Compared to young and adult mice, aged mice displayed: (i) increased activation of epithelial cells with a decreased expression of TLR3; (ii) increased activation of dendritic cells with increased expression of MHC-I, MHC-II, and CD80/86; (iii) decreased production of type-I interferons; (iv) delayed production of anti-inflammatory cytokines and chemokines in the lungs; and (v) impairment frequencies of functional HSV-specific CD107+IFN-γ+CD8+ T cells associated with the increased incidence of viral infection and disease. This evidence concerns the gene CD8A and viral infectious disease.