Two DRB3 residues predictively associate with the progression to type 1 diabetes among DR3 carriers

Area of Science:

• Immunogenetics
• Autoimmune diseases
• Molecular biology

Background:

• Human Leukocyte Antigen (HLA) genes, particularly HLA-DR and HLA-DQ, are strongly associated with type 1 diabetes (T1D) susceptibility and progression.
• Previous studies indicate high linkage disequilibrium between HLA-DR and HLA-DQ genes, complicating the precise role of each.
• Understanding the specific genetic factors within HLA-DR that influence T1D progression is crucial for developing targeted interventions.

Purpose of the Study:

• To investigate the association of specific HLA-DRB3 alleles and amino acid motifs with the progression of type 1 diabetes (T1D) in a cohort of DR3 carriers.
• To identify key residues and molecular motifs within the HLA-DRB3 molecule that modulate T1D progression rates.
• To explore the potential role of differential autoantigenic epitope binding in T1D pathogenesis.

Main Methods:

• Analysis of an integrated cohort from two completed clinical trials.
• Genotyping for HLA-DRB3 alleles and identification of specific amino acid motifs (RY and LF) within the DRB3 molecule.
• Statistical analysis, including hazard ratio calculations, to assess the association of genetic factors with T1D progression.

Main Results:

• Specific HLA-DRB3 alleles (DRB3*01:01:02 and *02:02:01) showed negative and positive associations, respectively, with T1D progression in DR3 carriers.
• Two residues (β11 and β26) in pockets 6 and 4 of the DRB3 molecule were identified as critical for T1D progression.
• The RY motif was associated with delayed progression (HR=0.73), while the LF motif was linked to accelerated progression (HR=2.38) among DR3 carriers. Carriers of the LF motif showed significantly faster progression than RY motif carriers (HR=1.39).

Conclusions:

• Specific HLA-DRB3 alleles and amino acid motifs significantly influence the rate of type 1 diabetes progression.
• The identified residues and motifs (RY and LF) within the DRB3 molecule play a role in modulating T1D progression, potentially through differential binding of autoantigenic epitopes.
• These findings warrant further investigation into DRB3-binding peptides as potential therapeutic targets for T1D.