Identification of Almond ( Prunus dulcis) Vicilin As a Food Allergen

A systematic review of allergen cross-reactivity: Translating basic concepts into clinical relevance

Access to the molecular culprits of allergic reactions allows for the leveraging of molecular allergology as a new precision medicine approach-one built on interdisciplinary, basic, and clinical knowledge. Molecular allergology relies on the use of allergen molecules as in vitro tools for the diagnosis and management of allergic patients. It complements the conventional approach based on skin and in vitro allergen extract testing. Major applications of molecular allergology comprise accurate identification of the offending allergen thanks to discrimination between genuine sensitization and allergen cross-reactivity, evaluation of potential severity, patient-tailored choice of the adequate allergen immunotherapy, and prediction of its expected efficacy and safety. Allergen cross-reactivity, defined as the recognition of 2 or more allergen molecules by antibodies or T cells of the same specificity, frequently interferes with allergen extract testing. At the mechanistic level, allergen cross-reactivity depends on the allergen, the host's immune response, and the context of their interaction. The multiplicity of allergen molecules and families adds further difficulty. Understanding allergen cross-reactivity at the immunologic level and translating it into a daily tool for the management of allergic patients is further complicated by the ever-increasing number of characterized allergenic molecules, the lack of dedicated resources, and the need for a personalized, patient-centered approach. Conversely, knowledge sharing paves the way for improved clinical use, innovative diagnostic tools, and further interdisciplinary research. Here, we aimed to provide a comprehensive and unbiased state-of-the art systematic review on allergen cross-reactivity. To optimize learning, we enhanced the review with basic, translational, and clinical definitions, clinical vignettes, and an overview of online allergen databases.

Food Allergens of Plant Origin

This review presents an update on the physical, chemical, and biological properties of food allergens in plant sources, focusing on the few protein families that contribute to multiple food allergens from different species and protein families recently found to contain food allergens. The structures and structural components of the food allergens in the allergen families may provide further directions for discovering new food allergens. Answers as to what makes some food proteins allergens are still elusive. Factors to be considered in mitigating food allergens include the abundance of the protein in a food, the property of short stretches of the sequence of the protein that may constitute linear IgE binding epitopes, the structural properties of the protein, its stability to heat and digestion, the food matrix the protein is in, and the antimicrobial activity to the microbial flora of the human gastrointestinal tract. Additionally, recent data suggest that widely used techniques for mapping linear IgE binding epitopes need to be improved by incorporating positive controls, and methodologies for mapping conformational IgE binding epitopes need to be developed.

SlMBP3 Knockout/down in Tomato: Normal-Sized Fruit with Increased Dry Matter Content through Non-Liquefied Locular Tissue by Altered Cell Wall Formation

The phenotypic effect of the knockdown/out of AGAMOUS clade MADS-box gene SlMBP3 in tomato was evaluated using a transferred DNA (T-DNA)-tagged mutant of SlMBP3 and SlMBP3-RNA interference lines. SlMBP3 was preferentially expressed in the locular tissue of fruit and the seed coat combined with the endoderm. Consistent with where SlMBP3 is expressed, the SlMBP3-knockout/down lines showed non-liquefied locular tissues and increased number of seed hairs than the wild type (WT). The early cell degradation of the locular tissue was not observed in the fruits of the SlMBP3-knockout/down lines, and the cells were elongated like placental cells resulting in non-liquefied locular tissues. As the result, the fruits of the SlMBP3-knockout/down lines exhibited higher dry matter contents and titratable acidity than those of the WT. During locular tissue cell development under the SlMBP3 knockout/down, the expression of cell-enlargement-related genes (beta-expansin gene SlEXPB1 and endo-beta-1,4-D-glucanase gene Cel8) and pectinase-inhibitor-related genes (pectin esterase inhibitor gene PE inhibitor and polygalacturonase inhibitor gene PG inhibitor) was upregulated and that of pectinase-encoding genes (polygalacturonase gene QRT3-like and pectin lyase gene PL2) was downregulated. In the seed coat of the SlMBP3-knockout/down lines, tomato trichome-formation-related genes such as MYB genes containing R2 and R3 repeats (R2R3-MYB) transcription factor SlMYB75, B-type cyclin SlCycB2 and Homeodomain Leucine Zipper (HD-Zip) IV transcription factor Woolly were downregulated. Our results demonstrate that SlMBP3 is involved in the liquefaction of the locular tissue through the modification of cell development and degradation processes and seed hair formation in tomato fruits, and the SlMBP3 knockout/down results in normal-sized fruit with increased dry matter content.

Oilseed Cakes in the Food Industry; A Review on Applications, Challenges, and Future Perspectives

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By-products from the food sector now have a wide range of applications. Low-cost raw materials, followed by low-cost goods, are regarded as one of the sectors’ top goals. Because of its economic relevance, reduced price, and nutrients such as protein, fiber, carbs, and antioxidants, oilseed cakes (OCs) have found a desirable place in livestock and poultry feed. Furthermore, because the cake has the same desirable nutrients, its usage in the food business is unavoidable. However, its use in this sector is not simply for nutritious purposes and has it has different impacts on flavor, texture, color, and antioxidant qualities. Therefore, as a result of its desirable qualities, the cake can be more useful in extensive applications in the food business, as well as in the manufacture of supplements and novel foods. The current review looks at the reapplications of byproducts obtained from oilseeds (soybean, sunflower, sesame, canola, palm kernel, peanut, mustard, and almond) in the food sector in the future. Furthermore, allergenicity, toxicity, antinutritional compounds, and techniques of extracting cakes from oilseeds have been discussed.

Rosaceae food allergy: a review

This review provides a global overview on Rosaceae allergy and details the particularities of each fruit allergy induced by ten Rosaceae species: almond/peach/cherry/apricot/plum (Amygdaleae), apple/pear (Maleae), and raspberry/blackberry/strawberry (Rosoideae). Data on clinical symptoms, prevalence, diagnosis, and immunotherapies for the treatment of Rosaceae allergy are herein stated. Allergen molecular characterization, cross-reactivity/co-sensitization phenomena, the impact of food processing and digestibility, and the methods currently available for the Rosaceae detection/quantification in foods are also described. Rosaceae allergy has a major impact in context to pollen-food allergy syndrome (PFAS) and lipid transfer protein (LTP) allergies, being greatly influenced by geography, environment, and presence of cofactors. Peach, apple, and almond allergies are probably the ones most affecting the quality of life of the allergic-patients, although allergies to other Rosaceae fruits cannot be overlooked. From patients' perspective, self-allergy management and an efficient avoidance of multiple fruits are often difficult to achieve, which might raise the risk for cross-reactivity and co-sensitization phenomena and increase the severity of the induced allergic responses with time. At this point, the absence of effective allergy diagnosis (lack of specific molecular markers) and studies advancing potential immunotherapies are some gaps that certainly will prompt the progress on novel strategies to manage Rosaceae food allergies.

Shotgun proteomics of Brassica rapa seed proteins identifies vicilin as a major seed storage protein in the mature seed

Proteins make up a large percentage of the Brassica seed and are second only to the oil in economic importance with uses for both animal and human nutrition. The most abundant proteins reported in the seeds of Brassica are the seed storage proteins cruciferin and napin, belonging to the 12S globulin and 2S albumin families of proteins, respectively. To gain insight into the Brassica rapa seed proteome and to confirm the presence and relative quantity of proteins encoded by candidate seed storage genes in the mature seed, shotgun proteomics was carried out on protein extracts from seeds of B. rapa inbred line R-o-18. Following liquid chromatography tandem mass spectrometry, a total of 34016 spectra were mapped to 323 proteins, where 233 proteins were identified in 3 out of 4 biological replicates by at least 2 unique peptides. 2S albumin like napin seed storage proteins (SSPs), 11/12S globulin like cruciferin SSPs and 7S globulin like vicilin SSPs were identified in the samples, along with other notable proteins including oil body proteins, namely ten oleosins and two oil body-associated proteins. The identification of vicilin like proteins in the mature B. rapa seed represents the first account of these proteins in the Brassicaceae and analysis indicates high conservation of sequence motifs to other 7S vicilin-like allergenic proteins as well as conservation of major allergenic epitopes in the proteins. This study enriches our existing knowledge on rapeseed seed proteins and provides a robust foundation and rational basis for plant bioengineering of seed storage proteins.

Identification of Pru du 6 as a potential marker allergen for almond allergy

BACKGROUND

Oral food challenges have demonstrated that diagnosis of almond allergy based on extract-sIgE tests displays low specificity. Molecular allergy diagnosis is expected to improve accuracy, but its value in diagnosing almond allergy remains unknown. The aim of this study was to identify relevant almond allergens and examine their ability to improve almond allergy diagnosis.

METHODS

IgE-reactive proteins were purified from almond kernels. IgE binding to almond extract and the allergens was analyzed by quantitative ELISA using sera from 18 subjects with a proven almond allergy. The control group consisted of sera from 18 subjects allergic to peanut and/or tree nuts but tolerant to almond.

RESULTS

Three IgE-binding proteins were identified: legumin (Pru du 6), alpha-hairpinin (Pru du 8), and mandelonitrile lyase (Pru du 10). Positive IgE (≥0.35 kU/L) to almond extract showed 94% sensitivity but only 33% specificity. IgE to Pru du 6 maintained high sensitivity (83%) and provided superior specificity (78%). Sera from almond-allergic subjects had significantly higher IgE levels to almond extract (P < .0001) and Pru du 6 (P < .0001) than sera from tolerant donors. Sensitization to Pru du 6 was highly specific for almond allergy, while frequencies of sensitization to legumins from peanut, walnut, hazelnut, and cashew were similar in both groups. IgE to Pru du 8 and Pru du 10 was less sensitive (41% and 67%), but showed specificities of 100% and 61%.

CONCLUSION

The use of almond allergens markedly increases the diagnostic specificity compared to the extract. Pru du 6 is a potential new molecular marker for almond allergy.

Almond allergens: update and perspective on identification and characterization

Almond (Prunus dulcis) is not only widely used as a human food as a result of its flavor, nutrients, and health benefits, but it is also one of the most likely tree nuts to trigger allergies. Almond allergens, however, have not been studied as extensively as those of peanuts and other selected tree nuts. This review provides an update of the molecular properties of almond allergens to clarify some confusion about the identities of almond allergens and our perspective on characterizing putative almond allergens. At present, the following almond allergens have been designated by the World Health Organization/International Union of Immunological Societies Allergen Nomenclature Sub-Committee: Pru du 3 (a non-specific lipid transfer protein 1, nsLTP1), Pru du 4 (a profilin), Pru du 5 (60S acidic ribosomal protein 2), Pru du 6 (an 11S legumin known as prunin) and Pru du 8 (an antimicrobial protein with cC3C repeats). Besides, almond vicilin and almond γ-conglutin have been identified as food allergens, although further characterization of these allergens is still of interest. In addition, almond 2S albumin was reported as a food allergen as a result of the misidentification of Pru du 8. Two more almond proteins have been called allergens based on their sequence homology with known food allergens and their 'membership' in relevant protein families that contain allergens in many species. These include the pathogenesis related-10 protein (referred to as Pru du 1) and the thaumatin-like protein (referred to as Pru du 2). Almonds thus have five known food allergens and five more likely ones that need to be investigated further. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Review of New Trends in the Analysis of Allergenic Residues in Foods and Cosmetic Products

BACKGROUND

Allergies represent an important health problem in industrialized countries. Allergen sensitization is an important risk factor for the development of allergic diseases; thus, the identification of an individual's allergen sensitization is essential for the diagnosis and treatment of diseases.

OBJECTIVE

This review compares different modern methods applied for the analysis of allergens in various matrices (from 2015 to the end of September 2019).

CONCLUSIONS

Immunological methods are still most frequently used for detection of allergens. These methods are sensitive, but the lack of specificity and cross-reaction of some antibodies can still be a relevant source of errors. DNA-based methods are fast and reliable for determination of protein allergens, but the epitopes of protein allergens with posttranslational modifications and their changes, originated during various processing, cannot be identified through the use of this method. Methods based on application of biosensors are very rapid and easy to use, and can be readily implemented as screening methods to monitor allergens. Recent developments of new high-resolution MS instruments are encouraging and enable development in the analysis of allergens. Fast, very sensitive, reliable, and accurate detection and quantification of allergens in complex samples can be used in the near future. Mass spectrometry coupled with LC, GC, or electrophoretic methods bring additional advances in allergen analysis. The use of LC-MS or LC-MS/MS for the quantitative detection of allergens in various matrices is at present gaining acceptance as a protein-based confirmatory technique over the routinely performed enzyme-linked immunosorbent assays.

Heat induced denaturation, aggregation and gelation of almond proteins in skim and full fat almond milk

The effect of thermal treatment (45-95 °C for 30 min) on the structure of almond milk proteins was assessed, as the unfolding and association of these proteins in response to heat is not well understood. Above 55 °C, protein surface hydrophobicity and particle size increased and alpha helical structure decreased, reducing the stability of skim or full fat milk. Fractal protein clusters were observed at 65-75 °C and weakly flocculated gels with a continuous protein network occurred at 85-95 °C, resulting in gels with high water holding capacity and a strength similar to dairy gels. The presence of almond fat increased gel strength but led to a more heterogenous microstructure, which may be improved by homogenisation. Elasticity could also be increased with protein concentration. This study improves our understanding of the heat stability of almond milk proteins and indicates their potential as a gelling ingredient for vegan and vegetarian products.

Almond (Prunus dulcis) Allergen Pru du 8, the First Member of a New Family of Food Allergens

An almond allergen with two known short peptide sequences was reported as the almond 2S albumin but was later suspected to be almond vicilin. However, this allergen was not designated by the World Health Organization/International Union of Immunological Societies. This study aimed to determine the true identity of this elusive almond allergen. cDNAs were synthesized from total RNA of the Nonpareil almond. The complete sequence of the previously reported almond allergen was determined from its coding sequence. The deduced protein was produced recombinantly and was confirmed to be a food allergen by testing with 18 almond-allergic sera. The allergen is a potential cysteine-rich antimicrobial protein with characteristic C[X]₃C-[X]_10-12-C[X]₃C motifs of the hairpinin antimicrobial protein. This first member of a novel family of food allergens was named Pru du 8. The signature motif of the hairpinin antimicrobial protein can be found in the N-terminal region of some vicilin allergens (e.g., Ara h 1). It can also be found in the signal peptide of other vicilin allergens (e.g., Car i 2). In many species, however, vicilins do not contain such a motif, indicating that the presence of the signature motifs of the hairpinin antimicrobial protein in vicilins might be a result of translocation during evolution.