Behcet’s patient-derived HLA class I immunopeptidome is ERAP1-dependent and displays disease-specific candidate peptides 4513

Abstract Description Specific HLA I (HLA-B51) confers risk for Behcet’s disease (BD), augmented by allotypic ERAP1 with low peptide trimming activity. We previously demonstrated the impact of ERAP1 KO on the HLA I/ B51 peptidome in a genome-edited in vitro model. Here, we aimed to extend our findings to native biospecimens and identify disease-associated peptides directly from humans. We immunoprecipitated HLA I-peptide from biomaterial of 103 Turkish donors (n BD = 86, n HD = 17), followed by mass spectrometry of HLA I-eluted peptides and determined ERAP1 allotypes. Group analyses included BD vs. HD and low vs. high trimmers, dependent on, or independent of, HLA-B51 carrier status. We compared peptide lengths and applied penalized logistic regression to identify BD-specific candidate peptides. Low ERAP1 activity was associated with longer peptides. Analysis of an independent cohort of BD/ HD HLA-B51 carriers revealed increased peptide lengths above 9mer in BD. A set of distinct HLA I-eluted peptides was found in approximately 40% of BD patients but not in HD. Penalized logistic regression identified peptides that differentiated BD from HD with high accuracy. We show that the HLA I peptidome is modulated by ERAP1 in actual human subjects rather than cell lines alone, with a propensity for longer peptides for low-trimming ERAP1 and HLA-B51+ BD. This peptidome includes potentially BD-specific, HLA I-restricted peptides, identifying targets for biomarker development and pathogenic T-cell recognition. Funding Sources R01EY031383 (Nowatzky), R01EY033495 (Nowatzky) Topic Categories Immune Mechanisms of Human Disease (HUM)