Development of a quantitative antigen assay to detect coccidioidal chitinase-1 (CTS1) in human serum

Abstract

Background. Coccidioidomycosis is often diagnosed with a collection of tests that rely on the patient′s ability to mount an immune response to the fungus (antibody-based diagnostics), making diagnosis of this infection challenging. Here we present an antigen-based assay that detects and quantifies coccidioidal chitinase-1 (CTS1) in human serum. Methods. An inhibition-based enzyme-linked immunoassay (ELISA) was developed that utilizes a monoclonal antibody specific for coccidioidal CTS1. CTS1 was quantified in commercial antigen preparations using recombinant CTS1 as a standard. Sera from 192 individuals from an endemic area were tested which included 78 patients (40.6%) with proven or probable coccidioidomycosis. Results. The quantity of CTS1 in diagnostic commercial antigen preparations from different suppliers varied. CTS1 antigenemia was detected in 87.2% of patients with proven or probable coccidioidomycosis. Specificity was determined to be 96.94% using serum from individuals who reside in the Phoenix, Arizona area who did not have coccidioidomycosis. Levels of CTS1 correlated with low- and high-titer serology from patients with a coccidioidomycosis diagnosis. Conclusions. Since the CTS1 inhibition ELISA described in this report does not depend on the host immune response, it is a promising diagnostic tool to aid in diagnosis and disease monitoring of coccidioidomycosis.

Humanization and expression of IgG and IgM antibodies in plants as potential diagnostic reagents for Valley Fever

“…Since chitinase 1 (CTS1) is an important immunogenic component of MCF and commercial antigen preparations used clinically in Valley Fever diagnostic kits (Pishko et al, 1995;Mitchell et al, 2020;Grill et al, 2021), we anticipated that the plant produced mAb bound to Coccidioides CTS1. We therefore tested P-4H2 IgG and IgM for the ability to bind to recombinant CTS1 as well as CTS1 in MCF.…”

Clinical Microbiology in 2021: My Favorite Studies about Everything Except My Least Favorite Virus

“…Another study out of Arizona, a Coccidioides hotspot, demonstrated promising results for a single test that attained relatively high sensitivity for coccidioidomycosis. Grill et al developed a quantitative inhibition-based ELISA for detection of CTS1 (coccidioidal chitinase 1) in serum [ 7 ]. Among patients with proven or probable Coccidioides infections, the sensitivity was 87% when a cutoff that yielded 97% specificity for control subjects living in Phoenix, AZ, was used.…”