IMMUNE-RESPONSE AND TRYPANOSOMA-CRUZI INFECTION IN TRYPANOSOMA-RANGELI-IMMUNIZED MICE

The capacity of Trypanosoma rangeli antigens to induce immune response in mice was analyzed and the course of the infection was studied in immunized animals challenged with virulent forms of T. cruzi. BALB/c mice were immunized with supernatant of disrupted epimastigotes of T. rangeli and with epimastigotes (EPI) of T. rangeli fixed with glutaraldehyde. Both of the antigens were emulsified with incomplete Freund's adjuvant (IFrAdj). All of the animals received T. cruzi Tulahuen antigens in the footpad and the skin reactivity was later studied. The mice that received EPI with or without IFrAdj showed significantly higher skin reactivity than controls, both in Arthus (3 hr) and delayed type hypersensitivity (24 hr) reactions. Furthermore, the mice immunized with T. rangeli developed antibodies against T. cruzi detectable through hemagglutination and immunofluorescence tests. When the animals were challenged with trypomastigotes of T. cruzi, only the groups immunized with EPI-IFrAdj had significantly lower parasitemias and greater survival against infection than controls. These results suggest that T. rangeli can induce humoral and cellular immune response against T. cruzi and attenuate the acute period of the infection produced by this parasite. This is the first time that partial resistance to T. cruzi in T. rangeli-immunized mice is reported. These findings may provide a useful tool for future studies directed at the immunoprevention of Chagas' disease.