HLA Class I-T Cell Epitopes from trans-Sialidase Proteins Reveal Functionally Distinct Subsets of CD8+ T Cells in Chronic Chagas Disease

Background: Previously, we identified a set of HLA-A020.1-restricted trans-sialidase peptides as targets of CD8(+) T cell responses in HLA-A0201(+) individuals chronically infected by T. cruzi. Methods and Findings: Herein, we report the identification of peptides encoded by the same trans-sialidase gene family that bind alleles representative of the 6 most common class I HLA-supertypes. Based on a combination of bioinformatic predictions and HLA-supertype considerations, a total of 1001 epitopes predicted to bind to HLA A01, A02, A03, A24, B7 and B44 supertypes was selected. Ninety-six supertype-binder epitopes encoded by multiple trans-sialidase genes were tested for the ability to stimulate a recall CD8(+) T cell response in the peripheral blood from subjects with chronic T. cruzi infection regardless the HLA haplotype. An overall hierarchy of antigenicity was apparent, with the A02 supertype peptides being the most frequently recognized in the Chagas disease population followed by the A03 and the A24 supertype epitopes. CD8(+) T cell responses to promiscuous epitopes revealed that the CD8(+) T cell compartment specific for T. cruzi displays a functional profile with T cells secreting interferon-gamma alone as the predominant pattern and very low prevalence of single IL-2-secreting or dual IFN-gamma/IL-2 secreting T cells denoting a lack of polyfunctional cytokine responses in chronic T. cruzi infection. Conclusions: This study identifies a set of T. cruzi peptides that should prove useful for monitoring immune competence and changes in infection and disease status in individuals with chronic Chagas disease.