This study sought to quantify CD8(+) T cell responses to Trypanosoma cruzi and to identify potential links between these responses and the severity of disease in humans. In the majority of patients with Chagas disease, staining with class I major histocompatibility complex tetramers and analysis of interferon (IFN)- gamma ELISPOT responses to a panel of known cytotoxic T lymphocyte target epitopes from T. cruzi failed to identify parasite-specific CD8(+) T cells. However, the frequency of individuals with positive ELISPOT responses was higher in areas of active transmission. Analysis of IFN- gamma ELISPOT responses to a parasite lysate revealed a very high frequency of responders among patients with mild clinical disease and a very low frequency of responders among those with the most severe form of the disease. These data suggest that the frequency of IFN- gamma -producing T cells in patients with chronic Chagas disease is associated with the history of recent exposure and with the clinical status of the patient.

SUMMARYThe pathogenesis of Chagas' disease has been subject of active research and still remains to be ascertained. Galectin-1 (Gal-1), a member of a conserved family of animal b-galactoside-binding proteins, localized in human heart tissue, has been suggested to play key roles in immunological and inflammatory processes. In the present study we demonstrated the occurrence of anti-Gal-1 autoAb in sera from patients in the acute and chronic stages of Chagas' disease (ACD and CCD) by means of ELISA and Western blot analysis. We found a marked increase in the level and frequency of Ig E antiGal-1 antibodies in sera from patients with ACD, but a low frequency of Ig M anti-Gal-1 immunoreactivity. Moreover, Ig G immunoreactivity to this b-galactoside-binding protein was found to be correlated with the severity of cardiac damage in CCD, but was absent in nonrelated cardiomyopathies. We could not detect immunoreactivity with Trypanosoma cruzi antigens using a polyclonal antibody raised to human Gal-1 and no hemagglutinating activity could be specifically eluted from a lactosyl-agarose matrix from parasite lysates. Moreover, despite sequence homology between Gal-1 and shed acute phase antigen (SAPA) of T. cruzi, anti-Gal-1 antibodies eluted from human sera failed to cross-react with SAPA. In an attempt to explore whether Gal-1 immunoreactivity was originated from endogenous human Gal-1, we finally investigated its expression levels in cardiac tissue (the main target of Chagas' disease). This protein was found to be markedly upregulated in cardiac tissue from patients with severe CCD, compared to cardiac tissue from normal individuals.

ABSTRACT

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Cytokines and soluble cellular receptors are involved in inflammatory processes and probably in the pathogenesis of parasite and bacterial diseases. In a previous study, we reported increased levels of soluble receptors of interleukin-2 (sIL2-R) in children with acute Chagas' disease, one of the main parasitic infections that is endemic in Latin America. We sought to analyze the pattern of different cytokines and soluble receptors in the sera of children with chagasic infection. Children with acute and indeterminate stages of Chagas' disease, as well as nonchagasic children, were studied. Sera were assayed by enzyme-linked immunosorbent assay to measure the levels of tumor necrosis factor alpha (TNF-␣), IL-6, IL-2, IL-8, IL-12, sIL-2R, and the soluble receptors of CD8 and CD4 (sCD8 and sCD4). sIL-2R and sCD8 showed the highest levels in serum in acutely infected children, decreasing after specific antiparasite therapy. Chronic children showed a pattern similar to the one of nonchagasic children. Although they were not statistically significant, TNF-␣, IL-6, and sCD4 showed a tendency to reach high levels in the acutely infected group, whereas IL-2, IL-8, and IL-12 did not reveal changes with respect to the noninfected children. In summary, we report here the patterns of cytokines and soluble receptors in in the sera of children infected with Trypanosoma cruzi; we found significantly increased levels of sIL-2R and sCD8 in acute infection that decreased after therapy, and high levels of TNF-␣, IL-6, and sCD4 in some of the acute patients.