THE UL4 GENE OF HERPES-SIMPLEX VIRUS TYPE-1 IS DISPENSABLE FOR LATENCY, REACTIVATION AND PATHOGENESIS IN MICE

The UL4 gene of herpes simplex virus type 1 is predicted to encode a 2 1.5 kDa protein of 199 amino acids. Although UL4 is dispensable for gr owth in cell culture, its function is not known. In the present study, the promoter of UL4 was examined and found to contain a cAMP-response element which bound the transcription factor CREB, and was strongly a ctivated by cAMP, A recombinant virus, termed UL4HS, was constructed w ith a nonsense linker inserted into the UL4 open reading frame, to mak e a truncated UL4 protein of 60 amino acids. In addition, a marker-res cued virus, UL4HSMR, was constructed. Western immunoblot analysis reve aled a 23 kDa band in extracts of wild-type and marker-rescued virus i nfected cells which was missing for UL4HS, Only modest differences wer e observed in the abilities of wild-type and UL4-mutant viruses to gro w in Vero cells or in contact-inhibited mouse C3H/10T1/2 cells. In add ition, there were only modest differences between the ability of UL4HS to replicate in murine corneas and trigeminal ganglia relative to wil d-type viruses, and reactivation of UL4HS from latency was unaffected. Taken together, these data demonstrate that UL4 is dispensable for la tency and pathogenesis in mice.