Genetic Diversity among Varicella-Zoster Virus Vaccine Strains

ƒThis is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ license/by-nc/3.0/). Varicella-zoster virus (VZV) is a causative agent for chickenpox in primary infection and shingles after reactivation from latency. Both varicella and zoster can be prevented by live attenuated vaccines, but the molecular mechanism of attenuation is not clearly understood. In this study, the genome sequences of three varicella vaccine strains were analyzed for the genetic diversity including single nucleotide polymorphism (SNP) and genetic polymorphism. A total of 38 SNPs were identified including 29 substitutions and 9 insertion/deletions. The number of genetically polymorphic sites (GPS) was highest in Varivax and lowest in Varilrix. GPS in the R region including R1, R2, and R3 appeared to be responsible for the genetic polymorphisms in the open reading frame (ORF) 11, 14, and 22 in all three vaccine strains. A relatively large number of GPS were observed in ORF31, 55, and 62, which are known to be essential for virus replication, suggesting that the attenuation of the vaccine strains may be attributed by the diversity of these genes.