2株2023年禽源H7N9亚型禽流感病毒的分离鉴定及遗传进化分析

Isolation,Identification and Phylogenetic Analysis of Two Strains of Avian-origin H7N9 Subtype Avian Influenza Virus in 2023

为了解H7N9亚型禽流感病毒(Avian influenza virus,AIV)的遗传进化特点,探究我国H7N9亚型AIV的流行特征,试验对2023年采集自四川、河北两地活禽市场禽类咽拭子及泄殖腔拭子进行病原分离鉴定,并对分离株进行全基因组序列测定,进一步构建进化树并分析其遗传演化情况和分子特征。结果显示:共分离2株H7N9亚型AIV,其遗传距离较近,HA基因均属于YRD-B分支;2株AIV的HA蛋白裂解位点均含有连续碱性氨基酸,具有高致病性的分子特征;PB2、HA和NA蛋白均具有哺乳动物适应性突变,其中HA蛋白第226位受体结合位点均由谷氨酰胺(Q)突变为亮氨酸(L),使其能够识别人流感病毒唾液酸受体,并且HA蛋白A27S、I96V、V143T、A169T、I187V和D457N抗原位点发生突变;2株AIV虽均能与Re-4和H7N9rHN7903灭活疫苗免疫血清产生交叉血凝抑制反应,但HI抗体效价较低。研究表明,从活禽市场分离到2株H7N9亚型AIV,其对家禽具有高致病性,且抗原性发生变化。

In order to understand the genetic and evolutionary characteristics of avian influenza virus(AIV)and explore the epidemic characteristics of H7N9 subtype AIV in China,throat swabs and cloaca swabs from live poultry markets in Sichuan and Hebei province in 2023 were collected.The whole genome sequence of the isolates was determined to construct the evolutionary tree and analyze their genetic evolution and molecular characteristics.The results showed that two strains of H7N9 subtype AIV were isolated,and the genetic distance of which was relatively close.The HA gene of the two AIV strains belonged to the group YRD-B branch.The cleavage sites of the two AIV strains contained consecutive basic amino acids.The PB2,HA,and NA fragments all manifested mammalian adaptive mutations.Notably,the mutation of the HA receptor binding site at position 266 from glutamine(Q)to leucine(L)amplified the recognition of sialic acid receptors of the human influenza virus.The antigen sites A27S,I96V,V143T,A169T,I187V and D457N of HA protein were mutated in the two AIV strains.These mutations allowed the two strains to induce cross-hemagglutination inhibition(HI)with Re-4 and H7N9 rHN7-903 inactivated vaccine immune sera,but resulted in low HI antibody titers.The results showed that two strains of H7N9 subtype AIV isolated from live poultry markets were highly pathogenic to poultry and their antigenicity had changed.