A glycan FRET assay for detection and characterization of catalytic antibodies to theCryptococcus neoformanscapsule

Significance Cryptococcus neoformans is a global fungal pathogen that is a frequent cause of a life-threatening meningoencephalitis. There is a need for new therapies and vaccines. A better understanding of antibodies associated with its major virulence factor, the capsule, will allow the development of new antibody therapeutics, inform vaccine design, and further basic knowledge of antibody structure-function. Here, we demonstrate several antibodies against the capsule have innate glycosidase activity, and these antibodies can cause hydrolysis of the native capsule. This catalytic activity results in a disruption of cellular integrity and increased ease of phagocytosis by macrophages. To date, identifying this elusive quality in antibodies has been difficult. We have simplified this process by the development of a high-throughput FRET assay. This approach could be generalized to identify other antibodies catalytic against glycans.