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

Abstract

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.

HLA‐DR3 mediated CD4 T cell response against GAD65 in type 1 diabetes patients

“…[15][16][17] Further, HLA-DRB1*03-DQA1*05-DQB1*02 haplotype is reported to be strongly associated with the presence of GADA in T1D patients. 19,20,[26][27][28] A recent study that investigated the association between epitope-specific GADA and the HLA-DR-DQ haplotypes revealed that T1D-susceptible HLA haplotypes, particularly DR3 positive haplotypes, associate strongly with GAD65Ab multiepitope positivity, suggesting that an important pathological mechanism in T1D might involve the presentation of GAD65 peptides by both HLA-DR and HLA-DQ molecules. 29 The present study was carried out to characterize the GAD65 epitopes possibly presented by HLA-DR3/DQ2 molecules to CD4 T cells and compare them between T1D patients and HC.…”

“…For GADA screening, we used commercially available ELISA assay kit, ElisaRSR™GADAb kit (RSR Ltd., United Kingdom). The GADA was estimated by following the protocol as described previously 19 …”

“…One hundred and ten (110) T1D patients, clinically diagnosed as per the criteria described under the Registry of Youth Onset Diabetes in India, 19,22 were recruited from Out Patients Department/Diabetes of the Young (DOY) Clinic, Department of Endocrinology and Metabolism, All India Institute of Medical Sciences, New Delhi, India. This study did not include prediabetic individuals and all patients who were part of this study were already on exogenous insulin therapy for diabetes management.…”

“…[15][16][17][18] Further, studies revealed that glutamic acid decarboxylase 65 autoantibody (GADA) is also associated with HLA-DRB1*03 and DQB1*02 alleles in T1D patients, suggesting an important role of these HLA class II alleles in the generation of GADA. [19][20][21] However, the exact mechanism behind these genetic associations remains elusive and, therefore, it is of great interest to identify diabetogenic GAD65 peptides and their role in HLA-DR3-DQ2 mediated autoimmune response in T1D. Further, it is not known whether there is a difference in the T cell response against the diabetogenic peptides, particularly that of CD4 T cells, between T1D patients and healthy controls (HCs) carrying HLA-DRB1*03-DQA1*05-DQB1*02 haplotype.…”

“…Immunogenetic studies have reported a strong association of HLA‐DRB1*03‐DQA1*05‐DQB1*02 (DR3‐DQ2) haplotype with North Indian T1D patients 15–18 . Further, studies revealed that glutamic acid decarboxylase 65 autoantibody (GADA) is also associated with HLA‐DRB1*03 and DQB1*02 alleles in T1D patients, suggesting an important role of these HLA class II alleles in the generation of GADA 19–21 . However, the exact mechanism behind these genetic associations remains elusive and, therefore, it is of great interest to identify diabetogenic GAD65 peptides and their role in HLA‐DR3‐DQ2 mediated autoimmune response in T1D.…”