Highly variable aggregation and glycosylation profiles and their roles in immunogenicity to protein-based therapeutics

Production of antibodies against protein-based therapeutics (e.g., monoclonal antibodies (mAbs)) by a recipient's immune system can vary from benign symptoms to chronic neutralization of the compound, and in rare cases, a lethal cytokine storm. One critical factor that can induce or contribute to an anti-drug antibody (ADA) response is believed to be the presence of aggregated proteins in protein-based therapeutics. There is a high level of variability in the aggregation of different proteins, which adds to the complexity in understanding the immune response to these drugs. Furthermore, the level of glycosylation of proteins, which increases drug stability, functionality, and serum half-life, is highly variable and may influence their immunogenicity. Considering the abundance of literature on the effect of aggregation and glycosylation on the immunogenicity of protein-based therapeutics, this review aims to summarize the current knowledge and clarify the immunogenic effects of different protein-based therapeutics such as mAbs. This review focuses on the properties of aggregated proteins and elucidates their relationship with immunogenicity. The contribution of different immune cell subsets and the mechanisms in aggregation-induced immunogenicity are also reviewed. Finally, the potential effects of each glycan, such as sialic acid, mannose, and fucose, on protein-based therapeutics’ immunogenicity and stability is discussed.