HLA-DPB1 and HLA class I confer risk of and protection from narcolepsy

High-resolution HLA sequencing and hypocretin receptor 2 autoantibodies in narcolepsy type 1 and type 2

Narcolepsy is a sleep disorder caused by an apparent degeneration of orexin/hypocretin neurons in the lateral hypothalamic area and a subsequent decrease in orexin/hypocretin levels in the cerebrospinal fluid. Narcolepsy is classified into type 1 (NT1) and type 2 (NT2). While genetic associations in the human leukocyte antigen (HLA) region and candidate autoantibodies have been investigated in NT1 to imply an autoimmune origin, less is known about the pathogenesis in NT2. Twenty-six NT1 and 15 NT2 patients were included, together with control groups of 24 idiopathic hypersomnia (IH) patients and 778 general population participants. High-resolution sequencing was used to determine the alleles, the extended haplotypes, and the genotypes of HLA-DRB3, -DRB4, -DRB5, -DRB1, -DQA1, -DQB1, -DPA1, and -DPB1. Radiobinding assay was used to determine autoantibodies against hypocretin receptor 2 (anti-HCRTR2 autoantibodies). NT1 was associated with HLA-DRB5*01:01:01, -DRB1*15:01:01, -DQA1*01:02:01, -DQB1*06:02:01, -DRB5*01:01:01, -DRB1*15:01:01, -DQA1*01:02:01, -DQB1*06:02:01 (odds ratio [OR]: 9.15; p = 8.31 × 10-4) and HLA-DRB5*01:01:01, -DRB1*15:01:01, -DQA1*01:02:01, -DQB1*06:02:01, -DRB4*01:03:01, -DRB1*04:01:01, -DQA1*03:02//03:03:01, -DQB1*03:01:01 (OR: 23.61; p = 1.58 × 10-4) genotypes. Lower orexin/hypocretin levels were reported in the NT2 subgroup (n = 5) that was associated with the extended HLA-DQB1*06:02:01 haplotype (p = .001). Anti-HCRTR2 autoantibody levels were not different between study groups (p = .8524). We confirmed the previous association of NT1 with HLA-DQB1*06:02:01 extended genotypes. A subgroup of NT2 patients with intermediate orexin/hypocretin levels and association with HLA-DQB1*06:02:01 was identified, indicating a possible overlap between the two distinct narcolepsy subtypes, NT1 and NT2. Low anti-HCRTR2 autoantibody levels suggest that these receptors might not function as autoimmune targets in either NT1 or NT2.

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.

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.

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.

The progress of autoimmune hepatitis research and future challenges

Autoimmune hepatitis (AIH) is a chronic liver inflammatory disease with various immune system manifestations, showing a global trend of increased prevalence. AIH is diagnosed through histological abnormalities, clinical manifestations, and biochemical indicators. The biochemical markers involve interfacial hepatitis, transaminase abnormalities, positive autoantibodies, etc. Although AIH pathogenesis is unclear, gene mutations and immunological factors could be the leading factors. AIH usually presents as a chronic liver disease and sometimes as acute hepatitis, making it challenging to distinguish it from drug-related hepatitis due to similar clinical symptoms. Normalizing transaminases and serum IgG levels is essential in assessing the remission status of AIH treatment. Glucocorticoids and azathioprine are the first-line AIH treatment, with lifelong maintenance therapy in some patients. The quality of life and survival can be improved after appropriate treatment. However, certain limitations jeopardize the quality of treatment, including long treatment cycles, side effects, poor patient compliance, and inability to inhibit liver fibrosis and cirrhosis. Accurate AIH animal models will help us understand the pathophysiology of the disease while providing fresh perspectives for avoiding and treating AIH. This review will help us understand AIH better, from the cellular and molecular causes to the clinical features, and will provide insight into new therapy techniques with fewer side effects.

Genome-wide association study identifies risk loci within the major histocompatibility complex region for Hunner-type interstitial cystitis

Hunner-type interstitial cystitis (HIC) is a rare, chronic inflammatory disease of the urinary bladder with unknown etiology and genetic background. Here, we conduct a genome-wide association study of 144 patients with HIC and 41,516 controls of Japanese ancestry. The genetic variant, rs1794275, in the major histocompatibility complex (MHC) region (chromosome 6p21.3) is associated with HIC risk (odds ratio [OR] = 2.32; p = 3.4 × 10^-9). The association is confirmed in a replication set of 26 cases and 1,026 controls (p = 0.014). Fine mapping demonstrates the contribution to the disease risk of a completely linked haplotype of three human leukocyte antigen HLA-DQβ1 amino acid positions, 71, 74, and 75 (OR = 1.94; p = 5 × 10^-8) and of HLA-DPβ1 amino acid position 178, which tags HLA-DPB1∗04:02 (OR = 2.35; p = 7.5 × 10^-8). The three HLA-DQβ1 amino acid positions are located together at the peptide binding groove, suggesting their functional importance in antigen presentation. Our study reveals genetic contributions to HIC risk that may be associated with class II MHC molecule antigen presentation.

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 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®.

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.

Human Leukocyte Antigen (HLA) Modulates the Dependence on Age of the Variability of Synchronous Neural Interactions

Recent evidence documented a protective effect of Class II human leukocyte antigen (HLA) DRB1*13 on brain health across the lifespan including evidence of reduced neural network variability relative to non-carriers. Here, in an extension of those findings, we evaluated the influence of a large number of Class I and Class II HLA alleles on aging-related changes in neural network variability. Cognitively healthy women (N = 178) ranging in age from 28 to 99 years old underwent a magnetoencephalography scan from which neural network variability was calculated and provided a blood sample from which HLA and apolipoprotein E (ApoE) genotype were determined. The primary analyses assessed the dependence of network variability on age in carriers of a specific HLA allele compared to non-carriers. Effects were considered protective if there was a significant increase of network variability with age in the absence of a given HLA allele but not in its presence, and were considered to confer susceptibility if the converse was documented; HLA alleles that did not influence the dependence of network variability on age in their presence or absence were considered neutral. Of 50 alleles investigated, 22 were found to be protective, 7 were found to confer susceptibility, and 21 were neutral. The frequencies of those 50 alleles were not associated significantly with ApoE genotype. The findings, which document the influence of HLA on age-related brain changes and highlight the role of HLA in healthy brain function, are discussed in terms of the role of HLA in the human immune response to foreign antigens.

Narcolepsy-A Neuropathological Obscure Sleep Disorder: A Narrative Review of Current Literature

Narcolepsy is a chronic, long-term neurological disorder characterized by a decreased ability to regulate sleep-wake cycles. Some clinical symptoms enter into differential diagnosis with other neurological diseases. Excessive daytime sleepiness and brief involuntary sleep episodes are the main clinical symptoms. The majority of people with narcolepsy experience cataplexy, which is a loss of muscle tone. Many people experience neurological complications such as sleep cycle disruption, hallucinations or sleep paralysis. Because of the associated neurological conditions, the exact pathophysiology of narcolepsy is unknown. The differential diagnosis is essential because relatively clinical symptoms of narcolepsy are easy to diagnose when all symptoms are present, but it becomes much more complicated when sleep attacks are isolated and cataplexy is episodic or absent. Treatment is tailored to the patient's symptoms and clinical diagnosis. To facilitate the diagnosis and treatment of sleep disorders and to better understand the neuropathological mechanisms of this sleep disorder, this review summarizes current knowledge on narcolepsy, in particular, genetic and non-genetic associations of narcolepsy, the pathophysiology up to the inflammatory response, the neuromorphological hallmarks of narcolepsy, and possible links with other diseases, such as diabetes, ischemic stroke and Alzheimer's disease. This review also reports all of the most recent updated research and therapeutic advances in narcolepsy. There have been significant advances in highlighting the pathogenesis of narcolepsy, with substantial evidence for an autoimmune response against hypocretin neurons; however, there are some gaps that need to be filled. To treat narcolepsy, more research should be focused on identifying molecular targets and novel autoantigens. In addition to therapeutic advances, standardized criteria for narcolepsy and diagnostic measures are widely accepted, but they may be reviewed and updated in the future with comprehension. Tailored treatment to the patient's symptoms and clinical diagnosis and future treatment modalities with hypocretin agonists, GABA agonists, histamine receptor antagonists and immunomodulatory drugs should be aimed at addressing the underlying cause of narcolepsy.

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.

Leveraging genetic discoveries for sleep to determine causal relationships with common complex traits

Sleep occurs universally and is a biological necessity for human functioning. The consequences of diminished sleep quality impact physical and physiological systems such as neurological, cardiovascular, and metabolic processes. In fact, people impacted by common complex diseases experience a wide range of sleep disturbances. It is challenging to uncover the underlying molecular mechanisms responsible for decreased sleep quality in many disease systems owing to the lack of suitable sleep biomarkers. However, the discovery of a genetic component to sleep patterns has opened a new opportunity to examine and understand the involvement of sleep in many disease states. It is now possible to use major genomic resources and technologies to uncover genetic contributions to many common diseases. Large scale prospective studies such as the genome wide association studies (GWAS) have successfully revealed many robust genetic signals associated with sleep-related traits. With the discovery of these genetic variants, a major objective of the community has been to investigate whether sleep-related traits are associated with disease pathogenesis and other health complications. Mendelian Randomization (MR) represents an analytical method that leverages genetic loci as proxy indicators to establish causal effect between sleep traits and disease outcomes. Given such variants are randomly inherited at birth, confounding bias is eliminated with MR analysis, thus demonstrating evidence of causal relationships that can be used for drug development and to prioritize clinical trials. In this review, we outline the results of MR analyses performed to date on sleep traits in relation to a multitude of common complex diseases.

Influenza vaccination induces autoimmunity against orexinergic neurons in a mouse model for narcolepsy

Narcolepsy with cataplexy or narcolepsy type 1 is a disabling chronic sleep disorder resulting from the destruction of orexinergic neurons in the hypothalamus. The tight association of narcolepsy with HLA-DQB1*06:02 strongly suggest an autoimmune origin to this disease. Furthermore, converging epidemiological studies have identified an increased incidence for narcolepsy in Europe following Pandemrix® vaccination against the 2009-2010 pandemic 'influenza' virus strain. The potential immunological link between the Pandemrix® vaccination and narcolepsy remains, however, unknown. Deciphering these mechanisms may reveal pathways potentially at play in most cases of narcolepsy. Here, we developed a mouse model allowing to track and study the T-cell response against 'influenza' virus haemagglutinin, which was selectively expressed in the orexinergic neurons as a new self-antigen. Pandemrix® vaccination in this mouse model resulted in hypothalamic inflammation and selective destruction of orexin-producing neurons. Further investigations on the relative contribution of T-cell subsets in this process revealed that haemagglutinin-specific CD4 T cells were necessary for the development of hypothalamic inflammation, but insufficient for killing orexinergic neurons. Conversely, haemagglutinin-specific CD8 T cells could not initiate inflammation but were the effectors of the destruction of orexinergic neurons. Additional studies revealed pathways potentially involved in the disease process. Notably, the interferon-γ pathway was proven essential, as interferon-γ-deficient CD8 T cells were unable to elicit the loss of orexinergic neurons. Our work demonstrates that an immunopathological process mimicking narcolepsy can be elicited by immune cross-reactivity between a vaccine antigen and a neuronal self-antigen. This process relies on a synergy between autoreactive CD4 and CD8 T cells for disease development. This work furthers our understanding of the mechanisms and pathways potentially involved in the development of a neurological side effect due to a vaccine and, likely, to narcolepsy in general.

Narcolepsy: a model interaction between immune system, nervous system, and sleep-wake regulation

Narcolepsy is a rare chronic neurological disorder characterized by an irresistible excessive daytime sleepiness and cataplexy. The disease is considered to be the result of the selective disruption of neuronal cells in the lateral hypothalamus expressing the neuropeptide hypocretin, which controls the sleep-wake cycle. Diagnosis and management of narcolepsy represent still a substantial medical challenge due to the large heterogeneity in the clinical manifestation of the disease as well as to the lack of understanding of the underlying pathophysiological mechanisms. However, significant advances have been made in the last years, thus opening new perspective in the field. This review describes the current knowledge of clinical presentation and pathology of narcolepsy as well as the existing diagnostic criteria and therapeutic intervention for the disease management. Recent evidence on the potential immune-mediated mechanisms that may underpin the disease establishment and progression are also highlighted.

Human Leukocyte Antigen Association Study Reveals DRB1*04:02 Effects Additional to DRB1*07:01 in Anti-LGI1 Encephalitis

BACKGROUND AND OBJECTIVES

To study human leukocyte antigen (HLA) allele associations in anti-leucine-rich glioma-inactivated 1 (LGI1) encephalitis.

METHODS

A multiethnic cohort of 269 patients with anti-LGI1 encephalitis and 1,359 controls was included. Four-digit HLA sequencing and genome wide association single-nucleotide polymorphism typing imputation (0.99 concordance) were used for HLA typing. Significance of primary and secondary associations was tested using χ2, Fisher exact tests, or logistic regression with the control of population stratification covariates when applicable.

RESULTS

DRB1*07:01 and DQA1*02:01, 2 alleles in strong linkage disequilibrium, were associated with the disease (90% vs 24%, OR = 27.8, p < 10e-50) across ethnicity independent of variation at DRB3 and DQB1, 2 flanking HLA loci. DRB1*07:01 homozygosity was associated with a doubling of risk (OR = 2.1, p = 0.010), suggesting causality. DRB1*07:01 negative subjects were younger (p = 0.003) and more frequently female (p = 0.015). Three patients with malignant thymomas did not carry DRB1*07:01, whereas patients with other tumors had high DRB1*07:01 frequency, suggesting that the presence of tumors other than thymomas may be coincidental and not causal. In both DRB1*07:01 heterozygous individuals and DRB1*07:01 negative subjects, DRB1*04:02 was associated with anti-LGI1 encephalitis, indicating an independent effect of this allele (OR = 6.85, p = 4.57 × 10-6 and OR = 8.93, p = 2.50 × 10-3, respectively). DRB1*04:02 was also independently associated with younger age at onset (β = -6.68, p = 9.78 × 10-3). Major histocompatibility complex peptide-binding predictions using LGI1-derived peptides revealed divergent binding propensities for DRB1*04:02 and DRB1*07:01 alleles, suggesting independent pathogenic mechanisms.

DISCUSSION

In addition to the established primary DRB1*07:01 association in anti-LGI1 encephalitis, we observe a secondary effect of DRB1*04:02 with lower age at onset. Our study provides evidence for secondary effects within HLA locus that correlate with clinical phenotypes in anti-LGI1 encephalitis.

The role of mtDNA haplogroups on metabolic features in narcolepsy type 1

Narcolepsy type 1 (NT1) is due to selective loss of hypocretin (hcrt)-producing-neurons. Hcrt is a neuropeptide regulating the sleep/wake cycle, as well as feeding behavior. A subset of NT1 patients become overweight/obese, with a dysmetabolic phenotype. We hypothesized that mitochondrial DNA (mtDNA) sequence variation might contribute to the metabolic features in NT1 and we undertook an exploratory survey of mtDNA haplogroups in a cohort of well-characterized patients. We studied 246 NT1 Italian patients, fully defined for their metabolic features, including obesity, hypertension, low HDL, hypertriglyceridemia and hyperglycemia. For haplogroup assignment, the mtDNA control region was sequenced in combination with an assessment of diagnostic markers in the coding region. NT1 patients displayed the same mtDNA haplogroups (H, HV, J, K, T, U) frequency as those reported in the general Italian population. The majority of NT1 patients (64%) were overweight: amongst these, 35% were obese, 48% had low HDL cholesterol levels, and 31% had hypertriglyceridemia. We identified an association between haplogroups J, K and hypertriglyceridemia (P=0.03, 61.5% and 61.5%, respectively vs. 31.3% of the whole sample) and after correction for age and sex, we observed a reduction of these associations (OR=3.65, 95%CI=0.76-17.5, p=0.106 and 1.73, 0.52-5.69, p=0.368, respectively). The low HDL level showed a trend for association with haplogroup J (P=0.09, 83.3% vs. 47.4% of the whole sample) and after correction we observed an OR=6.73, 95%CI=0.65-69.9, p=0.110. Our study provides the first indication that mtDNA haplogroups J and K can modulate metabolic features of NT1 patients, linking mtDNA variation to the dysmetabolic phenotype in NT1.

Germline HLA landscape does not predict efficacy of pembrolizumab monotherapy across solid tumor types

We evaluated the impact of class I and class II human leukocyte antigen (HLA) genotypes, heterozygosity, and diversity on the efficacy of pembrolizumab. Seventeen pembrolizumab clinical trials across eight tumor types and one basket trial in patients with advanced solid tumors were included (n > 3,500 analyzed). Germline DNA was genotyped using a custom genotyping array. HLA diversity (measured by heterozygosity and evolutionary divergence) across class I loci was not associated with improved response to pembrolizumab, either within each tumor type evaluated or across all patients. Similarly, HLA heterozygosity at each class I and class II gene was not associated with response to pembrolizumab after accounting for the number of tests conducted. No conclusive association between HLA genotype and response to pembrolizumab was identified in this dataset. Germline HLA genotype or diversity alone is not an important independent determinant of response to pembrolizumab and should not be used for clinical decision-making in patients treated with pembrolizumab.

Orexin/Hypocretin System Dysfunction in ESSENCE (Early Symptomatic Syndromes Eliciting Neurodevelopmental Clinical Examinations)

Early Symptomatic Syndromes Eliciting Neurodevelopmental Clinical Examinations (ESSENCE) is an umbrella term covering a wide range of neurodevelopmental difficulties and disorders. Thus, ESSENCE includes attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and other neurodevelopmental disorders (NDDs) and difficulties, with a variety of symptoms in cognitive, motor, sensory, social, arousal, regulatory, emotional, and behavioral developmental domains, frequently co-occurring and likely having partly common neurobiological substrates. The ESSENCE concept is a clinical paradigm that promotes organizing NDDs in everyday clinical practice according to their coexistence, symptom dimensions overlapping, and treatment possibilities. Despite increased knowledge regarding NDDs, the neurobiological mechanisms that underlie them and other ESSENCE-related problems, are not well understood. With its wide range of neural circuits and interactions with numerous neurotransmitters, the orexin/hypocretin system (Orx-S) is possibly associated with a variety of neurocognitive, psychobiological, neuroendocrine, and physiological functions and behaviors. Dysfunction of Orx-S has been implicated in various psychiatric and neurological disorders. This article provides an overview of Orx-S dysfunctions' possible involvement in the development, presentation, and maintenance of ESSENCE. We provide a focused review of current research evidence linking orexin neuropeptides with specific clinical NDDs symptoms, mostly in ADHD and ASD, within the Research Domain Criteria (RDoC) framework. We propose that Orx-S dysfunction might have an important role in some of these neurodevelopmental symptom domains, such as arousal, wakefulness, sleep, motor and sensory processing, mood and emotional regulation, fear processing, reward, feeding, attention, executive functions, and sociability. Our perspective is presented from a clinical point of view. Further, more thorough systematic reviews are needed as well as planning of extensive new research into the Orx-S's role in ESSENCE, especially considering RDoC elements.

Non-infectious mechanisms of neurological damage due to infection

Infections of the nervous system is a growing aspect of clinical neurology. Accumulating knowledge in early diagnosis, course, therapy and prognosis is enlarging the clinical tools required for effective therapy. Of special importance is the ability to differentiate between proper infections, where anti-microbial agents, when available, should be introduced and used and post infectious conditions where therapy is mainly directed against the host immune system. The two conditions sometimes overlap, a situation that requires the ability to combine clinical skills with the use of laboratory tools such as polymerase chain reaction (PCR), serology, and antigenic detection. In the era of the SARS-CoV-2 pandemic, the need to make this distinction is emphasized as correct diagnosis of post infectious conditions and expedited therapy is important and sometimes lifesaving. We here attempt to present several infectious agents and their possible indirect damage to the nervous system causing in some cases significant neurological deficits. We try to limit our focus on those mechanisms which do not involve the direct tissue damage by the infectious agents but rather are connected to para- and post-infectious mechanisms. We attempt to delineate the features that will enable to tailor the correct diagnosis and following the effective therapy.

HLA alleles measured from COVID-19 patient transcriptomes reveal associations with disease prognosis in a New York cohort

BACKGROUND

The Human Leukocyte Antigen (HLA) gene locus plays a fundamental role in human immunity, and it is established that certain HLA alleles are disease determinants. Previously, we have identified prevalent HLA class I and class II alleles, including DPA1*02:02, in two small patient cohorts at the COVID-19 pandemic onset.

METHODS

We have since analyzed a larger public patient cohort data (n = 126 patients) with controls, associated demographic and clinical data. By combining the predictive power of multiple in silico HLA predictors, we report on HLA-I and HLA-II alleles, along with their associated risk significance.

RESULTS

We observe HLA-II DPA1*02:02 at a higher frequency in the COVID-19 positive cohort (29%) when compared to the COVID-negative control group (Fisher's exact test [FET] p = 0.0174). Having this allele, however, does not appear to put this cohort's patients at an increased risk of hospitalization. Inspection of COVID-19 disease severity outcomes, including admission to intensive care, reveal nominally significant risk associations with A*11:01 (FET p = 0.0078) and C*04:01 (FET p = 0.0087). The association with severe disease outcome is especially evident for patients with C*04:01, where disease prognosis measured by mechanical ventilation-free days was statistically significant after multiple hypothesis correction (Bonferroni p = 0.0323). While prevalence of some of these alleles falls below statistical significance after Bonferroni correction, COVID-19 patients with HLA-I C*04:01 tend to fare worse overall. This HLA allele may hold potential clinical value.

Peptides of H. sapiens and P. falciparum that are predicted to bind strongly to HLA-A*24:02 and homologous to a SARS-CoV-2 peptide

AIM

This study is looking for a common pathogenicity between SARS-CoV-2 and Plasmodium species, in individuals with certain HLA serotypes.

METHODS

1. Tblastx searches of SARS-CoV-2 are performed by limiting searches to five Plasmodium species that infect humans. 2. Aligned sequences in the respective organisms' proteomes are searched with blastp. 3. Binding predictions of the identified SARS-CoV-2 peptide to HLA supertype representatives are performed. 4. Blastp searches of predicted epitopes that bind strongly to the identified HLA allele are performed by limiting searches to H. sapiens and Plasmodium species, separately. 5. Peptides with minimum 60% identity to the predicted epitopes are found in results. 6. Peptides among those, which bind strongly to the same HLA allele, are predicted. 7. Step-4 is repeated by limiting searches to H. sapiens, followed by the remaining steps until step-7, for peptides sourced by Plasmodium species after step-6.

RESULTS

SARS-CoV-2 peptide with single letter amino acid code CFLGYFCTCYFGLFC has the highest identity to P. vivax. Its YFCTCYFGLF part is predicted to bind strongly to HLA-A*24:02. Peptides in the human proteome both homologous to YFCTCYFGLF and with a strong binding affinity to HLA-A*24:02 are YYCARRFGLF, YYCHCPFGVF, and YYCQQYFFLF. Such peptides in the Plasmodium species' proteomes are FFYTFYFELF, YFVACLFILF, and YFPTITFHLF. The first one belonging to P. falciparum has a homologous peptide (YFYLFSLELF) in the human proteome, which also has a strong binding affinity to the same HLA allele.

CONCLUSION

Immune responses to the identified-peptides with similar sequences and strong binding affinities to HLA-A*24:02 can be related to autoimmune response risk in individuals with HLA-A*24:02 serotypes, upon getting infected with SARS-CoV-2 or P. falciparum.

Narcolepsy type 1 patients have lower levels of effector memory CD4+ T cells compared to their siblings when controlling for H1N1-(Pandemrix™)-vaccination and HLA DQB1∗06:02 status

STUDY OBJECTIVES

Evidence suggests a cell-mediated autoimmune pathogenesis for narcolepsy type 1 (NT1), but it is not clear whether the disease is associated with overall changes in T cell subsets. The increase in NT1 incidence after H1N1 vaccination campaign with the Pandemrix™ vaccine suggests that disease-relevant changes in the immune system following this vaccination were important. In this study, we aimed to investigate differentiated T cell subsets and levels of CD25 and CD69 activation markers in a cohort of mainly Pandemrix™-vaccinated NT1 patients compared with their vaccinated and unvaccinated siblings.

METHODS

Peripheral blood mononuclear cells were collected in parallel and analysed with flow cytometry in 31 NT1 patients with disease onset after the 2009 influenza A (H1N1) pandemic and/or Pandemrix™ vaccination and 45 of their non-narcoleptic siblings (29/31 and 34/45 vaccinated, respectively).

RESULTS

We observed significantly lower effector memory CD4⁺ T cell levels in NT1 patients compared to their siblings, when controlling for HLA DQB1∗06:02 and vaccination status. Further, within the sibling group, vaccination status significantly affected frequencies of central memory and CD8⁺CD25⁺ T cells, and HLA DQB1∗06:02 status significantly affected frequencies of CD4⁺CD25⁺ T cells.

CONCLUSION

We confirm that NT1 is associated with lower levels of effector memory CD4⁺ T cells in peripheral blood. Importantly, this finding was only significant when controlling for vaccination and HLA status in both patients and controls. We thus demonstrate the importance of characterizing such factors (eg HLA and vaccination) when studying T cell subsets in NT1. This might explain earlier conflicting results.

Fundamental mechanistic insights from rare but paradigmatic neuroimmunological diseases

The pathophysiology of complex neuroimmunological diseases, such as multiple sclerosis and autoimmune encephalitis, remains puzzling - various mechanisms that are difficult to dissect seem to contribute, hampering the understanding of the processes involved. Some rare neuroimmunological diseases are easier to study because their presentation and pathogenesis are more homogeneous. The investigation of these diseases can provide fundamental insights into neuroimmunological pathomechanisms that can in turn be applied to more complex diseases. In this Review, we summarize key mechanistic insights into three such rare but paradigmatic neuroimmunological diseases - Susac syndrome, Rasmussen encephalitis and narcolepsy type 1 - and consider the implications of these insights for the study of other neuroimmunological diseases. In these diseases, the combination of findings in humans, different modalities of investigation and animal models has enabled the triangulation of evidence to validate and consolidate the pathomechanistic features and to develop diagnostic and therapeutic strategies; this approach has provided insights that are directly relevant to other neuroimmunological diseases and applicable in other contexts. We also outline how next-generation technologies and refined animal models can further improve our understanding of pathomechanisms, including cell-specific and antigen-specific CNS immune responses, thereby paving the way for the development of targeted therapeutic approaches.

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.

Narcolepsy type 1: what have we learned from genetics?

Type-1 narcolepsy is a severe neurological disorder with distinct characteristic of loss of hypocretin neurotransmitter. Genetic analysis in type-1 narcolepsy have revealed a unique signal pointing toward autoimmune, rather than psychiatric origin. While type-1 narcolepsy has been intensively studied, the other subtypes of hypersomnolence, narcolepsy, and hypersomnia are less thoroughly understood. This review summarizes the latest breakthroughs in the field in narcolepsy. The goal of this article is to help the reader to understand better the risk from genetic factors and their interplay with immune, genetic, and epidemiological aspects in narcolepsy.

T cell reactivity to regulatory factor X4 in type 1 narcolepsy

Type 1 narcolepsy is strongly (98%) associated with human leukocyte antigen (HLA) class II DQA1*01:02/DQB1*06:02 (DQ0602) and highly associated with T cell receptor (TCR) alpha locus polymorphism as well as other immune regulatory loci. Increased incidence of narcolepsy was detected following the 2009 H1N1 pandemic and linked to Pandemrix vaccination, strongly supporting that narcolepsy is an autoimmune disorder. Although recent results suggest CD4+ T cell reactivity to neuropeptide hypocretin/orexin and cross-reactive flu peptide is involved, identification of other autoantigens has remained elusive. Here we study whether autoimmunity directed against Regulatory Factor X4 (RFX4), a protein co-localized with hypocretin, is involved in some cases of narcolepsy. Studying human serum, we found that autoantibodies against RFX4 were rare. Using RFX4 peptides bound to DQ0602 tetramers, antigen RFX4-86, -95, and -60 specific human CD4+ T cells were detected in 4/10 patients and 2 unaffected siblings, but not in others. Following culture with each cognate peptide, enriched autoreactive TCRαβ clones were isolated by single-cell sorting and TCR sequenced. Homologous clones bearing TRBV4-2 and recognizing RFX4-86 in patients and one twin control of patient were identified. These results suggest the involvement of RFX4 CD4+ T cell autoreactivity in some cases of narcolepsy, but also in healthy donors.

Narcolepsy Type I as an autoimmune disorder

Narcolepsy Type 1 (NT1) is hypothesized to be an autoimmune disease targeting the hypocretin/orexin neurons in the lateral hypothalamus. Ample genetic and epidemiologic evidence point in the direction of a pathogenesis involving the immune system. Many autoantibodies have been detected in blood samples from NT1 patients, but none in a consistent manner. Importantly, T cells directed toward hypocretin/orexin neurons have been detected in samples from NT1 patients. However, it remains to be seen if these potentially autoreactive T cells are also present in the hypothalamus and if they are pathogenic. For this reason, NT1 does still not fully meet the criteria for being classified as a genuine autoimmune disease, even though more and more results are pointing in that direction as will be described in this chapter. The autoimmune hypothesis has led to many attempts at slowing or stopping disease progression with immunomodulatory treatment, but so far the overall results have not been very encouraging. It is clear that more research into the pathogenesis of NT1 is needed to establish the precise role of the immune system in disease development.

Reviewing the Clinical Implications of Treating Narcolepsy as an Autoimmune Disorder

Narcolepsy type 1 (NT1) is a lifelong sleep disorder, primarily characterized clinically by excessive daytime sleepiness and cataplexy and pathologically by the loss of hypocretinergic neurons in the lateral hypothalamus. Despite being a rare disorder, the NT1-related burden for patients and society is relevant due to the early onset and chronic nature of this condition. Although the etiology of narcolepsy is still unknown, mounting evidence supports a central role of autoimmunity. To date, no cure is available for this disorder and current treatment is symptomatic. Based on the hypothesis of the autoimmune etiology of this disease, immunotherapy could possibly represent a valid therapeutic option. However, contrasting and limited results have been provided so far. This review discusses the evidence supporting the use of immunotherapy in narcolepsy, the outcomes obtained so far, current issues and future directions.

Retrospective in silico HLA predictions from COVID-19 patients reveal alleles associated with disease prognosis

BACKGROUND

The Human Leukocyte Antigen (HLA) gene locus plays a fundamental role in human immunity, and it is established that certain HLA alleles are disease determinants.

METHODS

By combining the predictive power of multiple in silico HLA predictors, we have previously identified prevalent HLA class I and class II alleles, including DPA1*02:02, in two small cohorts at the COVID-19 pandemic onset. Since then, newer and larger patient cohorts with controls and associated demographic and clinical data have been deposited in public repositories. Here, we report on HLA-I and HLA-II alleles, along with their associated risk significance in one such cohort of 126 patients, including COVID-19 positive (n=100) and negative patients (n=26).

RESULTS

We recapitulate an enrichment of DPA1*02:02 in the COVID-19 positive cohort (29%) when compared to the COVID-negative control group (Fisher's exact test [FET] p=0.0174). Having this allele, however, does not appear to put this cohort's patients at an increased risk of hospitalization. Inspection of COVID-19 disease severity outcomes reveal nominally significant risk associations with A*11:01 (FET p=0.0078), C*04:01 (FET p=0.0087) and DQA1*01:02 (FET p=0.0121).

CONCLUSIONS

While enrichment of these alleles falls below statistical significance after Bonferroni correction, COVID-19 patients with the latter three alleles tend to fare worse overall. This is especially evident for patients with C*04:01, where disease prognosis measured by mechanical ventilation-free days was statistically significant after multiple hypothesis correction (Bonferroni p = 0.0023), and may hold potential clinical value.

Mass Spectrometric Characterization of Narcolepsy-Associated Pandemic 2009 Influenza Vaccines

The onset of narcolepsy, an irreversible sleep disorder, has been associated with 2009 influenza pandemic (pH1N1) infections in China, and with ASO3-adjuvanted pH1N1 vaccinations using Pandemrix in Europe. Intriguingly, however, the increased incidence was only observed following vaccination with Pandemrix but not Arepanrix in Canada. In this study, the mutational burden of actual vaccine lots of Pandemrix (n = 6) and Arepanrix (n = 5) sourced from Canada, and Northern Europe were characterized by mass spectrometry. The four most abundant influenza proteins across both vaccines were nucleoprotein NP, hemagglutinin HA, matrix protein M1, with the exception that Pandemrix harbored a significantly increased proportion of neuraminidase NA (7.5%) as compared to Arepanrix (2.6%). Most significantly, 17 motifs in HA, NP, and M1 harbored mutations, which significantly differed in Pandemrix versus Arepanrix. Among these, a 6-fold higher deamidation of HA146 (p.Asn146Asp) in Arepanrix was found relative to Pandemrix, while NP257 (p.Thr257Ala) and NP424 (p.Thr424Ile) were increased in Pandemrix. DQ0602 binding and tetramer analysis with mutated epitopes were conducted in Pandemrix-vaccinated cases versus controls but were unremarkable. Pandemrix harbored lower mutational burden than Arepanrix, indicating higher similarity to wild-type 2009 pH1N1, which could explain differences in narcolepsy susceptibility amongst the vaccines.

Mortality in COVID-19 disease patients: Correlating the association of major histocompatibility complex (MHC) with severe acute respiratory syndrome 2 (SARS-CoV-2) variants

Genetic factors such as the HLA type of patients may play a role in regard to disease severity and clinical outcome of patients with COVID-19. Taking the data deposited in the GISAID database, we made predictions using the IEDB analysis resource (TepiTool) to gauge how variants in the SARS-CoV-2 genome may change peptide binding to the most frequent MHC-class I and -II alleles in Africa, Asia and Europe. We caracterized how a single mutation in the wildtype sequence of of SARS-CoV-2 could influence the peptide binding of SARS-CoV-2 variants to MHC class II, but not to MHC class I alleles. Assuming the ORF8 (L84S) mutation is biologically significant, selective pressure from MHC class II alleles may select for viral varients and subsequently shape the quality and quantity of cellular immune responses aginast SARS-CoV-2. MHC 4-digit typing along with viral sequence analysis should be considered in studies examining clinical outcomes in patients with COVID-19.

Immune dysregulation in depression: Evidence from genome-wide association

A strong body of evidence supports a role for immune dysregulation across many psychiatric disorders including depression, the leading cause of global disability. Recent progress in the search for genetic variants associated with depression provides the opportunity to strengthen our current understanding of etiological factors contributing to depression and generate novel hypotheses. Here, we provide an overview of the literature demonstrating a role for immune dysregulation in depression, followed by a detailed discussion of the immune-related genes identified by the most recent genome-wide meta-analysis of depression. These genes represent strong evidence-based targets for future basic and translational research which aims to understand the role of the immune system in depression pathology and identify novel points for therapeutic intervention.

HLA-DPB1*03 as Risk Allele and HLA-DPB1*04 as Protective Allele for Both Early- and Adult-Onset Multiple Sclerosis in a Hellenic Cohort

Background: Human Leucocyte Antigens (HLA) represent the genetic loci most strongly linked to Multiple Sclerosis (MS). Apart from HLA-DR and HLA–DQ, HLA-DP alleles have been previously studied regarding their role in MS pathogenesis, but to a much lesser extent. Our objective was to investigate the risk/resistance influence of HLA-DPB1 alleles in Hellenic patients with early- and adult-onset MS (EOMS/AOMS), and possible associations with the HLA-DRB1*15:01 risk allele. Methods: One hundred MS-patients (28 EOMS, 72 AOMS) fulfilling the McDonald-2010 criteria were enrolled. HLA genotyping was performed with standard low-resolution Sequence-Specific Oligonucleotide techniques. Demographics, clinical and laboratory data were statistically processed using well-defined parametric and nonparametric methods and the SPSSv22.0 software. Results: No significant HLA-DPB1 differences were found between EOMS and AOMS patients for 23 distinct HLA-DPB1 and 12 HLA-DRB1 alleles. The HLA-DPB1*03 allele frequency was found to be significantly increased, and the HLA-DPB1*02 allele frequency significantly decreased, in AOMS patients compared to controls. The HLA-DPB1*04 allele was to be found significantly decreased in AOMS and EOMS patients compared to controls. Conclusions: Our study supports the previously reported risk susceptibility role of the HLA-DPB1*03 allele in AOMS among Caucasians. Additionally, we report for the first time a protective role of the HLA-DPB1*04 allele among Hellenic patients with both EOMS and AOMS.

HLA predictions from the bronchoalveolar lavage fluid samples of five patients at the early stage of the wuhan seafood market COVID-19 outbreak

We are in the midst of a global viral pandemic, one with no cure and a high mortality rate. The Human Leukocyte Antigen (HLA) gene complex plays a critical role in host immunity. We predicted HLA class I and II alleles from the transcriptome sequencing data prepared from the bronchoalveolar lavage fluid samples of five patients at the early stage of the COVID-19 outbreak. We identified the HLA-I allele A*24:02 in four out of five patients, which is higher than the expected frequency (17.2%) in the South Han Chinese population. The difference is statistically significant with a p-value less than 10-4. Our analysis results may help provide future insights on disease susceptibility.

HLA associations in narcolepsy type 1 persist after the 2009 H1N1 pandemic

We aimed to compare HLA-DQB1-associations in narcolepsy type 1 (NT1) patients with disease onset before and after the 2009 H1N1 pandemic in a large Dutch cohort. 525 NT1 patients and 1272 HLA-DQB1*06:02-positive healthy controls were included. Because of the discussion that has arisen on the existence of sporadic and post-H1N1 NT1, HLA-DQB1-associations in pre- and post-H1N1 NT1 patients were compared. The associations between HLA-DQB1 alleles and NT1 were not significantly different between pre- and post-H1N1 NT1 patients. Both HLA-DQB1-associations with pre- and -post H1N1 NT1 reported in recent smaller studies were replicated. Our findings combine the results of studies in pre- and post-H1N1 NT1 and argue against considering post-H1N1 NT1 as a different entity.

Immunotherapy in Narcolepsy

PURPOSE OF REVIEW

Narcolepsy type 1 (NT1) is a chronic and disabling sleep disorder due to the loss of hypocretinergic neurons in the lateral hypothalamus pathophysiologically linked to an autoimmune process. Current treatment is symptomatic, and no cure is available to date. Immunotherapy is considered a promising future therapeutic option, and this review discusses the rationale for immunotherapy in narcolepsy, current evidences of its effects, outcome measures, and future directions.

RECENT FINDINGS

A limited number of case reports and uncontrolled small case series have reported the effect of different immunotherapies in patients with NT1. These studies were mainly based on the use of intravenous immunoglobulin (IVig), followed by corticosteroids, plasmapheresis, and monoclonal antibodies. Although initial reports showed an improvement of symptoms, particularly when patients were treated close to disease onset, other observations have not confirmed these results. Inadequate timing of treatment, placebo effects, and spontaneous improvement due to the natural disease course can account for these contrasting findings. Moreover, clear endpoints and standardized outcome measures have not been used and are currently missing in the pediatric population. On the basis of the available data, there are no enough evidences to support the use of immunotherapy in NT1. Randomized, controlled studies using clear endpoints and new outcome measures are needed to achieve a definitive answer about the usefulness of these treatments in narcolepsy.

[Narcolepsy: From the discovery of a wake promoting peptide to autoimmune T cell biology and molecular mimicry with flu epitopes]

Narcolepsy-cataplexy was first described in the late 19th century in Germany and France. Prevalence was established to be 0.05 % and a canine model was discovered in the 1970s. In 1983, a Japanese study found that all patients carried HLA-DR2, suggesting autoimmunity as the cause of the disease. Studies in the canine model established that dopaminergic stimulation underlies anti-narcoleptic action of psychostimulants, while antidepressants were found to suppress cataplexy through adrenergic reuptake inhibition. No HLA association was found in canines. A linkage study initiated in 1988 revealed in hypocretin (orexin) receptor two mutations as the cause of canine narcolepsy in 1999. In 1992, studies on African Americans showed that DQ0602 was a better marker than DR2 across all ethnic groups. In 2000, hypocretin-1/orexin A levels were measured in the cerebrospinal fluid (CSF) and found to be undetectable in most patients, establishing hypocretin deficiency as the cause of narcolepsy. Decreased CSF hypocretin-1 was then found to be secondary to the loss of the 70,000 neurons producing hypocretin in the hypothalamus, suggesting immune destruction of these cells as the cause of the disease. Additional genetic studies, notably genome wide associations (GWAS), found multiple genetic predisposing factors for narcolepsy. These were almost all involved in other autoimmune diseases, although a strong and unique association with T cell receptor (TCR) alpha and beta loci were observed. Nonetheless, all attempts to demonstrate presence of autoantibodies against hypocretin cells in narcolepsy failed, and the presumed autoimmune cause remained unproven. In 2009, association with strep throat infections were found, and narcolepsy onsets were found to occur more frequently in spring and summer, suggesting upper away infections as triggers. Following reports that narcolepsy cases were triggered by vaccinations and infections against influenza A 2009 pH1N1, a new pandemic strain that erupted in 2009, molecular mimicry with influenza A virus was suggested in 2010. This hypothesis was later confirmed by peptide screening showing higher activity of CD4⁺ T cell reactivity to a specific post-translationally amidated segment of hypocretin (HCRT-_NH2) and cross-reactivity of specific TCRs with a pH1N1-specific segment of hemagglutinin that shares homology with HCRT-_NH2. Strikingly, the most frequent TCR recognizing these antigens was found to carry sequences containing TRAJ24 or TRVB4-2, segments modulated by narcolepsy-associated genetic polymorphisms. Cross-reactive CD4⁺ T cells with these cross-reactive TCRs likely subsequently recruit CD8⁺ T cells that are then involved in hypocretin cell destruction. Additional flu mimics are also likely to be discovered since narcolepsy existed prior to 2009. The work that has been conducted over the years on narcolepsy offers a unique perspective on the conduct of research on the etiopathogeny of a specific disease.

Narcolepsy in Children and Adults: A Guide to Improved Recognition, Diagnosis and Management

Narcolepsy is a rare condition that affects children and adults, and commonly has an onset in childhood. Time to appropriate diagnosis frequently is at least a decade. Unrecognized or misdiagnosed symptoms of narcolepsy contribute to increased morbidity, disability and socioeconomic liability in these patients. Delays in diagnosis may be related to variability in presentation in childhood, lack of familiarity with symptoms or appropriate diagnostic testing or misdiagnosis with accidental introduction of treatment that may modify or mask narcolepsy features. Improved awareness about the diagnosis and tailored therapies improve clinical and socioeconomic outcomes by reducing time to effective treatment. Application of effective treatment results in long-term benefits by improving clinical outcomes, potentially enabling improved education, increased employment opportunity, and improved work productivity and quality of life. This review provides a comprehensive stepwise approach to improve knowledge and comfort for recognition of symptoms, diagnostic strategies and management considerations of narcolepsy in children and adults.

Children with Narcolepsy type 1 have increased T-cell responses to orexins

Narcolepsy type 1 (NT1) is caused by severe loss of the orexin neurons, and is highly associated with HLA DQB1*06:02. Using intracellular cytokine staining, we observed a higher frequency of IFN‐γ‐ and TNF‐α‐producing CD4⁺ and CD8⁺ T‐cells in response to orexins in 27 children with NT1 compared to 15 healthy control children. Conversely, no such difference was observed between 14 NT1 and 16 HC adults. In addition, priming with flu peptides amplified the T‐cell response to orexins in children with NT1. Our data suggests that NT1 may be caused by an autoimmune T‐cell response to orexins, possibly triggered by flu antigens.

Positive oligoclonal bands and CSF pleocytosis in narcolepsy type 1: A case report supporting the immune-mediated hypothesis

Narcolepsy-type 1 is a neurological sleep-disorder caused by a selective loss of hypothalamic orexin/hypocretin-producing neurons whose underlying mechanism is considered to be immune-mediated. We report the case of a 16 year-old girl with excessive daytime sleepiness, hypnagogic/hypnopompic hallucinations and cataplexy, fulfilling narcolepsy-type 1 diagnostic criteria. She was HLA-DQB1*06:02/DQA1*01:02 positive. CSF analysis demonstrated positive IgG oligoclonal bands, pleocytosis and hypocretin-1 below detection limit. Other autoimmune processes were excluded, including autoimmune encephalitis. After treatment with intravenous immunoglobulins sleep-related hallucinations transiently improved for a month. This case's CSF inflammatory findings support the role of neuroinflammation in narcolepsy-type 1 development in genetically predisposed patients.

HLA and sleep parameter associations in post-H1N1 narcolepsy type 1 patients and first-degree relatives

Study Objectives

To explore HLA (human leukocyte antigen) in post-H1N1 narcolepsy type 1 patients (NT1), first-degree relatives and healthy controls, and assess HLA associations with clinical and sleep parameters in patients and first-degree relatives.

Methods

Ninety post-H1N1 NT1 patients and 202 of their first-degree relatives were HLA-genotyped (next generation sequencing) and phenotyped (semistructured interviews, Stanford Sleep Questionnaire, polysomnography, and multiple sleep latency test). HLA allele distributions were compared between DQB1*06:02-heterozygous individuals (77 patients, 59 parents, 1230 controls). A subsample (74 patients, 114 relatives) was investigated for associations between HLA-loci and continuous sleep variables using logistic regression. Identified candidate HLA-loci were explored for HLA allele associations with hypnagogic hallucinations and sleep paralysis in 90 patients, and patient allele findings were checked for similar associations in 202 relatives.

Results

DQB1*06:02 heterozygous post-H1N1 NT1 patients (84.4% H1N1-vaccinated) showed several significant HLA associations similar to those reported previously in samples of mainly sporadic NT1, i.e. DQB1*03:01, DRB1*04:01, DRB1*04:02, DRB1*04:07, DRB1*11:04, A*25:01, B*35:03, and B*51:01, and novel associations, i.e. B*14:02, C*01:02, and C*07:01. Parents HLA alleles did not deviate significantly from controls. The HLA-C locus was associated with sleep parameters in patients and relatives. In patients C*02:02 seems to be associated with protective effects against sleep paralysis and hypnagogic hallucinations.

Conclusions

Our findings of similar risk/protective HLA-alleles in post-H1N1 as in previous studies of mainly sporadic narcolepsy support similar disease mechanisms. We also report novel allelic associations. Associations between HLA-C and sleep parameters were seen independent of NT1 diagnosis, supporting involvement of HLA-C in sleep subphenotypes.