Synaptic and Neuronal Autoantibody-Associated Psychiatric Syndromes: Controversies and Hypotheses

Exploring causal mechanisms of psychosis risk

Robust epidemiological evidence of risk and protective factors for psychosis is essential to inform preventive interventions. Previous evidence syntheses have classified these risk and protective factors according to their strength of association with psychosis. In this critical review we appraise the distinct and overlapping mechanisms of 25 key environmental risk factors for psychosis, and link these to mechanistic pathways that may contribute to neurochemical alterations hypothesised to underlie psychotic symptoms. We then discuss the implications of our findings for future research, specifically considering interactions between factors, exploring universal and subgroup-specific factors, improving understanding of temporality and risk dynamics, standardising operationalisation and measurement of risk and protective factors, and developing preventive interventions targeting risk and protective factors.

The serum metabolomic profile of a distinct, inflammatory subtype of acute psychosis

A range of studies suggest that a proportion of psychosis may have an autoimmune basis, but this has not translated through into clinical practice-there is no biochemical test able to accurately identify psychosis resulting from an underlying inflammatory cause. Such a test would be an important step towards identifying who might require different treatments and have the potential to improve outcomes for patients. To identify novel subgroups within patients with acute psychosis we measured the serum nuclear magnetic resonance (NMR) metabolite profiles of 75 patients who had identified antibodies (anti-glycine receptor [GlyR], voltage-gated potassium channel [VGKC], Contactin-associated protein-like 2 [CASPR2], leucine-rich glioma inactivated 1 [LGI1], N-methyl-D-aspartate receptor [NMDAR] antibody) and 70 antibody negative patients matched for age, gender, and ethnicity. Clinical symptoms were assessed using the positive and negative syndrome scale (PANSS). Unsupervised principal component analysis identified two distinct biochemical signatures within the cohort. Orthogonal partial least squared discriminatory analysis revealed that the serum metabolomes of NMDAR, LGI1, and CASPR2 antibody psychosis patients were indistinct from the antibody negative control group while VGKC and GlyR antibody patients had significantly decreased lipoprotein fatty acids and increased amino acid concentrations. Furthermore, these patients had more severe presentation with higher PANSS scores than either the antibody negative controls or the NMDAR, LGI1, and CASPR2 antibody groups. These results suggest that a proportion of patients with acute psychosis have a distinct clinical and biochemical phenotype that may indicate an inflammatory subtype.

The clinical relevance of serum versus CSF NMDAR autoantibodies associated exclusively with psychiatric features: a systematic review and meta-analysis of individual patient data

BACKGROUND

A variety of psychiatric syndromes are associated with NMDAR autoantibodies; however, their clinical relevance when only present in the serum is unclear. We explored whether patients with CSF NMDAR autoantibodies could be distinguished from patients with serum-only NMDAR autoantibodies.

METHODS

The electronic databases MEDLINE, EMBASE, PubMed, and PsycINFO were searched. Articles reporting adult patients with isolated psychiatric features and positive for NMDAR autoantibodies with relevant investigations were included. Patient level meta-analysis compared patients positive for CSF NMDAR autoantibodies with patients positive for serum NMDAR autoantibodies, but negative for CSF NMDAR autoantibodies. Dichotomous data were analysed using crude odds ratios (OR), whilst continuous data were analysed using Mann-Whitney Test (U). The protocol was prospectively registered (CRD42018082210).

RESULTS

Of 4413 publications, 42 were included, reporting 79 patients. Median age was 34 years (IQR 19 years); 56% (45/79) were female and 24% (16/68) had a tumour. In total, 41 patients were positive for CSF autoantibodies and 20 were positive for serum-only autoantibodies. Patients with CSF autoantibodies were significantly more likely to be female (p < 0.001) and have a rapid (< 3 month) onset of symptoms (p = 0.02) than patients with serum-only autoantibodies. They were also more likely to present with psychosis (p < 0.001), exhibit EEG (p = 0.006), MRI (p = 0.002), and CSF (p = 0.001) abnormalities, but less likely to present with insomnia (p = 0.04).

CONCLUSIONS

Patients with an isolated psychiatric syndrome with CSF NMDAR autoantibodies can potentially be distinguished from those with serum-only NMDAR autoantibodies based on clinicodemographic and investigation findings.

Cerebrospinal fluid findings in adult patients with obsessive-compulsive disorder: A retrospective analysis of 54 samples

OBJECTIVES

Obsessive-compulsive disorder (OCD) can rarely be associated with immunological aetiologies, most notably in Paediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcal Infections and possibly in autoimmune encephalitis. As cerebrospinal fluid (CSF) analysis is a sensitive method for assessing neuroinflammation, this retrospective study analysed basic CSF parameters and well-characterised as well as novel neuronal autoantibodies in OCD to screen for signs of autoimmunity.

METHODS

Basic CSF findings of 54 adult OCD patients suspected of an organic aetiology were retrospectively compared to a control group of mentally healthy patients (N = 39) with idiopathic intracranial hypertension. Further subgroup analysis included testing for well-characterised neuronal IgG autoantibodies and tissue-based assays using indirect immunofluorescence to screen for novel brain autoantibodies.

RESULTS

Elevated protein in the CSF of OCD patients compared to the control group (p = 0.043) was identified. Inflammatory markers (pleocytosis/oligoclonal bands/increased IgG-index) were detected in 7% of all patients with OCD. Well-characterised neuronal autoantibodies were not found in any OCD patient, whereas 6/18 (33%) CSF samples showed binding on mouse brain sections in tissue-based assays (binding to neuropil in the basal ganglia/brainstem, cilia of granule cells, blood vessels, nuclear/perinuclear structures).

CONCLUSIONS

While elevated CSF protein is merely a weak indicator of blood CSF barrier dysfunction, the presence of inflammatory CSF changes and novel brain autoantibodies in CSF may indicate OCD subtypes with inflammatory pathomechanism and supports the hypothesis of a rare "autoimmune OCD" subtype.

Autoantibody-associated psychiatric syndromes: a systematic literature review resulting in 145 cases

BACKGROUND

Autoimmune encephalitis (AE) is an important consideration during the diagnostic work-up of secondary mental disorders. Indeed, isolated psychiatric syndromes have been described in case reports of patients with underlying AE. Therefore, the authors performed a systematic literature review of published cases with AE that have predominant psychiatric/neurocognitive manifestations. The aim of this paper is to present the clinical characteristics of these patients.

METHODS

The authors conducted a systematic Medline search via Ovid, looking for case reports/series of AEs with antineuronal autoantibodies (Abs) against cell surface/intracellular antigens combined with predominant psychiatric/neurocognitive syndromes. The same was done for patients with Hashimoto encephalopathy/SREAT. Only patients with signs of immunological brain involvement or tumors in their diagnostic investigations or improvement under immunomodulatory drugs were included.

RESULTS

We identified 145 patients with AE mimicking predominant psychiatric/neurocognitive syndromes. Of these cases, 64% were female, and the mean age among all patients was 43.9 (±22.1) years. Most of the patients had Abs against neuronal cell surface antigens (55%), most frequently against the NMDA-receptor (N = 46). Amnestic/dementia-like (39%) and schizophreniform (34%) syndromes were the most frequently reported. Cerebrospinal fluid changes were found in 78%, electroencephalography abnormalities in 61%, and magnetic resonance imaging pathologies in 51% of the patients. Immunomodulatory treatment was performed in 87% of the cases, and 94% of the patients responded to treatment.

CONCLUSIONS

Our findings indicate that AEs can mimic predominant psychiatric and neurocognitive disorders, such as schizophreniform psychoses or neurodegenerative dementia, and that affected patients can be treated successfully with immunomodulatory drugs.

Autoimmune Encephalitis With Psychotic Manifestations and Cognitive Impairment Presenting as Schizophrenia: Case Report and Literature Review

Autoimmune encephalitis is characterized by mental and behavioral symptoms, seizures, and cognitive impairment. The presence of schizophrenia needs to be distinguished from that of autoimmune encephalitis. Herein, we describe the case of a woman who exhibited abnormal mental behavior and cognitive impairment. The patient had experienced similar symptoms more than 20 years previously and had been diagnosed with schizophrenia. The patient's psychotic symptoms improved after treatment with antipsychotic drugs; however, cognitive impairment persisted. She was diagnosed with anti-N-methyl-D-aspartate (NMDA)-receptor concurrent with anti-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-receptor encephalitis. She showed improvement after treatment with steroids and intravenous immunoglobulins (IVIgs). Furthermore, we reviewed the literature and found that, including the present case, 10 patients have been diagnosed with anti-NMDA concurrent with anti-AMPA-receptor encephalitis. Three of these patients were men and seven were women, and their ages ranged from 21 to 71 years. Moreover, seven (70%) patients had a history of tumors. Symptoms of these patients included psychotic symptoms, varying degrees of consciousness disturbance, seizures, dyskinesia, dystonia, autonomic dysfunction, agitation, and verbal reduction. Brain magnetic resonance imaging findings showed scattered fluid-attenuated inversion recovery hyperintensity in subcortical white matter and/or medial temporal lobe in seven (70%) patients. After combination treatment, including tumor removal and administration of steroids, IVIg, plasma exchange, or immunity inhibitors, the symptoms improved in part of the patients. It is necessary to exclude autoimmune encephalitis for patients with psychiatric manifestations and cognitive impairment. Timely combination therapy is important in anti-NMDA-receptor concurrent with anti-AMPA-receptor encephalitis.

Autoantibody-associated psychiatric symptoms and syndromes in adults: A narrative review and proposed diagnostic approach

Background

Autoimmune-mediated encephalitis is a disease that often encompasses psychiatric symptoms as its first clinical manifestation’s predominant and isolated characteristic. Novel guidelines even distinguish autoimmune psychosis from autoimmune encephalitis. The aim of this review is thus to explore whether a wide range of psychiatric symptoms and syndromes are associated or correlate with autoantibodies.

Methods

We conducted a PubMed search to identify appropriate articles concerning serum and/or cerebrospinal fluid (CSF) autoantibodies associated with psychiatric symptoms and syndromes between 2000 and 2020. Relying on this data, we developed a diagnostic approach to optimize the detection of autoantibodies in psychiatric patients, potentially leading to the approval of an immunotherapy.

Results

We detected 10 major psychiatric symptoms and syndromes often reported to be associated with serum and/or CSF autoantibodies comprising altered consciousness, disorientation, memory impairment, obsessive-compulsive behavior, psychosis, catatonia, mood dysfunction, anxiety, behavioral abnormalities (autism, hyperkinetic), and sleeping dysfunction. The following psychiatric diagnoses were associated with serum and/or CSF autoantibodies: psychosis and schizophrenia spectrum disorders, mood disorders, minor and major neurocognitive impairment, obsessive-compulsive disorder, autism spectrum disorders (ASD), attention deficit hyperactivity disorder (ADHD), anxiety disorders, eating disorders and addiction. By relying on these symptom clusters and diagnoses in terms of onset and their duration, we classified a subacute or subchronic psychiatric syndrome in patients that should be screened for autoantibodies. We propose further diagnostics entailing CSF analysis, electroencephalography and magnetic resonance imaging of the brain. Exploiting these technologies enables standardized and accurate diagnosis of autoantibody-associated psychiatric symptoms and syndromes to deliver early immunotherapy.

Conclusions

We have developed a clinical diagnostic pathway for classifying subgroups of psychiatric patients whose psychiatric symptoms indicate a suspected autoimmune origin.

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Autoantibodies are associated with a broad spectrum of psychiatric syndromes.

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More systematic studies are needed to elucidate the significance of autoantibodies.

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We developed a pathway to identify autoantibody-associated psychiatric syndromes.

Anti-N-methyl-D-aspartate receptor encephalitis presenting as atypical psychosis in multiple sclerosis: a case report

BACKGROUND

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is an autoimmune disorder which often presents with neuropsychiatric symptoms. A large proportion of cases are associated with an identifiable tumor, most commonly ovarian teratoma. However, recent literature has also described an overlap of anti-NMDAR encephalitis and demyelinating syndromes. Cases have been reported of anti-NMDAR encephalitis in patients with ADEM, optic neuritis, myelitis and multiple sclerosis. This link is considered rare, however has important clinical implications as treatments and prognosis may differ.

CASE PRESENTATION

A 33-year-old female with a history of multiple sclerosis presented with new-onset neuropsychiatric symptoms. After substance-induced psychosis was ruled out, she was admitted to the medical ward for work up of psychosis secondary to multiple sclerosis. However, the consultation-liaison psychiatry service noted atypical symptoms which were concerning for autoimmune encephalitis. Admission to a psychiatric inpatient ward was deferred. Anti-NMDAR encephalitis was diagnosed with CSF analysis demonstrating lymphocytic pleocytosis and anti-NMDAR antibodies. In addition to first-line treatment of encephalitis with steroids, second-line immunotherapies were also implemented given the patient's underlining demyelinating syndrome. The patient's neurologic and psychiatric symptoms began to improve.

CONCLUSIONS

There is literature to demonstrate a possible connection between anti-NMDAR encephalitis and demyelinating syndromes. As such, autoimmune encephalitis should be considered in patients with multiple sclerosis presenting with atypical symptoms. Determining the correct diagnosis is crucial to inform the appropriate treatment protocol, and to improve prognosis.

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.

Clinical, cognitive and neuroanatomical associations of serum NMDAR autoantibodies in people at clinical high risk for psychosis

Serum neuronal autoantibodies, such as those to the NMDA receptor (NMDAR), are detectable in a subgroup of patients with psychotic disorders. It is not known if they are present before the onset of psychosis or whether they are associated with particular clinical features or outcomes. In a case-control study, sera from 254 subjects at clinical high risk (CHR) for psychosis and 116 healthy volunteers were tested for antibodies against multiple neuronal antigens implicated in CNS autoimmune disorders, using fixed and live cell-based assays (CBAs). Within the CHR group, the relationship between NMDAR antibodies and symptoms, cognitive function and clinical outcomes over 24 month follow-up was examined. CHR subjects were not more frequently seropositive for neuronal autoantibodies than controls (8.3% vs. 5.2%; OR = 1.50; 95% CI: 0.58-3.90). The NMDAR was the most common target antigen and NMDAR IgGs were more sensitively detected with live versus fixed CBAs (p < 0.001). Preliminary phenotypic analyses revealed that within the CHR sample, the NMDAR antibody seropositive subjects had higher levels of current depression, performed worse on the Rey Auditory Verbal Learning Task (p < 0.05), and had a markedly lower IQ (p < 0.01). NMDAR IgGs were not more frequent in subjects who later became psychotic than those who did not. NMDAR antibody serostatus and titre was associated with poorer levels of functioning at follow-up (p < 0.05) and the presence of a neuronal autoantibody was associated with larger amygdala volumes (p < 0.05). Altogether, these findings demonstrate that NMDAR autoantibodies are detectable in a subgroup of CHR subjects at equal rates to controls. In the CHR group, they are associated with affective psychopathology, impairments in verbal memory, and overall cognitive function: these findings are qualitatively and individually similar to core features of autoimmune encephalitis and/or animal models of NMDAR antibody-mediated CNS disease. Overall the current work supports further evaluation of NMDAR autoantibodies as a possible prognostic biomarker and aetiological factor in a subset of people already meeting CHR criteria.

Exploratory investigation on antibodies to GluN1 and cognitive dysfunction in patients with chronic autoimmune psychosis

INTRODUCTION

Mild cognitive dysfunction has been implicated in a number of psychiatric diseases and affects social functioning. Although clinical criteria were recently proposed for autoimmune psychosis (AP), biomarkers have not yet been established for the severity and prognosis of cognitive dysfunction. We herein investigated the relationships between 3 types of serum antibodies and cognitive dysfunction in chronic psychiatric patients suspected of AP.

METHODS

We included 31 patients suspected of AP and obtained information on their clinical characteristics. Three types of autoantibodies (the anti-N-methyl-_D-aspartate receptor (anti-NMDAR Ab), anti-N-terminal of GluN1 (anti-GluN1-NT Ab), and anti-thyroid antibodies) were evaluated in serum. Cognitive function was assessed using Wechsler Adult Intelligence Scale-III. We examined the relationships between serum autoantibodies and cognitive dysfunction in patients using multiple regression models.

RESULTS

Serum titers of anti-GluN1-NT Ab significantly contributed to the estimated score of working memory (B= -55.85, β= -0.46, p= 0.01), while no correlation was observed between the other 2 types of antibodies and cognitive function.

CONCLUSIONS

The present results indicate the potential of serum anti-GluN1-NT Ab as a biomarker for the severity and prognosis of cognitive dysfunction underlying various psychiatric symptoms in patients with AP. The pathological significance of anti-GluN1-NT Ab needs to be verified in future studies.

Seizures in steroid-responsive encephalopathy

Steroid-responsive encephalopathy is a general term for diseases that are characterized by diffuse brain injury and respond well to corticosteroids or immunosuppressive agents, including Hashimoto's encephalopathy (HE), limbic encephalitis (LE), systemic lupus erythematosus encephalopathy (SLEE), antineutrophil cytoplasmic antibodies (ANCA)-associated systemic vasculitis encephalopathy (AASV), viral encephalitis (VE), and primary central nervous system lymphoma (PCNSL). Epilepsy and status epilepticus are the main manifestations of steroid-responsive encephalopathy. The spectrum of "autoimmune epilepsy" diseases, which has been approved by the epilepsy diagnostic recommendations of the International Antiepileptic League, is characterized by a high prevalence of epilepsy in central nervous system (CNS) autoimmune diseases and a variety of neuron-specific autoantibodies. Steroid-responsive encephalopathy with different causes may have different pathogeneses and has been suggested to be associated with some internal commonality producing seizure as the main symptom. Determining the regularity of seizures caused by steroid-responsive encephalopathy and implementing appropriate measures will help us improve the prognosis of patients. This paper summarizes the epidemiology, seizure onset, seizure type, and other characteristics of seizures in steroid-responsive encephalopathy (including HE, LE, SLEE, ANCA-associated systemic vasculitis encephalopathy, VE, and PCNSL) and then discusses the use of antiepileptic drugs to treat steroid-responsive encephalopathy.

Exploring autoantibody signatures in brain tissue from patients with severe mental illness

In recent years, studies have shown higher prevalence of autoantibodies in patients with schizophrenia compared to healthy individuals. This study applies an untargeted and a targeted affinity proteomics approach to explore and characterize the autoantibody repertoire in brain tissues from 73 subjects diagnosed with schizophrenia and 52 control subjects with no psychiatric or neurological disorders. Selected brain tissue lysates were first explored for IgG reactivity on planar microarrays composed of 11,520 protein fragments representing 10,820 unique proteins. Based on these results of ours and other previous studies of autoantibodies related to psychosis, we selected 226 fragments with an average length of 80 amino acids, representing 127 unique proteins. Tissue-based analysis of IgG reactivities using antigen suspension bead arrays was performed in a multiplex and parallel fashion for all 125 subjects. Among the detected autoantigens, higher IgG reactivity in subjects with schizophrenia, as compared to psychiatrically healthy subjects, was found against the glutamate ionotropic receptor NMDA type subunit 2D (anti-GluN2D). In a separate cohort with serum samples from 395 young adults with a wider spectrum of psychiatric disorders, higher levels of serum autoantibodies targeting GluN2D were found when compared to 102 control individuals. By further validating GluN2D and additional potential autoantigens, we will seek insights into how these are associated with severe mental illnesses.

Cost-Effectiveness of Routine Screening for Autoimmune Encephalitis in Patients With First-Episode Psychosis in the United States

OBJECTIVE

Autoimmune encephalitis (AE) is a highly treatable neurologic condition that can cause psychosis. Screening for AE is not currently recommended in routine workup for first-episode psychosis (FEP), owing partly to the high cost of testing for AE-associated neuronal autoantibodies.

METHODS

This study used a decision-analytic model to estimate the cost-effectiveness of routine serum screening for AE compared with clinically targeted screening in patients with FEP. Model parameters drawn from prior published literature included the prevalence of neuronal autoantibodies in FEP (4.5%), serum autoantibody panel cost (US $291), remission probability with antipsychotics (0.58), and remission probability with immunotherapy for patients diagnosed with AE (0.85). Outcomes included quality-adjusted life-years (QALYs), costs, and incremental cost-effectiveness ratios (ICERs), assessed over a 5-year horizon from the US health care sector and societal perspectives. ICER thresholds of $50,000/QALY to $150,000/QALY were used to define cost-effectiveness. The analysis was conducted between June 2018 and January 2020.

RESULTS

Routine screening led to mean QALY gains of 0.008 among all patients and 0.174 among the subgroup of patients with neuronal autoantibodies. Mean costs increased by $780 from a societal perspective and $1,150 from a health care sector perspective, resulting in ICERs of $99,330/QALY and $147,460/QALY, respectively. Incorporating joint input data uncertainty, the likelihood routine screening has an ICER ≤ $150,000/QALY was 55% from a societal perspective and 37% from a health care sector perspective. The model parameter with the greatest contribution to overall uncertainty was the effectiveness of immunotherapy relative to antipsychotics.

CONCLUSIONS

Routine screening for AE in patients with FEP may be cost-effective in the United States. As further immunotherapy effectiveness data become available, a more definitive recommendation to perform routine screening could be warranted.

The Challenge of Assessing Mild Neuroinflammation in Severe Mental Disorders

Recent psychoneuroimmunology research has provided new insight into the etiology and pathogenesis of severe mental disorders (SMDs). The mild encephalitis (ME) hypothesis was developed with the example of human Borna disease virus infection years ago and proposed, that a subgroup SMD patients, mainly from the broad schizophrenic and affective spectrum, could suffer from mild neuroinflammation, which remained undetected because hard to diagnose with available diagnostic methods. Recently, in neurology an emerging new subgroup of autoimmune encephalitis (AE) cases suffering from various neurological syndromes was described in context with the discovery of an emerging list of Central Nervous System (CNS) autoantibodies. Similarly in psychiatry, consensus criteria of autoimmune psychosis (AP) were developed for patients presenting with CNS autoantibodies together with isolated psychiatric symptoms and paraclinical findings of (mild) neuroinflammation, which in fact match also the previously proposed ME criteria. Nevertheless, identifying mild neuroinflammation in vivo in the individual SMD case remains still a major clinical challenge and the possibility that further cases of ME remain still under diagnosed appears an plausible possibility. In this paper a critical review of recent developments and remaining challenges in the research and clinical diagnosis of mild neuroinflammation in SMDs and in general and in transdisciplinary perspective to psycho-neuro-immunology and neuropsychiatry is given. Present nosological classifications of neuroinflammatory disorders are reconsidered with regard to findings from experimental and clinical research. A refined grading list of clinical states including "classical" encephalitis, AE, AP/ME,and newly proposed terms like parainflammation, stress-induced parainflammation and neuroprogression, and their respective relation to neurodegeneration is presented, which may be useful for further research on the possible causative role of mild neuroinflammation in SMDs. Beyond, an etiology-focused subclassification of ME subtypes, like autoimmune ME or infectious ME, appears to be required for differential diagnosis and individualized treatment. The present status of the clinical diagnosis of mild neuroinflammatory mechanisms involved in SMDs is outlined with the example of actual diagnosis and therapy in AP. Ideas for future research to unravel the contribution of mild neuroinflammation in the causality of SMDs and the difficulties expected to come to novel immune modulatory, anti-infectious or anti-inflammatory therapeutic principles in the sense of precision medicine are discussed.

Lack of association between unipolar or bipolar depression and serum aquaporin-4 autoantibodies

Aquaporin-4 (AQP4), an astrocyte water channel protein, is the target antigen of serum immunoglobulin G (IgG) autoantibody in neuromyelitis optica spectrum disorders (NMOsd), a group of inflammatory, demyelinating diseases of the central nervous system. Recently, a reduction in blood vessels coverage by AQP4-immunoreactive astrocytes was demonstrated in depressed patients, indicating a role for AQP4 in mood disorders. Moreover, a possible association between depression and serum AQP4-IgG was suggested in a case report of a treatment resistant depression (TRD) patient diagnosed with NMOsd with positive serum AQP4 autoantibodies. We investigated, for the first time, the presence of serum AQP4-IgG in patients with unipolar and bipolar depression and healthy controls (HCs). In this multicenter study, 25 major depressive disorder (MDD) and 25 bipolar disorder (BD) patients, during an acute major depressive episode (MDE), and 30 matched HCs were screened for the presence of serum AQP4-IgG, using a cell-based assay. The MDE patients underwent a repeated AQP4-IgG assessment at a 3-month follow-up visit. The MDE group (N = 50) had illness duration of 12.7 years (SD = 10.5), 12% of them were psychotropic medication-free and 26% were defined as TRD. All MDE patients and HCs, including three BD patients who experienced a manic switch, were seronegative for AQP4-IgG at baseline and follow-up assessments. In conclusion, contrary to our hypothesis, AQP4 autoantibodies were not detected in serum of unipolar and bipolar depressed patients. However, AQP4 may still play a role in the pathogenesis of mood disorders through different mechanisms of action such as altered brain AQP4 expression.

Autoimmune encephalitis with psychosis: Warning signs, step-by-step diagnostics and treatment

Objectives: Despite intensive research, schizophrenia and schizoaffective disorders continue to be theoretical constructs that describe clinical syndromes and no pathophysiologically defined diseases. Moreover, there are no clear biomarkers at hand. Therefore, these diagnoses are still set up based on clinical ICD-10/DSM-5 criteria and the exclusion of alcohol-/drug-associated, systemic or other brain organic causes.Methods: Recently, autoimmune encephalitis with psychotic symptoms caused by specific antineuronal antibodies has been identified as a rare, but potentially treatable differential diagnosis. However, these inflammatory brain diseases are not reliably detected by our current routine diagnostic workup in psychiatry. This qualitative review provides structured diagnostic and therapeutic support for clinical practice.Results: Disturbances of consciousness and orientation, catatonia, speech dysfunction, focal neurological signs, epileptic seizures/EEG abnormalities or autonomic dysfunction are warning signs in psychiatric patients which should always induce cerebrospinal fluid analysis with determination of antineuronal autoantibodies. Currently established immunotherapy strategies are summarised, taking into account international expert advice.Conclusions: Guided by clinical warning signs, our qualitative review enables rapid and reliable diagnosis of definite autoimmune encephalitis. This is of high relevance for the affected individuals, since early and sufficiently intense immunotherapy often leads to a good prognosis despite severe illness.

Schizophrenia and Influenza at the Centenary of the 1918-1919 Spanish Influenza Pandemic: Mechanisms of Psychosis Risk

Associations between influenza infection and psychosis have been reported since the eighteenth century, with acute "psychoses of influenza" documented during multiple pandemics. In the late 20th century, reports of a season-of-birth effect in schizophrenia were supported by large-scale ecological and sero-epidemiological studies suggesting that maternal influenza infection increases the risk of psychosis in offspring. We examine the evidence for the association between influenza infection and schizophrenia risk, before reviewing possible mechanisms via which this risk may be conferred. Maternal immune activation models implicate placental dysfunction, disruption of cytokine networks, and subsequent microglial activation as potentially important pathogenic processes. More recent neuroimmunological advances focusing on neuronal autoimmunity following infection provide the basis for a model of infection-induced psychosis, potentially implicating autoimmunity to schizophrenia-relevant protein targets including the N-methyl-D-aspartate receptor. Finally, we outline areas for future research and relevant experimental approaches and consider whether the current evidence provides a basis for the rational development of strategies to prevent schizophrenia.

Autoimmune encephalitis as a differential diagnosis of schizophreniform psychosis: clinical symptomatology, pathophysiology, diagnostic approach, and therapeutic considerations

Primary schizophreniform psychoses are thought to be caused by complex gene-environment interactions. Secondary forms are based on a clearly identifiable organic cause, in terms of either an etiological or a relevant pathogenetic factor. The secondary or "symptomatic" forms of psychosis have reentered the focus stimulated by the discovery of autoantibody (Ab)-associated autoimmune encephalitides (AEs), such as anti-NMDA-R encephalitis, which can at least initially mimic variants of primary psychosis. These newly described secondary, immune-mediated schizophreniform psychoses typically present with the acute onset of polymorphic psychotic symptoms. Over the course of the disease, other neurological phenomena, such as epileptic seizures, movement disorders, or reduced levels of consciousness, usually arise. Typical clinical signs for AEs are the acute onset of paranoid hallucinatory symptoms, atypical polymorphic presentation, psychotic episodes in the context of previous AE, and additional neurological and medical symptoms such as catatonia, seizure, dyskinesia, and autonomic instability. Predominant psychotic courses of AEs have also been described casuistically. The term autoimmune psychosis (AP) was recently suggested for these patients. Paraclinical alterations that can be observed in patients with AE/AP are inflammatory cerebrospinal fluid (CSF) pathologies, focal or generalized electroencephalographic slowing or epileptic activity, and/or suspicious "encephalitic" imaging findings. The antibody analyses in these patients include the testing of the most frequently found Abs against cell surface antigens (NMDA-R, CASPR2, LGI1, AMPA-R, GABA_B-R), intracellular antigens (Hu, Ri, Yo, CV2/CRMP5, Ma2 [Ta], amphiphysin, GAD65), thyroid antigens (TG, TPO), and antinuclear Abs (ANA). Less frequent antineuronal Abs (e.g., against DPPX, GABA_A-R, glycine-R, IgLON5) can be investigated in the second step when first step screening is negative and/or some specific clinical factors prevail. Beyond, tissue-based assays on brain slices of rodents may detect previously unknown antineuronal Abs in some cases. The detection of clinical and/or paraclinical pathologies (e.g., pleocytosis in CSF) in combination with antineuronal Abs and the exclusion of alternative causes may lead to the diagnosis of AE/AP and enable more causal therapeutic immunomodulatory opportunities.

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.

N-Methyl-D-Aspartate(NMDA) Receptor and Voltage-Gated Potassium Channel (VGKC) Antibody-Associated Encephalitides Presenting as First Episode Acute Psychosis

Aim: Acute psychosis is not an uncommon presenting feature in immune-mediated encephalitides. Most patients improve if properly diagnosed and treated expediently with immunotherapy. Our study aimed to describe the frequency, clinical spectrum, and long-term outcomes in patients presenting with acute psychosis who have anti-N-methyl-D-aspartate (NMDA) receptor or anti-voltage-gated potassium channel (VGKC) encephalitis. Method: We recruited patients aged 16-50 years presenting with less than 1 month of psychotic and neurological symptoms including cognitive dysfunction, seizures, abnormal movements, and/or autonomic dysfunction. Results: Between September 2011 and October 2013, 60 patients with first episode acute psychosis were screened; 15 were recruited and included for analyses. Four (26.7%) patients were diagnosed with anti-NMDA receptor encephalitis and 1 (6.7%) with anti-VGKC encephalitis. We found that the mean serum white blood cell (WBC) count (12.8 × 109/L ± 4.8 vs. 7.9 × 109/L ± 2.6; p = 0.05) and cerebrospinal fluid WBC count (106 cells/µl ± 101 vs. 8.5 cells/µl ± 18.9; p = 0.05) were higher in positive cases. Certain prodromal features such as fever, headache, confusion, facial dyskinesia, and hypersalivation were also more likely to be present in positive cases. Patients with autoimmune encephalitis also tended to be more unwell, with the majority requiring intensive care, had lower global assessment of functioning scores (30 ± 10 vs. 53.7 ± 21.2, p = 0.09), and were not well enough to complete standard psychiatric and cognitive assessments at presentation. Conclusion: Autoimmune encephalitis is not uncommon in patients with acute psychosis. Elevated WBC counts, certain prodromal features, and a more severe illness at presentation should prompt appropriate evaluation.

Autoimmune encephalitis in the elderly: who to test and what to test for

The awareness and understanding of autoimmune encephalitis are blossoming in neurology, and patients are being diagnosed and successfully treated with immunotherapy. The diverse symptomatology associated with autoimmune encephalitis means that patients may present initially to mental health services, which are, as yet, less well equipped to identify and investigate such phenomena. Older adult mental health services are used to managing complexity, but the range of pathologies presenting with unusual symptoms that may mimic autoimmune encephalitis is wide and there is no clear guidance as to when and how to investigate for possible autoimmune encephalitis. This paper examines the evidence supporting investigation and management strategies for patients with possible autoimmune encephalitis presenting to older adult psychiatrists.

The immunobiology of autoimmune encephalitides

Autoimmune encephalitides, with an estimated incidence of 1.5 per million population per year, although described only 15 years ago, have already had a remarkable impact in neurology and paved the field to autoimmune neuropsychiatry. Many patients traditionally presented with aberrant behavior, especially of acute or subacute onset, and treated with anti-psychotic therapies, turn out to have a CNS autoimmune disease with pathogenic autoantibodies against synaptic antigens responding to immunotherapies. The review describes the clinical spectrum of these disorders, and the pathogenetic role of key autoantibodies directed against: a) cell surface synaptic antigens and receptors, including NMDAR, GABAa, GABAb, AMPA and glycine receptors; b) channels such as AQP4 water-permeable channel or voltage-gated potassium channels; c) proteins that stabilize voltage-gated potassium channel complex into the membrane, like the LGI1 and CASPR2; and d) enzymes that catalyze the formation of neurotransmitters such as Glutamic Acid Decarboxylase (GAD). These antibodies, effectively target excitatory or inhibitory synapses in the limbic system, basal ganglia or brainstem altering synaptic function and resulting in uncontrolled neurological excitability disorder clinically manifested with psychosis, agitation, behavioral alterations, depression, sleep disturbances, seizure-like phenomena, movement disorders such as ataxia, chorea and dystonia, memory changes or coma. Some of the identified triggering factors include: viruses, especially herpes simplex, accounting for the majority of relapses occurring after viral encephalitis, which respond to immunotherapy rather than antiviral agents; tumors especially teratoma, SCLC and thymomas; and biological cancer therapies (immune-check-point inhibitors). As anti-synaptic antibodies persist after viral infections or tumor removal, augmentation of autoreactive B cells which release autoantigens to draining lymph nodes, molecular mimicry and infection-induced bystander immune activation products play a role in autoimmunization process or perpetuating autoimmune neuroinflammation. The review stresses the importance of early detection, clinical recognition, proper antibody testing and early therapy initiation as these disorders, regardless of a known or not trigger, are potentially treatable responding to systemic immunotherapy with intravenous steroids, IVIg, rituximab or even bortezomid.

[Autoantibody-associated schizophreniform psychoses: clinical symptomatology]

According to present concepts, primary psychotic disorders in the schizophrenia spectrum are probably caused by a complex interaction between multigenetic vulnerability and causally relevant environmental factors. In contrast, secondary psychotic disorders are the result of likely identifiable organic factors either in terms of a first causation (etiology) or a secondary cause (pathogenesis). In this context, autoantibody(ab)-associated autoimmune encephalitis (AE) plays an increasingly important role. Within the group of ab-associated AE with neuropsychiatric symptoms, anti-N-methyl-D-aspartate receptor encephalitis is the most prevalent one. Psychopathologically, polymorphic psychotic symptoms are often observed at onset of AE; however, over the course of this condition or even initially other neuropsychiatric phenomena are also common. The ill-defined entity of a steroid-responsive encephalopathy with thyroid antibodies (Hashimoto's encephalitis) is a heterogeneous syndrome that may also comprise isolated psychotic disorders presenting as classical schizophrenia.

[Autoimmune encephalitis with psychotic symptoms : Diagnostics, warning signs and practical approach]

Despite intensive research, a precise cause of schizophrenic and schizoaffective disorders has not yet been identified. Therefore, psychiatric diagnoses are still made based on clinical ICD-10/DSM‑5 criteria and not on any objective markers; however, various causes or pathophysiological processes may ultimately lead to similar symptoms. An important task for the future of psychiatry is to identify disease subtypes with a distinct pathophysiology to develop more specific and causally acting therapies. A new diagnostic entity has become established in clinical neurology and psychiatry in recent years: autoimmune encephalitis with psychotic symptoms caused by specific antineuronal antibodies has been identified as a rare but potentially treatable cause of psychotic disorders; however, these inflammatory brain diseases are not reliably detected by routine psychiatric diagnostics. Therefore, this qualitative review is intended to provide structured support for clinical practice, which, guided by clinical warning signals, enables a rapid and reliable diagnosis as well as the initiation of immunotherapy. In the case of psychiatric symptoms, the additional onset of focal neurological signs, disturbances of consciousness and orientation, autonomic instability or epileptic seizures and electroencephalograph (EEG) abnormalities should always be followed by a more specific cerebrospinal fluid analysis with determination of antineuronal autoantibodies. Although the scientific evidence indicates that only a small subgroup of patients is affected, the swift and correct diagnosis is of high therapeutic and prognostic relevance for the affected individuals.

Autoimmunity in psychotic disorders. Where we stand, challenges and opportunities

Psychotic disorders are debilitating mental illnesses associated with abnormalities in various neurotransmitter systems. The development of disease-modifing therapies has been hampered by the mostly unknown etiologies and pathophysiologies. Autoantibodies against several neuronal antigens are responsible for autoimmune encephalitis. These autoantibodies disrupt neurotransmission within the brain, resulting in a wide range of psychiatric and neurologic manifestations, including psychosis. The overlap of symptoms of autoimmune encephalitis with psychotic disorders raised the question as to whether autoantibodies against a number of receptors, ion channel and associated proteins could ultimately be responsible for some forms of psychosis. Here we review our current knowledge, on antibody mediated autoimmunity in psychotic disorders, the different diagnostic methods and their limitations, as well as on varying therapeutic approaches targeting the immune system.

Autoimmune Diseases and Psychotic Disorders

The notion of immunological pathways playing a role in the etiology of a subset of psychotic disorders has received increased interest in the last decades. One of the findings that has spiked interest herein, is an apparent link between autoimmune diseases and psychotic disorders. This is supported by genetic findings associating immune-related genetic markers with schizophrenia and clinical studies finding increased levels of inflammatory markers in patients with psychosis. Several large-scale epidemiologic studies have found positive associations between autoimmune diseases and psychosis. Particularly, autoimmune diseases as multiple sclerosis and lupus are known to have higher frequencies of neuropsychiatric symptoms, including psychosis, compared to healthy controls. Cross sectional studies have found higher prevalence of psychiatric diagnoses among those with autoimmune diseases, and longitudinal studies have shown bidirectional associations between several autoimmune diseases and increased risks associated with schizophrenia. Moreover, a family history of autoimmune diseases has been shown to be associated with an increased risk of psychotic disorders and vice versa. In this review we will summarize the epidemiologic evidence on associations between autoimmune diseases and psychosis. Possible mechanisms accountable for the association will be discussed, amongst others the probable role of shared genetic risk factors, the impact of infections on both autoimmunity and the development of psychotic disorders, and the potential role of the microbiome. We discuss the findings on and influence of autoantibodies and dysregulation of T- and B-cells in both disease categories, and why further research hereon is needed. In addition to the potential importance of autoimmunity in etiological mechanisms of psychotic disorders, the association also brings important attention to somatic comorbidity in patients with psychotic disorders.

Subtle Phenotype Differences in Psychiatric Patients With and Without Serum Immunoglobulin G Antibodies to Synapsin

The discovery that antibodies targeting neuronal antigens can induce severe psychiatric symptoms has been a significant progress in the understanding of psychiatric disorders. Antibodies targeting synapsin I in serum and cerebrospinal fluid (CSF) were first reported in 2015 in a patient with limbic encephalitis. Because of its regulatory function for neurotransmitter release, synapsin I has been suggested to play a role in psychiatric disorders. It is, however, unknown whether or not synapsin antibodies are of clinical significance in patients with psychiatric disorders. In the present study, we aimed to investigate if synapsin I immunoglobulin (Ig)G serum antibody positive patients admitted to acute psychiatric care have a different psychiatric phenotype than synapsin IgG antibody negative patients. A total of 13 anti-synapsin positive patients were matched for age, sex, and psychiatric diagnosis with 39 anti-synapsin negative patients from the same cohort. The groups were compared regarding 11 clinical features frequently seen in anti-neuronal antibody associated disorders. Anti-synapsin positive patients had higher agitation scores as measured with the Positive and Negative Syndrome Scale Excited Component [median (interquartile range) 11 (8) versus 7 (7), p = 0.04] compared to controls. However, the absolute scores were low in both groups, and the difference may not be clinically significant. Other clinical features assessed (e.g. hallucinations, delusions) did not differ between groups. We conclude that synapsin serum IgG antibodies lack syndrome specificity in patients admitted to acute psychiatric inpatient care. However, further studies addressing functional effects of synapsin antibodies are needed to conclude whether or not they have a pathophysiological relevance.

Antibodies in the Diagnosis, Prognosis, and Prediction of Psychotic Disorders

Blood-based biomarker discovery for psychotic disorders has yet to impact upon routine clinical practice. In physical disorders antibodies have established roles as diagnostic, prognostic and predictive (theranostic) biomarkers, particularly in disorders thought to have a substantial autoimmune or infective aetiology. Two approaches to antibody biomarker identification are distinguished: a "top-down" approach, in which antibodies to specific antigens are sought based on the known function of the antigen and its putative role in the disorder, and emerging "bottom-up" or "omics" approaches that are agnostic as to the significance of any one antigen, using high-throughput arrays to identify distinctive components of the antibody repertoire. Here we review the evidence for antibodies (to self-antigens as well as infectious organism and dietary antigens) as biomarkers of diagnosis, prognosis, and treatment response in psychotic disorders. Neuronal autoantibodies have current, and increasing, clinical utility in the diagnosis of organic or atypical psychosis syndromes. Antibodies to selected infectious agents show some promise in predicting cognitive impairment and possibly other symptom domains (eg, suicidality) within psychotic disorders. Finally, infectious antibodies and neuronal and other autoantibodies have recently emerged as potential biomarkers of response to anti-infective therapies, immunotherapies, or other novel therapeutic strategies in psychotic disorders, and have a clear role in stratifying patients for future clinical trials. As in nonpsychiatric disorders, combining biomarkers and large-scale use of "bottom-up" approaches to biomarker identification are likely to maximize the eventual clinical utility of antibody biomarkers in psychotic disorders.

Optimization of an Anti-NMDA Receptor Autoantibody Diagnostic Bioassay

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is one of the most frequently encountered autoimmune encephalitis. The pathogenesis of both anti-NMDAR encephalitis and schizophrenia involve down-regulation of NMDA receptors. Whether autoantibody-mediated destruction of neuronal NMDA receptors is associated with schizophrenia or first-episode psychosis (FEP) remains unclear, as the current findings from different groups are inconsistent. The main culprits are likely due to heterogeneity of autoantibodies (autoAbs) in a patient's blood or cerebrospinal fluid (CSF), as well as due to limitation of the current detection methods for anti-NMDAR autoAbs. Here, we optimized the current diagnostic method based on the only commercially-available anti-NMDAR test kit. We first increased detection sensitivity by replacing reporter fluorophore fluorescein isothiocyanate (FITC) in the kit with Alexa Fluor 488, which is superior in resisting photobleaching. We also found that using an advanced imaging system could increase the detection limit, compared to using a simple fluorescence microscope. To improve test accuracy, we implemented secondary labeling with a well-characterized mouse anti-NR1 monoclonal antibody (mAb) after immunostaining with a patient's sample. The degree of colocalization between mouse and human antisera in NMDAR-expressing cells served to validate test results to be truly anti-NMDAR positive or false-positive. We also incorporated DNA-specific DAPI to simultaneously differentiate autoAbs targeting the plasma membrane from those targeting cell nuclei or perinuclear compartments. All the technical implementation could be integrated in a general hospital laboratory setting, without the need of specialized expertise or equipment. By sharing our experience, we hope this may help improve sensitivity and accuracy of the mainstream method for anti-NMDAR detection.

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.

Encephalitis, Mild Encephalitis, Neuroprogression, or Encephalopathy-Not Merely a Question of Terminology

Background: Psychoneuroimmunology research has presented emerging evidence of the involvement of inflammatory and immune mechanisms in the pathogenesis of severe mental disorders. In this context, new terms with increasing clinical relevance have been proposed, challenging the existing terms, and requiring consensus definitions of the new ones. Method: From a perspective of longstanding personal involvement in clinical settings and research in psychoneuroimmunology, the new and the existing terms are critically reconsidered. Results: Meningoencephalitis and encephalitis are comparably well defined clinical terms in neuropsychiatry, although in the individual case approach diagnosis can be difficult, for example in some cases of encephalitis that are described with normal cerebrospinal fluid findings, or often in chronic encephalitis. Encephalopathy is also a widely accepted term, however, with a surprisingly broad meaning with regard to the assigned underlying pathophysiology, ranging from one-hit traumatic encephalopathy to inflammatory encephalopathy, the latter term addressing a type of brain dysfunction secondary to acute systemic inflammation without proven brain autochthonus inflammation (neuroinflammation). However, this latter assumption and term may be wrong as neuroinflammation is difficult to prove in vivo. With emerging insights into prevailing inflammatory and neuroinflammatory mechanisms that are involved in the pathogenesis of severe mental disorders, the interdependent aspects of sensitive assessment and potential clinical relevance of mild neuroinflammation are becoming more apparent and of increasing clinical interest. The new terms "mild encephalitis," "parainflammation," and "neuroprogression" show considerable overlap in addition to gaps and hardly defined borders. However, details are hard to discuss as available studies use many biomarkers, but most of these are done without an established categorical attribution to exclusive terms. Most important, the three new concepts (neruoprogression, parainflammation, and mild encephalitis) are not mutually exclusive, even at the individual case level, and therefore will require state-related individual assessment approaches beyond large confirmatory studies. Conclusion: The newly proposed terms of mild encephalitis, parainflammation, and neuroprogression have an emerging clinical relevance, but respective borders, gaps and overlap in between them remain unclear, and these concepts may even be seen as complementary. Categorical delineation of the new and reconsideration of the existing terms with respect to individualized psychiatric treatment is required for better clinical use, eventually requiring a consensus approach. Here, a critique based on available data and a focus on clinical perspective was outlined, which may help to enhance fruitful discussion. The idea followed here is in line with pillar number six as proposed for the Research Diagnostic Domains, i.e., to provide and follow new concepts in psychiatric research.

Deficits in the Proline-Rich Synapse-Associated Shank3 Protein in Multiple Neuropsychiatric Disorders

Signaling between neurons in the human central nervous system (CNS) is accomplished through a highly interconnected network of presynaptic and postsynaptic elements essential in the conveyance of electrical and neurochemical information. One recently characterized core postsynaptic element essential to the efficient operation of this complex network is a relatively abundant ~184.7 kDa proline-rich synapse-associated cytoskeletal protein known as Shank3 (SH3-ankyrin repeat domain; encoded at human chr 22q13.33). In this “Perspectives” article, we review and comment on current advances in Shank3 research and include some original data that show common Shank3 deficits in a number of seemingly unrelated human neurological disorders that include sporadic Alzheimer’s disease (AD), autism spectrum disorder (ASD), bipolar disorder (BD), Phelan–McDermid syndrome (PMS; 22q13.3 deletion syndrome), and schizophrenia (SZ). Shank3 was also found to be downregulated in the CNS of the transgenic AD (TgAD) 5x familial Alzheimer’s disease murine model engineered to overexpress the 42 amino acid amyloid-beta (Aβ42) peptide. Interestingly, the application of known pro-inflammatory stressors, such as the Aβ42 peptide and the metal-neurotoxin aluminum sulfate, to human neuronal–glial cells in primary culture resulted in a significant decrease in the expression of Shank3. These data indicate that deficits in Shank3-expression may be one common denominator linking a wide-range of human neurological disorders that exhibit a progressive or developmental synaptic disorganization that is temporally associated with cognitive decline.

Psychosis: an autoimmune disease?

Psychotic disorders are common and disabling. Overlaps in clinical course in addition to epidemiological and genetic associations raise the possibility that autoimmune mechanisms may underlie some psychoses, potentially offering novel therapeutic approaches. Several immune loci including the major histocompatibility complex and B-cell markers CD19 and CD20 achieve genome-wide significance in schizophrenia. Emerging evidence suggests a potential role via neurodevelopment in addition to classical immune pathways. Additionally, lymphocyte biology is increasingly investigated. Some reports note raised peripheral CD19+ and reduced CD3+ lymphocyte counts, with altered CD4 : CD8 ratios in acute psychosis. Also, post-mortem studies have found CD3+ and CD20+ lymphocyte infiltration in brain regions that are of functional relevance to psychosis. More specifically, the recent paradigm of neuronal surface antibody-mediated (NSAb) central nervous system disease provides an antigen-specific model linking adaptive autoimmunity to psychopathology. NSAbs bind extracellular epitopes of signalling molecules that are classically implicated in psychosis such as NMDA and GABA receptors. This interaction may cause circuit dysfunction leading to psychosis among other neurological features in patients with autoimmune encephalitis. The detection of these cases is crucial as autoimmune encephalitis is ameliorated by commonly available immunotherapies. Meanwhile, the prevalence and relevance of these antibodies in people with isolated psychotic disorders is an area of emerging scientific and clinical interest. Collaborative efforts to achieve larger sample sizes, comparison of assay platforms, and placebo-controlled randomized clinical trials are now needed to establish an autoimmune contribution to psychosis.

Neuronal Surface Autoantibodies in Neuropsychiatric Disorders: Are There Implications for Depression?

Autoimmune diseases are affecting around 7.6-9.4% of the general population. A number of central nervous system disorders, including encephalitis and severe psychiatric disorders, have been demonstrated to associate with specific neuronal surface autoantibodies (NSAbs). It has become clear that specific autoantibodies targeting neuronal surface antigens and ion channels could cause severe mental disturbances. A number of studies have focused or are currently investigating the presence of autoantibodies in specific mental conditions such as schizophrenia and bipolar disorders. However, less is known about other conditions such as depression. Depression is a psychiatric disorder with complex etiology and pathogenesis. The diagnosis criteria of depression are largely based on symptoms but not on the origin of the disease. The question which arises is whether in a subgroup of patients with depression, the symptoms might be caused by autoantibodies targeting membrane-associated antigens. Here, we describe how autoantibodies targeting membrane proteins and ion channels cause pathological effects. We discuss the physiology of these antigens and their role in relation to depression. Finally, we summarize a number of studies detecting NSAbs with a special focus on cohorts that include depression diagnosis and/or show depressive symptoms.