Different glycan residues have different effects on antibody effector function. CD BioGlyco provides clients with efficient Antibody Remodeling services through chemoenzymatic glycoengineering methods.
The Crystallizable fragment (Fc) region of immunoglobulin G (IgG) has glycans at asparagine (Asn) 297, which exerts antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) of IgG influence. IgG-Fc glycans typically consist of a core complex biantennary heptose nucleus. Highly heterogeneous glycans can be obtained by adding fucose, galactose, and sialic acid residues to the biantennary heptose core. IgG-Fc glycans are divided into G0, G1, and G2 according to the number of galactose residues in the outer arms of the glycan. Each class of glycans is in turn divided into four subclasses based on the presence or absence of core fucose and bisected N-acetylglucosamine (GlcNAc).
Each component of IgG-Fc glycans affects the effector function of the antibody differently. The high mannose content varies from 5-9 in the Fc glycans linked to the core GlcNAc. It is found that high mannose-type Fc glycans have a positive effect on ADCC activity, but negatively affected the CDC activity of IgG molecules. Fucose residues are added to the GlcNAc residues in the core of IgG-Fc glycans, reducing antibody interaction with Fc receptor IIIa (FcRIIIa) and ADCC activity. Human serum contains approximately 10% bisecting GlcNAc residues. The addition of bisected GlcNAc residues has been reported to enhance the binding affinity of IgG to FcγRIIIa, resulting in a 10~30-fold higher ADCC activity. Human endogenous IgG-Fc glycans have 0, 1, or 2 terminal galactose moieties, respectively. Terminal galactose residue content has been shown to have a significant effect on CDC of IgG, but does not appear to have any effect on ADCC. Sialic acid is usually linked to the terminal galactose of human serum IgG via α-2,3 or α-2,6 linkages. Fc sialylation increases the anti-inflammatory response to intravenous Ig (IVIG).
Fig.1 Schematic representation of IgG glycosylation. (Sjögren, et al., 2020)
Different glycan residues have different effects on antibody effector function. To improve the safety and efficacy of therapeutic antibodies, chemoenzymatic glycoengineering is regarded as one of the most promising approaches to synthesizing homogeneous glycoforms of a given glycoprotein. CD BioGlyco integrates various advanced technologies and has developed efficient Antibody Glycoengineering strategies. We provide clients with homogeneous Fc G2 glycoforms of human IgG (including human IgG1, IgG2, and IgG4) through chemoenzymatic glycoengineering methods. Our workflow is as follows:
1) Trim Fc glycans to the innermost GlcNAc by IgG-specific endoglycosidases.
2) Glycosynthase catalyzes the reaction of pre-assembled G2 glycan oxazoline with core GlcNAc to generate human IgG with homologous G2 glycoforms.
Fig.2 Process of remodeling an antibody with G2 Glycoform. (CD BioGlyco)
CD BioGlyco has been recognized by scientists from several countries in Glycoengineering field. We are willing to share our knowledge and experience in remodeling antibodies with G2 glycoforms. If you are interested in remodeling antibody services with G2 glycoforms, please contact us for more details without any hesitation.
References:
