Human Influenza A Virus-Specific CD8⁺ T-Cell Response Is Long-lived

Animal and human studies have demonstrated the importance of influenza A virus (IAV)-specific CD8⁺ cytotoxic T lymphocytes (CTLs) in heterosubtypic cross-protective immunity. Using peripheral blood mononuclear cells obtained intermittently from healthy HLA-typed blood donors between 1999 and 2012, we were able to demonstrate that IAV-specific CTLs are long-lived. Intercurrent IAV infections transiently increase the frequency of functionally distinct subsets of IAV-specific CTLs, in particular effector and effector memory T cells.