Genotyping And Epidemiologic Survey Toward Clinical Varicella-zoster Virus Isolates Collected In China

Objective Genotyping of varicella-zoster virus (VZV) strains isolated from patients with chickenpox or zoster and differentiating them from Oka vaccine strain by molecular analysis.To adapt the"gold standard"serology assay-fluorescent antibody to membrane antigen (FAMA), use it to investigate the prevalent status of varicella-zoster virus infection in Guangzhou and provide theoretic basis for the prevention of varicella. Methods In the present study, SNP based VZV genotypes were analyzed in 19 VZV isolates using the polymerase chain reaction, restriction fragment length polymorphisms analysis and nucleotide sequencing of DNA fragments of the open reading frames 1, 21, 22, 38, 54, 62, and the R5 repeat regions.The FAMA test was established by using VZV infected human embryo fibroblasts as antigens and FITC labeled goat anti-human IgG as the secondary antibody. The sero-prevalence of anti-VZV IgG in 529 serum specimens randomly sellected from a pool of serum in the clinical laboratory was analyzed with FAMA.Results Thirty-six vesicle samples from patients with chickenpox or zoster were collected among which 19 VZV isolates were obtained The restriction fragment length polymorphism (RFLP) analysis of the isolates include two different groups with 47.3% of PstI+BglI+ SmaI-R5A and 52.7% of PstI+BglI+ SmaI-R5B, which is very different from those found in North America, Europe and Japan. All the Chinese isolates are wild-type strains with ORF62 SmaI-. No Oka vaccine strain was revealed among the isolates. Based on the sequencing data in ORFs 1, 21, 22, and 54, all of the 19 Chinese strains could be grouped to genotype J or J1. A novel in-frame three nucleotide insertion (CGG) in ORF1 was found in 4 (21%) of the 19 isolates.The FAMA test showed no cross-reaction with other herpesviruses when it was used to detect VZV antibodies. The overall prevalence of VZV antibody in the study population was 76.52%. Age-specific prevalence of VZV antibody in age groups of 1-3, 4-6, 7-13, 14-19, 20-29, 30-39, 40-49, >50 were 14.67%, 51.56%, 73.91%, 91.26%, 92.78%, 95.65%, 98.11% and 100%, respectively. The sero-prevalence of 1-3 age group is the lowest, and it then rises sharply with age but shows no association with the gender.Conclusion VZV strains currently circulating in Hefei, China in this study showed different molecular characteristics from those circulating in Europe, North America and Japan. The SNPs in ORF62 and ORF38 may be used to distinguish VZV wild-type strains and vaccine strain in clinical isolates in China.The data demonstrated that VZV infection occurs early in childhood. Therefore the primary recipients of VZV vaccine should be the age group 1-3. Additional subjects for vaccination would be children above 3 years old with no history of VZV infection, and serology test for VZV is negative. This study validated FAMA is a sensitive and specific method for detection of VZV IgG antibodies. It could be the method of choice in detection of protective antibodies against VZV infection.