Der p2 activates airway smooth muscle cells in a TLR2/MyD88-dependent manner to induce an inflammatory response

Tyrosine nitration enhances the allergenic potential of house dust mite allergen Der p 2

Nitration of allergenic proteins caused by atmospheric pollutants O3 and NO2 may enhance their allergenic potential. In the study, the influence of nitration was investigated on the allergenicity of Der p 2, which is a main allergen from house dust mites and plays an important role in allergenic rhinitis and asthma. The results reveal that nitrated Der p 2 enhanced the IgE-binding capacity, upregulated the mRNA expression and release of IL-6 and IL-8 from bronchial epithelial cells, and induced higher levels of specific-IgE, TH2 cytokines and white blood cells in mice. Besides, nitrated Der p 2 caused more severe oxidative stress and allergenic symptoms in mice. It is concluded that nitration enhanced the allergenicity of Der p 2 through not only directly inducing higher amount of specific-IgE and stronger responses of TH2 cytokines, but also indirectly aggravating allergic symptoms by oxidative stress and adjuvant-like activation airway epithelial cells. The study suggests that the contribution of nitration to the promotion in allergenicity should not be ignored when precisely assessing the risk of house dust mite allergens in real environment.

The HDM allergen orchestra and its cysteine protease maestro: Stimulators of kaleidoscopic innate immune responses

House dust mite (HDM) encloses an explosive cocktail of allergenic proteins sensitizing hundreds of millions of people worldwide. To date, the innate cellular and molecular mechanism(s) orchestrating the HDM-induced allergic inflammation remains partially deciphered. Understanding the kaleidoscope of HDM-induced innate immune responses is hampered by (1) the large complexity of the HDM allergome with very diverse functional bioreactivities, (2) the perpetual presence of microbial compounds (at least LPS, β-glucan, chitin) promoting as well pro-Th2 innate signaling pathways and (3) multiple cross-talks involving structural, neuronal and immune cells. The present review provides an update on the innate immune properties, identified so far, of multiple HDM allergen groups. Experimental evidence highlights the importance of HDM allergens displaying protease or lipid-binding activities on the initiation of the allergic responses. Specifically, group 1 HDM cysteine proteases are considered as the key initiators of the allergic response through their capacities to impair the epithelial barrier integrity, to stimulate the release of pro-Th2 danger-associated molecular patterns (DAMPs) in epithelial cells, to produce super-active forms of IL-33 alarmin and to mature thrombin leading to Toll-like receptor 4 (TLR4) activation. Remarkably, the recently evidenced primary sensing of cysteine protease allergens by nociceptive neurons confirms the critical role of this HDM allergen group in the early events leading to Th2 differentiation.

Home Dust Mites Promote MUC5AC Hyper-Expression by Modulating the sNASP/TRAF6 Axis in the Airway Epithelium

House dust mites (HDMs) are a common source of respiratory allergens responsible for allergic asthma and innate immune responses in human diseases. Since HDMs are critical factors in the triggering of allergen-induced airway mucosa from allergic asthma, we aimed to investigate the mechanisms of Toll-like receptors (TLR) in the signaling of the HDM extract that is involved in mucus hypersecretion and airway inflammation through the engagement of innate immunity. Previously, we reported that the somatic nuclear autoantigenic sperm protein (sNASP)/tumor necrosis factor receptor-associated factor 6 (TRAF6) axis controls the initiation of TLRs to maintain the homeostasis of the innate immune response. The present study showed that the HDM extract stimulated the biogenesis of Mucin 5AC (MUC5AC) in bronchial epithelial cells via the TLR2/4 signaling pathway involving MyD88 and TRAF6. Specifically, sNASP binds to TRAF6 in unstimulated bronchial epithelial cells to prevent the activation of TRAF6-depenedent kinases. Upon on HDMs’ stimulation, sNASP is phosphorylated, leading to the activation of TRAF6 downstream of the p38 MAPK and NF-κB signaling pathways. Further, NASP-knockdown enhanced TRAF6 signaling and MUC5AC biogenesis. In the HDM-induced mouse asthma model, we found that the HDM extract promoted airway hyperresponsiveness (AHR), MUC5AC, and allergen-specific IgE production as well as IL-5 and IL-13 for recruiting inflammatory cells. Treatment with the PEP-NASP peptide, a selective TRAF6-blocking peptide, ameliorated HDM-induced asthma in mice. In conclusion, this study indicated that the sNASP/TRAF6 axis plays a regulatory role in asthma by modulating mucus overproduction, and the PEP-NASP peptide might be a potential target for asthma treatment.

Participation of MAPK and PI3K in Regulation of Cytokine Secretion by Peripheral Blood Monocular Cells in Response to Escherichia coli LPS and rDer p 2 Combination

Search for the effective approaches to treat acute inflammation caused by combination of allergens and infectious agents is an important task for public health worldwide. House dust mites Dermatophagoides pteronyssinus are the source of allergens of the Der p groups and of microbial compounds, in particular, lipopolysaccharides (LPS). LPS and Der p 2 induce secretion of pro-inflammatory cytokines via activation of kinases p38 MAPK, MEK1/2, and PI3K. Participation of these kinases in the regulation of cells response to combined exposure to LPS and Der p 2 has not been sufficiently studied. We studied the effects of kinases (p38 MAPK, MEK1/2, and PI3K) inhibition on secretion of cytokines (TNF, IL-8, and IL-6) by peripheral blood mononuclear cells (PBMC) of healthy volunteers in response to E. coli LPS and rDer p 2. Contribution of kinases to the regulation of cell response to different agents (rDer p 2 and/or LPS) was revealed. It was found that p38 MAPK plays a key role in the regulation of secretion TNF by PBMC in response to the combination of LPS and rDer p 2. MEK1/2-dependent signaling is the main pathway for the synthesis of TNF and IL-8 in response to LPS and rDer p 2. PI3K-dependent signaling negatively regulates TNF production during rDer p 2-induced cell activation, but is not involved in the response to the combination of LPS and rDer p 2. PI3K-dependent signaling in the regulation of PBMC cytokine synthesis is most pronounced in response to their activation by rDer p 2. Understanding the mechanisms of immune cell responses to combinations of inflammatory agents could facilitate the search for new intracellular targets for anti-inflammatory therapy.

Der p 38 Is a Bidirectional Regulator of Eosinophils and Neutrophils in Allergy

The house dust mite is the most common cause of allergic diseases, and TLR4 acts as an overarching receptor for allergic responses. This study aimed to identify novel allergen binding to TLR4 in house dust mites and unveil its unique role in allergic responses. Der p 38 was purified and characterized by liquid chromatography tandem mass spectrometry-based peptide mapping. Biolayer interferometry and structure modeling unveiled TLR4-binding activity and the structure of recombinant Der p 38. The allergenicity of Der p 38 was confirmed by a skin prick test, and basophil activation and dot blot assays. The skin prick test identified 24 out of 45 allergic subjects (53.3%) as Der p 38⁺ subjects. Der p 38-augmented CD203c expression was noted in the basophils of Der p 38⁺ allergic subjects. In animal experiments with wild-type and TLR4 knockout BALB/c mice, Der p 38 administration induced the infiltration of neutrophils as well as eosinophils and exhibited clinical features similar to asthma via TLR4 activation. Persistent Der p 38 administration induced severe neutrophil inflammation. Der p 38 directly suppressed the apoptosis of allergic neutrophils and eosinophils, and enhanced cytokine production in human bronchial epithelial cells, inhibiting neutrophil apoptosis. The mechanisms involved TLR4, LYN, PI3K, AKT, ERK, and NF-κB. These findings may contribute to a deep understanding of Der p 38 as a bridge allergen between eosinophilic and neutrophilic inflammation in the pathogenic mechanisms of allergy.

Oral Exposure to House Dust Mite Activates Intestinal Innate Immunity

SCOPE

House dust mite (HDM) induces Th2 responses in lungs and skin, but its effects in the intestine are poorly known. We aimed to study the involvement of HDM in the initial events that would promote sensitization through the oral route and eventually lead to allergy development.

METHODS AND RESULTS

BALB/c mice were exposed intragastrically to proteolytically active and inactive HDM, as such, or in combination with egg white (EW), and inflammatory and type 2 responses were evaluated. Oral administration of HDM, by virtue of its proteolytic activity, promoted the expression, in the small intestine, of genes encoding tight junction proteins, proinflammatory and Th2-biasing cytokines, and it caused expansion of group 2 innate immune cells, upregulation of Th2 cytokines, and dendritic cell migration and activation. In lymphoid tissues, its proteolytically inactivated counterpart also exerted an influence on the expression of surface DC molecules involved in interactions with T cells and in Th2 cell differentiation, which was confirmed in in vitro experiments. However, in our experimental setting we did not find evidence for the promotion of sensitization to coadministered EW.

CONCLUSION

Orally administered HDM upregulates tissue damage factors and also acts as an activator of innate immune cells behaving similarly to potent oral Th2 adjuvants.

B Cell Responses in the Development of Mammalian Meat Allergy

Studies of meat allergic patients have shown that eating meat poses a serious acute health risk that can induce severe cutaneous, gastrointestinal, and respiratory reactions. Allergic reactions in affected individuals following meat consumption are mediated predominantly by IgE antibodies specific for galactose-α-1,3-galactose (α-gal), a blood group antigen of non-primate mammals and therefore present in dietary meat. α-gal is also found within certain tick species and tick bites are strongly linked to meat allergy. Thus, it is thought that exposure to tick bites promotes cutaneous sensitization to tick antigens such as α-gal, leading to the development of IgE-mediated meat allergy. The underlying immune mechanisms by which skin exposure to ticks leads to the production of α-gal-specific IgE are poorly understood and are key to identifying novel treatments for this disease. In this review, we summarize the evidence of cutaneous exposure to tick bites and the development of mammalian meat allergy. We then provide recent insights into the role of B cells in IgE production in human patients with mammalian meat allergy and in a novel mouse model of meat allergy. Finally, we discuss existing data more generally focused on tick-mediated immunomodulation, and highlight possible mechanisms for how cutaneous exposure to tick bites might affect B cell responses in the skin and gut that contribute to loss of oral tolerance.

The allergenic activity and clinical impact of individual IgE-antibody binding molecules from indoor allergen sources

A large number of allergens have been discovered but we know little about their potential to induce inflammation (allergenic activity) and symptoms. Nowadays, the clinical importance of allergens is determined by the frequency and intensity of their IgE antibody binding (allergenicity). This is a rather limited parameter considering the development of experimental allergology in the last 20 years and the criteria that support personalized medicine. Now it is known that some allergens, in addition to their IgE antibody binding properties, can induce inflammation through non IgE mediated pathways, which can increase their allergenic activity. There are several ways to evaluate the allergenic activity, among them the provocation tests, the demonstration of non-IgE mediated pathways of inflammation, case control studies of IgE-binding frequencies, and animal models of respiratory allergy. In this review we have explored the current status of basic and clinical research on allergenic activity of indoor allergens and confirm that, for most of them, this important property has not been investigated. However, during recent years important advances have been made in the field, and we conclude that for at least the following, allergenic activity has been demonstrated: Der p 1, Der p 2, Der p 5 and Blo t 5 from HDMs; Per a 10 from P. americana; Asp f 1, Asp f 2, Asp f 3, Asp f 4 and Asp f 6 from A. fumigatus; Mala s 8 and Mala s 13 from M. sympodialis; Alt a 1 from A. alternata; Pen c 13 from P. chrysogenum; Fel d 1 from cats; Can f 1, Can f 2, Can f 3, Can f 4 and Can f 5 from dogs; Mus m 1 from mice and Bos d 2 from cows. Defining the allergenic activity of other indoor IgE antibody binding molecules is necessary for a precision-medicine-oriented management of allergic diseases.

A WAO - ARIA - GA2LEN consensus document on molecular-based allergy diagnosis (PAMD@): Update 2020

Precision allergy molecular diagnostic applications (PAMD@) is increasingly entering routine care. Currently, more than 130 allergenic molecules from more than 50 allergy sources are commercially available for in vitro specific immunoglobulin E (sIgE) testing. Since the last publication of this consensus document, a great deal of new information has become available regarding this topic, with over 100 publications in the last year alone. It thus seems quite reasonable to publish an update. It is imperative that clinicians and immunologists specifically trained in allergology keep abreast of the new and rapidly evolving evidence available for PAMD@.

PAMD@ may initially appear complex to interpret; however, with increasing experience, the information gained provides relevant information for the allergist. This is especially true for food allergy, Hymenoptera allergy, and for the selection of allergen immunotherapy. Nevertheless, all sIgE tests, including PAMD@, should be evaluated within the framework of a patient's clinical history, because allergen sensitization does not necessarily imply clinical relevant allergies.

House dust mite allergens induce interleukin 33 (IL-33) synthesis and release from keratinocytes via ATP-mediated extracellular signaling

In atopic diseases, the epithelium releases cytokines and chemokines that initiate skin inflammation. Atopic dermatitis (AD) is characterized by a disrupted epidermal barrier and is triggered or exacerbated by environmental stimuli such as house dust mite (HDM) allergens. The proinflammatory cytokine interleukin 33 (IL-33) plays an important role in the pathogenesis of AD, but how IL-33 production in keratinocytes is elicited by HDM is unknown. To that end, here we stimulated monolayer-cultured human keratinocytes and human living skin equivalents with Dermatophagoides pteronyssinus HDM extract to investigate its effects on IL-33 production from keratinocytes. The HDM extract induced intracellular expression of IL-33 and modulated its processing and maturation, triggering rapid IL-33 release from keratinocytes. Group 1 HDM allergen but not group 2 HDM allergen elicited IL-33 production. An ATP assay of keratinocyte culture supernatants revealed an acute and transient accumulation of extracellular ATP immediately after the HDM extract stimulation. Using the broad-spectrum P2 antagonist suramin, the specific purinergic receptor P2Y2 (P2RY2) antagonist AR-C118925XX, and P2RY2-specific siRNA, we discovered that the HDM extract-induced IL-33 expression was mainly dependent on extracellular ATP/P2Y2 signaling mediated by transactivation of epidermal growth factor receptor, followed by activation of the ERK kinase signaling pathway. Moreover, HDM extract-induced release of 25-kDa IL-33 from the keratinocytes depended on an extracellular ATP/P2 signaling-mediated intracellular Ca²⁺ increase. Our study demonstrates the new mechanism controlling the induction and maturation of keratinocyte-produced IL-33 by HDM allergens, an innate immune process that might play a role in AD development or severity.

IL-17 and CD40 ligand synergistically stimulate the chronicity of diabetic nephropathy

Background

Early stages of diabetic nephropathy (DN) are characterized by an influx of inflammatory cells. Interactions between infiltrating T cells and podocytes may play an important role in the ongoing inflammatory response and remodelling. The aim of this study was to explore the role of IL-17 and CD40 ligand (CD40L) in DN.

Methods

The study design involved a case series. Kidney biopsy samples of 69 patients with type 2 diabetes were assessed for the presence of CD4+ IL-17+ T cells. The number of CD4+ IL-17+ T cells were counted and correlated with clinical and laboratory findings. Additionally, advanced glycation end-products (AGEs) were added to cultured podocytes to imitate diabetic conditions and thus to elucidate the role of CD4+ IL-17+ T cells in renal sclerosis.

Results

CD80 expression was detected in early phases of DN but was absent during diffused glomerurosclerosis in DN kidney specimens. In DN samples, CD40 expression was not only observed in most of the infiltrating cells, but also increased in podocytes and tubular epithelial cells. CD40L is locally expressed on infiltrating cells. CD4+ IL-17+ T cells were found in DN, and the number of CD4+ IL-17+ T cells was positively correlated with the deterioration in glomerular filtration rate (GFR). IL-17A was the key cytokine produced by CD4+ IL-17+ T cells. IL-17A levels were elevated in DN renal tissue and were correlated with declining GFR. IL-17 and CD40L synergistically enhanced IL-6, monocyte chemoattractant protein-1 (MCP-1), regulated on activation, normal T cell expressed and secreted (RANTES), transforming growth factor beta 1 (TGF-β1) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) production in vitro. AGEs induced podocyte activation with increasing expression of IL-17A, CD40 and TGF-β1 in vitro. Blockade with an anti-IL-17 monoclonal antibody reduced the expression of CD40 and TGF-β1, but increased the viability of cultured podocytes.

Conclusions

IL-17 and CD40L synergistically mediate the inflammatory response and remodelling associated with tissue injury and glomerular sclerosis in DN.

Cutaneous Exposure to Clinically Relevant Lone Star Ticks Promotes IgE Production and Hypersensitivity through CD4+ T Cell- and MyD88-Dependent Pathways in Mice

Tick-borne allergies are a growing public health concern and have been associated with the induction of IgE-mediated food allergy to red meat. However, despite the increasing prevalence of tick bite-induced allergies, the mechanisms by which cutaneous exposure to ticks leads to sensitization and the production of IgE Abs are poorly understood. To address this question, an in vivo approach was used to characterize the IgE response to lone star tick proteins administered through the skin of mice. The results demonstrated that tick sensitization and challenge induced a robust production of IgE Abs and supported a role for IgE-mediated hypersensitivity reactions in sensitized animals following oral administration of meat. The induction of IgE responses was dependent on cognate CD4⁺ T cell help during both the sensitization phase and challenge phase with cutaneous tick exposure. In addition, IgE production was dependent on B cell-intrinsic MyD88 expression, suggesting an important role for TLR signaling in B cells to induce IgE responses to tick proteins. This model of tick-induced IgE responses could be used to study the factors within tick bites that cause allergies and to investigate how sensitization to food Ags occurs through the skin that leads to IgE production.

Effects of Ser47-Point Mutation on Conformation Structure and Allergenicity of the Allergen of Der p 2, a Major House Dust Mite Allergen

PURPOSE

Hypoallergenic recombinant Der p 2 has been produced by various genetic manipulations, but mutation of a naturally polymorphic amino acid residue known to affect IgE binding has not been studied. This study aimed to determine the effect of a point mutation (S47W) of residue 47 of Der p 2 on its structure and immunoglobulin (Ig) E binding. Its ability to induce pro-inflammatory responses and to induce blocking IgG antibody was also determined.

METHODS

S47 of recombinant Der p 2.0110, one of the predominant variants in Bangkok, was mutated to W (S47W). S47W secreted from Pichia pastoris was examined for secondary structure and for the formation of a hydrophobic cavity by 8-Anilino-1-naphthalenesulfonic acid (ANS) staining. Monoclonal and human IgE-antibody binding was determined by enzyme-linked immunosorbent assay. Allergen-induced degranulation by human epsilon receptor expressed-rat basophil was determined. Stimulation of the pro-inflammatory cytokine interleukin (IL)-8 release from human bronchial epithelial (BEAS2B) cells and inhibition of IgE binding to the wild type allergen by S47W-induced IgG were determined.

RESULTS

S47W reduced secondary structure and failed to bind the hydrophobic ANS ligand as well as a monoclonal antibody known to be dependent on the nature of the side chain of residue 114 in an adjacent loop. It could also not stimulate IL-8 release from BEAS2B cells. IgE from house dust mite (HDM)-allergic Thais bound S47W with 100-fold weaker avidity, whereas IgE of HDM-allergic Australians did not. S47W still induced basophil degranulation, although requiring higher concentrations for some subjects. Anti-S47W antiserum-immunized mice blocked the binding of human IgE to wild type Der p 2.

CONCLUSIONS

The mutant S47W had altered structure and reduced ability to stimulate pro-inflammatory responses and to bind IgE, but retained its ability to induce blocking antibodies. It thus represents a hypoallergen produced by a single mutation of a non-solvent-accessible amino acid.

House Dust Mite Allergy Under Changing Environments

Environmental variations induced by industrialization and climate change partially explain the increase in prevalence and severity of allergic disease. One possible mechanism is the increase in allergen production leading to more exposure and sensitization in susceptible individuals. House dust mites (HDMs) are important sources of allergens inducing asthma and rhinitis, and experimentally they have been demonstrated to be very sensitive to microenvironment modifications; therefore, global or regional changes in temperature, humidity, air pollution or other environmental conditions could modify natural HDM growth, survival and allergen production. There is evidence that sensitization to HDMs has increased in some regions of the world, especially in the subtropical and tropical areas; however, the relationship of this increase with environmental changes is not so clear as has reported for pollen allergens. In this review, we address this point and explore the effects of current and predicted environmental changes on HDM growth, survival and allergen production, which could lead to immunoglobulin E (IgE) sensitization and allergic disease prevalence. We also assess the role of adjuvants of IgE responses, such as air pollution and helminth infections, and discuss the genetic and epigenetic aspects that could influence the adaptive process of humans to drastic and relatively recent environmental changes we are experiencing.

Newly designed hemagglutinin-Der p 2 chimera is a potential candidate for allergen specific immunotherapy

Aim To investigate the immunomodulatory potential of a chimera composed of the receptor-binding domain of hemagglutinin 1 (H1s) from Influenza virus and Der p 2 (D2) allergen for allergen-specific immunotherapy of house-dust mite allergy (HDM).

MAIN METHODS

H1sD2 chimera and D2 allergen were produced by genetic engineering in E. coli. Recombinant antigens were extracted from inclusion bodies by urea, then refolded and purified by immobilized- metal affinity chromatography (IMAC). Purity was verified by 2D-PAGE and secondary structures were assessed by CD spectroscopy. IgE reactivity of H1sD2 and D2 was tested in western blot with sera from 8 persons with clinical history of HDM allergy. Immunogenicity of H1sD2 and D2 were analyzed in Balb/c mice. Cytokine profile was analyzed by ELISA after stimulation of mouse spleen cells with H1sD2 and D2. Leukocyte population abundance of cells isolated from spleen and lymph node was assessed by flow cytometry.

KEY FINDINGS

Purified recombinant proteins H1sD2 (42 kDa) and D2 (15 kDa) revealed well defined secondary structures, and preserved IgE reactive epitopes. Analysis of supernatants of mouse spleen cells after stimulation with H1sD2 and D2, revealed a qualitatively different cytokine profile from H1sD2 immunized mouse cells (increase in IL10). CD8+ cells were decreased in the lymph node of D2 immunized mice, whereas H1sD2 immunization led to an increase of CD8+ cells in both the lymph node and the spleen.

SIGNIFICANCE

H1sD2 chimera attenuates Der p 2-inherent Th2 response and directs the immune response toward Th1 and Treg phenotype.

The house dust mite allergen Der p 5 binds lipid ligands and stimulates airway epithelial cells through a TLR2-dependent pathway

BACKGROUND

Protein crystallographic studies suggest that the house dust mite (HDM) allergen Der p 5 potentially interacts with hydrophobic ligands. Der p 5, in association with its ligand(s), might therefore trigger innate immune signalling pathways in the airway epithelium and influence the initiation of the HDM-allergic response.

OBJECTIVE

We investigated the lipid binding propensities of recombinant (r)Der p 5 and characterized the signalling pathways triggered by the allergen in airway epithelial cells.

METHODS

rDer p 5 was produced in Pichia pastoris and characterized by mass spectrometry, multi-angle light scattering and circular dichroism. Its interactions with hydrophobic ligands were investigated in fluorescence-based lipid binding assays and in-silico docking simulations. Innate immune signalling pathways triggered by rDer p 5 were investigated in airway epithelial cell activation assays in vitro.

RESULTS

Biophysical analysis showed that rDer p 5 was monomeric and adopted a similar α-helix-rich fold at both physiological and acidic pH. Spectrofluorimetry experiments showed that rDer p 5 is able to selectively bind lipid ligands, but only under mild acidic pH conditions. Computer-based docking simulations identified potential binding sites for these ligands. This allergen, with putatively associated lipid(s), triggered the production of IL-8 in respiratory epithelial cells through a TLR2-, NF-kB- and MAPK-dependent signalling pathway.

CONCLUSIONS AND CLINICAL RELEVANCE

Despite the fact that Der p 5 represents a HDM allergen of intermediate prevalence, our findings regarding its lipid binding and activation of TLR2 indicate that it could participate in the initiation of the HDM-allergic state.

Roles of airway smooth muscle dysfunction in chronic obstructive pulmonary disease

The airway smooth muscle (ASM) plays an indispensable role in airway structure and function. Dysfunction in ASM plays a central role in the pathogenesis of chronic obstructive pulmonary disease (COPD) and contributes to alterations of contractility, inflammatory response, immunoreaction, phenotype, quantity, and size of airways. ASM makes a key contribution in COPD by various mechanisms including altered contractility and relaxation induce by [Ca²⁺]_i, cell proliferation and hypertrophy, production and modulation of extracellular cytokines, and release of pro-and-anti-inflammatory mediators. Multiple dysfunctions of ASM contribute to modulating airway responses to stimuli, remodeling, and fibrosis, as well as influence the compliance of lungs. The present review highlights regulatory roles of multiple factors in the development of ASM dysfunction in COPD, aims to understand the regulatory mechanism by which ASM dysfunctions are initiated, and explores the clinical significance of ASM on alterations of airway structure and function in COPD and development of novel therapeutic strategies for COPD.

Innate Immunity Induced by the Major Allergen Alt a 1 From the Fungus Alternaria Is Dependent Upon Toll-Like Receptors 2/4 in Human Lung Epithelial Cells

Allergens are molecules that elicit a hypersensitive inflammatory response in sensitized individuals and are derived from a variety of sources. Alt a 1 is the most clinically important secreted allergen of the ubiquitous fungus, Alternaria. It has been shown to be a major allergen causing IgE-mediated allergic response in the vast majority of Alternaria-sensitized individuals. However, no studies have been conducted in regards to the innate immune eliciting activities of this clinically relevant protein. In this study, recombinant Alt a 1 was produced, purified, labeled, and incubated with BEAS-2B, NHBE, and DHBE human lung epithelial cells. Alt a 1 elicited strong induction of IL-8, MCP-1, and Gro-a/b/g. Using gene-specific siRNAs, blocking antibodies, and chemical inhibitors such as LPS-RS, it was determined that Alt a 1-induced immune responses were dependent upon toll-like receptors (TLRs) 2 and 4, and the adaptor proteins MYD88 and TIRAP. Studies utilizing human embryonic kidney cells engineered to express single receptors on the cell surface such as TLRs, further confirmed that Alt a 1-induced innate immunity is dependent upon TLR4 and to a lesser extent TLR2.

Effects of the Th2-dominant milieu on allergic responses in Der f 1-activated mouse basophils and mast cells

Although basophils and mast cells share similar phenotypic and functional properties, little is known about the difference in the initial Th2 immune responses of these cells following exposure to proteolytic allergens. Here, we investigated the mechanisms of Th2-mediated immune responses in mouse bone marrow-derived basophils (BMBs) and mast cells (BMMCs) via stimulation with the cysteine protease allergen Der f 1. Our results showed that Th2 cytokines were induced from BMBs by active recombinant Der f 1 (rDer f 1 independently with Toll-like receptor (TLR) 2 and TLR4. Although both BMBs and BMMCs expressed protease-activated receptors on their surfaces, PAR expression following exposure to rDer f 1 was altered only in basophils. G protein-coupled receptors in basophils were found to be associated with interleukin (IL)-4 and IL-13 production from BMBs upon Der f 1 treatment. Secretion of Th2 cytokines from rDer f 1-treated basophils was mediated by G protein βγ and phosphatidylinositol 3-kinase γ through the extracellular signal-regulated kinase and c-Jun N-terminal kinase pathways. These findings provide insights into the roles of cysteine proteases in Th2 immune responses, such as allergic diseases, and improve our understanding of the mechanisms of Th2 cytokine production.

Heparinoid suppresses Der p-induced IL-1β production by inhibiting ERK and p38 MAPK pathways in keratinocytes

Epidermal keratinocytes initiate skin inflammation by activating immune cells. The skin barrier is disrupted in atopic dermatitis (AD) and epidermal keratinocytes can be exposed to environmental stimuli, such as house dust mite (HDM) allergens. We showed previously that HDM allergens activate the NLRP3 inflammasome of keratinocytes, thereby releasing pro-inflammatory cytokines. Heparinoid is an effective moisturizer for atopic dry skin. However, a recent report showed that heparinoid treatment can improve inflammation of lichen planus. Therefore, we hypothesized that it acts on epidermal keratinocytes not only as a moisturizer, but also as a suppressant of the triggers of skin inflammation. We found that HDM allergen-induced interleukin (IL)-1β release from keratinocytes was inhibited significantly by heparinoid pretreatment without affecting cell viability. However, heparinoid did not affect caspase-1 release, suggesting that heparinoid did not affect HDM allergen-induced inflammasome activation. Heparinoid treatment not only decreased intracellular levels of pro-IL-1β, but also suppressed IL-1β messenger RNA (mRNA) expression in keratinocytes. Among the intracellular signalling pathways, the activation of extracellular signal-regulated kinase and p38 pathways, which are required for IL-1β expression in keratinocytes, was inhibited by heparinoid treatment. The inhibitory effect of heparinoid on IL-1β mRNA expression was also confirmed with living skin equivalents. Our results demonstrated that heparinoid suppresses the initiation of keratinocyte-mediated skin inflammation.

The Blomia tropicalis allergen Blo t 7 stimulates innate immune signalling pathways through TLR2

BACKGROUND

Although the house dust mite species Blomia tropicalis is a leading cause of allergic diseases in tropical and subtropical regions, the identification and characterization of the allergenic proteins remain incomplete.

OBJECTIVE

We aimed to characterize a recombinant form of Blo t 7 (rBlo t 7) in terms of IgE reactivity, lipid-binding activity and ability to stimulate innate immunity.

METHODS

The mature Blo t 7 cDNA was cloned by PCR methods for the expression of a secreted form of the allergen in P. pastoris. The IgE reactivity to purified rBlo t 7 as well as the potential cross-reactivity with Der p 7 was determined by ELISA. The lipid-binding capacity of rBlo t 7 was assayed using fluorescent lipid probes. The stimulation of TLR2 signalling pathway by rBlo t 7 was examined in cell activation and reporter assays.

RESULTS

The amplified mature Blo t 7 cDNA revealed the presence of a 60 base pair insertion compared with the reference sequence registered in the GenBank database. Multiple protein sequence alignments of group 7 mite allergens confirmed that this longer deduced amino acid sequence was the authentic Blo t 7 polypeptide chain. Analysis of IgE reactivity can classify rBlo t 7 as an intermediate B. tropicalis allergen which displayed weak cross-reactivity with Der p 7. Purified rBlo t 7 was shown to bind selectively the naturally fluorescent lipid probe cis-parinaric (cPNA) with a dissociation constant of 2 μmol/L. The group 7 Blomia allergen stimulated the TLR2-, NF-kB- and MAPK-dependent production of IL-8 and GM-CSF in respiratory epithelial cells.

CONCLUSIONS & CLINICAL RELEVANCE

Through its propensity to transport fatty acids/lipids and to stimulate TLR2 signalling pathways in airway epithelial cells, Blo t 7 can represent a key allergen for the initiation of the B. tropicalis-induced airway inflammation.

Toll-Like Receptor 4 Is Essential for the Expression of Sphingosine-1-Phosphate-Dependent Asthma-Like Disease in Mice

Sphingosine-1-phosphate (S1P) levels significantly increase in bronchoalveolar lavage (BAL) of asthmatic patients following segmental allergen challenge and this increase well correlates with pulmonary inflammation. Epidemiological, genetic, clinical, and experimental data indicate a potential for the toll-like receptor 4 (TLR4) to initiate and exacerbate allergic airway diseases. The aim of this study was to evaluate the contribution of TLR4 in S1P-dependent asthma-like disease in mice. BALB/c or TLR4 defective (C3H/HeJ) mice received S1P (10 ng/mouse), LPS (0.1 μg/mouse) or S1P + LPS. Furthermore, S1P-treated BALB/c mice were injected with the purified rabbit anti-TLR4 antibody (10 μg/mouse). S1P administration induced airway hyperreactivity and pulmonary inflammation associated to an increase in the percentage of dendritic cells (DCs) and macrophages into the lung of BALB/c mice. These effects were coupled to a reduction of DCs in the mediastinic lymph node. All these S1P-mediated effects were absent in TLR4 defective mice or reversed by treatment with a purified rabbit anti-TLR4 antibody. Confocal analysis of pulmonary sections showed a significant increase in TLR4⁺ cells and a similar presence of S1P₁ and TLR4 following S1P challenge. Accordingly, the immunoprecipitation evidenced an increased S1P₁/TLR4 interaction. In conclusion, our findings suggest that a functional interaction between S1P₁ and TLR4 leads to an enhanced allergic inflammatory response. Thus, S1P pathway contributes to the sentinel role played by innate immunity providing new targets for prevention and treatment of allergic airway diseases.

House dust mite allergy: Its innate immune response and immunotherapy

Over the past few decades, allergic diseases have become increasingly prevalent worldwide. House dust mite (HDM) is the most important domestic source for allergic diseases such as allergic rhinitis, asthma and atopic dermatitis. Dermatophagoides pteronyssinus (Der p) is the major environmental allergen in southeast Asia because of the humid and warm environment is suitable for its growth. In the recent year, role of HDM allergen in allergic inflammation through innate immune system has been well studied. Toll-like receptors (TLRs), protease-activated receptors (PARs) and DC-SIGN could be activated by different HDM major allergens and proinflammatory cytokines also be upregulated. Treatment efficacy for HDM allergy is unsatisfied to the patients and the medication is limited. Immunotherapy provided an alternative option for treating HDM allergy through targeted to the mechanisms of allergic reaction and represented a long-term symptoms relief. Gene specific immunotherapy was currently being developed and it could decrease allergic inflammation and improve the efficacy of treatment. In this report, we reviewed recent studies about the role of HDM allergy in innate immune system and its immunotherapy. Understanding the HDM allergen induced signal transduction pathway and developed allergen specific immunotherapy could help physicians to create precise diagnosis and solve unmet need in HDM allergy.

An alternative biomarker-based approach for the prediction of proteins known to sensitize the respiratory tract

Many natural and industrial proteins are known to have properties that can result in type I hypersensitivity, however, to date, no validated test system exists that can predict the sensitizing potential of these allergens. Thus, the objective of this study was to develop a protocol based on the myeloid cell-based Genomic Allergen Rapid Detection (GARD) assay that can be used to assess and predict the capacity of protein allergens known to induce sensitization in the respiratory tract. Cellular responses induced by eight selected proteins were assessed using transcriptional profiling, flow cytometry and multiplex cytokine analysis. 391 potential biomarkers were identified as a predictive signature and a series of cross-validations supported the validity of the model. These results together with biological pathway analysis of the transcriptomic data indicate that the investigated cell system is able to capture relevant events linked to type I hypersensitization.

Aeroallergen Der p 2 promotes motility of human non-small cell lung cancer cells via toll-like receptor-mediated up-regulation of urokinase-type plasminogen activator and integrin/focal adhesion kinase signaling

House dust mite (HDM) allergens are one of the major causes leading to respiratory hypersensitiveness and airway remodeling. Here we hypothesized that a major HDM allergen Der p 2 could increase cell motility and invasiveness of non-small cell lung cancer (NSCLC) cells. Our results showed that low dose (1 and 3 μg/mL) recombinant Der p 2 protein (DP2) enhanced the migration and invasiveness of human NSCLC cell A549, H1299 and CL1-5, but nonsignificantly altered their growth. Further investigation revealed that integrin αV level was increased and its downstream signaling including focal adhesion kinase (FAK) and paxillin were activated in A549 cells exposed to DP2. In parallel, DP2 also activated the FAK-associated signaling effectors such as Src, phosphatidyl inositol 3-kinase (PI3K), AKT, p38 mitogen-activated protein kinase (P38), extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK). Our findings also revealed that DP2 increased expression level of urokinase type plasminogen-activated kinase (uPA) and uPA receptor (uPAR), and subsequently enhanced the binding of uPAR to integrin αV. Moreover, the involvement of toll-like receptor 2/4 (TLR2/4)-triggered ERK1/2 activation in the increased expression of uPA and uPAR was also demonstrated. Collectively, these findings indicate that DP2 can enhance cell motility and invasiveness of NSCLC cells, attributing to TLR2/4-ERK1/2 activation, increased uPA and uPAR expression, enhanced binding of uPAR to integrin αV, and the consequent FAK signaling cascades. Thus, we suggest that DP2 may exacerbate NSCLC via promoting metastatic ability of carcinoma cell.

The minor house dust mite allergen Der p 13 is a fatty acid-binding protein and an activator of a TLR2-mediated innate immune response

BACKGROUND

The house dust mite (HDM) allergen Der p 13 could be a lipid-binding protein able to activate key innate signaling pathways in the initiation of the allergic response. We investigated the IgE reactivity of recombinant Der p 13 (rDer p 13), its lipid-binding activities, and its capacity to stimulate airway epithelium cells.

METHODS

Purified rDer p 13 was characterized by mass spectrometry, circular dichroism, fluorescence-based lipid-binding assays, and in silico structural prediction. IgE-binding activity and allergenic potential of Der p 13 were examined by ELISA, basophil degranulation assays, and in vitro airway epithelial cell activation assays.

RESULTS

Protein modeling and biophysical analysis indicated that Der p 13 adopts a β-barrel structure with a predominately apolar pocket representing a potential binding site for hydrophobic ligands. Fluorescent lipid-binding assays confirmed that the protein is highly selective for ligands and that it binds a fatty acid with a dissociation constant typical of lipid transporter proteins. The low IgE-binding frequency (7%, n = 224) in Thai HDM-allergic patients as well as the limited propensity to activate basophil degranulation classifies Der p 13 as a minor HDM allergen. Nevertheless, the protein with its presumptively associated lipid(s) triggered the production of IL-8 and GM-CSF in respiratory epithelial cells through a TLR2-, MyD88-, NF-kB-, and MAPK-dependent signaling pathway.

CONCLUSIONS

Although a minor allergen, Der p 13 may, through its lipid-binding capacity, play a role in the initiation of the HDM-allergic response through TLR2 activation.

Allergens and Activation of the Toll-Like Receptor Response

Pattern recognition receptors (PRRs) provide a crucial function in the detection of exogenous and endogenous danger signals. The Toll-like receptors (TLRs) were the first family of PRRs to be discovered and have been extensively studied since. Whilst TLRs remain the best characterized family of PRRs there is still much to be learnt about their mode of activation and the mechanisms of signal transduction they employ. Much of our understanding of these processes has been gathered through the use of cell based signaling assays utilizing specific gene-reporters or cytokine secretion based readouts. More recently it has become apparent that the repertoire of ligands recognized by these receptors may be wider than originally assumed and that their activation may be sensitized, or at least modulated by the presence of common household allergens such as the cat dander protein Fel d 1, or the house dust mite allergen Der p 2. In this chapter we provide an overview of the cell culture and stimulation processes required to study TLR signaling in HEK293 based assays and in bone marrow-derived macrophages.

Aeroallergen Der p 2 induces apoptosis of bronchial epithelial BEAS-2B cells via activation of both intrinsic and extrinsic pathway

BACKGROUND

Excessive apoptosis of airway epithelium is reported to induce airway remodeling and inhibited airway epithelium repair is highly associated with development of asthma and chronic obstructive pulmonary disease. Der p 2 is a major allergen derived from Dermatophagoides pteronyssinus and commonly causes airway hypersensitiveness and asthma; however, the connection between Der p 2 and epithelial apoptosis remains unclear. This study was aimed to explore whether Der p 2 induces apoptosis of airway epithelial cells and the underlying mechanisms.

RESULTS

Our results showed that recombinant Der p 2 (rDP2) inhibited cell growth and induced apoptosis of human bronchial epithelial cell BEAS-2B. Further investigation revealed that rDP2 increased intracellular reactive oxygen species, level of cytosolic cytochrome c and cleavage of caspase-9 and caspase-3. rDP2 also induced activation of p38 mitogen-activated protein kinase (P38) and c-Jun N-terminal kinase (JNK), and triggered proapoptotic signals including decrease of Bcl-2, increase of Bax and Bak, and upregulation of Fas and Fas ligand. In parallel, rDP2 inhibited glycogen synthase kinase 3beta and consequently enhanced degradation of cellular (FADD-like IL-1β-converting enzyme)-inhibitory protein (c-FLIP). Involvement of toll-like receptor (TLR)2 in rDP2-induced apoptosis was also demonstrated using specific small inhibitory RNA.

CONCLUSIONS

Our findings indicate that rDP2 suppresses cell growth and trigger apoptosis of BEAS-2B cells, which may attribute to induction of both intrinsic and extrinsic pathway via TLR2 and P38/JNK signaling and c-FLIP degradation. It suggests that Der p 2 may aggravate respiratory disorders through enhancement of apoptosis and the consequent airway injury.

TLR3 activation increases chemokine expression in human fetal airway smooth muscle cells

Viral infections, such as respiratory syncytial virus and rhinovirus, adversely affect neonatal and pediatric populations, resulting in significant lung morbidity, including acute asthma exacerbation. Studies in adults have demonstrated that human airway smooth muscle (ASM) cells modulate inflammation through their ability to secrete inflammatory cytokines and chemokines. The role of ASM in the developing airway during infection remains undefined. In our study, we used human fetal ASM cells as an in vitro model to examine the effect of Toll-like receptor (TLR) agonists on chemokine secretion. We found that fetal ASM express multiple TLRs, including TLR3 and TLR4, which are implicated in the pathogenesis of respiratory syncytial virus and rhinovirus infection. Cells were treated with TLR agonists, polyinosinic-polycytidylic acid [poly(I:C)] (TLR3 agonist), lipopolysaccharide (TLR4 agonist), or R848 (TLR7/8 agonist), and IL-8 and chemokine (C-C motif) ligand 5 (CCL5) secretion were evaluated. Interestingly, poly(I:C), but neither lipopolysaccharide nor R848, increased IL-8 and chemokine (C-C motif) ligand 5 secretion. Examination of signaling pathways suggested that the poly(I:C) effects in fetal ASM involve TLR and ERK signaling, in addition to another major inflammatory pathway, NF-κB. Moreover, there are variations between fetal and adult ASM with respect to poly(I:C) effects on signaling pathways. Pharmacological inhibition suggested that ERK pathways mediate poly(I:C) effects. Overall, our data show that poly(I:C) initiates activation of proinflammatory pathways in developing ASM, which may contribute to immune responses to infection and exacerbation of asthma.

Enhanced Allergic Inflammation of Der p 2 Affected by Polymorphisms of MD-2 Promoter

Purpose

Myeloid differentiation-2 (MD-2) has been associated with endotoxin and inflammatory disorders because it can recognize lipopolysaccharide (LPS) binding and attenuate Toll-like receptor 4 (TLR4)-mediated signaling. However, its role in allergic inflammation has yet to be clarified. We examined whether single nucleotide polymorphisms (SNPs) in MD-2 promoter can affect MD-2 expression and aimed to clarify the relationship between Der p 2 allergy and SNPs of MD-2 promoter.

Methods

The function of SNPs of MD-2 promoter and the effects of cytokines and immunoglobulin on the secretion and mRNA expression were investigated in 73 allergic subjects with different MD-2 gene promoter variants. Peripheral blood mononuclear cells were cultured with or without LPS in the presence of Dermatophagoides pteronyssinus group 2 allergen (Der p 2), followed by mRNA extraction and cytokine expression analysis. The culture supernatants were collected for cytokine measurement.

Results

Patients with the MD-2 promoter SNPs (rs1809441/rs1809442) had increased mRNA expressions of MD-2, ε heavy chain of IgE (Cε), and interleukin (IL)-8; however, only MD-2 and IL-8 were further up-regulated after Der p 2 stimulation. Patients with SNPs of MD-2 promoter tended to have high levels of IL-1β, IL-6, IL-8, IL-10, and tumor necrosis factor (TNF)-α after Der p 2 and LPS stimulation. Increased secretions of IL-6, IL-8, and IL-10 were found to be up-regulated by Der p 2 stimulation, and an increased secretion of IFN-γ and decreased secretion of IL-4 were noted after LPS stimulation.

Conclusions

The high levels of proinflammatory cytokines secreted by Der p 2 were predetermined by MD-2 promoter SNPs (rs1809441/rs1809442). Through cytokine secretion by Der p 2 and LPS, these SNPs may serve as an indicator of the pathological phenotype of Der p 2-induced allergic inflammation.

Airway epithelium interactions with aeroallergens: role of secreted cytokines and chemokines in innate immunity

Airway epithelial cells are the first line of defense against the constituents of the inhaled air, which include allergens, pathogens, pollutants, and toxic compounds. The epithelium not only prevents the penetration of these foreign substances into the interstitium, but also senses their presence and informs the organism’s immune system of the impending assault. The epithelium accomplishes the latter through the release of inflammatory cytokines and chemokines that recruit and activate innate immune cells at the site of assault. These epithelial responses aim to eliminate the inhaled foreign substances and minimize their detrimental effects to the organism. Quite frequently, however, the innate immune responses of the epithelium to inhaled substances lead to chronic and high level release of pro-inflammatory mediators that may mediate the lung pathology seen in asthma. The interactions of airway epithelial cells with allergens will be discussed with particular focus on interactions-mediated epithelial release of cytokines and chemokines and their role in the immune response. As pollutants are other major constituents of inhaled air, we will also discuss how pollutants may alter the responses of airway epithelial cells to allergens.

Der p2 Internalization by Epithelium Synergistically Augments Toll-like Receptor-Mediated Proinflammatory Signaling

Purpose

House-dust-mite (HDM) major allergen Der p2 shares homology and function with Toll-like receptor (TLR) signaling protein myeloid differentiation-2 (MD2) and may lead to airway inflammation. Should Der p2 be internalized by human airway epithelium, it has the theoretical propensity to potentiate epithelium activation. This study aimed to demonstrate the internalization of Der p2 by airway epithelium and to investigate the effects of Der p2 on MD2 expression and epithelium activation.

Methods

Internalization of recombinant, enhanced green fluorescent protein-labelled Der p2 (rDer p2-EGFP) into human airway epithelium (BEAS-2B) was tracked by laser confocal microscopy and confirmed by immunoblotting. Reverse-transcription polymerase chain reaction (RT-PCR), immunoblotting, and immunohistochemical staining were used to determine the effect of Der p2 on MD2 expression in vitro and ex vivo. Expression of messenger RNA (mRNA) encoding receptors/cytokines was measured by RT-PCR. Secretion of interleukin-6/interleukin-8 (IL-6/IL-8) was measured by enzyme-linked immunosorbent assay (ELISA).

Results

Internalization of Der p2 by BEAS-2B was confirmed by confocal microscopy and immunoblotting using rDer p2-EGFP and rDer p2, respectively. Expression of MD2 protein was increased in BEAS-2B and human nasal polyp airway epithelium cultured with rDer p2. Recombinant Der p2-cultured BEAS-2B caused little spontaneous IL-6/IL-8 secretion but significantly augmented by TLR ligand LPS. IL-6 secretion was up-regulated after MD2 transfection. Internalization of Der p2 was reduced by TLR2 RNA knockdown. Dexamethasone, calcitriol, anti-MD2/anti-TLR2 antibodies, and signalling inhibitors significantly reduced LPS+Der p2-induced IL-6/IL-8 secretion.

Conclusions

Human airway epithelium may internalize Der p2, which potentiates the response to environmental proinflammatory stimuli through MD2 and TLRs. This study highlights a novel mechanism and alleviates IL-6/IL-8 secretion in mite-induced airway inflammation.

Mode of dendritic cell activation: the decisive hand in Th2/Th17 cell differentiation. Implications in asthma severity?

Asthma is a heterogeneous chronic inflammatory disease of the airways, with reversible airflow limitations and airway remodeling. The classification of asthma phenotypes was initially based on different combinations of clinical symptoms, but they are now unfolding to link biology to phenotype. As such, patients can suffer from a predominant eosinophilic, neutrophilic or even mixed eosinophilic/neutrophilic inflammatory response. In adult asthma patients, eosinophilic inflammation is usually seen in mild-to-moderate disease and neutrophilic inflammation in more severe disease. The underlying T cell response is predominated by T helper (Th) 2, Th17, or a mixed Th2/Th17 cell immune response. Dendritic cells (DCs) are "professional" antigen presenting cells (APCs), since their principal function is to present antigens and induce a primary immune response in resting naive T cells. DCs also drive the differentiation into distinctive Th subsets. The expression of co-stimulatory molecules and cytokines by DCs and surrounding cells determines the outcome of Th cell differentiation. The nature of DC activation will determine the expression of specific co-stimulatory molecules and cytokines, specifically needed for induction of the different Th cell programs. Thus DC activation is crucial for the subsequent effector Th immune responses. In this review, we will discuss underlying mechanisms that initiate DC activation in favor of Th2 differentiation versus Th1/Th17 and Th17 differentiation in the development of mild versus moderate to severe asthma.

Epicutaneously applied Der p 2 induces a strong TH 2-biased antibody response in C57BL/6 mice, independent of functional TLR4

Background

The major house dust mite allergen Der p 2 is a structural and functional homologue of MD-2 within the TLR4–CD14–MD-2 complex. An asthma mouse model in TLR4-deficient mice recently suggested that the allergic immune response against Der p 2 is solely dependent on TLR4 signaling. We investigated whether similar mechanisms are important for Der p 2 sensitization via the skin.

Methods

In an epicutaneous sensitization model, the response to recombinant Der p 2 in combination with or without lipopolysaccharide (LPS) was compared between C57BL/6 WT and TLR4-deficient mice. We further analyzed possible adjuvant function of exogenous cysteine proteases.

Results

Sensitization with rDer p 2 induced similar levels of allergen-specific IgG1 and IgE antibodies in both mouse strains. LPS increased the systemic (antibody levels, cytokine release by restimulated splenocytes) and local (infiltration of immune cells into the skin) Th2 immune responses, which against our expectations were stronger in the absence of functional TLR4 expression. Barrier disruption by papain, a protease with structural homology to Der p 1, did not enhance the sensitization capacity of rDer p 2. However, the presence of LPS increased the stability of rDer p 2 against the protease.

Conclusion

Our data suggest that rDer p 2 alone can cause a strong T_H2-biased response via the skin being enhanced in the presence of LPS. This response is not reliant on functional TLR4, but vice versa TLR4 expression rather protects against epicutaneous sensitization to house dust mite allergen Der p 2.

Characterization of the house dust mite allergen Der p 21 produced in Pichia pastoris

BACKGROUND

The development of recombinant house dust mite (HDM) allergens opened the way for the in-depth characterization of these molecules but also provided new opportunities to refine the diagnostic procedures of HDM allergy as well as the allergen-specific immunotherapy through tailor-made treatments.

OBJECTIVE

In the present study, the HDM allergen Der p 21 was expressed in Pichia pastoris under a secreted form. The physico-chemical as well as the allergenic characterizations of recombinant Der p 21 (rDer p 21) were performed.

METHODS

Purified rDer p 21, secreted from recombinant P. pastoris was characterized by CD and MS analysis and the frequency of IgE reactivity was determined by ELISA using 96 sera of HDM-allergic patients from Bangkok. The direct airway epithelial cell activation by rDer p 21 was also evaluated.

RESULTS

rDer p 21 was highly expressed under a secreted form in P. pastoris. The physico-chemical characterization of purified rDer p 21 showed that the allergen displayed appropriate α-helix secondary structure content although a two amino acids truncation at the N-terminus of the protein was evidenced by MS. The prevalence of IgE reactivity to rDer p 21 reached 25% in the cohort of the HDM-allergic patients. rDer p 21 could trigger IL-8 production in airway epithelial cells through TLR2-dependent signaling.

CONCLUSION

Properly folded rDer p 21 produced in P. pastoris is appropriate for HDM allergy diagnosis as well for future recombinant allergen-based specific immunotherapy.

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.

Comparison of the interleukin-1β-inducing potency of allergenic spores from higher fungi (basidiomycetes) in a cryopreserved human whole blood system

BACKGROUND

Spores from basidiomycete fungi (basidiospores) are highly prevalent in the atmosphere of urban and rural settings. Studies have confirmed their potential to affect human health as allergens. Less is known about their potential to serve as stimuli of the innate immune system and induce proinflammatory reactions.

METHODS

In this study, we evaluated the proinflammatory potential of spores from 11 allergenic basidiomycete species (gilled: Pleurotus ostreatus,Oudemansiella radicata,Armillaria tabescens,Coprinus micaceus,Pluteus cervinus, and Chlorophyllum molybdites, and nongilled: Pisolithus arhizus,Merulius tremellosus,Calvatia cyathiformis,Lycoperdon pyriforme, andBoletus bicolor) based on their potency to induce the release of the proinflammatory cytokine interleukin (IL)-1β in a cryopreserved human whole blood system. In addition, the roles of morphological features of the spores (surface area, shape, and pigmentation) were examined for their role in the IL-1β-including potency of spores. Peripheral blood from healthy volunteers was collected, pooled, and cryopreserved. After stimulating the cryopreserved pooled blood with 10(6) to 10(3) basidiospores/ml, the concentration of IL-1β in culture supernatants was determined with ELISA.

RESULTS

Basidiospores manifested concentration-dependent IL-1β-inducing potency, which was more marked among basidiospores from gilled basidiomycetes. At higher concentrations of basidiospores, the IL-1β-inducing potency could be differentiated in the cryopreserved human whole blood system. Morphological features did not correlate with the IL-1β-inducing potency of the basidiospores, suggesting that nonmorphological properties modulate the IL-1β-inducing potency.

CONCLUSION

Our data provide evidence of the proinflammatory potential of basidiospores, and the utility of cryopreserved human whole blood as a human-based in vitro system to study the immune reactivity of allergenic basidiospores.

Allergen recognition by innate immune cells: critical role of dendritic and epithelial cells

Allergy is an exacerbated response of the immune system against non-self-proteins called allergens and is typically characterized by biased type-2 T helper cell and deleterious IgE mediated immune responses. The allergic cascade starts with the recognition of allergens by antigen presenting cells, mainly dendritic cells (DCs), leading to Th2 polarization, switching to IgE production by B cells, culminating in mast cell sensitization and triggering. DCs have been demonstrated to play a crucial role in orchestrating allergic diseases. Using different C-type lectin receptors DCs are able to recognize and internalize a number of allergens from diverse sources leading to sensitization. Furthermore, there is increasing evidence highlighting the role of epithelial cells in triggering and modulating immune responses to allergens. As well as providing a physical barrier, epithelial cells can interact with allergens and influence DCs behavior through the release of a number of Th2 promoting cytokines. In this review we will summarize current understanding of how allergens are recognized by DCs and epithelial cells and what are the consequences of such interaction in the context of allergic sensitization and downstream events leading to allergic inflammation. Better understanding of the molecular mechanisms of allergen recognition and associated signaling pathways could enable developing more effective therapeutic strategies that target the initial steps of allergic sensitization hence hindering development or progression of allergic diseases.

Innate immune response of alveolar macrophage to house dust mite allergen is mediated through TLR2/-4 co-activation

House dust mite, Dermatophagoides pteronyssinus (Der p), is one of the major allergens responsible for allergic asthma. However, the putative receptors involved in the signalization of Der p to the innate immune cells are still poorly defined as well as the impact of their activation on the outcome of the allergen-induced cell response. We previously reported that the HDM activation of mouse alveolar macrophages (AM) involves the TLR4/CD14 cell surface receptor complex. Here using a TLR ligand screening essay, we demonstrate that HDM protein extract engages the TLR2, in addition to the TLR4, in engineered TLR-transfected HEK cells but also in the MH-S mouse alveolar macrophage cell line model. Moreover we found that the concomitant recruitment of the MH-S cell’s TLR2 and TLR4 receptors by the HDM extract activates the MyD88-dependent signaling pathway and leads to the secretion of the NF-κB regulated pro-inflammatory factors NO and TNF-α. However unlike with the canonical TLR4 ligand (i.e. the bacterial LPS) mobilization of TLR4 by the HDM extract induces a reduced production of the IL-12 pro-inflammatory cytokine and fails to trigger the expression of the T-bet transcription factor. Finally we demonstrated that HDM extract down-regulates LPS induced IL-12 and T-bet expression through a TLR2 dependent mechanism. Therefore, we propose that the simultaneous engagement of the TLR2 and TLR4 receptors by the HDM extract results in a cross regulated original activation pattern of the AM which may contribute to the Th2 polarization of the allergen-induced immune response. The deciphering of these cross-regulation networks is of prime importance to open the way for original therapeutic strategies taking advantage of these receptors and their associated signaling pathways to treat allergic asthma.

House dust mite-induced calcium signaling instigates epithelial barrier dysfunction and CCL20 production

BACKGROUND

House dust mite (HDM) affects the immunological and physical barrier function of airway epithelium, leading to allergic sensitization, airway remodeling, and eosinophilic inflammation in mouse models, although the mechanisms are still largely unknown.

OBJECTIVE

Given the implications for adenosine triphosphate (ATP)-dependent Ca(2+) signaling in allergic sensitization in mice, we sought to determine the role of intracellular Ca(2+) concentration ([Ca(2+)](i)) in HDM-induced barrier dysfunction and pro-inflammatory activity of bronchial epithelium.

METHODS

We investigated the effect of HDM on accumulation of [Ca(2+)](i) levels, barrier function, and CCL20 release in human bronchial epithelial 16HBE cells and primary bronchial epithelial cells (PBECs) from healthy subjects and asthma patients. Involvement of ATP-dependent activation of purinergic receptors and downstream Ca(2+) influx was studied, using the ATP hydrolyzing agent apyrase, the purinergic receptor agonist PPADS, the calcium chelator BAPTA-AM, and calpain inhibitors.

RESULTS

Asthma PBECs were more susceptible to HDM-induced barrier dysfunction, CCL20 secretion, and Ca(2+) influx than healthy PBECs. Furthermore, we show that the HDM-induced increase in CCL20 in PBECs and 16HBE cells and the HDM-induced barrier dysfunction in 16HBE cells are dependent on [Ca(2+)](i) accumulation. Additionally, we demonstrate that [Ca(2+)](i) accumulation is initiated partly through the activation of purinergic receptors, which contributes to HDM-induced epithelial barrier dysfunction by disruption of cell-cell contacts, but not CCL20 secretion.

CONCLUSION

Our data show for the first time that Ca(2+) signaling plays a crucial role in barrier dysfunction and the pro-inflammatory response of bronchial epithelium upon HDM exposure and may thus have important implications for the development of allergic asthma.

Immunology of atopic eczema: overcoming the Th1/Th2 paradigm

Atopic eczema (AE) is a challenge for modern medicine, because it is prevalent, severely affects quality of life of patients and their families, and causes high socioeconomic costs. The pathogenesis of AE is complex. While initial studies suggested a Th2 deviation as primary reason for the disease, numerous studies addressed a genetically predetermined impaired epidermal barrier as leading cause in a subgroup of patients. Recently, immune changes beyond the initial Th2 concept were defined in AE, with a role for specialized dendritic cells as well as newly identified T helper cell subsets such as Th17 and Th22 cells. Furthermore, trigger factors are expanded beyond classical Th2 allergens such as pollen or house dust mites to microbial products as well as self-antigens. This review pieces together our current understanding of immune as well as barrier abnormalities into the pathogenesis mosaic of AE.

Allergens as immunomodulatory proteins: the cat dander protein Fel d 1 enhances TLR activation by lipid ligands

Allergic responses can be triggered by structurally diverse allergens. Most allergens are proteins, yet extensive research has not revealed how they initiate the allergic response and why the myriad of other inhaled proteins do not. Among these allergens, the cat secretoglobulin protein Fel d 1 is a major allergen and is responsible for severe allergic responses. In this study, we show that similar to the mite dust allergen Der p 2, Fel d 1 substantially enhances signaling through the innate receptors TLR4 and TLR2. In contrast to Der p 2, however, Fel d 1 does not act by mimicking the TLR4 coreceptor MD2 and is not able to bind stably to the TLR4/MD2 complex in vitro. Fel d 1 does, however, bind to the TLR4 agonist LPS, suggesting that a lipid transfer mechanism may be involved in the Fel d 1 enhancement of TLR signaling. We also show that the dog allergen Can f 6, a member of a distinct class of lipocalin allergens, has very similar properties to Fel d 1. We propose that Fel d 1 and Can f 6 belong to a group of allergen immunomodulatory proteins that enhance innate immune signaling and promote airway hypersensitivity reactions in diseases such as asthma.

Innate immune responses in house dust mite allergy

Sensitizations to house dust mites (HDM) trigger strong exacerbated allergen-induced inflammation of the skin and airways mucosa from atopic subjects resulting in atopic dermatitis as well as allergic rhinitis and asthma. Initially, the Th2-biased HDM allergic response was considered to be mediated only by allergen B- and T-cell epitopes to promote allergen-specific IgE production as well as IL-4, IL-5, and IL-13 to recruit inflammatory cells. But this general molecular model of HDM allergenicity must be revisited as a growing literature suggests that stimulations of innate immune activation pathways by HDM allergens offer new answers to the following question: what makes an HDM allergen an allergen? Indeed, HDM is a carrier not only for allergenic proteins but also microbial adjuvant compounds, both of which are able to stimulate innate signaling pathways leading to allergy. This paper will describe the multiple ways used by HDM allergens together with microbial compounds to control the initiation of the allergic response through engagement of innate immunity.

The innate immune response in house dust mite-induced allergic inflammation

Hypersensitivity to house dust mite (HDM; Dermatophagoides sp.) allergens is one of the most common allergic responses, affecting up to 85% of asthmatics. Sensitization to indoor allergens is the strongest independent risk factor associated with asthma. Additionally, >50% of children and adolescents with asthma are sensitized to HDM. Although allergen-specific CD4⁺ Th2 cells orchestrate the HDM allergic response through induction of IgE directed toward mite allergens, activation of innate immunity also plays a critical role in HDM-induced allergic inflammation. This review highlights the HDM components that lead to activation of the innate immune response. Activation may due to HDM proteases. Proteases may be recognized by protease-activation receptors (PARs), Toll-like receptors (TLRs), or C-type lectin receptors (CTRs), or act as a molecular mimic for PAMP activation signaling pathways. Understanding the role of mite allergen-induced innate immunity will facilitate the development of therapeutic strategies that exploit innate immunity receptors and associated signaling pathways for the treatment of allergic asthma.

Correlation of Der p 2 T-cell responses with clinical characteristics of children allergic to house dust mite

BACKGROUND

An understanding of the mechanisms responsible for the development and maintenance of allergic inflammation and their clinical implications is needed to develop specific and successful treatment for allergy.

OBJECTIVES

To characterize in vitro T-cell responses to Der p 2, one of the major allergens of house dust mite (HDM), and investigate potential correlations between clinical and laboratory parameters.

METHODS

Forty-two patients monosensitized to HDM and 10 age-matched, healthy children were studied. Dendritic cells pulsed with Der p 2 were used to stimulate autologous CD14(-) cells. Der p 2-specific T-cell activation markers, proliferation, and cytokine production profiles were examined.

RESULTS

Der p 2-specific T-cell activation markers, proliferation, and T(H)2 cytokine production were significantly higher in HDM patients compared with healthy controls. Moreover, a significant correlation between proliferation and T(H)2 cytokine production was observed. Within the allergic group, skin reaction to HDM was significantly stronger in patients with a Der p 2-specific T-cell response. Levels of HDM-specific IgE directly correlated with interleukin 5 and interleukin 13 levels and with skin prick test results and, ultimately, with the patient's family history of allergy. Furthermore, the presence of atopic march correlated with T-cell proliferation.

CONCLUSION

We found that, in HDM patients, Der p 2-specific T(H)2 responses, promoted by autologous dendritic cells in vitro, correlate with clinical parameters.