Distinct epitope-specific memory kinetics within influenza B nucleoprotein shape long-term CD8+ T cell differentiation in the lung

CD8 + T cell memory inflation, originally described during murine cytomegalovirus infection, is characterized by the progressive accumulation of antigen-specific memory T cells that retain effector-like features rather than undergoing gradual contraction. Here, using intranasal immunization of CB6F1 mice with a recombinant adenoviral vector expressing influenza B nucleoprotein (NP), we identified two immunodominant epitopes within a single antigen. Whereas D b /BNP 352 -specific CD8 + T cells dominated during the effector phase, D d /BNP 166 -specific cells progressively increased during late memory, consistent with memory inflation. During the effector phase, D d /BNP 166 -specific CD8 + T cells exhibited higher inhibitory receptor expression and reduced antigen sensitivity compared with D b /BNP 352 -specific cells, indicating a regulated effector state. Notably, however, these cells showed greater enrichment of cell-cycle-associated programs and enhanced proliferative capacity. By the memory phase, D d /BNP 166 -specific cells displayed increased expression of tissue-resident memory T cell (TRM)-associated markers and higher functional avidity than at earlier time points. Together, these findings reveal divergence in CD8 + T cell memory trajectories between two peptide-MHC-specific populations after intranasal influenza B vaccination and indicate an association between a distinct early effector phenotype, subsequent memory inflation, and the persistence of lung TRM-like CD8 + T cells.