鸡传染性支气管炎病毒QX基因型毒株的分离鉴定与致病性分析

Isolation,identification and pathogenicity analysis of Avian infectious bronchitis virus QX genotype

为了确定发病鸡场的致病原以及掌握致病原的分子特征和致病性,试验采用临床病料样品RT-PCR检测、病毒分离、S1基因序列分析、半数感染量(EID_(50))测定、新城疫病毒干扰试验和致病性试验等方法对临床疑似鸡传染性支气管炎病毒(Infectious bronchitis virus,IBV)感染病例进行了研究。结果表明:临床病料样品经RT-PCR检测初步显示IBV核酸为阳性;分离毒株可引起10日龄SPF鸡胚规律性死亡以及鸡胚发生生长发育不良、蜷缩、变小等特征性病变;分离毒株S1基因核苷酸序列与GenBank中的QX型IBV毒株S1基因核苷酸序列同源性在93.6%以上;在遗传进化关系中,分离毒株与近几年流行的QX型IBV毒株处于同一个分支中,而与H120、M41、491等疫苗株处于不同分支中;分离毒株对SPF鸡胚的EID50为1×10^(-5.68)/0.1 mL,可以干扰新城疫病毒的血凝效价;对SPF雏鸡的致死率为70%,并可引起SPF雏鸡呼吸困难、气管出血、肾脏肿大和出血、明显的"花斑肾"等典型症状。说明试验成功从临床病料中分离得到一株QX型IBV流行毒株。

In order to determine the pathogenic agent of the chicken farm and to grasp the molecular characteristics and pathogenicity of the pathogen,infectious bronchitis virus-suspected clinical samples were detected in this experiment by RT-PCR,virus isolation,S1 gene sequence analysis,EID_(50) determination,Newcastle disease virus interference test,and pathogenicity test. The results showed that the clinical samples were initially positive for IBV nucleic acid by RT-PCR. The isolated strains could cause the regular death of 10-day-old SPF chicken embryos,and the characteristic lesions of chicken embryos such as dysplasia,curling up and becoming smaller. The nucleotide sequence of S1 gene of isolated virus strain had more than 93.6% homology with that of S1 gene of QX type IBV strain in GenBank. In the genetic evolution relationship,the isolated strain was in the same branch as QX IBV strains which were prevalent in recent years,but in different branches with H120,M41,491 vaccine strains. The EID50 of the isolated strain to SPF chicken embryos was 1×10^(-5.68)/0.1 mL,which could interfere with the hemagglutination titer of Newcastle disease virus. The isolated strain had a mortality rate of 70% for SPF chickens,and could cause typical symptoms of SPF chickens such as dyspnea,trachea hemorrhage,kidney enlargement and bleeding,and obvious spotted kidney. The results suggested that an epidemic strain of QX genotype IBV was successfully isolated from clinical samples.