1
|
McLean FE, Azasi Y, Sutherland C, Toboh E, Ansong D, Agbenyega T, Awandare G, Rowe JA. Detection of naturally acquired, strain-transcending antibodies against rosetting Plasmodium falciparum strains in humans. Infect Immun 2024; 92:e0001524. [PMID: 38842304 PMCID: PMC11238554 DOI: 10.1128/iai.00015-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Accepted: 04/29/2024] [Indexed: 06/07/2024] Open
Abstract
Strain-transcending antibodies against virulence-associated subsets of P. falciparum-infected erythrocyte surface antigens could protect children from severe malaria. However, the evidence supporting the existence of such antibodies is incomplete and inconsistent. One subset of surface antigens associated with severe malaria, rosette-mediating Plasmodium falciparum Erythrocyte Membrane Protein one (PfEMP1) variants, cause infected erythrocytes to bind to uninfected erythrocytes to form clusters of cells (rosettes) that contribute to microvascular obstruction and pathology. Here, we tested plasma from 80 individuals living in malaria-endemic regions for IgG recognition of the surface of four P. falciparum rosetting strains using flow cytometry. Broadly reactive plasma samples were then used in antibody elution experiments in which intact IgG was eluted from the surface of infected erythrocytes and transferred to heterologous rosetting strains to look for strain-transcending antibodies. We found that seroprevalence (percentage of positive plasma samples) against allopatric rosetting strains was high in adults (63%-93%) but lower in children (13%-48%). Strain-transcending antibodies were present in nine out of eleven eluted antibody experiments, with six of these recognizing multiple heterologous rosetting parasite strains. One eluate had rosette-disrupting activity against heterologous strains, suggesting PfEMP1 as the likely target of the strain-transcending antibodies. Naturally acquired strain-transcending antibodies to rosetting P. falciparum strains in humans have not been directly demonstrated previously. Their existence suggests that such antibodies could play a role in clinical protection and raises the possibility that conserved epitopes recognized by strain-transcending antibodies could be targeted therapeutically by monoclonal antibodies or vaccines.
Collapse
Affiliation(s)
- Florence E. McLean
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Yvonne Azasi
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Cameron Sutherland
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | | | - Daniel Ansong
- Kwame Nkrumah University of Science and Technology, School of Medical Sciences, Kumasi, Ghana
- Departments of Child Health and Medicine, Komfo Anokye Teaching Hospital, Kumasi, Ghana
- Malaria Research Centre, Agogo, Ghana
| | - Tsiri Agbenyega
- Kwame Nkrumah University of Science and Technology, School of Medical Sciences, Kumasi, Ghana
- Departments of Child Health and Medicine, Komfo Anokye Teaching Hospital, Kumasi, Ghana
- Malaria Research Centre, Agogo, Ghana
| | - Gordon Awandare
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, Legon, Ghana
| | - J. Alexandra Rowe
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| |
Collapse
|
2
|
Lenz T, Zhang X, Chakraborty A, Ardakany AR, Prudhomme J, Ay F, Deitsch K, Le Roch KG. Chromatin structure and var2csa - a tango in regulation of var gene expression in the human malaria parasite, Plasmodium falciparum? BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.13.580059. [PMID: 38405848 PMCID: PMC10888805 DOI: 10.1101/2024.02.13.580059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Over the last few decades, novel methods have been developed to study how chromosome positioning within the nucleus may play a role in gene regulation. Adaptation of these methods in the human malaria parasite, Plasmodium falciparum, has recently led to the discovery that the three-dimensional structure of chromatin within the nucleus may be critical in controlling expression of virulence genes (var genes). Recent work has implicated an unusual, highly conserved var gene called var2csa in contributing to coordinated transcriptional switching, however how this gene functions in this capacity is unknown. To further understand how var2csa influences var gene switching, targeted DNA double-strand breaks (DSBs) within the sub-telomeric region of chromosome 12 were used to delete the gene and the surrounding chromosomal region. To characterize the changes in chromatin architecture stemming from this deletion and how these changes could affect var gene expression, we used a combination of RNA-seq, Chip-seq and Hi-C to pinpoint epigenetic and chromatin structural modifications in regions of differential gene expression. We observed a net gain of interactions in sub-telomeric regions and internal var gene regions following var2csa knockout, indicating an increase of tightly controlled heterochromatin structures. Our results suggest that disruption of var2csa results not only in changes in var gene transcriptional regulation but also a significant tightening of heterochromatin clusters thereby disrupting coordinated activation of var genes throughout the genome. Altogether our result confirms a strong link between the var2csa locus, chromatin structure and var gene expression.
Collapse
Affiliation(s)
- Todd Lenz
- Department of Molecular, Cell and Systems Biology, University of California Riverside, 900 University Avenue, Riverside, CA 92521, USA
| | - Xu Zhang
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, USA
| | - Abhijit Chakraborty
- La Jolla Institute for Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA
| | | | - Jacques Prudhomme
- Department of Molecular, Cell and Systems Biology, University of California Riverside, 900 University Avenue, Riverside, CA 92521, USA
| | - Ferhat Ay
- La Jolla Institute for Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA
| | - Kirk Deitsch
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, USA
| | - Karine G. Le Roch
- Department of Molecular, Cell and Systems Biology, University of California Riverside, 900 University Avenue, Riverside, CA 92521, USA
| |
Collapse
|
3
|
Walker IS, Rogerson SJ. Pathogenicity and virulence of malaria: Sticky problems and tricky solutions. Virulence 2023; 14:2150456. [PMID: 36419237 PMCID: PMC9815252 DOI: 10.1080/21505594.2022.2150456] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2022] [Revised: 10/18/2022] [Accepted: 10/19/2022] [Indexed: 11/25/2022] Open
Abstract
Infections with Plasmodium falciparum and Plasmodium vivax cause over 600,000 deaths each year, concentrated in Africa and in young children, but much of the world's population remain at risk of infection. In this article, we review the latest developments in the immunogenicity and pathogenesis of malaria, with a particular focus on P. falciparum, the leading malaria killer. Pathogenic factors include parasite-derived toxins and variant surface antigens on infected erythrocytes that mediate sequestration in the deep vasculature. Host response to parasite toxins and to variant antigens is an important determinant of disease severity. Understanding how parasites sequester, and how antibody to variant antigens could prevent sequestration, may lead to new approaches to treat and prevent disease. Difficulties in malaria diagnosis, drug resistance, and specific challenges of treating P. vivax pose challenges to malaria elimination, but vaccines and other preventive strategies may offer improved disease control.
Collapse
Affiliation(s)
- Isobel S Walker
- Department of Infectious Diseases, The University of Melbourne, The Doherty Institute, Melbourne, Australia
| | - Stephen J Rogerson
- Department of Infectious Diseases, The University of Melbourne, The Doherty Institute, Melbourne, Australia
| |
Collapse
|
4
|
Jugha VT, Anchang JA, Taiwe GS, Kimbi HK, Anchang-Kimbi JK. Association between malaria and undernutrition among pregnant women at presentation for antenatal care in health facilities in the Mount Cameroon region. PLoS One 2023; 18:e0292550. [PMID: 37824491 PMCID: PMC10569528 DOI: 10.1371/journal.pone.0292550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Accepted: 09/24/2023] [Indexed: 10/14/2023] Open
Abstract
In resource limited settings, malaria and undernutrition are major public health problems in pregnancy. Therefore, this study assessed the association between malaria infection and undernutrition among pregnant women in the Mount Cameroon area. This cross-sectional study enrolled 1,014 pregnant women consecutively over a year. A structured questionnaire was used to collect socio-demographic information and clinical data. Maternal nutrition was assessed using dietary diversity (DD). Peripheral blood samples collected were used for the diagnosis of malaria parasitaemia by microscopy whereas haemoglobin (Hb) levels were determined using an Hb meter. Logistic regression was used to determine factors associated with malaria and dietary diversity. The prevalence of malaria infection and undernutrition was 17.8% and 89.6% respectively. In addition, of those infected with malaria, geometric mean parasite density was 301/μL of blood (range: 40-9280) while mean DD score was 3.57±0.82 (range: 1-7). The odds of being infected with malaria parasitaemia was highest among women enrolled in the rainy season (OR = 1.58, P = 0.043), who were farmers (OR = 2.3, P = 0.030), had a household size of < 4 individuals (OR = 1.48, P = 0.026) and who were febrile (OR = 1.87, P < 0.001). Also, attending clinic visits in Mutengene Medical Centre (OR = 2.0, P = 0.012) or Buea Integrated Health Centre (OR = 2.9, P = < 0.001), being < 25 years (OR = 2.4, P = 0.002) and a farmer (OR = 10.6, P = 0.024) as well as < 4 clinic visits (OR = 1.62, P = 0.039) were identified as predictors of undernutrition. Furthermore, the association between malaria and DD was statistically significant (P = 0.015). In this study, undernutrition was highly frequent than malaria infection. Thus, there is an urgent need to improve maternal awareness through nutritional counselling and health campaigns on the benefits of consuming at least five food groups. Besides, improved maternal dietary nutrient intake is likely to have impact on the burden of malaria parasite infection.
Collapse
Affiliation(s)
- Vanessa Tita Jugha
- Department of Animal Biology and Conservation, University of Buea, Buea, Cameroon
| | - Juliana Adjem Anchang
- International Centre for Agricultural Research in the Dry Areas, ICARDA, Cairo, Eygpt
| | | | - Helen Kuokuo Kimbi
- Department of Animal Biology and Conservation, University of Buea, Buea, Cameroon
- Department of Biomedical Sciences, University of Bamenda, Bamenda, Cameroon
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | | |
Collapse
|
5
|
Wiser MF. Knobs, Adhesion, and Severe Falciparum Malaria. Trop Med Infect Dis 2023; 8:353. [PMID: 37505649 PMCID: PMC10385726 DOI: 10.3390/tropicalmed8070353] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 06/30/2023] [Accepted: 07/02/2023] [Indexed: 07/29/2023] Open
Abstract
Plasmodium falciparum can cause a severe disease with high mortality. A major factor contributing to the increased virulence of P. falciparum, as compared to other human malarial parasites, is the sequestration of infected erythrocytes in the capillary beds of organs and tissues. This sequestration is due to the cytoadherence of infected erythrocytes to endothelial cells. Cytoadherence is primarily mediated by a parasite protein expressed on the surface of the infected erythrocyte called P. falciparum erythrocyte membrane protein-1 (PfEMP1). PfEMP1 is embedded in electron-dense protuberances on the surface of the infected erythrocytes called knobs. These knobs are assembled on the erythrocyte membrane via exported parasite proteins, and the knobs function as focal points for the cytoadherence of infected erythrocytes to endothelial cells. PfEMP1 is a member of the var gene family, and there are approximately 60 antigenically distinct PfEMP1 alleles per parasite genome. Var gene expression exhibits allelic exclusion, with only a single allele being expressed by an individual parasite. This results in sequential waves of antigenically distinct infected erythrocytes and this antigenic variation allows the parasite to establish long-term chronic infections. A wide range of endothelial cell receptors can bind to the various PfEMP1 alleles, and thus, antigenic variation also results in a change in the cytoadherence phenotype. The cytoadherence phenotype may result in infected erythrocytes sequestering in different tissues and this difference in sequestration may explain the wide range of possible clinical manifestations associated with severe falciparum malaria.
Collapse
Affiliation(s)
- Mark F Wiser
- Department of Tropical Medicine and Infectious Disease, Tulane University School of Public Health and Tropical Medicine, 1440 Canal Street, New Orleans, LA 70112, USA
| |
Collapse
|
6
|
Schneider V, Visone J, Harris C, Florini F, Hadjimichael E, Zhang X, Gross M, Rhee K, Ben Mamoun C, Kafsack B, Deitsch K. The human malaria parasite Plasmodium falciparum can sense environmental changes and respond by antigenic switching. Proc Natl Acad Sci U S A 2023; 120:e2302152120. [PMID: 37068249 PMCID: PMC10151525 DOI: 10.1073/pnas.2302152120] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 03/20/2023] [Indexed: 04/19/2023] Open
Abstract
The primary antigenic and virulence determinant of the human malaria parasite Plasmodium falciparum is a variant surface protein called PfEMP1. Different forms of PfEMP1 are encoded by a multicopy gene family called var, and switching between active genes enables the parasites to evade the antibody response of their human hosts. var gene switching is key for the maintenance of chronic infections; however, what controls switching is unknown, although it has been suggested to occur at a constant frequency with little or no environmental influence. var gene transcription is controlled epigenetically through the activity of histone methyltransferases (HMTs). Studies in model systems have shown that metabolism and epigenetic control of gene expression are linked through the availability of intracellular S-adenosylmethionine (SAM), the principal methyl donor in biological methylation modifications, which can fluctuate based on nutrient availability. To determine whether environmental conditions and changes in metabolism can influence var gene expression, P. falciparum was cultured in media with altered concentrations of nutrients involved in SAM metabolism. We found that conditions that influence lipid metabolism induce var gene switching, indicating that parasites can respond to changes in their environment by altering var gene expression patterns. Genetic modifications that directly modified expression of the enzymes that control SAM levels similarly led to profound changes in var gene expression, confirming that changes in SAM availability modulate var gene switching. These observations directly challenge the paradigm that antigenic variation in P. falciparum follows an intrinsic, programed switching rate, which operates independently of any external stimuli.
Collapse
Affiliation(s)
- Victoria M. Schneider
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
- Laboratory of Chemical Biology and Microbial Pathogenesis, Rockefeller University, New York, NY 10065
| | - Joseph E. Visone
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| | - Chantal T. Harris
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| | - Francesca Florini
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| | - Evi Hadjimichael
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| | - Xu Zhang
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| | - Mackensie R. Gross
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| | - Kyu Y. Rhee
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
- Division of Infectious Diseases, Department of Medicine, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| | - Choukri Ben Mamoun
- Section of Infectious Disease, Department of Microbial Pathogenesis, Yale School of Medicine, Yale University New Haven, CT 06510
| | - Björn F. C. Kafsack
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| | - Kirk W. Deitsch
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell University, Ithaca, NY14853
| |
Collapse
|
7
|
Zhang X, Florini F, Visone JE, Lionardi I, Gross MR, Patel V, Deitsch KW. A coordinated transcriptional switching network mediates antigenic variation of human malaria parasites. eLife 2022; 11:e83840. [PMID: 36515978 PMCID: PMC9833823 DOI: 10.7554/elife.83840] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 12/13/2022] [Indexed: 12/15/2022] Open
Abstract
Malaria parasites avoid immune clearance through their ability to systematically alter antigens exposed on the surface of infected red blood cells. This is accomplished by tightly regulated transcriptional control of individual members of a large, multicopy gene family called var and is the key to both the virulence and chronic nature of malaria infections. Expression of var genes is mutually exclusive and controlled epigenetically, however how large populations of parasites coordinate var gene switching to avoid premature exposure of the antigenic repertoire is unknown. Here, we provide evidence for a transcriptional network anchored by a universally conserved gene called var2csa that coordinates the switching process. We describe a structured switching bias that shifts overtime and could shape the pattern of var expression over the course of a lengthy infection. Our results provide an explanation for a previously mysterious aspect of malaria infections and shed light on how parasites possessing a relatively small repertoire of variant antigen-encoding genes can coordinate switching events to limit antigen exposure, thereby maintaining chronic infections.
Collapse
Affiliation(s)
- Xu Zhang
- Department of Microbiology and Immunology, Weill Cornell Medical CollegeNew YorkUnited States
| | - Francesca Florini
- Department of Microbiology and Immunology, Weill Cornell Medical CollegeNew YorkUnited States
| | - Joseph E Visone
- Department of Microbiology and Immunology, Weill Cornell Medical CollegeNew YorkUnited States
| | - Irina Lionardi
- Jill Roberts Center for Inflammatory Bowel Disease, Weill Cornell Medical CollegeNew YorkUnited States
| | - Mackensie R Gross
- Department of Microbiology and Immunology, Weill Cornell Medical CollegeNew YorkUnited States
| | - Valay Patel
- Department of Microbiology and Immunology, Weill Cornell Medical CollegeNew YorkUnited States
| | - Kirk W Deitsch
- Department of Microbiology and Immunology, Weill Cornell Medical CollegeNew YorkUnited States
| |
Collapse
|
8
|
Webster R, Sekuloski S, Odedra A, Woolley S, Jennings H, Amante F, Trenholme KR, Healer J, Cowman AF, Eriksson EM, Sathe P, Penington J, Blanch AJ, Dixon MWA, Tilley L, Duffy MF, Craig A, Storm J, Chan JA, Evans K, Papenfuss AT, Schofield L, Griffin P, Barber BE, Andrew D, Boyle MJ, de Labastida Rivera F, Engwerda C, McCarthy JS. Safety, infectivity and immunogenicity of a genetically attenuated blood-stage malaria vaccine. BMC Med 2021; 19:293. [PMID: 34802442 PMCID: PMC8606250 DOI: 10.1186/s12916-021-02150-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 09/30/2021] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND There is a clear need for novel approaches to malaria vaccine development. We aimed to develop a genetically attenuated blood-stage vaccine and test its safety, infectivity, and immunogenicity in healthy volunteers. Our approach was to target the gene encoding the knob-associated histidine-rich protein (KAHRP), which is responsible for the assembly of knob structures at the infected erythrocyte surface. Knobs are required for correct display of the polymorphic adhesion ligand P. falciparum erythrocyte membrane protein 1 (PfEMP1), a key virulence determinant encoded by a repertoire of var genes. METHODS The gene encoding KAHRP was deleted from P. falciparum 3D7 and a master cell bank was produced in accordance with Good Manufacturing Practice. Eight malaria naïve males were intravenously inoculated (day 0) with 1800 (2 subjects), 1.8 × 105 (2 subjects), or 3 × 106 viable parasites (4 subjects). Parasitemia was measured using qPCR; immunogenicity was determined using standard assays. Parasites were rescued into culture for in vitro analyses (genome sequencing, cytoadhesion assays, scanning electron microscopy, var gene expression). RESULTS None of the subjects who were administered with 1800 or 1.8 × 105 parasites developed parasitemia; 3/4 subjects administered 3× 106 parasites developed significant parasitemia, first detected on days 13, 18, and 22. One of these three subjects developed symptoms of malaria simultaneously with influenza B (day 17; 14,022 parasites/mL); one subject developed mild symptoms on day 28 (19,956 parasites/mL); and one subject remained asymptomatic up to day 35 (5046 parasites/mL). Parasitemia rapidly cleared with artemether/lumefantrine. Parasitemia induced a parasite-specific antibody and cell-mediated immune response. Parasites cultured ex vivo exhibited genotypic and phenotypic properties similar to inoculated parasites, although the var gene expression profile changed during growth in vivo. CONCLUSIONS This study represents the first clinical investigation of a genetically attenuated blood-stage human malaria vaccine. A P. falciparum 3D7 kahrp- strain was tested in vivo and found to be immunogenic but can lead to patent parasitemia at high doses. TRIAL REGISTRATION Australian New Zealand Clinical Trials Registry (number: ACTRN12617000824369 ; date: 06 June 2017).
Collapse
Affiliation(s)
- Rebecca Webster
- QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Silvana Sekuloski
- QIMR Berghofer Medical Research Institute, Brisbane, Australia.,Current address: PharmOut, 111 Eagle Street, Brisbane, Queensland, 4000, Australia
| | - Anand Odedra
- QIMR Berghofer Medical Research Institute, Brisbane, Australia.,Liverpool School of Tropical Medicine, Liverpool, UK
| | - Stephen Woolley
- QIMR Berghofer Medical Research Institute, Brisbane, Australia.,Liverpool School of Tropical Medicine, Liverpool, UK.,Centre of Defence Pathology, Royal Centre for Defence Medicine, Joint Hospital Group, Birmingham, UK
| | - Helen Jennings
- QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Fiona Amante
- QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Katharine R Trenholme
- QIMR Berghofer Medical Research Institute, Brisbane, Australia.,The University of Queensland, Brisbane, Australia
| | - Julie Healer
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
| | - Alan F Cowman
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Department of Microbiology and Immunology, University of Melbourne, Melbourne, Australia
| | - Emily M Eriksson
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Priyanka Sathe
- Current address: Medicines Development for Global Health Limited, 18 Kavanagh Street, Southbank, Victoria, 3006, Australia
| | - Jocelyn Penington
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
| | - Adam J Blanch
- Bio21 Molecular Science and Biotechnology Institute, Melbourne, Australia.,Department of Biochemistry and Molecular Biology, University of Melbourne, Melbourne, Australia
| | - Matthew W A Dixon
- Bio21 Molecular Science and Biotechnology Institute, Melbourne, Australia.,Department of Biochemistry and Molecular Biology, University of Melbourne, Melbourne, Australia
| | - Leann Tilley
- Bio21 Molecular Science and Biotechnology Institute, Melbourne, Australia.,Department of Biochemistry and Molecular Biology, University of Melbourne, Melbourne, Australia
| | - Michael F Duffy
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, Australia.,Bio21 Molecular Science and Biotechnology Institute, Melbourne, Australia.,The Peter Doherty Institute for Infection and Immunity, Melbourne, Australia.,Department of Medicine, Royal Melbourne Hospital, Melbourne, Australia
| | - Alister Craig
- Liverpool School of Tropical Medicine, Liverpool, UK
| | - Janet Storm
- Liverpool School of Tropical Medicine, Liverpool, UK
| | | | - Krystal Evans
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Current address: GSK, 436 Johnston Street, Abbotsford, Victoria, 3067, Australia
| | - Anthony T Papenfuss
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Louis Schofield
- The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, Australia
| | - Paul Griffin
- QIMR Berghofer Medical Research Institute, Brisbane, Australia.,The University of Queensland, Brisbane, Australia.,Department of Medicine and Infectious Diseases, Mater Hospital and Mater Research, Brisbane, Australia
| | | | - Dean Andrew
- QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | | | | | | | - James S McCarthy
- QIMR Berghofer Medical Research Institute, Brisbane, Australia. .,The Peter Doherty Institute for Infection and Immunity, Melbourne, Australia.
| |
Collapse
|
9
|
Djokic V, Rocha SC, Parveen N. Lessons Learned for Pathogenesis, Immunology, and Disease of Erythrocytic Parasites: Plasmodium and Babesia. Front Cell Infect Microbiol 2021; 11:685239. [PMID: 34414129 PMCID: PMC8369351 DOI: 10.3389/fcimb.2021.685239] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 07/15/2021] [Indexed: 11/24/2022] Open
Abstract
Malaria caused by Plasmodium species and transmitted by Anopheles mosquitoes affects large human populations, while Ixodes ticks transmit Babesia species and cause babesiosis. Babesiosis in animals has been known as an economic drain, and human disease has also emerged as a serious healthcare problem in the last 20–30 years. There is limited literature available regarding pathogenesis, immunity, and disease caused by Babesia spp. with their genomes sequenced only in the last decade. Therefore, using previous studies on Plasmodium as the foundation, we have compared similarities and differences in the pathogenesis of Babesia and host immune responses. Sexual life cycles of these two hemoparasites in their respective vectors are quite similar. An adult Anopheles female can take blood meal several times in its life such that it can both acquire and transmit Plasmodia to hosts. Since each tick stage takes blood meal only once, transstadial horizontal transmission from larva to nymph or nymph to adult is essential for the release of Babesia into the host. The initiation of the asexual cycle of these parasites is different because Plasmodium sporozoites need to infect hepatocytes before egressed merozoites can infect erythrocytes, while Babesia sporozoites are known to enter the erythrocytic cycle directly. Plasmodium metabolism, as determined by its two- to threefold larger genome than different Babesia, is more complex. Plasmodium replication occurs in parasitophorous vacuole (PV) within the host cells, and a relatively large number of merozoites are released from each infected RBC after schizogony. The Babesia erythrocytic cycle lacks both PV and schizogony. Cytoadherence that allows the sequestration of Plasmodia, primarily P. falciparum in different organs facilitated by prominent adhesins, has not been documented for Babesia yet. Inflammatory immune responses contribute to the severity of malaria and babesiosis. Antibodies appear to play only a minor role in the resolution of these diseases; however, cellular and innate immunity are critical for the clearance of both pathogens. Inflammatory immune responses affect the severity of both diseases. Macrophages facilitate the resolution of both infections and also offer cross-protection against related protozoa. Although the immunosuppression of adaptive immune responses by these parasites does not seem to affect their own clearance, it significantly exacerbates diseases caused by coinfecting bacteria during coinfections.
Collapse
Affiliation(s)
- Vitomir Djokic
- Department for Bacterial Zoonozes, Laboratory for Animal Health, French Agency for Food, Environmental and Occupational Health & Safety, UPEC, University Paris-Est, Maisons-Alfort, France
| | - Sandra C Rocha
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers New Jersey Medical School, Newark, NJ, United States
| | - Nikhat Parveen
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers New Jersey Medical School, Newark, NJ, United States
| |
Collapse
|
10
|
Jafari-Guemouri S, Courtois L, Mama A, Rouas B, Neto Braga G, Accrombessi M, Massougbodji A, Ding XC, Tuikue Ndam N, Fievet N, Briand V. A Genotyping Study in Benin Comparing the Carriage of Plasmodium falciparum Infections Before Pregnancy and in Early Pregnancy: Story of a Persistent Infection. Clin Infect Dis 2021; 73:e355-e361. [PMID: 32569359 PMCID: PMC8282262 DOI: 10.1093/cid/ciaa841] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 06/17/2020] [Indexed: 12/16/2022] Open
Abstract
Background Malaria infections in the first trimester of pregnancy are frequent and deleterious for both mother and child health. To investigate if these early infections are newly acquired or already present in the host, we assessed whether parasites detected before pregnancy and those detected in early pregnancy are the same infection. Methods We used data from the preconceptional “RECIPAL” study (Benin, 2014–2017). Sixty-three pregnant women of 411 included who had a malaria infection detected by quantitative polymerase chain reaction both before pregnancy and at the first antenatal care (ANC) visit were selected for this study. Two highly polymorphic markers, msp-2 and glurp, and a fragment-analysis method were used to enumerate the Plasmodium falciparum genotypes and to quantify their proportions within isolates. An infection was considered as persistent when identical msp-2 and glurp genotypes were found in the corresponding prepregnancy and early-pregnancy samples. Results The median time between the 2 malaria screenings was 3 months. The median gestational age at the first ANC visit was 6.4 weeks. Most infections before pregnancy were submicroscopic infections. Based on both msp-2 and glurp genotyping, the infection was similar before and in early pregnancy in 46% (29/63) of cases. Conclusions Almost half of P. falciparum infections detected in the first trimester originate before pregnancy. Protecting young women from malaria infection before pregnancy might reduce the prevalence of malaria in early pregnancy and its related poor maternal and birth outcomes.
Collapse
Affiliation(s)
- Sayeh Jafari-Guemouri
- Université de Paris, UMR261-MERIT, Institut de Recherche pour le Développement, Paris, France
| | - Laura Courtois
- Université de Paris, UMR261-MERIT, Institut de Recherche pour le Développement, Paris, France
| | - Atika Mama
- Clinical Research Institute of Benin (IRCB), Abomey-Calavi, Benin
| | - Baptiste Rouas
- Université de Paris, UMR261-MERIT, Institut de Recherche pour le Développement, Paris, France
| | - Gabriel Neto Braga
- Université de Paris, UMR261-MERIT, Institut de Recherche pour le Développement, Paris, France
| | - Manfred Accrombessi
- Clinical Research Institute of Benin (IRCB), Abomey-Calavi, Benin.,Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | | | | | - Nicaise Tuikue Ndam
- Université de Paris, UMR261-MERIT, Institut de Recherche pour le Développement, Paris, France
| | - Nadine Fievet
- Université de Paris, UMR261-MERIT, Institut de Recherche pour le Développement, Paris, France
| | - Valérie Briand
- Université de Paris, UMR261-MERIT, Institut de Recherche pour le Développement, Paris, France.,University of Bordeaux, Inserm, Institut de Recherche pour le Développement, Inserm, University of Bordeaux, UMR, Bordeaux, France
| |
Collapse
|
11
|
McLean ARD, Opi DH, Stanisic DI, Cutts JC, Feng G, Ura A, Mueller I, Rogerson SJ, Beeson JG, Fowkes FJI. High Antibodies to VAR2CSA in Response to Malaria Infection Are Associated With Improved Birthweight in a Longitudinal Study of Pregnant Women. Front Immunol 2021; 12:644563. [PMID: 34220804 PMCID: PMC8242957 DOI: 10.3389/fimmu.2021.644563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 05/17/2021] [Indexed: 11/23/2022] Open
Abstract
Introduction Pregnant women have an increased risk of P. falciparum infection, which is associated with low birth weight and preterm delivery. VAR2CSA, a variant surface antigen expressed on the parasitized erythrocyte surface, enables sequestration in the placenta. Few studies have prospectively examined relationships between antibody responses during pregnancy and subsequent adverse birth outcomes, and there are limited data outside Africa. Methods Levels of IgG against VAR2CSA domains (DBL3; DBL5) and a VAR2CSA-expressing placental-binding P. falciparum isolate (PfCS2-IE) were measured in 301 women enrolled at their first visit to antenatal care which occurred mid-pregnancy (median = 26 weeks, lower and upper quartiles = 22, 28). Associations between antibody levels at enrolment and placental infection, birthweight and estimated gestational age at delivery were assessed by linear and logistic regression with adjustment for confounders. For all outcomes, effect modification by gravidity and peripheral blood P. falciparum infection at enrolment was assessed. Results Among women who had acquired P. falciparum infection at enrolment, those with higher levels of VAR2CSA antibodies (75th percentile) had infants with higher mean birthweight (estimates varied from +35g to +149g depending on antibody response) and reduced adjusted odds of placental infection (aOR estimates varied from 0.17 to 0.80), relative to women with lower levels (25th percentile) of VAR2CSA antibodies. However, among women who had not acquired an infection at enrolment, higher VAR2CSA antibodies were associated with increased odds of placental infection (aOR estimates varied from 1.10 to 2.24). Conclusions When infected by mid-pregnancy, a better immune response to VAR2CSA-expressing parasites may contribute to protecting against adverse pregnancy outcomes.
Collapse
Affiliation(s)
- Alistair R D McLean
- Burnet Institute, Melbourne, VIC, Australia.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - D Herbert Opi
- Burnet Institute, Melbourne, VIC, Australia.,Department of Immunology and Pathology, Monash University, Melbourne, VIC, Australia.,Department of Medicine at the Doherty Institute, University of Melbourne, Melbourne, VIC, Australia
| | - Danielle I Stanisic
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea.,Institute for Glycomics, Griffith University, Southport, QLD, Australia
| | - Julia C Cutts
- Burnet Institute, Melbourne, VIC, Australia.,Department of Medicine at the Doherty Institute, University of Melbourne, Melbourne, VIC, Australia
| | - Gaoqian Feng
- Burnet Institute, Melbourne, VIC, Australia.,Department of Medicine at the Doherty Institute, University of Melbourne, Melbourne, VIC, Australia
| | - Alice Ura
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Ivo Mueller
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea.,Population, Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia.,Département Parasites et Insectes Vecteurs, Institute Pasteur, Paris, France
| | - Stephen J Rogerson
- Department of Medicine at the Doherty Institute, University of Melbourne, Melbourne, VIC, Australia
| | - James G Beeson
- Burnet Institute, Melbourne, VIC, Australia.,Department of Medicine at the Doherty Institute, University of Melbourne, Melbourne, VIC, Australia.,Department of Microbiology, Monash University, Clayton, VIC, Australia
| | - Freya J I Fowkes
- Burnet Institute, Melbourne, VIC, Australia.,Department of Infectious Diseases, Central Clinical School, Monash University, Melbourne, VIC, Australia.,Centre for Epidemiology and Biostatistics, University of Melbourne, Melbourne, VIC, Australia.,Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, VIC, Australia
| |
Collapse
|
12
|
Wichers JS, Tonkin-Hill G, Thye T, Krumkamp R, Kreuels B, Strauss J, von Thien H, Scholz JAM, Smedegaard Hansson H, Weisel Jensen R, Turner L, Lorenz FR, Schöllhorn A, Bruchhaus I, Tannich E, Fendel R, Otto TD, Lavstsen T, Gilberger TW, Duffy MF, Bachmann A. Common virulence gene expression in adult first-time infected malaria patients and severe cases. eLife 2021; 10:e69040. [PMID: 33908865 PMCID: PMC8102065 DOI: 10.7554/elife.69040] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 04/18/2021] [Indexed: 12/22/2022] Open
Abstract
Sequestration of Plasmodium falciparum(P. falciparum)-infected erythrocytes to host endothelium through the parasite-derived P. falciparum erythrocyte membrane protein 1 (PfEMP1) adhesion proteins is central to the development of malaria pathogenesis. PfEMP1 proteins have diversified and expanded to encompass many sequence variants, conferring each parasite a similar array of human endothelial receptor-binding phenotypes. Here, we analyzed RNA-seq profiles of parasites isolated from 32 P. falciparum-infected adult travellers returning to Germany. Patients were categorized into either malaria naive (n = 15) or pre-exposed (n = 17), and into severe (n = 8) or non-severe (n = 24) cases. For differential expression analysis, PfEMP1-encoding var gene transcripts were de novo assembled from RNA-seq data and, in parallel, var-expressed sequence tags were analyzed and used to predict the encoded domain composition of the transcripts. Both approaches showed in concordance that severe malaria was associated with PfEMP1 containing the endothelial protein C receptor (EPCR)-binding CIDRα1 domain, whereas CD36-binding PfEMP1 was linked to non-severe malaria outcomes. First-time infected adults were more likely to develop severe symptoms and tended to be infected for a longer period. Thus, parasites with more pathogenic PfEMP1 variants are more common in patients with a naive immune status, and/or adverse inflammatory host responses to first infections favor the growth of EPCR-binding parasites.
Collapse
Affiliation(s)
- J Stephan Wichers
- Molecular Biology and Immunology, Bernhard Nocht Institute for Tropical MedicineHamburgGermany
- Centre for Structural Systems BiologyHamburgGermany
- Biology Department, University of HamburgHamburgGermany
| | | | - Thorsten Thye
- Epidemiology and Diagnostics, Bernhard Nocht Institute for Tropical MedicineHamburgGermany
| | - Ralf Krumkamp
- Epidemiology and Diagnostics, Bernhard Nocht Institute for Tropical MedicineHamburgGermany
- German Center for Infection Research (DZIF), Partner Site Hamburg-Lübeck-Borstel-RiemsHamburgGermany
| | - Benno Kreuels
- Department of Tropical Medicine, Bernhard Nocht Institute for Tropical Medicine, GermanyHamburgGermany
- Department of Medicine, College of MedicineBlantyreMalawi
- Department of Medicine, University Medical Center Hamburg-EppendorfHamburgGermany
| | - Jan Strauss
- Molecular Biology and Immunology, Bernhard Nocht Institute for Tropical MedicineHamburgGermany
- Centre for Structural Systems BiologyHamburgGermany
- Biology Department, University of HamburgHamburgGermany
| | - Heidrun von Thien
- Molecular Biology and Immunology, Bernhard Nocht Institute for Tropical MedicineHamburgGermany
- Centre for Structural Systems BiologyHamburgGermany
- Biology Department, University of HamburgHamburgGermany
| | - Judith AM Scholz
- Molecular Biology and Immunology, Bernhard Nocht Institute for Tropical MedicineHamburgGermany
| | | | | | | | | | - Anna Schöllhorn
- Institute of Tropical Medicine, University of TübingenTübingenGermany
| | - Iris Bruchhaus
- Molecular Biology and Immunology, Bernhard Nocht Institute for Tropical MedicineHamburgGermany
- Biology Department, University of HamburgHamburgGermany
| | - Egbert Tannich
- Epidemiology and Diagnostics, Bernhard Nocht Institute for Tropical MedicineHamburgGermany
- German Center for Infection Research (DZIF), Partner Site Hamburg-Lübeck-Borstel-RiemsHamburgGermany
| | - Rolf Fendel
- Institute of Tropical Medicine, University of TübingenTübingenGermany
- German Center for Infection Research (DZIF), Partner Site TübingenTübingenGermany
| | - Thomas D Otto
- Institute of Infection, Immunity and Inflammation, University of GlasgowGlasgowUnited Kingdom
| | | | - Tim W Gilberger
- Molecular Biology and Immunology, Bernhard Nocht Institute for Tropical MedicineHamburgGermany
- Centre for Structural Systems BiologyHamburgGermany
- Biology Department, University of HamburgHamburgGermany
| | - Michael F Duffy
- Department of Microbiology and Immunology, University of MelbourneMelbourneAustralia
| | - Anna Bachmann
- Molecular Biology and Immunology, Bernhard Nocht Institute for Tropical MedicineHamburgGermany
- Centre for Structural Systems BiologyHamburgGermany
- Biology Department, University of HamburgHamburgGermany
- German Center for Infection Research (DZIF), Partner Site Hamburg-Lübeck-Borstel-RiemsHamburgGermany
| |
Collapse
|
13
|
De Niz M, Carvalho T, Penha-Gonçalves C, Agop-Nersesian C. Intravital imaging of host-parasite interactions in organs of the thoracic and abdominopelvic cavities. Cell Microbiol 2020; 22:e13201. [PMID: 32149435 DOI: 10.1111/cmi.13201] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 03/03/2020] [Accepted: 03/06/2020] [Indexed: 12/16/2022]
Abstract
Infections with protozoan and helminthic parasites affect multiple organs in the mammalian host. Imaging pathogens in their natural environment takes a more holistic view on biomedical aspects of parasitic infections. Here, we focus on selected organs of the thoracic and abdominopelvic cavities most commonly affected by parasites. Parasitic infections of these organs are often associated with severe medical complications or have health implications beyond the infected individual. Intravital imaging has provided a more dynamic picture of the host-parasite interplay and contributed not only to our understanding of the various disease pathologies, but has also provided fundamental insight into the biology of the parasites.
Collapse
Affiliation(s)
- Mariana De Niz
- Institute of Cell Biology, University of Bern, Bern, Switzerland.,Instituto de Medicina Molecular - João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - Tânia Carvalho
- Instituto de Medicina Molecular - João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | | | | |
Collapse
|
14
|
Bachmann A, Bruske E, Krumkamp R, Turner L, Wichers JS, Petter M, Held J, Duffy MF, Sim BKL, Hoffman SL, Kremsner PG, Lell B, Lavstsen T, Frank M, Mordmüller B, Tannich E. Controlled human malaria infection with Plasmodium falciparum demonstrates impact of naturally acquired immunity on virulence gene expression. PLoS Pathog 2019; 15:e1007906. [PMID: 31295334 PMCID: PMC6650087 DOI: 10.1371/journal.ppat.1007906] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 07/23/2019] [Accepted: 06/10/2019] [Indexed: 12/14/2022] Open
Abstract
The pathogenesis of Plasmodium falciparum malaria is linked to the variant surface antigen PfEMP1, which mediates tethering of infected erythrocytes to the host endothelium and is encoded by approximately 60 var genes per parasite genome. Repeated episodes of malaria infection result in the gradual acquisition of protective antibodies against PfEMP1 variants. The antibody repertoire is believed to provide a selective pressure driving the clonal expansion of parasites expressing unrecognized PfEMP1 variants, however, due to the lack of experimental in vivo models there is only limited experimental evidence in support of this concept. To get insight into the impact of naturally acquired immunity on the expressed var gene repertoire early during infection we performed controlled human malaria infections of 20 adult African volunteers with life-long malaria exposure using aseptic, purified, cryopreserved P. falciparum sporozoites (Sanaria PfSPZ Challenge) and correlated serological data with var gene expression patterns from ex vivo parasites. Among the 10 African volunteers who developed patent infections, individuals with low antibody levels showed a steep rise in parasitemia accompanied by broad activation of multiple, predominantly subtelomeric var genes, similar to what we previously observed in naïve volunteers. In contrast, individuals with intermediate antibody levels developed asymptomatic infections and the ex vivo parasite populations expressed only few var gene variants, indicative of clonal selection. Importantly, in contrast to parasites from naïve volunteers, expression of var genes coding for endothelial protein C receptor (EPCR)-binding PfEMP1 that are associated with severe childhood malaria was rarely detected in semi-immune adult African volunteers. Moreover, we followed var gene expression for up to six parasite replication cycles and demonstrated for the first time in vivo a shift in the dominant var gene variant. In conclusion, our data suggest that P. falciparum activates multiple subtelomeric var genes at the onset of blood stage infection facilitating rapid expansion of parasite clones which express PfEMP1 variants unrecognized by the host's immune system, thus promoting overall parasite survival in the face of host immunity.
Collapse
Affiliation(s)
- Anna Bachmann
- Department of Molecular Parasitology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
- German Center for Infection Research (DZIF), partner site Hamburg-Borstel-Lübeck-Riems, Germany
| | - Ellen Bruske
- Institute of Tropical Medicine, University Hospital Tübingen, Tübingen, Germany
| | - Ralf Krumkamp
- German Center for Infection Research (DZIF), partner site Hamburg-Borstel-Lübeck-Riems, Germany
- Infectious Disease Epidemiology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - Louise Turner
- Centre for Medical Parasitology, University of Copenhagen, Copenhagen K, Denmark
| | - J. Stephan Wichers
- Department of Molecular Parasitology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - Michaela Petter
- Mikrobiologisches Institut–Klinische Mikrobiologie, Immunologie und Hygiene, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Erlangen, Germany
- School of BioSciences, Bio21 Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Jana Held
- Institute of Tropical Medicine, University Hospital Tübingen, Tübingen, Germany
| | - Michael F. Duffy
- School of BioSciences, Bio21 Institute, University of Melbourne, Parkville, Victoria, Australia
| | | | | | - Peter G. Kremsner
- Institute of Tropical Medicine, University Hospital Tübingen, Tübingen, Germany
- German Center for Infection Research (DZIF), partner site Tübingen, Germany
| | - Bertrand Lell
- Institute of Tropical Medicine, University Hospital Tübingen, Tübingen, Germany
- Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon
- German Center for Infection Research (DZIF), African partner institution, CERMEL, Gabon
| | - Thomas Lavstsen
- Centre for Medical Parasitology, University of Copenhagen, Copenhagen K, Denmark
| | - Matthias Frank
- Institute of Tropical Medicine, University Hospital Tübingen, Tübingen, Germany
| | - Benjamin Mordmüller
- Institute of Tropical Medicine, University Hospital Tübingen, Tübingen, Germany
- German Center for Infection Research (DZIF), partner site Tübingen, Germany
| | - Egbert Tannich
- Department of Molecular Parasitology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
- German Center for Infection Research (DZIF), partner site Hamburg-Borstel-Lübeck-Riems, Germany
| |
Collapse
|
15
|
Dynamics of Plasmodium falciparum gametocyte carriage in pregnant women under intermittent preventive treatment with sulfadoxine-pyrimethamine in Benin. Malar J 2018; 17:356. [PMID: 30305101 PMCID: PMC6180446 DOI: 10.1186/s12936-018-2498-8] [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: 05/08/2018] [Accepted: 09/29/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In sub-Saharan Africa, malaria is a major cause of morbidity and mortality, in particular in children and pregnant women. During pregnancy, Plasmodium falciparum infected red blood cells expressing VAR2CSA are selected from circulation by selective cytoadherence to chondroitin sulfate proteoglycan receptors expressed in the placenta, leading to an increased susceptibility to malaria, long-lasting infections and poor pregnancy outcome. Partly because of these long-lasting infections, women were reported to have a higher density of gametocytes in their peripheral blood, and are considered as a potential reservoir for malaria transmission. To improve pregnancy outcome in areas of high malaria transmission, The WHO recommends intermittent preventive treatment with sulfadoxine/pyrimethamine (IPTp-SP) during antenatal care visits. The effect of IPTp-SP on gametocyte carriage in infected pregnant women was studied. METHODS The levels of transcription of three gametocytes stage-specific genes Pfs16 (expressed by sexually-committed ring stage parasites and fully matured gametocytes), Pfs25 (expressed by female mature gametocytes) and Pfs230 (expressed by male mature gametocytes) were assessed by real-time PCR in 50 P. falciparum infected women at early pregnancy (before implementation of IPTp-SP), and in 50 infected women at delivery. Sex ratios of male and female gametocytes were determined in these women to assess the effect of IPTp-SP on the gametocyte populations. RESULTS The data show that the three transcript types specific to Pfs16, Pfs25 and Pfs230 were detected in all samples, both at inclusion and delivery. Levels of Pfs25 and Pfs230 transcripts were higher at delivery than at inclusion (p = 0.042 and p = 0.003), while the opposite was observed for Pfs16 (p = 0.048). The ratio of male/female gametocyte transcript levels was higher at delivery than at inclusion (p = 0.018). Since a mixed gender late stage gametocyte culture was used as a positive control, male and female gametocytes could not be quantified in an absolute way in the samples. However, the amplification reliability of the Pfs25 and Pfs230 markers in the samples could be checked. A relative quantity of each type of Pfs transcript was, therefore, used to calculate the sex ratio proxy. CONCLUSION This study demonstrates that IPTp-SP treatment contributes to modify the parasite populations' structure during pregnancy. In line with previous studies, we suggest that the continued use of SP in pregnant women as IPTp, despite having a beneficial effect on the pregnancy outcome, could be a risk factor for increased transmission. This reinforces the need for an alternative to the SP drug for malaria prevention during pregnancy.
Collapse
|
16
|
Chan JA, Stanisic DI, Duffy MF, Robinson LJ, Lin E, Kazura JW, King CL, Siba PM, Fowkes FJ, Mueller I, Beeson JG. Patterns of protective associations differ for antibodies to P. falciparum-infected erythrocytes and merozoites in immunity against malaria in children. Eur J Immunol 2017; 47:2124-2136. [PMID: 28833064 DOI: 10.1002/eji.201747032] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 07/09/2017] [Accepted: 08/16/2017] [Indexed: 11/10/2022]
Abstract
Acquired antibodies play an important role in immunity to P. falciparum malaria and are typically directed towards surface antigens expressed by merozoites and infected erythrocytes (IEs). The importance of specific IE surface antigens as immune targets remains unclear. We evaluated antibodies and protective associations in two cohorts of children in Papua New Guinea. We used genetically-modified P. falciparum to evaluate the importance of PfEMP1 and a P. falciparum isolate with a virulent phenotype. Our findings suggested that PfEMP1 was the dominant target of antibodies to the IE surface, including functional antibodies that promoted opsonic phagocytosis by monocytes. Antibodies were associated with increasing age and concurrent parasitemia, and were higher among children exposed to a higher force-of-infection as determined using molecular detection. Antibodies to IE surface antigens were consistently associated with reduced risk of malaria in both younger and older children. However, protective associations for antibodies to merozoite surface antigens were only observed in older children. This suggests that antibodies to IE surface antigens, particularly PfEMP1, play an earlier role in acquired immunity to malaria, whereas greater exposure is required for protective antibodies to merozoite antigens. These findings have implications for vaccine design and serosurveillance of malaria transmission and immunity.
Collapse
Affiliation(s)
- Jo-Anne Chan
- Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, Australia.,Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Danielle I Stanisic
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Institute for Glycomics, Griffith University, Southport, Queensland, Australia
| | - Michael F Duffy
- Department of Medicine and Melbourne School of Public Health, University of Melbourne, Parkville, Victoria, Australia
| | - Leanne J Robinson
- Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, Australia.,Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Enmoore Lin
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - James W Kazura
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, OH, USA
| | - Christopher L King
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, OH, USA
| | - Peter M Siba
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Freya Ji Fowkes
- Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, Australia.,Melbourne School of Public Health, University of Melbourne, Parkville, Victoria, Australia.,Department of Epidemiology and Preventive Medicine and Department of Infectious Diseases, Monash University, Melbourne, Victoria, Australia
| | - Ivo Mueller
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - James G Beeson
- Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, Australia.,Department of Medicine and Melbourne School of Public Health, University of Melbourne, Parkville, Victoria, Australia.,Department of Microbiology, Monash University, Melbourne, Victoria, Australia
| |
Collapse
|
17
|
TLR4-Mediated Placental Pathology and Pregnancy Outcome in Experimental Malaria. Sci Rep 2017; 7:8623. [PMID: 28819109 PMCID: PMC5561130 DOI: 10.1038/s41598-017-08299-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 07/06/2017] [Indexed: 12/13/2022] Open
Abstract
Malaria-associate pregnancy has a significant impact on infant morbidity and mortality. The detrimental effects of malaria infection during pregnancy have been shown to correlate with immune activation in the placental tissue. Herein we sought to evaluate the effect of Toll-like receptors (TLRs) activation on placental malaria (PM) development by using the Plasmodium berghei NK65GFP infection model. We observed that activation of the innate immune system by parasites leads to PM due to local inflammation. We identified TLR4 activation as the main pathway involved in the inflammatory process in the placental tissue since the absence of functional TLR4 in mice leads to a decrease in the pro-inflammatory responses, which resulted in an improved pregnancy outcome. Additionally, a similar result was obtained when infected pregnant mice were treated with IAXO-101, a TLR4/CD14 blocker. Together, this study illustrates the importance of TLR4 signalling for the generation of the severe inflammatory response involved in PM pathogenesis. Therefore, our results implicate that TLR4 blockage could be a potential candidate for therapeutic interventions to reduce malaria-induced pathology both in the mother and the fetus.
Collapse
|
18
|
Fonseca AM, Quinto L, Jiménez A, González R, Bardají A, Maculuve S, Dobaño C, Rupérez M, Vala A, Aponte JJ, Sevene E, Macete E, Menéndez C, Mayor A. Multiplexing detection of IgG against Plasmodium falciparum pregnancy-specific antigens. PLoS One 2017; 12:e0181150. [PMID: 28715465 PMCID: PMC5513451 DOI: 10.1371/journal.pone.0181150] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 06/27/2017] [Indexed: 11/18/2022] Open
Abstract
Background Pregnant women exposed to Plasmodium falciparum generate antibodies against VAR2CSA, the parasite protein that mediates adhesion of infected erythrocytes to the placenta. There is a need of high-throughput tools to determine the fine specificity of these antibodies that can be used to identify immune correlates of protection and exposure. Here we aimed at developing a multiplex-immunoassay to detect antibodies against VAR2CSA antigens. Methods and findings We constructed two multiplex-bead arrays, one composed of 3 VAR2CSA recombinant-domains (DBL3X, DBL5Ɛ and DBL6Ɛ) and another composed of 46 new peptides covering VAR2CSA conserved and semi-conserved regions. IgG reactivity was similar in multiplexed and singleplexed determinations (Pearson correlation, protein array: R2 = 0.99 and peptide array: R2 = 0.87). IgG recognition of 25 out of 46 peptides and all recombinant-domains was higher in pregnant Mozambican women (n = 106) than in Mozambican men (n = 102) and Spanish individuals (n = 101; p<0.05). Agreement of IgG levels detected in cryopreserved plasma and in elutions from dried blood spots was good after exclusion of inappropriate filter papers. Under heterogeneous levels of exposure to malaria, similar seropositivity cutoffs were obtained using finite mixture models applied to antibodies measured on pregnant Mozambican women and average of antibodies measured on pregnant Spanish women never exposed to malaria. The application of the multiplex-bead array developed here, allowed the assessment of higher IgG levels and seroprevalences against VAR2CSA-derived antigens in women pregnant during 2003–2005 than during 2010–2012, in accordance with the levels of malaria transmission reported for these years in Mozambique. Conclusions The multiplex bead-based immunoassay to detect antibodies against selected 25 VAR2CSA new-peptides and recombinant-domains was successfully implemented. Analysis of field samples showed that responses were specific among pregnant women and dependent on the level of exposure to malaria. This platform provides a high-throughput approach to investigating correlates of protection and identifying serological markers of exposure for malaria in pregnancy.
Collapse
Affiliation(s)
- Ana Maria Fonseca
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
- Graduate Program in Areas of Basic and Applied Biology (GABBA), Universidade do Porto, Porto, Portugal
| | - Llorenç Quinto
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
| | - Alfons Jiménez
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
- Spanish Consortium for Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain
| | - Raquel González
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
- Centro de Investigação em Saúde da Manhiça (CISM), Maputo, Mozambique
| | - Azucena Bardají
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
- Centro de Investigação em Saúde da Manhiça (CISM), Maputo, Mozambique
| | - Sonia Maculuve
- Centro de Investigação em Saúde da Manhiça (CISM), Maputo, Mozambique
| | - Carlota Dobaño
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
- Centro de Investigação em Saúde da Manhiça (CISM), Maputo, Mozambique
| | - Maria Rupérez
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
- Centro de Investigação em Saúde da Manhiça (CISM), Maputo, Mozambique
| | - Anifa Vala
- Centro de Investigação em Saúde da Manhiça (CISM), Maputo, Mozambique
| | - John J. Aponte
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
- Centro de Investigação em Saúde da Manhiça (CISM), Maputo, Mozambique
| | - Esperanza Sevene
- Centro de Investigação em Saúde da Manhiça (CISM), Maputo, Mozambique
- Eduardo Mondlane University, Maputo, Mozambique
| | - Eusebio Macete
- Centro de Investigação em Saúde da Manhiça (CISM), Maputo, Mozambique
| | - Clara Menéndez
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
- Centro de Investigação em Saúde da Manhiça (CISM), Maputo, Mozambique
| | - Alfredo Mayor
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
- Centro de Investigação em Saúde da Manhiça (CISM), Maputo, Mozambique
- * E-mail:
| |
Collapse
|
19
|
CRISPR/Cas9 Genome Editing Reveals That the Intron Is Not Essential for var2csa Gene Activation or Silencing in Plasmodium falciparum. mBio 2017; 8:mBio.00729-17. [PMID: 28698275 PMCID: PMC5513710 DOI: 10.1128/mbio.00729-17] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Plasmodium falciparum relies on monoallelic expression of 1 of 60 var virulence genes for antigenic variation and host immune evasion. Each var gene contains a conserved intron which has been implicated in previous studies in both activation and repression of transcription via several epigenetic mechanisms, including interaction with the var promoter, production of long noncoding RNAs (lncRNAs), and localization to repressive perinuclear sites. However, functional studies have relied primarily on artificial expression constructs. Using the recently developed P. falciparum clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system, we directly deleted the var2csa P. falciparum 3D7_1200600 (Pf3D7_1200600) endogenous intron, resulting in an intronless var gene in a natural, marker-free chromosomal context. Deletion of the var2csa intron resulted in an upregulation of transcription of the var2csa gene in ring-stage parasites and subsequent expression of the PfEMP1 protein in late-stage parasites. Intron deletion did not affect the normal temporal regulation and subsequent transcriptional silencing of the var gene in trophozoites but did result in increased rates of var gene switching in some mutant clones. Transcriptional repression of the intronless var2csa gene could be achieved via long-term culture or panning with the CD36 receptor, after which reactivation was possible with chondroitin sulfate A (CSA) panning. These data suggest that the var2csa intron is not required for silencing or activation in ring-stage parasites but point to a subtle role in regulation of switching within the var gene family.IMPORTANCEPlasmodium falciparum is the most virulent species of malaria parasite, causing high rates of morbidity and mortality in those infected. Chronic infection depends on an immune evasion mechanism termed antigenic variation, which in turn relies on monoallelic expression of 1 of ~60 var genes. Understanding antigenic variation and the transcriptional regulation of monoallelic expression is important for developing drugs and/or vaccines. The var gene family encodes the antigenic surface proteins that decorate infected erythrocytes. Until recently, studying the underlying genetic elements that regulate monoallelic expression in P. falciparum was difficult, and most studies relied on artificial systems such as episomal reporter genes. Our study was the first to use CRISPR/Cas9 genome editing for the functional study of an important, conserved genetic element of var genes-the intron-in an endogenous, episome-free manner. Our findings shed light on the role of the var gene intron in transcriptional regulation of monoallelic expression.
Collapse
|
20
|
Chan S, Frasch A, Mandava CS, Ch'ng JH, Quintana MDP, Vesterlund M, Ghorbal M, Joannin N, Franzén O, Lopez-Rubio JJ, Barbieri S, Lanzavecchia A, Sanyal S, Wahlgren M. Regulation of PfEMP1-VAR2CSA translation by a Plasmodium translation-enhancing factor. Nat Microbiol 2017; 2:17068. [PMID: 28481333 DOI: 10.1038/nmicrobiol.2017.68] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 03/29/2017] [Indexed: 12/22/2022]
Abstract
Pregnancy-associated malaria commonly involves the binding of Plasmodium falciparum-infected erythrocytes to placental chondroitin sulfate A (CSA) through the PfEMP1-VAR2CSA protein. VAR2CSA is translationally repressed by an upstream open reading frame. In this study, we report that the P. falciparum translation enhancing factor (PTEF) relieves upstream open reading frame repression and thereby facilitates VAR2CSA translation. VAR2CSA protein levels in var2csa-transcribing parasites are dependent on the expression level of PTEF, and the alleviation of upstream open reading frame repression requires the proteolytic processing of PTEF by PfCalpain. Cleavage generates a C-terminal domain that contains a sterile-alpha-motif-like domain. The C-terminal domain is permissive to cytoplasmic shuttling and interacts with ribosomes to facilitate translational derepression of the var2csa coding sequence. It also enhances translation in a heterologous translation system and thus represents the first non-canonical translation enhancing factor to be found in a protozoan. Our results implicate PTEF in regulating placental CSA binding of infected erythrocytes.
Collapse
Affiliation(s)
- Sherwin Chan
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Box 280, Nobels väg 16, 171 77 Stockholm, Sweden
| | - Alejandra Frasch
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Box 280, Nobels väg 16, 171 77 Stockholm, Sweden
| | - Chandra Sekhar Mandava
- Department of Cell and Molecular Biology, Uppsala University, Box-596, 751 24 Uppsala, Sweden
| | - Jun-Hong Ch'ng
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Box 280, Nobels väg 16, 171 77 Stockholm, Sweden.,Department of Microbiology, National University of Singapore 117545, Singapore
| | - Maria Del Pilar Quintana
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Box 280, Nobels väg 16, 171 77 Stockholm, Sweden.,Escuela de Medicina y Ciencias de la Salud, Facultad de Ciencias Naturales y Matemáticas, Universidad del Rosario, Calle 12C No. 6-25, Bogotá, Colombia
| | - Mattias Vesterlund
- Cancer Proteomics, Department of Oncology-Pathology, Karolinska Institutet, 17176 Stockholm, Sweden
| | - Mehdi Ghorbal
- University of Montpellier, Faculty of Medicine, Laboratory of Parasitology-Mycology, Montpellier F34090, France.,CNRS - 5290, IRD 224 - University of Montpellier (UMR 'MiVEGEC'), Montpellier, France
| | - Nicolas Joannin
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Box 280, Nobels väg 16, 171 77 Stockholm, Sweden
| | - Oscar Franzén
- Department of Genetics and Genomic Sciences, Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York 10029, USA
| | - Jose-Juan Lopez-Rubio
- University of Montpellier, Faculty of Medicine, Laboratory of Parasitology-Mycology, Montpellier F34090, France.,CNRS - 5290, IRD 224 - University of Montpellier (UMR 'MiVEGEC'), Montpellier, France
| | - Sonia Barbieri
- Institute for Research in Biomedicine, Università della Svizzera italiana, Bellinzona 6500, Switzerland
| | - Antonio Lanzavecchia
- Institute for Research in Biomedicine, Università della Svizzera italiana, Bellinzona 6500, Switzerland.,Institute of Microbiology, ETH Zurich, Zurich 8093, Switzerland
| | - Suparna Sanyal
- Department of Cell and Molecular Biology, Uppsala University, Box-596, 751 24 Uppsala, Sweden
| | - Mats Wahlgren
- Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Box 280, Nobels väg 16, 171 77 Stockholm, Sweden
| |
Collapse
|
21
|
Pehrson C, Salanti A, Theander TG, Nielsen MA. Pre-clinical and clinical development of the first placental malaria vaccine. Expert Rev Vaccines 2017; 16:613-624. [PMID: 28434376 DOI: 10.1080/14760584.2017.1322512] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
INTRODUCTION Malaria during pregnancy is a massive health problem in endemic areas. Placental malaria infections caused by Plasmodium falciparum are responsible for up to one million babies being born with a low birth weight every year. Significant efforts have been invested into preventing the condition. Areas covered: Pub Med was searched using the broad terms 'malaria parasite placenta' to identify studies of interactions between parasite and host, 'prevention of placental malaria' to identify current strategies to prevent placental malaria, and 'placental malaria vaccine' to identify pre-clinical vaccine development. However, all papers from these searches were not systematically included. Expert commentary: The first phase I clinical trials of vaccines are well underway. Trials testing efficacy are more complicated to carry out as only women that are exposed to parasites during pregnancy will contribute to endpoint measurements, further it may require extensive follow-up to establish protection. Future second generation vaccines may overcome the inherent challenges in making an effective placental malaria vaccine.
Collapse
Affiliation(s)
- Caroline Pehrson
- a Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Science , University of Copenhagen , Copenhagen , Denmark.,b Department of Infectious Diseases , Copenhagen University Hospital (Rigshospitalet) , Copenhagen , Denmark
| | - Ali Salanti
- a Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Science , University of Copenhagen , Copenhagen , Denmark.,b Department of Infectious Diseases , Copenhagen University Hospital (Rigshospitalet) , Copenhagen , Denmark
| | - Thor G Theander
- a Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Science , University of Copenhagen , Copenhagen , Denmark.,b Department of Infectious Diseases , Copenhagen University Hospital (Rigshospitalet) , Copenhagen , Denmark
| | - Morten A Nielsen
- a Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Science , University of Copenhagen , Copenhagen , Denmark.,b Department of Infectious Diseases , Copenhagen University Hospital (Rigshospitalet) , Copenhagen , Denmark
| |
Collapse
|
22
|
Duffy MF, Tang J, Sumardy F, Nguyen HHT, Selvarajah SA, Josling GA, Day KP, Petter M, Brown GV. Activation and clustering of a Plasmodium falciparum var gene are affected by subtelomeric sequences. FEBS J 2016; 284:237-257. [PMID: 27860263 DOI: 10.1111/febs.13967] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 10/12/2016] [Accepted: 11/15/2016] [Indexed: 11/30/2022]
Abstract
The Plasmodium falciparum var multigene family encodes the cytoadhesive, variant antigen PfEMP1. P. falciparum antigenic variation and cytoadhesion specificity are controlled by epigenetic switching between the single, or few, simultaneously expressed var genes. Most var genes are maintained in perinuclear clusters of heterochromatic telomeres. The active var gene(s) occupy a single, perinuclear var expression site. It is unresolved whether the var expression site forms in situ at a telomeric cluster or whether it is an extant compartment to which single chromosomes travel, thus controlling var switching. Here we show that transcription of a var gene did not require decreased colocalisation with clusters of telomeres, supporting var expression site formation in situ. However following recombination within adjacent subtelomeric sequences, the same var gene was persistently activated and did colocalise less with telomeric clusters. Thus, participation in stable, heterochromatic, telomere clusters and var switching are independent but are both affected by subtelomeric sequences. The var expression site colocalised with the euchromatic mark H3K27ac to a greater extent than it did with heterochromatic H3K9me3. H3K27ac was enriched within the active var gene promoter even when the var gene was transiently repressed in mature parasites and thus H3K27ac may contribute to var gene epigenetic memory.
Collapse
Affiliation(s)
- Michael F Duffy
- Department of Medicine, Royal Melbourne Hospital, The University of Melbourne at The Peter Doherty Institute for Infection and Immunity, Victoria, Australia.,The School of BioSciences, Bio21, The University of Melbourne, Victoria, Australia
| | - Jingyi Tang
- Department of Medicine, Royal Melbourne Hospital, The University of Melbourne at The Peter Doherty Institute for Infection and Immunity, Victoria, Australia.,The School of BioSciences, Bio21, The University of Melbourne, Victoria, Australia
| | - Fransisca Sumardy
- Department of Medicine, Royal Melbourne Hospital, The University of Melbourne at The Peter Doherty Institute for Infection and Immunity, Victoria, Australia.,The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
| | - Hanh H T Nguyen
- Department of Medicine, Royal Melbourne Hospital, The University of Melbourne at The Peter Doherty Institute for Infection and Immunity, Victoria, Australia.,The School of BioSciences, Bio21, The University of Melbourne, Victoria, Australia
| | - Shamista A Selvarajah
- Department of Medicine, Royal Melbourne Hospital, The University of Melbourne at The Peter Doherty Institute for Infection and Immunity, Victoria, Australia.,The School of BioSciences, Bio21, The University of Melbourne, Victoria, Australia
| | - Gabrielle A Josling
- Department of Medicine, Royal Melbourne Hospital, The University of Melbourne at The Peter Doherty Institute for Infection and Immunity, Victoria, Australia.,Department of Biochemistry and Molecular Biology, The Pennsylvania State University, State College, PA, USA
| | - Karen P Day
- The School of BioSciences, Bio21, The University of Melbourne, Victoria, Australia
| | - Michaela Petter
- Department of Medicine, Royal Melbourne Hospital, The University of Melbourne at The Peter Doherty Institute for Infection and Immunity, Victoria, Australia.,The School of BioSciences, Bio21, The University of Melbourne, Victoria, Australia
| | - Graham V Brown
- The Nossal Institute for Global Health, The University of Melbourne, Victoria, Australia
| |
Collapse
|
23
|
Jackson AP. Gene family phylogeny and the evolution of parasite cell surfaces. Mol Biochem Parasitol 2016; 209:64-75. [DOI: 10.1016/j.molbiopara.2016.03.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 03/18/2016] [Accepted: 03/19/2016] [Indexed: 11/30/2022]
|
24
|
Duffy MF, Noviyanti R, Tsuboi T, Feng ZP, Trianty L, Sebayang BF, Takashima E, Sumardy F, Lampah DA, Turner L, Lavstsen T, Fowkes FJI, Siba P, Rogerson SJ, Theander TG, Marfurt J, Price RN, Anstey NM, Brown GV, Papenfuss AT. Differences in PfEMP1s recognized by antibodies from patients with uncomplicated or severe malaria. Malar J 2016; 15:258. [PMID: 27149991 PMCID: PMC4858840 DOI: 10.1186/s12936-016-1296-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 04/15/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) variants are encoded by var genes and mediate pathogenic cytoadhesion and antigenic variation in malaria. PfEMP1s can be broadly divided into three principal groups (A, B and C) and they contain conserved arrangements of functional domains called domain cassettes. Despite their tremendous diversity there is compelling evidence that a restricted subset of PfEMP1s is expressed in severe disease. In this study antibodies from patients with severe and uncomplicated malaria were compared for differences in reactivity with a range of PfEMP1s to determine whether antibodies to particular PfEMP1 domains were associated with severe or uncomplicated malaria. METHODS Parts of expressed var genes in a severe malaria patient were identified by RNAseq and several of these partial PfEMP1 domains were expressed together with others from laboratory isolates. Antibodies from Papuan patients to these parts of multiple PfEMP1 proteins were measured. RESULTS Patients with uncomplicated malaria were more likely to have antibodies that recognized PfEMP1 of Group C type and recognized a broader repertoire of group A and B PfEMP1s than patients with severe malaria. CONCLUSION These data suggest that exposure to a broad range of group A and B PfEMP1s is associated with protection from severe disease in Papua, Indonesia.
Collapse
Affiliation(s)
- Michael F. Duffy
- />Department of Medicine, Royal Melbourne Hospital, The University of Melbourne, The Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria Australia
| | - Rintis Noviyanti
- />The Eijkman Institute for Molecular Biology, Jakarta, Indonesia
| | - Takafumi Tsuboi
- />Division of Malaria Research, Proteo-Science Center, Ehime University, Matsuyama, Ehime Japan
| | - Zhi-Ping Feng
- />Bioinformatics Division, The Walter & Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- />Department of Medical Biology, University of Melbourne, Parkville, Victoria Australia
| | - Leily Trianty
- />The Eijkman Institute for Molecular Biology, Jakarta, Indonesia
| | - Boni F. Sebayang
- />The Eijkman Institute for Molecular Biology, Jakarta, Indonesia
| | - Eizo Takashima
- />Division of Malaria Research, Proteo-Science Center, Ehime University, Matsuyama, Ehime Japan
| | - Fransisca Sumardy
- />Department of Medicine, Royal Melbourne Hospital, The University of Melbourne, The Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria Australia
| | - Daniel A. Lampah
- />Timika Malaria Research Program, Papuan Health and Community Development Foundation, Timika, Papua Indonesia
| | - Louise Turner
- />Centre for Medical Parasitology, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Lavstsen
- />Centre for Medical Parasitology, University of Copenhagen, Copenhagen, Denmark
| | | | - Peter Siba
- />The Papua New Guinea Institute for Medical Research, Madang, Papua New Guinea
| | - Stephen J. Rogerson
- />Department of Medicine, Royal Melbourne Hospital, The University of Melbourne, The Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria Australia
| | - Thor G. Theander
- />Centre for Medical Parasitology, University of Copenhagen, Copenhagen, Denmark
| | - Jutta Marfurt
- />Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, NT Australia
| | - Ric N. Price
- />Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, NT Australia
- />Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Nicholas M. Anstey
- />Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, NT Australia
| | - Graham V. Brown
- />The Nossal Institute for Global Health, The University of Melbourne, Parkville, Victoria Australia
| | - Anthony T. Papenfuss
- />Bioinformatics Division, The Walter & Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- />Department of Medical Biology, University of Melbourne, Parkville, Victoria Australia
- />Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia
- />Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria Australia
| |
Collapse
|
25
|
Kumar M, Srinivas V, Patankar S. Upstream AUGs and upstream ORFs can regulate the downstream ORF in Plasmodium falciparum. Malar J 2015; 14:512. [PMID: 26692187 PMCID: PMC4687322 DOI: 10.1186/s12936-015-1040-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2015] [Accepted: 12/08/2015] [Indexed: 11/10/2022] Open
Abstract
Background Upstream open reading frames (uORFs) and upstream AUGs (uAUGs) can regulate the translation of downstream ORFs. The AT rich genome of Plasmodium falciparum, due to the higher AT content of start and stop codons, has the potential to give rise to a large number of uORFs and uAUGs that may affect expression of their flanking ORFs. Methods A bioinformatics approach was used to detect uATGs associated with different genes in the parasite. To study the effect of some of these uAUGs on the expression of the downstream ORF, promoters and 5′ leaders containing uAUGs and uORFs were cloned upstream of a luciferase reporter gene. Luciferase assays were carried out in transient transfection experiments to assess the effects of uAUGs and mutations on reporter expression. Results The average number of uATGs and uORFs seen in P. falciparum coding sequences (CDS) is expectedly high compared to other less biased genomes. Certain genes, including the var gene family contain the maximum number of uATGs and uORFs in the parasite. They possess ~5 times more uORFs and ~4.5 times more uAUGs within 100 bases upstream of the start codons than other CDS of the parasite. A 60 bp upstream region containing three ORFs and five ATGs from var gene PF3D7_0400100 and a gene of unknown function (PF3D7_0517100) when cloned upstream of the luciferase start codon, driven by the hsp86 promoter, resulted in loss of luciferase activity. This was restored when all the ATGs present in the −60 bp were mutated to TTGs. Point mutations in the ATGs showed that even one AUG was sufficient to repress the luciferase gene. Conclusions Overall, this work indicates that the P. falciparum genome has a large number of uATGs and uORFs that can repress the expression of flanking ORFs. The role of AUGs in translation initiation suggests that this repression is mediated by preventing the translation initiation complex from reaching the main AUG of the downstream ORF. How the P. falciparum ribosome is able to bypass these uAUGs and uORFs for highly expressed genes remains a question for future research. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-1040-5) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Mayank Kumar
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
| | - Vivek Srinivas
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
| | - Swati Patankar
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
| |
Collapse
|
26
|
Ukaegbu UE, Zhang X, Heinberg AR, Wele M, Chen Q, Deitsch KW. A Unique Virulence Gene Occupies a Principal Position in Immune Evasion by the Malaria Parasite Plasmodium falciparum. PLoS Genet 2015; 11:e1005234. [PMID: 25993442 PMCID: PMC4437904 DOI: 10.1371/journal.pgen.1005234] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 04/21/2015] [Indexed: 12/13/2022] Open
Abstract
Mutually exclusive gene expression, whereby only one member of a multi-gene family is selected for activation, is used by the malaria parasite Plasmodium falciparum to escape the human immune system and perpetuate long-term, chronic infections. A family of genes called var encodes the chief antigenic and virulence determinant of P. falciparum malaria. var genes are transcribed in a mutually exclusive manner, with switching between active genes resulting in antigenic variation. While recent work has shed considerable light on the epigenetic basis for var gene activation and silencing, how switching is controlled remains a mystery. In particular, switching seems not to be random, but instead appears to be coordinated to result in timely activation of individual genes leading to sequential waves of antigenically distinct parasite populations. The molecular basis for this apparent coordination is unknown. Here we show that var2csa, an unusual and highly conserved var gene, occupies a unique position within the var gene switching hierarchy. Induction of switching through the destabilization of var specific chromatin using both genetic and chemical methods repeatedly led to the rapid and exclusive activation of var2csa. Additional experiments demonstrated that these represent "true" switching events and not simply de-silencing of the var2csa promoter, and that activation is limited to the unique locus on chromosome 12. Combined with translational repression of var2csa transcripts, frequent "default" switching to this locus and detection of var2csa untranslated transcripts in non-pregnant individuals, these data suggest that var2csa could play a central role in coordinating switching, fulfilling a prediction made by mathematical models derived from population switching patterns. These studies provide the first insights into the mechanisms by which var gene switching is coordinated as well as an example of how a pharmacological agent can disrupt antigenic variation in Plasmodium falciparum.
Collapse
Affiliation(s)
- Uchechi E. Ukaegbu
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Xu Zhang
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
- Key Laboratory of Zoonosis, College of Veterinary Medicine, Jilin University, Xi An Da Lu, Changchun, China
| | - Adina R. Heinberg
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Mamadou Wele
- University of Sciences Techniques and Technologies of Bamako, Bamako, Mali
| | - Qijun Chen
- Key Laboratory of Zoonosis, College of Veterinary Medicine, Jilin University, Xi An Da Lu, Changchun, China
| | - Kirk W. Deitsch
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| |
Collapse
|
27
|
Boudová S, Cohee LM, Kalilani-Phiri L, Thesing PC, Kamiza S, Muehlenbachs A, Taylor TE, Laufer MK. Pregnant women are a reservoir of malaria transmission in Blantyre, Malawi. Malar J 2014; 13:506. [PMID: 25520145 PMCID: PMC4301453 DOI: 10.1186/1475-2875-13-506] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Accepted: 12/09/2014] [Indexed: 11/16/2022] Open
Abstract
Background During pregnancy, women living in malaria-endemic regions are at increased risk of malaria infection and can harbour chronic placental infections. Intermittent preventive treatment with sulphadoxine-pyrimethamine (SP-IPTp) is administered to reduce malaria morbidity. It was hypothesized that the presence of placental malaria infection and SP-IPTp use would increase the risk of peripheral blood gametocytes, the parasite stage that is transmissible to mosquitoes. This would suggest that pregnant women may be important reservoirs of malaria transmission. Methods Light microscopy was used to assess peripheral gametocytaemia in pregnant women enrolled in a longitudinal, observational study in Blantyre, Malawi to determine the association between placental malaria and maternal gametocytaemia. The relationship between SP-IPTp and gametocytaemia was also examined. Results 2,719 samples from 448 women were analysed and 32 episodes of microscopic gametocytaemia were detected in 27 women. At the time of enrolment 22 of 446 women (4.9%) had gametocytaemia and of the 341 women for whom there was sufficient sampling to analyse infection over the entire course of pregnancy, 27 (7.9%) were gametocytaemic at least once. Gametocytaemia at enrolment was associated with placental malaria, defined as malaria pigment or parasites detected by histology or qPCR, respectively (OR: 32.4, 95% CI: 4.2-250.2), but was not associated with adverse maternal or foetal outcomes. Administration of SP-IPTp did not affect gametocyte clearance or release into peripheral blood. Conclusions Gametocytaemia is present in 5% of pregnant women at their first antenatal visit and associated with placental malaria. SP-IPTp does not alter the risk of gametocytaemia. These data suggest that pregnant women are a significant reservoir of gametocyte transmission and should not be overlooked in elimination efforts. Interventions targeting this population would benefit from reaching women prior to first antenatal visit.
Collapse
Affiliation(s)
- Sarah Boudová
- Center for Vaccine Development, School of Medicine, University of Maryland, Baltimore, MD, USA.
| | | | | | | | | | | | | | | |
Collapse
|
28
|
Doritchamou J, Sossou-tchatcha S, Cottrell G, Moussiliou A, Hounton Houngbeme C, Massougbodji A, Deloron P, Ndam NT. Dynamics in the cytoadherence phenotypes of Plasmodium falciparum infected erythrocytes isolated during pregnancy. PLoS One 2014; 9:e98577. [PMID: 24905223 PMCID: PMC4048182 DOI: 10.1371/journal.pone.0098577] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 05/05/2014] [Indexed: 11/19/2022] Open
Abstract
Pregnant women become susceptible to malaria infection despite their acquired immunity to this disease from childhood. The placental sequestration of Plasmodium falciparum infected erythrocytes (IE) is the major feature of malaria during pregnancy, due to ability of these parasites to bind chondroitin sulfate A (CSA) in the placenta through the VAR2CSA protein that parasites express on the surface of IE. We collected parasites at different times of pregnancy and investigated the adhesion pattern of freshly collected isolates on the three well described host receptors (CSPG, CD36 and ICAM-1). Var genes transcription profile and VAR2CSA surface-expression were assessed in these isolates. Although adhesion of IE to CD36 and ICAM-1 was observed in some isolates, CSA-adhesion was the predominant binding feature in all isolates analyzed. Co-existence in the peripheral blood of several adhesion phenotypes in early pregnancy isolates was observed, a diversity that gradually tightens with gestational age in favour of the CSA-adhesion phenotype. Infections occurring in primigravidae were often by parasites that adhered more to CSA than those from multigravidae. Data from this study further emphasize the specificity of CSA adhesion and VAR2CSA expression by parasites responsible for pregnancy malaria, while drawing attention to the phenotypic complexity of infections occurring early in pregnancy as well as in multigravidae.
Collapse
Affiliation(s)
- Justin Doritchamou
- PRES Sorbonne Paris Cité, Faculté de Pharmacie, Université Paris Descartes, Paris, France
- UMR216 Mère et enfant face aux infections tropicales, Institut de Recherche pour le Développement, Paris, France
- Centre d'Etude et de Recherche sur le paludisme associé à la Grossesse et à l'Enfance, Université d'Abomey-Calavi, Cotonou, Benin
| | - Sylvain Sossou-tchatcha
- Centre d'Etude et de Recherche sur le paludisme associé à la Grossesse et à l'Enfance, Université d'Abomey-Calavi, Cotonou, Benin
| | - Gilles Cottrell
- PRES Sorbonne Paris Cité, Faculté de Pharmacie, Université Paris Descartes, Paris, France
- UMR216 Mère et enfant face aux infections tropicales, Institut de Recherche pour le Développement, Paris, France
| | - Azizath Moussiliou
- UMR216 Mère et enfant face aux infections tropicales, Institut de Recherche pour le Développement, Paris, France
- ED Physiologie Physiopathologie et thérapeutique Sorbone Université, Université Pierre Marie Curie, Paris, France
| | | | - Achille Massougbodji
- Centre d'Etude et de Recherche sur le paludisme associé à la Grossesse et à l'Enfance, Université d'Abomey-Calavi, Cotonou, Benin
| | - Philippe Deloron
- PRES Sorbonne Paris Cité, Faculté de Pharmacie, Université Paris Descartes, Paris, France
- UMR216 Mère et enfant face aux infections tropicales, Institut de Recherche pour le Développement, Paris, France
| | - Nicaise Tuikue Ndam
- PRES Sorbonne Paris Cité, Faculté de Pharmacie, Université Paris Descartes, Paris, France
- UMR216 Mère et enfant face aux infections tropicales, Institut de Recherche pour le Développement, Paris, France
- Centre d'Etude et de Recherche sur le paludisme associé à la Grossesse et à l'Enfance, Université d'Abomey-Calavi, Cotonou, Benin
- * E-mail:
| |
Collapse
|
29
|
Genetic diversity of VAR2CSA ID1-DBL2Xb in worldwide Plasmodium falciparum populations: impact on vaccine design for placental malaria. INFECTION GENETICS AND EVOLUTION 2014; 25:81-92. [PMID: 24768682 DOI: 10.1016/j.meegid.2014.04.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 04/11/2014] [Accepted: 04/12/2014] [Indexed: 12/18/2022]
Abstract
In placental malaria (PM), sequestration of infected erythrocytes in the placenta is mediated by an interaction between VAR2CSA, a Plasmodium falciparum protein expressed on erythrocytes, and chondroitin sulfate A (CSA) on syncytiotrophoblasts. Recent works have identified ID1-DBL2Xb as the minimal CSA-binding region within VAR2CSA able to induce strong protective immunity, making it the leading candidate for the development of a vaccine against PM. Assessing the existence of population differences in the distribution of ID1-DBL2Xb polymorphisms is of paramount importance to determine whether geographic diversity must be considered when designing a candidate vaccine based on this fragment. In this study, we examined patterns of sequence variation of ID1-DBL2Xb in a large collection of P. falciparum field isolates (n=247) from different malaria-endemic areas, including Africa (Benin, Senegal, Cameroon and Madagascar), Asia (Cambodia), Oceania (Papua New Guinea), and Latin America (Peru). Detection of variants and estimation of their allele frequencies were performed using next-generation sequencing of DNA pools. A considerable amount of variation was detected along the whole gene segment, suggesting that several allelic variants may need to be included in a candidate vaccine to achieve broad population coverage. However, most sequence variants were common and extensively shared among worldwide parasite populations, demonstrating long term persistence of those polymorphisms, probably maintained through balancing selection. Therefore, a vaccine mixture including such stable antigen variants will be putatively applicable and efficacious in all world regions where malaria occurs. Despite similarity in ID1-DBL2Xb allele repertoire across geographic areas, several peaks of strong population differentiation were observed at specific polymorphic loci, pointing out putative targets of humoral immunity subject to positive immune selection.
Collapse
|
30
|
MyD88 signaling is directly involved in the development of murine placental malaria. Infect Immun 2013; 82:830-8. [PMID: 24478096 DOI: 10.1128/iai.01288-13] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Malaria is a widespread infectious disease caused by the parasite Plasmodium. During pregnancy, malaria infection leads to a range of complications that can affect both the mother and fetus, including stillbirth, infant mortality, and low birth weight. In this study, we utilized a mouse model of placental malaria (PM) infection to determine the importance of the protein MyD88 in the host immune response to Plasmodium during pregnancy. Initially, we demonstrated that Plasmodium berghei NK65GFP adhered to placental tissue via chondroitin sulfate A and induced PM in mice with a C57BL/6 genetic background. To evaluate the involvement of MyD88 in the pathology of PM, we performed a histopathological analysis of placentas obtained from MyD88(-/-) and wild-type (WT) mice following infection on the 19th gestational day. Our data demonstrated that the detrimental placental alterations observed in the infected mice were correlated with the expression of MyD88. Moreover, in the absence of this protein, production of interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α) was significantly reduced in the infected mice. More importantly, in contrast to fetuses from infected WT mice, which exhibited a reduction in body weight, the fetuses from infected MyD88(-/-) mice did not display significant weight loss compared to their noninfected littermates. In addition, we observed a decrement of maternal care associated with malaria infection, which was attenuated in the MyD88-deficient mice. Collectively, the results of this study illustrate the pivotal importance of the MyD88 signaling pathway in the pathogenesis of placental malaria, thus presenting new possibilities for targeting MyD88 in therapeutic interventions.
Collapse
|
31
|
Castillo P, Menéndez C, Mayor A, Carrilho C, Ismail M, Lorenzoni C, Machungo F, Osman N, Quintó L, Romagosa C, Dobaño C, Alonso P, Ordi J. Massive Plasmodium falciparum visceral sequestration: a cause of maternal death in Africa. Clin Microbiol Infect 2013; 19:1035-41. [DOI: 10.1111/1469-0691.12068] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Revised: 10/04/2012] [Accepted: 10/04/2012] [Indexed: 11/30/2022]
|
32
|
Bancells C, Deitsch KW. A molecular switch in the efficiency of translation reinitiation controls expression of var2csa, a gene implicated in pregnancy-associated malaria. Mol Microbiol 2013; 90:472-88. [PMID: 23980802 DOI: 10.1111/mmi.12379] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2013] [Indexed: 12/16/2022]
Abstract
Plasmodium falciparum malaria parasites export the protein PfEMP1 to the surface of infected erythrocytes, enabling them to adhere to receptors in the microvasculature and thereby avoid clearance by the spleen. The gene var2csa encodes the form of PfEMP1 that binds specifically within the placenta, causing pregnancy-associated malaria, and appears to not be expressed in the absence of a placenta. We previously described an upstream open reading frame (uORF) that is responsible for repression of translation of the downstream ORF (dORF) that encodes VAR2CSA, thus keeping the gene silent when parasites infect non-pregnant individuals. To elucidate the molecular mechanism by which this repression is overcome during pregnancy, we stably transformed parasites with reporter gene constructs designed to detect switches in the efficiency of dORF translation. We found that proper regulation of switching relies on two separate components, (i) active translation of the uORF and (ii) sequence-specific characteristics of the surrounding transcript, which together control the ability of the ribosome complex to reinitiate a second round of translation and thus express VAR2CSA. These results provide the first details of a molecular switch that allows parasites take advantage of the unique niche provided by the placenta.
Collapse
Affiliation(s)
- Cristina Bancells
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY, 10065, USA
| | | |
Collapse
|
33
|
Doritchamou J, Bigey P, Nielsen MA, Gnidehou S, Ezinmegnon S, Burgain A, Massougbodji A, Deloron P, Salanti A, Ndam NT. Differential adhesion-inhibitory patterns of antibodies raised against two major variants of the NTS-DBL2X region of VAR2CSA. Vaccine 2013; 31:4516-22. [PMID: 23933341 DOI: 10.1016/j.vaccine.2013.07.072] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 07/19/2013] [Accepted: 07/29/2013] [Indexed: 11/18/2022]
Abstract
BACKGROUND VAR2CSA is a large polymorphic Plasmodium falciparum protein expressed on infected erythrocytes (IE) that allows their binding in the placenta, thus precipitating placental malaria (PM). The N-terminal part of VAR2CSA that contains the binding site to placental chondroitin sulfate A (CSA) is currently recognized as the most attractive region for vaccine development. An ultimate challenge is to define epitopes in this region that induce a broad cross-reactive adhesion inhibitory antibody response. METHODS Based on phylogenetic data that identified a dimorphic sequence motif in the VAR2CSA DBL2X, we raised antibodies against the NTS-DBL2X constructs containing one sequence or the other (3D7 and FCR3) and tested their functional properties on P. falciparum isolates from pregnant women and on laboratory-adapted strains. RESULTS The CSA binding inhibitory capacity of the antibodies induced varied from one parasite isolate to another (range, 10%–100%), but the combined analysis of individual activity highlighted a broader functionality that increased the total number of isolates inhibited. Interestingly, the differential inhibitory effect of the antibodies observed on field isolates resulted in significant inhibition of all field isolates tested, suggesting that optimal inhibitory spectrum on field isolates from pregnant women might be achieved with antibodies targeting limited variants of the N-terminal VAR2CSA. CONCLUSIONS Our findings indicate that the NTS-DBL2X region of VAR2CSA can elicit strain-transcending anti-adhesion antibodies and suggest that the combination of the two major variants used here could represent the basis for an effective bivalent VAR2CSA-based vaccine.
Collapse
Affiliation(s)
- Justin Doritchamou
- PRES Sorbonne Paris Cité, Faculté de Pharmacie, Université Paris Descartes, France; Institut de Recherche pour le Développement, UMR216 Mère et enfant face aux infections tropicales, Paris, France; Centre d'Etude et de Recherche sur le paludisme associé à la Grossesse et à l'Enfance, Université d'Abomey-Calavi, Cotonou, Benin
| | | | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Rovira-Vallbona E, Monteiro I, Bardají A, Serra-Casas E, Neafsey DE, Quelhas D, Valim C, Alonso P, Dobaño C, Ordi J, Menéndez C, Mayor A. VAR2CSA signatures of high Plasmodium falciparum parasitemia in the placenta. PLoS One 2013; 8:e69753. [PMID: 23936092 PMCID: PMC3723727 DOI: 10.1371/journal.pone.0069753] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Accepted: 06/11/2013] [Indexed: 11/18/2022] Open
Abstract
Plasmodium falciparum infected erythrocytes (IE) accumulate in the placenta through the interaction between Duffy-binding like (DBL) domains of parasite-encoded ligand VAR2CSA and chondroitin sulphate-A (CSA) receptor. Polymorphisms in these domains, including DBL2X and DBL3X, may affect their antigenicity or CSA-binding affinity, eventually increasing parasitemia and its adverse effects on pregnancy outcomes. A total of 373 DBL2X and 328 DBL3X sequences were obtained from transcripts of 20 placental isolates infecting Mozambican women, resulting in 176 DBL2X and 191 DBL3X unique sequences at the protein level. Sequence alignments were divided in segments containing combinations of correlated polymorphisms and the association of segment sequences with placental parasite density was tested using Bonferroni corrected regression models, taking into consideration the weight of each sequence in the infection. Three DBL2X and three DBL3X segments contained signatures of high parasite density (P<0.003) that were highly prevalent in the parasite population (49-91%). Identified regions included a flexible loop that contributes to DBL3X-CSA interaction and two DBL3X motifs with evidence of positive natural selection. Limited antibody responses against signatures of high parasite density among malaria-exposed pregnant women could not explain the increased placental parasitemia. These results suggest that a higher binding efficiency to CSA rather than reduced antigenicity might provide a biological advantage to parasites with high parasite density signatures in VAR2CSA. Sequences contributing to high parasitemia may be critical for the functional characterization of VAR2CSA and the development of tools against placental malaria.
Collapse
MESH Headings
- Adolescent
- Amino Acid Sequence
- Antibodies, Protozoan/blood
- Antibodies, Protozoan/immunology
- Antigens, Protozoan/chemistry
- Antigens, Protozoan/genetics
- Antigens, Protozoan/metabolism
- Binding Sites
- Chondroitin Sulfates/chemistry
- Chondroitin Sulfates/metabolism
- Erythrocytes/metabolism
- Erythrocytes/parasitology
- Female
- Humans
- Malaria, Falciparum/immunology
- Malaria, Falciparum/metabolism
- Malaria, Falciparum/parasitology
- Malaria, Falciparum/pathology
- Molecular Docking Simulation
- Molecular Sequence Data
- Placenta/immunology
- Placenta/parasitology
- Placenta/pathology
- Plasmodium falciparum/chemistry
- Plasmodium falciparum/genetics
- Plasmodium falciparum/metabolism
- Pregnancy
- Pregnancy Complications, Parasitic/immunology
- Pregnancy Complications, Parasitic/metabolism
- Pregnancy Complications, Parasitic/parasitology
- Pregnancy Complications, Parasitic/pathology
- Protein Binding
- Protein Structure, Tertiary
- Protozoan Proteins/chemistry
- Protozoan Proteins/genetics
- Protozoan Proteins/metabolism
- Transcriptome
- Young Adult
Collapse
Affiliation(s)
- Eduard Rovira-Vallbona
- Barcelona Centre for International Health Research (CRESIB, Hospital Clínic-Universitat de Barcelona), Barcelona, Spain
| | - Isadora Monteiro
- Barcelona Centre for International Health Research (CRESIB, Hospital Clínic-Universitat de Barcelona), Barcelona, Spain
| | - Azucena Bardají
- Barcelona Centre for International Health Research (CRESIB, Hospital Clínic-Universitat de Barcelona), Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Elisa Serra-Casas
- Barcelona Centre for International Health Research (CRESIB, Hospital Clínic-Universitat de Barcelona), Barcelona, Spain
| | | | - Diana Quelhas
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Clarissa Valim
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, United States of America
| | - Pedro Alonso
- Barcelona Centre for International Health Research (CRESIB, Hospital Clínic-Universitat de Barcelona), Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Carlota Dobaño
- Barcelona Centre for International Health Research (CRESIB, Hospital Clínic-Universitat de Barcelona), Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Jaume Ordi
- Barcelona Centre for International Health Research (CRESIB, Hospital Clínic-Universitat de Barcelona), Barcelona, Spain
- Department of Pathology, Hospital Clínic-Universitat de Barcelona, Barcelona, Spain
| | - Clara Menéndez
- Barcelona Centre for International Health Research (CRESIB, Hospital Clínic-Universitat de Barcelona), Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Alfredo Mayor
- Barcelona Centre for International Health Research (CRESIB, Hospital Clínic-Universitat de Barcelona), Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
- * E-mail:
| |
Collapse
|
35
|
Gangnard S, Badaut C, Ramboarina S, Baron B, Ramdani T, Gamain B, Deloron P, Lewit-Bentley A, Bentley GA. Structural and immunological correlations between the variable blocks of the VAR2CSA domain DBL6ε from two Plasmodium falciparum parasite lines. J Mol Biol 2013; 425:1697-711. [PMID: 23429057 DOI: 10.1016/j.jmb.2013.02.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Revised: 01/23/2013] [Accepted: 02/11/2013] [Indexed: 11/29/2022]
Abstract
Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1), a family of adhesins of the falciparum species of the malaria parasite, is exposed on the surface of the infected erythrocyte. In general, only one PfEMP1 variant is expressed at a time but switching between variants occurs, changing both host-cell receptor specificity and serotype. The PfEMP1 variant VAR2CSA causes sequestration of infected erythrocytes in the intervillous spaces of the placenta via the glycosaminoglycan chondroitin sulfate A. This leads to pregnancy-associated malaria, which has severe consequences for the fetus and mother. The extracellular region of VAR2CSA comprises six DBL (Duffy-binding-like) domains and a single CIDR (cysteine-rich inter-domain region) domain. The C-terminal domain DBL6ε, the most polymorphic domain of VAR2CSA, has seven regions of high variability termed variable blocks (VBs). Here we have determined the crystal structure of DBL6ε from the FCR3 parasite line and have compared it with the previously determined structure of that from the 3D7 line. We found significant differences particularly in the N-terminal region, which contains the first VB (VB1). Although DBL6ε is the most variable VAR2CSA domain, DBL6ε-FCR3 and DBL6ε-3D7 react with IgG purified from immune sera of pregnant women. Furthermore, IgG purified on one domain cross-reacts with the other, confirming the presence of cross-reactive epitopes. We also examined reactivity of immune sera to the four least variable VB (VB1, VB2, VB4 and VB5) using peptides with the consensus sequence closest, in turn, to the FCR3 or 3D7 domain. These results provide new molecular insights into immune escape by parasites expressing the VAR2CSA variant.
Collapse
Affiliation(s)
- Stéphane Gangnard
- Unité d'Immunologie Structurale, Département de Biologie Structurale et Chimie, Institut Pasteur, 25 rue du Docteur Roux, 75724 Paris, France
| | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Plasmodium falciparum variability and immune evasion proceed from antigenicity of consensus sequences from DBL6ε; generalization to all DBL from VAR2CSA. PLoS One 2013; 8:e54882. [PMID: 23372786 PMCID: PMC3555990 DOI: 10.1371/journal.pone.0054882] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Accepted: 12/17/2012] [Indexed: 11/18/2022] Open
Abstract
We studied all consensus sequences within the four least ‘variable blocks’ (VB) present in the DBL6ε domain of VAR2CSA, the protein involved in the adhesion of infected red blood cells by Plasmodium falciparum that causes the Pregnancy-Associated Malaria (PAM). Characterising consensus sequences with respect to recognition of antibodies and percentage of responders among pregnant women living in areas where P. falciparum is endemic allows the identification of the most antigenic sequences within each VB. When combining these consensus sequences among four serotypes from VB1 or VB5, the most often recognized ones are expected to induce pan-reactive antibodies recognizing VAR2CSA from all plasmodial strains. These sequences are of main interest in the design of an immunogenic molecule. Using a similar approach than for DBL6ε, we studied the five other DBL and the CIDRpam from VAR2CSA, and again identified VB segments with highly conserved consensus sequences. In addition, we identified consensus sequences in other var genes expressed by non-PAM parasites. This finding paves the way for vaccine design against other pathologies caused by P. falciparum.
Collapse
|
37
|
Doritchamou J, Bertin G, Moussiliou A, Bigey P, Viwami F, Ezinmegnon S, Fievet N, Massougbodji A, Deloron P, Tuikue Ndam N. First-trimester Plasmodium falciparum infections display a typical "placental" phenotype. J Infect Dis 2012; 206:1911-9. [PMID: 23045626 DOI: 10.1093/infdis/jis629] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Plasmodium falciparum-infected erythrocytes (IEs) adhere to host cell receptors, allowing parasites to sequester into deep vascular beds of various organs. This defining phenomenon of malaria pathogenesis is key to the severe clinical complications associated with cerebral and placental malaria. The principal ligand associated with the binding to chondroitin sulfate A (CSA) that allows placental sequestration of IEs is a P. falciparum erythrocyte membrane protein 1 (PfEMP1) family member encoded by the var2csa gene. METHODS Here, we investigated the transcription pattern of var genes by real-time polymerase chain reaction, the expression of VAR2CSA, protein by flow cytometry, and the CSA-binding ability of IEs collected at different stages of pregnancy using a static-based Petri dish assay. RESULTS Through comparison with the profiles of isolates from nonpregnant hosts, we report several lines of evidence showing that parasites infecting women during pregnancy preferentially express VAR2CSA protein, and that selection for the capacity to adhere to CSA via VAR2CSA expression occurs early in pregnancy. CONCLUSIONS Our data suggest that the placental tropism of P. falciparum is already established in the first trimester of pregnancy, with consequent implications for the development of the pathology associated with placental malaria.
Collapse
Affiliation(s)
- Justin Doritchamou
- PRES Sorbonne Paris Cité, Faculté de Pharmacie, Université Paris Descartes, Paris, France
| | | | | | | | | | | | | | | | | | | |
Collapse
|
38
|
Hviid L. The case for PfEMP1-based vaccines to protect pregnant women against Plasmodium falciparum malaria. Expert Rev Vaccines 2012; 10:1405-14. [PMID: 21988306 DOI: 10.1586/erv.11.113] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Vaccines are very cost-effective tools in combating infectious disease mortality and morbidity. Unfortunately, vaccines efficiently protecting against infection with malaria parasites are not available and are not likely to appear in the near future. An alternative strategy would be vaccines protecting against the disease and its consequences rather than against infection per se, by accelerating the development of the protective immunity that is normally acquired after years of exposure to malaria parasites in areas of stable transmission. This latter strategy is being energetically pursued to develop a vaccine protecting pregnant women and their offspring against mortality and morbidity caused by the accumulation of Plasmodium falciparum-infected erythrocytes in the placenta. It is based on a detailed understanding of the parasite antigen and the host receptor involved in this accumulation, as well as knowledge regarding the protective immune response that is acquired in response to placental P. falciparum infection. Nevertheless, it remains controversial in some quarters whether such a vaccine would have the desired impact, or indeed whether the strategy is meaningful. This article critically examines the relevance of several perceived obstacles to development of a vaccine against placental malaria.
Collapse
Affiliation(s)
- Lars Hviid
- Centre for Medical Parasitology, University of Copenhagen and Copenhagen University Hospital (Rigshospitalet), Copenhagen, Denmark.
| |
Collapse
|
39
|
Bordbar B, Tuikue-Ndam N, Bigey P, Doritchamou J, Scherman D, Deloron P. Identification of Id1-DBL2X of VAR2CSA as a key domain inducing highly inhibitory and cross-reactive antibodies. Vaccine 2012; 30:1343-8. [PMID: 22226864 DOI: 10.1016/j.vaccine.2011.12.065] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Revised: 12/09/2011] [Accepted: 12/13/2011] [Indexed: 11/29/2022]
Abstract
PURPOSE OF THE RESEARCH VAR2CSA is considered as the main target of protective immunity against pregnancy-associated malaria. VAR2CSA high molecular weight complicates scaling up production of VAR2CSA recombinant protein for large-scale vaccination programmes. We previously demonstrated that antibodies induced by NTS-DBL1X-Id1-DBL2X efficiently block parasite binding to CSA in a similar manner to antibodies induced by the full-length extracellular part of VAR2CSA. In order to identifying the shortest fragment of VAR2CSA carrying major protective epitopes able to elicit inhibitory antibodies, we performed a refined antigenic mapping of NTS-DBL1X-Id1-DBL2X through a DNA vaccination technique. PRINCIPAL RESULTS Five single or double domains constructs encoding NTS-DBL1X, NTS-DBL1X-Id1, Id1, Id1-DBL2X and DBL2X were made and used to immunize mice. The NTS-DBL1X, NTS-DBL1X-Id1, and Id1-DBL2X fragments all raised high titer immune response, as measured by ELISA. The DBL2X fragment raised a weaker antibody titer, and the Id1 construct failed to elicit antibody. Sera from mice immunized with NTS-DBL1X or DBL2X constructs failed to block infected erythrocytes binding to CSA, whereas sera from mice immunized with NTS-DBL1X-Id1 showed partial inhibitory activity, and the Id1-DBL2X fragment elicited antisera that totally abrogated infected erythrocytes adhesion to CSA. IgG purified from Id1-DBL2X antisera showed a similar inhibitory profile than Id1-DBL2X antisera. Anti-FCR3 anti-Id1-DBL2X antibodies also efficiently block the adhesion of erythrocytes infected by the HB3 parasite line to CSA. Id1-DBL2X antisera recognized the surface of field isolates from pregnant women, and inhibited CSA-binding of all 8 isolates tested, although to a variable level. MAJOR CONCLUSIONS We raised high-titer antibodies against several parts of the protein, and identified Id1-DBL2X as the minimal VAR2CSA fragment inducing antibodies with CSA-binding inhibitory efficiency in the same range as the full-length extracellular part of VAR2CSA.
Collapse
Affiliation(s)
- Bita Bordbar
- Université Paris Descartes, Sorbonne Paris Cité, 75006 Paris, France
| | | | | | | | | | | |
Collapse
|
40
|
Bordbar B, Gnidehou S, Ndam NT, Doritchamou J, Moussiliou A, Quiviger M, Deloron P, Scherman D, Bigey P. Electroporation-mediated genetic vaccination for antigen mapping: application to Plasmodium falciparum VAR2CSA protein. Bioelectrochemistry 2011; 87:132-7. [PMID: 22265101 DOI: 10.1016/j.bioelechem.2011.12.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Revised: 11/22/2011] [Accepted: 12/21/2011] [Indexed: 01/28/2023]
Abstract
Genetic vaccination, consisting in delivering a genetically engineered plasmid DNA by a non-viral vector or technique into a tissue, is currently of great interest. New delivery technique including DNA transfer by electroporation recently greatly improved the potency of this concept. Because it avoids the step of producing a recombinant protein, it is particularly of use in studying the immunogenic properties of large proteins. Here we describe the use of electroporation mediated DNA immunization to identify important protective epitopes from the large VAR2CSA protein from Plasmodium falciparum implicated in the pathology of placental malaria. Immunizing mice and rabbit with DNA plasmids encoding different fragments of VAR2CSA leads to high titer antisera. Moreover an N-terminal region of the protein was found to induce protective functional antibodies.
Collapse
Affiliation(s)
- Bita Bordbar
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Bigey P, Gnidehou S, Doritchamou J, Quiviger M, Viwami F, Couturier A, Salanti A, Nielsen MA, Scherman D, Deloron P, Tuikue Ndam N. The NTS-DBL2X region of VAR2CSA induces cross-reactive antibodies that inhibit adhesion of several Plasmodium falciparum isolates to chondroitin sulfate A. J Infect Dis 2011; 204:1125-33. [PMID: 21881129 DOI: 10.1093/infdis/jir499] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Binding to chondroitin sulfate A by VAR2CSA, a parasite protein expressed on infected erythrocytes, allows placental sequestration of Plasmodium falciparum-infected erythrocytes. This leads to severe consequences such as maternal anemia, stillbirths, and intrauterine growth retardation. The latter has been clearly associated to increased morbidity and mortality of the infants. Acquired anti-VAR2CSA antibodies have been associated with improved pregnancy outcomes, suggesting a vaccine could prevent the syndrome. However, identifying functionally important regions in the large VAR2CSA protein is difficult. METHODS Using genetic immunization, we raised polyclonal antisera against overlapping segments of VAR2CSA in mice and rabbits. The adhesion-inhibition capacities of induced antisera and of specific antibodies purified from plasma of malaria-exposed pregnant women were assessed on laboratory-adapted parasite lines and field isolates expressing VAR2CSA. Competition enzyme-linked immunosorbent assay (ELISA) was employed to analyze functional resemblance between antibodies induced in animals and those naturally acquired by immune multigravidae. RESULTS Antibodies targeting the N-terminal sequence (NTS) up to DBL2X (NTS-DBL2X) efficiently blocked parasite adhesion to chondroitin sulfate A in a manner similar to that of antibodies raised against the entire VAR2CSA extracellular domain. Interestingly, naturally acquired antibodies and those induced by vaccination against NTS-DBL2X target overlapping strain-transcendent anti-adhesion epitopes. CONCLUSIONS This study highlights an important step achieved toward development of a protective vaccine against placental malaria.
Collapse
Affiliation(s)
- Pascal Bigey
- Unité de Pharmacologie Chimique et Génétique, Université Paris Descartes, ENSCP Chimie ParisTech, CNRS UMR8151, Inserm U 1022, France
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
42
|
Rovira-Vallbona E, Dobaño C, Bardají A, Cisteró P, Romagosa C, Serra-Casas E, Quintó L, Bassat Q, Sigaúque B, Alonso PL, Ordi J, Menéndez C, Mayor A. Transcription of var genes other than var2csa in Plasmodium falciparum parasites infecting Mozambican pregnant women. J Infect Dis 2011; 204:27-35. [PMID: 21628655 DOI: 10.1093/infdis/jir217] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Increased susceptibility to Plasmodium falciparum infection during pregnancy has been attributed to the accumulation of infected erythrocytes in the placenta. This phenomenon is mediated by a var gene coding for VAR2CSA, which adheres to chondroitin sulphate A. However, the contribution of parasites transcribing other var genes to maternal infections has not been well characterized. METHODS Transcription of var2csa and var groups A, B, and C was measured by real-time polymerase chain reaction in 30 placental and 21 peripheral P. falciparum isolates from pregnant women and in 42 isolates from nonpregnant adults and children. Associations of infections with non-var2csa isolates with maternal parasitemia and immune responses were assessed. RESULTS Placental parasites showed the highest levels of var2csa. ABC var genes were transcribed by 20 (67%) of 30 placental isolates and were associated with higher parasitemia compared with infections by parasites only transcribing var2csa (P = .004). Peripheral isolates from pregnant women transcribed ABC var genes at levels similar to those of parasites infecting nonpregnant adults with clinical malaria (P[varA] = .420, P[varB] = .808, and P[varC] = .619). CONCLUSIONS Transcripts of var2csa are abundant in pregnancy-associated P. falciparum infections; however, ABC var types are also common, especially in peripheral blood, with transcription levels similar to those of infections out of pregnancy. These findings are of interest for the design of malaria vaccines for pregnant women.
Collapse
Affiliation(s)
- Eduard Rovira-Vallbona
- Barcelona Centre for International Health Research, Hospital Clínic-Universitat de Barcelona, Barcelona, Spain
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
43
|
Var2CSA minimal CSA binding region is located within the N-terminal region. PLoS One 2011; 6:e20270. [PMID: 21625526 PMCID: PMC3098292 DOI: 10.1371/journal.pone.0020270] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Accepted: 04/17/2011] [Indexed: 11/24/2022] Open
Abstract
Var2CSA, a key molecule linked with pregnancy-associated malaria (PAM), causes sequestration of Plasmodium falciparum infected erythrocytes (PEs) in the placenta by adhesion to chondroitin sulfate A (CSA). Var2CSA possesses a 300 kDa extracellular region composed of six Duffy-binding like (DBL) domains and a cysteine-rich interdomain region (CIDRpam) module. Although initial studies implicated several individual var2CSA DBL domains as important for adhesion of PEs to CSA, new studies revealed that these individual domains lack both the affinity and specificity displayed by the full-length extracellular region. Indeed, recent evidence suggests the presence of a single CSA-binding site formed by a higher-order domain organization rather than several independent binding sites located on the different domains. Here, we search for the minimal binding region within var2CSA that maintains high affinity and specificity for CSA binding, a characteristic feature of the full-length extracellular region. Accordingly, truncated recombinant var2CSA proteins comprising different domain combinations were expressed and their binding characteristics assessed against different sulfated glycosaminoglycans (GAGs). Our results indicate that the smallest region within var2CSA with similar binding properties to those of the full-length var2CSA is DBL1X-3X. We also demonstrate that inhibitory antibodies raised in rabbit against the full-length DBL1X-6ε target principally DBL3X and, to a lesser extent, DBL5ε. Taken together, our results indicate that efforts should focus on the DBL1X-3X region for developing vaccine and therapeutic strategies aimed at combating PAM.
Collapse
|
44
|
Avril M, Hathaway MJ, Srivastava A, Dechavanne S, Hommel M, Beeson JG, Smith JD, Gamain B. Antibodies to a full-length VAR2CSA immunogen are broadly strain-transcendent but do not cross-inhibit different placental-type parasite isolates. PLoS One 2011; 6:e16622. [PMID: 21326877 PMCID: PMC3034725 DOI: 10.1371/journal.pone.0016622] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Accepted: 01/01/2011] [Indexed: 11/22/2022] Open
Abstract
The high molecular weight, multidomain VAR2CSA protein mediating adhesion of Plasmodium falciparum-infected erythrocytes in the placenta is the leading candidate for a pregnancy malaria vaccine. However, it has been difficult so far to generate strong and consistent adhesion blocking antibody responses against most single-domain VAR2CSA immunogens. Recent advances in expression of the full-length recombinant protein showed it binds with much greater specificity and affinity to chondroitin sulphate A (CSA) than individual VAR2CSA domains. This raises the possibility that a specific CSA binding pocket(s) is formed in the full length antigen and could be an important target for vaccine development. In this study, we compared the immunogenicity of a full-length VAR2CSA recombinant protein containing all six Duffy binding-like (DBL) domains to that of a three-domain construct (DBL4-6) in mice and rabbits. Animals immunized with either immunogen acquired antibodies reacting with several VAR2CSA individual domains by ELISA, but antibody responses against the highly conserved DBL4 domain were weaker in animals immunized with full-length DBL1-6 recombinant protein compared to DBL4-6 recombinant protein. Both immunogens induced cross-reactive antibodies to several heterologous CSA-binding parasite lines expressing different VAR2CSA orthologues. However, antibodies that inhibited adhesion of parasites to CSA were only elicited in rabbits immunized with full-length immunogen and inhibition was restricted to the homologous CSA-binding parasite. These findings demonstrate that partial and full-length VAR2CSA immunogens induce cross-reactive antibodies, but inhibitory antibody responses to full-length immunogen were highly allele-specific and variable between animal species.
Collapse
MESH Headings
- Amino Acid Sequence/physiology
- Animals
- Antibodies, Protozoan/immunology
- Antibodies, Protozoan/pharmacology
- Antibodies, Protozoan/therapeutic use
- Antibody Specificity/immunology
- Antibody Specificity/physiology
- Antigens, Protozoan/chemistry
- Antigens, Protozoan/immunology
- Antigens, Protozoan/isolation & purification
- Cells, Cultured
- Cross Reactions/immunology
- Female
- Humans
- Immunization
- Malaria Vaccines/immunology
- Malaria Vaccines/pharmacology
- Malaria Vaccines/therapeutic use
- Malaria, Falciparum/parasitology
- Malaria, Falciparum/pathology
- Malaria, Falciparum/prevention & control
- Malaria, Falciparum/transmission
- Mice
- Mice, Inbred BALB C
- Placenta/immunology
- Placenta/parasitology
- Pregnancy
- Pregnancy Complications, Parasitic/parasitology
- Pregnancy Complications, Parasitic/pathology
- Pregnancy Complications, Parasitic/therapy
- Protein Isoforms/immunology
- Rabbits
- Species Specificity
Collapse
Affiliation(s)
- Marion Avril
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
| | - Marianne J. Hathaway
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
| | - Anand Srivastava
- Institut Pasteur, Unité de Biologie des Interactions Hôte-Parasite, Centre National de la Recherche Scientifique (CNRS), Unité de Recherche Associée (URA), 2581, Paris, France
| | - Sébastien Dechavanne
- Institut Pasteur, Unité de Biologie des Interactions Hôte-Parasite, Centre National de la Recherche Scientifique (CNRS), Unité de Recherche Associée (URA), 2581, Paris, France
| | - Mirja Hommel
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - James G. Beeson
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Joseph D. Smith
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America
- Department of Global Health, University of Washington, Seattle, Washington, United States of America
- * E-mail: (BG); (JDS)
| | - Benoît Gamain
- Institut Pasteur, Unité de Biologie des Interactions Hôte-Parasite, Centre National de la Recherche Scientifique (CNRS), Unité de Recherche Associée (URA), 2581, Paris, France
- Institut National de la Transfusion Sanguine, Paris, France
- INSERM, UMRS 665, Paris, France
- Université Paris Diderot, Paris 7, Paris, France
- * E-mail: (BG); (JDS)
| |
Collapse
|
45
|
Parity and placental infection affect antibody responses against Plasmodium falciparum during pregnancy. Infect Immun 2011; 79:1654-9. [PMID: 21300778 DOI: 10.1128/iai.01000-10] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Women are at higher risk of Plasmodium falciparum infection when pregnant. The decreasing risk of malaria with subsequent pregnancies is attributed to parity-dependent acquisition of antibodies against placental parasites expressing variant surface antigens, VAR2CSA, that mediate placental sequestration through adhesion to chondroitin sulfate A (CSA). However, modulation of immunity during pregnancy may also contribute to increase the risk of malaria. We compared antibody responses among 30 Mozambican primigravidae and 60 multigravidae at delivery, 40 men, and 40 children. IgG levels were measured against the surface antigens of erythrocytes infected with P. falciparum isolated from 12 pregnant women (4 placental and 8 peripheral blood isolates) and 26 nonpregnant hosts. We also measured IgG levels against merozoite recombinant antigens and total IgG. Placental P. falciparum infection was associated with increased levels of total IgG as well as IgG levels against merozoite antigens and parasite isolates from pregnant and nonpregnant hosts. We therefore stratified comparisons of antibody levels by placental infection. Compared to multigravidae, uninfected primigravidae had lower total IgG as well as lower levels of IgGs against peripheral blood isolates from both pregnant and nonpregnant hosts. These differences were not explained by use of bed nets, season at delivery, neighborhood of residence, or age. Compared to men, infected primigravidae had higher levels of IgGs against isolates from pregnant women and CSA-binding lines but not against other isolates, supporting the concept of a pregnancy-specific development of immunity to these parasite variants. Results of this study show that parity and placental infection can modulate immune responses during pregnancy against malaria parasites.
Collapse
|
46
|
Gatton ML, Cheng Q. Interrupting malaria transmission: quantifying the impact of interventions in regions of low to moderate transmission. PLoS One 2010; 5:e15149. [PMID: 21152042 PMCID: PMC2996295 DOI: 10.1371/journal.pone.0015149] [Citation(s) in RCA: 12] [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: 08/12/2010] [Accepted: 10/26/2010] [Indexed: 11/19/2022] Open
Abstract
Malaria has been eliminated from over 40 countries with an additional 39 currently planning for, or committed to, elimination. Information on the likely impact of available interventions, and the required time, is urgently needed to help plan resource allocation. Mathematical modelling has been used to investigate the impact of various interventions; the strength of the conclusions is boosted when several models with differing formulation produce similar data. Here we predict by using an individual-based stochastic simulation model of seasonal Plasmodium falciparum transmission that transmission can be interrupted and parasite reintroductions controlled in villages of 1,000 individuals where the entomological inoculation rate is <7 infectious bites per person per year using chemotherapy and bed net strategies. Above this transmission intensity bed nets and symptomatic treatment alone were not sufficient to interrupt transmission and control the importation of malaria for at least 150 days. Our model results suggest that 1) stochastic events impact the likelihood of successfully interrupting transmission with large variability in the times required, 2) the relative reduction in morbidity caused by the interventions were age-group specific, changing over time, and 3) the post-intervention changes in morbidity were larger than the corresponding impact on transmission. These results generally agree with the conclusions from previously published models. However the model also predicted changes in parasite population structure as a result of improved treatment of symptomatic individuals; the survival probability of introduced parasites reduced leading to an increase in the prevalence of sub-patent infections in semi-immune individuals. This novel finding requires further investigation in the field because, if confirmed, such a change would have a negative impact on attempts to eliminate the disease from areas of moderate transmission.
Collapse
Affiliation(s)
- Michelle L Gatton
- Malaria Drug Resistance and Chemotherapy Laboratory, Queensland Institute of Medical Research, Brisbane, Queensland, Australia.
| | | |
Collapse
|
47
|
Magistrado PA, Minja D, Doritchamou J, Ndam NT, John D, Schmiegelow C, Massougbodji A, Dahlbäck M, Ditlev SB, Pinto VV, Resende M, Lusingu J, Theander TG, Salanti A, Nielsen MA. High efficacy of anti DBL4ɛ-VAR2CSA antibodies in inhibition of CSA-binding Plasmodium falciparum-infected erythrocytes from pregnant women. Vaccine 2010; 29:437-43. [PMID: 21075162 DOI: 10.1016/j.vaccine.2010.10.080] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Revised: 10/26/2010] [Accepted: 10/29/2010] [Indexed: 11/24/2022]
Abstract
Malaria during pregnancy is a major cause of intra-uterine growth-retardation and infant death in sub-Saharan Africa. Ideally, this could be prevented by a vaccine delivered before the first pregnancy. Antibodies against domain DBL4ɛ from VAR2CSA has been shown to inhibit adhesion of laboratory isolates to the placental receptor chondroitin sulfate A. In this study, the binding inhibitory efficacy of IgG elicited by two different DBL4ɛ recombinant proteins was tested on a panel of fresh clinical isolates from pregnant women living in Benin and Tanzania. The most promising recombinant protein elicited antibodies with similar efficacy as pooled plasma from immune multi-gravid African women.
Collapse
Affiliation(s)
- Pamela A Magistrado
- Centre for Medical Parasitology, Department of International Health, Immunology and Microbiology, University of Copenhagen, Denmark.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
48
|
Badaut C, Bertin G, Rustico T, Fievet N, Massougbodji A, Gaye A, Deloron P. Towards the rational design of a candidate vaccine against pregnancy associated malaria: conserved sequences of the DBL6epsilon domain of VAR2CSA. PLoS One 2010; 5:e11276. [PMID: 20585655 PMCID: PMC2890577 DOI: 10.1371/journal.pone.0011276] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Accepted: 05/30/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Placental malaria is a disease linked to the sequestration of Plasmodium falciparum infected red blood cells (IRBC) in the placenta, leading to reduced materno-fetal exchanges and to local inflammation. One of the virulence factors of P. falciparum involved in cytoadherence to chondroitin sulfate A, its placental receptor, is the adhesive protein VAR2CSA. Its localisation on the surface of IRBC makes it accessible to the immune system. VAR2CSA contains six DBL domains. The DBL6epsilon domain is the most variable. High variability constitutes a means for the parasite to evade the host immune response. The DBL6epsilon domain could constitute a very attractive basis for a vaccine candidate but its reported variability necessitates, for antigenic characterisations, identifying and classifying commonalities across isolates. METHODOLOGY/PRINCIPAL FINDINGS Local alignment analysis of the DBL6epsilon domain had revealed that it is not as variable as previously described. Variability is concentrated in seven regions present on the surface of the DBL6epsilon domain. The main goal of our work is to classify and group variable sequences that will simplify further research to determine dominant epitopes. Firstly, variable sequences were grouped following their average percent pairwise identity (APPI). Groups comprising many variable sequences sharing low variability were found. Secondly, ELISA experiments following the IgG recognition of a recombinant DBL6epsilon domain, and of peptides mimicking its seven variable blocks, allowed to determine an APPI cut-off and to isolate groups represented by a single consensus sequence. CONCLUSIONS/SIGNIFICANCE A new sequence approach is used to compare variable regions in sequences that have extensive segmental gene relationship. Using this approach, the VAR2CSA DBL6 domain is composed of 7 variable blocks with limited polymorphism. Each variable block is composed of a limited number of consensus types. Based on peptide based ELISA, variable blocks with 85% or greater sequence identity are expected to be recognized equally well by antibody and can be considered the same consensus type. Therefore, the analysis of the antibody response against the classified small number of sequences should be helpful to determine epitopes.
Collapse
Affiliation(s)
- Cyril Badaut
- Mother and Child Faced with Tropical Infections Research Unit, Institut de Recherche pour le Développement, UMR216, Paris, France
- Université Paris Descartes, Paris, France
- * E-mail: (CB); (PD)
| | - Gwladys Bertin
- Mother and Child Faced with Tropical Infections Research Unit, Institut de Recherche pour le Développement, UMR216, Paris, France
- Université Paris Descartes, Paris, France
| | - Tatiana Rustico
- Mother and Child Faced with Tropical Infections Research Unit, Institut de Recherche pour le Développement, UMR216, Paris, France
| | - Nadine Fievet
- Mother and Child Faced with Tropical Infections Research Unit, Institut de Recherche pour le Développement, UMR216, Paris, France
| | - Achille Massougbodji
- Département de Zoologie et Génétique, Faculté des Sciences et Techniques, Université d'Abomey-Calavi, Cotonou, Benin
| | - Alioune Gaye
- Centre de Santé Roi Baudoin de Guédiawaye, Dakar, Senegal
| | - Philippe Deloron
- Mother and Child Faced with Tropical Infections Research Unit, Institut de Recherche pour le Développement, UMR216, Paris, France
- Université Paris Descartes, Paris, France
- * E-mail: (CB); (PD)
| |
Collapse
|
49
|
Ndam NT, Deloron P. Molecular aspects of Plasmodium falciparum Infection during pregnancy. J Biomed Biotechnol 2010; 2007:43785. [PMID: 17641725 PMCID: PMC1906705 DOI: 10.1155/2007/43785] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2006] [Accepted: 03/21/2007] [Indexed: 11/17/2022] Open
Abstract
Cytoadherence of Plasmodium-falciparum-parasitized red blood cells (PRBCs) to host receptors is the key phenomenon in the pathological process of the malaria disease. Some of these interactions can originate poor outcomes responsible for 1 to 3 million annual deaths mostly occurring among children in sub-Saharan Africa. Pregnancy-associated malaria (PAM) represents an important exception of the disease occurring at adulthood in malaria endemic settings. Consequences of this are shared between the mother (maternal anemia) and the baby (low birth weight and infant mortality). Demonstrating that parasites causing PAM express specific variant surface antigens (VSA(PAM)), including the P. falciparum erythrocyte membrane protein 1 (P f EMP1) variant VAR2CSA, that are targets for protective immunity has strengthened the possibility for the development of PAM-specific vaccine. In this paper, we review the molecular basis of malaria pathogenesis attributable to the erythrocyte stages of the parasites, and findings supporting potential anti-PAM vaccine components evidenced in PAM.
Collapse
Affiliation(s)
- Nicaise Tuikue Ndam
- UR 010, Laboratoire de Parasitologie, Institut de Recherche pour le Développement, Université Paris Descartes, IFR 71, 4 avenue de l'Observatoire, 75006 Paris, France
- *Nicaise Tuikue Ndam:
| | - Philippe Deloron
- UR 010, Laboratoire de Parasitologie, Institut de Recherche pour le Développement, Université Paris Descartes, IFR 71, 4 avenue de l'Observatoire, 75006 Paris, France
| |
Collapse
|
50
|
Rogerson SJ. Malaria in pregnancy and the newborn. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 659:139-52. [PMID: 20204762 DOI: 10.1007/978-1-4419-0981-7_12] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Stephen J Rogerson
- Department of Medicine (RMH/WH), Post Office Royal Melbourne Hospital, Parkville, VIC, Australia.
| |
Collapse
|