Genotyping of varicella-zoster virus strains after serial passages in cell culture.

There is little information in the literature about the stability of single nucleotide polymorphisms (SNP) used for genotyping of varicella-zoster virus (VZV) in sequencing studies. The objective of this study was to genotype VZV wild-type and vaccine isolates representing the four major clades A, B, C and J before and after serial passages in cell culture. Eleven VZV strains were genotyped by sequencing of the open reading frames (ORF) 1, 21, 37, 50, 54 and 60 as well as by restriction fragment length polymorphism (RFLP) analysis of the ORFs 38 and 62 after 1-16 passages in human embryonic lung fibroblasts (HELF). Results revealed no variations of nucleotide sequences in the ORFs 1, 21, 37, 50, 54 and 60 within 16 cell culture passages. Additionally, there were no changes in the RFLP profile of the ORFs 38 and 62. In conclusion, VZV can be isolated in HELF and propagated for at least 16 passages before genotyping by sequencing without the risk of intra-strain variations. For rapid diagnostic identification of vaccine versus wild-type strains, the RFLP profile that is stable within several cell culture passages can be determined using DNA prepared from clinical specimens.