The intestinal gut microbiota is essential for maintaining host health. Concerns have been raised about the possible connection between antibiotic use, causing microbiota disturbances, and the increase in allergic and autoimmune diseases observed during the last decades. To elucidate the putative connection between antibiotic use and immune regulation, we have assessed the effects of the antibiotic amoxicillin on immune regulation, protein uptake, and bacterial community structure in a Brown Norway rat model. Daily intra-gastric administration of amoxicillin resulted in an immediate and dramatic shift in fecal microbiota, characterized by a reduction of within sample (α) diversity, reduced variation between animals (β diversity), increased relative abundance of Bacteroidetes and Gammaproteobacteria, with concurrent reduction of Firmicutes, compared to a water control group. In the small intestine, amoxicillin also affected microbiota composition significantly, but in a different way than observed in feces. The small intestine of control animals was vastly dominated by Lactobacillus, but this genus was much less abundant in the amoxicillin group. Instead, multiple different genera expanded after amoxicillin administration, with high variation between individual animals, thus the small intestinal α and β diversity were higher in the amoxicillin group compared to controls. After 1 week of daily amoxicillin administration, total fecal IgA level, relative abundance of small intestinal regulatory T cells and goblet cell numbers were higher in the amoxicillin group compared to controls. Several bacterial genera, including Escherichia/Shigella, Klebsiella (Gammaproteobacteria), and Bifidobacterium, for which the relative abundance was higher in the small intestine in the amoxicillin group than in controls, were positively correlated with the fraction of small intestinal regulatory T cells. Despite of epidemiologic studies showing an association between early life antibiotic consumption and later prevalence of inflammatory bowel diseases and food allergies, our findings surprisingly indicated that amoxicillin-induced perturbation of the gut microbiota promotes acute immune regulation. We speculate that the observed increase in relative abundance of small intestinal regulatory T cells is partly mediated by immunomodulatory lipopolysaccharides derived from outgrowth of Gammaproteobacteria.

Background: Allergic sensitisation to foods may occur in infancy without prior oral exposure to the offending food, leading to the assumption that food allergy sensitisation may occur through the skin. Concerns have been raised regarding the safety of use of personal care products containing hydrolysed wheat proteins, since these products have been shown to induce allergy through the skin, and even cause an abrogation of an already established oral tolerance. Objective: To establish an animal model for food allergy skin sensitisation and compare the sensitising capacity of an unmodified and an acid-hydrolysed gluten product via slightly damaged skin in naïve versus tolerant rats. Methods: Gluten products were applied on the slightly damaged skin of naïve or tolerant Brown Norway (BN) rats without adjuvant 3 times per week for 3 or 5 consecutive weeks. The effect of the skin applications was evaluated by means of different ELISAs and immunoblotting. Results: A robust animal model was developed for food allergy skin sensitisation. In naïve rats, both gluten products were able to induce a statistically significant level of specific antibodies and sensitise through the skin, but in the wheat-tolerant rats, only the acid-hydrolysed gluten was able to sensitise through the skin, albeit at a level much lower than in the naïve rats. Results showed that new epitopes had been developed as a result of acid hydrolysis but original epitopes were maintained. This may explain why only the acid-hydrolysed gluten could induce specific antibody responses in the tolerant animals. Conclusions: This study showed that it is possible to sensitise BN rats through slightly damaged skin, and that the sensitising capacity is heavily influenced by the tolerance status of their immune system and the degree of modification of the wheat products.

Background: When breastfeeding is impossible or insufficient, the use of cow’s milk-based hypoallergenic infant formulas is an option for infants suffering from or at risk of developing cow’s milk allergy. As the Camelidae family has a large evolutionary distance to the Bovidae family and as camel milk differs from cow’s milk protein composition, there is a growing interest in investigating the suitability of camel milk as an alternative to cow’s milk-based hypoallergenic infant formulas. Methods: The aim of the study was to compare the allergenicity and immunogenicity of camel and cow’s milk as well as investigating their cross-reactivity using a Brown Norway rat model. Rats were immunised intraperitoneally with one of four products: camel milk, cow’s milk, cow’s milk casein or cow’s milk whey fraction. Immunogenicity, sensitising capacity, antibody avidity and cross-reactivity were evaluated by means of different ELISAs. The eliciting capacity was evaluated by an ear swelling test. Results: Camel and cow’s milk showed similarity in their inherent immunogenicity, sensitising and eliciting capacity. Results show that there was a lower cross-reactivity between caseins than between whey proteins from camel and cow’s milk. Conclusions: The study showed that camel and cow’s milk have a low cross-reactivity, indicating a low protein similarity. Results demonstrate that camel milk could be a promising alternative to cow’s milk-based hypoallergenic infant formulas.

Background: Food processing, including heat-treatment, can affect protein structure and stability, and consequently affect protein immunogenicity and allergenicity. A few studies have shown that structural changes induced by heat-treatment impact the intestinal protein uptake and suggest this as a contributing factor for altered allergenicity.Objective: To investigate the impact of heat-treatment of a whey-based protein product on allergenicity and tolerogenicity as well as on intestinal uptake in various animal models.Methods: Immunogenicity and sensitizing capacity of the heat-treated whey product were compared to that of the unmodified product by intraperitoneal and oral exposure studies, while tolerogenic properties were assessed by oral primary prevention and desensitization studies in high-IgE responder Brown Norway rats. Results:Heat-treatment of whey induced partial protein denaturation and aggregation, which reduced the intraperitoneal sensitizing capacity but not immunogenicity. In contrast, heat-treatment did not influence the oral sensitizing capacity, but the heat-treated whey showed a significantly reduced eliciting capacity compared to unmodified whey upon oral challenge. Heat-treatment did not reduce the tolerogenic properties of whey, as both products were equally good at preventing sensitization in naïve rats as well as desensitizing already sensitized rats. Results from inhibitory ELISA and immunoblots with sera from sensitized rats demonstrated that heat-treatment caused an altered protein and epitope reactivity. Protein uptake studies showed that heat-treatment changed the route of uptake with less whey being absorbed through the epithelium but more into the Peyer's patches. Conclusion and Clinical Relevance:These results support the notion that the physicochemical features of proteins affect their route of uptake and that the route of uptake may affect the protein allergenicity. Furthermore, the study highlights the potential for heat-treatment in the production of efficient and safe cow's milk proteinbased products for prevention and treatment of cow's milk allergy. K E Y W O R D S allergens and epitopes, animal models, food allergy, food processing, IgE, intestinal uptake, paediatrics | 709 GRAVERSEN Et Al. How to cite this article: Graversen KB, Ballegaard A-SR, Kraemer LH, et al. Cow's milk allergy prevention and treatment by heat-treated whey-A study in Brown Norway rats. Clin Exp Allergy. 2020;50:708-721. https://doi.

Scope: Personal care products containing hydrolyzed gluten have been linked to spontaneous sensitization through the skin, however the impact of the hydrolysate characteristics on the sensitizing capacity is generally unknown. Methods and Results: The physicochemical properties of five different wheat-derived gluten products (one unmodified, one enzyme hydrolyzed, and three acid hydrolyzed) are investigated, and the skin sensitizing capacity is determined in allergy-prone Brown Norway rats. Acid hydrolyzed gluten products exhibited the strongest intrinsic sensitizing capacity via the skin. All hydrolyzed gluten products induced cross-reactivity to unmodified gluten in the absence of oral tolerance to wheat, but were unable to break tolerance in animals on a wheat-containing diet. Still, the degree of deamidation in acid hydrolyzed products is associated with product-specific sensitization in wheat tolerant rats. Sensitization to acid hydrolyzed gluten products is associated with a more diverse IgE reactivity profile to unmodified gluten proteins compared to sensitization induced by unmodified gluten or enzyme hydrolyzed gluten. Conclusion: Acid hydrolysis enhances the skin sensitizing capacity of gluten and drives IgE reactivity to more gluten proteins. This property of acid hydrolyzed gluten may be related to the degree of product deamidation, and could be a strong trigger of wheat allergy in susceptible individuals.

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Scope: Within the last decade, quinoa seeds have gained much popularity as a new food and have recently been proposed as an appropriate food for early introduction in infants. Quinoa contains high levels of saponins, which are known for their adjuvant activity and effect on the intestinal barrier function. The aim of this study is to investigate the impact of quinoa on intestinal permeability and inflammation in comparison with the positive controls; cholera toxin (CT), and capsaicin. Methods and results: The effect of quinoa on intestinal barrier function and inflammation is investigated in vitro using a Caco-2 cell line and in vivo using a Brown Norway rat model. Effects in vivo are analyzed by protein uptake, histology, gene expression, antibody levels, and flow cytometry. Quinoa and the positive controls all increased the intestinal permeability, but distinct patterns of absorbed protein are observed in the epithelium, Peyer's patches, lamina propria, and serum. The quinoa-mediated effect on intestinal barrier function is found to be distinct from the effect of the two positive controls. Conclusion:The findings demonstrate the ability of quinoa to increase intestinal permeability and to promote compartment-specific protein uptake via mechanisms that may differ from CT and capsaicin.

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