2017年河北省蛋鸡养殖场H9N2亚型禽流感病毒的遗传演化和抗原性分析

Genetic evolution and antigenic characteristics of H9N2 avian influenza viruses in laying-hen farms in Hebei province in 2017

【背景】H9N2亚型禽流感病毒在鸡群中广泛流行,引起巨大损失。【目的】了解河北省蛋鸡养殖场H9N2亚型禽流感病毒(Avian influenza virus,AIV)的基因序列和抗原性的变异情况,为该病原的科学防控提供理论依据。【方法】于2017年从河北省部分蛋鸡养殖场分离鉴定出7株H9N2亚型AIV,对其HA基因进行序列测定,并进行遗传演化、关键氨基酸位点及抗原性分析。【结果】7株分离毒株HA基因同源性在95.5%-97.2%之间;与2016年前的流行毒株相比,分离病毒HA裂解位点均为典型低致病性AIV特征,在受体结合区域出现变异,潜在糖基化位点无明显差异;抗原分析结果显示分离毒株与早期分离株相比抗原性发生了变异,形成了新的抗原群;抗原性相关位点分析显示,分离毒株在9个位点发生了较为明显的突变,可能是导致抗原性变异的分子基础。【结论】河北省蛋鸡养殖场H9N2亚型AIV中的流行毒株在关键功能区发生基因突变,并且抗原性发生变异,提示应持续监测H9N2亚型AIV的遗传变异情况,并及时更换疫苗株。

[Background] H9 N2 avian influenza viruses are widespread in chickens and cause great losses.[Objective] Elucidate the sequence characteristics and the variation of antigenicity of H9 N2 subtype avian influenza virus(AIV) in Hebei province to understand heterologous protection of AIV.[Methods] Seven strains of H9 N2 subtype AIV were isolated and identified from farms in Hebei province in 2017.We sequenced the HA genome of 7 H9 N2 isolated strains.Then,the phylogenetic trees,amino acid in key functional sites and antigenicity were analyzed.[Results] The homology of HA genes for 7 isolated strainswas between 95.5% and 97.2%.Comparing with the epidemic strains before 2016,the cleavage sites and the glycosylation sites were not significantly different from those of the previous strains,except the receptor binding sites of the HA proteins.The antigenicity of the isolated strains changed and a new antigen group formed.The analysis of the HA amino acid sites related to the antigenicity shows that there was a significant mutation in 9 antigenic sites of the newly isolated strains,which may be the molecular basis of antigenic variation.[Conclusion] The prevalent strains of H9 N2 subtype AIV in laying-hen farms in Hebei province have mutated in key functional areas and presented antigenic variation,reminding us the importance of continuous surveillance of the genetic evolution and antigenic variation of H9 N2 AIV.Changing the candidate strain of vaccine in time is important for the prevention and control of H9 N2 AIV.