Abstract
A deletion mutant derived from herpes simplex virus type 1 (HSV-1) strain ANG was analysed. The deletion mapped within the polypeptide- coding region of the immediate-early ICP4 gene. Based on DNA sequence data the deletion was shown to comprise 84 base pairs. In the wild-type genome of strain ANG these sequences were almost completely homologous to the known sequences of HSV-1 strain 17. The ICP4 polypeptide induced by the mutant was similar in size to the wild-type ICP4 protein and was recognized by a monoclonal antibody against ICP4. The data presented suggest that the deletion corresponds to a region on the ICP4 polypeptide that is nonessential for the replication of the virus in vitro.