HLA-B*51 in epistasis with the ERAP1 haplotype Hap10 confers the strongest known risk for Behcet's Disease (BD) and Behcet's Eye Disease (BED), but the pathogenic mechanism of this relationship is entirely unknown. The main objective of this application is to identify the mechanism mediating this risk. This is in line with our long- term goal to find, comprehend and correct aberrancies in immune-pathways that drive Behcet's Eye Disease (BED). Based on our preliminary studies we propose as our central hypothesis that ERAP1 Hap10 shapes immune responses in BED through alteration of the HLA-B51 peptidome causing aberrant antigen presentation, which results in the activation of effector cell responses that drive the disease. We follow the rationale that elucidation of the biological consequences of HLA-B51/ERAP1 Hap10 will provide mechanistic understanding of BED and therefore enable targeted therapy design. We will test our central hypothesis in two specific aims: 1) We will identify clonal effector responses in BED patients carrying the risk variant by combining access to large patient cohorts of our own and those of our international collaborators with single cell transcriptomics, large-scale flow cytometric analyses using computational tools we have developed, as well as applying our established methods of T cell cloning. 2) We will determine through which mechanism HLA-B51/ERAP Hap10 initiates immune-dysfunction in BED via a series of genome-editing experiments in a CRISPR approach using Cas9 stable LCL clones we have generated. This will allow us to identify the functional contribution of ERAP1 Hap10 to the HLA-B51 peptidome and its consequences for antigen-presentation to CD8+ effector cells. The proposed research is innovative because it approaches the HLA-B51 challenge from a conceptually new, testable angle, and it uses, refines and develops novel, state-of-the-art approaches. Our proposal is significant because meeting its objective will generate mechanistic understanding and knowledge providing strong scientific rationale for the design of targeted therapies for BED, which is one of the most devastating forms of non- infectious uveitis with significant prevalence in large parts of the world. We expect additional positive impact by cross-fertilizing research of other HLA-I/ERAP-related diseases including HLA-B27-associated uveitis and spondylitis, Birdshot's choroidopathy, psoriasis-associated conditions, and inflammatory bowel disease (IBD).
This project aims to clarify how certain genes act to cause a form of uveitis (inflammation within the eye) which is common in many parts of the world as well as in Americans of Hispanic, East Asian, Middle Eastern and South European descent: Behcet's Eye Disease (BED). This form of uveitis often leads to blindness if not treated, and current treatments can fail or cause serious side effects. Successful completion of this project will help design better medications for BED and similar diseases which pose large public health problems such as psoriasis, certain types of arthritis and bowel inflammation as well as other forms of uveitis.
