title: Antigen reversal identifies targets of opsonizing IgGs against pregnancy-associated malaria.
abstract: Clinical immunity to pregnancy associated-malaria (PAM) in multigravida women has been attributed to antibodies that recognize VAR2CSA on the infected erythrocyte (IE) surface. The size and complexity of VAR2CSA have focused efforts on selecting one or more of its six Duffy binding-like (DBL) domains for vaccine development. Presently, however, there is no consensus as to which DBL domain(s) would be most effective in eliciting immunity. This is because antibodies to a number of the DBL domains have been found to block the adhesion of VAR2CSA-expressing erythrocytes to chondroitin sulfate A (CSA)-a major criterion for evaluating vaccine candidacy. Opsonization of IEs by cytophilic antibodies that recognize VAR2CSA represents an important yet understudied effector mechanism in acquired immunity to PAM. To date, no studies have sought to determine the targets of those antibodies. In this study, we found that IgGs from multigravida Malian women showed (i) higher reactivity to recombinant DBL domains by enzyme-linked immunosorbent assay (ELISA), (ii) more binding to VAR2CSA-expressing IEs, and (iii) greater opsonization of these IEs by human monocytic cells than IgGs from malaria-exposed Malian men and malaria-naive American adults. Preincubation of IgGs from multigravida women with recombinant DBL2χ, DBL3χ, or DBL5ε domains significantly diminished opsonization of VAR2CSA-expressing IEs by human monocytes. These data identify the DBL2χ, DBL3χ, and DBL5ε domains as the primary targets of opsonizing IgGs for the first time. Our study introduces a new approach to determining the antigenic targets of opsonizing IgGs in phagocytosis assays.
authors.affiliation: Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA.
authors.forename: Lester H
authors.initials: LH
authors.lastname: Lambert
authors.affiliation: Structural Biology Section, Research Technologies Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA.
authors.forename: Jeanee L
authors.initials: JL
authors.lastname: Bullock
authors.affiliation: Structural Biology Section, Research Technologies Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA.
authors.forename: Sharma T
authors.initials: ST
authors.lastname: Cook
authors.affiliation: Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA.
authors.forename: Kazutoyo
authors.initials: K
authors.lastname: Miura
authors.affiliation: Structural Biology Section, Research Technologies Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA.
authors.forename: David N
authors.initials: DN
authors.lastname: Garboczi
authors.affiliation: Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odontostomatology, University of Bamako, Bamako, Mali.
authors.forename: Mahamadou
authors.initials: M
authors.lastname: Diakite
authors.affiliation: Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA.
authors.forename: Rick M
authors.initials: RM
authors.lastname: Fairhurst
authors.affiliation: Structural Biology Section, Research Technologies Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA.
authors.forename: Kavita
authors.initials: K
authors.lastname: Singh
authors.affiliation: Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA clong@niaid.nih.gov.
authors.forename: Carole A
authors.initials: CA
authors.lastname: Long
mesh_terms: D000913:Antibodies, Protozoan / Q000276:immunology*; D000915:Antibody Affinity; D000953:Antigens, Protozoan / Q000502:physiology*; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D008288:Malaria / Q000097:blood / Q000276:immunology*; D008297:Male; D008302:Mali / Q000453:epidemiology; D009895:Opsonin Proteins / Q000378:metabolism*; D011247:Pregnancy; D015597:Pregnancy Complications, Parasitic / Q000276:immunology*; D017452:Receptors, IgG; D014481:United States
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D007074:Immunoglobulin G; D009895:Opsonin Proteins; D017452:Receptors, IgG