Incidence and pathogenesis of clinical relapse after herpes simplex encephalitis in adults

A Diagnostically Challenging Case of Recurrent Encephalitis With Impending Herniation

Encephalitis is characterized by inflammation of the brain parenchyma with typical presenting symptoms of altered mental status and seizures. However, diagnostic workup is complex given the multitude of possible etiologies for encephalitis. Further, recurrence of encephalitis is rare, and understanding its risk factors, mechanisms, prognosis, and optimal treatment remains incomplete. Here, we present the case of a 69-year-old woman admitted to our hospital with altered mental status who was diagnosed with encephalitis based on clinical and imaging findings. This case highlights the diagnostic approaches required to obtain the final diagnosis and the treatment plan that resulted in the patient's eventual return to baseline and functional independence.

Predictors of Neurological Disability at Hospital Discharge for Acyclovir-treated Pediatric Herpes Simplex Virus Encephalitis

BACKGROUND

Herpes simplex virus encephalitis (HSE) is a rare but serious neurological infection that causes neurological dysfunction. Research is lacking on the clinical predictors of neurological outcomes and the optimal duration of therapy for pediatric HSE patients. In this study of pediatric HSE patients, we identified factors predicting neurological disability at hospital discharge and examined associations of acyclovir therapy duration with neurological outcomes.

METHODS

This was a retrospective cohort study on 37 children diagnosed with HSE confirmed by polymerase chain reaction at age 1 month to 16 years from 2015 to 2021 in Ho Chi Minh City's Children's Hospital No. 2, Vietnam. For the acyclovir duration analysis, we examined 22 children with negative polymerase chain reaction on day 14 of treatment. Poisson regression was used to obtain the risk ratio and 95% confidence interval.

RESULTS

The study population consisted of 73% males, with a median age of 14 months (interquartile range: 9-35). Coma at acyclovir treatment, hypotension and the need for mechanical ventilation ≥48 hours significantly predicted neurological disability in the bivariate analysis. There were no significant associations between acyclovir duration (14 vs. 21 days) and neurological outcomes, adjusting for age at diagnosis and pediatric Glasgow Coma Scale score at acyclovir initiation.

CONCLUSION

We identified significant predictors of neurological disability unaffected by postacyclovir treatment factors. Among patients with negative HSE polymerase chain reaction on day 14, 14 days of acyclovir treatment may be as effective as 21 days. Additional studies on the effects of acyclovir duration are needed.

The immunobiology of herpes simplex virus encephalitis and post-viral autoimmunity

Herpes simplex virus encephalitis (HSE) is the leading cause of non-epidemic encephalitis in the developed world and, despite antiviral therapy, mortality and morbidity is high. The emergence of post-HSE autoimmune encephalitis reveals a new immunological paradigm in autoantibody-mediated disease. A reductionist evaluation of the immunobiological mechanisms in HSE is crucial to dissect the origins of post-viral autoimmunity and supply rational approaches to the selection of immunotherapeutics. Herein, we review the latest evidence behind the phenotypic progression and underlying immunobiology of HSE including the cytokine/chemokine environment, the role of pathogen-recognition receptors, T- and B-cell immunity and relevant inborn errors of immunity. Second, we provide a contemporary review of published patients with post-HSE autoimmune encephalitis from a combined cohort of 110 patients. Third, we integrate novel mechanisms of autoimmunization in deep cervical lymph nodes to explore hypotheses around post-HSE autoimmune encephalitis and challenge these against mechanisms of molecular mimicry and others. Finally, we explore translational concepts where neuroglial surface autoantibodies have been observed with other neuroinfectious diseases and those that generate brain damage including traumatic brain injury, ischaemic stroke and neurodegenerative disease. Overall, the clinical and immunological landscape of HSE is an important and evolving field, from which precision immunotherapeutics could soon emerge.

Case report: Overlapping anti-AMPAR encephalitis with anti-IgLON5 disease post herpes simplex virus encephalitis

Autoimmune encephalitis (AE) is the result of an autoimmune process that occurs as a rapidly advancing encephalopathy. Autoimmune encephalitis was commonly linked to herpes simplex virus 1 (HSV-1) as the most frequently identified virus. The main areas affected by this invasion are the temporal lobe, frontal lobe, and limbic system. Limbic encephalitis is a highly uncommon occurrence involving anti-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) encephalitis and anti-IgLON family member 5 (IgLON5) disease, both belonging to the rare category. As far as we know, this is the first report showing that a patient diagnosed with AMPAR encephalitis overlapped with anti-IgLON5 disease post herpes simplex virus encephalitis (HSE), which helps to broaden the range of this uncommon autoimmune disease. We recommend autoantibody testing in all patients with HSE, particularly those involving neurological relapses or progression.

Herpes Simplex Virus Encephalitis after Recovery from Coronavirus Disease 2019: A Rare Case Report

An 85-year-old woman was diagnosed with coronavirus disease 2019 (COVID-19). The patient was treated with dexamethasone, and the infection was cured. She later developed a low-grade fever and fell unconscious. Positivity for herpes simplex virus deoxyribonucleic acid polymerase chain reaction (HSV-DNA PCR) was detected in the cerebrospinal fluid, so she was diagnosed with HSV encephalitis. The patient was treated with antiviral drugs and recovered from the HSV encephalitis. This case suggests that, in patients with COVID-19 and disorders of consciousness, the possibility of HSV encephalitis should be considered along with COVID-19 encephalitis.

Early autoimmunity and outcome in virus encephalitis: a retrospective study based on tissue-based assay

To explore the autoimmune response and outcome in the central nervous system (CNS) at the onset of viral infection and correlation between autoantibodies and viruses.

METHODS

A retrospective observational study was conducted in 121 patients (2016-2021) with a CNS viral infection confirmed via cerebrospinal fluid (CSF) next-generation sequencing (cohort A). Their clinical information was analysed and CSF samples were screened for autoantibodies against monkey cerebellum by tissue-based assay. In situ hybridisation was used to detect Epstein-Barr virus (EBV) in brain tissue of 8 patients with glial fibrillar acidic protein (GFAP)-IgG and nasopharyngeal carcinoma tissue of 2 patients with GFAP-IgG as control (cohort B).

RESULTS

Among cohort A (male:female=79:42; median age: 42 (14-78) years old), 61 (50.4%) participants had detectable autoantibodies in CSF. Compared with other viruses, EBV increased the odds of having GFAP-IgG (OR 18.22, 95% CI 6.54 to 50.77, p<0.001). In cohort B, EBV was found in the brain tissue from two of eight (25.0%) patients with GFAP-IgG. Autoantibody-positive patients had a higher CSF protein level (median: 1126.00 (281.00-5352.00) vs 700.00 (76.70-2899.00), p<0.001), lower CSF chloride level (mean: 119.80±6.24 vs 122.84±5.26, p=0.005), lower ratios of CSF-glucose/serum-glucose (median: 0.50[0.13-0.94] vs 0.60[0.26-1.23], p=0.003), more meningitis (26/61 (42.6%) vs 12/60 (20.0%), p=0.007) and higher follow-up modified Rankin Scale scores (1 (0-6) vs 0 (0-3), p=0.037) compared with antibody-negative patients. A Kaplan-Meier analysis revealed that autoantibody-positive patients experienced significantly worse outcomes (p=0.031).

CONCLUSIONS

Autoimmune responses are found at the onset of viral encephalitis. EBV in the CNS increases the risk for autoimmunity to GFAP.

A case report of long-delayed diagnosis of pseudorabies virus encephalitis with endophthalmitis: lessons from metagenomic next generation sequencing

BACKGROUND

Pseudorabies virus (PRV) was thought to only infect animals. Recent studies have shown that it can also infect human.

CASE PRESENTATION

We report a case of pseudorabies virus encephalitis and endophthalmitis, diagnosed 89 days after onset, confirmed with intraocular fluid metagenomic next generation sequencing (mNGS) after the result of two cerebrospinal fluid (CSF) mNGS tests were negative. Although treatment with intravenous acyclovir, foscarnet sodium, and methylprednisolone improved the symptoms of encephalitis, significant diagnostic delay resulted in permanent visual loss.

CONCLUSIONS

This case suggests that pseudorabies virus (PRV) DNA in the intraocular fluid may have a higher positivity than that in the CSF. PRV may persist in the intraocular fluid for an extended period and may thus require extended antiviral therapy. Patients with severe encephalitis and PRV should be examined with the focus on pupil reactivity and light reflex. A fundus examination should be performed in patients with a central nervous system infection, specifically, those in a comatose state, to help reduce eye disability.

Epilepsy following herpes simplex encephalitis - A case series

BACKGROUND

Herpes simplex encephalitis (HSE) is associated with severe mortality and morbidity. Its incidence is estimated at 1:250 000, and the typical symptomatology of acute disease including headaches, mental state disturbances, confusion, sleepiness, and seizures. The chronic phase of the disease is occasionally characterized by epilepsy and neurological deficits.

STUDY RATIONALE

The present retrospective single-center study aims to identify risk factors for predicting the development of epilepsy (epileptogenesis) following HSE.

METHODS

Medical records were screened for patients older than 18 years, hospitalized between January 2005 and September 2019 with a diagnosis of "encephalitis" and "herpes simplex virus, HSV" infection. HSE diagnosis was based on an analysis of the cerebrospinal fluid with positive HSV testing results.

RESULTS

Twenty-three patients fit our inclusion criteria: fever and behavioral changes, followed by seizures, were reported in 58.3 % of patients. On follow-up (59.7 ± 38.8 months), eight patients (34.8 %) developed epilepsy. Pathological imaging and EEG were correlated with acute symptomatic seizures (ASS). ASS was associated with an 8-fold risk increase to develop post-encephalitis epilepsy (PE). PE was associated with younger age but not with CSF results, imaging, or EEG.

CONCLUSION

Our retrospective single-center study on PE, following HSE, shows that younger age and ASS were associated with PE. Brain imaging, CSF analysis, and EEG were not associated with the development of epilepsy following HSE.

Herpes simplex virus encephalitis: An atypical presentation of delirium

Herpes simplex encephalitis (HSE) is the most common cause of infectious encephalitis. Our case is of a 75-year-old woman who presented with dysuria and altered mental status. Our case addresses the difficulties in diagnosis and highlights the importance of early recognition of HSE and its associated neurological sequelae.

Recurrent herpes simplex virus encephalitis with presumptive Human Herpesvirus 6 chromosomal integration

Viral encephalitis can lead to encephalopathy, epileptic activity, focal neurological deficits, and death. Prompt recognition and a high index of clinical suspicion can lead to early initiation of appropriate management. We describe an interesting case of a 61-year-old presenting with fever and altered mental status, diagnosed with numerous episodes of viral encephalitis caused by divergent and recurrent viruses. On his initial presentation, lumbar puncture revealed lymphocytic pleocytosis and positivity for Human Herpesvirus 6 (HHV-6), and he was treated with ganciclovir. On subsequent admissions, he was diagnosed with recurrent HHV-6 encephalitis as well as Herpes Simplex Virus 1 encephalitis and treated with ganciclovir, foscarnet and acyclovir. Despite prolonged courses of treatment and resolution of symptoms, he continued to have persistently high plasma viral loads of HHV-6, consistent with probable chromosomal integration. In this report, we emphasize the clinical pearl of chromosomally integrated HHV-6 that can present in a patient with persistently high plasma viral loads of HHV-6, that are non-responsive to treatment. Individuals with chromosomally integrated HHV-6 may be more susceptible to other viral infections.

Autoimmune Encephalitis with Autoantibodies to NMDAR1 following Herpes Encephalitis in Children and Adolescents

Herpes simplex virus (HSV) type 1 is a frequent pathogen causing infectious encephalitis (HSVE). Early treatment with intravenous acyclovir has led to a significant decrease in mortality. However, especially in children, deterioration during or after HSVE may occur without any evidence of HSV reactivation or improvement following repeated antiviral therapy. Here, we report 15 patients (age range 3 months to 15 years) who suffered from autoimmune encephalitis with autoantibodies to NMDAR1 following Herpes encephalitis, presenting with movement abnormalities (young children) or neuropsychiatric symptoms (older children) as major complaints, respectively. The diagnosis was based on positive cerebrospinal fluid (CSF) and/or serum anti-NMDAR-antibodies with two children showing only positive CSF antibody findings. The time lag between first symptoms and diagnosis of autoimmune encephalitis was significantly longer than between first symptoms and diagnosis of HSVE (p <0.01). All patients improved during immunosuppressive treatment, during which plasmapheresis or rituximab treatments were applied in 11 patients, irrespective of their age. Despite immunotherapy, no patients relapsed with HSVE. Early diagnosis and treatment of autoimmune encephalitis after HSVE may be associated with a better outcome so that high clinical awareness and routine testing for anti-NMDAR-antibodies after HSVE seems advisable. If autoimmune encephalitis is suspected, antibody testing should also be performed on CSF if negative in serum.

[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.

Neurofilament Light in Cerebrospinal Fluid is Associated With Disease Staging in European Lyme Neuroborreliosis

Background

Drivers of differences in disease presentation and symptom duration in Lyme neuroborreliosis (LNB) are currently unknown.

Objectives

We hypothesized that neurofilament light (NfL) in cerebrospinal fluid (CSF) would predict disease location and sequelae in a historic LNB cohort.

Design

Using a cross-sectional design and archived CSF samples from 185 patients diagnosed with LNB, we evaluated the content of NfL in the total cohort and in a subgroup of 84 patients with available clinical and paraclinical information.

Methods

Individuals were categorized according to disease location: a. Central nervous system (CNS) with stroke (N=3), b. CNS without stroke (N=11), c. Peripheral nervous system (PNS) with cranial nerve palsy (CNP) (N=40) d. PNS without CNP (N=30). Patients with hospital follow-up more than 6 months after completed antibiotic therapy were categorized as having LNB associated sequelae (N=15).

Results

At diagnosis concentration of NfL exceeded the upper reference level in 60% (105/185), especially among individuals above 30 years. Age-adjusted NfL was not found to be associated with symptom duration. Age-adjusted NfL was significantly higher among individuals with CNS involvement. Category a. (stroke) had significantly higher NfL concentrations in CSF compared to all other categories, category b. (CNS involvement without stroke) had significantly higher values compared to the categories of PNS involvement. We found no significant difference between the categories with PNS involvement (with or without CNP). Significantly higher NfL was found among patients with follow-up in hospital setting.

Conclusion

Comparison of NfL concentrations between the 4 groups of LNB disease manifestations based on clinical information revealed a hierarchy of neuron damage according to disease location and suggested evolving mechanisms with accelerated injury especially when disease is complicated by stroke. Higher values of NfL among patients with need of follow-up in hospital setting suggest NfL could be useful to identify rehabilitative needs.

Case Report: A Case Report of Neurosyphilis Mimicking Limbic Encephalitis

Neurosyphilis (NS) is an infection of the central nervous system caused by Treponema pallidum. It mimics various neurological and psychiatric diseases. In recent years, there have been several NS cases that manifest as limbic encephalitis (LE). Therefore, the diagnosis of neurosyphilis in the early stages is difficult. Here, we present a case of an NS patient who presented with LE manifestation. The 62-year-old woman presented with acute clinical manifestations of gibberish speech, poor memory, and seizures. Brain MRI showed abnormal signals on the right medial temporal lobe. In addition, the patient had a positive serum leucine-rich glioma inactivated 1 (LGI1) antibody with a titer of 1:16. Therefore, an initial diagnosis of anti-LGI1 encephalitis was made. However, further tests carried out showed positive rapid plasma reagin (RPR), and treponema pallidum particle agglutination (TPPA) tests both in the serum and the cerebrospinal fluid (CSF). Therefore, uncertainty arose as to whether the patient had both anti-LGI1 encephalitis and NS or whether the LGI1 antibody and LE manifestations were due to the NS. The patient was initiated on the recommended dose of penicillin G sodium. Following treatment, the patient reported a significant improvement in clinical symptoms, normal signals in the right temporal lobe, and a negative serum LGI1 antibody. These findings suggested that NS induced the LE manifestations and the production of the LGI1 antibody. This case demonstrates that testing syphilis in patients with LE is important and positive autoimmune encephalitis (AE) antibodies in NS patients need to be viewed and interpreted with greater caution.

Virus reactivation after immunotherapy of anti-NMDAR encephalitis secondary to herpes simplex encephalitis: A case report

Herpes simplex encephalitis is the most common cause of sporadic fatal encephalitis. More than half of patients with herpes simplex encephalitis will die and the vast majority of survivors have severe neurologic sequelae without effective antiviral therapy. Some people experience relapses such as secondary anti-N-methyl-d-aspartate receptor encephalitis despite appropriate antiviral treatment. It is rare that virus reactivation after immunotherapy of anti-N-methyl-d-aspartate receptor encephalitis after herpes simplex encephalitis. In the present study, we retrospectively review one patient who showed this rare situation.

Protocol for DexEnceph: a randomised controlled trial of dexamethasone therapy in adults with herpes simplex virus encephalitis

INTRODUCTION

Herpes simplex virus (HSV) encephalitis is a rare severe form of brain inflammation that commonly leaves survivors and their families with devastating long-term consequences. The virus particularly targets the temporal lobe of the brain causing debilitating problems in memory, especially verbal memory. It is postulated that immunomodulation with the corticosteroid, dexamethasone, could improve outcomes by reducing brain swelling. However, there are concerns (so far not observed) that such immunosuppression might facilitate increased viral replication with resultant worsening of disease. A previous trail closed early because of slow recruitment.

METHOD

DexEnceph is a pragmatic multicentre, randomised, controlled, open-label, observer-blind trial to determine whether adults with HSV encephalitis who receive dexamethasone alongside standard antiviral treatment with aciclovir for have improved clinical outcomes compared with those who receive standard treatment alone. Overall, 90 patients with HSV encephalitis are being recruited from a target of 45 recruiting sites; patients are randomised 1:1 to the dexamethasone or control arms of the study. The primary outcome measured is verbal memory as assessed by the Weschler Memory Scale fourth edition Auditory Memory Index at 26 weeks after randomisation. Secondary outcomes are measured up to 72 weeks include additional neuropsychological, clinical and functional outcomes as well as comparison of neuroimaging findings. Patient safety monitoring occurs throughout and includes the detection of HSV DNA in cerebrospinal fluid 2 weeks after randomisation, which is indicative of ongoing viral replication. Innovative methods are being used to ensure recrutiment targets are met for this rare disease.

DISCUSSION

DexEnceph aims to be the first completed randomised controlled trial of corticosteroid therapy in HSV encephalitis. The results will provide evidence for future practice in managing adults with the condition and has the potential to improve outcomes .

ETHICS AND DISSEMINATION

The trial has ethical approval from the UK National Research Ethics Committee (Liverpool Central, REF: 15/NW/0545, 10 August 2015). Protocol V.2.1, July 2019. The results will be published and presented as soon as possible on completion.

TRIAL REGISTRATION NUMBERS

ISRCTN11774734, EUDRACT 2015-001609-16.

Post-herpetic encephalitis cerebral abscess: Viral reactivation or latency site within central nervous system?

Herpetic encephalitis results from central nervous system invasion by herpes simplex virus. We report the case of a man who developed a cerebral abscess fifteen months after initial Herpetic encephalitis. Retrospectively, antiviral should not have been associated with antibiotics during abscess episode, as transcriptomic analysis reported no viral reactivation.

Post-infectious neurological disorders

A multitude of environmental factors can result in breakdown of immune tolerance in susceptible hosts. Infectious pathogens are among the most important environmental triggers in the pathogenesis of autoimmunity. Certain autoimmune disorders have a strong association with specific infections. Several neurological autoimmune disorders are thought to occur through post-infectious mechanisms. In this review, we discuss the proposed mechanisms underlying pathogen-induced autoimmunity, and highlight the clinical presentation and treatment of several post-infectious autoimmune neurological disorders. We also highlight post-infectious neurological disorders in the setting of recent outbreaks.

[A case of herpes simplex virus encephalitis recurring after a seven-year interval]

In January 2008, a 59-year-old man with a history of diabetes mellitus was admitted to our hospital with herpes simplex virus (HSV) encephalitis of his right temporal lobe, which was diagnosed by PCR testing of his cerebrospinal fluid (CSF). He was treated with intravenous acyclovir for three weeks and made a full recovery. On discharge, his CSF was negative for HSV on PCR testing. Seven years later, in March 2015, the man was readmitted to our hospital with fever, disorientation, and nominal dysphasia. Diffusion-weighted MRI of his head revealed a high-intensity area in his left temporal lobe. Testing of his CSF revealed a moderately increased monocyte count and HSV on PCR testing, so he was diagnosed with recurrent HSV encephalitis. He was treated with intravenous acyclovir for three weeks. On discharge, his CSF was negative for HSV on PCR testing, but he had mild residual amnesia. There have been few reports of HSV encephalitis with viral reactivation recurring after a long remission period in adults. This case illustrates the need for prolonged follow up of individuals with HSV encephalitis in order to detect recurrences.

Immune-mediated encephalitis for the infectious disease specialist

PURPOSE OF REVIEW

Autoimmune encephalitis is increasingly recognized and must be distinguished from infectious forms of encephalitis. Moreover, physicians should be aware of infectious triggers of autoimmune encephalitis and of infectious complications associated with treatment.

RECENT FINDINGS

Recent epidemiological studies suggest that the incidence of autoimmune encephalitis may rival that of infectious encephalitis. Although distinguishing autoimmune from infectious forms of encephalitis on clinical grounds can be challenging, recently proposed diagnostic criteria can provide some assistance. There has been an explosion in our knowledge of autoimmune encephalitis associated with antibodies to neuronal cell surface antigens, and two of the most common forms, anti-NMDA receptor encephalitis and anti-LGI1 encephalitis, are typically associated with distinctive clinical features. Although tumors have long been known to trigger autoimmune encephalitis, it has been recently recognized that herpes simplex encephalitis may trigger the generation of antineuronal autoantibodies resulting in an autoimmune neurologic relapse. Both first and second-line therapies for autoimmune encephalitis are associated with infectious complications, whereas emerging treatments, including anakinra and tocilizumab, may also result in increased susceptibility to certain infections.

SUMMARY

The diagnosis and management of autoimmune encephalitis is complex, and awareness of diagnostic criteria and modalities, typical clinical syndromes, infectious triggers of disease, and infectious complications of therapies is critical in optimizing care for affected patients.

Anti-NMDAR Encephalitis Following Herpes Simplex Virus Encephalitis: 2 Cases From Portugal

Herpes simplex virus encephalitis (HSVE) usually presents as a monophasic disease. Symptomatic HSVE relapsing with seizures, encephalopathy, or involuntary movements associated with anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis have been recently reported. We report 2 cases of adult post-HSVE anti-NMDAR encephalitis from Portugal. Two female patients aged 50 years and 30 years were diagnosed with herpes simplex virus type 2 and type 1 encephalitis, respectively. After the initial improvement with specific treatment and despite virologic negativization, both patients suffered clinical, electroencephalographic, and imaging deterioration. The autoimmune encephalitis hypothesis was confirmed with the demonstration of anti-NMDAR antibodies in both cerebrospinal fluid and serum. Both responded to human immunoglobulin and methylprednisolone, with progressive gain of autonomy along the follow-up period. Thymectomy for thymic hyperplasia diagnosed during follow-up was performed in 1 patient. Although being rare, post-HSVE anti-NMDAR encephalitis should be considered in all cases of symptomatic recrudescence after HSVE, since adequate immune-modulating treatment improves the outcome. The role of thyme hyperplasia in autoimmune encephalitis pathogenesis needs better understanding.

Pediatric postviral autoimmune disorders of the CNS

Infections caused by various viruses, mainly belonging to the Herpesviridae family, can trigger the autoimmune process in the CNS in children. This can break brain immune tolerance and induce many molecular and cellular pathways of the immune response. This can lead to the appearance of neuronal auto-antibodies to intracellular, cell-surface or extracellular synaptic antigens. Children may also display a wide spectrum of neurological problems from encephalitis to obsessive–compulsive or tic disorders. In these cases, patients rarely respond to traditional treatment, based on antiviral or/and symptomatic drugs, but early immunotherapy is very effective. The implementation of routine immune tests in all children with acute neurological disorders should be recommended.

Opsoclonus-myoclonus syndrome associated with herpes simplex virus infection: a case report

Purpose: Opsoclonus-myoclonus syndrome (OMS) is a rare neurological disease that can be associated with autoimmunity, paraneoplastic tumour, infection or unknown aetiology.Methods: We describe a 54-year-old woman who developed severe OMS, with the clinical onset occurring 2 months and 15 days after she experienced dizziness, vomiting and fever related to a herpes simplex virus infection. The patient was treated with hormones and clonazepam, and the symptoms of myoclonus and ataxia disappeared.Results: The patient was followed up for 1 year with no recurrence of symptoms.Conclusions: The case suggests that herpes simplex virus infection is a possible cause of OMS.

Immunomodulatory Strategies in Herpes Simplex Virus Encephalitis

Herpes simplex virus 1 (HSV-1) can be responsible for life-threatening HSV encephalitis (HSE). The mortality rate of patients with HSE who do not receive antiviral treatment is 70%, with most survivors suffering from permanent neurological sequelae. The use of intravenous acyclovir together with improved diagnostic technologies such as PCR and magnetic resonance imaging has resulted in a reduction in the mortality rate to close to 20%. However, 70% of surviving patients still do not recover complete neurological functions. Thus, there is an urgent need to develop more effective treatments for a better clinical outcome. It is well recognized that cerebral damage resulting from HSE is caused by viral replication together with an overzealous inflammatory response. Both of these processes constitute potential targets for the development of innovative therapies against HSE. In this review, we discuss recent progress in therapy that may be used to ameliorate the outcome of patients with HSE, with a particular emphasis on immunomodulatory agents. Ideally, the administration of adjunctive immunomodulatory drugs should be initiated during the rise of the inflammatory response, and its duration should be limited in time to reduce undesired effects. This critical time frame should be optimized by the identification of reliable biomarkers of inflammation.

HSV-1 encephalitis relapse after epilepsy surgery: a case report and review of the literature

Herpes simplex encephalitis relapses have been rarely reported, with only few cases occurring after neurosurgical interventions. A young man presented a late herpes simplex encephalitis relapse after left antero-mesial temporal resection for his refractory temporal lobe epilepsy. Eight days after surgery, he developed fever and aphasia. CSF PCR revealed more than 12,000 copies/ml of HSV-1 DNA. Intravenous acyclovir was immediately started with a complete recovery. Postoperative herpes simplex encephalitis can occur as primary infection or as relapse of previous infection. Surgical manipulation of brain parenchyma in the site of a previous infection can act as a trigger for viral reactivation. Early onset of antiviral therapy is fundamental and it is a strong predictor of clinical outcome. Despite no studies on prophylactic treatment with acyclovir in patients with previous herpes simplex encephalitis candidate to neurosurgery are available, we suggest that prophylactic treatment should be recommended.

High neopterin and IP-10 levels in cerebrospinal fluid are associated with neurotoxic tryptophan metabolites in acute central nervous system infections

Background

The host response to intruders in the central nervous system (CNS) may be beneficial but could also be harmful and responsible for neurologic symptoms and sequelae in CNS infections. This immune response induces the activation of the kynurenine pathway (KP) with the production of neuroactive metabolites. Herein, we explored cytokine and KP responses in cerebrospinal fluid (CSF) and serum in patients with encephalitis, aseptic, and bacterial meningitis.

Methods

Cytokines were measured in CSF and serum by multiplex assay in adult patients with encephalitis of infectious, autoimmune or unknown etiology (n = 10), aseptic meningitis (ASM, n = 25), acute bacterial meningitis (ABM, n = 6), and disease control patients with similar symptoms but without pleocytosis in CSF (n = 42). Liquid chromatography-tandem mass spectrometry (LC-MS/ MS) was used to measure KP metabolites in CSF and serum.

Results

A characteristic pattern of increasing cytokine levels and KP metabolites was found in CSF from encephalitis to ASM, with the highest levels in ABM. In ASM and ABM, most inflammatory mediators, including IL-6, IL-8, and IFN-inducible protein-10 (IP-10), showed markedly elevated levels in CSF compared with serum, indicating production within the CNS. In contrast to most mediators, the highest level of IP-10 was found in the ASM group, suggesting a potential role for IP-10 in aseptic/viral meningitis. Neopterin and IP-10 were associated with marked changes in KP metabolites in CSF with increasing kynurenine/tryptophan ratio reflecting indoleamine 2,3-dioxygenase activity. Neopterin, a marker of IFN-γ activity, was associated with an unfavorable balance between neuroprotective and neurotoxic tryptophan metabolites.

Conclusion

We show that parenchymal and meningeal inflammations in CNS share a characteristic cytokine profile with a general immune response in the CSF with limited influence from the systemic circulation. IFN-γ activity, assessed by neopterin and IP-10 levels, may play a role in the activation of the KP pathway in these patients, potentially mediating neurotoxic effects.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1366-3) contains supplementary material, which is available to authorized users.

Increased level of compleasomes in cerebrospinal fluid of patients with herpes simplex encephalitis

Herpes simplex encephalitis (HSE) is a common cause of viral encephalitis (HSV-1) characterised by pronounced inflammation and elevated intracranial pressure. We have shown in a rat model that HSV-1 infection causes an interaction between complement factors and proteasomes, leading to formation of proteasome/complement complexes (compleasomes). Exposure of the proteasome regulatory subunit antisecretory factor 1 (AF1) leads to a decrease in intracranial pressure. The aim of this study was to evaluate the acute and prolonged formation of compleasomes in cerebrospinal fluid (CSF) from patients with HSE. Cerebrospinal fluid samples (n = 55) from 24 HSE patients were analysed for compleasome complexes. Samples from healthy controls (n = 23) and patient controls (n = 27) served as baseline information. Sandwich enzyme-linked immunosorbent assay (ELISA) for proteasomes and their complex formation with complement factor 3 or 4, and Western blot for C3 activation were performed on CSF samples. Increased compleasome formation, both presenting as an initial formation and showing exposure of subunit AF1 in the compleasomes, was found in CSF samples drawn from patients with HSE compared with samples from the control groups (p < 0.0005). The total protein CSF concentration was equal in all groups. The levels were higher in the acute phase compared with late in the disease course (p < 0.0005). Complement 3 breakdown product iC3b was detected in CSF samples of the HSE patients. The early increased formation of compleasomes in CSF suggests that this complex may be involved in host defence against HSE.

Frequency, symptoms, risk factors, and outcomes of autoimmune encephalitis after herpes simplex encephalitis: a prospective observational study and retrospective analysis

BACKGROUND

Herpes simplex encephalitis can trigger autoimmune encephalitis that leads to neurological worsening. We aimed to assess the frequency, symptoms, risk factors, and outcomes of this complication.

METHODS

We did a prospective observational study and retrospective analysis. In the prospective observational part of this study, we included patients with herpes simplex encephalitis diagnosed by neurologists, paediatricians, or infectious disease specialists in 19 secondary and tertiary Spanish centres (Cohort A). Outpatient follow-up was at 2, 6, and 12 months from onset of herpes simplex encephalitis. We studied another group of patients retrospectively, when they developed autoimmune encephalitis after herpes simplex encephalitis (Cohort B). We compared demographics and clinical features of patients who developed autoimmune encephalitis with those who did not, and in patients who developed autoimmune encephalitis we compared these features by age group (patients ≤4 years compared with patients >4 years). We also used multivariable binary logistic regression models to assess risk factors for autoimmune encephalitis after herpes simplex encephalitis.

FINDINGS

Between Jan 1, 2014, and Oct 31, 2017, 54 patients with herpes simplex encephalitis were recruited to Cohort A, and 51 were included in the analysis (median age 50 years [IQR 5-68]). At onset of herpes simplex encephalitis, none of the 51 patients had antibodies to neuronal antigens; during follow-up, 14 (27%) patients developed autoimmune encephalitis and all 14 (100%) had neuronal antibodies (nine [64%] had NMDA receptor [NMDAR] antibodies and five [36%] had other antibodies) at or before onset of symptoms. The other 37 patients did not develop autoimmune encephalitis, although 11 (30%) developed antibodies (n=3 to NMDAR, n=8 to unknown antigens; p<0·001). Antibody detection within 3 weeks of herpes simplex encephalitis was a risk factor for autoimmune encephalitis (odds ratio [OR] 11·5, 95% CI 2·7-48·8; p<0·001). Between Oct 7, 2011, and Oct 31, 2017, there were 48 patients in Cohort B with new-onset or worsening neurological symptoms not caused by herpes simplex virus reactivation (median age 8·8 years [IQR 1·1-44·2]; n=27 male); 44 (92%) patients had antibody-confirmed autoimmune encephalitis (34 had NMDAR antibodies and ten had other antibodies). In both cohorts (n=58 patients with antibody-confirmed autoimmune encephalitis), patients older than 4 years frequently presented with psychosis (18 [58%] of 31; younger children not assessable). Compared with patients older than 4 years, patients aged 4 years or younger (n=27) were more likely to have shorter intervals between onset of herpes simplex encephalitis and onset of autoimmune encephalitis (median 26 days [IQR 24-32] vs 43 days [25-54]; p=0·0073), choreoathetosis (27 [100%] of 27 vs 0 of 31; p<0·001), decreased level of consciousness (26 [96%] of 27 vs seven [23%] of 31; p<0·001), NMDAR antibodies (24 [89%] of 27 vs 19 [61%] of 31; p=0·033), and worse outcome at 1 year (median modified Rankin Scale 4 [IQR 4-4] vs 2 [2-3]; p<0·0010; seizures 12 [63%] of 19 vs three [13%] of 23; p=0·001).

INTERPRETATION

The results of our prospective study show that autoimmune encephalitis occurred in 27% of patients with herpes simplex encephalitis. It was associated with development of neuronal antibodies and usually presented within 2 months after treatment of herpes simplex encephalitis; the symptoms were age-dependent, and the neurological outcome was worse in young children. Prompt diagnosis is important because patients, primarily those older than 4 years, can respond to immunotherapy.

FUNDING

Mutua Madrileña Foundation, Fondation de l'Université de Lausanne et Centre Hospitalier Universitaire Vaudois, Instituto Carlos III, CIBERER, National Institutes of Health, Generalitat de Catalunya, Fundació CELLEX.

Neurological syndromes driven by postinfectious processes or unrecognized persistent infections

PURPOSE OF REVIEW

The immune system serves a critical role in protecting the host against various pathogens. However, under circumstances, once triggered by the infectious process, it may be detrimental to the host. This may be as a result of nonspecific immune activation or due to a targeted immune response to a specific host antigen. In this opinion piece, we discuss the underlying mechanisms that lead to such an inflammatory or autoimmune syndrome affecting the nervous system. We examine these hypotheses in the context of recent emerging infections to provide mechanistic insight into the clinical manifestations and rationale for immunomodulatory therapy.

RECENT FINDINGS

Some pathogens endure longer than previously thought. Persistent infections may continue to drive immune responses resulting in chronic inflammation or development of autoimmune processes, resulting in damage to the nervous system. Patients with genetic susceptibilities in immune regulation may be particularly vulnerable to pathogen driven autoimmune responses.

SUMMARY

The presence of prolonged pathogens may result in chronic immune stimulations that drives immune-mediated neurologic complications. Understanding the burden and mechanisms of these processes is challenging but important.

Clinical significance of IgM and IgA class anti-NMDAR antibodies in herpes simplex encephalitis

BACKGROUND

Herpes simplex encephalitis (HSE) is a devastating disease, often leaving patients with severe disabilities. It has been shown that IgG anti-N-methyl-d-aspartate receptor (NMDAR) antibodies appear in approximately 25% of HSE patients and could be associated with impaired recovery of cognitive performance.

OBJECTIVES

To characterize the prevalence of IgM and IgA anti-NMDAR antibodies in HSE patients, in relation to subsequent development of IgG anti-NMDAR and correlation to cognitive performance.

STUDY DESIGN

A total of 48 subjects were included from a previously described cohort of patients with HSE verified by HSV-1 PCR. Cerebrospinal fluid (CSF) and serum samples drawn close to onset of disease, after 14-21 days of iv aciclovir treatment and after 90 days of follow-up, were analyzed for the presence of IgM and IgA anti-NMDAR, and related to IgG anti-NMDAR. Antibody levels were correlated to the recovery of cognitive performance, as estimated by the Mattis Dementia Rating Scale (MDRS), for a total of 24 months.

RESULTS

In total, 27 of 48 (56%) study subjects were anti-NMDAR positive, defined as the presence of IgG (12/48, 25%), IgM (14/48, 29%) or IgA (13/48, 27%) antibodies in CSF and/or serum. IgM or IgA anti-NMDAR did not predict subsequent IgG autoimmunization and did not correlate to cognitive outcome. IgG anti-NMDAR serostatus, but not antibody titers, correlated to impaired recovery of cognitive performance.

CONCLUSIONS

A majority of HSE patients develop IgG, IgM or IgA anti-NMDAR antibodies. However, the predictive value and clinical relevance of non-IgG isotypes remains to be shown in this setting.

Cytokine expression profile in hospitalized children with herpes simplex virus-1 infection

Aim: We aim to demonstrate the cytokine expression profile of children with herpes simplex virus-1 (HSV-1) infection. Methods: One hundred eighty three children with acute encephalitis were enrolled in this study. Out of those with HSV-1, multiple cytokines were measured. Results: Cytokine analysis of 13 HSV-1-infected patients revealed that IL-8 and granulocyte macrophage colony stimulating factor accumulated at significantly higher levels than macrophage inflammatory protein-1β in the cerebrospinal fluid. Additionally, IFN-γ in serum and cerebrospinal fluid was positively correlated with course of illness, while IL-10 in cerebrospinal fluid was negatively correlated with course of illness. Conclusion: Granulocyte macrophage colony stimulating factor, IL-8, macrophage inflammatory protein-1β, IFN-γ and IL-10 are involved in the HSV-1 immune response and pathogenesis.

Cerebrospinal fluid cyto-/chemokine profile during acute herpes simplex virus induced anti-N-methyl-d-aspartate receptor encephalitis and in chronic neurological sequelae

AIM

To examine the cytokine/chemokine profile of cerebrospinal fluid (CSF) during acute herpes simplex virus-induced N-methyl-d-aspartate receptor (NMDAR) autoimmunity and in chronic/relapsing post-herpes simplex virus encephalitis (HSE) neurological syndromes.

METHOD

We measured longitudinal serial CSF cyto-/chemokines (n=34) and a glial marker (calcium-binding astroglial protein, S100B) in one patient during acute HSE and subsequent anti-NMDAR encephalitis, and compared the results with those from two patients with anti-NMDAR encephalitis without preceding HSE. We also compared cyto-/chemokines in cross-sectional CSF samples from three children with previous HSE who had ongoing chronic or relapsing neurological symptoms (2yr 9 mo-16y after HSE) with those in a group of children having non-inflammatory neurological conditions (n=20).

RESULTS

Acute HSE showed elevation of a broad range of all T-helper-subset-related cyto-/chemokines and S100B whereas the post-HSE anti-NMDAR encephalitis phase showed persistent elevation of two of five T-helper-1 (chemokine [C-X-C motif] ligand 9 [CXCL9], CXCL10), three of five predominantly B-cell (CXCL13, CCL19, a proliferation-inducing ligand [APRIL])-mediated cyto-/chemokines, and interferon-α. The post-HSE anti-NMDAR encephalitis inflammatory response was more pronounced than anti-NMDAR encephalitis. All three chronic post-HSE cases showed persistent elevation of CXCL9, CXCL10, and interferon-α, and there was histopathological evidence of chronic lymphocytic inflammation in one biopsied case 7 years after HSE. Two of three chronic cases showed a modest response to immune therapy.

INTERPRETATION

HSE-induced anti-NMDAR encephalitis is a complex and pronounced inflammatory syndrome. There is persistent CSF upregulation of cyto-/chemokines in chronic or relapsing post-HSE neurological symptoms, which may be modifiable with immune therapy. The elevated cyto-/chemokines may be targets of monoclonal therapies.

Herpes simplex virus-induced anti-N-methyl-d-aspartate receptor encephalitis: a systematic literature review with analysis of 43 cases

AIM

To conduct a systematic literature review on patients with biphasic disease with herpes simplex virus (HSV) encephalitis followed by anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis.

METHOD

We conducted a case report and systematic literature review (up to 10 December 2016), focused on differences between herpes simplex encephalitis (HSE) and anti-NMDAR encephalitis phases, age-related characteristics of HSV-induced anti-NMDAR encephalitis, and therapy. For statistical analyses, McNemar's test, Fisher's test, and Wilcoxon rank sum test were used (two-tailed significance level set at 5%).

RESULTS

Forty-three patients with biphasic disease were identified (31 children). Latency between HSE and anti-NMDAR encephalitis was significantly shorter in children than adults (median 24 vs 40.5d; p=0.006). Compared with HSE, anti-NMDAR encephalitis was characterized by significantly higher frequency of movement disorder (2.5% vs 75% respectively; p<0.001), and significantly lower rate of seizures (70% vs 30% respectively; p=0.001). Compared with adults, during anti-NMDAR encephalitis children had significantly more movement disorders (86.7% children vs 40% adults; p=0.006), fewer psychiatric symptoms (41.9% children vs 90.0% adults; p=0.025), and a slightly higher median modified Rankin Scale score (5 in children vs 4 in adults; p=0.015). During anti-NMDAR encephalitis, 84.6 per cent of patients received aciclovir (for ≤7d in 22.7%; long-term antivirals in 18.0% only), and 92.7 per cent immune therapy, but none had recurrence of HSE clinically or using cerebrospinal fluid HSV polymerase chain reaction (median follow-up 7mo).

INTERPRETATION

Our review suggests that movement disorder may help differentiate clinically an episode of HSV-induced anti-NMDAR encephalitis from HSE relapse. Compared with adults, children have shorter latency between HSE and anti-NMDAR encephalitis and, during anti-NMDAR encephalitis, more movement disorder, fewer psychiatric symptoms, and slightly more severe disease. According to our results, immune therapy given for HSV-induced anti-NMDAR encephalitis does not predispose patients to HSE recurrence.

Anti-N-Methyl-D-aspartate Receptor Encephalitis: A Severe, Potentially Reversible Autoimmune Encephalitis

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is potentially lethal, but it is also a treatable autoimmune disorder characterized by prominent psychiatric and neurologic symptoms. It is often accompanied with teratoma or other neoplasm, especially in female patients. Anti-NMDAR antibodies in cerebrospinal fluid (CSF) and serum are characteristic features of the disease, thereby suggesting a pathogenic role in the disease. Here, we summarize recent studies that have clearly documented that both clinical manifestations and the antibodies may contribute to early diagnosis and multidisciplinary care. The clinical course of the disorder is reversible and the relapse could occur in some patients. Anti-NMDAR encephalitis coexisting with demyelinating disorders makes the diagnosis more complex; thus, clinicians should be aware of the overlapping diseases.

Herpes Simplex Encephalitis: an Update

PURPOSE OF REVIEW

The goal of this review is to provide an update on current thinking regarding herpes simplex encephalitis (HSE), emphasizing new information about pathogenesis, diagnosis, and immune responses. Specific questions to be addressed are the following: (1) Is there a genetic predisposition to HSE? (2) What clinical approaches have the greatest impact on improving the long-term outcomes in patients with HSE? And (3) are there immune-mediated mechanisms that may account for relapsing HSE?

RECENT FINDINGS

Toll-like receptor 3 (TLR 3) plays an important role in innate immune responses, including generation of interferons. Multiple single-gene errors in TLR 3 interferon pathways have recently been described in children that result in increased susceptibility to HSE. Conversely, studies in both animal models and humans indicate that both cytolytic viral replication and immune-mediated responses (including cytotoxic T lymphocytes and immune mechanisms mediated by TLR 2) contribute to the pathology of HSV, suggesting possible new therapeutic approaches. In terms of treatment, data clearly indicate that a longer duration between onset of symptoms and initiation of effective antiviral therapy correlates directly with less favorable clinical outcome. Recurrent or relapsing HSE may occasionally occur, but recent observations indicate that many instances of "relapsing HSE", especially in children, are more often anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis triggered by the antecedent HSV infection. Innate immune responses are critical for defense against HSV; genetic defects in this system may predispose patients to HSE. During acute HSE, exuberant immune responses may contribute to the CNS pathology, suggesting that selective immunosuppressive therapy, coupled with potent antiviral drugs, may eventually play a role in the therapeutic management of HSV. While overall clinical outcomes of HSE remain suboptimal, the initiation of high-dose acyclovir therapy as early as possible in the course of the illness provides the best chance for a patient to survive with minimal neurologic damage. Distinguishing relapsing HSE from autoimmune anti-NMDAR antibody encephalitis is critically important because therapeutic approaches will be very different.

A Feasibility Study of Quantifying Longitudinal Brain Changes in Herpes Simplex Virus (HSV) Encephalitis Using Magnetic Resonance Imaging (MRI) and Stereology

OBJECTIVES

To assess whether it is feasible to quantify acute change in temporal lobe volume and total oedema volumes in herpes simplex virus (HSV) encephalitis as a preliminary to a trial of corticosteroid therapy.

METHODS

The study analysed serially acquired magnetic resonance images (MRI), of patients with acute HSV encephalitis who had neuroimaging repeated within four weeks of the first scan. We performed volumetric measurements of the left and right temporal lobes and of cerebral oedema visible on T2 weighted Fluid Attenuated Inversion Recovery (FLAIR) images using stereology in conjunction with point counting.

RESULTS

Temporal lobe volumes increased on average by 1.6% (standard deviation (SD 11%) in five patients who had not received corticosteroid therapy and decreased in two patients who had received corticosteroids by 8.5%. FLAIR hyperintensity volumes increased by 9% in patients not receiving treatment with corticosteroids and decreased by 29% in the two patients that had received corticosteroids.

CONCLUSIONS

This study has shown it is feasible to quantify acute change in temporal lobe and total oedema volumes in HSV encephalitis and suggests a potential resolution of swelling in response to corticosteroid therapy. These techniques could be used as part of a randomized control trial to investigate the efficacy of corticosteroids for treating HSV encephalitis in conjunction with assessing clinical outcomes and could be of potential value in helping to predict the clinical outcomes of patients with HSV encephalitis.

N-methyl-d-aspartate receptor autoimmunity affects cognitive performance in herpes simplex encephalitis

OBJECTIVES

To investigate the prevalence and temporal development of N-methyl-d-aspartate receptor (NMDAR) autoantibodies in relation to neurocognitive performance in patients with herpes simplex encephalitis (HSE).

METHODS

This prospective observational study enrolled a total of 49 HSE patients within a randomized controlled trial of valacyclovir. Cerebrospinal fluid and serum samples were drawn in the initial stage of disease, after 2 to 3 weeks and after 3 months. Anti-NMDAR IgG was detected with HEK293 cells transfected with plasmids encoding the NMDA NR1 type glutamate receptor. A batch of neurocognitive tests, including the Mattis Dementia Rating Scale (MDRS), Glasgow Coma Scale (GCS), Reaction Level Scale (RLS85), Mini-Mental State Examination (MMSE) and National Institutes of Health (NIH) stroke scale, was performed during 24 months' follow-up.

RESULTS

Anti-NMDAR IgG was detected in 12 of 49 participants. None were antibody positive in the initial stage of disease. In ten of 12 positive cases, specific antibodies were detectable only after 3 months. Notably, the development of NMDAR autoantibodies was associated with significantly impaired recovery of neurocognitive performance. After 24 months' follow-up, the median increase in MDRS total score was 1.5 vs. 10 points in antibody-positive and -negative participants (p=0.018).

CONCLUSIONS

Anti-NMDAR autoimmunity is a common complication to HSE that develops within 3 months after onset of disease. The association to impaired neurocognitive recovery could have therapeutical implications, as central nervous system autoimmunity is potentially responsive to immunotherapy.

Anti-N-Methyl-D-Aspartate Receptor Antibody Mediated Neurologic Relapse Post Herpes Simplex Encephalitis: A Case Series

Despite the advent of antiviral therapy, herpes simplex encephalitis (HSE) remains a devastating condition with significant morbidity and mortality. Neurologic relapse after initial improvement is generally attributed to herpes simplex virus reactivation. In 2013, inflammation caused by anti-N-methyl-D-aspartate receptor antibodies was reported in association with cases of neurologic relapse after herpes simplex encephalitis. We present 3 such cases and discuss diagnostic and management dilemmas.

Herpes Simplex Virus-1 Encephalitis in Adults: Pathophysiology, Diagnosis, and Management

Herpetic infections have plagued humanity for thousands of years, but only recently have advances in antiviral medications and supportive treatments equipped physicians to combat the most severe manifestations of disease. Prompt recognition and treatment can be life-saving in the care of patients with herpes simplex-1 virus encephalitis, the most commonly identified cause of sporadic encephalitis worldwide. Clinicians should be able to recognize the clinical signs and symptoms of the infection and familiarize themselves with a rational diagnostic approach and therapeutic modalities, as early recognition and treatment are key to improving outcomes. Clinicians should also be vigilant for the development of acute complications, including cerebral edema and status epilepticus, as well as chronic complications, including the development of autoimmune encephalitis associated with antibodies to the N-methyl-D-aspartate receptor and other neuronal cell surface and synaptic epitopes. Herein, we review the pathophysiology, differential diagnosis, and clinical and radiological features of herpes simplex virus-1 encephalitis in adults, including a discussion of the most common complications and their treatment. While great progress has been made in the treatment of this life-threatening infection, a majority of patients will not return to their previous neurologic baseline, indicating the need for further research efforts aimed at improving the long-term sequelae.

Resident T Cells Are Unable To Control Herpes Simplex Virus-1 Activity in the Brain Ependymal Region during Latency

HSV type 1 (HSV-1) is one of the leading etiologies of sporadic viral encephalitis. Early antiviral intervention is crucial to the survival of herpes simplex encephalitis patients; however, many survivors suffer from long-term neurologic deficits. It is currently understood that HSV-1 establishes a latent infection within sensory peripheral neurons throughout the life of the host. However, the tissue residence of latent virus, other than in sensory neurons, and the potential pathogenic consequences of latency remain enigmatic. In the current study, we characterized the lytic and latent infection of HSV-1 in the CNS in comparison with the peripheral nervous system following ocular infection in mice. We used RT-PCR to detect latency-associated transcripts and HSV-1 lytic cycle genes within the brain stem, the ependyma (EP), containing the limbic and cortical areas, which also harbor neural progenitor cells, in comparison with the trigeminal ganglia. Unexpectedly, HSV-1 lytic genes, usually identified during acute infection, are uniquely expressed in the EP 60 d postinfection when animals are no longer suffering from encephalitis. An inflammatory response was also mounted in the EP by the maintenance of resident memory T cells. However, EP T cells were incapable of controlling HSV-1 infection ex vivo and secreted less IFN-γ, which correlated with expression of a variety of exhaustion-related inhibitory markers. Collectively, our data suggest that the persistent viral lytic gene expression during latency is the cause of the chronic inflammatory response leading to the exhaustion of the resident T cells in the EP.

Von Willebrand Factor Gene Variants Associate with Herpes simplex Encephalitis

Herpes simplex encephalitis (HSE) is a rare complication of Herpes simplex virus type-1 infection. It results in severe parenchymal damage in the brain. Although viral latency in neurons is very common in the population, it remains unclear why certain individuals develop HSE. Here we explore potential host genetic variants predisposing to HSE. In order to investigate this we used a rat HSE model comparing the HSE susceptible SHR (Spontaneously Hypertensive Rats) with the asymptomatic infection of BN (Brown Norway). Notably, both strains have HSV-1 spread to the CNS at four days after infection. A genome wide linkage analysis of 29 infected HXB/BXH RILs (recombinant inbred lines-generated from the prior two strains), displayed variable susceptibility to HSE enabling the definition of a significant QTL (quantitative trait locus) named Hse6 towards the end of chromosome 4 (160.89-174Mb) containing the Vwf (von Willebrand factor) gene. This was the only gene in the QTL with both cis-regulation in the brain and included several non-synonymous SNPs (single nucleotide polymorphism). Intriguingly, in human chromosome 12 several SNPs within the intronic region between exon 43 and 44 of the VWF gene were associated with human HSE pathogenesis. In particular, rs917859 is nominally associated with an odds ratio of 1.5 (95% CI 1.11-2.02; p-value = 0.008) after genotyping in 115 HSE cases and 428 controls. Although there are possibly several genetic and environmental factors involved in development of HSE, our study identifies variants of the VWF gene as candidates for susceptibility in experimental and human HSE.