Heat-Induced Structural Changes Affect OVA-Antigen Processing and Reduce Allergic Response in Mouse Model of Food Allergy

Jaroslav Golias,Ludmila Tuckova,Klara Klimesova,Hana Kozakova,Dagmar Srutkova,Miloslav Kverka,Fatima Ferreira,Petr Sotkovsky,Martin Schwarzer,Lenka Palova-Jelinkova,Michael Wallner,Lucienne Chatenoud

doi:10.1371/journal.pone.0037156

Abstract

Background and AimsThe egg protein ovalbumin (OVA) belongs to six most frequent food allergens. We investigated how thermal processing influences its ability to induce allergic symptoms and immune responses in mouse model of food allergy.Methodology/Principal FindingsEffect of increased temperature (70°C and 95°C) on OVA secondary structure was characterized by circular dichroism and by the kinetics of pepsin digestion with subsequent HPLC. BALB/c mice were sensitized intraperitoneally and challenged with repeated gavages of OVA or OVA heated to 70°C (h-OVA). Levels of allergen-specific serum antibodies were determined by ELISA (IgA and IgGs) or by β-hexosaminidase release test (IgE). Specific activities of digestive enzymes were determined in brush border membrane vesicles of jejunal enterocytes. Cytokine production and changes in regulatory T cells in mesenteric lymph nodes and spleen were assessed by ELISA and FACS. Heating of OVA to 70°C caused mild irreversible changes in secondary structure compared to boiling to 95°C (b-OVA), but both OVA treatments led to markedly different digestion kinetics and Tregs induction ability in vitro, compared to native OVA. Heating of OVA significantly decreased clinical symptoms (allergic diarrhea) and immune allergic response on the level of IgE, IL-4, IL-5, IL-13. Furthermore, h-OVA induced lower activities of serum mast cell protease-1 and enterocyte brush border membrane alkaline phosphatase as compared to native OVA. On the other hand h-OVA stimulated higher IgG2a in sera and IFN-γ secretion by splenocytes.ConclusionsMinor irreversible changes in OVA secondary structure caused by thermal processing changes both its digestion and antigenic epitopes formation, which leads to activation of different T cell subpopulations, induces shift towards Th1 response and ultimately reduces its allergenicity.

Highlights

Food allergy is a serious health concern affecting 6–8% of young children and about 2–4% of adults
Minor irreversible changes in ovalbumin-treated group (OVA) secondary structure caused by thermal processing changes both its digestion and antigenic epitopes formation, which leads to activation of different T cell subpopulations, induces shift towards Th1 response and reduces its allergenicity
Since eggs could be consumed after various kinds of processing, we analyzed the effect of different temperatures on the secondary structure of OVA allergen

Summary

Introduction

Food allergy is a serious health concern affecting 6–8% of young children and about 2–4% of adults. In mouse models of food allergy, oral administration of allergen usually results in oral tolerance induction, but its co-administration with strong mucosal adjuvant such as cholera toxin or with anti acid drugs (increasing gastric pH) could be used for allergic sensitization [7,8,9,10] Another reliable and effective approach to overcome the oral tolerance induction is pretreatment of mice by systemic intraperitoneal (i.p.) administration of allergen with aluminum hydroxide (alum) as adjuvant followed by repeated intra-gastric treatments. This experimental model mimics a mild form of human allergy with IgE–mediated mast cell degranulation causing increased small intestine permeability [2,11,12] with diarrhea as one of the symptoms of anaphylaxis. We investigated how thermal processing influences its ability to induce allergic symptoms and immune responses in mouse model of food allergy

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