Paola Smaldini

In vivo Evidence of Cross-Reactivity between Cow’s Milk and Soybean Proteins in a Mouse Model of Food Allergy

Background: Cow’s milk allergy (CMA) is an important problem worldwide and the development of an in vivo system to study new immunotherapeutic strategies is of interest. Intolerance to soybean formula has been described in CMA patients, but it is not fully understood. In this work, we used a food allergy model in BALB/c mice to study the cross-reactivity between cow’s milk protein (CMP) and soy proteins (SP). Methods: Mice were orally sensitized with cholera toxin and CMP, and then challenged with CMP or SP to induce allergy. Elicited symptoms, plasma histamine, humoral and cellular immune response were analyzed. Th1- and Th2-associated cytokines and transcription factors were assessed at mucosal sites and in splenocytes. Cutaneous tests were also performed. Results: We found that the immediate symptoms elicited in CMP-sensitized mice orally challenged with SP were consistent with a plasma histamine increase. The serum levels of CMP-specific IgE and IgG1 antibodies were increased. These antibodies also recognized soy proteins. Splenocytes and mesenteric lymph node cells incubated with CMP or SP secreted IL-5 and IL-13. mRNA expression of Th2-associated genes (IL-5, IL-13, and GATA-3) was upregulated in mucosal samples. In addition, sensitized animals exhibited positive cutaneous tests after the injection of CMP or SP. Conclusions: We demonstrate that CMP-sensitized mice, without previous exposure to soy proteins, elicited hypersensitivity signs immediately after the oral administration of SP, suggesting that the immunochemical cross-reactivity might be clinically relevant. This model may provide an approach to further characterize cross-allergenicity phenomena and develop new immunotherapeutic treatments for allergic patients.

Orally-Induced Intestinal CD4+ CD25+ FoxP3+ Treg Controlled Undesired Responses towards Oral Antigens and Effectively Dampened Food Allergic Reactions.

The induction of peripheral tolerance may constitute a disease-modifying treatment for allergic patients. We studied how oral immunotherapy (OIT) with milk proteins controlled allergy in sensitized mice (cholera toxin plus milk proteins) upon exposure to the allergen. Symptoms were alleviated, skin test was negativized, serum specific IgE and IgG1 were abrogated, a substantial reduction in the secretion of IL-5 and IL-13 by antigen-stimulated spleen cells was observed, while IL-13 gene expression in jejunum was down-regulated, and IL-10 and TGF-β were increased. In addition, we observed an induction of CD4+CD25+FoxP3+ cells and IL-10- and TGF-β-producing regulatory T cells in the lamina propria. Finally, transfer experiments confirmed the central role of these cells in tolerance induction. We demonstrated that the oral administration of milk proteins pre- or post-sensitization controlled the Th2-immune response through the elicitation of mucosal IL-10- and TGF-β-producing Tregs that inhibited hypersensitivity symptoms and the allergic response.

Targeting a Cross-Reactive Gly m 5 Soy Peptide as Responsible for Hypersensitivity Reactions in a Milk Allergy Mouse Model

Background Cross-reactivity between soybean allergens and bovine caseins has been previously reported. In this study we aimed to map epitopes of the major soybean allergen Gly m 5 that are co-recognized by casein specific antibodies, and to identify a peptide responsible for the cross-reactivity. Methods Cows milk protein (CMP)-specific antibodies were used in different immunoassays (immunoblotting, ELISA, ELISA inhibition test) to evaluate the in vitro recognition of soybean proteins (SP). Recombinant Gly m 5 (α), a truncated fragment containing the C-terminal domain (α-T) and peptides of α-T were obtained and epitope mapping was performed with an overlapping peptide assay. Bioinformatics tools were used for epitope prediction by sequence alignment, and for modelling the cross-recognized soy proteins and peptides. The binding of SP to a monoclonal antibody was studied by surface Plasmon resonance (SPR). Finally, the in vivo cross-recognition of SP was assessed in a mouse model of milk allergy. Results Both α and α-T reacted with the different CMP-specific antibodies. α-T contains IgG and IgE epitopes in several peptides, particularly in the peptide named PA. Besides, we found similar values of association and dissociation constants between the α-casein specific mAb and the different milk and soy components. The food allergy mouse model showed that SP and PA contain the cross-reactive B and T epitopes, which triggered hypersensitivity reactions and a Th2-mediated response on CMP-sensitized mice. Conclusions Gly m 5 is a cross-reactive soy allergen and the α-T portion of the molecule contains IgG and IgE immunodominant epitopes, confined to PA, a region with enough conformation to be bound by antibodies. These findings contribute to explain the intolerance to SP observed in IgE-mediated CMA patients, primarily not sensitised to SP, as well as it sets the basis to propose a mucosal immunotherapy for milk allergy using this soy peptide.

Unlipidated Outer Membrane Protein Omp16 (U-Omp16) from Brucella spp. as Nasal Adjuvant Induces a Th1 Immune Response and Modulates the Th2 Allergic Response to Cow’s Milk Proteins

The discovery of novel mucosal adjuvants will help to develop new formulations to control infectious and allergic diseases. In this work we demonstrate that U-Omp16 from Brucella spp. delivered by the nasal route (i.n.) induced an inflammatory immune response in bronchoalveolar lavage (BAL) and lung tissues. Nasal co-administration of U-Omp16 with the model antigen (Ag) ovalbumin (OVA) increased the amount of Ag in lung tissues and induced OVA-specific systemic IgG and T helper (Th) 1 immune responses. The usefulness of U-Omp16 was also assessed in a mouse model of food allergy. U-Omp16 i.n. administration during sensitization ameliorated the hypersensitivity responses of sensitized mice upon oral exposure to Cow’s Milk Protein (CMP), decreased clinical signs, reduced anti-CMP IgE serum antibodies and modulated the Th2 response in favor of Th1 immunity. Thus, U-Omp16 could be used as a broad Th1 mucosal adjuvant for different Ag formulations.

Down-regulation of NF-κB signaling by Gordonia bronchialis prevents the activation of gut epithelial cells

The immunomodulatory power of heat-killed Gordonia bronchialis was studied on gut epithelial cells activated with pro-inflammatory stimuli (flagellin, TNF-α or IL-1β). Light emission of luciferase-transfected epithelial cells and mRNA expression of IL-1β, TNF-α, IL-6, CCL20, IL-8 and MCP-1 were measured. NF-κB activation was assessed by immunofluorescence and immunoblotting, and induction of reactive oxygen species (ROS) was evaluated. In vivo inhibitory properties of G. bronchialis were studied with ligated intestinal loop assay and in a mouse model of food allergy. G. bronchialis promoted the down-regulation of the expression of CCL20 and IL-1β on activated epithelial cells in a dose-dependent manner. A concomitant blocking of nuclear p65 translocation with increased production of ROS was found. In vivo experiments confirmed the inhibition of CCL20 expression and the suppression of IgE sensitization and hypersensitivity symptoms in the food allergy mouse model. In conclusion, heat-killed G. bronchialis inhibited the activation of NF-κB pathway in human epithelial cells, and suppressed the expression of CCL20. These results indicate that G. bronchialis may be used to modulate the initial steps of innate immune activation, which further suppress the allergic sensitization. This approach may be exploited as a therapy for intestinal inflammation.

Inflammation Controls Sensitivity of Human and Mouse Intestinal Epithelial Cells to Galectin-1

Galectins play key roles in the inflammatory cascade. In this study, we aimed to analyze the effect of galectin‐1 (Gal‐1) in the function of intestinal epithelial cells (IECs) isolated from healthy and inflamed mucosa. IECs isolated from mice or patients with inflammatory bowel diseases (IBD) were incubated with different pro‐inflammatory cytokines, and Gal‐1 binding, secretion of homeostatic factors and viability were assessed. Experimental models of food allergy and colitis were used to evaluate the in vivo influence of inflammation on Gal‐1 binding and modulation of IECs. We found an enhanced binding of Gal‐1 to: (a) murine IECs exposed to IL‐1β, TNF, and IL‐13; (b) IECs from inflamed areas in intestinal tissue from IBD patients; (c) small bowel of allergic mice; and (d) colon from mice with experimental colitis. Our results showed that low concentrations of Gal‐1 favored a tolerogenic micro‐environment, whereas high concentrations of this lectin modulated viability of IECs through mechanisms involving activation of caspase‐9 and modulation of Bcl‐2 protein family members. Our results showed that, when added in the presence of diverse pro‐inflammatory cytokines such as tumor necrosis factor (TNF), IL‐13 and IL‐5, Gal‐1 differentially promoted the secretion of growth factors including thymic stromal lymphopoietin (TSLP), epidermal growth factor (EGF), IL‐10, IL‐25, and transforming growth factor (TGF‐β1). In conclusion, we found an augmented binding of Gal‐1 to IECs when exposed in vitro or in vivo to inflammatory stimuli, showing different effects depending on Gal‐1 concentration. These findings highlight the importance of the inflammatory micro‐environment of mucosal tissues in modulating IECs susceptibility to the immunoregulatory lectin Gal‐1 and its role in epithelial cell homeostasis. J. Cell. Physiol. 231: 1575–1585, 2016.

Cross-Reactivity Between the Soybean Protein P34 and Bovine Caseins

Purpose Soy-based formulas are widely used as dairy substitutes to treat milk allergy patients. However, reactions to soy have been reported in a small proportion of patients with IgE-mediated milk allergies. The aim of this work was to explore whether P34, a mayor soybean allergen, is involved in this cross-reactivity. Methods In vitro recognition of P34 was evaluated by immunoblotting, competitive ELISA and basophil activation tests (BAT) using sera from allergic patients. In vivo cross-reactivity was examined using an IgE-mediated milk allergy mouse model. Results P34 was recognized by IgE antibodies from the sera of milk allergic patients, casein-specific monoclonal antibodies, and sera from milk-allergic mice. Spleen cells from sensitized mice incubated with milk, soy or P34 secreted IL-5 and IL-13, while IFN-γ remained unchanged. In addition, the cutaneous test was positive with cows milk proteins (CMP) and P34 in the milk allergy mouse model. Moreover, milk-sensitized mice developed immediate symptoms following sublingual exposure to P34. Conclusions Our results demonstrate that P34 shares epitopes with bovine casein, which is responsible for inducing hypersensitivity symptoms in milk allergic mice. This is the first report of the in vivo cross-allergenicity of P34.

Oral delivery of Brucella spp. recombinant protein U-Omp16 abrogates the IgE-mediated milk allergy

Food allergies are increasingly common disorders and no therapeutic strategies are yet approved. The unlipidated Omp16 (U-Omp16) is the outer membrane protein of 16 kDa from B. abortus and possesses a mucosal adjuvant property. In this study, we aimed to examine the U-Omp16 capacity to abrogate an allergen-specific Th2 immune response when it is administered as an oral adjuvant in a mouse model of food allergy. Balb/c mice were sensitized with cholera toxin and cow’s milk proteins (CMP) by gavage and simultaneously treated with U-Omp16 and CMP. Oral challenge with CMP was performed to evaluate the allergic status of mice. Symptoms, local (small bowel cytokine and transcription factor gene expression) and systemic (specific isotypes and spleen cell-secreted cytokines) parameters, and skin tests were done to evaluate the immune response. We found that the oral administration of U-Omp16 with CMP during sensitization dampened the allergic symptoms, with negativization of immediate skin test and increased skin DTH response. Serum specific IgE and IL-5 were inhibited and a Th1 response was promoted (specific IgG2a antibodies and CMP-induced IFN-γ secretion). We found at the mucosal site an inhibition of the gene expression corresponding to IL-13 and Gata-3, with an induction of IFN-γ and T-bet. These results indicated that the oral administration of U-Omp16 significantly controlled the allergic response in sensitized mice with a shift of the balance of Th1- and Th2-T cells toward Th1 predominance. These findings suggest that U-Omp16 may be useful as a Th1-directing adjuvant in an oral vaccine.

Systemic IL-2/anti-IL-2Ab complex combined with sublingual immunotherapy suppresses experimental food allergy in mice through induction of mucosal regulatory T cells

Therapeutic tolerance restoration has been proven to modify food allergy in patients and animal models and although sublingual immunotherapy (SLIT) has showed promise, combined therapy may be necessary to achieve a strong and long‐term tolerance.

Use of a Collagen Membrane to Enhance the Survival of Primary Intestinal Epithelial Cells

Intestinal epithelial cell culture is important for biological, functional, and immunological studies. Since enterocytes have a short in vivo life span due to anoikis, we aimed to establish a novel and reproducible method to prolong the survival of mouse and human cells. Cells were isolated following a standard procedure, and cultured on ordered‐cows collagen membranes. A prolonged cell life span was achieved; cells covered the complete surface of bio‐membranes and showed a classical enterocyte morphology with high expression of enzymes supporting the possibility of cryopreservation. Apoptosis was dramatically reduced and cultured enterocytes expressed cytokeratin and LGR5 (low frequency). Cells exposed to LPS or flagellin showed the induction of TLR4 and TLR5 expression and a functional phenotype upon exposure to the probiotic Bifidobacterium bifidum or the pathogenic Clostridium difficile. The secretion of the homeostatic (IL‐25 and TSLP), inhibitory (IL‐10 and TGF‐β), or pro‐inflammatory mediators (IL‐1β and TNF) were induced. In conclusion, this novel protocol using cows collagen‐ordered membrane provides a simple and reproducible method to maintain intestinal epithelial cells functional for cell‐microorganism interaction studies and stem cell expansion. J. Cell. Physiol. 232: 2489–2496, 2017.