近年来国内越来越多的免疫鸡群发生H9N2禽流感病毒感染，表明在宿主免疫选择压下H9N2禽流感病毒正通过抗原变异逃脱疫苗的有效保护。然而对当前国内H9N2免疫逃逸株抗原变异关键氨基酸知之甚少。本项目以当前H9N2免疫逃逸株HA独特氨基酸突变位点为靶点，拟通过反向遗传、定点突变、病毒拯救、Glycan Array及HA-HI等技术，解析H9N2免疫逃逸株HA蛋白H34Q、N87H、N97D、R139K、A150E和R183G突变对病毒抗原性、受体结合、病毒致病性及免疫逃逸作用。本项目的顺利开展不仅将鉴定出影响H9N2抗原性及免疫逃逸的部分关键氨基酸，而且将为进一步开展国内H9N2免疫逃逸株分子流行预警与高效疫苗设计提供靶点及理论基础。

The increasing numbers of the vaccinated chicken flocks infected with H9N2 avian influenza viruses were found in China in recent years, which demonstrates that H9N2 avian influenza virus is under being escaped from vaccines by variation. However, little is known about the key amino acids of antigen variation of H9N2 immune escape strains in China. In this project, the effects of the unique amino acid mutations (H34Q, N87H, N97D, R139K, A150E and R183G) in HA of a H9N2 immune escape strain on the antigenicity, receptor binding, pathogenicity and immune escape will be elucidated by reverse genetics, site mutations, virus rescue, Glycan Array and HA-HI assays. The results of this project will not only identify part of the key amino acids of HA that affect the antigenicity and immune escape of H9N2, but also help to develop molecular epidemic early warning system of H9N2 immune escape strains and provide targets for high-efficient vaccine design in China.