Abstract
Therapeutic antibodies constitute one of the fastest areas of growth in the field of biologic drugs. A molecular understanding of how antibodies interact with their target antigens is known as epitope mapping. The data provided by epitope mapping is extremely valuable in the process of antibody humanization, as well as in vaccine design. In many cases the epitope recognized by the antibody is a complex, discontinuous 3D conformational epitope. Mapping the interactions of an antibody to a conformational epitope is difficult by many standard approaches. X-ray crystallography is considered to be the gold standard of epitope mapping as it can provide a near atomic resolution model of the antibody-antigen interaction. An X-ray structure allows for inspection of specific antibody-antigen interactions, even in the case of complex conformational epitopes. The method described here can be adapted for structure determination and epitope mapping of any antibody fragment to a simple or complex antigen.