Towards the design of an antibody that recognises a given protein epitope

We have explored the possibility of designing repertoires of antibodies com plementary to a given protein epitope, specifically the face of the ribonuc lease inhibitor barstar that binds to the enzyme barnase. An antibody reper toire was created by mutation of ten residues in the hypervariable loops of a synthetic antibody fragment and displayed on filamentous bacteriophage. The positions of three of the ten residues of the antibody (VL 32, 50 and 9 4) were chosen to match a triangle of three negative charges on the face of barstar and mutated to favour residues of opposite charge or those with hy drogen-bonding potential. The other seven residues, chosen to allow for var iation in the surface of interaction, were mutated at random. One of the an tibody fragments isolated after selectin of the repertoire (10(8) clones pe r library) was shown to bind to barstar with an affinity of 1.0 x 10(-7) M and the binding was competed by barnase. Furthermore, the binding of the an tibody to barstar was highly sensitive to mutation of any of five residues of barstar known to contact barnase. This indicates that it may be possible , by a contamination of design and selection, to build antibodies to a give n epitope. (C) 1999 Academic Press.