Human herpesvirus 6 rhombencephalitis in immunocompetent children

The Eruptive Fevers at Sixes and Sevens

Sixth Disease (roseola infantum) and its primary causative agent, HHV-6, share names that numerically concur. This article examines and answers the question of whether that correspondence is by design or coincidental by briefly reviewing the history and nomenclature of the HHV viruses and the classic febrile rashes of childhood while highlighting some clinical and microbiologic features of HHV-6 infection.

Paraneoplastic Cerebellar Degeneration Associated with Breast Cancer: A Case Report and a Narrative Review

Paraneoplastic neurological syndromes (PNSs) are an uncommon complication of cancer, affecting nearby 1/10,000 subjects with a tumour. PNSs can involve all the central and peripheral nervous systems, the muscular system, and the neuromuscular junction, causing extremely variable symptomatology. The diagnosis of the paraneoplastic disease usually precedes the clinical manifestations of cancer, making an immediate recognition of the pathology crucial to obtain a better prognosis. PNSs are autoimmune diseases caused by the expression of common antigens by the tumour and the nervous system. Specific antibodies can help clinicians diagnose them, but unfortunately, they are not always detectable. Immunosuppressive therapy and the treatment of cancer are the cornerstones of therapy for PNSs. This paper reports a case of PNSs associated with breast tumours and focuses on the most common paraneoplastic neurological syndromes. We report a case of a young female with a clinical syndrome of the occurrence of rigidity in the right lower limb with postural instability with walking supported and diplopia, with a final diagnosis of paraneoplastic cerebellar degeneration and seronegative rigid human syndrome associated with infiltrating ductal carcinoma of the breast.

Tissue specific signature of HHV-6 infection in ME/CFS

First exposure to various human herpesviruses (HHVs) including HHV-6, HCMV and EBV does not cause a life-threatening disease. In fact, most individuals are frequently unaware of their first exposure to such pathogens. These herpesviruses acquire lifelong latency in the human body where they show minimal genomic activity required for their survival. We hypothesized that it is not the latency itself but a timely, regionally restricted viral reactivation in a sub-set of host cells that plays a key role in disease development. HHV-6 (HHV-6A and HHV-6B) and HHV-7 are unique HHVs that acquire latency by integration of the viral genome into sub-telomeric region of human chromosomes. HHV-6 reactivation has been linked to Alzheimer's Disease, Chronic Fatigue Syndrome, and many other diseases. However, lack of viral activity in commonly tested biological materials including blood or serum strongly suggests tissue specific localization of active HHV-6 genome. Here in this paper, we attempted to analyze active HHV-6 transcripts in postmortem tissue biopsies from a small cohort of ME/CFS patients and matched controls by fluorescence in situ hybridization using a probe against HHV-6 microRNA (miRNA), miR-aU14. Our results show abundant viral miRNA in various regions of the human brain and associated neuronal tissues including the spinal cord that is only detected in ME/CFS patients and not in controls. Our findings provide evidence of tissue-specific active HHV-6 and EBV infection in ME/CFS, which along with recent work demonstrating a possible relationship between herpesvirus infection and ME/CFS, provide grounds for renewed discussion on the role of herpesviruses in ME/CFS.

Family Herpesviridae and neuroinfections: current status and research in progress

This article addresses the relationship between human herpesviruses (HHVs) and neuroinfections. Alphaherpesviruses, betaherpesviruses and gammaherpesviruses are neurotropic viruses that establish latency and exhibit reactivation capacity. Encephalitis and meningitis are common in cases of HHV. The condition promoted by HHV infection is a purported trigger for certain neurodegenerative diseases. Ongoing studies have identified an association between HSV-1 and the occurrence of Alzheimer's disease, multiple sclerosis and infections by HHV-6 and Epstein-Barr virus. In this review, we highlight the importance of research investigating the role of herpesviruses in the pathogenesis of diseases that affect the nervous system and describe other studies in progress.

Differential Impacts of HHV-6A versus HHV-6B Infection in Differentiated Human Neural Stem Cells

Within the family Herpesviridae, sub-family β-herpesvirinae, and genus Roseolovirus, there are only three human herpesviruses that have been described: HHV-6A, HHV-6B, and HHV-7. Initially, HHV-6A and HHV-6B were considered as two variants of the same virus (i.e., HHV6). Despite high overall genetic sequence identity (~90%), HHV-6A and HHV-6B are now recognized as two distinct viruses. Sequence divergence (e.g., >30%) in key coding regions and significant differences in physiological and biochemical profiles (e.g., use of different receptors for viral entry) underscore the conclusion that HHV-6A and HHV-6B are distinct viruses of the β-herpesvirinae. Despite these viruses being implicated as causative agents in several nervous system disorders (e.g., multiple sclerosis, epilepsy, and chronic fatigue syndrome), the mechanisms of action and relative contributions of each virus to neurological dysfunction are unclear. Unresolved questions regarding differences in cell tropism, receptor use and binding affinity (i.e., CD46 versus CD134), host neuro-immunological responses, and relative virulence between HHV-6A versus HHV-6B prevent a complete characterization. Although it has been shown that both HHV-6A and HHV-6B can infect glia (and, recently, cerebellar Purkinje cells), cell tropism of HHV-6A versus HHV-6B for different nerve cell types remains vague. In this study, we show that both viruses can infect different nerve cell types (i.e., glia versus neurons) and different neurotransmitter phenotypes derived from differentiated human neural stem cells. As demonstrated by immunofluorescence, HHV-6A and HHV-6B productively infect VGluT1-containing cells (i.e., glutamatergic neurons) and dopamine-containing cells (i.e., dopaminergic neurons). However, neither virus appears to infect GAD67-containing cells (i.e., GABAergic neurons). As determined by qPCR, expression of immunological factors (e.g., cytokines) in cells infected with HHV-6A versus HHV6-B also differs. These data along with morphometric and image analyses of infected differentiated neural stem cell cultures indicate that while HHV-6B may have greater opportunity for transmission, HHV-6A induces more severe cytopathic effects (e.g., syncytia) at the same post-infection end points. Cumulatively, results suggest that HHV-6A is more virulent than HHV-6B in susceptible cells, while neither virus productively infects GABAergic cells. Consistency between these in vitro data and in vivo experiments would provide new insights into potential mechanisms for HHV6-induced epileptogenesis.

Neuroimaging in cerebellar ataxia in childhood: A review

Ataxia is one of the most common pediatric movement disorders and can be caused by a large number of congenital and acquired diseases affecting the cerebellum or the vestibular or sensory system. It is mainly characterized by gait abnormalities, dysmetria, intention tremor, dysdiadochokinesia, dysarthria, and nystagmus. In young children, ataxia may manifest as the inability or refusal to walk. The diagnostic approach begins with a careful clinical history including the temporal evolution of ataxia and the inquiry of additional symptoms, is followed by a meticulous physical examination, and, depending on the results, is complemented by laboratory assays, electroencephalography, nerve conduction velocity, lumbar puncture, toxicology screening, genetic testing, and neuroimaging. Neuroimaging plays a pivotal role in either providing the final diagnosis, narrowing the differential diagnosis, or planning targeted further workup. In this review, we will focus on the most common form of ataxia in childhood, cerebellar ataxia (CA). We will discuss and summarize the neuroimaging findings of either the most common or the most important causes of CA in childhood or present causes of pediatric CA with pathognomonic findings on MRI. The various pediatric CAs will be categorized and presented according to (a) the cause of ataxia (acquired/disruptive vs. inherited/genetic) and (b) the temporal evolution of symptoms (acute/subacute, chronic, progressive, nonprogressive, and recurrent). In addition, several illustrative cases with their key imaging findings will be presented.

Myoclonus and cerebellar ataxia associated with COVID-19: a case report and systematic review

Background

Since the beginning of the coronavirus disease 2019 (COVID-19) pandemic in December 2019, neurological manifestations have been recognized as potential complications. Relatively rare movement disorders associated with COVID-19 are increasingly reported in case reports or case series. Here, we present a case and systematic review of myoclonus and cerebellar ataxia associated with COVID-19.

Methods

A systematic review was performed according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guideline using the PubMed and Ovid MEDLINE databases, from November 1, 2019 to December 6, 2020.

Results

51 cases of myoclonus or ataxia associated with COVID-19, including our case, were identified from 32 publications. The mean age was 59.6 years, ranging from 26 to 88 years, and 21.6% were female. Myoclonus was multifocal or generalized and had an acute onset, usually within 1 month of COVID-19 symptoms. Myoclonus occurred in isolation (46.7%), or with ataxia (40.0%) or cognitive changes (30.0%). Most cases improved within 2 months, and treatment included anti-epileptic medications or immunotherapy. Ataxia had an acute onset, usually within 1 month of COVID-19 symptoms, but could be an initial symptom. Concurrent neurological symptoms included cognitive changes (45.5%), myoclonus (36.4%), or a Miller Fisher syndrome variant (21.2%). Most cases improved within 2 months, either spontaneously or with immunotherapy.

Conclusions

This systematic review highlights myoclonus and ataxia as rare and treatable post-infectious or para-infectious, immune-mediated phenomena associated with COVID-19. The natural history is unknown and future investigation is needed to further characterize these movement disorders and COVID-19.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-021-10458-0.

Pathogen or Bystander: Clinical Significance of Detecting Human Herpesvirus 6 in Pediatric Cerebrospinal Fluid

Human herpesvirus 6 (HHV-6) is an important cause of meningitis and meningoencephalitis. As testing for HHV-6 in cerebrospinal fluid (CSF) is more readily available using the FilmArray Meningitis/Encephalitis panel (FA-ME; BioFire Diagnostics, Salt Lake City, UT), we aimed to determine the clinical significance of detecting HHV-6 in order to identify true infections and to ensure appropriate antiviral initiation. Chart review on 25 patients positive for HHV-6 by FA-ME was performed to determine clinical presentation, comorbidity, treatment, and outcome. The presence of chromosomally integrated HHV-6 (ciHHV-6) DNA was also investigated. Of 1,005 children tested by FA-ME, HHV-6 was detected in 25 (2.5%). Five patients were diagnosed with either HHV-6 meningitis or meningoencephalitis based on HHV-6 detection in CSF, clinical presentation, and radiographic findings. Detection of HHV-6 by FA-ME led to discontinuation of acyclovir within 12.0 h in all 12 patients empirically treated with acyclovir. Six of the 12 patients were started on ganciclovir therapy within 6.8 h; 4 of these were treated specifically for HHV-6 infection, whereas therapy was discontinued in the remaining 2 patients. CSF parameters were not generally predictive of HHV-6 positivity. The presence of ciHHV-6 was confirmed in 3 of 18 patients who could be tested. Five of the 25 patients included in the study were diagnosed with HHV-6 meningitis/meningoencephalitis. FA-ME results led to discontinuation of empirical antiviral treatment in 12 patients and appropriate initiation of ganciclovir in 4 patients. In our institution, detection of HHV-6 using FA-ME led to faster establishment of disease etiology and optimization of antimicrobial therapy.

HHV-6-Associated Neurological Disease in Children: Epidemiologic, Clinical, Diagnostic, and Treatment Considerations

Human herpesviruses 6A and 6B, often referred to collectively as human herpesvirus 6, are a pair of beta-herpesviruses known to cause a variety of clinical syndromes in both immunocompetent and immunocompromised individuals. Most humans are infected with human herpesvirus 6B, and many with human herpesvirus 6A. Primary infection typically occurs in early childhood, although large-scale reviews on the topic are limited. Herein, the authors explore the clinical manifestations of human herpesvirus 6-associated disease in both immunocompetent and immunocompromised pediatric patients, the risk factors for development of human herpesvirus 6-associated neurological disease, the risk of autoimmunity associated with development of active or latent infection, the relevance of human herpesvirus 6-specific diagnostic tests, and the medications used to treat human herpesvirus 6. The goal of this review is to improve the current understanding of human herpesvirus 6 in pediatric populations and to examine the most effective diagnostic and therapeutic interventions in this disease state.

Update on opsoclonus-myoclonus syndrome in adults

Opsoclonus-myoclonus syndrome in adults is a rare and heterogeneous disorder with the clinical features of opsoclonus, myoclonus, ataxia, and behavioral and sleep disturbances. The pathophysiology is thought to be immunological on the basis of paraneoplastic or infectious etiologies. Immunomodulatory therapies should be performed although the response may be incomplete. A number of autoantibodies have been identified against a variety of antigens, but no diagnostic immunological marker has yet been identified. This review focuses on underlying mechanisms of opsoclonus-myoclonus syndrome, including findings that have been identified recently, and provides an update on the clinical features and treatments of this condition.

Human herpesvirus 6 associated post-transplant acute limbic encephalitis: Clinical observations of biomarkers for risk of seizure in a pediatric population

BACKGROUND

Human herpesvirus 6 (HHV6) is a cause of post-transplant acute limbic encephalitis (PALE). Seizures are associated with this disorder yet no predictive biomarkers have been identified. The objective of this study was to evaluate lab and neurodiagnostic biomarkers in patients with HHV6 associated PALE.

METHODS

A retrospective chart review was performed at our institutions between 2000 and 2017. Patients were identified through a clinical database. Inclusion criteria included: age less than 18 years, HHV6 (quantitative real-time PCR or meningoencephalitis panel) tested in CSF and serum. Biomarkers of serum and CSF viral load, EEG, and MRI were reviewed along with clinical data.

RESULTS

In total, 11 patients met inclusion criteria. All patients had undergone hematopoietic stem cell transplantation. Five of 11 patients had seizures as part of their clinical course, all being controlled with antiepileptic monotherapy. Seizure semiology was focal-onset in three cases and generalized in two. Neuroimaging was normal in all patients within seven days but six patients developed T2 signal intensities in the temporal lobes on repeat imaging between 14-28 days. The median CSF HHV6 viral load for all patients was 47 300 copies/mL although the median viral load was 2586 copies/mL in patients who had seizure compared to 473 969 copies/mL in those who had not (P = 0.02). Those with seizures tended to be younger (median 6.5 years compared to 11 years, P = 0.27). All patients with seizures had an EEG with 80% demonstrating abnormalities.

CONCLUSION

In patients with post-hematopoietic stem cell transplant HHV6 associated PALE, lower CSF viral load may be associated with a higher likelihood to have seizures. This may indicate a primary infection as opposed to secondary reactivation phenomenon.

Detection of HHV-6 and EBV and Cytokine Levels in Saliva From Children With Seizures: Results of a Multi-Center Cross-Sectional Study

Background and Objective: One third of children with epilepsy are refractory to medications. Growing data support a role of common childhood infections with neurotropic viruses and inflammation in epileptogenesis. Our objective was to determine the frequency of Human Herpesvirus-6 (HHV-6) and Epstein-Barr Virus (EBV) infection and cytokine levels in saliva from children with seizures compared to healthy controls and to controls with a febrile illness without seizures. Methods: In this cross-sectional multi-center study, we collected saliva from 115 consecutive children with acute seizures (cases), 51 children with a fever and no seizures or underlying neurological disease (fever controls) and 46 healthy children (healthy controls). Specimens were analyzed by a novel droplet digital PCR for HHV-6 and EBV viral DNA and a bead-based immunoassay for neuroinflammatory cytokines. Results: Cases included febrile seizures (n = 30), acute seizures without (n = 53) and with fever (n = 4) in chronic epilepsy, new onset epilepsy (n = 13), febrile status epilepticus (n = 3), and first lifetime seizure (n = 12). HHV-6 DNA was found in 40% of cases vs. 37% fever controls and 35% healthy controls, with no statistically significant differences. EBV DNA was also detected with no differences in 17% cases, 16% fever controls, and 28% healthy controls. IL-8 and IL-1β were increased in saliva of 32 random samples from cases compared with 30 fever controls: IL-8 cases mean (SD): 1158.07 pg/mL (1427.41); controls 604.92 (754.04); p = 0.02. IL-1β 185.76 (230.57); controls 86.99 (187.39); p = 0.0002. IL-1β level correlated with HHV6 viral load (p = 0.007). Conclusion: Increase in inflammatory cytokines may play a role in the onset of acute seizures and saliva could represent an inexpensive and non-invasive method for detection of viral DNA and cytokines.

Viral Encephalitis

Viruses are a frequent cause of encephalitis. Common or important viruses causing encephalitis include herpesviruses, arboviruses, enteroviruses, parechoviruses, mumps, measles, rabies, Ebola, lymphocytic choriomeningitis virus, and henipaviruses. Other viruses may cause an encephalopathy. Host factors and clinical features of infection are important to consider in identifying the cause for encephalitis. Cerebrospinal fluid evaluation, serologic/polymerase chain reaction studies, and neuroimaging are cornerstones of diagnostic evaluation in encephalitis. Treatable forms of encephalitis are important to consider in all cases. Central nervous system inflammation may also occur because of postinfectious autoimmunity, such as acute disseminated encephalomyelitis or antibody-mediated encephalitis after herpes simplex virus encephalitis.

Acute transverse myelitis following an opsoclonus-myoclonus syndrome: An unusual presentation

Opso-myoclonus syndrome (OMS) is a very rare and severe condition. Ataxia, opsoclonus, myoclonus and/or behavioral and sleeping disturbances define that autoimmune disorder syndrome which is paraneoplastic or triggered by an infection. Here, we report a 3 year-old immunocompetent boy who developed an atypical OMS which was later complicated by an acute transverse myelitis. Screening for neuroblastoma was negative and extensive infectious screening revealed an active HHV-6 infection confirmed by blood and cerebrospinal fluid PCR. A parainfectious disease was suggested and immunosuppressive treatment was initiated. After 2 years of follow-up, the patient has a left leg paresia needing a splint and is otherwise normal. Transverse myelitis can be associated with parainfectious OMS and earlier immunosuppressive treatment in these cases may be useful especially in young and immunocompetent children.

Roseolovirus-associated encephalitis in immunocompetent and immunocompromised individuals

The roseoloviruses, human herpesvirus (HHV)-6A, HHV-6B, and HHV-7, can cause severe encephalitis or encephalopathy. In immunocompetent children, primary HHV-6B infection is occasionally accompanied by diverse clinical forms of encephalitis. Roseolovirus coinfections with heterologous viruses and delayed primary HHV-7 infection in immunocompetent adults result in very severe neurological and generalized symptoms. Recovery from neurological sequelae is slow and sometimes incomplete. In immunocompromised patients with underlying hematological malignancies and transplantation, frequent single or simultaneous reactivation of roseoloviruses elicit severe, lethal organ dysfunctions, including damages in the limbic system, brain stem, and hippocampus. Most cases have been due to HHV-6B with HHV-6A accounting for 2-3%. The most severe manifestation of HHV-6B reactivation is post-transplantation limbic encephalitis. Seizures, cognitive problems, and abnormal EEG are common. Major risk factors for HHV-6B-associated encephalitis include unrelated cord blood cell transplantation and repeated hematopoietic stem cell transplantation. Rare genetic disorders, male gender, certain HLA constellation, and immune tolerance to replicating HHV-6 in persons carrying chromosomally integrated HHV-6 might also predispose an individual to roseolovirus-associated brain damage. At this time, little is known about the risk factors for HHV-7-associated encephalitis. Intrathecal glial cell destruction due to virus replication, overexpression of proinflammatory cytokines, and viral mimicry of chemokines all contribute to brain dysfunction. High virus load in the cerebrospinal fluid, hippocampal astrogliosis, and viral protein expression in HHV-6B-associated cases and multiple microscopic neuronal degeneration in HHV-7-associated cases are typical laboratory findings. Early empirical therapy with ganciclovir or foscarnet might save the life of a patient with roseolovirus-associated encephalitis.

Update on infections with human herpesviruses 6A, 6B, and 7

Human herpesviruses 6A, 6B, and 7 (HHV-6A, HHV-6B, HHV-7) are genetically related to cytomegalovirus. They belong to the Roseolovirus genus and to the Betaherpesvirinae subfamily. They infect T cells, monocytes-macrophages, epithelial cells, and central nervous system cells. These viruses are ubiquitous and are responsible for lifelong chronic infections, most often asymptomatic, in the vast majority of the general adult population. HHV-6B is responsible for exanthema subitum, which is a benign disease of infants. HHV-6A and HHV-6B also cause opportunistic infections in immunocompromised patients: encephalitis, hepatitis, bone marrow suppression, colitis, and pneumonitis. Their etiological role in chronic diseases such as multiple sclerosis, cardiomyopathy, and thyroiditis is still controversial. The pathogenicity of HHV-7 is less clear and seems to be much more restricted. Chromosomal integration of HHV-6A and HHV-6B is transmissible from parents to offspring and observed in about 1% of the general population. This integration raises the question of potential associated diseases and can be a confounding factor for the diagnosis of active infections by both viruses. The diagnosis of HHV-6A, HHV-6B, and HHV-7 infections is rather based on gene amplification (PCR), which allows for the detection and quantification of the viral genome, than on serology, which is mainly indicated in case of primary infection. Ganciclovir, foscarnet, and cidofovir inhibit the replication of HHV-6A, HHV-6B, and HHV-7. Severe infections may thus be treated but these therapeutic indications are still poorly defined.

HHV-6 and seizure: A systematic review and meta-analysis

Human herpesvirus-6 (HHV-6) is a common infection in childhood. This systematic review aims to assess the relationship between HHV-6 infection and seizure disorders based on available literature. MEDLINE database was searched using a search strategy. We included studies that were published after 1993 in English, and described patients with HHV-6 infection and accompanying seizure or status epilepticus. We identified 503 articles, and included 147 studies. Meta-analysis results showed a 0.21 detection rate of HHV-6 in febrile seizure patients. In the febrile seizure group (110 cases), 76 patients had simple and 34 had complex febrile seizures. Patients with "HHV-6 infection and status epilepticus" had a mean age of 16.24 months. In children with febrile illnesses, a higher index of clinical suspicion for HHV-6 infection may be required. Further studies including CSF and brain tissue may be needed to validate relationships between HHV6 infection and epilepsy. J. Med. Virol. 89:161-169, 2017. © 2016 Wiley Periodicals, Inc.

Fatal human herpesvirus 6-associated encephalitis in two boys with underlying POLG mitochondrial disorders

BACKGROUND

Human herpesvirus 6 is a significant cause of the febrile illness roseola infantum in young children. Infection with human herpesvirus 6 typically causes a self-limited febrile illness but occasionally is associated with central nervous system manifestations, including febrile seizures and encephalitis. Host factors associated with severe manifestations of human herpesvirus 6-associated neurological disease remain poorly characterized.

CASE REPORTS

We report two previously healthy young boys with human herpesvirus 6-associated encephalitis who developed a progressive, and ultimately fatal, encephalopathy with refractory movement disorder concurrent with acquisition of acute human herpesvirus 6 infection. Both children were treated with the antiviral ganciclovir without improvement of their neurological symptoms, although quantitative human herpesvirus 6 polymerase chain reaction of cerebrospinal fluid and/or blood confirmed a decline in viral load with treatment. The clinical course in both cases was most consistent with Alpers-Huttenlocher syndrome, given the intractable seizures, developmental regression, and, ultimately, death due to liver and renal failure. In support of this, postmortem analysis identified both children to be compound heterozygous for mutations in the mitochondrial polymerase γ gene, POLG.

CONCLUSIONS

POLG mutations are associated with Alpers-Huttenlocher syndrome; however, no prior studies have examined the role of acute human herpesvirus 6 infection in these patients presenting with severe neurological disease. It is possible the POLG mutation phenotype was unmasked and/or exacerbated by human herpesvirus 6 infection in these two patients, potentially contributing to a more rapid clinical deterioration. This report provides new insight into a previously unrecognized association between POLG mutations and poor neurological outcome after human herpesvirus 6 infection.

Classification of HHV-6A and HHV-6B as distinct viruses

Shortly after the discovery of human herpesvirus 6 (HHV-6), two distinct variants, HHV-6A and HHV-6B, were identified. In 2012, the International Committee on Taxonomy of Viruses (ICTV) classified HHV-6A and HHV-6B as separate viruses. This review outlines several of the documented epidemiological, biological, and immunological distinctions between HHV-6A and HHV-6B, which support the ICTV classification. The utilization of virus-specific clinical and laboratory assays for distinguishing HHV-6A and HHV-6B is now required for further classification. For clarity in biological and clinical distinctions between HHV-6A and HHV-6B, scientists and physicians are herein urged, where possible, to differentiate carefully between HHV-6A and HHV-6B in all future publications.

Associations between human herpesvirus-6, human papillomavirus and cervical cancer

Cervical cancer (CxCa) is the second most common cancer among women globally. Human papillomavirus (HPV) infection is thought to be a necessary, but not sufficient, causal factor in CxCa development. Why some women are able to clear HPV infection with no adverse effects, whereas others develop cancer, remains unclear. HHV-6 has demonstrated transformative abilities and has been shown to be present in the genital tract. However, based on the current evidence, we cannot conclude that HHV-6 is a co-factor in HPV-associated carcinogenesis. Nonetheless, future research is warranted because of several crucial gaps in the literature.

Calibrated real-time polymerase chain reaction for specific quantitation of HHV-6A and HHV-6B in clinical samples

The recent classification of human herpesvirus 6 (HHV-6) A and B, previously considered as two variants of the same virus, as two distinct herpesvirus species, emphasizes the need to develop and standardize specific methods for their detection and quantitation for clinical use. The development of two highly sensitive calibrated real-time PCR to quantify HHV-6A and -6B variants in clinical specimen is described. Both assays displayed the same wide linear dynamic range from 10(0) to 10(6) copies of viral DNA in a single reaction and sensitivity of one copy/reaction. These systems allow for HHV-6A/B DNA load quantitation in different types of clinical specimens: blood or tissue cells when combined with the CCR5 assay; cell-free samples (plasma or other biological fluids) in combination with the calibrator technology. Due to the absence of cross-amplification and cross-hybridization, these methods detect minute amounts of one viral species even in the presence of a large excess of the other, allowing a specific quantitation of both viruses in the case of mixed infections. The new qPCR methods provide sensitive and specific tool for monitoring HHV-6A/B DNA load in clinical samples, facilitating the study of these viruses in human diseases.

Chromosomally-integrated human herpesvirus 6 in familial glioma etiology

Human herpesvirus 6 (HHV-6) is a highly neurotropic beta-herpesvirus with demonstrated transformative properties. HHV-6 infection has been implicated in the etiologies of cancers, including lymphoma and leukemia; conditions with brain involvement, including epilepsy and encephalitis; and other disorders. HHV-6 is also the only human herpesvirus that has been proven to integrate into the chromosomes of a proportion (1-12%) of infected individuals. Because several traditional genetic association studies have failed to identify a variant that can account for the established relationship between family history and glioma risk, the possibility that chromosomally-integrated HHV-6 (CI-HHV-6), as a heritable factor, may explain a proportion of familial glioma cases warrants evaluation. To test this hypothesis, the prevalence of CI-HHV-6 in familial glioma cases and related and unrelated cancer-free control groups should be compared. Among glioma-affected families, the inheritance pattern of CI-HHV-6 could be evaluated by constructing pedigrees. If CI-HHV-6 is found to be associated with familial glioma risk, this knowledge could potentially lead to the future development of novel therapeutic and preventive approaches, including vaccines and immunotherapies targeted at the HHV-6 sequences.

Rhombencephalitis / brainstem encephalitis

Rhombencephalitis (RE) is a syndrome of multiple causes and multiple outcomes. Most authors now use the terms "rhombencephalitis" and "brainstem encephalitis" interchangeably even though anatomically they are slightly different. The etiologic categories of RE include infections, autoimmune diseases, and paraneoplastic syndromes (PNS). Listeria is the most common cause of infectious RE. Listeria RE primary occurs in healthy young adults. It usually occurs as a biphasic time course with a flu-like syndrome followed by brainstem dysfunction; 75% of patients have a cerebrospinal fluid (CSF) pleocytosis, and almost 100% have an abnormal brain MRI scan. Positive CSF and blood cultures are the most specific for diagnosis. Treatment primarily is with ampicillin. Enterovirus 71 is probably the second most common infectious cause of RE; however, 95% of cases have occurred in the Asian-Pacific region and there is no specific treatment. Herpes simplex virus (HSV) is the third most common infectious cause of RE, and about 80% of cases are caused by HSV1 and 20% by HSV2. About 50% only had involvement of the brainstem whereas the other 50% also had supratentorial involvement of the temporal and frontal lobes. Mortality with acyclovir treatment was 22% versus those not on acyclovir 75%. Epstein-Barr virus (EBV) and human herpesvirus 6 (HHV6) have caused a few cases. The most common autoimmune etiology is Behçet disease. Over 90% of those with Behçet RE had abnormal MRI scans and 94% had a CSF pleocytosis. Treatment is with corticosteroids and immunosuppressive agents, but only 25% have complete recovery. Paraneoplastic causes are the third category of RE. Brain MRIs are usually normal; there is usually a CSF pleocytosis but the protein is usually normal. Often anti-neuronal antibodies can be found. Prognosis is poor and treatment is only partially beneficial. Because Listeria and HSV are the most common treatable acute causes of RE, we recommend empiric therapy with ampicillin and acyclovir for all cases after samples have been obtained from CSF and blood for cultures and the polymerase chain reaction (PCR). Antibiotics can be changed based upon MRI, culture results, PCR results, and antibody studies.

Chromosomally integrated human herpesvirus 6: questions and answers

Chromosomally integrated human herpesvirus 6 (ciHHV-6) is a condition in which the complete HHV-6 genome is integrated into the host germ line genome and is vertically transmitted in a Mendelian manner. The condition is found in less than 1% of controls in the USA and UK, but has been found at a somewhat higher prevalence in transplant recipients and other patient populations in several small studies. HHV-6 levels in whole blood that exceed 5.5 log10 copies/ml are strongly suggestive of ciHHV-6. Monitoring DNA load in plasma and serum is unreliable, both for identifying and for monitoring subjects with ciHHV-6 due to cell lysis and release of cellular DNA. High HHV-6 DNA loads associated with ciHHV-6 can lead to erroneous diagnosis of active infection. Transplant recipients with ciHHV-6 may be at increased risk for bacterial infection and graft rejection. ciHHV-6 can be induced to a state of active viral replication in vitro. It is not known whether ciHHV-6 individuals are put at clinical risk by the use of drugs that have been associated with HHV-6 reactivation in vivo or in vitro. Nonetheless, we urge careful observation when use of such drugs is indicated in individuals known to have ciHHV-6. Little is known about whether individuals with ciHHV-6 develop immune tolerance for viral proteins. Further research is needed to determine the role of ciHHV-6 in disease. Copyright © 2011 John Wiley & Sons, Ltd.

Ganciclovir-resistant human herpesvirus-6 encephalitis in a liver transplant patient: a case report

Human herpesvirus-6 (HHV-6) was initially isolated in 1986 from patients with lymphoproliferative disorders (Ablashi et al. 1987). Since that time, two genetically distinct variants were sequenced, HHV-6A and HHV-6B (Ablashi and Balachandran 1991). Both variants have been linked with neurologic disease (Crawford et al. 2007). HHV-6 encephalitis has been well described in literature, typically presenting with confusion, coma, seizure, and headache. The majority of HHV-6 encephalitis has been limited to post-transplant recipients (Singh and Paterson 2000). Encephalitis due to HHV-6 infection has been reported in two liver transplant recipients (Massih and Razonable 2009 and Montejo et al. 2002). Although there has been in vitro studies regarding the potential resistance patterns for HHV-6 virus, there has been only one clinic case report supporting these findings (Isegawa et al. 2009). We describe the first case of ganciclovir-resistant HHV-6 encephalitis in a post-liver transplant patient.

Update on diagnosis, treatment, and prognosis in opsoclonus-myoclonus-ataxia syndrome

PURPOSE OF REVIEW

Opsoclonus-myoclonus-ataxia syndrome (OMS) is a severe autoimmune central nervous system disorder, which predominantly affects young children and causes lifelong neurological disability. Early recognition and treatment may yield better outcomes.

RECENT FINDINGS

Appreciation of the spectrum of clinical presentations of OMS, awareness of common misdiagnoses, and utilization of diagnostic criteria may facilitate the timely diagnosis of OMS. Approximately 50% of patients have an associated neuroblastoma, which may escape detection by traditional methods and require MRI or computed tomography of the torso for diagnosis. In nonparaneoplastic cases, many associated infections have been reported. Although there has been progress in autoantibody identification and cerebrospinal fluid B cell expansion is a common finding, there is no diagnostic biomarker for OMS currently. Approximately 80% of reported patients, typically treated with conventional therapies such as adrenocorticotropin hormone, corticosteroids, and/or intravenous immunoglobulin, develop long-term neurological morbidity. Newer treatment approaches using early, aggressive therapy with cyclophosphamide or rituximab are promising.

SUMMARY

The diagnosis of OMS requires a high level of suspicion and a systematic approach for diagnostic testing, particularly for neuroblastoma. Future collaborative studies are required to determine whether early, aggressive therapy will improve the typically poor long-term neurological outcome.

Human herpesvirus-6 in patients with Crohn's disease

Human herpesvirus-6 (HHV-6) infections are usually asymptomatic reactivations in immunocompetent persons, but may be severe in immunocompromised individuals. Although primary HHV-6 infection is mainly associated with roseola infantum, it has also been associated with gastroenteritis, diarrhea, and nausea in children. In this study, we investigated the potential role of HHV-6 in Crohn's disease (CD). Evidence of HHV-6 infection in CD patients and controls was determined by immunohistochemistry (IHC), polymerase chain reaction (PCR), and quantitative real-time PCR (qPCR). Fifty-one tissue blocks from 23 CD patients and 20 tissue blocks from 20 controls were examined. Quantitativereal-time PCR was used to assess HHV-6 viral loads. IHC, PCR and qPCR indicated the presence of HHV-6 in both CD patients and controls. Immunohistochemistry of tissues revealed an almost equal frequency and distribution of positive cells; however, non-specific immunostaining confounded interpretation. HHV-6 DNA was detected in 52% (12/23) of CD and 55% (11/20) of control patients by PCR and in 69.5% (16/23) of CD cases and 65% (13/20) of controls by qPCR. Mean viral load in intestinal tissues was similar in CD and controls (33.4 and 57.9 copies microg(-1) DNA, respectively). Finding equal evidence of HHV-6 in patients and controls by multiple methods suggests that this virus is ubiquitous and probably not a cause of CD.

A suggested approach to the etiologic evaluation of status epilepticus in children: what to seek after the usual causes have been ruled out

Status epilepticus represents a true neurologic emergency that requires immediate treatment to stop seizure activity and prompt diagnostic evaluation to recognize potentially treatable causes. Although an etiology may be detected in many cases, in a significant number of patients the cause is not established by the usual laboratory or neuroimaging studies. We performed an extensive literature review of all unusual and often overlooked causes of status epilepticus in children, in an attempt to provide physicians with practical information on the diagnostic approach to patients, particularly those with refractory status epilepticus, for whom an etiology can not be detected by routine diagnostic protocols.

HHV-6 infection of tonsils and adenoids in children with hypertrophy and upper airway recurrent infections

OBJECTIVE

Human herpes virus 6 (HHV-6), the agent of a self-limiting exanthematic disease in childhood, persists in a silent state in the secondary lymphoid organs and the reactivation is characterized by HHV-6-induced inflammatory cytokines. This study investigates the possible etiological role of HHV-6 in children affected by tonsil and adenoid hypertrophy.

METHODS

55 tonsils, 80 adenoids fresh tissues and 74 blood samples were collected from 80 children (mean age 4.8 years, 43.5% female) undergoing elective tonsillectomy and/or adenoidectomy for tissue hypertrophy. Moreover, patients with <5 years old documented upper airway recurrent infections not related to relapsing of acute tonsillitis. Specific IgG antibodies and virus detection (by PCR, variant A/B enzymatic genotyping and real-time PCR) were performed.

RESULTS

In our series, HHV-6 seroprevalence was tested at 50%. HHV-6 variant B was the unique strain finding in 25% of adenoids, in 12.7% of tonsils and in 4% of peripheral blood mononuclear cells (PBMCs). HHV-6-B was prevalent in tonsils of children affected by upper airway infections (17.8% vs 7.4%) while the adenoids represented the more frequent reservoir (30.7% vs 19.5%) in patients with hypertrophy. HHV-6 viral load was low, ranging from 80 to 600 copies/10(6) cells suggesting a latent/persistent phase of infection.

CONCLUSION

These results reinforce the role of the secondary lymphoid organs as an important reservoir for HHV-6B. Nevertheless, infection of lymphoid cells, sustained by a low level of replication, could be sufficient to increase the local injury through an autologous mechanism of inflammation.

Fatal human herpesvirus-6 infection after renal transplantation

INTRODUCTION

Human herpesvirus (HHV)-6 infection is common after organ transplantation; however, most cases are associated with a mild clinical course. Donor-derived infection is rare, and there are no reports of HHV-6 infection in more than one recipient from a common donor.

METHODS

We describe two patients who developed severe, and in one case fatal, HHV-6 variant A infection after renal transplantation.

RESULTS

Both patients presented with severe colitis followed by the development of liver dysfunction and cytopenia. Multiple specimens from both recipients were positive for HHV-6 polymerase chain reaction variant A. Serum and white cells from the donor were positive for HHV-6 DNA, suggesting a donor-derived infection in these patients.

CONCLUSIONS

We report two cases of donor-derived HHV-6 infection from the same deceased donor, resulting in a fatal outcome in one patient. Treatment with valganciclovir was successfully instigated in one patient with a full recovery from the infection.

Spectrum of imaging findings in immunocompromised patients with HHV-6 infection

OBJECTIVE

The aim of this article is to review systemic manifestations of human herpes virus 6 (HHV-6) associated diseases in immunocompromised patients.

CONCLUSION

The spectrum of HHV-6 associated disorders is broad, but radiologists are frequently not familiar with these disorders. In the clinical setting of acute infection in an immunocompromised patient, the presence of one of these findings (e.g., limbic encephalitis; atypical interstitial pneumonia; pericarditis or myocarditis; or, less commonly, gastrointestinal or hepatobiliary disorders) should raise the suspicion of a possible HHV-6 related complication.

Effect of (r)-9-[4-hydroxy-2-(hydroxymethyl)butyl]guanine (H2G) and AZT-lipid-PFA on human herpesvirus-6B infected cells

BACKGROUND

Human herpesvirus-6 (HHV-6) has been associated with a wide spectrum of diseases. (r)-9-[4-Hydroxy-2-(hydroxymethyl)butyl]guanine (H2G) is an acyclic guanosine analogue that is structurally similar to acyclovir and is in clinical development for treatment of herpesvirus infections. H2G has been found to have activity against HSV type 1, HSV type 2, and HHV-6 in lymphoblast cell lines. A new anti-viral duplex drug, 3'-azido-3'-deoxythymidylyl-(5'-->2-O)-3-O-octadecyl-sn-glycerol (AZT-lipid-PFA), linking zidovudine (AZT) and foscarnet (PFA) via a lipophilic octadecylglycerol residue (lipid) also exhibits anti-viral activities against HIV, HSV type 1 and HCMV.

OBJECTIVE

To assess the efficacy of H2G and AZT-lipid-PFA conjugate against HHV-6.

STUDY DESIGN

Drug-associated toxicity and proliferative response were evaluated. We conducted in vitro experiments to determine the efficacy of H2G and an AZT-lipid-PFA conjugate in interfering with expression HHV-6 viral transcript in primary human peripheral blood mononuclear cells (PBMC).

RESULTS

Both H2G and AZT-lipid-PFA were effective at inhibiting expression of HHV-6 gene transcript at comparable concentrations. Additionally, while AZT-lipid-PFA treatment was toxic to cells at concentrations above 5microM, H2G treatment was associated with minimal cytotoxicity.

CONCLUSION

These data suggest the potential application of these anti-viral compounds in controlling HHV-6 infection.

Detection of human herpesvirus-6 variants in pediatric brain tumors: association of viral antigen in low grade gliomas

BACKGROUND

Human herpesvirus-6 (HHV-6) has been associated with a diverse spectrum of central nervous system (CNS) diseases and reported glial tropism.

OBJECTIVE

To determine if HHV-6 is present in a series of pediatric brain tumors.

STUDY DESIGN

Pediatric gliomas from 88 untreated patients represented in a tissue microarray (TMA) were screened for HHV-6 by nested polymerase chain reaction (PCR), in situ hybridization (ISH), and immunohistochemistry (IHC) and compared to non-glial tumors (N=22) and control brain (N=32). Results were correlated with tumor grade and overall survival.

RESULTS

HHV-6 U57 was detected by nested PCR in 68/120 (57%) tumors and 7/32 (22%) age-matched non-tumor brain (P=0.001). HHV-6 U31 was positive in 73/120 (61%) tumors and 11/32 (34%) controls (P=0.019). Seventy-two percent (43/60) of tumors were HHV-6 Variant A. HHV-6 U57 was confirmed by ISH in 83/150 (54%) tumors and 10/32 (31%) controls (P=0.021), revealing a non-lymphocytic origin of HHV-6. HHV-6A/B gp116/64/54 late antigen was detected by IHC in 50/124 (40%) tumors and 6/32 (18%) controls (P=0.013). Interestingly, 58% of low grade gliomas (N=67) were IHC positive compared to 19% of high grade gliomas (N=21, P=0.002) and 25% of non-gliomas (N=36, P=0.001). HHV-6A/B gp116/64/54 antigen co-localized with glial fibrillary acidic protein, confirming the astrocytic origin of antigen. Overall, there was no primary association between HHV-6A/B gp116/64/54 antigen detection and survival (P=0.861).

CONCLUSIONS

We provide the first reported series of HHV-6 detection in pediatric brain tumors. The predominance of HHV-6 in glial tumors warrants further investigation into potential neurooncologic disease mechanisms.

Detection of human herpesvirus-6 in adult central nervous system tumors: predominance of early and late viral antigens in glial tumors

The purpose is to determine the incidence of active and latent human herpesvirus-6 (HHV-6) infection in a large cohort of adult primary and recurrent CNS tumors. We screened a tissue microarray (TMA) containing more than 200 adult primary and recurrent CNS tumors with known clinical information for the presence of HHV-6 DNA by in situ hybridization (ISH) and protein by immunohistochemistry (IHC). One hundred six of 224 (47%) CNS tumors were positive for HHV-6 U57 Major Capsid Protein (MCP) gene by ISH compared to 0/25 non tumor control brain (P = 0.001). Fourteen of 30 (47%) tumors were HHV-6 MCP positive by nested PCR compared to 0/25 non-tumor brain controls (P = 0.001), revealing HHV-6 Variant A in 6 of 14 samples. HHV-6A/B early (p41) and late (gp116/64/54) antigens were detected by IHC in 66 of 277 (24%) (P = 0.003) and 84 of 282 (35%) (P = 0.002) tumors, respectively, suggesting active infection. HHV-6 p41 (P = 0.645) and gp116/64/54 (P = 0.198) antigen detection was independent of recurrent disease. Glial tumors were 3 times more positive by IHC compared to non glial tumors for both HHV-6 gp116/64/54 (P = 0.0002) and HHV-6 p41 (P = 0.004). Kaplan Meier survival analysis showed no effect of HHV-6 gp116/64/54 (P = 0.852) or HHV-6 p41 (P = 0.817) antigen detection on survival. HHV-6 early and late antigens are detected in adult primary and recurrent CNS tumors more frequently in glial tumors. We hypothesize that the glial-tropic features of HHV-6 may play an important modifying role in tumor biology that warrants further investigation.

Predominant human herpesvirus 6 variant A infant infections in an HIV-1 endemic region of Sub-Saharan Africa

Human herpesvirus 6, HHV-6, commonly infects children, causing febrile illness and can cause more severe pathology, especially in an immune compromised setting. There are virulence distinctions between variants HHV-6A and B, with evidence for increased severity and neurotropism for HHV-6A. While HHV-6B is the predominant infant infection in USA, Europe and Japan, HHV-6A appears rare. Here HHV-6 prevalence, loads and variant genotypes, in asymptomatic compared to symptomatic infants were investigated from an African region with endemic HIV-1/AIDS. DNA was extracted from blood or sera from asymptomatic infants at 6 and 18 months age in a population-based micronutrient study, and from symptomatic infants hospitalised for febrile disease. DNA was screened by qualitative and quantitative real-time PCR, then genotyped by sequencing at variable loci, U46 (gN) and U47 (gO). HIV-1 serostatus of infants and mothers were also determined. HHV-6 DNA prevalence rose from 15% to 22% (80/371) by 18 months. At 6 months, infants born to HIV-1 positive mothers had lower HHV-6 prevalence (11%, 6/53), but higher HCMV prevalence (25%, 17/67). HHV-6 positive febrile hospitalized infants had higher HIV-1, 57% (4/7), compared to asymptomatic infants, 3% (2/74). HHV-6A was detected exclusively in 86% (48/56) of asymptomatic HHV-6 positive samples genotyped. Co-infections with both strain variants were linked with higher viral loads and found in 13% (7/56) asymptomatic infants and 43% (3/7) HIV-1 positive febrile infants. Overall, the results show HHV-6A as the predominant variant significantly associated with viremic infant-infections in this African population, distinct from other global cohorts, suggesting emergent infections elsewhere.

Detection of human herpesvirus-6 in cerebrospinal fluid of patients with encephalitis

OBJECTIVE

Virus infections are the most common causes of encephalitis, a syndrome characterized by acute inflammation of the brain. More than 150 different viruses have been implicated in the pathogenesis of encephalitis; however, because of limitations with diagnostic testing, causative factors of more than half of the cases remain unknown.

METHODS

To investigate whether human herpesvirus-6 (HHV-6) is a causative agent of encephalitis, we examined for evidence of virus infection by determining the presence of viral sequence using polymerase chain reaction and assessed HHV-6 antibody reactivity in the cerebrospinal fluid of encephalitis patients with unknown cause. In a cohort study, we compared virus-specific antibody levels in cerebrospinal fluid samples of patients with encephalitis, relapsing-remitting multiple sclerosis, and other neurological diseases.

RESULTS

Our results demonstrated increased levels of HHV-6 IgG, as well as IgM levels, in a subset of encephalitis patients compared with other neurological diseases. Moreover, cell-free viral DNA that is indicative of active infection was detected in 40% (14/35) of encephalitis patients, whereas no amplifiable viral sequence was found in either relapsing-remitting MS or other neurological diseases patients. In addition, a significant correlation between polymerase chain reaction detection and anti-HHV-6 antibody response was also demonstrated.

INTERPRETATION

Collectively, these results suggested HHV-6 as a possible pathogen in a subset of encephalitis cases.