GENOTYPING OF VARICELLA-ZOSTER VIRUS IN CANADA: 1900-2000

*G.A. Tipples (1), M. Gray (1), M. Cossitt (1), M. Song (1),
K. Makowski (1), S. Forgie (2), D. Cook (3) and R. Garceau (4)
(1) Viral Exanthemata, National Microbiology Laboratory, Winnipeg,
Manitoba, (2) Department of Medical Microbiology, University of
Manitoba, Winnipeg, Manitoba, (3) BC Centre for Disease Control, Vancouver, BC,
and (4) L'Hôpital Régional Dr GL Dumont, Moncton, New Brunswick, Canada.

The objective of our study was to assess methods for differentiating vaccine from wild-type (wt) varicella-zoster virus (VZV) strains and to determine the genotypic variety of wt VZV strains in Canada over the past century. The wt strains were isolated from people in a variety of age groups. Those older than 40 years of age were presumed to have zoster. In zoster cases, where reactivation of virus occurs, the approximate year
of primary infection was estimated. A vaccine strain (Oka/Merck), a laboratory strain (Ellen) and 60 clinical isolates were analysed using a combination of previously published PCR-based methods. Restriction endonuclease site analysis was determined for open reading frames (ORF) 38 (Pst I), 54 (Bgl I) and 62 (Sma I). Variable copy numbers of repeated sequences in regions R2 and R5 were determined by amplicon size differentiation.

The Sma I site in ORF62 was present in the vaccine and Ellen strains, but was absent in all 60 wt isolates. The Pst I site in ORF38 was absent in the vaccine strain and present in the Ellen and wt strains. The Bgl I site in ORF 54 was present in the vaccine strain and a proportion of wt strains. Repeat copy numbers ranged from 4 to 10 (7 for vaccine strain) for R2. Three repeat copies in R5 were detected in the vaccine strain and one wt strain and 2 copies were detected in all other strains analysed.

In conclusion, the VZV vaccine strain can be differentiated from wt strains in Canada using restriction endonuclease analysis of ORF 38, 54 and 62 amplicons. At least 14 VZV genotypes could be differentiated using a combination of genotyping methods. Our collection of wt isolates gives an approximate representation of strains circulating in Canada over the past 100 years. Ongoing work includes analysing more representative isolates from past years from all regions of Canada as well as ongoing monitoring of
current wt and vaccine strains in Canada.

Corresponding Author: Graham A. Tipples, PhD, Head of Viral Exanthemata, National Microbiology Laboratory, Health Canada, 1015 Arlington Street, Winnipeg, Manitoba, R3E 3R2, Canada