This term represents the abbreviation for “variable surface antigens,” which are produced by the parasite and found on the surface of, e.g., parasitized erythrocytes (in the case of Plasmodium infections). These VSAs promote the adhesion of infected erythrocytes to endothelium cells of the host and also act antigenetically to the host immune system. In order to mitigate host immune defense, the malarial parasites (and others) have evolved from a variety of VSA genes.