PROTECTIVE IMMUNITY INDUCED IN SQUIRREL-MONKEYS WITH RECOMBINANT APICAL MEMBRANE ANTIGEN-1 OF PLASMODIUM FRAGILE

Saimiri sciureus boliviensis monkeys were immunized with the Plasmodiu m fragile form of the merozoite apical membrane antigen-1 produced usi ng the baculovirus expression system and combined with Montanide ISA 7 20 adjuvant. Following three immunizations, monkeys were challenged wi th 10,000 P. fragile trophozoite parasites. Antibody titers determined by fluorescence microscopy indicated an enhanced response following t he second immunization. Four of five control animals had parasite coun ts > 5% 18-26 days following challenge. Four of five immunized monkeys had reduced levels of maximum parasitemia or delays in accumulated pa rasite counts, suggestive of protection. Rechallenge of the animals wi th P. falciparum resulted in three of four adjuvant control animals de veloping patent parasitemia whereas none of five immunized animals wer e infected, suggesting some level of heterologous protection.