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Bachmann A, Metwally NG, Allweier J, Cronshagen J, Del Pilar Martinez Tauler M, Murk A, Roth LK, Torabi H, Wu Y, Gutsmann T, Bruchhaus I. CD36-A Host Receptor Necessary for Malaria Parasites to Establish and Maintain Infection. Microorganisms 2022; 10. [PMID: 36557610 DOI: 10.3390/microorganisms10122356] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 11/21/2022] [Accepted: 11/27/2022] [Indexed: 11/30/2022] Open
Abstract
Plasmodium falciparum-infected erythrocytes (PfIEs) present P. falciparum erythrocyte membrane protein 1 proteins (PfEMP1s) on the cell surface, via which they cytoadhere to various endothelial cell receptors (ECRs) on the walls of human blood vessels. This prevents the parasite from passing through the spleen, which would lead to its elimination. Each P. falciparum isolate has about 60 different PfEMP1s acting as ligands, and at least 24 ECRs have been identified as interaction partners. Interestingly, in every parasite genome sequenced to date, at least 75% of the encoded PfEMP1s have a binding domain for the scavenger receptor CD36 widely distributed on host endothelial cells and many other cell types. Here, we discuss why the interaction between PfIEs and CD36 is optimal to maintain a finely regulated equilibrium that allows the parasite to multiply and spread while causing minimal harm to the host in most infections.
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Lee EH, Mancuso JD, Koehlmoos T, Stewart VA, Bennett JW, Olsen C. Quality and Integrated Service Delivery: A Cross-Sectional Study of the Effects of Malaria and Antenatal Service Quality on Malaria Intervention Use in Sub-Saharan Africa. Trop Med Infect Dis 2022; 7:363. [DOI: 10.3390/tropicalmed7110363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 10/14/2022] [Accepted: 11/04/2022] [Indexed: 11/11/2022] Open
Abstract
Using regionally linked facility and household surveys, we measured the quality of integrated antenatal care and malaria in pregnancy services in Kenya, Namibia, Senegal, and Tanzania. We examined country heterogeneities for the association of integrated antenatal and malaria service quality scores with insecticide-treated bed net (ITN) use in pregnant women and children under-five and intermittent preventive treatment in pregnancy (IPTp-2) uptake. Malaria in pregnancy service quality was low overall. Our findings suggest modest, positive associations between malaria in pregnancy quality and ITN use and IPTp-2 uptake across pooled models and for most studied countries, with evidence of heterogeneity in the strength of associations and relevant confounding factors. Antenatal care quality generally was not associated with the study outcomes, although a positive interaction with malaria in pregnancy quality was present for pooled ITN use models. The improved quality of malaria services delivered during formal antenatal care can help address low coverage and usage rates of preventive malaria interventions in pregnancy and childhood. Study findings may be used to target quality improvement efforts at the sub-national level. Study methods may be adapted to identify low-performing facilities for intervention and adaption to other areas of care, such as HIV/AIDS, child immunizations, and postnatal care.
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Talundzic E, Scott S, Owino SO, Campo DS, Lucchi NW, Udhayakumar V, Moore JM, Peterson DS. Polymorphic Molecular Signatures in Variable Regions of the Plasmodium falciparum var2csa DBL3x Domain Are Associated with Virulence in Placental Malaria. Pathogens 2022; 11:520. [PMID: 35631041 PMCID: PMC9147263 DOI: 10.3390/pathogens11050520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 04/15/2022] [Accepted: 04/24/2022] [Indexed: 11/17/2022] Open
Abstract
The Plasmodium falciparum protein VAR2CSA allows infected erythrocytes to accumulate within the placenta, inducing pathology and poor birth outcomes. Multiple exposures to placental malaria (PM) induce partial immunity against VAR2CSA, making it a promising vaccine candidate. However, the extent to which VAR2CSA genetic diversity contributes to immune evasion and virulence remains poorly understood. The deep sequencing of the var2csa DBL3X domain in placental blood from forty-nine primigravid and multigravid women living in malaria-endemic western Kenya revealed numerous unique sequences within individuals in association with chronic PM but not gravidity. Additional analysis unveiled four distinct sequence types that were variably present in mixed proportions amongst the study population. An analysis of the abundance of each of these sequence types revealed that one was inversely related to infant gestational age, another was inversely related to placental parasitemia, and a third was associated with chronic PM. The categorization of women according to the type to which their dominant sequence belonged resulted in the segregation of types as a function of gravidity: two types predominated in multigravidae whereas the other two predominated in primigravidae. The univariate logistic regression analysis of sequence type dominance further revealed that gravidity, maternal age, placental parasitemia, and hemozoin burden (within maternal leukocytes), reported a lack of antimalarial drug use, and infant gestational age and birth weight influenced the odds of membership in one or more of these sequence predominance groups. Cumulatively, these results show that unique var2csa sequences differentially appear in women with different PM exposure histories and segregate to types independently associated with maternal factors, infection parameters, and birth outcomes. The association of some var2csa sequence types with indicators of pathogenesis should motivate vaccine efforts to further identify and target VAR2CSA epitopes associated with maternal morbidity and poor birth outcomes.
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Affiliation(s)
- Eldin Talundzic
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30329, USA; (E.T.); (N.W.L.); (V.U.)
| | - Stephen Scott
- Department of Infectious Diseases, University of Georgia, Athens, GA 30602, USA;
| | - Simon O. Owino
- Boehringer Ingelheim Animal Health, Athens, GA 30601, USA;
| | - David S. Campo
- Molecular Epidemiology and Bioinformatics Laboratory, Division of Viral Hepatitis, Centers for Disease Control and Prevention, Atlanta, GA 30329, USA;
| | - Naomi W. Lucchi
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30329, USA; (E.T.); (N.W.L.); (V.U.)
| | - Venkatachalam Udhayakumar
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30329, USA; (E.T.); (N.W.L.); (V.U.)
| | - Julie M. Moore
- Department of Infectious Diseases and Immunology, University of Florida, Gainesville, FL 32611, USA
| | - David S. Peterson
- Department of Infectious Diseases, University of Georgia, Athens, GA 30602, USA;
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602, USA
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Kassegne K, Komi Koukoura K, Shen HM, Chen SB, Fu HT, Chen YQ, Zhou XN, Chen JH, Cheng Y. Genome-Wide Analysis of the Malaria Parasite Plasmodium falciparum Isolates From Togo Reveals Selective Signals in Immune Selection-Related Antigen Genes. Front Immunol 2020; 11:552698. [PMID: 33193320 PMCID: PMC7645038 DOI: 10.3389/fimmu.2020.552698] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 09/02/2020] [Indexed: 12/19/2022] Open
Abstract
Malaria is a public health concern worldwide, and Togo has proven to be no exception. Effective approaches to provide information on biological insights for disease elimination are therefore a research priority. Local selection on malaria pathogens is due to multiple factors including host immunity. We undertook genome-wide analysis of sequence variation on a sample of 10 Plasmodium falciparum (Pf) clinical isolates from Togo to identify local-specific signals of selection. Paired-end short-read sequences were mapped and aligned onto > 95% of the 3D7 Pf reference genome sequence in high fold coverage. Data on 266 963 single nucleotide polymorphisms were obtained, with average nucleotide diversity π = 1.79 × 10−3. Both principal component and neighbor-joining tree analyses showed that the Togo parasites clustered according to their geographic (Africa) origin. In addition, the average genome-wide diversity of Pf from Togo was much higher than that from other African samples. Tajima’s D value of the Togo isolates was −0.56, suggesting evidence of directional selection and/or recent population expansion. Against this background, within-population analyses identifying loci of balancing and recent positive selections evidenced that host immunity has been the major selective agent. Importantly, 87 and 296 parasite antigen genes with Tajima’s D values > 1 and in the top 1% haplotype scores, respectively, include a significant representation of membrane proteins at the merozoite stage that invaded red blood cells (RBCs) and parasitized RBCs surface proteins that play roles in immunoevasion, adhesion, or rosetting. This is consistent with expectations that elevated signals of selection due to allele-specific acquired immunity are likely to operate on antigenic targets. Collectively, our data suggest a recent expansion of Pf population in Togo and evidence strong host immune selection on membrane/surface antigens reflected in signals of balancing/positive selection of important gene loci. Findings from this study provide a fundamental basis to engage studies for effective malaria control in Togo.
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Affiliation(s)
- Kokouvi Kassegne
- Laboratory of Pathogen Infection and Immunity, Department of Public Health and Preventive Medicine, Wuxi School of Medicine, Jiangnan University, Wuxi, China
| | - Komi Komi Koukoura
- Laboratoire des Sciences Biomédicales, Alimentaires et Santé Environnementale, Département des Analyses Biomédicales, Ecole Supérieure des Techniques Biologiques et Alimentaires, Université de Lomé, Lomé, Togo
| | - Hai-Mo Shen
- National Institute of Parasitic Diseases, Chinese Centre for Disease Control and Prevention, Chinese Centre for Tropical Diseases Research, WHO Collaborating Centre for Tropical Diseases, National Centre for International Research on Tropical Diseases, Ministry of Science and Technology, Key Laboratory of Parasite and Vector Biology, Ministry of Health, Shanghai, China.,National Institute of Parasitic Diseases, Chinese Centre for Disease Control and Prevention-Shenzhen Centre for Disease Control and Prevention Joint Laboratory for Imported Tropical Disease Control, Shanghai, China.,The School of Global Health, Chinese Centre for Tropical Diseases Research, Shanghai JiaoTong University School of Medicine, Shanghai, China
| | - Shen-Bo Chen
- National Institute of Parasitic Diseases, Chinese Centre for Disease Control and Prevention, Chinese Centre for Tropical Diseases Research, WHO Collaborating Centre for Tropical Diseases, National Centre for International Research on Tropical Diseases, Ministry of Science and Technology, Key Laboratory of Parasite and Vector Biology, Ministry of Health, Shanghai, China.,National Institute of Parasitic Diseases, Chinese Centre for Disease Control and Prevention-Shenzhen Centre for Disease Control and Prevention Joint Laboratory for Imported Tropical Disease Control, Shanghai, China.,The School of Global Health, Chinese Centre for Tropical Diseases Research, Shanghai JiaoTong University School of Medicine, Shanghai, China
| | - Hai-Tian Fu
- Laboratory of Pathogen Infection and Immunity, Department of Public Health and Preventive Medicine, Wuxi School of Medicine, Jiangnan University, Wuxi, China
| | - Yong-Quan Chen
- Laboratory of Pathogen Infection and Immunity, Department of Public Health and Preventive Medicine, Wuxi School of Medicine, Jiangnan University, Wuxi, China.,School of Food Science and Technology, State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China
| | - Xiao-Nong Zhou
- National Institute of Parasitic Diseases, Chinese Centre for Disease Control and Prevention, Chinese Centre for Tropical Diseases Research, WHO Collaborating Centre for Tropical Diseases, National Centre for International Research on Tropical Diseases, Ministry of Science and Technology, Key Laboratory of Parasite and Vector Biology, Ministry of Health, Shanghai, China.,National Institute of Parasitic Diseases, Chinese Centre for Disease Control and Prevention-Shenzhen Centre for Disease Control and Prevention Joint Laboratory for Imported Tropical Disease Control, Shanghai, China.,The School of Global Health, Chinese Centre for Tropical Diseases Research, Shanghai JiaoTong University School of Medicine, Shanghai, China
| | - Jun-Hu Chen
- National Institute of Parasitic Diseases, Chinese Centre for Disease Control and Prevention, Chinese Centre for Tropical Diseases Research, WHO Collaborating Centre for Tropical Diseases, National Centre for International Research on Tropical Diseases, Ministry of Science and Technology, Key Laboratory of Parasite and Vector Biology, Ministry of Health, Shanghai, China.,National Institute of Parasitic Diseases, Chinese Centre for Disease Control and Prevention-Shenzhen Centre for Disease Control and Prevention Joint Laboratory for Imported Tropical Disease Control, Shanghai, China.,The School of Global Health, Chinese Centre for Tropical Diseases Research, Shanghai JiaoTong University School of Medicine, Shanghai, China
| | - Yang Cheng
- Laboratory of Pathogen Infection and Immunity, Department of Public Health and Preventive Medicine, Wuxi School of Medicine, Jiangnan University, Wuxi, China
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Abstract
Parasitic diseases, such as sleeping sickness, Chagas disease and malaria, remain a major cause of morbidity and mortality worldwide, but particularly in tropical, developing countries. Controlling these diseases requires a better understanding of host-parasite interactions, including a deep appreciation of parasite distribution in the host. The preferred accumulation of parasites in some tissues of the host has been known for many years, but recent technical advances have allowed a more systematic analysis and quantifications of such tissue tropisms. The functional consequences of tissue tropism remain poorly studied, although it has been associated with important aspects of disease, including transmission enhancement, treatment failure, relapse and clinical outcome. Here, we discuss current knowledge of tissue tropism in Trypanosoma infections in mammals, describe potential mechanisms of tissue entry, comparatively discuss relevant findings from other parasitology fields where tissue tropism has been extensively investigated, and reflect on new questions raised by recent discoveries and their potential impact on clinical treatment and disease control strategies.
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Affiliation(s)
- Sara Silva Pereira
- Instituto de Medicina Molecular-João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa , Lisbon , Portugal
| | - Sandra Trindade
- Instituto de Medicina Molecular-João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa , Lisbon , Portugal
| | - Mariana De Niz
- Instituto de Medicina Molecular-João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa , Lisbon , Portugal
| | - Luisa M Figueiredo
- Instituto de Medicina Molecular-João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa , Lisbon , Portugal
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Otto TD, Assefa SA, Böhme U, Sanders MJ, Kwiatkowski D, Berriman M, Newbold C. Evolutionary analysis of the most polymorphic gene family in falciparum malaria. Wellcome Open Res 2019; 4:193. [PMID: 32055709 PMCID: PMC7001760 DOI: 10.12688/wellcomeopenres.15590.1] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/26/2019] [Indexed: 12/22/2022] Open
Abstract
The var gene family of the human malaria parasite Plasmodium falciparum encode proteins that are crucial determinants of both pathogenesis and immune evasion and are highly polymorphic. Here we have assembled nearly complete var gene repertoires from 2398 field isolates and analysed a normalised set of 714 from across 12 countries. This therefore represents the first large scale attempt to catalogue the worldwide distribution of var gene sequences We confirm the extreme polymorphism of this gene family but also demonstrate an unexpected level of sequence sharing both within and between continents. We show that this is likely due to both the remnants of selective sweeps as well as a worrying degree of recent gene flow across continents with implications for the spread of drug resistance. We also address the evolution of the var repertoire with respect to the ancestral genes within the Laverania and show that diversity generated by recombination is concentrated in a number of hotspots. An analysis of the subdomain structure indicates that some existing definitions may need to be revised From the analysis of this data, we can now understand the way in which the family has evolved and how the diversity is continuously being generated. Finally, we demonstrate that because the genes are distributed across the genome, sequence sharing between genotypes acts as a useful population genetic marker.
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Affiliation(s)
- Thomas D. Otto
- Parasite Genetics, Wellcome Trust Sanger Institute, Hinxton, UK
- Institute of Infection, Immunity & Inflammation, MVLS, University of Glasgow, Glasgow, UK
| | - Sammy A. Assefa
- Parasite Genetics, Wellcome Trust Sanger Institute, Hinxton, UK
| | - Ulrike Böhme
- Parasite Genetics, Wellcome Trust Sanger Institute, Hinxton, UK
| | | | - Dominic Kwiatkowski
- Parasite Genetics, Wellcome Trust Sanger Institute, Hinxton, UK
- The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Pf3k consortium
- Parasite Genetics, Wellcome Trust Sanger Institute, Hinxton, UK
- Institute of Infection, Immunity & Inflammation, MVLS, University of Glasgow, Glasgow, UK
- The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
- Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - Matt Berriman
- Parasite Genetics, Wellcome Trust Sanger Institute, Hinxton, UK
| | - Chris Newbold
- Parasite Genetics, Wellcome Trust Sanger Institute, Hinxton, UK
- Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK
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7
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Okamgba OC, Ifeanyichukwu MO, Ilesanmi AO, Chigbu LN. Variations in the leukocyte and cytokine profiles between placental and maternal circulation in pregnancy-associated malaria. Res Rep Trop Med 2018; 9:1-8. [PMID: 30050350 PMCID: PMC6047617 DOI: 10.2147/rrtm.s137829] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND Activation of immune cells by malaria infection induces the secretion of cytokines and the synthesis of other inflammatory mediators. This study compared the cytokine levels and leukocyte count between malaria-infected peripheral and placental blood of pregnant women before delivery and postpartum. The cytokines assessed include interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), interleukin-4 (IL-4), interleukin-6 (IL-6) and interleukin-10 (IL-10). MATERIALS AND METHODS The subjects comprised 144 malaria-infected pregnant women and 60 malaria-infected women at post-partum stage (for placental blood collection). Others were 60 malaria-uninfected pregnant women and 40 malaria-uninfected women at postpartum stage (for placental blood collection). Forty malaria-infected and 40 malaria-uninfected nonpregnant women served as control subjects. The test groups were asymptomatic, and the control groups were apparently healthy subjects. All were aged between 17 and 44 years. Ethical approval for the study was obtained at Abia State University Teaching Hospital and Living Word Mission Hospital, Aba. Informed consent was obtained from the participants. Blood samples were aseptically collected initially from the maternal peripheral circulation and from the placenta on delivery, and tested for HIV and malaria using standard methods. IFN-γ, TNF-α, IL-4, IL-6 and IL-10 were measured by enzyme-linked immunosorbent assay technique. Kruskal-Wallis test was used for comparison of the groups. RESULTS IFN-γ was significantly higher in the peripheral than in placental blood (P=0.001). IL-4 and IL-10 were significantly lower in the peripheral than in placental blood (P=0.001 and P=0.004, respectively). The total leukocytes, neutrophils and lymphocyte counts were significantly higher in the placenta than in peripheral blood (P=0.001), and the mixed differential count was significantly higher in the placenta than in peripheral blood (P=0.012). CONCLUSION This study has shown that the cytokine levels and leukocyte counts may differ between the peripheral and placental blood of the same women. Therefore, measurement of parameters in the peripheral circulation may not always reflect the levels in the placental blood for the assessment of immune cellular response at the materno-fetal interface.
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Affiliation(s)
- Okezie Caleb Okamgba
- Department of Medical Laboratory Science, Faculty of Health Sciences and Technology, Nnamdi Azikwe University, Nnewi Campus, Nnewi, Anambra State
| | - Martin O Ifeanyichukwu
- Department of Medical Laboratory Science, Faculty of Health Sciences and Technology, Nnamdi Azikwe University, Nnewi Campus, Nnewi, Anambra State
| | - Ayodele O Ilesanmi
- Department of Medical Laboratory Science, Kwara State University, Malete, Kwara State,
| | - Lawrence N Chigbu
- Department of Microbiology, College of Medicine, Abia State University, Uturu, Abia State, Nigeria
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Fodjo BA, Atemnkeng N, Esemu L, Yuosembom EK, Quakyi IA, Tchinda VH, Smith J, Salanti A, Bigoga J, Taylor DW, Leke RG, Babakhanyan A. Antibody responses to the full-length VAR2CSA and its DBL domains in Cameroonian children and teenagers. Malar J 2016; 15:532. [PMID: 27814765 DOI: 10.1186/s12936-016-1585-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 10/28/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Antigenic variation of Plasmodium falciparum erythrocyte membrane protein 1 is a key parasite mechanism for immune evasion and parasite survival. It is assumed that the number of parasites expressing the same var gene must reach high enough numbers before the host can produce detectable levels of antibodies (Ab) to the variant. VAR2CSA is a protein coded for by one of 60 var genes that is expressed on the surface of infected erythrocytes (IE) and mediates IE binding to the placenta. The idea that Ab to VAR2CSA are pregnancy-associated was challenged when VAR2CSA-specific Ab were reported in children and men. However, the frequency and conditions under which Ab to VAR2CSA are produced outside pregnancy is unclear. This study sought to determine frequency, specificity and level of Ab to VAR2CSA produced in children and whether children with hyperparasitaemia and severe malaria are more likely to produce Ab to VAR2CSA compared to healthy children. METHODS Antibody responses to a panel of recombinant proteins consisting of multiple VAR2CSA Duffy-binding-like domains (DBL) and full-length VAR2CSA (FV2) were characterized in 193 1-15 year old children from rural Cameroonian villages and 160 children with severe malaria from the city. RESULTS Low Ab levels to VAR2CSA were detected in children; however, Ab levels to FV2 in teenagers were rare. Children preferentially recognized DBL2 (56-70%) and DBL4 (50-60%), while multigravidae produced high levels of IgG to DBL3, DBL5 and FV2. Sixty-seven percent of teenage girls (n = 16/24) recognized ID1-ID2a region of VAR2CSA. Children with severe forms of malaria had significantly higher IgG to merozoite antigens (all p < 0.05), but not to VAR2CSA (all p > 0.05) when compared to the healthy children. CONCLUSION The study suggests that children, including teenage girls acquire Ab to VAR2CSA domains and FV2, but Ab levels are much lower than those needed to protect women from placental infections and repertoire of Ab responses to DBL domains is different from those in pregnant women. Interestingly, children with severe malaria did not have higher Ab levels to VAR2CSA compared to healthy children.
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Subudhi AK, Boopathi PA, Pandey I, Kohli R, Karwa R, Middha S, Acharya J, Kochar SK, Kochar DK, Das A. Plasmodium falciparum complicated malaria: Modulation and connectivity between exportome and variant surface antigen gene families. Mol Biochem Parasitol 2015; 201:31-46. [PMID: 26022315 DOI: 10.1016/j.molbiopara.2015.05.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 05/20/2015] [Accepted: 05/21/2015] [Indexed: 12/27/2022]
Abstract
In temperate and sub-tropical regions of Asia and Latin America, complicated malaria manifested as hepatic dysfunction or renal dysfunction is seen in all age groups. There has been a concerted focus on understanding the patho-physiological and molecular basis of complicated malaria in children, much less is known about it in adults. We report here, the analysis of data from a custom, cross strain microarray (Agilent Platform) using material from adult patient samples, showing hepatic dysfunction or renal failure. These are the most common manifestations seen in adults along with cerebral malaria. The data has been analyzed with reference to variant surface antigens, encoded by the var, rifin and stevor gene families. The differential regulation profiles of key genes (comparison between Plasmodium falciparum complicated and uncomplicated isolates) have been observed. The exportome has been analyzed using similar parameters. Gene ontology term based functional enrichment of differentially regulated genes identified, up-regulated genes statistically enriched (P<0.05) to critical biological processes like generation of precursor metabolite and energy, chromosome organization and electron transport chain. Systems network based functional enrichment of overall differentially regulated genes yielded a similar result. We are reporting here, up-regulation of var group B and C genes whose proteins are predicted to interact with CD36 receptor in the host, the up-regulation of domain cassette 13 (DC13) containing var group A, as also the up-regulation of group A rifins and many of the stevors. This is contrary to most other reports from pediatric patients, with cerebral malaria where the up-regulation of mostly var A group genes have been seen. A protein-protein interaction based network has been created and analysis performed. This co-expression and text mining based network has shown overall connectivity between the variant surface antigens (VSA) and the exportome. The up-regulation of var group B and C genes encoding PfEMP1 with different domain architecture would be important for deciding strategies for disease prevention.
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Affiliation(s)
- Amit Kumar Subudhi
- Department of Biological Sciences, Birla Institute of Technology and Science (BITS), Pilani, Rajasthan, India.
| | - P A Boopathi
- Department of Biological Sciences, Birla Institute of Technology and Science (BITS), Pilani, Rajasthan, India.
| | - Isha Pandey
- Department of Biological Sciences, Birla Institute of Technology and Science (BITS), Pilani, Rajasthan, India.
| | - Ramandeep Kohli
- Department of Biological Sciences, Birla Institute of Technology and Science (BITS), Pilani, Rajasthan, India.
| | - Rohan Karwa
- Department of Biological Sciences, Birla Institute of Technology and Science (BITS), Pilani, Rajasthan, India.
| | - Sheetal Middha
- Department of Medicine, S.P. Medical College, Bikaner, Rajasthan, India.
| | - Jyoti Acharya
- Department of Medicine, S.P. Medical College, Bikaner, Rajasthan, India.
| | - Sanjay K Kochar
- Department of Medicine, S.P. Medical College, Bikaner, Rajasthan, India.
| | - Dhanpat K Kochar
- Rajasthan University of Health Sciences, Jaipur, Rajasthan, India.
| | - Ashis Das
- Department of Biological Sciences, Birla Institute of Technology and Science (BITS), Pilani, Rajasthan, India.
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10
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Gaida A, Becker MM, Schmid CD, Bühlmann T, Louis EJ, Beck HP. Cloning of the repertoire of individual Plasmodium falciparum var genes using transformation associated recombination (TAR). PLoS One 2011; 6:e17782. [PMID: 21408186 PMCID: PMC3049791 DOI: 10.1371/journal.pone.0017782] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Accepted: 02/10/2011] [Indexed: 01/31/2023] Open
Abstract
One of the major virulence factors of the malaria causing parasite is the Plasmodium falciparum encoded erythrocyte membrane protein 1 (PfEMP1). It is translocated to It the membrane of infected erythrocytes and expressed from approximately 60 var genes in a mutually exclusive manner. Switching of var genes allows the parasite to alter functional and antigenic properties of infected erythrocytes, to escape the immune defense and to establish chronic infections. We have developed an efficient method for isolating VAR genes from telomeric and other genome locations by adapting transformation-associated recombination (TAR) cloning, which can then be analyzed and sequenced. For this purpose, three plasmids each containing a homologous sequence representing the upstream regions of the group A, B, and C var genes and a sequence homologous to the conserved acidic terminal segment (ATS) of var genes were generated. Co-transfection with P. falciparum strain ITG2F6 genomic DNA in yeast cells yielded 200 TAR clones. The relative frequencies of clones from each group were not biased. Clones were screened by PCR, as well as Southern blotting, which revealed clones missed by PCR due to sequence mismatches with the primers. Selected clones were transformed into E. coli and further analyzed by RFLP and end sequencing. Physical analysis of 36 clones revealed 27 distinct types potentially representing 50% of the var gene repertoire. Three clones were selected for sequencing and assembled into single var gene containing contigs. This study demonstrates that it is possible to rapidly obtain the repertoire of var genes from P. falciparum within a single set of cloning experiments. This technique can be applied to individual isolates which will provide a detailed picture of the diversity of var genes in the field. This is a powerful tool to overcome the obstacles with cloning and assembly of multi-gene families by simultaneously cloning each member.
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Affiliation(s)
- Annette Gaida
- Department for Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Marion M. Becker
- Centre for Genetics and Genomics, The University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom
| | - Christoph D. Schmid
- Department for Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Tobias Bühlmann
- Department for Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Edward J. Louis
- Centre for Genetics and Genomics, The University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom
- * E-mail:
| | - Hans-Peter Beck
- Department for Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
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11
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Vignali M, Armour CD, Chen J, Morrison R, Castle JC, Biery MC, Bouzek H, Moon W, Babak T, Fried M, Raymond CK, Duffy PE. NSR-seq transcriptional profiling enables identification of a gene signature of Plasmodium falciparum parasites infecting children. J Clin Invest 2011; 121:1119-29. [PMID: 21317536 DOI: 10.1172/jci43457] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Accepted: 12/15/2010] [Indexed: 11/17/2022] Open
Abstract
Malaria caused by Plasmodium falciparum results in approximately 1 million annual deaths worldwide, with young children and pregnant mothers at highest risk. Disease severity might be related to parasite virulence factors, but expression profiling studies of parasites to test this hypothesis have been hindered by extensive sequence variation in putative virulence genes and a preponderance of host RNA in clinical samples. We report here the application of RNA sequencing to clinical isolates of P. falciparum, using not-so-random (NSR) primers to successfully exclude human ribosomal RNA and globin transcripts and enrich for parasite transcripts. Using NSR-seq, we confirmed earlier microarray studies showing upregulation of a distinct subset of genes in parasites infecting pregnant women, including that encoding the well-established pregnancy malaria vaccine candidate var2csa. We also describe a subset of parasite transcripts that distinguished parasites infecting children from those infecting pregnant women and confirmed this observation using quantitative real-time PCR and mass spectrometry proteomic analyses. Based on their putative functional properties, we propose that these proteins could have a role in childhood malaria pathogenesis. Our study provides proof of principle that NSR-seq represents an approach that can be used to study clinical isolates of parasites causing severe malaria syndromes as well other blood-borne pathogens and blood-related diseases.
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Affiliation(s)
- Marissa Vignali
- Seattle Biomedical Research Institute, Seattle, Washington, USA
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12
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Abstract
Malaria during pregnancy is caused when parasite-infected erythrocytes accumulate within the placenta through interactions between the VAR2CSA protein on the infected erythrocyte surface and placental CSPGs (chondroitin sulfate proteoglycans). This interaction is the major target for therapeutics to treat or prevent pregnancy-associated malaria. Here we review the structural characterization of CSPG-binding DBL (Duffy-binding like) domains from VAR2CSA and summarize the growing evidence that the exquisite ligand specificity of VAR2CSA results from the adoption of higher-order architecture in which these domains fold together to form a ligand-binding pocket.
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13
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Martin-Blondel G, Soumah M, Camara B, Chabrol A, Porte L, Delobel P, Cuzin L, Berry A, Massip P, Marchou B. [Impact of malaria on HIV infection]. Med Mal Infect 2009; 40:256-67. [PMID: 19951829 DOI: 10.1016/j.medmal.2009.10.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2009] [Revised: 09/15/2009] [Accepted: 10/28/2009] [Indexed: 10/20/2022]
Abstract
Malaria and HIV are two major public health issues, especially in sub-Saharan Africa. HIV infection increases the incidence of clinical malaria, inversely correlated with the degree of immunodepression. The effect of malaria on HIV infection is not as well established. Malaria, when fever and parasitemia are high, may be associated with transient increases in HIV viral load. The effect of subclinical malaria on HIV viral load is uncertain. During pregnancy, placental malaria is associated with higher plasma and placental HIV viral loads, independently of the severity of immunodeficiency. However, the clinical impact of these transient increases of HIV viral load remains unknown. Although some data suggests that malaria might enhance sexual and mother-to-child transmissions, no clinical study has confirmed this. Nevertheless pregnant women and children with malaria-induced anemia are also exposed to HIV through blood transfusions. Integrated HIV and malaria control programs in the regions where both infections overlap are necessary.
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Affiliation(s)
- G Martin-Blondel
- Service des maladies infectieuses et tropicales, hôpital Purpan, place du Docteur-Baylac, TSA 40031, 31059 Toulouse cedex 9, France
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14
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Sander AF, Salanti A, Lavstsen T, Nielsen MA, Magistrado P, Lusingu J, Ndam NT, Arnot DE. Multiple var2csa-type PfEMP1 genes located at different chromosomal loci occur in many Plasmodium falciparum isolates. PLoS One 2009; 4:e6667. [PMID: 19690615 PMCID: PMC2723927 DOI: 10.1371/journal.pone.0006667] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Accepted: 07/13/2009] [Indexed: 12/03/2022] Open
Abstract
Background The var2csa gene encodes a Plasmodium falciparum adhesion receptor which binds chondroitin sulfate A (CSA). This var gene is more conserved than other PfEMP1/var genes and is found in all P. falciparum isolates. In isolates 3D7, FCR3/It4 and HB3, var2csa is transcribed from a sub-telomeric position on the left arm of chromosome 12, but it is not known if this location is conserved in all parasites. Genome sequencing indicates that the var2csa gene is duplicated in HB3, but whether this is true in natural populations is uncertain. Methodology/Principal Findings To assess global variation in the VAR2CSA protein, sequence variation in the DBL2X region of var2csa genes in 54 P.falciparum samples was analyzed. Chromosome mapping of var2csa loci was carried out and a quantitative PCR assay was developed to estimate the number of var2csa genes in P.falciparum isolates from the placenta of pregnant women and from the peripheral circulation of other malaria patients. Sequence analysis, gene mapping and copy number quantitation in P.falciparum isolates indicate that there are at least two loci and that both var2csa-like genes can be transcribed. All VAR2CSA DBL2X domains fall into one of two distinct phylogenetic groups possessing one or the other variant of a large (∼26 amino acid) dimorphic motif, but whether either motif variant is linked to a specific locus is not known. Conclusions/Significance Two or more related but distinct var2csa-type PfEMP1/var genes exist in many P. falciparum isolates. One gene is on chromosome 12 but additional var2csa-type genes are on different chromosomes in different isolates. Multiplicity of var2csa genes appears more common in infected placentae than in samples from non-pregnant donors indicating a possible advantage of this genotype in pregnancy associated malaria.
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Affiliation(s)
- Adam F. Sander
- Centre for Medical Parasitology, Department of International Health, Immunology & Microbiology, Faculty of Health Sciences, University of Copenhagen & Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - Ali Salanti
- Centre for Medical Parasitology, Department of International Health, Immunology & Microbiology, Faculty of Health Sciences, University of Copenhagen & Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - Thomas Lavstsen
- Centre for Medical Parasitology, Department of International Health, Immunology & Microbiology, Faculty of Health Sciences, University of Copenhagen & Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - Morten A. Nielsen
- Centre for Medical Parasitology, Department of International Health, Immunology & Microbiology, Faculty of Health Sciences, University of Copenhagen & Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
| | - Pamela Magistrado
- Centre for Medical Parasitology, Department of International Health, Immunology & Microbiology, Faculty of Health Sciences, University of Copenhagen & Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
- JMP-ENRICA Project, National Institute for Medical Research, Korogwe Laboratory, Tanga, Tanzania
| | - John Lusingu
- JMP-ENRICA Project, National Institute for Medical Research, Korogwe Laboratory, Tanga, Tanzania
| | - Nicaise Tuikue Ndam
- Institut de Recherche pour le Developpment, UR010, Universite Paris Descartes, Paris, France
| | - David E. Arnot
- Centre for Medical Parasitology, Department of International Health, Immunology & Microbiology, Faculty of Health Sciences, University of Copenhagen & Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark
- Institute of Immunology & Infection Research, School of Biology, University of Edinburgh, Edinburgh, Scotland, United Kingdom
- * E-mail:
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15
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Khunrae P, Philip JMD, Bull DR, Higgins MK. Structural comparison of two CSPG-binding DBL domains from the VAR2CSA protein important in malaria during pregnancy. J Mol Biol 2009; 393:202-13. [PMID: 19695262 PMCID: PMC3778748 DOI: 10.1016/j.jmb.2009.08.027] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Accepted: 08/11/2009] [Indexed: 11/26/2022]
Abstract
Severe malaria during pregnancy is associated with accumulation of parasite-infected erythrocytes in the placenta due to interactions between VAR2CSA protein, expressed on the surface of infected-erythrocytes, and placental chondroitin sulfate proteoglycans (CSPG). VAR2CSA contains multiple CSPG-binding domains, including DBL3X and DBL6ɛ. Previous structural studies of DBL3X suggested CSPG to bind to a positively charged patch and sulfate-binding site on the concave surface of the domain. Here we present the structure of the DBL6ɛ domain from VAR2CSA. This domain displays the same overall architecture and secondary structure as that of DBL3X but differs in loop structures, disulfide bond positions and surface charge distribution. In particular, despite binding to CSPG, DBL6ɛ lacks the key features of the CSPG-binding site of DBL3X. Instead DBL6ɛ binds to CSPG through a positively charged surface on the distal side of subdomain 2 that is exposed in intact VAR2CSA on the erythrocyte surface. Finally, unlike intact VAR2CSA, both DBL3X and DBL6ɛ bind to various carbohydrates, with greatest affinity for ligands with high sulfation and negative charge. These studies provide further insight into the structure of DBL domains and suggest a model for the role of individual domains in CSPG binding by VAR2CSA in placental malaria.
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Affiliation(s)
- Pongsak Khunrae
- Department of Biochemistry, University of Cambridge, 80, Tennis Court Road, Cambridge CB2 1GA, UK
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16
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Rowe JA, Claessens A, Corrigan RA, Arman M. 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: 268] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [What about the content of this article? (0)] [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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17
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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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Ghumra A, Semblat JP, McIntosh RS, Raza A, Rasmussen IB, Braathen R, Johansen FE, Sandlie I, Mongini PK, Rowe JA, Pleass RJ. Identification of residues in the Cmu4 domain of polymeric IgM essential for interaction with Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1). J Immunol 2008; 181:1988-2000. [PMID: 18641336 DOI: 10.4049/jimmunol.181.3.1988] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The binding of nonspecific human IgM to the surface of infected erythrocytes is important in rosetting, a major virulence factor in the pathogenesis of severe malaria due to Plasmodium falciparum, and IgM binding has also been implicated in placental malaria. Herein we have identified the IgM-binding parasite ligand from a virulent P. falciparum strain as PfEMP1 (TM284var1 variant), and localized the region within this PfEMP1 variant that binds IgM (DBL4beta domain). We have used this parasite IgM-binding protein to investigate the interaction with human IgM. Interaction studies with domain-swapped Abs, IgM mutants, and anti-IgM mAbs showed that PfEMP1 binds to the Fc portion of the human IgM H chain and requires the IgM Cmu4 domain. Polymerization of IgM was shown to be crucial for the interaction because PfEMP1 binding did not occur with mutant monomeric IgM molecules. These results with PfEMP1 protein have physiological relevance because infected erythrocytes from strain TM284 and four other IgM-binding P. falciparum strains showed analogous results to those seen with the DBL4beta domain. Detailed investigation of the PfEMP1 binding site on IgM showed that some of the critical amino acids in the IgM Cmu4 domain are equivalent to those regions of IgG and IgA recognized by Fc-binding proteins from bacteria, suggesting that this region of Ig molecules may be of major functional significance in host-microbe interactions. We have therefore shown that PfEMP1 is an Fc-binding protein of malaria parasites specific for polymeric human IgM, and that it shows functional similarities with Fc-binding proteins from pathogenic bacteria.
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Affiliation(s)
- Ashfaq Ghumra
- Institute of Genetics, Queens Medical Centre, University of Nottingham, Nottingham, England, United Kingdom
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19
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Abstract
Adhesive PfEMP1 proteins are displayed on the surface of malaria-infected red blood cells. They play a critical role in the disease, tethering infected cells away from destruction by the spleen and causing many severe symptoms. A molecular understanding of how these domains maintain their binding properties while evading immune detection will be important in developing therapeutics. In malaria of pregnancy, domains from the var2csa-encoded PfEMP1 protein interact with chondroitin sulfate on the placenta surface. This causes accumulation of infected red blood cells, leading to placental inflammation and block of blood flow to the developing fetus. This is associated with maternal anemia, low birth weight, and premature delivery and can lead to the death of mother and child. Here I present the structure of the chondroitin sulfate-binding DBL3X domain from a var2csa-encoded PfEMP1 protein. The domain adopts a fold similar to malarial invasion proteins, with extensive loop insertions. One loop is flexible in the unliganded structure but observed in the presence of sulfate or disaccharide, where it completes a sulfate-binding site. This loop, and others surrounding this putative carbohydrate-binding site, are flexible and polymorphic, perhaps protecting the binding site from immune detection. This suggests a model for how the domain maintains ligand binding while evading the immune response and will guide future drug and vaccine development.
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Affiliation(s)
- Matthew K Higgins
- Department of Biochemistry, University of Cambridge, 80, Tennis Court Road, Cambridge CB2 1GA, United Kingdom.
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20
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Ayouba A, Badaut C, Kfutwah A, Cannou C, Juillerat A, Gangnard S, Behr C, Mercereau-Puijalon O, Bentley GA, Barré-Sinoussi F, Menu E. Specific stimulation of HIV-1 replication in human placental trophoblasts by an antigen of Plasmodium falciparum. AIDS 2008; 22:785-7. [PMID: 18356610 DOI: 10.1097/QAD.0b013e3282f560ee] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Epidemiological data point to an increased risk of HIV-1 mother-to-child transmission in pregnant women with malaria, by unknown mechanisms. We show here that surface binding of a recombinant Plasmodium falciparum adhesin to chondroitin sulphate A proteoglycans increases HIV-1 replication in the human placental cell line BeWo, probably by a P. falciparum adhesin-induced long-terminal repeat-driven TNF-alpha stimulation. This suggests that placental malaria could increase the risk of HIV-1 transmission in utero.
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21
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Higgins MK. Overproduction, purification and crystallization of a chondroitin sulfate A-binding DBL domain from a Plasmodium falciparum var2csa-encoded PfEMP1 protein. Acta Crystallogr Sect F Struct Biol Cryst Commun 2008; 64:221-3. [PMID: 18323614 PMCID: PMC2374165 DOI: 10.1107/s1744309108004211] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2007] [Accepted: 02/11/2008] [Indexed: 11/10/2022]
Abstract
The PfEMP1 proteins of the malaria parasite Plasmodium falciparum are inserted into the membrane of infected red blood cells, where they mediate adhesion to a variety of human receptors. The DBL domains of the var2csa-encoded PfEMP1 protein play a critical role in malaria of pregnancy, tethering infected cells to the surface of the placenta through interactions with the glycosaminoglycan carbohydrate chondroitin sulfate A (CSA). A CSA-binding DBL domain has been overproduced in a bacterial expression system, purified and crystallized. Native data sets extending to 1.9 A resolution have been collected and phasing is under way.
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Affiliation(s)
- Matthew K Higgins
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, England.
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22
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Abstract
The malaria parasite, Plasmodium falciparum, invades the red blood cells (RBCs) of its human host and initiates a series of morphological rearrangements within the host cell cytoplasm. The mature RBC has no endogenous trafficking machinery; therefore, the parasite generates novel structures to mediate protein transport. These include compartments called the Maurer's clefts (MC), which play an important role in the trafficking of parasite proteins to the surface of the host cell. Recent electron tomography studies have revealed MC as convoluted flotillas of flattened discs that are tethered to the RBC membrane, prompting speculation that the MC could, in one respect, represent an extracellular equivalent of the Golgi apparatus. Visualization of both resident and cargo proteins has helped decipher the signals and routes for trafficking of parasite proteins to the MC and beyond.
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Affiliation(s)
- Leann Tilley
- Department of Biochemistry, La Trobe University, Melbourne, Victoria 3086, Australia
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23
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Affiliation(s)
- Stephen J. Rogerson
- Department of Medicine (RMH/WH), The University of Melbourne, Royal Melbourne Hospital, Australia; Department of Community Health, College of Medicine, University of Malawi, Blantyre, Malawi; Department of Epidemiology, Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina
| | - Victor Mwapasa
- Department of Medicine (RMH/WH), The University of Melbourne, Royal Melbourne Hospital, Australia; Department of Community Health, College of Medicine, University of Malawi, Blantyre, Malawi; Department of Epidemiology, Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina
| | - Steven R. Meshnick
- Department of Medicine (RMH/WH), The University of Melbourne, Royal Melbourne Hospital, Australia; Department of Community Health, College of Medicine, University of Malawi, Blantyre, Malawi; Department of Epidemiology, Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina
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24
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Hu G, Llinás M, Li J, Preiser PR, Bozdech Z. Selection of long oligonucleotides for gene expression microarrays using weighted rank-sum strategy. BMC Bioinformatics 2007; 8:350. [PMID: 17880708 PMCID: PMC2099447 DOI: 10.1186/1471-2105-8-350] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2006] [Accepted: 09/19/2007] [Indexed: 01/28/2023] Open
Abstract
Background The design of long oligonucleotides for spotted DNA microarrays requires detailed attention to ensure their optimal performance in the hybridization process. The main challenge is to select an optimal oligonucleotide element that represents each genetic locus/gene in the genome and is unique, devoid of internal structures and repetitive sequences and its Tm is uniform with all other elements on the microarray. Currently, all of the publicly available programs for DNA long oligonucleotide microarray selection utilize various combinations of cutoffs in which each parameter (uniqueness, Tm, and secondary structure) is evaluated and filtered individually. The use of the cutoffs can, however, lead to information loss and to selection of suboptimal oligonucleotides, especially for genomes with extreme distribution of the GC content, a large proportion of repetitive sequences or the presence of large gene families with highly homologous members. Results Here we present the program OligoRankPick which is using a weighted rank-based strategy to select microarray oligonucleotide elements via an integer weighted linear function. This approach optimizes the selection criteria (weight score) for each gene individually, accommodating variable properties of the DNA sequence along the genome. The designed algorithm was tested using three microbial genomes Escherichia coli, Saccharomyces cerevisiae and the human malaria parasite species Plasmodium falciparum. In comparison to other published algorithms OligoRankPick provides significant improvements in oligonucleotide design for all three genomes with the most significant improvements observed in the microarray design for P. falciparum whose genome is characterized by large fluctuations of GC content, and abundant gene duplications. Conclusion OligoRankPick is an efficient tool for the design of long oligonucleotide DNA microarrays which does not rely on direct oligonucleotide exclusion by parameter cutoffs but instead optimizes all parameters in context of each other. The weighted rank-sum strategy utilized by this algorithm provides high flexibility of oligonucleotide selection which accommodates extreme variability of DNA sequence properties along genomes of many organisms.
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Affiliation(s)
- Guangan Hu
- School of Biological Sciences, Nanyang Technological University, No. 60 Nanyang Drive, 637551, Singapore
| | - Manuel Llinás
- Department of Molecular Biology, Lewis-Sigler Institute for Integrative Genomics, Princeton University 246 Carl Icahn Laboratory, Princeton NJ 08544, USA
| | - Jingguang Li
- Department of Pathology & Laboratory Medicine, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, 308433, Singapore
| | - Peter Rainer Preiser
- School of Biological Sciences, Nanyang Technological University, No. 60 Nanyang Drive, 637551, Singapore
| | - Zbynek Bozdech
- School of Biological Sciences, Nanyang Technological University, No. 60 Nanyang Drive, 637551, Singapore
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25
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Abstract
Sexual differentiation and parasite transmission are intimately linked in the life cycle of malaria parasites. The specialized cells providing this crucial link are the Plasmodium gametocytes. These are formed in the vertebrate host and are programmed to mature into gametes emerging from the erythrocytes in the midgut of a blood-feeding mosquito. The ensuing fusion into a zygote establishes parasite infection in the insect vector. Although key mechanisms of gametogenesis and fertilization are becoming progressively clear, the fundamental biology of gametocyte formation still presents open questions, some of which are specific to the human malaria parasite Plasmodium falciparum. Developmental commitment to sexual differentiation, regulation of stage-specific gene expression, the profound molecular and cellular changes accompanying gametocyte specialization, the requirement for tissue-specific sequestration in P. falciparum gametocytogenesis are proposed here as areas for future investigation. The epidemiological relevance of parasite transmission from humans to mosquito in the spread of malaria and of Plasmodium drug resistance genes indicates that understanding molecular mechanisms of gametocyte formation is highly relevant to design strategies able to interfere with the transmission of this disease.
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Affiliation(s)
- Pietro Alano
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, Viale Regina Elena n. 299, 00161 Rome, Italy.
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26
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Adisa A, Frankland S, Rug M, Jackson K, Maier AG, Walsh P, Lithgow T, Klonis N, Gilson PR, Cowman AF, Tilley L. Re-assessing the locations of components of the classical vesicle-mediated trafficking machinery in transfected Plasmodium falciparum. Int J Parasitol 2007; 37:1127-41. [PMID: 17428488 DOI: 10.1016/j.ijpara.2007.02.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2007] [Revised: 02/15/2007] [Accepted: 02/16/2007] [Indexed: 11/16/2022]
Abstract
The malaria parasite, Plasmodium falciparum, exports proteins beyond the confines of its own plasma membrane, however there is debate regarding the machinery used for these trafficking events. We have generated transgenic parasites expressing chimeric proteins and used immunofluorescence studies to determine the locations of plasmodial homologues of the COPII component, Sar1p, and the Golgi-docking protein, Bet3p. The P. falciparum Sar1p (PfSar1p) chimeras bind to the endoplasmic reticulum surface and define a network of membranes wrapped around parasite nuclei. As the parasite matures, the endomembrane systems of individual merozoites remain interconnected until very late in schizogony. Antibodies raised against plasmodial Bet3p recognise two foci of reactivity in early parasite stages that increase in number as the parasite matures. Some of the P. falciparum Bet3p (PfBet3p) compartments are juxtaposed to compartments defined by the cis Golgi marker, PfGRASP, while others are distributed through the cytoplasm. The compartments defined by the trans Golgi marker, PfRab6, are separate, suggesting that the Golgi is dispersed. Bet3p-green fluorescent protein (GFP) is partly associated with punctate structures but a substantial population diffuses freely in the parasite cytoplasm. By contrast, yeast Bet3p is very tightly associated with immobile structures. This study challenges the view that the COPII complex and the Golgi apparatus are exported into the infected erythrocyte cytoplasm.
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Affiliation(s)
- Akinola Adisa
- Department of Biochemistry, La Trobe University, Melbourne 3086, Vic., Australia
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27
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Beeson JG, Andrews KT, Boyle M, Duffy MF, Choong EK, Byrne TJ, Chesson JM, Lawson AM, Chai W. Structural Basis for Binding of Plasmodium falciparum Erythrocyte Membrane Protein 1 to Chondroitin Sulfate and Placental Tissue and the Influence of Protein Polymorphisms on Binding Specificity. J Biol Chem 2007; 282:22426-36. [PMID: 17562715 DOI: 10.1074/jbc.m700231200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Chondroitin sulfate (CS) A is a key receptor for adhesion of Plasmodium falciparum-infected erythrocytes (IEs) in the placenta and can also mediate adhesion to microvascular endothelial cells. IEs that adhere to CSA express var2csa-type genes, which encode specific variants of the IE surface antigen P. falciparum erythrocyte membrane protein 1 (PfEMP1). We report direct binding of native PfEMP1, isolated from IEs and encoded by var2csa, to immobilized CSA. Binding of PfEMP1 was dependent on 4-O-sulfated disaccharides and glucuronic acid rather than iduronic acid, consistent with the specificity of intact IEs. Using immobilized CS oligosaccharides as neoglycolipid probes, the minimum chain length for direct binding of PfEMP1 was eight monosaccharide units. Similarly for IE adhesion to placental tissue there was a requirement for 4-O-sulfated GalNAc and glucuronic acid mixed with non-sulfated disaccharides; 6-O-sulfation interfered with the interaction between placental CSA and IEs. The minimum chain length for maximal inhibition of adhesion was 10 monosaccharide residues. Partially 4-O-sulfated CS oligosaccharides (45-55% sulfation) were highly effective inhibitors of placental adhesion (IC(50), 0.15 microg/ml) and may have potential for therapeutic development. We used defined P. falciparum isolates expressing different variants of var2csa in adhesion assays and found that there were isolate-specific differences in the preferred structural motifs for adhesion to CSA that correlated with polymorphisms in PfEMP1 encoded by var2csa-type genes. This may influence sites of IE sequestration or parasite virulence. These findings have significant implications for understanding the pathogenesis and biology of malaria, particularly during pregnancy, and the development of targeted interventions.
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Affiliation(s)
- James G Beeson
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3050, Australia.
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28
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Frankland S, Elliott SR, Yosaatmadja F, Beeson JG, Rogerson SJ, Adisa A, Tilley L. Serum lipoproteins promote efficient presentation of the malaria virulence protein PfEMP1 at the erythrocyte surface. Eukaryot Cell 2007; 6:1584-94. [PMID: 17644656 PMCID: PMC2043375 DOI: 10.1128/ec.00063-07] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The virulence of the malaria parasite Plasmodium falciparum is related to its ability to express a family of adhesive proteins known as P. falciparum erythrocyte membrane protein 1 (PfEMP1) at the infected red blood cell surface. The mechanism for the transport and delivery of these adhesins to the erythrocyte membrane is only poorly understood. In this work, we have used specific immune reagents in a flow cytometric assay to monitor the effects of serum components on the surface presentation of PfEMP1. We show that efficient presentation of the A4 and VAR2CSA variants of PfEMP1 is dependent on the presence of serum in the bathing medium during parasite maturation. Lipid-loaded albumin supports parasite growth but allows much less efficient presentation of PfEMP1 at the red blood cell surface. Analysis of the serum components reveals that lipoproteins, especially those of the low-density lipoprotein fraction, promote PfEMP1 presentation. Cytoadhesion of infected erythrocytes to the host cell receptors CD36 and ICAM-1 is also decreased in infected erythrocytes cultured in the absence of serum. The defect appears to be in the transfer of PfEMP1 from parasite-derived structures known as the Maurer's clefts to the erythrocyte membrane or in surface conformation rather than a down-regulation or switching of particular PfEMP1 variants.
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Affiliation(s)
- Sarah Frankland
- Department of Biochemistry, La Trobe University, Melbourne 3086, Australia
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29
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Barry AE, Leliwa-Sytek A, Tavul L, Imrie H, Migot-Nabias F, Brown SM, McVean GAV, Day KP. Population genomics of the immune evasion (var) genes of Plasmodium falciparum. PLoS Pathog 2007; 3:e34. [PMID: 17367208 PMCID: PMC1828697 DOI: 10.1371/journal.ppat.0030034] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2006] [Accepted: 01/24/2007] [Indexed: 12/01/2022] Open
Abstract
Var genes encode the major surface antigen (PfEMP1) of the blood stages of the human malaria parasite Plasmodium falciparum. Differential expression of up to 60 diverse var genes in each parasite genome underlies immune evasion. We compared the diversity of the DBLα domain of var genes sampled from 30 parasite isolates from a malaria endemic area of Papua New Guinea (PNG) and 59 from widespread geographic origins (global). Overall, we obtained over 8,000 quality-controlled DBLα sequences. Within our sampling frame, the global population had a total of 895 distinct DBLα “types” and negligible overlap among repertoires. This indicated that var gene diversity on a global scale is so immense that many genomes would need to be sequenced to capture its true extent. In contrast, we found a much lower diversity in PNG of 185 DBLα types, with an average of approximately 7% overlap among repertoires. While we identify marked geographic structuring, nearly 40% of types identified in PNG were also found in samples from different countries showing a cosmopolitan distribution for much of the diversity. We also present evidence to suggest that recombination plays a key role in maintaining the unprecedented levels of polymorphism found in these immune evasion genes. This population genomic framework provides a cost effective molecular epidemiological tool to rapidly explore the geographic diversity of var genes. Malaria parasites live in red blood cells of the human host for part of the life cycle, during which a family of diverse antigens known as PfEMP1 are placed on the surface. PfEMP1 variants switch by sequential expression of up to 60 var genes. This allows the parasite to evade immune detection within an individual host, enhancing its chances to be transmitted to the mosquito vector in situations where mosquitoes are seasonally available. Methods to rapidly assess var gene diversity in parasite populations are needed to measure antigenic diversity and define relationships with malaria transmission. Using a specialized framework, we completed the first systematic sampling of var genes from parasite genomes obtained from the same (Papua New Guinea [PNG]) and different (global) populations. Globally, there was no limit to the number of var genes because parasites rarely shared var genes. In PNG, var gene numbers were restricted due to high levels of sharing, and most were only found in that population. Recombination was important to the evolution of var genes in PNG. The data suggest there are distinct var genes in different populations, which may have consequences for the spread of malarial disease from one geographic area to another.
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Affiliation(s)
- Alyssa E Barry
- Peter Medawar Building for Pathogen Research, University of Oxford, Oxford, United Kingdom
- Department of Zoology, University of Oxford, Oxford, United Kingdom
- * To whom correspondence should be addressed. E-mail:
| | - Aleksandra Leliwa-Sytek
- Peter Medawar Building for Pathogen Research, University of Oxford, Oxford, United Kingdom
- Department of Zoology, University of Oxford, Oxford, United Kingdom
| | - Livingston Tavul
- Papua New Guinea Institute for Medical Research, Madang, Papua New Guinea
| | - Heather Imrie
- Peter Medawar Building for Pathogen Research, University of Oxford, Oxford, United Kingdom
- Department of Zoology, University of Oxford, Oxford, United Kingdom
| | - Florence Migot-Nabias
- Centre International de Recherches Médicales de Franceville (CIRMF), Franceville, Gabon
| | - Stuart M Brown
- Research Computing Resource, New York University School of Medicine, New York, New York, United States of America
| | | | - Karen P Day
- Peter Medawar Building for Pathogen Research, University of Oxford, Oxford, United Kingdom
- Department of Zoology, University of Oxford, Oxford, United Kingdom
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30
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Abstract
Malaria infects 5-10% of humanity and causes around two million deaths annually, mostly in children. The disease is of significant interest to immunologists, as acquired host immunity can limit the clinical impact of infection and partially reduces parasite replication; however, immunological reactions also contribute significantly to pathogenesis and fatalities. This review addresses the view that immunopathology in severe malaria arises predominantly from intravascular lesions resulting from a pathogen-initiated cascade of activated immune effector and regulatory cells infiltrating the vascular beds of diverse target organs, including bone marrow, spleen, brain, placenta and lungs. The main feature distinguishing these processes from classical cellular inflammation is the absence of extravasation, resulting from the intravascular location of the pathogen. Clinical and epidemiological observations combined with experimental infections in animal models suggest that parasite 'molecular patterns' or toxins cause cytokine and chemokine enhancement of infiltrates, composed of macrophages, neutrophils, natural killer (NK) cells, invariant natural killer T (iNKT) cells, gamma/delta T cells and both CD4(+) and CD8(+) effector T cells, leading to local vascular and organ derangement. Diverse pattern recognition and NK receptors crucially regulate these responding cell populations. Thus, innate immune mechanisms lie at the heart of this massive global public health problem.
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Affiliation(s)
- Louis Schofield
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.
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31
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Keen J, Serghides L, Ayi K, Patel SN, Ayisi J, van Eijk A, Steketee R, Udhayakumar V, Kain KC. HIV impairs opsonic phagocytic clearance of pregnancy-associated malaria parasites. PLoS Med 2007; 4:e181. [PMID: 17535103 PMCID: PMC1880852 DOI: 10.1371/journal.pmed.0040181] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2006] [Accepted: 03/30/2007] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Primigravid (PG) women are at risk for pregnancy-associated malaria (PAM). Multigravid (MG) women acquire protection against PAM; however, HIV infection impairs this protective response. Protection against PAM is associated with the production of IgG specific for variant surface antigens (VSA-PAM) expressed by chondroitin sulfate A (CSA)-adhering parasitized erythrocytes (PEs). We hypothesized that VSA-PAM-specific IgG confers protection by promoting opsonic phagocytosis of PAM isolates and that HIV infection impairs this response. METHODS AND FINDINGS We assessed the ability of VSA-PAM-specific IgG to promote opsonic phagocytosis of CSA-adhering PEs and the impact of HIV infection on this process. Opsonic phagocytosis assays were performed using the CSA-adherent parasite line CS2 and human and murine macrophages. CS2 PEs were opsonized with plasma or purified IgG subclasses from HIV-negative or HIV-infected PG and MG Kenyan women or sympatric men. Levels of IgG subclasses specific for VSA-PAM were compared in HIV-negative and HIV-infected women by flow cytometry. Plasma from HIV-negative MG women, but not PG women or men, promoted the opsonic phagocytosis of CSA-binding PEs (p < 0.001). This function depended on VSA-PAM-specific plasma IgG1 and IgG3. HIV-infected MG women had significantly lower plasma opsonizing activity (median phagocytic index 46 [interquartile range (IQR) 18-195] versus 251 [IQR 93-397], p = 0.006) and levels of VSA-PAM-specific IgG1 (mean fluorescence intensity [MFI] 13 [IQR 11-20] versus 30 [IQR 23-41], p < 0.001) and IgG3 (MFI 17 [IQR 14-23] versus 28 [IQR 23-37], p < 0.001) than their HIV-negative MG counterparts. CONCLUSIONS Opsonic phagocytosis may represent a novel correlate of protection against PAM. HIV infection may increase the susceptibility of multigravid women to PAM by impairing this clearance mechanism.
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Affiliation(s)
- Jessica Keen
- Faculty of Medicine, University of Toronto, Toronto, Canada
| | - Lena Serghides
- Faculty of Medicine, University of Toronto, Toronto, Canada
- McLaughlin-Rotman Centre, McLaughlin Center for Molecular Medicine, University of Toronto, Toronto, Canada
- University Health Network, Toronto, Canada
| | - Kodjo Ayi
- Faculty of Medicine, University of Toronto, Toronto, Canada
| | - Samir N Patel
- Faculty of Medicine, University of Toronto, Toronto, Canada
| | - John Ayisi
- Center for Vector Biology and Control Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Anne van Eijk
- Center for Vector Biology and Control Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Richard Steketee
- Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - Venkatachalam Udhayakumar
- Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - Kevin C Kain
- Faculty of Medicine, University of Toronto, Toronto, Canada
- McLaughlin-Rotman Centre, McLaughlin Center for Molecular Medicine, University of Toronto, Toronto, Canada
- University Health Network, Toronto, Canada
- * To whom correspondence should be addressed. E-mail:
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32
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Abstract
Malaria persists as an undiminished global problem, but the resources available to address it have increased. Many tools for understanding its biology and epidemiology are well developed, with a particular richness of comparative genome sequences. Targeted genetic manipulation is now effectively combined with in vitro culture assays on the most important human parasite, Plasmodium falciparum, and with in vivo analysis of rodent and monkey malaria parasites in their laboratory hosts. Studies of the epidemiology, prevention, and treatment of human malaria have already been influenced by the availability of molecular methods, and analyses of parasite polymorphisms have long had useful and highly informative applications. However, the molecular epidemiology of malaria is currently undergoing its most substantial revolution as a result of the genomic information and technologies that are available in well-resourced centers. It is a challenge for research agendas to face the real needs presented by a disease that largely exists in extremely resource-poor settings, but it is one that there appears to be an increased willingness to undertake. To this end, developments in the molecular epidemiology of malaria are reviewed here, emphasizing aspects that may be current and future priorities.
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Affiliation(s)
- David J Conway
- Medical Research Council Laboratories, Fajara, P.O. Box 273, Banjul, The Gambia.
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33
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Affiliation(s)
- D Channe Gowda
- Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine Hershey, Pennsylvania 17033, USA
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34
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Nielsen MA, Resende M, Alifrangis M, Turner L, Hviid L, Theander TG, Salanti A. Plasmodium falciparum: VAR2CSA expressed during pregnancy-associated malaria is partially resistant to proteolytic cleavage by trypsin. Exp Parasitol 2007; 117:1-8. [PMID: 17442305 DOI: 10.1016/j.exppara.2007.03.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2006] [Revised: 03/01/2007] [Accepted: 03/02/2007] [Indexed: 10/23/2022]
Abstract
In areas of high Plasmodium falciparum transmission, immunity to malaria is acquired during childhood, so that adults in general are clinically immune. One exception is that first-time pregnant women are susceptible to pregnancy-associated malaria caused by accumulation of parasites in the placenta. Pregnancy-associated variant surface antigens (VSAPAM) mediate binding of the infected erythrocyte to chondroitin sulphate proteoglycans in the placental intervillous space. Several lines of evidence indicate that the molecular identity of VSAPAM is VAR2CSA, a relatively conserved member of the P. falciparum erythrocyte membrane protein 1 (PfEMP1) family. While native PfEMP1 molecules expressed on the infected erythrocyte surface generally are sensitive to mild trypsinization, some VSAPAM expressing parasite lines are resistant. This finding has led to the suggestion that molecules other than PfEMP1, or at least several different PfEMP1 families mediate the VSAPAM phenotype. To address this issue we incubated three different VAR2CSA expressing parasite lines with trypsin and found that polymorphic VAR2CSA variants can be both protease resistant and sensitive. Trypsin treatment resulted in loss of ability to adhere to CSA and loss of sex-specific antibody recognition of the surface of the infected erythrocyte in one sensitive isolate, whereas CSA binding and sex-specific recognition were largely unaffected by trypsin treatment in two resistant isolates. These results support the hypothesis that VAR2CSA mediates the adhesive and antigenic phenotypes shown by parasites causing placental malaria.
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Affiliation(s)
- Morten A Nielsen
- Centre for Medical Parasitology, Department of Infectious Diseases M4701, Copenhagen University Hospital (Rigshospitalet), Blegdamsvej 9, 2100 Copenhagen Ø, Denmark.
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35
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Peters JM, Fowler EV, Krause DR, Cheng Q, Gatton ML. Differential changes in Plasmodium falciparum var transcription during adaptation to culture. J Infect Dis 2007; 195:748-55. [PMID: 17262719 PMCID: PMC1866257 DOI: 10.1086/511436] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2006] [Accepted: 10/02/2006] [Indexed: 11/03/2022] Open
Abstract
Plasmodium falciparum erythrocyte membrane protein 1, which is encoded by the var multigene family, is expressed on the surface of P. falciparum-infected erythrocytes and has been implicated in many of the complications associated with falciparum malaria. Transcriptional switching of var is commonly investigated using in vitro cultured parasites, because parasite material from patients is limited. We investigated the affect of short-term in vitro cultivation on var gene transcription in patient samples. A significant reduction in the overall abundance of var transcripts was observed during the first approximately 10 days of culture. The rate of down-regulation was not constant among all var genes; genes with an upsA, -D, and -E 5' flanking region had a significantly faster rate than genes with an upsB or -C flanking region. These results have significant implications for the investigation of associations between var transcription and clinical manifestations using parasites that have been enriched by in vitro culture.
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Affiliation(s)
- Jennifer M Peters
- Malaria Drug Resistance and Chemotherapy Laboratory, Queensland Institute of Medical Research, Herston, Australia
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36
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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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37
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Badaut C, Faure G, Tuikue Ndam NG, Bertin G, Chaffotte A, Khattab A, Klinkert MQ, Deloron P, Bentley GA. Receptor-binding studies of the DBLgamma domain of Plasmodium falciparum erythrocyte membrane protein 1 from a placental isolate. Mol Biochem Parasitol 2006; 151:89-99. [PMID: 17118469 DOI: 10.1016/j.molbiopara.2006.10.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2006] [Revised: 10/18/2006] [Accepted: 10/20/2006] [Indexed: 11/24/2022]
Abstract
We have previously identified a number of DBLgamma domains in Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) transcripts obtained from placental parasite isolates, showing that they bind specifically to chondroitin sulfate A (CSA) (Khattab A, Kun J, Deloron P, Kremsner PG, Klinkert MQ. Variants of Plasmodium falciparum erythrocyte membrane protein 1 expressed by different placental parasites are closely related and adhere to chondroitin sulfate A. J Infect Dis 2001;183:1165-9). Here we give a more detailed physico-chemical and binding characterisation of the soluble, recombinant DBLgamma domain derived from one of these isolates. Results from circular dichroism and limited proteolysis experiments are consistent with the recombinant domain being expressed with the native fold. Specific binding of DBLgamma to placental cryosections was demonstrated by labeling with antibodies raised against the recombinant domain; binding was diminished after treatment of the cryosections with chondroitinase or by blocking with anti-CSA antibody, showing that CSA mediates the interaction. Binding of the DBLgamma domain to purified placental chondroitin sulfate proteoglycan (CSPG) was also studied using surface plasmon resonance techniques, with DBLgamma as analyte and CSPG immobilised on the sensor chip; these quantitative measurements gave an affinity constant in the mu-molar range under the conditions used. The native conformation of the DBLgamma domain is essential for CSPG recognition since binding to the sensor chip is abolished when the protein is irreversibly reduced. As with the placental cryosections, association was significantly reduced after treating the immobilised CSPG with chondroitinase. Together, these results demonstrate specific interaction between the DBLgamma domain and the placental receptor.
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Affiliation(s)
- Cyril Badaut
- Unité d'Immunologie Structurale, CNRS URA 2185, Département de Biologie Structurale et Chime, Institut Pasteur, 25-28 rue du Dr. Roux, 75724 Paris cedex 15, France
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38
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Gowda ASP, Madhunapantula SV, Achur RN, Valiyaveettil M, Bhavanandan VP, Gowda DC. Structural basis for the adherence of Plasmodium falciparum-infected erythrocytes to chondroitin 4-sulfate and design of novel photoactivable reagents for the identification of parasite adhesive proteins. J Biol Chem 2006; 282:916-28. [PMID: 17085451 DOI: 10.1074/jbc.m604741200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A dodecasaccharide motif of the low-sulfated chondroitin 4-sulfate (C4S) mediate the binding of Plasmodium falciparum-infected red blood cells (IRBCs) in human placenta. Here we studied the detailed C4S structural requirements by assessing the ability of chemically modified C4S to inhibit IRBC binding to the placental chondroitin sulfate proteoglycan. Replacement of the N-acetyl groups with bulky N-acyl or N-benzoyl substituents had no effect on the inhibitory activity of C4S, whereas reduction of the carboxyl groups abrogated the activity. Dermatan sulfates showed approximately 50% inhibitory activity when compared with C4Ss with similar sulfate contents. These data demonstrate that the C4S carboxyl groups and their equatorial orientation but not the N-acetyl groups are critical for IRBC binding. Conjugation of bulky substituents to the reducing end N-acetylgalactosamine residues of C4S dodecasaccharide had no effect on its inhibitory activity. Based on these results, we prepared photoaffinity reagents for the identification of the parasite proteins involved in C4S binding. Cross-linking of the IRBCs with a radioiodinated photoactivable C4S dodecasaccharide labeled a approximately 22-kDa novel parasite protein, suggesting strongly for the first time that a low molecular weight IRBC surface protein rather than a 200-400-kDa PfEMP1 is involved in C4S binding. Conjugation of biotin to the C4S dodecasaccharide photoaffinity probe afforded a strategy for the isolation of the labeled protein by avidin affinity precipitation, facilitating efforts to identify the C4S-adherent IRBC protein(s). Our results also have broader implications for designing oligosaccharide-based photoaffinity probes for the identification of proteins involved in glycosaminoglycan-dependent attachment of microbes to hosts.
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Affiliation(s)
- A S Prakasha Gowda
- Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA
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39
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Abstract
An immunovariant adhesion protein family in Plasmodium falciparum named erythrocyte membrane protein 1 (PfEMP1), encoded by var genes, is responsible for both antigenic variation and cytoadhesion of infected erythrocytes at blood microvasculature sites throughout the body. Elucidation of the genome sequence of P. falciparum has revealed that var genes can be classified into different groups, each with distinct 5' flanking sequences, chromosomal locations and gene orientations. Recent binding and serological comparisons suggest that this genomic organization might cause var genes to diversify into separately recombining adhesion groups that have different roles in infection and disease. Detailed understanding of PfEMP1 expression and receptor binding mechanisms during infection and of the antigenic relatedness of disease variants might lead to new approaches in prevention of malaria disease.
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Affiliation(s)
- Susan M Kraemer
- Seattle Biomedical Research Institute, Seattle, WA 98109-5219, USA
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40
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Lucchi NW, Koopman R, Peterson DS, Moore JM. Plasmodium falciparum-infected Red Blood Cells Selected for Binding to Cultured Syncytiotrophoblast Bind to Chondroitin Sulfate A and Induce Tyrosine Phosphorylation in the Syncytiotrophoblast. Placenta 2006; 27:384-94. [PMID: 16009422 DOI: 10.1016/j.placenta.2005.04.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2005] [Revised: 04/24/2005] [Accepted: 04/25/2005] [Indexed: 11/23/2022]
Abstract
An important pathogenic complication of malaria during human pregnancy is sequestration of Plasmodium-infected red blood cells (iRBCs) in the placental intervillous spaces. This sequestration is thought to be mediated in part by binding of the iRBCs to receptors expressed on the syncytiotrophoblast (ST) membrane. We report here the use of a dynamic system to study the consequences of this cytoadherence on ST function using human syncytiotrophoblast and the choriocarcinoma cell line, BeWo. Laboratory isolates of Plasmodium falciparum were selected for their ability to bind to ST and used to investigate binding-induced cellular changes in the ST. Treatment of the ST cells with chondroitinase ABC suggested that the selected parasites bind predominantly to chondroitin sulfate A, but other receptors for parasite binding may be involved. Intracellular signaling in the ST induced by iRBCs binding was investigated by assessing tyrosine phosphorylation of ST proteins following iRBC binding. We demonstrate for the first time that iRBC cytoadherence to syncytiotrophoblast enhances tyrosine phosphorylation of a series of proteins in these cells. This approach will be useful in further studies of ST function in the malaria-infected placenta, the dynamics of selection of syncytiotrophoblast-binding parasites, and the identification of new receptors for parasite cytoadherence in the placenta.
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Affiliation(s)
- N W Lucchi
- Department of Infectious Diseases, College of Veterinary Medicine and Center for Tropical and Emerging Global Diseases, Medical Microbiology and Parasitology, 501 DW Brooks Dr, University of Georgia, Athens, GA 30602, USA
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41
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Viebig NK, Gamain B, Scheidig C, Lépolard C, Przyborski J, Lanzer M, Gysin J, Scherf A. A single member of the Plasmodium falciparum var multigene family determines cytoadhesion to the placental receptor chondroitin sulphate A. EMBO Rep 2006; 6:775-81. [PMID: 16025132 PMCID: PMC1369142 DOI: 10.1038/sj.embor.7400466] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2005] [Revised: 05/13/2005] [Accepted: 05/31/2005] [Indexed: 11/08/2022] Open
Abstract
In high-transmission regions, protective clinical immunity to Plasmodium falciparum develops during the early years of life, limiting serious complications of malaria in young children. Pregnant women are an exception and are especially susceptible to severe P. falciparum infections resulting from the massive adhesion of parasitized erythrocytes to chondroitin sulphate A (CSA) present on placental syncytiotrophoblasts. Epidemiological studies strongly support the feasibility of an intervention strategy to protect pregnant women from disease. However, different parasite molecules have been associated with adhesion to CSA. In this work, we show that disruption of the var2csa gene of P. falciparum results in the inability of parasites to recover the CSA-binding phenotype. This gene is a member of the var multigene family and was previously shown to be composed of domains that mediate binding to CSA. Our results show the central role of var2CSA in CSA adhesion and support var2CSA as a leading vaccine candidate aimed at protecting pregnant women and their fetuses.
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MESH Headings
- Animals
- Antibodies, Protozoan
- Antigenic Variation
- Blotting, Northern
- Blotting, Southern
- CD36 Antigens/biosynthesis
- CD36 Antigens/metabolism
- Cell Adhesion
- Chondroitin Sulfates/chemistry
- Cloning, Molecular
- Crossing Over, Genetic
- Exons
- Female
- Genome
- Genome, Protozoan
- Humans
- Malaria, Falciparum/prevention & control
- Malaria, Falciparum/transmission
- Models, Biological
- Models, Genetic
- Multigene Family
- Mutation
- Phenotype
- Placenta/metabolism
- Plasmids/metabolism
- Plasmodium falciparum/genetics
- Plasmodium falciparum/metabolism
- Pregnancy
- Pregnancy Complications, Parasitic/prevention & control
- Protein Binding
- Protozoan Proteins/genetics
- RNA/metabolism
- Time Factors
- Trophoblasts/metabolism
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Affiliation(s)
- Nicola K Viebig
- Unité de Biologie des Interactions Hôte-Parasite, CNRS URA 2581, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
| | - Benoit Gamain
- Unité de Biologie des Interactions Hôte-Parasite, CNRS URA 2581, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
| | - Christine Scheidig
- Unité de Biologie des Interactions Hôte-Parasite, CNRS URA 2581, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
| | - Catherine Lépolard
- Unité de Parasitologie Expérimentale URA IPP/UNIV-MED EA 3282, IFR 48, Université de la Méditerranée (Aix-Marseille II), 27 Boulevard Jean Moulin, 13385, Marseille Cedex 5, France
| | - Jude Przyborski
- Hygiene Institut, Abteilung Parasitologie, Universitätsklinikum Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
| | - Michael Lanzer
- Hygiene Institut, Abteilung Parasitologie, Universitätsklinikum Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
| | - Jürg Gysin
- Unité de Parasitologie Expérimentale URA IPP/UNIV-MED EA 3282, IFR 48, Université de la Méditerranée (Aix-Marseille II), 27 Boulevard Jean Moulin, 13385, Marseille Cedex 5, France
| | - Artur Scherf
- Unité de Biologie des Interactions Hôte-Parasite, CNRS URA 2581, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
- Tel: +33 1 45 68 86 16; Fax: +33 1 45 68 83 48; E-mail:
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42
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Semblat JP, Raza A, Kyes SA, Rowe JA. Identification of Plasmodium falciparum var1CSA and var2CSA domains that bind IgM natural antibodies. Mol Biochem Parasitol 2006; 146:192-7. [PMID: 16442168 PMCID: PMC2869447 DOI: 10.1016/j.molbiopara.2005.12.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2005] [Revised: 11/11/2005] [Accepted: 12/15/2005] [Indexed: 10/25/2022]
Abstract
Malaria in pregnancy is responsible for maternal anaemia, low-birth-weight babies and infant deaths. Plasmodium falciparum infected erythrocytes are thought to cause placental pathology by adhering to host receptors such as chondroitin sulphate A (CSA). CSA binding infected erythrocytes also bind IgM natural antibodies from normal human serum, a process that may facilitate placental adhesion or promote immune evasion. The parasite ligands that mediate placental adhesion are thought to be members of the variant erythrocyte surface antigen family P. falciparum erythrocyte membrane protein 1 (PfEMP1), encoded by the var genes. Two var gene sub-families, var1CSA and var2CSA, have been identified as parasite CSA binding ligands and are leading candidates for a vaccine to prevent pregnancy-associated malaria. We investigated whether these two var gene subfamilies implicated in CSA binding are also the molecules responsible for IgM natural antibody binding. By heterologous expression of domains in COS-7 cells, we found that both var1CSA and var2CSA PfEMP1 variants bound IgM, and in both cases the binding region was a DBL epsilon domain occurring proximal to the membrane. None of the domains from a control non-IgM-binding parasite (R29) bound IgM when expressed in COS-7 cells. These results show that PfEMP1 is a parasite ligand for non-immune IgM and are the first demonstration of a specific adhesive function for PfEMP1 epsilon type domains.
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Affiliation(s)
- Jean-Philippe Semblat
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JT, UK
| | - Ahmed Raza
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JT, UK
| | - Sue A. Kyes
- Molecular Parasitology Group, Weatherall Institute of Molecular Medicine, Headington, Oxford OX3 9DS, UK
| | - J. Alexandra Rowe
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JT, UK
- Corresponding author at: Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JT, UK. Tel.: +44 131 650 5492; fax: +44 131 650 6564. (J.A. Rowe)
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Abstract
Women in endemic areas become highly susceptible to malaria during first and second pregnancies, despite immunity acquired after years of exposure. Recent insights have advanced our understanding of pregnancy malaria caused by Plasmodium falciparum, which is responsible for the bulk of severe disease and death. Accumulation of parasitized erythrocytes in the blood spaces of the placenta is a key feature of maternal infection with P. falciparum. Placental parasites express surface ligands and antigens that differ from those of other P. falciparum variants, facilitating evasion of existing immunity, and mediate adhesion to specific molecules, such as chondroitin sulfate A, in the placenta. The polymorphic and clonally variant P. falciparum erythrocyte membrane protein 1, encoded by var genes, binds to placental receptors in vitro and may be the target of protective antibodies. An intense infiltration of immune cells, including macrophages, into the placental intervillous spaces, and the production of pro-inflammatory cytokines often occur in response to infection, and are associated with low birth weight and maternal anemia. Expression of alpha and beta chemokines may initiate or facilitate this cellular infiltration during placental malaria. Specific immunity against placental-binding parasites may prevent infection or facilitate clearance of parasites prior to the influx of inflammatory cells, thereby avoiding a cascade of events leading to disease and death. Much less is known about pathogenic processes in P. vivax infections, and corresponding immune responses. Emerging knowledge of the pathogenesis and immunology of malaria in pregnancy will increasingly lead to new opportunities for the development of therapeutic and preventive interventions and new tools for diagnosis and monitoring.
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Affiliation(s)
- J G Beeson
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.
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Abstract
That humans in endemic areas become immune to malaria offers encouragement to the idea of developing protective vaccines. However natural immunity is relatively inefficient, being bought at the cost of substantial childhood mortality, and current vaccines are only partially protective. Understanding potential targets and mechanisms of protective immunity is important in the development and evaluation of future vaccines. Some of the problems in identifying such targets and mechanisms in humans naturally exposed to malaria may stem from conceptual and methodological issues related to defining who in a population is susceptible, problems in defining immune responsiveness at single time points and issues related to antigenic polymorphism, as well as the failure of many current approaches to examine functional aspects of the immune response. Protective immune responses may be directed to the pre erythrocytic parasite, to the free merozoite of the blood stage parasite or to new antigens induced on the infected red cell surface. Tackling the methodological issues of defining protection and immune response, together with studies that combine functional assays with new approaches such as allelic exchange and gene knock out offer opportunities for better defining key targets and mechanisms.
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Affiliation(s)
- K Marsh
- KEMRI Centre for Geographic Medicine Research Coast (CGMRC), PO Box 230, Kilifi, Kenya.
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Abstract
Malaria is possibly the most serious infectious disease of humans, infecting 5-10% of the world's population, with 300-600 million clinical cases and more than 2 million deaths annually. Adaptive immune responses in the host limit the clinical impact of infection and provide partial, but incomplete, protection against pathogen replication; however, these complex immunological reactions can contribute to disease and fatalities. So, appropriate regulation of immune responses to malaria lies at the heart of the host-parasite balance and has consequences for global public health. This Review article addresses the innate and adaptive immune mechanisms elicited during malaria that either cause or prevent disease and fatalities, and it considers the implications for vaccine design.
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Affiliation(s)
- Louis Schofield
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3050, Australia.
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Megnekou R, Staalsoe T, Taylor DW, Leke R, Hviid L. Effects of pregnancy and intensity of Plasmodium falciparum transmission on immunoglobulin G subclass responses to variant surface antigens. Infect Immun 2005; 73:4112-8. [PMID: 15972500 PMCID: PMC1168589 DOI: 10.1128/iai.73.7.4112-4118.2005] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Placenta-sequestering Plasmodium falciparum involved in the pathogenesis of pregnancy-associated malaria (PAM) in otherwise clinically immune women expresses particular variant surface antigens (VSA(PAM)) on the surface of infected erythrocytes that differ from VSA found in parasitized nonpregnant individuals (non-PAM type VSA). We studied levels of immunoglobulin G (IgG) and IgG subclasses with specificity for VSA(PAM) and for non-PAM type VSA in pregnant and nonpregnant women from two sites with different endemicities in Cameroon. We found that VSA(PAM)-specific responses depended on the pregnancy status, parity, gestational age, and parasite transmission intensity, whereas only the parasite transmission intensity influenced the levels of IgG specific for non-PAM type VSA. For both types of VSA, the responses were dominated by the cytophilic subclass IgG1, followed by IgG3. In pregnant women, the levels of VSA(PAM)-specific antibodies either were very low or negative or were very high, whereas the levels of the antibodies specific for non-PAM type VSA were uniformly high. Interestingly, the levels of VSA(PAM)-specific IgG1 increased with increasing gestational age, while the levels of the corresponding IgG3 tended to decrease with increasing gestational age. The IgG subclass responses with specificity for non-PAM type VSA did not vary significantly with gestational age. Taken together, our data indicate that IgG1 and to a lesser extent IgG3 are the main subclasses involved in acquired VSA(PAM)-specific immunity to pregnancy-associated malaria.
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Affiliation(s)
- Rosette Megnekou
- Center for Medical Parasitology, Department of Infectious Diseases M7641, Copenhagan University Hospital (Rigshospitalet), Blegdamsvej 9, 2100 Copenhagen Ø, Denmark
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Korir CC, Galinski MR. Proteomic studies of Plasmodium knowlesi SICA variant antigens demonstrate their relationship with P. falciparum EMP1. Infect Genet Evol 2005; 6:75-9. [PMID: 16376842 DOI: 10.1016/j.meegid.2005.01.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2004] [Revised: 01/11/2005] [Accepted: 01/14/2005] [Indexed: 10/25/2022]
Abstract
Malaria variant antigens are encoded by large multigene families and expressed on the surface of infected erythrocytes. The Plasmodium knowlesi Schizont-infected cell agglutination (SICA) antigens are encoded by the SICAvar multigene family, and the P. falciparum erythrocyte membrane protein-1 (PfEMP1) antigens are encoded by the var gene family. Although these variant antigens share many fundamental features, P. knowlesi and P. falciparum are phylogenetically distantly related, and so far a significant level of sequence identity has not been observed in alignments of either the SICAvar and var gene families or their encoded proteins. In support of their orthologous relationship, however, here we demonstrate through proteomic analysis that the P. knowlesi SICA variant antigens share significant common sequences with P. falciparum EMP1 molecules. As many as forty P. knowlesi SICA peptides show identity with a particular P. falciparum EMP1, mapping throughout all characterized domains, including the externally exposed cysteine-rich domains that are characteristic of both proteins. These findings provide further validation of the classical in vivo P. knowlesi-rhesus monkey model system for advancing our understanding of the immunobiology of antigenic variation and variant antigen gene expression in Plasmodium.
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Affiliation(s)
- Cindy C Korir
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, 954 Gatewood Road, Atlanta, GA 30329, USA
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Abstract
Aided by the Plasmodium falciparum genome project, recent discoveries regarding the molecular basis of malaria pathogenesis have led to a better understanding of the interactions between host and parasite. Although vaccines that prevent infection by malaria parasites remain only hopes for the future, there are now more immediate prospects for vaccines that protect against specific disease syndromes. Here, we discuss the latest advances in the development of a vaccine that specifically targets pregnancy-associated malaria (PAM).
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Affiliation(s)
- Joseph D Smith
- Seattle Biomedical Research Institute, 307 Westlake Ave. N., Ste. 500, Seattle, WA 98109-5219, USA.
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Abstract
Women living in areas of intense P. falciparum transmission have acquired substantial protective immunity to malaria when they reach childbearing age. Nevertheless, pregnancies in such areas are associated with substantial malaria-related morbidity and mortality, particularly among women of low parity. The parity-dependency of susceptibility to malaria in pregnant women suggests that protective immunity to this type of malaria can be developed. However, until recently it has been poorly understood why the clinical protection against malaria, which young women in endemic areas acquire well before their first pregnancy, is suddenly rendered inadequate when they become pregnant, only to be regained during the course of a few pregnancies. In this article, I discuss some recent immuno-epidemiological studies of pregnancy-associated malaria, which, in combination with the generally improved understanding of how protective immunity to P. falciparum malaria operates and is acquired, have provided important insights into this enigma.
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Affiliation(s)
- L Hviid
- Centre for Medical Parasitology at Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet) and Institute for Medical Microbiology and Immunology, University of Copenhagen, Copenhagen Ø, Denmark.
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