Varicella-zoster Virus Open Reading Frame Research Articles

Genetic characterization of varicella-zoster virus in people aged 20 years and under in Yichang City of Hubei Province, 2019-2020

Objective: To analyze the genetic characteristics of varicella-zoster virus (VZV) in people aged 20 years and under in Yichang City of Hubei Province from 2019 to 2020. Methods: Based on the Yichang Health Big Data Platform, we investigated cases 20 and under clinically diagnosed as herpes zoster in three hospitals from March 2019 to September 2020. Collecting vesicle fluid and throat swab samples of the cases and completing questionnaires to obtain basic information. Real-time fluorescent quantitative PCR was used for positive identification of the virus. PCR amplification of VZV's open reading frame (ORF) and sequencing of the products to determine the VZV genotype. Analyze mutations at some specific single nucleotide polymorphism (SNP) sites. Results: Among 46 cases of herpes zoster, the male to female ratio was 1.3∶1 (26∶20) and the age ranged from 7 to 20 years old. Fifteen cases had been vaccinated against varicella, including 13 and 2 cases of 1 and 2 doses, respectively. VZV strains were detected in 34 samples (73.91%), all belonging to Clade 2. Phylogenetic tree analysis of the nucleotide of ORF22 showed, compared with Clade 2 referenced strains, the sequence matching degree of nucleotide for all 34 samples was 99.0% to 100.0%. Conclusion: The main VZV strain causing herpes zoster in people aged 20 years and under in Yichang from 2019 to 2020 was Clade 2.

Varicella-Zoster Virus ORF39 Transmembrane Protein Suppresses Interferon-Beta Promoter Activation by Interacting with STING.

Varicella-Zoster virus (VZV) causes varicella in primary infection of children and zoster during reactivation in adults. Type I interferon (IFN) signaling suppresses VZV growth, and stimulator of interferon genes (STING) plays an important role in anti-VZV responses by regulating type I IFN signaling. VZV-encoded proteins are shown to inhibit STING-mediated activation of the IFN-β promoter. However, the mechanisms by which VZV regulates STING-mediated signaling pathways are largely unknown. In this study, we demonstrate that the transmembrane protein encoded by VZV open reading frame (ORF) 39 suppresses STING-mediated IFN-β production by interacting with STING. In IFN-β promoter reporter assays, ORF39 protein (ORF39p) inhibited STING-mediated activation of the IFN-β promoter. ORF39p interacted with STING in co-transfection assays, and this interaction was comparable to that of STING dimerization. The cytoplasmic N-terminal 73 amino acids region of ORF39P was not necessary for ORF39 binding and suppression of STING-mediated IFN-β activation. ORF39p also formed a complex containing both STING and TBK1. A recombinant VZV expressing HA-tagged ORF39 was produced using bacmid mutagenesis and showed similar growth to its parent virus. During HA-ORF39 virus infection, the expression level of STING was markedly reduced, and HA-ORF39 interacted with STING. Moreover, HA-ORF39 also colocalized with glycoprotein K (encoded by ORF5) and STING at the Golgi during virus infection. Our results demonstrate that the transmembrane protein ORF39p of VZV plays a role in evading the type I IFN responses by suppressing STING-mediated activation of the IFN-β promoter.

Varicella Zoster Virus Impairs Expression of the Nonclassical Major Histocompatibility Complex Class I-Related Gene Protein (MR1).

The antigen presentation molecule MR1 (major histocompatibility complex, class I-related) presents ligands derived from the riboflavin (vitamin B) synthesis pathway, which is not present in mammalian species or viruses, to mucosal-associated invariant T (MAIT) cells. In this study, we demonstrate that varicella zoster virus (VZV) profoundly suppresses MR1 expression. We show that VZV targets the intracellular reservoir of immature MR1 for degradation, while preexisting, ligand-bound cell surface MR1 is protected from such targeting, thereby highlighting an intricate temporal relationship between infection and ligand availability. We also identify VZV open reading frame (ORF) 66 as functioning to suppress MR1 expression when this viral protein is expressed during transient transfection, but this is not apparent during infection with a VZV mutant virus lacking ORF66 expression. This indicates that VZV is likely to encode multiple viral genes that target MR1. Overall, we identify an immunomodulatory function of VZV whereby infection suppresses the MR1 biosynthesis pathway.

398 Identification of Varicella Zoster by Novel Salivary and Esophageal Muscle Tissue Assay in Patients With Achalasia: A Two Center Prospective Study

INTRODUCTION: Achalasia is an esophageal motor disorder characterized by impaired relaxation of the lower esophageal sphincter (LES) but the etiology of this neuronal damage is unknown. Varicella zoster virus (VZV) is an exclusively human neurotrophic alpha herpes virus that becomes latent in ganglionic neurons after initial infection. We tested the hypothesis that reactivation of latent VZV within esophageal enteric neurons initiates an inflammatory cascade that damages the innervation of the smooth muscle of the LES giving rise to achalasia. We aimed to determine whether VZV DNA, transcripts, and proteins are present in tissue and saliva of patients with achalasia and controls. METHODS: Fifteen patients with achalasia (60% Male, average age 60 years and BMI 28 kg/m2) diagnosed with high resolution manometry (7/15 with Type II Achalasia) who underwent surgical myotomy had prospective collection of saliva and LES muscle tissue with IRB approval. Salivary samples were collected by passive drool, DNA was extracted with the DNeasy Blood and Tissue Kit, and VZV DNA was amplified with PCR. All methods examined the presence of transcripts (cDNA) and DNA encoding VZV open reading frames (ORFs) 29, 40, and 67. Immunofluorescence (IMF) was used to demonstrate the neuronal markers, beta-3 tubulin or peripherin simultaneously with the VZV late protein, gE. Antigen retrieval at 100°C in citrate buffer (pH 6.0) was employed. RESULTS: VZV DNA was detected in the saliva in 12/15 (80%) of achalasia cases (Table 1). Transcripts encoding at least one ORF were found in esophageal myotomy samples 12/15 (80%), while DNA was detected in 7/15 (47%). All 15 patients had active VZV infection by salivary VZV DNA and/or VZV transcription in esophageal tissue (Figure 1). Detection of transcripts was more sensitive and specific indicator of tissue infection than DNA. IMF revealed the presence of gE within the cell bodies of enteric neurons (when present) (Figure 2). VZV DNA was not detected in the saliva of 20 controls. CONCLUSION: Direct ex-vivo examination of saliva and tissue from patients with achalasia revealed the presence of active VZV infection of the esophagus. Transcripts encoding VZV gene products, and DNA, support actively replicating virus, not just latent VZV. Immunocytochemistry suggested that enteric neurons were the site of VZV infection. These findings support VZV is a potential esophageal pathogen that reactivates from latency in enteric neurons to give rise to achalasia, which may be a therapeutic target.

Varicella-Zoster Virus ORF63 Protects Human Neuronal and Keratinocyte Cell Lines from Apoptosis and Changes Its Localization upon Apoptosis Induction.

There are many facets of varicella-zoster virus (VZV) pathogenesis that are not fully understood, such as the mechanisms involved in the establishment of lifelong latency, reactivation, and development of serious conditions like postherpetic neuralgia (PHN). Virus-encoded modulation of apoptosis has been suggested to play an important role in these processes. VZV open reading frame 63 (ORF63) has been shown to modulate apoptosis in a cell-type-specific manner, but the impact of ORF63 on cell death pathways has not been examined in isolation in the context of human cells. We sought to elucidate the effect of VZV ORF63 on apoptosis induction in human neuron and keratinocyte cell lines. VZV ORF63 was shown to protect differentiated SH-SY5Y neuronal cells against staurosporine-induced apoptosis. In addition, VZV infection did not induce high levels of apoptosis in the HaCaT human keratinocyte line, highlighting a delay in apoptosis induction. VZV ORF63 was shown to protect HaCaT cells against both staurosporine- and Fas ligand-induced apoptosis. Confocal microscopy was utilized to examine VZV ORF63 localization during apoptosis induction. In VZV infection and ORF63 expression alone, VZV ORF63 became more cytoplasmic, with aggregate formation during apoptosis induction. Taken together, this suggests that VZV ORF63 protects both differentiated SH-SY5Y cells and HaCaT cells from apoptosis induction and may mediate this effect through its localization change during apoptosis. VZV ORF63 is a prominent VZV gene product in both productive and latent infection and thus may play a critical role in VZV pathogenesis by aiding neuron and keratinocyte survival.IMPORTANCE VZV, a human-specific alphaherpesvirus, causes chicken pox during primary infection and establishes lifelong latency in the dorsal root ganglia (DRG). Reactivation of VZV causes shingles, which is often followed by a prolonged pain syndrome called postherpetic neuralgia. It has been suggested that the ability of the virus to modulate cell death pathways is linked to its ability to establish latency and reactivate. The significance of our research lies in investigating the ability of ORF63, a VZV gene product, to inhibit apoptosis in novel cell types crucial for VZV pathogenesis. This will allow an increased understanding of critical enigmatic components of VZV pathogenesis.

A spliced latency-associated VZV transcript maps antisense to the viral transactivator gene 61

Varicella-zoster virus (VZV), an alphaherpesvirus, establishes lifelong latent infection in the neurons of >90% humans worldwide, reactivating in one-third to cause shingles, debilitating pain and stroke. How VZV maintains latency remains unclear. Here, using ultra-deep virus-enriched RNA sequencing of latently infected human trigeminal ganglia (TG), we demonstrate the consistent expression of a spliced VZV mRNA, antisense to VZV open reading frame 61 (ORF61). The spliced VZV latency-associated transcript (VLT) is expressed in human TG neurons and encodes a protein with late kinetics in productively infected cells in vitro and in shingles skin lesions. Whereas multiple alternatively spliced VLT isoforms (VLTly) are expressed during lytic infection, a single unique VLT isoform, which specifically suppresses ORF61 gene expression in co-transfected cells, predominates in latently VZV-infected human TG. The discovery of VLT links VZV with the other better characterized human and animal neurotropic alphaherpesviruses and provides insights into VZV latency.

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.

Zoster Vaccination Increases the Breadth of CD4+ T Cells Responsive to Varicella Zoster Virus.

The live, attenuated varicella vaccine strain (vOka) is the only licensed therapeutic vaccine. Boost of varicella zoster virus (VZV)-specific cellular immunity is a likely mechanism of action. We examined memory CD4(+) T-cell responses to each VZV protein at baseline and after zoster vaccination. Serial blood samples were collected from 12 subjects vaccinated with Zostavax and immunogenicity confirmed by ex vivo VZV-specific T-cell and antibody assays. CD4(+) T-cell lines enriched for VZV specificity were generated and probed for proliferative responses to every VZV protein and selected peptide sets. Zoster vaccination increased the median magnitude (2.3-fold) and breadth (4.2-fold) of VZV-specific CD4(+) T cells one month post-vaccination. Both measures declined by 6 months. The most prevalent responses at baseline included VZV open reading frames (ORFs) 68, 4, 37, and 63. After vaccination, responses to ORFs 40, 67, 9, 59, 12, 62, and 18 were also prevalent. The immunogenicity of ORF9 and ORF18 were confirmed using peptides, defining a large number of discrete CD4 T-cell epitopes. The breadth and magnitude of the VZV-specific CD4(+) T-cell response increase after zoster vaccination. In addition to glycoprotein E (ORF68), we identified antigenic ORFs that may be useful components of subunit vaccines.

A Varicella Outbreak in Diffuse Large B-Cell Lymphoma Patients Receiving Rituximab-Containing Chemotherapy

Background: Varicella, characterized by a vesicular rash, occurs primarily in young children. Although older individuals can also be affected or vaccinated, outbreaks among adults are rare. We experienced sequential four cases of varicella after an index herpes zoster case in hematological wards.Methods: All varicella cases were confirmed varicella zoster virus (VZV) infection by PCR. We analyzed presence of anti-VZV IgG and IgM antibodies at the first hospital admission (cryopreserved serum) and the onset of VZV infection by enzyme immunoassay. To identify VZV-positive specimens and to differentiate these strains from the Oka vaccine virus, PCR designed to target the initial part of VZV open reading frame (ORF) 62 was performed on PBMCs or vesicular swabs. Furthermore, we investigated the incidence of localized zoster and generalized zoster/ varicella in rituximab administered patients. Between January 2010 and December 2013 (48 months), we collected data including the number ofrituximab administered patients, rituximab administration, localized zoster patients, and generalized zoster/varicella patients.Findings: All varicella cases occured in diffuse large B-cell lymphoma patients receiving rituximab-containing chemotherapy (Table 1). On the other hand, only three of the 18 non-varicella patients in the same room were receiving rituximab-containing chemotherapy (P= 0.005, Table 2). Furthermore, all varicella patients had anti-VZV IgG antibody at the first hospital admission (Table 1). Sequencing the first part of ORF 62 in these cases showed the identical sequences and could be distinguished from the Oka vaccine virus, Oka parental virus and Dumas strain. During the 48 months, there were 340 patients who received rituximab. The total number of rituximab administrations was 2086. There were 29 patients with localized zoster (8.5%), and 5 patients with generalized zoster/varicella (1.4%). Four of these patients constituted the cluster reported here. The incidence of generalized zoster/ varicella for 2 months in this case was significantly higher than another 46 months (p<0.001).Conclusions: Even in the presence of neutralizing antibodies to the virus, lymphoma patients treated with rituximab-containing chemotherapy can possibly become re-infected with varicella. These findings suggest that zoster patients should be strictly isolated in hematology and oncology ward, and prophylactic acyclovir should be considered for such patients when exposed to zoster/varicella.Abstract 5439. Table 1Patient characteristicsCaseAgeWardTreatment and onsetDisease typeOnset WBC (x109/L)Onset Lymphocyte (x109/L )Onset serum VZV copy (Copies/mL)preserved IgG (EIA)Onset IgM (EIA)Onset IgG (EIA)Duration of ACV (Days)Complication175A2ndrelapse #1 R-EPOCH Day30Zoster3.60.65NDNDNDND8None250APrimary #8 R-CyclOBEAP Day1varicella1.70.021.0×1067.5<0.80512None381Bprimary #3 R-CHOP Day14varicella5.00.031.7 × 1075.8<0.80<2.044* Hepatitis DIC463Aprimary #3 R-CyclOBEAP Day8varicella11.80.352.7 × 10417.8<0.8013.55None568B2ndrelapse After #4 R-DeVIC +Rx24Gyvaricella2.20.292.6 × 1032.8<0.802.47NoneR-EPOCH (rituximab, etoposide, prednisolone, vincristine cyclophosphamide and doxorubicin); R-CyclOBEAP (rituximab, cyclophosphamide, vincristine, etoposide, bleomycin, doxorubicin and prednisolone); R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisolone); R-DeVIC (dexamethasone, etoposide, ifosfamide and carboplatin); Rx, radiotherapy: ND, not done: ACV, acyclovir: DIC, disseminated intravenous coagulation; * treatment dose.Table 2Patients and control cohort characteristics.Varicella (N = 4)Without varicella (N = 18)PAge(median/range)66/50–6868/37–820.966Male gender418-History of chemotherapy (%)4 (100)8 (44)0.096Rituximab administered (%)4 (100)3 (17)0.005WBCx109/L (median)3.63.30.898Lymphocytex109/L (median/)0.160.950.068Albuming/dL (median)3.63.90.392Creatininemg/dL (median)0.710.720.831ASTIU/L (median)18220.670These data were at onset or exposure. WBC: white blood cell, AST: aspartate aminotransferase, T-Bil: total bilirubin. DisclosuresNo relevant conflicts of interest to declare.

The Varicella-Zoster Virus Portal Protein Is Essential for Cleavage and Packaging of Viral DNA

The varicella-zoster virus (VZV) open reading frame 54 (ORF54) gene encodes an 87-kDa monomer that oligomerizes to form the VZV portal protein, pORF54. pORF54 was hypothesized to perform a function similar to that of a previously described herpes simplex virus 1 (HSV-1) homolog, pUL6. pUL6 and the associated viral terminase are required for processing of concatemeric viral DNA and packaging of individual viral genomes into preformed capsids. In this report, we describe two VZV bacterial artificial chromosome (BAC) constructs with ORF54 gene deletions, Δ54L (full ORF deletion) and Δ54S (partial internal deletion). The full deletion of ORF54 likely disrupted essential adjacent genes (ORF53 and ORF55) and therefore could not be complemented on an ORF54-expressing cell line (ARPE54). In contrast, Δ54S was successfully propagated in ARPE54 cells but failed to replicate in parental, noncomplementing ARPE19 cells. Transmission electron microscopy confirmed the presence of only empty VZV capsids in Δ54S-infected ARPE19 cell nuclei. Similar to the HSV-1 genome, the VZV genome is composed of a unique long region (UL) and a unique short region (US) flanked by inverted repeats. DNA from cells infected with parental VZV (VZVLUC strain) contained the predicted UL and US termini, whereas cells infected with Δ54S contained neither. This result demonstrates that Δ54S is not able to process and package viral DNA, thus making pORF54 an excellent chemotherapeutic target. In addition, the utility of BAC constructs Δ54L and Δ54S as tools for the isolation of site-directed ORF54 mutants was demonstrated by recombineering single-nucleotide changes within ORF54 that conferred resistance to VZV-specific portal protein inhibitors. Importance: Antivirals with novel mechanisms of action would provide additional therapeutic options to treat human herpesvirus infections. Proteins involved in the herpesviral DNA encapsidation process have become promising antiviral targets. Previously, we described a series of N-α-methylbenzyl-N'-aryl thiourea analogs that target the VZV portal protein (pORF54) and prevent viral replication in vitro. To better understand the mechanism of action of these compounds, it is important to define the structural and functional characteristics of the VZV portal protein. In contrast to HSV, no VZV mutants have been described for any of the seven essential DNA encapsidation genes. The VZV ORF54 deletion mutant described in this study represents the first VZV encapsidation mutant reported to date. We demonstrate that the deletion mutant can serve as a platform for the isolation of portal mutants via recombineering and provide a strategy for more in-depth studies of VZV portal structure and function.

Varicella-Zoster Virus Open Reading Frame 48 Encodes an Active Nuclease

Based on a DNA sequence and relative genomic position similar to those other herpesviruses, varicella-zoster virus (VZV) open reading frame 48 (ORF48) is predicted to encode an alkaline nuclease. Here we report the cloning, expression, purification, and characterization of recombinant VZV ORF48 protein and a VZV ORF48 point mutation (T172P). Protein encoded by wild-type ORF48, but not mutant protein, displayed both endo- and exonuclease activity, identifying ORF48 as a potential therapeutic target in VZV disease since efficient viral replication requires viral nuclease activity.

VZV ischemic optic neuropathy and subclinical temporal artery infection without rash

A 75-year-old woman developed periorbital pain and blurred vision OS. Visual acuity (VA) was 20/40 OD, 20/400 OS with mild left relative afferent pupillary defect (APD). Left optic nerve was swollen and hyperemic with peripapillary flame hemorrhages (figure, A). Erythrocyte sedimentation rate (ESR) was 124 mm/h. She was treated with IV methylprednisolone, 250 mg every 6 h. On day 3, headache and vision improved. ESR was 98 mm/h and C-reactive protein was 1.40 mg/L. Rheumatoid factor, antinuclear antibodies, and antineutrophil cytoplasmic antibodies titers were negative. On day 4, left temporal artery biopsy revealed thickened intima and intact internal elastic lamina (figure, B) but no medial necrosis characteristic of giant cell arteritis (GCA). Sections of the temporal artery were deparaffinized and incubated with 10% normal sheep serum (NSS) in phosphate-buffered saline (PBS) for 1 hour at room temperature, rinsed 3 times in PBS, and incubated overnight at 4°C with polyclonal antibodies raised against the varicella-zoster virus (VZV) open reading frame 63 protein (1:1,000 dilution) or with normal rabbit serum (1:1,000 dilution). The next day, sections were washed 3 times in PBS, incubated with a 1:300 dilution of biotinylated goat antirabbit immunoglobulin G (IgG) in PBS containing 5% NSS, washed 3 times in PBS, incubated for 1 hour at room temperature with alkaline phosphatase–conjugated streptavidin (1:100 dilution), and washed 3 times with PBS. The color reaction was developed for 5–30 minutes with fresh fuchsin substrate system. Levamisole was added to the color reaction to block endogenous phosphatase. Uninfected and VZV-infected human fibroblast lung cells were used as controls (not shown). Steroids were changed to oral prednisone 60 mg daily. On day 7, brain MRI with gadolinium was negative. On day 9, pain and vision worsened. On day 11, orbital CT and head CT angiography were negative. On day 15, VA was 20/400 OS with relative left APD. On day 17, OS became blind without direct pupillary light reaction; fundus was obscured by vitreous hemorrhage. CSF contained 8 leukocytes/mm3, protein 72 mg/L, and glucose 54 mg/L. CSF cultures for bacteria, fungi, acid-fast bacilli, and cytology were negative. Because asymptomatic temporal artery biopsy was GCA-negative, VZV ischemic optic neuropathy (ION) was considered, and she was treated with IV acyclovir, 10 mg/kg every 8 hours for 7 days. On day 31, CSF contained anti-VZV IgG but not anti-herpes simplex virus IgG antibody, and serum-to-CSF ratio of anti-VZV IgG was reduced (14) compared to ratios for total IgG (121) and albumin (81). Immunohistochemistry and pathology revealed VZV antigen and neutrophils in the original left temporal artery specimen (figure, C). On day 31, she was treated with oral valacyclovir, 1 gram TID for 6 weeks; prednisone was reduced to 20 mg daily and tapered 5 mg/week. Six weeks later, pain resolved, and VA improved to finger counting. Left optic nerve was pale with clear margins and resolution of hemorrhage.

Serologic Analysis of the IgG Antibody Response in Children With Varicella Zoster Virus Wild-type Infection and Vaccination

In contrast to varicella zoster virus (VZV) primary infection, VZV vaccination does not seem to provide lifelong immunity against varicella. Because more people get vaccinated every year, the development of sensitive serological test systems for the detection of protective anti-VZV IgG will become important in the future. We have previously developed a novel VZV line assay based on 5 different recombinant VZV antigens. In this study, we compared this novel assay with a commercially available glycoprotein enzyme immunoassay (RIDASCREEN VZV IgG) in detecting anti-VZV IgG of children with previous varicella infection and VZV vaccination. One hundred twenty-five children were included in this study, 72 with a history of varicella infection and 53 with VZV vaccination. Both assays detected anti-VZV IgG antibodies in both study groups with similar sensitivities. The VZV line assay revealed striking differences in the anti-VZV IgG composition against the VZV open reading frames, 4, 14 and 49, between both study groups, indicating that wild-type varicella infection causes a more diverse immune response against VZV than does vaccination. The exploitation of these results enabled the discrimination of both study groups with a sensitivity of 0.93 and a specificity of 0.83, indicating that the serologic differentiation of children with previous varicella infection and VZV vaccination might be possible. The VZV line assay enables the detection of anti-VZV IgG with sensitivities comparable to glycoprotein enzyme immunoassays and might be suitable for the serologic discrimination between children with a history of varicella infection and VZV vaccination.

Novel Genetic Variation Identified at Fixed Loci in ORF62 of the Oka Varicella Vaccine and in a Case of Vaccine-Associated Herpes Zoster

The live attenuated Oka varicella vaccine (vOka), derived from clade 2 wild-type (wt) virus pOka, is used for routine childhood immunization in several countries, including the United States, which has caused dramatic declines in the incidence of varicella. vOka can cause varicella, establish latency, and reactivate to cause herpes zoster (HZ). Three loci in varicella-zoster virus (VZV) open reading frame 62 (ORF62) (106262, 107252, and 108111) are used to distinguish vOka from wt VZV. A fourth position (105705) is also fixed for the vOka allele in nearly all vaccine batches. These 4 positions and two vOka mutations (106710 and 107599) reportedly absent from Varivax were analyzed on Varivax-derived ORF62 TOPO TA clones. The wt allele was detected at positions 105705 and 107252 on 3% and 2% of clones, respectively, but was absent at positions 106262 and 108111. Position 106710 was fixed for the wt allele, whereas the vOka allele was present on 18.4% of clones at position 107599. We also evaluated the 4 vOka markers in an isolate obtained from a case of vaccine-caused HZ. The isolate carried the vOka allele at positions 105705, 106262, and 108111. However, at position 107252, the wt allele was present. Thus, all of the ORF62 vOka markers previously regarded as fixed occur as the wt allele in a small percentage of vOka strains. Characterization of all four vOka markers in ORF62 and of the clade 2 subtype marker in ORF38 is now necessary to confirm vOka adverse events.

Varicella-Zoster Virus Inhibition of the NF-κB Pathway during Infection of Human Dendritic Cells: Role for Open Reading Frame 61 as a Modulator of NF-κB Activity

Dendritic cells (DC) are antigen-presenting cells essential for initiating primary immune responses and therefore an ideal target for viral immune evasion. Varicella-zoster virus (VZV) can productively infect immature human DCs and impair their function as immune effectors by inhibiting their maturation, as evidenced by the expression modulation of functionally important cell surface immune molecules CD80, CD86, CD83, and major histocompatibility complex I. The NF-κB pathway largely regulates the expression of these immune molecules, and therefore we sought to determine whether VZV infection of DCs modulates the NF-κB pathway. Nuclear localization of NF-κB p50 and p65 indicates pathway activation; however, immunofluorescence studies revealed cytoplasmic retention of these NF-κB subunits in VZV-infected DCs. Western blotting revealed phosphorylation of the inhibitor of κBα (IκBα) in VZV-infected DCs, indicating that the pathway is active at this point. We conclude that VZV infection of DC inhibits the NF-κB pathway following protein phosphorylation but before the translocation of NF-κB subunits into the nucleus. An NF-κB reporter assay identified VZV open reading frame 61 (ORF61) as an inhibitor of tumor necrosis factor alpha-induced NF-κB reporter activity. Mutational analysis of ORF61 identified the E3 ubiquitin ligase domain as a region required for NF-κB pathway inhibition. In summary, we provide evidence that VZV inhibits the NF-κB signaling pathway in human DCs and that the E3 ubiquitin ligase domain of ORF61 is required to modulate this pathway. Thus, this work identifies a mechanism by which VZV modulates host immune function.

A Sequence within the Varicella-Zoster Virus (VZV) OriS Is a Negative Regulator of DNA Replication and Is Bound by a Protein Complex Containing the VZV ORF29 Protein

The architecture of the varicella-zoster virus (VZV) origin of DNA replication (OriS) differs significantly from that of the herpes simplex virus (HSV) DNA replication origin. Novel aspects of the VZV OriS include a GA-rich region, three binding sites for the VZV origin-binding protein (OBP) all on the same strand and oriented in the same direction, and a partial OBP binding site of unknown function. We have designated this partial binding site Box D and have investigated the role it plays in DNA replication and flanking gene expression. This has been done with a model system using a replication-competent plasmid containing OriS and a replication- and transcription-competent dual-luciferase reporter plasmid containing both the OriS and the intergenic region between VZV open reading frames (ORFs) 62 and 63. We have found that (i) Box D is a negative regulator of DNA replication independent of flanking gene expression, (ii) the mutation of Box D results in a decrease in flanking gene expression, thus a sequence within the VZV OriS affects transcription, which is in contrast to results reported for HSV-1, (iii) there is a specific Box D complex formed with infected cell extracts in electrophoretic mobility shift assay experiments, (iv) supershift assays show that this complex contains the VZV ORF29 single-strand DNA-binding protein, and (v) the formation of this complex is dependent on the presence of CGC motifs in Box D and its downstream flanking region. These findings show that the VZV ORF29 protein, while required for DNA replication, also plays a novel role in the suppression of that process.

Probing of the nuclear import and export signals and subcellular transport mechanism of varicella-zoster virus tegument protein open reading frame 10

Varicella-zoster virus open reading frame 10 (ORF10), a tegument protein present in the virion, is a member of the alphaherpesvirus UL48 gene family that shares considerable amino acid sequence homology with the UL48 prototype, herpes simplex virus type 1 VP16. VP16 serves multiple functions, including transcriptional activation of viral immediate-early genes. Furthermore, VP16 has been shown to be involved in some aspects of virus assembly and/or maturation. However, little is known concerning the function of ORF10. Here, we found that transient expression of ORF10 fused to enhanced yellow fluorescent protein (EYFP) in COS-7 cells showed the predominantly nuclear localization in the absence of other viral proteins. By constructing a series of ORF10 variants fused to EYFP, a bona fide bipartite nuclear localization signal of ORF10 was, for the first time, determined and mapped to amino acids (aa) 302-347. Additionally, the nuclear export signal (NES) was identified and found to be in a leucine-rich region at aa 226-236. Finally, ORF10 was demonstrated to be targeted to the cytoplasm through the functional NES by chromosomal region maintenance 1-dependent pathway, and to the nucleus via Ran and importin β1-dependent pathway that does not require importin α5.

Synthesis and decay of varicella zoster virus transcripts

Varicella zoster virus (VZV) is highly cell-associated. At least 68 VZV open reading frames (ORFs) are transcribed in varying amounts that increase as infection progresses. Using reverse transcriptase PCR, quantification of total and newly synthesized mRNA showed that ongoing VZV DNA replication is required for continued accumulation of VZV ORF 63, 9, and 40 transcripts. Analysis of stability of 4-thiouridine-labeled transcripts of nine VZV ORFs revealed a similar half-life for all VZV ORFs tested. Thus, difference in mRNA synthesis, and not mRNA decay, is the major factor contributing to the difference in the relative abundance of VZV transcripts in infected cells.

Varicella-Zoster Virus Transcriptome in Latently Infected Human Ganglia

We recently developed a novel multiplex reverse transcription (RT)-PCR assay that allows rapid and sensitive detection of transcripts corresponding to all 68 unique varicella-zoster virus (VZV) open reading frames (ORFs) in only five amplification reactions (M. A. Nagel, D. Gilden, T. Shade, B. Gao, and R. J. Cohrs, J. Virol. Methods 157:62-68, 2009). Herein, we applied multiplex RT-PCR analysis to mRNA extracted from 26 trigeminal ganglia latently infected with VZV and one control trigeminal ganglion negative for VZV DNA that were removed from 14 men and women, 16 to 84 years of age, within 24 h after death. Analysis identified VZV transcripts mapping to VZV ORFs 29, 62, and 63, previously detected and sequence verified; VZV ORFs 4 and 40, previously detected by in situ hybridization; and VZV ORFs 11, 41, 43, 57, and 68, not previously detected. VZV ORF 63 transcripts were the most prevalent. Comparison of the 10 VZV ORFs transcribed during latency to their herpes simplex virus type 1 homologues reveals that the latently transcribed VZV genes encode immediate-early, early, and late transcripts.

Characterization of the nuclear import and export signals, and subcellular transport mechanism of varicella-zoster virus ORF9

Varicella-zoster virus (VZV) open reading frame 9 (ORF9) mRNA is one of the most abundantly expressed messages during VZV infection. However, little is known concerning the function of ORF9 protein. Here, we found that transient expression of ORF9 fused to enhanced yellow fluorescent protein (EYFP) in COS-7 cells showed a predominantly cytoplasmic localization in the absence of other viral proteins. By constructing a series of ORF9 variants fused to EYFP, a bona fide bipartite nuclear localization signal of ORF9 was, for the first time, determined and mapped to aa 16-32 (RRKTTPSYSGQYRTARR). Additionally, the nuclear export signal (NES) was identified and found to be in a leucine-rich region at aa 103-117 (LRHELVEDAVYENPL). Finally, ORF9 was demonstrated to be targeted to the cytoplasm through the functional NES by Ran and the chromosomal region maintenance 1-dependent pathway, and to the nucleus via an importin β-dependent pathway that does not require importin α5.