Clinical and molecular aspects of varicella zoster virus infection

Zoster Eye Disease Study: Rationale and Design

PURPOSE

The purpose of this study was to describe the rationale and design of the Zoster Eye Disease Study (ZEDS).

METHODS

ZEDS is a National Eye Institute-supported randomized clinical trial designed to determine whether 1 year of suppressive valacyclovir in patients with herpes zoster ophthalmicus (HZO) reduces complications because there is currently no high-quality evidence to support its use. Eligible patients are 18 years and older, immunocompetent, have a history of a typical rash at disease onset, and have had a record of active epithelial or stromal keratitis or iritis within 1 year before enrollment. Exclusion criteria include estimated glomerular filtration rate less than 45 or pregnancy. The primary endpoint is the time to first occurrence of new or worsening dendriform epithelial keratitis, stromal keratitis without or with ulceration, endothelial keratitis, or iritis due to HZO during 12 months of study treatment requiring prespecified treatment changes. The study has 80% power to detect a 30% difference between treatment groups, with a 30% rate of endpoints by 1 year assumed among controls. Secondary and exploratory questions include whether there is a persistent treatment benefit during the 6 months after treatment, whether development of postherpetic neuralgia varies by treatment group, and whether vaccinations against herpes zoster affect study outcomes and coronavirus disease 19 status.

RESULTS

Over approximately 4 years, over 400 study participants have been enrolled.

CONCLUSIONS

ZEDS aims to provide scientific evidence on whether suppressive valacyclovir treatment improves outcomes in HZO and should become the standard of care.

Nectin-1 Is an Entry Mediator for Varicella-Zoster Virus Infection of Human Neurons

Varicella-zoster virus (VZV) maintains lifelong latency in neurons following initial infection and can subsequently be reactivated to result in herpes zoster or severe neurological manifestations such as encephalitis. Mechanisms of VZV neuropathogenesis have been challenging to study due to the strict human tropism of the virus. Although neuronal entry mediators of other herpesviruses, including herpes simplex virus, have been identified, little is known regarding how VZV enters neurons. Here, we utilize a human stem cell-based neuronal model to characterize cellular factors that mediate entry. Through transcriptional profiling of infected cells, we identify the cell adhesion molecule nectin-1 as a candidate mediator of VZV entry. Nectin-1 is highly expressed in the cell bodies and axons of neurons. Either knockdown of endogenous nectin-1 or incubation with soluble forms of nectin-1 produced in mammalian cells results in a marked decrease in infectivity of neurons. Notably, while addition of soluble nectin-1 during viral infection inhibits infectivity, addition after infection has no effect on infectivity. Ectopic expression of human nectin-1 in a cell line resistant to productive VZV infection confers susceptibility to infection. In summary, we have identified nectin-1 as a neuronal entry mediator of VZV. IMPORTANCE Varicella-zoster virus (VZV) causes chickenpox, gains access to neurons during primary infection where it resides lifelong, and can later be reactivated. Reactivation is associated with shingles and postherpetic neuralgia, as well as with severe neurologic complications, including vasculitis and encephalitis. Although the varicella vaccine substantially decreases morbidity and mortality associated with primary infection, the vaccine cannot prevent the development of neuronal latency, and vaccinated populations are still at risk for reactivation. Furthermore, immunocompromised individuals are at higher risk for VZV reactivation and associated complications. Little is known regarding how VZV enters neurons. Here, we identify nectin-1 as an entry mediator of VZV in human neurons. Identification of nectin-1 as a neuronal VZV entry mediator could lead to improved treatments and preventative measures to reduce VZV related morbidity and mortality.

Video Anthology of Movement Disorders Due to Infections in South Asia

South Asia, encompassing many populous countries including India, Pakistan, and Bangladesh, is home to a wide variety of infectious diseases several of which are disproportionately prevalent, endemic or distinctive to the region. These result in considerable morbidity and mortality, which can be greatly reduced through public-health measures, timely diagnosis and treatment. Some of these infectious diseases have neurological manifestations including movement disorders either due to the pathogen being neuroinvasive or via an immune-mediated response. For diseases such as Japanese encephalitis, movement disorders are the primary manifestation while for others, they can be a presenting feature. Thus, recognizing these movement disorders is often crucial to the diagnosis of the particular infection, and/or to exclude infection as a cause and arrive at the correct alternate diagnosis. Once diagnosed, the infection-related movement disorders are treated by targeting the infectious agent, or symptomatically. In this article, we describe and illustrate a variety of movement disorders that are seen in patients infected by viruses, bacteria and parasites in South Asia. This would be of value to neurologists practicing in the region and, with the increasing ease in movement of people and pathogens, those practicing elsewhere.

Herpes Zoster Vaccine Live and Risk of Stroke Among Medicare Beneficiaries: A Population-Based Cohort Study

[Figure: see text].

Effect of herpes zoster vaccine and antiviral treatment on risk of ischemic stroke

OBJECTIVE

To determine whether increased risk of acute ischemic stroke (AIS) following herpes zoster (HZ) might be modified by the status of zoster vaccine live (ZVL) vaccination and antiviral treatment following HZ.

METHODS

We included 87,405 Medicare fee-for-service beneficiaries aged ≥66 years diagnosed with HZ and AIS from 2008 to 2017. We used a self-controlled case series design to examine the association between HZ and AIS, and estimated incidence rate ratios (IRRs) by comparing incidence of AIS in risk periods vs control periods. To examine effect modification by ZVL and antiviral treatment, beneficiaries were classified into 4 mutually exclusive groups: (1) no vaccination and no antiviral treatment; (2) vaccination only; (3) antiviral treatment only; and (4) both vaccination and antiviral treatment. We tested for interaction to examine changes in IRRs across 4 groups.

RESULTS

Among 87,405 beneficiaries with HZ and AIS, 22.0%, 2.0%, 70.1%, and 5.8% were in groups 1 to 4, respectively. IRRs in 0-14, 15-30, 31-90, and 91-180 days following HZ were 1.89 (95% confidence interval [CI], 1.77-2.02), 1.58 (95% CI, 1.47-1.69), 1.36 (95% CI, 1.31-1.42), and 1.19 (95% CI, 1.15-1.23), respectively. There was no evidence of effect modification by ZVL and antiviral treatment on AIS (p = 0.067 for interaction). The pattern of association between HZ and risk for AIS was largely consistent across age group, sex, and race.

CONCLUSIONS

Risk of AIS increased significantly following HZ, and this increased risk was not modified by ZVL and antiviral treatment. Our findings suggest the importance of following recommended HZ vaccination in prevention of HZ and HZ-associated AIS.

Inhibitory effect of amenamevir on acute herpetic pain and postherpetic neuralgia in mice infected with herpes simplex virus-1

BACKGROUND

Amenamevir (AMNV) is a helicase-primase inhibitor with antiviral activity against herpesviruses [herpes simplex viruses (HSV)-1 and -2, and varicella-zoster virus], which are associated with the development of acute herpetic pain (AHP) and postherpetic neuralgia. However, the inhibitory effects of helicase-primase inhibitors on AHP and postherpetic neuralgia remain incompletely understood.

OBJECTIVE

In this study, we investigated the effects of AMNV on AHP and postherpetic pain (PHP) in HSV-1-infected mice accompanied by zosteriform-like skin lesions.

METHODS

HSV-1 was percutaneously infected on the femoral region of mice. AMNV was orally administered twice a day for 5 days. Pain-related response in the hind paw was evaluated using a paintbrush. The infiltration of inflammatory cells in dorsal root ganglion (DRG) and spinal cord (SC) was evaluated by hematoxylin and eosin staining. The viral load in DRG and the expression of pain-related genes in SC were measured by real-time PCR.

RESULTS

Pain response was begun to be observed from day 3 post-infection (pi) in HSV-1-infected mice. AMNV administered repeatedly from day 3 pi or day 4 pi, but not day 5 pi, showed an inhibitory effect on the development of AHP and the transition to PHP. Repeated AMNV administration inhibited inflammatory cell infiltration and increases in the viral load and the expression of pain-related genes (ATF-3, TNF-α, COX-2).

CONCLUSION

These results demonstrate that AMNV potently suppresses the development of AHP and the transition to PHP as a consequence of decreased viral load in DRG and reduced expression of pain-related genes in SC.

Varicella Zoster Virus Vasculitis and Adult Cerebrovascular Disease

The role of Varicella zoster virus (VZV) in neurological illness, particularly cerebrovascular disease, has been increasingly recognized. Primary infection by VZV causes varicella (chickenpox), after which the virus remains latent in neuronal ganglia. Later, during aging or immunosuppression, the virus can reactivate causing zoster (shingles). Virus reactivation can also spread to cerebral arteries causing vasculitis and stroke. Zoster is a recognized risk factor for stroke, but stroke can occur without preceding zoster rash. The diagnosis of VZV cerebral vasculitis is established by abnormal brain imaging and confirmed by presence of viral DNA or anti-VZV antibodies in cerebrospinal fluid. Treatment with acyclovir with or without prednisone is usually recommended. VZV vasculitis is a unique and uncommon stroke mechanism that has been under recognized. Careful diagnostic investigation may be warranted in a subgroup of patients with ischemic stroke to detect VZV vasculitis and initiate appropriate therapy. In the following review, we detail the clinical presentation of VZV vasculitis, diagnostic challenges in VZV detection, and suggest the ways to enhance recognition and treatment of this uncommon disease.

Longitudinal Extensive Transverse Myelitis in an Immunocompetent Older Individual-A Rare Complication of Varicella-Zoster Virus Reactivation

Varicella-zoster virus (VZV) is a human neurotropic herpes virus that causes chickenpox in children. After becoming latent in dorsal root ganglia, it can reactivate to cause dermatological manifestations, the most common one being shingles or herpes zoster. Severe neurologic dysfunctions can occur in immunocompromised patients such as encephalitis, meningitis, myelitis and neuropathy. Longitudinal extensive transverse myelitis (LETM) is an unusual neurological complication mainly described in immunocompromised patients, with very few cases described in immunocompetent ones. We hereby report a case of VZV-induced LETM in an immunocompetent older adult—a situation rarely described in the literature. LETM is a rare complication of VZV and its pathogenesis; therapeutic interventions and prognosis are far from being fully clarified. However, a prompt diagnosis is needed to allow a rapid initialization of treatment and ensure a better outcome. Although the therapeutic lines are not clear, immunosuppressive agents may have their place in cases of unsuccessful results and/or relapses following acyclovir coupled with a well conducted methylprednisolone therapy. Further studies are highly needed to improve the current understanding of the disease course and mechanisms, and to optimize therapeutic strategies.

The Role of the Microbiota in the Diabetic Peripheral Artery Disease

Vascular complications of diabetes mellitus represent a major public health problem. Although many steps forward have been made to define the causes and to find the best possible therapies, the problem remains crucial. In recent years, more and more evidences have defined a link between microbiota and the initiation, promotion, and evolution of atherosclerotic disease, even in the diabetic scenario. There is an urgency to develop the knowledge of modern medicine about the link between gut microbiota and its host's metabolic pathways, and it would be useful to understand and justify the interindividual diversity of clinical disease presentation of diabetic vascular complication even if an optimization of pharmacological treatment has been made or in the case of young patients where hypertension, dyslipidemia, and diabetes are not able to justify a very quick progress of atherosclerotic process. The aim of the present review is to gather all the best available evidence in this regard and to define a new role of the microbiota in this field, from biomarker to possible therapeutic target.

Acute pain and postherpetic neuralgia related to Varicella zoster virus reactivation: Comparison between typical herpes zoster and zoster sine herpete

Herpes zoster (HZ) is typically characterized by pain involving the area of vesicular eruption. Several patients, however, complain of unilateral radicular pain without rash (zoster sine herpete [ZSH]). To evaluate whether the severity and duration of pain and the use of analgesics are greater in ZSH patients than in typical HZ with rash, 16 consecutive patients with acute unilateral pain, without vesicular eruption (ZSH), were compared with 16 controls suffering from typical HZ eruption. Only patients with laboratory evidence of varicella-zoster virus (VZV) reactivation were selected. Serum samples were obtained from all patients at their initial visit and 1 and 2 months later. Monthly, the administered therapies and the average pain score (visual analog scale [VAS] score) were recorded. VZV DNA persisted statistically higher in ZSH sera than HZ sera 1 month after onset (P = 0.0007). ZSH patients averaged greater pain than HZ patients, scoring VAS 76.88 and 66.88 ( P = 0.0012), respectively. ZSH patients used significantly more opioid therapy than HZ patients ( P = 0.0449; OR, 9.00). This is the first study comparing pain in ZSH and HZ patients: greater severity and duration of pain and more opioid use was detected in patients with ZSH.

Effectiveness of continuous epidural analgesia on acute herpes zoster and postherpetic neuralgia: A retrospective study

Despite early treatment of herpes zoster (HZ), postherpetic neuralgia (PHN) can persist. This study was designed to compare the therapeutic and pain relief effects of continuous epidural analgesia (CEA) on the chronic phase as well as the acute phase of HZ with standard medical treatment.Medical records of 227 patients with moderate to severe zoster-associated pain that had not responded to standard medications were retrospectively reviewed. Patients received standard treatment alone (medical group) or standard treatment plus concurrent CEA (epidural group). The acute and chronic groups were classified according to a 4-week cut-off with regard to time between the onset of the rash and the first treatment. Four groups were studied: Group A (acute/medical group); Group B (acute/epidural group); Group C (chronic/medical group); and Group D (chronic/epidural group). Pain was assessed using the visual analog scale (VAS) and measured every 2 weeks for 6 months. We compared the pain rating at 6 months after the first treatment with the initial pain rating. Response to treatment was defined as a ≥50% reduction in pain severity since the initial visit. Remission was considered complete for patients whose VAS pain score was ≤2 for >3 successive visits and who no longer needed medical support.Patients who received a combination of standard treatment plus CEA (Groups B and D) had significantly higher response to treatment (P = .001) than patients receiving standard treatment alone (Groups A and C). The adjusted odds ratio (OR) for response to treatment in the epidural group versus the medical group was 5.17 (95% confidence interval [CI]: 1.75-15.23) in the acute group and 5.37 (95% CI: 1.62-17.79) in the chronic groups. The adjusted OR for complete remission in the epidural group versus the medical group was 3.05 (95% CI: 1.20-7.73) in the acute group and 4.46 (95% CI: 1.20-16.54) in the chronic group.CEA can effectively relieve pain caused by PHN and acute HZ and increase remission rates. Combining CEA with standard medical treatment may offer a clinical advantage in the management of pain caused by PHN as well as acute HZ.

Role of the JNK Pathway in Varicella-Zoster Virus Lytic Infection and Reactivation

Mechanisms of neuronal infection by varicella-zoster virus (VZV) have been challenging to study due to the relatively strict human tropism of the virus and the paucity of tractable experimental models. Cellular mitogen-activated protein kinases (MAPKs) have been shown to play a role in VZV infection of nonneuronal cells, with distinct consequences for infectivity in different cell types. Here, we utilize several human neuronal culture systems to investigate the role of one such MAPK, the c-Jun N-terminal kinase (JNK), in VZV lytic infection and reactivation. We find that the JNK pathway is specifically activated following infection of human embryonic stem cell-derived neurons and that this activation of JNK is essential for efficient viral protein expression and replication. Inhibition of the JNK pathway blocked viral replication in a manner distinct from that of acyclovir, and an acyclovir-resistant VZV isolate was as sensitive to the effects of JNK inhibition as an acyclovir-sensitive VZV isolate in neurons. Moreover, in a microfluidic-based human neuronal model of viral latency and reactivation, we found that inhibition of the JNK pathway resulted in a marked reduction in reactivation of VZV. Finally, we utilized a novel technique to efficiently generate cells expressing markers of human sensory neurons from neural crest cells and established a critical role for the JNK pathway in infection of these cells. In summary, the JNK pathway plays an important role in lytic infection and reactivation of VZV in physiologically relevant cell types and may provide an alternative target for antiviral therapy.IMPORTANCE Varicella-zoster virus (VZV) has infected over 90% of people worldwide. While primary infection leads to the typically self-limiting condition of chickenpox, the virus can remain dormant in the nervous system and may reactivate later in life, leading to shingles or inflammatory diseases of the nervous system and eye with potentially severe consequences. Here, we take advantage of newer stem cell-based technologies to study the mechanisms by which VZV infects human neurons. We find that the c-Jun N-terminal kinase (JNK) pathway is activated by VZV infection and that blockade of this pathway limits lytic replication (as occurs during primary infection). In addition, JNK inhibition limits viral reactivation, exhibiting parallels with herpes simplex virus reactivation. The identification of the role of the JNK pathway in VZV infection of neurons reveals potential avenues for the development of alternate antiviral drugs.

Risk of Stroke/Transient Ischemic Attack or Myocardial Infarction with Herpes Zoster: A Systematic Review and Meta-Analysis

BACKGROUND

Accumulating evidence indicates that herpes zoster (HZ) may increase the risk of stroke/transient ischemic attack (TIA) or myocardial infarction (MI), but the results are inconsistent. We aim to explore the relationship between HZ and risk of stroke/TIA or MI and between herpes zoster ophthalmicus (HZO) and stroke.

METHODS

We estimated the relative risk (RR) and 95% confidence intervals (CIs) with the meta-analysis. Cochran's Q test and Higgins I² statistic were used to check for heterogeneity.

RESULTS

HZ infection was significantly associated with increased risk of stroke/TIA (RR = 1.30, 95% CI: 1.17-1.46) or MI (RR = 1.18, 95% CI: 1.07-1.30). The risk of stroke after HZO was 1.91 (95% CI 1.32-2.76), higher than that after HZ. Subgroup analyses revealed increased risk of ischemic stroke after HZ infection but not hemorrhagic stroke. The risk of stroke was increased more at 1 month after HZ infection than at 1-3 months, with a gradual reduced risk with time. The risk of stroke after HZ infection was greater with age less than 40 years than 40-59 years and more than 60 years. Risk of stroke with HZ infection was greater without treatment than with treatment and was greater in Asia than Europe and America but did not differ by sex.

CONCLUSIONS

Our study indicated that HZ infection was associated with increased risk of stroke/TIA or MI, and HZO infection was the most marked risk factor for stroke. Further studies are needed to explore whether zoster vaccination could reduce the risk of stoke/TIA or MI.

The Short- and Long-Term Risk of Stroke after Herpes Zoster: A Meta-Analysis

Background

Accumulating evidence indicates that stroke risk may be increased following herpes zoster. The aim of this study is to perform a meta-analysis of current literature to systematically analyze and quantitatively estimate the short and long-term effects of herpes zoster on the risk of stroke.

Methods

Embase, PubMed and Cochrane library databases were searched for relevant studies up to March 2016. Studies were selected for analysis based on certain inclusion and exclusion criteria. Relative risks with 95% confidence interval (CI) were extracted to assess the association between herpes zoster and stroke.

Results

A total of 8 articles were included in our analysis. The present meta-analysis showed that the risks of stroke after herpes zoster were 2.36 (95% CI: 2.17–2.56) for first 2 weeks, 1.56 (95% CI: 1.46–1.66) for first month, 1.17 (95% CI: 1.13–1.22) for first year, and 1.09 (95% CI: 1.02–1.16) for more than 1 year, respectively.

Conclusion

The results of our study demonstrated that herpes zoster was associated with a higher risk of stroke, but the risks decreased along with the time after herpes zoster.

Acute longitudinal and hemorrhagic myelitis caused by varicella-zoster virus in an immunocompetent adolescent

OBJECTIVES

In immunocompetent person, varicella-zoster virus (VZV)-induced myelitis is rare and the lesion usually comprise focal spinal cord segment. VZV-induced hemorrhagic myelitis with lesions comprising longitudinal spinal cord has never been reported.

METHODS

We report a 15-year-old male patient who developed acute flaccid quadriplegia, days after a common cold. One week after the quadriplegia developed, he presented a typical herpes zoster on the lateral side of his left waist.

RESULTS

IgG antibody for VZV was detected in cerebrospinal fluid and the spinal cord magnetic resonance imaging findings were consistent with that of small vessel vasculitis. Treatment with acyclovir and corticosteroids resulted in no significant clinical improvement.

CONCLUSIONS

In this report, we wanted to emphasize the hemorrhage, the extensiveness of inflammatory changes induced by VZV in spinal cord. It is suggested that VZV should be considered as a possible cause of a severe hemorrhagic myelitis even in immunocompetent adolescent.

Incidence of herpes zoster and associated events including stroke--a population-based cohort study

BACKGROUND

More detailed understanding of herpes zoster (HZ) is called for in the context of an increasing observed frequency of disease, and ongoing discussions regarding potential consequences of the disease. Thus, population-based data on incidence and complications of HZ are needed.

METHODS

We conducted a register-based cohort study in Västra Götaland County (population 1.5 million) in Sweden. We collected data on all patients diagnosed with HZ during the years 2008 to 2010 from population-based registers. Incidence rates (IR) of HZ and related complications were calculated and stratified by age and sex.

RESULTS

There were 13 269 new HZ cases during the study period. Overall, the IR of herpes zoster in both genders was 3.25 (95% CI: 3.16-3.34) per 1000 person years in 2010. The incidence was consistently higher in women than in men and in older than in young. A history of immunosuppression was more common than in the general population. The incidence was highest in individuals over 80 years of age (IR 9.2 per 1000 person years, 95% CI: 8.8-9.6) during 2008-2010. The most common complications to HZ were ocular engagement and postherpetic neuralgia; risks for stroke and sepsis were significantly elevated during the one year following diagnosis, especially in the youngest age group of patients 0-39 years.

CONCLUSIONS

Herpes zoster is more common in women, the elderly and immunosuppressed individuals. We verify a population-based association between herpes zoster and risk for stroke and sepsis, which may merit concern.

Childhood infections and trauma as risk factors for stroke

Stroke is as common as brain tumor in children. The etiology of childhood arterial ischemic stroke (AIS) appears to be multifactorial, resulting from the interaction between genetic predisposition and environmental triggers. The risk factors for AIS in children are markedly different from the atherosclerotic risk factors in adults. Trauma and infections have been identified as associations in previous studies and are exposures of particular interest because of their increased prevalence in the children. The aim of this review article is to provide an overview of the research studies that have addressed the role of infections and trauma in pediatric AIS.

Association between Bacterial Infection and Peripheral Vascular Disease: A Review

There are an increasing number of data showing a clinically important association between bacterial infection and peripheral artery disease (PAD). Bacteria suspected of being involved in PAD pathogenesis are: periodontal bacteria, gut microbiota, Helicobacter pylori, and Chlamydia pneumoniae. Infectious agents may be involved in the pathogenesis of atherosclerosis via activation of a systemic or local host immunological response to contamination of extravascular tissues or the vascular wall, respectively. A systemic immunological reaction may damage vascular walls in the course of autoimmunological cross-reactions between anti-pathogen antibodies and host vascular antigens (immunological mimicry), pathogen burden mechanisms (nonspecific activation of inflammatory processes in the vascular wall), and neuroendocrine-immune cross-talk. Besides activating the inflammatory pathway, bacterial infection may trigger PAD progression or exacerbation by enhancement of platelet reactivity, by a stimulatory effect on von Willebrand factor binding, factor VIII, fibrinogen, P-selectin activation, disturbances in plasma lipids, increase in oxidative stress, and resistance to insulin. Local inflammatory host reaction and induction of atherosclerotic plaque progression and/or instability result mainly from atherosclerotic plaque colonization by microorganisms. Despite these premises, the role of bacterial infection in PAD pathogenesis should still be recognized as controversial, and randomized, controlled trials are required to evaluate the outcome of periodontal or gut bacteria modification (through diet, prebiotics, and probiotics) or eradication (using antibiotics) in hard and surrogate cardiovascular endpoints.

Varicella-zoster virus vaccine, successes and difficulties

Despite intensive efforts in recent decades to develop preventive or therapeutic vaccines against diseases caused by herpes simplex virus (HSV), or varicella-zoster virus (VZV), members of the Alpha herpes virinae subfamily of human herpes viruses,a safe and efficient vaccine has been approved for commercial development only against VZV. The VZV vaccine contains a live attenuated strain, OKA. It consists of amixture of at least 13 subpopulations of viruses, all with deletions, insertions or mutations in the genome; the most common mutations are observed in the open reading frame 62 (ORF62). Experience over more than 30 years in Japan, the USA and other countries where VZV vaccination is provided has demonstrated that the vaccine is safe and the effectiveness of two doses compared to unvaccinated children is 98-99%. When administered in a higher dose to stimulate the declining cell-mediated immunity, the same vaccine has been shown to reduce the incidence and severity of herpes zoster in immunocompetent individuals older than 60 years. Vaccination of immuno-compromised subjects with this VZV vaccine is problematic and various strategies need to be explored. Differences in the pathomechanisms of infection, latency and immune evasion of VZV and HSV, together with host genetic factors, may explain the availability of the successful VZV vaccine and the failures of the past HSV vaccine candidates.

Animal models of varicella zoster virus infection

Primary infection with varicella zoster virus (VZV) results in varicella (chickenpox) followed by the establishment of latency in sensory ganglia. Declining T cell immunity due to aging or immune suppressive treatments can lead to VZV reactivation and the development of herpes zoster (HZ, shingles). HZ is often associated with significant morbidity and occasionally mortality in elderly and immune compromised patients. There are currently two FDA-approved vaccines for the prevention of VZV: Varivax® (for varicella) and Zostavax® (for HZ). Both vaccines contain the live-attenuated Oka strain of VZV. Although highly immunogenic, a two-dose regimen is required to achieve a 99% seroconversion rate. Zostavax vaccination reduces the incidence of HZ by 51% within a 3-year period, but a significant reduction in vaccine-induced immunity is observed within the first year after vaccination. Developing more efficacious vaccines and therapeutics requires a better understanding of the host response to VZV. These studies have been hampered by the scarcity of animal models that recapitulate all aspects of VZV infections in humans. In this review, we describe different animal models of VZV infection as well as an alternative animal model that leverages the infection of Old World macaques with the highly related simian varicella virus (SVV) and discuss their contributions to our understanding of pathogenesis and immunity during VZV infection.

Risk factors associated with vestibular nerve schwannomas

INTRODUCTION

Vestibular nerve schwannoma is a benign tumor that originates in the sheath of Schwann of the eighth cranial nerve. It is considered one of the most common benign intracranial tumors, and its cause is unclear.

OBJECTIVE

To identify the risk factors associated with vestibular nerve schwannomas.

METHODS

A hospital-based exploratory case-control study was conducted between 2006 and 2010 in 2 municipalities in the northeast region of Brazil. We included individuals with unilateral vestibular nerve schwannomas confirmed by imaging. The controls, selected from the same institutions as the cases, exhibited unilateral hearing loss or tinnitus and had undergone investigatory examinations similar to those of the cases, but the presence of tumor had been excluded. A pretested structured questionnaire, administered by trained interviewers who were blind to the condition of the individual being interviewed, was used to obtain sociodemographic data and data on potential risk factor exposure. We performed a multivariate analysis using unconditional logistic regression.

RESULTS

A total of 44 patients with vestibular nerve schwannomas and 104 controls participated in the study. A history of chicken pox (odds ratio, 6.59; 95% confidence interval, 2.07-20.9) and the exposure to more than 1 cranial x-ray procedure (odds ratio, 4.55; 95% confidence interval, 1.10-19.2) were identified as potential risk factors.

CONCLUSION

This exploratory study brings new hypotheses to be tested and thus works toward clarifying the causes and mechanisms involved in the cause and development of vestibular nerve schwannoma.

Epidemiology of varicella in Mexico

BACKGROUND

The epidemiological patterns of varicella-zoster virus (VZV) infection, which are strongly associated with climate, are characterized by more frequent infections occurring among children in temperate regions than in the tropics. In temperate regions, varicella exhibits a seasonal cyclic behavior in which the number of cases increases significantly during the winter and spring seasons, further supporting the role of environmental factors in disease transmission. However, the underlying mechanisms responsible for this distinctive behavior are not fully understood. In Mexico, information regarding the epidemiology of varicella is scarce, and the distribution of VZV infection has not been analyzed.

OBJECTIVES

In this article we investigate the epidemiological patterns of varicella in Mexico and their relationship with different environmental and demographic factors.

STUDY DESIGN

A retrospective study was conducted using the data reported by the National Center of Epidemiological Surveillance and Disease Control. The overall varicella incidence was calculated and associated with temperature, overcrowding, age, gender and population density.

RESULTS

The epidemiology of varicella showed an intriguing pattern, in which warmer regions were characterized by higher incidences than in temperate regions. Young children were the most affected age group. There was no correlation between varicella incidence and overcrowding or population density.

CONCLUSIONS

The epidemiology of varicella in Mexico significantly departs from the characteristic patterns observed in other tropical latitudes, with some features resembling those commonly associated with temperate regions.

Resistance testing of clinical varicella-zoster virus strains

Acyclovir resistance of varicella-zoster virus (VZV) has been reported in rare cases of immunocompromised patients. In this study, the natural polymorphism of the thymidine kinase (TK) and DNA polymerase (pol) genes was examined in 51 clinical VZV isolates sensitive to acyclovir (ACV). In addition, 16 VZV strains with clinical resistance to ACV were analyzed. None of the ACV-sensitive strains of the clades 1, 3 and 5 showed gene polymorphism of the TK. By contrast, the DNA pol gene exhibited polymorphism-related substitutions as a function of the VZV clade. The novel substitutions M286I, E824Q, R984H and H1089Y were detected in strains of clades 3 and 5. In the TK gene of 7 VZV strains with clinical ACV resistance, the novel substitutions L73I, A163stop, W225R, T256M, N334stop and the deletion of nucleotides 19-223 were found to be associated most likely with resistance. In one strain showing the substitution W225R, ACV resistance could be confirmed by the viral phenotype. In the DNA pol gene, the novel amino acid substitutions T237K and A955T could be detected, but their significance remains unclear. In conclusion, the characterization of resistance using genetic analysis of the TK and DNA pol genes has to be considered the method of choice for the determination of VZV resistance to antiviral drugs. In a considerable number of patients with clinical ACV-resistant VZV infections, resistance cannot be verified by virological methods.

Virus reactivation: a panoramic view in human infections

Viruses are obligate intracellular parasites, relying to a major extent on the host cell for replication. An active replication of the viral genome results in a lytic infection characterized by the release of new progeny virus particles, often upon the lysis of the host cell. Another mode of virus infection is the latent phase, where the virus is 'quiescent' (a state in which the virus is not replicating). A combination of these stages, where virus replication involves stages of both silent and productive infection without rapidly killing or even producing excessive damage to the host cells, falls under the umbrella of a persistent infection. Reactivation is the process by which a latent virus switches to a lytic phase of replication. Reactivation may be provoked by a combination of external and/or internal cellular stimuli. Understanding this mechanism is essential in developing future therapeutic agents against viral infection and subsequent disease. This article examines the published literature and current knowledge regarding the viral and cellular proteins that may play a role in viral reactivation. The focus of the article is on those viruses known to cause latent infections, which include herpes simplex virus, varicella zoster virus, Epstein-Barr virus, human cytomegalovirus, human herpesvirus 6, human herpesvirus 7, Kaposi's sarcoma-associated herpesvirus, JC virus, BK virus, parvovirus and adenovirus.

Analysis of human alphaherpesvirus microRNA expression in latently infected human trigeminal ganglia

Analysis of cells infected by a wide range of herpesviruses has identified numerous virally encoded microRNAs (miRNAs), and several reports suggest that these viral miRNAs are likely to play key roles in several aspects of the herpesvirus life cycle. Here we report the first analysis of human ganglia for the presence of virally encoded miRNAs. Deep sequencing of human trigeminal ganglia latently infected with two pathogenic alphaherpesviruses, herpes simplex virus 1 (HSV-1) and varicella-zoster virus (VZV), confirmed the expression of five HSV-1 miRNAs, miR-H2 through miR-H6, which had previously been observed in mice latently infected with HSV-1. In addition, two novel HSV-1 miRNAs, termed miR-H7 and miR-H8, were also identified. Like four of the previously reported HSV-1 miRNAs, miR-H7 and miR-H8 are encoded within the second exon of the HSV-1 latency-associated transcript. Although VZV genomic DNA was readily detectable in the three human trigeminal ganglia analyzed, we failed to detect any VZV miRNAs, suggesting that VZV, unlike other herpesviruses examined so far, may not express viral miRNAs in latently infected cells.