人流感毒株的起源与AIV密切相关，因此AIV跨越种间屏障的现象引起了全球的关注。流感病毒受体结合方式的改变是病毒跨越种属的关键一步。本项目拟进行血凝素Gln226Leu突变对H9N2-AIV受体结合特性及宿主特异性影响的研究。首先利用流感病毒反向遗传操作系统，生产病毒受体结合区226位定点突变（Leu→Gln）H9N2-AIV。然后利用糖芯片技术精确检测并比较野生型226-Leu病毒与定点突变型226-Gln病毒的受体结合特性，评价226-Leu的存在是否影响病毒受体的特异性；最后利用小鼠实验系统，观察野生型226-Leu病毒与定点突变型226-Gln病毒对小鼠致病性的差异，明确H9N2-AIV对小鼠的极强致病性是否与受体结合位点226-Leu有关，为评价其宿主特异性转换（禽→小鼠）提供分子遗传学证据。本项目有助于了解目前流行的H9N2-AIV的受体结合特性及宿主特异性的的变迁规律。

Influenza viruses can be isolated from a variety of animals, but their range of hosts is restricted. We have reported an H9N2 virus sublineage with high lethality for mice isolated from chickens in northern China. These viruses have a Gln226Leu mutation in hemagglutinin that is known to be important for host range restriction. To observe the contributions of this Gln226Leu mutation to host range restriction, we will generate a site-specific mutant H9N2 virus with Leu226Gln mutation in hemagglutinin using reverse genetics technology. Then, we will compare the difference of receptor binding specificity between mutant H9N2 virus and wild virus by glycan microarray analysis. Finally, we will assess the pathogenicity of mutant and wild H9N2 viruses in mice. Our study may benefit further investigation into host range restriction of H9N2 viruses.