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.