Project description:In order to understand the appropriate use of potentially beneficial Gram positive microbes through their introduction in the gut microbiome, it is necessary to understand the influence of individual bacteria on the host response system at a cellular level. In the present study we showed that lipopolysaccharide (LPS), flagellated Gram negative bacteria, potentially beneficial Gram positive bacteria and yeast interact differently with human intestinal enterocytes (IEC) with a custom-designed expression microarray evaluating 17 specific host-response pathways. Only, LPS and flagellated Gram negative bacteria induced inflammatory response, while a subset of Gram positive microbes had anti-inflammatory potential. The main outcome from the study was the differential regulation of the central MAPK signaling pathway by these Gram positive microbes versus commensal/pathogenic Gram negative bacteria. The microarray was efficient to highlight the impact of individual bacteria on IEC response, but q-RT-PCR validation demonstrated some underestimation for down regulated genes by the microarray. This Immune Array will allow us to better understand the mechanisms underlying pathogen-induced host immune responses, aid in the selection potentially probiotic microbes and perhaps select biomarkers for future clinical studies. In this study, human immune response was assessed by stimulating HT-29 intestinal epithelial cells (IEC) with different microorganisms (or LPS) individually. For each of the 12 different treatments, between 4 and 8 biological replicates were performed, analyzed with dye-swaps and hybridized against control or untreated cells. Genes that were showing a 1.3 mRNA transcript abundance fold change and a P-value below 0.05 were considered to be differentially expressed.