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Screening and kinetic analysis of recombinant anti-CEA antibody fragments
Abstract:
Four different carcinoembryonic antigen (CEA)-binding antibody fragments were prepared using the genes of the variable regions of the T84 epitope-specific antibody 7F7 and phage display techniques. The genes were successfully cloned and expressed in the pCANTAB5 phage display vector to investigate the kinetic binding parameters of each synthesized construct. Single chain fragments, Fab fragments, and two diabodies were purified and compared in their CEA-binding properties with the parent IgG using surface plasmon resonance detection. The on-rates for all these molecules were in the same order of magnitude (about 1 x 10(5) M-1 s-1) whereas major differences were detected in the off-rates. IgG and diabodies had slow off-rates due to bivalent binding, while single chain and Fab fragments dissociated rather fast. We also present a method for the immobilization of large amounts of CEA on CM5 sensorchips. These high density surfaces can be used for observing mass transport limited binding of CEA-specific molecules and are convenient tools for screening and quality control.
Insights
Researchers developed novel carcinoembryonic antigen (CEA)-binding antibody fragments. Diabodies and IgG showed slower dissociation than single-chain and Fab fragments due to bivalent binding.
Area of Science:
- Biotechnology
- Immunology
- Protein Engineering
Background:
- Carcinoembryonic antigen (CEA) is a tumor marker.
- Antibody fragments offer advantages in targeted therapies and diagnostics.
- Efficient methods for characterizing antibody-antigen interactions are crucial.
Purpose of the Study:
- To engineer and characterize novel CEA-binding antibody fragments.
- To compare the kinetic binding properties of different antibody formats.
- To develop high-density CEA surfaces for screening.
Main Methods:
- Phage display techniques were used to generate antibody variable region genes.
- Genes were cloned and expressed in the pCANTAB5 phage display vector.
- Surface plasmon resonance (SPR) was employed to determine binding kinetics (on- and off-rates).
Main Results:
- Four CEA-binding antibody fragments (single-chain, Fab, two diabodies) were successfully prepared.
- All constructs exhibited similar association rates (on-rates).
- Significant differences in dissociation rates (off-rates) were observed, with IgG and diabodies showing slower dissociation due to bivalent binding.
Conclusions:
- Antibody format significantly impacts binding kinetics, particularly dissociation rates.
- Diabodies and IgG demonstrate enhanced binding stability compared to single-chain and Fab fragments.
- High-density CEA surfaces are effective for screening and quality control of CEA-specific molecules.