Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu, China; Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China.
Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu, China; Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China.
Vet Microbiol. 2018 Jun;219:200-211. doi: 10.1016/j.vetmic.2018.04.023. Epub 2018 Apr 18.
Clade 2.3.4.4 of H5N6 subtype Avian Influenza Viruses (AIVs) has become dominant clade in South-East Asia. So far, a total of 16 cases of human infection, including 6 deaths, have been confirmed since 2014. In this study, we systematically investigated the genetic evolution and biological characteristics of these viruses. We first carried out phylogenetic and statistical analysis of all H5N6 viruses that were downloaded from Influenza Research Database, GISAID and isolates from our lab. We found that H5N6 AIVs continued to reassort with other AIVs subtypes since 2014. Among these H5N6 reassortments, four main gene types were identified: A (internal genes of H5N1-origin), B (PB2 of H6-origin, and others of H5N1-origin), C (internal genes of H9-origin) and D (PB2 of H6-origin and PB1of H3-origin, and others of H5N1). In addition, after several years of evolution, gene type D is currently the dominant gene type. To systematically compare the genetic and evolutionary characteristics and pathogenicity of these viruses, four H5N6 AIVs of different gene types were selected for further analysis. S4, XZ6, GD1602 and YZ587 virus represented gene type A, B, C and D, respectively. Their NA genes were all originated from H6 and their whole genome showed a high similarity with human isolates. All these isolates could both bind with SA-α2,3 Gal and SA-α2,6 Gal receptors. Pathogenicity test showed that these viruses were highly pathogenic in chickens, while YZ587 showed the lowest virulence. Moreover, XZ6 and S4 viruses were highly pathogenic in ducks and moderately pathogenic in mice, while GD1602 and YZ587 viruses were no-pathogenic in these animals. Interestingly, GD1602 and YZ587-like viruses were responsible for 4 and 2 human infection cases in 2016, respectively. Therefore, our study showed that the YZ587 virus which has mixed internal genes, showed lower virulence in avian species and mammals compared to other genotype viruses. Overall, our findings suggest that the H5N6 avian influenza virus is undergoing constantly evolving and reassortment. Thus, our study highlights the necessary of continued surveillance of the H5N6 AIVs in birds and paying close attention to the spread of these novel reassortment viruses.
H5N6 亚型禽流感病毒（AIV）的 clade 2.3.4.4 已成为东南亚的主要流行 clade。自 2014 年以来，已确认共有 16 例人类感染病例，包括 6 例死亡。在本研究中，我们系统地研究了这些病毒的遗传进化和生物学特征。我们首先对从 Influenza Research Database、GISAID 和我们实验室分离株下载的所有 H5N6 病毒进行了系统发育和统计分析。我们发现，自 2014 年以来，H5N6 AIV 继续与其他 AIV 亚型重组。在这些 H5N6 重组中，鉴定出了四种主要的基因类型：A（H5N1 起源的内部基因）、B（H6 的 PB2 和 H5N1 起源的其他基因）、C（H9 起源的内部基因）和 D（H6 的 PB2 和 H3 的 PB1 起源，以及 H5N1 起源的其他基因）。此外，经过几年的进化，目前 D 型基因是主要的基因类型。为了系统比较这些病毒的遗传进化特征和致病性，我们选择了四种不同基因类型的 H5N6 AIV 进行进一步分析。S4、XZ6、GD1602 和 YZ587 病毒分别代表 A、B、C 和 D 型基因。它们的 NA 基因均起源于 H6，其全基因组与人类分离株具有高度相似性。所有这些分离株均能与 SA-α2,3Gal 和 SA-α2,6Gal 受体结合。致病性试验表明，这些病毒在鸡中具有高致病性，而 YZ587 显示出最低的毒力。此外，XZ6 和 S4 病毒在鸭中具有高致病性，在小鼠中具有中等致病性，而 GD1602 和 YZ587 病毒在这些动物中无致病性。有趣的是，GD1602 和 YZ587 样病毒分别导致 2016 年 4 例和 2 例人类感染。因此，我们的研究表明，与其他基因型病毒相比，混合了内部基因的 YZ587 病毒在禽类和哺乳动物中显示出较低的毒力。总体而言，我们的研究结果表明，H5N6 禽流感病毒正在不断进化和重组。因此，我们的研究强调了有必要继续监测鸟类和哺乳动物中的 H5N6 AIV，并密切关注这些新型重组病毒的传播。
