RT Journal Article SR Electronic(1) A1 Xu, Guanlong A1 Wang, Fang A1 Li, Qiuchen A1 Bing, Guoxia A1 Xie, Shijie A1 Sun, Shijing A1 Bian, Zengjie A1 Sun, HaoJie A1 Feng, Yu A1 Peng, Xiaowei A1 Jiang, Hui A1 Zhu, Liangquan A1 Fan, Xuezheng A1 Qin, Yuming A1 Ding, JiaboYR 2020 T1 Mutations in PB2 and HA enhanced pathogenicity of H4N6 avian influenza virus in mice JF Journal of General Virology, VO 101 IS 9 SP 910 OP 920 DO https://doi.org/10.1099/jgv.0.001192 PB Microbiology Society, SN 1465-2099, AB The H4 subtype avian influenza virus (AIV) continues to circulate in both wild birds and poultry, and occasionally infects mammals (e.g. pigs). H4-specific antibodies have also been detected in poultry farm workers, which suggests that H4 AIV poses a potential threat to public health. However, the molecular mechanism by which H4 AIVs could gain adaptation to mammals and whether this has occurred remain largely unknown. To better understand this mechanism, an avirulent H4N6 strain (A/mallard/Beijing/21/2011, BJ21) was serially passaged in mice and mutations were characterized after passaging. A virulent mouse-adapted strain was generated after 12 passages, which was tentatively designated BJ21-MA. The BJ21-MA strain replicated more efficiently than the parental BJ21, both in vivo and in vitro. Molecular analysis of BJ21-MA identified four mutations, located in proteins PB2 (E158K and E627K) and HA (L331I and G453R, H3 numbering). Further studies showed that the introduction of E158K and/or E627K substitutions into PB2 significantly increased polymerase activity, which led to the enhanced replication and virulence of BJ21-MA. Although individual L331I or G453R substitutions in HA did not change the pathogenicity of BJ21 in mice, both mutations significantly enhanced virulence. In conclusion, our data presented in this study demonstrate that avian H4 virus can adapt to mammals by point mutations in PB2 or HA, which consequently poses a potential threat to public health., UL https://www.microbiologyresearch.org/content/journal/jgv/10.1099/jgv.0.001192