Transcriptome Profiling of Antiviral Immune Responses of Macrophage-like Cells in Atlantic Salmon Fed Different Levels of Dietary Fish and Vegetable Oils

Atlantic salmon were fed diets containing 7.38% (FO7, EPA+DHA 1.41) or 5.09% (FO5, EPA+DHA 1.00) fish oil. These diets were designed to be relatively low in EPA+DHA, but near the requirement level, resulting in no significant change in salmon growth. After a 14-week feeding trial, macrophages isolated from fish in these dietary groups were stimulated by a viral mimic (dsRNA: pIC) for 24 h. The fatty acid composition of cells slightly varied between the two dietary groups (e.g. higher 20:5n3 in FO7 group). Following microarray assays using a 44K salmonid platform, Rank Products (RP) analysis showed 15 and 54 differentially expressed probe (DEP) (PFP<0.05) between the two diets in control and pIC groups (FO5/FO7), respectively. Nonetheless, Significance Analysis of Microarrays (SAM, FDR<0.05) identified only one (i.e. transmembrane protein 115-like) DEP between pIC groups of the two diets. Moreover, we identified a large number (i.e. 890 DEP in FO7 and 1128 DEP in FO5 overlapped between SAM and RP) of pIC-responsive transcripts involved in pattern-recognition receptor and cytokine-mediated pathways. Subsets of 9 diet- and 38 pIC-responsive transcripts were subjected to qPCR validation, and these assays confirmed the microarray results for 2 diet-responsive transcripts and all of the pIC-responsive transcripts. Fatty acid-binding protein adipocyte (fabp4) and proteasome subunit beta type-8 (psmb8) were significantly up- and down-regulated, respectively, in the diet with higher level of vegetable oil, suggesting them as important diet-responsive, immune-related biomarkers for future studies. The present study revealed that different levels of dietary fish and vegetable oils did not lead to a massive change in transcriptome profile of antiviral responses of salmon macrophages.