The initiation of antitumor immunity relies on dendritic cells (DCs) to cross-present cell-associated tumor Ag to CD8+ T cells (TCD8+) due to a lack of costimulatory molecules on tumor cells. Innate danger signals have been demonstrated to enhance cross-priming of TCD8+ to soluble as well as virally encoded Ags; however, their effect on enhancing TCD8+ cross-priming to cell genome-encoded Ags remains unknown. Furthermore, influenza A virus (IAV) has not been shown to enhance antitumor immunity. Using influenza-infected allogeneic cell lines, we show in this study that TCD8+ responses to cell-associated Ags can be dramatically enhanced due to enhanced TCD8+ expansion. This enhanced cross-priming in part involves TLR7- but not TLR3-mediated sensing of IAV and is entirely dependent on MyD88 and IFN signaling pathways. We also showed that the inflammasome-induced IL-1 and IFN-γ did not play a role in enhancing cross-priming in our system. We further demonstrated in our ex vivo system that CD8+ DCs are the only APCs able to prime TCR-transgenic TCD8+. Importantly, plasmacytoid DCs and CD8− DCs were both able to enhance such priming when provided in coculture. These observations suggest that IAV infection of tumor cells may facilitate improved cross-presentation of tumor Ags and may be used to augment clinical vaccine efficacy.

No abstract

T-cell repertoire is selected according to self peptide-MHC (major histocompatibility complex) complexes in the thymus. Although most peripheral T cells recognize specific pathogen-derived peptides complexed to self-MHC exclusively, some possess cross-reactivity to other self or foreign peptides presented by self-MHC molecules; a phenomenon often termed T-cell receptor (TCR) promiscuity or degeneracy. TCR promiscuity has been attributed to various autoimmune conditions. On the other hand, it is considered a mechanism for a relatively limited TCR repertoire to deal with a potentially much larger antigenic peptide repertoire. Such property has also been utilized to bypass self-tolerance for cancer vaccine development. Although many studies explored such degeneracy for peptide of the same length, few studies reported such properties for peptides of different length. In this study, we finely characterized the CD8(+) T-cell response specific for a 11mer peptide derived from influenza A viral polymerase basic protein 2. The short-term T-cell line, despite possessing highly biased TCR, was able to react with multiple peptides of different length sharing the same core sequence. Out data clearly showed the importance of detailed and quantitative assessments for such T-cell specificity. Our data also emphasize the importance of biochemical demonstration of the naturally presented minimal peptide.

The initiation of anti-tumor immunity relies on DCs to cross-present cell-associated tumor antigen to CD8+ T cells due to a lack of co-stimulatory molecules on tumor cells. Innate danger signals have been demonstrated to enhance cross-priming of TCD8+ to soluble as well as virally encoded Ags, however their effect on enhancing TCD8+ cross-priming to cell-genome encoded Ags remains unknown. Furthermore, Influenza A virus has not been shown to enhance anti-tumor immunity. Using influenza-infected allogeneic cell lines, we show here that TCD8+ responses to cell-associated Ags can be dramatically enhanced due to enhanced TCD8+ expansion. This enhanced cross-priming in part involves TLR7-, but not TLR3-, mediated sensing of IAV and is entirely dependent on MyD88 and IFN signaling pathways. We also showed that the inflammasome and IFN-r did not play a role in enhancing cross-priming in our system. We further demonstrated in our ex vivo system that CD8+ DCs are the only antigen-presenting cells able to prime TCR transgenic TCD8+. Importantly, pDCs and CD8- DCs were all able to enhance such priming when provided in co-culture. These observations suggest that IAV-infection of tumor cells may facilitate improved cross-presentation of tumor Ags and may be used to augment clinical vaccine efficacy.