Frequency of specific CD8⁺ T cells for a promiscuous epitope derived from Trypanosoma cruzi KMP-11 protein in chagasic patients

The K1 peptide is a CD8⁺T cell HLA-A*0201-restricted epitope derived from the Trypanosoma cruzi KMP-11 protein. We have previously shown that this peptide induces IFN-γ secretion by CD8⁺T cells. The aim of this study was to characterize the frequency of K1-specific CD8 ⁺T cells in chagasic patients. Nineteen HLA-A2⁺individuals were selected from 50 T. cruzi infected patients using flow cytometry and SSP-PCR assays. Twelve HLA-A*0201⁺noninfected donors were included as controls. Peripheral blood mononuclear cells were stained with HLA-A2-K1 tetramer, showing that 15 of 19 infected patients have K1-specific CD8⁺T cells (0·09-0·34% frequency) without differences in disease stages or severity. Of note, five of these responders were A*0205, A*0222, A*0226, A*0259 and A*0287 after molecular typing. Thus, a phenotypic and functional comparison of K1-specific CD8⁺T cells from non-HLA-A*0201 and HLA-A*0201 ⁺infected patients was performed. The results showed that both non-HLA-A*0201 and HLA-A*0201⁺individuals have a predominant effector memory CD8⁺T cell phenotype (CCR7-, CD62L-). Moreover, CD8⁺T cells from non-HLA-A*0201 and HLA-A*0201⁺individuals expressed IL-2, IFN-γ and perforin without any differences. These findings support that K1 peptide is a promiscuous epitope presented by HLA-A2 supertype molecules and is highly recognized by chagasic patients.