Varicella-zoster virus (VZV) is a causative agent for chickenpox and zoster. Live attenuated vaccines have been developed based on Oka and MAV/06 strains. In order to understand the molecular mechanisms of attenuation, complete genome sequences of vaccine and wild-type strains were compared and single nucleotide polymorphism (SNP) was analyzed. ORF22 and ORF62 contained the highest number of SNPs. The detailed analysis of the SNPs suggested 24 potential vaccine-specific sites. All the mutational events found in vaccine-specific sites were transitional, and most of them were substitution of AT to GC pair. Interestingly, 18 of the vaccine-specific sites of the vaccine strains appeared to be genetically heterogeneous. The probability of a single genome of vaccine strain to contain all 24 vaccine-type sequences was calculated to be less than 4%. The average codon adaptation index (CAI) value of the vaccine strains was significantly lower than the CAI value of the clinical strains.

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Varicella-zoster virus (VZV) is a causative agent for shingles and herpes zoster. The genomes of VZV contain five reiteration (R) sequences and an origin of replication (ORI) sequences composed of tandem repeats whose numbers vary among different strains. Variation of the genome lengths among VZV strains could be attributed by the lengths of R sequences. There was a strong correlation between the lengths of VZV genome and R sequences, while variation of ORI did not contribute the variation of VZV genome length. The high G+C contents of The R sequences in ORF11, 14 and 22 influenced the codon usage of VZV in these ORFs. None of the most frequent 5 codons in R sequences was included in the top 5 most frequent codon in ORF11-14-22 or VZV genome, and vice versa.