Antiglial Cell Autoantibodies and Childhood Epilepsy: A Case Report

An unusual case of coma related to glutamate receptor 3 (GluR3) auto-antibodies after a traumatic spinal cord injury: Clinical and pathological aspects

We report the case of a 28-year-old patient with a history of post-traumatic epilepsy who, following a spinal cord injury and the onset of nosocomial infection, went into a deep coma. A brain MRI revealed non-specific findings, anti-Glutamate Receptor 3 (GluR3) auto-antibodies were detected in the liquor, and the patient's serum and immunomodulatory therapy proved ineffective. Autopsy and histological investigations led to the diagnosis of autoimmune encephalitis. This case highlights the diagnostic difficulties of a rare and still poorly researched disease and the possible role that traumatic and infectious episodes may play in the progression or acceleration of an immune response. As for patients with unexplained encephalitis, tests for autoantibodies against GluR3 in cerebrospinal fluid and serum should be considered. Forensic pathologists should be aware of encephalitis and epilepsies and that complete post-mortem investigations are required in such cases.

Glutamate receptor antibodies in neurological diseases: anti-AMPA-GluR3 antibodies, anti-NMDA-NR1 antibodies, anti-NMDA-NR2A/B antibodies, anti-mGluR1 antibodies or anti-mGluR5 antibodies are present in subpopulations of patients with either: epilepsy, encephalitis, cerebellar ataxia, systemic lupus erythematosus (SLE) and neuropsychiatric SLE, Sjogren's syndrome, schizophrenia, mania or stroke. These autoimmune anti-glutamate receptor antibodies can bind neurons in few brain regions, activate glutamate receptors, decrease glutamate receptor's expression, impair glutamate-induced signaling and function, activate blood brain barrier endothelial cells, kill neurons, damage the brain, induce behavioral/psychiatric/cognitive abnormalities and ataxia in animal models, and can be removed or silenced in some patients by immunotherapy

Glutamate is the major excitatory neurotransmitter of the Central Nervous System (CNS), and it is crucially needed for numerous key neuronal functions. Yet, excess glutamate causes massive neuronal death and brain damage by excitotoxicity--detrimental over activation of glutamate receptors. Glutamate-mediated excitotoxicity is the main pathological process taking place in many types of acute and chronic CNS diseases and injuries. In recent years, it became clear that not only excess glutamate can cause massive brain damage, but that several types of anti-glutamate receptor antibodies, that are present in the serum and CSF of subpopulations of patients with a kaleidoscope of human neurological diseases, can undoubtedly do so too, by inducing several very potent pathological effects in the CNS. Collectively, the family of anti-glutamate receptor autoimmune antibodies seem to be the most widespread, potent, dangerous and interesting anti-brain autoimmune antibodies discovered up to now. This impression stems from taking together the presence of various types of anti-glutamate receptor antibodies in a kaleidoscope of human neurological and autoimmune diseases, their high levels in the CNS due to intrathecal production, their multiple pathological effects in the brain, and the unique and diverse mechanisms of action by which they can affect glutamate receptors, signaling and effects, and subsequently impair neuronal signaling and induce brain damage. The two main families of autoimmune anti-glutamate receptor antibodies that were already found in patients with neurological and/or autoimmune diseases, and that were already shown to be detrimental to the CNS, include the antibodies directed against ionotorpic glutamate receptors: the anti-AMPA-GluR3 antibodies, anti-NMDA-NR1 antibodies and anti-NMDA-NR2 antibodies, and the antibodies directed against Metabotropic glutamate receptors: the anti-mGluR1 antibodies and the anti-mGluR5 antibodies. Each type of these anti-glutamate receptor antibodies is discussed separately in this very comprehensive review, with regards to: the human diseases in which these anti-glutamate receptor antibodies were found thus far, their presence and production in the nervous system, their association with various psychiatric/behavioral/cognitive/motor impairments, their possible association with certain infectious organisms, their detrimental effects in vitro as well as in vivo in animal models in mice, rats or rabbits, and their diverse and unique mechanisms of action. The review also covers the very encouraging positive responses to immunotherapy of some patients that have either of the above-mentioned anti-glutamate receptor antibodies, and that suffer from various neurological diseases/problems. All the above are also summarized in the review's five schematic and useful figures, for each type of anti-glutamate receptor antibodies separately. The review ends with a summary of all the main findings, and with recommended guidelines for diagnosis, therapy, drug design and future investigations. In the nut shell, the human studies, the in vitro studies, as well as the in vivo studies in animal models in mice, rats and rabbit revealed the following findings regarding the five different types of anti-glutamate receptor antibodies: (1) Anti-AMPA-GluR3B antibodies are present in ~25-30% of patients with different types of Epilepsy. When these anti-glutamate receptor antibodies (or other types of autoimmune antibodies) are found in Epilepsy patients, and when these autoimmune antibodies are suspected to induce or aggravate the seizures and/or the cognitive/psychiatric/behavioral impairments that sometimes accompany the seizures, the Epilepsy is called 'Autoimmune Epilepsy'. In some patients with 'Autoimmune Epilepsy' the anti-AMPA-GluR3B antibodies associate significantly with psychiatric/cognitive/behavior abnormalities. In vitro and/or in animal models, the anti-AMPA-GluR3B antibodies by themselves induce many pathological effects: they activate glutamate/AMPA receptors, kill neurons by 'Excitotoxicity', and/or by complement activation modulated by complement regulatory proteins, cause multiple brain damage, aggravate chemoconvulsant-induced seizures, and also induce behavioral/motor impairments. Some patients with 'Autoimmune Epilepsy' that have anti-AMPA-GluR3B antibodies respond well (although sometimes transiently) to immunotherapy, and thanks to that have reduced seizures and overall improved neurological functions. (2) Anti-NMDA-NR1 antibodies are present in patients with autoimmune 'Anti-NMDA-receptor Encephalitis'. In humans, in animal models and in vitro the anti-NMDA-NR1 antibodies can be very pathogenic since they can cause a pronounced decrease of surface NMDA receptors expressed in hippocampal neurons, and also decrease the cluster density and synaptic localization of the NMDA receptors. The anti-NMDA-NR1 antibodies induce these effects by crosslinking and internalization of the NMDA receptors. Such changes can impair glutamate signaling via the NMDA receptors and lead to various neuronal/behavior/cognitive/psychiatric abnormalities. Anti-NMDA-NR1 antibodies are frequently present in high levels in the CSF of the patients with 'Anti-NMDA-receptor encephalitis' due to their intrathecal production. Many patients with 'Anti-NMDA receptor Encephalitis' respond well to several modes of immunotherapy. (3) Anti-NMDA-NR2A/B antibodies are present in a substantial number of patients with Systemic Lupus Erythematosus (SLE) with or without neuropsychiatric problems. The exact percentage of SLE patients having anti-NMDA-NR2A/B antibodies varies in different studies from 14 to 35%, and in one study such antibodies were found in 81% of patients with diffuse 'Neuropshychiatric SLE', and in 44% of patients with focal 'Neuropshychiatric SLE'. Anti-NMDA-NR2A/B antibodies are also present in subpopulations of patients with Epilepsy of several types, Encephalitis of several types (e.g., chronic progressive limbic Encephalitis, Paraneoplastic Encephalitis or Herpes Simplex Virus Encephalitis), Schizophrenia, Mania, Stroke, or Sjorgen syndrome. In some patients, the anti-NMDA-NR2A/B antibodies are present in both the serum and the CSF. Some of the anti-NMDA-NR2A/B antibodies cross-react with dsDNA, while others do not. Some of the anti-NMDA-NR2A/B antibodies associate with neuropsychiatric/cognitive/behavior/mood impairments in SLE patients, while others do not. The anti-NMDA-NR2A/B antibodies can undoubtedly be very pathogenic, since they can kill neurons by activating NMDA receptors and inducing 'Excitotoxicity', damage the brain, cause dramatic decrease of membranal NMDA receptors expressed in hippocampal neurons, and also induce behavioral cognitive impairments in animal models. Yet, the concentration of the anti-NMDA-NR2A/B antibodies seems to determine if they have positive or negative effects on the activity of glutamate receptors and on the survival of neurons. Thus, at low concentration, the anti-NMDA-NR2A/B antibodies were found to be positive modulators of receptor function and increase the size of NMDA receptor-mediated excitatory postsynaptic potentials, whereas at high concentration they are pathogenic as they promote 'Excitotoxcity' through enhanced mitochondrial permeability transition. (4) Anti-mGluR1 antibodies were found thus far in very few patients with Paraneoplastic Cerebellar Ataxia, and in these patients they are produced intrathecally and therefore present in much higher levels in the CSF than in the serum. The anti-mGluR1 antibodies can be very pathogenic in the brain since they can reduce the basal neuronal activity, block the induction of long-term depression of Purkinje cells, and altogether cause cerebellar motor coordination deficits by a combination of rapid effects on both the acute and the plastic responses of Purkinje cells, and by chronic degenerative effects. Strikingly, within 30 min after injection of anti-mGluR1 antibodies into the brain of mice, the mice became ataxic. Anti-mGluR1 antibodies derived from patients with Ataxia also caused disturbance of eye movements in animal models. Immunotherapy can be very effective for some Cerebellar Ataxia patients that have anti-mGluR1 antibodies. (5) Anti-mGluR5 antibodies were found thus far in the serum and CSF of very few patients with Hodgkin lymphoma and Limbic Encephalopathy (Ophelia syndrome). The sera of these patients that contained anti-GluR5 antibodies reacted with the neuropil of the hippocampus and cell surface of live rat hippocampal neurons, and immunoprecipitation from cultured neurons and mass spectrometry demonstrated that the antigen was indeed mGluR5. Taken together, all these evidences show that anti-glutamate receptor antibodies are much more frequent among various neurological diseases than ever realized before, and that they are very detrimental to the nervous system. As such, they call for diagnosis, therapeutic removal or silencing and future studies. What we have learned by now about the broad family of anti-glutamate receptor antibodies is so exciting, novel, unique and important, that it makes all future efforts worthy and essential.

Glutamate receptor antibodies directed against AMPA receptors subunit 3 peptide B (GluR3B) associate with some cognitive/psychiatric/behavioral abnormalities in epilepsy patients

Antibodies (Ab's) to glutamate receptors, directed specifically against AMPA receptors subunit 3 peptide B (i.e. GluR3 amino acids 372-395), named GluR3B Ab's, can by themselves activate GluR3-containing glutamate/AMPA receptors, evoke ion currents via the receptor's ion channel, kill neurons and damage the brain. Herein we first tested 14 consecutive epilepsy patients and 10 healthy controls, and found that 7 (50%) patients had GluR3B Ab's. Second, in 71 other consecutive epilepsy patients (20 generalized epilepsy, 51 partial epilepsy) and 49 controls, we found that 17 (24%) patients had GluR3B Ab's, of which 8 had generalized and 9 partial epilepsy. We then studied 41 epilepsy patients: 21 patients with GluR3B Ab's and 20 without such Ab's (pooled of both tests without biased selection), for possible association of GluR3B Ab's with disease severity and/or neurobehavioral/cognitive comorbidities. Of the 21 patients with GluR3B Ab's, 6 had symptomatic, 7 cryptogenic, and 8 idiopathic epilepsy. Of the 20 patients without GluR3B Ab's, 16 had idiopathic etiology, and 4 nonidiopathic epilepsy. We found that among the 21 patients with GluR3B Ab's, 19 patients (90%) had learning problems, 16 (76%) attention problems, and 15 (71%) psychiatric problems. In contrast, among the 20 patients without GluR3B Ab's, only 6 (30%) had learning problems (p<0.0001), 5 (25%) attention problems (p=0.0017), and 2 (10%) psychiatric problems (p<0.0001). These findings suggest either that neurobehavioral abnormalities occur more frequently in epilepsy patients already having GluR3B Ab's, and may be due to them, or that GluR3B Ab's are more frequent in patients already having neurobehavioral abnormalities.

[Rasmussen encephalitis and non-herpetic acute limbic encephalitis]

Rasmussen syndrome (RS) and non-herpetic acute limbic encephalitis (NHALE) have pathophysiological background related with autoimmunity to glutamate receptors (GluRs) after infections. RS and NHALE were reviewed, depending mainly on our recent studies. RS is the prototype of autoimmune-mediated epilepsy. In patients with RS, several kinds of autoantibodies against neuronal molecules, for example, GluR3, GluRepsilon2 (NMDA-R2B), etc., are reported. These autoantibodies are not specific for RS. About autoantibodies against GluR3, significance and stimulating effects to GluR3 are controversial. Autoantibodies against GluRepsilon2 were detected in all patients within six months from epilepsy onset, and in some patients at chronic stage. These data suggest that autoantibodies against GluRepsilon2 may be involved in the pathological mechanisms in the early stage, but we could not confirm the effect of the autoantibodies from RS patients on excitatory postsynaptic NMDA current using patch clump methods. However, anti-double-stranded DNA antibodies in patients with SLE are reported to cross-react with n-terminal of GluRepsilon2, and cause neuronal apoptosis in rat hippocampus, ensuing memory impairment, and emotional behavior impairment in mice. Therefore, autoantibodies against GluRepsilon2 may contribute to the cognitive and behavioral changes in RS. Concerning about cellular immunity in RS, lymphocytes stimulating tests revealed peripheral lymphocytes sensitized by antigens containing GluRepsilon2. Cytotoxic T cells (CTLs) excreting Granzyme B were reported in resected brain tissue, and we confirmed the elevated levels of Granzyme B, not in sera, but in CSF. These data suggest that CTLs activated by infection invade into CNS, and recognize neural antigens, and excrete Granzyme B. The incidence of NHALE is 4.1/1 million/year in Japanese adults. Our study in 91 adult patients with NHALE revealed the following characteristics. Mean onset age was 35.2 +/- 16.9 years old, and preceding infections existed in 68.7% of patients, and predominant symptoms at the onset were psychiatric symptoms (33.3%) and convulsions (25.0%). CSF showed slightly elevated cell counts (55.5 +/- 139.9), protein levels (48.1 +/- 36.0 mg/dl), and IgG levels (4.5 +/- 3.9 mg/dl). MRI lesions with high intensity were found in 40.8% (DWI) and 54.2% (FLAIR) of patients in various stages after onsets. Autoantibodies against GluRepsilon2 in sera were detected in approximately 60% of NHALE patients from acute to chronic stages, and the autoantibodies in CSF were detected in 51.8% (acute stage), 41.4% (recovery stage), 28.6% (chronic stage) of patients and included epitopes to n-terminal of GluRepsilon2 (NT1). These data suggest that autoantibodies against GluRepsilon2 produced in sera after infection infiltrate into CNS through damaged BBB in acute stages, and affect n-terminal of GluRepsilon2. In chronic stage, recovery of function of BBB reduces levels of the autoantibodies in CSF. Because BBB in hippocampi and amygdala are vulnerable, autoantibodies against GluRepsilon2 including epitopes to n-terminal may contribute to the limbic symptoms around onset. Among several autoantibodies related with NHALE, autoantibodies against GluRepsilon2 were found in patients around 15-34 years old, autoantibodies against VGKC were around 50.4 years old, autoantibodies against NAE were around 59 years old, autoantibodies against Hu were around 61.5 years old. These data suggest that autoantibodies related with NHALE have age-dependent heterogeneity.

No effect of immunomodulatory therapy in focal epilepsy with positive glutamate receptor type 3—antibodies

Antibodies against the glutamate receptor type 3-(GluR3) have been found in association with Rasmussen's encephalitis (RE) but were also detected in patients with non-inflammatory focal epilepsies. We report the case of an 18-year-old patient with treatment refractory left mesial temporal lobe epilepsy accompanied by high levels of GluR3 antibodies. Different from experiences in patients with RE immunomodulatory therapy by use of intravenous gammaglobulines neither altered GluR3 serum levels nor had any effect on seizure frequency in our patient. Interestingly, GluR3 serum levels remained positive after successful surgical intervention leading to patient's seizure freedom.

Infections as causative factors of epilepsy

Epilepsies bearing some relationship to infections or vaccinations are often encountered clinically. While the onset of epilepsy or aggravation of seizures may follow common infections or vaccinations, complete seizure control has also been observed after infections. However, the true mechanisms underlying the relationship between infections and epilepsies have not been fully elucidated. Recently, advances in immunology have contributed to the study of autoimmune mechanisms in Rasmussen’s syndrome, a prototype of autoimmune epilepsy related to infections. The roles of autoimmunity, including cytotoxic T cells and autoantibodies against neural molecules, have been demonstrated in Rasmussen’s syndrome. This review postulates the probable molecular mimicry of microbial and neural components in Rasmussen’s syndrome and proposes possible autoimmune mechanisms related to the development of symptomatic epilepsies.