LYMPHOCYTE-RESPONSES TO PLASMODIUM-FALCIPARUM RING-INFECTED ERYTHROCYTE SURFACE-ANTIGEN (PF155 RESA) PEPTIDES IN INDIVIDUALS WITH NATURALLYACQUIRED PLASMODIUM-FALCIPARUM MALARIA/

Antibody titers and lymphocyte responses to synthetic peptides corresp onding to repeated amino acid sequences of the 3' and 5' regions of Pf 155/ring-infected erythrocyte surface antigen (RESA) were studied in t wo groups of Thai subjects, soldiers (Rangers), and villagers who diff ered in their history of malaria exposure. The frequency of Pf155/RESA seropositivity was similar in the two groups while the frequency of h igh titer antibody was significantly greater in villagers than in Rang ers. Lymphocyte responsiveness in vitro to all Pf155/RESA peptides was infrequent for both groups although half of the subjects studied resp onded to crude Plasmodium falciparum asexual blood stage malaria antig en (MA). Among responders, Pf155/RESA peptides elicited lymphocyte res ponses in which proliferation and interferon-gamma (IFN-gamma) product ion were not associated, whereas with MA, the two responses were assoc iated. The MA-stimulated lymphocyte proliferation and IFN-gamma produc tion for both groups of volunteers appeared to be independent of antib ody titer. In this study, antibody, but not lymphocyte, responses to P f155/RESA peptides were shown to reflect differences in prior exposure and levels of acquired immunity to falciparum malaria.