Allergenic Proteins Research Articles

Food allergen detection by mass spectrometry: From common to novel protein ingredients.

Food allergens are molecules, mainly proteins, that trigger immune responses in susceptible individuals upon consumption even when they would otherwise be harmless. Symptoms of a food allergy can range from mild to acute; this last effect is a severe and potentially life-threatening reaction. The European Union (EU) has identified 14 common food allergens, but new allergens are likely to emerge with constantly changing food habits. Mass spectrometry (MS) is a promising alternative to traditional antibody-based assays for quantifying multiple allergenic proteins in complex matrices with high sensitivity and selectivity. Here, the main allergenic proteins and the advantages and drawbacks of some MS acquisition protocols, such as multiple reaction monitoring (MRM) and data-dependent analysis (DDA) for identifying and quantifying common allergenic proteins in processed foodstuffs are summarized. Sections dedicated to novel foods like microalgae and insects as new sources of allergenic proteins are included, emphasizing the significance of establishing stable marker peptides and validated methods using database searches. The discussion involves the in-silico digestion of allergenic proteins, providing insights into their potential impact on immunogenicity. Finally, case studies focussing on microalgae highlight the value of MS as an effective analytical tool for ensuring regulatory compliance throughout the food control chain.

Cross-reactive MHC class I T cell epitopes may dictate heterologous immune responses between respiratory viruses and food allergens

Respiratory virus infections play a major role in asthma, while there is a close correlation between asthma and food allergy. We hypothesized that T cell-mediated heterologous immunity may induce asthma symptoms among sensitized individuals and used two independent in silico pipelines for the identification of cross-reactive virus- and food allergen- derived T cell epitopes, considering individual peptide sequence similarity, MHC binding affinity and immunogenicity. We assessed the proteomes of human rhinovirus (RV1b), respiratory syncytial virus (RSVA2) and influenza-strains contained in the seasonal quadrivalent influenza vaccine 2019/2020 (QIV 2019/2020), as well as SARS-CoV-2 for human HLA alleles, in addition to more than 200 most common food allergen protein sequences. All resulting allergen-derived peptide candidates were subjected to an elaborate scoring system considering multiple criteria, including clinical relevance. In both bioinformatics approaches, we found that shortlisted peptide pairs that are potentially binding to MHC class II molecules scored up to 10 × lower compared to MHC class I candidate epitopes. For MHC class I food allergen epitopes, several potentially cross-reactive peptides from shrimp, kiwi, apple, soybean and chicken were identified. The shortlisted set of peptide pairs may be implicated in heterologous immune responses and translated to peptide immunization strategies with immunomodulatory properties.

Assessment of the Efficiency of Technological Processes to Modify Whey Protein Antigenicity.

Whey is a by-product that represents a cheap source of protein with a high nutritional value, often used to improve food quality. When used as a raw material to produce hypoallergenic infant formulas (HIF), a processing step able to decrease the allergenic potential is required to guarantee their safe use for this purpose. In the present paper, thermal treatments, high hydrostatic pressure (HHP), and enzymatic hydrolysis (EH) were assessed to decrease the antigenicity of whey protein solutions (WPC). For monitoring purposes, a competitive ELISA method, able to detect the major and most allergenic whey protein β-lactoglobulin (BLG), was developed as a first step to evaluate the efficiency of the processes. Results showed that EH together with HHP was the most effective combination to reduce WPC antigenicity. The evaluation method proved useful to monitor the processes and to be employed in the quality control of the final product, to guarantee the efficiency, and in protein antigenicity reduction.

Recombinant antigen 5 from Polybia paulista wasp venom (Hymenoptera, Vespidae): Antigen-specific antibody production and functional profile of CD4+ T cells in the immune response

Polybia paulista is a neotropical social wasp related to severe accidents and allergic reactions cases, including anaphylaxis, in southeastern Brazil. Antigen 5 (Poly p 5) is a major allergenic protein from its venom with potential use for component-resolved diagnostic. Therefore, the previous characterization of the immune response profile triggered by Poly p 5 should be evaluated. Recombinant Poly p 5 (rPoly p 5) was used to sensitize BALB/c mice with six weekly intradermal doses, and the specific antibody production and the functional profile of CD4+ T cells were assessed. rPoly p 5 induced the production of specific immunoglobulins (sIg) sIgE, sIgG1 and sIgG2a, which could recognize natural Poly p 5 presented in the venom of four different wasp species. rPoly p 5 stimulated in vitro the CD4+ T cells from immunized mice, which showed a significant proliferative response. These antigen-specific CD4+T cells produced IFN-γ and IL-17A cytokines and increased ROR-γT transcription factor expression. No differences between the control group and sensitized mice were found in IL-4 production and GATA-3 and T-bet expression. Interestingly, increased CD25+FoxP3+ regulatory T cells (Tregs) frequency was observed in the splenocyte cell cultures from rPoly p 5 immunized mice after the in vitro stimulation with both P. paulista venom extract and rPoly p 5. Here we showed that rPoly p 5 induces antigen-specific antibodies capable of recognizing Antigen 5 in the venom of four wasp species and modulates antigen-specific CD4+ T cells to IFN-γ production response associated with a Th17 profile in sensitized mice. These findings emphasize the potential use of rPoly p 5 as an essential source of a major wasp allergen with significant immunological properties.

Clinically and industrially relevant incurred reference materials to improve analysis of food allergens, milk, egg, almond, hazelnut and walnut

Measurement of food allergen protein concentrations against thresholds can improve allergen risk management and precautionary allergen labelling. Such measurement suffers well known problems which could be ameliorated by well characterised reference materials (RMs) providing meaningful information for risk assessors. We investigated the preparation and characterisation of the first consensus informed industrially and clinically relevant multi-allergen matrix RM kit for five priority allergens. It is a medium analytical difficulty processed food chocolate paste matrix (a) devoid of allergens, and (b) incurred with five allergens at the clinically relevant concentration of 10 mg kg−1 expressed as protein. The allergen raw materials: hens’ egg white powder, skimmed cows’ milk powder, almond powder (full fat), hazelnut powder (partially defatted), and walnut powder (partially defatted), are also available as RMs. The preparation, gravimetric traceability to the SI, homogeneity, and stability were found to be fit-for-purpose and the RMs are now available to the analytical community.

Revealing the proteolytic characteristics of lactobacillus, lacticaseibacillus, and lactiplantibacillus isolates by in vitro and in situ perspectives

This study examined in vitro and in situ proteolytic characteristics of 8 lactobacilli strains isolated from Turkish Tulum cheese, consisting of L. plantarum, L. helveticus, L. rhamnosus, and L. paracasei, whose beneficial properties and safety concerns previously evaluated. The studied isolates presented versatile proteolytic activity with acidic, neutral, and alkaline proteases. The proteolytic activity of isolates against azocasein substrate was determined between 10.30 and 19.90 U/mg, and L. plantarum isolates had the highest proteolytic activity at varying pH values. Isolates 15, 449, 480 and 675 harboured proteinase genes in the catalytic region of prtR and prtP, and in the prtP/prtM intergenic region. All isolates were also evaluated in the production of fermented milk. As a result of SDS-PAGE analysis of fermented milk samples, L. plantarum isolates 449, 480 and 675 showed more proteolytic activity on milk caseins. Besides, isolate 480 was also effective in hydrolysis of beta-lactoglobulin. L. plantarum isolates resulted in an increase in amino acid (AA) concentrations especially in arginine, alanine, histidine, and proline during the 24-h fermentation of milk. AA production abilities varied depending on the strain. Generally, isolate 675 offered superior AA production ability. The proteolytic properties of cultures are effective on both human health and technological properties of the product in terms of reducing the allergenicity of milk proteins, forming functional peptides, and improving the sensory properties of the product. Based on the results of this study, L. plantarum isolates 449, 480 and 675 could potentially be used as starter cultures or co-cultures for these purposes.

Effects of AAPH on structure, allergenicity and physicochemical properties of shrimp myofibrillar protein

Lipid peroxidation has been shown to associate with meat quality by affecting physicochemical properties of myofibrillar proteins. In this work, shrimp myofibrillar protein (MP) was oxidized using 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH), which could generate peroxyl radicals in lipid peroxidation. Results showed that increasing AAPH concentration led to an increase in carbonyl groups and a decrease in free amino and sulfhydryl thiol groups in MP. Secondary structural analysis of MP revealed a conversion of α-helix to β-sheet content after AAPH treatment. SDS-PAGE showed the band intensity of tropomyosin was reduced after AAPH treatment, indicating a reduced allergenicity of tropomyosin. Moderate oxidation (1–10 mmol/L AAPH) promoted the formation of a dense network of MP gel, resulting in enhanced textural and rheological properties. However, excessive oxidation (10–20 mmol/L AAPH) weakened the MP gel strength and decreased its water-holding capacity. These findings provide theoretical guidance for developing shrimp surimi products with desirable textures.

Aeroallergen Avoidance: Updated Evidence and How to Advise Patients

Allergic rhinitis (AR) is highly prevalent in Canada, affecting approximately 20–25% of the population. Asthma is estimated to affect approximately three million Canadians, and between 12% and 25% of Canadian children. Approximately two-thirds of individuals with asthma are allergic to aeroallergens, and these allergens act as triggers for asthma exacerbations. Overall, approximately 7.7 million individuals were affected by aeroallergens in Canada in 2016. High concentrations of ambient aeroallergens, including tree pollen and fungal spores have been associated with increased risk of premature birth, myocardial infarction (MI) and asthma-related Emergency Department visits and hospitalizations in cities across Canada. This demonstrates that nation-wide aeroallergen counts are associated with severe signs and symptoms. Children exposed to various indoor allergens are placed at an increased risk of developing asthma in later life, with sensitization in these individuals being a strong predictor of disease morbidity. Common indoor exposures for infants include house dust mite, pet, cockroach, mould, and rodent allergens. Sensitization to at least one indoor allergen has been demonstrated to be present in nine of every ten children hospitalized with asthma. It has been noted that more than 90% of children worldwide breathe polluted air. While the impact of climate change on aeroallergen exposure is not fully understood, there is increasing evidence that it may have an impact on outdoor aeroallergens and, by extension, asthma control in children. Global warming has been projected to influence the duration and intensity of pollen seasons, and may lead to increased pollen production, prolonged pollen seasons, and increased pollen protein allergenicity. The changing weather patterns including rainfall and wind may cause pollen species to reach environments in which they had not previously been present, contributing to a shift in geographic pollen distributions.

On-Chip Discovery of Allergens from the Exudate of Large Yellow Croaker (Larimichthys Crocea) Muscle Food by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry.

It is extremely crucial to establish facile, accurate, and fast methods for testing allergenic proteins (allergens) in seafood. The current study focuses on the evaluation of fish muscle exudate proteins in an effort to discover potential allergens in fish exudate for allergy tests. Large yellow croaker (Larimichthys crocea) was studied as a seafood model. Magnetic beads (MBs) modified with an IgE antibody were utilized to isolate allergens existing in the exudate sample. Immunoglobulin E (IgE) in blood is a class of antibodies that is mainly associated with allergic reactions. Potential allergens in the muscle exudate were fished by IgE-biofunctional MBs in microfluidic channels. The protein-attached MBs were isolated under a magnetic field, eluted, and collected. The collected eluent was digested and analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry to identify allergens. Eight allergens from large yellow croaker exudate were identified, i.e., parvalbumin beta, parvalbumin, protein S100, histone H4, cytochrome c, fatty acid binding protein 3 (FABP3), microsomal glutamate S-transfer 3 (MGST3), and C-C motif chemokine 21 (CCL21). The presently proposed microfluidic-magnetic-based allergen extraction protocol enables a facile and rapid test of potentials of seafood allergies, providing a solution to circumvent food safety issues, especially for allergic populations.

Muscle proteome profile and potential allergens of premature hilsa shad (Tenualosa ilisha)

In this study, for the first time, we profile the actual protein sequences of known and potential allergens of premature hilsa shad (Tenualosa ilisha), an economically important fish of South Asian countries. Proteomics was employed to dissect the muscle tissue proteome collected from the riverine habitat hilsa samples. We successfully identified and quantified >600 proteins wherein many known allergens such as parvalbumins, beta-enolase, and creatine kinases were identified as abundant proteins in muscle tissue. Label-free quantitative proteomics revealed significant differences in the abundance of myosin, dynein, gamma-enolase, creatine kinase B-type, and collagens between the two hilsa samples. In silico analysis determined the allergen potential of these proteins. Notably, our findings indicate that many well-characterized allergen proteins are developmentally regulated in the muscle tissue. Thus, the profiling of a muscle tissue proteome map would further facilitate fundamental and applied research on hilsa fish and greatly improve our understanding of the crucial issue of hilsa customers' nutritional safety.

In-house validation of an LC-MS method for the multiplexed quantitative determination of total allergenic food in chocolate.

Mass spectrometry has been widely accepted as a confirmatory tool for the sensitive detection of undeclared presence of allergenic ingredients. Multiple methods have been developed so far, achieving different levels of sensitivity and robustness, still lacking harmonization of the analytical validation and impairing comparability of results. In this investigation, a quantitative method has been validated in-house for the determination of six allergenic ingredients (cow's milk, hen's egg, peanut, soybean, hazelnut, and almond) in a chocolate-based matrix. The latter has been produced in a food pilot plant to provide a real and well-characterized matrix for proper assessment of method performance characteristics according to official guidelines. In particular, recent considerations issued by the European Committee for Standardization have been followed to guide a rigorous single-laboratory validation and to feature the main method performance, such as selectivity, linearity, and sensitivity. Synthetic surrogates of the peptide markers have been used both in native and labelled forms in matrix-matched calibration curves as external calibrants and internal standards, respectively. A two-order of magnitude range was investigated, focusing on the low concentration range for proper assessment of the detection and quantification limits (LOD and LOQ) by rigorous calibration approach. Conversion factors for all six allergenic ingredients have been determined for the first time to report the final quantitative information as fraction of total allergenic food protein (TAFP) per mass of food (µgTAFP/gfood), since such areporting unit isexploitable in allergenic risk assessment plans. The method achieved good sensitivity with LOD values ranging between 0.08 and 0.2 µgTAFP/gfood, for all ingredients besides egg and soybean, whose quantitative markers reported a slightly higher limit (1.1 and 1.2 µgTAFP/gfood, respectively). Different samples of chocolate bar incurred at four defined concentration levels close to the currently available threshold doses have been analyzed to test the quantitative performance of the analytical method, with a proper estimate of the measurement uncertainty from different sources of variability. The sensitivity achieved resulted in compliance with the various threshold doses issued or recommended worldwide.

Non-IgE-reactive allergen peptides deteriorate the skin barrier in house dust mite-sensitized atopic dermatitis patients.

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by type 2 cytokine-driven skin inflammation and epithelial barrier dysfunction. The latter is believed to allow the increased penetration of chemicals, toxins, and allergens into the skin. House dust mite allergens, particularly Der p 2, are important triggers in sensitized individuals with AD; the precise actions of these allergens in epithelial biology remain, however, incompletely understood. In this study, we compared the effects of the protein allergen Der p 2 and a mix of non-IgE-reactive Der p 2 peptides on skin cells using patch tests in AD patients and healthy participants. We then analyzed mRNA expression profiles of keratinocytes by single-cell RNA-sequencing. We report that existing barrier deficiencies in the non-lesional skin of AD patients allow deep penetration of Der p 2 and its peptides, leading to local microinflammation. Der p 2 protein specifically upregulated genes involved in the innate immune system, stress, and danger signals in suprabasal KC. Der p 2 peptides further downregulated skin barrier genes, in particular the expression of genes involved in cell-matrix and cell-cell adhesion. Peptides also induced genes involved in hyperproliferation and caused disturbances in keratinocyte differentiation. Furthermore, inflammasome-relevant genes and IL18 were overexpressed, while KRT1 was downregulated. Our data suggest that Der p 2 peptides contribute to AD initiation and exacerbation by augmenting hallmark features of AD, such as skin inflammation, barrier disruption, and hyperplasia of keratinocytes.

Limited hydrolysis combined with glycation modification of silkworm pupae (Bombyx mori) proteins: structure-function relationship

Abstract In order to explore the impacts of limited hydrolysis combined with glycation modification on the structure, functional properties, allergenicity, and volatile compounds of silkworm pupae protein, the crude silkworm pupae protein was firstly extracted by alkaline-solution method, followed by Alcalase-treated limited hydrolysis for 10-30 min. Xylose was subsequently added and reacted for 1 h at 95 °C. Afterwards, the structure, functionality, allergenicity, and volatile compounds before and after modification were analysed. The molecular weight of modified silkworm pupae protein was remarkably decreased. The solubility was improved from 4.7 to 28.6%. The foaming ability was elevated by 21%. The in vitro digestibility was elevated by 34.0-44.4%. Furthermore, the abundance of six potential allergic proteins was remarkably reduced. In addition, the contents of off-flavour compounds in modified silkworm pupae proteins substantially decreased. Overall, limited hydrolysis combined with glycation modification can improve the functionality and flavour of silkworm pupae protein, while reduce the allergenicity.

Development of a Two-Step Hydrolysis Hypoallergenic Cow's Milk Formula and Evaluation of Residue Allergenicity by Peptidomics and Immunoreactivity Analysis.

Cow's milk allergy (CMA) is an abnormal immune response that severely affects the nutritional supplementation of allergic infants. Currently, only a limited number of hypoallergenic formulas are available on the market, and these are only categorized according to their degree of hydrolysis, which still poses an allergy risk and cannot be consumed by CMA patients, especially infants. To address this issue, we developed a two-step hydrolysis hypoallergenic formula targeting destruction of allergen epitope from whey protein. Then, a comprehensive evaluation system was constructed, including peptidomics analysis, in vivo and in vitro allergenicity assessments, revealing allergic changes in the product from the epitope structure level to the immunological level. The results showed that 97.14% of hydrolyzed peptides from α-lactalbumin and β-lactoglobulin did not contain allergenic epitopes after treatment with trypsin and flavourzyme. In vitro and in vivo allergenicity assessment results confirmed that the two-step hydrolysis method effectively reduced the allergenicity of whey protein. Compared with the common milk powder, the hypoallergenic formula induced lower levels of basophil degranulation and relieved the body's anaphylactic symptoms caused by cow milk. This study provides a promising solution to the limited hypoallergenic formula problem and may benefit allergic infants who require nutritional supplements.

Evaluation of the immunoreactivity and quality characteristics of cow milk following combined fermentation and enzymatic hydrolysis

Cow milk (CM) allergy is one of the most common food allergies in infants and children, which causing serious health concern. To the best of our knowledge, there are few studies on the effects of Lactobacillus paracei (L. paracei) fermentation combined with Alcalase hydrolysis on the immunoreactivity and quality characteristics of CM. In this study, immunoreactivity, protein patterns, free amino acid (FAA) profiles, nutritional quality after L. paracei fermentation, and Alcalase hydrolysis were systematically evaluated. L. paracei fermentation assisted by Alcalase hydrolysis (CM-LpA) effectively decreased the intensity, antigenicity, and allergenicity of cow milk proteins in CM. The IgG-binding capacity was significantly reduced (P < 0.05), with a reduction rate ranging from 51.20 to 68.13%. The IgE-binding capacity was also markedly reduced, with a reduction rate of 59.46%. Additionally, most of the FAA profiles increased significantly (P < 0.05), particularly those of Met (354-fold), Phe (91-fold), and Leu (213-fold). The color of the CM further changed and gradually became light red and yellow. The taste also changed, with the levels of sourness and astringency increasing dramatically (P < 0.05). Our results will lay the foundation for the development of hypoallergenic dairy products.

Label-free quantitative proteomics to exploit the impact of sourdough fermentation on reducing wheat allergenic fractions

The microbial consortia of lactic acid bacteria and yeast of sourdough can partially degrade gluten subunits associated with wheat-related diseases. This study evaluated how sourdough fermentation interferes with wheat protein profiles and if it can be related to the reduction expression of allergenic proteins. Samples from five bread doughs (Saccharomyces cerevisiae -C1; chemical acidification -C2, and three sourdoughs formulations -S1, S2, and S3) were sequentially extracted, digested, and submitted to shotgun label-free proteomic analysis. Eight-five proteins were identified as allergenic, mainly belonging to gliadin fraction, including seven containing the 33-mer peptide sequence. The highest immunogenic potential was found in dough C1 and S3, while the least reactive group consisted of S1 and C2. The two folds down expression of an α-gliadin containing the 33-mer sequence corroborates this. This finding may indicate the role of organic acids produced by the microbiota sourdough type II during fermentation in changing the protein profile.

In-silico study of allergenic proteins of certain food legumes: peanut, lentil, sesame and cowpea

Peanuts, lentils, sesame and cowpeas are protein-rich legumes widely consumed in the human diet. However, some so-called allergenic proteins are capable of causing adverse reactions in genetically predisposed individuals. They contain portions consisting of contiguous linear segments of amino acids involved in binding with specific IgE. They also have three-dimensional conformational patterns that crosslink with antibodies from susceptible individuals. In this work, the identity and similarity between certain allergenic proteins of peanut, lentil, sesame and cowpea are studied by global alignment. The latter is carried out on 21 allergenic proteins (7 from peanuts, 3 from lentils, 3 from sesame and 8 from cowpea) using the EMBOSS Needle software which uses the Needleman-Wunsch algorithm and assigns scores to the pairs of amino acids aligned using a specific BLOSUM substitution matrix. For statistical analysis, the dependency test and the chi-square test are used in GraphPad Prism and R-studio.The results show that the overall alignment between allergenic proteins from the same food (Peanut - Peanut, Sesame - Sesame, and Lentil - Lentil) and different foods (Peanut - Lentil, Peanut - Sesame, Lentil - Sesame, Lentil - Cowpea, and Sesame - Cowpea) has low identity and similarity.The overall alignment between the allergenic proteins of the same food (Cowpea - Cowpea) and of different foods (Peanut - Cowpea) shows a strong identity and similarity, relative to the result of the chisquare test. The possibility of cross-reactivity between cowpea and peanut is shown.

On the Development of Metrological Support for the Identification and Quantitative Determination of the Content of Non-infectious Food Allergens of Animal or Plant Protein Origin in Food Products

In accordance with TR CU022/2011 «Food products in terms of their labeling», the content of allergens in food products is subject to mandatory control. Work on the creation of a metrological support complex for the identification and quantitative determination of the content of non-infectious food allergens of animal or plant protein origin in food products includes the development and certification of methods for identification and quantitative determination; conducting interlaboratory comparisons; creation and testing for type approval of reference materials.Within the framework of this research, work was carried out on the development and certification of methods for identifying and quantifying the content of non-infectious food allergens of plant (gluten, peanuts, nuts, soybeans) and animal (cow’s milk, chicken eggs, fish and seafood) protein origin in samples of all kinds of food products and objects related to the requirements for food products, swabs taken from work surfaces during production control using reagent kits for enzyme-linked immunosorbent assay produced by XEMA LLC.Certification of quantitative analysis methods in accordance with legal requirements in the field of ensuring the uniformity of measurements was conducted using imported reference materials of food allergens. The lowest sensitivity limits (detection limits) of the presence or absence of antigens by allergen protein weight ranged from 0.001 ppb to 5 ppm. The developed methods make it possible to ensure the safety of food products when establishing the conformity of products with the requirements of the legislation on technical regulation.

Food allergy and anaphylaxis to walnut

Among the wide variety of tree nuts, walnut is an allergen that deserves special attention in the context of acute allergic reactions, due to their severity, low inducing trigger dose, and minimal likelihood of developing tolerance. The overall consumption of walnut has been steadily increasing, while the importance of this allergen as a trigger for anaphylaxis is underestimated due to its often “hidden” presence in foods and the difficulty of trigger verification. This article presents the epidemiological aspects of walnut food allergy, provides current data on the molecular characteristics and properties of various allergen proteins, and their clinical significance for the development of anaphylaxis. The article is supplemented with two clinical cases of food anaphylaxis to walnuts from own clinical practice.

An Overview of Fruit Allergens: Structural, Functional, Phylogenetical, and Clinical Aspects

Most of the allergenic proteins from fruits identified so far belong to different families of pathogenesis-related (PR) proteins. These PR proteins have been classified in different families of structurally and functionally unrelated proteins, but the majority of all fruit allergens belong to three groups, in particular PR-5 thaumatin-like proteins (TLP), PR-10 Bet v 1-like proteins, and PR-14 non-specific lipid transfer proteins (nsTLP). Some allergenic proteins from fruits can also be found among PR-protein families of PR-2 β1,3-glucanase proteins, PR-3 chitinases I, II, IV–VII, and PR-8 chitinases III. In addition, other important fruit allergens occur in protein families unrelated to the PR-protein families, such as the profilins and the newly emerging group of gibberellin-regulated proteins (GBRP). Finally, proteins that belong to seed storage proteins from higher plants, including 2S albumins, 7S globulins (vicilin), and 11S globulins (legumin), must be retained as possible potential fruit allergens resulting from the unintended consumption of the seeds. Here, we present an overview of the structural organization, functional properties, and phylogenetical relationships among these different groups of fruit allergens, supporting the occurrence of cross-reactivity and cross-allergenicity often described between fruit allergens, and the corresponding allergens from vegetables and pollens.