Varicella-zoster virus ORF 58 gene is dispensable for viral replication in cell culture

BACKGROUND: Open reading frame 58 (ORF58) of varicella-zoster virus (VZV) lies at the 3'end of the Unique long (U(L)) region and its functional is unknown. In order to clarify whether ORF58 is essential for the growth of VZV, we constructed a deletion mutant of ORF58 (pOka-BACΔ58) from the Oka parental genome cloned into a bacterial artificial chromosome (pOka-BAC). RESULTS: The ORF58-deleted virus (rpOkaΔ58) was reconstituted from the pOka-BACΔ58 genome in MRC-5 cells, indicating that the ORF58 gene is non-essential for virus growth. Comparison of the growth rate of rpOkaΔ58 and recombinant wild-type virus by assessing plaque sizes revealed no significant differences between them both in MRC-5 cells and malignant melanoma cells. CONCLUSION: This study shows that the ORF58 gene is dispensable for viral replication and does not affect the virus' ability to form plaques in vitro.