Challenging immunodominance of influenza-specific CD8⁺ T cell responses restricted by the risk-associated HLA-A*68:01 allomorph

Although influenza viruses lead to severe illness in high-risk populations, host genetic factors associated with severe disease are largely unknown. As the HLA-A*68:01 allele can be linked to severe pandemic 2009-H1N1 disease, we investigate a potential impairment of HLA-A*68:01-restricted CD8+ T cells to mount robust responses. We elucidate the HLA-A*68:01+CD8+ T cell response directed toward an extended influenza-derived nucleoprotein (NP) peptide and show that only ~35% individuals have immunodominant A68/NP145 +CD8+ T cell responses. Dissecting A68/NP145 +CD8+ T cells in low vs. medium/high responders reveals that high responding donors have A68/NP145 +CD8+ memory T cells with clonally expanded TCRαβs, while low-responders display A68/NP145 +CD8+ T cells with predominantly naïve phenotypes and non-expanded TCRαβs. Single-cell index sorting and TCRαβ analyses link expansion of A68/NP145 +CD8+ T cells to their memory potential. Our study demonstrates the immunodominance potential of influenza-specific CD8+ T cells presented by a risk HLA-A*68:01 molecule and advocates for priming CD8+ T cell compartments in HLA-A*68:01-expressing individuals for establishment of pre-existing protective memory T cell pools.