Profilins constitute a novel family of functional plant pan-allergens

Molecular allergy diagnosis enabling personalized medicine

Allergic patients are characterized by complex and patient-specific IgE sensitization profiles to various allergens, which are accompanied by different phenotypes of allergic disease. Molecular allergy diagnosis establishes the patient's IgE reactivity profile at a molecular allergen level and has moved allergology into the era of precision medicine. Molecular allergology started in the late 1980s with the isolation of the first allergen-encoding DNA sequences. Already in 2002, the first allergen microarrays were developed for the assessment of complex IgE sensitization patterns. Recombinant allergens are used for a precise definition of personal IgE reactivity profiles, identification of genuine IgE sensitization to allergen sources for refined prescription of allergen-specific immunotherapy and allergen avoidance diagnosis of co- versus cross-sensitization, epidemiologic studies, and prediction of symptoms, phenotypes, and development of allergic disease. For example, molecular IgE sensitization patterns associated with more severe respiratory allergies, severe food allergy, and allergy to honeybee or vespids are already established. The implementation of molecular allergy diagnosis into daily clinical practice requires continuous medical education and training doctors in molecular allergy diagnosis, and may be facilitated by clinical decision support systems such as diagnostic algorithms that may take advantage of artificial intelligence.

Recombinant Art v4.01 protein produces immunological tolerance by subcutaneous immunotherapy in a wormwood pollen-driven allergic asthma female mouse model

Art v4.01 is a well-known profilin protein belonging to the pan-allergens group and is commonly involved in triggering allergic asthma, polyallergy, and cross-sensitization. It is also referred to as Wormwood due to its origin. Crude wormwood extracts are applied for allergen-specific immunotherapy (AIT). Whether the recombinant Art v4.01 (rArt v4.01) can produce in vivo immunological tolerance by subcutaneous immunotherapy (SCIT) remains elusive. In this study, to investigate the in vivo immunological response of rArt v4.01, Th2, Th1, Treg, Th17 type-related cytokines and phenotypes of immune cells were tested, facilitating the exploration of the underlying mechanisms. The expression and purification of Art v4.01 were carried out using recombinant techniques. Allergic asthma female BALB/c mice were induced by subcutaneous sensitization of wormwood pollen extract and intranasal challenges. SCIT without adjuvant was performed using the rArt v4.01 and wormwood pollen extract for 2 weeks. Following exposure to challenges, the levels of immunoglobulin E (IgE), cytokines, and inflammatory cells were assessed through enzyme-linked immunosorbent assay (ELISA) and histological examination of sera, bronchoalveolar lavage fluid (BALF), and lung tissue. These parameters were subsequently compared between treatment groups receiving rArt v4.01 and wormwood pollen extract. The rArt v4.01 protein was expressed, which had a high purity (>90%) and an allergenic potency. Compared with the pollen extract, rArt v4.01 was superior in terms of reducing the number of white blood cells (WBCs), total nucleated cells (TNCs), and monocytes (MNs) in BALF and the degree of lung inflammation (1.77±0.99 vs. 2.31±0.80, P > 0.05). Compared with the model group, only rArt v4.01 reduced serum IgE level (1.19±0.25 vs. 1.61±0.17 μg/ml, P = 0.062), as well as the levels of Th2 type-related cytokines (interleukin-4 (IL-4) (107.18±16.17 vs. 132.47±20.85 pg/ml, P < 0.05) and IL-2 (19.52±1.19 vs. 24.02±2.14 pg/ml, P < 0.05)). The study suggested that rArt v4.01 was superior to pollen extract in reducing the number of inflammatory cells in BALF, pneumonitis, levels of pro-inflammatory cytokines, and serum IgE level. These findings confirmed that Art v4.01 could be a potential candidate protein for allergen-specific immunotherapy.

Structural homology of mite profilins to plant profilins is not indicative of allergic cross-reactivity

Structural and allergenic characterization of mite profilins has not been previously pursued to a similar extent as plant profilins. Here, we describe structures of profilins originating from Tyrophagus putrescentiae (registered allergen Tyr p 36.0101) and Dermatophagoides pteronyssinus (here termed Der p profilin), which are the first structures of profilins from Arachnida. Additionally, the thermal stabilities of mite and plant profilins are compared, suggesting that the high number of cysteine residues in mite profilins may play a role in their increased stability. We also examine the cross-reactivity of plant and mite profilins as well as investigate the relevance of these profilins in mite inhalant allergy. Despite their high structural similarity to other profilins, mite profilins have low sequence identity with plant and human profilins. Subsequently, these mite profilins most likely do not display cross-reactivity with plant profilins. At the same time the profilins have highly conserved poly(l-proline) and actin binding sites.

The cytoskeletal protein profilin is an important allergen in saltwort (Salsola kali)

Pollen from Salsola kali, i.e., saltwort, Russian thistle, is a major allergen source in the coastal regions of southern Europe, in Turkey, Central Asia, and Iran. S. kali-allergic patients mainly suffer from hay-fever (i.e., rhinitis and conjunctivitis), asthma, and allergic skin symptoms. The aim of this study was to investigate the importance of individual S. kali allergen molecules. Sal k 1, Sal k 2, Sal k 3, Sal k 4, Sal k 5, and Sal k 6 were expressed in Escherichia coli as recombinant proteins containing a C-terminal hexahistidine tag and purified by nickel affinity chromatography. The purity of the recombinant allergens was analyzed by SDS-PAGE. Their molecular weight was determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and their fold and secondary structure were studied by circular dichroism (CD) spectroscopy. Sera from clinically well-characterized S. kali-allergic patients were used for IgE reactivity and basophil activation experiments. S. kali allergen-specific IgE levels and IgE levels specific for the highly IgE cross-reactive profilin and the calcium-binding allergen from timothy grass pollen, Phl p 12 and Phl p 7, respectively, were measured by ImmunoCAP. The allergenic activity of natural S. kali pollen allergens was studied in basophil activation experiments. Recombinant S. kali allergens were folded when studied by CD analysis. The sum of recombinant allergen-specific IgE levels and allergen-extract-specific IgE levels was highly correlated. Sal k 1 and profilin, reactive with IgE from 64% and 49% of patients, respectively, were the most important allergens, whereas the other S. kali allergens were less frequently recognized. Specific IgE levels were highest for profilin. Of note, 37% of patients who were negative for Sal k 1 showed IgE reactivity to Phl p 12, emphasizing the importance of the ubiquitous cytoskeletal actin-binding protein, profilin, for the diagnosis of IgE sensitization in S. kali-allergic patients. rPhl p 12 and rSal k 4 showed equivalent IgE reactivity, and the clinical importance of profilin was underlined by the fact that profilin-monosensitized patients suffered from symptoms of respiratory allergy to saltwort. Accordingly, profilin should be included in the panel of allergen molecules for diagnosis and in molecular allergy vaccines for the treatment and prevention of S. kali allergy.

Aerobiological Monitoring and Metabarcoding of Grass Pollen

Grass pollen is one of the leading causes of pollinosis, affecting 10-30% of the world's population. The allergenicity of pollen from different Poaceae species is not the same and is estimated from moderate to high. Aerobiological monitoring is a standard method that allows one to track and predict the dynamics of allergen concentration in the air. Poaceae is a stenopalynous family, and thus grass pollen can usually be identified only at the family level with optical microscopy. Molecular methods, in particular the DNA barcoding technique, can be used to conduct a more accurate analysis of aerobiological samples containing the DNA of various plant species. This study aimed to test the possibility of using the ITS1 and ITS2 nuclear loci for determining the presence of grass pollen from air samples via metabarcoding and to compare the analysis results with the results of phenological observations. Based on the high-throughput sequencing data, we analyzed the changes in the composition of aerobiological samples taken in the Moscow and Ryazan regions for three years during the period of active flowering of grasses. Ten genera of the Poaceae family were detected in airborne pollen samples. The representation for most of them for ITS1 and ITS2 barcodes was similar. At the same time, in some samples, the presence of specific genera was characterized by only one sequence: either ITS1 or ITS2. Based on the analysis of the abundance of both barcode reads in the samples, the following order could describe the change with time in the dominant species in the air: Poa, Alopecurus, and Arrhenatherum in early mid-June, Lolium, Bromus, Dactylis, and Briza in mid-late June, Phleum, Elymus in late June to early July, and Calamagrostis in early mid-July. In most samples, the number of taxa found via metabarcoding analysis was higher compared to that in the phenological observations. The semi-quantitative analysis of high-throughput sequencing data well reflects the abundance of only major grass species at the flowering stage.

Birch pollen-The unpleasant herald of spring

Type I respiratory allergies to birch pollen and pollen from related trees of the order Fagales are increasing in industrialized countries, especially in the temperate zone of the Northern hemisphere, but the reasons for this increase are still debated and seem to be multifaceted. While the most important allergenic molecules of birch pollen have been identified and characterized, the contribution of other pollen components, such as lipids, non-allergenic immunomodulatory proteins, or the pollen microbiome, to the development of allergic reactions are sparsely known. Furthermore, what also needs to be considered is that pollen is exposed to external influences which can alter its allergenicity. These external influences include environmental factors such as gaseous pollutants like ozone or nitrogen oxides or particulate air pollutants, but also meteorological events like changes in temperature, humidity, or precipitation. In this review, we look at the birch pollen from different angles and summarize current knowledge on internal and external influences that have an impact on the allergenicity of birch pollen and its interactions with the epithelial barrier. We focus on epithelial cells since these cells are the first line of defense in respiratory disease and are increasingly considered to be a regulatory tissue for the protection against the development of respiratory allergies.

Molecular Basis of Plant Profilins' Cross-Reactivity

Profilins are ubiquitous allergens with conserved structural elements. Exposure to profilins from different sources leads to IgE-cross-reactivity and the pollen-latex-food syndrome. Monoclonal antibodies (mAbs) that cross-react with plant profilins and block IgE-profilin interactions are relevant for diagnosis, epitope mapping, and specific immunotherapy. We generated IgGs mAbs, 1B4, and 2D10, against latex profilin (anti-rHev b 8) that inhibit the interaction of IgE and IgG4 antibodies from sera of latex- and maize-allergic patients by 90% and 40%, respectively. In this study, we evaluated 1B4 and 2D10 recognition towards different plant profilins, and mAbs recognition of rZea m 12 mutants by ELISAs. Interestingly, 2D10 highly recognized rArt v 4.0101 and rAmb a 8.0101, and to a lesser extent rBet v 2.0101, and rFra e 2.2, while 1B4 showed recognition for rPhl p 12.0101 and rAmb a 8.0101. We demonstrated that residue D130 at the α-helix 3 in profilins, which is part of the Hev b 8 IgE epitope, is essential for the 2D10 recognition. The structural analysis suggests that the profilins containing E130 (rPhl p 12.0101, rFra e 2.2, and rZea m 12.0105) show less binding with 2D10. The distribution of negative charges on the profilins' surfaces at the α-helices 1 and 3 is relevant for the 2D10 recognition, and that may be relevant to explain profilins' IgE cross-reactivity.

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.

Relationship between IgE Levels Specific for Ragweed Pollen Extract, Amb a 1 and Cross-Reactive Allergen Molecules

Ragweed (Ambrosia artemisiifolia) pollen is a major endemic allergen source responsible for severe allergic manifestations in IgE-sensitized allergic patients. It contains the major allergen Amb a 1 and cross-reactive allergen molecules, such as the cytoskeletal protein profilin, Amb a 8 and calcium-binding allergens Amb a 9 and Amb a 10. To assess the importance of Amb a 1, profilin and calcium-binding allergen, the IgE reactivity profiles of clinically well-characterized 150 ragweed pollen-allergic patients were analysed regarding specific IgE levels for Amb a 1 and cross-reactive allergen molecules by quantitative ImmunoCAP measurements, IgE ELISA and by basophil activation experiments. By quantifying allergen-specific IgE levels we found that Amb a 1-specific IgE levels accounted for more than 50% of ragweed pollen-specific IgE in the majority of ragweed pollen-allergic patients. However, approximately 20% of patients were sensitized to profilin and the calcium-binding allergens, Amb a 9 and Amb a 10, respectively. As shown by IgE inhibition experiments, Amb a 8 showed extensive cross-reactivity with profilins from birch (Bet v 2), timothy grass (Phl p 12) and mugwort pollen (Art v 4) and was identified as a highly allergenic molecule by basophil activation testing. Our study indicates that molecular diagnosis performed by the quantification of specific IgE to Amb a 1, Amb a 8, Amb a 9 and Amb a 10 is useful to diagnose genuine sensitization to ragweed pollen and to identify patients who are sensitized to highly cross-reactive allergen molecules present in pollen from unrelated plants, in order to enable precision medicine-based approaches for the treatment and prevention of pollen allergy in areas with complex pollen sensitization.

pH-dependent structural diversity of profilin allergens determines thermal stability

The family of profilin allergens is a common class of proteins found in plants, viruses and various eukaryotes including mammals. Profilins are characterized by an evolutionary conserved structural fold, which is responsible for their cross-reactive nature of Immunoglobulin E (IgE) antibodies. Despite their high overall structural similarity, they exhibit substantial differences in their biophysical properties, such as thermal and pH stability. To understand the origin of these functional differences of Amb a 8, Art v 4 and Bet v 2, we performed constant pH molecular dynamics simulation in combination with Gaussian accelerated MD simulations. Depending on the respective protonation at different pH levels, we find distinct differences in conformational flexibility, which are consistent with experimentally determined melting temperatures. These variations in flexibility are accompanied by ensemble shifts in the conformational landscape and quantified and localized by residue-wise B-factors and dihedral entropies. These findings strengthen the link between flexibility of profilin allergens and their thermal stability. Thus, our results clearly show the importance of considering protonation dependent conformational ensembles in solution to elucidate biophysical differences between these structurally similar allergens.

Taro raphide-associated proteins: Allergens and crystal growth

Calcium oxalate raphide crystals are found in bundles in intravacuolar membrane chambers of specialized idioblasts cells of most plant families. Aroid raphides are proposed to cause acridity in crops such as taro (Colocasia esculenta (L.) Schott). Acridity is irritation that causes itchiness and pain when raw/insufficiently cooked tissues are eaten. Since raphides do not always cause acridity and since acridity can be inactivated by cooking and/or protease treatment, it is possible that a toxin or allergen-like compound is associated with the crystals. Using two-dimensional (2D) gel electrophoresis and mass spectrometry (MS) peptide sequencing of selected peptides from purified raphides and taro apex transcriptome sequencing, we showed the presence on the raphides of peptides normally associated with mitochrondria (ATP synthase), chloroplasts (chaperonin ~60 kDa), cytoplasm (actin, profilin), and vacuole (V-type ATPase) that indicates a multistage biocrystallation process ending with possible invagination of the tonoplast and addition of mucilage that may be derived from the Golgi. Actin might play a crucial role in the generation of the needle-like raphides. One of the five raphide profilins genes was highly expressed in the apex and had a 17-amino acid insert that significantly increased that profilin's antigenic epitope peak. A second profilin had a 2-amino acid insert and also had a greater B-cell epitope prediction. Taro profilins showed 83% to 92% similarity to known characterized profilins. Further, commercial allergen test strips for hazelnuts, where profilin is a secondary allergen, have potential for screening in a taro germplasm to reduce acridity and during food processing to avoid overcooking.

Complex IgE sensitization patterns in ragweed allergic patients: Implications for diagnosis and specific immunotherapy

Background

Ragweed (Ambrosia artemisiifolia) is one of the most important allergen sources, worldwide, causing severe respiratory allergic reactions in late summer and fall, in sensitized patients. Amb a 1 has been considered as the most important allergen in ragweed but 12 ragweed pollen allergens are known. The aim of our study was to investigate IgE reactivity profiles of ragweed allergic patients and to associate them with clinical symptoms.

Methods

IgE sensitization profiles from clinically well-characterized ragweed allergic patients (n = 150) were analyzed using immunoblotted ragweed pollen extract. Immunoblot inhibition experiments were performed with two Amb a 1 isoforms and CCD markers and basophil activation experiments were performed with IgE serum before and after depletion of Amb a 1-specific IgE.

Results

By IgE-immunoblotting 19 different IgE reactivity patterns with and without Amb a 1-sensitization were found. The majority of patients (>95%) suffered from rhino-conjunctivitis, around 60% reported asthma-like symptoms and about 25% had skin reactions. Patients with complex IgE sensitization profiles tended to have more clinical symptoms. Serum with and without Amb a 1-specific IgE induced basophil activation.

Conclusions

Ragweed pollen allergic patients exhibit complex IgE reactivity profiles to ragweed allergens including Amb a 1 isoforms and cross-reactive carbohydrates indicating the importance of Amb a 1 isoforms and additional allergens for diagnosis and allergen-specific immunotherapy of ragweed allergy.

How Do Pollen Allergens Sensitize?

Plant pollen is one of the main sources of allergens causing allergic diseases such as allergic rhinitis and asthma. Several allergens in plant pollen are panallergens which are also present in other allergen sources. As a result, sensitized individuals may also experience food allergies. The mechanism of sensitization and development of allergic inflammation is a consequence of the interaction of allergens with a large number of molecular factors that often are acting in a complex with other compounds, for example low-molecular-mass ligands, which contribute to the induction a type 2-driven response of immune system. In this review, special attention is paid not only to properties of allergens but also to an important role of their interaction with lipids and other hydrophobic molecules in pollen sensitization. The reactions of epithelial cells lining the nasal and bronchial mucosa and of other immunocompetent cells will also be considered, in particular the mechanisms of the activation of B and T lymphocytes and the formation of allergen-specific antibody responses.

A comprehensive analysis of the components of common weed pollen and related allergens in patients with allergic diseases in southern China

BACKGROUND

Pollen allergens are vital contributors to allergic diseases. The frequency and coreactivity pattern of allergens are closely related to geographical distribution.

OBJECTIVE

In this study, we aimed to characterize the prevalence of the molecular components of the common weed pollen allergens, birch pollen, walnut, and cross-reactive carbohydrate determinant (CCD), as well as investigate the relationship between the allergens and CCD in Chinese pollen-sensitized patients with allergic diseases.

METHODS

Based on previous vegetation surveys, serum samples from 165 pollen-sensitized patients with allergic diseases in Guangdong Province in southern China were used to test 19 crude allergen extracts, their components, and CCD using component-resolved diagnosis (CRD). Moreover, the potential associations among CCD, allergens, and their components were described.

RESULTS

In the 165 samples, the most common sensitized allergens were goosefoot (43.0%), ragweed (40.6%), walnut (37.6%), walnut tree (37.6%), and mugwort (37.0%), followed by platane (35.2%), cocklebur (27.9%), and birch (24.2%). The positivity rate of CCD was 39.4%. Among the samples positive for mugwort, 11 (18.0%), 15 (24.6%), and 15 (24.6%) were positive for Art v 1, Art v 2, and Art v 3, respectively. Among the 67 patients sensitized to ragweed, only five (7.5%) were positive for Amb a 1. In the 40 patients sensitized to birch, Bet v 2 had the highest positivity rate (40.0%). There were 62 patients who were sensitized to walnut. Their components had a lower positivity rate (less than 15%). The hierarchical clustering and optimal scale analysis showed that Art v 4 and Bet v 2 were closely related, and 91.9% of CCD-positive samples were polysensitized. Meanwhile, Spearman's rank correlation method showed that CCD was closely correlated with the sensitization of crude allergen extracts, and there was a low correlation between CCD and allergen components. CCD was highly correlated with goosefoot, ragweed, and walnut trees (r＞0.8). Moreover, there was a strong relationship between the levels of Jug r 3 and Art v 3 (r = 0.78; P < 0.001).

CONCLUSIONS

In southern China, the weed pollens (ragweed, cocklebur, and goosefoot) exhibited higher positivity rates in adults and had a stronger relationship with CCD but not with mugwort. The positivity rate of allergen components was not high. CCD-positive samples were always polysensitized.

Tomato Allergy: The Characterization of the Selected Allergens and Antioxidants of Tomato (Solanum lycopersicum)-A Review

Tomatoes are one of the most broadly produced and consumed crop plants. They are the source of health-promoting nutrients such as antioxidants, including ascorbic acid, polyphenols, or carotenoids. Despite the beneficial role of tomatoes in the daily diet, they have been confirmed as one of the most prevalent allergenic vegetables. Food allergies can cause many clinical symptoms, e.g., in the gastrointestinal tract, skin, and lungs, as well as anaphylactic shock. A huge amount of clinical research has been carried out to improve the understanding of the immunological mechanisms that lead to the lack of tolerance of food antigens, which can result in either immunoglobulin E (IgE)-mediated reactions or non-IgE-mediated reactions. Lifestyle and diet play an important role in triggering food allergies. Allergy to tomatoes is also linked to other allergies, such as grass pollen and latex allergy. Numerous attempts have been made to identify and characterize tomato allergens; however, the data available on the subject are not sufficient.

Three patterns of sensitization to mugwort, timothy, birch and their major allergen components revealed by Latent class analysis

BACKGROUND

Mugwort, timothy, and birch are commonly spread pollen allergens across China. Although several studies have described the rates of sensitization to mugwort, timothy, and birch in China, most of them just on specific whole-allergen extracts but little was known about the co-sensitization characteristics of its allergen components. This study aimed to explore the patterns of sensitization to mugwort, timothy, birch, and their major allergen components.

METHOD

Serum specific IgE (sIgE) levels of allergen components of mugwort, timothy, birch, and cross-reactive carbohydrate determinants (CCD) were detected in 160 patients whose serum showed positive results to at least one of mugwort, timothy, and birch allergens via EUROBlotMaster system. Skin prick testing was utilized to assess the allergic reaction of grass, weed, and tree allergens. Latent class analysis was used to identify underlying patterns of sensitization to a series of allergen components and their corresponding extracts.

RESULTS

88.8% of patients with allergic rhinitis and/or asthma were positive for mugwort-sIgE, 30% for timothy-sIgE, and 32.5% for birch-sIgE. By using the LCA model, three sensitization patterns as "Mugwort, Art v 4, Bet v 2 and Phl p 12 co-sensitized", "Timothy, mugwort, and CCD co-sensitized", "Mugwort and Art v 1 co-sensitized" were revealed based on optimal statistical fit in this study. Compared with other clusters, participants in "Mugwort, Art v 4, Bet v 2 and Phl p 12 co-sensitized" pattern were associated with higher sensitization rates of common grass and tree pollens allergen. The spearman's coefficient between CCD and timothy was larger than the corresponding values of CCD with mugwort or birch.

CONCLUSION

CCD and profilin, as minor allergens in pollens, were associated with other pollen sIgE false positives presumably due to cross-reactivity. Patients sensitized with profilin had a significantly higher risk of sensitization to other pollens.

From Allergen Molecules to Molecular Immunotherapy of Nut Allergy: A Hard Nut to Crack

Peanuts and tree nuts are two of the most common elicitors of immunoglobulin E (IgE)-mediated food allergy. Nut allergy is frequently associated with systemic reactions and can lead to potentially life-threatening respiratory and circulatory symptoms. Furthermore, nut allergy usually persists throughout life. Whether sensitized patients exhibit severe and life-threatening reactions (e.g., anaphylaxis), mild and/or local reactions (e.g., pollen-food allergy syndrome) or no relevant symptoms depends much on IgE recognition of digestion-resistant class I food allergens, IgE cross-reactivity of class II food allergens with respiratory allergens and clinically not relevant plant-derived carbohydrate epitopes, respectively. Accordingly, molecular allergy diagnosis based on the measurement of allergen-specific IgE levels to allergen molecules provides important information in addition to provocation testing in the diagnosis of food allergy. Molecular allergy diagnosis helps identifying the genuinely sensitizing nuts, it determines IgE sensitization to class I and II food allergen molecules and hence provides a basis for personalized forms of treatment such as precise prescription of diet and allergen-specific immunotherapy (AIT). Currently available forms of nut-specific AIT are based only on allergen extracts, have been mainly developed for peanut but not for other nuts and, unlike AIT for respiratory allergies which utilize often subcutaneous administration, are given preferentially by the oral route. Here we review prevalence of allergy to peanut and tree nuts in different populations of the world, summarize knowledge regarding the involved nut allergen molecules and current AIT approaches for nut allergy. We argue that nut-specific AIT may benefit from molecular subcutaneous AIT (SCIT) approaches but identify also possible hurdles for such an approach and explain why molecular SCIT may be a hard nut to crack.

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.

Update on pollen-food allergy syndrome

INTRODUCTION

Allergies affect 20-30% of the population and respiratory allergies are mostly due to pollen grains from anemophilous plants. One to 5% of people suffer from food allergies and clinicians report increasing numbers of pollen-food allergy syndrome (PFAS), such that the symptoms have broadened from respiratory to gastrointestinal, and even to anaphylactic shock in the presence of cofactors. Thirty to 60% of food allergies are associated with pollen allergy while the percentage of pollen allergies associated to food allergy varies according to local environment and dietary habits.

AREAS COVERED

Articles published in peer-reviewed journals, covered by PubMed databank, clinical data are discussed including symptoms, diagnosis, and management. A chapter emphasizes the role of six well-known allergen families involved in PFAS: PR10 proteins, profilins, lipid transfer proteins, thaumatin-like proteins, isoflavone reductases, and β-1,3 glucanases. The relevance in PFAS of three supplementary allergen families is presented: oleosins, polygalacturonases, and gibberellin-regulated proteins. To support the discussion a few original relevant results were added.

EXPERT OPINION

Both allergenic sources, pollen and food, are submitted to the same stressful environmental changes resulting in an increase of pathogenesis-related proteins in which numerous allergens are found. This might be responsible for the potential increase of PFAS.

Heat-Stable Hazelnut Profilin: Molecular Dynamics Simulations and Immunoinformatics Analysis

Heat treatment can modify the allergenic potential, reducing allergenicity in specific proteins. Profilins are one of the important hazelnut allergens; these proteins are considered panallergens due to their high capacity for cross-reactivity with other allergens. In the present work, we evaluated the thermostability of hazelnut profilin, combining molecular dynamics simulation and immunoinformatic techniques. This approach helped us to have reliable results in immunogenicity studies. We modeled Cor a 2 profilin and applied annealing simulation, equilibrium, and production simulation at constant temperatures ranging from 300 to 500 K using Gromacs software. Despite the hazelnut profilins being able to withstand temperatures of up to 400 K, this does not seem to reduce its allergenicity. We have found that profilin subjected to temperatures of 450 and 500 K could generate cross-reactivity with other food allergens. In conclusion, we note a remarkable thermostability of Cor a 2 at 400 K which avoids its structural unfolding.

Profilin is a marker of severity in allergic respiratory diseases

BACKGROUND

The capacity of profilin to induce allergic symptoms in patients with respiratory allergy has been questioned. In this sense, the aim of this study was to investigate the correlation between profilin exposure and induction of symptoms in a prospective case-control study.

METHODS

The concentration of profilin as well as pollen levels in the air was measured. A diary score of symptoms was collected from allergic patients. Seventy-nine individuals were included in the study; fifty cases and 28 controls were positive or negative to profilin, respectively. Conjunctival and bronchial provocation tests were performed with purified profilin (Pho d 2) in a subgroup of cases and controls.

RESULTS

Profilin was detected in the environment on 133 days (maximum peak of 0.56 ng/m³ ). A positive correlation between profilin and pollen count of Olea and Poaceae was observed (ρ = 0.24; P < .001). Intensity of total, nasal and ocular symptoms was statistically higher in cases than in controls (P < .001). The risk of suffering symptoms, measured by the percentage of patients who presented any of the symptoms each day, was also higher in cases than in controls. The provocation test was positive in 95% of bronchial and 90% of conjunctival challenges in cases, and negative in all controls.

CONCLUSIONS

Profilin was detected in the environment and had the ability to induce a specific allergen response. Patients sensitized to this panallergen showed more symptoms and were more likely to have symptoms. Therefore, sensitization to profilin seems to be a marker of severity in patients with rhinoconjunctivitis and asthma mediated by pollen.

Production and Use of Recombinant Profilins Amb a 8, Art v 4, Bet v 2, and Phl p 12 for Allergenic Sensitization Studies

Four recombinant (r) allergens (rAmb a 8.0101, rArt v 4.0101, rBet v 2.0101, and rPhl p 12.0101) were successfully produced and used for sensitization studies. The allergens belong to the profilin family which is one of the most numerous allergen families. These four proteins represent allergens originating from pollen of weeds (rAmb a 8.0101 and rArt v 4.0101), tree (rBet v 2.0101) and grass (rPhl p 12.0101). The recombinant allergens were characterized using various biochemical and biophysical methods and tested for their ability to bind patient-derived antibodies. One hundred patients aged 2 to 50 years sensitized to pollen and plant-derived food allergens (IgE > 0.35 kU/L) were included. Sensitization to individual allergen sources and components of birch and timothy pollens was evaluated using multiparameter immunoblots. The presence of IgE to pollen-derived recombinant profilins rAmb a 8.0101, rArt v 4.0101, rBet v 2.0101, and rPhl p 12.0101 in serum was evaluated using ELISA method. The presence of IgE against pollen profilins was detected in 20 out of 100 studied patients. High correlation was seen between IgE ELISA results with individual pollen profilins. In summary, it was shown that the recombinant versions of the four allergenic profilins can be used for sensitization studies and for component-resolved allergy diagnostics.

Molecular characterization of a fungal cyclophilin allergen Rhi o 2 and elucidation of antigenic determinants responsible for IgE-cross-reactivity

Cyclophilins are structurally conserved pan-allergens showing extensive cross-reactivity. So far, no precise information on cross-reactive IgE-epitopes of cyclophilins is available. Here, an 18-kDa IgE-reactive cyclophilin (Rhi o 2) was purified from Rhizopus oryzae, an indoor mold causing allergic sensitization. Based on LC-MS/MS-derived sequences of natural Rhi o 2, the full-length cDNA was cloned, and expressed as recombinant (r) allergen. Purified rRhi o 2 displayed IgE-reactivity and basophil degranulation with sera from all cyclophilin-positive patients. The melting curve of properly folded rRhi o 2 showed partial refolding after heat denaturation. The allergen displayed monomeric functional peptidyl-prolyl cis-trans isomerase (PPIase) activity. In IgE-inhibition assays, rRhi o 2 exhibited extensive cross-reactivity with various other cyclophilins reported as allergens from diverse sources including its homologous human autoantigen. By generating a series of deletion mutants, a conserved 69-residue (Asn⁸¹-Asn¹⁴⁹) fragment at C terminus of Rhi o 2 was identified as crucial for IgE-recognition and cross-reactivity. Grafting of the Asn⁸¹-Asn¹⁴⁹ fragment within the primary structure of yeast cyclophilin CPR1 by replacing its homologous sequence resulted in a hybrid molecule with structural folds similar to Rhi o 2. The IgE-reactivity and allergenic activity of the hybrid cyclophilin were greater than that of CPR1. Therefore, the Asn⁸¹-Asn¹⁴⁹ fragment can be considered as the site of IgE recognition of Rhi o 2. Hence, Rhi o 2 serves as a candidate antigen for the molecular diagnosis of mold allergy, and determination of a major cross-reactive IgE-epitope has clinical potential for the design of next-generation immunotherapeutics against cyclophilin-induced allergies.

Clinical and immunological differences between asymptomatic HDM-sensitized and HDM-allergic rhinitis patients

BACKGROUND

Confirmation of the clinical relevance of sensitisation is important for the diagnosis of allergic rhinitis.

OBJECTIVE

To investigate the usefulness of an in vitro basophil activation test and component-resolved diagnosis in distinguishing between symptomatic allergic rhinitis patients and asymptomatic sensitization to house dust mites (HDMs).

METHODS

Thirty-six subjects with a positive skin prick test (SPT) for HDM were divided into a symptomatic (n = 17) and an asymptomatic (n = 19) group on the basis of their clinical history and a nasal provocation test. A basophil CD63 response to in vitro stimulation with Dermatophagoides pteronyssinus whole allergen extract and the IgE reactivity profiles for Der p 1, 2, 4, 5, 7, 10, 11, 14, 15, 18, 21, 23 were evaluated. Serum IgE and IgG specific to D pteronyssinus whole allergen extract and total IgE were measured.

RESULTS

There were no statistically significant differences in the levels of IgE (IgE levels were higher in symptomatic patients with P = 0.055) and IgG specific to D pteronyssinus and total IgE. Symptomatic patients showed a lower threshold for in vitro basophil activation (3.33 ng/mL vs 33.3 ng/mL), a higher area under the curve (AUC) of basophil activation (171 vs 127) (P = 0.017), a higher response to positive control with anti-FcεRI stimulation (97% vs 79%) (P < 0.001), a recognition of more HDM allergens (4 vs 2) and more frequent sensitization to rDer p 7 (P = 0.016) and rDer p 23 compared to asymptomatic subjects (P = 0.018). There was a positive correlation (r = 0.63; P < 0.001) between the number of recognized allergens and the AUC of basophil activation.

CONCLUSION AND CLINICAL RELEVANCE

In the subjects studied, the differences in the basophil response to D pteronyssinus allergen extract, number of recognized HDM allergens and reactivity to rDer p 7 and rDer p 23 distinguish symptomatic from asymptomatic HDM sensitisation better than SPT or allergen extract-specific IgE. Information regarding the clinical relevance of sensitization is important for the prescription of allergen-specific immunotherapy.

The occurrence of food hypersensitivity reactions and the relation to the sensitization to grass and trees in atopic dermatitis patients 14 years of age and older

Background:

Methods:

Results:

Conclusion:

Recombinant glycoproteins resembling carbohydrate-specific IgE epitopes from plants, venoms and mites

Background

N-linked glycans present in venoms, pollen and mites are recognized by IgE antibodies from >20% of allergic patients but have low or no allergenic activity.

Objectives

To engineer recombinant glycoproteins resembling carbohydrate-specific IgE epitopes from venoms, pollen and mites which can discriminate carbohydrate-specific IgE from allergenic, peptide-specific IgE.

Methods

One or two N-glycosylation sites were engineered into the N-terminus of the non-allergenic protein horse heart myoglobin (HHM) using synthetic gene technology. HHM 1 and HHM 2 containing one or two N-glycosylation sites were expressed in baculovirus-infected High-Five™ insect cells and a non-glycosylated version (HHM 0) was obtained by mutating the glycosylation motif. Recombinant HHM proteins were analyzed regarding fold and aggregation by circular dichroism and gel filtration, respectively. IgE reactivity was assessed by ELISA, immunoblotting and quantitative ImmunoCAP measurements. IgE inhibition assays were performed to study cross-reactivity with venom, plant and mite-derived carbohydrate IgE epitopes.

Results

HHM-glycovariants were expressed and purified from insect cells as monomeric and folded proteins. The HHM-glycovariants exhibited strictly carbohydrate-specific IgE reactivity, designed to quantify carbohydrate-specific IgE and resembled IgE epitopes of pollen, venom and mite-derived carbohydrates. IgE-reactivity and inhibition experiments established a hierarchy of plant glcyoallergens (nPhl p 4 > nCyn d 1 > nPla a 2 > nJug r 2 > nCup a 1 > nCry j 1) indicating a hitherto unknown heterogeneity of carbohydrate IgE epitopes in plants which were completely represented by HHM 2.

Conclusion

Defined recombinant HHM-glycoproteins resembling carbohydrate-specific IgE epitopes from plants, venoms and mites were engineered which made it possible to discriminate carbohydrate- from peptide-specific IgE reactivity.

Acanthamoeba profilin elicits allergic airway inflammation in mice

Background

In previous studies, we suggested that Acanthamoeba is a new aero-allergen and that patients who showed positive results for the skin-prick test response to Acanthamoeba cross-reacted with several pollen allergens. Additionally, patients with common antibodies reacted to the 13–15 kDa Acanthamoeba unknown allergen.

Objective

We examined whether profilin of Acanthamoeba is a human airway allergic agent because of its molecular weight.

Methods

We expressed recombinant Ac-PF (rAc-PF) protein using an Escherichia coli expression system and evaluated whether Ac-PF is an airway allergic agent using an allergic airway inflammation animal model.

Results

Airway hyperresponsiveness was increased in rAc-PF-inoculated mice. The number of eosinophils and levels of Th2 cytokines, interleukin (IL)-4, IL-5, and IL-13 were increased in the bronchial alveolar lavage fluid of rAc-PF-treated mice. The lungs of the rAc-PF-treated mice group showed enhanced mucin production and metaplasia of lung epithelial cells and goblet cells.

Conclusion

In this study, we demonstrated that rAc-PF may be an allergen in Acanthamoeba, but further studies needed to identify the mechanisms of allergenic reactions induced by Ac-PF.

Recently, the number of asthma patients have increased sharply. Among patients with asthma have a high serum IgE titer, but despite this, some of these patients do not react to known allergens in skin prick tests, that suggests the presence of unknown environmental allergens. The protozoa Acanthamoeba live in very diverse environment including water, soil, air and even human nasal cavities, throat, pharynx and lung. In previous study, Acanthamoeba could be a new aero-allergen. Patients who showed positive results for the skin-prick test response to Acanthamoeba, their serum could be cross-reacted with several pollen allergens as well as Acanthamoeba total proteins. Additionally, the patients have common antibodies reacted to the 13–15 kDa Acanthamoeba unknown allergen. Profilin, which is found in all eukaryotic organisms in most cells, is an actin-binding protein that interferes with nucleation and restructuring of new filaments. Recent studies showed that profilin functions as a pan-allergen recognized by IgE in approximately 20% of birch pollen and plant food allergic patients. In Acanthamoeba, two isoforms of profilin (Ac-PF) have been identified: profilin-I and profilin-II. We examined profilin from Acanthamoeba as a potential human airway allergic agent because of its molecular weight (13–14 kDa) and cross-reactivity with several pollen allergens in the skin prick test showing positive results for Acanthamoeba in chronic cough patients. In this study, we expressed recombinant Ac-PF (rAc-PF) protein using an Escherichia coli expression system and evaluated whether Ac-PF is an airway allergic agent using an asthma animal model. Our study showed that rAc-PF may be an allergen in Acanthamoeba, but further studies needed to identify the mechanisms of allergenic reactions induced by Ac-PF.

A robust method for the estimation and visualization of IgE cross-reactivity likelihood between allergens belonging to the same protein family

Among the vast number of identified protein families, allergens emanate from relatively few families which translates to only a small fraction of identified protein families. In allergy diagnostics and immunotherapy, interactions between immunoglobulin E and allergens are crucial because the formation of an allergen-antibody complex is necessary for triggering an allergic reaction. In allergic diseases, there is a phenomenon known as cross-reactivity. Cross-reactivity describes a situation where an individual has produced antibodies against a particular allergenic protein, but said antibodies fail to discriminate between the original sensitizer and other similar proteins that usually belong to the same family. To expound the concept of cross-reactivity, this study examines ten protein families that include allergens selected specifically for the analysis of cross-reactivity. The selected allergen families had at least 13 representative proteins, overall folds that differ significantly between families, and include relevant allergens with various potencies. The selected allergens were analyzed using information on sequence similarities and identities between members of the families as well as reports on clinically relevant cross-reactivities. Based on our analysis, we propose to introduce a new A-RISC index (Allergens’–Relative Identity, Similarity and Cross-reactivity) which describes homology between two allergens belonging to the same protein family and is used to predict the likelihood of cross-reactivity between them. Information on sequence similarities and identities, as well as on the values of the proposed A-RISC index is used to introduce four categories describing a risk of a cross-reactive reaction, namely: high, medium-high, medium-low and low. The proposed approach can facilitate analysis in component-resolved allergy diagnostics, generation of avoidance guidelines for allergic individuals, and help with the design of immunotherapy.

Influence of Heavy Metals (Ni, Cu, and Zn) on Nitro-Oxidative Stress Responses, Proteome Regulation and Allergen Production in Basil (Ocimum basilicum L.) Plants

One of the most significant biosphere contamination problems worldwide is derived from heavy metals. Heavy metals can be highly reactive and toxic according to their oxidation levels. Their toxic effects are associated with the increased production of reactive oxygen species (ROS) and cellular damage induced in plants. The present study focuses on the effects of nickel (Ni), copper (Cu), and zinc (Zn) applied to the soil on the antioxidant response and allergen production in the aromatic plant basil (Ocimum basilicum L.) following a combined physiological, biochemical and analytical approach. The concentrations used for the three heavy metals were based on the 2002 Regulation of the Polish Ministry of the Environment on Soil Quality Standards [(i) agricultural land (group B): Ni 100 ppm, Ni 210 ppm, Cu 200 ppm, Cu 500 ppm, Zn 720 ppm and (ii) industrial land (group C): Ni 500 ppm, Cu 1000 ppm, Zn 1500 ppm, Zn 3000 ppm]. The highest physiological and cellular damage in basil plants was caused by Cu and Zn. Increasing concentrations of Cu resulted in a further increase in cellular damage and nitro-oxidative stress, correlating with an induction in activity of reactive oxygen and nitrogen species metabolism enzymes (SOD, CAT, APX, NR). Treatment with Cu led to increased concentration of the allergenic protein profilin, while increasing concentrations of Cu and Zn led to a decrease in the concentration of total proteins (likely due to proteolysis) and antioxidant capacity. Interestingly, severe Cu stress resulted in the accumulation of specific proteins related to transpiration and photosynthetic processes. On the basis of these findings, Ni stress in basil plants appears to be less damaging and with lower allergenic potential compared with Cu and Zn stress, while Cu-stressed basil plants experience most detrimental effects and display highest allergen production.

Betamethasone prevents human rhinovirus- and cigarette smoke- induced loss of respiratory epithelial barrier function

The respiratory epithelium is a barrier against pathogens and allergens and a target for therapy in respiratory allergy, asthma and chronic obstructive pulmonary disease (COPD). We investigated barrier-damaging factors and protective factors by real-time measurement of respiratory cell barrier integrity. Barrier integrity to cigarette smoke extract (CSE), house dust mite (HDM) extract, interferon-γ (IFN-γ) or human rhinovirus (HRV) infection alone or in combination was assessed. Corticosteroids, lipopolysaccharide (LPS), and nasal mucus proteins were tested for their ability to prevent loss of barrier integrity. Real-time impedance-based measurement revealed different patterns of CSE-, HDM-, IFN-γ- and HRV-induced damage. When per se non-damaging concentrations of harmful factors were combined, a synergetic effect was observed only for CSE and HDM. Betamethasone prevented the damaging effect of HRV and CSE, but not damage caused by HDM or IFN-γ. Real-time impedance-based measurement of respiratory epithelial barrier function is useful to study factors, which are harmful or protective. The identification of a synergetic damaging effect of CSE and HDM as well as the finding that Betamethasone protects against HRV- and CSE-induced damage may be important for asthma and COPD.

Tree nut allergies: Allergen homology, cross-reactivity, and implications for therapy

Tree nut allergy is a potentially life-threatening disease that is increasing in prevalence, now affecting 1% of the general population in the United States. While other food allergies often resolve spontaneously, tree nut allergies are outgrown in less than 10% of cases. Due to the likelihood of cross-sensitization to multiple tree nut allergens, the current treatment guideline is strict avoidance of all nuts once one tree nut allergy has been diagnosed. For example, walnut and pecan are highly cross-reactive, along with cashew and pistachio, but the extent of clinical, IgE-mediated cross-reactivity among other tree nuts remains unclear, therefore making avoidance of all tree nuts a safe approach. There have been recent advances in immunotherapy for food allergies. For instance, there are investigational immunotherapies for milk, egg and peanut allergies, specifically oral immunotherapy, sublingual immunotherapy and epicutaneous immunotherapy. However, there are no large randomized controlled clinical trials for tree nut allergies. Even though there has been less research into tree nut allergy immunotherapies, the evidence of T-cell cross-reactivity among tree nuts exists in animal models and in T cells from allergic patients indicates that immunotherapeutic interventions may be possible. Here, we review the literature regarding epidemiology, allergen homology and cross-reactivity among tree nuts, and explore how current findings can be employed for effective therapy.

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

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

Diagnostic relevance of IgE sensitization profiles to eight recombinant Phleum pratense molecules

BACKGROUND

Grass pollen-related seasonal allergic rhinoconjunctivitis (SARg) is clinically heterogeneous in severity, comorbidities, and response to treatment. The component-resolved diagnostics disclosed also a high heterogeneity at molecular level. Our study aimed at analyzing the characteristics of the IgE sensitization to Phleum pratense molecules and investigating the diagnostic relevance of such molecules in childhood.

METHODS

We examined 1120 children (age 4-18 years) with SARg. Standardized questionnaires on atopy were acquired through informatics platform (AllergyCARD™). Skin prick tests were performed with pollen extracts. Serum IgE to airborne allergens and eight P. pratense molecules (rPhl p 1, rPhl p 2, rPhl p 4, rPhl p 5b, rPhl p 6, rPhl p 7, rPhl p 11, rPhl p 12) were tested by ImmunoCAP FEIA.

RESULTS

The analysis of IgE responses against eight P. pratense molecules showed 87 profiles. According to the number of molecules recognized by IgE, the more complex profiles were characterized by higher serum total IgE, higher grass-specific serum IgE, and higher number and degree of sensitization to pollens. The most frequent IgE sensitization profile was the monomolecular Phl p 1. Sensitization to Phl p 7 was a reliable biomarker of asthma, whereas Phl p 12 of oral allergy syndrome. Sensitization to Phl p 7 was associated with a higher severity of SARg, and complex profiles were associated with longer disease duration.

CONCLUSIONS

In a large pediatric population, the complexity of IgE sensitization profiles against P. pratense molecules is related to high atopic features although useless for predicting the clinical severity. The detection of serum IgE to Phl p 1, Phl p 7, and Phl p 12 can be used as clinical biomarkers of SARg and comorbidities. Further studies in different areas are required to test the impact of different IgE molecular profiles on AIT response.

House dust mites as potential carriers for IgE sensitization to bacterial antigens

Background

IgE reactivity to antigens from Gram‐positive and Gram‐negative bacteria is common in patients suffering from respiratory and skin manifestations of allergy, but the routes and mechanisms of sensitization are not fully understood. The analysis of the genome, transcriptome and microbiome of house dust mites (HDM) has shown that Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) species are abundant bacteria within the HDM microbiome. Therefore, our aim was to investigate whether HDM are carriers of bacterial antigens leading to IgE sensitization in patients suffering from atopic dermatitis.

Methods

Plasma samples from patients with AD (n = 179) were analysed for IgE reactivity to a comprehensive panel of microarrayed HDM allergen molecules and to S. aureus and E. coli by IgE immunoblotting. Antibodies specific for S. aureus and E. coli antigens were tested for reactivity to nitrocellulose‐blotted extract from purified HDM bodies, and the IgE‐reactive antigens were detected by IgE immunoblot inhibition experiments. IgE antibodies directed to bacterial antigens in HDM were quantified by IgE ImmunoCAP™ inhibition experiments.

Results

IgE reactivity to bacterial antigens was significantly more frequent in patients with AD sensitized to HDM than in AD patients without HDM sensitization. S. aureus and E. coli antigens were detected in immune‐blotted HDM extract, and the presence of IgE‐reactive antigens in HDM was demonstrated by qualitative and quantitative IgE inhibition experiments.

Conclusion

House dust mites (HDM) may serve as carriers of bacteria responsible for the induction of IgE sensitization to microbial antigens.

Poaceae pollen as the leading aeroallergen worldwide: A review

The Poaceae family comprises over 12 000 wind-pollinated species, which release large amounts of pollen into the atmosphere. Poaceae pollen is currently regarded as the leading airborne biological pollutant and the chief cause of pollen allergy worldwide. Sensitization rates vary by country, and those variations are reviewed here. Grass pollen allergens are grouped according to their protein structure and function. In Poaceae, although species belonging to different subfamilies are characterized by distinct allergen subsets, there is a considerable degree of cross-reactivity between many species. Cross-reactivity between grass pollen protein and fresh fruit pan-allergens is associated with the appearance of food allergies. The additional influence of urban pollution may prompt a more severe immunological response. The timing and the intensity of the pollen season are governed by species genetics, but plant phenology is also influenced by climate; as a result, climate changes may affect airborne pollen concentrations. This article reviews the findings of worldwide research which has highlighted the major impact of climate change on plant phenology and also on the prevalence and severity of allergic disease.

Immunotherapy: Treating with Fewer Allergens?

Polysensitization, sensitization to more than one allergen, is a common feature of patients with allergic rhinitis, and may be a risk factor for subsequent development of allergic diseases, especially allergic asthma. However, a polysensitized patient does not necessarily have polyallergy, a documented, causal relationship between exposure to 2 or more specific, sensitizing allergens and the subsequent occurrence of relevant clinical symptoms of allergy. Allergen immunotherapy treatment strategy for the polysensitized patient in Europe is to treat the single or 2 most clinically relevant allergen(s), whereas patients in the United States are usually treated for all potential clinically relevant allergens.

Minor allergen patterns in birch pollen allergen products-A question of pollen?

BACKGROUND

Contrary to the scientific differentiation between major and minor allergens, the regulatory framework controlling allergen products in the EU distinguishes relevant and non-relevant allergens. Given the lack of knowledge on their clinical relevance, minor allergens are usually not controlled by allergen product specifications. Especially, in birch pollen (BP) allergen products, minor allergens are commonly disregarded.

OBJECTIVES

To quantify three minor allergens in BP allergen products from different manufacturers and to assess the influence of the utilized BP on minor allergen patterns.

METHODS

Apart from common quality parameters such as Bet v 1 content, Bet v 4, Bet v 6 and Bet v 7 were quantified in 70 BP allergen product batches from six manufacturers, using ELISA systems developed in-house. Batch-to-batch variability was checked for agreement with a variability margin of 50%-200% from mean of the given batches for individual allergen content. Subsequently, minor allergen patterns were generated via multidimensional scaling and related to information on the pollen lots used in production of the respective product batches.

RESULTS

Like the already established Bet v 4 ELISA, the ELISA systems for quantification of Bet v 6 and Bet v 7 were successfully validated. Differences in minor allergen content between products and batch-to-batch consistency were observed. Correlations between minor and major allergen content were low to moderate. About 20% of batches exceeded the variability margin for at least one minor allergen. Interestingly, these fluctuations could not in all cases be linked to the use of certain BP lots.

CONCLUSIONS AND CLINICAL RELEVANCE

The impact of the observed minor allergen variability on safety and efficacy of BP allergen products can currently not be estimated. As the described differences could only in few cases be related to the used pollen lots, it is evident that additional factors influence minor allergens in BP allergen products.

Geographical differences in food allergy

BACKGROUND

Food allergy represents a health problem worldwide and leads to life-threatening reactions and even impairs quality of life. Epidemiological data during the past decades is very heterogeneous because of the use of different diagnostic procedures, and most studies have only been performed in specific geographical areas.

OBJECTIVES

The aim of this article is to review the available data on the geographical distribution of food allergies at the food source and molecular level and to link food allergy patterns to the aeroallergen influence in each area.

METHODS

Systematic reviews, meta-analysis, studies performed within the EuroPrevall Project and EAACI position papers regarding food allergy were analysed.

CONCLUSIONS

The prevalence of food allergy sensitization differs between geographical areas, probably as a consequence of differences among populations, their habits and the influence of the cross-reactivity of aeroallergens and other sources of allergens. Geographical differences in food allergy are clearly evident at the allergenic molecular level, which seems to be directly influenced by the aeroallergens of each region and associated with specific clinical patterns.

Blocking antibodies induced by immunization with a hypoallergenic parvalbumin mutant reduce allergic symptoms in a mouse model of fish allergy

BACKGROUND

Fish is a frequent elicitor of severe IgE-mediated allergic reactions. Beside avoidance, there is currently no allergen-specific therapy available. Hypoallergenic variants of the major fish allergen, parvalbumin, for specific immunotherapy based on mutation of the 2 calcium-binding sites have been developed.

OBJECTIVES

This study sought to establish a mouse model of fish allergy resembling human disease and to investigate whether mouse and rabbit IgG antibodies induced by immunization with a hypoallergenic mutant of the major carp allergen protect against allergic symptoms in sensitized mice.

METHODS

C3H/HeJ mice were sensitized with recombinant wildtype Cyp c 1 or carp extract by intragastric gavage. Antibody, cellular immune responses, and epitope specificity in sensitized mice were investigated by ELISA, rat basophil leukemia assay, T-cell proliferation experiments using recombinant wildtype Cyp c 1, and overlapping peptides spanning the Cyp c 1 sequence. Anti-hypoallergenic Cyp c 1 mutant mouse and rabbit sera were tested for their ability to inhibit IgE recognition of Cyp c 1, Cyp c 1-specific basophil degranulation, and Cyp c 1-induced allergic symptoms in the mouse model.

RESULTS

A mouse model of fish allergy mimicking human disease regarding IgE epitope recognition and symptoms as close as possible was established. Administration of antisera generated in mice and rabbits by immunization with a hypoallergenic Cyp c 1 mutant inhibited IgE binding to Cyp c 1, Cyp c 1-induced basophil degranulation, and allergic symptoms caused by allergen challenge in sensitized mice.

CONCLUSIONS

Antibodies induced by immunization with a hypoallergenic Cyp c 1 mutant protect against allergic reactions in a murine model of fish allergy.

Comparative Proteomic Analysis of Mature Pollen in Triploid and Diploid Populus deltoides

Ploidy affects plant growth vigor and cell size, but the relative effects of pollen fertility and allergenicity between triploid and diploid have not been systematically examined. Here we performed comparative analyses of fertility, proteome, and abundances of putative allergenic proteins of pollen in triploid poplar ‘ZhongHuai1’ (‘ZH1’, triploid) and ‘ZhongHuai2’ (‘ZH2’, diploid) generated from the same parents. The mature pollen was sterile in triploid poplar ‘ZH1’. By applying two-dimensional gel electrophoresis (2-DE), a total of 72 differentially expressed protein spots (DEPs) were detected in triploid poplar pollen. Among them, 24 upregulated and 43 downregulated proteins were identified in triploid poplar pollen using matrix-assisted laser desorption/ionisation coupled with time of-flight tandem mass spectrometer analysis (MALDI-TOF/TOF MS/MS). The main functions of these DEPs were related with “S-adenosylmethionine metabolism”, “actin cytoskeleton organization”, or “translational elongation”. The infertility of triploid poplar pollen might be related to its abnormal cytoskeletal system. In addition, the abundances of previously identified 28 putative allergenic proteins were compared among three poplar varieties (‘ZH1’, ‘ZH2’, and ‘2KEN8‘). Most putative allergenic proteins were downregulated in triploid poplar pollen. This work provides an insight into understanding the protein regulation mechanism of pollen infertility and low allergenicity in triploid poplar, and gives a clue to improving poplar polyploidy breeding and decreasing the pollen allergenicity.