Characterization of acyclovir susceptibility and genetic stability of varicella-zoster viruses isolated during acyclovir therapy.

We have characterized the susceptibility and genetic stability of varicella-zoster viruses (VZV) isolated from skin lesions of three patients with herpes zoster and six patients with varicella treated with conventional short-term acyclovir (ACV) administration. The susceptibilities to ACV of the serial isolates from the patients were examined, and there was no significant difference in the susceptibility to ACV among the isolates before and during the ACV treatment, indicating that conventional short-term ACV treatment did not generate ACV-resistant VZV infections. Polymerase chain reaction (PCR) analyses of these as well as seven thymidine kinase-deficient VZV strains derived from in vitro ACV treatment were carried out to examine their genomic stability. Five regions containing tandem direct reiterations (R1-R5) were amplified by PCR and compared, and the region containing the Pst I-site was also examined. PCR analyses demonstrated that the R1, R5 and the Pst I-sites were stable and useful in epidemiological studies even after ACV treatment. The R2, R3 and R4 sites were far less stable in these experimental conditions. In this paper we discuss the results of the PCR analyses with regard to the dynamics of VZV population in patients with VZV infection treated with conventional short-term ACV administration.