Localization of the tube precipitin and complement fixation antigens of Coccidioides immitis by immunoelectron microscopy with murine monoclonal antibodies

Molecular cloning and characterization of the Coccidioides immitis complement fixation/chitinase antigen

Detection of anti-Coccidioides complement-fixing (CF) antibody is a valuable diagnostic and prognostic aid in coccidioidomycosis. The CF antibody response is directed against a heat-labile antigen that has chitinase activity, hereafter referred to as the CF/chitinase protein. To identify and clone this immunoreactive enzyme, we constructed a Coccidioides immitis cDNA lambda ZAP expression library from spherule RNA and detected fusion peptides expressing CF epitopes by immunoscreening. A cDNA clone consisting of 1,623 bp was identified, sequenced, and found to contain a single open reading frame that encodes a protein of 47 kDa with 427 amino acids. Deduced amino acid sequence analyses showed that the cloned CF/chitinase cDNA contains a 35-amino-acid region, beginning at Ser-18 and ending at and ending at Arg-52 which has 92% homology with the reported N-terminal amino acid sequence of authentic CF/chitinase protein. The first 17 amino acids in the deduced sequence of the cloned cDNA are not present on the mature CF/chitinase protein, suggesting that it may be a signal peptide. Expression of the CF/chitinase cDNA insert by using the pGEX-4T-3 vector yields a fusion peptide that bears CF-specific epitopes and shows chitinase activity. The CF/chitinase clone will enable large-scale production of the recombinant CF antigen for use in immunoassays and facilitate studies on the role of chitinase in the morphogenesis of C. immitis.

Coccidioidomycosis

Coccidioidomycosis is a systemic fungal infection endemic to the southwestern United States and other parts of the western hemisphere. Although producing a wide range of disorders in healthy persons, immunosuppression predisposes to especially severe disease. Thus, a knowledge of the pathogenesis of coccidioidal infections and its relation to the normal immune responses is useful to understand the diversity of problems that Coccidioides immitis may cause. Diagnosis usually requires laboratory studies such as fungal culture or specific serologic testing. Fortunately, many patients do not need to be treated for the infection to resolve. Therapy for the more severe forms of coccidioidal infection was once limited to amphotericin B but now includes azole antifungal agents. These expanded alternatives now require physicians to weigh many factors in determining the best management for specific patients.