FIG 7.

TIV-immunized mice with repeated virus challenge have higher viral titers and more pathogenic damage in the lungs. (A) Viral titers were determined by a TCID₅₀ assay of lung tissues from immunized mice and controls at days 3 and 5 after the first challenge. Data are presented as mean values ± standard errors of the means. dpi, days postinfection. (B) Mouse lung tissue damage was analyzed and scored at day 5 after the first challenge. Data are shown as mean values ± standard errors of the means. ***, P < 0.0001; n.s., no significance. (C) Representative hematoxylin- and eosin-stained sections from each group of mice scarified on day 5 after the first infection. Original magnification, ×100.