Failure of trypanosomal membrane antigens to induce protection against tsetse-transmitted Trypanosoma vivax or T. brucei in goats and rabbits.

A purified protein, relative molecular weight 83 kilodalton (kD), and plasma membranes from Trypanosoma brucei were tested as potential vaccines against tsetse-transmitted T. vivax and T. brucei in goats and rabbits. The 83 kD protein was found in lysates of all clones of T. brucei examined, as well as in lysates of T. vivax, T. congolense and T. rhodesiense. Rabbits and goats were immunized with various amounts of antigen in Freund's complete adjuvant and boosted twice with antigen in Freund's incomplete adjuvant. Two weeks after the last inoculation, the goats were challenged with T. vivax-infected and the rabbits with T. brucei-infected Glossina morsitans morsitans. Although high antibody levels were detected in all the animals immunized with either antigen as measured by radioimmunoassay and immunodiffusion, they became infected and the course of disease was the same as that in unimmunized controls.