(A) Two receptors for apical attachment of P vivax merozoites to RBCs have been cloned: the Duffy binding protein and the reticulocyte binding protein.46,52 One strategy for vaccine development is to use these proteins as immunogens to induce antibodies that might block invasion of the parasite into the RBC. (B) Variant cytoadherence proteins of P falciparum have also been cloned.55-57 Antibodies against this protein can block cytoadherence of P falciparum–infected RBCs to endothelial cells, forcing the parasite to circulate through the spleen, where immunologic mechanisms (which have not been clearly defined) are brought into play against P falciparum parasites. The cytoadherence antigen is variant and antigenic variation is used by the parasite to escape antibody mediated blockade of cytoadherence. Another strategy for vaccine development is to identify domains that are shared among different variants of the cytoadherece protein of P falciparum; antibodies against shared domains could block cytoadherence in a variant-independent fashion.