Limbic Encephalitis Associated with Human Herpesvirus-7 (HHV-7) in an Immunocompetent Adult: The First Reported Case in Japan

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.

Human herpesvirus-7 meningitis in an immunocompetent adult patient: a case report

Aim

The underlying pathological mechanisms of CNS human herpesvirus-7 (HHV-7) related infections are still unknown, especially among immunocompetent adults. Although HHV-7 meningitis in immunocompetent adults is usually uncommon, serious consideration for possible HHV-7 involvement should be taken when assessing CNS infection of unknown etiology.

Case presentation

We report a 53-year-old female who presented for fever and progressive headaches. Cerebrospinal fluid (CSF) analysis was compatible with a viral meningitis. CSF cultures were negative and HHV-7 DNA was the only strain detected in the CSF analysis. The patient died 1 month later following complications and cardiac arrest.

Conclusion

HHV-7 CNS infection in immunocompetent patient can be a serious infection. Prompt diagnosis and treatment management are essential for better outcome.

Comprehensive analysis of HHV-6 and HHV-7-related gene signature in prognosis and response to temozolomide of glioma

Human herpesvirus (HHV)-6 and HHV-7 have been detected in central nervous system and glioma tissue, while their exact role in glioma remains uncertain. Omics profiles and clinical information were downloaded from public databases, including The Cancer Genome Atlas cohort for training set and the Chinese Glioma Genome Atlas cohorts for validation sets. Differentially expressed genes between HHV-6 and HHV-7 infected or noninfected glioma patients were screened for establishing the HHV-6 and HHV-7 infection (HI) model through Lasso regression analysis. Bioinformatics methods were used to analyze the correlation between HI scores and prognosis, metastasis in glioma patients. Predictable efficacy of HI in temozolomide-resistance and HI-related genetic signatures were also explored. The HI model was constructed as: Risk score = (0.014709*DIRAS3) + (0.029787*TEX26) + (0.223492*FBXO39) + (0.074951*MYBL1) + (0.060202*HILS1). The five gene signature showed good performance in predicting survival time for glioma patients, while higher HI score is correlated with malignant features. Moreover, DNA mismatch repair genes were augmented in glioma patients with higher HI score as well as nonresponse to temozolomide treatment, which was in parallel with the transcriptomic result of temozolomide-resistant glioma cell. Targeting the five gene signature is beneficial for prognosis of glioma patients, especially in glioma patients underwent temozolomide treatment.

Limbic Encephalitis Associated with Human Herpesvirus-7 Infection in an Immunocompetent Adolescent

Despite the ubiquitous nature of human herpesvirus-7 (HHV-7) infection, its clinical significance in the central nervous system (CNS) is poorly understood. However, the related human herpesvirus-6 (HHV-6), which has remarkable genomic similarity to HHV-7, is linked to encephalitis. We present the case of a 17-year-old immunocompetent male with remote history of seizure who arrived in status epilepticus. Upon resolution, he required hospitalization for worsening encephalopathy. Electroencephalogram (EEG) revealed bilateral temporal lobe dysfunction and magnetic resonance imaging (MRI) showed increased signaling in bilateral medial temporal lobes with hippocampal microhemorrhages. Empiric intravenous (IV) acyclovir was initiated despite initially negative cerebrospinal fluid (CSF) studies due to concern for herpes simplex virus (HSV) encephalitis. The patient improved and was discharged on hospital day 13 (HD13). After discharge, a human metagenomics CSF panel resulted positive only for HHV-7, making a case for possible etiology and empiric treatment of HHV-7 despite delayed CSF and serum studies.

Human herpesvirus 7 encephalitis in an immunocompetent adult and a literature review

BACKGROUND

Human herpesvirus 7 (HHV-7) is a common virus that infects children early and is accompanied by lifelong latency in cells, which is easy to reactivate in immunodeficient adults, but the underlying pathological mechanism is uncertain in immunocompetent adults without peculiar past medical history. Even though the clinical manifestation of the encephalitis caused by HHV-7 is uncommon in immunocompetent adults, the HHV-7 infection should not be neglected for encephalitis for unknown reasons.

CASE PRESENTATION

We reported here a case of HHV-7 encephalitis with epileptic seizures. While the brain computer tomography was standard, electroencephalography displayed slow waves in the temporal and bilateral frontal areas, then HHV-7 DNA was detected in the metagenomic next-generation sequencing of cerebrospinal fluid. Fortunately, the patient recovered after treatment and was discharged 2 months later. We also collected the related cases and explored a better way to illuminate the underlying mechanism.

CONCLUSION

The case indicates clinicians should memorize HHV-7 as an unusual etiology of encephalitis to make an early diagnosis and therapy.

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.

Enhanced Virus Detection and Metagenomic Sequencing in Patients with Meningitis and Encephalitis

Meningitis and encephalitis are leading causes of central nervous system (CNS) disease and often result in severe neurological compromise or death. Traditional diagnostic workflows largely rely on pathogen-specific tests, sometimes over days to weeks, whereas metagenomic next-generation sequencing (mNGS) profiles all nucleic acid in a sample. In this single-center, prospective study, 68 hospitalized patients with known (n = 44) or suspected (n = 24) CNS infections underwent mNGS from RNA and DNA to identify potential pathogens and also targeted sequencing of viruses using hybrid capture. Using a computational metagenomic classification pipeline based on KrakenUniq and BLAST, we detected pathogen nucleic acid in cerebrospinal fluid (CSF) from 22 subjects, 3 of whom had no clinical diagnosis by routine workup. Among subjects diagnosed with infection by serology and/or peripheral samples, we demonstrated the utility of mNGS to detect pathogen nucleic acid in CSF, importantly for the Ixodes scapularis tick-borne pathogens Powassan virus, Borrelia burgdorferi, and Anaplasma phagocytophilum. We also evaluated two methods to enhance the detection of viral nucleic acid, hybrid capture and methylated DNA depletion. Hybrid capture nearly universally increased viral read recovery. Although results for methylated DNA depletion were mixed, it allowed the detection of varicella-zoster virus DNA in two samples that were negative by standard mNGS. Overall, mNGS is a promising approach that can test for multiple pathogens simultaneously, with efficacy similar to that of pathogen-specific tests, and can uncover geographically relevant infectious CNS disease, such as tick-borne infections in New England. With further laboratory and computational enhancements, mNGS may become a mainstay of workup for encephalitis and meningitis. IMPORTANCE Meningitis and encephalitis are leading global causes of central nervous system (CNS) disability and mortality. Current diagnostic workflows remain inefficient, requiring costly pathogen-specific assays and sometimes invasive surgical procedures. Despite intensive diagnostic efforts, 40 to 60% of people with meningitis or encephalitis have no clear cause of CNS disease identified. As diagnostic uncertainty often leads to costly inappropriate therapies, the need for novel pathogen detection methods is paramount. Metagenomic next-generation sequencing (mNGS) offers the unique opportunity to circumvent these challenges using unbiased laboratory and computational methods. Here, we performed comprehensive mNGS from 68 prospectively enrolled patients with known (n = 44) or suspected (n = 24) CNS viral infection from a single center in New England and evaluated enhanced methods to improve the detection of CNS pathogens, including those not traditionally identified in the CNS by nucleic acid detection. Overall, our work helps elucidate how mNGS can become integrated into the diagnostic toolkit for CNS infections.

M, Biasolo A, Manganelli R, Palù G, Parisi SG. Viral Molecular Testing of Cerebrospinal Fluid in Adults with Suspected Central Nervous System Infection in an Italian University Hospital Laboratory: A Retrospective Study on 1462 Consecutive Patients

Background:

Generally, about half of the patients with central nervous system infections cases remain unexplained. Therefore, we aimed to describe which viruses were detected in unselected patients with a suspected central nervous system infection and the first diagnostic workflow in a university hospital laboratory.

Methods:

A comprehensive virus testing in cerebrospinal fluid with an in-house real-time PCR method was employed. Determining how many and which viruses to test was at the full discretion of the treating physician.

Results:

1462 patients were evaluated from 2011 to 2017 and 9 898 viral PCRs were made: 176 subjects (12%) had a positive result. There was great heterogeneity in the frequency of patients tested for each virus, ranging from 97.9% (1431 out of 1462) for herpes simplex virus (HSV) to 1.9% (28 out of 1462) for Parvovirus B19, positive in 1 patient. Enterovirus (EV) was the leading virus detected: the frequency was higher with respect to HSV (5.2% vs 2.4%, p=0.0004), varicella-zoster virus (VZV)(5.2% vs 2.9%, p=0.0052), human herpesvirus-6 (5.2% vs 1.7%, p=0.0014) and human herpesvirus-7 (HHV-7)(5.2% vs 2.5%, p=0.0406). Both VZV (83.5%) and HSV (97.9%) were tested significantly more than EV (68.7%, p<0.0001) and HHV-7 (24.1%, p<0.0001): the latter had a positivity comparable to HSV and it was detected in younger patients (median age 29 years), as for EV (median age 35 years). There was no difference found in the age of positive subjects with respect to negative ones for the other viruses tested.

Conclusion:

EV was the fifth virus frequently included in the diagnostic workflow but the most frequently detected, mostly in subjects aged less 40, as HHV-7 was. Testing these two viruses in all younger patients could reduce the number of unknown etiology.

Limbic Encephalitis Brain Damage Induced by Cocal Virus in Adult Mice Is Reduced by Environmental Enrichment: Neuropathological and Behavioral Studies

We previously demonstrated, using the Piry virus model, that environmental enrichment promotes higher T-cell infiltration, fewer microglial changes, and faster central nervous system (CNS) virus clearance in adult mice. However, little is known about disease progression, behavioral changes, CNS cytokine concentration, and neuropathology in limbic encephalitis in experimental models. Using Cocal virus, we infected C57Bl6 adult mice and studied the neuroanatomical distribution of viral antigens in correlation with the microglial morphological response, measured the CNS cytokine concentration, and assessed behavioral changes. C57Bl6 adult mice were maintained in an impoverished environment (IE) or enriched environment (EE) for four months and then subjected to the open field test. Afterwards, an equal volume of normal or virus-infected brain homogenate was nasally instilled. The brains were processed to detect viral antigens and microglial morphological changes using selective immunolabeling. We demonstrated earlier significant weight loss and higher mortality in IE mice. Additionally, behavioral analysis revealed a significant influence of the environment on locomotor and exploratory activity that was associated with less neuroinvasion and a reduced microglial response. Thus, environmental enrichment was associated with a more effective immune response in a mouse model of limbic encephalitis, allowing faster viral clearance/decreased viral dissemination, reduced disease progression, and less CNS damage.