Tolerance induction after specific immunotherapy with pollen allergoids adjuvanted by monophosphoryl lipid A in children

T-cell subset changes during the first year of pre-seasonal allergoid allergen-specific immunotherapy

Allergen-specific immunotherapy (AIT) is the only treatment for type I allergy, which achieves long-lasting effects. Repeated subcutaneous applications of allergen extracts cause a protective antibody response and an immune deviation of T cells. In AIT with allergoids, chemically modified allergen extracts are injected. During a so-called special pre-seasonal application scheme, after the initial phase of applying increased doses of allergoids is followed by natural allergen exposure as a maintenance phase. The effectiveness of allergoid vaccines has been described regarding the improvement of clinical symptoms and the development of protective humoral responses. In this longitudinal observational study, we sought to investigate changes at the T cell level in pre-seasonal AIT with allergoid. Different subsets within CD4+ and CD8+ T cells were monitored by flow cytometry in PBMC of patients known to possess protective antibody responses. Compared to before treatment, a small early boost among allergenic Th cells was observed after 4 months of AIT. In line, a slight Th2 bias was observed after 4 months within circulating T follicular T cells, Tfh and Tfc, representing pre-existing memory Th2 cells. Furthermore, it was demonstrated that responsiveness of CD8+ T cells to allergen stimulation decreased during the course of treatment. Apart from that, we found an influence of the meteorological season on the activation profile of Tfh and Tfc over the course of the treatment. Together, this is the first study investigating changes of different T cell subsets over the course of an allergoid AIT against airborne allergens. Our findings match previous reports on conventional AIT, especially the initial increase of Th2 responses. However, the observed changes were less pronounced which may be either due to the modification of allergens or to the reduced maintenance dose provided by natural allergen exposure compared to a perennial protocol.

A novel peanut allergy immunotherapy: Plant-based enveloped Ara h 2 Bioparticles activate dendritic cells and polarize T cell responses to Th1

Introduction

As the only market-authorized allergen immunotherapy (AIT) for peanut allergy is accompanied by a high risk of side effects and mainly induces robust desensitization without sustained efficacy, novel treatment options are required. Peanut-specific plant-derived eBioparticles (eBPs) surface expressing Ara h 2 at high density have been shown to be very hypoallergenic. Here, we assessed the dendritic cell (DC)-activating and T cell polarization capacity of these peanut-specific eBPs.

Methods

Route and kinetics of eBP uptake were studied by (imaging) flow cytometry using monocyte-derived DCs incubated with fluorescently-labelled Ara h 2 eBPs or natural Ara h 2 (nAra h 2) in the presence or absence of inhibitors that block pathways involved in macropinocytosis, phagocytosis, and/or receptor-mediated uptake. DC activation was monitored by flow cytometry (maturation marker expression) and ELISA (cytokine production). T cell polarization was assessed by co-culturing DCs exposed to Ara h 2 eBPs or nAra h 2 with naïve CD4+ T cells, followed by flow cytometry assessment of intracellular IFNγ+ (Th1) and IL-13+ (Th2), and CD25+CD127-Foxp3+ regulatory T cells (Tregs). The suppressive activity of Tregs was tested using a suppressor assay.

Results

Ara h 2 eBPs were taken up by DCs through actin-dependent pathways. They activated DCs demonstrated by an induced expression of CD83 and CD86, and production of TNFα, IL-6, and IL-10. eBP-treated DCs polarized naïve CD4+ T cells towards Th1 cells, while reducing Th2 cell development. Furthermore, eBP-treated DCs induced reduced the frequency of Foxp3+ Tregs but did not significantly affect T cell IL-10 production or T cells with suppressive capacity. In contrast, DC activation and Th1 cell polarization were not observed for nAra h 2.

Conclusion

Ara h 2 eBPs activate DCs that subsequently promote Th1 cell polarization and reduce Th2 cell polarization. These characteristics mark Ara h 2 eBPs as a promising novel candidate for peanut AIT.

TLR Signals in Epithelial Cells in the Nasal Cavity and Paranasal Sinuses

The respiratory tract is constantly at risk of invasion by microorganisms such as bacteria, viruses, and fungi. In particular, the mucosal epithelium of the nasal cavity and paranasal sinuses is at the very forefront of the battles between the host and the invading pathogens. Recent studies have revealed that the epithelium not only constitutes a physical barrier but also takes an essential role in the activation of the immune system. One of the mechanisms equipped in the epithelium to fight against microorganisms is the Toll-like receptor (TLR) response. TLRs recognize common structural components of microorganisms and activate the innate immune system, resulting in the production of a plethora of cytokines and chemokines in the response against microbes. As the epithelia-derived cytokines are deeply involved in the pathogenesis of inflammatory conditions in the nasal cavity and paranasal sinuses, such as chronic rhinosinusitis (CRS) and allergic rhinitis (AR), the molecules involved in the TLR response may be utilized as therapeutic targets for these diseases. There are several differences in the TLR response between nasal and bronchial epithelial cells, and knowledge of the TLR signals in the upper airway is sparse compared to that in the lower airway. In this review, we provide recent evidence on TLR signaling in the upper airway, focusing on the expression, regulation, and responsiveness of TLRs in human nasal epithelial cells (HNECs). We also discuss how TLRs in the epithelium are involved in the pathogenesis of, and possible therapeutic targeting, for CRS and AR.

Toll-Like Receptor Agonists as Adjuvants for Allergen Immunotherapy

Toll-like receptors (TLRs) are essential components of innate immunity and provide defensive inflammatory responses to invading pathogens. Located within the plasma membranes of cells and also intracellular endosomes, TLRs can detect a range of pathogen associated molecular patterns from bacteria, viruses and fungi. TLR activation on dendritic cells can propagate to an adaptive immune response, making them attractive targets for the development of both prophylactic and therapeutic vaccines. In contrast to conventional adjuvants such as aluminium salts, TLR agonists have a clear immunomodulatory profile that favours anti-allergic T lymphocyte responses. Consequently, the potential use of TLRs as adjuvants in Allergen Immunotherapy (AIT) for allergic rhinitis and asthma remains of great interest. Allergic Rhinitis is a Th2-driven, IgE-mediated disease that occurs in atopic individuals in response to exposure to otherwise harmless aeroallergens such as pollens, house dust mite and animal dander. AIT is indicated in subjects with allergic rhinitis whose symptoms are inadequately controlled by antihistamines and nasal corticosteroids. Unlike anti-allergic drugs, AIT is disease-modifying and may induce long-term disease remission through mechanisms involving upregulation of IgG and IgG4 antibodies, induction of regulatory T and B cells, and immune deviation in favour of Th1 responses that are maintained after treatment discontinuation. This process takes up to three years however, highlighting an unmet need for a more efficacious therapy with faster onset. Agonists targeting different TLRs to treat allergy are at different stages of development. Synthetic TLR4, and TLR9 agonists have progressed to clinical trials, while TLR2, TLR5 and TLR7 agonists been shown to have potent anti-allergic effects in human in vitro experiments and in vivo in animal studies. The anti-allergic properties of TLRs are broadly characterised by a combination of enhanced Th1 deviation, regulatory responses, and induction of blocking antibodies. While promising, a durable effect in larger clinical trials is yet to be observed and further long-term studies and comparative trials with conventional AIT are required before TLR adjuvants can be considered for inclusion in AIT. Here we critically evaluate experimental and clinical studies investigating TLRs and discuss their potential role in the future of AIT.

EAACI Allergen Immunotherapy User's Guide

Allergen immunotherapy is a cornerstone in the treatment of allergic children. The clinical efficiency relies on a well-defined immunologic mechanism promoting regulatory T cells and downplaying the immune response induced by allergens. Clinical indications have been well documented for respiratory allergy in the presence of rhinitis and/or allergic asthma, to pollens and dust mites. Patients who have had an anaphylactic reaction to hymenoptera venom are also good candidates for allergen immunotherapy. Administration of allergen is currently mostly either by subcutaneous injections or by sublingual administration. Both methods have been extensively studied and have pros and cons. Specifically in children, the choice of the method of administration according to the patient's profile is important. Although allergen immunotherapy is widely used, there is a need for improvement. More particularly, biomarkers for prediction of the success of the treatments are needed. The strength and efficiency of the immune response may also be boosted by the use of better adjuvants. Finally, novel formulations might be more efficient and might improve the patient's adherence to the treatment. This user's guide reviews current knowledge and aims to provide clinical guidance to healthcare professionals taking care of children undergoing allergen immunotherapy.

Immunotherapy in allergic diseases - improved understanding and innovation for enhanced effectiveness

Allergen immunotherapy leads to tolerance through multiple mechanisms that include tolerogenic dendritic cells and T and B regulatory cells. These induced cellular populations produce mediators to skew the immune response to a tolerogenic milieu that, among others, results in IgG4 blocking antibodies formation and lowered FcE receptors. All lead in decreased effector responses from mast cells, eosinophils, and basophils thus limiting the allergic inflammation. Clinically, this results in better allergic rhinitis control and, of importance, asthma prevention. Newer approaches include modified allergens, second generation adjuvants/carriers and routes of administration, all aiming to increased efficacy with parallel no compromise of safety.

Highlights of Novel Vaccination Strategies in Allergen Immunotherapy

Increasing safety while maintaining or even augmenting efficiency are the main goals of research for novel vaccine development and improvement of treatment schemes in allergen immunotherapy (AIT). To increase the efficacy of AIT, allergens have been coupled to innate immunostimulatory substances and new adjuvants have been introduced. Allergens have been modified to increase their uptake and presentation. Hypoallergenic molecules have been developed to improve the safety profile of the vaccines. Administration of recombinant IgG4 antibodies is a new, quick, passive immunization strategy with remarkable efficiency. Results of some current investigations aiming at further improvement of AIT vaccines have been summarized.

Immunostimulants in respiratory diseases: focus on Pidotimod

Usefulness of Pidotimod and its role as immunostimulant, has been discussed, we know, for several decades. Nevertheless, there is still much to know. Understanding its mechanisms and its potential usefulness in airway infections and its prevention, asthma both Th2 and non Th2 type, bronchiectasis, as adjuvant in vaccination and in allergen immunotherapy still remains to clearly unveil. The aim of this paper was to provide a useful updated review of the role of the main available immunostimulants, giving particular focus on Pidotimod use and its potentials utility in respiratory diseases. Pidotimod showed its usefulness in reducing need for antibiotics in airway infections, increasing the level of immunoglobulins (IgA, IgM, IgG) and T-lymphocyte subsets (CD3+, CD4+) endowed with immunomodulatory activity that affect both innate and adaptive immune responses. Higher expression of TLR2 and of HLA-DR molecules, induction of dendritic cell maturation and release of pro-inflammatory molecules, stimulation of T lymphocyte proliferation and differentiation toward a Th1 phenotype, as well as an increase of the phagocytosis have been demonstrated to be associated with Pidotimod in in vitro studies. All these activities are potentially useful for several respiratory conditions such as asthma, COPD, and recurrent respiratory tract infections.

Advances in allergen immunotherapy as a treatment of asthma

Introduction: Specific immunotherapy is the only treatment acting on causes and not only on symptoms of respiratory allergy. It was first introduced as subcutaneous immunotherapy (SCIT) with the aim to induce immunological tolerance to the administered allergen(s). In the 1980s, sublingual immunotherapy (SLIT) was developed, mainly to improve the safety, which was a critical issue at that time.Areas covered: This article reviews the available literature, including a large number of randomized controlled trials, meta-analyses, and real-life studies as well, on the outcomes of SCIT and SLIT concerning the treatment critical issues of the two routes, that are efficacy, safety, cost-effectiveness, and compliance to treatment.Expert opinion: SCIT and SLIT are similarly effective in treating patients with respiratory allergy, providing, based on the induction of typical changes in the immunologic response, an early control of symptoms that steadily increases during the treatment and, once reached the recommended duration of 3 years, continues to work after stopping. This outcome is the major factor influencing the economic advantage of SCIT and SLIT over drug treatment.

Food Allergies: Current and Future Treatments

Food allergies are an increasingly public health problem, affecting up to 10% of children and causing a significant burden on affected patients, resulting in dietary restrictions, fear of accidental ingestion and related risk of severe reactions, as well as a reduced quality of life. Currently, there is no specific cure for a food allergy, so the only available management is limited to strict dietary avoidance, education on prompt recognition of symptoms, and emergency treatment of adverse reactions. Several allergen specific- and nonspecific-therapies, aiming to acquire a persistent food tolerance, are under investigation as potential treatments; however, to date, only immunotherapy has been identified as the most promising therapeutic approach for food allergy treatment. The aim of this review is to provide an updated overview on changes in the treatment landscape for food allergies.

Immunologic mechanisms of a short-course of Lolium perenne peptide immunotherapy: A randomized, double-blind, placebo-controlled trial

BACKGROUND

A 3-week short-course of adjuvant-free hydrolysates of Lolium perenne peptide (LPP) immunotherapy for rhinoconjunctivitis with or without asthma over 4 physician visits is safe, well tolerated, and effective.

OBJECTIVE

We sought to investigate immunologic mechanisms of LPP immunotherapy in a subset of patients who participated in a phase III, multicenter, randomized, double-blind, placebo-controlled trial (clinical.govNCT02560948).

METHODS

Participants were randomized to receive LPP (n = 21) or placebo (n = 11) for 3 weeks over 4 visits. Grass pollen-induced basophil, T-cell, and B-cell responses were evaluated before treatment (visit [V] 2), at the end of treatment (V6), and after the pollen season (V8).

RESULTS

Combined symptom and rescue medication scores (CSMS) were lower during the peak pollen season (-35.1%, P = .03) and throughout the pollen season (-53.7%, P = .03) in the LPP-treated group compared with those in the placebo-treated group. Proportions of CD63⁺ and CD203c^brightCRTH2⁺ basophils were decreased following LPP treatment at V6 (10 ng/mL, P < .0001) and V8 (10 ng/mL, P < .001) compared to V2. No change in the placebo-treated group was observed. Blunting of seasonal increases in levels of grass pollen-specific IgE was observed in LPP-treated but not placebo-treated group. LPP immunotherapy, but not placebo, was associated with a reduction in proportions of IL-4⁺ T_H2 (V6, P = .02), IL-4⁺ (V6, P = .003; V8, P = .004), and IL-21⁺ (V6, P = .003; V8, P = .002) follicular helper T cells. Induction of FoxP3⁺, follicular regulatory T, and IL-10⁺ regulatory B cells were observed at V6 (all P < .05) and V8 (all P < .05) in LPP-treated group. Induction of regulatory B cells was associated with allergen-neutralizing IgG₄-blocking antibodies.

CONCLUSION

For the first time, we demonstrate that the immunologic mechanisms of LPP immunotherapy are underscored by immune modulation in the T- and B-cell compartments, which is necessary for its effect.

Next generation immunotherapy for tree pollen allergies

Tree pollen induced allergies are one of the major medical and public health burdens in the industrialized world. Allergen-Specific Immunotherapy (AIT) through subcutaneous injection or sublingual delivery is the only approved therapy with curative potential to pollen induced allergies. AIT often is associated with severe side effects and requires long-term treatment. Safer, more effective and convenient allergen specific immunotherapies remain an unmet need. In this review article, we discuss the current progress in applying protein and peptide-based approaches and DNA vaccines to the clinical challenges posed by tree pollen allergies through the lens of preclinical animal models and clinical trials, with an emphasis on the birch and Japanese red cedar pollen induced allergies.

Ragweed Pollen Allergy: Burden, Characteristics, and Management of an Imported Allergen Source in Europe

Ambrosia artemisiifolia, also known as common or short ragweed, is an invasive annual flowering herbaceous plant that has its origin in North America. Nowadays, ragweed can be found in many areas worldwide. Ragweed pollen is known for its high potential to cause type I allergic reactions in late summer and autumn and represents a major health problem in America and several countries in Europe. Climate change and urbanization, as well as long distance transport capacity, enhance the spread of ragweed pollen. Therefore ragweed is becoming domestic in non-invaded areas which in turn will increase the sensitization rate. So far 11 ragweed allergens have been described and, according to IgE reactivity, Amb a 1 and Amb a 11 seem to be major allergens. Sensitization rates of the other allergens vary between 10 and 50%. Most of the allergens have already been recombinantly produced, but most of them have not been characterized regarding their allergenic activity, therefore no conclusion on the clinical relevance of all the allergens can be made, which is important and necessary for an accurate diagnosis. Pharmacotherapy is the most common treatment for ragweed pollen allergy but fails to impact on the course of allergy. Allergen-specific immunotherapy (AIT) is the only causative and disease-modifying treatment of allergy with long-lasting effects, but currently it is based on the administration of ragweed pollen extract or Amb a 1 only. In order to improve ragweed pollen AIT, new strategies are required with higher efficacy and safety.

Long-term effect of monophosphoryl lipid A adjuvanted specific immunotherapy in patients with grass pollen allergy

BACKGROUND

Ultra-short course pollen immunotherapy adjuvanted with monophosphoryl lipid A (MPL) is attractive to conventional allergen-specific immunotherapy (AIT). Long term efficacy of MPL-AIT has not been evaluated.

METHODS

68 patients (age 16.75 ± 5.3 years) with allergic rhinitis to grass pollen were investigated. Group 1: 21 controls; Group 2: 19 after complete AIT, and Group 3: 28 with AIT and treatment cessation: 4 years range 3-6 years ago.

RESULTS

The clinical symptoms (running nose, sneezing, conjunctivitis and the weekly overall score) were significantly reduced in patients group 2 and 3 compared with controls without AIT p < 0.0001. T-regulatory cells and TH1/TH2 cytokine pattern did not differ between patient groups.

CONCLUSION

The patients in our trial with grass pollen allergy exhibited significant and long-lasting improvements after MPL-AIT, however larger trials are needed to support this finding.

The role of basophils as innate immune regulatory cells in allergy and immunotherapy

Basophils are circulating cells that are associated quite exclusively with allergy response and hypersensitivity reactions but their role in the immune network might be much more intriguing and complex than previously expected. The feasibility of testing their biology in vitro for allergy research and diagnosis, due fundamentally to their quite easy availability in the peripheral blood, made them the major source for assessing allergy in the laboratory assay, when yet many further cells such as mast cells and eosinophils are much more involved as effector cells in allergy than circulating basophils. Interestingly, basophil numbers change rarely in peripheral blood during an atopic response, while we might yet observe an increase in eosinophils and modification in the biology of mast cells in the tissue during an hypersensitivity response. Furthermore, the fact that basophils are very scanty in numbers suggests that they should mainly serve as regulatory cells in immunity, rather than effector leukocytes, as still believed by the majority of physicians. In this review we will try to describe and elucidate the possible role of these cells, known as "innate IL4-producing cells" in the immune regulation of allergy and their function in allergen immunotherapy.

The Potential for Emerging Microbiome-Mediated Therapeutics in Asthma

PURPOSE OF REVIEW

In terms of immune regulating functions, analysis of the microbiome has led the development of therapeutic strategies that may be applicable to asthma management. This review summarizes the current literature on the gut and lung microbiota in asthma pathogenesis with a focus on the roles of innate molecules and new microbiome-mediated therapeutics.

RECENT FINDINGS

Recent clinical and basic studies to date have identified several possible therapeutics that can target innate immunity and the microbiota in asthma. Some of these drugs have shown beneficial effects in the treatment of certain asthma phenotypes and for protection against asthma during early life. Current clinical evidence does not support the use of these therapies for effective treatment of asthma. The integration of the data regarding microbiota with technologic advances, such as next generation sequencing and omics offers promise. Combining comprehensive bioinformatics, new molecules and approaches may shape future asthma treatment.

Toll-like receptors as targets for allergen immunotherapy

PURPOSE OF REVIEW

Toll-like receptors (TLRs) are novel and promising targets for allergen immunotherapy. Bench studies suggest that TLR agonists reduce Th2 responses and ameliorate airway hyper-responsiveness. In addition, clinical trials are at initial phases to evaluate the safety and efficacy of TLR agonists for the allergen immunotherapy of patients with allergic rhinitis and asthma. (Figure is included in full-text article.)

RECENT FINDINGS

To date, two allergy vaccine-containing TLR agonists have been investigated in clinical trials; Pollinex Quattro and AIC. The former contains monophosphoryl lipid, a TLR4 agonist and the latter contains, CpG motifs activating the TLR9 cascade. Preseasonal subcutaneous injection of both of these allergy vaccines has been safe and efficacious in control of nasal symptoms of patients with allergic rhinitis. CRX-675 (a TLR4 agonist), AZD8848 (a TLR7 agonist), VTX-1463 (a TLR8 agonist) and 1018 ISS and QbG10 (TLR9 agonists) are currently in clinical development for allergic rhinitis and asthma.

SUMMARY

TLR agonists herald promising results for allergen immunotherapy of patients with allergic rhinitis and asthma. Future research should be directed at utilizing these agents for immunotherapy of food allergy (for instance, peanut allergy) as well.

New opportunities for allergen immunotherapy using synthetic peptide immuno-regulatory epitopes (SPIREs)

INTRODUCTION

Allergen immunotherapy (AIT) reduces allergic rhinoconjunctivitis (ARC) symptoms, but long-term efficacy requires treatment for 3-5 years. Synthetic peptide immuno-regulatory epitopes, a new class of AIT, are allergen peptides with a shorter, more convenient treatment regimen that could potentially have benefits on adherence and outcomes.

AREAS COVERED

Phase 2 trials of therapies derived from cat, house dust mite, grass, and ragweed allergen peptides demonstrated significant reduction in ARC symptoms after short-course treatment; improvement was sustained for 18-24 months posttreatment. We conducted a PubMed literature search for clinical publications using the search terms AIT; allergen peptides; ARC; cat, grass, house dust mite, and ragweed allergy; SCIT; SLIT; and synthetic peptides. Expert commentary: Long-term disease modification is a realistic goal of AIT. The inconvenience of conventional AIT regimens negatively impacts long-term persistence and, thus, efficacy. In comparison, SPIREs have a more convenient treatment regimen that could potentially have benefits on adherence and outcomes.

Induction of Bronchial Tolerance After 1 Cycle of Monophosphoryl-A-Adjuvanted Specific Immunotherapy in Children With Grass Pollen Allergies

PURPOSE

Subcutaneous allergen-specific immunotherapy (SCIT) is a well-established and clinically effective method to treat allergic diseases, such as rhinitis and asthma. It remains unclear how soon after initiation of an ultra-short course of grass pollen immunotherapy adjuvanted with monophosphoryl lipid A (MPL)-specific bronchial tolerance can be induced.

METHODS

In a prospective study of 69 children double-sensitized to birch and grass pollens (51 males, average age 11.1 years), development of bronchial tolerance after 1 cycle of SCIT for grass was evaluated. In all the patients, the bronchial allergen provocation test (BAP) was performed before and after treatment. According to the results of the first BAP, the patients were divided into 2 groups: those showing a negative BAP with a decrease in FEV1 of <20% (seasonal allergic rhinitis [SAR] group, n=47); and those showing a positive BAP with a decrease in FEV1 of ≥20% (SAR with allergic asthma [SAR and Asthma] group, n=22). All the patients received MPL-adjuvanted, ultra-short course immunotherapy for birch, but only those with a positive BAP to grass received MPL-SCIT for grass.

RESULTS

After the pollen season, the BAP in the SAR group remained unchanged, while it was improved in the SAR and Asthma group (decrease in FEV1 of 28.8% vs 12.5%, P<0.01). The IgG4 levels increased after SCIT (median before SCIT 0.34 to 11.4 after SCIT), whereas the total and specific IgE levels remained unchanged.

CONCLUSIONS

After 1 cycle of MPL-SCIT, specific bronchial tolerance may be significantly induced, whereas in patients without SCIT, bronchial hyperactivity may remain unchanged.

A review of allergoid immunotherapy: is cat allergy a suitable target?

To modify the course of allergy, different types of specific allergen immunotherapy have been developed such as sublingual immunotherapy and subcutaneous immunotherapy with native allergens or subcutaneous immunotherapy with polymerized allergoids. However, the optimal specific immunotherapy, especially for cat allergy, remains undetermined. Few studies investigating immunotherapy in cat allergy have been published, and the risk of serious adverse reactions and systemic reactions has often been an important issue. Monomeric allergoids have lower allergenic potential while their immunogenicity remains constant, resulting in excellent safety with notable efficacy. Specific immunotherapy with monomeric allergoids could, therefore, be of high value, especially in cat allergy as well as other types of allergy, and bring relief to a great community of patients.

Advances in allergen immunotherapy: aiming for complete tolerance to allergens

Allergen-specific immunotherapy (AIT) has been used for more than 100 years as a tolerance-inducing therapy for allergic diseases and represents a potentially curative method of treatment. AIT functions through multiple mechanisms, including regulating T and B cell responses, changing antibody isotypes, and decreasing mediator release and migration of eosinophils, basophils, and mast cells to affected tissues. Despite the relative success of AIT, attempts are being made to improve this therapy in order to overcome problems in standardization, efficacy, safety, long duration of treatment, and costs. These have led to the development of biotechnological products with successful clinical results.

Novel immunotherapy vaccine development

PURPOSE OF REVIEW

Allergen-specific immunotherapy is the only curative treatment for allergic diseases. In spite of the great progress in both vaccine development and the methods of allergen immunotherapy (AIT) in recent years, several key problems related to limited efficacy, side-effects, low patient adherence and the relatively high costs due to the long duration (3-5 years) remain to be solved. The current approaches aiming at optimization of AIT are reviewed, including both conceptual studies in experimental models and proof-of-concept - as well as large, multicenter clinical studies.

RECENT FINDINGS

The most promising approaches to improve efficacy and safety of vaccine-based AIT include bypassing IgE binding and targeting allergen-specific T cells using hypoallergenic recombinant allergen derivatives and immunogenic peptides, the use of new adjuvants and stimulators of the innate immune response, the fusion of allergens to immune modifiers and peptide carrier proteins and new routes of vaccine administration.

SUMMARY

The cloning of allergen proteins and genetic engineering enabled the production of vaccines that have well defined molecular, immunologic and biologic characteristics as well as modified molecular structure. These new compounds along with new immunization protocols can bring us closer to the ultimate goal of AIT, that is, complete cure of a large number of allergic patients.

The future of biologics: applications for food allergy

Allergic diseases affect millions worldwide, with growing evidence of an increase in allergy occurrence over the past few decades. Current treatments for allergy include corticosteroids to reduce inflammation and allergen immunotherapy; however, some subjects experience treatment-resistant inflammation or adverse reactions to these treatments, and there are currently no approved therapeutics for the treatment of food allergy. There is a dire need for new therapeutic approaches for patients with poorly controlled atopic diseases and a need to improve the safety and effectiveness of allergen immunotherapy. Improved understanding of allergy through animal models and clinical trials has unveiled potential targets for new therapies, leading to the development of several biologics to treat allergic diseases. This review focuses on the mechanisms that contribute to allergy, with an emphasis on future targets for biologics for the treatment of food allergy. These biologics include immunotherapy with novel anti-IgE antibodies and analogs, small-molecule inhibitors of cell signaling, anti-type 2 cytokine mAbs, and TH1-promoting adjuvants.

Differential activation of dendritic cells by toll-like receptors causes diverse differentiation of naïve CD4+ T cells from allergic patients

BACKGROUND

To avert the differentiation of allergen-specific Th2 cells in atopic individuals is a major goal in the prevention and therapy of IgE-mediated allergy. We aimed to compare different toll-like receptor (TLR) agonists regarding their effects on antigen-presenting cells and the differentiation of naïve T cells from allergic patients.

METHODS

Monocytes and monocyte-derived dendritic cells (mdDC) from allergic patients were stimulated with Pam3CSK4 (TLR1/2 ligand), FSL-1 (TLR2/6 ligand), monophosphoryl lipid (MPL)-A, lipopolysaccharide (LPS, both TLR4 ligands), and flagellin (TLR5 ligand). Allergen uptake and upregulation of CD40, CD80, CD83, CD86, CD58, CCR7 and PD-L1 were analyzed by flow cytometry. Functional maturation of mdDC was tested in mixed leukocyte reactions, and the synthesis of proinflammatory cytokines, IL-10 and members of the IL-12 family was assessed. TLR-ligand-activated mdDC were used to stimulate naïve CD4(+) T cells, and cytokine responses were assessed in supernatants and intracellularly.

RESULTS

All TLR ligands except flagellin enhanced allergen uptake. All TLR ligands induced functional maturation of mdDC with differential expression of surface molecules and cytokines and promoted the differentiation of IFN-γ-producing T cells. LPS-matured mdDC exclusively induced Th1-like responses, whereas mdDC stimulated with the other TLR ligands induced both Th1- and Th0-like cells. Pam3CSK4 and flagellin additionally induced Th2-like cells. Th1-like responses were associated with higher expression levels of co-stimulatory molecules, PD-L1, IL-6, TNF-α, and IL-12p70. None of the TLR-ligand-stimulated mdDC induced IL-10- or IL-17-producing T cells.

CONCLUSION

Different TLR ligands differently influence T-cell responses due to varying activation of the three signals relevant for T-cell activation, that is, antigen presentation, co-stimulation and cytokine milieu.

SA-4-1BBL as a novel adjuvant for the development of therapeutic cancer vaccines

Tumor associated antigen (TAA)-based therapeutic vaccines have great potential as a safe, practical, and cost-efficient alternative to standard treatments for cancer. Clinical efficacy of TAA-based vaccines, however, has yet to be realized and will require adjuvants with pleiotropic functions on immune cells. Such adjuvants need not only to generate/boost T cell responses, but also reverse intrinsic/extrinsic tumor immune evasion mechanisms for therapeutic efficacy. This review focuses on a novel agonistic ligand, SA-4-1BBL, for 4-1BB costimulatory receptor as an adjuvant of choice because of its ability to: i) serve as a vehicle to deliver TAAs to dendritic cells (DCs) for antigen uptake and cross-presentation to CD8(+) T cells; ii) augment adaptive Th1 and innate immune responses; and iii) overcome various immune evasion mechanisms, cumulatively translating into therapeutic efficacy in preclinical tumor models.

New treatments for allergen immunotherapy

Allergen-specific immunotherapy (SIT) represents the only curative and specific way for the treatment of allergic diseases, which have reached a pandemic dimension in industrial countries affecting up to 20-30% of the population. Although applied for 100 years to cure allergy, SIT still faces several problems related to side effects and limited efficacy. Currently, allergen-SIT is performed with vaccines based on allergen extracts that can cause severe, often life threatening, anaphylactic reactions as well as new IgE sensitization to other allergens present in the extract. Low patient adherence and high costs due to long duration (3 to 5 years) of treatment have been commonly reported. Several strategies have been developed to tackle these issues and it became possible to produce recombinant allergen-SIT vaccines with reduced allergenic activity.

A new era of targeting the ancient gatekeepers of the immune system: toll-like agonists in the treatment of allergic rhinitis and asthma

Toll-like receptors (TLR) belong to a large family of pattern recognition receptors known as the ancient 'gatekeepers' of the immune system. TLRs are located at the first line of defense against invading pathogens as well as aeroallergens, making them interesting targets to modulate the natural history of respiratory allergy. Agonists of TLRs have been widely employed in therapeutic or prophylactic preparations useful for asthma/allergic rhinitis (AR) patients. MPL® (a TLR4 agonist) and the CpG oligodeoxynucleotide of 1018 ISS, a TLR9 agonist, show strong immunogenicity effects that make them appropriate adjuvants for allergy vaccines. Targeting the TLRs can enhance the efficacy of specific allergen immunotherapy, currently the only available 'curative' treatment for respiratory allergies. In addition, intranasal administration of AZD8848 (a TLR7 agonist) and VTX-1463 (a TLR8 agonist) as stand-alone therapeutics have revealed efficacy in the relief of the symptoms of AR patients. No anaphylaxis has been so far reported with such compounds targeting TLRs, with the most common adverse effects being transient and local irritation (e.g. redness, swelling and pruritus). Many other compounds that target TLRs have been found to suppress airway inflammation, eosinophilia and airway hyper-responsiveness in various animal models of allergic inflammation. Indeed, in the future a wide variability of TLR agonists and even antagonists that exhibit anti-asthma/AR effects are likely to emerge.

Mechanisms of allergen-specific immunotherapy and novel ways for vaccine development

Allergen-specific immunotherapy (SIT) is the only available curative treatment of allergic diseases. Recent evidence provided a plausible explanation to its multiple mechanisms inducing both rapid desensitization and long-term allergen-specific immune tolerance, and suppression of allergic inflammation in the affected tissues. During SIT, peripheral tolerance is induced by the generation of allergen-specific regulatory T cells, which suppress proliferative and cytokine responses against the allergen of interest. Regulatory T cells are characterized by IL-10 and TGF-beta secretion and expression of important cell surface suppressive molecules such as cytotoxic T lymphocyte antigen-4 and programmed death-1 that directly or indirectly influence effector cells of allergic inflammation, such as mast cells, basophils and eosinophils. Regulatory T cells and particularly IL-10 also have an influence on B cells, suppressing IgE production and inducing the production of blocking type IgG4 antibodies. In addition, development of allergen-specific B regulatory cells that produce IL-10 and develop into IgG4 producing plasma cells represent essential players in peripheral tolerance. These findings together with the new biotechnological approaches create a platform for development of the advanced vaccines. Moreover, reliable biomarkers could be selected and validated with the intention to select the patients who will benefit most from this immune-modifying treatment. Thus, allergen-SIT could provide a complete cure for a larger number of allergic patients and novel preventive approaches need to be elaborated.

Bronchial allergen provocation: a useful method to assess the efficacy of specific immunotherapy in children

BACKGROUND

The clinical efficacy of subcutaneous allergen-specific immunotherapy (SCIT) varies between patients. New preparations are under development, and an objective tool with which to evaluate their efficacies in individual patients has become necessary. Our primary research question is whether bronchial allergen provocation (BAP) can be used to assess the efficacy of SCIT.

METHODS

In 42 house dust mite (HDM) allergic children (average age: 8.6 yr) with asthma, we analysed the clinical and objective improvements of a standardised HDM allergoid. All patients underwent two BAPs, one before SCIT and another 1 yr after SCIT. Fourteen patients who were recommended but chose not to undergo SCIT represented the control group. The total and specific IgE were analysed before SCIT; in addition, after SCIT, specific IgG and IgG4 were analysed.

RESULTS

After SCIT, the patients' allergen-specific bronchial hyper-reactivity (BHR) was significantly improved; specifically, their PD(20) FEV(1) was 34.4 AU before and 63.3 AU after SCIT (p < 0.01). The PD(20) FEV(1) of the control group remained unchanged. Although BHR improved significantly in the treatment group, we were able to differentiate between the responders (n = 17, 60.7%) and non-responders (n = 11, no improvement in BAP). The patients in both groups stated that SCIT had led to a subjective improvement in their symptoms, in contrast to the untreated control group, but only the responders required less medication after SCIT (p < 0.01).

CONCLUSIONS

After 1 yr of SCIT against HDM, 60.7% of the patients observed in this study exhibited significant improvements, as defined by BAP. However, BAP was also able to identify the non-responders to treatment. Thus, BAP is a useful and objective method of estimating the effectiveness of SCIT and is not influenced by a placebo effect.

Adjuvant activity of naturally occurring monophosphoryl lipopolysaccharide preparations from mucosa-associated bacteria

Natural heterogeneity in the structure of the lipid A portion of lipopolysaccharide (LPS) produces differential effects on the innate immune response. Gram-negative bacterial species produce LPS structures that differ from the classic endotoxic LPS structures. These differences include hypoacylation and hypophosphorylation of the diglucosamine backbone, both differences known to decrease LPS toxicity. The effect of decreased toxicity on the adjuvant properties of many of these LPS structures has not been fully explored. Here we demonstrate that two naturally produced forms of monophosphorylated LPS, from the mucosa-associated bacteria Bacteroides thetaiotaomicron and Prevotella intermedia, function as immunological adjuvants for antigen-specific immune responses. Each form of mucosal LPS increased vaccination-initiated antigen-specific antibody titers in both quantity and quality when given simultaneously with vaccine antigen preparations. Interestingly, adjuvant effects on initial T cell clonal expansion were selective for CD4 T cells. No significant increase in CD8 T cell expansion was detected. MyD88/Toll-like receptor 4 (TLR4) and TRIF/TLR4 signaling pathways showed equally decreased signaling with the LPS forms studied here as with endotoxic LPS or detoxified monophosphorylated lipid A (MPLA). Natural monophosphorylated LPS from mucosa-associated bacteria functions as a weak but effective adjuvant for specific immune responses, with preferential effects on antibody and CD4 T cell responses over CD8 T cell responses.

Pollinex Quattro: an innovative four injections immunotherapy in allergic rhinitis

The prevalence of seasonal allergic rhinitis in the western world is high and increasing. Besides considerably affecting physical and psychosocial aspects of patients' lives, allergic rhinitis is often associated with allergic asthma and may aggravate this condition over time. Specific immunotherapy is currently the only approved therapy that can modify the underlying disease process and induce long-term tolerance to allergens. Pollinex Quattro is a subcutaneous four injections immunotherapy consisting of tyrosine-absorbed specific allergoids and enhanced with the adjuvant monophosphoryl lipid A (MPL(®)). MPL(®) induces a significant Th 1-type immune response, characterized by an increase of allergen-specific IgG antibody levels and dampening of the IgE response during allergen exposure. Due to this dual action of stimulating the immune system, Pollinex Quattro is clinically effective after only four injections given pre-seasonally. A large clinical program has demonstrated efficacy and tolerability of Pollinex Quattro in children, adolescents and adults with grass and tree pollen allergy. A health economics study concluded that an immunotherapy with only 4 injections might be more cost-beneficial than other application forms of immunotherapy.

Reduced in vitro T-cell responses induced by glutaraldehyde-modified allergen extracts are caused mainly by retarded internalization of dendritic cells

Although allergen-specific immunotherapy is a clinically effective therapy for IgE-mediated allergic diseases, the risk of IgE-mediated adverse effects still exists. For this reason, chemically modified allergoids have been introduced, which may destroy IgE-binding sites while T-cell activation should be retained. The aim of the study was to analyse the differences between intact allergens and differently modified/aggregated allergoids concerning their internalization as well as T-cell and basophil activation. For this purpose human monocyte-derived immature dendritic cells (DC) were incubated with Phleum pratense or Betula verrucosa pollen extract or with the corresponding allergoids, modified with formaldehyde or glutaraldehyde. After an additional maturation process, the antigen-loaded mature DC were co-cultured with autologous CD4(+) T cells. Allergenicity was tested by leukotriene release from basophils. In addition, the uptake of intact allergens and allergoids by immature DC was analysed. The proliferation of, as well as the interleukin-4 (IL-4), IL-10, IL-13 and interferon-γ production by, CD4(+) T cells which had been stimulated with glutaraldehyde allergoid-treated DC was reduced compared with CD4(+) T cells stimulated with intact allergen-treated or formaldehyde allergoid-treated DC. In line with this, glutaraldehyde-modified allergoids were more aggregated and were internalized more slowly. Furthermore, only the allergoids modified with glutaraldehyde induced a decreased leukotriene release by activated basophils. These findings suggest that IgE-reactive epitopes were destroyed more efficiently by modification with glutaraldehyde than with formaldehyde under the conditions chosen for these investigations. Glutaraldehyde-modified allergoids also displayed lower T-cell stimulatory capacity, which is mainly the result of greater modification/aggregation and diminished uptake by DC.

Therapies for allergic inflammation: refining strategies to induce tolerance

Current therapies for asthma and allergy are relatively safe and effective at controlling symptoms but do not change the chronic course of disease. There is no established method to prevent asthma and allergy, and major unmet needs in this area include the better control of the severe forms of these diseases and the developments of curative therapies. Two major therapeutic strategies for asthma and allergy are currently being developed, and I here discuss the advances and challenges for future therapeutic development in these two areas. The first approach, allergen-specific immunotherapy, aims to induce specific immune tolerance and has a long-term disease-modifying effect. The second approach is the use of biological immune response modifiers to decrease pathological immune responses. Combination strategies using both of these approaches may also provide a route for addressing the unmet clinical needs in allergic diseases.

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.

Factors influencing the allergenicity and adjuvanticity of allergens

IgE-mediated allergic disorders affect up to 25% of the population in industrialized countries and result in a Th2-polarized immune response to innocuous environmental proteins, so-called allergens. Among a large number of proteins to which humans are exposed to, only a minute fraction are allergens. This observation suggests that allergens share special features of allergenicity (i.e., the capacity to induce the production of specific IgE antibodies in susceptible individuals). However, the question 'what makes a protein allergenic' still remains unanswered although some biochemical characteristics of allergens and their capacity to interact with the innate immune system could be associated with their allergenic potential. Allergen-specific immunotherapy aims at an alteration of the disease-eliciting immune response by repeated administration of allergens. Recently, approaches emerged to endow allergens with adjuvanticity, in particular aiming at an increase of their immunomodulatory capacity. This article summarizes factors of allergenicity and introduces recent concepts of adjuvanticity to improve allergen-specific immunotherapy.

Immune modulation for treatment of allergic disease

Immune modulation for treatment of allergic diseases aims to decrease the pathologic immune response rather than to cause a return to an immunologically naive or unresponsive state. Our expanding knowledge of innate and adaptive immune responses at the molecular level has led to development of immunomodulators for several allergic diseases, particularly asthma, allergic rhinitis, and eosinophilic esophagitis. Although successful immune modulation in mouse models of allergic disease have often failed to translate into significant results in human clinical trials, much has been learned about the pleotropic nature of cytokines and their effector mechanisms and of the varied phenotypes of allergic disease. We examine strategies of immune modulation in allergic diseases that have undergone human clinical trials, all with the common goal of decreasing the T-helper 2 (Th2) response, but through different mechanisms: blocking critical Th2 cytokines, inhibiting Th2 cytokine synthesis, blocking critical Th2 effector molecules, inhibiting important cells in the Th2 response, and stimulating Th1 responses. Therapies directed against specific effector molecules, such as immunoglobulin E and prostaglandin D2, hold promise in immune modulation of allergic disease, as do targeting the IL-4/IL-13 receptor and augmenting Th1/Th2 balance with Toll-like receptor agonists.

Evidence of effect of subcutaneous immunotherapy in children: complete and updated review from 2006 onward

OBJECTIVE

To update the scientific evidence of subcutaneous immunotherapy (SCIT) in children.

DATA SOURCES

PubMed, EMBASE, and known articles.

STUDY SELECTION

All publications on SCIT in pediatric patients from January 2006 to April 2011. Study design was not a restriction. The articles were analyzed according to their outcomes and evaluated on their scientific quality using the Grading of Recommendations Assessment, Development, and Evaluation and Jadad tools. Clinical, safety, and immunologic data were gathered.

RESULTS

The scientific evidence produced by the 31 articles analyzed showed that there is high-quality evidence that grass pollen SCIT causes a reduction in the combined symptom-medication score and increases the threshold of the conjunctival provocation test, immediately and 7 years after termination of SCIT, as well as the threshold of the specific bronchial provocation test and the skin prick test reactivity. Alternaria SCIT improves medication scores, combined symptom-medication scores, and quality of life. It augments the threshold in the nasal provocation test. High-quality evidence of house dust mite SCIT shows that asthma symptom and medication scores improve and emergency department visits and skin reactivity are reduced; moderate evidence indicates improvement in pulmonary function tests. Pollen SCIT prevents asthma (moderate evidence); evidence for long-term benefit of pollen SCIT (7-12 years after termination) is low to moderate. There is inconclusive evidence for SCIT reducing new sensitizations.

CONCLUSION

There is acceptable evidence that shows that grass pollen, Alternaria, and house dust mite SCIT is beneficial in allergic children.

Future forms of immunotherapy and immunomodulators in allergic disease

Future forms of immunotherapy, particularly toll-like receptor agonists, have shown promising results in animal models of allergic disease although most have failed to translate into successful human clinical trials. These results have helped to elucidate the pleotropic roles of cytokines as well as the diverse phenotypes of allergic diseases, particularly asthma. The goals of these therapies are to improve patient symptoms and quality of life, to prevent and favorably alter disease course, and to maintain a good risk/benefit ratio along with a cost-effective profile.

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.