Structural, Functional, and Immunological Characterization of Profilin Panallergens Amb a 8, Art v 4, and Bet v 2

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.

Heterogenous Induction of Blocking Antibodies against Ragweed Allergen Molecules by Allergen Extract-Based Immunotherapy Vaccines

Currently, allergen-specific immunotherapy (AIT) for ragweed allergy is still based on natural allergen extracts. This study aimed to analyse the ability of four commercially available AIT vaccines (CLUSTOID, TYRO-SIT, POLLINEX Quattro Plus and Diater Depot) regarding their ability to induce IgG antibodies against ragweed pollen allergens in rabbits. Accordingly, the IgG reactivity of AIT-induced rabbit sera was tested for ten different ragweed pollen allergens (Amb a 1, 3, 4, 5, 6, 8, 9, 10, 11 and 12) by an ELISA. Furthermore, the ability of rabbit AIT-specific sera to block allergic patients' IgE binding to relevant ragweed allergens (Amb a 1, 4, 6, 8 and 11) and to inhibit allergen-induced basophil activation was evaluated by an IgE inhibition ELISA and a mediator release assay. Only two AIT vaccines (Diater Depot > CLUSTOID) induced relevant IgG antibody levels to the major ragweed allergen Amb a 1. The IgG responses induced by the AIT vaccines against the other ragweed allergens were low and highly heterogeneous. Interestingly, the kinetics of IgG responses were different among the AIT vaccines and even within one AIT vaccine (Diater Depot) for Amb a 1 (long-lasting) versus Amb a 8 and Amb a 11 (short-lived). This could be due to variations in allergen contents, the immunogenicity of the allergens, and different immunization protocols. The IgE inhibition experiments showed that rabbit AIT-specific sera containing high allergen-specific IgG levels were able to inhibit patients' IgE binding and prevent the mediator release with Diater Depot. The high levels of allergen-specific IgG levels were associated with their ability to prevent the recognition of allergens by patients' IgE and allergen-induced basophil activation, indicating that the measurement of allergen-induced IgG could be a useful surrogate marker for the immunological efficacy of vaccines. Accordingly, the results of our study may be helpful for the selection of personalized AIT vaccination strategies for ragweed-allergic patients.

Worldwide Heterogeneity of Food Allergy: Focus on Peach Allergy in Southern Italy

Food allergy (FA) has shown an increasing prevalence in the last decades, becoming a major public health problem. However, data on the prevalence of FA across the world are heterogeneous because they are influenced by several factors. Among IgE-mediated FA, an important role is played by FA related to plant-derived food which can result from the sensitization to a single protein (specific FA) or to homologous proteins present in different foods (cross-reactive FA) including non-specific lipid transfer proteins (nsLTPs), profilins, and pathogenesis-related class 10 (PR-10). In addition, the clinical presentation of FA is widely heterogeneous ranging from mild symptoms to severe reactions up to anaphylaxis, most frequently associated with nsLTP-related FA (LTP syndrome). Considering the potential life-threatening nature of nsLTP-related FA, the patient's geographical setting should always be taken into account; thereby, it is highly recommended to build a personalized approach for managing FA across the world in the precision medicine era. For this reason, in this review, we aim to provide an overview of the prevalence of nsLTP-mediated allergies in the Mediterranean area and to point out the potential reasons for the different geographical significance of LTP-driven allergies with a particular focus on the allergenic properties of food allergens and their cross reactivity.

A comprehensive review on mango allergy: Clinical relevance, causative allergens, cross-reactivity, influence of processing techniques, and management strategies

Mangoes (Mangifera indica) are widely prized for their abundant nutritional content and variety of beneficial bioactive compounds and are popularly utilized in various foods, pharmaceuticals, and cosmetics industries. However, it is important to note that certain proteins present in mango can trigger various allergic reactions, ranging from mild oral allergy syndrome to severe life-threatening anaphylaxis. The immunoglobulin E-mediated hypersensitivity of mango is mainly associated with three major allergenic proteins: Man i 1 (class IV chitinase), Man i 2 (pathogenesis-related-10 protein; Bet v 1-related protein), and Man i 4 (profilin). Food processing techniques can significantly affect the structure of mango allergens, reducing their potential to cause allergies. However, it is worth mentioning that complete elimination of mango allergen immunoreactivity has not been achieved. The protection of individuals sensitized to mango should be carefully managed through an avoidance diet, immediate medical care, and long-term oral immunotherapy. This review covers various aspects related to mango allergy, including prevalence, pathogenesis, symptoms, and diagnosis. Furthermore, the characterization of mango allergens and their potential cross-reactivity with other fruits, vegetables, plant pollen, and seeds were discussed. The review also highlights the effects of food processing on mango and emphasizes the available strategies for managing mango allergy.

Outdoor airborne allergens: Characterization, behavior and monitoring in Europe

Aeroallergens or inhalant allergens, are proteins dispersed through the air and have the potential to induce allergic conditions such as rhinitis, conjunctivitis, and asthma. Outdoor aeroallergens are found predominantly in pollen grains and fungal spores, which are allergen carriers. Aeroallergens from pollen and fungi have seasonal emission patterns that correlate with plant pollination and fungal sporulation and are strongly associated with atmospheric weather conditions. They are released when allergen carriers come in contact with the respiratory system, e.g. the nasal mucosa. In addition, due to the rupture of allergen carriers, airborne allergen molecules may be released directly into the air in the form of micronic and submicronic particles (cytoplasmic debris, cell wall fragments, droplets etc.) or adhered onto other airborne particulate matter. Therefore, aeroallergen detection strategies must consider, in addition to the allergen carriers, the allergen molecules themselves. This review article aims to present the current knowledge on inhalant allergens in the outdoor environment, their structure, localization, and factors affecting their production, transformation, release or degradation. In addition, methods for collecting and quantifying aeroallergens are listed and thoroughly discussed. Finally, the knowledge gaps, challenges and implications associated with aeroallergen analysis are described.

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.

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.

A native IgE in complex with profilin provides insights into allergen recognition and cross-reactivity

Allergies have become a rising health problem, where plentiful substances can trigger IgE-mediated allergies in humans. While profilins are considered minor allergens, these ubiquitous proteins are primary molecules involved in cross-reactivity and pollen-food allergy syndrome. Here we report the first crystal structures of murine Fab/IgE, with its chains naturally paired, in complex with the allergen profilin from Hevea brasiliensis (Hev b 8). The crystallographic models revealed that the IgE's six complementarity-determining regions (CDRs) interact with the allergen, comprising a rigid paratope-epitope surface of 926 Å2, which includes an extensive network of interactions. Interestingly, we also observed previously unreported flexibility at Fab/IgE's elbow angle, which did not influence the shape of the paratope. The Fab/IgE exhibits a high affinity for Hev b 8, even when using 1 M NaCl in BLI experiments. Finally, based on the encouraging cross-reactivity assays using two mutants of the maize profilin (Zea m 12), this antibody could be a promising tool in IgE engineering for diagnosis and research applications.

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.

Crosstalk Between the Immune System and Plant-Derived Nanovesicles: A Study of Allergen Transporting

Background: Nanometer-sized membrane-surrounded vesicles from different parts of plants including fruits are gaining increasing attention due to their anti-inflammatory and anticancer effects demonstrated by in vitro and in vivo studies, and as nanovectors for molecular delivery of exogenous substances. These nanomaterials are very complex and contain a diverse arsenal of bioactive molecules, such as nucleic acids, proteins, and lipids. Our knowledge about the transport of allergens in vesicles isolated from plant food is limited today. Methods: Here, to investigate the allergenicity of strawberry-derived microvesicles (MVs), nanovesicles (NVs), and subpopulations of NV, we have set up a multidisciplinary approach. The strategy combines proteomics-based protein identification, immunological investigations, bioinformatics, and data mining to gain biological insights useful to evaluate the presence of potential allergens and the immunoglobulin E (IgE) inhibitory activity of vesicle preparations. Results: Immunological test showed that several proteins of strawberry-derived vesicles compete for IgE binding with allergens spotted on the FABER biochip. This includes the known strawberry allergens Fra a 1, Fra a 3, and Fra a 4, and also other IgE-binding proteins not yet described as allergens in this food, such as gibberellin-regulated proteins, 2S albumin, pectate lyase, and trypsin inhibitors. Proteomics identified homologous sequences of the three strawberry allergens and their isoforms in total protein extract (TPE) but only Fra a 1 and Fra a 4 in the vesicle samples. Label-free quantitative proteomic analysis revealed no significant enrichment of these proteins in strawberry vesicles with respect to TPE. Conclusion: Immunological tests and bioinformatics analysis of proteomics data sets revealed that MVs and NVs isolated from strawberries can carry functional allergens their isoforms as well as proteins potentially allergenic based on their structural features. This should be considered when these new nanomaterials are used for human nutraceutical or biomedical applications.

Sensitization to major Dermatophagoides pteronyssinus allergens in house dust mite allergic patients from North Eastern Poland developing rhinitis or asthma

PURPOSE

Recognition of individual allergens by IgE is crucial for triggering symptoms in allergic rhinitis (AR) or asthmatic (AA) patients. House dust mite (HDM) allergy is frequent around the world, the sensitization profile to individual HDM allergens varies in individual HDM-allergic patients (APs). The aim of this study was to evaluate the pattern of IgE sensitization to three major Dermatophagoides pteronyssinus (Dp) allergens among patients from North Eastern Poland suffering from HDM-AR and/or AA.

PATIENTS AND METHODS

The study was performed on 323 HDM-AR and/or AA patients and 106 controls (CG) including 30 healthy non-atopic subjects, 32 AR patients not sensitized to Dp and 44 non-atopic asthmatics. IgE levels to natural (n)Der p 1, nDer p 2, recombinant (r)Der p 2.0101 and rDer p 23 allergens were measured by ELISA.

RESULTS

The majority of HDM-APs were sensitized to nDer p 1 (72.1%), nDer p 2 (81.7%), rDer p 2.0101 (78.3%) and rDer p 23 (70.9%). The frequency of positive results to individual allergens depended on clinical manifestations and the level of IgE to the whole Dp extract. In HDM-AA patients, reactivity to nDer p 1 and rDer p 23 was detected more frequently than in HDM-AR patients. The whole Dp extract completely inhibited IgE binding to nDer p 1 and nDer p 2 but only partially to rDer p 23.

CONCLUSIONS

HDM-APs from North-Eastern Poland display sensitization profile to major allergens which is similarly observed in western Europe. HDM-based diagnostic and therapeutic products should include all major allergens.

Molecular approach to a patient's tailored diagnosis of the oral allergy syndrome

Oral allergy syndrome (OAS) is one of the most common IgE-mediated allergic reactions. It is characterized by a number of symptoms induced by the exposure of the oral and pharyngeal mucosa to allergenic proteins belonging to class 1 or to class 2 food allergens. OAS occurring when patients sensitized to pollens are exposed to some fresh plant foods has been called pollen food allergy syndrome (PFAS). In the wake of PFAS, several different associations of allergenic sources have been progressively proposed and called syndromes. Molecular allergology has shown that these associations are based on IgE co-recognition taking place between homologous allergens present in different allergenic sources. In addition, the molecular approach reveals that some allergens involved in OAS are also responsible for systemic reactions, as in the case of some food Bet v 1-related proteins, lipid transfer proteins and gibberellin regulated proteins. Therefore, in the presence of a convincing history of OAS, it becomes crucial to perform a patient's tailored molecule-based diagnosis in order to identify the individual IgE sensitization profile. This information allows the prediction of possible cross-reactions with homologous molecules contained in other sources. In addition, it allows the assessment of the risk of developing more severe symptoms on the basis of the features of the allergenic proteins to which the patient is sensitized. In this context, we aimed to provide an overview of the features of relevant plant allergenic molecules and their involvement in the clinical onset of OAS. The value of a personalized molecule-based approach to OAS diagnosis is also analyzed and discussed.

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.

Structural and computational examination of the Arabidopsis profilin-Poly-P complex reveals mechanistic details in profilin-regulated actin assembly

Profilins are abundant cytosolic proteins that are universally expressed in eukaryotes and that regulate actin filament elongation by binding to both monomeric actin (G-actin) and formin proteins. The atypical profilin Arabidopsis AtPRF3 has been reported to cooperate with canonical profilin isoforms in suppressing formin-mediated actin polymerization during plant innate immunity responses. AtPRF3 has a 37-amino acid-long N-terminal extension (NTE), and its suppressive effect on actin assembly is derived from enhanced interaction with the polyproline (Poly-P) of the formin AtFH1. However, the molecular mechanism remains unclear. Here, we solved the crystal structures of AtPRF3Δ22 and AtPRF3Δ37, as well as AtPRF2 apo form and in complex with AtFH1 Poly-P at 1.5-3.6 Å resolutions. By combining these structures with molecular modeling, we found that AtPRF3Δ22 NTE has high plasticity, with a primary "closed" conformation that can adopt an open conformation that enables Poly-P binding. Furthermore, using molecular dynamics simulation and free-energy calculations of protein-protein binding, along with experimental validation, we show that the AtPRF3Δ22 binds to Poly-P in an adaptive manner, thereby enabling different binding modes that maintain the interaction through disordered sequences. Together, our structural and simulation results suggest that the dynamic conformational changes of the AtPRF3 NTE upon Poly-P binding modulate their interactions to fine-tune formin-mediated actin assembly.

Analysis of Pollen Allergens in Lily by Transcriptome and Proteome Data

The lily (Lilium spp.) anther contains a lot of pollen. It is not known if lily pollen contains allergens, and therefore screening pollen allergy-related proteins and genes is necessary. The pollen development period of lily 'Siberia' was determined by microscope observation. Early mononuclear microspores and mature pollens were used as sequencing materials. The analysis of the pollen transcriptome identified differentially expressed genes (DEGs), e.g., Profilin, Phl p 7 (Polcalcin), Ole e 1, and Phl p 11, which are associated with pollen allergens. The proteome analysis positively verified a significant increase in pollen allergenic protein content. The expression levels of LoProfiilin and LoPolcalcin, annotated as allergen proteins, gradually increased in mature pollen. LoProfiilin and LoPolcalcin were cloned and their open reading frame lengths were 396 bp and 246 bp, which encoded 131 and 81 amino acids, respectively. Amino acid sequence and structure alignment indicated that the protein sequences of LoProfilin and LoPolcalcin were highly conserved. Subcellular localization analysis showed that LoProfilin protein was localized in the cell cytoplasm and nucleus. LoProfilin and LoPolcalcin were highly expressed in mature pollen at the transcriptional and protein levels. A tertiary structure prediction analysis identified LoProfilin and LoPolcalcin as potential allergens in lily pollen.

Comparative structural and thermal stability studies of Cuc m 2.0101, Art v 4.0101 and other allergenic profilins

Worldwide, more than one-third of the population suffers from allergies. A significant fraction of officially registered allergens originate from the profilin family of proteins. Profilins are small ubiquitous proteins which are found in plants, viruses and various eukaryotes including mammals. Although they are primarily regarded as minor allergens, profilins are important players in immunoglobulin E (IgE) cross-reactivity. However, in some populations profilins are recognized by IgE from at least 50% of patients allergic to a given allergen source. Cuc m 2.0101 is recognized by IgE in more than 80% of muskmelon-allergic patients. The recombinant isoallergen Cuc m 2.0101 was produced in significant quantities and its X-ray crystal structure was determined. In addition, a new Art v 4.0101 (mugwort profilin) structure was determined. The profilins Cuc m 2.0101 and Art v 4.0101 were compared in terms of their structure and thermal stability. Furthermore, structural similarities and IgE cross-reactivity between profilins from different sources are discussed to explain the molecular basis of various clinical syndromes involving this group of allergens. Special emphasis is placed on discussion of profilins' quaternary structures and their relation to biological function, as well as to protein allergenicity. Moreover, a potential impact of protein purification protocols on the structure of profilins is highlighted.

Mugwort Pollen-Related Food Allergy: Lipid Transfer Protein Sensitization and Correlation With the Severity of Allergic Reactions in a Chinese Population

PURPOSE

Little is known about the importance of lipid transfer protein (LTP) sensitization in China. In this study, we investigated the relationship between LTP sensitization and the severity of clinical symptoms in a population of patients with mugwort pollen-related food allergy.

METHODS

Food-induced symptoms were evaluated in 148 patients with mugwort pollen allergy by a standardized questionnaire. Specific immunoglobulin E (IgE) to Art v 1, Art v 3, Pru p 3, Ara h 9 and Cor a 8 were quantified by ImmunoCAP. Immunoblotting of peach extracts were performed with sera from peach-allergic patients.

RESULTS

In total, 72% (107/148) of the study population experienced food allergy. Forty-eight percent (51/107) of patients with mugwort pollen-related food allergy experienced at least 1 episode of food-induced anaphylaxis. Food allergy correlated with IgE reactivity to Art v 3, but not to Art v 1. Sensitization to Pru p 3, Ara h 9 or Cor a 8 was prevalent (80%, 69 or 63%, respectively) among individuals with food allergy. Food allergic patients with systemic reactions (SR) had higher values for Pru p 3, Ara h 9 and Cor a 8 than patients with oral allergy syndrome (OAS). Furthermore, the strong IgE reactivity detected in immunoblots of peach extracts indicated that Pru p 3 was the major allergen and was more prevalent in patients with SR than in patients with OAS (100% vs. 55%).

CONCLUSIONS

LTPs are major food allergens for mugwort pollen-related food allergy in China, and may contribute to SR.

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.

Molecular patterns in the isotype-specific antibody responses to the major cedar aeroallergen Jun a 1

Most studies of the immune responses in allergic rhinitis have focused on IgE antibodies to mixtures of allergenic proteins. Based on our previous studies of the major mountain cedar allergen Jun a 1, we sought to describe a broader assessment of the humoral immune responses to a single, dominant allergen, in three groups of allergic subjects, all of whom had similarly exposures to the whole cedar pollen. The major outcomes of this study was that, with the onset of allergic rhinitis symptoms, and after treatment with immunotherapy, serum IgE and IgG (but not IgA) antibodies to Jun a 1 increased. Interestingly, both IgE and IgG4 antibodies to the Jun a 1 allergen were strongly focused on its conformation epitopes. These IgG antibodies to conformationalstructures may be a useful marker of the therapeutic response to immunotherapy.

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.

Allergenicity of recombinant Humulus japonicus pollen allergen 1 after combined exposure to ozone and nitrogen dioxide

Ozone (O₃) and nitrogen dioxide (NO₂) are thought to play primary roles in aggravating air pollution-induced health problems. However, the effects of joint O₃/NO₂ on the allergenicity of pollen allergens are unclear. Humulus japonicus pollen allergen 1 (Hum j1) is a profilin protein that causes widespread pollinosis in eastern Asia. In order to study the effects of combined O₃/NO₂ on the allergenicity of Hum j1, tandem six-histidine peptide tag (His6)-fused recombinant Hum j1 (rHum j1) was expressed in a prokaryotic system and purified through His6 affinity chromatography. The purified rHum j1 was used to immunize SD rats. Rat sera with high titers of IgG and IgE antibodies against rHum j1 were used for allergenicity quantification. The rHum j1 was exposed to O₃/NO₂, and changes in allergenicity of the exposed rHum j1 were assayed using the immunized rat antibodies. Tandem LC-MS/LC (liquid chromatography-mass spectrometer/liquid chromatography spectrometer) chromatography and UV and circular dichroism (CD) spectroscopy were used to study the structural changes in rHum j1. Our data demonstrated that a novel disulfide bond between the sulfhydryl groups of two neighboring cysteine molecules was formed after the rHum j1 exposure to joint O₃/NO₂, and therefore IgE-binding affinity was increased and the allergenicity was reinforced. Our results provided clues to elucidate the mechanism behind air pollution-induced increase in pollinosis prevalence.

Impact of an N-terminal Polyhistidine Tag on Protein Thermal Stability

For years, the use of polyhistidine tags (His-tags) has been a staple in the isolation of recombinant proteins in immobilized metal affinity chromatography experiments. Their usage has been widely beneficial in increasing protein purity from crude cell lysates. For some recombinant proteins, a consequence of His-tag addition is that it can affect protein function and stability. Functional proteins are essential in the elucidation of their biological, kinetic, structural, and thermodynamic properties. In this study, we determine the effect of N-terminal His-tags on the thermal stability of select proteins using differential scanning fluorimetry and identify that the removal of the His-tag can have both beneficial and deleterious effects on their stability.

Two Distinct Conformations in Bet v 2 Determine Its Proteolytic Resistance to Cathepsin S

Birch pollen allergy affects more than 20% of the European allergic population. On a molecular level, birch pollen allergy can be linked to the two dominant allergens Bet v 1 and Bet v 2. Bet v 2 belongs to the profilin family, which is abundant in the plant kingdom. Importantly, the homologous plant profilins have a conserved cysteine motif with a currently unknown functional relevance. In particular, it is unknown whether the motif is relevant for disulfide formation and to what extent it would affect the profilins’ structural, functional and immunological properties. Here we present crystal structures of Bet v 2 in the reduced and the oxidized state, i.e., without and with a disulfide bridge. Despite overall structural similarity, the two structures distinctly differ at their termini which are stabilized to each other in the oxidized, i.e., disulfide-linked state. These structural differences translate into differences in their proteolytic resistance. Whereas the oxidized Bet v 2 is rather resistant towards the endolysosomal protease cathepsin S, it is rapidly degraded in the reduced form. By contrast, both Bet v 2 forms exhibit similar immunological properties as evidenced by their binding to IgE antibodies from birch pollen allergic patients and by their ability to trigger histamine release in a humanized rat basophilic leukemia cells (RBL) assay, independent of the presence or absence of the disulfide bridge. Taken together our findings suggest that the oxidized Bet v 2 conformation should be the relevant species, with a much longer retention time to trigger immune responses.

Intrinsic disorder in proteins involved in amyotrophic lateral sclerosis

Five structurally and functionally different proteins, an enzyme superoxide dismutase 1 (SOD1), a TAR-DNA binding protein-43 (TDP-43), an RNA-binding protein FUS, a cofilin-binding protein C9orf72, and polypeptides generated as a result of its intronic hexanucleotide expansions, and to lesser degree actin-binding profilin-1 (PFN1), are considered to be the major drivers of amyotrophic lateral sclerosis. One of the features common to these proteins is the presence of significant levels of intrinsic disorder. The goal of this study is to consider these neurodegeneration-related proteins from the intrinsic disorder perspective. To this end, we employed a broad set of computational tools for intrinsic disorder analysis and conducted intensive literature search to gain information on the structural peculiarities of SOD1, TDP-43, FUS, C9orf72, and PFN1 and their intrinsic disorder predispositions, and the roles of intrinsic disorder in their normal and pathological functions.

Structural insights into the IgE mediated responses induced by the allergens Hev b 8 and Zea m 12 in their dimeric forms

Oligomerization of allergens plays an important role in IgE-mediated reactions, as effective crosslinking of IgE- FcεRI complexes on the cell membrane is dependent on the number of exposed B-cell epitopes in a single allergen molecule or on the occurrence of identical epitopes in a symmetrical arrangement. Few studies have attempted to experimentally demonstrate the connection between allergen dimerization and the ability to trigger allergic reactions. Here we studied plant allergenic profilins rHev b 8 (rubber tree) and rZea m 12 (maize) because they represent an important example of cross-reactivity in the latex-pollen-food syndrome. Both allergens in their monomeric and dimeric states were isolated and characterized by exclusion chromatography and mass spectrometry and were used in immunological in vitro experiments. Their crystal structures were solved, and for Hev b 8 a disulfide-linked homodimer was found. Comparing the structures we established that the longest loop is relevant for recognition by IgE antibodies, whereas the conserved regions are important for cross-reactivity. We produced a novel monoclonal murine IgE (mAb 2F5), specific for rHev b 8, which was useful to provide evidence that profilin dimerization considerably increases the IgE-mediated degranulation in rat basophilic leukemia cells.