Overview: the biology of varicella-zoster virus infection

[Manifestations of herpes zoster ophthalmicus]

The article reviews the main ocular features of Herpes Zoster Ophthalmicus (HZO) including Ramsay-Hunt and Tolosa-Hunt syndromes that involve III, IV and VI pairs of cranial nerves and I branch of the trigeminal nerve, and describes treatment methods of its active manifestations and postherpetic neuralgia, as well as herpes zoster vaccination practices.

Microbiology laboratory and the management of mother-child varicella-zoster virus infection

Varicella-zoster virus, which is responsible for varicella (chickenpox) and herpes zoster (shingles), is ubiquitous and causes an acute infection among children, especially those aged less than six years. As 90% of adults have had varicella in childhood, it is unusual to encounter an infected pregnant woman but, if the disease does appear, it can lead to complications for both the mother and fetus or newborn. The major maternal complications include pneumonia, which can lead to death if not treated. If the virus passes to the fetus, congenital varicella syndrome, neonatal varicella (particularly serious if maternal rash appears in the days immediately before or after childbirth) or herpes zoster in the early years of life may occur depending on the time of infection. A Microbiology laboratory can help in the diagnosis and management of mother-child infection at four main times: (1) when a pregnant woman has been exposed to varicella or herpes zoster, a prompt search for specific antibodies can determine whether she is susceptible to, or protected against infection; (2) when a pregnant woman develops clinical symptoms consistent with varicella, the diagnosis is usually clinical, but a laboratory can be crucial if the symptoms are doubtful or otherwise unclear (atypical patterns in immunocompromised subjects, patients with post-vaccination varicella, or subjects who have received immunoglobulins), or if there is a need for a differential diagnosis between varicella and other types of dermatoses with vesicle formation; (3) when a prenatal diagnosis of uterine infection is required in order to detect cases of congenital varicella syndrome after the onset of varicella in the mother; and (4) when the baby is born and it is necessary to confirm a diagnosis of varicella (and its complications), make a differential diagnosis between varicella and other diseases with similar symptoms, or confirm a causal relationship between maternal varicella and malformations in a newborn.

Impact of varicella vaccine on varicella-zoster virus dynamics

The licensure and recommendation of varicella vaccine in the mid-1990s in the United States have led to dramatic declines in varicella incidence and varicella-related deaths and hospitalizations. Varicella outbreaks remain common and occur increasingly in highly vaccinated populations. Breakthrough varicella in vaccinated individuals is characteristically mild, typically with fewer lesions that frequently do not progress to a vesicular stage. As such, the laboratory diagnosis of varicella has grown increasingly important, particularly in outbreak settings. In this review the impact of varicella vaccine on varicella-zoster virus (VZV) disease, arising complications in the effective diagnosis and monitoring of VZV transmission, and the relative strengths and limitations of currently available laboratory diagnostic techniques are all addressed. Since disease symptoms often resolve in outbreak settings before suitable test specimens can be obtained, the need to develop new diagnostic approaches that rely on alternative patient samples is also discussed.

Ramsay Hunt syndrome in a 3-month-old infant

Ramsay Hunt syndrome is a disorder characterized by herpetic eruptions on the auricle, facial paralysis, and vestibulocochlear dysfunction, and is attributed to varicella zoster virus infection in the geniculate ganglion. Although it is a common cause of acute peripheral facial paralysis, children are not usually affected. We describe Ramsay Hunt syndrome in a 3-month-old infant who was referred because of a 2-day-old appearance of herpetic blisters on the right auricle and along the distribution of the right facial nerve. His mother had been infected with chickenpox during the second trimester of pregnancy. The infant presented with right facial palsy and was anxious, but had no fever. Otoscopy revealed herpetic eruptions in the right ear canal. Otoacoustic emissions were absent in the right ear and auditory brainstem responses confirmed moderate sensorineural hearing loss. Appropriate treatment resulted in slight improvement after the first week and complete recovery within 4 months. Infection with varicella zoster virus was proved by a significant increase in the serum anti-varicella zoster virus antibody titer during the convalescent phase of the disease.

New mosaic subgenotype of varicella-zoster virus in the USA: VZV detection and genotyping by oligonucleotide-microarray

A rapid and sensitive microarray-based method was used to distinguish the three major circulating genotypes of varicella-zoster virus (VZV). The method analyzes five variable positions located in a 447-nucleotide variable region 1 of open reading frame 22 (ORF 22r1); these single nucleotide polymorphisms (SNP) display in stably occurring patterns specific to each of the VZV genotypes established in previously published studies. Pairs of short oligonucleotide probes (oligoprobes) with sequences corresponding to all of the observed SNP were used to detect specific sequences. Fluorescently labeled ssRNA samples for hybridization with a chip were prepared by in vitro T7 polymerase driven transcription of the amplicons of ORF 22r1, followed by chemical labeling with Cy5 into RNA sample. Ratios between fluorescent hybridization signals from each pair of oligoprobes were used to assess the sequence at each SNP. We evaluated six reference VZV strains and 130 VZV clinical specimens to validate the method. The microarray method accurately identified strains isolated in the US in 2001-2002, representing all major genotypes as determined using more extensive sequence analysis, correctly assigning strains to genotypes E (81.5%), J (3%) and M (15.5%). In addition, a new M variant (M3) was identified.

Audiological assessment in Ramsay Hunt syndrome

Ramsay Hunt syndrome is known to cause symptoms and signs of vestibulocochlear dysfunction, including sensorineural hearing loss. The present study investigates the audiological features of a group of 15 patients with this syndrome. A complete otolaryngological, neurologic, and audiological workup was performed in every patient, including auditory brain stem response measurements and recording of transiently evoked otoacoustic emissions. In most patients, some degree of hearing loss was evident, and abnormal latencies and interpeak latencies of the auditory brain stem response, or even absence of the waves, were observed. Transiently evoked otoacoustic emissions were present in only 6 cases, and caloric tests showed unilateral weakness in the majority of the patients. In all of the performed tests, abnormalities were present only on the affected side. The audiological data suggested cochlear or retrocochlear involvement or involvement at more than one site along the auditory pathway.

Varicella-zoster virus immune evasion

CD4+ and CD8+ T cells play dual roles in varicella-zoster virus (VZV) pathogenesis. The first role is to deliver the virus to cutaneous sites during primary VZV infection, permitting replication at these sites and the successful transmission of the virus to other susceptible individuals. The second contribution of T cells is to provide the critical antigen-specific adaptive immunity needed to stop viral replication and maintain VZV latency in sensory ganglia. The equilibrium between VZV and the host can be predicted to be served by immune evasion mechanisms in at least two important ways, including the facilitation of cell-associated viremia during primary VZV infection and silent persistence in dorsal root ganglia. Interference with antigen presentation by MHC class I downregulation may be expected to play a role in both circumstances. Transient interference with MHC class II expression in varicella skin lesions should facilitate local replication and transmission. In addition, when VZV reactivates, the capacity of viral gene products to block the upregulation of MHC class II expression triggered by interferon-gamma should permit a sufficient period of viral replication to cause the lesions of herpes zoster, despite the presence of VZV-specific T cells, and to allow transmission of the virus to susceptible individuals. Although the effort is at an early stage compared to studies of other viral pathogens, identifying the VZV gene products that exert these effects and their mechanisms of interference has the potential to reveal novel aspects of MHC class I and class II antigen processing and presentation.

Pain caused by herpes zoster infection

Postherpetic neuralgia (PHN) is a neuropathic pain disorder that occurs most often in the elderly. This painful condition is uniquely suited for clinical research, resulting in an emerging understanding of the pathophysiology of the persistent pain. Until recently, only the tricyclic antidepressants proved effective for PHN. Controlled trials of a wide variety of therapeutic strategies are in progress or have been recently completed.

Virus infections of the eye

In reviewing the clinical features, diagnostic evaluations and therapies of the most common ocular viral infections we attempt to whet your appetite for attacking the numerous challenges in diagnosis and treatment of viral eye disease. The herpes viruses, HSV, VZV and CMV are the cause of significant ocular morbidity. HSV most commonly affects the cornea producing keratitis that can be recurrent and may lead to corneal clouding and neovascularisation. Manifestations can be purely infectious or immunological and treatment options must be tailored to the underlying pathophysiology. Herpes zoster ophthalmicus, caused by VZV infection of the first branch of the trigeminal nerve, produces a characteristic rash and can progress to keratitis and uveitis. HSV and VZV can cause retinitis in both immunocompetent and immunocompromised individuals. There has been a significant increase in the incidence of CMV retinitis since the beginning of the AIDS epidemic. We review the numerous new treatments, diagnostic tests and treatment strategies which have been developed in response to this potentially blinding retinal infection. Adenovirus produces an epidemic conjunctivitis and epidemic keratoconjunctivitis which are severe and extremely contagious conjunctival infections. HIV, molluscum contagiosum, EBV and rubeola also cause ocular diseases which are described.Copyright 1998 John Wiley & Sons, Ltd.

Campylobacter jejuni lipopolysaccharides in Guillain-Barré syndrome: molecular mimicry and host susceptibility

OBJECTIVE

This study was designed to determine if the presence of specific ganglioside-like moieties in Campylobacter lipopolysaccharides (LPSs) is related to the development of Guillain-Barré syndrome (GBS), and to discover how frequently such moieties, including GM1, are present in these LPSs.

METHODS

We studied Campylobacter isolates and sera from seven patients with GBS (five acute motor axonal neuropathy, one acute inflammatory demyelinating polyneuropathy, and one Fisher's syndrome), and compared them with similar specimens from patients with Campylobacter enteritis alone.

RESULTS

All GBS patients had antiganglioside antibodies. Anti-GM1 and anti-GD1a titers were significantly elevated in post-Campylobacter GBS, both axonal and demyelinating, compared with normal control subjects or those with uncomplicated Campylobacter diarrhea. Campylobacter isolated from patients with GBS and with enteritis alone had similar ganglioside-like moieties.

CONCLUSIONS

These results indicate that patients who develop GBS respond differently to the ganglioside-like epitopes on Campylobacter than do non-GBS diarrhea patients. Our findings support a role for host susceptibility as a determinant for the outcome following Campylobacter infection. These findings have important implications for the development of vaccines against Campylobacter jejuni.

Herpes zoster ophthalmicus

Images

Sensorimotor cerebral activation during optokinetic nystagmus. A functional MRI study

Self-motion or object motion can elicit optokinetic nystagmus (OKN), which is an integral part of dynamic spatial orientation. We used functional MR imaging during horizontal OKN to study cerebral activation patterns in sensory and ocular motor areas in 10 subjects. We found activation bilaterally in the primary visual cortex, the motion-sensitive areas in the occipitotemporal cortex (the middle temporal and medial superior temporal areas), and in areas known to control several types of saccades such as the precentral and posterior median frontal gyrus, the posterior parietal cortex, and the medial part of the superior frontal gyrus (frontal, parietal, and supplementary eye fields). Additionally, we observed cortical activation in the anterior and posterior parts of the insula and in the prefrontal cortex. Bilateral activation of subcortical structures such as the putamen, globus pallidus, caudate nucleus, and the thalamus traced the efferent pathways of OKN down to the brainstem. Functional MRI during OKN revealed a complex cerebral network of sensorimotor cortical and subcortical activation.

Temporal lobe epilepsy in childhood: clinical, EEG, and neuroimaging findings and syndrome classification in a cohort with new-onset seizures

Sixty-three children with new-onset temporal lobe epilepsy (TLE) underwent extensive clinical, EEG, and neuroimaging investigation as part of a prospective, community-based cohort study of the natural history of TLE in childhood. Complex partial seizures occurred in 94% of the children, and tonic-clonic seizures occurred in 14%. Developmental, behavioral, or learning problems were present in 38%. Eighteen children (29%) had a significant illness/event prior to the onset of TLE, including febrile status epilepticus in seven, meningitis in four, respiratory arrest in two, and head injury in one. Magnetic resonance imaging or computed tomography revealed structural abnormalities of the temporal lobe in 24 children (38%), including hippocampal sclerosis (HS) in 13 and tumor in eight. There was a strong association between HS and a history of significant illness/event prior to the onset of TLE (p < 0.001). Analysis of past history and neuroimaging findings led us to propose three etiologically defined subgroups of TLE; developmental TLE (10 children with long-standing, nonprogressive temporal lobe tumors and malformations), TLE with HS/significant antecedents (18 children with HS or a history of a significant illness/event), and cryptogenic TLE (34 children with normal neuroimaging findings and no significant past history). Etiologic differences between children with new-onset TLE may confer prognostic information that will be useful for counselling families and planning treatment.

Clinical and electrographic manifestations of lesional neocortical temporal lobe epilepsy

To determine whether lesional neocortical temporal lobe epilepsy (NTLE) can be differentiated from mesial temporal lobe epilepsy (MTLE) during the noninvasive presurgical evaluation, we compared the historical features, seizure symptomatology, and surface EEG of 8 patients seizure free after neocortical temporal resection with preservation of mesial structures and 20 patients after anterior temporal lobectomy for MTLE. Seizure symptomatology of 107 seizures (28 NTLE, 79 MTLE) was analyzed. One hundred one ictal EEGs (19 NTLE, 82 MTLE) were reviewed for activity at seizure onset; presence, distribution, and frequency of lateralized rhythmic activity (LRA); and distribution of postictal slowing. Seizure symptomatology and EEG data were compared between groups, and sensitivity, specificity, and positive and negative predictive values were determined for variables that differed significantly. Multiple logistic regression was used to determine whether patients could be correctly classified as having MTLE or NTLE. MTLE patients were younger at onset of habitual seizures and more likely to have a prior history of febrile seizures, CNS infection, perinatal complications, or head injury. NTLE seizures lacked features commonly exhibited in MTLE, including automatisms, contralateral dystonia, searching head movements, body shifting, hyperventilation, and postictal cough or sigh. NTLE ictal EEG recordings demonstrated lower mean frequency of LRA that frequently had a hemispheric distribution, whereas LRA in MTLE seizures was maximal over the ipsilateral temporal region. We conclude that it may be possible to differentiate lesional NTLE from MTLE on the basis of historical features, seizure symptomatology, and ictal surface EEG recordings. This may assist in the identification of patients with medically refractory nonlesional NTLE who frequently require intracranial monitoring and more extensive or tailored resections.

Crystal structure of varicella-zoster virus protease

Varicella-zoster virus (VZV), an alpha-herpes virus, is the causative agent of chickenpox, shingles, and postherpetic neuralgia. The three-dimensional crystal structure of the serine protease from VZV has been determined at 3.0-A resolution. The VZV protease is essential for the life cycle of the virus and is a potential target for therapeutic intervention. The structure reveals an overall fold that is similar to that recently reported for the serine protease from cytomegalovirus (CMV), a herpes virus of the beta subfamily. The VZV protease structure provides further evidence to support the finding that herpes virus proteases have a fold and active site distinct from other serine proteases. The VZV protease catalytic triad consists of a serine and two histidines. The distal histidine is proposed to properly orient the proximal histidine. The identification of an alpha-helical segment in the VZV protease that was mostly disordered in the CMV protease provides a better definition of the postulated active site cavity and reveals an elastase-like S' region. Structural differences between the VZV and CMV proteases also suggest potential differences in their oligomerization states.

Motor nerve terminal degeneration provides a potential mechanism for rapid recovery in acute motor axonal neuropathy after Campylobacter infection

We investigated the possible mechanisms of paralysis and recovery in a patient with the acute motor axonal neuropathy (AMAN) pattern of the Guillain-Barré syndrome. The AMAN pattern of GBS is characterized clinically by acute paralysis without sensory involvement and electrodiagnostically by low compound motor action potential amplitudes, suggesting axonal damage, without evidence of demyelination. Many AMAN patients have serologic or culture evidence of recent Campylobacter jejuni infection. Pathologically, the most severe cases are characterized by wallerian-like degeneration of motor axons affecting the ventral roots as well as peripheral nerves, but some fatal cases have only minor changes in the roots and peripheral nerves, and some paralyzed patients with the characteristic electrodiagnostic findings of AMAN recover rapidly. The mechanism of paralysis and recovery in such cases has been uncertain. A 64-year-old woman with culture-proven Campylobacter upsaliensis diarrhea developed typical features of AMAN. She improved quickly following plasmapheresis. Her serum contained IgG anti-GM1 antibodies. The lipopolysaccharide of the organism bound peanut agglutinin. This binding was blocked by cholera toxin, suggesting that the organism contained the Gal(beta1-3)GalNAc epitope of GM1 in its lipopolysaccharide. Motor-point biopsy showed denervated neuromuscular junctions and reduced fiber numbers in intramuscular nerves. In contrast, the sural nerve biopsy was normal and skin biopsy showed normal dermal and epidermal innervation. In AMAN the paralysis may reflect degeneration of motor nerve terminals and intramuscular axons. In addition, the anti-GM1 antibodies, which can bind at nodes of Ranvier, might produce failure of conduction. These processes are potentially reversible and likely to underlie the capacity for rapid recovery that characterizes some cases of AMAN.

Famciclovir for treatment of herpesvirus infections

OBJECTIVE

To discuss the antiviral activity, pharmacokinetics, clinical efficacy, and adverse effect profile of famciclovir, the oral prodrug of penciclovir (PCV), and to compare these features of famciclovir with those of acyclovir in the treatment of herpesvirus infections.

DATA SOURCES

Literature was identified by MEDLINE search, and abstracts from recent meetings were included where relevant. Data provided by the manufacturer were also used.

STUDY SELECTION

Data regarding antiviral activity were included if accepted and widely used methods were followed. Clinical trials in which a comparison with acyclovir or placebo was performed were given the highest priority.

DATA SYNTHESIS

In comparison with acyclovir, PCV has similar antiviral activity although its mode of action is not identical. When administered orally, faMciclovir, the oral prodrug of PCV, is better absorbed than acyclovir, yielding an absolute bioavailability of PCV of 77%. The predominant route of PCV elimination is via the kidneys, with a half-life of approximately 2.5 hours. In trials comparing famciclovir with acyclovir for the treatment of herpes zoster in immunocompetent individuals, comparable results were obtained. Famciclovir is also effective as therapy for recurrent episodes of genital herpes and may prove useful for chronic suppressive therapy. The most common adverse effects of famciclovir are headache and gastrointestinal upset. The dosage of famciclovir for herpes zoster in immunocompetent individuals is 500 mg po tid for 7 days; for recurrent genital herpes a dosage of 125 mg po bid for 5 days is recommended. Dosage adjustments are necessary in patients with renal dysfunction.

CONCLUSIONS

Given its comparable efficacy, similar adverse effect profile, and less frequent dosing schedule than acyclovir, famciclovir represents a viable alternative for treatment of herpes zoster and for episodic therapy of recurrent genital herpes in immunocompetent adults. Specific recommendations for other uses of famciclovir await the publication of recent clinical trial results.

Isolation and characterization of a novel oligodendrocyte-specific protein

Myelin plays a critical role in nervous system function and alterations in myelin-specific proteins cause a variety of neurologic disorders. We isolated a novel cDNA from the CNS that shares little nucleotide sequence homology with previously reported genes but appears to encode a protein related to peripheral myelin protein-22 (PMP-22) based on its amino acid sequence, predicted structure, and cellular localization. PMP-22 is important in peripheral myelination and Schwann cell proliferation, and mutations in its gene cause diseases of peripheral nerves. The isolated cDNA is 1.8 kb in length with an open reading frame of 621 bp. Northern blot analysis detected hybridization of labeled cDNA with a single 2.1-kb transcript only in the CNS. In situ hybridization revealed expression of this cDNA in oligodendrocytes of brain and spinal cord as well as in oligodendrocyte-enriched cultures; therefore we have named it oligodendrocyte-specific protein (OSP) cDNA. An OSP-specific polyclonal antibody reacted with a single 22-kd protein present in CNS myelin and oligodendrocytes. Developmental expression of OSP mRNA in the spinal cord was similar to that of the mRNA for a major myelin protein, proteolipid protein (PLP), and similar to PMP-22 in peripheral nerves. Since OSP is localized to oligodendrocytes and myelin, has a similar structure with PMP-22, and has a developmental pattern of expression like other myelin proteins, it probably has an important role in CNS myelinogenesis.

Differential changes in neurochemical markers of striatal dopamine nerve terminals in idiopathic Parkinson's disease

To determine the extent that different dopamine (DA) neuronal markers provide similar estimates of striatal (caudate and putamen) DA nerve terminal loss in idiopathic Parkinson's disease (PD), we compared, in postmortem striatum of 12 patients with PD and 10 matched controls, levels of five different DA neuronal markers. These markers included DA itself, three different estimates of the density of the DA transporter (DAT) ([3H])GBR 12,935 and [3H]WIN 35,428 binding; DAT protein immunoreactivity), and one estimate of the vesicular monoamine transporter (VMAT2; [3H]DTBZ binding). Striatal levels of all examined DA markers in PD were significantly intercorrelated. However, the magnitude of loss relative to controls was unequal (DAT protein = DA > [3H]WIN 35,428 > [3H]DTBZ > [3H]GBR 12, 935), with the differences more marked in the severely affected putamen. The less severe reduction of binding of the DAT/VMAT2 radioligands relative to DA and DAT protein could be explained by differential regulation/degeneration of different DA nerve terminal components or lack of specificity of the radioligands for the DA neuron. These postmortem data may help in interpretation of in vivo neuroimaging studies in PD in which only one radioligand is routinely employed.

Clinical research criteria for the diagnosis of progressive supranuclear palsy (Steele-Richardson-Olszewski syndrome): report of the NINDS-SPSP international workshop

To improve the specificity and sensitivity of the clinical diagnosis of progressive supranuclear palsy (PSP, Steele-Richardson-Olszewski syndrome), the National Institute of Neurological Disorders and Stroke (NINDS) and the Society for PSP, Inc. (SPSP) sponsored an international workshop to develop an accurate and universally accepted set of criteria for this disorder. The NINDS-SPSP criteria, which were formulated from an extensive review of the literature, comparison with other previously published sets of criteria, and the consensus of experts, were validated on a clinical data set from autopsy-confirmed cases of PSP. The criteria specify three degrees of diagnostic certainty: possible PSP, probable PSP, and definite PSP. Possible PSP requires the presence of a gradually progressive disorder with onset at age 40 or later, either vertical supranuclear gaze palsy or both slowing of vertical saccades and prominent postural instability with falls in the first year of onset, as well as no evidence of other diseases that could explain these features. Probable PSP requires vertical supranuclear gaze palsy, prominent postural instability, and falls in the first year of onset, as well as the other features of possible PSP. Definite PSP requires a history of probable or possible PSP and histopathologic evidence of typical PSP. Criteria that support the diagnosis of PSP, and that exclude diseases often confused with PSP, are presented. The criteria for probable PSP are highly specific, making them suitable for therapeutic, analytic epidemiologic, and biologic studies, but not very sensitive. The criteria for possible PSP are substantially sensitive, making them suitable for descriptive epidemiologic studies, but less specific. An appendix provides guidelines for diagnosing and monitoring clinical disability in PSP.

Cyclosporine-associated mutism in liver transplant patients

Four liver transplant recipients treated with cyclosporine developed a reversible neurologic syndrome characterized by a speech disorder leading to mutism. This complication, previously reported in a few liver transplant recipients treated with the immunosuppressive drug FK506, had not been described with cyclosporine. Recognition of this syndrome should prompt withdrawal of the drug and avoidance of unnecessary diagnostic procedures.

Rotational vertigo in embolic stroke of the vestibular and auditory cortices

We describe the unique case of a woman with embolic infarction within the right middle cerebral artery territory who had nonepileptic rotational vertigo, nausea, and unsteady gait that gradually resolved within a week. A well-demarcated lesion of the posterior insula (homologous to parieto-insular vestibular cortex in monkeys) was probably the cause. This is supported by a contraversive tilt of perceived vertical and by involvement of the adjacent auditory (Heschl's) cortex. Dipole source analysis of late auditory evoked potentials revealed a decreased amplitude of a dipole source in the right insular cortex, whereas two other dipoles situated in the temporal lobe showed symmetric activity.