Young Adult Influenza Vaccine Immunogenicity Substudy

The goals of this study are to provide in depth humoral and cellular immune responses to the standard-dose trivalent SV influenza virus vaccine containing 15 pg HA of each virus strain in healthy young adults. Serum samples will be submitted for the following analysis: measurement of serum anti-HA (hemagglutinin) IgG and IgA antibodies by ELISA, IgG antibody subclasses, IgG and IgA Avidity, Virus neutralizing functional assay, HAI antibody titer. Peripheral blood mononuclear cells (PBMC) isolated from these subjects will be evaluated for the following: "central" (TCM) and "effector" (TEM) memory T cell responses, including their proliferative responses and cytokine production profiles by flow cytometry, IFN-7 production by ELISPOT, following specific antigenic stimulation. Serum samples will be submitted for the following analysis: measurement ex vivo of the frequency of circulating influenza-specificT cells by using commercially available MHC/tetramers and/or MHC/pentamers and flow cytometry, role of regulatory T cells in the modulation of influenza responses in young adults. Fifteen healthy young adult subjects, age 18-40 years, inclusive, will be recruited from the general population to be enrolled in this study. No randomization or masking procedures will be used. All eligible subjects will be administered one intramuscular (IM) injection of the same FDA approved standard-dose (15 mcg HA per strain) trivalent inactivated influenza vaccine, 2004-2005 season, and key humoral and cell-mediated immunity (CMI) responses will be compared to those of elderly subjects enrolled under DMID 05-0028. On both Day 0 (pre-vaccination) and day 28 (post-vaccination), an 100 ml volume of whole blood will be obtained for a complete blood count (CBC) with differential and to isolate and cryopreserve serum and PBMCs. This study will evaluate key humoral and cell-mediated immunity (CMI) responses in healthy young adults to establish a baseline immune response which will be used to evaluate changes associated with immunosenescence. This study is linked to DMID protocol 05-0028.