Outcome of infection with IAV HK/68 (H3N2).

<p>Mice were inoculated with IAV HK/68 (groups 2 (▴), 3 (○), 6 (▪) and 7 (×)) or PBS (groups 1 (), 4 (▿) and 5 (⋄)). (A) Body weight after infection was determined daily and expressed as the percentage of the original body weight before infection. (B) Lung virus titers measured on day 4 p.i. in mice from the indicated experimental groups. Horizontal bars represent the average titers of five mice. The dotted line represents the cut-off value for obtaining a positive result. *This mouse from group 6 had before infection an HI antibody titer of 40. (C) Vaccination prevented the induction of iBALT after infection. Twenty-eight days post infection with IAV HK/68 iBALT was detected in mice from group 3, but not in mice from group 2. Lung tissue sections were stained with HE. (D) Virus-specific CD8+ T cell responses detected 28 days post infection. Splenocytes of mice from the indicated experimental groups were tested for the presence of CD8+ T cells that bound the H2-Db NP_HK Tetramer. Horizontal bars represent the average of 2–4 mice. The difference in %CD8+ Tm+ T cells between groups 2 and 3 was statistically significant (<i>P</i> = 0.030).