Trypanosoma cruzi paraflagellar rod proteins 2 and 3 contain immunodominant CD8+ T-cell epitopes that are recognized by cytotoxic T cells from Chagas disease patients

The protozoan parasite Trypanosoma cruzi is the etiological agent of Chagas disease. To date, no vaccine is available for protection against T. cruzi infection. The CD8+ T cells immune response against specific antigens has shown to efficiently control the spread of the parasite in murine experimental infection. However, data concerning CD8+ response in Chagas patients are still restricted to a few epitopes. We have studied the existence of immunodominant CD8+ T cell epitopes in the paraflagellar rod proteins 2 and 3 (PFR2 and PFR3) from T. cruzi in a mouse model, and analyzed their recognition by cytotoxic T lymphocytes from Chagas disease patients. Immunization of C57BL/6-A2/Kb transgenic mice with plasmids coding for the fusion proteins PFR2-HSP70 and PFR3-HSP70 induced a specific CTL response against two PFRs epitopes (PFR2449–457 and PFR3481–489), and showed specific lysis percentages of 24 and 12, respectively. Moreover, the PFR219–28, PFR2156–163, PFR2449–457, PFR3428–436, PFR3475–482 and PFR3481–489 peptides were observed to have a high binding affinity to the HLA-A*02:01 molecule. Remarkably, these HLA-A*02:01-binding peptides are successfully processed and presented during natural infection by T. cruzi in the context of MHC class I as evidenced by using peptide-pulsed K562-A2 cells as antigen presenting cells. The T cells from Chagas disease chronic patients specific for PFR2/PFR3 selected CD8+ epitopes showed a pro-inflammatory cytokine secretion profile (IFN-γ, TNF-α and IL-6). A positive Granzime B secretion was observed in three out of 16 patients in response to PFR2156–163 and PFR2449–457 peptides, two out of 11 patients in response to PFR219–28 peptide and one out of 14 and 11 patients in response to PFR3428–436 and PFR3481–489 peptides, respectively. The PFRs-specific cytotoxic activity in purified PBMC was only detected in patients in the indeterminate phase of the disease.

► PFR2 and PFR3 proteins contain immunodominant A2-restricted epitopes.
► Six PFR2/PFR3 CD8+ T epitopes are processed and presented during Chagas disease.
► Cytokine secretion profile of PFR2/PFR3 specific CD8+ T cells is proinflammatory.
► The PFRs specific CTL activity was only observed in IND chronic Chagasic patients.