Distribution of varicella-zoster virus strains carrying a PstI-site-less mutation in Japan and DNA change responsible for the mutation.

We have analyzed 53 varicella-zoster virus (VZV) strains isolated in Japan for the presence of a PstI cleavage site in a middle portion of the long unique region of VZV genome. About 25% of the strains examined did not have this PstI cleavage site, although the majority of strains retained this site. For several VZV strains lacking this PstI cleavage site, we sequenced a recombinant DNA-derived short segment containing the mutation. In all strains analyzed, we identified a base replacement from A to G within the PstI recognition sequence. Because no wild-type VZV strain carrying this mutation has been found so far in other countries, it is very likely that the mutation once occurred in the past and has been conserved in some strains in Japan. We have concluded that the PstI-site-less mutation is reliable marker for discrimination of VZV strains in Japan.