Figure 6

The relative expression levels of viral vRNAs and mRNAs in A549 cells infected with recombinant H9N2 viruses carrying the PB2 S155N and PA S49Y and D347G mutations. Monolayers of A549 cells were infected with different mutant viruses harbouring the PB2 S155N and PA S49Y and D347G mutations at an MOI of 2. The abundance of vRNAs and mRNAs encoding the NP gene of the indicated viruses is expressed as the fold-change in copy number compared with the wild-type group at 8 h post-infection. The data presented are the mean ± SD of three independent experiments. P values were calculated by using the Student’s t test, ***P < 0.001, ****P < 0.0001.