Caffeic acid-assisted cross-linking catalyzed by polyphenol oxidase decreases the allergenicity of ovalbumin in a Balb/c mouse model.
Ovalbumin (OVA) is the most abundant egg white protein, but is also a major egg allergen. Desensitization of OVA may be a good way to control an egg allergy. In this study, caffeic acid-assisted cross-linked OVA catalyzed by polyphenol oxidase (PPO) was prepared, the effect of cross-linking on the allergenicity of OVA was tested in a Balb/c mouse model. Mice were orally sensitized with OVA or cross-linked OVA using cholera toxin as adjuvant. Clinical signs of allergy, specific antibody levels, serum histamine levels, mast cell protease-1 (mMCP-1) concentrations, morphological structure of duodenum, and cytokines were determined after mice were challenged with OVA or cross-linked OVA. Both OVA and cross-linked OVA induced allergic diarrhea in Balb/c mice, however, histological symptoms of small intestine were much milder in mice fed with cross-linked OVA than in those fed with OVA. A tendency toward decreased allergen-specific IgE, IgG, IgG1 and IgG2a levels, as well as serum histamine and mMCP-1 concentration were observed in cross-linked OVA group, accompanied by an inhibition of IL-4, IL-5, IL-13 and IFN-γ production in the stimulated spleen cell. It could be concluded that caffeic acid-assisted PPO-catalyzed cross-linking significantly reduced the potential allergenicity of OVA, but may not completely eliminate it.