Screening And Identification Of The Epitopes On Human Immunoglobulin E With 7～(TM)phage Display Peptide Library

Type I or immediate hypersensitivity is characterized by development quickly, functional disorder, have an inheritance for predisposition and individuall inference. Such diseases include: penicillin hypersusceptibility, bronchial asthma , allergic rhinitis, atopic dermatitis, food Anaphylaxis and so on. Take asthma as an example, it is one of the most common chronic diseases in the world and nearly 200 million people suffer from it. In China, the prevalence rate is 1%, and there are above 10 million patients. Immediate hypersensitivity is mediated by human immunoglobulin E, Which has the smallest content among all kinds of Ig in serum of normal people, with Concentration of about 5×10~5 mg/ml. Excreted by Plasma cells of mucosal-aossciated lymphoid tissue (MALT), IgE is cytotropic antibody and its CH2 and CH3 domain can bind to the high-affinity FCεR I on Mast cell and basophilic granulocyte,which may induce Immediate hypersensitivity. Now anti-IgE treatment provides an effective method for patients of sensitive disease including asthma. But such kind of medicine has disadvantages of high-dose medication, long period of treatment, and induce hypersensitivity easily. However, a little amount of Epitope vaccine can evocate antibody, which has made IgE Epitope vaccine the most effective approach to cure immediate hypersensitivity.Phage-display technology is a new and powerful tool in finding the ligands for proteins, enzymes, antibodies etc. In this study, we aimed to identify and characterize epitopes of human immunoglobulin E screened from 7~TM phage display peptide library and to provide basis for further research on IgG related multipeptide vaccine and therapy of immediate hypersensitivity.The epitopes of human immunoglobulin E were screened from 7~TM phage display peptide library by using anti-IgE antibody as target protein and identified by sandwich ELISA. After 3 rounds of screening, 15 of 48 phage clones were identified as positive slones which can bind to anti-human IgE antibody. The amino acid sequences of the positive clones were DHIDMGL, DHMWLGL, DHQDAGF and DHMDQNL, which have not been reported by BLAST yet. CLUSTALW sequence comparison shows that the frameworks of the screened epitopes are similar, having extensive amino acid homology with IgE-CH3 region. Competitive ELISA results demonstrated the competitive binding of the 4 sequences and IgG to anti-IgE mAb .