Identification Of Chickenpox - Zoster Virus Genotype And Analysis Of Whole Genome Of Vaccine Strain In Jilin Province

Objective To clarify the genotype of wild-type strains of varicella-zoster virus (VZV) circulating in Jilin province in 2014 and to discriminate Oka-V vaccine strains from wild-type strains.To analyze the complete DNA sequence of varicella attenuated live vaccine (Oka-BK) in China.Methods The 13 vesicle fluid and throat swab samples with suspected varicella were collected in Jilin province from January to December,2014. The viral DNA was extracted and the fragments of 15 Open reading fragments (ORFs) were amplified by PCR. The viral genotypes were determined by single nucleotide polymorphism (SNP). The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to distinguish wild-type strains from Oka-V vaccine strains. The results were analyzed with the VZV reference strain sequences downloaded from GenBank by using the MEGA5 software. The genomic DNAs of varicella attenuated vaccine Oka-BK were amplified and sequenced by PCR separately,and the results were compared with those of VZV strains, based on which a phylogenetic tree was generated to analyze the homologies of Oka-BK strain to other strains. Results The 13 suspected samples,5 males and 8 females, were aged 11-27 years (average 16.69±5.48 years). Sampling date was 0-3 day.8 varicella samples were identified to be positive VZV strains and they were belonging to Clade 2. There was a synonymous mutation (T→C) in SNP 18082 comparing with the Oka-V vaccine strain. The analysis of PCR-RFLPs showed that 8 varicella samples were characterized as the wild-type strains (Pstl+BglI+SmaI-). The whole genome of VZV Oka-BK strain consisted of 125 095 bp, with a G+C content of of 46.1%.The lengths of regions UL, TRL, IRL,US, TRS and IRS were 104826,88,89,5235,7422 and 7435bp respectively. A total of 74 ORFs were found in the genome of Oka-BK, of which 3 genes were located within the repeat sequences, therefore the sequence of ORFs 69-71 in IRS region were completely identical to that of ORFs 62-64 in TRS region. A total of 327 nucleotide substitutions including a part of insertion and deletion mutations were observed as compared with Dumas strain, most of which were single nucleotide polymorphisms (SNPs). Transitions were more frequent than transversions(75% vs 6%).The analysis of VZV transactivator and glycoprotein showed that 13 amino acid were different between vaccine strains and wild-type strains.Phylogenetic tree showed that the homologies of Oka-BK was the most like Oka-VGSK. Conclusion The study disclosed that the VZV strains circulating in Jilin province in 2014 were wild-type strains and belonged to the Clade 2.Oka-BK was highly homologous to other VZV vaccine strains.