The lipid transfer proteins (LTP) essentially concentrate in the skin of Rosaceae fruits as cell surface exposed allergens

Effects of variety, maturity and storage conditions on the allergic potential of kiwifruit and its relationship with antioxidant activity

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Allergenicity of kiwifruit strongly associated with its physiological attributes.

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10-day storage of kiwifruit at 20 °C increased the Act d 2 content by 50 %.

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Act d 2 content in the seeds was 4-fold higher than that of peel.

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Act d 2 content showed a negative relationship with antioxidant activity.

This work aimed to study the influences of physiological characteristics (variety, maturity, and fruit components) and storage conditions on the allergenic potential of kiwifruit. The results found kiwifruit allergen (Act d 2) is only measured in the green kiwifruit rather than golden kiwifruit. The Act d 2 content of seed is 2-fold and 4-fold higher than that of pulp and peel, respectively. The highest Act d 2 allergen content was determined in ripe kiwifruit, followed by overripe fruit and unripe fruit. A 50 % of enhancement in Act d 2 content was observed after 10-day storage at 20 °C. Further, the Act d 2 content showed a negative relationship with the ascorbic acid content and total antioxidant activity at various conditions. Thus, antioxidants as important factors may involve the regulation of Act d 2 in kiwifruit. These findings could provide a deep understanding in the distribution of Act d 2.

Prevalence, clinical presentation, and associated atopic diseases of pediatric fruit and vegetable allergy: A population-based study

BACKGROUND

In children, fruit and vegetable allergies are often overlooked compared with well-known allergies such as those to eggs, milk, and shellfish. Therefore, this study aimed to analyze fruit and vegetable allergies in children, including prevalence, types of food allergens, clinical presentation, management, and associated comorbid atopic diseases.

METHODS

In 2012, a nationwide, cross-sectional, random sampling questionnaire-based survey for common fruit and vegetable allergies was conducted in Taiwan. Information regarding these plant food allergies was collected. Physicians diagnosed food allergies according to the descriptions of convincing symptoms. Enrolled questionnaires were reviewed by expert pediatricians.

RESULTS

A total of 9,982 valid questionnaires were analyzed. The overall prevalence of fruit and vegetable allergies was 5.6% (n = 560) and 3.0% (n = 304), respectively. The most common fruit allergen was mango, followed by kiwifruit, whereas taro and bamboo shoot were the most common vegetable allergens. Meanwhile, most allergic symptoms were of the mucocutaneous tissue, followed by the upper airway and gastrointestinal tract. Most only required avoidance of allergens and not medical treatment. Children with fruit or vegetable allergies had a higher percentage of comorbid atopic dermatitis, allergic rhinitis, and asthma than those without food allergies; additionally, the proportion of comorbid atopic diseases was similar between fruit and vegetable allergies and shellfish allergy. One child developed anaphylaxis due to a corn allergy.

CONCLUSIONS

Fruits and vegetables are common food allergens in Taiwanese children who present with diverse and potentially severe symptoms. Children with plant food allergies had a percentage of comorbid atopic diseases similar to that of shellfish allergy, the most common allergen. These findings indicate the importance of considering fruit and vegetable allergies in children.

Epinephrine Auto-Injector Prescription and Use: A Retrospective Analysis and Clinical Risk Assessment of Adult Patients Sensitized to Lipid Transfer Protein

Lipid transfer proteins (LTPs) are widely widespread plant food allergens which represents the main cause of food allergy in adults living in the Mediterranean basin. The purpose of this study was to investigate in LTP patients the actual use of prescribed epinephrine auto-injector and appropriateness of its prescription. In addition, we investigated in these patients: (1) occurrence of new food reaction in the following three years after to diagnosis; (2) need and number of access to emergency services; (3) presence of possible predictive factors to further food reactions. One-hundred sixty-five adult patients sensitized to LTPs have been included. During follow-up, we recorded 68 further reactions, most of them (77.9%) characterized by local symptoms; rarely the patients required an emergency-department visits (16.1%) and only one patient (1.7%) used the epinephrine auto-injector. The patients with a previous history of anaphylaxis at baseline turned back to access to emergency services also during the follow-up (p = 0.006). The majority of patients with recorded systemic reactions (p = 0.004) and treated in an emergency room (p = 0.028) did not have any co-factor-enhanced at diagnosis. We noted an association between platanus pollen sensitization and severity of further reactions during the follow-up (p = 0.026). Epinephrine auto-injector were prescribed to 108/165 patients (65.5%) with an over-prescription rate of 25%. The unforeseeable clinical presentation of LTP allergic reactions and the eventual role played by the cofactor make necessary schedule a follow-up to monitor the patients over time and to assess the actual use of epinephrine auto injectors prescribed.

Update on pollen-food allergy syndrome

INTRODUCTION

Allergies affect 20-30% of the population and respiratory allergies are mostly due to pollen grains from anemophilous plants. One to 5% of people suffer from food allergies and clinicians report increasing numbers of pollen-food allergy syndrome (PFAS), such that the symptoms have broadened from respiratory to gastrointestinal, and even to anaphylactic shock in the presence of cofactors. Thirty to 60% of food allergies are associated with pollen allergy while the percentage of pollen allergies associated to food allergy varies according to local environment and dietary habits.

AREAS COVERED

Articles published in peer-reviewed journals, covered by PubMed databank, clinical data are discussed including symptoms, diagnosis, and management. A chapter emphasizes the role of six well-known allergen families involved in PFAS: PR10 proteins, profilins, lipid transfer proteins, thaumatin-like proteins, isoflavone reductases, and β-1,3 glucanases. The relevance in PFAS of three supplementary allergen families is presented: oleosins, polygalacturonases, and gibberellin-regulated proteins. To support the discussion a few original relevant results were added.

EXPERT OPINION

Both allergenic sources, pollen and food, are submitted to the same stressful environmental changes resulting in an increase of pathogenesis-related proteins in which numerous allergens are found. This might be responsible for the potential increase of PFAS.

Molecular and Immunological Identification of Low Allergenic Fruits among Old and New Apple Varieties

About 50–70% of patients allergic to birch pollen suffer from sensitization after apple ingestion. Apple allergenicity was established in only few varieties. Studies were performed on apple fruits of 21 traditional and nine modern varieties organically, intensively, or integratively produced. The aim of the study was to assess whether the factors like cultivation method, maturity stage, genotype, or type of tissue place an impact on the allergenic potential of apples. To answer these questions, we used semiquantitative real-time PCR, ELISA, and immunoblotting. Apple allergen genes present divergent expression across apple cultivars. Expression of the Mal d 1.06A correlates with the Mal d 1 level and is affected by the cultivation method and maturity of the fruit. The content of the main allergen Mal d 1 varied widely across cultivars. Interestingly, in our study, the Gala variety presented a low Mal d 1 concentration regardless of the cultivation method. Based on the Mal d 1.06A expression, the Mal d 1 protein content, and the immunoreactivity assay, the Kandil Sinap, Kosztela, Rumianka from Alma-Ata, Kantówka Gdańska, Reinette Coulon, and Gala cultivars emerged as potentially hypoallergenic apple cultivars. Our study allowed distinguishing between potentially low, medium, and highly allergenic varieties.

LTP allergy/sensitization in a pediatric population

Plant lipid transfer proteins (LTPs) are widespread plant food allergens, highly resistant to food processing and to the gastrointestinal environment, which have been described as the most common food allergens in the Mediterranean area. LTP allergy is widely described in adults, but it represents an emerging allergen also in the pediatric population. Little is known about the real prevalence and the clinical features of this allergy in children and it still often remains underdiagnosed in these patients. An early identification and a deeper knowledge of this allergy in childhood can avoid severe systemic reactions and improve the child's quality of life. Pediatricians should always consider the possibility of LTP involvement in cases of plant-derived food allergy.

Evaluation of the phenolic profile and immunoreactivity of Mal d 3 allergen in ancient apple cultivars from Italy

BACKGROUND

Since the second half of the 20th century, the cultivation of ancient and local apple cultivars has almost disappeared from orchards in Italy. Some of these ancient apple cultivars often possess high nutraceutical values and display lower allergenicity than the modern ones, supporting the so-called 'green revolution' theory.

RESULTS

In this study, the phenolic composition and the antioxidant activity of five ancient apple cultivars ('Belfiore', 'Pomella Genovese', 'Gravenstein', 'Bella del Bosco', and 'Piatlin') were compared with a 'Golden Delicious' commercial cultivar. Additionally, apples were tested for their potential allergenicity by detecting the presence of Mal d 3, a non-specific lipid transfer protein that represents the main apples' allergen. All apples came from northern Italy (Trentino Region) and were organically produced. Results showed that, for all cultivars, the skins contained more polyphenols than the pulps. 'Bella del Bosco' had the highest amount of polyphenols and antioxidant activity, whereas 'Piatlin' had the lowest phenolic content. All ancient cultivars presented a higher amount of pulp phenolic compounds than 'Golden Delicious'. Immunoblotting techniques showed that 'Bella del Bosco' and 'Piatlin' had very low quantities of Mal d 3 allergen; hence, they can be considered hypoallergenic cultivars.

CONCLUSIONS

The preservation of ancient apple cultivars would be of great importance, not only to maintain the biodiversity but also for their nutritional properties. The hypoallergenic activity of some of these cultivars could be of interest also for the preparation of different apple-based products. © 2020 Society of Chemical Industry.

Influence of polyphenolic content on the in vitro allergenicity of old and new apple cultivars: A pilot study

OBJECTIVES

More than 70% of birch pollen-allergic individuals are affected by a cross-allergy from apples. The aim of this study was to determine if an increased polyphenolic content of apples is inversely related to clinical allergic reactions in sufferers.

METHODS

The polyphenolic content of two old and two new apple cultivars was analyzed using high performance liquid chromatography. The in vitro concentration of sulfidoleukotrienes and the CD63 basophil activation of 27 birch pollen sufferers with cross-reactivity to apples were determined with cellular antigen stimulation and basophil activation tests after incubation with different apple cultivars.

RESULTS

The flesh of old cultivars was characterized by significantly higher total polyphenolic content (86.1 ± 5.5 µg/g) than that of new cultivars (24.7 ± 7.2 µg/g). The concentration of sulfidoleukotrienes and the CD63 basophil activation of old apple cultivars was up to 62% lower than new ones and decreased as the degree of enzymatic browning increased.

CONCLUSION

Old apples cultivars are better tolerated than new ones by birch pollen-allergic individuals. The in vitro allergenicity (activation of effector cells) of apples depends on the total polyphenolic content and the degree of enzymatic browning.

A Cherry Seed-Derived Spice, Mahleb, is Recognized by Anti-Almond Antibodies Including Almond-Allergic Patient IgE

There are a number of examples of immunologic cross-reactivity elicited by pollens, fruits, seeds, and nuts of closely related plant species. Such cross-reactivity is of particular concern for patients with food allergies. In this report, we investigated a spice (mahleb) that is prepared from the kernel of the St. Lucie cherry, Prunus mahaleb, for cross-reactivity with almond (Prunus dulcis), using enzyme-linked immunosorbent assay (ELISA) and Western blot. Almond and mahleb are members of the same genus. Cross-reactivity between the mahleb and almond was demonstrated by reaction of cherry and almond kernel protein extracts with antibodies raised against almond proteins. Almond-specific murine monoclonal IgG, rabbit polyclonal IgG, and almond-allergic serum IgE each exhibited cross-reactivity with cherry kernel protein. Because of the demonstrated cross-reactivity between almond and mahleb, these findings should be of special concern to almond-allergic patients and attending medical personnel.

Identification of the ligand of Pru p 3, a peach LTP

Pru p 3, a peach LTP, is located in pollinated flower styles and secreting downy hairs, transporting a derivative of camptothecin bound to phytosphingosine. Pru p 3 may inhibit a second pollination and may keep away herbivores until seed maturation. The allergen Pru p 3, a peach lipid transfer protein, has been well studied. However, its physiological function remains to be elucidated. Our results showed that Pru p 3 usually carries a lipid ligand that play an essential role in its function in plants. Using ESI-qToF, we observed that the ligand was a derivative of camptothecin binding to phytosphingosine, wich that is inserted into the hydrophobic tunnel of the protein. In addition, the described ligand displayed topoisomerase I activity inhibition and self-fluorescence, both recognized as camptothecin properties. During flower development, the highest expression of Pru p 3 was detected in the styles of pollinated flowers, in contrast to its non-expression in unpollinated pistils, where expression decreased after anthesis. During ripening, the expression of Pru p 3 were observed mainly in peel but not in pulp. In this sense, Pru p 3 protein was also localized in trichomes covering the fruit epidermis.

Old Apple (Malus domestica L. Borkh) Varieties with Hypoallergenic Properties: An Integrated Approach for Studying Apple Allergenicity

Freshly consumed apples (Malus domestica L. Borkh) can cause allergic reactions because of the presence of four classes of allergens. Knowledge of the genetic factors affecting the allergenic potential of apples would provide important information for the selection of hypoallergenic genotypes, which can be combined with the adoption of new agronomical practices to produce fruits with a reduced amount of allergens. In the present research, a multiple analytical approach was adopted to characterize the allergenic potential of 24 apple varieties released at different ages (pre- and post-green revolution). A specific workflow was set up including protein quantification by means of polyclonal antibodies, immunological analyses with sera of allergic subjects, enzymatic assays, clinical assessments on allergic patients, and gene expression assays on fruit samples. Taken as a whole, the results indicate that most of the less allergenic genotypes were found among those deriving from selection processes carried out prior to the so-called "green revolution".

Mass spectrometry imaging for visualizing organic analytes in food

The demand for rapid chemical imaging of food products steadily increases. Mass spectrometry (MS) is featured by excellent molecular specificity of analysis and is, therefore, a very attractive method for chemical profiling. MS for food imaging has increased significantly over the past decade, aided by the emergence of various ambient ionization techniques that allow direct and rapid analysis in ambient environment. In this article, the current status of food imaging with MSI is reviewed. The described approaches include matrix-assisted laser desorption/ionization (MALDI), but emphasize desorption atmospheric pressure photoionization (DAPPI), electrospray-assisted laser desorption/ionization (ELDI), probe electrospray ionization (PESI), surface desorption atmospheric pressure chemical ionization (SDAPCI), and laser ablation flowing atmospheric pressure afterglow (LA-FAPA). The methods are compared with regard to spatial resolution; analysis speed and time; limit of detection; and technical aspects. The performance of each method is illustrated with the description of a related application. Specific requirements in food imaging are discussed.

The biochemical basis and clinical evidence of food allergy due to lipid transfer proteins: a comprehensive review

Plant lipid transfer proteins (LTPs) are ubiquitous proteins that are found in divergent plant species. Although the exact function of LTPs is not fully understood, LTPs are conserved across a broad range of plant species. Because LTPs share structural features, there is an increased probability for significant allergic cross-reactivity. The molecular features of LTPs also decrease the probability of degradation due to cooking or digestion, thereby increasing the probability of systemic absorption and severe allergic reactions. LTP allergy, unlike other forms of anaphylaxis, tends to occur more frequently in areas of lower latitude. The geographic distribution of LTP allergy, along with evidence of increased sensitization after respiratory exposure, has led to the hypothesis that LTP-related food allergy may be secondary to sensitization via the respiratory route. Clinical reactions associated with LTPs have broad clinical phenotypes and can be severe in nature. Life-threatening clinical reactions have been associated with ingestion of a multitude of plant products. Component-resolved diagnosis has played a significant role in research applications for LTP allergy. In the future, component-resolved diagnosis may play a significant role in day-to-day clinical care. Also, quantitative analysis of LTPs in foodstuffs may allow for the identification and/or production of low-LTP foods, thereby decreasing the risk to patients with LTP allergy. Furthermore, sublingual immunotherapy may provide a therapeutic option for patients with LTP allergy.

Peach allergy in Spanish children: tolerance to the pulp and molecular sensitization profile

BACKGROUND

Peach allergy is the main cause of vegetable food allergy in the Mediterranean area. Pru p 3 is the major allergen, and it is mainly found in the peel.

OBJECTIVE

We sought to calculate the frequency of tolerance to peach pulp in Spanish children suffering from allergic reactions after eating or having contact with peach and to analyze the sensitization pattern to peach allergens.

METHODS

Fifty-seven children (32 boys; median age, 7.4 yr) were included in the study. A systematized questionnaire on allergic reactions to peach was administered. Prick tests with peach peel and pulp, peach lipid transfer protein (LTP), and profilin were performed. Serum-specific IgE to peach, rPru p 1, rPru p 3, and rPru p 4 was determined by ImmunoCAP. Oral food challenges (OFCs) with peach pulp were performed on all but one child.

RESULTS

Eighty-eight percent of the children had positive prick tests with peach peel, 35% with peach pulp, 88% with peach LTP, and 9% with profilin. Serum-specific IgE to peach was demonstrated in 100% of the patients; rPru p 3-specific IgE in 96%; rPru p 1-specific IgE in 11%; and rPru p 4-specific IgE in 10%. Oral food challenge was negative in 52 (93%) children.

CONCLUSIONS

More than 90% of the study population tolerated peeled peach. Pru p 3 was the major allergen. Pru p 1 and 4 showed low prevalence.

[Cross reactions between pollens and vegetable food allergens]

INTRODUCTION

The association of food allergies and pollinosis are numerous, implicating tree, grass and weed pollens on one hand and on the other, several plant foods which after ingestion can induce an oral syndrome or more severe reactions such as urticaria, Quincke's edema, asthma and even anaphylactic shock.

BACKGROUND

The molecular basis of cross reactions between pollens and vegetable food allergens is increasingly understood. The principal allergens involved are those of the Bet v 1 family, and profilins found in all pollens as well as in many fruits and vegetables; these two groups of allergens are denatured by high temperatures and by gastric enzymes, in contrast to LTP, which is only found in weeds and some tree pollens. Other molecules can be involved in cross reactions such as Bet v 6 (an isoflavone reductase), 1 beta glucanases and thaumatine-like proteins. Inhibition experiments confirmed that the epitopes responsible for primary sensitization come mainly from pollen allergens; the cross-reactive molecular allergen is related to the geographic environment of the patients.

CONCLUSIONS

The practical aspects of managing these patients are underlined: explanations of co-sensitization, explanations for the lack of efficacy of some extracts, usefulness of a molecular diagnosis obtained either by CAP or microarray, prediction of severe clinical reactions induced by specific molecular allergens and the effectiveness of pollen immunotherapy on the cross-related food allergy.

Extraction and mass spectrometry identification of a major peach allergen Pru p 1

BACKGROUND

Peach allergy can be caused by the allergen Pru p 1. This occurs by cross-reactivity with the homologous birch pollen allergen Bet v 1. However, the direct identification of Pru p 1 as an immunoglobulin E (IgE)-binding protein extracted from peach fruit has never been reported.

RESULTS

Phosphate-buffered saline (PBS) and phenol extractions were applied to solubilise the proteins from peach peel and pulp, and IgE immunoblotting with sera of individual peach-allergic patients was used to detect the potential allergens. Most of the patients showed binding to an 18 kDa band in IgE immunoblotting performed with the phenolic extracts of peach peel and pulp, but not when the PBS extracts were used. Mass spectrometry of the 18 kDa spot excised from a two-dimensional electrophoretic gel showed this protein to correspond to the peach allergen Pru p 1.

CONCLUSION

Phenol extraction was necessary to detect by IgE immunoblotting a major peach allergen, which showed very low extractability with PBS, indicating the appropriateness of adopting different extraction procedures to identify plant allergens. The 18 kDa peach protein was definitively identified as the Bet v 1-homologous peach allergen Pru p 1.

Identification of european allergy patterns to the allergen families PR-10, LTP, and profilin from Rosaceae fruits

High fruit intakes are associated with significant health benefits but fruit allergy sufferers may be discouraged from eating fruit due to the symptoms they experience. Knowledge about allergens involved in fruit allergy and the frequent cross-reactions to other allergens is essential to (a) design the best strategy for fruit allergy testing (b) prescribe optimal avoidance diets, and (c) design technological solutions for development of hypoallergenic fruits. The objective of this review was to investigate whether some characteristic disease entities could be identified in Europe for allergy to Rosaceae fruits. Five allergy patterns were found involving the allergen families PR-10, LTP, and profilin. In the Western Mediterranean area allergies to Rosaceae fruits are caused by monosensitization to LTP, monosensitization to profilin, or co-sensitization to both these allergens. On the contrary, monosensitization to PR-10 and, to a lesser degree, co-sensitization to profilin and PR-10 is dominant in Northern and Central Europe. LTP sensitization is present both in pollinosis and non-pollinosis patients and is associated with peach allergy in particular. The disease pattern for patients sensitized to profilin is characterized by several concomitant allergies including grass and other pollens, Rosaceae and non-Rosaceae fruits. Finally, PR-10 sensitization is primarily associated to concomitant birch pollen and apple allergy.

Discovery, identification and comparative analysis of non-specific lipid transfer protein (nsLtp) family in Solanaceae

Plant non-specific lipid transfer proteins (nsLtps) have been reported to be involved in plant defense activity against bacterial and fungal pathogens. In this study, we identified 135 (122 putative and 13 previously identified) Solanaceae nsLtps, which are clustered into 8 different groups. By comparing with Boutrot’s nsLtp classification, we classified these eight groups into five types (I, II, IV, IX and X). We compared Solanaceae nsLtps with Arabidopsis and Gramineae nsLtps and found that (1) Types I, II and IV are shared by Solanaceae, Gramineae and Arabidopsis; (2) Types III, V, VI and VIII are shared by Gramineae and Arabidopsis but not detected in Solanaceae so far; (3) Type VII is only found in Gramineae whereas type IX is present only in Arabidopsis and Solanaceae; (4) Type X is a new type that accounts for 52.59% Solanaceae nsLtps in our data, and has not been reported in any other plant so far. We further built and compared the three-dimensional structures of the eight groups, and found that the major functional diversification within the nsLtp family could be predated to the monocot/dicot divergence, and many gene duplications and sequence variations had happened in the nsLtp family after the monocot/dicot divergence, especially in Solanaceae.

Quantification and characterization of maize lipid transfer protein, a food allergen, by liquid chromatography with ultraviolet and mass spectrometric detection

Maize (Zea mays) is not considered a major allergenic food; however, when food induced allergenic and immunologic reactions have been implicated to maize, lipid transfer proteins (LTPs) have been identified as major allergens. LTP is an extremely stable protein that is resistant to both proteolytic attack and food processing, which permits the allergen to reach the gastrointestinal immune system in an immunogenic and allergenic conformation, allowing sensitization and induction of systemic symptoms. They are considered a complete food allergen in that they are capable of inducing specific IgE as well as eliciting severe symptoms. We have purified and characterized an endogenous ~9 kDa LTP from maize kernels. The maize LTP consists of 93 amino acid residues and has a M(r) of 9046.1 Da, determined by electrospray ionization mass spectrometry. Following accurate identification and characterization of maize LTP, a highly specific and quantitative assay using liquid chromatography with ultraviolet and mass spectrometric detection was developed. The present assay enables determination of LTP over a concentration range from 29 to 1030 μg/g in maize kernel samples. Assay recovery (percent relative error, % RE) was measured at 11 different concentrations ranging from 4 to 147 μg/mL and did not exceed 5.1%. The precision (percent coefficient of variation, % CV) was measured at 3 concentrations on each of 4 days and did not exceed 14.4%. The method was applied to evaluate the levels of LTP in 14 different maize lines. To our knowledge, this represents the first quantitative liquid chromatography-ultraviolet/mass spectrometry (LC-UV/MS) assay for the determination of LTP for the assessment of a food allergen.

The role of lipid transfer proteins in allergic diseases

Nonspecific lipid transfer proteins (LTPs) are important allergens in fruits, vegetables, nuts, pollen, and latex. Despite their wide distribution throughout the plant kingdom, their clinical relevance is largely confined to the Mediterranean area. As they can sensitize via the gastrointestinal tract, LPTs are considered true food allergens, and IgE reactivity to LTPs is often associated with severe systemic symptoms. Although Pru p 3 represents the predominant LTP in terms of patients' IgE recognition, the contribution of pollen LTPs in primary sensitization cannot be ruled out. Due to structural homology, LTPs from different allergen sources are generally IgE cross-reactive. However, sensitization profiles among allergic patients are extremely heterogeneous, and individual cross-reactivity patterns can be restricted to a single LTP or encompass many different LTPs. Molecule-based approaches in allergy research and diagnosis are important for better understanding of LTP allergy and could assist clinicians with providing adequate patient-tailored advice.

Panallergens and their impact on the allergic patient

The panallergen concept encompasses families of related proteins, which are involved in general vital processes and thus, widely distributed throughout nature. Plant panallergens share highly conserved sequence regions, structure, and function. They are responsible for many IgE cross-reactions even between unrelated pollen and plant food allergen sources. Although usually considered as minor allergens, sensitization to panallergens might be problematic as it bears the risk of developing multiple sensitizations. Clinical manifestations seem to be tightly connected with geographical and exposure factors. Future population- and disease-based screenings should provide new insights on panallergens and their contribution to disease manifestations. Such information requires molecule-based diagnostics and will be valuable for developing patient-tailored prophylactic and therapeutic approaches. In this article, we focus on profilins, non-specific lipid transfer proteins, polcalcins, and Bet v 1-related proteins and discuss possible consequences of panallergen sensitization for the allergic patient. Based on their pattern of IgE cross-reactivity, which is reflected by their distribution in the plant kingdom, we propose a novel classification of panallergens into ubiquitously spread "real panallergens" (e.g. profilins) and widespread "eurallergens" (e.g. polcalcins). "Stenallergens" display more limited distribution and cross-reactivity patterns, and "monallergens" are restricted to a single allergen source.

Tomato allergy: detection of IgE-binding lipid transfer proteins in tomato derivatives and in fresh tomato peel, pulp, and seeds

There is an increasing consumption of tomatoes worldwide: fresh in salads, cooked in household sauces, or industrially processed. Although many tomato allergens have been identified, there is no information in the literature on the allergenic components found in commercial tomato products. The primary aim of the study was to evaluate the allergenic profile of commercial tomato products by skin prick tests (SPTs) and IgE/immunoblotting in tomato-allergic subjects. The secondary end point was the study of the IgE-binding profile of tomato peel, pulp, and seeds. Forty tomato-allergic patients, reporting oral allergy syndrome (OAS) at different grades of severity for fresh and, in some cases, also for cooked tomato, were selected on the basis of positive tomato allergy history or open food challenge (OFC). They were evaluated by SPTs with different experimental tomato extracts. SDS-PAGE/immunoblotting was performed to detect tomato allergens, which were then identified by Edman degradation. Twenty-three patients (57.5%) presented first-grade OAS at the OFC, whereas 17 (42.5%) reported severe symptoms. Ten of these 17 patients (25%) reported allergic reactions to cooked tomatoes; in immunoblotting tests, their sera reacted only to lipid transfer protein (LTP). In commercial products, LTP was the only detectable allergen. In contrast to other LTP-containing fruits, in tomato, an IgE-binding LTP was identified not only in the peel but also in the pulp and seeds. This study demonstrates that, in fresh tomato, different LTP isoforms are present and allergenic. Industrial tomato derivatives still contain LTP, thus presenting a problem for LTP-allergic patients.

Unambiguous characterization and tissue localization of Pru P 3 peach allergen by electrospray mass spectrometry and MALDI imaging

The lipid transfer protein (LTP), Pru p 3, has been identified as the major allergen present in peach, and its sequence obtained by direct amino acid sequencing has been previously reported. However, several sequences, obtained from c-DNA and available in databases, show differences among them and from the originally proposed structure. In this paper, we report the fast and unambiguous determination of the structure of Pru p 3 protein, extracted from three different varieties of peach, by electrospray ionization mass spectrometry (ESI-MS), both coupled to single stage (quadrupole) or advanced (FT-HRMS) analyzers. The structure was identical to one of the cDNA-derived sequences and different in two positions from the previously reported structure obtained by amino acid sequencing. Moreover, the exclusive localization of the protein in the outer part of the fruits was assessed by Matrix-Assisted Laser Desorption Ionization Mass Spectrometry Imaging (MALDI MSI). The results reported here demonstrate the full potential of mass spectrometry for rapidly obtaining high quality structural data of relevant food proteins.

Purification and structural stability of the peach allergens Pru p 1 and Pru p 3

Pru p 1 (a Bet v 1 homologue) and Pru p 3 (a nonspecific lipid transfer protein; nsLTP) are major allergenic proteins in peach fruit, but differ in their abundance and stability. Pru p 1 has low abundance and is highly labile and was purified after expression as a recombinant protein in Escherichia coli. Pru p 3 is highly abundant in peach peel and was purified by conventional methods. The identities of the proteins were confirmed by sequence analysis and their masses determined by MS analysis. The purified proteins reacted with antisera against related allergens from other species: Pru p 1 with antiserum to Bet v 1 and Pru p 3 with antiserum to Mal d 3 (from apple). The presence of secondary and tertiary structure was demonstrated by circular dichroism (CD) and high field NMR spectroscopy. CD spectroscopy also showed that the two proteins differed in their stability at pH 3 and in their ability to refold after heating to 95 degrees C. Thus, Pru p 1 was unfolded at pH 3 even at 25 degrees C but was able to refold after heating to 95 degrees C at pH 7.5. In contrast, Pru p 3 was unable to refold after heating under neutral conditions but readily refolded after heating at pH 3.

The potato StLTPa7 gene displays a complex Ca-associated pattern of expression during the early stage of potato-Ralstonia solanacearum interaction

Although nonspecific lipid transfer proteins (nsLTPs) are widely expressed during plant defence responses to pathogens, their functions and regulation are not fully understood. In this article, we report the isolation of a cDNA for the new nsLTP, StLTPa7, from cultivated potato (Solanum tuberosum) infected with Ralstonia solanacearum. The cDNA was predicted to encode a type 1 nsLTP containing an N-terminal signal sequence and possessing the characteristic features of nsLTPs. A phylogenetic analysis showed that the encoded amino acid sequence of the nsLTP was similar to those of other previously reported plant nsLTPs, which contain a putative calmodulin-binding site consisting of approximately 12 highly conserved amino acid residues. The expression of the StLTPa7 gene was studied during the early stages of potato-R. solanacearum interaction using real-time quantitative polymerase chain reaction (qRT-PCR) and Northern analyses, and a complex calcium (Ca2+)-associated pattern of expression was observed with the following features: (i) transcripts of the StLTPa7 gene were systemically up-regulated by infection with R. solanacearum; (ii) the StLTPa7 gene was stimulated by salicylic acid, methyl jasmonate, abscisic acid and Ca2+; (iii) qRT-PCR showed that, during the early stage of R. solanacearum infection, nsLTP transcripts accumulated over a time course that paralleled that of Ca2+ accumulation, detected using environmental scanning electron microscopy and energy-dispersive X-ray (EDAX) spectrometry; and (iv) the Ca2+ channel blocker, ruthenium red, partially blocked R. solanacearum-induced StLTPa7 expression. This report represents the first use of EDAX analysis to establish a synchrony between Ca2+ accumulation and nsLTP expression in response to potato-R. solanacearum interactions. Collectively, these results suggest that StLTPa7 may be a pathogen- and Ca(2+)-responsive plant defence gene.

Genetic and environmental factors affecting allergen-related gene expression in apple fruit (Malus domestica L. Borkh)

Freshly consumed apples can cause allergic reactions because of the presence of four classes of allergens, namely, Mal d 1, Mal d 2, Mal d 3, and Mal d 4, and their cross-reactivity with sensitizing allergens of other species. Knowledge of environmental and endogenous factors affecting the allergenic potential of apples would provide important information to apple breeders, growers, and consumers for the selection of hypoallergenic genotypes, the adoption of agronomical practices decreasing the allergenic potential, and the consumption of fruits with reduced amount of allergens. In the present research, expression studies were performed by means of real-time PCR for all the known allergen-encoding genes in apple. Fruit samples were collected from 15 apple varieties and from fruits of three different trials, set up to assess the effect of shadowing, elevation, storage, and water stress on the expression of allergen genes. Principal components analysis (PCA) was performed for the classification of varieties according to gene expression values, pointing out that the cultivars Fuji and Brina were two good hypoallergenic candidates. Shadowing, elevation, and storage significantly affected the transcription of the allergen-encoding genes, whereas water stress slightly influenced the expression of only two genes, in spite of the dramatic effect on both fruit size and vegetative growth of the trees. In particular, shadowing may represent an important cultural practice aimed at reducing apple cortex allergenicity. Moreover, elevation and storage may be combined to reduce the allergenic potential of apple fruits. The possible implications of the results for breeders, growers, and consumers are discussed critically.

Lipid transfer proteins from Rosaceae fruits share consensus epitopes responsible for their IgE-binding cross-reactivity

Four IgE-binding epitopes have been characterized that cover a large area (40%) of the molecular surface of lipid transfer protein allergens of Rosaceae (apple, peach, apricot, and plum). They mainly correspond to electropositively charged regions protruding on the molecular surface of the modeled apple (Mal d 3), apricot (Pru ar 3), and plum (Pru d 3) allergens. Two of these epitopes consist of consensus epitopes structurally conserved among the lipid transfer protein allergens from the Rosaceae. Their occurrence in different lipid transfer protein allergens presumably accounts for the IgE-binding cross-reactivity often observed among different Rosaceae fruits. In this respect, LTP consist of phylogenetically- and structurally-related pan allergens. However, the IgE-binding cross-reactivity due to fruit lipid transfer protein has varying degrees of clinical relevance and this cross-reactivity is not necessarily accompanied by a cross-allergenicity to the corresponding fruits.