Immunization of owl monkeys to Plasmodium falciparum with merozoites from cultures of a knobless clone

Abstract

A. trivirgatus of karyotype 2 were treated as follows: three received 2 injections of purified merozoites of a knobless (K-) clone of P. falciparum with muramyl dipeptide (MDP) as adjuvant; 3 received similiar injections but with merozoites of a wild-type knobby (K+) strain; 3 controls received MDP with human erythrocytes in the amounts estimated to be present as contaminants in the merozoite preparations. A month after the 2nd injection all 9 monkeys were inoculated with parasites of the wild-type knobby strain from another infected Aotus. The monkeys that had received the K- material developed only extremely low infections markedly different from the infections in the controls. Of those that received K+ material, 1 died early with low parasitemia, 1 was protected and 1 had the same level of infection as the controls. In the combined group of immunized animals, 4 of 6 were protected.