Zhao Lingcai, Tian Miao, Hu Xifeng, Fan Menglu, Hou Chenglin, Ping Jihui
MOE Joint International Research Laboratory of Animal Health and Food Safety, Engineering Laboratory of Animal Immunity of Jiangsu Province, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China.
MOE Joint International Research Laboratory of Animal Health and Food Safety, Engineering Laboratory of Animal Immunity of Jiangsu Province, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China.
Virol Sin. 2025 Feb;40(1):35-49. doi: 10.1016/j.virs.2024.12.003. Epub 2024 Dec 17.
The H9N2 subtype avian influenza virus (AIV) continues to propagate and undergo evolution within China, thereby posing a significant threat to the poultry industry. This study encompassed the collection of 436 samples and swabs in East China over the period spanning 2018 to 2019, from which 31 strains of the H9N2 subtype viruses were isolated and purified. We revealed that the HA and NA genes of the 31 isolates categorized within the Y280 branch, while the PB2 and M genes were associated with the G1 branch, and the remaining genes aligned with the F/98 branch. Despite this alignment, antigenic mapping demonstrated differences between the 2018 and 2019 strains, with the early vaccine strains displaying low serological reactivity toward these isolates. Notably, the CK/SH/49/19 isolate exhibited lethality in mice, characterized by a PB2 E627V mutation and a HA deletion at amino acid position 217. Mechanistically, in vitro studies showed that the influenza virus CK/SH/49/19 carrying PB2 627V and HA 217M mutations displayed enhanced replication capacity, attributed to the heightened activity of the polymerase with PB2 627V. Moreover, the absence of the amino acid at the HA 217 site obstructed viral adsorption and internalization, resulted in lower activation pH, and impeded the virus budding process. Critically, in vivo experiments revealed that CK/SH/49/19 (PB2 627V, HA 217Δ) triggered a robust activation of interferon response and interferon-stimulated genes. This study furnished a theoretical foundation for the scientific prevention and control strategies against H9N2 subtype avian influenza.
H9N2亚型禽流感病毒（AIV）在中国持续传播并发生进化，对家禽业构成重大威胁。本研究收集了2018年至2019年期间中国东部的436份样本和拭子，从中分离并纯化出31株H9N2亚型病毒。我们发现，31株分离株的HA和NA基因属于Y280分支，而PB2和M基因与G1分支相关，其余基因与F/98分支一致。尽管有这种一致性，但抗原图谱显示2018年和2019年的毒株之间存在差异，早期疫苗毒株对这些分离株的血清学反应较低。值得注意的是，CK/SH/49/19分离株在小鼠中表现出致死性，其特征为PB2 E627V突变和HA氨基酸位置217处的缺失。从机制上讲，体外研究表明，携带PB2 627V和HA 217M突变的流感病毒CK/SH/49/19显示出增强的复制能力，这归因于PB2 627V聚合酶活性的提高。此外，HA 217位点氨基酸的缺失阻碍了病毒的吸附和内化，导致较低的激活pH值，并阻碍了病毒出芽过程。至关重要的是，体内实验表明CK/SH/49/19（PB2 627V，HA 217Δ）引发了干扰素反应和干扰素刺激基因的强烈激活。本研究为H9N2亚型禽流感的科学防控策略提供了理论基础。
