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Sample records for plasmodium falciparum transcriptome

  1. Interactive transcriptome analysis of malaria patients and infecting Plasmodium falciparum

    PubMed Central

    Yamagishi, Junya; Natori, Anna; Tolba, Mohammed E.M.; Mongan, Arthur E.; Sugimoto, Chihiro; Katayama, Toshiaki; Kawashima, Shuichi; Makalowski, Wojciech; Maeda, Ryuichiro; Eshita, Yuki; Tuda, Josef

    2014-01-01

    To understand the molecular mechanisms of parasitism in vivo, it is essential to elucidate how the transcriptomes of the human hosts and the infecting parasites affect one another. Here we report the RNA-seq analysis of 116 Indonesian patients infected with the malaria parasite Plasmodium falciparum (Pf). We extracted RNAs from their peripheral blood as a mixture of host and parasite transcripts and mapped the RNA-seq tags to the human and Pf reference genomes to separate the respective tags. We were thus able to simultaneously analyze expression patterns in both humans and parasites. We identified human and parasite genes and pathways that correlated with various clinical data, which may serve as primary targets for drug developments. Of particular importance, we revealed characteristic expression changes in the human innate immune response pathway genes including TLR2 and TICAM2 that correlated with the severity of the malaria infection. We also found a group of transcription regulatory factors, JUND, for example, and signaling molecules, TNFAIP3, for example, that were strongly correlated in the expression patterns of humans and parasites. We also identified several genetic variations in important anti-malaria drug resistance-related genes. Furthermore, we identified the genetic variations which are potentially associated with severe malaria symptoms both in humans and parasites. The newly generated data should collectively lay a unique foundation for understanding variable behaviors of the field malaria parasites, which are far more complex than those observed under laboratory conditions. PMID:25091627

  2. Global response of Plasmodium falciparum to hyperoxia: a combined transcriptomic and proteomic approach

    PubMed Central

    2011-01-01

    Background Over its life cycle, the Plasmodium falciparum parasite is exposed to different environmental conditions, particularly to variations in O2 pressure. For example, the parasite circulates in human venous blood at 5% O2 pressure and in arterial blood, particularly in the lungs, at 13% O2 pressure. Moreover, the parasite is exposed to 21% O2 levels in the salivary glands of mosquitoes. Methods To study the metabolic adaptation of P. falciparum to different oxygen pressures during the intraerythrocytic cycle, a combined approach using transcriptomic and proteomic techniques was undertaken. Results Even though hyperoxia lengthens the parasitic cycle, significant transcriptional changes were detected in hyperoxic conditions in the late-ring stage. Using PS 6.0™ software (Ariadne Genomics) for microarray analysis, this study demonstrate up-expression of genes involved in antioxidant systems and down-expression of genes involved in the digestive vacuole metabolism and the glycolysis in favour of mitochondrial respiration. Proteomic analysis revealed increased levels of heat shock proteins, and decreased levels of glycolytic enzymes. Some of this regulation reflected post-transcriptional modifications during the hyperoxia response. Conclusions These results seem to indicate that hyperoxia activates antioxidant defence systems in parasites to preserve the integrity of its cellular structures. Moreover, environmental constraints seem to induce an energetic metabolism adaptation of P. falciparum. This study provides a better understanding of the adaptive capabilities of P. falciparum to environmental changes and may lead to the development of novel therapeutic targets. PMID:21223545

  3. A cross strain Plasmodium falciparum microarray optimized for the transcriptome analysis of Plasmodium falciparum patient derived isolates.

    PubMed

    Subudhi, Amit Kumar; Boopathi, P A; Middha, Sheetal; Acharya, Jyoti; Rao, Sudha Narayana; Mugasimangalam, Raja C; Sirohi, Paramendra; Kochar, Sanjay K; Kochar, Dhanpat K; Das, Ashis

    2016-09-01

    Malarial parasite P. falciparum, an apicomplexan protozoan has a 23.3 MB nuclear genome and encodes ~ 5600 transcripts. The genetic diversity of the parasite within and across geographical zones is a challenge to gene expression studies which are essential for understanding of disease process, outcome and developing markers for diagnostics and prognostics. Here, we describe the strategy involved in designing a custom P. falciparum 15K array using the Agilent platform and Genotypic's Right Design methodology to study the transcriptome of Indian field isolates for which genome sequence information is limited. The array contains probes representing genome sequences of two distinct geographical isolates (i.e. 3D7 and HB3) and sub-telomeric var gene sequences of a third isolate (IT4) known to adhere in culture condition. Probes in the array have been selected based on their efficiency to detect transcripts through a 244K array experimentation. Array performance for the 15K array, was evaluated and validated using RNA materials from P. falciparum clinical isolates. A large percentage (91%) of the represented transcripts was detected from Indian P. falciparum patient isolates. Replicated probes and multiple probes representing the same gene showed perfect correlation between them suggesting good probe performance. Additional transcripts could be detected due to inclusion of unique probes representing HB3 strain transcripts. Variant surface antigen (VSA) transcripts were detected by optimized probes representing the VSA genes of three geographically distinct strains. The 15K cross strain P. falciparum array has shown good efficiency in detecting transcripts from P. falciparum parasite samples isolated from patients. The low parasite loads and presence of host RNA makes arrays a preferred platform for gene expression studies over RNA-Seq. PMID:27489776

  4. Transcriptomic evidence for modulation of host inflammatory responses during febrile Plasmodium falciparum malaria

    PubMed Central

    Tran, Tuan M.; Jones, Marcus B.; Ongoiba, Aissata; Bijker, Else M.; Schats, Remko; Venepally, Pratap; Skinner, Jeff; Doumbo, Safiatou; Quinten, Edwin; Visser, Leo G.; Whalen, Elizabeth; Presnell, Scott; O’Connell, Elise M.; Kayentao, Kassoum; Doumbo, Ogobara K.; Chaussabel, Damien; Lorenzi, Hernan; Nutman, Thomas B.; Ottenhoff, Tom H. M.; Haks, Mariëlle C.; Traore, Boubacar; Kirkness, Ewen F.; Sauerwein, Robert W.; Crompton, Peter D.

    2016-01-01

    Identifying molecular predictors and mechanisms of malaria disease is important for understanding how Plasmodium falciparum malaria is controlled. Transcriptomic studies in humans have so far been limited to retrospective analysis of blood samples from clinical cases. In this prospective, proof-of-principle study, we compared whole-blood RNA-seq profiles at pre-and post-infection time points from Malian adults who were either asymptomatic (n = 5) or febrile (n = 3) during their first seasonal PCR-positive P. falciparum infection with those from malaria-naïve Dutch adults after a single controlled human malaria infection (n = 5). Our data show a graded activation of pathways downstream of pro-inflammatory cytokines, with the highest activation in malaria-naïve Dutch individuals and significantly reduced activation in malaria-experienced Malians. Newly febrile and asymptomatic infections in Malians were statistically indistinguishable except for genes activated by pro-inflammatory cytokines. The combined data provide a molecular basis for the development of a pyrogenic threshold as individuals acquire immunity to clinical malaria. PMID:27506615

  5. Transcriptomic evidence for modulation of host inflammatory responses during febrile Plasmodium falciparum malaria.

    PubMed

    Tran, Tuan M; Jones, Marcus B; Ongoiba, Aissata; Bijker, Else M; Schats, Remko; Venepally, Pratap; Skinner, Jeff; Doumbo, Safiatou; Quinten, Edwin; Visser, Leo G; Whalen, Elizabeth; Presnell, Scott; O'Connell, Elise M; Kayentao, Kassoum; Doumbo, Ogobara K; Chaussabel, Damien; Lorenzi, Hernan; Nutman, Thomas B; Ottenhoff, Tom H M; Haks, Mariëlle C; Traore, Boubacar; Kirkness, Ewen F; Sauerwein, Robert W; Crompton, Peter D

    2016-01-01

    Identifying molecular predictors and mechanisms of malaria disease is important for understanding how Plasmodium falciparum malaria is controlled. Transcriptomic studies in humans have so far been limited to retrospective analysis of blood samples from clinical cases. In this prospective, proof-of-principle study, we compared whole-blood RNA-seq profiles at pre-and post-infection time points from Malian adults who were either asymptomatic (n = 5) or febrile (n = 3) during their first seasonal PCR-positive P. falciparum infection with those from malaria-naïve Dutch adults after a single controlled human malaria infection (n = 5). Our data show a graded activation of pathways downstream of pro-inflammatory cytokines, with the highest activation in malaria-naïve Dutch individuals and significantly reduced activation in malaria-experienced Malians. Newly febrile and asymptomatic infections in Malians were statistically indistinguishable except for genes activated by pro-inflammatory cytokines. The combined data provide a molecular basis for the development of a pyrogenic threshold as individuals acquire immunity to clinical malaria. PMID:27506615

  6. Whole transcriptome expression analysis and comparison of two different strains of Plasmodium falciparum using RNA-Seq.

    PubMed

    Antony, Hiasindh Ashmi; Pathak, Vrushali; Parija, Subhash Chandra; Ghosh, Kanjaksha; Bhattacherjee, Amrita

    2016-06-01

    The emergence and distribution of drug resistance in malaria are serious public health concerns in tropical and subtropical regions of the world. However, the molecular mechanism of drug resistance remains unclear. In the present study, we performed a high-throughput RNA-Seq to identify and characterize the differentially expressed genes between the chloroquine (CQ) sensitive (3D7) and resistant (Dd2) strains of Plasmodium falciparum. The parasite cells were cultured in the presence and absence of CQ by in vitro method. Total RNA was isolated from the harvested parasite cells using TRIzol, and RNA-Seq was conducted using an Illumina HiSeq 2500 sequencing platform with paired-end reads and annotated using Tophat. The transcriptome analysis of P. falciparum revealed the expression of ~ 5000 genes, in which ~ 60% of the genes have unknown function. Cuffdiff program was used to identify the differentially expressed genes between the CQ-sensitive and resistant strains. Here, we furnish a detailed description of the experimental design, procedure, and analysis of the transcriptome sequencing data, that have been deposited in the National Center for Biotechnology Information (accession nos. PRJNA308455 and GSE77499). PMID:27222812

  7. Isoprenoid Biosynthesis in Plasmodium falciparum

    PubMed Central

    Guggisberg, Ann M.; Amthor, Rachel E.

    2014-01-01

    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

  8. Transcriptomic Analysis of Chloroquine-Sensitive and Chloroquine-Resistant Strains of Plasmodium falciparum: Toward Malaria Diagnostics and Therapeutics for Global Health.

    PubMed

    Antony, Hiasindh Ashmi; Pathak, Vrushali; Parija, Subhash Chandra; Ghosh, Kanjaksha; Bhattacherjee, Amrita

    2016-07-01

    Increasing drug resistance in Plasmodium falciparum is an important global health burden because it reverses the malarial control achieved so far. Hence, understanding the molecular mechanisms of drug resistance is the epicenter of the development agenda for novel diagnostic and therapeutic (drugs/vaccines) targets for malaria. In this study, we report global comparative transcriptome profiling (RNA-Seq) to characterize the difference in the transcriptome between 48-h intraerythrocytic stage of chloroquine-sensitive and chloroquine-resistant P. falciparum (3D7 and Dd2) strains. The two P. falciparum 3D7 and Dd2 strains have distant geographical origin, the Netherlands and Indochina, respectively. The strains were cultured by an in vitro method and harvested at the 48-h intraerythrocytic stage having 5% parasitemia. The whole transcriptome sequencing was performed using Illumina HiSeq 2500 platform with paired-end reads. The reads were aligned with the reference P. falciparum genome. The alignment percentages for 3D7, Dd2, and Dd2 w/CQ strains were 85.40%, 89.13%, and 84%, respectively. Nearly 40% of the transcripts had known gene function, whereas the remaining genes (about 60%) had unknown function. The genes involved in immune evasion showed a significant difference between the strains. The differential gene expression between the sensitive and resistant strains was measured using the cuffdiff program with the p-value cutoff ≤0.05. Collectively, this study identified differentially expressed genes between 3D7 and Dd2 strains, where we found 89 genes to be upregulated and 227 to be downregulated. On the contrary, for 3D7 and Dd2 w/CQ strains, 45 genes were upregulated and 409 were downregulated. These differentially regulated genes code, by and large, for surface antigens involved in invasion, pathogenesis, and host-parasite interactions, among others. The exhibition of transcriptional differences between these strains of P. falciparum contributes to our

  9. Changes in the transcriptome of the malaria parasite Plasmodium falciparum during the initial phase of transmission from the human to the mosquito

    PubMed Central

    2013-01-01

    Background The transmission of the malaria parasite Plasmodium falciparum from the human to the mosquito is mediated by dormant sexual precursor cells, the gametocytes, which become activated in the mosquito midgut. Because gametocytes are the only parasite stages able to establish an infection in the mosquito, they play a crucial role in spreading the tropical disease. The human-to-mosquito transmission triggers important molecular changes in the gametocytes, which initiate gametogenesis and prepare the parasite for life-cycle progression in the insect vector. Results To better understand gene regulations during the initial phase of malaria parasite transmission, we focused on the transcriptome changes that occur within the first half hour of parasite development in the mosquito. Comparison of mRNA levels of P. falciparum gametocytes before and 30 min following activation using suppression subtractive hybridization (SSH) identified 126 genes, which changed in expression during gametogenesis. Among these, 17.5% had putative functions in signaling, 14.3% were assigned to cell cycle and gene expression, 8.7% were linked to the cytoskeleton or inner membrane complex, 7.9% were involved in proteostasis and 6.4% in metabolism, 12.7% were cell surface-associated proteins, 11.9% were assigned to other functions, and 20.6% represented genes of unknown function. For 40% of the identified genes there has as yet not been any protein evidence. For a subset of 27 genes, transcript changes during gametogenesis were studied in detail by real-time RT-PCR. Of these, 22 genes were expressed in gametocytes, and for 15 genes transcript expression in gametocytes was increased compared to asexual blood stage parasites. Transcript levels of seven genes were particularly high in activated gametocytes, pointing at functions downstream of gametocyte transmission to the mosquito. For selected genes, a regulated expression during gametogenesis was confirmed on the protein level, using

  10. Plasmodium falciparum: attenuation by irradiation

    SciTech Connect

    Waki, S.; Yonome, I.; Suzuki, M.

    1983-12-01

    The effect of irradiation on the in vitro growth of Plasmodium falciparum was investigated. The cultured malarial parasites at selected stages of development were exposed to gamma rays and the sensitivity of each stage was determined. The stages most sensitive to irradiation were the ring forms and the early trophozoites; late trophozoites were relatively insensitive. The greatest resistance was shown when parasites were irradiated at a time of transition from the late trophozoite and schizont stages to young ring forms. The characteristics of radiosensitive variation in the parasite cycle resembled that of mammalian cells. Growth curves of parasites exposed to doses of irradiation upto 150 gray had the same slope as nonirradiated controls but parasites which were exposed to 200 gray exhibited a growth curve which was less steep than that for parasites in other groups. Less than 10 organisms survived from the 10(6) parasites exposed to this high dose of irradiation; the possibility exists of obtaining radiation-attenuated P. falciparum.

  11. Detectability of Plasmodium falciparum clones

    PubMed Central

    2010-01-01

    Background In areas of high transmission people often harbour multiple clones of Plasmodium falciparum, but even PCR-based diagnostic methods can only detect a fraction (the detectability, q) of all clones present in a host. Accurate measurements of detectability are desirable since it affects estimates of multiplicity of infection, prevalence, and frequency of breakthrough infections in clinical drug trials. Detectability can be estimated by typing repeated samples from the same host but it has been unclear what should be the time interval between the samples and how the data should be analysed. Methods A longitudinal molecular study was conducted in the Kassena-Nankana district in northern Ghana. From each of the 80 participants, four finger prick samples were collected over a period of 8 days, and tested for presence of different Merozoite Surface Protein (msp) 2 genotypes. Implications for estimating q were derived from these data by comparing the fit of statistical models of serial dependence and over-dispersion. Results The distribution of the frequencies of detection for msp2 genotypes was close to binomial if the time span between consecutive blood samples was at least 7 days. For shorter intervals the probabilities of detection were positively correlated, i.e. the shorter the interval between two blood collections, the more likely the diagnostic results matched for a particular genotype. Estimates of q were rather insensitive to the statistical model fitted. Conclusions A simple algorithm based on analysing blood samples collected 7 days apart is justified for generating robust estimates of detectability. The finding of positive correlation of detection probabilities for short time intervals argues against imperfect detection being directly linked to the 48-hour periodicity of P. falciparum. The results suggest that the detectability of a given parasite clone changes over time, at an unknown rate, but fast enough to regard blood samples taken one week

  12. Artemisinin-resistant Plasmodium falciparum malaria

    PubMed Central

    Fairhurst, Rick M.; Dondorp, Arjen M.

    2016-01-01

    For more than five decades, Southeast Asia (SEA) has been fertile ground for the emergence of drug-resistant Plasmodium falciparum malaria. After generating parasites resistant to chloroquine, sulfadoxine, pyrimethamine, quinine, and mefloquine, this region has now spawned parasites resistant to artemisinins – the world's most potent antimalarial drugs. In areas where artemisinin resistance is prevalent, artemisinin combination therapies (ACTs) – the first-line treatments for malaria – are failing fast. This worrisome development threatens to make malaria practically untreatable in SEA, and threatens to compromise global endeavors to eliminate this disease. A recent series of clinical, in-vitro, genomics, and transcriptomics studies in SEA have defined in-vivo and in-vitro phenotypes of artemisinin resistance; identified its causal genetic determinant; explored its molecular mechanism; and assessed its clinical impact. Specifically, these studies have established that artemisinin resistance manifests as slow parasite clearance in patients and increased survival of early ring-stage parasites in vitro; is caused by single nucleotide polymorphisms in the parasite's ‘K13’ gene; is associated with an upregulated “unfolded protein response” pathway that may antagonize the pro-oxidant activity of artemisinins; and selects for partner drug resistance that rapidly leads to ACT failures. In SEA, clinical studies are urgently needed to monitor ACT efficacy where K13 mutations are prevalent; test whether new combinations of currently-available drugs cure ACT failures; and advance new antimalarial compounds through preclinical pipelines and into clinical trials. Intensifying these efforts should help to forestall the spread of artemisinin and partner drug resistance from SEA to Sub-Saharan Africa, where the world's malaria transmission, morbidity, and mortality rates are highest. PMID:27337450

  13. UvrD helicase of Plasmodium falciparum.

    PubMed

    Shankar, Jay; Tuteja, Renu

    2008-03-15

    Malaria caused by the mosquito-transmitted parasite Plasmodium is the cause of enormous number of deaths every year in the tropical and subtropical areas of the world. Among four species of Plasmodium, Plasmodium falciparum causes most fatal form of malaria. With time, the parasite has developed insecticide and drug resistance. Newer strategies and advent of novel drug targets are required so as to combat the deadly form of malaria. Helicases is one such class of enzymes which has previously been suggested as potential antiviral and anticancer targets. These enzymes play an essential role in nearly all the nucleic acid metabolic processes, catalyzing the transient opening of the duplex nucleic acids in an NTP-dependent manner. DNA helicases from the PcrA/UvrD/Rep subfamily are important for the survival of the various organisms. Members from this subfamily can be targeted and inhibited by a variety of synthetic compounds. UvrD from this subfamily is the only member present in the P. falciparum genome, which shows no homology with UvrD from human and thus can be considered as a strong potential drug target. In this manuscript we provide an overview of UvrD family of helicases and bioinformatics analysis of UvrD from P. falciparum. PMID:18242886

  14. In Vitro Generation of Plasmodium falciparum Ookinetes

    PubMed Central

    Bounkeua, Viengngeun; Li, Fengwu; Vinetz, Joseph M.

    2010-01-01

    Plasmodium transmission from the human host to the mosquito depends on the ability of gametocytes to differentiate into ookinetes, the invasive form of the parasite that invades and establishes infection in the mosquito midgut. The biology of P. falciparum ookinetes is poorly understood, because sufficient quantities of this stage of this parasite species have not been obtained for detailed study. This report details methods to optimize production of P. falciparum sexual stage parasites, including ookinetes. Flow cytometric sorting was used to separate diploid/tetraploid zygotes and ookinetes from haploid gametetocytes and unfertilized gametes based on DNA content. Consistent production of 106–107 P. falciparum ookinetes per 10 mL culture was observed, with ookinete transformation present in 10–40% of all parasite forms. Transmission electron micrographs of cultured parasites confirmed ookinete development. PMID:21118920

  15. Epigenetic regulation of the Plasmodium falciparum genome.

    PubMed

    Duffy, Michael F; Selvarajah, Shamista A; Josling, Gabrielle A; Petter, Michaela

    2014-05-01

    Recent research has highlighted some unique aspects of chromatin biology in the malaria parasite Plasmodium falciparum. During its erythrocytic lifecycle P. falciparum maintains its genome primarily as unstructured euchromatin. Indeed there is no clear role for chromatin-mediated silencing of the majority of the developmentally expressed genes in P. falciparum. However discontinuous stretches of heterochromatin are critical for variegated expression of contingency genes that mediate key pathogenic processes in malaria. These range from invasion of erythrocytes and antigenic variation to solute transport and growth adaptation in response to environmental changes. Despite lack of structure within euchromatin the nucleus maintains functional compartments that regulate expression of many genes at the nuclear periphery, particularly genes with clonally variant expression. The typical components of the chromatin regulatory machinery are present in P. falciparum; however, some of these appear to have evolved novel species-specific functions, e.g. the dynamic regulation of histone variants at virulence gene promoters. The parasite also appears to have repeatedly acquired chromatin regulatory proteins through lateral transfer from endosymbionts and from the host. P. falciparum chromatin regulators have been successfully targeted with multiple drugs in laboratory studies; hopefully their functional divergence from human counterparts will allow the development of parasite-specific inhibitors. PMID:24326119

  16. Genetic distance in housekeeping genes between Plasmodium falciparum and Plasmodium reichenowi and within P. falciparum.

    PubMed

    Tanabe, Kazuyuki; Sakihama, Naoko; Hattori, Tetsuya; Ranford-Cartwright, Lisa; Goldman, Ira; Escalante, Ananias A; Lal, Altaf A

    2004-11-01

    The time to the most recent common ancestor of the extant populations of Plasmodium falciparum is controversial. The controversy primarily stems from the limited availability of sequences from Plasmodium reichenowi, a chimpanzee malaria parasite closely related to P. falciparum. Since the rate of nucleotide substitution differs in different loci and DNA regions, the estimation of genetic distance between P. falciparum and P. reichenowi should be performed using orthologous sequences that are evolving neutrally. Here, we obtained full-length sequences of two housekeeping genes, sarcoplasmic and endoplasmic reticulum Ca2+ -ATPase (serca) and lactate dehydrogenase (ldh), from 11 isolates of P. falciparum and 1 isolate of P. reichenowi and estimate the interspecific genetic distance (divergence) between the two species and intraspecific genetic distance (polymorphism) within P. falciparum. Interspecific distance and intraspecific distance at synonymous sites of interspecies-conserved regions of serca and ldh were 0.0672 +/- 0.0088 and 0.0011 +/- 0.0007, respectively, using the Nei and Gojobori method. Based on the ratio of interspecific distance to intraspecific distance, the time to the most recent common ancestor of P. falciparum was estimated to be (8.30 +/- 5.40) x 10(4) and (11.62 +/- 7.56) x 10(4) years ago, assuming the divergence time of the two parasite species to be 5 and 7 million years ago, respectively. PMID:15693624

  17. The paradoxical population genetics of Plasmodium falciparum.

    PubMed

    Hartl, Daniel L; Volkman, Sarah K; Nielsen, Kaare M; Barry, Alyssa E; Day, Karen P; Wirth, Dyann F; Winzeler, Elizabeth A

    2002-06-01

    Among the leading causes of death in African children is cerebral malaria caused by the parasitic protozoan Plasmodium falciparum. Endemic forms of this disease are thought to have originated in central Africa 5000-10000 years ago, coincident with the innovation of slash-and-burn agriculture and the diversification of the Anopheles gambiae complex of mosquito vectors. Population genetic studies of P. falciparum have yielded conflicting results. Some evidence suggests that today's population includes multiple ancient lineages pre-dating human speciation. Other evidence suggests that today's population derives from only one, or a small number, of these ancient lineages. Resolution of this issue is important for the evaluation of the long-term efficacy of drug and immunological control strategies. PMID:12036741

  18. Plasmodium falciparum: multifaceted resistance to artemisinins.

    PubMed

    Paloque, Lucie; Ramadani, Arba P; Mercereau-Puijalon, Odile; Augereau, Jean-Michel; Benoit-Vical, Françoise

    2016-01-01

    Plasmodium falciparum resistance to artemisinins, the most potent and fastest acting anti-malarials, threatens malaria elimination strategies. Artemisinin resistance is due to mutation of the PfK13 propeller domain and involves an unconventional mechanism based on a quiescence state leading to parasite recrudescence as soon as drug pressure is removed. The enhanced P. falciparum quiescence capacity of artemisinin-resistant parasites results from an increased ability to manage oxidative damage and an altered cell cycle gene regulation within a complex network involving the unfolded protein response, the PI3K/PI3P/AKT pathway, the PfPK4/eIF2α cascade and yet unidentified transcription factor(s), with minimal energetic requirements and fatty acid metabolism maintained in the mitochondrion and apicoplast. The detailed study of these mechanisms offers a way forward for identifying future intervention targets to fend off established artemisinin resistance. PMID:26955948

  19. Artemisinin Action and Resistance in Plasmodium falciparum.

    PubMed

    Tilley, Leann; Straimer, Judith; Gnädig, Nina F; Ralph, Stuart A; Fidock, David A

    2016-09-01

    The worldwide use of artemisinin-based combination therapies (ACTs) has contributed in recent years to a substantial reduction in deaths resulting from Plasmodium falciparum malaria. Resistance to artemisinins, however, has emerged in Southeast Asia. Clinically, resistance is defined as a slower rate of parasite clearance in patients treated with an artemisinin derivative or an ACT. These slow clearance rates associate with enhanced survival rates of ring-stage parasites briefly exposed in vitro to dihydroartemisinin. We describe recent progress made in defining the molecular basis of artemisinin resistance, which has identified a primary role for the P. falciparum K13 protein. Using K13 mutations as molecular markers, epidemiological studies are now tracking the emergence and spread of artemisinin resistance. Mechanistic studies suggest potential ways to overcome resistance. PMID:27289273

  20. Plasmodium falciparum RuvB proteins

    PubMed Central

    Ahmad, Moaz; Tuteja, Renu

    2012-01-01

    The urgent requirement of next generation antimalarials has been of recent interest due to the emergence of drug-resistant parasite. The genome-wide analysis of Plasmodium falciparum helicases revealed three RuvB proteins. Due to the presence of helicase motif I and II in PfRuvBs, there is a high probability that they contain ATPase and possibly helicase activity. The Plasmodium database has homologs of several key proteins that interact with RuvBs and are most likely involved in the cell cycle progression, chromatin remodeling, and other cellular activities. Phylogenetically PfRuvBs are closely related to Saccharomyces cerevisiae RuvB, which is essential for cell cycle progression and survival of yeast. Thus PfRuvBs can serve as potential drug target if they show an essential role in the survival of parasite. PMID:23060959

  1. Immunoregulatory alterations in Plasmodium falciparum and Plasmodium vivax infections.

    PubMed

    Merino, F; Layrisse, Z; Godoy, G; Volcán, G

    1986-09-01

    Studies on the immune function of patients with acute Plasmodium vivax or P. falciparum infections were performed. All subjects were residing in recent malaria endemic areas of Venezuela. Lymphopenia, reduction of peripheral blood T-lymphocytes positive for monoclonal antibody OKT4 (T helper) a decrease of in vitro mitogenic proliferative response and natural killer cell activity were observed. Serum lymphocytotoxic antibodies reactive at 37 degrees C were detected in both groups of patients as well as serum autoantibodies. The possible role of lymphocytotoxic autoantibodies in the etiology of the T-lymphocyte depletion and acquired immunological perturbations in human malaria is discussed. PMID:2947313

  2. Anaemia of Plasmodium falciparum malaria.

    PubMed

    Phillips, R E; Pasvol, G

    1992-04-01

    The pathophysiology of the anaemia of falciparum malaria is both complex and multifactorial, and results in a condition which is a major cause of mortality and morbidity in patients, especially children and pregnant women, living in malarial endemic areas. The importance of anaemia as a cause of death in malaria may well be underestimated because of difficulty in diagnosis, especially where parasitaemia may be low and the clinical picture may be confused with other causes of anaemia. Two clinical presentations predominate: severe acute malaria in which anaemia supervenes, and severe anaemia in patients in whom there have been repeated attacks of malaria. The major mechanisms are those of red cell destruction and decreased red cell production. Potential causes of haemolysis include loss of infected cells by rupture or phagocytosis, removal of uninfected cells due to antibody sensitization or other physicochemical membrane changes, and increased reticuloendothelial activity, particularly in organs such as the spleen. Decreased production results from marrow hypoplasia seen in acute infections, and dyserythropoiesis, a morphological appearance, which in functional terms results in ineffective erythropoiesis. The role of parvovirus B19 as a possible cause of bone marrow aplasia in a few cases is postulated. Finally, there is now evidence which points to genetic factors, HLA associated, which may protect against the development of malarial anaemia and which has become common in areas endemic for malaria. PMID:1511178

  3. Artemisinins target the SERCA of Plasmodium falciparum.

    PubMed

    Eckstein-Ludwig, U; Webb, R J; Van Goethem, I D A; East, J M; Lee, A G; Kimura, M; O'Neill, P M; Bray, P G; Ward, S A; Krishna, S

    2003-08-21

    Artemisinins are extracted from sweet wormwood (Artemisia annua) and are the most potent antimalarials available, rapidly killing all asexual stages of Plasmodium falciparum. Artemisinins are sesquiterpene lactones widely used to treat multidrug-resistant malaria, a disease that annually claims 1 million lives. Despite extensive clinical and laboratory experience their molecular target is not yet identified. Activated artemisinins form adducts with a variety of biological macromolecules, including haem, translationally controlled tumour protein (TCTP) and other higher-molecular-weight proteins. Here we show that artemisinins, but not quinine or chloroquine, inhibit the SERCA orthologue (PfATP6) of Plasmodium falciparum in Xenopus oocytes with similar potency to thapsigargin (another sesquiterpene lactone and highly specific SERCA inhibitor). As predicted, thapsigargin also antagonizes the parasiticidal activity of artemisinin. Desoxyartemisinin lacks an endoperoxide bridge and is ineffective both as an inhibitor of PfATP6 and as an antimalarial. Chelation of iron by desferrioxamine abrogates the antiparasitic activity of artemisinins and correspondingly attenuates inhibition of PfATP6. Imaging of parasites with BODIPY-thapsigargin labels the cytosolic compartment and is competed by artemisinin. Fluorescent artemisinin labels parasites similarly and irreversibly in an Fe2+-dependent manner. These data provide compelling evidence that artemisinins act by inhibiting PfATP6 outside the food vacuole after activation by iron. PMID:12931192

  4. The Acute Transcriptomic and Proteomic Response of HC-04 Hepatoma Cells to Hepatocyte Growth Factor and its Implications for Plasmodium falciparum Sporozoite Invasion*

    PubMed Central

    Tao, Dingyin; King, Jonas G.; Tweedell, Rebecca E.; Jost, Philipp J.; Boddey, Justin A.; Dinglasan, Rhoel R.

    2014-01-01

    The routine study of human malaria liver-stage biology in vitro is hampered by low infection efficiency of human hepatocellular carcinoma (HCC) lines (<0.1%), poor understanding of steady-state HCC biology, and lack of appropriate tools for trace sample analysis. HC-04 is the only HCC that supports complete development of human malaria parasites. We hypothesized that HCCs are in various intermediate stages of the epithelial-mesenchymal transition (EMT) and HC-04s retain epithelial characteristics that permit infection. We developed a facile analytical approach to test this hypothesis viz. the HC-04 response to hepatocyte growth factor (HGF). We used online two-dimensional liquid chromatography tandem mass spectrometry (2D-LC-MS/MS) to quantify protein expression profiles in HC-04 pre-/post-HGF treatment and validated these results by RT-qPCR and microscopy. We successfully increased protein identification efficiency over offline-2D methods by 12-fold, using less sample material, allowing robust protein quantification. We observed expected up-regulation and down-regulation of EMT protein markers in response to HGF, but also unexpected cellular responses. We also observed that HC-04 is generally more susceptible to HGF-mediated signaling than what was observed for HepG2, a widely used, but poor malaria liver stage-HCC model. Our analytical approach to understanding the basic biology of HC-04 helps us understand the factors that may influence its utility as a model for malaria liver-stage development. We observed that HC-04 treatment with HGF prior to the addition of Plasmodium falciparum sporozoites did not facilitate cell invasion, which suggests unlinking the effect of HGF on malaria liver stage development from hepatocyte invasion. Finally, our 2D-LC-MS/MS approach and broadly applicable experimental strategy should prove useful in the analysis of various hepatocyte-pathogen interactions, tumor progression, and early disease events. PMID:24532842

  5. Induction of gene amplification in Plasmodium falciparum

    SciTech Connect

    Rogers, P.L.

    1985-01-01

    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.

  6. The periodicity of Plasmodium vivax and Plasmodium falciparum in Venezuela.

    PubMed

    Grillet, María-Eugenia; El Souki, Mayida; Laguna, Francisco; León, José Rafael

    2014-01-01

    We investigated the periodicity of Plasmodium vivax and P. falciparum incidence in time-series of malaria data (1990-2010) from three endemic regions in Venezuela. In particular, we determined whether disease epidemics were related to local climate variability and regional climate anomalies such as the El Niño Southern Oscillation (ENSO). Malaria periodicity was found to exhibit unique features in each studied region. Significant multi-annual cycles of 2- to about 6-year periods were identified. The inter-annual variability of malaria cases was coherent with that of SSTs (ENSO), mainly at temporal scales within the 3-6 year periods. Additionally, malaria cases were intensified approximately 1 year after an El Niño event, a pattern that highlights the role of climate inter-annual variability in the epidemic patterns. Rainfall mediated the effect of ENSO on malaria locally. Particularly, rains from the last phase of the season had a critical role in the temporal dynamics of Plasmodium. The malaria-climate relationship was complex and transient, varying in strength with the region and species. By identifying temporal cycles of malaria we have made a first step in predicting high-risk years in Venezuela. Our findings emphasize the importance of analyzing high-resolution spatial-temporal data to better understand malaria transmission dynamics. PMID:24149288

  7. The Dynamics of Natural Plasmodium falciparum Infections

    PubMed Central

    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

    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

  8. Plasmodium falciparum Secretome in Erythrocyte and Beyond.

    PubMed

    Soni, Rani; Sharma, Drista; Bhatt, Tarun K

    2016-01-01

    Plasmodium falciparum is the causative agent of deadly malaria disease. It is an intracellular eukaryote and completes its multi-stage life cycle spanning the two hosts viz, mosquito and human. In order to habituate within host environment, parasite conform several strategies to evade host immune responses such as surface antigen polymorphism or modulation of host immune system and it is mediated by secretion of proteins from parasite to the host erythrocyte and beyond, collectively known as, malaria secretome. In this review, we will discuss about the deployment of parasitic secretory protein in mechanism implicated for immune evasion, protein trafficking, providing virulence, changing permeability and cyto-adherence of infected erythrocyte. We will be covering the possibilities of developing malaria secretome as a drug/vaccine target. This gathered information will be worthwhile in depicting a well-organized picture for host-pathogen interplay during the malaria infection and may also provide some clues for the development of novel anti-malarial therapies. PMID:26925057

  9. Plasmodium falciparum Secretome in Erythrocyte and Beyond

    PubMed Central

    Soni, Rani; Sharma, Drista; Bhatt, Tarun K.

    2016-01-01

    Plasmodium falciparum is the causative agent of deadly malaria disease. It is an intracellular eukaryote and completes its multi-stage life cycle spanning the two hosts viz, mosquito and human. In order to habituate within host environment, parasite conform several strategies to evade host immune responses such as surface antigen polymorphism or modulation of host immune system and it is mediated by secretion of proteins from parasite to the host erythrocyte and beyond, collectively known as, malaria secretome. In this review, we will discuss about the deployment of parasitic secretory protein in mechanism implicated for immune evasion, protein trafficking, providing virulence, changing permeability and cyto-adherence of infected erythrocyte. We will be covering the possibilities of developing malaria secretome as a drug/vaccine target. This gathered information will be worthwhile in depicting a well-organized picture for host-pathogen interplay during the malaria infection and may also provide some clues for the development of novel anti-malarial therapies. PMID:26925057

  10. Structure and expression of the Plasmodium falciparum SERA gene.

    PubMed

    Li, W B; Bzik, D J; Horii, T; Inselburg, J

    1989-02-01

    Plasmodium falciparum, strain FCR3, genomic DNA that encodes the SERA gene of P. falciparum was isolated and sequenced. The SERA gene coding region was interrupted by 3 introns, the largest number observed, so far, in any Plasmodium gene. Two SERA gene alleles, allele I and allele II, were identified in the FCR3 strain, while only allele I was found in the Honduras-1 strain. Allele I mRNA was abundant in vivo during the late trophozoite and schizont stages. Allele II mRNA was either not expressed, or it was labile. PMID:2651911

  11. Expression of Plasmodium falciparum lactate dehydrogenase in Escherichia coli.

    PubMed

    Bzik, D J; Fox, B A; Gonyer, K

    1993-05-01

    A Plasmodium falciparum gene is described which encodes lactate dehydrogenase activity (P. falciparum LDH). The P. falciparum LDH gene contains no introns and is present in a single copy on chromosome 13. P. falciparum LDH was expressed in all asexual blood stages as a 1.6-kb mRNA. The predicted 316 amino acid protein coding region of P. falciparum LDH was inserted into the prokaryotic expression vector pKK223-3 and a 33-kDa protein having LDH activity was synthesized in Escherichia coli. P. falciparum LDH primary structure displays high amino acid similarity (50-57%) to vertebrate and bacterial LDH, but lacks the amino terminal extension observed in all vertebrate LDH. The majority of amino acid residues implicated in substrate and coenzyme binding and catalysis of other LDH are well conserved in P. falciparum LDH. However, several notable differences in amino acid composition were observed. P. falciparum LDH contained several distinctive single amino acid insertions and deletions compared to other LDH enzymes, and most remarkably, it contained a novel insertion of 5 amino acids within the conserved mobile loop region near arginine residue 109, a residue which is known to make contact with pyruvate in the ternary complex of other LDH. These results suggest that novel features of P. falciparum LDH primary structure may be correlated with previously characterized and distinctive kinetic, biochemical, immunochemical, and electrophoretic properties of P. falciparum LDH. PMID:8515777

  12. Chloroquine-Resistant Haplotype Plasmodium falciparum Parasites, Haiti

    PubMed Central

    Londono, Berlin L.; Eisele, Thomas P.; Keating, Joseph; Bennett, Adam; Chattopadhyay, Chandon; Heyliger, Gaetan; Mack, Brian; Rawson, Ian; Vely, Jean-Francois; Désinor, Olbeg

    2009-01-01

    Plasmodium falciparum parasites have been endemic to Haiti for >40 years without evidence of chloroquine (CQ) resistance. In 2006 and 2007, we obtained blood smears for rapid diagnostic tests (RDTs) and filter paper blots of blood from 821 persons by passive and active case detection. P. falciparum infections diagnosed for 79 persons by blood smear or RDT were confirmed by PCR for the small subunit rRNA gene of P. falciparum. Amplification of the P. falciparum CQ resistance transporter (pfcrt) gene yielded 10 samples with amplicons resistant to cleavage by ApoI. A total of 5 of 9 samples had threonine at position 76 of pfcrt, which is consistent with CQ resistance (haplotypes at positions 72–76 were CVIET [n = 4] and CVMNT [n = 1]); 4 had only the wild-type haplotype associated with CQ susceptibility (CVMNK). These results indicate that CQ-resistant haplotype P. falciparum malaria parasites are present in Haiti. PMID:19402959

  13. [From malaria parasite point of view--Plasmodium falciparum evolution].

    PubMed

    Zerka, Agata; Kaczmarek, Radosław; Jaśkiewicz, Ewa

    2015-01-01

    Malaria is caused by infection with protozoan parasites belonging to the genus Plasmodium, which have arguably exerted the greatest selection pressure on humans in the history of our species. Besides humans, different Plasmodium parasites infect a wide range of animal hosts, from marine invertebrates to primates. On the other hand, individual Plasmodium species show high host specificity. The extraordinary evolution of Plasmodium probably began when a free-living red algae turned parasitic, and culminated with its ability to thrive inside a human red blood cell. Studies on the African apes generated new data on the evolution of malaria parasites in general and the deadliest human-specific species, Plasmodium falciparum, in particular. Initially, it was hypothesized that P. falciparum descended from the chimpanzee malaria parasite P. reichenowi, after the human and the chimp lineage diverged about 6 million years ago. However, a recently identified new species infecting gorillas, unexpectedly showed similarity to P. falciparum and was therefore named P. praefalciparum. That finding spurred an alternative hypothesis, which proposes that P. falciparum descended from its gorilla rather than chimp counterpart. In addition, the gorilla-to-human host shift may have occurred more recently (about 10 thousand years ago) than the theoretical P. falciparum-P. reichenowi split. One of the key aims of the studies on Plasmodium evolution is to elucidate the mechanisms that allow the incessant host shifting and retaining the host specificity, especially in the case of human-specific species. Thorough understanding of these phenomena will be necessary to design effective malaria treatment and prevention strategies. PMID:27259224

  14. Historical review: does stress provoke Plasmodium falciparum recrudescence?

    PubMed

    Shanks, G Dennis

    2015-06-01

    Plasmodium falciparum, unlike P. vivax, must maintain infection in the blood/bone marrow over many months/years in order to bridge periods between transmission periods. Asymptomatic parasitemia at very low concentrations is now known to be quite common due to molecular detection methods. Old tropical medicine texts commonly list many stressful events stated to provoke recrudescent falciparum parasitemia such as fatigue, heat/chill, trauma/surgery, famine/war, transit between areas and other febrile illness. The older literature is reviewed to discover the factual basis of such varied reports since they have not been recently confirmed. It seems likely that human stress sometimes induces falciparum recrudescence of an otherwise asymptomatic infection. Reproducing such observations today has been radically altered as malaria chemotherapy has evolved from suppressive quinine to curative artemisinin combinations. Host stress-provoked recrudescence may be part of P. falciparum's survival strategy. PMID:25918217

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

    PubMed Central

    2013-01-01

    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

  16. Human cytotoxic T lymphocytes against the Plasmodium falciparum circumsporozoite protein.

    PubMed Central

    Malik, A; Egan, J E; Houghten, R A; Sadoff, J C; Hoffman, S L

    1991-01-01

    Cytotoxic T lymphocytes (CTL) against the circumsporozoite (CS) protein of malaria sporozoites protect against malaria in rodents. Although there is interest in developing human vaccines that induce CTL against the Plasmodium falciparum CS protein, humans have never been shown to produce CTL against any Plasmodium species protein or other parasite protein. We report that when peripheral blood mononuclear cells (PBMC) from three of four volunteers immunized with irradiated P. falciparum sporozoites were stimulated in vitro with a recombinant vaccinia virus expressing the P. falciparum CS protein or a peptide including only amino acids 368-390 of the P. falciparum CS protein [CS-(368-390)], the PBMC lysed autologous Epstein-Barr virus-transformed B cells transfected with the P. falciparum CS protein gene or incubated with CS-(368-390) tricosapeptide. Activity was antigen specific, genetically restricted, and dependent on CD8+ T cells. In one volunteer, seven peptides reflecting amino acids 311-400 were tested, and, as in B10.BR mice, CTL activity was only associated with the CS-(368-390) peptide. Development of an assay for studying human CTL against the CS and other malaria proteins and a method for constructing target cells by direct gene transfection provide a foundation for studying the role of CTL in protection against malaria. PMID:1707538

  17. RIFINs are adhesins implicated in severe Plasmodium falciparum malaria.

    PubMed

    Goel, Suchi; Palmkvist, Mia; Moll, Kirsten; Joannin, Nicolas; Lara, Patricia; Akhouri, Reetesh R; Moradi, Nasim; Öjemalm, Karin; Westman, Mattias; Angeletti, Davide; Kjellin, Hanna; Lehtiö, Janne; Blixt, Ola; Ideström, Lars; Gahmberg, Carl G; Storry, Jill R; Hult, Annika K; Olsson, Martin L; von Heijne, Gunnar; Nilsson, IngMarie; Wahlgren, Mats

    2015-04-01

    Rosetting is a virulent Plasmodium falciparum phenomenon associated with severe malaria. Here we demonstrate that P. falciparum-encoded repetitive interspersed families of polypeptides (RIFINs) are expressed on the surface of infected red blood cells (iRBCs), where they bind to RBCs--preferentially of blood group A--to form large rosettes and mediate microvascular binding of iRBCs. We suggest that RIFINs have a fundamental role in the development of severe malaria and thereby contribute to the varying global distribution of ABO blood groups in the human population. PMID:25751816

  18. Integrative omics analysis. A study based on Plasmodium falciparum mRNA and protein data

    PubMed Central

    2014-01-01

    Background Technological improvements have shifted the focus from data generation to data analysis. The availability of large amounts of data from transcriptomics, protemics and metabolomics experiments raise new questions concerning suitable integrative analysis methods. We compare three integrative analysis techniques (co-inertia analysis, generalized singular value decomposition and integrative biclustering) by applying them to gene and protein abundance data from the six life cycle stages of Plasmodium falciparum. Co-inertia analysis is an analysis method used to visualize and explore gene and protein data. The generalized singular value decomposition has shown its potential in the analysis of two transcriptome data sets. Integrative Biclustering applies biclustering to gene and protein data. Results Using CIA, we visualize the six life cycle stages of Plasmodium falciparum, as well as GO terms in a 2D plane and interpret the spatial configuration. With GSVD, we decompose the transcriptomic and proteomic data sets into matrices with biologically meaningful interpretations and explore the processes captured by the data sets. IBC identifies groups of genes, proteins, GO Terms and life cycle stages of Plasmodium falciparum. We show method-specific results as well as a network view of the life cycle stages based on the results common to all three methods. Additionally, by combining the results of the three methods, we create a three-fold validated network of life cycle stage specific GO terms: Sporozoites are associated with transcription and transport; merozoites with entry into host cell as well as biosynthetic and metabolic processes; rings with oxidation-reduction processes; trophozoites with glycolysis and energy production; schizonts with antigenic variation and immune response; gametocyctes with DNA packaging and mitochondrial transport. Furthermore, the network connectivity underlines the separation of the intraerythrocytic cycle from the gametocyte and

  19. Simple Molecular Methods for Early Detection of Chloroquine Drug Resistance in Plasmodium vivax and Plasmodium falciparum

    PubMed Central

    Singh, Raksha; Urhehar, Anant Dattatraya

    2016-01-01

    Introduction Malaria is a human disease of which causes high morbidity and mortality. In Plasmodium falciparum malaria, the resistance to antimalarial drugs, especially chloroquine (CQ) is one of the paramount factors contributing to the global increase in morbidity and mortality, due to malaria. Hence, there is a need for detection of chloroquine drug resistance genes i.e., pfcrt-o (Plasmodium falciparum chloroquine resistance transporter-o) and pfmdr-1 (Plasmodium falciparum multidrug resistance-1) of P. falciparum and pvcrt-o (Plasmodium vivax chloroquine resistance transporter-o) and pvmdr-1 (Plasmodium vivax multidrug resistance-1) of P. vivax by using molecular methods to prevent mortality in malarial cases. Aim To standardize chloroquine drug sensitivity testing by molecular method so as to provide reports of chloroquine within 6-8 hours to physicians for better treatment. Materials and Methods This study was conducted over a period of one year from January to December 2014. A Total of 300 blood samples were collected from malaria suspected patient attending MGM Hospital, Kamothe, Navi Mumbai, India. Out of 300 blood samples, 44 were malaria positive as assessed by Thick and Thin blood smear stained, by Leishman’s method and examination with light microscope. Chloroquine drug sensitivity testing was performed using WHO III plate method (micro test). Nested PCR was done for detection of pfcrt-o and pfmdr-1 for P. falciparum and pvcrt-o, pvmdr-1 genes for P. vivax. Results Total 44 samples were included in this study, out of which 22 samples confirmed for Plasmodium falciparum and 22 samples confirmed for Plasmodium vivax. Out of 22 P. falciparum 15 (68.18%) samples were chloroquine resistant. P. vivax showed chloroquine resistance to 5 samples (22.73%) by method similar to WHO III plate method (micro test) and nested PCR. Conclusion Drug resistance testing by molecular methods is useful for early detection of antimalarial drug resistance. pfmdr-1 along with

  20. Impact of enhanced malaria control on the competition between Plasmodium falciparum and Plasmodium vivax in India.

    PubMed

    Prosper, Olivia; Martcheva, Maia

    2013-03-01

    The primary focus of malaria research and control has been on Plasmodium falciparum, the most severe of the four Plasmodium species causing human disease. However, the presence of both P. falciparum and Plasmodium vivax occurs in several countries, including India. We developed a mathematical model describing the dynamics of P. vivax and P. falciparum in the human and mosquito populations and fit this model to Indian clinical case data to understand how enhanced control measures affect the competition between the two Plasmodium species. Around 1997, funding for malaria control in India increased dramatically. Our model predicts that if India had not improved its control strategy, the two species of Plasmodium would continue to coexist. To determine which control measures contributed the most to the decline in the number of cases after 1997, we compared the fit of seven models to the 1997-2010 clinical case data. From this, we determined that increased use of bednets contributed the most to case reduction. During the enhanced control period, the best model predicts that P. vivax is out-competing P. falciparum. However, the reproduction numbers are extremely close to the invasion boundaries. Consequently, we cannot be confident that this outcome is the true future of malaria in India. We address this uncertainty by performing a parametric bootstrapping procedure for each of the seven models. This procedure, applied to the enhanced control period, revealed that the best model predicts that P. vivax outcompeting P. falciparum is the most likely outcome, whereas the remaining candidate models predict the opposite. Moreover, the predictions of the top model are counter to what one expects based on the case data alone. Although the proportion of cases due to falciparum has been increasing, the best fitting model reveals that this observation is insufficient to draw conclusions about the longterm competitive outcome of the two species. PMID:23261665

  1. Replication and maintenance of the Plasmodium falciparum apicoplast genome.

    PubMed

    Milton, Morgan E; Nelson, Scott W

    2016-08-01

    Members of the phylum Apicomplexa are responsible for many devastating diseases including malaria (Plasmodium spp.), toxoplasmosis (Toxoplasma gondii), babesiosis (Babesia bovis), and cyclosporiasis (Cyclospora cayetanensis). Most Apicomplexans contain a unique and essential organelle called the apicoplast. Derived from an ancient chloroplast, the apicoplast replicates and maintains a 35 kilobase (kb) circular genome. Due to its essential nature within the parasite, drugs targeted to proteins involved in DNA replication and repair of the apicoplast should be potent and specific. This review summarizes the current knowledge surrounding the replication and repair of the Plasmodium falciparum apicoplast genome and identifies several putative proteins involved in replication and repair pathways. PMID:27338018

  2. How specific is Plasmodium falciparum adherence to chondroitin 4-sulfate?

    PubMed Central

    Goel, Suchi; Gowda, D. Channe

    2011-01-01

    Plasmodium falciparum infection during pregnancy results in the sequestration of infected red blood cells (IRBCs) in the placenta, contributing to pregnancy associated malaria (PAM). IRBC adherence is mediated by the binding of a variant Plasmodium falciparum erythrocyte binding protein 1 named VAR2CSA to the low sulfated chondroitin 4-sulfate (C4S) proteoglycan (CSPG) present predominantly in the intervillous space of the placenta. IRBC binding is highly specific to the level and distribution of 4-sulfate groups in C4S. Given the strict specificity of IRBC-C4S interactions, it is better to use either placental CSPG or CSPGs bearing structurally similar C4S chains in defining VAR2CSA structural architecture that interact with C4S, evaluating VAR2CSA constructs for vaccine development or studying structure-based inhibitors as therapeutics for PAM. PMID:21507719

  3. Structure of Plasmodium falciparum ADP-ribosylation factor 1

    SciTech Connect

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

    2011-09-26

    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.

  4. Plasmodium falciparum genetic crosses in a humanized mouse model

    PubMed Central

    Vaughan, Ashley M.; Pinapati, Richard S.; Cheeseman, Ian H.; Camargo, Nelly; Fishbaugher, Matthew; Checkley, Lisa A.; Nair, Shalini; Hutyra, Carolyn A.; Nosten, François H.; Anderson, Timothy J. C.; Ferdig, Michael T.; Kappe, Stefan H. I.

    2015-01-01

    Genetic crosses of phenotypically distinct strains of the human malaria parasite Plasmodium falciparum are a powerful tool for identifying genes controlling drug resistance and other key phenotypes. Previous studies relied on the isolation of recombinant parasites from splenectomized chimpanzees, a research avenue that is no longer available. Here, we demonstrate that human-liver chimeric mice support recovery of recombinant progeny for the identification of genetic determinants of parasite traits and adaptations. PMID:26030447

  5. A Case Report of Plasmodium Vivax, Plasmodium Falciparum and Dengue Co-Infection in a 6 Months Pregnancy

    PubMed Central

    Pande, A; Guharoy, D

    2013-01-01

    India being a tropical country, parasitic infections especially with Plasmodium species are very common in this region. The present case report is that of Plasmodium vivax, Plasmodium falciparum and dengue co-infection in a 6 months pregnant lady who was timely diagnosed and appropriately treated followed by a complete recovery along with feto-maternal well-being. PMID:24349838

  6. Biochemical and functional characterization of Plasmodium falciparum GTP cyclohydrolase I

    PubMed Central

    2014-01-01

    Background Antifolates are currently in clinical use for malaria preventive therapy and treatment. The drugs kill the parasites by targeting the enzymes in the de novo folate pathway. The use of antifolates has now been limited by the spread of drug-resistant mutations. GTP cyclohydrolase I (GCH1) is the first and the rate-limiting enzyme in the folate pathway. The amplification of the gch1 gene found in certain Plasmodium falciparum isolates can cause antifolate resistance and influence the course of antifolate resistance evolution. These findings showed the importance of P. falciparum GCH1 in drug resistance intervention. However, little is known about P. falciparum GCH1 in terms of kinetic parameters and functional assays, precluding the opportunity to obtain the key information on its catalytic reaction and to eventually develop this enzyme as a drug target. Methods Plasmodium falciparum GCH1 was cloned and expressed in bacteria. Enzymatic activity was determined by the measurement of fluorescent converted neopterin with assay validation by using mutant and GTP analogue. The genetic complementation study was performed in ∆folE bacteria to functionally identify the residues and domains of P. falciparum GCH1 required for its enzymatic activity. Plasmodial GCH1 sequences were aligned and structurally modeled to reveal conserved catalytic residues. Results Kinetic parameters and optimal conditions for enzymatic reactions were determined by the fluorescence-based assay. The inhibitor test against P. falciparum GCH1 is now possible as indicated by the inhibitory effect by 8-oxo-GTP. Genetic complementation was proven to be a convenient method to study the function of P. falciparum GCH1. A series of domain truncations revealed that the conserved core domain of GCH1 is responsible for its enzymatic activity. Homology modelling fits P. falciparum GCH1 into the classic Tunnelling-fold structure with well-conserved catalytic residues at the active site. Conclusions

  7. Functional genomics of Plasmodium falciparum using metabolic modelling and analysis

    PubMed Central

    Oppenheim, Rebecca D.; Soldati-Favre, Dominique; Hatzimanikatis, Vassily

    2013-01-01

    Plasmodium falciparum is an obligate intracellular parasite and the leading cause of severe malaria responsible for tremendous morbidity and mortality particularly in sub-Saharan Africa. Successful completion of the P. falciparum genome sequencing project in 2002 provided a comprehensive foundation for functional genomic studies on this pathogen in the following decade. Over this period, a large spectrum of experimental approaches has been deployed to improve and expand the scope of functionally annotated genes. Meanwhile, rapidly evolving methods of systems biology have also begun to contribute to a more global understanding of various aspects of the biology and pathogenesis of malaria. Herein we provide an overview on metabolic modelling, which has the capability to integrate information from functional genomics studies in P. falciparum and guide future malaria research efforts towards the identification of novel candidate drug targets. PMID:23793264

  8. Nitric oxide inhibits falcipain, the Plasmodium falciparum trophozoite cysteine protease.

    PubMed

    Venturini, G; Colasanti, M; Salvati, L; Gradoni, L; Ascenzi, P

    2000-01-01

    Nitric oxide (NO) is a pluripotent regulatory molecule possessing, among others, an antiparasitic activity. In the present study, the inhibitory effect of NO on the catalytic activity of falcipain, the papain-like cysteine protease involved in Plasmodium falciparum trophozoite hemoglobin degradation, is reported. In particular, NO donors S-nitrosoglutathione (GSNO), (+/-)-(E)-p6ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenami de (NOR-3), 3-morpholinosydnonimine (SIN-1), and sodium nitroprusside (SNP) inhibit dose-dependently the falcipain activity present in the P. falciparum trophozoite extract, this effect likely attributable to S-nitrosylation of the Cys25 catalytic residue. The results represent a new insight into the modulation mechanism of falcipain activity, thereby being relevant in developing new strategies for inhibition of the P. falciparum life cycle. PMID:10623597

  9. Multiple independent introductions of Plasmodium falciparum in South America.

    PubMed

    Yalcindag, Erhan; Elguero, Eric; Arnathau, Céline; Durand, Patrick; Akiana, Jean; Anderson, Timothy J; Aubouy, Agnes; Balloux, François; Besnard, Patrick; Bogreau, Hervé; Carnevale, Pierre; D'Alessandro, Umberto; Fontenille, Didier; Gamboa, Dionicia; Jombart, Thibaut; Le Mire, Jacques; Leroy, Eric; Maestre, Amanda; Mayxay, Mayfong; Ménard, Didier; Musset, Lise; Newton, Paul N; Nkoghé, Dieudonné; Noya, Oscar; Ollomo, Benjamin; Rogier, Christophe; Veron, Vincent; Wide, Albina; Zakeri, Sedigheh; Carme, Bernard; Legrand, Eric; Chevillon, Christine; Ayala, Francisco J; Renaud, François; Prugnolle, Franck

    2012-01-10

    The origin of Plasmodium falciparum in South America is controversial. Some studies suggest a recent introduction during the European colonizations and the transatlantic slave trade. Other evidence--archeological and genetic--suggests a much older origin. We collected and analyzed P. falciparum isolates from different regions of the world, encompassing the distribution range of the parasite, including populations from sub-Saharan Africa, the Middle East, Southeast Asia, and South America. Analyses of microsatellite and SNP polymorphisms show that the populations of P. falciparum in South America are subdivided in two main genetic clusters (northern and southern). Phylogenetic analyses, as well as Approximate Bayesian Computation methods suggest independent introductions of the two clusters from African sources. Our estimates of divergence time between the South American populations and their likely sources favor a likely introduction from Africa during the transatlantic slave trade. PMID:22203975

  10. Monkey-derived monoclonal antibodies against Plasmodium falciparum.

    PubMed Central

    Stanley, H A; Reese, R T

    1985-01-01

    A system has been developed that allows efficient production of monkey monoclonal antibodies from owl monkeys. Splenocytes or peripheral blood lymphocytes from monkeys immune to the human malarial parasite, Plasmodium falciparum, were fused with P3X63 Ag8.653 mouse myelomas. The resulting hybridomas were screened by an indirect fluorescent antibody test for the production of monkey monoclonal antibodies (mAb) reactive with P. falciparum. Most of the mAb reacted with the P. falciparum merozoites and immunoprecipitated a parasite-derived glycoprotein having a relative molecular weight of 185,000. These mAb gave a minimum of five different immunoprecipitation patterns, thus demonstrating that a large number of polypeptides obtained when parasitized erythrocytes are solubilized share epitopes with this large glycoprotein. In addition, mAb were obtained that reacted with antigens associated with the infected erythrocyte membrane. One of these mAb bound a Mr 95,000 antigen. Images PMID:3898084

  11. Multiple independent introductions of Plasmodium falciparum in South America

    PubMed Central

    Yalcindag, Erhan; Elguero, Eric; Arnathau, Céline; Durand, Patrick; Akiana, Jean; Anderson, Timothy J.; Aubouy, Agnes; Balloux, François; Besnard, Patrick; Bogreau, Hervé; Carnevale, Pierre; D'Alessandro, Umberto; Fontenille, Didier; Gamboa, Dionicia; Jombart, Thibaut; Le Mire, Jacques; Leroy, Eric; Maestre, Amanda; Mayxay, Mayfong; Ménard, Didier; Musset, Lise; Newton, Paul N.; Nkoghé, Dieudonné; Noya, Oscar; Ollomo, Benjamin; Rogier, Christophe; Veron, Vincent; Wide, Albina; Zakeri, Sedigheh; Carme, Bernard; Legrand, Eric; Chevillon, Christine; Ayala, Francisco J.; Renaud, François; Prugnolle, Franck

    2012-01-01

    The origin of Plasmodium falciparum in South America is controversial. Some studies suggest a recent introduction during the European colonizations and the transatlantic slave trade. Other evidence—archeological and genetic—suggests a much older origin. We collected and analyzed P. falciparum isolates from different regions of the world, encompassing the distribution range of the parasite, including populations from sub-Saharan Africa, the Middle East, Southeast Asia, and South America. Analyses of microsatellite and SNP polymorphisms show that the populations of P. falciparum in South America are subdivided in two main genetic clusters (northern and southern). Phylogenetic analyses, as well as Approximate Bayesian Computation methods suggest independent introductions of the two clusters from African sources. Our estimates of divergence time between the South American populations and their likely sources favor a likely introduction from Africa during the transatlantic slave trade. PMID:22203975

  12. [Research Progress on Artemisinin Resistance in Plasmodium falciparum].

    PubMed

    Zhang, Yi-long; Pan, Wei-qing

    2015-12-01

    Artemisinin (ART) is a novel and effective antimalarial drug discovered in China. As recommended by the World Health Organization, the ART-based combination therapies (ACTs) have become the first-line drugs for the treatment of falciparum malaria. ART and its derivatives have contributed greatly to the effective control of malaria globally, leading to yearly decrease of malaria morbidity and mortality. However, there have recently been several reports on the resistance of Plasmodium falciparum to ART in Southeast Asia. This is deemed a serious threat to the global malaria control programs. In this paper, we reviewed recent research progress on ART resistance to P. falciparum, including new tools for resistance measurement, resistance-associated molecular markers, and the origin and spread of the ART-resistant parasite strains. PMID:27089770

  13. Plasmodium falciparum: growth response to potassium channel blocking compounds.

    PubMed

    Waller, Karena L; Kim, Kami; McDonald, Thomas V

    2008-11-01

    Potassium channels are essential for cell survival and regulate the cell membrane potential and electrochemical gradient. During its lifecycle, Plasmodium falciparum parasites must rapidly adapt to dramatically variant ionic conditions within the mosquito mid-gut, the hepatocyte and red blood cell (RBC) cytosols, and the human circulatory system. To probe the participation of K(+) channels in parasite viability, growth response assays were performed in which asexual stage P. falciparum parasites were cultured in the presence of various Ca(2+)-activated K(+) channel blocking compounds. These data describe the novel anti-malarial effects of bicuculline methiodide and tubocurarine chloride and the novel lack of effect of apamine and verruculogen. Taken together, the data herein imply the presence of K(+) channels, or other parasite-specific targets, in P. falciparum-infected RBCs that are sensitive to blockade with Ca(2+)-activated K(+) channel blocking compounds. PMID:18703053

  14. Hemoglobinopathies: slicing the Gordian knot of Plasmodium falciparum malaria pathogenesis.

    PubMed

    Taylor, Steve M; Cerami, Carla; Fairhurst, Rick M

    2013-01-01

    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 α-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

  15. Submicroscopic Plasmodium falciparum infections in pregnancy in Ghana.

    PubMed

    Mockenhaupt, F P; Rong, B; Till, H; Eggelte, T A; Beck, S; Gyasi-Sarpong, C; Thompson, W N; Bienzle, U

    2000-03-01

    Malarial parasitaemia below the threshold of microscopy but detectable by polymerase chain reaction (PCR) assays is common in endemic regions. This study was conducted to examine prevalence, predictors, and effects of submicroscopic Plasmodium falciparum infections in pregnancy. In a cross-sectional study among 530 pregnant women in Ghana, plasmodial infections were assessed by microscopy and PCR assays. Concentrations of haemoglobin and C-reactive protein (CRP) were measured and antimalarial drugs (chloroquine, pyrimethamine) in urine were demonstrated by ELISA dipsticks. By microscopy, 32% of the women were found to harbour malaria parasites. This rate increased to 63% adding the results of the parasite-specific PCR. P. falciparum was present in all but one infection. With increasing gravidity, infection rates and parasite densities decreased and the proportions of submicroscopic parasitaemia among infected women grew. Correspondingly, anaemia, fever and evidence of inflammation (CRP > 0.6 mg/dl) were more frequent in primigravidae than in multigravidae. Antimalarial drugs were detected in 65% of the women and were associated with a reduced prevalence of P. falciparum infections and a raised proportion of submicroscopic parasitaemia. Both gravidity and antimalarial drug use were independent predictors of submicroscopic P. falciparum infections. These infections caused a slight reduction of Hb levels and considerably increased serum concentrations of CRP. Conventional microscopy underestimates the actual extent of malarial infections in pregnancy in endemic regions. Submicroscopic P. falciparum infections are frequent and may contribute to mild anaemia and inflammation in seemingly aparasitaemic pregnant women. PMID:10747278

  16. Expression of Plasmodium falciparum surface antigens in Escherichia coli.

    PubMed Central

    Ardeshir, F; Flint, J E; Reese, R T

    1985-01-01

    The asexual blood stages of the human malarial parasite Plasmodium falciparum produce many antigens, only some of which are important for protective immunity. Most of the putative protective antigens are believed to be expressed in schizonts and merozoites, the late stages of the asexual cycle. With the aim of cloning and characterizing genes for important parasite antigens, we used late-stage P. falciparum mRNA to construct a library of cDNA sequences inserted in the Escherichia coli expression vector pUC8. Nine thousand clones from the expression library were immunologically screened in situ with serum from Aotus monkeys immune to P. falciparum, and 95 clones expressing parasite antigens were identified. Mice were immunized with lysates from 49 of the bacterial clones that reacted with Aotus sera, and the mouse sera were tested for their reactivity with parasite antigens by indirect immunofluorescence, immunoprecipitation, and immunoblotting assays. Several different P. falciparum antigens were identified by these assays. Indirect immunofluorescence studies of extracellular merozoites showed that three of these antigens appear to be located on the merozoite surface. Thus, we have identified cDNA clones to three different P. falciparum antigens that may be important in protective immunity. Images PMID:3887406

  17. Antimalarial Benzoxaboroles Target Plasmodium falciparum Leucyl-tRNA Synthetase.

    PubMed

    Sonoiki, Ebere; Palencia, Andres; Guo, Denghui; Ahyong, Vida; Dong, Chen; Li, Xianfeng; Hernandez, Vincent S; Zhang, Yong-Kang; Choi, Wai; Gut, Jiri; Legac, Jennifer; Cooper, Roland; Alley, M R K; Freund, Yvonne R; DeRisi, Joseph; Cusack, Stephen; Rosenthal, Philip J

    2016-08-01

    There is a need for new antimalarials, ideally with novel mechanisms of action. Benzoxaboroles have been shown to be active against bacteria, fungi, and trypanosomes. Therefore, we investigated the antimalarial activity and mechanism of action of 3-aminomethyl benzoxaboroles against Plasmodium falciparum Two 3-aminomethyl compounds, AN6426 and AN8432, demonstrated good potency against cultured multidrug-resistant (W2 strain) P. falciparum (50% inhibitory concentration [IC50] of 310 nM and 490 nM, respectively) and efficacy against murine Plasmodium berghei infection when administered orally once daily for 4 days (90% effective dose [ED90], 7.4 and 16.2 mg/kg of body weight, respectively). To characterize mechanisms of action, we selected parasites with decreased drug sensitivity by culturing with stepwise increases in concentration of AN6426. Resistant clones were characterized by whole-genome sequencing. Three generations of resistant parasites had polymorphisms in the predicted editing domain of the gene encoding a P. falciparum leucyl-tRNA synthetase (LeuRS; PF3D7_0622800) and in another gene (PF3D7_1218100), which encodes a protein of unknown function. Solution of the structure of the P. falciparum LeuRS editing domain suggested key roles for mutated residues in LeuRS editing. Short incubations with AN6426 and AN8432, unlike artemisinin, caused dose-dependent inhibition of [(14)C]leucine incorporation by cultured wild-type, but not resistant, parasites. The growth of resistant, but not wild-type, parasites was impaired in the presence of the unnatural amino acid norvaline, consistent with a loss of LeuRS editing activity in resistant parasites. In summary, the benzoxaboroles AN6426 and AN8432 offer effective antimalarial activity and act, at least in part, against a novel target, the editing domain of P. falciparum LeuRS. PMID:27270277

  18. Maternal-foetal transfer of Plasmodium falciparum and Plasmodium vivax antibodies in a low transmission setting.

    PubMed

    Charnaud, Sarah C; McGready, Rose; Herten-Crabb, Asha; Powell, Rosanna; Guy, Andrew; Langer, Christine; Richards, Jack S; Gilson, Paul R; Chotivanich, Kesinee; Tsuboi, Takafumi; Narum, David L; Pimanpanarak, Mupawjay; Simpson, Julie A; Beeson, James G; Nosten, François; Fowkes, Freya J I

    2016-01-01

    During pregnancy immunolglobulin G (IgG) antibodies are transferred from mother to neonate across the placenta. Studies in high transmission areas have shown transfer of P. falciparum-specific IgG, but the extent and factors influencing maternal-foetal transfer in low transmission areas co-endemic for both P. falciparum and P. vivax are unknown. Pregnant women were screened weekly for Plasmodium infection. Mother-neonate paired serum samples at delivery were tested for IgG to antigens from P. falciparum, P. vivax and other infectious diseases. Antibodies to malarial and non-malarial antigens were highly correlated between maternal and neonatal samples (median [range] spearman ρ = 0.78 [0.57-0.93]), although Plasmodium spp. antibodies tended to be lower in neonates than mothers. Estimated gestational age at last P. falciparum infection, but not P. vivax infection, was positively associated with antibody levels in the neonate (P. falciparum merozoite, spearman ρ median [range] 0.42 [0.33-0.66], PfVAR2CSA 0.69; P. vivax ρ = 0.19 [0.09-0.3]). Maternal-foetal transfer of anti-malarial IgG to Plasmodium spp. antigens occurs in low transmission settings. P. vivax IgG acquisition is not associated with recent exposure unlike P. falciparum IgG, suggesting a difference in acquisition of antibodies. IgG transfer is greatest in the final weeks of pregnancy which has implications for the timing of future malaria vaccination strategies in pregnant women. PMID:26861682

  19. Maternal-foetal transfer of Plasmodium falciparum and Plasmodium vivax antibodies in a low transmission setting

    PubMed Central

    Charnaud, Sarah C.; McGready, Rose; Herten-Crabb, Asha; Powell, Rosanna; Guy, Andrew; Langer, Christine; Richards, Jack S.; Gilson, Paul R.; Chotivanich, Kesinee; Tsuboi, Takafumi; Narum, David L.; Pimanpanarak, Mupawjay; Simpson, Julie A.; Beeson, James G.; Nosten, François; Fowkes, Freya J. I.

    2016-01-01

    During pregnancy immunolglobulin G (IgG) antibodies are transferred from mother to neonate across the placenta. Studies in high transmission areas have shown transfer of P. falciparum-specific IgG, but the extent and factors influencing maternal-foetal transfer in low transmission areas co-endemic for both P. falciparum and P. vivax are unknown. Pregnant women were screened weekly for Plasmodium infection. Mother-neonate paired serum samples at delivery were tested for IgG to antigens from P. falciparum, P. vivax and other infectious diseases. Antibodies to malarial and non-malarial antigens were highly correlated between maternal and neonatal samples (median [range] spearman ρ = 0.78 [0.57–0.93]), although Plasmodium spp. antibodies tended to be lower in neonates than mothers. Estimated gestational age at last P. falciparum infection, but not P. vivax infection, was positively associated with antibody levels in the neonate (P. falciparum merozoite, spearman ρ median [range] 0.42 [0.33–0.66], PfVAR2CSA 0.69; P. vivax ρ = 0.19 [0.09–0.3]). Maternal-foetal transfer of anti-malarial IgG to Plasmodium spp. antigens occurs in low transmission settings. P. vivax IgG acquisition is not associated with recent exposure unlike P. falciparum IgG, suggesting a difference in acquisition of antibodies. IgG transfer is greatest in the final weeks of pregnancy which has implications for the timing of future malaria vaccination strategies in pregnant women. PMID:26861682

  20. Pfcrt Gene in Plasmodium falciparum Field Isolates from Muzaffargarh, Pakistan

    PubMed Central

    Sahar, Sumrin; Tanveer, Akhtar; Ali, Akbar; Bilal, Hazrat; Muhammad Saleem, Rana

    2015-01-01

    Background: The aim of the study was to identify the prevalence of different species of Plasmodium and haplotypes of pfcrt in Plasmodium falciparum from the selected area. Methods: Overall, 10,372 blood films of suspected malarial patients were examined microscopically from rural health center Sinawan, district Muzaffargarh, Pakistan from November 2008 to November 2010. P. falciparum positive samples (both whole blood and FTA blood spotted cards) were used for DNA extraction. Nested PCR was used to amplify the pfcrt (codon 72–76) gene fragment. Sequencing was carried out to find the haplotypes in the amplified fragment of pfcrt gene. Result: Over all slide positivity rate (SPR), P. vivax and P. falciparum positivity rate was 21.40 %, 19.37 % and 2.03% respectively. FTA blood spotted cards were equally efficient in the blood storage for PCR and sequencing. Analysis of sequencing results of pfcrt showed only one type of haplotype SagtVMNT (AGTGTAATGAATACA) from codon 72–76 in all samples. Conclusion: The results show high prevalence of CQ resistance and AQ resistant genes. AQ is not recommended to be used as a partner drug in ACT in this locality, so as to ward off future catastrophes. PMID:26623432

  1. Plasmodium vivax Populations Are More Genetically Diverse and Less Structured than Sympatric Plasmodium falciparum Populations

    PubMed Central

    Jennison, Charlie; Arnott, Alicia; Tessier, Natacha; Tavul, Livingstone; Koepfli, Cristian; Felger, Ingrid; Siba, Peter M.; Reeder, John C.; Bahlo, Melanie; Mueller, Ivo; Barry, Alyssa E.

    2015-01-01

    Introduction The human malaria parasite, Plasmodium vivax, is proving more difficult to control and eliminate than Plasmodium falciparum in areas of co-transmission. Comparisons of the genetic structure of sympatric parasite populations may provide insight into the mechanisms underlying the resilience of P. vivax and can help guide malaria control programs. Methodology/Principle findings P. vivax isolates representing the parasite populations of four areas on the north coast of Papua New Guinea (PNG) were genotyped using microsatellite markers and compared with previously published microsatellite data from sympatric P. falciparum isolates. The genetic diversity of P. vivax (He = 0.83–0.85) was higher than that of P. falciparum (He = 0.64–0.77) in all four populations. Moderate levels of genetic differentiation were found between P. falciparum populations, even over relatively short distances (less than 50 km), with 21–28% private alleles and clear geospatial genetic clustering. Conversely, very low population differentiation was found between P. vivax catchments, with less than 5% private alleles and no genetic clustering observed. In addition, the effective population size of P. vivax (30353; 13043–69142) was larger than that of P. falciparum (18871; 8109–42986). Conclusions/Significance Despite comparably high prevalence, P. vivax had higher diversity and a panmictic population structure compared to sympatric P. falciparum populations, which were fragmented into subpopulations. The results suggest that in comparison to P. falciparum, P. vivax has had a long-term large effective population size, consistent with more intense and stable transmission, and limited impact of past control and elimination efforts. This underlines suggestions that more intensive and sustained interventions will be needed to control and eventually eliminate P. vivax. This research clearly demonstrates how population genetic analyses can reveal deeper insight into transmission

  2. Genetic structure of Plasmodium vivax and Plasmodium falciparum in the Bannu district of Pakistan

    PubMed Central

    2010-01-01

    Background Plasmodium vivax and Plasmodium falciparum are the major causative agents of malaria. While knowledge of the genetic structure of malaria parasites is useful for understanding the evolution of parasite virulence, designing anti-malarial vaccines and assessing the impact of malaria control measures, there is a paucity of information on genetic diversity of these two malaria parasites in Pakistan. This study sought to shed some light on the genetic structure of P. vivax and P. falciparum in this understudied region. Methods The genetic diversities of P. vivax and P. falciparum populations from the densely populated, malaria-endemic Bannu district of Pakistan were evaluated by analysis of their merozoite surface protein (msp) genes by PCR-RFLP. Specifically, the Pvmsp-3α and Pvmsp-3β genes of P. vivax and the Pfmsp-1 and Pfmsp-2 genes of P. falciparum were analysed. Results In P. vivax, genotyping of Pvmsp-3α and Pvmsp-3β genes showed a high level of diversity at these loci. Four distinct allele groups: A (1.9 kb), B (1.5 kb), C (1.2 kb), and D (0.3 kb) were detected for Pvmsp-3α, type A being the most prevalent (82%). Conversely, amplification of the P. vivax msp-3β locus produced two allele groups: A (1.7-2.2 kb, 62%) and B (1.4-1.5 kb, 33%), with 5% mixed-strain infections. Restriction analysis of Pvmsp-3α and Pvmsp-3β yielded 12 and 8 distinct alleles, respectively, with a combined mixed genotype prevalence of 20%. In P. falciparum, all three known genotypes of Pfmsp-1 and two of Pfmsp-2 were observed, with MAD20 occurring in 67% and 3D7/IC in 65% of the isolates, respectively. Overall, 24% P. falciparum samples exhibited mixed-strain infections. Conclusion These results indicate that both P. vivax and P. falciparum populations in Pakistan are highly diverse. PMID:20416089

  3. Symmetrical peripheral gangrene due to Plasmodium falciparum malaria

    PubMed Central

    Abdali, Nasar; Malik, Azharuddin Mohammed; Kamal, Athar; Ahmad, Mehtab

    2014-01-01

    A 45-year-old man presented with a 4-day history of high-grade fever with rigours and a 2-day history of painful bluish black discolouration of extremities (acrocyanosis). He was haemodynamically stable and all peripheral pulses palpable, but the extremities were cold with gangrene involving bilateral fingers and toes. Mild splenomegaly was present on abdominal examination but rest of the physical examinations were normal. On investigating he was found to have anaemia, thrombocytopaenia with gametocytes of Plasmodium falciparum on peripheral blood smear. His blood was uncoagulable during performance of prothrombin time with a raised D-dimer. Oxygen saturation was normal and the arterial Doppler test showed reduced blood flow to the extremities. A diagnosis of complicated P. falciparum malaria with disseminated intravascular coagulation (DIC) leading to symmetrical peripheral gangrene was performed. Artemisinin combination therapy was started and heparin was given for DIC. A final line of demarcation of gangrene started forming by 12th day. PMID:24862424

  4. Erythrocyte invasion receptors for Plasmodium falciparum: new and old.

    PubMed

    Satchwell, T J

    2016-04-01

    Understanding the complex process by which the invasive form of the Plasmodium falciparum parasite, the merozoite, attaches to and invades erythrocytes as part of its blood stage life cycle represents a key area of research in the battle to combat malaria. Central to this are efforts to determine the identity of receptors on the host cell surface, their corresponding merozoite-binding proteins and the functional relevance of these binding events as part of the invasion process. This review will provide an updated summary of studies identifying receptor interactions essential for or implicated in P. falciparum merozoite invasion of human erythrocytes, highlighting the recent identification of new receptors using groundbreaking high throughput approaches and with particular focus on the properties and putative involvement of the erythrocyte proteins targeted by these invasion pathways. PMID:26862042

  5. Plasmodium falciparum In Vitro Resistance to Monodesethylamodiaquine, Dakar, Senegal, 2014.

    PubMed

    Fall, Bécaye; Madamet, Marylin; Camara, Cheikhou; Amalvict, Rémy; Fall, Mansour; Nakoulima, Aminata; Diatta, Bakary; Diémé, Yaya; Wade, Boubacar; Pradines, Bruno

    2016-05-01

    We successfully cultured 36 Plasmodium falciparum isolates from blood samples of 44 malaria patients admitted to the Hôpital Principal de Dakar (Dakar, Senegal) during August-December 2014. The prevalence of isolates with in vitro reduced susceptibility was 30.6% for monodesethylamodiaquine, 52.8% for chloroquine, 44.1% for mefloquine, 16.7% for doxycycline, 11.8% for piperaquine, 8.3% for artesunate, 5.9% for pyronaridine, 2.8% for quinine and dihydroartemisinin, and 0.0% for lumefantrine. The prevalence of isolates with reduced in vitro susceptibility to the artemisinin-based combination therapy partner monodesethylamodiaquine increased from 5.6% in 2013 to 30.6% in 2014. Because of the increased prevalence of P. falciparum parasites with impaired in vitro susceptibility to monodesethylamodiaquine, the implementation of in vitro and in vivo surveillance of all artemisinin-based combination therapy partners is warranted. PMID:27088703

  6. Studies on serum requirements for the cultivation of Plasmodium falciparum

    PubMed Central

    Divo, A. A.; Jensen, J. B.

    1982-01-01

    Previous experiments using RPMI 1640 medium have indicated that the dialysis of human serum removes components of low relative molecular mass (6000-8000 RMM) that are essential for continuous cultivation of Plasmodium falciparum. To determine which low-RMM components are important for parasite development, we compared growth in normal serum to that in dialysed serum using a number of other commercially available media, which we considered to be richer than RPMI 1640. Through these comparisons, we determined that hypoxanthine was the major dialysable nutrient required for parasite development. High quality bovine serum requires 3 - 12 × 10-5 mol/litre of hypoxanthine as a supplement to support continuous cultures of P. falciparum. Thus far we have been unable to attain parasite growth in medium containing supplemented bovine serum that is as good as growth in medium containing human serum. PMID:6754122

  7. Plasmodium falciparum In Vitro Resistance to Monodesethylamodiaquine, Dakar, Senegal, 2014

    PubMed Central

    Fall, Bécaye; Madamet, Marylin; Camara, Cheikhou; Amalvict, Rémy; Fall, Mansour; Nakoulima, Aminata; Diatta, Bakary; Diémé, Yaya; Wade, Boubacar

    2016-01-01

    We successfully cultured 36 Plasmodium falciparum isolates from blood samples of 44 malaria patients admitted to the Hôpital Principal de Dakar (Dakar, Senegal) during August–December 2014. The prevalence of isolates with in vitro reduced susceptibility was 30.6% for monodesethylamodiaquine, 52.8% for chloroquine, 44.1% for mefloquine, 16.7% for doxycycline, 11.8% for piperaquine, 8.3% for artesunate, 5.9% for pyronaridine, 2.8% for quinine and dihydroartemisinin, and 0.0% for lumefantrine. The prevalence of isolates with reduced in vitro susceptibility to the artemisinin-based combination therapy partner monodesethylamodiaquine increased from 5.6% in 2013 to 30.6% in 2014. Because of the increased prevalence of P. falciparum parasites with impaired in vitro susceptibility to monodesethylamodiaquine, the implementation of in vitro and in vivo surveillance of all artemisinin-based combination therapy partners is warranted. PMID:27088703

  8. Modeling Combinations of Pre-erythrocytic Plasmodium falciparum Malaria Vaccines.

    PubMed

    Walker, Andrew S; Lourenço, José; Hill, Adrian V S; Gupta, Sunetra

    2015-12-01

    Despite substantial progress in the control of Plasmodium falciparum infection due to the widespread deployment of insecticide-treated bed nets and artemisinin combination therapies, malaria remains a prolific killer, with over half a million deaths estimated to have occurred in 2013 alone. Recent evidence of the development of resistance to treatments in both parasites and their mosquito vectors has underscored the need for a vaccine. Here, we use a mathematical model of the within-host dynamics of P. falciparum infection, fit to data from controlled human malaria infection clinical trials, to predict the efficacy of co-administering the two most promising subunit vaccines, RTS,S/AS01 and ChAd63-MVA ME-TRAP. We conclude that currently available technologies could be combined to induce very high levels of sterile efficacy, even in immune-naive individuals. PMID:26503278

  9. Squalestatin Is an Inhibitor of Carotenoid Biosynthesis in Plasmodium falciparum

    PubMed Central

    Gabriel, Heloisa B.; Silva, Marcia F.; Kimura, Emília A.; Wunderlich, Gerhard

    2015-01-01

    The increasing resistance of malaria parasites to almost all available drugs calls for the characterization of novel targets and the identification of new compounds. Carotenoids are polyisoprenoids from plants, algae, and some bacteria, and they are biosynthesized by Plasmodium falciparum but not by mammalian cells. Biochemical and reverse genetics approaches were applied to demonstrate that phytoene synthase (PSY) is a key enzyme for carotenoid biosynthesis in P. falciparum and is essential for intraerythrocytic growth. The known PSY inhibitor squalestatin reduces biosynthesis of phytoene and kills parasites during the intraerythrocytic cycle. PSY-overexpressing parasites showed increased biosynthesis of phytoene and its derived product phytofluene and presented a squalestatin-resistant phenotype, suggesting that this enzyme is the primary target of action of this drug in the parasite. PMID:25779575

  10. A genome-wide map of diversity in Plasmodium falciparum.

    PubMed

    Volkman, Sarah K; Sabeti, Pardis C; DeCaprio, David; Neafsey, Daniel E; Schaffner, Stephen F; Milner, Danny A; Daily, Johanna P; Sarr, Ousmane; Ndiaye, Daouda; Ndir, Omar; Mboup, Soulyemane; Duraisingh, Manoj T; Lukens, Amanda; Derr, Alan; Stange-Thomann, Nicole; Waggoner, Skye; Onofrio, Robert; Ziaugra, Liuda; Mauceli, Evan; Gnerre, Sante; Jaffe, David B; Zainoun, Joanne; Wiegand, Roger C; Birren, Bruce W; Hartl, Daniel L; Galagan, James E; Lander, Eric S; Wirth, Dyann F

    2007-01-01

    Genetic variation allows the malaria parasite Plasmodium falciparum to overcome chemotherapeutic agents, vaccines and vector control strategies and remain a leading cause of global morbidity and mortality. Here we describe an initial survey of genetic variation across the P. falciparum genome. We performed extensive sequencing of 16 geographically diverse parasites and identified 46,937 SNPs, demonstrating rich diversity among P. falciparum parasites (pi = 1.16 x 10(-3)) and strong correlation with gene function. We identified multiple regions with signatures of selective sweeps in drug-resistant parasites, including a previously unidentified 160-kb region with extremely low polymorphism in pyrimethamine-resistant parasites. We further characterized 54 worldwide isolates by genotyping SNPs across 20 genomic regions. These data begin to define population structure among African, Asian and American groups and illustrate the degree of linkage disequilibrium, which extends over relatively short distances in African parasites but over longer distances in Asian parasites. We provide an initial map of genetic diversity in P. falciparum and demonstrate its potential utility in identifying genes subject to recent natural selection and in understanding the population genetics of this parasite. PMID:17159979

  11. In vitro drug sensitivity of Plasmodium falciparum in Acre, Brazil.

    PubMed Central

    Kremsner, P. G.; Zotter, G. M.; Feldmeier, H.; Graninger, W.; Kollaritsch, M.; Wiedermann, G.; Rocha, R. M.; Wernsdorfer, W. H.

    1989-01-01

    In Acre, the westernmost state of Brazil in the Amazon region, the sensitivity of Plasmodium falciparum to chloroquine, amodiaquine, mefloquine, quinine and sulfadoxine/pyrimethamine was determined in vitro by the Rieckmann microtechnique. The study was performed between January and June 1987; the in vitro parasite responses to all antimalarial drugs were determined according to the recommendations of WHO. Of 83 isolates of P. falciparum, all were sensitive to mefloquine and of 87 isolates of P. falciparum, 84 (97%) were sensitive to quinine. The EC50 for mefloquine was 0.27 mumol/l and for quinine 4.60 mumol/l. In contrast, 65 of 89 (73%) and 70 of 83 (84%) isolates were resistant to amodiaquine and chloroquine, respectively; 11 isolates even grew at 6.4 mumol chloroquine/l. The EC50 for amodiaquine was 0.34 mumol/l and for chloroquine 0.73 mumol/l. Sulfadoxine/pyrimethamine resistance was seen in 23 of 25 (92%) cases. These data clearly indicate that in the western part of the Amazon region the 4-aminoquinolines, as well as sulfadoxine/pyrimethamine, can no longer be recommended for the treatment of P. falciparum infections. PMID:2670298

  12. Dissecting the role of glutathione biosynthesis in Plasmodium falciparum

    PubMed Central

    Patzewitz, Eva-Maria; Wong, Eleanor H; Müller, Sylke

    2012-01-01

    Glutathione (γ-glutamylcysteinyl-glycine, GSH) has vital functions as thiol redox buffer and cofactor of antioxidant and detoxification enzymes. Plasmodium falciparum possesses a functional GSH biosynthesis pathway and contains mM concentrations of the tripeptide. It was impossible to delete in P. falciparum the genes encoding γ-glutamylcysteine synthetase (γGCS) or glutathione synthetase (GS), the two enzymes synthesizing GSH, although both gene loci were not refractory to recombination. Our data show that the parasites cannot compensate for the loss of GSH biosynthesis via GSH uptake. This suggests an important if not essential function of GSH biosynthesis pathway for the parasites. Treatment with the irreversible inhibitor of γGCS L-buthionine sulfoximine (BSO) reduced intracellular GSH levels in P. falciparum and was lethal for their intra-erythrocytic development, corroborating the suggestion that GSH biosynthesis is important for parasite survival. Episomal expression of γgcs in P. falciparum increased tolerance to BSO attributable to increased levels of γGCS. Concomitantly expression of glutathione reductase was reduced leading to an increased GSH efflux. Together these data indicate that GSH levels are tightly regulated by a functional GSH biosynthesis and the reduction of GSSG. PMID:22151036

  13. Discrete-Event Simulation Models of Plasmodium falciparum Malaria

    PubMed Central

    McKenzie, F. Ellis; Wong, Roger C.; Bossert, William H.

    2008-01-01

    We develop discrete-event simulation models using a single “timeline” variable to represent the Plasmodium falciparum lifecycle in individual hosts and vectors within interacting host and vector populations. Where they are comparable our conclusions regarding the relative importance of vector mortality and the durations of host immunity and parasite development are congruent with those of classic differential-equation models of malaria, epidemiology. However, our results also imply that in regions with intense perennial transmission, the influence of mosquito mortality on malaria prevalence in humans may be rivaled by that of the duration of host infectivity. PMID:18668185

  14. [Artemisinin resistance in Plasmodium falciparum: global status and basic research].

    PubMed

    Zhao, Shao-min; Wang, Man-yuan

    2014-10-01

    Artemisinin-resistant Plasmodium falciparum has been identified by WHO in the Greater Mekong subregion. While there is no report on artemisinin resistance in Africa and South America by now, related surveillance measures have been taken place. The genes related artemisinin-resistance has been identified and the molecular markers will be used for large-scale surveillance efforts to contain artemisinin resistance. The emergence and spread of artemisinin resistance worldwide is a present danger and needs more attention. This article reviews the progress of artemisininresistance malaria parasites and artemisinin-based combination therapies. PMID:25726605

  15. Anti-Plasmodium falciparum activity of quinoline-sulfonamide hybrids.

    PubMed

    Pinheiro, Luiz C S; Boechat, Núbia; Ferreira, Maria de Lourdes G; Júnior, Carlos C S; Jesus, Antônio M L; Leite, Milene M M; Souza, Nicolli B; Krettli, Antoniana U

    2015-09-01

    Fifteen quinoline-sulfonamide hybrids, with a 7-chloroquinoline moiety connected by a linker group to arylsulfonamide moieties with different substituents in the 4-position were synthesized and assayed against Plasmodium falciparum. The compounds displayed high schizonticidal blood activity in vitro, with IC50 values ranging from 0.05 to 1.63 μM, in the anti-HPR2 assay against clone W2-chloroquine-resistant; ten of them showed an IC50 (ranging from 0.05 to 0.40 μM) lower than that of chloroquine and sulfadoxine. Among them, two compounds inhibited Plasmodium berghei parasitemia by 47% and 49% on day 5 after mice inoculation. The most active, in vivo, hybrid 13 is considered to be a new prototype for the development of an antimalarial drug against chloroquine-resistant parasites. PMID:26190461

  16. Plasmodium falciparum drug resistance in Angola.

    PubMed

    Fançony, Cláudia; Brito, Miguel; Gil, Jose Pedro

    2016-01-01

    Facing chloroquine drug resistance, Angola promptly adopted artemisinin-based combination therapy as the first-line to treat malaria. Currently, the country aims to consolidate malaria control, while preparing for the elimination of the disease, along with others African countries in the region. However, the remarkable capacity of Plasmodium to develop drug resistance represents an alarming threat for those achievements. Herein, the available, but relatively scarce and dispersed, information on malaria drug resistance in Angola, is reviewed and discussed. The review aims to inform but also to encourage future research studies that monitor and update the information on anti-malarial drug efficacy and prevalence of molecular markers of drug resistance, key fields in the context and objectives of elimination. PMID:26858018

  17. Caspar Controls Resistance to Plasmodium falciparum in Diverse Anopheline Species

    PubMed Central

    Garver, Lindsey S.; Dong, Yuemei; Dimopoulos, George

    2009-01-01

    Immune responses mounted by the malaria vector Anopheles gambiae are largely regulated by the Toll and Imd (immune deficiency) pathways via the NF-kappaB transcription factors Rel1 and Rel2, which are controlled by the negative regulators Cactus and Caspar, respectively. Rel1- and Rel2-dependent transcription in A. gambiae has been shown to be particularly critical to the mosquito's ability to manage infection with the rodent malaria parasite Plasmodium berghei. Using RNA interference to deplete the negative regulators of these pathways, we found that Rel2 controls resistance of A. gambiae to the human malaria parasite Plasmodium falciparum, whereas Rel 1 activation reduced infection levels. The universal relevance of this defense system across Anopheles species was established by showing that caspar silencing also prevents the development of P. falciparum in the major malaria vectors of Asia and South America, A. stephensi and A. albimanus, respectively. Parallel studies suggest that while Imd pathway activation is most effective against P. falciparum, the Toll pathway is most efficient against P. berghei, highlighting a significant discrepancy between the human pathogen and its rodent model. High throughput gene expression analyses identified a plethora of genes regulated by the activation of the two Rel factors and revealed that the Toll pathway played a more diverse role in mosquito biology than the Imd pathway, which was more immunity-specific. Further analyses of key anti-Plasmodium factors suggest they may be responsible for the Imd pathway–mediated resistance phenotype. Additionally, we found that the fitness cost caused by Rel2 activation through caspar gene silencing was undetectable in sugar-fed, blood-fed, and P. falciparum-infected female A. gambiae, while activation of the Toll pathway's Rel1 had a major impact. This study describes for the first time a single gene that influences an immune mechanism that is able to abort development of P

  18. Limitations of microscopy to differentiate Plasmodium species in a region co-endemic for Plasmodium falciparum, Plasmodium vivax and Plasmodium knowlesi

    PubMed Central

    2013-01-01

    Background In areas co-endemic for multiple Plasmodium species, correct diagnosis is crucial for appropriate treatment and surveillance. Species misidentification by microscopy has been reported in areas co-endemic for vivax and falciparum malaria, and may be more frequent in regions where Plasmodium knowlesi also commonly occurs. Methods This prospective study in Sabah, Malaysia, evaluated the accuracy of routine district and referral hospital-based microscopy, and microscopy performed by an experienced research microscopist, for the diagnosis of PCR-confirmed Plasmodium falciparum, P. knowlesi, and Plasmodium vivax malaria. Results A total of 304 patients with PCR-confirmed Plasmodium infection were enrolled, including 130 with P. knowlesi, 122 with P. falciparum, 43 with P. vivax, one with Plasmodium malariae and eight with mixed species infections. Among patients with P. knowlesi mono-infection, routine and cross-check microscopy both identified 94 (72%) patients as “P. malariae/P. knowlesi”; 17 (13%) and 28 (22%) respectively were identified as P. falciparum, and 13 (10%) and two (1.5%) as P. vivax. Among patients with PCR-confirmed P. falciparum, routine and cross-check microscopy identified 110/122 (90%) and 112/118 (95%) patients respectively as P. falciparum, and 8/122 (6.6%) and 5/118 (4.2%) as “P. malariae/P. knowlesi”. Among those with P. vivax, 23/43 (53%) and 34/40 (85%) were correctly diagnosed by routine and cross-check microscopy respectively, while 13/43 (30%) and 3/40 (7.5%) patients were diagnosed as “P. malariae/P. knowlesi”. Four of 13 patients with PCR-confirmed P. vivax and misdiagnosed by routine microscopy as “P. malariae/P. knowlesi” were subsequently re-admitted with P. vivax malaria. Conclusions Microscopy does not reliably distinguish between P. falciparum, P. vivax and P. knowlesi in a region where all three species frequently occur. Misdiagnosis of P. knowlesi as both P. vivax and P. falciparum, and vice versa, is

  19. Unraveling the 'DEAD-box' helicases of Plasmodium falciparum.

    PubMed

    Tuteja, Renu; Pradhan, Arun

    2006-07-01

    The causative agent for the most fatal form of malaria, Plasmodium falciparum, has developed insecticide and drug resistance with time. Therefore combating this disease is becoming increasingly difficult and this calls for finding alternate ways to control malaria. One of the feasible ways could be to find out inhibitors/drugs specific for the indispensable enzymes of malaria parasite such as helicases. These helicases, which contain intrinsic nucleic acid-dependent ATPase activity, are capable of enzymatically unwinding energetically stable duplex nucleic acids into single-stranded templates and are required for all the nucleic acid transactions. Most of the helicases contain a set of nine extremely conserved amino acid sequences, which are called 'helicase motifs'. Due to the presence of the DEAD (Asp-Glu-Ala-Asp) in one of the conserved motifs, this family is also known as the 'DEAD-box' family. In this review, using bioinformatic approach, we describe the 'DEAD-box' helicases of malaria parasite P. falciparum. An in depth analysis shows that the parasite contains 22 full-length genes, some of which are homologues of well-characterized helicases of this family from other organisms. Recently we have cloned and characterized the first member of this family, which is a homologue of p68 and is expressed during the schizont stage of the development of the parasite [Pradhan, A., Chauhan, V.S., Tuteja, R., 2005a. A novel 'DEAD-box' DNA helicase from Plasmodium falciparum is homologous to p68. Mol. Biochem. Parasitol. 140, 55-60.; Pradhan A., Chauhan V.S., Tuteja R., 2005b. Plasmodium falciparum DNA helicase 60 is a schizont stage specific, bipolar and dual helicase stimulated by PKC phosphorylation. Mol. Biochem. Parasitol. 144, 133-141.]. It will be really interesting to clone and characterize other members of the 'DEAD-box' family and understand their role in the replication and transmission of the parasite. These detailed studies may help to identify a parasite

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

    NASA Astrophysics Data System (ADS)

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

    1984-08-01

    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 β -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.

  1. Alternative Protein Secretion in the Malaria Parasite Plasmodium falciparum.

    PubMed

    Thavayogarajah, Thuvaraka; Gangopadhyay, Preetish; Rahlfs, Stefan; Becker, Katja; Lingelbach, Klaus; Przyborski, Jude M; Holder, Anthony A

    2015-01-01

    Plasmodium falciparum invades human red blood cells, residing in a parasitophorous vacuole (PV), with a parasitophorous vacuole membrane (PVM) separating the PV from the host cell cytoplasm. Here we have investigated the role of N-myristoylation and two other N-terminal motifs, a cysteine potential S-palmitoylation site and a stretch of basic residues, as the driving force for protein targeting to the parasite plasma membrane (PPM) and subsequent translocation across this membrane. Plasmodium falciparum adenylate kinase 2 (Pf AK2) contains these three motifs, and was previously proposed to be targeted beyond the parasite to the PVM, despite the absence of a signal peptide for entry into the classical secretory pathway. Biochemical and microscopy analyses of PfAK2 variants tagged with green fluorescent protein (GFP) showed that these three motifs are involved in targeting the protein to the PPM and translocation across the PPM to the PV. It was shown that the N-terminal 37 amino acids of PfAK2 alone are sufficient to target and translocate GFP across the PPM. As a control we examined the N-myristoylated P. falciparum ADP-ribosylation factor 1 (PfARF1). PfARF1 was found to co-localise with a Golgi marker. To determine whether or not the putative palmitoylation and the cluster of lysine residues from the N-terminus of PfAK2 would modulate the subcellular localization of PfARF1, a chimeric fusion protein containing the N-terminus of PfARF1 and the two additional PfAK2 motifs was analysed. This chimeric protein was targeted to the PPM, but not translocated across the membrane into the PV, indicating that other features of the N-terminus of PfAK2 also play a role in the secretion process. PMID:25909331

  2. Alternative Protein Secretion in the Malaria Parasite Plasmodium falciparum

    PubMed Central

    Thavayogarajah, Thuvaraka; Gangopadhyay, Preetish; Rahlfs, Stefan; Becker, Katja; Lingelbach, Klaus; Przyborski, Jude M.; Holder, Anthony A.

    2015-01-01

    Plasmodium falciparum invades human red blood cells, residing in a parasitophorous vacuole (PV), with a parasitophorous vacuole membrane (PVM) separating the PV from the host cell cytoplasm. Here we have investigated the role of N-myristoylation and two other N-terminal motifs, a cysteine potential S-palmitoylation site and a stretch of basic residues, as the driving force for protein targeting to the parasite plasma membrane (PPM) and subsequent translocation across this membrane. Plasmodium falciparum adenylate kinase 2 (Pf AK2) contains these three motifs, and was previously proposed to be targeted beyond the parasite to the PVM, despite the absence of a signal peptide for entry into the classical secretory pathway. Biochemical and microscopy analyses of PfAK2 variants tagged with green fluorescent protein (GFP) showed that these three motifs are involved in targeting the protein to the PPM and translocation across the PPM to the PV. It was shown that the N-terminal 37 amino acids of PfAK2 alone are sufficient to target and translocate GFP across the PPM. As a control we examined the N-myristoylated P. falciparum ADP-ribosylation factor 1 (PfARF1). PfARF1 was found to co-localise with a Golgi marker. To determine whether or not the putative palmitoylation and the cluster of lysine residues from the N-terminus of PfAK2 would modulate the subcellular localization of PfARF1, a chimeric fusion protein containing the N-terminus of PfARF1 and the two additional PfAK2 motifs was analysed. This chimeric protein was targeted to the PPM, but not translocated across the membrane into the PV, indicating that other features of the N-terminus of PfAK2 also play a role in the secretion process. PMID:25909331

  3. Laboratory detection of artemisinin-resistant Plasmodium falciparum.

    PubMed

    Chotivanich, Kesinee; Tripura, Rupam; Das, Debashish; Yi, Poravuth; Day, Nicholas P J; Pukrittayakamee, Sasithon; Chuor, Char Meng; Socheat, Duong; Dondorp, Arjen M; White, Nicholas J

    2014-06-01

    Conventional 48-h in vitro susceptibility tests have low sensitivity in identifying artemisinin-resistant Plasmodium falciparum, defined phenotypically by low in vivo parasite clearance rates. We hypothesized originally that this discrepancy was explained by a loss of ring-stage susceptibility and so developed a simple field-adapted 24-h trophozoite maturation inhibition (TMI) assay focusing on the ring stage and compared it to the standard 48-h schizont maturation inhibition (WHO) test. In Pailin, western Cambodia, where artemisinin-resistant P. falciparum is prevalent, the TMI test mean (95% confidence interval) 50% inhibitory concentration (IC50) for artesunate was 6.8 (5.2 to 8.3) ng/ml compared with 1.5 (1.2 to 1.8) ng/ml for the standard 48-h WHO test (P = 0.001). TMI IC50s correlated significantly with the in vivo responses to artesunate (parasite clearance time [r = 0.44, P = 0.001] and parasite clearance half-life [r = 0.46, P = 0.001]), whereas the standard 48-h test values did not. On continuous culture of two resistant isolates, the artemisinin-resistant phenotype was lost after 6 weeks (IC50s fell from 10 and 12 ng/ml to 2.7 and 3 ng/ml, respectively). Slow parasite clearance in falciparum malaria in western Cambodia results from reduced ring-stage susceptibility. PMID:24663013

  4. Population structure and recent evolution of Plasmodium falciparum

    PubMed Central

    Rich, Stephen M.; Ayala, Francisco J.

    2000-01-01

    Plasmodium falciparum is the agent of malignant malaria, one of mankind's most severe maladies. The parasite exhibits antigenic polymorphisms that have been postulated to be ancient. We have proposed that the extant world populations of P. falciparum have derived from one single parasite, a cenancestor, within the last 5,000–50,000 years. This inference derives from the virtual or complete absence of synonymous nucleotide polymorphisms at genes not involved in immune or drug responses. Seeking to conciliate this claim with extensive antigenic polymorphism, we first note that allele substitutions or polymorphisms can arise very rapidly, even in a single generation, in large populations subject to strong natural selection. Second, new alleles can arise not only by single-nucleotide mutations, but also by duplication/deletion of short simple-repeat DNA sequences, a process several orders of magnitude faster than single-nucleotide mutation. We analyze three antigenic genes known to be extremely polymorphic: Csp, Msp-1, and Msp-2. We identify regions consisting of tandem or proximally repetitive short DNA sequences, including some previously unnoticed. We conclude that the antigenic polymorphisms are consistent with the recent origin of the world populations of P. falciparum inferred from the analysis of nonantigenic genes. PMID:10860962

  5. Intrarectal quinine for treating Plasmodium falciparum malaria: a systematic review

    PubMed Central

    Eisenhut, Michael; Omari, Aika; MacLehose, Harriet G

    2005-01-01

    Background In children with malaria caused by Plasmodium falciparum, quinine administered rectally may be easier to use and less painful than intramuscular or intravenous administration. The objective of this review was to compare the effectiveness of intrarectal with intravenous or intramuscular quinine for treating falciparum malaria. Methods All randomized and quasi-randomized controlled trials comparing intrarectal with intramuscular or intravenous quinine for treating people with falciparum malaria located through the following sources were included: Cochrane Infectious Diseases Group Specialized Register, CENTRAL, MEDLINE, EMBASE, LILACS and CINAHL. Trial quality was assessed and data, including adverse event data, were extracted. Dichotomous data were analysed using odds ratios and continuous data using weighted mean difference. Results Eight randomized controlled trials (1,247 children) fulfilled the inclusion criteria. The same principal investigator led seven of the trials. Five compared intrarectal with intravenous quinine, and six compared intrarectal with intramuscular treatment. No statistically significant difference was detected for death, parasite clearance by 48 hours and seven days, parasite and fever clearance time, coma recovery time, duration of hospitalization and time before drinking began. One trial (898 children) reported that intrarectal was less painful than intramuscular administration. Conclusion No difference in the effect on parasites and clinical illness was detected for the use of intrarectal quinine compared with other routes, but most trials were small. Pain during application may be less with intrarectal quinine. Further larger trials, in patients with severe malaria and in adults, are required before the intrarectal route could be recommended. PMID:15904520

  6. Monkey-derived monoclonal antibodies against Plasmodium falciparum

    SciTech Connect

    Stanley, H.A.; Reese, R.T.

    1985-09-01

    A system has been developed that allows efficient production of monkey monoclonal antibodies from owl monkeys. Splenocytes or peripheral blood lymphocytes from monkeys immune to the human malarial parasite, Plasmodium falciparum, were fused with P3X63 Ag8.653 mouse myelomas. The resulting hybridomas were screened by an indirect fluorescent antibody test for the production of monkey monoclonal antibodies (mAb) reactive with P. falciparum. Most of the mAb reacted with the P. falciparum merozoites and immunoprecipitated a parasite-derived glycoprotein having a relative molecular weight of 185,000. These mAb gave a minimum of five different immunoprecipitation patterns, thus demonstrating that a large number of polypeptides obtained when parasitized erythrocytes are solubilized share epitopes with this large glycoprotein. In addition, mAb were obtained that reacted with antigens associated with the infected erythrocyte membrane. One of these mAb bound a M/sub r/ 95,000 antigen. Radioimmunoprecipitation assays using /sup 125/T-antibodies were done.

  7. Efficacy of scopadulcic acid A against Plasmodium falciparum in vitro.

    PubMed

    Riel, Michael A; Kyle, Dennis E; Milhous, Wilbur K

    2002-04-01

    Scoparia dulcis is a perennial herb widely distributed in many tropical countries. It is used as an herbal remedy for gastrointestinal and many other ailments, and in Nicaragua extracts are used to treat malaria. Phytochemical screening has shown that scopadulcic acid A (SDA), scopadulcic acid B (SDB), and semisynthetic analogues are pharmacologically active compounds from S. dulcis. SDB has antiviral activity against Herpes simplex virus type 1, antitumor activity in various human cell lines, and direct inhibitory activity against porcine gastric H(+), K(+)-ATPase. A methyl ester of scopadulcic acid B showed the most potent inhibitory activity against gastric proton pumps of 30 compounds tested in one study. Compounds with antiviral, antifungal, and antitumor activity often show activity against Plasmodium falciparum. In P. falciparum, the plasma membrane and food vacuole have H(+)-ATPases and the acidocalcisome has an H(+)-Ppase. These proton pumps are potential targets for antimalarial therapy and may have their function disrupted by compounds known to inhibit gastric proton pumps. We tested pure SDA and found in vitro activity against P. falciparum with an IC(50) of 27 and 19 microM against the D6 and W2 clones, respectively. The IC(50) against the multidrug-resistant isolate, TM91C235, was 23 microM. PMID:11975516

  8. Malaria morbidity in Papua Indonesia, an area with multidrug resistant Plasmodium vivax and Plasmodium falciparum

    PubMed Central

    Karyana, Muhammad; Burdarm, Lenny; Yeung, Shunmay; Kenangalem, Enny; Wariker, Noah; Maristela, Rilia; Umana, Ketut Gde; Vemuri, Ram; Okoseray, Maurits J; Penttinen, Pasi M; Ebsworth, Peter; Sugiarto, Paulus; Anstey, Nicholas M; Tjitra, Emiliana; Price, Richard N

    2008-01-01

    Background Multidrug resistance has emerged to both Plasmodium vivax and Plasmodium falciparum and yet the comparative epidemiology of these infections is poorly defined. Methods All laboratory-confirmed episodes of malaria in Timika, Papua, Indonesia, presenting to community primary care clinics and an inpatient facility were reviewed over a two-year period. In addition information was gathered from a house-to-house survey to quantify the prevalence of malaria and treatment-seeking behaviour of people with fever. Results Between January 2004 and December 2005, 99,158 laboratory-confirmed episodes of malaria were reported, of which 58% (57,938) were attributable to P. falciparum and 37% (36,471) to P. vivax. Malaria was most likely to be attributable to pure P. vivax in children under one year of age (55% 2,684/4,889). In the household survey, the prevalence of asexual parasitaemia was 7.5% (290/3,890) for P. falciparum and 6.4% (248/3,890) for P. vivax. The prevalence of P. falciparum infection peaked in young adults aged 15–25 years (9.8% 69/707), compared to P. vivax infection which peaked in children aged 1 to 4 years (9.5% 61/642). Overall 35% (1,813/5,255) of people questioned reported a febrile episode in the preceding month. Of the 60% of people who were estimated to have had malaria, only 39% would have been detected by the surveillance network. The overall incidence of malaria was therefore estimated as 876 per 1,000 per year (Range: 711–906). Conclusion In this region of multidrug-resistant P. vivax and P. falciparum, both species are associated with substantial morbidity, but with significant differences in the age-related risk of infection. PMID:18673572

  9. Heterologous Protection against Malaria after Immunization with Plasmodium falciparum Sporozoites

    PubMed Central

    van Gemert, Geert-Jan; Graumans, Wouter; van de Vegte-Bolmer, Marga; van Lieshout, Lisette; Haks, Mariëlle C.; Hermsen, Cornelus C.; Scholzen, Anja; Visser, Leo G.; Sauerwein, Robert W.

    2015-01-01

    Background Sterile protection in >90% of volunteers against homologous Plasmodium falciparum infection has been achieved only using the controlled human malaria infection (CHMI) model. This efficient model involves whole parasite immunizations under chloroquine prophylaxis (CPS-immunization), requiring only 30–45 mosquitoes bites infected with P. falciparum-sporozoites. Given the large diversity of P. falciparum parasites, it is essential to assess protection against heterologous parasite strains. Methods In an open-label follow-up study, 16 volunteers previously CPS-immunized and challenged with P. falciparum NF54 (West-Africa) in a dose de-escalation and challenge trial were re-challenged with clone NF135.C10 (Cambodia) at 14 months after the last immunization (NCT01660854). Results Two out of thirteen NF54 protected volunteers previously fully protected against NF54 were also fully protected against NF135.C10, while 11/13 showed a delayed patency (median prepatent period of 10.5 days (range 9.0–15.5) versus 8.5 days in 5 malaria-naïve controls (p = 0.0005). Analysis of patency by qPCR indicated a 91 to >99% estimated reduction of liver parasite load in 7/11 partially protected subjects. Three volunteers previously not protected against NF54, were also not protected against NF135.C10. Conclusion This study shows that CPS-immunization can induce heterologous protection for a period of more than one year, which is a further impetus for clinical development of whole parasite vaccines. Trial Registration Clinicaltrials.gov NCT01660854 PMID:25933168

  10. The Fragmented Mitochondrial Ribosomal RNAs of Plasmodium falciparum

    PubMed Central

    Feagin, Jean E.; Harrell, Maria Isabel; Lee, Jung C.; Coe, Kevin J.; Sands, Bryan H.; Cannone, Jamie J.; Tami, Germaine; Schnare, Murray N.; Gutell, Robin R.

    2012-01-01

    Background The mitochondrial genome in the human malaria parasite Plasmodium falciparum is most unusual. Over half the genome is composed of the genes for three classic mitochondrial proteins: cytochrome oxidase subunits I and III and apocytochrome b. The remainder encodes numerous small RNAs, ranging in size from 23 to 190 nt. Previous analysis revealed that some of these transcripts have significant sequence identity with highly conserved regions of large and small subunit rRNAs, and can form the expected secondary structures. However, these rRNA fragments are not encoded in linear order; instead, they are intermixed with one another and the protein coding genes, and are coded on both strands of the genome. This unorthodox arrangement hindered the identification of transcripts corresponding to other regions of rRNA that are highly conserved and/or are known to participate directly in protein synthesis. Principal Findings The identification of 14 additional small mitochondrial transcripts from P. falcipaurm and the assignment of 27 small RNAs (12 SSU RNAs totaling 804 nt, 15 LSU RNAs totaling 1233 nt) to specific regions of rRNA are supported by multiple lines of evidence. The regions now represented are highly similar to those of the small but contiguous mitochondrial rRNAs of Caenorhabditis elegans. The P. falciparum rRNA fragments cluster on the interfaces of the two ribosomal subunits in the three-dimensional structure of the ribosome. Significance All of the rRNA fragments are now presumed to have been identified with experimental methods, and nearly all of these have been mapped onto the SSU and LSU rRNAs. Conversely, all regions of the rRNAs that are known to be directly associated with protein synthesis have been identified in the P. falciparum mitochondrial genome and RNA transcripts. The fragmentation of the rRNA in the P. falciparum mitochondrion is the most extreme example of any rRNA fragmentation discovered. PMID:22761677

  11. Correlation between 'H' blood group antigen and Plasmodium falciparum invasion.

    PubMed

    Pathak, Vrushali; Colah, Roshan; Ghosh, Kanjaksha

    2016-06-01

    The ABO blood group system is the most important blood group system in clinical practice. The relationship between Plasmodium falciparum and ABO blood groups has been studied for many years. This study was undertaken to investigate the abilities of different blood group erythrocytes to support in vitro growth of P. falciparum parasites. P. falciparum parasites of four different strains (3D7, 7G8, Dd2 and RKL9) were co-cultured with erythrocytes of blood group 'A', 'B', 'O' (n = 10 for each) and 'O(h)' (Bombay group) (n = 7) for 5 days. Statistically significant differences were observed on the fourth day among the mean percent parasitemias of 'O', non-'O' ('A' and 'B') and 'O(h)' group cultures. The parasitemias of four strains ranged from 12.23 to 14.66, 11.68 to 13.24, 16.89 to 22.3, and 7.37 to 11.27 % in 'A', 'B', 'O' and Bombay group cultures, respectively. As the expression of H antigen decreased from 'O' blood group to 'A' and 'B' and then to Bombay blood group, parasite invasion (percent parasitemia) also decreased significantly (p < 0.01) and concomitantly, indicating the association of parasite invasion with the amount of H antigen present on the surface of erythrocyte. Thus, the question arises, could H antigen be involved in P. falciparum invasion? To evaluate erythrocyte invasion inhibition, 'O' group erythrocytes were virtually converted to Bombay group-like erythrocytes by the treatment of anti-H lectins extracted from Ulex europaeus seeds. Mean percent parasitemia of lectin-treated cultures on the fourth day was significantly lower (p < 0.05) than that of non-treated cultures and was found to be similar with the mean percent parasitemia demonstrated by the Bombay group erythrocyte cultures, thus further strengthening the hypothesis. PMID:27071756

  12. MOLECULAR SURVEILLANCE OF Plasmodium vivax AND Plasmodium falciparum DHFR MUTATIONS IN ISOLATES FROM SOUTHERN IRAN

    PubMed Central

    SHARIFI-SARASIABI, Khojasteh; HAGHIGHI, Ali; KAZEMI, Bahram; TAGHIPOUR, Niloofar; MOJARAD, Ehsan Nazemalhosseini; GACHKAR, Latif

    2016-01-01

    In Iran, both Plasmodium vivax and P. falciparum malaria have been detected, but P. vivax is the predominant species. Point mutations in dihydrofolate reductase (dhfr) gene in both Plasmodia are the major mechanisms of pyrimethamine resistance. From April 2007 to June 2009, a total of 134 blood samples in two endemic areas of southern Iran were collected from patients infected with P. vivax and P. falciparum. The isolates were analyzed for P. vivax dihydrofolate reductase (pvdhfr) and P. falciparum dihydrofolate reductase (pfdhfr) point mutations using various PCR-based methods. The majority of the isolates (72.9%) had wild type amino acids at five codons of pvdhfr. Amongst mutant isolates, the most common pvdhfr alleles were double mutant in 58 and 117 amino acids (58R-117N). Triple mutation in 57, 58, and 117 amino acids (57L/58R/117N) was identified for the first time in the pvdhfr gene of Iranian P. vivax isolates. All the P. falciparumsamples analyzed (n = 16) possessed a double mutant pfdhfrallele (59R/108N) and retained a wild-type mutation at position 51. This may be attributed to the fact that the falciparum malaria patients were treated using sulfadoxine-pyrimethamine (SP) in Iran. The presence of mutant haplotypes in P. vivax is worrying, but has not yet reached an alarming threshold regarding drugs such as SP. The results of this study reinforce the importance of performing a molecular surveillance by means of a continuous chemoresistance assessment. PMID:27007559

  13. Plasmodium falciparum full life cycle and Plasmodium ovale liver stages in humanized mice.

    PubMed

    Soulard, Valérie; Bosson-Vanga, Henriette; Lorthiois, Audrey; Roucher, Clémentine; Franetich, Jean-François; Zanghi, Gigliola; Bordessoulles, Mallaury; Tefit, Maurel; Thellier, Marc; Morosan, Serban; Le Naour, Gilles; Capron, Frédérique; Suemizu, Hiroshi; Snounou, Georges; Moreno-Sabater, Alicia; Mazier, Dominique

    2015-01-01

    Experimental studies of Plasmodium parasites that infect humans are restricted by their host specificity. Humanized mice offer a means to overcome this and further provide the opportunity to observe the parasites in vivo. Here we improve on previous protocols to achieve efficient double engraftment of TK-NOG mice by human primary hepatocytes and red blood cells. Thus, we obtain the complete hepatic development of P. falciparum, the transition to the erythrocytic stages, their subsequent multiplication, and the appearance of mature gametocytes over an extended period of observation. Furthermore, using sporozoites derived from two P. ovale-infected patients, we show that human hepatocytes engrafted in TK-NOG mice sustain maturation of the liver stages, and the presence of late-developing schizonts indicate the eventual activation of quiescent parasites. Thus, TK-NOG mice are highly suited for in vivo observations on the Plasmodium species of humans. PMID:26205537

  14. Plasmodium falciparum full life cycle and Plasmodium ovale liver stages in humanized mice

    PubMed Central

    Soulard, Valérie; Bosson-Vanga, Henriette; Lorthiois, Audrey; Roucher, Clémentine; Franetich, Jean- François; Zanghi, Gigliola; Bordessoulles, Mallaury; Tefit, Maurel; Thellier, Marc; Morosan, Serban; Le Naour, Gilles; Capron, Frédérique; Suemizu, Hiroshi; Snounou, Georges; Moreno-Sabater, Alicia; Mazier, Dominique

    2015-01-01

    Experimental studies of Plasmodium parasites that infect humans are restricted by their host specificity. Humanized mice offer a means to overcome this and further provide the opportunity to observe the parasites in vivo. Here we improve on previous protocols to achieve efficient double engraftment of TK-NOG mice by human primary hepatocytes and red blood cells. Thus, we obtain the complete hepatic development of P. falciparum, the transition to the erythrocytic stages, their subsequent multiplication, and the appearance of mature gametocytes over an extended period of observation. Furthermore, using sporozoites derived from two P. ovale-infected patients, we show that human hepatocytes engrafted in TK-NOG mice sustain maturation of the liver stages, and the presence of late-developing schizonts indicate the eventual activation of quiescent parasites. Thus, TK-NOG mice are highly suited for in vivo observations on the Plasmodium species of humans. PMID:26205537

  15. Plasmodium falciparum Rab1A Localizes to Rhoptries in Schizonts

    PubMed Central

    Morse, David; Webster, Wesley; Kalanon, Ming; Langsley, Gordon; McFadden, Geoffrey I.

    2016-01-01

    Over-expression of a GFP-PfRab1A fusion protein in Plasmodium falciparum schizonts produces a punctate pattern of fluorescence typical of rhoptries, secretory organelles involved in host cell invasion. The GFP-positive bodies were purified by a combination of differential and density gradient centrifugation and their protein content determined by MS/MS sequencing. Consistent with the GFP rhoptry-like pattern of transgenic parasites, four of the 19 proteins identified have been previously described to be rhoptry-associated and another four are ER or ER-associated proteins. Confirmation that GFP-PfRab1A decorates rhoptries was obtained by its co-localization with Rap1 and Ron4 in late phase schizonts. We conclude that PfRab1A potentially regulates vesicular traffic from the endoplasmic reticulum to the rhoptries in Apicomplexa parasites. PMID:27348424

  16. Multiple populations of artemisinin-resistant Plasmodium falciparum in Cambodia

    PubMed Central

    Miotto, Olivo; Almagro-Garcia, Jacob; Manske, Magnus; MacInnis, Bronwyn; Campino, Susana; Rockett, Kirk A; Amaratunga, Chanaki; Lim, Pharath; Suon, Seila; Sreng, Sokunthea; Anderson, Jennifer M; Duong, Socheat; Nguon, Chea; Chuor, Char Meng; Saunders, David; Se, Youry; Lon, Chantap; Fukuda, Mark M; Amenga-Etego, Lucas; Hodgson, Abraham VO; Asoala, Victor; Imwong, Mallika; Takala-Harrison, Shannon; Nosten, Francois; Su, Xin-zhuan; Ringwald, Pascal; Ariey, Frédéric; Dolecek, Christiane; Hien, Tran Tinh; Boni, Maciej F; Thai, Cao Quang; Amambua-Ngwa, Alfred; Conway, David J; Djimdé, Abdoulaye A; Doumbo, Ogobara K; Zongo, Issaka; Ouedraogo, Jean-Bosco; Alcock, Daniel; Drury, Eleanor; Auburn, Sarah; Koch, Oliver; Sanders, Mandy; Hubbart, Christina; Maslen, Gareth; Ruano-Rubio, Valentin; Jyothi, Dushyanth; Miles, Alistair; O’Brien, John; Gamble, Chris; Oyola, Samuel O; Rayner, Julian C; Newbold, Chris I; Berriman, Matthew; Spencer, Chris CA; McVean, Gilean; Day, Nicholas P; White, Nicholas J; Bethell, Delia; Dondorp, Arjen M; Plowe, Christopher V; Fairhurst, Rick M; Kwiatkowski, Dominic P

    2013-01-01

    We describe an analysis of genome variation in 825 Plasmodium falciparum samples from Asia and Africa that reveals an unusual pattern of parasite population structure at the epicentre of artemisinin resistance in western Cambodia. Within this relatively small geographical area we have discovered several distinct but apparently sympatric parasite subpopulations with extremely high levels of genetic differentiation. Of particular interest are three subpopulations, all associated with clinical resistance to artemisinin, which have skewed allele frequency spectra and remarkably high levels of haplotype homozygosity, indicative of founder effects and recent population expansion. We provide a catalogue of SNPs that show high levels of differentiation in the artemisinin-resistant subpopulations, including codon variants in various transporter proteins and DNA mismatch repair proteins. These data provide a population genetic framework for investigating the biological origins of artemisinin resistance and for defining molecular markers to assist its elimination. PMID:23624527

  17. Localization of heme biosynthesis pathway enzymes in Plasmodium falciparum.

    PubMed

    Rao, Aditya; Yeleswarapu, Sri Jyothsna; Srinivasan, Rajgopal; Bulusu, Gopalakrishnan

    2008-12-01

    Protein trafficking in the malarial parasite Plasmodium falciparum is dictated by a complex life-cycle that involves a variety of intra-cellular and host cell destinations, such as the mitochondrion, apicoplast, rhoptries and micronemes. Of these, the apicoplast and mitochondrion are believed to account for more than 10% of this traffic. Studies have shown that mechanisms for mitochondrion and apicoplast targeting are distinct, despite their close physical proximity. The heme biosynthesis pathway spans both these organelles, making trafficking studies crucial for the spatial demarcation of the constituent interactions. This minireview highlights the challenges in identifying the possible sub-cellular destinations of the heme pathway enzymes using gleanings from literature survey as well as focussed bioinformatic analysis. PMID:19239121

  18. Plasmodium falciparum STEVOR proteins impact erythrocyte mechanical properties.

    PubMed

    Sanyal, Sohini; Egée, Stéphane; Bouyer, Guillaume; Perrot, Sylvie; Safeukui, Innocent; Bischoff, Emmanuel; Buffet, Pierre; Deitsch, Kirk W; Mercereau-Puijalon, Odile; David, Peter H; Templeton, Thomas J; Lavazec, Catherine

    2012-01-12

    Infection of erythrocytes with the human malaria parasite, Plasmodium falciparum, results in dramatic changes to the host cell structure and morphology. The predicted functional localization of the STEVOR proteins at the erythrocyte surface suggests that they may be involved in parasite-induced modifications of the erythrocyte membrane during parasite development. To address the biologic function of STEVOR proteins, we subjected a panel of stevor transgenic parasites and wild-type clonal lines exhibiting different expression levels for stevor genes to functional assays exploring parasite-induced modifications of the erythrocyte membrane. Using this approach, we show that stevor expression impacts deformability of the erythrocyte membrane. This process may facilitate parasite sequestration in deep tissue vasculature. PMID:22106347

  19. Thalassemic erythrocytes inhibit in vitro growth of Plasmodium falciparum.

    PubMed Central

    Brockelman, C R; Wongsattayanont, B; Tan-ariya, P; Fucharoen, S

    1987-01-01

    Blood specimens from 100 thalassemic patients were screened in vitro for inhibitory effects on growth and multiplication of Plasmodium falciparum. The culture medium mixture designated REM consisted of 9 volumes of minimum essential medium (GIBCO Laboratories, Grand Island, N.Y.) and 1 volume of RPMI 1640 (GIBCO) supplemented with 10% heat-inactivated human serum. Parasite multiplication in erythrocytes containing normal hemoglobin cultured in RPMI or REM was similar. Significant reduction in parasite multiplication rates was observed in erythrocytes containing abnormal hemoglobin when these were cultured in REM. The degree of reduction in five types of thalassemic erythrocytes was in the following descending order: hemoglobin H disease with Hb Constant Spring, classical hemoglobin H disease, beta(0)-thalassemia-hemoglobin E in which blood harbored a high percentage of hemoglobin F-containing cells, beta (0)-thalassemia-hemoglobin E in which blood harbored few hemoglobin F-containing cells, and beta-thalassemia heterozygous variant. PMID:3539999

  20. Subcellular localization of adenylate kinases in Plasmodium falciparum.

    PubMed

    Ma, Jipeng; Rahlfs, Stefan; Jortzik, Esther; Schirmer, R Heiner; Przyborski, Jude M; Becker, Katja

    2012-09-21

    Adenylate kinases (AK) play a key role in nucleotide signaling processes and energy metabolism by catalyzing the reversible conversion of ATP and AMP to 2 ADP. In the malaria parasite Plasmodium falciparum this reaction is mediated by AK1, AK2, and a GTP:AMP phosphotransferase (GAK). Here, we describe two additional adenylate kinase-like proteins: PfAKLP1, which is homologous to human AK6, and PfAKLP2. Using GFP-fusion proteins and life cell imaging, we demonstrate a cytosolic localization for PfAK1, PfAKLP1, and PfAKLP2, whereas PfGAK is located in the mitochondrion. PfAK2 is located at the parasitophorous vacuole membrane, and this localization is driven by N-myristoylation. PMID:22819813

  1. Haem-activated promiscuous targeting of artemisinin in Plasmodium falciparum.

    PubMed

    Wang, Jigang; Zhang, Chong-Jing; Chia, Wan Ni; Loh, Cheryl C Y; Li, Zhengjun; Lee, Yew Mun; He, Yingke; Yuan, Li-Xia; Lim, Teck Kwang; Liu, Min; Liew, Chin Xia; Lee, Yan Quan; Zhang, Jianbin; Lu, Nianci; Lim, Chwee Teck; Hua, Zi-Chun; Liu, Bin; Shen, Han-Ming; Tan, Kevin S W; Lin, Qingsong

    2015-01-01

    The mechanism of action of artemisinin and its derivatives, the most potent of the anti-malarial drugs, is not completely understood. Here we present an unbiased chemical proteomics analysis to directly explore this mechanism in Plasmodium falciparum. We use an alkyne-tagged artemisinin analogue coupled with biotin to identify 124 artemisinin covalent binding protein targets, many of which are involved in the essential biological processes of the parasite. Such a broad targeting spectrum disrupts the biochemical landscape of the parasite and causes its death. Furthermore, using alkyne-tagged artemisinin coupled with a fluorescent dye to monitor protein binding, we show that haem, rather than free ferrous iron, is predominantly responsible for artemisinin activation. The haem derives primarily from the parasite's haem biosynthesis pathway at the early ring stage and from haemoglobin digestion at the latter stages. Our results support a unifying model to explain the action and specificity of artemisinin in parasite killing. PMID:26694030

  2. Haem-activated promiscuous targeting of artemisinin in Plasmodium falciparum

    PubMed Central

    Wang, Jigang; Zhang, Chong-Jing; Chia, Wan Ni; Loh, Cheryl C. Y.; Li, Zhengjun; Lee, Yew Mun; He, Yingke; Yuan, Li-Xia; Lim, Teck Kwang; Liu, Min; Liew, Chin Xia; Lee, Yan Quan; Zhang, Jianbin; Lu, Nianci; Lim, Chwee Teck; Hua, Zi-Chun; Liu, Bin; Shen, Han-Ming; Tan, Kevin S. W.; Lin, Qingsong

    2015-01-01

    The mechanism of action of artemisinin and its derivatives, the most potent of the anti-malarial drugs, is not completely understood. Here we present an unbiased chemical proteomics analysis to directly explore this mechanism in Plasmodium falciparum. We use an alkyne-tagged artemisinin analogue coupled with biotin to identify 124 artemisinin covalent binding protein targets, many of which are involved in the essential biological processes of the parasite. Such a broad targeting spectrum disrupts the biochemical landscape of the parasite and causes its death. Furthermore, using alkyne-tagged artemisinin coupled with a fluorescent dye to monitor protein binding, we show that haem, rather than free ferrous iron, is predominantly responsible for artemisinin activation. The haem derives primarily from the parasite's haem biosynthesis pathway at the early ring stage and from haemoglobin digestion at the latter stages. Our results support a unifying model to explain the action and specificity of artemisinin in parasite killing. PMID:26694030

  3. Amplification of a Gene Related to Mammalian mdr Genes in Drug-Resistant Plasmodium falciparum

    NASA Astrophysics Data System (ADS)

    Wilson, Craig M.; Serrano, Adelfa E.; Wasley, Annemarie; Bogenschutz, Michael P.; Shankar, Anuraj H.; Wirth, Dyann F.

    1989-06-01

    The malaria parasite Plasmodium falciparum contains at least two genes related to the mammalian multiple drug resistance genes, and at least one of the P. falciparum genes is expressed at a higher level and is present in higher copy number in a strain that is resistant to multiple drugs than in a strain that is sensitive to the drugs.

  4. Artesunate Misuse and Plasmodium falciparum Malaria in Traveler Returning from Africa

    PubMed Central

    Shahinas, Dea; Lau, Rachel; Khairnar, Krishna; Hancock, David

    2010-01-01

    Plasmodium falciparum malaria developed in an African-born traveler who returned to Canada after visiting Nigeria. While there, she took artesunate prophylactically. Isolates had an elevated 50% inhibitory concentration to artemisinin, artesunate, and artemether, compared with that of other African isolates. Inappropriate use of artemisinin derivatives can reduce P. falciparum susceptibility. PMID:20875291

  5. Artesunate misuse and Plasmodium falciparum malaria in traveler returning from Africa.

    PubMed

    Shahinas, Dea; Lau, Rachel; Khairnar, Krishna; Hancock, David; Pillai, Dylan R

    2010-10-01

    Plasmodium falciparum malaria developed in an African-born traveler who returned to Canada after visiting Nigeria. While there, she took artesunate prophylactically. Isolates had an elevated 50% inhibitory concentration to artemisinin, artesunate, and artemether, compared with that of other African isolates. Inappropriate use of artemisinin derivatives can reduce P. falciparum susceptibility. PMID:20875291

  6. Reduced erythrocyte deformability associated with hypoargininemia during Plasmodium falciparum malaria

    PubMed Central

    Rey, Juliana; Buffet, Pierre A.; Ciceron, Liliane; Milon, Geneviève; Mercereau-Puijalon, Odile; Safeukui, Innocent

    2014-01-01

    The mechanisms underlying reduced red blood cell (RBC) deformability during Plasmodium falciparum (Pf) malaria remain poorly understood. Here, we explore the possible involvement of the L-arginine and nitric oxide (NO) pathway on RBC deformability in Pf-infected patients and parasite cultures. RBC deformability was reduced during the acute attack (day0) and returned to normal values upon convalescence (day28). Day0 values correlated with plasma L-arginine levels (r = 0.69; p = 0.01) and weakly with parasitemia (r = −0.38; p = 0.006). In vitro, day0 patient's plasma incubated with ring-stage cultures at 41°C reduced RBC deformability, and this effect correlated strongly with plasma L-arginine levels (r = 0.89; p < 0.0001). Moreover, addition of exogenous L-arginine to the cultures increased deformability of both Pf-free and trophozoite-harboring RBCs. NO synthase activity, evidenced in Pf-infected RBCs, induced L-arginine-dependent NO production. These data show that hypoargininemia during P. falciparum malaria may altogether impair NO production and reduce RBC deformability, particularly at febrile temperature. PMID:24441939

  7. Immunogenicity of recombinant Plasmodium falciparum SERA proteins in rodents.

    PubMed

    Barr, P J; Inselburg, J; Green, K M; Kansopon, J; Hahm, B K; Gibson, H L; Lee-Ng, C T; Bzik, D J; Li, W B; Bathurst, I C

    1991-03-01

    We have expressed defined regions of the serine-repeat antigen (SERA) of the Honduras-1 strain of Plasmodium falciparum in the yeast Saccharomyces cerevisiae. Amino-terminal domains of the natural SERA protein have been shown previously to be targets for parasite-inhibitory murine monoclonal antibodies. Two recombinant SERA antigens were selected for purification and immunological analysis. The first (SERA 1), corresponding to amino acids 24-285 of the natural SERA precursor, was expressed by the ubiquitin fusion method. This allowed for in vivo cleavage by endogenous yeast ubiquitin hydrolase, and subsequent isolation of the mature polypeptide. The second, larger protein (SERA N), encompassing amino acids 24-506, was expressed at only low levels using this system, but could be isolated in high yields when fused to human gamma-interferon (gamma-IFN). Each purified protein was used to immunize mice with either Freund's adjuvant or a muramyl tripeptide adjuvant that has been used in humans. Sera from immunized mice were shown to be capable of in vitro inhibition of invasion of erythrocytes by the Honduras-1 strain of P. falciparum. The results suggest that a recombinant SERA antigen may be an effective component of a candidate malaria vaccine. PMID:2052035

  8. Plasmodium falciparum polypeptides released during in vitro cultivation*

    PubMed Central

    Da Silva, L. Rodriguez; Loche, M.; Dayal, R.; Perrin, L. H.

    1983-01-01

    Synchronous cultures of Plasmodium falciparum were successively labelled with (35S)-methionine and both the supernatants and the pellets of infected red blood cells were collected. The release of TCA-precipitable material in the culture supernatants was low during the development of ring forms and trophozoites, increased during schizogony, and was maximum at the time of schizont rupture and merozoite reinvasion. Analysis of the supernatants by SDS — PAGE and autoradiography showed that both polypeptides common to the various developmental stages of the parasite and schizont/merozoite-specific polypeptides were released. Polypeptides of relative molecular mass 140 000, 82 000 and, to a lower degree, 41 000 were present in high amounts in the culture supernatants. These polypeptides have been shown to be the target of monoclonal antibodies that are able to inhibit the growth of P. falciparum cultures, and may be involved in protective immunity. The released polypeptides may also be used as target antigens in immunodiagnostic tests aiming at the detection of malaria infection. ImagesFig. 2AFig. 2BFig. 3 PMID:6340846

  9. Resistance of Plasmodium falciparum to antimalarial drugs in Equatorial Guinea.

    PubMed

    Roche, J; Benito, A; Ayecaba, S; Amela, C; Molina, R; Alvar, J

    1993-10-01

    One hundred and sixty-six children from Equatorial Guinea, all under 10 years of age and with acute uncomplicated falciparum malaria, were randomly allocated to four groups and treated with one of the following regimens: chloroquine or amodiaquine (25 mg base/kg body weight over 3 days), quinine (8 mg/kg every 8 h for 3 or 5 days), and sulphadoxine-pyrimethamine (25-1.25 mg/kg, in one dose). The parasite clearance rates up to day 14 were 28% with chloroquine, 74% with amodiaquine, and 95% with quinine or sulphadoxine-pyrimethamine. The times required to clear asexual blood forms of Plasmodium falciparum in sensitive cases were 64, 70, 73 and 65 h, respectively. Although quinine and sulphadoxine-pyrimethamine are equally effective, quinine is recommended for treatment of multidrug-resistant malaria in paediatric patients, essentially because of the risk of serious reactions to sulpha drugs. Health providers are, however, encouraged to keep supplies of sulphadoxine-pyrimethamine as an option and to refer patients quickly, if required. PMID:8311568

  10. Atorvastatin prevents Plasmodium falciparum cytoadherence and endothelial damage

    PubMed Central

    2011-01-01

    Background The adhesion of Plasmodium falciparum parasitized red blood cell (PRBC) to human endothelial cells (EC) induces inflammatory processes, coagulation cascades, oxidative stress and apoptosis. These pathological processes are suspected to be responsible for the blood-brain-barrier and other organs' endothelial dysfunctions observed in fatal cases of malaria. Atorvastatin, a drug that belongs to the lowering cholesterol molecule family of statins, has been shown to ameliorate endothelial functions and is widely used in patients with cardiovascular disorders. Methods The effect of this compound on PRBC induced endothelial impairments was assessed using endothelial co-culture models. Results Atorvastatin pre-treatment of EC was found to reduce the expression of adhesion molecules and P. falciparum cytoadherence, to protect cells against PRBC-induced apoptosis and to enhance endothelial monolayer integrity during co-incubation with parasites. Conclusions These results might suggest a potential interest use of atorvastatin as a protective treatment to interfere with the pathophysiological cascades leading to severe malaria. PMID:21356073

  11. The Molecular Basis of Folate Salvage in Plasmodium falciparum

    PubMed Central

    Salcedo-Sora, J. Enrique; Ochong, Edwin; Beveridge, Susan; Johnson, David; Nzila, Alexis; Biagini, Giancarlo A.; Stocks, Paul A.; O'Neill, Paul M.; Krishna, Sanjeev; Bray, Patrick G.; Ward, Stephen A.

    2011-01-01

    Tetrahydrofolates are essential cofactors for DNA synthesis and methionine metabolism. Malaria parasites are capable both of synthesizing tetrahydrofolates and precursors de novo and of salvaging them from the environment. The biosynthetic route has been studied in some detail over decades, whereas the molecular mechanisms that underpin the salvage pathway lag behind. Here we identify two functional folate transporters (named PfFT1 and PfFT2) and delineate unexpected substrate preferences of the folate salvage pathway in Plasmodium falciparum. Both proteins are localized in the plasma membrane and internal membranes of the parasite intra-erythrocytic stages. Transport substrates include folic acid, folinic acid, the folate precursor p-amino benzoic acid (pABA), and the human folate catabolite pABAGn. Intriguingly, the major circulating plasma folate, 5-methyltetrahydrofolate, was a poor substrate for transport via PfFT2 and was not transported by PfFT1. Transport of all folates studied was inhibited by probenecid and methotrexate. Growth rescue in Escherichia coli and antifolate antagonism experiments in P. falciparum indicate that functional salvage of 5-methyltetrahydrofolate is detectable but trivial. In fact pABA was the only effective salvage substrate at normal physiological levels. Because pABA is neither synthesized nor required by the human host, pABA metabolism may offer opportunities for chemotherapeutic intervention. PMID:21998306

  12. Identification of a Plasmodium falciparum Phospholipid Transfer Protein*

    PubMed Central

    van Ooij, Christiaan; Withers-Martinez, Chrislaine; Ringel, Alessa; Cockcroft, Shamshad; Haldar, Kasturi; Blackman, Michael J.

    2013-01-01

    Infection of erythrocytes by the human malaria parasite Plasmodium falciparum results in dramatic modifications to the host cell, including changes to its antigenic and transport properties and the de novo formation of membranous compartments within the erythrocyte cytosol. These parasite-induced structures are implicated in the transport of nutrients, metabolic products, and parasite proteins, as well as in parasite virulence. However, very few of the parasite effector proteins that underlie remodeling of the host erythrocyte are functionally characterized. Using bioinformatic examination and modeling, we have found that the exported P. falciparum protein PFA0210c belongs to the START domain family, members of which mediate transfer of phospholipids, ceramide, or fatty acids between membranes. In vitro phospholipid transfer assays using recombinant PFA0210 confirmed that it can transfer phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine, and sphingomyelin between phospholipid vesicles. Furthermore, assays using HL60 cells containing radiolabeled phospholipids indicated that orthologs of PFA0210c can also transfer phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine. Biochemical and immunochemical analysis showed that PFA0210c associates with membranes in infected erythrocytes at mature stages of intracellular parasite growth. Localization studies in live parasites revealed that the protein is present in the parasitophorous vacuole during growth and is later recruited to organelles in the parasite. Together these data suggest that PFA0210c plays a role in the formation of the membranous structures and nutrient phospholipid transfer in the malaria-parasitized erythrocyte. PMID:24043620

  13. Characterization of N-myristoyltransferase from Plasmodium falciparum.

    PubMed Central

    Gunaratne, R S; Sajid, M; Ling, I T; Tripathi, R; Pachebat, J A; Holder, A A

    2000-01-01

    The gene coding for myristoyl-CoA:protein N-myristoyltransferase (NMT) has been cloned from the malaria parasite Plasmodium falciparum. The gene appears to be single copy and mRNA is expressed in asexual blood-stage forms. Comparison of cDNA and genomic sequences identified three small introns. The open reading frame codes for a 410-amino-acid protein and no evidence of forms with an extended N-terminal coding sequence was obtained. Residues important in substrate binding and in the catalytic mechanism in other species are conserved. The protein was expressed from a plasmid in Escherichia coli, partially purified and shown to have enzymic activity using a synthetic peptide substrate. Comparison of the malaria parasite protein with that derived from the human gene showed a different pattern of inhibition by chemical modification. Human NMT activity was inhibited by diethylpyrocarbonate and partially inhibited by iodacetamide, whereas P. falciparum NMT activity was not inhibited by either pre-treatment. Since the enzyme in infectious fungi is a target for potential chemotherapeutic drugs, it should also be investigated in the context of parasitic infections such as that responsible for malaria. PMID:10816442

  14. Genome sequence of the human malaria parasite Plasmodium falciparum

    PubMed Central

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

    2013-01-01

    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. Genes involved in antigenic variation are concentrated in the subtelomeric regions of the chromosomes. Compared to the genomes of free-living eukaryotic microbes, the genome of this intracellular parasite encodes fewer enzymes and transporters, but a large proportion of genes are devoted to immune evasion and host–parasite interactions. Many nuclear-encoded proteins are targeted to the apicoplast, an organelle involved in fatty-acid and isoprenoid metabolism. The genome sequence provides the foundation for future studies of this organism, and is being exploited in the search for new drugs and vaccines to fight malaria. PMID:12368864

  15. Characterization of the 26S proteasome network in Plasmodium falciparum

    PubMed Central

    Wang, Lihui; Delahunty, Claire; Fritz-Wolf, Karin; Rahlfs, Stefan; Helena Prieto, Judith; Yates, John R.; Becker, Katja

    2015-01-01

    In eukaryotic cells, the ubiquitin-proteasome system as a key regulator of protein quality control is an excellent drug target. We therefore aimed to analyze the 26S proteasome complex in the malaria parasite Plasmodium falciparum, which still threatens almost half of the world’s population. First, we established an affinity purification protocol allowing for the isolation of functional 26S proteasome complexes from the parasite. Subunit composition of the proteasome and component stoichiometry were studied and physiologic interacting partners were identified via in situ protein crosslinking. Furthermore, intrinsic ubiquitin receptors of the plasmodial proteasome were determined and their roles in proteasomal substrate recognition were analyzed. Notably, PfUSP14 was characterized as a proteasome-associated deubiquitinase resulting in the concept that targeting proteasomal deubiquitinating activity in P. falciparum may represent a promising antimalarial strategy. The data provide insights into a profound network orchestrated by the plasmodial proteasome and identified novel drug target candidates in the ubiquitin-proteasome system. PMID:26639022

  16. Molecular Aspects of Plasmodium falciparum Infection during Pregnancy

    PubMed Central

    Ndam, Nicaise Tuikue; Deloron, Philippe

    2007-01-01

    Cytoadherence of Plasmodium-falciparum-parasitized red blood cells (PRBCs) to host receptors is the key phenomenon in the pathological process of the malaria disease. Some of these interactions can originate poor outcomes responsible for 1 to 3 million annual deaths mostly occurring among children in sub-Saharan Africa. Pregnancy-associated malaria (PAM) represents an important exception of the disease occurring at adulthood in malaria endemic settings. Consequences of this are shared between the mother (maternal anemia) and the baby (low birth weight and infant mortality). Demonstrating that parasites causing PAM express specific variant surface antigens (VSAPAM), including the P. falciparum erythrocyte membrane protein 1 (P f EMP1) variant VAR2CSA, that are targets for protective immunity has strengthened the possibility for the development of PAM-specific vaccine. In this paper, we review the molecular basis of malaria pathogenesis attributable to the erythrocyte stages of the parasites, and findings supporting potential anti-PAM vaccine components evidenced in PAM. PMID:17641725

  17. In vitro sensitivity of Plasmodium falciparum to artesunate in Thailand.

    PubMed Central

    Wongsrichanalai, C.; Wimonwattrawatee, T.; Sookto, P.; Laoboonchai, A.; Heppner, D. G.; Kyle, D. E.; Wernsdorfer, W. H.

    1999-01-01

    Reported are the in vitro susceptibilities of Plasmodium falciparum to artesunate, mefloquine, quinine and chloroquine of 86 isolates and to dihydroartemisinin of 45 isolates collected from areas of high resistance to mefloquine within Thailand near the borders with Myanmar and Cambodia, and from southern Thailand where P. falciparum is generally still sensitive to mefloquine. All the isolates were highly sensitive to artesunate, but the geometric mean IC50S were higher in isolates from the Thai-Myanmar and Thai-Cambodian borders than in those from southern Thailand. The IC50S for mefloquine and artesunate were strongly correlated (Pearson r = 0.605; n = 86; P < 0.00001). As expected, the in vitro sensitivities to dihydroartemisinin and artesunate were similar and strongly correlated (at IC50, Pearson r = 0.695; n = 45; P < 0.00002). The correlation between the activity of mefloquine and artesunate requires further investigation in order to determine the potential for development of cross-resistance in nature. Our results suggest that combination with mefloquine is not the ideal way of protecting the usefulness of artemisinin and its derivatives. A search for more suitable partner drugs to these compounds and careful regulation of their use are necessary in the interest of ensuring their long therapeutic life span. PMID:10361756

  18. Plasmodium falciparum var genes expressed in children with severe malaria encode CIDRα1 domains.

    PubMed

    Jespersen, Jakob S; Wang, Christian W; Mkumbaye, Sixbert I; Minja, Daniel Tr; Petersen, Bent; Turner, Louise; Petersen, Jens Ev; Lusingu, John Pa; Theander, Thor G; Lavstsen, Thomas

    2016-01-01

    Most severe Plasmodium falciparum infections are experienced by young children. Severe symptoms are precipitated by vascular sequestration of parasites expressing a particular subset of the polymorphic P. falciparum erythrocyte membrane protein 1 (PfEMP1) adhesion molecules. Parasites binding human endothelial protein C receptor (EPCR) through the CIDRα1 domain of certain PfEMP1 were recently associated with severe malaria in children. However, it has remained unclear to which extend the EPCR-binding CIDRα1 domains epitomize PfEMP1 expressed in severe malaria. Here, we characterized the near full-length transcripts dominating the var transcriptome in children with severe malaria and found that the only common feature of the encoded PfEMP1 was CIDRα1 domains. Such genes were highly and dominantly expressed in both children with severe malarial anaemia and cerebral malaria. These observations support the hypothesis that the CIDRα1-EPCR interaction is key to the pathogenesis of severe malaria and strengthen the rationale for pursuing a vaccine or adjunctive treatment aiming at inhibiting or reducing the damaging effects of this interaction. PMID:27354391

  19. Amodiaquine failure associated with erythrocytic glutathione in Plasmodium falciparum malaria

    PubMed Central

    Zuluaga, Lina; Pabón, Adriana; López, Carlos; Ochoa, Aleida; Blair, Silvia

    2007-01-01

    Objective To establish the relationship between production of glutathione and the therapeutic response to amodiaquine (AQ) monotherapy in Plasmodium falciparum non-complicated malaria patients. Methodology Therapeutic response to AQ was evaluated in 32 patients with falciparum malaria in two townships of Antioquia, Colombia, and followed-up for 28 days. For every patient, total glutathione and enzymatic activity (glutathione reductase, GR, and γ-glutamylcysteine synthetase, γ-GCS) were determined in parasitized erythrocytes, non-infected erythrocytes and free parasites, on the starting day (day zero, before ingestion of AQ) and on the day of failure (in case of occurrence). Results There was found an AQ failure of 31.25%. Independent of the therapeutic response, on the starting day and on the day of failure, lower total glutathione concentration and higher GR activities in parasitized erythrocytes were found, compared with non-infected erythrocytes (p < 0.003). In addition, only on the day of failure, γ-GCS activity of parasitized erythrocytes was higher, compared with that of healthy erythrocytes (p = 0.01). Parasitized and non-parasitized erythrocytes in therapeutic failure patients (TF) had higher total glutathione on the starting day compared with those of adequate clinical response (ACR) (p < 0.02). Parasitized erythrocytes of TF patients showed lower total glutathione on the failure day, compared with starting day (p = 0.017). No differences was seen in the GR and γ-GCS activities by compartment, neither between the two therapeutic response groups nor between the two treatment days. Conclusion This study is a first approach to explaining P. falciparum therapeutic failure in humans through differences in glutathione metabolism in TF and ACR patients. These results suggest a role for glutathione in the therapeutic failure to antimalarials. PMID:17451604

  20. pfmdr2 confers heavy metal resistance to Plasmodium falciparum.

    PubMed

    Rosenberg, Elli; Litus, Ilena; Schwarzfuchs, Nurit; Sinay, Rosa; Schlesinger, Pnina; Golenser, Jacob; Baumeister, Stefan; Lingelbach, Klaus; Pollack, Yaakov

    2006-09-15

    Heavy metals are required by all organisms for normal function, but high levels of heavy metals are toxic. Therefore, homeostasis of these metals is crucial. In the human malaria-causing agent Plasmodium falciparum, the mechanisms of heavy metal transport have yet to be characterized. We have developed a P. falciparum line resistant to heavy metals from a wild-type line sensitive to heavy metals. A molecular and biochemical analysis of the involvement of the P. falciparum multidrug resistance 2 (pfmdr2) gene, an ABC-type transporter, in heavy metal homeostasis was studied. Using a novel uptake assay applied on these two strains, it was demonstrated that, when exposed to heavy metals, the sensitive line accumulates metal, whereas no accumulation was observed in the resistant line. The accumulation occurs within the parasite itself and not in the cytoplasm of the red blood cell. This difference in the accumulation pattern is not a result of amplification of the pfmdr2 gene or of a change in the expression pattern of the gene in the two lines. Sequencing of the gene from both lines revealed a major difference; a stop codon is found in the sensitive line upstream of the normal termination, resulting in a truncated protein that lacks 188 amino acids that contain a portion of the essential cytoplasmatic transporter domain, thereby rendering it inactive. In contrast, the resistant line harbors a full-length, active protein. These findings strongly suggest that the PFMDR2 protein acts as an efflux pump of heavy metals. PMID:16849328

  1. Malaria vaccines: identifying Plasmodium falciparum liver-stage targets

    PubMed Central

    Longley, Rhea J.; Hill, Adrian V. S.; Spencer, Alexandra J.

    2015-01-01

    The development of a highly efficacious and durable vaccine for malaria remains a top priority for global health researchers. Despite the huge rise in recognition of malaria as a global health problem and the concurrent rise in funding over the past 10–15 years, malaria continues to remain a widespread burden. The evidence of increasing resistance to anti-malarial drugs and insecticides is a growing concern. Hence, an efficacious and durable preventative vaccine for malaria is urgently needed. Vaccines are one of the most cost-effective tools and have successfully been used in the prevention and control of many diseases, however, the development of a vaccine for the Plasmodium parasite has proved difficult. Given the early success of whole sporozoite mosquito-bite delivered vaccination strategies, we know that a vaccine for malaria is an achievable goal, with sub-unit vaccines holding great promise as they are simple and cheap to both manufacture and deploy. However a major difficulty in development of sub-unit vaccines lies within choosing the appropriate antigenic target from the 5000 or so genes expressed by the parasite. Given the liver-stage of malaria represents a bottle-neck in the parasite’s life cycle, there is widespread agreement that a multi-component sub-unit malaria vaccine should preferably contain a liver-stage target. In this article we review progress in identifying and screening Plasmodium falciparum liver-stage targets for use in a malaria vaccine. PMID:26441899

  2. Artesunate Tolerance in Transgenic Plasmodium falciparum Parasites Overexpressing a Tryptophan-Rich Protein▿†

    PubMed Central

    Deplaine, Guillaume; Lavazec, Catherine; Bischoff, Emmanuel; Natalang, Onguma; Perrot, Sylvie; Guillotte-Blisnick, Micheline; Coppée, Jean-Yves; Pradines, Bruno; Mercereau-Puijalon, Odile; David, Peter H.

    2011-01-01

    Due to their rapid, potent action on young and mature intraerythrocytic stages, artemisinin derivatives are central to drug combination therapies for Plasmodium falciparum malaria. However, the evidence for emerging parasite resistance/tolerance to artemisinins in southeast Asia is of great concern. A better understanding of artemisinin-related drug activity and resistance mechanisms is urgently needed. A recent transcriptome study of parasites exposed to artesunate led us to identify a series of genes with modified levels of expression in the presence of the drug. The gene presenting the largest mRNA level increase, Pf10_0026 (PArt), encoding a hypothetical protein of unknown function, was chosen for further study. Immunodetection with PArt-specific sera showed that artesunate induced a dose-dependent increase of the protein level. Bioinformatic analysis showed that PArt belongs to a Plasmodium-specific gene family characterized by the presence of a tryptophan-rich domain with a novel hidden Markov model (HMM) profile. Gene disruption could not be achieved, suggesting an essential function. Transgenic parasites overexpressing PArt protein were generated and exhibited tolerance to a spike exposure to high doses of artesunate, with increased survival and reduced growth retardation compared to that of wild-type-treated controls. These data indicate the involvement of PArt in parasite defense mechanisms against artesunate. This is the first report of genetically manipulated parasites displaying a stable and reproducible decreased susceptibility to artesunate, providing new possibilities to investigate the parasite response to artemisinins. PMID:21464256

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

    PubMed Central

    Molina-Cruz, Alvaro; Barillas-Mury, Carolina

    2014-01-01

    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

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

    PubMed

    Molina-Cruz, Alvaro; Barillas-Mury, Carolina

    2014-08-01

    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

  5. Spread of Artemisinin Resistance in Plasmodium falciparum Malaria

    PubMed Central

    Ashley, E.A.; Dhorda, M.; Fairhurst, R.M.; Amaratunga, C.; Lim, P.; Suon, S.; Sreng, S.; Anderson, J.M.; Mao, S.; Sam, B.; Sopha, C.; Chuor, C.M.; Nguon, C.; Sovannaroth, S.; Pukrittayakamee, S.; Jittamala, P.; Chotivanich, K.; Chutasmit, K.; Suchatsoonthorn, C.; Runcharoen, R.; Hien, T.T.; Thuy-Nhien, N.T.; Thanh, N.V.; Phu, N.H.; Htut, Y.; Han, K-T.; Aye, K.H.; Mokuolu, O.A.; Olaosebikan, R.R.; Folaranmi, O.O.; Mayxay, M.; Khanthavong, M.; Hongvanthong, B.; Newton, P.N.; Onyamboko, M.A.; Fanello, C.I.; Tshefu, A.K.; Mishra, N.; Valecha, N.; Phyo, A.P.; Nosten, F.; Yi, P.; Tripura, R.; Borrmann, S.; Bashraheil, M.; Peshu, J.; Faiz, M.A.; Ghose, A.; Hossain, M.A.; Samad, R.; Rahman, M.R.; Hasan, M.M.; Islam, A.; Miotto, O.; Amato, R.; MacInnis, B.; Stalker, J.; Kwiatkowski, D.P.; Bozdech, Z.; Jeeyapant, A.; Cheah, P.Y.; Sakulthaew, T.; Chalk, J.; Intharabut, B.; Silamut, K.; Lee, S.J.; Vihokhern, B.; Kunasol, C.; Imwong, M.; Tarning, J.; Taylor, W.J.; Yeung, S.; Woodrow, C.J.; Flegg, J.A.; Das, D.; Smith, J.; Venkatesan, M.; Plowe, C.V.; Stepniewska, K.; Guerin, P.J.; Dondorp, A.M.; Day, N.P.; White, N.J.

    2014-01-01

    BACKGROUND Artemisinin resistance in Plasmodium falciparum has emerged in Southeast Asia and now poses a threat to the control and elimination of malaria. Mapping the geographic extent of resistance is essential for planning containment and elimination strategies. METHODS Between May 2011 and April 2013, we enrolled 1241 adults and children with acute, uncomplicated falciparum malaria in an open-label trial at 15 sites in 10 countries (7 in Asia and 3 in Africa). Patients received artesunate, administered orally at a daily dose of either 2 mg per kilogram of body weight per day or 4 mg per kilogram, for 3 days, followed by a standard 3-day course of artemisinin-based combination therapy. Parasite counts in peripheral-blood samples were measured every 6 hours, and the parasite clearance half-lives were determined. RESULTS The median parasite clearance half-lives ranged from 1.9 hours in the Democratic Republic of Congo to 7.0 hours at the Thailand–Cambodia border. Slowly clearing in fections (parasite clearance half-life >5 hours), strongly associated with single point mutations in the “propeller” region of the P. falciparum kelch protein gene on chromosome 13 (kelch13), were detected throughout mainland Southeast Asia from southern Vietnam to central Myanmar. The incidence of pretreatment and post-treatment gametocytemia was higher among patients with slow parasite clearance, suggesting greater potential for transmission. In western Cambodia, where artemisinin-based combination therapies are failing, the 6-day course of antimalarial therapy was associated with a cure rate of 97.7% (95% confidence interval, 90.9 to 99.4) at 42 days. CONCLUSIONS Artemisinin resistance to P. falciparum, which is now prevalent across mainland Southeast Asia, is associated with mutations in kelch13. Prolonged courses of artemisinin-based combination therapies are currently efficacious in areas where standard 3-day treatments are failing. (Funded by the U.K. Department of

  6. A World Malaria Map: Plasmodium falciparum Endemicity in 2007

    PubMed Central

    Hay, Simon I; Guerra, Carlos A; Gething, Peter W; Patil, Anand P; Tatem, Andrew J; Noor, Abdisalan M; Kabaria, Caroline W; Manh, Bui H; Elyazar, Iqbal R. F; Brooker, Simon; Smith, David L; Moyeed, Rana A; Snow, Robert W

    2009-01-01

    Background Efficient allocation of resources to intervene against malaria requires a detailed understanding of the contemporary spatial distribution of malaria risk. It is exactly 40 y since the last global map of malaria endemicity was published. This paper describes the generation of a new world map of Plasmodium falciparum malaria endemicity for the year 2007. Methods and Findings A total of 8,938 P. falciparum parasite rate (PfPR) surveys were identified using a variety of exhaustive search strategies. Of these, 7,953 passed strict data fidelity tests for inclusion into a global database of PfPR data, age-standardized to 2–10 y for endemicity mapping. A model-based geostatistical procedure was used to create a continuous surface of malaria endemicity within previously defined stable spatial limits of P. falciparum transmission. These procedures were implemented within a Bayesian statistical framework so that the uncertainty of these predictions could be evaluated robustly. The uncertainty was expressed as the probability of predicting correctly one of three endemicity classes; previously stratified to be an informative guide for malaria control. Population at risk estimates, adjusted for the transmission modifying effects of urbanization in Africa, were then derived with reference to human population surfaces in 2007. Of the 1.38 billion people at risk of stable P. falciparum malaria, 0.69 billion were found in Central and South East Asia (CSE Asia), 0.66 billion in Africa, Yemen, and Saudi Arabia (Africa+), and 0.04 billion in the Americas. All those exposed to stable risk in the Americas were in the lowest endemicity class (PfPR2−10 ≤ 5%). The vast majority (88%) of those living under stable risk in CSE Asia were also in this low endemicity class; a small remainder (11%) were in the intermediate endemicity class (PfPR2−10 > 5 to < 40%); and the remaining fraction (1%) in high endemicity (PfPR2−10 ≥ 40%) areas. High endemicity was widespread in the

  7. [Plasmodium falciparum malaria: evaluation of three imported cases].

    PubMed

    İnkaya, Ahmet Çağkan; Kaya, Filiz; Yıldız, İrem; Uzun, Ömrüm; Ergüven, Sibel

    2016-04-01

    Among Plasmodium species the causative agent of malaria in Turkey is P.vivax, however the incidence of imported falciparum malaria cases is steadily increasing. P.falciparum may cause severe malaria with the involvement of central nervous system, acute renal failure, severe anemia or acute respiratory distress syndrome. Furhermore most of the casualties due to malaria are related with P.falciparum. There is recently, a considerable increase in malaria infections especially in tropical areas. In this report, three cases, who have admitted to our hospital with three different clinical presentations of falciparum malaria, and all shared common history of travelling to Africa were presented. First case was a 27 years old, male patient who returned from Malawi seven days ago where he stayed for two weeks. He admitted to our hospital with the complaints of sensation of cold, shivering and fever. In physical examination his body temperature was 37.9°C, C-reactive protein level was high, and the other systemic results were normal. The second case was a 25 years old, male patient who returned from Gambia two weeks ago. He was suffering from fever, headache, shivering and unable to maintain his balance. The patient's body temperature was 38°C. Laboratory tests revealed hyperbilirubinemia and thrombocytopenia. Parasitological examination of the Giemsa-stained peripheral blood smear of these two patients demonstrated ring forms compatible with P.falciparum. Treatment was commenced with arthemeter plus lumefantrine, resulting with complete cure. Third case was a 46 years old, male patient who had been working in Uganda, and returned to Turkey two weeks ago. He had sudden onset of fever, headache, nausea and vomiting and impaired consciousness. His peripheral blood smear revealed ring-formed trophozoites and banana-shaped gametocytes of P.falciparum. Arthemeter plus lumefantrine therapy was started, however, he developed severe thrombocytopenia and jaundice under treatment

  8. Identification of inhibitors of Plasmodium falciparum gametocyte development

    PubMed Central

    2013-01-01

    Background Plasmodium falciparum gametocytes, specifically mature stages, are the only stage in man transmissible to the mosquito vector responsible for malaria transmission. Anti-malarial drugs capable of killing these forms are considered essential for the eradication of malaria. The comprehensive profiling of in vitro activity of anti-malarial compounds against both early (I-III) and late (IV-V) stage P. falciparum gametocytes, along with the high throughput screening (HTS) outcomes from the MMV malaria box are described. Method Two anti-gametocyte HTS assays based on confocal fluorescence microscopy, utilizing both a gametocyte specific protein (pfs16-Luc-GFP) and a viability marker (MitoTracker Red CM-H2XRos) (MTR), were used for the measurement of anti-gametocytocidal activity. This combination provided a direct observation of gametocyte number per assay well, whilst defining the viability of each gametocyte imaged. Results IC50 values were obtained for 36 current anti-malarial compounds for activities against asexual, early and late stage gametocytes. The MMV malaria box was screened and actives progressed for IC50 evaluation. Seven % of the “drug-like” and 21% of the “probe-like” compounds from the MMV malaria box demonstrated equivalent activity against both asexual and late stage gametocytes. Conclusions The assays described were shown to selectively identify compounds with gametocytocidal activity and have been demonstrated suitable for HTS with the capability of screening in the order of 20,000 compounds per screening campaign, two to three times per seven-day week. PMID:24206914

  9. Targeting the gyrase of Plasmodium falciparum with topoisomerase poisons.

    PubMed

    Tang Girdwood, Sonya C; Nenortas, Elizabeth; Shapiro, Theresa A

    2015-06-15

    Drug-resistant malaria poses a major public health problem throughout the world and the need for new antimalarial drugs is growing. The apicoplast, a chloroplast-like organelle essential for malaria parasite survival and with no counterpart in humans, offers an attractive target for selectively toxic new therapies. The apicoplast genome (plDNA) is a 35 kb circular DNA that is served by gyrase, a prokaryotic type II topoisomerase. Gyrase is poisoned by fluoroquinolone antibacterials that stabilize a catalytically inert ternary complex of enzyme, its plDNA substrate, and inhibitor. We used fluoroquinolones to study the gyrase and plDNA of Plasmodium falciparum. New methods for isolating and separating plDNA reveal four topologically different forms and permit a quantitative exam of perturbations that result from gyrase poisoning. In keeping with its role in DNA replication, gyrase is most abundant in late stages of the parasite lifecycle, but several lines of evidence indicate that even in these cells the enzyme is present in relatively low abundance: about 1 enzyme for every two plDNAs or a ratio of 1 gyrase: 70 kb DNA. For a spectrum of quinolones, correlation was generally good between antimalarial activity and gyrase poisoning, the putative molecular mechanism of drug action. However, in P. falciparum there is evidence for off-target toxicity, particularly for ciprofloxacin. These studies highlight the utility of the new methods and of fluoroquinolones as a tool for studying the in situ workings of gyrase and its plDNA substrate. PMID:25881748

  10. Characterization of native PfABCG protein in Plasmodium falciparum.

    PubMed

    Edaye, Sonia; Georges, Elias

    2015-09-15

    The Plasmodium falciparum genome encodes 16 members of ABC proteins, with one member of the ABCG subfamily (PfABCG). Analysis of PfABCG amino acid sequence shows equal sequence identity to hsABCG1 and G2. Using N-terminal directed antibody against a recombinant fragment of PfABCG, we show that PfABCG migrates with an apparent molecular mass of 65KDa polypeptide on SDS-PAGE. PfABCG is expressed in all four stages of the parasite erythrocytic life cycle, with lower and higher expression in ring and late trophozoite stages, respectively. The protein localizes to the plasma membrane and a novel spherical structure beneath the cell membrane. Similar localization is also observed in gametocytes where PfABCG is highly expressed. Analysis of PfABCG genomic sequences for polymorphisms and changes in protein expression between different strains of P. falciparum revealed identical nucleotide sequence among the different strains, but variable protein expression. PfABCG expression is least in HB3 chloroquine sensitive strain, while higher expression levels are seen in other chloroquine-sensitive and -resistant strains, with highest levels of expression in 7G8. The differential expression of PfABCG in three chloroquine-sensitive strains (e.g., 3D7, HB3 and D10) predicts the sensitivity of the different strains to ketotifen, an anti-histaminic drug, whereby low expression is associated with decreased sensitivity to ketotifen. Taken together, the results in this report provide the first description of native PfABCG expression and subcellular localization in asexual stages of the parasite and its localization in gametocytes. It remains to be determined if PfABCG is functionally equivalent to mammalian ABCG1, ABCG2 or both. PMID:26239803

  11. Fucosylated Chondroitin Sulfate Inhibits Plasmodium falciparum Cytoadhesion and Merozoite Invasion

    PubMed Central

    Bastos, Marcele F.; Albrecht, Letusa; Kozlowski, Eliene O.; Lopes, Stefanie C. P.; Blanco, Yara C.; Carlos, Bianca C.; Castiñeiras, Catarina; Vicente, Cristina P.; Werneck, Claudio C.; Wunderlich, Gerhard; Ferreira, Marcelo U.; Marinho, Claudio R. F.; Mourão, Paulo A. S.; Pavão, Mauro S. G.

    2014-01-01

    Sequestration of Plasmodium falciparum-infected erythrocytes (Pf-iEs) in the microvasculature of vital organs plays a key role in the pathogenesis of life-threatening malaria complications, such as cerebral malaria and malaria in pregnancy. This phenomenon is marked by the cytoadhesion of Pf-iEs to host receptors on the surfaces of endothelial cells, on noninfected erythrocytes, and in the placental trophoblast; therefore, these sites are potential targets for antiadhesion therapies. In this context, glycosaminoglycans (GAGs), including heparin, have shown the ability to inhibit Pf-iE cytoadherence and growth. Nevertheless, the use of heparin was discontinued due to serious side effects, such as bleeding. Other GAG-based therapies were hampered due to the potential risk of contamination with prions and viruses, as some GAGs are isolated from mammals. In this context, we investigated the effects and mechanism of action of fucosylated chondroitin sulfate (FucCS), a unique and highly sulfated GAG isolated from the sea cucumber, with respect to P. falciparum cytoadhesion and development. FucCS was effective in inhibiting the cytoadherence of Pf-iEs to human lung endothelial cells and placenta cryosections under static and flow conditions. Removal of the sulfated fucose branches of the FucCS structure virtually abolished the inhibitory effects of FucCS. Importantly, FucCS rapidly disrupted rosettes at high levels, and it was also able to block parasite development by interfering with merozoite invasion. Collectively, these findings highlight the potential of FucCS as a candidate for adjunct therapy against severe malaria. PMID:24395239

  12. Plasmodium falciparum var gene expression is modified by host immunity

    PubMed Central

    Warimwe, George M.; Keane, Thomas M.; Fegan, Gregory; Musyoki, Jennifer N.; Newton, Charles R. J. C.; Pain, Arnab; Berriman, Matthew; Marsh, Kevin; Bull, Peter C.

    2009-01-01

    Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is a potentially important family of immune targets, which play a central role in the host–parasite interaction by binding to various host molecules. They are encoded by a diverse family of genes called var, of which there are ≈60 copies in each parasite genome. In sub-Saharan Africa, although P. falciparum infection occurs throughout life, severe malarial disease tends to occur only in childhood. This could potentially be explained if (i) PfEMP1 variants differ in their capacity to support pathogenesis of severe malaria and (ii) this capacity is linked to the likelihood of each molecule being recognized and cleared by naturally acquired antibodies. Here, in a study of 217 Kenyan children with malaria, we show that expression of a group of var genes “cys2,” containing a distinct pattern of cysteine residues, is associated with low host immunity. Expression of cys2 genes was associated with parasites from young children, those with severe malaria, and those with a poorly developed antibody response to parasite-infected erythrocyte surface antigens. Cys-2 var genes form a minor component of all genomic var repertoires analyzed to date. Therefore, the results are compatible with the hypothesis that the genomic var gene repertoire is organized such that PfEMP1 molecules that confer the most virulence to the parasite tend also to be those that are most susceptible to the development of host immunity. This may help the parasite to adapt effectively to the development of host antibodies through modification of the host–parasite relationship. PMID:20018734

  13. A molecular mechanism of artemisinin resistance in Plasmodium falciparum malaria

    PubMed Central

    Mbengue, Alassane; Bhattacharjee, Souvik; Pandharkar, Trupti; Liu, Haining; Estiu, Guillermina; Stahelin, Robert V.; Rizk, Shahir; Njimoh, Dieudonne L.; Ryan, Yana; Chotivanich, Kesinee; Nguon, Chea; Ghorbal, Mehdi; Lopez-Rubio, Jose-Juan; Pfrender, Michael; Emrich, Scott; Mohandas, Narla; Dondorp, Arjen M.; Wiest, Olaf; Haldar, Kasturi

    2015-01-01

    Artemisinins are the corner stone of anti-malarial drugs1. Emergence and spread of resistance to them2–4 raises risk of wiping out recent gains achieved in reducing world-wide malaria burden and threatens future malaria control and elimination on a global level. Genome wide association studies (GWAS) have revealed parasite genetic loci associated with artemisinin resistance5–10. However, there is no consensus on biochemical targets of artemisinin. Whether and how these targets interact with genes identified by GWAS, remains unknown. Here we provide biochemical and cellular evidence that artemisinins are potent inhibitors of Plasmodium falciparum phosphatidylinositol-3-kinase (PfPI3K), revealing an unexpected mechanism of action. In resistant clinical strains, increased PfPI3K was associated with the C580Y mutation in P. falciparum Kelch13 (PfKelch13), a primary marker of artemisinin resistance. Polyubiquitination of PfPI3K and its binding to PfKelch13 were reduced by PfKelch13 mutation, which limited proteolysis of PfPI3K and thus increased levels of the kinase as well as its lipid product phosphatidylinositol 3-phosphate (PI3P). We find PI3P levels to be predictive of artemisinin resistance in both clinical and engineered laboratory parasites as well as across non-isogenic strains. Elevated PI3P induced artemisinin resistance in absence of PfKelch13 mutations, but remained responsive to regulation by PfKelch13. Evidence is presented for PI3P-dependent signaling, where transgenic expression of an additional kinase confers resistance. Together these data present PI3P as the key mediator of artemisinin resistance and the sole PfPI3K as an important target for malaria elimination. PMID:25874676

  14. Calmidazolium evokes high calcium fluctuations in Plasmodium falciparum.

    PubMed

    Budu, Alexandre; Gomes, Mayrim M; Melo, Pollyana M; El Chamy Maluf, Sarah; Bagnaresi, Piero; Azevedo, Mauro F; Carmona, Adriana K; Gazarini, Marcos L

    2016-03-01

    Calcium and calmodulin (CaM) are important players in eukaryote cell signaling. In the present study, by using a knockin approach, we demonstrated the expression and localization of CaM in all erythrocytic stages of Plasmodium falciparum. Under extracellular Ca(2+)-free conditions, calmidazolium (CZ), a potent CaM inhibitor, promoted a transient cytosolic calcium ([Ca(2+)]cyt) increase in isolated trophozoites, indicating that CZ mobilizes intracellular sources of calcium. In the same extracellular Ca(2+)-free conditions, the [Ca(2+)]cyt rise elicited by CZ treatment was ~3.5 fold higher when the endoplasmic reticulum (ER) calcium store was previously depleted ruling out the mobilization of calcium from the ER by CZ. The effects of the Ca(2+)/H(+) ionophore ionomycin (ION) and the Na(+)/H(+) ionophore monensin (MON) suggest that the [Ca(2+)]cyt-increasing effect of CZ is driven by the removal of Ca(2+) from at least one Ca(2+)-CaM-related (CaMR) protein as well as by the mobilization of Ca(2+) from intracellular acidic calcium stores. Moreover, we showed that the mitochondrion participates in the sequestration of the cytosolic Ca(2+) elicited by CZ. Finally, the modulation of membrane Ca(2+) channels by CZ and thapsigargin (THG) was demonstrated. The opened channels were blocked by the unspecific calcium channel blocker Co(2+) but not by 2-APB (capacitative calcium entry inhibitor) or nifedipine (L-type Ca(2+) channel inhibitor). Taken together, the results suggested that one CaMR protein is an important modulator of calcium signaling and homeostasis during the Plasmodium intraerythrocytic cell cycle, working as a relevant intracellular Ca(2+) reservoir in the parasite. PMID:26689736

  15. Impact of climate variability on Plasmodium vivax and Plasmodium falciparum malaria in Yunnan Province, China

    PubMed Central

    2013-01-01

    Background Malaria remains a public health problem in the remote and poor area of Yunnan Province, China. Yunnan faces an increasing risk of imported malaria infections from Mekong river neighboring countries. This study aimed to identify the high risk area of malaria transmission in Yunnan Province, and to estimate the effects of climatic variability on the transmission of Plasmodium vivax and Plasmodium falciparum in the identified area. Methods We identified spatial clusters of malaria cases using spatial cluster analysis at a county level in Yunnan Province, 2005–2010, and estimated the weekly effects of climatic factors on P. vivax and P. falciparum based on a dataset of daily malaria cases and climatic variables. A distributed lag nonlinear model was used to estimate the impact of temperature, relative humidity and rainfall up to 10–week lags on both types of malaria parasite after adjusting for seasonal and long-term effects. Results The primary cluster area was identified along the China–Myanmar border in western Yunnan. A 1°C increase in minimum temperature was associated with a lag 4 to 9 weeks relative risk (RR), with the highest effect at lag 7 weeks for P. vivax (RR = 1.03; 95% CI, 1.01, 1.05) and 6 weeks for P. falciparum (RR = 1.07; 95% CI, 1.04, 1.11); a 10-mm increment in rainfall was associated with RRs of lags 2-4 weeks and 9-10 weeks, with the highest effect at 3 weeks for both P. vivax (RR = 1.03; 95% CI, 1.01, 1.04) and P. falciparum (RR = 1.04; 95% CI, 1.01, 1.06); and the RRs with a 10% rise in relative humidity were significant from lag 3 to 8 weeks with the highest RR of 1.24 (95% CI, 1.10, 1.41) for P. vivax at 5-week lag. Conclusions Our findings suggest that the China–Myanmar border is a high risk area for malaria transmission. Climatic factors appeared to be among major determinants of malaria transmission in this area. The estimated lag effects for the association between temperature and malaria are consistent with the life

  16. Protease-associated cellular networks in malaria parasite Plasmodium falciparum

    PubMed Central

    2011-01-01

    Background Malaria continues to be one of the most severe global infectious diseases, responsible for 1-2 million deaths yearly. The rapid evolution and spread of drug resistance in parasites has led to an urgent need for the development of novel antimalarial targets. Proteases are a group of enzymes that play essential roles in parasite growth and invasion. The possibility of designing specific inhibitors for proteases makes them promising drug targets. Previously, combining a comparative genomics approach and a machine learning approach, we identified the complement of proteases (degradome) in the malaria parasite Plasmodium falciparum and its sibling species [1-3], providing a catalog of targets for functional characterization and rational inhibitor design. Network analysis represents another route to revealing the role of proteins in the biology of parasites and we use this approach here to expand our understanding of the systems involving the proteases of P. falciparum. Results We investigated the roles of proteases in the parasite life cycle by constructing a network using protein-protein association data from the STRING database [4], and analyzing these data, in conjunction with the data from protein-protein interaction assays using the yeast 2-hybrid (Y2H) system [5], blood stage microarray experiments [6-8], proteomics [9-12], literature text mining, and sequence homology analysis. Seventy-seven (77) out of 124 predicted proteases were associated with at least one other protein, constituting 2,431 protein-protein interactions (PPIs). These proteases appear to play diverse roles in metabolism, cell cycle regulation, invasion and infection. Their degrees of connectivity (i.e., connections to other proteins), range from one to 143. The largest protease-associated sub-network is the ubiquitin-proteasome system which is crucial for protein recycling and stress response. Proteases are also implicated in heat shock response, signal peptide processing, cell cycle

  17. Artemisinin-naphthoquine for treating uncomplicated Plasmodium falciparum malaria

    PubMed Central

    Isba, Rachel; Zani, Babalwa; Gathu, Michael; Sinclair, David

    2015-01-01

    Background The World Health Organization (WHO) recommends artemisinin-based combination therapy (ACT) for treating people with Plasmodium falciparum malaria. Five combinations are currently recommended, all administered over three days. Artemisinin-naphthoquine is a new combination developed in China, which is being marketed as a one-day treatment. Although shorter treatment courses may improve adherence, the WHO recommends at least three days of the short-acting artemisinin component to eliminate 90% P. falciparum parasites in the bloodstream, before leaving the longer-acting partner drug to clear the remaining parasites. Objectives To evaluate the efficacy and safety of the artemisinin-naphthoquine combination for treating adults and children with uncomplicated P. falciparum malaria. Search methods We searched the Cochrane Infectious Diseases Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL) published in The Cochrane Library; MEDLINE; EMBASE; and LILACS up to January 2015. We also searched the metaRegister of Controlled Trials (mRCT) using 'malaria' and 'arte* OR dihydroarte*' as search terms. Selection criteria Randomized controlled trials comparing artemisinin-naphthoquine combinations with established WHO-recommended ACTs for the treatment of adults and children with uncomplicated malaria due to P. falciparum. Data collection and analysis Two review authors independently assessed trials for eligibility and risk of bias, and extracted data. We analysed primary outcomes in line with the WHO 'Protocol for assessing and monitoring antimalarial drug efficacy' and compared drugs using risk ratios (RR) and 95% confidence intervals (CI). Secondary outcomes were effects on gametocytes, haemoglobin, and adverse events. We assessed the quality of evidence using the GRADE approach. Main results Four trials, enrolling 740 adults and children, met the inclusion criteria. Artemisinin-naphthoquine was administered as a single dose (two

  18. Aminoindoles, a novel scaffold with potent activity against Plasmodium falciparum.

    PubMed

    Barker, Robert H; Urgaonkar, Sameer; Mazitschek, Ralph; Celatka, Cassandra; Skerlj, Renato; Cortese, Joseph F; Tyndall, Erin; Liu, Hanlan; Cromwell, Mandy; Sidhu, Amar Bir; Guerrero-Bravo, Jose E; Crespo-Llado, Keila N; Serrano, Adelfa E; Lin, Jing-Wen; Janse, Chris J; Khan, Shahid M; Duraisingh, Manoj; Coleman, Bradley I; Angulo-Barturen, Inigo; Jiménez-Díaz, María Belén; Magán, Noemí; Gomez, Vanesa; Ferrer, Santiago; Martínez, María Santos; Wittlin, Sergio; Papastogiannidis, Petros; O'Shea, Thomas; Klinger, Jeffrey D; Bree, Mark; Lee, Edward; Levine, Mikaela; Wiegand, Roger C; Munoz, Benito; Wirth, Dyann F; Clardy, Jon; Bathurst, Ian; Sybertz, Edmund

    2011-06-01

    This study characterizes aminoindole molecules that are analogs of Genz-644442. Genz-644442 was identified as a hit in a screen of ~70,000 compounds in the Broad Institute's small-molecule library and the ICCB-L compound collection at Harvard Medical School. Genz-644442 is a potent inhibitor of Plasmodium falciparum in vitro (50% inhibitory concentrations [IC₅₀s], 200 to 285 nM) and inhibits P. berghei in vivo with an efficacy of > 99% in an adapted version of Peters' 4-day suppressive test (W. Peters, Ann. Trop. Med. Parasitol. 69:155-171, 1975). Genz-644442 became the focus of medicinal chemistry optimization; 321 analogs were synthesized and were tested for in vitro potency against P. falciparum and for in vitro absorption, distribution, metabolism, and excretion (ADME) properties. This yielded compounds with IC₅₀s of approximately 30 nM. The lead compound, Genz-668764, has been characterized in more detail. It is a single enantiomer with IC₅₀s of 28 to 65 nM against P. falciparum in vitro. In the 4-day P. berghei model, when it was dosed at 100 mg/kg of body weight/day, no parasites were detected on day 4 postinfection. However, parasites recrudesced by day 9. Dosing at 200 mg/kg/day twice a day resulted in cures of 3/5 animals. The compound had comparable activity against P. falciparum blood stages in a human-engrafted NOD-scid mouse model. Genz-668764 had a terminal half-life of 2.8 h and plasma trough levels of 41 ng/ml when it was dosed twice a day orally at 55 mg/kg/day. Seven-day rat safety studies showed a no-observable-adverse-effect level (NOAEL) at 200 mg/kg/day; the compound was not mutagenic in Ames tests, did not inhibit the hERG channel, and did not have potent activity against a broad panel of receptors and enzymes. Employing allometric scaling and using in vitro ADME data, the predicted human minimum efficacious dose of Genz-668764 in a 3-day once-daily dosing regimen was 421 mg/day/70 kg, which would maintain plasma trough levels

  19. A molecular marker of artemisinin-resistant Plasmodium falciparum malaria

    PubMed Central

    Ariey, Frédéric; Witkowski, Benoit; Amaratunga, Chanaki; Beghain, Johann; Langlois, Anne-Claire; Khim, Nimol; Kim, Saorin; Duru, Valentine; Bouchier, Christiane; Ma, Laurence; Lim, Pharath; Leang, Rithea; Duong, Socheat; Sreng, Sokunthea; Suon, Seila; Chuor, Char Meng; Bout, Denis Mey; Ménard, Sandie; Rogers, William O.; Genton, Blaise; Fandeur, Thierry; Miotto, Olivo; Ringwald, Pascal; Le Bras, Jacques; Berry, Antoine; Barale, Jean-Christophe; Fairhurst, Rick M.; Benoit-Vical, Françoise; Mercereau-Puijalon, Odile; Ménard, Didier

    2016-01-01

    Plasmodium falciparum resistance to artemisinin derivatives in southeast Asia threatens malaria control and elimination activities worldwide. To monitor the spread of artemisinin resistance, a molecular marker is urgently needed. Here, using whole-genome sequencing of an artemisinin-resistant parasite line from Africa and clinical parasite isolates from Cambodia, we associate mutations in the PF3D7_1343700 kelch propeller domain (‘K13-propeller’) with artemisinin resistance in vitro and in vivo. Mutant K13-propeller alleles cluster in Cambodian provinces where resistance is prevalent, and the increasing frequency of a dominant mutant K13-propeller allele correlates with the recent spread of resistance in western Cambodia. Strong correlations between the presence of a mutant allele, in vitro parasite survival rates and in vivo parasite clearance rates indicate that K13-propeller mutations are important determinants of artemisinin resistance. K13-propeller polymorphism constitutes a useful molecular marker for large-scale surveillance efforts to contain artemisinin resistance in the Greater Mekong Subregion and prevent its global spread. PMID:24352242

  20. Polycyclic amines as chloroquine resistance modulating agents in Plasmodium falciparum.

    PubMed

    Joubert, Jacques; Kapp, Erika; Taylor, Dale; Smith, Peter J; Malan, Sarel F

    2016-02-15

    Pentacycloundecylamines (PCUs) and adamantane amines, such as NGP1-01 (1) and amantadine, have shown significant channel blocking activities. They are postulated to act as chemosensitizers and circumvent the resistance of the plasmodia parasite against chloroquine (CQ) by inhibiting the p-glycoprotein efflux pump and enabling the accumulation of CQ inside the parasite digestive vacuole. Twelve polycyclic amines containing either a PCU or adamantane amine moiety conjugated to different aromatic functionalities through various tethered linkers were selected based on their channel blocking abilities and evaluated as potential chemosensitizers. Compounds 2, 4, 5 and 10 showed significant voltage-gated calcium channel (VGCC) blocking ability (IC50=0.27-35 μM) and were able to alter the CQ IC50 in differing degrees (45-81%) in the multidrug resistant Plasmodium falciparum Dd2 isolate. Among them, the PCU-dansyl amine compound (4) displayed the best potential to act as a chemosensitizer against the Dd2 strain at a 1 μM concentration (RMI=0.19) while displaying moderate antiplasmodial activity (Dd2 IC50=6.25 μM) and low in vitro cytotoxicity against a mammalian cell line (CHO, IC50=119 μM). Compounds 2 and 10 also showed some promising chemosensitizing abilities (RMI=0.36 and 0.35 respectively). A direct correlation was found between the VGCC blocking ability of these polycyclic amines and their capacity to act as CQ resistance modulating agents. PMID:26832222

  1. Human cerebral malaria and Plasmodium falciparum genotypes in Malawi

    PubMed Central

    2012-01-01

    Background Cerebral malaria, a severe form of Plasmodium falciparum infection, is an important cause of mortality in sub-Saharan African children. A Taqman 24 Single Nucleotide Polymorphisms (SNP) molecular barcode assay was developed for use in laboratory parasites which estimates genotype number and identifies the predominant genotype. Methods The 24 SNP assay was used to determine predominant genotypes in blood and tissues from autopsy and clinical patients with cerebral malaria. Results Single genotypes were shared between the peripheral blood, the brain, and other tissues of cerebral malaria patients, while malaria-infected patients who died of non-malarial causes had mixed genetic signatures in tissues examined. Children with retinopathy-positive cerebral malaria had significantly less complex infections than those without retinopathy (OR = 3.7, 95% CI [1.51-9.10]).The complexity of infections significantly decreased over the malaria season in retinopathy-positive patients compared to retinopathy-negative patients. Conclusions Cerebral malaria patients harbour a single or small set of predominant parasites; patients with incidental parasitaemia sustain infections involving diverse genotypes. Limited diversity in the peripheral blood of cerebral malaria patients and correlation with tissues supports peripheral blood samples as appropriate for genome-wide association studies of parasite determinants of pathogenicity. PMID:22314206

  2. Serological Evidence of Discrete Spatial Clusters of Plasmodium falciparum Parasites

    PubMed Central

    Bejon, Philip; Turner, Louise; Lavstsen, Thomas; Cham, Gerald; Olotu, Ally; Drakeley, Chris J.; Lievens, Marc; Vekemans, Johan; Savarese, Barbara; Lusingu, John; von Seidlein, Lorenz; Bull, Peter C.; Marsh, Kevin; Theander, Thor G.

    2011-01-01

    Background Malaria transmission may be considered to be homogenous with well-mixed parasite populations (as in the classic Ross/Macdonald models). Marked fine-scale heterogeneity of transmission has been observed in the field (i.e., over a few kilometres), but there are relatively few data on the degree of mixing. Since the Plasmodium falciparum Erythrocyte Membrane Protein 1 (PfEMP1) is highly polymorphic, the host's serological responses may be used to infer exposure to parasite sub-populations. Methods and Findings We measured the antibody responses to 46 individual PfEMP1 domains at four time points among 450 children in Kenya, and identified distinct spatial clusters of antibody responses to individual domains. 35 domains showed strongly significant sero-clusters at p = 0.001. Individuals within the high transmission hotspot showed the greatest diversity of anti-PfEMP1 responses. Individuals outside the hotspot had a less diverse range of responses, even if as individuals they were at relatively intense exposure. Conclusions We infer that antigenically distinct sub-populations of parasites exist on a fine spatial scale in a study area of rural Kenya. Further studies should examine antigenic variation over longer periods of time and in different study areas. PMID:21747921

  3. Genetic architecture of artemisinin-resistant Plasmodium falciparum

    PubMed Central

    Miotto, Olivo; Amato, Roberto; Ashley, Elizabeth A; MacInnis, Bronwyn; Almagro-Garcia, Jacob; Amaratunga, Chanaki; Lim, Pharath; Mead, Daniel; Oyola, Samuel O; Dhorda, Mehul; Imwong, Mallika; Woodrow, Charles; Manske, Magnus; Stalker, Jim; Drury, Eleanor; Campino, Susana; Amenga-Etego, Lucas; Thanh, Thuy-Nhien Nguyen; Tran, Hien Tinh; Ringwald, Pascal; Bethell, Delia; Nosten, Francois; Phyo, Aung Pyae; Pukrittayakamee, Sasithon; Chotivanich, Kesinee; Chuor, Char Meng; Nguon, Chea; Suon, Seila; Sreng, Sokunthea; Newton, Paul N; Mayxay, Mayfong; Khanthavong, Maniphone; Hongvanthong, Bouasy; Htut, Ye; Han, Kay Thwe; Kyaw, Myat Phone; Faiz, Md Abul; Fanello, Caterina I; Onyamboko, Marie; Mokuolu, Olugbenga A; Jacob, Christopher G; Takala-Harrison, Shannon; Plowe, Christopher V; Day, Nicholas P; Dondorp, Arjen M; Spencer, Chris C A; McVean, Gilean; Fairhurst, Rick M; White, Nicholas J; Kwiatkowski, Dominic P

    2015-01-01

    We report a large multicenter genome-wide association study of Plasmodium falciparum resistance to artemisinin, the frontline antimalarial drug. Across 15 locations in Southeast Asia, we identified at least 20 mutations in kelch13 (PF3D7_1343700) affecting the encoded propeller and BTB/POZ domains, which were associated with a slow parasite clearance rate after treatment with artemisinin derivatives. Nonsynonymous polymorphisms in fd (ferredoxin), arps10 (apicoplast ribosomal protein S10), mdr2 (multidrug resistance protein 2) and crt (chloroquine resistance transporter) also showed strong associations with artemisinin resistance. Analysis of the fine structure of the parasite population showed that the fd, arps10, mdr2 and crt polymorphisms are markers of a genetic background on which kelch13 mutations are particularly likely to arise and that they correlate with the contemporary geographical boundaries and population frequencies of artemisinin resistance. These findings indicate that the risk of new resistance-causing mutations emerging is determined by specific predisposing genetic factors in the underlying parasite population. PMID:25599401

  4. A molecular marker of artemisinin-resistant Plasmodium falciparum malaria

    NASA Astrophysics Data System (ADS)

    Ariey, Frédéric; Witkowski, Benoit; Amaratunga, Chanaki; Beghain, Johann; Langlois, Anne-Claire; Khim, Nimol; Kim, Saorin; Duru, Valentine; Bouchier, Christiane; Ma, Laurence; Lim, Pharath; Leang, Rithea; Duong, Socheat; Sreng, Sokunthea; Suon, Seila; Chuor, Char Meng; Bout, Denis Mey; Ménard, Sandie; Rogers, William O.; Genton, Blaise; Fandeur, Thierry; Miotto, Olivo; Ringwald, Pascal; Le Bras, Jacques; Berry, Antoine; Barale, Jean-Christophe; Fairhurst, Rick M.; Benoit-Vical, Françoise; Mercereau-Puijalon, Odile; Ménard, Didier

    2014-01-01

    Plasmodium falciparum resistance to artemisinin derivatives in southeast Asia threatens malaria control and elimination activities worldwide. To monitor the spread of artemisinin resistance, a molecular marker is urgently needed. Here, using whole-genome sequencing of an artemisinin-resistant parasite line from Africa and clinical parasite isolates from Cambodia, we associate mutations in the PF3D7_1343700 kelch propeller domain (`K13-propeller') with artemisinin resistance in vitro and in vivo. Mutant K13-propeller alleles cluster in Cambodian provinces where resistance is prevalent, and the increasing frequency of a dominant mutant K13-propeller allele correlates with the recent spread of resistance in western Cambodia. Strong correlations between the presence of a mutant allele, in vitro parasite survival rates and in vivo parasite clearance rates indicate that K13-propeller mutations are important determinants of artemisinin resistance. K13-propeller polymorphism constitutes a useful molecular marker for large-scale surveillance efforts to contain artemisinin resistance in the Greater Mekong Subregion and prevent its global spread.

  5. Kinetic mechanism of Plasmodium falciparum hypoxanthine-guanine-xanthine phosphoribosyltransferase.

    PubMed

    Roy, Sourav; Nagappa, Lakshmeesha K; Prahladarao, Vasudeva S; Balaram, Hemalatha

    2015-12-01

    Plasmodium falciparum hypoxanthine-guanine-xanthine phosphoribosyltransferase (PfHGXPRT) exhibits a kinetic mechanism that differs from that of the human homolog. Human HGPRT follows a steady-state ordered mechanism, wherein PRPP binding precedes the binding of hypoxanthine/guanine and release of product IMP/GMP is the rate limiting step. In the current study, initial velocity kinetics with PfHGXPRT indicates a steady-state ordered mechanism, wherein xanthine binding is conditional to the binding of PRPP. The value of the rate constant for IMP dissociation is greater by 183-fold than the kcat for hypoxanthine phosphoribosylation and this results in the absence of burst in progress curves from pre-steady-state kinetics. Further, IMP binding is 1000 times faster (4s(-1) at 0.5μM IMP) when compared to the kcat (3.9±0.2×10(-3)s(-1)) for the reverse IMP pyrophosphorolysis reaction. These results lend support to the fact that in both forward and reverse reactions, the process of chemical conversion (formation of IMP/hypoxanthine) is slow and the events of ligand association and dissociation are faster. PMID:26902413

  6. Genetic architecture of artemisinin-resistant Plasmodium falciparum.

    PubMed

    Miotto, Olivo; Amato, Roberto; Ashley, Elizabeth A; MacInnis, Bronwyn; Almagro-Garcia, Jacob; Amaratunga, Chanaki; Lim, Pharath; Mead, Daniel; Oyola, Samuel O; Dhorda, Mehul; Imwong, Mallika; Woodrow, Charles; Manske, Magnus; Stalker, Jim; Drury, Eleanor; Campino, Susana; Amenga-Etego, Lucas; Thanh, Thuy-Nhien Nguyen; Tran, Hien Tinh; Ringwald, Pascal; Bethell, Delia; Nosten, Francois; Phyo, Aung Pyae; Pukrittayakamee, Sasithon; Chotivanich, Kesinee; Chuor, Char Meng; Nguon, Chea; Suon, Seila; Sreng, Sokunthea; Newton, Paul N; Mayxay, Mayfong; Khanthavong, Maniphone; Hongvanthong, Bouasy; Htut, Ye; Han, Kay Thwe; Kyaw, Myat Phone; Faiz, Md Abul; Fanello, Caterina I; Onyamboko, Marie; Mokuolu, Olugbenga A; Jacob, Christopher G; Takala-Harrison, Shannon; Plowe, Christopher V; Day, Nicholas P; Dondorp, Arjen M; Spencer, Chris C A; McVean, Gilean; Fairhurst, Rick M; White, Nicholas J; Kwiatkowski, Dominic P

    2015-03-01

    We report a large multicenter genome-wide association study of Plasmodium falciparum resistance to artemisinin, the frontline antimalarial drug. Across 15 locations in Southeast Asia, we identified at least 20 mutations in kelch13 (PF3D7_1343700) affecting the encoded propeller and BTB/POZ domains, which were associated with a slow parasite clearance rate after treatment with artemisinin derivatives. Nonsynonymous polymorphisms in fd (ferredoxin), arps10 (apicoplast ribosomal protein S10), mdr2 (multidrug resistance protein 2) and crt (chloroquine resistance transporter) also showed strong associations with artemisinin resistance. Analysis of the fine structure of the parasite population showed that the fd, arps10, mdr2 and crt polymorphisms are markers of a genetic background on which kelch13 mutations are particularly likely to arise and that they correlate with the contemporary geographical boundaries and population frequencies of artemisinin resistance. These findings indicate that the risk of new resistance-causing mutations emerging is determined by specific predisposing genetic factors in the underlying parasite population. PMID:25599401

  7. Analysis of Breath Specimens for Biomarkers of Plasmodium falciparum Infection

    PubMed Central

    Berna, Amalia Z.; McCarthy, James S.; Wang, Rosalind X.; Saliba, Kevin J.; Bravo, Florence G.; Cassells, Julie; Padovan, Benjamin; Trowell, Stephen C.

    2015-01-01

    Currently, the majority of diagnoses of malaria rely on a combination of the patient's clinical presentation and the visualization of parasites on a stained blood film. Breath offers an attractive alternative to blood as the basis for simple, noninvasive diagnosis of infectious diseases. In this study, breath samples were collected from individuals during controlled malaria to determine whether specific malaria-associated volatiles could be detected in breath. We identified 9 compounds whose concentrations varied significantly over the course of malaria: carbon dioxide, isoprene, acetone, benzene, cyclohexanone, and 4 thioethers. The latter group, consisting of allyl methyl sulfide, 1-methylthio-propane, (Z)-1-methylthio-1-propene, and (E)-1-methylthio-1-propene, had not previously been associated with any disease or condition. Before the availability of antimalarial drug treatment, there was evidence of concurrent 48-hour cyclical changes in the levels of both thioethers and parasitemia. When thioether concentrations were subjected to a phase shift of 24 hours, a direct correlation between the parasitemia and volatile levels was revealed. Volatile levels declined monotonically approximately 6.5 hours after initial drug treatment, correlating with clearance of parasitemia. No thioethers were detected in in vitro cultures of Plasmodium falciparum. The metabolic origin of the thioethers is not known, but results suggest that interplay between host and parasite metabolic pathways is involved in the production of these thioethers. PMID:25810441

  8. Plasmodium falciparum Merozoite Surface Protein 6 Is a Dimorphic Antigen

    PubMed Central

    Pearce, J. Andrew; Triglia, Tony; Hodder, Anthony N.; Jackson, David C.; Cowman, Alan F.; Anders, Robin F.

    2004-01-01

    Merozoite surface protein 1 (MSP1) is a highly polymorphic Plasmodium falciparum merozoite surface protein implicated in the invasion of human erythrocytes during the asexual cycle. It forms a complex with MSP6 and MSP7 on the merozoite surface, and this complex is released from the parasite around the time of erythrocyte invasion. MSP1 and many other merozoite surface proteins contain dimorphic elements in their protein structures, and here we show that MSP6 is also dimorphic. The sequences of eight MSP6 genes indicate that the alleles of each dimorphic form of MSP6 are highly conserved. The smaller 3D7-type MSP6 alleles are detected in parasites from all malarious regions of the world, whereas K1-type MSP6 alleles have only been detected in parasites from mainland Southeast Asia. Cleavage of MSP6, which produces the p36 fragment in 3D7-type MSP6 and associates with MSP1, also occurs in K1-type MSP6 but at a different site in the protein. Anti-3D7 MSP6 antibodies weakly inhibited erythrocyte invasion by homologous 3D7 merozoites but did not inhibit a parasite line expressing the K1-type MSP6 allele. Antibodies from hyperimmune individuals affinity purified on an MSP3 peptide cross-reacted with MSP6; therefore, MSP6 may also be a target of antibody-dependent cellular inhibition. PMID:15039357

  9. Identification of two integral membrane proteins of Plasmodium falciparum

    SciTech Connect

    Smythe, J.A.; Coppel, R.L.; Brown, G.V.; Ramasamy, R.; Kemp, D.J.; Anders, R.F. )

    1988-07-01

    The authors describe the isolation and cloning of two integral membrane protein antigens of Plasmodium falciparum. The antigens were isolated by Triton X-114 temperature-dependent phase separation, electrophoretically transferred to nitrocellulose, and used to affinity-purify monospecific human antibodies. These antibodies were used to isolate the corresponding cDNA clones from a phage {lambda}gt11-Amp3 cDNA expression library. Clone Ag512 corresponds to a M{sub r} 55,000 merozoite rhoptry antigen, and clone Ag513 corresponds to a M{sub r} 45,000 merozoite surface antigen. Both proteins can be biosynthetically labeled with ({sup 3}H)glucosamine and ({sup 3}H)myristic acid, suggesting that they may be anchored in membranes via a glycosylphosphatidylinositol moiety. Similarities in the C-terminal sequences of the M{sub r} 45,000 merozoite surface antigen and the Trypanosoma brucei variant surface glycoproteins provides further evidence that this antigen has a glycosylphosphatidylinositol anchor.

  10. Platelets Potentiate Brain Endothelial Alterations Induced by Plasmodium falciparum

    PubMed Central

    Wassmer, Samuel C.; Combes, Valéry; Candal, Francisco J.; Juhan-Vague, Irène; Grau, Georges E.

    2006-01-01

    Brain lesions of cerebral malaria (CM) are characterized by a sequestration of Plasmodium falciparum-parasitized red blood cells (PRBC) and platelets within brain microvessels, as well as by blood-brain barrier (BBB) disruption. In the present study, we evaluated the possibility that PRBC and platelets induce functional alterations in brain endothelium. In a human brain endothelial cell line, named HBEC-5i, exhibiting most of the features demanded for a pathophysiological study of BBB, tumor necrosis factor (TNF) or lymphotoxin α (LT-α) reduced transendothelial electrical resistance (TEER), enhanced the permeability to 70-kDa dextran, and increased the release of microparticles, a recently described indicator of disease severity in CM patients. In vitro cocultures showed that platelets or PRBC can have a direct cytotoxic effect on activated, but not on resting, HBEC-5i cells. Platelet binding was required, as platelet supernatant had no effect. Furthermore, platelets potentiated the cytotoxicity of PRBC for TNF- or LT-α-activated HBEC-5i cells when they were added prior to these cells on the endothelial monolayers. This effect was not observed when platelets were added after PRBC. Both permeability and TEER were strongly affected, and the apoptosis rate of HBEC-5i cells was dramatically increased. These findings provide insights into the mechanisms by which platelets can be deleterious to the brain endothelium during CM. PMID:16369021

  11. The gene encoding topoisomerase II from Plasmodium falciparum.

    PubMed Central

    Cheesman, S; McAleese, S; Goman, M; Johnson, D; Horrocks, P; Ridley, R G; Kilbey, B J

    1994-01-01

    The gene for topoisomerase II has been isolated from genomic libraries of strain K1 of the human malarial parasite, Plasmodium falciparum. The sequence reveals an open reading frame of 4194 nucleotides which predicts a polypeptide of 1398 amino acids. There are apparently no introns. The sequence is present as a single copy which has an identity of 47.4% and a similarity of 65.4% with its human homologue. Sequences conserved in topoisomerase II from other species are present in Pftopoisomerase II but in addition it has two adjacent asparagine-rich insertions which are unique to it. We have also detected asparagine-rich regions in the gene for PfDNA polymerase alpha. The gene for Pftopoisomerase II has been localised to chromosome 14 and northern analysis reveals a transcript of 5.8 kb. Two independent antisera raised in mice against glutathione-S-transferase fusion proteins containing the amino terminal portion of the malarial protein detect a weak band on western blots at about 160kDa, the expected size of the protein. Use of the same antisera for immunofluorescence analysis suggests that the protein is present at all stages of intraerythrocytic growth of the parasite. Images PMID:8041616

  12. Plasmodium falciparum dolichol phosphate mannose synthase represents a novel clade

    SciTech Connect

    Shams-Eldin, Hosam Santos de Macedo, Cristiana; Niehus, Sebastian; Dorn, Caroline; Kimmel, Juergen; Azzouz, Nahid; Schwarz, Ralph T.

    2008-06-06

    Dolichol phosphate mannose synthase (DPM) catalyzes the reaction between dolichol phosphate (Dol-P) and guanosine diphosphate mannose (GDP-Man) to form dolichol-phosphate-mannose (Dol-P-Man). This molecule acts as mannose donor for N-glycosylation and glycosylphosphatidylinositol (GPI) biosynthesis. The Plasmodium falciparum DPM1 (Pfdpm1) possesses a single predicted transmembrane region near the N-, but not the C-terminus. Here we show that the cloned Pfdpm1 gene failed to complement a Saccharomyces cerevisiae mutant indicating that the parasite gene does not belong to the baker's yeast group, as was previously assumed. Furthermore, Pfdpm1 was unable to complement a mouse mutant deficient in DPM but efficiently complements the Schizosaccharomyces pombe fission yeast mutant, indicating a difference between fission yeast and mammalian DPM genes. Therefore, we reanalyzed the hydrophobicity scales of all known DPMs and consequently reclassify the DPM clade into six major novel subgroups. Furthermore, we show that Pfdpm1 represents a unique enzyme among these subgroups.

  13. Plasmodium falciparum and Plasmodium vivax specific lactate dehydrogenase: genetic polymorphism study from Indian isolates.

    PubMed

    Keluskar, Priyadarshan; Singh, Vineeta; Gupta, Purva; Ingle, Sanjay

    2014-08-01

    Control and eradication of malaria is hindered by the acquisition of drug resistance by Plasmodium species. This has necessitated a persistent search for novel drugs and more efficient targets. Plasmodium species specific lactate dehydrogenase is one of the potential therapeutic and diagnostic targets, because of its indispensable role in endoerythrocytic stage of the parasite. A target molecule that is highly conserved in the parasite population can be more effectively used in diagnostics and therapeutics, hence, in the present study polymorphism in PfLDH (Plasmodiumfalciparum specific LDH) and PvLDH (Plasmodiumvivax specific LDH) genes was analyzed using PCR-single strand confirmation polymorphism (PCR-SSCP) and sequencing. Forty-six P. falciparum and thirty-five P. vivax samples were screened from different states of India. Our findings have revealed presence of a single PfLDH genotype and six PvLDH genotypes among the studied samples. Interestingly, along with synonymous substitutions, nonsynonymous substitutions were reported to be present for the first time in the PvLDH genotypes. Further, through amino acid sequence alignment and homology modeling studies we observed that the catalytic residues were conserved in all PvLDH genotypes and the nonsynonymous substitutions have not altered the enzyme structure significantly. Evolutionary genetics studies have confirmed that PfLDH and PvLDH loci are under strong purifying selection. Phylogenetic analysis of the pLDH gene sequences revealed that P. falciparum compared to P. vivax, has recent origin. The study therefore supports PfLDH and PvLDH as suitable therapeutic and diagnostic targets as well as phylogenetic markers to understand the genealogy of malaria species. PMID:24953504

  14. Genome-Wide Collation of the Plasmodium falciparum WDR Protein Superfamily Reveals Malarial Parasite-Specific Features

    PubMed Central

    Chahar, Priyanka; Kaushik, Manjeri; Gill, Sarvajeet Singh; Gakhar, Surendra Kumar; Gopalan, Natrajan; Datt, Manish; Sharma, Amit; Gill, Ritu

    2015-01-01

    Despite a significant drop in malaria deaths during the past decade, malaria continues to be one of the biggest health problems around the globe. WD40 repeats (WDRs) containing proteins comprise one of the largest and functionally diverse protein superfamily in eukaryotes, acting as scaffolds for assembling large protein complexes. In the present study, we report an extensive in silico analysis of the WDR gene family in human malaria parasite Plasmodium falciparum. Our genome-wide identification has revealed 80 putative WDR genes in P. falciparum (PfWDRs). Five distinct domain compositions were discovered in Plasmodium as compared to the human host. Notably, 31 PfWDRs were annotated/re-annotated on the basis of their orthologs in other species. Interestingly, most PfWDRs were larger as compared to their human homologs highlighting the presence of parasite-specific insertions. Fifteen PfWDRs appeared specific to the Plasmodium with no assigned orthologs. Expression profiling of PfWDRs revealed a mixture of linear and nonlinear relationships between transcriptome and proteome, and only nine PfWDRs were found to be stage-specific. Homology modeling identified conservation of major binding sites in PfCAF-1 and PfRACK. Protein-protein interaction network analyses suggested that PfWDRs are highly connected proteins with ~1928 potential interactions, supporting their role as hubs in cellular networks. The present study highlights the roles and relevance of the WDR family in P. falciparum, and identifies unique features that lay a foundation for further experimental dissection of PfWDRs. PMID:26043001

  15. Artesunate plus pyronaridine for treating uncomplicated Plasmodium falciparum malaria

    PubMed Central

    Bukirwa, Hasifa; Unnikrishnan, B; Kramer, Christine V; Sinclair, David; Nair, Suma; Tharyan, Prathap

    2014-01-01

    Background The World Health Organization (WHO) recommends that people with uncomplicated Plasmodium falciparum malaria are treated using Artemisinin-based Combination Therapy (ACT). ACT combines three-days of a short-acting artemisinin derivative with a longer-acting antimalarial which has a different mode of action. Pyronaridine has been reported as an effective antimalarial over two decades of use in parts of Asia, and is currently being evaluated as a partner drug for artesunate. Objectives To evaluate the efficacy and safety of artesunate-pyronaridine compared to alternative ACTs for treating people with uncomplicated P. falciparum malaria. Search methods We searched the Cochrane Infectious Diseases Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL), published in The Cochrane Library; MEDLINE; EMBASE; LILACS; ClinicalTrials.gov; the metaRegister of Controlled Trials (mRCT); and the WHO International Clinical Trials Search Portal up to 16 January 2014. We searched reference lists and conference abstracts, and contacted experts for information about ongoing and unpublished trials. Selection criteria Randomized controlled trials of artesunate-pyronaridine versus other ACTs in adults and children with uncomplicated P. falciparum malaria. For the safety analysis, we also included adverse events data from trials comparing any treatment regimen containing pyronaridine with regimens not containing pyronaridine. Data collection and analysis Two authors independently assessed trial eligibility and risk of bias, and extracted data. We combined dichotomous data using risk ratios (RR) and continuous data using mean differences (MD), and presented all results with a 95% confidence interval (CI). We used the GRADE approach to assess the quality of evidence. Main results We included six randomized controlled trials enrolling 3718 children and adults. Artesunate-pyronaridine versus artemether-lumefantrine In two multicentre trials, enrolling

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

    PubMed Central

    2014-01-01

    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

  17. In Vitro Activity and Interaction of Clindamycin Combined with Dihydroartemisinin against Plasmodium falciparum

    PubMed Central

    Ramharter, M.; Noedl, H.; Winkler, H.; Graninger, W.; Wernsdorfer, W. H.; Kremsner, P. G.; Winkler, S.

    2003-01-01

    Combination regimens are considered a valuable tool for the fight against drug-resistant falciparum malaria. This study was conducted to evaluate the antimalarial potential of clindamycin in combination with dihydroartemisinin in continuously cultured and in freshly isolated Plasmodium falciparum parasites, measuring the inhibition of Plasmodium falciparum histidine-rich protein II synthesis. Interaction analysis revealed a synergistic or additive mode of interaction at various concentration ratios in all continuously cultured parasites at the 50% effective concentration (EC50) level. Antagonism was not found for any of the culture-adapted parasites. In fresh P. falciparum isolates, a fixed clindamycin-dihydroartemisinin combination exhibited additive activity at the EC50 and EC90 levels. The drug mixture showed no significant activity correlation to other commonly used antimalarials. The clindamycin-dihydroartemisinin combination appears to be a promising candidate for clinical investigation. PMID:14576107

  18. Primaquine or other 8-aminoquinoline for reducing Plasmodium falciparum transmission

    PubMed Central

    Graves, Patricia M; Gelband, Hellen; Garner, Paul

    2015-01-01

    Background Mosquitoes become infected with Plasmodium when they ingest gametocyte-stage parasites from an infected person's blood. Plasmodium falciparum gametocytes are sensitive to the drug primaquine (PQ) and other 8-aminoquinolines (8AQ); these drugs could prevent parasite transmission from infected people to mosquitoes, and consequently reduce the incidence of malaria. However, PQ will not directly benefit the individual, and could be harmful to those with glucose-6-phosphate dehydrogenase (G6PD) deficiency. In 2010, The World Health Organization (WHO) recommended a single dose of PQ at 0.75 mg/kg, alongside treatment for P. falciparum malaria to reduce transmission in areas approaching malaria elimination. In 2013 the WHO revised this to 0.25 mg/kg due to concerns about safety. Objectives To assess whether giving PQ or an alternative 8AQ alongside treatment for P. falciparum malaria reduces malaria transmission, and to estimate the frequency of severe or haematological adverse events when PQ is given for this purpose. Search methods We searched the following databases up to 10 Feb 2014 for trials: the Cochrane Infectious Diseases Group Specialized Register; the Cochrane Central Register of Controlled Trials (CENTRAL), published in The Cochrane Library; MEDLINE; EMBASE; LILACS; metaRegister of Controlled Trials (mRCT); and the WHO trials search portal using 'malaria*', 'falciparum', and 'primaquine' as search terms. In addition, we searched conference proceedings and reference lists of included studies, and contacted researchers and organizations. Selection criteria Randomized controlled trials (RCTs) or quasi-RCTs comparing PQ (or alternative 8AQ) given as a single dose or short course alongside treatment for P. falciparum malaria with malaria treatment given without PQ/8AQ in adults or children. Data collection and analysis Two authors independently screened all abstracts, applied inclusion criteria, and extracted data. We sought evidence of an impact on

  19. Artemisinin resistance in Plasmodium falciparum is associated with an altered temporal pattern of transcription

    PubMed Central

    2011-01-01

    Background Artemisinin resistance in Plasmodium falciparum malaria has emerged in Western Cambodia. This is a major threat to global plans to control and eliminate malaria as the artemisinins are a key component of antimalarial treatment throughout the world. To identify key features associated with the delayed parasite clearance phenotype, we employed DNA microarrays to profile the physiological gene expression pattern of the resistant isolates. Results In the ring and trophozoite stages, we observed reduced expression of many basic metabolic and cellular pathways which suggests a slower growth and maturation of these parasites during the first half of the asexual intraerythrocytic developmental cycle (IDC). In the schizont stage, there is an increased expression of essentially all functionalities associated with protein metabolism which indicates the prolonged and thus increased capacity of protein synthesis during the second half of the resistant parasite IDC. This modulation of the P. falciparum intraerythrocytic transcriptome may result from differential expression of regulatory proteins such as transcription factors or chromatin remodeling associated proteins. In addition, there is a unique and uniform copy number variation pattern in the Cambodian parasites which may represent an underlying genetic background that contributes to the resistance phenotype. Conclusions The decreased metabolic activities in the ring stages are consistent with previous suggestions of higher resilience of the early developmental stages to artemisinin. Moreover, the increased capacity of protein synthesis and protein turnover in the schizont stage may contribute to artemisinin resistance by counteracting the protein damage caused by the oxidative stress and/or protein alkylation effect of this drug. This study reports the first global transcriptional survey of artemisinin resistant parasites and provides insight to the complexities of the molecular basis of pathogens with drug

  20. Prevalence of mutation and phenotypic expression associated with sulfadoxine-pyrimethamine resistance in Plasmodium falciparum and Plasmodium vivax.

    PubMed

    Zakai, Haytham A; Khan, Wajihullah; Asma, Umme

    2013-09-01

    Therapeutic efficacy of sulfadoxine-pyrimethamine (SP), which is commonly used to treat falciparum malaria, was assessed in isolates of Plasmodium falciparum (Welch, 1897) and Plasmodium vivax (Grassi et Feletti, 1890) ofAligarh, Uttar Pradesh, North India and Taif, Saudi Arabia during 2011-2012. Both the species showed mutations in dihydrofolate reductase (DHFR) enzyme as they have common biochemical drug targets. Mutation rate for pfdhfr was higher compared to pvdhfr because the drug was mainly given to treat falciparum malaria. Since both the species coexist, P. vivax was also exposed to SP due to faulty species diagnosis or medication without specific diagnosis. Low level of mutations against SP in P. falciparum of Saudi isolates indicates that the SP combination is still effective for the treatment of falciparum malaria. Since SP is used as first-line of treatment because of high level of resistance against chloroquine (CQ), it may result in spread of higher level of mutations resulting in drug resistance and treatment failure in near future. Therefore, to avoid further higher mutations in the parasite, use of better treatment regimens such as artesunate combination therapy must be introduced against SP combination. PMID:24261139

  1. Crystal structure of truncated aspartate transcarbamoylase from Plasmodium falciparum.

    PubMed

    Lunev, Sergey; Bosch, Soraya S; Batista, Fernando de Assis; Wrenger, Carsten; Groves, Matthew R

    2016-07-01

    The de novo pyrimidine-biosynthesis pathway of Plasmodium falciparum is a promising target for antimalarial drug discovery. The parasite requires a supply of purines and pyrimidines for growth and proliferation and is unable to take up pyrimidines from the host. Direct (or indirect) inhibition of de novo pyrimidine biosynthesis via dihydroorotate dehydrogenase (PfDHODH), the fourth enzyme of the pathway, has already been shown to be lethal to the parasite. In the second step of the plasmodial pyrimidine-synthesis pathway, aspartate and carbamoyl phosphate are condensed to N-carbamoyl-L-aspartate and inorganic phosphate by aspartate transcarbamoylase (PfATC). In this paper, the 2.5 Å resolution crystal structure of PfATC is reported. The space group of the PfATC crystals was determined to be monoclinic P21, with unit-cell parameters a = 87.0, b = 103.8, c = 87.1 Å, α = 90.0, β = 117.7, γ = 90.0°. The presented PfATC model shares a high degree of homology with the catalytic domain of Escherichia coli ATC. There is as yet no evidence of the existence of a regulatory domain in PfATC. Similarly to E. coli ATC, PfATC was modelled as a homotrimer in which each of the three active sites is formed at the oligomeric interface. Each active site comprises residues from two adjacent subunits in the trimer with a high degree of evolutional conservation. Here, the activity loss owing to mutagenesis of the key active-site residues is also described. PMID:27380369

  2. Functional Analysis of Sirtuin Genes in Multiple Plasmodium falciparum Strains

    PubMed Central

    Merrick, Catherine J.; Jiang, Rays H. Y.; Skillman, Kristen M.; Samarakoon, Upeka; Moore, Rachel M.; Dzikowski, Ron; Ferdig, Michael T.; Duraisingh, Manoj T.

    2015-01-01

    Plasmodium falciparum, the causative agent of severe human malaria, employs antigenic variation to avoid host immunity. Antigenic variation is achieved by transcriptional switching amongst polymorphic var genes, enforced by epigenetic modification of chromatin. The histone-modifying ‘sirtuin’ enzymes PfSir2a and PfSir2b have been implicated in this process. Disparate patterns of var expression have been reported in patient isolates as well as in cultured strains. We examined var expression in three commonly used laboratory strains (3D7, NF54 and FCR-3) in parallel. NF54 parasites express significantly lower levels of var genes compared to 3D7, despite the fact that 3D7 was originally a clone of the NF54 strain. To investigate whether this was linked to the expression of sirtuins, genetic disruption of both sirtuins was attempted in all three strains. No dramatic changes in var gene expression occurred in NF54 or FCR-3 following PfSir2b disruption, contrasting with previous observations in 3D7. In 3D7, complementation of the PfSir2a genetic disruption resulted in a significant decrease in previously-elevated var gene expression levels, but with the continued expression of multiple var genes. Finally, rearranged chromosomes were observed in the 3D7 PfSir2a knockout line. Our results focus on the potential for parasite genetic background to contribute to sirtuin function in regulating virulence gene expression and suggest a potential role for sirtuins in maintaining genome integrity. PMID:25780929

  3. Product Release Pathways in Human and Plasmodium falciparum Phosphoribosyltransferase.

    PubMed

    Karmakar, Tarak; Roy, Sourav; Balaram, Hemalatha; Prakash, Meher K; Balasubramanian, Sundaram

    2016-08-22

    Atomistic molecular dynamics (MD) simulations coupled with the metadynamics technique were carried out to delineate the product (PPi.2Mg and IMP) release mechanisms from the active site of both human (Hs) and Plasmodium falciparum (Pf) hypoxanthine-guanine-(xanthine) phosphoribosyltransferase (HG(X)PRT). An early movement of PPi.2Mg from its binding site has been observed. The swinging motion of the Asp side chain (D134/D145) in the binding pocket facilitates the detachment of IMP, which triggers the opening of flexible loop II, the gateway to the bulk solvent. In PfHGXPRT, PPi.2Mg and IMP are seen to be released via the same path in all of the biased MD simulations. In HsHGPRT too, the product molecules follow similar routes from the active site; however, an alternate but minor escape route for PPi.2Mg has been observed in the human enzyme. Tyr 104 and Phe 186 in HsHGPRT and Tyr 116 and Phe 197 in PfHGXPRT are the key residues that mediate the release of IMP, whereas the motion of PPi.2Mg away from the reaction center is guided by the negatively charged Asp and Glu and a few positively charged residues (Lys and Arg) that line the product release channels. Mutations of a few key residues present in loop II of Trypanosoma cruzi (Tc) HGPRT have been shown to reduce the catalytic efficiency of the enzyme. Herein, in silico mutation of corresponding residues in loop II of HsHGPRT and PfHGXPRT resulted in partial opening of the flexible loop (loop II), thus exposing the active site to bulk water, which offers a rationale for the reduced catalytic activity of these two mutant enzymes. Investigations of the product release from these HsHGPRT and PfHGXPRT mutants delineate the role of these important residues in the enzymatic turnover. PMID:27404508

  4. In Vitro Activity of Fluorescent Dyes against Asexual Blood Stages of Plasmodium falciparum

    PubMed Central

    Joanny, Fanny; Held, Jana

    2012-01-01

    Many successful antimicrobial drugs originate from synthetic dyes. This paper reports the in vitro activity of 14 fluorescent dyes against Plasmodium falciparum. Five of these dyes (Hoechst 33342, MitoRed, DiOC6, SYTO 9, and rhodamine B) show activity at a low nanomolar concentration against two P. falciparum strains in the histidine-rich protein 2 drug sensitivity assay, while toxicity in HeLa cells is low. These dyes may be a starting point for developing new drugs against P. falciparum. PMID:22850520

  5. Plasmodium falciparum: analysis of chromosomes separated by contour-clamped homogenous electric fields.

    PubMed

    Gu, H; Inselburg, J W; Bzik, D J; Li, W B

    1990-08-01

    We have established improved conditions for separating the chromosomes of Plasmodium falciparum by pulsed field gradient gel electrophoresis (PFG) using a contour-clamped homogenous electric field (CHEF) apparatus. Thirteen clearly separable chromosomal bands were reproducibly isolated from the strain FCR3 and their sizes have been determined. Evidence that indicates one band may contain two chromosomes is presented. The relationship between the PFG separable DNA and the number of unique chromosomes in P. falciparum is considered. We have established a relationship between the maximum resolvable sizes of the chromosomes and the pulse times. The chromosomal location of twenty-seven P. falciparum DNA probes is also reported. PMID:2197113

  6. The extravascular compartment of the bone marrow: a niche for Plasmodium falciparum gametocyte maturation?

    PubMed Central

    2012-01-01

    Background Plasmodium falciparum immature gametocytes accumulate in the bone marrow, but their exact location in this tissue remains unclear. Methods The stage and deposition pattern of gametocytes was analysed on histological sections of a bone marrow sample collected in a patient with subacute P. falciparum malaria. Results A majority (89%) of immature stages II to IV gametocytes and a minority (29%) of mature stage V gametocytes were observed in extravascular spaces. Discussion and conclusion These observations represent a valuable step towards understanding sequestration patterns of P. falciparum gametocytes and may ultimately lead to novel transmission-blocking interventions. PMID:22905863

  7. Structure of the catalytic domain of Plasmodium falciparum ARF GTPase-activating protein (ARFGAP)

    SciTech Connect

    Cook, William J.; Senkovich, Olga; Chattopadhyay, Debasish

    2012-03-26

    The crystal structure of the catalytic domain of the ADP ribosylation factor GTPase-activating protein (ARFGAP) from Plasmodium falciparum has been determined and refined to 2.4 {angstrom} resolution. Multiwavelength anomalous diffraction (MAD) data were collected utilizing the Zn{sup 2+} ion bound at the zinc-finger domain and were used to solve the structure. The overall structure of the domain is similar to those of mammalian ARFGAPs. However, several amino-acid residues in the area where GAP interacts with ARF1 differ in P. falciparum ARFGAP. Moreover, a number of residues that form the dimer interface in the crystal structure are unique in P. falciparum ARFGAP.

  8. Integrated transcriptomic and proteomic analyses of P. falciparum gametocytes: molecular insight into sex-specific processes and translational repression.

    PubMed

    Lasonder, Edwin; Rijpma, Sanna R; van Schaijk, Ben C L; Hoeijmakers, Wieteke A M; Kensche, Philip R; Gresnigt, Mark S; Italiaander, Annet; Vos, Martijn W; Woestenenk, Rob; Bousema, Teun; Mair, Gunnar R; Khan, Shahid M; Janse, Chris J; Bártfai, Richárd; Sauerwein, Robert W

    2016-07-27

    Sexual differentiation of malaria parasites into gametocytes in the vertebrate host and subsequent gamete fertilization in mosquitoes is essential for the spreading of the disease. The molecular processes orchestrating these transitions are far from fully understood. Here, we report the first transcriptome analysis of male and female Plasmodium falciparum gametocytes coupled with a comprehensive proteome analysis. In male gametocytes there is an enrichment of proteins involved in the formation of flagellated gametes; proteins involved in DNA replication, chromatin organization and axoneme formation. On the other hand, female gametocytes are enriched in proteins required for zygote formation and functions after fertilization; protein-, lipid- and energy-metabolism. Integration of transcriptome and proteome data revealed 512 highly expressed maternal transcripts without corresponding protein expression indicating large scale translational repression in P. falciparum female gametocytes for the first time. Despite a high degree of conservation between Plasmodium species, 260 of these 'repressed transcripts' have not been previously described. Moreover, for some of these genes, protein expression is only reported in oocysts and sporozoites indicating that repressed transcripts can be partitioned into short- and long-term storage. Finally, these data sets provide an essential resource for identification of vaccine/drug targets and for further mechanistic studies. PMID:27298255

  9. Efficacy of Chloroquine for the Treatment of Uncomplicated Plasmodium falciparum Malaria in Honduras

    PubMed Central

    Torres, Rosa Elena Mejia; Banegas, Engels Ilich; Mendoza, Meisy; Diaz, Cesar; Bucheli, Sandra Tamara Mancero; Fontecha, Gustavo A.; Alam, Md Tauqeer; Goldman, Ira; Udhayakumar, Venkatachalam; Zambrano, Jose Orlinder Nicolas

    2013-01-01

    Chloroquine (CQ) is officially used for the primary treatment of Plasmodium falciparum malaria in Honduras. In this study, the therapeutic efficacy of CQ for the treatment of uncomplicated P. falciparum malaria in the municipality of Puerto Lempira, Gracias a Dios, Honduras was evaluated using the Pan American Health Organization—World Health Organization protocol with a follow-up of 28 days. Sixty-eight patients from 6 months to 60 years of age microscopically diagnosed with uncomplicated P. falciparum malaria were included in the final analysis. All patients who were treated with CQ (25 mg/kg over 3 days) cleared parasitemia by day 3 and acquired no new P. falciparum infection within 28 days of follow-up. All the parasite samples sequenced for CQ resistance mutations (pfcrt) showed only the CQ-sensitive genotype (CVMNK). This finding shows that CQ remains highly efficacious for the treatment of uncomplicated P. falciparum malaria in Gracias a Dios, Honduras. PMID:23458957

  10. Refrigeration provides a simple means to synchronize in vitro cultures of Plasmodium falciparum.

    PubMed

    Yuan, Lili; Hao, Mingming; Wu, Lanou; Zhao, Zhen; Rosenthal, Benjamin M; Li, Xiaomei; He, Yongshu; Sun, Ling; Feng, Guohua; Xiang, Zheng; Cui, Liwang; Yang, Zhaoqing

    2014-05-01

    Plasmodium falciparum is usually asynchronous during in vitro culture. Highly synchronized cultures of P. falciparum are routinely used in malaria research. Here, we describe a simple synchronization procedure for P. falciparum asexual erythrocytic culture, which involves storage at 4°C for 8-24 h followed by routine culture. When cultures with 27-60% of ring stage were synchronized using this procedure, 70-93% ring stages were obtained after 48 h of culture and relative growth synchrony remained for at least two erythrocytic cycles. To test the suitability of this procedure for subsequent work, drug sensitivity assays were performed using four laboratory strains and four freshly adapted clinical P. falciparum isolates. Parasites synchronized by sorbitol treatment or refrigeration showed similar dose-response curves and comparable IC50 values to four antimalarial drugs. The refrigeration synchronization method is simple, inexpensive, time-saving, and should be especially useful when large numbers of P. falciparum culture are handled. PMID:24632190

  11. Erythrocyte lysis and Xenopus laevis oocyte rupture by recombinant Plasmodium falciparum hemolysin III.

    PubMed

    Moonah, Shannon; Sanders, Natalie G; Persichetti, Jason K; Sullivan, David J

    2014-10-01

    Malaria kills more than 1 million people per year worldwide, with severe malaria anemia accounting for the majority of the deaths. Malaria anemia is multifactorial in etiology, including infected erythrocyte destruction and decrease in erythrocyte production, as well as destruction or clearance of noninfected erythrocytes. We identified a panspecies Plasmodium hemolysin type III related to bacterial hemolysins. The identification of a hemolysin III homologue in Plasmodium suggests a potential role in host erythrocyte lysis. Here, we report the first characterization of Plasmodium falciparum hemolysin III, showing that the soluble recombinant P. falciparum hemolysin III is a pore-forming protein capable of lysing human erythrocytes in a dose-, time-, and temperature-dependent fashion. The recombinant P. falciparum hemolysin III-induced hemolysis was partially inhibited by glibenclamide, a known channel antagonist. Studies with polyethylene glycol molecules of different molecular weights indicated a pore size of approximately 3.2 nm. Heterologous expression of recombinant P. falciparum hemolysin III in Xenopus oocytes demonstrated early hypotonic lysis similar to that of the pore-forming aquaporin control. Live fluorescence microscopy localized transfected recombinant green fluorescent protein (GFP)-tagged P. falciparum hemolysin III to the essential digestive vacuole of the P. falciparum parasite. These transfected trophozoites also possessed a swollen digestive vacuole phenotype. Native Plasmodium hemolysin III in the digestive vacuole may contribute to lysis of the parasitophorous vacuole membrane derived from the host erythrocyte. After merozoite egress from infected erythrocytes, remnant P. falciparum hemolysin III released from digestive vacuoles could potentially contribute to lysis of uninfected erythrocytes to contribute to severe life-threatening anemia. PMID:25148832

  12. Erythrocyte Lysis and Xenopus laevis Oocyte Rupture by Recombinant Plasmodium falciparum Hemolysin III

    PubMed Central

    Moonah, Shannon; Sanders, Natalie G.; Persichetti, Jason K.

    2014-01-01

    Malaria kills more than 1 million people per year worldwide, with severe malaria anemia accounting for the majority of the deaths. Malaria anemia is multifactorial in etiology, including infected erythrocyte destruction and decrease in erythrocyte production, as well as destruction or clearance of noninfected erythrocytes. We identified a panspecies Plasmodium hemolysin type III related to bacterial hemolysins. The identification of a hemolysin III homologue in Plasmodium suggests a potential role in host erythrocyte lysis. Here, we report the first characterization of Plasmodium falciparum hemolysin III, showing that the soluble recombinant P. falciparum hemolysin III is a pore-forming protein capable of lysing human erythrocytes in a dose-, time-, and temperature-dependent fashion. The recombinant P. falciparum hemolysin III-induced hemolysis was partially inhibited by glibenclamide, a known channel antagonist. Studies with polyethylene glycol molecules of different molecular weights indicated a pore size of approximately 3.2 nm. Heterologous expression of recombinant P. falciparum hemolysin III in Xenopus oocytes demonstrated early hypotonic lysis similar to that of the pore-forming aquaporin control. Live fluorescence microscopy localized transfected recombinant green fluorescent protein (GFP)-tagged P. falciparum hemolysin III to the essential digestive vacuole of the P. falciparum parasite. These transfected trophozoites also possessed a swollen digestive vacuole phenotype. Native Plasmodium hemolysin III in the digestive vacuole may contribute to lysis of the parasitophorous vacuole membrane derived from the host erythrocyte. After merozoite egress from infected erythrocytes, remnant P. falciparum hemolysin III released from digestive vacuoles could potentially contribute to lysis of uninfected erythrocytes to contribute to severe life-threatening anemia. PMID:25148832

  13. 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...

  14. A non-pharmaceutical form of Artemisia annua is not effective in preventing Plasmodium falciparum malaria.

    PubMed

    Lagarce, Laurence; Lerolle, Nicolas; Asfar, Pierre; Le Govic, Yohann; Lainé-Cessac, Pascale; de Gentile, Ludovic

    2016-05-01

    Non-pharmaceutical forms of Artemisia annua (a Chinese plant containing artemisinin) are used by some travellers who believe these products are safer than anti-malarial drugs. We report two cases of severe Plasmodium falciparum malaria requiring hospitalization in an Intensive Care Unit following prophylaxis with non-pharmaceutical A. annua in French travellers. PMID:27432906

  15. Plasmodium falciparum malaria occurring 8 years after leaving an endemic area.

    PubMed

    Szmitko, Paul E; Kohn, Magdie L; Simor, Andrew E

    2009-01-01

    A 29-year-old patient who was born in Angola developed Plasmodium falciparum malaria 8 years after leaving Africa. She had not returned to a malaria-endemic area, and there were no apparent risks of local or nosocomial acquisition of malaria in Canada. She recovered after treatment with oral quinine sulfate and doxycycline. PMID:18945569

  16. Novel Mutations in K13 Propeller Gene of Artemisinin-Resistant Plasmodium falciparum

    PubMed Central

    Uemura, Haruki; Kimata, Isao; Ichinose, Yoshio; Logedi, John; Omar, Ahmeddin H.; Kaneko, Akira

    2015-01-01

    We looked for mutations in the Plasmodium falciparum K13 propeller gene of an artemisinin-resistant parasite on islands in Lake Victoria, Kenya, where transmission in 2012–2013 was high. The 4 new types of nonsynonymous, and 5 of synonymous, mutations we detected among 539 samples analyzed provide clues to understanding artemisinin-resistant parasites. PMID:25695257

  17. Novel mutations in K13 propeller gene of artemisinin-resistant Plasmodium falciparum.

    PubMed

    Isozumi, Rie; Uemura, Haruki; Kimata, Isao; Ichinose, Yoshio; Logedi, John; Omar, Ahmeddin H; Kaneko, Akira

    2015-03-01

    We looked for mutations in the Plasmodium falciparum K13 propeller gene of an artemisinin-resistant parasite on islands in Lake Victoria, Kenya, where transmission in 2012-2013 was high. The 4 new types of nonsynonymous, and 5 of synonymous, mutations we detected among 539 samples analyzed provide clues to understanding artemisinin-resistant parasites. PMID:25695257

  18. A septate polycarbonate cell culture unit used for Plasmodium falciparum and hybridomas.

    PubMed

    Thélu, J; Ambroise-Thomas, P

    1988-01-01

    A new material, makrolon, is used for the construction of a large-scale cell culture vessel. It is strong, light, transparent, thermostable, septate and inexpensive. Several independent vessels of 500 ml each can be stacked. It has been used for Plasmodium falciparum and hybridoma cultures, where frequent renewal of the medium and a large gas/liquid interface are required. PMID:3068844

  19. Chloroquine resistance of Plasmodium falciparum is associated with severity of disease in Nigerian children.

    PubMed

    Olumese, P E; Amodu, O K; Björkman, A; Adeyemo, A A; Gbadegesin, R A; Walker, O

    2002-01-01

    Chloroquine resistance of Plasmodium falciparum in vitro was significantly higher in isolates from patients with severe malaria than those with uncomplicated disease. This association may be due to either progression of uncomplicated to severe disease following chloroquine failure or increased virulence of chloroquine-resistant parasites. The implication of this for antimalarial treatment policy is discussed. PMID:12497979

  20. A crucial piece in the puzzle of the artemisinin resistance mechanism in Plasmodium falciparum.

    PubMed

    Bozdech, Zbynek; Ferreira, Pedro E; Mok, Sachel

    2015-08-01

    The spread of resistance of malaria infections to artemisinin is a major concern for the future. The Plasmodium falciparum phosphatidylinositol-3-kinase (PfPI3K) may be a potential target of artemisinin and effector of resistance. This could be mediated by the Kelch13 protein, the molecular marker of resistance that modulates PfPI3K ubiquitination. PMID:26169358

  1. Slow Clearance of Plasmodium falciparum in Severe Pediatric Malaria, Uganda, 2011-2013.

    PubMed

    Hawkes, Michael; Conroy, Andrea L; Opoka, Robert O; Namasopo, Sophie; Zhong, Kathleen; Liles, W Conrad; John, Chandy C; Kain, Kevin C

    2015-07-01

    Plasmodium falciparum resistance to artemisinin derivatives is emerging in Asia. We examined molecular markers of resistance in 78 children in Uganda who had severe malaria and were treated with intravenous artesunate. We observed in the K13-propeller domain, A578S, a low-frequency (3/78), nonsynonymous, single-nucleotide polymorphism associated with prolonged parasite clearance. PMID:26079933

  2. Slow Clearance of Plasmodium falciparum in Severe Pediatric Malaria, Uganda, 2011–2013

    PubMed Central

    Hawkes, Michael; Conroy, Andrea L.; Opoka, Robert O.; Namasopo, Sophie; Zhong, Kathleen; Liles, W. Conrad; John, Chandy C.

    2015-01-01

    Plasmodium falciparum resistance to artemisinin derivatives is emerging in Asia. We examined molecular markers of resistance in 78 children in Uganda who had severe malaria and were treated with intravenous artesunate. We observed in the K13-propeller domain, A578S, a low-frequency (3/78), nonsynonymous, single-nucleotide polymorphism associated with prolonged parasite clearance. PMID:26079933

  3. Ingested human insulin inhibits the mosquito NF-¿B-dependent immune response to Plasmodium falciparum

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We showed previously that ingested human insulin activates the insulin/IGF-1 signaling pathway in Anopheles stephensi and increases the susceptibility of these mosquitoes to Plasmodium falciparum. In other organisms insulin can alter immune responsiveness through regulation of NF-kB transcription fa...

  4. DNA secondary structures are associated with recombination in major Plasmodium falciparum variable surface antigen gene families

    PubMed Central

    Sander, Adam F.; Lavstsen, Thomas; Rask, Thomas S.; Lisby, Michael; Salanti, Ali; Fordyce, Sarah L.; Jespersen, Jakob S.; Carter, Richard; Deitsch, Kirk W.; Theander, Thor G.; Pedersen, Anders Gorm; Arnot, David E.

    2014-01-01

    Many bacterial, viral and parasitic pathogens undergo antigenic variation to counter host immune defense mechanisms. In Plasmodium falciparum, the most lethal of human malaria parasites, switching of var gene expression results in alternating expression of the adhesion proteins of the Plasmodium falciparum-erythrocyte membrane protein 1 class on the infected erythrocyte surface. Recombination clearly generates var diversity, but the nature and control of the genetic exchanges involved remain unclear. By experimental and bioinformatic identification of recombination events and genome-wide recombination hotspots in var genes, we show that during the parasite’s sexual stages, ectopic recombination between isogenous var paralogs occurs near low folding free energy DNA 50-mers and that these sequences are heavily concentrated at the boundaries of regions encoding individual Plasmodium falciparum-erythrocyte membrane protein 1 structural domains. The recombinogenic potential of these 50-mers is not parasite-specific because these sequences also induce recombination when transferred to the yeast Saccharomyces cerevisiae. Genetic cross data suggest that DNA secondary structures (DSS) act as inducers of recombination during DNA replication in P. falciparum sexual stages, and that these DSS-regulated genetic exchanges generate functional and diverse P. falciparum adhesion antigens. DSS-induced recombination may represent a common mechanism for optimizing the evolvability of virulence gene families in pathogens. PMID:24253306

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

    PubMed Central

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

    2011-01-01

    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

  6. Human antisera detect a Plasmodium falciparum genomic clone encoding a nonapeptide repeat.

    PubMed

    Koenen, M; Scherf, A; Mercereau, O; Langsley, G; Sibilli, L; Dubois, P; Pereira da Silva, L; Müller-Hill, B

    Plasmodium falciparum causes malaria infections in its human host. Its wide distribution in tropical countries is a major world health problem. Before a vaccine can be produced, the identification and characterization of parasite antigens is necessary. This can be achieved by the cloning and subsequent analysis of genes coding for parasite antigens. Recently established cDNA banks allow the expression of cDNA derived from the simian parasite Plasmodium knowlesi and P. falciparum in Escherichia coli. Recombinants encoding parasite antigens have been identified by immunodetection in both banks. Two of them contain repetitive units of 11 (ref. 7) or 12 (ref. 5) amino acids. We describe here the construction of an expression bank made directly from randomly generated fragments of P. falciparum genomic DNA. We detect several clones which react strongly with human African immune sera. One clone expresses an antigenic determinant composed of occasionally degenerated repeats of a peptide nonamer. PMID:6090935

  7. Acyclic Immucillin Phosphonates. Second-Generation Inhibitors of Plasmodium falciparum Hypoxanthine- Guanine-Xanthine Phosphoribosyltransferase

    SciTech Connect

    Hazelton, Keith Z.; Ho, Meng-Chaio; Cassera, Maria B.; Clinch, Keith; Crump, Douglas R.; Rosario Jr., Irving; Merino, Emilio F.; Almo, Steve C.; Tyler, Peter C.; Schramm, Vern L.

    2012-06-22

    We found that Plasmodium falciparum is the primary cause of deaths from malaria. It is a purine auxotroph and relies on hypoxanthine salvage from the host purine pool. Purine starvation as an antimalarial target has been validated by inhibition of purine nucleoside phosphorylase. Hypoxanthine depletion kills Plasmodium falciparum in cell culture and in Aotus monkey infections. Hypoxanthine-guanine-xanthine phosphoribosyltransferase (HGXPRT) from P. falciparum is required for hypoxanthine salvage by forming inosine 5'-monophosphate, a branchpoint for all purine nucleotide synthesis in the parasite. We present a class of HGXPRT inhibitors, the acyclic immucillin phosphonates (AIPs), and cell permeable AIP prodrugs. The AIPs are simple, potent, selective, and biologically stable inhibitors. The AIP prodrugs block proliferation of cultured parasites by inhibiting the incorporation of hypoxanthine into the parasite nucleotide pool and validates HGXPRT as a target in malaria.

  8. Functional Antibodies against VAR2CSA in Nonpregnant Populations from Colombia Exposed to Plasmodium falciparum and Plasmodium vivax

    PubMed Central

    Doritchamou, Justin; Arango, Eliana M.; Cabrera, Ana; Arroyo, Maria Isabel; Kain, Kevin C.; Ndam, Nicaise Tuikue; Maestre, Amanda

    2014-01-01

    In pregnancy, parity-dependent immunity is observed in response to placental infection with Plasmodium falciparum. Antibodies recognize the surface antigen, VAR2CSA, expressed on infected red blood cells and inhibit cytoadherence to the placental tissue. In most settings of malaria endemicity, antibodies against VAR2CSA are predominantly observed in multigravid women and infrequently in men, children, and nulligravid women. However, in Colombia, we detected antibodies against multiple constructs of VAR2CSA among men and children with acute P. falciparum and Plasmodium vivax infection. The majority of men and children (>60%) had high levels of IgGs against three recombinant domains of VAR2CSA: DBL5ε, DBL3X, and ID1-ID2. Surprisingly, these antibodies were observed only in pregnant women, men, and children exposed either to P. falciparum or to P. vivax. Moreover, the anti-VAR2CSA antibodies are of high avidity and efficiently inhibit adherence of infected red blood cells to chondroitin sulfate A in vitro, suggesting that they are specific and functional. These unexpected results suggest that there may be genotypic or phenotypic differences in the parasites of this region or in the host response to either P. falciparum or P. vivax infection outside pregnancy. These findings may hold significant clinical relevance to the pathophysiology and outcome of malaria infections in this region. PMID:24686068

  9. Investigating the Roles of the C-Terminal Domain of Plasmodium falciparum GyrA

    PubMed Central

    Nagano, Soshichiro; Seki, Eiko; Lin, Ting-Yu; Shirouzu, Mikako; Yokoyama, Shigeyuki; Heddle, Jonathan G.

    2015-01-01

    Malaria remains as one of the most deadly diseases in developing countries. The Plasmodium causative agents of human malaria such as Plasmodium falciparum possess an organelle, the apicoplast, which is the result of secondary endosymbiosis and retains its own circular DNA. A type II topoisomerase, DNA gyrase, is present in the apicoplast. In prokaryotes this enzyme is a proven, effective target for antibacterial agents, and its discovery in P. falciparum opens up the prospect of exploiting it as a drug target. Basic characterisation of P. falciparum gyrase is important because there are significant sequence differences between it and the prokaryotic enzyme. However, it has proved difficult to obtain soluble protein. Here we have predicted a new domain boundary in P. falciparum GyrA that corresponds to the C-terminal domain of prokaryotic GyrA and successfully purified it in a soluble form. Biochemical analyses revealed many similarities between the C-terminal domains of GyrA from E. coli and P. falciparum, suggesting that despite its considerably larger size, the malarial protein carries out a similar DNA wrapping function. Removal of a unique Asn-rich region in the P. falciparum protein did not result in a significant change, suggesting it is dispensable for DNA wrapping. PMID:26566222

  10. J-dot targeting of an exported HSP40 in Plasmodium falciparum-infected erythrocytes.

    PubMed

    Petersen, Wiebke; Külzer, Simone; Engels, Sonja; Zhang, Qi; Ingmundson, Alyssa; Rug, Melanie; Maier, Alexander G; Przyborski, Jude M

    2016-07-01

    Plasmodium falciparum exports a large number of proteins to its host cell, the mature human erythrocyte, where they are involved in host cell modification. Amongst the proteins trafficked to the host cell, many are heat shock protein (HSP)40 homologues. We previously demonstrated that at least two exported PfHSP40s (referred to as PFE55 and PFA660) localise to mobile structures in the P. falciparum-infected erythrocyte (Kulzer et al., 2010), termed J-dots. The complete molecular content of these structures has not yet been completely resolved, however it is known that they also contain an exported HSP70, PfHSP70x, and are potentially involved in transport of the major cytoadherance ligand, PfEMP1, through the host cell. To understand more about the nature of the association of exported HSP40s with J-dots, here we have studied the signal requirements for recruitment of the proteins to these structures. By expressing various exported GFP chimeras, we can demonstrate that the predicted substrate binding domain is necessary and sufficient for J-dot targeting. This targeting only occurs in human erythrocytes infected with P. falciparum, as it is not conserved when expressing a P. falciparum HSP40 in Plasmodium berghei-infected murine red blood cells, suggesting that J-dots are P. falciparum-specific. This data reveals a new mechanism for targeting of exported proteins to intracellular structures in the P. falciparum-infected erythrocyte. PMID:27063072

  11. Impact of Plasmodium falciparum Coinfection on Longitudinal Epstein-Barr Virus Kinetics in Kenyan Children.

    PubMed

    Reynaldi, Arnold; Schlub, Timothy E; Chelimo, Kiprotich; Sumba, Peter Odada; Piriou, Erwan; Ogolla, Sidney; Moormann, Ann M; Rochford, Rosemary; Davenport, Miles P

    2016-03-15

    Endemic Burkitt lymphoma is associated with Epstein-Barr virus (EBV) and Plasmodium falciparum coinfection, although how P. falciparum exposure affects the dynamics of EBV infection is unclear. We have used a modeling approach to study EBV infection kinetics in a longitudinal cohort of children living in regions of high and low malaria transmission in Kenya. Residence in an area of high malaria transmission was associated with a higher rate of EBV expansion during primary EBV infection in infants and during subsequent episodes of EBV DNA detection, as well as with longer episodes of EBV DNA detection and shorter intervals between subsequent episodes of EBV DNA detection. In addition, we found that concurrent P. falciparum parasitemia also increases the likelihood of the first and subsequent peaks of EBV in peripheral blood. This suggests that P. falciparum infection is associated with increased EBV growth and contributes to endemic Burkitt lymphoma pathogenesis. PMID:26531246

  12. Targeting a Novel Plasmodium falciparum Purine Recycling Pathway with Specific Immucillins

    SciTech Connect

    Ting, L; Shi, W; Lewandowicz, A; Singh, V; Mwakingwe, A; Birck, M R; Taylor Ringia, E A; Bench, G; Madrid, D C; Tyler, P C; Evans, G B; Furneaux, R H; Schramm, V L; Kim, K

    2004-05-19

    Plasmodium falciparum is unable to synthesize purine bases and relies upon purine salvage and purine recycling to meet its purine needs. We report that purines formed as products of the polyamine pathway are recycled in a novel pathway in which 5'-methylthioinosine is generated by adenosine deaminase. The action of P. falciparum purine nucleoside phosphorylase is a convergent step of purine salvage, converting both 5'-methylthioinosine and inosine to hypoxanthine. We used accelerator mass spectrometry to verify that 5'-methylthioinosine is an active nucleic acid precursor in P. falciparum. Prior studies have shown that inhibitors of purine salvage enzymes kill malaria, but potent malaria-specific inhibitors of these enzymes have not previously been described. 5'-methylthio-Immucillin-H, a transition state analogue inhibitor that is selective for malarial over human purine nucleoside phosphorylase, kills P. falciparum in culture. Immucillins are currently in clinical trials for other indications and may have application as antimalarials.

  13. Pooled Amplicon Deep Sequencing of Candidate Plasmodium falciparum Transmission-Blocking Vaccine Antigens.

    PubMed

    Juliano, Jonathan J; Parobek, Christian M; Brazeau, Nicholas F; Ngasala, Billy; Randrianarivelojosia, Milijaona; Lon, Chanthap; Mwandagalirwa, Kashamuka; Tshefu, Antoinette; Dhar, Ravi; Das, Bidyut K; Hoffman, Irving; Martinson, Francis; Mårtensson, Andreas; Saunders, David L; Kumar, Nirbhay; Meshnick, Steven R

    2016-01-01

    Polymorphisms within Plasmodium falciparum vaccine candidate antigens have the potential to compromise vaccine efficacy. Understanding the allele frequencies of polymorphisms in critical binding regions of antigens can help in the designing of strain-transcendent vaccines. Here, we adopt a pooled deep-sequencing approach, originally designed to study P. falciparum drug resistance mutations, to study the diversity of two leading transmission-blocking vaccine candidates, Pfs25 and Pfs48/45. We sequenced 329 P. falciparum field isolates from six different geographic regions. Pfs25 showed little diversity, with only one known polymorphism identified in the region associated with binding of transmission-blocking antibodies among our isolates. However, we identified four new mutations among eight non-synonymous mutations within the presumed antibody-binding region of Pfs48/45. Pooled deep sequencing provides a scalable and cost-effective approach for the targeted study of allele frequencies of P. falciparum candidate vaccine antigens. PMID:26503281

  14. Functional characterization of a SUMO deconjugating protease of Plasmodium falciparum using newly identified small molecule inhibitors

    PubMed Central

    Ponder, Elizabeth L.; Albrow, Victoria E.; Leader, Brittany A.; Békés, Miklós; Mikolajczyk, Jowita; Fonović, Urša Pečar; Shen, Aimee; Drag, Marcin; Xiao, Junpeng; Deu, Edgar; Campbell, Amy J.; Powers, James C.; Salvesen, Guy S.; Bogyo, Matthew

    2011-01-01

    SUMMARY Small ubiquitin-related modifier (SUMO) is implicated in the regulation of numerous biological processes including transcription, protein localization, and cell cycle control. Protein modification by SUMO is found in Plasmodium falciparum; however, its role in the regulation of the parasite lifecycle is poorly understood. Here we describe functional studies of a SUMO-specific protease (SENP) of P. falciparum, PfSENP1 (PFL1635w). Expression of the catalytic domain of PfSENP1 and biochemical profiling using a positional scanning substrate library demonstrated that this protease has unique cleavage sequence preference relative to the human SENPs. In addition, we describe a novel class of small molecule inhibitors of this protease. The most potent lead compound inhibited both recombinant PfSENP1 activity and P. falciparum replication in infected human blood. These studies provide valuable new tools for the study of SUMOylation in P. falciparum. PMID:21700207

  15. Spatiotemporal Dynamics and Demographic Profiles of Imported Plasmodium falciparum and Plasmodium vivax Infections in Ontario, Canada (1990–2009)

    PubMed Central

    Nelder, Mark P.; Russell, Curtis; Williams, Dawn; Johnson, Karen; Li, Lennon; Baker, Stacey L.; Marshall, Sean; Bhanich-Supapol, Wendy; Pillai, Dylan R.; Ralevski, Filip

    2013-01-01

    We examined malaria cases reported to Ontario’s public health surveillance systems from 1990 through 2009 to determine how temporal scale (longitudinal, seasonal), spatial scale (provincial, health unit), and demography (gender, age) contribute to Plasmodium infection in Ontario travellers. Our retrospective study included 4,551 confirmed cases of imported malaria reported throughout Ontario, with additional analysis at the local health unit level (i.e., Ottawa, Peel, and Toronto). During the 20-year period, Plasmodium vivax accounted for 50.6% of all cases, P. falciparum (38.6%), Plasmodium sp. (6.0%), P. ovale (3.1%), and P. malariae (1.8%). During the first ten years of the study (1990–1999), P. vivax (64% of all cases) was the dominant agent, followed by P. falciparum (28%); however, during the second ten years (2000–2009) the situation reversed and P. falciparum (55%) dominated, followed by P. vivax (30%). The prevalence of P. falciparum and P. vivax cases varied spatially (e.g., P. falciparum more prevalent in Toronto, P. vivax more prevalent in Peel), temporally (e.g. P. falciparum incidence increased during the 20-year study), and demographically (e.g. preponderance of male cases). Infection rates per 100,000 international travellers were estimated: rates of infection were 2× higher in males compared to females; rates associated with travel to Africa were 37× higher compared to travel to Asia and 126× higher compared to travel to the Americas; rates of infection were 2.3–3.5× higher in June and July compared to October through March; and rates of infection were highest in those 65–69 years old. Where exposure country was reported, 71% of P. falciparum cases reported exposure in Ghana or Nigeria and 63% of P. vivax cases reported exposure in India. Our study provides insights toward improving pre-travel programs for Ontarians visiting malaria-endemic regions and underscores the changing epidemiology of imported malaria in the province. PMID

  16. Spatiotemporal dynamics and demographic profiles of imported Plasmodium falciparum and Plasmodium vivax infections in Ontario, Canada (1990-2009).

    PubMed

    Nelder, Mark P; Russell, Curtis; Williams, Dawn; Johnson, Karen; Li, Lennon; Baker, Stacey L; Marshall, Sean; Bhanich-Supapol, Wendy; Pillai, Dylan R; Ralevski, Filip

    2013-01-01

    We examined malaria cases reported to Ontario's public health surveillance systems from 1990 through 2009 to determine how temporal scale (longitudinal, seasonal), spatial scale (provincial, health unit), and demography (gender, age) contribute to Plasmodium infection in Ontario travellers. Our retrospective study included 4,551 confirmed cases of imported malaria reported throughout Ontario, with additional analysis at the local health unit level (i.e., Ottawa, Peel, and Toronto). During the 20-year period, Plasmodium vivax accounted for 50.6% of all cases, P. falciparum (38.6%), Plasmodium sp. (6.0%), P. ovale (3.1%), and P. malariae (1.8%). During the first ten years of the study (1990-1999), P. vivax (64% of all cases) was the dominant agent, followed by P. falciparum (28%); however, during the second ten years (2000-2009) the situation reversed and P. falciparum (55%) dominated, followed by P. vivax (30%). The prevalence of P. falciparum and P. vivax cases varied spatially (e.g., P. falciparum more prevalent in Toronto, P. vivax more prevalent in Peel), temporally (e.g. P. falciparum incidence increased during the 20-year study), and demographically (e.g. preponderance of male cases). Infection rates per 100,000 international travellers were estimated: rates of infection were 2× higher in males compared to females; rates associated with travel to Africa were 37× higher compared to travel to Asia and 126× higher compared to travel to the Americas; rates of infection were 2.3-3.5× higher in June and July compared to October through March; and rates of infection were highest in those 65-69 years old. Where exposure country was reported, 71% of P. falciparum cases reported exposure in Ghana or Nigeria and 63% of P. vivax cases reported exposure in India. Our study provides insights toward improving pre-travel programs for Ontarians visiting malaria-endemic regions and underscores the changing epidemiology of imported malaria in the province. PMID:24098780

  17. Comparative Ex Vivo Activity of Novel Endoperoxides in Multidrug-Resistant Plasmodium falciparum and P. vivax

    PubMed Central

    Chalfein, Ferryanto; Prayoga, Pak; Wabiser, Frans; Wirjanata, Grennady; Sebayang, Boni; Piera, Kim A.; Wittlin, Sergio; Haynes, Richard K.; Möhrle, Jörg J.; Anstey, Nicholas M.; Kenangalem, Enny; Price, Ric N.

    2012-01-01

    The declining efficacy of artemisinin derivatives against Plasmodium falciparum highlights the urgent need to identify alternative highly potent compounds for the treatment of malaria. In Papua Indonesia, where multidrug resistance has been documented against both P. falciparum and P. vivax malaria, comparative ex vivo antimalarial activity against Plasmodium isolates was assessed for the artemisinin derivatives artesunate (AS) and dihydroartemisinin (DHA), the synthetic peroxides OZ277 and OZ439, the semisynthetic 10-alkylaminoartemisinin derivatives artemisone and artemiside, and the conventional antimalarial drugs chloroquine (CQ), amodiaquine (AQ), and piperaquine (PIP). Ex vivo drug susceptibility was assessed in 46 field isolates (25 P. falciparum and 21 P. vivax). The novel endoperoxide compounds exhibited potent ex vivo activity against both species, but significant differences in intrinsic activity were observed. Compared to AS and its active metabolite DHA, all the novel compounds showed lower or equal 50% inhibitory concentrations (IC50s) in both species (median IC50s between 1.9 and 3.6 nM in P. falciparum and 0.7 and 4.6 nM in P. vivax). The antiplasmodial activity of novel endoperoxides showed different cross-susceptibility patterns in the two Plasmodium species: whereas their ex vivo activity correlated positively with CQ, PIP, AS, and DHA in P. falciparum, the same was not apparent in P. vivax. The current study demonstrates for the first time potent activity of novel endoperoxides against drug-resistant P. vivax. The high activity against drug-resistant strains of both Plasmodium species confirms these compounds to be promising candidates for future artemisinin-based combination therapy (ACT) regimens in regions of coendemicity. PMID:22850522

  18. The Limits and Intensity of Plasmodium falciparum Transmission: Implications for Malaria Control and Elimination Worldwide

    PubMed Central

    Guerra, Carlos A; Gikandi, Priscilla W; Tatem, Andrew J; Noor, Abdisalan M; Smith, Dave L; Hay, Simon I; Snow, Robert W

    2008-01-01

    Background The efficient allocation of financial resources for malaria control using appropriate combinations of interventions requires accurate information on the geographic distribution of malaria risk. An evidence-based description of the global range of Plasmodium falciparum malaria and its endemicity has not been assembled in almost 40 y. This paper aims to define the global geographic distribution of P. falciparum malaria in 2007 and to provide a preliminary description of its transmission intensity within this range. Methods and Findings The global spatial distribution of P. falciparum malaria was generated using nationally reported case-incidence data, medical intelligence, and biological rules of transmission exclusion, using temperature and aridity limits informed by the bionomics of dominant Anopheles vector species. A total of 4,278 spatially unique cross-sectional survey estimates of P. falciparum parasite rates were assembled. Extractions from a population surface showed that 2.37 billion people lived in areas at any risk of P. falciparum transmission in 2007. Globally, almost 1 billion people lived under unstable, or extremely low, malaria risk. Almost all P. falciparum parasite rates above 50% were reported in Africa in a latitude band consistent with the distribution of Anopheles gambiae s.s. Conditions of low parasite prevalence were also common in Africa, however. Outside of Africa, P. falciparum malaria prevalence is largely hypoendemic (less than 10%), with the median below 5% in the areas surveyed. Conclusions This new map is a plausible representation of the current extent of P. falciparum risk and the most contemporary summary of the population at risk of P. falciparum malaria within these limits. For 1 billion people at risk of unstable malaria transmission, elimination is epidemiologically feasible, and large areas of Africa are more amenable to control than appreciated previously. The release of this information in the public domain will

  19. Characterization of promoters and stable transfection by homologous and nonhomologous recombination in Plasmodium falciparum.

    PubMed Central

    Crabb, B S; Cowman, A F

    1996-01-01

    Genetic studies of the protozoan parasite Plasmodium falciparum have been severely limited by the inability to introduce or modify genes. In this paper we describe a system of stable transfection of P. falciparum using a Toxoplasma gondii dihydrofolate reductase-thymidylate synthase gene, modified to confer resistance to pyrimethamine, as a selectable marker. This gene was placed under the transcriptional control of the P. falciparum calmodulin gene flanking sequences. Transfected parasites generally maintained plasmids episomally while under selection; however, parasite clones containing integrated forms of the plasmid were obtained. Integration occurred by both homologous and nonhomologous recombination. In addition to the flanking sequence of the P. falciparum calmodulin gene, the 5' sequences of the P. falciparum and P. chabaudi dihydrofolate reductase-thymidylate synthase genes were also shown to be transcriptionally active in P. falciparum. The minimal 5' sequence that possessed significant transcriptional activity was determined for each gene and short sequences containing important transcriptional control elements were identified. These sequences will provide considerable flexibility in the future construction of plasmid vectors to be used for the expression of foreign genes or for the deletion or modification of P. falciparum genes of interest. Images Fig. 4 Fig. 5 PMID:8692985

  20. Adaptation of the Panama II strain of Plasmodium falciparum to Panamanian owl monkeys.

    PubMed

    Rossan, R N; Baerg, D C

    1987-09-01

    The Panama II strain of Plasmodium falciparum, acquired at the second passage level in splenectomized Colombian owl monkeys, was adapted to owl monkeys of Panamanian origin. Patent infections were induced in 22 of 27 unaltered and 20 of 21 splenectomized recipients during 19 serial passages. The infections were significantly more virulent in splenectomized than normal Panamanian owl monkeys, however recrudescences in seven normal monkeys achieved peak parasitemias 48 times greater than in the primary attack. These results describe the first reproducible infections of indigenous falciparum malaria in Panamanian owl monkeys. PMID:3310680

  1. Identification of Potent and Selective Non-covalent Inhibitors of the Plasmodium falciparum Proteasome

    PubMed Central

    2015-01-01

    We have identified short N,C-capped peptides that selectively inhibit the proteasome of the malaria-causing pathogen Plasmodium falciparum. These compounds are highly potent in culture with no toxicity in host cells. One cyclic biphenyl ether compound inhibited intraerythrocytic growth of P. falciparum with an IC50 of 35 nM, and we show that even a pulse treatment with this cyclic peptide induced parasite death due to proteasome inhibition. These compounds represent promising new antimalarial agents that target the essential proteasomal machinery of the parasite without toxicity toward the host. PMID:25226494

  2. A Lectin-Like Receptor is Involved in Invasion of Erythrocytes by Plasmodium falciparum

    NASA Astrophysics Data System (ADS)

    Jungery, M.; Pasvol, G.; Newbold, C. I.; Weatherall, D. J.

    1983-02-01

    Glycophorin both in solution and inserted into liposomes blocks invasion of erythrocytes by the malaria parasite Plasmodium falciparum. Furthermore, one sugar, N-acetyl-D-glucosamine (GlcNAc), completely blocks invasion of the erythrocyte by this parasite. GlcNAc coupled to bovine serum albumin to prevent the sugar entering infected erythrocytes was at least 100,000 times more effective than GlcNAc alone. Bovine serum albumin coupled to lactose or bovine serum albumin alone had no effect on invasion. These results suggest that the binding of P. falciparum to erythrocytes is lectin-like and is determined by carbohydrates on glycophorin.

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

    PubMed Central

    Olszewski, Kellen L.; Llinás, Manuel

    2012-01-01

    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

  4. Synthesis and in vitro evaluation of hydrazinyl phthalazines against malaria parasite, Plasmodium falciparum.

    PubMed

    Subramanian, Gowtham; Babu Rajeev, C P; Mohan, Chakrabhavi Dhananjaya; Sinha, Ameya; Chu, Trang T T; Anusha, Sebastian; Ximei, Huang; Fuchs, Julian E; Bender, Andreas; Rangappa, Kanchugarakoppal S; Chandramohanadas, Rajesh; Basappa

    2016-07-15

    In this report, we describe the synthesis of 1-(Phthalazin-4-yl)-hydrazine using bronsted acidic ionic liquids and demonstrate their ability to inhibit asexual stage development of human malaria parasite, Plasmodium falciparum. Through computational studies, we short-listed chemical scaffolds with potential binding affinity to an essential parasite protein, dihydroorotate dehydrogenase (DHODH). Further, these compounds were synthesized in the lab and tested against P. falciparum. Several compounds from our library showed inhibitory activity at low micro-molar concentrations with minimal cytotoxic effects. These results indicate the potential of hydralazine derivatives as reference scaffolds to develop novel antimalarials. PMID:27261180

  5. Asexual and sexual stages of Plasmodium falciparum in Nigerian pregnant women attending antenatal booking clinic

    PubMed Central

    Balogun, S T; Fehintola, F A; Adeyanju, O A; Adedeji, A A

    2010-01-01

    Susceptibility to infection by Plasmodium falciparum is increased in pregnant women. In sub-Saharan Africa, the consequences of maternal malaria include preterm birth, fetal growth restriction and increased infant mortality. Malaria transmission requires the circulation of viable gametocytes that can be ingested by the female mosquito taking a blood meal. This study was conducted to evaluate the presence of asexual and sexual stages of P. falciparum in pregnant women attending antenatal booking clinics in south-western Nigeria, an area hyper-endemic for malaria. Gametocyte carriage was about 13%, similar to that documented for children symptomatic for malaria in our area of study.

  6. Synergistic Mortality Caused by Plasmodium falciparum during the 1918 Influenza Pandemic

    PubMed Central

    Shanks, G. Dennis

    2015-01-01

    At the end of World War I, British medical officers noted that soldiers infected with malaria were more likely to die during the 1918 influenza pandemic than those without malaria. This synergistic mortality appeared to be specific to Plasmodium falciparum and has not been generally noted since 1920. A possible explanation is that a malaria-induced procoagulant state enhanced the activation of influenza virus to increase inflammation and subsequent severe clinical outcomes. Falciparum proteins bind and likely inhibit antithrombin 3 and other factors. Pathogens interact in ways that may inform pathophysiology studies of remote epidemics. PMID:25802427

  7. Dihydroartemisinin-piperaquine for treating uncomplicated Plasmodium falciparum malaria

    PubMed Central

    Zani, Babalwa; Gathu, Michael; Donegan, Sarah; Olliaro, Piero L; Sinclair, David

    2014-01-01

    Background The World Health Organization (WHO) recommends Artemisinin-based Combination Therapy (ACT) for treating uncomplicated Plasmodium falciparum malaria. This review aims to assist the decision-making of malaria control programmes by providing an overview of the relative effects of dihydroartemisinin-piperaquine (DHA-P) versus other recommended ACTs. Objectives To evaluate the effectiveness and safety of DHA-P compared to other ACTs for treating uncomplicated P. falciparum malaria in adults and children. Search methods We searched the Cochrane Infectious Diseases Group Specialized Register; the Cochrane Central Register of Controlled Trials (CENTRAL) published in The Cochrane Library; MEDLINE; EMBASE; LILACS, and the metaRegister of Controlled Trials (mRCT) up to July 2013. Selection criteria Randomized controlled trials comparing a three-day course of DHA-P to a three-day course of an alternative WHO recommended ACT in uncomplicated P. falciparum malaria. Data collection and analysis Two authors independently assessed trials for eligibility and risk of bias, and extracted data. We analysed primary outcomes in line with the WHO 'Protocol for assessing and monitoring antimalarial drug efficacy’ and compared drugs using risk ratios (RR) and 95% confidence intervals (CI). Secondary outcomes were effects on gametocytes, haemoglobin, and adverse events. We assessed the quality of evidence using the GRADE approach. Main results We included 27 trials, enrolling 16,382 adults and children, and conducted between 2002 and 2010. Most trials excluded infants aged less than six months and pregnant women. DHA-P versus artemether-lumefantrine In Africa, over 28 days follow-up, DHA-P is superior to artemether-lumefantrine at preventing further parasitaemia (PCR-unadjusted treatment failure: RR 0.34, 95% CI 0.30 to 0.39, nine trials, 6200 participants, high quality evidence), and although PCR-adjusted treatment failure was below 5% for both ACTs, it was consistently lower

  8. A Plasmodium falciparum copper-binding membrane protein with copper transport motifs

    PubMed Central

    2012-01-01

    Background Copper is an essential catalytic co-factor for metabolically important cellular enzymes, such as cytochrome-c oxidase. Eukaryotic cells acquire copper through a copper transport protein and distribute intracellular copper using molecular chaperones. The copper chelator, neocuproine, inhibits Plasmodium falciparum ring-to-trophozoite transition in vitro, indicating a copper requirement for malaria parasite development. How the malaria parasite acquires or secretes copper still remains to be fully elucidated. Methods PlasmoDB was searched for sequences corresponding to candidate P. falciparum copper-requiring proteins. The amino terminal domain of a putative P. falciparum copper transport protein was cloned and expressed as a maltose binding fusion protein. The copper binding ability of this protein was examined. Copper transport protein-specific anti-peptide antibodies were generated in chickens and used to establish native protein localization in P. falciparum parasites by immunofluorescence microscopy. Results Six P. falciparum copper-requiring protein orthologs and a candidate P. falciparum copper transport protein (PF14_0369), containing characteristic copper transport protein features, were identified in PlasmoDB. The recombinant amino terminal domain of the transport protein bound reduced copper in vitro and within Escherichia coli cells during recombinant expression. Immunolocalization studies tracked the copper binding protein translocating from the erythrocyte plasma membrane in early ring stage to a parasite membrane as the parasites developed to schizonts. The protein appears to be a PEXEL-negative membrane protein. Conclusion Plasmodium falciparum parasites express a native protein with copper transporter characteristics that binds copper in vitro. Localization of the protein to the erythrocyte and parasite plasma membranes could provide a mechanism for the delivery of novel anti-malarial compounds. PMID:23190769

  9. Plasmodium falciparum Choline Kinase Inhibition Leads to a Major Decrease in Phosphatidylethanolamine Causing Parasite Death.

    PubMed

    Serrán-Aguilera, Lucía; Denton, Helen; Rubio-Ruiz, Belén; López-Gutiérrez, Borja; Entrena, Antonio; Izquierdo, Luis; Smith, Terry K; Conejo-García, Ana; Hurtado-Guerrero, Ramon

    2016-01-01

    Malaria is a life-threatening disease caused by different species of the protozoan parasite Plasmodium, with P. falciparum being the deadliest. Increasing parasitic resistance to existing antimalarials makes the necessity of novel avenues to treat this disease an urgent priority. The enzymes responsible for the synthesis of phosphatidylcholine and phosphatidylethanolamine are attractive drug targets to treat malaria as their selective inhibition leads to an arrest of the parasite's growth and cures malaria in a mouse model. We present here a detailed study that reveals a mode of action for two P. falciparum choline kinase inhibitors both in vitro and in vivo. The compounds present distinct binding modes to the choline/ethanolamine-binding site of P. falciparum choline kinase, reflecting different types of inhibition. Strikingly, these compounds primarily inhibit the ethanolamine kinase activity of the P. falciparum choline kinase, leading to a severe decrease in the phosphatidylethanolamine levels within P. falciparum, which explains the resulting growth phenotype and the parasites death. These studies provide an understanding of the mode of action, and act as a springboard for continued antimalarial development efforts selectively targeting P. falciparum choline kinase. PMID:27616047

  10. Molecular surveillance of antimalarial drug resistance related genes in Plasmodium falciparum isolates from Eritrea.

    PubMed

    Menegon, Michela; Nurahmed, Abduselam M; Talha, Albadawi A; Nour, Bakri Y M; Severini, Carlo

    2016-05-01

    The introduction of artemisinin-based combination therapy has led to extraordinary results in malaria control, however the recent emergence of partial resistance to artemisinin therapy in Southeast Asia jeopardizes these successes. This study aimed at investigating resistance to the antimalarial drugs by evaluating the polymorphisms in the PfK13, Pfcrt and Pfmdr1 genes in Plasmodium falciparum isolates obtained from patients in Eritrea. PMID:26875763

  11. Loading of erythrocyte membrane with pentacyclic triterpenes inhibits Plasmodium falciparum invasion.

    PubMed

    Ziegler, Hanne L; Staalsø, Trine; Jaroszewski, Jerzy W

    2006-06-01

    Lupeol and betulinic acid inhibit the proliferation of Plasmodium falciparum parasites by inhibition of the invasion of merozoites into erythrocytes. This conclusion is based on experiments employing parasite cultures synchronized by magnetic cell sorting (MACS). Identical inhibitory effects were observed upon incubation of synchronous parasite cultures in the presence of the triterpenoids, and when the parasite cultures were grown in a triterpenoid-free medium with erythrocytes preloaded with the triterpenoids. PMID:16732511

  12. Field applications of agglutination and cytoadherence assays with Plasmodium falciparum from Papua New Guinea.

    PubMed

    Southwell, B R; Brown, G V; Forsyth, K P; Smith, T; Philip, G; Anders, R

    1989-01-01

    Plasmodium falciparum isolates obtained directly from patients in Papua New Guinea were tested in their first cycle of growth in vitro for adherence to melanoma cells and for susceptibility to agglutination by immune serum. Binding varied among isolates and, in many cases, increased with further rounds of replication under optimal culture conditions. Binding inhibition assays and agglutination assays demonstrated extreme heterogeneity of surface antigens; apparently none of the sera from adult patients recognized all of the variants presented. PMID:2694479

  13. Screening for Drugs Against the Plasmodium falciparum Digestive Vacuole by Imaging Flow Cytometry.

    PubMed

    Lee, Yan Quan; Hall, Brian E; Tan, Kevin S W

    2016-01-01

    Phenotypic assays are increasingly employed to provide clues about drug mechanisms. In antimalarial drug screening, however, the majority of assays are designed to only measure parasite-killing activity. We describe here a high-content assay to detect drug-mediated perturbation of the digestive vacuole integrity in the trophozoite stage of Plasmodium falciparum, using the ImageStream imaging flow cytometer. PMID:27460247

  14. Plasmodium falciparum in Haiti: susceptibility to pyrimethamine and sulfadoxine-pyrimethamine

    PubMed Central

    Nguyen-Dinh, Phuc; Zevallos-Ipenza, Arturo; Magloire, Roc

    1984-01-01

    Eighteen patients with Plasmodium falciparum infection were studied in Port-au-Prince, Haiti, to monitor the response of the malaria parasite to sulfadoxine-pyrimethamine. In all infections the parasitaemia was cleared rapidly following treatment with standard dose of the drug combination; no recrudescence was observed during follow-up periods of 1 week (4 patients) and 4 weeks (14 patients). Parallel in vitro tests indicated that 5 of the 16 isolates successfully tested were resistant to pyrimethamine alone. PMID:6386210

  15. Detection of Plasmodium falciparum-infected red blood cells by optical stretching

    NASA Astrophysics Data System (ADS)

    Mauritz, Jakob M. A.; Tiffert, Teresa; Seear, Rachel; Lautenschläger, Franziska; Esposito, Alessandro; Lew, Virgilio L.; Guck, Jochen; Kaminski, Clemens F.

    2010-05-01

    We present the application of a microfluidic optical cell stretcher to measure the elasticity of malaria-infected red blood cells. The measurements confirm an increase in host cell rigidity during the maturation of the parasite Plasmodium falciparum. The device combines the selectivity and sensitivity of single-cell elasticity measurements with a throughput that is higher than conventional single-cell techniques. The method has potential to detect early stages of infection with excellent sensitivity and high speed.

  16. N'Dribala (Cochlospermum planchonii) versus chloroquine for treatment of uncomplicated Plasmodium falciparum malaria.

    PubMed

    Benoit-Vical, F; Valentin, A; Da, B; Dakuyo, Z; Descamps, L; Mallié, M

    2003-11-01

    The aim of this work was to assess the efficacy of oral N'Dribala (tuberous roots decoction of Cochlospermum planchonii Hook) treatment versus chloroquine in non-severe malaria. The study included 85 patients with uncomplicated Plasmodium falciparum infection in Banfora, Burkina Faso. Forty-six patients that received N'Dribala beverage were compared to 21 patients treated with chloroquine. All patients were monitored with clinical examination and a parasitemia control by Giemsa-stained thick films. N'Dribala appeared safe and statistically as efficient as chloroquine for the treatment of uncomplicated Plasmodium falciparum malaria. At day 5 (D5), 57% of chloroquine-treated and 52% of N'Dribala-treated patients were cured with no detectable parasitemia (parasite density (Pd): 0) and more than 90% of whole patients were asymptomatic. N'Dribala is easily available in this country, cheap, without significant side effects and efficient with a clearly demonstrated activity on Plasmodium falciparum blood stages. This study enhances the traditional use of the Cochlospermum planchonii as alternative therapy for treatment of non-severe malaria. PMID:14522441

  17. [Falciform anemia and Plasmodium falciparum malaria: a threat to flap survival?].

    PubMed

    Mariéthoz, S; Pittet, B; Loutan, L; Humbert, J; Montandon, D

    1999-02-01

    Plasmodium falciparum malaria, a parasitic disease, and sickle cell anemia, a hereditary disease, are two diseases affecting erythrocyte cycle, occurring with a high prevalence in tropical Africa. They may induce microthrombosis inducing vaso-occlusion, organ dysfunction and flap necrosis. During the acute phase of Plasmodium falciparum malaria, destruction of parasitized and healthy erythrocytes, release of parasite and erythrocyte material into the circulation, and secondary host reaction occur. Plasmodium falciparum infected erythrocytes also sequester in the microcirculation of vital organs and may interfere with microcirculatory flow in the flap during the postoperative period. The lower legs of homozygous sickle cell anemia patients are areas of marginal vascularity where minor abrasions become foci of inflammation. Inflammation results in decreased local oxygen tension, sickling of erythrocytes, increased blood viscosity and thrombosis with consequent ischemia, tissue breakdown and leg ulcer. Tissue transfer has become the procedure of choice for reconstruction of the lower third of the leg although flaps may become necrotic. The aim of this study is to analyse circumstances predisposing to surgical complications and to define preventive and therapeutic measures. A review of the literature will describe the current research and the new perspectives to treat sickle cell anemia, for example hydroxyurea and vasoactive substances (pentoxifylline, naftidrofuryl, buflomedil). PMID:10188298

  18. Versatile control of Plasmodium falciparum gene expression with an inducible protein-RNA interaction

    PubMed Central

    Goldfless, Stephen J.; Wagner, Jeffrey C.; Niles, Jacquin C.

    2014-01-01

    The available tools for conditional gene expression in Plasmodium falciparum are limited. Here, to enable reliable control of target gene expression, we build a system to efficiently modulate translation. We overcame several problems associated with other approaches for regulating gene expression in P. falciparum. Specifically, our system functions predictably across several native and engineered promoter contexts, and affords control over reporter and native parasite proteins irrespective of their subcellular compartmentalization. Induction and repression of gene expression are rapid, homogeneous, and stable over prolonged periods. To demonstrate practical application of our system, we used it to reveal direct links between antimalarial drugs and their native parasite molecular target. This is an important out come given the rapid spread of resistance, and intensified efforts to efficiently discover and optimize new antimalarial drugs. Overall, the studies presented highlight the utility of our system for broadly controlling gene expression and performing functional genetics in P. falciparum. PMID:25370483

  19. Host iron status and iron supplementation mediate susceptibility to erythrocytic stage Plasmodium falciparum.

    PubMed

    Clark, Martha A; Goheen, Morgan M; Fulford, Anthony; Prentice, Andrew M; Elnagheeb, Marwa A; Patel, Jaymin; Fisher, Nancy; Taylor, Steve M; Kasthuri, Raj S; Cerami, Carla

    2014-01-01

    Iron deficiency and malaria have similar global distributions, and frequently co-exist in pregnant women and young children. Where both conditions are prevalent, iron supplementation is complicated by observations that iron deficiency anaemia protects against falciparum malaria, and that iron supplements increase susceptibility to clinically significant malaria, but the mechanisms remain obscure. Here, using an in vitro parasite culture system with erythrocytes from iron-deficient and replete human donors, we demonstrate that Plasmodium falciparum infects iron-deficient erythrocytes less efficiently. In addition, owing to merozoite preference for young erythrocytes, iron supplementation of iron-deficient individuals reverses the protective effects of iron deficiency. Our results provide experimental validation of field observations reporting protective effects of iron deficiency and harmful effects of iron administration on human malaria susceptibility. Because recovery from anaemia requires transient reticulocytosis, our findings imply that in malarious regions iron supplementation should be accompanied by effective measures to prevent falciparum malaria. PMID:25059846

  20. A forward genetic screen identifies erythrocyte CD55 as essential for Plasmodium falciparum invasion **

    PubMed Central

    Egan, Elizabeth S.; Jiang, Rays H.Y.; Moechtar, Mischka A.; Barteneva, Natasha S.; Weekes, Michael P.; Nobre, Luis V.; Gygi, Steven P.; Paulo, Joao A.; Frantzreb, Charles; Tani, Yoshihiko; Takahashi, Junko; Watanabe, Seishi; Goldberg, Jonathan; Paul, Aditya S.; Brugnara, Carlo; Root, David E.; Wiegand, Roger C.; Doench, John G.; Duraisingh, Manoj T.

    2015-01-01

    Efforts to identify host determinants for malaria have been hindered by the absence of a nucleus in erythrocytes, precluding genetic manipulation in the cell where the parasite replicates. We used cultured red blood cells derived from hematopoietic stem cells to carry out a forward genetic screen for Plasmodium falciparum host determinants. We found that CD55 is an essential host factor for P. falciparum invasion. CD55-null erythrocytes were refractory to invasion by all isolates of P. falciparum because parasites failed to attach properly to the erythrocyte surface. Thus, CD55 is an attractive target for the development of malaria therapeutics. Hematopoietic stem cell-based forward genetic screens may be valuable for the identification of additional host determinants of malaria pathogenesis. PMID:25954012

  1. Chloroquine and sulphadoxine-pyrimethamine sensitivity of Plasmodium falciparum parasites in a Brazilian endemic area

    PubMed Central

    Gama, Bianca Ervatti; de Oliveira, Natália K Almeida; Zalis, Mariano G; de Souza, José Maria; Santos, Fátima; Daniel-Ribeiro, Cláudio Tadeu; Ferreira-da-Cruz, Maria de Fátima

    2009-01-01

    Background The goal of the present study was the characterization of Plasmodium falciparum genes associated to malaria drug resistance (pfcrt, pfdhfr and pfdhps), in samples from two Brazilian localities. Methods Parasites from 65 P. falciparum samples were genotyped using nested-PCR and direct DNA sequencing. Results Six resistant sulphadoxine-pyrimethamine (SP) pfdhfr genotypes and one haplotype associated to SP sensitivity were detected. For pfcrt gene, SVMNT chloroquine (CQ)-resistant genotype was detected as well as the CVMNK CQ-sensitive haplotype in the same sample from Paragominas, that showed a SP-sensitive genotype. Conclusion This study is the first to document the sensitivity of P. falciparum parasites to CQ and SP in Brazilian field samples. The importance of these findings is discussed. PMID:19602248

  2. Identification and initial characterisation of a Plasmodium falciparum Cox17 copper metallochaperone.

    PubMed

    Choveaux, David L; Krause, Robert G E; Przyborski, Jude M; Goldring, J P Dean

    2015-01-01

    Copper is an essential micronutrient for all living organisms as an important catalytic co-factor for key enzymes. In higher eukaryotes intracellular copper is distributed by copper metallochaperones. Copper chelators such as neocuproine and tetrathiomolybdate inhibit Plasmodium falciparum erythrocytic development, indicating a requirement for copper by the parasite. A screen of the P. falciparum genome database identified eight potential copper-requiring protein orthologs, including four candidate copper metallochaperones implicated in the delivery of copper to cytochrome-c oxidase. A P. falciparum Cox17 ortholog (PfCox17) was recombinantly expressed and the purified protein bound reduced copper in vitro. PfCox17 was localised to the parasite cytoplasm. Characterisation of plasmodial proteins involved in copper metabolism will help us understand the role of this essential microelement in plasmodial homeostasis. PMID:25447123

  3. Antibodies to Pf155, a major antigen of Plasmodium falciparum: seroepidemiological studies in Haiti*

    PubMed Central

    Deloron, P.; Duverseau, Y. T.; Zevallos-Ipenza, A.; Magloire, R.; Stanfill, P. S.; Nguyen-Dinh, Phuc

    1987-01-01

    The presence of malaria parasites and the serological antibody responses against whole Plasmodium falciparum and the Pf155 antigen were studied in the population of a small rural locality in Haiti in December 1985. Only 7 (1.5%) of the individuals were found to be infected with P. falciparum, the only species observed. Antibodies to P. falciparum were detected in an ELISA in 38.2% of the sera, the positivity rates being age-related. Anti-Pf155 antibodies were detected in 12.5% and 13.6% of individuals by two different techniques used. The anti-Pf155 positivity rates increased only after 25 years of age. No trends were detected for a clear-cut protective value of Pf155 antibodies against clinical malaria and further longitudinally conducted field surveys are needed to satisfactorily assess the potential protective effect of Pf155 antibodies. ImagesFig. 2 PMID:3311436

  4. A new method for culturing Plasmodium falciparum shows replication at the highest erythrocyte densities

    NASA Technical Reports Server (NTRS)

    Li, Tao; Glushakova, Svetlana; Zimmerberg, Joshua

    2003-01-01

    Plasmodium falciparum replicates poorly in erythrocyte densities greater than a hematocrit of 20%. A new method to culture the major malaria parasite was developed by using a hollow fiber bioreactor that preserves healthy erythrocytes at hematocrit up to 100%. P. falciparum replicated equally well at all densities studied. This method proved advantageous for large-scale preparation of parasitized erythrocytes (and potentially immunogens thereof), because high yields ( approximately 10(10) in 4 days) could be prepared with less cost and labor. Concomitantly, secreted proteins were concentrated by molecular sieving during culture, perhaps contributing to the parasitemic limit of 8%-12% with the 3D7 strain. The finding that P. falciparum can replicate at packed erythrocyte densities suggests that this system may be useful for study of the pathogenesis of fatal cerebral malaria, of which one feature is densely packed blood cells in brain microvasculature.

  5. Synthesis of alpha-substituted fosmidomycin analogues as highly potent Plasmodium falciparum growth inhibitors.

    PubMed

    Haemers, Timothy; Wiesner, Jochen; Van Poecke, Sara; Goeman, Jan; Henschker, Dajana; Beck, Edwald; Jomaa, Hassan; Van Calenbergh, Serge

    2006-04-01

    In view of the promising antimalarial activity of fosmidomycin or its N-acetyl homologue FR900098, the objective of this work was to investigate the influence of aromatic substituents in the alpha-position of the phosphonate moiety. The envisaged analogues were prepared using a linear route involving a 3-aryl-3-phosphoryl propanal intermediate. The activities of all compounds were evaluated on Eschericia coli 1-deoxy-d-xylulose 5-phosphate reductoisomerase and against two Plasmodium falciparum strains. Compared with fosmidomycin, several analogues displayed enhanced activity towards the P. falciparum strains. Compound 1e with a 3,4-dichlorophenyl substitution in the alpha-position of fosmidomycin emerged as the most potent analogue of this series. It is approximately three times more potent in inhibiting the growth of P. falciparum than FR900098, the most potent representative of this class reported so far. PMID:16439126

  6. Crystal Structure Analyses of the Fosmidomycin-Target Enzyme from Plasmodium Falciparum

    NASA Astrophysics Data System (ADS)

    Umeda, Tomonobu; Kusakabe, Yoshio; Tanaka, Nobutada

    The human malaria parasite Plasmodium falciparum is responsible for the death of more than a million people each year. Fosmidomycin has proved to be efficient in the treatment of P. falciparum malaria through the inhibition of 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR), an enzyme of the non-mevalonate pathway of isoprenoid biosynthesis, which is absent in humans. Crystal structure analyses of P. falciparum DXR (PfDXR) revealed that (i) an intrinsic flexibility of the PfDXR molecule accounts for the induced-fit movement to accommodate the bound inhibitor in the active site, and (ii) a cis arrangement of the oxygen atoms of the hydroxamate group of the bound inhibitor is essential for tight binding of the inhibitor to the active site metal. We believe that our study will serve as a useful guide to develop more potent PfDXR inhibitors.

  7. Ca2+ monitoring in Plasmodium falciparum using the yellow cameleon-Nano biosensor

    PubMed Central

    Pandey, Kishor; Ferreira, Pedro E.; Ishikawa, Takeshi; Nagai, Takeharu; Kaneko, Osamu; Yahata, Kazuhide

    2016-01-01

    Calcium (Ca2+)-mediated signaling is a conserved mechanism in eukaryotes, including the human malaria parasite, Plasmodium falciparum. Due to its small size (<10 μm) measurement of intracellular Ca2+ in Plasmodium is technically challenging, and thus Ca2+ regulation in this human pathogen is not well understood. Here we analyze Ca2+ homeostasis via a new approach using transgenic P. falciparum expressing the Ca2+ sensor yellow cameleon (YC)-Nano. We found that cytosolic Ca2+ concentration is maintained at low levels only during the intraerythrocytic trophozoite stage (30 nM), and is increased in the other blood stages (>300 nM). We determined that the mammalian SERCA inhibitor thapsigargin and antimalarial dihydroartemisinin did not perturb SERCA activity. The change of the cytosolic Ca2+ level in P. falciparum was additionally detectable by flow cytometry. Thus, we propose that the developed YC-Nano-based system is useful to study Ca2+ signaling in P. falciparum and is applicable for drug screening. PMID:27006284

  8. Ca(2+) monitoring in Plasmodium falciparum using the yellow cameleon-Nano biosensor.

    PubMed

    Pandey, Kishor; Ferreira, Pedro E; Ishikawa, Takeshi; Nagai, Takeharu; Kaneko, Osamu; Yahata, Kazuhide

    2016-01-01

    Calcium (Ca(2+))-mediated signaling is a conserved mechanism in eukaryotes, including the human malaria parasite, Plasmodium falciparum. Due to its small size (<10 μm) measurement of intracellular Ca(2+) in Plasmodium is technically challenging, and thus Ca(2+) regulation in this human pathogen is not well understood. Here we analyze Ca(2+) homeostasis via a new approach using transgenic P. falciparum expressing the Ca(2+) sensor yellow cameleon (YC)-Nano. We found that cytosolic Ca(2+) concentration is maintained at low levels only during the intraerythrocytic trophozoite stage (30 nM), and is increased in the other blood stages (>300 nM). We determined that the mammalian SERCA inhibitor thapsigargin and antimalarial dihydroartemisinin did not perturb SERCA activity. The change of the cytosolic Ca(2+) level in P. falciparum was additionally detectable by flow cytometry. Thus, we propose that the developed YC-Nano-based system is useful to study Ca(2+) signaling in P. falciparum and is applicable for drug screening. PMID:27006284

  9. Risk factors for Plasmodium falciparum and Plasmodium vivax gametocyte carriage in Papua New Guinean children with uncomplicated malaria.

    PubMed

    Karl, Stephan; Laman, Moses; Moore, Brioni R; Benjamin, John M; Salib, Mary; Lorry, Lina; Maripal, Samuel; Siba, Peter; Robinson, Leanne J; Mueller, Ivo; Davis, Timothy M E

    2016-08-01

    There are limited data on gametocytaemia risk factors before/after treatment with artemisinin combination therapy in children from areas with transmission of multiple Plasmodium species. We utilised data from a randomised trial comparing artemether-lumefantrine (AL) and artemisinin-naphthoquine (AN) in 230 Papua New Guinean children aged 0.5-5 years with uncomplicated malaria in whom determinants of gametocytaemia by light microscopy were assessed at baseline using logistic regression and during follow-up using multilevel mixed effects modelling. Seventy-four (32%) and 18 (8%) children presented with P. falciparum and P. vivax gametocytaemia, respectively. Baseline P. falciparum gametocytaemia was associated with Hackett spleen grade 1 (odds ratio (95% CI) 4.01 (1.60-10.05) vs grade 0; P<0.001) and haemoglobin (0.95 (0.92-0.97) per 1g/L increase; P<0.001), and P. falciparum asexual parasitaemia in slide-positive cases (0.36 (0.19-0.68) for a 10-fold increase; P=0.002). Baseline P. vivax gametocytaemia was associated with Hackett grade 2 (12.66 (1.31-122.56); P=0.028), mixed P. falciparum/vivax infection (0.16 (0.03-1.00); P=0.050), P. vivax asexual parasitaemia (5.68 (0.98-33.04); P=0.053) and haemoglobin (0.94 (0.88-1.00); P=0.056). For post-treatment P. falciparum gametocytaemia, independent predictors were AN vs AL treatment (4.09 (1.43-11.65)), haemoglobin (0.95 (0.93-0.97)), presence/absence of P. falciparum asexual forms (3.40 (1.66-0.68)) and day post-treatment (0.086 (0.82-0.90)) (P<0.001). Post-treatment P. vivax gametocytaemia was predicted by presence of P. vivax asexual forms (596 (12-28,433); P<0.001). Consistent with slow P. falciparum gametocyte maturation, low haemoglobin, low asexual parasite density and higher spleen grading, markers of increased prior infection exposure/immunity, were strong associates of pre-treatment gametocyte positivity. The persistent inverse association between P. falciparum gametocytaemia and haemoglobin during follow

  10. Antibody responses to Plasmodium falciparum and Plasmodium vivax blood-stage and sporozoite antigens in the postpartum period

    PubMed Central

    McLean, Alistair R. D.; Boel, Machteld E.; McGready, Rose; Ataide, Ricardo; Drew, Damien; Tsuboi, Takafumi; Beeson, James G.; Nosten, François; Simpson, Julie A.; Fowkes, Freya J. I.

    2016-01-01

    During pregnancy a variety of immunological changes occur to accommodate the fetus. It is unknown whether these changes continue to affect humoral immunity postpartum or how quickly they resolve. IgG levels were measured to P. falciparum and P. vivax antigens in 201 postpartum and 201 controls over 12 weeks. Linear mixed-effects models assessed antibody maintenance over time and the effect of microscopically confirmed Plasmodium spp. infection on antibody levels, and whether this was different in postpartum women compared with control women. Postpartum women had reduced Plasmodium spp. antibody levels compared to controls at baseline. Over 12 weeks, mean antibody levels in postpartum women increased to levels observed in control women. Microscopically confirmed P. falciparum and P. vivax infections during follow-up were associated with an increase in species-specific antibodies with similar magnitudes of boosting observed in postpartum and control women. Antibodies specific for pregnancy-associated, VAR2CSA-expressing parasites did not rapidly decline postpartum and did not boost in response to infection in either postpartum or control women. After pregnancy, levels of malaria-specific antibodies were reduced, but recovered to levels seen in control women. There was no evidence of an impaired ability to mount a boosting response in postpartum women. PMID:27558000

  11. Antibody responses to Plasmodium falciparum and Plasmodium vivax blood-stage and sporozoite antigens in the postpartum period.

    PubMed

    McLean, Alistair R D; Boel, Machteld E; McGready, Rose; Ataide, Ricardo; Drew, Damien; Tsuboi, Takafumi; Beeson, James G; Nosten, François; Simpson, Julie A; Fowkes, Freya J I

    2016-01-01

    During pregnancy a variety of immunological changes occur to accommodate the fetus. It is unknown whether these changes continue to affect humoral immunity postpartum or how quickly they resolve. IgG levels were measured to P. falciparum and P. vivax antigens in 201 postpartum and 201 controls over 12 weeks. Linear mixed-effects models assessed antibody maintenance over time and the effect of microscopically confirmed Plasmodium spp. infection on antibody levels, and whether this was different in postpartum women compared with control women. Postpartum women had reduced Plasmodium spp. antibody levels compared to controls at baseline. Over 12 weeks, mean antibody levels in postpartum women increased to levels observed in control women. Microscopically confirmed P. falciparum and P. vivax infections during follow-up were associated with an increase in species-specific antibodies with similar magnitudes of boosting observed in postpartum and control women. Antibodies specific for pregnancy-associated, VAR2CSA-expressing parasites did not rapidly decline postpartum and did not boost in response to infection in either postpartum or control women. After pregnancy, levels of malaria-specific antibodies were reduced, but recovered to levels seen in control women. There was no evidence of an impaired ability to mount a boosting response in postpartum women. PMID:27558000

  12. 3-Iodo-4-aminoquinoline derivative sensitises resistant strains of Plasmodium falciparum to chloroquine.

    PubMed

    Edaye, Sonia; Tazoo, Dagobert; Bohle, D Scott; Georges, Elias

    2016-06-01

    Chloroquine (CQ), the first cost-effective synthetic antimalarial, is rendered ineffective in malaria-endemic regions owing to the rise and spread of CQ-resistant Plasmodium falciparum. In this report, we show that a halogen derivative of CQ, namely 3-iodo-CQ, inhibits the proliferation of CQ-sensitive and -resistant P. falciparum in a verapamil-insensitive manner. Similar to CQ, the antimalarial activity of 3-iodo-CQ is likely due to its inhibition of β-haematin formation. Interestingly, the presence of non-inhibitory concentrations of 3-iodo-CQ potentiated the antiproliferative activity of CQ against CQ-resistant strains or P. falciparum transfectants expressing wild-type or mutant P. falciparum CQ resistance transporter (PfCRT) (C2(GC03) or C4(Dd2), respectively). These findings demonstrate that halogenation of the third position of 4-aminoquinoline, with a simple one-step reaction from CQ, generates a novel derivative that is active against CQ-sensitive and -resistant P. falciparum, possibly by inhibiting the activity of mutant PfCRT. PMID:27211211

  13. Clustered local transmission and asymptomatic Plasmodium falciparum and Plasmodium vivax malaria infections in a recently emerged, hypoendemic Peruvian Amazon community

    PubMed Central

    Branch, OraLee; Casapia, W Martin; Gamboa, Dionicia V; Hernandez, Jean N; Alava, Freddy F; Roncal, Norma; Alvarez, Eugenia; Perez, Enrique J; Gotuzzo, Eduardo

    2005-01-01

    Background There is a low incidence of malaria in Iquitos, Peru, suburbs detected by passive case-detection. This low incidence might be attributable to infections clustered in some households/regions and/or undetected asymptomatic infections. Methods Passive case-detection (PCD) during the malaria season (February-July) and an active case-detection (ACD) community-wide survey (March) surveyed 1,907 persons. Each month, April-July, 100-metre at-risk zones were defined by location of Plasmodium falciparum infections in the previous month. Longitudinal ACD and PCD (ACP+PCD) occurred within at-risk zones, where 137 houses (573 persons) were randomly selected as sentinels, each with one month of weekly active sampling. Entomological captures were conducted in the sentinel houses. Results The PCD incidence was 0.03 P. falciparum and 0.22 Plasmodium vivax infections/person/malaria-season. However, the ACD+PCD prevalence was 0.13 and 0.39, respectively. One explanation for this 4.33 and 1.77-fold increase, respectively, was infection clustering within at-risk zones and contiguous households. Clustering makes PCD, generalized to the entire population, artificially low. Another attributable-factor was that only 41% and 24% of the P. falciparum and P. vivax infections were associated with fever and 80% of the asymptomatic infections had low-density or absent parasitaemias the following week. After accounting for asymptomatic infections, a 2.6-fold increase in ACD+PCD versus PCD was attributable to clustered transmission in at-risk zones. Conclusion Even in low transmission, there are frequent highly-clustered asymptomatic infections, making PCD an inadequate measure of incidence. These findings support a strategy of concentrating ACD and insecticide campaigns in houses adjacent to houses were malaria was detected one month prior. PMID:15975146

  14. Positive selection underlies the species-specific binding of Plasmodium falciparum RH5 to human basigin.

    PubMed

    Forni, Diego; Pontremoli, Chiara; Cagliani, Rachele; Pozzoli, Uberto; Clerici, Mario; Sironi, Manuela

    2015-09-01

    Plasmodium falciparum, the causative agent of the deadliest form of malaria, is a member of the Laverania subgenus, which includes ape-infecting parasites. P. falciparum is thought to have originated in gorillas, although infection is now restricted to humans. Laverania parasites display remarkable host-specificity, which is partially mediated by the interaction between parasite ligands and host receptors. We analyse the evolution of BSG (basigin) and GYPA (glycophorin A) in primates/hominins, as well as of their Plasmodium-encoded ligands, PfRH5 and PfEBA175. We show that, in primates, positive selection targeted two sites in BSG (F27 and H102), both involved in PfRH5 binding. A population genetics-phylogenetics approach detected the strongest selection for the gorilla lineage: one of the positively selected sites (K191) is a major determinant of PfRH5 binding affinity. Analysis of RH5 genes indicated episodic selection on the P. falciparum branch; the positively selected W447 site is known to stabilize the interaction with human basigin. Conversely, we detect no selection in the receptor-binding region of EBA175 in the P. falciparum lineage. Its host receptor, GYPA, shows evidence of positive selection in all hominid lineages; selected codons include glycosylation sites that modulate PfEBA175 binding affinity. Data herein provide an evolutionary explanation for species-specific binding of the PfRH5-BSG ligand-receptor pair and support the hypothesis that positive selection at these genes drove the host shift leading to the emergence of P. falciparum as a human pathogen. PMID:26302433

  15. Associations Between Helminth Infections, Plasmodium falciparum Parasite Carriage and Antibody Responses to Sexual and Asexual Stage Malarial Antigens.

    PubMed

    Ateba-Ngoa, Ulysse; Jones, Sophie; Zinsou, Jeannot Fréjus; Honkpehedji, Josiane; Adegnika, Ayola Akim; Agobe, Jean-Claude Dejon; Massinga-Loembe, Marguerite; Mordmüller, Benjamin; Bousema, Teun; Yazdanbakhsh, Maria

    2016-08-01

    Infections with helminths and Plasmodium spp. overlap in their geographical distribution. It has been postulated that helminth infections may influence malarial transmission by altering Plasmodium falciparum gametocytogenesis. This cross-sectional study assessed the effect of helminth infections on P. falciparum gametocyte carriage and on humoral immune responses to sexual stage antigens in Gabon. Schistosoma haematobium and filarial infections as well as P. falciparum asexual forms and gametocyte carriage were determined. The antibody responses measured were to sexual (Pfs230, Pfs48/45) and asexual P. falciparum antigens (AMA1, MSP1, and GLURP). A total of 287 subjects were included. The prevalence of microscopically detectable P. falciparum asexual parasites was higher in S. haematobium-infected subjects in comparison to their uninfected counterparts (47% versus 26%, P = 0.003), but this was not different when filarial infections were considered. Plasmodium falciparum gametocyte carriage was similar between Schistosoma- or filaria-infected and uninfected subjects. We observed a significant decrease of Pfs48/45 immunoglobulin G titer in S. haematobium-infected subjects (P = 0.037), whereas no difference was seen for Pfs230 antibody titer, nor for antibodies to AMA1, MSP1, or GLURP. Our findings suggest an effect of S. haematobium on antibody responses to some P. falciparum gametocyte antigens that may have consequences for transmission-blocking immunity. PMID:27273645

  16. Spatial association with PTEX complexes defines regions for effector export into Plasmodium falciparum-infected erythrocytes.

    PubMed

    Riglar, David T; Rogers, Kelly L; Hanssen, Eric; Turnbull, Lynne; Bullen, Hayley E; Charnaud, Sarah C; Przyborski, Jude; Gilson, Paul R; Whitchurch, Cynthia B; Crabb, Brendan S; Baum, Jake; Cowman, Alan F

    2013-01-01

    Export of proteins into the infected erythrocyte is critical for malaria parasite survival. The majority of effector proteins are thought to export via a proteinaceous translocon, resident in the parasitophorous vacuole membrane surrounding the parasite. Identification of the Plasmodium translocon of exported proteins and its biochemical association with exported proteins suggests it performs this role. Direct evidence for this, however, is lacking. Here using viable purified Plasmodium falciparum merozoites and three-dimensional structured illumination microscopy, we investigate remodelling events immediately following parasite invasion. We show that multiple complexes of the Plasmodium translocon of exported proteins localize together in foci that dynamically change in clustering behaviour. Furthermore, we provide conclusive evidence of spatial association between exported proteins and exported protein 2, a core component of the Plasmodium translocon of exported proteins, during native conditions and upon generation of translocation intermediates. These data provide the most direct cellular evidence to date that protein export occurs at regions of the parasitophorous vacuole membrane housing the Plasmodium translocon of exported proteins complex. PMID:23361006

  17. Spatial association with PTEX complexes defines regions for effector export into Plasmodium falciparum-infected erythrocytes

    PubMed Central

    Riglar, David T.; Rogers, Kelly L.; Hanssen, Eric; Turnbull, Lynne; Bullen, Hayley E.; Charnaud, Sarah C.; Przyborski, Jude; Gilson, Paul R.; Whitchurch, Cynthia B.; Crabb, Brendan S.; Baum, Jake; Cowman, Alan F.

    2013-01-01

    Export of proteins into the infected erythrocyte is critical for malaria parasite survival. The majority of effector proteins are thought to export via a proteinaceous translocon, resident in the parasitophorous vacuole membrane surrounding the parasite. Identification of the Plasmodium translocon of exported proteins and its biochemical association with exported proteins suggests it performs this role. Direct evidence for this, however, is lacking. Here using viable purified Plasmodium falciparum merozoites and three-dimensional structured illumination microscopy, we investigate remodelling events immediately following parasite invasion. We show that multiple complexes of the Plasmodium translocon of exported proteins localize together in foci that dynamically change in clustering behaviour. Furthermore, we provide conclusive evidence of spatial association between exported proteins and exported protein 2, a core component of the Plasmodium translocon of exported proteins, during native conditions and upon generation of translocation intermediates. These data provide the most direct cellular evidence to date that protein export occurs at regions of the parasitophorous vacuole membrane housing the Plasmodium translocon of exported proteins complex. PMID:23361006

  18. An impossible journey? The development of Plasmodium falciparum NF54 in Culex quinquefasciatus.

    PubMed

    Knöckel, Julia; Molina-Cruz, Alvaro; Fischer, Elizabeth; Muratova, Olga; Haile, Ashley; Barillas-Mury, Carolina; Miller, Louis H

    2013-01-01

    Although Anopheles mosquitoes are the vectors for human Plasmodium spp., there are also other mosquito species-among them culicines (Culex spp., Aedes spp.)-present in malaria-endemic areas. Culicine mosquitoes transmit arboviruses and filarial worms to humans and are vectors for avian Plasmodium spp., but have never been observed to transmit human Plasmodium spp. When ingested by a culicine mosquito, parasites could either face an environment that does not allow development due to biologic incompatibility or be actively killed by the mosquito's immune system. In the latter case, the molecular mechanism of killing must be sufficiently powerful that Plasmodium is not able to overcome it. To investigate how human malaria parasites develop in culicine mosquitoes, we infected Culex quinquefasciatus with Plasmodium falciparum NF54 and monitored development of parasites in the blood bolus and midgut epithelium at different time points. Our results reveal that ookinetes develop in the midgut lumen of C. quinquefasciatus in slightly lower numbers than in Anopheles gambiae G3. After 30 hours, parasites have invaded the midgut and can be observed on the basal side of the midgut epithelium by confocal and transmission electron microscopy. Very few of the parasites in C. quinquefasciatus are alive, most of them are lysed. Eight days after the mosquito's blood meal, no oocysts can be found in C. quinquefasciatus. Our results suggest that the mosquito immune system could be involved in parasite killing early in development after ookinetes have crossed the midgut epithelium and come in contact with the mosquito hemolymph. PMID:23658824

  19. Antibodies to a single, conserved epitope in Anopheles APN1 inhibit universal transmission of Plasmodium falciparum and Plasmodium vivax malaria.

    PubMed

    Armistead, Jennifer S; Morlais, Isabelle; Mathias, Derrick K; Jardim, Juliette G; Joy, Jaimy; Fridman, Arthur; Finnefrock, Adam C; Bagchi, Ansu; Plebanski, Magdalena; Scorpio, Diana G; Churcher, Thomas S; Borg, Natalie A; Sattabongkot, Jetsumon; Dinglasan, Rhoel R

    2014-02-01

    Malaria transmission-blocking vaccines (TBVs) represent a promising approach for the elimination and eradication of this disease. AnAPN1 is a lead TBV candidate that targets a surface antigen on the midgut of the obligate vector of the Plasmodium parasite, the Anopheles mosquito. In this study, we demonstrated that antibodies targeting AnAPN1 block transmission of Plasmodium falciparum and Plasmodium vivax across distantly related anopheline species in countries to which malaria is endemic. Using a biochemical and immunological approach, we determined that the mechanism of action for this phenomenon stems from antibody recognition of a single protective epitope on AnAPN1, which we found to be immunogenic in murine and nonhuman primate models and highly conserved among anophelines. These data indicate that AnAPN1 meets the established target product profile for TBVs and suggest a potential key role for an AnAPN1-based panmalaria TBV in the effort to eradicate malaria. PMID:24478095

  20. Effect of Farnesyltransferase Inhibitor R115777 on Mitochondria of Plasmodium falciparum

    PubMed Central

    Ha, Young Ran; Hwang, Bae-Geun; Hong, Yeonchul; Yang, Hye-Won; Lee, Sang Joon

    2015-01-01

    The parasite Plasmodium falciparum causes severe malaria and is the most dangerous to humans. However, it exhibits resistance to their drugs. Farnesyltransferase has been identified in pathogenic protozoa of the genera Plasmodium and the target of farnesyltransferase includes Ras family. Therefore, the inhibition of farnesyltransferase has been suggested as a new strategy for the treatment of malaria. However, the exact functional mechanism of this agent is still unknown. In addition, the effect of farnesyltransferase inhibitor (FTIs) on mitochondrial level of malaria parasites is not fully understood. In this study, therefore, the effect of a FTI R115777 on the function of mitochondria of P. falciparum was investigated experimentally. As a result, FTI R115777 was found to suppress the infection rate of malaria parasites under in vitro condition. It also reduces the copy number of mtDNA-encoded cytochrome c oxidase III. In addition, the mitochondrial membrane potential (ΔΨm) and the green fluorescence intensity of MitoTracker were decreased by FTI R115777. Chloroquine and atovaquone were measured by the mtDNA copy number as mitochondrial non-specific or specific inhibitor, respectively. Chloroquine did not affect the copy number of mtDNA-encoded cytochrome c oxidase III, while atovaquone induced to change the mtDNA copy number. These results suggest that FTI R115777 has strong influence on the mitochondrial function of P. falciparum. It may have therapeutic potential for malaria by targeting the mitochondria of parasites. PMID:26323840

  1. Biochemical and structural characterization of the apicoplast dihydrolipoamide dehydrogenase of Plasmodium falciparum

    PubMed Central

    Laine, Larissa M.; Biddau, Marco; Byron, Olwyn; Müller, Sylke

    2014-01-01

    PDC (pyruvate dehydrogenase complex) is a multi-enzyme complex comprising an E1 (pyruvate decarboxylase), an E2 (dihydrolipomide acetyltransferase) and an E3 (dihydrolipoamide dehydrogenase). PDC catalyses the decarboxylation of pyruvate and forms acetyl-CoA and NADH. In the human malaria parasite Plasmodium falciparum, the single PDC is located exclusively in the apicoplast. Plasmodium PDC is essential for parasite survival in the mosquito vector and for late liver stage development in the human host, suggesting its suitability as a target for intervention strategies against malaria. Here, PfaE3 (P. falciparum apicoplast E3) was recombinantly expressed and characterized. Biochemical parameters were comparable with those determined for E3 from other organisms. A homology model for PfaE3 reveals an extra anti-parallel β-strand at the position where human E3BP (E3-binding protein) interacts with E3; a parasite-specific feature that may be exploitable for drug discovery against PDC. To assess the biological role of Pfae3, it was deleted from P. falciparum and although the mutants are viable, they displayed a highly synchronous growth phenotype during intra-erythrocytic development. The mutants also showed changes in the expression of some mitochondrial and antioxidant proteins suggesting that deletion of Pfae3 impacts on the parasite's metabolic function with downstream effects on the parasite's redox homoeostasis and cell cycle. PMID:25387830

  2. Plasmodium falciparum Adhesins Play an Essential Role in Signalling and Activation of Invasion into Human Erythrocytes

    PubMed Central

    Tham, Wai-Hong; Lim, Nicholas T. Y.; Weiss, Greta E.; Lopaticki, Sash; Ansell, Brendan R. E.; Bird, Megan; Lucet, Isabelle; Dorin-Semblat, Dominique; Doerig, Christian; Gilson, Paul R.; Crabb, Brendan S.; Cowman, Alan F.

    2015-01-01

    The most severe form of malaria in humans is caused by the protozoan parasite Plasmodium falciparum. The invasive form of malaria parasites is termed a merozoite and it employs an array of parasite proteins that bind to the host cell to mediate invasion. In Plasmodium falciparum, the erythrocyte binding-like (EBL) and reticulocyte binding-like (Rh) protein families are responsible for binding to specific erythrocyte receptors for invasion and mediating signalling events that initiate active entry of the malaria parasite. Here we have addressed the role of the cytoplasmic tails of these proteins in activating merozoite invasion after receptor engagement. We show that the cytoplasmic domains of these type 1 membrane proteins are phosphorylated in vitro. Depletion of PfCK2, a kinase implicated to phosphorylate these cytoplasmic tails, blocks P. falciparum invasion of red blood cells. We identify the crucial residues within the PfRh4 cytoplasmic domain that are required for successful parasite invasion. Live cell imaging of merozoites from these transgenic mutants show they attach but do not penetrate erythrocytes implying the PfRh4 cytoplasmic tail conveys signals important for the successful completion of the invasion process. PMID:26694741

  3. Long-lived Plasmodium falciparum specific memory B cells in naturally exposed Swedish travelers.

    PubMed

    Ndungu, Francis M; Lundblom, Klara; Rono, Josea; Illingworth, Joseph; Eriksson, Sara; Färnert, Anna

    2013-11-01

    Antibodies (Abs) are critical for immunity to malaria. However, Plasmodium falciparum specific Abs decline rapidly in absence of reinfection, suggesting impaired immunological memory. This study determines whether residents of Sweden that were treated for malaria following international travel maintained long-lasting malaria-specific Abs and memory B cells (MBCs). We compared levels of malaria-specific Abs and MBCs between 47 travelers who had been admitted with malaria at the Karolinska University Hospital between 1 and 16 years previously, eight malaria-naïve adult Swedes without histories of travel, and 14 malaria-immune adult Kenyans. Plasmodium falciparum-lysate-specific Ab levels were above naïve control levels in 30% of the travelers, whereas AMA-1, merozoite surface protein-142 , and merozoite surface protein-3-specific Ab levels were similar. In contrast, 78% of travelers had IgG-MBCs specific for at least one malaria antigen (59, 45, and 28% for apical merozoite antigen-1, merozoite surface protein-1, and merozoite surface protein-3, respectively) suggesting that malaria-specific MBCs are maintained for longer than the cognate serum Abs in the absence of re-exposure to parasites. Five travelers maintained malaria antigen-specific MBC responses for up to 16 years since the diagnosis of the index episode (and had not traveled to malaria-endemic regions in the intervening time). Thus P. falciparum can induce long-lasting MBCs, maintained for up to 16 years without reexposure. PMID:23881859

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

    PubMed Central

    2013-01-01

    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

  5. DNA Repair Mechanisms and Their Biological Roles in the Malaria Parasite Plasmodium falciparum

    PubMed Central

    Lee, Andrew H.; Symington, Lorraine S.

    2014-01-01

    SUMMARY Research into the complex genetic underpinnings of the malaria parasite Plasmodium falciparum is entering a new era with the arrival of site-specific genome engineering. Previously restricted only to model systems but now expanded to most laboratory organisms, and even to humans for experimental gene therapy studies, this technology allows researchers to rapidly generate previously unattainable genetic modifications. This technological advance is dependent on DNA double-strand break repair (DSBR), specifically homologous recombination in the case of Plasmodium. Our understanding of DSBR in malaria parasites, however, is based largely on assumptions and knowledge taken from other model systems, which do not always hold true in Plasmodium. Here we describe the causes of double-strand breaks, the mechanisms of DSBR, and the differences between model systems and P. falciparum. These mechanisms drive basic parasite functions, such as meiosis, antigen diversification, and copy number variation, and allow the parasite to continually evolve in the contexts of host immune pressure and drug selection. Finally, we discuss the new technologies that leverage DSBR mechanisms to accelerate genetic investigations into this global infectious pathogen. PMID:25184562

  6. Biosynthesis of GDP-fucose and other sugar nucleotides in the blood stages of Plasmodium falciparum.

    PubMed

    Sanz, Sílvia; Bandini, Giulia; Ospina, Diego; Bernabeu, Maria; Mariño, Karina; Fernández-Becerra, Carmen; Izquierdo, Luis

    2013-06-01

    Carbohydrate structures play important roles in many biological processes, including cell adhesion, cell-cell communication, and host-pathogen interactions. Sugar nucleotides are activated forms of sugars used by the cell as donors for most glycosylation reactions. Using a liquid chromatography-tandem mass spectrometry-based method, we identified and quantified the pools of UDP-glucose, UDP-galactose, UDP-N-acetylglucosamine, GDP-mannose, and GDP-fucose in Plasmodium falciparum intraerythrocytic life stages. We assembled these data with the in silico functional reconstruction of the parasite metabolic pathways obtained from the P. falciparum annotated genome, exposing new active biosynthetic routes crucial for further glycosylation reactions. Fucose is a sugar present in glycoconjugates often associated with recognition and adhesion events. Thus, the GDP-fucose precursor is essential in a wide variety of organisms. P. falciparum presents homologues of GDP-mannose 4,6-dehydratase and GDP-L-fucose synthase enzymes that are active in vitro, indicating that most GDP-fucose is formed by a de novo pathway that involves the bioconversion of GDP-mannose. Homologues for enzymes involved in a fucose salvage pathway are apparently absent in the P. falciparum genome. This is in agreement with in vivo metabolic labeling experiments showing that fucose is not significantly incorporated by the parasite. Fluorescence microscopy of epitope-tagged versions of P. falciparum GDP-mannose 4,6-dehydratase and GDP-L-fucose synthase expressed in transgenic 3D7 parasites shows that these enzymes localize in the cytoplasm of P. falciparum during the intraerythrocytic developmental cycle. Although the function of fucose in the parasite is not known, the presence of GDP-fucose suggests that the metabolite may be used for further fucosylation reactions. PMID:23615908

  7. Biosynthesis of GDP-fucose and Other Sugar Nucleotides in the Blood Stages of Plasmodium falciparum*

    PubMed Central

    Sanz, Sílvia; Bandini, Giulia; Ospina, Diego; Bernabeu, Maria; Mariño, Karina; Fernández-Becerra, Carmen; Izquierdo, Luis

    2013-01-01

    Carbohydrate structures play important roles in many biological processes, including cell adhesion, cell-cell communication, and host-pathogen interactions. Sugar nucleotides are activated forms of sugars used by the cell as donors for most glycosylation reactions. Using a liquid chromatography-tandem mass spectrometry-based method, we identified and quantified the pools of UDP-glucose, UDP-galactose, UDP-N-acetylglucosamine, GDP-mannose, and GDP-fucose in Plasmodium falciparum intraerythrocytic life stages. We assembled these data with the in silico functional reconstruction of the parasite metabolic pathways obtained from the P. falciparum annotated genome, exposing new active biosynthetic routes crucial for further glycosylation reactions. Fucose is a sugar present in glycoconjugates often associated with recognition and adhesion events. Thus, the GDP-fucose precursor is essential in a wide variety of organisms. P. falciparum presents homologues of GDP-mannose 4,6-dehydratase and GDP-l-fucose synthase enzymes that are active in vitro, indicating that most GDP-fucose is formed by a de novo pathway that involves the bioconversion of GDP-mannose. Homologues for enzymes involved in a fucose salvage pathway are apparently absent in the P. falciparum genome. This is in agreement with in vivo metabolic labeling experiments showing that fucose is not significantly incorporated by the parasite. Fluorescence microscopy of epitope-tagged versions of P. falciparum GDP-mannose 4,6-dehydratase and GDP-l-fucose synthase expressed in transgenic 3D7 parasites shows that these enzymes localize in the cytoplasm of P. falciparum during the intraerythrocytic developmental cycle. Although the function of fucose in the parasite is not known, the presence of GDP-fucose suggests that the metabolite may be used for further fucosylation reactions. PMID:23615908

  8. Sensitivity of Plasmodium falciparum to Antimalarial Drugs in Hainan Island, China

    PubMed Central

    Wang, Shan-Qing; Wang, Guang-Ze; Li, Yu-Chun; Meng, Feng; Lin, Shi-Gan; Zhu, Zhen-Hu; Sun, Ding-Wei; He, Chang-Hua; Hu, Xi-Min; Du, Jian-Wei

    2015-01-01

    Pyronaridine and artesunate have been shown to be effective in falciparum malaria treatment. However, pyronaridine is rarely used in Hainan Island clinically, and artesunate is not widely used as a therapeutic agent. Instead, conventional antimalarial drugs, chloroquine and piperaquine, are used, explaining the emergence of chloroquine-resistant Plasmodium falciparum. In this article, we investigated the sensitivity of P. falciparum to antimalarial drugs used in Hainan Island for rational drug therapy. We performed in vivo (28 days) and in vitro tests to determine the sensitivity of P. falciparum to antimalarial drugs. Total 46 patients with falciparum malaria were treated with dihydroartemisinin/piperaquine phosphate (DUO-COTECXIN) and followed up for 28 day. The cure rate was 97.8%. The mean fever clearance time (22.5±10.6 hr) and the mean parasite clearance time (27.3±12.2 hr) showed no statistical significance with different genders, ages, temperatures, or parasite density (P>0.05). The resistance rates of chloroquine, piperaquine, pyronarididine, and artesunate detected in vitro were 71.9%, 40.6%, 12.5%, and 0%, respectively (P<0.0001). The resistance intensities decreased as follows: chloroquine>piperaquine>pyronarididine>artesunate. The inhibitory dose 50 (IC50) was 3.77×10-6 mol/L, 2.09×10-6 mol/L, 0.09×10-6 mol/L, and 0.05×10-6 mol/L, and the mean concentrations for complete inhibition (CIMC) of schizont formation were 5.60×10-6 mol/L, 9.26×10-6 mol/L, 0.55×10-6 mol/L, and 0.07×10-6 mol/L, respectively. Dihydroartemisinin showed a strong therapeutic effect against falciparum malaria with a low toxicity. PMID:25748707

  9. Short Report: Detection of the Dihydrofolate Reductase–164L Mutation in Plasmodium falciparum Infections from Malawi by Heteroduplex Tracking Assay

    PubMed Central

    Juliano, Jonathan J.; Trottman, Paul; Mwapasa, Victor; Meshnick, Steven R.

    2008-01-01

    Standard polymerase chain reaction methods often cannot detect drug-resistance mutations in Plasmodium falciparum infections if the mutation is present in ≤ 20% of the parasites. A heteroduplex tracking assay was developed that can detect dihydrofolate reductase 164-L mutations in variants representing 1% of the parasites in an individual host. Using this assay, we confirmed the presence of the mutation in P. falciparum infections in Malawi. PMID:18541765

  10. Adverse Pregnancy Outcomes in an Area Where Multidrug-Resistant Plasmodium vivax and Plasmodium falciparum Infections Are Endemic

    PubMed Central

    Poespoprodjo, Jeanne Rini; Fobia, Wendy; Kenangalem, Enny; Lampah, Daniel A.; Warikar, Noah; Seal, Andrew; McGready, Rose; Sugiarto, Paulus; Tjitra, Emiliana; Anstey, Nicholas M.; Price, Ric N.

    2009-01-01

    Background Plasmodium falciparum infection exerts a considerable burden on pregnant women, but less is known about the adverse consequences of Plasmodium vivax infection. Methods In Papua, Indonesia, where multiple drug resistance to both species has emerged, we conducted a cross-sectional hospital-based study to quantify the risks and consequences of maternal malaria. Results From April 2004 through December 2006, 3046 pregnant women were enrolled in the study. The prevalence of parasitemia at delivery was 16.8% (432 of 2570 women had infections), with 152 (35.2%) of these 432 infections being associated with fever. The majority of infections were attributable to P. falciparum (250 [57.9%]); 146 (33.8%) of the infections were attributable to P. vivax, and 36 (8.3%) were coinfections with both species. At delivery, P. falciparum infection was associated with severe anemia (hemoglobin concentration, <7 g/dL; odds ratio [OR], 2.8; 95% confidence interval [95% CI], 2.0–4.0) and a 192 g (95% CI, 119–265) reduction in mean birth weight (P < .001). P. vivax infection was associated with an increased risk of moderate anemia (hemoglobin concentration, 7–11 g/dL; OR, 1.8; 95% CI, 1.2–2.9; P = .01) and a 108 g (95% CI, 17.5–199) reduction in mean birth weight (P < .019). Parasitemia was associated with preterm delivery (OR, 1.5; 95% CI, 1.1–2.0; P = .02) and stillbirth (OR, 2.3; 95% CI, 1.3–4.1; P = .007) but was not associated with these outcomes after controlling for the presence of fever and severe anemia, suggesting that malaria increases the risk of preterm delivery and stillbirth through fever and contribution to severe anemia rather than through parasitemia per se. Conclusions These observations highlight the need for novel, safe, and effective treatment and prevention strategies against both multidrug-resistant P. falciparum and multidrug-resistant P. vivax infections in pregnant women in areas of mixed endemicity. PMID:18419439