The 2S albumin allergens of Arachis hypogaea, Ara h 2 and Ara h 6, are the major elicitors of anaphylaxis and can effectively desensitize peanut‐allergic mice

Abstract

Background Ara h 2 and Ara h 6, co-purified together in a 13-25 kD fraction (Ara h 2/6; 20 kD fraction) on gel filtration chromatography, account for the majority of effector activity in a crude peanut extract (CPE) when assayed with RBL SX-38 cells sensitized with IgE from human peanut allergic sera. Objectives To determine if Ara h 2/6 are the primary peanut allergens responsible for allergic reactions in vivo and to determine if Ara h 2/6 would be sufficient to prevent allergic reactions to a complete CPE. Methods An oral sensitization mouse model of peanut allergy was used to assess the activity of Ara h 2/6 (20 kD) and CPE without the 20 kD fraction (CPE w/o 20 kD) for allergic provocation challenge and immunotherapy. The activity of these preparations was also tested in an assay of histamine release from human basophils in whole blood. Results Compared to mice challenged with control CPE, mice challenged with CPE w/o 20 kD experienced reduced symptoms (p<0.05) and a smaller decrease in body temperature (p<0.01). Results with the basophil histamine release assay corroborated these findings (p<0.01). The mouse model was also used to administer Ara h 2/6 (20 kD) in an immunotherapy protocol, in which peanut-allergic mice treated with the 20 kD fraction experienced significantly reduced symptoms, changes in body temperature, and mast cell protease (MMCP-1) release compared to placebo (p<0.01 for all parameters). Importantly, immunotherapy with the 20 kD fraction was just as effective as treatment with CPE, whereas CPE w/o 20 kD was significantly less effective for higher dose peanut challenges. Conclusions and Clinical Relevance Ara h 2/6 are the most potent peanut allergens in vivo and can be used to desensitize peanut-allergic mice. These results have potential implications for clinical research in the areas of diagnosis and immunotherapy for peanut allergy.

Allergenic Properties of Enzymatically Hydrolyzed Peanut Flour Extracts

“…A previous report found that Ara h 2 treated with trypsin/chymotrypsin displayed minimal reduction in IgE binding capacity, and mediator release from rat basophilic leukemia cells was not reduced by protease treatment, which was attributed to the proteolytic resistant core of Ara h 2 [23]. Additionally, studies have examined the effector activity of the peanut 2S albumins, Ara h 2 and 6, and have demonstrated that these proteins are the most potent peanut allergens in terms of degranulating basophils [7] and inducing anaphylaxis in a mouse model of peanut allergy [25]. Our current data show Ara h 2 fragments are present following any of the enzymatic hydrolyses, and thus may account for the persistent basophil reactivity we measured in response to the hydrolysates.…”

Peanut allergens are rapidly transferred in human breast milk and can prevent sensitization in mice

“…In fact, these 2S albumins are the most seroprevalent in specific IgE immunoassays and the more potent ones in triggering effector cell activation in vitro and positive skin prick test in allergic patients (27,33,48,(49)(50)(51)(52)(53). Both Ara h 2 and Ara h 6 have been shown to be resistant to enzymatic digestion (54)(55)(56).…”

Commensal bacteria protect against food allergen sensitization

“…To explore this hypothesis, we developed an assay to measure the transient presence of allergen in the blood after intragastric gavage. Several Ara h proteins have been identified as the immunodominant allergens of PN (Arachis hypogaea) (20). We used sensitive capture ELISAs to measure the concentration of two of these proteins in the systemic circulation.…”