To determine whether the truncated infection cycle of S-FLU vaccine regulates the antigen sensitivity of memory CD8+ T cells, C57BL/6 mice were vaccinated intranasally with S-FLU(H1N1) or intranasally infected with influenza virus (PR8), and on days 28 to 30 after infection, we tested the antigen sensitivity of endogenous NP-specific CD8+ T cells in the spleen and lung by ex vivo stimulation with titrated doses of NP peptide followed by intracellular cytokine staining for the effector cytokine, IFN-γ. Here, CD8A is linked to infection.