Overlapping antigenic repertoires of variant antigens expressed on the surface of erythrocytes infected by Plasmodium falciparum

Antibodies against variable antigens expressed on the surface of Plasmodium falciparum-infected erythrocytes are believed to be important for protecti on against malaria. A target for these antibodies is the P. falciparum eryt hrocyte membrane protein 1, PfEMP1, which is encoded by around 50 var genes and undergoes clonal variation. Using agglutination and mixed agglutinatio n tests and flow cytometry to analyse the recognition of variant antigens o n parasitized erythrocytes by plasma antibodies from individuals living in Daraweesh in eastern Sudan, an area of seasonal and unstable malaria transm ission, we show that these antibodies recognize different variant antigens expressed by parasites of different genotype. Comparing the levels and acqu isition of antibody to variant antigens in pairs of parasite isolates expre ssing different variant types, there is a correlation between the acquisiti on of antibodies to some combinations of variant antigens but not to others . These results indicate that (1) a single infection will induce the produc tion of antibodies recognizing several variants of surface-expressed antige ns, (2) the repertoire of variable antigens expressed by different parasite s is overlapping and the degree of overlap differs between isolates, and (3 ) the expression of at least some variant antigens is genetically linked.