Genotype analysis of varicella-zoster virus isolates from suburban Shanghai Municipal Province, China

Genomic sequencing revealed recombination event between clade 1 and clade 2 occurs in circulating varicella-zoster virus in China

Varicella-zoster virus (VZV), a member of the Alphaherpesvirinae subfamily, causes varicella in primary infections and establishing a latent stage in sensory ganglia. Upon reactivation, VZV causes herpes zoster with severe neuralgia, especially in elderly patients. The mutation rate for VZV is comparatively lower than the other members of other alpha herpesviruses. Due to geographic isolation, different genotypes of VZV are circulating on separate continents. Here, we successfully isolated a VZV from the vesicular fluid of a youth zoster patient. Based on the single-nucleotide polymorphism profiles of different open reading frames that define the genotype, this newly isolated VZV primarily represents genotype clade 2 but also has characteristics of genotype clade 1. The next-generation sequencing provided a nearly full-length sequence, and further phylogenetic analysis revealed that this VZV isolate is distinct from clades 1 and 2. The Recombination Detection Program indicates that a possible recombinant event may occur between the VZV isolate and clade 1. In summary, we found that there is a circulating VZV isolate in China that may represent a recombinant between clade 1 and clade 2, providing new concerns that need to be considered in the future VZV vaccination program.

Characterization and Comparison of Genetic Variation in Clinical Varicella-Zoster Virus Isolates Collected from Shanghai and Urumqi, China

Varicella-zoster virus (VZV) is a ubiquitous human herpesvirus that causes chickenpox and zoster. Considering that VZV is a relatively and genetically stable virus, its global surveillance clades provide essential information for VZV evolution, immigration, and importation of different viral strains and recombination events. Eighty-eight VZV isolates from China (Shanghai and Urumqi) were genotyped using a scattered single-nucleotide polymorphism method in this prospective study. Our results were based on sequencing the open reading frames 1, 6, 12, 16, 17, 21, 22, 35, 37, 38, 50, 54, 55, 56, 60, and 66. We found that the majority of these 88 strains (81.8%) belonged to Clade 2 with significantly high homogeneity from Shanghai. However, in the Urumqi area, some strains were grouped to Clade 5, and some could not be attributed to any of the established VZV clades, although the majority of Urumqi strains belonged to Clade 2. Our results illustrated that due to geographical location, VZV could undergo genetic recombination, suggesting that VZV diversity is more complicated in certain areas and geographical separation contributes to VZV complexity.

Seroprevalence and molecular characteristics of varicella-zoster virus infection in Chinese children

Background

Varicella-zoster virus (VZV) infection in children is an important public health problem in China. We performed the current study to explore the seroprevalence of VZV infection in Chinese children in order to provide more information for improvement of varicella vaccination in China.

Methods

Three thousand fourteen children were recruited from Chinese kindergarten students aged from four to six years. Anti-VZV IgG and IgM were assayed using enzyme-linked immunosorbent assay. Both ORF22 and ORF62 of VZV were amplified, sequenced, and analyzed by nested PCR.

Results

Among 3014 children, 43.9% of boys and 46.3% of girls were vaccinated with varicella vaccine, respectively. The seroprevalence of anti-VZV IgG was 54.4% in the children with varicella vaccination, which was significantly higher than those in unvaccinated children (49.2%) (χ² = 8.206, P = 0.004). Among of the vaccinated children, the detection rates of VZV IgG antibody increased with age, with 49.4, 50.9 and 58.9% in 4, 5 and 6-year groups, respectively (Trend χ² = 17.202, P = 0.002). However, there was no difference in anti-VZV IgG detection rates among those unvaccinated children in different age groups (Trend χ² = 8.681, P = 0.070). In addition, 13 boys and 13 girls were positive for anti-VZV IgM, respectively. Among of them, eight children (0.6%) have received varicella vaccination, which was similar to those in unvaccinated children (1.1%). However, only one ORF22 sequence was isolated from an unvaccinated 5-year boy. Compared to the reference VZV sequences, the nucleotide homology was estimated to be 99.7% with genotype J.

Conclusions

Our study indicated that about half of Chinese children aged four to six years have a high risk of VZV infection. It should be helpful for the evaluation on the necessity of varicella immunization in China.

Targeted Genome Sequencing Reveals Varicella-Zoster Virus Open Reading Frame 12 Deletion

The neurotropic herpesvirus varicella-zoster virus (VZV) establishes a lifelong latent infection in humans following primary infection. The low abundance of VZV nucleic acids in human neurons has hindered an understanding of the mechanisms that regulate viral gene transcription during latency. To overcome this critical barrier, we optimized a targeted capture protocol to enrich VZV DNA and cDNA prior to whole-genome/transcriptome sequence analysis. Since the VZV genome is remarkably stable, it was surprising to detect that VZV32, a VZV laboratory strain with no discernible growth defect in tissue culture, contained a 2,158-bp deletion in open reading frame (ORF) 12. Consequently, ORF 12 and 13 protein expression was abolished and Akt phosphorylation was inhibited. The discovery of the ORF 12 deletion, revealed through targeted genome sequencing analysis, points to the need to authenticate the VZV genome when the virus is propagated in tissue culture.IMPORTANCE Viruses isolated from clinical samples often undergo genetic modifications when cultured in the laboratory. Historically, VZV is among the most genetically stable herpesviruses, a notion supported by more than 60 complete genome sequences from multiple isolates and following multiple in vitro passages. However, application of enrichment protocols to targeted genome sequencing revealed the unexpected deletion of a significant portion of VZV ORF 12 following propagation in cultured human fibroblast cells. While the enrichment protocol did not introduce bias in either the virus genome or transcriptome, the findings indicate the need for authentication of VZV by sequencing when the virus is propagated in tissue culture.