Antigenic determinants underlying IgE-mediated anaphylaxis to peanut.

Abstract

BACKGROUND Studies of human IgE and its targeted epitopes on allergens have been very limited. We have an established method to immortalize IgE encoding B cells from allergic individuals. OBJECTIVE To develop an unbiased and comprehensive panel of peanut-specific human IgE mAbs to characterize key immunodominant antigenic regions and epitopes on peanut allergens to map the molecular interactions responsible for inducing anaphylaxis. METHODS Using human hybridoma technology to immortalize IgE encoding B cells from peripheral blood of subjects with severe peanut allergy, we generated a panel of naturally occurring human IgE mAbs in an unbiased manner. Isolated IgE mAbs were characterized extensively in allergen binding assays, peptide array analysis, antigenic mapping, binding kinetic analysis, serum blocking, skin testing inhibition, and functional assessment using human FcεRI transgenic mice. RESULTS We created a large panel of 54 peanut-specific IgE mAbs, of which 63% were specific for Ara h 2 and/or 6. Pairs of IgE mAbs with the same antigen-specificity but different binding sites were able to mediate passive systemic anaphylaxis in FcεRI transgenic mice. A single mAb targeting the repetitive motif on Ara h 2 was able to induce degranulation and anaphylaxis on its own. IgG1 switched-variant immunoglobulins of the IgE mAb inhibited patients´ IgE binding to peanut extract between 30-60% (ImmunoCAP) and reduced peanut extract-induced skin wheal sizes by 1.6-7.4 millimeters in peanut allergic patients. CONCLUSION We created a molecular map of the IgE antibody response to the most important peanut allergen proteins to enable the design of new allergy immunotherapies and vaccines.