Piscirickettsiosis is the most important bacterial disease in the Chilean salmon industry, which has borne major economic losses due to failure to control it. Cells use extracellular vesicles (EVs) as an inter-cellular communicators to deliver several factors (e.g., microRNAs) that may regulate the responses of other cells. However, there is limited knowledge about the identification and characterization of EV-miRNAs in salmonids or the effect of infections on these. In this study, Illumina sequencing technology was used to identify Coho salmon plasma EV-miRNAs upon Piscirickettsia salmonis infection at four different time points. A total of 118 novels and 188 known EV-miRNAs, including key immune teleost miRNAs families (e.g., miR-146, miR-122), were identified. A total of 245 EV-miRNAs were detected as differentially expressed (FDR < 5%) in terms of control, with a clear down-regulation pattern throughout the disease. KEGG enrichment results of EV-miRNAs target genes showed that they were grouped mainly in cellular, stress, inflammation and immune responses. Therefore, it is hypothesized that P. salmonis could potentially benefit from unbalanced modulation response of Coho salmon EV-miRNAs in order to promote a hyper-inflammatory and compromised immune response through the suppression of different key immune host miRNAs during the course of the infection, as indicated by the results of this study.

Piscirickettsiosis 是智利三文鱼产业中最重要的细菌性疾病，由于未能对其进行控制，造成了重大的经济损失。细胞使用细胞外囊泡 (EV) 作为细胞间通讯器来传递几种可能调节其他细胞反应的因子 (例如 microRNA)。然而，关于鲑鱼中 EV-miRNA 的鉴定和表征或感染对这些的影响的知识有限。在这项研究中，Illumina测序技术被用来在识别银鲑等离子EV-miRNA的Piscirickettsia鲑四个不同时间点的感染。共鉴定了 118 篇小说和 188 种已知的 EV-miRNA，包括关键的免疫硬骨鱼 miRNA 家族（例如，miR-146、miR-122）。总共检测到 245 种 EV-miRNAs 差异表达（FDR < 5%），在整个疾病中具有明显的下调模式。EV-miRNA 靶基因的 KEGG 富集结果表明，它们主要分为细胞、应激、炎症和免疫反应。因此，假设P.salmonis 如本研究结果所示，通过在感染过程中抑制不同的关键免疫宿主 miRNA 来促进过度炎症和受损的免疫反应，可能会受益于 Coho 鲑鱼 EV-miRNA 的不平衡调节反应。