Neuronal Cell Surface Research Articles

Autoimmune Encephalitis, a Diagnostic and Therapeutic Challenge in the Intensive Care Unit.

Autoimmune encephalitis is a progressive inflammation of the brain, from acute to subacute, associated with antibodies against neuronal cell surface and synaptic protein, most commonly encephalitis against the N-methyl-D-aspartate (NMDA) receptor. New significant findings on etiology show that autoimmune encephalitis is triggered by several etiologies, for example neoplastic processes (breast, lung, kidney, thyroid cancer, ovarian teratoma, and B-cell lymphoma) but also by infections of the nervous system, such as herpes encephalitis. Antibodies against neuronal surface structures are usually direct pathogens and develop their effect through internalization of target proteins, through receptor blockade or complement activation. The type and titer of the antibody e.g. against NMDA receptors, Gamma Amino Butyric (GABA), αAmino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors or voltage-gated potassium channel complexes. An associated tumor, biomarkers, imaging studies, and cerebrospinal fluid are decisive for the prognosis. We present the clinical case of a male patient in the fourth decade of life who is diagnosed with autoimmune encephalitis, we will address the diagnosis and treatment

Psychiatric presentation and somatic complications in anti-glutamic acid decarboxylase (GAD) antibodies: A case report

Autoimmune encephalitis represents a rapidly evolving group of immune-mediated disorders characterized by brain inflammation and neuropsychiatric symptoms, resulting from antibodies targeting neuronal cell surface proteins, ion channels, or receptors. Among the antigens involved, autoantibodies against NMDAR, AMPAR, GAD, GABA-AR/BR, LGI1, CASPR2, mGluR5, DPPX, and Neurexin-3a are significant in the pathogenesis of autoimmune encephalitis (AE) in adults. Glutamic acid decarboxylase (GAD), specifically its isoform GAD65, is a key enzyme in the production of GABA, and its antibodies are associated with conditions like temporal lobe epilepsy and various neurological syndromes including stiff-person syndrome (SPS), limbic encephalitis, and cerebellar ataxia. Psychiatric symptoms, such as behavioral changes, memory loss, and executive function impairment, are common in anti-GAD antibody-associated encephalitis. We present the case of D.B.-V., a 40-year-old male with no psychiatric history, who developed severe neuropsychiatric symptoms leading to a diagnosis of anti-GAD autoimmune encephalitis. Initial symptoms included headache, fever, and rapid progression to severe confusion and altered consciousness, requiring intubation. MRI findings and anti-GAD antibodies in the cerebrospinal fluid confirmed the diagnosis. Despite immunotherapy with IVIG, plasmapheresis, and Rituximab, the patient remained agitated and noncompliant, necessitating psychiatric intervention. The management was complicated by infections and fluctuating metabolic parameters, highlighting the need for a multidisciplinary approach. After significant medical and psychiatric treatment, the patient was transferred to a specialized nursing home, with persistent cognitive and functional impairments. This case underscores the importance of early recognition and a comprehensive, multidisciplinary approach to managing autoimmune encephalitis, addressing both neurological and psychiatric symptoms to improve long-term outcomes.

Anti-NMDAR encephalitis with GFAPα IgG: a case report

BackgroundAnti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is an inflammatory disease of the central nervous system (CNS) in which antibodies within the serum and cerebrospinal fluid (CSF) target NMDA receptors. Glial fibrillary acidic protein (GFAP) astrocytopathy is an autoimmune disease affecting the central nervous system (CNS). Meningoencephalitis can affect any anatomical region rostrocaudally, from the optic nerve to the spinal cord. The clinical implications of NMDAR antibodies overlapping with other antibodies against glial or neuronal cell surface proteins have not been investigated.Case presentationA 35-year-old male presented with headaches along with amnesia, slurred and awkward speech, psychiatric symptoms, cognitive decline, and insomnia. His medical history revealed ankylosing spondylitis for six months. Ancillary findings included CSF pleocytosis and elevated protein levels. T2-weighted fluid attenuation inversion recovery was used to image high-intensity lesions of the bilateral paraventricular, radiate corona, semioval centre, and right subcortical regions. The CSF was positive for NMDAR and GFAP antibodies through transfected cell-based assays. A diagnosis of anti-GFAP encephalitis was made, although the prominent clinical features were of anti-NMDAR encephalitis.ConclusionsHerein, we describe a case of anti-NMDAR encephalitis with overlapping symptoms of GFAP antibody positivity. Patients with unusual symptoms of anti-NMDAR encephalitis should also be tested for anti-GFAP antibodies. However, because this was a single case study, caution should be exercised when interpreting the observations. Since the patient was diagnosed with autoimmune encephalitis, intravenous methylprednisolone was administered, which yielded a positive outcome.

Molecular determinants of the interaction between HSV-1 glycoprotein D and heparan sulfate.

Literature has well-established the importance of 3-O-sulfation of neuronal cell surface glycan heparan sulfate (HS) to its interaction with herpes simplex virus type 1 glycoprotein D (gD). Previous investigations of gD to its viral receptors HVEM and nectin-1 also highlighted the conformational dynamics of gD's N- and C-termini, necessary for viral membrane fusion. However, little is known on the structural interactions of gD with HS. Here, we present our findings on this interface from both the glycan and the protein perspective. We used C-terminal and N-terminal gD variants to probe the role of their respective regions in gD/HS binding. The N-terminal truncation mutants (with Δ1-22) demonstrate equivalent or stronger binding to heparin than their intact glycoproteins, indicating that the first 22 amino acids are disposable for heparin binding. Characterization of the conformational differences between C-terminal truncated mutants by sedimentation velocity analytical ultracentrifugation distinguished between the "open" and "closed" conformations of the glycoprotein D, highlighting the region's modulation of receptor binding. From the glycan perspective, we investigated gD interacting with heparin, heparan sulfate, and other de-sulfated and chemically defined oligosaccharides using surface plasmon resonance and glycan microarray. The results show a strong preference of gD for 6-O-sulfate, with 2-O-sulfation becoming more important in the presence of 6-O-S. Additionally, 3-O-sulfation shifted the chain length preference of gD from longer chain to mid-chain length, reaffirming the sulfation site's importance to the gD/HS interface. Our results shed new light on the molecular details of one of seven known protein-glycan interactions with 3-O-sulfated heparan sulfate.

Neuronal Ganglioside and Glycosphingolipid (GSL) Metabolism and Disease : Cascades of Secondary Metabolic Errors Can Generate Complex Pathologies (in LSDs).

Glycosphingolipids (GSLs) are a diverse group of membrane components occurring mainly on the surfaces of mammalian cells. They and their metabolites have a role in intercellular communication, serving as versatile biochemical signals (Kaltner et al, Biochem J 476(18):2623-2655, 2019) and in many cellular pathways. Anionic GSLs, the sialic acid containing gangliosides (GGs), are essential constituents of neuronal cell surfaces, whereas anionic sulfatides are key components of myelin and myelin forming oligodendrocytes. The stepwise biosynthetic pathways of GSLs occur at and lead along the membranes of organellar surfaces of the secretory pathway. After formation of the hydrophobic ceramide membrane anchor of GSLs at the ER, membrane-spanning glycosyltransferases (GTs) of the Golgi and Trans-Golgi network generate cell type-specific GSL patterns for cellular surfaces. GSLs of the cellular plasma membrane can reach intra-lysosomal, i.e. luminal, vesicles (ILVs) by endocytic pathways for degradation. Soluble glycoproteins, the glycosidases, lipid binding and transfer proteins and acid ceramidase are needed for the lysosomal catabolism of GSLs at ILV-membrane surfaces. Inherited mutations triggering a functional loss of glycosylated lysosomal hydrolases and lipid binding proteins involved in GSL degradation cause a primary lysosomal accumulation of their non-degradable GSL substrates in lysosomal storage diseases (LSDs). Lipid binding proteins, the SAPs, and the various lipids of the ILV-membranes regulate GSL catabolism, but also primary storage compounds such as sphingomyelin (SM), cholesterol (Chol.), or chondroitin sulfate can effectively inhibit catabolic lysosomal pathways of GSLs. This causes cascades of metabolic errors, accumulating secondary lysosomal GSL- and GG- storage that can trigger a complex pathology (Breiden and Sandhoff, Int J Mol Sci 21(7):2566, 2020).

Genome-wide association study meta-analysis of suicide death and suicidal behavior

Suicide is a worldwide health crisis. We aimed to identify genetic risk variants associated with suicide death and suicidal behavior. Meta-analysis for suicide death was performed using 3765 cases from Utah and matching 6572 controls of European ancestry. Meta-analysis for suicidal behavior using data across five cohorts (n = 8315 cases and 256,478 psychiatric or populational controls of European ancestry) was also performed. One locus in neuroligin 1 (NLGN1) passing the genome-wide significance threshold for suicide death was identified (top SNP rs73182688, with p = 5.48 × 10−8 before and p = 4.55 × 10−8 after mtCOJO analysis conditioning on MDD to remove genetic effects on suicide mediated by MDD). Conditioning on suicidal attempts did not significantly change the association strength (p = 6.02 × 10−8), suggesting suicide death specificity. NLGN1 encodes a member of a family of neuronal cell surface proteins. Members of this family act as splice site-specific ligands for beta-neurexins and may be involved in synaptogenesis. The NRXN-NLGN pathway was previously implicated in suicide, autism, and schizophrenia. We additionally identified ROBO2 and ZNF28 associations with suicidal behavior in the meta-analysis across five cohorts in gene-based association analysis using MAGMA. Lastly, we replicated two loci including variants near SOX5 and LOC101928519 associated with suicidal attempts identified in the ISGC and MVP meta-analysis using the independent FinnGen samples. Suicide death and suicidal behavior showed positive genetic correlations with depression, schizophrenia, pain, and suicidal attempt, and negative genetic correlation with educational attainment. These correlations remained significant after conditioning on depression, suggesting pleiotropic effects among these traits. Bidirectional generalized summary-data-based Mendelian randomization analysis suggests that genetic risk for the suicidal attempt and suicide death are both bi-directionally causal for MDD.

Anti-NMDA Receptor Encephalitis in Children

Anti-NMDAR encephalitis is a type of neurological syndrome that can be paraneoplastic or non-paraneoplastic in nature. It is a recently discovered that is becoming much more recognized in children. The symptoms of anti-NMDAR encephalitis occur as a result of autoimmune antibody binding to the NMDA receptor on certain neuronal cell surfaces. Patients with anti-NMDAR encephalitis are described as having a change in mental status manifested by abrupt changes from calm behaviors to agitation, aggression or extreme irritability. In children, the first symptom to be recognized is often non-psychiatric: convulsion, status epilepticus, dystonia, verbal reduction or mutism .The diagnosis is clinical and confirmation is easy with demonstration of antibodies in serum and CSF; Early diagnosis and aggressive immunotherapy are imperative. Anti-NMDA receptor encephalitis can be reversible if diagnosed and treated early.

Human Endogenous Retrovirus K Envelope in Spinal Fluid of Amyotrophic Lateral Sclerosis Is Toxic.

Human endogenous retroviruses have been implicated in neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). Expression of human endogenous retrovirus K (HERV-K) subtype HML-2 envelope (Env) in human neuronal cultures and in transgenic mice results in neurotoxicity and neurodegeneration, and mice expressing HML-2 Env display behavioral and neuromuscular characteristics resembling ALS. This study aims to characterize the neurotoxic properties of HML-2 Env. Env neurotoxicity was detected in ALS cerebrospinal fluid and confirmed using recombinant Env protein in a cell-based assay and a mouse model. The mechanism of neurotoxicity was assessed with immunoprecipitation followed by mass spectrometry and Western blot, and by screening a panel of inhibitors. We observed that recombinant HML-2 Env protein caused neurotoxicity resulting in neuronal cell death, retraction of neurites, and decreased neuronal electrical activity. Injection of the Env protein into the brains of mice also resulted in neuronal cell death. HML-2 Env protein was also found in the cerebrospinal fluid of patients with sporadic ALS. The neurotoxic properties of the Env and the cerebrospinal fluid could be rescued with the anti-Env antibody. The Env was found to bind to CD98HC complexed to β1 integrin on the neuronal cell surface. Using a panel of compounds to screen for their ability to block Env-induced neurotoxicity, we found that several compounds were protective and are linked to the β1 integrin pathway. HERV-K Env is released extracellularly in ALS and causes neurotoxicity via a novel mechanism. Present results pave the way for new treatment strategies in sporadic ALS. ANN NEUROL 2022;92:545-561.

Amyloid precursor protein (APP) and amyloid β (Aβ) interact with cell adhesion molecules: Implications in Alzheimer's disease and normal physiology.

Alzheimer’s disease (AD) is an incurable neurodegenerative disorder in which dysfunction and loss of synapses and neurons lead to cognitive impairment and death. Accumulation and aggregation of neurotoxic amyloid-β (Aβ) peptides generated via amyloidogenic processing of amyloid precursor protein (APP) is considered to play a central role in the disease etiology. APP interacts with cell adhesion molecules, which influence the normal physiological functions of APP, its amyloidogenic and non-amyloidogenic processing, and formation of Aβ aggregates. These cell surface glycoproteins also mediate attachment of Aβ to the neuronal cell surface and induce intracellular signaling contributing to Aβ toxicity. In this review, we discuss the current knowledge surrounding the interactions of cell adhesion molecules with APP and Aβ and analyze the evidence of the critical role these proteins play in regulating the processing and physiological function of APP as well as Aβ toxicity. This is a necessary piece of the complex AD puzzle, which we should understand in order to develop safe and effective therapeutic interventions for AD.

Titanium dioxide and carbon black nanoparticles disrupt neuronal homeostasis via excessive activation of cellular prion protein signaling

BackgroundEpidemiological emerging evidence shows that human exposure to some nanosized materials present in the environment would contribute to the onset and/or progression of Alzheimer’s disease (AD). The cellular and molecular mechanisms whereby nanoparticles would exert some adverse effects towards neurons and take part in AD pathology are nevertheless unknown.ResultsHere, we provide the prime evidence that titanium dioxide (TiO2) and carbon black (CB) nanoparticles (NPs) bind the cellular form of the prion protein (PrPC), a plasma membrane protein well known for its implication in prion diseases and prion-like diseases, such as AD. The interaction between TiO2- or CB-NPs and PrPC at the surface of neuronal cells grown in culture corrupts PrPC signaling function. This triggers PrPC-dependent activation of NADPH oxidase and subsequent production of reactive oxygen species (ROS) that alters redox equilibrium. Through PrPC interaction, NPs also promote the activation of 3-phosphoinositide-dependent kinase 1 (PDK1), which in turn provokes the internalization of the neuroprotective TACE α-secretase. This diverts TACE cleavage activity away from (i) TNFα receptors (TNFR), whose accumulation at the plasma membrane augments the vulnerability of NP-exposed neuronal cells to TNFα -associated inflammation, and (ii) the amyloid precursor protein APP, leading to overproduction of neurotoxic amyloid Aβ40/42 peptides. The silencing of PrPC or the pharmacological inhibition of PDK1 protects neuronal cells from TiO2- and CB-NPs effects regarding ROS production, TNFα hypersensitivity, and Aβ rise. Finally, we show that dysregulation of the PrPC-PDK1-TACE pathway likely occurs in the brain of mice injected with TiO2-NPs by the intra-cerebro-ventricular route as we monitor a rise of TNFR at the cell surface of several groups of neurons located in distinct brain areas.ConclusionOur in vitro and in vivo study thus posits for the first time normal cellular prion protein PrPC as being a neuronal receptor of TiO2- and CB-NPs and identifies PrPC-coupled signaling pathways by which those nanoparticles alter redox equilibrium, augment the intrinsic sensitivity of neurons to neuroinflammation, and provoke a rise of Aβ peptides. By identifying signaling cascades dysregulated by TiO2- and CB-NPs in neurons, our data shed light on how human exposure to some NPs might be related to AD.

Hippocampal Neuronal Cultures to Detect and Study New Pathogenic Antibodies Involved in Autoimmune Encephalitis

Over the last 15 years, a new category of antibody-mediated diseases of the central nervous system (CNS) has been characterized and is now defined as "autoimmune encephalitis" (AE). There are currently 17 known AE syndromes, and all are associated with antibodies against the neuronal cell surface or synaptic proteins. The clinical syndromes are complex and vary according to the type of associated antibody. The best-known of these diseases is anti-N-methyl D-aspartate receptor (NMDAR) encephalitis, which is a prominent neuropsychiatric disorder associated with severe memory and behavioral impairments. The associated antibodies react with the GluN1 subunit of the NMDAR at the N-terminal domain. The approach most frequently used for the discovery and characterization of AE antibodies includes the culture of dissociated, fetal, rodent hippocampal neurons. During the process of antibody characterization, live neurons in culture are exposed to patients' serum or CSF, and the detection of reactivity indicates that the serum or CSF samples of the patient contain antibodies against neuronal surface antigens. Hippocampal cultures can also be used to determine whether the antibodies in patients are potentially pathogenic by examining if they cause structural or functional alterations of the neurons. The level of success of these studies depends on the quality of the cultures and on the protocols used to obtain and detect the reactivity of patient samples. This article provides an optimized protocol for primary cell culture of fetal rat hippocampal neurons combined with immunostaining to determine the presence of antibodies in the serum or CSF of patients. An example of how to examine the potential pathogenic effects of NMDAR antibodies using cultured neurons and calcium imaging is also presented.

Hippocampal Neuronal Cultures to Detect and Study New Pathogenic Antibodies Involved in Autoimmune Encephalitis.

Over the last 15 years, a new category of antibody-mediated diseases of the central nervous system (CNS) has been characterized and is now defined as "autoimmune encephalitis" (AE). There are currently 17 known AE syndromes, and all are associated with antibodies against the neuronal cell surface or synaptic proteins. The clinical syndromes are complex and vary according to the type of associated antibody. The best-known of these diseases is anti-N-methyl D-aspartate receptor (NMDAR) encephalitis, which is a prominent neuropsychiatric disorder associated with severe memory and behavioral impairments. The associated antibodies react with the GluN1 subunit of the NMDAR at the N-terminal domain. The approach most frequently used for the discovery and characterization of AE antibodies includes the culture of dissociated, fetal, rodent hippocampal neurons. During the process of antibody characterization, live neurons in culture are exposed to patients' serum or CSF, and the detection of reactivity indicates that the serum or CSF samples of the patient contain antibodies against neuronal surface antigens. Hippocampal cultures can also be used to determine whether the antibodies in patients are potentially pathogenic by examining if they cause structural or functional alterations of the neurons. The level of success of these studies depends on the quality of the cultures and on the protocols used to obtain and detect the reactivity of patient samples. This article provides an optimized protocol for primary cell culture of fetal rat hippocampal neurons combined with immunostaining to determine the presence of antibodies in the serum or CSF of patients. An example of how to examine the potential pathogenic effects of NMDAR antibodies using cultured neurons and calcium imaging is also presented.

Pathogenic mechanisms in neuronal surface autoantibody-mediated encephalitis

In recent years, autoimmune encephalitis associated with antibodies against neuronal cell surface proteins has become a well-recognized phenomenon. Here, we describe clinical features and diagnosis of these conditions before turning to the mechanisms by which autoantibodies are generated and cause disease. The clinical syndrome typically evolves in a subacute fashion and is quite variable, although short-term memory loss, behavioral changes, and seizures are common. Laboratory and imaging parameters of inflammation are typically less overtly deranged than in infectious encephalitis. While the most common antibodies found are to the NMDA receptor or LGI1 protein, a growing number of autoantibodies have been described. Established triggers include tumors and infections, although in many cases neither is identified. It is becoming increasingly clear that host immunogenetics can play a part in disease susceptibility, with a prominent role of HLA haplotype in certain syndromes. Antibodies cause disease by several mechanisms, including direct blocking of ligand binding sites, receptor internalization, and activation of complement, governed in part by the subtype of IgG antibody present. Although in vitro and in vivo models have contributed to our understanding of the mechanisms of disease, numerous gaps in our knowledge of the immunopathogenesis remain, and newer disease models are needed. Insights gained from such approaches will inform our basic understanding of disease and will likely also translate into diagnostic and therapeutic advances.

A critical review and update on autoimmune encephalitis: understanding the alphabet soup.

Autoimmune encephalitis (AE) comprises a group of diseases mediated by antibodies against neuronal cell surface or synaptic antigens, such as ion channels or neurotransmitter receptors. New clinical syndromes and their associated antibodies were and are still being characterized over the last two decades. The fact that their main clinical features are interdisciplinary, - encompassing neuropsychiatric symptoms, cognitive dysfunction, epileptic seizures, movement and sleep disorders - has led to a surge of interest in this field. Some of these diseases present with a well-defined syndrome, being recognizable on clinical grounds. Correct diagnosis is important since AE are potentially treatable diseases, despite their severity. On the other hand, an increasing number of neuronal antibodies being described casts doubt upon the way we should utilize antibody testing and interpret results. In this article we review, summarize and update the current knowledge on antibody mediated encephalitis.

Cardamonin Antioxidant Effects Through the Modulation of Proteins and Genes Expressions in LPS‐Activated BV‐2 Microglial Cells

Neurodegeneration is characterized by slow and progressive loss of neuronal cells and synapses in different brain regions. These pathologic effects are the major feature of Alzheimer's disease (AD), leading to a decline in learning and memory function. The main hallmarks of AD are the aggregation and deposition of amyloid‐β peptides on the extracellular surface of neuronal cells. Hyperphosphorylation of tau protein and the formation of neurofibrillary tangles is another feature of AD. Neuroinflammation and oxidative stress follow the accumulation of amyloid‐β and neurofibrillary tangles. Continuous activation of microglia cells, known as the resident, innate immune cells in the brain, participates in producing numerous neurotoxic factors, including nitric oxide and reactive oxygen species (ROS), which induce neurodegeneration. Numerous natural compounds, such as cardamonin, a bioactive compound found in many plants, have been reported to exert multiple therapeutic properties, including anti‐cancer, anti‐inflammatory, antioxidant, antiviral antibiotic, antifungal, and antiallergic activities. This study examined the effects of cardamonin on LPS‐activated BV‐2 microglial cells. Results of this study showed that cardamonin concentrations of 6.25 to 50 µM reduced over 95% the release of NO in LPS‐activated BV‐2 cells, compared to the cells treated with LPS only (P<0.001). Moreover, cardamonin significantly decreased the cellular production of SOD 3‐fold (P < 0.05) and increased the levels of expression of CAT 2.5‐fold (P < 0.05) and glutathione 2‐fold (p < 0.05) in the LPS‐activated BV‐2 cells. In RT‐PCR assays, cardamonin increased the mRNA expression of CAT and decreased the levels of NOS2, the enzyme responsible for the production of NO and associated with inflammatory processes. Furthermore, cardamonin downregulated the mRNA expression of CCL5/RANTES (5‐fold), which promotes the recruitment and activation of inflammatory cells. Also, cardamonin downregulated SLC38A1 (3‐fold), whose expression is upregulated during oxidative stress, and TXNIP (2‐fold) that regulates thioredoxin, an important redox protein that controls levels of ROS in cells. The data show cardamonin efficacy in modulating proteins and genes involved in inflammation and the control of elevated intracellular levels of ROS. In conclusion, these findings suggest that cardamonin may have potential in the therapy of microglia‐derived neurodegeneration, helping to prevent or slow the progression of the disease in the CNS.

Antibody response to herpes simplex virus-1 is increased in autoimmune encephalitis.

Antibody response to herpes simplex virus-1 is increased in autoimmune encephalitis.

Autoimmune Encephalitis in COVID-19 Infection: Our Experience and Systematic Review of the Literature.

The neurologic complications of COVID-19 infection are frequent in hospitalized patients; a high percentage of them present neurologic manifestations at some point during the course of their disease. Headache, muscle pain, encephalopathy and dizziness are among the most common complications. Encephalitis is an inflammatory condition with many etiologies. There are several forms of encephalitis associated with antibodies against intracellular neuronal proteins, cell surfaces or synaptic proteins, referred to as autoimmune encephalitis. Several case reports published in the literature document autoimmune encephalitis cases triggered by COVID-19 infection. Our paper first presents our experience in this issue and then systematically reviews the literature on autoimmune encephalitis that developed in the background of SARS-CoV-2 infections and also discusses the possible pathophysiological mechanisms of auto-immune-mediated damage to the nervous system. This review contributes to improve the management and prognosis of COVID-19-related autoimmune encephalitis.

Kv5.1 antibody in epilepsy patients with unknown etiology

BackgroundNeuronal autoantibodies and favorable response to immunosuppressive treatment have been described in patients with chronic epilepsy of unknown cause, suggesting autoimmune etiology. Our aim was to identify novel epilepsy-specific autoantibodies reactive with neuronal surface antigens. MethodsSera of 172 epilepsy patients with unknown cause and 30 healthy controls were screened with indirect immunofluorescence to identify IgG reacting with primary rat neuronal cultures. Putative target autoantigens were investigated with immunoprecipitation (IP) and liquid chromatography-mass/mass spectrometry (LC-MS/MS) studies using SH-SY5Y cells. Validation of LC-MS/MS results was carried out by IP and immunocytochemistry assays. ResultsAntibodies to neuronal cell surface antigens were detected in 18 epilepsy patients. LC-MS/MS analysis identified voltage-gated potassium channel modifier subfamily F member 1 (KCNF1, Kv5.1) as the single common cell surface antigen in 4 patients with Lennox-Gastaut syndrome (n = 2), focal epilepsy of unknown cause (n = 1) and mesial temporal lobe epilepsy with hippocampal sclerosis (n = 1). These patients had the common features of early seizure onset and treatment-resistance. IP assays and co-localization (serum IgG and commercial Kv5.1-antibody) studies done with non-fixed Kv5.1-transfected HEK293 cells and primary neuronal cultures confirmed the presence of Kv5.1-antibody in 4 epilepsy patients identified by LC-MS/MS. Similar findings were not obtained by sera of other patients with epilepsy, patients with autoimmune encephalitis and healthy controls. ConclusionThe herein described novel neuronal surface antibody to Kv5.1 appears to be associated with treatment-resistant epilepsy of unknown cause. Exact clinical and pathogenic significance of this antibody remains to be elucidated.

Study on the pro-inflammatory mechanism of the HuD antibody in promoting M1 polarization and paraneoplastic neurological syndrome occurrence

ABSTRACT Paraneoplastic neurological syndrome (PNS) is a nonmetastatic complication of malignant tumors that may lead to immune-mediated neuronal dysfunction or death. The occurrence of PNS results from the binding of anti-neuronal antibodies to neuronal cell surface antigens or intracellular antigens, which hinders the function of target proteins and promotes cell death. The aim of this study is to research the effect and immune mechanism of the neuronal ELAV-like protein (HuD antibody) on PNS-related syndrome. Neuronal cells were co-cultured with monocyte macrophages with or without HuD antibody. Next, we detected the apoptosis of neuronal cells by flow cytometry. Meantime, macrophage M1/M2 polarization factors and the secretion of inflammatory factors in the co-culture system were also detected by quantitative polymerase chain reaction (qPCR), Western blots and ELISA technologies. The results showed that after adding the HuD antibody in the co-culture system, the apoptosis level of the neuroma cells were significantly increased, and the apoptosis level were not significant changed when co-culture with monocytes without HuD antibody. In addition, the level of factors of M1 macrophages TNF-α, IL-12, TGF-β and IFN-γ increased, while the level of factors of M2 macrophages IL-10, IL-4, and Arg-1 decreased. The outcomes demonstrated that absorption of the HuD antibody by cerebellar neuronal cells could promote the proliferation of M1 macrophages and stimulates macrophages to secrete inflammatory factors, further damage the neuronal cells, eventually resulting in the occurrence of PNS. This finding provided a theoretical basis for the subsequent treatment and prevention of PNS.

Neuropsychiatric Manifestations of Autoimmune Encephalitis in a Tertiary Hospital: A Case Series and Current Perspectives.

Importance:Autoimmune encephalitis (AE) refers to a group of neuropsychiatric conditions associated with specific circulating autoantibodies directed against synaptic receptors, neuronal cell surface proteins, and intracellular targets. Increased recognition of these disorders is of value, as affected patients prominently display cognitive impairment, behavioral disturbances, and seizures requiring multidisciplinary teams, with early recognition often impacting prognosis.Observations: This case series is based on a retrospective record review of adult patients diagnosed with AE between January 1, 2010- January 1, 2020. Cases 1 and 2, demonstrating anti- N-methyl-d-aspartate receptor (NMDAR) encephalitis with initial manifestations of neurologic and psychiatric symptoms, correlate with the literature describing a higher prevalence of this condition in young women. Case 3, despite being seronegative, exhibited classic features of anti-NMDAR encephalitis. Case 4 demonstrates a classic presentation of anti-leucine-rich glioma-inactivated 1 (LGI1) encephalitis: a middle-aged male with psychosis, altered mentation, and epilepsy. Case 5 had a more indolent neuropsychiatric presentation with mild elevation of N-type voltage-gated potassium channel (VGKC) antibody. Case 6, with glutamic acid decarboxylase 65 (GAD65) antibody, was an elderly female with speech dysfunction and altered mentation, and case 7 was an elderly male with GAD65 antibody who had stiff-person syndrome, ataxia, cognitive decline, and thymoma.Conclusions: This retrospective case series describes the clinical details of 7 individuals with AE and overlapping neuropsychiatric symptoms. This series is limited in scope, with a small number of cases and observational findings, which prevents specific conclusions from being drawn. Despite this limitation, the present article explores the nuances of variable presentations of this disease to inform better interdisciplinary management and emphasize the gap areas that need rigorous research.