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Mosquito Passage Dramatically Changes var Gene Expression in Controlled Human Plasmodium falciparum Infections. PLoS Pathog 2016; 12:e1005538. [PMID: 27070311 PMCID: PMC4829248 DOI: 10.1371/journal.ppat.1005538] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 03/10/2016] [Indexed: 11/19/2022] Open
Abstract
Virulence of the most deadly malaria parasite Plasmodium falciparum is linked to the variant surface antigen PfEMP1, which is encoded by about 60 var genes per parasite genome. Although the expression of particular variants has been associated with different clinical outcomes, little is known about var gene expression at the onset of infection. By analyzing controlled human malaria infections via quantitative real-time PCR, we show that parasite populations from 18 volunteers expressed virtually identical transcript patterns that were dominated by the subtelomeric var gene group B and, to a lesser extent, group A. Furthermore, major changes in composition and frequency of var gene transcripts were detected between the parental parasite culture that was used to infect mosquitoes and Plasmodia recovered from infected volunteers, suggesting that P. falciparum resets its var gene expression during mosquito passage and starts with the broad expression of a specific subset of var genes when entering the human blood phase.
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152
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Hora R, Kapoor P, Thind KK, Mishra PC. Cerebral malaria--clinical manifestations and pathogenesis. Metab Brain Dis 2016; 31:225-37. [PMID: 26746434 DOI: 10.1007/s11011-015-9787-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 12/22/2015] [Indexed: 01/28/2023]
Abstract
One of the most common central nervous system diseases in tropical countries is cerebral malaria (CM). Malaria is a common protozoan infection that is responsible for enormous worldwide mortality and economic burden on the society. Episodes of Plasmodium falciparum (Pf) caused CM may be lethal, while survivors are likely to suffer from persistent debilitating neurological deficits, especially common in children. In this review article, we have summarized the various symptoms and manifestations of CM in children and adults, and entailed the molecular basis of the disease. We have also emphasized how pathogenesis of the disease is effected by the parasite and host responses including blood brain barrier (BBB) disruption, endothelial cell activation and apoptosis, nitric oxide bioavailability, platelet activation and apoptosis, and neuroinflammation. Based on a few recent studies carried out in experimental mouse malaria models, we propose a basis for the neurological deficits and sequelae observed in human cerebral malaria, and summarize how existing drugs may improve prognosis in affected individuals.
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Affiliation(s)
- Rachna Hora
- Department of Molecular Biology and Biochemistry, Guru Nanak Dev University, Amritsar, 143005, India.
| | - Payal Kapoor
- Department of Molecular Biology and Biochemistry, Guru Nanak Dev University, Amritsar, 143005, India
| | - Kirandeep Kaur Thind
- Department of Molecular Biology and Biochemistry, Guru Nanak Dev University, Amritsar, 143005, India
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153
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Role of the ER and Golgi in protein export by Apicomplexa. Curr Opin Cell Biol 2016; 41:18-24. [PMID: 27019341 DOI: 10.1016/j.ceb.2016.03.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 03/06/2016] [Accepted: 03/07/2016] [Indexed: 12/31/2022]
Abstract
Apicomplexan parasites cause diseases of medical and agricultural importance linked to dramatic changes they impart upon infected host cells. Following invasion, the malaria parasite Plasmodium falciparum renovates the host erythrocyte using mechanisms previously believed to be malaria-specific. This involves proteolytic cleavage of effectors in the endoplasmic reticulum that licences proteins for translocation into the host cell. Recently, it was demonstrated that the related parasite Toxoplasma gondii, responsible for disease in immunocompromised individuals and congenital birth defects, has an analogous pathway with some differences, including proteolytic processing in the Golgi. Here we review the similarities and distinctions in export mechanisms between these and other Apicomplexan parasites to reconcile how this group of pathogens modify their host cells to survive and proliferate.
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154
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Recombination and Diversification of the Variant Antigen Encoding Genes in the Malaria Parasite Plasmodium falciparum. Microbiol Spectr 2016; 2. [PMID: 26104446 DOI: 10.1128/microbiolspec.mdna3-0022-2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The most severe form of human malaria is caused by the protozoan parasite Plasmodium falciparum. These parasites invade and replicate within the circulating red blood cells of infected individuals leading to numerous disease manifestations, including severe anemia, altered circulation, and tissue inflammation. Malaria parasites are also known for their ability to maintain a chronic infection through antigenic variation, the ability to systematically alter the antigens displayed on the surface of infected cells and thereby avoid clearance by the host's antibody response. The genome of P. falciparum includes several large, multicopy gene families that encode highly variable forms of the surface proteins that are the targets of host immunity. Alterations in expression of genes within these families are responsible for antigenic variation. This process requires the continuous generation of new antigenic variants within these gene families, and studies have shown that new variants arise through extensive recombination and gene conversion events between family members. Malaria parasites possess an unusual complement of DNA repair pathways, thus the study of recombination between variant antigen encoding genes provides a unique view into the evolution of mobile DNA in an organism distantly related to the more closely studied model eukaryotes.
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155
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Global selection of Plasmodium falciparum virulence antigen expression by host antibodies. Sci Rep 2016; 6:19882. [PMID: 26804201 PMCID: PMC4726288 DOI: 10.1038/srep19882] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 12/21/2015] [Indexed: 12/22/2022] Open
Abstract
Parasite proteins called PfEMP1 that are inserted on the surface of infected erythrocytes, play a key role in the severe pathology associated with infection by the Plasmodium falciparum malaria parasite. These proteins mediate binding of infected cells to the endothelial lining of blood vessels as a strategy to avoid clearance by the spleen and are major targets of naturally acquired immunity. PfEMP1 is encoded by a large multi-gene family called var. Mutually-exclusive transcriptional switching between var genes allows parasites to escape host antibodies. This study examined in detail the patterns of expression of var in a well-characterized sample of parasites from Kenyan Children. Instead of observing clear inverse relationships between the expression of broad sub-classes of PfEMP1, we found that expression of different PfEMP1 groups vary relatively independently. Parasite adaptation to host antibodies also appears to involve a general reduction in detectable var gene expression. We suggest that parasites switch both between different PfEMP1 variants and between high and low expression states. Such a strategy could provide a means of avoiding immunological detection and promoting survival under high levels of host immunity.
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156
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Abstract
Malaria is one of the most serious infectious diseases with most of the severe disease
caused by Plasmodium falciparum (Pf). Naturally acquired immunity
develops over time after repeated infections and the development of antimalarial
antibodies is thought to play a crucial role. Neonates and young infants are relatively
protected from symptomatic malaria through mechanisms that are poorly understood. The
prevailing paradigm is that maternal antimalarial antibodies transferred to the fetus in
the last trimester of pregnancy protect the infant from early infections. These
antimalarial antibodies wane by approximately 6 months of age leaving the infant
vulnerable to malaria, however direct evidence supporting this epidemiologically based
paradigm is lacking. As infants are the target population for future malaria vaccines,
understanding how they begin to develop immunity to malaria and the gaps in their
responses is key. This review summarizes the antimalarial antibody responses detected in
infants and how they change over time. We focus primarily on Pf antibody responses and
will briefly mention Plasmodium vivax responses in infants.
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157
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Abstract
The Plasmodium falciparum erythrocyte membrane protein 1 antigens that are inserted onto the surface of P. falciparum infected erythrocytes play a key role both in the pathology of severe malaria and as targets of naturally acquired immunity. They might be considered unlikely vaccine targets because they are extremely diverse. However, several lines of evidence suggest that underneath this molecular diversity there are a restricted set of epitopes which may act as effective targets for a vaccine against severe malaria. Here we review some of the recent developments in this area of research, focusing on work that has assessed the potential of these molecules as possible vaccine targets.
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158
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Dinko B, Pradel G. Immune evasion by <i>Plasmodium falciparum</i> parasites: converting a host protection mechanism for the parasite′s benefit. ACTA ACUST UNITED AC 2016. [DOI: 10.4236/aid.2016.62011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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159
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Differential Plasmodium falciparum surface antigen expression among children with Malarial Retinopathy. Sci Rep 2015; 5:18034. [PMID: 26657042 PMCID: PMC4677286 DOI: 10.1038/srep18034] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 11/10/2015] [Indexed: 11/08/2022] Open
Abstract
Retinopathy provides a window into the underlying pathology of life-threatening malarial coma ("cerebral malaria"), allowing differentiation between 1) coma caused by sequestration of Plasmodium falciparum-infected erythrocytes in the brain and 2) coma with other underlying causes. Parasite sequestration in the brain is mediated by PfEMP1; a diverse parasite antigen that is inserted into the surface of infected erythrocytes and adheres to various host receptors. PfEMP1 sub-groups called "DC8" and "DC13" have been proposed to cause brain pathology through interactions with endothelial protein C receptor. To test this we profiled PfEMP1 gene expression in parasites from children with clinically defined cerebral malaria, who either had or did not have accompanying retinopathy. We found no evidence for an elevation of DC8 or DC13 PfEMP1 expression in children with retinopathy. However, the proportional expression of a broad subgroup of PfEMP1 called "group A" was elevated in retinopathy patients suggesting that these variants may play a role in the pathology of cerebral malaria. Interventions targeting group A PfEMP1 may be effective at reducing brain pathology.
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160
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Nunes-Silva S, Dechavanne S, Moussiliou A, Pstrąg N, Semblat JP, Gangnard S, Tuikue-Ndam N, Deloron P, Chêne A, Gamain B. Beninese children with cerebral malaria do not develop humoral immunity against the IT4-VAR19-DC8 PfEMP1 variant linked to EPCR and brain endothelial binding. Malar J 2015; 14:493. [PMID: 26646943 PMCID: PMC4672576 DOI: 10.1186/s12936-015-1008-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 11/21/2015] [Indexed: 11/16/2022] Open
Abstract
Background Malaria is still one of the most prevalent infectious diseases in the world. Sequestration of infected erythrocytes (IEs) is the prime mediator of disease. Cytoadhesion of IEs is mediated by members of the highly diverse Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1). A restricted sub-set of var genes encoding for PfEMP1s possessing the domain cassettes DC8 and DC13 were found to bind to the endothelial protein C receptor (EPCR). These var genes were shown to be highly expressed by parasites from patients with severe malaria clinical outcomes compared to those from patients with uncomplicated symptoms. Methods In order to further study the molecular mechanisms underlying DC8/DC13 expressing IEs adhesion to EPCR, a method was developed to produce highly pure recombinant EPCR. The IT4 parasite strain was selected on either anti-IT4-VAR19 purified IgG, EPCR or human brain endothelial cell line and their var gene expression profiles as well as their binding phenotypes were compared. The N-terminal region of IT4-VAR19 comprising a full-length DC8 cassette as well as the single EPCR binding CIDRα1.1 domain were also produced, and their immune recognition (IgG) was assessed using plasma samples from Beninese children presenting acute mild malaria, severe malaria or cerebral malaria at the time of their admission to the clinic, and from convalescent-phase plasma collected 30 days after anti-malarial treatment. Results The multi-domain VAR19-NTS-DBLγ6 binds to EPCR with a greater affinity than the CIDRα1.1 domain alone and this study also demonstrates that VAR19-NTS-DBLγ6 binding to the EPCR-expressing endothelial cell line (HBEC5i) is more pronounced than that of the CIDRα1.1 domain alone. IT4-VAR19 represents the preferentially expressed-PfEMP1 when FCR3-IEs are selected based on their capability to bind EPCR. Notably, no significant difference in the levels of antibodies towards IT4-VAR19 antigens was observed within all clinical groups between plasma samples collected during the acute malaria phase compared to samples collected 30 days after anti-malaria treatment. Conclusions These data indicate that even being the preferentially selected IT4-EPCR-binding variant, the IT4-VAR19-DC8 region does not appear to be associated with the acquisition of antibodies during a single severe paediatric malaria episode in Benin. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-1008-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sofia Nunes-Silva
- Inserm UMR_1134, Paris, France. .,Université Paris Diderot, Sorbonne Paris Cité, UMR_S1134, Paris, France. .,Institut National de la Transfusion Sanguine, 6 rue Alexandre Cabanel, 75015, Paris, France. .,Laboratory of Excellence GR-Ex, Paris, France.
| | - Sébastien Dechavanne
- Inserm UMR_1134, Paris, France. .,Université Paris Diderot, Sorbonne Paris Cité, UMR_S1134, Paris, France. .,Institut National de la Transfusion Sanguine, 6 rue Alexandre Cabanel, 75015, Paris, France. .,Laboratory of Excellence GR-Ex, Paris, France.
| | - Azizath Moussiliou
- Laboratory of Excellence GR-Ex, Paris, France. .,Institut de Recherche pour le développement, UMR_216, Mère et enfant face aux infections tropicales, Paris, France. .,Faculté de pharmacie, PRES Sorbonne Paris Cité, Paris, France.
| | - Natalia Pstrąg
- Inserm UMR_1134, Paris, France. .,Université Paris Diderot, Sorbonne Paris Cité, UMR_S1134, Paris, France. .,Institut National de la Transfusion Sanguine, 6 rue Alexandre Cabanel, 75015, Paris, France. .,Laboratory of Excellence GR-Ex, Paris, France.
| | - Jean-Philippe Semblat
- Inserm UMR_1134, Paris, France. .,Université Paris Diderot, Sorbonne Paris Cité, UMR_S1134, Paris, France. .,Institut National de la Transfusion Sanguine, 6 rue Alexandre Cabanel, 75015, Paris, France. .,Laboratory of Excellence GR-Ex, Paris, France.
| | - Stéphane Gangnard
- Inserm UMR_1134, Paris, France. .,Université Paris Diderot, Sorbonne Paris Cité, UMR_S1134, Paris, France. .,Institut National de la Transfusion Sanguine, 6 rue Alexandre Cabanel, 75015, Paris, France. .,Laboratory of Excellence GR-Ex, Paris, France.
| | - Nicaise Tuikue-Ndam
- Laboratory of Excellence GR-Ex, Paris, France. .,Institut de Recherche pour le développement, UMR_216, Mère et enfant face aux infections tropicales, Paris, France. .,Faculté de pharmacie, PRES Sorbonne Paris Cité, Paris, France.
| | - Philippe Deloron
- Laboratory of Excellence GR-Ex, Paris, France. .,Institut de Recherche pour le développement, UMR_216, Mère et enfant face aux infections tropicales, Paris, France. .,Faculté de pharmacie, PRES Sorbonne Paris Cité, Paris, France.
| | - Arnaud Chêne
- Inserm UMR_1134, Paris, France. .,Université Paris Diderot, Sorbonne Paris Cité, UMR_S1134, Paris, France. .,Institut National de la Transfusion Sanguine, 6 rue Alexandre Cabanel, 75015, Paris, France. .,Laboratory of Excellence GR-Ex, Paris, France.
| | - Benoît Gamain
- Inserm UMR_1134, Paris, France. .,Université Paris Diderot, Sorbonne Paris Cité, UMR_S1134, Paris, France. .,Institut National de la Transfusion Sanguine, 6 rue Alexandre Cabanel, 75015, Paris, France. .,Laboratory of Excellence GR-Ex, Paris, France.
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161
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A spiral scaffold underlies cytoadherent knobs in Plasmodium falciparum-infected erythrocytes. Blood 2015; 127:343-51. [PMID: 26637786 DOI: 10.1182/blood-2015-10-674002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 11/30/2015] [Indexed: 12/11/2022] Open
Abstract
Much of the virulence of Plasmodium falciparum malaria is caused by cytoadherence of infected erythrocytes, which promotes parasite survival by preventing clearance in the spleen. Adherence is mediated by membrane protrusions known as knobs, whose formation depends on the parasite-derived, knob-associated histidine-rich protein (KAHRP). Knobs are required for cytoadherence under flow conditions, and they contain both KAHRP and the parasite-derived erythrocyte membrane protein PfEMP1. Using electron tomography, we have examined the 3-dimensional structure of knobs in detergent-insoluble skeletons of P falciparum 3D7 schizonts. We describe a highly organized knob skeleton composed of a spiral structure coated by an electron-dense layer underlying the knob membrane. This knob skeleton is connected by multiple links to the erythrocyte cytoskeleton. We used immuno-electron microscopy (EM) to locate KAHRP in these structures. The arrangement of membrane proteins in the knobs, visualized by high-resolution freeze-fracture scanning EM, is distinct from that in the surrounding erythrocyte membrane, with a structure at the apex that likely represents the adhesion site. Thus, erythrocyte knobs in P falciparum infection contain a highly organized skeleton structure underlying a specialized region of membrane. We propose that the spiral and dense coat organize the cytoadherence structures in the knob, and anchor them into the erythrocyte cytoskeleton. The high density of knobs and their extensive mechanical linkage suggest an explanation for the rigidification of the cytoskeleton in infected cells, and for the transmission to the cytoskeleton of shear forces experienced by adhering cells.
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162
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Sampath S, Brazier AJ, Avril M, Bernabeu M, Vigdorovich V, Mascarenhas A, Gomes E, Sather DN, Esmon CT, Smith JD. Plasmodium falciparum adhesion domains linked to severe malaria differ in blockade of endothelial protein C receptor. Cell Microbiol 2015; 17:1868-82. [PMID: 26118955 PMCID: PMC4661071 DOI: 10.1111/cmi.12478] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 06/22/2015] [Accepted: 06/23/2015] [Indexed: 11/28/2022]
Abstract
Cytoadhesion of Plasmodium falciparum-infected erythrocytes to endothelial protein C receptor (EPCR) is associated with severe malaria. It has been postulated that parasite binding could exacerbate microvascular coagulation and endothelial dysfunction in cerebral malaria by impairing the protein C-EPCR interaction, but the extent of binding inhibition has not been fully determined. Here we expressed the cysteine-rich interdomain region (CIDRα1) domain from a variety of domain cassette (DC) 8 and DC13 P. falciparum erythrocyte membrane protein 1 proteins and show they interact in a distinct manner with EPCR resulting in weak, moderate and strong inhibition of the activated protein C (APC)-EPCR interaction. Overall, there was a positive correlation between CIDRα1-EPCR binding activity and APC blockade activity. In addition, our analysis from a combination of mutagenesis and blocking antibodies finds that an Arg81 (R81) in EPCR plays a pivotal role in CIDRα1 binding, but domains with weak and strong APC blockade activity were distinguished by their sensitivity to inhibition by anti-EPCR mAb 1535, implying subtle differences in their binding footprints. These data reveal a previously unknown functional heterogeneity in the interaction between P. falciparum and EPCR and have major implications for understanding the distinct clinical pathologies of cerebral malaria and developing new treatment strategies.
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Affiliation(s)
- Sowmya Sampath
- Center for Infectious Disease Research (formerly Seattle Biomedical Research Institute), Seattle, Washington, 98109, USA
| | - Andrew Jay Brazier
- Center for Infectious Disease Research (formerly Seattle Biomedical Research Institute), Seattle, Washington, 98109, USA
| | - Marion Avril
- Center for Infectious Disease Research (formerly Seattle Biomedical Research Institute), Seattle, Washington, 98109, USA
| | - Maria Bernabeu
- Center for Infectious Disease Research (formerly Seattle Biomedical Research Institute), Seattle, Washington, 98109, USA
| | - Vladimir Vigdorovich
- Center for Infectious Disease Research (formerly Seattle Biomedical Research Institute), Seattle, Washington, 98109, USA
| | - Anjali Mascarenhas
- University of Washington, Department of Chemistry, Seattle, Washington, 98195, USA
| | - Edwin Gomes
- Goa Medical College & Hospital, Bambolim, Goa, India
| | - D. Noah Sather
- Center for Infectious Disease Research (formerly Seattle Biomedical Research Institute), Seattle, Washington, 98109, USA
| | - Charles T. Esmon
- Coagulation Biology Laboratory, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA
| | - Joseph D. Smith
- Center for Infectious Disease Research (formerly Seattle Biomedical Research Institute), Seattle, Washington, 98109, USA
- Department of Global Health, University of Washington, Seattle, Washington, 98195, USA
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163
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Abstract
Plasmodium falciparum is the protozoan parasite that causes most malaria-associated morbidity and mortality in humans with over 500,000 deaths annually. The disease symptoms are associated with repeated cycles of invasion and asexual multiplication inside red blood cells of the parasite. Partial, non-sterile immunity to P. falciparum malaria develops only after repeated infections and continuous exposure. The successful evasion of the human immune system relies on the large repertoire of antigenically diverse parasite proteins displayed on the red blood cell surface and on the merozoite membrane where they are exposed to the human immune system. Expression switching of these polymorphic proteins between asexual parasite generations provides an efficient mechanism to adapt to the changing environment in the host and to maintain chronic infection. This chapter discusses antigenic diversity and variation in the malaria parasite and our current understanding of the molecular mechanisms that direct the expression of these proteins.
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Affiliation(s)
- Michaela Petter
- Department of Medicine Royal Melbourne Hospital, Peter Doherty Institute, University of Melbourne, 792 Elizabeth Street, Melbourne, VIC, 3010, Australia.
| | - Michael F Duffy
- Department of Medicine Royal Melbourne Hospital, Peter Doherty Institute, University of Melbourne, 792 Elizabeth Street, Melbourne, VIC, 3010, Australia.
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164
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From within host dynamics to the epidemiology of infectious disease: Scientific overview and challenges. Math Biosci 2015; 270:143-55. [PMID: 26474512 DOI: 10.1016/j.mbs.2015.10.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Since their earliest days, humans have been struggling with infectious diseases. Caused by viruses, bacteria, protozoa, or even higher organisms like worms, these diseases depend critically on numerous intricate interactions between parasites and hosts, and while we have learned much about these interactions, many details are still obscure. It is evident that the combined host-parasite dynamics constitutes a complex system that involves components and processes at multiple scales of time, space, and biological organization. At one end of this hierarchy we know of individual molecules that play crucial roles for the survival of a parasite or for the response and survival of its host. At the other end, one realizes that the spread of infectious diseases by far exceeds specific locales and, due to today's easy travel of hosts carrying a multitude of organisms, can quickly reach global proportions. The community of mathematical modelers has been addressing specific aspects of infectious diseases for a long time. Most of these efforts have focused on one or two select scales of a multi-level disease and used quite different computational approaches. This restriction to a molecular, physiological, or epidemiological level was prudent, as it has produced solid pillars of a foundation from which it might eventually be possible to launch comprehensive, multi-scale modeling efforts that make full use of the recent advances in biology and, in particular, the various high-throughput methodologies accompanying the emerging -omics revolution. This special issue contains contributions from biologists and modelers, most of whom presented and discussed their work at the workshop From within Host Dynamics to the Epidemiology of Infectious Disease, which was held at the Mathematical Biosciences Institute at Ohio State University in April 2014. These contributions highlight some of the forays into a deeper understanding of the dynamics between parasites and their hosts, and the consequences of this dynamics for the spread and treatment of infectious diseases.
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165
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Abstract
Since discovering PfEMP1 virulence proteins in Plasmodium falciparum, malariologists have struggled to reconcile their limitless sequence diversity with their binding to relatively few host receptors. In this issue of Cell Host & Microbe, Lau et al. (2015) explore how diverse PfEMP1s embrace EPCR, promoting parasite survival and killing African children.
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Affiliation(s)
- Rick M Fairhurst
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Room 3E-10A, Rockville, MD 20852, USA.
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166
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Childs LM, Buckee CO. Dissecting the determinants of malaria chronicity: why within-host models struggle to reproduce infection dynamics. J R Soc Interface 2015; 12:20141379. [PMID: 25673299 PMCID: PMC4345506 DOI: 10.1098/rsif.2014.1379] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The duration of infection is fundamental to the epidemiological behaviour of any infectious disease, but remains one of the most poorly understood aspects of malaria. In endemic areas, the malaria parasite Plasmodium falciparum can cause both acute, severe infections and asymptomatic, chronic infections through its interaction with the host immune system. Frequent superinfection and massive parasite genetic diversity make it extremely difficult to accurately measure the distribution of infection lengths, complicating the estimation of basic epidemiological parameters and the prediction of the impact of interventions. Mathematical models have qualitatively reproduced parasite dynamics early during infection, but reproducing long-lived chronic infections remains much more challenging. Here, we construct a model of infection dynamics to examine the consequences of common biological assumptions for the generation of chronicity and the impact of co-infection. We find that although a combination of host and parasite heterogeneities are capable of generating chronic infections, they do so only under restricted parameter choices. Furthermore, under biologically plausible assumptions, co-infection of parasite genotypes can alter the course of infection of both the resident and co-infecting strain in complex non-intuitive ways. We outline the most important puzzles for within-host models of malaria arising from our analysis, and their implications for malaria epidemiology and control.
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Affiliation(s)
- Lauren M Childs
- Center for Communicable Disease Dynamics, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA
| | - Caroline O Buckee
- Center for Communicable Disease Dynamics, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA
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167
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Wassmer SC, Taylor TE, Rathod PK, Mishra SK, Mohanty S, Arevalo-Herrera M, Duraisingh MT, Smith JD. Investigating the Pathogenesis of Severe Malaria: A Multidisciplinary and Cross-Geographical Approach. Am J Trop Med Hyg 2015; 93:42-56. [PMID: 26259939 PMCID: PMC4574273 DOI: 10.4269/ajtmh.14-0841] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 03/10/2015] [Indexed: 01/14/2023] Open
Abstract
More than a century after the discovery of Plasmodium spp. parasites, the pathogenesis of severe malaria is still not well understood. The majority of malaria cases are caused by Plasmodium falciparum and Plasmodium vivax, which differ in virulence, red blood cell tropism, cytoadhesion of infected erythrocytes, and dormant liver hypnozoite stages. Cerebral malaria coma is one of the most severe manifestations of P. falciparum infection. Insights into its complex pathophysiology are emerging through a combination of autopsy, neuroimaging, parasite binding, and endothelial characterizations. Nevertheless, important questions remain regarding why some patients develop life-threatening conditions while the majority of P. falciparum-infected individuals do not, and why clinical presentations differ between children and adults. For P. vivax, there is renewed recognition of severe malaria, but an understanding of the factors influencing disease severity is limited and remains an important research topic. Shedding light on the underlying disease mechanisms will be necessary to implement effective diagnostic tools for identifying and classifying severe malaria syndromes and developing new therapeutic approaches for severe disease. This review highlights progress and outstanding questions in severe malaria pathophysiology and summarizes key areas of pathogenesis research within the International Centers of Excellence for Malaria Research program.
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Affiliation(s)
| | | | | | | | | | | | | | - Joseph D. Smith
- Division of Parasitology, Department of Microbiology, New York University School of Medicine, New York, New York; Department of Pathology, Sydney Medical School, The University of Sydney, Sydney, Australia; Department of Osteopathic Medical Specialties, College of Osteopathic Medicine, Michigan State University, East Lansing, Michigan; Blantyre Malaria Project, University of Malawi College of Medicine, Blantyre, Malawi; Departments of Chemistry and Global Health, University of Washington, Seattle, Washington; Department of Internal Medicine, Ispat General Hospital, Orissa, India; Caucaseco Scientific Research Center, Cali, Colombia; Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts; Seattle Biomedical Research Institute, Seattle, Washington; Department of Global Health, University of Washington, Seattle, Washington
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168
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Patel S, Joshi D, Soni R, Sharma D, Bhatt TK. Molecular modeling, in silico screening and molecular dynamics of PfPRL-PTP of P. falciparum for identification of potential anti-malarials. J Biomol Struct Dyn 2015; 34:1330-44. [PMID: 26313238 DOI: 10.1080/07391102.2015.1078746] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Millions of deaths occur every year due to malaria. Growing resistance against existing drugs for treatment of malaria has exaggerated the problem further. There is an intense demand of identifying drug targets in malaria parasite. PfPRL-PTP protein is PRL group of phosphatase, and one of the interesting drug targets being involved in three important pathways of malaria parasite (secretion, phosphorylation, and prenylation). Therefore, in this study, we have modeled three-dimensional structure of PfPRL-PTP followed by validation of 3D structure using RAMPAGE, verify3D, and other structure validation tools. We could identify 12 potential inhibitory compounds using in silico screening of NCI library against PfPRL-PTP with Glide. The molecular dynamics simulation was also performed using GROMACS on PfPRL-PTP model alone and PfPRL-PTP-inhibitor complex. This study of identifying potential drug-like molecules would add up to the process of drug discovery against malaria parasite.
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Affiliation(s)
- Sachin Patel
- a Department of Biotechnology , Central University of Rajasthan , NH-8, Bandarsindri 305801 , Rajasthan , India
| | - Deepti Joshi
- a Department of Biotechnology , Central University of Rajasthan , NH-8, Bandarsindri 305801 , Rajasthan , India
| | - Rani Soni
- a Department of Biotechnology , Central University of Rajasthan , NH-8, Bandarsindri 305801 , Rajasthan , India
| | - Drista Sharma
- a Department of Biotechnology , Central University of Rajasthan , NH-8, Bandarsindri 305801 , Rajasthan , India
| | - Tarun Kumar Bhatt
- a Department of Biotechnology , Central University of Rajasthan , NH-8, Bandarsindri 305801 , Rajasthan , India
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169
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Josling GA, Llinás M. Sexual development in Plasmodium parasites: knowing when it's time to commit. Nat Rev Microbiol 2015; 13:573-87. [DOI: 10.1038/nrmicro3519] [Citation(s) in RCA: 138] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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170
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Multiple Plasmodium falciparum Erythrocyte Membrane Protein 1 Variants per Genome Can Bind IgM via Its Fc Fragment Fcμ. Infect Immun 2015. [PMID: 26216422 PMCID: PMC4567627 DOI: 10.1128/iai.00337-15] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) adhesive proteins expressed on the surfaces of infected erythrocytes (IEs) are of key importance in the pathogenesis of P. falciparum malaria. Several structurally and functionally defined PfEMP1 types have been associated with severe clinical manifestations, such as cerebral malaria in children and placental malaria in pregnant women. PfEMP1 that can bind the Fc part of IgM (Fcμ) characterizes one such type, although the functional significance of this IgM binding to PfEMP1 remains unclear. In this study, we report the identification and functional analysis of five IgM-binding PfEMP1 proteins encoded by P. falciparum NF54. In addition to the VAR2CSA-type PFL0030c protein, already known to bind Fcμ and to mediate chondroitin sulfate A (CSA)-specific adhesion of IEs in the placenta, we found four PfEMP1 proteins not previously known to bind IgM this way. Although they all contained Duffy binding-like ε (DBLε) domains similar to those in VAR2CSA-type PfEMP1, they did not mediate IE adhesion to CSA, and IgM binding did not shield IEs from phagocytosis of IgG-opsonized IEs. In this way, these new IgM-binding PfEMP1 proteins resemble the rosette-mediating and IgM-binding PfEMP1 HB3VAR06, but none of them mediated formation of rosettes. We could map the capacity for Fc-specific IgM binding to DBLε domains near the C terminus for three of the four PfEMP1 proteins tested. Our study provides new evidence regarding Fc-dependent binding of IgM to PfEMP1, which appears to be a common and multifunctional phenotype.
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171
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Ukaegbu UE, Deitsch KW. The Emerging Role for RNA Polymerase II in Regulating Virulence Gene Expression in Malaria Parasites. PLoS Pathog 2015; 11:e1004926. [PMID: 26181323 PMCID: PMC4504705 DOI: 10.1371/journal.ppat.1004926] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Affiliation(s)
- Uchechi E. Ukaegbu
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Kirk W. Deitsch
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
- * E-mail:
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172
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IgG antibodies to endothelial protein C receptor-binding cysteine-rich interdomain region domains of Plasmodium falciparum erythrocyte membrane protein 1 are acquired early in life in individuals exposed to malaria. Infect Immun 2015; 83:3096-103. [PMID: 26015475 DOI: 10.1128/iai.00271-15] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 05/11/2015] [Indexed: 11/20/2022] Open
Abstract
Severe malaria syndromes are precipitated by Plasmodium falciparum parasites binding to endothelial receptors on the vascular lining. This binding is mediated by members of the highly variant P. falciparum erythrocyte membrane protein 1 (PfEMP1) family. We have previously identified a subset of PfEMP1 proteins associated with severe malaria and found that the receptor for these PfEMP1 variants is endothelial protein C receptor (EPCR). The binding is mediated through the amino-terminal cysteine-rich interdomain region (CIDR) of the subtypes α1.1 and α1.4 to α1.8. In this study, we investigated the acquisition of anti-CIDR antibodies using plasma samples collected in four study villages with different malaria transmission intensities in northeastern Tanzania during a period with a decline in malaria transmission. We show that individuals exposed to high levels of malaria transmission acquire antibodies to EPCR-binding CIDR domains early in life and that these antibodies are acquired more rapidly than antibodies to other CIDR domains. The rate by which antibodies to EPCR-binding CIDR domains are acquired in populations in areas where malaria is endemic is determined by the malaria transmission intensity, and on a population level, the antibodies are rapidly lost if transmission is interrupted. This indicates that sustained exposure is required to maintain the production of the antibodies.
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173
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Ukaegbu UE, Zhang X, Heinberg AR, Wele M, Chen Q, Deitsch KW. A Unique Virulence Gene Occupies a Principal Position in Immune Evasion by the Malaria Parasite Plasmodium falciparum. PLoS Genet 2015; 11:e1005234. [PMID: 25993442 PMCID: PMC4437904 DOI: 10.1371/journal.pgen.1005234] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 04/21/2015] [Indexed: 12/13/2022] Open
Abstract
Mutually exclusive gene expression, whereby only one member of a multi-gene family is selected for activation, is used by the malaria parasite Plasmodium falciparum to escape the human immune system and perpetuate long-term, chronic infections. A family of genes called var encodes the chief antigenic and virulence determinant of P. falciparum malaria. var genes are transcribed in a mutually exclusive manner, with switching between active genes resulting in antigenic variation. While recent work has shed considerable light on the epigenetic basis for var gene activation and silencing, how switching is controlled remains a mystery. In particular, switching seems not to be random, but instead appears to be coordinated to result in timely activation of individual genes leading to sequential waves of antigenically distinct parasite populations. The molecular basis for this apparent coordination is unknown. Here we show that var2csa, an unusual and highly conserved var gene, occupies a unique position within the var gene switching hierarchy. Induction of switching through the destabilization of var specific chromatin using both genetic and chemical methods repeatedly led to the rapid and exclusive activation of var2csa. Additional experiments demonstrated that these represent "true" switching events and not simply de-silencing of the var2csa promoter, and that activation is limited to the unique locus on chromosome 12. Combined with translational repression of var2csa transcripts, frequent "default" switching to this locus and detection of var2csa untranslated transcripts in non-pregnant individuals, these data suggest that var2csa could play a central role in coordinating switching, fulfilling a prediction made by mathematical models derived from population switching patterns. These studies provide the first insights into the mechanisms by which var gene switching is coordinated as well as an example of how a pharmacological agent can disrupt antigenic variation in Plasmodium falciparum.
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Affiliation(s)
- Uchechi E. Ukaegbu
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Xu Zhang
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
- Key Laboratory of Zoonosis, College of Veterinary Medicine, Jilin University, Xi An Da Lu, Changchun, China
| | - Adina R. Heinberg
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Mamadou Wele
- University of Sciences Techniques and Technologies of Bamako, Bamako, Mali
| | - Qijun Chen
- Key Laboratory of Zoonosis, College of Veterinary Medicine, Jilin University, Xi An Da Lu, Changchun, China
| | - Kirk W. Deitsch
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
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174
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Gutierrez JB, Galinski MR, Cantrell S, Voit EO. WITHDRAWN: From within host dynamics to the epidemiology of infectious disease: Scientific overview and challenges. Math Biosci 2015:S0025-5564(15)00085-1. [PMID: 25890102 DOI: 10.1016/j.mbs.2015.04.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.
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Affiliation(s)
- Juan B Gutierrez
- Department of Mathematics, Institute of Bioinformatics, University of Georgia, Athens, GA 30602, United States .
| | - Mary R Galinski
- Emory University School of Medicine, Division of Infectious Diseases, Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, 954 Gatewood Road, Atlanta, GA 30329, United States .
| | - Stephen Cantrell
- Department of Mathematics, University of Miami, Coral Gables, FL 33124, United States .
| | - Eberhard O Voit
- Department of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Drive, Suite 4103, Atlanta, GA 30332-0535, United States .
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175
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Brancucci NMB, Bertschi NL, Zhu L, Niederwieser I, Chin WH, Wampfler R, Freymond C, Rottmann M, Felger I, Bozdech Z, Voss TS. Heterochromatin protein 1 secures survival and transmission of malaria parasites. Cell Host Microbe 2015; 16:165-176. [PMID: 25121746 DOI: 10.1016/j.chom.2014.07.004] [Citation(s) in RCA: 187] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Revised: 04/28/2014] [Accepted: 06/06/2014] [Indexed: 12/14/2022]
Abstract
Clonally variant expression of surface antigens allows the malaria parasite Plasmodium falciparum to evade immune recognition during blood stage infection and secure malaria transmission. We demonstrate that heterochromatin protein 1 (HP1), an evolutionary conserved regulator of heritable gene silencing, controls expression of numerous P. falciparum virulence genes as well as differentiation into the sexual forms that transmit to mosquitoes. Conditional depletion of P. falciparum HP1 (PfHP1) prevents mitotic proliferation of blood stage parasites and disrupts mutually exclusive expression and antigenic variation of the major virulence factor PfEMP1. Additionally, PfHP1-dependent regulation of PfAP2-G, a transcription factor required for gametocyte conversion, controls the switch from asexual proliferation to sexual differentiation, providing insight into the epigenetic mechanisms underlying gametocyte commitment. These findings show that PfHP1 is centrally involved in clonally variant gene expression and sexual differentiation in P. falciparum and have major implications for developing antidisease and transmission-blocking interventions against malaria.
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Affiliation(s)
- Nicolas M B Brancucci
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Socinstrasse 57, Basel 4051, Switzerland; University of Basel, Petersplatz 1, Basel 4003, Switzerland
| | - Nicole L Bertschi
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Socinstrasse 57, Basel 4051, Switzerland; University of Basel, Petersplatz 1, Basel 4003, Switzerland
| | - Lei Zhu
- School of Biological Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Igor Niederwieser
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Socinstrasse 57, Basel 4051, Switzerland; University of Basel, Petersplatz 1, Basel 4003, Switzerland
| | - Wai Hoe Chin
- School of Biological Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Rahel Wampfler
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Socinstrasse 57, Basel 4051, Switzerland; University of Basel, Petersplatz 1, Basel 4003, Switzerland
| | - Céline Freymond
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Socinstrasse 57, Basel 4051, Switzerland; University of Basel, Petersplatz 1, Basel 4003, Switzerland
| | - Matthias Rottmann
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Socinstrasse 57, Basel 4051, Switzerland; University of Basel, Petersplatz 1, Basel 4003, Switzerland
| | - Ingrid Felger
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Socinstrasse 57, Basel 4051, Switzerland; University of Basel, Petersplatz 1, Basel 4003, Switzerland
| | - Zbynek Bozdech
- School of Biological Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Till S Voss
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Socinstrasse 57, Basel 4051, Switzerland; University of Basel, Petersplatz 1, Basel 4003, Switzerland.
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176
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Hviid L, Jensen ATR. PfEMP1 - A Parasite Protein Family of Key Importance in Plasmodium falciparum Malaria Immunity and Pathogenesis. ADVANCES IN PARASITOLOGY 2015; 88:51-84. [PMID: 25911365 DOI: 10.1016/bs.apar.2015.02.004] [Citation(s) in RCA: 107] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Plasmodium falciparum causes the most severe form of malaria and is responsible for essentially all malaria-related deaths. The accumulation in various tissues of erythrocytes infected by mature P. falciparum parasites can lead to circulatory disturbances and inflammation, and is thought to be a central element in the pathogenesis of the disease. It is mediated by the interaction of parasite ligands on the erythrocyte surface and a range of host receptor molecules in many organs and tissues. Among several proteins and protein families implicated in this process, the P. falciparum erythrocyte membrane protein 1 (PfEMP1) family of high-molecular weight and highly variable antigens appears to be the most prominent. In this chapter, we aim to provide a systematic overview of the current knowledge about these proteins, their structure, their function, how they are presented on the erythrocyte surface, and how the var genes encoding them are regulated. The role of PfEMP1 in the pathogenesis of malaria, PfEMP1-specific immune responses, and the prospect of PfEMP1-specific vaccination against malaria are also covered briefly.
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Affiliation(s)
- Lars Hviid
- Centre for Medical Parasitology, University of Copenhagen and Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - Anja T R Jensen
- Centre for Medical Parasitology, University of Copenhagen and Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
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177
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Tibúrcio M, Sauerwein R, Lavazec C, Alano P. Erythrocyte remodeling by Plasmodium falciparum gametocytes in the human host interplay. Trends Parasitol 2015; 31:270-8. [PMID: 25824624 DOI: 10.1016/j.pt.2015.02.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Revised: 02/20/2015] [Accepted: 02/26/2015] [Indexed: 12/31/2022]
Abstract
The spread of malaria critically relies on the presence of Plasmodium transmission stages - the gametocytes - circulating in the blood of an infected individual, which are taken up by Anopheles mosquitoes. A striking feature of Plasmodium falciparum gametocytes is their long development inside the erythrocytes while sequestered in the internal organs of the human host. Recent studies of the molecular and cellular remodeling of the host erythrocyte induced by P. falciparum during gametocyte maturation are shedding light on how these may affect the establishment and maintenance of sequestration of the immature transmission stages and the subsequent release and circulation of mature gametocytes in the peripheral bloodstream.
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Affiliation(s)
- Marta Tibúrcio
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, Viale Regina Elena n.299, 00161 Rome, Italy
| | - Robert Sauerwein
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, Nijmegen HB 6500, The Netherlands
| | - Catherine Lavazec
- Institut Cochin, INSERM U1016, CNRS UMR8104, Université Paris Descartes - Sorbonne Paris Cité, 75270 Paris, France
| | - Pietro Alano
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, Viale Regina Elena n.299, 00161 Rome, Italy.
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178
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Merrick CJ, Jiang RHY, Skillman KM, Samarakoon U, Moore RM, Dzikowski R, Ferdig MT, Duraisingh MT. Functional analysis of sirtuin genes in multiple Plasmodium falciparum strains. PLoS One 2015; 10:e0118865. [PMID: 25780929 PMCID: PMC4364008 DOI: 10.1371/journal.pone.0118865] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Accepted: 01/07/2015] [Indexed: 12/22/2022] Open
Abstract
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.
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Affiliation(s)
- Catherine J. Merrick
- Department of Immunology & Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, United States of America
| | - Rays H. Y. Jiang
- Department of Immunology & Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, United States of America
| | - Kristen M. Skillman
- Department of Immunology & Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, United States of America
| | - Upeka Samarakoon
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Rachel M. Moore
- Department of Immunology & Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, United States of America
| | - Ron Dzikowski
- Department of Microbiology & Molecular Genetics, The Kuvin Center for the Study of Infectious and Tropical Diseases, IMRIC, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Michael T. Ferdig
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Manoj T. Duraisingh
- Department of Immunology & Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, United States of America
- * E-mail:
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179
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Abstract
In this issue of Blood, Rieger et al show that malaria parasite infiltration in the human placenta requires a specific geometry and affinity of host receptors to facilitate strong adhesion.
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180
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Dynamic association of PfEMP1 and KAHRP in knobs mediates cytoadherence during Plasmodium invasion. Sci Rep 2015; 5:8617. [PMID: 25726759 PMCID: PMC4345318 DOI: 10.1038/srep08617] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2014] [Accepted: 01/26/2015] [Indexed: 11/27/2022] Open
Abstract
Plasmodium falciparum infected erythrocytes display membrane knobs that are essential for their adherence to vascular endothelia and for prevention of clearance by the spleen. The knob associated histidine rich protein (KAHRP) is indispensable to knob formation and has been implicated in the recruitment and tethering of P. falciparum erythrocyte membrane protein–1 (PfEMP1) by binding to its cytoplasmic domain termed VARC. However, the precise mechanism of interaction between KAHRP and VARC is not very well understood. Here we report that both the proteins co-localize to membrane knobs of P. falciparum infected erythrocytes and have identified four positively charged linear sequence motifs of high intrinsic mobility on KAHRP that interact electrostatically with VARC in solution to form a fuzzy complex. The current study provides molecular insight into interaction between KAHRP and VARC in solution that takes place at membrane knobs.
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181
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Antisense long noncoding RNAs regulate var gene activation in the malaria parasite Plasmodium falciparum. Proc Natl Acad Sci U S A 2015; 112:E982-91. [PMID: 25691743 DOI: 10.1073/pnas.1420855112] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The virulence of Plasmodium falciparum, the causative agent of the deadliest form of human malaria, is attributed to its ability to evade human immunity through antigenic variation. These parasites alternate between expression of variable antigens, encoded by members of a multicopy gene family named var. Immune evasion through antigenic variation depends on tight regulation of var gene expression, ensuring that only a single var gene is expressed at a time while the rest of the family is maintained transcriptionally silent. Understanding how a single gene is chosen for activation is critical for understanding mutually exclusive expression but remains a mystery. Here, we show that antisense long noncoding RNAs (lncRNAs) initiating from var introns are associated with the single active var gene at the time in the cell cycle when the single var upstream promoter is active. We demonstrate that these antisense transcripts are incorporated into chromatin, and that expression of these antisense lncRNAs in trans triggers activation of a silent var gene in a sequence- and dose-dependent manner. On the other hand, interference with these lncRNAs using complement peptide nucleic acid molecules down-regulated the active var gene, erased the epigenetic memory, and induced expression switching. Altogether, our data provide evidence that these antisense lncRNAs play a key role in regulating var gene activation and mutually exclusive expression.
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182
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Ye R, Zhang D, Chen B, Zhu Y, Zhang Y, Wang S, Pan W. Transcription of the var genes from a freshly-obtained field isolate of Plasmodium falciparum shows more variable switching patterns than long laboratory-adapted isolates. Malar J 2015; 14:66. [PMID: 25889871 PMCID: PMC4332720 DOI: 10.1186/s12936-015-0565-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 01/15/2015] [Indexed: 11/15/2022] Open
Abstract
Background Antigenic variation in Plasmodium falciparum involves switching among multicopy var gene family and is responsible for immune evasion and the maintenance of chronic infections. Current understanding of var gene expression and switching patterns comes from experiments conducted on long laboratory-adapted strains, with little known about their wild counterparts. Methods Genome sequencing was used to obtain 50 var genes from a parasite isolated from the China-Myanmar border. Four clones with different dominant var genes were cultured in vitro in replicates for 50 generations. Transcription of the individual var gene was detected by real-time PCR and then the switching process was analysed. Results The expression of multicopy var genes is mutually exclusive in clones of a wild P. falciparum isolate. The activation of distinct primary dominant var genes leads to different and favoured switching patterns in the four clones. The on/off rates of individual var genes are variable and the choice of subsequent dominant var genes are random, which results in the different switching patterns among replicates of each clonal wild P. falciparum isolate with near identical initial transcription profiles. Conclusions This study suggests that the switching patterns of var genes are abundant, which consist of both conserved and random parts. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0565-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Run Ye
- Department of Tropical Infectious Disease, Second Military Medical University, Shanghai, 200433, China.
| | - Dongmei Zhang
- Department of Tropical Infectious Disease, Second Military Medical University, Shanghai, 200433, China.
| | - Biaobang Chen
- Department of Tropical Infectious Disease, Second Military Medical University, Shanghai, 200433, China.
| | - Yongqiang Zhu
- Shanghai-Ministry of Science and Technology Key Laboratory of Health and Disease Genomics, Chinese National Human Genome Center at Shanghai, Shanghai, 201203, China.
| | - Yilong Zhang
- Institute for Infectious Diseases and Vaccine Development, Tongji University School of Medicine, Shanghai, 200092, China.
| | - Shengyue Wang
- Shanghai-Ministry of Science and Technology Key Laboratory of Health and Disease Genomics, Chinese National Human Genome Center at Shanghai, Shanghai, 201203, China.
| | - Weiqing Pan
- Department of Tropical Infectious Disease, Second Military Medical University, Shanghai, 200433, China. .,Institute for Infectious Diseases and Vaccine Development, Tongji University School of Medicine, Shanghai, 200092, China.
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183
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Stevenson L, Huda P, Jeppesen A, Laursen E, Rowe JA, Craig A, Streicher W, Barfod L, Hviid L. Investigating the function of Fc-specific binding of IgM to Plasmodium falciparum erythrocyte membrane protein 1 mediating erythrocyte rosetting. Cell Microbiol 2015; 17:819-31. [PMID: 25482886 PMCID: PMC4737123 DOI: 10.1111/cmi.12403] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 11/28/2014] [Accepted: 12/01/2014] [Indexed: 02/02/2023]
Abstract
Acquired protection from Plasmodium falciparum malaria takes years to develop, probably reflecting the ability of the parasites to evade immunity. A recent example of this is the binding of the Fc region of IgM to VAR2CSA‐type PfEMP1. This interferes with specific IgG recognition and phagocytosis of opsonized infected erythrocytes (IEs) without compromising the placental IE adhesion mediated by this PfEMP1 type. IgM also binds via Fc to several other PfEMP1 proteins, where it has been proposed to facilitate rosetting (binding of uninfected erythrocytes to a central IE). To further dissect the functional role of Fc‐mediated IgM binding to PfEMP1, we studied the PfEMP1 protein HB3VAR06, which mediates rosetting and binds IgM. Binding of IgM to this PfEMP1 involved the Fc domains Cμ3‐Cμ4 in IgM and the penultimate DBL domain (DBLζ2) at the C‐terminus of HB3VAR06. However, IgM binding did not inhibit specific IgG labelling of HB3VAR06 or shield IgG‐opsonized IEs from phagocytosis. Instead, IgM was required for rosetting, and each pentameric IgM molecule could bind two HB3VAR06 molecules. Together, our data indicate that the primary function of Fc‐mediated IgM binding in rosetting is not to shield IE from specific IgG recognition and phagocytosis as in VAR2CSA‐type PfEMP1. Rather, the function appears to be strengthening of IE–erythrocyte interactions. In conclusion, our study provides new evidence on the molecular details and functional significance of rosetting, a long‐recognized marker of parasites that cause severe P. falciparum malaria.
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Affiliation(s)
- Liz Stevenson
- Centre for Medical Parasitology, Department of International Health, Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - Pie Huda
- Niels Bohr Institute, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Anine Jeppesen
- Centre for Medical Parasitology, Department of International Health, Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - Erik Laursen
- Centre for Medical Parasitology, Department of International Health, Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - J Alexandra Rowe
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, UK
| | - Alister Craig
- Liverpool School of Tropical Medicine, Liverpool, UK
| | - Werner Streicher
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Lea Barfod
- Centre for Medical Parasitology, Department of International Health, Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - Lars Hviid
- Centre for Medical Parasitology, Department of International Health, Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
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184
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Tessema SK, Monk SL, Schultz MB, Tavul L, Reeder JC, Siba PM, Mueller I, Barry AE. Phylogeography of var gene repertoires reveals fine-scale geospatial clustering of Plasmodium falciparum populations in a highly endemic area. Mol Ecol 2015; 24:484-97. [PMID: 25482097 DOI: 10.1111/mec.13033] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 11/14/2014] [Accepted: 11/17/2014] [Indexed: 11/28/2022]
Abstract
Plasmodium falciparum malaria is a major global health problem that is being targeted for progressive elimination. Knowledge of local disease transmission patterns in endemic countries is critical to these elimination efforts. To investigate fine-scale patterns of malaria transmission, we have compared repertoires of rapidly evolving var genes in a highly endemic area. A total of 3680 high-quality DBLα-sequences were obtained from 68 P. falciparum isolates from ten villages spread over two distinct catchment areas on the north coast of Papua New Guinea (PNG). Modelling of the extent of var gene diversity in the two parasite populations predicts more than twice as many var gene alleles circulating within each catchment (Mugil = 906; Wosera = 1094) than previously recognized in PNG (Amele = 369). In addition, there were limited levels of var gene sharing between populations, consistent with local parasite population structure. Phylogeographic analyses demonstrate that while neutrally evolving microsatellite markers identified population structure only at the catchment level, var gene repertoires reveal further fine-scale geospatial clustering of parasite isolates. The clustering of parasite isolates by village in Mugil, but not in Wosera was consistent with the physical and cultural isolation of the human populations in the two catchments. The study highlights the microheterogeneity of P. falciparum transmission in highly endemic areas and demonstrates the potential of var genes as markers of local patterns of parasite population structure.
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Affiliation(s)
- Sofonias K Tessema
- Division of Infection and Immunity, Walter and Eliza Hall Institute, 3052, Melbourne, Vic., Australia; Department of Medical Biology, University of Melbourne, 3052, Melbourne, Vic., Australia
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185
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Abstract
Plasmodium falciparum-infected red blood cells (IRBC) adhere to the endothelium via receptors expressed on the surface of vascular endothelial cells (EC) and sequester in the microvasculature of several organs. Sequestration is the primary step leading to complications related to the severity of malaria. In order to study this cytoadhesion phenomenon, IRBC in vitro binding assays have been developed using a monolayer of primary or transformed endothelial cells. Here we describe the methodology of an assay to inhibit the binding of IRBC on vascular endothelial cells under static adhesion conditions. Similar techniques could be used for conducting a binding inhibition assay under flow assay conditions using an appropriate device.
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Affiliation(s)
- Marion Avril
- Center for Infectious Disease Research formerly known as Seattle Biomedical research Institute, 307 Westlake Avenue North, Suite 500, Seattle, WA, 98109, USA.
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186
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Llama immunization with full-length VAR2CSA generates cross-reactive and inhibitory single-domain antibodies against the DBL1X domain. Sci Rep 2014; 4:7373. [PMID: 25487735 PMCID: PMC5376981 DOI: 10.1038/srep07373] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 11/10/2014] [Indexed: 12/11/2022] Open
Abstract
VAR2CSA stands today as the leading vaccine candidate aiming to protect future pregnant women living in malaria endemic areas against the severe clinical outcomes of pregnancy associated malaria (PAM). The rational design of an efficient VAR2CSA-based vaccine relies on a profound understanding of the molecular interactions associated with P. falciparum infected erythrocyte sequestration in the placenta. Following immunization of a llama with the full-length VAR2CSA recombinant protein, we have expressed and characterized a panel of 19 nanobodies able to recognize the recombinant VAR2CSA as well as the surface of erythrocytes infected with parasites originating from different parts of the world. Domain mapping revealed that a large majority of nanobodies targeted DBL1X whereas a few of them were directed towards DBL4ε, DBL5ε and DBL6ε. One nanobody targeting the DBL1X was able to recognize the native VAR2CSA protein of the three parasite lines tested. Furthermore, four nanobodies targeting DBL1X reproducibly inhibited CSA adhesion of erythrocytes infected with the homologous NF54-CSA parasite strain, providing evidences that DBL1X domain is part or close to the CSA binding site. These nanobodies could serve as useful tools to identify conserved epitopes shared between different variants and to characterize the interactions between VAR2CSA and CSA.
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187
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Structural conservation despite huge sequence diversity allows EPCR binding by the PfEMP1 family implicated in severe childhood malaria. Cell Host Microbe 2014; 17:118-29. [PMID: 25482433 PMCID: PMC4297295 DOI: 10.1016/j.chom.2014.11.007] [Citation(s) in RCA: 129] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Revised: 09/27/2014] [Accepted: 10/30/2014] [Indexed: 11/20/2022]
Abstract
The PfEMP1 family of surface proteins is central for Plasmodium falciparum virulence and must retain the ability to bind to host receptors while also diversifying to aid immune evasion. The interaction between CIDRα1 domains of PfEMP1 and endothelial protein C receptor (EPCR) is associated with severe childhood malaria. We combine crystal structures of CIDRα1:EPCR complexes with analysis of 885 CIDRα1 sequences, showing that the EPCR-binding surfaces of CIDRα1 domains are conserved in shape and bonding potential, despite dramatic sequence diversity. Additionally, these domains mimic features of the natural EPCR ligand and can block this ligand interaction. Using peptides corresponding to the EPCR-binding region, antibodies can be purified from individuals in malaria-endemic regions that block EPCR binding of diverse CIDRα1 variants. This highlights the extent to which such a surface protein family can diversify while maintaining ligand-binding capacity and identifies features that should be mimicked in immunogens to prevent EPCR binding. EPCR binding is retained by PfEMP1 CIDRα1 domains despite huge sequence variation Diverse CIDRα1 domains retain structural and chemical features to bind to EPCR CIDRα1 domains mimic features of a natural ligand of EPCR and block its binding Patient sera contain neutralizing antibodies that prevent parasite binding to EPCR
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188
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Ay F, Bunnik EM, Varoquaux N, Vert JP, Noble WS, Le Roch KG. Multiple dimensions of epigenetic gene regulation in the malaria parasite Plasmodium falciparum: gene regulation via histone modifications, nucleosome positioning and nuclear architecture in P. falciparum. Bioessays 2014; 37:182-94. [PMID: 25394267 DOI: 10.1002/bies.201400145] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Plasmodium falciparum is the most deadly human malarial parasite, responsible for an estimated 207 million cases of disease and 627,000 deaths in 2012. Recent studies reveal that the parasite actively regulates a large fraction of its genes throughout its replicative cycle inside human red blood cells and that epigenetics plays an important role in this precise gene regulation. Here, we discuss recent advances in our understanding of three aspects of epigenetic regulation in P. falciparum: changes in histone modifications, nucleosome occupancy and the three-dimensional genome structure. We compare these three aspects of the P. falciparum epigenome to those of other eukaryotes, and show that large-scale compartmentalization is particularly important in determining histone decomposition and gene regulation in P. falciparum. We conclude by presenting a gene regulation model for P. falciparum that combines the described epigenetic factors, and by discussing the implications of this model for the future of malaria research.
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Affiliation(s)
- Ferhat Ay
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
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189
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Immune characterization of Plasmodium falciparum parasites with a shared genetic signature in a region of decreasing transmission. Infect Immun 2014; 83:276-85. [PMID: 25368109 DOI: 10.1128/iai.01979-14] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
As the intensity of malaria transmission has declined, Plasmodium falciparum parasite populations have displayed decreased clonal diversity resulting from the emergence of many parasites with common genetic signatures (CGS). We have monitored such CGS parasite clusters from 2006 to 2013 in Thiès, Senegal, using the molecular barcode. The first, and one of the largest observed clusters of CGS parasites, was present in 24% of clinical isolates in 2008, declined to 3.4% of clinical isolates in 2009, and then disappeared. To begin to explore the relationship between the immune responses of the population and the emergence and decline of specific parasite genotypes, we have determined whether antibodies to CGS parasites correlate with their prevalence. We measured (i) antibodies capable of inhibiting parasite growth in culture and (ii) antibodies recognizing the surfaces of infected erythrocytes (RBCs). IgG obtained from volunteers in 2009 showed increased reactivity to the surfaces of CGS-parasitized erythrocytes over IgG from 2008. Since P. falciparum EMP-1 (PfEMP-1) is a major variant surface antigen, we used var Ups quantitative reverse transcription-PCR (qRT-PCR) and sequencing with degenerate DBL1α domain primers to characterize the var genes expressed by CGS parasites after short-term in vitro culture. CGS parasites show upregulation of UpsA var genes and 2-cysteine-containing PfEMP-1 molecules and express the same dominant var transcript. Our work indicates that the CGS parasites in this cluster express similar var genes, more than would be expected by chance in the population, and that there is year-to-year variation in immune recognition of surface antigens on CGS parasite-infected erythrocytes. This study lays the groundwork for detailed investigations of the mechanisms driving the expansion or contraction of specific parasite clones in the population.
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190
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Madkhali AM, Alkurbi MO, Szestak T, Bengtsson A, Patil PR, Wu Y, Alharthi S, Jensen ATR, Pleass R, Craig AG. An analysis of the binding characteristics of a panel of recently selected ICAM-1 binding Plasmodium falciparum patient isolates. PLoS One 2014; 9:e111518. [PMID: 25360558 PMCID: PMC4216080 DOI: 10.1371/journal.pone.0111518] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 09/30/2014] [Indexed: 12/21/2022] Open
Abstract
The basis of severe malaria pathogenesis in part includes sequestration of Plasmodium falciparum-infected erythrocytes (IE) from the peripheral circulation. This phenomenon is mediated by the interaction between several endothelial receptors and one of the main parasite-derived variant antigens (PfEMP1) expressed on the surface of the infected erythrocyte membrane. One of the commonly used host receptors is ICAM-1, and it has been suggested that ICAM-1 has a role in cerebral malaria pathology, although the evidence to support this is not conclusive. The current study examined the cytoadherence patterns of lab-adapted patient isolates after selecting on ICAM-1. We investigated the binding phenotypes using variant ICAM-1 proteins including ICAM-1Ref, ICAM-1Kilifi, ICAM-1S22/A, ICAM-1L42/A and ICAM-1L44/A using static assays. The study also examined ICAM-1 blocking by four anti-ICAM-1 monoclonal antibodies (mAb) under static conditions. We also characterised the binding phenotypes using Human Dermal Microvascular Endothelial Cells (HDMEC) under flow conditions. The results show that different isolates have variant-specific binding phenotypes under both static and flow conditions, extending our previous observations that this variation might be due to variable contact residues on ICAM-1 being used by different parasite PfEMP1 variants.
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Affiliation(s)
- Aymen M. Madkhali
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- Department of Medical Laboratories Technology, College of Applied Medical Sciences, Jazan University, Jazan, Kingdom of Saudi Arabia
| | - Mohammed O. Alkurbi
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- Department of Laboratory Medicine, College of Applied Medical Sciences, Umm Al-Qura University, Makkah Al-Mukarramah, Kingdom of Saudi Arabia
| | - Tadge Szestak
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Anja Bengtsson
- Centre for Medical Parasitology, Department of International Health, Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Pradeep R. Patil
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Yang Wu
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Saeed Alharthi
- Department of Laboratory Medicine, College of Applied Medical Sciences, Umm Al-Qura University, Makkah Al-Mukarramah, Kingdom of Saudi Arabia
| | - Anja T. R. Jensen
- Centre for Medical Parasitology, Department of International Health, Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Richard Pleass
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Alister G. Craig
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- * E-mail:
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191
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Goel S, Muthusamy A, Miao J, Cui L, Salanti A, Winzeler EA, Gowda DC. Targeted disruption of a ring-infected erythrocyte surface antigen (RESA)-like export protein gene in Plasmodium falciparum confers stable chondroitin 4-sulfate cytoadherence capacity. J Biol Chem 2014; 289:34408-21. [PMID: 25342752 DOI: 10.1074/jbc.m114.615393] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family proteins mediate the adherence of infected erythrocytes to microvascular endothelia of various organs, including the placenta, thereby contributing to cerebral, placental, and other severe malaria pathogenesis. Several parasite proteins, including KAHRP and PfEMP3, play important roles in the cytoadherence by mediating the clustering of PfEMP1 in rigid knoblike structures on the infected erythrocyte surface. The lack of a subtelomeric region of chromosome 2 that contains kahrp and pfemp3 causes reduced cytoadherence. In this study, microarray transcriptome analysis showed that the absence of a gene cluster, comprising kahrp, pfemp3, and four other genes, results in the loss of parasitized erythrocytes adhering to chondroitin 4-sulfate (C4S). The role of one of these genes, PF3D7_0201600/PFB0080c, which encodes PHISTb (Plasmodium helical interspersed subtelomeric b) domain-containing RESA-like protein 1 expressed on the infected erythrocyte surface, was investigated. Disruption of PFB0080c resulted in increased var2csa transcription and VAR2CSA surface expression, leading to higher C4S-binding capacity of infected erythrocytes. Further, PFB0080c-knock-out parasites stably maintained the C4S adherence through many generations of growth. Although the majority of PFB0080c-knock-out parasites bound to C4S even after culturing for 6 months, a minor population bound to both C4S and CD36. These results strongly suggest that the loss of PFB0080c markedly compromises the var gene switching process, leading to a marked reduction in the switching rate and additional PfEMP1 expression by a minor population of parasites. PFB0080c interacts with VAR2CSA and modulates knob-associated Hsp40 expression. Thus, PFB0080c may regulate VAR2CSA expression through these processes. Overall, we conclude that PFB0080c regulates PfEMP1 expression and the parasite's cytoadherence.
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Affiliation(s)
- Suchi Goel
- From the Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033,
| | - Arivalagan Muthusamy
- From the Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033
| | - Jun Miao
- the Department of Entomology, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Liwang Cui
- the Department of Entomology, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Ali Salanti
- the Centre for Medical Parasitology at the Department of International Health, Immunology, and Microbiology, Copenhagen University Hospital, DK 2014 Copenhagen, Denmark, and
| | - Elizabeth A Winzeler
- the Department of Pediatrics, University of California San Diego School of Medicine, La Jolla, California 92093
| | - D Channe Gowda
- From the Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033,
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192
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Histone H3K9 acetylation level modulates gene expression and may affect parasite growth in human malaria parasitePlasmodium falciparum. FEBS J 2014; 281:5265-78. [DOI: 10.1111/febs.13067] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Revised: 09/15/2014] [Accepted: 09/19/2014] [Indexed: 12/22/2022]
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193
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Sundriyal S, Malmquist NA, Caron J, Blundell S, Liu F, Chen X, Srimongkolpithak N, Jin J, Charman SA, Scherf A, Fuchter MJ. Development of diaminoquinazoline histone lysine methyltransferase inhibitors as potent blood-stage antimalarial compounds. ChemMedChem 2014; 9:2360-2373. [PMID: 25044750 PMCID: PMC4177335 DOI: 10.1002/cmdc.201402098] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Indexed: 11/07/2022]
Abstract
Modulating epigenetic mechanisms in malarial parasites is an emerging avenue for the discovery of novel antimalarial drugs. Previously we demonstrated the potent in vitro and in vivo antimalarial activity of (1-benzyl-4-piperidyl)[6,7-dimethoxy-2-(4-methyl-1,4-diazepin-1-yl)-4-quinazolinyl]amine (BIX01294; 1), a known human G9a inhibitor, together with its dose-dependent effects on histone methylation in the malarial parasite. This work describes our initial medicinal chemistry efforts to optimise the diaminoquinazoline chemotype for antimalarial activity. A variety of analogues were designed by substituting the 2 and 4 positions of the quinazoline core, and these molecules were tested against Plasmodium falciparum (3D7 strain). Several analogues with IC50 values as low as 18.5 nM and with low mammalian cell toxicity (HepG2) were identified. Certain pharmacophoric features required for antimalarial activity were found to be analogous to the previously published SAR of these analogues for G9a inhibition, thereby suggesting potential similarities between the malarial and human HKMT targets of this chemotype. Physiochemical, in vitro activity, and in vitro metabolism studies were also performed for a select set of potent analogues to evaluate their potential as antimalarial leads.
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Affiliation(s)
- Sandeep Sundriyal
- Department of Chemistry, Imperial College London, London SW7 2AZ, United Kingdom
| | - Nicholas A. Malmquist
- Unité de Biologie des Interactions Hôte-Parasite, Institut Pasteur, F-75724 Paris CEDEX 15, France
- Centre National de la Recherche Scientifique, Unité de Recherche Associée 2581, F-75724 Paris CEDEX 15, France
| | - Joachim Caron
- Department of Chemistry, Imperial College London, London SW7 2AZ, United Kingdom
| | - Scott Blundell
- Monash Institute of Pharmaceutical Sciences, 381 Royal Parade, Parkville, Victoria 3052, Australia
| | - Feng Liu
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, 26 Chapel Hill, North Carolina 27599, United States
| | - Xin Chen
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, 26 Chapel Hill, North Carolina 27599, United States
| | | | - Jian Jin
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, 26 Chapel Hill, North Carolina 27599, United States
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Susan A. Charman
- Monash Institute of Pharmaceutical Sciences, 381 Royal Parade, Parkville, Victoria 3052, Australia
| | - Artur Scherf
- Unité de Biologie des Interactions Hôte-Parasite, Institut Pasteur, F-75724 Paris CEDEX 15, France
- Centre National de la Recherche Scientifique, Unité de Recherche Associée 2581, F-75724 Paris CEDEX 15, France
| | - Matthew J. Fuchter
- Department of Chemistry, Imperial College London, London SW7 2AZ, United Kingdom
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194
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Otto TD, Rayner JC, Böhme U, Pain A, Spottiswoode N, Sanders M, Quail M, Ollomo B, Renaud F, Thomas AW, Prugnolle F, Conway DJ, Newbold C, Berriman M. Genome sequencing of chimpanzee malaria parasites reveals possible pathways of adaptation to human hosts. Nat Commun 2014; 5:4754. [PMID: 25203297 PMCID: PMC4166903 DOI: 10.1038/ncomms5754] [Citation(s) in RCA: 114] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 07/18/2014] [Indexed: 01/19/2023] Open
Abstract
Plasmodium falciparum causes most human malaria deaths, having prehistorically evolved from parasites of African Great Apes. Here we explore the genomic basis of P. falciparum adaptation to human hosts by fully sequencing the genome of the closely related chimpanzee parasite species P. reichenowi, and obtaining partial sequence data from a more distantly related chimpanzee parasite (P. gaboni). The close relationship between P. reichenowi and P. falciparum is emphasized by almost complete conservation of genomic synteny, but against this strikingly conserved background we observe major differences at loci involved in erythrocyte invasion. The organization of most virulence-associated multigene families, including the hypervariable var genes, is broadly conserved, but P. falciparum has a smaller subset of rif and stevor genes whose products are expressed on the infected erythrocyte surface. Genome-wide analysis identifies other loci under recent positive selection, but a limited number of changes at the host-parasite interface may have mediated host switching.
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Affiliation(s)
- Thomas D. Otto
- Parasite Genomics, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge CB10 1SA, UK
| | - Julian C. Rayner
- Parasite Genomics, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge CB10 1SA, UK
| | - Ulrike Böhme
- Parasite Genomics, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge CB10 1SA, UK
| | - Arnab Pain
- Parasite Genomics, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge CB10 1SA, UK
- Biological and Environmental Sciences and Engineering (BESE) Division, Computational Bioscience Research Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Natasha Spottiswoode
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland 20852, USA
- Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | - Mandy Sanders
- Parasite Genomics, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge CB10 1SA, UK
| | - Michael Quail
- Parasite Genomics, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge CB10 1SA, UK
| | - Benjamin Ollomo
- Centre International de Recherches Médicales de Franceville, CIRMF, BP 769 Franceville, Gabon
| | - François Renaud
- Laboratoire MIVEGEC, UMR 5290 CNRS-IRD-UMI-UMII, IRD, BP 64501, 34394 Montpellier, France
| | - Alan W. Thomas
- Biomedical Primate Research Centre, Department of Parasitology, 2280 GH Rijswijk, The Netherlands
| | - Franck Prugnolle
- Centre International de Recherches Médicales de Franceville, CIRMF, BP 769 Franceville, Gabon
- Laboratoire MIVEGEC, UMR 5290 CNRS-IRD-UMI-UMII, IRD, BP 64501, 34394 Montpellier, France
| | - David J. Conway
- Department of Pathogen Molecular Biology, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK
| | - Chris Newbold
- Parasite Genomics, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge CB10 1SA, UK
- Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
- These authors contributed equally to this work
| | - Matthew Berriman
- Parasite Genomics, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge CB10 1SA, UK
- These authors contributed equally to this work
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195
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Coleman BI, Skillman KM, Jiang RHY, Childs LM, Altenhofen LM, Ganter M, Leung Y, Goldowitz I, Kafsack BF, Marti M, Llinás M, Buckee CO, Duraisingh MT. A Plasmodium falciparum histone deacetylase regulates antigenic variation and gametocyte conversion. Cell Host Microbe 2014; 16:177-186. [PMID: 25121747 PMCID: PMC4188636 DOI: 10.1016/j.chom.2014.06.014] [Citation(s) in RCA: 156] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Revised: 05/06/2014] [Accepted: 06/06/2014] [Indexed: 01/20/2023]
Abstract
The asexual forms of the malaria parasite Plasmodium falciparum are adapted for chronic persistence in human red blood cells, continuously evading host immunity using epigenetically regulated antigenic variation of virulence-associated genes. Parasite survival on a population level also requires differentiation into sexual forms, an obligatory step for further human transmission. We reveal that the essential nuclear gene, P. falciparum histone deacetylase 2 (PfHda2), is a global silencer of virulence gene expression and controls the frequency of switching from the asexual cycle to sexual development. PfHda2 depletion leads to dysregulated expression of both virulence-associated var genes and PfAP2-g, a transcription factor controlling sexual conversion, and is accompanied by increases in gametocytogenesis. Mathematical modeling further indicates that PfHda2 has likely evolved to optimize the parasite's infectious period by achieving low frequencies of virulence gene expression switching and sexual conversion. This common regulation of cellular transcriptional programs mechanistically links parasite transmissibility and virulence.
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Affiliation(s)
- Bradley I. Coleman
- Department of Immunology & Infectious Diseases Harvard School of Public Health, Boston, MA 02115 USA
| | - Kristen M. Skillman
- Department of Immunology & Infectious Diseases Harvard School of Public Health, Boston, MA 02115 USA
| | - Rays H. Y. Jiang
- Department of Immunology & Infectious Diseases Harvard School of Public Health, Boston, MA 02115 USA
| | - Lauren M. Childs
- Department of Epidemiology and Center for Communicable Disease Dynamics, Harvard School of Public Health, Boston MA 02115 USA
| | - Lindsey M. Altenhofen
- Department of Molecular Biology and Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton NJ 08544 USA
| | - Markus Ganter
- Department of Immunology & Infectious Diseases Harvard School of Public Health, Boston, MA 02115 USA
| | - Yvette Leung
- Department of Immunology & Infectious Diseases Harvard School of Public Health, Boston, MA 02115 USA
| | - Ilana Goldowitz
- Department of Immunology & Infectious Diseases Harvard School of Public Health, Boston, MA 02115 USA
| | - Björn F.C. Kafsack
- Department of Molecular Biology and Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton NJ 08544 USA
| | - Matthias Marti
- Department of Immunology & Infectious Diseases Harvard School of Public Health, Boston, MA 02115 USA
| | - Manuel Llinás
- Department of Molecular Biology and Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton NJ 08544 USA
| | - Caroline O. Buckee
- Department of Epidemiology and Center for Communicable Disease Dynamics, Harvard School of Public Health, Boston MA 02115 USA
| | - Manoj T. Duraisingh
- Department of Immunology & Infectious Diseases Harvard School of Public Health, Boston, MA 02115 USA
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196
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The role of PfEMP1 adhesion domain classification in Plasmodium falciparum pathogenesis research. Mol Biochem Parasitol 2014; 195:82-7. [PMID: 25064606 DOI: 10.1016/j.molbiopara.2014.07.006] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 06/14/2014] [Accepted: 07/14/2014] [Indexed: 11/24/2022]
Abstract
The Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family has a key role in parasite survival, transmission, and virulence. PfEMP1 are exported to the erythrocyte membrane and mediate binding of infected erythrocytes to the endothelial lining of blood vessels. This process aids parasite survival by avoiding spleen-dependent killing mechanisms, but it is associated with adhesion-based disease complications. Switching between PfEMP1 proteins enables parasites to evade host immunity and modifies parasite tropism for different microvascular beds. The PfEMP1 protein family is one of the most diverse adhesion modules in nature. This review covers PfEMP1 adhesion domain classification and the significant role it is playing in deciphering and deconvoluting P. falciparum cytoadhesion and disease.
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197
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Vembar SS, Scherf A, Siegel TN. Noncoding RNAs as emerging regulators of Plasmodium falciparum virulence gene expression. Curr Opin Microbiol 2014; 20:153-61. [PMID: 25022240 PMCID: PMC4157322 DOI: 10.1016/j.mib.2014.06.013] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 06/15/2014] [Accepted: 06/20/2014] [Indexed: 11/15/2022]
Abstract
The eukaryotic unicellular pathogen Plasmodium falciparum tightly regulates gene expression, both during development and in adaptation to dynamic host environments. This regulation is evident in the mutually exclusive expression of members of clonally variant virulence multigene families. While epigenetic regulators have been selectively identified at active or repressed virulence genes, their specific recruitment remains a mystery. In recent years, noncoding RNAs (ncRNAs) have emerged as lynchpins of eukaryotic gene regulation; by binding to epigenetic regulators, they provide target specificity to otherwise non-specific enzyme complexes. Not surprisingly, there is great interest in understanding the role of ncRNA in P. falciparum, in particular, their contribution to the mutually exclusive expression of virulence genes. The current repertoire of P. falciparum ncRNAs includes, but is not limited to, subtelomeric ncRNAs, virulence gene-associated ncRNAs and natural antisense RNA transcripts. Continued improvement in high-throughput sequencing methods is sure to expand this repertoire. Here, we summarize recent advances in P. falciparum ncRNA biology, with an emphasis on ncRNA-mediated epigenetic modes of gene regulation.
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Affiliation(s)
- Shruthi S Vembar
- Biology of Host-Parasite Interactions Unit, Institut Pasteur, Paris, France; CNRS URA2581, Paris, France
| | - Artur Scherf
- Biology of Host-Parasite Interactions Unit, Institut Pasteur, Paris, France; CNRS URA2581, Paris, France
| | - T Nicolai Siegel
- Research Center for Infectious Diseases, University of Wuerzburg, Josef-Schneider-Str. 2/Bau D15, 97080 Wuerzburg, Germany.
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198
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Brancucci NMB, Witmer K, Schmid C, Voss TS. A var gene upstream element controls protein synthesis at the level of translation initiation in Plasmodium falciparum. PLoS One 2014; 9:e100183. [PMID: 24937593 PMCID: PMC4061111 DOI: 10.1371/journal.pone.0100183] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Accepted: 05/23/2014] [Indexed: 01/14/2023] Open
Abstract
Clonally variant protein expression in the malaria parasite Plasmodium falciparum generates phenotypic variability and allows isogenic populations to adapt to environmental changes encountered during blood stage infection. The underlying regulatory mechanisms are best studied for the major virulence factor P. falciparum erythrocyte membrane protein 1 (PfEMP1). PfEMP1 is encoded by the multicopy var gene family and only a single variant is expressed in individual parasites, a concept known as mutual exclusion or singular gene choice. var gene activation occurs in situ and is achieved through the escape of one locus from epigenetic silencing. Singular gene choice is controlled at the level of transcription initiation and var 5' upstream (ups) sequences harbour regulatory information essential for mutually exclusive transcription as well as for the trans-generational inheritance of the var activity profile. An additional level of control has recently been identified for the var2csa gene, where an mRNA element in the 5' untranslated region (5' UTR) is involved in the reversible inhibition of translation of var2csa transcripts. Here, we extend the knowledge on post-transcriptional var gene regulation to the common upsC type. We identified a 5' UTR sequence that inhibits translation of upsC-derived mRNAs. Importantly, this 5' UTR element efficiently inhibits translation even in the context of a heterologous upstream region. Further, we found var 5' UTRs to be significantly enriched in uAUGs which are known to impair the efficiency of protein translation in other eukaryotes. Our findings suggest that regulation at the post-transcriptional level is a common feature in the control of PfEMP1 expression in P. falciparum.
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Affiliation(s)
- Nicolas M. B. Brancucci
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Kathrin Witmer
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Christoph Schmid
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Till S. Voss
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- * E-mail:
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199
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Torgbor C, Awuah P, Deitsch K, Kalantari P, Duca KA, Thorley-Lawson DA. A multifactorial role for P. falciparum malaria in endemic Burkitt's lymphoma pathogenesis. PLoS Pathog 2014; 10:e1004170. [PMID: 24874410 PMCID: PMC4038605 DOI: 10.1371/journal.ppat.1004170] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Accepted: 04/15/2014] [Indexed: 02/01/2023] Open
Abstract
Endemic Burkitt's lymphoma (eBL) arises from the germinal center (GC). It is a common tumor of young children in tropical Africa and its occurrence is closely linked geographically with the incidence of P. falciparum malaria. This association was noted more than 50 years ago. Since then we have learned that eBL contains the oncogenic herpes virus Epstein-Barr virus (EBV) and a defining translocation that activates the c-myc oncogene. However the link to malaria has never been explained. Here we provide evidence for a mechanism arising in the GC to explain this association. Accumulated evidence suggests that eBL arises in the GC when deregulated expression of AID (Activation-induced cytidine deaminase) causes a c-myc translocation in a cell latently infected with Epstein-Barr virus (EBV). Here we show that P. falciparum targets GC B cells via multiple pathways to increase the risk of eBL. 1. It causes deregulated expression of AID, thereby increasing the risk of a c-myc translocation. 2. It increases the number of B cells transiting the GC. 3. It dramatically increases the frequency of these cells that are infected with EBV and therefore protected from c-myc induced apoptosis. We propose that these activities combine synergistically to dramatically increase the incidence of eBL in individuals infected with malaria. Endemic Burkitt's lymphoma (eBL) is a common tumor of young children in tropical Africa that is closely linked geographically with P. falciparum malaria. This association was noted more than 50 years ago. Since then we have learned that eBL contains the oncogenic herpes virus Epstein-Barr virus and a defining translocation that activates the c-myc oncogene. However the link to malaria has never been explained. Here we show that malaria has multiple effects that all focus on germinal center (GC) B cells that are known to be the origin of eBL. Together these effects of malaria act synergistically to dramatically increase the risk of developing eBL in individuals infected with the parasite. Clinical interventions that lessen the impact of malaria on GC B cells should dramatically decrease the incidence eBL.
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Affiliation(s)
- Charles Torgbor
- Tufts University School of Medicine, Boston, Massachusetts, United States of America
- Department of Biochemistry and Biotechnology, Kwame Nkrumah University of Science and Technology (KNUST) and Kumasi Centre for Collaborative Research, Kumasi, Ghana
| | - Peter Awuah
- EENT Clinic, Komfo Anokye Teaching Hospital (KATH) and PAKS Hospital, Kumasi, Ghana
| | - Kirk Deitsch
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America
| | - Parisa Kalantari
- University of Massachusetts Medical School, Department of Medicine, Division of Immunology and Infectious Diseases, Worcester, Massachusetts, United States of America
| | - Karen A. Duca
- Department of Biochemistry and Biotechnology, Kwame Nkrumah University of Science and Technology (KNUST) and Kumasi Centre for Collaborative Research, Kumasi, Ghana
| | - David A. Thorley-Lawson
- Tufts University School of Medicine, Boston, Massachusetts, United States of America
- * E-mail:
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200
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Hasang W, Dembo EG, Wijesinghe R, Molyneux ME, Kublin JG, Rogerson S. HIV-1 infection and antibodies to Plasmodium falciparum in adults. J Infect Dis 2014; 210:1407-14. [PMID: 24795481 DOI: 10.1093/infdis/jiu262] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Coinfection with human immunodeficiency virus (HIV) may increase susceptibility to malaria by compromising naturally acquired immunity. METHODS In 339 adults (64% HIV infected), we measured antibodies to Plasmodium falciparum variant surface antigens (VSA) and antibodies that opsonise infected erythrocytes using parasite lines FCR3, E8B, and R29, and antibodies to merozoite antigens AMA-1 and MSP2. We determined the relationship between malaria antibodies, HIV infection, markers of immune compromise, and risk of incident parasitemia. RESULTS HIV-infected adults had significantly lower mean levels of opsonizing antibody to all parasite lines (P < .0001), and lower levels of antibody to AMA-1 (P = .01) and MSP2 (P < .0001). Levels of immunoglobulin G (IgG) to VSA were not affected by HIV status. Opsonising antibody titres against some isolates were positively correlated with CD4 count. There were negative associations between human immunodeficiency virus type 1 (HIV-1) viral load and opsonizing antibodies to FCR3 (P = .04), and levels of IgG to AMA-1 (P ≤ .03) and MSP2-3D7 (P = .05). Lower opsonizing antibody levels on enrollment were seen in those who became parasitemic during follow-up, independent of HIV infection (P ≤ .04 for each line). CONCLUSIONS HIV-1 infection decreases opsonizing antibodies to VSA, and antibody to merozoite antigens. Opsonizing antibodies were associated with lack of parasitemia during follow up, suggesting a role in protection.
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Affiliation(s)
- Wina Hasang
- Department of Medicine, Royal Melbourne Hospital, University of Melbourne Victorian Infectious Diseases Service, Royal Melbourne Hospital, Parkville, Victoria, Australia
| | - Edson G Dembo
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, University of Malawi College of Medicine, Blantyre
| | - Rushika Wijesinghe
- Department of Medicine, Royal Melbourne Hospital, University of Melbourne
| | - Malcolm E Molyneux
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, University of Malawi College of Medicine, Blantyre The Liverpool School of Tropical Medicine, United Kingdom
| | - James G Kublin
- Fred Hutchison Cancer Research Center, Seattle, Washington
| | - Stephen Rogerson
- Department of Medicine, Royal Melbourne Hospital, University of Melbourne Victorian Infectious Diseases Service, Royal Melbourne Hospital, Parkville, Victoria, Australia
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