Distribution Pattern of R5 Tandem Direct Repeats and PstI Cleavage Site Mutation from Clinical Isolates of Varicella - Zoster Virus in Korea

Na, Gun Yeon; Chung, Sang Lip; Kim, Jung Chul

Abstract

BACKGROUND: Chicken pox and herpes zoster are caused by the varicella-zoster virus(VZV). To investigate the epiderniologial relationship between clinical isolates of VZV, it is essential to distinguish different isolate.
OBJECTIVE
This study was conducted to classify the VZV strains according to R5 tandem direct reiterations(TDR) copy numbers and Pst I endonuclease cleavage site mutation, and to analyze the distribution pattern of VZV strains isolated in Korea.
METHODS
Strains of VZV were isolated from 61 patients with herpes zoster who had not been immunized with a live vaccine of VZV. Copy numbers of R5 TDR which was located in variable region IV were measured by PCR. The presence of a Pst I cleavage site in a middle portion of the long unique region of VZV genome was analyzed by PCR thereafter restriction enzyme digestion(PCR-RFLP).
RESULTS
VZV strains isolated in Korea contained one to three copy numbers of R5 TDR. Of 61 isolates, 43(70%) comtained 2 copies of R5 TDR, while 11(18%) isolates contained only one copy and 7(12%) isolat s contained 3 copies. About 16% of the strains examined did not have a PstI cleavage site, although the majority of strains retained this site. VZV strains could be classified into 6 strains on the basis of the copy number of R5 TDR and PstI cleavage site, in which the strain with 2 copies of R5 TDR and PstI cleavage site positive was the most frequent type (36 out of 61 isolates) in Korea. Four batches of live attenuated vaccine(Biken) that is now used in Korea showed 2 copy numbers of R5 TDR and PstI site negative.
CONCLUSION
The copy number of R5 TDR and the presence of PstI cleavage site seems to be a reliable marker for dicrimination of VZV strains in Korea. This discrimination can be used to study the molecular epiclemiology of VZV and as a criterion for identification of vaccine-related isolates.