The HLA region is responsible for almost 50% of the genetic risk of type 1 diabetes (T1D). However, haplotypes and their effects on risk or protection vary among different ethnic groups, mainly in an admixed population. We aimed to evaluate the HLA class II genetic profile of Brazilian individuals with T1D and its relationship with self-reported color/race. This was a nationwide multicenter study conducted in 10 Brazilian cities. We included 1,019 T1D individuals and 5,116 controls matched for the region of birth and self-reported color/race. control participants belonged to the bone marrow transplant donor registry of Brazil (REDOME). HLA-class II alleles (DRB1, DQA1, and DQB1) were genotyped using the SSO and NGS methods. The most frequent risk and protection haplotypes were HLA~DRB1*03:01~DQA1*05:01 g~DQB1*02:01 (OR 5.8, p < 0.00001) and HLA~DRB1*07:01~DQA1*02:01~DQB1*02:02 (OR 0.54, p < 0.0001), respectively, regardless of self-reported color/race. Haplotypes HLA~DRB1*03:01~DQA1*05:01 g~DQB1*02:01 and HLA~DRB1*04:02~DQA1*03:01 g~DQB1*03:02 were more prevalent in the self-reported White group than in the Black group (p = 0.04 and p = 0.02, respectively). The frequency of haplotype HLA~DRB1*09:01~DQA1*03:01 g~DQB1*02:02 was higher in individuals self-reported as Black than White (p = <0.00001). No difference between the Brazilian geographical regions was found. Individuals with T1D presented differences in frequencies of haplotypes within self-reported color/race, but the more prevalent haplotypes, regardless of self-reported color/race, were the ones described previously in Europeans. We hypothesize that, in the T1D population of Brazil, although highly admixed, the disease risk alleles come mostly from Europeans as a result of centuries of colonization and migration.Type 1 diabetes (T1D) is a chronic polygenic disease that arises from the combination of multiple genetic and environmental factors 1 . The HLA region on chromosome 6p21 is known to be responsible for almost 50% of the genetic risk, and it has been associated with diabetes since the 1970s 2 . Even though HLA Class I genes and non-HLA genes also contribute to T1D risk, Class II alleles such as DR and DQ demonstrate the strongest associations with the disease 1,3 .Susceptibility to T1D is mainly associated with haplotype DRB1*04~DQA1*03:01~DQB1*03:02, followed by DRB1*03:01~DQA1*05:01~DQB1*02:01 3 . More than 90% of patients carry one of those two haplotypes, and 30% carry both of them, while the prevalence in the general population is 2% 4-6 , including previous data from regional populations and familial studies from Brazil 7-9 .In recent years, several risk scores for the diagnosis and risk assessment of T1D have been proposed, using growing and extensive knowledge about T1D genetics 1 . Most of them are based on the presence of high-risk HLA alleles described in previous studies 10-12 .

Background Although the well-established role of the HLA genes on the predisposition of type 1 diabetes (T1D), its contribution to the development and progression of diabetic retinopathy is still unclear, especially in admixed populations. We aimed to study the relationship between HLA alleles and severe diabetic retinopathy in a highly admixed population of T1D patients. Methods This was a nested case-control study based on a cross-sectional, nationwide survey conducted in Brazil. We included 117 patients with severe diabetic retinopathy and 117 random controls composed of T1D patients without retinopathy, matched for diabetes duration. HLA-class II genes (HLA-DRB1, -DQA1, and -DQB1) were genotyped using the SSO and NGS methods. Results Haplotypes HLA-DRB1*04:05 ~ DQA1*03:01 g ~ DQB1*03:02 (OR 1.75, CI 0.97–3.16, p value 0.058) and HLA-DRB1*13:02 ~ DQA1*01:02 ~ DQB1*06:04 (OR 5.18, CI 1.12–23.09, p value 0.019) were more prevalent on the severe DR group but they did not present statistically difference after Bonferroni correction. The most frequent haplotype on both groups was HLA-DRB1*03:01 ~ DQA1*05:01 g ~ DQB1*02:01 (29.6% on severe DR and 33.33% on the control group). Conclusions Our study showed no influence of HLA genes on the development of DR. Further longitudinal data is needed to better understand the role of genetic factors on this multifactorial significant microvascular complication.

No abstract

No abstract