Computer-based Engineering of Thermostabilized Antibody Fragments

Area of Science:

• Protein Engineering
• Computational Biology
• Immunology

Background:

• Antibody fragments (scFvs and scAbs) are crucial in diagnostics and therapeutics.
• Improving protein stability is essential for antibody fragment applications, especially under thermal stress.
• Current methods for enhancing antibody stability can sometimes compromise antigen-binding affinity.

Purpose of the Study:

• To identify amino acid substitution clusters that enhance the global stability and thermal resistance of antibody fragments.
• To engineer thermostabilized variants of an antibody fragment targeting the Clostridium botulinum hemagglutinin protein (anti-HA33).
• To validate the stability improvements and retention of antigen-binding activity in engineered variants.

Main Methods:

• Utilized the molecular modeling program Rosetta to predict stabilizing amino acid substitutions.
• Designed antibody fragment variants incorporating identified amino acid replacement clusters.
• Assessed protein stability through melting temperature (T_m) measurements and heat treatment resistance assays.
• Confirmed antigen-binding activity post-incubation.
• Determined the crystal structure of a thermostabilized variant for structural validation.

Main Results:

• Identified specific amino acid substitution clusters that improve antibody fragment stability.
• Engineered two variants of the anti-HA33 antibody fragment with enhanced thermal stability.
• Achieved significantly higher melting temperatures (T_m) in designed variants compared to the parental scFv.
• Demonstrated retention of full antigen-binding activity after prolonged incubation at elevated temperatures (70 °C for 2 hours).
• Crystal structure analysis confirmed the accuracy of the RosettaAntibody model predictions for the thermostabilized variant.

Conclusions:

• Rosetta-based computational modeling is an effective strategy for designing thermostabilized antibody fragments.
• Engineered antibody fragments can exhibit improved stability without sacrificing antigen-binding function.
• The developed thermostabilized anti-HA33 antibody fragments hold promise for applications requiring heat resistance.