Identification of an Amino Acid Motif in HLA-DRβ1 That Distinguishes Uveitis in Patients With Juvenile Idiopathic Arthritis.

Abstract

Uveitis is a visually debilitating disorder that affects up to 30% of children with the most common forms of juvenile idiopathic arthritis (JIA). The disease mechanisms predisposing only a subgroup of children to uveitis are unknown. This study was undertaken to identify genetic susceptibility loci for uveitis in JIA, using a genome-wide association study in 522 children with JIA. Two cohorts of JIA patients with ophthalmologic follow-up data were genotyped. Data were then imputed using a genome-wide imputation reference panel, and an HLA-specific reference panel was used for imputing amino acids and HLA types in the major histocompatibility complex (MHC). After imputation, genome-wide and MHC-specific analyses were performed, and a reverse immunology approach was utilized to model antigen presentation at 13 common HLA-DRβ1 alleles. Presence of the amino acid serine at position 11 (serine 11) in HLA-DRβ1 was associated with an increased risk of uveitis in JIA patients (odds ratio [OR] 2.60, P = 5.43 × 10^-10 ) and was specific to girls (P_females = 7.61 × 10^-10 versus P_males = 0.18). Serine 11 resides in the YST motif in the peptide-binding groove of HLA-DRβ1; all 3 amino acids in this motif are in perfect linkage disequilibrium and show identical association with disease. Quantitative prediction of binding affinity revealed that HLA-DRβ1 alleles with the YST motif could be distinguished on the basis of discernable peptide-binding preferences. These findings highlight a genetically distinct, sexually dimorphic feature of JIA with uveitis as compared to JIA without uveitis. The association could be indicative of the potential involvement of antigen presentation by HLA-DRβ1 in the development of uveitis in JIA. The results of this study may advance our progress toward improved treatments for, and possible prevention of, the sight-threatening complications of uveitis in children with JIA.