Evaluation of Coccidioides Antigens, Enolase and Carboxypeptidase Y, as Vaccine Candidates Against Coccidioidomycosis

Coccidioidomycosis (CM) is a pulmonary mycosis caused by Coccidioides spp. that impacts the health of residents who live or travel in the southwest regions of the United States. Vaccination against CM is a promising prevention that offers long-term immunity. A CD4+ T helper (Th) cell-mediated response is essential for vaccine-induced protective immunity. A previous study identified enolase (Enl) and carboxypeptidase Y (Cpya) in the cell wall of spherules as seroreactive. The goal of this study is to characterize and evaluate potential of the proteins of being a vaccine candidate. rEnl and rCpya were produced in an E. coli expression system and purified to ≥ 95% purity via nickel affinity chromatography. Purified proteins were used for IgELISA, rEnl shows to be Coccidioides specific compared to rCpya. rEnl was selected for T-cell recall assays to reveal its immunogenicity. ioGenetics algorithm shows that Enl contains 3 potential immunogenic epitopes (22-23 mers). Vaccinated HLA-DR4 transgenic mice with rEnl loaded in glucan-chitin particles (GCPs) with GCP-MSA as a control. Harvested splenocytes were prepared for T-cell recall assays with full-length rEnl and epitope peptides at a concentration of 100 nM. Findings indicate that Enl is a Coccidioides specific immunogenic antigen capable of eliciting a Th-specific cell mediated and a humoral response making it a good candidate to be used to develop a vaccine against CM.