Lung-resident T-cell immunity dominates protection induced by an intranasal adenoviral nucleoprotein influenza vaccine.

Frequent antigenic drift in influenza viruses necessitates broadly protective vaccines. This study evaluated an intranasal adenoviral-vector vaccine expressing influenza A nucleoprotein (NP) fused to the autophagy-inducing peptide C5. A heterologous prime-boost regimen using chimpanzee and bovine adenoviral platforms induced strong NP-specific humoral and cellular immune responses in mice. High serum and lung IgG/IgA level were detected, accompanied by enhanced antibody-dependent cellular cytotoxicity. Cellular analyses revealed potent NP-specific cytokine responses and expansion of effector memory (TEM) and tissue-resident memory (TRM) T cells, particularly CD8+ TRM, in the lungs. Experiments using immune-deficient mice showed that B cells and CD8+ T cells independently contributed to early viral clearance. Adoptive transfer studies demonstrated that lung-derived T cells conferred the strongest heterosubtypic viral restriction, whereas systemic T cells and antibodies provided partial protection. Together, these findings highlight the critical role of lung-resident T cells in cross-protective viral control, supporting intranasal NP-based adenoviral vaccines as promising universal influenza vaccine candidates.