5'-Triphosphate-RNA-independent activation of RIG-I via RNA aptamer with enhanced antiviral activity.

RIG-I is a cytosolic receptor for non-self RNA that mediates immune responses against viral infections through IFNα/ß production. In an attempt to identify novel tools that modulate IFNα/ß production, we used SELEX technology to screen RNA aptamers that specifically target RIG-I protein. Most of the selected RIG-I aptamers contained polyU motifs in the second half regions that played critical roles in the activation of RIG-I-mediated IFNß production. Unlike other known ligands, RIG-I aptamer bound and activated RIG-I in a 5'-triphosphate-independent manner. The helicase and RD domain of RIG-I were used for aptamer binding, but intact RIG-I protein was required to exert aptamer-mediated signaling activation. Furthermore, replication of NDV, VSV and influenza virus in infected host cells was efficiently blocked by pre- or post-treatment with RIG-I aptamer. Based on these data, we propose that RIG-I aptamer has strong potential to be an antiviral agent that specifically boosts the RIG-I-dependent signaling cascade.