ABSTRACT
Cattle vaccinated with exoantigens of Babesia bovis and B. bigemina and dogs vaccinated with B. canis exoantigens produced strong immunologic responses and were clinically protected against tick and needle challenge. Prior to the development of cell culture systems, the only source of exoantigens was blood serum of animals acutely infected with various Babesia species. Inoculation of exoantigens into immunologically competent, Babesia-free animals was shown to induce transitory anemia in the animals. A major constraint in the isolation and purification of Babesia exoantigens is the high concentration of bovine serum contained in the MASP culture medium. In general, exoantigens of Babesia are proteinaceous in nature as determined by sensitivity to proteolytic enzymes trypsin and papain. Fresh blood serum from a Babesia-free cow was added to one portion of merozoites, and a fresh serum from an animal recovered from B. bovis infection and an immunized calf was added to the second and third portion of merozoites, respectively.
