Phylogenetic Analysis of a Swine Influenza A(H3N2) Virus Isolated in Korea in 2012

Influenza A virus (IAV) can infect avian and mammalian species, including humans. The genome nature of IAVs may contribute to viral adaptation in different animal hosts, resulting in gene reassortment and the reproduction of variants with optimal fitness. As seen again in the 2009 swine-origin influenza A H1N1 pandemic, pigs are known to be susceptible to swine, avian, and human IAVs and can serve as a ‘mixing vessel’ for the generation of novel IAV variants. To this end, the emergence of swine influenza viruses must be kept under close surveillance. Herein, we report the isolation and phylogenetic study of a swine IAV, A/swine/Korea/PL01/2012 (swPL01, H3N2 subtype). After screening nasopharyngeal samples from pigs in the Gyeongsangnam-do region of Korea from December 2011 to May 2012, we isolated the swPL01 virus and sequenced its all of 8 genome segments (polymerase basic 2, PB2; polymerase basic 1, PB1; polymerase acidic, PA; hemagglutinin, HA; nucleocapsid protein, NP; neuraminidase, NA; matrix protein, M; and nonstructural protein, NS). The phylogenetic study, analyzed with reference strains registered in the National Center for Biotechnology Information (NCBI) database, indicated that the swPL01 virus was similar to the North American triple-reassortant swine strains and that the HA gene of the swPL01 virus was categorized into swine H3 cluster IV. The swPL01 virus had the M gene of the triple-reassortant swine H3N2 viruses, whereas that of other contemporary strains in Korea was transferred from the 2009 pandemic H1N1 virus. These data suggest the possibility that various swine H3N2 viruses may co-circulate in Korea, which underlines the importance of a sustained surveillance system against swine IAVs.

甲型流感病毒（Influenza A virus, IAV）可感染禽类与哺乳动物类群，涵盖人类。甲型流感病毒的基因组特性可促进其在不同动物宿主中的适应性演化，进而引发基因重配，产生适配性最优的变异毒株。正如2009年猪源甲型H1N1流感大流行所再次印证的，猪可感染猪源、禽源及人源甲型流感病毒，并可作为“混合容器”催生新型甲型流感病毒变异株。有鉴于此，必须对猪流感病毒的出现实施严密监测。本研究报道了一株猪源甲型流感病毒A/swine/Korea/PL01/2012（简称swPL01，H3N2亚型）的分离与系统发育分析。研究团队于2011年12月至2012年5月间，对韩国庆尚南道地区的猪鼻咽拭子样本进行筛查，成功分离出swPL01病毒，并完成其全部8个基因组片段的测序，所测片段分别为：聚合酶碱性蛋白2（polymerase basic 2, PB2）、聚合酶碱性蛋白1（polymerase basic 1, PB1）、聚合酶酸性蛋白（polymerase acidic, PA）、血凝素（hemagglutinin, HA）、核衣壳蛋白（nucleocapsid protein, NP）、神经氨酸酶（neuraminidase, NA）、基质蛋白（matrix protein, M）以及非结构蛋白（nonstructural protein, NS）。以美国国家生物技术信息中心（National Center for Biotechnology Information, NCBI）数据库收录的参考毒株为参照进行系统发育分析，结果显示：swPL01病毒与北美三重重配猪源毒株亲缘关系相近，且其HA基因归属于猪H3亚型簇IV。swPL01病毒的M基因源自三重重配猪源H3N2病毒，而韩国其他同期毒株的M基因则来自2009年大流行H1N1病毒。上述数据表明，多种猪源H3N2流感病毒可能在韩国境内共同循环传播，这凸显了持续构建猪源甲型流感病毒监测体系的重要性。