Inhibition of glycosylation on a camelid antibody uniquely affects its FcγRI binding activity

• DOI: 10.1016/j.ejps.2016.09.040
• Publication Date: 2016-10-10T17:27:56Z
• Authors: Natalie Krahn; Maureen Spearman; Markus Meier; July Dorion-Thiba...; Matthew McDougall; Trushar R. Patel; Gregory De Crescenzo; Yves Durocher; Jörg Stetefeld; Michael Butler
• Keywords: 0301 basic medicine; N-linked glycosylation; Glycosylation; Receptors, IgG; CD spectroscopy; Antibodies, Monoclonal; dynamic light scattering; CHO Cells; glycosylation inhibitor; Protein Structure, Tertiary; 03 medical and health sciences; analytical ultracentrifuge; Cricetulus; monoclonal antibody; Cricetinae; Animals; Humans; Camelids, New World; surface plasmon resonance; Protein Binding

Glycoengineering of mAbs has become common practice in attempts to generate the ideal mAb candidate for a wide range of therapeutic applications. The effects of these glycan modifications on the binding affinity of IgG mAbs for FcγRIIIa and their cytotoxicity are well known. However, little is understood about the effect that these modifications have on binding to the high affinity FcγRI receptor. This study analyzed the effect of variable N-glycosylation on a human-llama hybrid mAb (EG2-hFc, 80kDa) binding to FcγRI including a comparison to a full-sized IgG1 (DP-12, 150kDa). This was achieved by the addition of three glycosylation inhibitors (swainsonine, castanospermine, and kifunensine) independently to Chinese hamster ovary (CHO) cell cultures to generate hybrid and high mannose glycan structures. Biophysical analysis by circular dichroism, dynamic light scattering and analytical ultra-centrifugation confirmed that the solution-behaviour of the mAbs remained constant over multiple concentrations and glycan treatments. However, changes were observed when studying the interaction of FcγRI with variously glycosylated mAbs. Both mAbs were observed to have a decreased binding affinity upon treatment with swainsonine which produced hybrid glycans. Following de-glycosylation the binding affinity for EG2-hFc was only marginally reduced (6-fold) compared to a drastic (118-fold) decrease for DP-12. In summary, our data suggest that the relatively low molecular weight of chimeric EG2-hFc may contribute to its enhanced stability against glycan changes making it a highly suitable mAb candidate for therapeutic applications.