New autoantibody mediated disorders of the central nervous system

Interest of rare autoantibodies in autoimmune encephalitis and paraneoplastic neurological syndromes: the utility (or futility) of rare antibody discovery

PURPOSE OF REVIEW

The increasing recognition and diagnosis of autoimmune encephalitis (AE) and paraneoplastic neurological syndromes (PNS) is partly due to neural autoantibody testing and discovery. The past two decades witnessed an exponential growth in the number of identified neural antibodies. This review aims to summarize recent rare antibody discoveries in the context of central nervous system (CNS) autoimmunity and evaluate the ongoing debate about their utility.

RECENT FINDINGS

In the last 5 years alone 15 novel neural autoantibody specificities were identified. These include rare neural antibody biomarkers of autoimmune encephalitis, cerebellar ataxia or other movement disorders, including multifocal presentations.

SUMMARY

Although the clinical applications of these rare antibody discoveries may be limited by the low number of positive cases, they still provide important diagnostic, prognostic, and therapeutic insights.

Autoimmune Epilepsy - Novel Multidisciplinary Analysis, Discoveries and Insights

Epilepsy affects ~50 million people. In ~30% of patients the etiology is unknown, and ~30% are unresponsive to anti-epileptic drugs. Intractable epilepsy often leads to multiple seizures daily or weekly, lasting for years, and accompanied by cognitive, behavioral, and psychiatric problems. This multidisciplinary scientific (not clinical) 'Perspective' article discusses Autoimmune Epilepsy from immunological, neurological and basic-science angles. The article includes summaries and novel discoveries, ideas, insights and recommendations. We summarize the characteristic features of the respective antigens, and the pathological activity in vitro and in animal models of autoimmune antibodies to: Glutamate/AMPA-GluR3, Glutamate/NMDA-NR1, Glutamate/NMDA-NR2, GAD-65, GABA-R, GLY-R, VGKC, LGI1, CASPR2, and β2 GP1, found in subpopulations of epilepsy patients. Glutamate receptor antibodies: AMPA-GluR3B peptide antibodies, seem so far as the most exclusive and pathogenic autoimmune antibodies in Autoimmune Epilepsy. They kill neural cells by three mechanisms: excitotoxicity, Reactive-Oxygen-Species, and complement-fixation, and induce and/or facilitate brain damage, seizures, and behavioral impairments. In this article we raise and discuss many more topics and new insights related to Autoimmune Epilepsy. 1. Few autoimmune antibodies tilt the balance between excitatory Glutamate and inhibitory GABA, thereby promoting neuropathology and epilepsy; 2. Many autoantigens are synaptic, and have extracellular domains. These features increase the likelihood of autoimmunity against them, and the ease with which autoimmune antibodies can reach and harm these self-proteins. 3. Several autoantigens have 'frenetic character'- undergoing dynamic changes that can increase their antigenicity; 4. The mRNAs of the autoantigens are widely expressed in multiple organs outside the brain. If translated by default to proteins, broad spectrum detrimental autoimmunity is expected; 5. The autoimmunity can precede seizures, cause them, and be detrimental whether primary or epiphenomenon; 6. Some autoimmune antibodies induce, and associate with, cognitive, behavioral and psychiatric impairments; 7. There are evidences for epitope spreading in Autoimmune Epilepsy; 8. T cells have different 'faces' in the brain, and in Autoimmune Epilepsy: Normal T cells are needed for the healthy brain. Normal T cells are damaged by autoimmune antibodies to Glutamate/AMPA GluR3, which they express, and maybe by additional autoantibodies to: Dopamine-R, GABA-R, Ach-R, Serotonin-R, and Adrenergic-R, present in various neurological diseases (summarized herein), since T cells express all these Neurotransmitter receptors. However, autoimmune and/or cytotoxic T cells damage the brain; 9. The HLA molecules are important for normal brain function. The HLA haplotype can confer susceptibility or protection from Autoimmune Epilepsy; 10. There are several therapeutic strategies for Autoimmune Epilepsy.

Establishing a conceptual framework of the impact of placental malaria on infant neurodevelopment

A novel conceptual framework to describe the relationship between placental malaria and adverse infant neurodevelopmental outcomes is proposed. This conceptual framework includes three distinct stages: (1) maternal and environmental risk factors for the development of placental malaria; (2) placental pathology and inflammation associated with placental malaria infection; and (3) postnatal impacts of placental malaria. The direct, indirect, and bidirectional effects of these risk factors on infant neurodevelopment across the three stages were critically examined. These factors ultimately culminate in an infant phenotype that not only leads to adverse birth outcomes, but also to increased risks of neurological, cognitive, and behavioural deficits that may impact the quality of life in this high-risk population. Multiple risk factors were identified in this conceptual framework; nonetheless, based on current evidence, a key knowledge gap is the uncertainty regarding which are the most important and how exactly they interact.

Reduction of expression of IL-18, IL-1β genes in the articular joint by sumac fruit extract (Rhus coriaria L.)

BACKGROUND

Osteoarthritis is the most common malignant disease in the world. The disease is caused by changes in the metabolism, the structure and function of multiple joints, and joint tissues. Sumac is one of the indigenous plants of Iran and has traditionally been used as a spice in Iran. The aim of this study was to investigate the reduction of expression of IL-18, IL-1β genes in the articular joint by sumac fruit extract (Rhus coriaria L.).

METHODS

The alcoholic extract of sumac fruit (E.E.R.C.L) was prepared from the Genetic Reserve Center. Bleeding was used to provide synoviocyte cells from the joint and fluid of the anatomical metacarpal limb of the 8-month-old Holstein healthy calf without any signs of inflammation. Using cell-hemocytometer count, their viability was evaluated by trypan blue and after lipopolysaccharide (LPS) proliferation and injection to enhance the level of cytokines. After isolating the RNA and preparing the cDNA, RT-PCR and PCR were performed and then, using the real-time PCR method, the expression of the desired genes was investigated.

RESULTS

In this study, after the expression of IL-18 cytokines, IL-1β increased to 100%, and following the treatment with alcoholic extract, the reduction of expression of these cytokines was 33.61% and 29.01%, respectively. The results of anti-inflammatory effects showed that the alcoholic extract of sumac reduced the IL-1β, IL-18 expression in LPS-stimulated cells.

CONCLUSION

Sumac fruit extract can be an effective medication for reducing pain.

The Utility of FDG-PET/CT in Clinically Suspected Paraneoplastic Neurological Syndrome: A Literature Review and Retrospective Case Series

Paraneoplastic neurological syndrome (PNS) describes a spectrum of rare, heterogeneous neurological conditions associated with an underlying malignancy. Diagnosis of PNS is inherently difficult, with frequent misdiagnosis and delay. The literature suggests an underlying immune-mediated pathophysiology, and patients are usually tested for the presence of onconeural antibodies. With direct tumor therapy being the most effective method of stabilizing patients, there is a strong emphasis on detecting underlying tumors. The sensitivity of conventional CT imaging is often inadequate in such patients. While FDG-PET imaging has already been shown to be effective at detecting these tumors, FDG-PET/CT, combining both structural and functional imaging in a single study, is a more recent technique. To study the utility of FDG-PET/CT, we conducted a systematic literature review and a retrospective study. We identified 41 patients who underwent imaging for clinically suspected PNS at the regional PET-CT and neurosciences center based at the Royal Preston Hospital between 2007 and 2014 and compared the results to conventional investigations. Five patients had FDG-PET/CT tracer avidity suspicious of malignant disease, and four of these were subsequently diagnosed with cancer. Sensitivity and specificity were calculated to be 100 and 97.3%, respectively, with positive predictive value 80% and negative predictive value 100%. This compares to a sensitivity and specificity of 50 and 100%, respectively, for CT and 50 and 89%, respectively, for onconeural antibodies. These findings are in line with previous studies and support the diagnostic accuracy of FDG-PET/CT for the detection of underlying malignancy.

Human traumatic brain injury induces autoantibody response against glial fibrillary acidic protein and its breakdown products

The role of systemic autoimmunity in human traumatic brain injury (TBI) and other forms of brain injuries is recognized but not well understood. In this study, a systematic investigation was performed to identify serum autoantibody responses to brain-specific proteins after TBI in humans. TBI autoantibodies showed predominant immunoreactivity against a cluster of bands from 38-50 kDa on human brain immunoblots, which were identified as GFAP and GFAP breakdown products. GFAP autoantibody levels increased by 7 days after injury, and were of the IgG subtype predominantly. Results from in vitro tests and rat TBI experiments also indicated that calpain was responsible for removing the amino and carboxyl termini of GFAP to yield a 38 kDa fragment. Additionally, TBI autoantibody staining co-localized with GFAP in injured rat brain and in primary rat astrocytes. These results suggest that GFAP breakdown products persist within degenerating astrocytes in the brain. Anti-GFAP autoantibody also can enter living astroglia cells in culture and its presence appears to compromise glial cell health. TBI patients showed an average 3.77 fold increase in anti-GFAP autoantibody levels from early (0-1 days) to late (7-10 days) times post injury. Changes in autoantibody levels were negatively correlated with outcome as measured by GOS-E score at 6 months, suggesting that TBI patients with greater anti-GFAP immune-responses had worse outcomes. Due to the long lasting nature of IgG, a test to detect anti-GFAP autoantibodies is likely to prolong the temporal window for assessment of brain damage in human patients.

Inflammatory pathways of seizure disorders

Epilepsy refers to a cluster of neurological diseases characterized by seizures. Although many forms of epilepsy have a well-defined immune etiology, in other forms of epilepsy an altered immune response is only suspected. In general, the hypothesis that inflammation contributes to seizures is supported by experimental results. Additionally, antiepileptic maneuvers may act as immunomodulators and anti-inflammatory therapies can treat seizures. Triggers of seizure include a bidirectional communication between the nervous system and organs of immunity. Thus, a crucial cellular interface protecting from immunological seizures is the blood-brain barrier (BBB). Here, we summarize recent advances in the understanding and treatment of epileptic seizures that derive from a non-neurocentric viewpoint and suggest key avenues for future research.

Intracellular and circulating neuronal antinuclear antibodies in human epilepsy

There are overwhelming data supporting the inflammatory origin of some epilepsies (e.g., Rasmussen's encephalitis and limbic encephalitis). Inflammatory epilepsies with an autoimmune component are characterized by autoantibodies against membrane-bound, intracellular or secreted proteins (e.g., voltage gated potassium channels). Comparably, little is known regarding autoantibodies targeting nuclear antigen. We tested the hypothesis that in addition to known epilepsy-related autoantigens, the human brain tissue and serum from patients with epilepsy contain autoantibodies recognizing nuclear targets. We also determined the specific nuclear proteins acting as autoantigen in patients with epilepsy. Brain tissue samples were obtained from patients undergoing brain resections to treat refractory seizures, from the brain with arteriovenous malformations or from post-mortem multiple sclerosis brain. Patients with epilepsy had no known history of autoimmune disease and were not diagnosed with autoimmune epilepsy. Tissue was processed for immunohistochemical staining. We also obtained subcellular fractions to extract intracellular IgGs. After separating nuclear antibody-antigen complexes, the purified autoantigen was analyzed by mass spectrometry. Western blots using autoantigen or total histones were probed to detect the presence of antinuclear antibodies in the serum of patients with epilepsy. Additionally, HEp-2 assays and antinuclear antibody ELISA were used to detect the staining pattern and specific presence of antinuclear antibodies in the serum of patients with epilepsy. Brain regions from patients with epilepsy characterized by blood-brain barrier disruption (visualized by extravasated albumin) contained extravasated IgGs. Intracellular antibodies were found in epilepsy (n=13/13) but not in multiple sclerosis brain (n=4/4). In the brain from patients with epilepsy, neurons displayed higher levels of nuclear IgGs compared to glia. IgG colocalized with extravasated albumin. All subcellular fractions from brain resections of patients with epilepsy contained extravasated IgGs (n=10/10), but epileptogenic cortex, where seizures originated from, displayed the highest levels of chromatin-bound IgGs. In the nuclear IgG pool, anti-histone autoantibodies were identified by two independent immunodetection methods. HEp-2 assay and ELISA confirmed the presence of anti-histone (n=5/8) and anti-chromatin antibodies in the serum from patients with epilepsy. We developed a multi-step approach to unmask autoantigens in the brain and sera of patients with epilepsy. This approach revealed antigen-bound antinuclear antibodies in neurons and free antinuclear IgGs in the serum of patients with epilepsy. Conditions with blood-brain barrier disruption but not seizures, were characterized by extravasated but not chromatin-bound IgGs. Our results show that the pool of intracellular IgG in the brain of patients with epilepsy consists of nucleus-specific autoantibodies targeting chromatin and histones. Seizures may be the trigger of neuronal uptake of antinuclear antibodies.

Central nervous system neuronal surface antibody associated syndromes: review and guidelines for recognition

The concept of antibody mediated CNS disorders is relatively recent. The classical CNS paraneoplastic neurological syndromes are thought to be T cell mediated, and the onconeural antibodies merely biomarkers for the presence of the tumour. Thus it was thought that antibodies rarely, if ever, cause CNS disease. Over the past 10 years, identification of autoimmune forms of encephalitis with antibodies against neuronal surface antigens, particularly the voltage gated potassium channel complex proteins or the glutamate N-methyl-D-aspartate receptor, have shown that CNS disorders, often without associated tumours, can be antibody mediated and benefit from immunomodulatory therapies. The clinical spectrum of these diseases is not yet fully explored, there may be others yet to be discovered and some types of more common disorders (eg, epilepsy or psychosis) may prove to have an autoimmune basis. Here, the known conditions associated with neuronal surface antibodies are briefly reviewed, some general aspects of these syndromes are considered and guidelines that could help in the recognition of further disorders are suggested.

Low serum IgA and increased expression of CD23 on B lymphocytes in peripheral blood in children with regressive autism aged 3-6 years old

INTRODUCTION

Immune system dysfunction is considered to be one of many medical disorders found in children with autism. The primary objective of the study was to assess if blood tests reflecting humoral immunity (IgA, IgG, IgM, IgE) are useful in identifying children with regressive autism. The secondary objective was to evaluate a part of the cellular arm of immunity (CD4/CD25 Tregs, CD4/CD23 cells) in those children.

MATERIAL AND METHODS

Using a clinical case-control design, the systemic levels of immunoglobulins and lymphocyte subpopulations analysed by flow cytometry were compared in children aged 3-6 years old with a new diagnosis of regressive autism (n = 24; mean age: 4.25 ±1.70 years; male 23/24) and in sex- and age-matched healthy children (n = 24; aged 4.25 ±2.20 years; male 23/24).

RESULTS

The humoral immunity profile, described by three binary variables, IgA < 0.97 g/l, IgE > 36 IU/ml, and IgG > 6.3 g/l, with a sensitivity of 79% and a specificity of 83% (p < 0.0001), was able to identify children with autism. The highest risk of autism diagnosis was associated with IgA < 0.97g/l (OR - 23.0; p < 0.001). A higher number of CD19/CD23 was found in children diagnosed with autism than in the control group (36.82 ±6.72% vs. 18.20 ±3.95%; p < 0.02). No correlation between the number of CD23-positive cells and serum IgE levels was observed.

CONCLUSIONS

A subtle shift of serum immunoglobulins consisting of low-normal IgA and B cell activation expressed by an increase of CD23-positive cells may characterize children with regressive autism aged 3-6 years old.

Late onset of cerebellar abiotrophy in a boxer dog

Cerebellar abiotrophy is a degenerative disorder of the central nervous system and has been reported in humans and animals. This case report documents clinical, histopathological, and immunohistochemical findings of cerebellar abiotrophy in an adult Boxer dog. A 3.5-year-old, female, tan Boxer dog presented with a six-week history of left-sided head tilt. Neurological examination and additional diagnostics during her three subsequent visits over 4.5 months revealed worsening of neurological signs including marked head pressing, severe proprioceptive deficits in all the four limbs, loss of menace response and palpebral reflex in the left eye, and a gradual seizure lasting one hour at her last visit. Based on the immunohistochemical staining for glial fibrillary acidic protein and histopathological examination of cerebellum, cerebellar cortical abiotrophy was diagnosed. This is the first reported case of cerebellar abiotrophy in a Boxer dog to our knowledge.

Transient life-threatening cerebral edema in a patient with systemic lupus erythematosus

Central nervous system symptoms occur in a substantial portion of patients with systemic lupus erythematosus. However, coma is a rare presentation and is usually secondary to complications such as subarachnoid hemorrhage, seizure, or ischemia. Here, we present a 49-year-old woman with lupus erythematosus and a history of recurrent aseptic meningitis and mild subarachnoid hemorrhage who presented with altered mental status and lethargy that progressed rapidly over hours to the herniation syndrome of coma, extensor posturing, and unilateral pupillary dilation. Spinal fluid showed massive protein elevation (>1600), and head computed tomography revealed global cerebral edema. The clinical and radiologic findings rapidly reversed with intravenous corticosteroids and mannitol within 24 hours, and her mental status improved to baseline. Her course was complicated by 2 episodes of recurrent encephalopathy when corticosteroids were tapered; these resolved after resuming high dosing. Because of ongoing pancytopenia, chemotherapy immunosuppression was delayed, and instead she received intravenous immunoglobulin with improvement in the pancytopenia. She remained cognitively intact during subsequent corticosteroid tapering. Rapid development of coma in lupus patients may be due to a primary process of the disease impacting blood brain barrier integrity. Although rare, this potentially fatal complication may be reversible with acute corticosteroid administration.

A 70-year-old male with peripheral neuropathy, ataxia and antigliadin antibodies shows improvement in neuropathy, but not ataxia, after intravenous immunoglobulin and gluten-free diet

This is a case of a 70-year-old man with severe peripheral neuropathy, type 2 diabetes and progressively worsening cerebellar ataxia. He was found to have circulating antigliadin and antireticulin antibodies compatible with celiac disease in the absence of intestinal pathology. The peripheral neuropathy improved with a gluten-free diet, antioxidants and intravenous immunoglobulin, whereas the ataxia did not. This case illustrates the need to test for celiac disease in patients with idiopathic ataxia and peripheral neuropathy and the need for alternative therapies for ataxia.

AUNX1, a novel locus responsible for X linked recessive auditory and peripheral neuropathy, maps to Xq23-27.3

BACKGROUND

We report here the genetic characterisation of a large five generation Chinese family with the phenotypic features of auditory neuropathy and progressive peripheral sensory neuropathy, and the genetic feature of X linked recessive inheritance. Disease onset was at adolescence (at an average age of 13 years for six affected subjects). The degree of hearing impairment varied from mild to severe, with decreased otoacoustic emissions; auditory brainstem responses were lacking from onset.

METHODS

Two-point and multipoint model based linkage analysis using the MILNK and LINKMAP programs of the FASTLINK software package produced maximum two-point and multipoint LOD scores of 2.41 and 2.41, respectively.

RESULTS

These findings define a novel X linked auditory neuropathy locus/region (AUNX1, Xq23-q27.3). This region is 42.09 cM long and contains a 28.07 Mb region with flanking markers DXS1220 and DXS8084, according to the Rutgers Combined Linkage-Physical Map, build 35. However, mutation screen of the candidate gene SLC6A14 within the region did not identify the causative genetic determinant for this large Chinese family.

Anti-ganglioside antibodies in coeliac disease with neurological disorders

BACKGROUND

Anti-ganglioside antibodies have been described in sera of coeliac patients with peripheral neuropathy and cerebellar ataxia.

AIMS

To investigate the correlation between anti-ganglioside antibodies and neurological involvement in coeliac disease before and after gluten-free diet.

PATIENTS AND METHODS

Twenty-two untreated coeliac patients with neurological dysfunction and 30 untreated coeliacs without neurological dysfunction, 20 patients with neurological disorders, 50 autoimmune disease and 20 blood donors were tested for anti-GM1, anti-GD1b and anti-GQ1b IgG and IgM antibodies by enzyme-linked immunosorbent assay.

RESULTS

IgG antibodies to at least one of the three antigens tested were positive in 64% of coeliac patients with neurological symptoms compared to 30% of coeliacs without neurological dysfunction (P=0.02), 50% of patients with neurological disorders (P=ns), 20% with autoimmune diseases (P=0.003) and none of blood donors (P=0.0001). A strict gluten-free diet determined anti-ganglioside antibody disappearance in about half of coeliacs.

CONCLUSIONS

A significant correlation between anti-ganglioside antibodies and neurological disorders in patients with an underlying coeliac disease has been found. Anti-ganglioside antibodies may represent a new immunological marker to identify neurological impairment in patients with coeliac disease.

Unveiling the enigma of the CNS as a B-cell fostering environment

This Opinion deals with the apparent paradox between the 'immune privileged' status of the central nervous system (CNS) and its propensity to act as a B-cell fostering environment in a variety of neurological disorders. Evidence will be reviewed that: (i) molecules regulating B-cell homing and survival are produced in the CNS, (ii) in different neuroinflammatory diseases, B cells can undergo a local recapitulation of the differentiation occurring in secondary lymphoid organs and (iii) ectopic lymphoid follicles develop in the meninges of multiple sclerosis (MS) patients.

Elevated immunoglobulin levels in the cerebrospinal fluid from lupus-prone mice

The systemic autoimmune disease lupus erythematosus (SLE) is frequently accompanied by neuropsychiatric manifestations and brain lesions of unknown etiology. The MRL-lpr mice show behavioral dysfunction concurrent with progression of a lupus-like disease, thus providing a valuable model in understanding the pathogenesis of autoimmunity-induced CNS damage. Profound neurodegeneration in the limbic system of MRL-lpr mice is associated with cytotoxicity of their cerebrospinal fluid (CSF) to mature and immature neurons. We have recently shown that IgG-rich CSF fraction largely accounts for this effect. The present study examines IgG levels in serum and CSF, as well as the permeability of the blood-brain barrier in mice that differ in immune status, age, and brain morphology. In comparison to young MRL-lpr mice and age-matched congenic controls, a significant elevation of IgG and albumin levels were detected in the CSF of aged autoimmune MRL-lpr mice. Two-dimensional gel electrophoresis and MALDI-TOF MS confirmed elevation in IgG heavy and Ig light chain isoforms in the CSF. Increased permeability of the blood-brain barrier correlated with neurodegeneration (as revealed by Fluoro Jade B staining) in periventricular areas. Although the source and specificity of neuropathogenic antibodies remain to be determined, these results support the hypothesis that a breached blood-brain barrier and IgG molecules are involved in the etiology of CNS damage during SLE-like disease.

Anti-glutamic acid decarboxylase antibodies in a patient with systemic lupus erythematosus and fibromyalgia symptoms

We report the case of a 29-year old female nurse with a five-year history of systemic lupus erythematosus (SLE) involving multiple systems and on chronic prednisone therapy. This patient has a coexisting diagnosis of fibromyalgia fulfilling ACR criteria. A recent deterioration in her level of functioning in addition to a flare of her inflammatory disease led to further evaluation. During the course of investigation an anti-glutamic acid decarboxylase antibody was found to be present and significantly elevated. A therapeutic trial of baclofen did result in improvement of her subjective myalgias. We raise the possibility of an autoimmune contribution to myalgic symptoms in a portion of SLE patients.

Behavioral heterogeneity in an animal model of neuropsychiatric lupus

BACKGROUND

Various psychiatric manifestations of unknown etiology are common in systemic autoimmune disease lupus erythematosus (SLE). Profound heterogeneity at clinical and neuropathological levels suggests distinct subpopulations of SLE patients and multiple mechanisms in the pathogenesis of aberrant behavior. Using inbred mice prone to SLE-like condition, we presently examine whether subpopulations of diseased mice can be identified on the basis of their behavioral performance.

METHODS

Hierarchical cluster analysis was used to classify 105 MRL-lpr males into clusters. Multivariate analysis of variance (MANOVA) and discriminant function analysis were used to detect overall differences and identify discriminative variables.

RESULTS

Cluster 1 was characterized by blunted responsiveness to palatable stimulation, as well as increased spleen mass and serum levels of interleukin-1. Cluster 2 comprised of animals with reduced ambulation speed and enlarged spleen. Mice from cluster 3 showed profound dilatation of brain ventricles, reduced brain mass, impaired nutrition and performance in task reflective of emotional reactivity.

CONCLUSIONS

Present results suggest that systemic autoimmunity compromises brain function via non-Mendelian mechanisms. Although neuroactive cytokines may impair reward systems, brain atrophy seems to underlie deficits in ingestive behavior and emotional reactivity. This study supports the hypothesis that multiple neuroimmunological pathways are involved in the etiology of aberrant behavior during SLE-like disease.