Analysis of the IgG subclass distribution and inflammatory infiltrates in patients with anti-Hu-associated paraneoplastic encephalomyelitis

HLA-DR3 ~ DQ2 associates with sensory neuropathy in paraneoplastic neurological syndromes with Hu antibodies

OBJECTIVES

To investigate the association between human leukocyte antigen (HLA) and paraneoplastic neurological syndromes (PNS) with Hu antibodies, and potential specificities according to clinical presentation and cancer status.

METHODS

HLA genotypes at four-digit resolution were imputed from available genome-wide association data. Allele carrier frequencies were compared between patients (whole cohort, n = 100, and according to clinical presentation and cancer status) and matched healthy controls (n = 508) using logistic regression controlled by the three main principal components.

RESULTS

The clinical presentation of 100 anti-Hu patients involved the central nervous system (28, 28%), the peripheral nervous system (36, 36%) or both combined (36, 36%). Cancer diagnosis was certain in 75 (75%). HLA association analyses revealed that anti-Hu PNS patients were more frequently carriers of DQA1*05:01 (39% vs. 19%, OR = 2.8 [1.74-4.49]), DQB1*02:01 (39% vs. 18%, OR = 2.88 [1.79-4.64]) and DRB1*03:01 (41% vs. 19%, OR = 2.92 [1.80-4.73]) than healthy controls. Remarkably, such DR3 ~ DQ2 association was absent in patients with pure central involvement, but more specific to those manifesting with peripheral involvement: DQA1*05:01 (OR = 3.12 [1.48-6.60]), DQB1*02:01 (OR = 3.35 [1.57-7.15]) and DRB1*03:01 (OR = 3.62 [1.64-7.97]); being even stronger in cases with sensory neuropathy, DQA1*05:01 (OR = 4.41 [1.89-10.33]), DQB1*02:01 (OR = 4.85 [2.04-11.53]) and DRB1*03:01 (OR = 5.79 [2.28-14.74]). Similarly, DR3 ~ DQ2 association was only observed in patients with cancer.

DISCUSSION

Patients with anti-Hu PNS show different HLA profiles according to clinical presentation and, probably, cancer status, suggesting pathophysiological differences.

Progressive Encephalomyelopathy in an Older Man: A Case Report From the National Multiple Sclerosis Society Case Conference Proceedings

We present a case of subacute onset progressive encephalomyelopathy in a 77-year-old man with symmetric lateral column signal abnormalities on spinal MRI. We discuss the differential and presumptive final diagnosis along with a review of the postulated disease immunopathogenesis.

Clinicopathologic Findings in Patients With Paraneoplastic Neuropathies and Antibodies Strongly Associated With Cancer

BACKGROUND AND OBJECTIVES

Pathologic descriptions of peripheral nerve involvement in paraneoplastic neuropathies are sparse, mostly from autopsies focusing on CNS and dorsal root ganglia tissues. Here, we describe the clinicopathologic features of peripheral nerve biopsies in patients with paraneoplastic neurologic syndromes to expand the currently limited knowledge.

METHODS

Retrospective review of the Mayo Clinic electronic medical record from 1995 to 2022 for patients identified to have subacute onset neuropathy with paraneoplastic antibodies identified in our neuroimmunology laboratory having available nerve biopsies performed at the time of diagnosis. Patients with another cause of neuropathy not linked to their subacute onset were excluded.

RESULTS

Nineteen patients met inclusion criteria: 4 with amphiphysin antibodies, 6 with antineuronal nuclear antibody (ANNA)-1 only, 3 with both ANNA-1 and collapsin response-mediator protein 5 (CRMP-5), 2 with ANNA-2, and 4 with CRMP-5 antibodies only. Fifteen biopsies had reduced the density of myelinated nerve fibers-4 with multifocality. Subperineurial edema was present in 17 biopsies. Prominent epineurial perivascular inflammation was present in 3 biopsies, all belonging to patients with a lumbosacral radiculoplexus neuropathy (LRPN) phenotype.

DISCUSSION

Axonal loss, subperineurial edema, and an absence of prominent inflammation are the most common findings in nerve biopsies of patients with paraneoplastic antibodies strongly associated with cancer. The LRPN phenotype was the only subset with inflammatory collections. Paraneoplastic autoantibody testing should be considered in patients with subacute onset neuropathies, with or without interstitial inflammatory findings.

Pathogenesis and immunopathology of paraneoplastic disorders

Paraneoplastic neurologic syndromes (PNS) represent a rare group of immune-mediated complications associated with an underlying tumor. Ectopic protein expression in neoplastic cells or an aberrant immune regulation in the course of hematooncologic diseases or thymomas trigger an autoimmune response that may affect any part of the central and/or peripheral nervous system. Recent advances in drug therapies as well as novel animal models and neuropathologic studies have led to further insights on the immune pathomechanisms of PNS. Although the syndromes share common paths in pathogenesis, they may differ in the disease course, prognosis, and therapy targets, depending on the localization and type of antibody epitope. Neuropathologic hallmarks of PNS associated with antibodies directed against intracellular epitopes are characterized by T cell-dominated inflammation, reactive gliosis including microglial nodules, and neuronal degeneration. By contrast, the neuropathology of cell surface antibody-mediated PNS strongly depends on the targeted antigen and varies from B cell/plasma cell-dominated inflammation and well-preserved neurons together with a reduced expression of the target antigen in anti-NMDAR encephalitis to irreversible Purkinje cell loss in anti-P/Q-type VGCC antibody-associated paraneoplastic cerebellar degeneration. The understanding of different pathomechanisms in PNS is important because they strongly correspond with therapy response and prognosis, and should guide treatment decisions.

Immune Mechanisms in Epileptogenesis: Update on Diagnosis and Treatment of Autoimmune Epilepsy Syndromes

Seizures and epilepsy can result from various aetiologies, yet the underlying cause of several epileptic syndromes remains unclear. In that regard, autoimmune-mediated pathophysiological mechanisms have been gaining attention in the past years and were included as one of the six aetiologies of seizures in the most recent classification of the International League Against Epilepsy. The increasing number of anti-neuronal antibodies identified in patients with encephalitic disorders has contributed to the establishment of an immune-mediated pathophysiology in many cases of unclear aetiology of epileptic syndromes. Yet only a small number of patients with autoimmune encephalitis develop epilepsy in the proper sense where the brain transforms into a state where it will acquire the enduring propensity to produce seizures if it is not hindered by interventions. Hence, the term autoimmune epilepsy is often wrongfully used in the context of autoimmune encephalitis since most of the seizures are acute encephalitis-associated and will abate as soon as the encephalitis is in remission. Given the overlapping clinical presentation of immune-mediated seizures originating from different aetiologies, a clear distinction among the aetiological entities is crucial when it comes to discussing pathophysiological mechanisms, therapeutic options, and long-term prognosis of patients. Moreover, a rapid and accurate identification of patients with immune-mediated epilepsy syndromes is required to ensure an early targeted treatment and, thereby, improve clinical outcome. In this article, we review our current understanding of pathogenesis and critically discuss current and potential novel treatment options for seizures and epilepsy syndromes of underlying or suspected immune-mediated origin. We further outline the challenges in proper terminology.

Paraneoplastic motor disorders

Paraneoplastic neurological disorders (PNDs) are heterogeneous clinicopathologic syndromes that occur throughout the neuraxis resulting from damage to organs or tissues remote from the site of a malignant neoplasm or its metastases. The discordance between severe neurological disability and even an indolent malignancy suggests an underlying neuroimmunologic host immune response that inflicts nervous tissue damage while inhibiting malignant tumor growth. Motor system involvement, like other symptoms and signs, is associated with focal or diffuse involvement of the brain, spinal cord, peripheral nerve, neuromuscular junction or muscle, alone or in combination due to an underlying neuroimmune and neuroinflammatory process targeting neural-specific antigens. Unrecognized and therefore untreated, PNDs are often lethal making early detection and aggressive treatment of paramount importance. While the combination of clinical symptoms and signs, and analysis of detailed body and neuroimaging, clinical neurophysiology and electrodiagnostic studies, and tumor and nervous system tissue biopsies are all vitally important, the certain diagnosis of a PND rests with the discovery of a corresponding neural-specific paraneoplastic autoantibody in the blood and/or spinal cerebrospinal fluid.

Paraneoplastic neurological syndrome with positive anti-Hu and anti-Yo antibodies: A case report

BACKGROUND

Paraneoplastic neurological syndrome (PNS) is a rare complication in patients with cancer. PNS can affect the central, peripheral, autonomic nervous system, neuromuscular junction, or muscles and cause various neurological symptoms. Anti-Yo antibody-positive neurological paraneoplasms and anti-Hu antibody-positive neurological paraneoplasms are common, but coexistence of both types has not been described in the literature.

CASE SUMMARY

Here we present a rare case of paraneoplastic neuropathy occurring in both breast and lung cancers. A 55-year-old woman was admitted to our hospital with unsteadiness while walking. The patient had a history of breast cancer two years previously. Chest computed tomography revealed a 4.6 cm × 3.6 cm mass in the right lung, which was diagnosed as small-cell lung cancer (SCLC). Blood test was positive for anti-Yo antibodies, and the cerebrospinal fluid was positive for both anti-Yo and anti-Hu antibodies, and the neurological symptoms were considered to be related to the paraneoplasm. The patient was treated with a course of intravenous immunoglobulin, without noticeable improvement. After being discharged from hospital, the patient underwent regular chemotherapy for SCLC and periodic reviews. The patient’s neurological symptoms continued to deteriorate at the follow-up visit in April 2021.

CONCLUSION

This case suggests the possibility of two types of tumors appearing simultaneously with two paraneoplastic antibodies. The clinical appearance of two or more paraneoplastic tumors requires additional attention.

Immune mechanisms, the role of complement, and related therapies in autoimmune neuropathies

INTRODUCTION

Autoimmune neuropathies have diverse presentations and underlying immune mechanisms. Demonstration of efficacy of therapeutic agents that inhibit the complement cascade would confirm the role of complement activation.

AREAS COVERED

A review of the pathophysiology of the autoimmune neuropathies, to identify those that are likely to be complement mediated.

EXPERT OPINION

Complement mediated mechanisms are implicated in the acute and chronic neuropathies associated with IgG or IgM antibodies that target the Myelin Associated Glycoprotein (MAG) or gangliosides in the peripheral nerves. Antibody and complement mechanisms are also suspected in the Guillain-Barré syndrome and chronic inflammatory demyelinating neuropathy, given the therapeutic response to plasmapheresis or intravenous immunoglobulins, even in the absence of an identifiable target antigen. Complement is unlikely to play a role in paraneoplastic sensory neuropathy associated with antibodies to HU/ANNA-1 given its intracellular localization. In chronic demyelinating neuropathy with anti-nodal/paranodal CNTN1, NFS-155, and CASPR1 antibodies, myotonia with anti-VGKC LGI1 or CASPR2 antibodies, or autoimmune autonomic neuropathy with anti-gAChR antibodies, the response to complement inhibitory agents would depend on the extent to which the antibodies exert their effects through complement dependent or independent mechanisms. Complement is also likely to play a role in Sjogren's, vasculitic, and cryoglobulinemic neuropathies.

Various clinical features of patients with anti-Hu associated paraneoplastic neurological syndromes: An observational study

To describe and analyze the clinical features and prognosis of patients with anti-Hu associated paraneoplastic neurological syndromes (PNS).The symptoms, MRI findings, cerebrospinal fluid (CSF) changes, electroencephalogram (EEG) characteristics and prognoses of 9 well-diagnosed anti-Hu associated PNS patients were analyzed.The study enrolled 6 female and 3 male patients. Three patients presented with vertigo and 6 patients exhibited a depressed mood, numbness of the lower limbs, generalized pains, seizures, mental disturbances, and a temporary unilateral hand tremor on initial presentation. Three patients presented with MRI abnormalities localized in the mesial temporal lobe and the thalamus. Abnormal interictal EEG readings were observed in all 5 patients who underwent EEG study. Four patients were found lung cancer (3 during hospitalization, 1 during follow-up). Seven patients were treated with immunotherapy and improved in symptoms. Three patients died during follow-up (2 with lung cancer).The clinical manifestation of anti-Hu associated PNS is diverse and multifocal. EEG may be more sensitive than MRI for early diagnosis of PNS. Long-term follow-up for patients with CT-negative anti-Hu associated PNS is necessary.

Immune-mediated disorders

Paraneoplastic and autoimmune encephalitis comprise a group of immune-mediated disorders that are associated with different immune effector mechanisms. Classic paraneoplastic neurologic syndromes are triggered by an antitumor immune response. The disease is considered to result from a T-cell response; in addition, patients harbour high titers of autoantibodies against intracellular antigens that are considered as epiphenomenon but are useful diagnostic markers. Neuropathology consists of T-cell-dominated inflammation, marked neuronal loss, and microglial activation with upregulation of HLA-DR. In the last decade, an increasing number of diseases associated with autoantibodies against neuronal surface antigens have been described. There is strong evidence that these autoantibodies are pathogenic and the associated syndromes are generally termed as antineuronal autoimmune encephalitis. Patients typically present with limbic, multifocal, or diffuse encephalitis and respond to immunotherapy. Neuropathologic descriptions are restricted to few biopsy and autopsy specimens and show mild inflammatory infiltrates and microglial activation, together with reduced expression of the respective target antigens, immunoglobulin deposits, and a variable degree of complement activation. Other putative autoimmune disorders of the central nervous system include, among others, Rasmussen encephalitis, chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS), acute cerebellitis, Susac syndrome, and Hashimoto encephalitis. While pathologic studies suggest an immune-mediated disease for Rasmussen encephalitis, CLIPPERS, acute cerebellitis, and Susac syndrome, neuropathologic descriptions of Hashimoto encephalitis are rare and the pathogenesis deserves further study.

CD4+ and CD8+ T cells are both needed to induce paraneoplastic neurological disease in a mouse model

Paraneoplastic neurological disorders (PNDs) are rare human autoimmune diseases that mostly affect the central nervous system (CNS). They are triggered by an efficient immune response against a neural self-antigen that is ectopically expressed in neoplastic tumors. Due to this shared antigenic expression, the immune system reacts not only to tumor cells but also to neural cells resulting in neurological damage. Growing data point to a major role of cell-mediated immunity in PNDs associated to autoantibodies against intracellular proteins. However, its precise contribution in the pathogenesis remains unclear. In this context, our study aimed at investigating the impact of anti-tumor cellular immune responses in the development of PND. To this end, we developed an animal model mimicking PND. We used a tumor cell line expressing the hemagglutinin (HA) of influenza virus to induce an anti-tumor response in CamK-HA mice, which express HA in CNS neurons. To promote and track the T cell response against the HA antigen, naïve HA-specific CD8+ and/or CD4+ T cells, originating from TCR-transgenic animals, were transferred into these mice. We demonstrate that HA-expressing tumors, but not control tumors, induce in vivo activation, proliferation and differentiation of naïve HA-specific CD4+ and CD8+ T cells into effector cells. Moreover, both T cell subsets were needed to control tumor growth and induce CNS inflammation in CamK-HA mice. Thus, this new mouse model provides further insight into the cellular mechanisms whereby a potent anti-tumor immunity triggers a cancer-associated autoimmune disease, and may therefore help to develop new therapeutic strategies against PND.

Neuropathology of autoimmune encephalitides

In recent years a large number of antibody-associated or antibody-defined encephalitides have been discovered. These conditions are often referred to as autoimmune encephalitides. The clinical features include prominent epileptic seizures, cognitive and psychiatric disturbance. These encephalitides can be divided in those with antibodies against intracellular antigens and those with antibodies against surface antigens. The discovery of new antibodies against targets on the surface of neurons is especially interesting since patients with such antibodies can be successfully treated immunologically. This chapter focuses on the pathology and the pathogenetic mechanisms involved in these encephalitides and discusses some of the questions that are raised in this exciting new field. It is important to realise, however, that because of the use of antibodies to diagnose the patients, and their improvement with treatment, there are relatively few biopsy or postmortem reports, limiting the neuropathological data and conclusions that can be drawn. For this reason we especially focus on the most frequent autoimmune encephalitides, those with antibodies to the NMDA receptor and with antibodies to the known protein components of the VGKC complex. Analysis of these encephalitides show completely different pathogenic mechanisms. In VGKC complex encephalitis, antibodies seem to bind to their target and activate complement, leading to destruction and loss of neurons. On the other hand, in NMDAR encephalitis, complement activation and neuronal degeneration seems to be largely absent. Instead, binding of antibodies leads to a decrease of NMDA receptors resulting in a hypofunction. This hypofunction offers an explanation for some of the clinical features such as psychosis and episodic memory impairment, but not for the frequent seizures. Thus, additional analysis of the few human brain specimens present and the use of specific animal models are needed to further understand the effects of these antibodies in autoimmune encephalitides.

Neurologic autoimmunity: mechanisms revealed by animal models

Over the last decade, neurologic autoimmunity has become a major consideration in the diagnosis and management of patients with many neurologic presentations. The nature of the associated antibodies and their targets has led to appreciation of the importance of the accessibility of the target antigen to antibodies, and a partial understanding of the different mechanisms that can follow antibody binding. This chapter will first describe the basic principles of autoimmune inflammation and tissue damage in the central and peripheral nervous system, and will then demonstrate what has been learnt about neurologic autoimmunity from circumstantial clinical evidence and from passive, active, and occasionally spontaneous or genetic animal models. It will cover neurologic autoimmune diseases ranging from disorders of neuromuscular transmission, peripheral and ganglionic neuropathy, to diseases of the central nervous system, where autoantibodies are either pathogenic and cause destruction or changes in function of their targets, where they are harmless bystanders of T-cell-mediated tissue damage, or are not involved at all. Finally, this chapter will summarize the relevance of current animal models for studying the different neurologic autoimmune diseases, and it will identify aspects where future animal models need to be improved to better reflect the disease reality experienced by affected patients, e.g., the chronicity or the relapsing/remitting nature of their disease.

Immunity and Inflammation in Epilepsy

This review reports the available evidence on the activation of the innate and adaptive branches of the immune system and the related inflammatory processes in epileptic disorders and the putative pathogenic role of inflammatory processes developing in the brain, as indicated by evidence from experimental and clinical research. Indeed, there is increasing knowledge supporting a role of specific inflammatory mediators and immune cells in the generation and recurrence of epileptic seizures, as well as in the associated neuropathology and comorbidities. Major challenges in this field remain: a better understanding of the key inflammatory pathogenic pathways activated in chronic epilepsy and during epileptogenesis, and how to counteract them efficiently without altering the homeostatic tissue repair function of inflammation. The relevance of this information for developing novel therapies will be highlighted.

Latest updates on antiretinal autoantibodies associated with vision loss and breast cancer

Cancer-associated retinopathy (CAR) is an uncommon paraneoplastic disorder of the retina that is frequently associated with breast cancer in pre- and postmenopausal women older than 50 years. In this review, we will give an update on the current knowledge regarding the association of antiretinal autoantibodies with the breast-CAR syndrome. Women with breast cancer and visual indications of CAR have a significantly increased incidence of autoantibodies (AAbs) against retinal proteins when compared to healthy women. The onset of visual loss in association with antiretinal AAbs peaks 2 to 3 years after the clinical diagnosis of breast cancer. Differences in severity of symptoms between women with or without antiretinal AAbs are evident, revealing more unfavorable presentation in seropositive women. The incidence of CAR in breast cancer is likely to rise as the survival time of patients with breast cancer increases; consequently, a prediction of breast-CAR based on autoimmunity to individual retinal antigens, or to panels of antigens (signatures), is clinically important.

Cell-mediated immune responses in paraneoplastic neurological syndromes

Paraneoplastic neurological syndromes (PNS) are disorders of the nervous system that are associated with remote effects of malignancy. PNS are considered to have an autoimmune pathology. It has been suggested that immune antitumor responses are the origin of improved outcome in PNS. We describe cell-mediated immune responses in PNS and their potential contributions to antitumor reactions. Experimental and neuropathological studies have revealed infiltrates in nervous tissue and disturbances in lymphocyte populations in both cerebrospinal fluid and peripheral blood. A predominance of cytotoxic T lymphocytes (CTLs) over T helper cells has been observed. CTLs can be specifically aggressive against antigens shared by tumors and nervous tissue. Based on genetic studies, a common clonal origin of lymphocytes from blood, tumor, and nervous tissue is suggested. Suppressive regulatory T (Treg) lymphocytes are dysfunctional. Simultaneously, in tumor tissue, more intense cell-mediated immune responses are observed, which often coincide with a less aggressive course of neoplastic disease. An increased titer of onconeural antibodies is also related to better prognoses in patients without PNS. The evaluation of onconeural and neuronal surface antibodies was recommended in current guidelines. The link between PNS emergence and antitumor responses may result from more active CTLs and less functional Treg lymphocytes.

Autoimmune encephalitis: A potentially reversible cause of status epilepticus, epilepsy, and cognitive decline

Objectives:

To review clinical characteristics and response to immunomodulation therapy in autoimmune encephalitis presenting with status epilepticus (SE), epilepsy, and cognitive decline.

Design:

Observational, prospective case series.

Setting:

All India Institute of Medical Sciences, New Delhi, India.

Materials and Methods:

Prospective analysis of 15 patients, who presented with SE, epilepsy, cognitive decline, and other neurological symptoms with positive autoantibodies. Demographic and clinical characteristics were recorded. Brain magnetic resonance imaging (MRI), cerebrospinal-fluid analysis (CSF), and tumor screening were done periodically. Treatment received and responses (categorized as per patients and treating doctor's information) were noted.

Results:

There were 15 (males = 10) patients of autoimmune encephalitis. The mean age of presentation was 24 years (range: 2-64 years). The most common onset was subacute (64%) and four (29%) patients presented as SE. Predominant clinical presentations were seizures (100%) almost of every semiology. CSF was done in 10 patients; it was normal in 60%. Brain MRI was done in all patients, in six (40%) it was normal, six (40%) showed T2W and FLAIR hyperintensities in bilateral limbic areas. Antibodies found were the N-methyl-D-aspartate receptor antibody in seven (50%), voltage-gated potassium channel antibody in five (36%), two of antiglutamic acid decarboxylase, and one patient with double stranded DNA (dsDNA) antibodies. None showed evidence of malignancy. Patients received immunotherapy, either steroids, intravenous immunoglobulin, or both. Follow-up showed significant improvement in majority of cases, neither further seizures nor relapse in nine (67%) cases. One death occurred, due to delayed presentation.

Conclusions:

Uncommon but potentially reversible causes of SE, epilepsy, and cognitive decline may be immune-related and high index of suspicion will prevent missing the diagnosis.

Immunopathogenesis of paraneoplastic neurological syndromes associated with anti-Hu antibodies: A beneficial antitumor immune response going awry

Paraneoplastic neurological disorders (PNDs) are syndromes that develop in cancer patients when an efficient antitumor immune response, directed against antigens expressed by both malignant cells and healthy neurons, damages the nervous system. Herein, we analyze existing data on the mechanisms of loss of self tolerance and nervous tissue damage that underpin one of the most frequent PNDs, the anti-Hu syndrome. In addition, we discuss future directions and propose potential strategies aimed at blocking deleterious encephalitogenic immune responses while preserving the antineoplastic potential of treatment.

Are onconeural antibodies a clinical phenomenology in paraneoplastic limbic encephalitis?

Paraneoplastic neurological syndromes (PNSs) occur in patients with cancer and can cause clinical symptoms and signs of dysfunction of the nervous system that are not due to a local effect of the tumor or its metastases. Most of these clinical syndromes in adults are associated with lung cancer, especially small cell lung cancer (SCLC), lymphoma, and gynecological tumors. The finding of highly specific antibodies directed against onconeural antigens has revolutionized the diagnosis and promoted the understanding of these syndromes and led to the current hypothesis of an autoimmune pathophysiology. Accumulating data strongly suggested direct pathogenicity of these antibodies. The field of PNS has expanded rapidly in the past few years with the discovery of limbic encephalitis associated with glutamic acid decarboxylase (GAD) 65, the voltage (VGKC-gated potassium channel) complex, the methyl (N-NMDA-D-aspartate), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), and gamma aminobutyric acid (GABA) (B) receptors, and so forth. Despite this, the clinical spectrum of these diseases has not yet been fully investigated. The clinical importance of these conditions lies in their frequent response to immunotherapies and, less commonly, their association with distinctive tumors. This review provides an overview on the pathogenesis and diagnosis of PNS, with emphasis on the role of antibodies in limbic encephalitis.

Elevated numbers of regulatory T cells, central memory T cells and class-switched B cells in cerebrospinal fluid of patients with anti-Hu antibody associated paraneoplastic neurological syndromes

Multi-parametric flow cytometry was used to study lymphocyte subsets and dendritic cells in paired blood and CSF samples from 11 newly diagnosed patients with progressive anti-Hu antibody associated paraneoplastic neurological syndromes (Hu-PNS), 9 patients with other inflammatory neurologic disorders (IND), and 12 patients with other non-inflammatory neurologic disorders (OND). Hu-PNS patients had elevated numbers of regulatory T cells, central memory T cells, class-switched B cells and dendritic cells in their CSF. These findings support the hypothesis that the immune system is locally activated in Hu-PNS, and suggests common etiological pathways between Hu-PNS and other inflammatory central nervous system disorders.

Cellular immune suppression in paraneoplastic neurologic syndromes targeting intracellular antigens

BACKGROUND Tumor treatment is the mainstay of therapy for paraneoplastic neurologic disorders (PNDs), but it is only effective in some cases and other treatment options are limited. OBJECTIVE To evaluate the short-term use of a combination of prednisone and tacrolimus for acute neurologic worsening in PND in which intracellular antigens are targeted. DESIGN Retrospective single-center case series of patients with PND treated with tacrolimus. SETTING The Rockefeller University Hospital, a research hospital in New York, New York. PATIENTS Twenty-six patients with PND with high titer (≥1:1000) anti-HuD, anti-Yo, or anti-CRMP5 autoantibodies were enrolled. Patients were referred from Memorial Sloan Kettering Cancer Center or self-referred. Two patients discontinued intervention owing to adverse events. INTERVENTIONS Patients were treated with tacrolimus, 0.15-0.30 mg/kg per day, in 2 divided oral doses with 60 mg per day of oral prednisone, tapered off during 1 to 4 weeks. MAIN OUTCOME MEASURES The primary outcome measure was median survival. Neurologic examinations before and after treatment as well as adverse events are described. RESULTS Median survival time was 52 months from time of diagnosis. Some patients experienced neurologic improvement that was functionally meaningful. The incidence of adverse events was similar to that generally reported with tacrolimus. CONCLUSIONS A short course of prednisone and tacrolimus to target central nervous system T cells in patients with PND with acute neurologic decline in which intracellular antigens are targeted was well tolerated and warrants further study. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00378326.

The diagnosis and treatment of limbic encephalitis

The term limbic encephalitis (LE) was first introduced in 1968. While this disease was initially considered rare and is often fatal with very few treatment options, several reports published in the last decade provide a better description of this condition as well as possible causes and some cases of successful treatment. The clinical manifestation of LE is primarily defined by the subacute onset of short-term memory loss, seizures, confusion and psychiatric symptoms suggesting the involvement of the limbic system. In addition, EEG often shows focal or generalized slow wave or epileptiform activity, and MRI findings reveal hyperintense signals of the medial temporal lobes in T2-weighted or FLAIR images. The current literature suggests that LE is not a single disorder but is comprised of a group of autoimmune disorders predominantly affecting the limbic system. Before the diagnosis of LE can be determined, other causes of subacute encephalopathy must be excluded, especially those resulting from infectious aetiologies. LE has previously been regarded as a paraneoplastic phenomenon associated with the classical onconeuronal antibodies that are primarily directed against intracellular antigens. However, recent literature suggests that LE is also associated with antibodies that are directed against cell surface antigens, and these cases of LE display a much weaker association to the neoplasm. The treatment options for LE largely depend on the aetiology of the disease and involve the removal of the primary neoplasm. Therefore, a search for the underlying tumour is mandatory. In addition, immunotherapy has been successful in a significant number of patients where LE is not associated with cancer.

Pathogenic and physiological autoantibodies in the central nervous system

In this article, we review the current knowledge on pathological and physiological autoantibodies directed toward structures in the central nervous system (CNS) with an emphasis on their regulation and origin. Pathological autoantibodies in the CNS that are associated with autoimmunity often lead to severe neurological deficits via inflammatory processes such as encephalitis. In some instances, however, autoantibodies function as a marker for diagnostic purposes without contributing to the pathological process and/or disease progression. The existence of naturally occurring physiological autoantibodies has been known for a long time, and their role in maintaining homeostasis is well established. Within the brain, naturally occurring autoantibodies targeting aggregated proteins have been detected and might be promising candidates for new therapeutic approaches for neurodegenerative disorders. Further evidence has demonstrated the existence of naturally occurring antibodies targeting antigens on neurons and oligodendrocytes that promote axonal outgrowth and remyelination. The numerous actions of physiological autoantibodies as well as their regulation and origin are summarized in this review.

Movement disorders in autoimmune diseases

Movement disorders have been known to be associated with a variety of autoimmune diseases, including Sydenham's chorea, pediatric autoimmune neuropsychiatric disorders associated with streptococcus, systemic lupus erythematosus, antiphospholipid syndrome, gluten sensitivity, paraneoplastic and autoimmune encephalopathies. Tremors, dystonia, chorea, ballism, myoclonus, parkinsonism, and ataxia may be the initial and even the only presentation of these autoimmune diseases. Although antibodies directed against various cellular components of the central nervous system have been implicated, the pathogenic mechanisms of these autoimmune movement disorders have not yet been fully elucidated. Clinical recognition of these autoimmune movement disorders is critically important as many improve with immunotherapy or dietary modifications, particularly when diagnosed early. We discuss here the clinical features, pathogenic mechanisms, and treatments of movement disorders associated with autoimmune diseases, based on our own experience and on a systematic review of the literature.

Epileptic encephalitis: the role of the innate and adaptive immune system

Seizures are a prominent clinical feature of encephalitis. Recent data suggest the adaptive as well as innate immune system to be involved directly in the pathomechanism of epileptogenesis. Cytotoxic T-cells and antibody-mediated complement activation are major components of the adaptive immune system, which can induce neurodegeneration, thereby probably contributing to epileptic encephalitis. The innate immune system operates via interleukin-1 and toll-like receptor-associated mechanisms and was shown to play a direct role in epileptogenesis. Here, we review neuropathology hallmarks of various encephalitis conditions such as Rasmussen encephalitis (RE) but also introduce the more recently discovered antibody-associated voltage-gated potassium channel complex (VGKC), N-methyl-D-aspartate receptor (NMDAR) or glutamic acid decarboxylase (GAD) 65 encephalitides. Neuropathological investigations are used to determine specific cellular components and molecular mechanisms used by the immune system to provoke neurodegeneration and to promote epileptogenesis. Based on recent findings, we propose concepts for the stratification of epileptic encephalitis. Knowledge of the role of the innate immunity has already translated into clinical treatment strategies and may help to discover novel drug targets for these epileptic disorders.

Immunopathology of autoantibody-associated encephalitides: clues for pathogenesis

Classical paraneoplastic encephalitis syndromes with 'onconeural' antibodies directed to intracellular antigens, and the recently described paraneoplastic or non-paraneoplastic encephalitides and antibodies against both neural surface antigens (voltage-gated potassium channel-complexes, N-methyl-d-aspartate receptors) and intracellular antigens (glutamic acid decarboxylase-65), constitute an increasingly recognized group of immune-mediated brain diseases. Evidence for specific immune mechanisms, however, is scarce. Here, we report qualitative and quantitative immunopathology in brain tissue (biopsy or autopsy material) of 17 cases with encephalitis and antibodies to either intracellular (Hu, Ma2, glutamic acid decarboxylase) or surface antigenic targets (voltage-gated potassium channel-complex or N-methyl-d-aspartate receptors). We hypothesized that the encephalitides with antibodies against intracellular antigens (intracellular antigen-onconeural and intracellular antigen-glutamic acid decarboxylase groups) would show neurodegeneration mediated by T cell cytotoxicity and the encephalitides with antibodies against surface antigens would be antibody-mediated and would show less T cell involvement. We found a higher CD8/CD3 ratio and more frequent appositions of granzyme-B(+) cytotoxic T cells to neurons, with associated neuronal loss, in the intracellular antigen-onconeural group (anti-Hu and anti-Ma2 cases) compared to the patients with surface antigens (anti-N-methyl-d-aspartate receptors and anti-voltage-gated potassium channel complex cases). One of the glutamic acid decarboxylase antibody encephalitis cases (intracellular antigen-glutamic acid decarboxylase group) showed multiple appositions of GrB-positive T cells to neurons. Generally, however, the glutamic acid decarboxylase antibody cases showed less intense inflammation and also had relatively low CD8/CD3 ratios compared with the intracellular antigen-onconeural cases. Conversely, we found complement C9neo deposition on neurons associated with acute neuronal cell death in the surface antigen group only, specifically in the voltage-gated potassium channel-complex antibody patients. N-methyl-d-aspartate receptors-antibody cases showed no evidence of antibody and complement-mediated tissue injury and were distinguished from all other encephalitides by the absence of clear neuronal pathology and a low density of inflammatory cells. Although tissue samples varied in location and in the stage of disease, our findings strongly support a central role for T cell-mediated neuronal cytotoxicity in encephalitides with antibodies against intracellular antigens. In voltage-gated potassium channel-complex encephalitis, a subset of the surface antigen antibody encephalitides, an antibody- and complement-mediated immune response appears to be responsible for neuronal loss and cerebral atrophy; the apparent absence of these mechanisms in N-methyl-d-aspartate receptors antibody encephalitis is intriguing and requires further study.

Paraneoplastic encephalomyelopathies: pathology and mechanisms

The last three decades have seen major advances in the understanding of paraneoplastic and idiopathic autoimmune disorders affecting the central nervous system (CNS). Neural-specific autoantibodies and their target antigens have been discovered, immunopathology and neuroimaging patterns recognized and pathogenic mechanisms elucidated. Disorders accompanied by autoantibody markers of neural peptide-specific cytotoxic effector T cells [such as anti-neuronal nuclear antibody type 1 (ANNA-1, aka anti-Hu), Purkinje cell antibody type 1 (PCA-1, aka anti-Yo) and CRMP-5 IgG] are generally poorly responsive to immunotherapy. Disorders accompanied by neural plasma membrane-reactive autoantibodies [the effectors of synaptic disorders, which include antibodies targeting voltage-gated potassium channel (VGKC) complex proteins, NMDA and GABA-B receptors] generally respond well to early immunotherapy. Here we describe in detail the neuropathological findings and pathophysiology of paraneoplastic CNS disorders with reference to antigen-specific serology and neurological and oncological contexts.

Progress in the management of paraneoplastic neurological disorders

Paraneoplastic neurological disorders (PNDs) are a rare and diverse group of neurological conditions that can involve any part of the nervous system. Diagnosis is facilitated by finding well-recognized autoantibodies directed against neural antigens in the sera and the cerebrospinal fluid. Identifying and eliminating the underlying malignancy is the mainstay of treatment. Immunomodulatory treatment is gaining more acceptance especially, where a malignancy could not be identified, oncology treatment is completed, or along with cancer treatment. Literature review shows only a handful of systematic prospective case series. Multicenter, prospective controlled clinical trials are needed for future therapeutic advances.

Update on paraneoplastic neurologic disorders

When patients with cancer develop neurologic symptoms, common causes include metastasis, infections, coagulopathy, metabolic or nutritional disturbances, and neurotoxicity from treatments. A thorough clinical history, temporal association with cancer therapies, and results of ancillary tests usually reveal one of these mechanisms as the etiology. When no etiology is identified, the diagnosis considered is often that of a paraneoplastic neurologic disorder (PND). With the recognition that PNDs are more frequent than previously thought, the availability of diagnostic tests, and the fact that, for some PNDs, treatment helps, PNDs should no longer be considered diagnostic zebras, and when appropriate should be included in the differential diagnosis early in the evaluation.

Tolerance to the neuron-specific paraneoplastic HuD antigen

Experiments dating back to the 1940's have led to the hypothesis that the brain is an immunologically privileged site, shielding its antigens from immune recognition. The paraneoplastic Hu syndrome provides a powerful paradigm for addressing this hypothesis; it is believed to develop because small cell lung cancers (SCLC) express the neuron-specific Hu protein. This leads to an Hu-specific tumor immune response that can develop into an autoimmune attack against neurons, presumably when immune privilege in the brain is breached. Interestingly, all SCLC express the onconeural HuD antigen, and clinically useful tumor immune responses can be detected in up to 20% of patients, yet the paraneoplastic neurologic syndrome is extremely rare. We found that HuD-specific CD8+ T cells are normally present in the mouse T cell repertoire, but are not expanded upon immunization, although they can be detected after in vitro expansion. In contrast, HuD-specific T cells could be directly activated in HuD null mice, without the need for in vitro expansion. Taken together, these results demonstrate robust tolerance to the neuronal HuD antigen in vivo, and suggest a re-evaluation of the current concept of immune privilege in the brain.

B and T cell imbalances in CSF of patients with Hu-antibody associated PNS

In paraneoplastic neurological syndromes associated with Hu-antibodies (Hu-PNS) an important role for cellular immunity is hypothesized. We characterized the cerebrospinal fluid (CSF) pleocytosis in Hu-PNS patients by assessing the major lymphocyte subsets by flow cytometry. The B cell subset in the CSF of Hu-PNS patients showed a significant absolute (approximately 20x) and relative (approximately 3x) expansion, while the numbers of CD4+ T cells, CD8+ T cells and NK cells only showed an absolute expansion (approximately 4-7x) compared to the controls. On the other hand, the NKT cell subset showed a significant relative reduction in CSF and in blood of Hu-PNS patients. The relative B cell expansion is consistent with the intrathecal synthesis of Hu-antibodies, while the increased number of T and NK cells supports an additional role for cellular immunity in the pathogenesis of Hu-PNS. In addition, the autoimmune hypothesis of Hu-PNS is supported by the relative NKT cell deficiency.

Imbalances in circulating lymphocyte subsets in Hu antibody associated paraneoplastic neurological syndromes

In paraneoplastic neurological syndromes (PNS) associated with small cell lung cancer (SCLC) and Hu antibodies, neuron-specific Hu antigens expressed by the tumour hypothetically trigger an immune response that cross-reacts with Hu antigens in the nervous system, resulting in tumour suppression and neuronal damage. To gain more insight into the hypothesized cell-mediated immune pathogenesis of these syndromes, we analysed the circulating lymphocyte subsets in untreated patients with SCLC, PNS and Hu antibodies (n = 18), SCLC without PNS (n = 19) and controls (n = 29) using flow cytometry. SCLC patients with PNS had a variety of imbalances within their circulating lymphocyte subsets as compared with SCLC patients without PNS and healthy controls: (i) a lymphopenia of the major subsets (i.e. B, CD4+ and CD8+ T lymphocytes); (ii) increased proportions of activated CD4+ and CD8+ T cells; (iii) reduced numbers of terminally differentiated effector CD8+ T cells and cells with a cytotoxic T-cell phenotype (CD56+ and CD57+). Although indirect, our data provide further support for the involvement of T cells in the pathogenesis of Hu antibody associated PNS.

Limbic encephalitis and variants: classification, diagnosis and treatment

BACKGROUND AND OBJECTIVE

Recent studies suggest that a substantial number of patients with autoimmune limbic encephalitis may improve if properly diagnosed and treated. This is due, in part, to the increasing recognition of disorders that associate with antibodies to neuronal cell membrane antigens. This review focuses in these disorders, framed in a clinically useful immunologic classification of limbic encephalitis.

REVIEW SUMMARY

Patients with limbic encephalitis usually present with rapidly progressive short-term memory deficits, psychiatric symptoms, and seizures. After excluding viral and systemic autoimmune disorders, many patients with limbic encephalitis (paraneoplastic or not) have cerebrospinal fluid inflammatory findings, EEG or MRI abnormalities in the temporal lobes, and antineuronal antibodies. These antibodies are directed against 2 broad categories of antigens: (1) intracellular or classic paraneoplastic antigens, including Hu, Ma2, CV2/CRMP5, and amphiphysin among others, and (2) cell membrane antigens, including voltage-gated potassium channels, N-methyl-D-aspartate receptor, and others expressed in the neuropil of hippocampus and cerebellum (pending characterization). Whereas the disorders related to the first category of antibodies associate with cancer (lung, testis and other), prominent brain infiltrates of cytotoxic T-cells, and limited response to treatment, the disorders related to the second category of antibodies associate less frequently with cancer (thymoma, teratoma), seem to be antibody-mediated, and respond significantly better to immunotherapy.

CONCLUSIONS

Once considered an extremely rare disorder, almost always related to cancer, and refractory to treatment, limbic encephalitis is now regarded as a relatively frequent disorder, often unrelated to cancer, and with clinical-immunologic variants that respond to treatment.

Paraneoplastic neurological syndromes and onconeural antibodies: clinical and immunological aspects

Paraneoplastic neurological syndromes (PNS) are infrequent disorders that are associated with cancer. The syndromes are highly heterogeneous and often affect several areas of the nervous system. Among the most well-known syndromes are paraneoplastic encephalomyelitis, cerebellar degeneration, sensory neuronopathy, and Lambert-Eaton myastenic syndrome. There are various associated tumors, in particular small cell lung cancer, cancer of the breast and ovary, and thymoma. The onset of neurological symptoms often precedes the cancer diagnosis, and the recognition of a paraneoplastic syndrome should lead to immediate search for cancer. The etiology of the paraneoplastic syndromes is believed to be autoimmune. Antibodies to onconeural antigens, expressed in the tumor of the affected individual and in normal neurons, are found in many of the patients. These antibodies are useful markers for paraneoplastic etiology. The pathogenesis of the PNS is uncertain, but cellular immune responses are thought to be the main effector mechanism. The cornerstone of therapy is the identification and treatment of the underlying malignancy. In some of the disorders, immunosuppressive therapy is of additional benefit. The prognosis of the different PNS varies depending on the level of affection and the degree of neuronal death.

Neuropathophysiology of functional gastrointestinal disorders

The investigative evidence and emerging concepts in neurogastroenterology implicate dysfunctions at the levels of the enteric and central nervous systems as underlying causes of the prominent symptoms of many of the functional gastrointestinal disorders. Neurogastroenterological research aims for improved understanding of the physiology and pathophysiology of the digestive subsystems from which the arrays of functional symptoms emerge. The key subsystems for defecation-related symptoms and visceral hyper-sensitivity are the intestinal secretory glands, the musculature and the nervous system that controls and integrates their activity. Abdominal pain and discomfort arising from these systems adds the dimension of sensory neurophysiology. This review details current concepts for the underlying pathophysiology in terms of the physiology of intestinal secretion, motility, nervous control, sensing function, immuno-neural communication and the brain-gut axis.

No evidence for circulating HuD-specific CD8+ T cells in patients with paraneoplastic neurological syndromes and Hu antibodies

AIM

In paraneoplastic neurological syndromes (PNS) associated with small cell lung cancer (SCLC) and Hu antibodies (Hu-PNS), Hu antigens expressed by the tumour hypothetically trigger an immune response that also reacts with Hu antigens in the nervous system, resulting in tumour suppression and neuronal damage. To gain more insight into the hypothesized CD8(+ )T cell-mediated immune pathogenesis of these syndromes, we searched for circulating HuD-specific CD8(+) T cells in a large cohort of Hu-PNS patients and controls.

PATIENTS AND METHODS

Blood was tested from 43 Hu-PNS patients, 31 Hu antibody negative SCLC patients without PNS and 54 healthy controls. Peripheral blood mononuclear cells (PBMC) were stimulated with HuD protein-spanning peptide pools (15-mers) and individual HuD-derived peptides (9-mers) and analysed by cytokine flow cytometry and interferon-gamma ELISPOT-assays. Additionally, HuD-based Class I HLA multimers were used to visualize HuD-specific CD8(+) T cells.

RESULTS

No HuD-specific CD8(+ )T cells could be detected in the blood of Hu-PNS patients or controls.

CONCLUSIONS

Our results do not support a role for HuD-specific CD8(+) T cells in Hu-PNS. Further studies should focus on the detection of circulating HuD-specific CD4(+ )T cells and examine the antigen specificity of T cells in affected tissues.

Clinical and immunological diversity of limbic encephalitis: a model for paraneoplastic neurologic disorders

The most important contribution to the understanding and management of paraneoplastic neurologic disorders (PND) is the discovery that many of these diseases are immune mediated. It is believed that cytotoxic T-cell responses and antibodies that target neuronal proteins usually expressed by the underlying tumor cause the neurologic symptoms. The detection of these antibodies has provided diagnostic tests that allow recognition of the disorder as paraneoplastic and direct the search of the tumor to selected organs. This article summarizes the authors' findings of limbic encephalitis and postulates that a similar approach can be used for syndromes involving other areas of the nervous system.

Managing paraneoplastic neurological disorders

Paraneoplastic neurological syndromes (PNS) are remote effects of cancer that are not caused by invasion of the tumor or its metastases. Immunologic factors appear important in the pathogenesis of PNS because antineuronal autoantibodies and T-cell responses against nervous system antigens have been defined for many of these disorders. The immunologic response is elicited by the ectopic expression of neuronal antigens by the tumor. Expression of these so-called "onconeural" antigens is limited to the tumor and the nervous system and sometimes also the testis. At the time of presentation of the neurological symptoms, most patients have not yet been diagnosed with cancer. Detection of paraneoplastic antibodies is extremely helpful in diagnosing an otherwise unexplained and often rapidly progressive neurological syndrome as paraneoplastic. In addition, the paraneoplastic antibodies may also direct the search for an underlying neoplasm. On the other hand, in patients known to have cancer, the presentation of a PNS may herald recurrence of the tumor or a second tumor. The number of paraneoplastic antibodies is still growing, and at least seven of these can now be considered well characterized. Based on the clinical syndrome, the type of antibody, and the presence or absence of cancer, patients are classified as having a "definite" or "possible" PNS. Despite the presumed autoimmune etiology of PNS, the results of various forms of immunotherapy have been disappointing, with some exceptions. Rapid detection and immediate treatment of the underlying tumor appears to offer the best chance of stabilizing the patient and preventing further neurological deterioration.