2019—2021年华东地区6株禽源H3亚型流感病毒的遗传进化分析

Genetic Evolution of Six Avian H3 Subtype Influenza Viruses from 2019 to 2021 in Eastern China

H3亚型流感病毒在自然界广泛存在,可感染人、猪、马、犬、禽等众多宿主并能发生跨种间传播,危害不容忽视。本研究于2019—2021年在华东地区活禽市场采集表观健康的家禽喉头与泄殖腔棉拭,通过血清学试验鉴定、筛选出6株代表性水禽源H3亚型流感病毒,并经RT-PCR试验确定5株为H3N2亚型、1株为H3N1亚型。进一步对6株分离株进行全基因组测序、同源性比对和遗传进化分析,结果显示:HA蛋白裂解位点处均为PEKQTR/GLF,不存在连续碱性氨基酸,符合低致病性禽流感病毒的分子特征;受体结合位点处均为禽源特征性的226Q和228S,提示其跨种传播至哺乳动物的潜能较低;内部基因片段来源多样化,与H3N8、H4N6、H5N8、H6N1、H7N7、H0N3等众多亚型禽流感病毒的亲缘关系密切;除JS1018/19和JS1094/19的NS基因属于北美谱系以外,其余均属于欧亚谱系的禽源分支,与犬、马、猪、人等哺乳动物源毒株的亲缘关系较远,提示虽然可能存在不同进化谱系间的基因重组但并未发生从禽到哺乳动物宿主的基因交换。该研究结果丰富了H3亚型禽流感病毒的流行病学数据,为进一步了解我国低致病性禽流感病毒的分布特征提供了参考依据。

H3 subtype influenza virus exists widely in nature and infects many hosts such as human,pig,horse,dog and poultry.As the virus can spread across species,its harm cannot be ignored.In this study,throat and cloacal swab samples were collected from 2019 to 2021 from apparently healthy chickens at live poultry markets in Eastern China.Six representative strains were selected from the waterfowl isolates of H3 subtype influenza viruses that had been identified by serological tests.RT-PCR test further revealed that five strains were H3N2 and the other strain was H3N1 subtype.Subsequently,whole genome sequencing,homology comparison and evolutionary analysis were conducted on the six H3 isolates.The results showed that the cleavage site of HA protein was uniformly PEKQTR/GLF without consecutive basic amino acids,and consistent with the molecular feature of low pathogenic Avian influenza virus(AIV).The receptor binding sites were all of avian-specific 226Q and 228S,suggesting a low potential for interspecies transmission to mammals.We found that the internal genes were of diverse sources and the six H3 subtype AIVs were closely related to many other subtypes including H3N8,H4N6,H5N8,H6N1,H7N7,H0N3 and so on.Except that the NS genes of JS1018/19 and JS1094/19 belonged to the North American lineage,other viruses were all of Avian Eurasian lineage that were distantly related to the mammalian strains of canine,horse,swine and human origin.Such analysis indicated the possible gene reassortment between different evolutionary lineages but not the gene exchange from avian to mammalian hosts.These results in this study would enrich the epidemiological data of H3 subtype AIVs and provided a reference for further understanding the distribution characteristics of low pathogenic AIVs in China.