HLA-associated genetic resistance and susceptibility to type I diabetes in French North Africans and French natives

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.

HLA-DQ genotypes - but not immune markers - differ by ethnicity in patients with childhood onset type 1 diabetes residing in Belgium

AIM

The aim of this study was to compare genetic (HLA-DQ) and immune markers in a large population of type 1 diabetic (T1D) children and adolescents residing in the same environment, but of different ethnic origin: European Caucasians (EC), Moghrabin Caucasians (MC), Black Africans (BA) and of Mixed Origin (MO).

METHODS

Retrospective study, including 452 patients with T1D aged 0.1-17.5 yr at diagnosis recruited at the Diabetology Clinic of the University Children's Hospital Queen Fabiola from May 1995 to March 2013. HLA-DQ genotyping, diabetes-associated autoantibodies, organ-specific autoantibodies, and other markers of autoimmunity were studied.

RESULTS

The proportion of the different ethnic groups was: 55% EC, 35% MC, 6% BA, and 4% MO. Between these four groups, there were no significant differences concerning age, hemoglobin A1c (HbA1c), presence of diabetic ketoacidosis, random C-peptide level at diagnosis and 2 yr later. The two most frequent haplotypes were DQA1*0501-DQB1*0201 and DQA1*0301-DQB1*0302 with a significant higher prevalence in MC and EC (p = 0.002 and 0.03, respectively). The high-risk heterozygous genotype DQA1*0301-DQB1*0302/DQA1*0501-DQB1*0201 was more frequent in EC than in MC, whereas the homozygous genotype DQA1*0501-DQB1*0201/DQA1*0501-DQB1*0201 was more prevalent in MC (p = 0.019). These susceptible genotypes were more frequent in youngest patients (p = 0.003). Diabetes-associated autoantibodies, organ-specific autoantibodies, and other immune markers did not statistically differ between ethnic groups.

CONCLUSIONS

These observations in a large population of T1D children and adolescents of different ethnic groups residing in Belgium show significant differences in HLA-DQ status, but not in diabetes-associated autoantibodies, organ-specific autoantibodies, or other immune markers.

The profile of HLA-DRB1 alleles in Arabs with type 1 diabetes; meta-analyses

Genes from the HLA complex have a major contribution in type 1 diabetes (T1D), which results from an interplay between environmental and genetic factors. The latter can explain some of the geographic variability in T1D occurrence around the world. Of a particular importance in this regard are the HLA-DR, -DP and -DQ loci. Consequently, we aimed at elucidating the collective genetic profiles of various alleles relating to HLA-DRB1 and -DP in T1D patients throughout the Arab World using the tools of meta-analysis. As for HLA-DQA1 and DQB1 alleles; this analysis was completed and published previously (see Introduction). As a result of limited availability of relevant studies of the HLA-DP locus, only HLA-DRB1 alleles were tackled in this paper. Our study showed that significant increases in T1D risk resulted from harboring the alleles DRB1*03:01 and *04:05 (odds ratio 7.76 and 7.52, respectively). DRB1*04:01 and *04:02 were also predisposing for T1D in Arabs. Very strong evidence supported the protective effects of DRB1*10:01, *13:01, *15:02 and *16:01, with low heterogeneity and no publication bias. The results from the series of meta-analyses performed in this study help to complete the global genetic epidemiological map of T1D by providing statistically robust data from the Arab World.

Family-based association study of HLA class II with type 1 diabetes in Moroccans

BACKGROUND

The T1D is a multifactorial disease; with a strong genetic control. The human leukocyte antigen (HLA) system plays a crucial role in the autoimmune process leading to childhood diabetes. About 440,000 of the childhood population of the world (1.8 billion children under 14 years of age), have type 1 diabetes, and each year an additional 70,000 develop this disorder. The objective of this study was to investigate the distribution of HLA class II in Moroccan families of diabetic children to identify susceptibility alleles of the Moroccan population.

SUBJECTS AND METHODS

We included in this study, Moroccan families who have at least one child with T1D. The age of onset of diabetes was less than 15 years. HLA class II (DRB1* and DQB1*) was carried out by molecular biology techniques (PCR-SSP and PCR-SSO). The FBAT test (family-based association test) was used to highlight the association between T1D and the HLA-DRB1* and -DQB1* polymorphism.

RESULTS

The association of HLA class II (DRB1*, DQB1*) in type 1 diabetes was analyzed in fifty-one Moroccan families, including 90 diabetics. The results revealed that the most susceptible haplotypes are the DRB1*03:01-DQB1*02:01, DRB1*04:05-DQB1*03:02 (Z=3.674, P=0.000239; Z=2.828, P=0.004678, respectively). And the most protective haplotype is the DRB1*15-DQB1*06.

CONCLUSION

This is the first family-based association study searching for an association between HLA class II and T1D in a Moroccan population. Despite the different ethnic groups forming Morocco, Moroccan diabetics share the most susceptible and protective HLA haplotypes with other Caucasians populations, specifically the European and Mediterranean populations.

Trends in the frequency of HLA DR-DQ haplotypes among children and adolescents with type 1 diabetes mellitus in the Southeast Region of Turkey

OBJECTIVE

The aim of this study was to determine the frequency of HLA DR-DQ haplotypes in children with type 1 diabetes mellitus (T1DM) in the Southeast Region of Turkey.

METHODS

Eighty children and adolescents with T1DM and eighty control subjects participated in the study. HLA-DR, DQ was typed using polymerase chain reaction and sequence-specific priming technique.

RESULTS

HLA DRB1*03 allele was significantly more common in patients than in control subjects. HLA DRB1*11, HLA DRB1*13 and HLA DRB1*14 allele frequencies were significantly lower in patients than in controls. DQB1*02 allele was more common in patients, whereas DQB1*03 allele was more frequent in control subjects. HLA DRB1*03-DQB1*02 haplotype was more frequently observed among patients.

CONCLUSION

These results confirm the similar potential trends in the frequency distribution of HLA susceptibility genes with T1DM previously observed in Turkey and in other Caucasian populations.

Etiopathogenesis of insulin autoimmunity

Autoimmunity against pancreatic islet beta cells is strongly associated with proinsulin, insulin, or both. The insulin autoreactivity is particularly pronounced in children with young age at onset of type 1 diabetes. Possible mechanisms for (pro)insulin autoimmunity may involve beta-cell destruction resulting in proinsulin peptide presentation on HLA-DR-DQ Class II molecules in pancreatic draining lymphnodes. Recent data on proinsulin peptide binding to type 1 diabetes-associated HLA-DQ2 and -DQ8 is reviewed and illustrated by molecular modeling. The importance of the cellular immune reaction involving cytotoxic CD8-positive T cells to kill beta cells through Class I MHC is discussed along with speculations of the possible role of B lymphocytes in presenting the proinsulin autoantigen over and over again through insulin-carrying insulin autoantibodies. In contrast to autoantibodies against other islet autoantigens such as GAD65, IA-2, and ZnT8 transporters, it has not been possible yet to standardize the insulin autoantibody test. As islet autoantibodies predict type 1 diabetes, it is imperative to clarify the mechanisms of insulin autoimmunity.

Time-resolved FRET method for typing polymorphic alleles of the human leukocyte antigen system by using a single DNA probe

By tens-of-picosecond resolved fluorescence detection we study Förster resonance energy transfer between a donor and a black-hole-quencher acceptor bound at the 5'- and 3'-positions of a probe-oligonucleotide matching an allelic region of a class II antigen of the human leukocyte antigen system, namely the region between codons 52 and 57 of the HLA DQB1 0201 allele. This dual-labelled probe is annealed with either the exactly complementary allelic sequence or with polymorphic sequences of the same region. We detect the longest-lived donor fluorescence in the case of the perfect hybridization achieved with the 0201 allele and definitely faster and distinct decays for the other allelic variants, some of which are single-nucleotide polymorphic variants.

Genetic determinants of Type 1 diabetes: immune response genes

Type 1 diabetes (T1D) is a polygenic autoimmune disease. Susceptibility to T1D is strongly linked to a major genetic locus that is the MHC, and several other minor loci including insulin, cytotoxic T-lymphocyte-associated antigen-4, PTPN22 and others that contribute to diabetes risk in an epistatic way. We have observed that there are three sets of DR3-positive autoimmunity-favoring haplotypes in the north-Indian population, including B50-DR3, B58-DR3 and B8-DR3. The classical Caucasian autoimmunity favoring AH8.1 (HLA-A1-B8-DR3) is rare in the Indian population, and has been replaced by a variant AH8.1v, which differs from the Caucasian AH8.1 at several gene loci. Similarly, there are additional HLA-DR3 haplotypes, A26-B8-DR3 (AH8.2), A24-B8-DR3 (AH8.3), A3-B8-DR3 (AH8.4) and A31-B8-DR3 (AH8.5), of which AH8.2 is the most common. The fact that disease-associated DR3-positive haplotypes show heterogeneity in different populations suggests that these might possess certain shared components that are involved in the development of autoimmunity.