The use of phage-peptide libraries to define the epitope specificity of a mouse monoclonal anti-Der p 1 antibody representative of a major component of the human immunoglobulin E anti-Der p 1 response

Background More than 80% of individuals who are sensitive to the dust mite Dermatophagoides pteronyssinus produce immunoglobulin (Ig) E antibodies to Der p 1, the most significant domestic allergen. There is therefore conside rable interest in elucidating the interaction between human IgE and Der p 1 , as a basis for developing strategies for therapeutic intervention. Objectives We have therefore sought to determine the Der p 1 epitope recogn ized by a mouse monoclonal anti-Der p 1 antibody (mAb 2C7) representative o f a major component of the human IgE anti-Der p 1 response. Methods M13 15mer and T7 9mer bacteriophage-peptide display libraries were screened with mAb 2C7. Mimotope sequences were defined and compared with th e native Der p 1 sequence and with those of three homologous molecules, nam ely chymopapain, papain and actinidin. The sequence of a candidate epitope was then located in the three-dimensional model of Der p 1 and the correspo nding sequences in the homologous molecules were studied for accessibility in the three-dimensional structure. Results We have demonstrated that it is possible to isolate phage clones wi th peptide inserts specific for mAb 2C7. Examination of the sequences obtai ned and the location of the corresponding epitope within the three-dimensio nal model of Der p 1 has shown that mAb 2C7 recognizes a conformational epi tope comprising the sequence Leu147-Gln160. The relevance of the identified epitope was established by showing that native Der p 1 can block the bindi ng of specific phage clones to mAb 2C7. Similar sequences were identified w ithin the three-dimensional structures of chymopapain, papain and actinidin , thereby providing a structure-based explanation for immunological cross-r eactivity. Conclusion The identification of the Der p 1 sequence Leu147-Gln160 as a po tential epitope recognized by a major component of the human IgE anti-Der p 1 response may provide therapeutic opportunities for disrupting the intera ction between IgE and this important allergen.