2017年中国部分地区白斑综合征病毒高变异区的序列分析

Variation analysis on highly variable regions of white spot syndrome virus from partial areas of China in 2017

白斑综合征病毒(WSSV)自暴发以来给全球范围内的对虾养殖产业带来了巨大的损失。为了解我国凡纳滨对虾(Litopenaeus vannamei)养殖区WSSV的流行变异情况,选取2017年中国部分地区的42个WSSV阳性样本,对ORF14/15、ORF23/24、ORF75、ORF94和ORF125共5个可变区进行PCR特异性扩增,分析其序列的缺失变异和重复单元(Ru)中单核苷酸多态性的变化。研究结果显示,在ORF14/15的扩增中共出现4种缺失片段;ORF23/24只出现11945bp的缺失片段;ORF75扩增中,总RUs数目为3、4、9,其中45bp的RUs在12、27、80位点发生多核苷酸多态性;ORF94的RUs数目为6,其各重复单元在48位发生单核苷酸多态性;ORF125的RUs数目为4、6、7不等,其各重复单元分别在20、27、50、53、61位发生碱基突变。研究结果表明,2017年样本中,WSSV在中国大部分地区均出现一定程度的缺失变异,其中部分可变区表现出缺失情况的稳定性,某些可变区的重复单元数目及SNP表现出地区的差异性以及不稳定性。

White spot syndrome has caused enormous losses to shrimp farming industry worldwide since its outbreak. In order to understand the epidemic variations of WSSV in shrimp culture areas of China, 42 WSSV positive samples from regions of China in 2017 were selected for PCR-specific amplification of five variable regions of ORF14/15, ORF23/24, ORF75, ORF94 and ORF125. Afterwards, the deletion variations and changes of single nucleotide polymorphism in the repeat unit were analyzed. The results showed that there were four deletion fragments in the amplification of ORF14/15, with the length of 6 530 bp, 6 533 bp, 5 950 bp and 5 949 bp, respectively. Only the 11 945 bp deletion fragment appeared in ORF23/24. In the ORF75 amplification, the total number of RUs was 3, 4, and 9, and the 45 bp RUs were polymorphic at the 12, 27, and 80 positions. ORF94 only amplified a positive sample with a number of RUs of 6, and the single nucleotide polymorphism of each repeat unit at position 48. The number of RUs of ORF125 varied from 4, 6, and 7. Base mutations occurred at positions of 20, 27, 50, 53, and 61 in each ORF125 region. The results showed that a certain degree of deletion variation of WSSV appeared in most parts of China, and some of the variable regions showed the stability of deletion. The number of repeating units in some variable regions and SNP showed regional differences and unstability.