Mixing two monoclonal antibodies yields enhanced affinity for antigen

Area of Science:

• Immunology
• Biochemistry
• Assay Development

Background:

• Monoclonal antibodies (mAbs) are crucial for specific antigen detection.
• Human chorionic gonadotropin (hCG) is a key biomarker in various physiological and pathological conditions.
• Current antigen-binding assays may have limitations in sensitivity.

Purpose of the Study:

• To investigate the effect of mixing monoclonal antibodies against human chorionic gonadotropin (hCG) on antigen-binding assay sensitivity.
• To determine the potential for enhanced affinity through antibody combinations.

Main Methods:

• Utilized solid-phase and liquid-phase double antibody radioimmunoassays.
• Tested various pairs of monoclonal antibodies targeting different epitopes of hCG.
• Investigated the role of antibody fragments (F(ab) and F(ab')2) in affinity enhancement.

Main Results:

• Mixing specific monoclonal antibody pairs against hCG resulted in up to a 10-fold increase in binding affinity compared to individual antibodies.
• The observed enhancement is attributed to the formation of a multicomponent complex, not avidity changes of individual antibodies.
• Antibody pairs targeting the same epitope or those not binding cooperatively did not show enhancement.
• Intact antibodies were more effective than F(ab) or F(ab')2 fragments in achieving affinity enhancement.

Conclusions:

• Combinatorial use of specific monoclonal antibodies against hCG can significantly enhance antigen-binding assay sensitivity and affinity.
• This strategy offers a novel approach to improve diagnostic accuracy for hCG-related conditions.
• The mechanism involves cooperative binding and multicomponent complex formation, highlighting the importance of antibody selection.