Coccidioidomycosis (CM) is an endemic mycosis caused by the fungi Coccidioides immitis and Coccidioides posadasii, which is native to arid regions of North and South America. It is estimated that up to 350,000 infections occur annually in the U.S. Additionally, up to a third of community acquired pneumonia cases in these areas are thought to be a result of CM. Morbidity associated with CM is substantial with a median illness duration of 120 days. The costs associated with CM are high, with an estimated annual direct healthcare cost of nearly $200 million. Currently, the diagnosis of CM is primarily based on detection of anti-Coccidioides antibodies. Once infection clears, the antibody eventually becomes undetectable making it difficult to determine if there was previous exposure. Classically, delayed-type hypersensitivity reactions using skin tests have been used to evaluate the cellular immune response, which is indicative of past infection. The commercially available Coccidioides skin test has suboptimal performance characteristics and is not utilized often in clinical care. The use of an ex vivo cytokine release assay (CRA) avoids the limitations associated with skin testing while allowing for the detection of cytokines produced by stimulation with a pathogen- specific antigen. Analogous to the commercially available CRA for tuberculosis, a Coccidioides CRA would be a major advance for patient care and for evaluation of CM prevalence within geographical regions and populations. Our data suggests a CRA for CM will be valuable as a tool to detect patients with acute CM and stratify those with latent CM (those at risk for reactivation if immunosuppressed). Climate change and incidence modelling predict endemicity to expand from 12 to 18 states and incidence to increase by 50%, stressing the need for a public health screening tool to establish changing boundaries and stratification for high risk occupations and future vaccine trials., The goal of this application is to develop a test to assist in the diagnosis, management, and epidemiology of CM, which increasingly afflicts people living in or travelling through areas where it is endemic. This phase 1 grant will utilize technological advances and prediction modeling to produce recombinant antigens with the highest likelihood of stimulating a cellular immune response. These antigens will then be used to develop an in-tube CRA, the first of its kind to assist in the management of a fungal disease.