Sublingual immunotherapy in children modulates allergen-induced in vitro expression of cytokine mRNA in PBMC

Immune Cell Alterations and PI3K-PKB Pathway Suppression in Patients with Allergic Rhinitis Undergoing Sublingual Immunotherapy

INTRODUCTION

Our prior clinical study assessed the efficacy and safety of sublingual immunotherapy (SLIT) with standardized Dermatophagoides farina drops on patients with allergic rhinitis (AR) while analyzing the characteristics of adverse reactions. This study was conducted to evaluate the immune cell composition alterations in AR patients before and after SLIT, and to comprehensively investigate the role and changes of antigen-specific immune cells associated with treatment efficacy.

METHODS

A total of 68 AR patients who completed 12 months of SLIT were included in the study. Before the trial's initiation and after 1 year of SLIT, 10 ml of venous blood was collected. Peripheral blood mononuclear cells were isolated using the Ficoll gradient method. The mRNA transcriptome was analyzed using an Affymetrix microarray. The proportions of 22 immune cell types were calculated via the CIBERSORTx platform. Correlations between each immune cell type and SLIT were analyzed. PI3K-PKB pathway dysregulation were analyzed using quantitative PCR and Western blot. Flow cytometry was utilized to assess the percentages of Th1 and Th2 cells.

RESULTS

Mono-sensitized AR patients exhibited marked increases in plasma cells, activated memory T cells, regulatory T cells, and activated dendritic cells, while experiencing decreased neutrophils and resting dendritic cells. In poly-sensitized AR patients, the most notable change was an increase in regulatory T cells, coupled with decreased T follicular helper cells, resting dendritic cells, and activated mast cells. These findings indicated that SLIT reshaped immune cell profiles in AR patients, and, notably, the specific changes differed between mono-sensitized and poly-sensitized individuals. Furthermore, SLIT appeared to shift the immune response towards a Th2 decrease profile in both groups. Importantly, suppression of the PI3K-PKB pathway was evidenced as inhibition of PKB phosphorylation and the decrease of glycogen synthase kinase 3 β (GSKβ) and mammalian target of rapamycin (mTOR) expression after SLIT.

CONCLUSION

Our study has demonstrated that SLIT treatment led to distinct changes in immune cell profiles between mono-sensitized and poly-sensitized AR patients. Furthermore, SLIT appeared to reduce a Th2 immune response, highlighting its efficacy in AR treatment. Importantly, the study revealed the suppression of the PI3K-PKB pathway, shedding light on the immunological mechanisms underlying SLIT's effectiveness.

Sublingual administration of liposomes enclosing alpha-galactosylceramide as an effective adjuvant of allergen immunotherapy in a murine model of allergic rhinitis

BACKGROUND

Sublingual immunotherapy (SLIT) is an established efficacious approach for the treatment of allergic rhinitis (AR). However, SLIT requires a long administration period to establish stable and adequate responses. This study investigated the efficacy of the sublingual administration of an allergen with liposomes enclosing α-GalCer (α-GC-liposome) as a potential adjuvant in mice with AR.

METHODS

Mice with AR induced by OVA received the sublingual administration of OVA, α-GC-liposomes, or OVA plus α-GC-liposomes for 7 days. After nasal re-challenge with OVA, nasal symptoms were evaluated. The serum levels of OVA-specific Ig, the cytokine production of CD4⁺ T cells in the cultures of cervical lymph node (CLN) cells, and the gene expression of CLNs were analyzed.

RESULTS

Although IL-4, IL-5 and IL-13 production from CD4⁺ T cells in CLN cells was significantly inhibited by the sublingual administration of OVA alone in mice with AR induced by OVA, their nasal symptoms were not significantly diminished. However, the combined sublingual administration of α-GC-liposomes and OVA completely suppressed nasal symptoms, downregulated Th2 and Th17 type cytokine production in CD4⁺ T cells as well as Th2 and Th17 gene expressions, and upregulated Th1 type cytokine production as well as Th1 gene expressions in CLN cells. Additionally, the serum levels of specific IgG2a were promoted, and specific IgE and IgG1 were inhibited.

CONCLUSIONS

Our findings suggest that the sublingual administration of an allergen with α-GC-liposomes as an adjuvant might increase the therapeutic efficacy and effectiveness of this treatment method.

Biomarkers for monitoring clinical efficacy of allergen immunotherapy for allergic rhinoconjunctivitis and allergic asthma: an EAACI Position Paper

BACKGROUND

Allergen immunotherapy (AIT) is an effective treatment for allergic rhinoconjunctivitis (AR) with or without asthma. It is important to note that due to the complex interaction between patient, allergy triggers, symptomatology and vaccines used for AIT, some patients do not respond optimally to the treatment. Furthermore, there are no validated or generally accepted candidate biomarkers that are predictive of the clinical response to AIT. Clinical management of patients receiving AIT and efficacy in randomised controlled trials for drug development could be enhanced by predictive biomarkers.

METHOD

The EAACI taskforce reviewed all candidate biomarkers used in clinical trials of AR patients with/without asthma in a literature review. Biomarkers were grouped into seven domains: (i) IgE (total IgE, specific IgE and sIgE/Total IgE ratio), (ii) IgG-subclasses (sIgG1, sIgG4 including SIgE/IgG4 ratio), (iii) Serum inhibitory activity for IgE (IgE-FAB and IgE-BF), (iv) Basophil activation, (v) Cytokines and Chemokines, (vi) Cellular markers (T regulatory cells, B regulatory cells and dendritic cells) and (vii) In vivo biomarkers (including provocation tests?).

RESULTS

All biomarkers were reviewed in the light of their potential advantages as well as their respective drawbacks. Unmet needs and specific recommendations on all seven domains were addressed.

CONCLUSIONS

It is recommended to explore the use of allergen-specific IgG4 as a biomarker for compliance. sIgE/tIgE and IgE-FAB are considered as potential surrogate candidate biomarkers. Cytokine/chemokines and cellular reponses provided insight into the mechanisms of AIT. More studies for confirmation and interpretation of the possible association with the clinical response to AIT are needed.

Grass pollen immunotherapy: where are we now

During allergen immunotherapy (AIT), the allergic patient is exposed to the disease-inducing antigens (allergens) in order to induce clinical and immunological tolerance and obtain disease modification. Large trials of grass AIT with highly standardized subcutaneous and sublingual tablet vaccines have been conducted to document the clinical effect. Induction of blocking antibodies as well as changes in the balance between T-cell phenotypes, including induction of regulatory T-cell subtypes, have been demonstrated for both treatment types. These observations increase the understanding of the immunological mechanism behind the clinical effect and may make it possible to use the immunological changes as biomarkers of clinical effect. The current review describes the recent mechanistic findings for subcutaneous immunotherapy and sublingual immunotherapy/tablet treatment and discusses how the observed immunological changes translate into a scientific foundation for the observed clinical effects of grass pollen immunotherapy and lead to new treatment strategies for grass AIT.

Allergen immunotherapy for birch pollen-allergic patients: recent advances

As of today, allergen immunotherapy is performed with aqueous natural allergen extracts. Recombinant allergen vaccines are not yet commercially available, although they could provide patients with well-defined and highly consistent drug substances. As Bet v 1 is the major allergen involved in birch pollen allergy, with more than 95% of patients sensitized to this allergen, pharmaceutical-grade recombinant Bet v 1-based vaccines were produced and clinically tested. Herein, we compare the clinical results and modes of action of treatments based on either a birch pollen extract or recombinant Bet v 1 expressed as hypoallergenic or natural-like molecules. We also discuss the future of allergen immunotherapy with improved drugs intended for birch pollen-allergic patients suffering from rhinoconjunctivitis.

Transportation of sublingual antigens across sublingual ductal epithelial cells to the ductal antigen-presenting cells in mice

BACKGROUND

Sublingual immunotherapy (SLIT) has proven to be safe and efficient for the treatment of type I allergies. However, the mechanisms underlying allergen transportation within the sublingual compartment, the localization of antigens, and the identities of the cells responsible for this immunization remain incompletely understood.

OBJECTIVE

In this study, we focused on the sublingual ductal system and analysed the localization and transportation of antigens after their sublingual application.

METHODS

In mice given adjuvant-free antigens sublingually, tissues were removed at 0, 0.5, 1, or 2 h after the application and subjected to immunohistochemistry. Cells isolated from the sublingual duct and mucosa were analysed by flow cytometry.

RESULTS

Substantial immunoreactivity to ovalbumin (OVA) was evident in sublingual ductal epithelial cells at 30 min and 1 h after sublingual administration of OVA, but it had disappeared at 2 h. The ductal epithelial cells incorporated not only OVA, but also particulate antigens such as latex or silica beads and microbes. MHC class II (MHCII)(+) antigen-presenting cells (APCs) were located around the sublingual ductal system, and MHCII(+) cells were co-localized with, and around, antigen-incorporated sublingual duct cells. CD11b(+) CD11c(-) cells were present among CD45(+) MHCII(+) cells at greater frequency in the sublingual duct than in the sublingual mucosa, and they were the main contributors to the incorporation of OVA in vitro.

CONCLUSIONS AND CLINICAL RELEVANCE

This study reveals that sublingual antigens can be transported across sublingual ductal epithelial cells to the ductal APCs. If the system is the same in humans as in mice, the ductal APCs may prove to be important target cells for SLIT.

Immunotherapy in all aspects

Allergen immunotherapy is a form of long-term treatment that decreases symptoms for many people with allergic rhinitis, allergic asthma, conjunctivitis (eye allergy) or stinging insect allergy. In this review, we presented the important topics in immunotherapy. The important aspects of immunotherapy are considered to be "Immunologıcal responses to immunotherapy"; "The principal types of immunotherapy"; "Effectiveness"; "Indications"; "Contraindications"; "Allergen immunotherapy in children"; "Safety"; and "Anaphylactic reactions after immunotherapy". The principal types of immunotherapy are subcutaneous immunotherapy (SCIT) and sublingual immunotherapy. Both of them can be used in indicated cases. When using SCIT, physicians must be more careful because of reported rare fatal cases. The risks and benefits of continuing allergen immunotherapy in patients who have experienced severe systemic reactions should be carefully considered.

Mechanisms of allergen-specific immunotherapy: multiple suppressor factors at work in immune tolerance to allergens

Allergen-specific immunotherapy (AIT) has been used for more than 100 years as a desensitizing therapy for IgE-mediated allergic diseases and represents a potentially curative way of treatment. The mechanisms of action of AIT include the induction of very early desensitization of mast cells and basophils; generation of regulatory T and regulatory B (Breg) cell responses; regulation of IgE and IgG4; decreases in numbers and activity of eosinophils and mast cells in mucosal allergic tissues; and decreases in the activity of basophils in circulation. Skewing of allergen-specific effector T and effector B cells to a regulatory phenotype appears as a key event in the course of AIT and normal immune response to allergens. Recently, inducible IL-10-secreting Breg cells were also demonstrated to contribute to allergen tolerance through suppression of effector T cells and selective induction of IgG4 isotype antibodies. Allergen-specific regulatory T and Breg cells orchestrate a general immunoregulatory activity, which can be summarized as suppression of cytokines from inflammatory dendritic cells; suppression of effector TH1, TH2, and TH17 cells; suppression of allergen-specific IgE and induction of IgG4; and suppression of migration of mast cells, basophils, eosinophils, and effector T cells to tissues. A detailed knowledge of the mechanisms of AIT is not only important in designing the prevention and treatment of allergic diseases but might also find applications in the treatment of autoimmune diseases, organ transplantation, chronic infection, and cancer.

Sublingual Immunotherapy for Asthma: Affects T-Cells but Does not Impact Basophil Activation

Objective: Allergen-specific immunotherapy (SIT) is the unique modifying treatment of atopic diseases. Dysregulation of T-cell apoptosis plays a crucial role in the in the development of asthma. Nevertheless, the effect of sublingual immunotherapy (SLIT) on T-cell apoptosis has not been elucidated. The aim of the study was to evaluate the influence of 1 year of SIT in atopic children on the frequency of Th1 and Th2 cells in peripheral blood, on T-cell apoptosis, and on the response of basophils to allergen challenge. Methods: Children suffering from bronchial asthma were treated with SLIT for 12 months (Staloral 300). Basophil activation was evaluated by measurement of CD203c antigen expression. Th1 and Th2 cells frequencies and their associated frequencies of apoptosis by the expression of Bcl-2 were evaluated with flow cytometry. Results: Basophil activation showed no difference in response before and after therapy. The frequency of Th1 cells increased (p=0.01, n=19), whereas the frequency of Th2 cells remained stable. Additionally, a significant increase of Bcl-2 positive Th1 cells was found (p=0.0465, n=19). Conclusions: We conclude that the increase in frequency of Th1 cells secondary to SLIT might be associated with increased resistance to apoptotic signals. The basophil activation is not useful in evaluation of patient desensitization.

Allergen-specific CD4+ T cell responses in peripheral blood do not predict the early onset of clinical efficacy during grass pollen sublingual immunotherapy

BACKGROUND

Surrogate biomarkers of efficacy are needed in support of allergen-specific immunotherapy.

OBJECTIVE

The aim of this study was to relate changes in peripheral CD4(+) T cell responses to clinical efficacy during sublingual immunotherapy (SLIT).

METHODS

Allergen-specific CD4(+) T cell responses were assessed in peripheral blood mononuclear cells (PBMCs) from 89 grass pollen-allergic individuals enrolled in a double-blind placebo-controlled SLIT study conducted in an allergen exposure chamber (ClinicalTrials.gov NCT00619827). Surface phenotype, proliferative responses, cytokine production and gene expression were analysed in coded samples at baseline, and after 2 and 4 months of SLIT, in PBMCs after in vitro allergen stimulation or among MHC class II/peptide (pMHCII)-tetramer-positive CD4(+) T cells.

RESULTS

SLIT induced a 29.3% improvement of the average rhinoconjunctivitis total symptom score in the active group, when compared to the placebo group. In parallel, only minor changes in proportions of CD4(+) T cells expressing Th1 (CCR5(+), CXCR3(+)), Th2 (CRTh2(+), CCR4(+)) and Treg (CD25(+), CD127(-), Foxp3(+)) markers were detected. A down-regulation of IL-4 and IL-10 gene expression and IL-10 secretion (P < 0.001) were observed, as well as a decrease in the frequency of potential "pro-allergic" CD27(-) Th2 cells from patients receiving active tablets (P < 0.001), but without any correlation with clinical benefit. pMHCII-tetramer analyses failed to document any major impact in both numbers and polarization of circulating Phl p 1- and Phl p 5-specific CD4(+) T cells, confirming that early clinical improvement during SLIT is not associated with dramatic alterations in T lymphocyte responses.

CONCLUSION & CLINICAL RELEVANCE

Changes in patterns of peripheral CD4(+) T cells are not markers for the early onset of efficacy during SLIT.

Update on immune mechanisms associated with sublingual immunotherapy: practical implications for the clinician

Sublingual immunotherapy (SLIT) is established as a safe and efficacious treatment for patients with type I respiratory allergies. The ability of SLIT to elicit antigen (allergen)-specific tolerance is linked to the peculiar biology of oral antigen-presenting cells. In the absence of danger signals, Langerhans cells, myeloid dendritic cells, and macrophages located in oral tissues, tonsils, and draining cervical lymph nodes are biased toward the induction of T(H)1 and IL-10-producing CD4(+) regulatory T cells, thus supporting tolerance as opposed to inflammation. Sublingual administration does not lead to any detectable systemic exposure of intact allergens nor to IgE neosensitization. Oral tissues contain limited numbers of mast cells located in submucosal areas, thereby explaining the well-established safety profile of SLIT, with mostly local but rare systemic reactions. The induction of CD4(+) regulatory T cells and blocking anti-inflammatory IgGs or IgAs are considered important for tolerance induction after SLIT. Specific molecular signatures associated with tolerogenic dendritic cells were recently reported during the onset of SLIT efficacy in the peripheral blood of patients exhibiting clinical benefit. Collectively, these observations confirm the induction of strong allergen-specific suppressive/tolerogenic immune responses during SLIT and pave the ground for the identification of biomarkers of efficacy. Practical implications of this emerging scientific knowledge are presented (1) to support the rational design of second-generation sublingual vaccines based on purified allergens, vector systems and/or adjuvants and (2) to help the clinician in decision making during his/her practice.

Allergen immunotherapy for allergic respiratory diseases

Allergen specific immunotherapy involves the repeated administration of allergen products in order to induce clinical and immunologic tolerance to the offending allergen. Immunotherapy is the only etiology-based treatment that has the potential for disease modification, as reflected by longterm remission following its discontinuation and possibly prevention of disease progression and onset of new allergic sensitizations. Whereas subcutaneous immunotherapy is of proven value in allergic rhinitis and asthma there is a risk of untoward side effects including rarely anaphylaxis. Recently the sublingual route has emerged as an effective and safer alternative. Whereas the efficacy of SLIT in seasonal allergy is now well-documented in adults and children, the available data for perennial allergies and asthma is less reliable and particularly lacking in children. This review evaluates the efficacy, safety and longterm benefits of SCIT and SLIT and highlights new findings regarding mechanisms, potential biomarkers and recent novel approaches for allergen immunotherapy.

Allergen-specific immunotherapy provides immediate, long-term and preventive clinical effects in children and adults: the effects of immunotherapy can be categorised by level of benefit -the centenary of allergen specific subcutaneous immunotherapy

Allergen Specific Immunotherapy (SIT) for respiratory allergic diseases is able to significantly improve symptoms as well as reduce the need for symptomatic medication, but SIT also has the capacity for long-term clinical effects and plays a protective role against the development of further allergies and symptoms. The treatment acts on basic immunological mechanisms, and has the potential to change the pathological allergic immune response. In this paper we discuss some of the most important achievements in the documentation of the benefits of immunotherapy, over the last 2 decades, which have marked a period of extensive research on the clinical effects and immunological background of the mechanisms involved. The outcome of immunotherapy is described as different levels of benefit from early reduction in symptoms over progressive clinical effects during treatment to long-term effects after discontinuation of the treatment and prevention of asthma. The efficacy of SIT increases the longer it is continued and immunological changes lead to potential long-term benefits. SIT alone and not the symptomatic treatment nor other avoidance measures has so far been documented as the therapy with long-term or preventive potential. The allergic condition is driven by a subset of T-helper lymphocytes (Th2), which are characterised by the production of cytokines like IL-4, and IL-5. Immunological changes following SIT lead to potential curative effects. One mechanism whereby immunotherapy suppresses the allergic response is through increased production of IgG4 antibodies. Induction of specific IgG4 is able to influence the allergic response in different ways and is related to immunological effector mechanisms, also responsible for the reduced late phase hyperreactivity and ongoing allergic inflammation. SIT is the only treatment which interferes with the basic pathophysiological mechanisms of the allergic disease, thereby creating the potential for changes in the long-term prognosis of respiratory allergy. SIT should not only be recognised as first-line therapeutic treatment for allergic rhinoconjunctivitis but also as secondary preventive treatment for respiratory allergic diseases.

Local immunological mechanisms of sublingual immunotherapy

PURPOSE OF REVIEW

To summarize novel insights into the immunological mechanisms of sublingual immunotherapy (SLIT). Within the recent decades, several alternative noninvasive allergen application strategies have been investigated in allergen-specific immunotherapy (AIT), of which intra-oral allergen application to sublingual mucosa has been proven to be well tolerated and effective.

RECENT FINDINGS

To date, SLIT is widely accepted by most allergists as an alternative option to conventional subcutaneous immunotherapy (SCIT). Although detailed immunological mechanisms remain to be elucidated, much scientific effort has been made to shed some light on local and systemic immunological responses to SLIT in mice as well as humans. Only a few studies focused on the detailed mechanisms following allergen application to the oral mucosa as part of the sophisticated mucosal immunological network. Within this network, the pro-tolerogenic properties of local antigen-presenting cells (APCs) such as dendritic cells - which are able to enforce tolerogenic mechanisms and to induce T-cell immune responses - play a central role. Further on, basic research focused not only on the immune response in nasal and bronchial mucosa but also on the systemic T-cell immune response.

SUMMARY

Thus, much exiting data have been published providing a better understanding of immunological features of SLIT but far more investigations are necessary to uncover further exciting details on the key mechanisms of SLIT.

Specific immunotherapy in children: the evidence

Specific immunotherapy (SIT) is the only treatment able to not only act on the symptoms of allergy but also act on the causes. At present, SIT may be administered in two forms: subcutaneous (SCIT) and sublingual immunotherapy (SLIT). SCIT represents the standard modality of treatment while SLIT has recently been introduced into clinical practice and today represents an accepted alternative to SCIT. The main advantages of SIT that are lacking with drug treatment are long-lasting clinical effects and alteration of the natural course of the disease. This prevents the new onset of asthma in patients with allergic rhinitis and the onset of new sensitizations. The mechanism of action of both routes is similar; they modify peripheral and mucosal Th2-responses into a prevalent Th1-polarization with subsequent reduction of the allergic inflammatory reaction. Both have long-term effects for years after they have been discontinued, although for SLIT these evidences are insufficient. To date several guidelines have defined indications, controindications, side-effects, and clinical aspect for SCIT and SLIT. New forms of immunotherapy, allergen products and approaches to food allergy and atopic eczema represents the future of SIT.

Oral macrophage-like cells play a key role in tolerance induction following sublingual immunotherapy of asthmatic mice

Sublingual allergen-specific immunotherapy (SLIT) is a safe and efficacious treatment for type 1 respiratory allergies. Herein, we investigated the key subset(s) of antigen-presenting cells (APCs) involved in antigen/allergen capture and tolerance induction during SLIT. Following sublingual administration, fluorochrome-labeled ovalbumin (OVA) is predominantly captured by oral CD11b⁺CD11c⁻ cells that migrate to cervical lymph nodes (CLNs) and present the antigen to naive CD4⁺ T cells. Conditional depletion with diphtheria toxin of CD11b⁺, but not CD11c⁺ cells, in oral tissues impairs CD4⁺ T-cell priming in CLNs. In mice with established asthma to OVA, specific targeting of the antigen to oral CD11b⁺ cells using the adenylate cyclase vector system reduces airway hyperresponsiveness (AHR), eosinophil recruitment in bronchoalveolar lavages (BALs), and specific Th2 responses in CLNs and lungs. Oral CD11b⁺CD11c⁻ cells resemble tolerogenic macrophages found in the lamina propria (LP) of the small intestine in that they express the mannose receptor CD206, as well as class-2 retinaldehyde dehydrogenase (RALDH2), and they support the differentiation of interferon-γ/interleukin-10 (IFNγ/IL-10)-producing Foxp3⁺ CD4⁺ regulatory T cells. Thus, among the various APC subsets present in oral tissues of mice, macrophage-like cells play a key role in tolerance induction following SLIT.

European Academy of Allergy and Clinical Immunology task force report on 'dose-response relationship in allergen-specific immunotherapy'

BACKGROUND

For a century, allergen-specific immunotherapy (SIT) has proven to be an effective treatment for allergic rhinitis, asthma, and insect sting allergy. However, as allergen doses are frequently adapted to the individual patient, there are few data on dose-response relationship in SIT. Allergen products for SIT are being increasingly required to conform to regulatory requirements for human medicines, which include the need to demonstrate dose-dependent effects.

METHODS

This report, produced by a Task Force of the EAACI Immunotherapy Interest Group, evaluates the currently available data on dose-response relationships in SIT and aims to provide recommendations for the design of future studies.

RESULTS

Fifteen dose-ranging studies fulfilled the inclusion criteria and twelve reported a dose-response relationship for clinical efficacy. Several studies also reported a dose-response relationship for immunological and safety endpoints. Due to the use of different reference materials and methodologies for the determination of allergen content, variations in study design, and choice of endpoints, no comparisons could be made between studies and, as a consequence, no general dosing recommendations can be made.

CONCLUSION

Despite recently introduced guidelines on the standardization of allergen preparations and study design, the Task Force identified a need for universally accepted standards for the measurement of allergen content in SIT preparations, dosing protocols, and selection of clinical endpoints to enable dose-response effects to be compared across studies.

Sublingual immunotherapy: other indications

Sublingual immunotherapy (SLIT) represents a significant advance and it seems particularly suitable in pediatric patients. There are favorable results for food allergy in controlled trials. For latex allergy, the results of several trials are encouraging. For atopic dermatitis, previous experience with subcutaneous immunotherapy and some earlier trials suggest the possible application of SLIT in children with mild to moderate dermatitis and sensitization to dust mite, but this recommendation is considered insufficiently evidence based. In hymenoptera allergy, the only trial available is a proof-of-concept study in large local reactions that needs to be confirmed in well-controlled studies.

Mechanisms of immunotherapy to aeroallergens

Allergen immunotherapy is allergen-specific, allergen dose- and time-dependent and is associated with long-term clinical and immunological tolerance that persists for years after discontinuation. Successful immunotherapy is accompanied by the suppression of numbers of T-helper 2 (Th2) effector cells, eosinophils, basophils, c-kit+mast cells and neutrophils infiltration in target organs, induction of IL-10 and/or TGF-β+Treg cells and increases in 'protective' non-inflammatory blocking antibodies, particularly IgG4 and IgA2 subclasses with inhibitory activity. These events are accompanied by a reduction and/or a redirection of underlying antigen-specific Th2-type T cell-driven hypersensitivity to the allergen(s) used for therapy. This suppression occurs within weeks or months as a consequence of the appearance of a population of regulatory T cells that exert their effects by mechanisms involving cell-cell contact, but also by the release of cytokines such as IL-10 (increases IgG4) and TGF-β (increases specific IgA). The more delayed-in-time appearance of antigen-specific T-helper 1 responses and alternative mechanisms such as Th2 cell anergy and/or apoptosis may also be involved. The mechanisms of sublingual immunotherapy are similar to those following a subcutaneous administration of allergen, whereas it is likely that additional events following antigen presentation in the sublingual mucosa and regional lymph nodes are involved. These insights have resulted in novel approaches and portend future biomarkers that may be surrogate or predictive of the clinical response to treatment.

Dendritic cells modification during sublingual immunotherapy in children with allergic symptoms to house dust mites

BACKGROUND

the importance of dendritic cells (DCs) in the initiation of the Th2-mediated inflammatory response to allergens is well known and more recently it has been proposed that DCs have a pivotal role in maintaining tolerance to allergens. The aim of this study was to investigate whether the success of sublingual immunotherapy (SLIT) in allergic asthma is mediated by the induction of changes of DCs functions.

METHODS

ten children with allergic asthma sensitive to house dust mite were studied before and after 12 months of SLIT. Immature DCs were derived from peripheral blood monocytes cultured for 6 days in presence of interleukin (IL)-4 and GM-CSF and stimulated with lipopolysaccharide for the last 24 hours to induce maturation.

RESULTS

after 12 months of SLIT, mature DCs derived from SLIT-treated patients showed a statistically significant defect of CD86 up-regulation, an increase of IL-10, and a reduction of IL-12 production.

CONCLUSION

SLIT induces changes in DCs functions that might be responsible for an impairment of T cell activation or drive T cells towards a regulatory activity, thus restoring immune tolerance to allergens.

Clinical practice: Allergen-specific immunotherapy in children: facts and FAQs

Allergen-specific immunotherapy (SIT) in its various application forms represents the main treatment approach of IgE-mediated allergic diseases in adults and children. Despite this clear recommendation, many particularities of products, patient characteristics, and product availability in different countries hamper the use of allergen-specific immunotherapy in particular in children. The frequently asked questions by parents, patients, and physicians are the backbone of this review. Thus, the potentials and limitations of allergen-specific immunotherapy in children and adolescents will be highlighted. IgE-mediated allergic diseases are affecting about 20% of the population. They manifest commonly early in life, and hence, the use of SIT should be considered also early in the course of the disease.

Immunological effects of sublingual immunotherapy: clinical efficacy is associated with modulation of programmed cell death ligand 1, IL-10, and IgG4

Sublingual immunotherapy (SLIT) is an alternate route of administration of allergen-specific immunotherapy with an improved safety profile; to clarify the immune mechanisms elicited by this therapy, we analyzed the clinical and immunologic effects of SLIT in patients with a clinical history of ragweed sensitization. To analyze possible difference among immunotherapeutic protocols, we also compared patients receiving preseasonal, seasonal, or prolonged sublingual therapy (≥ 3 y); patients receiving symptomatic therapy alone were enrolled as well in the study. Clinical and immunological parameters were measured twice in and out of the pollination period. Clinical benefits, as measured by the visual analog scale for symptoms and for use of drugs, were evident in all three groups of individuals receiving immunotherapy, but were significantly better in patients undergoing prolonged SLIT. Immunologically, SLIT resulted in increased IL-10 production, programmed cell death ligand 1 expression, and concentration of allergen-specific IgG4, as well as in the reduction of CD80 and CD86 expression and IL-4 production. SLIT, thus, is associated with modulation of programmed cell death ligand 1 expression and IL-10 synthesis and favors the production of allergen-specific IgG4. These effects are evident from the first pollen season, independently from therapeutic regimen (preseasonal or seasonal) even if a prolonged treatment is necessary to obtain full clinical efficacy. A more detailed understanding of the interaction of allergen and APCs within the oral mucosa will allow improved targeting of allergy vaccine.

Long-lasting effects of sublingual immunotherapy according to its duration: a 15-year prospective study

BACKGROUND

Data on the long-term effects of sublingual immunotherapy (SLIT) are sparse, and the optimal duration of treatment is a matter of debate.

OBJECTIVE

We sought to prospectively evaluate the long-term effect of SLIT given for 3, 4, or 5 years and to compare the effect of those different durations.

METHODS

In this prospective open controlled study we followed up patients with respiratory allergy who were monosensitized to mites for 15 years. The subjects were divided in 4 groups receiving drug therapy alone or SLIT for 3, 4, or 5 years. Clinical scores, skin sensitizations, methacholine reactivity, and nasal eosinophil counts were evaluated every year during the winter months. The clinical effect was considered to persist until clinical scores remained at less than 50% of the baseline value, and then patients underwent another course of SLIT.

RESULTS

Seventy-eight patients were enrolled, and 59 completed the study. In the 12 control subjects no relevant change in clinical scores was seen throughout the study. In the patients receiving SLIT for 3 years, the clinical benefit persisted for 7 years. In those receiving immunotherapy for 4 or 5 years, the clinical benefit persisted for 8 years. New sensitizations occurred in all the control subjects over 15 years and in less than a quarter of the patients receiving SLIT (21%, 12%, and 11%, respectively). The second course of vaccination induced a benefit more rapidly than the first course. The behavior of bronchial hyperreactivity and nasal eosinophils paralleled the clinical score.

CONCLUSION

Under the present conditions, it can be suggested that a 4-year duration of SLIT is the optimal choice because it induces a long-lasting clinical improvement similar to that seen with a 5-year course and greater than that of a 3-year vaccination.

T-cell responses induced by allergen-specific immunotherapy

Allergen-specific immunotherapy is recognized as a highly effective practice in the treatment of patients with severe allergic rhinitis and/or asthma and is recommended by World Health Organization as an integrated part of allergy management strategy. Several studies have shown that allergen-specific immunotherapy, based on the administration of increasing doses of allergen, achieves a hyposensitization and reduces both early and late responses occurring during the natural exposure to the allergen itself. This is the unique antigen-specific immunomodulatory treatment in current use for human diseases. Successful immunotherapy is associated with reductions in symptoms and medication scores and improved quality of life. After interruption it usually confers long-term remission of symptoms and prevents the onset of new sensitizations in children up to a number of years. Subcutaneous immunotherapy usually suppresses the allergen-induced late response in target organs, likely due to the reduction of the infiltration of T cells, eosinophils, basophils, mast cells and neutrophils. In addition to the reduction of cells of allergic inflammation, immunotherapy also decreases inflammatory mediators at the site of allergen exposure. This review provides an update on the immunological T cell responses induced by conventional subcutaneous and sublingual immunotherapy, and gives a unifying view to reconciling the old dualism between immunoredirecting and immunoregulating mechanisms.

Antigen-specific immunotherapy against allergic rhinitis: the state of the art

Allergic rhinitis is the most prevalent type I allergy in industrialized countries. Pollen scattering from trees or grasses often induces seasonal allergic rhinitis, which is known as pollinosis or hay fever. The causative pollen differs across different areas and times of the year. Impaired performance due to pollinosis and/or medication used for treating pollinosis is considered to be an important reason for the loss of concentration and productivity in the workplace. Antigen-specific immunotherapy is an only available curative treatment against allergic rhinitis. Subcutaneous injection of allergens with or without adjuvant has been commonly used as an immunotherapy; however, recently, sublingual administration has come to be considered a safer and convenient alternative administration route of allergens. In this review, we focus on the safety and protocol of subcutaneous and sublingual immunotherapy against seasonal allergic rhinitis. We also describe an approach to selecting allergens for the vaccine so as to avoid secondary sensitization and adverse events. The biomarkers and therapeutic mechanisms for immunotherapy are not fully understood. We discuss the therapeutic biomarkers that are correlated with the improvement of clinical symptoms brought about by immunotherapy as well as the involvement of Tr1 and regulatory T cells in the therapeutic mechanisms. Finally, we focus on the current immunotherapeutic approach to treating Japanese cedar pollinosis, the most prevalent pollinosis in Japan, including sublingual immunotherapy with standardized extract, a transgenic rice-based edible vaccine, and an immunoregulatory liposome encapsulating recombinant fusion protein.

Clinical outcome and IL-17, IL-23, IL-27 and FOXP3 expression in peripheral blood mononuclear cells of pollen-allergic children during sublingual immunotherapy

Induction of allergen-specific, tolerogenic, IL-10 and/or TGF-β-producing T-regulatory (Treg) cells that express transcription factor FOXP3 is considered as one of the key mechanisms of allergen-specific immunotherapy. However, little is known of the induction of FOXP3 expression in children during sublingual immunotherapy (SLIT). Recently, also, a novel subgroup of T-helper (Th) cells, the Th17 cells, secreting predominantly IL-17 (IL-17A), was identified. The expressions of IL-17 or the Th17-regulating cytokines IL-23 and IL-27 during SLIT are currently completely unexplored. This randomized, placebo-controlled dose-response study was performed to analyze the effects of SLIT on FOXP3, IL-17, IL-23, and IL-27 expressions in peripheral blood mononuclear cells (PBMC) of children with allergic rhinitis and their associations with clinical outcome. Thirty children were included: ten received SLIT with a glycerinated mixture of birch, hazel and alder with a cumulative weekly dose of 24,000 SQ-U, 10 with dose 200,000 SQ-U/wk, and ten received placebo. Cytokine and FOXP3 mRNA expressions in allergen-, purified protein derivative-stimulated and non-stimulated PBMC were determined at 0, 1 and 2 yr of SLIT by real-time RT-PCR (TaqMan). Symptoms and medications were recorded using diary cards. Allergen-induced IL-17 mRNA expression was significantly increased in the study subjects with elevated combined Symptom Medication Score (SMS) after 2 yr. There was also a significant positive correlation between the allergen-induced IL-17 and SMS in whole study group (r = 0.38, p = 0.039) and especially the 200,000 SQ-U dose-treated group (r = 0.74, p = 0.027) at 2 yr. Allergen-induced FOXP3 mRNA expression was significantly increased in the 200,000 SQ-U dose-treated children after two study years as compared with baseline (p = 0.016) and placebo-treated children (p = 0.028). The changes in FOXP3 mRNA expression positively correlated with IL-10 and TGF-β mRNAs during SLIT in whole study population. Increased allergen-induced IL-17 responses during SLIT are associated with elevated SMS. Increased tolerogenic, allergen-specific Treg responses are also observed in children during SLIT.

An immunological overview of allergen specific immunotherapy -- subcutaneous and sublingual routes

Allergen-specific immunotherapy remains the most likely effective treatment modality for allergic disorders by targeting the underlying immune mechanisms and possibly causing modifications in the disease course, as well as treating the symptoms. Treatment and compliance experiences been gained over nearly a century in injection-type allergen-specific immunotherapy have motivated the development of newer, alternative routes. Adverse events and safety concerns, efficacy and ease of application seem to be the stimulating factors for the development of a sublingual form of this treatment modality, wherein the principal factor is the capture of the antigen (allergen) by dendritic cells, in the location where oral tolerance arises. Due to the presence of high numbers of tolerogenic dendritic cell subsets in this region, programming of the immune system towards a regulatory state with unresponsiveness to specific allergens occurs. Induction of peripheral tolerance through the generation of regulatory T cells is the key event, with several functional modulations in the allergic immune response. With an increase in understanding of the mechanism of regulatory pathways, promising progresses in the field of allergen-specific immunotherapy will ensue and may provide new options for the treatment of allergic disorders.

[Allergen-specific Immunotherapy for children and adolescents - a review on available products in Austria]

A pediatric consensus report on allergen-specific immunotherapy for children and adolescents is presented for Austria. Products on the market in Austria are presented and categorised according to studies performed on the target population of children and adolescents, their effectiveness and indication. In general, more clinical studies on children and adolescents are mandatory for most of the available allergen-specific immunotherapeutics. In addition, the use of allergen-specific immunotherapy in general should be promoted as the exclusive treatment with long-lasting effects in type I allergies in particular in children.

Therapeutic manipulation of immune tolerance in allergic disease

Immune tolerance - the adaptation of the immune system to external antigens or allergens - might be therapeutically manipulated to restore normal immunity in conditions such as allergy, asthma and autoimmune diseases. The field of allergen-specific immunotherapy is experiencing exciting and novel developments for the treatment of allergic and autoimmune diseases, and recent insights into the reciprocal regulation and counter-balance between different T-cell subsets is foreseen to facilitate new strategies for immunointervention. This Review highlights current knowledge of immunomodulatory therapies for the manipulation of immune tolerance and highlights recent approaches to improve allergen-specific immunotherapy for the treatment of allergic diseases.

Immune tolerance in allergy

Research on the mechanisms of immune regulation in allergy and asthma has shown substantial progress in recent years and has led to a variety of allergen-specific therapeutic and preventive approaches. Studies on the area of allergen-specific immunotherapy (allergen-SIT) have provided substantial knowledge on the mechanisms of allergic disease with novel developments for treatment and prevention. Several studies have demonstrated that increased numbers and the activation of allergen-specific T regulatory cells correlate with successful allergen-SIT. Particularly, targeting of the molecular mechanisms of immune tolerance and reciprocal regulation of effector and regulatory T-cell subsets are foreseen for the development of new strategies for immune intervention. This review focuses on current knowledge of immune tolerance to allergens in healthy immune response to allergens and allergen-SIT.

House dust mite sublingual immunotherapy: the role for transforming growth factor-beta and functional regulatory T cells

RATIONALE

Sublingual allergen-specific immunotherapy is gaining popularity for treatment of allergic diseases, but underlying immunological mechanisms are unresolved.

OBJECTIVES

To perform detailed immunological investigation of sublingual house dust mite (HDM) immunotherapy.

METHODS

A 12-month randomized double-blind placebo-controlled study of sublingual HDM immunotherapy in 30 HDM-allergic subjects was performed, with 1-year open extension in 9 patients on active treatment. HDM-stimulated blood mononuclear cells were analyzed for proliferation, cytokines, and regulatory T cells (Tregs) by flow cytometry and ELISA. Effects of blocking transforming growth factor (TGF)-beta and IL-10 on proliferation were determined. Treg suppressor function and allergen-specific antibody levels were measured. Clinical efficacy was assessed by symptom, medication, and Juniper quality-of-life scores.

MEASUREMENTS AND MAIN RESULTS

Allergen-induced CD4(+) T-cell division and IL-5 production were significantly decreased after 6- and 12-months' active treatment but not placebo. sTGF-betaRII blocked immunotherapy-induced suppression of allergen-specific T-cell proliferation, maximal at 6 months. Decreased allergen-specific CD4(+) T-cell proliferation and increased IL-10 secretion and serum Der p 2-specific IgG(4) were maximal at 24 months' active treatment. Treg (CD4(+)CD25(+)CD127(lo)/Foxp3(+)) function was demonstrated by suppression of allergen-specific effector T-cell (CD4(+)CD25(-)CD127(hi)) proliferation and cytokine production. Clinical efficacy of immunotherapy was supported by significantly decreased rhinitis symptom score, total asthma score, and Juniper quality-of-life score.

CONCLUSIONS

This study establishes the novel finding that TGF-beta mediates the immunological suppression seen early in clinically effective sublingual HDM immunotherapy in addition to an increase in Tregs with suppressor function. Clinical trial registered with www.clinicaltrials.gov (NCT00250263).

Mechanisms of sublingual immunotherapy

Allergen-specific sublingual immunotherapy is now recognized to be an efficacious and well-tolerated treatment for allergic rhinitis. Emerging treatment strategies are also aimed at the primary treatment of allergic asthma, particularly allergy to house dust mites. Knowledge of the exact mechanisms of action of sublingual immunotherapy is at a basic level, although there appear to be similarities to the immunological changes seen in subcutaneous immunotherapy. An improved understanding should allow the development of more effective treatment programs and widen the potential use of this form of immunotherapy. This review discusses the possible mechanism of action of sublingual immunotherapy, including data from animal and clinical studies, while comparing this with the current understanding of subcutaneous immunotherapy.

Sublingual immunotherapy in children: complete and updated review supporting evidence of effect

PURPOSE OF REVIEW

The interest in sublingual immunotherapy (SLIT) is still growing worldwide and especially for the pediatric age group, this modality is appealing. Lately, some negative systematic review articles have been published on SLIT in children. However, high quality articles published from 2007 onward had not been included.

RECENT FINDINGS

Explanations are sought for the negative outcomes in these reviews and shortcomings are discussed. New pediatric studies - not included in the previous reviews -designed taking into account the golden rules for SLIT (high daily dose, starting at least 4 months before pollen season) do show statistically significant improvement in symptom and medication scores for rhinitis and asthma in pollen allergy. New house dust mite studies still show inconsistent data.

SUMMARY

Evidence of effect is confirmed for SLIT in children with allergic rhinitis or asthma caused by pollen exposure. For house dust mite asthma, evidence is still nonconcordant. New techniques to improve SLIT efficacy are under investigation.

Scientific rationale for the Finnish Allergy Programme 2008-2018: emphasis on prevention and endorsing tolerance

In similarity to many other western countries, the burden of allergic diseases in Finland is high. Studies worldwide have shown that an environment rich in microbes in early life reduces the subsequent risk of developing allergic diseases. Along with urbanization, such exposure has dramatically reduced, both in terms of diversity and quantity. Continuous stimulation of the immune system by environmental saprophytes via the skin, respiratory tract and gut appears to be necessary for activation of the regulatory network including regulatory T-cells and dendritic cells. Substantial evidence now shows that the balance between allergy and tolerance is dependent on regulatory T-cells. Tolerance induced by allergen-specific regulatory T-cells appears to be the normal immunological response to allergens in non atopic healthy individuals. Healthy subjects have an intact functional allergen-specific regulatory T-cell response, which in allergic subjects is impaired. Evidence on this exists with respect to atopic dermatitis, contact dermatitis, allergic rhinitis and asthma. Restoration of impaired allergen-specific regulatory T-cell response and tolerance induction has furthermore been demonstrated during allergen-specific subcutaneous and sublingual immunotherapy and is crucial for good therapeutic outcome. However, tolerance can also be strengthened unspecifically by simple means, e.g. by consuming farm milk and spending time in nature. Results so far obtained from animal models indicate that it is possible to restore tolerance by administering the allergen in certain circumstances both locally and systemically. It has become increasingly clear that continuous exposure to microbial antigens as well as allergens in foodstuffs and the environment is decisive, and excessive antigen avoidance can be harmful and weaken or even prevent the development of regulatory mechanisms. Success in the Finnish Asthma Programme was an encouraging example of how it is possible to reduce both the costs and morbidity of asthma. The time, in the wake of the Asthma Programme, is now opportune for a national allergy programme, particularly as in the past few years, fundamentally more essential data on tolerance and its mechanisms have been published. In this review, the scientific rationale for the Finnish Allergy Programme 2008-2018 is outlined. The focus is on tolerance and how to endorse tolerance at the population level.

Mechanisms and treatment of allergic disease in the big picture of regulatory T cells

Various populations of regulatory T (Treg) cells have been shown to play a central role in the maintenance of peripheral homeostasis and the establishment of controlled immune responses. Their identification as key regulators of immunologic processes in peripheral tolerance to allergens has opened an important era in the prevention and treatment of allergic diseases. Both naturally occurring CD4+CD25+ Treg cells and inducible populations of allergen-specific, IL-10-secreting Treg type 1 (T(R)1) cells inhibit allergen-specific effector cells in experimental models. Skewing of allergen-specific effector T cells to a regulatory phenotype appears to be a key event in the development of healthy immune response to allergens and successful outcome in allergen-specific immunotherapy. Forkhead box protein 3-positive CD4+CD25+ Treg cells and T(R)1 cells contribute to the control of allergen-specific immune responses in several major ways, which can be summarized as suppression of dendritic cells that support the generation of effector T cells; suppression of effector T(H)1, T(H)2, and T(H)17 cells; suppression of allergen-specific IgE and induction of IgG4; suppression of mast cells, basophils, and eosinophils; interaction with resident tissue cells and remodeling; and suppression of effector T-cell migration to tissues. Current strategies for drug development and allergen-specific immunotherapy exploit these observations, with the potential for preventive therapies and cure for allergic diseases.

Clinical and Immunological Correlates of Pre-Co-Seasonal Sublingual Immunotherapy with Birch Monomeric Allergoid in Patients with Allergic Rhinoconjunctivitis

Sublingual immunotherapy is safe and efficacious in the treatment of patients with allergic rhinitis. The clinical and biological efficacy of modified allergens (allergoids) has not been fully clarified. We investigated in birch allergic patients the effect of a pre-co-seasonal sublingual immunotherapy regimen with a modified allergen extract on clinical parameters and on T cell proliferation and regulatory cytokine production (IL-10, TGF-beta). We found that during the birch pollen season symptoms and drug usage scores were 30 and 40% improved, respectively, in treated versus control subjects (p<0.0001 for both comparisons) whereas well days were 23.5 (33%) versus 16.9 (23%) (p=0.0024), respectively. Bet v 1 allergen specific proliferation decreased (p = 0.0010), whereas IL-10 transcription increased (p = 0.0010) in treated, but not in control patients. Moreover, TGF-beta transcription was increased, although not significantly (p=0.066), following immunotherapy. Thus, sublingual immunotherapy with modified allergen in birch-allergic subjects was safe, clinically efficacious and associated with the reduction of allergen-specific proliferation and with the increased production of the IL-10 regulatory cytokine.

Current immunological approaches for management of allergic rhinitis and bronchial asthma

A large population world over is affected with allergic diseases and asthma. Pharmacotherapy for allergic diseases and asthma is effective in controlling symptoms but on discontinuation of medication, symptoms reoccur. In contrast, immunotherapy modifies and corrects the underlying pathological immune responses in an antigen-specific manner. Immunotherapy shows an increase in IgG (blocking antibody) that competes with IgE for allergen, inhibiting the release of inflammatory mediators. Recent studies suggest that immunotherapy acts by modifying CD4+ T-cell responses either by immune deviation, T-cell anergy and/or both. Current immunological approaches for management of allergies and asthma involve immunization with native allergen, modified allergen, peptides/cDNA of allergen, anti-IgE, adjuvants coupled allergen, including immunostimulatory DNA sequences, cytokines, and bacterial products. These approaches modulate the immune response and are intended to give long-term benefit.