NMDA Receptor Internalization by Autoantibodies: A Reversible Mechanism Underlying Psychosis?

Autoantibodies against acetylcholine receptors are increased in archived serum samples from patients with schizophrenia

Previous studies have demonstrated that the levels of IgG against neurotransmitter receptors are increased in patients with schizophrenia. Genome-wide association (GWA) studies of schizophrenia confirmed that 108 loci harbouring over 300 genes were associated with schizophrenia. Although the functional implications of genetic variants are unclear, theoretical functional alterations of these genes could be replicated by the presence of autoantibodies. This study examined the levels of plasma IgG antibodies against four neurotransmitter receptors, CHRM4, GRM3, CHRNA4 and CHRNA5, using an in-house ELISA in 247 patients with schizophrenia and 344 non-psychiatric controls. Four peptides were designed based on in silico analysis with computational prediction of HLA-DRB1 restricted and B-cell epitopes. The relationship between plasma IgG levels and psychiatric symptoms, as defined by the Operational Criteria Checklist for Psychotic Illness and Affective Illness (OPCRIT), were examined. The results showed that the levels of plasma IgG against peptides derived from CHRM4 and CHRNA4 were significantly increased in patients with schizophrenia compared with control subjects, but there was no significant association of plasma IgG levels with any symptom domain or any specific symptoms. These preliminary results suggest that CHRM4 and CHRNA4 may be novel targets for autoantibody responses in schizophrenia, although the pathogenic relationship between increased serum autoantibody levels and schizophrenia symptoms remains unclear.

Anti-NMDA and Anti-AMPA Receptor Antibodies in Central Disorders: Preclinical Approaches to Assess Their Pathological Role and Translatability to Clinic

Autoantibodies against NMDA and AMPA receptors have been identified in the central nervous system of patients suffering from brain disorders characterized by neurological and psychiatric symptoms. It has been demonstrated that these autoantibodies can affect the functions and/or the expression of the targeted receptors, altering synaptic communication. The importance to clarify, in preclinical models, the molecular mechanisms involved in the autoantibody-mediated effects has emerged in order to understand their pathogenic role in central disorders, but also to propose new therapeutic approaches for preventing the deleterious central consequences. In this review, we describe some of the available preclinical literature concerning the impact of antibodies recognizing NMDA and AMPA receptors in neurons. This review discusses the cellular events that would support the detrimental roles of the autoantibodies, also illustrating some contrasting findings that in our opinion deserve attention and further investigations before translating the preclinical observations to clinic.

Electroconvulsive therapy and seizure: a double-edged sword?

Electroconvulsive therapy (ECT) is a widely used therapeutic option of drug-refractory psychiatric disorders. ECT treats psychiatric symptoms by inducing brief controlled seizures through electrical stimulation, but ECT does not generally cause prolonged seizures or epilepsy. However, several studies have reported cases of prolonged seizures after ECT. This review aimed to determine the mechanism of epileptogenesis with neurobiological changes after ECT. Contrary to epileptogenesis by ECT, several cases have reported that ECT was successfully applied for treatment of refractory status epilepticus. In addition, ECT might be applied to hyperkinetic movement and psychiatric symptoms of encephalitis. We also investigated the anticonvulsant mechanism of ECT and how it controls encephalitis symptoms.

The Dysfunctional Mechanisms Throwing Tics: Structural and Functional Changes in Tourette Syndrome

Tourette Syndrome (TS) is a high-incidence multifactorial neuropsychiatric disorder characterized by motor and vocal tics co-occurring with several diverse comorbidities, including obsessive-compulsive disorder and attention-deficit hyperactivity disorder. The origin of TS is multifactorial, with strong genetic, perinatal, and immunological influences. Although almost all neurotransmettitorial systems have been implicated in TS pathophysiology, a comprehensive neurophysiological model explaining the dynamics of expression and inhibition of tics is still lacking. The genesis and maintenance of motor and non-motor aspects of TS are thought to arise from functional and/or structural modifications of the basal ganglia and related circuitry. This complex wiring involves several cortical and subcortical structures whose concerted activity controls the selection of the most appropriate reflexive and habitual motor, cognitive and emotional actions. Importantly, striatal circuits exhibit bidirectional forms of synaptic plasticity that differ in many respects from hippocampal and neocortical plasticity, including sensitivity to metaplastic molecules such as dopamine. Here, we review the available evidence about structural and functional anomalies in neural circuits which have been found in TS patients. Finally, considering what is known in the field of striatal plasticity, we discuss the role of exuberant plasticity in TS, including the prospect of future pharmacological and neuromodulation avenues.

Movement disorders in cell surface antibody mediated autoimmune encephalitis: a meta-analysis

Background

Autoimmune encephalitis (AE) is an increasingly recognized neuroinflammatory disease entity in which early detection and treatment leads to the best clinical outcomes. Movement disorders occur in AE but their characteristics are not well defined.

Objectives

To identify the frequency, classification, and prognostic significance of movement disorders in AE.

Methods

We conducted a systematic review and random-effects meta-analysis of movement disorders in cell surface antibody mediated AE. The frequency of any movement disorder as well as the classification of movement disorders in AE serotypes was determined. We looked at adults 18 years and older and included publications that described at least 10 cases. We used the following four electronic databases: Medline (Ovid), EMBASE (Ovid), APA Psychinfo, and Cochrane library.

Results

A total of 1,192 titles and abstracts were reviewed. Thirty-seven studies were included in the final meta-analysis. At least one kind of movement disorder was present in 40% of the entire AE cohort, 53% with anti-NMDA receptor antibodies, 33% with anti-CASPR2 antibodies, 30% with anti-LGI1 antibodies and 13% with anti-GABA receptor antibodies. Dyskinesia was the commonest movement disorder in anti-NMDA antibody mediated AE and faciobrachial dystonic seizures were most frequent in anti-LGI1 antibody mediated AE. Patients with a movement disorder tended to have a higher mortality. The risk of bias in the included studies was mostly moderate or high.

Conclusion

Movement disorders are common in AE and their identification, in conjunction with other clinical and paraclinical features, may facilitate earlier diagnosis. The prognostic implications of movement disorders in AE warrant further dedicated study.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier: CRD42023386920.

Cognitive Impairment in a Child With Anti-N-Methyl-D-Aspartate Receptor Encephalitis: A Case Report

Anti-N-methyl-D-aspartate-receptor encephalitis is a complex autoimmune inflammatory neurological disorder that presents with epileptic seizures and rapid functional deterioration, including movement disorders and cognitive impairment, especially in young patients. Despite aggressive initial treatment with immune therapy, such as corticosteroids, intravenous immunoglobulin, and plasmapheresis, patients often need intensive rehabilitative therapies for their long-lasting deficits. We report a pediatric case of anti-N-methyl-D-aspartate receptor encephalitis in Korea that presented with symptoms of muscle weakness of the four extremities, dysarthria, dysphagia, and cognitive impairment in the acute phase. The patient underwent 4 weeks of comprehensive rehabilitative treatment, including physical therapy, occupational therapy, swallowing rehabilitation therapy, cognitive rehabilitation therapy, and speech therapy. At the follow-up evaluation after 4 weeks of treatment, she showed significant improvements in limb muscle strength, balance ability, swallowing, language function, and the ability to perform activities of daily living. However, when assessed using the Korean Wechsler Intelligence Scale for Children-IV, there was little improvement in cognitive function, particularly in working memory. While only a few cases have reported the progression of cognitive function using a standardized cognitive evaluation tool in patients with anti-N-methyl-D-aspartate receptor encephalitis, this present case report adds to the accumulation of evidence of neurocognitive deficits in these patients.

The Leading Role of Brain and Abdominal Radiological Features in the Work-Up of Anti-NMDAR Encephalitis in Children: An Up-To-Date Review

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis (NMDARe) is the most common cause of nonviral encephalitis, mostly affecting young women and adolescents with a strong female predominance (F/M ratio of around 4:1). NMDARe is characterized by the presence of cerebrospinal fluid (CSF) antibodies against NMDARs, even though its pathophysiological mechanisms have not totally been clarified. The clinical phenotype of NMDARe is composed of both severe neurological and neuropsychiatric symptoms, including generalized seizures with desaturations, behavioral abnormalities, and movement disorders. NMDARe is often a paraneoplastic illness, mainly due to the common presence of concomitant ovarian teratomas in young women. Abdominal ultrasonography (US) is a key imaging technique that should always be performed in suspected patients. The timely use of abdominal US and the peculiar radiological features observed in NMDARe may allow for a quick diagnosis and a good prognosis, with rapid improvement after the resection of the tumor and the correct drug therapy.

Social interaction, psychotic disorders and inflammation: A triangle of interest

Social interaction difficulties are a hallmark of psychotic disorders, which in some cases can be definitely traced back to autoimmunological causes. Interestingly, systemic and intrathecal inflammation have been shown to significantly influence social processing by increasing sensitivity to threatening social stimuli, which bears some resemblance to psychosis. In this article, we review evidence for the involvement of systemic and intrathecal inflammatory processes in psychotic disorders and how this might help to explain some of the social impairments associated with this group of disorders. Vice versa, we also discuss evidence for the immunomodulatory function of social interactions and their potential role for therapeutic interventions in psychotic disorders.

An examination of plasma autoantibodies against voltage gated calcium channels in schizophrenia

Autoantibodies targeting the central nervous system have been shown to induce psychiatric symptoms resembling schizophrenia. Concurrently, genetic studies have characterised a number of risk variants associated with schizophrenia although their functional implications are largely unknown. Any biological effects of functional variants on protein function may potentially be replicated by the presence of autoantibodies against such proteins. Recent research has demonstrated that the R1346H variant in the CACNA1I gene coding for the Cav 3.3 protein results in a synaptic reduction of Cav3.3 voltage gated calcium channels and, consequently, sleep spindles, which have been shown to correlate with several symptom domains in patients with schizophrenia. The present study measured plasma levels of IgG against two peptides derived from CACNA1I and CACNA1C, respectively, in patients with schizophrenia and healthy controls. The results demonstrated that increased anti-CACNA1I IgG levels were associated with schizophrenia but not associated with any symptom domain related to the reduction of sleep spindles. In contrast to previously published work indicating that inflammation may be a marker for a depressive phenotype, plasma levels of IgG against either CACNA1I or CACNA1C peptides were not associated with depressive symptoms, suggesting that anti-Cav3.3 autoantibodies may function independently of pro-inflammatory processes.

Cerebrospinal fluid quinolinic acid is strongly associated with delirium and mortality in hip-fracture patients

BACKGROUNDThe kynurenine pathway (KP) has been identified as a potential mediator linking acute illness to cognitive dysfunction by generating neuroactive metabolites in response to inflammation. Delirium (acute confusion) is a common complication of acute illness and is associated with increased risk of dementia and mortality. However, the molecular mechanisms underlying delirium, particularly in relation to the KP, remain elusive.METHODSWe undertook a multicenter observational study with 586 hospitalized patients (248 with delirium) and investigated associations between delirium and KP metabolites measured in cerebrospinal fluid (CSF) and serum by targeted metabolomics. We also explored associations between KP metabolites and markers of neuronal damage and 1-year mortality.RESULTSIn delirium, we found concentrations of the neurotoxic metabolite quinolinic acid in CSF (CSF-QA) (OR 2.26 [1.78, 2.87], P < 0.001) to be increased and also found increases in several other KP metabolites in serum and CSF. In addition, CSF-QA was associated with the neuronal damage marker neurofilament light chain (NfL) (β 0.43, P < 0.001) and was a strong predictor of 1-year mortality (HR 4.35 [2.93, 6.45] for CSF-QA ≥ 100 nmol/L, P < 0.001). The associations between CSF-QA and delirium, neuronal damage, and mortality remained highly significant following adjustment for confounders and multiple comparisons.CONCLUSIONOur data identified how systemic inflammation, neurotoxicity, and delirium are strongly linked via the KP and should inform future delirium prevention and treatment clinical trials that target enzymes of the KP.FUNDINGNorwegian Health Association and South-Eastern Norway Regional Health Authorities.

The kynurenine pathway implicated in patient delirium: possible indications for indoleamine 2,3 dioxygenase inhibitors

Tryptophan (Trp) metabolism plays a central role in sleep, mood, and immune system regulation. The kynurenine pathway (KP), which is regulated by the enzymes tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3 dioxygenase (IDO), which catalyze the conversion of Trp to kynurenine (Kyn), facilitates immune regulation and influences neurocognition. Notably, Kyn metabolites bind the N-methyl-d-aspartate receptor (NMDAR), essential for memory encoding, and in turn, cognition. Aberrant NMDAR activity through agonist binding influences excitability and cell death. In this issue of the JCI, Watne and authors demonstrate that KP pathway end products were elevated in the serum and the cerebrospinal fluid (CSF) of subjects with delirium. This observation provides insight regarding the basis of a variety of commonly observed clinical conditions including sundowning, abnormal sleep-wake cycles in hospitalized patients, neurodegenerative cognitive impairment, radiation-induced cognitive impairment, neurocognitive symptomatology related to COVID-19, and clinical outcomes observed in patients with CNS tumors, such as gliomas.

Myelinating Co-Culture as a Model to Study Anti-NMDAR Neurotoxicity

Anti-NMDA receptor (NMDAR) encephalitis is frequently associated with demyelinating disorders (e.g., multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD), myelin oligodendrocyte glycoprotein-associated disease (MOGAD)) with regard to clinical presentation, neuropathological and cerebrospinal fluid findings. Indeed, autoantibodies (AABs) against the GluN1 (NR1) subunit of the NMDAR diminish glutamatergic transmission in both neurons and oligodendrocytes, leading to a state of NMDAR hypofunction. Considering the vital role of oligodendroglial NMDAR signaling in neuron-glia communication and, in particular, in tightly regulated trophic support to neurons, the influence of GluN1 targeting on the physiology of myelinated axon may be of importance. We applied a myelinating spinal cord cell culture model that contains all major CNS cell types, to evaluate the effects of a patient-derived GluN1-specific monoclonal antibody (SSM5) on neuronal and myelin integrity. A non-brain reactive (12D7) antibody was used as the corresponding isotype control. We show that in cultures at the late stage of myelination, prolonged treatment with SSM5, but not 12D7, leads to neuronal damage. This is characterized by neurite blebbing and fragmentation, and a reduction in the number of myelinated axons. However, this significant toxic effect of SSM5 was not observed in earlier cultures at the beginning of myelination. Anti-GluN1 AABs induce neurodegenerative changes and associated myelin loss in myelinated spinal cord cultures. These findings may point to the higher vulnerability of myelinated neurons towards interference in glutamatergic communication, and may refer to the disturbance of the NMDAR-mediated oligodendrocyte metabolic supply. Our work contributes to the understanding of the emerging association of NMDAR encephalitis with demyelinating disorders.

GluN1 antibody causes behavioral deficits in prepulse inhibition and memory through CaMKIIβ signaling

Accumulating evidence suggests that some patients with schizophrenia have high production of autoantibodies against the N-methyl-d-aspartate receptor (NMDAR) subunit GluN1 and that these antibodies lead to cognitive impairment. However, the molecular mechanisms of the deficits seen in these patients are largely unknown. In the present study, we found that passive infusion of GluN1 antibody into the hippocampus of mice for 7 days led to decreased expression of GluN1, phosphor-Ser897-GluN1, and EphrinB2 receptor (EphB2R); deficits in long-term potentiation (LTP) and synaptic transmission in the hippocampal CA1 area; impairment in prepulse inhibition (PPI); and deterioration of recognition memory in novel object recognition test. We also found decreased expression of CaMKIIβ, ERK1/2, CREB, and NF-κB after 7 days of GluN1 antibody exposure, as was the phosphorylation of these signaling molecules. The decrease in GluN1 and phosphor-Ser897-GluN1 expression and the deficits in LTP, PPI, and recognition memory were ameliorated by CaMKIIβ overexpression. These results suggest that downregulation of CaMKIIβ-ERK1/2-CREB-NF-κB signaling is responsiable for GluN1 antibody-associated impairment in PPI and memory and that GluN1 antibody-induced NMDAR hypofunction is the underlying mechanism of this impairment. Our findings indicate possible strategies to ameliorate NMDAR antibody-associated cognitive impairment in neuropsychiatric disease. They also provide evidence that NMDAR hypofunction is an underlying mechanism for cognitive impairment in schizophrenia.

Psychiatric Illness or Immune Dysfunction-Brain Perfusion Imaging Providing the Answer in a Case of Anti-NMDAR Encephalitis

BACKGROUND

We investigated the potential use of SPECT quantification in addition to qualitative brain perfusion analysis for the detection of anti-NMDAR encephalitis. The question is how to normalize brain activity to be able to quantitatively detect perfusion patterns. Usually, brain activity is normalized to a structure considered unaffected by the disease.

METHODS

Brain [99mTc]-HMPAO SPECT was performed as a method to detect brain perfusion patterns. The patterns of abnormal brain perfusion cannot always be reliably and qualitatively assessed when dealing with rare diseases. Recent advances in SPECT quantification using commercial software have enabled more objective and detailed analysis of brain perfusion. The cerebellum and whole brain were used as the normalization structures and were compared with visual analysis.

RESULTS

The quantification analysis performed with whole brain normalization confirmed right parietal lobe hypoperfusion while also detecting statistically significant left-to-right perfusion differences between the temporal lobe and thalamus. Whole brain normalization further described bilateral frontal lobe hyperperfusion, predominantly of the left lobe, and was in accordance with visual analysis.

CONCLUSION

SPECT quantitative brain perfusion analysis, using the whole brain as the normalization structure rather than the cerebellum, in this case, improved confidence in the visual detection of anti-NMDAR encephalitis and provided unexpected solutions to atypical psychiatric dilemmas.

Caught in vicious circles: a perspective on dynamic feed-forward loops driving oxidative stress in schizophrenia

A growing body of evidence has emerged demonstrating a pathological link between oxidative stress and schizophrenia. This evidence identifies oxidative stress as a convergence point or "central hub" for schizophrenia genetic and environmental risk factors. Here we review the existing experimental and translational research pinpointing the complex dynamics of oxidative stress mechanisms and their modulation in relation to schizophrenia pathophysiology. We focus on evidence supporting the crucial role of either redox dysregulation, N-methyl-D-aspartate receptor hypofunction, neuroinflammation or mitochondria bioenergetics dysfunction, initiating "vicious circles" centered on oxidative stress during neurodevelopment. These processes would amplify one another in positive feed-forward loops, leading to persistent impairments of the maturation and function of local parvalbumin-GABAergic neurons microcircuits and myelinated fibers of long-range macrocircuitry. This is at the basis of neural circuit synchronization impairments and cognitive, emotional, social and sensory deficits characteristic of schizophrenia. Potential therapeutic approaches that aim at breaking these different vicious circles represent promising strategies for timely and safe interventions. In order to improve early detection and increase the signal-to-noise ratio for adjunctive trials of antioxidant, anti-inflammatory and NMDAR modulator drugs, a reverse translation of validated circuitry approach is needed. The above presented processes allow to identify mechanism based biomarkers guiding stratification of homogenous patients groups and target engagement required for successful clinical trials, paving the way towards precision medicine in psychiatry.

Anti-NMDAR Encephalitis in the Netherlands, Focusing on Late-Onset Patients and Antibody Test Accuracy

Background and Objectives

To describe the clinical features of anti-NMDAR encephalitis, emphasizing on late-onset patients and antibody test characteristics in serum and CSF.

Methods

Nationwide observational Dutch cohort study, in patients diagnosed with anti-NMDAR encephalitis between 2007 and 2019.

Results

One hundred twenty-six patients with anti-NMDAR encephalitis were included with a median age of 24 years (range 1–86 years). The mean annual incidence was 1.00/million (95% CI 0.62–1.59). Patients ≥45 years of age at onset (19%) had fewer seizures (46% vs 71%, p = 0.021), fewer symptoms during disease course (3 vs 6 symptoms, p = 0.020), and more often undetectable serum antibodies compared with younger patients (p = 0.031). In the late-onset group, outcome was worse, and all tumors were carcinomas (both p < 0.0001). CSF was more accurate than serum to detect anti-NMDAR encephalitis (sensitivity 99% vs 68%, p < 0.0001). Using cell-based assay (CBA), CSF provided an unconfirmed positive test result in 11/2,600 patients (0.4%); 6/11 had a neuroinflammatory disease (other than anti-NMDAR encephalitis). Patients with anti-NMDAR encephalitis, who tested positive in CSF only, had lower CSF antibody titers (p = 0.003), but appeared to have an equally severe disease course.

Discussion

Anti-NMDAR encephalitis occurs at all ages and is less rare in the elderly patients than initially anticipated. In older patients, the clinical phenotype is less outspoken, has different tumor association, and a less favorable recovery. Detection of antibodies in CSF is the gold standard, and although the CBA has very good validity, it is not perfect. The clinical phenotype should be leading, and confirmation in a research laboratory is recommended, when in doubt.

Clinical characteristics and prognosis of anti-alpha-Amino-3-Hydroxy-5-Methyl-4-Isoxazolepropionic acid receptor encephalitis

BACKGROUND

Encephalitis associated with antibodies against alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) is an extremely rare type of antibody-mediated encephalitis. This research aims to investigate the clinical characteristics and prognosis of anti-AMPAR encephalitis.

METHODS

This retrospective study enrolled nine patients with anti-AMPAR encephalitis. Demographic information, clinical manifestations, laboratory and radiological findings, treatment and response were collected and analyzed. These patients were followed up with an average period of 72 weeks to gather prognostic information.

RESULTS

Nine patients (7 females and 2 males) were enrolled with a mean age at disease onset of 59 years old. Three clinical pictures, including limbic encephalitis (n = 7; 78%), pure amnesia (n = 1; 11%) and fulminant encephalitis (n = 1; 11%) were identified. New symptoms of dysphagia and deafness were identified in the clinical spectrum of anti-AMPAR encephalitis. All patients had positive blood AMPAR antibodies, and six of them (67%) had paired positive antibodies in cerebrospinal fluid (CSF). Brain magnetic resonance imaging (MRI) was abnormal in 75% of the patients with no specific patterns recognized. Six patients (67%) had tumors, including lung cancers and thymomas. After immunotherapy and oncotherapy, partial improvement of neurological symptoms was observed among all 6 patients with available records during their hospitalization. After a mean follow-up of 72 weeks, 3 patients had marked decrease of modified Rankin Scale (mRS) score, 1 patient had unchanged mRS score, 4 patients died and the other one was lost.

CONCLUSIONS

Anti-AMPAR encephalitis mainly presents as limbic encephalitis, and is paraneoplastic in 67% of cases. Thus, intensive screening for tumors is recommended for all anti-AMPAR patients. Although patients showed a good short-term therapeutic response, the overall prognosis was not satisfactory.

Prevention of oral and maxillofacial trauma secondary to orofacial dyskinesias associated with anti-N-methyl-D-aspartate receptor encephalitis: a case series

Background

Anti-N-methyl-d-aspartate receptor encephalitis (anti-NMDARE) is a multi-stage autoimmune-mediated disease associated with a multitude of neuropsychiatric and dysautonomic features. Orofacial dyskinesias are frequently associated with this condition and manifest as abnormal movements of the orofacial musculature. These involuntary movements may result in significant trauma to the oral and maxillofacial complex including the avulsion of the dentition and orofacial lacerations.

Case presentation

We describe the course of two female patients with anti-NMDARE in whom significant involuntary self-inflicted maxillofacial trauma was suffered despite the use of complex parenteral sedation regimens. The application of traditional maxillomandibular wiring techniques and pharmacologic strategies, including botulinum toxin, to immobilize the mandible were initially unsuccessful. These difficulties led to the fabrication and wire-based fixation of a patient-specific acrylic oral appliance that maintained the mandible in a depressed position and mitigated all lateral and protrusive movements.

Discussion and conclusions

These cases illustrate the first known successful use of an appliance-based therapy for managing orofacial dyskinesias in the anti-NMDARE patient population through an adaptation of traditional maxillomandibular fixation techniques. This approach eliminated further orofacial trauma and afforded physicians with safer means to manage and assess patients afflicted with this condition during their protracted intensive care unit admissions.

N-methyl-D-aspartate receptor antibody and the choroid plexus in schizophrenia patients with tardive dyskinesia

BACKGROUND

Immune disturbance has been postulated to be one of the mechanisms underlying the pathogenesis of tardive dyskinesia (TD). Recently, the role of autoimmune abnormality in TD has been increasingly recognized. Autoantibodies against neuronal N-methyl-D-aspartate receptor (NMDAR) may be cross-reactive in the brain in neuropsychiatric disorders, and the choroid plexus (CP) is a crucial immune barrier in the central nervous system (CNS). We supposed that NMDAR antibodies might underlie the pathophysiological process of TD through the mediation of CP.

METHODS

Serum NMDAR antibody levels were assessed by enzyme-linked immunosorbent assay, CP and ventricle volumes were assessed by magnetic resonance imaging in schizophrenia patients with TD (n = 61), without TD (NTD, n = 61), and in healthy controls (n = 74). Psychopathology and TD severity were assessed by the Positive and Negative Syndrome Scale and Abnormal Involuntary Movement Scale (AIMS).

RESULTS

NMDAR antibody levels were significantly higher, CP volumes were larger in the TD group than in the NTD group (p = 0.022; p = 0.019, respectively). In the TD group, higher NMDAR antibody level was correlated with larger CP volume (β = 0.406, p = 0.002). An elevated NMDAR antibody level and enlarged CP volume were correlated with orofacial AIMS score (β = 0.331, p = 0.011; β = 0.459, p = 3.34 × 10^-4, respectively). In a mediation model, the effect of NMDAR antibody level on the orofacial AIMS score was mediated by the CP volume (indirect effect: β = 0.08, 95% confidence interval = 0.002-0.225; direct effect: β = 0.14, p = 0.154).

CONCLUSIONS

Our findings highlight a potential NMDAR antibody-associated mechanism in orofacial TD, which may be mediated by increased CP volume.

Glial fibrillary acidic protein (GFAP)-antibody in children with focal seizures of undetermined cause

Anti-neuronal antibodies that are related with autoimmune encephalitis syndromes may also be found in children with new onset seizures or chronic epilepsy. To unravel the significance of autoimmune astrocytopathy in epilepsy, we investigated serum antibody to glial fibrillary acidic protein (GFAP), another autoantigen described in autoimmune encephalitis with seizures, in 38 children with focal seizures of undetermined cause. GFAP antibody was screened with cell based assay and indirect immunohistochemistry and was found in two boys with normal brain MRI and unrevealing medical history prior to seizures. The 2-year-old boy had chronic treatment-resistant frontal lobe epilepsy. The 2.5-year-old boy had a single episode of focal seizures and remained seizure free thereafter in a follow-up period of 4 years. Nevertheless, he showed severe cognitive and language impairment. These results suggest that autoimmune astrocytopathy may be present in some epilepsy patients. Whether this immune response is a bystander effect generated by seizure-induced astrocytosis or directly involved in epileptogenesis needs to be further studied.

Monoclonal Antibodies From Anti-NMDA Receptor Encephalitis Patient as a Tool to Study Autoimmune Seizures

Anti-N-methyl-D-aspartate (NMDA) receptor encephalitis manifests with precipitous cognitive decline, abnormal movements, and severe seizures that can be challenging to control with conventional anti-seizure medications. We previously demonstrated that intracerebroventricular (i.c.v.) administration of cerebrospinal fluid from affected patients, or purified NMDA receptor antibodies from encephalitis patients to mice precipitated seizures, thereby confirming that antibodies are directly pathogenic for seizures. Although different repertoires of anti-NMDA receptor antibodies could contribute to the distinct clinical manifestations in encephalitis patients, the role of specific antibodies in the expression of seizure, motor, and cognitive phenotypes remains unclear. Using three different patient-derived monoclonal antibodies with distinct epitopes within the N-terminal domain (NTD) of the NMDA receptor, we characterized the seizure burden, motor activity and anxiety-related behavior in mice. We found that continuous administration of 5F5, 2G6 or 3C11 antibodies for 2 weeks precipitated seizures, as measured with continuous EEG using cortical screw electrodes. The seizure burden was comparable in all three antibody-treated groups. The seizures were accompanied by increased hippocampal C-C chemokine ligand 2 (CCL2) mRNA expression 3 days after antibody infusion had stopped. Antibodies did not affect the motor performance or anxiety scores in mice. These findings suggest that neuronal antibodies targeting different epitopes within the NMDA receptor may result in a similar seizure phenotype.

Anti-NMDAR encephalitis for psychiatrists: the essentials

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis predominantly presents with psychiatric symptoms. Psychiatrists need to be alert to this diagnostic possibility, especially in female adolescents and young adults, as exemplified by the real (de-identified) case outlined below. Earlier diagnosis and immunotherapy improves long-term outcomes. Collaboration with neurology colleagues is essential for optimal care. 'Red flags' for autoimmune encephalitis and 'diagnostic clues' act as helpful aide memoires for this uncommon condition. The gold standard for testing is the detection of NMDAR antibodies in cerebrospinal fluid, but serum can be tested as a more accessible (but less reliable) preliminary step. The results of routine blood tests, magnetic resonance imaging of the head and electroencephalograms can be normal or show non-specific changes. Diagnostic criteria exist to define probable and definite cases. Immunotherapy for anti-NMDAR encephalitis is effective for many patients, but recovery is prolonged and relapses can occur.

Metabolomic Characterization of Pediatric Acute-Onset Neuropsychiatric Syndrome (PANS)

Introduction

PANS is a controversial clinical entity, consisting of a complex constellation of psychiatric symptoms, adventitious changes, and expression of various serological alterations, likely sustained by an autoimmune/inflammatory disease. Detection of novel biomarkers of PANS is highly desirable for both diagnostic and therapeutic management of affected patients. Analysis of metabolites has proven useful in detecting biomarkers for other neuroimmune-psychiatric diseases. Here, we utilize the metabolomics approach to determine whether it is possible to define a specific metabolic pattern in patients affected by PANS compared to healthy subjects.

Design

This observational case-control study tested consecutive patients referred for PANS between June 2019 to May 2020. A PANS diagnosis was confirmed according to the PANS working criteria (National Institute of Mental Health [NIMH], 2010). Healthy age and sex-matched subjects were recruited as controls.

Methods

Thirty-four outpatients referred for PANS (mean age 9.5 years; SD 2.9, 71% male) and 25 neurotypical subjects matched for age and gender, were subjected to metabolite analysis. Serum samples were obtained from each participant and were analyzed using Nuclear Magnetic Resonance (NMR) spectroscopy. Subsequently, multivariate and univariate statistical analyses and Receiver Operator Curves (ROC) were performed.

Results

Separation of the samples, in line with the presence of PANS diagnosis, was observed by applying a supervised model (R²X = 0.44, R²Y = 0.54, Q² = 0.44, p-value < 0.0001). The significantly altered variables were 2-Hydroxybutyrate, glycine, glutamine, histidine, tryptophan. Pathway analysis indicated that phenylalanine, tyrosine, and tryptophan metabolism, as well as glutamine and glutamate metabolism, exhibited the largest deviations from neurotypical controls.

Conclusion

We found a unique plasma metabolic profile in PANS patients, significantly differing from that of healthy children, that suggests the involvement of specific patterns of neurotransmission (tryptophan, glycine, histamine/histidine) as well as a more general state of neuroinflammation and oxidative stress (glutamine, 2-Hydroxybutyrate, and tryptophan-kynurenine pathway) in the disorder. This metabolomics study offers new insights into biological mechanisms underpinning the disorder and supports research of other potential biomarkers implicated in PANS.

Autoimmune Disorders of the Nervous System: Pathophysiology, Clinical Features, and Therapy

Remarkable discoveries over the last two decades have elucidated the autoimmune basis of several, previously poorly understood, neurological disorders. Autoimmune disorders of the nervous system may affect any part of the nervous system, including the brain and spinal cord (central nervous system, CNS) and also the peripheral nerves, neuromuscular junction and skeletal muscle (peripheral nervous system, PNS). This comprehensive overview of this rapidly evolving field presents the factors which may trigger breakdown of self-tolerance and development of autoimmune disease in some individuals. Then the pathophysiological basis and clinical features of autoimmune diseases of the nervous system are outlined, with an emphasis on the features which are important to recognize for accurate clinical diagnosis. Finally the latest therapies for autoimmune CNS and PNS disorders and their mechanisms of action and the most promising research avenues for targeted immunotherapy are discussed.

Anti N-Methyl-D-Aspartate (NMDA) receptor encephalitis: from psychosis to cognitive impairment

In this study, while presenting a clinical case with early psychiatric manifestations, we emphasized the need to pay attention to neurological diagnoses such as Anti N-Methyl-D-Aspartate Receptor (NMDAR) encephalitis at the time of manifestation of these common symptoms.

High serum creatinine is associated with reduction of psychiatric symptoms in female patients with anti-NMDAR encephalitis

OBJECTIVE

Serum creatinine (SCR) has been shown to be associated with many neurodegenerative diseases. In this study, we investigated the relationship between SCR levels and the incidence of psychiatric symptoms in patients with anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis.

METHODS

The SCR levels were tested in 69 patients with anti-NMDAR encephalitis at admission. Clinical characteristics and blood and CSF parameters were compared between the group of patients with psychiatric symptoms (P + group) and the group of those without psychiatric symptoms (P- group). The association between SCR and the incidence of psychiatric symptoms was determined by multivariate-adjusted linear regression analyses.

RESULTS

The SCR levels in the P + group were significantly lower than those in the P- group (P < 0.001). In the female subgroup, the SCR levels in the P + group were significantly lower compared to the P- group (P < 0.001), whereas in the male subgroup, the SCR levels did not differ between the two groups (P = 0.084). Furthermore, the highest SCR tercile overall had a significantly lower incidence of psychiatric symptoms than the lowest tercile (P < 0.001), and a significant negative correlation between the SCR levels and the occurrence of psychiatric symptoms was observed (r = -0.392, P < 0.001). Multivariate logistic regression analysis showed that the association was independent after adjusting for age, cystatin C and the modified Rankin Scale (mRS) score (P = 0.001). A similar result was found in the female subgroup (P = 0.010), but not in the male subgroup (P = 0.225).

CONCLUSION

Our study indicated that the SCR level was negatively correlated with incidence of psychiatric symptoms in female patients, and higher SCR level could be a protective factor for psychiatric symptoms in female patients with anti-NMDAR encephalitis.

Symptomatic treatments of N-methyl-D-aspartate receptor encephalitis

N-methyl-D-aspartate receptor (NMDAR) encephalitis presents with multiple symptoms including memory loss, seizure, psychosis, aphasia, altered mentality, dyskinesia, autonomic dysfunction, and central hypoventilation. While immunotherapy protocols are improving, morbidity and mortality in the disease largely depend on supportive care to control intractable symptoms. However, no prospective or controlled trials have been conducted on immunotherapy or supportive care principles in the disease. Thus, this study discusses and shares experience and ideas for symptomatic care of NMDAR encephalitis.

Autoimmunity and NMDA receptor in brain disorders: Where do we stand?

Over the past decades, the identification of autoimmune encephalitis in which patients express autoantibodies directed against neurotransmitter receptors has generated great hope to shed new light on the molecular mechanisms underpinning neurological and psychiatric conditions. Among these autoimmune encephalitides, the discovery of autoantibodies directed against the glutamatergic NMDA receptor (NMDAR-Ab), in the anti-NMDAR encephalitis, has provided some key information on how complex neuropsychiatric symptoms can be caused by a deficit in NMDAR signalling. Yet, NMDAR-Abs have also been detected in several neurological and psychiatric conditions, as well as in healthy individuals. In addition, these various NMDAR-Abs appear to have different molecular properties and pathogenicities onto receptors and synaptic functions. Here, we discuss the current view on the variety of NMDAR-Abs and, in particular, how these autoantibodies can lead to receptor dysfunction in neuronal networks. Since our mechanistic understanding on patients' NMDAR-Abs is still in its infancy, several complementary processes can be proposed and further in-depth molecular and cellular investigations will surely reveal key insights. Autoantibodies represent a great opportunity to gain knowledge on the etiology of neuropsychiatric disorders and pave the way for innovative therapeutic strategies. ONE SENTENCE SUMMARY: Current view on patients' autoantibody against NMDAR.

High-Dose Diazepam Controls Severe Dyskinesia in Anti-NMDA Receptor Encephalitis

Objective

Because there is no standard treatment to control dyskinesia in anti-NMDA receptor (NMDAR) encephalitis, we analyzed the therapeutic efficacy of high-dose diazepam in dyskinesia associated with NMDAR encephalitis.

Methods

We reviewed patients with NMDAR encephalitis with dyskinesia who were admitted to Seoul National University Hospital between November 2012 and July 2018. High-dose diazepam was administered orally or via a nasogastric tube 3-6 times a day. We assessed the treatment effect by comparing dyskinesia severity between the first day of the highest dose of diazepam and one week after the treatment.

Results

Among 68 patients with NMDAR encephalitis during the study period, 33 patients were treated with enteral diazepam (ranging from 6 to 180 mg) to control dyskinesia, along with immunotherapy. The severity of dyskinesia improved from average grade 2.4 ± 0.6 to 1.1 ± 0.7 after 1 week of the highest dose of diazepam (mean severity change -1.4 ± 0.6, 95% confidence interval -1.2 to -1.6; p < 0.001). No patients had serious adverse events except for mild sedation.

Conclusions

Dyskinesia in NMDAR encephalitis improved after treatment with enteral diazepam without significant side effects. This study suggests that enteral diazepam could be a treatment option for control dyskinesia in NMDAR encephalitis.

Classification of Evidence

This study provides Class IV evidence that for patients with dyskinesias associated with NMDAR encephalitis, enteral diazepam is effective and safe in dyskinesia control.

Reduced serial dependence suggests deficits in synaptic potentiation in anti-NMDAR encephalitis and schizophrenia

A mechanistic understanding of core cognitive processes, such as working memory, is crucial to addressing psychiatric symptoms in brain disorders. We propose a combined psychophysical and biophysical account of two symptomatologically related diseases, both linked to hypofunctional NMDARs: schizophrenia and autoimmune anti-NMDAR encephalitis. We first quantified shared working memory alterations in a delayed-response task. In both patient groups, we report a markedly reduced influence of previous stimuli on working memory contents, despite preserved memory precision. We then simulated this finding with NMDAR-dependent synaptic alterations in a microcircuit model of prefrontal cortex. Changes in cortical excitation destabilized within-trial memory maintenance and could not account for disrupted serial dependence in working memory. Rather, a quantitative fit between data and simulations supports alterations of an NMDAR-dependent memory mechanism operating on longer timescales, such as short-term potentiation.

Stein, Barbosa et al. show that anti-NMDAR encephalitis and schizophrenia are characterized by reduced serial dependence in spatial working memory. Cortical network simulations show that this can be parsimoniously explained by a reduction in NMDAR-dependent short-term synaptic potentiation in these diseases.

Evidence-based umbrella review of 162 peripheral biomarkers for major mental disorders

The literature on non-genetic peripheral biomarkers for major mental disorders is broad, with conflicting results. An umbrella review of meta-analyses of non-genetic peripheral biomarkers for Alzheimer's disease, autism spectrum disorder, bipolar disorder (BD), major depressive disorder, and schizophrenia, including first-episode psychosis. We included meta-analyses that compared alterations in peripheral biomarkers between participants with mental disorders to controls (i.e., between-group meta-analyses) and that assessed biomarkers after treatment (i.e., within-group meta-analyses). Evidence for association was hierarchically graded using a priori defined criteria against several biases. The Assessment of Multiple Systematic Reviews (AMSTAR) instrument was used to investigate study quality. 1161 references were screened. 110 met inclusion criteria, relating to 359 meta-analytic estimates and 733,316 measurements, on 162 different biomarkers. Only two estimates met a priori defined criteria for convincing evidence (elevated awakening cortisol levels in euthymic BD participants relative to controls and decreased pyridoxal levels in participants with schizophrenia relative to controls). Of 42 estimates which met criteria for highly suggestive evidence only five biomarker aberrations occurred in more than one disorder. Only 15 meta-analyses had a power >0.8 to detect a small effect size, and most (81.9%) meta-analyses had high heterogeneity. Although some associations met criteria for either convincing or highly suggestive evidence, overall the vast literature of peripheral biomarkers for major mental disorders is affected by bias and is underpowered. No convincing evidence supported the existence of a trans-diagnostic biomarker. Adequately powered and methodologically sound future large collaborative studies are warranted.

Astroglial Connexin 43 Deficiency Protects against LPS-Induced Neuroinflammation: A TSPO Brain µPET Study with [18F]FEPPA

Astroglial connexin 43 (Cx43) has been recognized as a crucial immunoregulating factor in the brain. Its inactivation leads to a continuous immune recruitment, cytokine expression modification and a specific humoral autoimmune response against the astrocytic extracellular matrix but without brain lesions or cell lysis. To assess the impact of Cx43 deletion on the brain’s inflammatory response, TSPO expression was studied by positron emission tomography (PET) imaging with a specific radioligand, [¹⁸F]FEPPA, in basal conditions or upon Lipopolysaccharides (LPS)-induced inflammatory challenge. Astroglial Cx43-deleted mice underwent [¹⁸F]FEPPA PET/CT dynamic imaging with or without LPS injection (5 mg/kg) 24 h before imaging. Quantification and pharmacokinetic data modelling with a 2TCM-1K compartment model were performed. After collecting the mice brains, TSPO expression was quantified and localized by Western blot and FISH analysis. We found that astroglial Cx43 deficiency does not significantly alter TSPO expression in the basal state as observed with [¹⁸F]FEPPA PET imaging, FISH and Western blot analysis. However, deletion of astrocyte Cx43 abolishes the LPS-induced TSPO increase. Autoimmune encephalopathy observed in astroglial Cx43-deleted mice does not involve TSPO overexpression. Consistent with previous studies showing a unique inflammatory status in the absence of astrocyte Cx43, we show that a deficient expression of astrocytic Cx43 protects the animals from LPS-induced neuroinflammation as addressed by TSPO expression.

Autoimmune psychosis: an international consensus on an approach to the diagnosis and management of psychosis of suspected autoimmune origin

There is increasing recognition in the neurological and psychiatric literature of patients with so-called isolated psychotic presentations (ie, with no, or minimal, neurological features) who have tested positive for neuronal autoantibodies (principally N-methyl-D-aspartate receptor antibodies) and who have responded to immunotherapies. Although these individuals are sometimes described as having atypical, mild, or attenuated forms of autoimmune encephalitis, some authors feel that that these cases are sufficiently different from typical autoimmune encephalitis to establish a new category of so-called autoimmune psychosis. We briefly review the background, discuss the existing evidence for a form of autoimmune psychosis, and propose a novel, conservative approach to the recognition of possible, probable, and definite autoimmune psychoses for use in psychiatric practice. We also outline the investigations required and the appropriate therapeutic approaches, both psychiatric and immunological, for probable and definite cases of autoimmune psychoses, and discuss the ethical issues posed by this challenging diagnostic category.

The origin of NMDA receptor hypofunction in schizophrenia

N-methyl-d-aspartate (NMDA) receptor (NMDAR) hypofunction plays a key role in pathophysiology of schizophrenia. Since NMDAR hypofunction has also been reported in autism, Alzheimer's disease and cognitive dementia, it is crucial to identify the location, timing, and mechanism of NMDAR hypofunction for schizophrenia for better understanding of disease etiology and for novel therapeutic intervention. In this review, we first discuss the shared underlying mechanisms of NMDAR hypofunction in NMDAR antagonist models and the anti-NMDAR autoantibody model of schizophrenia and suggest that NMDAR hypofunction could occur in GABAergic neurons in both models. Preclinical models using transgenic mice have shown that NMDAR hypofunction in cortical GABAergic neurons, in particular parvalbumin-positive fast-spiking interneurons, in the early postnatal period confers schizophrenia-related phenotypes. Recent studies suggest that NMDAR hypofunction can also occur in PV-positive GABAergic neurons with alterations of NMDAR-associated proteins, such as neuregulin/ErbB4, α7nAChR, and serine racemase. Furthermore, several environmental factors, such as oxidative stress, kynurenic acid and hypoxia, may also potentially elicit NMDAR hypofunction in GABAergic neurons in early postnatal period. Altogether, the studies discussed here support a central role for GABAergic abnormalities in the context of NMDAR hypofunction. We conclude by suggesting potential therapeutic strategies to improve the function of fast-spiking neurons.

An update on anti-NMDA receptor encephalitis for neurologists and psychiatrists: mechanisms and models

The identification of anti-NMDA receptor (NMDAR) encephalitis about 12 years ago made it possible to recognise that some patients with rapidly progressive psychiatric symptoms or cognitive impairment, seizures, abnormal movements, or coma of unknown cause, had an autoimmune disease. In this disease, autoantibodies serve as a diagnostic marker and alter NMDAR-related synaptic transmission. At symptom onset, distinguishing the disease from a primary psychiatric disorder is challenging. The severity of symptoms often requires intensive care. Other than clinical assessment, no specific prognostic biomarkers exist. The disease is more prevalent in women (with a female to male ratio of around 8:2) and about 37% of patients are younger than 18 years at presentation of the disease. Tumours, usually ovarian teratoma, and herpes simplex encephalitis are known triggers of NMDAR autoimmunity. About 80% of patients improve with immunotherapy and, if needed, tumour removal, but the recovery is slow. Animal models have started to reveal the complexity of the underlying pathogenic mechanisms and will lead to novel treatments beyond immunotherapy. Future studies should aim at identifying prognostic biomarkers and treatments that accelerate recovery.

Anti-NMDA Receptor Autoantibody Is an Independent Predictor of Hospital Mortality but Not Brain Dysfunction in Septic Patients

The presence of autoantibodies against neuronal cell surface or synaptic proteins and their relationship to autoimmune encephalitis have recently been characterized. These autoantibodies have been also reported in other pathologic conditions; however, their role during sepsis is not known. This study detected the presence of autoantibodies against neuronal cell surface or synaptic proteins in the serum of septic patients and determined their relationship to the occurrence of brain dysfunction and mortality. This prospective, observational cohort study was performed in four Brazilian intensive care units (ICUs). Sixty patients with community-acquired severe sepsis or septic shock admitted to the ICU were included. Blood samples were collected from patients within 24 h of ICU admission. Antibodies to six neuronal proteins were assessed, including glutamate receptors (types NMDA, AMPA1, and AMPA2); voltage-gated potassium channel complex (VGKC) proteins, leucine-rich glioma-inactivated protein 1 (LGI1), and contactin-associated protein-2 (Caspr2), as well as the GABAB1 receptor. There was no independent association between any of the measured autoantibodies and the occurrence of brain dysfunction (delirium or coma). However, there was an independent and significant relationship between anti-NMDAR fluorescence intensity and hospital mortality. In conclusion, anti-NMDAR was independently associated with hospital mortality but none of the measured antibodies were associated with brain dysfunction in septic patients.

A mouse model of seizures in anti-N-methyl-d-aspartate receptor encephalitis

OBJECTIVE

Seizures develop in 80% of patients with anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis, and these represent a major cause of morbidity and mortality. Anti-NMDAR antibodies have been linked to memory loss in encephalitis; however, their role in seizures has not been established. We determined whether anti-NMDAR antibodies from autoimmune encephalitis patients are pathogenic for seizures.

METHODS

We performed continuous intracerebroventricular infusion of cerebrospinal fluid (CSF) or purified immunoglobulin (IgG) from the CSF of patients with anti-NMDAR encephalitis or polyclonal rabbit anti-NMDAR IgG, in male C57BL/6 mice. Seizure status during a 2-week treatment was assessed with video-electroencephalography. We assessed memory, anxiety-related behavior, and motor function at the end of treatment and assessed the extent of neuronal damage and gliosis in the CA1 region of hippocampus. We also performed whole-cell patch recordings from the CA1 pyramidal neurons in hippocampal slices of mice with seizures.

RESULTS

Prolonged exposure to rabbit anti-NMDAR IgG, patient CSF, or human IgG purified from the CSF of patients with encephalitis induced seizures in 33 of 36 mice. The median number of seizures recorded in 2 weeks was 13, 39, and 35 per mouse in these groups, respectively. We observed only 18 brief nonconvulsive seizures in 11 of 29 control mice (median seizure count of 0) infused with vehicle (n = 4), normal CSF obtained from patients with noninflammatory central nervous system (CNS) conditions (n = 12), polyclonal rabbit IgG (n = 7), albumin (n = 3), and normal human IgG (n = 3). We did not observe memory deficits, anxiety-related behavior, or motor impairment measured at 2 weeks in animals treated with CSF from affected patients or rabbit IgG. Furthermore, there was no evidence of hippocampal cell loss or astrocyte proliferation in the same mice.

SIGNIFICANCE

Our findings indicate that autoantibodies can induce seizures in anti-NMDAR encephalitis and offer a model for testing novel therapies for refractory autoimmune seizures.

Immuno-Pharmacological Characterization of Presynaptic GluN3A-Containing NMDA Autoreceptors: Relevance to Anti-NMDA Receptor Autoimmune Diseases

Mouse hippocampal glutamatergic nerve endings express presynaptic release-regulating NMDA autoreceptors (NMDARs). The presence of GluN1, GluN2A, GluN2B, and GluN3A subunits in hippocampal vesicular glutamate transporter type 1-positive synaptosomes was confirmed with confocal microscopy. GluN2C, GluN2D, and GluN3B immunopositivity was scarcely present. Incubation of synaptosomes with the anti-GluN1, the anti-GluN2A, the anti-GluN2B, or the anti-GluN3A antibody prevented the 30 μM NMDA/1 μM glycine-evoked [³H]D-aspartate ([³H]D-ASP) release. The NMDA/glycine-evoked [³H]D-ASP release was reduced by increasing the external protons, consistent with the participation of GluN1 subunits lacking the N1 cassette to the receptor assembly. The result also excludes the involvement of GluN1/GluN3A dimers into the NMDA-evoked overflow. Complement (1:300) released [³H]D-ASP in a dizocilpine-sensitive manner, suggesting the participation of a NMDAR-mediated component in the releasing activity. Accordingly, the complement-evoked glutamate overflow was reduced in anti-GluN-treated synaptosomes when compared to the control. We speculated that incubation with antibodies had favored the internalization of NMDA receptors. Indeed, a significant reduction of the GluN1 and GluN2B proteins in the plasma membranes of anti-GluN1 or anti-GluN2B antibody-treated synaptosomes emerged in biotinylation studies. Altogether, our findings confirm the existence of presynaptic GluN3A-containing release-regulating NMDARs in mouse hippocampal glutamatergic nerve endings. Furthermore, they unveil presynaptic alteration of the GluN subunit insertion in synaptosomal plasma membranes elicited by anti-GluN antibodies that might be relevant to the central alterations occurring in patients suffering from autoimmune anti-NMDA diseases.

The Emerging Immunogenetic Architecture of Schizophrenia

Schizophrenia is a severe psychiatric disorder of complex etiology. Immune processes have long been proposed to contribute to the development of schizophrenia, and accumulating evidence supports immune involvement in at least a subset of cases. In recent years, large-scale genetic studies have provided new insights into the role of the immune system in this disease. Here, we provide an overview of the immunogenetic architecture of schizophrenia based on findings from genome-wide association studies (GWAS). First, we review individual immune loci identified in secondary analyses of GWAS, which implicate over 30 genes expressed in both immune and brain cells. The function of the proteins encoded by these immune candidates highlight the role of the complement system, along with regulation of apoptosis in both immune and neuronal cells. Next, we review hypothesis-free pathway analyses which have so far been inconclusive with respect to identifying immune pathways involved in schizophrenia. Finally, we explore the genetic overlap between schizophrenia and immune-mediated diseases. Although there have been some inconsistencies across studies, genome-wide pleiotropy has been reported between schizophrenia and Crohn's disease, multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, type 1 diabetes, and ulcerative colitis. Overall, there are multiple lines of evidence supporting the role of immune genes in schizophrenia. Current evidence suggests that specific immune pathways are involved-likely those with dual functions in the central nervous system. Future studies focused on further elucidating the relevant pathways hold the potential to identify novel biomarkers and therapeutic targets for schizophrenia.

Monoclonal antibodies from a patient with anti-NMDA receptor encephalitis

Objective

Anti‐NMDA receptor encephalitis (ANRE) is a potentially lethal encephalitis attributed to autoantibodies against the N‐methyl‐D‐aspartate receptor (NMDAR). We sought to clone and characterize monoclonal antibodies (mAbs) from an ANRE patient.

Methods

We used a hybridoma method to clone two IgG mAbs from a female patient with ANRE without teratoma, and characterized their binding activities on NMDAR‐transfected cell lines, cultured primary rat neurons, and mouse hippocampus. We also assessed their effects on voluntary locomotor activity in mice and binding to NMDAR in vivo.

Results

The mAbs are structurally distinct and arose from distinct B‐cell lineages. They recognize different epitopes on the GluN1 amino terminal domain (ATD), yet both require amino acids important for post‐translational modification. Both mAbs bind subsets of GluN1 on cultured rat hippocampal neurons. The 5F5 mAb binds mouse brain hippocampal tissues, and the GluN1 recognized on cultured rat neurons was substantially extra‐synaptic. Antibody binding to primary hippocampal neurons induced receptor internalization. The NMDAR inhibitor MK‐801 inhibited internalization without preventing mAb binding; AP5 inhibited both mAb binding and internalization. Exposure of mice to the mAbs following permeabilization of the blood brain barrier increased voluntary wheel running activity, similar to low doses of the NMDAR inhibitor, MK‐801.

Interpretation

These mAbs recapitulate features demonstrated in previous studies of ANRE patient CSF, and exert effects on NMDAR in vitro and in vivo consistent with modulation of NMDAR activity.

Membrane-bound and soluble forms of an NMDA receptor extracellular domain retain epitopes targeted in auto-immune encephalitis

Background

Anti-NMDA receptor encephalitis (ANRE) is a potentially lethal disease attributed to auto-antibodies against the N-methyl-D-aspartate receptor (NMDAR). Full recovery is possible if therapy is initiated early in the disease course. Detection of ANRE antibodies in the cerebrospinal fluid (CSF) is essential for diagnosis. The assays for ANRE-associated IgGs often rely on cells transiently transfected with NMDAR genes. A cell line that stably expresses pathogenic NMDAR epitopes could improve standardization of the assays and provide antigen that could be used in commercial solid state assay systems.

Results

We expressed the amino terminal domain (ATD) of the GluN1 NMDAR subunit (NR1) as a fusion protein on the outer plasma membrane of 293T cells, creating a stable cell population (293T-ATD) that is recognized by ANRE patient monoclonal antibodies in flow cytometry and immunofluorescence assays. The ATD fusion protein also contains a Myc tag and a 6XHIS tag, which provide functionality for immunoassays and antigen purification, and a TEV protease site, which allows the ATD domain to be specifically released from the cells in essentially pure form. ATD mobilized from the 293T ATD cell line maintained the pathogenic ANRE epitopes in ELISA binding assays. CSF (3/4) and sera (4/4) from ANRE patients also bound the 293T-ATD cell line, whereas normal CSF and sera did not.

Conclusions

The 293T-ATD cell line is potentially adaptable to a variety of formats to identify antibodies associated with ANRE, including cell-based and soluble antigen formats, and demonstrates a useful method to produce complex proteins for research, drug discovery, and clinical diagnosis.

Electronic supplementary material

The online version of this article (10.1186/s12896-018-0450-1) contains supplementary material, which is available to authorized users.

Pathogenicity of Antibodies against NMDA Receptor: Molecular Insights into Autoimmune Psychosis

Recent years have seen a flourishing literature on detection of circulating autoantibodies against neurotransmitter receptors in patients with neuropsychiatric disorders. These studies have generated hope for a better understanding of the underlying molecular dysfunctions and for appropriate therapeutic strategies. However, the detection of these autoantibodies in healthy subjects, and the lack of mechanistic insights have fostered debate about the pathogenic role of such autoantibodies. Here, we specifically discuss the biological evidence linking autoantibodies directed against the glutamatergic N-methyl-d-aspartate (NMDA) receptor (NMDAR-Abs) and psychosis, emphasising recent single-molecule imaging investigations that unveiled the impaired surface trafficking of NMDAR in the presence of NMDAR-Abs from psychotic patients. Although still in its infancy, the hypothesis that NMDAR-Abs from patients with psychosis play a pathogenic role is thus gaining support, opening avenues of fundamental and translational investigations.

Superficial white matter damage in anti-NMDA receptor encephalitis

BACKGROUND

Clinical brain MRI is normal in the majority of patients with anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. However, extensive deep white matter damage wasrecently identifiedin these patients using diffusion weighted imaging. Here, our aim was to study a particularly vulnerable brain compartment, the late myelinating superficial white matter.

METHODS

Forty-six patients with anti-NMDAR encephalitis were included. Ten out of these were considered neurologically recovered (modified Rankin scale of zero), while 36 patients were non-recovered. In addition, 30 healthy controls were studied. MRI data were collected from all subjects and superficial white matter mean diffusivity derived from diffusion tensor imaging was compared between groups in whole brain, lobar and vertex-based analyses. Patients underwent comprehensive cognitive testing, and correlation analyses were performed between cognitive performance and superficial white matter integrity.

RESULTS

Non-recovered patients showed widespread superficial white matter damage in comparison to recovered patients and healthy controls. Vertex-based analyses revealed that damage predominated in frontal and temporal lobes. In contrast, the superficial white matter was intact in recovered patients. Importantly, persistent cognitive impairments in working memory, verbal memory, visuospatial memory and attention significantly correlated with damage of the superficial white matter in patients.

CONCLUSIONS

Anti-NMDAR encephalitis is associated with extensive superficial white matter damage in patients with incomplete recovery. The strong association with impairment in several cognitive domains highlights the clinical relevance of white matter damage in this disorder and warrants investigations of the underlying pathophysiological mechanisms.

The prevalence and treatment outcomes of antineuronal antibody-positive patients admitted with first episode of psychosis

BACKGROUND

Antineuronal antibodies are associated with psychosis, although their clinical significance in first episode of psychosis (FEP) is undetermined.

AIMS

To examine all patients admitted for treatment of FEP for antineuronal antibodies and describe clinical presentations and treatment outcomes in those who were antibody positive.

METHOD

Individuals admitted for FEP to six mental health units in Queensland, Australia, were prospectively tested for serum antineuronal antibodies. Antibody-positive patients were referred for neurological and immunological assessment and therapy.

RESULTS

Of 113 consenting participants, six had antineuronal antibodies (anti-N-methyl-D-aspartate receptor antibodies [n = 4], voltage-gated potassium channel antibodies [n = 1] and antibodies against uncharacterised antigen [n = 1]). Five received immunotherapy, which prompted resolution of psychosis in four.

CONCLUSIONS

A small subgroup of patients admitted to hospital with FEP have antineuronal antibodies detectable in serum and are responsive to immunotherapy. Early diagnosis and treatment is critical to optimise recovery.

DECLARATION OF INTEREST

None.