3株H3N2亚型禽流感病毒的基因组特征与演化分析

Genetic Characterization and Evolution of Three Strains of H3N2 Avian Influenza Viruses

旨在了解浙江地区家禽H3N2亚型禽流感病毒(AIV)的流行变异情况,采用RT-PCR技术对2021年浙江923份样品进行检测,对AIV分离株进行分子特征及遗传演化分析。结果表明,AIV样品阳性率为7.69%(71/923);共分离到2株鸡源和1株鸭源H3N2亚型AIVs,其HA和NA基因相似性分别为93.4%~100%和94.0%~99.9%,分离株内部基因片段来源复杂,与H1N2、H1N4、H10N7等亚型亲缘关系密切;遗传进化分析显示,H3N2亚型AIV主要流行于华东地区,鸭是其主要宿主,3株H3N2亚型分离株HA和NA基因均属于禽源进化分支;分离株HA蛋白裂解位点均为PEKQTR↓GLF,符合低致病性禽流感病毒特征,HA蛋白与受体结合相关位点为226Q和228G,PB2蛋白与哺乳动物适应性相关的氨基酸位点为627E,均不同于人流感病毒对应蛋白的相关位点(226L、228S和627K),推测其跨种传播至人的潜力较低;分离株PB1蛋白的66位氨基酸突变为S,提示其对哺乳动物的致病性可能增强。综上所述,本研究分离的H3N2亚型AIV符合低致病性禽流感病毒特征,基因片段来源复杂,跨种传播至人的潜力较低,但是否影响对宿主的致病性仍需进一步探究。

To understand the prevalence and variation of the H3 N2 subtype avian influenza virus(AIV) in poultry in Zhejiang province,RT-PCR technology was utilized to detect a total of 923 samples from Zhejiang province in 2021,the isolated AIVs were subjected to molecular characteristics and genetic evolution analysis.The results showed that the positive rate of AIV in Zhejiang province in 2021 was 7.69%(71/923),2 chicken-derived AIVs and 1 duck-derived H3 N2 subtype AIVs were isolated,and their HA and NA genes homology were 93.4%-100% and 94.0%-99.9%,respectively.The origins of the internal gene fragments of the isolated AIVs were complex,and they were closely related to subtypes such as H1 N2,H1 N4,and H10 N7.The genetic evolution analysis showed that H3 N2 subtype AIV was mainly prevalent in East China,and the duck was its main host.The HA and NA genes of the three H3 N2 subtype isolates belonged to avian-derived evolutionary branches.Amino acid analysis revealed that the cleavage site of HA protein was PEKQTR↓GLF,which was in line with the characteristics of the low pathogenic AIV.The 226 Q and 228 G of HA protein as well as the 627 E of PB2 protein,which was related to receptor binding and mammalian adaptability respectively,were consistent with those of AIV,suggesting that the cross-species transmission to mammals appeared unlikely.However,amino acid 66 was mutated to S in the PB1 protein might increase the pathogenicity in mammals and need to be further investigated.In summary,the H3 N2 subtype AIVs isolated in this study were consistent with the characteristics of low pathogenic avian influenza virus,and the origins of the gene fragments were complex.The potential of the isolates for cross-species transmission to humans was low,but whether they affect the pathogenicity of the host remains to be further explored in the near future.