A model of lytic, latent, and reactivating varicella-zoster virus infections in isolated enteric neurons

Expanded spectrum of varicella disease and the need for vaccination in India

Varicella vaccine was first licensed in Japan and South Korea in 1989 for use in healthy children and was introduced in US in 1995. So far, 29 countries have adopted varicella vaccine in their universal immunization program (UIP). No Asian country, India included, has adopted the varicella vaccine as part of their UIP. The extra-cutaneous sites for VZV diseases are central nervous system and gastrointestinal tract, the expanded disease spectrum includes vasculopathy, myelitis, inflammatory bowel disease, perforated ulcers, and gastritis. The actual disease burden of varicella is not known as most of the infected individuals may not visit the physician. The amplifiable VZV DNA will not always be detectable in cerebrospinal fluid (CSF) samples in protracted illnesses such as vasculopathies, but demonstrable anti-VZV IgG in CSF has diagnostic value. The World Health Organization (WHO) position paper 2014 recommends two doses of varicella and zoster vaccines in targeted population. In India, varicella vaccine is not included in the UIP due to the cost and the belief that lifelong immunity occurs following primary infection. The expanded spectrum of VZV disease and the mounting body of evidence, however, suggest the need for both varicella and zoster vaccines in routine immunization schedule.

The mechanisms of nerve injury caused by viral infection in the occurrence of gastrointestinal motility disorder-related diseases

Gastrointestinal motility refers to the peristalsis and contractility of gastrointestinal muscles, including the force and frequency of gastrointestinal muscle contraction. Gastrointestinal motility maintains the normal digestive function of the human body and is a critical component of the physiological function of the digestive tract. At present, gastrointestinal motility disorder-related diseases are gradually affecting human production and life. In recent years, it has been consistently reported that the enteric nervous system has a coordinating and controlling role in gastrointestinal motility. Motility disorders are closely related to functional or anatomical changes in the gastrointestinal nervous system. At the same time, some viral infections, such as herpes simplex virus and varicella-zoster virus infections, can cause damage to the gastrointestinal nervous system. Therefore, this paper describes the mechanisms of viral infection in the gastrointestinal nervous system and the associated clinical manifestations. Studies have indicated that the means by which viruses can cause the infection of the enteric nervous system are various, including retrograde transport, hematogenous transmission and centrifugal transmission from the central nervous system. When viruses infect the enteric nervous system, they can cause clinical symptoms, such as abdominal pain, abdominal distension, early satiation, belching, diarrhea, and constipation, by recruiting macrophages, lymphocytes and neutrophils and regulating intestinal microbes. The findings of several case‒control studies suggest that viruses are the cause of some gastrointestinal motility disorders. It is concluded that one of the causes of gastrointestinal motility disorders is viral infection of the enteric nervous system. In such disorders, the relationships between viruses and nerves remain to be studied more deeply. Further studies are necessary to evaluate whether prophylactic antiviral therapy is feasible in gastrointestinal motility disorders.

[Transverse myelitis and cauda equina syndrome followed by varicella in a patient with varicella-zoster virus infection]

A 74-year-old man was admitted to our hospital with complaints of weakness in the lower extremities, urinary retention for 10 days, and generalized vesicular rash for 7 days. Spinal magnetic resonance imaging showed contrast enhancement at the Th12-L1 level of the spinal cord and cauda equina. Serum and cerebrospinal fluid varicella-zoster virus (VZV)-immunoglobulin (Ig) G antibody titers were markedly elevated, and VZV-IgM was detected in cerebrospinal fluid. The patient was diagnosed with VZV transverse myelitis and cauda equina syndrome with subsequent varicella and was treated with acyclovir and prednisolone. Two months later, muscle weakness, and dysuria had almost completely resolved. We hypothesize that latent VZV in the ganglia reactivated and caused transverse myelitis, which subsequently spread to the body via the bloodstream, resulting in the development of varicella.

Simian Varicella Virus: Molecular Virology and Mechanisms of Pathogenesis

Simian varicella virus (SVV) was first isolated in 1966 from African green monkeys (Cercopithecus aethiops) imported from Nairobi, Kenya, to the Liverpool School of Tropical Medicine in the United Kingdom (UK) (Clarkson et al., Arch Gesamte Virusforsch 22:219-234, 1967). SVV infection caused severe disease that resulted in a 56% case fatality rate (CFR) in the imported animals within 48 h of the appearance of a varicella-like rash (Clarkson et al., Arch Gesamte Virusforsch 22:219-234, 1967; Hemme et al., Am J Trop Med Hyg 94:1095-1099, 2016). The deceased animals presented with fever, widespread vesicular rash, and multiple hemorrhagic foci throughout the lungs, liver, and spleen (Clarkson et al., Arch Gesamte Virusforsch 22:219-234, 1967). This outbreak was quickly followed by a second outbreak in 47 patas monkeys (Erythrocebus patas) imported from Chad and Nigeria by Glaxo Laboratories (London, England, UK), which quickly spread within the facility (McCarthy et al., Lancet 2:856-857, 1968).

The Biology of Varicella-Zoster Virus Replication in the Skin

The replication of varicella-zoster virus (VZV) in skin is critical to its pathogenesis and spread. Primary infection causes chickenpox, which is characterised by centrally distributed skin blistering lesions that are rich in infectious virus. Cell-free virus in the cutaneous blistering lesions not only spreads to cause further cases, but infects sensory nerve endings, leading to the establishment of lifelong latency in sensory and autonomic ganglia. The reactivation of virus to cause herpes zoster is again characterised by localised painful skin blistering rash containing infectious virus. The development of in vitro and in vivo models of VZV skin replication has revealed aspects of VZV replication and pathogenesis in this important target organ and improved our understanding of the vaccine strain vOKa attenuation. In this review, we outline the current knowledge on VZV interaction with host signalling pathways, the viral association with proteins associated with epidermal terminal differentiation, and how these interconnect with the VZV life cycle to facilitate viral replication and shedding.

Varicella Zoster Virus Neuronal Latency and Reactivation Modeled in Vitro

Latency and reactivation in neurons are critical aspects of VZV pathogenesis that have historically been difficult to investigate. Viral genomes are retained in many human ganglia after the primary infection, varicella; and about one-third of the naturally infected VZV seropositive population reactivates latent virus, which most often clinically manifests as herpes zoster (HZ or Shingles). HZ is frequently complicated by acute and chronic debilitating pain for which there remains a need for more effective treatment options. Understanding of the latent state is likely to be essential in the design of strategies to reduce reactivation. Experimentally addressing VZV latency has been difficult because of the strict human species specificity of VZV and the fact that until recently, experimental reactivation had not been achieved. We do not yet know the neuron subtypes that harbor latent genomes, whether all can potentially reactivate, what the drivers of VZV reactivation are, and how immunity interplays with the latent state to control reactivation. However, recent advances have enabled a picture of VZV latency to start to emerge. The first is the ability to detect the latent viral genome and its expression in human ganglionic tissues with extraordinary sensitivity. The second, the subject of this chapter, is the development of in vitro human neuron systems permitting the modeling of latent states that can be experimentally reactivated. This review will summarize recent advances of in vitro models of neuronal VZV latency and reactivation, the limitations of the current systems, and discuss outstanding questions and future directions regarding these processes using these and yet to be developed models. Results obtained from the in vitro models to date will also be discussed in light of the recent data gleaned from studies of VZV latency and gene expression learned from human cadaver ganglia, especially the discovery of VZV latency transcripts that seem to parallel the long-studied latency-associated transcripts of other neurotropic alphaherpesviruses.

You Talking to Me? Says the Enteric Nervous System (ENS) to the Microbe. How Intestinal Microbes Interact with the ENS

Mammalian organisms form intimate interfaces with commensal and pathogenic gut microorganisms. Increasing evidence suggests a close interaction between gut microorganisms and the enteric nervous system (ENS), as the first interface to the central nervous system. Each microorganism can exert a different effect on the ENS, including phenotypical neuronal changes or the induction of chemical transmitters that interact with ENS neurons. Some pathogenic bacteria take advantage of the ENS to create a more suitable environment for their growth or to promote the effects of their toxins. In addition, some commensal bacteria can affect the central nervous system (CNS) by locally interacting with the ENS. From the current knowledge emerges an interesting field that may shape future concepts on the pathogen-host synergic interaction. The aim of this narrative review is to report the current findings regarding the inter-relationships between bacteria, viruses, and parasites and the ENS.

[Opportunistic infections by human herpes viruses]

Infections in immunosuppressed patients represent a particular challenge in the diagnostics and treatment. They often present with atypical and particularly severe courses, for which rapid diagnostics and treatment are decisive for treatment success. Opportunistic infections with human herpes viruses occur not only more frequently in immunocompromised patients compared to healthy people but also represent a special challenge. In the treatment of immunosuppressed patients, e.g. with human immunodeficiency virus infections and patients with solid organ transplantations, infections with herpes simplex virus, varicella zoster virus, Epstein-Barr virus and cytomegalovirus are particularly important. The symtoms are very variable, ranging from asymptomatic detection of viremia to vital life-threatening organ manifestations. This review article describes the most important clinical presentations of these opportunistic infections. Furthermore, the diagnostic, therapeutic and prophylactic strategies for human herpes viruses are summarized.

Live Attenuated Zoster Vaccine Boosts Varicella Zoster Virus (VZV)-Specific Humoral Responses Systemically and at the Cervicovaginal Mucosa of Kenyan VZV-Seropositive Women

Background

Attenuated varicella zoster virus (VZV) is a promising vector for recombinant vaccines. Because human immunodeficiencyvirus (HIV) vaccines are believed to require mucosal immunogenicity, we characterized mucosal VZV-specific humoral immunity following VZV_Oka vaccination.

Methods

Adult Kenyan VZV-seropositive women (n = 44) received a single dose of the live zoster VZV_Oka vaccine. The anamnestic responses to the virus were followed longitudinally in both plasma and mucosal secretions using an in-house glycoprotein enzyme-linked immunosorbent assay and safety and reactogenicity monitored. VZV seroprevalence and baseline responses to the virus were also characterized in our cohorts (n = 288).

Results

Besides boosting anti-VZV antibody responses systemically, vaccination also boosted anti-VZV immunity in the cervicovaginal mucosa with a 2.9-fold rise in immunoglobulin G (P < .0001) and 1.6-fold rise in immunoglobulin A (IgA) (P = .004) from the time before immunization and 4 weeks postvaccination. Baseline analysis demonstrated high avidity antibodies at the gastrointestinal and genital mucosa of VZV-seropositive women. Measurement of VZV-specific IgA in saliva is a sensitive tool for detecting prior VZV infection.

Conclusions

VZV_Oka vaccine was safe and immunogenic in VZV-seropositive adult Kenyan women. We provided compelling evidence of VZV ability to induce genital mucosa immunity.

Clinical Trials Registration

NCT02514018.

Modeling Varicella Zoster Virus Persistence and Reactivation - Closer to Resolving a Perplexing Persistent State

The latent state of the human herpesvirus varicella zoster virus (VZV) has remained enigmatic and controversial. While it is well substantiated that VZV persistence is established in neurons after the primary infection (varicella or chickenpox), we know little of the types of neurons harboring latent virus genomes, if all can potentially reactivate, what exactly drives the reactivation process, and the role of immunity in the control of latency. Viral gene expression during latency has been particularly difficult to resolve, although very recent advances indicate that it is more restrictive than was once thought. We do not yet understand how genes expressed in latency function in the maintenance and reactivation processes. Model systems of latency are needed to pursue these questions. This has been especially challenging for VZV because the development of in vivo models of VZV infection has proven difficult. Given that up to one third of the population will clinically reactivate VZV to develop herpes zoster (shingles) and suffer from its common long term problematic sequelae, there is still a need for both in vivo and in vitro model systems. This review will summarize the evolution of models of VZV persistence and address insights that have arisen from the establishment of new in vitro human neuron culture systems that not only harbor a latent state, but permit experimental reactivation and renewed virus production. These models will be discussed in light of the recent data gleaned from the study of VZV latency in human cadaver ganglia.

Current In Vivo Models of Varicella-Zoster Virus Neurotropism

Varicella-zoster virus (VZV), an exclusively human herpesvirus, causes chickenpox and establishes a latent infection in ganglia, reactivating decades later to produce zoster and associated neurological complications. An understanding of VZV neurotropism in humans has long been hampered by the lack of an adequate animal model. For example, experimental inoculation of VZV in small animals including guinea pigs and cotton rats results in the infection of ganglia but not a rash. The severe combined immune deficient human (SCID-hu) model allows the study of VZV neurotropism for human neural sub-populations. Simian varicella virus (SVV) infection of rhesus macaques (RM) closely resembles both human primary VZV infection and reactivation, with analyses at early times after infection providing valuable information about the extent of viral replication and the host immune responses. Indeed, a critical role for CD4 T-cell immunity during acute SVV infection as well as reactivation has emerged based on studies using RM. Herein we discuss the results of efforts from different groups to establish an animal model of VZV neurotropism.

Current In Vitro Models to Study Varicella Zoster Virus Latency and Reactivation

Varicella zoster virus (VZV) is a highly prevalent human pathogen that causes varicella (chicken pox) during primary infection and establishes latency in peripheral neurons. Symptomatic reactivation often presents as zoster (shingles), but it has also been linked to life-threatening diseases such as encephalitis, vasculopathy and meningitis. Zoster may be followed by postherpetic neuralgia, neuropathic pain lasting after resolution of the rash. The mechanisms of varicella zoster virus (VZV) latency and reactivation are not well characterized. This is in part due to the human-specific nature of VZV that precludes the use of most animal and animal-derived neuronal models. Recently, in vitro models of VZV latency and reactivation using human neurons derived from stem cells have been established facilitating an understanding of the mechanisms leading to VZV latency and reactivation. From the models, c-Jun N-terminal kinase (JNK), phosphoinositide 3-kinase (PI3K) and nerve growth factor (NGF) have all been implicated as potential modulators of VZV latency/reactivation. Additionally, it was shown that the vaccine-strain of VZV is impaired for reactivation. These models may also aid in the generation of prophylactic and therapeutic strategies to treat VZV-associated pathologies. This review summarizes and analyzes the current human neuronal models used to study VZV latency and reactivation, and provides some strategies for their improvement.

Varicella Virus-Host Interactions During Latency and Reactivation: Lessons From Simian Varicella Virus

Varicella zoster virus (VZV) is a neurotropic alphaherpesvirus and the causative agent of varicella (chickenpox) in humans. Following primary infection, VZV establishes latency in the sensory ganglia and can reactivate to cause herpes zoster, more commonly known as shingles, which causes significant morbidity, and on rare occasions mortality, in the elderly. Because VZV infection is highly restricted to humans, the development of a reliable animal model has been challenging, and our understanding of VZV pathogenesis remains incomplete. As an alternative, infection of rhesus macaques with the homologous simian varicella virus (SVV) recapitulates the hallmarks of VZV infection and thus constitutes a robust animal model to provide critical insights into VZV pathogenesis and the host antiviral response. In this model, SVV infection results in the development of varicella during primary infection, generation of an adaptive immune response, establishment of latency in the sensory ganglia, and viral reactivation upon immune suppression. In this review, we discuss our current knowledge about host and viral factors involved in the establishment of SVV latency and reactivation as well as the important role played by T cells in SVV pathogenesis and antiviral immunity.

Varicella-Zoster Virus and the Enteric Nervous System

Varicella zoster virus (VZV) infects and becomes latent in sensory, enteric, and other autonomic neurons during the viremia of varicella. Reactivation of VZV in neurons that project to the skin causes the rash of zoster; however, reactivation of VZV in enteric neurons can cause a painful gastrointestinal disorder ("enteric zoster") without cutaneous manifestations. Detection of VZV DNA in saliva of patients with gastrointestinal symptoms may suggest enteric zoster. This diagnosis is reinforced by observing a response to antiviral therapy and can be confirmed by detecting VZV gene products in intestinal mucosal biopsies. We developed an in vivo guinea pig model that may be useful in studies of VZV latency and reactivation. VZV-infected lymphocytes are used to induce latent infection in sensory and enteric neurons; evidence suggests that exosomes and stimulator of interferon genes (STING) may, by preventing proliferation play roles in the establishment of neuronal latency.

Molecular Aspects of Varicella-Zoster Virus Latency

Primary varicella-zoster virus (VZV) infection causes varicella (chickenpox) and the establishment of a lifelong latent infection in ganglionic neurons. VZV reactivates in about one-third of infected individuals to cause herpes zoster, often accompanied by neurological complications. The restricted host range of VZV and, until recently, a lack of suitable in vitro models have seriously hampered molecular studies of VZV latency. Nevertheless, recent technological advances facilitated a series of exciting studies that resulted in the discovery of a VZV latency-associated transcript (VLT) and provide novel insights into our understanding of VZV latency and factors that may initiate reactivation. Deducing the function(s) of VLT and the molecular mechanisms involved should now be considered a priority to improve our understanding of factors that govern VZV latency and reactivation. In this review, we summarize the implications of recent discoveries in the VZV latency field from both a virus and host perspective and provide a roadmap for future studies.

Simian Varicella Virus Infects Enteric Neurons and α4β7 Integrin-Expressing Gut-Tropic T-Cells in Nonhuman Primates

The pathogenesis of enteric zoster, a rare debilitating complication of reactivation of latent varicella-zoster virus (VZV) in the enteric nervous system (ENS), is largely unknown. Infection of monkeys with the closely related Varicellovirus simian varicella virus (SVV) mimics VZV disease in humans. In this study, we determined the applicability of the SVV nonhuman primate model to study Varicellovirus infection of the ENS. We confirmed VZV infection of the gut in latently infected adults and demonstrated that SVV DNA was similarly present in gut of monkeys latently infected with SVV using quantitative real-time PCR. In situ analyses showed that enteric neurons expressed SVV open reading frame (ORF) 63 RNA, but not viral nucleocapsid proteins, suggestive of latent ENS infection. During primary infection, SVV-infected T-cells were detected in gut-draining mesenteric lymph nodes and located in close vicinity to enteric nerves in the gut. Furthermore, flow cytometric analysis of blood from acutely SVV-infected monkeys demonstrated that virus-infected T-cells expressed the gut-homing receptor α4β7 integrin. Collectively, the data demonstrate that SVV infects ENS neurons during primary infection and supports the role of T-cells in virus dissemination to the gut. Because SVV reactivation can be experimentally induced, the SVV nonhuman primate model holds great potential to study the pathogenesis of enteric zoster.

Protocol of a randomised controlled trial characterising the immune responses induced by varicella-zoster virus (VZV) vaccination in healthy Kenyan women: setting the stage for a potential VZV-based HIV vaccine

INTRODUCTION

A protective HIV vaccine would be expected to induce durable effector immune responses at the mucosa, restricting HIV infection at its portal of entry. We hypothesise that use of varicella-zoster virus (VZV) as an HIV delivery vector could generate sustained and robust tissue-based immunity against HIV antigens to provide long-term protection against HIV. Given that HIV uniquely targets immune-activated T cells, the development of human vaccines against HIV must also involve a specific examination of the safety of the vector. Thus, we aim to evaluate the effects of VZV vaccination on the recipients' immune activation state, and on VZV-specific circulating humoral and cellular responses in addition to those at the cervical and rectal mucosa.

METHODS AND ANALYSIS

This open-label, randomised, longitudinal crossover study includes healthy Kenyan VZV-seropositive women at low risk for HIV infection. Participants receive a single dose of a commercial live-attenuated VZV_Oka vaccine at either week 0 (n=22) or at week 12 (n=22) of the study and are followed for 48 and 36 weeks postvaccination, respectively. The primary outcome is the change on cervical CD4⁺ T-cell immune activation measured by the coexpression of CD38 and HLA-DR 12 weeks postvaccination compared with the baseline (prevaccination). Secondary analyses include postvaccination changes in VZV-specific mucosal and systemic humoral and cellular immune responses, changes in cytokine and chemokine measures, study acceptability and feasibility of mucosal sampling and a longitudinal assessment of the bacterial community composition of the mucosa.

ETHICS AND DISSEMINATION

The study has ethical approval from Kenyatta National Hospital/University of Nairobi Ethics and Research Committee, the University of Toronto Research Ethics Board and by Kenyan Pharmacy and Poisons Board. Results will be presented at conferences, disseminated to participants and stakeholders as well as published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT02514018. Pre-results.

Is chickenpox so bad, what do we know about immunity to varicella zoster virus, and what does it tell us about the future?

Varicella and zoster continue to cause significant morbidity and even mortality in children and adults. Complications include bacterial superinfection, central nervous system manifestations such as meningitis, encephalitis, and cerebellar ataxia, and pain syndromes especially post herpetic neuralgia. Many developed countries but not all, are now administering live attenuated varicella vaccine routinely, with a decrease in the incidence of disease, providing personal and herd immunity. There is some controversy, however, in some countries concerning whether a decrease in the circulation of wild type virus will result in loss of immunity to VZV in persons who have already had varicella. This manuscript reviews the complications of varicella and zoster in detail, the reasons for development of vaccines against these diseases, complications of vaccinations, and mechanisms by which immunity to this virus develops and is maintained. There are strong indications that the best way to control disease and spread of this virus is by vaccination against both.

Varicella zoster virus infection

Infection with varicella zoster virus (VZV) causes varicella (chickenpox), which can be severe in immunocompromised individuals, infants and adults. Primary infection is followed by latency in ganglionic neurons. During this period, no virus particles are produced and no obvious neuronal damage occurs. Reactivation of the virus leads to virus replication, which causes zoster (shingles) in tissues innervated by the involved neurons, inflammation and cell death - a process that can lead to persistent radicular pain (postherpetic neuralgia). The pathogenesis of postherpetic neuralgia is unknown and it is difficult to treat. Furthermore, other zoster complications can develop, including myelitis, cranial nerve palsies, meningitis, stroke (vasculopathy), retinitis, and gastroenterological infections such as ulcers, pancreatitis and hepatitis. VZV is the only human herpesvirus for which highly effective vaccines are available. After varicella or vaccination, both wild-type and vaccine-type VZV establish latency, and long-term immunity to varicella develops. However, immunity does not protect against reactivation. Thus, two vaccines are used: one to prevent varicella and one to prevent zoster. In this Primer we discuss the pathogenesis, diagnosis, treatment, and prevention of VZV infections, with an emphasis on the molecular events that regulate these diseases. For an illustrated summary of this Primer, visit: http://go.nature.com/14xVI1.

An in vitro model of latency and reactivation of varicella zoster virus in human stem cell-derived neurons

Varicella zoster virus (VZV) latency in sensory and autonomic neurons has remained enigmatic and difficult to study, and experimental reactivation has not yet been achieved. We have previously shown that human embryonic stem cell (hESC)-derived neurons are permissive to a productive and spreading VZV infection. We now demonstrate that hESC-derived neurons can also host a persistent non-productive infection lasting for weeks which can subsequently be reactivated by multiple experimental stimuli. Quiescent infections were established by exposing neurons to low titer cell-free VZV either by using acyclovir or by infection of axons in compartmented microfluidic chambers without acyclovir. VZV DNA and low levels of viral transcription were detectable by qPCR for up to seven weeks. Quiescently-infected human neuronal cultures were induced to undergo renewed viral gene and protein expression by growth factor removal or by inhibition of PI3-Kinase activity. Strikingly, incubation of cultures induced to reactivate at a lower temperature (34°C) resulted in enhanced VZV reactivation, resulting in spreading, productive infections. Comparison of VZV genome transcription in quiescently-infected to productively-infected neurons using RNASeq revealed preferential transcription from specific genome regions, especially the duplicated regions. These experiments establish a powerful new system for modeling the VZV latent state, and reveal a potential role for temperature in VZV reactivation and disease.

Most adults worldwide harbor latent VZV in their ganglia, and reactivation from it causes herpes zoster. This painful disease is frequently complicated by long-term pain, neurological sequelae, or vision loss that require improved prevention and treatment strategies. Study of VZV latency and reactivation has been severely hampered by the inability to reproduce a persistent state in vitro or in vivo that can be experimentally reactivated. Our study establishes a system using human neurons derived from embryonic stem cells where multiple stimuli can induce reactivation from long term experimental latency. A potential role for temperature in VZV reactivation has been revealed with this system, which can now be used to study the latent/lytic switch of VZV for the first time.

Denervation suppresses gastric tumorigenesis

The nervous system plays an important role in the regulation of epithelial homeostasis and has also been postulated to play a role in tumorigenesis. We provide evidence that proper innervation is critical at all stages of gastric tumorigenesis. In three separate mouse models of gastric cancer, surgical or pharmacological denervation of the stomach (bilateral or unilateral truncal vagotomy, or local injection of botulinum toxin type A) markedly reduced tumor incidence and progression, but only in the denervated portion of the stomach. Vagotomy or botulinum toxin type A treatment also enhanced the therapeutic effects of systemic chemotherapy and prolonged survival. Denervation-induced suppression of tumorigenesis was associated with inhibition of Wnt signaling and suppression of stem cell expansion. In gastric organoid cultures, neurons stimulated growth in a Wnt-mediated fashion through cholinergic signaling. Furthermore, pharmacological inhibition or genetic knockout of the muscarinic acetylcholine M3 receptor suppressed gastric tumorigenesis. In gastric cancer patients, tumor stage correlated with neural density and activated Wnt signaling, whereas vagotomy reduced the risk of gastric cancer. Together, our findings suggest that vagal innervation contributes to gastric tumorigenesis via M3 receptor-mediated Wnt signaling in the stem cells, and that denervation might represent a feasible strategy for the control of gastric cancer.

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.

A comparison of herpes simplex virus type 1 and varicella-zoster virus latency and reactivation

Herpes simplex virus type 1 (HSV-1; human herpesvirus 1) and varicella-zoster virus (VZV; human herpesvirus 3) are human neurotropic alphaherpesviruses that cause lifelong infections in ganglia. Following primary infection and establishment of latency, HSV-1 reactivation typically results in herpes labialis (cold sores), but can occur frequently elsewhere on the body at the site of primary infection (e.g. whitlow), particularly at the genitals. Rarely, HSV-1 reactivation can cause encephalitis; however, a third of the cases of HSV-1 encephalitis are associated with HSV-1 primary infection. Primary VZV infection causes varicella (chickenpox) following which latent virus may reactivate decades later to produce herpes zoster (shingles), as well as an increasingly recognized number of subacute, acute and chronic neurological conditions. Following primary infection, both viruses establish a latent infection in neuronal cells in human peripheral ganglia. However, the detailed mechanisms of viral latency and reactivation have yet to be unravelled. In both cases latent viral DNA exists in an 'end-less' state where the ends of the virus genome are joined to form structures consistent with unit length episomes and concatemers, from which viral gene transcription is restricted. In latently infected ganglia, the most abundantly detected HSV-1 RNAs are the spliced products originating from the primary latency associated transcript (LAT). This primary LAT is an 8.3 kb unstable transcript from which two stable (1.5 and 2.0 kb) introns are spliced. Transcripts mapping to 12 VZV genes have been detected in human ganglia removed at autopsy; however, it is difficult to ascribe these as transcripts present during latent infection as early-stage virus reactivation may have transpired in the post-mortem time period in the ganglia. Nonetheless, low-level transcription of VZV ORF63 has been repeatedly detected in multiple ganglia removed as close to death as possible. There is increasing evidence that HSV-1 and VZV latency is epigenetically regulated. In vitro models that permit pathway analysis and identification of both epigenetic modulations and global transcriptional mechanisms of HSV-1 and VZV latency hold much promise for our future understanding in this complex area. This review summarizes the molecular biology of HSV-1 and VZV latency and reactivation, and also presents future directions for study.

Infected peripheral blood mononuclear cells transmit latent varicella zoster virus infection to the guinea pig enteric nervous system

Latent wild-type (WT) and vaccine (vOka) varicella zoster virus (VZV) are found in the human enteric nervous system (ENS). VZV also infects guinea pig enteric neurons in vitro, establishes latency and can be reactivated. We therefore determined whether lymphocytes infected in vitro with VZV secrete infectious virions and can transfer infection in vivo to the ENS of recipient guinea pigs. T lymphocytes (CD3-immunoreactive) were preferentially infected following co-culture of guinea pig or human peripheral blood mononuclear cells with VZV-infected HELF. VZV proliferated in the infected T cells and expressed immediate early and late VZV genes. Electron microscopy confirmed that VZV-infected T cells produced encapsulated virions. Extracellular virus, however, was pleomorphic, suggesting degradation occurred prior to release, which was confirmed by the failure of VZV-infected T cells to secrete infectious virions. Intravenous injection of WT- or vOka-infected PBMCs, nevertheless, transmitted VZV to recipient animals (guinea pig > human lymphocytes). Two days post-inoculation, lung and liver, but not gut, contained DNA and transcripts encoding ORFs 4, 40, 66 and 67. Twenty-eight days after infection, gut contained DNA and transcripts encoding ORFs 4 and 66 but neither DNA nor transcripts could any longer be found in lung or liver. In situ hybridization revealed VZV DNA in enteric neurons, which also expressed ORF63p (but not ORF68p) immunoreactivity. Observations suggest that VZV infects T cells, which can transfer VZV to and establish latency in enteric neurons in vivo. Guinea pigs may be useful for studies of VZV pathogenesis in the ENS.

Varicella-zoster virus (VZV) infection as a possible cause of Ogilvie's syndrome in an immunocompromised host

We describe an immunodeficient adult with Ogilvie's syndrome preceding a disseminated papulovesicular skin rash in whom varicella-zoster virus infection was demonstrated by PCR assay in cutaneous and colonic biopsy specimens. In view of the significant morbidity and mortality that this condition carries, early and accurate molecular diagnosis and timely treatment are strongly recommended.

Pathogenesis and current approaches to control of varicella-zoster virus infections

Varicella-zoster virus (VZV) was once thought to be a fairly innocuous pathogen. That view is no longer tenable. The morbidity and mortality due to the primary and secondary diseases that VZV causes, varicella and herpes zoster (HZ), are significant. Fortunately, modern advances, including an available vaccine to prevent varicella, a therapeutic vaccine to diminish the incidence and ameliorate sequelae of HZ, effective antiviral drugs, a better understanding of VZV pathogenesis, and advances in diagnostic virology have made it possible to control VZV in the United States. Occult forms of VZV-induced disease have been recognized, including zoster sine herpete and enteric zoster, which have expanded the field. Future progress should include development of more effective vaccines to prevent HZ and a more complete understanding of the consequences of VZV latency in the enteric nervous system.

Adenosine-mediated enteric neuromuscular function is affected during herpes simplex virus type 1 infection of rat enteric nervous system

Adenosine plays an important role in regulating intestinal motility and inflammatory processes. Previous studies in rodent models have demonstrated that adenosine metabolism and signalling are altered during chronic intestinal inflammatory diseases. However, the involvement of the adenosinergic system in the pathophysiology of gut dysmotility associated to a primary neurodysfunction is still unclear. Recently, we showed that the neurotropic Herpes simplex virus type-1 (HSV-1), orally inoculated to rodents, infects the rat enteric nervous system (ENS) and affects gut motor function without signs of systemic infection. In this study we examined whether changes in purinergic metabolism and signaling occur during permanent HSV-1 infection of rat ENS. Using isolated organ bath assays, we found that contraction mediated by adenosine engagement of A₁ or A_2A receptors was impaired at 1 and 6 weeks post-viral administration. Immunofluorescence studies revealed that viral infection of ENS led to a marked redistribution of adenosine receptors: A₁ and A_2B receptors were confined to the muscle layers whereas A_2A and A₃ receptors were expressed mainly in the myenteric plexus. Viral-induced ENS neurodysfunction influenced adenosine metabolism by increasing adenosine deaminase and CD73 levels in longitudinal muscle-myenteric plexus with no sign of frank inflammation. This study provides the first evidence for involvement of the adenosinergic system during HSV-1 infection of the ENS. As such, this may represent a valid therapeutic target for modulating gut contractility associated to a primary neurodysfunction.

An in-vitro preparation of isolated enteric neurons and glia from the myenteric plexus of the adult mouse

The enteric nervous system is a vast network of neurons and glia running the length of the gastrointestinal tract that functionally controls gastrointestinal motility. A procedure for the isolation and culture of a mixed population of neurons and glia from the myenteric plexus is described. The primary cultures can be maintained for over 7 days, with connections developing among the neurons and glia. The longitudinal muscle strip with the attached myenteric plexus is stripped from the underlying circular muscle of the mouse ileum or colon and subjected to enzymatic digestion. In sterile conditions, the isolated neuronal and glia population are preserved within the pellet following centrifugation and plated on coverslips. Within 24-48 hr, neurite outgrowth occurs and neurons can be identified by pan-neuronal markers. After two days in culture, isolated neurons fire action potentials as observed by patch clamp studies. Furthermore, enteric glia can also be identified by GFAP staining. A network of neurons and glia in close apposition forms within 5-7 days. Enteric neurons can be individually and directly studied using methods such as immunohistochemistry, electrophysiology, calcium imaging, and single-cell PCR. Furthermore, this procedure can be performed in genetically modified animals. This methodology is simple to perform and inexpensive. Overall, this protocol exposes the components of the enteric nervous system in an easily manipulated manner so that we may better discover the functionality of the ENS in normal and disease states.

Productive vs non-productive infection by cell-free varicella zoster virus of human neurons derived from embryonic stem cells is dependent upon infectious viral dose

Varicella Zoster virus (VZV) productively infects humans causing varicella upon primary infection and herpes zoster upon reactivation from latency in neurons. In vitro studies using cell-associated VZV infection have demonstrated productive VZV-infection, while a few recent studies of human neurons derived from stem cells incubated with cell-free, vaccine-derived VZV did not result in generation of infectious virus. In the present study, 90%-pure human embryonic stem cell-derived neurons were incubated with recombinant cell-free pOka-derived virus made with an improved method or VZV vaccine. We found that cell-free pOka and vOka at higher multiplicities of infection elicited productive infection in neurons followed by spread of infection, cytopathic effect and release of infectious virus into the medium. These results further validate the use of this unlimited source of human neurons for studying unexplored aspects of VZV interaction with neurons such as entry, latency and reactivation.

Human sensory neurons derived from induced pluripotent stem cells support varicella-zoster virus infection

After primary infection, varicella-zoster virus (VZV) establishes latency in neurons of the dorsal root and trigeminal ganglia. Many questions concerning the mechanism of VZV pathogenesis remain unanswered, due in part to the strict host tropism and inconsistent availability of human tissue obtained from autopsies and abortions. The recent development of induced pluripotent stem (iPS) cells provides great potential for the study of many diseases. We previously generated human iPS cells from skin fibroblasts by introducing four reprogramming genes with non-integrating adenovirus. In this study, we developed a novel protocol to generate sensory neurons from iPS cells. Human iPS cells were exposed to small molecule inhibitors for 10 days, which efficiently converted pluripotent cells into neural progenitor cells (NPCs). The NPCs were then exposed for two weeks to growth factors required for their conversion to sensory neurons. The iPS cell-derived sensory neurons were characterized by immunocytochemistry, flow cytometry, RT-qPCR, and electrophysiology. After differentiation, approximately 80% of the total cell population expressed the neuron-specific protein, βIII-tubulin. Importantly, 15% of the total cell population co-expressed the markers Brn3a and peripherin, indicating that these cells are sensory neurons. These sensory neurons could be infected by both VZV and herpes simplex virus (HSV), a related alphaherpesvirus. Since limited neuronal populations are capable of supporting the entire VZV and HSV life cycles, our iPS-derived sensory neuron model may prove useful for studying alphaherpesvirus latency and reactivation.

Gastric ulcers due to varicella-zoster reactivation

We report on an 18-year-old man with common variable immunodeficiency presenting with abdominal pain and vomiting due to gastric ulcers caused by reactivation of varicella-zoster virus (VZV). Endoscopy revealed multiple ulcers in the gastric antrum. Fever and rash developed the next day. Skin biopsy showed multinucleated cells with intranuclear inclusions highly suggestive of VZV infection, and high-dose intravenous acyclovir was started. VZV was detected on direct immunofluorescence from skin biopsy and polymerase chain reaction from endoscopic biopsy. His course was complicated by encephalopathy, pancreatitis, hepatitis, renal impairment, and hyponatremia. After 3 weeks of antiviral therapy, he gradually improved. Skin lesions cleared within a week. He remained well on follow-up 1 year later. Disseminated zoster presenting as gastric ulcers in the absence of the classic rash is unusual but has been reported in immunosuppressed patients with a history of bone marrow and stem cell transplant. We report this rare presentation in a patient with common variable immunodeficiency and highlight the importance of considering zoster as a cause for severe abdominal pain and of seeking endoscopic diagnosis to facilitate early therapy and reduced mortality risk.

Herpes simplex virus and varicella zoster virus, the house guests who never leave

Human alphaherpesviruses including herpes simplex viruses (HSV-1, HSV-2) and varicella zoster virus (VZV) establish persistent latent infection in sensory neurons for the life of the host. All three viruses have the potential to reactivate causing recurrent disease. Regardless of the homology between the different virus strains, the three viruses are characterized by varying pathologies. This review will highlight the differences in infection pattern, immune response, and pathogenesis associated with HSV-1 and VZV.

Varicella zoster virus (VZV) infects and establishes latency in enteric neurons

Case reports have linked varicella-zoster virus (VZV) to gastrointestinal disorders, including severe abdominal pain preceding fatal varicella and acute colonic pseudoobstruction (Ogilvie's syndrome). Because we had previously detected DNA and transcripts encoding latency-associated VZV gene products in the human gut, we sought to determine whether latent VZV is present in the human enteric nervous system (ENS) and, if so, to identify the cells in which it is located and its route to the bowel. Neither DNA, nor transcripts encoding VZV gene products, could be detected in resected gut from any of seven control children (<1 year old) who had not received the varicella vaccine or experienced varicella; however, VZV DNA and transcripts were each found to be present in resected bowel from 6/6 of children with a past history of varicella and in that of 6/7 of children who received the varicella vaccine. Both wild-type (WT) and vaccine-type (vOka) VZV thus establish latent infection in human gut. To determine routes by which VZV might gain access to the bowel, we injected guinea pigs with human or guinea pig lymphocytes expressing green fluorescent protein (GFP) under the control of the VZV ORF66 gene (VZV(OKA66.GFP)). GFP-expressing enteric neurons were found throughout the bowel within 2 days and continued to be present for greater than 6 weeks. DNA encoding VZV gene products also appeared in enteric and dorsal root ganglion (DRG) neurons following intradermal administration of WT-VZV and in enteric neurons after intradermal injection of VZV(OKA66.GFP); moreover, a small number of guinea pig DRG neurons were found to project both to the skin and the intraperitoneal viscera. Viremia, in which lymphocytes carry VZV, or axonal transport from DRG neurons infected through their epidermal projections are thus each potential routes that enable VZV to gain access to the ENS.

[Varicella-zoster virus (VZV)]

Varicella-zoster virus (VZV) causes varicella in primary infection and zoster after reactivation from latency. Both herpes simplex virus (HSV) and VZV are classified into the same alpha-herpesvirus subfamily. Although most VZV genes have their HSV homologs, VZV has many unique biological characteristics. In this review, we summarized recent studies on 1) animal models for VZV infection and outcomes from studies using the models, including 2) viral dissemination processes from respiratory mucosa, T cells, to skin, 3) cellular receptors for VZV entry, 4) functions of viral genes required uniquely for in vivo growth and for establishment of latency, 5) host immune responses and viral immune evasion mechanisms, and 6) varicella vaccine and anti-VZV drugs.

Varicella-zoster virus (VZV) infection of neurons derived from human embryonic stem cells: direct demonstration of axonal infection, transport of VZV, and productive neuronal infection

Study of the human neurotrophic herpesvirus varicella-zoster virus (VZV) and of its ability to infect neurons has been severely limited by strict viral human tropism and limited availability of human neurons for experimentation. Human embryonic stem cells (hESC) can be differentiated to all the cell types of the body including neurons and are therefore a potentially unlimited source of human neurons to study their interactions with human neurotropic viruses. We report here reproducible infection of hESC-derived neurons by cell-associated green fluorescent protein (GFP)-expressing VZV. hESC-derived neurons expressed GFP within 2 days after incubation with mitotically inhibited MeWo cells infected with recombinant VZV expressing GFP as GFP fusions to VZV proteins or under an independent promoter. VZV infection was confirmed by immunostaining for immediate-early and viral capsid proteins. Infection of hESC-derived neurons was productive, resulting in release into the medium of infectious virions that appeared fully assembled when observed by electron microscopy. We also demonstrated, for the first time, VZV infection of axons and retrograde transport from axons to neuronal cell bodies using compartmented microfluidic chambers. The use of hESC-derived human neurons in conjunction with fluorescently tagged VZV shows great promise for the study of VZV neuronal infection and axonal transport and has potential for the establishment of a model for VZV latency in human neurons.

Varicella-zoster virus infection of differentiated human neural stem cells

Primary varicella-zoster virus (VZV) infection in humans produces varicella (chickenpox), after which the virus becomes latent in ganglionic neurons. Analysis of the physical state of viral nucleic acid and virus gene expression during latency requires postmortem acquisition of fresh human ganglia. To provide an additional way to study the VZV-host relationship in neurons, we developed an in vitro model of infected differentiated human neural stem cells (NSCs). NSCs were induced to differentiate in culture dishes coated with poly-l-lysine and mouse laminin in the presence of fibroblast growth factor 2 (FGF-2), nerve growth factor (NGF), brain-derived neurotropic factor (BDNF), dibutyryl cyclic AMP, and retinoic acid. Immunostaining with neuronal (MAP2a and β-tubulin), astrocyte (GFAP), and oligodendrocyte (CNPase) markers revealed that differentiated neurons constituted approximately 90% of the cell population. These neurons were maintained in culture for up to 8 weeks. No cytopathic effect (CPE) developed in neurons infected with cell-free VZV (Zostavax vaccine) compared to human fetal lung fibroblasts infected with VZV. Weeks later, VZV DNA virus-specific transcripts (open reading frames [ORFs] 21, 29, 62, and 63) were detected in infected neurons, and dual immunofluorescence staining revealed the presence of VZV IE63 and gE exclusively in healthy-appearing neurons, but not in astrocytes. Neither the tissue culture medium nor a homogenate prepared from VZV-infected neurons produced a CPE in fibroblasts. VZV induced apoptosis in fibroblasts, as shown by activation of caspase 3 and by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) staining, but not in neurons. This model provides a unique in vitro system to study the VZV-neuronal relationship.

Perspectives on vaccines against varicella-zoster virus infections

Primary infection with varicella-zoster virus (VZV) results in varicella which, in populations where immunization is not used, occurs mostly in children. Varicella is a generalized rash illness with systemic features such as fever and malaise. During varicella, VZV becomes latent in sensory ganglia of the individual, and in 70% it remains asymptomatic for their lifetime. The remaining 30% develop reactivation from latency, resulting in herpes zoster (HZ). HZ usually occurs in persons over the age of 50, and is manifested by a painful unilateral rash that usually lasts about 2 weeks and then may be followed by a chronic pain syndrome called post-herpetic neuralgia (PHN). VZV infections are notoriously more severe in immunocompromised hosts than in healthy individuals. Despite gaps in our understanding of the details of immunity to VZV, successful vaccines have been developed against both varicella and zoster.

Experimental models to study varicella-zoster virus infection of neurons

Varicella zoster virus (VZV) infection results in the establishment of latency in human sensory neurons. Reactivation of VZV leads to herpes zoster which can be followed by persistent neuropathic pain, termed post-herpetic neuralgia (PHN). Humans are the only natural host for VZV, and the strict species specificity of the virus has restricted the development of an animal model of infection which mimics all phases of disease. In order to elucidate the mechanisms which control the establishment of latency and reactivation as well as the effect of VZV replication on neuronal function, in vitro models of neuronal infection have been developed. Currently these models involve culturing and infecting dissociated human fetal neurons, with or without their supporting cells, an intact explant fetal dorsal root ganglia (DRG) model, neuroblastoma cell lines and rodent neuronal cell models. Each of these models has distinct advantages as well as disadvantages, and all have contributed towards our understanding of VZV neuronal infection. However, as yet none have been able to recapitulate the full virus lifecycle from primary infection to latency through to reactivation. The development of such a model will be a crucial step towards advancing our understanding of the mechanisms involved in VZV replication in neuronal cells, and the design of new therapies to combat VZV-related disease.

Effectiveness of varicella vaccine in children infected with HIV

Although varicella vaccine is given to clinically stable human immunodeficiency virus (HIV)-infected children, its effectiveness is unknown. We assessed its effectiveness by reviewing the medical records of closely monitored HIV-infected children, including those receiving highly active antiretroviral therapy (HAART) between 1989 and 2007. Varicella immunization and development of varicella or herpes zoster were noted. Effectiveness was calculated by subtracting from 1 the rate ratios for the incidence rates of varicella or herpes zoster in vaccinated versus unvaccinated children. The effectiveness of the vaccine was 82% (95% confidence interval [CI], 24%-99%; P = .01) against varicella and was 100% (95% CI, 67%-100%; P < .001) against herpes zoster. When the analysis was controlled for receipt of HAART, vaccination remained highly protective against herpes zoster.

Advances in the understanding of the pathogenesis and epidemiology of herpes zoster

The primary varicella zoster virus (VZV) infection results in chickenpox (varicella), which is transmitted via the airborne route. VZV is highly infectious, but in the USA the incidence of varicella has been reduced by 76-87% as a result of the varicella vaccine. The virus establishes latency in the dorsal root ganglia during varicella and, when reactivated, travels along the sensory nerve axons to cause shingles (herpes zoster [HZ]). There are over 1 million cases of HZ in the USA each year, with an estimated lifetime attack rate of 30%. The incidence of HZ, which causes significant morbidity, increases with age and reaches approximately 10 cases per 1,000 patient-years by age 80. Cell-mediated immunity (CMI) is known to decline with age as part of immunosenescence, and decreased CMI is associated with reactivation of VZV. This article provides an overview of our emerging understanding of the epidemiology and pathogenesis of varicella and HZ, in addition to exploring the current theories on latency and reactivation. Understanding the risk factors for developing HZ and the complications associated with infection, particularly in older people, is important for prompt diagnosis and management of HZ in primary care, and they are therefore also reviewed.

Herpes simplex virus type 1 infection of the rat enteric nervous system evokes small-bowel neuromuscular abnormalities

BACKGROUND & AIMS

Infectious agents, such as neurotropic viruses, are proposed to disrupt the enteric neuromuscular system, leading to dysmotility, although the mechanisms are unknown. Our purpose was to assess whether herpes simplex virus type-1 (HSV-1) establishes an enteric-neuronal infection and induces gut dysmotility.

METHODS

Rats were inoculated with HSV-1 intranasally and after 4 weeks intragastrically. After 1-10 weeks, infection was determined by molecular analysis whereas neuromuscular function was evaluated by pharmacologic/electrical stimulation of longitudinal ileal segments and by gastrointestinal transit and by [(3)H]acetylcholine release measurements. Inflammation in the neuromuscular layer was assessed by myeloperoxidase and cytokine levels and by anti-CD3(+) immunohistochemistry.

RESULTS

After 1-10 weeks of intragastric inoculation, HSV-1 latency-associated messenger RNA transcripts were detected in the brain and in ileal neurons with no signs of illness or histologic gut abnormalities. By using a recombinant HSV-1 carrying the lacZ gene, HSV-1 virions were localized in myenteric ganglia by in situ X-gal staining. Interleukin-2 and IFN-gamma levels were increased significantly 1 and 6 weeks after inoculation. CD3(+) cells were found around the myenteric ganglia 6 weeks after inoculation. Smooth muscle responses to carbachol, CaCl(2), and gut transit were increased significantly after 1 and 6 weeks, whereas KCl- and electrical field stimulation-mediated contractions were modified significantly only 1-2 weeks after HSV-1 administration. The release of [(3)H]acetylcholine was reduced significantly in ileum segments after 1 and 6 weeks.

CONCLUSIONS

After intragastric inoculation, HSV-1 establishes a latent infection in the rat myenteric ganglia, which leads to gut dysmotility.

VZV infection of keratinocytes: production of cell-free infectious virions in vivo

Varicella-zoster virus (VZV) is the cause of varicella (chickenpox) and zoster (shingles). Varicella is a primary infection that spreads rapidly in epidemics while zoster is a secondary infection that occurs sporadically as a result of the reactivation of previously acquired VZV. Reactivation is made possible by the establishment of latency during the initial episode of varicella. The signature lesions of both varicella and zoster are cutaneous vesicles, which are filled with a clear fluid that is rich in infectious viral particles. It has been postulated that the skin is the critical organ in which both host-to-host transmission of VZV and the infection of neurons to establish latency occur. This hypothesis is built on evidence that the large cation-independent mannose 6-phosphate receptor (MPR(ci)) interacts with VZV in virtually all infected cells, except those of the suprabasal epidermis, in a way that prevents the release of infectious viral particles. Specifically, the virus is diverted in an MPR(ci)-dependent manner from the secretory pathway to late endosomes where VZV is degraded. Because nonepidermal cells are thus prevented from releasing infectious VZV, a slow process, possibly involving fusion of infected cells with their neighbors, becomes the means by which VZV is disseminated. In the epidermis, however, the maturation of keratinocytes to give rise to corneocytes in the suprabasal epidermis is associated uniquely with a downregulation of the MPR(ci). As a result, the diversion of VZV to late endosomes does not occur in the suprabasal epidermis where vesicular lesions occur. The formation of the waterproof, chemically resistant barrier of the epidermis, however, requires that constitutive secretion outlast the downregulation of the endosomal pathway. Infectious VZV is therefore secreted by default, accounting for the presence of infectious virions in vesicular fluid. Sloughing of corneocytes, aided by scratching, then aerosolizes the virus, which can float with dust to be inhaled by susceptible hosts. Infectious virions also bathe the terminals of those sensory neurons that innervate the epidermis. These terminals become infected with VZV and provide a route, retrograde transport, which can conduct VZV to cranial nerve (CNG), dorsal root ganglia (DRG), and enteric ganglia (EG) to establish latency. Reactivation returns VZV to the skin, now via anterograde transport in axons, to cause the lesions of zoster. Evidence in support of these hypotheses includes observations of the VZV-infected human epidermis and studies of guinea pig neurons in an in vitro model system.

Varicella vaccination in Europe - taking the practical approach

Varicella is a common viral disease affecting almost the entire birth cohort. Although usually self-limiting, some cases of varicella can be serious, with 2 to 6% of cases attending a general practice resulting in complications. The hospitalisation rate for varicella in Europe ranges from 1.3 to 4.5 per 100,000 population/year and up to 10.1% of hospitalised patients report permanent or possible permanent sequelae (for example, scarring or ataxia). However, in many countries the epidemiology of varicella remains largely unknown or incomplete. In countries where routine childhood vaccination against varicella has been implemented, it has had a positive effect on disease prevention and control. Furthermore, mathematical models indicate that this intervention strategy may provide economic benefits for the individual and society. Despite this evidence and recommendations for varicella vaccination by official bodies such as the World Health Organization, and scientific experts in the field, the majority of European countries (with the exception of Germany and Greece) have delayed decisions on implementation of routine childhood varicella vaccination, choosing instead to vaccinate high-risk groups or not to vaccinate at all. In this paper, members of the Working Against Varicella in Europe group consider the practicalities of introducing routine childhood varicella vaccination in Europe, discussing the benefits and challenges of different vaccination options (vaccination vs. no vaccination, routine vaccination of infants vs. vaccination of susceptible adolescents or adults, two doses vs. one dose of varicella vaccine, monovalent varicella vaccines vs. tetravalent measles, mumps, rubella and varicella vaccines, as well as the optimal interval between two doses of measles, mumps, rubella and varicella vaccines). Assessment of the epidemiology of varicella in Europe and evidence for the effectiveness of varicella vaccination provides support for routine childhood programmes in Europe. Although European countries are faced with challenges or uncertainties that may have delayed implementation of a childhood vaccination programme, many of these concerns remain hypothetical and with new opportunities offered by combined measles, mumps, rubella and varicella vaccines, reassessment may be timely.

Varicella-zoster virus immediate-early 63 protein interacts with human antisilencing function 1 protein and alters its ability to bind histones h3.1 and h3.3

Varicella-zoster virus (VZV) immediate-early 63 protein (IE63) is abundantly expressed during both acute infection in vitro and latent infection in human ganglia. Using the yeast two-hybrid system, we found that VZV IE63 interacts with human antisilencing function 1 protein (ASF1). ASF1 is a nucleosome assembly factor which is a member of the H3/H4 family of histone chaperones. IE63 coimmunoprecipitated and colocalized with ASF1 in transfected cells expressing IE63 and in VZV-infected cells. IE63 also colocalized with ASF1 in both lytic and latently VZV-infected enteric neurons. ASF1 exists in two isoforms, ASF1a and ASF1b, in mammalian cells. IE63 preferentially bound to ASF1a, and the amino-terminal 30 amino acids of ASF1a were critical for its interaction with IE63. VZV IE63 amino acids 171 to 208 and putative phosphorylation sites of IE63, both of which are critical for virus replication and latency in rodents, were important for the interaction of IE63 with ASF1. Finally, we found that IE63 increased the binding of ASF1 to histone H3.1 and H3.3, which suggests that IE63 may help to regulate levels of histones in virus-infected cells. Since ASF1 mediates eviction and deposition of histones during transcription, the interaction of VZV IE63 with ASF1 may help to regulate transcription of viral or cellular genes during lytic and/or latent infection.