Does narcolepsy symptom severity vary according to HLA-DQB1*0602 allele status?

Reliability and validity of the Chinese version of Narcolepsy Severity Scale in adult patients with narcolepsy type 1

OBJECTIVE

To evaluate reliability and validity of the Chinese version of Narcolepsy Severity Scale (NSS) in adult patients with narcolepsy type 1 (NT1).

METHODS

One hundred and fifty-one adult patients (≥18 years) with NT1 were recruited. All filled out the 15-item Chinese version of NSS. Item analysis included critical ratio and correlation analysis. The validity of NSS was assessed by exploratory factor analysis, discriminant validity and convergent validity. Reliability of NSS was assessed by Cronbach's α coefficient, spilt-half reliability and test-retest reliability.

RESULTS

Critical value of all 15 items ranged from 3.01 to 13.36. Each item was significantly correlated with the total score by a correlation coefficient (r) ranging from 0.219 to 0.700. Three common domains were extracted and 15 items explained 54.86% of the total variance. There was a shift in domains compared to the English version likely due to cultural differences. Cronbach's α coefficient for the total scale of 15 items was 0.821 and for three factors was 0.726, 0.748 and 0.760 respectively. The NSS had good correlation with Epworth sleepiness scale scores, Insomnia severity index scores and moderate correlation with mean the sleep latency of polysomnographic recording, and European Quality of Life-5 Dimensions Questionnaire. The Chinese version of NSS showed good spilt-half reliability and test-retest reliability.

CONCLUSION

The Chinese version of NSS shows satisfactory psychometric properties with good validity and reliability. It is applicable to evaluate the severity and consequences of symptoms in Chinese adult patients with NT1.

HLA-DQB1*06:02 allele frequency and clinic-polysomnographic features in Saudi Arabian patients with narcolepsy

BACKGROUND

Narcolepsy is an uncommon neurological disorder characterised by irresistible spells of sleep associated with abnormal rapid eye movement (REM) sleep. The association between narcolepsy and human leukocyte antigen HLA- DQB1*06:02 has been established elsewhere but remains to be investigated among Saudi Arabian patients with narcolepsy.

METHODS

A total of 29 Saudi patients with type I or type 2 narcolepsy comprising of 23 (79%) males and 6 (21%) females with a mean age of 17.2 ± 9.6 years were included in this study. Type 1 or type 2 narcolepsy was diagnosed by full polysomnography followed by a multiple sleep latency test in accordance with International Classifications of Sleep Disorders-3 criteria. HLA typing for DQB1 alleles was performed by polymerase chain reaction and hybridization with sequence-specific oligonucleotide probes. Differences in clinical and sleep parameters were compared by univariable analyses. HLA-DQB1*06:02 frequency was systematically compared with the published literature.

RESULTS

Type 1 narcolepsy was diagnosed in 19/29 (65.5%) patients, whereas 10/29 (34.5%) patients had type 2 narcolepsy. DQB1*06:02 was present in 25/29 (86.2%) patients; 15/19 (78.9%) narcolepsy type 1 patients and 10/10 (100%) narcolepsy type 2 patients harboured the DQB1*06:02 allele. REM latency was significantly lower in DQB1*06:02-positive patients compared to DQB1*06:02-negative patients (17.6 ± 32.3 min vs. 106.0 ± 86.0 min; p = 0.025). Epworth Sleepiness Scale scores were significantly higher among type 1 than type 2 narcolepsy patients (19.7 ± 3.2 vs 15.3 ± 3.6; p = 0.02).

CONCLUSIONS

DQB1*06:02 allele frequencies among Saudi patients with narcolepsy were consistent with previously published data.

Genetic Ancestry for Sleep Research: Leveraging Health Inequalities to Identify Causal Genetic Variants

Recent evidence has highlighted the health inequalities in sleep behaviors and sleep disorders that adversely affect outcomes in select populations, including African-American and Hispanic-American subjects. Race-related sleep health inequalities are ascribed to differences in multilevel and interlinked health determinants, such as sociodemographic factors, health behaviors, and biology. African-American and Hispanic-American subjects are admixed populations whose genetic inheritance combines two or more ancestral populations originating from different continents. Racial inequalities in admixed populations can be parsed into relevant groups of mediating factors (environmental vs genetic) with the use of measures of genetic ancestry, including the proportion of an individual's genetic makeup that comes from each of the major ancestral continental populations. This review describes sleep health inequalities in African-American and Hispanic-American subjects and considers the potential utility of ancestry studies to exploit these differences to gain insight into the genetic underpinnings of these phenotypes. The inclusion of genetic approaches in future studies of admixed populations will allow greater understanding of the potential biological basis of race-related sleep health inequalities.

Fine-mapping of the human leukocyte antigen locus as a risk factor for Alzheimer disease: A case-control study

BACKGROUND

Alzheimer disease (AD) is a progressive disorder that affects cognitive function. There is increasing support for the role of neuroinflammation and aberrant immune regulation in the pathophysiology of AD. The immunoregulatory human leukocyte antigen (HLA) complex has been linked to susceptibility for a number of neurodegenerative diseases, including AD; however, studies to date have failed to consistently identify a risk HLA haplotype for AD. Contributing to this difficulty are the complex genetic organization of the HLA region, differences in sequencing and allelic imputation methods, and diversity across ethnic populations.

METHODS AND FINDINGS

Building on prior work linking the HLA to AD, we used a robust imputation method on two separate case-control cohorts to examine the relationship between HLA haplotypes and AD risk in 309 individuals (191 AD, 118 cognitively normal [CN] controls) from the San Francisco-based University of California, San Francisco (UCSF) Memory and Aging Center (collected between 1999-2015) and 11,381 individuals (5,728 AD, 5,653 CN controls) from the Alzheimer's Disease Genetics Consortium (ADGC), a National Institute on Aging (NIA)-funded national data repository (reflecting samples collected between 1984-2012). We also examined cerebrospinal fluid (CSF) biomarker measures for patients seen between 2005-2007 and longitudinal cognitive data from the Alzheimer's Disease Neuroimaging Initiative (n = 346, mean follow-up 3.15 ± 2.04 y in AD individuals) to assess the clinical relevance of identified risk haplotypes. The strongest association with AD risk occurred with major histocompatibility complex (MHC) haplotype A*03:01~B*07:02~DRB1*15:01~DQA1*01:02~DQB1*06:02 (p = 9.6 x 10-4, odds ratio [OR] [95% confidence interval] = 1.21 [1.08-1.37]) in the combined UCSF + ADGC cohort. Secondary analysis suggested that this effect may be driven primarily by individuals who are negative for the established AD genetic risk factor, apolipoprotein E (APOE) ɛ4. Separate analyses of class I and II haplotypes further supported the role of class I haplotype A*03:01~B*07:02 (p = 0.03, OR = 1.11 [1.01-1.23]) and class II haplotype DRB1*15:01- DQA1*01:02- DQB1*06:02 (DR15) (p = 0.03, OR = 1.08 [1.01-1.15]) as risk factors for AD. We followed up these findings in the clinical dataset representing the spectrum of cognitively normal controls, individuals with mild cognitive impairment, and individuals with AD to assess their relevance to disease. Carrying A*03:01~B*07:02 was associated with higher CSF amyloid levels (p = 0.03, β ± standard error = 47.19 ± 21.78). We also found a dose-dependent association between the DR15 haplotype and greater rates of cognitive decline (greater impairment on the 11-item Alzheimer's Disease Assessment Scale cognitive subscale [ADAS11] over time [p = 0.03, β ± standard error = 0.7 ± 0.3]; worse forgetting score on the Rey Auditory Verbal Learning Test (RAVLT) over time [p = 0.02, β ± standard error = -0.2 ± 0.06]). In a subset of the same cohort, dose of DR15 was also associated with higher baseline levels of chemokine CC-4, a biomarker of inflammation (p = 0.005, β ± standard error = 0.08 ± 0.03). The main study limitations are that the results represent only individuals of European-ancestry and clinically diagnosed individuals, and that our study used imputed genotypes for a subset of HLA genes.

CONCLUSIONS

We provide evidence that variation in the HLA locus-including risk haplotype DR15-contributes to AD risk. DR15 has also been associated with multiple sclerosis, and its component alleles have been implicated in Parkinson disease and narcolepsy. Our findings thus raise the possibility that DR15-associated mechanisms may contribute to pan-neuronal disease vulnerability.

T cell epitope redundancy: cross-conservation of the TCR face between pathogens and self and its implications for vaccines and autoimmunity

T cells are extensively trained on 'self' in the thymus and then move to the periphery, where they seek out and destroy infections and regulate immune response to self-antigens. T cell receptors (TCRs) on T cells' surface recognize T cell epitopes, short linear strings of amino acids presented by antigen-presenting cells. Some of these epitopes activate T effectors, while others activate regulatory T cells. It was recently discovered that T cell epitopes that are highly conserved on their TCR face with human genome sequences are often associated with T cells that regulate immune response. These TCR-cross-conserved or 'redundant epitopes' are more common in proteins found in pathogens that have co-evolved with humans than in other non-commensal pathogens. Epitope redundancy might be the link between pathogens and autoimmune disease. This article reviews recently published data and addresses epitope redundancy, the "elephant in the room" for vaccine developers and T cell immunologists.

Narcolepsy in African Americans

STUDY OBJECTIVES

Although narcolepsy affects 0.02-0.05% of individuals in various ethnic groups, clinical presentation in different ethnicities has never been fully characterized. Our goal was to study phenotypic expression across ethnicities in the United States.

DESIGN/SETTING

Cases of narcolepsy from 1992 to 2013 were identified from searches of the Stanford Center for Narcolepsy Research database. International Classification of Sleep Disorders, Third Edition diagnosis criteria for type 1 and type 2 narcolepsy were used for inclusion, but subjects were separated as with and without cataplexy for the purpose of data presentation. Information extracted included demographics, ethnicity and clinical data, HLA-DQB1*06:02, polysomnography (PSG), multiple sleep latency test (MSLT) data, and cerebrospinal fluid (CSF) hypocretin-1 level.

PATIENTS

182 African-Americans, 839 Caucasians, 35 Asians, and 41 Latinos with narcolepsy.

RESULTS

Sex ratio, PSG, and MSLT findings did not differ across ethnicities. Epworth Sleepiness Scale (ESS) score was higher and age of onset of sleepiness earlier in African Americans compared with other ethnicities. HLA-DQB1*06:02 positivity was higher in African Americans (91.0%) versus others (76.6% in Caucasians, 80.0% in Asians, and 65.0% in Latinos). CSF hypocretin-1 level, obtained in 222 patients, was more frequently low (≤ 110 pg/ml) in African Americans (93.9%) versus Caucasians (61.5%), Asians (85.7%) and Latinos (75.0%). In subjects with low CSF hypocretin-1, African Americans (28.3%) were 4.5 fold more likely to be without cataplexy when compared with Caucasians (8.1%).

CONCLUSIONS

Narcolepsy in African Americans is characterized by earlier symptom onset, higher Epworth Sleepiness Scale score, higher HLA-DQB1*06:02 positivity, and low cerebrospinal fluid hypocretin-1 level in the absence of cataplexy. In African Americans, more subjects without cataplexy have type 1 narcolepsy.

Narcolepsy as an autoimmune disease: the role of H1N1 infection and vaccination

Narcolepsy is a sleep disorder characterised by loss of hypothalamic hypocretin (orexin) neurons. The prevalence of narcolepsy is about 30 per 100 000 people, and typical age at onset is 12-16 years. Narcolepsy is strongly associated with the HLA-DQB1*06:02 genotype, and has been thought of as an immune-mediated disease. Other risk genes, such as T-cell-receptor α chain and purinergic receptor subtype 2Y11, are also implicated. Interest in narcolepsy has increased since the epidemiological observations that H1N1 infection and vaccination are potential triggering factors, and an increase in the incidence of narcolepsy after the pandemic AS03 adjuvanted H1N1 vaccination in 2010 from Sweden and Finland supports the immune-mediated pathogenesis. Epidemiological observations from studies in China also suggest a role for H1N1 virus infections as a trigger for narcolepsy. Although the pathological mechanisms are unknown, an H1N1 virus-derived antigen might be the trigger.

Identification of the variations in the CPT1B and CHKB genes along with the HLA-DQB1*06:02 allele in Turkish narcolepsy patients and healthy persons

BACKGROUND

The HLA-DQB1*06:02 allele across all ethnic groups and the rs5770917 variation between CPT1B and CHKB genes in Japanese and Koreans are common genetic susceptibility factors for narcolepsy. This comprehensive genetic study sought to assess variations in CHKB and CPT1B susceptibility genes and HLA-DQB1*06:02 allele status in Turkish patients with narcolepsy and healthy persons.

METHODS

CHKB/CPT1B genes were sequenced in patients with narcolepsy (n=37) and healthy persons (n=100) to detect variations. The HLA-DQB1*06:02 allele status was determined by sequence specific polymerase chain reaction.

RESULTS

The HLA-DQB1*06:02 allele was significantly more frequent in narcoleptic patients than in healthy persons (p=2×10(-7)) and in patients with narcolepsy and cataplexy than in those without (p=0.018). The mean of the multiple sleep latency test, sleep-onset rapid eye movement periods, and frequency of sleep paralysis significantly differed in the HLA-DQB1*06:02-positive patients. rs5770917, rs5770911, rs2269381, and rs2269382 were detected together as a haplotype in three patients and 11 healthy persons. In addition to this haplotype, the indel variation (rs144647670) was detected in the 5' upstream region of the human CHKB gene in the patients and healthy persons carrying four variants together.

CONCLUSION

This study identified a novel haplotype consisting of the indel variation, which had not been detected in previous studies in Japanese and Korean populations, and observed four single-nucleotide polymorphisms in CHKB/CPT1B. The study confirmed the association of the HLA-DQB1*06:02 allele with narcolepsy and cataplexy susceptibility. The findings suggest that the presence of HLA-DQB1*06:02 may be a predictor of cataplexy in narcoleptic patients and could therefore be used as an additional diagnostic marker alongside hypocretin.

Use of PCR with sequence-specific primers for high-resolution human leukocyte antigen typing of patients with narcolepsy

Background

Narcolepsy is a neurologic disorder characterized by excessive daytime sleepiness, symptoms of abnormal rapid eye movement (REM) sleep, and a strong association with HLA-DRB1^*1501, -DQA1^*0102, and -DQB1^*0602. Here, we investigated the clinico-physical characteristics of Korean patients with narcolepsy, their HLA types, and the clinical utility of high-resolution PCR with sequence-specific primers (PCR-SSP) as a simple typing method for identifying DRB1^*15/16, DQA1, and DQB1 alleles.

Methods

The study population consisted of 67 consecutively enrolled patients having unexplained daytime sleepiness and diagnosed narcolepsy based on clinical and neurological findings. Clinical data and the results of the multiple sleep latency test and polysomnography were reviewed, and HLA typing was performed using both high-resolution PCR-SSP and sequence-based typing (SBT).

Results

The 44 narcolepsy patients with cataplexy displayed significantly higher frequencies of DRB1^*1501 (Pc= 0.003), DQA1^*0102 (Pc=0.001), and DQB1^*0602 (Pc=0.014) than the patients without cataplexy. Among patients carrying DRB1^*1501-DQB1^*0602 or DQA1^*0102, the frequencies of a mean REM sleep latency of less than 20 min in nocturnal polysomnography and clinical findings, including sleep paralysis and hypnagogic hallucination were significantly higher. SBT and PCR-SSP showed 100% concordance for high-resolution typing of DRB1^*15/16 alleles and DQA1 and DQB1 loci.

Conclusions

The clinical characteristics and somnographic findings of narcolepsy patients were associated with specific HLA alleles, including DRB1^*1501, DQA1^*0102, and DQB1^*0602. Application of high-resolution PCR-SSP, a reliable and simple method, for both allele- and locus-specific HLA typing of DRB1^*15/16, DQA1, and DQB1 would be useful for characterizing clinical status among subjects with narcolepsy.

TCRA, P2RY11, and CPT1B/CHKB associations in Chinese narcolepsy

OBJECTIVES

Polymorphisms in the TCRA and P2RY11, two immune related genes, are associated with narcolepsy in Caucasians and Asians. In contrast, CPT1B/CHKB polymorphisms have only been shown to be associated with narcolepsy in Japanese, with replication in a small group of Koreans. Our aim was to study whether these polymorphisms are associated with narcolepsy and its clinical characteristics in Chinese patients with narcolepsy.

METHODS

We collected clinical data on 510 Chinese patients presenting with narcolepsy/hypocretin deficiency. Patients were included either when hypocretin deficiency was documented (CSF hypocretin-1≤110 pg/ml, n=91) or on the basis of the presence of clear cataplexy and HLA-DQB1∗0602 positivity (n=419). Genetic data was compared to typing obtained in 452 controls matched for geographic origin within China. Clinical evaluations included demographics, the Stanford Sleep Inventory (presence and age of onset of each symptom), and Multiple Sleep Latency Test (MSLT) data.

RESULTS

Chinese narcolepsy was strongly and dose dependently associated with TCRA (rs1154155C) and P2RY11 (rs2305795A) but not CPT1B/CHKB (rs5770917C) polymorphisms. CPT1B/CHKB polymorphisms were not associated with any specific clinical characteristics. TCRA rs1154155A homozygotes (58 subjects) had a later disease onset, but this was not significant when corrected for multiple comparisons, thus replication is needed. CPT1B/CHKB or P2RY11 polymorphisms were not associated with any specific clinical characteristics.

CONCLUSIONS

The study extends on the observation of a strong multiethnic association of polymorphisms in the TCRA and P2RY11 with narcolepsy, but does not confirm the association of CPT1B/CHKB (rs5770917) in the Chinese population.