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Combined Transcriptome and Proteome Profiling for Role of pfEMP1 in Antimalarial Mechanism of Action of Dihydroartemisinin. Microbiol Spectr 2021; 9:e0127821. [PMID: 34908430 PMCID: PMC8672878 DOI: 10.1128/spectrum.01278-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Malaria parasites induce morphological and biochemical changes in the membranes of parasite-infected red blood cells (iRBCs) for propagation. Artemisinin combination therapies are the first-line antiplasmodials in countries of endemicity. However, the mechanism of action of artemisinin is unclear, and drug resistance decreases long-term efficacy. To understand whether artemisinin targets or interacts with iRBC membrane proteins, this study investigated the molecular changes caused by dihydroartemisinin (DHA), an artemisinin derivative, in Plasmodium falciparum 3D7 using a combined transcriptomic and membrane proteomic profiling approach. Optical microscopy and scanning electron microscopy showed that DHA can cause morphological variation in the iRBC membrane. We identified 125 differentially expressed membrane proteins, and functional analysis indicated structural molecule activity and protein export as key biological functions of the two omics studies. DHA treatment decreased the expression of var gene variants PF3D7_0415700 and PF3D7_0900100 dose-dependently. Western blotting and immunofluorescence analysis showed that DHA treatment downregulates the var gene encoding P. falciparum erythrocyte membrane protein-1 (pfEMP1). pfEMP1 knockout significantly increased artemisinin sensitivity. Results showed that pfEMP1 might be involved in the antimalarial mechanism of action of DHA and pfEMP1 or its regulated factors may be further exploited in antiparasitic drug design. The findings are beneficial for elucidating the potential effects of DHA on iRBC membrane proteins and developing new drugs targeting iRBC membrane. IMPORTANCE Malaria parasites induce morphological and biochemical changes in the membranes of parasite-infected red blood cells (iRBCs) for propagation, with artemisinin combination therapies as the first-line treatments. To understand whether artemisinin targets or interacts with iRBC membrane proteins, this study investigated the molecular changes caused by dihydroartemisinin (DHA), an artemisinin derivative, in Plasmodium falciparum 3D7 using a combined transcriptomic and membrane proteomic profiling approach. We found that DHA can cause morphological changes of iRBC membrane. Structural molecule activity and protein export are considered to be the key biological functions based on the two omics studies. pfEMP1 might be involved in the DHA mechanism of action. pfEMP1 or its regulated factors may be further exploited in antiparasitic drug design. The findings are beneficial for elucidating the potential effects of DHA on iRBC membrane proteins and developing new antimalarial drugs targeting iRBC membrane.
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Prata IO, Cubillos EFG, Krüger A, Barbosa D, Martins J, Setubal JC, Wunderlich G. Plasmodium falciparum Acetyl-CoA Synthetase Is Essential for Parasite Intraerythrocytic Development and Chromatin Modification. ACS Infect Dis 2021; 7:3224-3240. [PMID: 34766750 DOI: 10.1021/acsinfecdis.1c00414] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The malaria parasite Plasmodium falciparum possesses a unique Acetyl-CoA Synthetase (PfACS), which provides acetyl moieties for different metabolic and regulatory cellular pathways. We characterized PfACS and studied its role focusing on epigenetic modifications using the var gene family as reporter genes. For this, mutant lines to modulate plasmodial ACS expression by degron-mediated protein degradation and ribozyme-induced transcript decay were created. Additionally, an inhibitor of the human Acetyl-CoA Synthetase 2 was tested for its effectiveness in interfering with PfACS. The knockdown of PfACS or its inhibition resulted in impaired parasite growth. Decreased levels of PfACS also led to differential histone acetylation patterns, altered variant gene expression, and concomitantly decreased cytoadherence of infected red blood cells containing knocked-down parasites. Further, ChIP analysis revealed the presence of PfACS in many loci in ring stage parasites, underscoring its involvement in the regulation of chromatin. Due to its central function in the plasmodial metabolism and significant differences to human ACS, PfACS is an interesting target for drug development.
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Affiliation(s)
- Isadora Oliveira Prata
- Department of Parasitology, Institute for Biomedical Sciences, University of São Paulo, Avenida Professor Lineu Prestes 1374, 05508-000 São Paulo-SP, Brazil
| | - Eliana Fernanda Galindo Cubillos
- Department of Parasitology, Institute for Biomedical Sciences, University of São Paulo, Avenida Professor Lineu Prestes 1374, 05508-000 São Paulo-SP, Brazil
| | - Arne Krüger
- Department of Parasitology, Institute for Biomedical Sciences, University of São Paulo, Avenida Professor Lineu Prestes 1374, 05508-000 São Paulo-SP, Brazil
| | - Deibs Barbosa
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, Avenida Professor Lineu Prestes 748, 05508-000 São Paulo-SP, Brazil
| | - Joaquim Martins
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, Avenida Professor Lineu Prestes 748, 05508-000 São Paulo-SP, Brazil
| | - João Carlos Setubal
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, Avenida Professor Lineu Prestes 748, 05508-000 São Paulo-SP, Brazil
| | - Gerhard Wunderlich
- Department of Parasitology, Institute for Biomedical Sciences, University of São Paulo, Avenida Professor Lineu Prestes 1374, 05508-000 São Paulo-SP, Brazil
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Dimonte S, Bruske EI, Enderes C, Otto TD, Turner L, Kremsner P, Frank M. Identification of a conserved var gene in different Plasmodium falciparum strains. Malar J 2020; 19:194. [PMID: 32471507 PMCID: PMC7260770 DOI: 10.1186/s12936-020-03257-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 05/15/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The multicopy var gene family of Plasmodium falciparum is of crucial importance for pathogenesis and antigenic variation. So far only var2csa, the var gene responsible for placental malaria, was found to be highly conserved among all P. falciparum strains. Here, a new conserved 3D7 var gene (PF3D7_0617400) is identified in several field isolates. METHODS DNA sequencing, transcriptional analysis, Cluster of Differentiation (CD) 36-receptor binding, indirect immunofluorescence with PF3D7_0617400-antibodies and quantification of surface reactivity against semi-immune sera were used to characterize an NF54 clone and a Gabonese field isolate clone (MOA C3) transcribing the gene. A population of 714 whole genome sequenced parasites was analysed to characterize the conservation of the locus in African and Asian isolates. The genetic diversity of two var2csa fragments was compared with the genetic diversity of 57 microsatellites fragments in field isolates. RESULTS PFGA01_060022400 was identified in a Gabonese parasite isolate (MOA) from a chronic infection and found to be 99% identical with PF3D7_0617400 of the 3D7 genome strain. Transcriptional analysis and immunofluorescence showed expression of the gene in an NF54 and a MOA clone but CD36 binding assays and surface reactivity to semi-immune sera differed markedly in the two clones. Long-read Pacific bioscience whole genome sequencing showed that PFGA01_060022400 is located in the internal cluster of chromosome 6. The full length PFGA01_060022400 was detected in 36 of 714 P. falciparum isolates and 500 bp fragments were identified in more than 100 isolates. var2csa was in parts highly conserved (He = 0) but in other parts as variable (He = 0.86) as the 57 microsatellites markers (He = 0.8). CONCLUSIONS Individual var gene sequences exhibit conservation in the global parasite population suggesting that purifying selection may limit overall genetic diversity of some var genes. Notably, field and laboratory isolates expressing the same var gene exhibit markedly different phenotypes.
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Affiliation(s)
- Sandra Dimonte
- Institute of Tropical Medicine, University of Tuebingen, Wilhelmstr. 27, 72074, Tuebingen, Germany
| | - Ellen I Bruske
- Institute of Tropical Medicine, University of Tuebingen, Wilhelmstr. 27, 72074, Tuebingen, Germany
| | - Corinna Enderes
- Institute of Tropical Medicine, University of Tuebingen, Wilhelmstr. 27, 72074, Tuebingen, Germany
| | - Thomas D Otto
- Malaria Programme, Wellcome Trust Sanger Institute, Hinxton, CB10 1SA, UK.,Centre of Immunobiology, Institute of Infection, Immunity & Inflammation, College of MVLS, University of Glasgow, Glasgow, UK
| | - Louise Turner
- Centre for Medical Parasitology, Department of Immunology and Microbiology (ISIM), Faculty of Health and Medical Sciences, University of Copenhagen, 1165, Copenhagen, Denmark.,Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), 2100, Copenhagen, Denmark
| | - Peter Kremsner
- Institute of Tropical Medicine, University of Tuebingen, Wilhelmstr. 27, 72074, Tuebingen, Germany
| | - Matthias Frank
- Institute of Tropical Medicine, University of Tuebingen, Wilhelmstr. 27, 72074, Tuebingen, Germany.
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Bruske E, Otto TD, Frank M. Whole genome sequencing and microsatellite analysis of the Plasmodium falciparum E5 NF54 strain show that the var, rifin and stevor gene families follow Mendelian inheritance. Malar J 2018; 17:376. [PMID: 30348135 PMCID: PMC6198375 DOI: 10.1186/s12936-018-2503-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 10/03/2018] [Indexed: 12/30/2022] Open
Abstract
Background Plasmodium falciparum exhibits a high degree of inter-isolate genetic diversity in its variant surface antigen (VSA) families: P. falciparum erythrocyte membrane protein 1, repetitive interspersed family (RIFIN) and subtelomeric variable open reading frame (STEVOR). The role of recombination for the generation of this diversity is a subject of ongoing research. Here the genome of E5, a sibling of the 3D7 genome strain is presented. Short and long read whole genome sequencing (WGS) techniques (Ilumina, Pacific Bioscience) and a set of 84 microsatellites (MS) were employed to characterize the 3D7 and non-3D7 parts of the E5 genome. This is the first time that VSA genes in sibling parasites were analysed with long read sequencing technology. Results Of the 5733 E5 genes only 278 genes, mostly var and rifin/stevor genes, had no orthologues in the 3D7 genome. WGS and MS analysis revealed that chromosomal crossovers occurred at a rate of 0–3 per chromosome. var, stevor and rifin genes were inherited within the respective non-3D7 or 3D7 chromosomal context. 54 of the 84 MS PCR fragments correctly identified the respective MS as 3D7- or non-3D7 and this correlated with var and rifin/stevor gene inheritance in the adjacent chromosomal regions. E5 had 61 var and 189 rifin/stevor genes. One large non-chromosomal recombination event resulted in a new var gene on chromosome 14. The remainder of the E5 3D7-type subtelomeric and central regions were identical to 3D7. Conclusions The data show that the rifin/stevor and var gene families represent the most diverse compartments of the P. falciparum genome but that the majority of var genes are inherited without alterations within their respective parental chromosomal context. Furthermore, MS genotyping with 54 MS can successfully distinguish between two sibling progeny of a natural P. falciparum cross and thus can be used to investigate identity by descent in field isolates. Electronic supplementary material The online version of this article (10.1186/s12936-018-2503-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ellen Bruske
- Institute of Tropical Medicine, University of Tuebingen, Wilhelmstr. 27, 72074, Tuebingen, Germany
| | - Thomas D Otto
- Malaria Programme, Wellcome Trust Sanger Institute, Hinxton, CB10 1SA, UK. .,Centre of Immunobiology, Institute of Infection, Immunity & Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
| | - Matthias Frank
- Institute of Tropical Medicine, University of Tuebingen, Wilhelmstr. 27, 72074, Tuebingen, Germany.
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Abstract
Eukaryotic pathogens must survive in different hosts, respond to changing environments, and exploit specialized niches to propagate. Plasmodium parasites cause human malaria during bloodstream infections, where they must persist long enough to be transmitted. Parasites have evolved diverse strategies of variant gene expression that control critical biological processes of blood-stage infections, including antigenic variation, erythrocyte invasion, innate immune evasion, and nutrient acquisition, as well as life-cycle transitions. Epigenetic mechanisms within the parasite are being elucidated, with discovery of epigenomic marks associated with gene silencing and activation, and the identification of epigenetic regulators and chromatin proteins that are required for the switching and maintenance of gene expression. Here, we review the key epigenetic processes that facilitate transition through the parasite life cycle and epigenetic regulatory mechanisms utilized by Plasmodium parasites to survive changing environments and consider epigenetic switching in the context of the outcome of human infections.
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Affiliation(s)
- Manoj T Duraisingh
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115, USA; ,
| | - Kristen M Skillman
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115, USA; ,
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Abstract
Protozoan parasites colonize numerous metazoan hosts and insect vectors through their life cycles, with the need to respond quickly and reversibly while encountering diverse and often hostile ecological niches. To succeed, parasites must also persist within individuals until transmission between hosts is achieved. Several parasitic protozoa cause a huge burden of disease in humans and livestock, and here we focus on the parasites that cause malaria and African trypanosomiasis. Efforts to understand how these pathogens adapt to survive in varied host environments, cause disease, and transmit between hosts have revealed a wealth of epigenetic phenomena. Epigenetic switching mechanisms appear to be ideally suited for the regulation of clonal antigenic variation underlying successful parasitism. We review the molecular players and complex mechanistic layers that mediate the epigenetic regulation of virulence gene expression. Understanding epigenetic processes will aid the development of antiparasitic therapeutics.
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Affiliation(s)
- Manoj T Duraisingh
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, 651 Huntington Avenue, Boston, MA 02115, USA.
| | - David Horn
- Division of Biological Chemistry & Drug Discovery, School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK.
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Bruske EI, Dimonte S, Enderes C, Tschan S, Flötenmeyer M, Koch I, Berger J, Kremsner P, Frank M. In Vitro Variant Surface Antigen Expression in Plasmodium falciparum Parasites from a Semi-Immune Individual Is Not Correlated with Var Gene Transcription. PLoS One 2016; 11:e0166135. [PMID: 27907004 PMCID: PMC5132323 DOI: 10.1371/journal.pone.0166135] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 10/24/2016] [Indexed: 12/17/2022] Open
Abstract
Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is considered to be the main variant surface antigen (VSA) of Plasmodium falciparum and is mainly localized on electron-dense knobs in the membrane of the infected erythrocyte. Switches in PfEMP1 expression provide the basis for antigenic variation and are thought to be critical for parasite persistence during chronic infections. Recently, strain transcending anti-PfEMP1 immunity has been shown to develop early in life, challenging the role of PfEMP1 in antigenic variation during chronic infections. In this work we investigate how P. falciparum achieves persistence during a chronic asymptomatic infection. The infected individual (MOA) was parasitemic for 42 days and multilocus var gene genotyping showed persistence of the same parasite population throughout the infection. Parasites from the beginning of the infection were adapted to tissue culture and cloned by limiting dilution. Flow cytometry using convalescent serum detected a variable surface recognition signal on isogenic clonal parasites. Quantitative real-time PCR with a field isolate specific var gene primer set showed that the surface recognition signal was not correlated with transcription of individual var genes. Strain transcending anti-PfEMP1 immunity of the convalescent serum was demonstrated with CD36 selected and PfEMP1 knock-down NF54 clones. In contrast, knock-down of PfEMP1 did not have an effect on the antibody recognition signal in MOA clones. Trypsinisation of the membrane surface proteins abolished the surface recognition signal and immune electron microscopy revealed that antibodies from the convalescent serum bound to membrane areas without knobs and with knobs. Together the data indicate that PfEMP1 is not the main variable surface antigen during a chronic infection and suggest a role for trypsin sensitive non-PfEMP1 VSAs for parasite persistence in chronic infections.
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Affiliation(s)
- Ellen Inga Bruske
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
| | - Sandra Dimonte
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
| | - Corinna Enderes
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
| | - Serena Tschan
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
| | | | - Iris Koch
- Max Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Jürgen Berger
- Max Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Peter Kremsner
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
- CERMEL (Centre de Recherche Médicale de Lambaréné), Lambaréné, Gabon
| | - Matthias Frank
- Institute of Tropical Medicine, University of Tuebingen, Tuebingen, Germany
- CERMEL (Centre de Recherche Médicale de Lambaréné), Lambaréné, Gabon
- * E-mail:
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Molina-Cruz A, Zilversmit MM, Neafsey DE, Hartl DL, Barillas-Mury C. Mosquito Vectors and the Globalization of Plasmodium falciparum Malaria. Annu Rev Genet 2016; 50:447-465. [PMID: 27732796 DOI: 10.1146/annurev-genet-120215-035211] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Plasmodium falciparum malaria remains a devastating public health problem. Recent discoveries have shed light on the origin and evolution of Plasmodium parasites and their interactions with their vertebrate and mosquito hosts. P. falciparum malaria originated in Africa from a single horizontal transfer between an infected gorilla and a human, and became global as the result of human migration. Today, P. falciparum malaria is transmitted worldwide by more than 70 different anopheline mosquito species. Recent studies indicate that the mosquito immune system can be a barrier to malaria transmission and that the P. falciparum Pfs47 gene allows the parasite to evade mosquito immune detection. Here, we review the origin and globalization of P. falciparum and integrate this history with analysis of the biology, evolution, and dispersal of the main mosquito vectors. This new perspective broadens our understanding of P. falciparum population structure and the dispersal of important parasite genetic traits.
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Affiliation(s)
- Alvaro Molina-Cruz
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland 20852;
| | - Martine M Zilversmit
- Richard Guilder Graduate School and Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, NY 10024
| | - Daniel E Neafsey
- Genome Sequencing and Analysis Program, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142
| | - Daniel L Hartl
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Carolina Barillas-Mury
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland 20852;
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Dimonte S, Bruske EI, Hass J, Supan C, Salazar CL, Held J, Tschan S, Esen M, Flötenmeyer M, Koch I, Berger J, Bachmann A, Sim BKL, Hoffman SL, Kremsner PG, Mordmüller B, Frank M. Sporozoite Route of Infection Influences In Vitro var Gene Transcription of Plasmodium falciparum Parasites From Controlled Human Infections. J Infect Dis 2016; 214:884-94. [PMID: 27279526 DOI: 10.1093/infdis/jiw225] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 05/19/2016] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Antigenic variation in Plasmodium falciparum is mediated by the multicopy var gene family. Each parasite possesses about 60 var genes, and switching between active var loci results in antigenic variation. In the current study, the effect of mosquito and host passage on in vitro var gene transcription was investigated. METHODS Thirty malaria-naive individuals were inoculated by intradermal or intravenous injection with cryopreserved, isogenic NF54 P. falciparum sporozoites (PfSPZ) generated from 1 premosquito culture. Microscopic parasitemia developed in 22 individuals, and 21 in vitro cultures were established. The var gene transcript levels were determined in early and late postpatient cultures and in the premosquito culture. RESULTS At the early time point, all cultures preferentially transcribed 8 subtelomeric var genes. Intradermal infections had higher var gene transcript levels than intravenous infections and a significantly longer intrahost replication time (P = .03). At the late time point, 9 subtelomeric and 8 central var genes were transcribed at the same levels in almost all cultures. Premosquito and late postpatient cultures transcribed the same subtelomeric and central var genes, except for var2csa CONCLUSIONS The duration of intrahost replication influences in vitro var gene transcript patterns. Differences between premosquito and postpatient cultures decrease with prolonged in vitro growth.
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Affiliation(s)
- Sandra Dimonte
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Ellen I Bruske
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Johanna Hass
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Christian Supan
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Carmen L Salazar
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Jana Held
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Serena Tschan
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Meral Esen
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | | | - Iris Koch
- Max Planck Institute for Developmental Biology, Tübingen
| | - Jürgen Berger
- Max Planck Institute for Developmental Biology, Tübingen
| | - Anna Bachmann
- Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | | | | | - Peter G Kremsner
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen Centre de Recherches Médicales de Lambaréné (CERMEL), Fondation Internationale de l'Hôpital Albert Schweitzer, Lambaréné, Gabon
| | - Benjamin Mordmüller
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
| | - Matthias Frank
- Institute of Tropical Medicine University of Tübingen and German Center for Infection Research, Partner Site Tübingen
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10
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Mosquito Passage Dramatically Changes var Gene Expression in Controlled Human Plasmodium falciparum Infections. PLoS Pathog 2016; 12:e1005538. [PMID: 27070311 PMCID: PMC4829248 DOI: 10.1371/journal.ppat.1005538] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 03/10/2016] [Indexed: 11/19/2022] Open
Abstract
Virulence of the most deadly malaria parasite Plasmodium falciparum is linked to the variant surface antigen PfEMP1, which is encoded by about 60 var genes per parasite genome. Although the expression of particular variants has been associated with different clinical outcomes, little is known about var gene expression at the onset of infection. By analyzing controlled human malaria infections via quantitative real-time PCR, we show that parasite populations from 18 volunteers expressed virtually identical transcript patterns that were dominated by the subtelomeric var gene group B and, to a lesser extent, group A. Furthermore, major changes in composition and frequency of var gene transcripts were detected between the parental parasite culture that was used to infect mosquitoes and Plasmodia recovered from infected volunteers, suggesting that P. falciparum resets its var gene expression during mosquito passage and starts with the broad expression of a specific subset of var genes when entering the human blood phase.
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Childs LM, Buckee CO. Dissecting the determinants of malaria chronicity: why within-host models struggle to reproduce infection dynamics. J R Soc Interface 2015; 12:20141379. [PMID: 25673299 PMCID: PMC4345506 DOI: 10.1098/rsif.2014.1379] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The duration of infection is fundamental to the epidemiological behaviour of any infectious disease, but remains one of the most poorly understood aspects of malaria. In endemic areas, the malaria parasite Plasmodium falciparum can cause both acute, severe infections and asymptomatic, chronic infections through its interaction with the host immune system. Frequent superinfection and massive parasite genetic diversity make it extremely difficult to accurately measure the distribution of infection lengths, complicating the estimation of basic epidemiological parameters and the prediction of the impact of interventions. Mathematical models have qualitatively reproduced parasite dynamics early during infection, but reproducing long-lived chronic infections remains much more challenging. Here, we construct a model of infection dynamics to examine the consequences of common biological assumptions for the generation of chronicity and the impact of co-infection. We find that although a combination of host and parasite heterogeneities are capable of generating chronic infections, they do so only under restricted parameter choices. Furthermore, under biologically plausible assumptions, co-infection of parasite genotypes can alter the course of infection of both the resident and co-infecting strain in complex non-intuitive ways. We outline the most important puzzles for within-host models of malaria arising from our analysis, and their implications for malaria epidemiology and control.
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Affiliation(s)
- Lauren M Childs
- Center for Communicable Disease Dynamics, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA
| | - Caroline O Buckee
- Center for Communicable Disease Dynamics, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA
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Ukaegbu UE, Deitsch KW. The Emerging Role for RNA Polymerase II in Regulating Virulence Gene Expression in Malaria Parasites. PLoS Pathog 2015; 11:e1004926. [PMID: 26181323 PMCID: PMC4504705 DOI: 10.1371/journal.ppat.1004926] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Affiliation(s)
- Uchechi E. Ukaegbu
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Kirk W. Deitsch
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
- * E-mail:
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13
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Ye R, Zhang D, Chen B, Zhu Y, Zhang Y, Wang S, Pan W. Transcription of the var genes from a freshly-obtained field isolate of Plasmodium falciparum shows more variable switching patterns than long laboratory-adapted isolates. Malar J 2015; 14:66. [PMID: 25889871 PMCID: PMC4332720 DOI: 10.1186/s12936-015-0565-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 01/15/2015] [Indexed: 11/15/2022] Open
Abstract
Background Antigenic variation in Plasmodium falciparum involves switching among multicopy var gene family and is responsible for immune evasion and the maintenance of chronic infections. Current understanding of var gene expression and switching patterns comes from experiments conducted on long laboratory-adapted strains, with little known about their wild counterparts. Methods Genome sequencing was used to obtain 50 var genes from a parasite isolated from the China-Myanmar border. Four clones with different dominant var genes were cultured in vitro in replicates for 50 generations. Transcription of the individual var gene was detected by real-time PCR and then the switching process was analysed. Results The expression of multicopy var genes is mutually exclusive in clones of a wild P. falciparum isolate. The activation of distinct primary dominant var genes leads to different and favoured switching patterns in the four clones. The on/off rates of individual var genes are variable and the choice of subsequent dominant var genes are random, which results in the different switching patterns among replicates of each clonal wild P. falciparum isolate with near identical initial transcription profiles. Conclusions This study suggests that the switching patterns of var genes are abundant, which consist of both conserved and random parts. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0565-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Run Ye
- Department of Tropical Infectious Disease, Second Military Medical University, Shanghai, 200433, China.
| | - Dongmei Zhang
- Department of Tropical Infectious Disease, Second Military Medical University, Shanghai, 200433, China.
| | - Biaobang Chen
- Department of Tropical Infectious Disease, Second Military Medical University, Shanghai, 200433, China.
| | - Yongqiang Zhu
- Shanghai-Ministry of Science and Technology Key Laboratory of Health and Disease Genomics, Chinese National Human Genome Center at Shanghai, Shanghai, 201203, China.
| | - Yilong Zhang
- Institute for Infectious Diseases and Vaccine Development, Tongji University School of Medicine, Shanghai, 200092, China.
| | - Shengyue Wang
- Shanghai-Ministry of Science and Technology Key Laboratory of Health and Disease Genomics, Chinese National Human Genome Center at Shanghai, Shanghai, 201203, China.
| | - Weiqing Pan
- Department of Tropical Infectious Disease, Second Military Medical University, Shanghai, 200433, China. .,Institute for Infectious Diseases and Vaccine Development, Tongji University School of Medicine, Shanghai, 200092, China.
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14
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Tembo DL, Nyoni B, Murikoli RV, Mukaka M, Milner DA, Berriman M, Rogerson SJ, Taylor TE, Molyneux ME, Mandala WL, Craig AG, Montgomery J. Differential PfEMP1 expression is associated with cerebral malaria pathology. PLoS Pathog 2014; 10:e1004537. [PMID: 25473835 PMCID: PMC4256257 DOI: 10.1371/journal.ppat.1004537] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Accepted: 10/23/2014] [Indexed: 11/23/2022] Open
Abstract
Plasmodium falciparum is unique among human malarias in its ability to sequester in post-capillary venules of host organs. The main variant antigens implicated are the P. falciparum erythrocyte membrane protein 1 (PfEMP1), which can be divided into three major groups (A–C). Our study was a unique examination of sequestered populations of parasites for genetic background and expression of PfEMP1 groups. We collected post-mortem tissue from twenty paediatric hosts with pathologically different forms of cerebral malaria (CM1 and CM2) and parasitaemic controls (PC) to directly examine sequestered populations of parasites in the brain, heart and gut. Use of two different techniques to investigate this question produced divergent results. By quantitative PCR, group A var genes were upregulated in all three organs of CM2 and PC cases. In contrast, in CM1 infections displaying high levels of sequestration but negligible vascular pathology, there was high expression of group B var. Cloning and sequencing of var transcript tags from the same samples indicated a uniformly low expression of group A-like var. Generally, within an organ sample, 1–2 sequences were expressed at dominant levels. 23% of var tags were detected in multiple patients despite the P. falciparum infections being genetically distinct, and two tags were observed in up to seven hosts each with high expression in the brains of 3–4 patients. This study is a novel examination of the sequestered parasites responsible for fatal cerebral malaria and describes expression patterns of the major cytoadherence ligand in three organ-derived populations and three pathological states. One of the most severe forms of malarial disease is cerebral malaria, which disproportionally affects young children. In this disease, the parasite places proteins on the red blood cell surface, providing a “smokescreen” by which they evade host immunity and hide in organ blood vessels, blocking them and causing tissue damage. It is impossible to study parasites in the organs during life and autopsy studies on children with malaria are exceedingly rare. In Malawi, we examined parasites from the brain, heart and intestine of twenty cases of fatal malaria including controls with low numbers of malaria parasites but another identified cause of death. We found little difference in the category of proteins the parasites used in controls and cerebral malaria, although a small number of specific proteins were detected in multiple infections. In an alternative form of malaria in which the brain is heavily infected but shows no evidence of damage, we found a different set of proteins at high proportion. However, as these children were typically older and most were infected with HIV, we could not determine which of these factors was most important. Interactions between host and parasite have the potential to influence disease outcomes.
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Affiliation(s)
- Dumizulu L. Tembo
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, Blantyre, Malawi
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Benjamin Nyoni
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, Blantyre, Malawi
| | - Rekah V. Murikoli
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, Blantyre, Malawi
| | - Mavuto Mukaka
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, Blantyre, Malawi
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Danny A. Milner
- Blantyre Malaria Project, College of Medicine, Blantyre, Malawi
- Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts, United States of America
- Department of Immunology and Infectious Disease, Harvard School of Public Health, Boston, Massachusetts, United States of America
| | - Matthew Berriman
- Pathogen Sequencing Unit, Wellcome Trust Sanger Institute, Hinxton, United Kingdom
| | | | - Terrie E. Taylor
- Blantyre Malaria Project, College of Medicine, Blantyre, Malawi
- College of Osteopathic Medicine, Michigan State University, East Lansing, Michigan, United States of America
| | - Malcolm E. Molyneux
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, Blantyre, Malawi
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Wilson L. Mandala
- Department of Basic Medical Sciences, College of Medicine, Blantyre, Malawi
| | - Alister G. Craig
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Jacqui Montgomery
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, Blantyre, Malawi
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- * E-mail:
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15
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Ukaegbu UE, Kishore SP, Kwiatkowski DL, Pandarinath C, Dahan-Pasternak N, Dzikowski R, Deitsch KW. Recruitment of PfSET2 by RNA polymerase II to variant antigen encoding loci contributes to antigenic variation in P. falciparum. PLoS Pathog 2014; 10:e1003854. [PMID: 24391504 PMCID: PMC3879369 DOI: 10.1371/journal.ppat.1003854] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Accepted: 11/12/2013] [Indexed: 11/18/2022] Open
Abstract
Histone modifications are important regulators of gene expression in all eukaryotes. In Plasmodium falciparum, these epigenetic marks regulate expression of genes involved in several aspects of host-parasite interactions, including antigenic variation. While the identities and genomic positions of many histone modifications have now been cataloged, how they are targeted to defined genomic regions remains poorly understood. For example, how variant antigen encoding loci (var) are targeted for deposition of unique histone marks is a mystery that continues to perplex the field. Here we describe the recruitment of an ortholog of the histone modifier SET2 to var genes through direct interactions with the C-terminal domain (CTD) of RNA polymerase II. In higher eukaryotes, SET2 is a histone methyltransferase recruited by RNA pol II during mRNA transcription; however, the ortholog in P. falciparum (PfSET2) has an atypical architecture and its role in regulating transcription is unknown. Here we show that PfSET2 binds to the unphosphorylated form of the CTD, a property inconsistent with its recruitment during mRNA synthesis. Further, we show that H3K36me3, the epigenetic mark deposited by PfSET2, is enriched at both active and silent var gene loci, providing additional evidence that its recruitment is not associated with mRNA production. Over-expression of a dominant negative form of PfSET2 designed to disrupt binding to RNA pol II induced rapid var gene expression switching, confirming both the importance of PfSET2 in var gene regulation and a role for RNA pol II in its recruitment. RNA pol II is known to transcribe non-coding RNAs from both active and silent var genes, providing a possible mechanism by which it could recruit PfSET2 to var loci. This work unifies previous reports of histone modifications, the production of ncRNAs, and the promoter activity of var introns into a mechanism that contributes to antigenic variation by malaria parasites. Chemical modifications to histones, the proteins that serve as the primary units of chromatin, often determine whether specific genes are actively transcribed or condensed into transcriptionally silent regions of the genome. In the malaria parasite Plasmodium falciparum, histone modifications have been shown to play a significant role in controlling gene expression involved in many aspects of their lifecycle, including the complex gene expression patterns associated with antigenic variation. The various histone modifications that are found within the parasite's genome have now been extensively cataloged, and the enzymes that are responsible for adding and removing them have been identified. However, how these enzymes are recruited to specific regions of the genome to coordinate gene expression is not understood. In this paper, we provide the first evidence for recruitment of a unique histone methyltransferase to specific regions of the genome through its tethering to RNA polymerase II. We find that disruption of this interaction results in major changes in expression patterns of genes involved in antigenic variation, demonstrating the importance of regulated recruitment of histone modifiers for parasite biology.
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Affiliation(s)
- Uchechi E Ukaegbu
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Sandeep P Kishore
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Dacia L Kwiatkowski
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Chethan Pandarinath
- Program in Computational Biology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Noa Dahan-Pasternak
- Department of Microbiology and Molecular Genetics, The Institute for Medical Research Israel-Canada, The Kuvin Center for the Study of Infectious and Tropical Diseases, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Ron Dzikowski
- Department of Microbiology and Molecular Genetics, The Institute for Medical Research Israel-Canada, The Kuvin Center for the Study of Infectious and Tropical Diseases, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Kirk W Deitsch
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
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16
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Noble R, Christodoulou Z, Kyes S, Pinches R, Newbold CI, Recker M. The antigenic switching network of Plasmodium falciparum and its implications for the immuno-epidemiology of malaria. eLife 2013; 2:e01074. [PMID: 24062941 PMCID: PMC3778436 DOI: 10.7554/elife.01074] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 08/19/2013] [Indexed: 12/23/2022] Open
Abstract
Antigenic variation in the human malaria parasite Plasmodium falciparum involves sequential and mutually exclusive expression of members of the var multi-gene family and appears to follow a non-random pattern. In this study, using a detailed in vitro gene transcription analysis of the culture-adapted HB3 strain of P. falciparum, we show that antigenic switching is governed by a global activation hierarchy favouring short and highly diverse genes in central chromosomal location. Longer and more conserved genes, which have previously been associated with severe infection in immunologically naive hosts, are rarely activated, however, implying an in vivo fitness advantage possibly through adhesion-dependent survival rates. We further show that a gene’s activation rate is positively associated sequence diversity, which could offer important new insights into the evolution and maintenance of antigenic diversity in P. falciparum malaria. DOI:http://dx.doi.org/10.7554/eLife.01074.001 Our ability to acquire immunity to a disease depends on our immune system learning to recognise foreign molecules—called antigens—that are specific to the disease-causing virus, bacterium or parasite. However, some pathogens, such as the malaria-causing parasite Plasmodium falciparum, get around this defence through a process called antigenic variation. This involves the parasite switching between different antigens over the course of an infection, preventing the host immune system from learning to recognise them and leading to infections that last many weeks or even months. The main antigen in P. falciparum is a protein called PfEMP1, which is encoded by a family of genes called var (‘variable’). Var genes have evolved to be highly diverse, and different parasites have different repertoires of around 50–60 var genes. This ensures that there are a huge number of distinct variants of the PfEMP1 antigen available within the population, allowing the malaria parasite to maintain long-lasting infections and also to infect the same individuals again and again. Previous work has shown that the expression of var genes is not random, but it is not clear what determines which genes are expressed at any given time. Now, Noble et al. have performed a detailed investigation of antigenic switching in P. falciparum. Using clonal parasites, they closely monitored the expression of the entire var gene repertoire during many generations of parasite culture. They observed that although different cultures initially expressed distinct var genes, most of them ended up expressing two particular genes—var27 and var29—at high levels, indicating a hard-wired gene ‘activation hierarchy’. Noble et al. found that whenever the parasites switched antigens, var genes that were centrally located on chromosomes—such as var27 and var29—were more likely to be activated than those at the ends of chromosomes. Moreover, var genes that were highly diverse were more likely to be activated than more conserved genes: this is the first evidence linking var gene evolution with gene activation probabilities. Together, these factors gave rise to the proposed activation hierarchy, which favours genes optimised for immune evasion and aids their continued evolution and diversification. Further work is now needed to identify the molecular mechanisms that control antigenic switching and to determine whether these could represent new therapeutic targets for malaria. DOI:http://dx.doi.org/10.7554/eLife.01074.002
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Affiliation(s)
- Robert Noble
- Department of Zoology , University of Oxford , Oxford , United Kingdom
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17
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Guizetti J, Scherf A. Silence, activate, poise and switch! Mechanisms of antigenic variation in Plasmodium falciparum. Cell Microbiol 2013; 15:718-26. [PMID: 23351305 PMCID: PMC3654561 DOI: 10.1111/cmi.12115] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Revised: 01/11/2013] [Accepted: 01/14/2013] [Indexed: 12/17/2022]
Abstract
Phenotypic variation in genetically identical malaria parasites is an emerging topic. Although antigenic variation is only part of a more global parasite strategy to create adaptation through epigenetically controlled transcriptional variability, it is the central mechanism enabling immune evasion and promoting pathogenesis. The var gene family is the best-studied example in a wide range of clonally variant gene families in Plasmodium falciparum. It is unique in its strict selection of a single member for activation, a process termed monoallelic expression. The conceptual advances that have emerged from studying var genes show striking common epigenetic features with many other clonally variant gene families or even single-copy genes that show a variegated expression in parasite populations. However, major mechanistic questions, such as the existence of a potential expression site and the identity of transcription factors or genetic elements driving singular gene choice, are still unanswered. In this review we discuss the recent findings in the molecular processes essential for clonal variation, namely silencing, activation, poising and switching. Integrating findings about all clonally variant gene families and other mutually exclusive expression systems will hopefully drive mechanistic understanding of antigenic variation.
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Affiliation(s)
- Julien Guizetti
- Unité de Biologie des Interactions Hôte-Parasite, Département de Parasitologie et Mycologie, Institut Pasteur, 25 Rue du Dr. Roux, Cedex 15, F-75724 Paris, France
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18
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Noble R, Recker M. A statistically rigorous method for determining antigenic switching networks. PLoS One 2012; 7:e39335. [PMID: 22761765 PMCID: PMC3382232 DOI: 10.1371/journal.pone.0039335] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Accepted: 05/23/2012] [Indexed: 11/19/2022] Open
Abstract
Many vector-borne pathogens rely on antigenic variation to prolong infections and increase their likelihood of onward transmission. This immune evasion strategy often involves mutually exclusive switching between members of gene families that encode functionally similar but antigenically different variants during the course of a single infection. Studies of different pathogens have suggested that switching between variant genes is non-random and that genes have intrinsic probabilities of being activated or silenced. These factors could create a hierarchy of gene expression with important implications for both infection dynamics and the acquisition of protective immunity. Inferring complete switching networks from gene transcription data is problematic, however, because of the high dimensionality of the system and uncertainty in the data. Here we present a statistically rigorous method for analysing temporal gene transcription data to reconstruct an underlying switching network. Using artificially generated transcription profiles together with in vitro var gene transcript data from two Plasmodium falciparum laboratory strains, we show that instead of relying on data from long-term parasite cultures, accuracy can be greatly improved by using transcription time courses of several parasite populations from the same isolate, each starting with different variant distributions. The method further provides explicit indications about the reliability of the resulting networks and can thus be used to test competing hypotheses with regards to the underlying switching pathways. Our results demonstrate that antigenic switch pathways can be determined reliably from short gene transcription profiles assessing multiple time points, even when subject to moderate levels of experimental error. This should yield important new information about switching patterns in antigenically variable organisms and might help to shed light on the molecular basis of antigenic variation.
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Affiliation(s)
- Robert Noble
- Department of Zoology, University of Oxford, Oxford, United Kingdom
| | - Mario Recker
- Department of Zoology, University of Oxford, Oxford, United Kingdom
- * E-mail:
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19
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Antigenic variation and the generation of diversity in malaria parasites. Curr Opin Microbiol 2012; 15:456-62. [PMID: 22503815 DOI: 10.1016/j.mib.2012.03.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Accepted: 03/08/2012] [Indexed: 11/27/2022]
Abstract
Investigations into the genetic basis underlying antigenic variation in malaria parasites have primarily described transcriptional regulation of the large, multi-copy gene families that encode red cell surface antigens. In particular, extensive alterations to chromatin structure and subnuclear localization have been shown to play key roles in mutually exclusive expression, gene silencing and activation, and epigenetic memory. However the mechanisms responsible for the generation of sequence diversity within these gene families, a characteristic that is equally important for a parasite's ability to avoid the host's immune response, remains poorly understood in malaria. Recent work in model organisms suggests that the mechanisms controlling gene activation and silencing might also contribute to preferential recombination between antigen encoding genes, thus linking these two key processes.
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Fastman Y, Noble R, Recker M, Dzikowski R. Erasing the epigenetic memory and beginning to switch--the onset of antigenic switching of var genes in Plasmodium falciparum. PLoS One 2012; 7:e34168. [PMID: 22461905 PMCID: PMC3312910 DOI: 10.1371/journal.pone.0034168] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 02/23/2012] [Indexed: 11/19/2022] Open
Abstract
Antigenic variation in Plasmodium falciparum is regulated by transcriptional switches among members of the var gene family, each expressed in a mutually exclusive manner and encoding a different variant of the surface antigens collectively named PfEMP1. Antigenic switching starts when the first merozoites egress from the liver and begin their asexual proliferation within red blood cells. By erasing the epigenetic memory we created parasites with no var background, similar to merozoites that egress from the liver where no var gene is expressed. Creating a null-var background enabled us to investigate the onset of antigenic switches at the early phase of infection. At the onset of switching, var transcription pattern is heterogeneous with numerous genes transcribed at low levels including upsA vars, a subtype that was implicated in severe malaria, which are rarely activated in growing cultures. Analysis of subsequent in vitro switches shows that the probability of a gene to turn on or off is not associated with its chromosomal position or promoter type per se but on intrinsic properties of each gene. We concluded that var switching is determined by gene specific associated switch rates rather than general promoter type or locus associated switch rates. In addition, we show that fine tuned reduction in var transcription increases their switch rate, indicating that transcriptional perturbation can alter antigenic switching.
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Affiliation(s)
- Yair Fastman
- Department of Microbiology & Molecular Genetics, The Kuvin Center for the Study of Infectious and Tropical Diseases, IMRIC, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Robert Noble
- Department of Zoology, University of Oxford, Oxford, United Kingdom
| | - Mario Recker
- Department of Zoology, University of Oxford, Oxford, United Kingdom
| | - Ron Dzikowski
- Department of Microbiology & Molecular Genetics, The Kuvin Center for the Study of Infectious and Tropical Diseases, IMRIC, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
- * E-mail:
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21
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Frank M, Lehners N, Mayengue PI, Gabor J, Dal-Bianco M, Kombila DU, Ngoma GM, Supan C, Lell B, Ntoumi F, Grobusch MP, Dietz K, Kremsner PG. A thirteen-year analysis of Plasmodium falciparum populations reveals high conservation of the mutant pfcrt haplotype despite the withdrawal of chloroquine from national treatment guidelines in Gabon. Malar J 2011; 10:304. [PMID: 22004584 PMCID: PMC3215978 DOI: 10.1186/1475-2875-10-304] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2011] [Accepted: 10/17/2011] [Indexed: 11/23/2022] Open
Abstract
Background Chloroquine resistance (CR) decreased after the removal of chloroquine from national treatment guidelines in Malawi, Kenia and Tanzania. In this investigation the prevalence of the chloroquine resistance (CQR) conferring mutant pfcrt allele and its associated chromosomal haplotype were determined before and after the change in Gabonese national treatment guidelines from chloroquine (CQ) to artesunate plus amodiaquine (AQ) in 2003. Methods The prevalence of the wild type pfcrt allele was assessed in 144 isolates from the years 2005 - 07 by PCR fragment restriction digest and direct sequencing. For haplotype analysis of the chromosomal regions flanking the pfcrt locus, microsatellite analysis was done on a total of 145 isolates obtained in 1995/96 (43 isolates), 2002 (47 isolates) and 2005 - 07 (55 isolates). Results The prevalence of the mutant pfcrt allele decreased from 100% in the years 1995/96 and 2002 to 97% in 2005 - 07. Haplotype analysis showed that in 1995/96 79% of the isolates carried the same microsatellite alleles in a chromosomal fragment spanning 39 kb surrounding the pfcrt locus. In 2002 and 2005 - 07 the prevalence of this haplotype was 62% and 58%, respectively. Pfcrt haplotype analysis showed that all wild type alleles were CVMNK. Conclusion Four years after the withdrawal of CQ from national treatment guidelines the prevalence of the mutant pfcrt allele remains at 97%. The data suggest that the combination of artesunate plus AQ may result in continued selection for the mutant pfcrt haplotype even after discontinuance of CQ usage.
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Affiliation(s)
- Matthias Frank
- Institute of Tropical Medicine, University of Tübingen, Wilhelmstr.27, 72074 Tübingen, Germany.
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