VARICELLA-ZOSTER VIRUS ORF2 IS NOT REQUIRED FOR REPLICATION IN CELL CULTURE OR FOR ESTABLISHMENT OF LATENCY

*H. Sato, L. Pesnicak, and J.I. Cohen
Medical Virology Section, Laboratory of Clinical Investigation,
National Institute of Allergy and Infectious Diseases, Bethesda, Maryland

Varicella zoster virus (VZV) encodes six genes that do not have homologs in herpes simplex virus. One of these genes, VZV ORF2, is predicted to encode a protein containing 238 amino acids. Antibody to ORF2 protein detected a 31 kDa protein in the membrane fraction of VZV-infected cells. While homologs of VZV ORF2 in animal herpesviruses (e.g. Equine herpesvirus 1 and bovine herpesvirus 1) are associated with virions, purified VZV
virions contained little or no ORF2 protein. VZV sequences are also highly conserved with those of simian varicella virus (SVV). ORF2 is the only gene in VZV, however, that is not present in SVV. To determine the role of ORF2 in VZV infection, we constructed a recombinant VZV that is deleted for ORF2.

We found that recombinant VZV deleted for ORF2 grows to similar titers in cell culture as the parental recombinant virus. In preliminary studies, the ORF2 deletion mutant was able to establish a latent infection in the dorsal root ganglia of rodents, similar to the parental recombinant virus. Thus, VZV ORF2 encodes a protein that localizes to the membrane of VZV-infected
cells and is not required for VZV growth in vitro or for establishment of latent infection in animals.

Corresponding Author: H. Sato, MD., Ph.D., Medical Virology Section, Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, NIH, Bldg 10, Rm. 11N 214, 9000 Rockville Pike, Bethesda, MD 20892, USA