Immunization against blood-stage rodent malaria using purified parasite antigens

We have reported the production of several hybridoma lines secreting monoclonal antibodies recognizing antigens of the blood forms of a rodent malaria parasite, Plasmodium yoelii yoelii(1,2). Line WIC 25.77 secretes an IgG2a (antibody 25.77) which reacts specifically with merozoites in the indirect immunofluorescence (IIF) assay, and which was protective on passive transfer. Another of the hybridoma lines, WIC 25.1, secretes an IgG2a (antibody 25.1) which reacts with an antigen apparently associated with the membranes of schizonts, but this antibody was not protective on passive transfer. We have used our monoclonal antibodies to identify and purify antigens of P. y. yoelii, and we report here that mice immunized with either a 235,000 apparent molecular weight (MW) merozoite-specific protein or a 230,000 MW schizont protein and its proteolytic derivatives were protected against infection with P. y. yoelii.