草鱼呼肠孤病毒AH528株全基因组特征及进化分析

Genomic Characterization and Phylogenetic Analysis of Grass Carp Reovirus AH528 Strain

中文关键词: 草鱼出血病  草鱼呼肠孤病毒  VP1蛋白  水生呼肠孤病毒

英文关键词: Grass carp haemorrhage disease  Grass carp reovirus  VP1 protein  Aquareovirus

中文摘要:

      草鱼出血病是由草鱼呼肠孤病毒(Grass carp reovirus, GCRV)引起的严重危害1~2龄草鱼的一种传染性疾病。本研究从安徽合肥地区患典型草鱼出血病的病鱼组织中分离到1株新的GCRV致病株，暂命名为GCRV-AH528。鱼体人工感染实验结果显示，实验鱼出现典型的出血病症状：体背发黑，鳍基部、腹部、口腔、鳃丝、肠道充血发红。全基因组特征分析显示，GCRV-AH528由11个双链RNA节段组成，节段大小在1027~3925 bp之间，AT平均含量为50.2%，GC平均含量为49.8%。与其他GCRVⅡ型毒株相比，L1节段在701~702位置缺少3个核苷酸(TAT)，少编码1个酪氨基；M4节段出现突变，含2个开放阅读框，编码2个非结构蛋白NS9和NS69。所有节段两端均含有6 bp保守的末端核苷酸序列5¢-GUAAU/CUžžžUU/GCAUC-3¢；另除L1、M6节段外，其余9个节段均在编码区两侧发现5~9 bp的颠倒互补序列。GCRV-AH528与其他呼肠孤病毒核苷酸平均相似度在37.1%~98.1%之间；编码蛋白平均相似度在24.3%~98.3%之间。基于VP1蛋白的聚类分析结果显示，该病毒属于水生呼肠孤病毒属，在氨基酸水平上与典型株GCRV-873株的进化关系较远。本研究结果表明，该毒株为一株新的草鱼呼肠孤病毒Ⅱ型致病株。

英文摘要:

      Grass carp haemorrhage is an epidemic disease, which is caused by grass carp reovirus (GCRV). Grass carp fingerlings and yearlings are vulnerable to GCRV. A virulent reovirus, tentatively named GCRV-AH528, was isolated from a diseased grass carp exhibiting typical hemorrhage symptoms in Hefei, Anhui Province. Intraperitoneal injection with the virus suspension led to hemorrhage similar to the observed clinical symptoms of blackened dorsum and hemorrhage around the mouth cavity, gill, intestine, belly, and base of the fin ray. The GCRV-AH528 genome contained 11 double-stranded RNA segments ranging from 1027 to 3925 bp, and its average content of AT and GC was 50.2% and 49.8%, respectively. Compared with registered GCRV Ⅱ strains, the GCRV-AH528 L1 segment had lost three continuous nucleotides (TAT) at nt 701~702, leading to the loss of a tyrosine, and the M4 segment mutated two ORFs encoding two non-structural proteins (NS9 and NS69). All segments had 6 bp-conserved terminal nucleotides 5'-GUAAU/CUžžžUU/GCAUC-3'. Except for the L1 and M6 segments, the two ends in the coding region of the other nine segments existed at 5~9 bp short specific inverted complementary sequences. GCRV-AH528 showed 37.1%~98.1% nucleotide and 24.3%~98.3% AA sequence identities with other reovirus. A phylogenetic tree based on VP1 protein revealed that GCRV-AH528 clustered with members of the genus Aquareovirus and was far from GCRV-873. These results indicated that the GCRV-AH528 isolate was a new GCRV Ⅱ type virulent strain.