An oral Brown Norway rat model for food allergy: comparison of age, sex, dosing volume, and allergen preparation

Probiotic Bacteria from Human Milk Can Alleviate Oral Bovine Casein Sensitization in Juvenile Wistar Rats

This study aims to see if probiotic bacteria from human milk could ameliorate oral cow's milk sensitization. The probiotic potential of the SL42 strain isolated from the milk of a healthy young mother was first determined. Rats were then randomly gavaged with cow's milk casein without an adjuvant or assigned to the control group. Each group was further subdivided into three groups, with each receiving only Limosilactobacillus reuteri DSM 17938, SL42, or a phosphate-buffered saline solution. Body weight, temperature, eosinophils, serum milk casein-specific IgE (CAS-IgE), histamine, and serum S100A8/A9 and inflammatory cytokine concentrations were measured. The animals were sacrificed after 59 days; histological sections were prepared, and the spleen or thymus weights, as well as the diversity of the gut microbiota, were measured. On days 1 and 59, SL42 abridged systemic allergic responses to casein by dropping histamine levels (25.7%), CAS-specific IgE levels (53.6%), eosinophil numbers (17%), S100A8/9 (18.7%), and cytokine concentrations (25.4-48.5%). Analyses of histological sections of the jejunum confirmed the protective effect of probiotic bacteria in the CAS-challenged groups. Lactic acid bacteria and Clostridia species were also increased in all probiotic-treated groups. These findings suggest that probiotics derived from human milk could be used to alleviate cow's milk casein allergy.

Changes in inflammatory factors in the Brown Norway rat model of food allergy

BACKGROUND

The role of serum S100A8/A9 in intestinal inflammation has been confirmed, and its role in food allergy is currently being investigated.

OBJECTIVE

To explore the levels of S100A8/A9 and inflammatory factors, including Toll-like receptors 4 (TLR4), Nuclear transcription factors (NF-κB) and Tumor necrosis factor α (TNF-α), in mild food allergies.

METHODS

Eighty 3-week-old male Brown Norway rats were used. Forty rats were randomly assigned to the ovalbumin-sensitized experimental group, while 40 rats were assigned to the normal saline sham-sensitized control group. Body weight and length and the levels of serum ovalbumin-specific IgE (OVA-IgE), histamine, Th1-associated and Th2-associated factors, S100A8/A9 and inflammation-associated cytokines were compared.

RESULTS

Through the evaluation of OVA-IgE level and Th1/Th2 balance in the experimental group, a successful IgE-mediated food allergy model was constructed. Compared with the control group, the experimental group had higher serum S100A8/A9 levels on days 21, 28, 35 and 42 (all P < 0.05); higher TLR4 levels on days 28, 35 and 42 (all P < 0.05); higher TNF-α levels on days 28, 35 and 42 (all P < 0.05); higher NF-κB levels on days 35 and 42 (all P < 0.05); and higher IL-1β and IL-6 levels on days 7 to 42 (all P < 0.05). Moreover, positive correlations were found between the serum levels of S100A8/A9 and inflammation-associated cytokines [TNF-α: r = 0.378, P = 0.039; IL-1β: r = 0.679, P = 0.000; IL-6: r = 0.590, P = 0.001].

CONCLUSION

S100A8/A9 and inflammatory-related factors, including TLR4, NF-κB, TNF-α, IL-6 and IL-1β, is closely related to food allergies. Moreover, immune and inflammatory factors interact with each other in food allergies, which may provide insight into food allergy causes and treatments.

Applications of Mouse Models to the Study of Food Allergy

Mouse models of allergic disease offer numerous advantages when compared to the models of other animals. However, selection of appropriate mouse models is critical to advance the field of food allergy by revealing mechanisms of allergy and for testing novel therapeutic approaches. All current mouse models for food allergy have weaknesses that may limit their applicability to human disease. Aspects such as the genetic predisposition to allergy or tolerance from the strain of mouse used, allergen dose, route of exposure (oral, intranasal, intraperitoneal, or epicutaneous), damage of the epithelial barrier, use of adjuvants, food matrix effects, or composition of the microbiota should be considered prior to the selection of a specific murine model and contemplated according to the intended purpose of the study. This chapter reviews our current knowledge on the application of mouse models to food allergy research and the variables that may influence the successful development of each type of model.

Gluten tolerance prevents oral sensitization with enzymatic or acid hydrolyzed gluten: A study in Brown Norway rats

Background

There are several reports describing allergy to hydrolyzed wheat products. After a large outbreak in Japan it was established that sensitization was caused by skin contact with acid hydrolyzed gluten in soap. It is still not clear if other forms of hydrolyzed gluten may sensitize, and if the skin is the only relevant route of sensitization in humans and to what extent oral tolerance to wheat play a role.

Objectives

The aim of the present study was to examine if wheat-tolerant rats may be sensitized via the oral or i.p. route when exposed to gluten, enzymatic or acid hydrolyzed gluten.

Methods

Brown Norway rats, tolerant to wheat, were dosed by three i.p. injections without adjuvant or by oral gavage daily for 35 days with the three gluten products, respectively. Sera were analyzed by ELISA for specific IgG1 and IgE. In addition inhibition and avidity ELISAs were performed. Results were compared to a similar study in rats naïve to wheat.

Results

More than half the animals had measurable IgG1 at the start of the dosing period. I.p. immunization resulted in significant specific IgG1 and IgE to the antigen used for immunization but significantly lower than in naïve rats. The results of inhibition and avidity ELISA’s indicate that the underlying tolerance to epitopes common to the three products influences the immune response. Oral dosing did not induce significant changes in response to either gluten or the hydrolyzed gluten product used for dosing.

Conclusions

The study shows that i.p. immunization with the three products can break the underlying tolerance to wheat. Exposure by the oral route to enzymatic or acid hydrolyzed gluten is very unlikely to break an already established tolerance to gluten and induce sensitization.

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.

Influence of Hesperidin on the Systemic and Intestinal Rat Immune Response

Polyphenols, widely found in edible plants, influence the immune system. Nevertheless, the immunomodulatory properties of hesperidin, the predominant flavanone in oranges, have not been deeply studied. To establish the effect of hesperidin on in vivo immune response, two different conditions of immune system stimulations in Lewis rats were applied. In the first experimental design, rats were intraperitoneally immunized with ovalbumin (OVA) plus Bordetella pertussis toxin and alum as the adjuvants, and orally given 100 or 200 mg/kg hesperidin. In the second experimental design, rats were orally sensitized with OVA together with cholera toxin and fed a diet containing 0.5% hesperidin. In the first approach, hesperidin administration changed mesenteric lymph node lymphocyte (MLNL) composition, increasing the TCRαβ+ cell percentage and decreasing that of B lymphocytes. Furthermore, hesperidin enhanced the interferon (IFN)-γ production in stimulated MLNL. In the second approach, hesperidin intake modified the lymphocyte composition in the intestinal epithelium (TCRγδ+ cells) and the lamina propria (TCRγδ+, CD45RA+, natural killer, natural killer T, TCRαβ+CD4+, and TCRαβ+CD8+ cells). Nevertheless, hesperidin did not modify the level of serum anti-OVA antibodies in either study. In conclusion, hesperidin does possess immunoregulatory properties in the intestinal immune response, but this effect is not able to influence the synthesis of specific antibodies.

Development of a BALB/c mouse model for food allergy: comparison of allergy-related responses to peanut agglutinin, β-lactoglobulin and potato acid phosphatase

The purpose of this study was to develop a BALB/c mouse model for comprehensively assessing food allergies. Serum specific IgE and IgG1 antibodies against protein (PNA, β-LG, and PAP) were induced in intraperitoneally sensitized BALB/c mice. On day 28, blood was collected to obtain the serum, and the splenocytes were cultured. On day 30, mice were challenged with antigen by intraperitoneal injection or intragastric administration, and the physiological and immunological responses to the antigen were studied. A general finding was that allergenicity-related parameters in the mice treated with PNA were statistically higher than those in the mice treated with PAP (P < 0.05 for IL-4; P < 0.05 for specific IgE; P < 0.001 for specific IgG1), whereas parameters in those treated with β-LG were between the other two. Statistically higher histamine release was observed in PNA and β-LG-sensitized mice than in control mice challenged with the same protein by i.p. injection. Intraperitoneal challenge with PNA and β-LG in sensitized mice induced edema in the ear and inflammatory cell infiltration in the lung, which were not observed with the control mice. The results show a new model that covers many features of clinical food allergies that are not seen in other models. The order of potential allergenicity might be PNA > β-LG > PAP, and the intraperitoneal challenge could be more sensitive to induced systemic food allergy.

[Establishment of a rat model of oral food allergy]

OBJECTIVE

To establish a food allergy model in Brown Norway (BN) rats by gavage of ovalbumin (OVA) without any adjuvant, and to evaluate this model.

METHODS

A total of 20 male BN rats aged 3 weeks were randomly divided into allergy group and control group (n=10 each). BN rats in the allergy group were given OVA 1 mg per day by gavage, and all the rats were treated for 41 days continuously. On day 42, the rats in the allergy group were given OVA 100 mg by gavage for challenge. The rats in the control group were given normal saline of the same volume by gavage. Differences in body length, body weight, and food intake were compared between the two groups on days 7, 14, 21, 28, 35, and 42. ELISA was used to measure the serum OVA-IgE level and plasma histamine level after challenge on day 42, and the changes in rats' appearance and fecal properties were observed. The model of food allergy was considered successful when the serum OVA-IgE level in the allergy group was no less than the mean serum OVA-IgE level + 3 standard deviation in the control group.

RESULTS

There were no significant differences in body length, body weight or food intake between the allergy and control groups at all time points (P>0.05). On day 21, the control group had a significantly higher food intake than the allergy group (P<0.05). On day 42 after challenge, the allergy group showed significantly higher serum OVA-IgE and plasma histamine levels than the control group (P<0.05). The sensitization rate (rate of successful modeling) was 90%. The fecal properties showed no significant differences between the two groups.

CONCLUSIONS

OVA by gavage without any adjuvant can successfully establish the model of food allergy in BN rats and has a high success rate. Food allergy induced by OVA may reduce food intake within a short period of time, but no influence on rats' body length or body weight has been observed.

IgG Expression upon Oral Sensitization in Association with Maternal Exposure to Ovalbumin

The role of maternal allergen exposure in the allergenicity of the offspring remains controversial. Some studies have shown that maternal exposure is a risk factor for allergy in the offspring, whereas other studies have shown that maternal exposure induces immune tolerance and protects offspring from allergy disease. Therefore, we utilized maternal rat allergen exposure model to evaluate the offspring immune reactions to ovalbumin protein and to determine whether the Brown Norway (BN) rat model is a suitable animal model for studying the allergenicity of food proteins. For three generations, rats received an allergens or non-allergens by gavage during the pregnancy and lactation periods. After weaning, the offspring rats were used for oral sensitization experiment. In the sensitization experiment, the control rat, which had maternal exposure to phosphate-buffered saline (PBS), exhibited full response of IgG to oral exposure to OVA. The IgG level was significantly lower in F1 rats that were sensitized by maternal exposure to ovalbumin(OVA). Moreover, the lowest IgG level was found for the F3b sensitized by maternal rats exposed to OVA allergen for three continuous generations. Compared with maternal OVA exposure prior to postnatal sensitization, the sensitization via maternal PBS led to a higher serum level of OVA-specific IgG. However, the OVA-specific IgG levels for the two generations of maternal PBS exposure prior to postnatal sensitization was not higher than that for the one generation of maternal rats exposed to PBS prior to postnatal sensitization. Our studies demonstrate that maternal OVA exposure during the pregnancy and lactation can affect the results of oral sensitization studies using ovalbumin protein. BN rats must be bred in non-allergen conditions for at least one generation to avoid problems in rat models for studying the allergenicity of food proteins.

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

BACKGROUND

Food allergy (FA) is an adverse health effect produced by the exposure to a given food. Currently, there is no optimal animal model of FA for the screening of immunotherapies or for testing the allergenicity of new foods.

OBJECTIVE

The aim of the present study was to develop an effective and rapid model of FA in Brown Norway rats. In order to establish biomarkers of FA in rat, we compared the immune response and the anaphylactic shock obtained in this model with those achieved with only intraperitoneal immunization.

METHODS

Rats received an intraperitoneal injection of ovalbumin (OVA) with alum and toxin from Bordetella pertussis, and 14 days later, OVA by oral route daily for three weeks (FA group). A group of rats receiving only the i.p. injection (IP group) were also tested. Serum anti-OVA IgE, IgG1, IgG2a, IgG2b and IgA antibodies were quantified throughout the study. After an oral challenge, body temperature, intestinal permeability, motor activity, and mast cell protease II (RMCP-II) levels were determined. At the end of the study, anti-OVA intestinal IgA, spleen cytokine production, lymphocyte composition of Peyer's patches and mesenteric lymph nodes, and gene expression in the small intestine were quantified.

RESULTS

Serum OVA-specific IgG1, IgG2a and IgG2b concentrations rose with the i.p. immunization but were highly augmented after the oral OVA administration. Anti-OVA IgE increased twofold during the first week of oral OVA gavage. The anaphylaxis in both IP and FA groups decreased body temperature and motor activity, whereas intestinal permeability increased. Interestingly, the FA group showed a much higher RMCP II serum protein and intestinal mRNA expression.

CONCLUSIONS

These results show both an effective and relatively rapid model of FA assessed by means of specific antibody titres and the high production of RMCP-II and its intestinal gene expression.

Perinatal bisphenol A exposure beginning before gestation enhances allergen sensitization, but not pulmonary inflammation, in adult mice

Bisphenol A (BPA), a monomer of polycarbonate plastics and epoxide resin, is a high-production-volume chemical implicated in asthma pathogenesis when exposure occurs to the developing fetus. However, few studies have directly examined the effect of in utero and early-life BPA exposure on the pathogenesis of asthma in adulthood. This study examines the influence of perinatal BPA exposure through maternal diet on allergen sensitization and pulmonary inflammation in adult offspring. Two weeks before mating, BALB/c dams were randomly assigned to a control diet or diets containing 50 ng, 50 μg or 50 mg BPA/kg of rodent chow. Dams remained on the assigned diet throughout gestation and lactation until postnatal day (PND) 21 when offspring were weaned onto the control diet. Twelve-week-old offspring were sensitized to ovalbumin (OVA) and subsequently challenged with aerosolized OVA. Sera, splenocytes, bronchoalveolar lavage fluid and whole lungs were harvested to assess allergen sensitization and pulmonary inflammation after OVA challenge. Serum anti-OVA IgE levels were increased two-fold in offspring exposed to 50 μg and 50 mg BPA/kg diet, compared with control animals. In addition, production of interleukin-13 and interferon-γ were increased in OVA-stimulated splenocytes recovered from BPA-exposed mice. Pulmonary inflammation, as indicated by total and differential leukocyte counts, cytokines, chemokines and pulmonary histopathology inflammatory scores, however, was either not different or was reduced in offspring exposed to BPA. Although these data suggest that perinatal BPA exposure beginning before gestation enhances allergen sensitization by increasing serum IgE and splenocyte cytokine production, a substantial impact of BPA on OVA-induced pulmonary inflammation in adulthood was not observed.

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.

A BALB/c mouse model for assessing the potential allergenicity of proteins: comparison of allergen dose, sensitization frequency, timepoint and sex

The present study was to investigate the possibility of using the BALB/c mouse as an animal model for assessing the potential allergenicity of proteins. Specific IgE and IgG1 against ovalbumin were induced by dosing BALB/c mice via intraperitoneal injection (absence of adjuvant). The effects of various allergen doses (5 mg, 0.5 mg or 0.05 mg OVA), sensitization times (twice or five times), timepoints (day 14 or day 28) and sex (male or female) were studied. IL-4, IFN-γ, OVA-specific IgE and IgG1 were measured by enzyme-linked immunosorbent assay (ELISA). A general finding was that mice treated with 0.05 mg OVA had the highest OVA-specific IgE and IgG1, statistically significant higher specific IgE and IgG1 were observed in groups sensitized five times than twice, OVA-specific IgE and IgG1 on day 28 were statistically higher than day 14, and higher IL-4 was observed in OVA-allergic mice than control mice. These results demonstrate that the BALB/c mouse model treated with 0.05 mg OVA intraperitoneally on days 0, 3, 6, 9, 12 might be used for further experiments. OVA-specific IgE and IgG1 should be detected on day 28. Further studies including reproducibility and other conditions were required before using the BALB/c mouse model for assessing the potential allergenicity of proteins.

Allergic reactions compared between BN and Wistar rats after oral exposure to ovalbumin

There is currently no validated animal model for evaluating the potential allergenicity of food proteins. This study aimed to compare the allergic reactions between BN and Wistar rats after oral exposure to ovalbumin (OVA) by studying immune responses and clinical manifestations. Female BN and Wistar rats were orally exposed to OVA on days 1 and 14, and thereafter daily from day 15 to day 42. Sera and plasma were screened for OVA-specific antibodies and histamine. On day 49, all the OVA-sensitized animals were orally challenged with OVA before blood pressure was measured. One day later (on day 50), histopathology and differential cell counts were performed. The results indicate that oral exposure of BN rats to OVA yielded IgE, IgG, and IgG(2a) antibody responses that were generally of higher levels than those observed in Wistar rats (p < 0.05). However, the Wistar rats presented with more serious clinical manifestations and histopathologic changes that could have serious implications for any OVA-induced anaphylaxis. The studies here proved that OVA-sensitized BN and Wistar rats evinced different immune responses and clinical manifestations; these outcomes suggested that the two rat strains might differ in their immunologic mechanisms of allergy and that there was no correlation between immune responses and the severity of clinical symptoms. To be clear, the data from these studies should be viewed as 'preliminary', as only a single protein allergen was examined. Accordingly, further studies are needed to compare the allergic reactions between BN and Wistar rats by using purified strong-, weak-, and non-allergenic proteins based on the experiments reported here.

Evaluation of biotechnology-derived novel proteins for the risk of food-allergic potential: advances in the development of animal models and future challenges

Increasing concern from the public about the safety of genetically modified food has made critical to have suitable methods for recognizing associated potential hazards. Hierarchical approaches to allergenicity determination were proposed, and these include evaluation of the structural and sequence homology and serological identity of novel proteins with existing allergens, measuring the resistance to proteolytic digestion and assessment of sensitizing potential using animal models. Allergic individuals have a predisposed (i.e. atopic) genetic background, and a close resemblance to this setup is therefore desirable in animal models, which is possible by using a strain of an animal species that is prone for allergic disorders. So far, none of the animal model has been validated for the purpose of hazard identification in the context of safety assessment. However, the available knowledge suggests that the judicious use of an appropriate animal model could provide important information about the allergic potential of novel proteins. This paper provides an up-to-date review of the progress made in the field of development of in vivo models in this direction and the further goals that have to be achieved.

Effects of sulfur dioxide on expressions of p53, bax and bcl-2 in lungs of asthmatic rats

Inhibition of cell apoptosis is an increasingly important factor in modulating airway inflammation in asthma, which is related to environmental pollutants. To investigate the effects of sulfur dioxide (SO(2)) on the mRNA and protein expressions of apoptosis-related genes in lungs from asthmatic rats, male Wistar rats were challenged by ovalbumin (OVA) or SO(2) (2 ppm) inhalation alone or together. Examinations were performed 24 h after the last treatment. The mRNA and protein levels of p53, bax, and bcl-2 were analyzed in lungs using real-time reverse transcription-polymerase chain reaction (RT-PCR) assay and Western blot analysis, respectively. The results indicated that increases of bcl-2 or decreases of p53 and bax mRNA and protein levels were not significant in lungs of rats exposed to SO(2) alone, compared with controls, but elevated or reduced levels of these genes appeared in lungs of asthmatic rats exposed to SO(2) plus OVA, compared with controls, suggesting that SO(2) exposure could result in OVA-induced increases or decreases of transcription and translation levels of these apoptosis-related genes in rat lungs, and may have relations to airway inflammation in asthma. The regulation mechanism of apoptosis in asthma disease exposure to SO(2) needs further study.

Effects of sulfur dioxide on the expressions of EGF, EGFR, and COX-2 in airway of asthmatic rats

The pathogenesis of asthma involves a combination of genetic and environmental factors. The epidemiology studies have shown that SO(2)might play an important role in the initiation or exacerbation of the asthma disease. To investigate the asthmatic molecular mechanisms exposed to SO(2), male Wistar rats were divided randomly into four equal groups of six animals each: (1) SO(2) group, (2) ovalbumin (OVA) group (asthma group), (3) SO(2)plus OVA group, and (4) control group. The rats were challenged by ovalbumin (OVA) or SO(2) (5.6 mg/m(3)) inhalation alone or together. The mRNA and protein levels of asthma-related genes (EGF, EGFR, and COX-2) were analyzed in lungs and tracheas using real-time reverse transcription-polymerase chain reaction assay, radioimmunoassay method, and Western blot analysis, respectively. The results showed that inhaled SO(2) alone increased the mRNA and protein expressions of three tested genes in lung and trachea tissues, but only the mRNA levels of EGFR and COX-2 in tracheas were significantly increased compared with the control. However, OVA exposure significantly induced the mRNA and protein expressions of EGF, EGFR, and COX-2 compared with the control. Meanwhile, OVA plus SO(2) inhalation enhanced the mRNA and protein levels of these genes in rat airways, versus exposure to OVA alone. These results suggested that SO(2) could increase the expressions of EGF, EGFR, and COX-2 on the transcription and translation levels in the lungs and tracheas from asthmatic rats, which might be one of the possible mechanisms by which SO(2) pollution aggravates asthma disease.

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.

Bis(tributyltin)oxide (TBTO) decreases the food allergic response against peanut and ovalbumin in Brown Norway rats

Other factors than the allergen itself may be of importance in the development of food allergy. This report describes the influence of the immunosuppressive compound bis(tributyltin)oxide (TBTO), present in the food chain, on the development of food allergy to peanut or ovalbumin in Brown Norway (BN) rats. To study these effects BN rats were sensitized to either 1 or 10mg peanut or ovalbumin by daily oral gavage and the TBTO-groups were fed a diet containing 80 mg TBTO per kg diet. Co-exposure to TBTO not only resulted in decreased general immunologic parameters such as weights of mesenteric lymph nodes and Peyer's patches, lymphocyte proliferation rates in splenocytes, but also on allergic parameters. In the peanut allergen-model TBTO decreased allergen-specific Th2 cytokine production by spleen cells, number of eosinophilic and basophilic granulocytes in the blood and production of mast cell protease II after oral food challenge. In the ovalbumin allergen-model TBTO decreased the number of eosinophilic and basophilic granulocytes, allergen-specific IgE and production of mast cell protease II after oral food challenge. The data imply that in the process of risk assessment of food allergy attention should be given to immunomodulating compounds present in the diet.

Effects of sulfur dioxide on the expressions of MUC5AC and ICAM-1 in airway of asthmatic rats

Asthma is a chronic inflammatory disease characterized by infiltration and activation of various inflammatory cells and mucus secretion. To investigate the effects of SO(2) on the expressions of asthma related-genes, male Wistar rats were challenged by ovalbumin (OVA) or SO(2) (2 ppm) inhalation alone or together. Bronchoalveolar lavage and histopathologic examination were performed 24h after the last treatment. The mRNA and protein levels of MUC5AC and ICAM-1 were analyzed in lungs and tracheas using real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) assay, immunohistochemistry method and Western blot analysis, respectively. Exposure to OVA or to OVA plus inhaled SO(2) significantly caused increases of the mRNA and protein levels of MUC5AC and ICAM-1 in lungs and tracheas of rats compared with the control (P <0.05 or P <0.01), but the increases of mRNA and protein levels after SO(2) inhalation were not statistically significant. Exposure to OVA plus inhaled SO(2) significantly not only induced the mRNA and protein expressions of these genes, but also induced the infiltration of inflammatory cells in lungs and tracheas and the increase of the numbers of inflammatory cells in bronchoalveolar lavage fluids (BALF), versus exposure to OVA alone. Meanwhile, a synergistic effect on the pathological changes between SO(2) and OVA was observed in lungs after SO(2) and OVA exposure. These results suggested that SO(2) could increase the expressions of MUC5AC and ICAM-1 on the transcription and translation levels in the lungs and tracheas from asthmatic rats, which might be one of the possible mechanisms that SO(2) pollution aggravates asthma disease.

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.

Mechanisms of type I food allergy

The gastrointestinal tract represents the biggest immune organ of the human body and has 3 distinct functions: (1) barrier and defense against potential pathogens, (2) ignorance or tolerance of innocuous agents, and (3) digestion and nutritional uptake of alimentary compounds. Recent studies have indicated that especially structural features of dietary proteins seem to be a precondition for the induction of immediate type immune responses. Crystallographic studies of allergen molecules have been fundamental for epitope studies in a 3-dimensional format using peptides or mimotopes. The identified IgE epitopes were all conformational and responsible for high-affinity interactions with specific IgE. Moreover, numerous studies have indicated that allergens, among them food allergens, preferentially form di-, tri-, or multimers, thus leading to a repetitive display of epitopes. As B-lymphocytes are pattern recognizers, this feature is essential for a memory response, but may also be critical for the very first allergen contact and initiation of the IgE response. Here we review the key candidate cells in the gut, which are capable of recognizing conformation and molecular patterns, but may also be involved in skewing the immune response towards Th2. Animal models have been basic for understanding the molecular principles of food allergy and they will be increasingly indispensable for the definition of novel vaccination strategies. Therefore, the available models are critically analyzed in this review.