PLASMODIUM-FALCIPARUM INFECTION OF SPLENECTOMIZED AND INTACT GUYANAN-SAIMIRI MONKEYS

Spleen-intact and splenectomized Saimiri monkeys of Guyanan origin wer e examined for their potential suitability for Plasmodium falciparum p rotection studies. The animals could be readily infected with adapted strains of P. falciparum (Indochina 1/CDC and Uganda Pale Alto FUP str ains), but spontaneously recovered without drug treatment and without development of severe clinical disease. In intact animals, peak parasi temia prior to recovery generally ranged from 0.1% to 10%, whereas in splenectomized animals the peak parasitemia was generally higher so th at some animals were given drug treatment to assist in recovery from i nfection. In reinfection studies, previously infected spleen-intact mo nkeys demonstrated sterile immunity to the homologous parasite strain but not to a heterologous strain. However, in monkeys infected with th e heterologous strain, the peak parasitemia was less than in the first infection and of shorter duration. Splenectomized animals did not dem onstrate sterile immunity although the peak parasitemia achieved was l ess than in the previous infection of each of these monkeys. While the lack of major clinical disease indicated that these monkeys did not p rovide a good animal model for human malaria, the development of prote ctive immunity was consistent with a useful role in evaluating candida te vaccine antigens.