Amino Acid Mutations A286V and T437M in the Nucleoprotein Attenuate H7N9 Viruses in Mice

文献类型： 外文期刊

第一作者： Ma, Shujie

作者： Ma, Shujie;Zhang, Bo;Shi, Jianzhong;Yin, Xin;Wang, Guangwen;Cui, Pengfei;Liu, Liling;Deng, Guohua;Jiang, Yongping;Li, Chengjun;Chen, Hualan

作者机构：

关键词： H7N9; genetic basis; influenza; virulence

期刊名称：JOURNAL OF VIROLOGY （ 影响因子：5.103； 五年影响因子：5.078 ）

ISSN： 0022-538X

年卷期： 2020 年 94 卷 2 期

页码：

收录情况： SCI

摘要： The low-pathogenic H7N9 influenza viruses that emerged in 2013 acquired an insertion of four amino acids in their hemagglutinin cleavage site and thereby became highly pathogenic to chickens in 2017. Previous studies indicated that these highly pathogenic H7N9 viruses are virulent in chickens but have distinct pathotypes in mice. A/chicken/Guangdong/SD098/2017 (CK/SD098) is avirulent, with a 50% mouse lethal dose (MLD50) of >7.5 log(10) 50% egg infectious dose (EID50), whereas A/chicken/Hunan/S1220/2017 (CK/S1220) is virulent in mice, with an MLD50 of 3.2 log(10) EID50. In this study, we explored the genetic determinants that contribute to the difference in virulence between these two H7N9 viruses by generating a series of reassortants and mutants in the CK/S1220 virus background and testing their virulence in mice. We found that the reassortant CK/1220-SD098-NP, carrying the nucleoprotein (NP) of CK/SD098, was avirulent in mice, with an MLD50 of >10(7.5) EID50. The NPs of these two viruses differ by two amino acids, at positions 286 and 437. We further demonstrated that the amino acid mutations A286V and T437M of NP independently slowed the process of NP import to and export from the nucleus and thus jointly impaired the viral life cycle and attenuated the virulence of these H7N9 viruses in mice. Our study identified new virulence determinants in NP and provided novel targets for the development of live attenuated vaccines and antiviral drugs against influenza viruses. IMPORTANCE The H7N9 influenza viruses that emerged in China in 2013 have caused over 1,500 human infections, with a mortality rate of nearly 40%. The viruses were initially low pathogenic but became highly pathogenic in chickens at the beginning of 2017 and caused severe disease outbreaks in poultry. Several studies suggested that the highly pathogenic H7N9 viruses have increased virulence in mammals; however, the genetic basis of the virulence of H7N9 viruses in mammals is not fully understood. Here, we found that two amino acids, 286A and 437T, in NP are prerequisites for the virulence of H7N9 viruses in mice and the mutations A286V and T437M collectively eliminate the virulence of H7N9 viruses in mice. Our study further demonstrated that the virulence of influenza viruses is a polygenic trait, and the newly identified virulence-related residues in NP may provide new targets for attenuated influenza vaccine and antiviral drug development.

分类号：

  • 相关文献
作者其他论文 更多>>

微信小程序