Hu Junyi, Hu Zhe, Wei Yandi, Zhang Ming, Wang Senlin, Tong Qi, Sun Honglei, Pu Juan, Liu Jinhua, Sun Yipeng
Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, China.
Department of Epidemiology and Biostatistics, University of Georgia, Athens, GA, USA.
Vet Microbiol. 2022 Feb;265:109314. doi: 10.1016/j.vetmic.2021.109314. Epub 2021 Dec 21.
Genetic analyses indicated that the pandemic H1N1/2009 influenza virus originated from a swine influenza virus (SIV). However, SIVs bearing the same constellation of genetic features as H1N1/2009 have not been isolated. Understanding the adaptation of SIVs with such genotypes in a new host may provide clues regarding the emergence of pandemic strains such as H1N1/2009. In this study, an artificial SIV with the H1N1/2009 genotype (rH1N1) was sequentially passaged in mice through two independent series, yielding multiple mouse-adapted mutants with high genetic diversity and increased virulence. These experiments were meant to mimic genetic bottlenecks during adaptation of wild viruses with rH1N1 genotypes in a new host. Molecular substitutions in the mouse-adapted variants mainly occurred in genes encoding surface proteins (hemagglutinin [HA] and neuraminidase [NA]) and polymerase proteins (polymerase basic 2 [PB2], polymerase basic 1 [PB1], polymerase acid [PA] proteins and nucleoprotein [NP]). The PB2 and HA substitutions were detected at high frequencies in both passage lines and enhanced the replication and pathogenicity of rH1N1 in mice. Moreover, these substitutions also enabled direct transmission of rH1N1 in other mammals such as guinea pigs. PB2 showed enhanced polymerase activity and HA showed increased stability compared with the wild-type proteins. Our findings indicate that if SIVs with H1N1/2009 genotypes emerge in pigs, they could undergo rapid adaptive changes during infection of a new host, especially in the PB2 and HA genes. These changes may facilitate the emergence of pandemic strains such as H1N1/2009.
基因分析表明，2009年大流行的H1N1流感病毒源自一种猪流感病毒（SIV）。然而，尚未分离出具有与H1N1/2009相同基因特征组合的SIV。了解具有此类基因型的SIV在新宿主中的适应性，可能为诸如H1N1/2009等大流行毒株的出现提供线索。在本研究中，一种具有H1N1/2009基因型的人工SIV（rH1N1）通过两个独立的系列在小鼠中连续传代，产生了多个具有高遗传多样性和增强毒力的小鼠适应性突变体。这些实验旨在模拟野生病毒在新宿主中适应过程中的基因瓶颈。小鼠适应性变体中的分子替换主要发生在编码表面蛋白（血凝素[HA]和神经氨酸酶[NA]）和聚合酶蛋白（聚合酶基本蛋白2[PB2]、聚合酶基本蛋白1[PB1]、聚合酶酸性蛋白[PA]和核蛋白[NP]）的基因中。PB2和HA替换在两个传代系中均以高频率被检测到，并增强了rH1N1在小鼠中的复制和致病性。此外，这些替换还使rH1N1能够在豚鼠等其他哺乳动物中直接传播。与野生型蛋白相比，PB2显示出增强的聚合酶活性，HA显示出更高的稳定性。我们的研究结果表明，如果具有H1N1/2009基因型的SIV在猪中出现，它们在感染新宿主的过程中可能会经历快速的适应性变化，尤其是在PB2和HA基因中。这些变化可能有助于诸如H1N1/2009等大流行毒株的出现。
