Blocking Immunodominant Epitopes by Competitive Deselection

The development of combinatorial antibody (Ab) libraries displayed on the surface of phage has led to the production of a wide range of human monoclonal antibodies (MAbs) against a plethora of viral antigens (Ag) (1 -5 ). However, sometimes the isolation of a given Ab can be particularly difficult because of the predominance of some epitopes, and, in the case of impure Ags, because the protein or compound of interest is present in a low amount. Many techniques have been developed for overcoming this problem, including epitope-masking (6 ) or sandwich-capture (7 ) procedures. These approaches require a MAb against the Ab or epitope of interest, which is not always available. In this chapter, a new procedure of preadsorption panning is described, which facilitates the molecular cloning of MAb fragments against nonimmunodominant Ag determinants using phage-display immunoselection. The procedure, called competitive deselection, is easy, fast, inexpensive, and can be coupled with other described panning techniques; however, its chief advantage is in the isolation of Abs against less-represented Ag determinants.