Immunization of Monkeys against Plasmodium cynomolgi by X-irradiated Sporozoites

Abstract

THE development of protective immunity in a host against the sporozoite form of the malaria parasite would seem to be the ideal goal for total protection of the host. A number of workers have studied the feasibility of immunizing birds and rodents using killed or immobilized sporozoites. Sporozoites of Plasmodium gallinaceum, killed by several different techniques, are partially protective in that immunized birds were protected from dying, although all of the animals developed low grade parasitaemia¹. More recently, rodents have been totally protected by immunization with X-irradiated sporozoites^{2, 3}. Immunization of mice with 75,000 sporozoites of P. berghei irradiated with 8 or 10 krads of X-irradiation was sufficient to protect almost 98% of the animals². These studies have also indicated that immunization with sporozoites of one species may confer varying degrees of immunity to challenge with other species of rodent malaria.