The Effect of Camelina Oil-Containing Diets on the Expression of Genes Involved in the Innate Anti-Viral Immune Response in Atlantic Cod (Gadus Morhua)

This study was performed to investigate the effect of camelina oil-based diets on the immune function of Atlantic cod, as measured by gene expression in spleen. Atlantic cod were fed with one of three practical diets (three tanks per diet): a control diet using herring oil as a lipid source (FO diet), and two experimental diets using vegetable oil from Camelina sativa to replace 40% or 80% of herring oil (40CO and 80CO diets). We studied both the effect of the diet alone on basal spleen gene expression levels, as well as the effect of the diet after fish were injected with the synthetic double-stranded RNA polyriboinosinic polyribocytidylic acid (pIC), which mimics a viral immune stimulus. Atlantic cod were fed for 67 days with the FO, 40CO or 80CO diet (three tanks per diet). Then the fish from each tank were divided over two separate tanks and after 6 days of acclimation they were injected intra-peritoneally with either pIC (3 tanks per diet) or PBS (three tanks per diet). Spleen samples were taken from 6 fish from each tank at 0h (pre-injection), 6 hours post injection (HPI), and 24HPI. A universal reference design was used for the microarray experiment. For the test samples, RNA was used from individual spleens of fish from the following 9 treatment groups: FO 0h, 40CO 0h, 80CO 0h, FO 24HPI PBS, FO 24HPI pIC, 40CO 24HPI PBS, 40CO 24HPI pIC, 80CO 24HPI PBS, and 80CO 24HPI pIC. For each 0h group we used 12 biological replicates (2 fish from each of 6 tanks), and for each 24HPI group we used 9 biological replicates (3 fish from each of 3 tanks). All test samples were labeled with AlexaFluor 647. The common reference was a pool of 259 RNA samples from spleens of fish from all tanks, representing all 3 diets, both PBS and pIC treatments, and all 3 time points. The common reference was labeled with Alexafluor 555. Each individual test sample was hybridized together with the common reference sample on an array, so the experiment consisted of 90 microarrays