Fig. 3.

Viral titers and histopathological changes in lung tissues of challenged mice. The mice immunized with M2e-FP-1 and M2e-FP-2 proteins, respectively, or PBS as a control were challenged with A/PR/8/34(H1N1) influenza virus (10³ TCID₅₀), and collected for lung tissues at 5 days p.i. to detect viral titers (A) and histopathological changes (B). The data in (A) are presented as mean ± SD of 5 mice in each group. ***P < 0.001. For (B), Representative images from lung tissues of immunized mice and control mice are shown. The tissue sections were stained by H&E straining, and observed for pathological damages under light microscopy (10× magnification).