Human IgE Antibodies Recognize the Vicilin and Alpha-Hairpinin Domains of Peanut Allergen Ara h 1.

BACKGROUND: Most peanut allergic patients have antibodies to Ara h 1. Many studies have focused on the C-terminal vicilin region, with less attention concentrated on the N-terminal α-hairpinin domain. This study evaluated human monoclonal antibodies targeted to both regions. METHODS: Microarrays of Ara h 1 peptides were probed for serum IgE binding. Human monoclonal antibodies to Ara h 1 were discovered from single-cell sequencing and hybridoma technologies. Western blots evaluated the cleavage pattern of Ara h 1 in peanuts. A mouse model of passive systemic anaphylaxis (PSA) evaluated the functional coupling of antibodies. ELISAs established antibody specificities. RESULTS: In 75 allergic patients, the most frequently recognized peptides from Ara h 1 were in the unstructured region (91%), the α-hairpinin (86%), and the vicilin region (79%). Monoclonal antibodies were divided by specificity for the α-hairpinin and vicilin regions with no significant cross-reactivity observed. The anti-α-hairpinin mAb 40C7 blocked 55%-92% of patient IgE to the domain in seven patients; ELISA results showed the epitope of 40C7 was associated with a frequently recognized peptide found via microarray. Pairing of anti-α-hairpinin mAbs failed to induce anaphylaxis via PSA; however, a single mAb against the vicilin region induced anaphylaxis when challenged with nAra h 1. CONCLUSIONS: The α-hairpinin of Ara h 1 contains a dominant epitope that is both frequently recognized and blocks a majority of the IgE against this domain. Including this region in tests may improve diagnosis of peanut allergy. The trimeric structure of the vicilin region explains the ability of Ara h 1 to induce anaphylaxis with a single antibody.