Binding symmetry and surface flexibility mediate antibody self-association. Issue 7 (3rd October 2019)

• Record Type: Journal Article
• Authors: Schrag, Joseph D.; Picard, Marie-Ève; Gaudreault, Francis; Gagnon, Louis-Patrick; Baardsnes, Jason; Manenda, Mahder S.; Sheff, Joey; Deprez, Christophe; Baptista, Cassio; Hogues, Hervé; Kelly, John F.; Purisima, Enrico O.; Shi, Rong; Sulea, Traian
• Is Part Of: MAbs. Volume 11:Issue 7(2019)
• Page Start: 1300
• Page End: 1318
• Publication Date: 2019-10-03
• Subjects: Aggregation -- native folding -- single point mutation -- structure-aggregation relationship -- prediction method; Monoclonal antibodies -- Therapeutic use -- Periodicals; Monoclonal antibodies -- Periodicals; Antibodies, Monoclonal -- Periodicals; 616.0798
• DOI: 10.1080/19420862.2019.1632114
• Languages: English
• ISSNs: 1942-0862

Abstract

ABSTRACT: Solution stability is an important factor in the optimization of engineered biotherapeutic candidates such as monoclonal antibodies because of its possible effects on manufacturability, pharmacology, efficacy and safety. A detailed atomic understanding of the mechanisms governing self-association of natively folded protein monomers is required to devise predictive tools to guide screening and re-engineering along the drug development pipeline. We investigated pairs of affinity-matured full-size antibodies and observed drastically different propensities to aggregate from variants differing by a single amino-acid. Biophysical testing showed that antigen-binding fragments (Fabs) from the aggregating antibodies also reversibly associated with equilibrium dissociation constants in the low-micromolar range. Crystal structures (PDB accession codes 6MXR, 6MXS, 6MY4, 6MY5) and bottom-up hydrogen-exchange mass spectrometry revealed that Fab self-association occurs in a symmetric mode that involves the antigen complementarity-determining regions. Subtle local conformational changes incurred upon point mutation of monomeric variants foster formation of complementary polar interactions and hydrophobic contacts to generate a dimeric Fab interface. Testing of popular in silico tools generally indicated low reliabilities for predicting the aggregation propensities observed. A structure-aggregation data set is provided here in order to stimulate further improvements of in silico tools for prediction of native aggregation. Incorporation of intermolecular docking, conformational flexibility, and short-range packing interactions may all be necessary features of the ideal algorithm.