Project Summary/Abstract Psoriatic arthritis is a chronic and progressive inflammatory arthritis closely linked with psoriasis. Blockade of the IL-17 signaling pathway shows impressive efficacy and excellent safety for treatment of psoriasis but less so for PsA. Tissue penetrance limits the bioavailability of monoclonal antibodies to the joint and fibrocartilaginous enthesis and IL-17A signaling is diversified by local immune cells in tissues rendering IL-17A inhibition less effective. A higher dosage poses the risks of serious infections and certain types of cancer as all IL-17 inhibitors are immunosuppressive therefore to improve clinical outcomes in PsA more selective targeting is required. Herein, we have developed a novel animal model of IL-17A gene transfer where mice develop joint and skin inflammation associated with enthesitis, fingernail psoriasis and onycholysis hallmarks of PsA pathology. We will interrogate our murine model to define the early cellular and molecular pathways that dictate IL-17A-induced pathologies using state-of-the-art transgenic mice and molecular tools. Our work will uncover the pathogenic mechanisms of IL-17A and uncover novel molecular targets that can be exploited for therapeutic intervention and directly benefit PsA patients worldwide.