The distribution of HLA class II susceptible/protective haplotypes could partially explain the low incidence of type 1 diabetes in continental Italy (Lazio region)

Prognosis and outcome of latent autoimmune diabetes in adults: T1DM or T2DM?

Latent Autoimmune Diabetes in Adults (LADA) is a type of diabetes mellitus often overlooked in clinical practice for its dual resemblance to Type 1 Diabetes Mellitus (T1DM) in pathogenesis and to Type 2 Diabetes Mellitus (T2DM) in clinical presentation. To better understand LADA's distinctiveness from T1DM and T2DM, we conducted a comprehensive review encompassing etiology, pathology, clinical features, treatment modalities, and prognostic outcomes. With this comparative lens, we propose that LADA defies simple classification as either T1DM or T2DM. The specific treatments for the disease are limited and should be based on the therapies of T1DM or T2DM that address specific clinical issues at different stages of the disease. It is crucial to identify LADA cases potentially misdiagnosed as T2DM, warranting prompt screening for poor blood sugar control, short-term blood sugar deterioration, and other conditions. If the prognosis for LADA is similar to T2DM, it can be managed as T2DM. However, if the prognosis fundamentally differs, early LADA screening is crucial to optimize patient outcomes and enhance research on tailored treatments. The pathogenesis of LADA is clear, so the prognosis may be the key to determining whether it can be classified as T2DM, which is also the direction of future research. On the one hand, this paper aims to provide suggestions for the clinical screening and treatment of LADA based on the latest progress and provide worthy directions for future research on LADA.

Untangling the genetics of beta cell dysfunction and death in type 1 diabetes

BACKGROUND

Type 1 diabetes (T1D) is a complex multi-system disease which arises from both environmental and genetic factors, resulting in the destruction of insulin-producing pancreatic beta cells. Over the past two decades, human genetic studies have provided new insight into the etiology of T1D, including an appreciation for the role of beta cells in their own demise.

SCOPE OF REVIEW

Here, we outline models supported by human genetic data for the role of beta cell dysfunction and death in T1D. We highlight the importance of strong evidence linking T1D genetic associations to bona fide candidate genes for mechanistic and therapeutic consideration. To guide rigorous interpretation of genetic associations, we describe molecular profiling approaches, genomic resources, and disease models that may be used to construct variant-to-gene links and to investigate candidate genes and their role in T1D.

MAJOR CONCLUSIONS

We profile advances in understanding the genetic causes of beta cell dysfunction and death at individual T1D risk loci. We discuss how genetic risk prediction models can be used to address disease heterogeneity. Further, we present areas where investment will be critical for the future use of genetics to address open questions in the development of new treatment and prevention strategies for T1D.

Immune checkpoint modulators in early clinical development for the treatment of type 1 diabetes

INTRODUCTION

Despite the improvements of insulin therapy, people with type 1 diabetes (T1D) still suffer from a decreased quality of life and life expectancy. The search toward a cure for T1D is therefore still a scorching open field of research.

AREAS COVERED

Tackling the immune checkpoint signaling pathways has gained importance in the field of cancer immunotherapy. The same pathways can be targeted in autoimmunity with an opposite principle: to dampen the exaggerated immune response. In this review, we report a comprehensive excursus on the cellular and molecular mechanisms that lead to loss of immunological tolerance, and recent evidence on the role of immune checkpoint molecules in the development of T1D and their potential application for the mitigation of autoimmune diabetes.

EXPERT OPINION

Contrasting results about the efficacy of immune checkpoint modulators for T1D have been published, with very few molecules from preclinical studies eligible for use in humans. The heterogeneous and complex pathophysiology of T1D may explain the conflicting evidence. Designing clinical trials that acknowledge the pathophysiological and clinical complexity of T1D and that forecast the need of simultaneously tackling different disease pathways will be crucial to enhance the benefits which may be gained by such compounds.

Association of human leukocyte antigen (HLA) footprints with the comorbidity of latent autoimmune diabetes in adults (LADA) and hepatitis C virus (HCV) infection: A multicenter cross-sectional study

AIMS

This study aims to investigate the interplay between hepatitis C virus (HCV) infection and major forms of diabetes: type 1 diabetes (T1D), type 2 diabetes (T2D), and latent autoimmune diabetes in adults (LADA).

METHODS

This multicenter study analyzed a cohort of 2699 diabetic and 7344 non-diabetic subjects who visited medical centers in China from 2014 to 2021. T1D, T2D, LADA, and HCV were diagnosed using standard procedures. High-throughput sequencing was conducted to identify genetic footprints of human leukocyte antigen (HLA) alleles and haplotypes at the DRB1, DQA1, and DQB1 loci.

RESULTS

HCV infection was detected in 3 % (23/766) of LADA patients, followed by 1.5 % (15/977) of T2D patients, 1.4 % (13/926) of T1D patients, and 0.5 % (38/7344) of non-diabetic individuals. HCV prevalence was significantly higher in people with diabetes than in non-diabetic individuals (p < 0.01). HLA alleles (DQB1*060101, DQB1*040101) and haplotypes (DRB1*080302-DQA1*010301-DQB1*060101) in LADA patients with HCV revealed higher frequencies than in LADA patients without HCV (adjusted p < 0.03). Furthermore, a higher risk of diabetes complications was found among LADA patients with HCV infection (p < 0.001).

CONCLUSIONS

LADA patients are susceptible to HCV infection, potentially associated with certain HLA alleles/haplotypes. Early diagnosis and treatment of HCV infection among people with diabetes are important for the management of severe complications.

Update on the ZNT8 epitope and its role in the pathogenesis of type 1 diabetes

Type 1 diabetes (T1D) is an organ-specific chronic autoimmune disease mediated by autoreactive T cells. ZnT8 is a pancreatic islet-specific zinc transporter that is mainly located in β cells. It not only participates in the synthesis, storage and secretion of insulin but also maintains the structural integrity of insulin. ZnT8 is the main autoantigen recognized by autoreactive CD8+ T cells in children and adults with T1D. This article summarizes the latest research results on the T lymphocyte epitope and B lymphocyte epitope of ZnT8 in the current literature. The structure and expression of ZnT8, the role of ZnT8 in insulin synthesis and its role in autoimmunity are reviewed. ZnT8 is the primary autoantigen of T1D and is specifically expressed in pancreatic islets. Thus, it is one of biomarkers for the diagnosis of T1D. It has broad prospects for further research on immunomodulators for the treatment of T1D.

Prevalence, clinical characteristics and HLA genotypes of idiopathic type 1 diabetes: A cross-sectional study

AIMS

Idiopathic type 1 diabetes (T1D) is a neglected subtype of T1D. Our aim was to investigate the frequency, clinical characteristics, and human leucocyte antigen (HLA) genotypes of idiopathic T1D.

METHODS

We enrolled 1205 newly diagnosed T1D patients in our analysis. To exclude monogenic diabetes in autoantibody-negative patients, we utilised a custom monogenic diabetes gene panel. Individuals negative for autoantibodies and subsequently excluded for monogenic diabetes were diagnosed with idiopathic T1D. We collected clinical characteristics, measured islet autoantibodies by radioligand assay and obtained HLA data.

RESULTS

After excluding 11 patients with monogenic diabetes, 284 cases were diagnosed with idiopathic T1D, accounting for 23.8% (284/1194) of all newly diagnosed T1D cases. When compared with autoimmune T1D, idiopathic T1D patients showed an older onset age, higher body mass index among adults, lower haemoglobin A1c, higher levels of fasting C-peptide and 2-h postprandial C-peptide, and were likely to have type 2 diabetes (T2D) family history and carry 0 susceptible HLA haplotype (all p < 0.01). A lower proportion of individuals carrying 2 susceptible HLA haplotypes in idiopathic T1D was observed in the adult-onset subgroup (15.7% vs. 38.0% in child-onset subgroup, p < 0.001) and in subgroup with preserved beta-cell function (11.0% vs. 30.1% in subgroup with poor beta-cell function, p < 0.001). Multivariable correlation analyses indicated that being overweight, having T2D family history and lacking susceptible HLA haplotypes were associated with negative autoantibodies.

CONCLUSIONS

Idiopathic T1D represents about 1/4 of newly diagnosed T1D, with adult-onset and preserved beta-cell function patients showing lower HLA susceptibility and more insulin resistance.

HLA-DRB1 and -DQB1 Alleles, Haplotypes and Genotypes in Emirati Patients with Type 1 Diabetes Underscores the Benefits of Evaluating Understudied Populations

Background: HLA class II (DR and DQ) alleles and antigens have historically shown strong genetic predisposition to type 1 diabetes (T1D). This study evaluated the association of DRB1 and DQB1 alleles, genotypes, and haplotypes with T1D in United Arab Emirates. Materials and Methods: Study subjects comprised 149 patients with T1D, and 147 normoglycemic control subjects. Cases and controls were Emiratis and were HLA-DRB1 and -DQB1 genotyped using sequence-based typing. Statistical analysis was performed using Bridging Immunogenomic Data-Analysis Workflow Gaps R package. Results: In total, 15 DRB1 and 9 DQB1 alleles were identified in the study subjects, of which the association of DRB1*03:01, DRB1*04:02, DRB1*11:01, DRB1*16:02, and DQB1*02:01, DQB1*03:02, DQB1*03:01, and DQB1*06:01 with altered risk of T1D persisted after correcting for multiple comparisons. Two-locus haplotype analysis identified DRB1*03:01∼DQB1*02:01 [0.44 vs. 0.18, OR (95% CI) = 3.44 (2.33-5.1), Pc = 3.48 × 10^-10]; DRB1*04:02∼DQB1*03:02 [0.077 vs. 0.014, OR = 6.06 (2.03-24.37), Pc = 2.3 × 10^-3] and DRB1*04:05∼DQB1*03:02 [0.060 vs. 0.010, OR = 6.24 (1.79-33.34), Pc = 0.011] as positively associated, and DRB1*16:02∼DQB1*05:02 [0.024 vs. 0.075, OR = 0.3 (0.11-0.74), Pc = 0.041] as negatively associated with T1D, after applying Bonferroni correction. Furthermore, the highest T1D risk was observed for DR3/DR4 [0.104 vs. 0.006, OR = 25.03 (8.23-97.2), Pc = 2.6 × 10^-10], followed by DR3/DR3 [0.094 vs. 0.010, OR = 8.72 (3.17-25.32), Pc = 3.18 × 10^-8] diplotypes. Conclusion: While DRB1 and DQB1 alleles and haplotypes associated with T1D in Emiratis showed similarities to Caucasian and non-Caucasian populations, several alleles and haplotypes associated with T1D in European, African, and Asian populations, were not observed. This underscores the contribution of ethnic diversity and possible diverse associations between DRB1 and DQB1 and T1D across different populations.

Characteristics of Interferon-Associated Diabetes Mellitus in Past 30 Years: A Review

Interferon (IFN) is a broad-spectrum antiviral agent that activates cell surface receptors and causes cells to produce antiviral proteins, inhibiting viral replication. Interferon use has long been associated with diabetes. The PubMed database was searched for articles related to diabetes and interferon from March 30, 2020. Patients were divided into type 1 diabetes group and type 2 diabetes group. We reviewed the relevant literature to compare interferon-associated T1D and interferon-associated T2D differences. Interferon treatment shortened the incubation period of T2D and changed the original T2D to T1D. The onset of interferon-associated T1D required longer periods of IFN treatment than interferon-associated T2D, and the interferon-associated T1D group had higher GADA positive rates, lower BMI, lower fasting blood glucose, and greater insulin dependence (p<0.05). More patients in the T1D group were positive for HLA-DRB1*04, DRB1*03, DRB1*09, DRB1*14, HLA-DQB1*04, HLA-DQB1*02, HLA-DQB1*03, and HLA-DQB1*05. The combined detection of GAD antibodies and HLA alleles may be an effective method to predict the incidence of T1D after IFN treatment.

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.

Association of HLA-DR-DQ alleles, haplotypes, and diplotypes with type 1 diabetes in Saudis

AIMS

Type 1 diabetes (T1D) is an autoimmune disease that affects many children worldwide. Genetic factors and environmental triggers play crucial interacting roles in the aetiology. This study aimed to assess the contribution of HLA-DRB1-DQA1-DQB1 alleles, haplotypes, and genotypes to the risk of T1D among Saudis.

METHODS

A total of 222 children with T1D and 342 controls were genotyped for HLA-DRB1, -DQA1, and -DQB1 using reverse sequence-specific oligonucleotide (rSSO) Lab Type high definition (HD) kits. Alleles, haplotypes, and diplotypes were compared between cases and controls using the SAS statistical package.

RESULTS

DRB1*03:01-DQA1*05:01-DQB1*02:01 (32.4%; OR = 3.68; P_c < .0001), DRB1*04:05-DQA1*03:02-DQB1*03:02 (6.6%; OR = 6.76; P_c < .0001), DRB1*04:02-DQA1*03:01-DQB1*03:02 (6.0%; OR = 3.10; P_c = .0194), DRB1*04:01-DQA1*03:01-DQB1*03:02 (3.7%; OR = 4.22; P_c = .0335), and DRB1*04:05-DQA1*03:02-DQB1*02:02 (2.7%; OR = 6.31; P_c = .0326) haplotypes were significantly increased in cases compared to controls, whereas DRB1*07:01-DQA1*02:01-DQB1*02:02 (OR = 0.41; P_c = .0001), DRB1*13:01-DQA1*01:03-DQB1*06:03 (OR = 0.05; P_c < .0001), DRB1*15:01-DQA1*01:02-DQB1*06:02 (OR = 0.03; P_c < .0001), and DRB1*11:01-DQA1*05:05-DQB1*03:01 (OR = 0.07; P_c = .0291) were significantly decreased. Homozygous DRB1*03:01-DQA1*05:01-DQB1*02:01 genotypes and combinations of DRB1*03:01-DQA1*05:01-DQB1*02:01 with DRB1*04:05-DQA1*03:02-DQB1*03:02, DRB1*04:02-DQA1*03:01-DQB1*03:02, and DRB1*04:01-DQA1*03:01-DQB1*03:02 were significantly increased in cases than controls. Combinations of DRB1*03:01-DQA1*05:01-DQB1*02:01 with DRB1*07:01-DQA1*02:01-DQB1*02:02 and DRB1*13:02-DQA1*01:02-DQB1*06:04 showed low OR values but did not remain significantly decreased after Bonferroni correction.

CONCLUSIONS

HLA-DRB1-DQA1-DQB1 alleles, haplotypes, and diplotypes in Saudis with T1D are not markedly different from those observed in Western and Middle-Eastern populations but are quite different than those of East Asians.

Birth during the moderate weather seasons is associated with early onset of type 1 diabetes in the Mediterranean area

AIM

To assess the association of seasonal and perinatal parameters with early age of type 1 diabetes (T1D) onset.

METHODS

A cross-sectional review of all medical records of T1D patients born between the years 1990 and 2005, and diagnosed before/by the age of 10 years, from 13 university-affiliated paediatric medical centres in Israel, was performed. Data included: gender, ethnicity, seasons of birth and disease onset, birth gestational age and weight, and autoimmune diseases of the probands and their first-degree family members. Statistical analysis included the Chi-square test or Mann-Whitney test, as appropriate and multivariate regression analysis.

RESULTS

Enrolled were 1571 T1D patients at a median age of T1D onset 6.9 years (IQR 4.4,8.4); 336 of them presented before 4 years of age. The median age of this group was 2.5 years (IQR 1.7,3.2), and of the 1235 patients who presented after 4 years of age, median presentation age was 7.5 years (IQR 6.1,8.8). Multivariate regression analysis demonstrated that a more recent birth year; OR = 1.06, 95% CI 1.02-1.1, P = 0.003, and birth during the moderate weather months (September, October, March, and April) were significantly associated with younger age at T1D onset; OR = 1.68, 95% CI 1.17-2.4, P = 0.005.

CONCLUSIONS

Our novel finding demonstrates the association between younger than 4 years old age at presentation and birth during moderate weather months. The results also support previous reports, that there is a slight increase in the annual incidence of T1D in the youngest age groups.

Fulminant type 1 diabetes: A comprehensive review of an autoimmune condition

Fulminant type 1 diabetes (FT1D) is a subset of type 1 diabetes characterized by extremely rapid pancreatic β-cell destruction with aggressive progression of hyperglycaemia and ketoacidosis. It was initially classified as idiopathic type 1 diabetes due to the absence of autoimmune markers. However, subsequent studies provide evidences supporting the involvement of autoimmunity in rapid β-cell loss in FT1D pathogenesis, which are crucial for FT1D being an autoimmune disease. This article highlights the role of immunological aspects in FT1D according to the autoimmune-associated genetic background, viral infection, innate immunity, adaptive immunity, and pancreas histology.

Impact of obesity on the increasing incidence of type 1 diabetes

Published estimates of the incidence of type 1 diabetes (T1D) in children in the last decade varies between 2% and 4% per annum. If this trend continued, the disease incidence would double in the next 20 years. The risk of developing T1D is determined by a complex interaction between multiple genes (mainly human leukocyte antigens) and environmental factors. Notwithstanding that genetic susceptibility represents a relevant element in T1D risk, genetics alone cannot explain the increase in incidence. Various environmental factors have been suggested as potential triggers for T1D, including several viruses and the hygiene hypothesis; however, none of these seems to explain the large increase in T1D incidence observed over the last decades. Several studies have demonstrated that the prevalence of childhood/adolescence overweight and obesity has risen during the past 30 years in T1D. Currently, at diagnosis, the majority of patients with T1D have normal or elevated body weight and ~50% of patients with longstanding T1D are either overweight or obese. The growing prevalence of obesity in childhood and adolescence offers a plausible explanation for the increase in T1D incidence observed in recent decades. Possible mechanisms of the enhancement of β-cell autoimmunity by obesity include: a) insulin resistance-induced β-cell secretory demand triggering autoimmunity through cytokine release, neo-epitope antigen formation and increase in β-cell apoptosis, and b) obesity-induced low-grade inflammation with pro-inflammatory cytokines secreted by locally infiltrating macrophages, which contribute to the presentation by islet cells of autoantigens generally not accessible to T cells. Further studies are needed to clarify whether the control of body weight can prevent or delay the current and continuing rise in T1D incidence.

Comprehensive meta-analysis reveals an association of the HLA-DRB1*1602 allele with autoimmune diseases mediated predominantly by autoantibodies

The human leukocytes antigen (HLA)-DRB1*16:02 allele has been suggested to be associated with many autoimmune diseases. However, a validation of the results of the different studies by a comprehensive analysis of the corresponding meta data is lacking. In this study, we performed a meta-analysis of the association between HLA-DRB1*16:02 allele with various autoimmune disorders. Our analysis shows that HLA-DRB1*16:02 allele was associated with systemic lupus erythematosus, anti-N-Methyl-d-Aspartate receptor (NMDAR) encephalitis, Graves' disease, myasthenia gravis, neuromyelitis optica and antibody-associated systemic vasculitis with microscopic polyangiitis (AASV-MPA). However, no such association was found for multiple sclerosis, autoimmune hepatitis type 1, rheumatoid arthritis, type 1 diabetes and Vogt-Koyanagi-Harada syndrome. Re-analysis of the studies after their categorization into autoantibody-dependent and T cell-dependent autoimmune diseases revealed that the HLA-DRB1*16:02 allele was strongly associated with disorder predominantly mediated by autoantibodies (OR = 1.93; 95% CI = 1.63-2.28, P = 1.95 × 10^-14) but not with those predominantly mediated by T cells (OR = 1.08; 95% CI = 0.87-1.34, P = .474). In addition, amino acid sequence alignment of common HLA-DRB1 subtypes demonstrated that HLA-DRB1*16:02 carries a unique motif of amino acid residues at position 67-74 which encodes the third hypervariable region. Taken together, the distinct pattern of disease association and the unique amino acid sequence of the third hypervariable region of the HLA-DRB1 provide some hints on how HLA-DRB1*16:02 is involved in the pathogenesis of autoimmune diseases.

A pilot study of preproinsulin peptides reactivity in Chinese patients with type 1 diabetes

BACKGROUND

The aim of our study is to investigate whether preproinsulin (PPI) could trigger a proinflammatory CD4⁺ T cell response in Chinese patients with type 1 diabetes (T1D).

METHODS

Peripheral blood mononuclear cells were stimulated by a pool of 13 PPI peptides. Additional five PPI peptides previously proved to be antigenic in other cohorts of patients with T1D were also used. PPI reactive T cell responses were measured by interferon (IFN)-γ ELISPOT assay.

RESULTS

Fifty-one Chinese patients with T1D were enrolled in this study and 72.34% of them were positive for at least one islet autoantibody. The stimulation index (SI) value of IFN-γ response to PPI peptide pool or peptides with dominant epitopes was below 3 in patients when SI≥3 was used as the positive cut-off value. Two peptides (B9-23 and C19-A3) restricted to DQ8 or DR4 molecule failed to induce positive IFN-γ response in patients with high-risk HLA-DQ8 or HLA-DR4/DR9 alleles. RNA-seq analysis of PPI specific CD4⁺ T cell lines further showed that most of the IFN-γ associated genes remained unchanged.

CONCLUSIONS

This is the first report of CD4⁺ T cell epitope mapping of PPI in Chinese T1D. The lack of positive IFN-γ response to PPI peptides indicates that PPI might not be the principal antigenic candidate for autoreactive CD4⁺ T cells in Chinese T1D. Therefore, the efficacy of PPI-based immunotherapies in attenuating proinflammatory CD4⁺ T cell response requires further investigation.

High prevalence of diabetes-specific autoimmunity in first-degree relatives of Sardinian patients with type 1 diabetes

BACKGROUND

The incidence of type 1 diabetes mellitus (T1DM) in Sardinia is among the highest in the world (44.8 cases/100,000 person-years). Recommendations of the Immunology of Diabetes Society advise evaluating autoantibody positivity in first-degree relatives (FDRs) of patients with T1DM, for their higher risk to develop the disease. The aim of this study was to determine the prevalence of beta-cell autoimmunity in FDRs of T1DM patients in Sardinia.

METHODS

A total of 188 Sardinian families were recruited in collaboration between diabetes and pediatric units of university and district hospitals in Sardinia. The recruitment involved 188 patients with diagnosed T1DM and all their available FDRs (n = 447). Autoantibodies (Aabs) against GAD, IA2, insulin, and ZnT8 were measured in all subjects. Human leukocyte antigen (HLA) risk genotypes (HLA-DR and DQ loci) were analyzed in 43 Aabs-positive FDR.

RESULTS

The prevalence of Aabs (any type of autoantibody, single or multiple) in FDR was 11.9% (53/447). Of those with autoantibodies, 62.3% (33/53) were positive to only 1 autoantibody, 22.6% (12/53) had 2 autoantibodies, 7.55% (4/53) had 3 autoantibodies, and 7.55% (4/53) had all 4 autoantibodies. Typing of HLA-DR and DQ loci showed that 89% of FDR carried moderate- to high-risk genotypes, with only 5 FDR with low-risk genotypes.

CONCLUSIONS

The prevalence of T1DM autoantibodies in FDRs of T1DM patients was very high (11.9%) in the Sardinian population, higher than in other populations from the United States and Europe, and similar to that observed in Finland. Autoantibody positivity strongly associated with HLA risk. This study provides evidence of the high risk of T1DM in FDR of T1DM patients in Sardinia and warrants longitudinal follow-up to estimate the risk of progression to T1DM in high-risk populations.

Genetic Epidemiology of Type 1 Diabetes in the 22 Arab Countries

Type 1 diabetes (T1D) is a complex autoimmune disorder that results from the T cell-mediated destruction of the pancreatic β cells and is due to interactions between environmental and genetic factors. Although Arabs have one of the highest global incidence and prevalence rates of T1D, unfortunately, there is a dearth of information regarding the genetic epidemiology of T1D in the Arab world. Arabs share several HLA haplotypes with other ethnic groups, which confer either susceptibility or protection to T1D, but they have specific haplotypes that are distinctive from other ethnicities. Among different Arab countries, several non-HLA genes were reported to be associated with susceptibility to T1D, including CTLA4, CD28, PTPN22, TCRβ, CD3z, IL15, BANK1, and ZAP70. In Arab countries, consanguinity, endogamy, and first-cousin marriage rates are some of the highest reported worldwide and are responsible for the creation of several inbreeding communities within the Arab world that have led to an increase in homozygosity of both the HLA haplotypes and non-HLA genes associated with either protection or susceptibility to T1D among Arabs. Homozygosity reduces the HLA complexity and is expected to facilitate our understanding of the mode of inheritance of HLA haplotypes and provide valuable insight into the intricate genotype-phenotype correlations in T1D patients. In this review, based on literature studies, I will discuss the current epidemiological profile and molecular genetic risks of Arabs with T1D.

High GADA titer increases the risk of insulin requirement in LADA patients: a 7-year follow-up (NIRAD study 7)

OBJECTIVE

The aim of this study was to determine whether glutamic acid decarboxylase antibody (GADA) titer and other clinical parameters could define the risk of progression to insulin therapy in latent autoimmune diabetes in adults (LADA) patients during a 7-year follow-up.

METHODS

This study involved 220 LADA and 430 type 2 diabetes subjects followed up for 7 years from the time of GADA screening to evaluate their progression toward insulin therapy. Kaplan-Meier curves and multivariate logistic regression analysis were performed to identify the markers capable of influencing this progression.

RESULTS

During the follow-up, the drop out was 4% in both groups. A total of 119 (56.1%) out of 212 LADA patients required insulin during the 7 years of follow-up. The Kaplan-Meier plots showed that 74/104 (71.1%) of high GADA titer required insulin compared with 45/108 (41.6%) of low GADA titer and with 86/412 (20.9%) of type 2 diabetes (P<0.0001 for both). A BMI of ≤25 kg/m2 and IA-2IC and zinc transporter 8 (ZnT8) positivity were also shown as the markers of faster progression (P<0.0001 for both). The proportion of LADA patients requiring insulin was significantly higher in the group of subjects treated also with sulfonylurea in the first year from diagnosis compared with those treated with diet and/or insulin sensitizers (P<0.001). The multivariate analysis confirmed that the presence of high GADA titer was a significant predictor of insulin requirement (P<0.0001, OR=6.95).

CONCLUSIONS

High GADA titer, BMI ≤ 25, ZnT8 and IA-2IC positivity and sulfonylurea treatment, in the first year from diagnosis, significantly increase the progression toward insulin requirement in LADA patients.

HLA-DRB, -DQA, and DQB alleles and haplotypes in Iranian patients with diabetes mellitus type I

Specific alleles at the HLA-DRB1, -DQA1, and -DQB1 loci seem to be associated with variable risks of developing type 1 diabetes (T1D). This study assessed the distribution of HLA-DR and -DQ alleles among Iranian T1D patients and healthy controls. In this study, HLA-DRB1, -DQA1, and -DQB1 alleles were determined in 100 children with T1D and 100 unrelated healthy controls. The following alleles were found to have a strong positive association with T1D: DRB1*0301, DRB1*0401, DRB1*0402, DQA1*0301, DQA1*0501, DQB1*0201, and DQB1*0302. Meanwhile, protective associations were found for DRB1*1001, DRB1*1101, DRB1*15, DRB1*16, DQA1*0102, DQA1*0103, DQB1*0301, DQB1*0501, and DQB1*0602 alleles. The haplotypes found most frequently among patients with T1D were DRB1*0301-DQA1*0501-DQB1*0201, DRB1*0401-DQA1*0301- DQB1*0302, and DRB1*0402-DQA1*0301-DQB1*0302, whereas DRB1*1101-DQA1*0501-DQB1*0301 and DRB1*16-DQA1*0102- DQB1*0501 haplotypes were negatively associated with the disease. These results confirm the previously reported association of specific HLA-DR and HLA-DQ alleles and haplotypes with T1D in Iranian population. The notable difference was the identification of DRB1*16-DQA1*0102-DQB1*0501 as a protective haplotype and the absence of a negative association of DRB1*1301-DQA1*0103-DRB1*0603 with T1D.

Genetics of the HLA region in the prediction of type 1 diabetes

Type 1 diabetes (T1D) is one of the most widely studied complex genetic disorders, and the genes in HLA are reported to account for approximately 40-50% of the familial aggregation of T1D. The major genetic determinants of this disease are polymorphisms of class II HLA genes encoding DQ and DR. The DR-DQ haplotypes conferring the highest risk are DRB1*03:01-DQA1*05:01-DQB1*02:01 (abbreviated "DR3") and DRB1*04:01/02/04/05/08-DQA1*03:01-DQB1*03:02/04 (or DQB1*02; abbreviated "DR4"). The risk is much higher for the heterozygote formed by these two haplotypes (OR = 16.59; 95% CI, 13.7-20.1) than for either of the homozygotes (DR3/DR3, OR = 6.32; 95% CI, 5.12-7.80; DR4/DR4, OR = 5.68; 95% CI, 3.91). In addition, some haplotypes confer strong protection from disease, such as DRB1*15:01-DQA1*01:02-DQB1*06:02 (abbreviated "DR2"; OR = 0.03; 95% CI, 0.01-0.07). After adjusting for the genetic correlation with DR and DQ, significant associations can be seen for HLA class II DPB1 alleles, in particular, DPB1*04:02, DPB1*03:01, and DPB1*02:02. Outside of the class II region, the strongest susceptibility is conferred by class I allele B*39:06 (OR =10.31; 95% CI, 4.21-25.1) and other HLA-B alleles. In addition, several loci in the class III region are reported to be associated with T1D, as are some loci telomeric to class I. Not surprisingly, current approaches for the prediction of T1D in screening studies take advantage of genotyping HLA-DR and HLA-DQ loci, which is then combined with family history and screening for autoantibodies directed against islet-cell antigens. Inclusion of additional moderate HLA risk haplotypes may help identify the majority of children with T1D before the onset of the disease.

Autoimmune polyglandular syndrome type 2 shows the same HLA class II pattern as type 1 diabetes

Autoimmune polyglandular syndrome (APS) type 2 is defined by the manifestation of at least two autoimmune endocrine diseases. Only few data exist on genetic associations of APS type 2. In this controlled study, 98 patients with APS type 2, 96 patients with type 1 diabetes (T1D), and 92 patients with autoimmune thyroid disease, both as a single autoimmune endocrinopathy, were tested for association with alleles of the human leukocyte antigen (HLA) class II loci DRB1, DQA1, and DQB1. Patients with APS type 2 had significantly more often the alleles DRB1*03 (P(c) < 0.0001), DRB1*04 (P(c) < 0.000005), DQA1*03 (P(c) < 0.0001), and DQB1*02 (P(c) < 0.05), when compared with controls. Less frequent in APS were DRB1*15 (P(c) < 0.05), DQA1*01 (P(c) < 0.0005), and DQB1*05 (P(c) < 0.005). With regard to frequency and linkage of these alleles, the susceptible haplotypes DRB1*0301-DQA1*0501-DQB1*0201 and DRB1*0401/04-DQA1*0301-DQB1*0302 were deduced. Protective haplotypes in this study were DRB1*1501-DQA1*0102-DQB1*0602 and DRB1*0101-DQA1*0101-DQB1*0501. Comparing APS patients with vs without AD, no significant differences regarding HLA class II alleles were noted in our collective. Patients with T1D as a singular disease had the same susceptible and protective HLA alleles and haplotypes. The prevalence of DRB1*03 and DRB1*04 in APS patients was not because of the presence of diabetes, as the APS type 2 patients without diabetes had the same allele distribution. In conclusion, these data suggest a common immunogenetic pathomechanism for T1D and APS type 2, which might be different from the immunogenetic pathomechanism of other autoimmune endocrine disease.

The Co-operative Specificity Theory: phenotypic protection from T1D by certain HLA Class II DRB1 and DQ alleles identifies the absence of co-operation between the respective DR and DQ molecules eventuating in no T1D-predisposition

It is well established that both DR and DQ genes are involved in type 1 diabetes (T1D) -susceptibility. But how the DR and DQ molecules contrive to effect collectively the same function of T1D predisposition remains unexplained. We advance the Co-operative Specificity Theory which attempts to project the relationship by which this occurs. The Co-operative Specificity Theory says that what is involved and being observed is a phenomenon of specific reciprocal recognition between corresponding DR- and DQ-molecules in a haplotype, resulting in a co-operation that realizes effects: this specificity varies in degrees. It is a situation of co-operative participation restricted to a specific DR- and its corresponding specific DQ-molecules that results in susceptibility. Thus susceptibility may not result when a corresponding specific DR or DQ allele is substituted by a non-specific allele in the haplotype. It thus ensues that phenotypic protection identifies the absence of this specific co-operation between the respective DR and DQ molecules giving rise to no predisposition.

Genetic affinities of north and northeastern populations of India: inference from HLA-based study

India is like a microcosm of the world in terms of its diversity; religion, climate and ethnicity which leads to genetic variations in the populations. As a highly polymorphic marker, the human leukocyte antigen (HLA) system plays an important role in the genetic differentiation studies. To assess the genetic diversity of HLA class II loci, we studied a total of 1336 individuals from north India using DNA-based techniques. The study included four endogamous castes (Kayastha, Mathurs, Rastogies and Vaishyas), two inbreeding Muslim populations (Shias and Sunnis) from north India and three northeast Indian populations (Lachung, Mech and Rajbanshi). A total of 36 alleles were observed at DRB1 locus in both Hindu castes and Muslims from north, while 21 alleles were seen in northeast Indians. At the DQA1 locus, the number of alleles ranged from 11 to 17 in the studied populations. The total number of alleles at DQB1 was 19, 12 and 20 in the studied castes, Muslims and northeastern populations, respectively. The most frequent haplotypes observed in all the studied populations were DRB1*0701-DQA1*0201-DQB1*0201 and DRB1*1501-DQA1*0103-DQB1*0601. Upon comparing our results with other world populations, we observed the presence of Caucasoid element in north Indian population. However, differential admixturing among Sunnis and Shias with the other north Indians was evident. Northeastern populations showed genetic affinity with Mongoloids from southeast Asia. When genetic distances were calculated, we found the north Indians and northeastern populations to be markedly unrelated.

HLA class II similarities in Iranian Kurds and Azeris

The genetic relationship between Kurds and Azeris of Iran was investigated based on human leukocyte antigen (HLA) class II profiles. HLA typing was performed using polymerase chain reaction/restriction fragment-length polymorphism (PCR/RFLP) and PCR/sequence-specific primer (PCR/SSP) methods in 100 Kurds and 100 Azeris. DRB1*1103/04, DQA1*0501 and DQB1*0301 were the most common alleles and DRB1*1103/04-DQA1*0501-DQB1*0301 was the most frequent haplotype in both populations. No significant difference was observed in HLA class II allele distribution between these populations except for DQB1*0503 which showed a higher frequency in Kurds. Neighbor-joining tree based on Nei's genetic distances and correspondence analysis according to DRB1, DQA1 and DQB1 allele frequencies showed a strong genetic tie between Kurds and Azeris of Iran. The results of amova revealed no significant difference between these populations and other major ethnic groups of Iran. No close genetic relationship was observed between Azeris of Iran and the people of Turkey or Central Asians. According to the current results, present-day Kurds and Azeris of Iran seem to belong to a common genetic pool.

Islet autoantibodies are associated with HLA-DQ genotypes in Han Chinese patients with type 1 diabetes and their relatives

The objective of this study was to explore the relationship between islet autoantibodies of glutamic acid decarboxylase (GADA), islet antigen-2A (IA-2A), insulin autoantibody (IAA), and human leukocyte antigen (HLA)-DQ genotypes in type 1 diabetes (T1D) patients and their first-degree relatives (FDRs). Cross-sectional and case-control study. Four hundred and ninety-five T1D patients, 419 FDRs, and 376 control subjects in Han Chinese populations were recruited and tested for GADA and IA-2A, while 71 cases, all FDRs and 300 controls were tested for IAA. The 338 T1D patients (including 187 antibody-positive and 151 antibody-negative patients), 173 FDRs and 278 controls were genotyped for HLA-DQ with polymerase chain reaction sequencing-based method. Compared with the control, the frequency of DQA1*03-DQB1*0303, DQA1*05-DQB1*0201, and DQA1*03-DQB1*0401 haplotypes was higher (P < 0.05-0.01) but DQA1*0102-DQB1*0602 haplotype was lower (P < 0.01) in T1D patients. DQA1*03 allele was less in the FDRs than in their probands (P < 0.05). GADA was more prevalent in T1D patients carrying DQA1*05-DQB1*0201 or DQA1*03-DQB1*0401 haplotype (55.8% vs 41.0%, 65.5% vs 40.3%, P < 0.05-0.01), whereas IA-2A presented more in the patients carrying DQA1*03-DQB1*0303 haplotype (27.0% vs 7.9%, P < 0.05-0.01), both GADA and IA-2A showed frequently in the patients with DQA1*03-DQB1*0303/DQA1*05-DQB1*0201 haplotypes (34.5% vs 9.7%, P < 0.01). GADA positivity was lower in the patients with DQA1*0102-DQB1*0602 haplotype (16.7% vs 45.9%, P < 0.05). The frequency of IAA was not different between patients with and without susceptible DQ haplotypes (P > 0.05). GADA, IA-2A or IAA presented frequently in FDRs with DQA1*03-DQB1*0303 haplotype. The findings in the study indicate that some of specific HLA-DQA1/-DQB1 genotypes and haplotypes not only confer susceptibility to T1D but also are associated with the presence of the islet autoantibodies in the Han Chinese population.

Relative predispositional effects of HLA class II DRB1-DQB1 haplotypes and genotypes on type 1 diabetes: a meta-analysis

The direct involvement of the human leukocyte antigen class II DR-DQ genes in type 1 diabetes (T1D) is well established, and these genes display a complex hierarchy of risk effects at the genotype and haplotype levels. We investigated, using data from 38 studies, whether the DR-DQ haplotypes and genotypes show the same relative predispositional effects across populations and ethnic groups. Significant differences in risk within a population were considered, as well as comparisons across populations using the patient/control (P/C) ratio. Within a population, the ratio of the P/C ratios for two different genotypes or haplotypes is a function only of the absolute penetrance values, allowing ranking of risk effects. Categories of consistent predisposing, intermediate ('neutral'), and protective haplotypes were identified and found to correlate with disease prevalence and the marked ethnic differences in DRB1-DQB1 frequencies. Specific effects were identified, for example for predisposing haplotypes, there was a statistically significant and consistent hierarchy for DR4 DQB1*0302s: DRB1*0405 =*0401 =*0402 > *0404 > *0403, with DRB1*0301 DQB1*0200 (DR3) being significantly less predisposing than DRB1*0402 and more than DRB1*0404. The predisposing DRB1*0401 DQB1*0302 haplotype was relatively increased compared with the protective haplotype DRB1*0401 DQB1*0301 in heterozygotes with DR3 compared with heterozygotes with DRB1*0101 DQB1*0501 (DR1). Our results show that meta-analyses and use of the P/C ratio and rankings thereof can be valuable in determining T1D risk factors at the haplotype and amino acid residue levels.

High titer of autoantibodies to GAD identifies a specific phenotype of adult-onset autoimmune diabetes

OBJECTIVE

The aim of the present study was to define heterogeneity of adult-onset autoimmune diabetes based on characterization of GAD antibodies (GADAs).

RESEARCH DESIGN AND METHODS

Patients enrolled in a nationwide survey, the Non Insulin Requiring Autoimmune Diabetes (NIRAD) Study, have been screened for GADAs and IA-2 antibodies (IA-2As) and further characterized for GADA titer, antibodies to thyroid peroxidase (TPO), and HLA DRB1-DQB1 polymorphisms.

RESULTS

Of 4,250 consecutive type 2 diabetic patients, 4.5% had either GADAs and/or IA-2As. Patients with autoimmune diabetes showed a clinical phenotype significantly different from that of type 2 diabetes, including higher fasting glucose and A1C, lower BMI and uric acid, lower prevalence of metabolic syndrome and its components, and higher frequency of TPO antibodies. More interestingly, analysis of GADA titers showed a bimodal distribution that identified two subgroups of patients with high (>32 GADA arbitrary units) and low (< or =32 GADA arbitrary units) GADA titers. Compared with those with low GADA titers, patients with high GADA titers had more prominent traits of insulin deficiency and a profile of more severe autoimmunity resulting in higher A1C, lower BMI, a lower prevalence of metabolic syndrome and its components (P < 0.02 for all), a higher prevalence of IA-2As, TPO antibodies (P < 0.003 for both), and DRB1*03-DQB1*0201 (50 vs. 26.8%, P = 0.001), and a decreasing frequency of DQB1*0602 and DRB1*0403 (from type 2 to low and to high GADA titer autoimmune diabetes; P < 0.001 for trend for both comparisons).

CONCLUSIONS

GADA titers identify two subgroups of patients with adult-onset autoimmune diabetes having distinct clinical, autoimmune, and genetic features.

Immunogenetic risk and protective factors for juvenile dermatomyositis in Caucasians

OBJECTIVE

To define the relative importance (RI) of class II major histocompatibility complex (MHC) alleles and peptide binding motifs as risk or protective factors for juvenile dermatomyositis (DM), and to compare these with HLA associations in adult DM.

METHODS

DRB1 and DQA1 typing was performed in 142 Caucasian patients with juvenile DM, and the results were compared with HLA typing data from 193 patients with adult DM and 797 race-matched controls. Random Forests classification and multiple logistic regression were used to assess the RI of the HLA associations.

RESULTS

The HLA-DRB1*0301 allele was a primary risk factor (odds ratio [OR] 3.9), while DQA1*0301 (OR 2.8), DQA1*0501 (OR 2.1), and homozygosity for DQA1*0501 (OR 3.2) were additional risk factors for juvenile DM. These risk factors were not present in patients with adult DM without defined autoantibodies. DQA1 alleles *0201 (OR 0.37), *0101 (OR 0.38), and *0102 (OR 0.51) were identified as novel protective factors for juvenile DM, the latter 2 also being protective factors in adult DM. The peptide binding motif DRB1 (9)EYSTS(13) was a risk factor, and DQA1 motifs F(25), S(26), and (45)(V/A)W(R/K)(47) were protective. Random Forests classification analysis revealed that among the identified risk factors for juvenile DM, DRB1*0301 had a higher RI (100%) than DQA1*0301 (RI 57%), DQA1*0501 (RI 42%), or the peptide binding motifs. In a logistic regression model, DRB1*0301 and DQA1*0201 were the strongest risk and protective factors, respectively, for juvenile DM.

CONCLUSION

DRB1*0301 is ranked higher in RI than DQA1*0501 as a risk factor for juvenile DM. DQA1*0301 is a newly identified HLA risk factor for juvenile DM, while 3 of the DQA1 alleles studied are newly identified protective factors for juvenile DM.

Genetic determinants of type 1 diabetes across populations

T1D results from autoimmune-mediated destruction of the pancreatic beta cells, a process that is conditioned by multiple genes and environmental factors. The main genetic determinants map to the major histocompatibility complex (MHC), and in particular DR and DQ, although, genes outside the MHC contribute, including the insulin gene, PTPN22, and CTLA-4. There are remarkable differences in genetic susceptibility to T1D between populations. We believe this variation reflects differing frequencies of diabetes causative and protective alleles and haplotypes, and thus remains a major genetic influence linked to the MHC region not accounted for by DR and DQ alleles. In this article, we discuss global variations in genetic susceptibility to T1D in view of current genetic understanding.

GSTT1 and GSTM1 allelic polymorphisms in head and neck cancer patients from Italian Lazio Region

BACKGROUND

The association between head and neck squamous cell carcinoma (HNSCC) and allelic variants of glutathione S-transferase M1 (GSTM1) and -T1 (GSTT1) is currently controversial. The present study investigates the prevalences of GSTT1 and GSTM1 polymorphism in a cohort of 100 head and neck cancer patients, 100 healthy donors and 200 controls with non-neoplastic head and neck diseases from Italian Lazio Region.

METHODS

The patients with benign head and neck pathologies, as well as the healthy donors were matched for age, sex, cigarette smoke (yes/no) and alcohol consumption (yes/no). Molecular definition of GSTT1 and GSTM1 genotype has been performed by means of allele-specific PCR technique.

RESULTS

A significant association between head and neck cancer and GSTM1 null genotype was observed both considering benign disease controls (p=0.001, OR=2.613; 95% C.I.=1.48-4.62), and healthy donors (p=0.0003, OR=3.35; 95% C.I. 1.69-6.67) while no significant association was found with GSTT1 null genotype (p>or=0.14). No interactive association was observed when combining the different genotypes of the two polymorphisms. These results were confirmed after correction for daily number of cigarettes and period of tobacco exposure.

CONCLUSIONS

The present study confirms a role for genetic alterations of GSTM1 detoxifying enzyme as a risk factor for the development of HNSCC in patients from the Italian Lazio Region, independently of age, sex and other confounding variables.

Distribuição e freqüência de alelos e haplotipos HLA em brasileiros com diabetes melito tipo 1

A predisposição genética ao diabetes melito tipo 1 (DM1) é associada a múltiplos genes do sistema de histocompatibilidade humano (HLA) de classe II. Em caucasianos, os antígenos HLA-DR3 e -DR4 são associados à susceptibilidade e o -DR2, à proteção. No Brasil, um país constituído por grande miscigenação entre caucasianos europeus, índios nativos e negros africanos, a base genética do DM1 tem sido pouco estudada. O objetivo desse trabalho foi apresentar uma revisão crítica dos artigos indexados nos bancos de dados MEDLINE e LILACS-BIREME sobre a associação do HLA com DM1 em brasileiros. Todos os oito estudos encontrados foram realizados no sudeste do país. A susceptibilidade imunogenética para o DM1 em brasileiros foi associada com os alelos HLA-DRB1*03, -DRB1*04, -DQB1*0201, -DQB1*0302 e a proteção com os alelos -DQB1*0602 e -DQB1*0301 e os antígenos -DR2 e -DR7. Por ser o Brasil constituído por grande miscigenação, não se pode extrapolar para todo o país estudos realizados em apenas uma região. Faz-se necessário pesquisar populações de várias regiões, analisando sua diversidade alélica para identificar novas associações ou reforçar aquelas já existentes. Esse conhecimento contribuirá para futuras intervenções profiláticas e terapêuticas nos grupos de brasileiros com maior risco de desenvolver DM1.

HLA and disease

Association of HLA and diseases is well known. Several population studies are available suggesting evidence of association of HLAs in more than 40 diseases. HLA found across various populations vary widely. Some of the reasons attributed for such variation are occurrence of social stratification based on geography, language and religion, consequences of founder effect, racial admixture or selection pressure due to environmental factors. Hence certain HLA alleles that are predominantly associated with disease susceptibility or resistance in one population may or may not show any association in other populations for the same disease. Despite of these limitations, HLA associations are widely studied across the populations worldwide and are found to be important in prediction of disease susceptibility, resistance and of evolutionary maintenance of genetic diversity. This review consolidates the HLA data on some prominent autoimmune and infectious diseases among various ethnic groups and attempts to pinpoint differences in Indian and other population.

The rare HLA-DQA1*03-DQB1*02 haplotype confers susceptibility to type 1 diabetes in whites and is preferentially associated with early clinical disease onset in male subjects

The heterozygous combination of DQA1*03-DQB1*0302 (DQ8) and DQA1*05-DQB1*0201 (DQ2) confers the highest known HLA-DQ-linked risk for type 1 diabetes, suggesting a role for transcomplementation. The trans-heterodimer encoded by DQA1*03 and DQB1*02 is also rarely observed in cis in whites. Islet antibody-positive diabetic patients (P; n = 2,238) and control subjects (C; n = 2,223) of white descent were genotyped by a HLA-DQA1-DQB1 dot-blot method. The presence of the DQA1*03-DQB1*02 haplotype was observed in 22 patients (1%) versus 6 controls (0.3%) (odds ratio [OR] = 3.7, p = 0.005). It was more prevalent in whites of Northern African descent, but both in European (n = 3,813) and in Northern African whites (n = 648), the DQA1*03-DQB1*02 haplotype tended to be associated with diabetes (respectively, P 0.3% vs. C 0.03%, OR = 12.2, p = 0.005; and P 2.1% vs. C 0.6%, OR = 3.8, p = 0.03). DRB1 typing revealed that DQA1*03-DQB1*02 is usually associated with the DRB1*0405 risk allele in European patients and with DRB1*0405, DRB1*07 and DRB1*09 in Northern African whites. Like in DQ2/DQ8-positive patients, the presence of DQA1*03-DQB1*02 is preferentially associated with younger age at clinical onset than in other genotypes, but unlike in subjects carrying DQ2/DQ8, earlier clinical manifestation was mostly restricted to male subjects, often carrying DR3 and/or DQB1*02 on the other chromosome. These results are compatible with an effect of cis-encoded heterodimers or with previously suggested interactions of X-linked genetic factors with (DR3-)DQB1*02 haplotypes.

Specific HLA-DRB and -DQB alleles and haplotypes confer disease susceptibility or resistance in Bahraini type 1 diabetes patients

Insofar as genetic susceptibility to type 1 diabetes is associated with HLA class II genes, with certain allelic combinations conferring disease susceptibility or resistance, this study assessed the distributions of HLA-DR and -DQ among 107 unrelated patients with type 1 diabetes and 88 healthy controls from Bahrain, all of Arab origin. The HLA-DRB and -DQB genotypes were determined by PCR-sequence-specific priming. The following alleles showed the strongest association with type 1 diabetes among patients versus controls according to their frequencies: DRB1*030101 (0.430 versus 0.097; P < 0.001), DRB1*040101 (0.243 versus 0.034; P < 0.001), DQB1*0201 (0.467 versus 0.193; P < 0.001), and DQB1*0302 (0.229 versus 0.091; P < 0.001). When the frequencies of alleles in controls were compared to those in patients, negative associations were seen for DRB1*100101 (0.085 versus 0.014; P < 0.001), DRB1*110101 (0.210 versus 0.060; P < 0.001), DQB1*030101 (0.170 versus 0.075; P = 0.006), and DQB1*050101 (0.335 versus 0.121; P < 0.001). In addition, the DRB1*030101-DQB1*0201 (70.1 versus 22.7%; P < 0.001) and DRB1*030101-DQB1*0302 (21.5 versus 0.0%; P < 0.001) genotypes were more prevalent among patients, thereby conferring disease susceptibility, whereas the DRB1*100101-DQB1*050101 (20.5 versus 2.8%; P < 0.001), DRB1*110101-DQB1*030101 (28.4 versus 8.4%; P < 0.001), and DRB1*110101-DQB1*050101 (30.7 versus 0.9%; P < 0.001) genotypes were more prevalent among controls, thus assigning a protective role. These results confirm the association of specific HLA-DR and -DQ alleles and haplotypes with type 1 diabetes and may underline several characteristics that distinguish Bahraini patients from other Caucasians patients.

HLA DR phenotypic frequencies and genetic risk of Type 1 diabetes in west region of Algeria, Tlemcen

Background

The main genomic region controlling the predisposition to type 1 diabetes is the Human Leukocyte Antigens (HLA) class II of the major histocompatibility complex. Association with different HLA types depends also on the studied populations. In our investigation, we tried to measure the phenotypic HLA class II association frequencies of DR3 and/or DR4 antigens, using a serologic method called microlymphocytotoxicity analysis, in diabetic and nondiabetic (ND) subjects originating from the west-Algerian region of Tlemcen. The aim of the present study was to determine which HLA DR antigens represent a high susceptibility to develop the disease in this area. Using a case-control retrospective study design, we randomly recruited ninety-one related subjects, 39 type 1 diabetics and 52 ND as controls, at the Internal Medicine Board of Medical Centre University of Tlemcen.

Results

DR3 antigen frequencies were comparable between the type 1 diabetics and the ND subjects and showed no association with the disease (p = 1.000, OR = 0.95), whereas DR4 and DR3DR4 antigens were associated with susceptibility to develop type 1 diabetes (DR4; OR = 2.10, DR3DR4; OR = 1.30). Also, no incidence for DR3 (p = 0.2646) or DR3DR4 (p = 0.0699) antigen frequencies was related to the sex ratio. However, significant differences in HLA DR4 frequencies between type 1 diabetics and ND were found to be related to sex (p = 0.0085).

Conclusion

Taken together, our investigation showed that the strongest association with type 1 diabetes was noticed in the presence of HLA DR4 antigens followed by DR3DR4 antigens. This study highlighted a characteristic of Tlemcen population; a history of consanguineous marriages. Association studies between the disease and genetic polymorphisms should be undertaken in a population where consanguinity is more limited to reduce confounding in result interpretations.

HLA class II typing in newborns reveals a low frequency of the DRB1*04 allele and a high frequency of DRB1*11 allele in three regions of continental Italy

As part of a longitudinal study aimed at defining the natural history of prediabetic autoimmunity and predicting the risk of future cases of type 1 diabetes, 3607 newborns from three regions of continental Italy (Lombardia, Liguria, and Lazio) were subjected to genetic testing to determine human leukocyte antigen-DRB1 (HLA-DRB1) and -DQB1 allele and phenotype frequencies. Polymerase chain reaction and immobilized sequence-specific oligonucleotide probe assays were used to identify ten DRB1 allele lineages and three DQB1 alleles. No major inter-regional differences emerged in the allelic distribution indicating homogeneous distribution of the HLA DRB1-DQB1 alleles among the three regions analyzed. Comparison of our data with those published for other Caucasian populations reveals that these three regions are characterized by a very low frequency of DRB1*04 (8%) and a high frequency of DRB1*11 (25%). The phenotype frequencies of HLA-DQB1*0302 and DQB1*0602 observed are also lower than those reported for other populations. Furthermore, the DRB1*04-DQB1*0302 haplotype was relatively infrequent in our population (5.3% of the newborns tested). These findings furnish a genetic "portrait" of the populations of the analyzed regions that will be useful not only for investigation of the genetic risk of type 1 diabetes mellitus in Italy but also for studies of other autoimmune diseases related to HLA genotypes.

HLA DR-DQ-encoded genetic determinants of childhood-onset type 1 diabetes in Finland: an analysis of 622 nuclear families

The diabetes predisposing effect of HLA genes is defined by a complex interaction of various haplotypes. We analyzed the disease association of HLA DRB1-DQA1-DQB1 genotypes in a large nuclear family cohort (n = 622) collected in Finland. Using the affected family based artificial control approach we aimed at characterizing all detectable disease-specific HLA haplotype and genotype effects. The DRB1*0401-DQB1*0302 haplotype was the most prevalent disease susceptibility haplotype in the Finnish population followed by (DR3)-DQA1*05-DQB1*02 and DRB1*0404-DQB1*0302. DRB1*0405-DQB1*0302 conferred the highest disease risk, although this haplotype was very rare. The DRB1*04-DQB1*0304 was also associated with increased disease risk, an effect detected for the first time in the Finnish population. The following haplotypes showed significant protection from the disease and are listed in decreasing order of the strength of their effect: (DR7)-DQA1*0201-DQB1*0303, (DR14)-DQB1*0503, (DR15)-DQB1*0602, DRB1*0403-DQB1*0302, (DR13)-DQB1*0603, (DR11/12/13)-DQA1*05-DQB1*0301, (DR1)-DQB1*0501. In addition to the DRB1*0401/0404-DQB1*0302/(DR3)-DQA1*05-DQB1*02 genotype and DRB1*04-DQB1*0302 homozygous genotypes, heterozygous combinations DRB1*0401-DQB1*0302/(DR13)-DQB1*0604, approximately /(DR8)-DQB1*04, approximately /(DR9)-DQA1*03-DQB1*0303, approximately /(DR1)-DQB1*0501 and approximately /(DR7)-DQA1*0201-DQB1*02 were also disease-associated. As a new finding in this population, the (DR3)-DQA1*05-DQB1*02 homozygous and (DR3)-DQA1*05-DQB1*02/(DR9)-DQA1*03-DQB1*0303 heterozygous genotypes conferred disease susceptibility. Similarly, the DRB1*0401-DQB1*0302/(DR13)-DQB1*0603 genotype was disease predisposing, implying that DQB*0603-mediated protection from diabetes is not always dominant. Comparison of our findings with published data from other populations indicates a significant disease-specific heterogeneity of the (DR8)-DQB1*04, (DR7)-DQA1*0201-DQB1*02 and (DR3)-DQA1*05-DQB1*02 haplotypes.

Similar incidence of type 1 diabetes in two ethnically different populations (Italy and Slovenia) is sustained by similar HLA susceptible/protective haplotype frequencies

The incidence of type 1 diabetes (T1DM) seems to depend in part on the population frequencies of susceptible and protective HLA haplotypes. The present study aimed to (i): characterize the genetic susceptibility to T1DM in the Slovenian population, (ii) test the general hypothesis that T1DM incidence is related to the frequencies of susceptible/protective haplotypes, (iii) compare allele, haplotype and genotype frequencies in Slovenians and Italians that represent two white populations with a similar incidence of T1DM (7.9/100,000/year and 8.1/100,000/year, respectively). The haplotype found most frequently among Slovenian T1DM patients was DRB1*0301-DQA1*0501-DQB1*0201 (53%). The DR4-DQA1*0301-DQB1*0302 haplotypes conferring susceptibility to T1DM were those bearing DRB1*0401 (OR = 12), DRB1*0404 (OR = 4.7) and DRB1*0402 (OR = 4.5). Negative associations with the disease were found for the following haplotypes: DRB1*1501-DQA1*0102-DQB1*0602, DRB1*1301-DQA1*0102-DQB1*0603, DRB1*1101/1104-DQA1*0501-DQB1*0301, and DRB1*1401-DQA1*0101-DQB1*0503. Our findings indicate that the low frequencies of susceptible genotypes, in particular, DR3-DQA1*0501-DQB1*0201/DR4-DQA1*0301-DQB1*0302, together with a high frequency of protective haplotypes, could in part explain the low incidence of T1DM in the Slovenian population. The combined frequencies of susceptible genotypes were similar in the two populations (Slovenia = 19.2%, Italy = 17.6%), and the 95% confidence limits of the OR values for each genotype in the two populations overlapped, indicating no significant differences between the values. We conclude that the similar incidences of T1DM in Italian and Slovenian populations are in part a reflection of similar frequencies of HLA susceptible/protective haplotypes.