1617-P: Association of High-Affinity Autoantibodies with High-Risk HLA Haplotypes

Electrochemiluminescence (ECL) assays are high-affinity autoantibodies (Abs) that are more specific than radiobinding assay (RBA) Abs for the prediction of type 1 diabetes (T1D) in natural history studies screening for risk and progression to T1D. We analyzed 603 subjects from the TrialNet Pathway to Prevention Study who were positive for at least one RBA diabetes related Ab and for whom ECL and HLA data were available. We sought to characterize ECL-GADA and ECL-IAA positivity and levels (z-scores) by HLA genotype and haplotypes. Mean age at initial visit was 19.4 ± 13.7 years; 345 (57.2%) were female and 104 (17.2%) carried the high-risk HLA- DR3/4*0302 genotype. At initial visit 425 (70%) of subjects were positive for either ECL-GADA or ECL-IAA, with 207 (34.3%) ECL-IAA positive subjects and 367 (60.9%) ECL-GADA positive subjects. For subjects with high-risk HLA-DR3/4 genotype (n=104), 80 (76.9%) were positive for ECL-GADA, while 42 (40.4%) were positive for ECL-IAA. ECL and RBA-GADA z-scores were higher in subjects with HLA-DR3 haplotypes, while ECL-IAA (but not RBA-IAA) z-scores were associated with HLA-DR4 haplotypes. Associations of ECL and RIA Abs with high-risk HLA haplotypes are shown in the Table. In conclusion, ECL and RBA-GADA positivity are associated with both HLA-DR3 and DR4 haplotypes, whereas only ECL-IAA (but not RBA-IAA) positivity and levels are associated with HLA-DR4 haplotype.