Analysis of immune responses of different hosts to Babesia divergens isolates from different geographic areas and capacity of culture-derived exoantigens to induce efficient cross-protection.

The immunoprecipitation of [35S]methionine-radiolabelled antigens from different Babesia divergens isolates by using bovine, gerbil, and human immune sera has shown that many B. divergens proteins contain epitopes shared between isolates. The cross-protective capacity of culture-derived soluble immunogens from the B. divergens Rouen 1987 isolate was tested against different B. divergens isolates. Results showed complete protection against the 7107b French isolate and substantial protection against the Weybridge 8843 English isolate (80% protection) and the Munich 87 German isolate (60% protection). In order to explain these vaccination results and to assess both the common and variable antigenicity of B. divergens, the antigenic patterns of the challenge isolates (Rouen 1987, 7107b, Weybridge 8843, and Munich 87) were compared by immunoprecipitation, using gerbil antisera raised against the Rouen 1987 vaccine isolate. Differences in the antigenic patterns and in the cross-protection of gerbils in these heterologous challenges were examined by studying the virulence and the antigenic status of each isolate.