Development of a concise and rapid cell-based functional assay for evaluating human Dectin-1 antagonists

Dectin-1, a C-type lectin receptor that recognizes β-glucans, plays a vital role in antifungal immunity and is involved in inflammatory diseases and cancer, making it a promising therapeutic target for antagonists. However, current evaluations of these antagonists often depend on binding inhibition assays, which may not accurately reflect physiological functional suppression. This study addresses the need for a rapid, functional, cell-based assay for human Dectin-1 (hDectin-1) antagonists. We describe the development and validation of such an assay using THP-1 cells stably expressing hDectin-1 (dTHP-1 cells), which produce TNF-α upon Dectin-1 activation by depleted Zymosan (dZymosan). We established optimal assay conditions as 10 μg/mL dZymosan stimulation for 4 h. Under these conditions, laminarin, a soluble β-glucan, inhibited dZymosan-induced TNF-α production in a dose-dependent manner. This inhibition was specific, as Dextran T40, a non-Dectin-1-binding polysaccharide, had no inhibitory effect on dZymosan-induced responses. This novel, concise (4-hour) assay system directly measures the key physiological outcomes of Dectin-1 signaling, offering a significant improvement over binding-based assays. This provides a valuable platform for screening and characterizing hDectin-1 antagonists, facilitating the development of new therapeutics for Dectin-1-related pathologies.