A general strategy to identify mimotopes of pathological antigens using only random peptide libraries and human sera.

A strategy to identify disease-specific epitopes from phage-displayed random peptide libraries using human sera is described. Peptides on phage (phagotopes) that react with antibodies present in patient sera are purified from > 10(7) different sequences by affinity selection and immunological screening of plaques. Disease-specific phagotopes can be identified out of this pool through an 'antigen independent' procedure which avails itself only of patient and normal human sera. Using this strategy, we have selected antigenic mimics (mimotopes) of two different epitopes from the human hepatitis B virus envelope protein (HBsAg). We could show that a humoral response to these mimotopes is widespread in the immunized population, suggesting that the strategy identifies phagotopes that have a potential role as diagnostic reagents. Immunization of mice with the selected phagotopes elicited a strong specific response against the HBsAg. These results open new inroads into disease-related epitope discovery and provide the potential for vaccine development without a requirement for the use of, or even information about, the aetiological agent or its antigens.