There is an urgent need for an effective vaccine to prevent and treat Chagas disease. Our group has developed superantigen mutants (mSAg) that lack T cell activation capability but bind MHC-II on antigen presenting cells acting as immune modulators and helping to stablish a Th1 response. In this work, we engineered a chimeric antigen (chimera) between mSAg and a protective Trypanosoma cruzi antigen. Our goal was to evaluate the ability of chimera-DNA immunization through a Salmonella-based delivery system to induce protection in a murine model of T. cruzi. Chimera was genetically engineered, cloned and produced as a recombinant protein in E. coli. Attenuated Salmonella was transformed with plasmid pcDNA3.1- chimera (SChim). C3H/HeN mice were immunized with four doses of: I- 109 Schim (orally); II- chimera (10 μg/dose)/ODN-CpG (intramuscularly); III- two Schim + two boosts of chimera; IV- two Schim + two boosts of chimera/ODN-CpG; V- 109 Salmonella with empty pcDNA. Two weeks after the last immunization, T. cruzi antigen-specific IgG titers and IgG1/IgG2a isotypes were determined. Delayed-type hypersensitivity test was performed. Animals were then challenged with
bloodstream trypomastigotes (RA strain). In the acute phase parasitemia levels were registered every two days; in the chronic phase, animals were sacrificed, skeletal muscle was obtained and qPCR was performed to determine parasite loads. Specific antibody titers against T. cruzi antigen were detected in groups II, III and IV, showing significant differences against the control group (p<0.01). In these groups, IgG2a titers were significantly higher than IgG1. A significant cellular response was detected in groups I, III and IV (p<0,05). In groups I, II and IV parasitemia levels were low until 23 dpi, showing significant differences against the control group at the peak of parasite loads (14 dpi; p<0.05) during the acute phase, and also showed significant lower parasite loads in a target organ during the chronic phase (p<0,05). Altogether, these results suggest that the chimeric immunogen engineered with a mSAg and a pathogen´s antigen represents a promising strategy to further investigate as a vaccine candidate against T. cruzi infection and other pathogens.