Binding parameters of antibodies: pseudo-affinity and other misconceptions

Area of Science:

• Immunology
• Biochemistry
• Biotechnology

Background:

• Monoclonal antibodies (mAbs) are crucial in diagnostics and therapeutics.
• Functional affinity is commonly used to assess mAb binding to multivalent antigens, like cell surface receptors.
• Current methods assume mAb-antigen interactions can be simplified to monovalent binding models.

Purpose of the Study:

• To critically evaluate the concept of functional affinity for monoclonal antibodies (mAbs) binding to multivalent antigens.
• To demonstrate the inadequacy of functional affinity in describing complex mAb-antigen interactions.
• To provide a more accurate framework for understanding antibody binding kinetics.

Main Methods:

• Theoretical analysis of antibody-antigen binding kinetics.
• Modeling of bivalent antibody interactions with multivalent cell surface antigens.
• Comparison of functional affinity calculations versus true binding dynamics.

Main Results:

• The concept of functional affinity is demonstrated to be incorrect for multivalent interactions.
• Bivalent antibody binding to cell surfaces often behaves as an irreversible reaction.
• Calculated functional affinity values obscure the actual binding mechanisms and kinetics.

Conclusions:

• Functional affinity is an inappropriate metric for evaluating monoclonal antibody binding to multivalent targets.
• Understanding antibody binding as potentially irreversible is critical for accurate assessment.
• Accurate characterization of antibody-antigen interactions will advance the development of therapeutic antibodies.