Characterizing the Immunogenicity of a Coccidioides Eisosome Component

Coccidioidomycosis is a fungal infection that causes disease in immunocompromised and healthy individuals. The causative agents, Coccidioides immitis and Coccidioides posadasii, are endemic to the southwest United States. Currently, there is no clinically approved vaccine against Coccidioides. With the expansion of endemic areas and increases in the immunocompromised population, a human vaccine is needed against this mycosis. Protection against coccidioidomycosis is associated with CD4+ T cells that promote a mixed Th1- and Th17-type response. Viriyakosol, et al. differentiated C. immitis gene expression in mycelia, spherule initials, and mature spherules. An eisosome core component known as Lsp1 was upregulated in both spherule developmental stages compared to mycelia. This study focuses on identifying T-cell reactive epitopes in Lsp1 that elicit high affinity for binding human MHC-II molecules. An ioGenetics immunoinformatics platform identified one major T-cell epitope within the Lsp1 antigen. For immunological assays, a recombinant Lsp1 (rLsp1) was produced using an E. coli pET expression system and purified via Ni-NTA affinity chromatography. Purified rLsp1 was used to create vaccines with glucan-chitin particles (GCP) or incomplete Freud's adjuvant (IFA) and CpG oligodeoxynucleotides. HLA-DR4 transgenic mice were vaccinated subcutaneously three times at 2-week intervals. ELISA and ELISPOT assays were used to measure memory Th1 responses. Immune T cells stimulated with whole rLsp1 mounted a robust Th1 response compared to the predicted peptide. These findings suggest that rLsp1 contains immunogenic epitopes that can stimulate a T-cell-mediated memory response and serve as a potential vaccine candidate against Coccidioides infection.