Characterization of the T-cell proliferative response to a purified glycopeptide antigen (GP-25) present on the Trypanosoma cruzi cell surface

Induction of B- and T-cell responses to cruzipain in the murine model of Trypanosoma cruzi infection

Trypanosoma cruzi, the causative agent of Chagas' disease, is an important cause of heart disease in Latin America. The parasite is transmitted mucosally, with both intra- and extracellular life stages in the human host. Cruzipain, the major cysteinyl proteinase of T. cruzi, has been shown to be antigenic in both humans and mice during infection with the parasite. We extend these observations, showing here that multiple murine immune subsets of potential importance for vaccine-induced protection can be induced by cruzipain. Cruzipain-specific serum IgG responses were induced during chronic infection with T. cruzi. In addition, T. cruzi mucosal infection stimulated the development of cruzipain-specific secretory IgA detectable in fecal extracts from infected mice. Cruzipain-specific type 1 cytokine responses characterized by the production of IFN-gamma but not IL-4 were also detectable during murine infection. Furthermore, immunization of mice with a DNA vaccine encoding cruzipain was shown to stimulate cytotoxic T lymphocyte (CTL) responses capable of recognizing and lysing T. cruzi-infected cells. The induction of serum antibody, mucosal IgA, Th1 cytokine and CTL responses by cruzipain in mice supports the use of this parasite protein for further efforts in T. cruzi vaccine development.

Do self-heart-reactive T cells expand in Trypanosoma cruzi-immune hosts?

Anti-heart T-cell activity was evaluated by a lymph node cell proliferative assay in isogenic strains of mice immunized with several Trypanosoma cruzi epimastigote and trypomastigote antigenic preparations. In addition, chronically infected animals were boosted with trypomastigote antigens and their lymph node cells were tested by in vitro proliferative responses. Our results indicated that (i) use of allogeneic sources of heart antigens may induce alloreactive responses in T. cruzi-immune T cells, (ii) specific autoimmune T-cell reactivity against self-heart constituents could not be demonstrated after immunization of the host with T. cruzi, and (iii) a proportion of chronically infected mice showed a small but detectable level of auto-anti-heart T-cell reactivity. These results argue against the notion that T. cruzi epitopes cross-reactive with self-heart tissue play a role in initiating T-cell-mediated autoimmunity. Anti-heart autoreactive T cells, generated in a proportion of the animals, may result from heart lesions associated with the infection process.