Plasmodium vivax pre-erythrocytic-stage antigen discovery: exploiting naturally acquired humoral responses.

The development of pre-erythrocytic Plasmodium vivax vaccines is hindered by the lack of in vitro culture systems or experimental rodent models. To help bypass these roadblocks, we exploited the fact that naturally exposed Fy- individuals who lack the Duffy blood antigen (Fy) receptor are less likely to develop blood-stage infections; therefore, they preferentially develop immune responses to pre-erythrocytic-stage parasites, whereas Fy+ individuals experience both liver- and blood-stage infections and develop immune responses to both pre-erythrocytic and erythrocytic parasites. We screened 60 endemic sera from P. vivax-exposed Fy+ or Fy- donors against a protein microarray containing 91 P. vivax proteins with P. falciparum orthologs that were up-regulated in sporozoites. Antibodies against 10 P. vivax antigens were identified in sera from P. vivax-exposed individuals but not unexposed controls. This technology has promising implications in the discovery of potential vaccine candidates against P. vivax malaria.