Anti-neuronal autoantibodies: Current diagnostic challenges

Autoimmune/Paraneoplastic Encephalitis Antibody Biomarkers: Frequency, Age, and Sex Associations

OBJECTIVE

To determine the frequency of detection and the age and sex associations of autoimmune/paraneoplastic encephalitis antibody biomarkers (AE-Abs).

METHODS

There were 42,032 patients tested in the Mayo Clinic Neuroimmunology Laboratory between January 2018 and December 2019 for AE-Abs in serum or cerebrospinal fluid (CSF), including NMDA-R-IgG, AMPA-R-IgG, GABA_B-R-IgG, CASPR2-IgG, LGI1-IgG, GAD65-IgG, CRMP5-IgG, amphiphysin-IgG, PCA1/2/Tr-IgGs, ANNA1/2/3-IgGs, GFAP-IgG, mGluR1-IgG, DPPX-IgG, and MOG-IgG1. Results were examined to determine frequency of antibody positivity. Age and sex associations were examined by multivariable logistic regression.

RESULTS

Adult serum analysis (22,472 patients; 56% female) revealed that 814 (3.6%) were positive: NMDA-R-IgG (24.6%) > GAD65-IgG (21.5%) > LGI1-IgG (20.5%) > others. Of children (5649; 50% female), 251 (4.4%) were positive: NMDA-R-IgG (53.1%) > MOG-IgG1 (32%) > GAD65-IgG (7.1%) > others. Adult CSF analysis (18,745 patients; 54% female) revealed that 796 (4.2%) were positive: NMDA-R-IgG (39.7%) > GAD65-IgG (28.5%) > LGI1-IgG (11.4%) > others. Of children (5136; 50% female), 282 (5.5%) were positive: NMDA-R-IgG (88.1%) > GAD65-IgG (8.7%) > others. Age younger than 20 years was associated with NMDA-R-IgG and MOG-IgG1 (odds ratio [OR], 8.11 and 7.84, respectively; P<.001). Age older than 65 years was associated with GABA_B-R-IgG, LGI1-IgG, CASPR2-IgG, and ANNA1-IgG (OR, 7.33, 14.98, 3.67, and 14.53; P<.001). Women accounted for 60% of NMDA-R-IgG (CSF) and 78% of GAD65-IgG (CSF and serum) cohorts (OR, 1.32 [P=.002] and 2.23 [P<.001], respectively). Men accounted for 62% of the LGI1-IgG cohort (OR, 1.87; P<.001). Age and sex interacted for NMDA-R-IgG, particularly in female patients younger than 20 years (OR, 7.72; P<.001).

CONCLUSION

The most frequent AE-Abs detected were NMDA-R-IgG, GAD65-IgG, LGI1-IgG, and MOG-IgG1. Age and sex associations may suggest paraneoplastic, or aging influences on neurologic autoimmunity.

Research progress in teratoma-associated anti-N-methyl-D-aspartate receptor encephalitis: The gynecological perspective

AIM

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is one of the autoimmune encephalitis, which often occurs in children and young adults, especially in young women. In addition to viral infection, teratoma is an important causative factor. Anti-NMDAR encephalitis is well known to neurologist. However, this is less well known to gynecologists, who may have a decisive role in etiological management. Therefore, from the perspective of gynecologists, we provide an overview of the relationship between the encephalitis and ovarian teratoma, the clinical features and treatment of this disease, and prognosis of pregnant women with this encephalitis.

METHODS

We searched the PubMed database using the search terms in various combinations "teratoma," "dermoid cyst," "ovary," "ovarian," "anti-NMDAR encephalitis," and "N-methyl-D-aspartate receptor."

RESULTS

According to the current literature, the mechanism of anti-NMDAR encephalitis is probably due to the ectopic expression of the NMDAR in the teratomas tissue. The disease has a high mortality rate if not treated promptly and effectively. An important way to improve patients' outcome is to remove the ovarian tumor in time. Pregnant women are also at risk of developing anti-NMDAR encephalitis during pregnancy. The fetal outcome is usually better in patients with mid- to late-pregnancy onset than in early pregnancy, and patients are often able to maintain their pregnancies into late pregnancy.

CONCLUSION

Young women with sudden onset of abnormal psychiatric behavior should be actively screened for ovarian tumors and, if confirmed to be teratoma-associated anti-NMDAR encephalitis, should undergo gynecologic surgery as early as possible, which can help improve their prognosis.

Patients with a relapsing course of steroid-responsive encephalopathy associated with autoimmune thyroiditis exhibit persistent intrathecal CD4+ T-cell activation

BACKGROUND AND PURPOSE

Steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT) is a rare condition defined by encephalopathy with acute or subacute onset, the presence of serum anti-thyroid antibodies, and reasonable exclusion of alternative causes. Despite having strong response towards corticosteroid treatment, some patients exhibit a chronic-relapsing course and require long-term immunosuppression. Markers for early identification of those patients are still absent. Thus, we aimed to characterise clinical as well as laboratory parameters of our local SREAT cohort.

METHODS

We retrospectively evaluated a cohort of 22 SREAT patients treated in our hospital from January 2014.

RESULTS

A total of 14 patients with a monophasic disease course and eight patients with multiple relapses were identified. Neither baseline characteristics nor routine cerebrospinal fluid (CSF) parameters were able to distinguish between those patient groups. Flow cytometry following initial relapse therapy showed treatment-resistant sequestration of activated CD4+ T cells in patients with a relapsing disease course, whereas other lymphocyte subsets showed uniform changes. Such changes were also present in long-term follow-up CSF examination.

CONCLUSION

Our findings indicate a potential biomarker for risk stratification in patients with SREAT. Currently, it remains unclear whether the observed two phenotypes are different spectra of SREAT or represent separate diseases in terms of pathophysiology.

Clinical characteristics of GAD 65-associated autoimmune encephalitis

OBJECTIVES

To examine the clinical characteristics of autoimmune encephalitis associated with the glutamate decarboxylase 65 (GAD 65) antibody.

MATERIALS AND METHODS

Medical records of all patients that diagnosed with GAD 65 antibody-associated encephalitis were retrospectively analyzed. Data regarding demographics and symptoms, neurological signs, laboratory and imaging results, treatment and prognosis were collected.

RESULTS

We collected a total of seven patients, mainly young or middle-aged women with a subacute or chronic course. The main clinical symptoms mainly included chronic epilepsy, cerebellar ataxia, stiff-person syndrome, and limbic encephalitis. Three of seven (43%) patients had high CSF (cerebrospinal fluid) protein levels. Oligoclonal IgG bands (including IgG 1) and 24 hours intrathecal synthesis of IgG were detected in CSF and serum in six patients, five patients (83%) reported increased distribution of oligoclonal IgG bands (including IgG 1) and 24 hours intrathecal synthesis of IgG in serum and CSF. And six of seven patients (86%) had abnormal thyroid function or were positive for thyroid antibodies. By electroencephalogram examination, sharp or slow waves in the temporal region were often observed for six of seven patients (86%). Abnormal imaging signals (six of seven patients, 86%) of the temporal lobe and hippocampus were detected by brain magnetic resonance imaging, and decreased metabolism of the temporal lobe was detected by positron emission tomography/computed tomography (six of six patients, 100%). These patients were mainly treated with corticosteroid and gamma globulin. The clinical symptoms of the patients were alleviated.

CONCLUSIONS

The course of GAD 65 antibody-associated encephalitis is longer than other autoimmune encephalitides. The clinical symptoms of GAD 65 autoimmune encephalitis mainly manifested as chronic epilepsy, cerebellar ataxia, stiff-person syndrome, and limbic encephalitis, and combined with or without thyroid autoimmune diseases, type 1 diabetes, and thymoma. A comprehensive understanding of the disease is a way to prevent misdiagnosis and delayed treatment.

Clinical Characteristics of Anti-GABA-B Receptor Encephalitis

Objective: Anti-GABA-B (gamma aminobutyric acid-B) receptor encephalitis is an autoimmune disease mediated by GABA-B-related antibodies. To fully understand the disease, we collected clinical data from patients with GABA-B receptor encephalitis and conducted an analysis to draw conclusions. Methods: All patients with GABA-B receptor encephalitis from the Neurology Department of Beijing Tiantan Hospital, affiliated with Capital Medical University, from August 2015 to September 2019 were accepted as study subjects. The clinical data of the patients were analyzed retrospectively and included the general demographic characteristics, clinical manifestations, and auxiliary examinations, including laboratory results, electroencephalograms (EEGs), brain magnetic resonance imaging (MRI), and positron emission tomography (PET-CT) results, as well as treatments. Results: From August 2015 to September 2019, 14 cases of anti-GABA-B receptor encephalitis were diagnosed. Among these patients, middle-aged and elderly men were the main demographic, with an average age of 52 years; moreover, the onset of the disease was relatively sudden, and the time from onset to diagnosis was ~1 month. The main clinical symptoms were frequent epileptic seizures, cognitive dysfunction, and mental behavioral disorders. In seven (50%) patients, the leukocyte in cerebrospinal fluid (CSF) were increased. Five (36%) patients had elevated cerebrospinal fluid protein. In most patients, the oligoclonal bands (83%) of CSF were positive, and 24 h IgG levels (92%) were increased. Anti-Hu or anti-Yo antibodies were positive in two (14%) patients. Tumor markers in 10 (71%) patients indicated that neuron-specific enolase, gastrin-releasing precursor, non-small cell lung cancer-related antigen, or carcinoembryonic antigen levels were increased. EEG results often indicated slow waves, sharp waves, or spike waves in temporal areas. Brain MRI always showed high T2 signals in the medial temporal lobe, hippocampus, and amygdala and swelling in the medial temporal lobe and hippocampus. PET-CT scans almost showed abnormal metabolism in the hippocampus and temporal lobe. Three (21%) patients who underwent systemic PET-CT showed hypermetabolism in pulmonary parenchymal nodules and enlargement of mediastinal lymph nodes. All patients underwent high-dose hormone therapy or immunoglobulin immunotherapy. After treatment, the symptoms of epilepsy, cognitive disorders, and mental behavioral disorders improved to varying degrees. However, one patient died of lung cancer. Conclusion: Anti-GABA-B receptor encephalitis mainly occurred in middle-aged and elderly men, and the disease onset was relatively sudden. Before disease onset, some patients experienced fever and non-specific respiratory symptoms, which mainly manifested as frequent epileptic seizures, cognitive dysfunction, and abnormal mental behavior. MRI and PET-CT revealed abnormal signals and local metabolism, respectively, in the temporal lobe. Moreover, the disease has a close relationship with lung cancer, which requires long-term follow-up observation.

Association of antibodies against myelin and neuronal antigens with neuroinflammation in systemic lupus erythematosus

OBJECTIVES

To determine frequency and syndrome specificity of novel and known nervous system (NS)-directed antibodies in a large, unbiased cohort of SLE patients in the Swiss SLE Cohort Study.

METHODS

This retrospective pilot study included 174 patients in a cross-sectional and 102 in a longitudinal study. Antibodies against 12 NS antigens [myelin oligodendrocyte glycoprotein (MOG), neurofascin 186 (NF186), aquaporin-4 (AQP4), N-methyl-D-aspartate receptor (subunit NR1) (NMDAR-NR1), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (subunits 1 and 2) (AMPAR1/2), gamma-aminobutyric acid B receptor (subunits B1 and B2) (GABABR1/2), glutamate decarboxylase 65 (GAD65), glycine receptor (GlyR), contactin-associated protein-like 2 (CASPR2), leucine-rich glioma-inactivated 1 (LGI1), metabotropic glutamate receptor 5 (mGluR5) and dipeptidyl-peptidase-like protein 6 (DPPX)] were screened with validated cell-based assays and correlated with clinical and diagnostic findings.

RESULTS

Twenty-three of one hundred and seventy-four (13.2%) patients harboured antibodies against MOG (n = 14), NF186 (n = 6), GAD65 (n = 2), AQP4 and GlyR (n = 1). Anti-MOG antibodies were most frequently found in the cohort (8%). Thirteen of the anti-NS antibody-positive patients showed clinical symptoms of NS involvement, a subgroup of which (n = 8) resembled the syndrome associated with the antibody. Nine patients harboured antibodies without neurological symptoms and one patient was lost to follow-up. The frequency of NPSLE was significantly higher in the anti-NS antibody-positive patients (13/23, 56.5%: MOG 6/14, 42.9%; NF186 5/6, 83.3%; GAD65 2/2, 100%; AQP4/GlyR 0/1, 0%) compared with the antibody-negative cohort (21/151, 13.9%) (chi-square test, P < 0.0001).

CONCLUSION

Anti-NS antibodies, most prevalently anti-MOG antibodies, are significantly associated with NPSLE and manifest with the distinct neurological syndrome associated with the antibody in a subgroup. Follow-up studies in large, independent cohorts will reveal whether these anti-NS antibodies could serve as a diagnostic and prognostic biomarker for NPSLE and enable tailored treatment decisions in this challenging and diverse patient cohort.

A prospective three-year follow-up study on the clinical significance of anti-neuronal antibodies in acute psychiatric disorders

The clinical significance of anti-neuronal antibodies for psychiatric disorders is controversial. We investigated if a positive anti-neuronal antibody status at admission to acute psychiatric inpatient care was associated with a more severe neuropsychiatric phenotype and more frequent abnormalities during clinical work-up three years later. Patients admitted to acute psychiatric inpatient care who tested positive for N-methyl-D-aspartate receptor (NMDAR), contactin-associated protein 2 (CASPR2) and/or glutamic acid decarboxylase 65 (GAD65) antibodies (n = 24) were age - and sex matched with antibody-negative patients (1:2) from the same cohort (n = 48). All patients were invited to follow-up including psychometric testing (e.g. Symptom Checklist-90-Revised), serum and cerebrospinal fluid (CSF) sampling, EEG and 3 T brain MRI. Twelve antibody-positive (ab+) and 26 antibody-negative (ab-) patients consented to follow-up. Ab+ patients had more severe symptoms of depression (p = 0.03), psychoticism (p = 0.04) and agitation (p = 0.001) compared to ab- patients. There were no differences in CSF analysis (n = 6 ab+/12 ab-), EEG (n = 7 ab+/19 ab-) or brain MRI (n = 7 ab+/17 ab-) between the groups. In conclusion, anti-neuronal ab+ status during index admission was associated with more severe symptoms of depression, psychoticism and agitation at three-year follow-up. This supports the hypothesis that anti-neuronal antibodies may be of clinical significance in a subgroup of psychiatric patients.

Effects of IVIg treatment on autoantibody testing in neurological patients: marked reduction in sensitivity but reliable specificity

BACKGROUND

Therapy of autoimmune diseases of the central and peripheral nervous system with intravenous IgG immunoglobulin (IVIg) is well established. Since IVIg is produced from pooled human plasma, autoantibodies can be found in IVIg products and, accordingly, in patient sera after transfusion. The de novo evidence or disappearance of anti-neural autoantibodies after IVIg treatment has so far not been systematically examined.

METHODS

We screened 50 neurological patients before and after IVIg treatment for classical onconeural and the most common neurological surface autoantibodies as well as for ganglioside autoantibodies and 23 different antinuclear autoantibodies using immunoblot or cell-based indirect immunofluorescence assays. Furthermore, we screened 31 neurological patients with previously known seropositivity for disappearance of the corresponding antibody after treatment.

RESULTS

After IVIg treatment, 90% of all sera were de novo positive for antinuclear antibodies, especially for Ro-52. In contrast, 94% of all sera did not show any de novo-positive anti-neural antibodies. In the remaining three cases, titers were very low. Importantly, 12.9% of all tested sera of patients with known antibody positivity turned false negative after IVIg treatment and titers were falsely low in 37% of the remaining sera.

CONCLUSIONS

Here, we present for the first time results of a broad screening for clinically relevant autoantibodies before and after IVIg treatment in neurological patients. We identified a high specificity but reduced sensitivity for anti-neural antibody testing after IVIg transfusion. In contrast, antinuclear antibody testing is not reliable after IVIg treatment. These results are of high practical importance for diagnostic of neuroimmunological diseases.

Antibodies against neural antigens in patients with acute stroke: joint results of three independent cohort studies

BACKGROUND AND PURPOSE

Ischemic stroke (IS) and hemorrhagic stroke (HemS) typically lead to a breakdown of the blood-brain barrier with neural antigen presentation. This presentation could potentially generate destructive auto-immune responses. Pre-existing antineuronal and antiglial antibodies (AA), predominantly NMDA receptor antibodies, have been reported in patients with stroke. This article summarizes three independent prospective studies, the Lübeck cohort (LC), Barcelona cohort (BC), and Heidelberg cohort (HC), exploring the frequency and clinical relevance of AA in patients with acute stroke (AS).

METHODS

In all cohorts together, 344 consecutive patients admitted with AS (322 × IS, 22 × HemS) were screened for AA in serum at admission. Clinical outcome parameters as well as a second AA screening were available at 30 days in the LC or at 90 days in the BC. A control group was included in the BC (20 subjects free from neurological disease) and the HC (78 neurological and ophthalmological patients without evidence for stroke).

RESULTS

The rate of positivity for AA was similar in control subjects and AS patients (13%, 95% CI [7%, 22%] vs. 13%, 95% CI [10%, 17%]; p = 0.46) with no significant difference between cohorts (LC 25/171, BC 12/75, HC 9/98). No patient had developed new AA after 30 days, whereas 2 out of 60 patients had developed new AA after 90 days. AA positive patients did not exhibit significant differences to AA negative patients in stroke subtype (LC, BC), initial stroke severity (BC, LC, HC), infarct volume (BC), and functional status at admission (BC, LC, HC) and follow-up (BC, LC).

CONCLUSIONS

AS does not induce AA to a relevant degree. Pre-existing AA can be found in the serum of stroke patients, but they do not have a significant association with clinical features and outcomes.

The significance of anti-neuronal antibodies for acute psychiatric disorders: a retrospective case-controlled study

Background

The clinical significance of anti-neuronal antibodies in patients with psychiatric disorders, but without encephalitis, remains unknown. In patients admitted to acute psychiatric inpatient care we aimed to identify clinical features distinguishing anti-neuronal antibody positive patients from matched controls.

Results

Patients who were serum-positive to N-methyl d-aspartate receptor (NMDAR) (n = 21), contactin-associated protein 2 (CASPR2) (n = 14) and/or glutamic acid decarboxylase 65 (GAD65) (n = 9) antibodies (cases) were age and sex matched (1:2) with serum-negative patients from the same cohort (controls). The prevalence and severity of psychiatric symptoms frequently encountered in NMDAR, CASPR2 and GAD65 antibody associated disorders were compared in cases and controls. NMDAR, CASPR2 and GAD65 antibody positive patients did not differ in their clinical presentation from matched serum negative controls.

Conclusion

In this cohort, patients with and without NMDAR, CASPR2 and GAD65 antibodies admitted to acute psychiatric inpatient care had similar psychiatric phenotypes. This does not exclude their clinical relevance in subgroups of patients, and studies further investigating the clinical significance of anti-neuronal antibodies in patients with psychiatric symptomatology are needed.

Electronic supplementary material

The online version of this article (10.1186/s12868-018-0471-7) contains supplementary material, which is available to authorized users.

The role of the laboratory in the expanding field of neuroimmunology: Autoantibodies to neural targets

Accelerated identification of autoantibodies associated with previously idiopathic neurological disease has provided insights into disease mechanisms, enhanced understanding of neurological function, and opportunities for improved therapeutic interventions. The role of the laboratory in the expanding field of neuroimmunology is critical as specific autoantibody identification provides guidance to clinicians in diagnosis, prognosis, tumor search strategies, and therapeutic interventions. The number of specific autoantibodies identified continues to increase and newer testing strategies increase efficiencies in the laboratory and availability to clinicians. The need for broadly targeted efficient testing is underscored by the variability in clinical presentation and tumor associations attributable to a specific autoantibody, and conversely the various autoantibody specificities that can be the cause of a given clinical presentation. While many of the antineural antibodies were first recognized in the setting of neoplastic disease, idiopathic autoimmune neurological disease in the absence of underlying tumor is increasingly recognized. Appropriation of therapeutic modalities used to treat autoimmune disease to treat these autoantibody mediated neurological diseases has improved patient outcomes. Interaction between clinicians and laboratorians is critical to our understanding of these diseases and optimization of the clinical benefits of our increasing knowledge in neuroimmunology.

A Spectrum of Neural Autoantigens, Newly Identified by Histo-Immunoprecipitation, Mass Spectrometry, and Recombinant Cell-Based Indirect Immunofluorescence

Background

A plurality of neurological syndromes is associated with autoantibodies against neural antigens relevant for diagnosis and therapy. Identification of these antigens is crucial to understand the pathogenesis and to develop specific immunoassays. Using an indirect immunofluorescence assay (IFA)-based approach and applying different immunoprecipitation (IP), chromatographic and mass spectrometric protocols was possible to isolate and identify a spectrum of autoantigens from brain tissue.

Methods

Sera and CSF of 320 patients suspected of suffering from an autoimmune neurological syndrome were comprehensively investigated for the presence of anti-neural IgG autoantibodies by IFA using mosaics of biochips with brain tissue cryosections and established cell-based recombinant antigen substrates as well as immunoblots. Samples containing unknown brain tissue-specific autoantibodies were subjected to IP with cryosections of cerebellum and hippocampus (rat, pig, and monkey) immobilized to glass slides or with lysates produced from homogenized tissue, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, tryptic digestion, and matrix-assisted laser desorption/ionization–time of flight mass spectrometry analysis. Identifications were confirmed by IFA with recombinant HEK293 cells and by neutralizing the patients’ autoantibodies with the respective recombinantly expressed antigens in the tissue-based immunofluorescence test.

Results

Most samples used in this study produced speckled, granular, or homogenous stainings of the hippocampal and cerebellar molecular and/or granular layers. Others exclusively stained the Purkinje cells. Up to now, more than 20 different autoantigens could be identified by this approach, among them ATP1A3, CPT1C, Flotillin1/2, ITPR1, NBCe1, NCDN, RGS8, ROCK2, and Syntaxin-1B as novel autoantigens.

Discussion

The presented antigen identification strategy offers an opportunity for identifying up to now unknown neural autoantigens. Recombinant cell substrates containing the newly identified antigens can be used in serology and the clinical relevance of the autoantibodies can be rapidly evaluated in cohort studies.

Overinterpretation and Overtreatment of Low-Titer Antibodies Against Contactin-Associated Protein-2

Antibodies (abs) against neural or glial antigens have become important diagnostic markers of autoimmune encephalitides. A key requirement for interpretation of any test in clinical medicine is specificity. In this work, a 35-year-old female patient with low-titer contactin-associated protein-2 abs not satisfying clinical criteria of autoimmune encephalitis is reported. The patient had a recurrent depressive disorder and, at the time of the ab study, a moderate depressive episode. Overinterpretation and misinterpretation of patient’s complaints and paraclinical study results fueled the idea of an autoimmune encephalitis. It is suggested to check patients with supposedly positive ab test results critically for clinical criteria, titer cutoffs, and ab-typical epidemiological features like age and sex.

Anti-Yo-Associated Paraneoplastic Cerebellar Degeneration Manifesting as Acute Cerebellitis with Posterior Cranial Fossa Hypertension

BACKGROUND

Paraneoplastic cerebellar degeneration (PCD) is a rare complication of some malignant cancers. It is most commonly described in women with gynecologic or breast malignancies; however, there have been reports in other types of cancers. Symptoms include ataxia, dysarthria, and tremors, which could be the first manifestations of an underlying malignancy.

CASE DESCRIPTION

A 50-year-old woman had an acute PCD with anti-Yo antibodies from an underlying breast invasive ductal carcinoma. She presented with intracranial hypertension in the posterior cranial fossa that required an emergent decompressive craniectomy.

CONCLUSIONS

PCD is an uncommon disease that may manifest initially as posterior cranial fossa hypertension and subsequent acute hydrocephalus owing to diffuse cerebellar swelling. To our knowledge, this is the first described case of an anti-Yo PCD that has manifested as acute posterior cranial fossa hypertension owing to diffuse cerebellar edema. Early diagnosis and treatment should be pursued to improve long-term outcomes.

Retrospective study of paraneoplastic neurological syndromes in a Chinese Han population from Shandong, East China

OBJECTIVE

To analyze the clinical features, diagnostic strategies and therapeutic methods associated with paraneoplastic neurological syndromes.

METHODS

A retrospective study of paraneoplastic neurological syndromes was performed at a single center in Shandong, East China. The medical records and follow-up data of 28 patients were intensively reviewed between February 2011 and December 2014.

RESULTS

Twenty-four (85.7%) patients experienced subacute or chronic onset of disease, and the most common symptoms reported were mild myasthenia and paresthesias. Twenty-five (89.3%) patients presented nervous system lesions prior to occult tumors, and the median time frame between paraneoplastic neurological syndromes onset and the diagnosis of a tumor was 15 weeks. Sensorimotor neuropathy, Lambert-Eaton myasthenic syndrome and limbic encephalitis were the three most common neurological syndromes reported. Elevated serum tumor markers were observed in 44.0% of patients, while 40.7% of patients were positive for onconeural antibodies. Tumors were detected in 21 (75.0%) patients after repeated whole-body screening, and lung carcinomas were the most common primary tumor detected. Seventeen patients received anti-tumor or immunological therapy, and clinical symptoms were relieved in 13 (76.5%) of these patients.

CONCLUSIONS

In the majority of paraneoplastic neurological syndromes patients, the onset of disease is subacute or chronic with mild clinical symptoms. Nervous system lesions usually occur prior to occult tumors with complicated and various clinical manifestations. Neither tumor markers nor onconeural antibodies exhibit a high rate of occurrence, while repeated whole-body screening is helpful in identifying occult tumors. Early diagnosis and treatment are crucial to these patients.

Anti-neuronal anti-bodies in patients with early psychosis

It may be challenging to distinguish autoimmune encephalitis associated with anti-neuronal autoantibodies from primary psychiatric disorders. Here, serum was drawn from patients with a first-episode psychosis (n=70) or a clinical high-risk for psychosis (n=6) and controls (n=34). We investigated the serum prevalence of 24 anti-neuronal autoantibodies: IgG antibodies for anti-N-methyl-d-aspartate-type glutamate receptor (anti-NMDAR), glutamate and γ-aminobutyric acid alpha and beta receptors (GABA-a, GABA-b), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA), glycine receptor (GlyR), metabotropic glutamate receptor 1 and 5 (mGluR1, mGluR5), anti-Tr/Delta/notch-like epidermal growth factor-related receptor (DNER), contactin-associated protein-like 2 (CASPR2), myelin oligodendrocyte glycoprotein (MOG), glutamic acid decarboxylase-65 (GAD65), collapsin response mediator protein 5/crossveinless-2 (CV2), aquaporin-4 (AQP4), anti-dipeptidyl-peptidase-like protein-6 (DPPX), type 1 anti-neuronal nuclear antibody (ANNA-1, Hu), Ri, Yo, IgLON5, Ma2, zinc finger protein 4 (ZIC4), Rho GTPase-activating protein 26, amphiphysin, and recoverin, as well as IgA and IgM for dopamine-2-receptor (DRD2). Anti-NMDA IgG antibodies were positive with serum titer 1:320 in one patient with a clinical high risk for psychosis. He did not receive a diagnosis of encephalitis after comprehensive neurological evaluation. All other antineuronal autoantibodies were negative and there were no additional findings with immunohistochemistry of brain issues.

The Laboratory Diagnosis of Autoimmune Encephalitis

Autoimmune encephalitis is a group of encephalitis syndromes that cause altered mentality, memory decline, or seizures in association with the presence of serum and cerebrospinal fluid (CSF) autoantibodies (auto-Abs). An early diagnosis enables early treatments. The detection of auto-Abs is a confirmatory diagnosis. Tissue-based assay, cell-based immunoassay, and immunoblotting are used to detect various autoantibodies. The CSF test for the presence of antibodies is important because it is more sensitive and reflects disease activity in many autoimmune encephalitis, although antibody tests can be negative even in the presence of autoimmune encephalitis. EEG is often abnormal, but nonspecific. A unilateral or bilateral medial temporal T2 high signal is a common finding in MRI. Fludeoxyglucose-positron emission tomography is sometimes useful for diagnosis in patients with normal MRI.

Prevalence of serum anti-neuronal autoantibodies in patients admitted to acute psychiatric care

BACKGROUND

Autoimmune encephalitis associated with anti-neuronal antibodies may be challenging to distinguish from primary psychiatric disorders. The significance of anti-neuronal antibodies in psychiatric patients without clear evidence of autoimmune encephalitis is unknown. We investigated the serum prevalence of six anti-neuronal autoantibodies in a cohort of unselected patients admitted to acute psychiatric care.

METHOD

Serum was drawn from 925 patients admitted to acute psychiatric in-patient care. Psychiatric diagnoses were set according to International Classification of Diseases (ICD)-10 criteria. Antibody analysis was performed with an indirect immunofluorescence test for N-methyl d-aspartate receptor (NMDAR) antibodies and five other anti-neuronal autoantibodies of the immunoglobulin (Ig) classes IgA, IgG and IgM isotype.

RESULTS

Anti-neuronal autoantibodies were found in 11.6% of patients: NMDAR antibodies in 7.6%, contactin-associated protein-like 2 (CASPR2) antibodies in 2.5%, glutamic acid decarboxylase-65 (GAD65) antibodies in 1.9%, and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antibodies in 0.1%. Leucine-rich glioma-inactivated protein-1 (LGI1) and γ-aminobutyric acid B (GABAB) receptor antibodies were not detected. NMDAR antibodies of class IgG were present in five patients only (0.5%). NMDAR antibodies of all Ig classes were equally prevalent in patients with and without psychosis. There were no significant differences in antibody prevalence in the different diagnostic categories, except for a higher odds ratio of being NMDAR antibody positive for patients without a specific psychiatric diagnosis.

CONCLUSIONS

NMDAR IgG autoantibodies, which are known to be strongly associated with anti-NMDAR encephalitis, were rarely found. CASPR2 and GAD65 antibodies were more frequently encountered in the present study than previously reported. Further research on the clinical significance of anti-neuronal autoantibodies in patients with acute psychiatric symptoms is needed.

Multiparametric serological testing in autoimmune encephalitis using computer-aided immunofluorescence microscopy (CAIFM)

Autoantibodies against neuronal cell surface antigens are tightly associated with immunotherapy-responsive autoimmune encephalitis, and a considerable number of corresponding autoantigens has been identified in recent years. Most patients initially present with overlapping symptoms, and a broad range of autoantibodies has to be considered to establish the correct diagnosis and initiate treatment as soon as possible to prevent irreversible and sometimes even life-threatening damage to the brain. Recombinant cell-based immunofluorescence allows to authentically present fragile membrane-associated surface antigens and, in combination with multiparametric analysis in the form of biochip mosaics, has turned out to be highly beneficial for parallel and prompt determination of anti-neuronal autoantibodies and comprehensive differential diagnostics. For the evaluation of recombinant cell-based IIFT, a semi-automated novel function was introduced into an established platform for computer-aided immunofluorescence microscopy. The system facilitates the microscopic analysis of the tests and supports the laboratory personnel in the rapid issuance of diagnostic findings, which is of major importance for autoimmune encephalitis patients since timely initiation of treatment may lead to their full recovery.

Autoantibodies against glutamate receptor δ2 after allogenic stem cell transplantation

Objective:

To report on a Caucasian patient who developed steroid-responsive transverse myelitis, graft vs host disease of the gut, and anti-GluRδ2 after allogenic stem cell transplantation.

Methods:

Histoimmunoprecipitation (HIP) with the patient's serum and cryosections of rat and porcine cerebellum followed by mass spectrometry was used to identify the autoantigen. Correct identification was verified by indirect immunofluorescence using recombinant GluRδ2 expressed in HEK293 cells.

Results:

The patient's serum produced a granular staining of the cerebellar molecular layer (immunoglobulin G1 and immunoglobulin G3; endpoint titer: 1:1,000) but did not react with other CNS tissues or 28 established recombinant neural autoantigens. HIP revealed a unique protein band at ∼110 kDa that was identified as GluRδ2. The patient's serum also stained GluRδ2 transfected but not mock-transfected HEK293 cells. Control sera from 38 patients with multiple sclerosis, 85 patients with other neural autoantibodies, and 205 healthy blood donors were negative for anti-GluRδ2. Preadsorption with lysate from HEK293-GluRδ2 neutralized the patient's tissue reaction whereas control lysate had no effect. In addition to anti-GluRδ2, the patient's serum contained immunoglobulin G autoantibodies against the pancreatic glycoprotein CUZD1, which are known to be markers of Crohn disease.

Conclusions:

In the present case, the development of anti-GluRδ2 was associated with transverse myelitis, which was supposedly triggered by the stem cell transplantation. Similar to encephalitis in conjunction with anti-GluRδ2 reported in a few Japanese patients, the patient's neurologic symptoms ameliorated after steroid therapy.

Detection and Characterization of Autoantibodies to Neuronal Cell-Surface Antigens in the Central Nervous System

Autoimmune encephalitis (AIE) is a group of disorders in which autoantibodies directed at antigens located on the plasma membrane of neurons induce severe neurological symptoms. In contrast to classical paraneoplastic disorders, AIE patients respond well to immunotherapy. The detection of neuronal surface autoantibodies in patients' serum or CSF therefore has serious consequences for the patients' treatment and follow-up and requires the availability of sensitive and specific diagnostic tests. This mini-review provides a guideline for both diagnostic and research laboratories that work on the detection of known surface autoantibodies and/or the identification of novel surface antigens. We discuss the strengths and pitfalls of different techniques for anti-neuronal antibody detection: (1) Immunohistochemistry (IHC) and immunofluorescence on rat/primate brain sections; (2) Immunocytochemistry (ICC) of living cultured hippocampal neurons; and (3) Cell Based Assay (CBA). In addition, we discuss the use of immunoprecipitation and mass spectrometry analysis for the detection of novel neuronal surface antigens, which is a crucial step in further disease classification and the development of novel CBAs.

Detection methods for neural autoantibodies

Antibodies are part of the adaptive immune response that provides protection against microorganisms. In rare instances individuals can develop antibodies that bind to normal central nervous system structures. These antibodies have been classified into two groups depending on the subcellular location of their target antigens. Biomarker antibodies bind to cytosolic or nuclear targets. They do not impact on the normal function of the cell, but are most often paraneoplastic biomarkers that may suggest screening for different cancers. The second, more recently discovered group of antibodies recognize the three-dimensional structure of native proteins that are accessible on the cell surface. Understanding of this important difference is reflected in the nature of assays used to detect antibodies in these two groups. Western blots and, more recently, line blots, both of which use linear, denatured targets, are used to detect antibodies to intracellular targets. Newer assays have been developed that maintain the native structure of protein targets to permit detection of antibodies that recognize extracellular targets. In this chapter we describe the methods used to detect both antibody types, and discuss assay cut-offs, sample handling, and which biologic fluid to test.

Neurological disorders in patients with bullous pemphigoid: clinical and experimental investigations

BACKGROUND

Previous studies have shown that patients with bullous pemphigoid (BP) are more likely to have neurological diseases (ND).

OBJECTIVES

To compare clinical findings in BP patients with and without ND and to investigate BP180 autoantibody binding in different neuronal tissues of mammalians.

METHODS

Our database was searched for clinical findings of in-patients with the definitive diagnosis of BP. Moreover, brain tissue of mammalians was treated with serum of BP patients with elevated BP180 autoantibodies using biochip mosaics.

RESULTS

Of 85/161 (52.8%) patients had a history of at least one ND (BP+ND). BP180 (P = 0.018), eosinophils (P = 0.043) and patients' accommodation in nursing homes (P < 0.0001) remained in the logistic regression model as significant independent predictors for the presence of ND in patients with BP. Subgroup analysis of community-dwelling BP patients revealed 25/93 (26.9%) patients with ND. In this population, the presence of ND also significantly correlated with BP180 (r = 0.26; P = 0.0003) and eosinophils (r = 0.19; P = 0.0087). In the animal model, no BP180-specific immunofluorescence could be detected.

CONCLUSIONS

Our data support results of previous studies detecting significantly increased frequency of ND in BP patients. We have shown that raised BP180 titres and blood eosinophils are independent predictors for the presence of ND in BP patients. However, our experimental data do not support previous results indicating that specific binding of BP180 antibodies in neuronal tissue plays a pathogenetic role in ND.