Antigenic determinants of asthma-associated allergens for design of immunotherapy

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TITLE: Antigenic determinants of asthma-associated allergens for design of immunotherapy PROJECT SUMMARY/ABSTRACT House dust mite allergy is an important health problem worldwide, affecting up to 85% of asthmatic children, and a risk factor for emergency room admission with asthma. Group 1 and 2 mite allergens account for more than 50% of total house dust mite specific IgE reactivity in mite allergic patients. Recently, Der p 23 has also been identified as a major mite allergen, but its contribution to the total house dust mite specific IgE is small. Group 1 allergens are cysteine proteases that contribute to lung inflammation in asthma, whereas group 2 allergens are lipopolysaccharide binding proteins. Der p 2 has been reported to mimic a human structural- homolog that activates the innate immune system through toll like receptors. Despite these important molecular differences between proteolytic group 1 and non-proteolytic group 2, a high IgE prevalence of 83% to allergens from both groups has been observed in mite allergic patients in the U.S. However, the IgE repertoire and antigenic determinants associated with these two major allergens are not known. The main goal of this project is to investigate the antigenic structure of both groups of mite allergens for the design of immunotherapy. Allergen-specific IgE monoclonal antibodies (mAb) will be produced for the first time with the correct pairing of the heavy and light chains as they occur in vivo, using hybridomas obtained from the fusion of B cells from allergic donors with a myeloma partner that confers immortality. Allergens will be co-crystallized with recombinant IgE antibody constructs. The key amino acids involved in IgE antibody binding will be identified and modified. The specific aims are: 1) Isolation of IgE mAb specific for asthma-associated allergens by hybridoma technology; 2) mapping of antigenic determinants on groups 1 and 2 dust mite allergens by X-ray crystallography and analysis of IgE antibody binding epitopes; and 3) site-directed mutagenesis of IgE antibody epitopes for expression of hypoallergenic mutants with T cell reactivity as candidates for immunotherapy. An analysis of the association between mite allergen-specific IgE antibodies from the human repertoire and the epitopes recognized by these IgE antibodies will be performed with the information obtained in the first two aims. Aim #2 will generate experimental data sets of three-dimensional structures of B-cell epitopes, which are currently missing in databases used for developing tools for B cell epitope prediction. Most importantly, this project will define IgE antibody responses to mite allergens and will provide the structural basis for rational design of hypoallergens. In Aim #3, IgE antibody binding to the epitope mutants will be analyzed by immunoassays and cell mediator release assays, and T cell reactivity will be evaluated. Mutants will be compared and hypoallergenic forms will be selected for the design of vaccines for immunotherapy of mite allergy.