Participation of type I interferon in the decreased virulence of the UL13 gene-deleted mutant of herpes simplex virus type 1

We isolated a UL13 gene-deleted mutant of the herpes simplex virus type 1 ( HSV-1) strain VR3 (VR Delta 13) and its revertant virus (VR Delta 13R). Thi s deletion mutant still had virus host shutoff (vhs) activity, although a p revious report had suggested the possibility of a functional relation betwe en the UL13 product, that is protein kinase (PK), and vhs activity. We comp ared the in vivo growth of these viruses in BALB/c mice. VR Delta 13 was cl eared in the early period of intraperitoneal infection. VR Delta 13 had a h igher sensitivity to the mouse type I interferon (IFN) and showed a higher level of IFN induction in the study period of infection than did VR3 and VR Delta 13R. These results suggest that a nonspecific antiviral response (i. e., the IFN system) may contribute to this rapid inhibition of viral replic ation in vivo.