RESUMO
Varicella-zoster virus (VZV) is a causative agent for chickenpox and shingles. Comparative genomic sequence analysis of clinical and vaccine strains suggested potential sites responsible for attenuation. In this study, low and high passages of two VZV clinical strains cultured in human fibroblast cells were compared for genomic DNA sequences and growth characteristics. Mutations were detected at 187 and 162 sites in the strain YC01 and YC02, respectively. More than 86% of mutations were found in open reading frames, and ORF62 exhibited highest frequency of mutations. T to C and A to G transitions accounted for more 90% of all possible substitutions. Forty mutations were common to two strains, including 27 in ORF62. Mutations found in attenuated vaccine strains were also detected at 7 positions. Both high and low passage strains were infectious and grew similarly in human fibroblast cells. In guinea pig cells, however, high passage strain remained infectious while low passage strain lost infectivity. This study may provide new insight into the attenuating mutations associated with in vitro passaging of VZV.
Assuntos
Vacina contra Varicela/genética , Fibroblastos/virologia , Herpesvirus Humano 3/genética , Proteínas Imediatamente Precoces/genética , Mutação Puntual , Transativadores/genética , Proteínas do Envelope Viral/genética , Animais , Técnicas de Cultura de Células , Linhagem Celular , Vacina contra Varicela/imunologia , Fibroblastos/imunologia , Prepúcio do Pênis/citologia , Expressão Gênica , Cobaias , Herpesvirus Humano 3/crescimento & desenvolvimento , Herpesvirus Humano 3/imunologia , Especificidade de Hospedeiro , Humanos , Proteínas Imediatamente Precoces/imunologia , Pulmão/citologia , Masculino , Fases de Leitura Aberta , Transativadores/imunologia , Vacinas Atenuadas , Proteínas do Envelope Viral/imunologiaRESUMO
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.