Cells stimulated with a synthetic dsRNA, polyinosinic-polycytidylic acid [poly(I:C)], a known cytosolic receptor MDA5 and RIG-I trigger (21), rapidly induced an IFN-β response, which was blocked in the presence of an MRV infection (Fig. 1A), suggesting that MRV is antagonizing this response. This evidence concerns the gene IFNB1 and infection.