Herpes simplex virus encephalitis update

Profile of Cytokines and T Cell Subsets Transcription Factors in Cerebrospinal Fluid of Patients with Viral Encephalitis

This study investigates the demographic, clinical characteristics, virological profiles, and immunological responses of patients with viral encephalitis (VE) compared with a control group. The VE group displayed a wide range of neurological symptoms. Virological analysis revealed the predominance of Herpesviridae family viruses. Immune responses in cerebrospinal fluid (CSF) from patients with VE were examined, highlighting an immunological shift toward T helper 1 (Th1) cells dominance, altered T helper 17 cells/regulatory T cells (Th17/Tregs) balance, and high interleukin-6 expression. These findings provide insights into the complex immunological landscape of VE, highlighting the role of specific cytokines and T cell subsets in its pathogenesis and potentially guiding targeted therapeutic strategies.

An updated review of HSV-1 infection-associated diseases and treatment, vaccine development, and vector therapy application

Herpes simplex virus type 1 (HSV-1) is a globally widespread virus that causes and associates with a wide range of diseases, including herpes simplex encephalitis, herpes simplex keratitis, and herpes labialis. The interaction between HSV-1 and the host involves complex immune response mechanisms, including recognition of viral invasion, maintenance of latent infection, and triggering of reactivation. Antiviral therapy is the core treatment for HSV-1 infections. Meanwhile, vaccine development employs different strategies and methods, and several promising vaccine types have emerged, such as live attenuated, protein subunit, and nucleic acid vaccines, offering new possibilities for the prevention of HSV-1 infection. Moreover, HSV-1 can be modified into a therapeutic vector for gene therapy and tumour immunotherapy. This review provides an in-depth summary of HSV-1 infection-associated innate and adaptive immune responses, disease pathogenesis, current therapeutic approaches, recent advances in vaccine development, and vector therapy applications for cancer treatment. Through a systematic review of multiple aspects of HSV-1, this study aims to provide a comprehensive and detailed reference for the public on the prevention, control, and treatment of HSV-1.

Study of Hydrolysis Kinetics and Synthesis of Single Isomer of Phosphoramidate ProTide-Acyclovir

Acyclovir (ACV) is a vital treatment for herpes simplex (HSV) and varicella-zoster virus (VZV) infections that inhibit viral DNA polymerase. Phosphoramidate ProTides-ACV, a promising technology, circumvents the reliance on thymidine kinase (TK) for activation. Twelve novel single isomers of phosphoramidate ProTide-ACV were synthesized. Successful isomer separation was achieved, emphasizing the importance of single isomers in medical advancements. The enzymatic hydrolysis kinetics of the synthesized compounds were investigated by using carboxypeptidase Y (CPY). The results revealed a faster conversion for the isomer Rp- than for the Sp-diastereomer. Hydrolysis experiments confirmed steric hindrance effects, particularly with the tert-butyl and isopropyl groups. Molecular modeling elucidated the mechanisms of hydrolysis, supporting the results of the experiments. This research sheds light on the potential of phosphoramidate ProTides-ACV, bridging the gap in understanding their biological and metabolic properties, while supporting future investigations into anti-HSV activity. Preliminary screening revealed that three of the four single isomers demonstrated superior antiviral efficacy against wild-type HSV-1 compared to acyclovir, with isomer 24a ultimately reducing the viral yield at 200 μM. These findings emphasize the importance of isolating racemic ACV-ProTides as pure single isomers for future drug development.

Genetic defects of brain immunity in childhood herpes simplex encephalitis

Herpes simplex virus 1 (HSV-1) encephalitis (HSE) is the most common sporadic viral encephalitis in humans. It is life-threatening and has a first peak of incidence in childhood, during primary infection. Children with HSE are not particularly prone to other infections, including HSV-1 infections of tissues other than the brain. About 8-10% of childhood cases are due to monogenic inborn errors of 19 genes, two-thirds of which are recessive, and most of which display incomplete clinical penetrance. Childhood HSE can therefore be sporadic but genetic, enabling new diagnostic and therapeutic approaches. In this Review, we examine essential cellular and molecular mechanisms of cell-intrinsic antiviral immunity in the brain that are disrupted in individuals with HSE. These mechanisms include both known (such as mutations in the TLR3 pathway) and previously unknown (such as the TMEFF1 restriction factor) antiviral pathways, which may be dependent (for example, IFNAR1) or independent (for example, through RIPK3) of type I interferons. They operate in cortical or brainstem neurons, and underlie forebrain and brainstem infections, respectively. Conversely, the most severe inborn errors of leukocytes, including a complete lack of myeloid and/or lymphoid blood cells, do not underlie HSE. Thus congenital defects in intrinsic immunity in brain-resident neurons that underlie HSE broaden natural host defences against HSV-1 from the leukocytes of the immune system to other cells in the organism.

Protective and stochastic correlation between infectious diseases and autoimmune disorders

A priori, early exposure to a wide range of bacteria, viruses, and parasites appears to fortify and regulate the immune system, potentially reducing the risk of autoimmune diseases. However, improving hygiene conditions in numerous societies has led to a reduction in these microbial exposures, which, according to certain theories, could contribute to an increase in autoimmune diseases. Indeed, molecular mimicry is a key factor triggering immune system reactions; while it seeks pathogens, it can bind to self-molecules, leading to autoimmune diseases associated with microbial infections. On the other hand, a hygiene-based approach aimed at reducing the load of infectious agents through better personal hygiene can be beneficial for such pathologies. This review sheds light on how the evolution of the innate immune system, following the evolution of molecular patterns associated with microbes, contributes to our protection but may also trigger autoimmune diseases linked to microbes. Furthermore, it addresses how hygiene conditions shield us against autoimmune diseases related to microbes but may lead to autoimmune pathologies not associated with microbes.

Case report: Autoimmune glial fibrillary acidic protein astrocytopathy with overlapping autoimmune syndrome

Autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy is a rare autoimmune disease, which is characterized by the immune system attacking astrocytes in the central nervous system, resulting in inflammation and damage to the nervous system. We reported a 41-year-old female patient with only drowsiness for 3 months, who was, otherwise, healthy with no other signs of meningoencephalitis or myelitis. There were no obvious abnormalities in her neurological and ophthalmic tests. Brain magnetic resonance imaging (MRI) plain scan + enhancement with the gadolinium contrast agent revealed patchy hypointensity on T1-weighted imaging, hyperintensity on T2-weighted imaging, hyperintensity on T2-weighted fluid-attenuated inversion recovery in the left basal ganglia, corona radiata, and local septum pellucida, with no enhancement in the enhanced lesions. Cerebrospinal fluid (CSF) revealed white blood cell count of 5.00 × 106/L, CSF protein of 828.53 mg/L, and glucose of 2.83 mmol/L. Aquaporin-4 (AQP4) antibody, N-methyl-D-aspartate receptor (NMDAR) antibody and GFAP antibody were all positive, whereas the remaining autoimmune encephalitis antibody tests were negative. Oncology screening [including head, chest, and whole-abdomen (involving the pelvic cavity) CT and tumor markers] did not reveal any obvious evidence of tumor presence. The patient received systemic treatment with high-dose intravenous injection of steroids combined with immunosuppressive agents, and the clinical and imaging features of the patients improved. To the best of our knowledge, reports on overlapping positivity of AQP4 antibody and NMDAR antibody in patients with GFAP astrocytopathy were still very rare. We hope to supplement the existing literature on this topic, review the relevant literature, and strive to increase the understanding toward GFAP astrocytopathy with overlapping autoimmune syndrome so as to enable early diagnosis and early treatment and to improve the clinical outcome of patients.

Nanotechnology-driven therapies for neurodegenerative diseases: a comprehensive review

Neurological diseases, characterized by neuroinflammation and neurodegeneration, impose a significant global burden, contributing to substantial morbidity, disability and mortality. A common feature of these disorders, including stroke, traumatic brain injury and Alzheimer's disease, is the impairment of the blood-brain barrier (BBB), a critical structure for maintaining brain homeostasis. The compromised BBB in neurodegenerative conditions poses a significant challenge for effective treatment, as it allows harmful substances to accumulate in the brain. Nanomedicine offers a promising approach to overcoming this barrier, with nanoparticles (NPs) engineered to deliver therapeutic agents directly to affected brain regions. This review explores the classification and design of NPs, divided into organic and inorganic categories and further categorized based on their chemical and physical properties. These characteristics influence the ability of NPs to carry and release therapeutic agents, target specific tissues and ensure appropriate clearance from the body. The review emphasizes the potential of NPs to enhance the diagnosis and treatment of neurodegenerative diseases through targeted delivery, improved drug bioavailability and real-time therapeutic efficacy monitoring. By addressing the challenges of the compromised BBB and targeting inflammatory biomarkers, NPs represent a cutting-edge strategy in managing neurological disorders, promising better patient outcomes.

From a focal skin issue to a systemic disease: the multifaceted nature of cold sores, novel findings

Cold sores, a viral infection caused by the herpes simplex virus, are a prevalent affliction affecting millions of people across the globe. In this article, we explore the constitutional symptoms of cold sores in more detail to reveal what patients experience during an outbreak. A total of 400 participants with cold sores were enrolled in our cross-sectional study. Participants were interviewed using a structured questionnaire that collected information on demographic characteristics, clinical symptoms, and constitutional symptoms associated with cold sores such as fever, headache, muscle aches, swollen lymph nodes, malaise, and nervousness. Participants were asked to rate the severity of each symptom on a scale of 1-10. The commonly reported constitutional symptom was malaise (51.4%), and fever (48.8%), followed by headache (39.3%), muscle aches (33.8%), swollen lymph nodes (28.3%), and nervousness (32.2%). Nervousness was reported by 91 patients (22%) on the first day, which was followed by the appearance of a cold sore later. The median severity score for fever was 5.0 (IQR = 3.0), for headache was 5.0 (interquartile ranges = 4.0), for muscle aches was 4.0 (interquartile ranges = 3.0), and for swollen lymph nodes was 4.0 (interquartile ranges = 2.0). Our study provides important insights into the prevalence and impact of constitutional symptoms in individuals with cold sores. Our findings demonstrate that constitutional symptoms such as fever, headache, malaise, and nervousness are common in individuals with cold sores, with a prevalence of up to 51.4% in our study.

Management of Refractory/Resistant Herpes Simplex Virus Infections in Haematopoietic Stem Cell Transplantation Recipients: A Literature Review

Herpes simplex virus (HSV) infections in allogeneic haematopoietic stem cell transplantation (HSCT) recipients pose significant challenges, with higher incidence, severity, and risk of emergence of resistance to antivirals due to impaired T-cell mediated immunity. This literature review focuses on acyclovir-refractory/resistant HSV infections in HSCT recipients. The review addresses the efficacy of antiviral prophylaxis, the incidence of acyclovir-refractory/resistant HSV infections, and the identification of risk factors and potential prognostic impact associated with those infections. Additionally, alternative therapeutic options are discussed. While acyclovir prophylaxis demonstrates a significant benefit in reducing HSV infections in HSCT recipients and, in some cases, overall mortality, concerns arise about the emergence of drug-resistant HSV strains. Our systematic review reports a median incidence of acyclovir-resistant HSV infections of 16.1%, with an increasing trend in recent years. Despite limitations in available studies, potential risk factors of emergence of HSV resistance to acyclovir include human leucocyte antigen (HLA) mismatches, myeloid neoplasms and acute leukaemias, and graft-versus-host disease (GVHD). Limited evidences suggest a potentially poorer prognosis for allogeneic HSCT recipients with acyclovir-refractory/resistant HSV infection. Alternative therapeutic approaches, such as foscarnet, cidofovir, topical cidofovir, optimised acyclovir dosing, and helicase-primase inhibitors offer promising options but require further investigations. Overall, larger studies are needed to refine preventive and therapeutic strategies for acyclovir-refractory/resistant HSV infections in allogeneic HSCT recipients and to identify those at higher risk.

Synthetic Naphthoquinone Inhibits Herpes Simplex Virus Type-1 Replication Targeting Na+, K+ ATPase

Since 1970 acyclovir (ACV) has been the reference drug in treating herpes simplex virus (HSV) infections. However, resistant herpes simplex virus type 1 (HSV-1) strains have emerged, narrowing the treatment efficacy. The antiviral activity of classical Na+, K+ ATPase enzyme (NKA) inhibitors linked the viral replication to the NKA's activity. Herein, we evaluated the anti-HSV-1 activity of synthetic naphthoquinones, correlating their antiviral activity with NKA inhibition. We tested seven synthetic naphthoquinones initially at 50 μM on HSV-1-infected African green monkey kidney cells (VERO cells). Only one compound, 2-hydroxy-3-(2-thienyl)-1,4-naphthoquinone (AN-06), exhibited higher antiviral activity with a low cytotoxicity. AN-06 reduced the viral titer of 9 (log10) to 1.32 (log10) and decreased the steps of attachment and penetration. The addition of AN-06 up to 20 h postinfection (hpi) interfered with the viral cycle. The viral infection alone increases NKA activity 3 h postinfection (hpi), scaling up to 6 hpi. The addition of AN-06 in a culture infected with HSV-1 decreased NKA activity, suggesting that its antiviral action is linked to NKA inhibition. Also, docking results showed that this compound binds at the same site of NKA in which adenosine triphosphate (ATP) binds. AN-06 exhibited promising pharmacokinetic and toxicology properties. Thus, we postulate that AN-06 may be a good candidate for antiviral compounds with a mechanism of action targeting NKA activity.

Human TMEFF1 is a restriction factor for herpes simplex virus in the brain

Most cases of herpes simplex virus 1 (HSV-1) encephalitis (HSE) remain unexplained1,2. Here, we report on two unrelated people who had HSE as children and are homozygous for rare deleterious variants of TMEFF1, which encodes a cell membrane protein that is preferentially expressed by brain cortical neurons. TMEFF1 interacts with the cell-surface HSV-1 receptor NECTIN-1, impairing HSV-1 glycoprotein D- and NECTIN-1-mediated fusion of the virus and the cell membrane, blocking viral entry. Genetic TMEFF1 deficiency allows HSV-1 to rapidly enter cortical neurons that are either patient specific or derived from CRISPR-Cas9-engineered human pluripotent stem cells, thereby enhancing HSV-1 translocation to the nucleus and subsequent replication. This cellular phenotype can be rescued by pretreatment with type I interferon (IFN) or the expression of exogenous wild-type TMEFF1. Moreover, ectopic expression of full-length TMEFF1 or its amino-terminal extracellular domain, but not its carboxy-terminal intracellular domain, impairs HSV-1 entry into NECTIN-1-expressing cells other than neurons, increasing their resistance to HSV-1 infection. Human TMEFF1 is therefore a host restriction factor for HSV-1 entry into cortical neurons. Its constitutively high abundance in cortical neurons protects these cells from HSV-1 infection, whereas inherited TMEFF1 deficiency renders them susceptible to this virus and can therefore underlie HSE.

TMEFF1 is a neuron-specific restriction factor for herpes simplex virus

The brain is highly sensitive to damage caused by infection and inflammation1,2. Herpes simplex virus 1 (HSV-1) is a neurotropic virus and the cause of herpes simplex encephalitis3. It is unknown whether neuron-specific antiviral factors control virus replication to prevent infection and excessive inflammatory responses, hence protecting the brain. Here we identify TMEFF1 as an HSV-1 restriction factor using genome-wide CRISPR screening. TMEFF1 is expressed specifically in neurons of the central nervous system and is not regulated by type I interferon, the best-known innate antiviral system controlling virus infections. Depletion of TMEFF1 in stem-cell-derived human neurons led to elevated viral replication and neuronal death following HSV-1 infection. TMEFF1 blocked the HSV-1 replication cycle at the level of viral entry through interactions with nectin-1 and non-muscle myosin heavy chains IIA and IIB, which are core proteins in virus-cell binding and virus-cell fusion, respectively4-6. Notably, Tmeff1-/- mice exhibited increased susceptibility to HSV-1 infection in the brain but not in the periphery. Within the brain, elevated viral load was observed specifically in neurons. Our study identifies TMEFF1 as a neuron-specific restriction factor essential for prevention of HSV-1 replication in the central nervous system.

Herpes simplex (HSV-1) encephalitis in an infant: a case report study

Introduction and importance

The herpes simplex virus (HSV) is the most common cause of acute sporadic encephalitis, a severe and often fatal disease in humans. It is associated with high mortality and morbidity rates in untreated patients.

Case presentation

An 11-month-old child was admitted to the hospital presenting with acute fever and seizures characterized by staring episodes and spastic movements affecting the left side of the body. Diagnostic workup revealed abnormal T2 flair hyperintense foci in bi-temporoparietal lobes and right thalamus, and bilateral otomastoiditis were detected. A positive result for HSV-1 was obtained through HSV type 1/2 polymerase chain reaction (PCR) testing, leading to a diagnosis of herpes encephalitis.

Clinical discussion

While acyclovir has proven to be an effective therapeutic option, mortality and neurological sequelae continue to be reported in a notable fraction of patients. HSV encephalitis is mainly caused by two strains of the herpes simplex virus: HSV-1, more frequently observed in children and adults, and HSV-2, commonly seen in neonates and those with compromised immune systems. MRI scans often reveal that the brain lesions are localized to certain areas, although temporal involvement may not always be evident. The symptoms of herpetic encephalitis can greatly vary, making early diagnosis and treatment vital for improving patient outcomes.

Conclusion

This case report highlights the clinical presentation, diagnostic challenges, and treatment strategies for HSV-1 encephalitis and underscores the importance of early recognition and prompt initiation of antiviral therapy in suspected cases of HSV-1 encephalitis.

Herpes simplex encephalitis due to a mutation in an E3 ubiquitin ligase

Encephalitis is a rare and potentially fatal manifestation of herpes simplex type 1 infection. Following genome-wide genetic analyses, we identified a previously uncharacterized and very rare heterozygous variant in the E3 ubiquitin ligase WWP2, in a 14-month-old girl with herpes simplex encephalitis. The p.R841H variant (NM_007014.4:c.2522G > A) impaired TLR3 mediated signaling in inducible pluripotent stem cells-derived neural precursor cells and neurons; cells bearing this mutation were also more susceptible to HSV-1 infection compared to control cells. The p.R841H variant increased TRIF ubiquitination in vitro. Antiviral immunity was rescued following the correction of p.R841H by CRISPR-Cas9 technology. Moreover, the introduction of p.R841H in wild type cells reduced such immunity, suggesting that this mutation is linked to the observed phenotypes.

Management of oral herpes simplex virus infections: The problem of resistance. A narrative review

Herpes Simplex Virus (HSV) type 1 (HSV-1) and type 2 (HSV-2) are among the most common human viral pathogens, affecting several billion people worldwide. Although in healthy patients clinical signs and symptoms of HSV infection are usually mild and self-limiting, HSV-infections in immunocompromised patients are frequently more aggressive, persistent, and even life-threatening. Acyclovir and its derivatives are the gold standard antiviral drugs for the prevention and treatment of HSV infections. Although the development of acyclovir resistance is a rather uncommon condition, it may be associated with serious complications, especially in immunocompromised patients. In this review, we aim to address the problem of drug resistant HSV infection and discuss the available alternative therapeutic interventions. All relative studies concerning alternative treatment modalities of acyclovir resistant HSV infection published in PubMed between 1989 to 2022 were reviewed. Long-term treatment and prophylaxis with antiviral agents predisposes to drug resistance, especially in immunocompromised patients. Cidofovir and foscarnet could serve as alternative treatments in these cases. Although rare, acyclovir resistance may be associated with severe complications. Hopefully, in the future, novel antiviral drugs and vaccines will be available in order to avoid the existing drug resistance.

Developing Systems of Emergency and Inpatient Neurologic Care in Resource-Limited Settings

Neurologic diseases represent a significant global health challenge, leading to disability and mortality worldwide. Healthcare systems in low- and middle-income countries are disproportionally affected. In these resource-limited settings, numerous barriers hinder the effective delivery of emergency and inpatient neurologic care, including shortages of trained personnel, limited access to diagnostics and essential medications, inadequate facilities, and absence of rehabilitation services. Disparities in the neurology workforce, limited access to neuroimaging, and availability of acute interventions further exacerbate the problem. This article explores strategies to enhance global capacity for inpatient neurologic care, emphasizing the importance of workforce development, context-specific protocols, telehealth solutions, advocacy efforts, and collaborations.

Herpes simplex encephalitis initially presenting without fever or cerebrospinal fluid pleocytosis and with typical neuroimaging findings: a case report

Herpes simplex encephalitis (HSE) is a common viral encephalitis that can be fatal if not adequately treated. Fever, cerebrospinal fluid (CSF) pleocytosis, and typical neuroimaging findings are commonly observed in HSE cases. We encountered a patient with HSE who did not exhibit these classic clinical features. A 63-year-old male presented with his first-ever seizure. Fever did not develop until the fourth day of admission, and neither neuroimaging nor CSF analysis revealed abnormalities. Under suspicion of autoimmune encephalitis, methylprednisolone was administered. Subsequently, when the patient developed fever, a follow-up neuroimaging study was performed and revealed abnormalities consistent with HSE. The patient was promptly treated with acyclovir, which led to a full recovery. Diagnosing HSE in patients who present without fever or CSF pleocytosis and with typical neuroimaging findings poses a challenge. Therefore, prior to initiating immunosuppressive treatment, it is crucial to closely observe patients and to conduct follow-up tests, including neuroimaging and CSF analysis.

Clinical epidemiology, determinants, and outcomes of viral encephalitis in Ghana; a cross-sectional study

Viral encephalitis is a rare, yet severe neurological disorder. It poses a significant public health threat due to its high morbidity and mortality. Despite the disproportionate burden of the disease in impoverished African countries, the true extent of the problem remains elusive due to the scarcity of accurate diagnostic methods. The absence of timely and effective diagnostic tools, particularly Real-time Polymerase Chain Reaction, has led to misguided treatment, and an underestimation of the disease burden in Ghana. We conducted a prospective cross-sectional study to determine the viral aetiologies of encephalitis among patients presenting to a major referral hospital in Ghana from May 2019 and August 2022. The study aimed at providing a comprehensive information on the clinical epidemiology, and outcomes of viral encephalitis in Ghana. Clinical samples were collected from patients presenting with signs and symptoms of encephalitis and tested for viral agents using real-time polymerase chain reaction. We assessed the clinical epidemiology, risk factors and outcome of individuals using descriptive and logistic regression analysis. Seventy-seven (77) patients were enrolled unto the study. The participants frequently presented with fever (85.7%), seizures (80.5%), lethargy (64.9%) and headache (50.6%). Viruses were detected in 40.3% of the study participants in either cerebrospinal fluid, rectal or oral swab samples. The most frequently detected viruses were cytomegalovirus (48.4%), enteroviruses (38.7%) and HSV (29.0%). Twenty-one (27.3%) of the patients died while on hospital admission. Gender (OR = 5.70 (1.536-1.172), p = 0.01), and negative polymerase chain reaction test results were identified as significant factors associated with death. Antiviral treatment increased the chance of survival of viral encephalitis patients by 21.8%. Our results validate the crucial role of molecular tools as essential for the rapid diagnosis of viral encephalitis, enabling effective treatment and improved patient outcomes. This study contributes valuable epidemiological and clinical insight into viral encephalitis in Ghana.

Vulnerability of the Hippocampus to Insults: Links to Blood-Brain Barrier Dysfunction

The hippocampus is a critical brain substrate for learning and memory; events that harm the hippocampus can seriously impair mental and behavioral functioning. Hippocampal pathophysiologies have been identified as potential causes and effects of a remarkably diverse array of medical diseases, psychological disorders, and environmental sources of damage. It may be that the hippocampus is more vulnerable than other brain areas to insults that are related to these conditions. One purpose of this review is to assess the vulnerability of the hippocampus to the most prevalent types of insults in multiple biomedical domains (i.e., neuroactive pathogens, neurotoxins, neurological conditions, trauma, aging, neurodegenerative disease, acquired brain injury, mental health conditions, endocrine disorders, developmental disabilities, nutrition) and to evaluate whether these insults affect the hippocampus first and more prominently compared to other brain loci. A second purpose is to consider the role of hippocampal blood-brain barrier (BBB) breakdown in either causing or worsening the harmful effects of each insult. Recent research suggests that the hippocampal BBB is more fragile compared to other brain areas and may also be more prone to the disruption of the transport mechanisms that act to maintain the internal milieu. Moreover, a compromised BBB could be a factor that is common to many different types of insults. Our analysis indicates that the hippocampus is more vulnerable to insults compared to other parts of the brain, and that developing interventions that protect the hippocampal BBB may help to prevent or ameliorate the harmful effects of many insults on memory and cognition.

Global Landscape of Encephalitis: Key Priorities to Reduce Future Disease Burden

Encephalitis affects people across the lifespan, has high rates of mortality and morbidity, and results in significant neurological sequelae with long-term consequences to quality of life and wider society. The true incidence is currently unknown due to inaccurate reporting systems. The disease burden of encephalitis is unequally distributed across the globe being highest in low- and middle-income countries where resources are limited. Here countries often lack diagnostic testing, with poor access to essential treatments and neurological services, and limited surveillance and vaccination programs. Many types of encephalitis are vaccine preventable, whereas others are treatable with early diagnosis and appropriate management. In this viewpoint, we provide a narrative review of key aspects of diagnosis, surveillance, treatment, and prevention of encephalitis and highlight priorities for public health, clinical management, and research, to reduce the disease burden.

Korean Chestnut Honey Suppresses HSV-1 Infection by Regulating the ROS-NLRP3 Inflammasome Pathway

Herpes simplex virus 1 (HSV-1) is double-stranded DNA virus that belongs to the Orthoherpesviridae family. It causes serious neurological diseases of the central nervous system, such as encephalitis. The current U.S. Food and Drug Administration (FDA)-approved drugs for preventing HSV-1 infection include acyclovir (ACV) and valacyclovir; however, their long-term use causes severe side effects and often results in the emergence of drug-resistant strains. Therefore, it is important to discover new antiviral agents that are safe and effective against HSV-1 infection. Korean chestnut honey (KCH) has various pharmacological activities, such as antioxidant, antibacterial, and anti-inflammation effects; however, antiviral effects against HSV-1 have not yet been reported. Therefore, we determined the antiviral activity and mechanism of action of KCH after HSV-1 infection on the cellular level. KCH inhibited the HSV-1 infection of host cells through binding and virucidal steps. KCH decreased the production of reactive oxygen species (ROS) and calcium (Ca2+) following HSV-1 infection and suppressed the production of inflammatory cytokines by inhibiting nuclear factor kappa-light-chain-enhancer of activated B cells (NF-кB) activity. Furthermore, we found that KCH inhibited the expression of the nod-like receptor protein 3 (NLRP3) inflammasome during HSV-1 infection. Taken together, the antiviral effects of KCH occur through multiple targets, including the inhibition of viral replication and the ROS-mediated NLRP3 inflammasome pathway. Our findings suggest that KCH has potential for the treatment of HSV-1 infection and related diseases.

TLR3/TRIF pathway confers protection against herpes simplex encephalitis through NK cell activation mediated by a loop of type I IFN and IL-15 from epithelial and dendritic cells

Autosomal recessive (AR) and dominant (AD) deficiencies of TLR3 and TRIF are believed to be crucial genetic causes of herpes simplex encephalitis (HSE), which is a fatal disease causing focal or global cerebral dysfunction following infection with herpes simplex virus type 1 (HSV-1). However, few studies have been conducted on the immunopathological networks of HSE in the context of TLR3 and TRIF defects at the cellular and molecular levels. In this work, we deciphered the crosstalk between type I IFN (IFN-I)-producing epithelial layer and IL-15-producing dendritic cells (DC) to activate NK cells for the protective role of TLR3/TRIF pathway in HSE progression after vaginal HSV-1 infection. TLR3- and TRIF-ablated mice showed enhanced susceptibility to HSE progression, along with high HSV-1 burden in vaginal tract, lymphoid tissues and CNS. The increased HSV-1 burden in TLR3- and TRIF-ablated mice did not correlate with increased infiltration of Ly-6C+ monocytes, but it was closely associated with impaired NK cell activation in vaginal tract. Furthermore, using delicate ex vivo experiments and bone marrow transplantation, TRIF deficiency in tissue-resident cells, such as epithelial cells in vaginal tract, was found to cause impaired NK cell activation by means of low IFN-I production, whereas IFN-I receptor in DC was required for NK cell activation via IL-15 production in response to IFN-I produced from epithelial layer. These results provide new information about IFN-I- and IL-15-mediated crosstalk between epithelial cells and DC at the primary infection site, which suppresses HSE progression in a TLR3- and TRIF-dependent manner.

Gliomatosis cerebri with blindness: A case report with literature review

Cerebral gliomatosis (GC) is a rare diffuse infiltrative growth pattern of glioma with nonspecific clinical manifestations like visual impairment that may involve bilateral temporal lobes. Herpes simplex encephalitis (HSE) and limbic encephalitis (LE) can also lead to temporal lobe involvement. Differentiating these entities is necessary for patients with misleading presentations and imaging findings. To the best of our knowledge, this is the third case of GC presenting with blindness. The patient was a 35 years-old male in a drug rehabilitation center for heroin addiction. He presented with a headache, a single episode of seizure, and a 2-month history of bilateral decrease in visual acuity, which had acutely worsened. Magnetic resonance imaging (MRI) and computed tomography (CT) showed bilateral temporal lobe involvement. Ophthalmological studies showed bilateral papilledema, absence of visual evoked potential, and thickening of the retinal nerve fiber layer. Due to this clinical presentation, normal laboratory data, and suspicious MRI findings, further investigation with magnetic resonance spectroscopy (MRS) was performed. Results showed a greatly increased ratio of choline to creatinine(Cr) or N-acetyl aspartate (NAA), suggesting a neoplastic nature of the disease. Subsequently, the patient was referred for a brain tissue biopsy with a suspicion of malignancy. The pathology results revealed adult-type diffuse glioma with isocitrate dehydrogenase (IDH) mutation. Bilateral blindness, as well as bilateral temporal lobe involvement, each has many different causes. However, as demonstrated in this study, adult-type diffuse glioma must be considered a rare cause of concomitant bilateral temporal lobe involvement and blindness.

TREM2 is down-regulated by HSV1 in microglia and involved in antiviral defense in the brain

Immunological control of viral infections in the brain exerts immediate protection and also long-term maintenance of brain integrity. Microglia are important for antiviral defense in the brain. Here, we report that herpes simplex virus type 1 (HSV1) infection of human induced pluripotent stem cell (hiPSC)-derived microglia down-regulates expression of genes in the TREM2 pathway. TREM2 was found to be important for virus-induced IFNB induction through the DNA-sensing cGAS-STING pathway in microglia and for phagocytosis of HSV1-infected neurons. Consequently, TREM2 depletion increased susceptibility to HSV1 infection in human microglia-neuron cocultures and in the mouse brain. TREM2 augmented STING signaling and activation of downstream targets TBK1 and IRF3. Thus, TREM2 is important for the antiviral immune response in microglia. Since TREM2 loss-of-function mutations and HSV1 serological status are both linked to Alzheimer's disease, this work poses the question whether genetic or virus-induced alterations of TREM2 activity predispose to post-infection neurological pathologies.

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.

Encephalitis: diagnosis, management and recent advances in the field of encephalitides

Encephalitis describes inflammation of the brain parenchyma, typically caused by either an infectious agent or through an autoimmune process which may be postinfectious, paraneoplastic or idiopathic. Patients can present with a combination of fever, alterations in behaviour, personality, cognition and consciousness. They may also exhibit focal neurological deficits, seizures, movement disorders and/or autonomic instability. However, it can sometimes present non-specifically, and this combined with its many causes make it a difficult to manage neurological syndrome. Despite improved treatments in some forms of encephalitides, encephalitis remains a global concern due to its high mortality and morbidity. Prompt diagnosis and administration of specific and supportive management options can lead to better outcomes. Over the last decade, research in encephalitis has led to marked developments in the understanding, diagnosis and management of encephalitis. In parallel, the number of autoimmune encephalitis syndromes has rapidly expanded and clinically characteristic syndromes in association with pathogenic autoantibodies have been defined. By focusing on findings presented at the Encephalitis Society's conference in December 2021, this article reviews the causes, clinical manifestations and management of encephalitis and integrate recent advances and challenges of research into encephalitis.

ICP4-Associated Activation of Rap1b Facilitates Herpes Simplex Virus Type I (HSV-1) Infection in Human Corneal Epithelial Cells

The strong contribution of RAS-related protein 1b (Rap1b) to cytoskeleton remodeling determines intracellular and extracellular physiological activities, including the successful infection of viruses in permissive cells, but its role in the HSV-1 life cycle is still unclear. Here, we demonstrated that the HSV-1 immediate early (IE) gene ICP4 inhibits protein kinase A (PKA) phosphorylation to induce Rap1b-activation-mediated viral infection. Rap1b activation and membrane enrichment begin at the early stage of HSV-1 infection and remain active during the proliferation period of the virus. Treating the cells with Rap1b small interfering RNA (siRNA) showed a dose-dependent decrease in viral infection levels, but no dose-dependent increase was observed after Rap1b overexpression. Further investigation indicated that the suppression of Rap1b activation derives from phosphorylated PKA and Rap1b mutants with partial or complete prenylation instead of phosphorylation, which promoted viral infection in a dose-dependent manner. Furthermore, the PKA agonist Forskolin disturbed Rap1b activation in a dose-dependent manner, accompanied by a decreasing trend in viral infection. Moreover, the HSV-1 IE gene ICP4 induced PKA dephosphorylation, leading to continuous Rap1b activation, followed by cytoskeleton rearrangement induced by cell division control protein 42 (CDC42) and Ras-related C3 botulinum toxin substrate 1 (RAC1). These further stimulated membrane-triggered physiological processes favoring virus infection. Altogether, we show the significance of Rap1b during HSV-1 infection and uncover the viral infection mechanism determined by the posttranslational regulation of the viral ICP4 gene and Rap1b host protein.

CLEAR Strategy Inhibited HSV Proliferation Using Viral Vectors Delivered CRISPR-Cas9

Herpes simplex virus type 1 (HSV-1) is a leading cause of encephalitis and infectious blindness. The commonly used clinical therapeutic drugs are nucleoside analogues such as acyclovir. However, current drugs for HSV cannot eliminate the latent virus or viral reactivation. Therefore, the development of new treatment strategies against latent HSV has become an urgent need. To comprehensively suppress the proliferation of HSV, we designed the CLEAR strategy (coordinated lifecycle elimination against viral replication). VP16, ICP27, ICP4, and gD-which are crucial genes that perform significant functions in different stages of the HSV infection lifecycle-were selected as targeting sites based on CRISPR-Cas9 editing system. In vitro and in vivo investigations revealed that genome editing by VP16, ICP27, ICP4 or gD single gene targeting could effectively inhibit HSV replication. Moreover, the combined administration method (termed "Cocktail") showed superior effects compared to single gene editing, which resulted in the greatest decrease in viral proliferation. Lentivirus-delivered CRISPR-Cas9/gRNA editing could effectively block HSV replication. The CLEAR strategy may provide new insights into the potential treatment of refractory HSV-1-associated diseases, particularly when conventional approaches have encountered resistance.

Analysis of Metagenomic Next-Generation Sequencing (mNGS) in the Diagnosis of Herpes Simplex Virus (HSV) Encephalitis with Normal Cerebrospinal Fluid (CSF)

Background

Metagenomic next-generation sequencing (mNGS) is becoming increasingly extensive in diagnosing herpes simplex encephalitis (HSE). However, many HSE patients with normal cerebrospinal fluid (CSF) diagnosed by mNGS have been found during the clinical application. This study aimed to summarize and analyze the clinical characteristics, supplementary examinations, and prognosis of patients with HSE whose cerebrospinal fluid was confirmed to be normal by mNGS.

Methods

This retrospective study evaluated the clinical characteristics, auxiliary examinations, and patient prognosis of patients with HSE that were diagnosed by mNGS but had normal CSF. Clinical data collected included baseline information, signs and symptoms upon admission, and risk factors for infection. Auxiliary examinations included indirect immunofluorescence assay (IIF), cell-based assay (CBA), and CSF testing. Prognosis was evaluated based on hospital stay and patient survival.

Results

Seven of the nine patients (77.8%) experienced headaches, and four (44.4%) had a fever of 38°C or higher. The average leukocyte count in the CSF was 2.6 ± 2.3/L. According to the mNGS, the median sequence count of HSV was 2 (1, 16). Magnetic resonance imaging (MRI) revealed one bilateral temporal lobe lesion (11.1%), two isolated bilateral frontal lobe lesions (22.2%), and one bilateral cingulate gyrus lesion (11.1%). One patient (11.1%) was admitted to the intensive care unit and passed away in the hospital. The remaining patients (88.9%) had a positive prognosis upon discharge.

Conclusion

Patients with HSE who had normal CSF were typically middle-aged women with normal immune function. They showed typical HSE clinical features, such as fever, headache and epilepsy, that did not differ from those of other HSE patients. A normal CSF result is generally associated with a low viral load and the body's ability to mount an effective immune response. Most of these patients have a favorable prognosis.

Viral infections in critical care: a narrative review

Viral infections form a substantial part of the intensive care workload, even before the recent and ongoing COVID-19 pandemic. The growing availability of molecular diagnostics for viral infections has led to increased recognition of these pathogens. This additional information, however, provides new challenges for interpretation and management. As the SARS-CoV-2 pandemic has amply demonstrated, the emergence and global spread of novel viruses are likely to provide continued challenges for critical care physicians into the future. This article will provide an overview of viral infections relevant to the critical care physician, discussing the diagnosis and management of respiratory viral infections, blood borne and enteric viruses. We will also discuss herpesviridae complications, commonly seen due to reactivation of latent infections. Further, we explore some rarer and emerging viruses, including recognition of viral haemorrhagic fevers, and briefly discuss post-viral syndromes which may present to the intensive care unit. Finally, we will discuss infection control and its importance in preventing nosocomial viral transmission.

Encephalitis and poor neuronal death-mediated control of herpes simplex virus in human inherited RIPK3 deficiency

Inborn errors of TLR3-dependent type I IFN immunity in cortical neurons underlie forebrain herpes simplex virus-1 (HSV-1) encephalitis (HSE) due to uncontrolled viral growth and subsequent cell death. We report an otherwise healthy patient with HSE who was compound heterozygous for nonsense (R422*) and frameshift (P493fs9*) RIPK3 variants. Receptor-interacting protein kinase 3 (RIPK3) is a ubiquitous cytoplasmic kinase regulating cell death outcomes, including apoptosis and necroptosis. In vitro, the R422* and P493fs9* RIPK3 proteins impaired cellular apoptosis and necroptosis upon TLR3, TLR4, or TNFR1 stimulation and ZBP1/DAI-mediated necroptotic cell death after HSV-1 infection. The patient's fibroblasts displayed no detectable RIPK3 expression. After TNFR1 or TLR3 stimulation, the patient's cells did not undergo apoptosis or necroptosis. After HSV-1 infection, the cells supported excessive viral growth despite normal induction of antiviral IFN-β and IFN-stimulated genes (ISGs). This phenotype was, nevertheless, rescued by application of exogenous type I IFN. The patient's human pluripotent stem cell (hPSC)-derived cortical neurons displayed impaired cell death and enhanced viral growth after HSV-1 infection, as did isogenic RIPK3-knockout hPSC-derived cortical neurons. Inherited RIPK3 deficiency therefore confers a predisposition to HSE by impairing the cell death-dependent control of HSV-1 in cortical neurons but not their production of or response to type I IFNs.

TRPV4 channel is involved in HSV-2 infection in human vaginal epithelial cells through triggering Ca2+ oscillation

Herpes simplex virus (HSV) infection induces a rapid and transient increase in intracellular calcium concentration ([Ca2+]i), which plays a critical role in facilitating viral entry. T-type calcium channel blockers and EGTA, a chelate of extracellular Ca2+, suppress HSV-2 infection. But the cellular mechanisms mediating HSV infection-activated Ca2+ signaling have not been completely defined. In this study we investigated whether the TRPV4 channel was involved in HSV-2 infection in human vaginal epithelial cells. We showed that the TRPV4 channel was expressed in human vaginal epithelial cells (VK2/E6E7). Using distinct pharmacological tools, we demonstrated that activation of the TRPV4 channel induced Ca2+ influx, and the TRPV4 channel worked as a Ca2+-permeable channel in VK2/E6E7 cells. We detected a direct interaction between the TRPV4 channel protein and HSV-2 glycoprotein D in the plasma membrane of VK2/E6E7 cells and the vaginal tissues of HSV-2-infected mice as well as in phallic biopsies from genital herpes patients. Pretreatment with specific TRPV4 channel inhibitors, GSK2193874 (1-4 μM) and HC067047 (100 nM), or gene silence of the TRPV4 channel not only suppressed HSV-2 infectivity but also reduced HSV-2-induced cytokine and chemokine generation in VK2/E6E7 cells by blocking Ca2+ influx through TRPV4 channel. These results reveal that the TRPV4 channel works as a Ca2+-permeable channel to facilitate HSV-2 infection in host epithelial cells and suggest that the design and development of novel TRPV4 channel inhibitors may help to treat HSV-2 infections.

Microglia innate immune response contributes to the antiviral defense and blood-CSF barrier function in human choroid plexus organoids during HSV-1 infection

The choroid plexus (ChP) is the source of cerebrospinal fluid (CSF). The ChP-CSF system not only provides the necessary cushion for the brain but also works as a sink for waste clearance. During sepsis, pathogens and host immune cells can weaken the ChP barrier and enter the brain, causing cerebral dysfunctions known as sepsis-associated encephalophagy. Here, we used human ChP organoid (ChPO) to model herpes simplex virus type 1 (HSV-1) infection and found ChP epithelial cells were highly susceptible to HSV-1. Since the current ChPO model lacks a functional innate immune component, particularly microglia, we next developed a new microglia-containing ChPO model, and found microglia could effectively limit HSV-1 infection and protect epithelial barrier in ChPOs. Furthermore, we found the innate immune cyclic GMP-AMP synthase (cGAS)-STING pathway and its downstream interferon response were essential, as cGAS inhibitor RU.512 or STING inhibitor H-151 abolished microglia antiviral function and worsened ChP barrier in organoids. These results together indicated that cGAS-STING pathway coordinates antiviral response in ChP and contributes to treating sepsis or related neurological conditions.

When herpes simplex virus encephalitis meets antiviral innate immunity

Herpes simplex virus (HSV) is the most common pathogen of infectious encephalitis, accounting for nearly half of the confirmed cases of encephalitis. Its clinical symptoms are often atypical. HSV PCR in cerebrospinal fluid is helpful for diagnosis, and the prognosis is usually satisfactory after regular antiviral treatment. Interestingly, some patients with recurrent encephalitis have little antiviral effect. HSV PCR in cerebrospinal fluid is negative, but glucocorticoid has a significant effect after treatment. Specific antibodies, such as the NMDA receptor antibody, the GABA receptor antibody, and even some unknown antibodies, can be isolated from cerebrospinal fluid, proving that the immune system contributes to recurrent encephalitis, but the specific mechanism is still unclear. Based on recent studies, we attempt to summarize the relationship between herpes simplex encephalitis and innate immunity, providing more clues for researchers to explore this field further.

Encephalitis in adults in the Auckland and Northland regions of New Zealand, 2009 to 2018

We conducted a retrospective study to determine the incidence and frequency of different subtypes of encephalitis in patients aged 15 and older in the Auckland and Northland regions of New Zealand between 2009 and 2018. Residents in Auckland and Northland presenting with encephalitis between 2009 and 2018 were identified from three overlapping databases: positive cerebrospinal fluid (CSF) viral polymerase chain reaction (PCR) tests, CSF neuronal antibody requests, and CSF neuronal antibody tests sent overseas. A diagnosis of autoimmune encephalitis required fulfilment of diagnostic criteria published by Graus and colleagues (2016). One hundred and thirty-six (69, 50.7% female) patients met study inclusion criteria. The median age was 59 (range 15-92). The annual incidence was 1.10 cases per 100,000 person-years. Of these 136 patients, 56 (41.2%) had an infectious aetiology, with varicella zoster (26, 46.4%) and herpes simplex (23, 41.1%) being the most common agents. Autoimmune encephalitis was diagnosed in 32 patients (23.5%). LGI-1 antibody was the most commonly identified neuronal autoantibody (10 patients, 13.2%). Forty-eight patients (35.3%) had encephalitis of unknown cause. In-hospital mortality for infectious encephalitis was 12.5%, autoimmune encephalitis 6.3%, and encephalitis of unknown cause 10.4%. Compared to a previous analysis of encephalitis in adults in Auckland, the incidence of encephalitis and autoimmune encephalitis had increased. The proportion of patients with an unknown cause for encephalitis had decreased.

Nicotinamide n-Oxide Attenuates HSV-1-Induced Microglial Inflammation through Sirtuin-1/NF-κB Signaling

HSV-1 is a typical neurotropic virus that infects the brain and causes keratitis, cold sores, and occasionally, acute herpes simplex encephalitis (HSE). The large amount of proinflammatory cytokines induced by HSV-1 infection is an important cause of neurotoxicity in the central nervous system (CNS). Microglia, as resident macrophages in CNS, are the first line of defense against neurotropic virus infection. Inhibiting the excessive production of inflammatory cytokines in overactivated microglia is a crucial strategy for the treatment of HSE. In the present study, we investigated the effect of nicotinamide n-oxide (NAMO), a metabolite mainly produced by gut microbe, on HSV-1-induced microglial inflammation and HSE. We found that NAMO significantly inhibits the production of cytokines induced by HSV-1 infection of microglia, such as IL-1β, IL-6, and TNF-α. In addition, NAMO promotes the transition of microglia from the pro-inflammatory M1 type to the anti-inflammatory M2 type. More detailed studies revealed that NAMO enhances the expression of Sirtuin-1 and its deacetylase enzymatic activity, which in turn deacetylates the p65 subunit to inhibit NF-κB signaling, resulting in reduced inflammatory response and ameliorated HSE pathology. Therefore, Sirtuin-1/NF-κB axis may be promising therapeutic targets against HSV-1 infection-related diseases including HSE.

Herpes Simplex Encephalitis: Detection, Management, and Outcomes

The pathophysiology of herpes simplex encephalitis (HSE) is incompletely understood and proposed to be secondary to the retrograde transport of the herpes simplex virus type 1 (HSV-1) via the trigeminal and/or olfactory nerves to the central nervous system (CNS). In this case report, we present a 68-year-old female who presents to our emergency department after a fall. Upon initial admission, her neurological examination was benign, and a computer tomography (CT) scan of her brain showed a subdural hematoma for which she was treated conservatively. Day 4 of her hospitalization marked a rapid decline in her course of illness, beginning with confusion and hallucinations, progressing to subclinical seizures, and culminating in irreversible brain damage and palliative extubation on day 16 of hospitalization. This case report discusses our insight into the challenges of early diagnosis and treatment of herpes encephalitis and their impact on improving patient outcomes.

Influences of Magnetic Resonance Imaging Superresolution Algorithm-Based Transition Care on Prognosis of Children with Severe Viral Encephalitis

Objective

Its goal was to see how convolutional neural network- (CNN-) based superresolution (SR) technology magnetic resonance imaging- (MRI-) assisted transition care (TC) affected the prognosis of children with severe viral encephalitis (SVE) and how effective it was.

Methods

90 SVE children were selected as the research objects and divided into control group (39 cases receiving conventional nursing intervention) and observation group (51 cases performed with conventional nursing intervention and TC intervention) according to their nursing purpose. Based on SR-CNN-optimized MRI images, diagnosis was implemented. Life treatment and sequelae in two groups were compared.

Results

After the processing by CNN algorithm-based SR, peak signal to noise ratio (PSNR) (40.08 dB) and structural similarity (SSIM) (0.98) of MRI images were both higher than those of fully connected neural network (FNN) (38.01 dB, 0.93) and recurrent neural network (RNN) (37.21 dB, 0.93) algorithms. Diagnostic sensitivity (95.34%), specificity (75%), and accuracy (94.44%) of MRI images were obviously superior to those of conventional MRI (81.40%, 50%, and 80%). PedsQLTM 4.0 scores of the observation group 1 to 3 months after discharge were all higher than those of the control group (54.55 ± 5.76 vs. 52.32 ± 5.12 and 66.32 ± 8.89 vs. 55.02 ± 5.87). Sequela incidence in the observation group (13.73%) was apparently lower than that in the control group (43.59%) (P < 0.05).

Conclusion

(1) SR-CNN algorithm could increase the definition and diagnostic ability of MRI images. (2) TC could reduce sequelae incidence among SVE children and improve their quality of life (QOL).

Development of a multiplex droplet digital PCR assay for detection of enterovirus, parechovirus, herpes simplex virus 1 and 2 simultaneously for diagnosis of viral CNS infections

Background

Enterovirus (EV), parechovirus (HPeV), herpes simplex virus 1 and 2 (HSV1/2) are common viruses leading to viral central nervous system (CNS) infections which are increasingly predominant but exhibit deficiency in definite pathogen diagnosis with gold-standard quantitative PCR method. Previous studies have shown that droplet digital PCR (ddPCR) has great potential in pathogen detection and quantification, especially in low concentration samples.

Methods

Targeting four common viruses of EV, HPeV, HSV1, and HSV2 in cerebrospinal fluid (CSF), we developed a multiplex ddPCR assay using probe ratio-based multiplexing strategy, analyzed the performance, and evaluated it in 97 CSF samples collected from patients with suspected viral CNS infections on a two-channel ddPCR detection system.

Results

The four viruses were clearly distinguished by their corresponding fluorescence amplitude. The limits of detection for EV, HPeV, HSV1, and HSV2 were 5, 10, 5, and 10 copies per reaction, respectively. The dynamic range was at least four orders of magnitude spanning from 2000 to 2 copies per reaction. The results of 97 tested clinical CSF specimens were identical to those deduced from qPCR/qRT-PCR assays using commercial kits.

Conclusion

The multiplex ddPCR assay was demonstrated to be an accurate and robust method which could detect EV, HPeV, HSV1, and HSV2 simultaneously. It provides a useful tool for clinical diagnosis and disease monitoring of viral CNS infections.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-022-01798-y.

The Causes and Long-Term Consequences of Viral Encephalitis

Reports regarding brain inflammation, known as encephalitis, have shown an increasing frequency during the past years. Encephalitis is a relevant concern to public health due to its high morbidity and mortality. Infectious or autoimmune diseases are the most common cause of encephalitis. The clinical symptoms of this pathology can vary depending on the brain zone affected, with mild ones such as fever, headache, confusion, and stiff neck, or severe ones, such as seizures, weakness, hallucinations, and coma, among others. Encephalitis can affect individuals of all ages, but it is frequently observed in pediatric and elderly populations, and the most common causes are viral infections. Several viral agents have been described to induce encephalitis, such as arboviruses, rhabdoviruses, enteroviruses, herpesviruses, retroviruses, orthomyxoviruses, orthopneumovirus, and coronaviruses, among others. Once a neurotropic virus reaches the brain parenchyma, the resident cells such as neurons, astrocytes, and microglia, can be infected, promoting the secretion of pro-inflammatory molecules and the subsequent immune cell infiltration that leads to brain damage. After resolving the viral infection, the local immune response can remain active, contributing to long-term neuropsychiatric disorders, neurocognitive impairment, and degenerative diseases. In this article, we will discuss how viruses can reach the brain, the impact of viral encephalitis on brain function, and we will focus especially on the neurocognitive sequelae reported even after viral clearance.

HSV-Encephalitis Resembling Acute Cerebral Infarction in a Patient With Atrial Fibrillation: Beware of Stroke Mimics

INTRODUCTION

Herpes simplex virus-1 (HSV-1) encephalitis, the most common and potentially life-threatening type of encephalitis, may rarely present as a stroke mimic. Prompt diagnosis is of paramount importance for the timely initiation of antiviral treatment and to avert intravenous thrombolysis.

CASE REPORT

A 60-year-old man with a history of lone paroxysmal atrial fibrillation without prior antithrombotic treatment was admitted due to mild gait unsteadiness and intermittent dysarthria of acute onset. On admission, the patient was afebrile, whereas neurological examination revealed only a mild pronator drift on the left. Brain magnetic resonance imaging (MRI) showed an extensive right temporo-occipital and thalamic lesion with restricted diffusion and 3 small-sized hemorrhagic foci. Brain MR-angiography did not show large vessel stenosis or occlusion. On the basis of careful observation and the depiction of several imaging discrepancies, such as early vasogenic edema and hemorrhagic transformation, as well as uncus involvement, but also the lack of significant neurological deficits despite the size of the brain lesion we suspected viral encephalitis which was confirmed by the detection of HSV-1 DNA in the cerebrospinal fluid.

CONCLUSION

HSV-encephalitis might occasionally result in the development of unilateral brain MRI lesions with extensive cytotoxic edema, resembling an acute ischemic stroke. Therefore, HSV-encephalitis must be considered in the differential diagnosis of acute ischemic stroke with atypical presentation. The presence of a significant dissociation between the brain MRI lesion volume and the neurological deficits, as well as certain brain MRI imaging discrepancies might serve as "red flags" to extend the diagnostic workup.

Innate Immune Signaling and Role of Glial Cells in Herpes Simplex Virus- and Rabies Virus-Induced Encephalitis

The environment of the central nervous system (CNS) represents a double-edged sword in the context of viral infections. On the one hand, the infectious route for viral pathogens is restricted via neuroprotective barriers; on the other hand, viruses benefit from the immunologically quiescent neural environment after CNS entry. Both the herpes simplex virus (HSV) and the rabies virus (RABV) bypass the neuroprotective blood-brain barrier (BBB) and successfully enter the CNS parenchyma via nerve endings. Despite the differences in the molecular nature of both viruses, each virus uses retrograde transport along peripheral nerves to reach the human CNS. Once inside the CNS parenchyma, HSV infection results in severe acute inflammation, necrosis, and hemorrhaging, while RABV preserves the intact neuronal network by inhibiting apoptosis and limiting inflammation. During RABV neuroinvasion, surveilling glial cells fail to generate a sufficient type I interferon (IFN) response, enabling RABV to replicate undetected, ultimately leading to its fatal outcome. To date, we do not fully understand the molecular mechanisms underlying the activation or suppression of the host inflammatory responses of surveilling glial cells, which present important pathways shaping viral pathogenesis and clinical outcome in viral encephalitis. Here, we compare the innate immune responses of glial cells in RABV- and HSV-infected CNS, highlighting different viral strategies of neuroprotection or Neuroinflamm. in the context of viral encephalitis.

Clinical, neuropathological, and immunological short- and long-term feature of a mouse model mimicking human herpes virus encephalitis

Herpes simplex encephalitis (HSE) is one of the most serious diseases of the nervous system in humans. However, its pathogenesis is still only poorly understood. Although several mouse models of predominantly herpes simplex virus 1 (HSV-1) infections mimic different crucial aspects of HSE, central questions remain unanswered. They comprise the specific temporofrontal tropism, viral spread within the central nervous system (CNS), as well as potential molecular and immunological barriers that drive virus into latency while only rarely resulting in severe HSE. We have recently proposed an alternative mouse model by using a pseudorabies virus (PrV) mutant that more faithfully represents the striking features of human HSE: temporofrontal meningoencephalitis with few severely, but generally only moderately to subclinically affected mice as well as characteristic behavioral abnormalities. Here, we characterized this animal model using 6- to 8-week-old female CD-1 mice in more detail. Long-term investigation over 6 months consistently revealed a biphasic course of infection accompanied by recurring clinical signs including behavioral alterations and mainly mild meningoencephalitis restricted to the temporal and frontal lobes. By histopathological and immunological analyses, we followed the kinetics and spatial distribution of inflammatory lesions as well as the underlying cytokine expression in the CNS over 21 days within the acute phase of infection. Affecting the temporal lobes, the inflammatory infiltrate was composed of lymphocytes and macrophages showing a predominantly lymphocytic shift 15 days after infection. A strong increase was observed in cytokines CXCL10, CCL2, CCL5, and CXCL1 recruiting inflammatory cells to the CNS. Unlike the majority of infected mice, strongly affected animals demonstrated extensive temporal lobe edema, which is typically present in severe human HSE cases. In summary, these results support the validity of our animal model for in-depth investigation of HSE pathogenesis.

Pathogenesis and virulence of herpes simplex virus

Two of the most prevalent human viruses worldwide, herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2, respectively), cause a variety of diseases, including cold sores, genital herpes, herpes stromal keratitis, meningitis and encephalitis. The intrinsic, innate and adaptive immune responses are key to control HSV, and the virus has developed mechanisms to evade them. The immune response can also contribute to pathogenesis, as observed in stromal keratitis and encephalitis. The fact that certain individuals are more prone than others to suffer severe disease upon HSV infection can be partially explained by the existence of genetic polymorphisms in humans. Like all herpesviruses, HSV has two replication cycles: lytic and latent. During lytic replication HSV produces infectious viral particles to infect other cells and organisms, while during latency there is limited gene expression and lack of infectious virus particles. HSV establishes latency in neurons and can cause disease both during primary infection and upon reactivation. The mechanisms leading to latency and reactivation and which are the viral and host factors controlling these processes are not completely understood. Here we review the HSV life cycle, the interaction of HSV with the immune system and three of the best-studied pathologies: Herpes stromal keratitis, herpes simplex encephalitis and genital herpes. We also discuss the potential association between HSV-1 infection and Alzheimer's disease.

Neuron-intrinsic immunity to viruses in mice and humans

Viral encephalitis is a major neglected medical problem. Host defense mechanisms against viral infection of the central nervous system (CNS) have long remained unclear. The few previous studies of CNS-specific immunity to viruses in mice in vivo and humans in vitro have focused on the contributions of circulating leukocytes, resident microglial cells and astrocytes, with neurons long considered passive victims of viral infection requiring protection from extrinsic antiviral mechanisms. The last decade has witnessed the gradual emergence of the notion that neurons also combat viruses through cell-intrinsic mechanisms. Forward genetic approaches in humans have shown that monogenic inborn errors of TLR3, IFN-α/β, or snoRNA31 immunity confer susceptibility to herpes simplex virus 1 (HSV-1) infection of the forebrain, whereas inborn errors of DBR1 underlie brainstem infections due to various viruses, including HSV-1. The study of human pluripotent stem cell (hPSC)-derived CNS-resident cells has unraveled known (i.e. TLR3-dependent IFN-α/β immunity) and new (i.e. snoRNA31-dependent or DBR1-dependent immunity) cell-intrinsic antiviral mechanisms operating in neurons. Reverse genetic approaches in mice have confirmed that some known antiviral mechanisms also operate in mouse neurons (e.g. TLR3 and IFN-α/β immunity). The search for human inborn errors of immunity (IEIs) underlying various forms of viral encephalitis, coupled with mouse models in vivo, and hPSC-based culture models of CNS and peripheral nervous system cells and organoids in vitro, should shed further light on the cell-specific and tissue-specific mechanisms of host defense against viruses in the human brain.