Prevents establishment of cellular antiviral state by blocking virus-induced phosphorylation and activation of interferon regulatory factor 3 (IRF3), a transcription factor critical for the induction of interferons alpha and beta. This blockage is produced through the interaction with and inhibition host IKBKE and TBK1 producing a strong inhibition of the phosphorylation and activation of IRF3. Also inhibits the antiviral effect mediated by the interferon-induced, double-stranded RNA-activated protein kinase EIF2AK2/PKR. Acts as a polymerase cofactor in the RNA polymerase transcription and replication complex.