Figure 2
Viral polymerase activities of different PB2 mutants and their virus pathogenicity in mice. The polymerase activity of RNP complexes reconstituted from the PB2, PB1, PA and NP plasmids of the A/chicken/Jiangsu/875/2018 (A), A/chicken/Jiangsu/99/2017 (B) and A/chicken/Shandong/6/1996 (C) viruses and their single or double mutants were assessed by a dual luciferase reporter assay in three independent experiments. P values were calculated by using the Student’s t test, *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. Six-week-old female BALB/c mice (n = 5/group) were inoculated intranasally with 4 × 105 PFU of rJS/875 WT or its PB2 mutant viruses or an equal volume of PBS as the mock inoculation. Body weight changes (D) and survival rate (E) were recorded as the percentage of the weight on the day of inoculation (day 0). Mice that lost more than 25% of their original body weight were euthanized. The data presented are the mean ± SD of three independent experiments.