Antibodies against Sporozoites of Human and Simian Malaria Produced in Rats

The various methods commonly used for the detection of antimalarial antibodies employ, in nearly all instances, the erythrocytic stages of these parasites as antigen source (1). The antigenic components of the different stages of development of the malaria parasites, however, differ considerably, in spite of the existence of some shared or common antigens (2, 3). Furthermore, the common antigens do not account for all of the antigenic components of the parasites, nor do they include the functional, i.e., protective, antigens of the various developmental stages. This is suggested by the finding that rodents immunized with attenuated sporozoites become totally resistant to an otherwise lethal sporozoite inoculum, but remain fully susceptible to challenge with erythrocytic stages of the same parasite strain (4). Anti-sporozoite antibodies, i.e., antibodies directed against the infective stages of all malaria parasites, have previously been shown to occur in avian and rodent malaria. In both instances, these antibodies were observed upon immunization of the animals with attenuated, irradiated sporozoites. Sporozoite agglutination was first observed in avian malaria (5). In the rodent malaria system, incubation of Plasmodium berghei sporozoites with immune serum led to the formation of a precipitate at one end of the sporozoite. This precipitate was easily distinguishable under phase microscopy, and was termed the circum-sporozoite precipitate (CSP) 2 reaction (6).The antibodies involved in the CSP reaction were shown to be strictly stage, i.e., sporozoite, specific; no reaction was observed with other developmental stages of these parasites (7).