Evidence that HLA class I and II associations with type 1 diabetes, autoantibodies to GAD and autoantibodies to IA-2, are distinct

Antigen-specific T cell responses in autoimmune diabetes

Autoimmune diabetes is a disease characterized by the selective destruction of insulin-secreting β-cells of the endocrine pancreas by islet-reactive T cells. Autoimmune disease requires a complex interplay between host genetic factors and environmental triggers that promote the activation of such antigen-specific T lymphocyte responses. Given the critical involvement of self-reactive T lymphocyte in diabetes pathogenesis, understanding how these T lymphocyte populations contribute to disease is essential to develop targeted therapeutics. To this end, several key antigenic T lymphocyte epitopes have been identified and studied to understand their contributions to disease with the aim of developing effective treatment approaches for translation to the clinical setting. In this review, we discuss the role of pathogenic islet-specific T lymphocyte responses in autoimmune diabetes, the mechanisms and cell types governing autoantigen presentation, and therapeutic strategies targeting such T lymphocyte responses for the amelioration of disease.

Decoding the immune dance: Unraveling the interplay between beta cells and type 1 diabetes

BACKGROUND

Type 1 diabetes (T1D) is an autoimmune disease characterized by the specific destruction of insulin-producing beta cells in the pancreas by the immune system, including CD4 cells which orchestrate the attack and CD8 cells which directly destroy the beta cells, resulting in the loss of glucose homeostasis.

SCOPE OF REVIEW

This comprehensive document delves into the complex interplay between the immune system and beta cells, aiming to shed light on the mechanisms driving their destruction in T1D. Insights into the genetic predisposition, environmental triggers, and autoimmune responses provide a foundation for understanding the autoimmune attack on beta cells. From the role of viral infections as potential triggers to the inflammatory response of beta cells, an intricate puzzle starts to unfold. This exploration highlights the importance of beta cells in breaking immune tolerance and the factors contributing to their targeted destruction. Furthermore, it examines the potential role of autophagy and the impact of cytokine signaling on beta cell function and survival.

MAJOR CONCLUSIONS

This review collectively represents current research findings on T1D which offers valuable perspectives on novel therapeutic approaches for preserving beta cell mass, restoring immune tolerance, and ultimately preventing or halting the progression of T1D. By unraveling the complex dynamics between the immune system and beta cells, we inch closer to a comprehensive understanding of T1D pathogenesis, paving the way for more effective treatments and ultimately a cure.

Relative Frequency of Islet Autoimmunity in Children and Adolescents with Autoimmune Thyroid Disease

Objective

The aim of the present study was to investigate islet autoimmunity and susceptibility to type 1 diabetes (T1D) in children/adolescents with autoimmune thyroid disease (AITD, and in family members of AITD patients with islet autoimmunity.

Methods

Islet-cell cytoplasmic, glutamic-acid decarboxylase, and tyrosine-phosphatase autoantibodies (AAbs) were measured in 161 AITD patients [127 with autoimmune thyroiditis (AT); 34 with Graves’ disease (GD)], 20 family members of AITD patients with islet autoimmunity, and 155 age-matched controls.

Results

Islet autoimmunity was found in 10.6% of AITD patients, significantly more frequent than in controls (1.9%; p=0.002). A higher prevalence of islet AAbs was found in females with AITD (p=0.011) but not in males (p=0.16) and in AT (p=0.013) but not in GD patients (p=0.19), compared to corresponding controls. Two or three islet AAbs were found concurrently in six AITD patients with islet autoimmunity. They all developed T1D and had significantly higher islet AAbs titers (p=0.01) than AITD patients with single islet AAbs but normal glucose metabolism. T1D was found in 3.7% of AITD patients compared to 0.2% of the age-matched, general Croatian population. Islet AAbs were found in 5/20 family members of AITD patients with islet autoimmunity, among whom two developed T1D. None of the controls was positive for more than one islet AAb or developed T1D.

Conclusion

Children/adolescents with AITD, particularly females and patients with AT, appear to represent a risk group for islet autoimmunity and T1D, as do family members of AITD patients with positive islet AAbs. However, these findings should be validated in larger studies.

HLA Class I Association With Autoimmune Diabetes in Chinese People: Distinct Implications in Classic Type 1 Diabetes and LADA

CONTEXT

We aimed to investigate whether human leukocyte antigen (HLA) Class I loci differentially modulated the risk for and clinical features of Chinese people with classic type 1 diabetes (T1D) and latent autoimmune diabetes in adults (LADA).

METHODS

In this case-control study, genotypes of HLA-A, -B, -C, -DRB1, -DQA1, and -DQB1 loci were obtained from 1067 cases with classic T1D, 1062 cases with LADA, and 1107 normal controls using next-generation sequencing.

RESULTS

Despite 4 alleles shared between classic T1D and LADA (protective: A*02:07 and B*46:01; susceptible: B*54:01 and C*08:01), 7 Class I alleles conferred risk exclusively for classic T1D (A*24:02, B*15:02, B*15:18, B*39:01, B*40:06, B*48:01, and C*07:02) whereas only A*02:01 was an additional risk factor for LADA. Class I alleles affected a wide spectrum of T1D clinical features, including positive rate of protein tyrosine phosphatase autoantibody and zinc transporter 8 autoantibody (A*24:02), C-peptide levels (A*24:02), and age at diagnosis (B*46:01, C*01:02, B*15:02, C*07:02, and C*08:01). By contrast, except for the detrimental effect of C*08:01 on C-peptide concentrations in LADA, no other Class I associations with clinical characteristics of LADA could be reported. The addition of Class I alleles refined the risk model consisting only of DR-DQ data in classic T1D while the overall predictive value of the LADA risk model comprising both Class I and II information was relatively low.

CONCLUSION

The attenuated HLA Class I susceptibility to LADA was indicative of a less deleterious immunogenetic nature compared with classic T1D. These autoimmune diabetes-related Class I variants might serve as additional markers in future screening among Chinese people.

HLA and amyotrophic lateral sclerosis: a systematic review and meta-analysis

Background: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease associated with loss of upper and lower motor neurones. It leads to death by respiratory failure and has a typical prognosis of 2-3 years. The immune system has been shown to play a role in the pathophysiology of ALS. Some of the most important immune genes are within the human leukocyte antigen (HLA) region, and a recent genome-wide association study (GWAS) has identified a risk allele for ALS within the HLA region. Older studies have also suggested an HLA association with ALS, with certain HLA alleles showing differing expression between patients and controls. This systematic review and meta-analysis examines the previous studies performed in this field.Methods: We used established publication search engines. Findings were excluded if they did not meet the selection criteria. We then undertook statistical meta-analysis on the eligible papers, using a fixed effects model.Results: There were eight eligible papers. There were three statistically significant meta-analysis findings, although these would not be significant after correction for multiple comparisons. The frequencies of HLA-A9 and HLA-DR4 genotypes were lower in ALS subjects than controls, and HLA-B35 was higher in ALS subjects.Discussion: This systematic review and meta-analysis do not confirm all the previously reported associations of HLA with ALS, but shows three alleles of interest. However, there are limitations to the studies, which include the use of older serotyping methodology and the small numbers of subjects. Given the recent GWAS association with HLA, further modern HLA studies are warranted.

MICA Polymorphism and Genetic Predisposition to T1D in Jordanian Patients: A Case-Control Study

Type 1 diabetes (T1D) is an autoimmune disorder whose etiology includes genetic and environmental factors. The non-classical Major Histocompatibility Complex (MHC) class I chain-related gene A (MICA) gene has been associated with increased susceptibility to T1D as the interaction of MICA to the Natural Killer Group 2D (NK2GD) receptors found on the cell surface of natural killer (NK) cells and T cells is responsible for inducing immune responses. MICA polymorphisms were reported in association with T1D among different ethnic groups. However, data from different populations revealed conflicting results, so the association of MICA polymorphisms with predisposition to T1D remains uncertain. The aim of this sequencing-based study was to identify, for the first time, the possible MICA alleles and/or genotypes that could be associated with T1D susceptibility in the Jordanian population. Polymorphisms in exons 2–4 and the short tandem repeats (STR) in exon 5 of the highly polymorphic MICA gene were analyzed. No evidence for association between T1D and MICA alleles/genotypes was found in this study, except for the MICA*011 allele which was found to be negatively associated with T1D (p = 0.023, OR = 0.125). In conclusion, MICA polymorphisms seem not to be associated with increasing T1D susceptibility in Jordanian patients.

The longitudinal loss of islet autoantibody responses from diagnosis of type 1 diabetes occurs progressively over follow-up and is determined by low autoantibody titres, early-onset, and genetic variants

The clinical usefulness of post-diagnosis islet autoantibody levels is unclear and factors that drive autoantibody persistence are poorly defined in type 1 diabetes (T1D). Our aim was to characterise the longitudinal loss of islet autoantibody responses after diagnosis in a large, prospectively sampled UK cohort. Participants with T1D [n = 577] providing a diagnosis sample [range -1.0 to 2.0 years] and at least one post-diagnosis sample (<32.0 years) were tested for autoantibodies to glutamate decarboxylase 65 (GADA), islet antigen-2 (IA-2A), and zinc transporter 8 (ZnT8A). Select HLA and non-HLA SNPs were considered. Non-genetic and genetic factors were assessed by multivariable logistic regression models for autoantibody positivity at initial sampling and autoantibody loss at final sampling. For GADA, IA-2A, and ZnT8A, 70.8%, 76.8%, and 40.1%, respectively, remained positive at the final sampling. Non-genetic predictors of autoantibody loss were low baseline autoantibody titres (P < 0.0001), longer diabetes duration (P < 0.0001), and age-at-onset under 8 years (P < 0.01--0.05). Adjusting for non-genetic covariates, GADA loss was associated with low-risk HLA class II genotypes (P = 0.005), and SNPs associated with autoimmunity RELA/11q13 (P = 0.017), LPP/3q28 (P = 0.004), and negatively with IFIH1/2q24 (P = 0.018). IA-2A loss was not associated with genetic factors independent of other covariates, while ZnT8A loss was associated with the presence of HLA A*24 (P = 0.019) and weakly negatively with RELA/11q13 (P = 0.049). The largest longitudinal study of islet autoantibody responses from diagnosis of T1D shows that autoantibody loss is heterogeneous and influenced by low titres at onset, longer duration, earlier age-at-onset, and genetic variants. These data may inform clinical trials where post-diagnosis participants are recruited.

Persistence of islet autoantibodies after diagnosis in type 1 diabetes

The presence of islet autoantibodies remains a reliable biomarker to identify individuals at high risk of developing type 1 diabetes. As such, these autoantibodies play a pivotal role in understanding the prodrome of diabetes and selecting individuals for both prevention and intervention clinical trials. Over the last few decades, studies have sought to investigate autoantibody prevalence after diabetes onset to better understand ongoing islet autoimmunity; however, many findings are contradictory, and little is known about factors that may influence autoantibody persistence. Generally, glutamate decarboxylase autoantibodies (GADAs) are the most prevalent autoantibodies after diagnosis, particularly in adults, whilst zinc transporter 8 autoantibodies (ZnT8A) prevalence declines more rapidly. However, when studies with islet autoantibody data at diagnosis are considered, it becomes clear that overall islet antigen-2 autoantibodies (IA-2A) tend to persist for longer than GADA or ZnT8A. In this review, we assess the major studies that have contributed to our understanding of autoantibody persistence after diabetes onset and what factors affect this. Islet autoantibodies may provide biomarkers for long-term β-cell function and insights into how to prevent ongoing islet autoimmunity but larger studies collecting samples at and decades after diabetes onset are required to leverage the information they could provide.

HLA class I genes modulate disease risk and age at onset together with DR-DQ in Chinese patients with insulin-requiring type 1 diabetes

AIMS/HYPOTHESIS

The study aimed to investigate the effects of HLA class I genes on susceptibility to type 1 diabetes with different onset ages, in addition to the well-established effects of HLA class II genes.

METHODS

A total of 361 patients with type 1 diabetes (192 patients with onset <18 years and 169 patients with onset ≥18 years) and 500 healthy control participants from China were enrolled and genotyped for the HLA-A, -B, -C, -DQA1, -DQB1 and -DRB1 genes using next-generation sequencing.

RESULTS

The susceptible DR3 (β = -0.09, p = 0.0009) and DR4-DQ8 (β = -0.13, p = 0.0059) haplotypes were negatively associated with onset age, while the protective DR11 (β = 0.21, p = 0.0314) and DR12 (β = 0.27, p < 0.0001) haplotypes were positively associated with onset age. After adjustment for linkage disequilibrium with DR-DQ haplotypes, A*11:01:01 was positively associated with onset age (β = 0.06, p = 0.0370), while the susceptible C*15:02:01 was negatively associated with onset age (β = -0.21, p = 0.0050). The unit for β was double square-root (fourth root) transformed years of change in onset age associated with per copy of the HLA haplotype/allele. In addition, B*46:01:01 was protective (OR 0.41, 0.46; pc [corrected for multiple comparisons] = 0.0044, 0.0040), whereas A*24:02:01 (OR 2.71, 2.25; pc = 0.0003, 0.0002) and B*54:01:01 (OR 3.96, 3.79; pc = 0.0018, 0.0004) were predisposing in both the <18 group and the ≥18 group compared with healthy control participants. In the context of DR4-DQ4, A*11:01:01 (61.29% vs 28.26%, pc = 0.0144) was increased while the predisposing A*24:02:01 (19.35% vs 47.83%, pc = 0.0403) was decreased in patients with onset ≥18 years when compared with patients with onset <18 years.

CONCLUSIONS/INTERPRETATION

In addition to DR-DQ haplotypes, novel HLA class I alleles were detected to play a role in susceptibility to type 1 diabetes with different onset ages, which could improve the understanding of disease heterogeneity and has implications for the design of future studies.

HLA Alleles Cw12 and DQ4 in Kidney Transplant Recipients Are Independent Risk Factors for the Development of Posttransplantation Diabetes

Supplemental Digital Content is available in the text.

The association between specific HLA alleles and risk for posttransplantation diabetes (PTDM) in a contemporary and multiethnic kidney transplant recipient cohort is not clear.

Association of HLA-DRB1 and -DQ Alleles and Haplotypes with Type 1 Diabetes in Jordanians

BACKGROUND

The Human Leukocyte Antigen (HLA) class II genes, particularly the HLADR and -DQ loci, have been shown to play a crucial role in Type 1 Diabetes (T1D) development.

OBJECTIVE

This study is the first to examine the contribution of the HLA-DR/DQ alleles and haplotypes to T1D susceptibility in Jordanians.

METHODS

Polymerase chain reaction sequence-specific primers (PCR-SSP) were used to genotype 41 Jordanian healthy controls and 50 insulin-dependent diabetes mellitus (IDDM) patients.

RESULTS

The following alleles were found to be significant high risk alleles in T1D Jordanian patients: DRB1*04 (OR=3.95, p<0.001), DRB1*0301(OR=5.27, p<0.001), DQA1*0301 (OR=5.67, p<0.001), DQA1*0501(OR=3.18, p=0.002), DQB1*0201(OR=2.18, p=0.03), DQB1*0302 (OR=5.67, p<0.001). However, Jordanians harboring the DRB1*0701 (OR=0.37, p=0.01), DRB1*1101 (OR=0.2, p=0.01), DQA1*0505 (OR=0.31, p=0.02), DQA1*0103 (OR=0.33, p=0.04), DQA1*0201 (OR=0.45, p=0.04), DQB1*0301 (OR=0.23, p=0.001), DQB1*0501 (OR=0.18, p=0.009) alleles had a significantly lower risk of developing T1D.

CONCLUSION

A strong positive association of DRB1*04-DQA1*0301-DQBl*0302 (OR=5.67, p<0.001) and DRB1*0301-DQA1*0501-DQB1*0201 (OR=6.24, p<0.001) putative haplotypes with IDDM was evident in Jordanian IDDM patients whereas DRB1*1101-DQA1*0505- DQB1*0301 (OR=0.23, p=0.03) was shown to have a protective role against T1D in Jordanians. Our findings show that specific HLA class II alleles and haplotypes are significantly associated with susceptibility to T1D in Jordanians.

Differential HLA Association of GAD65 and IA2 Autoantibodies in North Indian Type 1 Diabetes Patients

The human leucocyte antigen (HLA) association with type 1 diabetes (T1D) is well known but there are limited studies investigating the association between β-cell autoantibodies and HLA genes. We evaluated the prevalence of GAD65 and IA-2 autoantibodies (GADA and IA2A) in 252 T1D patients from North India and investigated the genetic association of GADA and IA2A with HLA class I and class II genes/haplotypes. GADA and IA2A were detected in 50.79% and 15.87% of T1D patients, respectively, while only 8.73% had both GADA and IA2A. HLA-DRB1^∗03 was observed to be significantly higher in GADA+ T1D patients as compared to GADA- (91.41% vs. 66.13%, Bonferroni-corrected P (P _c) = 1.11 × 10^-5; OR = 5.45; 95% CI: 2.67-11.08). Similarly, HLA-DQB1^∗02 was found to be significantly increased in GADA+ patients (94.53%, P _c = 2.19 × 10^-5; OR = 6.27; 95% CI: 2.7-14.49) as compared to GADA- (73.39%). The frequencies of HLA-DRB1^∗04 and DQB1^∗03 were increased in IA2A+ patients (45.0% and 52.5%, respectively) as compared to that in IA2A- (25.94% and 33.96%, respectively). Further, the frequency of DRB1^∗03-DQB1^∗02 haplotype was found to be significantly increased in GADA+ T1D patients as compared to GADA- (60.55% vs. 41.94%, P = 3.94 × 10^-5; OR = 2.13; 95%CI = 1.49-3.03). Similarly, HLA-DRB1^∗04-DQB1^∗03 haplotype was found to be significantly increased in IA2A+ T1D patients compared to IA2A- patients (22.5% vs. 12.97%; P = 0.041; OR = 1.95; 95%CI = 1.08-3.52). None of the HLA class I genes (HLA-A, B, and Cw) was found to be associated with GADA or IA2A in people with T1D. Our findings suggest that HLA-DRB1^∗03/DQB1^∗02 and HLA-DRB1^∗04/DQB1^∗03 might play an important role in the development of GADA and IA2A, respectively.

Prevalence of autoantibodies in type 1 diabetes mellitus pediatrics in Mazandaran, North of Iran

Objectives Type 1 diabetes is an autoimmune disease. Its most important immunologic markers are pancreatic beta-cell autoantibodies. This study aimed to determine diabetes mellitus antibodies frequency among children and adolescents with type 1 diabetes. Methods This descriptive study evaluated the frequency of four diabetes autoantibodies (glutamic acid decarboxylase 65 autoantibodies [GADA], islet cell autoantibodies [ICA], insulin autoantibodies [IAA], tyrosine phosphatase-like insulinoma antigen-2 antibodies [IA-2A]) and their serum level in children and adolescents diagnosed with type 1 diabetes mellitus at the diabetes department of Bou-Ali-Sina Hospital and Baghban Clinic, Sari, Iran, from March 2012 to March 2018. The relationship between the level of different antibodies and age, gender, and diabetes duration were determined. A two-sided p value less than 0.05 indicated statistical significance. Results One hundred forty-two eligible patient records were screened. The average age at diabetes diagnosis was 4.2 ± 4.4 years. The median duration of diabetes was 34.0 (12.7-69.7) months. 53.5% of patients were female, and 81.7% of them had at least one positive autoantibody, and ICA in 66.2%, GADA in 56.3%, IA-2A in 40.1%, and IAA in 21.8% were positive. The type of the autoantibodies and their serum level was similar between females and males but there was a higher rate of positive autoantibodies in females. The level of IA-2A and ICA were in positive and weak correlation with age at diagnosis. Conclusions More than 80% of pediatric and adolescent patients with type 1 diabetes were autoantibody-positive. ICA and GADA were the most frequently detected autoantibodies. The presence of antibodies was significantly higher in females.

Primary DQ effect in the association between HLA and neurological syndromes with anti-GAD65 antibodies

The primary cause of neurological syndromes with antibodies against glutamic acid decarboxylase 65 (GAD65-Ab) is unknown, but genetic predisposition may exist as it is suggested by the co-occurrence in patients and their relatives of other organ-specific autoimmune diseases, notably type 1 diabetes mellitus (T1DM), and by the reports of a few familial cases. We analyzed the human leukocyte antigen (HLA) in 32 unrelated patients and compared them to an ethnically matched sample of 137 healthy controls. Four-digit resolution HLA alleles were imputed from available Genome Wide Association data, and full HLA next-generation sequencing-based typing was also performed. HLA DQA1*05:01-DQB1*02:01-DRB1*03:01 was the most frequent class II haplotype in patients (13/32, 41%). DQB1*02:01 was the only allele found to be significantly more common in patients than in controls (20/137, 15%, corrected p = 0.03, OR 3.96, 95% CI [1.54-10.09]). There was also a trend towards more frequent DQA1*05:01 among patients compared to controls (22/137, 16%; corrected p = 0.05, OR 3.54, 95% CI [1.40-8.91]) and towards a protective effect of DQB1*03:01 (2/32, 6% in patients vs. 42/137, 31% in control group; corrected p = 0.05, OR 0.15, 95% CI [0.02-0.65]). There was no significant demographic or clinical difference between DQ2 and non-DQ2 carriers (p > 0.05). Taken together, these findings suggest a primary DQ effect on GAD65-Ab neurological diseases, partially shared with other systemic organ-specific autoimmune diseases such as T1DM. However, it is likely that other non-HLA loci are involved in the genetic predisposition of GAD65-Ab neurological syndromes.

Circulating β cell-specific CD8+ T cells restricted by high-risk HLA class I molecules show antigen experience in children with and at risk of type 1 diabetes

In type 1 diabetes (T1D), autoreactive cytotoxic CD8+ T cells are implicated in the destruction of insulin-producing β cells. The HLA-B*3906 and HLA-A*2402 class I genes confer increased risk and promote early disease onset, suggesting that CD8+ T cells that recognize peptides presented by these class I molecules on pancreatic β cells play a pivotal role in the autoimmune response. We examined the frequency and phenotype of circulating preproinsulin (PPI)-specific and insulin B (InsB)-specific CD8+ T cells in HLA-B*3906+ children newly diagnosed with T1D and in high-risk HLA-A*2402+ children before the appearance of disease-specific autoantibodies and before diagnosis of T1D. Antigen-specific CD8+ T cells were detected using human leucocyte antigen (HLA) class I tetramers and flow cytometry was used to assess memory status. In HLA-B*3906+ children with T1D, we observed an increase in PPI5-12 -specific transitional memory CD8+ T cells compared to non-diabetic, age- and HLA-matched subjects. Furthermore, PPI5-12 -specific CD8+ T cells in HLA-B*3906+ children with T1D showed a significantly more antigen-experienced phenotype compared to polyclonal CD8+ T cells. In longitudinal samples from high-risk HLA-A*2402+ children, the percentage of terminal effector cells within the InsB15-24 -specific CD8+ T cells was increased before diagnosis relative to samples taken before the appearance of autoantibodies. This is the first study, to our knowledge, to report HLA-B*3906-restricted autoreactive CD8+ T cells in T1D. Collectively, our results provide evidence that β cell-reactive CD8+ T cells restricted by disease-associated HLA class I molecules display an antigen-experienced phenotype and acquire enhanced effector function during the period leading to clinical diagnosis, implicating these cells in driving disease.

Genetic Discrimination Between LADA and Childhood-Onset Type 1 Diabetes Within the MHC

OBJECTIVE

The MHC region harbors the strongest loci for latent autoimmune diabetes in adults (LADA); however, the strength of association is likely attenuated compared with that for childhood-onset type 1 diabetes. In this study, we recapitulate independent effects in the MHC class I region in a population with type 1 diabetes and then determine whether such conditioning in LADA yields potential genetic discriminators between the two subtypes within this region.

RESEARCH DESIGN AND METHODS

Chromosome 6 was imputed using SNP2HLA, with conditional analysis performed in type 1 diabetes case subjects (n = 1,985) and control subjects (n = 2,219). The same approach was applied to a LADA cohort (n = 1,428) using population-based control subjects (n = 2,850) and in a separate replication cohort (656 type 1 diabetes case, 823 LADA case, and 3,218 control subjects).

RESULTS

The strongest associations in the MHC class II region (rs3957146, β [SE] = 1.44 [0.05]), as well as the independent effect of MHC class I genes, on type 1 diabetes risk, particularly HLA-B*39 (β [SE] = 1.36 [0.17]), were confirmed. The conditional analysis in LADA versus control subjects showed significant association in the MHC class II region (rs3957146, β [SE] = 1.14 [0.06]); however, we did not observe significant independent effects of MHC class I alleles in LADA.

CONCLUSIONS

In LADA, the independent effects of MHC class I observed in type 1 diabetes were not observed after conditioning on the leading MHC class II associations, suggesting that the MHC class I association may be a genetic discriminator between LADA and childhood-onset type 1 diabetes.

Distinct HLA Associations with Rheumatoid Arthritis Subsets Defined by Serological Subphenotype

Rheumatoid arthritis (RA) is the most common immune-mediated arthritis. Anti-citrullinated peptide antibodies (ACPA) are highly specific to RA and assayed with the commercial CCP2 assay. Genetic drivers of RA within the MHC are different for CCP2-positive and -negative subsets of RA, particularly at HLA-DRB1. However, aspartic acid at amino acid position 9 in HLA-B (B^pos-9) increases risk to both RA subsets. Here we explore how individual serologies associated with RA drive associations within the MHC. To define MHC differences for specific ACPA serologies, we quantified a total of 19 separate ACPAs in RA-affected case subjects from four cohorts (n = 6,805). We found a cluster of tightly co-occurring antibodies (canonical serologies, containing CCP2), along with several independently expressed antibodies (non-canonical serologies). After imputing HLA variants into 6,805 case subjects and 13,467 control subjects, we tested associations between the HLA region and RA subgroups based on the presence of canonical and/or non-canonical serologies. We examined CCP2(+) and CCP2(−) RA-affected case subjects separately. In CCP2(−) RA, we observed that the association between CCP2(−) RA and B^pos-9 was derived from individuals who were positive for non-canonical serologies (omnibus_p = 9.2 × 10⁻¹⁷). Similarly, we observed in CCP2(+) RA that associations between subsets of CCP2(+) RA and B^pos-9 were negatively correlated with the number of positive canonical serologies (p = 0.0096). These findings suggest unique genetic characteristics underlying fine-specific ACPAs, suggesting that RA may be further subdivided beyond simply seropositive and seronegative.

Clinical and biochemical features at diagnosis of type 1 diabetes in patients between 0 and 18 years of age from Jordan

OBJECTIVE

Data regarding type 1 diabetes mellitus (T1D) in Jordan are extremely scarce. We aim to evaluate the clinical and laboratory characteristics at diagnosis of T1D in a group of children from Jordan.

METHODS

The records of 437 (boys/girls: 224/213) children with type 1 diabetes followed in the years 2012 to 2016 were evaluated retrospectively. The data were assessed by sex and age subgroups (<5, 6-10, and 11-18 years).

RESULTS

Mean age of children at diagnosis was 7.3 ± 3.6 years. The first peak in the number of T1D cases in terms of age at diagnosis was observed in the age group between 6 and 8 years (n = 116 [26.5%], 95% confidence interval [CI]: 22.3%-30.6%). This was followed by the age group of 3 to 5 years (n = 108 [24.7%], 95% CI: 20.6%-28.7%). Although the patients mostly presented in winter (30.0%, 95% CI: 25.6%-34.3%), no season-related significant differences were found. The frequency of ketoacidosis at diagnosis was 40.7% (95% CI: 36%-45.3%). At presentation, 22.8% (95% CI: 18.9%-26.7) of our patients had a positive history of T1D in their extended families. In addition, 61.1% (95% CI: 56.5%-65.7%) of the patients were started on premixed insulin at diagnosis.

CONCLUSION

The findings possibly indicate a decreasing age of T1D onset in Jordanian patients. The high frequency of ketoacidosis at presentation is noteworthy. In addition, the initial insulin protocols are not in accordance with the recommended insulin therapy for children and adolescents with T1D.

Accelerated Progression to Type 1 Diabetes in the Presence of HLA-A*24 and -B*18 Is Restricted to Multiple Islet Autoantibody-Positive Individuals With Distinct HLA-DQ and Autoantibody Risk Profiles

OBJECTIVE

We investigated the effect of HLA class I risk alleles on disease progression in various phases of subclinical islet autoimmunity in first-degree relatives of patients with type 1 diabetes.

RESEARCH DESIGN AND METHODS

A registry-based group of siblings/offspring (aged 0-39 years) was monitored from single- to multiple-autoantibody positivity (n = 267) and from multiple-autoantibody positivity to clinical onset (n = 252) according to HLA-DQ, -A*24, -B*18, and -B*39 status. Genetic markers were determined by PCR sequence-specific oligotyping.

RESULTS

Unlike HLA-B*18 or -B*39, HLA-A*24 was associated with delayed progression from single- to multiple-autoantibody positivity (P = 0.009) but not to type 1 diabetes. This occurred independently from older age (P < 0.001) and absence of HLA-DQ2/DQ8 or -DQ8 (P < 0.001 and P = 0.003, respectively), and only in the presence of GAD autoantibodies. In contrast, HLA-A*24 was associated with accelerated progression from multiple-autoantibody positivity to clinical onset (P = 0.006), but its effects were restricted to HLA-DQ8⁺ relatives with IA-2 or zinc transporter 8 autoantibodies (P = 0.002). HLA-B*18, but not -B*39, was also associated with more rapid progression, but only in HLA-DQ2 carriers with double positivity for GAD and insulin autoantibodies (P = 0.004).

CONCLUSIONS

HLA-A*24 predisposes to a delayed antigen spreading of humoral autoimmunity, whereas HLA-A*24 and -B*18 are associated with accelerated progression of advanced subclinical autoimmunity in distinct risk groups. The relation of these alleles to the underlying disease process requires further investigation. Their typing should be relevant for the preparation and interpretation of observational and interventional studies in asymptomatic type 1 diabetes.

Immunoglobulin M gene association with autoantibody reactivity and type 1 diabetes

Several lines of evidence show that autoimmune responses evolving in type 1 diabetes (T1D) patients include the generation of multi-reactive autoantibody (AutoAb) repertoires, but their role in T1D pathogenesis remains elusive. We tested the hypothesis that variants at the immunoglobulin heavy chain (IGH) locus are genetic determinants of AutoAbs against pancreatic antigens and contribute to T1D susceptibility. With this aim, two independent study designs were used: a case-control study and a family-based cohort comprising a total of 240 T1D patients, 172 first-degree relatives (mother and/or father), and 130 unrelated healthy controls living in Portugal. We found that three SNPs in the IGH locus show suggestive association with T1D with the highest nominal association at rs1950942 (in the IGHM-IGHJ gene region) in both the case-control study (P = 9.35E-03) and the family-based cohort (P = 3.08E-03). These SNPs were also associated with IgG AutoAbs against pancreatic antigens and with AutoAb multi-reactivity in T1D patients. Notably, we found that the SNP with the highest association with T1D susceptibility and IgG autoantibody reactivity (rs1950942) was also associated with anti-GAD IgM reactivity in T1D patients (P = 5.98E-03) and in non-affected parents (P = 4.17E-03). This finding implies that IGH association with autoreactive IgM is detectable irrespective of disease status.These results suggest that genetic variants at the IgM gene region of the IGH locus contribute to antibody autoreactivity and are associated with T1D. We propose that the control of autoantibody generation by IGH polymorphisms is a component of the complex architecture of T1D genetic susceptibility.

Anti-Zinc Transporter Protein 8 Antibody Testing Is Not Informative in Routine Prediabetes Screening in Young Patients with Autoimmune Thyroiditis and Celiac Disease

BACKGROUND/AIMS

Patients with type 1 diabetes mellitus (T1DM), autoimmune thyroiditis (ATD), and celiac disease (CD) are at increased risk for developing other autoimmune diseases. We evaluated zinc transporter 8 (ZnT8) prevalence in patients with ATD and/or CD in order to define the usefulness of ZnT8 autoantibodies for prediabetes screening.

METHODS

Eighty-one young patients with ATD and/or CD were included in the study; 32 subjects with clinical onset of T1DM were enrolled as a control group. GAD65, IA-2, and ZnT8 antibodies were measured. An intravenous glucose tolerance test, C-peptide, glycosylated hemoglobin levels, and genomic analysis of HLA-DQA1* and -DQB1* were also considered in patients positive for autoantibodies.

RESULTS

The ZnT8 prevalence was higher in T1DM patients than in patients with other autoimmune diseases (p < 0.001); positive ZnT8 detection was found in 2 ATD (p = 0.004) and 3 ATD + CD (p = 0.04) patients. Positive ZnT8 was associated with GAD65 (p = 0.01) but not with IA-2 positivity. No correlation between ZnT8 detection and the number of T1DM-susceptible HLA-DQ heterodimers was found. Pathological C-peptide levels and insulin response were found in subjects with islet autoimmunity and genetic susceptibility.

CONCLUSION

ZnT8 autoantibodies detection in ATD and/or CD patients is low, and routine ZnT8 screening is not justified. ZnT8 evaluation may be recommended in subjects with autoimmune diseases as a marker for predicting compromised insulin secretion.

Shared Genetic Basis for Type 1 Diabetes, Islet Autoantibodies, and Autoantibodies Associated With Other Immune-Mediated Diseases in Families With Type 1 Diabetes

Type 1 diabetes (T1D) is a polygenic autoimmune disease that is often present with autoantibodies directed against pancreatic islet proteins. Many genetic susceptibility loci are shared with other autoimmune or immune-mediated diseases that also cosegregate in families with T1D. The aim of this study was to investigate whether susceptibility loci identified in genome-wide association studies (GWAS) of T1D were also associated with autoantibody positivity in individuals with diabetes. Fifty single nucleotide polymorphisms (SNPs) were genotyped in 6,556 multiethnic cases collected by the Type 1 Diabetes Genetics Consortium (T1DGC). These were tested for association with three islet autoantibodies-against autoantibodies to GAD (GADA), IA-2 (IA-2A), and zinc transporter 8 (ZnT8A)-and autoantibodies against thyroid peroxidase (TPOA) in autoimmune thyroid disease, gastric parietal cells (PCA) in autoimmune gastritis, transglutaminase (TGA) in celiac disease, and 21-hydroxylase (21-OHA) in autoimmune hypoadrenalism. In addition to the MHC region, we identify SNPs in five susceptibility loci (IFIH1, PTPN22, SH2B3, BACH2, and CTLA4) as significantly associated with more than one autoantibody at a false discovery rate less than 5%. IFIH1/2q24 demonstrated the most unrestricted association, as significant association was demonstrated for PCA, TPOA, GADA, 21-OHA, and IA-2A. In addition, 11 loci were significantly associated with a single autoantibody.

Attenuated humoral responses in HLA-A*24-positive individuals at risk of type 1 diabetes

AIMS/HYPOTHESIS

The rate of progression from islet autoimmunity to clinical type 1 diabetes depends on the rate of beta cell destruction. The HLA-A*24 gene is associated with early diabetes onset, but previous studies have shown attenuated humoral responses to islet antigens in individuals with both recent and long-standing type 1 diabetes carrying HLA-A*24. We aimed to establish whether HLA-A*24 is also associated with attenuated humoral responses in individuals at high risk of type 1 diabetes.

METHODS

We established HLA-A*24, DQ and rs9258750 (an HLA-A*24 tagged single-nucleotide polymorphism) genotype, as well as GAD, zinc transporter 8 (ZnT8), insulin, islet antigen-2 (IA-2), and IA-2β autoantibody status in 373 islet cell antibody-positive first-degree relatives participating in the European Nicotinamide Diabetes Intervention Trial.

RESULTS

Univariate regression analyses showed that humoral responses to GAD, ZnT8 and insulin were less common in relatives carrying HLA-A*24. The prevalence of GAD and ZnT8 autoantibodies remained negatively associated with HLA-A*24 and rs9258750 after adjusting for age, sex, proband relationship and HLA class II genotype.

CONCLUSIONS/INTERPRETATION

HLA-A*24 is associated with attenuated humoral responses in individuals at high risk of type 1 diabetes, and this may reflect a distinct phenotype of rapid beta cell loss.

Novel Association Between Immune-Mediated Susceptibility Loci and Persistent Autoantibody Positivity in Type 1 Diabetes

Islet autoantibodies detected at disease onset in patients with type 1 diabetes are signs of an autoimmune destruction of the insulin-producing β-cells. To further investigate the genetic determinants of autoantibody positivity, we performed dense immune-focused genotyping on the Immunochip array and tested for association with seven disease-specific autoantibodies in a large cross-sectional cohort of 6,160 type 1 diabetes-affected siblings. The genetic association with positivity for GAD autoantibodies (GADAs), IA2 antigen (IA-2A), zinc transporter 8, thyroid peroxidase, gastric parietal cells (PCAs), tissue transglutaminase, and 21-hydroxylase was tested using a linear mixed-model regression approach to simultaneously control for population structure and family relatedness. Four loci were associated with autoantibody positivity at genome-wide significance. Positivity for GADA was associated with 3q28/LPP, for IA-2A with 1q23/FCRL3 and 11q13/RELA, and for PCAs with 2q24/IFIH1. The 3q28 locus showed association after only 3 years duration and might therefore be a marker of persistent GADA positivity. The 1q23, 11q13, and 2q24 loci were associated with autoantibodies close to diabetes onset and constitute candidates for early screening. Major susceptibility loci for islet autoantibodies are separate from type 1 diabetes risk, which may have consequences for intervention strategies to reduce autoimmunity.

Evaluation of Association Between HLA Class II DR4-DQ8 Haplotype and Type I Diabetes Mellitus in Children of East Azerbaijan State of Iran

PURPOSE

Association between HLA-DR4-DQ8 haplotype and type 1 Diabetes Mellitus (DM-1A) was investigated in children of East Azerbaijan state of Iran because such an association has not been previously studied in this population.

METHODS

HLA-typing was performed by polymerase chain reaction sequence-specific priming. For haplotype analysis, the logistic regression model was performed.

RESULTS

Of the three investigated alleles, the frequency of DRB1*0401 was significantly higher among patients compared with that in healthy subjects (76.74% vs. 23.26%).

CONCLUSION

The findings of the current study are consistent with those of previous studies and show that DRB1*0401 is associated with DM-1A; the frequencies of the two other alleles were also higher among patients, although the differences were not statistically significant. Two haplotypes associated with these alleles were also surveyed, and DRB1*0401--DQA1*0301-, and DRB1*0401--DQA1*0301--DQB1*0302- were the most frequent haplotypes among the patient group.

Impact of disease heterogeneity on treatment efficacy of immunotherapy in Type 1 diabetes: different shades of gray

Type 1 diabetes results from selective destruction of insulin-producing pancreatic β-cells by a progressive autoimmune process. Type 1 diabetes proves very heterogeneous in pathology, disease progression and efficacy of therapeutic intervention. Indeed, several immunotherapies that appear ineffective for the entire treated patient population in fact look promising in subgroups of patients. It therefore seems inconceivable that one standard therapy will provide the golden bullet of disease intervention. Instead, personalized medicine may improve immune intervention efficacy rates. We discuss the effect of disease heterogeneity on treatment outcome of immunotherapies, identifying apparent gaps in our understanding of treatment efficacy in subgroups of Type 1 diabetic patients as well as identifying future opportunities for immunotherapy.

Heterogeneity in diabetes-associated autoantibodies and susceptibility to Type 1 diabetes: lessons for disease prevention

Autoantibodies against pancreatic islets are strong predictors of Type 1 diabetes. When persistent β-cell autoantibodies against at least two autoantigens are detected, the probability of diabetes is extremely high, although the time period before disease development can vary from days up to more than 20 years. Insulin autoantibodies or antibodies specific to glutamate decarboxylase 65 enzyme are in most cases, the first autoantibodies to appear. Insulin autoantibodies typically emerge very early with a peak at the age of 1.5 years, whereas the onset of glutamic acid decarboxylase 65 antibody positivity has a more even distribution, peaking later in childhood. These differences in the timing of appearance suggest that different environmental factors might be involved in the initiation of β-cell autoimmunity beginning either already in infancy or later on. This should be taken into account in studies aimed at identifying environmental factors triggering islet cell-specific autoimmunity and also in the design of prevention trials.

Molecular mechanisms for contribution of MHC molecules to autoimmune diseases

It will soon be 50 years since the first MHC associations with human disease were described. These seminal studies opened a flourishing area of research, yet much remains to be discovered. Genome-wide association studies of autoimmune diseases have demonstrated that the MHC region has effect sizes that supersede those for any non-MHC locus for most diseases. Thus, an understanding of how particular MHC alleles confer susceptibility will be essential for a comprehensive understanding of autoimmune disease pathogenesis. Here we review recent exciting findings in this important field.

HLA-DR4-associated T and B cell responses to specific determinants on the IA-2 autoantigen in type 1 diabetes

Autoantibodies to IA-2 in type 1 diabetes are associated with HLA-DR4, suggesting influences of HLA-DR4-restricted T cells on IA-2-specific B cell responses. The aim of this study was to investigate possible T-B cell collaboration by determining whether autoantibodies to IA-2 epitopes are associated with T cell responses to IA-2 peptides presented by DR4. T cells secreting the cytokines IFN-γ and IL-10 in response to seven peptides known to elicit T cell responses in type 1 diabetes were quantified by cytokine ELISPOT in HLA-typed patients characterized for Abs to IA-2 epitopes. T cell responses were detected to all peptides tested, but only IL-10 responses to 841-860 and 853-872 peptides were associated with DR4. Phenotyping by RT-PCR of FACS-sorted CD45RO(hi) T cells secreting IL-10 in response to these two peptides indicated that these expressed GATA-3 or T-bet, but not FOXP3, consistent with these being Th2 or Th1 memory T cells rather than of regulatory phenotype. T cell responses to the same two peptides were also associated with specific Abs: those to 841-860 peptide with Abs to juxtamembrane epitopes, which appear early in prediabetes, and those to peptide 853-872 with Abs to an epitope located in the 831-862 central region of the IA-2 tyrosine phosphatase domain. Abs to juxtamembrane and central region constructs were both DR4 associated. This study identifies a region of focus for B and T cell responses to IA-2 in HLA-DR4 diabetic patients that may explain HLA associations of IA-2 autoantibodies, and this region may provide a target for future immune intervention to prevent disease.

GAD autoantibody affinity in schoolchildren from the general population

AIMS/HYPOTHESIS

Subtyping GAD autoantibody (GADA) responses using affinity measurement allows the identification of GADA-positive children with a family history of type 1 diabetes who are at risk of developing diabetes. Here, we asked whether GADA affinity is a useful marker to stratify the risk of type 1 diabetes in GADA-positive schoolchildren from the general population.

METHODS

GADA affinity was measured by competitive binding experiments with [(125)I]-labelled and unlabelled human 65 kDa isoform of GAD (GAD65) in sera from 97 GADA-positive children identified in the Karlsburg Type 1 Diabetes Risk Study of a general schoolchild population in north-eastern Germany. GADA epitope specificity was determined using radiobinding assays with [(35)S]-labelled GAD65/67 kDa isoform of GAD (GAD67) chimeric proteins.

RESULTS

GADA affinity was high, ≥ 10(10) l/mol, in 33 of 35 multiple islet autoantibody-positive children. In contrast, the affinity ranged widely among 62 single GADA-positive children (median 3.1 × 10(9) l/mol; range 5.6 × 10(6) to >4.0 × 10(11) l/mol; p < 0.0001). High-affinity GADA were associated with HLA-DRB1*03 (p = 0.02) and predominantly directed against the C-terminal and/or middle part of the GAD65 protein. At follow-up, the affinity remained relatively constant. Five of the single GADA-positive children developed additional islet autoantibodies and had high-affinity GADA. Twenty-six children progressed to type 1 diabetes; among them, 23 had GADA affinities of ≥ 10(10) l/mol before disease onset.

CONCLUSIONS/INTERPRETATION

Schoolchildren from the general population may develop heterogeneous GADA responses, and a high affinity can identify those GADA-positive children who are more likely to progress to type 1 diabetes.

Immune modulation in humans: implications for type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is the result of autoimmune destruction of pancreatic β cells in genetically predisposed individuals with impaired immune regulation. The insufficiency in the modulation of immune attacks on the β cells might be partly due to genetic causes; indeed, several of the genetic variants that predispose individuals to T1DM have functional features of impaired immune regulation. Whilst defects in immune regulation in patients with T1DM have been identified, many patients seem to have immune regulatory capacities that are indistinguishable from those of healthy individuals. Insight into the regulation of islet autoimmunity might enable us to restore immune imbalances with therapeutic interventions. In this Review, we discuss the current knowledge on immune regulation and dysfunction in humans that is the basis of tissue-specific immune regulation as an alternative to generalized immune suppression.

Limited promiscuity of HLA-DRB1 presented peptides derived of blood coagulation factor VIII

The formation of inhibitory antibodies directed against coagulation factor VIII (FVIII) is a severe complication in the treatment of hemophilia A patients. The induction of anti-FVIII antibodies is a CD4⁺ T cell-dependent process. Activation of FVIII-specific CD4⁺ T cells is dependent on the presentation of FVIII-derived peptides on MHC class II by antigen-presenting cells. Previously, we have shown that FVIII-pulsed human monocyte-derived dendritic cells can present peptides from several FVIII domains. In this study we show that FVIII peptides are presented on immature as well as mature dendritic cells. In immature dendritic cells half of the FVIII-loaded MHC class II molecules are retained within the cell, whereas in LPS-matured dendritic cells the majority of MHC class II/peptide complexes is present on the plasma membrane. Time-course studies revealed that presentation of FVIII-derived peptides was optimal between 12 and 24 hours after maturation but persisted for at least 96 hours. We also show that macrophages are able to internalize FVIII as efficiently as dendritic cells, however FVIII was presented on MHC class II with a lower efficiency and with different epitopes compared to dendritic cells. In total, 48 FVIII core-peptides were identified using a DCs derived of 8 different donors. Five HLA-promiscuous FVIII peptide regions were found – these were presented by at least 4 out of 8 donors. The remaining 42 peptide core regions in FVIII were presented by DCs derived from a single (30 peptides) or two to three donors (12 peptides). Overall, our findings show that a broad repertoire of FVIII peptides can be presented on HLA-DR.

Thyroid autoimmunity in relation to islet autoantibodies and HLA-DQ genotype in newly diagnosed type 1 diabetes in children and adolescents

AIMS/HYPOTHESIS

The aim of this work was to investigate, in children newly diagnosed with type 1 diabetes: (1) the prevalence of autoantibodies against thyroid peroxidase (TPOAb) and thyroglobulin (TGAb); and (2) the association between TPOAb, TGAb or both, with either islet autoantibodies or HLA-DQ genes.

METHODS

Blood samples from 2,433 children newly diagnosed with type 1 diabetes were analysed for TPOAb and TGAb in addition to autoantibodies against arginine zinc transporter 8 (ZnT8RA), tryptophan zinc transporter 8 (ZnT8WA), glutamine zinc transporter 8 (ZnT8QA), glutamic acid decarboxylase (GADA), insulin (IAA), insulinoma-associated protein-2 (IA-2A), HLA-DQA-B1 genotypes, thyroid-stimulating hormone (TSH) and free thyroxine (T4).

RESULTS

At type 1 diabetes diagnosis, 12% of the children had thyroid autoantibodies (60% were girls; p < 0.0001). GADA was positively associated with TPOAb (p < 0.001) and with TGAb (p < 0.001). In addition, ZnT8A was associated with both TPOAb (p = 0.039) and TGAb (p = 0.015). DQB1*05:01 in any genotype was negatively associated with TPOAb (OR 0.55, 95% CI 0.37, 0.83, p value corrected for multiple comparisons (p c) = 0.012) and possibly with TGAb (OR 0.55, 95% CI 0.35, 0.87, p c = 0.07). Thyroid autoimmunity in children newly diagnosed with type 1 diabetes was rarely (0.45%) associated with onset of clinical thyroid disease based on TSH and free T4.

CONCLUSIONS/INTERPRETATION

GADA and ZnT8A increased the risk for thyroid autoimmunity at the time of clinical diagnosis of type 1 diabetes, while HLA-DQB1*05:01 reduced the risk. However, the associations between thyroid autoimmunity and HLA-DQ genotype were weak and did not fully explain the co-occurrence of islet and thyroid autoimmunity.

HLA class II gene associations in African American type 1 diabetes reveal a protective HLA-DRB1*03 haplotype

AIMS

Owing to strong linkage disequilibrium between markers, pinpointing disease associations within genetic regions is difficult in European ancestral populations, most notably the very strong association of the HLA-DRB1*03-DQA1*05:01-DQB1*02:01 haplotype with Type 1 diabetes risk, which is assumed to be because of a combination of HLA-DRB1 and HLA-DQB1. In contrast, populations of African ancestry have greater haplotype diversity, offering the possibility of narrowing down regions and strengthening support for a particular gene in a region being causal. We aimed to study the human leukocyte antigen (HLA) region in African American Type 1 diabetes.

METHODS

Two hundred and twenty-seven African American patients with Type 1 diabetes and 471 African American control subjects were tested for association at the HLA class II genes, HLA-DRB1, HLA-DQA1, HLA-DQB1 and 5147 single nucleotide polymorphisms across the major histocompatibility complex region using logistic regression models. Population admixture was accounted for with principal components analysis.

RESULTS

Single nucleotide polymorphism marker associations were explained by the HLA associations, with the major peak over the class II loci. The HLA association overall was extremely strong, as expected for Type 1 diabetes, even in African Americans in whom diabetes diagnosis is heterogeneous. In addition, there were unique features: the HLA-DRB1*03 haplotype was split into HLA-DRB1*03:01, which confers greatest susceptibility in these samples (odds ratio 3.17, 95% CI 1.72-5.83) and HLA-DRB1*03:02, an allele rarely observed in Europeans, which confers the greatest protection in these African American samples (odds ratio 0.22, 95% CI 0.09-0.55).

CONCLUSIONS

The unique diversity of the African HLA region we have uncovered supports a specific and major role for HLA-DRB1 in HLA-DRB1*03 haplotype-associated Type 1 diabetes risk.

Humoral responses to islet antigen-2 and zinc transporter 8 are attenuated in patients carrying HLA-A*24 alleles at the onset of type 1 diabetes

The HLA-A*24 allele has shown negative associations with autoantibodies to islet antigen-2 (IA-2) and zinc transporter 8 (ZnT8) in patients with established type 1 diabetes. Understanding how this HLA class I allele affects humoral islet autoimmunity gives new insights into disease pathogenesis. We therefore investigated the epitope specificity of associations between HLA-A*24 and islet autoantibodies at disease onset. HLA-A*24 genotype and autoantibody responses to insulin (IAA), glutamate decarboxylase (GADA), IA-2, IA-2β, and ZnT8 were analyzed in samples collected from patients with recent-onset type 1 diabetes. After correction for age, sex, and HLA class II genotype, HLA-A*24 was shown to be a negative determinant of IA-2A and ZnT8A. These effects were epitope specific. Antibodies targeting the protein tyrosine phosphatase domains of IA-2 and IA-2β, but not the IA-2 juxtamembrane region, were less common in patients carrying HLA-A*24 alleles. The prevalence of ZnT8A specific or cross-reactive with the ZnT8 tryptophan-325 polymorphic residue, but not those specific to arginine-325, was reduced in HLA-A*24-positive patients. No associations were found between HLA-A*24 and IAA or GADA. Association of an HLA class I susceptibility allele with altered islet autoantibody phenotype at diagnosis suggests CD8 T-cell and/or natural killer cell-mediated killing modulates humoral autoimmune responses.

Antigen targets of type 1 diabetes autoimmunity

Type 1 diabetes is characterized by recognition of one or more β-cell proteins by the immune system. The list of target antigens in this disease is ever increasing and it is conceivable that additional islet autoantigens, possibly including pivotal β-cell targets, remain to be discovered. Many knowledge gaps remain with respect to the disorder's pathogenesis, including the cause of loss of tolerance to islet autoantigens and an explanation as to why targeting of proteins with a distribution of expression beyond β cells may result in selective β-cell destruction and type 1 diabetes. Yet, our knowledge of β-cell autoantigens has already led to translation into tissue-specific immune intervention strategies that are currently being assessed in clinical trials for their efficacy to halt or delay disease progression to type 1 diabetes, as well as to reverse type 1 diabetes. Here we will discuss recently gained insights into the identity, biology, structure, and presentation of islet antigens in relation to disease heterogeneity and β-cell destruction.

Functional IL6R 358Ala allele impairs classical IL-6 receptor signaling and influences risk of diverse inflammatory diseases

Inflammation, which is directly regulated by interleukin-6 (IL-6) signaling, is implicated in the etiology of several chronic diseases. Although a common, non-synonymous variant in the IL-6 receptor gene (IL6R Asp358Ala; rs2228145 A>C) is associated with the risk of several common diseases, with the 358Ala allele conferring protection from coronary heart disease (CHD), rheumatoid arthritis (RA), atrial fibrillation (AF), abdominal aortic aneurysm (AAA), and increased susceptibility to asthma, the variant's effect on IL-6 signaling is not known. Here we provide evidence for the association of this non-synonymous variant with the risk of type 1 diabetes (T1D) in two independent populations and confirm that rs2228145 is the major determinant of the concentration of circulating soluble IL-6R (sIL-6R) levels (34.6% increase in sIL-6R per copy of the minor allele 358Ala; rs2228145 [C]). To further investigate the molecular mechanism of this variant, we analyzed expression of IL-6R in peripheral blood mononuclear cells (PBMCs) in 128 volunteers from the Cambridge BioResource. We demonstrate that, although 358Ala increases transcription of the soluble IL6R isoform (P = 8.3×10⁻²²) and not the membrane-bound isoform, 358Ala reduces surface expression of IL-6R on CD4+ T cells and monocytes (up to 28% reduction per allele; P≤5.6×10⁻²²). Importantly, reduced expression of membrane-bound IL-6R resulted in impaired IL-6 responsiveness, as measured by decreased phosphorylation of the transcription factors STAT3 and STAT1 following stimulation with IL-6 (P≤5.2×10⁻⁷). Our findings elucidate the regulation of IL-6 signaling by IL-6R, which is causally relevant to several complex diseases, identify mechanisms for new approaches to target the IL-6/IL-6R axis, and anticipate differences in treatment response to IL-6 therapies based on this common IL6R variant.

Interleukin-6 (IL-6) is a complex cytokine, which plays a critical role in the regulation of inflammatory responses. Genetic variation in the IL-6 receptor gene is associated with the risk of several human diseases with an inflammatory component, including coronary heart disease, rheumatoid arthritis, and asthma. A common non-synonymous single nucleotide polymorphism in this gene (Asp358Ala) has been suggested to be the causal variant in this region by affecting the circulatory concentrations of soluble IL-6R (sIL-6R). In this study we extend the genetic association of this variant to type 1 diabetes and provide evidence that this variant exerts its functional mechanism by regulating the balance between sIL-6R (generated through cleavage of the surface receptor and by alternative splicing of a soluble IL6R isoform) and membrane-bound IL-6R. These data show for the first time that the minor allele of this non-synonymous variant (Ala358) directly controls the surface levels of IL-6R on individual immune cells and that these differences in protein levels translate into a functional impairment in IL-6R signaling. These findings may have implications for clinical trials targeting inflammatory mechanisms involving IL-6R signaling and may provide tools for identifying patients with specific benefit from therapeutic intervention in the IL-6R signaling pathway.

Serum proteomics reveals systemic dysregulation of innate immunity in type 1 diabetes

Proteomics analysis identifies human serum proteins involved with innate immune responses, complement activation, and blood coagulation that are diagnostic for type 1 diabetes.

Using global liquid chromatography-mass spectrometry (LC-MS)–based proteomics analyses, we identified 24 serum proteins that were significantly variant between those with type 1 diabetes (T1D) and healthy controls. Functionally, these proteins represent innate immune responses, the activation cascade of complement, inflammatory responses, and blood coagulation. Targeted verification analyses were performed on 52 surrogate peptides representing these proteins, with serum samples from an antibody standardization program cohort of 100 healthy control and 50 type 1 diabetic subjects. 16 peptides were verified as having very good discriminating power, with areas under the receiver operating characteristic curve ≥0.8. Further validation with blinded serum samples from an independent cohort (10 healthy control and 10 type 1 diabetics) demonstrated that peptides from platelet basic protein and C1 inhibitor achieved both 100% sensitivity and 100% specificity for classification of samples. The disease specificity of these proteins was assessed using sera from 50 age-matched type 2 diabetic individuals, and a subset of proteins, C1 inhibitor in particular, were exceptionally good discriminators between these two forms of diabetes. The panel of biomarkers distinguishing those with T1D from healthy controls and those with type 2 diabetes suggests that dysregulated innate immune responses may be associated with the development of this disorder.

Evidence of gene-gene interaction and age-at-diagnosis effects in type 1 diabetes

The common genetic loci that independently influence the risk of type 1 diabetes have largely been determined. Their interactions with age-at-diagnosis of type 1 diabetes, sex, or the major susceptibility locus, HLA class II, remain mostly unexplored. A large collection of more than 14,866 type 1 diabetes samples (6,750 British diabetic individuals and 8,116 affected family samples of European descent) were genotyped at 38 confirmed type 1 diabetes-associated non-HLA regions and used to test for interaction of association with age-at-diagnosis, sex, and HLA class II genotypes using regression models. The alleles that confer susceptibility to type 1 diabetes at interleukin-2 (IL-2), IL2/4q27 (rs2069763) and renalase, FAD-dependent amine oxidase (RNLS)/10q23.31 (rs10509540), were associated with a lower age-at-diagnosis (P = 4.6 × 10⁻⁶ and 2.5 × 10⁻⁵, respectively). For both loci, individuals carrying the susceptible homozygous genotype were, on average, 7.2 months younger at diagnosis than those carrying the protective homozygous genotypes. In addition to protein tyrosine phosphatase nonreceptor type 22 (PTPN22), evidence of statistical interaction between HLA class II genotypes and rs3087243 at cytotoxic T-lymphocyte antigen 4 (CTLA4)/2q33.2 was obtained (P = 7.90 × 10⁻⁵). No evidence of differential risk by sex was obtained at any loci (P ≥ 0.01). Statistical interaction effects can be detected in type 1 diabetes although they provide a relatively small contribution to our understanding of the familial clustering of the disease.

Humoral autoimmunity in type 1 diabetes: prediction, significance, and detection of distinct disease subtypes

Type 1 diabetes mellitus (T1D) is an autoimmune disease encompassing the T-cell-mediated destruction of pancreatic β cells and the production of autoantibodies against islet proteins. In humoral autoimmunity in T1D, the detection of islet autoantibodies and the examination of their associations with genetic factors and cellular autoimmunity constitute major areas in both basic research and clinical practice. Although insulin is a key autoantigen and may be primus inter pares in importance among T1D autoantigens, an abundant body of research has also revealed other autoantigens associated with the disease process. Solid evidence indicates that autoantibodies against islet targets serve as key markers to enroll newly diagnosed T1D patients and their family members in intervention trials aimed at preventing or halting the disease process. The next challenge is perfecting mechanistic bioassays to be used as end points for disease amelioration following immunomodulatory therapies aimed at blocking immune-mediated β-cell injury and, in turn, preserving β-cell function in type 1 diabetes mellitus.

Insights into type 1 diabetes provided by genetic analyses

PURPOSE OF REVIEW

Recent identification of over 60 loci contributing to the susceptibility of developing type 1 diabetes (T1D) provides a timely opportunity to assess what is currently known of the genetics of T1D, and what these discoveries may tell us about the disease itself.

RECENT FINDINGS

The major findings will be discussed under five main themes: T1D risk gene identification, molecular mechanisms of susceptibility, shared genetic cause with other diseases, development of novel analytical methods, and understanding disease heterogeneity.

SUMMARY

The plethora of T1D risk genes that have been identified risk overwhelming clinicians with lists of gene names and symbols that have little bearing on management, and provide a challenge for researchers to place the genetics of T1D in a more amenable clinical context.

[Type 1 diabetes mellitus: most recent advances in its pathogenesis and treatment]

The incidence and prevalence of diabetes mellitus is globally increasing. The causes of this trend are relatively obvious in the case of type 2 diabetes. In contrast, in case of type 1 diabetes the amount of available data is continuously growing, but the causes are not so well defined. The genetic risk, especially related to the MHC genes is well known, and the increasing amount of data underlines the role of additional risks due to non-MHC genetic polimorphisms. Hopefully, they will provide the basis for future diagnostic and therapeutic approaches. There is increasing knowledge about the pathophysiological aspects including the role of immunological disregulation (balance of autotolerance, role of regulatory T-cells) and environmental triggers (nutrients, viruses). Information on the entero-insular axis and the β-cell protective role of incretin hormones might offer an opportunity for new therapeutic strategies. In this paper, the authors try to summarize some current aspects of the pathomechanism and related therapeutic approaches.

Association of variants in HLA-DQA1-DQB1, PTPN22, INS, and CTLA4 with GAD autoantibodies and insulin secretion in nondiabetic adults of the Botnia Prospective Study

OBJECTIVE

Previously, we observed an association between family history of type 1 diabetes and development of non-insulin-dependent diabetes. The aims of this study were to assess whether type 1 diabetes susceptibility gene variants explain this association and investigate the effect of the variants on insulin secretion and presence of glutamic acid decarboxylase autoantibodies (GADA) in nondiabetic adults.

DESIGN AND METHODS

Polymorphisms in INS (rs689), PTPN22 (rs2476601), CTLA4 (rs3087243), and the HLA-DQA1-DQB1 regions (rs2187668 and rs7454108 tagging HLA-DQ2.5 and HLA-DQ8 respectively) were genotyped in the Botnia Prospective Study (n=2764), in which initially nondiabetic participants were followed for a mean of 8.1 years.

RESULTS

The variants did not explain the association between family history of type 1 diabetes and development of non-insulin-dependent diabetes. In these nondiabetic adults, HLA-DQ AND PTPN22 risk genotypes were associated with GADA (HLA-DQ2.5/HLA-DQ8 or HLA-DQ8: OR (95% CI): 1.7 (1.3-2.3), P=0.0004; PTPN22 CT/TT: OR: 1.6 (1.2-2.2), P=0.003; P values were adjusted for sex, age, BMI, and follow-up time). A higher genetic risk score was associated with lower insulin secretion (insulinogenic index: 13.27 (16.27) vs 12.69 (15.27) vs 10.98 (13.06), P=0.02) and better insulin sensitivity index (risk score of 0-1 vs 2-3 vs 4-6: 142 (111) vs 144 (118) vs 157 (127), P=0.01) at baseline and a poorer capacity to compensate for the increased insulin demand after follow-up.

CONCLUSIONS

In nondiabetic adults, HLA-DQ2.5/HLA-DQ8 and PTPN22 CT/TT genotypes were associated with GADA.

Genetic association of zinc transporter 8 (ZnT8) autoantibodies in type 1 diabetes cases

AIMS/HYPOTHESIS

Autoantibodies to zinc transporter 8 (ZnT8A) are associated with risk of type 1 diabetes. Apart from the SLC30A8 gene itself, little is known about the genetic basis of ZnT8A. We hypothesise that other loci in addition to SLC30A8 are associated with ZnT8A.

METHODS

The levels of ZnT8A were measured in 2,239 British type 1 diabetic individuals diagnosed before age 17 years, with a median duration of diabetes of 4 years. Cases were tested at over 775,000 loci genome wide (including 53 type 1 diabetes associated regions) for association with positivity for ZnT8A. ZnT8A were also measured in an independent dataset of 855 family members with type 1 diabetes.

RESULTS

Only FCRL3 on chromosome 1q23.1 and the HLA class I region were associated with positivity for ZnT8A. rs7522061T>C was the most associated single nucleotide polymorphism (SNP) in the FCRL3 region (p = 1.13 × 10(-16)). The association was confirmed in the family dataset (p ≤ 9.20 × 10(-4)). rs9258750A>G was the most associated variant in the HLA region (p = 2.06 × 10(-9) and p = 0.0014 in family cases). The presence of ZnT8A was not associated with HLA-DRB1, HLA-DQB1, HLA-A, HLA-B or HLA-C (p > 0.05). Unexpectedly, the two loci associated with the presence of ZnT8A did not alter risk of having type 1 diabetes, and the 53 type 1 diabetes risk loci did not influence positivity for ZnT8A, despite them being disease specific.

CONCLUSIONS/INTERPRETATION

ZnT8A are not primary pathogenic factors in type 1 diabetes. Nevertheless, ZnT8A testing in combination with other autoantibodies facilitates disease prediction, despite the biomarker not being under the same genetic control as the disease.