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

Abstract

When the nucleotide sequences of the Oka vaccine and its parental varicella-zoster virus (VZV) were compared in 6 open reading frames (ORFs), glycoprotein C (gC) and 5 transactivator genes, mutations were detected only in the immediate-early gene 62. The vaccine virus contained a mixture of different sequences that had variations at 15 nucleotide positions, but only one sequence 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 simplified restriction-enzyme fragment length polymorphism analysis, using NaeI and BssHII. This analysis was based on the sequence data obtained in this study. Studies of the regulatory activities of the ORF62 gene product (IE62) in 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 suggest that IE62 might play an important role in the attenuation of VZV.

Mutational Analysis of Open Reading Frames 62 and 71, Encoding the Varicella-Zoster Virus Immediate-Early Transactivating Protein, IE62, and Effects on Replication In Vitro and in Skin Xenografts in the SCID-hu Mouse In Vivo

“…An A-to-G transition at position 2872 (A2872G) resulted in an arginine-to-glycine substitution at position 958 (R958G), and a T-to-C substitution at position 3172 (T3172C) produced a tyrosine-to-histidine substitution at position 1058 (Y1058H). Sequencing of ORF62 in plasmid clones made from cells infected with vaccine Oka virus has shown considerable heterogeneity, as confirmed in two independent reports (3,17). The A2872G substitution present in the vOka cosmid was one of the numerous mutations that have been identified in ORF62 from vaccine Oka virus stocks, but the T3172C mutation has not been reported previously.…”

Recombination of Globally Circulating Varicella-Zoster Virus

“…It is therefore likely that the vaccine strains have already been involved in recombination events, either in vivo or in vitro. The vaccine preparation has previously been shown to be heterogeneous (49,61) and thus may have recombined during passaging in vitro or within the host following inoculation. In any case, it is only the detection of interclade vaccine/wild-type recombinants that can reliably reveal in vivo recombination between vaccine and wild-type strains after vaccination, since no strains from other clades are present in the vaccine batches (49).…”

Genetic Profile of an Oka Varicella Vaccine Virus Variant Isolated from an Infant with Zoster

“…Almost half of these mutations were clustered in ORF 62, which encodes IE62, a critical transactivating protein and major virion tegument protein. In recent studies IE62 has emerged as a probable contributor to the attenuation of VZV vaccine (1,9,10,11). Of the eight ORF62 mutations conferring an amino acid change, all but one (position 108838) in V-Oka-zoster displayed the vaccine SNP.…”

“…A safe and effective live-attenuated varicella vaccine was developed in 1968 and has been licensed and recommended in the United States since 1995 (25). Commercial varicella vaccines (all of which are derived from the Japanese Oka strain) have never been cloned, and complete genomic sequencing of the V-Oka-Biken vaccine revealed that it contained several strains that could be separated in tissue culture (9,10). Three manufacturers (Merck & Co Inc., Pasteur Merieux Connaught, and Biken Inc.) accepted the original V-Oka vaccine preparations, and each has the vaccine in production, with some variation in manufacturing processes.…”