The hexamerization of natural, human IgG antibodies after cell surface antigen binding can induce activation of the classical complement pathway. Mutations stimulating Fc domain-mediated... Show moreThe hexamerization of natural, human IgG antibodies after cell surface antigen binding can induce activation of the classical complement pathway. Mutations stimulating Fc domain-mediated hexamerization can potentiate complement activation and induce the clustering of cell surface receptors, a finding that was applied to different clinically investigated antibody therapeutics. Here, we biophysically characterized how increased self-association of IgG1 antibody variants with different hexamerization propensity may impact their developability, rather than functional properties. Self-Interaction Chromatography, Dynamic Light Scattering and PEG-induced precipitation showed that IgG variant self-association at neutral pH increased in the order wild type (WT) < E430G < E345K < E345R < E430G-E345R-S440Y, consistent with functional activity. Self-association was strongly pH-dependent, and single point mutants were fully monomeric at pH 5. Differential Scanning Calorimetry and Fluorimetry showed that mutation E430G decreased conformational stability. Interestingly, heat-induced unfolding facilitated by mutation E430G was reversible at 60 degrees C, while a solvent-exposed hydrophobic mutation caused irreversible aggregation. Remarkably, neither increased dynamic self-association propensity at neutral pH nor decreased conformational stability substantially affected the stability of concentrated variants E430G or E345K during storage for two years at 2-8 degrees C. We discuss how these findings may inform the design and development of IgG-based therapeutics. (C) 2022 The Authors. Published by Elsevier Inc. on behalf of American Pharmacists Association. Show less
IgG antibodies play a central role in protection against pathogens by their ability to alert and activate the innate immune system. Here, we show that IgGs assemble into oligomers on antigenic... Show moreIgG antibodies play a central role in protection against pathogens by their ability to alert and activate the innate immune system. Here, we show that IgGs assemble into oligomers on antigenic surfaces through an ordered, Fc domain-mediated process that can be modulated by protein engineering. Using high-speed atomic force microscopy, we unraveled the molecular events of IgG oligomer formation on surfaces. IgG molecules were recruited from solution although assembly of monovalently binding molecules also occurred through lateral diffusion. Monomers were observed to assemble into hexamers with all intermediates detected, but in which only hexamers bound Cl. Functional characterization of oligomers on cells also demonstrated that Cl binding to IgG hexamers was a prerequisite for maximal activation, whereas tetramers, trimers, and dimers were mostly inactive. We present a dynamic IgG oligomerization model, which provides a framework for exploiting the macromolecular assembly of IgGs on surfaces for tool, immunotherapy, and vaccine design. Show less
Dyachenko, A.; Wang, G.B.; Belov, M.; Makarov, A.; Jong, R.N. de; Bremer, E.T.J. van den; ... ; Heck, A.J.R. 2015
