Trypanosoma cruzi: analysis of cellular and humoral response against a protective recombinant antigen during experimental Chagas' disease

In previous studies we have shown the protective value of T. cruzi excretory/secretory antigens (ESA) as well as a synthetic peptide derived from the primary sequence of a 24-kDa protein present among ESA in mice and rats challenged with a lethal dose of T. cruzi. In the present study, the 24-kDa polypeptide was produced as a fusion protein in the pGEX-2T vector system. Western blot assays revealed that Tc24 is expressed by all T. cruzi strains so far examined (CL, ECH, C23, Tehuantepec, Tulahuen, and Y). The immunization of BALB/c mice with Tc24 fusion protein showed that the protein has the capacity to induce a significant level of protection in BALB/c mice against lethal T. cruzi infection. Moreover, splenic cells from T. cruzi chronically infected mice recognize the recombinant antigen since they proliferate after in vitro stimulation. A typical Th1 pattern of lymphokine secretion (IL-2 and IFN-gamma) was detected in splenic cell culture supernatants from Tc24-immunized mice. In addition, high levels of IFN-gamma were detected in cell culture supernatants from both acute and chronically infected mice after Tc24 antigen stimulation. In contrast, no detectable amounts of IL-4, IL-5 or Th-10 could be detected in those supernatants. Finally, antibodies (IgG isotype) involved in the immune clearance of T. cruzi are elicited by the Tc24 recombinant protein. Taken together, these results demonstrated that the recombinant T. cruzi antigen is able to induce cellular and humoral immune responses which could explain the protection achieved when this protein is used as immunizing agent.