MECHANISMS OF PROTECTIVE IMMUNITY AGAINST ASEXUAL BLOOD STAGES OF PLASMODIUM-FALCIPARUM IN THE EXPERIMENTAL HOST SAIMIRI

In the Saimiri monkey, an experimental host for human malaria, acquire d protection against Plasmodium falciparum blood stages depends on the IgG antibody populations developed. In vivo protective anti-falciparu rn activity of IgG antibodies is correlated with the in vitro opsonizi ng activity promoting phagocytosis of parasitized red blood cells. In contrast, non protective antibodies inhibit this mechanism by competin g at the target level. A similar phenomenon can be observed in human i nfection. Anti-cytoadherent and anti-rosette antibodies developed by S aimiri and humans prevent the development of physiopathological events like cerebral malaria which can also occur in this experimental host. Furthermore, transfer to protective human anti-falciparum IgG antibod ies into infected Saimiri monkeys exerts an anti parasite activity as efficient as that observed when it is transferred into acute falciparu m malaria patients, making the Saimiri an even more attractive host. S tudies on the role of immunocompetent cells in the protective immune r esponse are still in their infancy, however the existence of a restric ted polymorphism of MHC II class molecules in the Sairniri confers add itional theoretical and practical importance to this model.