Oral tolerance induced to house dust mite extract in naive and sensitized mice: evaluation of immunoglobulin G anti-immunoglobulin E autoantibodies and IgG-IgE complexes

Prevention Is Better than Cure: Impact of Allergen Immunotherapy on the Progression of Airway Disease

Allergen immunotherapy is highly effective for seasonal pollinosis. Three years of treatment results in long-term efficacy. This disease modification is accompanied by downregulation of allergen-specific Th2 responses and the induction of persistent specific IgG- and IgA-associated IgE-blocking activity. In children with seasonal rhinitis, both subcutaneous and sublingual pollen immunotherapy have been shown to reduce the development of asthma symptoms and asthma medication requirements. House dust mite tablet allergen immunotherapy has been shown to be effective for perennial mite-driven rhinitis in adults and children and may suppress asthma exacerbations, whereas its long-term efficacy has yet to be explored. The success of primary prevention of peanut allergy in childhood by introduction of peanut into the diet during infancy provides a strong rationale to explore whether primary prevention of inhalant allergies and asthma may also be possible. House dust mite allergy is a major risk factor for developing asthma. Preliminary data in at-risk children suggest that sublingual house dust mite immunotherapy initiated during infancy could reduce the onset of multiple allergen sensitizations and prevent the development of asthma at age 6 years. This possibility should now be explored in an adequately powered, prospectively randomized controlled trial.

Increasing severity of early-onset atopic dermatitis, but not late-onset, associates with development of aeroallergen sensitization and allergic rhinitis in childhood

BACKGROUND

Early exposure to allergens through a defect skin barrier has been proposed as a mechanism for inducing sensitization and development of allergic diseases. We hypothesized that early-onset, severe atopic dermatitis (AD) is associated with development of aeroallergen sensitization and allergic rhinitis.

METHODS

We included 368 children from the Copenhagen Prospective Studies on Asthma in Childhood₂₀₀₀ (COPSAC₂₀₀₀ ) at-risk mother-child cohort. AD was diagnosed prospectively based on Hanifin&Rajka's criteria and severity assessed using the Scoring Atopic Dermatitis (SCORAD) index. Early-onset AD was defined as debut ≤1 year, late-onset as debut from 1-6 years. Aeroallergen sensitization and allergic rhinitis were diagnosed at ages 6-7 and 12 years. Associations between early-onset and late-onset AD and allergy endpoints were calculated using general estimating equations (GEE) models to compute the overall odds ratios (OR) for both time points.

RESULTS

Early-onset AD (yes/no) and severity (SCORAD) were associated with development of aeroallergen sensitization during childhood; GEE OR = 1.68 [1.08; 2.62], p = .02 and 1.08 [1.03; 1.12], p < .001, whereas late-onset AD showed a borderline significant association and late-onset severity showed no association; GEE OR = 1.65 [0.92; 2.94], p = .08 and 1.01 [0.97; 1.06], p = .55. The same trend was seen for allergic rhinitis with significant association between early-onset AD and allergic rhinitis; GEE OR = 1.56 [1.01; 2.41], p = .04 and severity; GEE OR = 1.09 [1.05; 1.13], p < .001, whereas late-onset AD showed no association. The effects on sensitization and rhinitis of early-onset versus late-onset AD severity were significantly different: p-interaction_{sensitization}  = .03 and p-interaction_rhinitis  < .01.

CONCLUSION

Increasing severity of early-onset AD, but not late-onset AD, associates with aeroallergen sensitization and allergic rhinitis later in childhood.

Anti-Interleukin-9 Antibody Increases the Effect of Allergen-Specific Immunotherapy in Murine Allergic Rhinitis

Purpose

Interleukin (IL)-9 induces allergic responses; however, the roles of anti-IL-9 antibody in the induction of tolerance remain unclear. This study investigated the effects of anti-IL-9 antibody on oral tolerance (OT) in a mouse model of allergic rhinitis (AR).

Methods

BALB/c mice were divided into 4 groups: the control, AR, OT, and OT with anti-IL-9 antibody (OT+IL9AB) groups. Ovalbumin (OVA) was used for sensitization and challenge. Mice in the OT and OT+IL9AB groups were fed OVA for immunotherapy. During immunotherapy, OT+IL9AB mice were injected with anti-IL-9 antibody. Allergic symptoms, tissue eosinophil counts, and serum OVA-specific immunoglobulin E (IgE) were measured. The mRNA expressions of cytokines and transcription factors of T cells of nasal mucosa were determined by real-time polymerase chain reaction (PCR). The protein levels of GATA3, ROR-γt, and Foxp3 in nasal mucosa were determined by Western blot. CD4⁺CD25⁺Foxp3⁺ T cells in the spleen were analyzed by flow cytometry.

Results

Administration of anti-IL-9 antibody decreased allergic symptoms, OVA-specific IgE levels, and eosinophil counts. In addition, it inhibited T-helper (Th) 2 responses, but had no effect on Th1 responses. Protein levels of ROR-γt and mRNA levels of PU.1 and ROR-γt were reduced by anti-IL-9 antibody. Anti-IL-9 antibody increased Foxp3 and IL-10 mRNA expression, Foxp3 protein, and induction of CD4⁺CD25⁺Foxp3⁺ T cells.

Conclusions

Anti-IL-9 antibody decreased allergic inflammation through suppression of Th2 and Th17 cells. Anti-IL-9 antibody enhanced the tolerogenic effects of regulatory T cells. These results suggest that anti-IL-9 antibody might represent a potential therapeutic agent for allergen immunotherapy in patients with uncontrolled allergic airway disease.

Randomized controlled trial of primary prevention of atopy using house dust mite allergen oral immunotherapy in early childhood

BACKGROUND

Children born to atopic parents are at increased risk of sensitization to environmental allergens.

OBJECTIVE

We sought to demonstrate proof of concept for oral immunotherapy to high-dose house dust mite (HDM) allergen in infancy in the prevention of allergen sensitization and allergic diseases.

METHODS

This was a prospective, randomized, double-blind, placebo-controlled, proof-of-concept study involving 111 infants less than 1 year of age at high risk of atopy (≥ 2 first-degree relatives with allergic disease) but with negative skin prick test responses to common allergens at randomization. HDM extract (active) and appropriate placebo solution were administered orally twice daily for 12 months, and children were assessed every 3 months. Coprimary outcomes were cumulative sensitization to HDM and sensitization to any common allergen during treatment, whereas development of eczema, wheeze, and food allergy were secondary outcomes. All adverse events were recorded.

RESULTS

There was a significant (P = .03) reduction in sensitization to any common allergen (16.0%; 95% CI, 1.7% to 30.4%) in the active (5 [9.4%]) compared with placebo (13 [25.5%]) treatment groups. There was no treatment effect on the coprimary outcome of HDM sensitization and the secondary outcomes of eczema, wheeze, and food allergy. The intervention was well tolerated, with no differences between active and placebo treatments in numbers or nature of adverse events.

CONCLUSION

Prophylactic HDM oral immunotherapy is well tolerated in children at high heredity risk. The results met the trial's prespecified criteria for proof of concept in reducing sensitization to any allergen; however, no significant preventive effect was observed on HDM sensitization or allergy-related symptoms.

Sublingual immunotherapy reduces allergic symptoms in a mouse model of rhinitis

BACKGROUND

Sublingual immunotherapy (SLIT) is a clinically effective treatment in both pollen and house dust mite-induced rhinitis and asthma. However, the mechanisms by which this is accomplished are not clear.

OBJECTIVE

The objective of the current study was to establish a mouse model of rhinitis in order to study the effect and mechanisms of SLIT.

METHODS

Mice were sensitized by intraperitoneal injections of alum-adsorbed Phleum pratense extract. Sensitized mice were SLIT-treated and subsequently challenged intranasally and analysed for clinical symptoms, antibody levels, eosinophilia and T cell response.

RESULTS

Intranasal challenge of sensitized mice led to the development of rhinitis characterized by significantly increased sneezing and influx of eosinophils into the nose. Levels of specific IgE were fivefold increased in nasopharyngeal lavage (NAL) fluid and more than doubled in serum. Furthermore, a T-helper type 2 (Th2) like T cell response was observed in local draining lymph nodes. SLIT treatment of sensitized mice reduced sneezing, eosinophilia and IgE levels in the NAL by more than 50%. Moreover, serum levels of IgE and IgG1 as well as T cell response in the draining lymph nodes were also significantly reduced. Treatment for a shorter time or with a lower dose only led to minor reductions of the clinical and immunological parameters, indicating that the effect of SLIT is time and dose dependent.

CONCLUSION

In the present study, we have established a mouse model displaying the hallmarks of allergic rhinitis using a clinically relevant allergen. Using this model, we have demonstrated that SLIT treatment is able to reduce allergic symptoms in a time- and dose-dependent manner.

Long-term anergy in orally tolerized mice is linked to decreased B7.2 expression on B cells

Durable antigen (Ag)-specific T- and B-cell anergy induced by oral tolerance is an attractive strategy for immunotherapy of allergic diseases. Here, we address the lasting effect of oral tolerance induction in naïve or primed mice to ovalbumin (OVA) on antibody production. Single feeding with OVA prior to immunization or double feeding, before and after Ag priming, in A/Sn mice, induced a long-lasting suppression of IgE, IgG1 and IgG2a responses up to 8 months after immunization. In contrast, primed-fed mice had transient IgE inhibition. Naive and double-treated mice showed marked Ag-specific unresponsiveness and scarce cytokines production. Inhibition of IL-2 and IFN-gamma secretion in naïve-fed mice were restored in the presence of anti-CD28 mAb plus Ag stimulation. The durable inhibition of Ab production in OVA-fed mice was related to the persistent decrease of B7.2 expression on B cells. Ag feeding in naive and primed status may be a prophylactic measure to avoid later Ag sensitization.

Oral tolerance

Multiple mechanisms of tolerance are induced by oral antigen. Low doses favor active suppression, whereas higher doses favor clonal anergy/deletion. Oral antigen induces T-helper 2 [interleukin (IL)-4/IL-10] and Th3 [transforming growth factor (TGF)-beta] T cells plus CD4+CD25+ regulatory cells and latency-associated peptide+ T cells. Induction of oral tolerance is enhanced by IL-4, IL-10, anti-IL-12, TGF-beta, cholera toxin B subunit, Flt-3 ligand, and anti-CD40 ligand. Oral (and nasal) antigen administration suppresses animal models of autoimmune diseases including experimental autoimmune encephalitis, uveitis, thyroiditis, myasthenia, arthritis, and diabetes in the non-obese diabetic (NOD) mouse, plus non-autoimmune diseases such as asthma, atherosclerosis, graft rejection, allergy, colitis, stroke, and models of Alzheimer's disease. Oral tolerance has been tested in human autoimmune diseases including multiple sclerosis (MS), arthritis, uveitis, and diabetes and in allergy, contact sensitivity to dinitrochlorobenzene (DNCB), and nickel allergy. Although positive results have been observed in phase II trials, no effect was observed in phase III trials of CII in rheumatoid arthritis or oral myelin and glatiramer acetate (GA) in MS. Large placebo effects were observed, and new trials of oral GA are underway. Oral insulin has recently been shown to delay onset of diabetes in at-risk populations, and confirmatory trials of oral insulin are being planned. Mucosal tolerance is an attractive approach for treatment of autoimmune and inflammatory diseases because of lack of toxicity, ease of administration over time, and antigen-specific mechanisms of action. The successful application of oral tolerance for the treatment of human diseases will depend on dose, developing immune markers to assess immunologic effects, route (nasal versus oral), formulation, mucosal adjuvants, combination therapy, and early therapy.

Current issues in the treatment of human diseases by mucosal tolerance

Tolerance has been defined as a lack of response to self but a more appropriate definition of tolerance is "any mechanism by which a potentially injurious immune response is prevented, suppressed, or shifted to a non-injurious class of immune response." Thus, tolerance is related to productive self-recognition, rather than blindness of the immune system to its auto-components. Oral tolerance, in this sense, is of unique immunologic importance, as it is a continuous natural immunologic event driven by exogenous antigen. Because of their privileged access to the internal milieu, antigens that are continuously in contact with the mucosa are a frontier between foreign and self-components. Thus, oral tolerance is an immunological mechanism that evolved to treat external agents that gain access to the body via a natural route as internal components that then become part of self. Given this, it would seem logical that autoimmune diseases caused by an inappropriate response to self-antigens might ultimately be treated by presenting such autoantigens to the mucosal surface where they can be dealt with in a non-injurious (noninflammatory) immunologic environment. Furthermore, mucosal tolerance as a treatment for autoimmune diseases is an attractive concept, as antigen-specific therapy is the most physiologic means to manipulate immune responses, and mucosal antigen is nontoxic and can be given on a chronic basis. The efficacy of mucosal tolerance has been clearly demonstrated in several animal models.

Oral tolerance induction to Dermatophagoides pteronyssinus and Blomia tropicalis in sensitized mice: occurrence of natural autoantibodies to immunoglobulin E

BACKGROUND

The dust mites Dermatophagoides pteronyssinus (Dp) and Blomia tropicalis (Bt) are important sources of indoor allergens in tropical and subtropical countries. Murine models allow the analysis of the immune response and regulation of IgE production to Dp and Bt allergens. Oral tolerance induces unresponsiveness in naive animals, but its application in sensitized animals can provide useful information to improve allergy therapy.

OBJECTIVE

To study the profile of IgE and IgG subclasses antibody upon oral administration with Bt and Dp extract in previously sensitized mice. Further, the occurrence of autoantibodies IgG anti-IgE in the immunization and in the oral tolerance was investigated.

METHODS

A/Sn mice were immunized with Bt or Dp extract in alum, orally administrated with 0.25 mg of Bt or Dp extract or PBS at the 6th, 7th and 8th days after immunization and boosted twice with their respective allergens. To analyse the mice groups, specific IgE antibodies were measured by passive anaphylaxis reaction and specific IgG subclasses and anti-IgE IgG autoantibody by ELISA assay.

RESULTS

IgE levels were markedly increased in Bt-immunized mice compared with Dp-immunized mice. A distinct profile of the specific isotypes was verified in Bt-immunized mice with a preferential production of IgG3 and IgA antibodies, whereas Dp-immunized mice developed high titres of anti-Dp IgG1, IgG2a and IgG2b antibodies. The antigen feeding inhibited IgE response in both fed-mice groups but only Dp-fed mice presented decreased levels of IgG antibodies. Free anti-IgE IgG autoantibodies were detected mainly in the Dp-immunization and they correlated with the antibody isotypes found against the allergen.

CONCLUSIONS

This is the first time that the murine-type I hypersensitivity is employed to study Bt-immunization, showing a marked IgE production, associated with IgG response, which is at least in part driven by T-independent antigens. The oral tolerance protocol in previously sensitized animals was able to down-modulate IgE response and points out this route as a strategy for allergy therapy.

Oral tolerance induction in dermatophagoides pteronyssinus-sensitized mice induces inhibition of IgE response and upregulation of TGF-beta secretion

Oral antigen administration induces peripheral tolerance in naive animals. Studies of oral tolerance induction in sensitized mice have clinical relevance as a strategy to modulate allergy. In this study, the A/Sn mice sensitized with extract of Dermatophagoides pteronyssinus (Dp) and submitted to oral Dp administration showed a marked decrease in IgE anti-Dp antibody production compared with sensitized phosphate-buffered saline (PBS)-fed mice. T cells from Dp-fed mice cocultured with spleen cells from PBS-fed mice were able to inhibit IgE anti-Dp antibody production and did not interfere in IgG1 antibody levels. The analysis of cytokine profile after Dp feeding showed a significant decrease in interleukin-4 (IL-4), IL-5, and IL-13 antigen-induced secretion levels by spleen cells, without shifting to IL-2 and interferon-gamma (IFN-gamma) production. Both transforming growth factor-beta (TGF-beta) baseline and TGF-beta antigen-stimulated levels were increased in Dp-fed mice. The effects of regulatory cytokines on anti-Dp IgE antibody production were investigated in vitro. The addition of recombinant TGF-beta (rTGF-beta) to spleen cell cultures stimulated by Dp inhibited IgE antibody secretion in both mouse groups. Neutralizing antibodies to IL-4, but not anti-TGF-beta, induced a marked inhibition of IgE production. Therefore, a negative modulatory effect on IgE response by inhibition of the axis Th2 was observed in sensitized Dp-fed mice, possibly mediated by induction of regulatory cytokines.

Modulation of IgE response and cytokine production in Peyer's patches and draining lymph nodes in sensitized mice made tolerant by oral dust mite administration

Such allergic diseases as rhinitis and asthma are IgE-mediated type I reactions and are controlled primarily by Th2 cells. One of the major dust mites, Dermatophagoides pteronyssinus (Dp), is considered to cause allergic reactions. Oral tolerance, largely used to modulate immune response, opens the possibility of modulating Th2 allergic responses. We observed downmodulation of total and specific IgE antibody levels as well as the number of specific IgE-secreting cells with Dp feeding in previously sensitized mice. Analysis of the cytokine profile in mucosal lymphoid tissues in the protocol revealed altered patterns of interferon-gamma (IFN-gamma), interleukin-5 (IL-5), and transforming growth factor-beta (TGF-beta) secretion in Dp-fed animals. The results suggest that both the Th and B cell populations are modulated in mice made tolerant by oral Dp feeding. Understanding the mechanisms at the mucosal level that underlie oral tolerance can improve its use in allergy immunotherapy.

Low dose of orally administered antigen down-regulates the T helper type 2-response in a murine model of dust mite hypersensitivity

One of the main goals of immunotherapy of allergic diseases is the down-regulation of the type I hypersensitivity reaction. We investigated in this study the effect of oral administration of varying doses (0.25, 1.0, 4.0 and 10 mg) of dust mite extract (Dermatophagoides pteronyssinus, Dp) in sensitized A/Sn mice. A marked decrease of the allergen-specific immunoglobulin E (IgE) response was observed with all antigen doses. The mice orally tolerized with low Dp dose (0.25 mg) had a significant decrease in the total serum IgE and in the immunoglobulin G1 (IgG1), IgG2a and IgG2b antibody levels. The higher Dp dose (10.0 mg), however, enhanced the IgG1 antibody response, suggesting the stimulation of a pre-existing immune response of the sensitized animals. Animals fed with the low Dp dose had a significant decrease in the frequency of interleukin-4 (IL-4) secreting cells. These animals also showed a significant decrease in the frequency of Dp-specific IgE- and IgG1-positive plasma cells. Our data suggest that feeding dust mite extract to Dp-sensitized mice down-regulates the development of type I hypersensitivity, by inhibition of the T helper 2 response.