ROLE OF THE VIRION HOST SHUTOFF (VHS) OF HERPES-SIMPLEX VIRUS TYPE-1 IN LATENCY AND PATHOGENESIS

The herpes simplex virus type 1 (HSV-1) UL41 gene product, virion host shutoff (vhs), has homologs among five alphaherpesviruses (HSV-1, HSV -2, pseudorabies virus, varicella-zoster virus, and equine herpesvirus 1), suggesting a role for this protein in neurotropism. A mutant viru s, termed UL41NHB, which carries a nonsense linker in the UL41 open re ading frame at amino acid position 238 was generated, UL41NHB and a ma rker-rescued virus, UL41NHB-R, were characterized in vitro and tested for their ability to replicate in vitro and in vivo and to establish a nd reactivate from latency in a mouse eye model, As demonstrated by We stern blotting (immunoblotting) and Northern (RNA) blotting procedures , UL41NHB encodes an appropriately truncated vhs protein and, as expec ted for a vhs null mutant, fails to induce the degradation of cellular glyceraldehyde-3-phosphate dehydrogenase mRNA, The growth of UL41NHB was not significantly altered in one-step growth curves in Vero or mou se C3H/10T1/2 cells but was impaired in corneas, in trigeminal ganglia , and in brains of mice compared with the growth of KOS and UL41NHB-R. As a measure of establishment of latency, quantitative DNA PCR showed that the amount of viral DNA within trigeminal ganglia latently infec ted with UL41NHB was reduced by approximately 30-fold compared with th at in KOS-infected ganglia and by 50-fold compared with that in UL41NH B-R-infected ganglia. Explant cocultivation studies revealed a low rea ctivation frequency for UL41NHB (1 of 28 ganglia, or 4%) compared with that for KOS (56 of 76, or 74%) or UL41NHB-R (13 of 20 or 65%), Taken together, these results demonstrate that vhs represents a determinant of viral pathogenesis.