Detecting serum antibodies to a purified recombinant proline-rich antigen of Coccidioides immitis in patients with coccidioidomycosis.

In previous work, antibodies in serum samples from patients with coccidioidomycosis were found to react with a proline-rich antigen (PRA) isolated from spherules of Coccidioides immitis, and the gene encoding this antigen was cloned. We expressed and purified recombinant PRA (rPRA) by removing the majority of amino acids contributed by the vector from the fusion protein. Purified rPRA reacted with serum IgG antibodies in 37 of 42 patients with culture-proven progressive pulmonary or extrapulmonary coccidioidal disease; specific antibodies in dilutions ranging from 1:40 to 1:102,400 were demonstrated (sensitivity, 88%). In contrast, for > 95% of patients without coccidioidomycosis reactivity of < 1:40 was demonstrated (specificity, 97%). Of 18 patients with primary self-limited coccidioidomycosis, none had detectable antibodies in serum samples collected up to 141 days after illness began. The association of antibodies to rPRA with progressive infection may have prognostic value.