We undertook an investigation to assess the utility of a recombinant Coccidioides immitis
complement-fixing (
CF) antigen for detecting CF antibody in sera from patients with
coccidioidomycosis.
Enzyme-linked
immunosorbent assays established that recombinant
CF antigen and, for comparison, a commercially available
coccidioidin were reactive with 19 of 19 sera from patients with active
coccidioidomycosis. The recombinant
antigen was significantly more sensitive than
coccidioidin. The median titer obtained when patients' sera were assayed against recombinant
CF antigen was 1:51,200 compared to 1:25,600 with
coccidioidin (P < 0.027). The recombinant
antigen was also more effective in distinguishing the antibody levels in sera from patients with pulmonary
coccidioidomycosis than in sera from those with disseminated disease. Whereas patients with
pulmonary disease showed a median antibody titer of 1:25,600, those with multifocal disease showed a median titer of 1:102,400 (P < 0.028). The recombinant
CF antigen was found, however, to express an
epitope(s) that reacted with sera from 6 of 12 patients with
histoplasmosis and 2 of 12 patients with
blastomycosis.