Figure 8.
IL-6 in BALF, lung viral titers, and mucosal and systemic IFN-γ secreting cell spots at 12 months after immunization upon heterosubtypic challenge. Levels of IL-6 cytokine and lung viral titers were determined in mice immunized with influenza split vaccine alone (Split) or influenza split vaccine supplemented with M2e5x VLP (Split+M2e5x) day 4 postchallenge with 5xLD50 of A/Philippines/2/82 (H3N2) virus at 12 months after boost vaccination. (a) IL-6 cytokine in BALF. IL-6 was determined by a cytokine ELISA (N = 4). (b) Lung viral titers. Lung viral titers were determined by an egg inoculation assay day 4 postchallenge (N = 4). Splenocytes and lung cells were isolated from mice day 4 postchallenge (N = 4). IFN-γ secreting cells were detected in the presence of A/California/04/09 (H1N1) virus, M2e peptide, or M2e5x VLPs as a stimulator (2 µg/ml). (c) IFN-γ secreting splenocytes. (d) IFN-γ secreting lung cells. IFN-γ– or IL-4 cytokine–producing cells were counted by enzyme-linked immunosorbent spot (ELISPOT) reader. P value indicates significant difference between split+M2e5x and split vaccinated or naive groups. Data represent mean ± SEM. BALF, bronchoalveolar lavage fluid; IFN, interferon; M2e, M2 ectodomain; VLP, virus-like particles.