Homozygous HLA-DQB1*06:02 combined with T-cell receptor alpha polymorphism results in narcolepsy onset - A familial case report

Narcolepsy is a life-long neurological disorder with well-established genetic risk factors. Human leukocyte antigen-DQB1*06:02 remains the strongest genetic predeterminant; however, polymorphisms in genes encoding the T-cell receptor alpha chain are also strongly linked. This case report shows the inheritance pathway of these genetic markers contributing to narcolepsy onset in a 17-year-old female.

Enhanced influenza A H1N1 T cell epitope recognition and cross-reactivity to protein-O-mannosyltransferase 1 in Pandemrix-associated narcolepsy type 1

Narcolepsy type 1 (NT1) is a chronic neurological disorder having a strong association with HLA-DQB1*0602, thereby suggesting an immunological origin. Increased risk of NT1 has been reported among children or adolescents vaccinated with AS03 adjuvant-supplemented pandemic H1N1 influenza A vaccine, Pandemrix. Here we show that pediatric Pandemrix-associated NT1 patients have enhanced T-cell immunity against the viral epitopes, neuraminidase 175-189 (NA175-189) and nucleoprotein 214-228 (NP214-228), but also respond to a NA175-189-mimic, brain self-epitope, protein-O-mannosyltransferase 1 (POMT1675-689). A pathogenic role of influenza virus-specific T-cells and T-cell cross-reactivity in NT1 are supported by the up-regulation of IFN-γ, perforin 1 and granzyme B, and by the converging selection of T-cell receptor TRAV10/TRAJ17 and TRAV10/TRAJ24 clonotypes, in response to stimulation either with peptide NA175-189 or POMT1675-689. Moreover, anti-POMT1 serum autoantibodies are increased in Pandemrix-vaccinated children or adolescents. These results thus identify POMT1 as a potential autoantigen recognized by T- and B-cells in NT1.

Reassessment of the risk of narcolepsy in children in England 8 years after receipt of the AS03-adjuvanted H1N1 pandemic vaccine: A case-coverage study

BACKGROUND

Early studies of narcolepsy after AS03-adjuvanted pandemic A/H1N12009 vaccine (Pandemrix) could not define the duration of elevated risk post-vaccination nor the risk in children aged under 5 years who may not present until much older.

METHODS/FINDINGS

Clinical information and sleep test results, extracted from hospital notes at 3 large pediatric sleep centers in England between September 2017 and June 2018 for narcolepsy cases aged 4-19 years with symptom onset since January 2009, were reviewed by an expert panel to confirm the diagnosis. Vaccination histories were independently obtained from general practitioners (GPs). The odds of vaccination in narcolepsy cases compared with the age-matched English population was calculated after adjustment for clinical conditions that were indications for vaccination. GP questionnaires were returned for 242 of the 244 children with confirmed narcolepsy. Of these 5 were under 5 years, 118 were 5-11 years, and 119 were 12-19 years old at diagnosis; 39 were vaccinated with Pandemrix before onset. The odds ratio (OR) for onset at any time after vaccination was 1.94 (95% confidence interval [CI] 1.30-2.89), The elevated risk period was restricted to onsets within 12 months of vaccination (OR 6.65 [3.44-12.85]) and was highest within the first 6 months. After one year, ORs were not significantly different from 1 up to 8 years after vaccination. The ORs were similar in under five-year-olds and older ages. The estimated attributable risk was 1 in 34,500 doses. Our study is limited by including cases from only 3 sleep centers, who may differ from cases diagnosed in nonparticipating centers, and by imprecision in defining the centers' catchment population. The potential for biased recall of onset shortly after vaccination in cases aware of the association cannot be excluded.

CONCLUSIONS

In this study, we found that vaccine-attributable cases have onset of narcolepsy within 12 months of Pandemrix vaccination. The attributable risk is higher than previously estimated in England because of identification of vaccine-attributable cases with late diagnoses. Absence of a compensatory drop in risk 1-8 years after vaccination suggests that Pandemrix does not trigger onsets in those in whom narcolepsy would have occurred later.

CD8+ T cells from patients with narcolepsy and healthy controls recognize hypocretin neuron-specific antigens

Narcolepsy Type 1 (NT1) is a neurological sleep disorder, characterized by the loss of hypocretin/orexin signaling in the brain. Genetic, epidemiological and experimental data support the hypothesis that NT1 is a T-cell-mediated autoimmune disease targeting the hypocretin producing neurons. While autoreactive CD4+ T cells have been detected in patients, CD8+ T cells have only been examined to a minor extent. Here we detect CD8+ T cells specific toward narcolepsy-relevant peptides presented primarily by NT1-associated HLA types in the blood of 20 patients with NT1 as well as in 52 healthy controls, using peptide-MHC-I multimers labeled with DNA barcodes. In healthy controls carrying the disease-predisposing HLA-DQB1*06:02 allele, the frequency of autoreactive CD8+ T cells was lower as compared with both NT1 patients and HLA-DQB1*06:02-negative healthy individuals. These findings suggest that a certain level of CD8+ T-cell reactivity combined with HLA-DQB1*06:02 expression is important for NT1 development.

Neural network analysis of sleep stages enables efficient diagnosis of narcolepsy

Analysis of sleep for the diagnosis of sleep disorders such as Type-1 Narcolepsy (T1N) currently requires visual inspection of polysomnography records by trained scoring technicians. Here, we used neural networks in approximately 3,000 normal and abnormal sleep recordings to automate sleep stage scoring, producing a hypnodensity graph-a probability distribution conveying more information than classical hypnograms. Accuracy of sleep stage scoring was validated in 70 subjects assessed by six scorers. The best model performed better than any individual scorer (87% versus consensus). It also reliably scores sleep down to 5 s instead of 30 s scoring epochs. A T1N marker based on unusual sleep stage overlaps achieved a specificity of 96% and a sensitivity of 91%, validated in independent datasets. Addition of HLA-DQB1*06:02 typing increased specificity to 99%. Our method can reduce time spent in sleep clinics and automates T1N diagnosis. It also opens the possibility of diagnosing T1N using home sleep studies.

Autoimmunity in narcolepsy

PURPOSE OF REVIEW

Summarize the recent findings in narcolepsy focusing on the environmental and genetic risk factors in disease development.

RECENT FINDINGS

Both genetic and epidemiological evidence point towards an autoimmune mechanism in the destruction of orexin/hypocretin neurons. Recent studies suggest both humoral and cellular immune responses in the disease development.

SUMMARY

Narcolepsy is a severe sleep disorder, in which neurons producing orexin/hypocretin in the hypothalamus are destroyed. The core symptoms of narcolepsy are debilitating, extreme sleepiness, cataplexy, and abnormalities in the structure of sleep. Both genetic and epidemiological evidence point towards an autoimmune mechanism in the destruction of orexin/hypocretin neurons. Importantly, the highest environmental risk is seen with influenza-A infection and immunization. However, how the cells are destroyed is currently unknown. In this review we summarize the disease symptoms, and focus on the immunological findings in narcolepsy. We also discuss the environmental and genetic risk factors as well as propose a model for disease development.

Association Study of HLA-DQB1*0602 Allele in Iranian Patients with Narcolepsy

Narcolepsy is a rare, disabling disorder characterized by excessive daytime sleepiness, cataplexy, hypnagogic hallucinations and sleep paralysis. Several studies demonstrated its association with HLA-DQB1*0602 in various ethnic groups. Our study aimed to determine the prevalence of HLA-DQB1*0602 allele in Iranian patients with narcolepsy and assess its predictive parameters for diagnosing narcolepsy. In addition, car accidents and job problems were assessed among narcoleptic patients. We studied 44 narcoleptic patients, 30 patients with other types of excessive daytime sleepiness (EDS)  and 50 healthy age and sex matched individuals in this case-control study. Patients and controls filled out a questionnaire including items about car accidents due to sleepiness and job problems. International classification of sleep disorders-2 criteria was used as the gold standard for diagnosis of narcolepsy. The DNAs isolated from whole blood samples were collected from the patients and controls to assess the presence of HLA-DQB1*0602. The results showed that HLA DQB1*0602 was present in 4 (8%) individual of controls and 20 (45.5%) patients with higher prevalence in patients with cataplexy (78.9%) than patients without cataplexy (p<0.001). The sensitivities of the DQB1*0602 for diagnosing narcolepsy with cataplexy and narcolepsy without cataplexy were 78.9 and 20; specificities were 88 and 72.4, respectively. 18.2% of patients had car accidents due to sleepiness and 68.2% suffered from job problems. Our study shows that evaluation of DQB1*0602 in patients suspected to narcolepsy could be helpful especially in complex cases with atypical cataplexy and indistinguishable multiple sleep latency test MSLT results. Moreover, high rates of car accidents and job problems are found among narcoleptic patients.

The Safety of Adjuvanted Vaccines Revisited: Vaccine-Induced Narcolepsy

Despite the very high benefit-to-risk ratio of vaccines, the fear of negative side effects has discouraged many people from getting vaccinated, resulting in the reemergence of previously controlled diseases such as measles, pertussis and diphtheria. This fear has been amplified more recently by multiple epidemiologic studies that confirmed the link of an AS03-adjuvanted pandemic influenza vaccine (Pandemrix, GlaxoSmithKline Biologicals, Germany) used in Europe during the 2009 H1N1 influenza pandemic [A(H1N1) pdm09] with the development of narcolepsy, a chronic sleep disorder, in children and adolescents. However, public misperceptions of what adjuvants are and why they are used in vaccines has created in some individuals a closed "black box" attitude towards all vaccines. The focus of this review article is to revisit this "black box" using the example of narcolepsy associated with the European AS03-adjuvanted pandemic influenza vaccine.

Cerebrospinal fluid cytokine levels in type 1 narcolepsy patients very close to onset

Type 1 narcolepsy is caused by a loss of hypocretin (orexin) signaling in the brain. Genetic data suggests the disorder is caused by an autoimmune attack on hypocretin producing neurons in hypothalamus. This hypothesis has however not yet been confirmed by consistent findings of autoreactive antibodies or T-cells in patient samples. One explanation for these negative results may be that the autoimmune process is no longer active when patients present to the clinic. With increasing awareness in recent years, more and more patients have been diagnosed closer and closer to disease onset. In this study, we tested whether an active immune process in the brain could be detected in these patients, as reflected by increased cytokine levels in the cerebrospinal fluid (CSF). Using multiplex analysis, we measured the levels of 51 cytokines and chemokines in the CSF of 40 type 1 narcolepsy patients having varying disease duration. For comparison, we used samples from 9 healthy controls and 9 patients with other central hypersomnia. Cytokine levels did not differ significantly between controls and patients, even in 5 patients with disease onset less than a month prior to CSF sampling.

Autoantibodies against ganglioside GM3 are associated with narcolepsy-cataplexy developing after Pandemrix vaccination against 2009 pandemic H1N1 type influenza virus

Following the mass vaccinations against pandemic influenza A/H1N1 virus in 2009, a sudden increase in juvenile onset narcolepsy with cataplexy (NC) was detected in several European countries where AS03-adjuvanted Pandemrix vaccine had been used. NC is a chronic neurological disorder characterized by excessive daytime sleepiness and cataplexy. In human NC, the hypocretin-producing neurons in the hypothalamus or the hypocretin signaling pathway are destroyed by an autoimmune reaction. Both genetic (e.g. HLA-DQB1*0602) and environmental risk factors (e.g. Pandemrix) contribute to the disease development, but the underlying and the mediating immunological mechanisms are largely unknown. Influenza virus hemagglutinin is known to bind gangliosides, which serve as host cell virus receptors. Anti-ganglioside antibodies have previously been linked to various neurological disorders, like the Guillain-Barré syndrome which may develop after infection or vaccination. Because of these links we screened sera of NC patients and controls for IgG anti-ganglioside antibodies against 11 human brain gangliosides (GM1, GM2, GM3, GM4, GD1a, GD1b, GD2, GD3, GT1a, GT1b, GQ1b) and a sulfatide by using a line blot assay. Samples from 173 children and adolescents were analyzed: 48 with Pandemrix-associated NC, 20 with NC without Pandemrix association, 57 Pandemrix-vaccinated and 48 unvaccinated healthy children. We found that patients with Pandemrix-associated NC had more frequently (14.6%) anti-GM3 antibodies than vaccinated healthy controls (3.5%) (P = 0.047). Anti-GM3 antibodies were significantly associated with HLA-DQB1*0602 (P = 0.016) both in vaccinated NC patients and controls. In general, anti-ganglioside antibodies were more frequent in vaccinated (18.1%) than in unvaccinated (7.3%) individuals (P = 0.035). Our data suggest that autoimmunity against GM3 is a feature of Pandemrix-associated NC and that autoantibodies against gangliosides were induced by Pandemrix vaccination.

Neuronal Antibodies in Children with or without Narcolepsy following H1N1-AS03 Vaccination

Type 1 narcolepsy is caused by deficiency of hypothalamic orexin/hypocretin. An autoimmune basis is suspected, but no specific antibodies, either causative or as biomarkers, have been identified. However, the AS03 adjuvanted split virion H1N1 (H1N1-AS03) vaccine, created to protect against the 2009 Pandemic, has been implicated as a trigger of narcolepsy particularly in children. Sera and CSFs from 13 H1N1-AS03-vaccinated patients (12 children, 1 young adult) with type 1 narcolepsy were tested for autoantibodies to known neuronal antigens including the N-methyl-D-aspartate receptor (NMDAR) and contactin-associated protein 2 (CASPR2), both associated with encephalopathies that include disordered sleep, to rodent brain tissue including the lateral hypothalamus, and to live hippocampal neurons in culture. When sufficient sample was available, CSF levels of melanin-concentrating hormone (MCH) were measured. Sera from 44 H1N1-ASO3-vaccinated children without narcolepsy were also examined. None of these patients' CSFs or sera was positive for NMDAR or CASPR2 antibodies or binding to neurons; 4/13 sera bound to orexin-neurons in rat brain tissue, but also to other neurons. MCH levels were a marginally raised (n = 8; p = 0.054) in orexin-deficient narcolepsy patients compared with orexin-normal children (n = 6). In the 44 H1N1-AS03-vaccinated healthy children, there was no rise in total IgG levels or in CASPR2 or NMDAR antibodies three weeks following vaccination. In conclusion, there were no narcolepsy-specific autoantibodies identified in type 1 narcolepsy sera or CSFs, and no evidence for a general increase in immune reactivity following H1N1-AS03 vaccination in the healthy children. Antibodies to other neuronal specific membrane targets, with their potential for directing use of immunotherapies, are still an important goal for future research.

[Narcolepsy as an autoimmune disease]

Narcolepsy is a sleep disorder of central origin. Hypocretin deficiency is the essential feature of type 1 narcolepsy. The biological background of type 2 narcolepsy (without cataplexy) is less clear. Infections or other external factors are thought to function as triggers of narcolepsy. After the H1N1 vaccination campaign, the incidence of narcolepsy increased clearly in countries where a vaccine boosted with the AS03 adjuvant was used. According to the current view, the increase of narcolepsy in connection with the pandemic vaccine especially in children and adolescents was associated with the virus component of the vaccine, but the adjuvant may also have boosted the development of autoimmune response.

Antigenic differences between AS03 adjuvanted influenza A (H1N1) pandemic vaccines: implications for pandemrix-associated narcolepsy risk

Background

Narcolepsy results from immune-mediated destruction of hypocretin secreting neurons in hypothalamus, however the triggers and disease mechanisms are poorly understood. Vaccine-attributable risk of narcolepsy reported so far with the AS03 adjuvanted H1N1 vaccination Pandemrix has been manifold compared to the AS03 adjuvanted Arepanrix, which contained differently produced H1N1 viral antigen preparation. Hence, antigenic differences and antibody response to these vaccines were investigated.

Methods and Findings

Increased circulating IgG-antibody levels to Pandemrix H1N1 antigen were found in 47 children with Pandemrix-associated narcolepsy when compared to 57 healthy children vaccinated with Pandemrix. H1N1 antigen of Arepanrix inhibited poorly these antibodies indicating antigenic difference between Arepanrix and Pandemrix. High-resolution gel electrophoresis quantitation and mass spectrometry identification analyses revealed higher amounts of structurally altered viral nucleoprotein (NP) in Pandemrix. Increased antibody levels to hemagglutinin (HA) and NP, particularly to detergent treated NP, was seen in narcolepsy. Higher levels of antibodies to NP were found in children with DQB1*06∶02 risk allele and in DQB1*06∶02 transgenic mice immunized with Pandemrix when compared to controls.

Conclusions

This work identified 1) higher amounts of structurally altered viral NP in Pandemrix than in Arepanrix, 2) detergent-induced antigenic changes of viral NP, that are recognized by antibodies from children with narcolepsy, and 3) increased antibody response to NP in association of DQB1*06∶02 risk allele of narcolepsy. These findings provide a link between Pandemrix and narcolepsy. Although detailed mechanisms of Pandemrix in narcolepsy remain elusive, our results move the focus from adjuvant(s) onto the H1N1 viral proteins.

[Narcolepsy as an autoimmune disease]

Narcolepsy is a chronic sleep disorder characterized by excessive daytime sleepiness and irresistible sleep attacks that occur during the activities of daily living. Falling asleep in the middle of essential activities such as driving or crossing the street may lead to life-threatening situations. Narcolepsy is estimated to affect 0.002% of the Israeli population. By using animal models, human autopsies and brain biopsies, it has recently been shown that the destruction of the orexin-secreting neurons underlies the pathogenicity of this disease. Orexin is a neurotransmitter involved in the sleep arousal cycle and also in the development of hunger sensations. Based on circumstantial evidence, it is estimated that the autoimmune system is responsible for the destruction of the orexin-secreting neurons. There are several findings in the literature that might connect the autoimmunity with the narcolepsy existence. For instance: narcolepsy is associated with high frequency of specific HLA system alleles, especially DQB1*0602. Furthermore, polymorphism in the alpha chain of the T cell receptors was found among narcolepsy patients. A more direct connection is the discovery of the Trib--an autoantigen. This protein is presented by orexin-secreting neurons and was recently found in narcoleptic patients exclusively, and not in the healthy control group. Nevertheless, there is still no agreement within the scientific community since a direct link between the autoimmune mechanism and narcolepsy has not yet been proved. Several trials using immune modulator therapy did not show any significant improvement.

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.

While there is now broad consensus that narcolepsy-hypocretin deficiency results from a highly specific autoimmune attack on hypocretin cells, little is understood regarding the initiation and progression of the underlying autoimmune process. We have taken advantage of a unique high-density genotyping platform (the ImmunoChip) designed to study variants in genes known to be important to autoimmune and inflammatory diseases. Our study of nearly 2000 narcolepsy cases compared to 10,000 controls underscored important roles for HLA DQB1*06:02 and the T cell receptor alpha genes and implicated two additional genes, Cathepsin H and TNFSF4/OX40L, in disease pathogenesis. These findings are particularly important, as these encoded proteins have key roles in antigen processing, presentation, and T cell response, and they suggest that specific interactions at the immunological synapse constitute the pathway to the disease. Further studies of these genes and encoded proteins may therefore reveal the mechanism leading to this highly selective and unique autoimmune disease.

[Diagnostic and therapeutic update in narcolepsy]

Narcolepsy is an emblematic, unique disease within sleep disorders that is characterised by excessive daytime sleepiness, cataplexy and other abnormal manifestations of REM sleep. In the last 14 years truly spectacular progress has been made in our knowledge of this disease, since the discovery of its cause, i.e. a loss of the hypothalamic neurons that synthesise hypocretin, a previously unknown neurotransmitter, and its probable aetiopathogenic mechanisms, i.e. an autoimmune process in a patient with very precise immunological characteristics - a specific type of HLA and a specific type of T-cell receptor. The cause of this autoimmune process remains unknown. The definitive treatment - the administration of hypocretin, which is the substance missing in the organism - is still unavailable, but there are powerful drugs for treating its main symptoms, the sleepiness and the cataplexy. Some of these are classic compounds (methylphenidate, clomipramine), while others are more recent (modafinil, venlafaxine, sodium oxybate), but together they allow many patients to experience significant improvements. Lack of knowledge about the disease, both on the part of patients and their relatives as well as physicians, is the reason for the great delay in its diagnosis, with even more dramatic consequences when the disease begins in infancy.

DQB1*06:02 allele-specific expression varies by allelic dosage, not narcolepsy status

The association of narcolepsy-cataplexy, a sleep disorder caused by the loss of hypocretin/orexin neurons in the hypothalamus, with DQA1*01:02-DQB1*06:02 is one of the tightest known single-allele human leukocyte antigen (HLA) associations. In this study, we explored genome-wide expression in peripheral white blood cells of 50 narcolepsy versus 47 controls (half of whom were DQB1*06:02 positive) and observed the largest differences between the groups in the signal from HLA probes. Further studies of HLA-DQ expression (mRNA and protein in a subset) in 125 controls and 147 narcolepsy cases did not reveal any difference, a result we explain by the lack of proper control of allelic diversity in Affymetrix HLA probes. Rather, a clear effect of DQB1*06:02 allelic dosage on DQB1*06:02 mRNA levels (1.65-fold) and protein (1.59-fold) could be demonstrated independent of disease status. These results indicate that allelic dosage is transmitted into changes in heterodimer availability, a phenomenon that may explain the increased risk for narcolepsy in DQB1*06:02 homozygotes versus heterozygotes.

Genome-wide gene expression profiling of human narcolepsy

The objective of this study was to perform global gene expression profiling of patients affected by narcolepsy with cataplexy (NRLCP). This enabled identifying new potential biomarkers and relevant molecules possibly involved in the disease pathogenesis. In this study 10 NRLCP patients and 10 healthy controls were compared. Total RNA isolated from blood specimens was analyzed using microarray technology followed by statistical data analysis to detect genome-wide differential gene expression between patients and controls. Functional analysis of the gene list was performed in order to interpret the biological significance of the data. One hundred and seventy-three genes showed significant (p < 0.01) differential expression between the two tested conditions. The biological interpretation allowed categorizing differentially expressed genes involved in neurite outgrowth/extension and brain development, which could be possibly regarded as peripheral markers of the disease. Moreover, the NRLCP-related gene expression profiles indicated a dysregulation of metabolic and immune-related mechanisms. In conclusion, the gene expression profile associated to NRLCP suggested that molecular markers of neurological impairment, dysmetabolic and immune-related mechanisms, can be detected in blood of NRLCP patients.

IgG abnormality in narcolepsy and idiopathic hypersomnia

Background

A close association between narcolepsy and the Human Leukocyte Antigen (HLA)-DQB1*0602 allele suggests the involvement of the immune system, or possibly an autoimmune process. We investigated serum IgG levels in narcolepsy.

Methodology/Principal Findings

We measured the serum total IgG levels in 159 Japanese narcolepsy-cataplexy patients positive for the HLA-DQB1*0602 allele, 28 idiopathic hypersomnia patients with long sleep time, and 123 healthy controls (the HLA-DQB1*0602 allele present in 45 subjects). The serum levels of each IgG subclass were subsequently measured. The distribution of serum IgG was significantly different among healthy controls negative for the HLA-DQB1*0602 allele (11.66±3.55 mg/ml), healthy controls positive for the HLA-DQB1*0602 allele (11.45±3.43), narcolepsy patients (9.67±3.38), and idiopathic hypersomnia patients (13.81±3.80). None of the following clinical variables, age, disease duration, Epworth Sleepiness Scale, smoking habit and BMI at the time of blood sampling, were associated with IgG levels in narcolepsy or idiopathic hypersomnia. Furthermore we found the decrease in IgG1 and IgG2 levels, stable expression of IgG3, and the increase in the proportion of IgG4 in narcolepsy patients with abnormally low IgG levels. The increase in the proportion of IgG4 levels was also found in narcolepsy patients with normal serum total IgG levels. Idiopathic hypersomnia patients showed a different pattern of IgG subclass distribution with high IgG3 and IgG4 level, low IgG2 level, and IgG1/IgG2 imbalance.

Conclusions/Significance

Our study is the first to determine IgG abnormalities in narcolepsy and idiopathic hypersomnia by measuring the serum IgG levels in a large number of hypersomnia patients. The observed IgG abnormalities indicate humoral immune alterations in narcolepsy and idiopathic hypersomnia. Different IgG profiles suggest immunological differences between narcolepsy and idiopathic hypersomnia.

A study of T CD4, CD8 and B lymphocytes in narcoleptic patients

Narcolepsy is characterized by excessive daytime sleep and cataplexy. Little is known about the possible difference in pathophysiology between patients with or without cataplexy.

OBJECTIVE

To quantify T CD4, T CD8 and B lymphocytes in subgroups of patients with narcolepsy and the presence or absence of the HLA-DQB1*0602 allele between groups.

METHOD

Our study was prospective and controlled (transversal) with 22 narcoleptic patients and 23 health control subjects. Patients underwent an all-night polysomnographic recording (PSG) and a multiple sleep latency Test (MSLT). The histocompatibility antigen allele (HLA-DQB1*0602), T CD4, CD8 and B lymphocytes were quantified in control subjects and in narcoleptics.

RESULTS

The HLA-DQB1*0602 allele was identified in 10 (62.5%) of our 16 cataplexic subjects and in 2 (33.3%) of the 6 patients without cataplexy (p=0.24). In control subjects, HLA-DQB1*0602 allele was identified in 5 (20%). A significant decrease in T CD4 and B lymphocytes was found in narcoleptic patients with recurrent cataplexy when compared with our patients without cataplexy.

CONCLUSION

Autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis were associated with a decrease in sub-group of T CD4 and B lymphocytes. A drop in B lymphocytes count in reumathoid arthritis might, it is posited, be correlated to the presence of HLA-DRB1 allele along with an overall worsened outcome of the affliction. The theory of an increase in consumption of B lymphocytes over the maturation phase has likewise been put forward. Our study reinforces the view that narcolepsy should be considered from an immunological perspective.

Identification of differentially expressed genes in blood cells of narcolepsy patients

STUDY OBJECTIVE

A close association between the human leukocyte antigen (HLA)-DRB1*1501/DQB1*0602 and abnormalities in some inflammatory cytokines have been demonstrated in narcolepsy. Specific alterations in the immune system have been suggested to occur in this disorder. We attempted to identify alterations in gene expression underlying the abnormalities in the blood cells of narcoleptic patients.

DESIGNS

Total RNA from 12 narcolepsy-cataplexy patients and from 12 age- and sex-matched healthy controls were pooled. The pooled samples were initially screened for candidate genes for narcolepsy by differential display analysis using annealing control primers (ACP). The second screening of the samples was carried out by semiquantitative PCR using gene-specific primers. Finally, the expression levels of the candidate genes were further confirmed by quantitative real-time PCR using a new set of samples (20 narcolepsy-cataplexy patients and 20 healthy controls).

RESULTS

The second screening revealed differential expression of 4 candidate genes. Among them, MX2 was confirmed as a significantly down-regulated gene in the white blood cells of narcoleptic patients by quantitative real-time PCR.

CONCLUSION

We found the MX2 gene to be significantly less expressed in comparison with normal subjects in the white blood cells of narcoleptic patients. This gene is relevant to the immune system. Although differential display analysis using ACP technology has a limitation in that it does not help in determining the functional mechanism underlying sleep/wakefulness dysregulation, it is useful for identifying novel genetic factors related to narcolepsy, such as HLA molecules. Further studies are required to explore the functional relationship between the MX2 gene and narcolepsy pathophysiology.

Evaluation of hypothalamic-specific autoimmunity in patients with narcolepsy

An autoimmune-mediated mechanism is considered the most probable etiology for narcolepsy. However, this hypothesis remains unproven. Since narcolepsy is characterized by dysfunction of the hypothalamic hypocretinergic (orexinergic) system, we evaluated the presence of hypothalamic-specific antibodies in sera and CSF of 25 hypocretin-deficient and 6 non-deficient narcoleptic patients by immunohistochemistry and analyzing a screening of a rat cDNA expression hypothalamic library. There was no hypothalamic-specific reactivity in serum or CSF by inmmunohistochemistry. The screening of the hypothalmic library detected some reactive clones but not a common reactivity. Our study did not find any evidence of hypothalamic-specific autoimmunity in narcolepsy.

Analysis of extended HLA haplotypes in multiple sclerosis and narcolepsy families confirms a predisposing effect for the class I region in Tasmanian MS patients

Human leucocyte antigen (HLA)-DRB1*15 is associated with predisposition to multiple sclerosis (MS), although conjecture surrounds the possible involvement of an alternate risk locus in the class I region of the HLA complex. We have shown previously that an alternate MS risk allele(s) may be encompassed by the telomerically extended DRB1*15 haplotype, and here, we have attempted to map the putative variant. Thirteen microsatellite markers encompassing a 6.79-megabase (D6S2236-G51152) region, and the DRB1 and DQB1 genes, were genotyped in 166 MS simplex families and 104 control families from the Australian State of Tasmania and 153 narcolepsy simplex families (trios) from the USA. Complementary approaches were used to investigate residual predisposing effects of microsatellite alleles comprising the extended DRB1*15 haplotype taking into account the strong predisposing effect of DRB1*15: (1) Disease association of the extended DRB1*15 haplotype was compared for MS and narcolepsy families--predisposing effects were observed for extended class I microsatellite marker alleles in MS families, but not narcolepsy families; (2) disease association of the extended DRB1*15 haplotype was investigated after conditioning MS and control haplotypes on the absence of DRB1*15--a significant predisposing effect was observed for a 627-kb haplotype (D6S258 allele 8-MOGCA allele 4; MOG, myelin oligodendrocyte glycoprotein) spanning the extended class I region. MOGCA allele 4 displayed the strongest predisposing effect in DRB1*15-conditioned haplotypes (p = 0.0006; OR 2.83 [1.54-5.19]). Together, these data confirm that an alternate MS risk locus exists in the extended class I region in Tasmanian MS patients independent of DRB1*15.

Antibodies in narcolepsy–cataplexy patient serum bind to rat hypocretin neurons

Autoimmunity is considered the most likely cause of human narcolepsy-cataplexy, but no specific autoantibodies or antigen(s) have yet been identified. By means of indirect avidin-biotin immunohistochemical method, we searched for antibodies in serum from narcolepsy-cataplexy patients and controls that bind to rat hypocretin neurons. No staining was found in eight out of nine narcolepsy-cataplexy patients or controls. The serum from one narcolepsy-cataplexy patient, however, strongly produced staining of the membrane and superficial cytoplasm of neurons in the lateral hypothalamus. Dual staining revealed that the vast majority of the hypocretin-positive neurons were positive, but nonhypocretin neurons in the same area were binding antibodies from the patient's serum. These results show that antibodies bind to specific hypocretin- and nonhypocretin-containing neurons in the hypothalamus and indicate the presence of autoantibodies in narcolepsy patients.

Selected sleep disorders: restless legs syndrome and periodic limb movement disorder, sleep apnea syndrome, and narcolepsy

Sleep disorders, including restless legs syndrome and periodic limb movement disorder, sleep apnea syndrome, and narcolepsy, are prevalent medical conditions, likely to be seen by practicing psychiatrists. Awareness of these conditions and their presentations, pathophysiology, and treatment allows psychiatrists to treat these conditions where appropriate, to minimize complications and health consequences associated with delayed diagnosis, and to reduce the burden of disease that these conditions may place on patients already experiencing primary psychiatric disorders.

Plasma Levels of Tumor Necrosis Factor α and Soluble Tumor Necrosis Factor Receptors in Patients With Narcolepsy

BACKGROUND

Narcolepsy is a disabling sleep disorder characterized by excessive daytime sleepiness, cataplexy, hypnagogic hallucinations, and sleep paralysis. Recent studies suggest that the immune system might play a pathogenic role pointing to a possible involvement of inflammatory cytokines.

METHODS

We investigated a sample of 30 patients with narcolepsy in comparison with 120 sex- and age-matched and 101 sex-, body mass index (BMI)-, and age-matched randomly selected normal controls. In these groups, plasma concentrations of tumor necrosis factor alpha (TNF-alpha) and its soluble receptors p55 and p75 (soluble TNF receptor [sTNF-R] p55 and sTNF-R p75) were measured using commercial enzyme-linked immunosorbent assays.

RESULTS

The narcoleptic patients showed a significantly higher BMI compared with controls of the same age. Soluble TNF-R p75 levels were consistently elevated in the narcoleptic patients compared with their sex- and age-matched (P = .001) as well as sex-, BMI-, and age-matched counterparts (P = .003). Female narcoleptic patients exhibited higher sTNF-R p55 levels compared with their sex- and age-matched controls (P = .01), but this difference disappeared when comparing patients with sex-, BMI-, and age-matched normal controls. Tumor necrosis factor alpha levels did not differ significantly between groups.

CONCLUSION

Narcoleptic patients show increased plasma levels of sTNF-R p75, suggesting a functional alteration of the TNF-alpha cytokine system, further corroborating a possible pathogenic role of the immune system in this sleep disorder.

The neurobiology of hypocretins (orexins), narcolepsy and related therapeutic interventions

Narcolepsy is characterized by excessive daytime sleepiness, cataplexy and other manifestations of dissociated rapid eye movement sleep. Narcolepsy is typically treated with amphetamine-like stimulants (sleepiness) and antidepressants (cataplexy). Newer compounds, such as modafinil (non-amphetamine wake-promoting compound for excessive daytime sleepiness) and sodium oxybate (short-acting sedative for fragmented nighttime sleep, cataplexy, excessive daytime sleepiness), are increasingly used. Recent discoveries indicate that the major pathophysiology of human narcolepsy is the loss of lateral hypothalamic neurons that produce the neuropeptide hypocretin (orexin). Approximately 90% of people diagnosed as having narcolepsy with cataplexy are hypocretin ligand deficient. This has led to the development of new diagnostic tests (cerebrospinal fluid hypocretin-1 measurements). Hypocretin receptor agonists are likely to be ideal therapeutic options for hypocretin-deficient narcolepsy but such compounds are still not available in humans.

Immunohistochemical screening for autoantibodies against lateral hypothalamic neurons in human narcolepsy

Most human patients with narcolepsy have no detectable hypocretin-1 in their cerebrospinal fluid. The cause of this hypocretin deficiency is unknown, but the prevailing hypothesis states that an autoimmune-mediated mechanism is responsible. We screened for the presence of autoantibodies against neurons in the lateral hypothalamus in 76 patients and 63 controls, using immunohistochemistry. Autoantibodies were present in two patients, but also in two controls. However, one of the patients had a clearly different staining pattern and nerve endings of immunolabeled cells were found to project onto hypocretin-producing neurons, suggesting a possible pathophysiological role. Humoral immune mechanisms appear not to play a role in the pathogenesis of narcolepsy, at least not in the clinically overt stage of the disease.

Analysis of hypocretin (orexin) antibodies in patients with narcolepsy

STUDY OBJECTIVES

We tested the hypothesis that patients with narcolepsy have serum antibodies specific for preprohypocretin and its derivatives.

DESIGN

We tested sera from strictly diagnosed HLA DQB1*0602-positive narcoleptic patients with cataplexy for evidence of autoantibodies against human preprohypocretin, hypocretin 1 and 2, N-terminal leader and C-terminal peptides of preprohypocretin using enzyme-linked immunosorbent assays (ELISA). These results were compared to samples from nonnarcoleptic psychiatric and sleep apnea controls. Laboratory personnel were blinded to subject status.

SETTING

Narcoleptic patients and nonnarcoleptic controls were recruited from the Mayo Clinic facilities in Rochester, Minnesota; Scottsdale, Arizona; and Jacksonville, Florida. Laboratory testing was conducted in the Mayo Psychogenomic Laboratory at the Rochester Mayo Clinic.

PARTICIPANTS

A sample of 34 narcoleptic patients and 49 nonnarcoleptic controls.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

ELISA measurements were in optical density. Primary analyses were of the entire narcoleptic and control groups for each potential antigen, and none of the differences reached P values required for significance after Bonferroni adjustment. Secondary analyses by age and sex yielded P values that were significant after Bonferroni adjustment in only 2 cases, but further statistical analyses cast doubt on the veracity of these differences. In all cases where a significant difference was recorded, the hypothesis was not supported because the control optical density reading was higher than the narcoleptic values.

CONCLUSIONS

These ELISA assay results do not support the hypothesis that HLA DQB1*0602-positive narcolepsy with cataplexy is associated with serum antibodies against preprohypocretin or its cleavage products.

Narcolepsy: a review of evidence for autoimmune diathesis

Sporadic narcolepsy with cataplexy is a disabling disease that is strongly associated with the major histocompatibility class II allele HLA DQB1*0602 and is characterized by profound reduction in the cerebrospinal fluid (CSF) concentration of hypocretin 1 levels. This article provides a comprehensive review of the evidence that neurologic autoimmunity is the pathogenic basis of narcolepsy with cataplexy. Despite this evidence, specific antibody markers for narcolepsy have been elusive. Clinical trials using intravenous immunoglobulin infusions in recent onset narcolepsy with cataplexy have led to improvement in cataplexy in some patients. Future research must focus on elucidation of immune markers and early ameliorative treatments for narcolepsy.

Symptomatic narcolepsy, cataplexy and hypersomnia, and their implications in the hypothalamic hypocretin/orexin system

Human narcolepsy is a chronic sleep disorder affecting 1:2000 individuals. The disease is characterized by excessive daytime sleepiness, cataplexy and other abnormal manifestations of REM sleep, such as sleep paralysis and hypnagogic hallucinations. Recently, it was discovered that the pathophysiology of (idiopathic) narcolepsy-cataplexy is linked to hypocretin ligand deficiency in the brain and cerebrospinal fluid (CSF), as well as the positivity of the human leukocyte antigen (HLA) DR2/DQ6 (DQB1*0602). The symptoms of narcolepsy can also occur during the course of other neurological conditions (i.e. symptomatic narcolepsy). We define symptomatic narcolepsy as those cases that meet the International Sleep Disorders Narcolepsy Criteria, and which are also associated with a significant underlying neurological disorder that accounts for excessive daytime sleepiness (EDS) and temporal associations. To date, we have counted 116 symptomatic cases of narcolepsy reported in literature. As, several authors previously reported, inherited disorders (n=38), tumors (n=33), and head trauma (n=19) are the three most frequent causes for symptomatic narcolepsy. Of the 116 cases, 10 are associated with multiple sclerosis, one case of acute disseminated encephalomyelitis, and relatively rare cases were reported with vascular disorders (n=6), encephalitis (n=4) and degeneration (n=1), and hererodegenerative disorder (three cases in a family). EDS without cataplexy or any REM sleep abnormalities is also often associated with these neurological conditions, and defined as symptomatic cases of EDS. Although it is difficult to rule out the comorbidity of idiopathic narcolepsy in some cases, review of the literature reveals numerous unquestionable cases of symptomatic narcolepsy. These include cases with HLA negative and/or late onset, and cases in which the occurrences of the narcoleptic symptoms are parallel with the rise and fall of the causative disease. A review of these cases (especially those with brain tumors), illustrates a clear picture that the hypothalamus is most often involved. Several cases of symptomatic cataplexy (without EDS) were also reported and in contrast, these cases appear to be often associated with non-hypothalamic structures. CSF hypocretin-1 measurement were also carried out in a limited number of symptomatic cases of narcolepsy/EDS, including narcolepsy/EDS associated with tumors (n=5), head trauma (n=3), vascular disorders (n=5), encephalopathies (n=3), degeneration (n=30), demyelinating disorder (n=7), genetic/congenital disorders (n=11) and others (n=2). Reduced CSF hypocretin-1 levels were seen in most symptomatic narcolepsy cases of EDS with various etiologies and EDS in these cases is sometimes reversible with an improvement of the causative neurological disorder and an improvement of the hypocretin status. It is also noted that some symptomatic EDS cases (with Parkinson diseases and the thalamic infarction) appeared, but they are not linked with hypocretin ligand deficiency. In contrast to idiopathic narcolepsy cases, an occurrence of cataplexy is not tightly associated with hypocretin ligand deficiency in symptomatic cases. Since CSF hypocretin measures are still experimental, cases with sleep abnormalities/cataplexy are habitually selected for CSF hypocretin measures. Therefore, it is still not known whether all or a large majority of cases with low CSF hypocretin-1 levels with CNS interventions, exhibit EDS/cataplexy. It appears that further studies of the involvement of the hypocretin system in symptomatic narcolepsy and EDS are helpful to understand the pathophysiological mechanisms for the occurrence of EDS and cataplexy.

A functional autoantibody in narcolepsy

Narcolepsy is widely believed to have an autoimmune basis, but conventional immunological approaches have failed to detect a serum autoantibody marker. Since cholinergic hyperactivity is a feature of narcolepsy-cataplexy, we transferred IgG from nine patients with narcolepsy and nine healthy controls to mice and assessed the effect on smooth muscle contractile responses to cholinergic stimulation. IgG from all narcolepsy patients significantly enhanced bladder contractile responses to the muscarinic agonist carbachol and to neuronally released acetylcholine compared with control IgG (p<0.0001), whereas contraction of the sympathetically innervated vas deferens was unaltered. Our findings provide direct evidence for the autoimmune hypothesis of narcolepsy.

The clinical spectrum of narcolepsy with cataplexy: a reappraisal

In the absence of a golden standard for the diagnosis of narcolepsy, the clinical spectrum of disorder remains controversial. The aims of this study were (1) to determine frequency and characteristics of sleep-wake symptoms in patients with narcolepsy with cataplexy, (2) to compare clinical characteristics with results of ancillary tests, and (3) to identify factors that discriminate narcolepsy from other conditions with excessive daytime sleepiness (EDS). We prospectively studied 57 narcoleptics with cataplexy, 56 patients with non-narcoleptic hypersomnia (H), and 40 normal controls (No). Based on suggested and published criteria, we differentiated between narcoleptics with definite cataplexy (N) and narcoleptics without definite cataplexy (possible cataplexy, NpC). Assessment consisted of questionnaires [all patients and controls, including the Ullanlinna Narcolepsy Score (UNS)], polysomnography (all patients), multiple sleep latency test (MSLT) and human leukocyte antigen typing (in most narcoleptics). A new narcolepsy score based on five questions was developed. Data were compared with those of 12 hypocretin-deficient narcoleptics (N-hd). There were significant differences between N and NpC (including mean sleep latency on MSLT), but none between N and N-hd. A score of sleep propensity during active situations (SPAS) and the frequency of sleep paralysis/hallucinations at sleep onset, dreams of flying, and history of sleep shouting discriminated N from H and No (P < 0.001). Cataplexy-like symptoms in H (18%) and No (8%) could be discriminated from 'true' cataplexy in N on the basis of topography of motor effects, triggering emotions and triggering situations (P < 0.001). Our narcolepsy score had a similar sensitivity (96% versus 98%) but a higher specificity (98% versus 56%) than the UNS. Analysis of co-occurring symptoms in narcolepsy revealed two symptom complexes: EDS, cataplexy, automatic behaviors; and sleep paralysis, hallucinations, parasomnias. Low/undetectable cerebrospinal fluid hypocretin-1 levels and a history of definite cataplexy identify similar subgroups of narcoleptics. Specific questions on severity of EDS (SPAS score) and characteristics of cataplexy allow the recognition of subgroups of narcoleptics and their differentiation from non-narcoleptic EDS patients, including those reporting cataplexy-like episodes. The existence of co-occurring symptoms supports the hypothesis of a distinct pathophysiology of single narcoleptic symptoms.

Treatment with immunosuppressive and anti-inflammatory agents delays onset of canine genetic narcolepsy and reduces symptom severity

All Doberman pinschers and Labrador retrievers homozygous for a mutation of the hypocretin (orexin) receptor-2 (hcrtr2) gene develop narcolepsy under normal conditions. Degenerative changes and increased display of major histocompatibility complex class II antigens have been linked to symptom onset in genetically narcoleptic Doberman pinschers. This suggests that the immune system may contribute to neurodegenerative changes and narcoleptic symptomatology in these dogs. We therefore attempted to alter the course of canine genetic narcolepsy, as an initial test of principle, by administering a combination of three immunosuppressive and anti-inflammatory drugs chosen to suppress the immune response globally. Experimental dogs were treated with a combination of methylprednisolone, methotrexate and azathioprine orally starting within 3 weeks after birth, and raised in an environment that minimized pathogen exposure. Symptoms in treated and untreated animals were quantified using the food elicited cataplexy test (FECT), modified FECT and actigraphy. With drug treatment, time to cataplexy onset more than doubled, time spent in cataplexy during tests was reduced by more than 90% and nighttime sleep periods were consolidated. Short-term drug administration to control dogs did not reduce cataplexy symptoms, demonstrating that the drug regimen did not directly affect symptoms. Treatment was stopped at 6 months, after which experimental animals remained less symptomatic than controls until at least 2 years of age. This treatment is the first shown to affect symptom development in animal or human genetic narcolepsy. Our findings show that hcrtr2 mutation is not sufficient for the full symptomatic development of canine genetic narcolepsy and suggest that the immune system may play a role in the development of this disorder.