Project Summary/Abstract Many different disease states and surgical interventions result in a period of inadequate tissue/organ blood supply (i.e., ischemia), that result in reperfusion injury when blood flow is restored, known as ischemia-reperfusion injury (IRI). IRI causes local inflammation, cell death, excessive tissue destruction and possible organ failure. Examples are found in transplantation, trauma, myocardial infarction, stroke, and in particular, IRI is a main cause of liver dysfunction and failure after liver surgery. Unfortunately, there are currently no therapies available in clinical practice addressing IRI, where a major problem is the harmful systemic side effects and toxicities of existing drugs. To address this problem, we are innovating a new therapeutic technology aiming to program immune cells toward a metabolic state blocking excessive inflammation by directing tryptophan metabolism through delivery of an enzyme into circulation. This represents a new class of anti- inflammatory/immunosuppressive biologic drug, with potential to limit systemic toxicities/side effects, and with potential to be significantly less immunocompromising. Lack of treatment options for liver IRI and a catalog of in vivo preliminary data strongly supporting the foundational rationale of IDO as an innovative new anti-inflammatory agent, make this proposal highly significant. Looking to the future, success would open opportunity to expand to other anti-inflammatory applications, for example, pre-conditioning donor grafts for transplantation.