Campbell S, Collet B, Einer-Jensen K, Secombes C J, Snow M
Scottish Fish Immunology Research Centre, University of Aberdeen, Aberdeen, UK.
Dis Aquat Organ. 2009 Nov 9;86(3):205-12. doi: 10.3354/dao02127.
We identified viral haemorrhagic septicaemia virus (VHSV) isolates classified within Genotype Ib which are genetically similar (>99.4% glycoprotein amino acid identity) yet, based on their isolation history, were suspected to differ in virulence in juvenile rainbow trout. The virulence of an isolate recovered in 2000 from a viral haemorrhagic septicaemia disease episode in a marine rainbow trout farm in Sweden (SE-SVA-1033) was evaluated in juvenile rainbow trout via intraperitoneal injection and immersion challenge alongside 3 isolates recovered from wild-caught marine fish (DK-4p37, DK-5e59 and UKMLA98/6HE1) suspected of being of low pathogenicity to trout. Mortality data revealed that isolate SE-SVA-1033 caused VHSV-specific mortality in both intraperitoneal and immersion challenges (75.0 and 15.4%, respectively). The remaining Genotype Ib isolates caused significantly lower mortalities using the same experimental infection routes (<35.0 and <2.0%, respectively). Having identified VHSV isolates with clear differences in their pathogenicity, coding and inter-genic non-coding regions of 2 isolates (SE-SVA-1033 and DK-4p37) were determined and compared in order to identify potential markers responsible for the observed differences in virulence. Only 4 predicted amino acid substitutions were identified across the genome sequenced; these occurred in the N (R46G), G (S113G), NV (L12F) and L (S56A) proteins. These findings form the basis for further studies aimed at determining the biological significance of these mutations and suggest that small changes at the molecular level can cause significant changes in the virulence properties of VHSV isolates.
我们鉴定出了属于基因型Ib的病毒性出血性败血症病毒（VHSV）分离株，这些分离株在基因上相似（糖蛋白氨基酸同一性>99.4%），然而，根据它们的分离历史，怀疑它们对幼年虹鳟的毒力有所不同。2000年从瑞典一个海水虹鳟养殖场的病毒性出血性败血症疾病暴发中分离出的一株病毒（SE-SVA-1033），通过腹腔注射和浸泡攻毒，在幼年虹鳟中评估其毒力，同时还有从野生捕获的海水鱼中分离出的3株病毒（DK-4p37、DK-5e59和UKMLA98/6HE1），怀疑它们对虹鳟的致病性较低。死亡率数据显示，分离株SE-SVA-1033在腹腔注射和浸泡攻毒中均导致了VHSV特异性死亡（分别为75.0%和15.4%）。其余基因型Ib分离株使用相同的实验感染途径导致的死亡率显著较低（分别<35.0%和<2.0%）。在确定了致病性存在明显差异的VHSV分离株后，对2株分离株（SE-SVA-1033和DK-4p37）的编码区和基因间非编码区进行了测定和比较，以确定导致观察到的毒力差异的潜在标志物。在测序的全基因组中仅鉴定出4个预测的氨基酸替换；这些替换发生在N（R46G）、G（S113G）、NV（L12F）和L（S56A）蛋白中。这些发现为进一步研究这些突变的生物学意义奠定了基础，并表明分子水平上的微小变化可导致VHSV分离株毒力特性的显著变化。
