Grass tablet sublingual immunotherapy downregulates the TH2 cytokine response followed by regulatory T-cell generation

Regulatory T cells in children with allergy and asthma: it is time to act

Nowadays allergy and asthma are a huge medical problem. Despite deeper and more precise knowledge concerning their pathogenesis and the role of the immune system in these processes, so far immunotherapy is the only treatment which can modify the course of these diseases. Considering that regulatory T cells (Treg cells) have a great significance in pathogenesis of both diseases it seems appropriate to pay attention to their role in the treatment process. This work summarizes the Treg cells characteristics, the influence of allergen specific immunotherapy and other treatment modalities on Treg cells, and the possibility of using Treg cells in therapy.

Sublingual immunotherapy alters expression of IL-4 and its soluble and membrane-bound receptors

Seasonal allergic rhinitis (SAR) is a disease of increasing prevalence, which results from an inappropriate T helper cell, type 2 (Th2) response to pollen. Specific immunotherapy (SIT) involves repeated treatment with small doses of pollen and can result in complete and lasting reversal of SAR. Here, we assayed the key Th2 cytokine, IL-4, and its soluble and membrane-bound receptor in patients with SAR before and after SIT. Using allergen-challenge assays, we found that SIT treatment decreased IL-4 cytokine levels, as previously reported. We also observed a significant decrease in the IL-4 membrane-bound receptor (mIL4R) at the level of both mRNA and protein. SIT treatment resulted in a significant increase in the inhibitory soluble IL-4 receptor (sIL4R). Reciprocal changes in mIL4R and sIL4R were also observed in patient serum. Altered mIL4R and sIL4R is a novel explanation for the positive effects of immunotherapy with potential basic and clinical research implications.

Regulatory functions of B cells in allergic diseases

B cells are essentially described for their capacity to produce antibodies ensuring anti-infectious immunity or deleterious responses in the case of autoimmunity or allergy. However, abundant data described their ability to restrain inflammation by diverse mechanisms. In allergy, some regulatory B-cell subsets producing IL-10 have been recently described as potent suppressive cells able to restrain inflammatory responses both in vitro and in vivo by regulatory T-cell differentiation or directly inhibiting T-cell-mediated inflammation. A specific deficit in regulatory B cells participates to more severe allergic inflammation. Induction of allergen tolerance through specific immunotherapy induces a specific expansion of these cells supporting their role in establishment of allergen tolerance. However, the regulatory functions carried out by B cells are not exclusively IL-10 dependent. Indeed, other regulatory mechanisms mediated by B cells are (i) the production of TGF-β, (ii) the promotion of T-cell apoptosis by Fas-Fas ligand or granzyme-B pathways, and (iii) their capacity to produce inhibitory IgG4 and sialylated IgG able to mediate anti-inflammatory mechanisms. This points to Bregs as interesting targets for the development of new therapies to induce allergen tolerance. In this review, we highlight advances in the study of regulatory mechanisms mediated by B cells and outline what is known about their phenotype as well as their suppressive role in allergy from studies in both mice and humans.

The efficacy and safety of the Timothy grass allergy sublingual immunotherapy tablet in Canadian adults and children

BACKGROUND

The effect of sublingual Timothy grass immunotherapy tablet 2800 BAU (grass SLIT-T) has been evaluated in three North American trials in adults and children who have allergic rhinitis with or without conjunctivitis (AR/C). This paper examines the effects of grass SLIT-T in Canadians.

METHODS

Data for grass-allergic Canadians in three randomized, placebo-controlled, double-blind trials were analyzed post hoc: 1) adults ≥18 y, grass-pollen season [GPS] 2009; 2) children 5- <18 y, 2009; and 3) adults 18-65 y and children 5- <18 y, GPS 2012. Data from the GPS 2009 trials were pooled to provide a more precise estimate of treatment effects than the individual studies would provide. In every trial, participants received once-daily grass SLIT-T or placebo approximately 12 weeks before and continuing throughout the GPS. Participants used daily electronic diaries to record AR/C symptoms and medication use for treatment of symptoms. The therapeutic effect of grass SLIT-T was measured as a total combined score (TCS = daily symptom score + daily medication score) averaged over the entire GPS. Safety was assessed by monitoring adverse events (AEs).

RESULTS

In the three trials, 386 Canadian participants were randomized; the overall population had 2284 participants. Canadian participants treated with grass SLIT-T in the pooled adult-pediatric 2009 trials showed a 38% mean TCS reduction relative to placebo (-2.06 difference [95% CI: -3.72, -0.39]; 3.32 vs. 5.37). Participants treated with grass SLIT-T in the adult-pediatric 2012 trial showed a 37% median TCS reduction relative to placebo (-1.53 difference [95% CI: -2.1, -0.3]; 2.58 vs. 4.11). Similar efficacy findings were observed over the peak GPS. Approximately 90% of treatment-related AEs were mild or moderate in severity. Two Canadian participants had moderate systemic allergic reactions (skin, respiratory, abdominal symptoms) to grass SLIT-T; symptoms resolved within 1 hour without medical intervention or treatment. No serious or life-threatening treatment-related AEs occurred.

CONCLUSION

The 2800 BAU Timothy grass SLIT-T significantly improved AR/C induced by Timothy grass pollen in adults and children ≥5 y in Canadians, which was consistent with the robust efficacy observed in the overall trial population. The treatment was generally well tolerated.

TRIAL REGISTRATION

Clinicaltrials.gov identifiers NCT00562159, NCT00550550, NCT01385371.

A milestone in house dust-mite-allergen immunotherapy: the new sublingual tablet S-524101 (actair)

Subcutaneous allergen-specific immunotherapy has long been used in the treatment of allergic rhinitis and/or asthma and its efficacy has been confirmed. However, due to the discomfort of injections and the risk of severe adverse reactions, alternative routes of allergen administration have emerged. Delivery of allergens through the mucosal route had been proposed and investigated thoroughly, confirming the sublingual route to be the most efficacious. Later, the efficacy and safety of this route have been documented by numerous controlled trials both for house dust mite (HDM) and pollens. Recently, sublingual orodispersable grass pollen allergen tablets were in use followed by the newly developed HDM allergen tablets with satisfactory clinical results: Moreover, very recently 1 year of HDM tablet treatment was demonstrated to exert its clinical efficacy 1 year after discontinuation of tablet IT. The persistence of efficacy after only 1 year of treatment is a new and promising era. Currently, Sublingual Immunotherapy is the most easily administered and safe treatment option until more immunogenic, less allergenic and more efficient allergen extracts are developed.

Immune mechanisms of sublingual immunotherapy

Sublingual immunotherapy (SLIT) is a well-established allergen-specific immunotherapy and a safe and effective strategy to reorient inappropriate immune responses in allergic patients. SLIT takes advantage of the tolerogenic environment of the oral mucosa to promote tolerance to the allergen. Several clinical studies have investigated the complex interplay of innate and adaptive immune responses that SLIT exploits. The oral immune system is composed of tolerogenic dendritic cells that, following uptake of allergen during SLIT, support the differentiation of T helper cell type 1 (Th1) and the induction of IL-10-producing regulatory T cells. Following SLIT, allergic disease-promoting T helper cell type 2 (Th2) responses shift to a Th1 inflammatory response, and IL-10 and transforming growth factor (TGF)-β production by regulatory T cells and tolerogenic dendritic cells suppress allergen-specific T cell responses. These immune changes occur both in the sublingual mucosa and in the periphery of a patient following SLIT. SLIT also promotes the synthesis of allergen-specific IgG and IgA antibodies that block allergen-IgE complex formation and binding to inflammatory cells, thus encouraging an anti-inflammatory environment. Several of these revealing findings have also paved the way for the identification of biomarkers of the clinical efficacy of SLIT. This review presents the emerging elucidation of the immune mechanisms mediated by SLIT.

Modulation of dendritic cell innate and adaptive immune functions by oral and sublingual immunotherapy

Sublingual (SLIT) and oral immunotherapy (OIT) are promising treatments for food allergy, but underlying mechanisms are poorly understood. Dendritic cells (DCs) induce and maintain Th2-type allergen-specific T cells, and also regulate innate immunity through their expression of Toll-like receptors (TLRs). We examined how SLIT and OIT influenced DC innate and adaptive immune responses in children with IgE-mediated cow's milk (CM) allergy. SLIT, but not OIT, decreased TLR-induced IL-6 secretion by myeloid DCs (mDCs). SLIT and OIT altered mDC IL-10 secretion, a potent inhibitor of FcεRI-dependent pro-inflammatory responses. OIT uniquely augmented IFN-α and decreased IL-6 secretion by plasmacytoid DCs (pDCs), which was associated with reduced TLR-induced IL-13 release in pDC-T cell co-cultures. Both SLIT and OIT decreased Th2 cytokine secretion to CM in pDC-T, but not mDC-T, co-cultures. Therefore, SLIT and OIT exert unique effects on DC-driven innate and adaptive immune responses, which may inhibit allergic inflammation and promote tolerance.

Regulatory T cells and immune regulation of allergic diseases: roles of IL-10 and TGF-β

The prevalence of allergic diseases has significantly increased in industrialized countries. Allergen-specific immunotherapy (AIT) remains as the only curative treatment. The knowledge about the mechanisms underlying healthy immune responses to allergens, the development of allergic reactions and restoration of appropriate immune responses to allergens has significantly improved over the last decades. It is now well-accepted that the generation and maintenance of functional allergen-specific regulatory T (Treg) cells and regulatory B (Breg) cells are essential for healthy immune responses to environmental proteins and successful AIT. Treg cells comprise different subsets of T cells with suppressive capacity, which control the development and maintenance of allergic diseases by various ways of action. Molecular mechanisms of generation of Treg cells, the identification of novel immunological organs, where this might occur in vivo, such as tonsils, and related epigenetic mechanisms are starting to be deciphered. The key role played by the suppressor cytokines interleukin (IL)-10 and transforming growth factor (TGF)-β produced by functional Treg cells during the generation of immune tolerance to allergens is now well established. Treg and Breg cells together have a role in suppression of IgE and induction of IgG4 isotype allergen-specific antibodies particularly mediated by IL-10. Other cell types such as subsets of dendritic cells, NK-T cells and natural killer cells producing high levels of IL-10 may also contribute to the generation of healthy immune responses to allergens. In conclusion, better understanding of the immune regulatory mechanisms operating at different stages of allergic diseases will significantly help the development of better diagnostic and predictive biomarkers and therapeutic interventions.

Modulation of immune responses by immunotherapy in allergic diseases

Allergen immunotherapy (AIT) has been used for 100 years and until now different immunoregulatory pathways have been shown to take place in its mechanisms of action. It is characterized by administration of the causative allergen and is shown to be clinically efficient even after discontinuation of therapy particularly in allergic respiratory diseases, bee venom allergy, and food allergy. Generation of antigen/allergen-specific peripheral tolerance is the key mechanism during immunotherapy. It is mediated by development of T and B regulatory cells, IgG4 isotype allergen-specific antibodies and the involvement of multiple suppressor factors, which lead to decreased tissue inflammation, early and late phase responses. Describing novel regulatory mechanisms in the process of immune tolerance induction will help to identify treatment modalities not only for allergic disorders, but also for autoimmune diseases, organ transplantation, chronic infections, and cancer.