An antibody may be defined also by its epitope, i.e. the set of specific amino acids of the antigen which are specifically recognised and bound by the antibody.
However, since an antibody defined in this way cannot be easily compared with known antibodies binding to the same antigen, the same principles as for the functional features apply (see G-II, 126.96.36.199).
If the epitope is a "linear epitope" (i.e. the antibody interacts with continuous amino acids on the antigen), it needs to be defined as a clearly limited fragment using closed wording (e.g. epitope consisting of).
If the epitope is "non-linear" or "discontinuous" (i.e. the antibody interacts with multiple, distinct segments from the primary amino-acid sequence of the antigen), the specific amino acid residues of the epitope need to be clearly identified.
The method for determining this discontinuous epitope must also be indicated in the claim and the application must provide an enabling disclosure allowing the skilled person to determine whether further antibodies bind this epitope. The application must also enable the production without undue burden of additional antibodies binding to the same epitope.