南方养殖草鱼呼肠孤病毒的分子特性比较及双重PCR检测方法的建立

本实验室2009年从广东省患典型出血病的养殖草鱼中分离到一株具强致病性的水生呼肠孤病毒GCRV-GD108株,该毒株具有11个节段双链RNA。全基因组序列分析显示与草鱼呼肠孤病毒GCRV及水生呼肠孤病毒属其它已知种存在较大的分子差异。本研究进一步检测了广东、福建、湖南等地草鱼出血病流行毒株的分子特性。根据已克隆到的GCRV-GD108株11个节段序列分别设计合成特异引物,从各地收集患出血病草鱼,提取组织总RNA,RT-PCR检测。结果表明各检测样品均可扩增到特异性条带,而GCRV标准株则无特异条带;同时根据GCRV标准株序列合成的特异引物进行扩增,GCRV标准株有特异性条带,而各检测样品则均无带。测序结果显示各样品间相应片段序列的同源性很高(95.2%~99.4%),与GCRV-GD108的相应序列也具高同源性(95.0%~99.8%),说明检测样品与GCRV-GD108株具有相似的分子特性,均与GCRV及水生呼肠孤病毒属的其它种存在较大差异。本研究结果提示我国养殖草鱼出血病病毒存在着不同的分子类型,GCRV-GD108株在南方具有一定的代表性,在病害防控上尤其是疫苗研制与使用上应予关注。此外,从上述引物中筛选出适合于双重PCR的引物对,建立了双重PCR检测方法,可在一次PCR反应中鉴别所感染的病毒属于GCRV或GCRV-GD108株。

Molecular properties of grass carp reovirus in southern China and establishment of a duplex PCR detection method

A strain of grass carp reovirus was isolated from sick grass carp with symptoms of haemorrhage in Guangdong province in 2009. The strain was tentatively named as GCRV-GD108 because it was isolated from grass carp and possessed 11 segments of dsRNA. Complete genome sequence analysis showed that significant differences existed between GCRV-GD108 and GCRV, as well as other known species of aquareovirus. In this study, molecular characteristics of diseased grass carp collected from different farms in Guangdong, Fujian and Hunan provinces were assayed. Based on the sequences of the 11 segments of GCRV-GD108, PCR primers corresponding to each of the segments were designed and synthesized. Total RNA of the diseased fish was extracted and used as templates of RT-PCR reaction. Specific amplification bands were obtained from all of the samples whereas no band was produced from GCRV standard strain. While using the primers specific to GCRV produced specific band in GCRV standard strain rather than in these collected samples. Sequencing of the amplification products showed that these samples displayed high similarities with each other (95.2%-99.4%), and they also shared high sequence similarities with that of GCRV-GD108 (95.0%-99.8%), suggesting that these samples shared similar molecular characteristics with those of GCRV-GD108, and were quite different from GCRV as well as the known species of genus aquareovirus. The results indicated that there are different molecular types of reovirus existed in the pond-cultured grass carp in China, and GCRV-GD108 is a representative strain in southern China, therefore great attention should be paid in order to control the disease efficiently, especially in vaccine preparation. Two pairs of primers were chosen to establish a duplex PCR assay method by combining each pair of the primers specific to GCRV-GD108 with the GCRV primer pair respectively. The duplex PCR assay method will enable the identification of GCRV-GD108 or GCRV by only a single PCR reaction.