广西地区2014-2015年IBDV的分离鉴定及代表株全基因序列的分析

发布时间：2018-11-06 09:22

【摘要】：传染性法氏囊病(infectious bursal disease,IBD)是由双RNA病毒科禽双RNA病毒属传染性法氏囊病毒(infectious bursal disease virus,IBDV).引起的一种急性、溶淋巴细胞性疾病。IBDV有四种致病型(pathotypes),即经典毒力株(classicalIBDV,cIBDV)及其致弱疫苗毒株(attenuated IBDV,attIBDV)、超强毒株(very virulent IBDV,vvIBDV)以及抗原变异株(variant IBDV,vIBDV)。它们的致病性和抗原性均存在许多差异,这给疾病的防控带来困难。课题对广西2014-2015年临床发生的疑似病例进行IBDV的分离鉴定,并利用实验室准备的单因子血清在细胞培养上完成分离株的病毒中和试验。结果显示,获得的14个分离株全部属于基因重组毒株即其基因组A、B节段来自不同类型毒株,其中11株的A节段属于vvIBDV-type分支、B节段属于HLJ-0504-type分支,1株(141203)A节段属于vvIBDV-type分支、B节段为新的分支,1株(14007)A节段属于attIBDV-type分支、B节段属于HLJ-0504-type分支,1株(140021)A节段属于中等毒力分支、B节段为新的分支;血清学鉴定则表明,它们均属于血清Ⅰ型亚型1。课题对分离株中的代表GX151120进行了克隆纯化并对其全基因序列进行了测定与分析。结果显示,其A节段长度为3 260nt,含有两个完整的阅读框架 ORF A1 和 ORFA2,ORF A1 范围 131nt-3 169nt,ORF A2 范围97nt-534nt,分别编码VP2-VP4-VP3和VP5蛋白;B节段长度为2 827nt,阅读框范围112nt-2751nt,编码VP1蛋白,两节段均未发生碱基的缺失和插入;遗传进化树分析显示,该毒株为重组毒株,即其A节段来源于vvIBDV-type,B节段与HLJ-0504同属一个分支。A节段核苷酸相似性分析显示,它与vvIBDV的重组株HLJ-0504的相似性最高(98%),B节段核苷酸相似性也是与HLJ-0504的最高(98.4%)。核苷酸序列比对结果显示,A节段VP2高变区的特征性核苷酸位点为222A、256I、294I、299S、279D和284A,符合vvIBDV的特征。其B节段与中国分离株HLJ-0504、GX、Harbin-1等属于基因Ⅱ亚群,该分离毒株的220R具有特异性,不同于其他参考毒株的220K。课题还选用不同市售的IBD疫苗对广西地方品种鸡进行免疫试验,结果证明雏鸡1日龄孵化房免疫1次,仍然存在危险期,2周龄的加强免疫有助于延长抗体水平保护期,对于饲养期较长的地方品种而言免疫两次更合适。
[Abstract]:Infectious bursal disease (infectious bursal disease,IBD) is a kind of infectious bursal virus (infectious bursal disease virus,IBDV) belonging to double RNA virus, avian double RNA virus. IBDV has four pathogenic types of (pathotypes),: classical virulent strain (classicalIBDV,cIBDV) and attenuated vaccine strain (attenuated IBDV,attIBDV), supervirulent strain (very virulent IBDV,vvIBDV, and antigenic variant strain (variant IBDV,. VIBDV). There are many differences in pathogenicity and antigenicity, which makes it difficult to prevent and control diseases. IBDV was isolated from suspected cases in Guangxi in 2014-2015, and the virus neutralization test of the isolated strain was carried out in cell culture using single-factor serum prepared by laboratory. The results showed that all of the 14 isolates belonged to the recombinant gene strain, that is, the B segment of the genome was from different types of virus strains. The A segment of 11 strains belonged to the vvIBDV-type branch, and the B segment belonged to the HLJ-0504-type branch. One strain (141203) A belongs to vvIBDV-type branch, B segment is new branch, one strain (14007) A segment belongs to attIBDV-type branch, B segment belongs to HLJ-0504-type branch, 1 strain (140021) A segment belongs to medium virulence branch. Segment B is a new branch; Serological identification showed that they all belong to serotype 鈪，

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