H9N2亚型AIV福建分离株血凝素蛋白的特征

Genetics and phylogenetic analysis of hemagglutinin of H9N2 subtype avian influenza virus isolated in Fujian province

H9N2亚型禽流感病毒（AIV）已在多个国家多种禽类中检测到，由于H9N2亚型AIV的低致病力特征，导致其在疫病防控中不被重视，目前该病在全世界范围内不断进化和流行。为明确H9N2亚型禽流感病毒（AIV）福建分离株血凝素基因编码蛋白的特征，丰富福建省H9N2亚型AIV分子流行病学信息。本研究通过选取NCBI数据库流感病毒资源库（influenza virus resource）中所有28株HgN2亚型AIV血凝素基因编码蛋白（仅选择有完整ORF毒株），其中鸡源22株和鸭源6株，通过分析其左侧结合域、右侧结合域和血凝素蛋白裂解位点的氨基酸特征，并通过和H9N2亚型AIV代表株来绘制相互之间遗传进化树。分析发现，28株H9N2亚型AIV福建株相互之间氨基酸同源性在90．5％～99．5％之间。从血凝素蛋白切割位点的氨基酸序列特征来看，所有H9N2亚型AIV血凝素裂解位点氨基酸序列均为非连续碱性氨基酸。血凝素蛋白切割位点为PARSSR＋GLF的毒株均处于H9N2亚型AIV的H9．4分支上H9Y280分支的下部（H9．4．0分支、H9．4．1分支和H9．4．2分支），而血凝素蛋白切割位点为PSRSSR＋GLF的毒株均处于H9N2亚型AIV的H9．4分支上H9Y280分支的上部（H9．4．3分支、H9．4．4分支、H9．4．5分支和H9．4．6分支），提示我们可根据H9N2亚型AIV血凝素裂解位点氨基酸序列特征，将我国H9N2亚型AIV分为2个大的基因亚群。对226位氨基酸位点研究发现，除5株鸭源H9N2亚型AIV早期分离株（A／Muscovyduck／Fujian／CL／1997、A／duck／Fujian／MH／2003、A／duck／Fujian／FQ107／2007、A／duck／Fujian／T7／2007和A／duck／Fujian／T14／2007）此处为Q，其他所有毒株均为L。该结果说明，鸡源H9N2亚型AIV在进化的过程中也可直接获得和人源受体结合位点能力，具有直接跨种感染的潜力。通过分析研究发现，福建地区H9N2亚型AIV基因亚群复杂，应加强对该区域H9N2亚型AIV的分子流行病学调查和生物学特性研究。

H9N2 subtype influenza virus have been detected in many species in many countries all o- ver the world for several years. Because the H9N2 AIV has low pathogenicity,causing it is not pri- ority in animal control in many developing countries, and allowed it to continue to evolve and spread widely. In order to know the genetics and phylogenetic characterization of H9N2 AIV isola- ted in Fujian, China. 28 sequences of the hemagglutinin obtained were analyze for the cleavage site, the binding pocket, the receptor binding sites of hemagglutinin protein. Sequence alignment and phylogentic analysis were performed by MEGA 6 using the Neighbor-Joining method. The num- bers on the branches represented bootstrap support for 1 000 replicates. We found that the HA de- duced amino acids homology ranges from 90. 5%-99. 5%. All 28 isolated had no continuous basic amino acid. The cleavage site within the HA protein at clade H9.4.0,clade H9.4. land clade H9.4.2 had PARSSR ↓ GLF motif,while clade H9.4.3,clade Hg. 4.4,clade H9.4.5 and clade Hg. 4.6 had PSRSSR ↓ GLF motif. Furthermore, excepted for the A/Muscovy duck/Fujian/CL/ 1997, A/duck/Fujian/MH/2003, A/duck/Fujian/FQ107/2007, A/duck/Fujian/T7/2007 and A/ duck/Fujian/T14/2007,23 out of 28 Fujian isolated had leucine residue at position 216, which means the virus had human influenza virus-like receptor. The higher risk avian-to-human transmis- sion of H9N2 subtype influenza A viruses maybe a candidate for the next influenza pandemic in humans,which demands more epidemiology and genetics to be done in the H9N2 AIV in Fujian, China.