H9N2亚型AIV HA蛋白第226位点氨基酸多样性分析及3株病毒受体结合能力检测

Characterization of the diversity of HA226 amino acids of AVI subtype H9N2 and detection of the receptor binding ability of three virus strains

目的了解目前我国家禽业中流行的H9N2亚型AIV的HA蛋白第226位氨基酸残基的多样性,并用固相糖链ELISA方法检测实验室保存的3株H9N2亚型AIV病毒的受体结合能力。方法从NCBI数据库中下载我国分离的H9N2流感病毒的HA氨基酸序列,对其第226位(参照H3亚型HA位点)氨基酸残基的种类进行统计分析,并利用固相糖链ELISA方法对3株H9N2亚型AIV的受体结合能力进行检测。结果与H9N2流感病毒受体结合能力相关的HA226位点已呈现出多样性,分别为HAL226、HAQ226、HAM226和HAF226,其占有比率分别为81.85%、17.57%、4.81%和0.11%;进一步统计分析表明,我国近几年分离的H9N2流感病毒以HAL226为主。受体结合能力检测显示,CK/JN/3(HAL226)只具有结合人样受体的能力,CK/JL/06(HAQ226)只具有结合禽样受体的能力,而CK/JN/2(HAF226)则具有双受体结合特性,其中与人样受体结合能力稍高。结论当前我国家禽中流行的H9N2亚型AIV中以具有HAL226位点特征的毒株占优势,而这一位点特征与病毒结合人样受体有关。因此,H9N2亚型AIV具有突破种间屏障并引发新的流感大流行的潜在威胁。

Objectives The purposes of this study were to characterize the diversity of HA226 amino acids of avian influenza virus（AIV）subtype H9N2 prevalent in the poultry industry in China and to evaluate the receptor binding ability of three strains of the H9N2 subtype using a solid-phase binding assay. Methods The amino acid sequence of the HA gene of H9N2 viruses isolated in China was obtained from the NCBI database and amino acids at position 226 in the HA protein were analyzed to characterize this site（compared to the HA protein of the H3subtype）.In addition,receptor binding specificity of three strains of the H9N2 subtype was identified with a solid-phase enzyme-linked receptor-binding assay. Results The HA226 site is associated with receptor binding ability.Results indicated substantial diversity of this site with L as the amino acid in 81.85%,Q as the amino acid in 17.57%,M as the amino acid in 4.81%,and F as the amino acid in 0.11%.Before 2006,strains of the H9N2 subtype mainly contained HAQ226 and reached its peak at2005.Further analysis revealed most strains of the H9N2 subtype that were isolated in China over the past few years had HAL226.CK/JN/2（HAF226）possesses the ability to bind to both avian and human receptors and prefers to bind human-like receptors.In contrast,CK/JN/3（HAL226）binds only to human-like receptors and CK/JL/06（HAQ226）binds only to avian-like receptors. Conclusion HAL226 is associated with binding to human-like receptors.Results indicated that strains of the H9N2 subtype with HAL226 predominate in China.Thus,these viruses may acquire the ability to spread across species and have the potential to cause a pandemic.