Evaluation of IFN-γ production by CD8⁺ T lymphocytes in response to the K1 peptide from KMP-11 protein in patients infected with Trypanosoma cruzi

The cellular response mediated by MHC class I restricted CD8⁺T cells has been shown to be crucial in the control of Chagas disease. The K1 peptide derived from T. cruzi KMP-11 protein has a high binding affinity to the HLA-A*0201 molecule. Nevertheless, it is not known whether this peptide is processed and displayed as an MHC class I epitope during natural infection by T. cruzi. The aim of this study was to evaluate, by ELISPOT assay, the ability of K1 peptide to activate CD8⁺T lymphocytes to produce IFN-γ. Therefore, CD8⁺T lymphocytes from 22 HLA-A*0201 ⁺individuals, 12 chronic chagasic patients and 10 uninfected controls, were analysed. The results revealed that two of the chagasic patients had IFN-γ-secreting CD8⁺T cells that were able to respond to K1 peptide with a relative frequency of 110 and 230 per million CD8⁺T cells. In contrast, none of HLA-A*0201⁺uninfected controls responded to K1 peptide. Responses to HLA-A*0201 restricted peptide from the influenza matrix protein were found in six chagasic patients and four uninfected controls with an average frequency of 175 and 111 cells per million CD8⁺T cells, respectively. Moreover, a flow cytometric assay for degranulation showed that chagasic responders had K1-specific cytotoxic CD8 ⁺ T cells. It is shown here for the first time that the K1 peptide is efficiently processed, presented and recognized by CD8⁺T lymphocytes during the natural course of Chagas disease.