Immunization of Aotus trivirgatus against Plasmodium falciparum with irradiated blood forms

Five owl monkeys, Aotus trivirgatus, were immunized against falciparum malaria by the intravenous injection of gamma-irradiated parasitized blood from donor monkeys with high parasitaemias. Each animal received approximately 1 x 10(8) parasitized erythrocytes per immunizing dose. Three monkeys received 4 doses and 2 monkeys received a single dose. After challenge, 3 control monkeys that received saline and the 2 monkeys that received a single dose of parasitized blood died with fulminant parasitaemias. The 3 monkeys that received 4 immunizing doses had either no parasitaemia at all (one monkey) or low-grade (<2.5%) parasitaemias (two monkeys); one of the latter monkeys died after the malaria had run a prolonged course. No striking haematological abnormalities were noted in animals as a result of the immunization procedure. These results confirm that immunity to Plasmodium falciparum can be induced in owl monkeys by inoculation with parasitized erythrocytes that have not undergone culture and without the use of adjuvant.