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

Airborne indoor allergen serine proteases and their contribution to sensitisation and activation of innate immunity in allergic airway disease

Common airborne allergens (pollen, animal dander and those from fungi and insects) are the main triggers of type I allergic disorder in the respiratory system and are associated with allergic rhinitis, allergic asthma, as well as immunoglobulin E (IgE)-mediated allergic bronchopulmonary aspergillosis. These allergens promote IgE crosslinking, vasodilation, infiltration of inflammatory cells, mucosal barrier dysfunction, extracellular matrix deposition and smooth muscle spasm, which collectively cause remodelling of the airways. Fungus and insect (house dust mite and cockroaches) indoor allergens are particularly rich in proteases. Indeed, more than 40 different types of aeroallergen proteases, which have both IgE-neutralising and tissue-destructive activities, have been documented in the Allergen Nomenclature database. Of all the inhaled protease allergens, 85% are classed as serine protease activities and include trypsin-like, chymotrypsin-like and collagenolytic serine proteases. In this article, we review and compare the allergenicity and proteolytic effect of allergen serine proteases as listed in the Allergen Nomenclature and MEROPS databases and highlight their contribution to allergic sensitisation, disruption of the epithelial barrier and activation of innate immunity in allergic airways disease. The utility of small-molecule inhibitors of allergen serine proteases as a potential treatment strategy for allergic airways disease will also be discussed.

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.

Establishment of a homogeneous chemiluminescence immunoassay for cat dander sIgE antibody detection

BACKGROUND

In vitro specific IgE (sIgE) testing has become an important tool for the diagnosis of IgE-mediated allergic diseases. Current methods used to detect allergen sIgE are time consuming and/or expensive. Therefore, a new method was developed for rapid quantitative detection of cat dander-sIgE antibody based on homogeneous chemiluminescence immunoassay.

METHODS

Selection of chemibeads with different chemical groups, and the best Light-initiated chemiluminescence assay (LiCA) analytical mode for cat dander-sIgE detection. To validate and eliminate the interference of IgE on the detection of cat dander-sIgE, concentration of biotinylated anti-human IgE antibody was optimized. For quantification of cat dander-sIgE, a calibration curve was established, and the performance of the assay was evaluated according to clinical guidelines.

RESULTS

Indirect LiCA is the best mode of analysis and biotinylated anti-human IgE antibody at a dilution ratio of 1:250 minimizes IgE interference. The coefficient of variation of the developed LiCA was 1.49% to 4.66%, with an intermediate precision of 6.90% to 8.21%. The LoB, LoD, and LoQ of the assay were 0.023 kUA/L, 0.056 kUA/L and 0.185 kUA/L. The coefficient of correlation (r) between LiCA and ImmounoCAP was 0.9478.

CONCLUSIONS

A cat dander-sIgE quantitation assay based on homogeneous chemiluminescence immunoassay was established, which could be a new reliable analytical tool for the determination of cat dander-sIgE.

Advocacy of Precision Allergy Molecular Diagnosis in Decision Making for the Eligibility of Customized Allergen Immunotherapy

Allergen immunotherapy (AIT) with aeroallergens is the only disease-modifying treatment for patients with different allergic conditions. Despite the effectiveness of AIT having been proven in both randomized controlled trials and real-world studies, it remains underused in less than 10% of subjects with allergic rhinitis (AR) and/or asthma (A). We aimed to determine the current eligibility for house dust mite (HDM) AIT by means of a precision allergy molecular diagnosis (PAMD@) model in a selected cohort of youngsters with different allergic phenotypes according to the available evidence. A complex response to both HDM and storage mite allergens was depicted regardless of the subjects' basal atopic condition. No solely specific IgE-binding responses to Der p 1, Der p 2, and/or Der p 23 were found in the studied cohort. Despite the patients with A and atopic dermatitis showing significantly higher serum titers to six mite allergens than subjects with AR, no specific molecular profile was regarded as disease specific. Given the increasing complexity of specific IgE responses to the local prevailing aeroallergens, the identification and presence of such molecules are needed in commercially available AIT in the era of precision medicine.

Allergenic Activity of Individual Cat Allergen Molecules

More than 10% of the world's population suffers from an immunoglobulin E (IgE)-mediated allergy to cats which is accompanied mainly by respiratory symptoms such as rhinitis and asthma. Several cat allergen molecules have been identified, but their allergenic activity has not been investigated in depth. Purified cat allergen molecules (Fel d 1, Fel d 2, Fel d 3, Fel d 4, Fel d 6, Fel d 7 and Fel d 8) were characterized via mass spectrometry and circular dichroism spectroscopy regarding their molecular mass and fold, respectively. Cat-allergen-specific IgE levels were quantified via ImmunoCAP measurements in IgE-sensitized subjects with (n = 37) and without (n = 20) respiratory symptoms related to cat exposure. The allergenic activity of the cat allergens was investigated by loading patients' IgE onto rat basophils expressing the human FcεRI receptor and studying the ability of different allergen concentrations to induce β-hexosaminidase release. Purified and folded cat allergens with correct masses were obtained. Cat-allergen-specific IgE levels were much higher in patients with a respiratory allergy than in patients without a respiratory allergy. Fel d 1, Fel d 2, Fel d 4 and Fel d 7 bound the highest levels of specific IgE and already-induced basophil degranulation at hundred-fold-lower concentrations than the other allergens. Fel d 1, Fel d 4 and Fel d 7 were recognized by more than 65% of patients with a respiratory allergy, whereas Fel d 2 was recognized by only 30%. Therefore, in addition to the major cat allergen Fel d 1, Fel d 4 and Fel d 7 should also be considered to be important allergens for the diagnosis and specific immunotherapy of cat allergy.

Albumins represent highly cross-reactive animal allergens

Albumins from animals are highly cross-reactive allergens for patients suffering from immunoglobulin E (IgE)-mediated allergy. Approximately 20-30% of cat and dog allergic patients show IgE reactivity and mount IgE-mediated allergic reactions to cat and dog albumin. It is astonishing that allergic patients can develop specific IgE responses against animal albumins because these proteins exhibit a more than 70% sequence identity to human serum albumin (HSA) which is the most abundant protein in the blood of the human body. The sequence identity of cat albumin (Fel d 2) and dog albumin (Can f 3) and HSA are 82% and 80%, respectively. Given the high degree of sequence identity between the latter two allergens and HSA one would expect that immunological tolerance would prohibit IgE sensitization to Fel d 2 and Can f 3. Here we discuss two possibilities for how IgE sensitization to Fel d 2 and Can f 3 may develop. One possibility is the failed development of immune tolerance in albumin-allergic patients whereas the other possibility is highly selective immune tolerance to HSA but not to Fel d 2 and Can f 3. If the first assumption is correct it should be possible to detect HSA-specific T cell responses and HSA-containing immune complexes in sensitized patients. In the latter scenario few differences in the sequences of Fel d 2 and Can f 3 as compared to HSA would be responsible for the development of selective T cell and B cell responses towards Fel d 2 as well as Can f 3. However, the immunological mechanisms of albumin sensitization have not yet been investigated in detail although this will be important for the development of allergen-specific prevention and allergen-specific immunotherapy (AIT) strategies for allergy to albumin.

Modern Concept of Molecular Diagnostics of Allergy to Dogs

The number of people suffering from allergies is increasing worldwide every year. With the prevalence of domestic animals, especially dogs, allergens associated with them can be found ubiquitously, thereby increasing the risk of anaphylaxis in sensitized individuals. Currently, there are 8 known dog allergens, but not all of them have been thoroughly studied. The commonly used skin prick tests often fall short and fail to provide a comprehensive assessment of a patient's condition, thus making allergy diagnosis challenging. Fortunately, the introduction of new allergy diagnostic methods has made it possible to accurately identify clinically significant allergens for patients. These findings can then be used to prescribe appropriate therapy or provide specific recommendations to the patients. This review focuses on the most important dog allergens and modern allergy diagnostic techniques that are gradually being incorporated into medical practice, thus expanding the capabilities of allergists.

The Relationship of Parasite Allergens to Allergic Diseases

PURPOSE OF REVIEW

Helminth infections modify the natural history of allergic diseases, by either decreasing or increasing their symptoms. Several helminth components are involved in the increasing of the allergic response and symptoms, overcoming the concomitant immunosuppression of helminthiases. However, the role of individual IgE-binding molecules in this process remains to be defined.

RECENT FINDINGS

We updated the list of helminth allergens and IgE-binding molecules, their effects on asthma presentation, and their impact on allergy diagnosis. Data from genetic and epigenetic studies of ascariasis are analyzed. A new species-specific A. lumbricoides allergen has been discovered, with potential use in molecular diagnosis. Most helminth IgE-binding components are not officially classified as allergens in the WHO/IUIS database, although there is evidence of their influence increasing allergic manifestations. Further immunological characterization of these components is needed to better understand their mechanisms of action and evaluate the ways in which they can influence the diagnosis of allergy.

Molecular Mapping of Allergen Exposome among Different Atopic Phenotypes

Climate change and exposure to environmental pollutants play a key role in the onset and aggravation of allergic diseases. As different climate-dependent patterns of molecular immunoglobulin E (IgE) reactivity have been regionally described, we sought to investigate the evolving allergen exposome in distinctive allergic phenotypes and subtropical weather conditions through a Precision Allergy Molecular Diagnosis (PAMD@) model. Concurrent sensitization to several house dust mites (HDM) and storage mite molecules were broadly dominant in the investigated cohort, followed by the major cat allergen Fel d 1, and regardless of the basal allergic disease. Although a complex repertoire of allergens was recognized, a steadily increasing number of IgE binding molecules was associated with the complexity of the underlying atopic disease. Besides the highly prevalent IgE responses to major HDM allergens, Der p 21, Der p 5, and Der p 7 also showed up as serodominant molecules, especially in subjects bothered by asthma and atopic dermatitis. The accurate characterization of the external exposome at the molecular level and their putative role as clinically relevant allergens is essential to elucidate the phenotypic diversity of atopic disease in terms of personalized diagnosis and therapy.

Assessing the relevance of allergenic pollen in indoor environments-current knowledge base and research needs

Airborne pollen allergens-a relevant component of bioaerosols and, therefore, of airborne particulate matter-are considered an important metric in air quality assessments. Although the measurement of airborne pollen allergen concentrations in outdoor environments (namely, in urban areas) has been recognized as a key environmental health indicator, no such obligation exists for indoor environments (dwellings or occupational settings). However, people spend most of their daily time (80-90%) indoors, where the majority of their exposure to air pollution, including pollen allergens, occurs. Nonetheless, the relative importance of airborne pollen allergen exposure indoors differs from outdoors because of differences in pollen loads, sources, dispersion, and degree of penetration from the outdoor surroundings, as well as the differences in the allergenic pollen profiles. In this brief review, we mined the literature over the last 10 years to summarize what existing measurements reveal about the relevance of airborne allergenic pollen in indoor environments. The research priorities on this topic are presented, highlighting the challenges and the motivations for obtaining pollen data in built environments which are key to understand the extent and mechanisms of human exposure to airborne pollen allergens. Thus, we provide a comprehensive assessment of the relevance of airborne allergenic pollen in indoor environments, highlighting knowledge gaps and research needs related to their health effects.

Site-specific tyrosine nitration of group 1 allergens of house dust mite Dermatophagoides farinae (der f 1) and Dermatophagoides pteronyssinus (der p 1) in indoor dusts

Nitration can enhance the allergenicity of proteins. The nitration status of house dust mite (HDM) allergens in indoor dusts, however, remains to be elucidated. In the study, site-specific tyrosine nitration degrees of the two important HDM allergens Der f 1 and Der p 1 in indoor dust samples were investigated by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The measured concentrations of native and nitrated allergens in the dusts were in the range of 0.86-29 μg g^-1 for Der f 1 and from below the detection limit to 29 μg g^-1 for Der p 1. Site-specific analysis revealed that all ten tyrosine residues in Der f 1 and Der p 1 were nitrated to different degrees in the investigated samples. The preferred nitration sites were Y₅₆ in Der f 1 and Y₃₇ in Der p 1 with the nitration degrees of 7.6-84% and 17-96% among the detected tyrosine residues, respectively. The measurements reveal high site-specific nitration degrees for tyrosine in Der f 1 and Der p 1 detected in the indoor dust samples. Further investigations are required to find out if the nitration really aggravates the health effects of HDM allergens and if the effects are tyrosine site-dependent.

Protease allergens as initiators-regulators of allergic inflammation

Tremendous progress in the last few years has been made to explain how seemingly harmless environmental proteins from different origins can induce potent Th2-biased inflammatory responses. Convergent findings have shown the key roles of allergens displaying proteolytic activity in the initiation and progression of the allergic response. Through their propensity to activate IgE-independent inflammatory pathways, certain allergenic proteases are now considered as initiators for sensitization to themselves and to non-protease allergens. The protease allergens degrade junctional proteins of keratinocytes or airway epithelium to facilitate allergen delivery across the epithelial barrier and their subsequent uptake by antigen-presenting cells. Epithelial injuries mediated by these proteases together with their sensing by protease-activated receptors (PARs) elicit potent inflammatory responses resulting in the release of pro-Th2 cytokines (IL-6, IL-25, IL-1β, TSLP) and danger-associated molecular patterns (DAMPs; IL-33, ATP, uric acid). Recently, protease allergens were shown to cleave the protease sensor domain of IL-33 to produce a super-active form of the alarmin. At the same time, proteolytic cleavage of fibrinogen can trigger TLR4 signaling, and cleavage of various cell surface receptors further shape the Th2 polarization. Remarkably, the sensing of protease allergens by nociceptive neurons can represent a primary step in the development of the allergic response. The goal of this review is to highlight the multiple innate immune mechanisms triggered by protease allergens that converge to initiate the allergic response.

The Allergenic Activity of Blo t 2, a Blomia tropicalis IgE-Binding Molecule

Only few allergens derived from house dust mite (HDM) species have been evaluated in terms of their potential to induce allergic inflammation. In this study, we aimed to evaluate different aspects of the allergenicity and allergenic activity of Blo t 2, a Blomia tropicalis allergen. Blo t 2 was produced as a recombinant protein in Escherichia coli. Its allergenic activity was tested in humans by skin prick test and basophil activation assays, and in mice, by passive cutaneous anaphylaxis and a model of allergic airway inflammation. Sensitization rate to Blo t 2 (54.3%) was similar to that found to Blo t 21 (57.2%) and higher than to Der p 2 (37.5%). Most Blo t 2-sensitized patients showed a low intensity response (99.5%). Blo t 2 elicited CD203c upregulation and allergen induced skin inflammation. Additionally, immunized animals produced anti-Blo t 2 IgE antibodies and passive transfer of their serum to non-immunized animals induced skin inflammation after allergen exposure. Immunized animals developed bronchial hyperreactivity and a strong inflammatory lung reaction (eosinophils and neutrophils). These results confirm the allergenic activity of Blo t 2 and supports its clinical relevance.

EAACI Molecular Allergology User's Guide 2.0

Since the discovery of immunoglobulin E (IgE) as a mediator of allergic diseases in 1967, our knowledge about the immunological mechanisms of IgE-mediated allergies has remarkably increased. In addition to understanding the immune response and clinical symptoms, allergy diagnosis and management depend strongly on the precise identification of the elicitors of the IgE-mediated allergic reaction. In the past four decades, innovations in bioscience and technology have facilitated the identification and production of well-defined, highly pure molecules for component-resolved diagnosis (CRD), allowing a personalized diagnosis and management of the allergic disease for individual patients. The first edition of the "EAACI Molecular Allergology User's Guide" (MAUG) in 2016 rapidly became a key reference for clinicians, scientists, and interested readers with a background in allergology, immunology, biology, and medicine. Nevertheless, the field of molecular allergology is moving fast, and after 6 years, a new EAACI Taskforce was established to provide an updated document. The Molecular Allergology User's Guide 2.0 summarizes state-of-the-art information on allergen molecules, their clinical relevance, and their application in diagnostic algorithms for clinical practice. It is designed for both, clinicians and scientists, guiding health care professionals through the overwhelming list of different allergen molecules available for testing. Further, it provides diagnostic algorithms on the clinical relevance of allergenic molecules and gives an overview of their biology, the basic mechanisms of test formats, and the application of tests to measure allergen exposure.

Recombinant T-cell epitope conjugation: A new approach for Dermatophagoides hypoallergen design

BACKGROUND

Allergen-specific immunotherapy (AIT) is the only clinical approach that can potentially cure some allergic diseases by inducing immunological tolerance. Dermatophagoides pteronyssinus is considered as the most important source of mite allergens worldwide, with high sensitization rates for the major allergens Der p 1, Der p 2 and Der p 23. The aim of this work is to generate a hypoallergenic hybrid molecule containing T-cell epitopes from these three major allergens.

METHODS

The hybrid protein termed Der p 2231 containing T-cell epitopes was purified by affinity chromatography. The human IgE reactivity was verified by comparing those with the parental allergens. The hybrid was also characterized immunologically through an in vivo mice model.

RESULTS

The hybrid rDer p 2231 stimulated in peripheral blood mononuclear cells (PBMCs) isolated from allergic patients with higher levels of IL- 2, IL-10, IL-15 and IFN-γ, as well as lower levels of IL-4, IL-5, IL-13, TNF-α and GM-CSF. The use of hybrid molecules as a therapeutic model in D. pteronyssinus allergic mice led to the reduction of IgE production and lower eosinophilic peroxidase activity in the airways. We found increased levels of IgG antibodies that blocked the IgE binding to the parental allergens in the serum of allergic patients. Furthermore, the stimulation of splenocytes from mice treated with rDer p 2231 induced higher levels of IL-10 and IFN-γ and decreased the secretion of IL-4 and IL-5, when compared with parental allergens and D. pteronyssinus extract.

CONCLUSIONS

rDer p 2231 has the potential to be used in AIT in patients co-sensitized with D. pteronyssinus major allergens, once it was able to reduce IgE production, inducing allergen-specific blocking antibodies, restoring and balancing Th1/Th2 immune responses, and inducing regulatory T-cells.

Changes in Serum Protein-Peptide Patterns in Atopic Children Allergic to Plant Storage Proteins

Next to cow's milk and eggs, plant foods, i.e., legumes, tree nuts and cereal grains, most often sensitise atopic children. Storage proteins constitutes the most relevant protein fraction of plant foods, causing primary sensitisation. They exhibit strong allergenic properties and immunogenicity. Our goal was to analyse sensitisation to 26 plant storage proteins in a group of 76 children aged 0-5 years with chronic symptoms of atopic dermatitis using Allergy Explorer ALEX2 and to discover changes in serum protein-peptide patterns in allergic patients with the use of MALDI-TOF-MS. We reported that 25% of children were allergic to 2S albumins, 19.7% to 7S globulins, 13.2% to 11S globulins and 1.3% to cereal prolamins. The most common allergenic molecules were Ara h 1 (18.4%), Ara h 2 (17.1%), Ara h 6 (15.8%) and Ara h 3 (11.8%) from peanuts, and the mean serum sIgE concentrations in allergic patients were 10.93 kUA/L, 15.353 kUA/L, 15.359 kUA/L and 9.038 kUA/L, respectively. In children allergic to storage proteins compared to the other patients (both allergic and non-allergic), the cell cycle control protein 50A, testis-expressed sequence 13B, DENN domain-containing protein 5A and SKI family transcriptional corepressor 2 were altered. Our results indicate that the IgE-mediated allergy to storage proteins is a huge problem in a group of young, atopic children, and show the potential of proteomic analysis in the prediction of primary sensitisation to plant foods. It is the next crucial step for understanding the molecular consequences of allergy to storage proteins.

Molecular Allergen-Specific IgE Recognition Profiles and Cumulative Specific IgE Levels Associated with Phenotypes of Cat Allergy

Cat allergy is a major trigger factor for respiratory reactions (asthma and rhinitis) in patients with immunoglobulin E (IgE) sensitization. In this study, we used a comprehensive panel of purified cat allergen molecules (rFel d 1, nFel d 2, rFel d 3, rFel d 4, rFel d 7, and rFel d 8) that were obtained by recombinant expression in Escherichia coli or by purification as natural proteins to study possible associations with different phenotypes of cat allergy (i.e., rhinitis, conjunctivitis, asthma, and dermatitis) by analyzing molecular IgE recognition profiles in a representative cohort of clinically well-characterized adult cat allergic subjects (n = 84). IgE levels specific to each of the allergen molecules and to natural cat allergen extract were quantified by ImmunoCAP measurements. Cumulative IgE levels specific to the cat allergen molecules correlated significantly with IgE levels specific to the cat allergen extract, indicating that the panel of allergen molecules resembled IgE epitopes of the natural allergen source. rFel d 1 represented the major cat allergen, which was recognized by 97.2% of cat allergic patients; however, rFel d 3, rFel d 4, and rFel d 7 each showed IgE reactivity in more than 50% of cat allergic patients, indicating the importance of additional allergens in cat allergy. Patients with cat-related skin symptoms showed a trend toward higher IgE levels and/or frequencies of sensitization to each of the tested allergen molecules compared with patients suffering only from rhinitis or asthma, while there were no such differences between patients with rhinitis and asthma. The IgE levels specific to allergen molecules, the IgE levels specific to cat allergen extract, and the IgE levels specific to rFel d 1 were significantly higher in patients with four different symptoms compared with patients with 1–2 symptoms. This difference was more pronounced for the sum of IgE levels specific to the allergen molecules and to cat extract than for IgE levels specific for rFel d 1 alone. Our study indicates that, in addition to rFel d 1, rFel d 3, rFel d 4, and rFel d 7 must be considered as important cat allergens. Furthermore, the cumulative sum of IgE levels specific to cat allergen molecules seems to be a biomarker for identifying patients with complex phenotypes of cat allergy. These findings are important for the diagnosis of IgE sensitization to cats and for the design of allergen-specific immunotherapies for the treatment and prevention of cat allergy.

Review: The Nose as a Route for Therapy. Part 2 Immunotherapy

The nose provides a route of access to the body for inhalants and fluids. Unsurprisingly it has a strong immune defense system, with involvement of innate (e.g., epithelial barrier, muco- ciliary clearance, nasal secretions with interferons, lysozyme, nitric oxide) and acquired (e.g., secreted immunoglobulins, lymphocytes) arms. The lattice network of dendritic cells surrounding the nostrils allows rapid uptake and sampling of molecules able to negotiate the epithelial barrier. Despite this many respiratory infections, including SARS-CoV2, are initiated through nasal mucosal contact, and the nasal mucosa is a significant "reservoir" for microbes including Streptococcus pneumoniae, Neisseria meningitidis and SARS -CoV-2. This review includes consideration of the augmentation of immune defense by the nasal application of interferons, then the reduction of unnecessary inflammation and infection by alteration of the nasal microbiome. The nasal mucosa and associated lymphoid tissue (nasopharynx-associated lymphoid tissue, NALT) provides an important site for vaccine delivery, with cold-adapted live influenza strains (LAIV), which replicate intranasally, resulting in an immune response without significant clinical symptoms, being the most successful thus far. Finally, the clever intranasal application of antibodies bispecific for allergens and Intercellular Adhesion Molecule 1 (ICAM-1) as a topical treatment for allergic and RV-induced rhinitis is explained.

The Effector Function of Allergens

Allergens are antigens that generate an IgE response (sensitization) in susceptible individuals. The allergenicity of an allergen can be thought of in terms of its ability to sensitize as well as its ability to cross-link IgE/IgE receptor complexes on mast cells and basophils leading to release of preformed and newly formed mediators (effector activity). The identity of the allergens responsible for sensitization may be different from those that elicit an allergic response. Effector activity is determined by (1) the amount of specific IgE (sIgE) and in some circumstances the ratio of sIgE to total IgE, (2) the number of high affinity receptors for IgE (FcεR1) on the cell surface, (3) the affinity of binding of sIgE for its epitope and, in a polyclonal response, the collective avidity, (4) the number and spatial relationships of IgE binding epitopes on the allergen and (5) the presence of IgG that can bind to allergen and either block binding of sIgE and/or activate low affinity IgG receptors that activate intracellular inhibitory pathways. This review will discuss these important immunologic and physical properties that contribute to the effector activity of allergens.

Scientific Opinion on development needs for the allergenicity and protein safety assessment of food and feed products derived from biotechnology

This Scientific Opinion addresses the formulation of specific development needs, including research requirements for allergenicity assessment and protein safety, in general, which is urgently needed in a world that demands more sustainable food systems. Current allergenicity risk assessment strategies are based on the principles and guidelines of the Codex Alimentarius for the safety assessment of foods derived from 'modern' biotechnology initially published in 2003. The core approach for the safety assessment is based on a 'weight-of-evidence' approach because no single piece of information or experimental method provides sufficient evidence to predict allergenicity. Although the Codex Alimentarius and EFSA guidance documents successfully addressed allergenicity assessments of single/stacked event GM applications, experience gained and new developments in the field call for a modernisation of some key elements of the risk assessment. These should include the consideration of clinical relevance, route of exposure and potential threshold values of food allergens, the update of in silico tools used with more targeted databases and better integration and standardisation of test materials and in vitro/in vivo protocols. Furthermore, more complex future products will likely challenge the overall practical implementation of current guidelines, which were mainly targeted to assess a few newly expressed proteins. Therefore, it is timely to review and clarify the main purpose of the allergenicity risk assessment and the vital role it plays in protecting consumers' health. A roadmap to (re)define the allergenicity safety objectives and risk assessment needs will be required to inform a series of key questions for risk assessors and risk managers such as 'what is the purpose of the allergenicity risk assessment?' or 'what level of confidence is necessary for the predictions?'.

Immunotherapy With Recombinant Alt a 1 Suppresses Allergic Asthma and Influences T Follicular Cells and Regulatory B Cells in Mice

Background

Alternaria is a major source of asthma-inducing allergens. Allergen-specific immunotherapy improves the progression of allergic asthma. The current treatment is based on crude Alternaria extracts. Alt a 1 is the predominant allergen in Alternaria. However, the treatment efficacy of recombinant Alt a 1 (rAlt a 1) in an asthmatic animal model and its influence on Tfh and Breg cells are unknown.

Objective

To explore the therapeutic treatment effects of rAlt a 1 on the progress of an asthmatic mouse model and its effect on Tfh and Breg cells.

Methods

We synthesized and purified rAlt a 1. Alternaria-sensitized and challenged mice received subcutaneous immunotherapy (SCIT) with four different rAlt a 1 dosages (5, 50, 100, and 150 µg) or PBS only. Finally, lung and airway inflammation, mouse mast cell protease 1 (MMCP-1), serum immunoglobulin responses, Tfh and Breg cell levels, and the correlation between asthmatic features (inflammation grades and IL-4 and IL-10 levels) and these two cell types were measured after Alternaria rechallenge.

Results

High purity and allergenic potency of rAlt a 1 protein were obtained. Following treatment with four different rAlt a 1 dosages, both lung and airway inflammation ameliorated, including lung pathology, serum MMCP-1 levels, inflammatory cell numbers, and cytokine levels in bronchoalveolar lavage fluid (BALF). Additionally, rAlt a 1-SCIT increased the expression of Alternaria-sIgG1, rAlt a 1-sIgG1, rAlt a 1-sIgG2a, and rAlt a 1-sIgG2b in serum. Moreover, the number and percentage of CXCR5⁺PD-1⁺Tfh cells were increased in the PC control, while they decreased in the rAlt a 1-SCIT groups. Meanwhile, the absolute numbers and proportions of Breg cells were evaluated after administration of rAlt a 1. A positive correlation was observed between CXCR5⁺PD-1⁺Tfh cells and inflammation grades (r = 0.50, p = 0.01), as well as a slightly strong positive relationship with IL-4 (r = 0.55, p = 0.005) and IL-10 (r = 0.58, p = 0.003) levels; Breg cells showed an opposite correlation with the grades of inflammation (r = -0.68, p = 0.0003), along with a negative correlation to IL-4 (r = -0.61, p = 0.001) and IL-10 (r = -0.53, p = 0.008) levels.

Conclusions

We verified that treatment with rAlt a 1 can alleviate asthma progression and further have a regulatory effect on Tfh and Breg cells in an Alternaria-induced asthmatic mouse model.

Clinical relevance of Alternaria alternata sensitization in patients within type 2-high and type 2-low asthma

Alternaria sensitization is correlated with persistent asthma. Type 2 (T2)-asthma endotypes are characterized by the release of eosinophils. However, the prevalence and sensitization patterns in patients with Alternaria asthma between T2-high and T2-low endotypes are unknown. We retrospectively reviewed 582 patients with Alternaria asthma and divided them into T2-high (n = 376) and T2-low (n = 206) groups with a threshold of 300 cells/µL in blood eosinophil counts. Data for basic information, skin test or IgE detection results, and blood eosinophil counts were collected. The age of patients in the T2-high group (13.66 ± 13.23) was lower than that of the T2-low group (18.02 ± 15.03). Patients with T2-high asthma had relatively higher rates of taking inhaled corticosteroids (ICS) and positive family history than the T2-low group. Pet keepers and allergen immunotherapy (AIT) patients were comparable between these groups, In the T2-high group, patients had higher levels of total serum IgE (T-IgE) and showed a significant positive correlation with eosinophil counts (r = 0.166, P = 0.001), followed by higher Alternaria-specific IgE (sIgE) levels (median, 13.7; range, 4.86-25.3). Compared to the T2-low group, the frequency of poly-sensitized patients and the rate of each allergen among the nine common allergens were all higher in the T2-high group; the statistical differences mainly focused on pollens such as birch (P = 0.005), firmiana (P = 0.004), and mugwort (P = 0.005). Young, male patients had a high prevalence of T2-high Alternaria asthma, along with higher rates of T-IgE, sIgE levels, and poly-sensitized patterns.

Alternaria as an Inducer of Allergic Sensitization

Alternaria alternata is a saprophytic mold whose spores are disseminated in warm dry air, the typical weather of the Mediterranean climate region (from 30° to 45°), with a peak during the late summer and early autumn. Alternaria spores are known to be biological contaminants and a potent source of aeroallergens. One consequence of human exposure to Alternaria is an increased risk of developing asthma, with Alt a 1 as its main elicitor and a marker of primary sensitization. Although the action mechanism needs further investigation, a key role of the epithelium in cytokine production, TLR-activated alveolar macrophages and innate lymphoid cells in the adaptive response was demonstrated. Furthermore, sensitization to A. alternata seems to be a trigger for the development of co-sensitization to other allergen sources and may act as an exacerbator of symptoms and an elicitor of food allergies. The prevalence of A. alternata allergy is increasing and has led to expanding research on the role of this fungal species in the induction of IgE-mediated respiratory diseases. Indeed, recent research has allowed new perspectives to be considered in the assessment of exposure and diagnosis of fungi-induced allergies, although more studies are needed for the standardization of immunotherapy formulations.

The Molecular Allergen Recognition Profile in China as Basis for Allergen-Specific Immunotherapy

Approximately 30% of the world population suffers from immunoglobulin-E (IgE)-mediated allergy. IgE-mediated allergy affects the respiratory tract, the skin and the gastrointestinal tract and may lead to life-threatening acute systemic manifestations such as anaphylactic shock. The symptoms of allergy are mediated by IgE-recognition of causative allergen molecules from different allergen sources. Today, molecular allergy diagnosis allows determining the disease-causing allergens to develop allergen-specific concepts for prevention and treatment of allergy. Allergen-specific preventive and therapeutic strategies include allergen avoidance, vaccination, and tolerance induction. The implementation of these preventive and therapeutic strategies requires a detailed knowledge of the relevant allergen molecules affecting a given population. China is the world´s most populous country with around 1.4 billion inhabitants and an estimated number of more than 400 million allergic patients. Research in allergy in China has dramatically increased in the last decade. We summarize in this review article what is known about the dominating allergen sources and allergen molecules in China and what further investigations could be performed to draw a molecular map of IgE sensitization for China as a basis for the implementation of systematic and rational allergen-specific preventive and therapeutic strategies to combat allergic diseases in this country.

IgE recognition of the house dust mite allergen Der p 37 is associated with asthma

BACKGROUND

House dust mite (HDM) allergens are major elicitors of allergic reactions worldwide.

OBJECTIVE

Identification, characterization, and evaluation of diagnostic utility of a new important HDM allergen was performed.

METHODS

A cDNA coding for a new Dermatophagoides pteronyssinus (Dp) allergen, Der p 37, was isolated from a Dp expression library with allergic patients' IgE antibodies. Recombinant Der p 37 (rDer p 37) expressed in Escherichia coli was purified, then characterized by mass spectrometry, circular dichroism, and IgE reactivity by ImmunoCAP ISAC technology with sera from 111 clinically defined HDM-allergic patients. The allergenic activity of rDer p 37 was studied by basophil activation and CD4⁺ T-cell responses by carboxyfluorescein diacetate succinimidyl ester dilution assays. Specific antibodies raised against rDer p 37 were used for the ultrastructural localization of Der p 37 in mites by immunogold transmission electron microscopy.

RESULTS

Der p 37, a 26 kDa allergen with homology to chitin-binding proteins, is immunologically distinct from Der p 15, 18, and 23. It is located in the peritrophic membrane of fecal pellets. Der p 37 reacted with IgE antibodies from a third of HDM-allergic patients and induced specific basophil- and CD4⁺ T-cell activation. Der p 37 IgE-positive patients had significantly higher IgE levels to major HDM allergens, reacted with more HDM allergens, and had a higher risk (odds ratio = 3.1) of asthma compared to Der p 37-negative patients.

CONCLUSIONS

Der p 37, a new Dp allergen recognized by a third of HDM-allergic patients, may serve as a surrogate marker for severe HDM sensitization and asthma.

Insect Protein-Based Diet as Potential Risk of Allergy in Dogs

Before insects can be used widely as an alternative source of dietary protein, their allerginicity should be investigated. Therefore, the aim of our study was to assess the potential adverse reactions of the immune system of dogs against Tenebrio molitor proteins. Dogs sensitised to storage mites T. putrescentiae and A. siro were included. Clinically healthy and clinically allergic dogs were compared. Proteins were extracted from mealworm larvae and their digestibility determined by in vitro incubation with digestive proteases. Mealworm protein extracts and digests were analysed by SDS-PAGE. Canine sera tested for the presence of mite-specific IgEs were used for subsequent Western blotting. LC-MS/MS analysis was used to identify mealworm proteins and their allergenic potential was predicted with the AllermatchTM tool. The binding of canine sera IgEs to mealworm proteins was confirmed; however, the differences between the two groups of dogs were not significant. Moreover, no clear correlation was found between sensitisation to storage mites and clinical status of the dogs. Altogether, 17 different proteins were identified, including tropomyosin, α-amylase, and Tm-E1a cuticular protein that are known cross-reacting IgE-binding allergens. Our results suggest that dogs allergic to mites may clinically express also the cross-reactivity with mealworm proteins.

IgE Epitopes of the House Dust Mite Allergen Der p 7 Are Mainly Discontinuous and Conformational

Background

Several studies indicate that Der p 7 is an important and clinically relevant allergen of Dermatophagoides pteronyssinus which should be included in vaccines for treatment of house dust mite (HDM) allergy. Aim of this study was to characterize the IgE epitopes of Der p 7.

Methods

Recombinant Der p 7 was expressed and purified, analyzed for fold by circular dichroism and tested for its allergenic activity by basophil activation. Seven overlapping, surface-exposed peptides (P1–P7) with a length of 27 to 37 amino acids, which spanned the Der p 7 sequence, were synthesized and tested for IgE reactivity and allergenic activity by basophil activation assay. Carrier-bound peptides were studied for their ability to induce allergen-specific IgG antibodies in rabbits. Peptide-specific antibodies were used to inhibit allergic patients` IgE binding to Der p 7 by ELISA for mapping of IgE epitopes.

Results

rDer p 7 showed high allergenic activity comparable with Der p 5, Der p 21, and Der p 23. None of the seven tested peptides showed any IgE reactivity or allergenic activity when tested with HDM- allergic patients indicating lack of sequential IgE epitopes on Der p 7. IgE inhibition experiments using anti-peptide specific IgGs and molecular modeling enabled us to identify discontinuous, conformational IgE epitopes of Der p 7.

Conclusion and Clinical Relevance

IgE epitopes of Der p 7 belong to the conformational and discontinuous type whereas sequential Der p 7 peptides lack IgE reactivity. It should thus be possible to construct hypoallergenic vaccines for Der p 7 based on carrier-bound allergen peptides.

Allergological Importance of Invertebrate Glutathione Transferases in Tropical Environments

Glutathione-S transferases (GSTs) are part of a ubiquitous family of dimeric proteins that participate in detoxification reactions. It has been demonstrated that various GSTs induce allergic reactions in humans: those originating from house dust mites (HDM), cockroaches, and helminths being the best characterized. Evaluation of their allergenic activity suggests that they have a clinical impact. GST allergens belong to different classes: mu (Blo t 8, Der p 8, Der f 8, and Tyr p 8), sigma (Bla g 5 and Asc s 13), or delta (Per a 5). Also, IgE-binding molecules belonging to the pi-class have been discovered in helminths, but they are not officially recognized as allergens. In this review, we describe some aspects of the biology of GST, analyze their allergenic activity, and explore the structural aspects and clinical impact of their cross-reactivity.

Lactic Acid Bacteria and Natural Product Complex Ameliorates Ovalbumin-Induced Airway Hyperresponsiveness in Mice

The incidence of respiratory diseases, such as asthma, has substantially increased in recent times owing to environmental changes, such as air pollution. Induction of a chronic inflammatory response begins with production of biologically active mediators from the airway epithelium, which attracts and recruits inflammatory cells into the lung airway. In our previous study, we confirmed that Lactobacillus casei HY2782 and Bifidobacterium animalis spp. lactis HY8002 could improve lung inflammation in the COPD animal model. In this study, we investigated the effect of the HY2782 complex against airway hyperresponsiveness by using an ovalbumin (OVA)-induced animal model. An orally administered HY2782 complex on OVA-induced allergic asthma in a BALB/c mouse model was used. The present results showed that the HY2782 complex suppressed total immunoglobulin E in serum and bronchoalveolar lavage fluid (BALF). The cytokine production profile in BALF and serum revealed that the HY2782 complex showed reduced levels of Th2 cytokines among immune factors released due to the elevated allergic response. Levels of inflammatory mediators in BALF, MCP-1, MIP-2, and CXCL-9 were decreased by oral administration of the HY2782 complex. Lower numbers of eosinophils and neutrophils in BALF suggested that inflammation was ameliorated by the HY2782 complex. Histological observation of lung sections also showed infiltration of fewer cells. From results, we suggested that the HY2782 complex effectively responds to improvement of the immune response and airway hypersensitivity reaction because of the anti-inflammatory effect of the Pueraria lobata root extract and antioxidant effect of HY2782.

Molecular diagnosis in cat allergy

Domestic cats represent one of the most common sources of indoor allergens. All over the world, many households own cats, whose allergens are persistent and widespread. Cat allergy itself is frequent, and its symptoms vary from rhinoconjunctivitis to life-threatening asthma. In vitro diagnosis using precision medicine allergy immunoassays is important because natural cat dander extracts may differ in quality and quantity of some of the individual allergen components and other molecules. In the component-resolved diagnosis of cat allergy, singleplex and multiplex specific immunoglobulin (Ig) E assays include use of the cat-specific major allergen, secretoglobin Fel d 1 (as a species-specific molecule), other allergen components (such as lipocalins Fel d 4, cross-reacting with other animal similar molecules, and Fel d 7, present in small quantities in natural extracts), and serum albumin Fel d 2 (related to the cat-pork syndrome). IgA Fel d 5 and IgM Fel d 6 are not available as allergen components in the current commercial IgE immunoassays, but they may impair the in vitro diagnostic evaluation of cat allergy because galactose-α1,3-galactose is an IgE-binding epitope of these native feline allergens. The benefits of molecular-based cat allergy diagnosis are continually evaluated, as the role of recombinant allergen components already known is detailed and new other molecules of interest may be discovered in the future.

Helminth-derived cystatins: the immunomodulatory properties of an Ascaris lumbricoides cystatin

Helminth infections such as ascariasis elicit a type 2 immune response resembling that involved in allergic inflammation, but differing to allergy, they are also accompanied with strong immunomodulation. This has stimulated an increasing number of investigations, not only to better understand the mechanisms of allergy and helminth immunity but to find parasite-derived anti-inflammatory products that could improve the current treatments of chronic non-communicable inflammatory diseases such as asthma. A great number of helminth-derived immunomodulators have been discovered and some of them extensively analysed, showing their potential use as anti-inflammatory drugs in clinical settings. Since Ascaris lumbricoides is one of the most successful parasites, several groups have focused on the immunomodulatory properties of this helminth. As a result, several excretory/secretory components and purified molecules have been analysed, revealing interesting anti-inflammatory activities potentially useful as therapeutic tools. One of these molecules is A. lumbricoides cystatin, whose genomic, cellular, molecular, and immunomodulatory properties are described in this review.

Mite Molecular Profile in the Th2-Polarized Moderate-to-Severe Persistent Asthma Endotype Subjected to High Allergen Exposure

BACKGROUND

The association among the IgE responses to prevailing groups of house dust mite (HDM) allergens in the concurrent asthma phenotypes has not been determined.

OBJECTIVE

The aim of the present study lays on a component-resolved diagnosis (CRD) model to investigate the mite molecular signature in subjects with type-2 inflammation asthma.

METHODS

We selected patients showing a clinically relevant sensitization to HDMs with moderate-to-severe persistent asthma. Skin prick test (SPT) with standardized mite extracts, a broad customized CRD serum sIgE panel including 9 Dermatophagoides pteronyssinus allergens and the related protein allergenic characterization, was investigated in all serum samples.

RESULTS

Ninety out of 93 (96.77%) patients with a positive SPT to HDM showed a concordant sIgE (≥0.35 kUA/L) to the crude extract of D. pteronyssinus. Major allergens (Der p 2, Der p 23, and Der p 1) were present in >70% of all subjects, with mid-tier allergens (Der p 5, Der p 7, and Der p 21) reaching up to 51% in the present cohort. A complex pleomorphic repertoire of HDM molecules recognized by IgE was depicted, including 38 distinct profiles.

CONCLUSIONS AND CLINICAL RELEVANCE

The proposed CRD panel approach, containing the most prevalent HDM allergens, appeared to be sufficient to obtain a precise D. pteronyssinus molecular diagnosis in asthmatics with a climate-dependent high-mite allergen exposure and coexisting sensitization. A dominant role of both major and mid-tier allergens has been confirmed in moderate and severe persistent asthmatics with the preponderant Th2-high endotype.