Induction of alphadelta- and alphabeta-mediated T cell responses in healthy elderly subjects after influenza vaccination.

Influenza is an important cause of morbidity and mortality in the elderly and influenza vaccination has shown a decreased efficacy in aged people. Both gammadelta- and alphabeta-T cell responses, which are believed to play an important role in controlling influenza infection, are impaired during aging. The aim of this study was to evaluate the ability of influenza vaccine to induce cellular immune responses mediated by gammadelta- and alphabeta-T cells in healthy elderly subjects. After influenza vaccination, an increased proportion of Vgamma9Vdelta2 T cells having reduced proliferative capacity and increased perforin production, and then a differentiated effector/memory phenotype, was present. The peripheral number and the cytokine production of gammadelta T cells were not changed. A significant decrease of CD4 and CD8 naïve T cells and a corresponding increase of CD4 and CD8 memory T cells were found. The in vitro stimulation of PBMCs from elderly subjects with influenza antigens increased their proliferative capacity and the production of both IFNgamma and IL-4. The vaccine was clinically effective, since in the outbreak period, only one influenza case was noted. The results reported in this study demonstrate the activation of both gammadelta- and alphabeta-T cell responses in healthy elderly after influenza vaccination.