Protective monoclonal antibodies recognising stage-specific merozoite antigens of a rodent malaria parasite.

Immunity to malaria is mediated, at least in part, by antibody. Resistance to infection has been passively transferred with immune serum or its immunoglobulin fraction in human, simian and rodent malaria. However, because of the structural and antigenic complexity of the malaria parasites, it has proved difficult to identify and characterise those parasite antigens against which protective antibody is directed. We have produced several hybrid cell lines secreting monoclonal antibodies against the rodent malaria parasite, Plasmodium yoelii, and we now report that, of the antibodies tested, only those specific for antigens exclusive to the merozoite were protective in passive transfer experiments. Other anti-P. yoelii monoclonal antibodies, apparently recognising antigens in the membrane of the infected erythrocyte, were not protective on passive transfer. The protective monoclonal antibodies should be useful in the isolation of the important antigens of this parasite.