Abstract Coccidioidomycosis (Valley Fever) is a systemic infection caused by the fungi, Coccidioides immitis or Coccidioides posadasii, which are endemic to Arizona, California and other parts of the United States. Illness ranges from pneumonia to life-threatening spread to other parts of the body (disseminated infection), including the brain. Valley Fever causes an average of 160 deaths annually, and produced $2 billion in hospital charges from 2000 – 2011. Current therapies are not curative and may be need to be continued for life. This proposal responds to RFA-AI-16-034 which explicitly invites vaccines for Coccidioides spp. Our vaccine candidate appears i) safe, ii) highly effective, and iii) feasible to produce commercially. It is based upon a deletion of the CPS1 gene from the fungus, resulting in complete loss of virulence in mice. When used as a vaccine against experimental murine coccidioidomycosis, it is very protective. The vaccine candidate (∆cps1) is “manufactured” by simply growing arthroconidia on solid media and so the cost of goods is likely to be low, making commercial development feasible. We propose to develop our vaccine candidate first to prevent Valley Fever in dogs. This will provide pre-clinical information for its safety and efficacy in a large animal and further support an FDA IND for humans. The specific aims are to first use fungal genetic analysis of the CPS1 mutation to determine why it is essential for virulence. A complete understanding of its role in the fungus could provide a better assessment about its safety as a live vaccine. Second, we will develop a formulation that would be used in both dogs and humans. Third, we will determine exactly which lymphocyte subsets and their cytokines mediate protection. This information will be useful for the rational identification of future surrogate markers of protection in immunized dogs and humans. Finally, we will develop an experimental model of coccidioidal infection in canines and use it to test the efficacy of ∆cps1 to prevent disease. In addition to the studies proposed in this application, we have identified an industrial partner, Anivive Lifesciences, that has agreed to partner with us and will provide additional investment and expertise to fully develop a veterinary vaccine. We believe that with the success of this program, risk of developing our vaccine candidate for humans will be substantially reduced to the point that further investment will be forthcoming to complete the ultimate objective of our work.