A herpes simplex virus type 1 variant which fails to synthesize immediate early polypeptide VmwIE63

We report the isolation of a variant (X2D) of herpes simplex virus type 1 strain 17 which has a deletion of 5 X 10(6) mol. wt. in the long unique and long inverted repeat regions, such that one copy of the immediate early (IE) gene 1 and two unique open reading frames coding for polypeptides of 20K and 22K are deleted. The mutant X2D synthesizes reduced levels of VmwIE110, and also apparently fails to synthesize VmwIE63, at both the protein and RNA levels, despite there being no apparent deletion in the coding or controlling regions of the IE2 gene. X2D also fails to synthesize the thymidine kinase polypeptide but exhibits normal growth characteristics in tissue culture.