Integrated innate mechanisms involved in airway allergic inflammation to the serine protease subtilisin

Comparison of high- and low-molecular-weight sensitizing agents causing occupational asthma: an evidence-based insight

INTRODUCTION

The many substances used at the workplace that can cause sensitizer-induced occupational asthma are conventionally categorized into high-molecular-weight (HMW) agents and low-molecular-weight (LMW) agents, implying implicitly that these two categories of agents are associated with distinct phenotypic profiles and pathophysiological mechanisms.

AREAS COVERED

The authors conducted an evidence-based review of available data in order to identify the similarities and differences between HMW and LMW sensitizing agents.

EXPERT OPINION

Compared with LMW agents, HMW agents are associated with a few distinct clinical features (i.e. concomitant work-related rhinitis, incidence of immediate asthmatic reactions and increase in fractional exhaled nitric oxide upon exposure) and risk factors (i.e. atopy and smoking). However, some LMW agents may exhibit 'HMW-like' phenotypic characteristics, indicating that LMW agents are a heterogeneous group of agents and that pooling them into a single group may be misleading. Regardless of the presence of detectable specific IgE antibodies, both HMW and LMW agents are associated with a mixed Th1/Th2 immune response and a predominantly eosinophilic pattern of airway inflammation. Large-scale multicenter studies are needed that use objective diagnostic criteria and assessment of airway inflammatory biomarkers to identify the pathobiological pathways involved in OA caused by the various non-protein agents.

Immune sensing of food allergens promotes avoidance behaviour

In addition to its canonical function of protection from pathogens, the immune system can also alter behaviour1,2. The scope and mechanisms of behavioural modifications by the immune system are not yet well understood. Here, using mouse models of food allergy, we show that allergic sensitization drives antigen-specific avoidance behaviour. Allergen ingestion activates brain areas involved in the response to aversive stimuli, including the nucleus of tractus solitarius, parabrachial nucleus and central amygdala. Allergen avoidance requires immunoglobulin E (IgE) antibodies and mast cells but precedes the development of gut allergic inflammation. The ability of allergen-specific IgE and mast cells to promote avoidance requires cysteinyl leukotrienes and growth and differentiation factor 15. Finally, a comparison of C57BL/6 and BALB/c mouse strains revealed a strong effect of the genetic background on the avoidance behaviour. These findings thus point to antigen-specific behavioural modifications that probably evolved to promote niche selection to avoid unfavourable environments.

Purification and characterization of a serine protease from organic dust and elucidation of its inductive effects on lung inflammatory mediators

Organic dust inhalation is associated with the development of respiratory diseases. Serine protease activities in organic dusts were previously reported to contribute to the induction of lung inflammatory mediators however, the identities of the proteases and the mechanisms by which they induce inflammatory mediators are unknown. The goal of this study was to purify and characterize serine protease(s) from organic dust and elucidate mechanisms by which they induce lung inflammatory mediators. A serine protease was purified from poultry organic dust by benzamidine-agarose affinity chromatography. Mass spectrometry and amino-terminal sequence analysis identified the purified protease as chicken trypsin II-P29. Purified protease induced proinflammatory cytokine levels in Beas2B and NHBE epithelial and THP-1 macrophage cells. Treatment with the purified protease increased cellular and mitochondrial reactive oxygen species (ROS) generation. Induction of inflammatory mediators and ROS were suppressed by serine protease inhibitors and antioxidants. Purified protease activated protein kinase C (PKC), mitogen-activated protein kinase (MAPK)1/3 and MAPK14 signaling, and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and signal transducer and activator of transcription 3 (Stat-3), and chemical inhibitors targeting these pathways suppressed induction of inflammatory mediators. Calcium mobilization studies showed that the purified protease activated protease-activated receptors (PAR) F2R, F2RL1, F2RL2, F2RL3, and F2R and F2RL1 knockdown suppressed the induction of inflammatory mediators. Intranasal instillation of purified protease increased lung chemokine (C-X-C motif) ligand (CXCL)1, interleukin (IL)-6, and tumor necrosis factor (TNF) levels in mice. Our studies have shown that chicken trypsin is a proinflammatory constituent of poultry organic dust, and induces lung inflammatory mediators via increased ROS and PAR activation in a cell signaling pathway involving PKC, MAPK1/3 and MAPK14, and NF-κB and Stat-3.NEW & NOTEWORTHY Inhalation of dust in industrial agricultural operations is linked to the development of lung diseases. Our studies have isolated for the first time a trypsin protease from poultry farm dust and have shown that it stimulates lung inflammation. The protease stimulates the production of oxidants and cell signaling pathways to increase inflammatory mediator production. Targeting trypsin protease in poultry farm environment may be a useful strategy to counter the harmful effects of dust.

Modes of type 2 immune response initiation

Type 2 immunity defends against macro-parasites and can cause allergic diseases. Our understanding of the mechanisms governing the initiation of type 2 immunity is limited, whereas we know more about type 1 immune responses. Type 2 immunity can be triggered by a wide array of inducers that do not share common features and via diverse pathways and mechanisms. To address the complexity of the type 2 initiation pathways, we suggest a framework that conceptualizes different modes of induction of type 2 immunity. We discuss categories of type 2 inducers and their immunogenicity, types of tissue perturbations that are caused by these inducers, sensing strategies for the initiation of Th2 immune responses, and categorization of the signals that are produced in response to type 2 challenges. We describe tissue-specific examples of functional disruption that could lead to type 2 inflammation and propose that different sensing strategies that operate at the tissue level converge on the initiation of type 2 immune responses.

Initiation of type 2 immunity at barrier surfaces

Although seemingly unrelated, parasitic worms, venoms, and allergens all induce a type 2 immune response. The effector functions and clinical features of type 2 immunity are well-defined, but fundamental questions about the initiation of type 2 immunity remain unresolved. How are these enormously diverse type 2 stimuli first detected? How are type 2 helper T cells primed and regulated? And how do mechanisms of type 2 initiation vary across tissues? Here, we review the common themes governing type 2 immune sensing and explore aspects of T cell priming and effector reactivation that make type 2 helper T cells a unique T helper lineage. Throughout the review, we emphasize the importance of non-hematopoietic cells and highlight how the unique anatomy and physiology of each barrier tissue shape mechanisms of type 2 immune initiation.

Immune sensing of food allergens promotes aversive behaviour

In addition to its canonical function in protecting from pathogens, the immune system can also promote behavioural alterations ^1â€"3 . The scope and mechanisms of behavioural modifications by the immune system are not yet well understood. Using a mouse food allergy model, here we show that allergic sensitization drives antigen-specific behavioural aversion. Allergen ingestion activates brain areas involved in the response to aversive stimuli, including the nucleus of tractus solitarius, parabrachial nucleus, and central amygdala. Food aversion requires IgE antibodies and mast cells but precedes the development of gut allergic inflammation. The ability of allergen-specific IgE and mast cells to promote aversion requires leukotrienes and growth and differentiation factor 15 (GDF15). In addition to allergen-induced aversion, we find that lipopolysaccharide-induced inflammation also resulted in IgE-dependent aversive behaviour. These findings thus point to antigen-specific behavioural modifications that likely evolved to promote niche selection to avoid unfavourable environments.

Allergen protease-activated stress granule assembly and gasdermin D fragmentation control interleukin-33 secretion

Interleukin-33 (IL-33), an epithelial cell-derived cytokine that responds rapidly to environmental insult, has a critical role in initiating airway inflammatory diseases. However, the molecular mechanism underlying IL-33 secretion following allergen exposure is not clear. Here, we found that two cell events were fundamental for IL-33 secretion after exposure to allergens. First, stress granule assembly activated by allergens licensed the nuclear-cytoplasmic transport of IL-33, but not the secretion of IL-33. Second, a neo-form murine amino-terminal p40 fragment gasdermin D (Gsdmd), whose generation was independent of inflammatory caspase-1 and caspase-11, dominated cytosolic secretion of IL-33 by forming pores in the cell membrane. Either the blockade of stress granule assembly or the abolishment of p40 production through amino acid mutation of residues 309-313 (ELRQQ) could efficiently prevent the release of IL-33 in murine epithelial cells. Our findings indicated that targeting stress granule disassembly and Gsdmd fragmentation could reduce IL-33-dependent allergic airway inflammation.

Integrated OMICs Approach for the Group 1 Protease Mite-Allergen of House Dust Mite Dermatophagoides microceras

House dust mites (HDMs) are one of the most important allergy-causing agents of asthma. In central Taiwan, the prevalence of sensitization to Dermatophagoides microceras (Der m), a particular mite species of HDMs, is approximately 80% and is related to the IgE crossing reactivity of Dermatophagoides pteronyssinus (Der p) and Dermatophagoides farinae (Der f). Integrated OMICs examination was used to identify and characterize the specific group 1 mite-allergic component (Der m 1). De novo draft genomic assembly and comparative genome analysis predicted that the full-length Der m 1 allergen gene is 321 amino acids in silico. Proteomics verified this result, and its recombinant protein production implicated the cysteine protease and α chain of fibrinogen proteolytic activity. In the sensitized mice, pathophysiological features and increased neutrophils accumulation were evident in the lung tissues and BALF with the combination of Der m 1 and 2 inhalation, respectively. Principal component analysis (PCA) of mice cytokines revealed that the cytokine profiles of the allergen-sensitized mice model with combined Der m 1 and 2 were similar to those with Der m 2 alone but differed from those with Der m 1 alone. Regarding the possible sensitizing roles of Der m 1 in the cells, the fibrinogen cleavage products (FCPs) derived from combined Der m 1 and Der m 2 induced the expression of pro-inflammatory cytokines IL-6 and IL-8 in human bronchial epithelium cells. Der m 1 biologically functions as a cysteine protease and contributes to the α chain of fibrinogen digestion in vitro. The combination of Der m 1 and 2 could induce similar cytokines expression patterns to Der m 2 in mice, and the FCPs derived from Der m 1 has a synergistic effect with Der m 2 to induce the expression of pro-inflammatory cytokines in human bronchial epithelium cells.

Exposure to Bioaerosols During Fish Processing on Board Norwegian Fishing Trawlers

OBJECTIVES

The main objective was to gain more knowledge on exposure to bioaerosols in the processing area on board fishing trawlers.

METHODS

Exposure sampling was carried out during the work shifts when processing fish in the processing area on board five deep-sea fishing trawlers (trawlers 1-5). Exposure samples were collected from 64 fishermen breathing zone and from stationary sampling stations on board five deep-sea fishing trawlers (1-5). Trawlers 2, 3, and 4 were old ships, not originally built for on board processing of the catch. Trawlers 1 and 5 were relatively new and built to accommodate processing machineries. On trawlers 1-4 round fish was produced; the head and entrails were removed before the fishes were frozen in blocks. Trawler 5 had the most extensive processing, producing fish fillets. Samples were analysed for total protein, trypsin activity, parvalbumin, and endotoxin. One side analysis of variance and Kruskal-Wallis H test were used to compare levels of exposure on the different trawlers.

RESULTS

Personal exposure to total protein were higher on the three oldest trawlers (2, 3, and 4) compared with the two new trawlers (1 and 5). Highest activity of trypsin was detected on the four trawlers producing round fish (1-4). Parvalbumin was detected in 58% of samples from the fillet-trawler (5) compared with 13% of samples from the four trawlers producing round fish. The highest level of endotoxin was detected when using high-pressure water during cleaning machines and floors in the processing area.

CONCLUSIONS

Fishermen in the processing area on board Norwegian trawlers are exposed to airborne bioaerosols as proteins, trypsin, fish allergen parvalbumin, and endotoxin. Levels varied between trawlers and type of production.

Food allergy as a biological food quality control system

Food is simultaneously a source of essential nutrients and a potential source of lethal toxins and pathogens. Consequently, multiple sensory mechanisms evolved to monitor the quality of food based on the presence and relative abundance of beneficial and harmful food substances. These include the olfactory, gustatory, and gut chemosensory systems. Here we argue that, in addition to these systems, allergic immunity plays a role in food quality control by mounting allergic defenses against food antigens associated with noxious substances. Exaggeration of these defenses can result in pathological food allergy.

Aspergillus fumigatus Protease Alkaline Protease 1 (Alp1): A New Therapeutic Target for Fungal Asthma

We review three recent findings that have fundamentally altered our understanding of causative mechanisms underlying fungal-related asthma. These mechanisms may be partially independent of host inflammatory processes but are strongly dependent upon the actions of Alp1 on lung structural cells. They entail (i) bronchial epithelial sensing of Alp1; (ii) Alp1-induced airway smooth muscle (ASM) contraction; (iii) Alp1-induced airflow obstruction. Collectively, these mechanisms point to Alp1 as a new target for intervention in fungal asthma.

TLR2 favors OVA-induced allergic airway inflammation in mice through JNK signaling pathway with activation of autophagy

AIMS

Numerous studies indicate that toll-like receptor 2 (TLR2) led to divergent effects in asthma. The occurrence of autophagy in asthma pathogenesis is still incompletely understood. Here, we aimed to investigate the role of TLR2 and the underlying mechanisms in allergic airway inflammation and autophagy activation.

MAIN METHODS

C57BL/6 and TLR2 knockout (TLR2^-/-) mice were subjected to an ovalbumin (OVA)-immunized allergic airway model, and were treated with SP600125. Differential cell counts in bronchoalveolar lavage fluid were determined by Wright's staining. Histological analysis of airway inflammation was determined by haematoxylin and eosin (H&E) and periodic acid-Schiff (PAS) staining. The levels of OVA-specific immunoglobulin E (IgE), tumor necrosis factor α (TNF-α) and interleukin 10 (IL-10) were detected by enzyme-linked immunosorbent assay (ELISA). Proteins expression in lung tissues was detected by western blot, expression of TLR2 was further observed by immunofluorescence. Autophagy activation was determined by western blot and transmission electron microscopy (TEM).

KEY FINDINGS

TLR2 expression was increased upon OVA challenge, and TLR2 deficiency was associated with decreased allergic airway inflammation. Meanwhile, TLR2 deficiency weakened autophagy activation. Moreover, inhibition of c-Jun N-terminal kinase (JNK) by SP600125 also suppressed OVA-induced allergic airway inflammation and autophagy activation. Interestingly, treating TLR2^-/- mice with SP600125 showed similar OVA-induced allergic airway inflammation and autophagy activation compared to that in vehicle-treated TLR2^-/- mice.

SIGNIFICANCE

TLR2 might contribute to the maintenance of allergic airway inflammation through JNK signaling pathway accompanying with autophagy activation. These findings may provide a novel signal target for prevention of allergic airway inflammation.

Club Cell TRPV4 Serves as a Damage Sensor Driving Lung Allergic Inflammation

Airway epithelium is the first body surface to contact inhaled irritants and report danger. Here, we report how epithelial cells recognize and respond to aeroallergen alkaline protease 1 (Alp1) of Aspergillus sp., because proteases are critical components of many allergens that provoke asthma. In a murine model, Alp1 elicits helper T (Th) cell-dependent lung eosinophilia that is initiated by the rapid response of bronchiolar club cells to Alp1. Alp1 damages bronchiolar cell junctions, which triggers a calcium flux signaled through calcineurin within club cells of the bronchioles, inciting inflammation. In two human cohorts, we link fungal sensitization and/or asthma with SNP/protein expression of the mechanosensitive calcium channel, TRPV4. TRPV4 is also necessary and sufficient for club cells to sensitize mice to Alp1. Thus, club cells detect junction damage as mechanical stress, which signals danger via TRPV4, calcium, and calcineurin to initiate allergic sensitization.

MyD88 regulates a prolonged adaptation response to environmental dust exposure-induced lung disease

BACKGROUND

Environmental organic dust exposures enriched in Toll-like receptor (TLR) agonists can reduce allergic asthma development but are associated with occupational asthma and chronic bronchitis. The TLR adaptor protein myeloid differentiation factor88 (MyD88) is fundamental in regulating acute inflammatory responses to organic dust extract (ODE), yet its role in repetitive exposures is unknown and could inform future strategies.

METHODS

Wild-type (WT) and MyD88 knockout (KO) mice were exposed intranasally to ODE or saline daily for 3 weeks (repetitive exposure). Repetitively exposed animals were also subsequently rested with no treatments for 4 weeks followed by single rechallenge with saline/ODE.

RESULTS

Repetitive ODE exposure induced neutrophil influx and release of pro-inflammatory cytokines and chemokines were profoundly reduced in MyD88 KO mice. In comparison, ODE-induced cellular aggregates, B cells, mast cell infiltrates and serum IgE levels remained elevated in KO mice and mucous cell metaplasia was increased. Expression of ODE-induced tight junction protein(s) was also MyD88-dependent. Following recovery and then rechallenge with ODE, inflammatory mediators, but not neutrophil influx, was reduced in WT mice pretreated with ODE coincident with increased expression of IL-33 and IL-10, suggesting an adaptation response. Repetitively exposed MyD88 KO mice lacked inflammatory responsiveness upon ODE rechallenge.

CONCLUSIONS

MyD88 is essential in mediating the classic airway inflammatory response to repetitive ODE, but targeting MyD88 does not reduce mucous cell metaplasia, lymphocyte influx, or IgE responsiveness. TLR-enriched dust exposures induce a prolonged adaptation response that is largely MyD88-independent. These findings demonstrate the complex role of MyD88-dependent signaling during acute vs. chronic organic dust exposures.

Future research trends in understanding the mechanisms underlying allergic diseases for improved patient care

The specialties of allergy and clinical immunology have entered the era of precision medicine with the stratification of diseases into distinct disease subsets, specific diagnoses, and targeted treatment options, including biologicals and small molecules. This article reviews recent developments in research and patient care and future trends in the discipline. The section on basic mechanisms of allergic diseases summarizes the current status and defines research needs in structural biology, type 2 inflammation, immune tolerance, neuroimmune mechanisms, role of the microbiome and diet, environmental factors, and respiratory viral infections. In the section on diagnostic challenges, clinical trials, precision medicine and immune monitoring of allergic diseases, asthma, allergic and nonallergic rhinitis, and new approaches to the diagnosis and treatment of drug hypersensitivity reactions are discussed in further detail. In the third section, unmet needs and future research areas for the treatment of allergic diseases are highlighted with topics on food allergy, biologics, small molecules, and novel therapeutic concepts in allergen‐specific immunotherapy for airway disease. Unknowns and future research needs are discussed at the end of each subsection.

Protease/antiprotease network in allergy: The role of Staphylococcus aureus protease-like proteins

Staphylococcus aureus is being recognized as a major cofactor in atopic diseases such as atopic dermatitis, chronic rhinosinusitis with nasal polyps, and asthma. The understanding of the relationship between S aureus virulence factors and the immune system is continuously improving. Although the precise mechanism of the host's immune response adaptation to the variable secretion profile of S aureus strains continues to be a matter of debate, an increasing number of studies have reported on central effects of S aureus secretome in allergy. In this review, we discuss how colonization of S aureus modulates the innate and adaptive immune response, thereby predisposing the organism to allergic sensitization and disrupting immune tolerance in the airways of patients with asthma and chronic rhinosinusitis with nasal polyps. Next, we provide a critical overview of novel concepts dealing with S aureus in the initiation and persistence of chronic rhinosinusitis with nasal polyps and asthma. The role of the S aureus serine protease-like proteins in the initiation of a type 2 response and the contribution of the IL-33/ST2 signaling axis in allergic responses induced by bacterial allergens are discussed.

Airway mycosis in allergic airway disease

The allergic airway diseases, including chronic rhinosinusitis (CRS), asthma, allergic bronchopulmonary mycosis (ABPM) and many others, comprise a heterogeneous collection of inflammatory disorders affecting the upper and lower airways and lung parenchyma that represent the most common chronic diseases of humanity. In addition to their shared tissue tropism, the allergic airway diseases are characterized by a distinct pattern of inflammation involving the accumulation of eosinophils, type 2 macrophages, innate lymphoid cells type 2 (ILC2), IgE-secreting B cells, and T helper type 2 (Th2) cells in airway tissues, and the prominent production of type 2 cytokines including interleukin (IL-) 33, IL-4, IL-5, IL-13, and many others. These factors and related inflammatory molecules induce characteristic remodeling and other changes of the airways that include goblet cell metaplasia, enhanced mucus secretion, smooth muscle hypertrophy, tissue swelling and polyp formation that account for the major clinical manifestations of nasal obstruction, headache, hyposmia, cough, shortness of breath, chest pain, wheezing, and, in the most severe cases of lower airway disease, death due to respiratory failure or disseminated, systemic disease. The syndromic nature of the allergic airway diseases that now include many physiological variants or endotypes suggests that distinct endogenous or environmental factors underlie their expression. However, findings from different perspectives now collectively link these disorders to a single infectious source, the fungi, and a molecular pathogenesis that involves the local production of airway proteinases by these organisms. In this review, we discuss the evidence linking fungi and their proteinases to the surprisingly wide variety of chronic airway and systemic disorders and the immune pathogenesis of these conditions as they relate to environmental fungi. We further discuss the important implications these new findings have for the diagnosis and future therapy of these common conditions.

Selective cleavage of fibrinogen by diverse proteinases initiates innate allergic and antifungal immunity through CD11b

Proteinases are essential drivers of allergic airway disease and innate antifungal immunity in part through their ability cleave the clotting factor fibrinogen (FBG) into fibrinogen cleavage products (FCPs) that signal through Toll-like receptor 4 (TLR4). However, the mechanism by which FCPs engage TLR4 remains unknown. Here, we show that the proteinases from Aspergillus melleus (PAM) and other allergenic organisms rapidly hydrolyze FBG to yield relatively few FCPs that drive distinct antifungal mechanisms through TLR4. Functional FCPs, termed cryptokines, were characterized by rapid loss of the FBG α chain with substantial preservation of the β and γ chains, including a γ chain sequence (Fibγ390-396) that binds the integrin Mac-1 (CD11b/CD18). PAM-derived cryptokines could be generated from multiple FBG domains, and the ability of cryptokines to induce fungistasis in vitro and innate allergic airway disease in vivo strongly depended on both Mac-1 and the Mac-1-binding domain of FBG (Fibγ390-396). Our findings illustrate the essential concept of proteinase-activated immune responses and for the first time link Mac-1, cryptokines, and TLR4 to innate antifungal immunity and allergic airway disease.

Noninvasive allergic sinus congestion and resolution assessments using microcomputed tomography imaging

Sinus congestion resultant of allergic rhinosinusitis is associated with development and worsening of asthma and can result in difficulty breathing, headaches, and missed days of school and work. Quantification of sinus congestion is important in the understanding of allergic rhinosinusitis and the development of new drugs for its treatment. Noninvasive microcomputed tomography (micro-CT) was investigated in a guinea pig model of allergic rhinosinusitis to determine its utility to determine accurately the degree of sinus congestion and resolution with anti-inflammatory drug administration. Three-dimensional sinus air-space volume, two-dimensional sinus width, sinus image air-space area, and sinus image sinus perimeter were measured in guinea pigs administered ragweed pollen (RWP), intranasally (i.n.), followed by administration of fluticasone, i.n. To determine their relative accuracy in assessing sinus congestion, the micro-CT image results were compared with the "gold-standard" method of sinus fluid fill-volume (SFFV) measurements. As measured by SFFV method, RWP increased sinus congestion in a RWP concentration-dependent fashion, approaching near-total sinus blockage with concentrations ≥22 µg of RWP. At this level of congestion, fluticasone (25-100 µg) progressively decreased sinus congestion in a concentration-dependent fashion. The noninvasive micro-CT methods were found to accurately determine the amount of sinus congestion and resolution, with patterns of increases and decreases of congestion that were nearly identical to the SFFV method. We conclude that noninvasive micro-CT measurements of allergic sinus congestion can be useful as an investigative tool in the assessment of congestion intensity and the development of new drug therapies for its treatment. NEW & NOTEWORTHY Allergic rhinosinusitis afflicts significant portions of the world population, resulting in loss of work productivity and decreased quality of life. Thus the development of methodological approaches, which incorporate accurate and reproducible noninvasive assessments of sinus congestion, are desirable. Microcomputed tomography of the guinea pig sinuses offers a noninvasive evaluation tool in an animal model of IgE-dependent allergy similar to that in humans, with potential relevance toward development of therapeutics for human sinus diseases.

Benefits of antifungal therapy in asthma patients with airway mycosis: A retrospective cohort analysis

INTRODUCTION

Fungal airway infection (airway mycosis) is increasingly recognized as a cause of asthma and related disorders. However, prior controlled studies of patients treated with antifungal antibiotics have produced conflicting results. Our objective is to measure the effect of antifungal therapy in moderate to severe adult asthmatics with positive fungal sputum cultures in a single center referral-based academic practice.

METHODS

We retrospectively evaluated 41 patients with asthma and culture-proven airway mycosis treated with either terbinafine, fluconazole, itraconazole, voriconazole, or posaconazole for 4 to >12 weeks together with standard bronchodilator and anti-inflammatory agents. Asthma control (1 = very poorly controlled; 2 = not well controlled; and 3 = well controlled), peak expiratory flow rates (PEFR), serum total IgE, and absolute blood eosinophil counts before and after antifungal therapy were assessed. In comparison, we also studied nine patients with airway mycosis and moderate to severe asthma who received standard therapy but no antifungals.

RESULTS

Treatment with azole-based and allylamine antifungals was associated with improved asthma control (mean change in asthma control 1.72-2.25; p = 0.004), increased PEFR (69.4% predicted to 79.3% predicted, p = 0.0011) and markedly reduced serum IgE levels (1,075 kU/L to 463 kU/L, p = 0.0005) and blood eosinophil counts (Mean absolute count 530-275, p = 0.0095). Reduction in symptoms, medication use, and relapse rates decreased as duration of therapy increased. Asthmatics on standard therapy who did not receive antifungals showed no improvement in asthma symptoms or PEFR. Antifungals were usually well tolerated, but discontinuation (12.2%) and relapse (50%) rates were relatively high.

CONCLUSION

Antifungals help control symptoms in a subset of asthmatics with culture-proven airway mycosis. Additional randomized clinical trials are warranted to extend and validate these findings.

Environmental allergens induce allergic inflammation through proteolytic maturation of IL-33

Allergic inflammation has crucial roles in allergic diseases such as asthma. It is therefore important to understand why and how the immune system responds to allergens. Here we found that full-length interleukin 33 (IL-33_FL), an alarmin cytokine with critical roles in type 2 immunity and asthma, functioned as a protease sensor that detected proteolytic activities associated with various environmental allergens across four kingdoms, including fungi, house dust mites, bacteria and pollens. When exposed to allergen proteases, IL-33_FL was rapidly cleaved in its central 'sensor' domain, which led to activation of the production of type 2 cytokines in group 2 innate lymphoid cells. Preventing cleavage of IL-33_FL reduced allergic airway inflammation. Our findings reveal a molecular mechanism for the rapid induction of allergic type 2 inflammation following allergen exposure, with important implications for allergic diseases.

Orchestration of epithelial-derived cytokines and innate immune cells in allergic airway inflammation

Allergic asthma, a chronic respiratory disease, is a leading worldwide health problem, which inflames and constricts the airways, leading to breathing difficulty. Many studies have focused on the pathogenesis contributed by the adaptive immune system, including CD4+ T lymphocytes in delayed type hypersensitivity and B cell-produced IgE in anaphylaxis. More recently, a focus on the airway mucosal barrier and the innate immune system has highlighted, in coordination with T and B cells, to initiate and establish disease. This review highlights the impacts of epithelial-derived cytokines and innate immune cells on allergic airway reactions.

Characterization of a novel, papain-inducible murine model of eosinophilic rhinosinusitis

BACKGROUND

Eosinophilic chronic rhinosinusitis (ECRS) is a disease characterized by eosinophilic inflammatory infiltrate and a local type 2 cytokine milieu. Current animal models fail to recapitulate many of the innate and adaptive immunologic hallmarks of the disease, thus hindering the development of effective therapeutics. In the present study, mice were exposed intranasally to the cysteine protease papain, which shares functional similarities with parasitic proteases and aeroallergens, to generate a rapidly inducible murine model of eosinophilic rhinosinusitis.

METHODS

C57BL/6 mice were intranasally instilled with 20 μg papain or heat-inactivated papain (HP) on days 0-2 and days 7-10, and then euthanized on day 11. Nasal lavage fluid (NALF) was analyzed to quantify eosinophils and inflammatory cytokine secretion. Sinonasal tissue was sectioned and stained for goblet cells or homogenized to analyze cytokine levels. Serum samples were assayed for immunoglobulin E (IgE) by enzyme-linked immunoassay. Sinonasal mucosal tissue was dissociated and analyzed by flow cytometry.

RESULTS

Compared with HP treatment, papain induced significant eosinophilia in NALF, goblet cell hyperplasia, innate and adaptive immune cell infiltration, type 2 cytokine production, and IgE responses. Flow cytometric analysis of sinonasal tissues revealed significant inflammatory cell infiltration and interleukin-13-producing cell populations.

CONCLUSION

In this study, we demonstrated that the cysteine protease papain induces allergic sinonasal eosinophilic rhinosinusitis and resembles T-helper 2 cell inflammation and innate immune characteristics of ECRS. This model permits further study into the molecular mechanisms underlying ECRS pathology and provides a model system for the evaluation of potential pharmacologic interventions.

Stenotrophomonas maltophilia Serine Protease StmPr1 Induces Matrilysis, Anoikis, and Protease-Activated Receptor 2 Activation in Human Lung Epithelial Cells

Stenotrophomonas maltophilia is an emerging, opportunistic nosocomial pathogen that can cause severe disease in immunocompromised individuals. We recently identified the StmPr1 and StmPr2 serine proteases to be the substrates of the Xps type II secretion system in S. maltophilia strain K279a. Here, we report that a third serine protease, StmPr3, is also secreted in an Xps-dependent manner. By constructing a panel of protease mutants in strain K279a, we were able to determine that StmPr3 contributes to the previously described Xps-mediated rounding and detachment of cells of the A549 human lung epithelial cell line as well as the Xps-mediated degradation of fibronectin, fibrinogen, and the cytokine interleukin-8 (IL-8). We also determined that StmPr1, StmPr2, and StmPr3 account for all Xps-mediated effects toward A549 cells and that StmPr1 contributes the most to Xps-mediated activities. Thus, we purified StmPr1 from the S. maltophilia strain K279a culture supernatant and evaluated the protease's activity toward A549 cells. Our analyses revealed that purified StmPr1 behaves more similarly to subtilisin than to trypsin. We also determined that purified StmPr1 likely induces cell rounding and detachment of A549 cells by targeting cell integrin-extracellular matrix connections (matrilysis) as well as adherence and tight junction proteins for degradation. In this study, we also identified anoikis as the mechanism by which StmPr1 induces the death of A549 cells and found that StmPr1 induces A549 IL-8 secretion via activation of protease-activated receptor 2. Altogether, these results suggest that the degradative and cytotoxic activities exhibited by StmPr1 may contribute to S. maltophilia pathogenesis in the lung by inducing tissue damage and inflammation.

A critical review on serine protease: Key immune manipulator and pathology mediator

Proteolytic activity is fundamental to survival, so it is not surprising that all living organisms have proteases, especially seine protease. This enzyme in its numerous isoforms and homologues, constitutes the quintessential offence and defence factors, in the form of surface proteins, secreted molecules, gut digestive enzymes, venom in specialised glands or plant latex, among other manifestations. Occurring as trypsin, chymotrypsin, elastase, collagenase, thrombin, subtilisin etc., it mediates a diverse array of functions, including pathological roles as inflammatory, coagulatory to haemorrhagic. This review emphasizes that despite the superficial differences in mechanisms, most health issues, be they infectious, allergic, metabolic, or neural have a common conduit. This enzyme, in its various glycosylated forms leads to signal misinterpretations, wreaking havoc. However, organisms are endowed with serine protease inhibitors which might restrain this ubiquitous yet deleterious enzyme. Hence, serine proteases-driven pathogenesis and antagonising role of inhibitors is the focal point of this critical review.

Multi-Approach Analysis for the Identification of Proteases within Birch Pollen

Birch pollen allergy is highly prevalent, with up to 100 million reported cases worldwide. Proteases in such allergen sources have been suggested to contribute to primary sensitisation and exacerbation of allergic disorders. Until now the protease content of Betula verrucosa, a birch species endemic to the northern hemisphere has not been studied in detail. Hence, we aim to identify and characterise pollen and bacteria-derived proteases found within birch pollen. The pollen transcriptome was constructed via de novo transcriptome sequencing and analysis of the proteome was achieved via mass spectrometry; a cross-comparison of the two databases was then performed. A total of 42 individual proteases were identified at the proteomic level. Further clustering of proteases into their distinct catalytic classes revealed serine, cysteine, aspartic, threonine, and metallo-proteases. Further to this, protease activity of the pollen was quantified using a fluorescently-labelled casein substrate protease assay, as 0.61 ng/mg of pollen. A large number of bacterial strains were isolated from freshly collected birch pollen and zymographic gels with gelatinase and casein, enabled visualisation of proteolytic activity of the pollen and the collected bacterial strains. We report the successful discovery of pollen and bacteria-derived proteases of Betula verrucosa.

Identification of Proteases and Protease Inhibitors in Allergenic and Non-Allergenic Pollen

Pollen is one of the most common causes of allergy worldwide, making the study of their molecular composition crucial for the advancement of allergy research. Despite substantial efforts in this field, it is not yet clear why some plant pollens strongly provoke allergies while others do not. However, proteases and protease inhibitors from allergen sources are known to play an important role in the development of pollen allergies. In this study, we aim to uncover differences in the transcriptional pattern of proteases and protease inhibitors in Betula verrucosa and Pinus sylvestris pollen as models for high and low allergenic potential, respectively. We applied RNA sequencing to Betula verrucosa and Pinus sylvestris pollen. After de-novo assembly we derived general functional profiles of the protein coding transcripts. By utilization of domain based functional annotation we identified potential proteases and protease inhibitors and compared their expression in the two types of pollen. Functional profiles are highly similar between Betula verrucosa and Pinus sylvestris pollen. Both pollen contain proteases and inhibitors from 53 and 7 Pfam families, respectively. Some of the members comprised within those families are implicated in facilitating allergen entry, while others are known allergens themselves. Our work revealed several candidate proteins which, with further investigation, represent exciting new leads in elucidating the process behind allergic sensitization.

Exposure to Aedes aegypti Bites Induces a Mixed-Type Allergic Response following Salivary Antigens Challenge in Mice

Classical studies have shown that Aedes aegypti salivary secretion is responsible for the sensitization to mosquito bites and many of the components present in saliva are immunogenic and capable of inducing an intense immune response. Therefore, we have characterized a murine model of adjuvant-free systemic allergy induced by natural exposure to mosquito bites. BALB/c mice were sensitized by exposure to A. aegypti mosquito bites and intranasally challenged with phosphate-buffered saline only or the mosquito’s salivary gland extract (SGE). Blood, bronchoalveolar lavage (BAL) and lung were collected and evaluated for cellularity, histopathological analyses, cytokines and antibody determination. Respiratory pattern was analyzed by Penh measurements and tracheal segments were obtained to study in vitro reactivity to methacholine. BAL recovered from sensitized mice following challenge with SGE showed an increased number of eosinophils and Th2 cytokines such as IL-4, IL-5 and IL-13. Peribronchoalveolar eosinophil infiltration, mucus and collagen were also observed in lung parenchyma of sensitized mice, suggesting the development of a typical Th2 response. However, the antibody profile in serum of these mice evidenced a mixed-type response with presence of both, IgG1/IgE (Th2-related) and IgG2a (Th1-related) isotypes. In addition, changes in breathing pattern and tracheal reactivity to methacholine were not found. Taken together, our results show that A. aegypti bites trigger an atypical allergic reaction, with some classical cellular and soluble Th2 components in the lung, but also systemic Th1 and Th2 antibody isotypes and no change in either the respiratory pattern or the trachea responsiveness to agonist.

Allergen-encoded signals that control allergic responses

PURPOSE OF REVIEW

The purpose is to review the important recent advances made in how innate immune cells, microbes, and the environment contribute to the expression of allergic disease, emphasizing the allergen-related signals that drive allergic responses.

RECENT FINDINGS

The last few years have seen crucial advances in how innate immune cells such as innate lymphoid cells group 2 and airway epithelial cells and related molecular pathways through organismal proteinases and innate immune cytokines, such as thymic stromal lymphopoietin, IL-25, and IL-33 contribute to allergy and asthma. Simultaneously with these advances, important progress has been made in our understanding of how the environment, and especially pathogenic organisms, such as bacteria, viruses, helminths, and especially fungi derived from the natural and built environments, either promote or inhibit allergic inflammation and disease. Of specific interest are how lipopolysaccharide mediates its antiallergic effect through the ubiquitin modifying factor A20 and the antiallergic activity of both helminths and protozoa.

SUMMARY

Innate immune cells and molecular pathways, often activated by allergen-derived proteinases acting on airway epithelium and macrophages as well as additional unknown factors, are essential to the expression of allergic inflammation and disease. These findings suggest numerous future research opportunities and new opportunities for therapeutic intervention in allergic disease.

Innate and Adaptive Immune Response to Fungal Products and Allergens

Exposure to fungi and their products is practically ubiquitous, yet most of this is of little consequence to most healthy individuals. This is because there are a number of elaborate mechanisms to deal with these exposures. Most of these mechanisms are designed to recognize and neutralize such exposures. However, in understanding these mechanisms it has become clear that many of them overlap with our ability to respond to disruptions in tissue function caused by trauma or deterioration. These responses involve the innate and adaptive immune systems usually through the activation of nuclear factor kappa B and the production of cytokines that are considered inflammatory accompanied by other factors that can moderate these reactivities. Depending on different genetic backgrounds and the extent of activation of these mechanisms, various pathologies with resulting symptoms can ensue. Complicating this is the fact that these mechanisms can bias toward type 2 innate and adaptive immune responses. Thus, to understand what we refer to as allergens from fungal sources, we must first understand how they influence these innate mechanisms. In doing so it has become clear that many of the proteins that are described as fungal allergens are essentially homologues of our own proteins that signal or cause tissue disruptions.