Pomegranate chitinase III: Identification of a new allergen and analysis of sensitization patterns to chitinases

Comprehensive Review on Fruit Seeds: Nutritional, Phytochemical, Nanotechnology, Toxicity, Food Biochemistry, and Biotechnology Perspective

Fruit seeds are leftovers from a variety of culinary sectors. They are generally unutilized and contribute greatly to global disposals. These seeds not only possess various nutritional attributes but also have many heath-beneficial properties. One way to make use of these seeds is to extract their bioactive components and create fortified food items. Nowadays, researchers are highly interested in creating innovative functional meals and food components from these unconventional resources. The main objective of this manuscript was to determine the usefulness of seed powder from 70 highly consumed fruits, including Apple, Apricot, Avocado, Banana, Blackberry, Blackcurrant, Blueberry, Cherry, Common plum, Cranberry, Gooseberry, Jackfruit, Jamun, Kiwi, Lemon, Mahua, Mango, Melon, Olive, Orange, and many more have been presented. The nutritional attributes, phytochemical composition, health advantages, nanotechnology applications, and toxicity of these fruit seeds have been fully depicted. This study also goes into in-depth detailing on creating useful food items out of these seeds, such as bakery goods, milk products, cereal-based goods, and meat products. It also identifies enzymes purified from these seeds along with their biochemical applications and any research openings in this area.

Isolation, Characterization and IgE Binding of Two 2S Albumins of Pomegranate Seeds

Literature reports suggest that the presence of proteins in pomegranate seeds is responsible for sensitization and IgE-mediated allergic reactions. The objective of this study was the analysis of a pomegranate seed extract and the isolation and characterization of proteins contained in high amounts. The extract characterization showed a protein profile with main bands at about 18 kDa and below 10 kDa upon SDS-PAGE, and molecules were recognized by specific IgEs upon immunoblotting. Then, two new 2S albumins, a monomeric and a heterodimeric one, were isolated by using classical biochemical methods. They were identified via direct protein sequencing and mass spectrometry, and their primary structure was analyzed and compared with homologous allergenic proteins via bioinformatics. In an Italian population of 703 suspected allergic patients, analyzed by using the FABER® test, the frequency of sensitization to the monomeric and heterodimeric 2S albumins was 1.7% and 0.28%, respectively. This study reports for the first time the isolation and characterization of two 2S albumins from pomegranate seeds. The clinical relevance of these molecules needs further investigation, for instance in populations having different exposures and allergy profiles.

Tomato (Solanum lycopersicum L.) accumulation and allergenicity in response to nickel stress

Vegetables represent a major source of Ni exposure. Environmental contamination and cultural practices can increase Ni amount in tomato posing significant risk for human health. This work assesses the tomato (Solanum lycopersicum L.) response to Ni on the agronomic yield of fruits and the related production of allergens. Two cultivars were grown in pots amended with Ni 0, 30, 60, 120, and 300 mg kg⁻¹, respectively. XRF and ICP-MS analyses highlighted the direct increase of fruit Ni content compared to soil Ni, maintaining a stable biomass. Leaf water content increased at Ni 300 mg kg⁻¹. Total protein content and individual allergenic components were investigated using biochemical (RP-HPLC and N-terminal amino acid sequencing) and immunological (inhibition tests of IgE binding by SPHIAa assay on the FABER testing system) methodologies. Ni affected the fruit tissue concentration of pathogenesis-related proteins and relevant allergens (LTP, profilin, Bet v 1-like protein and TLP). This study elucidates for the first time that tomato reacts to exogenous Ni, uptaking the metal while changing its allergenic profiles, with potential double increasing of exposure risks for consumers. This evidence highlighted the importance of adequate choice of low-Ni tomato cultivars and practices to reduce Ni uptake by potentially contaminated matrices.

Pattern of sensitization to Juniperus oxycedrus 4EF-hand polcalcin, Jun o 4, compared with the 2EF-hand grass homolog Phl p 7 in a general Italian population of subjects suffering from pollinosis

Cupressaceae pollen causes allergic reactions worldwide with long-lasting symptomatic periods. Currently, no cypress polcalcin is available for diagnostic purposes. With the aim to investigate the pattern of sensitization to a cypress polcalcin, a synthetic gene of Jun o 4, the Juniperus oxycedrus 4EF-hand polcalcin, was cloned and expressed in Escherichia coli. Its features were investigated in comparison with the grass 2EF-hand Phl p 7. Rhinitis was the symptom most frequently reported in a cohort of Italian patients sensitized to rJun o 4 and/or rPhl p 7. The detection of many pollen allergic patients sensitized to the cypress polcalcin, but negative to Phl p 7, indicates that Phl p 7 cannot be further considered a marker of sensitization towards all the polcalcins. A 4EF-hand cypress polcalcin claims the inclusion in allergy diagnostic tests. In addition, the sensitivity of polcalcins to gastrointestinal digestion is reported and discussed for the first time.

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.

Newly defined allergens in the WHO/IUIS Allergen Nomenclature Database during 01/2019-03/2021

The WHO/IUIS Allergen Nomenclature Database (http://allergen.org) provides up‐to‐date expert‐reviewed data on newly discovered allergens and their unambiguous nomenclature to allergen researchers worldwide. This review discusses the 106 allergens that were accepted by the Allergen Nomenclature Sub‐Committee between 01/2019 and 03/2021. Information about protein family membership, patient cohorts, and assays used for allergen characterization is summarized. A first allergenic fungal triosephosphate isomerase, Asp t 36, was discovered in Aspergillus terreus. Plant allergens contained 1 contact, 38 respiratory, and 16 food allergens. Can s 4 from Indian hemp was identified as the first allergenic oxygen‐evolving enhancer protein 2 and Cic a 1 from chickpeas as the first allergenic group 4 late embryogenesis abundant protein. Among the animal allergens were 19 respiratory, 28 food, and 3 venom allergens. Important discoveries include Rap v 2, an allergenic paramyosin in molluscs, and Sal s 4 and Pan h 4, allergenic fish tropomyosins. Paramyosins and tropomyosins were previously known mainly as arthropod allergens. Collagens from barramundi, Lat c 6, and salmon, Sal s 6, were the first members from the collagen superfamily added to the database. In summary, the addition of 106 new allergens to the previously listed 930 allergens reflects the continuous linear growth of the allergen database. In addition, 17 newly described allergen sources were included.

Potential allergenicity of Medicago sativa investigated by a combined IgE-binding inhibition, proteomics and in silico approach

BACKGROUND

Alfalfa (Medicago sativa L) is one of the most planted crops worldwide primarily used to feed animals. The use of alfalfa in human diet as sprouts, infusions and nutritional supplements is rapidly gaining popularity. Despite this, allergenicity assessment of this novel plant food is largely lacking.

RESULTS

Here, leaf protein extract of alfalfa was studied using a combined proteomics, Immunoglobulin E (IgE)-binding inhibition assay and in silico approach to find potential allergens. We have identified and annotated 129 proteins using in-gel digestion proteomics and Blast2Go suit. A search against COMPARE database, using the identified proteins as query sequences, revealed high similarity with several allergenic proteins. The Single Point Highest Inhibition Achievable assay (SPHIAa) performed on the multiplex FABER^® allergy testing system confirmed the in silico results and showed some additional potential allergens. This approach allowed the detection of proteins in alfalfa leaves cross-reacting with plant allergens from three different allergen families such as lipid transfer, thaumatin-like and Bet v 1-like protein families. In addition, the absence of structural determinants cross-reacting with seed storage allergenic proteins and with animal allergens was recorded.

CONCLUSION

This study reports for the first time potential allergenic proteins in alfalfa. The results suggest that this plant food can be safely introduced, as a protein-rich supplement, in the diet of patients allergic to animal food allergens. Allergic patients towards certain plant food allergens need to be careful about consuming alfalfa because they might have allergic symptoms. © 2020 Society of Chemical Industry.

Structural Characterization of Act c 10.0101 and Pun g 1.0101-Allergens from the Non-Specific Lipid Transfer Protein Family

(1) Background: Non-specific lipid transfer proteins (nsLTPs), which belong to the prolamin superfamily, are potent allergens. While the biological role of LTPs is still not well understood, it is known that these proteins bind lipids. Allergen nsLTPs are characterized by significant stability and resistance to digestion. (2) Methods: nsLTPs from gold kiwifruit (Act c 10.0101) and pomegranate (Pun g 1.0101) were isolated from their natural sources and structurally characterized using X-ray crystallography (3) Results: Both proteins crystallized and their crystal structures were determined. The proteins have a very similar overall fold with characteristic compact, mainly α-helical structures. The C-terminal sequence of Act c 10.0101 was updated based on our structural and mass spectrometry analysis. Information on proteins’ sequences and structures was used to estimate the risk of cross-reactive reactions between Act c 10.0101 or Pun g 1.0101 and other allergens from this family of proteins. (4) Conclusions: Structural studies indicate a conformational flexibility of allergens from the nsLTP family and suggest that immunoglobulin E binding to some surface regions of these allergens may depend on ligand binding. Both Act c 10.0101 and Pun g 1.0101 are likely to be involved in cross-reactive reactions involving other proteins from the nsLTP family.

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.

ENEA, a peach and apricot IgE-binding protein cross-reacting with the latex major allergen Hev b 5

Peach and apricot can cause allergic reactions with symptoms ranging from mild to very severe, including anaphylaxis. Sometimes subjects allergic to fruits of the Prunus genus have been reported to be also allergic to rubber latex products. The objective of this study is the characterization of a newly identified peach and apricot protein showing similarities with the allergens Hev b 5 from rubber latex and Man e 5 from manioc. This protein has been named ENEA on the basis of the single letter amino acid code of the first four N-terminal residues of the isolated molecule. It has been found in very variable amounts in different peach cultivars and batches. ENEA was isolated from peach pulp extracts by chromatographic separations and identified by direct protein sequencing. At that time, the full length sequence was available only for the homologous protein of the taxonomically closely related apricot, which was produced as a recombinant molecule in Escherichia coli. The following availability of the full length sequence of peach ENEA revealed a very high identity (97%) with the apricot homolog. Similarly to Hev b 5 and to Man e 5, the structural characterization indicated that ENEA is an intrinsically disordered protein. The immunological properties, investigated by dot blotting, the ABA system and the FABER test, showed that ENEA is recognized by specific IgE of allergic patients. In a selected population of 31 patients reporting allergic reactions to peach fruit and/or IgE positive to Hev b 5, 28 and 27 subjects resulted co-sensitized to rENEA and Hev b 5 in the ABA and ISAC test, respectively. In a random population of 3305 suspected allergic patients, analyzed with the FABER test, 17 of them were sensitized to rENEA and 10 of them were also positive to Hev b 5. In addition, both the natural molecule from peach and the recombinant protein of apricot partially inhibited the IgE binding to Hev b 5. In conclusion, a new peach and apricot IgE-binding protein, cross-reacting with the major latex allergen Hev b 5, has been identified. Its variable concentration in the fruit might explain some occasionally occurring allergic reactions. The apricot molecule has recently been registered by the WHO/IUIS Allergen Nomenclature Sub-Committee with the allergen name Pru ar 5. The recombinant form of apricot ENEA, now available, will contribute to allergy diagnosis.

Chitinases as Food Allergens

Food allergies originate from adverse immune reactions to some food components. Ingestion of food allergens can cause effects of varying severity, from mild itching to severe anaphylaxis reactions. Currently there are no clues to predict the allergenic potency of a molecule, nor are cures for food allergies available. Cutting-edge research on allergens is aimed at increasing information on their diffusion and understanding structure-allergenicity relationships. In this context, purified recombinant allergens are valuable tools for advances in the diagnostic and immunotherapeutic fields. Chitinases are a group of allergens often found in plant fruits, but also identified in edible insects. They are classified into different families and classes for which structural analyses and identification of epitopes have been only partially carried out. Moreover, also their presence in common allergen databases is not complete. In this review we provide a summary of the identified food allergenic chitinases, their main structural characteristics, and a clear division in the different classes.

Plant-Made Bet v 1 for Molecular Diagnosis

Allergic disease diagnosis is currently experiencing a breakthrough due to the use of allergenic molecules in serum-based assays rather than allergen extracts in skin tests. The former methodology is considered a very innovative technology compared with the latter, since it is characterized by flexibility and adaptability to the patient's clinical history and to microtechnology, allowing multiplex analysis. Molecular-based analysis requires pure allergens to detect IgE sensitization, and a major goal, to maintain the diagnosis cost-effective, is to limit their production costs. In addition, for the production of recombinant eukaryotic proteins similar to natural ones, plant-based protein production is preferred to bacterial-based systems due to its ability to perform most of the post-translational modifications of eukaryotic molecules. In this framework, Plant Molecular Farming (PMF) may be useful, being a production platform able to produce complex recombinant proteins in short time-frames at low cost. As a proof of concept, PMF has been exploited for the production of Bet v 1a, a major allergen associated with birch (Betula verrucosa) pollen allergy. Bet v 1a has been produced using two different transient expression systems in Nicotiana benthamiana plants, purified and used in a new generation multiplex allergy diagnosis system, the patient-Friendly Allergen nano-BEad Array (FABER). Plant-made Bet v 1a is immunoreactive, binding IgE and inhibiting IgE-binding to the Escherichia coli expressed allergen currently available in the FABER test, thus suggesting an overall similar though non-overlapping immune activity compared with the E. coli expressed form.