FIG 1.

The GFP-DDDHA strain provides cross-protection and does not cause persistent infection. (A) C3H mice were inoculated with the GFP-DDDHA Tulahuen strain and then challenged with the Brazil strain. Immunized mice did not develop parasitemia, while nonimmunized mice developed high parasitemia (n = 10). (B) Immunized mice survived the challenge, while nonimmunized mice all died during the acute infection phase (n = 10). (C) Histology (hematoxylin and eosin [H&E] staining) of heart tissues at day 14 postchallenge demonstrates that nonimmunized C3H mice infected with the Brazil strain had numerous amastigotes within myocardial tissue, associated with extensive myocarditis, while GFP-DDDHA-immunized mice infected with the Brazil strain had no amastigotes and did not exhibit myocarditis. ×20 magnification. Bar, 25 μm. (D) C57BL/6 mice immunized with the GFP-DDDHA Tulahuen strain and then challenged with half a million wild-type Tulahuen strain parasites. Similarly to C3H mice, immunized mice did not develop parasitemia and survived, while nonimmunized mice developed high parasitemia and all died in the acute phase (n = 10). (E) C57BL/6 mice immunized with the GFP-DDDHA Tulahuen strain did not have persistent infection, as real-time PCR did not detect T. cruzi DNA in heart and adipose tissues (n = 5). See Materials and Methods for details. Data presented are one representative example of two separate experiments. Both experiments produced similar results.