Investigation of varicella-zoster virus DNA by the polymerase chain reaction in healthy children with varicella vaccination.

Investigation of varicella-zoster virus (VZV) DNA in 20 healthy children with varicella vaccination was carried out by using the polymerase chain reaction (PCR) and nested double PCR. Samples of peripheral blood mononuclear cells (PBMC) and throat swabs were simultaneously collected 3 times (before, 1 week, and 4 weeks after vaccination) for PCR analysis. One sample of PBMC was also obtained from each of the 12 healthy children with varicella during the acute phase as a positive control. VZV DNA was not found by the first PCR in any samples except one PBMC of a control subject. The nested double PCR, which is a more sensitive method for VZV DNA detection, was applied to the same samples. The viral DNA was detected in every PBMC of the controls, and in 2 (16.7%) PBMC at 1 week and in 6 (50%) PBMC at 4 weeks after vaccination in the 12 vaccinees with seroconversion. In 3 of 4 vaccinees who were seropositive before vaccination, VZV DNA was detected in PBMC at 1 or 4 weeks after vaccination. The three vaccinees showed a booster immunization with a significant increase in antibody titers. In contrast, no VZV DNA could be detected in any throat swabs of all the vaccinees nor in PBMC of the vaccinees who did not seroconvert.