自2013年首次报告人类感染以来,H7N9禽流感病毒(AIV)一直被视为严重威胁人类健康的病毒。在这项研究中,我们试图确定哺乳动物宿主中H7N9病毒的毒力决定因素。通过比较SH/4664H7N9病毒的毒力,一种无毒的H9N2病毒,和感染小鼠中的各种H7N9-H9N2杂种病毒,我们首先指出PB2是解释H7N9和H9N2在哺乳动物毒力中差异的主要病毒因子。我们进一步分析了单独突变与密切相关的H9N2病毒不同的H7N9PB2残基的体内作用,因此发现残基473以及众所周知的残基627对于小鼠中H7N9病毒的毒力和其重组病毒聚合酶在哺乳动物细胞中的活性至关重要。通过研究H9N2背景中的反向H7N9取代,进一步加强了PB2-473的重要性。最后,我们惊讶地发现,特定物种使用ANP32A,与PB2-627多态性相关的宿主因子家族成员,介导PB2473残基对哺乳动物适应AIV聚合酶的贡献,因为PB2M473T对H7N9病毒的病毒聚合酶活性和病毒生长的减弱作用可以通过共表达鸡ANP32A而不是小鼠ANP32A和ANP32B来有效补充。一起,我们的研究发现,PB2473残基是一种新型的AIV病毒宿主范围决定因素,通过物种特异性共同选择ANP32宿主因子来支持病毒聚合酶活性.H7N9禽流感病毒自2013年报告第一例人类感染病例以来,被认为有可能引发下一次大流行。在这项研究中,我们将PB2残基473鉴定为H7N9病毒及其非致病性H9N2对应物的病毒聚合酶的小鼠毒力和哺乳动物适应性的新决定因素.我们进一步证明,PB2-473的变异与宿主ANP32A蛋白在支持病毒聚合酶活性方面的差异共选功能相关,类似于众所周知的PB2-627多态性,尽管两个PB2位置在空间上相距遥远。通过对甲型流感病毒PB2介导的宿主范围测定提供新的机制见解,我们的研究提示可能存在多个PB2-ANP32接口,这些接口可能成为开发针对H7N9病毒以及其他哺乳动物适应性流感病毒的新型抗病毒药物的靶标.
Since the first human infection reported in 2013,
H7N9 avian influenza virus (AIV) has been regarded as a serious threat to human health. In this study, we sought to identify the virulence determinant of the
H7N9 virus in mammalian hosts. By comparing the virulence of the SH/4664
H7N9 virus, a non-virulent H9N2 virus, and various
H7N9-H9N2 hybrid viruses in infected mice, we first pinpointed PB2 as the primary viral factor accounting for the difference between H7N9 and H9N2 in mammalian virulence. We further analyzed the in vivo effects of individually mutating
H7N9 PB2 residues different from the closely related H9N2 virus and consequently found residue 473, alongside the well-known residue 627, to be critical for the virulence of the H7N9 virus in mice and the activity of its reconstituted viral polymerase in mammalian cells. The importance of PB2-473 was further strengthened by studying reverse
H7N9 substitutions in the H9N2 background. Finally, we surprisingly found that species-specific usage of ANP32A, a family member of host factors connecting with the PB2-627 polymorphism, mediates the contribution of PB2 473 residue to the mammalian adaption of AIV polymerase, as the attenuating effect of PB2 M473T on the viral polymerase activity and viral growth of the H7N9 virus could be efficiently complemented by co-expression of chicken ANP32A but not mouse ANP32A and ANP32B. Together, our studies uncovered the PB2 473 residue as a novel viral host range determinant of AIVs via species-specific co-opting of the ANP32 host factor to support viral polymerase activity.IMPORTANCEThe H7N9 avian influenza virus has been considered to have the potential to cause the next pandemic since the first case of human infection reported in 2013. In this study, we identified PB2 residue 473 as a new determinant of mouse virulence and mammalian adaptation of the viral polymerase of the H7N9 virus and its non-pathogenic H9N2 counterparts. We further demonstrated that the variation in PB2-473 is functionally linked to differential co-opting of the host ANP32A protein in supporting viral polymerase activity, which is analogous to the well-known PB2-627 polymorphism, albeit the two PB2 positions are spatially distant. By providing new mechanistic insight into the PB2-mediated host range determination of influenza A viruses, our study implicated the potential existence of multiple PB2-ANP32 interfaces that could be targets for developing new antivirals against the H7N9 virus as well as other mammalian-adapted influenza viruses.