Coccidioides immitis is a fungal respiratory pathogen of humans and causative agent of valley fever (coccidioidomycosis). Exposure to the airborne, infectious cells (arthroconidia) can lead to a range of clinical disease from a benign, self-limited infectious cells (arthroconidia) can lead to a range of clinical disease from a benign, self-limited infection to a severe, progressive and often fatal mycosis involving pulmonary and extrapulmonary tissues. Immunologically compromising illnesses, although present in some patients, are not prerequisite to infection by C. immitis. There exists a consistent and predictable immunological pattern in patients at various stages of coccidioidomycosis, which may be related to initial exposure to the arthroconidia, followed by repeated exposure to soluble antigenic fractions of primarily wall origin during the parasitic cycle (i.e., spherule-endospore phase). Our hypothesis is that arthroconidia, spherules, and endospores of C. immitis elicit different host responses because of qualitative and/or quantitative differences in the antigenic composition of their cell wall to which the host is originally exposed. It has been possible to isolate soluble, antigenic complexes from the cell envelopes off arthroconidia and spherules grown in vitro, characterize their immunoreactivity in humoral and cellular immunoassays, and obtain purified components using various separation techniques. In the proposed investigations we will characterize these purified components on the basis of their chemical composition, antigenic identity in standardized immunoelectrophoresis and immunodiffusion tests, and relative immunoreactivity in assays which measure patient antibody adsorption and T-cell response to the homogeneous fractions. We will also examine the biological function of these purified components, with focus on their possible enzymatic activity and impact on fungal morphogenesis and host invasion. Our recent development of a cDNA expression library and the availability of a genomic library for C. immitis permits application of recombinant DNA technology in our further characterization of these purified, wall-associated fractions. Initially, we will screen the libraries using selected immunoprobes and oligonucleotide probes corresponding to those selected fractions with established significance in host antibody response, tissue invasion, or C. immitis morphogenesis, and clone the genes which regulate production off the homologous fusion peptides. Ultimately, we will determine expression of these genes during arthroconidium-spherule-endospore development in vitro. We believe that this comprehensive approach to the study of C. immitis antigens will lead to a better understanding of the pattern of immunological response by the host and factors which contribute to pathogenicity, as well as identify potential diagnostic DNA probes and molecular targets for development of novel antifungal compounds.
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