Immune response in mice to ingested soya protein: antibody production, oral tolerance and maternal transfer

Percutaneous Sensitization to Soybean Proteins Is Attenuated by Oral Tolerance

Oral tolerance prevents allergic responses, but cutaneous exposure to food allergens predisposes individuals to food allergies. Soybean, a major allergenic food, is also an ingredient in various cosmetic products. However, it remains to be determined whether oral tolerance prevents percutaneous sensitization to soybean proteins in humans or animal models. In this study, BALB/c mice were divided into three groups; the SS group fed a soybean-containing diet, and the CS and control (C) groups fed a soybean-free diet. After being dorsally shaved, the CS and SS groups were epicutaneously exposed to a soybean extract while the control group was exposed to only the carrier. Specific IgE and IgG1 immunoglobulins secreted in response to the soybean proteins were measured using enzyme-linked immunosorbent assays. Exposure to the soybean extract elicited the secretion of IgE and IgG1 specific for Gly m 5 and Gly m 6, and trypsin inhibitor. Oral soybean consumption attenuated the secretion of all the soybean-specific IgEs and IgG1s, suggesting that percutaneous sensitization to soybean proteins is attenuated by oral tolerance.

Acid hydrolysis of wheat gluten induces formation of new epitopes but does not enhance sensitizing capacity by the oral route: a study in "gluten free" Brown Norway rats

Background

Acid hydrolyzed wheat proteins (HWPs) are used in the food and cosmetic industry as emulsifiers. Cases of severe food allergic reactions caused by HWPs have been reported. Recent data suggest that these reactions are caused by HWPs produced by acid hydrolysis.

Objectives

To examine the sensitizing capacity of gluten proteins per se when altered by acid or enzymatic hydrolysis relative to unmodified gluten in rats naïve to gluten.

Methods

High IgE-responder Brown Norway (BN) rats bred on a gluten-free diet were sensitized without the use of adjuvant to three different gluten products (unmodified, acid hydrolyzed and enzymatic hydrolyzed). Rats were sensitized by intraperitoneal (i.p.) immunization three times with 200 µg gluten protein/rat or by oral dosing for 35 days with 0.2, 2 or 20 mg gluten protein/rat/day. Sera were analyzed for specific IgG and IgE and IgG-binding capacity by ELISA. IgE functionality was measured by rat basophilic leukemia (RBL) assay.

Results

Regardless of the route of dosing, all products had sensitizing capacity. When sensitized i.p., all three gluten products induced a strong IgG1 response in all animals. Acid hydrolyzed gluten induced the highest level of specific IgE but with a low functionality. Orally all three gluten products induced specific IgG1 and IgE but with different dose-response relations. Sensitizing rats i.p. or orally with unmodified or enzymatic hydrolyzed gluten induced specific IgG1 responses with similar binding capacity which was different from that of acid hydrolyzed gluten indicating that acid hydrolysis of gluten proteins induces formation of ‘new’ epitopes.

Conclusions

In rats not tolerant to gluten acid hydrolysis of gluten enhances the sensitizing capacity by the i.p. but not by the oral route. In addition, acid hydrolysis induces formation of new epitopes. This is in contrast to the enzymatic hydrolyzed gluten having an epitope pattern similar to unmodified gluten.

In vivo acute and humoral response to three-dimensional porous soy protein scaffolds

Increasing interest in using soy biomaterials for tissue engineering applications has prompted investigation into the in vivo biocompatibility of soy implants. In this study, the biocompatibility of soy protein scaffolds fabricated using freeze-drying and 3-D printing was assessed using a subcutaneous implant model in BALB/c mice. The main objectives of this study were: (1) to compare soy protein with bovine collagen, a well-characterized natural protein implant, by implanting scaffolds of the same protein weight, and (2) to observe the effects of soy scaffold microstructure and amount of protein loading, which also alters the degradation properties, on the acute and humoral immune responses towards soy. Results showed that freeze-dried soy scaffolds fully degraded after 14 days, whereas collagen scaffolds (of the same protein weight) remained intact for 56 days. Furthermore, Masson's trichrome staining showed little evidence of damage or fibrosis at the soy implant site. Scaffolds of higher soy protein content, however, were still present after 56 days. H&E staining revealed that macrophage infiltration was hindered in the denser bioplotted soy scaffolds, causing slower degradation. Analysis of soy-specific antibodies in mouse serum after implantation revealed levels of IgG1 that correlated with higher scaffold weight and protein density. However, no soy-specific IgE was detected, indicating the absence of an allergic response to the soy implants. These results demonstrate that soy protein could be an acceptable biocompatible implant for tissue regeneration, and that scaffold porosity, soy protein density and scaffold degradation rate significantly affect the acute and humoral immune response.

Sensitization with 7S globulins from peanut, hazelnut, soy or pea induces IgE with different biological activities which are modified by soy tolerance

BACKGROUND

It is not known why some foods sensitizing via the gastrointestinal tract are prevalent allergenic foods and others are not. Eating habits, processing, and the food matrix have been suggested to influence the allergenicity of a given food. Factors related to protein structure, such as stability to digestion, have also been suggested. 7S globulins from peanut, hazelnut, soy, and pea were studied to determine whether related proteins would induce a similar sensitization when removed from their 'normal' matrix.

METHODS

Brown Norway rats (soy tolerant or nontolerant) were immunized i.p. 3 times with 100 μg purified peanut, hazelnut, soy, or pea 7S without adjuvant. Sera were analyzed for specific antibodies by different ELISAs (IgG1, IgG2a, and IgE), inhibition ELISA, and rat basophilic leukemia cell assay.

RESULTS

The 4 related 7S globulins induced a response with an almost identical level of specific antibodies, but peanut 7S induced IgE of higher avidity than hazelnut and pea 7S which, again, had a higher avidity than IgE induced by soy 7S. Soy tolerance reduced the functionality of IgE without influencing antibody titers.

CONCLUSIONS

Although the 4 7S globulins are structurally related allergens, they induce antibodies with different antigen-binding characteristics. Peanut 7S induces IgE of a higher avidity than hazelnut and pea 7S which, again, has a higher avidity than IgE induced by soy 7S. We also show that soy tolerance influences the function of antibodies to peanut 7S. These findings may help explain how antibodies of different clinical significances can develop in different individuals sensitized to the same allergen.

(Xeno)estrogen regulation of food allergy

Food allergy and other types of allergies are becoming epidemic in both the developed and developing countries. A large amount of information is available in literature that (xeno)estrogens can regulate the immune response in general, and the development of allergy in particular; however, the effect of (xeno)estrogens on food allergy is basically unknown. With increasing use of xenobiotics worldwide, chemicals with estrogenic activity have been accumulating in our environment. This review has summarized the current literature relating to the topic (xeno)estrogen regulation of food allergy. The effect of (xeno)estrogens on enterocytes, proteases for protein hydrolysis, dendritic cells and T-regulatory cells in the gastrointestinal tract has been discussed. Finally, considering the current confusion in literature regarding the effect of phytoestrogen genistein on the immune system, a brief discussion has been included for its effect on T(H)1-T(H)2 polarization, and possibly food allergy in its relation to windows of exposure. Sufficient evidences exist to support the notion that (xeno)estrogens can regulate food allergy, with the developmental periods more sensitive. Further clinical and animal studies are needed to determine the causal relationship between the exposure of (xeno)estrogens and incidence of food allergy, and the underlying mechanisms.

Immunotoxicological studies of genetically modified rice expressing PHA-E lectin or Bt toxin in Wistar rats

As part of the SAFOTEST project the immunmodulating effect of Cry1Ab protein from Bacillus thuringiensis (Bt) and PHA-E lectin from kidney bean (Phaseolus vulgaris erythroagglutinin) was examined in 28- and 90-day feeding studies in Wistar rats. PHA-E lectin was chosen as positive control. Rats were fed control rice, transgenic rice expressing Cry1Ab protein or PHA-E lectin, or transgenic rice spiked with the purified recombinant protein. Total immunoglobulin levels, mitogen-induced cell proliferation, T-dependent antibody response to sheep red blood cells and the antigen-specific antibody response in serum were examined at the end of the studies. A dose-dependent increase in mesenteric lymph node weight and total immunoglobulin A was seen when feeding PHA-E transgenic rice alone or spiked with 0.1% purified PHA-E lectin for 90 days indicating a local effect of PHA-E in the intestine. No adverse effects of Cry1Ab protein were found. An anti-PHA-E and anti-Cry1Ab antibody response was induced both after inhalation (control groups) and after inhalation/ingestion (groups fed recombinant protein alone or together with transgenic rice). In conclusion, only PHA-E lectin was found to have an immunomodulating effect when feeding rats for 90 days with approximately 70 mg PHA-E/kg bodyweight per day. As both PHA-E lectin and Cry1Ab protein were capable of inducing an antigen-specific antibody response it is important to make careful considerations when designing future animal studies to avoid intake of proteins from the other groups by inhalation as well as to examine the sensitization and elicitation potential of 'foreign' proteins before introduction to the world market.

The importance of dietary control in the development of a peanut allergy model in Brown Norway rats

This report describes the further development of a peanut allergy model in Brown Norway (BN) rats and in particular the importance of allergen-free breeding of the laboratory animals for the allergen to be used. For this purpose BN rats were bred for 3 generations on soy- and peanut-free feed since it is known that the legumes peanut and soy are cross-reactive. In addition, the effect of cholera toxin (CT), an oral adjuvant often used to increase the sensitivity of food allergy models, was investigated in the BN rat model. BN rats that were bred on both soy- and peanut-free feed could be sensitized orally to peanut (all exposed rats developed peanut-specific IgE, IgG2a and IgG1) and the adjuvant CT could only enhance this sensitization to a limited extent. We also found different protein recognition patterns against purified peanut allergens (Ara h1, Ara h2 and Ara h3) between intraperitoneally (i.p.) and orally sensitized BN rats. Orally sensitized rats recognized all tested allergens whereas i.p. sensitized rats only recognized Ara h1 and Ara h2. Our conclusion is that a model for food allergy should preferably be (A) oral and (B) if possible without the use of adjuvantia. Our model in BN rats unites these preferred characteristics. In addition, we show the importance of dietary control when conducting oral sensitization studies. Special attention must be paid to unscheduled dietary pre-exposure of the animals to the protein under investigation to obtain optimal oral sensitization.

Effect of maternal dietary cow's milk on the immune response to beta-lactoglobulin in the offspring: a four-generation study in mice

BACKGROUND

Evaluation of immune responses to food proteins in animal models requires that the animals are not already sensitized or orally tolerized against the proteins in question. Since maternal transfer of specific immune responses has been observed, breeding of animals on an antigen-free diet for several generations may be necessary to obtain immunologically naive animals.

METHODS

To determine the most appropriate breeding conditions of mice to be used in immunological studies on food proteins, we examined immune responses towards beta-lactoglobulin (BLG) in mice bred on a milk-containing diet (F0) and then for three generations (F1-F3) on a commercially available milk-free diet. The specific antibody and cell-proliferative response to BLG was compared in non-immunized and immunized BALB/c mice, and in mice orally tolerized to BLG prior to immunization.

RESULTS

The immune response to BLG in the F1 generation deviated from the response observed in the F0 and F2/F3 generations. Importantly, trace amounts of BLG detected in the commercial milk-free diet did not induce oral tolerance.

CONCLUSIONS

The study showed that breeding mice on an antigen-free diet for at least two generations is required to attain animals appropriate for immunological studies of food proteins. Although the small quantity of BLG in the milk-free diet did not induce detectable oral tolerance in the present study, it is strongly recommended that the potential effect of contaminating dietary antigen is considered in future studies on food proteins.