Experimental Therapy of Peanut Allergy with Ara h2-Fcgamma Fusion Protein in Mice

Abstract

RATIONALE: Conventional immunotherapy for peanut allergy of using crude peanut extracts is not recommended because of the unacceptably high risk of anaphylaxis. Allergen-specific immunotherapy is not currently undertaken for peanut allergy.METHODS: We genetically designed and expressed a novel plant-human fusion protein composed of the major peanut allergen Ara h2 and the human IgG Fcγ1. We tested the Ara h2-Fcγ fusion protein's function in purified human basophils. Transgenic mice expressing human FcεRIα and a peanut allergy murine model were used.RESULTS: The Ara h2-Fcγ fusion protein inhibited histamine release induced by whole peanut extract (WPE) in a dose-dependent manner in human basophils. The fusion protein itself did not induce mediator release in peanut-specific IgE sensitized basophils. The Ara h2-Fcγ fusion protein inhibited the WPE-induced peanut-specific IgE-mediated degranulation in transgenic mice. The Ara h2-Fcγ fusion protein also significantly inhibited acute anaphylactic reaction and the prototypical drop of body temperature in oral WPE-sensitized mice challenged with crude peanuts. The WPE-sensitized mice did not have any drops in body temperature nor did they experience any anaphylactic reactions after the Ara h2-Fcγ fusion protein challenge. Histologic evaluation of the airways showed that the Ara h2-Fcγ fusion protein definitely decreased the inflammatory infiltration induced by WPE. The fusion protein itself did not cause any inflammation in the airway of WPE-sensitized mice.CONCLUSIONS: The Ara h2-Fcγ fusion protein inhibited peanut-specific IgE-mediated allergic reactions in vitro and in vivo. Linking specific peanut allergen to Fcγ can provide a new approach for the allergen immunotherapy of peanut allergy. RATIONALE: Conventional immunotherapy for peanut allergy of using crude peanut extracts is not recommended because of the unacceptably high risk of anaphylaxis. Allergen-specific immunotherapy is not currently undertaken for peanut allergy. METHODS: We genetically designed and expressed a novel plant-human fusion protein composed of the major peanut allergen Ara h2 and the human IgG Fcγ1. We tested the Ara h2-Fcγ fusion protein's function in purified human basophils. Transgenic mice expressing human FcεRIα and a peanut allergy murine model were used. RESULTS: The Ara h2-Fcγ fusion protein inhibited histamine release induced by whole peanut extract (WPE) in a dose-dependent manner in human basophils. The fusion protein itself did not induce mediator release in peanut-specific IgE sensitized basophils. The Ara h2-Fcγ fusion protein inhibited the WPE-induced peanut-specific IgE-mediated degranulation in transgenic mice. The Ara h2-Fcγ fusion protein also significantly inhibited acute anaphylactic reaction and the prototypical drop of body temperature in oral WPE-sensitized mice challenged with crude peanuts. The WPE-sensitized mice did not have any drops in body temperature nor did they experience any anaphylactic reactions after the Ara h2-Fcγ fusion protein challenge. Histologic evaluation of the airways showed that the Ara h2-Fcγ fusion protein definitely decreased the inflammatory infiltration induced by WPE. The fusion protein itself did not cause any inflammation in the airway of WPE-sensitized mice. CONCLUSIONS: The Ara h2-Fcγ fusion protein inhibited peanut-specific IgE-mediated allergic reactions in vitro and in vivo. Linking specific peanut allergen to Fcγ can provide a new approach for the allergen immunotherapy of peanut allergy.