- OmniGen-AF® (OG; Prince Agri Products, Inc., Quincy, IL) is a feed additive containing brewers dehydrated yeast and B-vitamins that supports immune function in ruminant livestock. Targeted profiling of immune-associated genes in whole blood is an effective platform for identification of a) novel molecular pathways and b) immune response markers to feed additives with immune-altering properties. The objectives of this study were to identify novel molecular pathways and immune response markers that are increased by dietary OG during a 28-d supplementation period. We hypothesized that several immune-associated genes in whole blood are up- or down-regulated during a 28 d supplementation period. Thirty-seven healthy, unchallenged, 180-200 g male CD rats received a diet containing 0 (control; n = 5, only 28 days), 0.5% (n = 15), or 1% (n = 17) of OG for 7 (n = 4/group), 14 (n = 3 or 4/group), 21 (n = 3 or 4/group), or 28 (n = 5/group) days. Whole blood was collected at the end of the feeding periods. RNA was purified from whole blood samples and used to generate cDNA that acted as template in the Rat Innate and Adaptive Immune Responses RT² Profiler PCR array (SABiosciences). Using PROC GLM, we compared cDNA abundance of immune-associated genes between control and supplemented groups (0.5 or 1%) with a P < 0.05 cut-off value for
significance. Of the 73 immune-associated genes that were expressed above the detection limit in >90% of all samples, 8 genes were altered at both OG supplementation dosages. Three bacterial pattern recognition receptors TLR1 (0.5%: +2.01; 1%: +2.38), TLR6 (0.5%: +2.11; 1%: +2.34), and Nod2 (0.5%: +2.32; 1%: +2.23), two antigen presenting cell surface receptors Cd1d1 (0.5%: +1.75; 1%: +2.33) and Cd80 (0.5%: +2.45; 1%: +3.00), and the cell signaling molecule Mapk8 (0.5%: +1.87; 1%: +2.35) were up-regulated by OG supplementation. In contrast, the Treg/Th2 marker Gata3 (0.5%: -2.16; 1%: -2.13) and IL10 (0.5%: -1.98; 1%: -2.05) were down-regulated for the first 3 wk of OG supplementation. Our results suggest that in whole blood of healthy, unchallenged rats OG supplementation stimulates bacterial recognition and T-cell activation for the host defense against bacterial pathogens. Three genes, Cd80, Mapk8, and TLR1, were consistently up-regulated after 7 d (Cd80: +2.82; MAPK8: +2.14; TLR1: +2.54 fold-change), 14 d (Cd80: +2.46; Mapk8: +2.04; TLR1: +1.87 fold-change), 21 d (Cd80: +3.71; Mapk8: +2.66; TLR1: +2.66 fold-change), and 28 d of OG supplementation (Cd80: +2.09; Mapk8: +1.67; TLR1: +1.81 fold-change) and, thus, could serve as potential immune response markers to OG supplementation.