[Immunologic protection against Chagas disease. Independent effects upon infection, dissemination and lesions of Trypanosoma cruzi].

An attenuated T. cruzi strain (TCC) can exert immunizing effects against homologous virulent parasites. Titration of infective and protective TCC doses shows a wide immunizing dose range for epimastigotes and a subpatent infective capacity for trypomastigotes at high doses. As increasingly sensitive methods are applied to detect infection in immunized-challenged animals, different levels of resistance can be revealed. These range from total prevention of infection in very few animals to mere prevention of mortality and high parasitemia. Potentiation of each of these resistance levels was tested after immunization with two live and two killed vaccine preparations. All vaccines significantly strengthened intermediate or incomplete resistance levels. None of them seemed to produce significant changes regarding total rejection of low challenge doses. Whereas these levels of resistance do not seem useful against infection in humans, they can conceivably be used to interfere the domestic transmission cycle of the parasite by vaccination of domestic animals. Preliminary evidence for this possibility has been demonstrated in the field by vaccinating domestic guinea pigs against natural T. cruzi infection with either live attenuated or killed parasite vaccines.