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Mechanism-based model of parasite growth and dihydroartemisinin pharmacodynamics in murine malaria. Antimicrob Agents Chemother 2012; 57:508-16. [PMID: 23147722 DOI: 10.1128/aac.01463-12] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Murine models are used to study erythrocytic stages of malaria infection, because parasite morphology and development are comparable to those in human malaria infections. Mechanism-based pharmacokinetic-pharmacodynamic (PK-PD) models for antimalarials are scarce, despite their potential to optimize antimalarial combination therapy. The aim of this study was to develop a mechanism-based growth model (MBGM) for Plasmodium berghei and then characterize the parasiticidal effect of dihydroartemisinin (DHA) in murine malaria (MBGM-PK-PD). Stage-specific (ring, early trophozoite, late trophozoite, and schizont) parasite density data from Swiss mice inoculated with Plasmodium berghei were used for model development in S-ADAPT. A single dose of intraperitoneal DHA (10 to 100 mg/kg) or vehicle was administered 56 h postinoculation. The MBGM explicitly reflected all four erythrocytic stages of the 24-hour P. berghei life cycle. Merozoite invasion of erythrocytes was described by a first-order process that declined with increasing parasitemia. An efflux pathway with subsequent return was additionally required to describe the schizont data, thus representing parasite sequestration or trapping in the microvasculature, with a return to circulation. A 1-compartment model with zero-order absorption described the PK of DHA, with an estimated clearance and distribution volume of 1.95 liters h(-1) and 0.851 liter, respectively. Parasite killing was described by a turnover model, with DHA inhibiting the production of physiological intermediates (IC(50), 1.46 ng/ml). Overall, the MBGM-PK-PD described the rise in parasitemia, the nadir following DHA dosing, and subsequent parasite resurgence. This novel model is a promising tool for studying malaria infections, identifying the stage specificity of antimalarials, and providing insight into antimalarial treatment strategies.
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202
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Pathogenesis of malaria in tissues and blood. Mediterr J Hematol Infect Dis 2012; 4:e2012061. [PMID: 23170190 PMCID: PMC3499994 DOI: 10.4084/mjhid.2012.061] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Accepted: 09/21/2012] [Indexed: 01/07/2023] Open
Abstract
The clinical manifestations of severe malaria are several and occur in different anatomical sites. Both parasite- and host-related factors contribute to the pathogenicity of the severe forms of the disease. Cytoadherence of infected red blood cells to the vascular endothelium of different organs and rosetting are unique features of malaria parasites which are likely to contribute to the vascular damage and the consequent excessive inflammatory/immune response of the host. In addition to cerebral malaria or severe anaemia, which are quite common manifestation of severe malaria, clinical evidences of thrombocytopenia, acute respiratory distress syndrome (ARDS), liver and kidney disease, are reported. In primigravidae from endemic areas, life threatening placental malaria may also be present. In the following pages, some of the pathogenetic aspects will be briefly reviewed and then data on selected and less frequent manifestation of severe malaria, such as liver or renal failure or ARDS will be discussed.
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203
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Rout R, Dhangadamajhi G, Ghadei M, Mohapatra BN, Kar SK, Ranjit M. Blood group phenotypes A and B are risk factors for cerebral malaria in Odisha, India. Trans R Soc Trop Med Hyg 2012; 106:538-43. [DOI: 10.1016/j.trstmh.2012.05.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 05/30/2012] [Accepted: 05/30/2012] [Indexed: 11/25/2022] Open
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204
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Cserti-Gazdewich CM, Dhabangi A, Musoke C, Ssewanyana I, Ddungu H, Nakiboneka-Ssenabulya D, Nabukeera-Barungi N, Mpimbaza A, Dzik WH. Cytoadherence in paediatric malaria: ABO blood group, CD36, and ICAM1 expression and severe Plasmodium falciparum infection. Br J Haematol 2012; 159:223-36. [PMID: 22909232 PMCID: PMC3470923 DOI: 10.1111/bjh.12014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Accepted: 07/12/2012] [Indexed: 11/28/2022]
Abstract
As a leading cause of childhood mortality worldwide, selection pressure by Plasmodium falciparum continues to shape the human genome. Severe disturbances within the microcirculation result from the adhesion of infected erythrocytes to host receptors on monocytes, platelets, and endothelium. In this prospective study, we compared expression of all major host cytoadhesion receptors among Ugandan children presenting with uncomplicated malaria (n = 1078) versus children with severe malaria (n = 855), including cerebral malaria (n = 174), severe anaemia (n = 522), and lactic acidosis (n = 154). We report a significant survival advantage attributed to blood group O and increased monocyte expression of CD36 and ICAM1 (CD54). The high case fatality rate syndromes of cerebral malaria and lactic acidosis were associated with high platelet CD36 expression and thrombocytopenia, and severe malaria anaemia was characterized by low ICAM1 expression. In a logistic regression model of disease severity, odds ratios for the mitigating effects of blood group O, CD36, and ICAM1 phenotypes were greater than that of sickle haemoglobin. Host genetic adaptations to Plasmodium falciparum suggest new potential malaria treatment strategies.
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205
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Avril M, Tripathi AK, Brazier AJ, Andisi C, Janes JH, Soma VL, Sullivan DJ, Bull PC, Stins MF, Smith JD. A restricted subset of var genes mediates adherence of Plasmodium falciparum-infected erythrocytes to brain endothelial cells. Proc Natl Acad Sci U S A 2012; 109:E1782-90. [PMID: 22619321 PMCID: PMC3387091 DOI: 10.1073/pnas.1120534109] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Cerebral malaria (CM) is a deadly complication of Plasmodium falciparum infection, but specific interactions involved in cerebral homing of infected erythrocytes (IEs) are poorly understood. In this study, P. falciparum-IEs were characterized for binding to primary human brain microvascular endothelial cells (HBMECs). Before selection, CD36 or ICAM-1-binding parasites exhibited punctate binding to a subpopulation of HBMECs and binding was CD36 dependent. Panning of IEs on HBMECs led to a more dispersed binding phenotype and the selection of three var genes, including two that encode the tandem domain cassette 8 (DC8) and were non-CD36 binders. Multiple domains in the DC8 cassette bound to brain endothelium and the cysteine-rich interdomain region 1 inhibited binding of P. falciparum-IEs by 50%, highlighting a key role for the DC8 cassette in cerebral binding. It is mysterious how deadly binding variants are maintained in the parasite population. Clonal parasite lines expressing the two brain-adherent DC8-var genes did not bind to any of the known microvascular receptors, indicating unique receptors are involved in cerebral binding. They could also adhere to brain, lung, dermis, and heart endothelial cells, suggesting cerebral binding variants may have alternative sequestration sites. Furthermore, young African children with CM or nonsevere control cases had antibodies to HBMEC-selected parasites, indicating they had been exposed to related variants during childhood infections. This analysis shows that specific P. falciparum erythrocyte membrane protein 1 types are linked to cerebral binding and suggests a potential mechanism by which individuals may build up immunity to severe disease, in the absence of CM.
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Affiliation(s)
- Marion Avril
- Seattle Biomedical Research Institute, Seattle, WA 98109-5219
| | - Abhai K. Tripathi
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205
| | | | - Cheryl Andisi
- Kenya Medical Research Institute–Wellcome Trust Research Programme, 80108, Kilifi, Kenya
| | - Joel H. Janes
- Seattle Biomedical Research Institute, Seattle, WA 98109-5219
- Department of Global Health, University of Washington, Seattle, WA 98109
| | - Vijaya L. Soma
- Seattle Biomedical Research Institute, Seattle, WA 98109-5219
| | - David J. Sullivan
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205
| | - Peter C. Bull
- Kenya Medical Research Institute–Wellcome Trust Research Programme, 80108, Kilifi, Kenya
- Nuffield Department of Clinical Medicine, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DU, United Kingdom; and
| | - Monique F. Stins
- Department of Neurology, School of Medicine, Johns Hopkins University, Baltimore, MD 21287
| | - Joseph D. Smith
- Seattle Biomedical Research Institute, Seattle, WA 98109-5219
- Department of Global Health, University of Washington, Seattle, WA 98109
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206
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Cruz LN, Wu Y, Craig AG, Garcia CRS. Signal transduction in Plasmodium-Red Blood Cells interactions and in cytoadherence. AN ACAD BRAS CIENC 2012; 84:555-72. [PMID: 22634746 DOI: 10.1590/s0001-37652012005000036] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 03/09/2012] [Indexed: 12/19/2022] Open
Abstract
Malaria is responsible for more than 1.5 million deaths each year, especially among children (Snow et al. 2005). Despite of the severity of malaria situation and great effort to the development of new drug targets (Yuan et al. 2011) there is still a relative low investment toward antimalarial drugs. Briefly there are targets classes of antimalarial drugs currently being tested including: kinases, proteases, ion channel of GPCR, nuclear receptor, among others (Gamo et al. 2010). Here we review malaria signal transduction pathways in Red Blood Cells (RBC) as well as infected RBCs and endothelial cells interactions, namely cytoadherence. The last process is thought to play an important role in the pathogenesis of severe malaria. The molecules displayed on the surface of both infected erythrocytes (IE) and vascular endothelial cells (EC) exert themselves as important mediators in cytoadherence, in that they not only induce structural and metabolic changes on both sides, but also trigger multiple signal transduction processes, leading to alteration of gene expression, with the balance between positive and negative regulation determining endothelial pathology during a malaria infection.
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Affiliation(s)
- Laura N Cruz
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, Brasil
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207
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Qidwai T, Khan F. Antimalarial Drugs and Drug Targets Specific to Fatty Acid Metabolic Pathway of Plasmodium falciparum. Chem Biol Drug Des 2012; 80:155-72. [DOI: 10.1111/j.1747-0285.2012.01389.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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208
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Plasmodium falciparum erythrocyte membrane protein 1 domain cassettes 8 and 13 are associated with severe malaria in children. Proc Natl Acad Sci U S A 2012; 109:E1791-800. [PMID: 22619319 DOI: 10.1073/pnas.1120455109] [Citation(s) in RCA: 202] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The clinical outcome of Plasmodium falciparum infections ranges from asymptomatic parasitemia to severe malaria syndromes associated with high mortality. The virulence of P. falciparum infections is associated with the type of P. falciparum erythrocyte membrane protein 1 (PfEMP1) expressed on the surface of infected erythrocytes to anchor these to the vascular lining. Although var2csa, the var gene encoding the PfEMP1 associated with placental malaria, was discovered in 2003, the identification of the var/PfEMP1 variants associated with severe malaria in children has remained elusive. To identify var/PfEMP1 variants associated with severe disease outcome, we compared var transcript levels in parasites from 88 children with severe malaria and 40 children admitted to the hospital with uncomplicated malaria. Transcript analysis was performed by RT-quantitative PCR using a set of 42 primer pairs amplifying var subtype-specific loci covering most var/PfEMP1 subtypes. In addition, we characterized the near-full-length sequence of the most prominently expressed var genes in three patients diagnosed with severe anemia and/or cerebral malaria. The combined analysis showed that severe malaria syndromes, including severe anemia and cerebral malaria, are associated with high transcript levels of PfEMP1 domain cassette 8-encoding var genes. Transcript levels of group A var genes, including genes encoding domain cassette 13, were also significantly higher in patients with severe syndromes compared with those with uncomplicated malaria. This study specifies the var/PfEMP1 types expressed in severe malaria in children, and thereby provides unique targets for future efforts to prevent and treat severe malaria infections.
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209
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A subset of group A-like var genes encodes the malaria parasite ligands for binding to human brain endothelial cells. Proc Natl Acad Sci U S A 2012; 109:E1772-81. [PMID: 22619330 DOI: 10.1073/pnas.1120461109] [Citation(s) in RCA: 158] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Cerebral malaria is the most deadly manifestation of infection with Plasmodium falciparum. The pathology of cerebral malaria is characterized by the accumulation of infected erythrocytes (IEs) in the microvasculature of the brain caused by parasite adhesins on the surface of IEs binding to human receptors on microvascular endothelial cells. The parasite and host molecules involved in this interaction are unknown. We selected three P. falciparum strains (HB3, 3D7, and IT/FCR3) for binding to a human brain endothelial cell line (HBEC-5i). The whole transcriptome of isogenic pairs of selected and unselected parasites was analyzed using a variant surface antigen-supplemented microarray chip. After selection, the most highly and consistently up-regulated genes were a subset of group A-like var genes (HB3var3, 3D7_PFD0020c, ITvar7, and ITvar19) that showed 11- to >100-fold increased transcription levels. These var genes encode P. falciparum erythrocyte membrane protein (PfEMP)1 variants with distinct N-terminal domain types (domain cassette 8 or domain cassette 13). Antibodies to HB3var3 and PFD0020c recognized the surface of live IEs and blocked binding to HBEC-5i, thereby confirming the adhesive function of these variants. The clinical in vivo relevance of the HBEC-selected parasites was supported by significantly higher surface recognition of HBEC-selected parasites compared with unselected parasites by antibodies from young African children suffering cerebral malaria (Mann-Whitney test, P = 0.029) but not by antibodies from controls with uncomplicated malaria (Mann-Whitney test, P = 0.58). This work describes a binding phenotype for virulence-associated group A P. falciparum erythrocyte membrane protein 1 variants and identifies targets for interventions to treat or prevent cerebral malaria.
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210
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Abstract
Molecules involved in leukocyte trafficking have a central role in the development of inflammatory and immune responses. We performed F(ST) analysis of the selectin cluster, as well as of SELPLG, ICAM1 and VCAM1. Peaks of significantly high population genetic differentiation were restricted to two regions in SELP and one in SELPLG. Resequencing data indicated that the region covering SELP exons 11-13 displays high nucleotide diversity in Africans and Europeans (CEU), and a high level of within-species diversity compared with inter-specific divergence. Analysis of inferred haplotypes revealed a complex phylogeny with two deeply separated clades that coalesce at ~3.5 million years (MY) plus a minor clade with a TMRCA (time to the most recent common ancestor) of ~2.2 MY. A splicing assay indicated no haplotype-specific effect on SELP exon 14 inclusion. These data are consistent with a model of multiallelic balancing selection; single-nucleotide polymorphism analysis indicated that the Val640Leu variant represents a likely selection target. In populations of Asian ancestry a distinct haplotype, possibly carrying regulatory variants, has been driven to high frequency by positive selection. No deviation from neutrality was observed for the SELPLG region. Resequencing of SELP in chimpanzees revealed a haplotype phylogeny with extremely deep basal branches, suggesting either long-standing balancing selection or ancestral population structure. Thus, SELP has experienced a complex selective history, possibly as a result of local adaptation. Variants in the gene have been associated with autoimmune and cardiovascular diseases. Association studies would benefit from both taking the complex SELP haplotype structure into account and from analysis of possible regulatory variants in the gene.
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211
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Ghumra A, Semblat JP, Ataide R, Kifude C, Adams Y, Claessens A, Anong DN, Bull PC, Fennell C, Arman M, Amambua-Ngwa A, Walther M, Conway DJ, Kassambara L, Doumbo OK, Raza A, Rowe JA. Induction of strain-transcending antibodies against Group A PfEMP1 surface antigens from virulent malaria parasites. PLoS Pathog 2012; 8:e1002665. [PMID: 22532802 PMCID: PMC3330128 DOI: 10.1371/journal.ppat.1002665] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2011] [Accepted: 03/08/2012] [Indexed: 12/22/2022] Open
Abstract
Sequence diversity in pathogen antigens is an obstacle to the development of interventions against many infectious diseases. In malaria caused by Plasmodium falciparum, the PfEMP1 family of variant surface antigens encoded by var genes are adhesion molecules that play a pivotal role in malaria pathogenesis and clinical disease. PfEMP1 is a major target of protective immunity, however, development of drugs or vaccines based on PfEMP1 is problematic due to extensive sequence diversity within the PfEMP1 family. Here we identified the PfEMP1 variants transcribed by P. falciparum strains selected for a virulence-associated adhesion phenotype (IgM-positive rosetting). The parasites transcribed a subset of Group A PfEMP1 variants characterised by an unusual PfEMP1 architecture and a distinct N-terminal domain (either DBLα1.5 or DBLα1.8 type). Antibodies raised in rabbits against the N-terminal domains showed functional activity (surface reactivity with live infected erythrocytes (IEs), rosette inhibition and induction of phagocytosis of IEs) down to low concentrations (<10 µg/ml of total IgG) against homologous parasites. Furthermore, the antibodies showed broad cross-reactivity against heterologous parasite strains with the same rosetting phenotype, including clinical isolates from four sub-Saharan African countries that showed surface reactivity with either DBLα1.5 antibodies (variant HB3var6) or DBLα1.8 antibodies (variant TM284var1). These data show that parasites with a virulence-associated adhesion phenotype share IE surface epitopes that can be targeted by strain-transcending antibodies to PfEMP1. The existence of shared surface epitopes amongst functionally similar disease-associated P. falciparum parasite isolates suggests that development of therapeutic interventions to prevent severe malaria is a realistic goal. Malaria remains one of the world's most deadly diseases. Life-threatening malaria is linked to a process called rosetting, in which malaria parasite-infected red blood cells bind to uninfected red cells to form aggregates that block blood flow in vital organs such as the brain. Current efforts to develop drugs or vaccines against rosetting are hindered by variation in the parasite rosette-mediating proteins, found on the surface of infected red cells. We studied these parasite-derived surface proteins and discovered that although they are variable, they share some common features. We raised antibodies against the rosette-mediating proteins, and found that they cross-reacted with multiple rosetting parasite strains from different countries around the world, including samples collected directly from African children with severe malaria. These findings provide new insights into malaria parasite interactions with human cells, and provide proof of principle that variable parasite molecules from virulent malaria parasites can induce strain-transcending antibodies. Hence, this work provides the foundation for the development of new therapies to treat or prevent life-threatening malaria.
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Affiliation(s)
- Ashfaq Ghumra
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Jean-Philippe Semblat
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Ricardo Ataide
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Carolyne Kifude
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Yvonne Adams
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Antoine Claessens
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Damian N. Anong
- Biotechnology Unit, Faculty of Science, University of Buea, Buea, Cameroon
| | - Peter C. Bull
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Clare Fennell
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Monica Arman
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | | | - Michael Walther
- Medical Research Council Laboratories, Fajara, Banjul, The Gambia
| | - David J. Conway
- Medical Research Council Laboratories, Fajara, Banjul, The Gambia
| | - Lalla Kassambara
- Malaria Research and Training Centre, University of Bamako, Bamako, Mali
| | - Ogobara K. Doumbo
- Malaria Research and Training Centre, University of Bamako, Bamako, Mali
| | - Ahmed Raza
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - J. Alexandra Rowe
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail:
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212
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Bei AK, Duraisingh MT. Functional analysis of erythrocyte determinants of Plasmodium infection. Int J Parasitol 2012; 42:575-82. [PMID: 22726752 DOI: 10.1016/j.ijpara.2012.03.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Revised: 03/14/2012] [Accepted: 03/14/2012] [Indexed: 11/18/2022]
Abstract
The Plasmodium falciparum parasite is an obligate intracellular pathogen whose invasion and remodelling of the human erythrocyte results in the clinical manifestations of malarial disease. The functional analysis of erythrocyte determinants of invasion and growth is a relatively unexplored frontier in malaria research, encompassing studies of natural variation of the erythrocyte, as well as genomic, biochemical and chemical biological and transgenic approaches. These studies have allowed the functional analysis of the erythrocyte in vitro, resulting in the discovery of critical erythrocyte determinants of Plasmodium infection. Here, we will focus on the varied approaches used for the study of the erythrocyte in Plasmodium infection, with a particular emphasis on erythrocyte invasion.
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Affiliation(s)
- Amy K Bei
- Harvard School of Public Health, 665, Huntington Avenue, Building 1, Room 715, Boston, MA 02115, USA
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213
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Warimwe GM, Fegan G, Musyoki JN, Newton CR, Opiyo M, Githinji G, Andisi C, Menza F, Kitsao B, Marsh K, Bull PC. Prognostic indicators of life-threatening malaria are associated with distinct parasite variant antigen profiles. Sci Transl Med 2012; 4:129ra45. [PMID: 22496547 PMCID: PMC3491874 DOI: 10.1126/scitranslmed.3003247] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
PfEMP1 is a family of cytoadhesive surface antigens expressed on erythrocytes infected with Plasmodium falciparum, the parasite that causes the most severe form of malaria. These surface antigens play a role in immune evasion and are thought to contribute to the pathogenesis of the malaria parasite. Previous studies have suggested a role for a specific subset of PfEMP1 called "group A" in severe malaria. To explore the role of group A PfEMP1 in disease, we measured the expression of the var genes that encode them in parasites from clinical isolates collected from children suffering from malaria. We also looked at the ability of these clinical isolates to induce rosetting of erythrocytes, which indicates a cytoadhesion phenotype that is thought to be important in pathogenesis. These two sets of data were correlated with the presence of two life-threatening manifestations of severe malaria in the children: impaired consciousness and respiratory distress. Using regression analysis, we show that marked rosetting was associated with respiratory distress, whereas elevated expression of group A-like var genes without elevated rosetting was associated with impaired consciousness. The results suggest that manifestations of malarial disease may reflect the distribution of cytoadhesion phenotypes expressed by the infecting parasite population.
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Affiliation(s)
- George M. Warimwe
- Kenya Medical Research Institute-Wellcome Trust Research Programme, P.O. Box 230-80108 Kilifi, Kenya
| | - Gregory Fegan
- Kenya Medical Research Institute-Wellcome Trust Research Programme, P.O. Box 230-80108 Kilifi, Kenya
- Nuffield Department of Clinical Medicine, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK
| | - Jennifer N. Musyoki
- Kenya Medical Research Institute-Wellcome Trust Research Programme, P.O. Box 230-80108 Kilifi, Kenya
| | - Charles R.J.C. Newton
- Kenya Medical Research Institute-Wellcome Trust Research Programme, P.O. Box 230-80108 Kilifi, Kenya
| | - Michael Opiyo
- Kenya Medical Research Institute-Wellcome Trust Research Programme, P.O. Box 230-80108 Kilifi, Kenya
| | - George Githinji
- Kenya Medical Research Institute-Wellcome Trust Research Programme, P.O. Box 230-80108 Kilifi, Kenya
| | - Cheryl Andisi
- Kenya Medical Research Institute-Wellcome Trust Research Programme, P.O. Box 230-80108 Kilifi, Kenya
| | - Francis Menza
- Kenya Medical Research Institute-Wellcome Trust Research Programme, P.O. Box 230-80108 Kilifi, Kenya
| | - Barnes Kitsao
- Kenya Medical Research Institute-Wellcome Trust Research Programme, P.O. Box 230-80108 Kilifi, Kenya
| | - Kevin Marsh
- Kenya Medical Research Institute-Wellcome Trust Research Programme, P.O. Box 230-80108 Kilifi, Kenya
- Nuffield Department of Clinical Medicine, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK
| | - Peter C. Bull
- Kenya Medical Research Institute-Wellcome Trust Research Programme, P.O. Box 230-80108 Kilifi, Kenya
- Nuffield Department of Clinical Medicine, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK
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214
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Lawton J, Brugat T, Yan YX, Reid AJ, Böhme U, Otto TD, Pain A, Jackson A, Berriman M, Cunningham D, Preiser P, Langhorne J. Characterization and gene expression analysis of the cir multi-gene family of Plasmodium chabaudi chabaudi (AS). BMC Genomics 2012; 13:125. [PMID: 22458863 PMCID: PMC3384456 DOI: 10.1186/1471-2164-13-125] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Accepted: 03/29/2012] [Indexed: 11/13/2022] Open
Abstract
Background The pir genes comprise the largest multi-gene family in Plasmodium, with members found in P. vivax, P. knowlesi and the rodent malaria species. Despite comprising up to 5% of the genome, little is known about the functions of the proteins encoded by pir genes. P. chabaudi causes chronic infection in mice, which may be due to antigenic variation. In this model, pir genes are called cirs and may be involved in this mechanism, allowing evasion of host immune responses. In order to fully understand the role(s) of CIR proteins during P. chabaudi infection, a detailed characterization of the cir gene family was required. Results The cir repertoire was annotated and a detailed bioinformatic characterization of the encoded CIR proteins was performed. Two major sub-families were identified, which have been named A and B. Members of each sub-family displayed different amino acid motifs, and were thus predicted to have undergone functional divergence. In addition, the expression of the entire cir repertoire was analyzed via RNA sequencing and microarray. Up to 40% of the cir gene repertoire was expressed in the parasite population during infection, and dominant cir transcripts could be identified. In addition, some differences were observed in the pattern of expression between the cir subgroups at the peak of P. chabaudi infection. Finally, specific cir genes were expressed at different time points during asexual blood stages. Conclusions In conclusion, the large number of cir genes and their expression throughout the intraerythrocytic cycle of development indicates that CIR proteins are likely to be important for parasite survival. In particular, the detection of dominant cir transcripts at the peak of P. chabaudi infection supports the idea that CIR proteins are expressed, and could perform important functions in the biology of this parasite. Further application of the methodologies described here may allow the elucidation of CIR sub-family A and B protein functions, including their contribution to antigenic variation and immune evasion.
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Affiliation(s)
- Jennifer Lawton
- Division of Parasitology, MRC National Institute for Medical Research, London, UK
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215
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Ingmundson A, Nahar C, Brinkmann V, Lehmann MJ, Matuschewski K. The exported Plasmodium berghei protein IBIS1 delineates membranous structures in infected red blood cells. Mol Microbiol 2012; 83:1229-43. [PMID: 22329949 PMCID: PMC3502748 DOI: 10.1111/j.1365-2958.2012.08004.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/31/2012] [Indexed: 12/01/2022]
Abstract
The importance of pathogen-induced host cell remodelling has been well established for red blood cell infection by the human malaria parasite Plasmodium falciparum. Exported parasite-encoded proteins, which often possess a signature motif, termed Plasmodium export element (PEXEL) or host-targeting (HT) signal, are critical for the extensive red blood cell modifications. To what extent remodelling of erythrocyte membranes also occurs in non-primate hosts and whether it is in fact a hallmark of all mammalian Plasmodium parasites remains elusive. Here we characterize a novel Plasmodium berghei PEXEL/HT-containing protein, which we term IBIS1. Temporal expression and spatial localization determined by fluorescent tagging revealed the presence of IBIS1 at the parasite/host interface during both liver and blood stages of infection. Targeted deletion of the IBIS1 protein revealed a mild impairment of intra-erythrocytic growth indicating a role for these structures in the rapid expansion of the parasite population in the blood in vivo. In red blood cells, the protein localizes to dynamic, punctate structures external to the parasite. Biochemical and microscopic data revealed that these intra-erythrocytic P. berghei-induced structures (IBIS) are membranous indicating that P. berghei, like P. falciparum, creates an intracellular membranous network in infected red blood cells.
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Affiliation(s)
- Alyssa Ingmundson
- Max Planck Institute for Infection Biology, Charitéplatz 1, 10117 Berlin, Germany.
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216
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Francischetti IMB, Oliveira CJ, Ostera GR, Yager SB, Debierre-Grockiego F, Carregaro V, Jaramillo-Gutierrez G, Hume JCC, Jiang L, Moretz SE, Lin CK, Ribeiro JMC, Long CA, Vickers BK, Schwarz RT, Seydel KB, Iacobelli M, Ackerman HC, Srinivasan P, Gomes RB, Wang X, Monteiro RQ, Kotsyfakis M, Sá-Nunes A, Waisberg M. Defibrotide interferes with several steps of the coagulation-inflammation cycle and exhibits therapeutic potential to treat severe malaria. Arterioscler Thromb Vasc Biol 2012; 32:786-98. [PMID: 22116094 PMCID: PMC3288196 DOI: 10.1161/atvbaha.111.240291] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Accepted: 11/05/2011] [Indexed: 11/16/2022]
Abstract
OBJECTIVE The coagulation-inflammation cycle has been implicated as a critical component in malaria pathogenesis. Defibrotide (DF), a mixture of DNA aptamers, displays anticoagulant, anti-inflammatory, and endothelial cell (EC)-protective activities and has been successfully used to treat comatose children with veno-occlusive disease. DF was investigated here as a drug to treat cerebral malaria. METHODS AND RESULTS DF blocks tissue factor expression by ECs incubated with parasitized red blood cells and attenuates prothrombinase activity, platelet aggregation, and complement activation. In contrast, it does not affect nitric oxide bioavailability. We also demonstrated that Plasmodium falciparum glycosylphosphatidylinositol (Pf-GPI) induces tissue factor expression in ECs and cytokine production by dendritic cells. Notably, dendritic cells, known to modulate coagulation and inflammation systemically, were identified as a novel target for DF. Accordingly, DF inhibits Toll-like receptor ligand-dependent dendritic cells activation by a mechanism that is blocked by adenosine receptor antagonist (8-p-sulfophenyltheophylline) but not reproduced by synthetic poly-A, -C, -T, and -G. These results imply that aptameric sequences and adenosine receptor mediate dendritic cells responses to the drug. DF also prevents rosetting formation, red blood cells invasion by P. falciparum and abolishes oocysts development in Anopheles gambiae. In a murine model of cerebral malaria, DF affected parasitemia, decreased IFN-γ levels, and ameliorated clinical score (day 5) with a trend for increased survival. CONCLUSION Therapeutic use of DF in malaria is proposed.
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MESH Headings
- Animals
- Anti-Inflammatory Agents/pharmacology
- Anticoagulants/pharmacology
- Antimalarials/pharmacology
- Blood Coagulation/drug effects
- Cells, Cultured
- Complement Activation/drug effects
- Cytokines/blood
- Dendritic Cells/drug effects
- Dendritic Cells/immunology
- Dendritic Cells/parasitology
- Disease Models, Animal
- Dose-Response Relationship, Drug
- Endothelial Cells/drug effects
- Endothelial Cells/immunology
- Endothelial Cells/metabolism
- Endothelial Cells/parasitology
- Female
- Glycosylphosphatidylinositols/metabolism
- Hemoglobins/metabolism
- Humans
- Inflammation Mediators/blood
- Malaria, Cerebral/blood
- Malaria, Cerebral/drug therapy
- Malaria, Cerebral/immunology
- Malaria, Cerebral/parasitology
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Nitric Oxide/metabolism
- Plasmodium berghei/drug effects
- Plasmodium berghei/pathogenicity
- Plasmodium falciparum/drug effects
- Plasmodium falciparum/growth & development
- Plasmodium falciparum/metabolism
- Plasmodium falciparum/pathogenicity
- Platelet Aggregation/drug effects
- Polydeoxyribonucleotides/pharmacology
- Receptors, Purinergic P1/drug effects
- Receptors, Purinergic P1/metabolism
- Severity of Illness Index
- Thromboplastin/metabolism
- Time Factors
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Affiliation(s)
- Ivo M B Francischetti
- Section of Vector Biology, Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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217
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Ponsford MJ, Medana IM, Prapansilp P, Hien TT, Lee SJ, Dondorp AM, Esiri MM, Day NPJ, White NJ, Turner GDH. Sequestration and microvascular congestion are associated with coma in human cerebral malaria. J Infect Dis 2012; 205:663-71. [PMID: 22207648 PMCID: PMC3266137 DOI: 10.1093/infdis/jir812] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2010] [Accepted: 04/04/2011] [Indexed: 01/04/2023] Open
Abstract
The pathogenesis of coma in severe Plasmodium falciparum malaria remains poorly understood. Obstruction of the brain microvasculature because of sequestration of parasitized red blood cells (pRBCs) represents one mechanism that could contribute to coma in cerebral malaria. Quantitative postmortem microscopy of brain sections from Vietnamese adults dying of malaria confirmed that sequestration in the cerebral microvasculature was significantly higher in patients with cerebral malaria (CM; n = 21) than in patients with non-CM (n = 23). Sequestration of pRBCs and CM was also significantly associated with increased microvascular congestion by infected and uninfected erythrocytes. Clinicopathological correlation showed that sequestration and congestion were significantly associated with deeper levels of premortem coma and shorter time to death. Microvascular congestion and sequestration were highly correlated as microscopic findings but were independent predictors of a clinical diagnosis of CM. Increased microvascular congestion accompanies coma in CM, associated with parasite sequestration in the cerebral microvasculature.
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Affiliation(s)
| | | | - Panote Prapansilp
- Nuffield Department of Clinical Laboratory Sciences
- Nuffield Department of Clinical Medicine, The John Radcliffe Hospital, University of Oxford, United Kingdom
- Department of Tropical Pathology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Tran Tinh Hien
- Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | | | - Arjen M. Dondorp
- Nuffield Department of Clinical Medicine, The John Radcliffe Hospital, University of Oxford, United Kingdom
- Mahidol-Oxford Research Unit
| | | | - Nicholas P. J. Day
- Nuffield Department of Clinical Medicine, The John Radcliffe Hospital, University of Oxford, United Kingdom
- Mahidol-Oxford Research Unit
| | - Nicholas J. White
- Nuffield Department of Clinical Medicine, The John Radcliffe Hospital, University of Oxford, United Kingdom
- Mahidol-Oxford Research Unit
| | - Gareth D. H. Turner
- Nuffield Department of Clinical Medicine, The John Radcliffe Hospital, University of Oxford, United Kingdom
- Mahidol-Oxford Research Unit
- Department of Tropical Pathology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
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218
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Del Portillo HA, Ferrer M, Brugat T, Martin-Jaular L, Langhorne J, Lacerda MVG. The role of the spleen in malaria. Cell Microbiol 2012; 14:343-55. [PMID: 22188297 DOI: 10.1111/j.1462-5822.2011.01741.x] [Citation(s) in RCA: 134] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The spleen is a complex organ that is perfectly adapted to selectively filtering and destroying senescent red blood cells (RBCs), infectious microorganisms and Plasmodium-parasitized RBCs. Infection by malaria is the most common cause of spleen rupture and splenomegaly, albeit variably, a landmark of malaria infection. Here, the role of the spleen in malaria is reviewed with special emphasis in lessons learned from human infections and mouse models.
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Affiliation(s)
- Hernando A Del Portillo
- Barcelona Centre for International Health Research (CRESIB, Hospital Clinic-Universitat de Barcelona), Barcelona, Spain.
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219
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Hanssen E, Knoechel C, Dearnley M, Dixon MW, Le Gros M, Larabell C, Tilley L. Soft X-ray microscopy analysis of cell volume and hemoglobin content in erythrocytes infected with asexual and sexual stages of Plasmodium falciparum. J Struct Biol 2012; 177:224-32. [DOI: 10.1016/j.jsb.2011.09.003] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 09/05/2011] [Accepted: 09/09/2011] [Indexed: 12/13/2022]
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220
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Grau GER, Craig AG. Cerebral malaria pathogenesis: revisiting parasite and host contributions. Future Microbiol 2012; 7:291-302. [DOI: 10.2217/fmb.11.155] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Cerebral malaria is one of a number of clinical syndromes associated with infection by human malaria parasites of the genus Plasmodium. The etiology of cerebral malaria derives from sequestration of parasitized red cells in brain microvasculature and is thought to be enhanced by the proinflammatory status of the host and virulence characteristics of the infecting parasite variant. In this article we examine the range of factors thought to influence the development of Plasmodium falciparum cerebral malaria in humans and review the evidence to support their role.
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Affiliation(s)
- Georges Emile Raymond Grau
- Vascular Immunology Unit, Department of Pathology, Sydney Medical School, The University of Sydney, Camperdown NSW 2042, Australia
- La Jolla Infectious Disease Institute, San Diego, CA 92109, USA
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221
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Uyoga S, Skorokhod OA, Opiyo M, Orori EN, Williams TN, Arese P, Schwarzer E. Transfer of 4-hydroxynonenal from parasitized to non-parasitized erythrocytes in rosettes. Proposed role in severe malaria anemia. Br J Haematol 2012; 157:116-24. [PMID: 22352722 PMCID: PMC3412292 DOI: 10.1111/j.1365-2141.2011.09015.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Severe anaemia is a life-threatening complication of falciparum malaria associated with loss of predominantly non-parasitized red blood cells (npRBCs). This poorly elucidated process might be influenced by (i) rosettes, i.e. npRBCs cytoadherent to haemozoin-containing parasitized RBCs (pRBCs) and (ii) generation in pRBCs of 4-hydroxynonenal (4-HNE) through haemozoin-catalysed lipid peroxidation. We explored whether close proximity in rosettes may facilitate 4-HNE transfer to npRBCs, which is likely to enhance their phagocytosis and contribute to malaria anaemia. Fluorescence microscopy and flow cytometry data indicated 4-HNE transfer to npRBCs in rosettes. Rosettes were formed by 64·8 ± 1·8% varO-expressing pRBCs, and 8·7 ± 1·1% npRBCs were positive for 4-HNE-protein-conjugates, while low-rosetting parasites generated only 2·4 ± 1·1% 4-HNE-conjugate-positive npRBCs. 4-HNE transfer decreased after blocking rosetting by monoclonal antibodies. A positive linear relationship between rosette frequency and 4-HNE-conjugates in npRBCs was found in 40 malaria patients, a first indication for a role of rosetting in npRBCs modifications in vivo. Children with severe malaria anaemia had significantly higher percentages of 4-HNE-conjugate-positive npRBCs compared to children with uncomplicated malaria. In conclusion, 4-HNE transfer from pRBCs to npRBCs in rosettes is suggested to play a role in the phagocytic removal of large numbers of npRBCs, the hallmark of severe malaria anaemia.
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Affiliation(s)
- Sophie Uyoga
- Department of Genetics, Biology and Biochemistry, University of Torino Medical School, Turin, Italy
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222
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Claessens A, Rowe JA. Selection of Plasmodium falciparum parasites for cytoadhesion to human brain endothelial cells. J Vis Exp 2012:e3122. [PMID: 22230803 PMCID: PMC3369769 DOI: 10.3791/3122] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Most human malaria deaths are caused by blood-stage Plasmodium falciparum parasites. Cerebral malaria, the most life-threatening complication of the disease, is characterised by an accumulation of Plasmodium falciparum infected red blood cells (iRBC) at pigmented trophozoite stage in the microvasculature of the brain2-4. This microvessel obstruction (sequestration) leads to acidosis, hypoxia and harmful inflammatory cytokines (reviewed in 5). Sequestration is also found in most microvascular tissues of the human body2, 3. The mechanism by which iRBC attach to the blood vessel walls is still poorly understood. The immortalized Human Brain microvascular Endothelial Cell line (HBEC-5i) has been used as an in vitro model of the blood-brain barrier6. However, Plasmodium falciparum iRBC attach only poorly to HBEC-5i in vitro, unlike the dense sequestration that occurs in cerebral malaria cases. We therefore developed a panning assay to select (enrich) various P. falciparum strains for adhesion to HBEC-5i in order to obtain populations of high-binding parasites, more representative of what occurs in vivo. A sample of a parasite culture (mixture of iRBC and uninfected RBC) at the pigmented trophozoite stage is washed and incubated on a layer of HBEC-5i grown on a Petri dish. After incubation, the dish is gently washed free from uRBC and unbound iRBC. Fresh uRBC are added to the few iRBC attached to HBEC-5i and incubated overnight. As schizont stage parasites burst, merozoites reinvade RBC and these ring stage parasites are harvested the following day. Parasites are cultured until enough material is obtained (typically 2 to 4 weeks) and a new round of selection can be performed. Depending on the P. falciparum strain, 4 to 7 rounds of selection are needed in order to get a population where most parasites bind to HBEC-5i. The binding phenotype is progressively lost after a few weeks, indicating a switch in variant surface antigen gene expression, thus regular selection on HBEC-5i is required to maintain the phenotype. In summary, we developed a selection assay rendering P. falciparum parasites a more "cerebral malaria adhesive" phenotype. We were able to select 3 out of 4 P. falciparum strains on HBEC-5i. This assay has also successfully been used to select parasites for binding to human dermal and pulmonary endothelial cells. Importantly, this method can be used to select tissue-specific parasite populations in order to identify candidate parasite ligands for binding to brain endothelium. Moreover, this assay can be used to screen for putative anti-sequestration drugs7.
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Affiliation(s)
- Antoine Claessens
- Centre for Immunity, Infection and Evolution, University of Edinburgh
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223
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Abstract
We describe a technology for imaging the sequestration of infected red blood cells (iRBC) of the rodent malaria parasite Plasmodium berghei both in the bodies of live mice and in dissected organs, using a transgenic parasite that expresses luciferase. Real-time imaging of sequestered iRBC is performed by measuring bioluminescence produced by the enzymatic reaction in parasites between the luciferase enzyme and its substrate luciferin injected into the mice several minutes prior to imaging. The bioluminescence signal is detected by a sensitive I-CCD photon-counting video camera. Using a reporter parasite that expresses luciferase under the control of a schizont-specific promoter (i.e., the ama-1 promoter), the schizont stage is made visible when detecting bioluminescence signals. Schizont sequestration is imaged during short-term infections with parasites that are synchronized in development or during ongoing infections. Real-time in vivo imaging of iRBC will provide increased insights into the dynamics of sequestration and its role in pathology, and can be used to evaluate strategies that prevent sequestration.
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224
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Fonager J, Pasini EM, Braks JAM, Klop O, Ramesar J, Remarque EJ, Vroegrijk IOCM, van Duinen SG, Thomas AW, Khan SM, Mann M, Kocken CHM, Janse CJ, Franke-Fayard BMD. Reduced CD36-dependent tissue sequestration of Plasmodium-infected erythrocytes is detrimental to malaria parasite growth in vivo. ACTA ACUST UNITED AC 2011; 209:93-107. [PMID: 22184632 PMCID: PMC3260870 DOI: 10.1084/jem.20110762] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Adherence of parasite-infected red blood cells (irbc) to the vascular endothelium of organs plays a key role in the pathogenesis of Plasmodium falciparum malaria. The prevailing hypothesis of why irbc adhere and sequester in tissues is that this acts as a mechanism of avoiding spleen-mediated clearance. Irbc of the rodent parasite Plasmodium berghei ANKA sequester in a fashion analogous to P. falciparum by adhering to the host receptor CD36. To experimentally determine the significance of sequestration for parasite growth, we generated a mutant P. berghei ANKA parasite with a reduced CD36-mediated adherence. Although the cognate parasite ligand binding to CD36 is unknown, we show that nonsequestering parasites have reduced growth and we provide evidence that in addition to avoiding spleen removal, other factors related to CD36-mediated sequestration are beneficial for parasite growth. These results reveal for the first time the importance of sequestration to a malaria infection, with implications for the development of strategies aimed at reducing pathology by inhibiting tissue sequestration.
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Affiliation(s)
- Jannik Fonager
- Leiden Malaria Research Group, Department of Parasitology, Leiden University Medical Center, 2333 ZA Leiden, Netherlands
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225
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Davis SP, Amrein M, Gillrie MR, Lee K, Muruve DA, Ho M. Plasmodium falciparum-induced CD36 clustering rapidly strengthens cytoadherence via p130CAS-mediated actin cytoskeletal rearrangement. FASEB J 2011; 26:1119-30. [PMID: 22106368 DOI: 10.1096/fj.11-196923] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The adhesion of infected red blood cells (IRBCs) to microvascular endothelium is critical in the pathogenesis of severe malaria. Here we used atomic force and confocal microscopy to examine the adhesive forces between IRBCs and human dermal microvascular endothelial cells. Initial contact of the cells generated a mean ± sd adhesion force of 167 ± 208 pN from the formation of single or multiple bonds with CD36. The strength of adhesion increased by 5- to 6-fold within minutes of contact through a signaling pathway initiated by CD36 ligation by live IRBCs, or polystyrene beads coated with anti-CD36 or PpMC-179, a recombinant peptide representing the minimal binding domain of the parasite ligand PfEMP1 to CD36. Engagement of CD36 led to localized phosphorylation of Src family kinases and the adaptor protein p130CAS, resulting in actin recruitment and CD36 clustering by 50-60% of adherent beads. Uninfected red blood cells or IgG-coated beads had no effect. Inhibition of the increase in adhesive strength by the Src family kinase inhibitor PP1 or gene silencing of p130CAS decreased adhesion by 39 ± 12 and 48 ± 20%, respectively, at 10 dyn/cm(2) in a flow chamber assay. Modulation of adhesive strength at PfEMP1-CD36-actin cytoskeleton synapses could be a novel target for antiadhesive therapy.
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Affiliation(s)
- Shevaun P Davis
- Department of Microbiology, Immunology, and Infectious Diseases, 3330 Hospital Dr. NW, Calgary, AB, Canada T2N 4N1
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226
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Wu Y, Szestak T, Stins M, Craig AG. Amplification of P. falciparum Cytoadherence through induction of a pro-adhesive state in host endothelium. PLoS One 2011; 6:e24784. [PMID: 22043276 PMCID: PMC3197193 DOI: 10.1371/journal.pone.0024784] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Accepted: 08/17/2011] [Indexed: 01/03/2023] Open
Abstract
This study examined the ability of P.falciparum-infected erythrocytes (IE) to induce a pro-adhesive environment in the host endothelium during malaria infection, prior to the systemic cytokine activation seen in the later phase of disease. Previous work had shown increases in receptor levels but had not measured to actual impact on IE binding. Using a co-culture system with a range of endothelial cells (EC) and IE with different cytoadherent properties, we have characterised the specific expression of adhesion receptors and subsequent IE binding by FACS and adhesion assays. We have also examined the specific signalling pathways induced during co-culture that are potentially involved in the induction of receptor expression. The results confirmed that ICAM-1 is up-regulated, albeit at much lower levels than seen with TNF activation, in response to co-culture with infected erythrocytes in all three tissue endothelial cell types tested but that up-regulation of VCAM-1 is tissue-dependent. This small increase in the levels of EC receptors correlated with large changes in IE adhesion ability. Co-culture with either RBC or IE increased the potential of subsequent adhesion indicating priming/modulation effects on EC which make them more susceptible to adhesion and thereby the recruitment of IE. Trypsin surface digestion of IE and the use of a Pfsbp1-knockout (ko) parasite line abrogated the up-regulation of ICAM-1 and reduced IE binding to EC suggesting that PfEMP-1 and other molecules exported to the IE surface via the PfSBP1 pathway are major mediators of this phenotype. This was also supported by the higher induction of EC adhesion receptors by adherent IE compared to isogenic, non-adherent lines.
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Affiliation(s)
- Yang Wu
- Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Tadge Szestak
- Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Monique Stins
- RT Johnson Division of NeuroImmunology, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - Alister G. Craig
- Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- * E-mail:
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227
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Dixon MWA, Kenny S, McMillan PJ, Hanssen E, Trenholme KR, Gardiner DL, Tilley L. Genetic ablation of a Maurer's cleft protein prevents assembly of the Plasmodium falciparum virulence complex. Mol Microbiol 2011; 81:982-93. [PMID: 21696460 DOI: 10.1111/j.1365-2958.2011.07740.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The malaria parasite Plasmodium falciparum assembles knob structures underneath the erythrocyte membrane that help present the major virulence protein, P. falciparum erythrocyte membrane protein-1 (PfEMP1). Membranous structures called Maurer's clefts are established in the erythrocyte cytoplasm and function as sorting compartments for proteins en route to the RBC membrane, including the knob-associated histidine-rich protein (KAHRP), and PfEMP1. We have generated mutants in which the Maurer's cleft protein, the ring exported protein-1 (REX1) is truncated or deleted. Removal of the C-terminal domain of REX1 compromises Maurer's cleft architecture and PfEMP1-mediated cytoadherance but permits some trafficking of PfEMP1 to the erythrocyte surface. Deletion of the coiled-coil region of REX1 ablates PfEMP1 surface display, trapping PfEMP1 at the Maurer's clefts. Complementation of mutants with REX1 partly restores PfEMP1-mediated binding to the endothelial cell ligand, CD36. Deletion of the coiled-coil region or complete deletion of REX1 is tightly associated with the loss of a subtelomeric region of chromosome 2, encoding KAHRP and other proteins. A KAHRP-green fluorescent protein (GFP) fusion expressed in the REX1-deletion parasites shows defective trafficking. Thus, loss of functional REX1 directly or indirectly ablates the assembly of the P. falciparum virulence complex at the surface of host erythrocytes.
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Affiliation(s)
- Matthew W A Dixon
- La Trobe Institute for Molecular Science, Department of Biochemistry and Centre of Excellence for Coherent X-ray Science, La Trobe University, Vic. 3086, Australia.
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228
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Claessens A, Ghumra A, Gupta AP, Mok S, Bozdech Z, Rowe JA. Design of a variant surface antigen-supplemented microarray chip for whole transcriptome analysis of multiple Plasmodium falciparum cytoadherent strains, and identification of strain-transcendent rif and stevor genes. Malar J 2011; 10:180. [PMID: 21718533 PMCID: PMC3155837 DOI: 10.1186/1475-2875-10-180] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Accepted: 06/30/2011] [Indexed: 12/02/2022] Open
Abstract
Background The cytoadherence of Plasmodium falciparum is thought to be mediated by variant surface antigens (VSA), encoded by var, rif, stevor and pfmc-2tm genes. The last three families have rarely been studied in the context of cytoadherence. As most VSA genes are unique, the variability among sequences has impeded the functional study of VSA across different P. falciparum strains. However, many P. falciparum genomes have recently been sequenced, allowing the development of specific microarray probes for each VSA gene. Methods All VSA sequences from the HB3, Dd2 and IT/FCR3 genomes were extracted using HMMer software. Oligonucleotide probes were designed with OligoRankPick and added to the 3D7-based microarray chip. As a proof of concept, IT/R29 parasites were selected for and against rosette formation and the transcriptomes of isogenic rosetting and non-rosetting parasites were compared by microarray. Results From each parasite strain 50-56 var genes, 125-132 rif genes, 26-33 stevor genes and 3-8 pfmc-2tm genes were identified. Bioinformatic analysis of the new VSA sequences showed that 13 rif genes and five stevor genes were well-conserved across at least three strains (83-100% amino acid identity). The ability of the VSA-supplemented microarray chip to detect cytoadherence-related genes was assessed using P. falciparum clone IT/R29, in which rosetting is known to be mediated by PfEMP1 encoded by ITvar9. Whole transcriptome analysis showed that the most highly up-regulated gene in rosetting parasites was ITvar9 (19 to 429-fold up-regulated over six time points). Only one rif gene (IT4rifA_042) was up-regulated by more than four fold (five fold at 12 hours post-invasion), and no stevor or pfmc-2tm genes were up-regulated by more than two fold. 377 non-VSA genes were differentially expressed by three fold or more in rosetting parasites, although none was as markedly or consistently up-regulated as ITvar9. Conclusions Probes for the VSA of newly sequenced P. falciparum strains can be added to the 3D7-based microarray chip, allowing the analysis of the entire transcriptome of multiple strains. For the rosetting clone IT/R29, the striking transcriptional upregulation of ITvar9 was confirmed, and the data did not support the involvement of other VSA families in rosette formation.
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Affiliation(s)
- Antoine Claessens
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, West Mains Rd, Edinburgh, EH9 3JT, UK
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Tilley L, Dixon MWA, Kirk K. The Plasmodium falciparum-infected red blood cell. Int J Biochem Cell Biol 2011; 43:839-42. [PMID: 21458590 DOI: 10.1016/j.biocel.2011.03.012] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2010] [Revised: 02/27/2011] [Accepted: 03/24/2011] [Indexed: 11/30/2022]
Abstract
Plasmodium falciparum, the most virulent of the human malaria parasites, causes up to one million deaths per year. The parasite spends part of its lifecycle inside the red blood cells (RBCs) of its host. As it grows it ingests the RBC cytoplasm, digesting it in an acidic vacuole. Free haem released during haemoglobin digestion is detoxified by conversion to inert crystals of haemozoin. Malaria pathology is evident during the blood stage of the infection and is exacerbated by adhesion of infected RBCs to blood vessel walls, which prevents splenic clearance of the infected cells. Cytoadherence is mediated by surface-exposed virulence proteins that bind to endothelial cell receptors. These 'adhesins' are exported to the RBC surface via an exomembrane system that is established outside the parasite in the host cell cytoplasm. Antimalarial drugs that interfere with haem detoxification, or target other parasite-specific processes, have been effective in the treatment of malaria, but their use has been dogged by the development of resistance. Similarly, efforts to develop an effective blood vaccine are hindered by the variability of surface-exposed antigens.
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Affiliation(s)
- Leann Tilley
- Department of Biochemistry, La Trobe University, Melbourne, VIC, Australia.
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230
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Janes JH, Wang CP, Levin-Edens E, Vigan-Womas I, Guillotte M, Melcher M, Mercereau-Puijalon O, Smith JD. Investigating the host binding signature on the Plasmodium falciparum PfEMP1 protein family. PLoS Pathog 2011; 7:e1002032. [PMID: 21573138 PMCID: PMC3088720 DOI: 10.1371/journal.ppat.1002032] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Accepted: 03/01/2011] [Indexed: 12/03/2022] Open
Abstract
The Plasmodium falciparum erythrocyte membrane protein 1
(PfEMP1) family plays a central role in antigenic variation and cytoadhesion of
P. falciparum infected erythrocytes. PfEMP1
proteins/var genes are classified into three main
subfamilies (UpsA, UpsB, and UpsC) that are hypothesized to have different roles
in binding and disease. To investigate whether these subfamilies have diverged
in binding specificity and test if binding could be predicted by adhesion domain
classification, we generated a panel of 19 parasite lines that primarily
expressed a single dominant var transcript and assayed binding
against 12 known host receptors. By limited dilution cloning, only UpsB and UpsC
var genes were isolated, indicating that UpsA
var gene expression is rare under in vitro
culture conditions. Consequently, three UpsA variants were obtained by rosette
purification and selection with specific monoclonal antibodies to create a more
representative panel. Binding assays showed that CD36 was the most common
adhesion partner of the parasite panel, followed by ICAM-1 and TSP-1, and that
CD36 and ICAM-1 binding variants were highly predicted by adhesion domain
sequence classification. Binding to other host receptors, including CSA, VCAM-1,
HABP1, CD31/PECAM, E-selectin, Endoglin, CHO receptor “X”, and
Fractalkine, was rare or absent. Our findings identify a category of larger
PfEMP1 proteins that are under dual selection for ICAM-1 and CD36 binding. They
also support that the UpsA group, in contrast to UpsB and UpsC
var genes, has diverged from binding to the major
microvasculature receptor CD36 and likely uses other mechanisms to sequester in
the microvasculature. These results demonstrate that CD36 and ICAM-1 have left
strong signatures of selection on the PfEMP1 family that can be detected by
adhesion domain sequence classification and have implications for how this
family of proteins is specializing to exploit hosts with varying levels of
anti-malaria immunity. The malaria parasite Plasmodium falciparum persists in the human
host partly by avoiding elimination in the spleen during blood stage infection.
This strategy depends principally upon members of the large and diverse PfEMP1
family of proteins that are exported to the surface of infected erythrocytes.
PfEMP1 proteins are important targets for host protective antibody responses and
encode binding to several different host receptor proteins. Switches in PfEMP1
expression allow parasites to evade host antibodies and may precipitate severe
disease when infected erythrocytes accumulate in brain or placenta.
Consequently, the severity of malaria infection may depend on the type of PfEMP1
protein expressed. In this study, we employ a representative panel of distinct
PfEMP1 types and host receptor proteins to demonstrate that CD36 and ICAM-1
binding properties of full-length PfEMP1 are highly predicted by their domain
composition. We also find that CD36 binding is under strong selection in many
PfEMP1 proteins, but that a group of PfEMP1s associated with more severe
infections does not bind CD36 and may utilize alternative means to sequester
infected erythrocytes. These findings have implications for understanding the
molecular basis for severe malaria.
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Affiliation(s)
- Joel H. Janes
- Department of Global Health, University of Washington, Seattle,
Washington, United States of America
| | - Christopher P. Wang
- Seattle Biomedical Research Institute, Seattle, Washington, United States
of America
| | - Emily Levin-Edens
- Seattle Biomedical Research Institute, Seattle, Washington, United States
of America
| | - Inès Vigan-Womas
- Institut Pasteur, Unité d'Immunologie Moléculaire des
Parasites, Paris, France
| | - Micheline Guillotte
- Institut Pasteur, Unité d'Immunologie Moléculaire des
Parasites, Paris, France
| | - Martin Melcher
- Seattle Biomedical Research Institute, Seattle, Washington, United States
of America
| | - Odile Mercereau-Puijalon
- Institut Pasteur, Unité d'Immunologie Moléculaire des
Parasites, Paris, France
- CNRS URA 2581, Paris, France
| | - Joseph D. Smith
- Department of Global Health, University of Washington, Seattle,
Washington, United States of America
- Seattle Biomedical Research Institute, Seattle, Washington, United States
of America
- * E-mail:
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231
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Grimberg BT, Mehlotra RK. Expanding the Antimalarial Drug Arsenal-Now, But How? Pharmaceuticals (Basel) 2011; 4:681-712. [PMID: 21625331 PMCID: PMC3102560 DOI: 10.3390/ph4050681] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2011] [Revised: 04/09/2011] [Accepted: 04/19/2011] [Indexed: 01/24/2023] Open
Abstract
The number of available and effective antimalarial drugs is quickly dwindling. This is mainly because a number of drug resistance-associated mutations in malaria parasite genes, such as crt, mdr1, dhfr/dhps, and others, have led to widespread resistance to all known classes of antimalarial compounds. Unfortunately, malaria parasites have started to exhibit some level of resistance in Southeast Asia even to the most recently introduced class of drugs, artemisinins. While there is much need, the antimalarial drug development pipeline remains woefully thin, with little chemical diversity, and there is currently no alternative to the precious artemisinins. It is difficult to predict where the next generation of antimalarial drugs will come from; however, there are six major approaches: (i) re-optimizing the use of existing antimalarials by either replacement/rotation or combination approach; (ii) repurposing drugs that are currently used to treat other infections or diseases; (iii) chemically modifying existing antimalarial compounds; (iv) exploring natural sources; (v) large-scale screening of diverse chemical libraries; and (vi) through parasite genome-based ("targeted") discoveries. When any newly discovered effective antimalarial treatment is used by the populus, we must maintain constant vigilance for both parasite-specific and human-related factors that are likely to hamper its success. This article is neither comprehensive nor conclusive. Our purpose is to provide an overview of antimalarial drug resistance, associated parasite genetic factors (1. Introduction; 2. Emergence of artemisinin resistance in P. falciparum), and the antimalarial drug development pipeline (3. Overview of the global pipeline of antimalarial drugs), and highlight some examples of the aforementioned approaches to future antimalarial treatment. These approaches can be categorized into "short term" (4. Feasible options for now) and "long term" (5. Next generation of antimalarial treatment-Approaches and candidates). However, these two categories are interrelated, and the approaches in both should be implemented in parallel with focus on developing a successful, long-lasting antimalarial chemotherapy.
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Affiliation(s)
- Brian T. Grimberg
- Center for Global Health and Diseases, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA; E-Mails: (B.T.G.); (R.K.M.); Tel.: +1-216-368-6328 or +1-216-368-6172, Fax: +1-216-368-4825
| | - Rajeev K. Mehlotra
- Center for Global Health and Diseases, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA; E-Mails: (B.T.G.); (R.K.M.); Tel.: +1-216-368-6328 or +1-216-368-6172, Fax: +1-216-368-4825
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232
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Goel S, Gowda DC. How specific is Plasmodium falciparum adherence to chondroitin 4-sulfate? Trends Parasitol 2011; 27:375-81. [PMID: 21507719 DOI: 10.1016/j.pt.2011.03.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Revised: 03/16/2011] [Accepted: 03/19/2011] [Indexed: 11/16/2022]
Abstract
Plasmodium falciparum infection during pregnancy results in the sequestration of infected red blood cells (IRBCs) in the placenta, contributing to pregnancy associated malaria (PAM). IRBC adherence is mediated by the binding of a variant Plasmodium falciparum erythrocyte binding protein 1 named VAR2CSA to the low sulfated chondroitin 4-sulfate (C4S) proteoglycan (CSPG) present predominantly in the intervillous space of the placenta. IRBC binding is highly specific to the level and distribution of 4-sulfate groups in C4S. Given the strict specificity of IRBC-C4S interactions, it is better to use either placental CSPG or CSPGs bearing structurally similar C4S chains in defining VAR2CSA structural architecture that interact with C4S, evaluating VAR2CSA constructs for vaccine development or studying structure-based inhibitors as therapeutics for PAM.
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Affiliation(s)
- Suchi Goel
- Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, USA
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233
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Paton D, Faragher B, Mustaffa KMF, Szestak T, Barrett SD, Craig AG. Automated counting for Plasmodium falciparum cytoadherence experiments. Malar J 2011; 10:91. [PMID: 21496305 PMCID: PMC3094228 DOI: 10.1186/1475-2875-10-91] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Accepted: 04/16/2011] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND The ability of mature forms of Plasmodium falciparum infected erythrocytes to bind to a range of host receptors including those displayed on endothelial cells has been associated with the pathology of this infection. Investigations into this adhesive phenomenon have used protein and cell-based adhesion assays to quantify the ability of infected red blood cells to bind. These adhesion assays tend to have relatively high inherent variability and so require multiple experiments in order to provide good quantitation. This means that investigators doing these experiments must count many fields of adherent parasites, a task that is time-consuming and laborious. To address this issue and to facilitate cytoadherence research, developed automated protocols were developed for counting parasite adhesion. METHODS Parasite adhesion assays were mainly carried out under static conditions using purified receptors, which is the simplest form of these assays and is translatable to the field. Two different software platforms were used, one commercial (Image Pro-Plus (Media Cybernetics)) and one available in the public domain (ImageSXM) based on the freely available NIH Image software. The adhesion assays were performed and parasite binding quantified using standard manual techniques. Images were also captured using video microscopy and analysed using the two automated systems. The results generated by each system were compared using the Bland and Altman method for assessing the agreement between two methods. RESULTS Both automated counting programs showed concordance compared to the 'gold standard' manual counting within the normal range of adhesion seen with these assays, although the ImageSXM technique had some systematic bias. There was some fall-off in accuracy at very high parasite densities, but this can be resolved through good design of the experiments. Cell based assays were also used as inputs to one of the automated systems (ImageSXM) and produced variable, but encouraging, results. CONCLUSIONS The automated counting programs are an accurate and practical way of quantifying static parasite binding assays to purified proteins. They are less accurate when applied to cell based systems, but can still provide a reasonable level of accuracy to give a semi-quantitative readout.
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Affiliation(s)
- Douglas Paton
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
- Research Institute for Science and Technology in Medicine, Keele University, Keele, Staffordshire ST5 5BG, UK
| | - Brian Faragher
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Khairul MF Mustaffa
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
- Institute for Research in Molecular Medicine (INFORMM), Health Campus, Universiti Sains Malaysia, Kubang Kerian, 16150 Kelantan, Malaysia
| | - Tadge Szestak
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Steve D Barrett
- Department of Physics, University of Liverpool, Liverpool L69 3BX, UK
| | - Alister G Craig
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
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234
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Cserti-Gazdewich CM, Mayr WR, Dzik WH. Plasmodium falciparum malaria and the immunogenetics of ABO, HLA, and CD36 (platelet glycoprotein IV). Vox Sang 2011; 100:99-111. [PMID: 21175660 DOI: 10.1111/j.1423-0410.2010.01429.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Plasmodium falciparum malaria has long been a killer of the young, and has selected for polymorphisms affecting not only erythrocytes, but the immunogenetics of three histocompatibility systems: ABO, human leukocyte antigen (HLA), and CD36. The ABO system is important because the original allele, encoding glycosylation with the A sugar, acts as an adhesion ligand with infected red blood cells (iRBC), thereby promoting vasoocclusion. The prevalence of blood group O, which reduces this cytoadhesion, has increased in endemic areas. Other adaptations which could mitigate A-mediated rosetting include weaker A expression and increased soluble A secretion. The role of the HLA system in malaria has been harder to verify. Although HLA-B53 and DRB1*04 may be associated with clinical outcome, HLA studies are challenged by numerous comparisons in this most polymorphic of systems, and confounded by increasingly heterogeneous populations. Certain HLA markers may also reflect linkage artefact with other malaria-relevant polymorphisms. HLA may be less important because the parasite predominantly invades a compartment which does not express HLA. Adhesion of iRBCs is also mediated by CD36, expressed on platelets, monocytes, and microvascular endothelium. CD36 on monocytes is involved in clearing iRBC, while CD36 on platelets and the endothelium may play a role in tissue sequestration. The genetics of CD36 expression are complex, and recent research is fraught with inconsistent results. The solution may lie in examining genotype-phenotype correlations, zygosity effects on differential tissue expression, or other mechanisms altering CD36 tissue expression. Carefully designed prospective studies should bridge the gap between in-vitro observations and clinical outcomes.
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Affiliation(s)
- C M Cserti-Gazdewich
- Department of Medicine (Hematology), University Health Network/Toronto General Hospital, Toronto, ON,
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235
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Mimche PN, Taramelli D, Vivas L. The plant-based immunomodulator curcumin as a potential candidate for the development of an adjunctive therapy for cerebral malaria. Malar J 2011; 10 Suppl 1:S10. [PMID: 21411011 PMCID: PMC3059458 DOI: 10.1186/1475-2875-10-s1-s10] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The clinical manifestations of cerebral malaria (CM) are well correlated with underlying major pathophysiological events occurring during an acute malaria infection, the most important of which, is the adherence of parasitized erythrocytes to endothelial cells ultimately leading to sequestration and obstruction of brain capillaries. The consequent reduction in blood flow, leads to cerebral hypoxia, localized inflammation and release of neurotoxic molecules and inflammatory cytokines by the endothelium. The pharmacological regulation of these immunopathological processes by immunomodulatory molecules may potentially benefit the management of this severe complication. Adjunctive therapy of CM patients with an appropriate immunomodulatory compound possessing even moderate anti-malarial activity with the capacity to down regulate excess production of proinflammatory cytokines and expression of adhesion molecules, could potentially reverse cytoadherence, improve survival and prevent neurological sequelae. Current major drug discovery programmes are mainly focused on novel parasite targets and mechanisms of action. However, the discovery of compounds targeting the host remains a largely unexplored but attractive area of drug discovery research for the treatment of CM. This review discusses the properties of the plant immune-modifier curcumin and its potential as an adjunctive therapy for the management of this complication.
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Affiliation(s)
- Patrice N Mimche
- Faculty of Infectious and Tropical Diseases, Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, Keppel St, London WC1E 7HT, UK.
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236
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Ochola LB, Siddondo BR, Ocholla H, Nkya S, Kimani EN, Williams TN, Makale JO, Liljander A, Urban BC, Bull PC, Szestak T, Marsh K, Craig AG. Specific receptor usage in Plasmodium falciparum cytoadherence is associated with disease outcome. PLoS One 2011; 6:e14741. [PMID: 21390226 PMCID: PMC3048392 DOI: 10.1371/journal.pone.0014741] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Accepted: 01/07/2011] [Indexed: 12/22/2022] Open
Abstract
Our understanding of the basis of severe disease in malaria is incomplete. It is clear that pathology is in part related to the pro-inflammatory nature of the host response but a number of other factors are also thought to be involved, including the interaction between infected erythrocytes and endothelium. This is a complex system involving several host receptors and a major parasite-derived variant antigen (PfEMP1) expressed on the surface of the infected erythrocyte membrane. Previous studies have suggested a role for ICAM-1 in the pathology of cerebral malaria, although these have been inconclusive. In this study we have examined the cytoadherence patterns of 101 patient isolates from varying clinical syndromes to CD36 and ICAM-1, and have used variant ICAM-1 proteins to further characterise this adhesive phenotype. Our results show that increased binding to CD36 is associated with uncomplicated malaria while ICAM-1 adhesion is raised in parasites from cerebral malaria cases.
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Affiliation(s)
- Lucy B Ochola
- KEMRI/Wellcome Trust Research Programme, Centre for Geographic Medicine Research, Kilifi, Kenya.
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237
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Ghumra A, Khunrae P, Ataide R, Raza A, Rogerson SJ, Higgins MK, Rowe JA. Immunisation with recombinant PfEMP1 domains elicits functional rosette-inhibiting and phagocytosis-inducing antibodies to Plasmodium falciparum. PLoS One 2011; 6:e16414. [PMID: 21305024 PMCID: PMC3031562 DOI: 10.1371/journal.pone.0016414] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2010] [Accepted: 12/14/2010] [Indexed: 11/24/2022] Open
Abstract
Background Rosetting is a Plasmodium falciparum virulence factor implicated in the pathogenesis of life-threatening malaria. Rosetting occurs when parasite–derived P. falciparum Erythrocyte Membrane Protein One (PfEMP1) on the surface of infected erythrocytes binds to human receptors on uninfected erythrocytes. PfEMP1 is a possible target for a vaccine to induce antibodies to inhibit rosetting and prevent severe malaria. Methodology/Findings We examined the vaccine potential of the six extracellular domains of a rosette-mediating PfEMP1 variant (ITvar9/R29var1 from the R29 parasite strain) by immunizing rabbits with recombinant proteins expressed in E. coli. Antibodies raised to each domain were tested for surface fluorescence with live infected erythrocytes, rosette inhibition and phagocytosis-induction. Antibodies to all PfEMP1 domains recognized the surface of live infected erythrocytes down to low concentrations (0.02–1.56 µg/ml of total IgG). Antibodies to all PfEMP1 domains except for the second Duffy-Binding-Like region inhibited rosetting (50% inhibitory concentration 0.04–4 µg/ml) and were able to opsonize and induce phagocytosis of infected erythrocytes at low concentrations (1.56–6.25 µg/ml). Antibodies to the N-terminal region (NTS-DBL1α) were the most effective in all assays. All antibodies were specific for the R29 parasite strain, and showed no functional activity against five other rosetting strains. Conclusions/Significance These results are encouraging for vaccine development as they show that potent antibodies can be generated to recombinant PfEMP1 domains that will inhibit rosetting and induce phagocytosis of infected erythrocytes. However, further work is needed on rosetting mechanisms and cross-reactivity in field isolates to define a set of PfEMP1 variants that could induce functional antibodies against a broad range of P. falciparum rosetting parasites.
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Affiliation(s)
- Ashfaq Ghumra
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Pongsak Khunrae
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Ricardo Ataide
- Department of Medicine, University of Melbourne, Post Office Royal Melbourne Hospital, Melbourne, Australia
- Graduate Program in Areas of Basic and Applied Biology, Universidade do Porto, Porto, Portugal
| | - Ahmed Raza
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Stephen J. Rogerson
- Department of Medicine, University of Melbourne, Post Office Royal Melbourne Hospital, Melbourne, Australia
| | - Matthew K. Higgins
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - J. Alexandra Rowe
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail:
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238
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Franke-Fayard B, Fonager J, Braks A, Khan SM, Janse CJ. Sequestration and tissue accumulation of human malaria parasites: can we learn anything from rodent models of malaria? PLoS Pathog 2010; 6:e1001032. [PMID: 20941396 PMCID: PMC2947991 DOI: 10.1371/journal.ppat.1001032] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The sequestration of Plasmodium falciparum–infected red blood cells (irbcs) in the microvasculature of organs is associated with severe disease; correspondingly, the molecular basis of irbc adherence is an active area of study. In contrast to P. falciparum, much less is known about sequestration in other Plasmodium parasites, including those species that are used as models to study severe malaria. Here, we review the cytoadherence properties of irbcs of the rodent parasite Plasmodium berghei ANKA, where schizonts demonstrate a clear sequestration phenotype. Real-time in vivo imaging of transgenic P. berghei parasites in rodents has revealed a CD36-dependent sequestration in lungs and adipose tissue. In the absence of direct orthologs of the P. falciparum proteins that mediate binding to human CD36, the P. berghei proteins and/or mechanisms of rodent CD36 binding are as yet unknown. In addition to CD36-dependent schizont sequestration, irbcs accumulate during severe disease in different tissues, including the brain. The role of sequestration is discussed in the context of disease as are the general (dis)similarities of P. berghei and P. falciparum sequestration.
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Affiliation(s)
- Blandine Franke-Fayard
- Leiden Malaria Research Group, Department of Parasitology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Jannik Fonager
- Leiden Malaria Research Group, Department of Parasitology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Anneke Braks
- Leiden Malaria Research Group, Department of Parasitology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Shahid M. Khan
- Leiden Malaria Research Group, Department of Parasitology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Chris J. Janse
- Leiden Malaria Research Group, Department of Parasitology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
- * E-mail:
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239
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Abstract
Previous work has shown that human donors vary in the magnitude and pattern of cytokines induced when peripheral blood mononuclear cells (PBMCs) are co-cultured with Plasmodium falciparum–infected erythrocytes. Whether P. falciparum strains vary in their ability to induce cytokines has not been studied in detail and is an important question, because variation in cytokine induction could affect parasite virulence and patterns of clinical disease. We investigated the early inflammatory cytokine response to four P. falciparum laboratory strains and five field isolates. Initial studies showed that parasite strain, parasitaemia and PBMC donor all had significant effects on the magnitude of pro-inflammatory cytokine responses (IFN-γ, GM-CSF, IL-1β, TNF-α, IL-6, P < 0·005 in all cases). However, we noticed that the most highly inducing parasite strain consistently reached schizont rupture more rapidly than the other strains. When timing of schizont rupture was taken into account, parasite strains no longer differed in their cytokine induction (P = 0·383), although donor effects remained significant (P < 0·001). These data do not support the hypothesis that P. falciparum strains vary in induction of early innate cytokine responses from PBMCs, and instead are consistent with the suggestion that conserved parasite products such as haemozoin or GPI-anchors are the parasite-derived stimuli for cytokine induction.
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Affiliation(s)
- R A Corrigan
- Centre for Immunity, Infection and Evolution, Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
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240
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Rask TS, Hansen DA, Theander TG, Gorm Pedersen A, Lavstsen T. Plasmodium falciparum erythrocyte membrane protein 1 diversity in seven genomes--divide and conquer. PLoS Comput Biol 2010; 6. [PMID: 20862303 PMCID: PMC2940729 DOI: 10.1371/journal.pcbi.1000933] [Citation(s) in RCA: 261] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2010] [Accepted: 08/16/2010] [Indexed: 12/21/2022] Open
Abstract
The var gene encoded hyper-variable Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family mediates cytoadhesion of infected erythrocytes to human endothelium. Antibodies blocking cytoadhesion are important mediators of malaria immunity acquired by endemic populations. The development of a PfEMP1 based vaccine mimicking natural acquired immunity depends on a thorough understanding of the evolved PfEMP1 diversity, balancing antigenic variation against conserved receptor binding affinities. This study redefines and reclassifies the domains of PfEMP1 from seven genomes. Analysis of domains in 399 different PfEMP1 sequences allowed identification of several novel domain classes, and a high degree of PfEMP1 domain compositional order, including conserved domain cassettes not always associated with the established group A–E division of PfEMP1. A novel iterative homology block (HB) detection method was applied, allowing identification of 628 conserved minimal PfEMP1 building blocks, describing on average 83% of a PfEMP1 sequence. Using the HBs, similarities between domain classes were determined, and Duffy binding-like (DBL) domain subclasses were found in many cases to be hybrids of major domain classes. Related to this, a recombination hotspot was uncovered between DBL subdomains S2 and S3. The VarDom server is introduced, from which information on domain classes and homology blocks can be retrieved, and new sequences can be classified. Several conserved sequence elements were found, including: (1) residues conserved in all DBL domains predicted to interact and hold together the three DBL subdomains, (2) potential integrin binding sites in DBLα domains, (3) an acylation motif conserved in group A var genes suggesting N-terminal N-myristoylation, (4) PfEMP1 inter-domain regions proposed to be elastic disordered structures, and (5) several conserved predicted phosphorylation sites. Ideally, this comprehensive categorization of PfEMP1 will provide a platform for future studies on var/PfEMP1 expression and function. About one million African children die from malaria every year. The severity of malaria infections in part depends on which type of the parasitic protein PfEMP1 is expressed on the surface of the infected red blood cells. Natural immunity to malaria is mediated through antibodies to PfEMP1. Therefore hopes for a malaria vaccine based on PfEMP1 proteins have been raised. However, the large sequence variation among PfEMP1 molecules has caused great difficulties in executing and interpreting studies on PfEMP1. Here, we present an extensive sequence analysis of all currently available PfEMP1 sequences and show that PfEMP1 variation is ordered and can be categorized at different levels. In this way, PfEMP1 belong to group A–E and are composed of up to four components, each component containing specific DBL or CIDR domain subclasses, which in some cases form entire conserved domain combinations. Finally, each PfEMP1 can be described in high detail as a combination of 628 homology blocks. This dissection of PfEMP1 diversity also enables predictions of several functional sequence motifs relevant to the fold of PfEMP1 proteins and their ability to bind human receptors. We therefore believe that this description of PfEMP1 diversity is necessary and helpful for the design and interpretation of future PfEMP1 studies.
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Affiliation(s)
- Thomas S. Rask
- Center for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark
- Centre for Medical Parasitology, Department of Medical Microbiology and Immunology, University of Copenhagen, Copehagen, Denmark
- * E-mail: (TSR); (TL)
| | - Daniel A. Hansen
- Center for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark
| | - Thor G. Theander
- Centre for Medical Parasitology, Department of Medical Microbiology and Immunology, University of Copenhagen, Copehagen, Denmark
| | - Anders Gorm Pedersen
- Center for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark, Lyngby, Denmark
| | - Thomas Lavstsen
- Centre for Medical Parasitology, Department of Medical Microbiology and Immunology, University of Copenhagen, Copehagen, Denmark
- * E-mail: (TSR); (TL)
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241
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Dhangadamajhi G, Kar SK, Ranjit M. The survival strategies of malaria parasite in the red blood cell and host cell polymorphisms. Malar Res Treat 2010; 2010:973094. [PMID: 22332025 PMCID: PMC3277829 DOI: 10.4061/2010/973094] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Accepted: 07/07/2010] [Indexed: 11/20/2022] Open
Abstract
Parasite growth within the erythrocyte causes dramatic alterations of host cell which on one hand facilitates nutrients acquisition from extracellular environment and on other hand contributes to the symptoms of severe malaria. The current paper focuses on interactions between the Plasmodium parasite and its metabolically highly reduced host cell, the natural selection of numerous polymorphisms in the genes encoding hemoglobin and other erythrocyte proteins.
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Affiliation(s)
- Gunanidhi Dhangadamajhi
- Regional Medical Research Centre, Indian Council of Medical Research, Chandrasekharpur, Bhubaneswar 751023, India
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242
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Rout R, Dhangadamajhi G, Mohapatra BN, Kar SK, Ranjit M. Genetic diversity of PfEMP1-DBL 1-α and its association with severe malaria in a hyperendemic state of India. ASIAN PAC J TROP MED 2010. [DOI: 10.1016/s1995-7645(10)60122-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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243
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Cserti-Gazdewich CM. Plasmodium falciparum malaria and carbohydrate blood group evolution. ACTA ACUST UNITED AC 2010. [DOI: 10.1111/j.1751-2824.2010.01380.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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244
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Karl S, Davis TME, St Pierre TG. Parameterization of high magnetic field gradient fractionation columns for applications with Plasmodium falciparum infected human erythrocytes. Malar J 2010; 9:116. [PMID: 20433771 PMCID: PMC2877061 DOI: 10.1186/1475-2875-9-116] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Accepted: 05/03/2010] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Magnetic fractionation of erythrocytes infected with Plasmodium falciparum has several research uses including enrichment of infected cells from parasite cultures or enhanced detection of P. falciparum gametocytes. The aim of the present study was to quantitatively characterize the magnetic fractionation process and thus enable optimization of protocols developed for specific uses. METHODS Synchronized cultures of P. falciparum parasites incubated with human erythrocytes were magnetically fractionated with commercially available columns. The timing of the fractionation experiments was such that the parasites were in second half of their erythrocytic life cycle with parasite densities ranging from 1 to 9%. Fractionations were carried out in a single pass through the columns. Cells were enumerated and differentiated in the initial samples as well as in the positive and negative fractions. The capture of cells by the fractionation column was described by a saturation binding model. RESULTS The magnetic binding affinity to the column matrix was approximately 350 times greater for infected cells compared with uninfected cells. The purity of infected cells in the captured fraction was generally >80% but decreased rapidly (to less than 50%) when the number of infected cells that passed through the column was substantially decreased (to less than 9 +/- 5 x 105 cells). The distribution of captured parasite developmental stages shifted to mature stages as the number of infected cells in the initial samples and flow rate increased. The relationship between the yield of infected cells in the captured fraction and flow rate of cells conformed to a complementary cumulative log-normal equation with flow rates >1.6 x 105 cells per second resulting in yields <50%. CONCLUSIONS A detailed quantitative analysis of a batchwise magnetic fractionation process for malaria infected erythrocytes using high gradient magnetic fractionation columns was performed. The models applied in this study allow the prediction of capture efficiency if the initial infected cell concentration and the flow rate are known.
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Affiliation(s)
- Stephan Karl
- School of Physics, M013, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
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245
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Sijwali PS, Rosenthal PJ. Functional evaluation of Plasmodium export signals in Plasmodium berghei suggests multiple modes of protein export. PLoS One 2010; 5:e10227. [PMID: 20419102 PMCID: PMC2856681 DOI: 10.1371/journal.pone.0010227] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2009] [Accepted: 03/29/2010] [Indexed: 12/20/2022] Open
Abstract
The erythrocytic stage development of malaria parasites occurs within the parasitophorous vacuole inside the infected-erythrocytes, and requires transport of several parasite-encoded proteins across the parasitophorous vacuole to several locations, including the cytosol and membrane of the infected cell. These proteins are called exported proteins; and a large number of such proteins have been predicted for Plasmodium falciparum based on the presence of an N-terminal motif known as the Plasmodium export element (PEXEL) or vacuolar transport signal (VTS), which has been shown to mediate export. The majority of exported proteins contain one or more transmembrane domains at the C-terminus and one of three types of N-terminus domain architectures. (1) The majority, including the knob-associated histidine rich protein (KAHRP), contain a signal/hydrophobic sequence preceding the PEXEL/VTS motif. (2) Other exported proteins, including the P. berghei variant antigen family bir and the P. falciparum skeleton binding protein-1, do not appear to contain a PEXEL/VTS motif. (3) The P. falciparum erythrocyte membrane protein-1 (PfEMP1) family lacks a signal/hydrophobic sequence before the motif. These different domain architectures suggest the presence of multiple export pathways in malaria parasites. To determine if export pathways are conserved in plasmodia and to develop an experimental system for studying these processes, we investigated export of GFP fused with N- and C-terminus putative export domains in the rodent malaria parasite P. berghei. Export was dependent on specific N- and C-terminal domains. Constructs with a KAHRP-like or bir N-terminus, but not the PfEMP1 N-terminus, exported GFP into the erythrocyte. The C-terminus of a P. falciparum variant antigen rifin prevented GFP export by the KAHRP-like N-terminus. In contrast, GFP chimeras containing KAHRP-like N-termini and the PfEMP1 C-terminus were exported to the surface of erythrocytes. Taken together, these results suggest that proteins with KAHRP-like architecture follow a common export pathway, but that PfEMP1s utilize an alternative pathway. Functional validation of common putative export domains of malaria parasites in P. berghei provides an alternative and simpler system to investigate export mechanisms.
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Affiliation(s)
- Puran Singh Sijwali
- Centre for Cellular and Molecular Biology, Hyderabad, India
- * E-mail: (PSS); (PJR)
| | - Philip J. Rosenthal
- Department of Medicine, San Francisco General Hospital, University of California San Francisco, San Francisco, California, United States of America
- * E-mail: (PSS); (PJR)
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246
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Can any lessons be learned from the ambiguous glycan binding of PfEMP1 domains? Trends Parasitol 2010; 26:230-5. [PMID: 20189879 DOI: 10.1016/j.pt.2010.02.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Revised: 12/18/2009] [Accepted: 02/04/2010] [Indexed: 11/22/2022]
Abstract
Pregnancy-associated malaria (PAM) is caused by Plasmodium falciparum-infected erythrocytes (IEs) accumulating in the placenta and has dire consequences for both mother and child. The multi-domain antigen VAR2CSA confers specific adhesion of IEs to chondroitin sulphate A (CSA) in the placenta, and is the leading PAM vaccine candidate. Recent data from different laboratories show that the binding properties of individual VAR2CSA domains do not reflect the native CSA-specific adhesion of IEs, which questions the relevance of the information obtained from single domain binding assays and co-crystallization experiments. Here, we discuss the implications of these findings for VAR2CSA vaccine development and highlight the need for studying the native structure of this protein.
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247
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Protein export in Plasmodium parasites: from the endoplasmic reticulum to the vacuolar export machine. Int J Parasitol 2010; 40:509-13. [PMID: 20170656 DOI: 10.1016/j.ijpara.2010.02.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Revised: 02/05/2010] [Accepted: 02/08/2010] [Indexed: 11/22/2022]
Abstract
It is somewhat paradoxical that the malaria parasite's survival strategy involves spending almost all of its blood-stage existence residing behind a two-membrane barrier in a host red blood cell, yet giving considerable attention to exporting parasite-encoded proteins back across these membranes. These exported proteins are thought to play diverse roles and are crucial in pathogenic processes, such as re-modelling of the erythrocyte cytoskeleton and mediating the export of a major virulence protein known as Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1), and in metabolic processes such as nutrient uptake and solute exchange. Despite these varied roles most exported proteins have at least one common link; they share a trafficking pathway that begins with entry into the endoplasmic reticulum and concludes with passage across the vacuole membrane via a proteinaceous translocon known as the Plasmodium translocon of exported proteins (PTEX). In this commentary we review recent advances in our understanding of this export pathway and suggest several models by which different aspects of the process may be interconnected.
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248
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Khunrae P, Dahlbäck M, Nielsen MA, Andersen G, Ditlev SB, Resende M, Pinto VV, Theander TG, Higgins MK, Salanti A. Full-length recombinant Plasmodium falciparum VAR2CSA binds specifically to CSPG and induces potent parasite adhesion-blocking antibodies. J Mol Biol 2010; 397:826-34. [PMID: 20109466 PMCID: PMC3715698 DOI: 10.1016/j.jmb.2010.01.040] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Revised: 01/08/2010] [Accepted: 01/19/2010] [Indexed: 11/27/2022]
Abstract
Plasmodium falciparum malaria remains one of the world's leading causes of human suffering and poverty. Each year, the disease takes 1–3 million lives, mainly in sub-Saharan Africa. The adhesion of infected erythrocytes (IEs) to vascular endothelium or placenta is the key event in the pathogenesis of severe P. falciparum infection. In pregnant women, the parasites express a single and unique member of the P. falciparum erythrocyte membrane protein 1 (PfEMP1) family named VAR2CSA, which is associated with the ability of the IEs to adhere specifically to chondroitin sulphate A (CSA) in the placenta. Several Duffy-binding-like domains from VAR2CSA molecules have been shown in vitro to bind to CSA, but it has also been demonstrated that Duffy-binding-like domains from PfEMP1 proteins other than VAR2CSA can bind CSA. In addition, the specificity of the binding of VAR2CSA domains to glycosaminoglycans does not match that of VAR2CSA-expressing IEs. This has led to speculation that the domains of native VAR2CSA need to come together to form a specific binding site or that VAR2CSA might bind to CSA through a bridging molecule. Here, we describe the expression and purification of the complete extracellular region of VAR2CSA secreted at high yields from insect cells. Using surface plasmon resonance, we demonstrate that VAR2CSA alone binds with nanomolar affinity to human chondroitin sulphate proteoglycan and with significantly weaker affinity to other glycosaminoglycans, showing a specificity similar to that observed for IEs. Antibodies raised against full-length VAR2CSA completely inhibit recombinant VAR2CSA binding, as well as parasite binding to chondroitin sulphate proteoglycan. This is the first study to describe the successful production and functionality of a full-length PfEMP1. The specificity of the binding and anti-adhesion potency of induced IgG, together with high-yield production, encourages the use of full-length PfEMP1 in vaccine development strategies.
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Affiliation(s)
- Pongsak Khunrae
- Department of Biochemistry, University of Cambridge, Cambridge, UK
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249
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Blood groups and malaria: fresh insights into pathogenesis and identification of targets for intervention. Curr Opin Hematol 2010; 16:480-7. [PMID: 19812491 DOI: 10.1097/moh.0b013e3283313de0] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW This review summarizes recent advances in our understanding of the interaction between malaria parasites and blood group antigens and discusses how the knowledge gleaned can be used to target the development of new antimalarial treatments and vaccines. RECENT FINDINGS Studies of the interaction between Plasmodium vivax and the Duffy antigen provide the clearest example of the potential for basic research on blood groups and malaria to be translated into a vaccine that could have a major impact on global health. Progress is also being made in understanding the effects of other blood group antigens on malaria. After years of controversy, the effect of ABO blood groups on falciparum malaria has been clarified, with the non-O blood groups emerging as significant risk factors for life-threatening malaria, through the mechanism of enhanced rosette formation. The Knops blood group system may also influence malaria susceptibility, although conflicting results from different countries mean that further research is required. Unanswered questions remain about the interactions between malaria parasites and other blood group antigens, including the Gerbich, MNS and Rhesus systems. SUMMARY The interplay between malaria parasites and blood group antigens remains a fascinating subject with potential to contribute to the development of new interventions to reduce the global burden of malaria.
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250
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Doumbo OK, Thera MA, Koné AK, Raza A, Tempest LJ, Lyke KE, Plowe CV, Rowe JA. High levels of Plasmodium falciparum rosetting in all clinical forms of severe malaria in African children. Am J Trop Med Hyg 2009; 81:987-93. [PMID: 19996426 PMCID: PMC2877664 DOI: 10.4269/ajtmh.2009.09-0406] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Plasmodium falciparum rosetting (the spontaneous binding of infected erythrocytes to uninfected erythrocytes) is a well-recognized parasite virulence factor. However, it is currently unclear whether rosetting is associated with all clinical forms of severe malaria, or only with specific syndromes such as cerebral malaria. We investigated the relationship between rosetting and clinical malaria in 209 Malian children enrolled in a case-control study of severe malaria. Rosetting was significantly higher in parasite isolates from severe malaria cases compared with non-severe hyperparasitemia and uncomplicated malaria controls (F(2,117) = 8.15, P < 0.001). Analysis of sub-categories of severe malaria (unrousable coma, severe anemia, non-comatose neurological impairment, repeated seizures or a small heterogeneous group with signs of renal failure or jaundice) showed high levels of rosetting in all sub-categories, and no statistically significant differences in rosetting between sub-categories (F(4,67) = 1.28, P = 0.28). Thus rosetting may contribute to the pathogenesis of all severe malaria syndromes in African children, and interventions to disrupt rosetting could be potential adjunctive therapies for all forms of severe malaria in Africa.
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Affiliation(s)
- Ogobara K Doumbo
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Dentistry, University of Bamako, Mali.
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