Mali Einen

Narcolepsy is strongly associated with the T-cell receptor alpha locus

Narcolepsy with cataplexy, characterized by sleepiness and rapid onset into REM sleep, affects 1 in 2,000 individuals. Narcolepsy was first shown to be tightly associated with HLA-DR2 (ref. 3) and later sublocalized to DQB1*0602 (ref. 4). Following studies in dogs and mice, a 95% loss of hypocretin-producing cells in postmortem hypothalami from narcoleptic individuals was reported. Using genome-wide association (GWA) in Caucasians with replication in three ethnic groups, we found association between narcolepsy and polymorphisms in the TRA@ (T-cell receptor alpha) locus, with highest significance at rs1154155 (average allelic odds ratio 1.69, genotypic odds ratios 1.94 and 2.55, P < 10−21, 1,830 cases, 2,164 controls). This is the first documented genetic involvement of the TRA@ locus, encoding the major receptor for HLA-peptide presentation, in any disease. It is still unclear how specific HLA alleles confer susceptibility to over 100 HLA-associated disorders; thus, narcolepsy will provide new insights on how HLA–TCR interactions contribute to organ-specific autoimmune targeting and may serve as a model for over 100 other HLA-associated disorders.

Common variants in P2RY11 are associated with narcolepsy

Growing evidence supports the hypothesis that narcolepsy with cataplexy is an autoimmune disease. We here report genome-wide association analyses for narcolepsy with replication and fine mapping across three ethnic groups (3,406 individuals of European ancestry, 2,414 Asians and 302 African Americans). We identify a SNP in the 3′ untranslated region of P2RY11, the purinergic receptor subtype P2Y11 gene, which is associated with narcolepsy (rs2305795, combined P = 6.1 × 10−10, odds ratio = 1.28, 95% CI 1.19–1.39, n = 5689). The disease-associated allele is correlated with reduced expression of P2RY11 in CD8+ T lymphocytes (72% reduced, P = 0.003) and natural killer (NK) cells (70% reduced, P = 0.031), but not in other peripheral blood mononuclear cell types. The low expression variant is also associated with reduced P2RY11-mediated resistance to ATP-induced cell death in T lymphocytes (P = 0.0007) and natural killer cells (P = 0.001). These results identify P2RY11 as an important regulator of immune-cell survival, with possible implications in narcolepsy and other autoimmune diseases.

ImmunoChip Study Implicates Antigen Presentation to T Cells in Narcolepsy

Recent advances in the identification of susceptibility genes and environmental exposures provide broad support for a post-infectious autoimmune basis for narcolepsy/hypocretin (orexin) deficiency. We genotyped loci associated with other autoimmune and inflammatory diseases in 1,886 individuals with hypocretin-deficient narcolepsy and 10,421 controls, all of European ancestry, using a custom genotyping array (ImmunoChip). Three loci located outside the Human Leukocyte Antigen (HLA) region on chromosome 6 were significantly associated with disease risk. In addition to a strong signal in the T cell receptor alpha (TRA@), variants in two additional narcolepsy loci, Cathepsin H (CTSH) and Tumor necrosis factor (ligand) superfamily member 4 (TNFSF4, also called OX40L), attained genome-wide significance. These findings underline the importance of antigen presentation by HLA Class II to T cells in the pathophysiology of this autoimmune disease.

Predictors of hypocretin (orexin) deficiency in narcolepsy without cataplexy.

STUDY OBJECTIVES To compare clinical, electrophysiologic, and biologic data in narcolepsy without cataplexy with low (≤ 110 pg/ml), intermediate (110-200 pg/ml), and normal (> 200 pg/ml) concentrations of cerebrospinal fluid (CSF) hypocretin-1. SETTING University-based sleep clinics and laboratories. PATIENTS Narcolepsy without cataplexy (n = 171) and control patients (n = 170), all with available CSF hypocretin-1. DESIGN AND INTERVENTIONS Retrospective comparison and receiver operating characteristics curve analysis. Patients were also recontacted to evaluate if they developed cataplexy by survival curve analysis. MEASUREMENTS AND RESULTS The optimal cutoff of CSF hypocretin-1 for narcolepsy without cataplexy diagnosis was 200 pg/ml rather than 110 pg/ml (sensitivity 33%, specificity 99%). Forty-one patients (24%), all HLA DQB1*06:02 positive, had low concentrations (≤ 110 pg/ml) of CSF hypocretin-1. Patients with low concentrations of hypocretin-1 only differed subjectively from other groups by a higher Epworth Sleepiness Scale score and more frequent sleep paralysis. Compared with patients with normal hypocretin-1 concentration (n = 117, 68%), those with low hypocretin-1 concentration had higher HLA DQB1*06:02 frequencies, were more frequently non-Caucasians (notably African Americans), with lower age of onset, and longer duration of illness. They also had more frequently short rapid-eye movement (REM) sleep latency (≤ 15 min) during polysomnography (64% versus 23%), and shorter sleep latencies (2.7 ± 0.3 versus 4.4 ± 0.2 min) and more sleep-onset REM periods (3.6 ± 0.1 versus 2.9 ± 0.1 min) during the Multiple Sleep Latency Test (MSLT). Patients with intermediate concentrations of CSF hypocretin-1 (n = 13, 8%) had intermediate HLA DQB1*06:02 and polysomnography results, suggesting heterogeneity. Of the 127 patients we were able to recontact, survival analysis showed that almost half (48%) with low concentration of CSF hypocretin-1 had developed typical cataplexy at 26 yr after onset, whereas only 2% had done so when CSF hypocretin-1 concentration was normal. Almost all patients (87%) still complained of daytime sleepiness independent of hypocretin status. CONCLUSION Objective (HLA typing, MSLT, and sleep studies) more than subjective (sleepiness and sleep paralysis) features predicted low concentration of CSF hypocretin-1 in patients with narcolepsy without cataplexy.

CD4+ T Cell Autoimmunity to Hypocretin/Orexin and Cross-Reactivity to a 2009 H1N1 Influenza A Epitope in Narcolepsy

Patients with narcolepsy carry CD4+ T cells that react to peptides from both the sleep-regulating neuropeptide hypocretin and a 2009 H1N1 influenza A protein. New Clues About Narcolepsy Most adults long for more sleep, but patients with narcolepsy would rather be free of their excessive sleepiness. Some things about narcolepsy are clear: It is caused by the loss of the peptide hypocretin from neurons that control wakefulness, and it has a remarkably strong association with a particular human leukocyte antigen (HLA) molecule (DQ0602), suggesting that there is an immune contribution to the disease. Other things are not so clear: We do not know what triggers the disease, and there is no way to prevent it. The neurons that are destroyed in narcolepsy contain the body’s only store of hypocretin, so an immune response against hypocretin could conceivably be responsible for the disease. Although no antibodies to hypocretin have been found in patients, now De la Herrán-Arita et al. have identified CD4+ T cells that react against several peptides derived from hypocretin when they are presented by HLA DQ0602. The two 13–amino acid peptides, corresponding to the N-terminal ends of the mature, secreted forms of hypocretin, triggered responses in T cells from 23 patients with narcolepsy but not in matched DQ0602-positive healthy control subjects. Similarly, in pairs of twins discordant for narcolepsy, the twin with disease carried cells that were activated by hypocretin peptides, whereas the healthy twin did not. Clues about environmental factors that might contribute to narcolepsy have come from epidemiology studies that associate Streptococcus, influenza, and other infections with the disease. In Scandinavia, a particular flu vaccine was associated with increased narcolepsy risk. To investigate these associations further, the authors searched for epitopes in proteins from the flu virus that might activate the same T cells that responded to the hypocretin peptides. Within the flu protein hemagglutinin, they found a small segment that had this effect, amino acids 275 to 287. When cells from patients were incubated with this peptide presented by DQ0602, there was an increase in the number of cells reactive to both the hemagglutinin peptide and the hypocretin peptides, suggesting cross-reactivity between these epitopes. Although more research is necessary to understand the effects of the hypocretin-reactive cells in patients, these results point to a possible molecular mimicry between epitopes on hypocretin and the influenza hemagglutinin protein. Narcolepsy, a disorder strongly associated with human leukocyte antigen (HLA)–DQA1*01:02/DQB1*06:02 (DQ0602), is characterized by excessive daytime sleepiness, cataplexy, and rapid eye movement sleep abnormalities. It is caused by the loss of ~70,000 posterior hypothalamic neurons that produce the wake-promoting neuropeptide hypocretin (HCRT) (orexin). We identified two DQ0602-binding HCRT epitopes, HCRT56–68 and HCRT87–99, that activated a subpopulation of CD4+ T cells in narcolepsy patients but not in DQ0602-positive healthy control subjects. Because of the established association of narcolepsy with the 2009 H1N1 influenza A strain (pH1N1), we administered a seasonal influenza vaccine (containing pH1N1) to patients with narcolepsy and found an increased frequency of circulating HCRT56–68– and HCRT87–99–reactive T cells. We also identified a hemagglutinin (HA) pHA1 epitope specific to the 2009 H1N1 strain, pHA1275–287, with homology to HCRT56–68 and HCRT87–99. In vitro stimulation of narcolepsy CD4+ T cells with pH1N1 proteins or pHA1275–287 increased the frequency of HCRT56–68– and HCRT87–99–reactive T cells. Our data indicate the presence of CD4+ T cells that are reactive to HCRT in narcolepsy patients and possible molecular mimicry between HCRT and a similar epitope in influenza pH1N1, pHA1275–287.

Retraction of the research article: "CD4⁺ T cell autoimmunity to hypocretin/orexin and cross-reactivity to a 2009 H1N1 influenza A epitope in narcolepsy".

Post date 24 September 2014 Our Letter “Comment on ‘CD4+ T cell autoimmunity to hypocretin/orexin and cross-reactivity to a 2009 H1N1 influenza A epitope in narcolepsy’ ” ([ 1 ][1]) discussed the article by De la Herran-Arita et al . ([ 2 ][2]). That article provided evidence for CD4+ T

Dual Cases of Type 1 Narcolepsy with Schizophrenia and Other Psychotic Disorders

OBJECTIVE Cases of narcolepsy in association with psychotic features have been reported but never fully characterized. These patients present diagnostic and treatment challenges and may shed new light on immune associations in schizophrenia. METHOD Our case series was gathered at two narcolepsy specialty centers over a 9-year period. A questionnaire was created to improve diagnosis of schizophrenia or another psychotic disorder in patients with narcolepsy. Pathophysiological investigations included full HLA Class I and II typing, testing for known systemic and intracellular/synaptic neuronal antibodies, recently described neuronal surface antibodies, and immunocytochemistry on brain sections to detect new antigens. RESULTS Ten cases were identified, one with schizoaffective disorder, one with delusional disorder, two with schizophreniform disorder, and 6 with schizophrenia. In all cases, narcolepsy manifested first in childhood or adolescence, followed by psychotic symptoms after a variable interval. These patients had auditory hallucinations, which was the most differentiating clinical feature in comparison to narcolepsy patients without psychosis. Narcolepsy therapy may have played a role in triggering psychotic symptoms but these did not reverse with changes in narcolepsy medications. Response to antipsychotic treatment was variable. Pathophysiological studies did not reveal any known autoantibodies or unusual brain immunostaining pattern. No strong HLA association outside of HLA DQB1*06:02 was found, although increased DRB3*03 and DPA1*02:01 was notable. CONCLUSION Narcolepsy can occur in association with schizophrenia, with significant diagnostic and therapeutic challenges. Dual cases maybe under diagnosed, as onset is unusually early, often in childhood. Narcolepsy and psychosis may share an autoimmune pathology; thus, further investigations in larger samples are warranted.

Narcolepsy in African Americans.

STUDY OBJECTIVES Although narcolepsy affects 0.02-0.05% of individuals in various ethnic groups, clinical presentation in different ethnicities has never been fully characterized. Our goal was to study phenotypic expression across ethnicities in the United States. DESIGN/SETTING Cases of narcolepsy from 1992 to 2013 were identified from searches of the Stanford Center for Narcolepsy Research database. International Classification of Sleep Disorders, Third Edition diagnosis criteria for type 1 and type 2 narcolepsy were used for inclusion, but subjects were separated as with and without cataplexy for the purpose of data presentation. Information extracted included demographics, ethnicity and clinical data, HLA-DQB1*06:02, polysomnography (PSG), multiple sleep latency test (MSLT) data, and cerebrospinal fluid (CSF) hypocretin-1 level. PATIENTS 182 African-Americans, 839 Caucasians, 35 Asians, and 41 Latinos with narcolepsy. RESULTS Sex ratio, PSG, and MSLT findings did not differ across ethnicities. Epworth Sleepiness Scale (ESS) score was higher and age of onset of sleepiness earlier in African Americans compared with other ethnicities. HLA-DQB1*06:02 positivity was higher in African Americans (91.0%) versus others (76.6% in Caucasians, 80.0% in Asians, and 65.0% in Latinos). CSF hypocretin-1 level, obtained in 222 patients, was more frequently low (≤ 110 pg/ml) in African Americans (93.9%) versus Caucasians (61.5%), Asians (85.7%) and Latinos (75.0%). In subjects with low CSF hypocretin-1, African Americans (28.3%) were 4.5 fold more likely to be without cataplexy when compared with Caucasians (8.1%). CONCLUSIONS Narcolepsy in African Americans is characterized by earlier symptom onset, higher Epworth Sleepiness Scale score, higher HLA-DQB1*06:02 positivity, and low cerebrospinal fluid hypocretin-1 level in the absence of cataplexy. In African Americans, more subjects without cataplexy have type 1 narcolepsy.

The structured diagnostic interview for sleep patterns and disorders: rationale and initial evaluation.

OBJECTIVES We aimed to describe and report the initial validity of a newly developed structured interview for sleep disorders (Diagnostic Interview for Sleep Patterns and Disorders [DISP]) administered by trained lay interviewers. METHODS A total of 225 patients with various sleep disorders were recruited from two nationally recognized sleep centers in the United States. The International Classification of Sleep Disorders, second edition (ICSD-2) criteria, were used to classify sleep disorders (e.g., delayed sleep phase disorder, hypersomnia, narcolepsy with cataplexy [NC], restless legs syndrome [RLS], periodic limb movement disorder [PLMD], insomnia, rapid eye movement sleep behavior disorder [RBD], and obstructive sleep apnea [OSA]). Interview diagnoses were compared with final diagnoses by sleep specialists (reference diagnosis based on clinical history, examination, and polysomnography [PSG] when indicated). RESULTS DISP diagnoses had fair to substantial concordance with clinician diagnoses for various sleep disorders, with area under the receiver operator characteristic curves (AUC) ranging from 0.65 to 0.84. Participants classified by the clinician as having a sleep disorder were moderately well-detected (sensitivity ranging from 0.50 for RBD disorder to 0.87 for insomnia). Substantial specificity (>0.8) also was seen for five of the eight sleep disorders (i.e., delayed sleep phase, hypersomnia, NC, PLMD, and RBD). Interviews were more likely than clinicians to detect disorders secondary to the primary sleep problem. CONCLUSIONS The DISP provides an important tool for the detection of a wide range of sleep disorders in clinical settings and is particularly valuable in the detection of secondary disorders that were not the primary referral diagnosis.

The MSLT is Repeatable in Narcolepsy Type 1 But Not Narcolepsy Type 2: A Retrospective Patient Study

STUDY OBJECTIVES To examine repeatability of Multiple Sleep Latency Test (MSLT) results in narcolepsy type 1 (NT1) and narcolepsy type 2 (NT2) according to the criteria of the International Classification of Sleep Disorders, Third Edition (ICSD-3). METHODS Repeatability of the MSLT was retrospectively evaluated in NT1 (n = 60) and NT2 (n = 54) cases, and controls (n = 15). All subjects had documented HLA-DQB1*06:02 status and/or hypocretin-1 levels from cerebrospinal fluid. All subjects had undergone 2 MSLTs (≥ 1 meeting ICSD-3 criteria for narcolepsy). Repeatability was explored in children versus adults and in those on versus not on medication(s). Subsample and multivariate analysis were performed. RESULTS Both MSLTs in unmedicated patients were positive for narcolepsy in 78%, 18%, and 7% of NT1, NT2, and controls, respectively. NT2 cases changed to idiopathic hypersomnia or to a negative MSLT 26% and 57% of the time, respectively. Although NT1 cases were 10 to 14 times more likely to demonstrate a second positive MSLT compared to NT2 cases (P < 10-5) and controls (P < 10-4), respectively, NT2 cases were not significantly different from controls (P = .64). Medication use (P = .009) but not adult versus children status (P = .85) significantly decreased the likelihood of a repeat positive MSLT. CONCLUSIONS In a clinical setting, a positive MSLT for narcolepsy is a more reproducible and stable feature in NT1 than NT2. The retrospective design of this study hinders interpretation of these data, as there are many different, and possibly opposing, reasons to repeat a MSLT in NT1 versus NT2 (ie, ascertainment bias). Additional systematic MSLT repeatability studies independent of confounds are ideally needed to confirm these findings.