Isolation and Characterization of a Herpes Simplex Virus Type 1 Mutant Containing a Deletion within the Gene Encoding the Immediate Early Polypeptide Vmw110

• Published in: Journal of general virology 1986-12, Vol.67 (12), p.2571-2585
• Main Authors: Stow, Nigel D, Stow, Elizabeth C
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Cell Line; Cricetinae; DNA, Viral - biosynthesis; Fundamental and applied biological sciences. Psychology; Genes, Viral; Genetics; herpes simplex virus 1; Humans; Microbiology; Mutation; Simplexvirus - genetics; Simplexvirus - growth & development; Simplexvirus - metabolism; Viral Plaque Assay; Viral Proteins - biosynthesis; Viral Proteins - genetics; Viral Proteins - physiology; Virology
• ISSN: 0022-1317; 1465-2099
• DOI: 10.1099/0022-1317-67-12-2571

Medical Research Council Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, U.K. Transfection experiments with plasmids containing immediate early (IE) genes of herpes simplex virus type 1 (HSV-1) have previously demonstrated a role for the IE polypeptide Vmw110 (ICP0) in stimulating expression from plasmid-encoded early gene promoters. To gain further insights into the function of Vmw110 we isolated a deletion mutant specifying a truncated form of the polypeptide which had been shown to be inactive in transfection assays. This mutant, dl 1403, contained a 2 kb deletion within both the TR L and IR L copies of the Vmw110 gene, and encoded a polypeptide consisting of the original N-terminal 105 amino acids followed by 56 amino acids specified by a reading frame not used by Vmw110. dl 1403 was able to replicate and produce plaques on baby hamster kidney (BHK) cells but the yield of infectious virus was 20- to 100-fold lower than obtained with wild-type HSV-1. Surprisingly, comparison of polypeptide synthesis, DNA replication and DNA encapsidation in cells infected with 5 p.f.u./cell dl 1403 or wild-type HSV-1 revealed no significant differences. In addition similar numbers of particles were produced in cells infected with the two viruses, resulting in stocks of dl 1403 exhibiting significantly higher particle/p.f.u. ratios. The efficiency of plaquing of dl 1403 was greatly reduced in Vero and human foetal lung cells compared with BHK cells, but following infection with 5 p.f.u./cell similar yields of infectious virus were obtained from all three cell lines. Marker rescue experiments verified that the reduced yield of dl 1403 in BHK cells was a consequence of the deletion within the Vmw110 gene. The results suggest that the effect of this deletion is manifest primarily at low multiplicities of infection and can be largely overcome by increasing the virus dose. Keywords: HSV-1, immediate early polypeptide Vmw110, deletion mutant Received 22 May 1986; accepted 7 August 1986.