Size-exclusion HPLC analysis of epitopes

Area of Science:

• Biochemistry
• Immunology
• Analytical Chemistry

Background:

• Determining the spatial relationship of epitopes on antigens is crucial for understanding antibody binding and developing targeted therapeutics.
• Traditional methods for epitope mapping can be complex and time-consuming.

Purpose of the Study:

• To develop and validate a size-exclusion chromatography (SEC) based method for assessing the relative spatial locations of epitopes.
• To evaluate the dissociation rate constant of antigen-antibody reactions using SEC.

Main Methods:

• Utilizing size-exclusion chromatography to analyze competition between intact monoclonal antibodies (mAbs) and their antigen-binding fragments (Fabs).
• Monitoring molecular weight shifts in antigen-antibody complexes formed in the presence of competing Fabs.
• Employing enzymatically prepared Fabs for competition assays and kinetic analysis.

Main Results:

• The SEC method unambiguously distinguishes between spatially distinct and overlapping/identical epitopes based on molecular weight distribution shifts.
• Higher molecular weight complexes indicate distinct epitopes, while lower molecular weight complexes suggest overlapping epitopes or conformational changes.
• The method allows for the evaluation of antigen-antibody dissociation rate constants.

Conclusions:

• Size-exclusion chromatography offers a robust and unambiguous method for epitope spatial mapping.
• This technique provides valuable insights into antibody-antigen interactions and can be applied to kinetic analyses.