Immunization with Recombinant Duffy Binding-Like- gamma 3 Induces Pan-Reactive and Adhesion-Blocking Antibodies against Placental Chondroitin Sulfate A-Binding Plasmodium falciparum Parasites

Maternal malaria is associated with the sequestration, in the placenta, of Plasmodium falciparum-infected erythrocytes onto chondroitin sulfate A (CSA), via the duffy binding-like (DBL)- gamma 3 domain of the P. falciparum erythrocyte membrane protein 1 (PfEMP1 super(CSA)) (DBL- gamma 3 super(CSA)). The production of antibodies against CSA-binding infected erythrocytes (IEs super(CSA)) is correlated with resistance to maternal malaria in multiparous women. We produced recombinant DBL- gamma 3 super(CSA) (rDBL- gamma 3 super(CSA)) in insect cells, corresponding to 2 variant DBL- gamma 3 super(CSA) subtypes that mediate binding to CSA in laboratory lines and placental isolates. Both recombinant cysteine-rich DBL- gamma 3 super(CSA) domains blocked IEs super(CSA) binding to CSA. Immunization of mice, with the rDBL- gamma 3 super(CSA)-FCR3 and rDBL- gamma 3 super(CSA)-3D7 domains, resulted in the generation of antibodies recognizing homologous and heterologous rDBL- gamma 3 super(CSA), a finding indicating conserved epitopes inducing a pan-reactive immune response. Mouse monoclonal antibodies (MAbs) against both recombinant proteins were pan-reactive with various IEs super(CSA). One MAb efficiently inhibited and reversed IE super(CSA) cytoadhesion to endothelial cells in vitro. Thus, DBL- gamma 3 super(CSA) is the target of inhibitory and pan-reactive antibodies. Saimiri sciureus monkeys immunized with FCR3-rDBL- gamma 3 super(CSA) developed pan-reactive and inhibitory antibodies, a finding suggesting that the development of a vaccine to prevent maternal malaria is feasible.