Structure of varicella-zoster virus DNA

Abstract

Varicella-zoster virus (VZV) DNA was prepared om nucleocapsids and from enveloped virions of a laboratory strain (Ellen) and directly from the vesicle fluids of patients with zoster infections. VZV Ellen nucleocapsid DNA was cleaved with 11 different restriction endonucleases and electrophoresed in agarose gels. The restriction profiles of the nucleocapsid DNA were identical to those of the DNA recovered from purified virions but differed from those of another VZV strain (KM). In vitro-labeled VZV KM DNA purified directly from vesicle fluid yielded a distinct restriction pattern which appeared to be unchanged after several tissue culture [human diploid fibroblast WI-38] passages of the isolate from that fluid. Restriction endonuclease analysis (EcoRI or BglII) of VZV DNA revealed the presence of 4 cleavage fragments with a molar ratio of .apprx. 0.5. No individual fragments with molar ratios of 0.25 were noted. The VZV genome may thus contain 1 invertible segment. Comparison of the electrophoretic migrations of VZV DNA fragments relative to those of DNA of known size permitted calculation of the VZV genome size to be 72 .times. 106-80 .times. 106 daltons. These results were confirmed by EM which demonstrated a genome size of .apprx. 76 .times. 106 daltons for passaged and unpassaged VZV DNA. EM also revealed that some of the DNA molecules recovered from nucleocapsids or directly from vesicle fluids were superhelical circles.