Human herpesvirus 6 and 7 in febrile status epilepticus: the FEBSTAT study

Update on human herpesvirus 7 pathogenesis and clinical aspects as a roadmap for future research

Human herpesvirus 7 (HHV-7) is a common virus that is associated with various human diseases including febrile syndromes, dermatological lesions, neurological defects, and transplant complications. Still, HHV-7 remains one of the least studied members of all human betaherpesviruses. In addition, HHV-7-related research is mostly confined to case reports, while in vitro or in vivo studies unraveling basic virology, transmission mechanisms, and viral pathogenesis are sparse. Here, we discuss HHV-7-related literature linking clinical syndromes to the viral life cycle, epidemiology, and viral immunopathogenesis. Based on our review, we propose a hypothetical model of HHV-7 pathogenesis inside its host. Furthermore, we identify important knowledge gaps and recommendations for future research to better understand HHV-7 diseases and improve therapeutic interventions.

Neurological autoantibody prevalence in chronic epilepsy: Clinical and neuropathologic findings

BACKGROUND

We aimed to explore the prevalence of autoimmune antibodies (Abs) in a large consecutive series with "chronic" epilepsy and without symptoms of autoimmune encephalitis; and to compare the immunopathology of brain tissue from drug-resistant epilepsy (DRE) with and without Abs positivity.

METHODS

Neuronal and glial antibodies were detected in the serum of patients who were admitted to the wards of West China Hospital from October 2016 to September 2019 and had epilepsy by cell-based assays and tissue-based assays.

RESULTS

Twenty-one (6.8 %) of 328 patients had positive Ab findings for the following: dipeptidyl-peptidase-like protein-6 (n = 7), contactin-associated protein-like 2 (n = 5), glutamic acid decarboxylase 65 (n = 4), gamma aminobutyric acid beta receptor (n = 2), N-methyl-d-aspartate receptor (n = 2), and dopamine D2 receptor (n = 1). Antibodies were detected in 6.9 % (13/187) of epilepsy people with unknown etiology and 5.6 % (8/141) of patients with known etiology, respectively. Among 190 patients with DRE, 14 (7.3 %) patients were Abs-positive. There was no significant difference between individuals with seropositive and seronegative results in clinical manifestations, except that the history of febrile seizure was significantly more frequent in the seropositive group. Moreover, brain samples from 3 patients with Abs-positive DRE (with DPPX in 2 patients, and CASPR2 in 1 patient) and 18 patients with Abs-negative DRE were analyzed for immunopathology. We found higher expression of CD8-positive T-cells in the hippocampus of Abs-positive DRE group.

CONCLUSIONS

Neuronal antibodies are potentially involved in the process of "chronic" epilepsy, and CD8-positive T-cells may play an important role in this process.

Febrile seizure in children with COVID-19 during the Omicron variant-predominant era: A single-center study

OBJECTIVE

Coronavirus disease 2019 (COVID-19) has significantly impacted medical services worldwide. During the Omicron variant-predominant era, febrile seizure (FS) in patients with COVID-19 increased compared to that in the pre-Omicron variant era. Therefore, this study aimed to demonstrate the clinical characteristics of FS in patients with COVID-19.

METHODS

We surveyed patients aged < 16 years who presented with FS to the emergency room of Tottori University Hospital. The patients were divided into two groups: FS patients with COVID-19 (FS with COVID-19 group) and FS patients without COVID-19 (FS without COVID-19 group) as per the results of the respiratory multiplex array test. Patients with positive results for both SARS-CoV-2 and other microorganisms were excluded. We obtained data on the patients' clinical backgrounds, symptoms, seizure duration, type of FS (simple or complex), diagnostic examinations, laboratory test results, and treatment. We compared the data between the FS with and without COVID-19 groups.

RESULT

A total of 128 patients with FS met the inclusion criteria. Of these, 18 patients and 110 patients were included in the FS with COVID-19 group and without COVID-19 group, respectively. The late FS onset (>60 months) were significantly more common in the FS with COVID-19 group than that in the FS without COVID-19 group. Moreover, patients in the FS with COVID-19 group had significantly longer seizure durations than those in the FS without COVID-19 group. A diazepam (DZP) suppository was administered to 72% of FS patients with COVID-19 after the first seizure during a febrile episode.

CONCLUSION

FS patients with COVID-19 had different distributions of age at onset and seizure duration than those without COVID-19. The use of DZP suppositories was more frequent in FS patients with COVID-19 compared to those without COVID-19.

HHV-6 infections in hospitalized young children of Gabon

PURPOSE

Fever is a common cause for hospitalization among the pediatric population. The spectrum of causative agents is diverse. Human herpesvirus 6 (HHV-6) is a ubiquitous virus that often causes hospitalization of children in western countries. Previously, we investigated the cause of fever of 600 febrile hospitalized children in Gabon, and in 91 cases the causative pathogen was not determined. In this study, we assessed HHV-6 infection as potential cause of hospitalization in this group.

METHODS

Blood samples were assessed for HHV-6 using real-time quantitative PCR. Three groups were investigated: (1) group of interest: 91 hospitalized children with febrile illness without a diagnosed causing pathogen; (2) hospitalized control: 91 age-matched children hospitalized with febrile illness with a potentially disease-causing pathogen identified; both groups were recruited at the Albert Schweitzer Hospital in Lambaréné, Gabon and (3) healthy control: 91 healthy children from the same area.

RESULTS

Samples from 273 children were assessed. Age range was two months to 14 years, median (IQR) age was 36 (12-71) months; 52% were female. HHV-6 was detected in 64% (58/91), 41% (37/91), and 26% (24/91) of the samples from groups 1, 2, and 3, respectively; with statistically significant odds of being infected with HHV-6 in group 1 (OR = 4.62, 95% CI [2.46, 8.90]). Only HHV-6B was detected.

CONCLUSIONS

Although tropical diseases account for a large proportion of children's hospitalizations, considering common childhood diseases such as HHV-6 when diagnosing febrile illnesses in pediatric populations in tropical countries is of importance.

Febrile Seizures

Febrile seizures (FSs) are the most common cause of pediatric seizures. They are defined as seizures in children age 6 months to 5 years with a temperature higher than 100.4°F, although they are more common at higher temperatures. A family history of FS is the most common risk factor. FSs are classified into three types (simple, complex, or febrile status epilepticus) based on duration and quality, with simple FSs accounting for many cases. Most FSs persist for less than 10 minutes and are self-limiting. Approximately one-third of patients will have recurrence of FSs. Safe and effective prophylaxis for FS has yet to be identified. Most patients will not have any long-term sequelae, although there is an increased risk of epilepsy, particularly for those with febrile status epilepticus. FSs are associated with caregiver anxiety, "fever phobia," and high health care use, emphasizing the importance of education and reassurance for both the provider and family. [Pediatr Ann. 2023;52(10):e388-e393.].

The elusive role of herpesviruses in Alzheimer's disease: current evidence and future directions

Alzheimer's disease (AD) is the most common cause of dementia. While pathologic hallmarks, such as extracellular beta-amyloid plaques, are well-characterized in affected individuals, the pathogenesis that causes plaque formation and eventual cognitive decline is not well understood. A recent resurgence of the decades-old "infectious hypothesis" has garnered increased attention on the potential role that microbes may play in AD. In this theory, it is thought that pathogens such as viruses may act as seeds for beta-amyloid aggregation, ultimately leading to plaques. Interest in the infectious hypothesis has also spurred further investigation into additional characteristics of viral infection that may play a role in AD progression, such as neuroinflammation, latency, and viral DNA integration. While a flurry of research in this area has been recently published, with herpesviruses being of particular interest, the role of pathogens in AD remains controversial. In this review, the insights gained thus far into the possible role of herpesviruses in AD are summarized. The challenges and potential future directions of herpesvirus research in AD and dementia are also discussed.

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.

[Reactivation of latent viruses in Neurology]

After establishing latent infection, some viruses can be reactivated by the alteration of host immunological conditions. First, we reviewed viruses that can cause neuronal damage by reactivation. Then we focused on the herpes simplex virus (HSV). The reactivation leads to neuronal damages through two possible mechanisms; "reactivation of a latent herpes virus" by which viruses can cause direct virus neurotoxicity, and "post-infectious immune inflammatory response" by which a focal reactivation of HSV leads to an inflammatory reaction. The former is radiologically characterized by cortical lesions, the latter is characterized by subcortical white matter lesions. We experienced a female, who underwent the right posterior quadrantectomy and then developed recurrent herpes encephalitis caused by herpes simplex reactivation, which pathologically demonstrated inflammation in the white matter, suggesting a post-infectious immune inflammatory response. The patient was successfully treated with immunosuppressants. The reactivation of the HSV is extremely rare in Japan. Neurologists should recognize this condition because this disorder will increase as epilepsy surgery gains more popularity.

Molecular Mechanisms in the Genesis of Seizures and Epilepsy Associated With Viral Infection

Seizures are a common presenting symptom during viral infections of the central nervous system (CNS) and can occur during the initial phase of infection ("early" or acute symptomatic seizures), after recovery ("late" or spontaneous seizures, indicating the development of acquired epilepsy), or both. The development of acute and delayed seizures may have shared as well as unique pathogenic mechanisms and prognostic implications. Based on an extensive review of the literature, we present an overview of viruses that are associated with early and late seizures in humans. We then describe potential pathophysiologic mechanisms underlying ictogenesis and epileptogenesis, including routes of neuroinvasion, viral control and clearance, systemic inflammation, alterations of the blood-brain barrier, neuroinflammation, and inflammation-induced molecular reorganization of synapses and neural circuits. We provide clinical and animal model findings to highlight commonalities and differences in these processes across various neurotropic or neuropathogenic viruses, including herpesviruses, SARS-CoV-2, flaviviruses, and picornaviruses. In addition, we extensively review the literature regarding Theiler's murine encephalomyelitis virus (TMEV). This picornavirus, although not pathogenic for humans, is possibly the best-characterized model for understanding the molecular mechanisms that drive seizures, epilepsy, and hippocampal damage during viral infection. An enhanced understanding of these mechanisms derived from the TMEV model may lead to novel therapeutic interventions that interfere with ictogenesis and epileptogenesis, even within non-infectious contexts.

Case Report: Overlapping Syndrome of Anti-NMDAR Encephalitis and MOG Inflammatory Demyelinating Disease in a Patient With Human Herpesviruses 7 Infection

Objectives

This study reported a case of overlapping anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis and myelin oligodendrocyte glycoprotein (MOG) inflammatory demyelinating disease with human herpesviruses 7 (HHV-7) infection.

Methods

The detailed clinical characteristics, neuroimaging features, and outcomes of the patient were collected. Polymerase chain reaction (PCR), cell-based assay (CBA) and the tissue-based indirect immunofluorescence assay (TBA) were used for diagnosis.

Results

The clinical manifestations included headache, dizziness, fever, optic neuritis, and epileptic-seizures. Brain magnetic resonance imaging (MRI) showed hyperintensities involving the left frontal, orbital gyrus and bilateral optic nerve with substantial contrast enhancement. Moreover, test for HHV-7 DNA by using the next generation sequencing metagenomics and polymerase chain reaction showed positive result in CSF but not in the serum samples. Anti-HHV-7 IgM and IgG antibodies were detected in both the serum and cerebrospinal fluid. NMDAR antibodies (1:10) were found positive in the patient’s CSF by a cell-based assay, and MOG antibodies were positive in the serum (1:10) and CSF (1:32). The patient appeared to respond well to immune therapy and it was found that the clinical symptoms including epileptic-seizure as well as headache were relieved and cerebral lesions almost disappeared after the treatment. However, his vision was not completely restored even at the 8-month follow-up, especially the vision in his right eye which was more seriously damaged.

Discussion

We report a rare case of MOG antibodies and anti-NMDAR encephalitis overlapping syndrome (MNOS) with HHV-7 infection for the first time. The possibility of MNOS needs be considered when optic neuritis occurs in the patients diagnosed with anti-NMDAR encephalitis. Besides, immunotherapy should be initiated as early as possible to improve the treatment outcomes and facilitate complete cure.

A Rare Case of HHV-6 Encephalitis in an Immunocompetent Host: Case Report and Literature Review

Human herpesvirus-6 (HHV-6) is a virus known for causing the highly contagious infection, roseola infantum, and has been associated with causing encephalitis in pediatric patients and less commonly in adult patients as well. Regardless of the patient's age, the primary HHV-6 infection could be complicated by neurological sequelae including encephalitis, acute encephalopathy with biphasic seizures syndrome, or demyelinating disease. HHV-6 encephalitis does occur in an adult as a primary infection or reactivation. However, immunocompromised, hematopoietic stem cell transplantation patients, and solid organ transplant recipients are the most affected population. Here we present a rare case of HHV-6 encephalitis in a 26-year-old healthy immunocompetent male. HHV-6 viral DNA was detected in the cerebrospinal fluid during the acute stage of the disease, and the diagnosis was confirmed by quantitative polymerase chain reaction (PCR). The patient was treated with ganciclovir and had a complete response to treatment without any further complication. The pathophysiology, clinical course, and treatment in otherwise immunocompetent adult patients are also discussed.

Herpesviruses and Inflammasomes: One Sensor Does Not Fit All

Herpesviruses are ubiquitous double-stranded DNA viruses that cause lifelong infections and are associated with a variety of diseases. While they have evolved multiple mechanisms to evade the immune system, they are all recognized by the innate immune system, which can lead to both localized and systemic inflammation. A more recently appreciated mechanism of herpesvirus innate immune activation is through inflammasome signaling. The inflammasome is an intracellular multiprotein complex that, when activated, leads to the release of proinflammatory cytokines, including IL-1β and IL-18, and activation of the inflammatory programed cell death pathway known as pyroptosis. Despite the herpesviruses sharing a similar structure, their mechanisms of inflammasome activation and the consequences of inflammasome activation in cases of virus-associated disease are not uniform. This review will highlight the similarities and differences among herpesviruses with regard to their mechanisms of inflammasome activation and impacts on diseases caused by herpesviruses. Furthermore, it will identify areas where additional studies are warranted to better understand the impact of this important innate immune signaling program on the pathogenesis of these common viruses.

Fever-Associated Seizures or Epilepsy: An Overview of Old and Recent Literature Acquisitions

In addition to central nervous system infections, seizures and fever may occur together in several neurological disorders. Formerly, based on the clinical features and prognostic evolution, the co-association of seizure and fever included classical febrile seizures (FS) divided into simple, complex, and prolonged FS (also called febrile status epilepticus). Later, this group of disorders has been progressively indicated, with a more inclusive term, as "fever-associated seizures or epilepsy" (FASE) that encompasses: (a) FS divided into simple, complex, and prolonged FS; (b) FS plus; (c) severe myoclonic epilepsy in infancy (Dravet syndrome); (d) genetic epilepsy with FS plus; and (e) febrile infection-related epilepsy syndrome (FIRES). Among the FASE disorders, simple FS, the most common and benign condition, is rarely associated with subsequent epileptic seizures. The correlation of FS with epilepsy and other neurological disorders is highly variable. The pathogenesis of FASE is unclear but immunological and genetic factors play a relevant role and the disorders belonging to the FASE group show to have an underlying common clinical, immunological, and genetic pathway. In this study, we have reviewed and analyzed the clinical data of each of the heterogeneous group of disorders belonging to FASE.

Persistent viremia in an immunocompetent patient with inherited chromosomally integrated HHV-6B

Human herpesvirus-6 (HHV-6), the virus which causes roseola, has traditionally been associated with benign and self-limited childhood illness. However, HHV-6 establishes lifelong latency and can reactivate in immunocompromised adult patients. In about 1% of cases, it integrates into the human genome as inherited chromosomally integrated HHV-6 (iciHHV-6). We report the case of a 70-year-old man presenting with altered mental status and agitation. His infectious workup revealed a cerebrospinal fluid sample positive for HHV-6 with virus detectable in the blood as well. He was subsequently treated with ganciclovir. HHV-6 viremia (DNAemia) persisted, and the antiviral medications were switched to foscarnet under the assumption of treatment failure due to drug resistance. After several admissions to the hospital for the same complaint, and after noticing that DNAemia persisted despite adequate treatment for HHV-6, infectious disease specialists ordered testing for chromosomally integrated virus. Test results confirmed the presence of iciHHV-6, explaining his consistently elevated serum viral load. Primary HHV-6 infection in adults causes a transient increase in viral load with resolution and clearance after a few weeks while iciHHV-6 is characterized by persistent detection of viral DNA at a high copy number. Individuals with iciHHV-6 can develop HHV-6 disease and are at increased risk for active viral replication when treated with immunosuppressive medications, but only mRNA testing, which is not widely available can differentiate between latent and active infection. This makes the decision to treat challenging in this patient population. When faced with a positive HHV-6 DNA result in the setting of equivocal symptoms, clinicians should consider the possibility of chromosomally integrated virus rather than drug-resistant virus in order to reduce exposure to potentially toxic antiviral medications.

Human herpesvirus 6 and epilepsy

We investigated the association between human herpesvirus 6 (HHV‐6) and mesial temporal sclerosis (MTS) in 87 patients who had surgery for drug‐resistant epilepsy. Fifty‐four had MTS, 22 focal cortical dysplasia (FCD), four tumors, three vascular malformations, and three a history of encephalitis. We extracted DNA from fresh brain tissue immediately after surgery and performed viral detection with quantitative real‐time polymerase chain reaction (PCR) or digital droplet PCR specific for HHV‐6A and HHV‐6B. Tissue was studied with standard clinical techniques, including hematoxylin and eosin, glial fibrillary acidic protein, and NeuN stains. Twenty‐nine of 54 patients with MTS, six of 23 with focal cortical dysplasia (FCD), and one of three with a history of encephalitis were positive for HHV‐6 (P < .02). Febrile seizure history was not associated with HHV‐6 detection. Patients with MTS had significantly lower seizure onset age than those with other pathologies. Thirteen patients had positron emission tomography with [11C]PBR28, a marker for reactive astrocytes and activated microglia; there was a trend for HHV‐6‐positive patients to have higher binding in their seizure foci, suggesting inflammation. Our study supports a potential role for HHV‐6 in the etiology of MTS.

T cell numbers correlate with neuronal loss rather than with seizure activity in medial temporal lobe epilepsy

OBJECTIVE

Medial temporal lobe epilepsy (MTLE) is a drug-resistant focal epilepsy that can be caused by a broad spectrum of different inciting events, including tumors, febrile seizures, and viral infections. In human epilepsy surgical resections as well as in animal models, an involvement of the adaptive immune system was observed. We here analyzed the presence of T cells in various subgroups of MTLE. We aimed to answer the question of how much inflammation was present and whether the presence of T cells was associated with seizures or associated with hippocampal neurodegeneration.

METHODS

We quantified the numbers of CD3⁺ T cells and CD8⁺ cytotoxic T cells in the hippocampus of patients with gangliogliomas (GGs; intrahippocampal and extrahippocampal, with and without sclerosis), febrile seizures, and postinfectious encephalitic epilepsy and compared this with Rasmussen encephalitis, Alzheimer disease, and normal controls.

RESULTS

We could show that T cell numbers were significantly elevated in MTLE compared to healthy controls. CD3⁺ as well as CD8⁺ T cell numbers, however, varied highly among MTLE subgroups. By comparing GG patients with and without hippocampal sclerosis (HS), we were able to show that T-cell numbers were increased in extrahippocampal GG patients with hippocampal neuronal loss and HS, whereas extrahippocampal GG cases without hippocampal neuronal loss (i.e., absence of HS) did not differ from healthy controls. Importantly, T cell numbers in MTLE correlated with the degree of neuronal loss, whereas no correlation with seizure frequency or disease duration was found. Finally, we found that in nearly all MTLE groups, T cell numbers remained elevated even years after the inciting event.

SIGNIFICANCE

We here provide a detailed histopathological investigation of the involvement of T cells in various subgroups of MTLE, which suggests that T cell influx correlates to neuronal loss rather than seizure activity.

Human Herpes Virus 7-related encephalopathy in children

BACKGROUND

Primary HHV7 infection is almost ubiquitous, and it can present as exanthema subitem. Little is known on the clinical relevance of HHV7 neuroinvasion in immunocompetent children.

METHODS

We describe 12 patients (median age 9.45 years, 50% males) with acute encephalopathy and active HHV7 infection. In all patients, HHV7-DNA was detected on cerebrospinal fluid (CSF) by RT-PCR.

RESULTS

7/12 patients had meningoencephalitis (two with ADEM and one with MOG antibody-associated CIS); 5/12 showed acute neuropsychiatric symptoms. EEG showed anomalies exclusively in patients with meningoencephalitis. Six patients had RMN anomalies. CSF HHV7 copies ranged between 20 and 3,500 copies/mL (median 66 copies/mL) and mean HHV7 CSF/blood ratio was 0.75. Outcome was favorable in all children, although 3/12 had minor neurobehavioral sequelae. Mean follow-up period of 5.2 months.

CONCLUSIONS

HHV7 can determine neuroinvasion in immunocompetent children, leading to acute encephalopathy. Blood-brain barrier damage and high CSF/blood viral copies ratio correlated with a more severe presentation. We speculate on the importance of immune-mediated mechanisms in provoking clinical features.

An adolescent with herpes simplex encephalitis, presenting with mild symptoms and rapid deterioration: A case report

Headaches in children are a common, but unspecific symptom that can have many underlying causes, ranging from unspecific tension headache through migraine and up to encephalitis and intracranial hypertension. We present the case of a 14-year-old boy who presented to our emergency department with headache, nausea as well as vomiting and developed seizures later on. The initial diagnosis was complicated by a magnetic resonance imaging which did not show any signs of inflammation, but was of limited informative value due to orthodontic appliances. Despite the unremarkable imaging, prophylactic antiviral and antibiotic treatment was started after lumbar puncture. Herpes simplex virus as well as human herpes virus 7 were confirmed in the cerebrospinal fluid. Although both viruses are ubiquitous, severe infections are a rare complication. Immunodeficiency syndromes are predisposing factors for serious complications and genetic analysis of UNC93B and TLR-3 might be helpful for decision-making. No genetic or immunologic predisposition was found in our patient. The patient’s condition deteriorated rapidly, so he had to be admitted to the pediatric intensive care unit, where he was intubated and his antiviral treatment with acyclovir was extended by foscarnet. After prolonged mechanical ventilation, he slowly improved. With intensive neurorehabilitation, he could finally return to his daily life activities 3 months after diagnosis. Despite headaches being an unspecific symptom, the possibility of a herpes simplex virus encephalitis should always kept in mind, especially in patients presenting with additional symptoms such as vomiting, altered mental status and/or focal neurological deficits. An initial magnetic resonance imaging might be misleading if orthodontic appliances are in place. Initiation of treatment without delay is crucial for neurologic outcome of herpes simplex virus encephalitis.

Human Herpesviruses 6A and 6B in Brain Diseases: Association versus Causation

Human herpesvirus 6A (HHV-6A) and human herpesvirus 6B (HHV-6B), collectively termed HHV-6A/B, are neurotropic viruses that permanently infect most humans from an early age. Although most people infected with these viruses appear to suffer no ill effects, the viruses are a well-established cause of encephalitis in immunocompromised patients. In this review, we summarize the evidence that the viruses may also be one trigger for febrile seizures (including febrile status epilepticus) in immunocompetent infants and children, mesial temporal lobe epilepsy, multiple sclerosis (MS), and, possibly, Alzheimer's disease. We propose criteria for linking ubiquitous infectious agents capable of producing lifelong infection to any neurologic disease, and then we examine to what extent these criteria have been met for these viruses and these diseases.

Acute Seizures-Work-Up and Management in Children

Seizures are common in the pediatric population; however, most children do not go on to develop epilepsy later in life. Selecting appropriate diagnostic modalities to determine an accurate diagnosis and appropriate treatment as well as with counseling families regarding the etiology and prognosis of seizures, is essential. This article will review updated definitions of seizures, including provoked versus unprovoked, as well as the International League Against Epilepsy operational definition of epilepsy. A variety of specific acute symptomatic seizures requiring special consideration are discussed, along with neonatal seizures and seizure mimics, which are common in pediatric populations.

The Presence of Human Herpesvirus 6 in the Brain in Health and Disease

The human herpesvirus 6 (HHV-6) -A and -B are two dsDNA beta-herpesviruses infectingalmost the entire worldwide population. These viruses have been implicated in multipleneurological conditions in individuals of various ages and immunological status, includingencephalitis, epilepsy, and febrile seizures. HHV-6s have also been suggested as playing a role inthe etiology of neurodegenerative diseases such as multiple sclerosis and Alzheimer's disease. Theapparent robustness of these suggested associations is contingent on the accuracy of HHV-6detection in the nervous system. The effort of more than three decades of researching HHV-6 in thebrain has yielded numerous observations, albeit using variable technical approaches in terms oftissue preservation, detection techniques, sample sizes, brain regions, and comorbidities. In thisreview, we aimed to summarize current knowledge about the entry routes and direct presence ofHHV-6 in the brain parenchyma at the level of DNA, RNA, proteins, and specific cell types, inhealthy subjects and in those with neurological conditions. We also discuss recent findings relatedto the presence of HHV-6 in the brains of patients with Alzheimer's disease in light of availableevidence.

The role of herpesvirus 6A and 6B in multiple sclerosis and epilepsy

Human herpesvirus 6A (HHV‐6A) and 6B (HHV‐6B) are two closely related viruses that can infect cells of the central nervous system (CNS). The similarities between these viruses have made it difficult to separate them on serological level. The broad term HHV‐6 remains when referring to studies where the two species were not distinguished, and as such, the seroprevalence is over 90% in the adult population. HHV‐6B has been detected in up to 100% of infants with the primary infection roseola infantum, but less is known about the primary infection of HHV‐6A. Both viruses are neurotropic and have capacity to establish lifelong latency in cells of the central nervous system, with potential to reactivate and cause complications later in life. HHV‐6A infection has been associated with an increased risk of multiple sclerosis (MS), whereas HHV‐6B is indicated to be involved in pathogenesis of epilepsy. These two associations show how neurological diseases might be caused by viral infections, but as suggested here, through completely different molecular mechanisms, in an autoimmune disease, such as MS, by triggering an overreaction of the immune system and in epilepsy by hampering internal cellular functions when the immune system fails to eliminate the virus. Understanding the viral mechanisms of primary infection and reactivation and their spectrum of associated symptoms will aid our ability to diagnose, treat and prevent these severe and chronic diseases. This review explores the role of HHV‐6A and HHV‐6B specifically in MS and epilepsy, the evidence to date and the future directions of this field.

Status Epilepticus in Children

For various reasons, status epilepticus in children is different than in adults. Pediatric specificities include status epilepticus epidemiology, underlying etiologies, pathophysiological mechanisms, and treatment options. Relevant data from the literature are presented for each of them, and questions remaining open for future studies on status epilepticus in childhood are listed.

HHV-6 and hippocampal volume in patients with mesial temporal sclerosis

Objective

To study the effects of human herpes virus 6 (HHV‐6) on the hippocampal volume in patients with mesial temporal sclerosis (MTS).

Background

HHV‐6 may play an etiologic role in MTS. Previous studies found a possible association with febrile status epilepticus. Several investigators have reported a higher prevalence of HHV‐6 in MTS resections compared to other epilepsy etiologies.

Design/Methods

We used FreeSurfer to segment cortical structures and obtain whole hippocampal and subfield volumes in 41 patients with intractable epilepsy. In addition, an investigator blinded to other data traced hippocampi manually on each slice. The main study outcome measure was the asymmetry index (AI) between hippocampal volumes ipsilateral and contralateral to seizure foci compared between HHV‐6 positive and negative patients. Viral DNA was isolated from fresh brain tissue obtained at temporal lobectomy. For 25 patients, viral detection was performed using quantitative real‐time PCR specific for HHV‐6A and HHV‐6B. For 16 patients, viral DNA detection was performed using digital droplet PCR specific for HHV‐6A and HHV‐6B.

Results

Twenty‐two patients were positive (14 of 25 tested with real‐time PCR, and 8 of 16 with digital droplet PCR), and 19 negatives for HHV‐6. HHV‐6 negative patients had significantly greater AI and lower total hippocampal volume ipsilateral to seizure foci than HHV‐6 positive patients. Epilepsy duration and age of onset did not affect results.

Interpretation

Our data suggest multiple potential etiologies for MTS. HHV‐6 may have a less severe effect on the hippocampus than other etiologies.

Endogenization and excision of human herpesvirus 6 in human genomes

Sequences homologous to human herpesvirus 6 (HHV-6) are integrated within the nuclear genome of about 1% of humans, but it is not clear how this came about. It is also uncertain whether integrated HHV-6 can reactivate into an infectious virus. HHV-6 integrates into telomeres, and this has recently been associated with polymorphisms affecting MOV10L1. MOV10L1 is located on the subtelomere of chromosome 22q (chr22q) and is required to make PIWI-interacting RNAs (piRNAs). As piRNAs block germline integration of transposons, piRNA-mediated repression of HHV-6 integration has been proposed to explain this association. In vitro, recombination of the HHV-6 genome along its terminal direct repeats (DRs) leads to excision from the telomere and viral reactivation, but the expected "solo-DR scar" has not been described in vivo. Here we screened for integrated HHV-6 in 7,485 Japanese subjects using whole-genome sequencing (WGS). Integrated HHV-6 was associated with polymorphisms on chr22q. However, in contrast to prior work, we find that the reported MOV10L1 polymorphism is physically linked to an ancient endogenous HHV-6A variant integrated into the telomere of chr22q in East Asians. Unexpectedly, an HHV-6B variant has also endogenized in chr22q; two endogenous HHV-6 variants at this locus thus account for 72% of all integrated HHV-6 in Japan. We also report human genomes carrying only one portion of the HHV-6B genome, a solo-DR, supporting in vivo excision and possible viral reactivation. Together these results explain the recently-reported association between integrated HHV-6 and MOV10L1/piRNAs, suggest potential exaptation of HHV-6 in its coevolution with human chr22q, and clarify the evolution and risk of reactivation of the only intact (non-retro)viral genome known to be present in human germlines.

Three Adolescents With Primary Human Herpesvirus 7 Infection During a Measles Outbreak

During local small measles outbreak in Japan, 3 adolescents with febrile skin rash suspected as having measles were diagnosed with primary human herpesvirus (HHV)-7 infection. Primary HHV-7 infection can cause exanthem subitum in not only young children but also adolescents. HHV-7 should be considered as a possible causative agent for adolescent febrile skin rash during the measles outbreak.

Clinical Features of Complex Febrile Seizure Caused by Primary Human Herpesvirus 6B Infection

BACKGROUND

It is well known that febrile seizures are commonly occur in children with exanthem subitum. In this study, we compared the clinical features and backgrounds of patients with complex febrile seizures with and without primary human herpesvirus 6B infection.

METHODS

Sixty-two patients were enrolled after experiencing their first febrile seizure. Primary human herpesvirus 6B infection was confirmed when human herpesvirus 6B DNA was detected and human herpesvirus 6B antibody was negative in serum obtained during the acute phase of infection. Patient age, gender, and features of seizures were evaluated between patients with and without human herpesvirus 6B infection.

RESULTS

Thirty patients with complex febrile seizure were diagnosed with primary human herpesvirus 6B infection. Those with primary human herpesvirus 6B infection (median, 13 months; range, seven to 39 months) were significantly younger than those without primary human herpesvirus 6B infection (median, 19 months; range, 10 to 59 months) (P = 0.001), and the proportion of males was significantly higher in patients without primary human herpesvirus 6B infection (male/female, 25/7) than in those with the infection (male/female, 14/16) (P = 0.017). An interval between fever onset and seizures of more than 24 hours was significantly more common in patients with primary human herpesvirus 6B infection (15 of the 30 patients) than in those without primary HHV-6B infection (two of 32 patients) (P < 0.001).

CONCLUSIONS

A younger age at onset, a different gender ratio compared with febrile seizure due to other causes, and the length of interval between fever and seizures were features of complex febrile seizure associated human herpesvirus 6B infection. These findings may suggest a mechanism of complex febrile seizure onset different from that due to other causes.

Persistent Roseoloviruses Infection in Adult Patients with Epilepsy

Background: Human herpesviruses (HHV)-6A, HHV-6B and HHV-7 are considered to be involved in the pathogenesis of epilepsy, a common neurological disorder. The objective of this study was to determine the association of roseoloviruses infection with epilepsy. Methods: 53 epilepsy patients and 104 ordinary blood donors were analyzed to determine presence of virus-specific antibodies by enzyme-linked immunosorbent assay (ELISA) and immunofluorescence assay (IFA), genomic sequences, viral load and gene expression by polymerase chain reactions (PCRs) and restriction analysis, HHV-6 protein expression by IFA and level of cytokines by ELISA. Results: Roseoloviruses genomic sequences in DNA samples from whole blood were found in 86.8% of patients versus 54.8% of controls and active infection was revealed only in patients with epilepsy (19.6% of roseolovirus-positive patients). Significantly higher viral load and more frequent gene expression was detected in patients compared to the controls. HHV-6-encoded protein expression was demonstrated in 53.3% of patients with previously detected HHV-6 DNA. Changes in level of cytokines were determined in patients with elevated viral load compared to the patients without elevated viral loads and to the controls. Conclusions: Results on frequent active HHV-6 and HHV-7 infection in epilepsy patient’ peripheral blood indicate on possible involvement of these viruses in the disease development.

The current approach of the Epilepsy Therapy Screening Program contract site for identifying improved therapies for the treatment of pharmacoresistant seizures in epilepsy

The Epilepsy Therapy Screening Program (ETSP), formerly known as the Anticonvulsant Screening Program (ASP), has played an important role in the preclinical evaluation of many of the antiseizure drugs (ASDs) that have been approved by the FDA and thus made available for the treatment of seizures. Recent changes to the animal models used at the contract site of the ETSP at the University of Utah have been implemented in an attempt to better model the unmet clinical needs of people with pharmacoresistant epilepsy and thus identify improved therapies. In this review, we describe the changes that have occurred over the last several years in the screening approach used at the contract site and, in particular, detail the pharmacology associated with several of the animal models and assays that are either new to the program or have been recently characterized in more depth. There is optimism that the refined approach used by the ETSP contract site, wherein etiologically relevant models that include those with spontaneous seizures are used, will identify novel, potentially disease modifying therapies for people with pharmacoresistant epilepsy and those at risk for developing epilepsy. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

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.

Prevention and treatment of temporal lobe epilepsy: lessons from hepatitis B story!

Temporal lobe epilepsy (TLE) is the most common type of drug-resistant epilepsy and hippocampal sclerosis (HS) is the most common pathological substrate of TLE. Considering the significant consequences of uncontrolled seizures (e.g. increased morbidity and mortality), epilepsy prevention remains a necessity that potentially could save many lives. Human herpes virus-6 (HHV-6) has been linked to TLE in humans. The relationship between HHV-6 and HS-TLE could be attributed to a neuro-inflammatory cascade triggered by the infection, involving direct neuronal damage and production of several pro-inflammatory cytokines under certain conditions that are still incompletely understood. Hepatitis B virus (HBV) infection is another chronic viral infection with a life-long latency. HBV infection is linked to various clinical conditions, including liver cirrhosis. There are currently three ways to fight HBV infection and its consequences; primary prevention (by vaccination), secondary prevention (by drug therapy), and tertiary prevention (by liver transplantation). Considering the similarities between the natural histories of HHV-6 and HBV infections, and also the successful strategies which are currently available to fight HBV infection and its long-term consequences, here, we propose three strategies to fight HHV-6 and its possible long-term consequence (i.e. HS-TLE): Primary prevention: by developing vaccines to prevent HHV-6 infection; Secondary prevention: by considering trials of antiviral drugs to treat HHV-6 infection, when it happens in the childhood to hopefully prevent its long-term consequences; and, Tertiary prevention: by stem cell therapy for drug-resistant epilepsy.

Betaherpesvirus assembly and egress: Recent advances illuminate the path

The human betaherpesviruses, human cytomegalovirus (HCMV; species Human betaherpesvirus 5) and human herpesviruses 6A, 6B, and 7 (HHV-6A, -6B, and -7; species Human betaherpesviruses 6A, 6B, and 7) are highly prevalent and can cause severe disease in immune-compromised and immune-naive populations in well- and under-developed communities. Herpesvirus virion assembly is an intricate process that requires viral orchestration of host systems. In this review, we describe recent advances in some of the many cellular events relevant to assembly and egress of betaherpesvirus virions. These include modifications of host metabolic, immune, and autophagic/recycling systems. In addition, we discuss unique aspects of betaherpesvirus virion structure, virion assembly, and the cellular pathways employed during virion egress.

Comparative Analysis of Roseoloviruses in Humans, Pigs, Mice, and Other Species

Viruses of the genus Roseolovirus belong to the subfamily Betaherpesvirinae, family Herpesviridae. Roseoloviruses have been studied in humans, mice and pigs, but they are likely also present in other species. This is the first comparative analysis of roseoloviruses in humans and animals. The human roseoloviruses human herpesvirus 6A (HHV-6A), 6B (HHV-6B), and 7 (HHV-7) are relatively well characterized. In contrast, little is known about the murine roseolovirus (MRV), also known as murine thymic virus (MTV) or murine thymic lymphotrophic virus (MTLV), and the porcine roseolovirus (PRV), initially incorrectly named porcine cytomegalovirus (PCMV). Human roseoloviruses have gained attention because they can cause severe diseases including encephalitis in immunocompromised transplant and AIDS patients and febrile seizures in infants. They have been linked to a number of neurological diseases in the immunocompetent including multiple sclerosis (MS) and Alzheimer's. However, to prove the causality in the latter disease associations is challenging due to the high prevalence of these viruses in the human population. PCMV/PRV has attracted attention because it may be transmitted and pose a risk in xenotransplantation, e.g., the transplantation of pig organs into humans. Most importantly, all roseoloviruses are immunosuppressive, the humoral and cellular immune responses against these viruses are not well studied and vaccines as well as effective antivirals are not available.

[First results of application of an enzyme immunoassay in the serological diagnostics of infection caused by herpesvirus type 7.]

HHV-7 (Human Herpes virus type 7) is a relatively recently discovered, ubiquitous beta herpes virus. In Russia, the diagnosis of HHV-7 infection is carried out by PCR, which determines the DNA in serum or plasma, if there are clinical indications. Laboratory serological tests for HHV-7 are not performed. Currently, in the scientific literature, information on clinical studies of HHV-7 infection, its epidemiology, and its role in the etiopathogenesis of various diseases is insufficient. This article presents the results of the development of a test kit "ELISA-HHV-7-IgG", designed to detect specific IgG to HHV-7 by enzyme-linked immunosorbent assay (ELISA). Studies of the sensitivity and specificity of the developed test kit, including potential cross-reactive samples positive for other herpesvirus infections, were carried out. In the context of serological diagnostics, we studied samples of the sera of children (n = 167) and old people (n = 238) for the presence of IgG to HHV-7 with confirmation of the results in the indirect immunofluorescence reaction and the immune blotting reaction. The research results are evidence of the possibility of using the developed test kit for serological diagnosis of HHV-7 infection.

Clinical Characteristics of Primary HHV-6B Infection in Children Visiting the Emergency Room

OBJECTIVE

This cohort study, based on the design of a prior study in the United States, was conducted to elucidate the clinical features of primary human herpesvirus-6B (HHV-6B) infection.

METHODS

Between June 2014 and May 2016, febrile children younger than 5 years who visited the emergency room (ER) and underwent blood examination were enrolled in this study.

RESULTS

Fifty-nine (12%) of the 491 patients were diagnosed with primary HHV-6B infection. The rates of both simple and complex febrile seizure were significantly higher in patients with primary HHV-6B infection than in those without (P < 0.001 and P = 0.008, respectively). The median age at primary HHV-6B infection was 15 months. Forty-seven (79.7%) of the 59 patients with primary HHV-6B infection were younger than 2-year-old. Clinical features were compared between HHV-6B-infected patients older and younger than 2 years. The frequency of apparent infection (exanthema subitum) was significantly higher in the younger patients (P = 0.01). The median leukocyte (P = 0.01) and lymphocyte (P < 0.001) counts in the patients older than 2 years were significantly lower than those in the younger patients.

CONCLUSIONS

Primary HHV-6B infection accounted for 12% of ER visits. Secondary febrile seizures, in particular the complex type, were considered to be a major contributor to the disease burden of primary HHV-6B infection. The timing of primary HHV-6B infection occurred at older ages than in past reports, and the frequency of inapparent infection was higher in older patients.

HHV-6B reduces autophagy and induces ER stress in primary monocytes impairing their survival and differentiation into dendritic cells

HHV-6A and HHV-6B are ubiquitous human betaherpesviruses sharing more than 80% homology. HHV-6B is the most common cause of encephalitis in transplant patients and its primary infection may cause the exanthema subitum and febrile seizures in infants. HHV-6A and HHV-6B are able to infect several immune cell types such as T cells, monocytes and dendritic cells (DCs). In this study we found that HHV-6 B derived from patients affected by exanthema subitum impaired monocyte differentiation into DCs, as the infected cells acquired less CD1a DC marker and retained more CD14 monocyte marker. In agreement with the previous finding that HHV-6B dysregulated autophagy and induced endoplasmic reticulum (ER) stress in cells in which it replicated, here we found that these effects occurred also in differentiating monocytes and that ER stress relief, by using the chemical chaperone sodium 4-phenylbutirate (PBA), partially restored DC formation. This suggests that the induction of ER stress, likely exacerbated by autophagy inhibition, could contribute to the immune suppression induced by HHV-6B derived from exanthema subitem patients.

Leukocytoclastic Vasculitis Associated with HHV6-A/ciHHV6-A and HHV6-B Coinfection in an Immunocompetent Woman

Conclusion:

In light of the transcriptional activity documented in our case, further examination of a possible role for HHV-6 in the etiology of LCV is warranted.

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.

Mesial temporal lobe epilepsy with hippocampal sclerosis is infrequently associated with neuronal autoantibodies

Mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) is characterized by its well-defined clinical profile. Limbic encephalitis is increasingly recognized as a possible etiology of adult-onset MTLE-HS, and neuronal autoantibodies have been detected in patients even without previous signs of encephalitis. The aim of this study is to analyze the frequency of specific autoantibodies in patients with MTLE-HS. A case-control study was carried out with 100 patients with MTLE-HS and 50 healthy controls. Sera samples from subjects were tested by indirect immunofluorescence assay for detection of anti-N-methyl-d-aspartate receptor (NMDA-R), anti-contactin-associated protein-like 2 (CASPR2), anti-leucine-rich glioma inactivated 1 (LGI1), anti-gamma aminobutyric acid B receptor (GABA-B-R), anti-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid 1 and 2 receptors (AMPA-1-R and AMPA-2-R), and enzyme-linked immunosorbent assay for detection of anti-glutamic acid decarboxylase 65 (GAD65). Mean age of patients and controls was 41.2 vs 42 years, and 55% vs 56% were female. Mean duration of epilepsy was 27.2 years. No neuronal autoantibodies were found in either group, except for anti-GAD65 in 3 patients and 2 controls. This study adds to the mounting evidence that, in Brazilian patients, MTLE-HS without signs and symptoms of autoimmune encephalitis may be infrequently associated with these autoantibodies. Differences regarding accuracy of used methodologies for autoantibody detection and genetic and environmental characteristics are discussed. Further works with different methodologies tested simultaneously in different populations may help clarify the incongruent study results about autoantibodies in MTLE-HS.

Children infected by human herpesvirus 6B with febrile seizures are more likely to develop febrile status epilepticus: A case-control study in a referral hospital in Zambia

BACKGROUND

Human herpesvirus 6B (HHV-6B) is the causative agent of Roseola infantum, and has also been suggested to play a role in the pathogenesis of febrile seizures in young children, a percentage of whom go on to develop febrile status epilepticus (FSE), but the existing data is conflicting and inconclusive. HHV-6A is a distinct species, rarely detected in most parts of the world, but prior studies suggest a higher prevalence in febrile African children. We describe a case-control study comparing the frequency of HHV-6A and/or HHV-6B infections in children with febrile seizures (including FSE) and a control group of febrile children without seizures.

METHODS

We recruited children aged 6 to 60 months admitted with a febrile illness with (cases) or without (controls) seizures presenting within 48 hours of commencement of fever. Three milliliters of whole blood was centrifuged and plasma stored at -80°C for pooled screening for HHV-6B and HHV-6A by Taqman real-time polymerase chain reaction.

RESULTS

102 cases and 95 controls were recruited. The prevalence of HHV-6B DNA detection did not differ significantly between cases (5.8% (6/102)) and controls (10.5% (10/95)) but HHV-6B infection was associated with FSE (OR, 15; 95% CI, [1.99-120]; P= 0.009). HHV-6A was not detected.

CONCLUSION

Prevalence of HHV-6B was similar among cases and controls. Within the FS group, HHV-6B infection was associated with FSE, suggesting HHV-6B infections could play a role in the pathogenesis of FSE.

Viral Triggers and Inflammatory Mechanisms in Pediatric Epilepsy

Experimental and clinical findings suggest a crucial role for inflammation in the onset of pediatric seizures; this mechanism is not targeted by conventional antiepileptic drugs and may contribute to refractory epilepsy. Several triggers, including infection with neurotropic viruses such as human herpesvirus 6 (HHV-6), other herpesviruses, and picornaviruses, appear to induce activation of the innate and adaptive immune systems, which results in several neuroinflammatory responses, leading to enhanced neuronal excitability, and ultimately contributing to epileptogenesis. This review discusses the proposed mechanisms by which infection with herpesviruses, and particularly with HHV-6, and ensuing inflammation may lead to seizure generation, and later development of epilepsy. We also examine the evidence that links herpesvirus and picornavirus infections with acute seizures and chronic forms of epilepsy. Understanding the mechanisms by which specific viruses may trigger a cascade of alterations in the CNS ultimately leading to epilepsy appears critical for the development of therapeutic agents that may target the virus or inflammatory mechanisms early and prevent progression of epileptogenesis.

Molecular detection of human herpesvirus 7 DNA in cerebrospinal fluid from adult patients with neurological disorders

Neurological manifestations associated with HHV-7 have been described in primary infection in children, and very occasionally in immunocompromised adult patients. However, the role of HHV-7 reactivation as a cause of central nervous system (CNS) diseases in immunocompetent adults has not yet been defined. We retrospectively analyzed clinical and microbiological features of adults with neurological symptoms who underwent lumbar puncture and a multiplex polymerase chain reaction (PCR) for herpesviruses (HHV-1-8) and enteroviruses performed in cerebrospinal fluid (CSF), during a 4-year period. A total of 251 subjects were included. Mean age was 55 years, ranging 15-89. Globally, HHV-7 DNA was detected in CSF in 14 patients (5.6%). It was detected in 1 of 36 patients with microbiologically confirmed CNS infections, and in 7 of 172 patients with diagnoses of non-infectious neurological disorders (Specificity 0.96, 95% confidence interval 0.93-0.99). Additionally, HHV-7 DNA was detected in 6 of 21 patients (28.6%) with probable CNS infections (compatible clinical syndrome and CSF changes) in the absence of other causative agent: four meningitis, one myelitis, and one encephalitis. Treatment with foscarnet was effective in achieving improvement of symptoms and clearance of HHV-7 DNA in CSF in the cases of encephalitis and myelitis, while ganciclovir was ineffective in the case of encephalitis. Our results show that HHV-7 reactivation may cause CNS disease in immunocompetent adults and that detection of HHV-7 DNA in CSF as a false-positive result or as asymptomatic reactivation in adult patients with neurological diseases is uncommon. Foscarnet seems the first-line treatment for HHV-7 CNS disease.

Betaherpesvirus Complications and Management During Hematopoietic Stem Cell Transplantation

Two of the four betaherpesviruses, Cytomegalovirus (CMV) and human herpesvirus 6B (HHV-6B), play an important role in opportunistic infections in hematopoietic stem cell transplant (HSCT) recipients. These viruses are ubiquitous in humans and can latently infect mononuclear lymphocytes, complicating the diagnosis of the diseases they cause. Although the detection of viral DNA in a patient's peripheral blood by real-time PCR is widely used for monitoring viral infection, it is insufficient for the diagnosis of virus-associated disease. Theoretically, end-organ disease should be confirmed by detecting either viral antigen or significant amounts of viral DNA in a tissue sample obtained from the involved organ; however, this is often difficult to perform in clinical practice. The frequency of CMV-associated diseases has decreased gradually as a result of the introduction of preemptive or prophylactic treatments; however, CMV and HHV-6B infections remain a major problem in HSCT recipients. Measurement of viral DNA load in peripheral blood or plasma using real-time PCR is commonly used for monitoring these infections. Additionally, recent data suggest that an assessment of host immune response, particularly cytotoxic T-cell response, may be a reliable tool for predicting these viral infections. The antiviral drugs ganciclovir and foscarnet are used as first-line treatments; however, it is well known that these drugs have side effects, such as bone marrow suppression and nephrotoxicity. Further research is required to develop less-toxic antiviral drugs.