Modeling antibody dynamics following herpes zoster indicates that higher varicella-zoster virus viremia generates more VZV-specific antibodies.

Introduction: Studying antibody dynamics following re-exposure to infection and/or vaccination is crucial for a better understanding of fundamental immunological processes, vaccine development, and health policy research. Methods: We adopted a nonlinear mixed modeling approach based on ordinary differential equations (ODE) to characterize varicella-zoster virus specific antibody dynamics during and after clinical herpes zoster. Our ODEs models convert underlying immunological processes into mathematical formulations, allowing for testable data analysis. In order to cope with inter- and intra-individual variability, mixed models include population-averaged parameters (fixed effects) and individual-specific parameters (random effects). We explored the use of various ODE-based nonlinear mixed models to describe longitudinally collected markers of immunological response in 61 herpes zoster patients. Results: Starting from a general formulation of such models, we study different plausible processes underlying observed antibody titer concentrations over time, including various individual-specific parameters. Among the converged models, the best fitting and most parsimonious model implies that once Varicella-zoster virus (VZV) reactivation is clinically apparent (i.e., Herpes-zoster (HZ) can be diagnosed), short-living and long-living antibody secreting cells (SASC and LASC, respectively) will not expand anymore. Additionally, we investigated the relationship between age and viral load on SASC using a covariate model to gain a deeper understanding of the population's characteristics. Conclusion: The results of this study provide crucial and unique insights that can aid in improving our understanding of VZV antibody dynamics and in making more accurate projections regarding the potential impact of vaccines.

Analysis of the reiteration regions (R1 to R5) of varicella-zoster virus.

The varicella-zoster virus (VZV) genome, comprises both unique and repeated regions. The genome also includes reiteration regions, designated R1 to R5, which are tandemly repeating sequences termed elements. These regions represent an understudied feature of the VZV genome. The R4 region is duplicated, with one copy in the internal repeat short (IRs) which we designated R4A and a second copy in the terminal repeat short (TRs) termed R4B. We developed primers to amplify and Sanger sequence these regions, including independent amplification of both R4 regions. Reiteration regions from >80 cases of PCR-confirmed shingles were sequenced and analyzed. Complete genome sequences for the remaining portions of these viruses were determined using Illumina MiSeq. We identified 28 elements not previously reported, including at least one element for each R region. Length heterogeneity was substantial in R3, R4A and R4B. Length heterogeneity between the two copies of R4 was common.

Viral load and antibody boosting following herpes zoster diagnosis.

BACKGROUND: Acute varicella zoster virus (VZV) replication in shingles is accompanied by VZV antibody boosting. It is unclear whether persisting virus shedding affects antibody levels. OBJECTIVES: To investigate the relationship between VZV viral load and antibody titres in shingles patients during six months following diagnosis and assess whether VZV antibody titre could discriminate patients with recent shingles from healthy population controls. STUDY DESIGN: A prospective study of 63 patients with active zoster. Blood samples were collected at baseline, one, three and six months to measure VZV DNA and IgG antibody titre. We compared VZV antibody titres of zoster patients and 441 controls. RESULTS: In acute zoster, viral load was highest at baseline and declined gradually over the following six months. Mean antibody titres rose fourfold, peaking at one month and remaining above baseline levels throughout the study. Antibody levels at one, three and six months after zoster were moderately correlated with baseline but not subsequent viral load. Regarding use of antibody titres to identify recent shingles, to achieve 80% sensitivity, specificity would be 23.4%, 67.7%, 64.8% and 52.6%, at baseline, visit 2, 3 and 4 respectively, whilst to achieve 80% specificity, sensitivity would be 28.3%, 66.1%, 52.6%, 38.6%, at baseline, visit 2, 3 and 4 respectively. CONCLUSIONS: Clinical VZV reactivation boosted VZV antibody levels and the level of boosting was dependent upon baseline viral replication. While antibody titres could discriminate patients with shingles 1-6 months earlier from blood donor controls, there was a large trade-off between sensitivity and specificity.

Revisiting the genotyping scheme for varicella-zoster viruses based on whole-genome comparisons.

We report whole-genome sequences (WGSs) for four varicella-zoster virus (VZV) samples from a shingles study conducted by Kaiser Permanente of Southern California. Comparative genomics and phylogenetic analysis of all published VZV WGSs revealed that strain KY037798 is in clade IX, which shall henceforth be designated clade 9. Previously published single nucleotide polymorphisms (SNP)-based genotyping schemes fail to discriminate between clades 6 and VIII and employ positions that are not clade-specific. We provide an updated list of clade-specific positions that supersedes the list determined at the 2008 VZV nomenclature meeting. Finally, we propose a new targeted genotyping scheme that will discriminate the circulating VZV clades with at least a twofold redundancy. Genotyping strategies using a limited set of targeted SNPs will continue to provide an efficient 'first pass' method for VZV strain surveillance as vaccination programmes for varicella and zoster influence the dynamics of VZV transmission.

Anti-cytokine autoantibodies in postherpetic neuralgia.

BACKGROUND: The mechanisms by which varicella zoster virus (VZV) reactivation causes postherpetic neuralgia (PHN), a debilitating chronic pain condition, have not been fully elucidated. Based on previous studies identifying a causative role for anti-cytokine autoantibodies in patients with opportunistic infections, we explored this possibility in PHN. METHODS: Sera from herpes zoster (HZ) patients without and with PHN (N = 115 and 83, respectively) were examined for the presence of autoantibodies against multiple cytokines, and other known autoantigens. In addition, a cohort of patients with complex regional pain syndrome or neuropathic pain was tested for autoantibodies against selected cytokines. Antibody levels against VZV, Epstein Barr virus, and herpes simplex virus-2 were also measured in the HZ and PHN patients. Patient sera with high levels of anti-cytokine autoantibodies were functionally tested for in vitro neutralizing activity. RESULTS: Six PHN subjects demonstrated markedly elevated levels of single, autoantibodies against interferon-α, interferon-γ, GM-CSF, or interleukin-6. In contrast, the HZ and the pain control group showed low or no autoantibodies, respectively, against these four cytokines. Further analysis revealed that one PHN patient with high levels of anti-interleukin-6 autoantibodies had a markedly depressed antibody level to VZV, potentially reflecting poor T cell immunity against VZV. In vitro functional testing revealed that three of the five anti-cytokine autoantibody positive PHN subjects had neutralizing autoantibodies against interferon-α, GM-CSF or interleukin-6. In contrast, none of the HZ patients without PHN had neutralizing autoantibodies. CONCLUSIONS: These results suggest the possibility that sporadic anti-cytokine autoantibodies in some subjects may cause an autoimmune immunodeficiency syndrome leading to uncontrolled VZV reactivation, nerve damage and subsequent PHN.

Cytomegalovirus seropositivity is associated with herpes zoster.

Herpes zoster (HZ) is caused by VZV reactivation that is facilitated by a declined immunity against varicella-zoster virus (VZV), but also occurs in immunocompetent individuals. Cytomegalovirus (CMV) infection is associated with immunosenescence meaning that VZV-specific T-cells could be less responsive. This study aimed to determine whether CMV infection could be a risk factor for the development of HZ. CMV IgG serostatus was determined in stored serum samples from previously prospectively recruited ambulatory adult HZ patients in the UK (N = 223) in order to compare the results with those from UK population samples (N = 1545) by means of a logistic regression (controlling for age and gender). Furthermore, we compared the UK population CMV seroprevalence with those from population samples from other countries (from Belgium (N1 = 1741, N2 = 576), USA (N = 5572) and Australia (N = 2080)). Furthermore, CMV IgG titers could be compared between UK HZ patients and Belgium N2 population samples because the same experimental set-up for analysis was used. We found UK ambulatory HZ patients to have a higher CMV seroprevalence than UK population samples (OR 1.56 [1.11 2.19]). CMV IgG seropositivity was a significant risk factor for HZ in the UK (OR 3.06 [1.32 7.04]. Furthermore, high CMV IgG titers (exceeding the upper threshold) were less abundant in CMV-seropositive Belgian N2 population samples than in CMV-seropositive UK HZ patients (OR 0.51 [0.31 0.82]. We found CMV-seroprevalence to increase faster with age in the UK than in other countries (P < 0.05). We conclude that CMV IgG seropositivity is associated with HZ. This finding could add to the growing list of risk factors for HZ.

Clinical and molecular aspects of the live attenuated Oka varicella vaccine.

VZV is a ubiquitous member of the Herpesviridae family that causes varicella (chicken pox) and herpes zoster (shingles). Both manifestations can cause great morbidity and mortality and are therefore of significant economic burden. The introduction of varicella vaccination as part of childhood immunization programs has resulted in a remarkable decline in varicella incidence, and associated hospitalizations and deaths, particularly in the USA. The vaccine preparation, vOka, is a live attenuated virus produced by serial passage of a wild-type clinical isolate termed pOka in human and guinea pig cell lines. Although vOka is clinically attenuated, it can cause mild varicella, establish latency, and reactivate to cause herpes zoster. Sequence analysis has shown that vOka differs from pOka by at least 42 loci; however, not all genomes possess the novel vOka change at all positions, creating a heterogeneous population of genetically distinct haplotypes. This, together with the extreme cell-associated nature of VZV replication in cell culture and the lack of an animal model, in which the complete VZV life cycle can be replicated, has limited studies into the molecular basis for vOka attenuation. Comparative studies of vOka with pOka replication in T cells, dorsal root ganglia, and skin indicate that attenuation likely involves multiple mutations within ORF 62 and several other genes. This article presents an overview of the clinical aspects of the vaccine and current progress on understanding the molecular mechanisms that account for the clinical phenotype of reduced virulence.

Use of oral fluid to examine the molecular epidemiology of varicella zoster virus in the United Kingdom and continental Europe.

We investigated oral fluid (OF) as an alternative to sampling of rashes for varicella zoster virus (VZV) genotyping and further characterized VZV clade prevalence in the United Kingdom and Europe. VZV was detected in up to 91% of OF specimens. Paired OF and vesicle fluid samples contained identical VZV clades. While clades 1 and 3 were the most prevalent across the United Kingdom and Europe, in Western Europe, clade 5 viruses were circulating. Viruses from the same outbreak belonged to different clades, but no clade was associated with a severe-disease phenotype. OF is suitable and convenient for large-scale molecular epidemiological studies of VZV.

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.

Molecular studies of the Oka varicella vaccine.

Varicella zoster virus (VZV) is one of eight members of the Herpesviridae family for which humans are the primary host; it causes two distinct diseases, varicella (chickenpox) and zoster (shingles). Varicella results from primary infection, during which the virus establishes latency in sensory neurons, a characteristic of all members of the Alphaherpesvirinae subfamily. Zoster is caused by reactivation of latent virus, which typically occurs when cellular immunity is impaired. VZV is the first human herpesvirus for which a vaccine has been licensed. The vaccine preparation, v-Oka, is a live-attenuated virus stock produced by the classic method of tissue culture passage in animal and human cell lines. Over 90 million doses of the vaccine have been administered in countries worldwide, including the USA, where varicella morbidity and mortality has declined dramatically. Over the last decade, several laboratories have been committed to investigating the mechanism by which the Oka vaccine is attenuated. Mutations have accumulated across the genome of the vaccine during the attenuation process; however, studies of the contribution of these changes to vaccine attenuation have been hampered by the lack of a suitable animal model of VZV disease and by the heterogeneity that exists among the viral population within the vaccine preparation. Notwithstanding, a wealth of data has been generated using various laboratory methodologies. Studies of the vaccine virus in human xenografts implanted in severe combined immunodeficiency-hu mice, have enabled analyses of the replication dynamics of the vaccine in dorsal root ganglia, T lymphocytes and skin. In vitro assays have been used to investigate the effect of vaccine mutations on viral gene expression and sequence analysis of vaccine rash viruses has permitted investigations into spread of the vaccine virus in a human host. We present here a review of what has been learned thus far about the molecular and phenotypic characteristics of the Oka vaccine.

Actinic varicella vaccine rash.

The case of an 18-month-old girl with vesicular rash confined to a sunburned area after significant ultraviolet radiation exposure is reported. The child had been vaccinated 32 days before presentation, and a high viral load of Oka strain virus was detected in vesicular fluid. Possible pathogenesis is discussed.

Safety profile of live varicella virus vaccine (Oka/Merck): five-year results of the European Varicella Zoster Virus Identification Program (EU VZVIP).

BACKGROUND: VARIVAX (Oka/Merck) is a live varicella vaccine, licensed in Europe since 2003. In addition to routine safety surveillance, the Varicella Zoster Virus Identification Program (VZVIP) analyzes clinical samples to establish whether adverse events (AEs) are associated with wild-type (wt) or vaccine varicella zoster virus (vVZV) strain. The European VZVIP provides data on VZV clade distribution. METHODS: Samples were collected from patients with selected AEs; the VZV strain was determined using polymerase chain reaction. RESULTS: From October 2003 to September 2008, 1006 spontaneous AE reports were analyzed (88% non-serious). Samples from 76/585 cases with selected AEs were collected. Of 55 VZV-positive/typable samples, wtVZV was detected in 40 and vVZV in 15 samples. Most rashes (32/44)

Vaccine-associated herpes zoster ophthalmicus [correction of opthalmicus] and encephalitis in an immunocompetent child.

Varicella-zoster virus vaccine has diminished the consequences of chicken pox in terms of health and economical burden. The increasing number of doses administered worldwide has revealed rare but important adverse effects that had not occurred during clinical trials. We report here the case of an immunocompetent 3(1/2)-year-old girl who developed encephalitis and herpes zoster opthalmicus 20 months after her immunization with varicella-zoster virus vaccine. Molecular analysis confirmed the vaccine strain as the causative agent. After an intravenous course with acyclovir, the child made a full recovery with no neurologic sequelae.

Debilitating clinical disease in a wild-born captive western lowland gorilla (Gorilla gorilla gorilla) co-infected with varicella zoster virus (VZV) and simian T-lymphotropic virus (STLV).

A wild-born, 34-yr-old female western lowland gorilla (Gorilla gorilla gorilla) was transferred between zoologic collections in the United Kingdom. Adjustment to its new environment was difficult and a series of health problems ensued. Progressive severe illness of multiple etiologies, and a failure to respond to multiple therapies, led to its euthanasia 5 mo later. Disease processes included severe thoracic and axillary cutaneous ulceration of T2-3 dermatome distribution, gastroenteritis, ulcerative stomatitis, emaciation, hind limb weakness or paresis, and decubitus ulcers of the ankles and elbows. Ante- and postmortem infectious disease screening revealed that this animal was not infected with Mycobacterium tuberculosis, simian varicella virus (SVV), simian immunodeficiency virus (SIV), or hepatitis B virus; but was infected with varicella-zoster virus (VZV) and simian T-lymphotropic virus (STLV). It is hypothesized that recrudescence of VZV and other disease processes described were associated with chronic STLV infection and the end of a characteristically long incubation period.

Natural selection for rash-forming genotypes of the varicella-zoster vaccine virus detected within immunized human hosts.

The Oka vaccine strain is a live attenuated virus that is routinely administered to children in the United States and Europe to prevent chickenpox. It is effective and safe but occasionally produces a rash. The vaccine virus has accumulated mutations during its attenuation, but the rashes are not explained by their reversion, unlike complications reported for other viral vaccines. Indeed, most of the novel mutations distinguishing the Oka vaccine from the more virulent parental virus have not actually become fixed. Because the parental alleles are still present, the vaccine is polymorphic at >30 loci and therefore contains a mixture of related viruses. The inoculation of >40 million patients has consequently created a highly replicated evolutionary experiment that we have used to assess the competitive ability of these different viral genotypes in a human host. Using virus recovered from rash vesicles, we show that two vaccine mutations, causing amino acid substitutions in the major transactivating protein IE62, are outcompeted by the ancestral alleles. Standard interpretations of varicella disease severity concentrate on the undeniably important effects of host genotype and immune status, yet our results allow us to demonstrate that the viral genotype is associated with virulence and to identify the key sites. We propose that these loci have pleiotropic effects on the immunogenic properties of the virus, rash formation, and its epidemiological spread, which mould the evolution of its virulence. These findings are of practical importance for reducing the incidence of vaccine-associated rash and promoting public acceptance of the vaccine.

Molecular studies of Varicella zoster virus.

VZV is a highly cell-associated member of the Herpesviridae family and one of the eight herpesviruses to infect humans. The virus is ubiquitous in most populations worldwide, primary infection with which causes varicella, more commonly known as chickenpox. Characteristic of members of the alphaherpesvirus sub-family, VZV is neurotropic and establishes latency in sensory neurones. Reactivation from latency, usually during periods of impaired cellular immunity, causes herpes zoster (shingles). Despite being one of the most genetically stable human herpesviruses, nucleotide alterations in the virus genome have been used to classify VZV strains from different geographical regions into distinct clades. Such studies have also provided evidence that, despite pre-existing immunity to VZV, subclinical reinfection and reactivation of reinfecting strains to cause zoster is also occurring. During both primary infection and reactivation, VZV infects several PBMC and skin cell lineages. Difficulties in studying the pathogenesis of VZV because of its high cell association and narrow host range have been overcome through the development of the VZV severe combined immunodeficient mouse model carrying human tissue implants. This model has provided a valuable tool for studying the importance of individual viral proteins during both the complex intracellular replication and assembly of new virions and for understanding the underlying mechanism of attenuation of the live varicella vaccine. In addition, a rat model has been developed and successfully used to uncover which viral proteins are important for both the establishment and maintenance of latent VZV infection.

Vaccine Oka varicella-zoster virus genotypes are monomorphic in single vesicles and polymorphic in respiratory tract secretions.

We previously found that, after immunization with vaccine Oka varicella-zoster virus, virus obtained from a single vesicle were monomorphic, and virus obtained from different individuals were heterogeneous. Here we show that virus obtained from the lungs of a patient were a mixture of vaccine Oka variants. We hypothesize that complications after immunization are unlikely to be caused by expansion of a single, biologically more virulent clone of virus that either pre-exists in the vaccine or develops after random mutation of different clones. We hypothesize that some clones are more trophic than others for skin.

Molecular and therapeutic aspects of varicella-zoster virus infection.

Varicella-zoster virus (VZV) is a highly species-specific member of the Herpesviridae family. The virus exhibits multiple cell tropisms, infecting peripheral blood mononuclear cells and skin cells before establishing latency in sensory neurons. Such tropisms are essential both for primary infection, which manifests itself as chickenpox (varicella), and subsequent reactivation to cause herpes zoster (shingles). The highly cell-associated nature of the virus, coupled with its narrow host range, has resulted in the lack of an animal model that mimics its diseases in humans, thereby greatly hindering the study of events in VZV pathogenesis. Despite this, extensive studies both in vitro and in vivo in small-animal models have provided a fascinating insight into molecular events that govern VZV diseases. In addition, VZV has become the first human herpes virus for which a live attenuated vaccine has been developed.