CYT003, a TLR9 agonist, in persistent allergic asthma - a randomized placebo-controlled Phase 2b study

The role of IL-2 cytokine family in asthma

BACKGROUND

The interleukin-2 (IL-2) family of cytokines, including IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21, are pivotal regulators of the immune response, impacting both innate and adaptive immunity. Understanding their molecular characteristics, receptor interactions, and signalling pathways is essential for elucidating their roles in health and disease.

OBJECTIVES

This review provides a comprehensive overview of the IL-2 family of cytokines, highlighting their molecular biology, receptor interactions, and signalling mechanisms. Furthermore, it explores the involvement of IL-2 family cytokines in the pathogenesis of chronic respiratory diseases, with a specific focus on chronic obstructive pulmonary disease (COPD) and asthma.

METHODS

A thorough literature review was conducted to gather insights into the molecular biology, receptor interactions, and signalling pathways of IL-2 family cytokines. Additionally, studies investigating the roles of these cytokines in chronic respiratory diseases, particularly COPD and asthma, were analysed to discern their implications in wider pathophysiology of disease.

RESULTS

IL-2 family cytokines exert pleiotropic effects on immune cells, modulating cellular proliferation, differentiation, and survival. Dysregulation of IL-2 family cytokines has been implicated in the pathogenesis of chronic respiratory illnesses, including COPD and asthma. Elevated levels of IL-2 and IL-9 have been associated with disease severity in COPD, while IL-4 and IL-9 play crucial roles in asthma pathogenesis by promoting airway inflammation and remodelling.

CONCLUSION

Understanding the intricate roles of IL-2 family cytokines in chronic respiratory diseases provides valuable insights into potential therapeutic targets for these conditions. Targeting specific cytokines or their receptors may offer novel treatment modalities to attenuate disease progression and improve clinical outcomes in patients with COPD and asthma.

Virus-like Particles as Vaccines for Allergen-Specific Therapy: An Overview of Current Developments

Immune engineering and modulation are the basis of a novel but powerful tool to treat immune diseases using virus-like particles (VLPs). VLPs are formed by the viral capsid without genetic material making them non-infective. However, they offer a wide variety of possibilities as antigen-presenting platforms, resulting in high immunogenicity and high efficacy in immune modulation, with low allergenicity. Both animal and plant viruses are being studied for use in the treatment of food allergies. These formulations are combined with adjuvants, T-stimulatory epitopes, TLR ligands, and other immune modulators to modulate or enhance the immune response toward the presented allergen. Here, the authors present an overview of VLP production systems, their immune modulation capabilities, and the applicability of actual VLP-based formulations targeting allergic diseases.

The combination of allergen immunotherapy and biologics for inhalant allergies: Exploring the synergy

The development of monoclonal antibodies that selectively target IgE and type 2 immunity has opened new possibilities in the treatment of allergies. Although they have been used mainly as single therapies found to have efficacy in the management of asthma and other T2-mediated diseases, there is a growing interest in using these monoclonal antibodies in combination with allergen immunotherapy (AIT). AIT has transformed the treatment of allergic diseases by aiming to modify the underlying immune response to allergens rather than just providing temporary symptom relief. Despite the proven efficacy and safety of AIT, unmet needs call for further research and innovation. Combination strategies involving biologics and AIT exhibit potential in improving short-term efficacy, reducing adverse events, and increasing immunologic tolerance. Anti-IgE emerges as the most promising therapeutic strategy, not only enhancing AIT's safety and tolerability but also providing additional evidence of efficacy compared with AIT alone. Anti-interleukin-4 receptor offers a reduction in adverse effects and an improved immunologic profile when combined with AIT; however, its impact on short-term efficacy seems limited. The combination of cat dander subcutaneous immunotherapy with anti-thymic stromal lymphopoietin was synergistic with enhanced efficacy and altered immune responses that persisted for 1 year after discontinuation compared with AIT alone. Long-term studies are needed to evaluate the sustained benefits and safety profiles of combination strategies.

Novel adjuvants in allergen-specific immunotherapy: where do we stand?

Type I hypersensitivity, or so-called type I allergy, is caused by Th2-mediated immune responses directed against otherwise harmless environmental antigens. Currently, allergen-specific immunotherapy (AIT) is the only disease-modifying treatment with the potential to re-establish clinical tolerance towards the corresponding allergen(s). However, conventional AIT has certain drawbacks, including long treatment durations, the risk of inducing allergic side effects, and the fact that allergens by themselves have a rather low immunogenicity. To improve AIT, adjuvants can be a powerful tool not only to increase the immunogenicity of co-applied allergens but also to induce the desired immune activation, such as promoting allergen-specific Th1- or regulatory responses. This review summarizes the knowledge on adjuvants currently approved for use in human AIT: aluminum hydroxide, calcium phosphate, microcrystalline tyrosine, and MPLA, as well as novel adjuvants that have been studied in recent years: oil-in-water emulsions, virus-like particles, viral components, carbohydrate-based adjuvants (QS-21, glucans, and mannan) and TLR-ligands (flagellin and CpG-ODN). The investigated adjuvants show distinct properties, such as prolonging allergen release at the injection site, inducing allergen-specific IgG production while also reducing IgE levels, as well as promoting differentiation and activation of different immune cells. In the future, better understanding of the immunological mechanisms underlying the effects of these adjuvants in clinical settings may help us to improve AIT.

The Dual Role of the Airway Epithelium in Asthma: Active Barrier and Regulator of Inflammation

Chronic airway inflammation is the cornerstone on which bronchial asthma arises, and in turn, chronic inflammation arises from a complex interplay between environmental factors such as allergens and pathogens and immune cells as well as structural cells constituting the airway mucosa. Airway epithelial cells (AECs) are at the center of these processes. On the one hand, they represent the borderline separating the body from its environment in order to keep inner homeostasis. The airway epithelium forms a multi-tiered, self-cleaning barrier that involves an unstirred, discontinuous mucous layer, the dense and rigid mesh of the glycocalyx, and the cellular layer itself, consisting of multiple, densely interconnected cell types. On the other hand, the airway epithelium represents an immunologically highly active tissue once its barrier has been penetrated: AECs play a pivotal role in releasing protective immunoglobulin A. They express a broad spectrum of pattern recognition receptors, enabling them to react to environmental stressors that overcome the mucosal barrier. By releasing alarmins-proinflammatory and regulatory cytokines-AECs play an active role in the formation, strategic orientation, and control of the subsequent defense reaction. Consequently, the airway epithelium is of vital importance to chronic inflammatory diseases, such as asthma.

The clinical efficacy of type 2 monoclonal antibodies in eosinophil-associated chronic airway diseases: a meta-analysis

Background

Anti-type 2 inflammation therapy has been proposed as a treatment strategy for eosinophil-associated chronic airway disorders that could reduce exacerbations and improve lung function. We performed a meta-analysis of randomized controlled trials to assess the effectiveness of type 2 monoclonal antibodies (anti-T2s) for eosinophil-associated chronic airway disorders.

Methods

PubMed, Embase, Web of Science, and Cochrane Library were searched from their inception to 21 August 2022. Randomized clinical trials evaluating the effectiveness of anti-T2s versus placebo in the treatment of chronic airway diseases were selected. The outcomes were exacerbation rate and change in pre-bronchodilator forced expiratory volume in 1 s (FEV1) from baseline. The Cochrane Risk of Bias Assessment Tool 1.0 was used to evaluate the risk of bias, and the random-effects or fixed-effect model were used to pool the data.

Results

Thirty-eight articles concerning forty-one randomized clinical trials with 17,115 patients were included. Compared with placebo, anti-T2s therapy yielded a significant reduction in exacerbation rate in COPD and asthma (Rate Ratio (RR)=0.89, 95%CI, 0.83-0.95, I2 = 29.4%; RR= 0.59, 95%CI, 0.52-0.68, I2 = 83.9%, respectively) and improvement in FEV1 in asthma (Standard Mean Difference (SMD)=0.09, 95%CI, 0.08-0.11, I2 = 42.6%). Anti-T2s therapy had no effect on FEV1 improvement in COPD (SMD=0.05, 95%CI, -0.01-0.10, I2 = 69.8%).

Conclusion

Despite inconsistent findings across trials, anti-T2s had a positive overall impact on patients' exacerbation rate in asthma and COPD and FEV1 in asthma. Anti-T2s may be effective in treating chronic airway illnesses related to eosinophils.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42022362280.

Allergen immunotherapy: past, present and future

Allergen immunotherapy is a form of therapeutic vaccination for established IgE-mediated hypersensitivity to common allergen sources such as pollens, house dust mites and the venom of stinging insects. The classical protocol, introduced in 1911, involves repeated subcutaneous injection of increasing amounts of allergen extract, followed by maintenance injections over a period of 3 years, achieving a form of allergen-specific tolerance that provides clinical benefit for years after its discontinuation. More recently, administration through the sublingual route has emerged as an effective, safe alternative. Oral immunotherapy for peanut allergy induces effective ‘desensitization’ but not long-term tolerance. Research and clinical trials over the past few decades have elucidated the mechanisms underlying immunotherapy-induced tolerance, involving a reduction of allergen-specific T helper 2 (T_H2) cells, an induction of regulatory T and B cells, and production of IgG and IgA ‘blocking’ antibodies. To better harness these mechanisms, novel strategies are being explored to achieve safer, effective, more convenient regimens and more durable long-term tolerance; these include alternative routes for current immunotherapy approaches, novel adjuvants, use of recombinant allergens (including hypoallergenic variants) and combination of allergens with immune modifiers or monoclonal antibodies targeting the T_H2 cell pathway.

Durham and Shamji review the history and future of allergen immunotherapy for established IgE-mediated hypersensitivity to common allergens. They describe the mechanisms of immunotherapy-induced tolerance and the new strategies being explored to achieve safer, more effective, long-term tolerance.

Therapeutic Interventions Targeting Innate Immune Receptors: A Balancing Act

The innate immune system is an organism's first line of defense against an onslaught of internal and external threats. The downstream adaptive immune system has been a popular target for therapeutic intervention, while there is a relative paucity of therapeutics targeting the innate immune system. However, the innate immune system plays a critical role in many human diseases, such as microbial infection, cancer, and autoimmunity, highlighting the need for ongoing therapeutic research. In this review, we discuss the major innate immune pathways and detail the molecular strategies underpinning successful therapeutics targeting each pathway as well as previous and ongoing efforts. We will also discuss any recent discoveries that could inform the development of novel therapeutic strategies. As our understanding of the innate immune system continues to develop, we envision that therapies harnessing the power of the innate immune system will become the mainstay of treatment for a wide variety of human diseases.

Toll-Like Receptors in Stem/Progenitor Cells

One of the bridges that control the cross-talk between the innate and adaptive immune systems is toll-like receptors (TLRs). TLRs interact with molecules shared and maintained by the source pathogens, but also with endogenous molecules derived from injured tissues (damage/danger-associated molecular patterns - DAMPs). This is likely why some kinds of stem/progenitor cells (SCs) have been found to express TLRs. The role of TLRs in regulating basal motility, proliferation, processes of differentiation, self-renewal, and immunomodulation has been demonstrated in these cells. In this book chapter, we will discuss the many different functions assumed by the TLRs in SCs, pointing out that, depending on the context and the type of ligands they perceive, they may have different effects. In addition, the role of TLR in SC's response to specific tissue damage and in reparative processes will be addressed, as well as how the discovery of molecules mediating TLR signaling's differential function may be decisive for the development of new therapeutic strategies. Given the available studies on TLRs in SCs, the significance of TLRs in sensing an injury to stem/progenitor cells and evaluating their action and reparative activity, which depends on the circumstances, will be discussed here. It could also be possible that SCs used in therapy could theoretically be exposed to TLR ligands, which could modulate their in vivo therapeutic potential. In this context, we need to better understand the mechanisms of action of TLRs on SCs and learn how to regulate these receptors and their downstream pathways in a precise way in order to modulate SC proliferation, survival, migration, and differentiation in the pathological environment. In this way, cell therapy may be strengthened and made safer in the future.

Recent trends of NFκB decoy oligodeoxynucleotide-based nanotherapeutics in lung diseases

Nuclear factor κB (NFκB) is a unique protein complex that plays a major role in lung inflammation and respiratory dysfunction. The NFκB signaling pathway, therefore becomes an avenue for the development of potential pharmacological interventions, especially in situations where chronic inflammation is often constitutively active and plays a key role in the pathogenesis and progression of the disease. NFκB decoy oligodeoxynucleotides (ODNs) are double-stranded and carry NFκB binding sequences. They prevent the formation of NFκB-mediated inflammatory cytokines and thus have been employed in the treatment of a variety of chronic inflammatory diseases. However, the systemic administration of naked decoy ODNs restricts their therapeutic effectiveness because of their poor pharmacokinetic profile, instability, degradation by cellular enzymes and their low cellular uptake. Both structural modification and nanotechnology have shown promising results in enhancing the pharmacokinetic profiles of potent therapeutic substances and have also shown great potential in the treatment of respiratory diseases such as asthma, chronic obstructive pulmonary disease and cystic fibrosis. In this review, we examine the contribution of NFκB activation in respiratory diseases and recent advancements in the therapeutic use of decoy ODNs. In addition, we also highlight the limitations and challenges in use of decoy ODNs as therapeutic molecules, cellular uptake of decoy ODNs, and the current need for novel delivery systems to provide efficient delivery of decoy ODNs. Furthermore, this review provides a common platform for discussion on the existence of decoy ODNs, as well as outlining perspectives on the latest generation of delivery systems that encapsulate decoy ODNs and target NFκB in respiratory diseases.

Anti-Inflammatory Activity of Melatonin: a Focus on the Role of NLRP3 Inflammasome

Melatonin is a hormone of the pineal gland that contributes to the regulation of physiological activities, such as sleep, circadian rhythm, and neuroendocrine processes. Melatonin is found in several plants and has pharmacological activities including antioxidant, anti-inflammatory, hepatoprotective, cardioprotective, and neuroprotective. It also has shown therapeutic efficacy in treatment of cancer and diabetes. Melatonin affects several molecular pathways to exert its protective effects. The NLRP3 inflammasome is considered a novel target of melatonin. This inflammasome contributes to enhanced level of IL-1β, caspase-1 activation, and pyroptosis stimulation. The function of NLRP3 inflammasome has been explored in various diseases, including cancer, diabetes, and neurological disorders. By inhibiting NLRP3, melatonin diminishes inflammation and influences various molecular pathways, such as SIRT1, microRNA, long non-coding RNA, and Wnt/β-catenin. Here, we discuss these molecular pathways and suggest that melatonin-induced inhibition of NLRP3 should be advanced in disease therapy.

Role of innate immunity and myeloid cells in susceptibility to allergic disease

Allergic diseases, including asthma, food allergy, eczema, and allergic rhinitis, are common diseases increasing in prevalence. Allergy, a failure of immune tolerance to innocuous environmental allergens, is characterized by allergen-specific immune responses, including IgE antibodies and T helper and T follicular helper cells producing type 2 cytokines. Despite the central role of adaptive immunity in pathophysiology of allergy, there is a growing body of evidence indicating an important role for the innate immune system in allergic disease. In this review, we focus on epithelial-mononuclear phagocyte communication in the control of allergy and tolerance. We discuss studies on early life environmental exposures and allergy susceptibility, and the evidence for innate training of mononuclear phagocytes as the mechanistic link between exposure and health or disease.

One Hundred Ten Years of Allergen Immunotherapy: A Broad Look Into the Future

Allergen immunotherapy (AIT) is the only disease-modifying treatment option for patients with type 1-mediated allergic diseases such as allergic rhinitis/rhinoconjunctivitis with/without allergic asthma. Although many innovations have been developed since the first clinical report of Noon et al in 1911, the improvement of clinical efficacy and tolerability of this treatment is still an important unmet need. Hence, much progress has been made in the characterization of the cell types, cytokines, and intracellular signaling events involved in the development, maintenance, and regulation of allergic reactions, and also in the understanding of the mechanisms of tolerance induction in AIT. This comprehensive review aims to summarize the current innovative approaches in AIT, but also gives an outlook on promising candidates of the future. On the basis of an extensive literature review, integrating a clinical point of view, this article focuses on recent and future innovations regarding biologicals, allergen-derived peptides, recombinant allergens, "Toll"-like receptor agonists and other adjuvants, and novel application routes being developed for future AIT.

CpG oligodeoxynucleotides attenuate RORγt-mediated Th17 response by restoring histone deacetylase-2 in cigarette smoke-exposure asthma

BACKGROUND

Cigarette smoke (CS) exposure increases corticosteroid insensitive asthma related to increased Th17 phenotype, and new treatment strategies are needed for CS-associated asthma. Histone deacetylase 2 (HDAC2), found in the airway epithelium, is critical for ameliorating glucocorticoids insensitivity. We recently demonstrated the anti-inflammatory effects of CpG oligodeoxynucleotides (CpG-ODNs) on CS-exposure asthma. However, the effects of CpG-ODNs on HDAC2 expression and enzymatic activity remain unclear. This study aimed to assess whether CpG-ODNs protect against excessive Th17 immune responses in CS-induced asthma through HDAC2-dependent mechanisms and compared their effects with those of corticosteroids.

METHODS

The effects of CpG-ODNs alone and in combination with budesonide (BUD) on airway inflammation and Th2/Th17-related airway immune responses were determined using an in vivo model of CS-induced asthma and in cultured bronchial epithelial (HBE) cells administered ovalbumin (OVA) and/or cigarette smoke extract (CSE). HDAC2 and retinoid-related orphan nuclear receptor γt (RORγt) expression were also assessed in mouse lung specimens and HBE cells.

RESULTS

CpG-ODNs and BUD synergistically attenuated CS exposure asthmatic responses in vivo by modulating the influx of eosinophils and neutrophils, airway remodeling, Th2/Th17 associated cytokine and chemokine production, and airway hyperresponsiveness and blocking RORγt-mediated Th17 inflammation through induced HDAC2 expression/activity. In vitro, CpG-ODNs synergized with BUD to inhibit Th17 cytokine production in OVA- and CSE-challenged HBE cells while suppressing RORγt and increasing epithelial HDAC2 expression/activity.

CONCLUSIONS

CpG-ODNs reversed CS-induced HDAC2 downregulation and enhanced the sensitivity of CS-exposed asthmatic mice and CSE-induced HBE cells to glucocorticoid treatment. This effect may be associated with HDAC2 restoration via RORγt/IL-17 pathway regulation, suggesting that CpG-ODNs are potential corticosteroid-sparing agents for use in CS-induced asthma with Th17-biased immune conditions.

CpG Adjuvant in Allergen-Specific Immunotherapy: Finding the Sweet Spot for the Induction of Immune Tolerance

Prevalence and incidence of IgE-mediated allergic diseases have increased over the past years in developed and developing countries. Allergen-specific immunotherapy (AIT) is currently the only curative treatment available for allergic diseases that has long-term efficacy. Although AIT has been proven successful as an immunomodulatory therapy since its beginnings, it still faces several unmet needs and challenges today. For instance, some patients can experience severe side effects, others are non-responders, and prolonged treatment schedules can lead to lack of patient adherence and therapy discontinuation. A common strategy to improve AIT relies on the use of adjuvants and immune modulators to boost its effects and improve its safety. Among the adjuvants tested for their clinical efficacy, CpG oligodeoxynucleotide (CpG-ODN) was investigated with limited success and without reaching phase III trials for clinical allergy treatment. However, recently discovered immune tolerance-promoting properties of CpG-ODN place this adjuvant again in a prominent position as an immune modulator for the treatment of allergic diseases. Indeed, it has been shown that the CpG-ODN dose and concentration are crucial in promoting immune regulation through the recruitment of pDCs. While low doses induce an inflammatory response, high doses of CpG-ODN trigger a tolerogenic response that can reverse a pre-established allergic milieu. Consistently, CpG-ODN has also been found to stimulate IL-10 producing B cells, so-called B regulatory cells (Bregs). Accordingly, CpG-ODN has shown its capacity to prevent and revert allergic reactions in several animal models showing its potential as both preventive and active treatment for IgE-mediated allergy. In this review, we describe how CpG-ODN-based therapies for allergic diseases, despite having shown limited success in the past, can still be exploited further as an adjuvant or immune modulator in the context of AIT and deserves additional attention. Here, we discuss the past and current knowledge, which highlights CpG-ODN as a potential adjuvant to be reevaluated for the enhancement of AIT when used in appropriate conditions and formulations.

A highly specific and sensitive indirect competitive monoclonal ELISA for the detection of brombuterol in animal feed, swine urine, pork and liver samples

Brombuterol, a new β-adrenergic agonist to enhance animal growth and increase feeding efficiency, is forbidden as an additive in animal feed for livestock production due to its adverse effects on consumers. In this study, a highly specific and sensitive monoclonal antibody was obtained and an indirect competitive monoclonal ELISA was developed to detect brombuterol, with an IC₅₀ value of 0.1 μg/kg (μg/L) and no cross-reactivity to other structurally related β-adrenergic agonists. The average recovery of brombuterol using the icELISA method ranged from 72.9% to 106.4% with the coefficient of variation lower than 18.9%, which was determined by analysing spiked animal feed, swine urine, pork and liver samples (n = 5). Finally, the icELISA gave results having a good correlation with those obtained by liquid chromatography-tandem mass spectrometry. These results demonstrated that the developed icELISA for the detection of brombuterol is highly specific, sensitive, and reliable, indicating good potential for use in the area of food safety to improve consumer protection.

Bioengineering of Virus-like Particles for the Prevention or Treatment of Allergic Diseases

Recent findings on the mechanism of allergen-specific immunotherapy (AIT) have revisited the role of immunoglobulin G (IgG) as the development of specific blocking IgG antibodies appeared critical for the successful suppression of T-helper 2 (Th2)-biased allergic responses. Consequently, any form of molecular AIT-promoting potent allergen-specific neutralizing antibodies would be preferred to conventional administration of allergen extracts. The potent immunogenicity of virus-like particles (VLPs) could be harnessed for that purpose. The particle size (20–200 nm) optimizes uptake by antigen-presenting cells as well as lymphatic trafficking. Moreover, the display of antigens in repetitive arrays promotes potent B cell activation for the development of sustained antibody responses. The presentation of self-antigens on the particle surface was even capable to break B cell tolerance. In this review, we describe the immunomodulatory properties of the 3 VLP-based strategies designed so far for the treatment of allergic disease: VLP packaged with CpG motifs as well as chimeric particles displaying pro-Th2/Th2 cytokines or allergens (full-length or B cell epitopes).

Toll-like receptor signalling in B cells during systemic lupus erythematosus

B lymphocytes have a central role in autoimmune diseases, which are often defined by specific autoantibody patterns and feature a loss of B cell tolerance. A prototypic disease associated with B cell hyperactivity is systemic lupus erythematosus (SLE). In patients with SLE, the loss of B cell tolerance to autoantigens is controlled in a cell-intrinsic manner by Toll-like receptors (TLRs), which sense nucleic acids in endosomes. TLR7 drives the extrafollicular B cell response and the germinal centre reaction that are involved in autoantibody production and disease pathogenesis. Surprisingly, TLR9 seems to protect against SLE, even though it is required for the production of autoantibodies recognizing double-stranded DNA-associated antigens, which are abundant in SLE and are a hallmark of this disease. The protective function of TLR9 is at least partly mediated by its capacity to limit the stimulatory activity of TLR7. The roles of TLR7 and TLR9 in the effector function of B cells in lupus-like disease and in patients with SLE, and the unique features of TLR signalling in B cells, suggest that targeting TLR signalling in SLE might be therapeutically beneficial.

Loss of B cell tolerance to autoantigens in systemic lupus erythematosus (SLE) is driven by TLR7, whereas TLR9 appears to protect against SLE by limiting the stimulatory activity of TLR7. The unique features of Toll-like receptor signalling in B cells implicate it as a therapeutic target in SLE.

Intrinsic TLR7 and TLR9 signalling in B cells plays an important role in the development and pathogenesis of systemic lupus erythematosus (SLE).

In patients with SLE, effector plasma cells are generated via the extrafollicular response and via the formation of spontaneous germinal centres.

TLR7 plays key roles in the extrafollicular response and the response mediated by germinal centres.

Some plasma cells produce IL-10 and can have protective roles in lupus-like disease.

Role of the Intestinal Epithelium and Its Interaction With the Microbiota in Food Allergy

The intestinal epithelial tract forms a dynamic lining of the digestive system consisting of a range of epithelial cell sub-types with diverse functions fulfilling specific niches. The intestinal epithelium is more than just a physical barrier regulating nutrient uptake, rather it plays a critical role in homeostasis through its intrinsic innate immune function, pivotal regulation of antigen sensitization, and a bi-directional interplay with the microbiota that evolves with age. In this review we will discuss these functions of the epithelium in the context of food allergy.

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.

Mechanisms of Particles in Sensitization, Effector Function and Therapy of Allergic Disease

Humans have always been in contact with natural airborne particles from many sources including biologic particulate matter (PM) which can exhibit allergenic properties. With industrialization, anthropogenic and combustion-derived particles have become a major fraction. Currently, an ever-growing number of diverse and innovative materials containing engineered nanoparticles (NPs) are being developed with great expectations in technology and medicine. Nanomaterials have entered everyday products including cosmetics, textiles, electronics, sports equipment, as well as food, and food packaging. As part of natural evolution humans have adapted to the exposure to particulate matter, aiming to protect the individual's integrity and health. At the respiratory barrier, complications can arise, when allergic sensitization and pulmonary diseases occur in response to particle exposure. Particulate matter in the form of plant pollen, dust mites feces, animal dander, but also aerosols arising from industrial processes in occupational settings including diverse mixtures thereof can exert such effects. This review article gives an overview of the allergic immune response and addresses specifically the mechanisms of particulates in the context of allergic sensitization, effector function and therapy. In regard of the first theme (i), an overview on exposure to particulates and the functionalities of the relevant immune cells involved in allergic sensitization as well as their interactions in innate and adaptive responses are described. As relevant for human disease, we aim to outline (ii) the potential effector mechanisms that lead to the aggravation of an ongoing immune deviation (such as asthma, chronic obstructive pulmonary disease, etc.) by inhaled particulates, including NPs. Even though adverse effects can be exerted by (nano)particles, leading to allergic sensitization, and the exacerbation of allergic symptoms, promising potential has been shown for their use in (iii) therapeutic approaches of allergic disease, for example as adjuvants. Hence, allergen-specific immunotherapy (AIT) is introduced and the role of adjuvants such as alum as well as the current understanding of their mechanisms of action is reviewed. Finally, future prospects of nanomedicines in allergy treatment are described, which involve modern platform technologies combining immunomodulatory effects at several (immuno-)functional levels.

IgE-mediated regulation of IL-10 and type I IFN enhances rhinovirus-induced Th2 differentiation by primary human monocytes

Rhinovirus (RV) infections are linked to the development and exacerbation of allergic diseases including allergic asthma. IgE, another contributor to atopic disease pathogenesis, has been shown to regulate DC antiviral functions and influence T cell priming by monocytes. We previously demonstrated that IgE-mediated stimulation of monocytes alters multiple cellular functions including cytokine secretion, phagocytosis, and influenza-induced Th1 development. In this study, we investigate the effects of IgE-mediated stimulation on monocyte-driven, RV-induced T cell development utilizing primary human monocyte-T cell co-cultures. We demonstrate that IgE crosslinking of RV-exposed monocytes enhances monocyte-driven Th2 differentiation. This increase in RV-induced Th2 development was regulated by IgE-mediated inhibition of virus-induced type I IFN and induction of IL-10. These findings suggest an additional mechanism by which two clinically significant risk factors for allergic disease exacerbations-IgE-mediated stimulation and rhinovirus infection-may synergistically promote Th2 differentiation and allergic inflammation.

Toll-like receptors as a therapeutic target in cancer, infections and inflammatory diseases

Toll-like receptors (TLRs) are widely expressed pattern recognition receptors that bind to conserved molecular patterns expressed by pathogens and damaged cells. After recognition, activated TLRs induce the expression of various proinflammatory and antiviral molecules. Thus, TLRs are potential targets for treatment strategies aimed at boosting the adaptive immune response to vaccines, controlling infections, enhancing immune responses during tumor treatment and attenuating immune responses in inflammatory disorders. This Special Report examines the potential of TLRs as targets for the treatment of cancer, infections and inflammatory diseases. Here, we make a particular emphasis on molecules capable of modulating TLRs and their therapeutic applications.

Antibody Opsonization of a TLR9 Agonist-Containing Virus-like Particle Enhances In Situ Immunization

The immunologic and therapeutic effects of intratumoral (IT) delivery of a novel virus-like particle as a lymphoma immunotherapy were evaluated in preclinical studies with human cells and a murine model. CMP-001 is a virus-like particle composed of the Qβ bacteriophage capsid protein encapsulating an immunostimulatory CpG-A oligodeoxynucleotide TLR9 agonist. In vitro, CMP-001 induced cytokine production, including IFN-α from plasmacytoid dendritic cells, but only in the presence of anti-Qβ Ab. In vivo, IT CMP-001 treatment of murine A20 lymphoma enhanced survival and reduced growth of both injected and contralateral noninjected tumors in a manner dependent on both the ability of mice to generate anti-Qβ Ab and the presence of T cells. The combination of IT CMP-001 with systemic anti-PD-1 enhanced antitumor responses in both injected and noninjected tumors. IT CMP-001 alone or combined with anti-PD-1 augmented T cell infiltration in tumor-draining lymph nodes. We conclude IT CMP-001 induces a robust antitumor T cell response in an anti-Qβ Ab-dependent manner and results in systemic antitumor T cell effects that are enhanced by anti-PD-1 in a mouse model of B cell lymphoma. Early-phase clinical evaluation of CMP-001 and anti-PD-1 combination therapy in lymphoma will begin shortly, based in part on these results.

All the small things: How virus-like particles and liposomes modulate allergic immune responses

Recent years have seen a dramatic increase in the range of applications of virus‐like nanoparticle (VNP)‐ and liposome‐based antigen delivery systems for the treatment of allergies. These platforms rely on a growing number of inert virus‐backbones or distinct lipid formulations and intend to engage the host's innate and/or adaptive immune system by virtue of their co‐delivered immunogens. Due to their particulate nature, VNP and liposomal preparations are also capable of breaking tolerance against endogenous cytokines, Igs, and their receptors, allowing for the facile induction of anti‐cytokine, anti‐IgE, or anti‐FcεR antibodies in the host. We here discuss the “pros and cons” of inducing such neutralizing autoantibodies. Moreover, we cover another major theme of the last years, i.e., the engineering of non‐anaphylactogenic particles and the elucidation of the parameters relevant for the specific trafficking and processing of such particles in vivo. Finally, we put the various technical advances in VNP‐ and liposome‐research into (pre‐)clinical context by referring and critically discussing the relevant studies performed to treat allergic diseases.

Pattern recognition receptors as potential drug targets in inflammatory disorders

Pattern recognition receptors (PRRs) are a key part of the innate immune system, the body's first line of defense against infection and tissue damage. This superfamily of receptors including Toll-like receptors (TLRs), NOD-like receptors (NLRs), C-type lectin-like receptors (CLRs) and RIG-like receptors (RLRs) are responsible for initiation of the inflammatory response by their recognition of molecular patterns present in invading microorganisms (such as bacteria, viruses or fungi) during infection or in molecules released following tissue damage during acute or chronic disease states (such as sepsis or arthritis). These receptors are widely expressed and located on the cell surface, in intracellular compartments or in the cytoplasm can detect a single or subset of molecules including lipoproteins, carbohydrates or nucleic acids. In response, they initiate an intracellular signaling cascade that culminates in the synthesis and release of cytokines, chemokines and vasoactive molecules. These steps are necessary to maintain tissue homeostasis and remove potentially dangerous pathogens. However, during extreme or acute responses or during chronic disease, this can be damaging and even lead to death. Therefore, it is thought that targeting such receptors may offer a therapeutic approach in chronic inflammatory diseases or in cases of acute infection leading to sepsis. Herein, the current knowledge on the molecular biology of PRRs is reviewed along with their association with inflammatory and infectious diseases. Finally, the testing of therapeutic compounds and their future merit as targets is discussed.

Melatonin biosynthesis restored by CpG oligodeoxynucleotides attenuates allergic airway inflammation via regulating NLRP3 inflammasome

AIMS

Both CpG oligodeoxynucleotide (CpG-ODN) and melatonin have been reported to induce Th1 response and contribute to allergic asthma resistance. Here, we aimed to reveal how they confer such effect as well as whether they crosstalk with each other.

MAIN METHODS

Six-week-old Female C57BL/6 mice were challenged by OVA to induce allergic airway inflammation, and were treated with CpG-ODN, CpG-ODN plus Luzindole or melatonin respectively. Bronchoalveolar lavage fluid (BALF) cellularity was classified and counted by Wright's-Giemsa staining. HE and PAS staining were used to analyze airway inflammation. The levels of IL-4, IL-5, IL-13,GM-CSF and IFN-γ, as well as IL-1β and IL-18 were analyzed by ELISA. Protein expressions of ASMT, AANAT, NLRP3, IL-1β and caspase-1 in lung tissue were detected by Western blotting, expression of ASMT and AANAT were further observed by immunohistochemistry.

KEY FINDINGS

We found that CpG-ODN considerably suppressed OVA-induced airway leukocytes infiltration, goblet cell hyperplasia and Th2 cytokines production. Furthermore, the resolution effect of CpG-ODN on OVA-induced allergic airway inflammation occurred in parallel with decreased-activation of NLRP3 inflammasome and increased biosynthesis of melatonin. Blocking the effect of endogenous melatonin by Luzindole abolished the suppressive effect of CpG-ODN on OVA-induced airway inflammation and activation of NLRP3 inflammasome, suggesting such effect was mediated by endogenous melatonin. Moreover, exogenous melatonin pronouncedly ameliorated airway inflammation and decreased the activation of NLRP3 inflammasome.

SIGNIFICANCE

These results proven that CpG-ODN protects against allergic airway inflammation via suppressing the activation of NLRP3 inflammasome, and such effect may be resulted from the restored-production of melatonin.

Intratumoural immunotherapy: activation of nucleic acid sensing pattern recognition receptors

Recently, it has become clear that the tumour microenvironment (TME) is important in cancer immunotherapy. While immune checkpoint inhibitors are effective for some patients, the heterogeneous nature and status of the TME (‘cold’ tumours) play a critical role in suppressing antitumour immunity in non-responding patients. Converting ‘cold’ to ‘hot’ tumours through modulation of the TME may enable expansion of the therapeutic efficacy of immunotherapy to a broader patient population. This paper describes advances in intratumoural immunotherapy, specifically activation of nucleic acid sensing pattern recognition receptors to modulate the TME.

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Intratumoural immunotherapy to modulate the tumour microenvironment.

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Use of novel immunostimulatory agents which activate nucleic acid sensing pattern recognition receptors.

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Harnessing innate and adaptive immunity induced by receptor-mediated immune cascade.

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Intratumoural therapy leads to local and anenestic tumour responses.

Toll-Like Receptors and Relevant Emerging Therapeutics with Reference to Delivery Methods

The built-in innate immunity in the human body combats various diseases and their causative agents. One of the components of this system is Toll-like receptors (TLRs), which recognize structurally conserved molecules derived from microbes and/or endogenous molecules. Nonetheless, under certain conditions, these TLRs become hypofunctional or hyperfunctional, thus leading to a disease-like condition because their normal activity is compromised. In this regard, various small-molecule drugs and recombinant therapeutic proteins have been developed to treat the relevant diseases, such as rheumatoid arthritis, psoriatic arthritis, Crohn’s disease, systemic lupus erythematosus, and allergy. Some drugs for these diseases have been clinically approved; however, their efficacy can be enhanced by conventional or targeted drug delivery systems. Certain delivery vehicles such as liposomes, hydrogels, nanoparticles, dendrimers, or cyclodextrins can be employed to enhance the targeted drug delivery. This review summarizes the TLR signaling pathway, associated diseases and their treatments, and the ways to efficiently deliver the drugs to a target site.

Role of Toll-Like Receptors in Actuating Stem/Progenitor Cell Repair Mechanisms: Different Functions in Different Cells

Toll-like receptors (TLRs) represent one of the bridges that regulate the cross-talk between the innate and adaptive immune systems. TLRs interact with molecules shared and preserved by the pathogens of origin but also with endogenous molecules (damage/danger-associated molecular patterns (DAMPs)) that derive from injured tissues. This is probably why TLRs have been found to be expressed on several kinds of stem/progenitor cells (SCs). In these cells, the role of TLRs in the regulation of the basal motility, proliferation, differentiation processes, self-renewal, and immunomodulation has been demonstrated. In this review, we analyze the many different functions that the TLRs assume in SCs, pointing out that they can have different effects, depending on the background and on the kind of ligands that they recognize. Moreover, we discuss the TLR involvement in the response of SC to specific tissue damage and in the reparative processes, as well as how the identification of molecules mediating the differential function of TLR signaling could be decisive for the development of new therapeutic strategies. Considering the available studies on TLRs in SCs, here we address the importance of TLRs in sensing an injury by stem/progenitor cells and in determining their behavior and reparative activity, which is dependent on the conditions. Therefore, it could be conceivable that SCs employed in therapy could be potentially exposed to TLR ligands, which might modulate their therapeutic potential in vivo. In this context, to modulate SC proliferation, survival, migration, and differentiation in the pathological environment, we need to better understand the mechanisms of action of TLRs on SCs and learn how to control these receptors and their downstream pathways in a precise way. In this manner, in the future, cell therapy could be improved and made safer.

Toll-like receptor 9-dependent interferon production prevents group 2 innate lymphoid cell-driven airway hyperreactivity

BACKGROUND

Group 2 innate lymphoid cells (ILC2s) are important mediators of allergic asthma. Bacterial components, such as unmethylated CpG DNA, a Toll-like receptor (TLR) 9 agonist, are known to possess beneficial immunomodulatory effects in patients with T cell-mediated chronic asthma. However, their roles in regulating ILC2s remain unclear.

OBJECTIVE

We sought to determine the role of TLR9 activation in regulating ILC2 function and to evaluate the therapeutic utility of an immunomodulatory microparticle containing natural TLR9 ligand (MIS416).

METHODS

We evaluated the immunomodulatory effects of CpG A in IL-33-induced airway hyperreactivity (AHR) and airway inflammation. The roles of interferons were examined in vivo and in vitro by using signal transducer and activator of transcription 1 (Stat1)^-/- mice and neutralizing antibodies against IFN-γ and IFN-α/β receptor subunit 1, and their cellular sources were identified. The therapeutic utility of MIS416 was investigated in the Alternaria alternata model of allergic asthma and in humanized NSG mice.

RESULTS

We show that TLR9 activation by CpG A suppresses IL-33-mediated AHR and airway inflammation through inhibition of ILC2s. Activation of TLR9 leads to production of IFN-α, which drives IFN-γ production by natural killer cells. Importantly, IFN-γ is essential for TLR9-driven suppression, and IFN-α cannot compensate for impaired IFN-γ signaling. We further show that IFN-γ directly inhibits ILC2 function through a STAT1-dependent mechanism. Finally, we demonstrate the therapeutic potential of MIS416 in A alternata-induced airway inflammation and validated these findings in human subjects.

CONCLUSION

TLR9 activation alleviates ILC2-driven AHR and airway inflammation through direct suppression of cell function. Microparticle-based delivery of TLR9 ligands might serve as a therapeutic strategy for asthma treatment.

Recent clinical trends in Toll-like receptor targeting therapeutics

Toll‐like receptors (TLRs) are germline‐encoded receptors that are central to innate and adaptive immune responses. Owing to their vital role in inflammation, TLRs are rational targets in clinics; thus, many ligands and biologics have been reported to overcome the progression of various inflammatory and malignant conditions and support the immune system. For each TLR, at least one, and often many, drug formulations are being evaluated. Ligands reported as stand‐alone drugs may also be reported based on their use in combinatorial therapeutics as adjuvants. Despite their profound efficacy in TLR‐modulation in preclinical studies, multiple drugs have been terminated at different stages of clinical trials. Here, TLR modulating drugs that have been evaluated in clinical trials are discussed, along with their mode of action, suggestive failure reasons, and ways to improve the clinical outcomes. This review presents recent advances in TLR‐targeting drugs and provides directions for more successful immune system manipulation.

DNA and mRNA vaccination against allergies

Allergen-specific immunotherapy, which is performed by subcutaneous injection or sublingual application of allergen extracts, represents an effective treatment against type I allergic diseases. However, due to the long duration and adverse reactions, only a minority of patients decides to undergo this treatment. Alternatively, early prophylactic intervention in young children has been proposed to stop the increase in patient numbers. Plasmid DNA and mRNA vaccines encoding allergens have been shown to induce T helper 1 as well as T regulatory responses, which modulate or counteract allergic T helper 2-biased reactions. With regard to prophylactic immunization, additional safety measurements are required. In contrast to crude extracts, genetic vaccines provide the allergen at high purity. Moreover, by targeting the encoded allergen to subcellular compartments for degradation, release of native allergen can be avoided. Due to inherent safety features, mRNA vaccines could be the candidates of choice for preventive allergy immunizations. The subtle priming of T helper 1 immunity induced by this vaccine type closely resembles responses of non-allergic individuals and-by boosting via natural allergen exposure-could suffice for long-term protection from type I allergy.

TLR Activation and Allergic Disease: Early Life Microbiome and Treatment

PURPOSE OF REVIEW

Allergy and asthma are growing problems in the developed world. The accelerated increase of these diseases may be related to microbiome modification that leads to aberrant activation of Toll-like receptors (TLRs). Current research supports the concept that changes in microbial communities in early life impact TLR activation, resulting in an altered risk for the development of asthma and allergies.

RECENT FINDINGS

Prenatal and early childhood events that generate microbiome modification are closely related with TLR activation. Early childhood exposure to a rich array of TLR agonists, particularly lipopolysaccharide, strongly predicts protection against allergic disease later in life even when other lifestyle factors are accounted for. Genetic deletion of TLR signaling components in mice results in reduced function of tolerogenic cell populations in the gut. In contrast, weak TLR signaling can promote allergic sensitization later in life. This review summarizes the role of TLR signaling in microbiome-mediated protection against allergy.

The potential of anti-infectives and immunomodulators as therapies for asthma and asthma exacerbations

Asthma is responsible for approximately 25,000 deaths annually in Europe despite available medicines that maintain asthma control and reduce asthma exacerbations. Better treatments are urgently needed for the control of chronic asthma and reduction in asthma exacerbations, the major cause of asthma mortality. Much research spanning >20 years shows a strong association between microorganisms including pathogens in asthma onset, severity and exacerbation, yet with the exception of antibiotics, few treatments are available that specifically target the offending pathogens. Recent insights into the microbiome suggest that modulating commensal organisms within the gut or lung may also be a possible way to treat/prevent asthma. The European Academy of Allergy & Clinical Immunology Task Force on Anti-infectives in Asthma was initiated to investigate the potential of anti-infectives and immunomodulators in asthma. This review provides a concise summary of the current literature and aimed to identify and address key questions that concern the use of anti-infectives and both microbe- and host-based immunomodulators and their feasibility for use in asthma.

Treatment of allergic rhinitis with CpG oligodeoxynucleotides alleviates the lower airway outcomes of combined allergic rhinitis and asthma syndrome via a mechanism that possibly involves in TSLP

PURPOSE

Thymic stromal lymphopoietin (TSLP) is a critical regulator of immune responses associated with Th2 cytokine-mediated inflammation. Intranasal administration of oligodeoxynucleotides with CpG motifs (CpG-ODNs) might improve lower airway outcomes of combined allergic rhinitis and asthma syndrome (CARAS), but the inherent mechanisms of CpG-ODNs are not well defined. This study investigated whether CpG-ODNs treated to upper airway could reduce lower airway TSLP expression as well as whether this reduction could contribute to the alleviation of lower allergic inflammation and airway hyper-reactivity (AHR) in CARAS mice.

MATERIALS AND METHODS

Ovalbumin (OVA)-sensitized BALB/c mice were intranasal OVA exposure three times a week for 3 weeks. CpG-ODNs or an anti-TSLP mAb was administered to a subset of these mice 1 hour after intranasal OVA challenge, followed by 5 days of OVA aerosol challenge. The resulting immunological variables, nasal symptoms, and nasal mucosa and lung tissues pathology were evaluated. TSLP production in the lung tissues and bronchoalveolar lavage fluid (BALF) were determined by RT-PCR, western blotting or enzyme-linked immunosorbent assay.

RESULTS

The CARAS mice exhibited overexpression of TSLP in the lung tissues and BALF, and also demonstrated significant increases in BALF and splenocyte Th2-associated cytokine production, serum OVA-specific IgE, nose and lung pathologies, and AHR. Intranasal administration of CpG-ODNs restored TSLP in the lower airway, and it significantly reduced the following parameters: Th2-type cytokine production levels; the percentage of eosinophils in the BALF; IL-4 and IL-5 concentrations in the supernatants of cultured splenic lymphocytes; serum OVA-specific IgE; peribronchial inflammation score in the lungs; and nose pathology and nasal symptoms. Similar results were obtained when the CARAS mice were treated with an anti-TSLP mAb to block intranasal TSLP activity.

CONCLUSIONS

Treatment with intranasal CpG-ODNs improves lower airway immunological variable outcomes in the CARAS model via a mechanism that possibly involves in suppressing pulmonary TSLP-triggered allergic inflammation.

CpG oligodeoxynucleotide nanomedicines for the prophylaxis or treatment of cancers, infectious diseases, and allergies

Unmethylated cytosine-guanine dinucleotide-containing oligodeoxynucleotides (CpG ODNs), which are synthetic agonists of Toll-like receptor 9 (TLR9), activate humoral and cellular immunity and are being developed as vaccine adjuvants to prevent or treat cancers, infectious diseases, and allergies. Free CpG ODNs have been used in many clinical trials implemented to verify their effects. However, recent research has reported that self-assembled CpG ODNs, protein/peptide–CpG ODN conjugates, and nanomaterial–CpG ODN complexes demonstrate higher adjuvant effects than free CpG ODNs, owing to their improved uptake efficiency into cells expressing TLR9. Moreover, protein/peptide–CpG ODN conjugates and nanomaterial–CpG ODN complexes are able to deliver CpG ODNs and antigens (or allergens) to the same types of cells, which enables a higher degree of prophylaxis or therapeutic effect. In this review, the author describes recent trends in the research and development of CpG ODN nanomedicines containing self-assembled CpG ODNs, protein/peptide–CpG ODN conjugates, and nanomaterial–CpG ODN complexes, focusing mainly on the results of preclinical and clinical studies.

IgE-associated allergic disorders: recent advances in etiology, diagnosis, and treatment

IgE-associated allergic diseases belong to the most common inflammatory conditions. Their clinical manifestation ranges from mild symptoms to life-threatening episodes. Often patients experience a reduction in physical and psychologic well-being and suffer from a decreased quality of life due to disease activity. The continuously rising number of people that are affected by an allergic condition indicates an urgent need for better diagnostics and more efficient treatment options. Recent progress in the understanding of pathophysiologic mechanisms underlying IgE-associated allergic disorders has led to the identification of novel therapeutic targets and the development of drug candidates that are currently under evaluation. In this review, we highlight studies and clinical trials, which have helped to gain further insight in the etiology of IgE-associated allergic conditions as well as advances in the development of diagnostic tools and therapeutic approaches recently published in Allergy (European Journal of Allergy and Clinical Immunology).

The epithelial barrier and immunoglobulin A system in allergy

Airway and intestinal epithelial layers represent first-line physical barriers, playing a key role in mucosal immunity. Barrier dysfunction, characterized by alterations such as disruption of cell-cell apical junctions and aberrant epithelial responses, probably constitutes early and key events for chronic immune responses to environmental antigens in the skin and in the gut. For instance, barrier dysfunction drives Th2 responses in atopic disorders or eosinophilic esophagitis. Such epithelial impairment is also a salient feature of allergic asthma and growing evidence indicates that barrier alterations probably play a driving role in this disease. IgA has been identified as the most abundant immunoglobulin in mucosa, where it acts as an active barrier through immune exclusion of inhaled or ingested antigens or pathogens. Historically, it has been thought to represent the serum factor underlying reaginic activity before IgE was discovered. Despite several studies about regulation and major functions of IgA at mucosal surfaces, its role in allergy remains largely unclear. This review aims at summarizing findings about epithelial functions and IgA biology that are relevant to allergy, and to integrate the emerging concepts and the recent developments in mucosal immunology, and how these could translate to clinical observations in allergy.

Microbes and asthma: Opportunities for intervention

The worldwide incidence and prevalence of asthma continues to increase. Asthma is now understood as an umbrella term for different phenotypes or endotypes, which arise through different pathophysiologic pathways. Understanding the many factors contributing to development of the disease is important for the identification of novel therapeutic targets for the treatment of certain asthma phenotypes. The hygiene hypothesis has been formulated to explain the increasing prevalence of allergic disease, including asthma. This hypothesis postulates that decreased exposure at a young age to certain infectious agents as a result of improved hygiene, increased antibiotic use and vaccination, and changes in lifestyle and dietary habits is associated with changes in the immune system, which predispose subjects to allergy. Many microbes, during their coevolution with human subjects, developed mechanisms to manipulate the human immune system and to increase their chances of survival. Improving models of asthma, as well as choosing adequate end points in clinical trials, will lead to a more complete understanding of the underlying mechanisms, thus providing an opportunity to devise primary and secondary interventions at the same time as identifying new molecular targets for treatment. This article reports the discussion and conclusion of a workshop under the auspices of the Netherlands Lung Foundation to extend our understanding of how modulation of the immune system by bacterial, parasitic, and viral infections might affect the development of asthma and to map out future lines of investigation.

Molecularly targeted therapies for asthma: Current development, challenges and potential clinical translation

Extensive research into the therapeutics of asthma has yielded numerous effective interventions over the past few decades. However, adverse effects and ineffectiveness of most of these medications especially in the management of steroid resistant severe asthma necessitate the development of better medications. Numerous drug targets with inherent airway smooth muscle tone modulatory role have been identified for asthma therapy. This article reviews the latest understanding of underlying molecular aetiology of asthma towards design and development of better antiasthma drugs. New drug candidates with their putative targets that have shown promising results in the preclinical and/or clinical trials are summarised. Examples of these interventions include restoration of Th1/Th2 balance by the use of newly developed immunomodulators such as toll-like receptor-9 activators (CYT003-QbG10 and QAX-935). Clinical trials revealed the safety and effectiveness of chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2) antagonists such as OC0000459, BI-671800 and ARRY-502 in the restoration of Th1/Th2 balance. Regulation of cytokine activity by the use of newly developed biologics such as benralizumab, reslizumab, mepolizumab, lebrikizumab, tralokinumab, dupilumab and brodalumab are at the stage of clinical development. Transcription factors are potential targets for asthma therapy, for example SB010, a GATA-3 DNAzyme is at its early stage of clinical trial. Other candidates such as inhibitors of Rho kinases (Fasudil and Y-27632), phosphodiesterase inhibitors (GSK256066, CHF 6001, roflumilast, RPL 554) and proteinase of activated receptor-2 (ENMD-1068) are also discussed. Preclinical results of blockade of calcium sensing receptor by the use of calcilytics such as calcitriol abrogates cardinal signs of asthma. Nevertheless, successful translation of promising preclinical data into clinically viable interventions remains a major challenge to the development of novel anti-asthmatics.

TLR9 expression is required for the development of cigarette smoke-induced emphysema in mice

The expression of Toll-like receptor (TLR)-9, a pathogen recognition receptor that recognizes unmethylated CpG sequences in microbial DNA molecules, is linked to the pathogenesis of several lung diseases. TLR9 expression and signaling was investigated in animal and cell models of chronic obstructive pulmonary disease (COPD). We observed enhanced TLR9 expression in mouse lungs following exposure to cigarette smoke. Tlr9(-/-) mice were resistant to cigarette smoke-induced loss of lung function as determined by mean linear intercept, total lung capacity, lung compliance, and tissue elastance analysis. Tlr9 expression also regulated smoke-mediated immune cell recruitment to the lung; apoptosis; expression of granulocyte-colony stimulating factor (G-CSF), the CXCL5 protein, and matrix metalloproteinase-2 (MMP-2); and protein tyrosine phosphatase 1B (PTP1B) activity in the lung. PTP1B, a phosphatase with anti-inflammatory abilities, was identified as binding to TLR9. In vivo delivery of a TLR9 agonist enhanced TLR9 binding to PTP1B, which inactivated PTP1B. Ptp1b(-/-) mice had elevated lung concentrations of G-CSF, CXCL5, and MMP-2, and tissue expression of type-1 interferon following TLR9 agonist administration, compared with wild-type mice. TLR9 responses were further determined in fully differentiated normal human bronchial epithelial (NHBE) cells isolated from nonsmoker, smoker, and COPD donors, and then cultured at air liquid interface. NHBE cells from smokers and patients with COPD expressed more TLR9 and secreted greater levels of G-CSF, IL-6, CXCL5, IL-1β, and MMP-2 upon TLR9 ligand stimulation compared with cells from nonsmoker donors. Although TLR9 combats infection, our results indicate that TLR9 induction can affect lung function by inactivating PTP1B and upregulating expression of proinflammatory cytokines.