Development and characterization of an effective food allergy model in Brown Norway rats

Feeding Docosahexaenoic Acid and Arachidonic Acid during Suckling and Weaning Contributes to Oral Tolerance Development by Beneficially Modulating the Intestinal Cytokine and Immunoglobulin Levels in an Allergy-Prone Brown Norway Rat Model

BACKGROUND

Suckling and weaning arachidonic acid (ARA) + docosahexaenoic acid (DHA) supplementation promoted oral tolerance (OT) development in pups, however, the effect of it on the intestine to promote OT development remains unknown.

OBJECTIVE

We aimed to explore the impact of this supplementation on intestinal fatty acid composition, structure, and indicators that are supportive of OT development.

METHODS

Allergy-prone Brown Norway dams were randomly assigned to a control (0% ARA, 0% DHA) or ARA + DHA diet (0.45% ARA, 0.8% DHA) during suckling (0-3 wk). At weaning (3-8 wk), offspring were randomly assigned to a control (0% ARA, 0% DHA) or ARA + DHA diet (0.5% ARA, 0.5% DHA). At 3 wk, offspring in each group received an oral gavage of sucrose or ovalbumin (OVA) solution for five consecutive days. At 7 wk, all offspring received an intraperitoneal OVA injection. At 8 wk, offspring were terminated to evaluate jejunum morphology and measure mucosal food allergy-related secretory immunoglobulin A (sIgA) and cytokines, ileum phospholipid and triglyceride fatty acid compositions, and fecal calprotectin.

RESULTS

Weaning ARA + DHA resulted in a higher percentage of DHA in ileum phospholipids and triglycerides (both P < 0.001), without affecting the percentage of ARA. Despite no lasting effect of suckling ARA + DHA on the DHA content in ileum phospholipids, a programming effect was found on the allergy-related intestinal immune profile [higher concentrations of mucosal IL-2 (P = 0.049) and sIgA (P = 0.033)]. OVA treatment resulted in a lower concentration of mucosal IL-6 (P = 0.026) regardless of dietary interventions. Offspring fed ARA + DHA during suckling and/or weaning had a higher concentration of mucosal transforming growth factor-beta (TGF-β) after OVA treatment but this was not observed in offspring fed control diets during suckling and weaning (P = 0.04).

CONCLUSIONS

Early life dietary ARA + DHA supplementation to allergy-prone rats enhanced the DHA concentration in intestinal phospholipids (weaning period) and increased the mucosal sIgA, IL-2, and TGF-β levels (suckling and weaning period), indicating its ability to create a tolerogenic intestinal environment to support OT development.

Integrating Widely Targeted Lipidomics and Transcriptomics Unravels Aberrant Lipid Metabolism and Identifies Potential Biomarkers of Food Allergies in Rats

SCOPE

Oral food challenges (OFCs) are currently the gold standard for determining the clinical reactivity of food allergy (FA) but are time-consuming, expensive, and risky. To screen novel peripheral biomarkers of FA and characterize the aberrant lipid metabolism in serum, 24 rats are divided into four groups: peanut, milk, and shrimp allergy (PA, MA, and SA, respectively) and control groups, with six rats in each group, and used for widely targeted lipidomics and transcriptomics analysis.

METHODS AND RESULTS

Widely targeted lipidomics reveal 144, 162, and 206 differentially accumulated lipids in PA, MA, and SA groups, respectively. The study integrates widely targeted lipidomics and transcriptomics and identifies abnormal lipid metabolism correlated with widespread differential accumulation of diverse lipids (including triacylglycerol, diacylglycerol, sphingolipid, and glycerophospholipid) in PA, MA, and SA. Simplified random forest classifier is constructed through five repetitions of 10-fold cross-validation to distinguish allergy from control. A subset of 15 lipids as potential biomarkers allows for more reliable and more accurate prediction of FA. Independent replication validates the reproducibility of potential biomarkers.

CONCLUSION

The results reveal the major abnormalities in lipid metabolism and suggest the potential role of lipids as novel molecular signatures for FA.

Biomarkers associated with persistence and severity of IgE-mediated food allergies: a systematic review

OBJECTIVE

The prevalence of food allergies (FA) has increased worldwide over the last few decades. Milk, eggs, and peanuts are among the most common allergens and can cause anaphylaxis. Therefore, we aimed to identify biomarkers that could predict the persistence and/or severity of IgE-mediated allergies to milk, eggs, and peanuts via a systematic review.

METHODS

This systematic review proceeded according to a protocol registered in the International Prospective Register of Systematic Reviews. Two independent authors extracted studies of interest from PubMed, SciELO, EMBASE, Scopus, and Ebsco databases and assessed their quality using the Newcastle-Ottawa Scale.

RESULTS

We selected 14 articles describing 1,398 patients. Among eight identified biomarkers, total IgE, specific IgE (sIgE), and IgG4 were the most often cited biomarkers of persistent allergies to milk, eggs, and peanuts. Skin prick tests, endpoint tests, and sIgE cutoff levels may predict positive responses to challenges with these foods. The basophil activation test is a biomarker for the severity and/or threshold of allergic reactions to milk and peanuts.

CONCLUSION

Only a few publications identified possible prognostic indicators of the persistence or severity of FA and outcomes of oral food challenges, indicating that more accessible biomarkers are needed to determine the likelihood of having a severe food allergic reaction.

Hypoxia modeling techniques: A review

Hypoxia is the main cause and effect of a large number of diseases, including the most recent one facing the world, the coronavirus disease (COVID-19). Hypoxia is divided into short-term, long-term, and periodic, it can be the result of diseases, climate change, or living and traveling in the high mountain regions of the world. Since each type of hypoxia can be a cause and a consequence of various physiological changes, the methods for modeling these hypoxias are also different. There are many techniques for modeling hypoxia under experimental conditions. The most common animal for modeling hypoxia is a rat. Hypoxia models (hypoxia simulations) in rats are a tool to study the effect of various conditions on the oxygen supply of the body. These models can provide a necessary information to understand hypoxia and also provide effective treatment, highlighting the importance of various reactions of the body to hypoxia. The main parameters when choosing a model should be reproducibility and the goal that the scientist wants to achieve. Hypoxia in rats can be reproduced both ways exogenously and endogenously. The reason for writing this review was the aim to systematize the models of rats available in the literature in order to facilitate their selection by scientists. The relative strengths and limitations of each model need to be identified and understood in order to evaluate the information obtained from these models and extrapolate these results to humans to develop the necessary generalizations. Despite these problems, animal models have been and remain vital to understanding the mechanisms involved in the development and progression of hypoxia. The eligibility criteria for the selected studies was a comprehensive review of the methods and results obtained from the studies. This made it possible to make generalizations and give recommendations on the application of these methods. The review will assist scientists in choosing an appropriate hypoxia simulation method, as well as assist in interpreting the results obtained with these methods.

Influence of Consumption of Two Peruvian Cocoa Populations on Mucosal and Systemic Immune Response in an Allergic Asthma Rat Model

Different cocoa populations have demonstrated a protective role in a rat model of allergic asthma by attenuating the immunoglobulin (Ig) E synthesis and partially protecting against anaphylactic response. The aim of this study was to ascertain the effect of diets containing two native Peruvian cocoa populations (“Amazonas Peru” or APC, and “Criollo de Montaña” or CMC) and an ordinary cocoa (OC) on the bronchial compartment and the systemic and mucosal immune system in the same rat model of allergic asthma. Among other variables, cells and IgA content in the bronchoalveolar lavage fluid (BALF) and serum anti-allergen antibody response were analyzed. The three cocoa populations prevented the increase of the serum specific IgG1 (T helper 2 isotype). The three cocoa diets decreased asthma-induced granulocyte increase in the BALF, which was mainly due to the reduction in the proportion of eosinophils. Moreover, both the OC and CMC diets were able to prevent the leukocyte infiltration caused by asthma induction in both the trachea and nasal cavity and decreased the IgA in both fecal and BALF samples. Overall, these results highlight the potential of different cocoa populations in the prevention of allergic asthma.

Protective Effect of Glycomacropeptide on Food Allergy with Gastrointestinal Manifestations in a Rat Model through Down-Regulation of Type 2 Immune Response

Glycomacropeptide (GMP) is a bioactive peptide derived from milk κ-casein with immune-modulatory and anti-inflammatory properties. Food allergy (FA) is an adverse immune reaction with a broad spectrum of manifestations. Allergen intake induces persistent intestinal inflammation and tissue damage. In this study, the anti-allergic activity of GMP was evaluated using a rat ovalbumin (OVA)-induced FA model with gastrointestinal manifestation. Rats were orally GMP treated from 3 days prior and during FA development. The severity of food anaphylaxis and diarrheal episodes, antibody production and histamine level were measured. Histopathological changes, inflammation and predominant cytokine profile at intestine were analyzed. Oral GMP intake decreased clinical signs and diarrhea severity induced by allergen, with a significant reduction in intestinal edema and expression level of IL-1β and TNF-α. Prophylaxis with GMP also diminished serum anti-OVA IgE and IgG1, and histamine levels. GMP treatment markedly decreased eosinophil infiltration, mast cell and goblet cell hyperplasia, total IgE expression in intestine, and prevented histological changes in villi, crypts and internal muscularis layer. The treatment effectively suppressed IL-5, IL-13 and GATA3 expression and skewed the intestinal cytokine profile toward type 1 and regulatory. These results suggest that GMP may protect against FA through down-regulating the type 2 inflammatory response.

Attenuating Effect of Peruvian Cocoa Populations on the Acute Asthmatic Response in Brown Norway Rats

Cocoa contains bioactive components, which vary according to genetic and environmental factors. The present study aimed to ascertain the anti-allergic properties of native Peruvian cocoa populations ("Blanco de Piura" or BPC, "Amazonas Peru" or APC, "Criollo de Montaña" or CMC, "Chuncho" or CCC, and an ordinary cocoa or OC). To do so, after an initial in vitro approach, an in vivo study focused on the induction of an anaphylactic response associated with allergic asthma in Brown Norway rats was carried out. Based on their polyphenol content, antioxidant activity and in vitro effects, the APC and CMC were selected to be included in the in vivo study. Cocoa diets were tested in a model of allergic asthma in which anaphylactic response was assessed by changes in body temperature, motor activity and body weight. The concentration of specific immunoglobulin E (IgE), mast cell protease and leukotrienes was also quantified in serum and/or bronchoalveolar lavage fluid. CMC and OC populations exhibited a protective effect on the allergic asthma rat model as evidenced by means of a partial protection against anaphylactic response and, above all, in the synthesis of IgE and the release of mast cell protease.

Development and Characterization of an Allergic Asthma Rat Model for Interventional Studies

Allergic asthma is one of the most common chronic diseases of the airways, however it still remains underdiagnosed and hence undertreated. Therefore, an allergic asthma rat model would be useful to be applied in future therapeutic strategy studies. The aim of the present study was to develop an objective model of allergic asthma in atopic rats that allows the induction and quantification of anaphylactic shock with quantitative variables. Female Brown Norway rats were intraperitoneally sensitized with ovalbumin (OVA), alum and Bordetella pertussis toxin and boosted a week later with OVA in alum. At day 28, all rats received an intranasal challenge with OVA. Anaphylactic response was accurately assessed by changes in motor activity and body temperature. Leukotriene concentration was determined in the bronchoalveolar lavage fluid (BALF), and total and IgE anti-OVA antibodies were quantified in blood and BALF samples. The asthmatic animals' motility and body temperature were reduced after the shock for at least 20 h. The asthmatic animals developed anti-OVA IgE antibodies both in BALF and in serum. These results show an effective and relatively rapid model of allergic asthma in female Brown Norway rats that allows the quantification of the anaphylactic response.

Short-Term Amoxicillin-Induced Perturbation of the Gut Microbiota Promotes Acute Intestinal Immune Regulation in Brown Norway Rats

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.

Overview of in vivo and ex vivo endpoints in murine food allergy models: Suitable for evaluation of the sensitizing capacity of novel proteins?

Significant efforts are necessary to introduce new dietary protein sources to feed a growing world population while maintaining food supply chain sustainability. Such a sustainable protein transition includes the use of highly modified proteins from side streams or the introduction of new protein sources that may lead to increased clinically relevant allergic sensitization. With food allergy being a major health problem of increasing concern, understanding the potential allergenicity of new or modified proteins is crucial to ensure public health protection. The best predictive risk assessment methods currently relied on are in vivo models, making the choice of endpoint parameters a key element in evaluating the sensitizing capacity of novel proteins. Here, we provide a comprehensive overview of the most frequently used in vivo and ex vivo endpoints in murine food allergy models, addressing their strengths and limitations for assessing sensitization risks. For optimal laboratory‐to‐laboratory reproducibility and reliable use of predictive tests for protein risk assessment, it is important that researchers maintain and apply the same relevant parameters and procedures. Thus, there is an urgent need for a consensus on key food allergy parameters to be applied in future food allergy research in synergy between both knowledge institutes and clinicians.

Influence of Leptin and Adiponectin Supplementation on Intraepithelial Lymphocyte and Microbiota Composition in Suckling Rats

Dietary components in early life play a role in both microbiota and intestinal immune system maturation in mammalian species. Adipokines, as endogenously produced hormones from breast milk, may have an impact on this process. The aim of the present study was to establish the influence of leptin and adiponectin supplementation during suckling on the intraepithelial lymphocyte composition, intestinal barrier function, intestinal gene expression, and gut microbiota in rat. For this purpose, newborn Wistar rats were supplemented daily with leptin, adiponectin, or whey protein concentrate during the first 21 days of life. Lymphocyte composition was established by immunofluorescence staining and flow cytometry analysis; intestinal gene expression by real-time PCR and cecal microbiota were analyzed through 16S rRNA gene sequencing. Although leptin and adiponectin were able to increase the Tc TCRαβ⁺ and NKT cell proportion, they decreased the NK cell percentage in IEL. Moreover, adipokine supplementation differentially modified CD8⁺ IEL. While the supplementation of leptin increased the proportion of CD8αα⁺ IEL (associated to a more intestinal phenotype), adiponectin enhanced that of CD8αβ⁺ (related to a peripheral phenotype). Furthermore, both adipokines enhanced the gene expression of TNF-α, MUC-2, and MUC-3, and decreased that of FcRn. In addition, the adipokine supplementations decreased the abundance of the Proteobacteria phylum and the presence of Blautia. Moreover, leptin-supplemented animals had lower relative abundance of Sutterella and a higher proportion of Clostridium genus, among others. However, supplementation with adiponectin resulted in lower abundance of the Roseburia genus and a higher proportion of the Enterococcus genus. In conclusion, the supplementation with leptin and adiponectin throughout the suckling period had an impact on both the IEL composition and the gut microbiota pattern, suggesting a modulatory role of these adipokines on the development of intestinal functionality.

Mouse Models for Food Allergies: Where Do We Stand?

Food allergies are a steadily increasing health and economic problem. Immunologically, food allergic reactions are caused by pathological, allergen-specific Th2 responses resulting in IgE-mediated mast cell degranulation and associated inflammatory reactions. Clinically, food allergies are characterized by local inflammation of the mouth mucosa, the face, the throat, the gastrointestinal tract, are frequently paralleled by skin reactions, and can result in life-threatening anaphylactic reactions. To better understand food allergies and establish novel treatment options, mouse models are indispensable. This review discusses the available mouse food allergy models, dividing them into four categories: (1) adjuvant-free mouse models, (2) mouse models relying on adjuvants to establish allergen-specific Th2 responses, (3) mouse models using genetically-modified mouse strains to allow for easier sensitization, and (4) humanized mouse models in which different immunodeficient mouse strains are reconstituted with human immune or stem cells to investigate humanized immune responses. While most of the available mouse models can reproducibly portray the immunological parameters of food allergy (Th2 immune responses, IgE production and mast cell activation/expansion), so far, the recreation of the clinical parameters has proven more difficult. Therefore, up to now none of the available mouse models can reproduce the complete human pathology.

Relationship between Cocoa Intake and Healthy Status: A Pilot Study in University Students

Due to its polyphenol content, cocoa's potential health effects are attracting much attention, showing, among other things, cardioprotective, anti-inflammatory, anti-obesity, and neuroprotective actions. However, there is very limited information regarding the effect of cocoa on human immunity. This study aimed to establish the relationship between cocoa consumption and health status, focusing on physical activity habits and allergy prevalence in young people. For this, a sample of 270 university students was recruited to complete a food frequency questionnaire, the International Physical Activity Questionnaire (IPAQ), and a lifestyle and health status questionnaire. The results were analysed by classifying the participants into tertiles defined according to their cocoa consumption: low (LC), moderate (MC), and high (HC) consumers. The consumption of cocoa inversely correlated with physical activity and the MC group had significantly less chronic disease frequency than the LC group. The percentage of allergic people in the MC and HC groups was lower than that in the LC group and, moreover, the cocoa intake, especially moderate consumption, was also associated with a lower presence of allergic symptoms. Thus, from these results a positive effect of cocoa intake on allergy can be suggested in the young population.

Upregulation of calprotectin in mild IgE-mediated ovalbumin hypersensitivity

Calprotectin, also known as S100A8/A9, has been linked to gut inflammation caused by IgE-mediated food hypersensitivities, but the pathophysiologic abnormalities it causes remain to be determined. We created a mild food hypersensitivity model through oral gavage of ovalbumin in Norway brown rats without using immune adjuvant. Changes in the levels of calprotectin and inflammation-associated cytokines were then observed over time. We found that fecal calprotectin as well as jejunal and liver TLR4, TNF-α, NF-κB, IL-1β, and IL-6 were upregulated in hypersensitive rats. Additionally, the influence of calprotectin on CD4⁺ T and dendritic cells was observed by co-culturing CD4⁺ T cells with dendritic cells, which revealed a shift toward increased Th2 T cells in calprotectin-treated cultures. These results suggest that calprotectin, along with other inflammatory factors, promotes the inflammation seen in mild food allergy.

V-set and Ig domain-containing 4 (VSIG4)-expressing hepatic F4/80+ cells regulate oral antigen-specific responses in mouse

Oral tolerance can prevent unnecessary immune responses against dietary antigens. Members of the B7 protein family play critical roles in the positive and/or negative regulation of T cell responses to interactions between APCs and T cells. V-set and Ig domain-containing 4 (VSIG4), a B7-related co-signaling molecule, has been known to act as a co-inhibitory ligand and may be critical in establishing immune tolerance. Therefore, we investigated the regulation of VSIG4 signaling in a food allergy and experimental oral tolerance murine models. We analyzed the contributions of the two main sites involved in oral tolerance, the mesenteric lymph node (MLN) and the liver, in VSIG4-mediated oral tolerance induction. Through the comparative analysis of major APCs, dendritic cells (DCs) and macrophages, we found that Kupffer cells play a critical role in inducing regulatory T cells (Tregs) and establishing immune tolerance against oral antigens via VSIG4 signaling. Taken together, these results suggest the possibility of VSIG4 signaling-based regulation of orally administered antigens.

Cocoa Diet Prevents Antibody Synthesis and Modifies Lymph Node Composition and Functionality in a Rat Oral Sensitization Model

Cocoa powder, a rich source of polyphenols, has shown immunomodulatory properties in both the intestinal and systemic immune compartments of rats. The aim of the current study was to establish the effect of a cocoa diet in a rat oral sensitization model and also to gain insight into the mesenteric lymph nodes (MLN) activities induced by this diet. To achieve this, three-week-old Lewis rats were fed either a standard diet or a diet with 10% cocoa and were orally sensitized with ovalbumin (OVA) and with cholera toxin as a mucosal adjuvant. Specific antibodies were quantified, and lymphocyte composition, gene expression, and cytokine release were established in MLN. The development of anti-OVA antibodies was almost totally prevented in cocoa-fed rats. In addition, this diet increased the proportion of TCRγδ+ and CD103+CD8+ cells and decreased the proportion of CD62L+CD4+ and CD62L+CD8+ cells in MLN, whereas it upregulated the gene expression of OX40L, CD11c, and IL-1β and downregulated the gene expression of IL-17α. In conclusion, the cocoa diet induced tolerance in an oral sensitization model accompanied by changes in MLN that could contribute to this effect, suggesting its potential implication in the prevention of food allergies.

Effect of a cocoa-enriched diet on immune response and anaphylaxis in a food allergy model in Brown Norway rats

Previous studies have demonstrated that cocoa intake decreased Th2 immune-related antibodies in rats. In consequence, we aimed to study in depth this cocoa action, particularly assessing its effect on a rat model of food allergy (FA) and also on an anaphylactic response. The involvement of the intestinal immune system was analyzed to allow the action mechanisms to be investigated. The role of cocoa flavonoids in the antiallergic properties of cocoa was also established. Brown Norway rats were fed either a reference diet or diets containing conventional cocoa (CC) or nonfermented cocoa (NFC). FA to ovalbumin (OVA) was induced and, later, an anaphylactic response was provoked. As expected, the synthesis of anti-OVA IgE and other Th2-related antibodies was inhibited by CC diet. In addition, the release of mast cell protease II after anaphylaxis was partially prevented by CC, although other variables were not modified. The CC diet also attenuated the increase of some Th2-related cytokines released from mesenteric lymph node and spleen cells, and modulated the intestinal gene expression of molecules involved in allergic response. These results demonstrated the local and systemic influence of CC diet. The effects of the NFC diet were weaker than those of CC, suggesting that cocoa components other than flavonoids play a role in cocoa's action. In conclusion, by acting on intestinal and systemic immune functions, a cocoa-enriched diet in rats exhibited a protective effect against FA and partially against anaphylaxis, making this a food of high interest to the fields of health and immunonutrition.