Interferon beta-1a-induced changes in gene expression in PBMCs derived from CIS patients

IFNβ, an effective therapy against relapsing-remitting (RR) multiple sclerosis (MS) is naturally secreted during the innate immune response against viral pathogens. The objective of this study was to characterize the immunomodulatory mechanisms of IFNβ targeting innate immune response and their effects on DC-mediated regulation of T-cell differentiation. We found that IFNβ−1a in-vitro treatment of human monocyte-derived dendritic cells (DCs) induced the expression of TLR7 and the members of its downstream signaling pathway, including myeloid differentiation factor 88 (MyD88), IL-1R-associated kinase (IRAK)4, and TNF receptor-associated factor (TRAF)6, while it inhibited the expression of IL-1R. Using siRNA TLR7 gene silencing, we confirmed that IFNβ-1a-induced changes in MyD88, IRAK4 and IL-1R expression were dependent on TLR7. TLR7 expression was also necessary for the IFNβ-1a-induced inhibition of IL-1β and IL-23, and the induction of IL-27 secretion by DCs. Supernatant (SN) transfer experiments confirmed that IFNβ-1a-induced changes in DCs’ cytokine secretion inhibit Th17 cell differentiation as evidenced by the inhibition of retinoic acid-related orphan nuclear hormone receptor C (RORC) and IL-17A gene expression and IL-17A secretion. Our study has identified a novel therapeutic mechanism of IFNβ−1a, that selectively targets the autoimmune response in MS. Keywords: The effect of IFN beta-1a on the gene expression in patients with clinically isolated syndrome suggestive of MS Gene expression changes induced by IFNβ−1a were tested using Affymetrix Human Genome U133 (HG-U133) arrays (Affymetrix) that contain 45,000 probe sets representing 39,000 transcripts derived from approximately 33,000 human genes. 107 PBMCs per condition derived from 15 CIS patients were stimulated with plate-immobilized αCD3 (1 μg/ml) and αCD28 (5 μg/ml) mAb (BD Biosciences) in the absence or presence of IFNβ-1a (1000 U/ml) (EMD Serono Inc) for 24 h in serum-free medium (Gibco). Cells were harvested and the total RNA was isolated using a Rneasy kit (Quiagen). Arrays were hybridized for 16 hours at 45oC in the GeneChip® Hybridization Oven 640 (Affymetrix). The arrays were washed and stained with R-phycoerythrin streptavidin in the GeneChip® Fluidics Station 400 (Affymetrix). The arrays were scanned with a Hewlett Packard GeneArray Scanner. Affymetrix GeneChip® Microarray Suite 5.0 software was used for washing, scanning and basic analysis.