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Published on: September 10, 2018
Association energetics of cross-reactive and specific antibodies
S Mohan1, Katerina Kourentzi, Kari A Schick
1Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, USA.
Biochemistry
|January 27, 2009
Summary
Three monoclonal antibodies (HyHEL-8, HyHEL-10, HyHEL-26) binding hen egg white lysozyme (HEL) exhibit varying cross-reactivity and specificity. Thermodynamic analysis reveals distinct molecular recognition mechanisms, linking antibody flexibility to antigen binding.
Area of Science:
- Immunology and Molecular Biophysics
- Protein-Antigen Interactions
- Thermodynamics of Molecular Recognition
Background:
- Murine monoclonal antibodies HyHEL-8, HyHEL-10, and HyHEL-26 (HH8, HH10, HH26) recognize identical epitopes on hen egg white lysozyme (HEL).
- These antibodies exhibit significant differences in epitope mutation tolerance, ranging from highly cross-reactive (HH8) to highly specific (HH26).
- Previous studies indicated that HH26 possesses greater structural rigidity due to intramolecular salt links, influencing its binding kinetics.
Purpose of the Study:
- To thermodynamically characterize the binding energetics of HH8, HH10, and HH26 with native HEL and a variant antigen (JQL).
- To correlate calorimetric data with observed antibody cross-reactivity and specificity.
- To elucidate the fundamental thermodynamic differences underlying cross-reactive versus specific molecular recognition.
Main Methods:
- Isothermal titration calorimetry (ITC) to measure the association energetics (enthalpy and entropy) of antibody-antigen binding.
- Comparison of binding thermodynamics with hen egg white lysozyme (HEL) and Japanese quail egg white lysozyme (JQL).
- Analysis of thermodynamic parameters in relation to antibody structural properties and functional cross-reactivity.
Main Results:
- Calorimetric data demonstrate a clear correlation between binding energetics, cross-reactivity, and specificity across the three antibodies.
- HH8's higher cross-reactivity is associated with conformational flexibility, incurring a larger entropic penalty but smaller enthalpic loss with variant antigens.
- HH26's high specificity is linked to structural rigidity, resulting in a significant loss of enthalpic driving force upon binding variant antigens.
Conclusions:
- The thermodynamic characteristics of antibody-antigen interactions directly reflect and explain differences in functional cross-reactivity and specificity.
- Antibody flexibility and intermolecular interaction modes are key determinants of thermodynamic profiles in molecular recognition.
- This study provides fundamental insights into the thermodynamic basis of selective versus promiscuous molecular binding.
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