Protective immunity against Chagas disease induced by a superantigen-based chimeric DNA vaccine delivered by attenuated Salmonella

Abstract

Chagas disease is a chronic parasitic infection endemic to Latin America that affects more than 7 million people and is increasingly spreading worldwide due to human migration. Trypanosoma cruzi is the etiological agent of this disease, for which no effective vaccine has yet been approved for human use. We previously developed a heterologous chimeric immunogen, CruSEG, composed of the N-terminal domain of the major cysteine protease cruzipain (Nt-Cz) fused to a genetically detoxified mutant of the staphylococcal superantigen G (SEGN24A). This modified superantigen preserves innate immune activation while avoiding deleterious T-cell effects associated with native superantigens. Here, we evaluated the immunogenicity and protective efficacy of CruSEG using different vaccination strategies, including recombinant protein formulated with CpG-ODN, oral DNA immunization delivered by attenuated Salmonella enterica, and a heterologous prime–boost regimen combining both platforms. All vaccination protocols induced Nt-Cz–specific immune responses, albeit with distinct qualitative profiles. Recombinant protein vaccination elicited robust humoral immunity characterized by Th1-skewed IgG2a responses and strong parasite-neutralizing activity, whereas DNA delivery preferentially promoted potent cellular immunity, including polyfunctional CD4⁺ T cells and IFN-γ–producing CD8⁺ T cells. The prime–boost strategy generated a broader immune profile but did not confer superior protection compared with homologous regimens. Upon challenge with T. cruzi strains belonging to different discrete typing units, vaccinated mice exhibited significant reductions in parasitemia during the acute phase and sustained control of parasite burden and tissue damage during chronic infection. Although sterilizing immunity was not achieved, the attenuation of parasite persistence and pathology represents a biologically relevant outcome. Collectively, these findings demonstrate that incorporating a detoxified bacterial superantigen into chimeric antigens across multiple platforms enhances immune quality and protective efficacy, highlighting engineered superantigens as promising immune modulators for the development of effective vaccines against Chagas disease.