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Antibodies to the Cryptococcus neoformans Capsule have Innate Glycosidase Activity

preprint
revised on 18.05.2020, 12:51 and posted on 19.05.2020, 05:02 by Conor Crawford, Maggie P. Wear, Daniel F. Q. Smith, Clotilde d'Errico, Arturo Casadevall, Stefan Oscarson
Classical antibody functions include opsonization, complement activation and enhancement of cellular antimicrobial function. Antibodies can also have catalytic activity, although the contribution of catalysis to their biological functions has been more difficult to establish. In this study, we mapped the epitopes of several monoclonal antibodies (mAbs) against the capsule of Cryptococcus neoformans using a synthetic glycan array. From this, we designed and synthesized two glycan based Förster Resonance Energy Transfer (FRET) probes, which allowed the discovery of antibodies with innate glycosidase activity, and analysis of their enzyme kinetics. We confirmed that the mAbs mediate glycosidase activity on intact cryptococcal capsules, by reacting antibody-treated capsules with a hydroxylamine-armed fluorescent probe, which revealed the appearance of reducing ends from polysaccharide hydrolysis in the capsule. Our results raise questions over the ubiquity of antibodies with catalytic activity against glycans and establish the utility of glycan-based FRET and hydroxylamine-armed fluorescent probes as tools for investigating this activity.

Funding

Design, Synthesis, and Development of Carbohydrate-Based Vaccines against Cryptococcus neoformans

Irish Research Council

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Design, Synthesis, and Development of Carbohydrate–Based Vaccines, Therapeutics, Diagnostics, and Medical Devices.

Science Foundation Ireland

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NIH HL059842 19

NIH AI052733 16

History

Email Address of Submitting Author

conor.crawford@ucdconnect.ie

Institution

University College Dublin

Country

Ireland

ORCID For Submitting Author

0000-0002-1314-1019

Declaration of Conflict of Interest

none

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