Identification of naturally-presented influenza A virus CD8+ T cell epitopes

Influenza viruses (IV) infection is a public health concern worldwide. Currently, all available vaccines as well as antiviral drugs that target the virus itself are prone to resistance. Lessons learned from previous pandemic outbreaks is that people with a preexisting cellular immune response are either protected or developed less severe disease against the infection. Understanding CD8+ T cell immunity to IV across prominent HLA types is pivotal to rationally designing a universal influenza vaccine and generating protective immunity, especially for high-risk populations. Using mass spectroscopy, an immunopeptidomics analysis was carried out to characterize the entire landscape of peptides presented by MHC-I molecules post IV infection at different time points. We were able to identify sixteen naturally-presented MHC-I ligands restricted to different HLA allotypes including HLA-A*68, HLA-A*24, HLA-B*51, and HLA-B*07. Of these, nine peptides were immunogenic with multifunctional memory CD8 T cell response in different donors. These results highlight novel broadly protective IAV-derived CD8+ epitopes that reflect physiological peptide processing and presentation mechanisms that can work cooperatively with other distinct epitopes to provide optimal protection in particular against the newly-emerging variants.