Balancing Tolerance or Allergy to Food Proteins

Moringa oleifera Leaves Protein Enhances Intestinal Permeability by Activating TLR4 Upstream Signaling and Disrupting Tight Junctions

Changes in intestinal mucosal barrier permeability lead to antigen sensitization and mast cell-mediated allergic reactions, which are considered to play important roles in the occurrence and development of food allergies. It has been suggested that protein causes increased intestinal permeability via mast cell degranulation, and we investigated the effect of camellia Moringa oleifera leaves protein on intestinal permeability and explored its role in the development of food allergies. The current study investigated the effect of M. oleifera leaves protein on intestinal permeability through assessments of transepithelial electrical resistance (TEER) and transmembrane transport of FITC-dextran by Caco-2 cells. The expression levels of Toll-like receptor 4 (TLR4), IL-8, Occludin, Claudin-1, and perimembrane protein family (ZO-1) were detected by real-time PCR and Western blotting. The effect of M. oleifera leaves protein on intestinal permeability was verified in mice in vivo. The serum fluorescence intensity was measured using the FITC-dextran tracer method, and the expression of tight junction proteins was detected using Western blotting. The results showed that M. oleifera leaves protein widened the gaps between Caco-2 cells, reduced transmembrane resistance, and increased permeability. This protein also reduced the mRNA and protein levels of Occludin, Claudin-1, and ZO-1. Animal experiments showed that intestinal permeability was increased, and that the expression of the tight junction proteins Occludin and Claudin-1 were downregulated in mice. This study shows that M. oleifera leaves protein has components that increase intestinal permeability, decrease tight junction protein expression, promote transmembrane transport in Caco-2 cells, and increase intestinal permeability in experimental animals. The finding that M. oleifera leaves active protein increases intestinal permeability suggests that this protein may be valuable for the prevention, diagnosis, and treatment of M. oleifera leaves allergy.

Ultrasound-assisted glycation and the allergenicity of α-lactalbumin

BACKGROUND

Ultrasound-assisted glycation is a promising method for decreasing the allergenicity of α-lactalbumin (ALA). However, there is a lack of in vivo studies on the allergenicity of ultrasound-assisted glycated ALA. In this study, the effects of the ultrasound-assisted glycation of ALA on the allergenicity and intestinal microflora were characterized using a BALB/c mouse model.

RESULTS

Increased immunoglobulin -G/ immunoglobulin-E (IgG/IgE) and interleukin-4/6 (IL-4/6) secretions, and reduced interferon-γ (IFN-γ) secretions were found in the serum of ALA sensitized and challenged, mice in comparison with a control group. However, there was no significant difference between the mice fed with ultrasound-assisted glycated ALA and the control group. Mice that were sensitized and challenged with ALA showed disrupted intestinal microflora, manifesting in significantly decreased Firmicutes and significantly increased Proteobacteria. It was found that 100ALA-gal could maintain the intestinal microflora of mice in a normal state. Pearson's rank correlation showed that Proteobacteria and Spirochaetota were correlated positively with the IL-4/IL-6 level and were correlated negatively with the expression of IFN-γ. Proteobacteria were also significantly positively correlated with IL-6 and negatively correlated with IFN-γ (P < 0.05).

CONCLUSION

These results suggested that ultrasound-assisted glycation on ALA can maintain the intestinal microflora in a normal state thus balancing the proportion of Th1/Th2 to decrease allergic reaction. © 2022 Society of Chemical Industry.

Depolymerized sulfated galactans from Eucheuma serra ameliorate allergic response and intestinal flora in food allergic mouse model

The ameliorative effect of depolymerized sulfated polysaccharides from Eucheuma serra (DESP) on ovalbumin (OVA)-caused induced food allergy was investigated in this work. Results showed that OVA stimulated the secretion of allergy-related cytokines (OVA-specific IgE, mMCP-1, IgA, TNF-α) and led to diarrhea, intestinal epithelial damage, and intestinal microflora dysbiosis in sensitized mice. After the administration of DESP, however, the anaphylactic symptoms (shortness of breath, hypothermia, diarrhea), along with the allergy-related cytokines, were effectively suppressed. Moreover, the reduced intestinal inflammation was discovered in the DESP-treated group. Additionally, 16S rRNA sequencing of fecal samples was performed, and gene count and α-diversity analysis revealed that DESP improved microbial community richness. Taxonomic composition analysis showed that DESP modulated the proportion of Firmicutes and Bacteroidetes/Proteobacteria. Particularly, DESP increased probiotics (Lactobacillaceae, Bifidobacteriaceae and Prevotellaceae) and decreased pathogenic bacteria (Helicobacteraceae and Desulfovibrionaceae). These findings, therefore, suggest that DESP may ameliorate food allergy through the regulation of intestinal microbiota.

Oral immunotherapy with omalizumab reverses the Th2 cell-like programme of regulatory T cells and restores their function

BACKGROUND

Oral immunotherapy (OIT) successfully desensitizes patients with food allergies, but the immune mechanisms mediating its efficacy remain obscure.

OBJECTIVES

We tested the hypothesis that allergen-specific regulatory T (Treg) cell function is impaired in food allergy and is restored by anti-IgE antibody (omalizumab)-supplemented OIT.

METHODS

Peanut-specific T effector (Teff) and Treg cell proliferative responses, activation markers and cytokine expression were analysed by flow cytometry in 13 peanut-allergic subjects before the start of omalizumab-supplemented OIT and periodically in some subjects thereafter for up to 2 years. Peripheral blood regulatory T cells (Treg cells) were analysed for their peanut-specific suppressor function before and at 1 year following OIT. This study was registered on ClinicalTrials.gov (NCT01290913).

RESULTS

Proliferation of allergen-specific Teff and Treg cells precipitously declined following the initiation of omalizumab therapy prior to OIT, followed by partial recovery after the initiation of OIT. At baseline, peanut-specific Treg cells exhibited a Th2 cell-like phenotype, characterized by increased IL-4 expression, which progressively reversed upon OIT. Peanut-specific Treg cell suppressor activity was absent at the start of omalizumab/OIT therapy but became robust following OIT. Absent peanut-specific Treg cell function could also be recovered by the acute blockade of IL-4/IL-4R receptor signalling in Treg cells, which inhibited their IL-4 production.

CONCLUSIONS AND CLINICAL RELEVANCE

OIT supplemented by omalizumab promotes allergen desensitization through an initial omalizumab-dependent step that acutely depletes allergen-reactive T cells, followed by an increase in allergen-specific Treg cell activity due to the reversal of their Th2 cell-like programme. Improved Treg cell function may be a key mechanism by which OIT ameliorates food allergy.

Childhood food allergies: An evolutionary mismatch hypothesis

For hominins living in the Paleolithic era, early food antigen exposures—in utero and throughout infancy—closely matched later exposures, and therefore immune system tolerance mechanisms evolved under the expectation of this condition being met. This predicts that the degree of mismatch between early and downstream food antigen exposures is a key variable underlying the development of childhood food allergies. Three historical periods are identified in which the degree of mismatch climbs from near zero to substantial, as we transition from one period to another. The first encompasses our long history as foragers; the second begins with the advent of farming and the third spans only the most recent two or three decades, and manifests from social changes driven largely by an explosion in access to information. Testable predictions are generated and evaluated in light of available evidence, and an approach for primary prevention of childhood food allergies is proposed.

Spontaneous food allergy in Was-/- mice occurs independent of FcεRI-mediated mast cell activation

BACKGROUND

Food allergies are a growing health problem, and the development of therapies that prevent disease onset is limited by the lack of adjuvant-free experimental animal models. We compared allergic sensitization in patients with food allergy or Wiskott-Aldrich syndrome (WAS) and defined whether spontaneous disease in Was^-/- mice recapitulates the pathology of a conventional disease model and/or human food allergy.

METHODS

Comparative ImmunoCAP ISAC microarray was performed in patients with food allergy or WAS. Spontaneous food allergy in Was^-/- mice was compared to an adjuvant-based model in wild-type mice (WT-OVA/alum). Intestinal and systemic anaphylaxis was assessed, and the role of the high-affinity IgE Fc receptor (FcεRI) in allergic sensitization was evaluated using Was^-/- Fcer1a^-/- mice.

RESULTS

Polysensitization to food was detected in both WAS and food-allergic patients which was recapitulated in the Was^-/- model. Oral administration of ovalbumin (OVA) in Was^-/- mice induced low titers of OVA-specific IgE compared to the WT-OVA/alum model. Irrespectively, 79% of Was^-/- mice developed allergic diarrhea following oral OVA challenge. Systemic anaphylaxis occurred in Was^-/- mice (95%) with a mortality rate >50%. Spontaneous sensitization and intestinal allergy occurred independent of FcεRI expression on mast cells (MCs) and basophils.

CONCLUSIONS

Was^-/- mice provide a model of food allergy with the advantage of mimicking polysensitization and low food-antigen IgE titers as observed in humans with clinical food allergy. This model will facilitate studies on aberrant immune responses during spontaneous disease development. Our results imply that therapeutic targeting of the IgE/FcεRI activation cascade will not affect sensitization to food.

Murine models for mucosal tolerance in allergy

Immunity is established by a fine balance to discriminate between self and non-self. In addition, mucosal surfaces have the unique ability to establish and maintain a state of tolerance also against non-self constituents such as those represented by the large numbers of commensals populating mucosal surfaces and food-derived or air-borne antigens. Recent years have seen a dramatic expansion in our understanding of the basic mechanisms and the involved cellular and molecular players orchestrating mucosal tolerance. As a direct outgrowth, promising prophylactic and therapeutic models for mucosal tolerance induction against usually innocuous antigens (derived from food and aeroallergen sources) have been developed. A major theme in the past years was the introduction of improved formulations and novel adjuvants into such allergy vaccines. This review article describes basic mechanisms of mucosal tolerance induction and contrasts the peculiarities but also the interdependence of the gut and respiratory tract associated lymphoid tissues in that context. Particular emphasis is put on delineating the current prophylactic and therapeutic strategies to study and improve mucosal tolerance induction in allergy.