Figure 4
Effect of the PB2 S155N and PA S49Y and D347G mutations on viral pathogenicity in mice. Five 6-week-old female BALB/c mice were inoculated with 2 × 106 PFU of the wild-type and PB2 and PA mutant viruses. Body weight loss (A) and mortality (B) were observed at 14 days after infection. Virus replication ability (C) in mouse turbinate and lung tissue and lung histopathology (D) on day 3 post-infection were determined. Mice that lost more than 25% of their original body weight were euthanized.