A herpes simplex virus type 1 mutant containing a deletion within immediate-early gene 1 is latency competent in mice

We have investigated the behaviour in mice of the herpes simplex virus type 1 (HSV-1) mutant d/1403, which contains a deletion within the g ne encoding the immediate early polypeptide Vmw110. The deletion was responsible for a reduction in virulence assayed by both the intracranial nd footpad routes of inoculation. Following injection into the footpad, dl1403 was able to reach the spinal cord and establish a latent infection in sensory ganglia from which virus spontaneously reactivated upon explantation. The Vmw 110 polypeptide is therefore dispensable for the establishment and maintenance of latency and for reactivation from the latent state. The immediate arly (IE) gene 1, which encodes the polypeptide Vmw110 (ICP0), is one of the five genes expressed at the onset of lyric infection of permissive cells by herpes simplex virus type 1 (HSV-1) (reviewed by Wagner, 1985; Everett, 1987). Transient expression assays have demonstrated that Vmw 110 is a potent activator of transcription which is able to act alone or in concert with the IE polypeptide Vmw 175 to stimulate xpression from viral promoters carrie