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Interactome mapping in malaria parasites: Challenges and opportunities.

CiteULike malaria tags - 16 February 2017 - 2:22pm
Methods Mol. Biol., Vol. 812 (2012), pp. 121-145, doi:10.1007/978-1-61779-455-1_7

Nearly two-thirds of the proteins encoded by Plasmodium falciparum, the parasite that causes the most deadly form of malaria, are annotated as "hypothetical." The yeast two-hybrid assay, which requires no prior knowledge about the target protein, has great potential to provide functional information about these uncharacterized proteins. However, P. falciparum yeast two-hybrid screens are hampered by the poor expression of P. falciparum genes in yeast. AU-rich sequences in nascent P. falciparum transcripts resemble the 3' end processing sites in yeast mRNAs, and are prematurely cleaved and polyadenylated. In most cases, these aberrant messages are degraded and yield no protein. To overcome this limitation, we have developed methods to extensively fragment P. falciparum genes. Novel yeast two-hybrid vectors, in which auxotrophic markers are fused to the 3' ends of the cloned inserts, are employed to identify those gene fragments that are expressed in yeast. In this chapter, we provide detailed protocols for fragmenting P. falciparum genes, creating P. falciparum activation domain libraries, and performing P. falciparum yeast two-hybrid screens. Though focused on P. falciparum, the approaches described here are applicable to other organisms and are likely to be especially useful for those with AT-rich genomes, which are also likely to be poorly expressed in yeast.
DJ LaCount
Categories: malaria news feeds

A comprehensive Plasmodium falciparum protein interaction map reveals a distinct architecture of a core interactome.

CiteULike malaria tags - 16 February 2017 - 2:22pm
Proteomics, Vol. 9, No. 7. (2009), pp. 1841-1849, doi:10.1002/pmic.200800383

We derive a map of protein interactions in the parasite Plasmodium falciparum from conserved interactions in Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, and Escherichia coli and pool them with experimental interaction data. The application of a clique-percolation algorithm allows us to find overlapping clusters, strongly correlated with yeast specific conserved protein complexes. Such clusters contain core activities that govern gene expression, largely dominated by components of protein production and degradation processes as well as RNA metabolism. A critical role of protein hubs in the interactome of P. falciparum is supported by their appearance in multiple clusters and the tendencies of their interactions to reach into many distinct protein clusters. Parasite proteins with a human ortholog tend to appear in single complexes. Annotating each protein with the stage where it is maximally expressed we observe a high level of cluster integrity in the ring stage. While we find no signal in the trophozoite phase, expression patterns are reversed in the schizont phase, implying a preponderance of parasite specific functions in this late, invasive schizont stage. As such, the inference of potential protein interactions and their analysis contributes to our understanding of the parasite, indicating basic pathways and processes as unique targets for therapeutic intervention.
S Wuchty, JH Adams, MT Ferdig
Categories: malaria news feeds

Proteomic and genetic analyses demonstrate that Plasmodium berghei blood stages export a large and diverse repertoire of proteins.

CiteULike malaria tags - 16 February 2017 - 2:22pm
Mol. Cell Proteomics, Vol. 12, No. 2. (2013), pp. 426-448, doi:10.1074/mcp.M112.021238

Malaria parasites actively remodel the infected red blood cell (irbc) by exporting proteins into the host cell cytoplasm. The human parasite Plasmodium falciparum exports particularly large numbers of proteins, including proteins that establish a vesicular network allowing the trafficking of proteins onto the surface of irbcs that are responsible for tissue sequestration. Like P. falciparum, the rodent parasite P. berghei ANKA sequesters via irbc interactions with the host receptor CD36. We have applied proteomic, genomic, and reverse-genetic approaches to identify P. berghei proteins potentially involved in the transport of proteins to the irbc surface. A comparative proteomics analysis of P. berghei non-sequestering and sequestering parasites was used to determine changes in the irbc membrane associated with sequestration. Subsequent tagging experiments identified 13 proteins (Plasmodium export element (PEXEL)-positive as well as PEXEL-negative) that are exported into the irbc cytoplasm and have distinct localization patterns: a dispersed and/or patchy distribution, a punctate vesicle-like pattern in the cytoplasm, or a distinct location at the irbc membrane. Members of the PEXEL-negative BIR and PEXEL-positive Pb-fam-3 show a dispersed localization in the irbc cytoplasm, but not at the irbc surface. Two of the identified exported proteins are transported to the irbc membrane and were named erythrocyte membrane associated proteins. EMAP1 is a member of the PEXEL-negative Pb-fam-1 family, and EMAP2 is a PEXEL-positive protein encoded by a single copy gene; neither protein plays a direct role in sequestration. Our observations clearly indicate that P. berghei traffics a diverse range of proteins to different cellular locations via mechanisms that are analogous to those employed by P. falciparum. This information can be exploited to generate transgenic humanized rodent P. berghei parasites expressing chimeric P. berghei/P. falciparum proteins on the surface of rodent irbc, thereby opening new avenues for in vivo screening adjunct therapies that block sequestration.
EM Pasini, JA Braks, J Fonager, O Klop, E Aime, R Spaccapelo, TD Otto, M Berriman, JA Hiss, AW Thomas, M Mann, CJ Janse, CHM Kocken, B Franke-Fayard
Categories: malaria news feeds

Cell biology and immunology of malaria.

CiteULike malaria tags - 16 February 2017 - 2:22pm
Immunol. Rev., Vol. 240, No. 1. (2011), pp. 297-316, doi:10.1111/j.1600-065X.2010.00988.x

Malaria is a vector-borne infectious disease caused by unicellular parasites of the genus Plasmodium. These obligate intracellular parasites have the unique capacity to infect and replicate within erythrocytes, which are terminally differentiated host cells that lack antigen presentation pathways. Prior to the cyclic erythrocytic infections that cause the characteristic clinical symptoms of malaria, the parasite undergoes an essential and clinically silent expansion phase in the liver. By infecting privileged host cells, employing programs of complex life stage conversions and expressing varying immunodominant antigens, Plasmodium parasites have evolved mechanisms to downmodulate protective immune responses against ongoing and even future infections. Consequently, anti-malaria immunity develops only gradually over many years of repeated and multiple infections in endemic areas. The identification of immune correlates of protection among the abundant non-protective host responses remains a research priority. Understanding the molecular and immunological mechanisms of the crosstalk between the parasite and the host is a prerequisite for the rational discovery and development of a safe, affordable, and protective anti-malaria vaccine.
JC Hafalla, O Silvie, K Matuschewski
Categories: malaria news feeds

Phylogenomic analyses of malaria parasites and evolution of their exported proteins.

CiteULike malaria tags - 16 February 2017 - 2:22pm
BMC Evol. Biol., Vol. 11 (2011), doi:10.1186/1471-2148-11-167

Our phylogenomic analyses strongly support the hypotheses that the Laverania have been founded by a single Plasmodium species switching from birds to African great apes or vice versa. The deviations from the canonical PEXEL motif in orthologs may explain the comparably low number of exported proteins that have been predicted in non-Laverania.
C Pick, I Ebersberger, T Spielmann, I Bruchhaus, T Burmester
Categories: malaria news feeds

Uncovering common principles in protein export of malaria parasites.

CiteULike malaria tags - 16 February 2017 - 2:22pm
Cell Host Microbe, Vol. 12, No. 5. (2012), pp. 717-729, doi:10.1016/j.chom.2012.09.010

For proliferation, the malaria parasite Plasmodium falciparum needs to modify the infected host cell extensively. To achieve this, the parasite exports proteins containing a Plasmodium export element (PEXEL) into the host cell. Phosphatidylinositol-3-phosphate binding and cleavage of the PEXEL are thought to mediate protein export. We show that these requirements can be bypassed, exposing a second level of export control in the N terminus generated after PEXEL cleavage that is sufficient to distinguish exported from nonexported proteins. Furthermore, this region also corresponds to the export domain of a second group of exported proteins lacking PEXELs (PNEPs), indicating shared export properties among different exported parasite proteins. Concordantly, export of both PNEPs and PEXEL proteins depends on unfolding, revealing translocation as a common step in export. However, translocation of transmembrane proteins occurs at the parasite plasma membrane, one step before translocation of soluble proteins, indicating unexpectedly complex translocation events at the parasite periphery.
C Grüring, A Heiber, F Kruse, S Flemming, G Franci, SF Colombo, E Fasana, H Schoeler, N Borgese, HG Stunnenberg, JM Przyborski, TW Gilberger, T Spielmann
Categories: malaria news feeds

Thioredoxin and glutathione systems in Plasmodium falciparum.

CiteULike malaria tags - 16 February 2017 - 2:22pm
Int. J. Med. Microbiol., Vol. 302, No. 4膒5. (2012), pp. 187-194, doi:10.1016/j.ijmm.2012.07.007

Despite a 50% decrease in malaria infections between 2000 and 2010, malaria is still one of the three leading infectious diseases with an estimated 216 million cases worldwide in 2010. More than 90% of all malaria infections were caused by Plasmodium falciparum, a unicellular eukaryotic parasite that faces oxidative stress challenges while developing in Anopheles mosquitoes and humans. Reactive oxygen and nitrogen species threatening the parasite are either endogenously produced by heme derived from hemoglobin degradation or they are from exogenous sources such as the host immune defense. In order to maintain the intracellular redox balance, P. falciparum employs a complex thioredoxin and glutathione system based on the thioredoxin reductase/thioredoxin and glutathione reductase/glutathione couples. P. falciparum thioredoxin reductase reduces thioredoxin and a range of low molecular weight compounds, while glutathione reductase is highly specific for its substrate glutathione disulfide. Since Plasmodium spp. lack catalase and a classical glutathione peroxidase, their redox balance depends on a complex set of five peroxiredoxins differentially located in the cytosol, apicoplast, mitochondria, and nucleus with partially overlapping substrate preferences. Moreover, P. falciparum employs a set of members belonging to the thioredoxin superfamily such as three thioredoxins, two thioredoxin-like proteins, a dithiol and three monocysteine glutaredoxins, and a redox-active plasmoredoxin with largely redundant functions. This review aims at summarizing our current knowledge on the functional redox networks of the malaria parasite P. falciparum.
E Jortzik, K Becker
Categories: malaria news feeds

Wherever I may roam: Protein and membrane trafficking in P. Falciparum-infected red blood cells.

CiteULike malaria tags - 16 February 2017 - 2:22pm
Mol. Biochem. Parasitol., Vol. 186, No. 2. (2012), pp. 95-116, doi:10.1016/j.molbiopara.2012.09.007

Quite aside from its immense importance as a human pathogen, studies in recent years have brought to light the fact that the malaria parasite Plasmodium falciparum is an interesting eukaryotic model system to study protein trafficking. Studying parasite cell biology often reveals an overrepresentation of atypical cell biological features, possibly driven by the parasites' need to survive in an unusual biological niche. Malaria parasites possess uncommon cellular compartments to which protein traffic must be directed, including secretory organelles such as rhoptries and micronemes, a lysosome-like compartment referred to as the digestive vacuole and a complex (four membrane-bound) plastid, the apicoplast. In addition, the parasite must provide proteins to extracellular compartments and structures including the parasitophorous vacuole, the parasitophorous vacuolar membrane, the Maurer's clefts and both cytosol and plasma membrane of the host cell, the mature human red blood cell. Although some of these unusual destinations are possessed by other cell types, only Plasmodium parasites contain them all within one cell. Here we review what is known about protein and membrane transport in the P. falciparum-infected cell, highlighting novel features of these processes. A growing body of evidence suggests that this parasite is a real "box of tricks" with regards to protein traffic. Possibly, these tricks may be turned against the parasite by exploiting them as novel therapeutic targets.
M Deponte, HC Hoppe, MCS Lee, AG Maier, D Richard, M Rug, T Spielmann, JM Przyborski
Categories: malaria news feeds

A protein interaction network of the malaria parasite Plasmodium falciparum.

CiteULike malaria tags - 16 February 2017 - 2:22pm
Nature, Vol. 438, No. 7064. (2005), pp. 103-107, doi:10.1038/nature04104

Plasmodium falciparum causes the most severe form of malaria and kills up to 2.7 million people annually. Despite the global importance of P. falciparum, the vast majority of its proteins have not been characterized experimentally. Here we identify P. falciparum protein-protein interactions using a high-throughput version of the yeast two-hybrid assay that circumvents the difficulties in expressing P. falciparum proteins in Saccharomyces cerevisiae. From more than 32,000 yeast two-hybrid screens with P. falciparum protein fragments, we identified 2,846 unique interactions, most of which include at least one previously uncharacterized protein. Informatic analyses of network connectivity, coexpression of the genes encoding interacting fragments, and enrichment of specific protein domains or Gene Ontology annotations were used to identify groups of interacting proteins, including one implicated in chromatin modification, transcription, messenger RNA stability and ubiquitination, and another implicated in the invasion of host cells. These data constitute the first extensive description of the protein interaction network for this important human pathogen.
DJ LaCount, M Vignali, R Chettier, A Phansalkar, R Bell, JR Hesselberth, LW Schoenfeld, I Ota, S Sahasrabudhe, C Kurschner, S Fields, RE Hughes
Categories: malaria news feeds

Characterization of the ubiquitylating components of the human malaria parasite's protein degradation pathway.

CiteULike malaria tags - 16 February 2017 - 2:22pm
PLoS ONE, Vol. 7, No. 8. (2012), doi:10.1371/journal.pone.0043477

Ubiquitin-dependent protein degradation within malarial parasites is a burgeoning field of interest due to several encouraging reports of proteasome inhibitors that were able to confer antimalarial activity. Despite the growing interest in the Plasmodium proteasome system, relatively little investigation has been done to actually characterize the parasite degradation machinery. In this report, we provide an initial biological investigation of the ubiquitylating components of the endoplasmic reticulum-associated degradation (ERAD) system, which is a major pathway in targeting misfolded proteins from the ER to the cytosol for proteasome degradation. We are able to show that the ERAD system is essential for parasite survival and that the putative Plasmodium HRD1 (E3 ubiquitin ligase), UBC (E2 ubiquitin conjugating enzyme) and UBA1 (E1 ubiquitin activating enzyme) are able to mediate in vitro ubiquitylation. Furthermore, by using immunofluorescence, we report that Plasmodium HRD1 localizes to the ER membranes, while the Plasmodium UBC and UBA1 localize to the cytosol. In addition, our gene disruption experiments indicate that the Plasmodium HRD1 is likely essential. We have conducted an initial characterization of the ubiquitylating components of the Plasmodium ERAD system, a major pathway for protein degradation and parasite maintenance. In conjunction with promising proteasome inhibitor studies, we explore the possibility of targeting the Plasmodium ERAD system for future bottom-up drug development approaches.
Chung, N Ponts, J Prudhomme, EM Rodrigues, Le Roch
Categories: malaria news feeds

Unraveling the ubiquitome of the human malaria parasite.

CiteULike malaria tags - 16 February 2017 - 2:22pm
Journal of Biological Chemistry, Vol. 286, No. 46. (2011), pp. 40320-40330, doi:10.1074/jbc.M111.238790

Malaria is one of the deadliest infectious diseases worldwide. The most severe form is caused by the eukaryotic protozoan parasite Plasmodium falciparum. Recent studies have highlighted the importance of post-translational regulations for the parasite's progression throughout its life cycle, protein ubiquitylation being certainly one of the most abundant. The specificity of its components and the wide range of biological processes in which it is involved make the ubiquitylation pathway a promising source of suitable targets for anti-malarial drug development. Here, we combined immunofluorescent microscopy, biochemical assays, in silico prediction, and mass spectrometry analysis using the multidimensional protein identification technology, or MudPIT, to describe the P. falciparum ubiquitome. We found that ubiquitin conjugates are detected at every morphological stage of the parasite erythrocytic cycle. Furthermore, we detected that more than half of the parasite's proteome represents possible targets for ubiquitylation, especially proteins found to be present at the most replicative stage of the asexual cycle, the trophozoite stage. A large proportion of ubiquitin conjugates were also detected at the schizont stage, consistent with a cell activity slowdown to prepare for merozoite differentiation and invasion. Finally, for the first time in the human malaria parasite, our results strongly indicate the presence of heterologous mixed conjugations, SUMO/UB. This discovery suggests that sumoylated proteins may be regulated by ubiquitylation in P. falciparum. Altogether, our results present the first stepping stone toward a better understanding of ubiquitylation and its role(s) in the biology of the human malaria parasite.
N Ponts, A Saraf, Chung, A Harris, J Prudhomme, MP Washburn, L Florens, Le Roch
Categories: malaria news feeds

A scalable pipeline for highly effective genetic modification of a malaria parasite.

CiteULike malaria tags - 16 February 2017 - 2:22pm
Nat. Methods, Vol. 8, No. 12. (2011), pp. 1078-1082, doi:10.1038/nmeth.1742

In malaria parasites, the systematic experimental validation of drug and vaccine targets by reverse genetics is constrained by the inefficiency of homologous recombination and by the difficulty of manipulating adenine and thymine (A+T)-rich DNA of most Plasmodium species in Escherichia coli. We overcame these roadblocks by creating a high-integrity library of Plasmodium berghei genomic DNA (>77% A+T content) in a bacteriophage N15-based vector that can be modified efficiently using the lambda Red method of recombineering. We built a pipeline for generating P. berghei genetic modification vectors at genome scale in serial liquid cultures on 96-well plates. Vectors have long homology arms, which increase recombination frequency up to tenfold over conventional designs. The feasibility of efficient genetic modification at scale will stimulate collaborative, genome-wide knockout and tagging programs for P. berghei.
C Pfander, B Anar, F Schwach, TD Otto, M Brochet, K Volkmann, MA Quail, A Pain, B Rosen, W Skarnes, JC Rayner, O Billker
Categories: malaria news feeds

Multiple populations of artemisinin-resistant Plasmodium falciparum in Cambodia.

CiteULike malaria tags - 16 February 2017 - 2:22pm
Nat. Genet., Vol. 45, No. 6. (2013), pp. 648-655, doi:10.1038/ng.2624

We describe an analysis of genome variation in 825 P. falciparum samples from Asia and Africa that identifies an unusual pattern of parasite population structure at the epicenter of artemisinin resistance in western Cambodia. Within this relatively small geographic 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 high levels of haplotype homozygosity, indicative of founder effects and recent population expansion. We provide a catalog of SNPs that show high levels of differentiation in the artemisinin-resistant subpopulations, including codon variants in transporter proteins and DNA mismatch repair proteins. These data provide a population-level genetic framework for investigating the biological origins of artemisinin resistance and for defining molecular markers to assist in its elimination.
O Miotto, J Almagro-Garcia, M Manske, B Macinnis, S Campino, KA Rockett, C Amaratunga, P Lim, S Suon, S Sreng, JM Anderson, S Duong, C Nguon, CM Chuor, D Saunders, Y Se, C Lon, MM Fukuda, L Amenga-Etego, AVO Hodgson, V Asoala, M Imwong, S Takala-Harrison, F Nosten, XZ Su, P Ringwald, F Ariey, C Dolecek, TT Hien, MF Boni, CQ Thai, A Amambua-Ngwa, DJ Conway, AA Djimdé, OK Doumbo, I Zongo, JB Ouedraogo, D Alcock, E Drury, S Auburn, O Koch, M Sanders, C Hubbart, G Maslen, V Ruano-Rubio, D Jyothi, A Miles, J O'Brien, C Gamble, SO Oyola, JC Rayner, CI Newbold, M Berriman, CCA Spencer, G McVean, NP Day, NJ White, D Bethell, AM Dondorp, CV Plowe, RM Fairhurst, DP Kwiatkowski
Categories: malaria news feeds

Analysis of protein palmitoylation reveals a pervasive role in Plasmodium development and pathogenesis.

CiteULike malaria tags - 16 February 2017 - 2:22pm
Cell Host Microbe, Vol. 12, No. 2. (2012), pp. 246-258, doi:10.1016/j.chom.2012.06.005

Asexual stage Plasmodium falciparum replicates and undergoes a tightly regulated developmental process in human erythrocytes. One mechanism involved in the regulation of this process is posttranslational modification (PTM) of parasite proteins. Palmitoylation is a PTM in which cysteine residues undergo a reversible lipid modification, which can regulate target proteins in diverse ways. Using complementary palmitoyl protein purification approaches and quantitative mass spectrometry, we examined protein palmitoylation in asexual-stage P. falciparum parasites and identified over 400 palmitoylated proteins, including those involved in cytoadherence, drug resistance, signaling, development, and invasion. Consistent with the prevalence of palmitoylated proteins, palmitoylation is essential for P. falciparum asexual development and influences erythrocyte invasion by directly regulating the stability of components of the actin-myosin invasion motor. Furthermore, P. falciparum uses palmitoylation in diverse ways, stably modifying some proteins while dynamically palmitoylating others. Palmitoylation therefore plays a central role in regulating P. falciparum blood stage development.
ML Jones, MO Collins, D Goulding, JS Choudhary, JC Rayner
Categories: malaria news feeds

An evolutionary perspective on the kinome of malaria parasites.

CiteULike malaria tags - 16 February 2017 - 2:22pm
Philos. Trans. R. Soc. Lond., B, Biol. Sci., Vol. 367, No. 1602. (2012), pp. 2607-2618, doi:10.1098/rstb.2012.0014

Malaria parasites belong to an ancient lineage that diverged very early from the main branch of eukaryotes. The approximately 90-member plasmodial kinome includes a majority of eukaryotic protein kinases that clearly cluster within the AGC, CMGC, TKL, CaMK and CK1 groups found in yeast, plants and mammals, testifying to the ancient ancestry of these families. However, several hundred millions years of independent evolution, and the specific pressures brought about by first a photosynthetic and then a parasitic lifestyle, led to the emergence of unique features in the plasmodial kinome. These include taxon-restricted kinase families, and unique peculiarities of individual enzymes even when they have homologues in other eukaryotes. Here, we merge essential aspects of all three malaria-related communications that were presented at the Evolution of Protein Phosphorylation meeting, and propose an integrated discussion of the specific features of the parasite's kinome and phosphoproteome.
E Talevich, AB Tobin, N Kannan, C Doerig
Categories: malaria news feeds

Global kinomic and phospho-proteomic analyses of the human malaria parasite Plasmodium falciparum.

CiteULike malaria tags - 16 February 2017 - 2:22pm
Nat Commun, Vol. 2 (2011), doi:10.1038/ncomms1558

The role of protein phosphorylation in the life cycle of malaria parasites is slowly emerging. Here we combine global phospho-proteomic analysis with kinome-wide reverse genetics to assess the importance of protein phosphorylation in Plasmodium falciparum asexual proliferation. We identify 1177 phosphorylation sites on 650 parasite proteins that are involved in a wide range of general cellular activities such as DNA synthesis, transcription and metabolism as well as key parasite processes such as invasion and cyto-adherence. Several parasite protein kinases are themselves phosphorylated on putative regulatory residues, including tyrosines in the activation loop of PfGSK3 and PfCLK3; we show that phosphorylation of PfCLK3 Y526 is essential for full kinase activity. A kinome-wide reverse genetics strategy identified 36 parasite kinases as likely essential for erythrocytic schizogony. These studies not only reveal processes that are regulated by protein phosphorylation, but also define potential anti-malarial drug targets within the parasite kinome.
L Solyakov, J Halbert, MM Alam, JP Semblat, D Dorin-Semblat, L Reininger, AR Bottrill, S Mistry, A Abdi, C Fennell, Z Holland, C Demarta, Y Bouza, A Sicard, MP Nivez, S Eschenlauer, T Lama, DC Thomas, P Sharma, S Agarwal, S Kern, G Pradel, M Graciotti, AB Tobin, C Doerig
Categories: malaria news feeds

Finding the needle in the haystack

CiteULike malaria tags - 16 February 2017 - 1:14pm
Nature Reviews Microbiology, Vol. 15, No. 3. (13 February 2017), pp. 136-136, doi:10.1038/nrmicro.2017.7

This month's Genome Watch discusses the potential of selective whole-genome amplification for overcoming the challenges of whole-genome sequencing of malaria parasites in clinical samples in which they are low in abundance.
Gavin Rutledge, Cristina Ariani
Categories: malaria news feeds

P113 is a merozoite surface protein that binds the N terminus of Plasmodium falciparum RH5

CiteULike malaria tags - 16 February 2017 - 11:36am
Nature Communications, Vol. 8 (10 February 2017), 14333, doi:10.1038/ncomms14333
Francis Galaway, Laura Drought, Maria Fala, Nadia Cross, Alison Kemp, Julian Rayner, Gavin Wright
Categories: malaria news feeds

Phenoplasm: a database of disruption phenotypes for malaria parasite genes

CiteULike malaria tags - 9 February 2017 - 1:21pm
bioRxiv (02 February 2017), 101717, doi:10.1101/101717

bioRxiv - the preprint server for biology, operated by Cold Spring Harbor Laboratory, a research and educational institution
Theo Sanderson, Julian Rayner
Categories: malaria news feeds

The spread of artemisinin-resistant Plasmodium falciparum in the Greater Mekong Subregion: a molecular epidemiology observational study

CiteULike malaria tags - 9 February 2017 - 11:36am
The Lancet Infectious Diseases (February 2017), doi:10.1016/s1473-3099(17)30048-8

Evidence suggests that the PfKelch13 mutations that confer artemisinin resistance in falciparum malaria have multiple independent origins across the Greater Mekong subregion, which has motivated a regional malaria elimination agenda. We aimed to use molecular genotyping to assess antimalarial drug resistance selection and spread in the Greater Mekong subregion. In this observational study, we tested Plasmodium falciparum isolates from Myanmar, northeastern Thailand, southern Laos, and western Cambodia for PfKelch13 mutations and for Pfplasmepsin2 gene amplification (indicating piperaquine resistance). We collected blood spots from patients with microscopy or rapid test confirmed uncomplicated falciparum malaria. We used microsatellite genotyping to assess genetic relatedness. As part of studies on the epidemiology of artemisinin-resistant malaria between Jan 1, 2008, and Dec 31, 2015, we collected 434 isolates. In 2014–15, a single long PfKelch13 C580Y haplotype (−50 to +31·5 kb) lineage, which emerged in western Cambodia in 2008, was detected in 65 of 88 isolates from northeastern Thailand, 86 of 111 isolates from southern Laos, and 14 of 14 isolates from western Cambodia, signifying a hard transnational selective sweep. Pfplasmepsin2 amplification occurred only within this lineage, and by 2015 these closely related parasites were found in ten of the 14 isolates from Cambodia and 15 of 15 isolates from northeastern Thailand. C580Y mutated parasites from Myanmar had a different genetic origin. Our results suggest that the dominant artemisinin-resistant P falciparum C580Y lineage probably arose in western Cambodia and then spread to Thailand and Laos, outcompeting other parasites and acquiring piperaquine resistance. The emergence and spread of fit artemisinin-resistant P falciparum parasite lineages, which then acquire partner drug resistance across the Greater Mekong subregion, threatens regional malaria control and elimination goals. Elimination of falciparum malaria from this region should be accelerated while available antimalarial drugs still remain effective. The Wellcome Trust and the Bill and Melinda Gates Foundation.
Mallika Imwong, Kanokon Suwannasin, Chanon Kunasol, Kreepol Sutawong, Mayfong Mayxay, Huy Rekol, Frank Smithuis, Tin Hlaing, Kyaw Tun, Rob van der Pluijm, Rupam Tripura, Olivo Miotto, Didier Menard, Mehul Dhorda, Nicholas Day, Nicholas White, Arjen Dondorp
Categories: malaria news feeds