Immunogenicity of a 48-kilodalton recombinant T-cell-reactive protein of Coccidioides immitis

The outcome of coccidioidomycosis depends to a large extent on the effectiveness of the T-cell-mediated immune (CMI) response to the fungal pathogen. For this reason, identification of Coccidioides immitis antigens which stimulate T cells is important for understanding the nature of host defense against the organism and essential for the development of an effective vaccine. Here we describe the immunogenicity of a 48-kDa T-cell-reactive protein (TCRP). The antigen is expressed by parasitic cells and localized in the cytoplasm. It stimulates the proliferative response and production of gamma interferon by T cells of mice immunized with C. immitis spherules. Specific antibody reactive with the recombinant TCRP (rTCRP) was detected in sera of patients with confirmed coccidioidal infection, and the highest titers of antibody to the recombinant protein correlated with elevated titers to the serodiagnostic complement fixation antigen of C. immitis. These results suggest that the TCRP is presented to the host during the course of infection. Immunization of BALB/c and C3H/HeN mice with the rTCRP affords a modest but significant level of protection against an intraperitoneal challenge with C. immitis. It is suggested that the rTCRP may be able to contribute to a multicomponent vaccine designed to stimulate CMI response against the parasitic cycle of C. immitis.