PROGRESS IN MALARIA VACCINE DEVELOPMENT
Abstract
Department of Chemical Pathology Guy's Hospital Medical School, London Vaccination against exoerythrocytic stages a Sporozoite vaccines b Antigens of sporozoites Vaccination against blood-stage parasites a Merozoite vaccines b Antigens of blood-stage parasites Vaccination against sexual forms Concluding remarks References a variety of methods (reviewed by Cohen & Mitchell, 1978). During recent years, attempts at experimental vaccination have focused mainly on the use of extracellular stages of the parasite le-cycleâparticularly sporozoites, erythrocytic merozoites and microgametes; the present discussion will be confined to these forms of malaria vaccine. Vaccination against Exoerythrocytic Stages The pattern of acquired immunity to malaria infection varies widely in dferent host-parasite combinations. In some instances, for example, Plasmodium knowlesi in the rhesus monkey, the immune response is clinically ineffective and the disease rapidly fatal. Other forms of experimental malaria, e.g. P. berghei in the rat, induce "sterilizing" immunity characterized by complete elimination of the parasite and lelong resistance to challenge. In the case of naturally occurring infections, acquired immunity usually controls but does not eliminate the parasite, which persists at low density over long periods. This is characteristic of the human malarias. Thus, the inhabitants of hyperendemic areas show a consistent pattern of susceptibility and resistance