Dietary Immunostimulant CpG Modulates MicroRNA Biomarkers Associated with Immune Responses in Atlantic Salmon (Salmo salar).

Xi Xue,Rune Andreassen,Matthew L Rise,Navaneethaiyer Umasuthan,Albert Caballero-Solares,Mark D Fast,Richard G Taylor,Nardos Tesfaye Woldemariam

doi:10.3390/cells8121592

Abstract

MicroRNAs (miRNAs) are key regulators in fish immune responses. However, no study has previously characterized the impact of polyriboinosinic polyribocytidylic acid (pIC) and formalin-killed typical Aeromonas salmonicida (ASAL) on miRNA expression in Atlantic salmon fed a commercial diet with and without immunostimulant CpG. To this end, first, we performed small RNA deep sequencing and qPCR analyses to identify and confirm pIC- and/or ASAL-responsive miRNAs in the head kidney of salmon fed a control diet. DESeq2 analyses identified 12 and 18 miRNAs differentially expressed in pIC and ASAL groups, respectively, compared to the controls. Fifteen of these miRNAs were studied by qPCR; nine remained significant by qPCR. Five miRNAs (miR-27d-1-2-5p, miR-29b-2-5p, miR-146a-5p, miR-146a-1-2-3p, miR-221-5p) were shown by qPCR to be significantly induced by both pIC and ASAL. Second, the effect of CpG-containing functional feed on miRNA expression was investigated by qPCR. In pre-injection samples, 6 of 15 miRNAs (e.g., miR-181a-5-3p, miR-462a-3p, miR-722-3p) had significantly lower expression in fish fed CpG diet than control diet. In contrast, several miRNAs (e.g., miR-146a-1-2-3p, miR-192a-5p, miR-194a-5p) in the PBS- and ASAL-injected groups had significantly higher expression in CpG-fed fish. Multivariate statistical analyses confirmed that the CpG diet had a greater impact on miRNA expression in ASAL-injected compared with pIC-injected fish. This study identified immune-relevant miRNA biomarkers that will be valuable in the development of diets to combat infectious diseases of salmon.

Highlights

Worldwide demand for seafood for human consumption, including a growing contribution from aquaculture (~50% in 2016), continues to climb because of a flat or decreasing global wild fisheries production in the face of rising human population [1,2,3]
The results showed that the comparisons between diets within pre-injection and two of the post-injected groups (i.e., phosphate-buffered saline (PBS) and Aeromonas salmonicida (ASAL)) were highly significant based on the expression of the 15 qPCR analyzed miRNAs (Table 5)
The present study identified and qPCR confirmed 9 miRNA biomarkers of Atlantic salmon response to polyribocytidylic acid (pIC) and/or ASAL immune stimulations

Summary

Introduction

Worldwide demand for seafood for human consumption, including a growing contribution from aquaculture (~50% in 2016), continues to climb because of a flat or decreasing global wild fisheries production in the face of rising human population [1,2,3]. Cells 2019, 8, 1592 in substantial mortality and losses to Atlantic salmon aquaculture worldwide, affecting the growth and sustainability of the industry [5]. Several well-known viruses that cause severe diseases in Atlantic salmon are RNA viruses [6]. These include viruses with single-stranded RNA genomes (e.g., salmonid alphavirus (SAV), infectious salmon anemia virus (ISAV) and viral hemorrhagic septicemia virus (VHSV)) and double-stranded RNA genomes (e.g., infectious pancreatic necrosis virus (IPNV)) [6]

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Discussion

Conclusion