Benaroya Research Institute at Virginia Mason, Seattle, WA 98101.
Laboratory of Biophysics, Biochemistry, Bioprocessing and Bioproducts, Faculty of Agricultural Technology, Technological Educational Institute of Epirus, GR47100 Arta, Greece.
J Immunol. 2018 Dec 15;201(12):3524-3533. doi: 10.4049/jimmunol.1800723. Epub 2018 Nov 19.
DRB401:01 (DRB4) is a secondary HLA-DR product that is part of the high-risk DR4/DQ8 haplotype that is associated with type 1 diabetes (T1D). DRB4 shares considerable homology with HLA-DR4 alleles that predispose to autoimmunity, including DRB104:01 and DRB104:04. However, the DRB4 protein sequence includes distinct residues that would be expected to alter the characteristics of its binding pockets. To identify high-affinity peptides that are recognized in the context of DRB4, we used an HLA class II tetramer-based approach to identify epitopes within multiple viral Ags. We applied a similar approach to identify antigenic sequences within glutamic acid decarboxylase 65 and pre-proinsulin that are recognized in the context of DRB4. Seven sequences were immunogenic, eliciting high-affinity T cell responses in DRB4 subjects. DRB104:01-restricted responses toward many of these peptides have been previously described, but responses to a novel pre-proinsulin 9-28 peptide were commonly observed in subjects with T1D. Furthermore, T cells that recognized this peptide in the context of DRB4 were present at significantly higher frequencies in patients with T1D than in healthy controls, implicating this as a disease-relevant specificity that may contribute to the breakdown of β cell tolerance in genetically susceptible individuals. We then deduced a DRB4 motif and confirmed its key features through structural modeling. This modeling suggested that the core epitope within the pre-proinsulin 9-28 peptide has a somewhat unusual binding motif, with tryptophan in the fourth binding pocket of DRB4, perhaps influencing the availability of this complex for T cell selection.
DRB401:01（DRB4）是 HLA-DR 的次要产物，是与 1 型糖尿病（T1D）相关的高危 DR4/DQ8 单体型的一部分。DRB4 与易患自身免疫性疾病的 HLA-DR4 等位基因具有相当大的同源性，包括 DRB104:01 和 DRB104:04。然而，DRB4 蛋白序列包含独特的残基，预计会改变其结合口袋的特征。为了鉴定在 DRB4 背景下被识别的高亲和力肽，我们使用基于 HLA Ⅱ类四聚体的方法来鉴定多种病毒抗原内的表位。我们应用类似的方法来鉴定谷氨酸脱羧酶 65 和前胰岛素内被 DRB4 识别的抗原序列。有 7 个序列具有免疫原性，在 DRB4 受试者中引发高亲和力 T 细胞反应。之前已经描述了针对许多这些肽的 DRB104:01 限制的反应，但在 T1D 患者中经常观察到对新的前胰岛素 9-28 肽的反应。此外，在 T1D 患者中，在 DRB4 背景下识别该肽的 T 细胞的频率明显高于健康对照者，表明这是一种与疾病相关的特异性，可能导致遗传易感个体中β细胞耐受的破坏。然后，我们推断出 DRB4 基序，并通过结构建模证实了其关键特征。该建模表明，前胰岛素 9-28 肽内的核心表位具有有点不寻常的结合基序，DRB4 的第四结合口袋中有色氨酸，可能影响该复合物对 T 细胞选择的可用性。
