Multitarget Selection Of Catalytic Antibodies With Beta-Lactamase Activity Using Phage Display

beta-lactamase enzymes responsible for bacterial resistance to antibiotics are among the most important health threats to the human population today. Understanding the increasingly vast structural motifs responsible for the catalytic mechanism of beta-lactamases will help improve the future design of new generation antibiotics and mechanism-based inhibitors of these enzymes. Here we report the construction of a large murine single chain fragment variable (scFv) phage display library of size 2.7 x 10(9) with extended diversity by combining different mouse models. We have used two molecularly different inhibitors of the R-TEM beta-lactamase as targets for selection of catalytic antibodies with beta-lactamase activity. This novel methodology has led to the isolation of five antibody fragments, which are all capable of hydrolyzing the beta-lactam ring. Structural modeling of the selected scFv has revealed the presence of different motifs in each of the antibody fragments potentially responsible for their catalytic activity. Our results confirm (a) the validity of using our two target inhibitors for the in vitro selection of catalytic antibodies endowed with beta-lactamase activity, and (b) the plasticity of the beta-lactamase active site responsible for the wide resistance of these enzymes to clinically available inhibitors and antibiotics.