Oka varicella vaccine is distinguishable from its parental virus in DNA sequence of open reading frame 62 and its transactivation activity

When the nucleotide sequences of the Oka vaccine and its parental varicella -zoster virus (VZV) were compared in 6 open reading frames (ORFs), glycopro tein C (gC) and 5 transactivator genes, mutations were detected only in the immediate-early gene 62. The vaccine virus contained a mixture of differen t sequences that had variations at 15 nucleotide positions, but only one se quence was found for the Oka parental virus gene 62. The Oka vaccine virus gene 62 could be distinguished from the parental virus gene using a simplif ied restriction-enzyme fragment length polymorphism analysis, using Nael an d BssHII. This analysis was based on the sequence data obtained in this stu dy. Studies of the regulatory activities of the ORF62 gene product (IE62) i n a transient transfection assay indicated that IE62 of the parental virus had a stronger transactivational activity than that of the vaccine virus in activating immediate-early, early, and late gene promoters. These data sug gest that IE62 might play an important role in the attenuation of VZV. J. M ed. Virol. 61:497-503, 2000. (C) 2000 Wiley-Liss, Inc.