; Carret, C.; Carver, T. J.; Cherevach, I.; Chillingworth, T.; Clark, T. G.; Galinski, M. R.; Hall, N.; Harper, D.; Harris, D.; Hauser, H.; Ivens, A.; Janssen, C. S.; Keane, T.; Larke, N.; Lapp, S.; Marti, M.; Moule, S.; Meyer, I. M.; Ormond, D.; Peters, N.; Sanders, M.; Sanders, S.; Sargeant, T. J.; Simmonds, M.; Smith, F.; Squares, R.; Thurston, S.; Tivey, A. R.; Walker, D.; White, B.; Zuiderwijk, E.; Churcher, C.; Quail, M. A.; Cowman, A. F.; Turner, C. M. R.; Rajandream, M. A.; Kocken, C. H. M.; Thomas, A. W.; Newbold, C. I.; Barrell, B. G.; Berriman, M.

2009-01-01

49

The genome of the simian and human malaria parasite Plasmodium knowlesi.  

PubMed

Plasmodium knowlesi is an intracellular malaria parasite whose natural vertebrate host is Macaca fascicularis (the 'kra' monkey); however, it is now increasingly recognized as a significant cause of human malaria, particularly in southeast Asia. Plasmodium knowlesi was the first malaria parasite species in which antigenic variation was demonstrated, and it has a close phylogenetic relationship to Plasmodium vivax, the second most important species of human malaria parasite (reviewed in ref. 4). Despite their relatedness, there are important phenotypic differences between them, such as host blood cell preference, absence of a dormant liver stage or 'hypnozoite' in P. knowlesi, and length of the asexual cycle (reviewed in ref. 4). Here we present an analysis of the P. knowlesi (H strain, Pk1(A+) clone) nuclear genome sequence. This is the first monkey malaria parasite genome to be described, and it provides an opportunity for comparison with the recently completed P. vivax genome and other sequenced Plasmodium genomes. In contrast to other Plasmodium genomes, putative variant antigen families are dispersed throughout the genome and are associated with intrachromosomal telomere repeats. One of these families, the KIRs, contains sequences that collectively match over one-half of the host CD99 extracellular domain, which may represent an unusual form of molecular mimicry. PMID:18843368

Pain, A; Böhme, U; Berry, A E; Mungall, K; Finn, R D; Jackson, A P; Mourier, T; Mistry, J; Pasini, E M; Aslett, M A; Balasubrammaniam, S; Borgwardt, K; Brooks, K; Carret, C; Carver, T J; Cherevach, I; Chillingworth, T; Clark, T G; Galinski, M R; Hall, N; Harper, D; Harris, D; Hauser, H; Ivens, A; Janssen, C S; Keane, T; Larke, N; Lapp, S; Marti, M; Moule, S; Meyer, I M; Ormond, D; Peters, N; Sanders, M; Sanders, S; Sargeant, T J; Simmonds, M; Smith, F; Squares, R; Thurston, S; Tivey, A R; Walker, D; White, B; Zuiderwijk, E; Churcher, C; Quail, M A; Cowman, A F; Turner, C M R; Rajandream, M A; Kocken, C H M; Thomas, A W; Newbold, C I; Barrell, B G; Berriman, M

2008-10-01

50

Prevalence Patterns of Avian Plasmodium and Haemoproteus Parasites and the Influence of Host Relative Abundance in Southern China  

PubMed Central

Infectious diseases threaten the health and survival of wildlife populations. Consequently, relationships between host diversity, host abundance, and parasite infection are important aspects of disease ecology and conservation research. Here, we report on the prevalence patterns of avian Plasmodium and Haemoproteus infections and host relative abundance influence based on sampling 728 wild-caught birds representing 124 species at seven geographically widespread sites in southern China. The overall prevalence of two haemoprotozoan parasites, Plasmodium and Haemoproteus, was 29.5%, with 22.0% attributable to Haemoproteus and 7.8% to Plasmodium. Haemoproteus prevalence differed significantly among different avian host families, with the highest prevalence in Nectariniidae, Pycnonotidae and Muscicapidae, whereas Plasmodium prevalence varied significantly among host species. Seventy-nine mitochondrial lineages including 25 from Plasmodium and 54 from Haemoproteus were identified, 80% of which were described here for the first time. The phylogenetic relationships among these parasites indicated stronger host-species specificity for Haemoproteus than Plasmodium. Well-supported host-family (Timaliidae) specific clades were found in both Plasmodium and Haemoproteus. The Haemoproteus tree shows regional subclades, whereas the Plasmodium clades are “scattered” among different geographical regions. Interestingly, there were statistically significant variations in the prevalence of Plasmodium and Haemoproteus among the geographical regions. Furthermore, the prevalence of Plasmodium and Haemoproteus were not significantly correlated with host relative abundance. Further efforts will focus on exploring the relationships between parasite prevalence and sex, age, and immune defense of the host. PMID:24911323

Zhang, Yanhua; Wu, Yuchun; Zhang, Qiang; Su, Dongdong; Zou, Fasheng

2014-01-01

51

An innovative shape equation to quantify the morphological characteristics of parasitized red blood cells by Plasmodium falciparum and Plasmodium vivax.  

PubMed

The morphology of red blood cells is affected significantly during maturation of malaria parasites, Plasmodium falciparum and Plasmodium vivax. A novel shape equation is presented that defines shape of parasitized red blood cells by P. falciparum (Pf-red blood cells) and P. vivax (Pv-red blood cells) at four stages of infection. The Giemsa-stained thin blood films are prepared using blood samples collected from healthy donors, patients having P. falciparum and P. vivax malaria. The diameter and thickness of healthy red blood cells plus Pf-red blood cells and Pv-red blood cells at each stage of infection are measured from their optical images using Olysia and Scanning Probe Image Processor softwares, respectively. Using diameters and thicknesses of parasitized red blood cells, a shape equation is fitted and relative two-dimensional shapes are plotted using MATHEMATICA. The shape of Pf-red blood cell drastically changes at ring stage as its thickness increases by 82%, while Pv-red blood cell remains biconcave (30% increase in thickness). By trophozoite and subsequent schizont stage, the Pf-red blood cell entirely loses its biconcave shape and becomes near spherical (diameter and thickness of ~8 µm). The Pv-red blood cell remains biconcave throughout the parasite development even though its volume increases. These results could have practical use for faster diagnosis, prediction, and treatment of human malaria and sickle-cell diseases. PMID:23637218

Karimi, Alireza; Navidbakhsh, Mahdi; Motevalli Haghi, Afsaneh; Faghihi, Shahab

2013-04-01

52

Landscape features associated with infection by a malaria parasite (Plasmodium mexicanum) and the importance of  

E-print Network

), and infection prevalence was calculated for each. Three sites with high ( 30%) infection prevalence had507 Landscape features associated with infection by a malaria parasite (Plasmodium mexicanum of ground cover, and nearest water source) that were potentially related to prevalence of infection

Schall, Joseph J.

53

Microsatellite Markers Reveal a Spectrum of Population Structures in the Malaria Parasite Plasmodium falciparum  

Microsoft Academic Search

Multilocus genotyping of microbial pathogens has revealed a range of population structures, with some bacteria showing extensive recombination and others showing almost complete clonality. The population structure of the protozoan parasite Plasmodium falciparum has been harder to evaluate, since most studies have used a limited number of antigen-encoding loci that are known to be under strong selection. We describe length

Timothy J. C. Anderson; Bernhard Haubold; Jeff T. Williams; Jose G. Estrada-Franco; Lynne Richardson; Rene Mollinedo; Moses Bockarie; John Mokili; Sungano Mharakurwa; Neil French; Jim Whitworth; Ivan D. Velez; Alan H. Brockman; Francois Nosten; Marcelo U. Ferreira; Karen P. Day

2000-01-01

54

Comparative Genomics of Transcriptional Control in the Human Malaria Parasite Plasmodium falciparum  

E-print Network

Comparative Genomics of Transcriptional Control in the Human Malaria Parasite Plasmodium falciparum Richard M.R. Coulson,1,3 Neil Hall,2 and Christos A. Ouzounis1 1 Computational Genomics Group10 1SD, United Kingdom; 2 The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus

Arnold, Jonathan

55

Scavenging of the cofactor lipoate is essential for the survival of the malaria parasite Plasmodium falciparum  

PubMed Central

Summary Lipoate is an essential cofactor for key enzymes of oxidative metabolism. Plasmodium falciparum possesses genes for lipoate biosynthesis and scavenging, but it is not known if these pathways are functional, nor what their relative contribution to the survival of intraerythrocytic parasites might be. We detected in parasite extracts four lipoylated proteins, one of which cross-reacted with antibodies against the E2 subunit of apicoplast-localized pyruvate dehydrogenase (PDH). Two highly divergent parasite lipoate ligase A homologues (LplA), LipL1 (previously identified as LplA) and LipL2, restored lipoate scavenging in lipoylation-deficient bacteria, indicating that Plasmodium has functional lipoate-scavenging enzymes. Accordingly, intraerythrocytic parasites scavenged radiolabelled lipoate and incorporated it into three proteins likely to be mitochondrial. Scavenged lipoate was not attached to the PDH E2 subunit, implying that lipoate scavenging drives mitochondrial lipoylation, while apicoplast lipoylation relies on biosynthesis. The lipoate analogue 8-bromo-octanoate inhibited LipL1 activity and arrested P. falciparum in vitro growth, decreasing the incorporation of radiolabelled lipoate into parasite proteins. Furthermore, growth inhibition was prevented by lipoate addition in the medium. These results are consistent with 8-bromo-octanoate specifically interfering with lipoate scavenging. Our study suggests that lipoate metabolic pathways are not redundant, and that lipoate scavenging is critical for Plasmodium intraerythrocytic survival. PMID:17244193

Allary, Marina; Lu, Jeff Zhiqiang; Zhu, Liqun; Prigge, Sean T.

2009-01-01

56

Detection of new Babesia microti-like parasites in a rhesus monkey (Macaca mulatta) with a suppressed Plasmodium cynomolgi infection.  

PubMed

A new type of piroplasm, phylogenetically closest to Babesia microti-like parasites previously detected in Eurasian red squirrels (Sciurus vulgaris orientis), was identified in a rhesus monkey (Macaca mulatta) imported from China. After challenge with Plasmodium cynomolgi M strain blood-stage parasites, the rhesus monkey repeatedly showed markedly reduced levels of Plasmodium parasitemia when compared with animals not infected with this organism. PMID:18385363

Voorberg-vd Wel, Annemarie; Kocken, Clemens H M; Zeeman, Anne-Marie; Thomas, Alan W

2008-04-01

57

High diversity of West African bat malaria parasites and a tight link with rodent Plasmodium taxa  

PubMed Central

As the only volant mammals, bats are captivating for their high taxonomic diversity, for their vital roles in ecosystems—particularly as pollinators and insectivores—and, more recently, for their important roles in the maintenance and transmission of zoonotic viral diseases. Genome sequences have identified evidence for a striking expansion of and positive selection in gene families associated with immunity. Bats have also been known to be hosts of malaria parasites for over a century, and as hosts, they possess perhaps the most phylogenetically diverse set of hemosporidian genera and species. To provide a molecular framework for the study of these parasites, we surveyed bats in three remote areas of the Upper Guinean forest ecosystem. We detected four distinct genera of hemosporidian parasites: Plasmodium, Polychromophilus, Nycteria, and Hepatocystis. Intriguingly, the two species of Plasmodium in bats fall within the clade of rodent malaria parasites, indicative of multiple host switches across mammalian orders. We show that Nycteria species form a very distinct phylogenetic group and that Hepatocystis parasites display an unusually high diversity and prevalence in epauletted fruit bats. The diversity and high prevalence of novel lineages of chiropteran hemosporidians underscore the exceptional position of bats among all other mammalian hosts of hemosporidian parasites and support hypotheses of pathogen tolerance consistent with the exceptional immunology of bats. PMID:24101466

Schaer, Juliane; Perkins, Susan L.; Decher, Jan; Leendertz, Fabian H.; Fahr, Jakob; Weber, Natalie; Matuschewski, Kai

2013-01-01

58

High diversity of West African bat malaria parasites and a tight link with rodent Plasmodium taxa.  

PubMed

As the only volant mammals, bats are captivating for their high taxonomic diversity, for their vital roles in ecosystems--particularly as pollinators and insectivores--and, more recently, for their important roles in the maintenance and transmission of zoonotic viral diseases. Genome sequences have identified evidence for a striking expansion of and positive selection in gene families associated with immunity. Bats have also been known to be hosts of malaria parasites for over a century, and as hosts, they possess perhaps the most phylogenetically diverse set of hemosporidian genera and species. To provide a molecular framework for the study of these parasites, we surveyed bats in three remote areas of the Upper Guinean forest ecosystem. We detected four distinct genera of hemosporidian parasites: Plasmodium, Polychromophilus, Nycteria, and Hepatocystis. Intriguingly, the two species of Plasmodium in bats fall within the clade of rodent malaria parasites, indicative of multiple host switches across mammalian orders. We show that Nycteria species form a very distinct phylogenetic group and that Hepatocystis parasites display an unusually high diversity and prevalence in epauletted fruit bats. The diversity and high prevalence of novel lineages of chiropteran hemosporidians underscore the exceptional position of bats among all other mammalian hosts of hemosporidian parasites and support hypotheses of pathogen tolerance consistent with the exceptional immunology of bats. PMID:24101466

Schaer, Juliane; Perkins, Susan L; Decher, Jan; Leendertz, Fabian H; Fahr, Jakob; Weber, Natalie; Matuschewski, Kai

2013-10-22

59

The remarkable journey of adaptation of the Plasmodium falciparum malaria parasite to New World anopheline mosquitoes  

PubMed Central

Plasmodium falciparum originated in Africa, dispersed around the world as a result of human migration and had to adapt to several different indigenous anopheline mosquitoes. Anophelines from the New World are evolutionary distant form African ones and this probably resulted in a more stringent selection of Plasmodium as it adapted to these vectors. It is thought that Plasmodium has been genetically selected by some anopheline species through unknown mechanisms. The mosquito immune system can greatly limit infection and P. falciparum evolved a strategy to evade these responses, at least in part mediated by Pfs47, a highly polymorphic gene. We propose that adaptation of P. falciparum to new vectors may require evasion of their immune system. Parasites with a Pfs47 haplotype compatible with the indigenous mosquito vector would be able to survive and be transmitted. The mosquito antiplasmodial response could be an important determinant of P. falciparum population structure and could affect malaria transmission in the Americas. PMID:25185006

Molina-Cruz, Alvaro; Barillas-Mury, Carolina

2014-01-01

60

Evaluation of immunity against malaria using luciferase-expressing Plasmodium berghei parasites  

PubMed Central

Background Measurement of liver stage development is of key interest in malaria biology and vaccine studies. Parasite development in liver cells can be visualized in real-time, both in culture and in live mice, using a transgenic Plasmodium berghei parasite, PbGFP-Luccon, expressing the bioluminescent reporter luciferase. This study explores the benefit of using these parasites for the evaluation of immunity against malaria, compared to qRT-PCR techniques in vivo and in vitro. Methods Mice were immunized with either radiation attenuated sporozoites (RAS) or wildtype sporozoites under chloroquine prophylaxis (CPS) and challenged with PbGFP-Luccon. The in vitro transgenic sporozoites neutralization assay (TSNA) was adapted by replacing PbCS(Pf) parasites for PbGFP-Luccon parasites. Results Application of PbGFP-Luccon transgenic parasites provides live quantitative visual information about the relation between parasite liver load and protection. Moreover, fast and reproducible results are obtained by using these parasites in the transgenic sporozoites neutralization assay, measuring functional antibody-mediated immune responses. Conclusions PbGFP-Luccon parasites are a straightforward and valuable tool for comprehension of the biological and immunological principles underlying protection against malaria. PMID:22152047

2011-01-01

61

Growth-inhibitory effect of a fucoidan from brown seaweed Undaria pinnatifida on Plasmodium parasites.  

PubMed

The present study was undertaken to investigate the inhibitory effects of fucoidan, a sulfated polysaccharide isolated from the edible brown seaweed Undaria pinnatifida, on the growth of Plasmodium parasites. In order to assess the anti-malarial activity of fucoidan, growth inhibition activities were evaluated using cultured Plasmodium falciparum parasites in vitro and on Plasmodium berghei-infected mice in vivo. Fucoidan significantly inhibited the invasion of erythrocytes by P. falciparum merozoites, and its 50% inhibition concentration was similar to those for the chloroquine-sensitive P. falciparum 3D7 strain and the chloroquine-resistant K1 strain. Four-day suppressive testing in P. berghei-infected mice with fucoidan resulted in a 37% suppressive effect versus the control group and a delay in death associated with anemia (P < 0.05). In addition, fucoidans had no toxic effect on RAW 264.7 cells. These findings indicate that fucoidans from the Korean brown algae U. pinnatifida inhibits the invasion of Plasmodium merozoites into erythrocytes in vitro and in vivo. PMID:18791738

Chen, Jun-Hu; Lim, Jung-Dae; Sohn, Eun-Hwa; Choi, Yong-Soon; Han, Eun-Taek

2009-01-01

62

The protein-phosphatome of the human malaria parasite Plasmodium falciparum  

Microsoft Academic Search

Background  Malaria, caused by the parasitic protist Plasmodium falciparum, represents a major public health problem in the developing world. The P. falciparum genome has been sequenced, which provides new opportunities for the identification of novel drug targets. We report an exhaustive\\u000a analysis of the P. falciparum genomic database (PlasmoDB) aimed at identifying and classifying all protein phosphatases (PP) in this organism.

Jonathan M Wilkes; Christian Doerig

2008-01-01

63

Mosquito immune responses and compatibility between Plasmodium parasites and anopheline mosquitoes  

PubMed Central

Background Functional screens based on dsRNA-mediated gene silencing identified several Anopheles gambiae genes that limit Plasmodium berghei infection. However, some of the genes identified in these screens have no effect on the human malaria parasite Plasmodium falciparum; raising the question of whether different mosquito effector genes mediate anti-parasitic responses to different Plasmodium species. Results Four new An. gambiae (G3) genes were identified that, when silenced, have a different effect on P. berghei (Anka 2.34) and P. falciparum (3D7) infections. Orthologs of these genes, as well as LRIM1 and CTL4, were also silenced in An. stephensi (Nijmegen Sda500) females infected with P. yoelii (17XNL). For five of the six genes tested, silencing had the same effect on infection in the P. falciparum-An. gambiae and P. yoelii-An. stephensi parasite-vector combinations. Although silencing LRIM1 or CTL4 has no effect in An. stephensi females infected with P. yoelii, when An. gambiae is infected with the same parasite, silencing these genes has a dramatic effect. In An. gambiae (G3), TEP1, LRIM1 or LRIM2 silencing reverts lysis and melanization of P. yoelii, while CTL4 silencing enhances melanization. Conclusion There is a broad spectrum of compatibility, the extent to which the mosquito immune system limits infection, between different Plasmodium strains and particular mosquito strains that is mediated by TEP1/LRIM1 activation. The interactions between highly compatible animal models of malaria, such as P. yoelii (17XNL)-An. stephensi (Nijmegen Sda500), is more similar to that of P. falciparum (3D7)-An. gambiae (G3). PMID:19643026

2009-01-01

64

Quantitative Time-course Profiling of Parasite and Host Cell Proteins in the Human Malaria Parasite Plasmodium falciparum*  

PubMed Central

Studies of the Plasmodium falciparum transcriptome have shown that the tightly controlled progression of the parasite through the intra-erythrocytic developmental cycle (IDC) is accompanied by a continuous gene expression cascade in which most expressed genes exhibit a single transcriptional peak. Because the biochemical and cellular functions of most genes are mediated by the encoded proteins, understanding the relationship between mRNA and protein levels is crucial for inferring biological activity from transcriptional gene expression data. Although studies on other organisms show that <50% of protein abundance variation may be attributable to corresponding mRNA levels, the situation in Plasmodium is further complicated by the dynamic nature of the cyclic gene expression cascade. In this study, we simultaneously determined mRNA and protein abundance profiles for P. falciparum parasites during the IDC at 2-hour resolution based on oligonucleotide microarrays and two-dimensional differential gel electrophoresis protein gels. We find that most proteins are represented by more than one isoform, presumably because of post-translational modifications. Like transcripts, most proteins exhibit cyclic abundance profiles with one peak during the IDC, whereas the presence of functionally related proteins is highly correlated. In contrast, the abundance of most parasite proteins peaks significantly later (median 11 h) than the corresponding transcripts and often decreases slowly in the second half of the IDC. Computational modeling indicates that the considerable and varied incongruence between transcript and protein abundance may largely be caused by the dynamics of translation and protein degradation. Furthermore, we present cyclic abundance profiles also for parasite-associated human proteins and confirm the presence of five human proteins with a potential role in antioxidant defense within the parasites. Together, our data provide fundamental insights into transcript-protein relationships in P. falciparum that are important for the correct interpretation of transcriptional data and that may facilitate the improvement and development of malaria diagnostics and drug therapy. PMID:21558492

Foth, Bernardo Javier; Zhang, Neng; Chaal, Balbir Kaur; Sze, Siu Kwan; Preiser, Peter Rainer; Bozdech, Zbynek

2011-01-01

65

The "Malaria's Eve" hypothesis and the debate concerning the origin of the human malaria parasite Plasmodium falciparum.  

PubMed

The debate over whether the human malaria parasite Plasmodium falciparum underwent a recent severe population bottleneck ("Malaria's Eve" hypothesis) has attracted great attention recently. Understanding the genetic diversity and evolutionary history of the parasite has practical implications for developing disease control measures. PMID:12919857

Su, Xin Zhuan; Mu, Jianbing; Joy, Deirdre A

2003-08-01

66

Analysis of Antibodies Directed against Merozoite Surface Protein 1 of the Human Malaria Parasite Plasmodium falciparum  

PubMed Central

The 190-kDa merozoite surface protein 1 (MSP-1) of Plasmodium falciparum, an essential component in the parasite's life cycle, is a primary candidate for a malaria vaccine. Rabbit antibodies elicited by the heterologously produced MSP-1 processing products p83, p30, p38, and p42, derived from strain 3D7, were analyzed for the potential to inhibit in vitro erythrocyte invasion by the parasite and parasite growth. Our data show that (i) epitopes recognized by antibodies, which inhibit parasite replication, are distributed throughout the entire MSP-1 molecule; (ii) when combined, antibodies specific for different regions of MSP-1 inhibit in a strictly additive manner; (iii) anti-MSP-1 antibodies interfere with erythrocyte invasion as well as with the intraerythrocytic growth of the parasite; and (iv) antibodies raised against MSP-1 of strain 3D7 strongly cross-inhibit replication of the heterologous strain FCB-1. Accordingly, anti-MSP-1 antibodies appear to be capable of interfering with parasite multiplication at more than one level. Since the overall immunogenicity profile of MSP-1 in rabbits closely resembles that found in sera of Aotus monkeys immunized with parasite-derived MSP-1 and of humans semi-immune to malaria from whom highly inhibiting antigen-specific antibodies were recovered, we consider the findings reported here to be relevant for the development of MSP-1-based vaccines against malaria. PMID:16428781

Woehlbier, Ute; Epp, Christian; Kauth, Christian W.; Lutz, Rolf; Long, Carole A.; Coulibaly, Boubacar; Kouyaté, Bocar; Arevalo-Herrera, Myriam; Herrera, Sócrates; Bujard, Hermann

2006-01-01

67

Return of chloroquine-sensitive Plasmodium falciparum parasites and emergence of chloroquine-resistant Plasmodium vivax in Ethiopia  

PubMed Central

Background Increased resistance by Plasmodium falciparum parasites led to the withdrawal of the antimalarial drugs chloroquine and sulphadoxine-pyrimethamine in Ethiopia. Since 2004 artemether-lumefantrine has served to treat uncomplicated P. falciparum malaria. However, increasing reports on delayed parasite clearance to artemisinin opens up a new challenge in anti-malarial therapy. With the complete withdrawal of CQ for the treatment of Plasmodium falciparum malaria, this study assessed the evolution of CQ resistance by investigating the prevalence of mutant alleles in the pfmdr1 and pfcrt genes in P. falciparum and pvmdr1 gene in Plasmodium vivax in Southern and Eastern Ethiopia. Methods Of the 1,416 febrile patients attending primary health facilities in Southern Ethiopia, 329 febrile patients positive for P. falciparum or P. vivax were recruited. Similarly of the 1,304 febrile patients from Eastern Ethiopia, 81 febrile patients positive for P. falciparum or P. vivax were included in the study. Of the 410 finger prick blood samples collected from malaria patients, we used direct sequencing to investigate the prevalence of mutations in pfcrt and pfmdr1. This included determining the gene copy number in pfmdr1 in 195 P. falciparum clinical isolates, and mutations in the pvmdr1 locus in 215 P. vivax clinical isolates. Results The pfcrt K76 CQ-sensitive allele was observed in 84.1% of the investigated P.falciparum clinical isolates. The pfcrt double mutations (K76T and C72S) were observed less than 3%. The pfcrt SVMNT haplotype was also found to be present in clinical isolates from Ethiopia. The pfcrt CVMNK-sensitive haplotypes were frequently observed (95.9%). The pfmdr1 mutation N86Y was observed only in 14.9% compared to 85.1% of the clinical isolates that carried sensitive alleles. Also, the sensitive pfmdr1 Y184 allele was more common, in 94.9% of clinical isolates. None of the investigated P. falciparum clinical isolates carried S1034C, N1042D and D1246Y pfmdr1 polymorphisms. All investigated P. falciparum clinical isolates from Southern and Eastern Ethiopia carried only a single copy of the mutant pfmdr1 gene. Conclusion The study reports for the first time the return of chloroquine sensitive P. falciparum in Ethiopia. These findings support the rationale for the use of CQ-based combination drugs as a possible future alternative. PMID:24964730

2014-01-01

68

A monkey's tale: The origin of Plasmodium vivax as a human malaria parasite  

PubMed Central

The high prevalence of Duffy negativity (lack of the Duffy blood group antigen) among human populations in sub-Saharan Africa has been used to argue that Plasmodium vivax originated on that continent. Here, we investigate the phylogenetic relationships among 10 species of Plasmodium that infect primates by using three genes, two nuclear (?-tubulin and cell division cycle 2) and a gene from the plastid genome (the elongation factor Tu). We find compelling evidence that P. vivax is derived from a species that inhabited macaques in Southeast Asia. Specifically, those phylogenies that include P. vivax as an ancient lineage from which all of the macaque parasites could originate are significantly less likely to explain the data. We estimate the time to the most recent common ancestor at four neutral gene loci from Asian and South American isolates (a minimum sample of seven isolates per locus). Our analysis estimates that the extant populations of P. vivax originated between 45,680 and 81,607 years ago. The phylogeny and the estimated time frame for the origination of current P. vivax populations are consistent with an “out of Asia” origin for P. vivax as hominoid parasite. The current debate regarding how the Duffy negative trait became fixed in Africa needs to be revisited, taking into account not only human genetic data but also the genetic diversity observed in the extant P. vivax populations and the phylogeny of the genus Plasmodium. PMID:15684081

Escalante, Ananias A.; Cornejo, Omar E.; Freeland, Denise E.; Poe, Amanda C.; Durrego, Ester; Collins, William E.; Lal, Altaf A.

2005-01-01

69

The multifunctional autophagy pathway in the human malaria parasite, Plasmodium falciparum  

PubMed Central

Autophagy is a catabolic pathway typically induced by nutrient starvation to recycle amino acids, but can also function in removing damaged organelles. In addition, this pathway plays a key role in eukaryotic development. To date, not much is known about the role of autophagy in apicomplexan parasites and more specifically in the human malaria parasite Plasmodium falciparum. Comparative genomic analysis has uncovered some, but not all, orthologs of autophagy-related (ATG) genes in the malaria parasite genome. Here, using a genome-wide in silico analysis, we confirmed that ATG genes whose products are required for vesicle expansion and completion are present, while genes involved in induction of autophagy and cargo packaging are mostly absent. We subsequently focused on the molecular and cellular function of P. falciparum ATG8 (PfATG8), an autophagosome membrane marker and key component of the autophagy pathway, throughout the parasite asexual and sexual erythrocytic stages. In this context, we showed that PfATG8 has a distinct and atypical role in parasite development. PfATG8 localized in the apicoplast and in vesicles throughout the cytosol during parasite development. Immunofluorescence assays of PfATG8 in apicoplast-minus parasites suggest that PfATG8 is involved in apicoplast biogenesis. Furthermore, treatment of parasite cultures with bafilomycin A1 and chloroquine, both lysosomotropic agents that inhibit autophagosome and lysosome fusion, resulted in dramatic morphological changes of the apicoplast, and parasite death. Furthermore, deep proteomic analysis of components associated with PfATG8 indicated that it may possibly be involved in ribophagy and piecemeal microautophagy of the nucleus. Collectively, our data revealed the importance and specificity of the autophagy pathway in the malaria parasite and offer potential novel therapeutic strategies. PMID:24275162

Cervantes, Serena; Bunnik, Evelien M; Saraf, Anita; Conner, Christopher M; Escalante, Aster; Sardiu, Mihaela E; Ponts, Nadia; Prudhomme, Jacques; Florens, Laurence; Le Roch, Karine G

2014-01-01

70

Direct Tests of Enzymatic Heme Degradation by the Malaria Parasite Plasmodium falciparum*  

PubMed Central

Malaria parasites generate vast quantities of heme during blood stage infection via hemoglobin digestion and limited de novo biosynthesis, but it remains unclear if parasites metabolize heme for utilization or disposal. Recent in vitro experiments with a heme oxygenase (HO)-like protein from Plasmodium falciparum suggested that parasites may enzymatically degrade some heme to the canonical HO product, biliverdin (BV), or its downstream metabolite, bilirubin (BR). To directly test for BV and BR production by P. falciparum parasites, we DMSO-extracted equal numbers of infected and uninfected erythrocytes and developed a sensitive LC-MS/MS assay to quantify these tetrapyrroles. We found comparable low levels of BV and BR in both samples, suggesting the absence of HO activity in parasites. We further tested live parasites by targeted expression of a fluorescent BV-binding protein within the parasite cytosol, mitochondrion, and plant-like plastid. This probe could detect exogenously added BV but gave no signal indicative of endogenous BV production within parasites. Finally, we recombinantly expressed and tested the proposed heme degrading activity of the HO-like protein, PfHO. Although PfHO bound heme and protoporphyrin IX with modest affinity, it did not catalyze heme degradation in vivo within bacteria or in vitro in UV absorbance and HPLC assays. These observations are consistent with PfHO's lack of a heme-coordinating His residue and suggest an alternative function within parasites. We conclude that P. falciparum parasites lack a canonical HO pathway for heme degradation and thus rely fully on alternative mechanisms for heme detoxification and iron acquisition during blood stage infection. PMID:22992734

Sigala, Paul A.; Crowley, Jan R.; Hsieh, Samantha; Henderson, Jeffrey P.; Goldberg, Daniel E.

2012-01-01

71

Large-scale growth of the Plasmodium falciparum malaria parasite in a wave bioreactor.  

PubMed

We describe methods for the large-scale in vitro culturing of synchronous and asynchronous blood-stage Plasmodium falciparum parasites in sterile disposable plastic bioreactors controlled by wave-induced motion (wave bioreactor). These cultures perform better than static flask cultures in terms of preserving parasite cell cycle synchronicity and reducing the number of multiple-infected erythrocytes. The straight-forward methods described here will facilitate the large scale production of malaria parasites for antigen and organelle isolation and characterisation, for the high throughput screening of compound libraries with whole cells or extracts, and the development of live- or whole-cell malaria vaccines under good manufacturing practice compliant standards. PMID:22326740

Dalton, John P; Demanga, Corine G; Reiling, Sarah J; Wunderlich, Juliane; Eng, Jenny W L; Rohrbach, Petra

2012-01-01

72

The malaria parasite Plasmodium vivax exhibits greater genetic diversity than Plasmodium falciparum.  

PubMed

We sequenced and annotated the genomes of four P. vivax strains collected from disparate geographic locations, tripling the number of genome sequences available for this understudied parasite and providing the first genome-wide perspective of global variability in this species. We observe approximately twice as much SNP diversity among these isolates as we do among a comparable collection of isolates of P. falciparum, a malaria-causing parasite that results in higher mortality. This indicates a distinct history of global colonization and/or a more stable demographic history for P. vivax relative to P. falciparum, which is thought to have undergone a recent population bottleneck. The SNP diversity, as well as additional microsatellite and gene family variability, suggests a capacity for greater functional variation in the global population of P. vivax. These findings warrant a deeper survey of variation in P. vivax to equip disease interventions targeting the distinctive biology of this neglected but major pathogen. PMID:22863733

Neafsey, Daniel E; Galinsky, Kevin; Jiang, Rays H Y; Young, Lauren; Sykes, Sean M; Saif, Sakina; Gujja, Sharvari; Goldberg, Jonathan M; Young, Sarah; Zeng, Qiandong; Chapman, Sinéad B; Dash, Aditya P; Anvikar, Anupkumar R; Sutton, Patrick L; Birren, Bruce W; Escalante, Ananias A; Barnwell, John W; Carlton, Jane M

2012-09-01

73

Conserved Mosquito/Parasite Interactions Affect Development of Plasmodium falciparum in Africa  

PubMed Central

In much of sub-Saharan Africa, the mosquito Anopheles gambiae is the main vector of the major human malaria parasite, Plasmodium falciparum. Convenient laboratory studies have identified mosquito genes that affect positively or negatively the developmental cycle of the model rodent parasite, P. berghei. Here, we use transcription profiling and reverse genetics to explore whether five disparate mosquito gene regulators of P. berghei development are also pertinent to A. gambiae/P. falciparum interactions in semi-natural conditions, using field isolates of this parasite and geographically related mosquitoes. We detected broadly similar albeit not identical transcriptional responses of these genes to the two parasite species. Gene silencing established that two genes affect similarly both parasites: infections are hindered by the intracellular local activator of actin cytoskeleton dynamics, WASP, but promoted by the hemolymph lipid transporter, ApoII/I. Since P. berghei is not a natural parasite of A. gambiae, these data suggest that the effects of these genes have not been drastically altered by constant interaction and co-evolution of A. gambiae and P. falciparum; this conclusion allowed us to investigate further the mode of action of these two genes in the laboratory model system using a suite of genetic tools and infection assays. We showed that both genes act at the level of midgut invasion during the parasite's developmental transition from ookinete to oocyst. ApoII/I also affects the early stages of oocyst development. These are the first mosquito genes whose significant effects on P. falciparum field isolates have been established by direct experimentation. Importantly, they validate for semi-field human malaria transmission the concept of parasite antagonists and agonists. PMID:18483558

Cohuet, Anna; Awono-Ambene, Parfait; De Iorio, Maria; Fontenille, Didier; Morlais, Isabelle; Christophides, George K.; Kafatos, Fotis C.; Vlachou, Dina

2008-01-01

74

Selection for high and low virulence in the malaria parasite Plasmodium chabaudi.  

PubMed Central

What stops parasites becoming ever more virulent? Conventional wisdom and most parasite-centred models of the evolution of virulence suppose that risk of host (and, hence, parasite) death imposes selection against more virulent strains. Here we selected for high and low virulence within each of two clones of the rodent malaria parasite Plasmodium chabaudi on the basis of between-host differences in a surrogate measure of virulence--loss of live weight post-infection. Despite imposing strong selection for low virulence which mimicked 50-75% host mortality, the low virulence lines increased in virulence as much as the high virulence lines. Thus, artificial selection on between-host differences in virulence was unable to counteract natural selection for increased virulence caused by within-host selection processes. The parasite's asexual replication rate and number of sexual transmission forms also increased in all lines, consistent with evolutionary models explaining high virulence. An upper bound to virulence, though not the asexual replication rate, was apparent, but this bound was not imposed by host mortality. Thus, we found evidence of the factors assumed to drive evolution of increased virulence, but not those thought to counter this selection. PMID:10331293

Mackinnon, M J; Read, A F

1999-01-01

75

Bloodmeal analysis reveals avian Plasmodium infections and broad host preferences of Culicoides (Diptera: Ceratopogonidae) vectors.  

PubMed

Changing environmental conditions and human encroachment on natural habitats bring human populations closer to novel sources of parasites, which might then develop into new emerging diseases. Diseases transmitted by host generalist vectors are of special interest due to their capacity to move pathogens into novel hosts. We hypothesize that humans using forests for recreation are exposed to a broad range of parasites from wild animals and their vectors. A corollary of this is that new vector-host, parasite-host, and vector-parasite associations could eventually develop. Thus, we expect to observe atypical vector-host associations. Using molecular bloodmeal analysis via amplification of the mtDNA COI gene we identified the vertebrate hosts of Culicoides (Diptera: Ceratopogonidae) species in a sub-urban forest of Southwestern Germany. Bloodmeals were also checked for haemosporidian infections by amplifying a fragment of the mtDNA cyt b gene. We identified a total of 20 Culicoides species, thirteen of which fed on humans. From 105 screened bloodmeals we obtained high quality sequences for 77 samples, 73 (94.8%) originated from humans, two from livestock (Bos taurus and Equus caballus), and two from wild birds (Sylvia atricapilla and Turdus merula). We found that four Culicoides species previously assumed to feed exclusively on either birds (C. kibunensis) or domestic mammals (C. chiopterus, C. deltus, C. scoticus) fed also on humans. A total of six Culicoides abdomens were infected with avian haemosporidian parasites (Plasmodium or Haemoproteus), four of those abdomens contained blood derived from humans. Our results suggest that parasites of wild animals may be transferred to humans through infectious bites of Culicoides vectors. Further, we show that Culicoides vectors believed to be a specialist on specific vertebrate groups can have plastic feeding preferences, and that Culicoides are susceptible to infection by Plasmodium parasites, though vector viability must still be experimentally demonstrated. PMID:22363557

Santiago-Alarcon, Diego; Havelka, Peter; Schaefer, Hinrich Martin; Segelbacher, Gernot

2012-01-01

76

Bloodmeal Analysis Reveals Avian Plasmodium Infections and Broad Host Preferences of Culicoides (Diptera: Ceratopogonidae) Vectors  

PubMed Central

Changing environmental conditions and human encroachment on natural habitats bring human populations closer to novel sources of parasites, which might then develop into new emerging diseases. Diseases transmitted by host generalist vectors are of special interest due to their capacity to move pathogens into novel hosts. We hypothesize that humans using forests for recreation are exposed to a broad range of parasites from wild animals and their vectors. A corollary of this is that new vector-host, parasite-host, and vector-parasite associations could eventually develop. Thus, we expect to observe atypical vector-host associations. Using molecular bloodmeal analysis via amplification of the mtDNA COI gene we identified the vertebrate hosts of Culicoides (Diptera: Ceratopogonidae) species in a sub-urban forest of Southwestern Germany. Bloodmeals were also checked for haemosporidian infections by amplifying a fragment of the mtDNA cyt b gene. We identified a total of 20 Culicoides species, thirteen of which fed on humans. From 105 screened bloodmeals we obtained high quality sequences for 77 samples, 73 (94.8%) originated from humans, two from livestock (Bos taurus and Equus caballus), and two from wild birds (Sylvia atricapilla and Turdus merula). We found that four Culicoides species previously assumed to feed exclusively on either birds (C. kibunensis) or domestic mammals (C. chiopterus, C. deltus, C. scoticus) fed also on humans. A total of six Culicoides abdomens were infected with avian haemosporidian parasites (Plasmodium or Haemoproteus), four of those abdomens contained blood derived from humans. Our results suggest that parasites of wild animals may be transferred to humans through infectious bites of Culicoides vectors. Further, we show that Culicoides vectors believed to be a specialist on specific vertebrate groups can have plastic feeding preferences, and that Culicoides are susceptible to infection by Plasmodium parasites, though vector viability must still be experimentally demonstrated. PMID:22363557

Santiago-Alarcon, Diego; Havelka, Peter; Schaefer, Hinrich Martin; Segelbacher, Gernot

2012-01-01

77

Malarial parasite diversity in chimpanzees: the value of comparative approaches to ascertain the evolution of Plasmodium falciparum antigens  

PubMed Central

Background Plasmodium falciparum shares its most recent common ancestor with parasites found in African apes; these species constitute the so-called Laverania clade. In this investigation, the evolutionary history of Plasmodium lineages found in chimpanzees (Pan troglodytes) was explored. Methods Here, the remainders of 74 blood samples collected as part of the chimpanzees’ routine health examinations were studied. For all positive samples with parasite lineages belonging to the Laverania clade, the complete mitochondrial genome (mtDNA), the gene encoding dihydrofolate reductase-thymidylate synthase (dhfr-ts), the chloroquine resistance transporter (Pfcrt), the circumsporozoite protein (csp), merozoite surface protein 2 (msp2), and the DBL-1 domain from var2CSA were amplified, cloned, and sequenced. Other Plasmodium species were included in the mtDNA, dhfr-ts, and csp analyses. Phylogenetic and evolutionary genetic analyses were performed, including molecular clock analyses on the mtDNA. Results/Conclusions Nine chimpanzees were malaria positive (12.2%); four of those infections were identified as P. falciparum, two as a Plasmodium reichenowi-like parasite or Plasmodium sp., one as Plasmodium gaboni, and two as Plasmodium malariae. All P. falciparum isolates were resistant to chloroquine indicating that the chimpanzees acquired such infections from humans in recent times. Such findings, however, are not sufficient for implicating chimpanzees as an animal reservoir for P. falciparum. Timing estimates support that the Laverania clade has co-existed with hominids for a long-period of time. The proposed species P. gaboni, Plasmodium billbrayi, and Plasmodium billcollinsi are monophyletic groups supporting that they are indeed different species. An expanded CSP phylogeny is presented, including all the Laverania species and other malarial parasites. Contrasting with other Plasmodium, the Laverania csp exhibits great conservation at the central tandem repeat region. Msp2 and var2CSA, however, show extended recent polymorphism in P. falciparum that likely originated after the P. reichenowi-P. falciparum split. The accumulation of such diversity may indicate adaptation to the human host. These examples support the notion that comparative approaches among P. falciparum and its related species will be of great value in understanding the evolution of proteins that are important in parasite invasion of the human red blood cell, as well as those involved in malaria pathogenesis. PMID:24044371

2013-01-01

78

Radioimmunoassay for detecting antibodies against murine malarial parasite antigens: monoclonal antibodies recognizing Plasmodium yoelii antigens  

SciTech Connect

A solid-phase radioimmunoassay (SPRIA) in microtiter wells was established for detecting antibodies against Plasmodium yoelii Ag. The SPRIA was found (1) to require as little as 5 ..mu..g of crude parasite Ag per well, (2) to be able to detect 0.5 ng of monoclonal Ab, and (3) to be 10/sup 4/ times more sensitive than the indirect fluorescent Ab staining technique. In a modification of the above assay using intact RBC as an Ag, hyperimmune serum showed significant binding to the surface of erythrocytes of mice infected with P. yoelii parasites but not to RBC of normal mice. Hybridomas were prepared by fusing infected mouse spleen cells with myeloma cells. Using the SPRIA, hybrids secreting Ab against P. yoelii 17XL Ag were detected.

Kim, K.J.; Taylor, D.W.; Evans, C.B.; Asofsky, R.

1980-12-01

79

Genetic diversity of chloroquine-resistant Plasmodium vivax parasites from the western Brazilian Amazon  

PubMed Central

The molecular basis of Plasmodium vivax chloroquine (CQ) resistance is still unknown. Elucidating the molecular background of parasites that are sensitive or resistant to CQ will help to identify and monitor the spread of resistance. By genotyping a panel of molecular markers, we demonstrate a similar genetic variability between in vitro CQ-resistant and sensitive phenotypes of P. vivax parasites. However, our studies identified two loci (MS8 and MSP1-B10) that could be used to discriminate between both CQ-susceptible phenotypes among P. vivax isolates in vitro. These preliminary data suggest that microsatellites may be used to identify and to monitor the spread of P. vivax-resistance around the world. PMID:25411001

Lizcano, Omaira Vera; Resende, Sarah Stela; Chehuan, Yonne F; Lacerda, Marcus VG; Brito, Cristiana FA; Zalis, Mariano G

2014-01-01

80

The Unique Structure of the Apicoplast Genome of the Rodent Malaria Parasite Plasmodium chabaudi chabaudi  

PubMed Central

The apicoplast, a non-photosynthetic plastid of apicomplexan species, has an extremely reduced but highly conserved genome. Here, the apicoplast genome of the rodent malaria parasite Plasmodium chabaudi chabaudi (Pcc) isolate CB was characterized. Although the set of genes in the genome is identical, the copy number of some tRNA genes differs between Pcc and other Plasmodium species because the Pcc DNA has only one rRNA/tRNA gene cluster, which is normally duplicated in other species. The location of the duplicated trnR(ACG) and trnM implies that one of the duplicated clusters in the ancestral molecule has been lost due to an intramolecular recombination event. The Pcc DNA occurs in two isoforms with an internal inversion between them. The presence of a unique variant in the duplicated trnT gene suggests that the two isoforms are interconvertible. This is the first report of the complete nucleotide sequence of a Plasmodium apicoplast DNA. PMID:23613931

Sato, Shigeharu; Sesay, Abdul K.; Holder, Anthony A.

2013-01-01

81

Plasmodium vivax: modern strategies to study a persistent parasite's life cycle.  

PubMed

Plasmodium vivax has unique attributes to support its survival in varying ecologies and climates. These include hypnozoite forms in the liver, an invasion preference for reticulocytes, caveola-vesicle complex structures in the infected erythrocyte membrane and rapidly forming and circulating gametocytes. These characteristics make this species very different from P. falciparum. Plasmodium cynomolgi and other related simian species have identical biology and can serve as informative models of P. vivax infections. Plasmodium vivax and its model parasites can be grown in non-human primates (NHP), and in short-term ex vivo cultures. For P. vivax, in the absence of in vitro culture systems, these models remain highly relevant side by side with human clinical studies. While post-genomic technologies allow for greater exploration of P. vivax-infected blood samples from humans, these come with restrictions. Two advantages of NHP models are that infections can be experimentally tailored to address hypotheses, including genetic manipulation. Also, systems biology approaches can capitalise on computational biology combined with set experimental infection periods and protocols, which may include multiple sampling times, different types of samples, and the broad use of "omics" technologies. Opportunities for research on vivax malaria are increasing with the use of existing and new methodological strategies in combination with modern technologies. PMID:23384620

Galinski, Mary R; Meyer, Esmeralda V S; Barnwell, John W

2013-01-01

82

A Droplet Microfluidics Platform for Highly Sensitive and Quantitative Detection of Malaria Causing Plasmodium Parasites Based on Enzyme Activity Measurement  

PubMed Central

We present an attractive new system for the specific and sensitive detection of the malaria causing Plasmodium parasites. The system relies on isothermal conversion of single DNA cleavage-ligation events catalyzed specifically by the Plasmodium enzyme topoisomerase I to micrometer sized products detectable at the single-molecule level. Combined with a droplet-microfluidics Lab-on-a-Chip platform, this design allowed for sensitive, specific and quantitative detection of all human malaria causing Plasmodium species in single drops of unprocessed blood with a detection limit of less than one parasite/?L. Moreover, the setup allowed for detection of Plasmodium parasites in non-invasive saliva samples from infected patients. During recent years malaria transmission has declined worldwide and with this the number of patients with low-parasite density has increased. Consequently, the need for accurate detection of even a few parasites is becoming increasingly important for the continued combat against the disease. We believe that the presented droplet-microfluidics platform, which has a high potential for adaptation to point-of-care setups suitable for low-resource settings may contribute significantly to meet this demand. Moreover, potential future adaptation of the presented setup for the detection of other microorganisms may form the basis for the development of a more generic platform for diagnosis, fresh water- or food quality control or other purposes within applied or basic science. PMID:23121492

Juul, Sissel; Nielsen, Christine J. F.; Labouriau, Rodrigo; Roy, Amit; Tesauro, Cinzia; Jensen, Pia W.; Harmsen, Charlotte; Kristoffersen, Emil L.; Chiu, Ya-Ling; Frøhlich, Rikke; Fiorani, Paola; Cox-Singh, Janet; Tordrup, David; Koch, Jørn; Bienvenu, Anne-Lise; Desideri, Alessandro; Picot, Stephane; Petersen, Eskild; Leong, Kam W.; Ho, Yi-Ping; Stougaard, Magnus; Knudsen, Birgitta R.

2012-01-01

83

Protein Export Marks the Early Phase of Gametocytogenesis of the Human Malaria Parasite Plasmodium falciparum*  

PubMed Central

Despite over a century of study of malaria parasites, parts of the Plasmodium falciparum life cycle remain virtually unknown. One of these is the early gametocyte stage, a round shaped cell morphologically similar to an asexual trophozoite in which major cellular transformations ensure subsequent development of the elongated gametocyte. We developed a protocol to obtain for the first time highly purified preparations of early gametocytes using a transgenic line expressing a green fluorescent protein from the onset of gametocytogenesis. We determined the cellular proteome (1427 proteins) of this parasite stage by high accuracy tandem mass spectrometry and newly determined the proteomes of asexual trophozoites and mature gametocytes, identifying altogether 1090 previously undetected parasite proteins. Quantitative label-free comparative proteomics analysis determined enriched protein clusters for the three parasite developmental stages. Gene set enrichment analysis on the 251 proteins enriched in the early gametocyte proteome revealed that proteins putatively exported and involved in erythrocyte remodeling are the most overrepresented protein set in these stages. One-tenth of the early gametocyte-enriched proteome is constituted of putatively exported proteins, here named PfGEXPs (P. falciparum gametocyte-exported proteins). N-terminal processing and N-acetylation at a conserved leucine residue within the Plasmodium export element pentamotif were detected by mass spectrometry for three such proteins in the early but not in the mature gametocyte sample, further supporting a specific role in protein export in early gametocytogenesis. Previous reports and results of our experiments confirm that the three proteins are indeed exported in the erythrocyte cytoplasm. This work indicates that protein export profoundly marks early sexual differentiation in P. falciparum, probably contributing to host cell remodeling in this phase of the life cycle, and that gametocyte-enriched molecules are recruited to modulate this process in gametocytogenesis. PMID:20332084

Silvestrini, Francesco; Lasonder, Edwin; Olivieri, Anna; Camarda, Grazia; van Schaijk, Ben; Sanchez, Massimo; Younis Younis, Sumera; Sauerwein, Robert; Alano, Pietro

2010-01-01

84

A next-generation genetically attenuated Plasmodium falciparum parasite created by triple gene deletion.  

PubMed

Immunization with live-attenuated Plasmodium sporozoites completely protects against malaria infection. Genetic engineering offers a versatile platform to create live-attenuated sporozoite vaccine candidates. We previously generated a genetically attenuated parasite (GAP) by deleting the P52 and P36 genes in the NF54 wild-type (WT) strain of Plasmodium falciparum (Pf p52(-)/p36(-) GAP). Preclinical assessment of p52(-)/p36(-) GAP in a humanized mouse model indicated an early and severe liver stage growth defect. However, human exposure to >200 Pf p52(-)/p36(-) GAP-infected mosquito bites in a safety trial resulted in peripheral parasitemia in one of six volunteers, revealing that this GAP was incompletely attenuated. We have now created a triple gene deleted GAP by additionally removing the SAP1 gene (Pf p52(-)/p36(-)/sap1(-) GAP) and employed flippase (FLP)/flippase recognition target (FRT) recombination for drug selectable marker cassette removal. This next-generation GAP was indistinguishable from WT parasites in blood stage and mosquito stage development. Using an improved humanized mouse model transplanted with human hepatocytes and human red blood cells, we show that despite a high-dose sporozoite challenge, Pf p52(-)/p36(-)/sap1(-) GAP did not transition to blood stage infection and appeared to be completely attenuated. Thus, clinical testing of Pf p52(-)/p36(-)/sap1(-) GAP assessing safety, immunogenicity, and efficacy against sporozoite challenge is warranted. PMID:24827907

Mikolajczak, Sebastian A; Lakshmanan, Viswanathan; Fishbaugher, Matthew; Camargo, Nelly; Harupa, Anke; Kaushansky, Alexis; Douglass, Alyse N; Baldwin, Michael; Healer, Julie; O'Neill, Matthew; Phuong, Thuan; Cowman, Alan; Kappe, Stefan H I

2014-09-01

85

Genome-wide functional analysis of Plasmodium protein phosphatases reveals key regulators of parasite development and differentiation.  

PubMed

Reversible protein phosphorylation regulated by kinases and phosphatases controls many cellular processes. Although essential functions for the malaria parasite kinome have been reported, the roles of most protein phosphatases (PPs) during Plasmodium development are unknown. We report a functional analysis of the Plasmodium berghei protein phosphatome, which exhibits high conservation with the P. falciparum phosphatome and comprises 30 predicted PPs with differential and distinct expression patterns during various stages of the life cycle. Gene disruption analysis of P. berghei PPs reveals that half of the genes are likely essential for asexual blood stage development, whereas six are required for sexual development/sporogony in mosquitoes. Phenotypic screening coupled with transcriptome sequencing unveiled morphological changes and altered gene expression in deletion mutants of two N-myristoylated PPs. These findings provide systematic functional analyses of PPs in Plasmodium, identify how phosphatases regulate parasite development and differentiation, and can inform the identification of drug targets for malaria. PMID:25011111

Guttery, David S; Poulin, Benoit; Ramaprasad, Abhinay; Wall, Richard J; Ferguson, David J P; Brady, Declan; Patzewitz, Eva-Maria; Whipple, Sarah; Straschil, Ursula; Wright, Megan H; Mohamed, Alyaa M A H; Radhakrishnan, Anand; Arold, Stefan T; Tate, Edward W; Holder, Anthony A; Wickstead, Bill; Pain, Arnab; Tewari, Rita

2014-07-01

86

Parasite impairment by targeting Plasmodium-infected RBCs using glyceryl-dilaurate nanostructured lipid carriers.  

PubMed

Antimalarial therapy is a major contributor to declining malaria morbidity and mortality. However, the high toxicity and low bioavailability of current antimalarials and emerging drug resistance necessitates drug-delivery research. We have previously developed glyceryl-dilaurate nanolipid carriers (GDL-NLCs) for antimalarial drug delivery. Here, we show evidence that GDL-NLCs themselves selectively target Plasmodium-infected red blood cells (iRBCs), and cause severe parasite impairment. The glyceryl-dilaurate lipid-moiety was important in the targeting. GDL-NLCs localized to the parasite mitochondrion and uptake led to mitochondrial-membrane polarization and Ca(2+) ion accumulation, ROS release, and stage-specific iRBC lysis. GDL-NLC treatment also resulted in externalization of iRBC-membrane phosphatidylserine and enhanced iRBC clearance by macrophages. GDL-NLC uptake disrupted the parasite-induced tubulovesicular network, which is vital for nutrient import by the parasite. Laser optical trap studies revealed that GDL-NLCs also restored iRBC flexibility. Such restoration of iRBC flexibility may help mitigate the vasculature clogging that can lead to cerebral malaria. We demonstrate the suitability of GDL-NLCs for intravenous delivery of antimalarial combinations artemether-clindamycin and artemether-lumefantrine in the murine model. Complete parasite clearance was achieved at 5-20% of the therapeutic dose of these combinations. Thus, this nanostructured lipid formulation can solubilize lipophilic drugs, selectively target and impair the parasite-infected red cell, and therefore constitutes a potent delivery vehicle for antimalarials. PMID:24818881

Jain, Soniya A; Basu, Himanish; Prabhu, Priyanka S; Soni, Umangi; Joshi, Medha D; Mathur, Deepak; Patravale, Vandana B; Pathak, Sulabha; Sharma, Shobhona

2014-08-01

87

Cytotoxic Effect of Curcumin on Malaria Parasite Plasmodium falciparum: Inhibition of Histone Acetylation and Generation of Reactive Oxygen Species  

Microsoft Academic Search

The emergence of multidrug-resistant parasites is a major concern for malaria control, and development of novel drugs is a high priority. Curcumin, a natural polyphenolic compound, possesses diverse pharmacological properties. Among its antiprotozoan activities, curcumin was potent against both chloroquine-sensitive and -resistant Plasmodium falciparum strains. Consistent with findings in mammalian cell lines, curcumin's prooxi- dant activity promoted the production in

Long Cui; Jun Miao; Liwang Cui

2007-01-01

88

Artemisinin-resistant Plasmodium falciparum in Pursat province, western Cambodia: a parasite clearance rate study  

PubMed Central

Summary Background Artemisinin-resistant Plasmodium falciparum has been reported in Pailin, western Cambodia, detected as a slow parasite clearance rate in vivo. Emergence of this phenotype in western Thailand and possibly elsewhere threatens to compromise the effectiveness of all artemisinin-based combination therapies. Parasite genetics is associated with parasite clearance rate but does not account for all variation. We investigated contributions of both parasite genetics and host factors to the artemisinin-resistance phenotype in Pursat, western Cambodia. Methods Between June 19 and Nov 28, 2009, and June 26 and Dec 6, 2010, we enrolled patients aged 10 years or older with uncomplicated falciparum malaria, a density of asexual parasites of at least 10 000 per ?L of whole blood, no symptoms or signs of severe malaria, no other cause of febrile illness, and no chronic illness. We gave participants 4 mg/kg artesunate at 0, 24, and 48 h, 15 mg/kg mefloquine at 72 h, and 10 mg/kg mefloquine at 96 h. We assessed parasite density on thick blood films every 6 h until undetectable. The parasite clearance half-life was calculated from the parasite clearance curve. We genotyped parasites with 18 microsatellite markers and patients for haemoglobin E, ?-thalassaemia, and a mutation of G6PD, which encodes glucose-6-phosphate dehydrogenase. To account for the possible effects of acquired immunity on half-life, we used three surrogates for increased likelihood of exposure to P falciparum: age, sex, and place of residence. This study is registered with ClinicalTrials.gov, number NCT00341003. Findings We assessed 3504 individuals from all six districts of Pursat province seeking treatment for malaria symptoms. We enrolled 168 patients with falciparum malaria who met inclusion criteria. The geometric mean half-life was 5.85 h (95% CI 5.54–6.18) in Pursat, similar to that reported in Pailin (p=0.109). We identified two genetically different parasite clone groups: parasite group 1 (PG1) and parasite group 2 (PG2). Non-significant increases in parasite clearance half-life were seen in patients with haemoglobin E (0.55 h; p=0.078), those of male sex (0.96 h; p=0.064), and in 2010 (0.68 h; p=0.068); PG1 was associated with a significant increase (0.79 h; p=0.033). The mean parasite heritability of half-life was 0.40 (SD 0.17). Interpretation Heritable artemisinin resistance is established in a second Cambodian province. To accurately identify parasites that are intrinsically susceptible or resistant to artemisinins, future studies should explore the effect of erythrocyte polymorphisms and specific immune responses on half-life variation. Funding Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health. PMID:22940027

Amaratunga, Chanaki; Sreng, Sokunthea; Suon, Seila; Phelps, Erika S; Stepniewska, Kasia; Lim, Pharath; Zhou, Chongjun; Mao, Sivanna; Anderson, Jennifer M; Lindegardh, Niklas; Jiang, Hongying; Song, Jianping; Su, Xin-zhuan; White, Nicholas J; Dondorp, Arjen M; Anderson, Tim J C; Fay, Michael P; Mu, Jianbing; Duong, Socheat; Fairhurst, Rick M

2013-01-01

89

Blood parasites in Owls with conservation implications for the Spotted Owl (Strix occidentalis)  

USGS Publications Warehouse

The three subspecies of Spotted Owl (Northern, Strix occidentalis courina; California, S. o. occidentalis; and Mexican, S. o. lucida) are all threatened by habitat loss and range expansion of the Barred Owl (S. varia). An unaddressed threat is whether Barred Owls could be a source of novel strains of disease such as avian malaria (Plasmodium spp.) or other blood parasites potentially harmful for Spotted Owls. Although Barred Owls commonly harbor Plasmodium infections, these parasites have not been documented in the Spotted Owl. We screened 111 Spotted Owls, 44 Barred Owls, and 387 owls of nine other species for haemosporidian parasites (Leucocytozoon, Plasmodium, and Haemoproteus spp.). California Spotted Owls had the greatest number of simultaneous multi-species infections (44%). Additionally, sequencing results revealed that the Northern and California Spotted Owl subspecies together had the highest number of Leucocytozoon parasite lineages (n=17) and unique lineages (n=12). This high level of sequence diversity is significant because only one leucocytozoon species (L. danilewskyi) has been accepted as valid among all owls, suggesting that L. danilewskyi is a cryptic species. Furthermore, a Plasmodium parasite was documented in a Northern Spotted Owl for the first time. West Coast Barred Owls had a lower prevalence of infection (15%) when compared to sympatric Spotted Owls (S. o. caurina 52%, S. o. occidentalis 79%) and Barred Owls from the historic range (61%). Consequently, Barred Owls on the West Coast may have a competitive advantage over the potentially immune compromised Spotted Owls. ?? 2008 Ishak et al.

Ishak, H.D.; Dumbacher, J.P.; Anderson, N.L.; Keane, J.J.; Valkiunas, G.; Haig, S.M.; Tell, L.A.; Sehgal, R.N.M.

2008-01-01

90

Blood Parasites in Owls with Conservation Implications for the Spotted Owl (Strix occidentalis)  

PubMed Central

The three subspecies of Spotted Owl (Northern, Strix occidentalis caurina; California, S. o. occidentalis; and Mexican, S. o. lucida) are all threatened by habitat loss and range expansion of the Barred Owl (S. varia). An unaddressed threat is whether Barred Owls could be a source of novel strains of disease such as avian malaria (Plasmodium spp.) or other blood parasites potentially harmful for Spotted Owls. Although Barred Owls commonly harbor Plasmodium infections, these parasites have not been documented in the Spotted Owl. We screened 111 Spotted Owls, 44 Barred Owls, and 387 owls of nine other species for haemosporidian parasites (Leucocytozoon, Plasmodium, and Haemoproteus spp.). California Spotted Owls had the greatest number of simultaneous multi-species infections (44%). Additionally, sequencing results revealed that the Northern and California Spotted Owl subspecies together had the highest number of Leucocytozoon parasite lineages (n?=?17) and unique lineages (n?=?12). This high level of sequence diversity is significant because only one Leucocytozoon species (L. danilewskyi) has been accepted as valid among all owls, suggesting that L. danilewskyi is a cryptic species. Furthermore, a Plasmodium parasite was documented in a Northern Spotted Owl for the first time. West Coast Barred Owls had a lower prevalence of infection (15%) when compared to sympatric Spotted Owls (S. o. caurina 52%, S. o. occidentalis 79%) and Barred Owls from the historic range (61%). Consequently, Barred Owls on the West Coast may have a competitive advantage over the potentially immune compromised Spotted Owls. PMID:18509541

Ishak, Heather D.; Dumbacher, John P.; Anderson, Nancy L.; Keane, John J.; Valki?nas, Gediminas; Haig, Susan M.; Tell, Lisa A.; Sehgal, Ravinder N. M.

2008-01-01

91

Host cell deformability is linked to transmission in the human malaria parasite Plasmodium falciparum  

PubMed Central

SUMMARY Gametocyte maturation in Plasmodium falciparum is a critical step in the transmission of malaria. While the majority of parasites proliferate asexually in red blood cells, a small fraction of parasites undergo sexual conversion and mature over two weeks to become competent for transmission to a mosquito vector. Immature gametocytes sequester in deep tissues while mature stages must be able to circulate, pass the spleen and present themselves to the mosquito vector in order to complete transmission. Sequestration of asexual red blood cell stage parasites has been investigated in great detail. These studies have demonstrated that induction of cytoadherence properties through specific receptor-ligand interactions coincides with a significant increase in host cell stiffness. In contrast, the adherence and biophysical properties of gametocyte-infected red blood cells have not been studied systematically. Utilizing a transgenic line for 3D live imaging, in vitro capillary assays and 3D finite element whole cell modeling, we studied the role of cellular deformability in determining the circulatory characteristics of gametocytes. Our analysis shows that the red blood cell deformability of immature gametocytes displays an overall decrease followed by rapid restoration in mature gametocytes. Intriguingly, simulations suggest that along with deformability variations, the morphological changes of the parasite may play an important role in tissue distribution in vivo. Taken together we present a model, which suggests that mature but not immature gametocytes circulate in the peripheral blood for uptake in the mosquito blood meal and transmission to another human host thus ensuring long term survival of the parasite. PMID:22417683

Aingaran, Mythili; Zhang, Rou; Law, Sue KaYee; Peng, Zhangli; Undisz, Andreas; Meyer, Evan; Diez-Silva, Monica; Burke, Thomas A.; Spielmann, Tobias; Lim, Chwee Teck; Suresh, Subra; Dao, Ming; Marti, Matthias

2012-01-01

92

Expression profiles of peroxiredoxins in liver stage of the rodent malaria parasite Plasmodium berghei.  

PubMed

mRNA and protein expression profiles for three peroxiredoxins (TPx-1, TPx-2 and 1-Cys Prx) of liver stage Plasmodium berghei were examined through quantitative reverse transcription-PCR (RT-PCR) and indirect immunofluorescence microscopy assay (IFA). RT-PCR experiments revealed that mRNA expression for the TPx-1 was detected shortly after the sporozoite infection and kept expressed until the schizont stage. In contrast, the mRNA expression for 1-Cys Prx had begun increasing when the parasite developed into the schizont stage. Using the IFA, TPx-1 and 1-Cys Prx were detected in the cytosol. This finding suggested the developmental stage-specific expression of the cytosolic enzymes in the liver stage parasite. On the other hand, the mRNA expression for TPx-2 had begun increasing at the trophozoite stage and peaked at the schizont stage. In the IFA, TPx-2 was found localized in the mitochondria. The increase of TPx-2 might be explained by the exponential development of the parasite during the schizont stage requiring ATP production which may induce reactive oxygen species (ROS) in the mitochondria. PMID:23237790

Usui, Miho; Masuda-Suganuma, Hirono; Fukumoto, Shinya; Angeles, Jose Ma M; Inoue, Noboru; Kawazu, Shin-ichiro

2013-06-01

93

The Clp Chaperones and Proteases of the Human Malaria Parasite Plasmodium falciparum  

SciTech Connect

The Clp chaperones and proteases play an important role in protein homeostasis in the cell. They are highly conserved across prokaryotes and found also in the mitochondria of eukaryotes and the chloroplasts of plants. They function mainly in the disaggregation, unfolding and degradation of native as well as misfolded proteins. Here, we provide a comprehensive analysis of the Clp chaperones and proteases in the human malaria parasite Plasmodium falciparum. The parasite contains four Clp ATPases, which we term PfClpB1, PfClpB2, PfClpC and PfClpM. One PfClpP, the proteolytic subunit, and one PfClpR, which is an inactive version of the protease, were also identified. Expression of all Clp chaperones and proteases was confirmed in blood-stage parasites. The proteins were localized to the apicoplast, a non-photosynthetic organelle that accommodates several important metabolic pathways in P. falciparum, with the exception of PfClpB2 (also known as Hsp101), which was found in the parasitophorous vacuole. Both PfClpP and PfClpR form mostly homoheptameric rings as observed by size-exclusion chromatography, analytical ultracentrifugation and electron microscopy. The X-ray structure of PfClpP showed the protein as a compacted tetradecamer similar to that observed for Streptococcus pneumoniae and Mycobacterium tuberculosis ClpPs. Our data suggest the presence of a ClpCRP complex in the apicoplast of P. falciparum.

Bakkouri, Majida El; Pow, Andre; Mulichak, Anne; Cheung, Kevin L.Y.; Artz, Jennifer D.; Amani, Mehrnaz; Fell, Stuart; de Koning-Ward, Tania F.; Goodman, C. Dean; McFadden, Geoffrey I.; Ortega, Joaquin; Hui, Raymond; Houry, Walid A. (Toronto); (McMaster U.); (HWMRI); (Melbourne); (Deakin)

2012-03-26

94

Leukocyte profiles for western fence lizards, Sceloporus occidentalis, naturally infected by the malaria parasite Plasmodium mexicanum.  

PubMed

Plasmodium mexicanum is a malaria parasite that naturally infects the western fence lizard, Sceloporus occidentalis , in northern California. We set out to determine whether lizards naturally infected with this malaria parasite have different leukocyte profiles, indicating an immune response to infection. We used 29 naturally infected western fence lizards paired with uninfected lizards based on sex, snout-to-vent length, tail status, and the presence-absence of ectoparasites such as ticks and mites, as well as the presence-absence of another hemoparasite, Schellackia occidentalis. Complete white blood cell (WBC) counts were conducted on blood smears stained with Giemsa, and the proportion of granulocytes per microliter of blood was estimated using the Avian Leukopet method. The abundance of each WBC class (lymphocytes, monocytes, heterophils, eosinophils, and basophils) in infected and uninfected lizards was compared to determine whether leukocyte densities varied with infection status. We found that the numbers of WBCs and lymphocytes per microliter of blood significantly differed (P < 0.05) between the 2 groups for females but not for males, whereas parasitemia was significantly correlated with lymphocyte counts for males, but not for females. This study supports the theory that infection with P. mexicanum stimulates the lizard's immune response to increase the levels of circulating WBCs, but what effect this has on the biology of the parasite remains unclear. PMID:24945903

Motz, Victoria L; Lewis, William D; Vardo-Zalik, Anne M

2014-10-01

95

Co-infections with Babesia microti and Plasmodium parasites along the China-Myanmar border  

PubMed Central

Background Babesiosis is an emerging health risk in several parts of the world. However, little is known about the prevalence of Babesia in malaria-endemic countries. The area along the China-Myanmar border in Yunnan is a main endemic area of malaria in P.R. China, however, human infection with Babesia microti (B. microti) is not recognized in this region, and its profile of co-infection is not yet clear. Methods To understand its profile of co-infections with B. microti, our investigation was undertaken in the malaria-endemic area along the China-Myanmar border in Yunnan between April 2012 and June 2013. Four parasite species, including B. microti, Plasmodium falciparum (P. falciparum), P. vivax, and P. malariae, were identified among 449 suspected febrile persons detected by nested polymerase chain reaction (PCR) assay based on small subunit ribosomal ribonucleic acid (RNA) genes of B. microti and Plasmodium spp. Results Of all the collected samples from febrile patients, mono-infection with B. microti, P. vivax, P. falciparum, and P. malariae accounted for 1.8% (8/449), 9.8% (44/449), 2.9% (13/449), and 0.2% (1/449), respectively. The rate of mixed infections of B. microti with P. falciparum or P. vivax are both 0.2% (1/449), and mixed infections of P. falciparum and P. vivax accounted for 1.1% (5/449). Conclusions This report supports the hypothesis that babesiosis caused by B. microti is emerging along the China-Myanmar border in the Yunnan province, P.R. China, but it was ignored because of low parasitemia or mixed infection with Plasmodium spp. More sensitive and specific diagnosis methods are needed to find the rapid response mechanism of emergency for babesiosis and malaria co-prevalence areas. PMID:24090043

2013-01-01

96

Role of the Plasmodium Export Element in Trafficking Parasite Proteins to the Infected Erythrocyte  

PubMed Central

The intracellular survival of Plasmodium falciparum within human erythrocytes is dependent on export of parasite proteins that remodel the host cell. Most exported proteins require a conserved motif (RxLxE/Q/D), termed the Plasmodium export element (PEXEL) or vacuolar targeting sequence (VTS), for targeting beyond the parasitophorous vacuole membrane and into the host cell; however, the precise role of this motif in export is poorly defined. We used transgenic P. falciparum expressing chimeric proteins to investigate the function of the PEXEL motif for export. The PEXEL constitutes a bifunctional export motif comprising a protease recognition sequence that is cleaved, in the endoplasmic reticulum, from proteins destined for export, in a PEXEL arginine- and leucine-dependent manner. Following processing, the remaining conserved PEXEL residue is required to direct the mature protein to the host cell. Furthermore, we demonstrate that N acetylation of proteins following N-terminal processing is a PEXEL-independent process that is insufficient for correct export to the host cell. This work defines the role of each residue in the PEXEL for export into the P. falciparum-infected erythrocyte. PMID:19055692

Boddey, Justin A; Moritz, Robert L; Simpson, Richard J; Cowman, Alan F

2009-01-01

97

Extensive lysine acetylation occurs in evolutionarily conserved metabolic pathways and parasite-specific functions during Plasmodium falciparum intraerythrocytic development  

PubMed Central

Summary Lysine acetylation has emerged as a major posttranslational modification involved in diverse cellular functions. Using a combination of immunoisolation and liquid chromatography coupled to accurate mass spectrometry, we determined the first acetylome of the human malaria parasite Plasmodium falciparum during its active proliferation in erythrocytes with 421 acetylation sites identified in 230 proteins. Lysine-acetylated proteins are distributed in the nucleus, cytoplasm, mitochondrion, and apicoplast. Whereas occurrence of lysine acetylation in a similarly wide range of cellular functions suggests conservation of lysine acetylation through evolution, the Plasmodium acetylome also revealed significant divergence from those of other eukaryotes and even the closely-related parasite Toxoplasma. This divergence is reflected in the acetylation of a large number of Plasmodium-specific proteins and different acetylation sites in evolutionarily conserved acetylated proteins. A prominent example is the abundant acetylation of proteins in the glycolysis pathway but relatively deficient acetylation of enzymes in the citrate cycle. Using specific transgenic lines and inhibitors, we determined that the acetyltransferase PfMYST and lysine deacetylases play important roles in regulating the dynamics of cytoplasmic protein acetylation. The Plasmodium acetylome provides an exciting start point for further exploration of functions of acetylation in the biology of malaria parasites. PMID:23796209

Miao, Jun; Lawrence, Matthew; Jeffers, Victoria; Zhao, Fangqing; Parker, Daniel; Ge, Ying; Sullivan, William J.; Cui, Liwang

2013-01-01

98

K13-Propeller Polymorphisms in Plasmodium falciparum Parasites From Sub-Saharan Africa.  

PubMed

Mutations in the Plasmodium falciparum K13-propeller domain have recently been shown to be important determinants of artemisinin resistance in Southeast Asia. This study investigated the prevalence of K13-propeller polymorphisms across sub-Saharan Africa. A total of 1212 P. falciparum samples collected from 12 countries were sequenced. None of the K13-propeller mutations previously reported in Southeast Asia were found, but 22 unique mutations were detected, of which 7 were nonsynonymous. Allele frequencies ranged between 1% and 3%. Three mutations were observed in >1 country, and the A578S was present in parasites from 5 countries. This study provides the baseline prevalence of K13-propeller mutations in sub-Saharan Africa. PMID:25367300

Kamau, Edwin; Campino, Susana; Amenga-Etego, Lucas; Drury, Eleanor; Ishengoma, Deus; Johnson, Kimberly; Mumba, Dieudonne; Kekre, Mihir; Yavo, William; Mead, Daniel; Bouyou-Akotet, Marielle; Apinjoh, Tobias; Golassa, Lemu; Randrianarivelojosia, Milijaona; Andagalu, Ben; Maiga-Ascofare, Oumou; Amambua-Ngwa, Alfred; Tindana, Paulina; Ghansah, Anita; MacInnis, Bronwyn; Kwiatkowski, Dominic; Djimde, Abdoulaye A

2014-11-01

99

Human Monoclonal Antibodies to Pf 155, a Major Antigen of Malaria Parasite Plasmodium falciparum  

NASA Astrophysics Data System (ADS)

Pf 155, a protein of the human malaria parasite Plasmodium falciparum, is strongly immunogenic in humans and is believed to be a prime candidate for the preparation of a vaccine. Human monoclonal antibodies to Pf 155 were obtained by cloning B cells that had been prepared from an immune donor and transformed with Epstein-Barr virus. When examined by indirect immunofluorescence, these antibodies stained the surface of infected erythrocytes, free merozoites, segmented schizonts, and gametocytes. They bound to a major polypeptide with a relative molecular weight of 155K and to two minor ones (135K and 120K), all having high affinity for human glycophorin. The antibodies strongly inhibited merozoite reinvasion in vitro, suggesting that they might be appropriate reagents for therapeutic administration in vivo.

Udomsangpetch, Rachanee; Lundgren, Katarina; Berzins, Klavs; Wahlin, Birgitta; Perlmann, Hedvig; Troye-Blomberg, Marita; Carlsson, Jan; Wahlgren, Mats; Perlmann, Peter; Bjorkman, Anders

1986-01-01

100

Reduced CD36-dependent tissue sequestration of Plasmodium-infected erythrocytes is detrimental to malaria parasite growth in vivo  

PubMed Central

Adherence of parasite-infected red blood cells (irbc) to the vascular endothelium of organs plays a key role in the pathogenesis of Plasmodium falciparum malaria. The prevailing hypothesis of why irbc adhere and sequester in tissues is that this acts as a mechanism of avoiding spleen-mediated clearance. Irbc of the rodent parasite Plasmodium berghei ANKA sequester in a fashion analogous to P. falciparum by adhering to the host receptor CD36. To experimentally determine the significance of sequestration for parasite growth, we generated a mutant P. berghei ANKA parasite with a reduced CD36-mediated adherence. Although the cognate parasite ligand binding to CD36 is unknown, we show that nonsequestering parasites have reduced growth and we provide evidence that in addition to avoiding spleen removal, other factors related to CD36-mediated sequestration are beneficial for parasite growth. These results reveal for the first time the importance of sequestration to a malaria infection, with implications for the development of strategies aimed at reducing pathology by inhibiting tissue sequestration. PMID:22184632

Fonager, Jannik; Pasini, Erica M.; Braks, Joanna A.M.; Klop, Onny; Ramesar, Jai; Remarque, Edmond J.; Vroegrijk, Irene O.C.M.; van Duinen, Sjoerd G.; Thomas, Alan W.; Khan, Shahid M.; Mann, Matthias; Kocken, Clemens H.M.; Janse, Chris J.

2012-01-01

101

Real-Time Imaging of the Intracellular Glutathione Redox Potential in the Malaria Parasite Plasmodium falciparum  

PubMed Central

In the malaria parasite Plasmodium falciparum, the cellular redox potential influences signaling events, antioxidant defense, and mechanisms of drug action and resistance. Until now, the real-time determination of the redox potential in malaria parasites has been limited because conventional approaches disrupt sub-cellular integrity. Using a glutathione biosensor comprising human glutaredoxin-1 linked to a redox-sensitive green fluorescent protein (hGrx1-roGFP2), we systematically characterized basal values and drug-induced changes in the cytosolic glutathione-dependent redox potential (EGSH) of drug-sensitive (3D7) and resistant (Dd2) P. falciparum parasites. Via confocal microscopy, we demonstrated that hGrx1-roGFP2 rapidly detects EGSH changes induced by oxidative and nitrosative stress. The cytosolic basal EGSH of 3D7 and Dd2 were estimated to be ?314.2±3.1 mV and ?313.9±3.4 mV, respectively, which is indicative of a highly reducing compartment. We furthermore monitored short-, medium-, and long-term changes in EGSH after incubation with various redox-active compounds and antimalarial drugs. Interestingly, the redox cyclers methylene blue and pyocyanin rapidly changed the fluorescence ratio of hGrx1-roGFP2 in the cytosol of P. falciparum, which can, however, partially be explained by a direct interaction with the probe. In contrast, quinoline and artemisinin-based antimalarial drugs showed strong effects on the parasites' EGSH after longer incubation times (24 h). As tested for various conditions, these effects were accompanied by a drop in total glutathione concentrations determined in parallel with alternative methods. Notably, the effects were generally more pronounced in the chloroquine-sensitive 3D7 strain than in the resistant Dd2 strain. Based on these results hGrx1-roGFP2 can be recommended as a reliable and specific biosensor for real-time spatiotemporal monitoring of the intracellular EGSH in P. falciparum. Applying this technique in further studies will enhance our understanding of redox regulation and mechanisms of drug action and resistance in Plasmodium and might also stimulate redox research in other pathogens. PMID:24348249

Kasozi, Denis; Mohring, Franziska; Rahlfs, Stefan; Meyer, Andreas J.; Becker, Katja

2013-01-01

102

The 'permeome' of the malaria parasite: an overview of the membrane transport proteins of Plasmodium falciparum  

PubMed Central

Background The uptake of nutrients, expulsion of metabolic wastes and maintenance of ion homeostasis by the intraerythrocytic malaria parasite is mediated by membrane transport proteins. Proteins of this type are also implicated in the phenomenon of antimalarial drug resistance. However, the initial annotation of the genome of the human malaria parasite Plasmodium falciparum identified only a limited number of transporters, and no channels. In this study we have used a combination of bioinformatic approaches to identify and attribute putative functions to transporters and channels encoded by the malaria parasite, as well as comparing expression patterns for a subset of these. Results A computer program that searches a genome database on the basis of the hydropathy plots of the corresponding proteins was used to identify more than 100 transport proteins encoded by P. falciparum. These include all the transporters previously annotated as such, as well as a similar number of candidate transport proteins that had escaped detection. Detailed sequence analysis enabled the assignment of putative substrate specificities and/or transport mechanisms to all those putative transport proteins previously without. The newly-identified transport proteins include candidate transporters for a range of organic and inorganic nutrients (including sugars, amino acids, nucleosides and vitamins), and several putative ion channels. The stage-dependent expression of RNAs for 34 candidate transport proteins of particular interest are compared. Conclusion The malaria parasite possesses substantially more membrane transport proteins than was originally thought, and the analyses presented here provide a range of novel insights into the physiology of this important human pathogen. PMID:15774027

Martin, Rowena E; Henry, Roselani I; Abbey, Janice L; Clements, John D; Kirk, Kiaran

2005-01-01

103

High-resolution three-dimensional imaging of red blood cells parasitized by Plasmodium falciparum and in situ hemozoin crystals using optical diffraction tomography  

E-print Network

We present high-resolution optical tomographic images of human red blood cells (RBC) parasitized by malaria-inducing Plasmodium falciparum (Pf)-RBCs. Three-dimensional (3-D) refractive index (RI) tomograms are reconstructed ...

Kim, Kyoohyun

104

Plasmodium falciparum parasites lacking histidine-rich protein 2 and 3: a review and recommendations for accurate reporting.  

PubMed

Malaria rapid diagnostic tests (RDTs) play a critical role in malaria case management, surveillance and case investigations. Test performance is largely determined by design and quality characteristics, such as detection sensitivity, specificity, and thermal stability. However, parasite characteristics such as variable or absent expression of antigens targeted by RDTs can also affect RDT performance. Plasmodium falciparum parasites lacking the PfHRP2 protein, the most common target antigen for detection of P. falciparum, have been reported in some regions. Therefore, accurately mapping the presence and prevalence of P. falciparum parasites lacking pfhrp2 would be an important step so that RDTs targeting alternative antigens, or microscopy, can be preferentially selected for use in such regions. Herein the available evidence and molecular basis for identifying malaria parasites lacking PfHRP2 is reviewed, and a set of recommended procedures to apply for future investigations for parasites lacking PfHRP2, is proposed. PMID:25052298

Cheng, Qin; Gatton, Michelle L; Barnwell, John; Chiodini, Peter; McCarthy, James; Bell, David; Cunningham, Jane

2014-01-01

105

Plasmodium falciparum parasites lacking histidine-rich protein 2 and 3: a review and recommendations for accurate reporting  

PubMed Central

Malaria rapid diagnostic tests (RDTs) play a critical role in malaria case management, surveillance and case investigations. Test performance is largely determined by design and quality characteristics, such as detection sensitivity, specificity, and thermal stability. However, parasite characteristics such as variable or absent expression of antigens targeted by RDTs can also affect RDT performance. Plasmodium falciparum parasites lacking the PfHRP2 protein, the most common target antigen for detection of P. falciparum, have been reported in some regions. Therefore, accurately mapping the presence and prevalence of P. falciparum parasites lacking pfhrp2 would be an important step so that RDTs targeting alternative antigens, or microscopy, can be preferentially selected for use in such regions. Herein the available evidence and molecular basis for identifying malaria parasites lacking PfHRP2 is reviewed, and a set of recommended procedures to apply for future investigations for parasites lacking PfHRP2, is proposed. PMID:25052298

2014-01-01

106

The Phosphoproteomes of Plasmodium falciparum and Toxoplasma gondii reveal unusual adaptations within and beyond the parasites’ boundaries  

PubMed Central

Summary Plasmodium falciparum and Toxoplasma gondii are obligate intracellular apicomplexan parasites that rapidly invade and extensively modify host cells. Protein phosphorylation is one mechanism by which these parasites can control such processes. Here we present a phosphoproteome analysis of peptides enriched from schizont stage P. falciparum and T. gondii tachyzoites that are either “intracellular” or purified away from host material. Using liquid chromatography and tandem mass-spectrometry we identified over 5,000 and 10,000 previously unknown phosphorylation sites in P. falciparum and T. gondii respectively, revealing that protein phosphorylation is an extensively used regulation mechanism both within and beyond parasite boundaries. Unexpectedly both parasites have phosphorylated tyrosines and P. falciparum has unusual phosphorylation motifs that are apparently shaped by its A:T-rich genome. This dataset provides important information on the role of phosphorylation in the host-pathogen interaction, and clues to the evolutionary forces operating on protein phosphorylation motifs in both parasites. PMID:22018241

Treeck, Moritz; Sanders, John L.; Elias, Joshua E.; Boothroyd, John C.

2012-01-01

107

Immune characterization of Plasmodium falciparum parasites with a shared genetic signature in a region of decreasing transmission.  

PubMed

As the intensity of malaria transmission has declined, Plasmodium falciparum parasite populations have displayed decreased clonal diversity resulting from the emergence of many parasites with common genetic signatures (CGS). We have monitored such CGS parasite clusters from 2006 to 2013 in Thiès, Senegal, using the molecular barcode. The first, and one of the largest observed clusters of CGS parasites, was present in 24% of clinical isolates in 2008, declined to 3.4% of clinical isolates in 2009, and then disappeared. To begin to explore the relationship between the immune responses of the population and the emergence and decline of specific parasite genotypes, we have determined whether antibodies to CGS parasites correlate with their prevalence. We measured (i) antibodies capable of inhibiting parasite growth in culture and (ii) antibodies recognizing the surfaces of infected erythrocytes (RBCs). IgG obtained from volunteers in 2009 showed increased reactivity to the surfaces of CGS-parasitized erythrocytes over IgG from 2008. Since P. falciparum EMP-1 (PfEMP-1) is a major variant surface antigen, we used var Ups quantitative reverse transcription-PCR (qRT-PCR) and sequencing with degenerate DBL1? domain primers to characterize the var genes expressed by CGS parasites after short-term in vitro culture. CGS parasites show upregulation of UpsA var genes and 2-cysteine-containing PfEMP-1 molecules and express the same dominant var transcript. Our work indicates that the CGS parasites in this cluster express similar var genes, more than would be expected by chance in the population, and that there is year-to-year variation in immune recognition of surface antigens on CGS parasite-infected erythrocytes. This study lays the groundwork for detailed investigations of the mechanisms driving the expansion or contraction of specific parasite clones in the population. PMID:25368109

Bei, Amy K; Diouf, Ababacar; Miura, Kazutoyo; Larremore, Daniel B; Ribacke, Ulf; Tullo, Gregory; Moss, Eli L; Neafsey, Daniel E; Daniels, Rachel F; Zeituni, Amir E; Nosamiefan, Iguosadolo; Volkman, Sarah K; Ahouidi, Ambroise D; Ndiaye, Daouda; Dieye, Tandakha; Mboup, Souleymane; Buckee, Caroline O; Long, Carole A; Wirth, Dyann F

2015-01-01

108

Cross-sectional study of specific antibodies to a polymorphic Plasmodium falciparum antigen and of parasite antigen genotypes in school children on the slope of Mount Cameroon  

Microsoft Academic Search

To investigate relationships between Plasmodium falciparum parasitaemia, parasite genotypes, and specific anti-parasite antibodies, 244 school children (aged 4 to 16 years) were studied in April\\/May 2002, the peak malaria transmission season in Buea, Cameroon. Antibody reactivities were analysed by ELISA using an array of recombinant antigens representing different sequences from the polymorphic block 2 region of the merozoite surface protein

Helen K Kimbi; Kevin K. A Tetteh; Spencer D Polley; David J Conway

2004-01-01

109

Mitochondrial metabolism of sexual and asexual blood stages of the malaria parasite Plasmodium falciparum  

PubMed Central

Background The carbon metabolism of the blood stages of Plasmodium falciparum, comprising rapidly dividing asexual stages and non-dividing gametocytes, is thought to be highly streamlined, with glycolysis providing most of the cellular ATP. However, these parasitic stages express all the enzymes needed for a canonical mitochondrial tricarboxylic acid (TCA) cycle, and it was recently proposed that they may catabolize glutamine via an atypical branched TCA cycle. Whether these stages catabolize glucose in the TCA cycle and what is the functional significance of mitochondrial metabolism remains unresolved. Results We reassessed the central carbon metabolism of P. falciparum asexual and sexual blood stages, by metabolically labeling each stage with 13C-glucose and 13C-glutamine, and analyzing isotopic enrichment in key pathways using mass spectrometry. In contrast to previous findings, we found that carbon skeletons derived from both glucose and glutamine are catabolized in a canonical oxidative TCA cycle in both the asexual and sexual blood stages. Flux of glucose carbon skeletons into the TCA cycle is low in the asexual blood stages, with glutamine providing most of the carbon skeletons, but increases dramatically in the gametocyte stages. Increased glucose catabolism in the gametocyte TCA cycle was associated with increased glucose uptake, suggesting that the energy requirements of this stage are high. Significantly, whereas chemical inhibition of the TCA cycle had little effect on the growth or viability of asexual stages, inhibition of the gametocyte TCA cycle led to arrested development and death. Conclusions Our metabolomics approach has allowed us to revise current models of P. falciparum carbon metabolism. In particular, we found that both asexual and sexual blood stages utilize a conventional TCA cycle to catabolize glucose and glutamine. Gametocyte differentiation is associated with a programmed remodeling of central carbon metabolism that may be required for parasite survival either before or after uptake by the mosquito vector. The increased sensitivity of gametocyte stages to TCA-cycle inhibitors provides a potential target for transmission-blocking drugs. PMID:23763941

2013-01-01

110

Antigenic Diversity of the Plasmodium vivax Circumsporozoite Protein in Parasite Isolates of Western Colombia  

PubMed Central

Circumsporozoite (CS) protein is a malaria antigen involved in sporozoite invasion of hepatocytes, and thus considered to have good vaccine potential. We evaluated the polymorphism of the Plasmodium vivax CS gene in 24 parasite isolates collected from malaria-endemic areas of Colombia. We sequenced 27 alleles, most of which (25/27) corresponded to the VK247 genotype and the remainder to the VK210 type. All VK247 alleles presented a mutation (Gly ? Asn) at position 28 in the N-terminal region, whereas the C-terminal presented three insertions: the ANKKAGDAG, which is common in all VK247 isolates; 12 alleles presented the insertion GAGGQAAGGNAANKKAGDAG; and 5 alleles presented the insertion GGNAGGNA. Both repeat regions were polymorphic in gene sequence and size. Sequences coding for B-, T-CD4+, and T-CD8+ cell epitopes were found to be conserved. This study confirms the high polymorphism of the repeat domain and the highly conserved nature of the flanking regions. PMID:21292878

Hernández-Martínez, Miguel Ángel; Escalante, Ananías A.; Arévalo-Herrera, Myriam; Herrera, Sócrates

2011-01-01

111

Long term persistence of clonal malaria parasite Plasmodium falciparum lineages in the Colombian Pacific region  

PubMed Central

Background Resistance to chloroquine and antifolate drugs has evolved independently in South America, suggesting that genotype - phenotype studies aimed at understanding the genetic basis of resistance to these and other drugs should be conducted in this continent. This research was conducted to better understand the population structure of Colombian Plasmodium falciparum in preparation for such studies. Results A set of 384 SNPs were genotyped in blood spot DNA samples from 447 P. falciparum infected subjects collected over a ten year period from four provinces of the Colombian Pacific coast to evaluate clonality, population structure and linkage disequilibrium (LD). Most infections (81%) contained a single predominant clone. These clustered into 136 multilocus genotypes (MLGs), with 32% of MLGs recovered from multiple (2 – 28) independent subjects. We observed extremely low genotypic richness (R?=?0.42) and long persistence of MLGs through time (median?=?537 days, range?=?1 – 2,997 days). There was a high probability (>5%) of sampling parasites from the same MLG in different subjects within 28 days, suggesting caution is needed when using genotyping methods to assess treatment success in clinical drug trials. Panmixia was rejected as four well differentiated subpopulations (FST?=?0.084 - 0.279) were identified. These occurred sympatrically but varied in frequency within the four provinces. Linkage disequilibrium (LD) decayed more rapidly (r2?=?0.17 for markers <10 kb apart) than observed previously in South American samples. Conclusions We conclude that Colombian populations have several advantages for association studies, because multiple clone infections are uncommon and LD decays over the scale of one or a few genes. However, the extensive population structure and low genotype richness will need to be accounted for when designing and analyzing association studies. PMID:23294725

2013-01-01

112

Proteomic Analysis of Detergent-resistant Membrane Microdomains in Trophozoite Blood Stage of the Human Malaria Parasite Plasmodium falciparum*  

PubMed Central

Intracellular pathogens contribute to a significant proportion of infectious diseases worldwide. The successful strategy of evading the immune system by hiding inside host cells is common to all the microorganism classes, which exploit membrane microdomains, enriched in cholesterol and sphingolipids, to invade and colonize the host cell. These assemblies, with distinct biochemical properties, can be isolated by means of flotation in sucrose density gradient centrifugation because they are insoluble in nonionic detergents at low temperature. We analyzed the protein and lipid contents of detergent-resistant membranes from erythrocytes infected by Plasmodium falciparum, the most deadly human malaria parasite. Proteins associated with membrane microdomains of trophic parasite blood stages (trophozoites) include an abundance of chaperones, molecules involved in vesicular trafficking, and enzymes implicated in host hemoglobin degradation. About 60% of the identified proteins contain a predicted localization signal suggesting a role of membrane microdomains in protein sorting/trafficking. To validate our proteomic data, we raised antibodies against six Plasmodium proteins not characterized previously. All the selected candidates were recovered in floating low-density fractions after density gradient centrifugation. The analyzed proteins localized either to internal organelles, such as the mitochondrion and the endoplasmic reticulum, or to exported membrane structures, the parasitophorous vacuole membrane and Maurer's clefts, implicated in targeting parasite proteins to the host erythrocyte cytosol or surface. The relative abundance of cholesterol and phospholipid species varies in gradient fractions containing detergent-resistant membranes, suggesting heterogeneity in the lipid composition of the isolated microdomain population. This study is the first report showing the presence of cholesterol-rich microdomains with distinct properties and subcellular localization in trophic stages of Plasmodium falciparum. PMID:24045696

Yam, Xue Yan; Birago, Cecilia; Fratini, Federica; Di Girolamo, Francesco; Raggi, Carla; Sargiacomo, Massimo; Bachi, Angela; Berry, Laurence; Fall, Gamou; Currà, Chiara; Pizzi, Elisabetta; Breton, Catherine Braun; Ponzi, Marta

2013-01-01

113

The Plasmodium vivax Merozoite Surface Protein 3? Sequence Reveals Contrasting Parasite Populations in Southern and Northwestern Thailand  

PubMed Central

Background Malaria control efforts have a significant impact on the epidemiology and parasite population dynamics. In countries aiming for malaria elimination, malaria transmission may be restricted to limited transmission hot spots, where parasite populations may be isolated from each other and experience different selection forces. Here we aim to examine the Plasmodium vivax population divergence in geographically isolated transmission zones in Thailand. Methodology We employed the P. vivax merozoite surface protein 3? (PvMSP3?) as a molecular marker for characterizing P. vivax populations based on the extensive diversity of this gene in Southeast Asian parasite populations. To examine two parasite populations with different transmission levels in Thailand, we obtained 45 P. vivax isolates from Tak Province, northwestern Thailand, where the annual parasite incidence (API) was more than 2%, and 28 isolates from Yala and Narathiwat Provinces, southern Thailand, where the API was less than 0.02%. We sequenced the PvMSP3? gene and examined its genetic diversity and molecular evolution between the parasite populations. Principal Findings Of 58 isolates containing single PvMSP3? alleles, 31 sequence types were identified. The overall haplotype diversity was 0.77±0.06 and nucleotide diversity 0.0877±0.0054. The northwestern vivax malaria population exhibited extensive haplotype diversity (HD) of PvMSP3? (HD?=?1.0). In contrast, the southern parasite population displayed a single PvMSP3? allele (HD?=?0), suggesting a clonal population expansion. This result revealed that the extent of allelic diversity in P. vivax populations in Thailand varies among endemic areas. Conclusion Malaria parasite populations in a given region may vary significantly in genetic diversity, which may be the result of control and influenced by the magnitude of malaria transmission intensity. This is an issue that should be taken into account for the implementation of P. vivax control measures such as drug policy and vaccine development. PMID:25412166

Kuamsab, Napaporn; Sattabongkot, Jetsumon; Sirichaisinthop, Jeeraphat; Jongwutiwes, Somchai; Cui, Liwang

2014-01-01

114

The Plasmodium falciparum chloroquine in vivo test: extended follow-up is more important than parasite counting.  

PubMed

349 in vivo tests of the susceptibility of Plasmodium falciparum to chloroquine, 25 mg/kg, were analysed. In some surveys, standard in vitro tests were also carried out. The proportions of sensitive and resistant infections in different areas found by the 2 methods were similar, but, within a given area, correlation between the two methods was often poor. Two RI cases and one RII/RIII case were sensitive in vitro, and it is suggested that the extended in vivo test may sometimes be more sensitive than the in vitro test, and that even in endemic areas, where reinfection is possible, patency on day 14 will nearly always be due to resistance. Parasite density data were analysed by calculating the geometric mean of each day's parasite density as a percentage of the day 0 parasite density + 0.1. Most resistant and sensitive infections attained minimal values on day 4, and it is proposed that assessment of sensitivity based on parasite densities should use day 4 values. Contrasts between materials were more clearly defined statistically when comparisons were based on ranking in vivo test classifications, than when based on day 4 parasitaemia. It is therefore suggested that, for epidemiological purposes, extension of tests to at least 14 d is more important than parasite counting. Parasitaemia above 20-25% of the day 0 value on day 2 in a severely ill patient, or persistent patency on day 4 in a symptomatic patient, are both indications for a change of treatment. PMID:3051548

Schapira, A; Almeida Franco, L T; Averkiev, L; Omawale; Schwalbach, J F; Suleimanov, G

1988-01-01

115

Assessing the Cost-Benefit Effect of a Plasmodium falciparum Drug Resistance Mutation on Parasite Growth In Vitro  

PubMed Central

Plasmodium falciparum mutations associated with antimalarial resistance may be beneficial for parasites under drug pressure, although they may also cause a fitness cost. We herein present an in vitro model showing how this combined effect on parasite growth varies with the drug concentration and suggest a calculated drug-specific cost-benefit index, indicating the possible advantage for mutated parasites. We specifically studied the D-to-Y change at position 1246 encoded by the pfmdr1 gene (pfmdr1 D1246Y) in relation to amodiaquine resistance. Susceptibilities to amodiaquine, desethylamodiaquine, and chloroquine, as well as relative fitness, were determined for two modified isogenic P. falciparum clones differing only in the pfmdr1 1246 position. Data were used to create a new comparative graph of relative growth in relation to the drug concentration and to calculate the ratio between the benefit of resistance and the fitness cost. Results were related to an in vivo allele selection analysis after amodiaquine or artesunate-amodiaquine treatment. pfmdr1 1246Y was associated with decreased susceptibility to amodiaquine and desethylamodiaquine but at a growth fitness cost of 11%. Mutated parasites grew less in low drug concentrations due to a predominating fitness cost, but beyond a breakpoint concentration they grew more due to a predominating benefit of increased resistance. The cost-benefit indexes indicated that pfmdr1 1246Y was most advantageous for amodiaquine-exposed parasites. In vivo, a first drug selection of mutant parasites followed by a fitness selection of wild-type parasites supported the in vitro data. This cost-benefit model may predict the risk for selection of drug resistance mutations in different malaria transmission settings. PMID:23208719

Ferreira, Pedro Eduardo; Mårtensson, Andreas; Ali, Abdullah; Björkman, Anders; Gil, José Pedro

2013-01-01

116

Accumulation of artemisinin trioxane derivatives within neutral lipids of Plasmodium falciparum malaria parasites is endoperoxide-dependent  

PubMed Central

The antimalarial trioxanes, exemplified by the naturally occurring sesquiterpene lactone artemisinin and its semi-synthetic derivatives, contain an endoperoxide pharmacophore that lends tremendous potency against Plasmodium parasites. Despite decades of research, their mechanism of action remains unresolved. A leading model of anti-plasmodial activity hypothesizes that iron-mediated cleavage of the endoperoxide bridge generates cytotoxic drug metabolites capable of damaging cellular macromolecules. To probe the malarial targets of the endoperoxide drugs, we studied the distribution of fluorescent dansyl trioxane derivatives in living, intraerythrocytic-stage P. falciparum parasites using microscopic imaging. The fluorescent trioxanes rapidly accumulated in parasitized erythrocytes, localizing within digestive vacuole-associated neutral lipid bodies of trophozoites and schizonts, and surrounding the developing merozoite membranes. Artemisinin pre-treatment significantly reduced fluorescent labeling of neutral lipid bodies, while iron chelation increased non-specific cytoplasmic localization. To further explore the effects of endoperoxides on cellular lipids, we used an oxidation-sensitive BODIPY lipid probe to show the presence of artemisinin-induced peroxyl radicals in parasite membranes. Lipid extracts from artemisinin-exposed parasites contained increased amounts of free fatty acids and a novel cholesteryl ester. The cellular accumulation patterns and effects on lipids were entirely endoperoxide-dependent, as inactive dioxolane analogs lacking the endoperoxide moiety failed to label neutral lipid bodies or induce oxidative membrane damage. In the parasite digestive vacuole, neutral lipids closely associate with heme and promote hemozoin formation. We propose that the trioxane artemisinin and its derivatives are activated by heme-iron within the neutral lipid environment where they initiate oxidation reactions that damage parasite membranes. PMID:19022224

Hartwig, Carmony L.; Rosenthal, Andrew S.; Angelo, John D'; Griffin, Carol E.; Posner, Gary H.; Cooper, Roland A.

2009-01-01

117

Baculovirus-vectored multistage Plasmodium vivax vaccine induces both protective and transmission-blocking immunities against transgenic rodent malaria parasites.  

PubMed

A multistage malaria vaccine targeting the pre-erythrocytic and sexual stages of Plasmodium could effectively protect individuals against infection from mosquito bites and provide transmission-blocking (TB) activity against the sexual stages of the parasite, respectively. This strategy could help prevent malaria infections in individuals and, on a larger scale, prevent malaria transmission in communities of endemicity. Here, we describe the development of a multistage Plasmodium vivax vaccine which simultaneously expresses P. vivax circumsporozoite protein (PvCSP) and P25 (Pvs25) protein of this species as a fusion protein, thereby acting as a pre-erythrocytic vaccine and a TB vaccine, respectively. A new-concept vaccine platform based on the baculovirus dual-expression system (BDES) was evaluated. The BDES-Pvs25-PvCSP vaccine displayed correct folding of the Pvs25-PvCSP fusion protein on the viral envelope and was highly expressed upon transduction of mammalian cells in vitro. This vaccine induced high levels of antibodies to Pvs25 and PvCSP and elicited protective (43%) and TB (82%) efficacies against transgenic P. berghei parasites expressing the corresponding P. vivax antigens in mice. Our data indicate that our BDES, which functions as both a subunit and DNA vaccine, can offer a promising multistage vaccine capable of delivering a potent antimalarial pre-erythrocytic and TB response via a single immunization regimen. PMID:25092912

Mizutani, Masanori; Iyori, Mitsuhiro; Blagborough, Andrew M; Fukumoto, Shinya; Funatsu, Tomohiro; Sinden, Robert E; Yoshida, Shigeto

2014-10-01

118

Studies on the effects of sida acuta and vetiveria zizanioides against the malarial vector, anopheles stephensi and malarial parasite, plasmodium berghei  

Technology Transfer Automated Retrieval System (TEKTRAN)

Methanolic extracts of Sida acuta and Vetiveria zizanioides leaves and root were studied for toxicity to Anopheles stephensi mosquitoes and to the malaria parasite Plasmodium berghei in mice. The extracts reduced parasitemia levels in mice by 17-69%, depending on extract concentration. Median le...

119

A programmed cell death pathway in the malaria parasite Plasmodium falciparum has general features of mammalian apoptosis but is mediated by clan CA cysteine proteases  

Microsoft Academic Search

Several recent discoveries of the hallmark features of programmed cell death (PCD) in Plasmodium falciparum have presented the possibility of revealing novel targets for antimalarial therapy. Using a combination of cell-based assays, flow cytometry and fluorescence microscopy, we detected features including mitochondrial dysregulation, activation of cysteine proteases and in situ DNA fragmentation in parasites induced with chloroquine (CQ) and staurosporine

J-H Ch'ng; S R Kotturi; A G-L Chong; M J Lear; K S-W Tan; KS-W Tan

2010-01-01

120

The origin and diversification of the merozoite surface protein 3 (msp3) multi-gene family in Plasmodium vivax and related parasites.  

PubMed

The genus Plasmodium is a diversified group of parasites with more than 200 known species that includes those causing malaria in humans. These parasites use numerous proteins in a complex process that allows them to invade the red blood cells of their vertebrate hosts. Many of those proteins are part of multi-gene families; one of which is the merozoite surface protein-3 (msp3) family. The msp3 multi-gene family is considered important in the two main human parasites, Plasmodium vivax and Plasmodium falciparum, as its paralogs are simultaneously expressed in the blood stage (merozoite) and are immunogenic. There are large differences among Plasmodium species in the number of paralogs in this family. Such differences have been previously explained, in part, as adaptations that allow the different Plasmodium species to invade their hosts. To investigate this, we characterized the array containing msp3 genes among several Plasmodium species, including P. falciparum and P. vivax. We first found no evidence indicating that the msp3 family of P. falciparum was homologous to that of P. vivax. Subsequently, by focusing on the diverse clade of nonhuman primate parasites to which P. vivax is closely related, where homology was evident, we found no evidence indicating that the interspecies variation in the number of paralogs was an adaptation related to changes in host range or host switches. Overall, we hypothesize that the evolution of the msp3 family in P. vivax is consistent with a model of multi-allelic diversifying selection where the paralogs may have functionally redundant roles in terms of increasing antigenic diversity. Thus, we suggest that the expressed MSP3 proteins could serve as "decoys", via antigenic diversity, during the critical process of invading the host red blood cells. PMID:24862221

Rice, Benjamin L; Acosta, Mónica M; Pacheco, M Andreína; Carlton, Jane M; Barnwell, John W; Escalante, Ananias A

2014-09-01

121

Target evaluation of deoxyhypusine synthase from Theileria parva the neglected animal parasite and its relationship to Plasmodium.  

PubMed

East Coast fever (ECF) is a tick-borne disease caused by the parasite Theileria parva which infects cattle. In Sub-Saharan Africa it leads to enormous economic costs. After a bite of a tick, sporozoites invade the host lymphocytes and develop into schizonts. At this stage the parasite transforms host lymphocytes resulting in the clonal expansion of infected lymphocytes. Animals develop a lymphoma like disorder after infection which is rapidly fatal. Hitherto, a few drugs of the quinone type can cure the disease. However, therapy can only be successful after early diagnosis. The genera Theileria and Plasmodium, which includes the causative agent of human malaria, are closely related apicomplexan parasites. Enzymes of the hypusine pathway, a posttranslational modification in eukaryotic initiation factor EIF-5A, have shown to be druggable targets in Plasmodium. We identified the first enzyme of the hypusine pathway from T. parva, the deoxyhypusine synthase (DHS), which is located on chromosome 2 of the Muguga strain. Transcription is significantly increased in schizonts. The expressed T. parva DHS reveals an open reading frame (ORF) of 370 amino acids after expression in Escherichia coli Rosetta cells with a molecular size of 41.26 kDa and a theoretical pI of 5.26. Screening of the Malaria Box which consists of 400 active compounds resulted in a novel heterocyclic compound with a guanyl spacer which reduced the activity of T. parva DHS to 45%. In sum, the guanyl residue seems to be an important lead structure for inhibition of Theileria DHS. Currently, more different guanyl analogues from the Malaria Box are tested in inhibitor experiments to determine their efficacy. PMID:24909679

Njuguna, James T; von Koschitzky, Imke; Gerhardt, Heike; Lämmerhofer, Michael; Choucry, Ali; Pink, Mario; Schmitz-Spahnke, Simone; Bakheit, Mohammed A; Strube, Christina; Kaiser, Annette

2014-08-01

122

Global distribution of polymorphisms associated with delayed Plasmodium falciparum parasite clearance following artemisinin treatment: Genotyping of archive blood samples.  

PubMed

The recent emergence and spread of artemisinin-resistant Plasmodium falciparum isolates is a growing concern for global malaria-control efforts. A recent genome-wide analysis study identified two SNPs at genomic positions MAL10-688956 and MAL13-1718319, which are linked to delayed clearance of parasites following artemisinin combination therapy (ACT). It is expected that continuous artemisinin pressure will affect the distribution of these SNPs. Here, we investigate the worldwide distribution of these SNPs using a large number of archived samples in order to generate baseline data from the period before the emergence of ACT resistance. The presence of SNPs in MAL10-688956 and MAL13-1718319 was assessed by nested PCR RFLP and direct DNA sequencing using 653 global P. falciparum samples obtained before the reported emergence of ACT resistance. SNPs at MAL10-688956 and MAL13-1718319 associated with delayed parasite clearance following ACT administration were observed in 8% and 3% of parasites, respectively, mostly in Cambodia and Thailand. Parasites harbouring both SNPs were found in only eight (1%) isolates, all of which were from Cambodia and Thailand. Linkage disequilibrium was detected between MAL10-688956 and MAL13-1718319, suggesting that this SNP combination may have been selected by ACT drug pressure. Neither of the SNPs associated with delayed parasite clearance were observed in samples from Africa or South America. Baseline information of the geographical difference of MAL10-688956 and MAL13-1718319 SNPs provides a solid basis for assessing whether these SNPs are selected by artemisinin-based combination therapies. PMID:25449286

Murai, Kenji; Culleton, Richard; Hisaoka, Teruhiko; Endo, Hiroyoshi; Mita, Toshihiro

2014-11-01

123

Loss of pH Control in Plasmodium falciparum Parasites Subjected to Oxidative Stress  

PubMed Central

The intraerythrocytic malaria parasite is susceptible to oxidative stress and this may play a role in the mechanism of action of some antimalarial agents. Here we show that exposure of the intraerythrocytic malaria parasite to the oxidising agent hydrogen peroxide results in a fall in the intracellular ATP level and inhibition of the parasite's V-type H+-ATPase, causing a loss of pH control in both the parasite cytosol and the internal digestive vacuole. In contrast to the V-type H+-ATPase, the parasite's digestive vacuole H+-pyrophosphatase is insensitive to hydrogen peroxide-induced oxidative stress. This work provides insights into the effects of oxidative stress on the intraerythrocytic parasite, as well as providing an alternative possible explanation for a previous report that light-induced oxidative stress causes selective lysis of the parasite's digestive vacuole. PMID:23536836

van Schalkwyk, Donelly A.; Saliba, Kevin J.; Biagini, Giancarlo A.; Bray, Patrick G.; Kirk, Kiaran

2013-01-01

124

Multiple genetic origins of histidine-rich protein 2 gene deletion in Plasmodium falciparum parasites from Peru  

PubMed Central

The majority of malaria rapid diagnostic tests (RDTs) detect Plasmodium falciparum histidine-rich protein 2 (PfHRP2), encoded by the pfhrp2 gene. Recently, P. falciparum isolates from Peru were found to lack pfhrp2 leading to false-negative RDT results. We hypothesized that pfhrp2-deleted parasites in Peru derived from a single genetic event. We evaluated the parasite population structure and pfhrp2 haplotype of samples collected between 1998 and 2005 using seven neutral and seven chromosome 8 microsatellite markers, respectively. Five distinct pfhrp2 haplotypes, corresponding to five neutral microsatellite-based clonal lineages, were detected in 1998-2001; pfhrp2 deletions occurred within four haplotypes. In 2003-2005, outcrossing among the parasite lineages resulted in eight population clusters that inherited the five pfhrp2 haplotypes seen previously and a new haplotype; pfhrp2 deletions occurred within four of these haplotypes. These findings indicate that the genetic origin of pfhrp2 deletion in Peru was not a single event, but likely occurred multiple times. PMID:24077522

Akinyi, Sheila; Hayden, Tonya; Gamboa, Dionicia; Torres, Katherine; Bendezu, Jorge; Abdallah, Joseph F.; Griffing, Sean M.; Quezada, Wilmer Marquiño; Arrospide, Nancy; De Oliveira, Alexandre Macedo; Lucas, Carmen; Magill, Alan J.; Bacon, David J.; Barnwell, John W.; Udhayakumar, Venkatachalam

2013-01-01

125

Multiple genetic origins of histidine-rich protein 2 gene deletion in Plasmodium falciparum parasites from Peru.  

PubMed

The majority of malaria rapid diagnostic tests (RDTs) detect Plasmodium falciparum histidine-rich protein 2 (PfHRP2), encoded by the pfhrp2 gene. Recently, P. falciparum isolates from Peru were found to lack pfhrp2 leading to false-negative RDT results. We hypothesized that pfhrp2-deleted parasites in Peru derived from a single genetic event. We evaluated the parasite population structure and pfhrp2 haplotype of samples collected between 1998 and 2005 using seven neutral and seven chromosome 8 microsatellite markers, respectively. Five distinct pfhrp2 haplotypes, corresponding to five neutral microsatellite-based clonal lineages, were detected in 1998-2001; pfhrp2 deletions occurred within four haplotypes. In 2003-2005, outcrossing among the parasite lineages resulted in eight population clusters that inherited the five pfhrp2 haplotypes seen previously and a new haplotype; pfhrp2 deletions occurred within four of these haplotypes. These findings indicate that the genetic origin of pfhrp2 deletion in Peru was not a single event, but likely occurred multiple times. PMID:24077522

Akinyi, Sheila; Hayden, Tonya; Gamboa, Dionicia; Torres, Katherine; Bendezu, Jorge; Abdallah, Joseph F; Griffing, Sean M; Quezada, Wilmer Marquiño; Arrospide, Nancy; De Oliveira, Alexandre Macedo; Lucas, Carmen; Magill, Alan J; Bacon, David J; Barnwell, John W; Udhayakumar, Venkatachalam

2013-01-01

126

Multicolor bioluminescence boosts malaria research: quantitative dual-color assay and single-cell imaging in Plasmodium falciparum parasites.  

PubMed

New reliable and cost-effective antimalarial drug screening assays are urgently needed to identify drugs acting on different stages of the parasite Plasmodium falciparum, and particularly those responsible for human-to-mosquito transmission, that is, the P. falciparum gametocytes. Low Z' factors, narrow dynamic ranges, and/or extended assay times are commonly reported in current gametocyte assays measuring gametocyte-expressed fluorescent or luciferase reporters, endogenous ATP levels, activity of gametocyte enzymes, or redox-dependent dye fluorescence. We hereby report on a dual-luciferase gametocyte assay with immature and mature P. falciparum gametocyte stages expressing red and green-emitting luciferases from Pyrophorus plagiophthalamus under the control of the parasite sexual stage-specific pfs16 gene promoter. The assay was validated with reference antimalarial drugs and allowed to quantitatively and simultaneously measure stage-specific drug effects on parasites at different developmental stages. The optimized assay, requiring only 48 h incubation with drugs and using a cost-effective luminogenic substrate, significantly reduces assay cost and time in comparison to state-of-the-art analogous assays. The assay had a Z' factor of 0.71 ± 0.03, and it is suitable for implementation in 96- and 384-well microplate formats. Moreover, the use of a nonlysing D-luciferin substrate significantly improved the reliability of the assay and allowed one to perform, for the first time, P. falciparum bioluminescence imaging at single-cell level. PMID:25102353

Cevenini, Luca; Camarda, Grazia; Michelini, Elisa; Siciliano, Giulia; Calabretta, Maria Maddalena; Bona, Roberta; Kumar, T R Santha; Cara, Andrea; Branchini, Bruce R; Fidock, David A; Roda, Aldo; Alano, Pietro

2014-09-01

127

Characterization of Plasmodium falciparum cdc2-related kinase and the effects of a CDK inhibitor on the parasites in erythrocytic schizogony.  

PubMed

The cell cycle of Plasmodium is unique among major eukaryotic cell cycle models. Cyclin-dependent kinases (CDKs) are thought to be the key molecular switches that regulate cell cycle progression in the parasite. However, little information is available about Plasmodium CDKs. The present study was performed to investigate the effects of a CDK inhibitor, olomoucine, on the erythrocytic growth of Plasmodium falciparum. This agent inhibited the growth of the parasite at the trophozoite/schizont stage. Furthermore, we characterized the Plasmodium CDK homolog, P. falciparum cdc2-related kinase-1 (Pfcrk-1), which is a potential target of olomoucine. We synthesized a functional kinase domain of Pfcrk-1 as a GST fusion protein using a wheat germ protein expression system, and examined its phosphorylation activity. The activity of this catalytic domain was higher than that of GST-GFP control, but the same as that of a kinase-negative mutant of Pfcrk-1. After the phosphatase treatment, the labeling of [?-(32)P]ATP was abolished. Recombinant human cyclin proteins were added to these kinase reactions, but there were no differences in activity. This report provides important information for the future investigation of Plasmodium CDKs. PMID:23688804

Iwanaga, Tatsuya; Sugi, Tatsuki; Kobayashi, Kyousuke; Takemae, Hitoshi; Gong, Haiyan; Ishiwa, Akiko; Murakoshi, Fumi; Recuenco, Frances C; Horimoto, Taisuke; Akashi, Hiroomi; Kato, Kentaro

2013-10-01

128

KAI407, a Potent Non-8-Aminoquinoline Compound That Kills Plasmodium cynomolgi Early Dormant Liver Stage Parasites In Vitro  

PubMed Central

Preventing relapses of Plasmodium vivax malaria through a radical cure depends on use of the 8-aminoquinoline primaquine, which is associated with safety and compliance issues. For future malaria eradication strategies, new, safer radical curative compounds that efficiently kill dormant liver stages (hypnozoites) will be essential. A new compound with potential radical cure activity was identified using a low-throughput assay of in vitro-cultured hypnozoite forms of Plasmodium cynomolgi (an excellent and accessible model for Plasmodium vivax). In this assay, primary rhesus hepatocytes are infected with P. cynomolgi sporozoites, and exoerythrocytic development is monitored in the presence of compounds. Liver stage cultures are fixed after 6 days and stained with anti-Hsp70 antibodies, and the relative proportions of small (hypnozoite) and large (schizont) forms relative to the untreated controls are determined. This assay was used to screen a series of 18 known antimalarials and 14 new non-8-aminoquinolines (preselected for blood and/or liver stage activity) in three-point 10-fold dilutions (0.1, 1, and 10 ?M final concentrations). A novel compound, designated KAI407 showed an activity profile similar to that of primaquine (PQ), efficiently killing the earliest stages of the parasites that become either primary hepatic schizonts or hypnozoites (50% inhibitory concentration [IC50] for hypnozoites, KAI407, 0.69 ?M, and PQ, 0.84 ?M; for developing liver stages, KAI407, 0.64 ?M, and PQ, 0.37 ?M). When given as causal prophylaxis, a single oral dose of 100 mg/kg of body weight prevented blood stage parasitemia in mice. From these results, we conclude that KAI407 may represent a new compound class for P. vivax malaria prophylaxis and potentially a radical cure. PMID:24366744

Zeeman, Anne-Marie; van Amsterdam, Sandra M.; McNamara, Case W.; Voorberg-van der Wel, Annemarie; Klooster, Els J.; van den Berg, Alexander; Remarque, Edmond J.; Plouffe, David M.; van Gemert, Geert-Jan; Luty, Adrian; Sauerwein, Robert; Gagaring, Kerstin; Borboa, Rachel; Chen, Zhong; Kuhen, Kelli; Glynne, Richard J.; Chatterjee, Arnab K.; Nagle, Advait; Roland, Jason; Winzeler, Elizabeth A.; Leroy, Didier; Campo, Brice; Diagana, Thierry T.; Yeung, Bryan K. S.; Thomas, Alan W.

2014-01-01

129

A Receptor for the Malarial Parasite Plasmodium vivax: The Erythrocyte Chemokine Receptor  

Microsoft Academic Search

Plasmodium vivax and P. falciparum are the major causes of human malaria, except in sub-Saharan Africa where people lack the Duffy blood group antigen, the erythrocyte receptor for P. vivax. Duffy negative human erythrocytes are resistant to invasion by P. vivax and the related monkey malaria, P. knowlesi. Several lines of evidence in the present study indicate that the Duffy

Richard Horuk; Chetan E. Chitnis; Walter C. Darbonne; Timothy J. Colby; Anne Rybicki; Terence J. Hadley; Louis H. Miller

1993-01-01

130

Disruption of the Plasmodium falciparum liver-stage antigen-1 locus causes a differentiation defect in late liver-stage parasites  

PubMed Central

Summary The malaria parasite Plasmodium falciparum infects humans and first targets the liver where liver-stage parasites undergo pre-erythrocytic replication. Liver-stage antigen-1 (LSA-1) is currently the only identified P. falciparum protein for which expression is restricted to liver stages. Yet, the importance of LSA-1 for liver-stage parasite development remains unknown. Here we deleted LSA-1 in the NF54 strain of P. falciparum and analysed the lsa-1? parasites throughout their life cycle. lsa-1? sporozoites had normal gliding motility and invasion into hepatocytes. Six days after infection of a hepatocytic cell line, lsa-1? parasites exhibited a moderate phenotype with an ?50% reduction of late liver-stage forms when compared with wild type. Strikingly, lsa-1? parasites growing in SCID/Alb-uPA mice with humanized livers showed a severe defect in late liver-stage differentiation and exo-erythrocytic merozoite formation 7 days after infection, a time point when wild-type parasites develop into mature merozoites. The lsa-1? parasites also showed aberrant liver-stage expression of key parasite proteins apical membrane antigen-1 and circumsporozoite protein. Our data show that LSA-1 plays a critical role during late liver-stage schizogony and is thus important in the parasite transition from the liver to blood. LSA-1 is the first P. falciparum protein identified to be required for this transitional stage of the parasite life cycle. PMID:21569184

Mikolajczak, Sebastian A.; Sacci, John B.; De La Vega, Patricia; Camargo, Nelly; VanBuskirk, Kelly; Krzych, Urszula; Cao, Jun; Jacobs-Lorena, Marcelo; Cowman, Alan F.; Kappe, Stefan H. I.

2014-01-01

131

Disruption of the Plasmodium falciparum liver-stage antigen-1 locus causes a differentiation defect in late liver-stage parasites.  

PubMed

The malaria parasite Plasmodium falciparum infects humans and first targets the liver where liver-stage parasites undergo pre-erythrocytic replication. Liver-stage antigen-1 (LSA-1) is currently the only identified P. falciparum protein for which expression is restricted to liver stages. Yet, the importance of LSA-1 for liver-stage parasite development remains unknown. Here we deleted LSA-1 in the NF54 strain of P. falciparum and analysed the lsa-1(-) parasites throughout their life cycle. lsa-1(-) sporozoites had normal gliding motility and invasion into hepatocytes. Six days after infection of a hepatocytic cell line, lsa-1(-) parasites exhibited a moderate phenotype with an ~50% reduction of late liver-stage forms when compared with wild type. Strikingly, lsa-1(-) parasites growing in SCID/Alb-uPA mice with humanized livers showed a severe defect in late liver-stage differentiation and exo-erythrocytic merozoite formation 7 days after infection, a time point when wild-type parasites develop into mature merozoites. The lsa-1(-) parasites also showed aberrant liver-stage expression of key parasite proteins apical membrane antigen-1 and circumsporozoite protein. Our data show that LSA-1 plays a critical role during late liver-stage schizogony and is thus important in the parasite transition from the liver to blood. LSA-1 is the first P. falciparum protein identified to be required for this transitional stage of the parasite life cycle. PMID:21569184

Mikolajczak, Sebastian A; Sacci, John B; De La Vega, Patricia; Camargo, Nelly; VanBuskirk, Kelly; Krzych, Urszula; Cao, Jun; Jacobs-Lorena, Marcelo; Cowman, Alan F; Kappe, Stefan H I

2011-08-01

132

Effect of thioredoxin peroxidase-1 gene disruption on the liver stages of the rodent malaria parasite Plasmodium berghei.  

PubMed

Phenotypic observation of thioredoxin peroxidase-1 (TPx-1) gene-disrupted Plasmodium berghei (TPx-1 KO) in the liver-stage was performed with an in vitro infection system in order to investigate defective liver-stage development in a mouse infection model. Indirect immunofluorescence microscopy assay with anti-circumsporozoite protein antibody revealed that in the liver schizont stage, TPx-1 KO parasite cells were significantly smaller than cells of the wild-type parent strain (WT). Indirect immunofluorescence microscopy assay with anti-merozoite surface protein-1 antibody, which was used to evaluate late schizont-stage development, indicated that TPx-1 KO schizont development was similar to WT strain development towards the merozoite-forming stage (mature schizont). However, fewer merozoites were produced in the mature TPx-1 KO schizont than in the mature WT schizont. Taken together, the results suggest that TPx-1 may be involved in merozoite formation during liver schizont development. PMID:25284813

Usui, Miho; Masuda-Suganuma, Hirono; Fukumoto, Shinya; Angeles, Jose Ma M; Hakimi, Hassan; Inoue, Noboru; Kawazu, Shin-Ichiro

2014-10-01

133

Plasmodium falciparum in vitro schizont maturation tests in Mozambique are not improved by removing immune parasite carriers' plasma.  

PubMed

To study the effect of immune parasite carriers' plasma on Plasmodium falciparum schizont maturation, peripheral blood stages were incubated for 24-40 h in RPMI medium with either 5% carrier's plasma + 5% non-immune AB serum or 10% non-immune serum. The number of schizonts per 200 asexual P. falciparum was lower in non-immune serum than in the presence of carrier's plasma in 19 of 26 cases, due to increased frequency of schizont rupture when carrier's plasma was absent. It is concluded that, under these test conditions, the replacement of immune plasma by non-immune serum makes schizont maturation tests, which are based on the proportion of schizonts among asexual P. falciparum as a measure of growth, more difficult to interpret. PMID:3329781

Schapira, A; Suleimanov, G; Averkiev, L; Schwalbach, J F

1987-01-01

134

Molecular Evidence of Plasmodium vivax Mono and Mixed Malaria Parasite Infections in Duffy-Negative Native Cameroonians  

PubMed Central

The malaria parasite Plasmodium vivax is known to be majorly endemic to Asian and Latin American countries with no or very few reports of Africans infected with this parasite. Since the human Duffy antigens act as receptors for P. vivax to invade human RBCs and Africans are generally Duffy-negative, non-endemicity of P. vivax in Africa has been attributed to this fact. However, recent reports describing P. vivax infections in Duffy-negative Africans from West and Central parts of Africa have been surfaced including a recent report on P. vivax infection in native Cameroonians. In order to know if Cameroonians living in the southern regions are also susceptible to P. vivax infection, we collected finger-prick blood samples from 485 malarial symptomatic patients in five locations and followed PCR diagnostic assays with DNA sequencing of the 18S ribosomal RNA gene. Out of the 201 malaria positive cases detected, 193 were pure P. falciparum, six pure P. vivax and two mixed parasite infections (P. falciparum + P. vivax). The eight P. vivax infected samples (six single + two mixed) were further subjected to DNA sequencing of the P. vivax multidrug resistance 1 (pvmdr1) and the P.vivax circumsporozoite (pvcsp) genes. Alignment of the eight Cameroonian pvmdr1 sequences with the reference sequence showed high sequence similarities, reconfirming P. vivax infection in all the eight patients. DNA sequencing of the pvcsp gene indicated all the eight P. vivax to be of VK247 type. Interestingly, DNA sequencing of a part of the human Duffy gene covering the promoter region in the eight P. vivax-infected Cameroonians to identify the T-33C mutation revealed all these patients as Duffy-negative. The results provide evidence of single P. vivax as well as mixed malaria parasite infection in native Cameroonians and add knowledge to the growing evidences of P. vivax infection in Duffy-negative Africans. PMID:25084090

Ngassa Mbenda, Huguette Gaelle; Das, Aparup

2014-01-01

135

Molecular cloning, characterization and expression profile of a glutathione peroxidase-like thioredoxin peroxidase (TPxGl) of the rodent malaria parasite Plasmodium berghei.  

PubMed

Glutathione peroxidases (GPx) comprise an important group of redox active proteins with diverse functions, including antioxidant defense and signaling. Although the genome of the malaria parasite Plasmodium does not contain a genuine GPx gene a glutathione peroxidase-like thioredoxin peroxidase (TPxGl) has recently been identified and biochemically characterized in the human malaria parasite P. falciparum. To gain more insight into the potential biological function of this enzyme we have cloned and expressed TPxGl of the rodent model system P. berghei (PbTPxGl). Biochemical characterization confirmed that the protein is redox active with the P. berghei thioredoxin system. We compared PbTPxGl to recently characterized thioredoxin-dependent GPx-type proteins of other organisms, and generated the first hypothetical 3D model of a Plasmodium TPxGl, which shows the conservation of the thioredoxin-fold as well as the spatial orientation of a classic GPx catalytic tetrad. In vivo studies indicate that PbTPxGl is continuously expressed in all P. berghei asexual blood stages, gametocytes and in early mosquito-stage parasites. Confocal microscopy suggest a cytoplasmic localization of PbTPxGl in all investigated parasite life stages, specifically in mature ookinetes. Our data provides new insights into the structure and ubiquitous expression of Plasmodium TPxGl and warrants further investigation into this potentially important redox enzyme. PMID:24637102

Haselton, Kyle J; David, Robin; Fell, Katherine; Schulte, Emily; Dybas, Matthew; Olsen, Kenneth W; Kanzok, Stefan M

2014-03-14

136

Parasite maturation and host serum iron influence the labile iron pool of erythrocyte stage Plasmodium falciparum.  

PubMed

Iron is a critical and tightly regulated nutrient for both the malaria parasite and its human host. The importance of the relationship between host iron and the parasite has been underscored recently by studies showing that host iron supplementation may increase the risk of falciparum malaria. It is unclear what host iron sources the parasite is able to access. We developed a flow cytometry-based method for measuring the labile iron pool (LIP) of parasitized erythrocytes using the nucleic acid dye STYO 61 and the iron sensitive dye, calcein acetoxymethyl ester (CA-AM). This new approach enabled us to measure the LIP of P. falciparum through the course of its erythrocytic life cycle and in response to the addition of host serum iron sources. We found that the LIP increases as the malaria parasite develops from early ring to late schizont stage, and that the addition of either transferrin or ferric citrate to culture media increases the LIP of trophozoites. Our method for detecting the LIP within malaria parasitized RBCs provides evidence that the parasite is able to access serum iron sources as part of the host vs. parasite arms race for iron. PMID:23398516

Clark, Martha; Fisher, Nancy C; Kasthuri, Raj; Cerami Hand, Carla

2013-04-01

137

Genetic Polymorphism and Natural Selection in the Malaria Parasite Plasmodium falciparum  

Microsoft Academic Search

We have studied the genetic polymorphism at 10 Plasmodium falciparum loci that are considered potential targets for specific antimalarial vaccines. The polymorphism is unevenly distributed among the loci; loci encoding proteins expressed on the surface of the sporozoite or the merozoite (AMA-1, CSP, LSA-1, MSP-1, MSP-2, and MSP-3) are more polymorphic than those expressed during the sexual stages or inside

Ananias A. Escalante; Altaf A. Lal; Francisco J. Ayala

1998-01-01

138

Purification of a recombinant histidine-tagged lactate dehydrogenase from the malaria parasite, Plasmodium vivax, and characterization of its properties.  

PubMed

Lactate dehydrogenase (LDH) of the malaria parasite, Plasmodium vivax (Pv), serves as a drug target and immunodiagnostic marker. The LDH cDNA generated from total RNA of a clinical isolate of the parasite was cloned into pRSETA plasmid. Recombinant his-tagged PvLDH was over-expressed in E. coli Rosetta2DE3pLysS and purified using Ni(2+)-NTA resin giving a yield of 25-30 mg/litre bacterial culture. The recombinant protein was enzymatically active and its catalytic efficiency for pyruvate was 5.4 × 10(8) min(-1) M(-1), 14.5 fold higher than a low yield preparation reported earlier to obtain PvLDH crystal structure. The enzyme activity was inhibited by gossypol and sodium oxamate. The recombinant PvLDH was reactive in lateral flow immunochromatographic assays detecting pan- and vivax-specific LDH. The soluble recombinant PvLDH purified using heterologous expression system can facilitate the generation of vivax LDH-specific monoclonals and the screening of chemical compound libraries for PvLDH inhibitors. PMID:25048245

Sundaram, Balamurugan; Varadarajan, Nandan Mysore; Subramani, Pradeep Annamalai; Ghosh, Susanta Kumar; Nagaraj, Viswanathan Arun

2014-12-01

139

The Evolutionary History of Plasmodium vivax as Inferred from Mitochondrial Genomes: Parasite Genetic Diversity in the Americas  

PubMed Central

Plasmodium vivax is the most prevalent human malaria parasite in the Americas. Previous studies have contrasted the genetic diversity of parasite populations in the Americas with those in Asia and Oceania, concluding that New World populations exhibit low genetic diversity consistent with a recent introduction. Here we used an expanded sample of complete mitochondrial genome sequences to investigate the diversity of P. vivax in the Americas as well as in other continental populations. We show that the diversity of P. vivax in the Americas is comparable to that in Asia and Oceania, and we identify several divergent clades circulating in South America that may have resulted from independent introductions. In particular, we show that several haplotypes sampled in Venezuela and northeastern Brazil belong to a clade that diverged from the other P. vivax lineages at least 30,000 years ago, albeit not necessarily in the Americas. We propose that, unlike in Asia where human migration increases local genetic diversity, the combined effects of the geographical structure and the low incidence of vivax malaria in the Americas has resulted in patterns of low local but high regional genetic diversity. This could explain previous views that P. vivax in the Americas has low genetic diversity because these were based on studies carried out in limited areas. Further elucidation of the complex geographical pattern of P. vivax variation will be important both for diversity assessments of genes encoding candidate vaccine antigens and in the formulation of control and surveillance measures aimed at malaria elimination. PMID:23733143

Taylor, Jesse E.; Pacheco, M. Andreína; Bacon, David J.; Beg, Mohammad A.; Machado, Ricardo Luiz; Fairhurst, Rick M.; Herrera, Socrates; Kim, Jung-Yeon; Menard, Didier; Póvoa, Marinete Marins; Villegas, Leopoldo; Mulyanto; Snounou, Georges; Cui, Liwang; Zeyrek, Fadile Yildiz; Escalante, Ananias A.

2013-01-01

140

Plasmodium falciparum Histology Taylor Bright  

E-print Network

mostly in children under 5 and pregnant women ­Latest WHO estimate - 880,000 (Sep 2008) ·Estimated mosquito. · Caused by four species of apicomplexan parasites. Plasmodium falciparum Plasmodium vivax

Gleeson, Joseph G.

141

Immune pressure selects for Plasmodium falciparum parasites presenting distinct red blood cell surface antigens and inducing strain-specific protection in Saimiri sciureus monkeys  

PubMed Central

The passive transfer of specific antibodies to a naive splenectomized Saimiri sciureus monkey infected with the Palo Alto FUP/SP strain of Plasmodium falciparum resulted in the emergence of parasites resistant to the transferred antibodies. Molecular typing indicated that the original and resistant parasites were isogenic. Saimiri monkeys primed with original parasites were fully susceptible to a challenge by the resistant ones, and vice versa. This absence of crossprotection indicates that strain-specific determinants would be the major targets of protective immunity developed in these monkeys. Phenotypic analysis showed that the surface of the infected red blood cells differed in both lines. Original parasites formed rosettes, autoagglutinated, presented characteristic knobs at the surface of the infected red blood cell, and did not agglutinate in the presence of a pool of human immune sera. In contrast, the resistant parasites did not form rosettes, did not spontaneously autoagglutinate, presented abnormal flattened knobs, and formed large aggregates in the presence of a pool of human immune sera. The presence of strain-specific determinants at the surface of the resistant parasites was confirmed by surface immunofluorescence and agglutination using homologous Saimiri serum. Neither the original nor the resistant parasites cytoadhered to an amelanotic melanoma cell line, suggesting that cytoadherence and agglutination can be dissociated. These results indicate that parasites that differ by the antigens exposed at the surface of the red blood cell induce strain- specific immunity. Furthermore they show that rosetting and nonrosetting parasites differ in their antigenic properties and do not crossprotect. PMID:7807008

1995-01-01

142

A New Single-Step PCR Assay for the Detection of the Zoonotic Malaria Parasite Plasmodium knowlesi  

PubMed Central

Background Recent studies in Southeast Asia have demonstrated substantial zoonotic transmission of Plasmodium knowlesi to humans. Microscopically, P. knowlesi exhibits several stage-dependent morphological similarities to P. malariae and P. falciparum. These similarities often lead to misdiagnosis of P. knowlesi as either P. malariae or P. falciparum and PCR-based molecular diagnostic tests are required to accurately detect P. knowlesi in humans. The most commonly used PCR test has been found to give false positive results, especially with a proportion of P. vivax isolates. To address the need for more sensitive and specific diagnostic tests for the accurate diagnosis of P. knowlesi, we report development of a new single-step PCR assay that uses novel genomic targets to accurately detect this infection. Methodology and Significant Findings We have developed a bioinformatics approach to search the available malaria parasite genome database for the identification of suitable DNA sequences relevant for molecular diagnostic tests. Using this approach, we have identified multi-copy DNA sequences distributed in the P. knowlesi genome. We designed and tested several novel primers specific to new target sequences in a single-tube, non-nested PCR assay and identified one set of primers that accurately detects P. knowlesi. We show that this primer set has 100% specificity for the detection of P. knowlesi using three different strains (Nuri, H, and Hackeri), and one human case of malaria caused by P. knowlesi. This test did not show cross reactivity with any of the four human malaria parasite species including 11 different strains of P. vivax as well as 5 additional species of simian malaria parasites. Conclusions The new PCR assay based on novel P. knowlesi genomic sequence targets was able to accurately detect P. knowlesi. Additional laboratory and field-based testing of this assay will be necessary to further validate its utility for clinical diagnosis of P. knowlesi. PMID:22363751

Lucchi, Naomi W.; Poorak, Mitra; Oberstaller, Jenna; DeBarry, Jeremy; Srinivasamoorthy, Ganesh; Goldman, Ira; Xayavong, Maniphet; da Silva, Alexandre J.; Peterson, David S.; Barnwell, John W.; Kissinger, Jessica; Udhayakumar, Venkatachalam

2012-01-01

143

Piperaquine Resistance Is Associated with a Copy Number Variation on Chromosome 5 in Drug-Pressured Plasmodium falciparum Parasites?†  

PubMed Central

The combination of piperaquine and dihydroartemisinin has recently become the official first-line therapy in several Southeast Asian countries. The pharmacokinetic mismatching of these drugs, whose plasma half-lives are ?20 days and ?1 h, respectively, implies that recrudescent or new infections emerging shortly after treatment cessation will encounter piperaquine as a monotherapy agent. This creates substantial selection pressure for the emergence of resistance. To elucidate potential resistance determinants, we subjected cloned Plasmodium falciparum Dd2 parasites to continuous piperaquine pressure in vitro (47 nM; ?2-fold higher than the Dd2 50% inhibitory concentration [IC50]). The phenotype of outgrowth parasites was assayed in two clones, revealing an IC50 against piperaquine of 2.1 ?M and 1.7 ?M, over 100-fold greater than that of the parent. To identify the genetic determinant of resistance, we employed comparative whole-genome hybridization analysis. Compared to the Dd2 parent, this analysis found (in both resistant clones) a novel single-nucleotide polymorphism in P. falciparum crt (pfcrt), deamplification of an 82-kb region of chromosome 5 (that includes pfmdr1), and amplification of an adjacent 63-kb region of chromosome 5. Continued propagation without piperaquine selection pressure resulted in “revertant” piperaquine-sensitive parasites. These retained the pfcrt polymorphism and further deamplified the chromosome 5 segment that encompasses pfmdr1; however, these two independently generated revertants both lost the neighboring 63-kb amplification. These results suggest that a copy number variation event on chromosome 5 (825600 to 888300) is associated with piperaquine resistance. Transgene expression studies are underway with individual genes in this segment to evaluate their contribution to piperaquine resistance. PMID:21576453

Eastman, Richard T.; Dharia, Neekesh V.; Winzeler, Elizabeth A.; Fidock, David A.

2011-01-01

144

Complete Gene Map of the Plastid-like DNA of the Malaria Parasite Plasmodium falciparum  

Microsoft Academic Search

Malaria parasites, and other parasitic protists of the Phylum Apicomplexa, carry a plastid-like genome with greatly reduced sequence complexity. This 35 kb DNA circle resembles the plastid DNA of non-photosynthetic plants, encoding almost exclusively components involved in gene expression. The complete gene map described here includes genes for duplicated large and small subunit rRNAs, 25 species of tRNA, three subunits

Paul W. Denny; Peter R. Preiser; Kaveri Rangachari; Kate Roberts; Anjana Roy; Andrea Whyte; Malcolm Strath; Daphne J. Moore; Peter W. Moore; Donald H. Williamson

1996-01-01

145

Plasmodium falciparum synthetic LbL microparticle vaccine elicits protective neutralizing antibody and parasite-specific cellular immune responses  

PubMed Central

Epitopes of the circumsporozoite (CS) protein of Plasmodium falciparum, the most pathogenic species of the malaria parasite, have been shown to elicit protective immunity in experimental animals and human volunteers. The mechanisms of immunity include parasite-neutralizing antibodies that can inhibit parasite motility in the skin at the site of infection and in the bloodstream during transit to the hepatocyte host cell and also block interaction with host cell receptors on hepatocytes. In addition, specific CD4+ and CD8+ cellular mechanisms target the intracellular hepatic forms, thus preventing release of erythrocytic stage parasites from the infected hepatocyte and the ensuing blood stage cycle responsible for clinical disease. An innovative method for producing particle vaccines, layer-by-layer (LbL) fabrication of polypeptide films on solid CaCO3 cores, was used to produce synthetic malaria vaccines containing a tri-epitope CS peptide T1BT* comprising the antibody epitope of the CS repeat region (B) and two T-cell epitopes, the highly conserved T1 epitope and the universal epitope T*. Mice immunized with microparticles loaded with T1BT* peptide developed parasite-neutralizing antibodies and malaria-specific T-cell responses including cytotoxic effector T-cells. Protection from liver stage infection following challenge with live sporozoites from infected mosquitoes correlated with neutralizing antibody levels. Although some immunized mice with low or undetectable neutralizing antibodies were also protected, depletion of T-cells prior to challenge resulted in the majority of mice remaining resistant to challenge. In addition, mice immunized with microparticles bearing only T-cell epitopes were not protected, demonstrating that cellular immunity alone was not sufficient for protective immunity. Although the microparticles without adjuvant were immunogenic and protective, a simple modification with the lipopeptide TLR2 agonist Pam3Cys increased the potency and efficacy of the LbL vaccine candidate. This study demonstrates the potential of LbL particles as promising malaria vaccine candidates using the T1BT* epitopes from the P. falciparum CS protein. PMID:23481177

Powell, Thomas J.; Tang, Jie; DeRome, Mary E.; Mitchell, Robert A.; Jacobs, Andrea; Deng, Yanhong; Palath, Naveen; Cardenas, Edwin; Boyd, James G.; Nardin, Elizabeth

2013-01-01

146

Plasmodium, Saurocytozoon and Haemocystidium parasites (Apicomplexa: Plasmodiidae) from the rock agama, Laudakia caucasia (Sauria: Agamidae), in southern Asia.  

PubMed

The rock agama, Laudakia caucasia Eichwald (Agamidae) is host to Plasmodium caucasica sp. n. and Saurocytozoon agamidorum sp. n. in western Pakistan. Plasmodium caucasica is characterized by very large meronts, 11-21 by 8-17 microm that produce 32-67 merozoites, which nearly fill the host erythrocyte, and smaller, ovoid to elongate gametocytes, 6-14 by 2.5-6 microm, with length by width (LW) 21-55 microm2, and L/W ratio 1.0-4.0. Host cells are usually mature erythrocytes. In Azerbaijan, P. caucasica parasitizes immature erythroid cells. Dimensions of meronts are 10-16 by 6-12 microm, and merozoite numbers are 12-44. Gametocytes are 6-14 by 3-6 microm, with LW 31-56 microm2, and L/W ratio 1.0-4.0. Saurocytozoon agamidorum sp. n. gametocytes are 6.5-13 microm in diameter, with LW 35-79 microm2, and L/W ratio 1.0-2.2. They occupy lymphocytes as host cells, which are greatly distorted by gametocyte presence and often show nuclei nearly divided into two portions, one portion at each end of the cell. Haemocystidium grahami (Shortt, 1922), redescribed from material found in L. caucasia from Azerbaijan, has rounded to elongate gametocytes, 8-19.5 by 4-8 microm, LW 60.5-102 microm2, and L/W ratio 1.0-4.5. The prominent light golden pigment granules often coalesce to nearly cover the surface of the gametocyte. The presence of P. caucasica and S. agamidorum extends the range of the two genera in saurian hosts throughout much of the southern Asia mainland. PMID:23951929

Telford, Sam R

2013-07-01

147

Crystal structure and solution characterization of the thioredoxin-2 from Plasmodium falciparum, a constituent of an essential parasitic protein export complex.  

PubMed

Survival of the malaria parasite Plasmodium falciparum when it infects red blood cells depends upon its ability to export hundreds of its proteins beyond an encasing vacuole. Protein export is mediated by a parasite-derived protein complex, the Plasmodium translocon of exported proteins (PTEX), and requires unfolding of the different cargos prior to their translocation across the vacuolar membrane. Unfolding is performed by the AAA+protein unfoldase HSP101/ClpB2 and the thioredoxin-2 enzyme (TRX2). Protein trafficking is dramatically impaired in parasites with defective HSP101 or lacking TRX2. These two PTEX subunits drive export and are targets for the design of a novel class of antimalarials: protein export inhibitors. To rationalize inhibitor design, we solved the crystal structure of Pfal-TRX2 at 2.2-Å resolution. Within the asymmetric unit, the three different copies of this protein disulfide reductase sample its two redox catalytic states. Size exclusion chromatography and small-angle X-ray scattering (SAXS) analyses demonstrate that Pfal-TRX2 is monomeric in solution. A non-conserved N-terminal extension precedes the canonical thioredoxin-fold; although it is not observed in our structure, our solution analysis suggests it is flexible in contrast to Plasmodium thioredoxin-1. This represents a first step towards the reconstitution of the entire PTEX for mechanistic and structural studies. PMID:25475729

Peng, Mindy; Cascio, Duilio; Egea, Pascal F

2015-01-01

148

Plasmodium falciparum Rab5B Is an N-Terminally Myristoylated Rab GTPase That Is Targeted to the Parasite's Plasma and Food Vacuole Membranes  

PubMed Central

Plasmodium falciparum (Pf) has a family of 11 Rab GTPases to regulate its vesicular transport. However, PfRab5B is unique in lacking a C-terminal geranyl-geranylation motif, while having N-terminal palmitoylation and myristoylation motifs. We show that the N-terminal glycine is required for PfRab5B myristoylation in vitro and when an N-terminal PfRab5B fragment possessing both acylation motifs is fused to GFP and expressed in transgenic P. falciparum parasites, the chimeric PfRab5B protein localizes to the plasma membrane. Upon substitution of the modified glycine by alanine the staining becomes diffuse and GFP is found in soluble subcellular fractions. Immuno-electron microscopy shows endogenous PfRab5B decorating the parasite's plasma and food vacuole membranes. Using reverse genetics rab5b couldn't be deleted from the haploid genome of asexual blood stage P. berghei parasites. The failure of PbRab5A or PbRab5C to complement for loss of PbRab5B function indicates non-overlapping roles for the three Plasmodium Rab5s, with PfRab5B involved in trafficking MSP1 to the food vacuole membrane and CK1 to the plasma membrane. We discuss similarities between Plasmodium Rab5B and Arabidopsis thaliana ARA6, a similarly unusual Rab5-like GTPase of plants. PMID:24498355

Ezougou, Carinne Ndjembo; Ben-Rached, Fathia; Moss, David K.; Lin, Jing-wen; Black, Sally; Knuepfer, Ellen; Green, Judith L.; Khan, Shahid M.; Mukhopadhyay, Amitabha; Janse, Chris J.; Coppens, Isabelle; Yera, Hélène; Holder, Anthony A.; Langsley, Gordon

2014-01-01

149

Molecular Characterization of a Novel Geranylgeranyl Pyrophosphate Synthase from Plasmodium Parasites*  

PubMed Central

We present here a study of a eukaryotic trans-prenylsynthase from the malaria pathogen Plasmodium vivax. Based on the results of biochemical assays and contrary to previous indications, this enzyme catalyzes the production of geranylgeranyl pyrophosphate (GGPP) rather than farnesyl pyrophosphate (FPP). Structural analysis shows that the product length is constrained by a hydrophobic cavity formed primarily by a set of residues from the same subunit as the product as well as at least one other from the dimeric partner. Furthermore, Plasmodium GGPP synthase (GGPPS) can bind nitrogen-containing bisphosphonates (N-BPs) strongly with the energetically favorable cooperation of three Mg2+, resulting in inhibition by this class of compounds at IC50 concentrations below 100 nm. In contrast, human and yeast GGPPSs do not accommodate a third magnesium atom in the same manner, resulting in their insusceptibility to N-BPs. This differentiation is in part attributable to a deviation in a conserved motif known as the second aspartate-rich motif: whereas the aspartates at the start and end of the five-residue motif in FFPP synthases and P. vivax GGPPSs both participate in the coordination of the third Mg2+, an asparagine is featured as the last residue in human and yeast GGPPSs, resulting in a different manner of interaction with nitrogen-containing ligands. PMID:21084289

Artz, Jennifer D.; Wernimont, Amy K.; Dunford, James E.; Schapira, Matthieu; Dong, Aiping; Zhao, Yong; Lew, Jocelyne; Russell, R. Graham G.; Ebetino, F. Hal; Oppermann, Udo; Hui, Raymond

2011-01-01

150

Polymorphism in dhfr/dhps genes, parasite density and ex vivo response to pyrimethamine in Plasmodium falciparum malaria parasites in Thies, Senegal?  

PubMed Central

Resistance to sulfadoxine–pyrimethamine (SP) in Plasmodium falciparum malaria parasites is associated with mutations in the dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) genes, and these mutations have spread resistance worldwide. SP, used for several years in Senegal, has been recommended for intermittent preventive treatment for malaria in pregnancy (IPTp) and has been widely implemented since 2003 in this country. There is currently limited data on SP resistance from molecular marker genotyping, and no data on pyrimethamine ex vivo sensitivity in Senegal. Molecular markers of SP resistance and pyrimethamine ex vivo sensitivity were investigated in 416 parasite samples collected from the general population, from the Thies region between 2003 and 2011. The prevalence of the N51I/C59R/S108N triple mutation in dhfr increased from 40% in 2003 to 93% in 2011. Furthermore, the prevalence of the dhfr N51I/C59R/S108N and dhps A437G quadruple mutation increased, from 20% to 66% over the same time frame, then down to 44% by 2011. There was a significant increase in the prevalence of the dhfr triple mutation, as well as an association between dhfr genotypes and pyrimethamine response. Conversely, dhps mutations in codons 436 and 437 did not show consistent variation between 2003 and 2011. These findings suggest that regular screening for molecular markers of antifolate resistance and ex vivo drug response monitoring should be incorporated with ongoing in vivo efficacy monitoring in areas where IPTp-SP is implemented and where pyrimethamine and sulfa drugs are still widely administered in the general population. PMID:24533303

Ndiaye, Daouda; Dieye, Baba; Ndiaye, Yaye D.; Tyne, Daria Van; Daniels, Rachel; Bei, Amy K.; Mbaye, Aminata; Valim, Clarissa; Lukens, Amanda; Mboup, Souleymane; Ndir, Omar; Wirth, Dyann F.; Volkman, Sarah

2013-01-01

151

Efficacy of a Plasmodium vivax malaria vaccine using ChAd63 and modified vaccinia Ankara expressing thrombospondin-related anonymous protein as assessed with transgenic Plasmodium berghei parasites.  

PubMed

Plasmodium vivax is the world's most widely distributed malaria parasite and a potential cause of morbidity and mortality for approximately 2.85 billion people living mainly in Southeast Asia and Latin America. Despite this dramatic burden, very few vaccines have been assessed in humans. The clinically relevant vectors modified vaccinia virus Ankara (MVA) and the chimpanzee adenovirus ChAd63 are promising delivery systems for malaria vaccines due to their safety profiles and proven ability to induce protective immune responses against Plasmodium falciparum thrombospondin-related anonymous protein (TRAP) in clinical trials. Here, we describe the development of new recombinant ChAd63 and MVA vectors expressing P. vivax TRAP (PvTRAP) and show their ability to induce high antibody titers and T cell responses in mice. In addition, we report a novel way of assessing the efficacy of new candidate vaccines against P. vivax using a fully infectious transgenic Plasmodium berghei parasite expressing P. vivax TRAP to allow studies of vaccine efficacy and protective mechanisms in rodents. Using this model, we found that both CD8+ T cells and antibodies mediated protection against malaria using virus-vectored vaccines. Our data indicate that ChAd63 and MVA expressing PvTRAP are good preerythrocytic-stage vaccine candidates with potential for future clinical application. PMID:24379295

Bauza, Karolis; Malinauskas, Tomas; Pfander, Claudia; Anar, Burcu; Jones, E Yvonne; Billker, Oliver; Hill, Adrian V S; Reyes-Sandoval, Arturo

2014-03-01

152

Parasite densities modulate susceptibility of mice to cerebral malaria during co-infection with Schistosoma japonicum and Plasmodium berghei  

PubMed Central

Background Malaria and schistosomiasis are endemic and co-exist in the same geographic areas, even co-infecting the same host. Previous studies have reported that concomitant infection with Schistosoma japonicum could offer protection against experimental cerebral malaria (ECM) in mice. This study was performed to evaluate whether alterations in parasite density could alter this protective effect. Methods Mice were inoculated with 100 or 200?S. japonicum cercariae followed by infection with high or low density of Plasmodium berghei ANKA strain eight weeks after the first infection. Then, parasitaemia, survival rate and blood–brain-barrier (BBB) damage were assessed. Interferon-gamma (IFN-?), interleukin (IL)-4, IL-5, IL-13, IL-10, and TGF-? levels were determined in splenocyte supernatants using enzyme-linked immunosorbent assay (ELISA). Cell surface/intracellular staining and flow cytometry were used to analyse the level of CD4+/CD8+ T cells, CD4+CD25+Foxp3+ Tregs, IL-10-secreting Tregs, and IL-10+Foxp3-CD4+ T cells in the spleen, and CD4+/CD8+ T cells infiltrating the brain. Results Co-infection with low density P. berghei and increased S. japonicum cercariae significantly increased the levels of IL-4, IL-5, IL-13, TGF-? and Tregs, but significantly decreased the levels of IFN-? and the percentage of CD4+ T cells and CD8+ T cells in the spleen and CD8+ T cell infiltration in the brain. Increased worm loads also significantly decreased mortality and BBB impairment during ECM. When challenged with higher numbers of P. berghei and increased cercariae, the observed cytokine changes were not statistically significant. The corresponding ECM mortality and BBB impairment also remained unchanged. Conclusions This study demonstrates that protection for ECM depends on the numbers of the parasites, S. japonicum and P. berghei, during co-infection. Alterations in the regulatory response appear to play a key role in this adaptation. PMID:24670210

2014-01-01

153

Distribution of Drug Resistance Genotypes in Plasmodium falciparum in an Area of Limited Parasite Diversity in Saudi Arabia  

PubMed Central

Two hundred and three Plasmodium falciparum isolates from Jazan area, southwest Saudi Arabia, were typed for Pfcrt, Pfmdr1, dhps, and dhfr mutations associated with resistance to chloroquine, mefloquine, halofantrine, artemisinin, sulfadoxine-pyrimethamine, and the neutral polymorphic gene Pfg377. A large proportion (33%) of isolates harbored double mutant dhfr genotype (51I,59C,108N). However, only one isolate contained mutation dhps-437G. For Pfcrt, almost all examined isolates (163; 99%) harbored the mutant genotype (72C,73V,74I,75E,76T), whereas only 49 (31%) contained the mutant Pfmdr1 genotype (86Y,184F,1034S,1042N), 109 (66%) harbored the single mutant genotype (86N,184F,1034S,1042N), and no mutations were seen in codons 1034, 1042, and 1246. Nonetheless, three new single-nucleotide polymorphisms were detected at codons 182, 192, and 102. No differences were seen in distribution of drug resistance genes among Saudis and expatriates. There was a limited multiplicity (5%), mean number of clones (1.05), and two dominant multilocus genotypes among infected individuals in Jazan. A pattern consistent with limited cross-mating and recombination among local parasite was apparent. PMID:22556074

Bin Dajem, Saad M.; Al-Farsi, Hissa M.; Al-Hashami, Zainab S.; Al-Sheikh, Adel Ali H.; Al-Qahtani, Ahmed; Babiker, Hamza A.

2012-01-01

154

High-resolution three-dimensional imaging of red blood cells parasitized by Plasmodium falciparum and in situ hemozoin crystals using optical diffraction tomography  

PubMed Central

Abstract. We present high-resolution optical tomographic images of human red blood cells (RBC) parasitized by malaria-inducing Plasmodium falciparum (Pf)-RBCs. Three-dimensional (3-D) refractive index (RI) tomograms are reconstructed by recourse to a diffraction algorithm from multiple two-dimensional holograms with various angles of illumination. These 3-D RI tomograms of Pf-RBCs show cellular and subcellular structures of host RBCs and invaded parasites in fine detail. Full asexual intraerythrocytic stages of parasite maturation (ring to trophozoite to schizont stages) are then systematically investigated using optical diffraction tomography algorithms. These analyses provide quantitative information on the structural and chemical characteristics of individual host Pf-RBCs, parasitophorous vacuole, and cytoplasm. The in situ structural evolution and chemical characteristics of subcellular hemozoin crystals are also elucidated. PMID:23797986

Kim, Kyoohyun; Yoon, HyeOk; Diez-Silva, Monica; Dao, Ming; Dasari, Ramachandra R.; Park, YongKeun

2013-01-01

155

High-resolution three-dimensional imaging of red blood cells parasitized by Plasmodium falciparum and in situ hemozoin crystals using optical diffraction tomography  

NASA Astrophysics Data System (ADS)

We present high-resolution optical tomographic images of human red blood cells (RBC) parasitized by malaria-inducing Plasmodium falciparum (Pf)-RBCs. Three-dimensional (3-D) refractive index (RI) tomograms are reconstructed by recourse to a diffraction algorithm from multiple two-dimensional holograms with various angles of illumination. These 3-D RI tomograms of Pf-RBCs show cellular and subcellular structures of host RBCs and invaded parasites in fine detail. Full asexual intraerythrocytic stages of parasite maturation (ring to trophozoite to schizont stages) are then systematically investigated using optical diffraction tomography algorithms. These analyses provide quantitative information on the structural and chemical characteristics of individual host Pf-RBCs, parasitophorous vacuole, and cytoplasm. The in situ structural evolution and chemical characteristics of subcellular hemozoin crystals are also elucidated.

Kim, Kyoohyun; Yoon, HyeOk; Diez-Silva, Monica; Dao, Ming; Dasari, Ramachandra R.; Park, YongKeun

2014-01-01

156

Plasmodium–Mosquito Interactions  

Microsoft Academic Search

Mosquitoes serve as the obligate vectors for the transmission of malaria parasites. During its sexual life cycle within the mosquito, the parasite must undergo several morphological changes and overcome developmental bottlenecks to ensure its successful transmission to a new vertebrate host. Here we review our current understanding of the molecular interactions that occur between Plasmodium parasites and its mosquito (Genus:

Ryan C. Smith; Marcelo Jacobs-Lorena

2010-01-01

157

The Clp Chaperones and Proteases of the Human Malaria Parasite Plasmodium falciparum  

SciTech Connect

The Clpchaperones and proteases play an important role in protein homeostasis in the cell. They are highly conserved across prokaryotes and found also in the mitochondria of eukaryotes and the chloroplasts of plants. They function mainly in the disaggregation, unfolding and degradation of native as well as misfolded proteins. Here, we provide a comprehensive analysis of the Clpchaperones and proteases in the humanmalariaparasitePlasmodiumfalciparum. The parasite contains four Clp ATPases, which we term PfClpB1, PfClpB2, PfClpC and PfClpM. One PfClpP, the proteolytic subunit, and one PfClpR, which is an inactive version of the protease, were also identified. Expression of all Clpchaperones and proteases was confirmed in blood-stage parasites. The proteins were localized to the apicoplast, a non-photosynthetic organelle that accommodates several important metabolic pathways in P. falciparum, with the exception of PfClpB2 (also known as Hsp101), which was found in the parasitophorous vacuole. Both PfClpP and PfClpR form mostly homoheptameric rings as observed by size-exclusion chromatography, analytical ultracentrifugation and electron microscopy. The X-ray structure of PfClpP showed the protein as a compacted tetradecamer similar to that observed for Streptococcus pneumoniae and Mycobacterium tuberculosis ClpPs. Our data suggest the presence of a ClpCRP complex in the apicoplast of P. falciparum.

M El Bakkouri; A Pow; A Mulichak; K Cheung; J Artz; M Amani; S Fell; T de Koning-Ward; C Goodman; et al.

2011-12-31

158

Asexual Populations of the Human Malaria Parasite, Plasmodium falciparum, Use a Two-Step Genomic Strategy to Acquire Accurate, Beneficial DNA Amplifications  

PubMed Central

Malaria drug resistance contributes to up to a million annual deaths. Judicious deployment of new antimalarials and vaccines could benefit from an understanding of early molecular events that promote the evolution of parasites. Continuous in vitro challenge of Plasmodium falciparum parasites with a novel dihydroorotate dehydrogenase (DHODH) inhibitor reproducibly selected for resistant parasites. Genome-wide analysis of independently-derived resistant clones revealed a two-step strategy to evolutionary success. Some haploid blood-stage parasites first survive antimalarial pressure through fortuitous DNA duplications that always included the DHODH gene. Independently-selected parasites had different sized amplification units but they were always flanked by distant A/T tracks. Higher level amplification and resistance was attained using a second, more efficient and more accurate, mechanism for head-to-tail expansion of the founder unit. This second homology-based process could faithfully tune DNA copy numbers in either direction, always retaining the unique DNA amplification sequence from the original A/T-mediated duplication for that parasite line. Pseudo-polyploidy at relevant genomic loci sets the stage for gaining additional mutations at the locus of interest. Overall, we reveal a population-based genomic strategy for mutagenesis that operates in human stages of P. falciparum to efficiently yield resistance-causing genetic changes at the correct locus in a successful parasite. Importantly, these founding events arise with precision; no other new amplifications are seen in the resistant haploid blood stage parasite. This minimizes the need for meiotic genetic cleansing that can only occur in sexual stage development of the parasite in mosquitoes. PMID:23717205

Ahyong, Vida; Patrapuvich, Rapatbhorn; White, John; Gujjar, Ramesh; Phillips, Margaret A.; DeRisi, Joseph; Rathod, Pradipsinh K.

2013-01-01

159

Genome-wide analysis of selection on the malaria parasite Plasmodium falciparum in West African populations of differing infection endemicity.  

PubMed

Locally varying selection on pathogens may be due to differences in drug pressure, host immunity, transmission opportunities between hosts, or the intensity of between-genotype competition within hosts. Highly recombining populations of the human malaria parasite Plasmodium falciparum throughout West Africa are closely related, as gene flow is relatively unrestricted in this endemic region, but markedly varying ecology and transmission intensity should cause distinct local selective pressures. Genome-wide analysis of sequence variation was undertaken on a sample of 100 P. falciparum clinical isolates from a highly endemic region of the Republic of Guinea where transmission occurs for most of each year and compared with data from 52 clinical isolates from a previously sampled population from The Gambia, where there is relatively limited seasonal malaria transmission. Paired-end short-read sequences were mapped against the 3D7 P. falciparum reference genome sequence, and data on 136,144 single nucleotide polymorphisms (SNPs) were obtained. Within-population analyses identifying loci showing evidence of recent positive directional selection and balancing selection confirm that antimalarial drugs and host immunity have been major selective agents. Many of the signatures of recent directional selection reflected by standardized integrated haplotype scores were population specific, including differences at drug resistance loci due to historically different antimalarial use between the countries. In contrast, both populations showed a similar set of loci likely to be under balancing selection as indicated by very high Tajima's D values, including a significant overrepresentation of genes expressed at the merozoite stage that invades erythrocytes and several previously validated targets of acquired immunity. Between-population FST analysis identified exceptional differentiation of allele frequencies at a small number of loci, most markedly for five SNPs covering a 15-kb region within and flanking the gdv1 gene that regulates the early stages of gametocyte development, which is likely related to the extreme differences in mosquito vector abundance and seasonality that determine the transmission opportunities for the sexual stage of the parasite. PMID:24644299

Mobegi, Victor A; Duffy, Craig W; Amambua-Ngwa, Alfred; Loua, Kovana M; Laman, Eugene; Nwakanma, Davis C; MacInnis, Bronwyn; Aspeling-Jones, Harvey; Murray, Lee; Clark, Taane G; Kwiatkowski, Dominic P; Conway, David J

2014-06-01

160

Genome-Wide Analysis of Selection on the Malaria Parasite Plasmodium falciparum in West African Populations of Differing Infection Endemicity  

PubMed Central

Locally varying selection on pathogens may be due to differences in drug pressure, host immunity, transmission opportunities between hosts, or the intensity of between-genotype competition within hosts. Highly recombining populations of the human malaria parasite Plasmodium falciparum throughout West Africa are closely related, as gene flow is relatively unrestricted in this endemic region, but markedly varying ecology and transmission intensity should cause distinct local selective pressures. Genome-wide analysis of sequence variation was undertaken on a sample of 100 P. falciparum clinical isolates from a highly endemic region of the Republic of Guinea where transmission occurs for most of each year and compared with data from 52 clinical isolates from a previously sampled population from The Gambia, where there is relatively limited seasonal malaria transmission. Paired-end short-read sequences were mapped against the 3D7 P. falciparum reference genome sequence, and data on 136,144 single nucleotide polymorphisms (SNPs) were obtained. Within-population analyses identifying loci showing evidence of recent positive directional selection and balancing selection confirm that antimalarial drugs and host immunity have been major selective agents. Many of the signatures of recent directional selection reflected by standardized integrated haplotype scores were population specific, including differences at drug resistance loci due to historically different antimalarial use between the countries. In contrast, both populations showed a similar set of loci likely to be under balancing selection as indicated by very high Tajima’s D values, including a significant overrepresentation of genes expressed at the merozoite stage that invades erythrocytes and several previously validated targets of acquired immunity. Between-population FST analysis identified exceptional differentiation of allele frequencies at a small number of loci, most markedly for five SNPs covering a 15-kb region within and flanking the gdv1 gene that regulates the early stages of gametocyte development, which is likely related to the extreme differences in mosquito vector abundance and seasonality that determine the transmission opportunities for the sexual stage of the parasite. PMID:24644299

Mobegi, Victor A.; Duffy, Craig W.; Amambua-Ngwa, Alfred; Loua, Kovana M.; Laman, Eugene; Nwakanma, Davis C.; MacInnis, Bronwyn; Aspeling-Jones, Harvey; Murray, Lee; Clark, Taane G.; Kwiatkowski, Dominic P.; Conway, David J.

2014-01-01

161

Parasites in Hosts with Special Life Histories  

Microsoft Academic Search

One-hundred and forty seven specimens of the Cuckoo Cuculus canorus, 356 individuals of the Crossbill Loxia curvirostra and 79 specimens of the Swift Apus apus were captured on the Curonian Spit in the Baltic Sea and investigated for haematozoa by microscopic examination of stained blood smears. Haemosporidian parasites (Sporozoa, Haemosporida) were not recorded in the Cuckoo and the Swift. However,

Gediminas Valki?nas; Tatjana Aleksandrovna Iezhova

2001-01-01

162

The antimalarial drug, Ro 42-1611 (arteflene), does not affect cytoadherence and cytokine-inducing properties of Plasmodium falciparum malaria parasites.  

PubMed

The purpose of this study was to investigate the ability of the antimalarial drug, Ro 42-1611 to block parasite mediated cytokine induction in vitro as well as cytoadherence of infected erythrocytes to melanoma cells in vitro. The biological activity of Ro 42-1611 was confirmed as it blocked Plasmodium falciparum growth in cultures. Ro 42-1611, had no major effect on TNF, IL-alpha or IL-6 cytokine release from mononuclear cells stimulated with malaria antigens or lipopolysaccharide and it did not affect cell viability. Ro 42-1611 only slightly suppressed cytoadherence of infected erythrocytes to melanoma cells. The therapeutic effect of To 42-1611 appears to be confined to its parasite killing activity. PMID:8525291

Jakobsen, P H; Staalsø, T; Bendtzen, K; Stürchler, D

1995-06-01

163

Multiple dimensions of epigenetic gene regulation in the malaria parasite Plasmodium falciparum: Gene regulation via histone modifications, nucleosome positioning and nuclear architecture in P. falciparum.  

PubMed

Plasmodium falciparum is the most deadly human malarial parasite, responsible for an estimated 207 million cases of disease and 627,000 deaths in 2012. Recent studies reveal that the parasite actively regulates a large fraction of its genes throughout its replicative cycle inside human red blood cells and that epigenetics plays an important role in this precise gene regulation. Here, we discuss recent advances in our understanding of three aspects of epigenetic regulation in P. falciparum: changes in histone modifications, nucleosome occupancy and the three-dimensional genome structure. We compare these three aspects of the P. falciparum epigenome to those of other eukaryotes, and show that large-scale compartmentalization is particularly important in determining histone decomposition and gene regulation in P. falciparum. We conclude by presenting a gene regulation model for P. falciparum that combines the described epigenetic factors, and by discussing the implications of this model for the future of malaria research. PMID:25394267

Ay, Ferhat; Bunnik, Evelien M; Varoquaux, Nelle; Vert, Jean-Philippe; Noble, William Stafford; Le Roch, Karine G

2014-11-13

164

Melatonin-Induced Temporal Up-Regulation of Gene Expression Related to Ubiquitin/Proteasome System (UPS) in the Human Malaria Parasite Plasmodium falciparum  

PubMed Central

There is an increasing understanding that melatonin and the ubiquitin/proteasome system (UPS) interact to regulate multiple cellular functions. Post-translational modifications such as ubiquitination are important modulators of signaling processes, cell cycle and many other cellular functions. Previously, we reported a melatonin-induced upregulation of gene expression related to ubiquitin/proteasome system (UPS) in Plasmodium falciparum, the human malaria parasite, and that P. falciparum protein kinase 7 influences this process. This implies a role of melatonin, an indolamine, in modulating intraerythrocytic development of the parasite. In this report we demonstrate by qPCR analysis, that melatonin induces gene upregulation in nine out of fourteen genes of the UPS, consisting of the same set of genes previously reported, between 4 to 5 h after melatonin treatment. We demonstrate that melatonin causes a temporally controlled gene expression of UPS members. PMID:25479077

Koyama, Fernanda C.; Azevedo, Mauro F.; Budu, Alexandre; Chakrabarti, Debopam; Garcia, Célia R. S.

2014-01-01

165

Serial Analysis of Gene Expression in Plasmodium falciparum Reveals the Global Expression Profile of Erythrocytic Stages and the Presence of Anti-Sense Transcripts in the Malarial Parasite  

PubMed Central

Serial analysis of gene expression (SAGE) was applied to the malarial parasite Plasmodium falciparum to characterize the comprehensive transcriptional profile of erythrocytic stages. A SAGE library of ?8335 tags representing 4866 different genes was generated from 3D7 strain parasites. Basic local alignment search tool analysis of high abundance SAGE tags revealed that a majority (88%) corresponded to 3D7 sequence, and despite the low complexity of the genome, 70% of these highly abundant tags matched unique loci. Characterization of these suggested the major metabolic pathways that are used by the organism under normal culture conditions. Furthermore several tags expressed at high abundance (30% of tags matching to unique loci of the 3D7 genome) were derived from previously uncharacterized open reading frames, demonstrating the use of SAGE in genome annotation. The open platform “profiling” nature of SAGE also lead to the important discovery of a novel transcriptional phenomenon in the malarial pathogen: a significant number of highly abundant tags that were derived from annotated genes (17%) corresponded to antisense transcripts. These SAGE data were validated by two independent means, strand specific reverse transcription-polymerase chain reaction and Northern analysis, where antisense messages were detected in both asexual and sexual stages. This finding has implications for transcriptional regulation of Plasmodium gene expression. PMID:11598196

Patankar, Swati; Munasinghe, Anusha; Shoaibi, Azadeh; Cummings, Leda M.; Wirth, Dyann F.

2001-01-01

166

Plasmodium falciparum??heat shock protein 110 stabilizes the asparagine repeat-rich parasite proteome during malarial fevers  

E-print Network

One-fourth of Plasmodium falciparum proteins have asparagine repeats that increase the propensity for aggregation, especially at elevated temperatures that occur routinely in malaria-infected patients. Here we report that ...

Muralidharan, Vasant

167

An interplay between 2 signaling pathways: melatonin-cAMP and IP3-Ca2+ signaling pathways control intraerythrocytic development of the malaria parasite Plasmodium falciparum.  

PubMed

Plasmodium falciparum spends most of its asexual life cycle within human erythrocytes, where proliferation and maturation occur. Development into the mature forms of P. falciparum causes severe symptoms due to its distinctive sequestration capability. However, the physiological roles and the molecular mechanisms of signaling pathways that govern development are poorly understood. Our previous study showed that P. falciparum exhibits stage-specific spontaneous Calcium (Ca(2+)) oscillations in ring and early trophozoites, and the latter was essential for parasite development. In this study, we show that luzindole (LZ), a selective melatonin receptor antagonist, inhibits parasite growth. Analyses of development and morphology of LZ-treated P. falciparum revealed that LZ severely disrupted intraerythrocytic maturation, resulting in parasite death. When LZ was added at ring stage, the parasite could not undergo further development, whereas LZ added at the trophozoite stage inhibited development from early into late schizonts. Live-cell Ca(2+) imaging showed that LZ treatment completely abolished Ca(2+) oscillation in the ring forms while having little effect on early trophozoites. Further, the melatonin-induced cAMP increase observed at ring and late trophozoite stage was attenuated by LZ treatment. These suggest that a complex interplay between IP3-Ca(2+) and cAMP signaling pathways is involved in intraerythrocytic development of P. falciparum. PMID:24607908

Furuyama, Wakako; Enomoto, Masahiro; Mossaad, Ehab; Kawai, Satoru; Mikoshiba, Katsuhiko; Kawazu, Shin-ichiro

2014-03-28

168

Inhibition of the growth and development of asexual and sexual stages of drug-sensitive and resistant strains of the human malaria parasite Plasmodium falciparum by Neem ( Azadirachta indica) fractions  

Microsoft Academic Search

Neem (Azadirachta indica) has been shown to possess anti-malarial activity. In this study we systematically evaluated extracts of neem seeds and purified fractions further enriched in polar or non-polar constituents for their effect on in vitro growth and development of asexual and sexual stages of the human malaria parasite Plasmodium falciparum. Use of synchronized stages of parasites suggested trophozoites\\/schizonts as

Ravi Dhar; Kunyan Zhang; G. P Talwar; Sanjay Garg; Nirbhay Kumar

1998-01-01

169

Role of complex II in anaerobic respiration of the parasite mitochondria from Ascaris suum and Plasmodium falciparum  

Microsoft Academic Search

Parasites have developed a variety of physiological functions necessary for existence within the specialized environment of the host. Regarding energy metabolism, which is an essential factor for survival, parasites adapt to low oxygen tension in host mammals using metabolic systems that are very different from that of the host. The majority of parasites do not use the oxygen available within

Kiyoshi Kita; Hiroko Hirawake; Hiroko Miyadera; Hisako Amino; Satoru Takeo

2002-01-01

170

Malaria Parasite Invasion of the Mosquito Salivary Gland Requires Interaction between the Plasmodium TRAP and the Anopheles Saglin Proteins  

PubMed Central

SM1 is a twelve-amino-acid peptide that binds tightly to the Anopheles salivary gland and inhibits its invasion by Plasmodium sporozoites. By use of UV-crosslinking experiments between the peptide and its salivary gland target protein, we have identified the Anopheles salivary protein, saglin, as the receptor for SM1. Furthermore, by use of an anti-SM1 antibody, we have determined that the peptide is a mimotope of the Plasmodium sporozoite Thrombospondin Related Anonymous Protein (TRAP). TRAP binds to saglin with high specificity. Point mutations in TRAP's binding domain A abrogate binding, and binding is competed for by the SM1 peptide. Importantly, in vivo down-regulation of saglin expression results in strong inhibition of salivary gland invasion. Together, the results suggest that saglin/TRAP interaction is crucial for salivary gland invasion by Plasmodium sporozoites. PMID:19148273

Ghosh, Anil K.; Devenport, Martin; Jethwaney, Deepa; Kalume, Dario E.; Pandey, Akhilesh; Anderson, Vernon E.; Sultan, Ali A.; Kumar, Nirbhay; Jacobs-Lorena, Marcelo

2009-01-01

171

Immunization of mice with live-attenuated late liver stage-arresting Plasmodium yoelii parasites generates protective antibody responses to preerythrocytic stages of malaria.  

PubMed

Understanding protective immunity to malaria is essential for the design of an effective vaccine to prevent the large number of infections and deaths caused by this parasitic disease. To date, whole-parasite immunization with attenuated parasites is the most effective method to confer sterile protection against malaria infection in clinical trials. Mouse model studies have highlighted the essential role that CD8(+) T cells play in protection against preerythrocytic stages of malaria; however, there is mounting evidence that antibodies are also important in these stages. Here, we show that experimental immunization of mice with Plasmodium yoelii fabb/f(-) (Pyfabb/f(-)), a genetically attenuated rodent malaria parasite that arrests late in the liver stage, induced functional antibodies that inhibited hepatocyte invasion in vitro and reduced liver-stage burden in vivo. These antibodies were sufficient to induce sterile protection from challenge by P. yoelii sporozoites in the absence of T cells in 50% of mice when sporozoites were administered by mosquito bite but not when they were administered by intravenous injection. Moreover, among mice challenged by mosquito bite, a higher proportion of BALB/c mice than C57BL/6 mice developed sterile protection (62.5% and 37.5%, respectively). Analysis of the antibody isotypes induced by immunization with Pyfabb/f(-) showed that, overall, BALB/c mice developed an IgG1-biased response, whereas C57BL/6 mice developed an IgG2b/c-biased response. Our data demonstrate for the first time that antibodies induced by experimental immunization of mice with a genetically attenuated rodent parasite play a protective role during the preerythrocytic stages of malaria. Furthermore, they highlight the importance of considering both the route of challenge and the genetic background of the mouse strains used when interpreting vaccine efficacy studies in animal models of malaria infection. PMID:25267837

Keitany, Gladys J; Sack, Brandon; Smithers, Hannah; Chen, Lin; Jang, Ihn K; Sebastian, Leslie; Gupta, Megha; Sather, D Noah; Vignali, Marissa; Vaughan, Ashley M; Kappe, Stefan H I; Wang, Ruobing

2014-12-01

172

Induction of Parasite Growth-Inhibitory Antibodies by a Virosomal Formulation of a Peptidomimetic of Loop I from Domain III of Plasmodium falciparum Apical Membrane Antigen 1  

PubMed Central

Apical membrane antigen 1 (AMA-1) of Plasmodium falciparum is a leading candidate antigen for inclusion in a malaria subunit vaccine. Its ectodomain can be divided into three subdomains, each with disulfide bond-stabilized structures. Since the majority of antibodies raised against the ectodomain appear to recognize strain-specific epitopes in domain I, we attempted to develop a vaccine formulation which directs the immune response to a region that contains more conserved epitopes. Here we demonstrate that a virosomal formulation of a peptide that mimics the semiconserved loop I of domain III elicits parasite growth-inhibitory antibodies. A synthetic peptide comprising residues 446 to 490 of AMA-1 (AMA-1446-490) was conjugated through the N terminus to a derivative of phosphatidylethanolamine and the phosphatidylethanolamine-peptide conjugate was incorporated into immunopotentiating reconstituted influenza virosomes as a human-compatible antigen delivery system. Both cyclized and linear versions of the peptide antigen elicited antibodies which specifically bound to parasite-expressed AMA-1 in Western blotting with parasite lysates as well as in immunofluorescence assays with blood stage parasites. All 11 peptidomimetic-specific monoclonal antibodies generated were cross-reactive with parasite-expressed AMA-1. Antigen binding assays with a library of overlapping cyclic peptides covering the target sequence revealed differences in the fine specificity of these monoclonal antibodies and provided evidence that at least some of them recognized discontinuous epitopes. The two immunodominant epitopes comprised the conserved linear sequences K459RIKLN464 and D467DEGNKKII475. A key feature of the synthetic vaccine formulation proposed here is the display of the peptide antigen in a native-like state on the surface of the virosome. PMID:12874357

Mueller, Markus S.; Renard, Annabelle; Boato, Francesca; Vogel, Denise; Naegeli, Martin; Zurbriggen, Rinaldo; Robinson, John A.; Pluschke, Gerd

2003-01-01

173

Anopheles gambiae APL1 Is a Family of Variable LRR Proteins Required for Rel1-Mediated Protection from the Malaria Parasite, Plasmodium berghei  

PubMed Central

Background We previously identified by genetic mapping an Anopheles gambiae chromosome region with strong influence over the outcome of malaria parasite infection in nature. Candidate gene studies in the genetic interval, including functional tests using the rodent malaria parasite Plasmodium berghei, identified a novel leucine-rich repeat gene, APL1, with functional activity against P. berghei. Principal Findings Manual reannotation now reveals APL1 to be a family of at least 3 independently transcribed genes, APL1A, APL1B, and APL1C. Functional dissection indicates that among the three known APL1 family members, APL1C alone is responsible for host defense against P. berghei. APL1C functions within the Rel1-Cactus immune signaling pathway, which regulates APL1C transcript and protein abundance. Gene silencing of APL1C completely abolishes Rel1-mediated host protection against P. berghei, and thus the presence of APL1C is required for this protection. Further highlighting the influence of this chromosome region, allelic haplotypes at the APL1 locus are genetically associated with and have high explanatory power for the success or failure of P. berghei parasite infection. Conclusions APL1C functions as a required transducer of Rel1-dependent immune signal(s) to efficiently protect mosquitoes from P. berghei infection, and allelic genetic haplotypes of the APL1 locus display distinct levels of susceptibility and resistance to P. berghei. PMID:18989366

Lazzaro, Brian P.; Rottschaefer, Susan M.; Coulibaly, Boubacar; Sacko, Madjou; Niare, Oumou; Morlais, Isabelle; Traore, Sekou F.; Vernick, Kenneth D.

2008-01-01

174

Geographical origin of Plasmodium vivax in the Republic of Korea: haplotype network analysis based on the parasite's mitochondrial genome  

Microsoft Academic Search

BACKGROUND: The Republic of Korea (South Korea) is one of the countries where vivax malaria had been successfully eradicated by the late 1970s. However, re-emergence of vivax malaria in South Korea was reported in 1993. Several epidemiological studies and some genetic studies using antigenic molecules of Plasmodium vivax in the country have been reported, but the evolutionary history of P.

Moritoshi Iwagami; Seung-Young Hwang; Megumi Fukumoto; Toshiyuki Hayakawa; Kazuyuki Tanabe; So-Hee Kim; Weon-Gyu Kho; Shigeyuki Kano

2010-01-01

175

Plasmodium falciparum UvrD activities are downregulated by DNA-interacting compounds and its dsRNA inhibits malaria parasite growth  

PubMed Central

Background Human malaria parasite infection and its control is a global challenge which is responsible for ~0.65 million deaths every year globally. The emergence of drug resistant malaria parasite is another challenge to fight with malaria. Enormous efforts are being made to identify suitable drug targets in order to develop newer classes of drug. Helicases play crucial roles in DNA metabolism and have been proposed as therapeutic targets for cancer therapy as well as viral and parasitic infections. Genome wide analysis revealed that Plasmodium falciparum possesses UvrD helicase, which is absent in the human host. Results Recently the biochemical characterization of P. falciparum UvrD helicase revealed that N-terminal UvrD (PfUDN) hydrolyses ATP, translocates in 3’ to 5’ direction and interacts with MLH to modulate each other’s activity. In this follow up study, further characterization of P. falciparum UvrD helicase is presented. Here, we screened the effect of various DNA interacting compounds on the ATPase and helicase activity of PfUDN. This study resulted into the identification of daunorubicin (daunomycin), netropsin, nogalamycin, and ethidium bromide as the potential inhibitor molecules for the biochemical activities of PfUDN with IC50 values ranging from ~3.0 to ~5.0 ?M. Interestingly etoposide did not inhibit the ATPase activity but considerable inhibition of unwinding activity was observed at 20 ?M. Further study for analyzing the importance of PfUvrD enzyme in parasite growth revealed that PfUvrD is crucial/important for its growth ex-vivo. Conclusions As PfUvrD is absent in human hence on the basis of this study we propose PfUvrD as suitable drug target to control malaria. Some of the PfUvrD inhibitors identified in the present study can be utilized to further design novel and specific inhibitor molecules. PMID:24707807

2014-01-01

176

Identification and characterization of the merozoite surface protein 1 (msp1) gene in a host-generalist avian malaria parasite, Plasmodium relictum (lineages SGS1 and GRW4) with the use of blood transcriptome  

PubMed Central

Background The merozoite surface protein 1 (msp1) is one of the most studied vaccine candidate genes in mammalian Plasmodium spp. to have been used for investigations of epidemiology, population structures, and immunity to infections. However methodological difficulties have impeded the use of nuclear markers such as msp1 in Plasmodium parasites causing avian malaria. Data from an infection transcriptome of the host generalist avian malaria parasite Plasmodium relictum was used to identify and characterize the msp1 gene from two different isolates (mtDNA lineages SGS1 and GRW4). The aim was to investigate whether the msp1 gene in avian malaria species shares the properties of the msp1 gene in Plasmodium falciparum in terms of block variability, conserved anchor points and repeat motifs, and further to investigate the degree to which the gene might be informative in avian malaria parasites for population and epidemiological studies. Methods Reads from 454 sequencing of birds infected with avian malaria was used to develop Sanger sequencing protocols for the msp1 gene of P. relictum. Genetic variability between variable and conserved blocks of the gene was compared within and between avian malaria parasite species, including P. falciparum. Genetic variability of the msp1 gene in P. relictum was compared with six other nuclear genes and the mtDNA gene cytochrome b. Results The msp1 gene of P. relictum shares the same general pattern of variable and conserved blocks as found in P. falciparum, although the variable blocks exhibited less variability than P. falciparum. The variation across the gene blocks in P. falciparum spanned from being as conserved as within species variation in P. relictum to being as variable as between the two avian malaria species (P. relictum and Plasmodium gallinaceum) in the variable blocks. In P. relictum the highly conserved p19 region of the peptide was identified, which included two epidermal growth factor-like domains and a fully conserved GPI anchor point. Conclusion This study provides protocols for evaluation of the msp1 gene in the avian malaria generalist parasite P. relictum. The msp1 gene in avian Plasmodium shares the genetic properties seen in P. falciparum, indicating evolutionary conserved functions for the gene. The data on the variable blocks of the gene show that the msp1 gene in P. relictum might serve as a good candidate gene for future population and epidemiological studies of the parasite. PMID:24172200

2013-01-01

177

Combining Parasite Lactate Dehydrogenase-Based and Histidine-Rich Protein 2-Based Rapid Tests To Improve Specificity for Diagnosis of Malaria Due to Plasmodium knowlesi and Other Plasmodium Species in Sabah, Malaysia  

PubMed Central

Plasmodium knowlesi causes severe and fatal malaria in Malaysia. Microscopic misdiagnosis is common and may delay appropriate treatment. P. knowlesi can cross-react with “species-specific” parasite lactate dehydrogenase (pLDH) monoclonal antibodies used in rapid diagnostic tests (RDTs) to detect P. falciparum and P. vivax. At one tertiary-care hospital and two district hospitals in Sabah, we prospectively evaluated two combination RDTs for malaria diagnosis by using both a pan-Plasmodium-pLDH (pan-pLDH)/P. falciparum-specific-pLDH (Pf-pLDH) RDT (OptiMAL-IT) and a non-P. falciparum VOM-pLDH/Pf-HRP2 RDT (CareStart). Differential cross-reactivity among these combinations was hypothesized to differentiate P. knowlesi from other Plasmodium monoinfections. Among 323 patients with PCR-confirmed P. knowlesi (n = 193), P. falciparum (n = 93), and P. vivax (n = 37) monoinfections, the VOM-pLDH individual component had the highest sensitivity for nonsevere (35%; 95% confidence interval [CI], 27 to 43%) and severe (92%; CI, 81 to 100%) P. knowlesi malaria. CareStart demonstrated a P. knowlesi sensitivity of 42% (CI, 34 to 49%) and specificity of 74% (CI, 65 to 82%), a P. vivax sensitivity of 83% (CI, 66 to 93%) and specificity of 71% (CI, 65 to 76%), and a P. falciparum sensitivity of 97% (CI, 90 to 99%) and specificity of 99% (CI, 97 to 100%). OptiMAL-IT demonstrated a P. knowlesi sensitivity of 32% (CI, 25 to 39%) and specificity of 21% (CI, 15 to 29%), a P. vivax sensitivity of 60% (CI, 42 to 75%) and specificity of 97% (CI, 94 to 99%), and a P. falciparum sensitivity of 82% (CI, 72 to 89%) and specificity of 39% (CI, 33 to 46%). The combination of CareStart plus OptiMAL-IT for P. knowlesi using predefined criteria gave a sensitivity of 25% (CI, 19 to 32%) and specificity of 97% (CI, 92 to 99%). Combining two RDT combinations was highly specific for P. knowlesi malaria diagnosis; however, sensitivity was poor. The specificity of pLDH RDTs was decreased for P. vivax and P. falciparum because of P. knowlesi cross-reactivity and cautions against their use alone in areas where P. knowlesi malaria is endemic. Sensitive P. knowlesi-specific RDTs and/or alternative molecular diagnostic tools are needed in areas where P. knowlesi malaria is endemic. PMID:24696029

William, Timothy; Barber, Bridget E.; Parameswaran, Uma; Bird, Elspeth; Piera, Kim; Aziz, Ammar; Dhanaraj, Prabakaran; Yeo, Tsin W.; Anstey, Nicholas M.

2014-01-01

178

Serum antibody immunoglobulin G of mice convalescent from Plasmodium yoelii infection inhibits growth of Plasmodium falciparum in vitro: blood stage antigens of P. falciparum involved in interspecies cross-reactive inhibition of parasite growth.  

PubMed Central

We demonstrated that antibodies in the serum of BALB/c mice convalescent from Plasmodium yoelii infection inhibit the in vitro growth of Plasmodium falciparum. Blood stage P. falciparum antigens that cross-react with the convalescent-phase mouse serum antibodies were identified and partially characterized. Convalescent-phase mouse serum immunoglobulin G (IgG) reacted with P. falciparum lysates at up to a 1:15,000 dilution of the immune sera and bound to P. falciparum-parasitized erythrocytes at up to a 1:5,000 dilution of the sera. The cross-reactive moieties of antigens in parasite lysates were resistant to oxidation by periodate but sensitive to trypsinization. About 15 polypeptides (M(r)s of 15,000 to 110,000) of P. falciparum blood stages were recognized by the convalescent-phase mouse anti-P. yoelii sera; many of these antigens were metabolically 35S labeled and specifically immunoprecipitated. Also, virtually all of the cross-reactive antigens were recognized by human malaria-immune sera. The anti-P. yoelii serum antibodies bound, with high affinity, to at least five of the cross-reactive antigens (M(r)s of 107,000, 84,000, 53,000, 36,000, and 30,000). By phase separation in Triton X-114, eight interspecies cross-reactive antigens (M(r)s of 84,000, 76,000, 51,000, 31,000, 29,000, 28,000, 23,000, and 22,000) were found to be integral membrane proteins. Convalescent-phase mouse serum IgG strongly inhibited the differentiation of P. falciparum from schizonts to rings; 75 micrograms of IgG per ml caused 80% inhibition of release of merozoites and their invasion into erythrocytes. On the other hand, the anti-P. yoelii serum antibodies also inhibited intracellular development of P. falciparum from rings to schizonts; 25 micrograms of IgG per ml caused 50% inhibition. Inhibition of P. falciparum growth by anti-P. yoelii serum IgG suggests that some of the interspecies cross-reactive antigens contain important conserved epitopes and induce protective antibodies against P. falciparum. Images PMID:8188358

Ray, P; Sahoo, N; Singh, B; Kironde, F A

1994-01-01

179

Structural Insights into Substrate Binding by PvFKBP35, a Peptidylprolyl cis-trans Isomerase from the Human Malarial Parasite Plasmodium vivax  

PubMed Central

The immunosuppressive drug FK506 binding proteins (FKBPs), an immunophilin family with the immunosuppressive drug FK506 binding property, exhibit peptidylprolyl cis-trans isomerase (PPIase) activity. While the cyclophilin-catalyzed peptidylprolyl isomerization of X-Pro peptide bonds has been extensively studied, the mechanism of the FKBP-mediated peptidylprolyl isomerization remains uncharacterized. Thus, to investigate the binding of FKBP with its substrate and the underlying catalytic mechanism of the FKBP-mediated proline isomerization, here we employed the FK506 binding domain (FKBD) of the human malarial parasite Plasmodium vivax FK506 binding protein 35 (PvFKBP35) and examined the details of the molecular interaction between the isomerase and a peptide substrate. The crystallographic structures of apo PvFKBD35 and its complex with the tetrapeptide substrate succinyl-Ala-Leu-Pro-Phe-p-nitroanilide (sALPFp) determined at 1.4 ? and 1.65 ? resolutions, respectively, showed that the substrate binds to PvFKBD35 in a cis conformation. Nuclear magnetic resonance (NMR) studies demonstrated the chemical shift perturbations of D55, H67, V73, and I74 residues upon the substrate binding. In addition, the X-ray crystal structure, along with the mutational studies, shows that Y100 is a key residue for the catalytic activity. Taken together, our results provide insights into the catalytic mechanism of PvFKBP35-mediated cis-trans isomerization of substrate and ultimately might aid designing substrate mimetic inhibitors targeting the malarial parasite FKBPs. PMID:23435727

Alag, Reema; Balakrishna, Asha Manikkoth; Rajan, Sreekanth; Qureshi, Insaf A.; Shin, Joon; Lescar, Julien; Grüber, Gerhard

2013-01-01

180

Bacterially Expressed Full-Length Recombinant Plasmodium falciparum RH5 Protein Binds Erythrocytes and Elicits Potent Strain-Transcending Parasite-Neutralizing Antibodies  

PubMed Central

Plasmodium falciparum reticulocyte binding-like homologous protein 5 (PfRH5) is an essential merozoite ligand that binds with its erythrocyte receptor, basigin. PfRH5 is an attractive malaria vaccine candidate, as it is expressed by a wide number of P. falciparum strains, cannot be genetically disrupted, and exhibits limited sequence polymorphisms. Viral vector-induced PfRH5 antibodies potently inhibited erythrocyte invasion. However, it has been a challenge to generate full-length recombinant PfRH5 in a bacterial-cell-based expression system. In this study, we have produced full-length recombinant PfRH5 in Escherichia coli that exhibits specific erythrocyte binding similar to that of the native PfRH5 parasite protein and also, importantly, elicits potent invasion-inhibitory antibodies against a number of P. falciparum strains. Antibasigin antibodies blocked the erythrocyte binding of both native and recombinant PfRH5, further confirming that they bind with basigin. We have thus successfully produced full-length PfRH5 as a functionally active erythrocyte binding recombinant protein with a conformational integrity that mimics that of the native parasite protein and elicits potent strain-transcending parasite-neutralizing antibodies. P. falciparum has the capability to develop immune escape mechanisms, and thus, blood-stage malaria vaccines that target multiple antigens or pathways may prove to be highly efficacious. In this regard, antibody combinations targeting PfRH5 and other key merozoite antigens produced potent additive inhibition against multiple worldwide P. falciparum strains. PfRH5 was immunogenic when immunized with other antigens, eliciting potent invasion-inhibitory antibody responses with no immune interference. Our results strongly support the development of PfRH5 as a component of a combination blood-stage malaria vaccine. PMID:24126527

Reddy, K. Sony; Pandey, Alok K.; Singh, Hina; Sahar, Tajali; Emmanuel, Amlabu; Chitnis, Chetan E.; Chauhan, Virander S.

2014-01-01

181

Bacterially expressed full-length recombinant Plasmodium falciparum RH5 protein binds erythrocytes and elicits potent strain-transcending parasite-neutralizing antibodies.  

PubMed

Plasmodium falciparum reticulocyte binding-like homologous protein 5 (PfRH5) is an essential merozoite ligand that binds with its erythrocyte receptor, basigin. PfRH5 is an attractive malaria vaccine candidate, as it is expressed by a wide number of P. falciparum strains, cannot be genetically disrupted, and exhibits limited sequence polymorphisms. Viral vector-induced PfRH5 antibodies potently inhibited erythrocyte invasion. However, it has been a challenge to generate full-length recombinant PfRH5 in a bacterial-cell-based expression system. In this study, we have produced full-length recombinant PfRH5 in Escherichia coli that exhibits specific erythrocyte binding similar to that of the native PfRH5 parasite protein and also, importantly, elicits potent invasion-inhibitory antibodies against a number of P. falciparum strains. Antibasigin antibodies blocked the erythrocyte binding of both native and recombinant PfRH5, further confirming that they bind with basigin. We have thus successfully produced full-length PfRH5 as a functionally active erythrocyte binding recombinant protein with a conformational integrity that mimics that of the native parasite protein and elicits potent strain-transcending parasite-neutralizing antibodies. P. falciparum has the capability to develop immune escape mechanisms, and thus, blood-stage malaria vaccines that target multiple antigens or pathways may prove to be highly efficacious. In this regard, antibody combinations targeting PfRH5 and other key merozoite antigens produced potent additive inhibition against multiple worldwide P. falciparum strains. PfRH5 was immunogenic when immunized with other antigens, eliciting potent invasion-inhibitory antibody responses with no immune interference. Our results strongly support the development of PfRH5 as a component of a combination blood-stage malaria vaccine. PMID:24126527

Reddy, K Sony; Pandey, Alok K; Singh, Hina; Sahar, Tajali; Emmanuel, Amlabu; Chitnis, Chetan E; Chauhan, Virander S; Gaur, Deepak

2014-01-01

182

The Clinical-Grade 42-Kilodalton Fragment of Merozoite Surface Protein 1 of Plasmodium falciparum Strain FVO Expressed in Escherichia coli Protects Aotus nancymai against Challenge with Homologous Erythrocytic-Stage Parasites  

Microsoft Academic Search

A 42-kDa fragment from the C terminus of major merozoite surface protein 1 (MSP1) is among the leading malaria vaccine candidates that target infection by asexual erythrocytic-stage malaria parasites. The MSP142 gene fragment from the Vietnam-Oak Knoll (FVO) strain of Plasmodium falciparum was expressed as a soluble protein in Escherichia coli and purified according to good manufacturing practices. This clinical-grade

Christian A. Darko; Evelina Angov; William E. Collins; Elke S. Bergmann-Leitner; Autumn S. Girouard; Stacy L. Hitt; Jana S. McBride; Carter L. Diggs; Anthony A. Holder; Carole A. Long; John W. Barnwell; Jeffrey A. Lyon

2005-01-01

183

Invited Review Malaria parasite colonisation of the mosquito midgut Placing  

E-print Network

Invited Review Malaria parasite colonisation of the mosquito midgut ­ Placing the Plasmodium 3 March 2012 Keywords: Malaria Plasmodium Mosquito Anopheles Ookinete Oocyst Midgut traversal drugs is emerging. Malaria parasite migration through the mosquito host constitutes a major population

McFadden, Geoff

184

Blood parasites from California ducks and geese  

USGS Publications Warehouse

Blood smears were procured from 1,011 geese and ducks of 19 species from various locations in California. Parasites were found in 28 individuals. The parasites observed included Haemoproteus hermani, Leucocytozoon simondi, microfilaria, Plasmodium relictum (=P. biziurae), and Plasmodium sp. with elongate gametocytes. This is the first report of a natural infection with a Plasmodium in North American wild ducks.

Herman, C.M.

1951-01-01

185

Counter-regulatory anti-parasite cytokine responses during concurrent Plasmodium yoelii and intestinal helminth infections in mice  

Technology Transfer Automated Retrieval System (TEKTRAN)

Malaria and helminth infections are two of the most prevalent parasitic diseases in tropical areas. While concomitant infection is common, mechanisms contributing to altered disease outcomes during co-infection remain poorly defined. We have previously reported exacerbation of normally non-lethal ...

186

Relative clonal proportions over time in mixed-genotype infections of the lizard malaria parasite Plasmodium mexicanum  

E-print Network

Relative clonal proportions over time in mixed-genotype infections of the lizard malaria parasite malaria Malaria life history Mixed-clone infections Clonal proportions Microsatellites a b s t r a c biology. However, how relative clonal proportions vary over time in a host is still poorly known

Schall, Joseph J.

187

Ribosomal protein P2 localizes to the parasite zoite-surface and is a target for invasion inhibitory antibodies in Toxoplasma gondii and Plasmodium falciparum.  

PubMed

In the malarial parasite Plasmodium falciparum, the conserved ribosomal stalk protein P2 (PfP2) exhibits extra-ribosomal stage-specific oligomerization and trafficking to the host red cell membrane. Antibodies directed against PfP2 arrested cell division. We sought to examine whether P2 from a closely related Apicomplexan parasite, Toxoplasma gondii, exhibits similar properties in terms of its oligomeric status as well as such unique host-cell localization. Circular dichroism spectroscopy of recombinant P2 from T. gondii (TgP2) showed a structure similar to that of PfP2, but unlike PfP2, which forms SDS- and DTT-resistant oligomers, TgP2 exhibited only a weak SDS-resistant dimerization. Also, unlike PfP2 localization to the infected erythrocyte surface, TgP2 did not localize to the host membrane in T. gondii infected human foreskin fibroblast cells. However, P2 protein was detected on the free tachyzoite surface, corroborated by localization of epitope-tagged P2 transfected in T. gondii. The presence of P2 on the surface of P. falciparum merozoites was also observed, and specific antibodies raised against the P2 protein blocked both T. gondii and P. falciparum zoite invasion of the host cells. Thus, although certain moonlighting functions of the acidic ribosomal protein P2 are different amongst P. falciparum and T. gondii, the P2 protein localizes to the surface of the invasive zoite form, and appears to constitute a potential target for host cell invasion inhibition in both the Apicomplexan infections. PMID:25280460

Sudarsan, Rajagopal; Chopra, Reshma Korde; Khan, Mudassar Ali; Sharma, Shobhona

2015-02-01

188

Atovaquone Tolerance in Plasmodium falciparum Parasites Selected for High-Level Resistance to a Dihydroorotate Dehydrogenase Inhibitor.  

PubMed

Atovaquone is a component of Malarone, a widely prescribed antimalarial combination, that targets malaria respiration. Here we show that parasites with high-level resistance to an inhibitor of dihydroorotate dehydrogenase demonstrate unexpected atovaquone tolerance. Fortunately, the tolerance is diminished with proguanil, the second partner in Malarone. It is important to understand such "genetic cross talk" between respiration and pyrimidine biosynthesis since many antimalarial drug development programs target these two seemingly independent pathways. PMID:25331708

Guler, Jennifer L; White, John; Phillips, Margaret A; Rathod, Pradipsinh K

2015-01-01

189

Whole cell imaging reveals novel modular features of the exomembrane system of the malaria parasite, Plasmodium falciparum.  

PubMed

During its intra-erythrocytic development Plasmodium falciparum establishes a membrane network beyond its own limiting membrane in the cytoplasm of its host. These membrane structures play an important role in the trafficking of virulence proteins to the erythrocyte surface, however their ultrastructure is only partly defined and there is on-going debate regarding their origin, organisation and connectivity. We have used two whole cell imaging modalities to explore the topography of parasitised erythrocytes. Three-dimensional structured illumination microscopy provides resolution beyond the optical diffraction limit and permits analysis of fluorescently labelled whole cells. Immunoelectron tomography offers the possibility of high resolution imaging of individual ultrastructural features in a cellular context. Combined with serial sectioning and immunogold labelling, this technique permits precise mapping of whole cell architecture. We show that the P. falciparum exported secretory system comprises a series of modular units, comprising flattened cisternae, known as Maurer's clefts, tubular connecting elements, two different vesicle populations and electron-dense structures that have fused with the erythrocyte membrane. The membrane network is not continuous, pointing to an important role for vesicle-mediated transport in the delivery of cargo to different destinations in the host cell. PMID:19766648

Hanssen, Eric; Carlton, Peter; Deed, Samantha; Klonis, Nectarios; Sedat, John; DeRisi, Joe; Tilley, Leann

2010-01-01

190

Patterns of haemosporidian prevalence along a range expansion in introduced Kenyan house sparrows Passer domesticus  

E-print Network

sparrows Passer domesticus Courtney A. C. Coon and Lynn B. Martin C. A. C. Coon (ccoon@mail.usf.edu) and L predicted avian haemosporidian prevalence in populations of house sparrows Passer domesticus introduced) found that house sparrows Passer domesticus; HOSP, one of the world's most successful introduced

Lajeunesse, Marc J.

191

A species of Plasmodium from sandhill cranes in Florida.  

PubMed

Infections of a species of Plasmodium (subgenus Giovannolaia) were diagnosed in 3 sandhill cranes (Grus canadensis) from north-central Florida. This parasite is close morphometrically to Plasmodium polare; this finding constitutes the first report of a species of Plasmodium from sandhill cranes in North America. PMID:8195957

Telford, S R; Nesbitt, S A; Spalding, M G; Forrester, D J

1994-06-01

192

Co-ordinated stage-dependent enhancement of Plasmodium falciparum antioxidant enzymes and heat shock protein expression in parasites growing in oxidatively stressed or G6PD-deficient red blood cells  

PubMed Central

Background Plasmodium falciparum-parasitized red blood cells (RBCs) are equipped with protective antioxidant enzymes and heat shock proteins (HSPs). The latter are only considered to protect against thermal stress. Important issues are poorly explored: first, it is insufficiently known how both systems are expressed in relation to the parasite developmental stage; secondly, it is unknown whether P. falciparum HSPs are redox-responsive, in view of redox sensitivity of HSP in eukaryotic cells; thirdly, it is poorly known how the antioxidant defense machinery would respond to increased oxidative stress or inhibited antioxidant defense. Those issues are interesting as several antimalarials increase the oxidative stress or block antioxidant defense in the parasitized RBC. In addition, numerous inhibitors of HSPs are currently developed for cancer therapy and might be tested as anti-malarials. Thus, the joint disruption of the parasite antioxidant enzymes/HSP system would interfere with parasite growth and open new perspectives for anti-malaria therapy. Methods Stage-dependent mRNA expression of ten representative P. falciparum antioxidant enzymes and hsp60/70–2/70–3/75/90 was studied by quantitative real-time RT-PCR in parasites growing in normal RBCs, in RBCs oxidatively-stressed by moderate H2O2 generation and in G6PD-deficient RBCs. Protein expression of antioxidant enzymes was assayed by Western blotting. The pentosephosphate-pathway flux was measured in isolated parasites after Sendai-virus lysis of RBC membrane. Results In parasites growing in normal RBCs, mRNA expression of antioxidant enzymes and HSPs displayed co-ordinated stage-dependent modulation, being low at ring, highest at early trophozoite and again very low at schizont stage. Additional exogenous oxidative stress or growth in antioxidant blunted G6PD-deficient RBCs indicated remarkable flexibility of both systems, manifested by enhanced, co-ordinated mRNA expression of antioxidant enzymes and HSPs. Protein expression of antioxidant enzymes was also increased in oxidatively-stressed trophozoites. Conclusion Results indicated that mRNA expression of parasite antioxidant enzymes and HSPs was co-ordinated and stage-dependent. Secondly, both systems were redox-responsive and showed remarkably increased and co-ordinated expression in oxidatively-stressed parasites and in parasites growing in antioxidant blunted G6PD-deficient RBCs. Lastly, as important anti-malarials either increase oxidant stress or impair antioxidant defense, results may encourage the inclusion of anti-HSP molecules in anti-malarial combined drugs. PMID:19480682

Akide-Ndunge, Oscar Bate; Tambini, Elisa; Giribaldi, Giuliana; McMillan, Paul J; Müller, Sylke; Arese, Paolo; Turrini, Francesco

2009-01-01

193

Geographic variation in malarial parasite lineages in the common yellowthroat ( Geothlypis trichas )  

Microsoft Academic Search

Our current understanding of migration routes of many birds is limited and researchers have employed various methods to determine\\u000a migratory patterns. Recently, parasites have been used to track migratory birds. The objective of this study was to determine\\u000a whether haemosporidian parasite lineages detect significant geographic structure in common yellowthroats (Geothlypis trichas). We examined liver tissue or blood from 552 birds

K. M. Pagenkopp; J. Klicka; K. L. Durrant; J. C. Garvin; R. C. Fleischer

2008-01-01

194

High-resolution three-dimensional imaging of red blood cells parasitized by  

E-print Network

High-resolution three-dimensional imaging of red blood cells parasitized by Plasmodium falciparum blood cells parasitized by Plasmodium falciparum and in situ hemozoin crystals using optical diffraction of human red blood cells (RBC) parasitized by malaria-inducing Plasmodium falciparum (Pf)-RBCs. Three

Dao, Ming

195

Comparison of Plasmodium berghei challenge models for the evaluation of pre-erythrocytic malaria vaccines and their effect on perceived vaccine efficacy  

Microsoft Academic Search

BACKGROUND: The immunological mechanisms responsible for protection against malaria infection vary among Plasmodium species, host species and the developmental stage of parasite, and are poorly understood. A challenge with live parasites is the most relevant approach to testing the efficacy of experimental malaria vaccines. Nevertheless, in the mouse models of Plasmodium berghei and Plasmodium yoelii, parasites are usually delivered by

Wolfgang W Leitner; Elke S Bergmann-Leitner; Evelina Angov

2010-01-01

196

TRANSACTIONS OFTHE ROYAL SOCIETY OFTROPICALMEDICINE AND HYGIENE (1997) 91,719-724 719 Molecular analysis of recrudescent parasites in a Plasmodium falciparum drug  

E-print Network

?falciparum antigen genes MSP-1, MSP-2 and GLURI? Seventy-seven children had identical parasites in their pre- and post-treatment samples, indicating genuine recrudescences of resistant parasites. Fourteen children had, perhaps due to sequestration.The remaining 17 children had a mixture of pre-treatment and new parasites

Read, Andrew

197

Nucleosome occupancy at transcription start sites in the human malaria parasite: A hard-wired evolution of virulence?  

E-print Network

Nucleosome occupancy at transcription start sites in the human malaria parasite: A hard-borne infectious disease caused by a eukaryotic protist of the genus Plasmodium. Plasmodium can parasitize a wide into mosquitoes of the genus Anopheles corresponds with the expan- sion of Plasmodium parasites into mammals

Lonardi, Stefano

198

A Clonal Theory of Parasitic Protozoa: The Population Structures of Entamoeba, Giardia, Leishmania, Naegleria, Plasmodium, Trichomonas, and Trypanosoma and their Medical and Taxonomical Consequences  

Microsoft Academic Search

We propose a general theory of clonal reproduction for parasitic protozoa, which has important medical and biological consequences. Many parasitic protozoa have been assumed to reproduce sexually, because of diploidy and occasional sexuality in the laboratory. However, a population genetic analysis of extensive data on biochemical polymorphisms indicates taht the two fundamental consequences of sexual reproduction (i.e., segregation and recombination)

Michel Tibayrenc; Finn Kjellberg; Francisco J. Ayala

1990-01-01

199

Immunization of Aotus monkeys with a functional domain of the Plasmodium falciparum variant antigen induces protection against a lethal parasite line  

Microsoft Academic Search

Immunity to Plasmodium falciparum in African children has been correlated with antibodies to the P. falciparum erythrocyte membrane protein 1 (PfEMP1) variant gene family expressed on the surface of infected red cells. We immunized Aotus monkeys with a subregion of the Malayan Camp variant antigen (MCvar1) that mediates adhesion to the host receptor CD36 on the endothelial surface and present

Dror I. Baruch; Benoit Gamain; John W. Barnwell; Joann S. Sullivan; Anthony Stowers; G. Gale Galland; Louis H. Miller; William E. Collins

2002-01-01

200

The Robust and Modulated Biomarker Network Elicited by the Plasmodium vivax Infection Is Mainly Mediated by the IL-6/IL-10 Axis and Is Associated with the Parasite Load  

PubMed Central

Background. Recent studies have shown that the inflammatory process, including the biomarker production, and the intense activation of innate immune responses are greater in the malaria caused by Plasmodium vivax than other species. Here, we examined the levels of serum biomarkers and their interaction during acute malaria. Material and Methods. Blood samples were collected from P. vivax-infected patients at admission and from healthy donors. Levels of serum biomarkers were measured by Cytometric Bead Assay or ELISA. Results. P. vivax infection triggered the production of both inflammatory and regulatory biomarkers. Levels of IL-6, CXCL-8, IFN-?, IL-5, and IL-10 were higher in P. vivax-infected patients than in healthy donors. On the other hand, malaria patients produced lower levels of TNF-?, IL-12p70, and IL-2 than healthy individuals. While the levels of IL-10 and IL-6 were found independent on the number of malaria episodes, higher levels of these cytokines were seen in patients with higher parasite load. Conclusion. A mixed pattern of proinflammatory and regulatory biomarkers is produced in P. vivax malaria. Analysis of biomarker network suggests that IL-10 and IL-6 are a robust axis in malaria patients and that this interaction seems to be associated with the parasite load. PMID:24741587

Guimarães da Costa, Allyson; do Valle Antonelli, Lis Ribeiro; Augusto Carvalho Costa, Pedro; Paulo Diniz Pimentel, João; Garcia, Nadja Pinto; Monteiro Tarragô, Andréa; Socorro Lopes dos Santos, Maria do Perpétuo; Nogueira, Paulo Afonso; Hekcmann, Maria Izabel Ovellar; Sadahiro, Aya; Teixeira-Carvalho, Andréa; Martins-Filho, Olindo Assis; Malheiro, Adriana

2014-01-01

201

Parasites and Parasitism (CAMB 549) Course organizer: Jay Farrell ( farrellj@vet.upenn.edu) 207 Rosenthal  

E-print Network

Parasites and Parasitism (CAMB 549) Course organizer: Jay Farrell ( farrellj@vet.upenn.edu) 207 and Plasmodium (Roos) 9/29 -- Helminth biology (Beiting) 10/1 -- Filariasis pathogenesis (Lok) 10/4 ­ Parasite protection and immunopathology (Nair) 10/15 -- Innate immunity to helminth parasites (Artis) 10

Plotkin, Joshua B.

202

Statistical Model To Evaluate In Vivo Activities of Antimalarial Drugs in a Plasmodium cynomolgi-Macaque Model for Plasmodium vivax Malaria  

Microsoft Academic Search

Preclinical animal models informing antimalarial drug development are scarce. We have used asexual erythrocytic Plasmodium cynomolgi infections of rhesus macaques to model Plasmodium vivax during preclinical development of compounds targeting parasite phospholipid synthesis. Using this malaria model, we accumu- lated data confirming highly reproducible infection patterns, with self-curing parasite peaks reproducibly preceding recrudescence peaks. We applied nonlinear mixed-effect (NLME) models,

Clemens H. M. Kocken; Edmond J. Remarque; Martin A. Dubbeld; Sharon Wein; Annemarie van der Wel; R. Joyce Verburgh; Henri J. Vial; Alan W. Thomas

2009-01-01

203

Plasmodium cynomolgi genome sequences provide insight into Plasmodium vivax and the monkey malaria clade  

PubMed Central

Plasmodium cynomolgi, a malaria parasite of Asian Old World monkeys, is the sister taxon of Plasmodium vivax, the most prevalent human malaria species outside Africa. Since P. cynomolgi shares many phenotypic, biologic and genetic characteristics of P. vivax, we generated draft genome sequences of three P. cynomolgi strains and performed comparative genomic analysis between them and P. vivax, as well as a third previously sequenced simian parasite, Plasmodium knowlesi. Here we show that genomes of the monkey malaria clade can be characterized by CNVs in multigene families involved in evasion of the human immune system and invasion of host erythrocytes. We identify genome-wide SNPs, microsatellites, and CNVs in the P. cynomolgi genome, providing a map of genetic variation for mapping parasite traits and studying parasite populations. The P. cynomolgi genome is a critical step in developing a model system for P. vivax research, and to counteract the neglect of P. vivax. PMID:22863735

Tachibana, Shin-Ichiro; Sullivan, Steven A.; Kawai, Satoru; Nakamura, Shota; Kim, Hyunjae R.; Goto, Naohisa; Arisue, Nobuko; Palacpac, Nirianne M. Q.; Honma, Hajime; Yagi, Masanori; Tougan, Takahiro; Katakai, Yuko; Kaneko, Osamu; Mita, Toshihiro; Kita, Kiyoshi; Yasutomi, Yasuhiro; Sutton, Patrick L.; Shakhbatyan, Rimma; Horii, Toshihiro; Yasunaga, Teruo; Barnwell, John W.; Escalante, Ananias A.; Carlton, Jane M.; Tanabe, Kazuyuki

2013-01-01

204

Evaluation of parasite subpopulations and genetic diversity of the msp1, msp2 and glurp genes during and following artesunate monotherapy treatment of Plasmodium falciparum malaria in Western Cambodia  

PubMed Central

Background Despite widespread coverage of the emergence of artemisinin resistance, relatively little is known about the parasite populations responsible. The use of PCR genotyping around the highly polymorphic Plasmodium falciparum msp1, msp2 and glurp genes has become well established both to describe variability in alleles within a population of parasites, as well as classify treatment outcome in cases of recurrent disease. The primary objective was to assess the emergence of minority parasite clones during seven days of artesunate (AS) treatment in a location with established artemisinin resistance. An additional objective was to investigate whether the classification of clinical outcomes remained valid when additional genotyping was performed. Methods Blood for parasite genotyping was collected from 143 adult patients presenting with uncomplicated falciparum malaria during a clinical trial of AS monotherapy in Western Cambodia. Nested allelic type-specific amplification of the genes encoding the merozoite surface proteins 1 and 2 (msp1 and msp2) and the glutamate-rich protein (glurp) was performed at baseline, daily during seven days of treatment, and again at failure. Allelic variants were analysed with respect to the size of polymorphisms using Quantity One software to enable identification of polyclonal infections. Results Considerable variation of msp2 alleles but well-conserved msp1 and glurp were identified. At baseline, 31% of infections were polyclonal for one or more genes. Patients with recurrent malaria were significantly more likely to have polyclonal infections than patients without recurrence (seven of nine versus 36 of 127, p?=?0.004). Emergence of minority alleles during treatment was detected in only one of twenty-three cases defined as being artemisinin resistant. Moreover, daily genotyping did not alter the final outcome classification in any recurrent cases. Conclusions The parasites responsible for artemisinin-resistant malaria in a clinical trial in Western Cambodia comprise the dominant clones of acute malaria infections rather than minority clones emerging during treatment. Additional genotyping during therapy was not beneficial. Disproportionately high rates of polyclonal infections in cases of recurrence suggest complex infections lead to poor treatment outcomes. Current research objectives should be broadened to include identification and follow-up of recurrent polyclonal infections so as to define their role as potential agents of emerging resistance. PMID:24206588

2013-01-01

205

Gene synteny and chloroquine resistance in Plasmodium chabaudi  

Microsoft Academic Search

Chloroquine resistance in the rodent malaria parasite Plasmodium chabaudi has been shown to be caused by a gene on chromosome 11, and is not linked to orthologues of the Plasmodium falciparum chloroquine resistance transporter (pfcrt) or Pgh-1 (pfmdr1) genes. In the current work, the progeny of crosses between chloroquine-resistant and sensitive clones of P. chabaudi have been analysed for the

Paul Hunt; Axel Martinelli; Richard Fawcett; Jane Carlton; Richard Carter; David Walliker

2004-01-01

206

Four new species of Plasmodium from New Guinea lizards: integrating morphology and molecules.  

PubMed

New Guinea is one of the most biodiverse regions of the world, particularly in terms of the herpetofauna present, yet surprisingly little is known about the parasites that infect these organisms. A survey of diverse scinid and agamid lizard hosts from this country showed a diversity of malaria parasites infecting these hosts. We combined morphological and morphometric observations of the parasites (primarily gametocytes) along with DNA sequence data from the mitochondrial cytochrome b and cytochrome oxidase I genes and here describe 4 new species of Plasmodium, i.e. Plasmodium minuoviride n. sp., Plasmodium koreafense n. sp., Plasmodium megalotrypa n. sp., and Plasmodium gemini n. sp. A fifth species, Plasmodium lacertiliae Thompson and Hart 1946, is redescribed based on new observations of hosts and localities and additional molecular data. This combined morphological and molecular approach is advised for all future descriptions of new malaria parasite species, particularly in light of situations where every life-history stage is not available. PMID:18823150

Perkins, Susan L; Austin, Christopher C

2009-04-01

207

A clonal theory of parasitic protozoa: the population structures of Entamoeba, Giardia, Leishmania, Naegleria, Plasmodium, Trichomonas, and Trypanosoma and their medical and taxonomical consequences.  

PubMed Central

We propose a general theory of clonal reproduction for parasitic protozoa, which has important medical and biological consequences. Many parasitic protozoa have been assumed to reproduce sexually, because of diploidy and occasional sexuality in the laboratory. However, a population genetic analysis of extensive data on biochemical polymorphisms indicates that the two fundamental consequences of sexual reproduction (i.e., segregation and recombination) are apparently rare or absent in natural populations of the parasitic protozoa. Moreover, the clones recorded appear to be stable over large geographical areas and long periods of time. A clonal population structure demands that the medical attributes of clones be separately characterized; ubiquitous clones call for priority characterization. Uniparental reproduction renders unsatisfactory Linnean taxonomy; this needs to be supplemented by the "natural clone" as an additional taxonomic unit, which is best defined by means of genetic markers. PMID:2320563

Tibayrenc, M; Kjellberg, F; Ayala, F J

1990-01-01

208

Immunisation with recombinant AMA1 protects mice against infection with Plasmodium chabaudi  

Microsoft Academic Search

The Plasmodium merozoite surface antigen apical membrane antigen-1 (AMA-1) has previously been shown to provide partial protection to Saimiri and rhesus monkeys immunised with recombinant Plasmodium fragile or parasite-derived Plasmodium knowlesi AMA-1, respectively. In the study reported here we have used the Plasmodium chabaudi\\/mouse model system to extend our pre-clinical assessment of an AMA-1 vaccine. We describe here the expression

Robin F. Anders; Pauline E. Crewther; Stirling Edwards; Mai Margetts; Mary L. S. M. Matthew; Bronwyn Pollock; David Pye

1998-01-01

209

Dimerization of Plasmodium vivax DBP is induced upon receptor binding and drives recognition of DARC  

Microsoft Academic Search

Plasmodium vivax and Plasmodium knowlesi depend on the Duffy-Binding Protein DBL domain (RII-PvDBP or RII-PkDBP) engaging Duffy Antigen\\/Receptor for Chemokines on red blood cells during invasion. Inhibition of this key interaction provides an excellent opportunity for parasite control. There are competing models for whether Plasmodium ligands engage receptors as monomers or dimers, resolution of which has profound implications for parasite

Joseph D. Batchelor; Jacob A. Zahm; Niraj H. Tolia

210

Dimerization of Plasmodium vivaxDBP is induced upon receptor binding and drives recognition of DARC  

Microsoft Academic Search

Plasmodium vivax and Plasmodium knowlesi invasion depends on the parasite Duffy-binding protein DBL domain (RII-PvDBP or RII-PkDBP) engaging the Duffy antigen receptor for chemokines (DARC) on red blood cells. Inhibition of this key interaction provides an excellent opportunity for parasite control. There are competing models for whether Plasmodium ligands engage receptors as monomers or dimers, a question whose resolution has

Joseph D Batchelor; Jacob A Zahm; Niraj H Tolia

2011-01-01

211

Evidence of tRNA cleavage in apicomplexan parasites: half-tRNAs as new potential regulatory molecules of Toxoplasma gondii and Plasmodium berghei  

Technology Transfer Automated Retrieval System (TEKTRAN)

Several lines of evidence demonstrated that organisms ranging from bacteria to higher animals possess a regulated endonucleolytic cleavage pathway producing half-tRNA fragments. In the present study, we investigated the occurrence of this phenomenon in two distantly related apicomplexan parasites, T...

212

Autophagy in Plasmodium, a multifunctional pathway?  

PubMed Central

Autophagy is a catabolic process that normally utilizes the lysosome. The far-reaching implications of this system in disease are being increasingly understood. Studying autophagy is complicated by its role in cell survival and programmed cell death and the involvement of the canonical marker of autophagy, Atg8/LC3, in numerous non-autophagic roles. The malaria parasite, Plasmodium, has conserved certain aspects of the autophagic machinery but for what purpose has long remained a mystery. Major advances have recently been gained and suggest a role for Atg8 in apicoplast maintenance, degradation of heme inside the food vacuole, and possibly trafficking of proteins or organelles outside the parasite membrane. Autophagy may also participate in programmed cell death under drug treatment or as a selective tool to limit parasite load. We review the current findings and discuss discrepancies in the field of autophagy in the Plasmodium parasite. PMID:24688742

Hain, Adelaide U.P.; Bosch, Jürgen

2013-01-01

213

Polymorphisms in Plasmodium falciparum Chloroquine Resistance Transporter and Multidrug Resistance 1 Genes: Parasite Risk Factors that Affect Treatment Outcomes for P. falciparum Malaria after Artemether-Lumefantrine and Artesunate-Amodiaquine  

PubMed Central

Adequate clinical and parasitologic cure by artemisinin combination therapies relies on the artemisinin component and the partner drug. Polymorphisms in the Plasmodium falciparum chloroquine resistance transporter (pfcrt) and P. falciparum multidrug resistance 1 (pfmdr1) genes are associated with decreased sensitivity to amodiaquine and lumefantrine, but effects of these polymorphisms on therapeutic responses to artesunate-amodiaquine (ASAQ) and artemether-lumefantrine (AL) have not been clearly defined. Individual patient data from 31 clinical trials were harmonized and pooled by using standardized methods from the WorldWide Antimalarial Resistance Network. Data for more than 7,000 patients were analyzed to assess relationships between parasite polymorphisms in pfcrt and pfmdr1 and clinically relevant outcomes after treatment with AL or ASAQ. Presence of the pfmdr1 gene N86 (adjusted hazards ratio = 4.74, 95% confidence interval = 2.29 – 9.78, P < 0.001) and increased pfmdr1 copy number (adjusted hazards ratio = 6.52, 95% confidence interval = 2.36–17.97, P < 0.001) were significant independent risk factors for recrudescence in patients treated with AL. AL and ASAQ exerted opposing selective effects on single-nucleotide polymorphisms in pfcrt and pfmdr1. Monitoring selection and responding to emerging signs of drug resistance are critical tools for preserving efficacy of artemisinin combination therapies; determination of the prevalence of at least pfcrt K76T and pfmdr1 N86Y should now be routine. PMID:25048375

Venkatesan, Meera; Gadalla, Nahla B.; Stepniewska, Kasia; Dahal, Prabin; Nsanzabana, Christian; Moriera, Clarissa; Price, Ric N.; Mårtensson, Andreas; Rosenthal, Philip J.; Dorsey, Grant; Sutherland, Colin J.; Guérin, Philippe; Davis, Timothy M. E.; Ménard, Didier; Adam, Ishag; Ademowo, George; Arze, Cesar; Baliraine, Frederick N.; Berens-Riha, Nicole; Björkman, Anders; Borrmann, Steffen; Checchi, Francesco; Desai, Meghna; Dhorda, Mehul; Djimdé, Abdoulaye A.; El-Sayed, Badria B.; Eshetu, Teferi; Eyase, Frederick; Falade, Catherine; Faucher, Jean-François; Fröberg, Gabrielle; Grivoyannis, Anastasia; Hamour, Sally; Houzé, Sandrine; Johnson, Jacob; Kamugisha, Erasmus; Kariuki, Simon; Kiechel, Jean-René; Kironde, Fred; Kofoed, Poul-Erik; LeBras, Jacques; Malmberg, Maja; Mwai, Leah; Ngasala, Billy; Nosten, Francois; Nsobya, Samuel L.; Nzila, Alexis; Oguike, Mary; Otienoburu, Sabina Dahlström; Ogutu, Bernhards; Ouédraogo, Jean-Bosco; Piola, Patrice; Rombo, Lars; Schramm, Birgit; Somé, A. Fabrice; Thwing, Julie; Ursing, Johan; Wong, Rina P. M.; Zeynudin, Ahmed; Zongo, Issaka; Plowe, Christopher V.; Sibley, Carol Hopkins

2014-01-01

214

Polymorphisms in Plasmodium falciparum chloroquine resistance transporter and multidrug resistance 1 genes: parasite risk factors that affect treatment outcomes for P. falciparum malaria after artemether-lumefantrine and artesunate-amodiaquine.  

PubMed

Adequate clinical and parasitologic cure by artemisinin combination therapies relies on the artemisinin component and the partner drug. Polymorphisms in the Plasmodium falciparum chloroquine resistance transporter (pfcrt) and P. falciparum multidrug resistance 1 (pfmdr1) genes are associated with decreased sensitivity to amodiaquine and lumefantrine, but effects of these polymorphisms on therapeutic responses to artesunate-amodiaquine (ASAQ) and artemether-lumefantrine (AL) have not been clearly defined. Individual patient data from 31 clinical trials were harmonized and pooled by using standardized methods from the WorldWide Antimalarial Resistance Network. Data for more than 7,000 patients were analyzed to assess relationships between parasite polymorphisms in pfcrt and pfmdr1 and clinically relevant outcomes after treatment with AL or ASAQ. Presence of the pfmdr1 gene N86 (adjusted hazards ratio = 4.74, 95% confidence interval = 2.29 - 9.78, P < 0.001) and increased pfmdr1 copy number (adjusted hazards ratio = 6.52, 95% confidence interval = 2.36-17.97, P < 0.001 : were significant independent risk factors for recrudescence in patients treated with AL. AL and ASAQ exerted opposing selective effects on single-nucleotide polymorphisms in pfcrt and pfmdr1. Monitoring selection and responding to emerging signs of drug resistance are critical tools for preserving efficacy of artemisinin combination therapies; determination of the prevalence of at least pfcrt K76T and pfmdr1 N86Y should now be routine. PMID:25048375

Venkatesan, Meera; Gadalla, Nahla B; Stepniewska, Kasia; Dahal, Prabin; Nsanzabana, Christian; Moriera, Clarissa; Price, Ric N; Mårtensson, Andreas; Rosenthal, Philip J; Dorsey, Grant; Sutherland, Colin J; Guérin, Philippe; Davis, Timothy M E; Ménard, Didier; Adam, Ishag; Ademowo, George; Arze, Cesar; Baliraine, Frederick N; Berens-Riha, Nicole; Björkman, Anders; Borrmann, Steffen; Checchi, Francesco; Desai, Meghna; Dhorda, Mehul; Djimdé, Abdoulaye A; El-Sayed, Badria B; Eshetu, Teferi; Eyase, Frederick; Falade, Catherine; Faucher, Jean-François; Fröberg, Gabrielle; Grivoyannis, Anastasia; Hamour, Sally; Houzé, Sandrine; Johnson, Jacob; Kamugisha, Erasmus; Kariuki, Simon; Kiechel, Jean-René; Kironde, Fred; Kofoed, Poul-Erik; LeBras, Jacques; Malmberg, Maja; Mwai, Leah; Ngasala, Billy; Nosten, Francois; Nsobya, Samuel L; Nzila, Alexis; Oguike, Mary; Otienoburu, Sabina Dahlström; Ogutu, Bernhards; Ouédraogo, Jean-Bosco; Piola, Patrice; Rombo, Lars; Schramm, Birgit; Somé, A Fabrice; Thwing, Julie; Ursing, Johan; Wong, Rina P M; Zeynudin, Ahmed; Zongo, Issaka; Plowe, Christopher V; Sibley, Carol Hopkins

2014-10-01

215

HIV Nonnucleoside Reverse Transcriptase Inhibitors and Trimethoprim-Sulfamethoxazole Inhibit Plasmodium Liver Stages  

PubMed Central

Background.?Although nonnucleoside reverse transcriptase inhibitors (NNRTIs) are usually part of first-line treatment regimens for human immunodeficiency virus (HIV), their activity on Plasmodium liver stages remains unexplored. Additionally, trimethoprim-sulfamethoxazole (TMP-SMX), used for opportunistic infection prophylaxis in HIV-exposed infants and HIV-infected patients, reduces clinical episodes of malaria; however, TMP-SMX effect on Plasmodium liver stages requires further study. Methods.?We characterized NNRTI and TMP-SMX effects on Plasmodium liver stages in vivo using Plasmodium yoelii. On the basis of these results, we conducted in vitro studies assessing TMP-SMX effects on the rodent parasites P. yoelii and Plasmodium berghei and on the human malaria parasite Plasmodium falciparum. Results.?Our data showed NNRTI treatment modestly reduced P. yoelii liver stage parasite burden and minimally extended prepatent period. TMP-SMX administration significantly reduced liver stage parasite burden, preventing development of patent parasitemia in vivo. TMP-SMX inhibited development of rodent and P. falciparum liver stage parasites in vitro. Conclusions.?NNRTIs modestly affect liver stage Plasmodium parasites, whereas TMP-SMX prevents patent parasitemia. Because drugs that inhibit liver stages target parasites when they are present in lower numbers, these results may have implications for eradication efforts. Understanding HIV drug effects on Plasmodium liver stages will aid in optimizing treatment regimens for HIV-exposed and HIV-infected infected patients in malaria-endemic areas. PMID:23125449

Hobbs, Charlotte V.; Voza, Tatiana; De La Vega, Patricia; Vanvliet, Jillian; Conteh, Solomon; Penzak, Scott R.; Fay, Michael P.; Anders, Nicole; Ilmet, Tiina; Li, Yonghua; Borkowsky, William; Krzych, Urszula; Duffy, Patrick E.; Sinnis, Photini

2012-01-01

216

Malarial Parasites Accumulate Labile Zinc Pools  

E-print Network

The malarial parasite, Plasmodium falciparum, is an intracellular pathogen and partially dependent on nutrient uptake for survival. In this issue of Chemistry & Biology, Marvin et al. demonstrate that zinc is essential for ...

Niles, Jacquin

217

The Origin of Malarial Parasites in Orangutans  

Microsoft Academic Search

BackgroundRecent findings of Plasmodium in African apes have changed our perspectives on the evolution of malarial parasites in hominids. However, phylogenetic analyses of primate malarias are still missing information from Southeast Asian apes. In this study, we report molecular data for a malaria parasite lineage found in orangutans.Methodology\\/Principal FindingsWe screened twenty-four blood samples from Pongo pygmaeus (Kalimantan, Indonesia) for Plasmodium

M. Andreína Pacheco; Michael J. C. Reid; Michael A. Schillaci; Carl A. Lowenberger; Biruté M. F. Galdikas; Lisa Jones-Engel; Ananias A. Escalante

2012-01-01

218

Dihydrofolate reductase I164L mutations in Plasmodium falciparum isolates: clinical outcome of 14 Kenyan adults infected with parasites harbouring the I164L mutation.  

PubMed

Recently, Plasmodium falciparum bearing dihydrofolate reductase (DHFR) I164L was isolated from Africa. Quadruple mutations containing I164L confer high-level resistance to antifolate antimalarials. We prospectively measured the effect of co-trimoxazole (CTX) prophylaxis on P. falciparum antifolate resistance development among HIV-infected persons. HIV-positive patients with CD4 cell count < 350 cells/microl (n=692) received CTX; HIV-positive patients with CD4 cell count > or = 350 cells/microl (n=336) and HIV-negative patients (n=132) received multivitamins. Malaria microscopy-positive samples (n=413) and selected microscopy-negative/PCR-positive samples (n=76) were analysed for DHFR mutations at baseline and during six months follow up. We identified I164L in 14 patients. Seven were malaria microscopy-positive: two failed sulfadoxine-pyrimethamine (SP). Among seven microscopy-negative/PCR-positive patients, none developed patent infections with I164L. I164L was not associated with high-level SP resistance or poor outcome among adults living where malaria is highly endemic. Surveillance to monitor spread of I164L is critical, especially among children and pregnant women, who are potentially a source for I164L amplification. PMID:18321547

Hamel, Mary J; Poe, Amanda; Bloland, Peter; McCollum, Andrea; Zhou, Zhiyong; Shi, Ya Ping; Ouma, Peter; Otieno, Kephas; Vulule, John; Escalante, Ananias; Udhayakumar, Venkatachalam; Slutsker, Laurence

2008-04-01

219

Proteasome Inhibitors Block Development of Plasmodium spp  

Microsoft Academic Search

Proteasomes degrade most of the proteins inside eukaryotic cells, including transcription factors and regulators of cell cycle progression. Here we show that nanomolar concentrations of lactacystin, a specific irreversible inhibitor of the 20S proteasome, inhibit development of the exoerythrocytic and erythrocytic stages of the malaria parasite. Although lactacystin-treated Plasmodium berghei sporozoites are still invasive, their development into exoerythrocytic forms (EEF)

SOREN M. GANTT; JOON MO MYUNG; MARCELO R. S. BRIONES; WEI DONG LI; E. J. COREY; SATOSHI OMURA; VICTOR NUSSENZWEIG; PHOTINI SINNIS

1998-01-01

220

Effects of Mosquito Genes on Plasmodium Development  

E-print Network

Effects of Mosquito Genes on Plasmodium Development Mike A. Osta,* George K. Christophides,* Fotis C. Kafatos Malaria parasites must complete a complex developmental cycle in an Anopheles mosquito is initiated in the lumen imme- diately after the mosquito ingests infected blood, and the resulting ooki

Arnold, Jonathan

221

The evolution and diversity of a low complexity vaccine candidate, merozoite surface protein 9 (MSP-9), in Plasmodium vivax and closely related species.  

PubMed

The merozoite surface protein-9 (MSP-9) has been considered a target for an anti-malarial vaccine since it is one of many proteins involved in the erythrocyte invasion, a critical step in the parasite life cycle. Orthologs encoding this antigen have been found in all known species of Plasmodium parasitic to primates. In order to characterize and investigate the extent and maintenance of MSP-9 genetic diversity, we analyzed DNA sequences of the following malaria parasite species: Plasmodium falciparum, Plasmodium reichenowi, Plasmodium chabaudi, Plasmodium yoelii, Plasmodium berghei, Plasmodium coatneyi, Plasmodium gonderi, Plasmodium knowlesi, Plasmodium inui, Plasmodium simiovale, Plasmodium fieldi, Plasmodium cynomolgi and Plasmodium vivax and evaluated the signature of natural selection in all MSP-9 orthologs. Our findings suggest that the gene encoding MSP-9 is under purifying selection in P. vivax and closely related species. We further explored how selection affected different regions of MSP-9 by comparing the polymorphisms in P. vivax and P. falciparum, and found contrasting patterns between these two species that suggest differences in functional constraints. This observation implies that the MSP-9 orthologs in human parasites may interact differently with the host immune response. Thus, studies carried out in one species cannot be directly translated into the other. PMID:24044894

Chenet, Stella M; Pacheco, M Andreína; Bacon, David J; Collins, William E; Barnwell, John W; Escalante, Ananias A

2013-12-01

222

A Transmission Model for the Ecology of an Avian Blood Parasite in a Temperate Ecosystem  

PubMed Central

Most of our knowledge about avian haemosporidian parasites comes from the Hawaiian archipelago, where recently introduced Plasmodiumrelictum has contributed to the extinction of many endemic avian species. While the ecology of invasive malaria is reasonably understood, the ecology of endemic haemosporidian infection in mainland systems is poorly understood, even though it is the rule rather than the exception. We develop a mathematical model to explore and identify the ecological factors that most influence transmission of the common avian parasite, Leucocytozoonfringillinarum (Apicomplexa). The model was parameterized from White-crowned Sparrow (Zonotrichialeucophrys) and S. silvestre / craigi black fly populations breeding in an alpine ecosystem. We identify and examine the importance of altricial nestlings, the seasonal relapse of infected birds for parasite persistence across breeding seasons, and potential impacts of seasonal changes in black fly emergence on parasite prevalence in a high elevation temperate system. We also use the model to identify and estimate the parameters most influencing transmission dynamics. Our analysis found that relapse of adult birds and young of the year birds were crucial for parasite persistence across multiple seasons. However, distinguishing between nude nestlings and feathered young of the year was unnecessary. Finally, due to model sensitivity to many black fly parameters, parasite prevalence and sparrow recruitment may be most affected by seasonal changes in environmental temperature driving shifts in black fly emergence and gonotrophic cycles. PMID:24073288

Murdock, Courtney C.; Foufopoulos, Johannes; Simon, Carl P.

2013-01-01

223

A proteomic view of the Plasmodium falciparum life cycle  

Microsoft Academic Search

The completion of the Plasmodium falciparum clone 3D7 genome provides a basis on which to conduct comparative proteomics studies of this human pathogen. Here, we applied a high-throughput proteomics approach to identify new potential drug and vaccine targets and to better understand the biology of this complex protozoan parasite. We characterized four stages of the parasite life cycle (sporozoites, merozoites,

Laurence Florens; Michael P. Washburn; J. Dale Raine; Robert M. Anthony; Munira Grainger; J. David Haynes; J. Kathleen Moch; Nemone Muster; John B. Sacci; David L. Tabb; Adam A. Witney; Dirk Wolters; Yimin Wu; Malcolm J. Gardner; Anthony A. Holder; Robert E. Sinden; John R. Yates; Daniel J. Carucci

2002-01-01

224

Deoxyhypusine Hydroxylase from Plasmodium vivax, the Neglected Human Malaria Parasite: Molecular Cloning, Expression and Specific Inhibition by the 5-LOX Inhibitor Zileuton  

PubMed Central

Primaquine, an 8-aminoquinoline, is the only drug which cures the dormant hypnozoites of persistent liver stages from P. vivax. Increasing resistance needs the discovery of alternative pathways as drug targets to develop novel drug entities. Deoxyhypusine hydroxylase (DOHH) completes hypusine biosynthesis in eukaryotic initiation factor (eIF-5A) which is the only cellular protein known to contain the unusual amino acid hypusine. Modified EIF-5A is important for proliferation of the malaria parasite. Here, we present the first successful cloning and expression of DOHH from P. vivax causing tertiary malaria. The nucleic acid sequence of 1041 bp encodes an open reading frame of 346 amino acids. Histidine tagged expression of P. vivax DOHH detected a protein of 39.01 kDa in E. coli. The DOHH protein from P. vivax shares significant amino acid identity to the simian orthologues from P. knowlesi and P. yoelii strain H. In contrast to P. falciparum only four E-Z-type HEAT-like repeats are present in P. vivax DOHH with different homology to phycocyanin lyase subunits from cyanobacteria and in proteins participating in energy metabolism of Archaea and Halobacteria. However, phycocyanin lyase activity is absent in P. vivax DOHH. The dohh gene is present as a single copy gene and transcribed throughout the whole erythrocytic cycle. Specific inhibition of recombinant P. vivax DOHH is possible by complexing the ferrous iron with zileuton, an inhibitor of mammalian 5-lipoxygenase (5-LOX). Ferrous iron in the active site of 5-LOX is coordinated by three conserved histidines and the carboxylate of isoleucine673. Zileuton inhibited the P. vivax DOHH protein with an IC50 of 12,5 nmol determined by a relative quantification by GC/MS. By contrast, the human orthologue is only less affected with an IC50 of 90 nmol suggesting a selective iron-complexing strategy for the parasitic enzyme. PMID:23505486

Atemnkeng, Veronika Anyigoh; Pink, Mario; Schmitz-Spanke, Simone; Wu, Xian-Jun; Dong, Liang-Liang; Zhao, Kai-Hong; May, Caroline; Laufer, Stefan; Langer, Barbara; Kaiser, Annette

2013-01-01

225

Chondroitin sulphate A (CSA)-binding of single recombinant Duffy-binding-like domains is not restricted to Plasmodium falciparum Erythrocyte Membrane Protein 1 expressed by CSA-binding parasites.  

PubMed

Individuals living in areas with high Plasmodium falciparum transmission acquire immunity to malaria over time and adults have a markedly reduced risk of contracting severe disease. However, pregnant women constitute an important exception. Pregnancy-associated malaria is a major cause of mother and offspring morbidity, such as severe maternal anaemia and low birth-weight, and is characterised by selective accumulation of parasite-infected erythrocytes (IE) in the placenta. A P. falciparum protein named VAR2CSA, which belongs to the large P. falciparum Erythrocyte Membrane Protein 1 (PfEMP1) family, enables the IE to bind chondroitin sulphate A (CSA) in the placenta. Knock-out studies have demonstrated the exclusive capacity of VAR2CSA to mediate IE binding to CSA, and it has been shown that four of the six Duffy-binding-like (DBL) domains of VAR2CSA have the ability to bind CSA in vitro. In this study, we confirm the CSA-binding of these DBL domains, however, the analysis of a number of DBL domains of a non-VAR2CSA origin shows that CSA-binding is not exclusively restricted to VAR2CSA DBL domains. Furthermore, we show that the VAR2CSA DBL domains as well as other DBL domains also bind heparan sulphate. These data explain a number of publications describing CSA-binding domains derived from PfEMP1 antigens not involved in placental adhesion. The data suggest that the ability of single domains to bind CSA does not predict the functional capacity of the whole PfEMP1 and raises doubt whether the CSA-binding domains of native VAR2CSA have been correctly identified. PMID:19324047

Resende, Mafalda; Ditlev, Sisse B; Nielsen, Morten A; Bodevin, Sabrina; Bruun, Silas; Pinto, Vera V; Clausen, Henrik; Turner, Louise; Theander, Thor G; Salanti, Ali; Dahlbäck, Madeleine

2009-09-01

226

Plasmodium vivax Merozoite Surface Protein-3 (PvMSP3): Expression of an 11 Member Multigene Family in Blood-Stage Parasites  

PubMed Central

Background Three members of the Plasmodium vivax merozoite surface protein-3 (PvMSP3) family (PvMSP3-?, PvMSP3-? and PvMSP3-?) were initially characterized and later shown to be part of a larger highly diverse family, encoded by a cluster of genes arranged head-to-tail in chromosome 10. PvMSP3-? and PvMSP3-? have become genetic markers in epidemiological studies, and are being evaluated as vaccine candidates. This research investigates the gene and protein expression of the entire family and pertinent implications. Methodology/Principal Findings A 60 kb multigene locus from chromosome 10 in P. vivax (Salvador 1 strain) was studied to classify the number of pvmsp3 genes present, and compare their transcription, translation and protein localization patterns during blood-stage development. Eleven pvmsp3 paralogs encode an N-terminal NLRNG signature motif, a central domain containing repeated variable heptad sequences, and conserved hydrophilic C-terminal features. One additional ORF in the locus lacks these features and was excluded as a member of the family. Transcripts representing all eleven pvmsp3 genes were detected in trophozoite- and schizont-stage RNA. Quantitative immunoblots using schizont-stage extracts and antibodies specific for each PvMSP3 protein demonstrated that all but PvMSP3.11 could be detected. Homologs were also detected by immunoblot in the closely related simian species, P. cynomolgi and P. knowlesi. Immunofluorescence assays confirmed that eight of the PvMSP3s are present in mature schizonts. Uniquely, PvMSP3.7 was expressed exclusively at the apical end of merozoites. Conclusion/Significance Specific proteins were detected representing the expression of 10 out of 11 genes confirmed as members of the pvmsp3 family. Eight PvMSP3s were visualized surrounding merozoites. In contrast, PvMSP3.7 was detected at the apical end of the merozoites. Pvmsp3.11 transcripts were present, though no corresponding protein was detected. PvMSP3 functions remain unknown. The ten expressed PvMSP3s are predicted to have unique and complementary functions in merozoite biology. PMID:23717506

Jiang, Jianlin; Barnwell, John W.; Meyer, Esmeralda V. S.; Galinski, Mary R.

2013-01-01

227

Plasmodium relictum (lineage SGS1) and Plasmodium ashfordi (lineage GRW2): The effects of the co-infection on experimentally infected passerine birds  

Microsoft Academic Search

The effects of avian malaria parasites of the genus Plasmodium on their hosts are insufficiently understood. This is particularly true for malarial co-infections, which predominant in many bird populations. We investigated effects of primary co-infection of Plasmodium relictum (lineage SGS1) and Plasmodium ashfordi (GRW2) on experimentally infected naive juveniles of siskin Spinus spinus, crossbill Loxia curvirostra and starling Sturnus vulgaris.

Vaidas Palinauskas; Gediminas Valki?nas; Casimir V. Bolshakov; Staffan Bensch

2011-01-01

228

Population Genomics of the Immune Evasion (var) Genes of Plasmodium falciparum  

Microsoft Academic Search

Var genes encode the major surface antigen (PfEMP1) of the blood stages of the human malaria parasite Plasmodium falciparum. Differential expression of up to 60 diverse var genes in each parasite genome underlies immune evasion. We compared the diversity of the DBL? domain of var genes sampled from 30 parasite isolates from a malaria endemic area of Papua New Guinea

Alyssa E Barry; Aleksandra Leliwa-Sytek; Livingston Tavul; Heather Imrie; Florence Migot-Nabias; Stuart M Brown; Gilean A. V McVean; Karen P Day

2007-01-01

229

Structure of the Plasmodium 6-cysteine s48/45 domain Silvia A. Arredondoa,1  

E-print Network

parasites one of which, Plasmodium falciparum, claims the lives of nearly a million children each year, members of the s48/45 family of proteins are localized on the surface of the parasite in different stages in erythrocytes, some parasites differentiate into male and female gametocytes and are subsequently taken up

Clore, G. Marius

230

Distinct physiological states of Plasmodium falciparum in malaria-infected patients  

E-print Network

with the malaria parasite Plasmodium falciparum leads to widely different clinical conditions in children, ranging few transcriptional differences between different parasite strains3 . Here we present a large study of in vivo expression profiles of parasites derived directly from blood sam- ples from infected patients

Cai, Long

231

The Evolutionary Consequences of Blood-Stage Vaccination on the Rodent Malaria Plasmodium  

E-print Network

partial protection to young children in a large phase 3 trial in Africa [10]. There are two ways parasites the impact of vaccination with a single highly purified antigen on the malaria parasite Plasmodium chabaudi parasites were then serially passaged through control or AMA-1 vaccinated mice and evaluated after 10 and 21

Read, Andrew

232

CLAG 9 is located in the rhoptries of Plasmodium falciparum  

Microsoft Academic Search

Clag 9, a gene located on chromosome 9 of Plasmodium falciparum has previously been associated with the cytoadherence of parasitized erythrocytes to CD36. This gene is part of a multi-gene family found in all Plasmodium species studied to date. Using data from the Malaria Genome Sequencing Project, peptides specific for clag 9 were designed, synthesized and used to immunize mice. This antisera was

Donald L. Gardiner; Tobias Spielmann; Matthew W. A. Dixon; Paula L. Hawthorne; Maria R. Ortega; Karen L. Anderson; Tina S. Skinner-Adams; David J. Kemp; Katharine R. Trenholme

2004-01-01

233

How to Scan Blood Smears, Identify, and Count Parasites  

E-print Network

How to Scan Blood Smears, Identify, and Count Parasites 1. Scanning for Leucocytozoon in bird blood in the blood, but are large parasites and can be spotted even under low power. 2. For Plasmodium. For bird smears, each field must be inspected because the parasite density (parasitemia) tends to be low. 4

Schall, Joseph J.

234

Plasmodium infection decreases fecundity and increases survival of mosquitoes.  

PubMed

Long-lived mosquitoes maximize the chances of Plasmodium transmission. Yet, in spite of decades of research, the effect of Plasmodium parasites on mosquito longevity remains highly controversial. On the one hand, many studies report shorter lifespans in infected mosquitoes. On the other hand, parallel (but separate) studies show that Plasmodium reduces fecundity and imply that this is an adaptive strategy of the parasite aimed at redirecting resources towards longevity. No study till date has, however, investigated fecundity and longevity in the same individuals to see whether this prediction holds. In this study, we follow for both fecundity and longevity in Plasmodium-infected and uninfected mosquitoes using a novel, albeit natural, experimental system. We also explore whether the genetic variations that arise through the evolution of insecticide resistance modulate the effect of Plasmodium on these two life-history traits. We show that (i) a reduction in fecundity in Plasmodium-infected mosquitoes is accompanied by an increase in longevity; (ii) this increase in longevity arises through a trade-off between reproduction and survival; and (iii) in insecticide-resistant mosquitoes, the slope of this trade-off is steeper when the mosquito is infected by Plasmodium (cost of insecticide resistance). PMID:22859589

Vézilier, J; Nicot, A; Gandon, S; Rivero, A

2012-10-01

235

Imaging Plasmodium Immunobiology in Liver, Brain, and Lung  

PubMed Central

Plasmodium falciparum malaria is responsible for the deaths of over half a million African children annually. Until a decade ago, dynamic analysis of the malaria parasite was limited to in vitro systems with the typical limitations associated with 2D monocultures or entirely artificial surfaces. Due to extremely low parasite densities, the liver was considered a black box in terms of Plasmodium sporozoite invasion, liver stage development, and merozoite release into the blood. Further, nothing was known about the behavior of blood stage parasites in organs such as brain where clinical signs manifest and the ensuing immune response of the host that may ultimately result in a fatal outcome. The advent of fluorescent parasites, advances in imaging technology, and availability of an ever-increasing number of cellular and molecular probes have helped illuminate many steps along the pathogenetic cascade of this deadly tropical parasite. PMID:24076429

Frevert, Ute; Nacer, Adéla; Cabrera, Mynthia; Movila, Alexandru; Leberl, Maike

2013-01-01

236

Conservation of a Gliding Motility and Cell Invasion Machinery in Apicomplexan Parasites  

Microsoft Academic Search

Most Apicomplexan parasites, including the human pathogens Plasmodium , Toxoplasma , and Cryptosporidium , actively invade host cells and display gliding motility, both actions powered by parasite mi- crofilaments. In Plasmodium sporozoites, thrombo- spondin-related anonymous protein (TRAP), a mem- ber of a group of Apicomplexan transmembrane proteins that have common adhesion domains, is neces- sary for gliding motility and infection

Stefan Kappe; Thomas Bruderer; Soren Gantt; Hisashi Fujioka; Victor Nussenzweig; Robert Ménard

1999-01-01

237

Host Switch Leads to Emergence of Plasmodium vivax Malaria in Humans  

Microsoft Academic Search

The geographical origin of Plasmodium vivax, the most widespread human malaria parasite, is controversial. Although genetic closeness to Asian primate malarias has been confirmed by phylogenetic analyses, genetic similarities between P. vivax and Plasmodium simium, a New World primate malaria, suggest that humans may have acquired P. vivax from New World monkeys or vice versa. Additionally, the near fixation of

Jianbing Mu; Deirdre A. Joy; Junhui Duan; Yaming Huang; Jane Carlton; John Walker; John Barnwell; Peter Beerli; Michael A. Charleston; Oliver G. Pybus; Xin-zhuan Su

2005-01-01

238

Evidence for clonal propagation in natural isolates of Plasmodium falciparum from Venezuela  

E-print Network

Evidence for clonal propagation in natural isolates of Plasmodium falciparum from Venezuela Ludmel, Estado Aragua, Venezuela; Division of Parasitic Diseases, National Center for Infectious Diseases, 2001 We have analyzed 75 isolates of Plasmodium falciparum, collected in Venezuela during both the dry

239

THE PRESENCE OF PLASMODIUM FALCIPARUM GAMETOCYTES IN HUMAN BLOOD INCREASES THE GRAVIDITY OF ANOPHELES GAMBIAE MOSQUITOES  

E-print Network

were simultaneously fed on either Plasmodium falciparum­infected blood from children or uninfected size or hemoglobin content between hosts. When children cleared their infections, the difference shown that malaria parasites (Plasmodium spp.) can reduce both the survival and fecundity

Read, Andrew

240

Vaccines 85: Molecular and chemical basis of resistance to parasitic, bacterial, and viral diseases  

SciTech Connect

This book contains 70 selections. Some of the selection titles are: Structure of the Gene Encoding of Immunodominant Surface Antigen on the Sprozoite of the Human Malaria Parasite Plasmodium falciparum; Cloning and Expression in Bacteria of the Genes for Merozite-specific Antigens from the Malaria Parasite Plasmodium falciparum; A Major Surface Antigen of Plasmodium falciparum in Merozoites: Studies on the Protein and its Gene; Genetic Construction of Cholera Vaccine Prototypes; and Viral Genes, Cytotoxic T Lymphocytes and Immunity.

Lerner, R.A.; Chanock, R.M.; Brown, F.

1985-01-01

241

Genome-wide SNP genotyping highlights the role of natural selection in Plasmodium falciparum population divergence  

E-print Network

Background: The malaria parasite Plasmodium falciparum exhibits abundant genetic diversity, and this diversity is key to its success as a pathogen. Previous efforts to study genetic diversity in P. falciparum have begun ...

Neafsey, Daniel E.

242

Development of an inducible transcriptional control system in plasmodium falciparum with applications to targeted genome editing  

E-print Network

Malaria accounts for over 500,000 deaths each year. While malaria is caused by multiple distinct parasites of the genus Plasmodium, P. falciparum is responsible for the majority of morbidity and mortality due to the disease. ...

Wagner, Jeffrey C. (Jeffrey Charles)

2014-01-01

243

Revisiting the Plasmodium falciparum RIFIN family: from comparative genomics to 3D-model prediction.  

E-print Network

Subtelomeric RIFIN genes constitute the most abundant multigene family in Plasmodium falciparum. RIFIN products are targets for the human immune response and contribute to the antigenic variability of the parasite. They ...

Bultrini, Emanuele; Mukherjee, Srayanta; Zhang, Yang; Silvestrini, Francesco; Alano, Pietro; Pizzi, Elisabetta

2009-09-21

244

Visualising plasmodium falciparum functional genomic data in MaGnET: malaria genome exploration tool   

E-print Network

Malaria affects the lives of 500 million people around the world each year. The disease is caused by protozoan parasites of the genus Plasmodium, whose ability to evade the immune system and quickly evolve resistance to ...

Sharman, Joanna Louise

2009-06-29

245

A Microscale Human Liver Platform that Supports the Hepatic Stages of Plasmodium falciparum and vivax  

E-print Network

The Plasmodium liver stage is an attractive target for the development of antimalarial drugs and vaccines, as it provides an opportunity to interrupt the life cycle of the parasite at a critical early stage. However, ...

Ng, Shengyong

246

Plasmodium simium/Plasmodium vivax infections in southern brown howler monkeys from the Atlantic Forest  

PubMed Central

Blood infection by the simian parasite, Plasmodium simium, was identified in captive (n = 45, 4.4%) and in wild Alouatta clamitans monkeys (n = 20, 35%) from the Atlantic Forest of southern Brazil. A single malaria infection was symptomatic and the monkey presented clinical and haematological alterations. A high frequency of Plasmodium vivax-specific antibodies was detected among these monkeys, with 87% of the monkeys testing positive against P. vivax antigens. These findings highlight the possibility of malaria as a zoonosis in the remaining Atlantic Forest and its impact on the epidemiology of the disease. PMID:25099335

Costa, Daniela Camargos; da Cunha, Vanessa Pecini; de Assis, Gabriela Maria Pereira; de Souza, Júlio César; Hirano, Zelinda Maria Braga; de Arruda, Mércia Eliane; Kano, Flora Satiko; Carvalho, Luzia Helena; de Brito, Cristiana Ferreira Alves

2014-01-01

247

The crystal structure of Plasmodium knowlesi DBP? DBL domain and its implications for immune evasion  

PubMed Central

Plasmodium vivax invasion of human erythrocytes requires that the ligand domain of the Duffy-binding protein (DBP) recognize its cognate erythrocyte receptor, making DBP a potential target for therapy. The recently determined crystal structure of the orthologous DBP ligand domain of the closely related simian malaria parasite Plasmodium knowlesi provides insight into the molecular basis for receptor recognition and raises important questions about the mechanism of immune evasion employed by the malaria parasite. PMID:16876418

McHenry, A.M.; Adams, J. H.

2009-01-01

248

Blood parasites of blue grouse: variation in prevalence and patterns of interspecific association  

Microsoft Academic Search

Blood parasites of blue grouse (Dendragapus obscurus) were sampled and the factors responsible for variation in prevalence of blood parasites, and patterns of association among parasite species, were investigated. Five genera of haematozoa were surveyed including four protozoans (Haemoproteus, Leucocytozoon, Plasmodium, and Trypanosoma) and a nematode (Splendidofilaria). Prevalence of blood parasites varied significantly between years; sexes differed in number of

M. Forbes; P. I. Weatherhead; G. E. Bennett

1994-01-01

249

Characterization of Plasmodium liver stage inhibition by halofuginone.  

PubMed

Malaria is a devastating parasitic disease that afflicts one-third of the world's population. Antimalarial drugs in common use address few targets, and their efficacy is being undermined by parasite resistance. Most therapeutics target blood-stage malaria, whereas only few compounds are active against malaria's liver stage, the first stage of the Plasmodium parasite's life cycle within the human host. The identification of inhibitors active against liver-stage malaria would benefit the development of chemical probes to elucidate the poorly understood biology of this phase of the parasite life cycle and could provide agents to prevent and eliminate the disease. Herein we report the development of a live-cell parasite traversal assay in 384-well format amenable to high-throughput screening that exploits the wounding of liver cells by the parasite. This method identifies small molecules that may inhibit the parasite's actin-myosin motor system. The traversal assay, in addition to established methods, was used to evaluate the activity of halofuginone, a synthetic halogenated derivative of the natural alkaloid febrifugine, against liver-stage Plasmodium berghei parasites. Halofuginone was found to inhibit P. berghei sporozoite load in HepG2 cells with an IC(50) value of 17 nM. While the compound does not affect parasite traversal through human liver cells, an inhibition time course assay indicates that it affects essential processes in both early- and late-stage parasite development. PMID:22438279

Derbyshire, Emily R; Mazitschek, Ralph; Clardy, Jon

2012-05-01

250

Branched Tricarboxylic Acid Metabolism in Plasmodium falciparum  

PubMed Central

A central hub of carbon metabolism is the tricarboxylic acid (TCA) cycle1, which serves to connect the processes of glycolysis, gluconeogenesis, respiration, amino acid synthesis and other biosynthetic pathways. The protozoan intracellular malaria parasites (Plasmodium spp.), however, have long been suspected of possessing a significantly streamlined carbon metabolic network in which TCA metabolism plays a minor role2. Blood-stage Plasmodium parasites rely almost entirely on glucose fermentation for energy and consume minimal amounts of oxygen3, yet the parasite genome encodes all of the enzymes necessary for a complete TCA cycle4. By tracing 13C-labeled compounds using mass spectrometry5 we show that TCA metabolism in the human malaria parasite P. falciparum is largely disconnected from glycolysis and is organized along a fundamentally different architecture than the canonical textbook pathway. We find that this pathway is not cyclic but rather a branched structure in which the major carbon sources are the amino acids glutamate and glutamine. As a consequence of this branched architecture, several reactions must run in the reverse of the standard direction thereby generating two-carbon units in the form of acetyl-coenzyme A (acetyl-CoA). We further show that glutamine-derived acetyl-CoA is used for histone acetylation while glucose-derived acetyl-CoA is used to acetylate aminosugars. Thus the parasite has evolved two independent acetyl-CoA-production mechanisms with different biological functions. These results significantly clarify our understanding of the Plasmodium metabolic network and highlight the ability of altered variants of central carbon metabolism to arise in response to unique environments. PMID:20686576

Olszewski, Kellen L.; Mather, Michael W.; Morrisey, Joanne M.; Garcia, Benjamin A.; Vaidya, Akhil B.; Rabinowitz, Joshua D.; Llinás, Manuel

2010-01-01

251

Transfection of Plasmodium falciparum within Human Red Blood Cells  

Microsoft Academic Search

Plasmodium falciparum malaria parasites within human red blood cells (RBCs) have been successfully transfected to produce chloramphenicol acetyltransferase (CAT). Electroporation of parasitized RBCs was used to introduce plasmids that have CAT-encoding DNA flanked by 5' and 3' untranslated sequences of the P. falciparum hsp86, hrp3, and hrp2 genes. These flanking sequences were required for expression as their excision abolished CAT

Yimin Wu; C. David Sifri; Hsien-Hsien Lei; Xin-Zhuan Su; Thomas E. Wellems

1995-01-01

252

WIDESPREAD AND STRUCTURED DISTRIBUTIONS OF BLOOD PARASITE HAPLOTYPES ACROSS A MIGRATORY DIVIDE OF THE SWAINSON'S THRUSH (CATHARUS USTULATUS)  

Microsoft Academic Search

We examined the phylogenetic distribution of cytochrome b haplotypes of the avian blood parasite genera Haemo- proteus and Plasmodium across the migratory divide of the Swainson's thrush (Catharus ustulatus) in British Columbia, Canada. From 87 host individuals, we identified 8 parasite haplotypes; 4 of Plasmodium and 4o fHaemoproteus. Six haplotypes were novel; 1 Haemoproteus haplotype was identical to H. majoris

L. M. E. Svensson; K. C. Ruegg; C. H. Sekercioglu; R. N. M. Sehgal

2007-01-01

253

Survey of resistance to chloroquine by Plasmodium vivax in Indonesia  

Microsoft Academic Search

In February 1995 we surveyed resistance to chloroquine among patients with Plasmodium vivax malaria at Nias Island, in the Indian Ocean near north-western Sumatra, Indonesa. The subjects, 21 indigenous males and females (6–50 years old) infected with > 40 asexual blood stage parasites of P. vivax per ?l of blood, had mild symptoms or none at all. Seven of these

J. K. Baird; M. F. Sustriayu Nalim; H. Basri; S. Masbar; B. Leksana; E. Tjitra; R. M. Dewi; M. Khairani; F. S. Wignall

1996-01-01

254

Plasmodium ookinetes coopt mammalian plasminogen to invade the mosquito midgut  

E-print Network

Plasmodium ookinetes coopt mammalian plasminogen to invade the mosquito midgut Anil K. Ghosha, and approved August 30, 2011 (received for review March 6, 2011) Ookinete invasion of the mosquito midgut is an essential step for the development of the malaria parasite in the mosquito. Invasion involves recognition

Arnold, Jonathan

255

Apoptosis stalks Plasmodium falciparum maintained in continuous culture condition  

Microsoft Academic Search

BACKGROUND: Growth kinetic of Plasmodium falciparum in culture or in the host fall short of expected growth rate considering that there are 4 x 106\\/µL red blood cell (RBCs) available for invasion and about 16 merozoites growing in each infected RBC. This study determined whether apoptotic machinery is operable to keep the parasite population under check. METHODS: A synchronized culture

Beth K Mutai; John N Waitumbi

2010-01-01

256

TRENDS in Parasitology Vol.18 No.6 June 2002 http://parasites.trends.com 1471-4922/02/$ see front matter 2002 Elsevier Science Ltd. All rights reserved. PII: S1471-4922(02)02268-7  

E-print Network

in African children is cerebral malaria caused by the parasitic protozoan Plasmodium falciparum. EndemicTRENDS in Parasitology Vol.18 No.6 June 2002 http://parasites.trends.com 1471-4922/02/$ ­ see front population of 2.4 billion. The most lethal form of the disease, caused by the protozoan parasite Plasmodium

Hartl, Daniel L.

257

Isoprenoid biosynthesis in Plasmodium falciparum.  

PubMed

Malaria kills nearly 1 million people each year, and the protozoan parasite Plasmodium falciparum has become increasingly resistant to current therapies. Isoprenoid synthesis via the methylerythritol phosphate (MEP) pathway represents an attractive target for the development of new antimalarials. The phosphonic acid antibiotic fosmidomycin is a specific inhibitor of isoprenoid synthesis and has been a helpful tool to outline the essential functions of isoprenoid biosynthesis in P. falciparum. Isoprenoids are a large, diverse class of hydrocarbons that function in a variety of essential cellular processes in eukaryotes. In P. falciparum, isoprenoids are used for tRNA isopentenylation and protein prenylation, as well as the synthesis of vitamin E, carotenoids, ubiquinone, and dolichols. Recently, isoprenoid synthesis in P. falciparum has been shown to be regulated by a sugar phosphatase. We outline what is known about isoprenoid function and the regulation of isoprenoid synthesis in P. falciparum, in order to identify valuable directions for future research. PMID:25217461

Guggisberg, Ann M; Amthor, Rachel E; Odom, Audrey R

2014-11-01

258

Quantitative Plasmodium sporozoite neutralization assay (TSNA).  

PubMed

The circumsporozoite (CS) protein is the major surface protein of Plasmodium sporozoites. Antibodies to the immunodominant repeat domain of CS immobilize sporozoites and prevent infection of hepatocytes. Plasmodium falciparum vaccines containing CS repeats are undergoing human trials in endemic areas, and proof of efficacy has been obtained. The correlates of protection are under investigation. Levels of anti-repeat antibodies in the serum of the human volunteers have been measured mostly by enzyme-linked immunosorbent assay (ELISA) and IFA. Assays that measure the effect of the serum antibodies on parasite infectivity (serum neutralization assays SNAs) are not usually performed because they require a susceptible host and P. falciparum sporozoites are highly infectious only to humans. To overcome this limitation, we developed a new assay named transgenic sporozoite neutralization assay (TSNA) that uses as neutralization target, a transgenic rodent malaria parasite Plasmodium berghei that bears the P. falciparum CS repeats [CS(Pf)]. Following incubation with human serum, CS(Pf) infectivity of HepG2 cells is evaluated by real-time PCR. We have compared ELISA titers and TSNAs in a limited number of sera from humans immunized with (T1B)4 MAP, a peptide vaccine containing P. falciparum CS repeats. A comparison between the two assays did not reach significance (p=0.175) when analyzed by non-parametric Spearman correlation method. Ongoing human trials of CS-based vaccines should provide an opportunity to determine whether TSNAs will provide better correlates of protective immunity than ELISA assays. PMID:15350520

Kumar, Kota Arun; Oliveira, Giane A; Edelman, Robert; Nardin, Elizabeth; Nussenzweig, Victor

2004-09-01

259

Carotenoid-based bill colour is an integrative signal of multiple parasite infection in blackbird  

NASA Astrophysics Data System (ADS)

In the study of parasite-mediated sexual selection, there has been controversial evidence for the prediction that brighter males should have fewer parasites. Most of these studies have focused on one parasite species. Our aim was to investigate the expression of carotenoid-based coloured signals in relation to patterns of multiple parasite infections, to determine whether colour reflects parasite load of all parasite species, or whether different relationships might be found when looking at each parasite species independently. We investigated the relationship between bill colour, body mass and plasma carotenoids and parasite load (feather chewing lice, blood parasite Plasmodium sp., intestinal parasites cestodes and coccidia) in the blackbird ( Turdus merula). Bill colour on its own appeared to be a poor predictor of parasite load when investigating its relationships with individual parasite species. Variation in parasite intensities at the community level was summarised using principal component analysis to derive synthetic indexes of relative parasite species abundance and absolute parasite load. The relative abundance of parasite species was strongly related to bill colour, plasma carotenoid levels and body mass: birds with relatively more cestodes and chewing lice and relatively less Plasmodium and coccidia had a more colourful bill, circulated more carotenoids and were heavier. These results suggest that bill colour more accurately reflects the relative intensities of parasite infection, rather than one-by-one relationships with parasites or absolute parasite burden. Investigating patterns of multiple parasite infection would thus improve our understanding of the information conveyed by coloured signals on parasite load.

Biard, Clotilde; Saulnier, Nicolas; Gaillard, Maria; Moreau, Jérôme

2010-11-01

260

An Image-Based Drug Susceptibility Assay Targeting the Placental Sequestration of Plasmodium falciparum-  

E-print Network

effects were quantified as the proportion of treated parasitized erythrocytes to BeWo cells compared Introduction Plasmodium falciparum is responsible for the most severe forms of human malaria that include endothelial cell types in the deep vasculature of the body, thus resulting in a sequestration of the parasites

Paris-Sud XI, Université de

261

Plasmodium falciparum Serine/Threonine Phosphoprotein Phosphatases (PPP): From Housekeeper to 'Holy Grail'  

Technology Transfer Automated Retrieval System (TEKTRAN)

Availability of complete genome sequence for Plasmodium falciparum has been useful in drawing a comprehensive metabolic map of the parasite. Distinct and unique metabolic characteristics of the parasite may be exploited as potential targets for new antimalarial drug discovery research. Reversible ph...

262

High prevalence of chloroquine resistant Plasmodium falciparum infection in Rajasthan epidemic  

Microsoft Academic Search

Plasmodium falciparum is the main killer among all human malaria parasites. In 1994, there was a falciparum malaria epidemic in Rajasthan, India, with many deaths. We have investigated active falciparum malaria cases from this epidemic and found that most of the parasite isolates (95%) were resistant to chloroquine. Nevertheless, all the tested isolates from the epidemic, were sensitive to mefloquine

Y. D. Sharma; S. Biswas; C. R. Pillai; M. A. Ansari; T. Adak; C. Usha Devi

1996-01-01

263

Selection and genetic drift of polymorphisms within the merozoite surface protein-1 gene of Plasmodium falciparum  

Microsoft Academic Search

Intragenic recombination in the merozoite surface protein-1 gene (Msp-1) of Plasmodium falciparum is a major mechanism for allelic variation among natural parasite populations. The frequency of recombination depends on the intensity of transmission in the vector mosquito. In the present study, linkage disequilibrium between polymorphic ‘loci’ in the 5?- and 3?-regions of Msp-1 was examined in parasite populations from Brazilian

Kazuyuki Tanabe; Naoko Sakihama; Yoshimitu Nakamura; Osamu Kaneko; Masatugu Kimura; Marcelo U. Ferreira; Kenji Hirayama

2000-01-01

264

Antigen-Displaying Lipid-Enveloped PLGA Nanoparticles as Delivery Agents for a Plasmodium vivax Malaria Vaccine  

E-print Network

The parasite Plasmodium vivax is the most frequent cause of malaria outside of sub-Saharan Africa, but efforts to develop viable vaccines against P. vivax so far have been inadequate. We recently developed pathogen-mimicking ...

Moon, James J.

265

Identification and Functional Validation of the Novel Antimalarial Resistance Locus PF10_0355 in Plasmodium falciparum  

E-print Network

The Plasmodium falciparum parasite's ability to adapt to environmental pressures, such as the human immune system and antimalarial drugs, makes malaria an enduring burden to public health. Understanding the genetic basis ...

Tyne, Daria Van

266

Does Plasmodium falciparum have an Achilles' heel?  

E-print Network

Plasmodium falciparum is the parasite that causes the most severe form of malaria. Currently, science has been established about its cellular structures, its metabolic processes, and even the molecular structures of its intrinsic membrane proteins responsible for transporting water, nutrient, and waste molecules across the parasite plasma membrane (PPM). I hypothesize that Plasmodium falciparum has an Achilles' heel that can be attacked with erythritol, the well-known sweetener that is classified as generally safe. Most organisms have in their cell membrane two types of water-channel proteins: aquaporins to maintain hydro-homeostasis across the membrane and aquaglyceroporins to uptake glycerols etc. In contrast, P. falciparum has only one type of such proteins---the multi-functional aquaglyceroporin (PfAQP) expressed in the PPM---to do both jobs. Moreover, the parasite also uses PfAQP to excrete its metabolic wastes (ammonia included) produced at a very high rate in the blood stage. This extremely high efficiency of the bug using one protein for multiple essential tasks makes the parasite fatally vulnerable. Erythritol in the blood stream can kill the parasite by clogging up its PfAQP channel that needs to be open for maintaining hydro-homeostasis and for excreting toxic wastes across the bug's PPM. In vitro tests are to measure the growth/death rate of P. falciparum in blood with various erythritol concentrations. In vivo experiments are to administer groups of infected mice with various doses of erythritol and monitor the parasite growth levels from blood samples drawn from each group. Clinic trials can be performed to observe the added effects of administering to patients erythritol along with the known drugs because erythritol was classified as a safe food ingredient.

Liao Y Chen

2013-05-21

267

Host Cell Phosphatidylcholine Is a Key Mediator of Malaria Parasite Survival during Liver Stage Infection  

PubMed Central

Summary During invasion, Plasmodium, the causative agent of malaria, wraps itself in a parasitophorous vacuole membrane (PVM), which constitutes a critical interface between the parasite and its host cell. Within hepatocytes, each Plasmodium sporozoite generates thousands of new parasites, creating high demand for lipids to support this replication and enlarge the PVM. Here, a global analysis of the total lipid repertoire of Plasmodium-infected hepatocytes reveals an enrichment of neutral lipids and the major membrane phospholipid, phosphatidylcholine (PC). While infection is unaffected in mice deficient in key enzymes involved in neutral lipid synthesis and lipolysis, ablation of rate-limiting enzymes in hepatic PC biosynthetic pathways significantly decreases parasite numbers. Host PC is taken up by both P. berghei and P. falciparum and is necessary for correct localization of parasite proteins to the PVM, which is essential for parasite survival. Thus, Plasmodium relies on the abundance of these lipids within hepatocytes to support infection. PMID:25498345

Itoe, Maurice A.; Sampaio, Júlio L.; Cabal, Ghislain G.; Real, Eliana; Zuzarte-Luis, Vanessa; March, Sandra; Bhatia, Sangeeta N.; Frischknecht, Friedrich; Thiele, Christoph; Shevchenko, Andrej; Mota, Maria M.

2014-01-01

268

A Cluster of Ring Stage-specific Genes Linked to a Locus Implicated in Cytoadherence in Plasmodium falciparum Codes for PEXEL-negative and PEXEL-positive Proteins Exported into the Host Cell  

Microsoft Academic Search

Blood stages of Plasmodium falciparum export proteins into their erythrocyte host, thereby inducing extensive host cell modifications that become apparent after the first half of the asexual development cycle (ring stage). This is responsible for a major part of parasite virulence. Export of many parasite proteins depends on a sequence motif termed Plasmodium export element (PEXEL) or vacuolar transport signal

Tobias Spielmann; Paula L. Hawthorne; Matthew W. A. Dixon; Mandy Hannemann; Kathleen Klotz; David J. Kemp; Nectarios Klonis; Leann Tilley; Katharine R. Trenholme; Donald L. Gardiner

2006-01-01

269

Population genetics of Plasmodium falciparum and Plasmodium vivax and asymptomatic malaria in Temotu Province, Solomon Islands  

PubMed Central

Background Temotu Province, Solomon Islands is progressing toward malaria elimination. A baseline survey conducted in 2008 showed that most Plasmodium infections in the province were of low parasite density and asymptomatic infections. To better understand mechanisms underlying these malaria transmission characteristics genetic diversity and relationships among Plasmodium falciparum and Plasmodium vivax populations in the province were examined. Methods Forty-five P. falciparum and 67 P. vivax samples collected in the 2008 baseline survey were successfully genotyped using eight P. falciparum and seven P. vivax microsatellite markers. Genetic diversity, relationships and distribution of both P. falciparum and P. vivax populations were analysed. Results Plasmodium falciparum population exhibited low diversity with 19 haplotypes identified and had closely related clusters indicating clonal expansion. Interestingly, a dominant haplotype was significantly associated with fever and high parasite density. In contrast, the P. vivax population was highly diverse with 58 haplotypes identified that were not closely related. Parasite populations between different islands in the province showed low genetic differentiation. Conclusion The low diversity and clonal population of P. falciparum population may partially account for clinical immunity developed against illness. However, it is possible that importation of a new P. falciparum strain was the major cause of illness. High diversity in P. vivax population and low relatedness between strains suggested clinical immunity to P. vivax may be maintained by different mechanisms. The genetic diversity, population structure and distribution of strains indicate that transmission of P. falciparum was low, but that of P. vivax was still high in 2008. These data will be useful for assessing changes in malaria transmission resulting from interventions. PMID:24261646

2013-01-01

270

RESEARCH Open Access Distinct patterns of blood-stage parasite antigens  

E-print Network

RESEARCH Open Access Distinct patterns of blood-stage parasite antigens detected by plasma Ig immunity against Plasmodium falciparum develops as a function of age and exposure to parasite infections immunoepidemiological studies have indicated an association of cytophilic anti-parasite IgG with protection against

Paris-Sud XI, Université de

271

The Origin of Malarial Parasites in Orangutans  

PubMed Central

Background Recent findings of Plasmodium in African apes have changed our perspectives on the evolution of malarial parasites in hominids. However, phylogenetic analyses of primate malarias are still missing information from Southeast Asian apes. In this study, we report molecular data for a malaria parasite lineage found in orangutans. Methodology/Principal Findings We screened twenty-four blood samples from Pongo pygmaeus (Kalimantan, Indonesia) for Plasmodium parasites by PCR. For all the malaria positive orangutan samples, parasite mitochondrial genomes (mtDNA) and two antigens: merozoite surface protein 1 42 kDa (MSP-142) and circumsporozoite protein gene (CSP) were amplified, cloned, and sequenced. Fifteen orangutans tested positive and yielded 5 distinct mitochondrial haplotypes not previously found. The haplotypes detected exhibited low genetic divergence among them, indicating that they belong to one species. We report phylogenetic analyses using mitochondrial genomes, MSP-142 and CSP. We found that the orangutan malaria parasite lineage was part of a monophyletic group that includes all the known non-human primate malaria parasites found in Southeast Asia; specifically, it shares a recent common ancestor with P. inui (a macaque parasite) and P. hylobati (a gibbon parasite) suggesting that this lineage originated as a result of a host switch. The genetic diversity of MSP-142 in orangutans seems to be under negative selection. This result is similar to previous findings in non-human primate malarias closely related to P. vivax. As has been previously observed in the other Plasmodium species found in non-human primates, the CSP shows high polymorphism in the number of repeats. However, it has clearly distinctive motifs from those previously found in other malarial parasites. Conclusion The evidence available from Asian apes indicates that these parasites originated independently from those found in Africa, likely as the result of host switches from other non-human primates. PMID:22536346

Pacheco, M. Andreína; Reid, Michael J. C.; Schillaci, Michael A.; Lowenberger, Carl A.; Galdikas, Biruté M. F.; Jones-Engel, Lisa; Escalante, Ananias A.

2012-01-01

272

Human Malaria Parasites in Continuous Culture  

Microsoft Academic Search

Plasmodium falciparum can now be maintained in continuous culture in human erythrocytes incubated at 38 degrees C in RPMI 1640 medium with human serum under an atmosphere with 7 percent carbon dioxide and low oxygen (1 or 5 percent). The original parasite material, derived from an infected Aotus trivirgatus monkey, was diluted more than 100 million times by the addition

William Trager; James B. Jensen

1976-01-01

273

Full-parasites: database of full-length cDNAs of apicomplexa parasites, 2010 update.  

PubMed

Full-Parasites (http://fullmal.hgc.jp/) is a transcriptome database of apicomplexa parasites, which include Plasmodium and Toxoplasma species. The latest version of Full-Parasites contains a total of 105,786 EST sequences from 12 parasites, of which 5925 full-length cDNAs have been completely sequenced. Full-Parasites also contain more than 30 million transcription start sites (TSS) for Plasmodium falciparum (Pf) and Toxoplasma gondii (Tg), which were identified using our novel oligo-capping-based protocol. Various types of cDNA data resources were interconnected with our original database functionalities. Specifically, in this update, we have included two unique RNA-Seq data sets consisting of 730 million mapped RNA-Seq tags. One is a dataset of 16 time-lapse experiments of cultured bradyzoite differentiation for Tg. The other dataset includes 31 clinical samples of Pf. Parasite RNA was extracted together with host human RNA, and the extracted mixed RNA was used for RNA sequencing, with the expectation that gene expression information from the host and parasite would be simultaneously represented. By providing the largest unique full-length cDNA and dynamic transcriptome data, Full-Parasites is useful for understanding host-parasite interactions and will help to eventually elucidate how monophyletic organisms have evolved to become parasites by adopting complex life cycles. PMID:21051343

Tuda, Josef; Mongan, Arthur E; Tolba, Mohammed E M; Imada, Mihoko; Yamagishi, Junya; Xuan, Xuenan; Wakaguri, Hiroyuki; Sugano, Sumio; Sugimoto, Chihiro; Suzuki, Yutaka

2011-01-01

274

Addition of thiols to o-quinone methide: new 2-hydroxy-3-phenylsulfanylmethyl[1,4]naphthoquinones and their activity against the human malaria parasite Plasmodium falciparum (3D7).  

PubMed

A series of 36 new phenylsulfanylmethyl[1,4]naphthoquinones (7-42) were synthesized by a three-component reaction that involves lawsone, the appropriate aldehyde and thiols with variable substitution patterns. These reactions involve the in situ generation of o-quinone methides (o-QM) via Knoevenagel condensation and 1,4-nucleophilic addition under conventional heating or microwave irradiation. The new naphthoquinones obtained by this methodology were shown to have moderate to good in vitro antimalarial activity against Plasmodium falciparum (3D7). PMID:23202850

Sharma, Abhinay; Santos, Isabela O; Gaur, Pratibha; Ferreira, Vitor F; Garcia, Celia R S; da Rocha, David R

2013-01-01

275

Natural Plasmodium infection in monkeys in the state of Rondônia (Brazilian Western Amazon)  

PubMed Central

Background Simian malaria is still an open question concerning the species of Plasmodium parasites and species of New World monkeys susceptible to the parasites. In addition, the lingering question as to whether these animals are reservoirs for human malaria might become important especially in a scenario of eradication of the disease. To aid in the answers to these questions, monkeys were surveyed for malaria parasite natural infection in the Amazonian state of Rondônia, Brazil, a state with intense environmental alterations due to human activities, which facilitated sampling of the animals. Methods Parasites were detected and identified in DNA from blood of monkeys, by PCR with primers for the 18S rRNA, CSP and MSP1 genes and sequencing of the amplified fragments. Multiplex PCR primers for the 18S rRNA genes were designed for the parasite species Plasmodium falciparum and Plasmodium vivax, Plasmodium malariae/Plasmodium brasilianum and Plasmodium simium. Results An overall infection rate of 10.9% was observed or 20 out 184 monkey specimens surveyed, mostly by P. brasilianum. However, four specimens of monkeys were found infected with P. falciparum, two of them doubly infected with P. brasilianum and P. falciparum. In addition, a species of monkey of the family Aotidae, Aotus nigriceps, is firstly reported here naturally infected with P. brasilianum. None of the monkeys surveyed was found infected with P. simium/P. vivax. Conclusion The rate of natural Plasmodium infection in monkeys in the Brazilian state of Rondônia is in line with previous surveys of simian malaria in the Amazon region. The fact that a monkey species was found that had not previously been described to harbour malaria parasites indicates that the list of monkey species susceptible to Plasmodium infection is yet to be completed. Furthermore, finding monkeys in the region infected with P. falciparum clearly indicates parasite transfer from humans to the animals. Whether this parasite can be transferred back to humans and how persistent the parasite is in monkeys in the wild so to be efficient reservoirs of the disease, is yet to be evaluated. Finding different species of monkeys infected with this parasite species suggests indeed that these animals can act as reservoirs of human malaria. PMID:23731624

2013-01-01

276

Extraction of Hydrophilic Metabolites from Plasmodium falciparum-Infected Erythrocytes for Metabolomic Analysis  

PubMed Central

Metabolomics is an increasingly common analytical approach for investigating metabolic networks of pathogenic organisms. This may be of particular use in the study of parasitic infections due to the intrinsic metabolic connection between the parasite and its host. In vitro cultures of the malaria parasite Plasmodium falciparum present a valuable platform to elucidate the structure and dynamics of the parasite’s metabolic network and to determine the mechanisms of action of antimalarial drugs and drug resistance mutations. Accurately measuring metabolite levels requires a reproducible method for quantifying intracellular metabolites. Here we present a simple protocol for extracting hydrophilic metabolites from P. falciparum-infected erythrocyte cultures. PMID:22990783

Olszewski, Kellen L.; Llinás, Manuel

2012-01-01

277

In Vitro Alterations Do Not Reflect a Requirement for Host Cell Cycle Progression during Plasmodium Liver Stage Infection.  

PubMed

Prior to invading nonreplicative erythrocytes, Plasmodium parasites undergo their first obligate step in the mammalian host inside hepatocytes, where each sporozoite replicates to generate thousands of merozoites. While normally quiescent, hepatocytes retain proliferative capacity and can readily reenter the cell cycle in response to diverse stimuli. Many intracellular pathogens, including protozoan parasites, manipulate the cell cycle progression of their host cells for their own benefit, but it is not known whether the hepatocyte cell cycle plays a role during Plasmodium liver stage infection. Here, we show that Plasmodium parasites can be observed in mitotic hepatoma cells throughout liver stage development, where they initially reduce the likelihood of mitosis and ultimately lead to significant acquisition of a binucleate phenotype. However, hepatoma cells pharmacologically arrested in S phase still support robust and complete Plasmodium liver stage development, which thus does not require cell cycle progression in the infected cell in vitro. Furthermore, murine hepatocytes remain quiescent throughout in vivo infection with either Plasmodium berghei or Plasmodium yoelii, as do Plasmodium falciparum-infected primary human hepatocytes, demonstrating that the rapid and prodigious growth of liver stage parasites is accomplished independent of host hepatocyte cell cycle progression during natural infection. PMID:25416236

Hanson, Kirsten K; March, Sandra; Ng, Shengyong; Bhatia, Sangeeta N; Mota, Maria M

2015-01-01

278

Does Plasmodium falciparum have an Achilles’ heel?  

PubMed Central

Background Plasmodium falciparum is the parasite that causes the most severe form of malaria responsible for nearly a million deaths a year. Currently, science has been established about its cellular structures, its metabolic processes, and even the molecular structures of its intrinsic membrane proteins responsible for transporting water, nutrient, and waste molecules across the parasite plasma membrane (PPM). Presentation of the hypothesis I hypothesize that Plasmodium falciparum has an Achilles’ heel that can be attacked with erythritol, the well-known sweetener that is classified as generally safe. This hypothesis is based on the molecular structure of the parasite’s membrane and the quantitative mechanics of how erythritol interacts with the multi-functional channel protein expressed in the PPM. Most organisms have in their cell membrane two types of water-channel proteins: aquaporins to maintain hydro-homeostasis across the membrane and aquaglyceroporins to uptake glycerols etc. In contrast, P. falciparum has only one type of such proteins---the multi-functional aquaglyceroporin (PfAQP) expressed in the PPM---to do both jobs. Moreover, the parasite also uses PfAQP to excrete its metabolic wastes (ammonia included) produced at a very high rate in the blood stage. This extremely high efficiency of the bug using one protein for multiple essential tasks makes the parasite fatally vulnerable. Erythritol in the blood stream can kill the parasite by clogging up its PfAQP channel that needs to be open for maintaining hydro-homeostasis and for excreting toxic wastes across the bug’s PPM. Testing the hypothesis In vitro tests are to measure the growth/death rate of P. falciparum in blood with various erythritol concentrations. In vivo experiments are to administer groups of infected mice with various doses of erythritol and monitor the parasite growth levels from blood samples drawn from each group. Clinic trials can be performed to observe the added effects of administering to patients erythritol along with the known drugs because erythritol was classified as a safe food ingredient. Implications of the hypothesis If proven true, erythritol will cure the most severe form of malaria without significant side effects. PMID:25346857

Chen, Liao Y.

2014-01-01

279

Mosquitoes as Potential Bridge Vectors of Malaria Parasites from Non-Human Primates to Humans  

PubMed Central

Malaria is caused by Plasmodium parasites which are transmitted by mosquitoes. Until recently, human malaria was considered to be caused by human-specific Plasmodium species. Studies on Plasmodium parasites in non-human primates (NHPs), however, have identified parasite species in gorillas and chimpanzees that are closely related to human Plasmodium species. Moreover, P. knowlesi, long known as a parasite of monkeys, frequently infects humans. The requirements for such a cross-species exchange and especially the role of mosquitoes in this process are discussed, as the latter may act as bridge vectors of Plasmodium species between different primates. Little is known about the mosquito species that would bite both humans and NHPs and if so, whether humans and NHPs share the same Plasmodium vectors. To understand the vector-host interactions that can lead to an increased Plasmodium transmission between species, studies are required that reveal the nature of these interactions. Studying the potential role of NHPs as a Plasmodium reservoir for humans will contribute to the ongoing efforts of human malaria elimination, and will help to focus on critical areas that should be considered in achieving this goal. PMID:22701434

Verhulst, Niels O.; Smallegange, Renate C.; Takken, Willem

2012-01-01

280

Chronic HIV Infection Impairs Nonopsonic Phagocytosis of Malaria Parasites.  

PubMed

: Malaria-specific immune responses are altered in HIV/malaria-coinfected individuals and are associated with higher parasite burdens and more severe clinical disease. Monocyte/macrophage phagocytosis is a major mechanism of malaria parasite clearance. We hypothesized that phagocytosis of malaria-parasitized erythrocytes is impaired in coinfected individuals and could contribute to the increased parasite burdens observed. We show that nonopsonic phagocytosis of Plasmodium falciparum parasitized erythrocytes is impaired in monocytes isolated from HIV-infected individuals. The observed defects in phagocytic capacity were rescued after 6 months of antiretroviral therapy, demonstrating the importance of HIV treatment and immune reconstitution in the context of coinfection. PMID:25415293

Serghides, Lena; Finney, Constance A M; Ayi, Kodjo; Loutfy, Mona; Kain, Kevin C

2015-02-01

281

Evolution and ecology of malaria parasites: from mating to mixed?species infections   

E-print Network

Despite over a century of research, malaria parasites (Plasmodium) still remain a major cause of mortality and morbidity worldwide. In recent years, the application of theoretical principles from ecology and evolutionary ...

Ramiro, Ricardo Filipe Serrote; Ricardo Filipe, Serrote Ramiro

2012-11-30

282

Static and dynamic light scattering of healthy and malaria-parasite blood cells  

E-print Network

We present the light scattering of individual Plasmodium falciparum-parasitized human red blood cells (Pf-RBCs), and demonstrate progressive alterations to the scattering signal arising from the development of malaria-inducing ...

Suresh, Subra

283

Development of a Real-Time PCR Assay for Detection of Plasmodium falciparum, Plasmodium vivax, and Plasmodium ovale for Routine Clinical Diagnosis  

Microsoft Academic Search

A TaqMan-based real-time PCR qualitative assay for the detection of three species of malaria parasitesPlasmodium falciparum, P. ovale, and P. vivax—was devised and evaluated using 122 whole-blood samples from patients who had traveled to areas where malaria is endemic and who presented with malaria-like symptoms and fever. The assay was compared to conventional microscopy and to an established nested-PCR

F. Perandin; N. Manca; A. Calderaro; G. Piccolo; L. Galati; L. Ricci; M. C. Medici; M. C. Arcangeletti; G. Snounou; G. Dettori; C. Chezzi

2004-01-01

284

Failure to detect Plasmodium vivax in West and Central Africa by PCR species typing  

PubMed Central

Background Plasmodium vivax is estimated to affect 75 million people annually. It is reportedly absent, however, from west and central Africa due to the high prevalence of the Duffy negative phenotype in the indigenous populations. Despite this, non-African travellers consistently return to their own countries with P. vivax malaria after visiting this region. An attempt was made, therefore, to detect the presence of P. vivax parasites in blood samples collected from the indigenous populations of west and central Africa. Methods Parasite species typing (for all four human malaria parasites) was carried out by PCR on 2,588 blood samples collected from individuals from nine African malaria-endemic countries. Results Most infections (98.5%) were Plasmodium falciparum, Plasmodium malariae was identified in 8.5% of all infections, and Plasmodium ovale in 3.9%. The prevalence of both parasites varied greatly by country. Only one case of P. vivax was detected from Sao Tome, an island off the west coast of Africa, confirming the scarcity of this parasite in Africa. Conclusion The prevalence of P. vivax in local populations in sub-Saharan Africa is very low, despite the frequent identification of this parasite in non-African travellers. PMID:18783630

Culleton, Richard L; Mita, Toshihiro; Ndounga, Mathieu; Unger, Holger; Cravo, Pedro VL; Paganotti, Giacomo M; Takahashi, Nobuyuki; Kaneko, Akira; Eto, Hideaki; Tinto, Halidou; Karema, Corine; D'Alessandro, Umberto; do Rosário, Virgilio; Kobayakawa, Takatoshi; Ntoumi, Francine; Carter, Richard; Tanabe, Kazuyuki

2008-01-01

285

Immunisation against a serine protease inhibitor reduces intensity of Plasmodium berghei infection in mosquitoes.  

PubMed

The mosquito innate immune response is able to clear the majority of Plasmodium parasites. This immune clearance is controlled by a number of regulatory molecules including serine protease inhibitors (serpins). To determine whether such molecules could represent a novel target for a malaria transmission-blocking vaccine, we vaccinated mice with Anopheles gambiae serpin-2. Antibodies against Anopheles gambiae serpin-2 significantly reduced the infection of a heterologous Anopheles species (Anopheles stephensi) by Plasmodium berghei, however this effect was not observed with Plasmodium falciparum. Therefore, this approach of targeting regulatory molecules of the mosquito immune system may represent a novel approach to transmission-blocking malaria vaccines. PMID:23872520

Williams, Andrew R; Zakutansky, Sara E; Miura, Kazutoyo; Dicks, Matthew D J; Churcher, Thomas S; Jewell, Kerry E; Vaughan, Aisling M; Turner, Alison V; Kapulu, Melissa C; Michel, Kristin; Long, Carole A; Sinden, Robert E; Hill, Adrian V S; Draper, Simon J; Biswas, Sumi

2013-10-01

286

Immunization against a serine protease inhibitor reduces intensity of Plasmodium berghei infection in mosquitoes  

PubMed Central

The mosquito innate immune response is able to clear the majority of Plasmodium parasites. This immune clearance is controlled by a number of regulatory molecules including serine protease inhibitors (serpins). To determine whether such molecules could represent a novel target for a malaria transmission-blocking vaccine, we vaccinated mice with Anopheles gambiae serpin-2 (AgSRPN2). Antibodies against AgSRPN2 significantly reduced the infection of a heterologous Anopheles species (Anopheles stephensi) by Plasmodium berghei, however this effect was not observed with Plasmodium falciparum. Therefore, this approach of targeting regulatory molecules of the mosquito immune system may represent a novel approach to transmission-blocking malaria vaccines. PMID:23872520

Williams, Andrew R.; Zakutansky, Sara E.; Miura, Kazutoyo; Dicks, Matthew J. D.; Churcher, Thomas S.; Jewell, Kerry E.; Vaughan, Aisling M.; Turner, Alison V.; Kapulu, Melissa C.; Michel, Kristin; Long, Carole A.; Sinden, Robert E.; Hill, Adrian V. S.; Draper, Simon J.; Biswas, Sumi

2013-01-01

287

DNA Cloning of Plasmodium falciparum Circumsporozoite Gene: Amino Acid Sequence of Repetitive Epitope  

NASA Astrophysics Data System (ADS)

A clone of complementary DNA encoding the circumsporozoite (CS) protein of the human malaria parasite Plasmodium falciparum has been isolated by screening an Escherichia coli complementary DNA library with a monoclonal antibody to the CS protein. The DNA sequence of the complementary DNA insert encodes a four-amino acid sequence: proline-asparagine-alanine-asparagine, tandemly repeated 23 times. The CS ? -lactamase fusion protein specifically binds monoclonal antibodies to the CS protein and inhibits the binding of these antibodies to native Plasmodium falciparum CS protein. These findings provide a basis for the development of a vaccine against Plasmodium falciparum malaria.

Enea, Vincenzo; Ellis, Joan; Zavala, Fidel; Arnot, David E.; Asavanich, Achara; Masuda, Aoi; Quakyi, Isabella; Nussenzweig, Ruth S.

1984-08-01

288

Navigating parasite webs and parasite flow: emerging and re-emerging parasitic zoonoses of wildlife origin.  

PubMed

Wildlife are now recognised as an important source of emerging human pathogens, including parasites. This paper discusses the linkages between wildlife, people, zoonotic parasites and the ecosystems in which they co-exist, revisits definitions for 'emerging' and 're-emerging', and lists zoonotic parasites that can be acquired from wildlife including, for some, estimates of the associated global human health burdens. The paper also introduces the concepts of 'parasite webs' and 'parasite flow', provides a context for parasites, relative to other infectious agents, as causes of emerging human disease, and discusses drivers of disease emergence and re-emergence, especially changes in biodiversity and climate. Angiostrongylus cantonensis in the Caribbean and the southern United States, Baylisascaris procyonis in California and Georgia, Plasmodium knowlesi in Sarawak, Malaysia, Human African Trypanosomiasis, Sarcoptes scabiei in carnivores, and Cryptosporidium, Giardia and Toxoplasma in marine ecosystems are presented as examples of wildlife-derived zoonotic parasites of particular recent interest. An ecological approach to disease is promoted, as is a need for an increased profile for this approach in undergraduate and graduate education in the health sciences. Synergy among scientists and disciplines is identified as critical for the study of parasites and parasitic disease in wildlife populations. Recent advances in techniques for the investigation of parasite fauna of wildlife are presented and monitoring and surveillance systems for wildlife disease are discussed. Some of the limitations inherent in predictions for the emergence and re-emergence of infection and disease associated with zoonotic parasites of wildlife are identified. The importance of public awareness and public education in the prevention and control of emerging and re-emerging zoonotic infection and disease are emphasised. Finally, some thoughts for the future are presented. PMID:16168994

Polley, Lydden

2005-10-01

289

New type of SSUrDNA sequence was detected from both Plasmodium ovale curtisi and Plasmodium ovale wallikeri samples  

PubMed Central

Background Plasmodium ovale is relatively unfamiliar to Chinese staff engaged in malaria diagnosis. In 2013, dried blood spots of four unidentified but suspected ovale malaria samples were sent to the National Malaria Reference Laboratory (NMRL) for reconfirmation. Methods Partial and complete, small, subunit ribosomal DNA (SSU rDNA) sequences of four samples were obtained with PCR-cloning-sequencing method. Obtained sequences were analyzed by aligning with each other and with nine SSU rDNA sequences of six known Plasmodium parasites. A phylogenetic tree was constructed based on complete SSU rDNA sequences and 12 same gene sequences derived from six known Plasmodium parasites and three Babesia parasites. Primary structure of conservative and variable regions of variant sequences was determined also by comparing them with those of six known Plasmodium parasites. To confirm their existence in genome, they were redetected with primers matching their variable regions. PCR systems aimed to roughly detect any eukaryotes and prokaryotes respectively were also applied to search for other pathogens in one of four patients. Results Totally, 19 partial and 23 complete SSU rDNA sequences obtained from four samples. Except eight variant sequences, similarities among sequences from same DNA sample were in general high (more than 98%). The phylogenetic analysis revealed that three cases were infected by P. ovale wallikeri and one by P. ovale curtisi. Four of the variant sequences which obtained from four samples relatively showed high similarities with each other (98.5%-100%). Identical variant sequences actually could be re-obtained from each DNA sample. Their primary structure of conservative and variable regions showed quite fit with that of six known Plasmodium parasites. The test for prokaryote pathogens showed negative and the tests for eukaryotes only found DNA sequences of Human and P. ovale parasites. Conclusion Both P. ovale wallikeri and P. ovale curtisi infections are present in imported malaria cases of China. New type of partial SSU rDNA sequence which assumed to express in a certain life stage of P. ovale was obtained from both P. ovale wallikeri and P. ovale curtisi samples. This discovery would supply information and clues to identify and understand P. ovale parasites more accurately. PMID:24893846

2014-01-01

290

Human Infections and Detection of Plasmodium knowlesi  

PubMed Central

SUMMARY Plasmodium knowlesi is a malaria parasite that is found in nature in long-tailed and pig-tailed macaques. Naturally acquired human infections were thought to be extremely rare until a large focus of human infections was reported in 2004 in Sarawak, Malaysian Borneo. Human infections have since been described throughout Southeast Asia, and P. knowlesi is now recognized as the fifth species of Plasmodium causing malaria in humans. The molecular, entomological, and epidemiological data indicate that human infections with P. knowlesi are not newly emergent and that knowlesi malaria is primarily a zoonosis. Human infections were undiagnosed until molecular detection methods that could distinguish P. knowlesi from the morphologically similar human malaria parasite P. malariae became available. P. knowlesi infections cause a spectrum of disease and are potentially fatal, but if detected early enough, infections in humans are readily treatable. In this review on knowlesi malaria, we describe the early studies on P. knowlesi and focus on the epidemiology, diagnosis, clinical aspects, and treatment of knowlesi malaria. We also discuss the gaps in our knowledge and the challenges that lie ahead in studying the epidemiology and pathogenesis of knowlesi malaria and in the prevention and control of this zoonotic infection. PMID:23554413

Daneshvar, Cyrus

2013-01-01

291

Predictions of avian Plasmodium expansion under climate change.  

PubMed

Vector-borne diseases are particularly responsive to changing environmental conditions. Diurnal temperature variation has been identified as a particularly important factor for the development of malaria parasites within vectors. Here, we conducted a survey across France, screening populations of the house sparrow (Passer domesticus) for malaria (Plasmodium relictum). We investigated whether variation in remotely-sensed environmental variables accounted for the spatial variation observed in prevalence and parasitemia. While prevalence was highly correlated to diurnal temperature range and other measures of temperature variation, environmental conditions could not predict spatial variation in parasitemia. Based on our empirical data, we mapped malaria distribution under climate change scenarios and predicted that Plasmodium occurrence will spread to regions in northern France, and that prevalence levels are likely to increase in locations where transmission already occurs. Our findings, based on remote sensing tools coupled with empirical data suggest that climatic change will significantly alter transmission of malaria parasites. PMID:23350033

Loiseau, Claire; Harrigan, Ryan J; Bichet, Coraline; Julliard, Romain; Garnier, Stéphane; Lendvai, Adám Z; Chastel, Olivier; Sorci, Gabriele

2013-01-01

292

Plasmodium falciparum gametocytes: with a view to a kill.  

PubMed

Drugs that kill or inhibit the sexual stages of Plasmodium in order to prevent transmission are important components of malaria control programmes. Reducing gametocyte carriage is central to the control of Plasmodium falciparum transmission as infection can result in extended periods of gametocytaemia. Unfortunately the number of drugs with activity against gametocytes is limited. Primaquine is currently the only licensed drug with activity against the sexual stages of malaria parasites and its use is hampered by safety concerns. This shortcoming is likely the result of the technical challenges associated with gametocyte studies together with the focus of previous drug discovery campaigns on asexual parasite stages. However recent emphasis on malaria eradication has resulted in an upsurge of interest in identifying compounds with activity against gametocytes. This review examines the gametocytocidal properties of currently available drugs as well as those in the development pipeline and examines the prospects for discovery of new anti-gametocyte compounds. PMID:23953486

Butterworth, Alice S; Skinner-Adams, Tina S; Gardiner, Don L; Trenholme, Katharine R

2013-12-01

293

Parasite Virulence 14Parasite Virulence  

E-print Network

Parasite Virulence 14Parasite Virulence Jos J. Schall Department of Biology, University of Vermont, Burlington, VT 05405, USA The Problem Some parasites exact a terrible price from their hosts, causing severe pathology and reducing the host's fitness, whereas other parasites are essentially benign. Several kinds

Schall, Joseph J.

294

Morphologic and molecular study of hemoparasites in wild corvids and evidence of sequence identity with Plasmodium DNA detected in captive black-footed penguins (Spheniscus demersus).  

PubMed

A morphologic and molecular epidemiologic investigation was conducted on a captive African black-footed penguin (Spheniscus demersus) colony with a history of Plasmodium infections at La Palmyre Zoo (France). Each penguin received 12.5 mg of pyrimethamine twice a week as a prophylaxis every year from April to November. Although Plasmodium parasites were not detected in blood smears and tissues collected from the penguins, various blood parasites were recorded in blood smears from wild Eurasian magpies (Pica pica) and carrion crows (Corvus corone) sampled at the same time in the study area. These parasites consisted of several Plasmodium spp. (P. lenoblei, P. dorsti, P bioccai, P. relictum, P. dherteae, P. beaucournui, P. maior, P. tranieri, and P. snounoui), Parahaemoproteus spp., Trypanosoma spp., and Leucocytozoon spp. On the other hand, nested polymerase chain reaction enabled detection of Plasmodium DNA in 28/44 (64%) penguins, 15/25 (60%) magpies, and 4/9 (44%) crows. Sequencing and phylogenetic analyses indicated that the parasite DNA amplified from the penguins, magpies, and crows were similar. Magpies and crows could therefore act as a reservoir for penguin Plasmodium infections, which may be more prevalent than previously thought. Morphologic characterization of the Plasmodium spp. detected in the penguins, as well as further biological and epidemiologic studies, are needed to fully understand the transmission of Plasmodium parasites to captive penguins. PMID:25314825

Leclerc, Antoine; Chavatte, Jean-Marc; Landau, Irène; Snounou, Georges; Petit, Thierry

2014-09-01

295

Structure of Plasmodium falciparum ADP-ribosylation factor 1  

SciTech Connect

Vesicular trafficking may play a crucial role in the pathogenesis and survival of the malaria parasite. ADP-ribosylation factors (ARFs) are among the major components of vesicular trafficking pathways in eukaryotes. The crystal structure of ARF1 GTPase from Plasmodium falciparum has been determined in the GDP-bound conformation at 2.5 {angstrom} resolution and is compared with the structures of mammalian ARF1s.

Cook, William J.; Smith, Craig D.; Senkovich, Olga; Holder, Anthony A.; Chattopadhyay, Debasish (UAB); (NIMR)

2011-09-26

296

Therapeutic potential of folate uptake inhibition in Plasmodium falciparum  

Microsoft Academic Search

Plasmodium falciparum parasites resistant to the combination sulfadoxine–pyrimethamine are spreading in Africa, particularly in East Africa. This is a matter of concern because there are no other affordable drugs available. This article provides the evidence indicating that sulfadoxine–pyrimethamine resistance can be reversed in vitro and discusses how this information might be exploited to extend the therapeutic lifetime of sulfadoxine–pyrimethamine in

Alexis M. Nzila; Gilbert Kokwaro; Peter A. Winstanley; Kevin Marsh; Steve A. Ward

2004-01-01

297

Induction of gene amplification in Plasmodium falciparum  

SciTech Connect

Human erythrocytic in vitro cultures of Honduras I strain of the malaria parasite Plasmodium falciparum have been stressed stepwise with increasing concentrations of methotrexate (MTX), a folate antagonist. This selection has produced a strain that is 450 times more resistant to the drug than the original culture. Uptake of sublethal doses of radiolabeled MTX by infected red blood cells was 6-36 times greater in the resistant cultures than in the nonresistant controls. DNA isolated from all of the parasites was probed by hybridization with /sup 35/S-labeled DNA derived from a clone of the yeast thymidylate synthetase (TS) gene. This showed 50 to 100 times more increased hybridization of the TS probe to the DNA from the resistant parasites is direct evidence of gene amplification because DHFR and TS are actually one and the same bifunctional enzyme in P. falciparum. Hence, the evidence presented indicates that induced resistance of the malaria parasite to MTX in this case is due to overproduction of DHFR resulting from amplification of the DHFR-TS gene.

Rogers, P.L.

1985-01-01

298

ATP Synthase Complex of Plasmodium falciparum  

PubMed Central

The rotary nanomotor ATP synthase is a central player in the bioenergetics of most organisms. Yet the role of ATP synthase in malaria parasites has remained unclear, as blood stages of Plasmodium falciparum appear to derive ATP largely through glycolysis. Also, genes for essential subunits of the FO sector of the complex could not be detected in the parasite genomes. Here, we have used molecular genetic and immunological tools to investigate the localization, complex formation, and functional significance of predicted ATP synthase subunits in P. falciparum. We generated transgenic P. falciparum lines expressing seven epitope-tagged canonical ATP synthase subunits, revealing localization of all but one of the subunits to the mitochondrion. Blue native gel electrophoresis of P. falciparum mitochondrial membranes suggested the molecular mass of the ATP synthase complex to be greater than 1 million daltons. This size is consistent with the complex being assembled as a dimer in a manner similar to the complexes observed in other eukaryotic organisms. This observation also suggests the presence of previously unknown subunits in addition to the canonical subunits in P. falciparum ATP synthase complex. Our attempts to disrupt genes encoding ? and ? subunits were unsuccessful, suggesting an essential role played by the ATP synthase complex in blood stages of P. falciparum. These studies suggest that, despite some unconventional features and its minimal contribution to ATP synthesis, P. falciparum ATP synthase is localized to the parasite mitochondrion, assembled as a large dimeric complex, and is likely essential for parasite survival. PMID:21984828

Nina, Praveen Balabaskaran; Morrisey, Joanne M.; Ganesan, Suresh M.; Ke, Hangjun; Pershing, April M.; Mather, Michael W.; Vaidya, Akhil B.

2011-01-01

299

Labelling of membrane glycoproteins of cultivated Plasmodium falciparum*  

PubMed Central

Membrane glycoprotein synthesis by Plasmodium falciparum was determined by metabolic labelling in the presence of 74 kBq/ml (2.5 ?Ci/ml) glucosamine-3H. Five major glycoprotein bands and four minor ones were demonstrated. A control experiment using normal, outdated, human erythrocytes indicates that there was no incorporation of the labelled glucosamine into the erythrocyte membrane. It was also demonstrated that the rate of membrane glycoprotein synthesis by mature parasites of the trophozoite and schizont stages was twice that of the ring-stage parasites. Cytochemical surface-labelling experiments had led to the conclusion that the membrane of malaria parasites contains little or no glycoprotein. Our studies indicate, however, that there is significant synthesis of membrane glycoprotein by the parasite and that this can be metabolically labelled and measured by using radioactive glucosamine as precursor of the glycoprotein. PMID:6998592

Udeinya, Iroka J.; Van Dyke, K.

1980-01-01

300

Parasitic Pneumonia and Lung Involvement  

PubMed Central

Parasitic infestations demonstrated a decline in the past decade as a result of better hygiene practices and improved socioeconomic conditions. Nevertheless, global immigration, increased numbers of the immunocompromised people, international traveling, global warming, and rapid urbanization of the cities have increased the susceptibility of the world population to parasitic diseases. A number of new human parasites, such as Plasmodium knowlesi, in addition to many potential parasites, have urged the interest of scientific community. A broad spectrum of protozoal parasites frequently affects the respiratory system, particularly the lungs. The diagnosis of parasitic diseases of airway is challenging due to their wide varieties of clinical and roentgenographic presentations. So detailed interrogations of travel history to endemic areas are critical for clinicians or pulmonologists to manage this entity. The migrating adult worms can cause mechanical airway obstruction, while the larvae can cause airway inflammation. This paper provides a comprehensive review of both protozoal and helminthic infestations that affect the airway system, particularly the lungs, including clinical and roentgenographic presentations, diagnostic tests, and therapeutic approaches. PMID:24995332

Cheepsattayakorn, Ruangrong

2014-01-01

301

Inference of the Oxidative Stress Network in Anopheles stephensi upon Plasmodium Infection  

PubMed Central

Ookinete invasion of Anopheles midgut is a critical step for malaria transmission; the parasite numbers drop drastically and practically reach a minimum during the parasite's whole life cycle. At this stage, the parasite as well as the vector undergoes immense oxidative stress. Thereafter, the vector undergoes oxidative stress at different time points as the parasite invades its tissues during the parasite development. The present study was undertaken to reconstruct the network of differentially expressed genes involved in oxidative stress in Anopheles stephensi during Plasmodium development and maturation in the midgut. Using high throughput next generation sequencing methods, we generated the transcriptome of the An. stephensi midgut during Plasmodium vinckei petteri oocyst invasion of the midgut epithelium. Further, we utilized large datasets available on public domain on Anopheles during Plasmodium ookinete invasion and Drosophila datasets and arrived upon clusters of genes that may play a role in oxidative stress. Finally, we used support vector machines for the functional prediction of the un-annotated genes of An. stephensi. Integrating the results from all the different data analyses, we identified a total of 516 genes that were involved in oxidative stress in An. stephensi during Plasmodium development. The significantly regulated genes were further extracted from this gene cluster and used to infer an oxidative stress network of An. stephensi. Using system biology approaches, we have been able to ascertain the role of several putative genes in An. stephensi with respect to oxidative stress. Further experimental validations of these genes are underway. PMID:25474020

Shrinet, Jatin; Nandal, Umesh Kumar; Adak, Tridibes; Bhatnagar, Raj K.; Sunil, Sujatha

2014-01-01

302

The Dynamics of Natural Plasmodium falciparum Infections  

PubMed Central

Background Natural immunity to Plasmodium falciparum has been widely studied, but its effects on parasite dynamics are poorly understood. Acquisition and clearance rates of untreated infections are key elements of the dynamics of malaria, but estimating these parameters is challenging because of frequent super-infection and imperfect detectability of parasites. Consequently, information on effects of host immune status or age on infection dynamics is fragmentary. Methods An age-stratified cohort of 347 individuals from Northern Ghana was sampled six times at 2 month intervals. High-throughput capillary electrophoresis was used to genotype the msp-2 locus of all P. falciparum infections detected by PCR. Force of infection (FOI) and duration were estimated for each age group using an immigration-death model that allows for imperfect detection of circulating parasites. Results Allowing for imperfect detection substantially increased estimates of FOI and duration. Effects of naturally acquired immunity on the FOI and duration would be reflected in age dependence in these indices, but in our cohort data FOI tended to increase with age in children. Persistence of individual parasite clones was characteristic of all age-groups. Duration peaked in 5–9 year old children (average duration 319 days, 95% confidence interval 318;320). Conclusions The main age-dependence is on parasite densities, with only small age-variations in the FOI and persistence of infections. This supports the hypothesis that acquired immunity controls transmission mainly by limiting blood-stage parasite densities rather than changing rates of acquisition or clearance of infections. PMID:23029082

Felger, Ingrid; Maire, Martin; Bretscher, Michael T.; Falk, Nicole; Tiaden, André; Sama, Wilson; Beck, Hans-Peter; Owusu-Agyei, Seth; Smith, Thomas A.

2012-01-01

303

Quantification of multiple infections of Plasmodium falciparum in vitro  

PubMed Central

Background Human malaria infections caused by the parasite Plasmodium falciparum often contain more than one genetically distinct parasite. Despite this fact, nearly all studies of multiple strain P. falciparum infections have been limited to determining relative densities of each parasite within an infection. In light of this, new methods are needed that can quantify the absolute number of parasites within a single infection. Methods A quantitative PCR (qPCR) method was developed to track the dynamic interaction of P. falciparum infections containing genetically distinct parasite clones in cultured red blood cells. Allele-specific primers were used to generate a standard curve and to quantify the absolute concentration of parasite DNA within multi-clonal infections. Effects on dynamic growth relationships between parasites under drug pressure were examined by treating mixed cultures of drug sensitive and drug resistant parasites with the anti-malarial drug chloroquine at different dosing schedules. Results An absolute quantification method was developed to monitor the dynamics of P. falciparum cultures in vitro. This method allowed for the observation of competitive suppression, the reduction of parasites numbers due to the presence of another parasite, and competitive release, the improved performance of a parasite after the removal of a competitor. These studies demonstrated that the presence of two parasites led to the reduction in density of at least one parasite. The introduction of drug to a mixed culture containing both a drug resistant and drug sensitive parasites resulted in an increased proportion of the drug resistant parasite. Moreover, following drug treatment, the resistant parasite experienced competitive release by exhibiting a fitness benefit greater than simply surviving drug treatment, due to the removal of competitive suppression by the sensitive parasite. Conclusions The newly developed assay allowed for the examination of the dynamics of two distinct clones in vitro; both competitive suppression and release were observed. A deeper understanding of the dynamic growth responses of multiple strain P. falciparum infections, with and without drug pressure, can improve the understanding of the role of parasite interactions in the spread of drug resistant parasites, perhaps suggesting different treatment strategies. PMID:22646748

2012-01-01

304

Plasmodium knowlesi Malaria in Children  

PubMed Central

Plasmodium knowlesi can cause severe malaria in adults; however, descriptions of clinical disease in children are lacking. We reviewed case records of children (age <15 years) with a malaria diagnosis at Kudat District Hospital, serving a largely deforested area of Sabah, Malaysia, during January–November 2009. Sixteen children with PCR-confirmed P. knowlesi monoinfection were compared with 14 children with P. falciparum monoinfection diagnosed by microscopy or PCR. Four children with knowlesi malaria had a hemoglobin level at admission of <10.0 g/dL (minimum lowest level 6.4 g/dL). Minimum level platelet counts were lower in knowlesi than in falciparum malaria (median 76,500/µL vs. 156,000/?L; p = 0.01). Most (81%) children with P. knowlesi malaria received chloroquine and primaquine; median parasite clearance time was 2 days (range 1–5 days). P. knowlesi is the most common cause of childhood malaria in Kudat. Although infection is generally uncomplicated, anemia is common and thrombocytopenia universal. Transmission dynamics in this region require additional investigation. PMID:21529389

William, Timothy; Jikal, Mohammad; Jilip, Jenarun; Dhararaj, Prabakaran; Menon, Jayaram; Yeo, Tsin W.; Anstey, Nicholas M.

2011-01-01

305

Plasmodium attenuation: connecting the dots between early immune responses and malaria disease severity  

PubMed Central

Sterile attenuation of Plasmodium parasites at the liver-stage either by irradiation or genetic modification, or at the blood-stage by chemoprophylaxis, has been shown to induce immune responses that can protect against subsequent wild-type infection. However, following certain interventions, parasite attenuation can be incomplete or non-sterile. Instead parasites are rendered developmentally stunted but still capable of establishing an acute infection. In experiments involving Plasmodium berghei ANKA, a model of experimental cerebral malaria, it has been observed that several forms of attenuated parasites do not induce cerebral pathology. In this perspective we collect evidence from studies on murine malaria in particular, and attempt to “connect the dots” between early immune responses and protection from severe cerebral disease, highlighting potential parallels to human infection. PMID:25520710

Fernandes, Priyanka; Frank, Roland; Lewis, Matthew D.; Mueller, Ann-Kristin

2014-01-01

306

Validation of an enzyme-linked immunosorbent assay for the quantification of human IgG directed against the repeat region of the circumsporozoite protein of the parasite Plasmodium falciparum  

PubMed Central

Background Several pre-erythrocytic malaria vaccines based on the circumsporozoite protein (CSP) antigen of Plasmodium falciparum are in clinical development. Vaccine immunogenicity is commonly evaluated by the determination of anti-CSP antibody levels using IgG-based assays, but no standard assay is available to allow comparison of the different vaccines. Methods The validation of an anti-CSP repeat region enzyme-linked immunosorbent assay (ELISA) is described. This assay is based on the binding of serum antibodies to R32LR, a recombinant protein composed of the repeat region of P. falciparum CSP. In addition to the original recombinant R32LR, an easy to purify recombinant His-tagged R32LR protein has been constructed to be used as solid phase antigen in the assay. Also, hybridoma cell lines have been generated producing human anti-R32LR monoclonal antibodies to be used as a potential inexhaustible source of anti-CSP repeats standard, instead of a reference serum. Results The anti-CSP repeats ELISA was shown to be robust, specific and linear within the analytical range, and adequately fulfilled all validation criteria as defined in the ICH guidelines. Furthermore, the coefficient of variation for repeatability and intermediate precision did not exceed 23%. Non-interference was demonstrated for R32LR-binding sera, and the assay was shown to be stable over time. Conclusions This ELISA, specific for antibodies directed against the CSP repeat region, can be used as a standard assay for the determination of humoral immunogenicity in the development of any CSP-based P. falciparum malaria vaccine. PMID:23173602

2012-01-01

307

Requirement of malarial protease in the invasion of human red cells by merozoites of Plasmodium falciparum  

Microsoft Academic Search

Highly synchronous cultures of the erythrocyte stages ofPlasmodium falciparum were used to determine the effects of a number of protease inhibitors on parasite development and merozoite invasion. Leupeptin, N-tosyl-L-lysyl chloromethylketone and pepstatin at a concentration greater than 0.05 mM were deleterious to both parasite development and merozoite invasion whereas aprotinin, antipain, a-1-antitrypsin and soybean trypsin inhibitor had no effect at

Porn-ngarm Dejkriengkraikhul; Prapon Wilairat

1983-01-01

308

Plasmodium berghei MAPK1 Displays Differential and Dynamic Subcellular Localizations during Liver Stage Development  

PubMed Central

Mitogen-activated protein kinases (MAPKs) regulate key signaling events in eukaryotic cells. In the genomes of protozoan Plasmodium parasites, the causative agents of malaria, two genes encoding kinases with significant homology to other eukaryotic MAPKs have been identified (mapk1, mapk2). In this work, we show that both genes are transcribed during Plasmodium berghei liver stage development, and analyze expression and subcellular localization of the PbMAPK1 protein in liver stage parasites. Live cell imaging of transgenic parasites expressing GFP-tagged PbMAPK1 revealed a nuclear localization of PbMAPK1 in the early schizont stage mediated by nuclear localization signals in the C-terminal domain. In contrast, a distinct localization of PbMAPK1 in comma/ring-shaped structures in proximity to the parasite’s nuclei and the invaginating parasite membrane was observed during the cytomere stage of parasite development as well as in immature blood stage schizonts. The PbMAPK1 localization was found to be independent of integrity of a motif putatively involved in ATP binding, integrity of the putative activation motif and the presence of a predicted coiled-coil domain in the C-terminal domain. Although PbMAPK1 knock out parasites showed normal liver stage development, the kinase may still fulfill a dual function in both schizogony and merogony of liver stage parasites regulated by its dynamic and stage-dependent subcellular localization. PMID:23544094

Wierk, Jannika Katharina; Langbehn, Annette; Kamper, Maria; Richter, Stefanie; Burda, Paul-Christian; Heussler, Volker Theo; Deschermeier, Christina

2013-01-01

309

Transmission of human and macaque Plasmodium spp. to ex-captive orangutans in Kalimantan, Indonesia.  

PubMed

Data are lacking on the specific diseases to which great apes are susceptible and the transmission dynamics and overall impact of these diseases. We examined the prevalence of Plasmodium spp. infections in semicaptive orangutans housed at the Orangutan Care Center and Quarantine, Central Kalimantan, Indonesia, by using a combination of microscopic and DNA molecular techniques to identify the Plasmodium spp. in each animal. Previous studies indicated 2 orangutan-specific Plasmodium spp., but our data show 4 Plasmodium spp. These findings provide evidence for P. vivax transmission between humans and orangutans and for P. cynomolgi transmission between macaques and orangutans. These data have potential implications for the conservation of orangutans and also for the bidirectional transmission of parasites between orangutans and humans visiting or living in the region. PMID:17326942

Reid, Michael J C; Ursic, Raul; Cooper, Dawn; Nazzari, Hamed; Griffiths, Melinda; Galdikas, Birute M; Garriga, Rosa M; Skinner, Mark; Lowenberger, Carl

2006-12-01

310

Transmission of Human and Macaque Plasmodium spp. to Ex-Captive Orangutans in Kalimantan, Indonesia  

PubMed Central

Data are lacking on the specific diseases to which great apes are susceptible and the transmission dynamics and overall impact of these diseases. We examined the prevalence of Plasmodium spp. infections in semicaptive orangutans housed at the Orangutan Care Center and Quarantine, Central Kalimantan, Indonesia, by using a combination of microscopic and DNA molecular techniques to identify the Plasmodium spp. in each animal. Previous studies indicated 2 orangutan-specific Plasmodium spp., but our data show 4 Plasmodium spp. These findings provide evidence for P. vivax transmission between humans and orangutans and for P. cynomolgi transmission between macaques and orangutans. These data have potential implications for the conservation of orangutans and also for the bidirectional transmission of parasites between orangutans and humans visiting or living in the region. PMID:17326942

Reid, Michael J.C.; Ursic, Raul; Cooper, Dawn; Nazzari, Hamed; Griffiths, Melinda; Galdikas, Birute M.; Garriga, Rosa M.; Skinner, Mark; Lowenberger, Carl

2006-01-01

311

The MB2 gene family of Plasmodium species has a unique combination of S1 and GTP-binding domains  

Microsoft Academic Search

BACKGROUND: Identification and characterization of novel Plasmodium gene families is necessary for developing new anti-malarial therapeutics. The products of the Plasmodium falciparum gene, MB2, were shown previously to have a stage-specific pattern of subcellular localization and proteolytic processing. RESULTS: Genes homologous to MB2 were identified in five additional parasite species, P. knowlesi, P. gallinaceum, P. berghei, P. yoelii, and P.

Lisa C. Romero; Thanh Vinh Nguyen; Benoit Deville; Oluwasanmi Ogunjumo; Anthony A. James

2004-01-01

312

Plasmodium durae Herman from the introduced common peafowl in northern Nigeria.  

PubMed

Plasmodium (Giovannolaia) durae Herman was originally described from Kenya, the type host being the common turkey, Meleagris gallopavo Linnaeus. There are no field records of this association outside of Africa, where the parasite, herein reported from another introduced and domesticated bird (the common peafowl, Pavo cristatus Linnaeus), was recently listed from 2 native Phasianidae of the genus Francolinus. The justification for the present identification is submitted against background data concerning malaria parasites from turkeys and other Galliformes in Africa and elsewhere, and restraint is urged in describing yet more "new species" of avian Plasmodium belonging to morphologically close taxa within Novyella and Giovannolaia. A near relative of P. durae, Plasmodium dissanaikei de Jong, is transferred from the former subgenus to the latter one. PMID:660569

Laird, M

1978-02-01

313

Melatonin Signaling and Its Modulation of PfNF-YB Transcription Factor Expression in Plasmodium falciparum  

PubMed Central

Malaria is one of the most severe tropical infectious diseases. More than 220 million people around the world have a clinical malaria infection and about one million die because of Plasmodium annually. This parasitic pathogen replicates efficiently in its human host making it difficult to eradicate. It is transmitted by mosquito vectors and so far mosquito control programs have not effectively eliminated this transmission. Because of malaria’s enormous health and economic impact and the need to develop new control and eventual elimination strategies, a big research effort has been made to better understand the biology of this parasite and its interactions with its vertebrate host. Determination of the genome sequence and organization, the elucidation of the role of key proteins, and cell signaling studies have helped to develop an understanding of the molecular mechanisms that provide the parasite’s versatility. The parasite can sense its environment and adapt to benefit its survival, indeed this is essential for it to complete its life cycle. For many years we have studied how the Plasmodium parasite is able to sense melatonin. In this review we discuss the melatonin signaling pathway and its role in the control of Plasmodium replication and development. PMID:23839089

Lima, Wânia Rezende; Holder, Anthony A.; Garcia, Célia R. S.

2013-01-01

314

Malaria parasite-infected erythrocytes inhibit glucose utilization in uninfected red cells  

E-print Network

-parasitized RBCs. This may be due to lowered pH leading to selective differ- ential inhibition of the regulatory,3-diphosphoglycerate (2,3-DPG) level produced in normal RBCs and Plasmodium falciparum infected red blood cell popu of the parasites in humans lead to the clinical manifestations of the disease. Hypoglycemia and lactic acidosis

Sharma, Shobhona

315

Gametogenesis in Malaria Parasites Is Mediated by the cGMP-Dependent Protein Kinase  

Microsoft Academic Search

Malaria parasite transmission requires differentiation of male and female gametocytes into gametes within a mosquito following a blood meal. A mosquito-derived molecule, xanthurenic acid (XA), can trigger gametogenesis, but the signalling events controlling this process in the human malaria parasite Plasmodium falciparum remain unknown. A role for cGMP was revealed by our observation that zaprinast (an inhibitor of phosphodiesterases that

Louisa McRobert; Cathy J Taylor; Wensheng Deng; Quinton L Fivelman; Ross M Cummings; Spencer D Polley; Oliver Billker; David A Baker

2008-01-01

316

Concentrations of Chloroquine and Malaria Parasites in Blood in Nigerian Children  

Microsoft Academic Search

Consumption of chloroquine (CQ) and subtherapeutic drug levels in blood are considered to be widespread in areas where malaria is endemic. A cross-sectional study was performed with 405 Nigerian children to assess factors associated with the presence of CQ in blood and to examine correlations of drug levels with malaria parasite species and densities. Infections with Plasmodium species and parasite

FRANK P. MOCKENHAUPT; J URGEN MAY; YNGVE BERGQVIST; OLUSEGUN G. ADEMOWO; PETER E. OLUMESE; ADEYINKA G. FALUSI; CHRISTIAN G. MEYER; ULRICH BIENZLE

2000-01-01

317

Maurer's clefts, the enigma of Plasmodium falciparum  

PubMed Central

Plasmodium falciparum, the causative agent of malaria, completely remodels the infected human erythrocyte to acquire nutrients and to evade the immune system. For this process, the parasite exports more than 10% of all its proteins into the host cell cytosol, including the major virulence factor PfEMP1 (P. falciparum erythrocyte surface protein 1). This unusual protein trafficking system involves long-known parasite-derived membranous structures in the host cell cytosol, called Maurer’s clefts. However, the genesis, role, and function of Maurer’s clefts remain elusive. Similarly unclear is how proteins are sorted and how they are transported to and from these structures. Recent years have seen a large increase of knowledge but, as yet, no functional model has been established. In this perspective we review the most important findings and conclude with potential possibilities to shed light into the enigma of Maurer’s clefts. Understanding the mechanism and function of these structures, as well as their involvement in protein export in P. falciparum, might lead to innovative control strategies and might give us a handle with which to help to eliminate this deadly parasite. PMID:24284172

Mundwiler-Pachlatko, Esther; Beck, Hans-Peter

2013-01-01

318

Plasmodium Vivax Infection Impersonating Plasmodium Falciparum Malaria  

PubMed Central

A 73-year-old woman came to the casualty ward with symptoms of syncopal attacks, weakness, fever with chills and rigors. A provisional diagnosis of Plasmodium vivax malaria was made after the blood investigations. She had deranged renal function tests, altered sensorium and low platelet count. Repeated tests for P. falciparum (Card test) were negative. Glucose-6-Phosphate dehydrogenise (G6PD) levels were within normal limits. Treatment for P. vivax was started with intravenous quinine initially followed by oral quinine for a period of seven days and patient responded to the treatment and was discharged within 2 weeks of admission. Most of the cases of P. vivax present with typical and predictable features, although atypical cases with characteristics of P. falciparum can occur, especially in the elderly. PMID:25610295

Kakaraparthi, Sweta; Prabhu, Raghunath

2014-01-01

319

Cloning and characterization of Plasmodium vivax thioredoxin peroxidase-1.  

PubMed

Reactive oxygen species produced from hemoglobin digestion and the host immune system could have adverse effects on malaria parasites. To protect themselves, malaria parasites are highly dependent on the antioxidant enzymes, including superoxide dismutases and thioredoxin-dependent peroxidases. To date, several thioredoxin peroxidases (TPx) have been characterized in Plasmodium falciparum, but the TPx in Plasmodium vivax has not yet been characterized. The complete sequence of gene coding for thioredoxin peroxidase-1 of P. vivax (PvTPx-1) was amplified by PCR and cloned. Using the recombinant PvTPx-1 (rPvTPx-1), polyclonal antibody was produced in mice for immunolocalization of the enzyme in the parasite. The antioxidant activity of rPvTPx-1 was evaluated by mixed-function oxidation assay. PvTPx-1 has two conserved cysteine residues in the amino acid sequence at the positions 50 and 170 which formed a dimer under a non-reducing condition. Using a thiol mixed-function oxidation assay, the antioxidant activity of rPvTPx-1 was revealed. Indirect immunofluorescence microscopy with the specific antibody indicated that PvTPx-1 was expressed in the cytoplasm of the erythrocytic stage of the parasite in a dots-like pattern. The results suggest that P. vivax uses TPx-1 to reduce and detoxify hydrogen peroxides in order to maintain their redox homeostasis and proliferation in the host body. PMID:22392134

Hakimi, Hassan; Asada, Masahito; Angeles, Jose Ma M; Inoue, Noboru; Kawazu, Shin-Ichiro

2012-08-01

320

Preerythrocytic, live-attenuated Plasmodium falciparum vaccine candidates by design.  

PubMed

Falciparum malaria is initiated when Anopheles mosquitoes transmit the Plasmodium sporozoite stage during a blood meal. Irradiated sporozoites confer sterile protection against subsequent malaria infection in animal models and humans. This level of protection is unmatched by current recombinant malaria vaccines. However, the live-attenuated vaccine approach faces formidable obstacles, including development of accurate, reproducible attenuation techniques. We tested whether Plasmodium falciparum could be attenuated at the early liver stage by genetic engineering. The P. falciparum genetically attenuated parasites (GAPs) harbor individual deletions or simultaneous deletions of the sporozoite-expressed genes P52 and P36. Gene deletions were done by double-cross-over recombination to avoid genetic reversion of the knockout parasites. The gene deletions did not affect parasite replication throughout the erythrocytic cycle, gametocyte production, mosquito infections, and sporozoite production rates. However, the deletions caused parasite developmental arrest during hepatocyte infection. The double-gene deletion line exhibited a more severe intrahepatocytic growth defect compared with the single-gene deletion lines, and it did not persist. This defect was assessed in an in vitro liver-stage growth assay and in a chimeric mouse model harboring human hepatocytes. The strong phenotype of the double knockout GAP justifies its human testing as a whole-organism vaccine candidate using the established sporozoite challenge model. GAPs might provide a safe and reproducible platform to develop an efficacious whole-cell malaria vaccine that prevents infection at the preerythrocytic stage. PMID:19625622

VanBuskirk, Kelley M; O'Neill, Matthew T; De La Vega, Patricia; Maier, Alexander G; Krzych, Urszula; Williams, Jack; Dowler, Megan G; Sacci, John B; Kangwanrangsan, Niwat; Tsuboi, Takafumi; Kneteman, Norman M; Heppner, Donald G; Murdock, Brant A; Mikolajczak, Sebastian A; Aly, Ahmed S I; Cowman, Alan F; Kappe, Stefan H I

2009-08-01

321

Preerythrocytic, live-attenuated Plasmodium falciparum vaccine candidates by design  

PubMed Central

Falciparum malaria is initiated when Anopheles mosquitoes transmit the Plasmodium sporozoite stage during a blood meal. Irradiated sporozoites confer sterile protection against subsequent malaria infection in animal models and humans. This level of protection is unmatched by current recombinant malaria vaccines. However, the live-attenuated vaccine approach faces formidable obstacles, including development of accurate, reproducible attenuation techniques. We tested whether Plasmodium falciparum could be attenuated at the early liver stage by genetic engineering. The P. falciparum genetically attenuated parasites (GAPs) harbor individual deletions or simultaneous deletions of the sporozoite-expressed genes P52 and P36. Gene deletions were done by double-cross-over recombination to avoid genetic reversion of the knockout parasites. The gene deletions did not affect parasite replication throughout the erythrocytic cycle, gametocyte production, mosquito infections, and sporozoite production rates. However, the deletions caused parasite developmental arrest during hepatocyte infection. The double-gene deletion line exhibited a more severe intrahepatocytic growth defect compared with the single-gene deletion lines, and it did not persist. This defect was assessed in an in vitro liver-stage growth assay and in a chimeric mouse model harboring human hepatocytes. The strong phenotype of the double knockout GAP justifies its human testing as a whole-organism vaccine candidate using the established sporozoite challenge model. GAPs might provide a safe and reproducible platform to develop an efficacious whole-cell malaria vaccine that prevents infection at the preerythrocytic stage. PMID:19625622

VanBuskirk, Kelley M.; O'Neill, Matthew T.; De La Vega, Patricia; Maier, Alexander G.; Krzych, Urszula; Williams, Jack; Dowler, Megan G.; Sacci, John B.; Kangwanrangsan, Niwat; Tsuboi, Takafumi; Kneteman, Norman M.; Heppner, Donald G.; Murdock, Brant A.; Mikolajczak, Sebastian A.; Aly, Ahmed S. I.; Cowman, Alan F.; Kappe, Stefan H. I.

2009-01-01

322

Deciphering apicoplast targeting signals – feature extraction from nuclear-encoded precursors of Plasmodium falciparum apicoplast proteins  

Microsoft Academic Search

The malaria causing protozoan Plasmodium falciparum contains a vestigal, non-photosynthetic plastid, the apicoplast. Numerous proteins encoded by nuclear genes are targeted to the apicoplast courtesy of N-terminal extensions. With the impending sequence completion of an entire genome of the malaria parasite, it is important to have software tools in place for prediction of subcellular locations for all proteins. Apicoplast targeting

Jochen Zuegge; Stuart Ralph; Michael Schmuker; Geoffrey I. McFadden; Gisbert Schneider

2001-01-01

323

On the estimation of sequestered infected erythrocytes in Plasmodium falciparum malaria patients  

E-print Network

On the estimation of sequestered infected erythrocytes in Plasmodium falciparum malaria patients D burden of the patient and the rate of infection in a malaria's intra-host model by using control theory parasite burden within a malaria patient. Moreover, our constructed observer does not use the uncertain

Boyer, Edmond

324

Changing Malaria Epidemiology and Diagnostic Criteria for Plasmodium falciparum Clinical Malaria  

E-print Network

Changing Malaria Epidemiology and Diagnostic Criteria for Plasmodium falciparum Clinical Malaria: In tropical Africa, where malaria is highly endemic, low grade infections are asymptomatic and the diagnosis of clinical malaria is usually based on parasite density. Here we investigate how changes in malaria control

Paris-Sud XI, Université de

325

The Transmembrane Isoform of Plasmodium falciparum MAEBL Is Essential for the Invasion of Anopheles Salivary Glands  

Microsoft Academic Search

Malaria transmission depends on infective stages in the mosquito salivary glands. Plasmodium sporozoites that mature in midgut oocysts must traverse the hemocoel and invade the mosquito salivary glands in a process thought to be mediated by parasite ligands. MAEBL, a homologue of the transmembrane EBP ligands essential in merozoite invasion, is expressed abundantly in midgut sporozoites. Alternative splicing generates different

Fabian E. Saenz; Bharath Balu; Jonah Smith; Sarita R. Mendonca; John H. Adams; Mauricio Martins Rodrigues

2008-01-01

326

Quantitative trait loci mapping reveals candidate pathways regulating cell cycle duration in Plasmodium falciparum  

Microsoft Academic Search

BACKGROUND: Elevated parasite biomass in the human red blood cells can lead to increased malaria morbidity. The genes and mechanisms regulating growth and development of Plasmodium falciparum through its erythrocytic cycle are not well understood. We previously showed that strains HB3 and Dd2 diverge in their proliferation rates, and here use quantitative trait loci mapping in 34 progeny from a

Heather B Reilly Ayala; Mark A Wacker; Geoffrey Siwo; Michael T Ferdig

2010-01-01

327

An AFLP-based genetic linkage map of Plasmodium chabaudi chabaudi  

Microsoft Academic Search

BACKGROUND: Plasmodium chabaudi chabaudi can be considered as a rodent model of human malaria parasites in the genetic analysis of important characters such as drug resistance and immunity. Despite the availability of some genome sequence data, an extensive genetic linkage map is needed for mapping the genes involved in certain traits. METHODS: The inheritance of 672 Amplified Fragment Length Polymorphism

Axel Martinelli; Paul Hunt; Richard Fawcett; Pedro VL Cravo; David Walliker; Richard Carter

2005-01-01

328

Plasmodium relictum (lineage P-SGS1): Effects on experimentally infected passerine birds  

Microsoft Academic Search

We evaluated the effects of Plasmodium relictum (lineage P-SGS1), which is a host generalist, to five species of passerine birds. Light infection of P. relictum was isolated from a naturally infected adult reed warbler Acrocephalus scirpaceus. The parasites were inoculated to naive juveniles of the chaffinch Fringilla coelebs, common crossbill Loxia curvirostra, house sparrow Passer domesticus, siskin Spinus spinus and

Vaidas Palinauskas; Gediminas Valki?nas; Casimir V. Bolshakov; Staffan Bensch

2008-01-01

329

Plasmodium gallinaceum: A Refractory Mechanism of Ookinete Killing in the Mosquito, Anopheles gambiae  

Microsoft Academic Search

We have identified a mechanism for refractoriness to a bird malaria, Plasmodium gallinaceum, in the African vector of human malaria, Anopheles gambiae. Oocysts fail to develop in the refractory mosquitoes as a result of ookinete death which occurs within 27 hr of midgut invasion. Ultrastructural studies showed that parasite death occurs while the ookinete lies free in the midgut epithelial

K. D. Vernick; H. Fujioka; D. C. Seeley; B. Tandler; M. Aikawa; L. H. Miller

1995-01-01

330

Genotyping of Plasmodium falciparum infections by PCR: a comparative multicentre study  

Microsoft Academic Search

Genetic diversity of malaria parasites represents a major issue in understanding several aspects of malaria infection and disease. Genotyping of Plasmodium falciparum infections with polymerase chain reaction (PCR)-based methods has therefore been introduced in epidemiological studies. Polymorphic regions of the msp1, msp2 and glurp genes are the most frequently used markers for genotyping, but methods may differ. A multicentre study

A. Färnert; A. P. Arez; H. A. Babiker; H. P. Beck; A. Benito; A. Björkman; M. C. Bruce; D. J. Conway; K. P. Day; L. Henning; O. Mercereau-Puijalon; L. C. Ranford-Cartwright; J. M. Rubio; G. Snounou; D. Walliker; J. Zwetyenga; V. E. do Rosario

2001-01-01

331

Plasmodium falciparum infection increases Anopheles gambiae attraction to nectar sources and sugar uptake  

Technology Transfer Automated Retrieval System (TEKTRAN)

Plasmodium parasites are known to manipulate the behaviour of their vectors so as to enhance their transmission. However, it is unknown if this vector manipulation also affects mosquito-plant interaction and sugar uptake. Dual-choice olfactometer and probing assays were used to study plant seeking b...

332

A cohort study of Plasmodium falciparum infection dynamics in Western Kenya Highlands  

E-print Network

parasite genotype during single episodes of Plasmodium falciparum malaria in Gabonese children.children resided [20]. Third, human travel may have facilitated parasiteparasite population genetic diversity and infec- tion dynamics in the western Kenya highlands based on a cohort of school children.

2010-01-01

333

Plasmodium yoelii: induction of attenuated mutants by irradiation  

SciTech Connect

When erythrocytic forms of Plasmodium yoelii nigeriensis, which is invariably fatal in mice, were exposed to X rays, the dose to reduce surviving parasites to one millionth was 100 gray (10 Krad). A suspension of 5 X 10(6) per ml of parasitized erythrocyte was irradiated at 100 gray, and 0.2 ml aliquots were inoculated into 22 mice. Eleven mice showed patent parasitemia, and in these the growth curves were less steep than that found in nonirradiated parasites. The infections of 8 mice of the 11 were self-resolving, and the attenuated feature of the parasites maintained following a limited number of blood passages. The parasites were slowly growing even in nude mice and cause self-resolving infections in intact mice. BALB/c mice immunized with the attenuated parasites were protected against subsequent challenge infections with the original virulent erythrocytic and sporogonic forms. These findings indicate that attenuated mutants of malaria parasites can be readily induced by this method.

Waki, S.; Yonome, I.; Suzuki, M.

1986-12-01

334

Malaria infected erythrocyte-derived microvesicles mediate cellular communication within the parasite population and with the host immune system  

PubMed Central

Summary Humans and mice infected with different Plasmodium strains are known to produce microvesicles derived from the infected red blood cells (RBC), denoted RMVs. Studies in mice have shown that RMVs are elevated during infection and have pro-inflammatory activity. Here we present a detailed characterization of RMV composition and function in the human malaria parasite Plasmodium falciparum. Proteomics profiling revealed the enrichment of multiple host and parasite proteins, in particular of parasite antigens associated with host cell membranes and proteins involved in parasite invasion into RBCs. RMVs are quantitatively released during the asexual parasite cycle prior to parasite egress. RMVs demonstrate potent immunomodulatory properties on human primary macrophages and neutrophils. Additionally, RMVs are internalized by infected red blood cells and stimulate production of transmission stage parasites in a dose-dependent manner. Thus, RMVs mediate cellular communication within the parasite population and with the host innate immune system. PMID:23684304

Mantel, Pierre-Yves; Hoang, Anh N.; Goldowitz, Ilana; Potashnikova, Daria; Hamza, Bashar; Vorobjev, Ivan; Ghiran, Ionita; Toner, Mehmet; Irimia, Daniel; Ivanov, Alexander R.; Barteneva, Natasha; Marti, Matthias

2013-01-01

335

Plasmodium cynomolgi genome sequences provide insight into Plasmodium vivax and the monkey malaria clade.  

PubMed

P. cynomolgi, a malaria-causing parasite of Asian Old World monkeys, is the sister taxon of P. vivax, the most prevalent malaria-causing species in humans outside of Africa. Because P. cynomolgi shares many phenotypic, biological and genetic characteristics with P. vivax, we generated draft genome sequences for three P. cynomolgi strains and performed genomic analysis comparing them with the P. vivax genome, as well as with the genome of a third previously sequenced simian parasite, Plasmodium knowlesi. Here, we show that genomes of the monkey malaria clade can be characterized by copy-number variants (CNVs) in multigene families involved in evasion of the human immune system and invasion of host erythrocytes. We identify genome-wide SNPs, microsatellites and CNVs in the P. cynomolgi genome, providing a map of genetic variation that can be used to map parasite traits and study parasite populations. The sequencing of the P. cynomolgi genome is a critical step in developing a model system for P. vivax research and in counteracting the neglect of P. vivax. PMID:22863735

Tachibana, Shin-Ichiro; Sullivan, Steven A; Kawai, Satoru; Nakamura, Shota; Kim, Hyunjae R; Goto, Naohisa; Arisue, Nobuko; Palacpac, Nirianne M Q; Honma, Hajime; Yagi, Masanori; Tougan, Takahiro; Katakai, Yuko; Kaneko, Osamu; Mita, Toshihiro; Kita, Kiyoshi; Yasutomi, Yasuhiro; Sutton, Patrick L; Shakhbatyan, Rimma; Horii, Toshihiro; Yasunaga, Teruo; Barnwell, John W; Escalante, Ananias A; Carlton, Jane M; Tanabe, Kazuyuki

2012-09-01

336

Regulation of Gene Expression in Protozoa Parasites  

PubMed Central

Infections with protozoa parasites are associated with high burdens of morbidity and mortality across the developing world. Despite extensive efforts to control the transmission of these parasites, the spread of populations resistant to drugs and the lack of effective vaccines against them contribute to their persistence as major public health problems. Parasites should perform a strict control on the expression of genes involved in their pathogenicity, differentiation, immune evasion, or drug resistance, and the comprehension of the mechanisms implicated in that control could help to develop novel therapeutic strategies. However, until now these mechanisms are poorly understood in protozoa. Recent investigations into gene expression in protozoa parasites suggest that they possess many of the canonical machineries employed by higher eukaryotes for the control of gene expression at transcriptional, posttranscriptional, and epigenetic levels, but they also contain exclusive mechanisms. Here, we review the current understanding about the regulation of gene expression in Plasmodium sp., Trypanosomatids, Entamoeba histolytica and Trichomonas vaginalis. PMID:20204171

Gomez, Consuelo; Esther Ramirez, M.; Calixto-Galvez, Mercedes; Medel, Olivia; Rodríguez, Mario A.

2010-01-01

337

The clonal theory of parasitic protozoa: 12 years on.  

PubMed

The question of population structure in parasitic protozoa has recently gained a renewed topicality with significant contributions on medically important pathogens, such as Plasmodium falciparum, Toxoplasma gondii and Cryptosporidium parvum. The proposals that initiated this debate are reviewed here and the subsequent developments of the clonal theory, in light of recent contributions, are examined. PMID:12377258

Tibayrenc, Michel; Ayala, Francisco J

2002-09-01

338

Plasmodium falciparum transmission stages accumulate in the human bone marrow  

PubMed Central

Transmission of Plasmodium falciparum malaria parasites requires formation and development of gametocytes, yet all but the most mature of these sexual parasite forms are absent from the blood circulation. We performed a systematic organ survey in pediatric cases of fatal malaria to characterize the spatial dynamics of gametocyte development in the human host. Histological studies revealed a niche in the extravascular space of the human bone marrow where gametocytes formed in erythroid precursor cells and underwent development before reentering the circulation. Accumulation of gametocytes in the hematopoietic system of human bone marrow did not rely on cytoadherence to the vasculature as does sequestration of asexual-stage parasites. This suggests a different mechanism for the sequestration of gametocytes that could potentially be exploited to block malaria transmission. PMID:25009232

Joice, Regina; Nilsson, Sandra K.; Montgomery, Jacqui; Dankwa, Selasi; Egan, Elizabeth; Morahan, Belinda; Seydel, Karl B.; Bertuccini, Lucia; Alano, Pietro; Williamson, Kim C.; Duraisingh, Manoj T.; Taylor, Terrie E.; Milner, Danny A.; Marti, Matthias

2014-01-01

339

Exploring Drug Targets in Isoprenoid Biosynthetic Pathway for Plasmodium falciparum  

PubMed Central

Emergence of rapid drug resistance to existing antimalarial drugs in Plasmodium falciparum has created the need for prediction of novel targets as well as leads derived from original molecules with improved activity against a validated drug target. The malaria parasite has a plant plastid-like apicoplast. To overcome the problem of falciparum malaria, the metabolic pathways in parasite apicoplast have been used as antimalarial drug targets. Among several pathways in apicoplast, isoprenoid biosynthesis is one of the important pathways for parasite as its multiplication in human erythrocytes requires isoprenoids. Therefore targeting this pathway and exploring leads with improved activity is a highly attractive approach. This report has explored progress towards the study of proteins and inhibitors of isoprenoid biosynthesis pathway. For more comprehensive analysis, antimalarial drug-protein interaction has been covered. PMID:24864210

Qidwai, Tabish; Khan, Mohd Y.; Sharma, Bechan

2014-01-01

340

Study on application of high doses plasmodium berghei in cell culture  

NASA Astrophysics Data System (ADS)

Malaria, one of the most important infection disease problems in the world, is caused by protozoan parasites of the genus Plasmodium. This disease is responsible for hundreds of the millions of clinical cases and more than one million deaths per year, for this reason, malaria is a priority and the WHO estimates that half of the world population is at risk. In this work we study how the absorbed dose inactivates the parasite (Plasmodium berghei) in rodent model (BALB/c mice), by applying X-ray irradiation. The dose was increased from 10 to 50 Gy in parasitized red blood cells (PRBC) with merozoite stage using in vitro short cultures. Also the reduction of the irradiation effect was determined by intra-peritoneal inoculations of irradiated parasites. Afterwards, the parasitaemia was assessed daily on smears made from tail blood and stained with Giemsa's reagent. Besides, the effect of irradiation was evaluated using an immunological test as indirect immunofluorescence assay (IFA). The results of this study showed that the most effective radiation for inactivation of parasites is about 50 Gy and the immunofluorescence pattern showed a different distribution of the fluorescence on parasites. These results showed direct correlation between the effect of irradiated parasites and parasitaemia in the group of mice infected with RBC after 50 Gy irradiation. Our results indicated that the threshold is between 30 to 50 Gy to inactivate the parasites.

Spencer, L. M.; De Santis, M.; Davila, J.; Foinquinos, A.; Salcedo, E.; Sajo-Bohus, L.

2012-02-01

341

Two putative protein export regulators promote Plasmodium blood stage development in vivo.  

PubMed

Protein export is considered an essential feature of malaria parasite blood stage development. Here, we examined five components of the candidate Plasmodium translocon of exported proteins (PTEX), a complex thought to mediate protein export across the parasitophorous vacuole membrane into the host cell. Using the murine malaria model parasite Plasmodium berghei, we succeeded in generating parasite lines lacking PTEX88 and thioredoxin 2 (TRX2). Repeated attempts to delete the remaining three translocon components failed, suggesting essential functions for EXP2, PTEX150, and heat shock protein 101 (HSP101) during blood stage development. To analyze blood infections of the null-mutants, we established a flow cytometry-assisted intravital competition assay using three novel high fluorescent lines (Bergreen, Beryellow, and Berred). Although blood stage development of parasites lacking TRX2 was affected, the deficit was much more striking in PTEX88 null-mutants. The multiplication rate of PTEX88-deficient parasites was strongly reduced resulting in out-competition by wild-type parasites. Endogenous tagging revealed that TRX2::tag resides in distinct punctate organelles of unknown identity. PTEX88::tag shows a diffuse intraparasitic pattern in blood stage parasites. In trophozoites, PTEX88::tag also localized to previously unrecognized extensions reaching from the parasite surface into the erythrocyte cytoplasm. Together, our results indicate auxiliary roles for TRX2 and PTEX88 and central roles for EXP2, PTEX150, and HSP101 during P. berghei blood infection. PMID:24076174

Matz, Joachim M; Matuschewski, Kai; Kooij, Taco W A

2013-09-01

342

DEVELOPMENT OF QUANTITATIVE RECEPTOR-LIGAND BINDING ASSAY FOR USE AS A TOOL TO ESTIMATE IMMUNE RESPONSES AGAINST PLASMODIUM VIVAX DUFFY BINDING PROTEIN REGION II  

Microsoft Academic Search

Antibodies generated against Region II of Plasmodium vivax Duffy binding protein (PvRII) can block binding of this parasite ligand to its receptor, the Duffy antigen receptor for chemokines (DARC) and prevent erythrocyte infection by the parasite. An in vitro functional assay that can serve as an immune correlate of an antigen activity is an important tool to guide vaccine development.

Ahmad Rushdi Shakri; M. Moshahid A. Rizvi; Chetan E. Chitnis

2012-01-01

343

Associations of Forest Type, Parasitism and Body Condition of Two European Passerines, Fringilla coelebs and Sylvia atricapilla  

PubMed Central

Human-induced forest modification can alter parasite-host interactions and might change the persistence of host populations. We captured individuals of two widespread European passerines (Fringilla coelebs and Sylvia atricapilla) in southwestern Germany to disentangle the associations of forest types and parasitism by haemosporidian parasites on the body condition of birds. We compared parasite prevalence and parasite intensity, fluctuating asymmetries, leukocyte numbers, and the heterophil to lymphocyte ratio (H/L-ratio) among individuals from beech, mixed-deciduous and spruce forest stands. Based on the biology of bird species, we expected to find fewer infected individuals in beech or mixed-deciduous than in spruce forest stands. We found the highest parasite prevalence and intensity in beech forests for F. coelebs. Although, we found the highest prevalence in spruce forests for S. atricapilla, the highest intensity was detected in beech forests, partially supporting our hypothesis. Other body condition or health status metrics, such as the heterophil to lymphocyte ratio (H/L-ratio), revealed only slight differences between bird populations inhabiting the three different forest types, with the highest values in spruce for F. coelebs and in mixed-deciduous forests for S. atricapilla. A comparison of parasitized versus non-parasitized individuals suggests that parasite infection increased the immune response of a bird, which was detectable as high H/L-ratio. Higher infections with blood parasites for S. atricapilla in spruce forest indicate that this forest type might be a less suitable habitat than beech and mixed-deciduous forests, whereas beech forests seem to be a suboptimal habitat regarding parasitism for F. coelebs. PMID:24339923

Lüdtke, Bruntje; Moser, Isabelle; Santiago-Alarcon, Diego; Fischer, Markus; Kalko, Elisabeth KV.; Schaefer, H. Martin; Suarez-Rubio, Marcela; Tschapka, Marco; Renner, Swen C.

2013-01-01

344

P. berghei Telomerase Subunit TERT is Essential for Parasite Survival  

PubMed Central

Telomeres define the ends of chromosomes protecting eukaryotic cells from chromosome instability and eventual cell death. The complex regulation of telomeres involves various proteins including telomerase, which is a specialized ribonucleoprotein responsible for telomere maintenance. Telomeres of chromosomes of malaria parasites are kept at a constant length during blood stage proliferation. The 7-bp telomere repeat sequence is universal across different Plasmodium species (GGGTTT/CA), though the average telomere length varies. The catalytic subunit of telomerase, telomerase reverse transcriptase (TERT), is present in all sequenced Plasmodium species and is approximately three times larger than other eukaryotic TERTs. The Plasmodium RNA component of TERT has recently been identified in silico. A strategy to delete the gene encoding TERT via double cross-over (DXO) homologous recombination was undertaken to study the telomerase function in P. berghei. Expression of both TERT and the RNA component (TR) in P. berghei blood stages was analysed by Western blotting and Northern analysis. Average telomere length was measured in several Plasmodium species using Telomere Restriction Fragment (TRF) analysis. TERT and TR were detected in blood stages and an average telomere length of ?950 bp established. Deletion of the tert gene was performed using standard transfection methodologies and we show the presence of tert? mutants in the transfected parasite populations. Cloning of tert- mutants has been attempted multiple times without success. Thorough analysis of the transfected parasite populations and the parasite obtained from extensive parasite cloning from these populations provide evidence for a so called delayed death phenotype as observed in different organisms lacking TERT. The findings indicate that TERT is essential for P. berghei cell survival. The study extends our current knowledge on telomere biology in malaria parasites and validates further investigations to identify telomerase inhibitors to induce parasite cell death. PMID:25275500

Religa, Agnieszka A.; Ramesar, Jai; Janse, Chris J.; Scherf, Artur; Waters, Andrew P.

2014-01-01

345

The Glutathione Biosynthetic Pathway of Plasmodium Is Essential for Mosquito Transmission  

PubMed Central

Infection of red blood cells (RBC) subjects the malaria parasite to oxidative stress. Therefore, efficient antioxidant and redox systems are required to prevent damage by reactive oxygen species. Plasmodium spp. have thioredoxin and glutathione (GSH) systems that are thought to play a major role as antioxidants during blood stage infection. In this report, we analyzed a critical component of the GSH biosynthesis pathway using reverse genetics. Plasmodium berghei parasites lacking expression of gamma-glutamylcysteine synthetase (?-GCS), the rate limiting enzyme in de novo synthesis of GSH, were generated through targeted gene disruption thus demonstrating, quite unexpectedly, that ?-GCS is not essential for blood stage development. Despite a significant reduction in GSH levels, blood stage forms of pbggcs? parasites showed only a defect in growth as compared to wild type. In contrast, a dramatic effect on development of the parasites in the mosquito was observed. Infection of mosquitoes with pbggcs? parasites resulted in reduced numbers of stunted oocysts that did not produce sporozoites. These results have important implications for the design of drugs aiming at interfering with the GSH redox-system in blood stages and demonstrate that de novo synthesis of GSH is pivotal for development of Plasmodium in the mosquito. PMID:19229315

Vega-Rodríguez, Joel; Janse, Chris J.; Pastrana-Mena, Rebecca; Waters, Andrew P.; Coppens, Isabelle; Rodríguez-Orengo, José F.; Jacobs-Lorena, Marcelo; Serrano, Adelfa E.

2009-01-01

346

Aminoacylation of Plasmodium falciparum tRNAAsn and Insights in the Synthesis of Asparagine Repeats*  

PubMed Central

Genome sequencing revealed an extreme AT-rich genome and a profusion of asparagine repeats associated with low complexity regions (LCRs) in proteins of the malarial parasite Plasmodium falciparum. Despite their abundance, the function of these LCRs remains unclear. Because they occur in almost all families of plasmodial proteins, the occurrence of LCRs cannot be associated with any specific metabolic pathway; yet their accumulation must have given selective advantages to the parasite. Translation of these asparagine-rich LCRs demands extraordinarily high amounts of asparaginylated tRNAAsn. However, unlike other organisms, Plasmodium codon bias is not correlated to tRNA gene copy number. Here, we studied tRNAAsn accumulation as well as the catalytic capacities of the asparaginyl-tRNA synthetase of the parasite in vitro. We observed that asparaginylation in this parasite can be considered standard, which is expected to limit the availability of asparaginylated tRNAAsn in the cell and, in turn, slow down the ribosomal translation rate when decoding asparagine repeats. This observation strengthens our earlier hypothesis considering that asparagine rich sequences act as “tRNA sponges” and help cotranslational folding of parasite proteins. However, it also raises many questions about the mechanistic aspects of the synthesis of asparagine repeats and about their implications in the global control of protein expression throughout Plasmodium life cycle. PMID:24196969

Filisetti, Denis; Théobald-Dietrich, Anne; Mahmoudi, Nassira; Rudinger-Thirion, Joëlle; Candolfi, Ermanno; Frugier, Magali

2013-01-01

347

Plasmodium genetic loci linked to host cytokine and chemokine responses  

PubMed Central

Both host and parasite factors contribute to disease severity of malaria infection; however, the molecular mechanisms responsible for the disease and the host-parasite interactions involved remain largely unresolved. To investigate effects of parasite factors on host immune responses and pathogenesis, we measured levels of plasma cytokines/chemokines (CC) and growth rates in mice infected with two Plasmodium yoelii strains having different virulence phenotypes and in progeny from a genetic cross of the two parasites. Quantitative trait loci (QTL) analysis linked levels of many CCs, particularly IL-1?, IP-10, IFN-?, MCP-1, and MIG, and early parasite growth rate to loci on multiple parasite chromosomes, including chromosomes 7, 9, 10, 12, and 13. Comparison of the genome sequences spanning the mapped loci revealed various candidate genes. The loci on chromosome 7 and 13 had significant (p < 0.005) additive effects on IL-1?, IL-5, and IP-10 responses, and the chromosome 9 and 12 loci had significant (p = 0.017) interaction. Infection of knockout mice showed critical roles of MCP-1 and IL-10 in parasitemia control and host mortality. These results provide important information for better understanding of malaria pathogenesis and can be used to examine the role of these factors in human malaria infection. PMID:24452266

Pattaradilokrat, Sittiporn; Li, Jian; Wu, Jian; Qi, Yanwei; Eastman, Richard T.; Zilversmit, Martine; Nair, Sethu C.; Huaman, Maria Cecilia; Quinones, Mariam; Jiang, Hongying; Li, Na; Zhu, Jun; Zhao, Keji; Kaneko, Osamu; Long, Carole A.; Su, Xin-zhuan

2014-01-01

348

Strain variation in early innate cytokine induction by Plasmodium falciparum  

PubMed Central

Previous work has shown that human donors vary in the magnitude and pattern of cytokines induced when peripheral blood mononuclear cells (PBMCs) are co-cultured with Plasmodium falciparum–infected erythrocytes. Whether P. falciparum strains vary in their ability to induce cytokines has not been studied in detail and is an important question, because variation in cytokine induction could affect parasite virulence and patterns of clinical disease. We investigated the early inflammatory cytokine response to four P. falciparum laboratory strains and five field isolates. Initial studies showed that parasite strain, parasitaemia and PBMC donor all had significant effects on the magnitude of pro-inflammatory cytokine responses (IFN-?, GM-CSF, IL-1?, TNF-?, IL-6, P < 0·005 in all cases). However, we noticed that the most highly inducing parasite strain consistently reached schizont rupture more rapidly than the other strains. When timing of schizont rupture was taken into account, parasite strains no longer differed in their cytokine induction (P = 0·383), although donor effects remained significant (P < 0·001). These data do not support the hypothesis that P. falciparum strains vary in induction of early innate cytokine responses from PBMCs, and instead are consistent with the suggestion that conserved parasite products such as haemozoin or GPI-anchors are the parasite-derived stimuli for cytokine induction. PMID:20591122

CORRIGAN, R A; ROWE, J A

2010-01-01

349

Plasmodium falciparum infection-induced changes in erythrocyte membrane proteins.  

PubMed

Over the past decade, advances in proteomic and mass spectrometry techniques and the sequencing of the Plasmodium falciparum genome have led to an increasing number of studies regarding the parasite proteome. However, these studies have focused principally on parasite protein expression, neglecting parasite-induced variations in the host proteome. Here, we investigated P. falciparum-induced modifications of the infected red blood cell (iRBC) membrane proteome, taking into account both host and parasite proteome alterations. Furthermore, we also determined if some protein changes were associated with genotypically distinct P. falciparum strains. Comparison of host membrane proteomes between iRBCs and uninfected red blood cells using fluorescence-based proteomic approaches, such as 2D difference gel electrophoresis revealed that more than 100 protein spots were highly up-represented (fold change increase greater than five) following P. falciparum infection for both strains (i.e. RP8 and Institut Pasteur Pregnancy Associated Malaria). The majority of spots identified by mass spectrometry corresponded to Homo sapiens proteins. However, infection-induced changes in host proteins did not appear to affect molecules located at the outer surface of the plasma membrane. The under-representation of parasite proteins could not be attributed to deficient parasite protein expression. Thus, this study describes for the first time that considerable host protein modifications were detected following P. falciparum infection at the erythrocyte membrane level. Further analysis of infection-induced host protein modifications will improve our knowledge of malaria pathogenesis. PMID:21744020

Fontaine, Albin; Bourdon, Stéphanie; Belghazi, Maya; Pophillat, Mathieu; Fourquet, Patrick; Granjeaud, Samuel; Torrentino-Madamet, Marylin; Rogier, Christophe; Fusai, Thierry; Almeras, Lionel

2012-02-01

350

A Nature-Inspired Betalainic Probe for Live-Cell Imaging of Plasmodium-Infected Erythrocytes  

PubMed Central

A model betalainic dye was semisynthesized from betanin, the magenta pigment of the red beet, and was effective for live-cell imaging of Plasmodium-infected red blood cells. This water-soluble fluorescent probe is photostable, excitable in the visible region and cell membrane-permeable, and its photophysical properties are not notably pH-sensitive. Fluorescence imaging microscopy of erythrocytes infected with Plasmodium falciparum, a causative agent of malaria in humans, showed that only the parasite was stained. Z-stacking analysis suggested that the probe accumulates proximal to the nucleus of the parasite. Indicaxanthin, one of the natural fluorescent betalains found in the petals of certain flowers, did not stain the parasite or the red blood cell. PMID:23342028

Gonçalves, Letícia Christina Pires; Tonelli, Renata Rosito; Bagnaresi, Piero; Mortara, Renato Arruda; Ferreira, Antonio Gilberto; Bastos, Erick Leite

2013-01-01

351

Intracellular proteolysis of kininogen by malaria parasites promotes release of active kinins  

PubMed Central

Background The malaria burden remains a major public health concern, especially in sub-Saharan Africa. The complex biology of Plasmodium, the apicomplexan parasite responsible for this disease, challenges efforts to develop new strategies to control the disease. Proteolysis is a fundamental process in the metabolism of malaria parasites, but roles for proteases in generating vasoactive peptides have not previously been explored. Results In the present work, it was demonstrated by mass spectrometry analysis that Plasmodium parasites (Plasmodium chabaudi and Plasmodium falciparum) internalize and process plasma kininogen, thereby releasing vasoactive kinins (Lys-BK, BK and des-Arg9-BK) that may mediate haemodynamic alterations during acute malaria. In addition, it was demonstrated that the P. falciparum cysteine proteases falcipain-2 and falcipain-3 generated kinins after incubation with human kininogen, suggesting that these enzymes have an important role in this process. The biologic activity of peptides released by Plasmodium parasites was observed by measuring ileum contraction and activation of kinin receptors (B1 and B2) in HUVEC cells; the peptides elicited an increase in intracellular calcium, measured by Fluo-3 AM fluorescence. This effect was suppressed by the specific receptor antagonists Des-Arg9[Leu8]-BK and HOE-140. Conclusions In previously undescribed means of modulating host physiology, it was demonstrated that malaria parasites can generate active kinins by proteolysis of plasma kininogen. PMID:22564457

2012-01-01

352

Severe Plasmodium knowlesi infection with multi-organ failure imported to Germany from Thailand/Myanmar.  

PubMed

During the last two decades human infections with Plasmodium knowlesi are increasingly diagnosed in South East Asia and have also been reported in travellers. A severe case of imported P. knowlesi infection in a 73-year old German is presented, who had been travelling through Myanmar and Thailand for three weeks. Microscopy showed a parasitaemia of 3% and different parasite stages including band-forms resembling Plasmodium malariae. Due to the clinical picture of severe malaria and the microscopical aspect (combination of parasites resembling P. malariae and Plasmodium falciparum), P. knowlesi was suspected. The patient was treated with intravenous quinine; he was put on mechanical ventilation and catecholamines due to cardiorespiratory failure. Parasitaemia was cleared rapidly but renal function deteriorated resulting in intermittent haemodialysis. The patient was hospitalized for six weeks but he recovered completely without any physical sequelae. Plasmodium knowlesi mono-infection was confirmed by molecular methods later on.Plasmodium knowlesi infection has to be taken into account in feverish travellers returning from Thailand/Myanmar. Moreover this species can cause life-threatening or even lethal complications. Accordingly severe P. knowlesi infection should be treated like severe P. falciparum infections. PMID:25367021

Seilmaier, Michael; Hartmann, Wulf; Beissner, Marcus; Fenzl, Thomas; Haller, Cathrine; Guggemos, Wolfgang; Hesse, Jan; Harle, Adinda; Bretzel, Gisela; Sack, Stefan; Wendtner, Clemens; Löscher, Thomas; Berens-Riha, Nicole

2014-01-01

353

Interspecific competition during transmission of two sympatric malaria parasite species to the mosquito vector.  

PubMed Central

The role of species interactions in structuring parasite communities remains controversial. Here, we show that interspecific competition between two avian malaria parasite species, Plasmodium gallinaceum and P. juxtanucleare, occurs as a result of interference during parasite fertilization within the bloodmeal of the mosquito. The significant reduction in the transmission success of P. gallinaceum to mosquitoes, due to the co-infecting P. juxtanucleare, is predicted to have compromised its colonization of regions occupied by P. juxtanucleare and, thus, may have contributed to the restricted global distribution of P. gallinaceum. Such interspecies interactions may occur between human malaria parasites and, thus, impact upon parasite species epidemiology, especially in regions of seasonal transmission. PMID:12573069

Paul, Rick E L; Nu, Van Anh Ton; Krettli, Antoniana U; Brey, Paul T

2002-01-01

354

New trends in chemotherapy on human and animal blood parasites.  

PubMed

Blood-parasite protozoa are causative agents of some of the major tropical or infectious diseases for humans and animals, such as Plasmodium for malaria (about 270 million infected people), Trypanosoma cruzi for Chagas' disease (about 18-20 million individuals), African trypanosomes for human and bovine trypanosomiasis, and Babesia for cattle and dogs. The absence of efficient vaccines against these diseases, the absence or the high toxicity of the few drugs against American and African trypanosomiasis, and the emergence of chemoresistance against Plasmodium falciparum emphasize the necessity to propose new antiparasitic strategies. Among these strategies, the biological strategy is based on the identification of key molecules for parasite development such that structural analogs can be designed that are parasite-specific or sufficiently inactive for the host. This requires a careful biochemical analysis of each step of the parasite life cycle. For blood-parasite protozoa, the lipid metabolism required for membrane biogenesis, antimicrotubular drugs or inhibitors of the mitotic spindle, and drug targeting offer new trends in chemotherapy against Plasmodium, Babesia, and trypanosomes. PMID:8801568

Schrével, J; Millerioux, V; Sinou, V; Frappier, F; Santus, R; Grellier, P

1996-01-01

355

A novel alternate secretory pathway for the export of Plasmodium proteins into the?host?erythrocyte  

PubMed Central

The malarial parasite dramatically alters its host cell by exporting and targeting proteins to specific locations within the erythrocyte. Little is known about the mechanisms by which the parasite is able to carry out this extraparasite transport. The fungal metabolite brefeldin A (BFA) has been used to study the secretory pathway in eukaryotes. BFA treatment of infected erythrocytes inhibits protein export and results in the accumulation of exported Plasmodium proteins into a compartment that is at the parasite periphery. Parasite proteins that are normally localized to the erythrocyte membrane, to nonmembrane bound inclusions in the erythrocyte cytoplasm, or to the parasitophorous vacuolar membrane accumulate in this BFA-induced compartment. A single BFA-induced compartment is detected per parasite and the various exported proteins colocalize to this compartment regardless of their final destinations. Parasite membrane proteins do not accumulate in this novel compartment, but accumulate in the endoplasmic reticulum (ER), suggesting that the parasite has two secretory pathways. This alternate secretory pathway is established immediately after merozoite invasion and at least some dense granule proteins also use the alternate pathway. The BFA-induced compartment exhibits properties that are similar to the ER, but it is clearly distinct from the ER. We propose to call this new organelle the secondary ER of apicomplexa. This ER-like organelle is an early, if not the first, step in the export of Plasmodium proteins into the host erythrocyte. PMID:9256443

Wiser, Mark F.; Lanners, H. Norbert; Bafford, Richard A.; Favaloro, Jenny M.

1997-01-01

356

Blood parasites in reptiles imported to Germany.  

PubMed

Though international trade is increasing, the significance of imported reptiles as carriers of pathogens with relevance to animal and human health is largely unknown. Reptiles imported to Germany were therefore investigated for blood parasites using light microscopy, and the detected parasites were morphologically characterized. Four hundred ten reptiles belonging to 17 species originating from 11 Asian, South American and African countries were included. Parasites were detected in 117 (29%) of individual reptiles and in 12 species. Haemococcidea (Haemogregarina, Hepatozoon, Schellackia) were found in 84% of snakes (Python regius, Corallus caninus), 20% of lizards (Acanthocercus atricollis, Agama agama, Kinyongia fischeri, Gekko gecko) and 50% of turtles (Pelusios castaneus). Infections with Hematozoea (Plasmodium, Sauroplasma) were detected in 14% of lizards (Acanthocercus atricollis, Agama agama, Agama mwanzae, K. fischeri, Furcifer pardalis, Xenagama batillifera, Acanthosaura capra, Physignathus cocincinus), while those with Kinetoplastea (Trypanosoma) were found in 9% of snakes (Python regius, Corallus caninus) and 25 % of lizards (K. fischeri, Acanthosaura capra, G. gecko). Nematoda including filarial larvae parasitized in 10% of lizards (Agama agama, Agama mwanzae, K. fischeri, Fu. pardalis, Physignathus cocincinus). Light microscopy mostly allowed diagnosis of the parasites' genus, while species identification was not possible because of limited morphological characteristics available for parasitic developmental stages. The investigation revealed a high percentage of imported reptiles being carriers of parasites while possible vectors and pathogenicity are largely unknown so far. The spreading of haemoparasites thus represents an incalculable risk for pet reptiles, native herpetofauna and even human beings. PMID:25324132

Ursula, Halla; Rüdiger, Korbel; Frank, Mutschmann; Monika, Rinder

2014-12-01

357

Healthy sweet inhibitor of Plasmodium falciparum aquaglyceroporin  

E-print Network

Plasmodium falciparum aquaglyceroporin (PfAQP) is a multifunctional channel protein in the plasma membrane of the malarial parasite that causes the most severe form of malaria infecting more than a million people a year. Finding a novel way to inhibit PfAQP, I conducted 3+ microseconds in silico experiments of an atomistic model of the PfAQP-membrane system and computed the chemical-potential profiles of six permeants (erythritol, water, glycerol, urea, ammonia, and ammonium) that can be efficiently transported across P. falciparum's plasma membrane through PfAQP's conducting pore. The profiles show that, with all the existent in vitro data being supportive, erythritol, a permeant of PfAQP itself having a deep ditch in its permeation passageway, strongly inhibits PfAQP's functions of transporting water, glycerol, urea, ammonia, and ammonium (The IC50 is in the range of high nanomolars). This suggests the possibility that erythritol, a sweetener generally considered safe, may be the drug needed to kill the malarial parasite in vivo without causing serious side effects.

Liao Y. Chen

2013-05-06

358

Ycf93 (Orf105), a Small Apicoplast-Encoded Membrane Protein in the Relict Plastid of the Malaria Parasite  

E-print Network

Ycf93 (Orf105), a Small Apicoplast-Encoded Membrane Protein in the Relict Plastid of the MalariaFadden* School of Botany, University of Melbourne, Parkville, Victoria, Australia Abstract Malaria parasites in the organelle kills parasites and protects against malaria. The apicoplast of Plasmodium falciparum encodes 30

McFadden, Geoff

359

Sarcocystis tupaia, sp. nov., a new parasite species employing treeshrews (Tupaiidae, Tupaia belangeri chinensis) as natural intermediate hosts  

Technology Transfer Automated Retrieval System (TEKTRAN)

Plasmodium falciparum is the causative agent of malignant malaria, which is among the most severe human infectious diseases. Despite its overwhelming significance to human health, the parasite’s origins remain unclear. The favored origin hypothesis holds that P. falciparum and its closest known rel...

360

Parasites: Water  

MedlinePLUS

... every day. Not only do all people need drinking water to survive, but water plays an important role ... been contaminated by certain parasites. For example, individuals drinking water contaminated with fecal matter containing the ameba Entamoeba ...

361

Regulation of Anti-Plasmodium Immunity by a LITAF-like Transcription Factor in the Malaria Vector Anopheles gambiae  

PubMed Central

The mosquito is the obligate vector for malaria transmission. To complete its development within the mosquito, the malaria parasite Plasmodium must overcome the protective action of the mosquito innate immune system. Here we report on the involvement of the Anopheles gambiae orthologue of a conserved component of the vertebrate immune system, LPS-induced TNF? transcription factor (LITAF), and its role in mosquito anti-Plasmodium immunity. An. gambiae LITAF-like 3 (LL3) expression is up-regulated in response to midgut invasion by both rodent and human malaria parasites. Silencing of LL3 expression greatly increases parasite survival, indicating that LL3 is part of an anti-Plasmodium defense mechanism. Electrophoretic mobility shift assays identified specific LL3 DNA-binding motifs within the promoter of SRPN6, a gene that also mediates mosquito defense against Plasmodium. Further experiments indicated that these motifs play a direct role in LL3 regulation of SRPN6 expression. We conclude that LL3 is a transcription factor capable of modulating SRPN6 expression as part of the mosquito anti-Plasmodium immune response. PMID:23093936

Smith, Ryan C.; Eappen, Abraham G.; Radtke, Andrea J.; Jacobs-Lorena, Marcelo

2012-01-01

362

Greater Endothelial Activation, Weibel-Palade Body Release and Host Inflammatory Response to Plasmodium vivax, compared with Plasmodium falciparum: A Prospective Study in Papua, Indonesia  

PubMed Central

Pathogenic mechanisms underlying vivax malaria are poorly understood, with few studies comparing endothelial and inflammatory responses with falciparum malaria. In adults with uncomplicated vivax or falciparum malaria, we compared plasma measurements of endothelial Weibel-Palade body release (angiopoietin-2) and activation (ICAM-1, E-selectin), as well as selected cytokines. Despite a lower median parasite count, angiopoietin-2 concentrations were higher in patients with vivax malaria, compared with falciparum malaria. Per peripheral parasite, median plasma angiopoietin-2, ICAM-1, E-selectin, interleukin-6, and interleukin-10 concentrations were higher in patients with malaria due to Plasmodium vivax. P. vivax induces greater endothelial Weibel-Palade body release and activation and greater host inflammatory responses, compared with Plasmodium falciparum. PMID:20497057

Yeo, Tsin W.; Lampah, Daniel A.; Tjitra, Emiliana; Piera, Kim; Gitawati, Retno; Kenangalem, Enny; Price, Ric N.; Anstey, Nicholas M.

2015-01-01

363

Determination of the Plasmodium vivax schizont stage proteome  

PubMed Central

With the genome of the malaria parasite Plasmodium vivax sequenced, it is important to determine the proteomes of the parasite in order to assist efforts in antigen and drug target discovery. Since a method for continuous culture of P. vivax parasite is not available, we tried to study the proteome of the erythrocytic stages using fresh parasite isolates from patients. In schizont-enriched samples, 316 proteins were confidently identified by tandem mass spectrometry. Almost 50% of the identified proteins were hypothetical, while other major categories include proteins with binding function, protein fate, protein synthesis, metabolism and cellular transport. To identify proteins that are recognized by host humoral immunity, parasite proteins were separated by two-dimensional gel electrophoresis and screened by Western blot using an immune serum from a P. vivax patient. Mass spectrometry analysis of protein spots recognized by the serum identified four potential antigens including PV24. The recombinant protein PV24 was recognized by antibodies from vivax malaria patients even during the convalescent period, indicating that PV24 could elicit long-lasting antibody responses in P. vivax patients. PMID:21515433

Roobsoong, Wanlapa; Roytrakul, Sittiruk; Sattabongkot, Jetsumon; Li, Jianyong; Udomsangpetch, Rachanee; Cui, Liwang

2011-01-01

364

A cascade of DNA binding proteins for sexual commitment and development in Plasmodium  

PubMed Central

Commitment to and completion of sexual development are essential for malaria parasites (protists of the genus Plasmodium) to be transmitted through mosquitoes1. The molecular mechanism(s) responsible for commitment have been hitherto unknown. Here we show that PBAP2-G, a conserved member of the ApiAP2 family of transcription factors, is essential for the commitment of asexually replicating forms to sexual development in P. berghei, a malaria parasite of rodents. PBAP2-G was identified from mutations in its encoding gene, PBANKA_143750, which account for the loss of sexual development frequently observed in parasites transmitted artificially by blood passage. Systematic gene deletion of conserved ApiAP2 genes in Plasmodium confirmed the role of PBAP2-G and revealed a second ApiAP2 member (PBANKA_103430, termed PBAP2-G2) that significantly modulates but does not abolish gametocytogenesis indicating that a cascade of ApiAP2 proteins are involved in commitment to the production and maturation of gametocytes. The data suggest a mechanism of commitment to gametocytogenesis in Plasmodium consistent with a positive feedback loop involving PBAP2G which might be exploited to prevent the transmission of this pernicious parasite. PMID:24572359

Otto, Thomas D.; Pfander, Claudia; Dickens, Nicholas J.; Religa, Agnieszka A.; Bushell, Ellen; Graham, Anne L.; Cameron, Rachael; Kafsack, Bjorn F.C.; Williams, April E.; Llinas, Manuel; Berriman, Matthew; Billker, Oliver; Waters, Andrew P.

2014-01-01

365

Direct evidence for the atovaquone action on the Plasmodium cytochrome bc1 complex.  

PubMed

Atovaquone, a coenzyme Q analogue has been indicated to specifically target the cytochrome bc1 complex of the mitochondrial respiratory chain in the malarial parasite and other protozoan. Various mutations in the quinone binding site of the cytochrome b gene of Plasmodium spp. such as M133I, L144S, L271V, K272R, Y268C, Y268S, Y268N, and V284F are suggesting to associate with resistance to atovaquone. There is no direct evidence of relation between the mutations and resistance to atovaquone in Plasmodium parasite that has been available. Technical difficulties in isolating active assayable mitochondria in the malarial parasite hinder us to obtain direct biochemical evidence to support the relation between the mutations and drug resistance. The establishment of a mitochondrial isolation method for the malaria parasite has allowed us to test the degree of resistance of Plasmodium berghei isolates to atovaquone directly. We have tested the activity of dihydroorotate (DHO)-cytochrome c reductase in various P. berghei atovaquone resistant clones in the presence of a wide concentration range of atovaquone. Our results show the IC50 of P. berghei atovaquone resistant clones is much higher (1.5 up to 40nM) in comparison to the atovaquone sensitive clones (0.132-0.465nM). The highest IC50 was revealed in clones carrying Y268C and Y268N mutations (which play an important role in atovaquone resistance in Plasmodium falciparum), with an approximately 100-fold increase. The findings indicate the importance of the mutation in the quinone binding site of the cytochrome b gene and that provide a direct evidence for the atovaquone inhibitory mechanism in the cytochrome bc1 complex of the parasite. PMID:25264100

Siregar, Josephine E; Kurisu, Genji; Kobayashi, Tamaki; Matsuzaki, Motomichi; Sakamoto, Kimitoshi; Mi-Ichi, Fumika; Watanabe, Yoh-Ichi; Hirai, Makoto; Matsuoka, Hiroyuki; Syafruddin, Din; Marzuki, Sangkot; Kita, Kiyoshi

2014-09-28

366

Plasmodium falciparum evades mosquito immunity by disrupting JNK-mediated apoptosis of invaded midgut cells.  

PubMed

The malaria parasite, Plasmodium, must survive and develop in the mosquito vector to be successfully transmitted to a new host. The Plasmodium falciparum Pfs47 gene is critical for malaria transmission. Parasites that express Pfs47 (NF54 WT) evade mosquito immunity and survive, whereas Pfs47 knockouts (KO) are efficiently eliminated by the complement-like system. Two alternative approaches were used to investigate the mechanism of action of Pfs47 on immune evasion. First, we examined whether Pfs47 affected signal transduction pathways mediating mosquito immune responses, and show that the Jun-N-terminal kinase (JNK) pathway is a key mediator of Anopheles gambiae antiplasmodial responses to P. falciparum infection and that Pfs47 disrupts JNK signaling. Second, we used microarrays to compare the global transcriptional responses of A. gambiae midguts to infection with WT and KO parasites. The presence of Pfs47 results in broad and profound changes in gene expression in response to infection that are already evident 12 h postfeeding, but become most prominent at 26 h postfeeding, the time when ookinetes invade the mosquito midgut. Silencing of 15 differentially expressed candidate genes identified caspase-S2 as a key effector of Plasmodium elimination in parasites lacking Pfs47. We provide experimental evidence that JNK pathway regulates activation of caspases in Plasmodium-invaded midgut cells, and that caspase activation is required to trigger midgut epithelial nitration. Pfs47 alters the cell death pathway of invaded midgut cells by disrupting JNK signaling and prevents the activation of several caspases, resulting in an ineffective nitration response that makes the parasite undetectable by the mosquito complement-like system. PMID:25552553

Ramphul, Urvashi N; Garver, Lindsey S; Molina-Cruz, Alvaro; Canepa, Gaspar E; Barillas-Mury, Carolina

2015-02-01

367

Plasmodium falciparum evades mosquito immunity by disrupting JNK-mediated apoptosis of invaded midgut cells  

PubMed Central

The malaria parasite, Plasmodium, must survive and develop in the mosquito vector to be successfully transmitted to a new host. The Plasmodium falciparum Pfs47 gene is critical for malaria transmission. Parasites that express Pfs47 (NF54 WT) evade mosquito immunity and survive, whereas Pfs47 knockouts (KO) are efficiently eliminated by the complement-like system. Two alternative approaches were used to investigate the mechanism of action of Pfs47 on immune evasion. First, we examined whether Pfs47 affected signal transduction pathways mediating mosquito immune responses, and show that the Jun-N-terminal kinase (JNK) pathway is a key mediator of Anopheles gambiae antiplasmodial responses to P. falciparum infection and that Pfs47 disrupts JNK signaling. Second, we used microarrays to compare the global transcriptional responses of A. gambiae midguts to infection with WT and KO parasites. The presence of Pfs47 results in broad and profound changes in gene expression in response to infection that are already evident 12 h postfeeding, but become most prominent at 26 h postfeeding, the time when ookinetes invade the mosquito midgut. Silencing of 15 differentially expressed candidate genes identified caspase-S2 as a key effector of Plasmodium elimination in parasites lacking Pfs47. We provide experimental evidence that JNK pathway regulates activation of caspases in Plasmodium-invaded midgut cells, and that caspase activation is required to trigger midgut epithelial nitration. Pfs47 alters the cell death pathway of invaded midgut cells by disrupting JNK signaling and prevents the activation of several caspases, resulting in an ineffective nitration response that makes the parasite undetectable by the mosquito complement-like system. PMID:25552553

Ramphul, Urvashi N.; Garver, Lindsey S.; Molina-Cruz, Alvaro; Canepa, Gaspar E.; Barillas-Mury, Carolina

2015-01-01

368

Generation of quinolone antimalarials targeting the Plasmodium falciparum mitochondrial respiratory chain for the treatment and prophylaxis of malaria.  

PubMed

There is an urgent need for new antimalarial drugs with novel mechanisms of action to deliver effective control and eradication programs. Parasite resistance to all existing antimalarial classes, including the artemisinins, has been reported during their clinical use. A failure to generate new antimalarials with novel mechanisms of action that circumvent the current resistance challenges will contribute to a resurgence in the disease which would represent a global health emergency. Here we present a unique generation of quinolone lead antimalarials with a dual mechanism of action against two respiratory enzymes, NADH:ubiquinone oxidoreductase (Plasmodium falciparum NDH2) and cytochrome bc(1). Inhibitor specificity for the two enzymes can be controlled subtly by manipulation of the privileged quinolone core at the 2 or 3 position. Inhibitors display potent (nanomolar) activity against both parasite enzymes and against multidrug-resistant P. falciparum parasites as evidenced by rapid and selective depolarization of the parasite mitochondrial membrane potential, leading to a disruption of pyrimidine metabolism and parasite death. Several analogs also display activity against liver-stage parasites (Plasmodium cynomolgi) as well as transmission-blocking properties. Lead optimized molecules also display potent oral antimalarial activity in the Plasmodium berghei mouse malaria model associated with favorable pharmacokinetic features that are aligned with a single-dose treatment. The ease and low cost of synthesis of these inhibitors fulfill the target product profile for the generation of a potent, safe, and inexpensive drug with the potential for eventual clinical deployment in the control and eradication of falciparum malaria. PMID:22566611

Biagini, Giancarlo A; Fisher, Nicholas; Shone, Alison E; Mubaraki, Murad A; Srivastava, Abhishek; Hill, Alisdair; Antoine, Thomas; Warman, Ashley J; Davies, Jill; Pidathala, Chandrakala; Amewu, Richard K; Leung, Suet C; Sharma, Raman; Gibbons, Peter; Hong, David W; Pacorel, Bénédicte; Lawrenson, Alexandre S; Charoensutthivarakul, Sitthivut; Taylor, Lee; Berger, Olivier; Mbekeani, Alison; Stocks, Paul A; Nixon, Gemma L; Chadwick, James; Hemingway, Janet; Delves, Michael J; Sinden, Robert E; Zeeman, Anne-Marie; Kocken, Clemens H M; Berry, Neil G; O'Neill, Paul M; Ward, Stephen A

2012-05-22

369

Revealing natural antisense transcripts from Plasmodium vivax isolates: evidence of genome regulation in complicated malaria.  

PubMed

Plasmodium vivax is the most geographically widespread human malaria parasite causing approximately 130-435 million infections annually. It is an economic burden in many parts of the world and poses a public health challenge along with the other Plasmodium sp. The biology of this parasite is less studied and poorly understood, in spite of these facts. Emerging evidence of severe complications due to infections by this parasite provides an impetus to focus research on the same. Investigating the parasite directly from infected patients is the best way to study its biology and pathogenic mechanisms. Gene expression studies of this parasite directly obtained from the patients has provided evidence of gene regulation resulting in varying amount of transcript levels in the different blood stages. The mechanisms regulating gene expression in malaria parasites are not well understood. Discovery of Natural Antisense Transcripts (NATs) in Plasmodium falciparum has suggested that these might play an important role in regulating gene expression. We report here the genome-wide occurrence of NATs in P. vivax parasites from patients with differing clinical symptoms. A total of 1348 NATs against annotated gene loci have been detected using a custom designed microarray with strand specific probes. Majority of NATs identified from this study shows positive correlation with the expression pattern of the sense (S) transcript. Our data also shows condition specific expression patterns of varying S and antisense (AS) transcript levels. Genes with AS transcripts enrich to various biological processes. To our knowledge this is the first report on the presence of NATs from P. vivax obtained from infected patients with different disease complications. The data suggests differential regulation of gene expression in diverse clinical conditions, as shown by differing sense/antisense ratios and would lead to future detailed investigations of gene regulation. PMID:24121022

Boopathi, P A; Subudhi, Amit Kumar; Garg, Shilpi; Middha, Sheetal; Acharya, Jyoti; Pakalapati, Deepak; Saxena, Vishal; Aiyaz, Mohammed; Chand, Bipin; Mugasimangalam, Raja C; Kochar, Sanjay K; Sirohi, Parmendra; Kochar, Dhanpat K; Das, Ashis

2013-12-01

370

Plasmodium vivax and Plasmodium chabaudi: intraerythrocytic traffic of antigenically homologous proteins involves a brefeldin A-sensitive secretory pathway.  

PubMed

We have used a monoclonal antibody (mAb 7C5B71) raised against the erythrocytic stages of Plasmodium vivax to identify a 148-kDa P vivax protein antigen (Pv-148) which crossreacts with an antigenically homologous 190-kDa protein of P. chabaudi (Pc-190). During parasite intraerythrocytic development Pv-148 and Pc-190 are exported into the host cell cytosol and become located in the surface membrane of the infected erythrocyte. Immunofluorescence confocal microscopy and immunoelectron microscopy studies showed that both Pv-148 and Pc-190 are released from the parasite and exported to the host cell cytoplasm in association with tubovesicular membrane (TVM) structures. Fluorescent in vivo labelling of P. chabaudi with Bodipy-ceramide followed by immunofluorescence staining with the mAb supported the association of antigenically homologous Pc-190 with TVM structures. In the presence of brefeldin A (BFA), secretion of antigenically homologous Pc-190 into the host cell cytoplasm was inhibited and the antigen remained in the parasite cytoplasm. BFA also arrested the maturation of the parasite. Taken together these results suggest that Pv-148 and Pc-190 are related parasite proteins that are transported into the host cell through a BFA-sensitive secretory pathway. PMID:11302521

Bracho, C; Dunia, I; Romano, M; Benedetti, E L; Perez, H A

2001-02-01

371

Naturally Acquired and Vaccine-Elicited Antibodies Block Erythrocyte Cytoadherence of the Plasmodium vivax Duffy Binding Protein  

Microsoft Academic Search

Malaria merozoites require the presence of specific surface receptors on the red blood cell for invasion. Plasmodium vivax, requires the Duffy blood group antigen as an obligate receptor for invasion. The parasite Duffy binding protein (DBP) is the ligand involved in this process, making the DBP a potential vaccine candidate. A preliminary objective was to study whether people exposed to

PASCAL MICHON; TRESA FRASER; JOHN H. ADAMS

2000-01-01

372

Multiplex PCR and Oligonucleotide Microarray for Detection of Single-Nucleotide Polymorphisms Associated with Plasmodium falciparum Drug Resistance  

Microsoft Academic Search

Drug resistance in Plasmodium falciparum is a serious public health threat in the countries where this organism is endemic. Since resistance has been associated with specific single-nucleotide polymorphisms (SNPs) in parasite genes, molecular markers are becoming useful surrogates for monitoring the emergence and dispersion of drug resistance. In this study, a multiplex PCR (mPCR) and oligonucleotide microarray method was developed

Guo Qing Zhang; Ya Yi Guan; Hai Hui Sheng; Bin Zheng; Song Wu; Hua Sheng Xiao; Lin Hua Tang

2008-01-01

373

Structure and Function of Plasmodium falciparum malate dehydrogenase: Role of Critical Amino Acids in C-substrate Binding Procket  

Technology Transfer Automated Retrieval System (TEKTRAN)

Malaria parasite thrives on anaerobic fermentation of glucose for energy. Earlier studies from our lab have demonstrated that a cytosolic malate dehydrogenase (PfMDH) with striking similarity to lactate dehydrogenase (PfLDH) might complement PfLDH function in Plasmodium falciparum. The N-terminal g...

374

Mining the Plasmodium genome database to define organellar function: what does the apicoplast do?  

PubMed Central

Apicomplexan species constitute a diverse group of parasitic protozoa, which are responsible for a wide range of diseases in many organisms. Despite differences in the diseases they cause, these parasites share an underlying biology, from the genetic controls used to differentiate through the complex parasite life cycle, to the basic biochemical pathways employed for intracellular survival, to the distinctive cell biology necessary for host cell attachment and invasion. Different parasites lend themselves to the study of different aspects of parasite biology: Eimeria for biochemical studies, Toxoplasma for molecular genetic and cell biological investigation, etc. The Plasmodium falciparum Genome Project contributes the first large-scale genomic sequence for an apicomplexan parasite. The Plasmodium Genome Database (http://PlasmoDB.org) has been designed to permit individual investigators to ask their own questions, even prior to formal release of the reference P. falciparum genome sequence. As a case in point, PlasmoDB has been exploited to identify metabolic pathways associated with the apicomplexan plastid, or 'apicoplast' - an essential organelle derived by secondary endosymbiosis of an alga, and retention of the algal plastid. PMID:11839180

Roos, David S; Crawford, Michael J; Donald, Robert G K; Fraunholz, Martin; Harb, Omar S; He, Cynthia Y; Kissinger, Jessica C; Shaw, Michael K; Striepen, Boris

2002-01-01

375

Lack of Molecular Correlates of Plasmodium vivax Ookinete Development  

PubMed Central

Previous studies of Plasmodium vivax transmission to Anopheles spp. mosquitoes have not been able to predict mosquito infectivity on the basis of microscopic or molecular quantification of parasites (total parasites in the sample or total number of gametocytes) in infected blood. Two methods for production of P. vivax ookinete cultures in vitro, with yields of 106 macrogametocytes, 104 zygotes, and 103 ookinetes, respectively, per 10 mL of P. vivax-infected patient blood with approximately 0.01% parasitemia, were used to study P. vivax sexual stage development. The quantity of gametocytes, determined by counting Giemsa-stained blood smears, and quantity and type of gametocyte as determined by quantitative reverse transcriptase–polymerase chain reaction for Pvalpha tubulin II and macrogametocyte-specific pvg377 did not predict ookinete yield. Factors that affect the efficiency of in vitro P. vivax ookinete transformation remain poorly understood. PMID:21813836

Bounkeua, Viengngeun; Li, Fengwu; Chuquiyauri, Raul; Abeles, Shira R.; McClean, Colleen M.; Neyra, Victor; Llanos-Cuentas, Alejandro; Yori, Pablo P.; Vinetz, Joseph M.

2011-01-01

376

First Evidence and Predictions of Plasmodium Transmission in Alaskan Bird Populations  

PubMed Central

The unprecedented rate of change in the Arctic climate is expected to have major impacts on the emergence of infectious diseases and host susceptibility to these diseases. It is predicted that malaria parasites will spread to both higher altitudes and latitudes with global warming. Here we show for the first time that avian Plasmodium transmission occurs in the North American Arctic. Over a latitudinal gradient in Alaska, from 61°N to 67°N, we collected blood samples of resident and migratory bird species. We found both residents and hatch year birds infected with Plasmodium as far north as 64°N, providing clear evidence that malaria transmission occurs in these climates. Based on our empirical data, we make the first projections of the habitat suitability for Plasmodium under a future-warming scenario in Alaska. These findings raise new concerns about the spread of malaria to naïve host populations. PMID:23028595

Loiseau, Claire; Harrigan, Ryan J.; Cornel, Anthony J.; Guers, Sue L.; Dodge, Molly; Marzec, Timothy; Carlson, Jenny S.; Seppi, Bruce; Sehgal, Ravinder N. M.

2012-01-01

377

A microscale human liver platform that supports the hepatic stages of Plasmodium falciparum and vivax  

PubMed Central

SUMMARY The Plasmodium liver stage is an attractive target for the development of anti-malarial drugs and vaccines, as it provides an opportunity to interrupt the life cycle of the parasite at a critical early stage. However, targeting the liver stage has been difficult. Undoubtedly, a major barrier has been the lack of robust, reliable and reproducible in vitro liver stage cultures. Here, we establish the liver stages for both Plasmodium falciparum and Plasmodium vivax in a microscale human liver platform composed of cryopreserved, micropatterned human primary hepatocytes surrounded by supportive stromal cells. Using this system, we have successfully recapitulated the full liver stage of P. falciparum including the release of infected merozoites and infection of overlaid erythrocytes, and also the establishment of small forms in late liver stages of P. vivax. Finally, we validate the potential of this platform as a tool for medium-throughput anti-malarial drug screening and vaccine development. PMID:23870318

March, Sandra; Ng, Shengyong; Velmurugan, Soundarapandian; Galstian, Ani; Shan, Jing; Logan, David; Carpenter, Anne; Thomas, David; Lee Sim, B. Kim; Mota, Maria M.; Hoffman, Stephen L.; Bhatia, Sangeeta N.

2013-01-01

378

Targeting Plasmodium phosphatidylinositol 4-kinase to eliminate malaria  

PubMed Central

Summary Achieving the goal of malaria elimination will depend on targeting Plasmodium pathways essential across all life stages. Here, we identify a lipid kinase, phosphatidylinositol 4-kinase (PI4K), as the target of imidazopyrazines, a novel antimalarial compound class that inhibits the intracellular development of multiple Plasmodium species at each stage of infection in the vertebrate host. Imidazopyrazines demonstrate potent preventive, therapeutic, and transmission-blocking activity in rodent malaria models, are active against blood-stage field isolates of the major human pathogens, P. falciparum and P. vivax, and inhibit liver stage hypnozoites in the simian parasite P. cynomolgi. We show that imidazopyrazines exert their effect through inhibitory interaction with the ATP-binding pocket of PI4K, altering the intracellular distribution of phosphatidylinositol 4-phosphate. Collectively, our data define PI4K as a key Plasmodium vulnerability, opening up new avenues of target-based discovery to identify drugs with an ideal activity profile for the prevention, treatment and elimination of malaria. PMID:24284631

Lim, Chek Shik; Lim, Siau Hoi; Roland, Jason; Simon, Oliver; Yeung, Bryan KS; Chatterjee, Arnab K; McCormack, Susan L; Manary, Micah J; Zeeman, Anne-Marie; Dechering, Koen J; Kumar, TR Santha; Henrich, Philipp P; Gagaring, Kerstin; Ibanez, Maureen; Kato, Nobutaka; Kuhen, Kelli L; Fischli, Christoph; Nagle, Advait; Rottmann, Matthias; Plouffe, David M; Bursulaya, Badry; Meister, Stephan; Rameh, Lucia; Trappe, Joerg; Haasen, Dorothea; Timmerman, Martijn; Sauerwein, Robert W; Suwanarusk, Rossarin; Russell, Bruce; Renia, Laurent; Nosten, Francois; Tully, David C; Kocken, Clemens HM; Glynne, Richard J; Bodenreider, Christophe; Fidock, David A; Diagana, Thierry T; Winzeler, Elizabeth A

2014-01-01

379

Targeting Plasmodium PI(4)K to eliminate malaria.  

PubMed

Achieving the goal of malaria elimination will depend on targeting Plasmodium pathways essential across all life stages. Here we identify a lipid kinase, phosphatidylinositol-4-OH kinase (PI(4)K), as the target of imidazopyrazines, a new antimalarial compound class that inhibits the intracellular development of multiple Plasmodium species at each stage of infection in the vertebrate host. Imidazopyrazines demonstrate potent preventive, therapeutic, and transmission-blocking activity in rodent malaria models, are active against blood-stage field isolates of the major human pathogens P. falciparum and P. vivax, and inhibit liver-stage hypnozoites in the simian parasite P. cynomolgi. We show that imidazopyrazines exert their effect through inhibitory interaction with the ATP-binding pocket of PI(4)K, altering the intracellular distribution of phosphatidylinositol-4-phosphate. Collectively, our data define PI(4)K as a key Plasmodium vulnerability, opening up new avenues of target-based discovery to identify drugs with an ideal activity profile for the prevention, treatment and elimination of malaria. PMID:24284631

McNamara, Case W; Lee, Marcus C S; Lim, Chek Shik; Lim, Siau Hoi; Roland, Jason; Nagle, Advait; Simon, Oliver; Yeung, Bryan K S; Chatterjee, Arnab K; McCormack, Susan L; Manary, Micah J; Zeeman, Anne-Marie; Dechering, Koen J; Kumar, T R Santha; Henrich, Philipp P; Gagaring, Kerstin; Ibanez, Maureen; Kato, Nobutaka; Kuhen, Kelli L; Fischli, Christoph; Rottmann, Matthias; Plouffe, David M; Bursulaya, Badry; Meister, Stephan; Rameh, Lucia; Trappe, Joerg; Haasen, Dorothea; Timmerman, Martijn; Sauerwein, Robert W; Suwanarusk, Rossarin; Russell, Bruce; Renia, Laurent; Nosten, Francois; Tully, David C; Kocken, Clemens H M; Glynne, Richard J; Bodenreider, Christophe; Fidock, David A; Diagana, Thierry T; Winzeler, Elizabeth A

2013-12-12

380

Assessing the role of reproduction and stress in the spring emergence of haematozoan parasites in birds.  

PubMed

A spring emergence of avian haemosporidian infections is nearly universal among temperate zone birds and is often described as a cost of reproductive effort. We take advantage of the opportunistic (i.e. aseasonal) breeding schedule of the red crossbill (Loxia curvirostra) to determine the relative contributions of season versus host physiology to the timing and intensity of Haemoproteus infections in the temperate zone. Despite breeding activity in both the winter and summer, Haemoproteus infections were highly seasonal--occurring largely from May through September--and measures of host physiology (i.e. reproductive condition and stress parameters) did not explain parasite prevalence. However, within the spring-summer peak, infection intensity (i.e. parasite density) was positively correlated with plasma levels of testosterone and free corticosterone and negatively correlated with corticosterone binding globulin capacity. These data are discussed in terms of the behavioral ecology of host and vector, and suggest that both seasonal increases in vector activity and relapse of latent (i.e. dormant) infections contribute to the spring emergence in birds. Relapse of latent infections does not appear to be induced by reproductive activity or increased allostatic (i.e. energy) load, but rather by a season-specific change in host or parasite physiology (e.g. melatonin or endogenous rhythms). PMID:24265426

Cornelius, J M; Zylberberg, M; Breuner, C W; Gleiss, A C; Hahn, T P

2014-03-15

381

Temporal stability of insular avian malarial parasite communities.  

PubMed Central

Avian malaria is caused by a diverse community of genetically differentiated parasites of the genera Plasmodium and Haemoproteus. Rapid seasonal and annual antigenic allele turnover resulting from selection by host immune systems, as observed in some parasite populations infecting humans, may extend analogously to dynamic species compositions within communities of avian malarial parasites. To address this issue, we examined the stability of avian malarial parasite lineages across multiple time-scales within two insular host communities. Parasite communities in Puerto Rico and St Lucia included 20 and 14 genetically distinct parasite lineages, respectively. Lineage composition of the parasite community in Puerto Rico did not vary seasonally or over a 1 year interval. However, over intervals approaching a decade, the avian communities of both islands experienced an apparent loss or gain of one malarial parasite lineage, indicating the potential for relatively frequent lineage turnover. Patterns of temporal variation of parasite lineages in this study suggest periodic colonization and extinction events driven by a combination of host-specific immune responses, competition between lineages and drift. However, the occasional and ecologically dynamic lineage turnover exhibited by insular avian parasite communities is not as rapid as antigenic allele turnover within populations of human malaria. PMID:15129959

Fallon, S. M.; Ricklefs, R. E.; Latta, S. C.; Bermingham, E.

2004-01-01

382

Hemoglobinopathies: Slicing the Gordian Knot of Plasmodium falciparum Malaria Pathogenesis  

PubMed Central

Plasmodium falciparum malaria kills over 500,000 children every year and has been a scourge of humans for millennia. Owing to the co-evolution of humans and P. falciparum parasites, the human genome is imprinted with polymorphisms that not only confer innate resistance to falciparum malaria, but also cause hemoglobinopathies. These genetic traits—including hemoglobin S (HbS), hemoglobin C (HbC), and ?-thalassemia—are the most common monogenic human disorders and can confer remarkable degrees of protection from severe, life-threatening falciparum malaria in African children: the risk is reduced 70% by homozygous HbC and 90% by heterozygous HbS (sickle-cell trait). Importantly, this protection is principally present for severe disease and largely absent for P. falciparum infection, suggesting that these hemoglobinopathies specifically neutralize the parasite's in vivo mechanisms of pathogenesis. These hemoglobin variants thus represent a “natural experiment” to identify the cellular and molecular mechanisms by which P. falciparum produces clinical morbidity, which remain partially obscured due to the complexity of interactions between this parasite and its human host. Multiple lines of evidence support a restriction of parasite growth by various hemoglobinopathies, and recent data suggest this phenomenon may result from host microRNA interference with parasite metabolism. Multiple hemoglobinopathies mitigate the pathogenic potential of parasites by interfering with the export of P. falciparum erythrocyte membrane protein 1 (PfEMP1) to the surface of the host red blood cell. Few studies have investigated their effects upon the activation of the innate and adaptive immune systems, although recent murine studies suggest a role for heme oxygenase-1 in protection. Ultimately, the identification of mechanisms of protection and pathogenesis can inform future therapeutics and preventive measures. Hemoglobinopathies slice the “Gordian knot” of host and parasite interactions to confer malaria protection, and offer a translational model to identify the most critical mechanisms of P. falciparum pathogenesis. PMID:23696730

Taylor, Steve M.; Cerami, Carla; Fairhurst, Rick M.

2013-01-01

383

Parasite Sleuth  

NSDL National Science Digital Library

In this activity (on pages 26-33), learners play parasitologists, solving several "mysteries" about people who got sick from various parasites. In teams of four, each member solves one mystery. They highlight clues in the reading, identify and glue down "Clue Cards" that summarize the clues, and choose and glue down the "Parasite I.D. Card" so that it can be folded to hide the answer. Learners then trade mysteries, and can solve and check their solution. Older learners or more advanced readers can do this activity on their own, while an educator can read it aloud to younger learners.

Museum, University O.; Nebraska Cooperative Extension 4-H Youth Development

2001-01-01

384

Widespread and structured distributions of blood parasite haplotypes across a migratory divide of the Swainson's thrush (Catharus ustulatus).  

PubMed

We examined the phylogenetic distribution of cytochrome b haplotypes of the avian blood parasite genera Haemoproteus and Plasmodium across the migratory divide of the Swainson's thrush (Catharus ustulatus) in British Columbia, Canada. From 87 host individuals, we identified 8 parasite haplotypes; 4 of Plasmodium and 4 of Haemoproteus. Six haplotypes were novel; 1 Haemoproteus haplotype was identical to H. majoris found in the blue tit (Parus caeruleus) in Sweden, and another halotype was identical to a Plasmodium haplotype found in the white-crowned sparrow (Zonotrichia leucophrys) in Oregon. The 2 most abundant parasite haplotypes were widely distributed across the contact zone, whereas 2 other parasite haplotypes seem to have structured distributions. Compared with 74 Plasmodium and Haemoproteus haplotypes published in GenBank, haplotypes recovered from Swainson's thrushes do not form monophyletic groups, and they are closely related to haplotypes from a variety of other hosts and localities. In addition, we recovered 2 Swainson's thrush Plasmodium haplotypes from the nonmigratory orange-billed nightingale thrush (Catharus aurantiirostris) in Costa Rica. This study is the first to elucidate avian blood parasite transmission, distribution, and phylogenetic relationships in an avian contact zone in North America. PMID:18314697

Svensson, L M E; Ruegg, K C; Sekercioglu, C H; Sehgal, R N M

2007-12-01

385

Morphogenesis of Plasmodium zoites is uncoupled from tensile strength  

PubMed Central

A shared feature of the motile stages (zoites) of malaria parasites is a cortical cytoskeletal structure termed subpellicular network (SPN), thought to define and maintain cell shape. Plasmodium alveolins comprise structural components of the SPN, and alveolin gene knockout causes morphological abnormalities that coincide with markedly reduced tensile strength of the affected zoites, indicating the alveolins are prime cell shape determinants. Here, we characterize a novel SPN protein of Plasmodium berghei ookinetes and sporozoites named G2 (glycine at position 2), which is structurally unrelated to alveolins. G2 knockout abolishes parasite transmission and causes zoite malformations and motility defects similar to those observed in alveolin null mutants. Unlike alveolins, however, G2 contributes little to tensile strength, arguing against a cause-effect relationship between tensile strength and cell shape. We also show that G2 null mutant sporozoites display an abnormal arrangement of their subpellicular microtubules. These results provide important new understanding of the factors that determine zoite morphogenesis, as well as the potential roles of the cortical cytoskeleton in gliding motility. PMID:23773015

Tremp, Annie Z; Carter, Victoria; Saeed, Sadia; Dessens, Johannes T

2013-01-01

386

Carotenoid Biosynthesis in Intraerythrocytic Stages of Plasmodium falciparum*S?  

PubMed Central

Carotenoids are widespread lipophilic pigments synthesized by all photosynthetic organisms and some nonphotosynthetic fungi and bacteria. All carotenoids are derived from the C40 isoprenoid precursor geranylgeranyl pyrophosphate, and their chemical and physical properties are associated with light absorption, free radical scavenging, and antioxidant activity. Carotenoids are generally synthesized in well defined subcellular organelles, the plastids, which are also present in the phylum Apicomplexa, which comprises a number of important human parasites, such as Plasmodium and Toxoplasma. Recently, it was demonstrated that Toxoplasma gondii synthesizes abscisic acid. We therefore asked if Plasmodium falciparum is also capable of synthesizing carotenoids. Herein, biochemical findings demonstrated the presence of carotenoid biosynthesis in the intraerythrocytic stages of the apicomplexan parasite P. falciparum. Using metabolic labeling with radioisotopes, in vitro inhibition tests with norflurazon, a specific inhibitor of plant carotenoid biosynthesis, the results showed that intraerythrocytic stages of P. falciparum synthesize carotenoid compounds. A plasmodial enzyme that presented phytoene synthase activity was also identified and characterized. These findings not only contribute to the current understanding of P. falciparum evolution but shed light on a pathway that could serve as a chemotherapeutic target. PMID:19203994

Tonhosolo, Renata; D'Alexandri, Fabio L.; de Rosso, Veridiana V.; Gazarini, Marcos L.; Matsumura, Miriam Y.; Peres, Valnice J.; Merino, Emilio F.; Carlton, Jane M.; Wunderlich, Gerhard; Mercadante, Adriana Z.; Kimura, Emília A.; Katzin, Alejandro M.

2009-01-01

387

Deformability of Plasmodium falciparum parasitized red blood cells  

E-print Network

The biophysical properties of the human red blood cell (RBC) permit large deformations required for passage through narrow capillaries and spleen sinusoids. Several pathologic conditions alter RBC deformability that can ...

Mills, John Philip, Ph. D. Massachusetts Institute of Technology

2007-01-01

388

Comparative genomics of the neglected human malaria parasite Plasmodium vivax  

E-print Network

biological features, and as a means to drive development of new drugs and vaccines. Here we describe the scientific community with a valuable resource that can be used to advance investigation into this neglected, vivax malaria traps many societies in a relentless cycle of poverty. Intermittent transmission makes

Cai, Long

389

Genome-Wide Patterns of Genetic Polymorphism and Signatures of Selection in Plasmodium vivax  

PubMed Central

Plasmodium vivax is the most prevalent human malaria parasite outside of Africa. Yet, studies aimed to identify genes with signatures consistent with natural selection are rare. Here, we present a comparative analysis of the pattern of genetic variation of five sequenced isolates of P. vivax and its divergence with two closely related species, Plasmodium cynomolgi and Plasmodium knowlesi, using a set of orthologous genes. In contrast to Plasmodium falciparum, the parasite that causes the most lethal form of human malaria, we did not find significant constraints on the evolution of synonymous sites genome wide in P. vivax. The comparative analysis of polymorphism and divergence across loci allowed us to identify 87 genes with patterns consistent with positive selection, including genes involved in the “exportome” of P. vivax, which are potentially involved in evasion of the host immune system. Nevertheless, we have found a pattern of polymorphism genome wide that is consistent with a significant amount of constraint on the replacement changes and prevalent negative selection. Our analyses also show that silent polymorphism tends to be larger toward the ends of the chromosomes, where many genes involved in antigenicity are located, suggesting that natural selection acts not only by shaping the patterns of variation within the genes but it also affects genome organization. PMID:25523904

Cornejo, Omar E.; Fisher, David; Escalante, Ananias A.

2015-01-01

390

Glycophorin B is the erythrocyte receptor of Plasmodium falciparum erythrocyte-binding ligand, EBL-1  

PubMed Central

In the war against Plasmodium, humans have evolved to eliminate or modify proteins on the erythrocyte surface that serve as receptors for parasite invasion, such as the Duffy blood group, a receptor for Plasmodium vivax, and the Gerbich-negative modification of glycophorin C for Plasmodium falciparum. In turn, the parasite counters with expansion and diversification of ligand families. The high degree of polymorphism in glycophorin B found in malaria-endemic regions suggests that it also may be a receptor for Plasmodium, but, to date, none has been identified. We provide evidence from erythrocyte-binding that glycophorin B is a receptor for the P. falciparum protein EBL-1, a member of the Duffy-binding-like erythrocyte-binding protein (DBL-EBP) receptor family. The erythrocyte-binding domain, region 2 of EBL-1, expressed on CHO-K1 cells, bound glycophorin B+ but not glycophorin B-null erythrocytes. In addition, glycophorin B+ but not glycophorin B-null erythrocytes adsorbed native EBL-1 from the P. falciparum culture supernatants. Interestingly, the Efe pygmies of the Ituri forest in the Democratic Republic of the Congo have the highest gene frequency of glycophorin B-null in the world, raising the possibility that the DBL-EBP family may have expanded in response to the high frequency of glycophorin B-null in the population. PMID:19279206

Mayer, D. C. Ghislaine; Cofie, Joann; Jiang, Lubin; Hartl, Daniel L.; Tracy, Erin; Kabat, Juraj; Mendoza, Laurence H.; Miller, Louis H.

2009-01-01

391

Distinct temporal recruitment of Plasmodium alveolins to the subpellicular network.  

PubMed

The zoite stages of malaria parasites (merozoite, ookinete and sporozoite) possess a distinctive cortical structure termed the pellicle, which is defined by a double membrane layer named the inner membrane complex (IMC). The IMC is supported by a cytoskeleton of intermediate filaments, termed the subpellicular network (SPN). Plasmodium IMC1 proteins, or alveolins, make up a conserved family of structurally related proteins that comprise building blocks of the SPN. Here, using green fluorescent protein (GFP) tagging in P. berghei, we show that the alveolins PbIMC1c and PbIMC1e are expressed in all three zoite stages. Our data reveal that PbIMC1e is assembled into the SPN concurrent with pellicle development, while PbIMC1c is assembled after pellicle formation. In the sexual stages, these processes are accompanied by different gene expressions from maternal and paternal alleles: PbIMC1e is expressed uniquely from the maternal allele, while PbIMC1c is expressed from the maternal allele in gametocytes, but from both parental alleles during ookinete development. These findings establish biogenesis of the cortical cytoskeleton in Plasmodium to be a complex and dynamic process, involving distinct parental gene expression and chronological recruitment of its protein constituents. While allelic replacement of the pbimc1c and pbimc1e genes with GFP-tagged versions was readily achieved using double crossover homologous recombination, attempts to disrupt these genes by this strategy only resulted in the integration of the selectable marker and GFP reporter into non-specific genomic locations. The recurrent inability to disrupt these genes provides the first genetic evidence that alveolins are necessary for asexual blood-stage parasite development in Plasmodium. PMID:25185663

Tremp, Annie Z; Al-Khattaf, Fatimah S; Dessens, Johannes T

2014-11-01

392

Human Plasmodium knowlesi infection in Ranong province, southwestern border of Thailand  

PubMed Central

Background Plasmodium knowlesi, a simian malaria parasite, has been reported in humans in many Southeast Asian countries. In Thailand, most of the limited numbers of cases reported so far were from areas near neighbouring countries, including Myanmar. Methods Blood samples collected from 171 Thai and 248 Myanmese patients attending a malaria clinic in Ranong province, Thailand, located near the Myanmar border were investigated for P. knowlesi using nested PCR assays. Positive samples were also investigated by PCR for Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium ovale, and were confirmed by sequencing the gene encoding the circumsporozoite protein (csp). Results Two samples, one obtained from a Thai and the other a Myanmese, were positive for P. knowlesi only. Nucleotide sequences of the csp gene derived from these two patients were identical and phylogenetically indistinguishable from other P. knowlesi sequences derived from monkeys and humans. Both patients worked in Koh Song, located in the Kawthoung district of Myanmar, which borders Thailand. Conclusion This study indicates that transmission of P. knowlesi is occurring in the Ranong province of Thailand or the Kawthoung district of Myanmar. Further studies are required to assess the incidence of knowlesi malaria and whether macaques in these areas are the source of the infections. PMID:22313518

2012-01-01

393

MicroRNA-regulation of Anopheles gambiae immunity to Plasmodium falciparum infection and midgut microbiota.  

PubMed

Invasion of the malaria vector Anopheles gambiae midgut by Plasmodium parasites triggers transcriptional changes of immune genes that mediate the antiparasitic defense. This response is largely regulated by the Toll and Immune deficiency (IMD) pathways. To determine whether A.?gambiae microRNAs (miRNAs) are involved in regulating the anti-Plasmodium defense, we showed that suppression of miRNA biogenesis results in increased resistance to Plasmodium falciparum infection. In silico analysis of A.?gambiae immune effector genes identified multiple transcripts with miRNA binding sites. A comparative miRNA microarray abundance analysis of P.?falciparum infected and naïve mosquito midgut tissues showed elevated abundance of miRNAs aga-miR-989 and aga-miR-305 in infected midguts. Antagomir inhibition of aga-miR-305 increased resistance to P.?falciparum infection and suppressed the midgut microbiota. Conversely, treatment of mosquitoes with an artificial aga-miR-305 mimic increased susceptibility to P.?falciparum infection and resulted in expansion of midgut microbiota, suggesting that aga-miR-305 acts as a P.?falciparum and gut microbiota agonist by negatively regulating the mosquito immune response. In silico prediction of aga-miR-305 target genes identified several anti-Plasmodium effectors. Our study shows that A.?gambiae aga-miR-305 regulates the anti-Plasmodium response and midgut microbiota, likely through post-transcriptional modification of immune effector genes. PMID:25445902

Dennison, Nathan J; BenMarzouk-Hidalgo, Omar J; Dimopoulos, George

2015-03-01

394

Detection of avian malaria (Plasmodium spp.) in native land birds of American Samoa  

USGS Publications Warehouse

This study documents the presence of Plasmodium spp. in landbirds of central Polynesia. Blood samples collected from eight native and introduced species from the island of Tutuila, American Samoa were evaluated for the presence of Plasmodium spp. by nested rDNA PCR, serology and/or microscopy. A total of 111/188 birds (59%) screened by nested PCR were positive. Detection of Plasmodium spp. was verified by nucleotide sequence comparisons of partial 18S ribosomal RNA and TRAP (thrombospondin-related anonymous protein) genes using phylogenetic analyses. All samples screened by immunoblot to detect antibodies that cross-react with Hawaiian isolates of Plasmodium relictum (153) were negative. Lack of cross-reactivity is probably due to antigenic differences between the Hawaiian and Samoan Plasmodium isolates. Similarly, all samples examined by microscopy (214) were negative. The fact that malaria is present, but not detectable by blood smear evaluation is consistent with low peripheral parasitemia characteristic of chronic infections. High prevalence of apparently chronic infections, the relative stability of the native land bird communities, and the presence of mosquito vectors which are considered endemic and capable of transmitting avian Plasmodia, suggest that these parasites are indigenous to Samoa and have a long coevolutionary history with their hosts.

Jarvi, S.I.; Farias, M.E.M.; Baker, H.; Freifeld, H.B.; Baker, P.E.; Van Gelder, E.; Massey, J.G.; Atkinson, C.T.

2003-01-01

395

EVIDENCE FOR TRANSMISSION OF PLASMODIUM VIVAX AMONG A DUFFY ANTIGEN NEGATIVE POPULATION IN WESTERN KENYA  

Microsoft Academic Search

We present evidence that a parasite with characteristics of Plasmodium vivax is being transmitted among Duffy blood group-negative inhabitants of Kenya. Thirty-two of 4,901 Anopheles gambiae and An. funestus (0.65%) collected in Nyanza Province were ELISA positive for the P. vivax circumsporozoite protein VK 247. All positives were found late in the rainy season, when An. funestus predominated, and disproportionately

JEFFREY R. RYAN; JOSÉ A. STOUTE; JOSEPH AMON; RAYMOND F. DUNTON; RAMADHAN MTALIB; JOSEPH KOROS; BOAZ OWOUR; SHIRLEY LUCKHART; ROBERT A. WIRTZ; JOHN W. BARNWELL; RONALD ROSENBERG

2006-01-01

396

Plasmodium vivax Invasion of Human Erythrocytes Inhibited by Antibodies Directed against the Duffy Binding Protein  

Microsoft Academic Search

BackgroundPlasmodium vivax invasion requires interaction between the human Duffy antigen on the surface of erythrocytes and the P. vivax Duffy binding protein (PvDBP) expressed by the parasite. Given that Duffy-negative individuals are resistant and that Duffy-negative heterozygotes show reduced susceptibility to blood-stage infection, we hypothesized that antibodies directed against region two of P. vivax Duffy binding protein (PvDBPII) would inhibit

Brian T Grimberg; Rachanee Udomsangpetch; Jia Xainli; Amy McHenry; Tasanee Panichakul; Jetsumon Sattabongkot; Liwang Cui; Moses Bockarie; Chetan Chitnis; John Adams; Peter A Zimmerman; Christopher L King

2007-01-01

397

Membrane-associated phosphoproteins in Plasmodium berghei-infected murine erythrocytes  

Microsoft Academic Search

Normal and Plasmodium berghei (NYU-2 strain)-infected murine erythrocytes dis- play substantially different patterns of plasma membrane phosphoproteins phosphorylation. Intact erythrocytes (normal and parasite infected) incubated with 32p~ and isolated washed erythrocyte plasma membranes incubated with ~,-32P-ATP were analyzed for phosphoproteins by SDS PAGE and autoradiography. Two new phosphoproteins of molecular weight 45,000 (pp45) and 68,000 (pp68), which are absent in

MARK F. WISER; PATRICIA A. WOOD; JOHN W. EATON; J. R. SHEPPARD

1983-01-01

398

Plasmodium falciparum Histone Acetyltransferase, a Yeast GCN5 Homologue Involved in Chromatin Remodeling  

Microsoft Academic Search

The yeast transcriptional coactivator GCN5 (yGCN5), a histone acetyltransferase (HAT), is part of large multimeric complexes that are required for chromatin remodeling and transcriptional activation. Like other eukaryotes, the malaria parasite DNA is organized into nucleosomes and the genome encodes components of chromatin-remodeling complexes. Here we show that GCN5 is conserved in Plasmodium species and that the most homologous regions

Qi Fan; Lijia An; Liwang Cui

2004-01-01

399

Acute respiratory distress syndrome and acute renal failure from Plasmodium ovale infection with fatal outcome  

PubMed Central

Background Plasmodium ovale is one of the causative agents of human malaria. Plasmodium ovale infection has long been thought to be non-fatal. Due to its lower morbidity, P. ovale receives little attention in malaria research. Methods Two Malaysians went to Nigeria for two weeks. After returning to Malaysia, they fell sick and were admitted to different hospitals. Plasmodium ovale parasites were identified from blood smears of these patients. The species identification was further confirmed with nested PCR. One of them was successfully treated with no incident of relapse within 12-month medical follow-up. The other patient came down with malaria-induced respiratory complication during the course of treatment. Although parasites were cleared off the circulation, the patient’s condition worsened. He succumbed to multiple complications including acute respiratory distress syndrome and acute renal failure. Results Sequencing of the malaria parasite DNA from both cases, followed by multiple sequence alignment and phylogenetic tree construction suggested that the causative agent for both malaria cases was P. ovale curtisi. Discussion In this report, the differences between both cases were discussed, and the potential capability of P. ovale in causing severe complications and death as seen in this case report was highlighted. Conclusion Plasmodium ovale is potentially capable of causing severe complications, if not death. Complete travel and clinical history of malaria patient are vital for successful diagnoses and treatment. Monitoring of respiratory and renal function of malaria patients, regardless of the species of malaria parasites involved is crucial during the course of hospital admission. PMID:24180319

2013-01-01

400

Design, Synthesis, and Evaluation of 10-N-Substituted Acridones as Novel Chemosensitizers in Plasmodium falciparum  

Microsoft Academic Search

A series of novel 10-N-substituted acridones, bearing alkyl side chains with tertiary amine groups at the terminal position, were designed, synthesized, and evaluated for the ability to enhance the potency of quinoline drugs against multidrug-resistant (MDR) Plasmodium falciparum malaria parasites. A number of acridone derivatives, with side chains bridged three or more carbon atoms apart between the ring nitrogen and

Jane X. Kelly; Martin J. Smilkstein; Roland A. Cooper; Robert A. Johnson; Aaron Janowsky; Rozalia A. Dodean; David J. Hinrichs; Rolf Winter; Michael Riscoe

2007-01-01

401

Comparative evaluation of four techniques for the diagnosis of Plasmodium falciparum infections  

Microsoft Academic Search

Four diagnostic techniques for Plasmodium falciparum infection were evaluated against serial parasite dilutions and on identical field samples. These were (i) Giemsa-stained thick blood films (GTF), (ii) acridine orange-stained thick (AOTF) and thin (AOTnF) blood films, (iii) the quantitative buffy coat technique (QBC®); and (iv) the ParaSight TM-F dipstick test (PS). PS had a consistently higher sensitivity and speed, was

Marlies H. Craig; Brian L. Sharp

1997-01-01

402

Cerebral Edema and Cerebral Hemorrhages in Interleukin-10-Deficient Mice Infected with Plasmodium chabaudi  

PubMed Central

During a Plasmodium chabaudi infection in interleukin-10 (IL-10) knockout mice, there is greater parasite sequestration, more severe cerebral edema, and a high frequency of cerebral hemorrhage compared with infection of C57BL/6 mice. Anti-tumor necrosis factor alpha treatment ameliorated both cerebral edema and hemorrhages, suggesting that proinflammatory responses contributed to cerebral complications in infected IL-10?/? mice. PMID:15102820

Sanni, Latifu A.; Jarra, William; Li, Ching; Langhorne, Jean

2004-01-01

403

Sequence of Plasmodium falciparum chromosomes 1, 3-9 and 13  

Microsoft Academic Search

Since the sequencing of the first two chromosomes of the malaria parasite, Plasmodium falciparum, there has been a concerted effort to sequence and assemble the entire genome of this organism. Here we report the sequence of chromosomes 1, 3-9 and 13 of P. falciparum clone 3D7-these chromosomes account for approximately 55% of the to