5株H9N2亚型禽流感病毒血凝素蛋白分子特征分析和豚鼠间传播能力的评估

Hemagglutinin protein molecular characterization of 5 H9N2 influenza and evaluation transmissibility in guinea pigs

为研究H9N2亚型禽流感病毒(AIV)在哺乳动物间的传播能力,本研究以豚鼠为模型评价了5株H9N2亚型AIV在豚鼠体内的复制能力和水平传播能力,并分析了5株病毒血凝素(HA)蛋白的分子特征。结果表明,5株病毒均属于CK/Beijing谱系,其中2株病毒的HA具有人样受体特征(Lys226),2株病毒具有禽样受体特征(Gln226),而A/Chicken/JN/Li-2/2010(H9N2)株在该位点的氨基酸残基为苯丙氨酸(Phe226)。裂解位点分析表明,5株病毒均具有低致病性AIV特征。个别病毒的潜在糖基化位点存在增加或缺失现象。感染试验表明,5株病毒均能够在豚鼠呼吸道复制。并且在鼻甲骨处复制稳定,平均病毒滴度为2.01 Log EID50/mL～4.5 Log EID50/mL。传播试验表明,所有病毒株的人工接种豚鼠的鼻洗液中均能够检测到病毒,最长排毒期为接毒后第8 d,而接触组豚鼠鼻洗液中未检测到病毒。本研究表明,5株H9N2亚型AIV均属于CK/Beijing谱系,部分病毒株的HA蛋白已具备人样受体结合特征,并且关键氨基酸位点(226位)处出现新的突变。5株病毒均能够在豚鼠呼吸道复制并通过上呼吸道排毒,但不能在豚鼠间同群传播。

In this study, The guinea pig was used to evaluated replication and transmissibility of 5 H9N2 avian influenza virus （AIV） strains and hemagglutinin （HA） protein molecular characterization of the 5 H9N2 AIV strains were analyzed. Phylogcnetic analysis of HA gene indicated that all strains belonged to CK/Beijing lineage. Two of them possessed human-like receptor sites （Lys^226） in HA, whereas other two had a avian-like receptor sites （Gln^226）. However, A/Chicken/JN/Li-2/2010 （H9N2） was Phc^226. All strains were low pathogenic strain according to HA cleavage site and could be detected in respiratory tract and mucosalturbinate of experimental infected guinea pig with average virus titer ranging 2.01 Log EIDso/mL to 4.5 Log E1DsdmL. Among virus stains tested, virus could be detected in nasal wash of all inoculated guinea pig, however, virus was not detected in nasal wash of all contact guinea pig.