Figure 5

Effect of the PB2 S155N and PA S49Y and D347G mutations on viral replication in mammalian cells. A549 (A) or MDCK (B) cells were infected with wild-type and mutant viruses carrying these three mutant residues alone or simultaneously at an MOI of 0.01 or 0.001, respectively, and viral supernatants were collected at 12, 24 and 48 h post-infection to determine viral titres using a plaque assay. The data presented are the mean ± SD of three independent experiments. P values were calculated by using Student’s t test, *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.