Naturally acquired and vaccine-elicited antibodies block erythrocyte cytoadherence of the Plasmodium vivax Duffy binding protein

Malaria merozoites require the presence of specific surface receptors on th e red blood cell for invasion. Plasmodium vivax, requires the Duffy blood g roup antigen as an obligate receptor for invasion, The parasite Duffy bindi ng protein (DBP) is the ligand involved in this process, making the DBP a p otential vaccine candidate. A preliminary objective was to study whether pe ople exposed to vivax: malaria acquire antibodies that have the ability to block erythrocyte cytoadherence to the PvDBP, In comparison, we studied the immunogenicity of various recombinant DBP vaccines and investigated their potential to induct antifunctional antibodies. In order to do so, recombina nt proteins to different regions of the putative ectodomain of the DBP and a DNA vaccine were used to immunize laboratory animals. An in vitro cytoadh erence assay was used to investigate the presence of antifunctional antibod ies in plasmas from people naturally exposed to vivax malaria, as well as i n antisera obtained by animal vaccination, Our results showed that human pl asma from populations naturally exposed to vivax malaria, as well as antise ra obtained by vaccination using recombinant proteins, a DNA vaccine, and a synthetic peptide to DBP, inhibited in vitro binding of human erythrocytes to the DBP ligand domain (DBPII) in correlation to their previously measur ed antibody titer, Our results provide further evidence for the vaccine pot ential of this essential parasite adhesion molecule.