CSIRO Agriculture and Food, Livestock and Aquaculture, Castray Esplanade, Battery Point, Tasmania 7004, Australia.
CSIRO Australian Centre for Disease Preparedness (ACDP) (formerly Australian Animal Health Laboratory, AAHL), 5 Portarlington Rd, East Geelong, Victoria 3220, Australia.
Fish Shellfish Immunol. 2020 Oct;105:415-426. doi: 10.1016/j.fsi.2020.06.050. Epub 2020 Jul 3.
The Tasmanian Atlantic salmon (Salmo salar) aquaculture industry had remained relatively free of major viral diseases until the recent emergence of pilchard orthomyxovirus (POMV). The virus originally isolated from wild pilchards in Southern Australia is of great concern to the industry as it can cause high mortality. Despite its classification in the Orthomyxoviridae family, POMV is genetically divergent from infectious salmon anaemia virus (ISAV) and potentially represents a new genus within the family. Previous research has produced a formal case definition for clinical POMV, but the molecular events that underpin viral infection have not been characterized. Here we have undertaken a comparative transcriptome analysis of the response of Atlantic salmon kidney cells (ASK) in vitro to both POMV and ISAV using RNA sequencing, by harvesting cells at 6 and 24 h post infection (hpi). Despite their genomic differences, both orthomyxoviruses induced significant, and in some cases similar, innate antiviral responses. Early up-regulation of pathogen recognition receptor genes, RIG-I and TLR3, was observed in response to both viruses and triggered downstream interferon (IFN) responses. Interferon transcripts (IFN-alpha1 and INF-alpha2) were only induced in POMV infected cells at 24 hpi, but IFN-alpha3 was up-regulated in all time points and with both viruses. In addition, a strong induction of antiviral response genes (Mx and ISG15) was observed during the early infection with both viruses. Analysis of transcription factor binding sites in the up-regulated gene sets indicated that the host response to both viruses was largely driven by interferon regulatory factors (IRF) 1 and 2. Only three genes (slc35f2, odf2, LOC106608698) were differentially expressed in opposite directions, up-regulated with POMV and strongly down-regulated with ISAV at 24 hpi. Differential expression of these transcripts is possibly a consequence of virus divergence, but could also be associated to higher viral loads observed in the infection with POMV. Results from this study improve our understanding of the innate immune responses and host-pathogen interactions between POMV and Atlantic salmon. Early host response genes could potentially be exploited as subclinical biomarkers specific to POMV, and improved the development of tools for disease surveillance.
塔斯马尼亚大西洋鲑（Salmo salar）养殖业在最近出现鲱鱼正粘病毒（POMV）之前，一直相对没有受到重大病毒性疾病的影响。该病毒最初从澳大利亚南部的野生鲱鱼中分离出来，对该行业构成了巨大威胁，因为它会导致高死亡率。尽管它被归类为正粘病毒科，但 POMV 在遗传上与传染性鲑鱼贫血病毒（ISAV）不同，并且可能代表该科的一个新属。先前的研究已经提出了临床 POMV 的正式病例定义，但支持病毒感染的分子事件尚未得到表征。在这里，我们通过在感染后 6 和 24 小时（hpi）收获细胞，使用 RNA 测序对体外大西洋鲑肾细胞（ASK）对 POMV 和 ISAV 的反应进行了比较转录组分析。尽管它们的基因组存在差异，但两种正粘病毒都引起了显著的，并且在某些情况下相似的先天抗病毒反应。在两种病毒的作用下，观察到病原体识别受体基因 RIG-I 和 TLR3 的早期上调，并引发了下游干扰素（IFN）反应。IFN 转录物（IFN-α1 和 IFN-α2）仅在感染 POMV 的细胞中于 24 hpi 时诱导，但 IFN-α3 在所有时间点和两种病毒中均上调。此外，在两种病毒的早期感染中，观察到抗病毒反应基因（Mx 和 ISG15）的强烈诱导。上调基因集的转录因子结合位点分析表明，宿主对两种病毒的反应主要由干扰素调节因子（IRF）1 和 2 驱动。只有三个基因（slc35f2、odf2、LOC106608698）表现出相反的差异表达，在感染 POMV 时上调，而在感染 ISAV 时强烈下调。这些转录物的差异表达可能是病毒分化的结果，但也可能与 POMV 感染中观察到的更高病毒载量有关。本研究的结果提高了我们对 POMV 与大西洋鲑之间先天免疫反应和宿主-病原体相互作用的理解。早期宿主反应基因可能有潜力作为针对 POMV 的亚临床生物标志物，并改进了疾病监测工具的开发。
