Oral allergy induction through skin exposure to previously tolerated food antigens in murine models.

Food allergies (FAs) are caused by a failure of the immune system to regulate oral tolerance (OT). The use of soap containing hydrolyzed wheat overrides acquired OT to wheat through skin exposure. However, in mouse models, the experimental OT is robust, suggesting that acquired OT to allergens prevents the development of FAs. We aimed to analyze the mechanisms and developed a mouse model of FA that overrides acquired OT via skin exposure. Three murine FA models (intraperitoneal [IP], epicutaneous [EC], and intradermal [ID]) were compared to evaluate if allergies to ovalbumin (OVA) that had been previously tolerated orally could be induced. In the ID model, OT was overridden, and allergic reactions of severe anaphylaxis were developed. To analyze this effect in the ID model, we measured the migration of dendritic cells (DCs) into lymph nodes. The induction of OT promoted the migration of CD103+ dermal DCs; moreover, repeated percutaneous doses of OVA for sensitization gradually increased the migration of CD11b+ dermal DCs. The difference in the proportion of regulatory T cells between ID-sensitized groups at the first ID injection disappeared at the tenth injection. Although OT was robust in the IP model, ID sensitization was found to override OT.

Allergen Release Profiles of Fast-Dissolving Freeze-Dried Orodispersible Sublingual Allergy Immunotherapy Tablets.

Background: Sublingual allergy immunotherapy tablets (SLIT-tablets) provide a well-tolerated and clinically efficacious treatment for allergic disease such as allergic rhinitis and allergic asthma. In SLIT, uptake of allergen by immune-competent cells in the oral mucosa activates the immune system and leads to tolerance toward the sensitizing allergen. The ability to deliver the full allergen content into solution within the recommended sublingual holding time is therefore an essential quality of SLIT-tablets that must be supported by the tablet formulation for all relevant allergen sources. SLIT-tablets based on a fast-dissolving orodispersible freeze-dried formulation (Zydis) are currently available for 5 of the most prevalent allergens: tree (birch and related species from the birch-homologous group), grass, ragweed, Japanese cedar, and house dust mite. Objectives: The purpose of this study was to examine the allergen release properties of three freeze-dried SLIT-tablets containing tree, ragweed, and Japanese cedar extracts, respectively. The correlation between SLIT-tablet allergen release and the level of allergen-specific T-cell activation was examined for the tree SLIT-tablet. Methods: Allergen release kinetics and tablet disintegration times for the 3 freeze-dried SLIT-tablets were examined. For all 3 tablets, the magnitude of solubilized major allergen relative to time in solution was compared to external controls to achieve a measure of the total allergen release. Additional assessments of allergen release occurring after the initial timepoint (15 or 30 seconds in solution) were done independently of external controls by linear regression analyses. For the tree SLIT-tablet, the immunological potency of the released major allergen was assessed at each experimental timepoint by a Bet v-specific T-cell activation assay. Results: All 3 SLIT-tablets disintegrated within 1 second after contact with assay buffer without any detectible residue. Complete release of major allergens (Bet v 1, Amb a 1, and Cry j 1, respectively) was seen at the earliest experimental time points (15 or 30 seconds). For the tree SLIT-tablet, full T-cell activation was achieved at 30 seconds (earliest experimental time point). Conclusions: The freeze-dried SLIT-tablet formulation consistently provides rapid and complete release of allergen from a wide range of species in a standardized in vitro assay. Full release of the SLIT-tablet allergen content within the sublingual holding time is a prerequisite for maximal exposure of allergens to the sublingual mucosa immune system. The freeze-dried SLIT-tablet formulation examined here supports short sublingual holding times and furthermore offers a convenient administration form of allergy immunotherapy.

CD44 is critical for the enhancing effect of hyaluronan in allergen-specific sublingual immunotherapy in a murine model of chronic asthma.

Allergen-specific sublingual immunotherapy (SLIT) is a potentially effective disease-modification treatment for patients with allergic asthma. Because CD44 signaling enhances regulatory T (Treg) cell-induction, administering CD44 ligands such as hyaluronan (HA) with allergen-specific SLIT may enhance the therapeutic effects. We evaluated the role of CD44 in Treg cell-induction in T helper type 2 (Th2)-mediated chronic airway inflammation using CD44-/- mice and the efficacy of HA on SLIT in a Dermatophagoides farinae (Df)-induced murine model of chronic asthma. Th2 responses and Treg cell induction were evaluated in CD44-/- mice. We devised a new SLIT model of Df-induced chronic asthma utilizing HA as an adjuvant. The effects of HA added to the new SLIT model were evaluated by the early asthmatic response (EAR) and airway hyperresponsiveness (AHR), eosinophilic airway inflammation, and serum Df-specific IgE levels. Th2-mediated chronic eosinophilic airway inflammation was worse in CD44-/- mice compared with Df-sensitized wild-type (WT) mice. HA enhanced the effect of Df-induced Treg cells in a CD44-dependent manner. Sublingual Df treatment in combination with HA, but not alone, normalized EAR and AHR, and significantly reduced the serum IgE levels and the bronchoalveolar lavage fluid (BALF) eosinophil number. HA also induced Treg cells in a Df-sensitized spleen cell culture in a CD44-dependent manner. The treatment-enhancing effects of HA in this SLIT model were diminished in CD44-/- mice. CD44 is a key contributor to Treg cell induction and critical for the enhancing effects of HA in a Df-induced murine model of chronic asthma.

Latent 1,3-ß-D-glucan acts as an adjuvant for allergen-specific IgE production induced by Japanese cedar pollen exposure.

BACKGROUND: The pollen grains of several plant species contain 1,3-ß-D-glucan (BG). BG activates dendritic cells (DCs) and subsequently regulates the innate immune responses. Within Japan, the most common disease associated with type-I hypersensitivity is Japanese cedar pollinosis. However, the role of BG in Japanese cedar pollen (JCP) remains unclear. This study examined the localization and immunological effects of BG in JCP. METHODS: The localization of BG in JCP grain was determined by immunohistochemical staining using a soluble dectin-1 protein probe and a BG recognition protein (BGRP). The content of BG extracted from JCP was measured by a BGRP-based ELISA-like assay. The cytokine production by bone marrow-derived DCs (BMDCs) obtained from wild-type and BG receptor (dectin-1) knock-out mice was examined in vitro. The mice were intranasally administered JCP grains and the specific serum Ig levels were then quantified. RESULTS: BG was detected in the exine and cell wall of the generative cell and tube cell of the JCP grain. Moreover, BG in the exine stimulated production of TNF-α and IL-6 in the BMDCs via a dectin-1-dependent mechanism. Meanwhile, JCP-specific IgE and IgG were detected in the serum of wild-type mice that had been intranasally administered with JCP grains. These mice also exhibited significantly enhanced sneezing behavior. However, dectin-1 knock-out mice exhibited significantly lower JCP-specific IgE and IgG levels compared to wild-type mice. CONCLUSIONS: Latent BG in JCP can act as an adjuvant to induce JCP-specific antibody production via dectin-1.

Formation of IgE-Allergen-CD23 Complex Changes in Children Treated with Subcutaneous Immunotherapy for Japanese Cedar Pollinosis.

BACKGROUND: Subcutaneous immunotherapy (SCIT) is used to treat Japanese cedar (JC) pollinosis. The formation of IgE-allergen-CD23 complex after SCIT for JC pollinosis has not yet been fully elucidated. OBJECTIVE: The objective of this study was to investigate the formation of IgE-allergen-CD23 complex after SCIT for JC pollinosis. METHODS: Eleven patients were treated with 3-year SCIT for JC pollinosis at Sa-gamihara National Hospital from 2013 to 2014. Nasal and ocular symptoms (in terms of symptom scores) during the scattering of JC pollen and immunological changes were investigated. Levels of JC pollen-specific antibodies (IgE and IgG4) were measured by ImmunoCAP assays. To detect the changes in allergen-presenting ability of B cells, the levels of IgE-allergen-CD23 complexes in serum were measured by a cell-free, enzyme-linked immunosorbent-facilitated antigen-binding assay. RESULTS: The median (interquartile range) age of the subjects was 8 (6-10) years. Three patients (27%) had comorbid atopic dermatitis, and 5 patients (45%) had comorbid bronchial asthma. Before starting SCIT, the total IgE level was 373 (75-2,870) kU/L, and the level of JC pollen-specific IgE was 77.2 (15.4-528) kUA/L. Symptom scores improved significantly from the year after treatment. JC pollen-specific IgE levels did not change after 3 years of treatment. JC pollen-specific IgG4 levels increased significantly throughout the treatment period. The levels of IgE-allergen-CD23 complexes decreased significantly after 3 years of treatment. CONCLUSION: The ability of IgE-allergen complexes to bind to CD23 decreased after SCIT, suggesting that increasing levels of IgE-blocking antibodies, including IgG4, may play an important role in the mechanism of SCIT.

Allergen Stability and Immunological Reactivity during Co-dissolution and Incubation of House Dust Mite and Japanese Cedar Pollen SLIT-Tablets.

Japanese allergic subjects are commonly sensitized to both house dust mite (HDM) and Japanese cedar pollen (JCP) and combined treatment with sublingual immunotherapy (SLIT) tablets is desirable. However, mixing extracts of two non-homologous allergens may compromise allergen stability and affect the clinical outcome. Therefore, we investigated the stability of major allergens and total allergenic reactivity of HDM and JCP SLIT-tablets following dissolution in human saliva or artificial gastric juice. Two fast-dissolving freeze-dried SLIT-tablets were completely dissolved and incubated at 37 °C. Major allergen concentrations and total allergenic reactivity were measured. After mixing and co-incubation of HDM and JCP SLIT tablets in human saliva for 10 min at 37°C, there were no statistically significant changes in major allergen concentrations. In addition, no loss of allergenic reactivity of the mixed two SLIT-tablet solutions was seen. In contrast, complete loss of allergenic reactivity and detectable major allergen concentrations occurred when the two SLIT-tablets were dissolved and incubated in artificial gastric juice. These results demonstrate that HDM or JCP major allergens and the total allergenic reactivity of both SLIT-tablets measured here remain intact after dissolution and co-incubation in human saliva, supporting the possibility of a dual HDM and JCP SLIT-tablet administration regimen if clinically indicated. The complete loss of allergenic reactivity after incubation in artificial gastric juice can furthermore be taken to indicate that the immunological activity of the allergen extracts contained in the two SLIT-tablets is likely to be lost or severely compromised upon swallowing.

Immune suppression of food allergy by maternal IgG in murine models.

BACKGROUND: Most of the patients develop food allergy early in life. The factors related to parental immune condition might be one of the conceivable causes. METHODS: We reported murine models of food allergy and oral OVA tolerance. To investigate the influence of parental immune condition on infant food allergy, female and male mice with food allergy or oral tolerance were mated with each other. RESULTS: Food allergy was suppressed by decreased IgE production in the offspring of mice with food allergy. On the contrary, anaphylaxis for OVA was induced in the offspring of mice with oral tolerance. The suppression of food allergy being dependent on a maternal factor was revealed in the offspring after cross-mating mice with food allergy and oral tolerance. Because OVA-specific IgG, presumed to be from the allergic mother, was detected in the serum of naïve infants from mothers allergic to food, we assumed that the suppression was dependent on a specific IgG. The serum IgG purified by a G-protein column was administered before OVA sensitization in the food allergy model, and OVA-specific IgE production was found to be diminished in the administered mice. However, OVA-specific monoclonal IgG1 and IgG2a administration could not suppress food allergy. Because we detected OVA-IgG immune complex in the serum of mothers allergic to food, it might be a cause of maternal immune suppression. CONCLUSIONS: We demonstrated that maternal specific IgG conjugated food antigen is an important factor related to the development of food allergy and acquiring tolerance.