West Nile virus (WNV) infection of aged patients typically leads to the development of severe neuroencephalitis. Studies in mice have elucidated an important role for CD8+ T cell function in controlling WNV infection and we hypothesized that the increased severity of WNV illness in the aged results from impaired CD8+ T cell function due to immunosenescence. We examined the functional profile of WNV-specific CD8+ T cell memory responses from a cohort of young and aged WNV infected patients using polychromatic flow cytometry. We quantified production of IFN-γ, TNF-α, IL-2 and CD107a mobilization by WNV-specific CD8+ T cells. We did not observe any relationship between advanced age and either the breadth or the magnitude of CD8+ T cell function. The magnitude of IFN-γ and TNF-α responses to WNV epitope stimulation did not decline with advanced age. Production of IL-2 was not detected from either young or aged CD8+ T cells. The ability to degranulate in response to virus peptide was also the same in young and aged patients. Collectively these data fail to support our hypothesis and suggest that, contrary to current models of immunosenescence, aged patients do develop functional CD8+ T cell immunity following exposure to a novel virus infection. This work was funded by a contract from NIAID (N01-AI-40066).