Identification of the Oka strain of the live attenuated varicella vaccine from other clinical isolates by molecular epidemiologic analysis

A method was developed to distinguish the Oka vaccine strain of varicella-zoster virus (VZV) from other clinical isolates. The molecular characteristics of 52 clinical isolates from varicella or tester patients with no history of VZV vaccination and the Oka strain, including vaccine and parental viruses, were analyzed by PstI cleavage of the PstI site-less (PSL) region. This was followed by single-strand conformational polymorphism (SSCP) after polymerase chain reaction amplification of repeating region 2 (R2). Most of the clinical isolates tested, especially recent isolates, had a PstI site in the PSL region, but the Oka strain did not, The SSCP patterns of R2 in Oka strain virus differed from those of other viruses. These results suggest that analysis of the PstI site followed by SSCP of R2 will be useful for identifying the Oka vaccine virus in isolates.