title: Human pregnancy-associated malaria-specific B cells target polymorphic, conformational epitopes in VAR2CSA.
abstract: Pregnancy-associated malaria (PAM) is caused by Plasmodium falciparum-infected erythrocytes (IEs) that bind to chondroitin sulphate A (CSA) in the placenta by PAM-associated clonally variant surface antigens (VSA). Pregnancy-specific VSA (VSA(PAM)), which include the PfEMP1 variant VAR2CSA, are targets of IgG-mediated protective immunity to PAM. Here, we report an investigation of the specificity of naturally acquired immunity to PAM, using eight human monoclonal IgG1 antibodies that react exclusively with intact CSA-adhering IEs expressing VSA(PAM). Four reacted in Western blotting with high-molecular-weight (> 200 kDa) proteins, while seven reacted with either the DBL3-X or the DBL5-epsilon domains of VAR2CSA expressed either as Baculovirus constructs or on the surface of transfected Jurkat cells. We used a panel of recombinant antigens representing DBL3-X domains from P. falciparum field isolates to evaluate B-cell epitope diversity among parasite isolates, and identified the binding site of one monoclonal antibody using a chimeric DBL3-X construct. Our findings show that there is a high-frequency memory response to VSA(PAM), indicating that VAR2CSA is a primary target of naturally acquired PAM-specific protective immunity, and demonstrate the value of human monoclonal antibodies and conformationally intact recombinant antigens in VSA characterization.
authors.affiliation: Centre for Medical Parasitology at Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet) and Institute for Medical Microbiology and Immunology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Lea
authors.initials: L
authors.lastname: Barfod
authors.forename: Nadia L
authors.initials: NL
authors.lastname: Bernasconi
authors.forename: Madeleine
authors.initials: M
authors.lastname: Dahlbäck
authors.forename: David
authors.initials: D
authors.lastname: Jarrossay
authors.forename: Pernille Haste
authors.initials: PH
authors.lastname: Andersen
authors.forename: Ali
authors.initials: A
authors.lastname: Salanti
authors.forename: Michael F
authors.initials: MF
authors.lastname: Ofori
authors.forename: Louise
authors.initials: L
authors.lastname: Turner
authors.forename: Mafalda
authors.initials: M
authors.lastname: Resende
authors.forename: Morten A
authors.initials: MA
authors.lastname: Nielsen
authors.forename: Thor G
authors.initials: TG
authors.lastname: Theander
authors.forename: Federica
authors.initials: F
authors.lastname: Sallusto
authors.forename: Antonio
authors.initials: A
authors.lastname: Lanzavecchia
authors.forename: Lars
authors.initials: L
authors.lastname: Hviid
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000953:Antigens, Protozoan / Q000737:chemistry / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D015153:Blotting, Western; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D018604:Epitope Mapping; D018985:Epitopes, B-Lymphocyte / Q000276:immunology*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D019169:Jurkat Cells; D016778:Malaria, Falciparum / Q000276:immunology*; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000276:immunology*; D011247:Pregnancy; D015597:Pregnancy Complications, Parasitic / Q000276:immunology*; D016415:Sequence Alignment
chemical_list: D000911:Antibodies, Monoclonal; D000953:Antigens, Protozoan; D018985:Epitopes, B-Lymphocyte; C512601:VAR2CSA protein, Plasmodium falciparum