Recently, RNA ligands of RIG-I have also been reported to be highly immune stimulatory: a short, 5′ppp-containing RNA derived from the 3′ UTR of foot-and-mouth disease virus was shown to be an efficient type I IFNs inducer that protected against challenge viral infections [11]; two 5′ppp-containing RNA hairpins, both of which effectively activated the RIG-I signaling pathway, were shown to elicit protective antiviral immunity [12], [13]. This evidence concerns the gene RIGI and viral infectious disease.