Improved identification and differentiation of varicella-zoster virus (VZV) wild-type strains and an attenuated varicella vaccine strain using a VZV open reading frame 62-based PCR

Nanopore sequencing in distinguishing between wild-type and vaccine strains of Varicella-Zoster virus

BACKGROUND

The introduction of varicella vaccines into routine pediatric immunization programs has led to a considerable reduction in varicella incidence. However, there have been reports of varicella, herpes zoster, and meningitis caused by the vaccine strain of varicella-zoster virus (VZV), raising concerns. Establishing the relationship between the wild-type and vaccine strains in VZV infections among previously vaccinated individuals is crucial. Differences in the single nucleotide polymorphisms (SNPs) among vaccine strains can be utilized to identify the strain. In this study, we employed nanopore sequencing to identify VZV strains and analyzed clinical samples.

METHODS

We retrospectively examined vesicle and cerebrospinal fluid samples from patients with VZV infections. One sample each of the wild-type and vaccine strains, previously identified using allelic discrimination real-time PCR and direct sequencing, served as controls. Ten samples with undetermined VZV strains were included. After DNA extraction, a long PCR targeting the VZV ORF62 region was executed. Nanopore sequencing identified SNPs, allowing discrimination between the vaccine and wild-type strains.

RESULTS

Nanopore sequencing confirmed SNPs at previously reported sites (105,705, 106,262, 107,136, and 107,252), aiding in distinguishing between wild-type and vaccine strains. Among the ten unknown samples, nine were characterized as wild strains and one as a vaccine strain. Even in samples with low VZV DNA levels, nanopore sequencing was effective in strain identification.

CONCLUSION

This study validates that nanopore sequencing is a reliable method for differentiating between the wild-type and vaccine strains of VZV. Its ability to produce long-read sequences is remarkable, allowing simultaneous confirmation of known SNPs and the detection of new mutations. Nanopore sequencing can serve as a valuable tool for the swift and precise identification of wild-type and vaccine strains and has potential applications in future VZV surveillance.

A booster administration of the OKA/SK strain causes fatal disseminated varicella in an immunocompetent child

Live varicella vaccines are known to provide robust immunity against varicella zoster virus (VZV) infections. However, problems with viral attenuation have led to pathogenic VZV vaccine strains causing varicella-like rash and herpes zoster in immunocompetent children after immunization. We report the first fatal case of VZV infection caused by OKA/SK strain contained in the vaccine administrated as a booster shot in an immunocompetent child, which has been independently developed from any currently available varicella vaccines that are OKA strain or MAV/06 strain based. The patient died due to sudden pulmonary alveolar hemorrhage as a secondary complication of VZV pneumonitis. Sequencing of the four SNPs unique to the OKA/SK strain (SNP loci 14 035T; 32 626C; 58 777G; 70 319G) enabled discrimination of the strain responsible for the disseminated infection. OKA/SK strain does not have any SNPs in ORF62 postulated to be responsible for the attenuation of varicella vaccines which have been safely and effectively used world-wide or locally, and exclusively enriches a virulent factor in ORF31 identified in parental OKA strain, thus possibly resulting in disseminated VZV infection leading to mortality. Therefore, actions need to be taken to prevent vaccine related morbidity and mortality in children.

First detection of Varicella Zoster Virus clade 9 cases in India during mpox surveillance

BACKGROUND

The multi-country mpox outbreak across the globe has led to the systematic surveillance of mpox cases in India. During the surveillance of mpox, we encountered cases of Varicella Zoster Virus (VZV) in suspected mpox cases amongst children & adults. This study focused on the genomic characterization of VZV in India.

METHODS

A total of 331 mpox suspected cases were tested for VZV through real-time PCR, and the positive samples were subjected to next-generation sequencing to retrieve the whole genome of VZV using CLC genomics software. Phylogenetic analysis has been done in MEGA 11.0 software to identify circulating clades.

RESULT

Of the 331 suspected cases, 28 cases with vesicular rashes were found to be positive for VZV. The maximum genome could be retrieved from the clinical specimens of 16 cases with coverage greater than 98% when mapped with reference strain Dumas (NC 001348). The phylogenetic analyses of these sequences determined the circulation of clades 1, 5, and 9 in India. Further, the sequence analysis demonstrated non-synonymous single nucleotide polymorphism (SNPs) among specific ORF of VZV including ORF 14, ORF 22, ORF 36, ORF 37 and ORF 51. Although clade 1 and 5 has been reported earlier, the circulation of clade 9 of VZV has been determined for the first time in India.

CONCLUSION

Although the circulation of different clades of VZV was reported from India, the presence of clade 9 was detected for the first time during the mpox surveillance.

Diagnostic and Immunologic Testing for Varicella in the Era of High-Impact Varicella Vaccination: An Evolving Problem

The clinical presentation of varicella in unvaccinated persons, with skin vesicles and scabs, has facilitated the use of rapid diagnostic methods for confirming disease. Polymerase chain reaction (PCR) assays are the diagnostic method of choice. The sharp decline in unmodified cases of varicella due to the US varicella vaccination program has led to fewer healthcare providers being familiar with varicella presentation and an increased reliance on laboratory diagnosis to confirm suspected cases. The mild, atypical presentation of the disease in vaccinated persons (fewer skin lesions, mostly maculopapular) has made it more challenging for providers to recognize and also to collect samples to detect the virus. Nonetheless, PCR is highly sensitive and specific in confirming modified disease if adequate samples are provided. While a positive PCR result is confirmatory, interpreting a negative result can prove to be more challenging in determining whether suspected varicella is falsely negative or attributable to other causes. Enhanced education of healthcare providers is critical for adequate specimen collection from modified varicella cases. In addition, more sensitive commercial serologic assays are needed in the United States for varicella immunity testing in the vaccine era.

A Case of Herpes Zoster Due to Varicella-Zoster Virus Vaccines in a 14-Month-old Girl

Herpes zoster (HZ) due to Varicella-Zoster virus (VZV) vaccines is rare and the accurate incidence remains unknown. We report a case of HZ due to VZV vaccines presented in an immunocompetent 14-month-old girl 62 days after vaccination which is the youngest case from the first dose of the VZV vaccine in immunocompetent children.

Development of a skin- and neuro-attenuated live vaccine for varicella

Varicella caused by the primary infection of varicella-zoster virus (VZV) exerts a considerable disease burden globally. Current varicella vaccines consisting of the live-attenuated vOka strain of VZV are generally safe and effective. However, vOka retains full neurovirulence and can establish latency and reactivate to cause herpes zoster in vaccine recipients, raising safety concerns. Here, we rationally design a live-attenuated varicella vaccine candidate, v7D. This virus replicates like wild-type virus in MRC-5 fibroblasts and human PBMCs, the carrier for VZV dissemination, but is severely impaired for infection of human skin and neuronal cells. Meanwhile, v7D shows immunogenicity comparable to vOka both in vitro and in multiple small animal species. Finally, v7D is proven well-tolerated and immunogenic in nonhuman primates. Our preclinical data suggest that v7D is a promising candidate as a safer live varicella vaccine with reduced risk of vaccine-related complications, and could inform the design of other herpes virus vaccines.

Current varicella vaccines retain neurovirulence and can establish latency and reactivate. Here, the authors present preclinical results of a rationally-designed, skin- and neuro-attenuated varicella vaccine candidate, v7D, showing its attenuation in human skin and neuronal cells and its immunogenicity in small animal models and nonhuman primates

Increased risk of rhinovirus infection in children during the coronavirus disease-19 pandemic

Background

Coronavirus disease (COVID‐19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), was first detected in Japan in January 2020 and has spread throughout the country. Previous studies have reported that viral interference among influenza virus, rhinovirus, and other respiratory viruses can affect viral infections at the host and population level.

Methods

To investigate the impact of COVID‐19 on influenza and other respiratory virus infections, we analyzed clinical specimens collected from 2244 patients in Japan with respiratory diseases between January 2018 and September 2020.

Results

The frequency of influenza and other respiratory viruses (coxsackievirus A and B; echovirus; enterovirus; human coronavirus 229E, HKU1, NL63, and OC43; human metapneumovirus; human parainfluenza virus 1, 2, 3, and 4; human parechovirus; human respiratory syncytial virus; human adenovirus; human bocavirus; human parvovirus B19; herpes simplex virus type 1; and varicella‐zoster virus) was appreciably reduced among all patients during the COVID‐19 pandemic except for that of rhinovirus in children younger than 10 years, which was appreciably increased. COVID‐19 has not spread among this age group, suggesting an increased risk of rhinovirus infection in children.

Conclusions

Rhinovirus infections should be continuously monitored to understand their increased risk during the COVID‐19 pandemic and viral interference with SARS‐CoV‐2.

Clinico-epidemiological investigation on Varicella Zoster Virus indicates multiple clade circulation in Maharashtra state, India

BACKGROUND

Varicella Zoster Virus (VZV) is consistently in circulation and shows an increase in disease burden during the spring season. Due to a wide range of clinical presentation from a vesicular rash to bleeding or neurological complications, it makes the clinical diagnosis difficult. The present study aims to understand whether the same strain of virus is responsible for the increase in the seasonal outbreaks occurring in different parts of the country with reference to the samples from Maharashtra, Rajasthan and Gujarat states of India.

MATERIALS AND METHODS

This study reports the clinico-epidemiological and laboratory findings of suspected Varicella cases. To understand the circulating clade few representative real-time Polymerase Chain Reaction (PCR) positive were analyzed by conventional PCR and partial Open Reading Frame (ORF) 22, partial ORF 38 and partial ORF 54 were sequenced to identify single nucleotide polymorphisms responsible for clade determination. Further partial glycoprotein B gene was sequenced, and a phylogenetic tree was generated.

RESULTS

A total of 50 cases from Maharashtra (Mumbai district) and referred clinical samples of Rajasthan (Barmer district; n = 12) and Gujarat States (Gandhi Nagar, Surat districts; n = 17) were tested for the presence of VZV. Vesicular rash with fever was a common clinical presentation with 82% cases having contact history with VZV positive cases, suggesting higher secondary attack rate. The vesicular fluid of all 50 cases from Mumbai revealed the presence of VZV by real-time PCR. Urine, serum and throat swab samples showed positivity by real-time PCR. Healthcare provider's samples from Rajasthan showed 36.4% [4/11] positivity. Clinical samples from Gujarat had positivity of 41.2% [7/17].

CONCLUSIONS

This study analyses the clade based circulation of VZV in three states in India and suggests different clades circulating in Maharashtra state. Health education amongst the general population is suggested to reduce the secondary cases by early diagnosis, effective isolation policies and vaccination to reduce the burden of disease.

Single-dose varicella vaccine effectiveness in Brazil: A case-control study

BACKGROUND

Varicella vaccine was introduced into the Brazilian Immunization Program in October 2013, as a single-dose schedule administered at 15 months of age. Its effectiveness had not yet been assessed in the country.

METHODS

A matched case-control study was carried out in São Paulo and Goiânia (Southeast and Midwest regions, respectively), Brazil. Suspected cases, were identified through a prospective surveillance established in the study sites. All cases had specimens from skin lesion collected for molecular laboratory testing. Cases were confirmed by either clinical or PCR of skin lesions and classified as mild, moderate, and severe disease. Two neighborhood controls were selected for each case. Cases and controls were aged 15-32 months and interviewed at home. Evidence of prior vaccination was obtained from vaccination cards. Univariate and multivariate logistic regression models were used, and odds ratio and its respective 95% confidence intervals were estimated. Vaccine effectiveness was estimated by comparing de odds of having received varicella vaccine among cases and controls.

RESULTS

A total of 168 cases and 301 controls were enrolled. Moderate and severe illness, was found in 33.3% and 9.9% of the cases. Effectiveness of a single dose varicella vaccine was 86% (95%CI 72-92%) against disease of any severity and 93% (95%CI 82-97%) against moderate and severe disease. Out of 168 cases, 81.8% had positive PCR results for wild-type strains, and 22.0% were breakthrough varicella cases. Breakthrough cases were milder compared to non-breakthrough cases (p < .001).

CONCLUSIONS

Effectiveness of single dose varicella vaccine in Brazil is comparable to that in other countries where breakthrough varicella cases have also been found to occur. The goal of the varicella vaccination program, along with disease burden and affordability should be taken into consideration when considering the adoption of a second dose of varicella vaccine into national immunization programs.

Characterization and phylogenetic analysis of Varicella-zoster virus strains isolated from Korean patients

Varicella-zoster virus (VZV) is a causative agent of chickenpox in primary infection and shingles after its reactivation from latency. Complete or almost-complete genomic DNA sequences for various VZV strains have been reported. Recently, clinical VZV strains were isolated from Korean patients whose genome was sequenced using high-throughput sequencing technology. In this study, we analyzed single nucleotide polymorphism (SNP) of VZV strains to genetically characterize Korean clinical isolates. Phylogenetic analyses revealed that three Korean strains, YC01, YC02, and YC03, were linked to clade 2. Comprehensive SNP analysis identified 86 sites specific for the 5 VZV clades. VZV strains isolated from Korea did not form a phylogenetic cluster. Rather, YC02 and YC03 clustered strongly with Chinese strain 84-7 within clade 2, more specifically cluster 2a. Signature sequences for the cluster 2a were identified and found to play an important role in the separation of cluster 2a strains from other clade 2 strains, as shown in substitution studies. Further genetic analysis with additional strains isolated from Japan, China, and other Asian countries would provide a novel insight into the significance of two distinct subclades within clade 2.

Differentiation between wild-type and vaccines strains of varicella zoster virus (VZV) based on four single nucleotide polymorphisms

Varicella-zoster virus (VZV) infection (chickenpox) results in latency and subsequent reactivation manifests as shingles. Effective attenuated vaccines (vOka) are available for prevention of both illnesses. In this study, an amplicon-based sequencing method capable of differentiating between VZV wild-type (wt) strains and vOka vaccine is described. A total of 44 vesicular fluid specimens collected from 43 patients (16 from China and 27 from the UK) with either chickenpox or shingles were investigated, of which 10 had received previous vaccination. Four sets of polymerase chain reactions were set up simultaneously with primers amplifying regions encompassing four single nucleotide polymorphisms (SNPs), '69349-106262-107252-108111'. Nucleotide sequences were generated by Sanger sequencing. All samples except one had a wt SNP profile of 'A-T-T-T'. The sample collected from a patient who received vaccine 7-10 days ago, along with VZV vaccine preparations, Zostavax and Baike-varicella gave a SNP profile 'G-C-C-C'. The results show that this method can distinguish vaccine-derived virus from wt viruses from main four clades, (clades 1-4) and should be of utility worldwide.

Herpes Simplex Virus and Varicella-Zoster Virus

The most common specimens from immunocompromised patients that are analyzed for detection of herpes simplex virus (HSV) or varicella-zoster virus (VZV) are from skin lesions. Many types of assays are applicable to these samples, but some, such as virus isolation and direct fluorescent antibody testing, are useful only in the early phases of the lesions. In contrast, nucleic acid (NA) detection methods, which generally have superior sensitivity and specificity, can be applied to skin lesions at any stage of progression. NA methods are also the best choice, and sometimes the only choice, for detecting HSV or VZV in blood, cerebrospinal fluid, aqueous or vitreous humor, and from mucosal surfaces. NA methods provide the best performance when reliability and speed (within 24 hours) are considered together. They readily distinguish the type of HSV detected or the source of VZV detected (wild type or vaccine strain). Nucleic acid detection methods are constantly being improved with respect to speed and ease of performance. Broader applications are under study, such as the use of quantitative results of viral load for prognosis and to assess the efficacy of antiviral therapy.

Genetic analysis of varicella-zoster virus in the aqueous humor in uveitis with severe hyphema

BACKGROUND

Genetic variations have been identified in the genome of varicella-zoster virus (VZV) strains using vesicle fluid, varicella scabs and throat swab samples. We report a rare case of VZV-associated uveitis with severe hyphema, which was immediately diagnosed by polymerase chain reaction (PCR) using the aqueous humor, in which we were able to analyze the VZV genotype for the first time.

CASE PRESENTATION

A 16-year-old Japanese boy was referred to our hospital with a 20-day history of unilateral anterior uveitis and 11-day history of hyphema. At presentation, details of the iris, the iridocorneal angle, and the fundus were not visible due to the severe hyphema. Serum anti-VZV IgG and anti-VZV IgM were elevated, and 1.61 × 10⁹ copies/mL of VZV-DNA were detected by real-time PCR using the aqueous humor. As there were no eruptions on his face or body, we diagnosed zoster sine herpete and started intravenous administration of prednisolone and acyclovir. The hyphema completely disappeared 2 weeks after presentation, while sectorial iris atrophy and mild periphlebitis of the fundus became gradually apparent. Anterior inflammation and periphlebitis gradually improved and VZV-DNA in the aqueous humor was reduced to 1.02 × 10⁶ copies/mL at 4 weeks after presentation. Examination by slit lamp microscope revealed no inflammation after 5 months, and VZV-DNA could no longer be detected in the aqueous humor. Serum anti-VZV IgG and anti-VZV IgM also showed a gradual decrease along with improvement in ocular inflammation. The genetic analysis of multiple open reading frames and the R5 variable repeat region in the VZV genes, using DNA extracted from the aqueous humor at presentation, showed that the isolate was a wild-type clade 2 VZV strain (prevalent in Japan and surrounding countries) with R5A allele and one SNP unique to clade 1 (both are major types in Europe and North America).

CONCLUSIONS

VZV-associated uveitis may develop hyphema that obscures ocular inflammation, thus PCR analysis using the aqueous humor is the key investigation necessary for the diagnosis. The measurement of VZV-DNA copies by real-time PCR would be useful for evaluation of therapeutic effects. We could amplify and analyze VZV genotype using the aqueous humor including a very large number of VZV-DNA copies (1.61 × 10⁹ copies/mL).

Genotype analysis of ORF 62 identifies varicella-zoster virus infections caused by a vaccine strain in children

This study was performed to differentiate vaccine-type strains from wild-type strains and determine the genotype of varicella-zoster virus (VZV) in 51 Korean children. A sequencing analysis of ORF 62 identified two cases of herpes zoster caused by the vaccine-type virus, without a previous history of varicella, 22 months and 5 months after VZV vaccination. The wild-type strain was identified in the remaining children. A genotype analysis of ORF 22 amino acids revealed genotype J in all children except one. Genotype E was identified in an infant with varicella imported from Egypt.

Nationwide distribution of varicella-zoster virus clades in China

Background

In 2010, a universal nomenclature for varicella-zoster virus (VZV) clades was established, which is very useful in the monitoring of viral evolution, recombination, spread and genetic diversity. Currently, information about VZV clades has been disclosed worldwide, however, there are limited data regarding the characterization of circulating VZV clades in China, even where varicella remains widely epidemic.

Methods

From 2008 to 2012, clinical samples with varicella or zoster were collected in General Hospital in eight provinces and analyzed by PCR, restriction endonuclease digestion and sequencing. The viral clades were determined by analysis of five single nucleotide polymorphisms (SNPs) within the 447-bp fragment of open reading frame (ORF) 22, and the restriction fragment length polymorphisms (RFLPs) of ORF 38 (PstI), ORF 54 (BglI) and ORF 62 (SmaI) were evaluated to understand genetic diversity of VZV and determinate varicella vaccine adverse event (VVAE).

Results

Seventy-seven varicella and 11 zoster samples were identified as being positive for VZV. The five SNPs profile showed that the majority of VZV strains belonged to clade 2, but clade 5 and clade 4 strains were also found in Guangdong. The RFLPs analysis of the DNA fragments of ORF 38, 54 and 62 showed that 85 of these samples were characterized as PstI + BglI + SamI-, and the remaining three VZV strains from varicella patients were characterized as PstI-BglI + SamI+ which is the genetic profile of VVAEs.

Conclusions

The study suggested that the predominant clade 2 VZVs had been continually circulating since at least the 1950s in China. Nearly all VZV strains except VVAEs possessed the genetic profile of PstI + BglI + Sam-. However, the other clades were also found to be co-circulating with clade 2, especially in the border regions. These results highlighted the need for the constant and broad use of virologic surveillance to provide an important genetic baseline for varicella control and vaccination programs in China.

Varicella Vaccine Effectiveness in Preventing Community Transmission in the 2-Dose Era

OBJECTIVES

We examined overall and incremental effectiveness of 2-dose varicella vaccination in preventing community transmission of varicella among children aged 4 to 18 years in 2 active surveillance sites. One-dose varicella vaccine effectiveness (VE) was examined in those aged 1 to 18 years.

METHODS

From May 2009 through June 2011, varicella cases identified during active surveillance in Antelope Valley, CA and Philadelphia, PA were enrolled into a matched case-control study. Matched controls within 2 years of the patient's age were selected from immunization registries. A standardized questionnaire was administered to participants' parents, and varicella vaccination history was obtained from health care provider, immunization registry, or parent records. We used conditional logistic regression to estimate varicella VE against clinically diagnosed and laboratory-confirmed varicella.

RESULTS

A total of 125 clinically diagnosed varicella cases and 408 matched controls were enrolled. Twenty-nine cases were laboratory confirmed. One-dose VE (1-dose versus unvaccinated) was 75.6% (95% confidence interval [CI], 38.7%-90.3%) in preventing any clinically diagnosed varicella and 78.1% (95% CI, 12.7%-94.5%) against moderate or severe, clinically diagnosed disease (≥50 lesions). Among subjects aged ≥4 years, 2-dose VE (2-dose versus unvaccinated) was 93.6% (95% CI, 75.6%-98.3%) against any varicella and 97.9% (95% CI, 83.0%-99.7%) against moderate or severe varicella. Incremental effectiveness (2-dose versus 1-dose) was 87.5% against clinically diagnosed varicella and 97.3% against laboratory-confirmed varicella.

CONCLUSIONS

Two-dose varicella vaccination offered better protection against varicella from community transmission among school-aged children compared with 1-dose vaccination.

Genotyping of clinical varicella-zoster virus isolates collected from Yunnan in Southwestern China

Varicella-zoster virus (VZV) belongs to the α-herpesvirus family. Genetically, it is stable and is divided into several genotypes based upon the genetic variations. The genotypes of VZV are rarely studied in the Southwestern region of China. In the present study, the common genetic variations in the VZV genes were examined in 42 VZV isolates collected from the patients with herpes zoster in the Yunnan province (Southwestern China). The restriction fragment length polymorphism analysis of open reading frames (ORFs) 38, 54 and 62 in the VZV genes showed that all the collected VZV isolates were PstI, BglI and SmaI positive. The R5 variable-repeat region in these isolates was variable (R5A: 46.4%; R5B: 53.6%). The sequencing data of ORFs 1, 21, 22 and 54 indicated that 41 of the 42 collected VZV isolates could be grouped into genotype J or J1. Only one VZV isolate was identified as genotype A1 or M2. No new substitutions in the sequenced fragments were found in the collected VZV isolates. The results of the present study provided a preliminary genetic characterization of the VZV strains in the Yunnan province of Southwestern China.

Use of Saliva to Identify Varicella Zoster Virus Infection of the Gut

BACKGROUND

Varicella zoster virus (VZV) establishes latency in dorsal root, cranial nerve, and enteric ganglia and can reactivate to cause zoster. Serious gastrointestinal dysfunction can result from VZV reactivation in enteric neurons (enteric zoster), but an absence of rash makes diagnosis difficult. We thus determined whether detecting VZV DNA in saliva facilitates identification of enteric zoster.

METHODS

Nested and real-time polymerase chain reaction were used to validate salivary VZV DNA as a surrogate marker of VZV reactivation and then to determine the utility of that marker for the identification of those individuals within a population defined by abdominal pain that might have enteric zoster.

RESULTS

Salivary VZV DNA was detected in 0 of 20 healthy negative controls, 11 of 16 positive controls with zoster or varicella (P < .0001), 2 of 2 patients with zoster sine herpete (P < .01), 6 of 11 patients with unexplained abdominal pain (P < .001), and 0 of 8 patients with unrelated gastrointestinal disorders. Salivary VZV DNA disappeared after recovery in 9 of 9 tested subjects with zoster, 2 of 2 with zoster sine herpete, and 5 of 5 with abdominal pain. One patient with abdominal pain and salivary VZV DNA had perforated gastric ulcers, necessitating a wedge gastrectomy. VZV DNA (vaccine type) was found in the resected stomach; immediate early (ORF63p) and late (gE) VZV proteins were immunocytochemically detected in gastric epithelium. After recovery, VZV DNA and proteins were not detected in gastric biopsies or saliva.

CONCLUSIONS

Detection of salivary VZV DNA in patients with abdominal pain helps to identify putative enteric zoster for investigation and treatment.

Disseminated, persistent, and fatal infection due to the vaccine strain of varicella-zoster virus in an adult following stem cell transplantation

Live attenuated varicella vaccine is recommended for healthy individuals who are susceptible to varicella. Although the vaccine is safe, effective, and used worldwide, serious adverse events have been reported, mainly in immunocompromised patients who subsequently recovered. Here, we describe the fatality of an immunocompromised patient who received the varicella vaccine. His medical history provides a cautionary lens through which to view the decision of when vaccination is appropriate. A middle-aged man with non-Hodgkin lymphoma received chemotherapy and a stem cell transplant. He was vaccinated 4 years post-transplantation, despite diagnosis of a new low-grade lymphoma confined to the lymph nodes. Within 3 months of vaccination, he developed recurrent rashes with fever, malaise, weakness, hepatitis, weight loss, and renal failure. The syndrome was eventually determined to be associated with persistent disseminated zoster caused by the vaccine virus. This case illustrates a circumstance when a live viral vaccine should not be used.

Herpes zoster caused by vaccine-strain varicella zoster virus in an immunocompetent recipient of zoster vaccine

We report the first laboratory-documented case of herpes zoster caused by the attenuated varicella zoster virus (VZV) contained in Zostavax in a 68-year-old immunocompetent adult with strong evidence of prior wild-type VZV infection. The complete genome sequence of the isolate revealed that the strain carried 15 of 42 (36%) recognized varicella vaccine-associated single-nucleotide polymorphisms, including all 5 of the fixed vaccine markers present in nearly all of the strains in the vaccine. The case of herpes zoster was relatively mild and resolved without complications.

Cycling probe technology to quantify and discriminate between wild-type varicella-zoster virus and Oka vaccine strains

Rapid differentiation between wild-type varicella zoster virus (VZV) and Oka-vaccine (vOka) strains is important for monitoring side reactions of varicella vaccination. To develop a high-throughput molecular diagnostic method for the differentiation of wild-type VZV and vOka strains based on cycling probe technology. The primers were designed to amplify common sequences spanning a single nucleotide polymorphism (SNP) in gene 62 of VZV. DNA-RNA chimeric probes (cycling probes) were designed to detect the SNP at nucleotide 105705. The cycling probe real-time PCR assays for VZV wild-type and vOka strains specifically amplified plasmids containing target sequences that ranged between 10 and 1×10(6) copies per reaction. The inter- and intra-assay coefficients of variation were less than 5%. After initial validation studies, the clinical reliability of this method was evaluated using 38 swab samples that were collected from patients suspected of being zoster. Compared to the loop mediated isothermal amplification method, which is defined as the gold standard, cycling probe real-time PCR was highly sensitive and specific. The cycling probe real-time PCR technology is a reliable tool for differentiating between wild-type VZV and vOka strains in clinical samples.

Analysis of enzymatic digestion pattern of two open reading frames of Varciella-Zoster genome from Kuwaiti patients using the RFLP technique

BACKGROUND AND OBJECTIVES

Varicella-Zoster virus (VZV) is a human herpes virus that usually attacks young children and commonly causes chicken pox (Varicella). Following primary infection, a lifelong latent infection is established. The virus often reactivates during adulthood or senesces to cause shingles (Zoster). Little is known regarding the genotypes of Varicella in Kuwait. The aim of this study was to genotype Varicella samples collected from patients in Kuwait.

MATERIALS AND METHODS

Samples from 60 cases of chicken pox were typed. The DNA extraction was performed using the commercially available DNA extraction kit. Two sets of oligonucleotide primers were used to amplify the intervening sequences with polymerase chain reaction to identify VZV DNA in clinical samples. The BglI and PstI endonucleases were used to digest. The PCR amplicons for PCR-RFLP typing.

RESULTS

Relatively consistent restriction enzyme digestion profiles for different VZV strains were observed. Limited genetic differences between VZV samples were found. Three VZV strains were identified (A, B and C) with type B representing 86.6%, type A 11.7% and type C being 1.7%. We found that distinct restriction fragment length polymorphism isolates from the same origin or nationality were very similar.

CONCLUSION

Varicella strains with cutting sites for both enzyme PstI and BglI (typeB) were more prevalent. Molecular amplification of viral DNA by PCR and restriction digestion could be used for VZV typing as an alternative method to serological assays.

Latency of varicella zoster virus in dorsal root, cranial, and enteric ganglia in vaccinated children

Despite vaccination, varicella-zoster virus (VZV) remains an important pathogen. We investigated VZV latency in autopsy specimens from vaccinees, in gastrointestinal tissue removed surgically, and in a guinea pig model. We propose that retrograde transport from infected skin and viremia deliver VZV to neurons in which it becomes latent. Wild type (WT) VZV was found to be latent in many ganglia of vaccinated children with no history of varicella, suggesting that subclinical infection with WT-VZV occurs with subsequent viremic dissemination. The 30% to 40% rate of WT-VZV zoster reported in vaccinees and occasional trigeminal zoster due to vaccine type VZV (vOka) are consistent with viremic delivery of VZV to multiple ganglia. Most human intestinal specimens contained latent VZV within neurons of the enteric nervous system (ENS). Induction of viremia in guinea pigs led to VZV latency throughout the ENS. The possibility VZV reactivation in the ENS is an unsuspected cause of gastrointestinal disease requires future investigation.

Sequencing of 21 varicella-zoster virus genomes reveals two novel genotypes and evidence of recombination

Genotyping of 21 varicella-zoster virus (VZV) strains using a scattered single nucleotide polymorphism (SNP) method revealed ambiguous SNPs and two nontypeable isolates. For a further genetic characterization, the genomes of all strains were sequenced using the 454 technology. Almost-complete genome sequences were assembled, and most remaining gaps were closed with Sanger sequencing. Phylogenetic analysis of 42 genomes revealed five established and two novel VZV genotypes, provisionally termed VIII and IX. Genotypes VIII and IX are distinct from the previously reported provisional genotypes VI and VII as judged from the SNP pattern. The alignments showed evidence of ancient recombination events in the phylogeny of clade 4 and recent recombinations within single strains: 3/2005 (clade 1), 11 and 405/2007 (clade 3), 8 and DR (clade 4), CA123 and 413/2000 (clade 5), and strains of the novel genotypes VIII and IX. Bayesian tree inference of the thymidine kinase and the polymerase genes of the VZV clades and other varicelloviruses revealed that VZV radiation began some 110,000 years ago, which correlates with the out-of-Africa dispersal of modern humans. The split of ancestral clades 2/4 and 1/3/5/VIII/IX shows the greatest node height.

Disseminated varicella infection caused by varicella vaccine strain in a child with low invariant natural killer T cells and diminished CD1d expression

BACKGROUND

Live attenuated varicella vaccine is considered a safe vaccine with serious adverse effects reported only in immunocompromised children. We describe a severe life-threatening infection with varicella vaccine virus causing rash and pneumonitis in a 6-year-old boy with no apparent immunodeficiency.

METHODS AND RESULTS

Polymerase chain reaction (PCR) analysis of vesicle swab samples demonstrated varicella zoster virus (VZV). Sequencing of the PCR product demonstrated 100% homology with human herpesvirus 3 strain VZV-Oka ORF62 gene. Routine immunologic investigations failed to demonstrate any abnormality. Total leukocyte, lymphocyte, and neutrophil counts and lymphocyte subsets were normal. Immunoglobulins, C3, C4, and CH50 were intact. Specific IgG to protein and polysaccharide antigens and to Epstein-Barr virus and cytomegalovirus were present. Normal lymphocyte proliferation to phytohemagglutinin and VZV antigens was detected. Neutrophil function and natural killer (NK) cell activity were normal. The analysis of invariant NK T (iNKT) cell numbers and function revealed diminished iNKT cells, reported once previously and unique to our patient, deficient expression of the cognate receptor, CD1d.

CONCLUSIONS

This report provides a further link between deficiency of the iNKT/CD1d pathway and increased susceptibility to varicella vaccine virus, suggesting an important role of this innate pathway in host defense against yet another member of the herpesvirus family.

Genotype of varicella-zoster virus isolates in South Korea

Information about the genotype of varicella-zoster virus (VZV) is useful to monitor outbreaks of vaccine strains. However, in South Korea, where varicella vaccine was introduced in 1988, there are limited data about the genotype of VZV. VZV was isolated from vesicular lesions of patients with herpes zoster or varicella in South Korea between January 2007 and June 2009. DNAs were purified from single-passage isolates. The genotype was determined by sequence analysis of open reading frame (ORF) 22. The PstI restriction enzyme site in ORF 38 and the BglI restriction enzyme site in ORF 54 were evaluated by restriction enzyme analysis. Forty-four patients with herpes zoster and nine patients with varicella were enrolled. The median age of patients with herpes zoster was 59.5 (range, 10 to 77) years, and the median age of patients with varicella was 8 (range, 6 to 9) years. In sequence analysis of ORF 22, all isolates were genotype J, irrespective of the age group. In restriction enzyme analysis, 51 of 54 (94.3%) isolates contained a PstI site in ORF 38, and all isolates contained a BglI site in ORF 54. Our data suggest that genotype J has been circulating since the 1940s in South Korea.

Transmission of varicella vaccine virus to a non-family member in China

A 23-year-old teacher presented to hospital with a mild case of varicella. VZV vaccine strain vOka that resembles Varilrix but not Varivax or Biken strains was isolated from the skin lesion of the patient and was identified by single nucleotide polymorphism (SNP) analysis. The teacher denied having varicella vaccine before. Retrospective analysis suggests the transmission came from a pupil who developed zoster 13 months after varicella vaccine Varilrix. This is the first report in China in which an adult with varicella was attributable to vaccine virus and the 6th report of transmission of vaccine virus to a susceptible adult around the world.

Monitoring prevalence of varicella-zoster virus clades in Germany

The global surveillance of varicella-zoster virus (VZV) clades is an important tool for investigation into viral evolution, host-virus interactions, role of immigration and travel for importation of viral strains as well as possible recombination events between wild- and vaccine-type VZV strains. In this prospective study, comprehensive data on the current distribution of VZV clades in Germany were collected. VZV strains from 213 patients with varicella and 109 with zoster were genotyped using the scattered single-nucleotide polymorphism method on the basis of sequencing open reading frames 1, 21, 22, 37, 50, 54 and 60. In varicella, clade 3 was detected in 45.5%, clade 1 in 30.0%, clade 5 in 21.1% and clade 2 in 0.9% of the cases. The analysis of zoster strains revealed clade 3 in 50.5%, clade 1 in 46.8%, clade 2 and clade 4 in 0.9% of the cases each. Five strains from varicella and one strain from zoster could not be attributed to any of the major and provisional VZV clades. Statistical analysis verified significantly lower frequency of clade 1 and significantly higher frequency of clade 5 in patients with varicella compared to zoster. In addition, varicella patients with clade 5 strains were significantly younger than the patients with clade 3. In conclusion, almost one half of VZV infections in Germany were caused currently by VZV clade 3. In primary VZV infection, nearly 20% of clade 1 has been replaced by clade 5 that might spread more effectively in the population than the European VZV clades.

Incremental effectiveness of second dose varicella vaccination for outbreak control at an elementary school in Philadelphia, pennsylvania, 2006

BACKGROUND

In 2006, the Philadelphia Department of Public Health conducted an investigation of a varicella outbreak at an elementary school in which second-dose vaccination for outbreak control (VOC) was implemented. We evaluated the effectiveness of this intervention.

METHODS

Self-administered questionnaires collected varicella disease and vaccination information. Students eligible for second-dose VOC were 1-dose vaccine recipients without prior varicella disease. A breakthrough varicella case was defined as a maculopapulovesicular rash in a student with onset >42 days after 1-dose vaccination without other apparent cause. Vaccine effectiveness was evaluated using survival analysis techniques and analyzed by vaccine status (first dose versus second dose). Multivariable Cox proportional hazard models were used to identify statistical interactions and adjust for confounders.

RESULTS

The questionnaire response rate was 92% (342/370). Of the 286 eligible students, 187 (65%) received a second-dose VOC. The crude attack rate was 9/187 (5%) among second-dose VOC recipients; 43/99 (43%) among 1-dose recipients, and 5/6 (83%) among unvaccinated students. Second-dose VOC recipients had milder rashes, compared with 1-dose or unvaccinated students. The adjusted incremental second-dose vaccine effectiveness was 76% (95% confidence interval: 44%-90%) for students with classroom exposure. Incremental effectiveness was similar (79%) when we extended the immune response time from 4 days to 7 days after second-dose VOC.

CONCLUSIONS

Second-dose VOC resulted in a substantial reduction in varicella incidence for students with classroom exposure. Until high rates of routine second-dose vaccine coverage are achieved, clinicians should consider second-dose VOC an appropriate intervention to reduce disease transmission in institution-based outbreaks.

Prevalence of varicella-zoster virus genotypes in Australia characterized by high-resolution melt analysis and ORF22 gene analyses

DNA sequence variation analysis has divided varicella-zoster virus (VZV; Human herpesvirus 3) into distinct geographical clades: European, Asian, African and Japanese. These genotypes are becoming increasingly prevalent within regions atypical to their original source and there has been the suggestion of recombination between genotypes. Seventy-eight clinical isolates from hospitalized patients with varicella were collected in New South Wales, the Northern Territory, Western Australia and Victoria from 2006 to 2009. The wild-type strains and the vaccine strain (vOka) were differentiated by single nucleotide polymorphism detection using high-resolution melt analysis of five target genes (ORF1, -21, -37, -60 and -62), and by DNA sequence analysis of a 484 bp region of ORF22. Phylogenetic analysis showed that 46 % (36/78) of the clinical isolates were European clade 1 (C/E1) strains, 21 % (16/78) were European clade 3 (B/E2) strains, 12 % (9/78) were Asian/African clade 5 (A/M1) strains, 10 % (8/78) were clade 4 (J2/M2), 6 % (5/78) were clade 2 (J/J) and 5 % (4/78) belonged to the novel clade VI. No significant association was shown between VZV genotype and region, age or gender. Although European strains were most common, the results suggest an increase in African/Asian, Japanese and clade VI genotypes circulating in Australia.

Varicella-zoster virus vaccine: molecular genetics

The genetic differences that potentially account for the attenuation of the Oka vaccine VZV preparation are more clearly defined than for perhaps any other vaccine in current use. This is due in large part to the small number of differences between the vaccine and the parental strain from which it was derived, and to the high level of genomic conservation that characterizes VZV. This information has been used with great success to develop methods that discriminate vaccine from wild-type strains, to begin determining which specific vaccine markers contribute to the attenuated phenotype, to improve evaluations of vaccine efficacy and safety, and to observe the behavior of the live, attenuated preparation as it becomes more prevalent through widespread immunization.

Impact of varicella vaccine on varicella-zoster virus dynamics

The licensure and recommendation of varicella vaccine in the mid-1990s in the United States have led to dramatic declines in varicella incidence and varicella-related deaths and hospitalizations. Varicella outbreaks remain common and occur increasingly in highly vaccinated populations. Breakthrough varicella in vaccinated individuals is characteristically mild, typically with fewer lesions that frequently do not progress to a vesicular stage. As such, the laboratory diagnosis of varicella has grown increasingly important, particularly in outbreak settings. In this review the impact of varicella vaccine on varicella-zoster virus (VZV) disease, arising complications in the effective diagnosis and monitoring of VZV transmission, and the relative strengths and limitations of currently available laboratory diagnostic techniques are all addressed. Since disease symptoms often resolve in outbreak settings before suitable test specimens can be obtained, the need to develop new diagnostic approaches that rely on alternative patient samples is also discussed.

Divergence and genotyping of human alpha-herpesviruses: an overview

Herpesviruses are large DNA viruses that are highly disseminated among animals. Of the eight herpesviruses identified in humans, three are classified into the alpha-herpesvirus subfamily: herpes simplex virus types 1 (HSV-1) and 2 (HSV-2), which are typically associated with mucocutaneous lesions, and varicella-zoster virus (VZV), which is the cause of chicken pox and herpes zoster. All three viruses establish lifelong infections and may also induce more severe symptoms, such as neurological manifestations and fatal neonatal infections. Despite thorough investigation of the genetic variability among circulating strains of each virus in recent decades, little is known about possible associations between the genetic setups of the viruses and clinical manifestations in human hosts. This review focuses mainly on evolutionary studies of and genotyping strategies for these three human alpha-herpesviruses, emphasizing the ambiguities induced by a high frequency of circulating recombinant strains. It also aims to shed light on the challenges of establishing a uniform genotyping strategy for all three viruses.

A real-time PCR assay to identify and discriminate among wild-type and vaccine strains of varicella-zoster virus and herpes simplex virus in clinical specimens, and comparison with the clinical diagnoses

A real-time PCR assay was developed to identify varicella-zoster virus (VZV) and herpes simplex virus (HSV) DNA in clinical specimens from subjects with suspected herpes zoster (HZ; shingles). Three sets of primers and probes were used in separate PCR reactions to detect and discriminate among wild-type VZV (VZV-WT), Oka vaccine strain VZV (VZV-Oka), and HSV DNA, and the reaction for each virus DNA was multiplexed with primers and probe specific for the human beta-globin gene to assess specimen adequacy. Discrimination of all VZV-WT strains, including Japanese isolates and the Oka parent strain, from VZV-Oka was based upon a single nucleotide polymorphism at position 106262 in ORF 62, resulting in preferential amplification by the homologous primer pair. The assay was highly sensitive and specific for the target virus DNA, and no cross-reactions were detected with any other infectious agent. With the PCR assay as the gold standard, the sensitivity of virus culture was 53% for VZV and 77% for HSV. There was 92% agreement between the clinical diagnosis of HZ by the Clinical Evaluation Committee and the PCR assay results.

Genotyping of clinical varicella-zoster virus isolates collected in China

Varicella-zoster virus (VZV) is genetically stable; and various schemes for the genotyping of VZV based on restriction fragment length polymorphisms (RFLPs), PCR, and sequencing have been developed. At least three major genotypes have been recognized among VZV isolates or clinical samples from different locations around the world; however, few data were available for viral isolates from China. In the current study, a collection of 19 VZV isolates from patients with zoster or varicella in the middle eastern region of China was examined for genetic variations. RFLP analysis of DNA fragments of open reading frames (ORFs) 38, 54, and 62 showed that all 19 isolates were PstI and BglI positive and SmaI negative, and this may represent the major restriction pattern of wild-type VZV strains in China. Further analysis of the R5 variable-repeat region in those strains revealed that 9 (47.4%) were type R5A, while the remaining 10 strains (52.6%) were type R5B. On the basis of the sequencing data for ORFs 1, 21, 22, and 54, all 19 Chinese strains could be grouped into genotype J or J1. A novel in-frame 3-nucleotide insertion (CGG) in ORF1 was found in 4 (21%) of the 19 isolates. Additionally three new nucleotide substitutions were detected in two of the isolates. A varicella isolate from the United States, strain MLS, was included in this study as a control for American wild-type VZV, and was found to be type M1, which represents one of the minor genotypes in North America.

Distribution of varicella-zoster virus (VZV) wild-type genotypes in northern and southern Europe: evidence for high conservation of circulating genotypes

Phylogenetic analysis of 19 complete VZV genomic sequences resolves wild-type strains into 5 genotypes (E1, E2, J, M1, and M2). Complete sequences for M3 and M4 strains are unavailable, but targeted analyses of representative strains suggest they are stable, circulating VZV genotypes. Sequence analysis of VZV isolates identified both shared and specific markers for every genotype and validated a unified VZV genotyping strategy. Despite high genotype diversity no evidence for intra-genotypic recombination was observed. Five of seven VZV genotypes were reliably discriminated using only four single nucleotide polymorphisms (SNP) present in ORF22, and the E1 and E2 genotypes were resolved using SNP located in ORF21, ORF22 or ORF50. Sequence analysis of 342 clinical varicella and zoster specimens from 18 European countries identified the following distribution of VZV genotypes: E1, 221 (65%); E2, 87 (25%); M1, 20 (6%); M2, 3 (1%); M4, 11 (3%). No M3 or J strains were observed.

Laboratory diagnosis and characteristics of breakthrough varicella in children

The atypical features of varicella in vaccinated persons (breakthrough varicella [BTV]) present diagnostic challenges. We examined varicella-zoster virus (VZV) polymerase chain reaction (PCR) and immunoglobulin (Ig) M and IgG serologic test results for confirming BTV cases. Among 33 vaccinated children with varicella-like rash, we identified wild-type VZV in 58% overall and in 76% of those with adequate tissue specimens; no vaccine-type virus was found. Of the 12 subjects with PCR-confirmed BTV and acute-phase serum samples, 9 had detectable IgM, and all had highly elevated acute-phase IgG titers. Six subjects with negative PCR results had lower IgG titers and negative IgM results. Although PCR is the preferred method for laboratory confirmation of BTV, a positive serum varicella IgM test result should also be considered to be diagnostic in a suspected BTV case; however, a negative IgM test result cannot be used to rule out the diagnosis. The value of highly elevated IgG titers needs further evaluation. Larger studies are needed to confirm these results.

Genotyping of varicella-zoster virus strains after serial passages in cell culture

There is little information in the literature about the stability of single nucleotide polymorphisms (SNP) used for genotyping of varicella-zoster virus (VZV) in sequencing studies. The objective of this study was to genotype VZV wild-type and vaccine isolates representing the four major clades A, B, C and J before and after serial passages in cell culture. Eleven VZV strains were genotyped by sequencing of the open reading frames (ORF) 1, 21, 37, 50, 54 and 60 as well as by restriction fragment length polymorphism (RFLP) analysis of the ORFs 38 and 62 after 1-16 passages in human embryonic lung fibroblasts (HELF). Results revealed no variations of nucleotide sequences in the ORFs 1, 21, 37, 50, 54 and 60 within 16 cell culture passages. Additionally, there were no changes in the RFLP profile of the ORFs 38 and 62. In conclusion, VZV can be isolated in HELF and propagated for at least 16 passages before genotyping by sequencing without the risk of intra-strain variations. For rapid diagnostic identification of vaccine versus wild-type strains, the RFLP profile that is stable within several cell culture passages can be determined using DNA prepared from clinical specimens.

Herpes zoster due to Oka vaccine strain of varicella zoster virus in an immunosuppressed child post cord blood transplant

A 5-year-old boy was vaccinated with the Oka strain of varicella zoster virus vaccine before cord blood transplant for chronic granulomatous disease in 2005. In 2006, he developed herpes zoster on his left arm. DNA from the vesicular rash confirmed the Oka vaccine strain of varicella zoster virus caused this complication. He responded well to 10 days of aciclovir treatment.