Fig. 2: Viral load and lung histology of vaccinated mouse challenged with A/Hong Kong/415742Md (pH1N1).

The mice were challenged with 10x LD₅₀ of A/Hong Kong/415742Md 14 days after one dose i.d. vaccination. Lung samples were analyzed at 2 and 4 days post infection (dpi). a Lung infectious viral titer determined by plaque forming assay on MDCK cells. n = 3 mice per group. b Representative images of influenza nucleoprotein (NP) expression in the lung at 2 dpi stained by immunohistochemistry. Scale bars = 100 µm. c Representative images of hematoxylin and eosin-stained lung sections at 2 dpi. Scale bars = 100 µm. The chart on the right was histology scores, n = 3 for each group. d Real-time RT-PCR determined the relative expression of cytokines and chemokines in lung homogenate. Fold changes of the gene expression were relative to the uninfected mouse lung samples. n = 3 mice per group. Error bars indicate standard error of mean. ^*p < 0.05; ^**p < 0.01; ^***p < 0.001 when compared with PBS group by two-way ANOVA.