BACKGROUND:Recent immunological data demonstrated that dendritic cells preferentially recognize advanced glycation end product (AGE)-modified proteins, upregulate expression of the receptor for AGE (RAGE), and consequently bias the immune response toward allergy. METHODS:Peanut extract was characterized by mass spectrometry (MS) to elucidate the specific residues and specific AGE modifications found in raw and roasted peanuts and on rAra h 1 that was artificially glycated by incubation with glucose or xylose. The binding of the RAGE-V1C1 domain to peanut allergens was assessed by PAGE and Western analysis with anti-Ara h 1, 2, and 3 antibodies. IgE binding to rAra h 1 was also assessed using the same methods. RESULTS:AGE modifications were found on Ara h 1 and Ara h 3 in both raw and roasted peanut extract. No AGE modifications were found on Ara h 2. Mass spectrometry and Western blot analysis demonstrated that RAGE binds selectively to Ara h 1 and Ara h 3 derived from peanut extract, whereas the analysis failed to demonstrate Ara h 2 binding to RAGE. rAra h 1 with no AGE modifications did not bind RAGE; however, after AGE modification with xylose, rAra h 1 bound to RAGE. CONCLUSIONS:AGE modifications to Ara h 1 and Ara h 3 can be found in both raw and roasted peanuts. Receptor for AGE was demonstrated to selectively interact with AGE-modified rAra h 1. If sensitization to peanut allergens occurs in dendritic cells via RAGE interactions, these cells are likely interacting with modified Ara h 1 and Ara h 3, but not Ara h 2.

BACKGROUND:Peanut allergy affects 1% of the population and causes the most fatal food-related anaphylactic reactions. The protein Ara h 2 is the most potent peanut allergen recognized by 80-90% of peanut allergic patients. METHODS:The crystal structure of the major peanut allergen Ara h 2 was determined for the first time at 2.7 Å resolution using a customized maltose-binding protein (MBP)-fusion system. IgE antibody binding to the MBP fusion construct vs the natural allergen was compared by ELISA using sera from peanut allergic patients. RESULTS:The structure of Ara h 2 is a five-helix bundle held together by four disulfide bonds and related to the prolamin protein superfamily. The fold is most similar to other amylase and trypsin inhibitors. The MBP--Ara h 2 fusion construct was positively recognized by IgE from 76% of allergic patients (25/33). Two populations of patients could be identified. Subpopulation 1 (n = 14) showed an excellent correlation of IgE antibody binding to natural vs recombinant Ara h 2. Subpopulation 2 (n = 15) showed significantly reduced IgE binding to the MBP fusion protein. Interestingly, about 20% of the IgE binding in subpopulation 2 could be recovered by increasing the distance between MBP and Ara h 2 in a second construct. DISCUSSION:The reduced IgE binding to the MBP--Ara h 2 of subpopulation 2 indicates that the MBP molecule protects an immunodominant epitope region near the first helix of Ara h 2. Residues involved in the epitope(s) are suggested by the crystal structure. The MBP--Ara h 2 fusion constructs will be useful to further elucidate the relevance of certain epitopes to peanut allergy.