The association of the HLA-A*24:02, B*39:01 and B*39:06 alleles with type 1 diabetes is restricted to specific HLA-DR/DQ haplotypes in Finns.

BACKGROUND: We analysed the previously reported association of the HLA-A*24:02, B*18 and B*39 alleles with type 1 diabetes and diabetes associated autoimmunity in the Finnish population applying HLA-DR/DQ stratification. MATERIALS & METHODS: Haplotype transmission was analysed in 2424 nuclear families from the Finnish Paediatric Diabetes Register. Survival analysis was applied to study the development of islet autoantibodies and further progression to clinical diabetes in the prospective follow-up cohort from the Finnish Type 1 Diabetes Prediction and Prevention (DIPP) Study. The subjects were genotyped for specific HLA class I alleles by sequence-specific hybridization using lanthanide labelled nucleotide probes. RESULTS: The HLA-B*39:06 allele was found almost exclusively on the (DR8)-DQB1*04 haplotype in which its presence changed the disease risk status of the whole haplotype from neutral to predisposing. The HLA-A*24:02 and the B*39:01 alleles increased the diabetes-associated risk of the DRB1*04:04-DQA1*03-DQB1*03:02 haplotype but the alleles were in linkage disequilibrium and no independent effect could be detected. Within the DIPP cohort, neither the A*24:02 nor the B*39:01 allele were associated with seroconversion but were in contrast associated with increased progression from seroconversion to clinical disease. DISCUSSION & CONCLUSIONS: The independent predisposing effect of the HLA-B*39:06 allele with type 1 diabetes was confirmed in the Finnish population but the association of the A*24:02 and B*39:01 alleles remained inconclusive whilst both A*24:02 and B*39:01 affected the progression rate from seroconversion to autoantibody positivity to overt type 1 diabetes.

The HLA-B*39 allele increases type 1 diabetes risk conferred by HLA-DRB1*04:04-DQB1*03:02 and HLA-DRB1*08-DQB1*04 class II haplotypes.

To further characterise the effect of the HLA-B*39 allele on type 1 diabetes risk we assessed its role in different HLA-DR/DQ haplotypes and genotypes using 1764 nuclear families with a diabetic child collected in the framework of the Finnish Paediatric Diabetes Register. HLA assays were based on sequence specific hybridization using lanthanide labelled oligonucleotide probes. Transmissions of major HLA-DR/DQ haplotypes with and without the HLA-B*39 allele to diabetic index cases were analysed by direct haplotype and allele counting. The HLA-B*39 allele significantly increased the disease risk conferred by DRB1*04:04-DQA1*03-DQB1*03:02 and (DR8)-DQB1*04 haplotypes. The same effect was observed on genotype level as disease association for the HLA-B*39 allele was observed in multiple genotypes containing DRB1*04:04-DQA1*03-DQB1*03:02 or (DR8)-DQB1*04 haplotypes. Finally we considered the two common subtypes of the HLA-B*39 allele, B*39:01 and B*39:06 and observed their unequal distribution when stratified for specific DR-DQ haplotypes. The risk for type 1 diabetes conferred by certain DR/DQ haplotypes is modified by the presence of the HLA-B*39 and this confirms the independent disease predisposing effect of the HLA-B*39 allele. The results can be applied in enhancing the sensitivity and specificity of DR/DQ based screening programs for subjects at disease risk.

Associations of polymorphisms in non-HLA loci with autoantibodies at the diagnosis of type 1 diabetes: INS and IKZF4 associate with insulin autoantibodies.

OBJECTIVE: More than 50 loci outside the human leukocyte antigen (HLA) region have been confirmed to affect type 1 diabetes (T1D) risk but their effect on ß-cell autoimmunity is poorly defined. We analyzed the association of 35 single nucleotide polymorphism (SNP) markers previously associated with T1D with the presence of disease-predictive autoantibodies at the time of T1D diagnosis. SUBJECTS AND METHODS: The study cohort comprised 1554 children diagnosed with T1D before the age of 15 yr. The associations between various genotypes and positivity for antibodies against islet cells [islet cell antibodies (ICA)], insulin [insulin autoantibodies (IAA)], glutamic acid decarboxylase (GADA), islet antigen 2 (IA2A), and zinc transporter 8 (ZnT8A) were analyzed. RESULTS: INS gene polymorphism rs689 and IKZF4 polymorphism (rs1701704) were strongly associated with IAA positivity at the time of T1D diagnosis (p = 0.000004 and 0.00044, respectively). The presence of the T1D-risk conferring INS AA genotype was associated with IAA. In contrast, the presence of the susceptible C allele of the IKZF4 marker was inversely associated with IAA. The INS and IKZF4 polymorphisms were not significantly associated with ICA, GADA, IA2A, or ZnT8A positivity. CONCLUSIONS: Both INS and IKZF4 polymorphisms modified the probability of IAA positivity at time of T1D onset but the inverse association of IKZF4 risk allele with IAA suggests that the IKZF4 polymorphism is involved in a pathway of ß-cell autoimmunity alternate to the route characterized by IAA and development of T1D in early childhood. The IKZF4 gene encodes Eos, which is implicated to play an important role in Treg programming where this gene might exert its influence on T1D risk.

Evidence for linkage to and association with type 1 diabetes at the 3q21 region in the Finnish population.

IDDM9-region on chromosome 3q has shown suggestive evidence for linkage to type 1 diabetes in some but not all genome scans. We analyzed 22 microsatellite markers in 121 Finnish type 1 diabetes multiplex families across the IDDM9-region. Two-point maximum LOD scores of 3.4 and 2.5 were detected with markers D3S1589 and D3S3606, respectively. Two markers were further tested for association using the transmission disequilibrium test in 384 Finnish type 1 diabetes simplex families. Marker AFM203wd10 showed association with type 1 diabetes (P = 0.0002 for allele R16). Association was present in families with children carrying the HphI-23 AA risk genotype at IDDM2 but not in families with children carrying protective AT or TT genotypes implying interaction between the two loci. Our data gives credence to earlier findings of linkage in this region and suggests a location for a polymorphism affecting type 1 diabetes susceptibility in the area surrounding AFM203wd10.

Type 1 diabetes is insulin -2221 MspI and CTLA-4 +49 A/G polymorphism dependent.

BACKGROUND: Several studies have demonstrated an association of type 1 diabetes with specific alleles of HLA class II molecules, as with polymorphisms of insulin gene region. The aim of our study was to evaluate the interaction of insulin -2221 MspI polymorphism to type 1 diabetes susceptibility in connection with autoimmunity associated gene--CTLA-4 polymorphism. MATERIALS AND METHODS: Insulin -2221 MspI C/T and CTLA-4 +49 A/G polymorphisms were detected by restriction fragment-length polymorphism analysis or oligonucleotide hybridization in type 1 (n = 69), type 2 diabetes (n = 301) patients and 158 healthy controls. Regression model adjusted for age, gender and gene polymorphisms was studied. RESULTS: C-allele of insulin -2221 MspI and G-allele of +49 CTLA-4 were significant risk factors for type 1 diabetes (crude OR 3.53 and 1.59, respectively) and this impact increased in the homozygous form of both alleles. The regression model supported the idea of insulin CC and CTLA-4 GG genotypes for an independent and clearly significant risk for developing type 1 diabetes. We could not detect any significant correlation between investigated polymorphisms and type 2 diabetes. CONCLUSIONS: There exists a significant association between the C-allele of -2221 MspI in the insulin gene and type 1 diabetes. The CTLA-4 G-allele is also positively correlated with type 1 diabetes. According to the regression model the investigated gene polymorphisms are independent risk factors for development of type 1 diabetes in the Estonian population. We propose that -2221 MspI is a good marker for evaluation of risk of insulin gene haplotype in type 1 diabetes patients.

Temporal changes in the frequencies of HLA genotypes in patients with Type 1 diabetes--indication of an increased environmental pressure?

AIMS/HYPOTHESIS: The incidence of Type 1 diabetes has increased 2.5 times during the time period from 1966 to 2000 in Finland-a general trend seen in almost all developed countries that can only be explained by environmental factors. The aim of this study was to test the possible effect of a changing environment on distribution of genotypes associated with disease susceptibility. METHODS: HLA DRB1-DQA1-DQB1 genes and two diabetes-associated polymorphisms at IDDM2 and IDDM12 were analyzed. The frequencies of genotypes were compared between cases diagnosed with childhood-onset Type 1 diabetes during the period of 1939-1965 (n=367) and those diagnosed between 1990 and 2001 (n=736). Chi-square statistics or the Fisher's Exact test were used for the comparison of frequencies of analyzed haplotypes and genotypes in the two groups. RESULTS: The frequencies of (DR3) -DQA1*05-DQB1*02 and (DR4) -DQB1*0302 risk haplotypes and the high risk (DR3) -DQA1*05-DQB1*02/DRB1*0401-DQB1*0302 genotype were higher while proportion of patients carrying protective haplotypes-(DR15) -DQB1*0602 and (DR1301) -DQB1*0603-or protective genotypes was lower in patients diagnosed before 1965 as compared to those who developed disease after 1990. No temporal variation was found in the frequencies of genotypes at IDDM2 and IDDM12. CONCLUSION/INTERPRETATION: Our data suggest that the need for genetic susceptibility to develop Type 1 diabetes has decreased over time due to an increasing environmental pressure and this results in a higher disease progression rate especially in subjects with protective HLA genotypes.