Varicella-zoster virus ORF57, unlike its pseudorabies virus UL3.5 homolog, is dispensable for viral replication in cell culture.

Varicella zoster virus (VZV) encodes five genes that do not have homologs in herpes simplex virus. One of these genes, VZV ORF57, is predicted to encode a protein containing 71 amino acids. Antibody to ORF57 protein immunoprecipitated a 6-kDa protein in the cytosol of VZV-infected cells. Although the homolog of VZV ORF57 in pseudorabies virus, UL3.5, is critical for viral egress and growth in cell culture, VZV unable to express ORF57 replicated to titers similar to those seen with parental virus. Thus VZV ORF57 has a different role in viral replication than its pseudorabies virus homolog.