Complete protection offered by i.n. immunization of rAd/NP during heterologous H1N1 or heterosubtypic H3N2 virus challenge rendered us to investigate whether the observed cross-protection correlates with the magnitude NP-specific CD8 T-cell responses, given that influenza NP contains a conserved immunodominant CD8 T-cell epitope as indicated previously. This evidence concerns the gene CD8A and influenza.