Gerlinde Agate Platais Brasil Teixeira

Modulation of mucosal immunity in a murine model of food-induced intestinal inflammation

Background Hypersensitivity or uncontrolled responses against dietary antigens can lead to inflammatory disorders like food allergy and current models reflect a variety of causes but do not reveal the detailed modulation of gut immunity in response to food antigens after breakdown in mucosal tolerance.

IL-4 regulates susceptibility to intestinal inflammation in murine food allergy

Allergies involve a state of immediate hypersensitivity to antigens, including food proteins. The mechanism underlying the initiation and development of allergic responses involves IL-4 that directly induces the differentiation of committed effector Th2 lymphocytes. Although it is clear that Th2 responses play a pivotal role in the development of allergic responses, it remains unclear which mechanisms are involved in the development of the intestinal damages observed in food allergy. Accordingly, this work aimed to study the role of Th2/IL-4-dependent responses in the development of food allergy and intestinal pathology. C57BL/6 wild-type (WT) and IL-4-/- mice were sensitized with peanut proteins, challenged with peanut seeds, and followed for the development of food allergy and intestinal inflammation. Results demonstrated that exposure to peanut seeds led to weight loss in WT but not in IL-4-/- mice that preserved gut integrity with no signs of mucosal inflammation. These animals presented increased levels of IgG2a in sera, suggesting a role for allergic antibodies in the pathogenesis of WT animals. Most importantly, results also showed that lack of IL-4 modulated gut mucosal response in food allergy through diminished expression of TNF-alpha mRNA, increased Th1 IFN-gamma, IL-12p40, regulatory cytokines, and Foxp3, demonstrating their relevance in the control of allergic inflammatory processes, especially in the intestine. Finally, this study highlighted some of the complex mechanisms involved in the pathogenesis of allergic responses to food antigens in the gut, thereby providing valuable tools for directing novel therapeutic or preventive strategies to the control of allergic enteropathy.

The serum D-xylose test as a useful tool to identify malabsorption in rats with antigen specific gut inflammatory reaction

The inappropriate immune response to foods, such as peanut, wheat and milk may be the basis in the pathogenesis of enteropathies like coeliac and Crohn disease, which present small intestinal malabsorption. A number of recent studies have utilized d‐xylose absorption as an investigative tool to study small intestinal function in a variety of clinical settings. Thus, the aim of this experimental study was to evaluate the intestinal absorption of d‐xylose in an antigen‐specific gut inflammatory reaction rat model. Animals of the experimental group were inoculated with peanut protein extract before their exposure to a challenge diet containing exclusively peanut seeds to induce the gut inflammatory reaction caused by peanut allergy. Our results show that systemic inoculation with peanut protein extract renders significantly higher antibody titres (5.085 ± 0.126 units) (P < 0.0001) than control rats (0.905 ± 0.053 units) and that the antibody titres correlate positively to an inflammatory alteration of the gut morphology (P < 0.0001). Animals pertaining to the experimental group showed an intestinal absorption of d‐xylose lower than control rats (P < 0.0001). We also observed that d‐xylose absorption correlates negatively with IgG titres and positively with morphometric parameters (Pearson correlation). In conclusion, the use of serum d‐xylose test was useful to identify the presence of small intestinal malabsorption in our antigen specific gut inflammatory reaction rat model.

Diet selection in immunologically manipulated mice

Diet selection is a complex problem that animals in wildlife have to deal with daily. In their natural environment, these animals meet a great variety of foods some of which they are able and prepared to eat, yet, not all of it is eaten. In addition to the biological factors, some of which we shall discuss deeper in this paper, an important factor in food preference is social contact. Alterations in the physiology of mammals can have profound effects on the choice or preference for certain foods. On the other hand the decline of taste and smell perception in the elderly, the degree of food restriction, the sensorial properties of foods (such as presentation, taste, and smell) can be considered factors that influence feeding behavior leading to aversion. Many species, including man, learn to associate nausea with taste, and as a consequence avoid its specific intake, which has been shown to be persistent. Conditioned taste aversion is a form of associative learning in which animals display an aversion to the taste of a food that has previously been paired with illness. Our group has investigated the pattern of ingestion of foods that are frequently eaten by mice in wildlife and are potentially allergenic to humans in order to study the immunological consequences to these foods such as oral tolerance and inflammatory processes of the gut. We have chosen two seeds, peanuts (Arachis hypogea) and cashew nuts (Anacardium occidentale), as our source of antigens as the first is considered to be one of the most potent food allergens and for the second there seems to be very little allergy in the human setting. We used male and female, normal, adult CBA/J, A/J, C57BL/6 and Balb/c mice 2-3 months old and hybrid (C57Bl/6xBalb/c) F1, (Balb/cxC57Bl/6) F1), (C57Bl/6xDBA2) F1 mice. Food preference appeared to be strain-specific. Animals tolerized to a determined seed, then immunized with its protein extract and re-exposed to the seed in natura alter their feeding pattern. We suggest that diet selection, a multi-factorial event, is influenced by genetic factors such as the MHC and the immunological status of the animal.

Evaluation of the acute toxicity of dolabelladienotriol, a potential antiviral from the brown alga Dictyota pfaffii, in BALB/c mice

Dolabelladienotriol is a product extracted from the brown marine alga Dictyota pfaffii from Brazil that has been shown to have antiviral activity and low cytotoxicity. Our studies have evaluated the acute toxicity of dolabelladienotriol in BALB/c mice for ten days after administration of a single dose. Among the parameters considered were behavior, weight, biochemical and histological analyses of blood samples taken at three different times (Bs.0, Bs.1 and Bs.2) and optical microscopic examination of organs like liver, kidney, stomach and small intestine. Mice deaths were not observed at any dose during the ten day period. There were some changes in the biochemical analysis results for urea nitrogen (BUN) and alanine aminotransferase (ALT), but the changes were not significantly different from the reference levels of the animals before administration of the substance. Histological analyses of tissues were very similar for all animals. The alterations in liver and kidney tissues did not affect the animals´ behavior at any concentration, not even at 50 mg/kg, where the most significant changes in tissues were seen. This study indicates that dolabelladienotriol has low toxicity in administered dose range.

Cross-sectional study of serum reactivity to Anisakis simplex in healthy adults in Niterói, Brazil.

Although the incidence of anisakiasis is rising worldwide, its frequency is still unknown in Brazil. The aim of this study was to verify immunoreactivity to Anisakis simplex antigens in healthy adults and determine its possible relationship with frequency of fish consumption and allergy symptoms. A prospective cross-sectional study was carried out with 67 volunteers recruited from a military facility in Niterói, Brazil. The subjects completed a structured questionnaire and serum titers of specific anti-Anisakis IgE and IgG antibodies were measured. The association between frequency of fish intake and IgE reactivity was evaluated by Fisher’s exact test. Almost all subjects (97.0%, 65/67) that consumed seafood; 64.6% (42/65) ate fish at least once weekly. Of all seafood consumers, 56.9% (37/65) reported allergy symptoms, being gut allergies most often cited (35.5%). IgE seroreactivity to Anisakis simplex was found in 20.9% of subjects (14/67), with 13.4% (9/67) reacting exclusively to somatic antigen, 3.0% (2/67) exclusively to excretory/secretory antigens and 4.5% (3/67) to both antigens. There was a significant association between frequency of fish consumption and positive serology (p = 0.019). An immunoblot assay for Anisakis antigens showed different positive bands for IgG. The direct relationship between ELISA reactivity and frequency of fish intake and absence of association with allergy symptoms suggests previous contact with Anisakis simplex antigens.

A technique for the intra-gastric administration of live larvae of Anisakis simplex in mice

To understand the mechanisms of infection and to attempt to simulate human infection by the Anisakidae family, many in vivo experimental approaches have been developed. The aim was to develop and present a technique for the induction of an oral infection through the use of an intra-gastric gavage of live Anisakis simplex in mice. A commercial pediatric gastric tube (No. 4) was cut longitudinally to produce a 3-cm slit at the distal end where the larva was placed to then be administered to the stomach of the mouse. There were no abnormal clinical complications before, during or after the procedure. In conclusion oral infection through the direct delivery of larvae in the stomach is simple and effective.

Food allergy/hypersensitivity: antigenicity or timing?

Mechanisms involved in the induction of oral tolerance (OT) or systemic immunization through the oral rout are still poorly understood. In our previous studies, we have shown that when normal mice eat peanuts they become tolerant, with no gut alterations. Conversely, if immunized with peanut proteins prior to a challenge diet (CD) containing peanuts they develop chronic inflammation of the gut. Our aim is to evaluate the consequences of the introduction of a novel protein in the diet of animals presenting antigen-specific gut inflammation. Adult, female C57BL/6J mice were divided in control (C) and experimental (E) groups. C1-C3 received peanut protein immunization, animals of the control groups C4 were sham immunized, and control group C5 received ovalbumin (OVA) immunization. The experimental group was immunized with peanut protein extract. Before initial exposure to a 30-day peanut containing CD, the experimental group was divided into 5 groups (E1-E5). OVA feeding began 7 days prior CD (E1) on day 0 (E2), 7 (E3), 14 (E4) and 21 (E5) during CD. Our results show that oral exposure to a novel protein (OVA) in the absence of gut inflammation (E1) leads to low levels of systemic antibody (Ab) titers, comparable to tolerant animals. Conversely, as off initial induction of inflammation, groups submitted to OVA (OT) protocol develop increasingly higher systemic Ab titers similar to animals of the immune control group. In conclusion, our protocol indicates that timing is more important than the antigenicity when a novel protein is offered, in the diet.

Experimental anisakid infections in mice.

Anisakidosis is a human parasitic disease caused by infections with members of the Anisakidae family. Accidental infection after fish intake affects the gastrointestinal tract as a consequence of mechanical damage caused by migrating larvae. Infections can also trigger allergies, hives, severe asthma or anaphylaxis with angioedema. Although mouse models of intraperitoneal antigenic stimulation exist, enabling immunological studies, few models using gastric introduction of live larvae are available for the study of immunological and gastrointestinal damage in mice. This study was designed to characterize serum reactivity against Anisakis spp. and Contracaecum spp. in Balb/c mice following orogastric inoculation and to assess gastrointestinal damage. These anisakid species were classified at the Universidade Federal Fluminense (UFF) School of Veterinary Medicine and materials for live larval inoculation were developed at the UFF Immunobiology laboratory. Live larvae were inoculated following injection with a NaCl solution. Blood samples were collected and sera screened for immunoglobulin (Ig)E and IgG anti-larva responses to both nematodes, specific for somatic and excretory/secretory antigens, by enzyme-linked immunosorbent assay (ELISA). The means of the optical densities were analysed using analysis of variance (ANOVA) with Tukeys post-hoc test and the general linear model. This analysis identified the presence of anti-IgG seroreactivity to both somatic and excretory/secretory Anisakis antigens in inoculated animals compared with controls (P< 0.001), and no gastric or intestinal damage was observed. These experiments demonstrated that introduction of live Contracaecum spp. into the gastrointestinal tract did not elicit serum sensitization in animals.

Induction of an antigen specific gut inflammatory reaction in mice and rats: a model for human Inflammatory Bowel Disease

A alergia alimentar consiste em uma reacao adversa que ocorre em pessoas susceptiveis quando ingerem alimentos sensibilizantes, sendo uma das causas das Doencas Inflamatorias Intestinais (IBD). O objetivo deste estudo foi desenvolver um protocolo experimental de inducao de um processo inflamatorio intestinal antigeno-especifico em camundongos e ratos. Foi escolhida para a inducao deste processo a semente de amendoim. Os animais foram imunizados com o extrato proteico previamente a exposicao com a semente in natura. Nossos resultados mostram que a imunizacao sistemica com extratos proteicos de amendoim ocasiona titulos significativamente maiores de anticorpos quando comparado ao grupo controle e que os animais imunizados submetidos ao desafio com a dieta contendo exclusivamente amendoim apresentam alteracoes intestinais tempo-dependente similares aquelas observadas na doenca celiaca. Os resultados obtidos sugerem que este modelo experimental constitui uma ferramenta conveniente para avaliar as alteracoes no processo inflamatorio intestinal cronico antigeno-especifico