鸡传染性支气管炎强毒分离株遗传进化分析和免疫保护试验

从山东省发病鸡群中分离鉴定了一株鸡传染性支气管炎病毒（Infectious bronchitis virus,IBV）强毒株SDIB821/2012,对其进行S1基因序列测定分析和免疫保护试验。S1基因遗传进化分析结果显示,SDIB821/2012属于以QXIBV为代表的基因型,与同属一个基因型的IBV参考株氨基酸同源性为91.6%～98.5%,与疫苗株491同源性为77.6%,与H120和MA5同源性均为74.8%。免疫保护试验结果显示,根据试验鸡临床症状和发病死亡情况,弱毒活疫苗491对SDIB821/2012的保护率为90%,而H120和MA5对SDIB821/2012的保护率分别仅为40%和33%。攻毒后各免疫组喉头、泄殖腔棉拭样品以及气管、肺脏和肾脏组织均可检测到病毒,表明3种IB疫苗均不能对SDIB821/2012提供完全的免疫保护。

PHYLOGENETIC ANALYSIS AND IMMUNE PROTECTION OF A VIRULENT INFECTIOUS BRONCHITIS VIRUS RECENTLY ISOLATED IN SHANDONG

A virulent avian Infectious bronchitis virus （IBV） was isolated in 2012 from diseased chickens in Shandong Province and designated as IBV strain SDIB821/2012. The S1 gene of SDIB821/2012 was sequenced and compared with published IBV strains in GenBank. Phylogenetic analysis on the S1 gene sequence revealed that SDIB821/2012 together with twelve Shandong IBV isolates belonged to QX genotype. The IBV strain SDIB821/2012 shared amino acid identity at 91.6%-98.5%, 77.6%and 74.8%with other strains of QX type, vaccine strain 491, and vaccine strains H120 and MA5, respectively. A vaccination-challenge experiment was performed to evaluate if the currently used live vaccines could provide satisfactory protection against challenge of SDIB821/2012. The results showed that 90% of chickens immunized with vaccine strain 491 were protected against subsequent challenge with SDIB821/2012 based on clinical signs and deaths while only 40%and 33%of chickens vaccinated with H120 and MA5 were protected. The avian Infectious bronchitis virus was recovered from laryngeal and cloacal swabs, trachea, lung and kidney tissues of vaccinated-challenged birds. These results suggested that the current 3 live vaccines could not provide complete protection against challenge of the recently isolated IBV strain SDIB821/2012.