Choice of Host Cell Line Is Essential for the Functional Glycosylation of the Fc Region of Human IgG1 Inhibitors of Influenza B Viruses

Key Points Choice of cell line is critical for functional glycosylation of human IgG1-Fc. Sialylated IgG1-Fc monomers block influenza B only when made by CHO-K1 cells.
Abs are glycoproteins that carry a conserved N-linked carbohydrate attached to the Fc whose presence and fine structure profoundly impacts on their in vivo immunogenicity, pharmacokinetics, and functional attributes. The host cell line used to produce IgG plays a major role in this glycosylation, as different systems express different glycosylation enzymes and transporters that contribute to the specificity and heterogeneity of the final IgG-Fc glycosylation profile. In this study, we compare two panels of glycan-adapted IgG1-Fc mutants expressed in either the human endothelial kidney 293-F or Chinese hamster ovary–K1 systems. We show that the types of N-linked glycans between matched pairs of Fc mutants vary greatly and in particular, with respect, to sialylation. These cell line effects on glycosylation profoundly influence the ability of the engineered Fcs to interact with either human or pathogen receptors. For example, we describe Fc mutants that potently disrupted influenza B–mediated agglutination of human erythrocytes when expressed in Chinese hamster ovary–K1, but not in human endothelial kidney 293-F cells.