Neurological autoimmune disorders with prominent gastrointestinal manifestations: A review of presentation, evaluation, and treatment.

BACKGROUND: The identification of autoantibodies directed against neuronal antigens has led to the recognition of a wide spectrum of neurological autoimmune disorders (NAD). With timely recognition and treatment, many patients with NAD see rapid improvement. Symptoms associated with NAD can be diverse and are determined by the regions of the nervous system affected. In addition to neurological symptoms, a number of these disorders present with prominent gastrointestinal (GI) manifestations such as nausea, diarrhea, weight loss, and gastroparesis prompting an initial evaluation by gastroenterologists. PURPOSE: This review provides a general overview of autoantibodies within the nervous system, focusing on three scenarios in which nervous system autoimmunity may initially present with gut symptoms. A general approach to evaluation and treatment, including antibody testing, will be reviewed.

Kctd9 Deficiency Impairs Natural Killer Cell Development and Effector Function.

We previously showed that potassium channel tetramerization domain containing 9 (KCTD9) is aberrantly expressed in natural killer (NK) cells in patients with hepatitis B virus-associated acute-on-chronic liver failure and mice with experimental fulminant hepatitis. However, the mechanism underlying the regulation of NK cell function and fulminant hepatitis progression by KCTD9 is unknown. Here, we investigated the role of Kctd9 in regulation of early development, maturation, and function of NK cells using Kctd9-knockout mice. Compared to wild-type mice, Kctd9-deficient mice exhibited impaired NK cell lineage commitment, as evidenced by selective reduction in the refined NK progenitors, and incomplete NK cell maturation, as manifested by a higher proportion of CD11b- NK cells and a lower percentage of CD11b+ NK cells with high proliferative potential. Moreover, Kctd9-depleted NK cells displayed insufficient IFN-γ production, degranulation, and granzyme B production in response to cytokine stimulation, and attenuated cytotoxicity to tumor cells in vitro. The defect in NK cells was further supported by ameliorated liver damage and improved survival in Kctd9-deficient mice following murine hepatitis virus strain-3 (MHV-3) infection, which otherwise leads to immune-mediated fulminant hepatitis, a phenotype homologous to that caused by NK cell depletion in wild-type mice. Further investigation to identify the underlying mechanism revealed that Kctd9 deficiency hindered the expression of transcription factors, including Ets1, Nfil3, Eomes, and Id2 in NK cells. Collectively, our data reveal that Kctd9 acts as a novel regulator for NK cell commitment, maturation, and effector function.

Interference with KCTD9 inhibits NK cell activation and ameliorates fulminant liver failure in mice.

BACKGROUND: Potassium channel tetramerisation domain containing 9 (KCTD9), a member of KCTD family with a DNA-like pentapeptide repeat domain, was found to be increased particularly in NK cells of patients with HBV-induced acute-on-chronic liver failure (HBV-ACLF) and experimental viral fulminant hepatitis. Knockdown of KCTD9 in immortalized NK cells inhibits cytokines production and cytotoxicity. As NK cell activation was shown to exacerbate liver damage in viral fulminant hepatitis, we propose that target inhibition of KCTD9 may prohibit NK cells activity and thus ameliorate liver damage in viral fulminant hepatitis. RESULT: Hydrodynamic delivery of plasmid expressing short-hairpin RNA against KCTD9 resulted in impaired NK cells function as demonstrated by reduced cytokine production and cytotoxicity, and ameliorated liver injury as manifested by improved liver histology and survival rate. In contrast, delivery of plasmid expressing KCTD9 led to deteriorated disease progression. CONCLUSION: Interference with KCTD9 expression exert beneficial effect in viral fulminant hepatitis therapy. Such effect may be mediated by impairment of NK cell activation.

Monogenic Diabetes Not Caused By Mutations in Mody Genes: A Very Heterogenous Group of Diabetes.

Monogenic diabetes represents a heterogeneous group of disorders resulting from a single gene defect leading to disruption of insulin secretion or a reduction in the number of beta cells. Despite the classification of monogenic diabetes into neonatal diabetes or maturity onset diabetes of the young (MODY) according to age of onset, not every case can be classified into those 2 groups. We evaluated patients with monogenic diabetes diagnosed during the last 10 year period. Type 1 DM, MODY, and patients with negative autoantibodies and no mutation in a known gene were excluded from the study. Thirteen patients were diagnosed with monogenic diabetes in Department of Pediatric Endocrinology, Ankara University School of Medicine, Ankara, Turkey. Five of them were diagnosed after 6 months of age. Five had a KATP channel defect. Mutations in genes resulting in destruction of beta cells were detected in 7 patients, with 4 cases having a WFS, 2 an LRBA, and one a IL2RA mutation. Additional systemic findings were seen in 6/13 patients, with 5/6 having severe immune system dysfunction. Treatment with sulphonylurea was successful in two patients.. The other patients were given insulin in differing doses. Four patients died during follow-up, three of which had immune system dysfunction. Monogenic diabetes can be diagnosed after 6 months of age, even with positive autoantibodies. Immune dysfunction was a common feature in our cohort and should be investigated in all patients with early-onset monogenic diabetes. Mortality of patients with monogenic diabetes and additional autoimmunity was high in our cohort and is likely to reflect the multisystem nature of these diseases.

Changes in phagocytosis and potassium channel activity in microglia of 5xFAD mice indicate alterations in purinergic signaling in a mouse model of Alzheimer's disease.

As the immunocompetent cells of the central nervous system, microglia accumulate at amyloid beta plaques in Alzheimer's disease (AD) and acquire a morphological phenotype of activated microglia. Recent functional studies, however, indicate that in mouse models of amyloidosis and AD, these cells are rather dysfunctional indicated by a reduced phagocytic activity. Here, we report that this reduction in phagocytic activity is associated with perturbed purinergic receptor signaling, since phagocytosis could be stimulated by P2Y6 receptor activation in control, but not in 5xFAD transgenic animals, an animal model of amyloid deposition. Impaired phagocytosis is not innate, and develops only at later stages of amyloidosis. Furthermore, we show that membrane currents induced by uridine diphosphate, a ligand activating P2Y6 receptors, are altered in response rate and amplitude in microglia in close vicinity to plaques, but not in plaque-free areas of 5xFAD animals. These changes were accompanied by changes in membrane properties and potassium channel activity of plaque-associated microglia in early and late stages of amyloidosis. As a conclusion, the physiological properties of plaque-associated microglia are altered with a strong impact on purinergic signaling.

Autoimmune channelopathies as a novel mechanism in cardiac arrhythmias.

Cardiac arrhythmias confer a considerable burden of morbidity and mortality in industrialized countries. Although coronary artery disease and heart failure are the prevalent causes of cardiac arrest, in 5-15% of patients, structural abnormalities at autopsy are absent. In a proportion of these patients, mutations in genes encoding cardiac ion channels are documented (inherited channelopathies), but, to date, the molecular autopsy is negative in nearly 70% of patients. Emerging evidence indicates that autoimmunity is involved in the pathogenesis of cardiac arrhythmias. In particular, several arrhythmogenic autoantibodies targeting specific calcium, potassium, or sodium channels in the heart have been identified. Experimental and clinical studies demonstrate that these autoantibodies can promote conduction disturbances and life-threatening tachyarrhythmias by inducing substantial electrophysiological changes. In this Review, we propose the term 'autoimmune cardiac channelopathies' to define this novel pathogenic mechanism of cardiac arrhythmias, which could be more frequent and clinically relevant than previously appreciated. Indeed, pathogenic autoantibodies against ion channels are detectable not only in patients with manifest autoimmune disease, but also in apparently healthy individuals, which suggests a causal role in some cases of unexplained arrhythmias and cardiac arrest. Considering this possibility and performing specific testing in patients with 'idiopathic' rhythm disturbances could create novel treatment opportunities.

DPPX antibody-associated encephalitis: Main syndrome and antibody effects.

OBJECTIVE: To report the main syndrome of dipeptidyl-peptidase-like protein 6 (DPPX) antibody-associated encephalitis, immunoglobulin G (IgG) subclass, and the antibody effects on DPPX/Kv4.2 potassium channels. METHODS: A retrospective analysis of new patients and cases reported since 2013 was performed. IgG subclass and effects of antibodies on cultured neurons were determined with described techniques. RESULTS: Nine new patients were identified (median age 57 years, range 36-69 years). All developed severe prodromal weight loss or diarrhea followed by cognitive dysfunction (9), memory deficits (5), CNS hyperexcitability (8; hyperekplexia, myoclonus, tremor, or seizures), or brainstem or cerebellar dysfunction (7). The peak of the disease was reached 8 months (range 1-54 months) after onset. All patients had both IgG4 and IgG1 DPPX antibodies. In cultured neurons, the antibodies caused a decrease of DPPX clusters and Kv4.2 protein that was reversible on removal of the antibodies. Considering the current series and previously reported cases (total 39), 67% developed the triad: weight loss (median 20 kg; range 8-53 kg)/gastrointestinal symptoms, cognitive-mental dysfunction, and CNS hyperexcitability. Outcome was available from 35 patients (8 not treated with immunotherapy): 60% had substantial or moderate improvement, 23% had no improvement (most of them not treated), and 17% died. Relapses occurred in 8 of 35 patients (23%) and were responsive to immunotherapy. CONCLUSIONS: DPPX antibodies are predominantly IgG1 and IgG4 and associate with cognitive-mental deficits and symptoms of CNS hyperexcitability that are usually preceded by diarrhea, other gastrointestinal symptoms, and weight loss. The disorder is responsive to immunotherapy, and this is supported by the reversibility of the antibody effects in cultured neurons.

Potassium channels of T lymphocytes take center stage in the fight against cancer.

A recent study by Eil at al. published in Nature in September 2016 provides evidence that alterations of the K+ homeostasis of tumor infiltrating lymphocytes (TILs) in necrotic areas of the tumor microenvironment (TME) suppress the function of effector T cells. Furthermore, they establish that overexpression of K+ channels in T lymphocytes counterbalances this negative effect of the TME and restores the ability of TILs to function, ultimately leading to increased survival of tumor bearing mice. Thus, K+ channels in T lymphocytes become interesting new targets for novel immunotherapies in cancer. This Commentary discusses Eil's finding in the context of the central role that K+ channels play in the suppressed state of TILs as they mediate the immunosuppressive effects of multiple conditions of the TME including hypoxia and adenosine.

Human Monocytes Engage an Alternative Inflammasome Pathway.

Interleukin-1ß (IL-1ß) is a cytokine whose bioactivity is controlled by activation of the inflammasome. However, in response to lipopolysaccharide, human monocytes secrete IL-1ß independently of classical inflammasome stimuli. Here, we report that this constituted a species-specific response that is not observed in the murine system. Indeed, in human monocytes, lipopolysaccharide triggered an "alternative inflammasome" that relied on NLRP3-ASC-caspase-1 signaling, yet was devoid of any classical inflammasome characteristics including pyroptosome formation, pyroptosis induction, and K(+) efflux dependency. Genetic dissection of the underlying signaling pathway in a monocyte transdifferentiation system revealed that alternative inflammasome activation was propagated by TLR4-TRIF-RIPK1-FADD-CASP8 signaling upstream of NLRP3. Importantly, involvement of this signaling cascade was limited to alternative inflammasome activation and did not extend to classical NLRP3 activation. Because alternative inflammasome activation embraces both sensitivity and promiscuity of TLR4, we propose a pivotal role for this signaling cascade in TLR4-driven, IL-1ß-mediated immune responses and immunopathology in humans.

Electronegative LDL induces priming and inflammasome activation leading to IL-1ß release in human monocytes and macrophages.

BACKGROUND: Electronegative LDL (LDL(−)), a modified LDL fraction found in blood, induces the release of inflammatory mediators in endothelial cells and leukocytes. However, the inflammatory pathways activated by LDL(−) have not been fully defined. We aim to study whether LDL(−) induced release of the first-wave proinflammatory IL-1ß in monocytes and monocyte-derived macrophages (MDM) and the mechanisms involved. METHODS: LDL(−) was isolated from total LDL by anion exchange chromatography. Monocytes and MDM were isolated from healthy donors and stimulated with LDL(+) and LDL(−) (100 mg apoB/L). RESULTS: In monocytes, LDL(−) promoted IL-1ß release in a time-dependent manner, obtaining at 20 h-incubation the double of IL-1ß release induced by LDL(−) than by native LDL. LDL(−)-induced IL-1ß release involved activation of the CD14-TLR4 receptor complex. LDL(−) induced priming, the first step of IL-1ß release, since it increased the transcription of pro-IL-1ß (8-fold) and NLRP3 (3-fold) compared to native LDL. Several findings show that LDL(−) induced inflammasome activation, the second step necessary for IL-1ß release. Preincubation of monocytes with K+ channel inhibitors decreased LDL(−)-induced IL-1ß release. LDL(−) induced formation of the NLRP3-ASC complex. LDL(−) triggered 2-fold caspase-1 activation compared to native LDL and IL-1ß release was strongly diminished in the presence of the caspase-1 inhibitor Z-YVAD. In MDM, LDL(−) promoted IL-1ß release, which was also associated with caspase-1 activation. CONCLUSIONS: LDL(−) promotes release of biologically active IL-1ß in monocytes and MDM by induction of the two steps involved: priming and NLRP3 inflammasome activation. SIGNIFICANCE: By IL-1ß release, LDL(−) could regulate inflammation in atherosclerosis.

Evidence of specialized tissue in human interatrial septum: histological, immunohistochemical and ultrastructural findings.

BACKGROUND: There is a paucity of information on structural organization of muscular bundles in the interatrial septum (IAS). The aim was to investigate histologic and ultrastructural organization of muscular bundles in human IAS, including fossa ovalis (FO) and flap valve. METHODS: Macroscopic and light microscopy evaluations of IAS were performed from postmortem studies of 40 patients. Twenty three IAS specimens underwent serial transverse sectioning, and 17--longitudinal sectioning. The transverse sections from 10 patients were immunolabeled for HCN4, Caveolin3 and Connexin43. IAS specimens from 6 other patients underwent electron microscopy. RESULTS: In all IAS specimens sections the FO, its rims and the flap valve had muscle fibers consisting of working cardiac myocytes. Besides the typical cardiomyocytes there were unusual cells: tortuous and horseshoe-shaped intertangled myocytes, small and large rounded myocytes with pale cytoplasm. The cells were aggregated in a definite structure in 38 (95%) cases, which was surrounded by fibro-fatty tissue. The height of the structure on transverse sections positively correlated with age (P = 0.03) and AF history (P = 0.045). Immunohistochemistry showed positive staining of the cells for HCN4 and Caveolin3. Electron microscopy identified cells with characteristics similar to electrical conduction cells. CONCLUSIONS: Specialized conduction cells in human IAS have been identified, specifically in the FO and its flap valve. The cells are aggregated in a structure, which is surrounded by fibrous and fatty tissue. Further investigations are warranted to explore electrophysiological characteristics of this structure.

DPPX potassium channel antibody: frequency, clinical accompaniments, and outcomes in 20 patients.

OBJECTIVE: To describe the detection frequency and clinical associations of immunoglobulin G (IgG) targeting dipeptidyl-peptidase-like protein-6 (DPPX), a regulatory subunit of neuronal Kv4.2 potassium channels. METHODS: Specimens from 20 patients evaluated on a service basis by tissue-based immunofluorescence yielded a synaptic immunostaining pattern consistent with DPPX-IgG (serum, 20; CSF, all 7 available). Transfected HEK293 cell-based assay confirmed DPPX specificity in all specimens. Sixty-nine patients with stiff-person syndrome and related disorders were also evaluated by DPPX-IgG cell-based assay. RESULTS: Of 20 seropositive patients, 12 were men; median symptom onset age was 53 years (range, 13-75). Symptom onset was insidious in 15 and subacute in 5. Twelve patients reported prodromal weight loss. Neurologic disorders were multifocal. All had one or more brain or brainstem manifestations: amnesia (16), delirium (8), psychosis (4), depression (4), seizures (2), and brainstem disorders (15; eye movement disturbances [8], ataxia [7], dysphagia [6], dysarthria [4], respiratory failure [3]). Nine patients reported sleep disturbance. Manifestations of central hyperexcitability included myoclonus (8), exaggerated startle (6), diffuse rigidity (6), and hyperreflexia (6). Dysautonomia involved the gastrointestinal tract (9; diarrhea [6], gastroparesis, and constipation [3]), bladder (7), cardiac conduction system (3), and thermoregulation (1). Two patients had B-cell neoplasms: gastrointestinal lymphoma (1), and chronic lymphocytic leukemia (1). Substantial neurologic improvements followed immunotherapy in 7 of 11 patients with available treatment data. DPPX-IgG was not detected in any of the stiff-person syndrome patients. CONCLUSIONS: DPPX-IgG is a biomarker for an immunotherapy-responsive multifocal neurologic disorder of the central and autonomic nervous systems.

Autoimmune encephalitis as differential diagnosis of infectious encephalitis.

PURPOSE OF REVIEW: This review describes the main types of autoimmune encephalitis with special emphasis on those associated with antibodies against neuronal cell surface or synaptic proteins, and the differential diagnosis with infectious encephalitis. RECENT FINDINGS: There is a continuous expansion of the number of cell surface or synaptic proteins that are targets of autoimmunity. The most recently identified include the metabotropic glutamate receptor 5 (mGluR5), dipeptidyl-peptidase-like protein-6 (DPPX), and γ-aminobutyric acid-A receptor (GABAAR). In these and previously known types of autoimmune encephalitis [N-methyl-D-aspartate receptor (NMDAR), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), γ-aminobutyric acid-B receptor (GABABR), leucine-rich glioma inactivated protein 1 (LGI1), contactin-associated protein-like 2 (CASPR2)], the prodromal symptoms or types of presentations often suggest a viral encephalitis. We review here clues that help in the differential diagnosis with infectious encephalitis. Moreover, recent investigations indicate that viral encephalitis (e.g., herpes simplex) can trigger synaptic autoimmunity. In all these disorders, immunotherapy is usually effective. SUMMARY: Autoimmune encephalitis comprises an expanding group of potentially treatable disorders that should be included in the differential diagnosis of any type of encephalitis. VIDEO ABSTRACT: http://links.lww.com/CONR/A25,

Progressive encephalomyelitis with rigidity and myoclonus: a new variant with DPPX antibodies.

OBJECTIVE: To describe a novel and distinct variant of progressive encephalomyelitis with rigidity and myoclonus (PERM) associated with antibodies directed against dipeptidyl peptidase-like protein 6 (DPPX), a regulatory subunit of the Kv4.2 potassium channels on the surface of neurons. METHODS: Case series describing the clinical, paraclinical, and serologic features of 3 patients with PERM. A recombinant, cell-based indirect immunofluorescence assay with DPPX-expressing HEK293 cells was used to detect DPPX antibodies in conjunction with mammalian tissues. RESULTS: All patients presented with a distinct syndrome involving hyperekplexia, prominent cerebellar ataxia with marked eye movement disorder, and trunk stiffness of variable intensity. Additional symptoms comprised allodynia, neurogenic pruritus, and gastrointestinal symptoms. Symptoms began insidiously and progressed slowly. An inflammatory CSF profile with mild pleocytosis and intrathecal immunoglobulin G synthesis was found in all patients. High DPPX antibody titers were detected in the patients' serum and CSF, with specific antibody indices suggestive of intrathecal synthesis of DPPX antibodies. Response to immunotherapy was good, but constant and aggressive treatment may be required. CONCLUSION: These cases highlight the expanding spectrum of both PERM and anti-neuronal antibodies. Testing for DPPX antibodies should be considered in the diagnostic workup of patients with acquired hyperekplexia, cerebellar ataxia, and stiffness, because such patients might benefit from immunotherapy. Further studies are needed to elucidate both the entire clinical spectrum associated with DPPX antibodies and their role in pathogenesis.

A virus-encoded potassium ion channel is a structural protein in the chlorovirus Paramecium bursaria chlorella virus 1 virion.

Most chloroviruses encode small K(+) channels, which are functional in electrophysiological assays. The experimental finding that initial steps in viral infection exhibit the same sensitivity to channel inhibitors as the viral K(+) channels has led to the hypothesis that the channels are structural proteins located in the internal membrane of the virus particles. This hypothesis was questioned recently because proteomic studies failed to detect the channel protein in virions of the prototype chlorovirus Paramecium bursaria chlorella virus 1 (PBCV-1). Here, we used a mAb raised against the functional K(+) channel from chlorovirus MA-1D to search for the viral K(+) channel in the virus particle. The results showed that the antibody was specific and bound to the tetrameric channel on the extracellular side. The antibody reacted in a virus-specific manner with protein extracts from chloroviruses that encoded channels similar to that from MA-1D. There was no cross-reactivity with chloroviruses that encoded more diverse channels or with a chlorovirus that lacked a K(+) channel gene. Together with electron microscopic imaging, which revealed labelling of individual virus particles with the channel antibody, these results establish that the viral particles contain an active K(+) channel, presumably located in the lipid membrane that surrounds the DNA in the mature virions.

Prediction of conformational epitopes with the use of a knowledge-based energy function and geometrically related neighboring residue characteristics.

BACKGROUND: A conformational epitope (CE) in an antigentic protein is composed of amino acid residues that are spatially near each other on the antigen's surface but are separated in sequence; CEs bind their complementary paratopes in B-cell receptors and/or antibodies. CE predication is used during vaccine design and in immuno-biological experiments. Here, we develop a novel system, CE-KEG, which predicts CEs based on knowledge-based energy and geometrical neighboring residue contents. The workflow applied grid-based mathematical morphological algorithms to efficiently detect the surface atoms of the antigens. After extracting surface residues, we ranked CE candidate residues first according to their local average energy distributions. Then, the frequencies at which geometrically related neighboring residue combinations in the potential CEs occurred were incorporated into our workflow, and the weighted combinations of the average energies and neighboring residue frequencies were used to assess the sensitivity, accuracy, and efficiency of our prediction workflow. RESULTS: We prepared a database containing 247 antigen structures and a second database containing the 163 non-redundant antigen structures in the first database to test our workflow. Our predictive workflow performed better than did algorithms found in the literature in terms of accuracy and efficiency. For the non-redundant dataset tested, our workflow achieved an average of 47.8% sensitivity, 84.3% specificity, and 80.7% accuracy according to a 10-fold cross-validation mechanism, and the performance was evaluated under providing top three predicted CE candidates for each antigen. CONCLUSIONS: Our method combines an energy profile for surface residues with the frequency that each geometrically related amino acid residue pair occurs to identify possible CEs in antigens. This combination of these features facilitates improved identification for immuno-biological studies and synthetic vaccine design. CE-KEG is available at http://cekeg.cs.ntou.edu.tw.