Table_14_Host-Parasite Interaction of Atlantic salmon (Salmo salar) and the Ectoparasite Neoparamoeba perurans in Amoebic Gill Disease.xlsx

Marine farmed Atlantic salmon (Salmo salar) are susceptible to recurrent amoebic gill disease (AGD) caused by the ectoparasite Neoparamoeba perurans over the growout production cycle. The parasite elicits a highly localized response within the gill epithelium resulting in multifocal mucoid patches at the site of parasite attachment. This host-parasite response drives a complex immune reaction, which remains poorly understood. To generate a model for host-parasite interaction during pathogenesis of AGD in Atlantic salmon the local (gill) and systemic transcriptomic response in the host, and the parasite during AGD pathogenesis was explored. A dual RNA-seq approach together with differential gene expression and system-wide statistical analyses of gene and transcription factor networks was employed. A multi-tissue transcriptomic data set was generated from the gill (including both lesioned and non-lesioned tissue), head kidney and spleen tissues naïve and AGD-affected Atlantic salmon sourced from an in vivo AGD challenge trial. Differential gene expression of the salmon host indicates local and systemic upregulation of defense and immune responses. Two transcription factors, znfOZF-like and znf70-like, and their associated gene networks significantly altered with disease state. The majority of genes in these networks are candidates for mediators of the immune response, cellular proliferation and invasion. These include Aurora kinase B-like, rho guanine nucleotide exchange factor 25-like and protein NDNF-like inhibited. Analysis of the N. perurans transcriptome during AGD pathology compared to in vitro cultured N. perurans trophozoites, as a proxy for wild type trophozoites, identified multiple gene candidates for virulence and indicates a potential master regulatory gene system analogous to the two-component PhoP/Q system. Candidate genes identified are associated with invasion of host tissue, evasion of host defense mechanisms and formation of the mucoid lesion. We generated a novel model for host-parasite interaction during AGD pathogenesis through integration of host and parasite functional profiles. Collectively, this dual transcriptomic study provides novel molecular insights into the pathology of AGD and provides alternative theories for future research in a step towards improved management of AGD.

海水养殖大西洋鲑（Salmo salar）在养殖生产周期中，易感染由体外寄生虫尼氏新阿米巴（Neoparamoeba perurans）引发的复发性鳃阿米巴病（amoebic gill disease，AGD）。该寄生虫会在鳃上皮内引发强烈的局域化应答，最终在寄生虫附着部位形成多灶性黏液斑。这种宿主-寄生虫互作应答会触发复杂的免疫反应，但其具体机制目前仍未被充分阐明。为构建大西洋鲑AGD发病过程中宿主-寄生虫互作模型，本研究探究了宿主局部（鳃组织）与全身的转录组应答，以及AGD发病阶段寄生虫的转录组变化。研究采用双转录组测序（dual RNA-seq）技术，结合差异基因表达分析以及基因与转录因子（transcription factor）网络的全系统统计分析方法。本研究通过体内AGD攻毒试验（in vivo AGD challenge trial）获取未感染与感染AGD的大西洋鲑样本，采集其鳃组织（包含病灶与非病灶组织）、头肾及脾脏组织，进而构建了多组织转录组数据集。对宿主大西洋鲑的差异基因表达分析显示，其局部与全身的防御及免疫应答均出现上调。两个转录因子——类znfOZF与类znf70，及其关联的基因网络随疾病状态发生显著改变。该网络中的多数基因可作为免疫应答、细胞增殖与侵袭的调控候选因子，其中包括类极光激酶B（Aurora kinase B-like）、类rho鸟苷酸交换因子25（rho guanine nucleotide exchange factor 25-like）以及受抑制的类蛋白NDNF（protein NDNF-like inhibited）。以体外培养的尼氏新阿米巴滋养体（trophozoites）作为野生型滋养体的对照样本，对比分析AGD病理过程中尼氏新阿米巴的转录组，本研究共鉴定出多个毒力候选基因，并发现一个潜在的主调控基因系统，其结构类似双组分PhoP/Q系统（two-component PhoP/Q system）。所鉴定的候选基因与宿主组织侵袭、宿主防御机制逃逸及黏液斑形成密切相关。本研究通过整合宿主与寄生虫的功能特征，构建了AGD发病过程中宿主-寄生虫互作的全新模型。综上，本项双转录组研究为AGD的病理机制提供了全新的分子视角，并为未来优化AGD防控管理的相关研究提供了新思路。