The present invention provides an oligonucleotide which is capable of activating RIG-I and inducing an anti-viral, in particular, an IFN, response in cells expressing RIG-I. The oligonucleotide of the present invention has a double-stranded section of at least 21bp, at least one 5' triphosphate, and at least one blunt end which bears a 5' triphosphate. The present invention further provides the use said oligonucleotide for inducing an anti-viral, in particular, an IFN, response in vitro and in vivo. The present invention additionally provides the use of said oligonucleotide for preventing and/or treating diseases or conditions such as infections, tumors/cancers, and immune disorders.
