Les allergènes croisants à l'échelle moléculaire : comparaison nord-sud

Fruit of the Rosaceae family, in particular apples and peachs, are frequent causes of food allergy. The clinical manifestations of these allergies differ as a function of geographic location. In the context of the SAFE project (QLK1-CT-2000-01394), financed by the European Community, the apple has been chosen as a model for the study of the relationship between the clinical presentation and the profile of sensitivity to Rosaceae allergens. This study included 389 patients allergic to apples and who live in four European regions: the Netherlands (Utrecht), Austria (Vienna), northern Italy (Milan) and central Spain (Madrid). Two different profiles of apple allergy were found in Europe: one in the Netherlands, Austria and in most of the patients (90%) in northern Italy, the other in Spain and in a minority (10%) of the Italians patients. Patients coming from regions where birch pollen is present become allergic to this pollen and to its major allergen Bet v 1 through contact via the respiratory tract; allergy to apple begins later as a consequence of cross-reactivity between Bet v 1 and Mal d 1. In Spain, allergy to apple is a result of primary sensitization to peach and its major allergen Pru p 3, subsequent allergy to apple being the consequence of cross-reactivity between lipid transfer proteins Pru p 3 and Mal d 3.     

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.     

Cross-Reactivity of Peanut Allergens

Peanut seeds are currently widely used as source of human food ingredients in the United States of America and in European countries due to their high quality protein and oil content. This article describes the classification and molecular biology of peanut seed allergens with particular reference to their cross-reactivities. Currently, the IUIS allergen nomenclature subcommittee accepts 12 peanut allergens. Two allergens belong to the cupin and four to the prolamin superfamily, and six are distributed among profilins, Bet v 1-like proteins, oleosins, and defensins. Clinical observations frequently report an association of peanut allergy with allergies to legumes, tree nuts, seeds, fruits and pollen. Molecular cross-reactivity has been described between members of the Bet v 1-like proteins, the non-specific lipid transfer proteins, and the profilins. This review also addresses the less well-studied cross-reactivity between cupin and prolamin allergens of peanuts and of other plant food sources and the recently discovered cross-reactivity between peanut allergens of unrelated protein families.     

Tree nut allergy

Tree nuts are clinically associated with severe immunoglobulin E-mediated systemic allergic reactions independent of pollen allergy and with reactions that are usually confined to the oral mucosa in patients with immunoglobulin E directed toward cross-reacting pollen allergens. The latter reactions can progress to severe and life-threatening episodes in some patients. Many patients with severe tree nut allergy are co-sensitized to peanut. Clinical studies on cross-reactivity between the tree nuts are few in number, but based on reports to date, avoidance of the other tree nuts once sensitivity is diagnosed appears prudent unless specific challenges are performed to ensure clinical tolerance. Even then, great care must be taken to avoid crosscontamination. As with other severe food allergies, a recurrent problem in clinical management is the failure of physicians to prescribe self-injectable epinephrine to patients who are at risk of anaphylaxis.     

Prevalence of cypress pollen sensitization and its clinical importance in Izmir, Turkey, with cypress allergy assessed by nasal provocation.

BACKGROUND AND OBJECTIVE: Pollens from the Cupressaceae family are considered important allergens in the Mediterranean area, though reports of the prevalence of allergic symptoms have ranged from 1.04% to 35.4%. Our aim was to detect the prevalence of cypress pollen sensitization and determine its clinical importance in patients with seasonal respiratory allergy. METHODS: We used skin prick tests (SPT) and serum specific IgE assays to reveal sensitization to cypress pollen. In patients who showed positive results to cypress pollen, a nasal provocation test (NPT) with pollen extract was used to assess the target organ response. RESULTS: Sixty-five (14.3%) of 455 patients showed positive SPT responses to Cupressus sempervirens extract. Only 1 patient was monosensitized while 64 patients were polysensitized. Among those, 2 pollen cosensitizations were found to be significant (86% were cosensitized to grasses and 72% were cosensitized to olive (P < .001). Serum specific IgE to cypress pollen was measured in 50 of the 65 patients; findings were positive for 37. When these 37 patients underwent NPT with C sempervirens allergen extract, only the single monosensitized patient had a positive NPT. CONCLUSION: A positive SPT to cypress pollen may not reflect the true prevalence of sensitization. We assume that in the absence of a positive NPT, positive SPT results might be related to the presence of cross-reactivity between pollen species.     

Cross-reactivity between fruit and vegetables

Vegetable foods are the most frequent cause of food allergy after the age of 5 years. The most commonly implicated foods are fruit and dried fruits, followed in Spain by legumes and fresh garden produce. In patients allergic to fruit and garden produce, multiple sensitizations to other vegetable products, whether from the same family or taxonomically unrelated, are frequent, although they do not always share the same clinical expression. Furthermore, more than 75 % of these patients are allergic to pollen, the type of pollen varying in relation to the aerobiology of the area. The basis of these associations among vegetable foods and with pollens lies in the existence of IgE antibodies against "panallergens", which determines cross-reactivity. Panallergens are proteins that are spread throughout the vegetable kingdom and are implicated in important biological functions (generally defense) and consequently their sequences and structures are highly conserved. The three best-known groups are allergens homologous to Bet v 1, profilins, and lipid transfer proteins (LTP). Allergens homologous to Bet v 1 (major birch pollen allergen) constitute a group of defense proteins (PR-10), with a molecular weight of 17 kDa, which behave as major allergens in patients from northern and central Europe with allergy to vegetables associated with birch pollen allergy. In these patients, the primary sensitization seems to be produced through the inhalation route on exposure to birch pollen. The symptomatology characteristically associated with sensitization to this family of allergens is oral allergy syndrome (OAS). Profilins are highly conserved proteins in all eukaryotic organisms and are present in pollen and a wide variety of vegetable foods. They have a molecular weight of 14 kDa and present a high degree of structural homology as well as marked cross-reactivity among one another. The presence of anti-profilin IgE broadens the spectrum of sensitizations to vegetable foods detected through skin tests and/or in vitro tests but whether it correlates with the clinical expression of food allergy is unclear.LTPs are the most commonly implicated allergens in allergy to Rosaceae fruits in patients from the Mediterranean area without birch pollen sensitization. LTPs are a family of 9kDA polypeptides, widely found in the vegetable kingdom and implicated in cuticle formation and defense against pathogens (PR-14). They are thermostable and resistant to pepsin digestion, which makes them potent food allergens and explains the frequent development of systemic symptoms (urticaria, anaphylaxis) in patients allergic to Rosaceae fruits in Spain. LTPs have also been identified in other vegetable foods and in pollens and a marked degree of cross-reactivity among them has been demonstrated, which may explain (together with profilin) the frequency of individuals sensitized to vegetable foods in the Mediterranean area.     

What are the links between food allergy and atopy ?

Food allergy and atopy are closely linked. In children, food allergy is often the first clinical manifestation of atopy and involved in flares of atopic dermatitis. It is usually disappearing with ageing except for some particular allergens. Asthma and/or allergic rhinitis might develop later particularly if there are some risk factors as familial history of atopy or sensitization to aeroallergens. However some food allergies as allergy to peanut or tree nuts may persist in adulthood sometimes inducing severe clinical manifestations especially in asthmatic patients. In adult, food allergy is mostly associated with oral syndrome linked to cross reactivity between pollen and raw food (fruits or vegetables). Systemic manifestations are more frequent in patients living in the Mediterranean area in relation to direct sensitization (without pollen allergy) to lipid transfer proteins that are particularly resistant.     

Allergies associated with both food and pollen

Recent progress in understanding structural relationships between allergens has allowed their classification into molecular families. Proteins belonging to a molecular family often show some degree of IgE cross-reactivity. These cross-reactions can lead to a clinical association like birch-apple syndrome whose basis is a sensitization to a PR-10 protein (birch pollen Bet v 1) and then oral symptoms in contact to apple Mal d 1, another PR-10 family member. Food allergens implicated into pollen-food allergy syndromes differ from those linked to crustacea or milk cross-allergies: they seem unable to sensitize the patient through oral route. As a result, they most often induce weaker clinical reactions than complete allergens like those present in shrimp or cow milk. Numerous molecular families have been isolated from pollens. PR-10 and profilins have a well established role in inducing clinical reactions to food like fruits and vegetables. Some molecular families need more studies to delineate their true impact on pollen-driven food reactions: polygalacturonases, pectate lyases, isoflavone reductases, thaumatin-like, cyclophilins.... Others are found in pollen but not in eaten products: 2-EF-hand calcium binding proteins, beta expansins,... Lipid transfer proteins (LTP) are widespread plant food allergens (e.g. in peach): these proteins seem able to directly sensitize the patient through oral route. But recent data have suggested a possible additional effect of some LTP present in pollens (mugwort, olive, pellitory).     

Anaphylaxis to pine nuts and immunological cross-reactivity with pine pollen proteins.

Despite the wide use of pine nuts, the fruit of Pinus pinea, only a few reports of allergic reactions to them have been published. We present herein a case of food allergy to pine nuts in a patient who showed no clinical symptoms to pine pollen despite the presence in her serum of specific IgE antibodies. In order to verify whether the reaction against pine nuts was IgE mediated, specific IgE against pine nuts and pollen were evaluated by skin-prick test, prick by prick and RAST. Immunoblotting and immunoblotting-inhibition were used to evaluate the allergenic components of both extracts and their cross-reactivity. Prick by prick with fresh pine nuts and RAST with pine nut and pine pollen extracts showed that the patient had high levels of specific IgE against both extracts. Immunoblotting experiments showed the presence in serum of IgE antibodies against several components in pine nuts and pollen. Immunoblotting-inhibition experiments demonstrated the presence of some cross-reacting components. These data confirm the existence of food allergy induced by pine nuts. This sensitization to pine nuts developed with no symptoms of pine pollinosis. Development of pollinosis may require a longer time of exposure to allergens. Based on the cross-reactivity between pine nut and pine pollen extracts, cosensitization to these two allergens could be possible.     

Cross-reactivity of pollen allergens

Pollen cross-allergenicity has practical implications on the management of inhalant allergy, in both evaluation and therapy, especially with allergen vaccine immunotherapy. The study of cross-reactivity among pollen allergens has expanded beyond investigation of crude extracts to the characterization and cloning of numerous pollen proteins. In this review, the interrelationships between these pollen allergens in the context of botanical systematics are examined, to provide a framework for cross-reactivity understanding. Recommendations for choices in evaluation and therapy are given.     

Recombinant cypress allergens

Cedar/cypress/juniper pollen allergy is probably one of the most common worldwide pollen allergy. Purification, identification and characterization of allergens increased the knowledge about the IgE reactivity of allergic subjects toward defined allergenic components. Molecular biology give the opportunity to produce the allergens in virtually unlimited reproducible amount, to further characterize the IgE reactivity of the allergenic molecule, and finally how this reactivity can be modified for therapeutic purposes. The DNA recombinant technique has been applied to the study of cedar/cypress/juniper pollen allergens and several molecules have been cloned. These molecules can be divided in four groups depending on their biologic activity: he Pectate lyases (rCry j 1, rCha o 1, rJun a 1); the Polygalacturonase (rCry j 2, rCha o 2); the Thaumatin-like pathogenesis-related protein (rJun a 3); the Calcium-binding protein (rJun o 2). Main immunobiologic features of these cedar/cypress/juniper recombinant allergens will be summarized.     

Pollen Allergens for Molecular Diagnosis

Pollen allergens are one of the main causes of type I allergies affecting up to 30 % of the population in industrialized countries. Climatic changes affect the duration and intensity of pollen seasons and may together with pollution contribute to increased incidences of respiratory allergy and asthma. Allergenic grasses, trees, and weeds often present similar habitats and flowering periods compromising clinical anamnesis. Molecule-based approaches enable distinction between genuine sensitization and clinically mostly irrelevant IgE cross-reactivity due to, e. g., panallergens or carbohydrate determinants. In addition, sensitivity as well as specificity can be improved and lead to identification of the primary sensitizing source which is particularly beneficial regarding polysensitized patients. This review gives an overview on relevant pollen allergens and their usefulness in daily practice. Appropriate allergy diagnosis is directly influencing decisions for therapeutic interventions, and thus, reliable biomarkers are pivotal when considering allergen immunotherapy in the context of precision medicine.     

Identification of peroxidase-1 and beta-glucosidase as cross-reactive wheat allergens in grass pollen-related wheat allergy

BackgroundSome patients with wheat-dependent exercise-induced anaphylaxis (WDEIA) or wheat allergy showed negative ω-5 gliadin-specific IgE test and high level of grass pollen-specific IgE. It was presumed that these patients developed allergic reaction upon cross-reaction of their IgE antibodies raised against grass pollen allergens to wheat allergens. This study aimed to clarify clinical characteristics and wheat allergens of this phenotype of WDEIA/wheat allergy, which were tentatively diagnosed as grass pollen-related wheat allergy (GPWA).MethodsA total of six patients with GPWA were enrolled, and controls were 17 patients with grass pollen allergy but no episode of wheat allergy, and 29 patients with other wheat allergies: 18 with conventional WDEIA and 11 with hydrolyzed wheat protein allergy. Sensitization to wheat proteins was determined by basophil activation test (BAT). IgE-binding proteins in wheat flour were identified by immunoblotting followed by mass spectrometry. Wheat allergen-specific IgE tests were established by CAP-FEIA system.ResultsAll the six patients with GPWA were sensitized to water-soluble wheat proteins in BAT and IgE-immunoblotting, and peroxidase-1 (35 kDa) and beta-glucosidase (60 kDa) were identified as specific IgE-binding wheat proteins. The binding of patient IgE to these proteins was inhibited by pre-incubation of patient sera with grass pollen. The peroxidase-1- and beta-glucosidase-specific IgE tests identified three and four of six patients with GPWA, respectively, but only two of 29 controls, indicating high specificity of these tests.ConclusionsPeroxidase-1 and beta-glucosidase are specific wheat allergens for GPWA among grass pollen allergy and other types of wheat-induced food allergies.     

Management of the Patient with Multiple Food Allergies

Food allergies affect 6% of children and 3% to 4% of adults in the United States. Although several studies have examined the prevalence of food allergy, little information is available regarding the prevalence of multiple food allergies. Estimates of prevalence of people allergic to multiple foods is difficult to ascertain because those with allergy to one food may avoid additional foods for concerns related to cross-reactivity, positive tests, or prior reactions, or they may be reluctant to introduce foods known to be common allergens. Diagnosis relies on an accurate history and selective IgE testing. It is important to understand the limitations of the available tests and the role of cross-reactivity between allergens. Allergen avoidance and readily accessible emergency medications are the cornerstones of management. In addition, a multidisciplinary approach to management of individuals with multiple food allergies may be needed, as avoidance of several food groups can have nutritional, developmental, and psychosocial consequences.     

Hypersensitivity to members of the botanical order Fabales (legumes).

Legumes are an important source of proteins and their consumption is very frequent in the Mediterranean region and in some Asian and African countries. In some of these regions, lentils and chickpeas are one of the main food allergens. Legumes are also used as food additives due to their emulsifying properties and can be present in many manufactured foods. These hidden food allergens have the potential of causing adverse reactions in legume-sensitive subjects. The allergenic composition of various legumes has been investigated. They have been found to contain multiple allergens, a few of which have been cloned and sequenced. Legumes contain acid-resistant and thermostable allergens. There is a significant degree of cross-reactivity among legumes, the clinical relevance of which seems to be dependent on the dietary habits in different communities. In Spain, the consumption of several legumes is frequent and, therefore, clinical allergy to more than one species in children is common. Clinical manifestations include cutaneous, digestive and respiratory symptoms. Legumes can cause life-threatening reactions in sensitized individuals. Inhalation of steam, powder or flour from some legumes may cause respiratory diseases such as rhinitis, asthma and hypersensitivity pneumonitis. Soybean allergy is generally transitory, but clinical allergy to peanuts is rarely outgrown. The natural history of other legume allergies is less known and more studies are necessary to reach definite conclusions.     

Diagnostic biologique de l'allergie respiratoire : évaluation du réactif Vidas Stallergy genévrier dans l'allergie au cyprès

Cypress allergy is an important health issue in Mediterranean areas but its diagnosis is still difficult in some cases. The fact that cypress and juniper tree pollens share a number of allergens, together with the higher allergenic protein contents of the latter have recently led allergologists to use juniper pollen extracts while testing for cypress allergy. In the present study we have evaluated a new Vidas bioMérieux reagent, Stallergy ST6, designed for the detection and quantification of anti-juniper serum IgE, when applied to cypress allergy diagnosis. In thirty-one Respiratory Diseases Department outpatients clinically suspected of cypress pollen allergy, Stallergy ST6 results were compared to those of prick tests and of serum IgE quantification using the CAP System (Phadia). There is a good class concordance between IgE results yielded by the two methods. We conclude that Stallergy ST6 provides a sensitive and specific reagent for cypress allergy diagnosis.     

Allergies cyprès-pêche : allergie croisée ou simple coïncidence ?

Recently, a cross reactivity between cypress pollens and peach has been published. In this paper, we have tried to confirm this possibility in 33 patients suffering from cypress pollen allergy. The analysis of the collected patients data lead to the following classification of them into two groups: nine patients (27.3%) had a sensitivity to peach (four patients were allergic to peach and five patients were only sensitised to this fruit but could eat it without experiencing any symptoms), the second group of 24 patients were allergic to cypress pollens, but not sensitive to peach. These results clearly confirm that the cypress-peach syndrome exists together with the apple-birch syndrome. Other analysis on these patients will enable to characterise the cross-reacting allergens.     

Allergy to cypress pollen: preparation of a reference and standardization extract in vivo

Development of Cypress allergy frequency led to the standardization of commercial cypress extract used for diagnosis and immunotherapy. Previous in vitro studies on two cypress pollen species (Cupressus sempervirens and Cupressus arizonica) allowed us to produce an allergenic solution composed by a mixture of both extracts for in vivo standardization. Dilutions of this allergenic solution were tested by prick-test on 44 patients with clinical allergy to cypress pollen to define the dilution that corresponds to a 6 mm wheal conformed to the definition of 100 IR. The mixture of the two major species found in France is justified by the in vitro study results. Extracts revealed complementary allergenic composition: Cup sempervirens showed a wider diversity of allergens whereas Cup arizonica showed a higher content of the major 43 kDa allergen. Thus, according to in vivo analysis, we are able to produce a standardized extract of Cypress pollen expressed in IR.     

IgE cross-reactivity between meadow fescue pollen and kiwi fruit in patients' sera with sensitivity to both extracts.

BACKGROUND: The presence of IgE reactivity to kiwi fruit and grass pollen allergens which could be caused by cross-reactivity has been detected in many patients with allergy. Proper identification of allergens as well as cross-reactive components is essential for understanding fruit- and pollen-associated hypersensitivity. METHODS: Using the sera from the polysensitized patients with specific IgE to grass pollen and kiwi fruit we tested reactivity to both allergen sources. IgE reactivity was exhibited in 8 serum samples by immunoblot. A serum pool formed by 8 individual sera was used for the investigation of IgE crossreactivity. SDS-PAGE immunoblot-inhibition assay was performed by preincubation of the sera with meadow fescue pollen, kiwi fruit extract, and isolated 24 kDa kiwi protein. To determine the allergens of kiwi fruit extract, we performed 2D PAGE immunoblot. In order to detect the crossreactive components between two allergen sources, a specific IgE for the 24 kDa kiwi allergen was purified. RESULTS: SDS-PAGE immunoblot meadow fescue pollen showed allergens ranging from 94 to 16 kDa, and kiwi fruit had 12 allergens ranging from 94 to 17 kDa. 2D-PAGE analysis revealed at least 15 spots in the kiwi extract and about 10 allergens. The most prominent allergen in 2D PAGE immunoblot was protein with 24 kDa and pI 9.4-9.5. Using an affinity-purified specific IgE we found that the 24 kDa kiwi allergen shared IgE-reactive epitopes with the meadow fescue group 4 and allergen about 36 kDa. Crossreactivity between isolated 24 kDa kiwi allergen and Fes p 4 was confirmed by anti-grass group 4 moab 2D8. CONCLUSION: Our findings showed that fescue meadow pollen cross-sensitize to kiwi fruits. A 24 kDa kiwi glycoprotein represent potential major allergen, which share common epitopes with Fes p 4 and 36 kDa meadow fescue allergen.     

Airborne allergy to sunflower seed.

BACKGROUND: There is increasing evidence that bird fanciers may develop airborne allergies to unusual allergens. OBJECTIVE: To detect the allergen source in a bird fancier with a history of asthma associated with bird cage cleaning activities and with contact with a Brazil parrot. METHODS: SPT with a large series of both airborne and food allergens were carried out. IgE reactivity to allergens causing wheal and flare reactions was confirmed by in-vitro investigations including ELISA/ELISA inhibition and immunoblot analysis. RESULTS: Strong skin reactivity to sunflower seed was observed. Immunoblot analysis showed IgE reactivity to low m.w. proteins, most probably 2S albumin, and ELISA inhibition studies showed the absence of cross-reactivity to mustard. CONCLUSION: Sunflower seed dust may sensitize patients via the respiratory tract. Differently from previously reported cases of sunflower seed allergy, no cross-reactivity to 2S albumin from botanically unrelated seeds was found.