Identification and immunogenicity of two new HLA-A*0201-restricted CD8+ T-cell epitopes on dengue NS1 protein

Immunopathogenesis of dengue virus (DEN) infection remains poorly studied. Identification and characterization of human CD8(+) T-cell epitopes on DEN are necessary for a better understanding of the immunopathogenesis of dengue infection and would facilitate the development of immunotherapy and vaccines to protect from dengue infection. Here, we identified two new HLA-A*0201-restricted CD8(+) T-cell epitopes, DEN-4 NS1(990-998) and DEN-4 NS1(997-1005) that are conserved in three or four major DEN serotypes, respectively. Unexpectedly, we found that immunization of HLA-A*0201 transgenic mice with DEN-4 NS1(990-998) or DEN-4 NS1(997-1005) epitope peptide induced de novo synthesis of tumor necrosis factor (TNF)-alpha and IFN-gamma, two important pro-inflammatory molecules that are hard to be detected directly without in vitro antigenic re-stimulation. Importantly, we demonstrated that CD8(+) T cells specifically activated by DEN-4 NS1(990-998) or DEN-4 NS1(997-1005) epitope peptide induced de novo synthesis of perforin. Furthermore, we observed that DEN-4 NS1(990-998) or DEN-4 NS1(997-1005)-specific CD8(+) T cells capable of producing large amounts of perforin, TNF-alpha and IFN-gamma preferentially displayed CD27(+)CD45RA(-), but not CD27(-)CD45RA(+), phenotypes. This study, therefore, suggested the importance of synergistic effects of pro-inflammatory cytokines and cytotoxic molecules which were produced by dengue-specific CD8(+) T cells in immunopathogenesis or anti-dengue immunity during dengue infection.