Affinity Maturation of Monoclonal Antibodies: An Overview

Monoclonal antibodies (mAbs) are frequently used to treat a wide range of conditions, including cancer, autoimmune disorders, and infectious diseases. However, not all mAbs are equally effective in treating these diseases, and the affinity maturation process is critical in improving binding affinity and therapeutic efficacy.  

Affinity maturation of monoclonal antibodies (mAbs) is a crucial process in the development of therapeutic antibodies. It involves iteratively mutating the antibodies to increase their binding affinity to the target antigen, resulting in high-affinity mAbs that are more effective in treating diseases and have improved pharmacokinetic properties compared to low-affinity mAbs.

Traditionally, affinity maturation has been achieved using conventional techniques such as cryo-electron microscopy (cryoEM) and surface plasmon resonance (SPR). These procedures, however, are time-consuming, complicated, and costly. Furthermore, they necessitate large amounts of purified protein, which can be difficult to obtain. In addition, these approaches have resolution limitations and are unsuitable for high-throughput analysis of large numbers of mAbs.

Hydroxyl radical footprinting (HRF) is a new technology that has the potential to significantly improve and simplify the affinity maturation process. HRF is based on the reactivity of hydroxyl radicals with proteins, which results in peptide bond cleavage. Researchers can assess the position of the antigen-antibody interface and identify key amino acids that contribute to binding affinity by measuring the level of cleavage.

HRF offers various advantages over typical affinity maturation procedures. For starters, HRF may be performed with modest amounts of protein, making it more accessible and affordable. Second, HRF can assess many mAbs in parallel, making it a more efficient and high-throughput approach. Finally, HRF provides a high-resolution map of the antigen-antibody interface that can be used to guide the rational design of mAbs with higher binding affinity.

A study used HRF to discover the epitope of the anti-TNF-alpha monoclonal antibody adalimumab. The researchers employed mass spectrometry to determine the cleavage sites after obtaining hydroxyl radicals via the Fenton reaction. They then employed molecular modeling to predict the orientation of adalimumab relative to TNF-alpha, and their findings agreed with prior research that used other approaches.

While HRF has several advantages for affinity maturation, this method has several drawbacks. For starters, HRF necessitates specialized equipment and experience, which may limit its broad use. Second, HRF can be challenging to understand, especially in the case of complicated protein-protein interactions. Finally, HRF may not be appropriate for all mAbs and antigens, and more research is needed to determine the best conditions for this technique.

Despite these obstacles, HRF has been used in several real-world applications, demonstrating its potential in mAb development. For example, a recent work published in Cell Reports employed HRF to identify key amino acids involved in the interaction of the SARS-CoV-2 spike protein and neutralizing mAbs. The researchers discovered that HRF could detect small changes in the interaction of different mAbs with the spike protein, which might be utilized to guide the development of more effective neutralizing mAbs.

Another study published in the Journal of Biological Chemistry employed HRF to identify key amino acids involved in the interaction between the HIV gp120 protein and mAbs that target it. The researchers discovered that HRF could be utilized to identify crucial binding affinity residues that might be targeted for modification to improve the efficacy of the mAbs.

Affinity maturation of monoclonal antibodies is an important step in generating therapeutic antibodies, and hydroxyl radical footprinting can enhance and simplify the process. HRF generates a high-resolution map of the antigen-antibody interface, making it a valuable tool for rationally designing mAbs with higher binding affinity. However, more research is required to address the difficulties associated with this method and determine its optimal conditions.

‍