Page 1 of 49 Diabetes EPITOPE STEALING AS MECHANISM OF DOMINANT PROTECTION BY HLA-DQ6 IN TYPE 1 DIABETES Menno van Lummel1, David T. P. Buis1, Cherish Ringeling1, Arnoud H. de Ru1, Jos Pool1, George K. Papadopoulos2, Peter A. van Veelen1, Helena Reijonen3, Jan W. Drijfhout1 and Bart O. Roep1, 3 1Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, the Netherlands, The Netherlands; 2Laboratory of Biochemistry and Biophysics, Faculty of Agricultural Technology, Epirus Institute of Technology, Arta, Greece 3Department of Diabetes Immunology, Diabetes & Metabolism Research Institute at the Beckman Research Institute, City of Hope, Duarte, USA; *Running title: islet epitope stealing by protective HLA-DQ6 Corresponding author: Prof. Bart O Roep, PhD Department of Immunohematology and Blood Transfusion, LUMC, E3-Q, PO Box 9600, 2300 RC Leiden, the Netherlands Tel: +31.71.5266673; Fax: +31.71.5266801; Email:
[email protected] Keywords: type 1 diabetes, HLA-DQ6, HLA-DQ8, protection, immunotherapy 1 Diabetes Publish Ahead of Print, published online January 9, 2019 Diabetes Page 2 of 49 ABSTRACT The heterozygous DQ2/8 (DQA1*05:01-DQB1*02:01/DQA1*03:01-DQB1*03:02) genotype confers the highest risk in T1D, whereas the DQ6/8 (DQA1*02:01-DQB1*06:02/ DQA1*03:01-DQB1*03:02) genotype is protective. The mechanism of dominant protection by DQ6 (DQB1*06:02) is unknown. We tested the hypothesis that DQ6 interferes with peptide- binding to DQ8 by competition for islet epitope (‘epitope stealing’) by analysis of the islet ligandome presented by HLA-DQ6/8 and -DQ8/8 on dendritic cells pulsed with islet autoantigens preproinsulin (PPI), GAD65 and IA2, followed by competition assays employing a newly established ‘epitope stealing’ HLA/peptide binding assay.