Protein Kinase R (PKR): is also one of the sensors of viral invasion. PKR is a cytosolic protein composed of dsRNA bindign motifs and a serine/threonine kianse domain. Binding of PKR with viral dsRNA resutls in the phosphorylation of the translation initiation factor, eIF2?, and translational inhibition. In addition, production of type I IFNs by dsRNA is possibly regulated by PKR.

RIG-I: retinoic-acid inducible gene-I can recognize viral dsRNA to induce the type I IFN response in vitro. RIG-I contains an N-terminal caspase recruitment domain (CARD) and a C-terminal DExD/H box RNA helicase domain. The helicase domain is responsible for dsRNA recognition, and the CARD domain activates downstream signaling pathways.

RIG-I, but not the TLR system plays an essential role in antiviral responses in various cells except pDCs. Reciprocally, the TLR system, but not RIG-I, is indispensable to IFN-? secretion in pDCs.

TLRs are critical for the recongition of pathogen-specific molecular patterns (PAMPs) derived from viral species. Among 11 reported TLRs, TLR3, TLR4, TLR7, TLR8, and TLR9 are involved int he recognition of viral components