Figure 1

Quantification and visualization of serine protease activities in lung homogenates from C57Bl/6J and DBA/2J. Each mouse was infected intra-nasally with 2 × 10³ FFU of the H1N1 PR8 virus and lung homogenates were prepared at different days p.i. A) The detected trypsin-like protease activity in lung homogenates from infected C57BL/6J and DBA/2J mice (pooled from day 3, 4 and 6 p.i.) using the specific substrate Bz-Val-Gly-Arg-p-NA had an alkaline pH optimum. Each data point represents the mean of three individual measurements (+/- 1 SD) in pooled lung homogenates from three individual mice. B) At the optimal pH 10.00, the serine protease activities (mean values +/- 1 SD) in lung homogenates from both mouse strains (n = 3 mice for each time point) showed a gradual increase with time after infection with no significant differences (P > 0.05) between lung homogenates from C57Bl/6J (black bars) and DBA/2J (white bars) mice. C) Zymograms showing the molecular weights of proteolytic enzyme activities in lung homogenates from uninfected (CD) or infected DBA/2J mice at days 1 (Dd1), 3 (Dd3) and 7 (Dd7) p.i., respectively, and uninfected (CB) or infected C57BL/6J mice at days 1 (Bd1), 3 (Bd3) and 7 (Bd7) p.i., respectively.