Antibody library and method

A method of generating/producing a library of variant antibody molecules, wherein said variant antibody molecules are variants of a reference antibody, said method comprising the steps:

• a) providing a nucleotide sequence encoding the reference antibody,
• b) in said nucleotide sequence, identifying one or more DNA motifs susceptible to deamination by Activation-Induced Deaminase (AID), wherein said one or more DNA motifs is DGYW or WRCH, wherein D is adenine, guanine, or thymine, R is adenine or guanine G is guanine C is cytosine H is adenine cytosine, or thymine, W is adenine or thymine, and Y is cytosine or thymine;
• c) for one or more of said DNA motifs of which at least one is in a nucleotide sequence encoding a framework region, selecting at least one variant nucleotide residue to substitute for a residue of said DNA motif, wherein said substitution will result in a variant nucleotide sequence which encodes a variant antibody molecule having, relative to the reference antibody, a change in the amino acid sequence being encoded by said DNA motif, and wherein at least one of said residues substituted with at least one variant nucleotide residue is in a codon which encodes an amino acid of a framework region;
• and
• d) repeating steps (b) and (c);
• such that a library containing a plurality of variants of said reference antibody is generated.