Synthesis and characterization of a functional intact IgG in a prokaryotic cell-free expression system

Abstract

AbstractAntibodies are an important component of the immune system of higher eukaryotes. Furthermore, they are effective tools in basic research, medical diagnostics and therapy. Recombinant expression of these heterotetrameric, disulfide-bridged proteins is usually performed in mammalian cells. Here, we describe the cell-free expression of a mouse monoclonal antibody, MAK33, in a coupled transcription/translation system, based on anEscherichia colilysate. Both the heavy and the light chain can be produced efficiently in this setup. However, they fail to form functional antibodies. With a view to overcome folding and oxidation defects, we supplemented the system with the oxidoreductases PDI (protein disulfide isomerase) and DsbC and the ER-specific chaperones Grp94 and BiP; furthermore, we optimized the redox conditions. We found that functional antibodies can only be obtained in the presence of an oxidoreductase. In contrast, the addition of Grp94 and/or BiP had no influence on the productive folding reaction. The comparison of the antibody expressedin vitrowith MAK33 expressed in cell culture showed that thein vitroexpressed antibody is correctly assembled, disulfide-bridged and shows identical antigen affinity. The stability of thein vitroexpressed non-glycosylated IgG is comparable to that of the authentic antibody.