Cell display library for gene cloning of variable regions of human antibodies to hepatitis B surface antigen

A novel cell display system was developed for cloning the variable region (V) genes of antigen-specific human antibodies. The system is based on an antibody library displayed on the surface of COS cells, using a plasmid vector designed to direct expression of membrane-bound antibodies. COS cells expressing antigen-specific antibodies were separated using a flow cytometer for their binding to a fluorescent dye-labeled antigen. To test the performance of this system, we cloned V genes of 4 antibodies directed against hepatitis B surface antigen (HBsAg) from a library prepared from peripheral blood lymphocytes of a vaccinated donor. These membrane-bound anti-HBsAg antibodies were easily converted to soluble forms, all of which showed a size similar to human serum IgG in SDS-PAGE and the same specific binding to HBsAg as membrane-bound forms in ELISA. All V-H and V-kappa gene segments of the 4 clones isolated in this study belonged to VHIII and VkappaI subgroups, respectively. These findings demonstrate the potential and selection capabilities of our cell display system for cloning the V genes of antigen-specific human antibodies.