Related Experiment Videos
Mapping of a Coccidioides immitis-specific epitope that reacts with complement-fixing antibody
1Department of Clinical Investigation, Texas Center for Infectious Disease, San Antonio 78223, USA.
Insights
Researchers identified a specific peptide for detecting Coccidioides immitis (CI) infection. This new tool shows high sensitivity and specificity for anti-CI complement fixation (CF) antibodies, improving diagnostic accuracy for CI.
Area of Science:
- Mycology
- Immunology
- Medical Diagnostics
Background:
- Previous Coccidioides immitis (CI) complement fixation (CF) antigen recombinant protein showed high sensitivity but lacked specificity.
- Cross-reactivity was observed with sera from patients with histoplasmosis and blastomycosis.
Purpose of the Study:
- To determine if the epitope(s) reacting with CI CF antibody are shared with other fungal species.
- To identify a specific epitope for improved CI diagnostic assays.
Main Methods:
- PCR-generated CF/chitinase cDNA fragments were cloned.
- Recombinant peptides were tested using enzyme-linked immunosorbent assays (ELISAs) with patient sera.
- Peptide reactivity was assessed against sera from coccidioidomycosis, histoplasmosis, blastomycosis, and healthy subjects.
Main Results:
- A specific peptide domain (residues 20-310) expressed an epitope specific to anti-CI CF antibody.
- This peptide detected antibodies in 95% of active coccidioidomycosis patients.
- No reactivity was observed with sera from patients with histoplasmosis, blastomycosis, or healthy controls.
Conclusions:
- A recombinant peptide with both sensitivity and specificity for detecting anti-CI CF antibody was delineated.
- This peptide represents a valuable tool for diagnosing coccidioidomycosis.
- It will aid in evaluating the role of CF antibody in host response to C. immitis.
Abstract:
We have previously cloned the cDNA fragment that encodes the complement fixation antigen of Coccidioides immitis. The recombinant protein was highly sensitive in detecting CF antibody in sera from patients with coccidioidomycosis but was not specific to C. immitis, as evidenced by its reactivity with sera from patients with histoplasmosis and, to lesser extent, blastomycosis. We undertook this study to determine if the epitope(s) that reacts with CF antibody is the same or differs from the epitopes that are shared with Histoplasma capsulatum and Blastomyces dermatitidis. PCR-generated CF/chitinase cDNA fragments were cloned and examined for their reactivity in enzyme-linked immunosorbent assays using sera from patients with coccidioidomycosis, histoplasmosis, or blastomycosis. A peptide domain comprised of amino acid residues 20 through 310 was shown to express an epitope(s) that is specific to anti-Coccidioides CF antibody. The peptide detected serum antibody in 21 (95%) of 22 patients with active coccidioidomycosis and was without reactivity with sera from 20 patients with histoplasmosis, 15 patients with blastomycosis, and 14 healthy subjects. Antibody titers to the recombinant peptide directly correlated with CF antibody titers (P < 0.01), and preadsorption of reference CF antiserum with the peptide ablated the reactivity of the antiserum in the immunodiffusion assay for CF antibody. The delineation of a recombinant peptide that has both sensitivity and specificity will provide a valuable tool for detecting CF antibody and for evaluating the role of CF antibody in the host response to C. immitis.