CD8⁺ T-cell responses towards conserved influenza B virus epitopes across anatomical sites and age

Influenza B viruses (IBVs) cause substantive morbidity and mortality, and yet immunity towards IBVs remains understudied. CD8⁺ T-cells provide broadly cross-reactive immunity and alleviate disease severity by recognizing conserved epitopes. Despite the IBV burden, only 18 IBV-specific T-cell epitopes restricted by 5 HLAs have been identified currently. A broader array of conserved IBV T-cell epitopes is needed to develop effective cross-reactive T-cell based IBV vaccines. Here we identify 9 highly conserved IBV CD8⁺ T-cell epitopes restricted to HLA-B*07:02, HLA-B*08:01 and HLA-B*35:01. Memory IBV-specific tetramer⁺CD8⁺ T-cells are present within blood and tissues. Frequencies of IBV-specific CD8⁺ T-cells decline with age, but maintain a central memory phenotype. HLA-B*07:02 and HLA-B*08:01-restricted NP_30-38 epitope-specific T-cells have distinct T-cell receptor repertoires. We provide structural basis for the IBV HLA-B*07:02-restricted NS1_196-206 (11-mer) and HLA-B*07:02-restricted NP_30-38 epitope presentation. Our study increases the number of IBV CD8⁺ T-cell epitopes, and defines IBV-specific CD8⁺ T-cells at cellular and molecular levels, across tissues and age.