中文摘要：

本研究于2013年从广东某发病鸡场分离到一株H9N2亚型AIV，命名为A／chickerd Guangdong／LGl／2013。对病毒进行全基因组克隆测序和进化分析，其HA基因裂解基序为333PSRSSR↓GLF341，呈典型低致病性A1V分子特征。其HA基因发生Q226L突变和A316S突变，NA基因出现第63～65位氨基酸缺失。该病毒株HA、NA和NS基因属于类BJ／1／94分支，PB2属于类SD／H／09分支，PBl、PA、NP基因属于类SH／F／98分支，M基因属于类HK／G1／97分支，该基因型在广东地区未见报道，其内部基因与H7N9亚型人流感病毒SH／02／2013株核苷酸同源性在95．6％～98．6％之间。本研究表明我国H9N2亚型AIV呈现遗传演化的多样性及基因重组的复杂性，对该亚型病毒的监测和研究具有重要的兽医和公共卫生意义。

英文摘要：

To investigate the genetic and evolutionary characteristics of H9N2 avian influenza virus （A1V） in poultry flocks in Guangdong province, an H9N2 A1V was isolated and designated A/chicken/Guangdong/LG1/2013 （CK/GD/LG1/13）. The phylogenetic and molecular characteristics of the isolate were analyzed. The HA cleavage sequence of the isolate possessed the 333pSRSSR ↓ GLF341 motif, suggesting that this isolate was of a low pathogenicity in avian species. However, this isolate had an A316S mutation at the HA cleavage site and a 3-amino-acid deletion at position 63 to 65 on the NA stalk, which indicated an enhanced virulence in chickens and mice. Furthermore, CK/GD/LG1/13 also had the Q~6L mutation at HA receptor-binding site which could increase the binding of the virus to human-type receptors, SAct-2, 6. The HA, NA and NS genes of the isolate belong to BJ/1/94-1ike lineage. The PB2 belongs to H-like and the M gene belongs to Gl-like lineage, while the PBI, PA and NP genes belong to F98-1ike lineage. The genotype of the isolate in poultry flocks in Guangdong province has never been reported before. It is noteworthy that six internal genes of the isolate share 95.6%-98.6% nucleotide identities with that of SH/1/2013 （H7N9）. The findings of mammalian-adapting mutations and probable efficient replication in mammalians in this novel AIV are caused for concem a novel benefit. Ke This study demonstrated that H9N2 virus in south China had undergone extensive evolution and reassortment to generate viruses possesses significant veterinary and public health