The role of profilin and lipid transfer protein in strawberry allergy in the Mediterranean area

Generalized allergic reaction in response to exercise due to strawberry gibberellin-regulated protein: a case report

Background

The Rosaceae family includes fruits, such as peach, apple, Japanese apricot, cherry (Prunoideae subfamily), and strawberry (Rosoideae subfamily). The allergens responsible for Rosaceae fruit allergies have been reported to include Bet v 1 and profilin, which mainly cause oral symptoms, and lipid transfer protein (LTP). Recently, gibberellin-regulated protein (GRP) has been identified as an allergen that induces generalized symptoms in peach-, orange-, and plum-related allergies. Most patients with food allergies induced by GRP show allergic symptoms accompanied by cofactors, such as exercise or drugs. To date, there are very few reports of generalized symptoms induced by strawberry.

Case presentation

We evaluated the reactivity of strawberry GRP in a 15-year-old boy who was confirmed to have generalized symptoms induced by strawberry with exercise using an oral food challenge test (OFCT). The patient’s serum exhibited a strong positive reaction to strawberry GRP but not to peach GRP or peach LTP. The patient’s basophils reacted to strawberry and peach GRP but not to peach LTP.

Conclusions

Strawberry GRP may be a causative component for strawberry with exercise-induced generalized symptoms in this patient. This is the first study to investigate the role of GRP in strawberry with cofactor-induced allergic symptoms. Further epidemiological and clinical researches are necessary to improve diagnostic and therapeutic approaches for patients with strawberry allergy.

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.

The diagnosis and management of allergic reactions in patients sensitized to non-specific lipid transfer proteins

Sensitization to one or more non-specific lipid transfer proteins (nsLTPs), initially thought to exist mainly in southern Europe, is becoming accepted as a cause of allergic reactions to plant foods across Europe and beyond. The peach nsLTP allergen Pru p 3 is a dominant sensitizing allergen and peaches a common food trigger, although multiple foods can be involved. A frequent feature of reactions is the requirement for a cofactor (exercise, alcohol, non-steroidal anti-inflammatory drugs, Cannabis sativa) to be present for a food to elicit a reaction. The variability in the food and cofactor triggers makes it essential to include an allergy-focused diet and clinical history in the diagnostic workup. Testing on suspected food triggers should also establish whether sensitization to nsLTP is present, using purified or recombinant nsLTP allergens such as Pru p 3. The avoidance of known trigger foods and advice on cofactors is currently the main management for this condition. Studies on immunotherapy are promising, but it is unknown whether such treatments will be useful in populations where Pru p 3 is not the primary sensitizing allergen. Future research should focus on the mechanisms of cofactors, improving diagnostic accuracy and establishing the efficacy of immunotherapy.

Structural Bases for the Allergenicity of Fra a 1.02 in Strawberry Fruits

Although strawberries are highly appreciated fruits, their intake can induce allergic reactions in atopic patients. These reactions can be due to the patient's previous sensitization to the major birch pollen allergen Bet v 1, by which IgE generated in response to Bet v 1 cross-reacts with the structurally related strawberry Fra a 1 protein family. Fra a 1.02 is the most expressed paralog in ripe strawberries and is highly allergenic. To better understand the molecular mechanisms regulating this allergic response, we have determined the three-dimensional structure of Fra a 1.02 and four site-directed mutants that were designed based on their positions in potential epitopes. Fra a 1.02 and mutants conform to the START fold. We show that the cross-reactivity of all the mutant variants to IgE from patients allergic to Bet v 1 was significantly reduced without altering the conserved structural fold, so that they could potentially be used as hypoallergenic Fra a 1 variants for the generation of vaccines against strawberry allergy in atopic patients.

Evaluation of serum IgE in peach-allergic patients with systemic reaction by using recombinant Pru p 7 (gibberellin-regulated protein)

BACKGROUND

Lipid transfer protein (LTP) is a major fruit allergen. It has, however, recently been revealed that the systemic reaction in peach-allergic patients is related not only to LTP (Pru p 3) but also to gibberellin-regulated protein (Pru p 7). We investigated recombinant Pru p 7 (rPru p 7) for its potential use in worldwide standardization for the diagnosis of peach allergy.

METHODS

Natural Pru p 7 (nPru p 7) was purified from peach crude extract using a monoclonal antibody affinity column. Complementary DNA for Pru p 7 was cloned and expressed in Escherichia coli and Pichia pastoris. Serum immunoglobulin (Ig) E in peach-allergic patients was examined by enzyme-linked immunosorbent assay (ELISA) using nPru p 7 and rPru p 7 (E. coli product: erPru p 7 and P. pastoris product: prPru p 7).

RESULTS

Peach-allergic patients (n=27) were diagnosed and categorized into oral reaction (n=10) or systemic reaction (n=17). The nPru p 7 positivity based on serum IgE levels was 52% in the systemic-reaction group and 0% in the oral-reaction group (P<0.05). In the systemic-reaction group, there was no significant difference in reactivity between nPru p 7 and prPru p 7, but the reactivity of erPru p 7 was significantly lower than those of nPru p 7 and prPru p 7 (P<0.05).

CONCLUSIONS

We found that prPru p 7 exhibited reactivity in ELISA comparable to that of nPru p 7 for the diagnosis of peach allergy with systemic reaction.

Protease resistance of food proteins: a mixed picture for predicting allergenicity but a useful tool for assessing exposure

Background

Susceptibility to pepsin digestion of candidate transgene products is regarded an important parameter in the weight-of-evidence approach for allergenicity risk assessment of genetically modified crops. It has been argued that protocols used for this assessment should better reflect physiological conditions encountered in representative food consumption scenarios.

Aim

To evaluate whether inclusion of more physiological conditions, such as sub-optimal and lower pepsin concentrations, in combination with pancreatin digestion, improved the performance of digestibility protocols used in characterization of protein stability.

Methods

Four pairs of established allergens and their related non/weakly-allergenic counterparts (seed albumins, muscle tropomyosins, plant lipid transfer proteins [LTP] and collagens) plus fish parvalbumin, were subjected to nine combinations of pH (1.2-2.5-4.0) and pepsin-to-protein ratio (PPR: 10-1-0.1 U/µg) for pepsin digestion, followed by pancreatin digestion in the presence of bile salts. Digestion was monitored by SDS-PAGE in conjunction with Coomassie staining and immunoblotting using rabbit antisera and human IgE.

Results

At pH 4.0 and at PPR 0.1 most proteins, both allergen and non-allergen, were highly resistant to pepsin. Under conditions known to favor pepsin proteolysis, the established major allergens Ara h 2, Pru p 3 and Pen a 1 were highly resistant to proteolysis, while the allergen Cyp c 1 was not. However, this resistance to pepsin digestion only made Ara h 2 and to a lesser extent Pen a 1 and Pru p 3 stand out compared to their non-allergenic counterparts. Largely irrespective of preceding pepsin digestion conditions, pancreatin digestion was very effective for all tested proteins, allergens and non-allergens, except for Cyp c 1 and bovine collagen.

Conclusions

Sub-optimal pH, low pepsin-to protein ratio, and sequential pepsin and pancreatin digestion protocols do not improve the predictive value in distinguish allergens from non-allergens. Digestion conditions facilitating such distinction differ per protein pair.

Effect of the Strawberry Genotype, Cultivation and Processing on the Fra a 1 Allergen Content

Birch pollen allergic patients show cross-reactivity to vegetables and fruits, including strawberries (Fragaria × ananassa). The objective of this study was to quantify the level of the Fra a 1 protein, a Bet v 1-homologous protein in strawberry fruits by a newly developed ELISA, and determine the effect of genotype, cultivation and food processing on the allergen amount. An indirect competitive ELISA using a specific polyclonal anti-Fra a 1.02 antibody was established and revealed high variability in Fra a 1 levels within 20 different genotypes ranging from 0.67 to 3.97 µg/g fresh weight. Mature fruits of red-, white- and yellow-fruited strawberry cultivars showed similar Fra a 1 concentrations. Compared to fresh strawberries, oven and solar-dried fruits contained slightly lower levels due to thermal treatment during processing. SDS-PAGE and Western blot analysis demonstrated degradation of recombinant Fra a 1.02 after prolonged (>10 min) thermal treatment at 99 °C. In conclusion, the genotype strongly determined the Fra a 1 quantity in strawberries and the color of the mature fruits does not relate to the amount of the PR10-protein. Cultivation conditions (organic and conventional farming) do not affect the Fra a 1 level, and seasonal effects were minor.

Analysis of major paralogs encoding the Fra a 1 allergen based on their organ-specificity in Fragaria × ananassa

Fra a 1 protein in strawberry causes oral allergic syndrome. Over 39 Fra a 1 paralogs have been identified in strawberry genome. Fra a 1.01 is major accumulating protein in edible organs. Strawberry fruits contain allergenic proteins that cause oral allergic syndrome. The hypothesized major allergen is Fra a 1, an ortholog of the birch pollen allergen protein Bet v 1. We organized Fra a 1 genes and analyzed their localizations at the transcriptional and translational levels. In total, 15 new Fra a 1 proteins were identified from the genomic database, increasing the total number of Fra a 1 to 30 proteins encoded by 39 genes. Fra a 1.02 was mostly expressed in receptacles, and Fra a 1.01 in achenes, when analyzed by RNA sequencing. Immunoblotting showed that the Fra a 1.01 protein was broadly accumulated in strawberry organs, while the Fra a 1.02 protein was mostly expressed in receptacles. Recombinant Fra a 1.01 strongly reacted with human IgE. The mRNA and protein expression levels of Fra a 1 did not correlate, indicating the importance of protein levels when evaluating the abundance of allergens in strawberry. Based on the localizations, accumulation levels and reactivity to human IgE, we determined that Fra a 1.01 was the most important allergen, followed by Fra a 1.02, and then other Fra a 1 proteins. The information obtained here will be useful for selecting the target Fra a 1 paralogs when breeding hypoallergenic strawberry.

White-fruited strawberry genotypes are not per se hypoallergenic

The strawberry fruit Fra a 1-proteins are homologues of the major birch pollen allergen Bet v 1 and have essential biological functions in pigment formation during fruit ripening. Patients affected by allergy against birch pollen tolerated fruits of a naturally occurring white-fruited F.×ananassa genotype, which showed reduced levels of Fra a 1 proteins along with enzymes of the anthocyanin pigment pathway. We evaluated the cross-reactive allergenic potential of a number of naturally occurring white- and red-fruited strawberry varieties to detect genotypes with low allergenic reactivity, whose fruit might be tolerated by patients with mild allergy. Protein extracts of 51 different strawberry varieties (Fragaria×ananassa, F. vesca, and F. nilgerensis) were screened by Western blot analysis with a polyclonal Fra a 1.02 antibody. Besides, activation of basophils of eight atopic patients allergic to birch pollen were studied using Bet v 1a and different concentrations of 15 selected strawberry protein extracts out of the 51 strawberry genotypes. Median percentages of activated basophils stimulated by extracts from white- and red-fruited genotypes ranged from 36 to 84% and 44 to 76%, respectively indicating that white-fruited strawberry are not per se hypoallergenic. Protein extracts from white-fruited F. vesca cv. Yellow Wonder showed the lowest cross-reactivity but high biological variability. The knowledge about the allergenic potential of different strawberry genotypes may help to improve food safety and can serve as starting point for the development of red-fruited hypoallergenic strawberry cultivars.

Cross-reactive LTP sensitization in food-dependent exercise-induced urticaria/anaphylaxis: a pilot study of a component-resolved and in vitro depletion approach

Background

Challenge tests for food-dependent exercise-induced anaphylaxis (FDEIA) carry some risk and have a high rate of false negatives. Our aim was to explore the usefulness of an in vitro immunodepletion assay and an allergen microarray test in the identification of IgE-mediated cross-reactive food allergens in patients with suspected FDEIA or food-dependent exercise-induced urticaria and panallergen sensitization.

Methods

Three patients with a history of food dependent exercise induced urticaria/anaphylaxis and food panallergen sensitization in whom a food-exercise challenge was not feasible were selected: a 25-year-old man with cholinergic urticaria who experienced generalized urticaria and angioedema during a soccer match after drinking a peach-based soft drink; a 19-year-old woman with allergic rhinitis and controlled asthma who experienced anaphylactic shock while playing soccer, having eaten walnuts in the previous 90 min; and a 57-year-old man with baker’s asthma who experienced four episodes of anaphylaxis during exercise after ingesting wheat-containing food. All individuals underwent a diagnostic work-up with skin prick tests, specific IgE (sIgE) and ImmunoCAP ISAC test. For the in vitro immunodepletion procedure, patients’ serum was pre-incubated with the suspected native allergen (peach, walnut, or wheat) in solid phase (ImmunoCAP). The eluted serum, containing unbound IgE, was collected and samples were re-tested using Immunocap ISAC 112 and compared with baseline results.

Results

All individuals were sensitized to lipid transfer proteins. The first patient was sensitized to Pru p 3, Cor a 8, Jug r 3, and Ara h 9; after pre-incubation with peach there was 100% depletion of sIgE to all components. The second patient was sensitized to Pru p 3, Cor a 8, Jug r 3, and Ara h 9; immunodepletion with walnut depleted sIgE to Ara h 9 by 67%, Pru p 3 and Pla a 3 (60%), Art v 3 (75%), Jug r 3 (88%), and Cor a 8 (100%). The third patient was sensitized to Pru p 3, Jug r 3, Ara h 9, and Tri a 14; immunodepletion with wheat depleted Tri a 14 only (100%).

Conclusions

In vitro immunodepletion might be a useful diagnostic tool in food dependent exercise induced urticaria/anaphylaxis with panallergen sensitization, particularly for identifying the culprit allergen and guiding dietary elimination recommendations.

In silico allergenicity prediction of several lipid transfer proteins

Non-specific lipid transfer proteins (nsLTPs) are common allergens and they are particularly widespread within the plant kingdom. They have a highly conserved three-dimensional structure that generate a strong cross-reactivity among the members of this family. In the last years several web tools for the prediction of allergenicity of new molecules based on their homology with known allergens have been released, and guidelines to assess potential allergenicity of proteins through bioinformatics have been established. Even if such tools are only partially reliable yet, they can provide important indications when other kinds of molecular characterization are lacking. The potential allergenicity of 28 amino acid sequences of LTPs homologs, either retrieved from the UniProt database or in silico deduced from the corresponding EST coding sequence, was predicted using 7 publicly available web tools. Moreover, their similarity degree to their closest known LTP allergens was calculated, in order to evaluate their potential cross-reactivity. Finally, all sequences were studied for their identity degree with the peach allergen Pru p 3, considering the regions involved in the formation of its known conformational IgE-binding epitope. Most of the analyzed sequences displayed a high probability to be allergenic according to all the software employed. The analyzed LTPs from bell pepper, cassava, mango, mungbean and soybean showed high homology (>70%) with some known allergenic LTPs, suggesting a potential risk of cross-reactivity for sensitized individuals. Other LTPs, like for example those from canola, cassava, mango, mungbean, papaya or persimmon, displayed a high degree of identity with Pru p 3 within the consensus sequence responsible for the formation, at three-dimensional level, of its major conformational epitope. Since recent studies highlighted how in patients mono-sensitized to peach LTP the levels of IgE seem directly proportional to the chance of developing cross-reactivity to LTPs from non-Rosaceae foods, and these chances increase the more similar the protein is to Pru p 3, these proteins should be taken into special account for future studies aimed at evaluating the risk of cross-allergenicity in highly sensitized individuals.

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.

FAST: towards safe and effective subcutaneous immunotherapy of persistent life-threatening food allergies

The FAST project (Food Allergy Specific Immunotherapy) aims at the development of safe and effective treatment of food allergies, targeting prevalent, persistent and severe allergy to fish and peach. Classical allergen-specific immunotherapy (SIT), using subcutaneous injections with aqueous food extracts may be effective but has proven to be accompanied by too many anaphylactic side-effects. FAST aims to develop a safe alternative by replacing food extracts with hypoallergenic recombinant major allergens as the active ingredients of SIT. Both severe fish and peach allergy are caused by a single major allergen, parvalbumin (Cyp c 1) and lipid transfer protein (Pru p 3), respectively. Two approaches are being evaluated for achieving hypoallergenicity, i.e. site-directed mutagenesis and chemical modification. The most promising hypoallergens will be produced under GMP conditions. After pre-clinical testing (toxicology testing and efficacy in mouse models), SCIT with alum-absorbed hypoallergens will be evaluated in phase I/II^a and II^b randomized double-blind placebo-controlled (DBPC) clinical trials, with the DBPC food challenge as primary read-out. To understand the underlying immune mechanisms in depth serological and cellular immune analyses will be performed, allowing identification of novel biomarkers for monitoring treatment efficacy. FAST aims at improving the quality of life of food allergic patients by providing a safe and effective treatment that will significantly lower their threshold for fish or peach intake, thereby decreasing their anxiety and dependence on rescue medication.

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.

Epidemiology of food allergy

Food allergy (FA) is perceived as a common problem, especially during childhood. Accurate assessment of incidence and prevalence of FA has been difficult to establish, however, due to lack of universally accepted diagnostic criteria. Although many foods are reported to cause IgE-mediated FA, most studies focus on 4 common food groups: cow's milk, hen's egg, peanut/tree nuts, and fish/shellfish. There may be variation in the prevalence of FA in regions of the world and a likely increase in prevalence has been observed in recent decades. This cannot be stated with confidence, however, without the use of consistent methodology and diagnostic criteria.

Profilins: mimickers of allergy or relevant allergens?

Profilins are ubiquitous proteins, present in all eukaryotic cells and identified as allergens in pollen, latex and plant foods. The highly conserved structure justifies the cross-reactive nature of IgE antibodies against plant profilins and their designation as pan-allergens. Primary sensitization to profilin seems to arise from pollen sensitization with later development of cross-reactive IgE antibodies against plant food (and possibly latex) profilins. The role of profilin in inducing allergic symptoms needs to be evaluated and raises important issues in allergy diagnosis due to cross-reactivity. IgE cross-reactivity among profilins is associated with multiple pollen sensitization and with various pollen-food syndromes. In respiratory allergy, sensitization to pollen to which the patient has virtually no environmental exposure has been identified as a manifestation of profilin sensitization. As a food allergen, profilin usually elicits mild reactions, such as oral allergy syndrome, is not modified by processing and is especially important in allergy to some fruits, such as melon, watermelon, banana, tomato, citrus fruit and persimmon. Purified natural and recombinant profilins for in vitro and in vivo allergy tests are helpful in the diagnostic work-up. Herein we review the current state of knowledge about the allergen profilin and its implications in the diagnosis and treatment of allergic diseases. We conclude that, although its role in triggering allergic symptoms is still controversial, profilin is undoubtedly a relevant allergen. As a pan-allergen, profilin is associated with multiple pollen sensitization and pollen-food-latex syndromes that the allergist has to be aware of in order to accomplish an accurate diagnosis and successful treatment of allergic diseases.

Identification and quantification of tomato allergens: in vitro characterization of six different varieties

BACKGROUND

The prevalence of sensitization to tomato has been estimated in 6.5% in a Mediterranean population.

OBJECTIVES

To characterize the allergenic profile of 6 commonly ingested varieties of tomato and to identify and quantify the most representative allergens.

METHODS

Rama, Rambo, Canario, Kumato, Pera and Raf tomato varieties were carefully peeled and extracts from peel and pulp prepared. The extracts were characterized by SDS-PAGE and immunoblot. Lyc e 3 and osmotin-like protein (OLP) were identified by LC MS/MS and PG2A by immunoblot with a specific polyclonal antibody. Protein content and allergen concentration (Lyc e 3 and PG2A) were measured by scanning densitometry after identification. One hundred and ninety-one patients were enrolled in the study. Specific IgE to all tomato extracts was evaluated by direct ELISA.

RESULTS

Eighty (41.7%) individuals reported symptoms after contact/ingestion with tomato, most of them oral symptoms. Protein profile and allergen quantification of the 6 varieties showed differences in the allergen composition. Lyc e 3 was visualized in all extracts, being the most abundant in all cases. PG2A and OLP were identified in all peel extracts and in some pulp extracts. Higher specific IgE values were obtained for the Kumato variety. Immunoblot showed the existence of several bands with IgE-binding capacity, especially at 12 and 45-50 kDa.

CONCLUSIONS

The study demonstrates differences in the antigenic and allergenic profiles of the analyzed varieties and variations in their allergenic composition, affecting the diagnostic capacity. LTP and PG2A are important tomato allergens in our population but other IgE-binding capacity proteins are also involved.

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.

Biochemical, immunological and clinical characterization of a cross-reactive nonspecific lipid transfer protein 1 from mulberry

BACKGROUND

Mulberry (Morus spp.) is a genus comprising several species of deciduous trees whose fruits are commonly eaten in southern Europe. Subjects with severe systemic reaction have been described. The aim of this study was to isolate the allergens of this species.

METHODS

A nonspecific lipid transfer protein 1 (ns-LTP1) was purified from black mulberry by ion exchange and reverse phase high-performance liquid chromatography, and the primary structure was elucidated by direct protein sequencing. Its allergenic activity was evaluated in vivo by skin prick test and in vitro by Western Blot, CD203c basophil activation assay and high throughput multiplex inhibition method on immunosolid-phase allergen chip (ISAC).

RESULTS

Mulberry ns-LTP (Mor n 3) comprises 91 amino acids producing a molecular mass of 9246 Da. This protein shows high sequence identity with several allergenic ns-LTP1. Immunoblot analysis and CD203c activation assay demonstrated its allergenic activity in symptomatic subjects and in ns-LTP allergic patients who are not mulberry consumers. Immunological co-recognition was studied in vivo on a selected group of well-characterized ns-LTP allergic patients showing a high percentage of nMor n 3(+) subjects (88.46%) even in patients who have never eaten mulberry before. IgE inhibition on ISAC micro-array demonstrated an almost complete cross-reactivity to nArt v 3, rCor a 8 and a very high percentage of inhibition to nPru p 3.

CONCLUSIONS

Mor n 3 is the first allergen isolated in black mulberry and immunologically characterized. It displayed allergenic activity among symptomatic and nonconsumer patients and a pattern of cross-reactivity to other plant-derived LTPs.

The non-specific lipid transfer protein, Ara h 9, is an important allergen in peanut

BACKGROUND

Plant food allergy in the Mediterranean area is mainly caused by non-specific lipid transfer proteins (nsLTP). The aim of this study was to characterize peanut nsLTP in comparison with peach nsLTP, Pru p 3, and assess its importance in peanut allergy.

METHODS

Peanut-allergic patients from Spain (n=32) were included on the basis of a positive case history and either a positive skin prick test or specific IgE to peanut. For comparison, sera of 41 peanut-allergic subjects from outside the Mediterranean area were used. Natural Ara h 9 and two isoforms of recombinant Ara h 9, expressed in Pichia pastoris, were purified using a two-step chromatographic procedure. Allergen characterization was carried out by N-terminal sequencing, circular dichroism (CD) spectroscopy, immunoblotting, IgE inhibition tests and basophil histamine release assays.

RESULTS

Compared with natural peanut nsLTP, the recombinant proteins could be purified in high amounts from yeast supernatant (> or =45 mg/L). The identity of the proteins was verified by N-terminal amino acid sequencing and with rabbit nsLTP-specific antibodies. CD spectroscopy revealed similar secondary structures for all preparations and Pru p 3. The Ara h 9 isoforms showed 62-68% amino acid sequence identity with Pru p 3. IgE antibody reactivity to rAra h 9 was present in 29/32 Spanish and 6/41 non-Mediterranean subjects. Recombinant Ara h 9 showed strong cross-reactivity to nPru p 3 and similar IgE-binding capacity as nAra h 9. The two Ara h 9 isoforms displayed similar IgE reactivity. In peanut-allergic patients with concomitant peach allergy, Ara h 9 showed a weaker allergenic potency than Pru p 3 in histamine release assays.

CONCLUSIONS

Ara h 9 is a major allergen in peanut-allergic patients from the Mediterranean area. Ara h 9 is capable of inducing histamine release from basophils, but to a lesser extent than Pru p 3.

Functional genomics of allergen gene families in fruits

Fruit consumption is encouraged for health reasons; however, fruits may harbour a series of allergenic proteins that may cause discomfort or even represent serious threats to certain individuals. Thus, the identification and characterization of allergens in fruits requires novel approaches involving genomic and proteomic tools. Since avoidance of fruits also negatively affects the quality of patients' lives, biotechnological interventions are ongoing to produce low allergenic fruits by down regulating specific genes. In this respect, the control of proteins associated with allergenicity could be achieved by fine tuning the spatial and temporal expression of the relevant genes.

The identification of allergen proteins in sugar beet (Beta vulgaris) pollen causing occupational allergy in greenhouses

Background

During production of sugar beet (Beta vulgaris) seeds in greenhouses, workers frequently develop allergic symptoms. The aim of this study was to identify and characterize possible allergens in sugar beet pollen.

Methods

Sera from individuals at a local sugar beet seed producing company, having positive SPT and specific IgE to sugar beet pollen extract, were used for immunoblotting. Proteins in sugar beet pollen extracts were separated by 1- and 2-dimensional electrophoresis, and IgE-reactive proteins analyzed by liquid chromatography tandem mass spectrometry.

Results

A 14 kDa protein was identified as an allergen, since IgE-binding was inhibited by the well-characterized allergen Che a 2, profilin, from the related species Chenopodium album. The presence of 17 kDa and 14 kDa protein homologues to both the allergens Che a 1 and Che a 2 were detected in an extract from sugar beet pollen, and partial amino acid sequences were determined, using inclusion lists for tandem mass spectrometry based on homologous sequences.

Conclusion

Two occupational allergens were identified in sugar beet pollen showing sequence similarity with Chenopodium allergens. Sequence data were obtained by mass spectrometry (70 and 25%, respectively for Beta v 1 and Beta v 2), and can be used for cloning and recombinant expression of the allergens. As for treatment of Chenopodium pollinosis, immunotherapy with sugar beet pollen extracts may be feasible.

Expression analysis and characteristics of profilin gene from silkworm, Bombyx mori

A recombinant Bombyx mori profilin protein (rBmPFN) was overexpressed in Escherichia coli BL21. Purified rBmPFN was used to generate anti-BmPFN polyclonal antibody, which were used to determine the subcellular localization of BmPFN. Immunostaining indicated that profilin can be found in both the nucleus and cytoplasm but is primarily located in the cytoplasm. Real-time RT-PCR and Western blot analyses indicated that, during the larvae stage, profilin expression levels are highest in the silk gland, followed by the gonad, and are lowest in the fatty body. Additionally, BmPFN expression begins during the egg stage, increases during the larvae stage, reaches a peak during the pupa stage, and decreases significantly in the moth. Therefore, we propose that BmPFN may play an important role during larva stage development, especially in the silk gland.

A structural basis for food allergy: the role of cross-reactivity

PURPOSE OF REVIEW

Immunologic cross-reactivity, which is important in many aspects of host defense and immune-mediated diseases, is a prominent feature of allergic disorders. The goal of this article is to define allergenic cross-reactivity and its role in food allergy, review current understanding of mechanisms of cross-reactivity, and consider how advances in our ability to predict cross-reactivity can impact diagnosis and treatment of food allergy.

RECENT FINDINGS

Recent evidence suggests that specific T cells, in addition to IgE, developed in response to inhaled allergens can cross-react with related food allergens, leading to distinct clinical reactions. Several new cross-reactivities have been identified, including food-food, pollen-food, and latex-venom associations. Debate continues regarding prediction of allergenicity based on protein structure, and clinical relevance of in-vitro testing. Cross-reactivity is also being used to develop specific immunotherapy for treatment of food allergy.

SUMMARY

A thorough understanding of immunologic cross-reactivity is essential to advancing our knowledge about food allergy. This knowledge will help elucidate the pathogenesis of the disorder and prevent exposures to allergenic, genetically engineered foods. New insight will allow for better utilization of current diagnostic tools and the development of more accurate tests and therapies for food allergy.

Advances in functional research of antioxidants and organoleptic traits in berry crops

Berry species are economically-important crops worldwide and represent an invaluable source of vitamins and other health-related compounds. Species belonging to the families Rosaceae, Ericaceae and Grossulariaceae provide the most popular fruits, showing a strong diversity in natural and breeding populations as to berry traits (fruit type, size, color, flavor, antioxidant capacity), resistance to a/biotic stress, adaptation to different environment/culture conditions. The small genome size of most diploid berry genera is a remarkable feature for last-generation genomics technologies, molecular genetics and functional studies. This review will cover the literature dealing with molecular research in berry crops, focusing on antioxidant- and flavor-related compounds.

Screening and identification of putative allergens in berry fruits of the Rosaceae family: technical challenges

Cross-reactive proteins in small fruits of the Rosaceae family like strawberry, raspberry and blackberry revealed an unexpected complex IgE-reactivity pattern. Several copies of PR-10 and PR-14 proteins were detected by Southern blots in strawberry, raspberry and blackberry. In raspberry, the highest similarity at the DNA level for PR-10 and PR-14 (Rub i 1 and Rub i 3) was detected to strawberry sequences of Fra a 1 and Fra a 3. At the protein level, Rub i 1 and Rub i 3 showed more than 70% identity with homologous proteins of rosaceous fruits. Furthermore, raspberries contained additional putative allergens, e.g. class III acidic chitinases and cyclophilins. Blackberries were shown to share at least two well-known major fruit allergens with other rosaceous fruits, namely PR-10s and PR-14s homologous proteins. However the IgE-reactive proteins of small fruits are still not extensively investigated. The main challenges in studying small fruit allergens are the complexity of the fruit matrix, the diversity of physico-chemical properties of fruit proteins, the lack of appropriate protein extraction procedures and the missing information about the influence of processing treatments on food components.

Identification of a plane pollen lipid transfer protein (Pla a 3) and its immunological relation to the peach lipid-transfer protein, Pru p 3

BACKGROUND

An association between plane tree pollen allergy and plant food allergy has been described, but the cross-reacting allergens have not yet been identified. The aim of this study was the identification of homologous non-specific lipid-transfer proteins (nsLTPs) in plane pollen, and to investigate its immunological relationship with the peach LTP, Pru p 3.

METHODS

Three different patient groups were recruited in Spain: 22 plane pollen-allergic patients without food allergy (A), 36 plane pollen-allergic patients with peach allergy (B) and 10 peach-allergic patients without plane pollen allergy (C). Proteins from plane pollen extract were fractionated by ion-exchange and reversed-phase chromatography. Further methods applied were N-terminal amino acid sequence analysis, immunoblotting, enzyme allergosorbent test, CAP and basophil histamine release assays.

RESULTS

A 10 kDa IgE-reactive protein was purified from plane pollen and identified as nsLTP. Pla a 3 was characterized as a minor allergen (27.3%) in plane pollen-allergic patients without food allergy (A) and as a major allergen in plane pollen-allergic patients with peach allergy (B) showing a prevalence of IgE-reactivity of 63.8%. Group B contained patients sensitized to Pru p 3 without IgE-reactivity to plane-LTP (16.6%). By contrast, Pla a 3 IgE-reactive patients without sensitization to Pru p 3 could be found (16.6%). The sera of patients sensitized to both LTPs (50%), Pla a 3 and Pru p 3, showed different biological activity in histamine release assay: depending on individual patient's sera tested, Pla a 3 showed a similar, a stronger or a weaker allergenic potency in comparison with Pru p 3.

CONCLUSIONS

Plane LTP is a major allergen in plane pollen-allergic patients with peach allergy recruited in the Mediterranean area. The results of histamine release tests and different IgE-binding profiles pointed towards the existence of species-specific IgE epitopes. Likewise, no general conclusion on the sensitizer could be made.

Lipid transfer protein allergy: primary food allergy or pollen/food syndrome in some cases

PURPOSE OF REVIEW

To summarize recent findings on non-specific lipid transfer proteins in food allergy, with a specific focus on the localization, stability and route of sensitization.

RECENT FINDINGS

Plant non-specific lipid transfer proteins are major food allergens, especially in the Mediterranean area. They have been identified as allergens in a number of foods and the list grows ever longer. As non-specific lipid transfer proteins are considered to be "true" food allergens that sensitize directly via the gastrointestinal tract their stability during food processing and gastric digestion has been studied in more detail. In addition, several groups have tried to determine the sensitization patterns of lipid transfer protein-reactive patients, to determine and possibly clarify the observed geographical differences in sensitization. Different sensitization routes (via the respiratory tract or even transdermally) have been suggested.

SUMMARY

As the structure and molecular properties of non-specific lipid transfer proteins are resolved and more purified non-specific lipid transfer proteins become available for diagnostic purposes, detailed studies on the sensitization pattern and route are becoming feasible. Continuing studies on the pattern of lipid transfer protein sensitization will give more insight into the development and possible treatment of lipid transfer protein-related food allergy.

Severe immediate allergic reactions to grapes: part of a lipid transfer protein-associated clinical syndrome

BACKGROUND

Grape allergy is considered rare; grape lipid transfer protein (LTP; Vit v 1), an endochitinase and a thaumatin-like protein (TLP) have been reported as grape allergens. A considerable number of patients have referred to our department for severe reactions to grapes, and several IgE binding proteins were detected.

OBJECTIVES

The aim of this study was to identify and characterise the allergens involved in severe allergic reactions to grapes and describe the population in which they occur.

METHODS

Patients with reported severe allergic reactions to grapes (n = 37) are described. Grape allergens were purified/fractionated by a combination of chromatographic techniques, identified by proteomic analysis and biochemically characterised. Immunoreactivity was assessed by blot (inhibitions) and RAST (inhibitions), and skin prick tests were performed with the isolated allergens.

RESULTS

All subjects were polyallergic, sensitised and reactive to several additional foods and pollen. All patients were sensitised to grape LTP. A 28-kDa expansin, a 37.5-kDa polygalacturonase-inhibiting protein, a 39-kDa beta-1,3-glucanase and a 60-kDa protein were identified as minor grape allergens. Endochitinase and TLP did not play a role. Inhibition experiments revealed the possible cross-reactive role of LTP for clinical sensitivities to other LTP-containing plant foods, but also the involvement of cross-reactive carbohydrate determinants of minor allergens in IgE cross-reactivity.

CONCLUSIONS

LTP is the major grape allergen, while additional minor allergens may contribute to clinical reactivity. Severe grape allergy presents in atopic patients who frequently react to other LTP-containing, plant-derived foods. The 'LTP syndrome' is the appropriate term to describe this condition.

Plant non-specific lipid transfer proteins: an interface between plant defence and human allergy

Plant non-specific LTPs (lipid transfer proteins) form a protein family of basic polypeptides of 9 kDa ubiquitously distributed throughout the plant kingdom. The members of this family are located extracellularly, usually associated with plant cell walls, and possess a broad lipid-binding specificity closely related to their three-dimensional structure. The nsLTP fold is characterized by a compact domain composed of 4 alpha-helices, firmly held by a network of 4 conserved disulphide bridges. This fold presents a large internal tunnel-like cavity, which can accommodate different types of lipids. nsLTPs are involved in plant defence mechanisms against phytopathogenic bacteria and fungi, and, possibly, in the assembly of hydrophobic protective layers of surface polymers, such as cutin. In addition, several members of the nsLTP family have been identified as relevant allergens in plant foods and pollens. Their high resistance to both heat treatment and digestive proteolytic attack has been related with the induction by these allergens of severe symptoms in many patients. Therefore, they are probably primary sensitizers by the oral route. nsLTP sensitization shows an unexpected pattern throughout Europe, with a high prevalence in the Mediterranean area, but a low incidence in Northern and Central European countries.