Seroprevalence of anti-N-methyl-d-aspartate receptor antibodies in women with ovarian teratoma

Ovarian Teratoma-Related Paraneoplastic Neurological Syndromes

Paraneoplastic neurological syndromes (PNSs) are a group of neurological disorders triggered by an underlying remote tumor. Ovarian teratoma (OT) is the most common histologic type of germ cell tumor in females. The most common PNSs associated with OT is anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. However, with the increasing number of new antibodies reported over the last decade, the clinical spectrum of OT-related PNSs is also expanding. Our knowledge of OT-related PNSs is still far from complete. Here, we provide a comprehensive review of the most recent findings in the field of OT-related PNSs, with a particular focus on their clinical and pathological characteristics. Overall, the description of neuronal antibodies in PNSs associated with OT strongly suggests that antibodies may be responsible for the clinical symptoms in some cases. OT-related PNSs are associated with various clinical manifestations, including anti-NMDAR encephalitis, limbic encephalitis, encephalomyelitis, progressive cerebellar syndrome and opsoclonus-myoclonus syndrome. The pathological characteristics of the OT suggest that the mechanism of PNSs is probably due to heteromorphic neurons in the tumor tissue, the ectopic expression of the antigens in neural tissue within the teratomas and patients' unusual immune response. Despite the severity of the neurological syndromes, most patients with OT-related PNSs showed good neurologic response to early tumor resection combined with immunotherapy. To further advance the management of OT-related PNSs, additional studies are needed to explore this complex topic.

HLA-A and HLA-DRB1 may play a unique role in ovarian teratoma-associated anti-N-methyl-D-aspartate receptor encephalitis

BACKGROUND

Ovarian teratoma-associated anti-N-methyl-D-aspartate receptor encephalitis (NMDAR-E) is a severe autoimmune neurological disorder, and the influence of teratoma-induced autoantibodies on the pathogenesis remains unclear.

METHODS

Ovarian teratoma tissues were collected from teratoma patients with and without NMDAR-E. Proteins were extracted and then analyzed using iTRAQ-coupled LC-MS/MS, which was followed by bioinformatics analysis. Candidate proteins were verified by Western blotting and immunohistochemistry.

RESULTS

In total, 36 differentially expressed proteins (DEPs) were identified between the control group and NMDAR-E group, and the bioinformatics analysis revealed that the DEPs were mainly involved in immune-related pathways, especially HLA-A and HLA-DRB1. The western blotting results for HLA-A and HLA-DRB1 were consistent with the results of the iTRAQ analysis. Additionally, the immunohistochemical data revealed that the aggregation of HLA-A (+) and HLA-DRB1 (+) cells was more apparent in the teratoma tissues of NMDAR-E patients compared with that in the tissues of controls.

CONCLUSION

Our investigation indicated that HLA-A and HLA-DRB1 might be involved in mediating ovarian teratoma-associated NMDAR-E. These findings provide new insights into the pathophysiological mechanisms and provide information for the functional exploration of proteins in the future.

Incidence of anti-NMDAR encephalitis in patients undergoing resection of ovarian teratoma in a single institution

OBJECTIVE

The objective of this study was to determine the incidence of anti-NMDAR encephalitis in patients in whom a teratoma was removed. As far as we know, there has been no report on the incidence of anti-NMDAR encephalitis in patients in whom a teratoma was removed.

METHODS

This study was a single-institutional observational study. We enrolled patients who were diagnosed with teratoma in the Department of Pathology, Sapporo City General Hospital during a nine-year period between January 2008 and December 2016.

RESULTS

In Sapporo City General Hospital, 6 NMDAR encephalitis cases were detected during the 9-year period. In the same 9-year period, a pathological diagnosis of teratoma was made in 343 cases in the hospital. Anti-NMDAR encephalitis patients with a teratoma accounted for only 1.17% of all teratoma patients. Three of the 4 anti-NMDAR encephalitis patients with a teratoma underwent second removal of a teratoma, and no nervous tissue was detected pathologically.

CONCLUSIONS

In this study, we determined the association between teratoma with anti-NMDAR encephalitis and teratoma without anti-NMDAR encephalitis in cases in a single institution. As far as we know, this report is the first report on the incidence of anti-NMDAR encephalitis in teratoma patients.

Immunopathological characterization of ovarian teratomas associated with anti-N-methyl-D-aspartate receptor encephalitis

Encephalitis with anti-NMDAR antibodies (NMDAR-E) is a severe autoimmune neurological disorder, defined by a clinical presentation of encephalitis and the presence of IgG targeting the GluN1 subunit of NMDA receptors in the CSF. An underlying ovarian teratoma is commonly associated with this autoimmune disease suggesting a role of the tumor in immunopathogenesis. In this study, we characterized the salient histopathological features of 27 ovarian teratomas associated with NMDAR-E (3 immature and 24 mature teratomas) and 40 controls without associated encephalitis. All but one NMDAR-E-associated teratomas contained a nervous tissue component, while less than 40% of control teratomas did (p < 0.001). GluN1 expression by teratomatous nervous tissue seemed to be more often glial in NMDAR-E teratomas than in control teratomas (73% vs. 29%, p < 0.05). Strikingly, 3 out of 24 NMDAR-E-associated mature teratomas contained neuroglial tissue exhibiting histopathological features of central nervous system neuroglial tumor, while such glioma-like features are exceptionally described in the literature on ovarian teratomas. Moreover, NMDAR-E associated teratomas differed from sporadic ovarian teratomas by consistent and prominent infiltration of the nervous tissue component by immune cells, comprised of T- and B-cells and mature dendritic cells organized in tertiary lymphoid structures, with IgG and IgA deposits and plasma cells in close contact to the neuroglial tissue.

These data demonstrate an association between massive infiltration of NMDAR-E-associated teratomas by immune cells and particular glial features of its neuroglial component, suggesting that this glial tissue might be involved in triggering or sustaining the anti-tumor response associated with the auto-immune neurological disease.

Mechanisms of Autoantibody-Induced Pathology

Autoantibodies are frequently observed in healthy individuals. In a minority of these individuals, they lead to manifestation of autoimmune diseases, such as rheumatoid arthritis or Graves' disease. Overall, more than 2.5% of the population is affected by autoantibody-driven autoimmune disease. Pathways leading to autoantibody-induced pathology greatly differ among different diseases, and autoantibodies directed against the same antigen, depending on the targeted epitope, can have diverse effects. To foster knowledge in autoantibody-induced pathology and to encourage development of urgently needed novel therapeutic strategies, we here categorized autoantibodies according to their effects. According to our algorithm, autoantibodies can be classified into the following categories: (1) mimic receptor stimulation, (2) blocking of neural transmission, (3) induction of altered signaling, triggering uncontrolled (4) microthrombosis, (5) cell lysis, (6) neutrophil activation, and (7) induction of inflammation. These mechanisms in relation to disease, as well as principles of autoantibody generation and detection, are reviewed herein.

Anti-NMDAR encephalitis and other glutamate and GABA receptor antibody encephalopathies

Over the last few year, antibodies to various central nervous system receptors, particularly the glutamate and γ-aminobutyric acid (GABA) receptors, have been found to be associated with autoimmune neurologic disorders. The receptors include the N-methyl-d-aspartate receptor (NMDAR), the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), the metabotropic glutamate receptors (mGluRs), and GABA type A and B receptors (respectively GABAAR and GABABR). Compared to the previously described paraneoplastic antibodies directed at intracellular targets, the patients with receptor antibodies are often younger, they less frequently have malignancies, and they respond better to immunotherapy. Many of the patients have limbic encephalitis with amnesia, disorientation, seizures, and psychological or psychiatric symptoms, but those with NMDAR antibodies usually develop a more widespread form of encephalitis, often leading to a decrease in consciousness and requirement for long-term intensive care treatment. The autoantibodies bind directly to the synaptic or extrasynaptic receptors on the membrane surface, and have direct effects on signal transduction in central synapses. These conditions are very important to recognize as the symptoms and complications can be fatal when not treated in time, whereas with immunotherapy many patients recover considerably.

Ovarian teratoma-associated anti-NMDAR encephalitis: a systematic review of reported cases

The association of ovarian teratoma and anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is a serious and potentially fatal pathology that occurs in young women and that is under-recognized. Our objectives were to analyze prevalence and outcome of this association, and increase awareness over this pathology. MEDLINE and SCOPUS for all studies published prior to November 30, 2013 including the search terms: "encephalitis" and "teratoma" were considered. All articles (119) reporting one or more cases of anti-NMDAR encephalitis and confirmed ovarian teratoma (174 cases) were included. No language restrictions were applied. Suspicious cases with no evidence of ovarian teratoma (n = 40) and another type of encephalitis also associated to ovarian teratoma (n = 20) were also considered for comparison and discussion. Data of publication and case report, surgery and outcome were collected. The distribution of published cases is heterogeneous among different countries and continents, probably in relation with level of development and health care. The mean patient age is 24 years and in the majority of cases (74%), a mature teratoma was identified, sometimes microscopically following ovarian removal or at autopsy. The clinical presentation featured psychiatric symptoms and behavioural changes, with a median delay for surgery of 28 days. Twelve women died (7%), most frequently from encephalitis-related complications. In conclusion, the association ovarian teratoma and anti-NMDAR encephalitis is relatively unknown or not reported in many countries and among gynecologists. Heightened recognition of behavioral changes, diagnosis through transvaginal ultrasound and subsequent tumor removal in addition to diagnostic confirmation through the presence of anti-NMDAR antibodies must be emphasized.

Paraneoplastic neurological syndromes associated with ovarian tumors

Introduction

Paraneoplastic neurological syndromes (PNS) are neurologic deficits triggered by an underlying remote tumor. PNS can antedate clinical manifestation of ovarian malignancy and enable its diagnosis at an early stage. Interestingly, neoplasms associated with PNS are less advanced and metastasize less commonly than those without PNS. This suggests that PNS may be associated with a naturally occurring antitumor response.

Methods

We review the literature on the diagnosis, pathogenesis and management of PNS associated with ovarian tumors: paraneoplastic cerebellar degeneration (PCD) and anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis. An approach to the diagnostic workup of underlying tumors is discussed.

Results

PCD can precede the manifestation of ovarian carcinoma. Anti-NMDAR encephalitis in young women appears often as a result of ovarian teratoma. Since ovarian tumors and nervous tissue share common antigens (e.g., cdr2, NMDAR), autoimmune etiology is a probable mechanism of these neurologic disorders. The concept of cross-presentation, however, seems insufficient to explain entirely the emergence of PNS. Early resection of ovarian tumors is a significant part of PNS management and improves the outcome.

Conclusions

The diagnosis of PNS potentially associated with ovarian tumor indicates a need for a thorough diagnostic procedure in search of the neoplasm. In some patients, explorative laparoscopy/laparotomy can be considered.

Glutamatergic autoencephalitides: an emerging field

Autoimmune responses targeting synaptic proteins are associated with a wide range of neurologic symptoms. Among these disorders are those associated with antibodies to ionotropic glutamate receptors, including the NMDAR (N-methyl-D-aspartate receptor) and AMPAR (α-amino-3-hydrozy-5-methyl-4-isoxazolepropionic acid receptor). Patients with anti-NMDAR encephalitis present with psychiatric symptoms, seizures, movement disorders, impaired consciousness, and autonomic derangements; half of patients have an associated ovarian teratoma, and most patients respond to immunosuppressive therapies. Patients' antibodies bind to the amino terminal domain of the NMDAR, and result in loss of NMDARs from synapses with subsequent NMDAR hypofunction. Anti-NMDAR antibodies have now been reported in other neuropsychiatric conditions, including psychosis, dementia, and HSV encephalitis. The pathophysiologic relevance of anti-NMDAR antibodies in these disorders is not yet clear, but their presence may indicate a role for immunotherapy in some patients. Although considerable work remains to be done, our understanding of disorders associated with anti-glutamate receptor antibodies has grown exponentially since they were first described just over 7 years ago, revolutionizing neurology. These antibodies, by interfering with synaptic function, readily link basic science and clinical medicine, and have revealed the impact of sudden but sustained loss of specific neurotransmitter receptors in humans. Improved understanding of their pathophysiology will lead to better treatments for these diseases while providing novel insights regarding the roles of glutamate receptors in learning, memory, and neuropsychiatric disease.