Humoral and Cellular Immune Responses following Vaccination with Purified Recombinant Hemagglutinin from Influenza A (H3N2) Virus

Adults were immunized with either baculovirus-expressed, purified recombinant hemagglutinin (rHA) from influenza A/Beijing/32/92 (H3N2) virus or saline placebo and evaluated for humoral and in vitro cellular immune responses. Compared with responses in placebo recipients, vaccinees had greater postvaccination H3(Beijing/32) HA (H3)-specific lymphoproliferation and interleukin (IL)-2, IL-10, and interferon-gamma (IFN-gamma) production. Mean increases in the production of IL-10 (> or = 20-fold) and IL-2 (10-fold) were relatively greater than that of IFN-gamma (4-fold) or IL-4 (no change). Serum H3 antibodies were induced in 80% of rHA recipients, and the rise in antibody titer was significantly correlated with changes in IL-2, IL-10, and IFN-gamma concentrations. Vaccination with rHA only minimally enhanced anti-influenza virus cytotoxic T lymphocyte activity. These data demonstrate that rHA immunization of adults elicits a significant recall response by memory B and T lymphocytes and suggest that the cytokine response to vaccination has a T helper cell type 0-like profile.