STAT1 and viral infectious disease: Consistent with this, adults with impaired IFN Type I and Type II responses, due to either a deficiency in the signal transduction and transcription factor 1 (Stat1), Toll-like receptor 3 (TLR3), or UNC-93B (an endoplasmic reticulum protein important for TLR signaling), show increased susceptibility to HSV and other viral infections [4], [5], [6], [7].