2017年国内大型鸡场分离的H9N2禽流感病毒的遗传进化和分子特征分析

Genetic evolution and molecular analysis of H9N2 avian influenza virus isolated from chicken farms in China in 2017

H9N2禽流感病毒自1994年在广东首次报道暴发以来,已在国内广泛地流行,给养禽业带来了极大的损失,甚至威胁着人类的健康。为了解2017年国内H9N2亚型禽流感病毒的遗传进化和分子特征变化,本研究从江苏、安徽、山东等地区的大型鸡场中分离到了10株H9N2亚型禽流感病毒。对10株分离株的基因分析表明,所有分离株均属于在2013年后占主导地位的G57型,由BJ/94系的HA、NA和NS基因,DK1系的PB2基因,F/98系的PB1,PA和NP基因以及G1/97系的M基因的四重组病毒组成,并且分离株的EID50显著低于早期分离的H9N2禽流感病毒。10株分离株中有7株受体结合位点的198位发生了A到T,或者A到V的替换,并发生糖基化位点在218位的缺失,313位的增加。与近5年已经发表的流行株HA蛋白比较,所有分离株的抗原位点均发生了S127R、S183N、D216E、T220I、Q235M、S283R突变,NA基因在61~63位缺失NIT;表明分离株的抗原发生了变异。而分离株内部基因PB2上的K318R突变,PB1上的L13P突变,PA上的K356R突变、Q/T/S400P突变,NS上的E227K突变,NP上的D34S、K398Q突变,M1上的V15I突变以及M2上的I28V、L55F突变,使分离株更易感染哺乳动物,说明必需要继续加强H9N2禽流感病毒的监测,密切关注其对人类可能造成的影响。特别是10株分离株中首次出现的NA基因的E433D突变和PB2基因的E627V突变是否会给H9N2禽流感病毒增加新的生物学特性还有待进一步研究。

Since an outbreak of H9N2 avian influenza virus was first reported in Guangdong in 1994 in China,the virus spread quickly to most regions of the country,posing great threat to humans,and has caused severe economic loss in poultry industry.In order to understand the genetic evolution and molecular characteristics of the H9N2 avian influenza virus in China in 2017,10 H9N2 viruses were isolated from some chicken farms in Jiangsu,Anhui,and Shandong.Genetic analysis showed that all the isolates were G57 type which is four recombinant viruses consisting of HA,NA,NS gene from BJ/94-like lineage,PB2 gene from DK1-like lineage,PB1,PA,NP from F/98-like lineage and M gene from G1-like lineage.And the EID50 of the isolates was lower significantly than that of previous isolates.A198T and A198 V mutations in receptor binding sites were presented in 7 isolates.All the isolates had a deletion of glycosylation site at position 218 and an increase of glycosylation site at position 313.Compared with the HA protein of isolates in the last 5 years,S127R,S183N,D216E,T220I,Q235M,S283R mutations were found in the antigenic sites of all the isolates,suggesting that these isolates have shown antigenic site variation.A deletion of 61 NIT63 in NA was found in all the 10 H9N2 isolates.Also there were many mutations in isolates that help the H9N2 isolates to infect mammals,such as the K318R mutation in PB2,L13P mutation in PB1,K356 Rand Q/T/S400P mutations in PA,E227K mutation in NS,D34 Sand K398Q mutations in NP,V15 Iin M1 and I28V,L55 Fmutations in M2.It was indicated that we should keep on studying on H9N2 virus and pay close attention to their possible influences on humans.In particular,the biological characteristics of E433D mutation in NA and E627V mutation in PB2 which were first detected in the isolates remain to be further studied.