Antigenic determinants underlying IgE-mediated anaphylaxis to peanut.

Background: Studies of human IgE and its targeted epitopes on allergens have been very limited. We established a method to immortalize IgE-encoding B cells from patients with allergy.

Objective: We sought 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 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 Ara h 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. IgG switch variant immunoglobulins of the IgE mAb inhibited binding of 30% to 60% of patients' IgE to peanut extract (ImmunoCAP) and reduced peanut extract-induced skin wheal sizes by 1.6 to 7.4 mm in patients with peanut allergy.

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.