Review: The neurobiology of varicella zoster virus infection

Immunizations in Pediatric and Adult Patients with Inflammatory Bowel Disease: A Practical Case-based Approach

As the treatment of inflammatory bowel disease (IBD) becomes more complex and increasingly relies on combinations of immunosuppression in patients with moderate to severe ulcerative colitis or Crohn's disease, the provider must be aware of recommendations for the appropriate use of vaccines-both inactivated and live. The timing and type of vaccination required may be altered based on the underlying medical treatment for the IBD. In some instances, titers may be required to assess for vaccine response. Vaccination recommendations have changed dramatically over the past 5 years with direct implications for the protection of the patients with IBD. There are several newly licensed vaccines and new recommendations by the U.S. Advisory Committee on Immunization Practices and Infectious Diseases Society of America defining degrees of immunosuppression and the use of certain live vaccines based on these levels. This review provides a case-based approach to vaccinating the pediatric and adult patients with IBD, with an emphasis on practicality. Case scenarios include children and adults with newly diagnosed and chronic IBD. Recommendations for vaccine management in these scenarios are provided, including special circumstances such as pregnancy and infant vaccinations when the mother is receiving immunosuppressive medication.

Interferon Gamma Prolongs Survival of Varicella-Zoster Virus-Infected Human Neurons In Vitro

Infection of human neurons in vitro with varicella-zoster virus (VZV) at a low multiplicity of infection does not result in a cytopathic effect (CPE) within 14 days postinfection (dpi), despite production of infectious virus. We showed that by 28 dpi a CPE ultimately developed in infected neurons and that interferon gamma inhibited not only the CPE but also VZV DNA accumulation, transcription, and virus production, thereby prolonging the life of VZV-infected neurons.

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.

The number of alphaherpesvirus particles infecting axons and the axonal protein repertoire determines the outcome of neuronal infection

Infection by alphaherpesviruses invariably results in invasion of the peripheral nervous system (PNS) and establishment of either a latent or productive infection. Infection begins with long-distance retrograde transport of viral capsids and tegument proteins in axons toward the neuronal nuclei. Initial steps of axonal entry, retrograde transport, and replication in neuronal nuclei are poorly understood. To better understand how the mode of infection in the PNS is determined, we utilized a compartmented neuron culturing system where distal axons of PNS neurons are physically separated from cell bodies. We infected isolated axons with fluorescent-protein-tagged pseudorabies virus (PRV) particles and monitored viral entry and transport in axons and replication in cell bodies during low and high multiplicities of infection (MOIs of 0.01 to 100). We found a threshold for efficient retrograde transport in axons between MOIs of 1 and 10 and a threshold for productive infection in the neuronal cell bodies between MOIs of 1 and 0.1. Below an MOI of 0.1, the viral genomes that moved to neuronal nuclei were silenced. These genomes can be reactivated after superinfection by a nonreplicating virus, but not by a replicating virus. We further showed that viral particles at high-MOI infections compete for axonal proteins and that this competition determines the number of viral particles reaching the nuclei. Using mass spectrometry, we identified axonal proteins that are differentially regulated by PRV infection. Our results demonstrate the impact of the multiplicity of infection and the axonal milieu on the establishment of neuronal infection initiated from axons.

Alphaherpesvirus genomes may remain silent in peripheral nervous system (PNS) neurons for the lives of their hosts. These genomes occasionally reactivate to produce infectious virus that can reinfect peripheral tissues and spread to other hosts. Here, we use a neuronal culture system to investigate the outcome of axonal infection using different numbers of viral particles and coinfection assays. We found that the dynamics of viral entry, transport, and replication change dramatically depending on the number of virus particles that infect axons. We demonstrate that viral genomes are silenced when the infecting particle number is low and that these genomes can be reactivated by superinfection with UV-inactivated virus, but not with replicating virus. We further show that viral invasion rapidly changes the profiles of axonal proteins and that some of these axonal proteins are rate limiting for efficient infection. Our study provides new insights into the establishment of silent versus productive alphaherpesvirus infections in the PNS.

The immunogenicity and safety of zoster vaccine in Taiwanese adults

The efficacy and safety of ZOSTAVAX in subjects 60 years of age and older was established in the Shingles Prevention Study (SPS) and in subjects 50 to 59 years of age in the ZOSTAVAX Efficacy and Safety Trial (ZEST). We evaluated the safety and immunogenicity of ZOSTAVAX in a total of 150 Taiwanese subjects ≥50 years of age, who received a single dose of ZOSTAVAX. gpELISA was used to determine geometric mean titers (GMT) of the varicella-zoster virus (VZV) antibody. The geometric mean fold rise (GMFR) of the VZV antibody from the pre-vaccination to the 4 week post-vaccination time point was calculated. There was an overall increase in GMT from 128.45 to 391.85 at 4 weeks post-vaccination. The estimated GMFR was 3.05 (95% CI: 2.60 to 3.57).There were no serious adverse events for 28 days following vaccination. This study demonstrated the safety and immunogenicity of ZOSTAVAX among healthy Taiwanese adults.

Rates of vaccine evolution show strong effects of latency: implications for varicella zoster virus epidemiology

Varicella-zoster virus (VZV) causes chickenpox and shingles, and is found in human populations worldwide. The lack of temporal signal in the diversity of VZV makes substitution rate estimates unreliable, which is a barrier to understanding the context of its global spread. Here, we estimate rates of evolution by studying live attenuated vaccines, which evolved in 22 vaccinated patients for known periods of time, sometimes, but not always undergoing latency. We show that the attenuated virus evolves rapidly (∼ 10(-6) substitutions/site/day), but that rates decrease dramatically when the virus undergoes latency. These data are best explained by a model in which viral populations evolve for around 13 days before becoming latent, but then undergo no replication during latency. This implies that rates of viral evolution will depend strongly on transmission patterns. Nevertheless, we show that implausibly long latency periods are required to date the most recent common ancestor of extant VZV to an "out-of-Africa" migration with humans, as has been previously suggested.

Evaluation of 2 multiplex real-time PCR assays for the detection of HSV-1/2 and Varicella zoster virus directly from clinical samples

We compared the performance of 2 multiplex assays (Focus Simplexa and Quidel Lyra) to individual real-time PCR for the detection of herpes simplex virus-1 (HSV-1), HSV-2, and Varicella zoster virus (VZV) from clinical specimens. Results were compared to a consensus standard, defined as the result obtained by at least 2 of the 3 molecular methods. The sensitivity of the Quidel assay ranged from 92.0% for HSV-1 to 97.7% for HSV-2, while the specificity for all targets was 100%. The Focus assay demonstrated 100% sensitivity for all targets, and the percent specificity ranged from 96.8% for HSV-1 to 100% for HSV-2 and VZV.

Varicella-zoster DNA in saliva of patients with meningoencephalitis: a preliminary study

OBJECTIVES

Since the routine use of polymerase chain reaction testing (PCR) in diagnosing herpes infections, varicella-zoster virus is increasingly recognized as a cause of varicella-zoster meningoencephalitis (VZV ME) among immunocompetent patients. We were interested to determine whether patients with VZV ME had VZV DNA in their saliva during the acute phase of the illness.

MATERIALS AND METHODS

Forty-five consecutive patients who underwent a lumbar puncture for diagnostic purposes were included in the study. The cerebrospinal fluid was examined for the presence of VZV DNA by PCR, and patients with positive findings were treated with acyclovir. The saliva was later analyzed in a blinded fashion for the presence of VZV DNA.

RESULTS

VZV DNA was found in saliva in four of five (80%) patients with PCR confirmed VZV ME (sensitivity 0.8, specificity 0.84, and likelihood ratio 5). This was significantly more than in patients with non-zoster viral ME (0%, P = 0.009), parainfectious headache (12%, P = 0.03) and controls (9.5%, P = 0.007). In immunocompromised patients with systemic lymphoma and AIDS, VZV DNA was present at a similar rate (67%, P = 0.6).

CONCLUSIONS

We have found VZV DNA in saliva of patients with PCR confirmed VZV ME at a higher proportion than in controls and patients with non-VZV viral ME. This finding might be of clinical importance, especially in immunocompetent individuals with suspected VZV ME where the results of genetic and immunological testing are not conclusive.

Multiple latent viruses reactivate in astronauts during Space Shuttle missions

Latent virus reactivation and diurnal salivary cortisol and dehydroepiandrosterone were measured prospectively in 17 astronauts (16 male and 1 female) before, during, and after short-duration (12-16 days) Space Shuttle missions. Blood, urine, and saliva samples were collected during each of these phases. Antiviral antibodies and viral load (DNA) were measured for Epstein-Barr virus (EBV), varicella-zoster virus (VZV), and cytomegalovirus (CMV). Three astronauts did not shed any virus in any of their samples collected before, during, or after flight. EBV was shed in the saliva in all of the remaining 14 astronauts during all 3 phases of flight. Seven of the 14 EBV-shedding subjects also shed VZV during and after the flight in their saliva samples, and 8 of 14 EBV-shedders also shed CMV in their urine samples before, during, and after flight. In 6 of 14 crewmembers, all 3 target viruses were shed during one or more flight phases. Both EBV and VZV DNA copies were elevated during the flight phase relative to preflight or post-flight levels. EBV DNA in peripheral blood was increased preflight relative to post-flight. Eighteen healthy controls were also included in the study. Approximately 2-5% of controls shed EBV while none shed VZV or CMV. Salivary cortisol measured preflight and during flight were elevated relative to post-flight. In contrast DHEA decreased during the flight phase relative to both preflight and post-flight. As a consequence, the molar ratio of the area under the diurnal curve of cortisol to DHEA with respect to ground (AUCg) increased significantly during flight. This ratio was unrelated to viral shedding. In summary, three herpes viruses can reactivate individually or in combination during spaceflight.

Evolution of Plastic Transmission Strategies in Avian Malaria

Malaria parasites have been shown to adjust their life history traits to changing environmental conditions. Parasite relapses and recrudescences—marked increases in blood parasite numbers following a period when the parasite was either absent or present at very low levels in the blood, respectively—are expected to be part of such adaptive plastic strategies. Here, we first present a theoretical model that analyses the evolution of transmission strategies in fluctuating seasonal environments and we show that relapses may be adaptive if they are concomitant with the presence of mosquitoes in the vicinity of the host. We then experimentally test the hypothesis that Plasmodium parasites can respond to the presence of vectors. For this purpose, we repeatedly exposed birds infected by the avian malaria parasite Plasmodium relictum to the bites of uninfected females of its natural vector, the mosquito Culex pipiens, at three different stages of the infection: acute (∼34 days post infection), early chronic (∼122 dpi) and late chronic (∼291 dpi). We show that: (i) mosquito-exposed birds have significantly higher blood parasitaemia than control unexposed birds during the chronic stages of the infection and that (ii) this translates into significantly higher infection prevalence in the mosquito. Our results demonstrate the ability of Plasmodium relictum to maximize their transmission by adopting plastic life history strategies in response to the availability of insect vectors.

Seasonal fluctuations in the environment affect dramatically the abundance of insect species. These fluctuations have important consequences for the transmission of vector-borne diseases. Here we contend that malaria parasites may have evolved plastic transmission strategies as an adaptation to the fluctuations in mosquito densities. First, our theoretical analysis identifies the conditions for the evolution of such plastic transmission strategies. Second, we show that in avian malaria Plasmodium parasites have the ability to increase transmission after being bitten by uninfected Culex mosquitoes. This demonstrates the ability of Plasmodium parasites to adopt plastic transmission strategies and challenges our understanding of malaria epidemiology.

Varicella zoster virus DNA does not accumulate in infected human neurons

Varicella zoster virus (VZV) is an exclusively human neurotropic alphaherpesvirus. It is unclear why human neurons infected in vitro with VZV at low multiplicity of infection do not exhibit a cytopathic effect (CPE) even though all VZV genes are transcribed, VZV proteins from all kinetic classes are translated and minimal infectious virus is produced. Here, we show that the lack of VZV-induced CPE correlates with the low abundance of viral DNA.

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.

Analysis of T cell responses during active varicella-zoster virus reactivation in human ganglia

Varicella-zoster virus (VZV) is responsible for both varicella (chickenpox) and herpes zoster (shingles). During varicella, the virus establishes latency within the sensory ganglia and can reactivate to cause herpes zoster, but the immune responses that occur in ganglia during herpes zoster have not previously been defined. We examined ganglia obtained from individuals who, at the time of death, had active herpes zoster. Ganglia innervating the site of the cutaneous herpes zoster rash showed evidence of necrosis, secondary to vasculitis, or localized hemorrhage. Despite this, there was limited evidence of VZV antigen expression, although a large inflammatory infiltrate was observed. Characterization of the infiltrating T cells showed a large number of infiltrating CD4(+) T cells and cytolytic CD8(+) T cells. Many of the infiltrating T cells were closely associated with neurons within the reactivated ganglia, yet there was little evidence of T cell-induced neuronal apoptosis. Notably, an upregulation in the expression of major histocompatibility complex class I (MHC-I) and MHC-II molecules was observed on satellite glial cells, implying these cells play an active role in directing the immune response during herpes zoster. This is the first detailed characterization of the interaction between T cells and neuronal cells within ganglia obtained from patients suffering herpes zoster at the time of death and provides evidence that CD4(+) and cytolytic CD8(+) T cell responses play an important role in controlling VZV replication in ganglia during active herpes zoster.

IMPORTANCE

VZV is responsible for both varicella (chickenpox) and herpes zoster (shingles). During varicella, the virus establishes a life-long dormant infection within the sensory ganglia and can reawaken to cause herpes zoster, but the immune responses that occur in ganglia during herpes zoster have not previously been defined. We examined ganglia obtained from individuals who, at the time of death, had active herpes zoster. We found that specific T cell subsets are likely to play an important role in controlling VZV replication in ganglia during active herpes zoster.

Enforced expression of microRNA-21 influences the replication of varicella-zoster virus by triggering signal transducer and activator of transcription 3

Varicella-zoster virus (VZV) causes chronic pain and serious complications, including zoster paresis. However, the mechanism of VZV replication, a critical part of VZV pathogenesis, remains largely unknown and was investigated in the present study. The upregulation of microRNA-21 (miR-21) was identified following VZV infection in vitro by quantitative polymerase chain reaction. The hypothesis that the overexpression of miR-21 activates the signal transducer and activator of transcription 3 (STAT3) signaling pathway was validated by measuring the mRNA expression levels of STAT3 and the anti-apoptotic protein survivin in human malignant melanoma (MeWo) and human embryonic lung fibroblast (HELF) cell lines transfected with miR-21-mimic and comparing them with those in cells transfected with miR-control. To further study the interaction of miR-21, STAT3 and VZV replication, the effects of miR-21 overexpression and STAT3 knockdown were evaluated. Higher virus titers were detected when miR-21 was upregulated in vitro. Moreover, it was identified that significantly lower virus titers were present in MeWo cells in which STAT3 was knocked down. In addition, the overexpression of miR-21 did not stimulate VZV replication in the MeWo cell line when the STAT3 gene was silenced. Therefore, the observations of the present study indicate that the enforced expression of miR-21 promotes the replication of VZV by activating STAT3 in vitro.

The fraction of varicella zoster virus-specific antibodies among all intrathecally-produced antibodies discriminates between patients with varicella zoster virus reactivation and multiple sclerosis

Background

Primary infection with or reactivation of varicella zoster virus (VZV) can cause neurologic complications, which typically result in an intrathecal production of VZV-specific antibodies. Intrathecal antibodies to VZV are detectable by an elevated antibody index (AI). However, elevated VZV AIs are also found in more than half of patients with multiple sclerosis (MS), where they are thought to be part of a polyspecific intrathecal immune response. Determination of the fraction of intrathecally-produced virus-specific antibodies among all intrathecally produced antibodies may discriminate between virus-specific and polyspecific intrathecal immune responses, but the fraction of intrathecally-produced VZV-specific immunoglobulin (Ig)G of the total intrathecally produced IgG (F_S anti-VZV) in patients with MS and VZV reactivation has hitherto not been compared.

Findings

F_S anti-VZV was calculated in patients with a clinically isolated syndrome suggestive of multiple sclerosis (MS) or MS (n = 20) and in patients with VZV reactivation (7 samples from 5 patients), which all had elevated VZV AIs. The median F_S anti-VZV was 35-fold higher in patients with VZV reactivation (45.1%, range 13.5-73%) than in patients with CIS/MS (1.3%, range 0.3-5.3%; p = 0.0001). While there was thus no overlap of F_S anti-VZV values between groups, VZV AIs completely overlapped in patients with CIS/MS (1.6-14.8) and VZV reactivation (2.1-8.1).

Conclusions

The fraction of intrathecally-produced VZV-specific IgG of the total intrathecally produced IgG discriminates between patients with VZV reactivation and MS. Our results provide further evidence that intrathecally-produced VZV antibodies are part of the polyspecific immune response in patients with MS.

Primary angiitis of the central nervous system and reversible cerebral vasoconstriction syndrome

Primary angiitis of the central nervous system (PACNS) is one of the most devastating pathologic processes that affect the central nervous system (CNS). It results in exclusive inflammation and destruction of CNS blood vessels. Progressive debilitating unexplained neurological deficit associated with abnormal cerebrospinal fluid (CSF) analysis findings is the typical picture of the disease. CNS biopsy is the gold standard diagnostic test. Immunosuppressive therapy is the core treatment. Reversible cerebral vasoconstriction syndrome (RCVS) is a main mimic of PACNS. RCVS is characterized clinically by recurrent thunderclap headache with or without neurological deficit and normal CSF analysis findings and angiographically by reversible diffuse segmental vasospasm of intracranial vessels. A stepwise diagnostic approach should be followed to differentiate PACNS from RCVS and exclude the other clinical, radiographic, and angiographic mimics.

Basics of virology

Viruses are important pathogens of the nervous system. Here we describe the basic properties of viruses and the principles of virus classification, evolution, structure, and replication, with a focus on neurotropic viruses that are important neuropathogens of humans. These properties then provide the background for introductions to pathogenesis of viral diseases of the nervous system, host immune responses to virus infection, and the diagnosis and treatment of virus infections of the nervous system.

Nervous System Complications of Systemic Viral Infections

Invasion of the central nervous system (CNS) by viral agents typically produces a meningoencephalitis in which either meningitis or encephalitis may predominate. Viruses may also infect cranial or spinal blood vessels to produce ischemic injury. Viral and other infections may also elicit a host immune response which is cross-reactive with components of the neural tissue, resulting in encephalomyelitis, transverse myelitis, injury to peripheral nerves, or optic neuritis. This chapter discusses the pathogenesis of CNS viral infections and reviews clinical features of these disorders, major agents responsible in immunocompromised and immunocompetent individuals, and treatment. Prion diseases and postinfectious viral CNS syndromes including postinfectious encephalomyelitis, acute hemorrhagic leukoencephalitis, cerebellar ataxia, and transverse myelitis are also discussed.

Interaction of allergy history and antibodies to specific varicella-zoster virus proteins on glioma risk

Glioma is the most common cancer of the central nervous system but with few confirmed risk factors. It has been inversely associated with chicken pox, shingles and seroreactivity to varicella virus (VZV), as well as to allergies and allergy-associated IgE. The role of antibody reactivity against individual VZV antigens has not been assessed. Ten VZV-related proteins, selected for high immunogenicity or known function, were synthesized and used as targets for antibody measurements in the sera of 143 glioma cases and 131 healthy controls selected from the San Francisco Bay Area Adult Glioma Study. Glioma cases exhibited significantly reduced seroreactivity compared to controls for six antigens, including proteins IE63 [odds ratio (OR) = 0.26, 95% confidence interval (CI): 0.12-0.58, comparing lowest quartile to highest) and the VZV-unique protein ORF2p (OR = 0.44, 95% CI: 0.21-0.96, lowest quartile to highest). When stratifying the study population into those with low and high self-reported allergy history, VZV protein seroreactivity was only associated inversely with glioma among individuals self-reporting more than two allergies. The data provide insight into both allergy and VZV effects on glioma: strong anti-VZV reactions in highly allergic individuals are associated with reduced occurrence of glioma. This result suggests a role for specificity in the anti-VZV immunity in brain tumor suppression for both individual VZV antigens and in the fine-tuning of the immune response by allergy. Anti-VZV reactions may also be a biomarker of effective CNS immunosurveillance owing to the tropism of the virus.

Varicella zoster virus (VZV)-human neuron interaction

Varicella zoster virus (VZV) is a highly neurotropic, exclusively human herpesvirus. Primary infection causes varicella (chickenpox), wherein VZV replicates in multiple organs, particularly the skin. Widespread infection in vivo is confirmed by the ability of VZV to kill tissue culture cells in vitro derived from any organ. After varicella, VZV becomes latent in ganglionic neurons along the entire neuraxis. During latency, virus DNA replication stops, transcription is restricted, and no progeny virions are produced, indicating a unique virus-cell (neuron) relationship. VZV reactivation produces zoster (shingles), often complicated by serious neurological and ocular disorders. The molecular trigger(s) for reactivation, and thus the identity of a potential target to prevent it, remains unknown due to an incomplete understanding of the VZV-neuron interaction. While no in vitro system has yet recapitulated the findings in latently infected ganglia, recent studies show that VZV infection of human neurons in SCID mice and of human stem cells, including induced human pluripotent stem cells and normal human neural progenitor tissue-like assemblies, can be established in the absence of a cytopathic effect. Usefulness of these systems in discovering the mechanisms underlying reactivation awaits analyses of VZV-infected, highly pure (>90%), terminally differentiated human neurons capable of prolonged survival in vitro.

The variegate neurological manifestations of varicella zoster virus infection

Varicella zoster virus (VZV) is an exclusively human neurotropic alphaherpesvirus. Primary infection causes varicella (chickenpox), after which the virus becomes latent in ganglionic neurons along the entire neuraxis. With advancing age or immunosuppression, cell-mediated immunity to VZV declines, and the virus reactivates to cause zoster (shingles), dermatomal distribution, pain, and rash. Zoster is often followed by chronic pain (postherpetic neuralgia), cranial nerve palsies, zoster paresis, vasculopathy, meningoencephalitis, and multiple ocular disorders. This review covers clinical, laboratory, and pathological features of neurological complications of VZV reactivation, including diagnostic testing to verify active VZV infection in the nervous system. Additional perspectives are provided by discussions of VZV latency, animal models to study varicella pathogenesis and immunity, and of the value of vaccination of elderly individuals to boost cell-mediated immunity to VZV and prevent VZV reactivation.

Unusual trigeminal autonomic pain heralding hemichorea due to zoster sine Herpete vasculopathy

BACKGROUND

Varicella zoster virus primary infection is responsible for chickenpox, whereas secondary infection or reactivation can lead to a variety of clinical scenarios. If latent infection is established in trigeminal ganglion, the reactivation can determine viral migration to cerebral arteries, which causes a cerebral vasculopathy and subsequently an ischemic stroke.

PATIENTS

Here we report on a child experiencing recurrent episodes of headache mimicking a trigeminal autonomic cephalalgia, in the absence of any skin rash, which were followed by the occurrence of an ipsilateral hemiparesis associated with a choreic movement disorder a month later.

RESULTS

Magnetic resonance angiography showed evidence of a right-sided infarction of basal ganglia and anterior limb of the internal capsule, corresponding to the vascular territory of the recurrent artery of Heubner, as a consequence of a focal varicella zoster virus arteriopathy.

CONCLUSIONS

We suggest that the recognition of this prodromal manifestation, which can be interpreted as a zoster sine herpete, could provide clinicians an extremely useful time window to start promptly with a prophylactic treatment.

Complications of varicella zoster virus reactivation

OPINION STATEMENT

Varicella zoster virus (VZV) is an exclusively human neurotropic alphaherpesvirus. Primary infection causes varicella (chickenpox), after which virus becomes latent in ganglionic neurons along the entire neuraxis. With advancing age or immunosuppression, cell-mediated immunity to VZV declines and virus reactivates to cause zoster (shingles), which can occur anywhere on the body. Skin lesions resolve within 1-2 weeks, while complete cessation of pain usually takes 4-6 weeks. Zoster can be followed by chronic pain (postherpetic neuralgia), cranial nerve palsies, zoster paresis, meningoencephalitis, cerebellitis, myelopathy, multiple ocular disorders and vasculopathy that can mimic giant cell arteritis. All of the neurological and ocular disorders listed above may also develop without rash. Diagnosis of VZV-induced neurological disease may require examination of cerebrospinal fluid (CSF), serum and/ or ocular fluids. In the absence of rash in a patient with neurological disease potentially due to VZV, CSF should be examined for VZV DNA by PCR and for anti-VZV IgG and IgM. Detection of VZV IgG antibody in CSF is superior to detection of VZV DNA in CSF to diagnose vasculopathy, recurrent myelopathy, and brainstem encephalitis. Oral antiviral drugs speed healing of rash and shorten acute pain. Immunocompromised patients require intravenous acyclovir. First-line treatments for post-herpetic neuralgia include tricyclic antidepressants, gabapentin, pregabalin, and topical lidocaine patches. VZV vasculopathy, meningoencephalitis, and myelitis are all treated with intravenous acyclovir.

Three-dimensional normal human neural progenitor tissue-like assemblies: a model of persistent varicella-zoster virus infection

Varicella-zoster virus (VZV) is a neurotropic human alphaherpesvirus that causes varicella upon primary infection, establishes latency in multiple ganglionic neurons, and can reactivate to cause zoster. Live attenuated VZV vaccines are available; however, they can also establish latent infections and reactivate. Studies of VZV latency have been limited to the analyses of human ganglia removed at autopsy, as the virus is strictly a human pathogen. Recently, terminally differentiated human neurons have received much attention as a means to study the interaction between VZV and human neurons; however, the short life-span of these cells in culture has limited their application. Herein, we describe the construction of a model of normal human neural progenitor cells (NHNP) in tissue-like assemblies (TLAs), which can be successfully maintained for at least 180 days in three-dimensional (3D) culture, and exhibit an expression profile similar to that of human trigeminal ganglia. Infection of NHNP TLAs with cell-free VZV resulted in a persistent infection that was maintained for three months, during which the virus genome remained stable. Immediate-early, early and late VZV genes were transcribed, and low-levels of infectious VZV were recurrently detected in the culture supernatant. Our data suggest that NHNP TLAs are an effective system to investigate long-term interactions of VZV with complex assemblies of human neuronal cells.

Varicella-zoster virus (VZV), the alphaherpesvirus that typically causes childhood chickenpox and shingles in adults, becomes latent in neurons, thus remaining in the body for a lifetime. Unfortunately, few models are available to study the establishment of VZV latency since the virus infects only humans and establishes persistent infections and latency only in neurons, a slowly proliferating, short-lived cell in culture. We have successfully maintained normal human neural progenitor cells (NHNP) in tissue-like assemblies (TLAs) in 3-dimensional (3D) cultures for up to 6 months. The 3D NHNP TLAs show some characteristics as those found in the human trigeminal ganglia, the site of VZV latency. NHNP TLAs infected with VZV remain viable for 3 months during which time VZV DNA replicates and remains genetically stable, virus genes are transcribed, and infectious VZV is sporadically released. The ability to maintain VZV infected NHNP cells in culture for extended times provides the unique opportunity to study the molecular interactions between this important human pathogen and neuronal tissue to an extent previously unattainable.

[Current management of post-varicella stroke in children: a literature review]

Among infectious factors, varicella-zoster virus (VZV) is a leading cause of central nervous system vasculopathy and stroke in childhood. Not only have viral markers been detected in the cerebrospinal fluid of affected patients, but also direct evidence of viral particles in the wall of cerebral arteries has been demonstrated in rare pathological specimens. This certainly reflects a localized infectious process likely associated with variable indirect inflammatory responses. Yet the usefulness in this setting of a lumbar puncture as well as of subsequent targeted antiviral and/or anti-inflammatory therapies is uncertain. Indeed, in the majority of cases, the so-called post-varicella angiopathy has a monophasic evolution with spontaneous resolution or stabilization, explaining diverging diagnostic and treatment approaches. In this paper, we have addressed this problematic area by reviewing 26 published cases from the year 2000 and three unpublished cases. Post-varicella stroke is typically associated with angiopathy most often involving the initial portion of the middle cerebral artery, causing a basal ganglia stroke. It tends to occur in young immunocompetent children. Thrombophilia work-up is in general negative. Lumbar puncture was performed in 17 out of 29 cases. Viral markers were examined in 14 cases, but were positive in only eight cases. Antiviral therapy was administrated in 11 children. In this small retrospective study, the treated children's vasculopathy did not progress more favorably nor was there a better outcome compared with untreated subjects.

Recombinant varicella-zoster virus vaccines as platforms for expression of foreign antigens

Varicella-zoster virus (VZV) vaccines induce immunity against childhood chickenpox and against shingles in older adults. The safety, efficacy, and widespread use of VZV vaccines suggest that they may also be effective as recombinant vaccines against other infectious diseases that affect the young and the elderly. The generation of recombinant VZV vaccines and their evaluation in animal models are reviewed. The potential advantages and limitations of recombinant VZV vaccines are addressed.

Varicella-zoster meningoencephaloradiculoneuropathy in an immunocompetent young woman

The clinical manifestations of varicella-zoster virus infections can be divided into primary infection with chickenpox and reactivated infection with dermatomal shingles, disseminated herpes zoster, zoster sine herpete and varicella-zoster virus encephalitis, meningitis and vasculopathy. We present a case of zoster sine herpete leading to meningitis with cranial and peripheral nerve palsies. A 17-year-old woman was admitted to hospital with intermittent fever, drowsiness, slowness and subsequent frontal headache and horizontal diplopia. Cerebrospinal fluid examination revealed lymphocytic pleocytosis and PCR amplified varicella-zoster virus DNA. Laboratory and clinical findings were suggestive of meningoencephaloradiculoneuropathy, stemming from varicella-zoster virus and affecting cranial and peripheral nerves. Only 5% of patients with zoster develop cranial and peripheral nerve palsies. Diagnosis is imperative in order to initiate prompt antiviral therapy so as to minimize morbidity and the risk of death.

Comprehensive analysis of varicella-zoster virus proteins using a new monoclonal antibody collection

Varicella-zoster virus (VZV) is the etiological agent of chickenpox and shingles. Due to the virus's restricted host and cell type tropism and the lack of tools for VZV proteomics, it is one of the least-characterized human herpesviruses. We generated 251 monoclonal antibodies (MAbs) against 59 of the 71 (83%) currently known unique VZV proteins to characterize VZV protein expression in vitro and in situ. Using this new set of MAbs, 44 viral proteins were detected by Western blotting (WB) and indirect immunofluorescence (IF); 13 were detected by WB only, and 2 were detected by IF only. A large proportion of viral proteins was analyzed for the first time in the context of virus infection. Our study revealed the subcellular localization of 46 proteins, 14 of which were analyzed in detail by confocal microscopy. Seven viral proteins were analyzed in time course experiments and showed a cascade-like temporal gene expression pattern similar to those of other herpesviruses. Furthermore, selected MAbs tested positive on human skin lesions by using immunohistochemistry, demonstrating the wide applicability of the MAb collection. Finally, a significant portion of the VZV-specific antibodies reacted with orthologs of simian varicella virus (SVV), thus enabling the systematic analysis of varicella in a nonhuman primate model system. In summary, this study provides insight into the potential function of numerous VZV proteins and novel tools to systematically study VZV and SVV pathogenesis.

Natural history of herpes zoster: late follow-up of 3.9 years (n=43) and 7.7 years (n=10)

Postherpetic neuralgia (PHN) is a common complication after herpes zoster (HZ). Subjects who completed a longitudinal observational 6-month study (4 visits) of the natural history of HZ were recontacted for 2 additional follow-up visits that included pain and sensory symptom assessment, quantitative sensory testing, capsaicin response test, and 3-mm punch skin biopsies in HZ-affected, mirror-image, and control skin sites. Forty-three subjects (14 with PHN at 6 months) of the original 94 subjects in the cohort were comprehensively assessed at a median 3.9 years after HZ onset (visit 5), and 10 subjects underwent a final assessment at a median 7.7 years after HZ onset (visit 6). At 3.9 years, none of the 29 subjects who had been pain free at 6 months had a recurrence of pain. Only 2 of the 14 subjects with PHN at 6 months still had pain at 3.9 years. One subject with PHN at 6 months was free of symptoms at 3.9 years but had very mild pain at 7.7 years. Sensory function continued on a path toward normalization, but was still abnormal in many subjects, especially those who met criteria for PHN at 6 months. Even at 7.7 years, reinnervation of HZ-affected skin was not apparent.

Peripheral nerve surgery for the treatment of postherpetic neuralgia

Postherpetic neuralgia is a chronic pain condition that develops in some patients after the resolution of herpes zoster, and has no medical cure. Medications used to treat chronic pain do not hasten resolution of the disorder and may impair function. In this brief case report, we describe our experience with excision and implantation to muscle of peripheral sensory nerves in the affected dermatomes as a novel surgical treatment to reduce pain and improve quality of life for patients with this condition. Of the 3 treated patients, all had resolution of chronic pain after surgery. It is concluded that peripheral nerve surgery offers a promising option to improve pain and quality of life in postherpetic neuralgia patients, without affecting systemic functioning.

Varicella zoster virus infection of highly pure terminally differentiated human neurons

In vitro analyses of varicella zoster virus (VZV) reactivation from latency in human ganglia have been hampered by the inability to isolate virus by explantation or cocultivation techniques. Furthermore, attempts to study interaction of VZV with neurons in experimentally infected ganglion cells in vitro have been impaired by the presence of nonneuronal cells, which become productively infected and destroy the cultures. We have developed an in vitro model of VZV infection in which highly pure (>95 %) terminally differentiated human neurons derived from pluripotent stem cells were infected with VZV. At 2 weeks post-infection, infected neurons appeared healthy compared to VZV-infected human fetal lung fibroblasts (HFLs), which developed a cytopathic effect (CPE) within 1 week. Tissue culture medium from VZV-infected neurons did not produce a CPE in uninfected HFLs and did not contain PCR-amplifiable VZV DNA, but cocultivation of infected neurons with uninfected HFLs did produce a CPE. The nonproductively infected neurons contained multiple regions of the VZV genome, as well as transcripts and proteins corresponding to VZV immediate-early, early, and late genes. No markers of the apoptotic caspase cascade were detected in healthy-appearing VZV-infected neurons. VZV infection of highly pure terminally differentiated human neurons provides a unique in vitro system to study the VZV-neuronal relationship and the potential to investigate mechanisms of VZV reactivation.

Infectious feline herpesvirus detected in distant bone and tendon following mucosal inoculation of specific pathogen-free cats

Emerging evidence suggests that cats infected with feline herpesvirus-1 (FHV-1) may experience a brief viremic phase. The objective of this study was to determine whether natural routes of FHV-1 inoculation could result in viremic transmission of infectious virus to connective tissues (cortical bone, tendon). Three specific pathogen-free cats were experimentally inoculated with FHV-1 via a combined mucosal (oronasal, ocular) route. Cats were euthanized at the peak of clinical signs to aseptically harvest tissues (cortical bone, tendon, trachea/tongue) for co-culture with a susceptible cell line to promote spread of infectious virus. Viral infection of Crandall-Rees feline kidney cells was microscopically visualized by cytopathic effect (CPE). Additionally, co-culture DNA was extracted either at the point of CPE or 16 days of culture without evidence of CPE, to amplify FHV-1 glycoprotein B gene using real-time PCR. Infectious virus was detected in distant cortical bone (two cats, moderate to severe clinical signs) and tendon (one cat, severe clinical signs). Direct infection of mucosal (trachea, tongue) tissues also was confirmed in these two cats. In contrast, all co-cultured tissues from the third cat (mild clinical signs) were negative for FHV-1 by CPE and PCR. Results of this study demonstrated that early primary FHV-1 viremia may be distributed to distant connective tissues.

Shingles with secondary asymptomatic CNS involvement!

A 32-year-old married Asian woman, previously fit and well, presented with a 3-day history of interscapular back pain followed by a 1-day history of frontal headache and a few episodes of vomiting. She did not have photophobia or neck stiffness. On examination, there was evidence of herpes zoster infection involving the right T3 dermatome. There were no signs of meningeal irritation, cognitive impairment or any neurological deficit. As it is uncommon to have reactivation of herpes zoster infection at a young age, HIV serology was requested to exclude immunodeficiency state. While awaiting serology, a lumbar puncture was performed to exclude opportunistic infections of the central nervous system as she had transient headache and vomiting at the onset. The cerebrospinal fluid showed an elevated level of protein, an increase in lymphocytes and a strongly positive PCR for varicella zoster. The HIV test was negative. Oral acyclovir was changed to intravenous therapy and, a week later, she was discharged with uneventful recovery.

Varicella-zoster virus infects human embryonic stem cell-derived neurons and neurospheres but not pluripotent embryonic stem cells or early progenitors

Pluripotent human stem cells are a powerful tool for the generation of differentiated cells that can be used for the study of human disease. We recently demonstrated that neurons derived from pluripotent human embryonic stem cells (hESC) can be infected by the highly host-restricted human alphaherpesvirus varicella-zoster virus (VZV), permitting the interaction of VZV with neurons to be readily evaluated in culture. In the present study, we examine whether pluripotent hESC and neural progenitors at intermediate stages of differentiation are permissive for VZV infection. We demonstrate here that VZV infection is blocked in naïve hESC. A block to VZV replication is also seen when a bacterial artificial chromosome (BAC) containing the VZV genome is transfected into hESC. In contrast, related alphaherpesviruses herpes simplex virus 1 (HSV-1) and pseudorabies virus (PrV) productively infect naïve hESC in a cell-free manner, and PrV replicates from a BAC transfected into hESC. Neurons differentiate from hESC via neural progenitor intermediates, as is the case in the embryo. The first in vitro stage at which permissiveness of hESC-derived neural precursors to VZV replication is observed is upon formation of "neurospheres," immediately after detachment from the inductive stromal feeder layer. These findings suggest that hESC may be useful in deciphering the yet enigmatic mechanisms of specificity of VZV infection and replication.

Varicella zoster virus-induced pain and post-herpetic neuralgia in the human host and in rodent animal models

Pain and post-herpetic neuralgia (PHN) are common and highly distressing complications of herpes zoster that remain a significant public health concern and in need of improved therapies. Zoster results from reactivation of the herpesvirus varicella zoster virus (VZV) from a neuronal latent state established at the primary infection (varicella). PHN occurs in some one fifth to one third of zoster cases with severity, incidence, and duration of pain increasing with rising patient age. While VZV reactivation and the ensuing ganglionic damage trigger the pain response, the mechanisms underlying protracted PHN are not understood, and the lack of an animal model of herpes zoster (reactivation) makes this issue more challenging. A recent preclinical rodent model has developed that opens up the potential to allow the exploration of the underlying mechanisms and treatments for VZV-induced pain. Rats inoculated with live cell-associated human VZV into the hind paw reliably demonstrate thermal hyperalgesia and mechanical allodynia for extended periods and then spontaneously recover. Dorsal root ganglia express a limited VZV gene subset, including the IE62 regulatory protein, and upregulate expression of markers suggesting a neuropathic pain state. The model has been used to investigate treatment modalities and aspects of pain signaling and is under investigation by the authors to delineate VZV genetics involved in the induction of pain. This article compares human zoster-associated pain and PHN to the pain indicators in the rat and poses important questions that, if answered, could be the basis for new treatments.