TRYPANOSOMA-CRUZI GLUTATHIONE-BINDING PROTEINS (TCGBP) - PROTECTION INDUCED BY NATIVE PROTEINS IN AN EXPERIMENTAL-MODEL AND ANALYSIS OF THEANTIBODY-RESPONSE

Three Trypanosoma cruzi glutathione-binding proteins (TcGBP) of 45, 30 and 25 kDa presenting glutathione S transferase activity were charact erized from T. cruzi epimastigotes. We show here that immunization of mice using TcGBP and complete Freund's adjuvant (CFA) did not protect the animals against a challenge with bloodstream trypomastigotes. In c ontrast, immunization of mice using TcGBP in association with Bordetel la pertussis plus alum (BpAl) resulted in greatly diminished parasitae mia and significantly protected the animals from lethal infection. Usi ng TcGBP mixed with BpAI and a lower challenge dose, we obtained stron gly diminished parasitaemia and 100 % protection in terms of survival. Only sera from mice immunized with TcGBP plus BpAl were able to kill trypomastigotes by complement-mediated lysis, whereas sera from mice i mmunized with TcGBP plus CFA did not. Interestingly, sera from mice im munized with TcGBP plus BpAl showed significant levels of specific IgE , IgG2a and IgG2b antibodies, whereas these isotypes were not detected in sera from mice immunized with TcGBP in CFA. All these levels were increased in sera of protected animals. These results demonstrate that TcGBP antigens can confer resistance to T. cruzi acute infection in m ice, and suggest a possible functional role for both IgE and IgG2 isot ypes in the induction of protective immunity.