Parasite polypeptides lost during schizogony and erythrocyte invasion by the malaria parasites, Plasmodium chabaudi and Plasmodium knowlesi

By biosynthetically labelling Plasmodium chabaudi and P. knowlesi stage-specific polypeptides and allowing continued development, schizogony and reinvasion in vivo or in vitro, we have identified parasite polypeptides not taken into the erythrocyte by the invading mezozoite. Three major and two minor parasite polypeptides synthesized by rings or mid-stage trophozoites of P. chabaudi were either degraded preferentially during further development, or lost during schizogony and reinvasion. For both P. chabaudi and P. knowlesi, a 250 000 mol. wt. polypeptide synthesized during maturation of trophozoites to schizonts and merozoites was not taken into the erythrocyte by the invading merozoite. The late stage synthesis of this polypeptide by P. chabaudi and its loss at schizogony and reinvasion was confirmed by immunofluorescence staining with a monoclonal antibody to this antigen. The importance of these antigens in the erythrocyte invasion process and in the induction and expression of immunity to malaria is discussed.