State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China.
Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou 510642, People's Republic of China.
Proc Natl Acad Sci U S A. 2022 Aug 23;119(34):e2203919119. doi: 10.1073/pnas.2203919119. Epub 2022 Aug 15.
Previous studies have shown that the Eurasian avian-like H1N1 (EA H1N1) swine influenza viruses circulated widely in pigs around the world and formed multiple genotypes by acquiring non-hemagglutinin and neuraminidase segments derived from other swine influenza viruses. Swine influenza control is not a priority for the pig industry in many countries, and it is worrisome that some strains may become more pathogenic and/or transmissible during their circulation in nature. Our routine surveillance indicated that the EA H1N1 viruses obtained different internal genes from different swine influenza viruses and formed various new genotypes. In this study, we found that a naturally isolated swine influenza reassortant, A/swine/Liaoning/265/2017 (LN265), a representative strain of one of the predominant genotypes in recent years, is lethal in mice and transmissible in ferrets. LN265 contains the hemagglutinin, neuraminidase, and matrix of the EA H1N1 virus; the basic polymerase 2, basic polymerase 1, acidic polymerase (PA), and nucleoprotein of the 2009 H1N1 pandemic virus; and the nonstructural protein of the North American triple-reassortment H1N2 virus. By generating and testing a series of reassortants and mutants, we found that four gradually accumulated mutations in PA are responsible for the increased pathogenicity and transmissibility of LN265. We further revealed that these mutations increase the messenger RNA transcription of viral proteins by enhancing the endonuclease cleavage activity and viral RNA-binding ability of the PA protein. Our study demonstrates that EA H1N1 swine influenza virus became pathogenic and transmissible in ferrets by acquiring key mutations in PA and provides important insights for monitoring field strains with pandemic potential.
先前的研究表明，欧亚类禽 H1N1（EA H1N1）猪流感病毒在全球范围内广泛传播，并通过获得源自其他猪流感病毒的非血凝素和神经氨酸酶片段形成多种基因型。在许多国家，猪流感的控制并不是养猪业的优先事项，令人担忧的是，在自然循环过程中，一些毒株可能变得更具致病性和/或传染性。我们的常规监测表明，EA H1N1 病毒从不同的猪流感病毒获得不同的内部基因，并形成各种新的基因型。在这项研究中，我们发现一种自然分离的猪流感重配病毒，A/swine/Liaoning/265/2017（LN265），是近年来主要基因型之一的代表性毒株，对小鼠具有致死性且可在雪貂中传播。LN265 包含 EA H1N1 病毒的血凝素、神经氨酸酶和基质；2009 年 H1N1 大流行病毒的基本聚合酶 2、基本聚合酶 1、酸性聚合酶（PA）和核蛋白；以及北美三重重配 H1N2 病毒的非结构蛋白。通过生成和测试一系列重配体和突变体，我们发现 PA 中四个逐渐积累的突变导致 LN265 的致病性和传染性增加。我们进一步揭示，这些突变通过增强 PA 蛋白的内切酶切割活性和病毒 RNA 结合能力，增加了病毒蛋白的信使 RNA 转录，从而导致 LN265 的毒力和传染性增加。我们的研究表明，EA H1N1 猪流感病毒通过在 PA 中获得关键突变而在雪貂中变得具有致病性和传染性，并为监测具有大流行潜力的田间株提供了重要的见解。
