Improved identification and differentiation of varicella-zoster virus (VZV) wild-type strains and an attenuated varicella vaccine strain using a VZV open reading frame 62-based PCR

A new method was developed to identify and differentiate varicella-zoster v irus (VZV) wild-type strains from the attenuated varicella Oka vaccine stra in, The PCR technique was used to amplify a VZV open reading frame (ORF) 62 region. A single specific amplicon of 268 bp was obtained from 71 VZV clin ical isolates and several laboratory strains. Subsequent digestion of the V ZV ORF 62 amplicons with SmaI enabled accurate strain differentiation (thre e SmaI sites were present in amplicons of vaccine strain VZV, compared with two enzyme cleavage sites for all other VZV strains tested). This method a ccurately differentiated the Oka vaccine strain from wild-type VZV strains circulating in countries representing all six populated continents. Moreove r, the assay more reliably distinguished wild-type Japanese strains from th e vaccine strain than did previously described methods.