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Variant Exported Blood-Stage Proteins Encoded by Plasmodium Multigene Families Are Expressed in Liver Stages Where They Are Exported into the Parasitophorous Vacuole

CiteULike malaria tags - 17 November 2016 - 11:30am
PLOS Pathogens, Vol. 12, No. 11. (16 November 2016), e1005917, doi:10.1371/journal.ppat.1005917

Author Summary Malaria-parasites invade and multiply in hepatocytes and erythrocytes. The human parasite P. falciparum transports proteins encoded by multigene families onto the surface of erythrocytes, mediating interactions between infected red blood cells (iRBCs) and other host-cells and are thought to play a key role in parasite survival during blood-stage development. The function of other exported Plasmodium protein families remains largely unknown. We provide novel insights into expression and cellular location of proteins encoded by three large multigene families of rodent malaria parasites (Fam-a, Fam-b and PIR). Multiple members of the same family are expressed in a single iRBC, unlike P. falciparum PfEMP1 proteins where individual iRBCs express only a single member. Most proteins we examined are located in the RBC cytoplasm and are not transported onto the iRBC surface membrane, indicating that these proteins are unlikely to mediate interactions between iRBCs and host-cells. Unexpectedly, liver stages also express many of these proteins, where they locate to the vacuole surrounding the parasite inside the hepatocyte. In support of a role of these proteins for parasite growth within their host cells we provide evidence that Fam-A proteins have a role in uptake and transport of (host) phosphatidylcholine for parasite-membrane synthesis.
Aurélie Fougère, Andrew Jackson, Dafni Paraskevi Bechtsi, Joanna Braks, Takeshi Annoura, Jannik Fonager, Roberta Spaccapelo, Jai Ramesar, Séverine Chevalley-Maurel, Onny Klop, Annelies van der Laan, Hans Tanke, Clemens Kocken, Erica Pasini, Shahid Khan, Ulrike Böhme, Christiaan van Ooij, Thomas Otto, Chris Janse, Blandine Franke-Fayard
Categories: malaria news feeds

Molecular mechanisms of host cell traversal by malaria sporozoites

CiteULike malaria tags - 12 November 2016 - 1:23pm
International Journal for Parasitology (November 2016), doi:10.1016/j.ijpara.2016.09.002

Malaria sporozoites traverse host cells to establish infection in the mammalian host. Sporozoite traversal of host cells can involve transient vacuoles. Parasite escape from transient vacuoles requires perforin-like protein 1 (PLP1). The formation and nature of the sporozoite-host cell tight junction is unknown. The molecular step-wise events of cell traversal are largely unknown and require further research. Malaria is a pernicious infectious disease caused by apicomplexan parasites of the genus Plasmodium. Each year, malaria afflicts over 200 million people, causing considerable morbidity, loss to gross domestic product of endemic countries, and more than 420,000 deaths. A central feature of the virulence of malaria parasites is the ability of sporozoite forms injected by a mosquito to navigate from the inoculation site in the skin through host tissues to infect the liver. The ability for sporozoites to traverse through different host cell types is very important for the successful development of parasites within the mammalian host. Over the past decade, our understanding of the role of host cell traversal has become clearer through important studies with rodent models of malaria. However, we still do not understand the stepwise process of host cell entry and exit or know the molecular mechanisms governing each step. We know even less about cell traversal by malaria parasite species that infect humans. Here, we review current knowledge regarding the role and molecular mechanisms of sporozoite cell traversal and highlight recent advances that prompt new ways of thinking about this important process.
Annie Yang, Justin Boddey
Categories: malaria news feeds

Analysis of anti-malarial resistance markers in pfmdr1 and pfcrt across Southeast Asia in the Tracking Resistance to Artemisinin Collaboration

CiteULike malaria tags - 10 November 2016 - 1:21pm
Malaria Journal, Vol. 15, No. 1. (8 November 2016), doi:10.1186/s12936-016-1598-6
Krongkan Srimuang, Olivo Miotto, Pharath Lim, Rick Fairhurst, Dominic Kwiatkowski, Charles Woodrow, Mallika Imwong
Categories: malaria news feeds

Genetic markers associated with dihydroartemisinin–piperaquine failure in Plasmodium falciparum malaria in Cambodia: a genotype–phenotype association study

CiteULike malaria tags - 10 November 2016 - 11:00am
The Lancet Infectious Diseases (November 2016), doi:10.1016/s1473-3099(16)30409-1
Roberto Amato, Pharath Lim, Olivo Miotto, Chanaki Amaratunga, Dalin Dek, Richard Pearson, Jacob Almagro-Garcia, Aaron Neal, Sokunthea Sreng, Seila Suon, Eleanor Drury, Dushyanth Jyothi, Jim Stalker, Dominic Kwiatkowski, Rick Fairhurst
Categories: malaria news feeds

Metabolomics-Based Screening of the Malaria Box Reveals both Novel and Established Mechanisms of Action

CiteULike malaria tags - 10 November 2016 - 10:38am
Antimicrobial Agents and Chemotherapy, Vol. 60, No. 11. (01 November 2016), pp. 6650-6663, doi:10.1128/aac.01226-16

High-throughput phenotypic screening of chemical libraries has resulted in the identification of thousands of compounds with potent antimalarial activity, although in most cases, the mechanism(s) of action of these compounds remains unknown. Here we have investigated the mode of action of 90 antimalarial compounds derived from the Malaria Box collection using high-coverage, untargeted metabolomics analysis. Approximately half of the tested compounds induced significant metabolic perturbations in in vitro cultures of Plasmodium falciparum. In most cases, the metabolic profiles were highly correlated with known antimalarials, in particular artemisinin, the 4-aminoquinolines, or atovaquone. Select Malaria Box compounds also induced changes in intermediates in essential metabolic pathways, such as isoprenoid biosynthesis (i.e., 2-C-methyl-d-erythritol 2,4-cyclodiphosphate) and linolenic acid metabolism (i.e., traumatic acid). This study provides a comprehensive database of the metabolic perturbations induced by chemically diverse inhibitors and highlights the utility of metabolomics for triaging new lead compounds and defining specific modes of action, which will assist with the development and optimization of new antimalarial drugs.
Darren Creek, Hwa Chua, Simon Cobbold, Brunda Nijagal, James MacRae, Benjamin Dickerman, Paul Gilson, Stuart Ralph, Malcolm McConville
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Metabolomic Profiling of the Malaria Box Reveals Antimalarial Target Pathways

CiteULike malaria tags - 10 November 2016 - 10:37am
Antimicrobial Agents and Chemotherapy, Vol. 60, No. 11. (01 November 2016), pp. 6635-6649, doi:10.1128/aac.01224-16

The threat of widespread drug resistance to frontline antimalarials has renewed the urgency for identifying inexpensive chemotherapeutic compounds that are effective against Plasmodium falciparum, the parasite species responsible for the greatest number of malaria-related deaths worldwide. To aid in the fight against malaria, a recent extensive screening campaign has generated thousands of lead compounds with low micromolar activity against blood stage parasites. A subset of these leads has been compiled by the Medicines for Malaria Venture (MMV) into a collection of structurally diverse compounds known as the MMV Malaria Box. Currently, little is known regarding the activity of these Malaria Box compounds on parasite metabolism during intraerythrocytic development, and a majority of the targets for these drugs have yet to be defined. Here we interrogated the in vitro metabolic effects of 189 drugs (including 169 of the drug-like compounds from the Malaria Box) using ultra-high-performance liquid chromatography–mass spectrometry (UHPLC-MS). The resulting metabolic fingerprints provide information on the parasite biochemical pathways affected by pharmacologic intervention and offer a critical blueprint for selecting and advancing lead compounds as next-generation antimalarial drugs. Our results reveal several major classes of metabolic disruption, which allow us to predict the mode of action (MoA) for many of the Malaria Box compounds. We anticipate that future combination therapies will be greatly informed by these results, allowing for the selection of appropriate drug combinations that simultaneously target multiple metabolic pathways, with the aim of eliminating malaria and forestalling the expansion of drug-resistant parasites in the field.
Erik Allman, Heather Painter, Jasmeet Samra, Manuela Carrasquilla, Manuel Llinás
Categories: malaria news feeds

Independent Origin and Global Distribution of Distinct Plasmodium vivax Duffy Binding Protein Gene Duplications

CiteULike malaria tags - 3 November 2016 - 12:02pm
PLoS Negl Trop Dis, Vol. 10, No. 10. (31 October 2016), e0005091, doi:10.1371/journal.pntd.0005091

Plasmodium vivax causes the majority of malaria episodes outside Africa, but remains a relatively understudied pathogen. The pathology of P. vivax infection depends critically on the parasite’s ability to recognize and invade human erythrocytes. This invasion process involves an interaction between P. vivax Duffy Binding Protein (PvDBP) in merozoites and the Duffy antigen receptor for chemokines (DARC) on the erythrocyte surface. Whole-genome sequencing of clinical isolates recently established that some P. vivax genomes contain two copies of the PvDBP gene. The frequency of this duplication is particularly high in Madagascar, where there is also evidence for P. vivax infection in DARC-negative individuals. The functional significance and global prevalence of this duplication, and whether there are other copy number variations at the PvDBP locus, is unknown. Using whole-genome sequencing and PCR to study the PvDBP locus in P. vivax clinical isolates, we found that PvDBP duplication is widespread in Cambodia. The boundaries of the Cambodian PvDBP duplication differ from those previously identified in Madagascar, meaning that current molecular assays were unable to detect it. The Cambodian PvDBP duplication did not associate with parasite density or DARC genotype, and ranged in prevalence from 20% to 38% over four annual transmission seasons in Cambodia. This duplication was also present in P. vivax isolates from Brazil and Ethiopia, but not India. PvDBP duplications are much more widespread and complex than previously thought, and at least two distinct duplications are circulating globally. The same duplication boundaries were identified in parasites from three continents, and were found at high prevalence in human populations where DARC-negativity is essentially absent. It is therefore unlikely that PvDBP duplication is associated with infection of DARC-negative individuals, but functional tests will be required to confirm this hypothesis. Malaria parasites must be adaptable to evade the human immune system and successfully transmit themselves to different individuals. Key to this adaptability is the fact that malaria parasite genomes are highly variable, containing mutations ranging from simple small changes in DNA sequence to complex large-scale changes in the number of copies of individual genes. Some samples of Plasmodium vivax, the parasite that causes most malaria episodes outside Africa, have recently been found to have duplicated the gene encoding Duffy Binding Protein, which enables P. vivax parasites to recognize and invade human red blood cells. By studying parasites from Cambodian patients with P. vivax malaria, we have discovered that there are actually two different types of gene duplication, with the new duplication type identified in this study present in 20% to 38% of Cambodian P. vivax isolates tested. The same gene duplication was also found in parasites from Brazilian and Ethiopian patients with P. vivax malaria, suggesting that variation in this gene is more complex and common than previously thought. The functional significance and origin of these two gene duplications requires further study.
Jessica Hostetler, Eugenia Lo, Usheer Kanjee, Chanaki Amaratunga, Seila Suon, Sokunthea Sreng, Sivanna Mao, Delenasaw Yewhalaw, Anjali Mascarenhas, Dominic Kwiatkowski, Marcelo Ferreira, Pradipsinh Rathod, Guiyun Yan, Rick Fairhurst, Manoj Duraisingh, Julian Rayner
Categories: malaria news feeds

A CRISPR outlook for apicomplexans

CiteULike malaria tags - 3 November 2016 - 11:10am
Nature Reviews Microbiology, Vol. 14, No. 11. (12 October 2016), pp. 668-668, doi:10.1038/nrmicro.2016.153
Manuela Carrasquilla, Christian Owusu
Categories: malaria news feeds

A structural variant encoding hybrid glycophorins is associated with resistance to severe malaria

CiteULike malaria tags - 27 October 2016 - 12:54pm
bioRxiv (26 October 2016), 083634, doi:10.1101/083634

bioRxiv - the preprint server for biology, operated by Cold Spring Harbor Laboratory, a research and educational institution
Ellen Leffler, Gavin Band, George Busby, Katja Kivinen, Quang Le, Geraldine Clarke, Kalifa Bojang, David Conway, Muminatou Jallow, Fatoumatta Sisay-Joof, Edith Bougouma, Valentina Mangano, David Modiano, Sodiomon Sirima, Eric Achidi, Tobias Apinjoh, Kevin Marsh, Carolyne Ndila, Norbert Peshu, Thomas Williams, Chris Drakeley, Alphaxard Manjurano, Hugh Reyburn, Eleanor Riley, David Kachala, Malcolm Molyneux, Vysaul Nyirongo, Terrie Taylor, Nicole Thornton, Louise Tilley, Shane Grimsley, Eleanor Drury, Jim Stalker, Victoria Cornelius, Christina Hubbart, Anna Jeffreys, Kate Rowlands, Kirk Rockett, Chris Spencer, Dominic Kwiatkowski, Malaria Genomic Epidemiology Network
Categories: malaria news feeds

Quantitative Seq-LGS: Genome-Wide Identification of Genetic Drivers of Multiple Phenotypes in Malaria Parasites

CiteULike malaria tags - 13 October 2016 - 11:59am
bioRxiv (30 September 2016), 078451, doi:10.1101/078451

bioRxiv - the preprint server for biology, operated by Cold Spring Harbor Laboratory, a research and educational institution
Hussein Abkallo, Axel Martinelli, Megumi Inoue, Abhinay Ramaprasad, Phonepadith Xangsayarath, Jesse Gitaka, Jianxia Tang, Kazuhide Yahata, Augustin Zoungrana, Hayato Mitaka, Paul Hunt, Richard Carter, Osamu Kaneko, Ville Mustonen, Christopher Illingworth, Arnab Pain, Richard Culleton
Categories: malaria news feeds

Genome-wide association analysis identifies genetic loci associated with resistance to multiple antimalarials in Plasmodium falciparum from China-Myanmar border

CiteULike malaria tags - 7 October 2016 - 11:11am
Scientific Reports, Vol. 6 (3 October 2016), 33891, doi:10.1038/srep33891
Zenglei Wang, Mynthia Cabrera, Jingyun Yang, Lili Yuan, Bhavna Gupta, Xiaoying Liang, Karen Kemirembe, Sony Shrestha, Awtum Brashear, Xiaolian Li, Stephen Porcella, Jun Miao, Zhaoqing Yang, Xin-zhuan Su, Liwang Cui
Categories: malaria news feeds

A computational lens for sexual-stage transmission, reproduction, fitness and kinetics in Plasmodium falciparum

CiteULike malaria tags - 29 September 2016 - 12:03pm
Malaria Journal, Vol. 15, No. 1. (21 September 2016), doi:10.1186/s12936-016-1538-5
Mara Lawniczak, Philip Eckhoff
Categories: malaria news feeds

Characterisation of Plasmodium invasive organelles; an ookinete microneme proteome

CiteULike malaria tags - 19 September 2016 - 1:32pm
Proteomics, Vol. 9, No. 5. (1 March 2009), pp. 1142-1151, doi:10.1002/pmic.200800404

Secretion of microneme proteins is essential to Plasmodium invasion but the molecular composition of these secretory organelles remains poorly defined. Here, we describe the first Plasmodium microneme proteome. Purification of micronemes by subcellular fractionation from cultured ookinetes was confirmed by enrichment of known micronemal proteins and electron microscopy. Quantitation of electron micrographs showed >14-fold microneme enrichment compared to the intact ookinete, such that micronemes comprised 85% of the identifiable organelles in the fraction. Gel LC-MS/MS of the most abundant protein constituents of the fraction identified three known micronemal proteins chitinase, CTRP, SOAP, together with protein disulphide isomerase (PDI) and HSP70. Highly sensitive MudPIT shotgun proteomics described a total of 345 proteins in the fraction. M1 aminopeptidase and PDI, the former a recognised target of drug development, were both shown to have a micronemal location by IFA. We further identified numerous proteins with established vesicle trafficking and signaling functions consistent with micronemes being part of a regulated secretory pathway. Previously uncharacterised proteins comprise the largest functional group of the microneme proteome and will include secreted proteins important to invasion.
Kalpana Lal, Judith Prieto, Elizabeth Bromley, Sanya Sanderson, John Yates, Jonathan Wastling, Fiona Tomley, Robert Sinden
Categories: malaria news feeds

Malaria research in the post-genomic era

CiteULike malaria tags - 19 September 2016 - 1:05pm
Nature, Vol. 455, No. 7214. (09 October 2008), pp. 751-756, doi:10.1038/nature07361

For many pathogens the availability of genome sequence, permitting genome-dependent methods of research, can partially substitute for powerful forward genetic methods (genome-independent) that have advanced model organism research for decades. In 2002 the genome sequence of Plasmodium falciparum, the parasite causing the most severe type of human malaria, was completed, eliminating many of the barriers to performing state-of-the-art molecular biological research on malaria parasites. Although new, licensed therapies may not yet have resulted from genome-dependent experiments, they have produced a wealth of new observations about the basic biology of malaria parasites, and it is likely that these will eventually lead to new therapeutic approaches. This review will focus on the basic research discoveries that have depended, in part, on the availability of the Plasmodium genome sequences.
Elizabeth Winzeler
Categories: malaria news feeds

Proteomic Profiling of Plasmodium Sporozoite Maturation Identifies New Proteins Essential for Parasite Development and Infectivity

CiteULike malaria tags - 19 September 2016 - 12:47pm
PLoS Pathog, Vol. 4, No. 10. (31 October 2008), e1000195, doi:10.1371/journal.ppat.1000195

Plasmodium falciparum sporozoites that develop and mature inside an Anopheles mosquito initiate a malaria infection in humans. Here we report the first proteomic comparison of different parasite stages from the mosquito—early and late oocysts containing midgut sporozoites, and the mature, infectious salivary gland sporozoites. Despite the morphological similarity between midgut and salivary gland sporozoites, their proteomes are markedly different, in agreement with their increase in hepatocyte infectivity. The different sporozoite proteomes contain a large number of stage specific proteins whose annotation suggest an involvement in sporozoite maturation, motility, infection of the human host and associated metabolic adjustments. Analyses of proteins identified in the P. falciparum sporozoite proteomes by orthologous gene disruption in the rodent malaria parasite, P. berghei, revealed three previously uncharacterized Plasmodium proteins that appear to be essential for sporozoite development at distinct points of maturation in the mosquito. This study sheds light on the development and maturation of the malaria parasite in an Anopheles mosquito and also identifies proteins that may be essential for sporozoite infectivity to humans. Human malaria is caused by Plasmodium falciparum, a unicellular protozoan parasite that is transmitted by Anopheles mosquitoes. An infectious mosquito injects saliva containing sporozoite forms of the parasite and these then migrate from the skin to the liver, where they establish an infection. Many intervention strategies are currently focused on preventing the establishment of infection by sporozoites. Clearly, an understanding of the biology of the sporozoite is essential for developing new intervention strategies. Sporozoites are produced within the oocyst, located on the outside wall of the mosquito midgut, and migrate after release from the oocysts to the salivary glands where they are stored as mature infectious forms. Comparison of the proteomes of sporozoites derived from either the oocyst or from the salivary gland reveals remarkable differences in the protein content of these stages despite their similar morphology. The changes in protein content reflect the very specific preparations the sporozoites make in order to establish an infection of the liver. Analysis of the function of several previously uncharacterized, conserved proteins revealed proteins essential for sporozoite development at distinct points of their maturation.
Edwin Lasonder, Chris Janse, Geert-Jan van Gemert, Gunnar Mair, Adriaan Vermunt, Bruno Douradinha, Vera van Noort, Martijn Huynen, Adrian Luty, Hans Kroeze, Shahid Khan, Robert Sauerwein, Andrew Waters, Matthias Mann, Hendrik Stunnenberg
Categories: malaria news feeds

The silent path to thousands of merozoites: the Plasmodium liver stage

CiteULike malaria tags - 19 September 2016 - 12:32pm
Nature Reviews Microbiology, Vol. 4, No. 11. (01 November 2006), pp. 849-856, doi:10.1038/nrmicro1529

Plasmodium sporozoites are deposited in the skin of their vertebrate hosts through the bite of an infected female Anopheles mosquito. Most of these parasites find a blood vessel and travel in the peripheral blood circulation until they reach the liver sinusoids. Once there, the sporozoites cross the sinusoidal wall and migrate through several hepatocytes before they infect a final hepatocyte, with the formation of a parasitophorous vacuole, in which the intrahepatic form of the parasite grows and multiplies. During this period, each sporozoite generates thousands of merozoites. As the development of Plasmodium sporozoites inside hepatocytes is an obligatory step before the onset of disease, understanding the parasite's requirements during this period is crucial for the development of any form of early intervention. This Review summarizes our current knowledge on this stage of the Plasmodium life cycle.
Miguel Prudencio, Ana Rodriguez, Maria Mota
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Invasion in vitro of mosquito midgut cells by the malaria parasite proceeds by a conserved mechanism and results in death of the invaded midgut cells

CiteULike malaria tags - 18 September 2016 - 6:23pm
Proceedings of the National Academy of Sciences, Vol. 97, No. 21. (10 October 2000), pp. 11516-11521, doi:10.1073/pnas.97.21.11516

Using an in vitro culture system, we observed the migration of malaria ookinetes on the surface of the mosquito midgut and invasion of the midgut epithelium. Ookinetes display constrictions during migration to the midgut surface and a gliding motion once on the luminal midgut surface. Invasion of a midgut cell always occurs at its lateral apical surface. Invasion is rapid and is often followed by invasion of a neighboring midgut cell by the ookinete. The morphology of the invaded cells changes dramatically after invasion, and invaded cells die rapidly. Midgut cell death is accompanied by activation of a caspase-3-like protease, suggesting cell death is apoptotic. The events occurring during invasion were identical for two different species of Plasmodium and two different genera of mosquitoes; they probably represent a universal mechanism of mosquito midgut penetration by the malaria parasite.
Helge Zieler, James Dvorak
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Role of host cell traversal by the malaria sporozoite during liver infection

CiteULike malaria tags - 17 September 2016 - 11:07pm
The Journal of Experimental Medicine, Vol. 210, No. 5. (06 May 2013), pp. 905-915, doi:10.1084/jem.20121130
Joana Tavares, Pauline Formaglio, Sabine Thiberge, Elodie Mordelet, Nico Van Rooijen, Alexander Medvinsky, Robert Ménard, Rogerio Amino
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A toolbox to study liver stage malaria

CiteULike malaria tags - 16 September 2016 - 8:32pm
Trends in Parasitology, Vol. 27, No. 12. (December 2011), pp. 565-574, doi:10.1016/

The first obligatory phase of mammalian infection by Plasmodium parasites, the causative agents of malaria, occurs in the liver of the host. This stage of Plasmodium infection bears enormous potential for anti-malarial intervention. Recent technological progress has strongly contributed to overcoming some of the long-standing difficulties in experimentally assessing hepatic infection by Plasmodium. Here, we review appropriate infection models and infection assessment tools, and provide a comprehensive description of recent advances in experimental strategies to investigate the liver stage of malaria. These issues are discussed in the context of current challenges in the field to provide researchers with the technical tools that enable effective experimental approaches to study liver stage malaria.
Miguel Prudêncio, Maria Mota, António Mendes
Categories: malaria news feeds

The cellular and molecular basis for malaria parasite invasion of the human red blood cell

CiteULike malaria tags - 16 September 2016 - 8:07pm
The Journal of Cell Biology, Vol. 198, No. 6. (17 September 2012), pp. 961-971, doi:10.1083/jcb.201206112

Malaria is a major disease of humans caused by protozoan parasites from the genus Plasmodium. It has a complex life cycle; however, asexual parasite infection within the blood stream is responsible for all disease pathology. This stage is initiated when merozoites, the free invasive blood-stage form, invade circulating erythrocytes. Although invasion is rapid, it is the only time of the life cycle when the parasite is directly exposed to the host immune system. Significant effort has, therefore, focused on identifying the proteins involved and understanding the underlying mechanisms behind merozoite invasion into the protected niche inside the human erythrocyte.
Alan Cowman, Drew Berry, Jake Baum
Categories: malaria news feeds