Sensitive ELISA and lateral flow immunoassay for the detection of walnut traces in processed food and working surfaces

Walnut represents one of the most allergenic nuts that can be found as a hidden allergen. In this study, sandwich ELISA and lateral flow immunoassay (LFIA), based on the determination of Jug r 1, were developed to detect walnut. Cross-reactivity was only found with Pecan nut among a panel of 88 food ingredients tested. ELISA and LFIA could detect 0.25 and 0.5 µg/g of walnut protein in complex food matrices spiked with walnut extract, respectively. Furthermore, walnut was detected in blended (chocolate) and incurred foods (ice cream and bread) added with ground walnut at levels of 0.5 and 1.5 µg protein/g by ELISA and LFIA, respectively. LFIA could also detect 0.1 μg of walnut protein in working surfaces. ELISA displayed acceptable precision and high recovery (71-97 %) and both tests were robust. This study shows that developed ELISA and LFIA are reliable tools to be applied in allergen control programs.

Novel post-translationally cleaved Ara h 2 proteoforms: Purification, characterization and IgE-binding properties

The 2S albumins Ara h 2 and Ara h 6 have been shown to be the most important source of allergenicity in peanut. Several isoforms of these allergens have been described. Using extraction and liquid chromatography we isolated proteins with homology to Ara h 2 and characterized hitherto unknown Ara h 2 proteoforms with additional post-translational cleavage. High-resolution mass spectrometry located the cleavage site on the non-structured loop of Ara h 2 while far UV CD spectroscopy showed a comparable structure to Ara h 2. The cleaved forms of Ara h 2 were present in genotypes of peanut commonly consumed. Importantly, we revealed that newly identified Ara h 2 cleaved proteoforms showed comparable IgE-binding using sera from 28 peanut-sensitized individuals, possessed almost the same IgE binding potency and are likely similarly allergenic as intact Ara h 2. This makes these newly identified forms relevant proteoforms of peanut allergen Ara h 2.

Purification and Initial Characterization of Ara h 7, a Peanut Allergen from the 2S Albumin Protein Family

2S albumins are important peanut allergens. Within this protein family, Ara h 2 and Ara h 6 have been described in detail, but Ara h 7 has received little attention. We now describe the first purification of Ara h 7 and its characterization. Two Ara h 7 isoforms were purified from peanuts. Mass spectrometry revealed that both the isoforms have a post-translation cleavage, a hydroxyproline modification near the N-terminus, and four disulfide bonds. The secondary structure of both Ara h 7 isoforms is highly comparable to those of Ara h 2 and Ara h 6. Both Ara h 7 isoforms bind IgE, and Ara h 7 is capable of inhibiting the binding between Ara h 2 and IgE, suggesting at least partially cross-reactive IgE epitopes. Ara h 7 was found in all main market types of peanut, at comparable levels. This suggests that Ara h 7 is a relevant allergen from the peanut 2S albumin protein family.

Seed Storage Proteins, 2S Albumin And 11S Globulin, Associated to Severe Allergic Reactions after Flaxseed Intake

BACKGROUND

Given the increased popularity of flaxseed in meals, several cases of allergy to these seeds have been reported. Little is known about allergens implicated in hypersensitivity reactions to these seeds. The present work aimed to identify the allergens involved in IgE-mediated reactions in five patients with a clinical history of severe systemic symptoms after flaxseed consumption.

METHODS

Proteins susceptible to be allergens with IgE-binding capacity were purified from flaxseed extract by chromatographic techniques. Their identification was achieved via MALDI-TOF mass spectrometry. Immunoassays were performed using the five allergic patient's era either by testing them individually or as a pool.

RESULTS

Proteins susceptible to be allergens with IgE-binding capacity were purified from flaxseed extract by chromatographic techniques. Their identification was achieved via MALDI-TOF mass spectrometry. Immunoassays were performed using the five allergic patient's era either by testing them individually or as a pool. Results: Four out of five patients recognized a low-molecular-mass protein (around 13kDa) by immunoblotting of the flaxseed extract, while two patients recognized a protein of approximately 55 kDa. They were identified by mass spectrometry as flaxseed 2S albumin, included into WHO/IUIS allergen nomenclature as Lin u 1,and 11S globulin, respectively. Inhibition assays revealed in vitro IgE-cross-reactivity of Lin u 1 with peanut and cashew nut proteins, while IgE recognition of 11S globulin by patients' sera was partially inhibited by several plant-derived sources.

CONCLUSIONS

Seed storage proteins from flaxseed were involved in the development of severe symptoms in five individuals and exhibited cross-reactivity with other allergenic sources. Besides the severity of flaxseed allergy in patients sensitized to 2S albumin, it is the first time that the 11S globulin is identified as a potential allergen. We consider that these data should be taken into account for a more accurate diagnosis of patients.

Characterization of Relevant Biomarkers for the Diagnosis of Food Allergies: An Overview of the 2S Albumin Family

2S albumins are relevant and often major allergens from several tree nuts and seeds, affecting mainly children and young people. The present study aims to assess how the structural features of 2S albumins could affect their immunogenic capacity, which is essential to comprehend the role of these proteins in food allergy. For this purpose, twelve 2S albumins were isolated from their respective extracts by chromatographic methods and identified by MALDI-TOF mass-spectrometry. Their molecular and structural characterization was conducted by electrophoretic, spectroscopic and in silico methods, showing that these are small proteins that comprise a wide range of isoelectric points, displaying a general high structure stability to thermal treatment. Despite low amino acid sequence identity, these proteins share structural features, pointing conformational epitopes to explain cross-reactivity between them. Immunoblotting with allergic patients’ sera revealed those possible correlations between evolutionarily distant 2S albumins from different sources. The availability of a well-characterized panel of 2S albumins from plant-derived sources allowed establishing correlations between their structural features and their allergenic potential, including their role in cross-reactivity processes.

Inhibition of SARS-CoV-2 3CL Mpro by Natural and Synthetic Inhibitors: Potential Implication for Vaccine Production Against COVID-19

COVID-19 has created a pandemic situation all over the world. It has spread in nearly every continent. Researchers all over the world are trying to produce an effective vaccine against this virus, however; no specific treatment for COVID-19 has been discovered -so far. The current work describes the inhibition study of the SARS-CoV-2 main proteinase or 3CL M^pro by natural and synthetic inhibitors, which include 2S albumin and flocculating protein from Moringa oleifera (M. oleifera) and Suramin. Molecular Docking study was carried out using the programs like AutoDock 4.0, HADDOCK2.4, patchdock, pardock, and firedock. The global binding energy of Suramin, 2S albumin, and flocculating proteins were −41.96, −9.12, and −14.78 kJ/mol, respectively. The docking analysis indicates that all three inhibitors bind at the junction of domains II and III. The catalytic function of 3CL M^pro is dependent on its dimeric form, and the flexibility of domain III is considered important for this dimerization. Our study showed that all three inhibitors reduce this flexibility and restrict their motion. The decrease in flexibility of domain III was further confirmed by analysis coming from Molecular dynamic simulation. The analysis results indicate that the temperature B-factor of the enzyme decreases tremendously when the inhibitors bind to it. This study will further explore the possibility of producing an effective treatment against COVID-19.

In Silico, Molecular Docking and In Vitro Antimicrobial Activity of the Major Rapeseed Seed Storage Proteins

BACKGROUND

In addition to their use as an edible oil and condiment crop, mustard and rapeseed (Brassica napus L., B. juncea (L.) Czern., B. nigra (L.) W.D.J.Koch, B. rapa L. and Sinapis alba L.) have been commonly used in traditional medicine for relieving pain, coughs and treating infections. The seeds contain high amounts of oil, while the remaining by-product meal after oil extraction, about 40% of seed dry weight, has a low value despite its high protein-content (~85%). The seed storage proteins (SSP) 2S albumin-type napin and 12S globulin-type cruciferin are the two predominant proteins in the seeds and show potential for value adding to the waste stream; however, information on their biological activities is scarce. In this study, purified napin and cruciferin were tested using in silico, molecular docking, and in vitro approaches for their bioactivity as antimicrobial peptides.

MATERIALS AND METHODS

The 3D-structure of 2S albumin and 12S globulin storage proteins from B. napus were investigated to predict antimicrobial activity employing an antimicrobial peptide database survey. To gain deeper insights into the potential antimicrobial activity of these SSP, in silico molecular docking was performed. The purified B. napus cruciferin and napin were then tested against both Gram-positive and Gram-negative bacteria for in vitro antimicrobial activity by disc diffusion and microdilution antimicrobial susceptibility testing.

RESULTS

In silico analysis demonstrated both SSP share similar 3D-structure with other well studied antimicrobial proteins. Molecular docking revealed that the proteins exhibited high binding energy to bacterial enzymes. Cruciferin and napin proteins appeared as a double triplet and a single doublet, respectively, following SDS-PAGE. SDS-PAGE and Western blotting also confirmed the purity of the protein samples used for assessment of antimicrobial activity. Antimicrobial susceptibility testing provided strong evidence for antimicrobial activity for the purified napin protein; however, cruciferin showed no antimicrobial activity, even at the highest dose applied.

DISCUSSION

In silico and molecular docking results presented evidence for the potential antimicrobial activity of rapeseed cruciferin and napin SSP. However, only the in vitro antimicrobial activity of napin was confirmed. These findings warrant further investigation of this SSP protein as a potential new agent against infectious disease.

Pea (Pisum sativum) allergy in children: Pis s 1 is an immunodominant major pea allergen and presents IgE binding sites with potential diagnostic value

BACKGROUND

Food allergy to pea (Pisum sativum) has been rarely studied in children at the clinical and molecular levels.

OBJECTIVE

To elucidate the allergenic relevance and diagnostic value of pea 7S globulin Pis s 1, nsLTP, and 2S albumins PA1 and PA2 in children.

METHODS

Children with pea-specific IgE ≥ 0.35 kUA /L and clinical evidence of pea allergy or tolerance were included in the study. IgE binding against pea total protein extract, recombinant (r) rPis s 1, rPA1, rPA2, and natural nsLTP was analysed using IgE immunoblot/inhibition. Mediator release potency was investigated in passively sensitized rat basophil leukaemia (RBL) 2H3-cells. IgE binding to synthetic overlapping peptides of Pis s 1 was detected on multipeptide microarrays.

RESULTS

19 pea-sensitized children were included, 14 with doctors' diagnosed allergy and 5 with tolerance to pea (median age 3.5 and 4.5 years, respectively). 11/14 (78%) pea-allergic and 1/5 (20%) tolerant children were sensitized to Pis s 1. Under the reducing conditions of immunoblot analysis, IgE binding to rPA1 was negligible, sensitization to rPA2 and nsLTP undetectable. Compared to pea total protein extract, rPis s 1 displayed on average 58% IgE binding capacity and a 20-fold higher mediator release potency. Selected Pis s 1-related peptides displayed IgE binding in pea-allergic but not in pea-tolerant children.

CONCLUSIONS AND CLINICAL RELEVANCE

In this study group, Pis s 1 is a major immunodominant allergen in pea-allergic children. Evidence for sensitization to nsLTP and 2S albumins was low but requires further verification with regard to conformational epitopes. Recombinant Pis s 1 and related peptides which were exclusively recognized by pea-allergic children may improve in vitro diagnosis of pea allergy once verified in prospective studies with larger study groups.

2S albumins and nsLTP are involved in anaphylaxis to pizza sauce: IgE recognition before and after allergen processing

Although pizza is one of the most popular foods in the world, allergic responses after ingesting pizza are relatively uncommon. However, precisely identifying the allergens responsible for these allergic reactions is challenging because of the high and diverse number of ingredients used in pizza preparation. In this report, we aim to identify the allergens responsible for systemic allergic reactions following ingestion of pizza in two patients. Using a skin prick by prick test (SPPT) and in vitro techniques, with natural and recombinant purified allergens from tomato and mustard seeds, we identified 2S albumin and non-specific lipid transfer proteins (nsLTP) as the proteins involved. However, IgE responses to the four nsLTPs differed before and after denaturation and reduction, thus suggesting additional complexity around nsLTP in food processing.

Simplified Tracking of a Soy Allergen in Processed Food Using a Monoclonal Antibody-Based Sandwich ELISA Targeting the Soybean 2S Albumin Gly m 8

Soybean allergens in food samples are currently detected in most cases using enzyme-linked immunosorbent assays (ELISAs) based on antibodies raised against bulk soybean proteins or specifically targeting soybean trypsin inhibitor, conglycinin, or glycinin. The various commercial ELISAs lack standardized reference material, and the results are often inaccurate because the antibodies cross-react with proteins from other legumes. Furthermore, the isolation of allergenic proteins involves laborious denaturing extraction conditions. To tackle these challenges, we have developed a novel sandwich ELISA based on monoclonal antibodies raised against the soybean 2S albumin Gly m 8 and a recombinant Gly m 8 reference protein with native-analogous characteristics. The antibodies do not cross-react with other legume proteins, and the extraordinary stability and solubility of Gly m 8 allows it to be extracted even from complex matrices after processing. The Gly m 8 ELISA therefore achieves greater specificity and reproducibility than current ELISA tests.

Gene expression and spatiotemporal localization of antifungal chitin-binding proteins during Moringa oleifera seed development and germination

Chitin-binding proteins behave as storage and antifungal proteins in the seeds of Moringa oleifera. Moringa oleifera is a tropical multipurpose tree. Its seed constituents possess coagulant, bactericidal, fungicidal, and insecticidal properties. Some of these properties are attributed to a group of polypeptides denominated M. oleifera chitin-binding proteins (in short, Mo-CBPs). Within this group, Mo-CBP₂, Mo-CBP₃, and Mo-CBP₄ were previously purified to homogeneity. They showed high amino acid similarity with the 2S albumin storage proteins. These proteins also presented antimicrobial activity against human pathogenic yeast and phytopathogenic fungi. In the present study, the localization and expression of genes that encode Mo-CBPs and the biosynthesis and degradation of the corresponding proteins during morphogenesis and maturation of M. oleifera seeds at 15, 30, 60, and 90 days after anthesis (DAA) and germination, respectively, were assessed. The Mo-CBP transcripts and corresponding proteins were not detected at 15 and 30 days after anthesis (DAA). However, they accumulated at the latter stages of seed maturation (60 and 90 DAA), reaching the maximum level at 60 DAA. The degradation kinetics of Mo-CBPs during seed germination by in situ immunolocalization revealed a reduction in the protein content 48 h after sowing (HAS). Moreover, Mo-CBPs isolated from seeds at 60 and 90 DAA prevented the spore germination of Fusarium spp. Taken together, these results suggest that Mo-CBPs play a dual role as storage and defense proteins in the seeds of M. oleifera.

High frequency of IgE sensitization towards kiwi seed storage proteins among peanut allergic individuals also reporting allergy to kiwi

Background

IgE sensitization to storage proteins from nuts and seed is often related to severe allergic symptoms. There is a risk of immunological IgE cross-reactivity between storage proteins from different species. The potential clinical implication of such cross-reactivity is that allergens other than the known sensitizer can cause allergic symptoms. Previous studies have suggested that kiwi seed storage proteins may constitute hidden food allergens causing cross-reactive IgE-binding with peanut and other tree nut homologs, thereby mediating a potential risk of causing allergy symptoms among peanut ant tree nut allergic individuals. The objective of this study was to investigate the degree of sensitization towards kiwi fruit seed storage proteins in a cohort of peanut allergic individuals.

Methods

A cohort of 59 adolescents and adults with peanut allergy was studied, and self reported allergies to a number of additional foods were collected. Quantitative IgE measurements to seed storage proteins from kiwi and peanut were performed.

Results

In the cohort, 23 out of the 59 individuals were reporting kiwi fruit allergy (39%). The frequency of IgE sensitization to kiwi fruit and to any kiwi seed storage protein was higher among peanut allergic individuals also reporting kiwi fruit allergy (P = 0.0001 and P = 0.01). A positive relationship was found between IgE levels to 11S globulin (r = 0.65) and 7S globulin (r = 0.48) allergens from kiwi and peanut, but IgE levels to 2S albumin homologs did not correlate. Patients reporting kiwi fruit allergy also reported allergy to hazelnut (P = 0.015), soy (P < 0.0001), pea (P = 0.0002) and almond (P = 0.016) to a higher extent than peanut allergic individuals without kiwi allergy.

Conclusions

Thirty-nine percent of the peanut allergic patients in this cohort also reported kiwi fruit allergy, they displayed a higher degree of sensitization to kiwi storage proteins from both kiwi and peanut, and they also reported a higher extent of allergy to other nuts and legumes. On the molecular level, there was a correlation between IgE levels to 11S and 7S storage proteins from kiwi and peanut. Taken together, reported symptoms and serological findings to kiwi in this cohort of patients with concurrent allergy to peanut and kiwi fruit, could be explained by a combination of cross-reactivity between the 11S and 7S globulins and co-sensitization to the 2S albumin Act d 13.

Specific IgE to peanut 2S albumin Ara h 7 has a discriminative ability comparable to Ara h 2 and 6

BACKGROUND

Little is known on the clinical relevance of peanut 2S albumin Ara h 7.

OBJECTIVE

To investigate the discriminative ability of Ara h 7 in peanut allergy and assess the role of cross-reactivity between Ara h 2, 6 and Ara h 7 isoforms.

METHODS

Sensitization to recombinant peanut storage proteins Ara h 1, 2, 3, 6, and 7 was assessed using a line blot in sera from 40 peanut-tolerant and 40 peanut-allergic patients, based on food challenge outcome. A dose-dependent ELISA inhibition experiment was performed with recombinant Ara h 2, 6 and Ara h 7 isoforms.

RESULTS

For Ara h 7.0201, an area under the ROC curve was found of 0.83, comparable to Ara h 2 (AUC 0.81) and Ara h 6 (AUC 0.85). Ara h 7 intensity values strongly correlated with those from Ara h 2 and 6 (r_s = 0.81). Of all patients sensitized to 2S albumins Ara h 2, 6, or 7, the majority was co-sensitized to all three (n = 24, 68%), although mono-sensitization to either 2S albumin was also observed in selected patients (Ara h 2: n = 6, 17%; Ara h 6: n = 2, 6%; Ara h 7: n = 2, 6%). Binding to Ara h 7.0101 could be strongly inhibited by Ara h 7.0201, but not the other way around.

CONCLUSIONS AND CLINICAL RELEVANCE

Specific IgE against Ara h 7.0201 has a predictive ability for peanut allergy similar to Ara h 2 and 6 and possesses unique IgE epitopes as well as epitopes shared between the other Ara h 7 isoform and Ara h 2 and 6. While co-sensitization to all three 2S albumins is most common, mono-sensitization to either Ara h 2, 6, or 7 occurs in selected patients, leading to a risk of misdiagnosis when testing for a single 2S albumin.

Structural Characterization of the Allergenic 2S Albumin Cor a 14: Comparing Proteoform Patterns across Hazelnut Cultivars

The hazelnut allergen Cor a 14 belongs to the 2S albumins, a family of heterodimeric seed storage proteins exhibiting a high degree of structural diversity. Given its relevance as an allergen and the potential to elicit severe reactions, elucidation of the sequence heterogeneity of naturally occurring Cor a 14 is essential for the development of reliable diagnostics and risk evaluation. We therefore performed a comprehensive survey on the proteoforms of Cor a 14 and determined their quantitative distribution in three different hazelnut cultivars by a combinatory HPLC-HRMS approach including bottom-up and intact mass analysis. Compared with the Cor a 14 prototype sequence, we identified three sequence polymorphisms, two of the small and one of the large subunit, and elucidated their specific pairing on the protein level. Furthermore, we located a pronounced microheterogeneity on the protein termini and, for the first time, provide data on varying proteoform patterns between different cultivars of an allergenic seed. Together, these data present the basis for a more detailed investigation on the allergenicity of Cor a 14 in different cultivars and constitute, to be best of our knowledge, the largest set of proteoforms so far reported for a 2S albumin.

Measurement of specific IgE antibodies to Ses i 1 improves the diagnosis of sesame allergy

BACKGROUND

The number of reported cases of allergic reactions to sesame seeds (Sesamum indicum) has increased significantly. The specific IgE tests and skin prick tests presently available for diagnosis of sesame allergy are all based on crude sesame extract and are limited by their low clinical specificity. Thus, oral food challenge (OFC) is still the gold standard in the diagnosis.

OBJECTIVE

The aim was to identify the allergen components useful to diagnose sesame-allergic children with the goal to reduce the number of OFCs needed.

METHODS

Ninety-two sesame-sensitized children were consecutively enrolled and diagnosed based on OFC or convincing history. Specific IgE to purified native 11S globulin (nSes i 11S), 7S globulin (nSes i 7S), 2S albumin (nSes i 2S), and two recombinant 2S albumins (rSes i 1 and rSes i 2) was measured by ELISA and/or ImmunoCAP (rSes i 1/streptavidin application).

RESULTS

Based on area under curve (AUC) values from receiver operating characteristic (ROC) analysis, rSes i 1 was shown to have the best diagnostic performance of the allergen components in ELISA. The experimental rSes i 1 ImmunoCAP test had larger AUC (0.891; 95% CI, 0.826-0.955) compared to the commercially available sesame ImmunoCAP (0.697; 95% CI, 0.589-0.805). The clinical sensitivity and specificity for the rSes i 1 ImmunoCAP test at optimal cut-off (3.96 kUA /L) were 86.1% and 85.7%, respectively.

CONCLUSION AND CLINICAL RELEVANCE

Sensitization to Ses i 1 is strongly associated with clinical sesame allergy. Measurement of specific IgE to rSes i 1 could reduce the numbers of OFCs needed.

Identification of IgE-binding peptide and critical amino acids of Jatropha curcas allergen involved in allergenic response

Increasing energy demand has spurred interest in the use of biofuels. Jatropha curcas (physic nut), an inedible oilseed, is a potential source of bioenergy. The seeds, however, contain allergens such as Jat c 1, a 2S albumin that can induce hypersensitivity reactions in humans and result in allergic diseases. Recent advances in identifying and characterizing plant allergens and, in particular, their immunoglobulin E (IgE)-binding epitopes have produced a wealth of information. We identified IgE-binding regions and the critical amino acids involved in the degranulation of mast cells and the release of histamine, preliminary steps for the prevention and treatment of this allergy. Four IgE-binding regions were identified in the sequence of Jat c 1. We identified and demonstrated the fundamental role of two glutamic acid residues in IgE binding. The sequence LEKQLEEGEVGS produces a random loop on the most exposed part of Jat c 1. This region is important to the stimulation of the allergic response. The possibility of using this information to produce vaccines and other pharmacological agents for allergy treatment is discussed.

Structural and functional characterization of recombinant napin-like protein of Momordica charantia expressed in methylotrophic yeast Pichia pastoris

Napin and napin-like proteins belong to the 2S albumin seed storage family of proteins and have been shown to display a variety of biological activities. However, due to a high degree of polymorphism, purification of a single napin or napin-like protein exhibiting biological activity is extremely difficult. In the present study, we have produced the napin-like protein of Momordica charantia using the methylotrophic Pichia pastoris expression system. The recombinant napin-like protein (rMcnapin) secreted in the extracellular culture supernatant was enriched by ammonium sulfate precipitation, and purified using size exclusion chromatography at a yield of ∼290 mg/L of culture. Secondary structure analysis of the purified rMcnapin revealed it to be predominantly α-helical with minimal β strand content. CD spectroscopic and fluorescence spectroscopic analyses revealed the rMcnapin to be stable at a wide range of temperatures and pH. The rMcnapin exhibited antifungal activity against Trichoderma viride with an IC50 of ∼3.7 μg/ml and trypsin inhibitor activity with an IC50 of 4.2 μM. Thus, large amounts of homogenous preparations of the biologically active rMcnapin could be obtained at shake flask level, which is otherwise difficult from its natural source.

Crystal structure of mature 2S albumin from Moringa oleifera seeds

2S albumins, the seed storage proteins, are the primary sources of carbon and nitrogen and are involved in plant defense. The mature form of Moringa oleifera (M. oleifera), a chitin binding protein isoform 3-1 (mMo-CBP3-1) a thermostable antifungal, antibacterial, flocculating 2S albumin is widely used for the treatment of water and is potentially interesting for the development of both antifungal drugs and transgenic crops. The crystal structure of mMo-CBP3-1 determined at 1.7 Å resolution demonstrated that it is comprised of two proteolytically processed α-helical chains, stabilized by four disulfide bridges that is stable, resistant to pH changes and has a melting temperature (TM) of approximately 98 °C. The surface arginines and the polyglutamine motif are the key structural factors for the observed flocculating, antibacterial and antifungal activities. This represents the first crystal structure of a 2S albumin and the model of the pro-protein indicates the structural changes that occur upon formation of mMo-CBP3-1 and determines the structural motif and charge distribution patterns for the diverse observed activities.

Cor a 14, the allergenic 2S albumin from hazelnut, is highly thermostable and resistant to gastrointestinal digestion

Scope

Allergens from nuts frequently induce severe allergic reactions in sensitive individuals. The aim of this study was to elucidate the physicochemical characteristics of natural Cor a 14, the 2S albumin from hazelnut.

Methods and results

Cor a 14 was purified from raw hazelnuts using a combination of precipitation and chromatographic techniques. The protein was analyzed using gel electrophoresis, MS, and far‐UV circular dichroism (CD) analyses. The immunoglobulin E (IgE) binding of native, heat‐treated, and in vitro digested Cor a 14 was studied. We identified two different Cor a 14 isoforms and showed microclipping at the C‐terminus. CD spectra at room temperature showed the typical characteristics of 2S albumins, and temperatures of more than 80°C were required to start unfolding of Cor a 14 demonstrating its high stability to heat treatment. In vitro digestion experiments revealed that Cor a 14 is resistant to proteolytic degradation. Native and heat‐treated protein was recognized by sera from hazelnut allergic patients. However, denaturation of the allergen led to significantly reduced IgE binding.

Conclusion

We identified two different isoforms of Cor a 14 displaying high stability under heating and gastric and duodenal conditions. Data from IgE‐binding experiments revealed the existence of both, linear and conformational epitopes.

Proteomic identification of allergenic seed proteins, napin and cruciferin, from cold-pressed rapeseed oils

In Finland and France atopic children commonly react to seeds of oilseed rape and turnip rape in skin prick tests (SPT) and open food challenges. These seeds are not as such in dietary use and therefore the routes of sensitization are unknown. Possible allergens were extracted from commercial cold-pressed and refined rapeseed oils and identified by gel-based tandem nanoflow liquid chromatography mass spectrometry (LC-MS/MS). Napin (a 2S albumin), earlier identified as a major allergen in the seeds of oilseed rape and turnip rape, and cruciferin (an 11S globulin), a new potential seed allergen, were detected in cold-pressed oils, but not in refined oils. Pooled sera from five children sensitized or allergic to oilseed rape and turnip rape seeds reacted to these proteins from cold-pressed oil preparations and individual sera from five children reacted to these proteins extracted from the seeds when examined with IgE immunoblotting. Hence cold-pressed rapeseed oil might be one possible route of sensitization for these allergens.

Transient expression of GUS and the 2S albumin gene from Brazil nut in peanut (Arachis hypogaea L.) seed explants using particle bombardment

The effect of parameters involved in the transformation efficiency of peanut (Arachis hypogaea L.) seed tissues by direct gene transfer using a helium inflow particle bombardment device was evaluated. Transient gene expression was affected by both particle and DNA amounts, and was positively correlated with gene copy number, as determined byβ-glucuronidase (GUS) activity assays. No influence of plasmid size on GUS gene expression was observed. Transcriptional control of GUS by either the CaMV 35S or the 2S promoter from Brazil nut 2S albumin gene varied with the developmental stage of the seed and was approximately tenfold greater under the influence of the 35S promoter than under the 2S promoter. The gene products of both the Brazil nut methionine-rich 2S albumin and GUS genes under the transcriptional control of the 35S promoter were detected by ELISA assays.