Characterization of the impact of dietary immunostimulant CpG on the expression of mRNA biomarkers involved in the immune responses in Atlantic salmon (Salmo salar)

Citation

Xue X, Eslamloo K, Caballero-Solares A, Katan T, Umasuthan N, Taylor RG, Fast MD, Andreassen R & Rise ML (2024) Characterization of the impact of dietary immunostimulant CpG on the expression of mRNA biomarkers involved in the immune responses in Atlantic salmon (Salmo salar). Fish & Shellfish Immunology, 153, Art. No.: 109840. https://doi.org/10.1016/j.fsi.2024.109840

Abstract
Infectious diseases have significantly impacted Atlantic salmon aquaculture worldwide. Modulating fish immunity with immunostimulant-containing functional feeds could be an effective strategy in mitigating disease problems. Previously, we characterized the impact of polyriboinosinic polyribocytidylic acid (pIC) and formalin-killed typical Aeromonas salmonicida bacterin on miRNA expression in Atlantic salmon fed a commercial diet with and without immunostimulant CpG. A set of miRNA biomarkers of Atlantic salmon head kidney responding to pIC and/or bacterin immune stimulations was identified (Xue et al., 2019) [1]. Herein, we report a complementary qPCR study that investigated the impact of the pIC, bacterin and dietary CpG on the expression of immune-relevant mRNAs (n = 31) using the same samples as in the previous study (Xue et al., 2019) [1]. Twenty-six of these genes were predicted target transcripts of the pIC- and/or bacterin-responsive miRNAs identified in the earlier study. The current data showed that pIC and/or bacterin stimulations significantly modulated the majority of the qPCR-analyzed genes involved in various immune pathways. Some genes responded to both stimulations (e.g. tnfa, il10rb, ifng, irf9, cxcr3, campb) while others appeared to be stimulation specific [e.g. irf3, irf7a, il1r1, mxa, mapk3 (pIC only); clra (bacterin only)]. A. salmonicida bacterin stimulation produced a strong inflammatory response (e.g. higher expression of il1b, il8a and tnfa), while salmon stimulated with pIC showed robust interferon responses (both type I and II). Furthermore, the current data indicated significant down-regulation of immune-relevant transcripts (e.g. tlr9, irf5, il1r1, hsp90ab1, itgb2) by dietary immunostimulant CpG, especially among pre-injection and PBS-injected fish. Together with our prior miRNA study, the present research provided complementary information on Atlantic salmon anti-viral and anti-bacterial immune responses and on how dietary CpG may modulate these responses.

Keywords
CpG ODN; Functional feed; Predicated target transcripts; miRNA; Salmo salar; Immune response; infectious diseases

Journal
Fish & Shellfish Immunology: Volume 153

• Published Version