STAT1 and infection: To address the possibility that the inhibitory effect of 4-OI was independent of type I IFN signaling, as suggested by the results in Vero cells that are deficient in type I IFN19, HaCaT cells deficient in IFN alpha receptor 2 (IFNAR2), Signal Transducer and Activator of Transcription 1 (STAT1) or STING were treated with 4-OI, followed by infection with HSV1 and VACV.