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Lee WC, Russell B, Rénia L. Sticking for a Cause: The Falciparum Malaria Parasites Cytoadherence Paradigm. Front Immunol 2019; 10:1444. [PMID: 31316507 PMCID: PMC6610498 DOI: 10.3389/fimmu.2019.01444] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 06/10/2019] [Indexed: 12/26/2022] Open
Abstract
After a successful invasion, malaria parasite Plasmodium falciparum extensively remodels the infected erythrocyte cellular architecture, conferring cytoadhesive properties to the infected erythrocytes. Cytoadherence plays a central role in the parasite's immune-escape mechanism, at the same time contributing to the pathogenesis of severe falciparum malaria. In this review, we discuss the cytoadhesive interactions between P. falciparum infected erythrocytes and various host cell types, and how these events are linked to malaria pathogenesis. We also highlight the limitations faced by studies attempting to correlate diversity in parasite ligands and host receptors with the development of severe malaria.
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Affiliation(s)
- Wenn-Chyau Lee
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (ASTAR), Singapore, Singapore
| | - Bruce Russell
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Laurent Rénia
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (ASTAR), Singapore, Singapore
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Horata N, Choowongkomon K, Ratanabunyong S, Tongshoob J, Khusmith S. Acquisition of naturally acquired antibody response to Plasmodium falciparum erythrocyte membrane protein 1-DBLα and differential regulation of IgG subclasses in severe and uncomplicated malaria. Asian Pac J Trop Biomed 2017. [DOI: 10.1016/j.apjtb.2017.09.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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Wahlgren M, Goel S, Akhouri RR. Variant surface antigens of Plasmodium falciparum and their roles in severe malaria. Nat Rev Microbiol 2017; 15:479-491. [DOI: 10.1038/nrmicro.2017.47] [Citation(s) in RCA: 142] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Quintana MDP, Angeletti D, Moll K, Chen Q, Wahlgren M. Phagocytosis-inducing antibodies to Plasmodium falciparum upon immunization with a recombinant PfEMP1 NTS-DBL1α domain. Malar J 2016; 15:416. [PMID: 27531359 PMCID: PMC4987995 DOI: 10.1186/s12936-016-1459-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 07/29/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Individuals living in endemic areas gradually acquire natural immunity to clinical malaria, largely dependent on antibodies against parasite antigens. There are many studies indicating that the variant antigen PfEMP1 at the surface of the parasitized red blood cell (pRBC) is one of the major targets of the immune response. It is believed that antibodies against PfEMP1 confer protection by blocking sequestration (rosetting and cytoadherence), inducing antibody-dependent cellular-inhibitory effect and opsonizing pRBCs for phagocytosis. METHODS A recombinant NTS-DBL1α domain from a rosette-mediating PfEMP1 was expressed in Escherichia coli. The resulting protein was purified and used for immunization to generate polyclonal (goat) and monoclonal (mouse) antibodies. The antibodies' ability to opsonize and induce phagocytosis in vitro was tested and contrasted with the presence of opsonizing antibodies naturally acquired during Plasmodium falciparum infection. RESULTS All antibodies recognized the recombinant antigen and the surface of live pRBCs, however, their capacity to opsonize the pRBCs for phagocytosis varied. The monoclonal antibodies isotyped as IgG2b did not induce phagocytosis, while those isotyped as IgG2a were in general very effective, inducing phagocytosis with similar levels as those naturally acquired during P. falciparum infection. These monoclonal antibodies displayed different patterns, some of them showing a concentration-dependent activity while others showed a prozone-like effect. The goat polyclonal antibodies were not able to induce phagocytosis. CONCLUSION Immunization with an NTS-DBL1-α domain of PfEMP1 generates antibodies that not only have a biological role in rosette disruption but also effectively induce opsonization for phagocytosis of pRBCs with similar activity to naturally acquired antibodies from immune individuals living in a malaria endemic area. Some of the antibodies with high opsonizing activity were not able to disrupt rosettes, indicating that epitopes of the NTS-DBL1-α other than those involved in rosetting are exposed on the pRBC surface and are able to induce functional antibodies. The ability to induce phagocytosis largely depended on the antibody isotype and on the ability to recognize the surface of the pRBC regardless of the rosette-disrupting capacity.
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Affiliation(s)
- Maria Del Pilar Quintana
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden.,Escuela de Medicina y Ciencias de la Salud, Facultad de Ciencias Naturales y Matemáticas, Universidad del Rosario, Bogotá, Colombia
| | - Davide Angeletti
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Kirsten Moll
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Qijun Chen
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden.,Key Laboratory of Zoonosis, Jilin University, Changchun, People's Republic of China.,Institute of Pathogen Biology, Chinese Academy of Medical Sciences, Beijing, People's Republic of China
| | - Mats Wahlgren
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, Sweden.
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Persistence and immunogenicity of chemically attenuated blood stage Plasmodium falciparum in Aotus monkeys. Int J Parasitol 2016; 46:581-91. [PMID: 27238088 DOI: 10.1016/j.ijpara.2016.05.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 04/05/2016] [Accepted: 05/03/2016] [Indexed: 12/24/2022]
Abstract
Malaria is a disease caused by a protozoan of the Plasmodium genus and results in 0.5-0.7million deaths per year. Increasing drug resistance of the parasite and insecticide resistance of mosquitoes necessitate alternative control measures. Numerous vaccine candidates have been identified but none have been able to induce robust, long-lived protection when evaluated in malaria endemic regions. Rodent studies have demonstrated that chemically attenuated blood stage parasites can persist at sub-patent levels and induce homologous and heterologous protection against malaria. Parasite-specific cellular responses were detected, with protection dependent on CD4+ T cells. To investigate this vaccine approach for Plasmodium falciparum, we characterised the persistence and immunogenicity of chemically attenuated P. falciparum FVO strain parasites (CAPs) in non-splenectomised Aotus nancymaae monkeys following administration of a single dose. Control monkeys received either normal red blood cells or wild-type parasites followed by drug treatment. Chemical attenuation was performed using tafuramycin A, which irreversibly binds to DNA. CAPs were detected in the peripheral blood for up to 2days following inoculation as determined by thick blood smears, and for up to 8days as determined by quantitative PCR. Parasite-specific IgG was not detected in monkeys that received CAPs; however, in vitro parasite-specific T cell proliferation was observed. Following challenge, the CAP monkeys developed an infection; however, one CAP monkey and the infection and drug-cure monkeys showed partial or complete resistance. These experiments lay the groundwork for further assessment of CAPs as a potential vaccine against malaria.
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Abstract
The Plasmodium falciparum erythrocyte membrane protein 1 antigens that are inserted onto the surface of P. falciparum infected erythrocytes play a key role both in the pathology of severe malaria and as targets of naturally acquired immunity. They might be considered unlikely vaccine targets because they are extremely diverse. However, several lines of evidence suggest that underneath this molecular diversity there are a restricted set of epitopes which may act as effective targets for a vaccine against severe malaria. Here we review some of the recent developments in this area of research, focusing on work that has assessed the potential of these molecules as possible vaccine targets.
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Riccio EKP, Pratt-Riccio LR, Bianco-Júnior C, Sanchez V, Totino PRR, Carvalho LJM, Daniel-Ribeiro CT. Molecular and immunological tools for the evaluation of the cellular immune response in the neotropical monkey Saimiri sciureus, a non-human primate model for malaria research. Malar J 2015; 14:166. [PMID: 25927834 PMCID: PMC4416248 DOI: 10.1186/s12936-015-0688-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Accepted: 04/10/2015] [Indexed: 02/07/2023] Open
Abstract
Background The neotropical, non-human primates (NHP) of the genus Saimiri and Aotus are recommended by the World Health Organization as experimental models for the study of human malaria because these animals can be infected with the same Plasmodium that cause malaria in humans. However, one limitation is the lack of immunological tools to assess the immune response in these models. The present study focuses on the development and comparative use of molecular and immunological methods to evaluate the cellular immune response in Saimiri sciureus. Methods Blood samples were obtained from nineteen uninfected Saimiri. Peripheral blood mononuclear cells (PBMC) from these animals and splenocytes from one splenectomized animal were cultured for 6, 12, 18, 24, 48, 72 and 96 hrs in the presence of phorbol-12-myristate-13-acetate and ionomycin. The cytokine levels in the supernatant were detected using human and NHP cytometric bead array Th1/Th2 cytokine kits, the Bio-Plex Pro Human Cytokine Th1/Th2 Assay, enzyme-linked immunosorbent assay, enzyme-linked immunospot assays and intracellular cytokine secretion assays. Cytokine gene expression was examined through TaqMan® Gene Expression Real-Time PCR using predesigned human gene-specific primers and probes or primers and probes designed based on published S. sciureus cytokine sequences. Results The use of five assays based on monoclonal antibodies specific for human cytokines facilitated the detection of IL-2, IL-4 and/or IFN-γ. TaqMan array plates facilitated the detection of 12 of the 28 cytokines assayed. However, only seven cytokines (IL-1A, IL-2, IL-10, IL-12B, IL-17, IFN-β, and TNF) presented relative expression levels of at least 70% of the gene expression observed in human PBMC. The use of primers and probes specific for S. sciureus cytokines facilitated the detection of transcripts that showed relative expression below the threshold of 70%. The most efficient evaluation of cytokine gene expression, in PBMC and splenocytes, was observed after 6–12 hrs of culture, except for LTA in PBMC, whose expression was best analysed after 24 hrs of culture. Conclusions Real-time PCR facilitates the analysis of a large number of cytokines altered during malaria infection, and this technique is considered the best tool for the evaluation of the cellular immune response in S. sciureus.
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Affiliation(s)
- Evelyn K P Riccio
- Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz, Fiocruz, Avenida Brasil 4365, Pavilhão Leônidas Deane, Salas 513-517, 5° andar Manguinhos, Rio de Janeiro, RJ, CEP: 21040-900, Brazil. .,Centro de Pesquisa, Diagnóstico e Treinamento em Malária (CPD-Mal), Fiocruz, Reference Centre for Malaria in the Extra-Amazonian Region for the Secretary for Health Surveillance, Ministry of Health, Rio de Janeiro, RJ, Brazil.
| | - Lilian R Pratt-Riccio
- Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz, Fiocruz, Avenida Brasil 4365, Pavilhão Leônidas Deane, Salas 513-517, 5° andar Manguinhos, Rio de Janeiro, RJ, CEP: 21040-900, Brazil. .,Centro de Pesquisa, Diagnóstico e Treinamento em Malária (CPD-Mal), Fiocruz, Reference Centre for Malaria in the Extra-Amazonian Region for the Secretary for Health Surveillance, Ministry of Health, Rio de Janeiro, RJ, Brazil.
| | - Cesare Bianco-Júnior
- Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz, Fiocruz, Avenida Brasil 4365, Pavilhão Leônidas Deane, Salas 513-517, 5° andar Manguinhos, Rio de Janeiro, RJ, CEP: 21040-900, Brazil. .,Centro de Pesquisa, Diagnóstico e Treinamento em Malária (CPD-Mal), Fiocruz, Reference Centre for Malaria in the Extra-Amazonian Region for the Secretary for Health Surveillance, Ministry of Health, Rio de Janeiro, RJ, Brazil.
| | - Violette Sanchez
- Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz, Fiocruz, Avenida Brasil 4365, Pavilhão Leônidas Deane, Salas 513-517, 5° andar Manguinhos, Rio de Janeiro, RJ, CEP: 21040-900, Brazil. .,Centro de Pesquisa, Diagnóstico e Treinamento em Malária (CPD-Mal), Fiocruz, Reference Centre for Malaria in the Extra-Amazonian Region for the Secretary for Health Surveillance, Ministry of Health, Rio de Janeiro, RJ, Brazil. .,Present address: Research Department, Sanofi Pasteur, Lyon, France.
| | - Paulo R R Totino
- Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz, Fiocruz, Avenida Brasil 4365, Pavilhão Leônidas Deane, Salas 513-517, 5° andar Manguinhos, Rio de Janeiro, RJ, CEP: 21040-900, Brazil. .,Centro de Pesquisa, Diagnóstico e Treinamento em Malária (CPD-Mal), Fiocruz, Reference Centre for Malaria in the Extra-Amazonian Region for the Secretary for Health Surveillance, Ministry of Health, Rio de Janeiro, RJ, Brazil.
| | - Leonardo J M Carvalho
- Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz, Fiocruz, Avenida Brasil 4365, Pavilhão Leônidas Deane, Salas 513-517, 5° andar Manguinhos, Rio de Janeiro, RJ, CEP: 21040-900, Brazil. .,Centro de Pesquisa, Diagnóstico e Treinamento em Malária (CPD-Mal), Fiocruz, Reference Centre for Malaria in the Extra-Amazonian Region for the Secretary for Health Surveillance, Ministry of Health, Rio de Janeiro, RJ, Brazil.
| | - Cláudio Tadeu Daniel-Ribeiro
- Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz, Fiocruz, Avenida Brasil 4365, Pavilhão Leônidas Deane, Salas 513-517, 5° andar Manguinhos, Rio de Janeiro, RJ, CEP: 21040-900, Brazil. .,Centro de Pesquisa, Diagnóstico e Treinamento em Malária (CPD-Mal), Fiocruz, Reference Centre for Malaria in the Extra-Amazonian Region for the Secretary for Health Surveillance, Ministry of Health, Rio de Janeiro, RJ, Brazil.
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Chan JA, Fowkes FJI, Beeson JG. Surface antigens of Plasmodium falciparum-infected erythrocytes as immune targets and malaria vaccine candidates. Cell Mol Life Sci 2014; 71:3633-57. [PMID: 24691798 PMCID: PMC4160571 DOI: 10.1007/s00018-014-1614-3] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 03/04/2014] [Accepted: 03/17/2014] [Indexed: 12/19/2022]
Abstract
Understanding the targets and mechanisms of human immunity to malaria caused by Plasmodium falciparum is crucial for advancing effective vaccines and developing tools for measuring immunity and exposure in populations. Acquired immunity to malaria predominantly targets the blood stage of infection when merozoites of Plasmodium spp. infect erythrocytes and replicate within them. During the intra-erythrocytic development of P. falciparum, numerous parasite-derived antigens are expressed on the surface of infected erythrocytes (IEs). These antigens enable P. falciparum-IEs to adhere in the vasculature and accumulate in multiple organs, which is a key process in the pathogenesis of disease. IE surface antigens, often referred to as variant surface antigens, are important targets of acquired protective immunity and include PfEMP1, RIFIN, STEVOR and SURFIN. These antigens are highly polymorphic and encoded by multigene families, which generate substantial antigenic diversity to mediate immune evasion. The most important immune target appears to be PfEMP1, which is a major ligand for vascular adhesion and sequestration of IEs. Studies are beginning to identify specific variants of PfEMP1 linked to disease pathogenesis that may be suitable for vaccine development, but overcoming antigenic diversity in PfEMP1 remains a major challenge. Much less is known about other surface antigens, or antigens on the surface of gametocyte-IEs, the effector mechanisms that mediate immunity, and how immunity is acquired and maintained over time; these are important topics for future research.
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Cavanagh DR, Kocken CHM, White JH, Cowan GJM, Samuel K, Dubbeld MA, der Wel AVV, Thomas AW, McBride JS, Arnot DE. Antibody responses to a novel Plasmodium falciparum merozoite surface protein vaccine correlate with protection against experimental malaria infection in Aotus monkeys. PLoS One 2014; 9:e83704. [PMID: 24421900 PMCID: PMC3885447 DOI: 10.1371/journal.pone.0083704] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Accepted: 11/06/2013] [Indexed: 11/29/2022] Open
Abstract
The Block 2 region of the merozoite surface protein-1 (MSP-1) of Plasmodium falciparum has been identified as a target of protective immunity by a combination of seroepidemiology and parasite population genetics. Immunogenicity studies in small animals and Aotus monkeys were used to determine the efficacy of recombinant antigens derived from this region of MSP-1 as a potential vaccine antigen. Aotus lemurinus griseimembra monkeys were immunized three times with a recombinant antigen derived from the Block 2 region of MSP-1 of the monkey-adapted challenge strain, FVO of Plasmodium falciparum, using an adjuvant suitable for use in humans. Immunofluorescent antibody assays (IFA) against erythrocytes infected with P. falciparum using sera from the immunized monkeys showed that the MSP-1 Block 2 antigen induced significant antibody responses to whole malaria parasites. MSP-1 Block 2 antigen-specific enzyme-linked immunosorbent assays (ELISA) showed no significant differences in antibody titers between immunized animals. Immunized animals were challenged with the virulent P. falciparum FVO isolate and monitored for 21 days. Two out of four immunized animals were able to control their parasitaemia during the follow-up period, whereas two out of two controls developed fulminating parasitemia. Parasite-specific serum antibody titers measured by IFA were four-fold higher in protected animals than in unprotected animals. In addition, peptide-based epitope mapping of serum antibodies from immunized Aotus showed distinct differences in epitope specificities between protected and unprotected animals.
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Affiliation(s)
- David R. Cavanagh
- Institute of Immunology and Infection Research, Center for Immunity, Infection and Evolution, Ashworth Laboratories, University of Edinburgh, Edinburgh, United Kingdom
| | - Clemens H. M. Kocken
- Biomedical Primate Research Center, Department of Parasitology, Rijswijk, The Netherlands
| | - John H. White
- Institute of Immunology and Infection Research, Center for Immunity, Infection and Evolution, Ashworth Laboratories, University of Edinburgh, Edinburgh, United Kingdom
| | - Graeme J. M. Cowan
- Institute of Immunology and Infection Research, Center for Immunity, Infection and Evolution, Ashworth Laboratories, University of Edinburgh, Edinburgh, United Kingdom
| | - Kay Samuel
- Scottish National Blood Transfusion Service, Cell Therapy Group, University of Edinburgh, Edinburgh, United Kingdom
| | - Martin A. Dubbeld
- Biomedical Primate Research Center, Department of Parasitology, Rijswijk, The Netherlands
| | | | - Alan W. Thomas
- Biomedical Primate Research Center, Department of Parasitology, Rijswijk, The Netherlands
| | - Jana S. McBride
- Institute of Immunology and Infection Research, Center for Immunity, Infection and Evolution, Ashworth Laboratories, University of Edinburgh, Edinburgh, United Kingdom
| | - David E. Arnot
- Institute of Immunology and Infection Research, Center for Immunity, Infection and Evolution, Ashworth Laboratories, University of Edinburgh, Edinburgh, United Kingdom
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Beeson JG, Chan JA, Fowkes FJI. PfEMP1 as a target of human immunity and a vaccine candidate against malaria. Expert Rev Vaccines 2013; 12:105-8. [PMID: 23414401 DOI: 10.1586/erv.12.144] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Angeletti D, Albrecht L, Blomqvist K, Quintana MDP, Akhter T, Bächle SM, Sawyer A, Sandalova T, Achour A, Wahlgren M, Moll K. Plasmodium falciparum rosetting epitopes converge in the SD3-loop of PfEMP1-DBL1α. PLoS One 2012; 7:e50758. [PMID: 23227205 PMCID: PMC3515580 DOI: 10.1371/journal.pone.0050758] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Accepted: 10/25/2012] [Indexed: 11/26/2022] Open
Abstract
The ability of Plasmodium falciparum parasitized RBC (pRBC) to form rosettes with normal RBC is linked to the virulence of the parasite and RBC polymorphisms that weaken rosetting confer protection against severe malaria. The adhesin PfEMP1 mediates the binding and specific antibodies prevent sequestration in the micro-vasculature, as seen in animal models. Here we demonstrate that epitopes targeted by rosette disrupting antibodies converge in the loop of subdomain 3 (SD3) which connects the h6 and h7 α-helices of PfEMP1-DBL1α. Both monoclonal antibodies and polyclonal IgG, that bound to epitopes in the SD3-loop, stained the surface of pRBC, disrupted rosettes and blocked direct binding of recombinant NTS-DBL1α to RBC. Depletion of polyclonal IgG raised to NTS-DBL1α on a SD3 loop-peptide removed the anti-rosetting activity. Immunizations with recombinant subdomain 1 (SD1), subdomain 2 (SD2) or SD3 all generated antibodies reacting with the pRBC-surface but only the sera of animals immunized with SD3 disrupted rosettes. SD3-sequences were found to segregate phylogenetically into two groups (A/B). Group A included rosetting sequences that were associated with two cysteine-residues present in the SD2-domain while group B included those with three or more cysteines. Our results suggest that the SD3 loop of PfEMP1-DBL1α is an important target of anti-rosetting activity, clarifying the molecular basis of the development of variant-specific rosette disrupting antibodies.
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Affiliation(s)
- Davide Angeletti
- Department of Microbiology, Tumor- and Cellbiology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Letusa Albrecht
- Department of Microbiology, Tumor- and Cellbiology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Karin Blomqvist
- Department of Microbiology, Tumor- and Cellbiology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - María del Pilar Quintana
- Department of Microbiology, Tumor- and Cellbiology (MTC), Karolinska Institutet, Stockholm, Sweden
- Escuela de Medicina y Ciencias de la Salud, Facultad de Ciencias Naturales y Matemáticas, Universidad del Rosario, Bogotá, Colombia
| | - Tahmina Akhter
- Department of Microbiology, Tumor- and Cellbiology (MTC), Karolinska Institutet, Stockholm, Sweden
| | - Susanna M. Bächle
- Center for Infectious Medicine, Department of Medicine, Karolinska University Hospital Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Alan Sawyer
- EMBL Monoclonal Antibodies Core Facility, Monterotondo-Scalo (RM), Italy
| | - Tatyana Sandalova
- Center for Infectious Medicine, Department of Medicine, Karolinska University Hospital Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Adnane Achour
- Center for Infectious Medicine, Department of Medicine, Karolinska University Hospital Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Mats Wahlgren
- Department of Microbiology, Tumor- and Cellbiology (MTC), Karolinska Institutet, Stockholm, Sweden
- * E-mail: (MW); (KM)
| | - Kirsten Moll
- Department of Microbiology, Tumor- and Cellbiology (MTC), Karolinska Institutet, Stockholm, Sweden
- * E-mail: (MW); (KM)
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Haque SJ, Majumdar T, Barik S. Redox-assisted protein folding systems in eukaryotic parasites. Antioxid Redox Signal 2012; 17:674-83. [PMID: 22122448 PMCID: PMC3373220 DOI: 10.1089/ars.2011.4433] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
SIGNIFICANCE The cysteine (Cys) residues of proteins play two fundamentally important roles. They serve as sites of post-translational redox modifications as well as influence the conformation of the protein through the formation of disulfide bonds. RECENT ADVANCES Redox-related and redox-associated protein folding in protozoan parasites has been found to be a major mode of regulation, affecting myriad aspects of the parasitic life cycle, host-parasite interactions, and the disease pathology. Available genome sequences of various parasites have begun to complement the classical biochemical and enzymological studies of these processes. In this article, we summarize the reversible Cys disulfide (S-S) bond formation in various classes of strategically important parasitic proteins, and its structural consequence and functional relevance. CRITICAL ISSUES Molecular mechanisms of folding remain under-studied and often disconnected from functional relevance. FUTURE DIRECTIONS The clinical benefit of redox research will require a comprehensive characterization of the various isoforms and paralogs of the redox enzymes and their concerted effect on the structure and function of the specific parasitic client proteins.
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Affiliation(s)
- Saikh Jaharul Haque
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
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Plasmodium yoelii blood-stage antigens newly identified by immunoaffinity using purified IgG antibodies from malaria-resistant mice. Immunobiology 2012; 217:823-30. [PMID: 22658767 DOI: 10.1016/j.imbio.2012.05.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Accepted: 05/07/2012] [Indexed: 12/12/2022]
Abstract
As the search for an effective human malaria vaccine continues, understanding immune responses to Plasmodium in rodent models is perhaps the key to unlocking new vaccine strategies. The recruitment of parasite-specific antibodies is an important component of natural immunity against infection in blood-stage malaria. Here, we describe the use of sera from naturally surviving ICR mice after infection with lethal doses of Plasmodium yoelii yoelii 17XL to identify highly immunogenic blood-stage antigens. Immobilized protein A/G was used for the affinity-chromatography purification of the IgGs present in pooled sera from surviving mice. These protective IgGs, covalently immobilized on agarose columns, were then used to isolate reactive antigens from whole P. yoelii yoelii 17XL protein extracts obtained from the blood-stage malaria infection. Through proteomics analysis of the recovered parasite antigens, we were able to identify two endoplasmic reticulum lumen proteins: protein disulfide isomerase and a member of the heat shock protein 70 family. Also identified were the digestive protease plasmepsin and the 39 kDa-subunit of eukaryotic translation initiation factor 3, a ribosome associated protein. Of these four proteins, three have not been previously identified as antigenic during blood-stage malaria infection. This procedure of isolating and identifying parasite antigens using serum IgGs from malaria-protected individuals could be a novel strategy for the development of multi-antigen-based vaccine therapies.
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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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Adhesion of Plasmodium falciparum-infected erythrocytes to human cells: molecular mechanisms and therapeutic implications. Expert Rev Mol Med 2009; 11:e16. [PMID: 19467172 PMCID: PMC2878476 DOI: 10.1017/s1462399409001082] [Citation(s) in RCA: 249] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Severe malaria has a high mortality rate (15–20%) despite treatment with
effective antimalarial drugs. Adjunctive therapies for severe malaria that target the
underlying disease process are therefore urgently required. Adhesion of erythrocytes
infected with Plasmodium falciparum to human cells has a key role in the
pathogenesis of life-threatening malaria and could be targeted with antiadhesion therapy.
Parasite adhesion interactions include binding to endothelial cells (cytoadherence),
rosetting with uninfected erythrocytes and platelet-mediated clumping of infected
erythrocytes. Recent research has started to define the molecular mechanisms of parasite
adhesion, and antiadhesion therapies are being explored. However, many fundamental
questions regarding the role of parasite adhesion in severe malaria remain unanswered.
There is strong evidence that rosetting contributes to severe malaria in sub-Saharan
Africa; however, the identity of other parasite adhesion phenotypes that are implicated in
disease pathogenesis remains unclear. In addition, the possibility of geographic variation
in adhesion phenotypes causing severe malaria, linked to differences in malaria
transmission levels and host immunity, has been neglected. Further research is needed to
realise the untapped potential of antiadhesion adjunctive therapies, which could
revolutionise the treatment of severe malaria and reduce the high mortality rate of the
disease.
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Maier AG, Cooke BM, Cowman AF, Tilley L. Malaria parasite proteins that remodel the host erythrocyte. Nat Rev Microbiol 2009; 7:341-54. [PMID: 19369950 DOI: 10.1038/nrmicro2110] [Citation(s) in RCA: 289] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Exported proteins of the malaria parasite Plasmodium falciparum interact with proteins of the erythrocyte membrane and induce substantial changes in the morphology, physiology and function of the host cell. These changes underlie the pathology that is responsible for the deaths of 1-2 million children every year due to malaria infections. The advent of molecular transfection technology, including the ability to generate deletion mutants and to introduce fluorescent reporter proteins that track the locations and dynamics of parasite proteins, has increased our understanding of the processes and machinery for export of proteins in P. falciparum-infected erythrocytes and has provided us with insights into the functions of the parasite protein exportome. We review these developments, focusing on parasite proteins that interact with the erythrocyte membrane skeleton or that promote delivery of the major virulence protein, PfEMP1, to the erythrocyte membrane.
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Affiliation(s)
- Alexander G Maier
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Melbourne, Victoria, Australia
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18
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Abstract
The persistence of the human malaria parasite Plasmodium falciparum during blood stage proliferation in its host depends on the successive expression of variant molecules at the surface of infected erythrocytes. This variation is mediated by the differential control of a family of surface molecules termed PfEMP1 encoded by approximately 60 var genes. Each individual parasite expresses a single var gene at a time, maintaining all other members of the family in a transcriptionally silent state. PfEMP1/var enables parasitized erythrocytes to adhere within the microvasculature, resulting in severe disease. This review highlights key regulatory mechanisms thought to be critical for monoallelic expression of var genes. Antigenic variation is orchestrated by epigenetic factors including monoallelic var transcription at separate spatial domains at the nuclear periphery, differential histone marks on otherwise identical var genes, and var silencing mediated by telomeric heterochromatin. In addition, controversies surrounding var genetic elements in antigenic variation are discussed.
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Affiliation(s)
- Artur Scherf
- Biology of Host-Parasite Interactions Unit, CNRS URA2581, Institut Pasteur 75724 Paris, France.
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19
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Klein MM, Gittis AG, Su HP, Makobongo MO, Moore JM, Singh S, Miller LH, Garboczi DN. The cysteine-rich interdomain region from the highly variable plasmodium falciparum erythrocyte membrane protein-1 exhibits a conserved structure. PLoS Pathog 2008; 4:e1000147. [PMID: 18773118 PMCID: PMC2518858 DOI: 10.1371/journal.ppat.1000147] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2008] [Accepted: 08/07/2008] [Indexed: 12/03/2022] Open
Abstract
Plasmodium falciparum malaria parasites, living in red blood cells, express proteins of the erythrocyte membrane protein-1 (PfEMP1) family on the red blood cell surface. The binding of PfEMP1 molecules to human cell surface receptors mediates the adherence of infected red blood cells to human tissues. The sequences of the 60 PfEMP1 genes in each parasite genome vary greatly from parasite to parasite, yet the variant PfEMP1 proteins maintain receptor binding. Almost all parasites isolated directly from patients bind the human CD36 receptor. Of the several kinds of highly polymorphic cysteine-rich interdomain region (CIDR) domains classified by sequence, only the CIDR1α domains bind CD36. Here we describe the CD36-binding portion of a CIDR1α domain, MC179, as a bundle of three α-helices that are connected by a loop and three additional helices. The MC179 structure, containing seven conserved cysteines and 10 conserved hydrophobic residues, predicts similar structures for the hundreds of CIDR sequences from the many genome sequences now known. Comparison of MC179 with the CIDR domains in the genome of the P. falciparum 3D7 strain provides insights into CIDR domain structure. The CIDR1α three-helix bundle exhibits less than 20% sequence identity with the three-helix bundles of Duffy-binding like (DBL) domains, but the two kinds of bundles are almost identical. Despite the enormous diversity of PfEMP1 sequences, the CIDR1α and DBL protein structures, taken together, predict that a PfEMP1 molecule is a polymer of three-helix bundles elaborated by a variety of connecting helices and loops. From the structures also comes the insight that DBL1α domains are approximately 100 residues larger and that CIDR1α domains are approximately 100 residues smaller than sequence alignments predict. This new understanding of PfEMP1 structure will allow the use of better-defined PfEMP1 domains for functional studies, for the design of candidate vaccines, and for understanding the molecular basis of cytoadherence. Malaria parasites express proteins of the erythrocyte membrane protein-1 family (PfEMP1) on the surfaces of the human red blood cells that they infect. These large proteins vary in sequence extensively, yet bind to host receptors to allow infected cells to adhere to host tissues. PfEMP1 proteins help parasites evade the immune system, as the 60 PfEMP1 genes are expressed one at a time. Sequence comparisons predict that PfEMP1 molecules are modular, made up of Duffy binding-like (DBL) and cysteine-rich interdomain region (CIDR) domains. Many CIDR domains bind to the human receptor CD36. We have analyzed the structure of the CD36-binding portion, known as MC179, of a CIDR domain. The MC179 protein is composed of a bundle of three helices connected by a loop and three additional helices. Based on the structure and sequence similarities, MC179 is a good model for the hundreds of known CIDR sequences. In addition, the MC179 three-helix bundle is remarkably similar to subdomain 3 of the known DBL structures. MC179 provides insight into the relatedness of both kinds of PfEMP1 domains and predicts that the large PfEMP1 molecules are polymers of three-helix bundles and their connecting polypeptides.
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Affiliation(s)
- Michael M. Klein
- Structural Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Apostolos G. Gittis
- Structural Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Hua-Poo Su
- Structural Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Morris O. Makobongo
- Malaria Vaccine Development Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Jaime M. Moore
- Structural Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Sanjay Singh
- Malaria Vaccine Development Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - Louis H. Miller
- Malaria Vaccine Development Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - David N. Garboczi
- Structural Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
- * E-mail:
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20
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Mackintosh CL, Christodoulou Z, Mwangi TW, Kortok M, Pinches R, Williams TN, Marsh K, Newbold CI. Acquisition of naturally occurring antibody responses to recombinant protein domains of Plasmodium falciparum erythrocyte membrane protein 1. Malar J 2008; 7:155. [PMID: 18706102 PMCID: PMC2533674 DOI: 10.1186/1475-2875-7-155] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2008] [Accepted: 08/16/2008] [Indexed: 11/21/2022] Open
Abstract
Background Antibodies targeting variant antigens expressed on the surface of Plasmodium falciparum infected erythrocytes have been associated with protection from clinical malaria. The precise target for these antibodies is unknown. The best characterized and most likely target is the erythrocyte surface-expressed variant protein family Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1). Methods Using recombinant proteins corresponding to five domains of the expressed A4 var gene, A4 PfEMP1, the naturally occurring antibody response was assessed, by ELISA, to each domain in serum samples obtained from individuals resident in two communities of differing malaria transmission intensity on the Kenyan coast. Using flow cytometry, the correlation in individual responses to each domain with responses to intact A4-infected erythrocytes expressing A4 PfEMP1 on their surface as well as responses to two alternative parasite clones and one clinical isolate was assessed. Results Marked variability in the prevalence of responses between each domain and between each transmission area was observed, as wasa strong correlation between age and reactivity with some but not all domains. Individual responses to each domain varied strikingly, with some individuals showing reactivity to all domains and others with no reactivity to any, this was apparent at all age groups. Evidence for possible cross-reactivity in responses to the domain DBL4γ was found. Conclusion Individuals acquire antibodies to surface expressed domains of a highly variant protein. The finding of potential cross-reactivity in responses to one of these domains is an important initial finding in the consideration of potential vaccine targets.
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Affiliation(s)
- Claire L Mackintosh
- Kenya Medical Research Institute Centre for Geographic Medicine Research Coast, Kilifi District Hospital, Kilifi, Kenya.
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21
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Recker M, Arinaminpathy N, Buckee CO. The effects of a partitioned var gene repertoire of Plasmodium falciparum on antigenic diversity and the acquisition of clinical immunity. Malar J 2008; 7:18. [PMID: 18215289 PMCID: PMC2265724 DOI: 10.1186/1475-2875-7-18] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2007] [Accepted: 01/23/2008] [Indexed: 12/04/2022] Open
Abstract
Background The human malaria parasite Plasmodium falciparum exploits antigenic diversity and within-host antigenic variation to evade the host's immune system. Of particular importance are the highly polymorphic var genes that encode the family of cell surface antigens PfEMP1 (Plasmodium falciparum Erythrocyte Membrane Protein 1). It has recently been shown that in spite of their extreme diversity, however, these genes fall into distinct groups according to chromosomal location or sequence similarity, and that recombination may be confined within these groups. Methods This study presents a mathematical analysis of how recombination hierarchies affect diversity, and, by using simple stochastic simulations, investigates how intra- and inter-genic diversity influence the rate at which individuals acquire clinical immunity. Results The analysis demonstrates that the partitioning of the var gene repertoire has a limiting effect on the total diversity attainable through recombination and that the limiting effect is strongly influenced by the respective sizes of each of the partitions. Furthermore, by associating expression of one of the groups with severe malaria it is demonstrated how a small number of infections can be sufficient to protect against disease despite a seemingly limitless number of possible non-identical repertoires. Conclusion Recombination hierarchies within the var gene repertoire of P. falciparum have a severe effect on strain diversity and the process of acquiring immunity against clinical malaria. Future studies will show how the existence of these recombining groups can offer an evolutionary advantage in spite of their restriction on diversity.
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Affiliation(s)
- Mario Recker
- Department of Zoology, South Parks Road, OX1 3PS, Oxford, UK.
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22
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Gölnitz U, Albrecht L, Wunderlich G. Var transcription profiling of Plasmodium falciparum 3D7: assignment of cytoadherent phenotypes to dominant transcripts. Malar J 2008; 7:14. [PMID: 18194571 PMCID: PMC2254424 DOI: 10.1186/1475-2875-7-14] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Accepted: 01/14/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Cytoadherence of Plasmodium falciparum-infected red blood cells is mediated by var gene-encoded P. falciparum erythrocyte membrane protein-1 and host receptor preference depends in most cases on which of the 50-60 var genes per genome is expressed. Enrichment of phenotypically homogenous parasites by panning on receptor expressing cells is fundamental for the identification of the corresponding var transcript. METHODS P. falciparum 3D7 parasites were panned on several transfected CHO-cell lines and their var transcripts analysed by i) reverse transcription/PCR/cloning/sequencing using a universal DBLalpha specific oligonucleotide pair and ii) by reverse transcription followed by quantitative PCR using 57 different oligonucleotide pairs. RESULTS Each cytoadherence selected parasite line also adhered to untransfected CHO-745 cells and upregulation of the var gene PFD995/PFD1000c was consistently associated with cytoadherence to all but one CHO cell line. In addition, parasites panned on different CHO cell lines revealed candidate var genes which reproducibly associated to the respective cytoadherent phenotype. The transcription profile obtained by RT-PCR/cloning/sequencing differed significantly from that of RT-quantitative PCR. CONCLUSION Transfected CHO cell lines are of limited use for the creation of monophenotypic cytoadherent parasite lines. Nevertheless, 3D7 parasites can be reproducibly selected for the transcription of different determined var genes without genetic manipulation. Most importantly, var transcription analysis by RT-PCR/cloning/sequencing may lead to erroneous interpretation of var transcription profiles.
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Affiliation(s)
- Uta Gölnitz
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, Avenida Prof, Lineu Prestes 1374, São Paulo - SP, Brazil.
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23
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D'Ombrain MC, Voss TS, Maier AG, Pearce JA, Hansen DS, Cowman AF, Schofield L. Plasmodium falciparum erythrocyte membrane protein-1 specifically suppresses early production of host interferon-gamma. Cell Host Microbe 2007; 2:130-8. [PMID: 18005727 DOI: 10.1016/j.chom.2007.06.012] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2007] [Revised: 06/12/2007] [Accepted: 06/28/2007] [Indexed: 11/16/2022]
Abstract
Plasmodium falciparum erythrocyte membrane protein-1 (PfEMP-1) is a variable antigen expressed by P. falciparum, the malarial parasite. PfEMP-1, present on the surface of infected host erythrocytes, mediates erythrocyte binding to vascular endothelium, enabling the parasite to avoid splenic clearance. In addition, PfEMP-1 is proposed to regulate host immune responses via interactions with the CD36 receptor on antigen-presenting cells. We investigated the immunoregulatory function of PfEMP-1 by comparing host cell responses to erythrocytes infected with either wild-type parasites or transgenic parasites lacking PfEMP-1. We showed that PfEMP-1 suppresses the production of the cytokine interferon-gamma by human peripheral blood mononuclear cells early after exposure to P. falciparum. Suppression of this rapid proinflammatory response was CD36 independent and specific to interferon-gamma production by gammadelta-T, NK, and alphabeta-T cells. These data demonstrate a parasite strategy for downregulating the proinflammatory interferon-gamma response and further establish transgenic parasites lacking PfEMP-1 as powerful tools for elucidating PfEMP-1 functions.
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Affiliation(s)
- Marthe C D'Ombrain
- Infection and Immunity Division, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3050, Australia
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Patel SN, Lu Z, Ayi K, Serghides L, Gowda DC, Kain KC. Disruption of CD36 impairs cytokine response to Plasmodium falciparum glycosylphosphatidylinositol and confers susceptibility to severe and fatal malaria in vivo. THE JOURNAL OF IMMUNOLOGY 2007; 178:3954-61. [PMID: 17339496 DOI: 10.4049/jimmunol.178.6.3954] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
CD36 is a scavenger receptor that has been implicated in malaria pathogenesis as well as innate defense against blood-stage infection. Inflammatory responses to Plasmodium falciparum GPI (pfGPI) anchors are believed to play an important role in innate immune response to malaria. We investigated the role of CD36 in pfGPI-induced MAPK activation and proinflammatory cytokine secretion. Furthermore, we explored the role of this receptor in an experimental model of acute malaria in vivo. We demonstrate that ERK1/2, JNK, p38, and c-Jun became phosphorylated in pfGPI-stimulated macrophages. In contrast, pfGPI-induced phosphorylation of JNK, ERK1/2, and c-Jun was reduced in Cd36(-/-) macrophages and Cd36(-/-) macrophages secreted significantly less TNF-alpha in response to pfGPI than their wild-type counterparts. In addition, we demonstrate a role for CD36 in innate immune response to malaria in vivo. Compared with wild-type mice, Cd36(-/-) mice experienced more severe and fatal malaria when challenged with Plasmodium chabaudi chabaudi AS. Cd36(-/-) mice displayed a combined defect in cytokine induction and parasite clearance with a dysregulated cytokine response to infection, earlier peak parasitemias, higher parasite densities, and higher mortality rates than wild-type mice. These results provide direct evidence that pfGPI induces TNF-alpha secretion in a CD36-dependent manner and support a role for CD36 in modulating host cytokine response and innate control of acute blood-stage malaria infection in vivo.
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Affiliation(s)
- Samir N Patel
- McLaughlin-Rotman Centre, University Health Network-Toronto General Hospital, McLaughlin Centre for Molecular Medicine, University of Toronto, 200 Elizabeth Street, Toronto, Ontario, Canada
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Magistrado PA, Lusingu J, Vestergaard LS, Lemnge M, Lavstsen T, Turner L, Hviid L, Jensen ATR, Theander TG. Immunoglobulin G antibody reactivity to a group A Plasmodium falciparum erythrocyte membrane protein 1 and protection from P. falciparum malaria. Infect Immun 2007; 75:2415-20. [PMID: 17283085 PMCID: PMC1865733 DOI: 10.1128/iai.00951-06] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Variant surface antigens (VSA) on the surface of Plasmodium falciparum-infected red blood cells play a major role in the pathogenesis of malaria and are key targets for acquired immunity. The best-characterized VSA belong to the P. falciparum erythrocyte membrane protein 1 (PfEMP1) family. In areas where P. falciparum is endemic, parasites causing severe malaria and malaria in young children with limited immunity tend to express semiconserved PfEMP1 molecules encoded by group A var genes. Here we investigated antibody responses of Tanzanians who were 0 to 19 years old to PF11_0008, a group A PfEMP1. PF11_0008 has previously been found to be highly transcribed in a nonimmune Dutch volunteer experimentally infected with NF54 parasites. A high proportion of the Tanzanian donors had antibodies against recombinant PF11_0008 domains, and in children who were 4 to 9 years old the presence of antibodies to the PF11_0008 CIDR2beta domain was associated with reduced numbers of malaria episodes. These results indicate that homologues of PF11_0008 are present in P. falciparum field isolates and suggest that PF11_0008 CIDR2beta-reactive antibodies might be involved in protection against malaria episodes.
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Affiliation(s)
- Pamela A Magistrado
- Centre for Medical Parasitology at Department of Medical Microbiology and Immunology, University of Copenhagen, Denmark.
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Fairhurst RM, Wellems TE. Modulation of malaria virulence by determinants of Plasmodium falciparum erythrocyte membrane protein-1 display. Curr Opin Hematol 2006; 13:124-30. [PMID: 16567953 DOI: 10.1097/01.moh.0000219655.73162.42] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW Plasmodium falciparum malaria parasites carry approximately 60 var genes that encode variable adhesins termed P. falciparum erythrocyte membrane protein-1. Clonal expression of a single P. falciparum erythrocyte membrane protein-1 variant on the surface of the parasitized host erythrocyte promotes binding of the cell to blood elements (including noninfected erythrocytes, leukocytes) and walls of microvessels. These binding events enable parasitized erythrocytes to sequester and avoid clearance by the spleen, and they also contribute to disease by causing microvascular inflammation and obstruction. RECENT FINDINGS Steps by which P. falciparum erythrocyte membrane protein-1 is exported to the parasitized erythrocyte surface have recently been elucidated. The ability of parasites to cytoadhere and cause disease depends on the variant of P. falciparum erythrocyte membrane protein-1 as well as its amount and distribution at the erythrocyte surface. An example of a host polymorphism that affects P. falciparum erythrocyte membrane protein-1 display is hemoglobin C, which may protect against malaria by impairing the parasite's ability to adhere to microvessels and induce inflammation. Interference with P. falciparum erythrocyte membrane protein-1-mediated phenomena appears to diminish cytoadherence in vivo and to protect against disease in animal models. SUMMARY Plasmodium falciparum erythrocyte membrane protein-1-mediated sequestration of parasitized erythrocytes plays a central role in malaria pathogenesis. Clinical interventions aimed at reducing cytoadherence and microvascular inflammation may improve disease outcome.
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Affiliation(s)
- Rick M Fairhurst
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20852-8132, USA
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27
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Abstract
Every year, forty percent of the world population is at risk of contracting malaria. Hopes for the erradication of this disease during the 20th century were dashed by the ability of Plasmodium falciparum, its most deadly causative agent, to develop resistance to available drugs. Efforts to produce an effective vaccine have so far been unsuccessful, enhancing the need to develop novel antimalarial drugs. In this review, we summarize our knowledge concerning existing antimalarials, mechanisms of drug-resistance development, the use of drug combination strategies and the quest for novel anti-plasmodial compounds. We emphasize the potential role of host genes and molecules as novel targets for newly developed drugs. Recent results from our laboratory have shown Hepatocyte Growth Factor/MET signaling to be essential for the establishment of infection in hepatocytes. We discuss the potential use of this pathway in the prophylaxis of malaria infection.
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28
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Ndungu FM, Sanni L, Urban B, Stephens R, Newbold CI, Marsh K, Langhorne J. CD4 T cells from malaria-nonexposed individuals respond to the CD36-Binding Domain of Plasmodium falciparum erythrocyte membrane protein-1 via an MHC class II-TCR-independent pathway. THE JOURNAL OF IMMUNOLOGY 2006; 176:5504-12. [PMID: 16622019 DOI: 10.4049/jimmunol.176.9.5504] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We have studied the human CD4 T cell response to a functionally conserved domain of Plasmodium falciparum erythrocyte membrane protein-1, cysteine interdomain region-1alpha (CIDR-1alpha). Responses to CIDR-1alpha were striking in that both exposed and nonexposed donors responded. The IFN-gamma response to CIDR-1alpha in the nonexposed donors was partially independent of TCR engagement of MHC class II and peptide. Contrastingly, CD4 T cell and IFN-gamma responses in malaria-exposed donors were MHC class II restricted, suggesting that the CD4 T cell response to CIDR-1alpha in malaria semi-immune adults also has a TCR-mediated component, which may represent a memory response. Dendritic cells isolated from human peripheral blood were activated by CIDR-1alpha to produce IL-12, IL-10, and IL-18. IL-12 was detectable only between 6 and 12 h of culture, whereas the IL-10 continued to increase throughout the 24-h time course. These data strengthen previous observations that P. falciparum interacts directly with human dendritic cells, and suggests that the interaction between CIDR-1alpha and the host cell may be responsible for regulation of the CD4 T cell and cytokine responses to P. falciparum-infected erythrocytes reported previously.
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Affiliation(s)
- Francis M Ndungu
- Division of Parasitology, National Institute for Medical Research, The Ridgeway, Mill Hill, London, United Kingdom
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Ahuja S, Pettersson F, Moll K, Jonsson C, Wahlgren M, Chen Q. Induction of cross-reactive immune responses to NTS-DBL-1alpha/x of PfEMP1 and in vivo protection on challenge with Plasmodium falciparum. Vaccine 2006; 24:6140-54. [PMID: 16837110 DOI: 10.1016/j.vaccine.2006.05.030] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2005] [Revised: 04/28/2006] [Accepted: 05/09/2006] [Indexed: 10/24/2022]
Abstract
The interactions of Plasmodium falciparum infected erythrocytes parasitized red blood cells (pRBC) with endothelial receptors and erythrocytes are mediated by multiple Duffy-binding like (DBL) and cysteine-rich interdomain region (CIDR) domains harboured in the Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1). The success of a subunit vaccine based on PfEMP1 depends on its ability to elicit cross-reactive responses to a substantial number of PfEMP1 variants. We have here evaluated serological PfEMP1 cross-reactivity by immunizing rats with phylogenetically diverse recombinant NTS-DBL-1alpha/x fusion domains from the 3D7 genome parasite emulsified in Montanide ISA 720. Cross-reactivity was elicited to these diverse DBL-1alpha/x domains as measured by ELISA and by immunoblotting. Employing a novel in vivo model of human infected erythrocyte sequestration, immunized animals were challenged with the FCR3S1.2 clone and cross-protection in terms of reduction in lung sequestration amounting to approximately 50% was demonstrated. Our results suggest that immunization with phylogenetically distant DBL-1alpha/x variants, can elicit partial cross-protection to challenge with the parasites harbouring a distant variant. These observations have implications for the design of multi-component vaccines against P. falciparum malaria.
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Affiliation(s)
- Sanjay Ahuja
- Microbiology and Tumor Biology Center (MTC), Karolinska Institute, P.O. Box 280, SE-17177 Stockholm, Sweden
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Pinzon-Charry A, Anderson V, McPhun V, Wykes M, Good MF. Malaria vaccines: New hope in old ideas. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/j.ddstr.2006.06.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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31
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Stephens R, Langhorne J. Priming of CD4+ T cells and development of CD4+ T cell memory; lessons for malaria. Parasite Immunol 2006; 28:25-30. [PMID: 16438673 DOI: 10.1111/j.1365-3024.2006.00767.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
CD4 T cells play a central role in the immune response to malaria. They are required to help B cells produce the antibody that is essential for parasite clearance. They also produce cytokines that amplify the phagocytic and parasitocidal response of the innate immune system, as well as dampening this response later on to limit immunopathology. Therefore, understanding the mechanisms by which T helper cells are activated and the requirements for development of specific, and effective, T cell memory and immunity is essential in the quest for a malaria vaccine. In this paper on the CD4 session of the Immunology of Malaria Infections meeting, we summarize discussions of CD4 cell priming and memory in malaria and in vaccination and outline critical future lines of investigation. B. Stockinger and M.K. Jenkins proposed cutting edge experimental systems to study basic T cell biology in malaria. Critical parameters in T cell activation include the cell types involved, the route of infection and the timing and location and cell types involved in antigen presentation. A new generation of vaccines that induce CD4 T cell activation and memory are being developed with new adjuvants. Studies of T cell memory focus on differentiation and factors involved in maintenance of antigen specific T cells and control of the size of that population. To improve detection of T cell memory in the field, efforts will have to be made to distinguish antigen-specific responses from cytokine driven responses.
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Affiliation(s)
- R Stephens
- National Institute for Medical Research, Division of Parasitology, London, UK
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Curtidor H, Ocampo M, Rodríguez LE, López R, García JE, Valbuena J, Vera R, Puentes A, Leiton J, Cortes LJ, López Y, Patarroyo MA, Patarroyo ME. Plasmodium falciparum TryThrA antigen synthetic peptides block in vitro merozoite invasion to erythrocytes. Biochem Biophys Res Commun 2005; 339:888-96. [PMID: 16329993 DOI: 10.1016/j.bbrc.2005.11.089] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2005] [Accepted: 11/14/2005] [Indexed: 11/27/2022]
Abstract
Tryptophan-threonine-rich antigen (TryThrA) is a Plasmodium falciparum homologue of Plasmodium yoelii-infected erythrocyte membrane pypAg-1 antigen. pypAg-1 binds to the surface of uninfected mouse erythrocytes and has been used successfully in vaccine studies. The two antigens are characterized by an unusual tryptophan-rich domain, suggesting similar biological properties. Using synthetic peptides spanning the TryThrA sequence and human erythrocyte we have done binding assays to identify possible TryThrA functional regions. We describe four peptides outside the tryptophan-rich domain having high activity binding to normal human erythrocytes. The peptides termed HABPs (high activity binding peptides) are 30884 ((61)LKEKKKKVLEFFENLVLNKKY(80)) located at the N-terminal and 30901 ((401)RKSLEQQFGDNMDKMNKLKKY(420)), 30902 ((421)KKILKFFPLFNYKSDLESIM(440)) and 30913 ((641)DLESTAEQKAEKKGGKAKAKY(660)) located at the C-terminal. Studies with polyclonal goat antiserum against synthetic peptides chosen to represent the whole length of the protein showed that TryThrA has fluorescence pattern similar to PypAg-1 of P. yoelii. All HABPs inhibited merozoite in vitro invasion, suggesting that TryThrA protein may be participating in merozoite-erythrocyte interaction during invasion.
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Affiliation(s)
- Hernando Curtidor
- Fundación Instituto de Inmunología de Colombia (FIDIC), Universidad Nacional de Colombia, Colombia.
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33
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Bull PC, Berriman M, Kyes S, Quail MA, Hall N, Kortok MM, Marsh K, Newbold CI. Plasmodium falciparum variant surface antigen expression patterns during malaria. PLoS Pathog 2005; 1:e26. [PMID: 16304608 PMCID: PMC1287908 DOI: 10.1371/journal.ppat.0010026] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2005] [Accepted: 10/11/2005] [Indexed: 11/23/2022] Open
Abstract
The variant surface antigens expressed on Plasmodium falciparum–infected erythrocytes are potentially important targets of immunity to malaria and are encoded, at least in part, by a family of var genes, about 60 of which are present within every parasite genome. Here we use semi-conserved regions within short var gene sequence “tags” to make direct comparisons of var gene expression in 12 clinical parasite isolates from Kenyan children. A total of 1,746 var clones were sequenced from genomic and cDNA and assigned to one of six sequence groups using specific sequence features. The results show the following. (1) The relative numbers of genomic clones falling in each of the sequence groups was similar between parasite isolates and corresponded well with the numbers of genes found in the genome of a single, fully sequenced parasite isolate. In contrast, the relative numbers of cDNA clones falling in each group varied considerably between isolates. (2) Expression of sequences belonging to a relatively conserved group was negatively associated with the repertoire of variant surface antigen antibodies carried by the infected child at the time of disease, whereas expression of sequences belonging to another group was associated with the parasite “rosetting” phenotype, a well established virulence determinant. Our results suggest that information on the state of the host–parasite relationship in vivo can be provided by measurements of the differential expression of different var groups, and need only be defined by short stretches of sequence data. Hope that it will be possible to develop a malaria vaccine is supported by the fact that individuals who have grown up in malaria endemic regions learn to carry malarial infections without suffering disease. Surprisingly little is still known about how this immunity develops. Much current research focuses on how the host develops immune responses to parasite antigens that are exposed to the host immune system. A major family of such antigens are inserted into the surface of parasite-infected erythrocytes, where they undergo antigenic switching to evade a developing antibody response. These proteins are encoded by a family of approximately 60 var genes, variants of which are present in every parasite genome. The extreme diversity of the var genes has prevented meaningful comparison of their expression in clinical isolates. However, the authors of this paper show that var genes can be placed in groups that have a similar representation in the genomes of all parasites that the authors collected from Kenyan children. Having demonstrated an underlying similarity at the genomic level, the authors show that the var expression patterns vary markedly between different patients. The expression levels of specific groups of var genes was associated with poorly developed antibody responses in the children and a well-established parasite virulence phenotype. The study provides tools for exploring how host and parasite adapt to one another as immunity develops.
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Affiliation(s)
- Peter C Bull
- Nuffield Department of Clinical Medicine, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom.
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34
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Abstract
The erythrocytic cycle of Plasmodium falciparum presents a particularity in relation to other Plasmodium species that infect man. Mature trophozoites and schizonts are sequestered from the peripheral circulation due to adhesion of infected erythrocytes to host endothelial cells. Modifications in the surface of infected erythrocytes, termed knobs, seem to facilitate adhesion to endothelium and other erythrocytes. Adhesion provides better maturation in the microaerophilic venous atmosphere and allows the parasite to escape clearance by the spleen which recognizes the erythrocytes loss of deformability. Adhesion to the endothelium, or cytoadherence, has an important role in the pathogenicity of the disease, causing occlusion of small vessels and contributing to failure of many organs. Cytoadherence can also describe adhesion of infected erythrocytes to uninfected erythrocytes, a phenomenon widely known as rosetting. Clinical aspects of severe malaria, as well as the host receptors and parasite ligands involved in cytoadherence and rosetting, are reviewed here. The erythrocyte membrane protein 1 of P. falciparum (PfEMP1) appears to be the principal adhesive ligand of infected erythrocytes and will be discussed in more detail. Understanding the role of host receptors and parasite ligands in the development of different clinical syndromes is urgently needed to identify vaccination targets in order to decrease the mortality rates of this disease.
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Affiliation(s)
- Karin Kirchgatter
- Núcleo de Estudos em Malária, Superintendência de Controle de Endemias (SUCEN), Instituto de Medicina Tropical de São Paulo (IMTSP), Universidade de São Paulo (USP), São Paulo, SP 05403-000, Brazil.
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35
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Martin MJ, Rayner JC, Gagneux P, Barnwell JW, Varki A. Evolution of human-chimpanzee differences in malaria susceptibility: relationship to human genetic loss of N-glycolylneuraminic acid. Proc Natl Acad Sci U S A 2005; 102:12819-24. [PMID: 16126901 PMCID: PMC1200275 DOI: 10.1073/pnas.0503819102] [Citation(s) in RCA: 138] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Chimpanzees are the closest evolutionary cousins of humans, sharing >99% identity in most protein sequences. Plasmodium falciparum is the major worldwide cause of malaria mortality. Plasmodium reichenowi, a morphologically identical and genetically very similar parasite, infects chimpanzees but not humans. Conversely, experimental P. falciparum infection causes brief moderate parasitization and no severe infection in chimpanzees. This surprising host specificity remains unexplained. We modified and enhanced traditional methods for measuring sialic acid (Sia)-dependent recognition of glycophorins by merozoite erythrocyte-binding proteins, eliminating interference caused by endogenous Sias on transfected cells, and by using erythroleukemia cells to allow experimental manipulation of Sia content. We present evidence that these remarkable differences among such closely related host-parasite pairs is caused by species-specific erythrocyte-recognition profiles, apparently related to the human-specific loss of the common primate Sia N-glycolylneuraminic acid. The major merozoite-binding protein erythrocyte-binding antigen-175 of P. falciparum apparently evolved to take selective advantage of the excess of the Sia N-acetylneuraminic acid (the precursor of N-glycolylneuraminic acid) on human erythrocytes. The contrasting preference of P. reichenowi erythrocyte-binding antigen-175 for N-glycolylneuraminic acid is likely the ancestral condition. The surprising ability of P. falciparum to cause disease in New World Aotus monkeys (geographically isolated from P. falciparum until arrival of peoples from the Old World) can be explained by parallel evolution of a human-like Sia expression pattern in these distantly related primates. These results also have implications for the prehistory of hominids and for the genetic origins and recent emergence of P. falciparum as a major human pathogen.
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Affiliation(s)
- Maria J Martin
- Glycobiology Research and Training Center and Department of Medicine, University of California at San Diego, La Jolla, CA 92093, USA
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36
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Cortés A, Mellombo M, Mgone CS, Beck HP, Reeder JC, Cooke BM. Adhesion of Plasmodium falciparum-infected red blood cells to CD36 under flow is enhanced by the cerebral malaria-protective trait South–East Asian ovalocytosis. Mol Biochem Parasitol 2005; 142:252-7. [PMID: 15978955 DOI: 10.1016/j.molbiopara.2005.03.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2005] [Revised: 03/04/2005] [Accepted: 03/13/2005] [Indexed: 10/25/2022]
Affiliation(s)
- Alfred Cortés
- Molecular Parasitology Laboratory, Papua New Guinea Institute of Medical Research, Madang, P.O. Box 378, MP511, Papua New Guinea.
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37
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Locher CP, Paidhungat M, Whalen RG, Punnonen J. DNA shuffling and screening strategies for improving vaccine efficacy. DNA Cell Biol 2005; 24:256-63. [PMID: 15812242 DOI: 10.1089/dna.2005.24.256] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The efficacy of vaccines can be improved by increasing their immunogenicity, broadening their crossprotective range, as well as by developing immunomodulators that can be coadministered with the vaccine antigen. One technology that can be applied to each of these aspects of vaccine development is MolecularBreeding directed molecular evolution. Essentially, this technology is used to evolve genes in vitro through an iterative process consisting of recombinant generation followed by selection of the desired recombinants. We have used DNA shuffling and screening strategies to develop and improve vaccine candidates against several infectious pathogens including Plasmodium falciparum (a common cause of severe and fatal human malaria), dengue virus, encephalitic alphaviruses such as Venezuelan, western and eastern equine encephalitis viruses (VEEV, WEEV, and EEEV, respectively), human immunodeficiency virus-1 (HIV-1), and hepatitis B virus (HBV). By recombining antigen-encoding genes from different serovar isolates, new chimeras are selected for crossreactivity; these vaccine candidates are expected to provide broader crossprotection than vaccines based on a single serovar. Furthermore, the vaccine candidates can be selected for improved immunogenicity, which would also improve their efficacy. In addition to vaccine candidates, we have applied the technology to evolve several immunomodulators that when coadministered with vaccines can improve vaccine efficacy by fine-tuning the T cell response. Thus, DNA shuffling and screening technology is a promising strategy to facilitate vaccine efficacy.
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Affiliation(s)
- Christopher P Locher
- Division of Infectious Diseases, Maxygen, Inc., Redwood City, California 94063, USA.
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38
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Hisaeda H, Yasutomo K, Himeno K. Malaria: immune evasion by parasites. Int J Biochem Cell Biol 2005; 37:700-6. [PMID: 15694829 DOI: 10.1016/j.biocel.2004.10.009] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2004] [Revised: 10/07/2004] [Accepted: 10/13/2004] [Indexed: 11/23/2022]
Abstract
Malaria is one of the most life-threatening infectious diseases worldwide. Specific immunity to natural infection is acquired slowly despite a high degree of repeated exposure and rarely continues for a long time even in endemic areas. Malaria parasites have evolved to acquire diverse immune evasion mechanisms that evoke poor immune responses and allow infection of individuals previously exposed. The shrewd schema of malaria parasites also hampers the development of effective vaccines. Furthermore, some of those mechanisms are essential for malaria pathogenesis. In this article, an outline of protective immunity to malaria is given, then strategies used by malaria parasites to evade host immunity, including antigen diversity/polymorphism, antigen variation and total immune suppression, are reviewed. Finally, trials to control malaria based on accumulating insights into the host-parasite relationship are discussed.
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Affiliation(s)
- Hajime Hisaeda
- Department of Parasitology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku Fukuoka 812-8582, Japan.
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39
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Eda S, Sherman IW. Selection of peptides recognized by human antibodies against the surface of Plasmodium falciparum-infected erythrocytes. Parasitology 2005; 130:1-11. [PMID: 15700752 DOI: 10.1017/s0031182004006328] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In an attempt to identify mimotopes of the surface antigens of P. falciparum-infected erythrocytes (iRBC), antibodies were eluted from iRBC that had been treated with a pool of sera from malaria-infected individuals (IHS), and were used to screen a phage display library (PDL). After repeated panning of the PDL on immobilized antibodies, phage that selectively bound to IHS were accumulated. Of 23 randomly chosen clones that were sequenced, 13 individual sequences were detected at varying frequencies and 3 of the 13 sequences had homology with membrane proteins known to exist on iRBC. The majority of phage clones (7 out of 8 clones) selected after the 4th panning bound selectively to IgG in IHS. Specific binding of the selected phage to IgG in IHS was also confirmed using 24 IHS and 11 sera from uninfected individuals. One phage clone was the most frequently found in the sequenced clones after the 4th panning, and the binding of this clone to IgG in all IHS was greater than in any serum from uninfected individuals. A rabbit antiserum against the peptide expressed on the clone specifically recognized the surface of iRBC and resulted in iRBC haemolysis.
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Affiliation(s)
- S Eda
- Department of Biology, University of California Riverside, Riverside, California 92521, USA
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40
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Locher CP, Heinrichs V, Apt D, Whalen RG. Overcoming antigenic diversity and improving vaccines using DNA shuffling and screening technologies. Expert Opin Biol Ther 2005; 4:589-97. [PMID: 15102607 DOI: 10.1517/14712598.4.4.589] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Viral, bacterial and parasitic pathogens have evolved multiple strategies to evade the immune response, facilitate transmission and establish chronic infections. One of the underlying strategies that pathogens have evolved is antigenic variation of immune response targets that reduce the affinity of antigen binding to antibodies and major histocompatability complex class I and II receptors. Vaccine candidates generally target a limited number of these antigen variants or combine antigens from several variants to include in multivalent vaccine formulations. DNA shuffling and screening technologies, also known as MolecularBreeding (Maxygen, Inc.) directed molecular evolution, have been successfully used to identify and develop novel and chimaeric vaccine candidates capable of inducing immune responses that recognise and control multiple antigenic variants. DNA shuffling and screening strategies also select vaccine candidates with improved immunogenicity, increased expression as recombinant polypeptides and improved growth of whole viruses in cell culture. As DNA shuffling and screening strategies can be applied to many pathogens, there remain numerous applications of DNA shuffling to solve challenging problems in vaccine process development and manufacture.
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41
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Flick K, Ahuja S, Chene A, Bejarano MT, Chen Q. Optimized expression of Plasmodium falciparum erythrocyte membrane protein 1 domains in Escherichia coli. Malar J 2004; 3:50. [PMID: 15601471 PMCID: PMC544839 DOI: 10.1186/1475-2875-3-50] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2004] [Accepted: 12/15/2004] [Indexed: 11/10/2022] Open
Abstract
Background The expression of recombinant proteins in Escherichia coli is an important and frequently used tool within malaria research, however, this method remains problematic. High A/T versus C/G content and frequent lysine and arginine repeats in the Plasmodium falciparum genome are thought to be the main reason for early termination in the mRNA translation process. Therefore, the majority of P. falciparum derived recombinant proteins is expressed only as truncated forms or appears as insoluble inclusion bodies within the bacterial cells. Methods Several domains of PfEMP1 genes obtained from different P. falciparum strains were expressed in E. coli as GST-fusion proteins. Expression was carried out under various culture conditions with a main focus on the time point of induction in relation to the bacterial growth stage. Results and conclusions When expressed in E. coli recombinant proteins derived from P. falciparum sequences are often truncated and tend to aggregate what in turn leads to the formation of insoluble inclusion bodies. The analysis of various factors influencing the expression revealed that the time point of induction plays a key role in successful expression of A/T rich sequences into their native conformation. Contrary to recommended procedures, initiation of expression at post-log instead of mid-log growth phase generated significantly increased amounts of soluble protein of a high quality. Furthermore, these proteins were shown to be functionally active. Other factors such as temperature, pH, bacterial proteases or the codon optimization for E. coli had little or no effect on the quality of the recombinant protein, nevertheless, optimizing these factors might be beneficial for each individual construct. In conclusion, changing the timepoint of induction and conducting expression at the post-log stage where the bacteria have entered a decelerated growth phase, greatly facilitates and improves the expression of sequences containing rare codons.
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Affiliation(s)
- Kirsten Flick
- Microbiology and Tumor Biology Centre (MTC), Karolinska Institutet, Stockholm, Sweden
- Swedish Institute for Infectious Disease Control, Box 280, 171 77, Stockholm, Sweden
| | - Sanjay Ahuja
- Microbiology and Tumor Biology Centre (MTC), Karolinska Institutet, Stockholm, Sweden
- Swedish Institute for Infectious Disease Control, Box 280, 171 77, Stockholm, Sweden
| | - Arnaud Chene
- Microbiology and Tumor Biology Centre (MTC), Karolinska Institutet, Stockholm, Sweden
- Center for Infectious Medicine, Department of Medicine, Karolinska University Hospital, Stockholm, Sweden
| | - Maria Teresa Bejarano
- Microbiology and Tumor Biology Centre (MTC), Karolinska Institutet, Stockholm, Sweden
- Center for Infectious Medicine, Department of Medicine, Karolinska University Hospital, Stockholm, Sweden
| | - Qijun Chen
- Microbiology and Tumor Biology Centre (MTC), Karolinska Institutet, Stockholm, Sweden
- Swedish Institute for Infectious Disease Control, Box 280, 171 77, Stockholm, Sweden
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Chen Q, Pettersson F, Vogt AM, Schmidt B, Ahuja S, Liljeström P, Wahlgren M. Immunization with PfEMP1-DBL1alpha generates antibodies that disrupt rosettes and protect against the sequestration of Plasmodium falciparum-infected erythrocytes. Vaccine 2004; 22:2701-12. [PMID: 15246600 DOI: 10.1016/j.vaccine.2004.02.015] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2003] [Revised: 01/30/2004] [Accepted: 02/03/2004] [Indexed: 10/26/2022]
Abstract
A family of parasite antigens known as Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is believed to play an important role in the binding of infected erythrocytes to host receptors in the micro-vasculature. Available data advocates the existence of a subset of very adhesive (rosetting, auto-agglutinating) and antigenic PfEMP1s implicated as virulence factors. Serum antibodies that disrupt rosettes are rarely found in children with severe malaria but are frequent in those with mild disease suggesting that they may be protective. Here we have developed a Semliki forest virus (SFV) vaccine construct with a recombinant gene (mini-var gene) encoding a mini-PfEMP1 (DBL1alpha-TM-ATS) obtained from a particularly antigenic and rosetting parasite (FCR3S1.2). The mini-PfEMP1 is presented to the host mimicking the location of the native molecule at the infected erythrocyte surface. Antibodies generated by a regimen of priming with SFV RNA particles and boosting with a recombinant protein recognize the infected erythrocyte surface (immuno-fluorescence/rosette-disruption) and prevent the sequestration of P. falciparum-infected erythrocytes in an in vivo model of severe malaria. The data prove the involvement of DBL1alpha in the adhesion of infected- and uninfected erythrocytes and the role of rosette-disruptive antibodies in preventing these cellular interactions. The work supports the use of DBL1alpha in a vaccine again severe malaria.
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Affiliation(s)
- Qijun Chen
- Microbiology and Tumorbiology Centre, Karolinska Institutet, Box 280, SE-171 77 Stockholm, Sweden.
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43
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Abstract
Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is an important virulence factor encoded by a family of roughly 60 var genes and is used by the parasite to interact with the human host. The parasite regularly exchanges the expressed var gene generating antigenic variation of the infected RBCs (pRBC) surface which is crucial for successful proliferation and transmission. PfEMP1 is also an adhesive molecule that binds to an array of human receptors. By sequestration in the post-capillary venules, pRBCs are able to escape the spleen-mediated clearance but severe malaria may develop if the local binding is extensive. Anti-PfEMP1 immunity is important for preventing the development of both cerebral malaria and placental malaria, but more immunological studies on PfEMP1 antigens and their interaction with the human host are needed. Over the last few years our knowledge about var genes and PfEMP1s has increased dramatically through genetic, biochemical, immunological and epidemiological studies. In addition, the genome sequence has also provided us with a new platform for further dissecting its biological functions. This review highlights the recent analyses of var genes in the P. falciparum genome and postulates significance of genome recombination to the diversity of parasite virulence.
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Affiliation(s)
- Kirsten Flick
- Microbiology and Tumour Biology Centre (MTC), Karolinska Institutet and Swedish Institute for Infectious Disease Control, Box 280, SE-171 77 Stockholm, Sweden
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44
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Becker K, Tilley L, Vennerstrom JL, Roberts D, Rogerson S, Ginsburg H. Oxidative stress in malaria parasite-infected erythrocytes: host–parasite interactions. Int J Parasitol 2004; 34:163-89. [PMID: 15037104 DOI: 10.1016/j.ijpara.2003.09.011] [Citation(s) in RCA: 420] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2003] [Revised: 09/18/2003] [Accepted: 09/18/2003] [Indexed: 01/09/2023]
Abstract
Experimenta naturae, like the glucose-6-phosphate dehydrogenase deficiency, indicate that malaria parasites are highly susceptible to alterations in the redox equilibrium. This offers a great potential for the development of urgently required novel chemotherapeutic strategies. However, the relationship between the redox status of malarial parasites and that of their host is complex. In this review article we summarise the presently available knowledge on sources and detoxification pathways of reactive oxygen species in malaria parasite-infected red cells, on clinical aspects of redox metabolism and redox-related mechanisms of drug action as well as future prospects for drug development. As delineated below, alterations in redox status contribute to disease manifestation including sequestration, cerebral pathology, anaemia, respiratory distress, and placental malaria. Studying haemoglobinopathies, like thalassemias and sickle cell disease, and other red cell defects that provide protection against malaria allows insights into this fine balance of redox interactions. The host immune response to malaria involves phagocytosis as well as the production of nitric oxide and oxygen radicals that form part of the host defence system and also contribute to the pathology of the disease. Haemoglobin degradation by the malarial parasite produces the redox active by-products, free haem and H(2)O(2), conferring oxidative insult on the host cell. However, the parasite also supplies antioxidant moieties to the host and possesses an efficient enzymatic antioxidant defence system including glutathione- and thioredoxin-dependent proteins. Mechanistic and structural work on these enzymes might provide a basis for targeting the parasite. Indeed, a number of currently used drugs, especially the endoperoxide antimalarials, appear to act by increasing oxidant stress, and novel drugs such as peroxidic compounds and anthroquinones are being developed.
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Affiliation(s)
- Katja Becker
- Interdisciplinary Research Center, Heinrich-Buff-Ring 26-32, Justus-Liebig University, D-35392 Giessen, Germany.
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45
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Mahanty S, Saul A, Miller LH. Progress in the development of recombinant and synthetic blood-stage malaria vaccines. J Exp Biol 2003; 206:3781-8. [PMID: 14506213 DOI: 10.1242/jeb.00646] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYThe use of asexual blood-stage proteins as malaria vaccines is strongly supported by experimental data directly implicating antibodies induced by these antigens in parasite clearance and protection from re-challenge. The selection of blood-stage antigens is based on their ability to interfere with the pathogenesis of clinical malaria by reducing parasitemias. These vaccines could complement other vaccines aimed at preventing infection, such as those targeted at pre-erythrocytic or mosquito stages of the parasite. Asexual blood-stage vaccines may reduce disease by blockade of red blood cell invasion, inhibition of parasite growth in red cells or interference in cytoadherence of infected red cells. Clearance of blood-stage parasites is dependent primarily on antibody-mediated mechanisms, but CD4 T cells may also play an important role in help for B cells and probably have a direct effector function in the clearance of blood-stage parasites. Since asexual blood-stage parasites reside within erythrocytes, they are accessible to immune clearance mechanisms only for a short time, which imposes special requirements on vaccines. For example, immunity that induces high titers of antibody will be required. Antigenic variation and extensive polymorphism of malarial proteins also needs to be addressed. Several recombinant antigens derived from blood-stage proteins have moved beyond basic research and are now poised for phase I trials in endemic countries. In this review we discuss the state of asexual blood-stage vaccines, focusing on recombinant antigens from Plasmodium falciparum. The significance of polymorphism and antigenic variation, the relevance of parasite immune evasion mechanisms, the need for reliable measures of successful intervention and new adjuvants are reviewed. Results from trials of asexual blood stage vaccine that support the continued effort to develop these antigens as key ingredients of multicomponent,multistage malaria vaccines are documented.
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Affiliation(s)
- Siddhartha Mahanty
- Malaria Vaccine Development Unit, NIAID, NIH, Twin Brook I, 5640 Fishers Lane, Rockville, MD 20852, USA.
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Gratepanche S, Gamain B, Smith JD, Robinson BA, Saul A, Miller LH. Induction of crossreactive antibodies against the Plasmodium falciparum variant protein. Proc Natl Acad Sci U S A 2003; 100:13007-12. [PMID: 14569009 PMCID: PMC240735 DOI: 10.1073/pnas.2235588100] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The variant antigen Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1), present on the surface of P. falciparum-parasitized erythrocytes (PE), plays a central role in naturally acquired immunity, although antibodies to PfEMP1 are predominantly variant specific. To overcome this major limitation for vaccine development, we immunized mice with three cysteine-rich interdomain 1 (CIDR1) domains of PfEMP1 that have the critical function of binding the PE to CD36 on endothelium and thus preventing spleen-dependent killing of the parasite. The immunizations consisted of different combinations of three CIDR1 encoded by DNA followed by recombinant protein boost. Immunizations with a single variant in a prime-boost regimen induced no or low cross-reactivity toward heterologous CIDR1; however, a broad range of crossreactivity was detected in mice that were immunized with all three variants simultaneously. The induced crossreactivity suggests that an anti-PfEMP1 vaccine may be possible.
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Affiliation(s)
- Sylvie Gratepanche
- Malaria Vaccine Development Unit, National Institute of Allergy and Infectious Diseases/National Institutes of Health, Rockville, MD 20852; Seattle Biomedical Research Institute, Seattle, WA 98109; Department of Pathobiology, University of Washington, Seattle, WA 98195; and University of Colorado Health Sciences Center, Denver, CO 80220
| | - Benoit Gamain
- Malaria Vaccine Development Unit, National Institute of Allergy and Infectious Diseases/National Institutes of Health, Rockville, MD 20852; Seattle Biomedical Research Institute, Seattle, WA 98109; Department of Pathobiology, University of Washington, Seattle, WA 98195; and University of Colorado Health Sciences Center, Denver, CO 80220
| | - Joseph D. Smith
- Malaria Vaccine Development Unit, National Institute of Allergy and Infectious Diseases/National Institutes of Health, Rockville, MD 20852; Seattle Biomedical Research Institute, Seattle, WA 98109; Department of Pathobiology, University of Washington, Seattle, WA 98195; and University of Colorado Health Sciences Center, Denver, CO 80220
| | - Bridget A. Robinson
- Malaria Vaccine Development Unit, National Institute of Allergy and Infectious Diseases/National Institutes of Health, Rockville, MD 20852; Seattle Biomedical Research Institute, Seattle, WA 98109; Department of Pathobiology, University of Washington, Seattle, WA 98195; and University of Colorado Health Sciences Center, Denver, CO 80220
| | - Allan Saul
- Malaria Vaccine Development Unit, National Institute of Allergy and Infectious Diseases/National Institutes of Health, Rockville, MD 20852; Seattle Biomedical Research Institute, Seattle, WA 98109; Department of Pathobiology, University of Washington, Seattle, WA 98195; and University of Colorado Health Sciences Center, Denver, CO 80220
| | - Louis H. Miller
- Malaria Vaccine Development Unit, National Institute of Allergy and Infectious Diseases/National Institutes of Health, Rockville, MD 20852; Seattle Biomedical Research Institute, Seattle, WA 98109; Department of Pathobiology, University of Washington, Seattle, WA 98195; and University of Colorado Health Sciences Center, Denver, CO 80220
- To whom correspondence should be addressed. E-mail:
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Affiliation(s)
- Lena Serghides
- Center for Travel and Tropical Medicine, Toronto General Hospital, Global Health Program, McLaughlin Center for Molecular Medicine, University of Toronto, 200 Elizabeth St. EN G-224, Toronto, Ontario M5G 2C4, Canada
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Baruch DI, Gamain B, Miller LH. DNA immunization with the cysteine-rich interdomain region 1 of the Plasmodium falciparum variant antigen elicits limited cross-reactive antibody responses. Infect Immun 2003; 71:4536-43. [PMID: 12874333 PMCID: PMC166004 DOI: 10.1128/iai.71.8.4536-4543.2003] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The variant surface antigens of Plasmodium falciparum are an important component of naturally acquired immunity and an important vaccine target. However, these proteins appear to elicit primarily variant-specific antibodies. We tested if naked DNA immunization can elicit more cross-reactive antibody responses and allow simultaneous immunization with several variant constructs. Mice immunized with plasmid DNA expressing variant cysteine-rich interdomain region 1 (CIDR1) domains of the P. falciparum erythrocyte membrane protein 1 (PfEMP1) developed antibodies that were reactive to the corresponding PfEMP1s as measured by an enzyme-linked immunosorbent assay, flow cytometry, and agglutination of parasitized erythrocytes (PEs). We observed some cross-reactive immune responses; for example, sera from mice immunized with one domain agglutinated PEs of various lines and recognized heterologous domains expressed on the surface of Chinese hamster ovary (CHO) cells. We found no significant antigenic competition when animals were immunized with a mixture of plasmids or immunized sequentially with individual constructs. Moreover, mixed or sequential immunizations resulted in greater cross-reactive agglutination responses than immunization with a single domain. Recombinant protein (Sc y179) immunization after priming with DNA (prime-boost regimen) increased antibody titers to the homologous domain substantially but seemed to diminish the cross-reactive responses somewhat. The titer of agglutinating antibodies was previously shown to correlate with protection. Surprisingly, the agglutination titers of sera from DNA immunization were high, similar to those of pooled human hyperimmune sera. These sera also appeared to give limited low-titer variant transcending agglutination. Thus, DNA immunization appears to be a very useful tool for developing variant antigen vaccines.
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Affiliation(s)
- Dror I Baruch
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Gatton ML, Peters JM, Fowler EV, Cheng Q. Switching rates of Plasmodium falciparum var genes: faster than we thought? Trends Parasitol 2003; 19:202-8. [PMID: 12763425 DOI: 10.1016/s1471-4922(03)00067-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Plasmodium falciparum undergoes antigenic variation by switching the expressed erythrocyte membrane protein (PfEMP)1. This family of proteins plays an important role in the development of chronic, recrudescent P. falciparum malaria, acquired immunity and severe malaria. However, little is known about the switching mechanism or switching rates in the human host. Here, we estimate the switch rate of var genes, using recently published data describing the var gene transcripts detected in blood taken from human volunteers during acute P. falciparum infections and a mathematical model of the in-host dynamics. The overall switch rate of PfEMP1 predicted during the initial stage of infection ( approximately 18% switching parasites per generation) is much higher than previously reported. The implications of the predicted switching rates are discussed.
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Affiliation(s)
- Michelle L Gatton
- Malaria Biology Laboratory, Queensland Institute of Medical Research, PO Royal Brisbane Hospital, Queensland 4029, Australia.
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Robinson BA, Welch TL, Smith JD. Widespread functional specialization of Plasmodium falciparum erythrocyte membrane protein 1 family members to bind CD36 analysed across a parasite genome. Mol Microbiol 2003; 47:1265-78. [PMID: 12603733 DOI: 10.1046/j.1365-2958.2003.03378.x] [Citation(s) in RCA: 151] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Plasmodium falciparum-infected erythrocytes sequester from blood circulation by binding host endothelium. A large family of variant proteins mediates cytoadherence and their binding specificity determines parasite sequestration patterns and potential for disease. The aim of the present study was to understand how binding properties are encoded into family members and to develop sequence algorithms for predicting binding. To accomplish these goals computational approaches and a binding assay were used to characterize adhesion across Plasmodium falciparum erythrocyte membrane 1 (PfEMP1) proteins in the 3D7 parasite genome. We report that most family members encode the capacity to bind CD36 in the protein's semi-conserved head structure and describe the sequence characteristics of a group of PfEMP1 proteins that do not. Structural and functional grouping of PfEMP1 proteins based upon head structure and additional domain architectural properties provide new insights into the protein family. These can be used to investigate the role of proteins in malaria pathogenesis and potentially tailor vaccines to recognize particular binding variants.
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Affiliation(s)
- Bridget A Robinson
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO 80525, USA
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