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 considerable 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 recognized by a mouse monoclonal anti-Der p 1 antibody (mAb 2C7) representative of 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 the native Der p 1 sequence and with those of three homologous molecules, namely chymopapain, papain and actinidin. The sequence of a candidate epitope was then located in the three-dimensional model of Der p 1 and the corresponding 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 with peptide inserts specific for mAb 2C7. Examination of the sequences obtained and the location of the corresponding epitope within the three-dimensional model of Der p 1 has shown that mAb 2C7 recognizes a conformational epitope comprising the sequence Leu147-Gln160. The relevance of the identified epitope was established by showing that native Der p 1 can block the binding of specific phage clones to mAb 2C7. Similar sequences were identified within the three-dimensional structures of chymopapain, papain and actinidin, thereby providing a structure-based explanation for immunological cross-reactivity.
Conclusion: The identification of the Der p 1 sequence Leu147-Gln160 as a potential epitope recognized by a major component of the human IgE anti-Der p 1 response may provide therapeutic opportunities for disrupting the interaction between IgE and this important allergen.