N-Glycosylation of Antibodies: Biological Effects During Infections and Therapeutic Applications.

Antibodies are produced by cells of the adaptive immune response and recognize epitopes of microbial structures with high affinity and specificity. Antibodies are recognized by Fc fragment receptors (FcRs) found on the surface of phagocytic cells (neutrophils, monocytes, macrophages) and NK cells, among others. Hence, antibodies link the adaptive immune response with the innate immune response. The functions of antibodies are related to the N-glycosylation profile of these proteins. In this review, we describe how N-glycosylation of the Fc fragment of the different antibody classes is carried out, and which oligosaccharides are most commonly found in these antibodies. Subsequently, we summarize the biological effects of N-glycosylation of antibodies: on the binding of antibodies to FcRs (which affects various functions, such as antibody-dependent cellular cytotoxicity, antibody-dependent phagocytosis, and the production of pro- or anti-inflammatory chemokines and cytokines), on the ability of antibodies to activate complement and on the ability of some antibodies to directly neutralize the adhesion of bacteria and viruses to host cells (independently of Fab recognition). We describe how the N-glycosylation profile of antibodies is modified during certain infections (such as tuberculosis, COVID-19, influenza and dengue) and in response to vaccination, and the potential use of this profile to identify the stage and severity of an infection. Finally, we review the importance of N-glycosylation for the pharmacokinetic, pharmacodynamic and safety profiles of therapeutic monoclonal antibodies.