Identification of HLA-A∗02:01-restricted CTL epitopes in Trypanosoma cruzi heat shock protein-70 recognized by Chagas disease patients

CD8+ cytotoxic T lymphocyte (CTL) response is critical for controlling the infection of the protozoan parasite Trypanosoma cruzi, the causative agent of Chagas disease. Since only a few CD8 antigens have been described in Chagas disease patients, the identification of new class I-restricted epitopes is urgently needed for the development of immunotherapies against T. cruzi infection. In this study, bioinformatic methods were used to predict HLA-A∗02:01-binders, and 30 peptides were selected, synthesized and tested for HLA-A∗02:01 binding. Among them, sixteen peptides with medium-to-high affinity were assayed for their recognition by CTL from HSP70-immunized or T. cruzi-infected transgenic B6-A2/Kb mice. Our results show that four immunodominant epitopes (HSP70210-8, HSP70255-63, HSP70316-24 and HSP70345−53) are contained in the T. cruzi HSP70 antigen. Indeed two of them (HSP70210-8 and HSP70316-24) were also recognized by CTL of HLA-A∗02:01+ Chagas disease patients, indicating that these peptides are processed and displayed as MHC class I epitopes during the natural history of T. cruzi infection. The HLA-A∗02:01 restriction was evidenced using peptide-pulsed K562-A2 cells as antigen-presenting cells. Both cytotoxic and cytokine-secreting activities were detected in response to the former two peptides and, moreover, 10/12 patients (83%) recognized at least one of these two HSP70-derived CD8+ epitopes.