Precision engineering of antibodies: A review of modification and design in the Fab region.

The binding of functional groups to antibodies is crucial for disease treatment, diagnosis, and basic scientific research. Traditionally, antibody modifications have focused on the Fc region to maintain antigen-antibody binding activity. However, such modifications may impact critical antibody functions, including immune cell surface receptor activation, cytokine release, and other immune responses. In recent years, modifications targeting the antigen-binding fragment (Fab) region have garnered increasing attention. Precise modifications of the Fab region not only maximize the retention of antigen-antibody binding capacity but also enhance numerous physicochemical properties of antibodies. This paper reviews the chemical, biological, biochemical, and computer-assisted methods for modifying the Fab region of antibodies, discussing their advantages, limitations, recent advances, and future trends.

Isolation of antibody by polymer microspheres embedded with E. coli displaying IgG-binding domain.

Antibody purification is an important aspect of quality and cost control in the production process of antibody drugs. In this study, modified E. coli was embedded into polymer microspheres (polyvinyl alcohol/alginate) for antibody separation and the IgG binding domain was displayed on the surface of E. coli. The results showed that ZZ protein (Fc binding domain of the antibody) was successfully displayed on the surface of E. coli and was embedded in polyvinyl alcohol/alginate microspheres. In addition, it has excellent specific adsorption capacity for antibodies, with a maximum adsorption capacity of 35.74 mg/g (wet microspheres). Through the adsorption isotherm and adsorption kinetics simulation, the adsorption of IgG on the microsphere matrix conforms to the Langmuir model and follows the pseudo-first-order kinetic equation. The microsphere matrix can undergo saturation adsorption at pH 7.2 and desorption at around pH 3.0. Desorption characteristics are consistent with those of rProtein A Sepharose FF®. After five cycles of the adsorption-desorption processes, the IgG adsorption capacity remains above 80%. Using polymer microspheres to separate antibodies from mouse ascites, the antibody purity reached 86.7% and the yield was 83.5%. These results provide an alternative to protein A matrix with low-cost, fast preparation and moderate efficiency.