T cells in patients with narcolepsy target self-antigens of hypocretin neurons

Comorbidity of obstructive sleep apnea and narcolepsy: A challenging diagnosis and complex management

Introduction

Narcolepsy and obstructive sleep apnea syndrome (OSA) are relevant causes of excessive daytime sleepiness (EDS); although different for etiopathogenesis and symptoms, differential diagnosis is sometimes difficult, and guidelines are lacking concerning their management when coexisting in a same patient.

Methods

A narrative review of the literature was realized including PubMed, Scopus and Embase, aimed to regroup studies and case reports evaluating epidemiology, clinical and instrumental features and treatment of patients presenting comorbid NT1 and OSA. Moreover, a snowball search on the pathophysiology underpinnings of the association of the two disorder was realized.

Results

For adults, the prevalence of OSA in NT1 ranged from 24.8 % to 51.4 %. No studies were found concerning the treatment of EDS in double-diagnosis patients, but only case reports; these latter and the experience on patients with either NT or OSA suggest that modafinil, methylphenidate, pitolisant and solriamfetol are effective.

Discussion

Adults with NT1 showed a higher prevalence of OSA compared to the general population, but the reach of the results reviewed here is limited by the retrospective design of most of the studies and by the inhomogeneous utilization of diagnostic criteria. The association with OSA is likely to be explained by the involvement of orexin in hypercapnic-hypoxic responses: a deficit of orexin may promote obstructive events during sleep. Open questions warrant further investigation, especially orexin's involvement in other sleep disorders associated with EDS, and the more appropriate treatment for the OSA-narcolepsy comorbidity.

Estimating the prevalence and clinical causality of obstructive sleep apnea in paediatric narcolepsy patients

BACKGROUND

Numerous risk factors in paediatric narcolepsy may predispose them to obstructive sleep apnea (OSA). The concurrent presence of OSA in these patients might lead to underdiagnosing narcolepsy. This research investigates the prevalence and potential causality between OSA and paediatric narcolepsy.

METHODS

A case-control study coupled with a two-sample Mendelian randomization (MR) analysis was employed to explore the prevalence and causal link between paediatric narcolepsy and OSA risk.

RESULTS

The case-control study revealed that paediatric narcolepsy patients are at an increased risk of OSA, with an Odds ratio (OR) of 4.87 (95% CI: 2.20-10.71; P < 0.001). The inverse-variance weighted (IVW) model further suggests a potential causal link between narcolepsy and OSA (IVW OR: 4.671, 95% CI: 1.925-11.290; P < 0.001). Additionally, sensitivity analysis confirmed these findings' reliability.

CONCLUSION

The findings highlight an elevated prevalence and genetic susceptibility to OSA among paediatric narcolepsy patients, underscoring the necessity for clinical screening of OSA. Continued research is essential to clarify the pathogenic mechanisms and develop potential treatments.

REM sleep in narcolepsy

Narcolepsy is mainly associated with excessive daytime sleepiness, but the characteristic feature is abnormal rapid eye movement (REM) sleep phenomena. REM sleep disturbances can manifest as cataplexy (in narcolepsy type 1), sleep paralysis, sleep-related hallucinations, REM sleep behavior disorder, abnormal dreams, polysomnographic evidence of REM sleep disruption with sleep-onset REM periods, and fragmented REM sleep. Characterization of REM sleep and related symptoms facilitates the differentiation of narcolepsy from other central hypersomnolence disorders and aids in distinguishing between narcolepsy types 1 and 2. A circuit comprising regions within the brainstem, forebrain, and hypothalamus is involved in generating and regulating REM sleep, which is influenced by changes in monoamines, acetylcholine, and neuropeptides. REM sleep is associated with brainstem functions, including autonomic control, and REM sleep disturbances may be associated with increased cardiovascular risk. Medications used to treat narcolepsy (and REM-related symptoms of narcolepsy) include stimulants/wake-promoting agents, pitolisant, oxybates, and antidepressants; hypocretin agonists are a potential new class of therapeutics. The role of REM sleep disturbances in narcolepsy remains an area of active research in pathophysiology, symptom management, and treatment. This review summarizes the current understanding of the role of REM sleep and its dysfunction in narcolepsy.

Crinophagic granules in pancreatic β cells contribute to mouse autoimmune diabetes by diversifying pathogenic epitope repertoire

Autoimmune attack toward pancreatic β cells causes permanent loss of glucose homeostasis in type 1 diabetes (T1D). Insulin secretory granules store and secrete insulin but are also thought to be tissue messengers for T1D. Here, we show that the crinophagic granules (crinosome), a minor set of vesicles formed by fusing lysosomes with the conventional insulin dense-core granules (DCG), are pathogenic in T1D development in mouse models. Pharmacological inhibition of crinosome formation in β cells delays T1D progression without affecting the dominant DCGs. Mechanistically, crinophagy inhibition diminishes the epitope repertoire in pancreatic islets, including cryptic, modified and disease-relevant epitopes derived from insulin. These unconventional insulin epitopes are largely undetectable in the MHC-II epitope repertoire of the thymus, where only canonical insulin epitopes are presented. CD4+ T cells targeting unconventional insulin epitopes display autoreactive phenotypes, unlike tolerized T cells recognizing epitopes presented in the thymus. Thus, the crinophagic pathway emerges as a tissue-intrinsic mechanism that transforms insulin from a signature thymic self-protein to a critical autoantigen by creating a peripheral-thymic mismatch in the epitope repertoire.

Recent insights into the pathophysiology of narcolepsy type 1

Narcolepsy type 1 (NT1) is a sleep-wake disorder in which people typically experience excessive daytime sleepiness, cataplexy and other sleep-wake disturbances impairing daily life activities. NT1 symptoms are due to hypocretin deficiency. The cause for the observed hypocretin deficiency remains unclear, even though the most likely hypothesis is that this is due to an auto-immune process. The search for autoantibodies and autoreactive T-cells has not yet produced conclusive evidence for or against the auto-immune hypothesis. Other mechanisms, such as reduced corticotrophin-releasing hormone production in the paraventricular nucleus have recently been suggested. There is no reversive treatment, and the therapeutic approach is symptomatic. Early diagnosis and appropriate NT1 treatment is essential, especially in children to prevent impaired cognitive, emotional and social development. Hypocretin receptor agonists have been designed to replace the attenuated hypocretin signalling. Pre-clinical and clinical trials have shown encouraging initial results. A better understanding of NT1 pathophysiology may contribute to faster diagnosis or treatments, which may cure or prevent it.

Immune Reconstitution Inflammatory Syndrome Due to HIV Treatment as a Potential Trigger: A Case Report with Late-Onset Narcolepsy

Narcolepsy type 1 (NT1) is a unique central sleepiness disorder that affects individuals with excessive daytime sleepiness (EDS), cataplexy, sleep paralysis, and hypnagogic hallucinations. The etiology and pathogenesis of NT1 remains unclear, although some viral infections are thought to be related to NT1. This paper reports an unusual case of late-onset NT1 with human immunodeficiency virus (HIV) infection and antiretroviral therapy for five years. The relationship between HIV infection, immune, Immune reconstitution inflammatory syndrome (IRIS) and NT1 should be further investigated, as excessive daytime sleepiness is more common in HIV-infected patients than in the general population.

Infection, vaccination and narcolepsy type 1: Evidence and potential molecular mechanisms

NT1 is a rare, chronic and disabling neurological disease causing excessive daytime sleepiness and cataplexy. NT1 is characterized pathologically by an almost complete loss of neurons producing the hypocretin (HCRT)/orexin neuropeptides in the lateral hypothalamus. While the exact etiology of NT1 is still unknown, numerous studies have provided compelling evidence supporting its autoimmune origin. The prevailing hypothetical view on the pathogenesis of NT1 involves an immune-mediated loss of HCRT neurons that can be triggered by Pandemrix® vaccination and/or by infection in genetically susceptible patients, specifically carriers of the HLA-DQB1*06:02 MHC class II allele. The molecular mechanisms by which infection/vaccination can induce autoimmunity in the case of NT1 remain to be elucidated. In this review, evidence regarding the involvement of vaccination and infection and the potential mechanisms by which it could be linked to the pathogenesis of NT1 will be discussed in light of the existing findings in other autoimmune diseases.

Child Neurology: Common Occurrence of Narcolepsy Type 1 and Myasthenia Gravis

Narcolepsy with cataplexy and myasthenia gravis are both chronic neurologic conditions causing symptoms of muscle weakness, often affecting facial muscles, and have both been attributed to an immune-mediated etiology. We report an adolescent girl diagnosed with both conditions and discuss possible shared mechanisms and the diagnostic challenges presented by her case to inform and aid clinicians managing children and young people with these rare conditions.

Narcolepsy and rapid eye movement sleep

Since the first description of narcolepsy at the end of the 19th Century, great progress has been made. The disease is nowadays distinguished as narcolepsy type 1 and type 2. In the 1960s, the discovery of rapid eye movement sleep at sleep onset led to improved understanding of core sleep-related disease symptoms of the disease (excessive daytime sleepiness with early occurrence of rapid eye movement sleep, sleep-related hallucinations, sleep paralysis, rapid eye movement parasomnia), as possible dysregulation of rapid eye movement sleep, and cataplexy resembling an intrusion of rapid eye movement atonia during wake. The relevance of non-sleep-related symptoms, such as obesity, precocious puberty, psychiatric and cardiovascular morbidities, has subsequently been recognized. The diagnostic tools have been improved, but sleep-onset rapid eye movement periods on polysomnography and Multiple Sleep Latency Test remain key criteria. The pathogenic mechanisms of narcolepsy type 1 have been partly elucidated after the discovery of strong HLA class II association and orexin/hypocretin deficiency, a neurotransmitter that is involved in altered rapid eye movement sleep regulation. Conversely, the causes of narcolepsy type 2, where cataplexy and orexin deficiency are absent, remain unknown. Symptomatic medications to treat patients with narcolepsy have been developed, and management has been codified with guidelines, until the recent promising orexin-receptor agonists. The present review retraces the steps of the research on narcolepsy that linked the features of the disease with rapid eye movement sleep abnormality, and those that do not appear associated with rapid eye movement sleep.

The Changed Nocturnal Sleep Structure and Higher Anxiety, Depression, and Fatigue in Patients with Narcolepsy Type 1

Purpose

This study aimed to evaluate nocturnal sleep structure and anxiety, depression, and fatigue in patients with narcolepsy type 1 (NT1).

Methods

Thirty NT1 patients and thirty-five healthy controls were enrolled and evaluated using the Epworth sleepiness scale (ESS), Generalized Anxiety Disorder-7, Patient Health Questionnaire-9, Fatigue Severity Scale (FSS), polysomnography, multiple sleep latency test, and brain function state monitoring. Statistical analyses were performed using SPSS Statistics for Windows, version 23.0. Benjamini-Hochberg correction was performed to control the false discovery rate.

Results

Apart from typical clinical manifestations, patients with NT1 are prone to comorbidities such as nocturnal sleep disorders, anxiety, depression, and fatigue. Compared with the control group, patients with NT1 exhibited abnormal sleep structure, including increased total sleep time (P adj=0.007), decreased sleep efficiency (P adj=0.002), shortening of sleep onset latency (P adj<0.001), elevated wake after sleep onset (P adj=0.002), increased N1% (P adj=0.006), and reduced N2%, N3%, and REM% (P adj=0.007, P adj<0.001, P adj=0.013). Thirty-seven percent of patients had moderate to severe obstructive sleep apnea-hypopnea syndrome. And sixty percent of patients were complicated with REM sleep without atonia. Patients with NT1 displayed increased anxiety propensity (P adj<0.001), and increased brain fatigue (P adj=0.020) in brain function state monitoring. FSS scores were positively correlated with brain fatigue (P adj<0.001) and mean sleep latency was inversely correlated with FSS scores and brain fatigue (P adj=0.013, P adj=0.029). Additionally, ESS scores and brain fatigue decreased after 3 months of therapy (P=0.012, P=0.030).

Conclusion

NT1 patients had abnormal nocturnal sleep structures, who showed increased anxiety, depression, and fatigue. Excessive daytime sleepiness and fatigue improved after 3 months of treatment with methylphenidate hydrochloride prolonged-release tablets in combination with venlafaxine.

Correlation analysis between HLA-DQA1*0102/DQB1*0602 genotypes and narcolepsy patients in China

Background and objective

At present, the etiology of narcolepsy is not fully understood, and it is generally believed to be an autoimmune reaction caused by interactions between environmental and genetic factors. Human leukocyte antigen (HLA) class II genes are strongly associated with this gene, especially HLA-DQB1*0602/DQA1*0102. In this study, we mainly analyzed the correlation between different genotypes of HLA-DQB1*0602/DQA1*0102 and clinical manifestations in Chinese patients with narcolepsy.

Experimental method

Narcolepsy patients who were treated at the Department of Neurology, The First Affiliated Hospital of Shandong First Medical University from January 2021 to September 2023 were selected. General information, sleep monitoring data, cerebrospinal fluid (CSF) orexin levels, and human leukocyte antigen gene typing data were collected. The statistical analysis was performed using SPSS 26.0, and the graphs were drawn using GraphPad Prism 9.5.

Main results

A total of 78 patients were included in this study. The DQA1 and DQB1 gene loci were detected in 54 patients, and only the DQB1 gene locus was detected in 24 narcoleptic patients. The most common allele at the HLA-DQB1 locus was *0602 (89.7%), and the most common genotype at this locus was *0602*0301 (19.2%), followed by *0602*0602 (17.9%). The most common phenotype of the HLA-DQA1 locus is *0102 (92.6%), and the most common genotype of this locus is *0102*0102 (27.8%), followed by *0102*0505 (14.8%). There were significant differences (p < 0.05) between HLA-DQB1*0602-positive and HLA-DQB1*0602-negative patients in terms of orexin-A levels, presence or absence of cataplexy, UNS, PSG sleep latency, REM sleep latency, N1 sleep percentage, oxygen depletion index, and average REM latency on the MSLT. The HLA-DQA1*0102-positive and HLA-DQA1*0102-negative patients showed significant differences (p < 0.05) in disease course, presence or absence of sudden onset, PSG REM sleep latency, N1 sleep percentage, and average REM latency on the MSLT. There were significant differences in the average REM latency of the MSLT between HLA-DQB1*0602/DQA1*0102 homozygous and heterozygous patients p < 0.05, and no differences were found in the baseline data, orexin-A levels, scale scores, or other sleep parameters.

Conclusion

Different genotypes of HLA-DQA1*0102/DQB1*0602 are associated with symptoms of cataplexy in Chinese narcoleptic patients. Homozygous individuals have a shorter mean REM latency in the MSLT, greater genetic susceptibility, and relatively more severe sleepiness.

Downregulation of hypocretin/orexin after H1N1 Pandemrix vaccination of adolescent mice

Narcolepsy type 1 (NT1), characterized by the loss of hypocretin/orexin (HCRT) production in the lateral hypothalamus, has been linked to Pandemrix vaccination during the 2009 H1N1 pandemic, especially in children and adolescents. It is still unknown why this vaccination increased the risk of developing NT1. This study investigated the effects of Pandemrix vaccination during adolescence on Hcrt mRNA expression in mice. Mice received a primary vaccination (50 µL i.m.) during prepubescence and a booster vaccination during peri-adolescence. Hcrt expression was measured at three-time points after the vaccinations. Control groups included both a saline group and an undisturbed group of mice. Hcrt expression was decreased after both Pandemrix and saline injections, but 21 days after the second injection, the saline group no longer showed decreased Hcrt expression, while the Pandemrix group still exhibited a significant reduction of about 60% compared to the undisturbed control group. This finding suggests that Pandemrix vaccination during adolescence influences Hcrt expression in mice into early adulthood. The Hcrt mRNA level did not reach the low levels known to induce NT1 symptoms, instead, our finding supports the multiple-hit hypothesis of NT1 that states that several insults to the HCRT system may be needed to induce NT1 and that Pandemrix could be one such insult.

Identification of bidirectional causal links between gut microbiota and narcolepsy type 1 using Mendelian randomization

STUDY OBJECTIVES

Narcolepsy type 1 (NT1), characterized by cataplexy and orexin deficiency, is a rare and frequently debilitating neurological disorder. It has been noted to have connections with the gut microbiota, yet the exact causal relationships remain unclear.

METHODS

We conducted a comprehensive bidirectional Mendelian randomization (MR) study to rigorously investigate the causal links between the gut microbiota and NT1, utilizing genetic datasets from the MiBioGen consortium and FinnGen consortium, respectively. The inverse-variance weighted (IVW) method was employed to obtain the primary MR estimates, supplemented by several alternative methods as well as sensitivity analyses including Cochran's Q, MR-Egger, MR pleiotropy residual sum and outlier, leave-one-out, and genetic colocalization.

RESULTS

Our findings indicated that an increased relative abundance of five genera including Blautia (p = 4.47E-5), Collinsella (p = 0.036), Gordonibacter (p = 0.047), Hungatella (p = 0.015), and Lachnospiraceae UCG010 (p = 0.027) may be associated with a decreased risk of NT1. Conversely, an increased relative abundance of class Betaproteobacteria (p = 0.032), genus Alloprevotella (p = 0.009), and genus Ruminiclostridium6 (p = 0.029) may potentially heighten the risk of NT1. The onset of NT1 may lead to a decrease in the relative abundance of genus Eubacterium eligens group (p = 0.022), while a increase in the family Family XI (p = 0.009), genus Hungatella (p = 0.005), genus Prevotella (p = 0.013), and unknown genus id.2001 (p = 0.019). These findings remained robust under all sensitivity analyses.

CONCLUSIONS

Our results offer robust evidence for the bidirectional causal links between particular gut microbial taxa and NT1, underscoring the significance of the microbiota-gut-brain axis in the pathological process of NT1.

Absence of specific autoantibodies in patients with narcolepsy type 1 as indicated by an unbiased random peptide-displayed phage screening

Narcolepsy type 1 (NT1) is an enigmatic sleep disorder characterized by the selective loss of neurons producing orexin (also named hypocretin) in the lateral hypothalamus. Although NT1 is believed to be an autoimmune disease, the orexinergic neuron-specific antigens targeted by the pathogenic immune response remain elusive. In this study, we evaluated the differential binding capacity of various peptides to serum immunoglobin G from patients with NT1 and other hypersomnolence complaints (OHCs). These peptides were selected using an unbiased phage display technology or based on their significant presence in the serum of NT1 patients as identified from previous studies. Although the subtractive biopanning strategy successfully enriched phage clones with high reactivity against NT1 serum IgG, the 101 randomly selected individual phage clones could not differentiate the sera from NT1 and OHC. Compared to the OHC control group, serum from several NT1 patients exhibited increased reactivity to the 12-mer peptides derived from TRBV7, BCL-6, NRXN1, RXRG, HCRT, and RTN4 proteins, although not statistically significant. Collectively, employing both unbiased and targeted methodologies, we were unable to detect the presence of specific autoantibodies in our NT1 patient cohort. This further supports the hypothesis that the autoimmune response in NT1 patients likely stems primarily from T cell-mediated immunity rather than humoral immunity.

Autoreactive T cells target peripheral nerves in Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is a rare heterogenous disorder of the peripheral nervous system, which is usually triggered by a preceding infection, and causes a potentially life-threatening progressive muscle weakness1. Although GBS is considered an autoimmune disease, the mechanisms that underlie its distinct clinical subtypes remain largely unknown. Here, by combining in vitro T cell screening, single-cell RNA sequencing and T cell receptor (TCR) sequencing, we identify autoreactive memory CD4+ cells, that show a cytotoxic T helper 1 (TH1)-like phenotype, and rare CD8+ T cells that target myelin antigens of the peripheral nerves in patients with the demyelinating disease variant. We characterized more than 1,000 autoreactive single T cell clones, which revealed a polyclonal TCR repertoire, short CDR3β lengths, preferential HLA-DR restrictions and recognition of immunodominant epitopes. We found that autoreactive TCRβ clonotypes were expanded in the blood of the same patient at distinct disease stages and, notably, that they were shared in the blood and the cerebrospinal fluid across different patients with GBS, but not in control individuals. Finally, we identified myelin-reactive T cells in the nerve biopsy from one patient, which indicates that these cells contribute directly to disease pathophysiology. Collectively, our data provide clear evidence of autoreactive T cell immunity in a subset of patients with GBS, and open new perspectives in the field of inflammatory peripheral neuropathies, with potential impact for biomedical applications.

Connecting the dots: An updated review of the role of autoimmunity in narcolepsy and emerging immunotherapeutic approaches

BACKGROUND

Narcolepsy type 1 (NT1) is a chronic disorder characterized by pathological daytime sleepiness and cataplexy due to the disappearance of orexin immunoreactive neurons in the hypothalamus. Genetic and environmental factors point towards a potential role for inflammation and autoimmunity in the pathogenesis of the disease. This study aims to comprehensively review the latest evidence on the autoinflammatory mechanisms and immunomodulatory treatments aimed at suspected autoimmune pathways in NT1.

METHODS

Recent relevant literature in the field of narcolepsy, its autoimmune hypothesis, and purposed immunomodulatory treatments were reviewed.

RESULTS

Narcolepsy is strongly linked to specific HLA alleles and T-cell receptor polymorphisms. Furthermore, animal studies and autopsies have found infiltration of T cells in the hypothalamus, supporting T cell-mediated immunity. However, the role of autoantibodies has yet to be definitively established. Increased risk of NT1 after H1N1 infection and vaccination supports the autoimmune hypothesis, and the potential role of coronavirus disease 2019 and vaccination in triggering autoimmune neurodegeneration is a recent finding. Alterations in cytokine levels, gut microbiota, and microglial activation indicate a potential role for inflammation in the disease's development. Reports of using immunotherapies in NT1 patients are limited and inconsistent. Early treatment with IVIg, corticosteroids, plasmapheresis, and monoclonal antibodies has seldomly shown some potential benefits in some studies.

CONCLUSION

The current body of literature supports that narcolepsy is an autoimmune disorder most likely caused by T-cell involvement. However, the potential for immunomodulatory treatments to reverse the autoinflammatory process remains understudied. Further clinical controlled trials may provide valuable insights into this area.

The immunopathogenesis of narcolepsy type 1

Narcolepsy type 1 (NT1) is a chronic sleep disorder resulting from the loss of a small population of hypothalamic neurons that produce wake-promoting hypocretin (HCRT; also known as orexin) peptides. An immune-mediated pathology for NT1 has long been suspected given its exceptionally tight association with the MHC class II allele HLA-DQB1*06:02, as well as recent genetic evidence showing associations with polymorphisms of T cell receptor genes and other immune-relevant loci and the increased incidence of NT1 that has been observed after vaccination with the influenza vaccine Pandemrix. The search for both self-antigens and foreign antigens recognized by the pathogenic T cell response in NT1 is ongoing. Increased T cell reactivity against HCRT has been consistently reported in patients with NT1, but data demonstrating a primary role for T cells in neuronal destruction are currently lacking. Animal models are providing clues regarding the roles of autoreactive CD4+ and CD8+ T cells in the disease. Elucidation of the pathogenesis of NT1 will allow for the development of targeted immunotherapies at disease onset and could serve as a model for other immune-mediated neurological diseases.

A series of 7 cases of patients with narcolepsy with hypocretin deficiency without the HLA DQB1*06:02 allele

STUDY OBJECTIVES

We report data collected from 2 reference European sleep centers on a series of patients with narcolepsy with hypocretin-1 deficiency and absence of the human leukocyte antigens (HLA) DQB1*06:02 allele.

METHODS

Clinical data, HLA DQ markers, and cerebrospinal fluid assessments were collected retrospectively from Caucasian patients with a diagnosis of narcolepsy type 1 with cerebrospinal fluid hypocretin-1 deficiency (< 110 pg/ml) and absence of the HLA DQB1*06:02 allele, with follow-up with at least 1 visit within the last 4 years, consecutively admitted to 2 European sleep centers (Lugano, Switzerland and Montpellier, France).

RESULTS

Seven patients (3 of 29 patients in Lugano and 4 of 328 in Montpellier) were diagnosed with narcolepsy with hypocretin-1 deficiency and absence of HLA DQB1*06:02 (ie, 2% of patients with narcolepsy type 1). Regarding the HLA-DQB1 genotyping, 4 cases were positive for HLA DQB1*03:01, 1 for DQB1*03:02, and 3 for DQB1*02:01. Three patients had atypical cataplexy and 1 had no cataplexy. Only 2 patients had both a mean sleep latency of less than 8 minutes and more than 2 sleep onset rapid eye movement periods on the Multiple Sleep Latency Test, indicative of a less severe condition.

CONCLUSIONS

Although rare, this series of 7 cases confirms that hypocretin-deficient narcolepsy should not be excluded in the absence of HLA DQB1*06:02, especially if patients are carriers of other high-risk HLA-DQB1 alleles (DQB1*03:01, *03:02, *02:01). These data support the hypothesis that narcolepsy type 1 is a wider disease spectrum linked to the loss of hypocretin peptide.

CITATION

Miano S, Barateau L, De Pieri M, et al. A series of 7 cases of patients with narcolepsy with hypocretin deficiency without the HLA DQB1*06:02 allele. J Clin Sleep Med. 2023;19(12):2053-2057.

Narcolepsy type 1 and Sydenham chorea - Report of 3 cases and review of the literature

OBJECTIVES/BACKGROUND

Narcolepsy type 1 (NT1) is an immune-mediated disorder characterized by excessive daytime sleepiness, cataplexy, low levels of hypocretin-1 in the cerebrospinal fluid, and a strong association with the HLA DQB1*06:02 allele. There is evidence for streptococcal infections as one pathogenic factor that may lead to NT1 as part of a multifactorial pathogenesis. Elevated titers of Antistreptolysin-O antibodies and increased inflammatory activity in response to streptococci antigens have been described in patients with NT1. Sydenham chorea (SC) results from a post-streptococcal autoimmune process targeting basal ganglia neurons. Despite this common trigger, SC has been interpreted as a misdiagnosis in a few described cases of patients who were first diagnosed with SC and later with NT1. Our goal was to analyze the association between SC and NT1.

PATIENTS/METHODS

We reviewed the literature and report three patients from three European sleep centers who were diagnosed with both SC and NT1 within a few months.

RESULTS

We describe the cases of one male (age 10) and two female (age 22 and 10) patients.

CONCLUSIONS

We argue that in those cases both diagnoses are justified, unlike reports of previous cases in which SC was considered a misdiagnosis in patients with NT1. It remains, however, unclear if the conditions occur independently or if there is an overlap disorder- an SC-like subtype of narcolepsy with a particular sequence of symptoms. Further studies need to clarify the causality of the relationship and the pathophysiology of the reported rare association.

Brain Circuits Underlying Narcolepsy

Narcolepsy is a sleep disorder manifesting symptoms such as excessive daytime sleepiness and often cataplexy, a sudden and involuntary loss of muscle activity during wakefulness. The underlying neuropathological basis of narcolepsy is the loss of orexin neurons from the lateral hypothalamus. To date numerous animal models of narcolepsy have been produced in the laboratory, being invaluable tools for delineating the brain circuits of narcolepsy. This review will examine the evidence regarding the function of the orexin system, and how loss of this wake-promoting system manifests in excessive daytime sleepiness. This review will also outline the brain circuits controlling cataplexy, focusing on the contribution of orexin signaling loss in narcolepsy. Although our understanding of the brain circuits of narcolepsy has made great progress in recent years, much remains to be understood.

The transcriptomics profiling of blood CD4 and CD8 T-cells in narcolepsy type I

Background

Narcolepsy Type I (NT1) is a rare, life-long sleep disorder arising as a consequence of the extensive destruction of orexin-producing hypothalamic neurons. The mechanisms involved in the destruction of orexin neurons are not yet elucidated but the association of narcolepsy with environmental triggers and genetic susceptibility (strong association with the HLA, TCRs and other immunologically-relevant loci) implicates an immuno-pathological process. Several studies in animal models and on human samples have suggested that T-cells are the main pathogenic culprits.

Methods

RNA sequencing was performed on four CD4 and CD8 T-cell subsets (naive, effector, effector memory and central memory) sorted by flow cytometry from peripheral blood mononuclear cells (PBMCs) of NT1 patients and HLA-matched healthy donors as well as (age- and sex-) matched individuals suffering from other sleep disorders (OSD). The RNAseq analysis was conducted by comparing the transcriptome of NT1 patients to that of healthy donors and other sleep disorder patients (collectively referred to as the non-narcolepsy controls) in order to identify NT1-specific genes and pathways.

Results

We determined NT1-specific differentially expressed genes, several of which are involved in tubulin arrangement found in CD4 (TBCB, CCT5, EML4, TPGS1, TPGS2) and CD8 (TTLL7) T cell subsets, which play a role in the immune synapse formation and TCR signaling. Furthermore, we identified genes (GZMB, LTB in CD4 T-cells and NLRP3, TRADD, IL6, CXCR1, FOXO3, FOXP3 in CD8 T-cells) and pathways involved in various aspects of inflammation and inflammatory response. More specifically, the inflammatory profile was identified in the "naive" subset of CD4 and CD8 T-cell.

Conclusion

We identified NT1-specific differentially expressed genes, providing a cell-type and subset specific catalog describing their functions in T-cells as well as their potential involvement in NT1. Several genes and pathways identified are involved in the formation of the immune synapse and TCR activation as well as inflammation and the inflammatory response. An inflammatory transcriptomic profile was detected in both "naive" CD4 and CD8 T-cell subsets suggesting their possible involvement in the development or progression of the narcoleptic process.

Narcolepsies, update in 2023

Narcolepsy type 1 (NT1) and type 2 (NT2), also known as narcolepsy with and without cataplexy, are sleep disorders that benefited from major scientific advances over the last two decades. NT1 is caused by the loss of hypothalamic neurons producing orexin/hypocretin, a neurotransmitter regulating sleep and wake, which can be measured in the cerebrospinal fluid (CSF). A low CSF level of hypocretin-1/orexin-A is a highly specific and sensitive biomarker, sufficient to diagnose NT1. Orexin-deficiency is responsible for the main NT1 symptoms: sleepiness, cataplexy, disrupted nocturnal sleep, sleep-related hallucinations, and sleep paralysis. In the absence of a lumbar puncture, the diagnosis is based on neurophysiological tests (nocturnal and diurnal) and the presence of the pathognomonic symptom cataplexy. In the revised version of the International Classification of sleep Disorders, 3rd edition (ICSD-3-TR), a sleep onset rapid eye movement sleep (REM) period (SOREMP) (i.e. rapid occurrence of REM sleep) during the previous polysomnography may replace the diurnal multiple sleep latency test, when clear-cut cataplexy is present. A nocturnal SOREMP is very specific but not sensitive enough, and the diagnosis of cataplexy is usually based on clinical interview. It is thus of crucial importance to define typical versus atypical cataplectic attacks, and a list of clinical features and related degrees of certainty is proposed in this paper (expert opinion). The time frame of at least three months of evolution of sleepiness to diagnose NT1 was removed in the ICSD-3-TR, when clear-cut cataplexy or orexin-deficiency are established. However, it was kept for NT2 diagnosis, a less well-characterized disorder with unknown clinical course and absence of biolo biomarkers; sleep deprivation, shift working and substances intake being major differential diagnoses. Treatment of narcolepsy is nowadays only symptomatic, but the upcoming arrival of non-peptide orexin receptor-2 agonists should be a revolution in the management of these rare sleep diseases.

A unique association? A narcolepsy type 1 case comorbid with Primary Biliary Cholangitis

The aim of the study was to present a woman affected of a narcolepsy with cataplexy (narcolepsy type 1) comorbid with an asymptomatic Primary Biliary Cholangitis (PBC). The HLA haplotype was DRB1*15:01, DQA1*01:02, DQB1*06:02. The allele DQB1*06:02 has been considered until now protective for PBC and dual pathology has not been published. We think the important clinical message of the Case would be of continuing to monitor adults with narcolepsy type 1 for late complications that may be associated with other autoimmune conditions. Clinicians should be aware of the relationship between Narcolepsy and PBC. This highlights the need for screening and management in these individuals.

Sleep Disturbances in Autoimmune Neurological Diseases

PURPOSE OF REVIEW

To summarize the current evidence on the associations between autoimmune neurological diseases (e.g., multiple sclerosis, myasthenia gravis) and sleep disturbances (e.g., insomnia, parasomnias), as well as to review the main characteristics of sleep disorders with an immune-related pathophysiology (e.g., narcolepsy, anti-IgLON5 disease).

RECENT FINDINGS

An immune-mediated damage of the areas in the central nervous system that control sleep and wake functions (e.g., hypothalamus, brainstem) can lead to sleep disorders and sleep symptoms. Sleep disturbances are the reason to seek for medical attention in certain neuroimmunological conditions (e.g., narcolepsy, anti-IgLON5 disease) where sleep-related alterations are the main clinical feature. The assessment of sleep-related symptomatology and disorders should be included in the routine evaluation of patients with autoimmune neurological diseases. Clinicians should be aware of the typical clinical presentation of certain neuroimmunological disorders mainly affecting sleep.

Molecular mimicry and autoimmunity in the time of COVID-19

Infectious diseases are commonly implicated as potential initiators of autoimmune diseases (ADs) and represent the most commonly known factor in the development of autoimmunity in susceptible individuals. Epidemiological data and animal studies on multiple ADs suggest that molecular mimicry is one of the likely mechanisms for the loss of peripheral tolerance and the development of clinical disease. Besides molecular mimicry, other mechanisms such as defects in central tolerance, nonspecific bystander activation, epitope-determinant spreading, and/or constant antigenic stimuli, may also contribute for breach of tolerance and to the development of ADs. Linear peptide homology is not the only mechanism by which molecular mimicry is established. Peptide modeling (i.e., 3D structure), molecular docking analyses, and affinity estimation for HLAs are emerging as critical strategies when studying the links of molecular mimicry in the development of autoimmunity. In the current pandemic, several reports have confirmed an influence of SARS-CoV-2 on subsequent autoimmunity. Bioinformatic and experimental evidence support the potential role of molecular mimicry. Peptide dimensional analysis requires more research and will be increasingly important for designing and distributing vaccines and better understanding the role of environmental factors related to autoimmunity.

Advances in Adjuvanted Influenza Vaccines

The numerous influenza infections that occur every year present a major public health problem. Influenza vaccines are important for the prevention of the disease; however, their effectiveness against infection can be suboptimal. Particularly in the elderly, immune induction can be insufficient, and the vaccine efficacy against infection is usually lower than that in young adults. Vaccine efficacy can be improved by the addition of adjuvants, and an influenza vaccine with an oil-in-water adjuvant MF59, FLUAD, has been recently licensed in the United States and other countries for persons aged 65 years and older. Although the adverse effects of adjuvanted vaccines have been a concern, many adverse effects of currently approved adjuvanted influenza vaccines are mild and acceptable, given the overriding benefits of the vaccine. Since sufficient immunity can be induced with a small amount of vaccine antigen in the presence of an adjuvant, adjuvanted vaccines promote dose sparing and the prompt preparation of vaccines for pandemic influenza. Adjuvants not only enhance the immune response to antigens but can also be effective against antigenically different viruses. In this narrative review, we provide an overview of influenza vaccines, both past and present, before presenting a discussion of adjuvanted influenza vaccines and their future.

Evaluation of the efficacy of the hypocretin/orexin receptor agonists TAK-925 and ARN-776 in narcoleptic orexin/tTA; TetO-DTA mice

The sleep disorder narcolepsy, a hypocretin deficiency disorder thought to be due to degeneration of hypothalamic hypocretin/orexin neurons, is currently treated symptomatically. We evaluated the efficacy of two small molecule hypocretin/orexin receptor-2 (HCRTR2) agonists in narcoleptic male orexin/tTA; TetO-DTA mice. TAK-925 (1-10 mg/kg, s.c.) and ARN-776 (1-10 mg/kg, i.p.) were injected 15 min before dark onset in a repeated measures design. EEG, EMG, subcutaneous temperature (Tsc ) and activity were recorded by telemetry; recordings for the first 6 h of the dark period were scored for sleep/wake and cataplexy. At all doses tested, TAK-925 and ARN-776 caused continuous wakefulness and eliminated sleep for the first hour. Both TAK-925 and ARN-776 caused dose-related delays in NREM sleep onset. All doses of TAK-925 and all but the lowest dose of ARN-776 eliminated cataplexy during the first hour after treatment; the anti-cataplectic effect of TAK-925 persisted into the second hour for the highest dose. TAK-925 and ARN-776 also reduced the cumulative amount of cataplexy during the 6 h post-dosing period. The acute increase in wakefulness produced by both HCRTR2 agonists was characterised by increased spectral power in the gamma EEG band. Although neither compound provoked a NREM sleep rebound, both compounds affected NREM EEG during the second hour post-dosing. TAK-925 and ARN-776 also increased gross motor activity, running wheel activity, and Tsc , suggesting that the wake-promoting and sleep-suppressing activities of these compounds could be a consequence of hyperactivity. Nonetheless, the anti-cataplectic activity of TAK-925 and ARN-776 is encouraging for the development of HCRTR2 agonists.

Central Disorders of Hypersomnolence

OBJECTIVE

The goals of this article are to describe the clinical approach to and management of patients with central disorders of hypersomnolence, and to understand and differentiate available diagnostic tools.

LATEST DEVELOPMENTS

Updated clinical practice guidelines for the treatment of central disorders of hypersomnolence and narcolepsy specifically highlight new treatment options. Approval for a lower-sodium oxybate formulation that contains 92% less sodium than the standard sodium oxybate for the treatment of narcolepsy and idiopathic hypersomnia adds to the number of medications available for these disorders, allowing for a more tailored management of symptoms.

ESSENTIAL POINTS

Central disorders of hypersomnolence are characterized by excessive daytime sleepiness that impacts daily functions. These disorders can be differentiated by obtaining a detailed clinical sleep history and by a thoughtful interpretation of sleep diagnostic testing. Tailoring treatment approaches to meet the needs of individuals and accounting for medical and psychiatric comorbidities may improve quality of life.

Pharmacological options for narcolepsy: are they the way forward?

INTRODUCTION

Narcolepsy is an under-recognized, rare neurologic disorder of hypersomnolence that is associated with increased mortality and medical and psychiatric co-morbidities. Narcolepsy exerts a substantial economic burden on patients and society. There is currently no cure, and life-long symptomatic therapy is needed. Available drugs do not modify the disease course.

AREAS COVERED

This manuscript provides an overview of narcolepsy symptoms, diagnosis, pathophysiology, current pharmacotherapies, and emerging treatments. Gaps and unresolved issues in diagnosis and management of narcolepsy are discussed to answer whether pharmacological options are the way forward.

EXPERT OPINION

Diagnostic criteria for narcolepsy (ICSD-3) need revision and greater clarity. Improved recognition of cataplexy and other symptoms through educational outreach, new biomarkers, improved test scoring through artificial intelligence algorithms, and use of machine learning may facilitate earlier diagnosis and treatment. Pharmacological options need improved symptomatic therapy in addition to targeted therapies that address the loss of hypocretin signaling. Optimal narcolepsy care also needs a better understanding of the pathophysiology, recognition of the different phenotypes in narcolepsy, identification of at-risk individuals and early recognition of symptoms, better diagnostic tools, and a database for research and disease monitoring of treatment, side-effects, and comorbidities.

Narcolepsy type I-associated DNA methylation and gene expression changes in the human leukocyte antigen region

Narcolepsy type 1 (NT1) is caused by a loss of hypothalamic orexin-producing cells, and autoreactive CD4⁺ and CD8⁺ T cells have been suggested to play a role in the autoimmune mechanism. Although NT1 showed a strong association with human leukocyte antigen (HLA)-DQB1*06:02, the responsible antigens remain unidentified. We analyzed array-based DNA methylation and gene expression data for the HLA region in CD4⁺ and CD8⁺ T cells that were separated from the peripheral blood mononuclear cells of Japanese subjects (NT1, N = 42; control, N = 42). As the large number of SNPs in the HLA region might interfere with the affinity of the array probes, we conducted a comprehensive assessment of the reliability of each probe. The criteria were based on a previous study reporting that the presence of frequent SNPs, especially on the 3' side of the probe, makes the probe unreliable. We confirmed that 90.3% of the probes after general filtering in the HLA region do not include frequent SNPs, and are thus suitable for analysis, particularly in Japanese subjects. We then performed an association analysis, and found that several CpG sites in the HLA class II region of the patients were significantly hypomethylated in CD4⁺ and CD8⁺ T cells. This association was not detected when the effect of HLA-DQB1*06:02 was considered, suggesting that the hypomethylation was possibly derived from HLA-DQB1*06:02. Further RNA sequencing revealed reduced expression levels of HLA-DQB1 alleles other than HLA-DQB1*06:02 in the patients with NT1. Our results suggest the involvement of epigenetic and expressional changes in HLA-DQB1 in the pathogenesis of NT1.

Narcolepsy and Idiopathic Hypersomnia

Narcolepsy types 1 and 2 and idiopathic hypersomnia are primary Central Nervous System (CNS) disorders of hypersomnolence characterized by profound daytime sleepiness and/or excessive sleep need. Onset of symptoms begins typically in childhood or adolescence, and children can have unique presentations compared with adults. Narcolepsy type 1 is likely caused by immune-mediated loss of orexin (hypocretin) neurons in the hypothalamus; however, the causes of narcolepsy type 2 and idiopathic hypersomnia are unknown. Existing treatments improve daytime sleepiness and cataplexy but there is no cure for these disorders.

Narcolepsy risk loci outline role of T cell autoimmunity and infectious triggers in narcolepsy

Narcolepsy type 1 (NT1) is caused by a loss of hypocretin/orexin transmission. Risk factors include pandemic 2009 H1N1 influenza A infection and immunization with Pandemrix®. Here, we dissect disease mechanisms and interactions with environmental triggers in a multi-ethnic sample of 6,073 cases and 84,856 controls. We fine-mapped GWAS signals within HLA (DQ0602, DQB1*03:01 and DPB1*04:02) and discovered seven novel associations (CD207, NAB1, IKZF4-ERBB3, CTSC, DENND1B, SIRPG, PRF1). Significant signals at TRA and DQB1*06:02 loci were found in 245 vaccination-related cases, who also shared polygenic risk. T cell receptor associations in NT1 modulated TRAJ*24, TRAJ*28 and TRBV*4-2 chain-usage. Partitioned heritability and immune cell enrichment analyses found genetic signals to be driven by dendritic and helper T cells. Lastly comorbidity analysis using data from FinnGen, suggests shared effects between NT1 and other autoimmune diseases. NT1 genetic variants shape autoimmunity and response to environmental triggers, including influenza A infection and immunization with Pandemrix®.

I-Ag7 β56/57 polymorphisms regulate non-cognate negative selection to CD4+ T cell orchestrators of type 1 diabetes

Genetic susceptibility to type 1 diabetes is associated with homozygous expression of major histocompatibility complex class II alleles that carry specific beta chain polymorphisms. Why heterozygous expression of these major histocompatibility complex class II alleles does not confer a similar predisposition is unresolved. Using a nonobese diabetic mouse model, here we show that heterozygous expression of the type 1 diabetes-protective allele I-Ag7 β56P/57D induces negative selection to the I-Ag7-restricted T cell repertoire, including beta-islet-specific CD4+ T cells. Surprisingly, negative selection occurs despite I-Ag7 β56P/57D having a reduced ability to present beta-islet antigens to CD4+ T cells. Peripheral manifestations of non-cognate negative selection include a near complete loss of beta-islet-specific CXCR6+ CD4+ T cells, an inability to cross-prime islet-specific glucose-6-phosphatase catalytic subunit-related protein and insulin-specific CD8+ T cells and disease arrest at the insulitis stage. These data reveal that negative selection on non-cognate self-antigens in the thymus can promote T cell tolerance and protection from autoimmunity.

Machine learning predictions of MHC-II specificities reveal alternative binding mode of class II epitopes

CD4⁺ T cells orchestrate the adaptive immune response against pathogens and cancer by recognizing epitopes presented on class II major histocompatibility complex (MHC-II) molecules. The high polymorphism of MHC-II genes represents an important hurdle toward accurate prediction and identification of CD4⁺ T cell epitopes. Here we collected and curated a dataset of 627,013 unique MHC-II ligands identified by mass spectrometry. This enabled us to precisely determine the binding motifs of 88 MHC-II alleles across humans, mice, cattle, and chickens. Analysis of these binding specificities combined with X-ray crystallography refined our understanding of the molecular determinants of MHC-II motifs and revealed a widespread reverse-binding mode in HLA-DP ligands. We then developed a machine-learning framework to accurately predict binding specificities and ligands of any MHC-II allele. This tool improves and expands predictions of CD4⁺ T cell epitopes and enables us to discover viral and bacterial epitopes following the aforementioned reverse-binding mode.

Origins and immunopathogenesis of autoimmune central nervous system disorders

The field of autoimmune neurology is rapidly evolving, and recent discoveries have advanced our understanding of disease aetiologies. In this article, we review the key pathogenic mechanisms underlying the development of CNS autoimmunity. First, we review non-modifiable risk factors, such as age, sex and ethnicity, as well as genetic factors such as monogenic variants, common variants in vulnerability genes and emerging HLA associations. Second, we highlight how interactions between environmental factors and epigenetics can modify disease onset and severity. Third, we review possible disease mechanisms underlying triggers that are associated with the loss of immune tolerance with consequent recognition of self-antigens; these triggers include infections, tumours and immune-checkpoint inhibitor therapies. Fourth, we outline how advances in our understanding of the anatomy of lymphatic drainage and neuroimmune interfaces are challenging long-held notions of CNS immune privilege, with direct relevance to CNS autoimmunity, and how disruption of B cell and T cell tolerance and the passage of immune cells between the peripheral and intrathecal compartments have key roles in initiating disease activity. Last, we consider novel therapeutic approaches based on our knowledge of the immunopathogenesis of autoimmune CNS disorders.

Genetics and epigenetics of rare hypersomnia

Herein we focus on connections between genetics and some central disorders of hypersomnolence - narcolepsy types 1 and 2 (NT1, NT2), idiopathic hypersomnia (IH), and Kleine-Levin syndrome (KLS) - for a better understanding of their etiopathogenetic mechanisms and a better diagnostic and therapeutic definition. Gene pleiotropism influences neurological and sleep disorders such as hypersomnia; therefore, genetics allows us to uncover common pathways to different pathologies, with potential new therapeutic perspectives. An important body of evidence has accumulated on NT1 and IH, allowing a better understanding of etiopathogenesis, disease biomarkers, and possible new therapeutic approaches. Further studies are needed in the field of epigenetics, which has a potential role in the modulation of biological specific hypersomnia pathways.

LC-MS/MS-Based Proteomics Approach for the Identification of Candidate Serum Biomarkers in Patients with Narcolepsy Type 1

Narcolepsy type 1 (NT1) is the most common type of narcolepsy known to be caused by the loss of specific neurons responsible for producing peptide neurotransmitters (orexins/hypocretins), resulting in a sleep-wake cycle disorder. It is characterized by its association with cataplexy and abnormalities in rapid eye movement. To date, no cure has been established for this life-threatening condition. Misdiagnosis of NT1 is also quite common, although it is not exceedingly rare. Therefore, successfully identifying candidate serum biomarkers for NT1 would be a head start for accurate diagnosis and development of therapeutics for this disorder. This study aims to identify such potential serum biomarkers. A depletion protocol was employed for 27 human serum samples (16 NT1 and 11 healthy controls), followed by applying LC-MS/MS bottom-up proteomics analysis, then LC-PRM-MS for validation. The comparison of the proteome profiles of the low-abundant proteins in the samples was then investigated based on age, sex, sample groups, and the presence of the Human Leukocyte Antigen (HLA) DQB1*0602 allele. The results were tracked to gene expression studies as well as system biology to identify key proteins and understand their relationship in the pathogenesis of NT1. Our results revealed 36 proteins significantly and differentially expressed. Among the impaired pathways and bioprocesses, the complement activation pathway is impaired by six of the differentially expressed proteins (DEPs). They are coded by the genes C2, CFB, C5, C1R, C1S, and MASP1, while 11 DEPs are involved in Acute Phase Response Signaling (APRS), which are coded by the genes FN1, AMBP, APOH, CFB, CP, ITIH2, C5, C2, F2, C1, and ITIH4. The combined AUCs of the downregulated and upregulated DEPs are 0.95 and 0.76, respectively. Overall, this study reveals potential serum-protein biomarkers of NT1 and explains the possible correlation between the biomarkers and pathophysiological effects, as well as important biochemical pathways involved in NT1.

HLA and tumour immunology: immune escape, immunotherapy and immune-related adverse events

PURPOSE

As molecules responsible for presenting antigens to T lymphocytes, leukocytes antigens (HLAs) play a vital role in cancer immunology. This review aims to provide current understanding of HLAs in tumour immunology.

METHODS

Perspectives on how HLA alterations may contribute to the immune escape of cancer cells and resistance to immunotherapy, and potential methods to overcome HLA defects were summarized. In addition, we discussed the potential association between HLA and immune-related adverse events (irAEs), which has not been reviewed elsewhere.

RESULTS

Downregulation, loss of heterogeneity and entire loss of HLAs are responsible for the immune escape of tumour cells. The strategies to overcome the HLA defects can be effective therapies of cancer. Compared with classical HLA-I, non-classical HLA-I molecules, such as HLA-E and HLA-G, appear to be more reliable predictors of prognosis, as they tend to play immunosuppressive roles in antitumor response. Relative diversified or high expression of classical HLA-I are potential predictors of favourable response of immunotherapy. Certain HLA types may be associated to enhanced affinity to self-antigen-mimicked tumour-antigens, thus may positively correlated to irAEs triggered by checkpoint inhibitors.

CONCLUSIONS

Further studies exploring the relationship between HLAs and cancer may not only lead to the development of novel therapies but also bring about better management of irAEs.

MHC Class II Presentation in Autoimmunity

Antigen presentation by major histocompatibility complex class II (MHC-II) molecules is crucial for eliciting an efficient immune response by CD4+ T cells and maintaining self-antigen tolerance. Some MHC-II alleles are known to be positively or negatively associated with the risk of the development of different autoimmune diseases (ADs), including those characterized by the emergence of autoreactive T cells. Apparently, the MHC-II presentation of self-antigens contributes to the autoimmune T cell response, initiated through a breakdown of central tolerance to self-antigens in the thymus. The appearance of autoreactive T cell might be the result of (i) the unusual interaction between T cell receptors (TCRs) and self-antigens presented on MHC-II; (ii) the posttranslational modifications (PTMs) of self-antigens; (iii) direct loading of the self-antigen to classical MHC-II without additional nonclassical MHC assistance; (iv) the proinflammatory environment effect on MHC-II expression and antigen presentation; and (v) molecular mimicry between foreign and self-antigens. The peculiarities of the processes involved in the MHC-II-mediated presentation may have crucial importance in the elucidation of the mechanisms of triggering and developing ADs as well as for clarification on the protective effect of MHC-II alleles that are negatively associated with ADs.

Cerebrospinal fluid proteomics in recent-onset Narcolepsy type 1 reveals activation of the complement system

Introduction

Narcolepsy type 1 (NT1) is a rare, chronic and disabling neurological disease causing excessive daytime sleepiness and cataplexy. NT1 is characterized pathologically by an almost complete loss of neurons producing the orexin neuropeptides in the lateral hypothalamus. Genetic and environmental factors strongly suggest the involvement of the immune system in the loss of orexin neurons. The cerebrospinal fluid (CSF), secreted locally and surrounding the central nervous system (CNS), represents an accessible window into CNS pathological processes.

Methods

To gain insight into the biological and molecular changes in NT1 patients, we performed a comparative proteomics analysis of the CSF from 21 recent-onset NT1 patients and from two control groups: group 1 with somatoform disorders, and group 2 patients with hypersomnia other than NT1, to control for any potential effect of sleep disturbances on CSF composition. To achieve an optimal proteomic coverage analysis, the twelve most abundant CSF proteins were depleted, and samples were analyzed by nano-flow liquid chromatography tandem mass spectrometry (nano-LC-MS/MS) using the latest generation of hybrid Orbitrap mass spectrometer.

Results and discussion

Our study allowed the identification and quantification of up to 1943 proteins, providing a remarkably deep analysis of the CSF proteome. Interestingly, gene set enrichment analysis indicated that the complement and coagulation systems were enriched and significantly activated in NT1 patients in both cohorts analyzed. Notably, the lectin and alternative complement pathway as well as the downstream lytic membrane attack complex were congruently increased in NT1. Our data suggest that the complement dysregulation in NT1 patients can contribute to immunopathology either by directly promoting tissue damage or as part of local inflammatory responses. We therefore reveal an altered composition of the CSF proteome in NT1 patients, which points to an ongoing inflammatory process contributed, at least in part, by the complement system.

Dysfunctional Sars-CoV-2-M protein-specific cytotoxic T lymphocytes in patients recovering from severe COVID-19

Although the importance of virus-specific cytotoxic T lymphocytes (CTL) in virus clearance is evident in COVID-19, the characteristics of virus-specific CTLs related to disease severity have not been fully explored. Here we show that the phenotype of virus-specific CTLs against immunoprevalent epitopes in COVID-19 convalescents might differ according to the course of the disease. We establish a cellular screening method that uses artificial antigen presenting cells, expressing HLA-A^*24:02, the costimulatory molecule 4-1BBL, SARS-CoV-2 structural proteins S, M, and N and non-structural proteins ORF3a and nsp6/ORF1a. The screen implicates SARS-CoV-2 M protein as a frequent target of IFNγ secreting CD8⁺ T cells, and identifies M_198-206 as an immunoprevalent epitope in our cohort of HLA-A^*24:02 positive convalescent COVID-19 patients recovering from mild, moderate and severe disease. Further exploration of M_198-206-specific CD8⁺ T cells with single cell RNA sequencing reveals public TCRs in virus-specific CD8⁺ T cells, and shows an exhausted phenotype with less differentiated status in cells from the severe group compared to cells from the moderate group. In summary, this study describes a method to identify T cell epitopes, indicate that dysfunction of virus-specific CTLs might be an important determinant of clinical outcomes.

Keeping T cell memories in mind

The mammalian central nervous system (CNS) contains a vibrant community of resident adaptive immune cells at homeostasis. Among these are memory CD8+ and CD4+ T cells, which reside in the CNS in the settings of health, aging, and neurological disease. These T cells commonly exhibit a tissue-resident memory (TRM) phenotype, suggesting that they are antigen-experienced and remain separate from the circulation. Despite these characterizations, T cell surveillance of the CNS has only recently been studied through the lens of TRM immunology. In this Review, we outline emerging concepts of CNS TRM generation, localization, maintenance, function, and specificity. In this way, we hope to highlight roles of CNS TRM in health and disease to inform future studies of adaptive neuroimmunity.

Central hypersomnia and chronic insomnia: expanding the spectrum of sleep disorders in long COVID syndrome - a prospective cohort study

Introduction

Long-onset COVID syndrome has been described in patients with COVID-19 infection with persistence of symptoms or development of sequelae beyond 4 weeks after the onset of acute symptoms, a medium- and long-term consequence of COVID-19. This syndrome can affect up to 32% of affected individuals, with symptoms of fatigue, dyspnea, chest pain, cognitive disorders, insomnia, and psychiatric disorders. The present study aimed to characterize and evaluate the prevalence of sleep symptoms in patients with long COVID syndrome.

Methodology

A total of 207 patients with post-COVID symptoms were evaluated through clinical evaluation with a neurologist and specific exams in the subgroup complaining of excessive sleepiness.

Results

Among 189 patients included in the long COVID sample, 48 (25.3%) had sleep-related symptoms. Insomnia was reported by 42 patients (22.2%), and excessive sleepiness (ES) was reported by 6 patients (3.17%). Four patients with ES were evaluated with polysomnography and test, multiple sleep latencies test, and actigraphic data. Two patients had a diagnosis of central hypersomnia, and one had narcolepsy. A history of steroid use was related to sleep complaints (insomnia and excessive sleepiness), whereas depression was related to excessive sleepiness. We observed a high prevalence of cognitive complaints in these patients.

Conclusion

Complaints related to sleep, such as insomnia and excessive sleepiness, seem to be part of the clinical post-acute syndrome (long COVID syndrome), composing part of its clinical spectrum, relating to some clinical data.

Narcolepsy and H1N1 influenza immunology a decade later: What have we learned?

In the wake of the A/California/7/2009 H1N1 influenza pandemic vaccination campaigns in 2009-2010, an increased incidence of the chronic sleep-wake disorder narcolepsy was detected in children and adolescents in several European countries. Over the last decade, in-depth epidemiological and immunological studies have been conducted to investigate this association, which have advanced our understanding of the events underpinning the observed risk. Narcolepsy with cataplexy (defined as type-1 narcolepsy, NT1) is characterized by an irreversible and chronic deficiency of hypocretin peptides in the hypothalamus. The multifactorial etiology is thought to include genetic predisposition, head trauma, environmental triggers, and/or infections (including influenza virus infections), and an increased risk was observed following administration of the A/California/7/2009 H1N1 vaccine Pandemrix (GSK). An autoimmune origin of NT1 is broadly assumed. This is based on its strong association with a predisposing allele (the human leucocyte antigen DQB1*0602) carried by the large majority of NT1 patients, and on links with other immune-related genetic markers affecting the risk of NT1. Presently, hypotheses on the underlying potential immunological mechanisms center on molecular mimicry between hypocretin and peptides within the A/California/7/2009 H1N1 virus antigen. This molecular mimicry may instigate a cross-reactive autoimmune response targeting hypocretin-producing neurons. Local CD4⁺ T-cell responses recognizing peptides from hypocretin are thought to play a central role in the response. In this model, cross-reactive DQB1*0602-restricted T cells from the periphery would be activated to cross the blood-brain barrier by rare, and possibly pathogen-instigated, inflammatory processes in the brain. Current hypotheses suggest that activation and expansion of cross-reactive T-cells by H1N1/09 influenza infection could have been amplified following the administration of the adjuvanted vaccine, giving rise to a “two-hit” hypothesis. The collective in silico, in vitro, and preclinical in vivo data from recent and ongoing research have progressively refined the hypothetical model of sequential immunological events, and filled multiple knowledge gaps. Though no definitive conclusions can be drawn, the mechanistical model plausibly explains the increased risk of NT1 observed following the 2009-2010 H1N1 pandemic and subsequent vaccination campaign, as outlined in this review.

T cell Repertoire Profiling and the Mechanism by which HLA-B27 Causes Ankylosing Spondylitis

Purpose of Review

Ankylosing spondylitis (AS) is strongly associated with the HLA-B27 gene. The canonical function of HLA-B27 is to present antigenic peptides to CD8 lymphocytes, leading to adaptive immune responses. The ‘arthritogenic peptide’ theory as to the mechanism by which HLA-B27 induces ankylosing spondylitis proposes that HLA-B27 presents peptides derived from exogenous sources such as bacteria to CD8 lymphocytes, which subsequently cross-react with antigens at the site of inflammation of the disease, causing inflammation. This review describes findings of studies in AS involving profiling of T cell expansions and discusses future research opportunities based on these findings.

Recent Findings

Consistent with this theory, there is an expanding body of data showing that expansion of a restricted pool of CD8 lymphocytes is found in most AS patients yet only in a small proportion of healthy HLA-B27 carriers.

Summary

These exciting findings strongly support the theory that AS is driven by presentation of antigenic peptides to the adaptive immune system by HLA-B27. They point to new potential approaches to identify the exogenous and endogenous antigens involved and to potential therapies for the disease.

Precocious puberty in narcolepsy type 1: Orexin loss and/or neuroinflammation, which is to blame?

Narcolepsy type 1 (NT1) is a rare neurological sleep disorder triggered by postnatal loss of the orexin/hypocretin neuropeptides. Overweight/obesity and precocious puberty are highly prevalent comorbidities of NT1, with a close temporal correlation with disease onset, suggesting a common origin. However, the underlying mechanisms remain unknown and merit further investigation. The main question we address in this review is whether the occurrence of precocious puberty in NT1 is due to the lack of orexin/hypocretin or rather to a wider hypothalamic dysfunction in the context of neuroinflammation, which is likely to accompany the disease given its autoimmune origins. Our analysis suggests that the suspected generalized neuroinflammation of the hypothalamus in NT1 would tend to delay puberty rather than hastening it. In contrast, that the brutal loss of orexin/hypocretin would favor an early reactivation of gonadotropin-releasing hormone (GnRH) secretion during the prepubertal period in vulnerable children, leading to early puberty onset. Orexin/hypocretin replacement could thus be envisaged as a potential treatment for precocious puberty in NT1. Additionally, we put forward an alternative hypothesis regarding the concomitant occurrence of sleepiness, weight gain and early puberty in NT1.

Increased incidence of pediatric narcolepsy following the 2009 H1N1 pandemic: a report from the pediatric working group of the sleep research network

This study was aimed to evaluate the yearly incidence of pediatric narcolepsy prior to and following the 2009 H1N1 pandemic and to evaluate seasonal patterns of narcolepsy onset and associations with H1N1 influenza infection in the United States. This was a multicenter retrospective study with prospective follow-up. Participants were recruited from members of the Pediatric Working Group of the Sleep Research Network including 22 sites across the United States. The main outcomes were monthly and yearly incident cases of childhood narcolepsy in the United States, and its relationship to historical H1N1 influenza data. A total of 950 participants were included in the analysis; 487 participants were male (51.3%). The mean age at onset of excessive daytime sleepiness (EDS) was 9.6  ±  3.9 years. Significant trend changes in pediatric narcolepsy incidence based on EDS onset (p  &lt;  .0001) occurred over the 1998–2016 period, peaking in 2010, reflecting a 1.6-fold increase in narcolepsy incidence. In addition, there was significant seasonal variation in narcolepsy incident cases, with increased cases in spring (p  &lt;  .05). Cross-correlation analysis demonstrated a significant correlation between monthly H1N1 infection and monthly narcolepsy incident cases (p  =  .397, p  &lt;  .0001) with a lag time of 8 months. We conclude that there is a significant increase in pediatric narcolepsy incidence after the 2009 H1N1 pandemic in the United States. However, the magnitude of increase is lower than reported in European countries and in China. The temporal correlation between monthly H1N1 infection and monthly narcolepsy incidence, suggests that H1N1 infection may be a contributing factor to the increased pediatric narcolepsy incidence after the 2009 H1N1 pandemics.

Clinical characteristics of a large cohort of patients with narcolepsy candidate for pitolisant: a cross-sectional study from the Italian PASS Wakix® Cohort

Introduction

Narcolepsy is a chronic and rare hypersomnia of central origin characterized by excessive daytime sleepiness and a complex array of symptoms as well as by several medical comorbidities. With growing pharmacological options, polytherapy may increase the possibility of a patient-centered management of narcolepsy symptoms. The aims of our study are to describe a large cohort of Italian patients with narcolepsy who were candidates for pitolisant treatment and to compare patients’ subgroups based on current drug prescription (drug-naïve patients in whom pitolisant was the first-choice treatment, switching to pitolisant from other monotherapy treatments, and adding on in polytherapy).

Methods

We conducted a cross-sectional survey based on Italian data from the inclusion visits of the Post Authorization Safety Study of pitolisant, a 5-year observational, multicenter, international study.

Results

One hundred ninety-one patients were enrolled (76.4% with narcolepsy type 1 and 23.6% with narcolepsy type 2). Most patients (63.4%) presented at least one comorbidity, mainly cardiovascular and psychiatric. Pitolisant was prescribed as an add-on treatment in 120/191 patients (62.8%), as switch from other therapies in 42/191 (22.0%), and as a first-line treatment in 29/191 (15.2%). Drug-naive patients presented more severe sleepiness, lower functional status, and a higher incidence of depressive symptoms.

Conclusion

Our study presents the picture of a large cohort of Italian patients with narcolepsy who were prescribed with pitolisant, suggesting that polytherapy is highly frequent to tailor a patient-centered approach.