Detection of latent varicella-zoster virus infection in human vestibular and spiral ganglia

A Guide to Preclinical Models of Zoster-Associated Pain and Postherpetic Neuralgia

Reactivation of latent varicella-zoster virus (VZV) causes herpes zoster (HZ), which is commonly accompanied by acute pain and pruritus over the time course of a zosteriform rash. Although the rash and associated pain are self-limiting, a considerable fraction of HZ cases will subsequently develop debilitating chronic pain states termed postherpetic neuralgia (PHN). How VZV causes acute pain and the mechanisms underlying the transition to PHN are far from clear. The human-specific nature of VZV has made in vivo modeling of pain following reactivation difficult to study because no single animal can reproduce reactivated VZV disease as observed in the clinic. Investigations of VZV pathogenesis following primary infection have benefited greatly from human tissues harbored in immune-deficient mice, but modeling of acute and chronic pain requires an intact nervous system with the capability of transmitting ascending and descending sensory signals. Several groups have found that subcutaneous VZV inoculation of the rat induces prolonged and measurable changes in nociceptive behavior, indicating sensitivity that partially mimics the development of mechanical allodynia and thermal hyperalgesia seen in HZ and PHN patients. Although it is not a model of reactivation, the rat is beginning to inform how VZV infection can evoke a pain response and induce long-lasting alterations to nociception. In this review, we will summarize the rat pain models from a practical perspective and discuss avenues that have opened for testing of novel treatments for both zoster-associated pain and chronic PHN conditions, which remain in critical need of effective therapies.

[A 73-year-old man with polyradiculopathy and multiple cranial neuropathies emerging separate from the originating dermatome of a varicella zoster skin lesion]

A 73-year-old man developed delayed-onset multiple cranial neuropathies of cranial nerves V, VII and VIII, and segmental paresis in the ipsilateral upper extremity related to the C4 to Th1 segment, after all skin lesions with varicella zoster (VZV) on the left neck of the C3-4 dermatome had dried and crusted over. On admission, cerebrospinal fluid (CSF) revealed pleocytosis (all mononuclear cells, 12/μl). Treatment was started with intravenous acyclovir (10 mg/kg, every 8 h for 14 days) and methylprednisolone (1,000 mg/day for 3 days). Four days after starting treatment, left segmental paresis was improved, but the multiple cranial neuropathies persisted. Oral prednisolone (0.5 mg/kg/day) was administered for 5 days, then tapered off. All neurological symptoms had disappeared by hospital day 23. Of particular interest was the discrepancy between skin regions affected by VZV (C3-4) and the regions of cranial neuropathy (cranial nerves V, VII, and VIII) and muscle weakness innervated by C4-Th1. Although CSF was negative for VZV DNA according to PCR testing, the antibody index for VZV was elevated. This suggests intrathecal synthesis of VZV antibodies and supports the diagnosis of VZV meningitis. Also, all cranial nerves involved in this case were reported to have the cranial nerve ganglia where VZV could have established latency and been reactivated. This suggests concurrent reactivation on each cranial nerve ganglia without cutaneous lesions, as zoster sine herpete. In addition, anastomoses among the upper cervical nerves, which are found in some patients, may have contributed to this condition. These mechanisms underlie various neurological symptoms associated with VZV infection.

Disseminated Varicella-Zoster Virus Infection Complicated by Encephalitis and Ramsay Hunt Syndrome in an HIV Patient

Varicella-zoster virus (VZV) is a human α-herpesvirus which cause primary varicella infection (chicken pox) or herpes zoster infection (shingles) after reactivation of the dormant virus. VZV infection is usually self-limited but disseminated infection can be seen in immunocompromised individuals. It can also get complicated by central nervous system (CNS) involvement. We describe a case of a 51-year-old male with human immunodeficiency virus (HIV) who presented with altered mental status and deficits in his right-sided cranial nerves of VI, VII, and VIII. The patient also had disseminated vesicular-pustular rash all over his body at different stages of healing. A diagnosis of disseminated VZV infection complicated by encephalitis and Ramsay Hunt syndrome was made and the patient was treated with intravenous acyclovir and oral prednisone with a rapid improvement. The coexistence of these conditions is rare. The purpose of this report is to increase awareness of the coexistence of these two conditions in HIV infected patients.

Post-mortem detection of six human herpesviruses (HSV-1, HSV-2, VZV, EBV, CMV, HHV-6) in trigeminal and facial nerve ganglia by PCR

Background

Among over 100 types of Herpesviridae viruses, eight can infect humans: herpes simplex viruses (HSV-1, HSV-2), varicella zoster virus (VZV), cytomegalovirus (CMV), Epstein-Barr virus (EBV), and human herpesviruses 6, 7, and 8 (HHV-6, HHV-7, HHV-8). After initial infection, the viruses remain latent for the lifetime of the host. The aim of this study was to determine the distribution of six different herpesviruses: HSV-1, HSV-2, VZV, EBV, CMV, and HHV-6 in trigeminal and facial nerve ganglia among a random group of Polish population.

Methods

The studied group consisted of 47 individuals (40 male, seven female); mean age of 47.4 ± 16.5 years) who died of independent causes (suicide, traffic accident, and poisoning, among others). Bilateral trigeminal and facial nerve ganglia of each cadaver were collected during the autopsy. Herpesviruses were detected using multiplex polymerase chain reaction technique.

Results

Herpesviruses were found in trigeminal and/or facial ganglia in 30/47 (63.8%) of cadavers. HHV-6 was the most prevalent of the herpesviruses and was found in nearly half of cadavers (n = 22; 46.8%), followed by HSV-1 (n = 7; 14.9%), VZV (n = 4; 8.5%), EBV (n = 4; 8.5%), HSV-2 (n = 2; 4.3%), and CMV (n = 1; 2.1%). Facial nerve ganglia (n = 23; 48.9%) were more often infected than trigeminal ganglia (n = 13; 27.7%).

Discussion

The results of this study have revealed a common presence of the herpesviruses in trigeminal and facial nerve ganglia among a random group of Polish population. Furthermore, the data also demonstrate simultaneous infection of the ganglia with different herpesviruses. This study has contributed to the knowledge of prevalence and localization of herpesviruses in different structures of the nervous system.

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.

Isolated cochlear neuritis from varicella reactivation mimicking a vestibular schwannoma

We present a case of a patient with progressive unilateral sensorineural hearing loss and tinnitus with internal auditory canal enhancement on magnetic resonance imaging (MRI) secondary to isolated cochlear neuritis from varicella reactivation. MRI following antiviral treatment showed resolution of enhancement. Varicella reactivation is commonly seen in the form of Ramsay Hunt syndrome, which is known to produce abnormal MRI enhancement from facial and vestibulocochlear neuritis; however, its characteristic clinical signs aid the diagnosis. This case is unique in that the only manifestation of varicella infection was unilateral hearing loss. This case outlines the importance of maintaining a broad differential diagnosis in the evaluation of unilateral hearing loss as well as recognizing the limited specificity of MRI.

[Successful treatment with acyclovir and a corticosteroid for lower cranial polyneuropathy in zoster sine herpete: a case report]

A 62-year-old woman developed meningitis as well as acute paralysis of glossopharyngeal, vagus, and accessory nerves on the right side and also had dysfunction of the left hypoglossal nerve. Although there was no evidence of a typical cutaneous or mucosal herpetic lesion, PCR detection of varicella zoster virus (VZV)-DNA in cerebrospinal fluid confirmed the clinical diagnosis of polyneuritis cranialis due to VZV infection and zoster sine herpete. After starting intravenous acyclovir and methylprednisolone, her hypoglossal nerve palsy disappeared within a day and all other symptoms and signs dramatically improved. A rapid improvement observed in our patient suggests that the right cranial polyneuropathy could be caused by inflammation associated with epineurial edema (where the ninth, tenth, and eleventh cranial nerves pass through the right jugular foramen), whereas the exact mechanism of the twelfth cranial nerve involvement on the contralateral side is unknown. Our clinical findings indicate that acute lower cranial polyneuropathy in patients with zoster sine herpete should be treated immediately with combined administration of acyclovir and an anti-inflammatory corticosteroid.

Pathogenesis of varicelloviruses in primates

Varicelloviruses in primates comprise the prototypic human varicella-zoster virus (VZV) and its non-human primate homologue, simian varicella virus (SVV). Both viruses cause varicella as a primary infection, establish latency in ganglionic neurons and reactivate later in life to cause herpes zoster in their respective hosts. VZV is endemic worldwide and, although varicella is usually a benign disease in childhood, VZV reactivation is a significant cause of neurological disease in the elderly and in immunocompromised individuals. The pathogenesis of VZV infection remains ill-defined, mostly due to the species restriction of VZV that impedes studies in experimental animal models. SVV infection of non-human primates parallels virological, clinical, pathological and immunological features of human VZV infection, thereby providing an excellent model to study the pathogenesis of varicella and herpes zoster in its natural host. In this review, we discuss recent studies that provided novel insight in both the virus and host factors involved in the three elementary stages of Varicellovirus infection in primates: primary infection, latency and reactivation.

Lack of Association between Human Herpesvirus and Vestibular Schwannoma

Objective

To assess for the presence of human herpesvirus (HHV) using immunohistochemical and polymerase chain reaction (PCR) assay in surgically excised vestibular schwannoma (VS) samples.

Study Design

Cross-sectional study.

Setting

A retrospective laboratory-based study of tumors from patients with vestibular schwannoma.

Subjects and Methods

Tissue microarrays (TMAs) representing sporadic and NF2-associated VS from 121 patients, as well as appropriate positive and negative controls, were studied. TMA sections were immunostained using antibodies directed against HHV-1, HHV-2, HHV-3, HHV-4, HHV-5, and HHV-8. PCR was used for the detection of all 8 known human herpesviruses.

Results

There was no detectable HHV (HHV-1, HHV-2, HHV-3, HHV-4, HHV-5, HHV-8) by immunohistochemistry in any of the 121 cases of sporadic and NF2 cases analyzed. These data were further validated by DNA sequence analyses using PCR in a subset of the VS samples, all of which were found to be negative for all HHV.

Conclusions

The data offer no support for an association between HHV and the development of sporadic or NF2-associated VS in humans.

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.

No increased risk of sudden sensorineural hearing loss following recent herpes zoster: a nationwide population-based study

CONCLUSION

There is no increased risk for sudden sensorineural hearing loss (SSNHL) among people who have experienced a recent herpes zoster attack, compared with a matching population.

OBJECTIVE

The pathogenesis of SSNHL remains unknown, but viral infection is considered to be one of the main causes. The objective of this case-cohort study was to investigate the frequency and risk for SSNHL following a recent herpes zoster attack in the general population.

METHODS

We extracted 313 612 patients with herpes zoster from a nationwide health registry in Taiwan, and also randomly selected 313 612 matched control subjects. Each participant was individually tracked for 2 months from their index ambulatory care visit to identify those who developed SSNHL. Stratified Cox proportional hazard regressions were conducted to analyze the risk of SSNHL for the sampled patients.

RESULTS

Of the sample of 627 224 patients, 121 (0.02%) had SSNHL during the 2-month follow-up period, 59 from the study group (0.02% of the herpes zoster patients) and 62 from the comparison group (0.02% of patients without herpes zoster). Regression analysis revealed no increased adjusted hazard of SSNHL during the 2-month follow-up period for patients with herpes zoster as compared to those without (hazard ratio = 0.89, 95% confidence interval (CI) = 0.63-1.28, p = 0.540).

[Ramsay Hunt syndrome: our experience]

INTRODUCTION

Ramsay Hunt syndrome (RHS) is a disease caused by the Varicella Zoster virus and characterised by skin rash, peripheral facial palsy and otologic symptoms.

OBJECTIVE

This was an epidemiological study on the incidence and prognosis of this syndrome.

METHODS

A retrospective study was carried out on the patients diagnosed with RHS who were seen in the emergency room between January 1995 and December 2004, and were followed up for more than 6 months.

RESULTS

Of the 54 patients included in this study, 7.5% had facial palsy as their first symptom, followed by otologic signs (20.2% had both simultaneously); 72.5% presented otologic signs before facial palsy. Hypoacusis was reported in 26% of the patients, but was objectively present in all of them. The level of facial palsy determined the prognosis.

CONCLUSION

In this syndrome, the prognosis of facial palsy depends on the initial symptoms and clinical findings. Otologic symptoms occur more frequently in patients having a greater degree of facial nerve affectation. Vestibular symptoms have a good prognosis. Hypoacusis is much more frequent than reported; as it may go unnoticed in these patients, it should always be confirmed by complementary tests.

Varicella-zoster virus load and cochleovestibular symptoms in Ramsay Hunt syndrome

OBJECTIVES

The mechanism by which varicella-zoster virus (VZV) reactivation causes cochleovestibular symptoms (CVSs) in patients with Ramsay Hunt syndrome (RHS) remains to be elucidated. The present study analyzed the relationship between VZV load and the onset of CVSs in RHS.

METHODS

The subjects consisted of 56 patients with RHS; 29 exhibited CVSs and facial paralysis (FP; group 1), and 27 exhibited FP without CVSs (group 2). The VZV DNA copy number in the saliva was measured with a quantitative polymerase chain reaction. Anti-VZV antibodies were assayed by an enzyme-linked immunosorbent assay with paired sera.

RESULTS

There was no significant difference in maximum viral copy number between the two groups. In group 1, CVSs occurred at various times between the early phase and the regression phase of VZV reactivation. In some patients, CVSs occurred in the early phase of VZV reactivation, before the onset of zoster lesions and FP.

CONCLUSIONS

There are various different patterns in the development of eighth cranial nerve dysfunction, which is caused by progression of neuritis or labyrinthitis following VZV reactivation. Our data suggest that CVSs in RHS may also be caused by reactivation of VZV in the spiral and/or vestibular ganglia.

Varicella-zoster virus DNA in cells isolated from human trigeminal ganglia

To determine the type of cell(s) that contain latent varicella-zoster virus (VZV) DNA, we prepared pure populations of neurons and satellite cells from trigeminal ganglia of 18 humans who had previously had a VZV infection. VZV DNA was present in 34 of 2,226 neurons (1.5%) and in none of 20,700 satellite cells. There was an average of 4.7 (range of 2 to 9) copies of VZV DNA per latently infected neuron. Latent VZV DNA was primarily present in large neurons, whereas the size distribution of herpes simplex virus DNA was markedly different.

Peripheral vestibular disorders with acute onset of vertigo

Disorders of the vestibular nerve and end organs are the most common causes of vertigo. The advances in recognizing different forms of canalolithiasis and cupulolithiasis, which sometimes present with continuous positional nystagmus, have revealed a peripheral vestibular aetiology in which central nervous system lesions were previously suspected. Treatments using repositioning manoeuvres are also successful in cases in which nystagmus does not appear, and when administered by less specialized physicians. In acute vestibulopathy, suspicions of the activation of herpes virus infections as a causative agent are increasing, but no reports on the treatment of such infections are yet available. New treatments are in development for use in Ménière's disease.

Prevalence of herpesviruses in cranial nerve ganglia

A number of cranial nerve disorders are known to result from viral infection or reactivation, including Bell's palsy, Ramsay Hunt syndrome and herpetic laryngitis. The consequences of these diseases are well established although the patient population at risk is not. Prevalence studies in the general population are an initial step toward defining individuals at risk. The aim of this study was to determine the prevalence of herpesvirus DNA in cranial nerve ganglia in a random population sample. Qualitative molecular biologic analysis using polymerase chain reaction assay of the trigeminal, geniculate, vestibular, spiral and vagal ganglia was used in 18 randomly selected fresh cadaver heads. Herpes simplex virus (HSV) DNA was detected in 42% of all ganglia surveyed. Varicella zoster virus (VZV) DNA was detected in 44% of all ganglia. The difference in the prevalence rate between viruses was not significant (p = 0.63). At least 1 of the 2 viruses was found in 65% of all ganglia. Both HSV and VZV can commonly be recovered from cranial nerve ganglia. In order to confirm a viral etiology for various cranial nerve disorders, demonstration of a significant difference in prevalence of the viruses in specimens from afflicted individuals will be necessary.

The pathology of facial and vestibular neuronitis

OBJECTIVE

To measure disease of idiopathic nature in the ganglia of the human facial (FN) and vestibular nerves (VN).

METHOD

One hundred horizontally sectioned human temporal bones (TB) were examined under light microscopy. The TB were sectioned at 20 microm, and every 10th section was stained with hematoxylin and eosin and mounted. The volume fractions (VF) of degenerated cells in the FN ganglion and focal axonal degeneration in the VN were measured with stereologic techniques.

RESULTS

Twenty-five TB were excluded because of artifact or poor staining of the FN and VN. Fifty-one TB contained degenerated cells in the FN meatal ganglion (MG) and/or focal axonal degeneration in the VN. Thirty-one FN had degenerated cells in the MG (VF = 1% to 55%) and none in the geniculate ganglion. In 45 TB, focal axonal degeneration was found in the VN (VF = 1% to 50%; the VF was less than 15% in all but one TB). MG and VN degeneration occurred together in 25 TB. None of the cases had a history of FN paralysis, but 20 had a history of vertigo. Twenty-four TB from patients of similar ages with similar otopathologies did not reveal degeneration in the FN or VN.

CONCLUSION

The FN and VN lesions in these 51 TB may be virus-induced and reflect a higher incidence of idiopathic FN and VN neuronitis than previously thought.