Optimized allergen extracts and recombinant allergens in diagnostic applications

Pattern of sensitization to yellow jacket venom and expression of recombinant antigen 5 (Ves v 5) from yellow jacket venom

BACKGROUND

Hymenoptera venom allergy is a significant allergic reaction that affects a substantial proportion of adults. Accurate diagnosis of this allergy using venom extracts is challenging due to molecular cross-reactivity. Pure recombinant allergens offer a promising solution to identify the specific venom responsible for allergic reactions. This study aimed to produce recombinant phospholipase A5 (Ves v 5) from yellow jacket venom and evaluate the pattern of bee venom sensitization in a group of sensitive patients.

METHODS AND RESULTS

A total of seven individuals, including four sensitive and three non-sensitive participants, were recruited for this study. Blood samples were collected, and serum was isolated to assess susceptibility to bee venom and recombinant allergens. Expression of Ves v 5 in Escherichia coli resulted in the production of soluble proteins, which were subsequently purified through affinity chromatography. The functionality of the recombinant allergens was evaluated through enzymatic and biophysical analyses, such as dot blot and SDS‒PAGE tests. The diagnostic relevance of Ves v 5 was further investigated using ELISA-based analyses of sera from yellow jacket venom-sensitized patients. Successful production of soluble Ves v 5 in Escherichia coli was achieved. The recombinant Ves v 5 exhibited distinct biochemical and functional characteristics. Evaluation of IgE reactivity in sera from patients underscored the importance of Ves v 5 in hymenoptera venom allergy.

CONCLUSIONS

Our findings suggest that recombinant allergens can serve as an alternative to natural extracts for diagnostic purposes. Furthermore, allergen-specific immunotherapy holds the potential to enhance efficiency and specificity in the treatment of hymenoptera venom allergy.

Value of microarray allergen assay in the management of eosinophilic oesophagitis

BACKGROUND

Eosinophilic oesophagitis (EoE) is a disorder characterised by oesophageal dysfunction and, histologically, by eosinophilic inflammation. Although treatment, which includes dilatations, oral corticosteroids and restrictive diets, is often effective, choosing the foods to be eliminated from the diet is difficult.

OBJECTIVE

Component resolved diagnostic by microarray allergen assay may be useful in detecting allergens that might be involved in the inflammatory process.

METHODS

We studied 67 patients with EoE, diagnosed clinically and histologically by endoscopic biopsy. CRD analysis with microarray technology was carried out in the 67 EoE patients, 50 patients with pollen allergy without digestive symptoms, and 50 healthy controls.

RESULTS

Allergies were not detected by microarray in only seven of the 67 patients with EoE. Controls with pollen allergy showed sensitisation to different groups of pollen proteins without significant differences. In EoE patients with response to some allergens, the predominant allergens were grasses group 1 and, in particular, nCyn d 1 (Cynodon dactylon) or Bermuda grass pollen in 59.5%, followed by lipid transfer proteins (LTP) of peach (19.40%), hazelnut (17.91%) and Artemisia (19.40%).

CONCLUSIONS

In patients with EoE, sensitisation to plant foods and pollen is important. The proteins most frequently involved are nCyn d 1 and lipid transfer proteins, hazelnuts and walnuts. After one year of an array-guided exclusion diet and pollen-specific immunotherapy in the case of high levels of response, patients with EoE showed preliminary significant improvements.

Diagnostic usefulness of component-resolved diagnosis by skin prick tests and specific IgE to single allergen components in children with allergy to fruits and vegetables

INTRODUCTION

The accurate identification of sensitizing proteins in patients allergic to plant-derived foods is extremely important, allowing a correct dietary advice. We aimed to evaluate the diagnostic usefulness of skin prick tests (SPT) and specific IgE (sIgE) with single molecular allergen components in children with allergy to fruits and vegetables.

METHODS

Twenty children underwent SPT with a palm profilin (Pho d 2, 50 μg/mL); a Mal d 1-enriched apple extract (2 μg/mL) (PR-10 allergen); and a peach Lipid Transfer Protein (LTP) (Pru p 3, 30 μg/mL). Detection of sIgE to rBet v 1, rBet v 2, Phl p 12 and Pru p 3 was also measured.

RESULTS

Allergy to multiple fruits and vegetables was observed in 11 (55%) children. Sensitization by SPT to Pho d 2, Mal d 1, and Pru p 3 occurred in 5, 7, and 8 cases, respectively. LTP sensitization appeared to be associated with peach allergy but not with severe reactions, and profilins sensitization to melon and tomato allergy. Kiwi sensitization (12 cases), the plant-derived food that caused more allergic reactions, seemed mostly species-specific. The concordance of SPT extracts and sIgE to the corresponding pan-allergens was high for profilins (k=0.857) and LTP (k=0.706), while for PR-10 allergens it was absent (k=0.079).

CONCLUSIONS

Pan-allergen sensitization in children with allergy to fruits and vegetables was common and often multiple. There was no association of severe reactions to LTP sensitization. The introduction of routine SPT to pan-allergens can be a simple and feasible way of improving diagnostic and therapeutic efficacy.

Dog saliva - an important source of dog allergens

BACKGROUND

Allergy to dog (Canis familiaris) is a worldwide common cause of asthma and allergic rhinitis. However, dander extract in routine diagnostics is not an optimal predictor of IgE-mediated dog allergy. Our objective was to evaluate saliva as an allergen source for improved diagnostics of allergy to dog.

METHODS

IgE-binding proteins in dog saliva and dander extract were analysed by immunoblot and mass spectrometry (LC-MS/MS) using pooled or individual sera from dog-allergic patients (n = 13). Sera from 59 patients IgE positive to dander and 55 patients IgE negative to dander but with symptoms to dog were analysed for IgE against saliva and dander by ELISA. Basophil stimulation with dog saliva and dander extract was measured by flow cytometry among three dog-allergic patients. Additionally, IgE-binding protein profiles of saliva from different breeds were investigated by immunoblot.

RESULTS

Greater number and diversity of IgE-binding proteins was found in saliva compared to dander extract and varied among dog breeds. In saliva, Can f 1, 2, 3 and 6 were identified but also four new saliva allergen candidates. The majority of the 59 dog dander-positive sera (n = 44) were IgE positive to dog saliva. Among patients IgE negative to dander, but with symptoms to dog, 20% were IgE positive to saliva. The biological activity of saliva was confirmed by basophil degranulation.

CONCLUSIONS

Dog saliva is an allergen source for improved diagnostics of dog allergy. The IgE-binding protein profile of saliva from different dogs varies.

Microarray based IgE detection in poly-sensitized allergic patients with suspected food allergy - an approach in four clinical cases

BACKGROUND

Component-resolved diagnosis and microarray technology have been recently introduced into clinical allergy practice, and may be particularly useful in poly-sensitized allergic patients.

METHODS

We compare the clinical usefulness of a microarray-based IgE detection assay (ISAC(®)) with skin tests and specific IgE with standard allergens (sIgE) or their monocomponents in four case reports of patients poly-sensitized to aeroallergens and food.

RESULTS

Case 1: a woman with rhinitis, oral allergy syndrome to several fruits and anaphylaxis to cherry. Diagnostic tests supported non-specific lipid transfer proteins (nsLTPs) primary sensitization. Case 2: a woman with exercise-induced asthma, rhino-conjunctivitis and oral allergy syndrome to fresh fruits of different families. A diagnosis of primary grass and weed pollen allergy with profilin and pathogenesis-related protein family 10 (PR-10) cross-reactive food allergy was proposed. Case 3: a man with atopic eczema, asthma, rhinitis, and multiple anaphylactic episodes with cashew nuts and oral allergy syndrome to fruits. The diagnostic workup supported a primary birch pollen allergy with PR-10 and nsLTPs cross-reactive food allergy. Case 4: a woman with rhino-conjunctivitis, per-operative anaphylaxis due to latex and recent pharyngeal angio-oedema episodes. The diagnosis was a primary grass and weed pollen allergy with equivocal profilin sensitization and no obvious cross-reactivity mediated by nsLTPs sensitization.

CONCLUSIONS

The possibility to carry out multiple sIgE measurements with single protein allergens, in particular with the microarray technique, is a useful, simple and non-invasive diagnostic tool in complex poly-sensitized allergic patients.

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.

Coordinated and standardized production, purification and characterization of natural and recombinant food allergens to establish a food allergen library

Reliable diagnosis of food allergy is dependent on the analytes used. Approaches based on well-defined individual molecules of either natural or recombinant origin are likely to replace those based on food extracts in the future. Therefore, a library comprising well-characterized authentic natural and recombinant allergens was formed within the EC funded IP EuroPrevall. The advantages and disadvantages of including either natural or recombinant proteins are summarized, together with inclusion criteria such as purity and the implications of both allergenic and nonallergenic impurities for the performance of diagnostic assays. In order to harmonize quality criteria of the individual food allergens included in the library, as suite of characteristics and associated methodologies used to define them, was agreed. The application of these methods and impact on the quality and performance of the final purified food allergens included in the EuroPrevall allergen library is discussed.

Variability of IgE reactivity profiles among European mite allergic patients

BACKGROUND

House dust mites (HDM) Dermatophagoides pteronyssinus are a frequent indoor allergen source. Our aim was to determine the frequencies of IgE reactivity to purified HDM allergen molecules in mite allergic patients from different parts of Europe in order to establish an allergen panel for diagnosis of HDM allergy.

MATERIALS AND METHODS

Populations of D. pteronyssinus-allergic patients from Austria (n = 56), France (n = 55), Italy (n = 67) and Sweden (n = 65) and storage mite allergic patients from Sweden (n = 31) were analysed for IgE reactivity to eight purified natural (n) and recombinant (r) D. pteronyssinus allergens (nDer p 1, rDer p 2, nDer p 4, rDer p 5, rDer p 7, rDer p 8, rDer p 10 and rDer p 14) in RAST-based dot blot assays.

RESULTS

Using a combination of Der p 1 and Der p 2, at least 97% of the D. pteronyssinus-allergic patients could be diagnosed in each of the HDM allergic populations. However, more than 50% of the patients also reacted with other allergens and significant variabilities regarding the frequencies of IgE reactivity to individual allergen molecules were found. Patients with a predominant storage mite allergy showed none or only very weak IgE reactivity to purified D. pteronyssinus allergens.

CONCLUSIONS

Purified Der p 1 and Der p 2 are sufficient for the diagnosis of > or = 97% of D. pteronyssinus allergic patients in Europe, but other allergens may also play an important role for the diagnosis and treatment of HDM allergy.

Quantification of Art v 1 and Act c 1 being major allergens of mugwort pollen and kiwi fruit extracts in mass-units by ion-exchange HPLC-UV method

A simple ion-exchange HPLC-UV method was developed for determination of major allergens from mugwort pollen and kiwi fruit extracts in mass-units. The separation of Art v 1 and Act c 1 from other components in the extracts was achieved in one step. The extinction coefficients used in the study were theoretically determined and compared to the extinction coefficients determined by gravimetry. We also reported a close correlation of the major allergen contents with the overall allergenic potency of the extracts determined by inhibition ELISA. This method could be a useful tool for standardization of allergenic extracts for clinical use.

Enhancement of hazelnut extract for IgE testing by recombinant allergen spiking

BACKGROUND

Hazelnuts are a common cause of food allergic reactions. Most hazelnut allergic individuals in central and northern Europe are sensitized to Cor a 1, a member of the PR-10 protein family, while the lipid transfer protein Cor a 8 acts as a major allergen in the south of Europe. Other allergens, including profilin and seed storage proteins, may be important in subgroups of patients. Reliable detection of specific IgE in the clinical diagnosis of food allergy requires allergen reagents with a sufficient representation of all relevant allergen components. Some reported observations suggest that natural hazelnut extract may not be fully adequate in this respect.

METHODS

The capacity of immobilized natural hazelnut extract to bind Cor a 1-, Cor a 2- and Cor a 8-specific IgE and IgG antibodies was investigated by serum adsorption and extract dilution experiments and by the use of allergen specific rabbit antisera. All measurements were performed with the ImmunoCAP assay platform.

RESULTS

The experimental results revealed an incomplete capacity of immobilized hazelnut extract to capture IgE antibodies directed to the major allergen Cor a 1. Spiking of hazelnut extract with recombinant Cor a 1.04 prior to solid phase coupling gave rise to significantly enhanced IgE antibody binding from Cor a 1 reactive sera. The spiking did not negatively affect the measurement of IgE to extract components other than Cor a 1.

CONCLUSION

A hazelnut allergen reagent with enhanced IgE detection capacity can be generated by supplementing the natural food extract with recombinant Cor a 1.04.

Optimized techniques for the extraction of grape allergens appropriate for in vivo and in vitro testing and diagnosis

Standardized allergen extracts are needed for diagnosis and therapy purposes. For grapes, standardization is hampered by low protein and high tannin and pectin concentrations. The aim of the current study was to develop an optimized method for the extraction of grape proteins and possibly extend this to other fruits. Several existing or modified extraction methods were compared by means of protein concentration determination, SDS-PAGE, immunoblotting and radioallergosorbent test (RAST). An optimized extraction protocol was obtained in which we combined a high concentration of plant tissue, a concentrated, enriched and neutral buffer able to remove sugars and keep proteins soluble and a bivalent buffer for pectin removal. Both the quantitative (protein concentration) and qualitative parameters (SDS-PAGE protein patterns and IgE reactivity) were compared to standard protocols and commercial extracts used as diagnostic tools in the clinical practice. This method proved to be the most efficient mainly compared to the standard Björksten protocol in extracting the low molecular weight proteins, including the major grape allergen (lipid transfer protein, Vit v 1). It proved to be an easy, low cost and reproducible method proposed to prepare grape extracts that could replace the commercially available ones, used for diagnosis and possibly extend the method to other fruits especially in extracting LTPs.

IgE-mediated food allergy diagnosis: Current status and new perspectives

In June 2005, the work of the EU Integrated Project EuroPrevall was started. EuroPrevall is the largest research project on food allergy ever performed in Europe. Major aims of the project are to generate for the first time reliable data on the prevalence of food allergies across Europe and on the natural course of food allergy development in infants. Improvement of in vitro diagnosis of food allergies is another important aim of the project. The present review summarizes current knowledge about the clinical presentation of food allergy and critically reviews available diagnostic tools at the beginning of the project period. A major problem in diagnosis is a relatively poor 'clinical specificity', i. e. both positive skin tests and in vitro tests for specific IgE are frequent in sensitized subjects without food allergy symptoms. So far, no in vitro test reliably predicts clinical food allergy. EuroPrevall aims at improving the predictive value of such tests by proceeding from diagnosis based on allergen extracts to purified allergen molecules, taking into account the affinity of the IgE-allergen interaction, and evaluating the potential of biological in vitro tests such as histamine release tests or basophil activation tests including assays performed with permanently growing cell lines.

A critical assessment of allergen component-based in vitro diagnosis in cherry allergy across Europe

BACKGROUND

Food allergy to cherry occurs throughout Europe, typically with restricted oral reactions in the central and northern parts but with frequent systemic reactions in the Mediterranean region. Previous studies have demonstrated insufficient sensitivity of commercially available cherry extract reagents in the diagnosis of cherry allergy.

OBJECTIVE

To assess the diagnostic performance of specific IgE tests based on recombinant cherry allergens in comparison with an extract-based assay and to skin prick test (SPT). A secondary objective was to analyse the frequency of systemic reactions in cherry-allergic subjects across Europe, including the largest population of LTP-sensitized subjects from central Europe studied to date.

METHODS

A total of 186 subjects from central Europe and Spain were studied. Serum IgE was analysed with ImmunoCAP tests carrying rPru av 1, 3 and 4, combined and separately, and cherry extract.

RESULTS

Among the central European cherry allergics, the mix of rPru av 1, 3 and 4 had a sensitivity of 95%, compared with 65% for cherry extract, and the IgE binding capacity of the recombinant mix was considerably higher. The sensitivity of the two tests was more comparable in the Spanish population, 95% and 86%, respectively. The recombinant allergen ImmunoCAP equalled SPT in terms of sensitivity and specificity. Consistent with previous reports, major geographic differences in sensitization pattern and prevalence of systemic reactions were found. A significantly higher rate of systemic reactions was found in Spanish patients sensitized to Pru av 3 whereas German patients sensitized to LTP only had oral allergy syndrome.

CONCLUSIONS

The recombinant cherry allergen ImmunoCAP is a highly sensitive diagnostic tool, clearly superior to any diagnostic method based on cherry extract. Three cherry allergens are sufficient for detecting sensitization in 95% of cherry-allergic subjects. Systemic reactions are common in LTP-sensitized individuals but seem to require at least one additional causative factor.

Overview of the most commonly used methods in allergen characterization

The characterization of an allergen is a troublesome and difficult process, as it requires both the precise biochemical characterization of a (glyco)protein molecule and the establishment of its susceptibility to IgE antibodies, as they are the main link to histamine release in some hypersensitivity states (type I allergies). As the characterization of an allergen includes molecular weight determination of the allergenic molecule, its structure determination, physicochemical properties, IgE binding properties of the allergen molecule, and its allergenicity, an overall review of which biochemical and immunochemical methods are used in achieving this goal are presented in this paper. The information on the molecular level on the structures of allergens indicates that allergens are considerably heterogeneous protein structures, and that there is no particular aminoacid sequence which is responsible for the allergenicity. Therefore, information gained from detailed structural, functional and immunochemical studies of these intriguing molecules, which nowadays modulate a variety of pathophysiological conditions, would greatly improve our understanding of the underlying disease mechanisms, and the way to handle them.

In vitro allergy diagnosis: should we follow the flow?

During the last 5 years, an increasing number of studies have demonstrated that flow cytometric quantification of in vitro basophil activation can be a quite performant and reliable tool to measure IgE-dependent allergen-specific responses in allergic patients. So far, most assays have used CD63 as a basophil activation marker and native allergen extracts for stimulation. However, other basophil markers and recombinant allergens have recently been introduced. The technique has been applied for the diagnosis of allergy to pollen, house dust mite, food, natural rubber latex, hymenoptera venom and drugs. In addition, the technique has proven to be useful in non-IgE-mediated reactions such as hypersensitivity to drugs as well as detection of auto-antibodies in chronic urticaria. This review will focus on some specific issues: (1) principles of flow cytometric analysis of in vitro-activated basophils, (2) general technical aspects of the technique (including passive sensitization), (3) clinical applications and (4) recommendations for further development and evaluation of the technique.

Improving diagnostic tests for food allergy with recombinant allergens

Food allergy is one important manifestation of atopic allergy. Primary food allergy mainly affects young children (class I), whereas adults frequently develop food allergy as a consequence of an inhalant sensitization (class II). At present, the diagnostic instrument for proving class II food allergy is not satisfactory. Skin tests as well as serological tests are in general neither very specific nor highly sensitive because they depend on food extracts, which differ in their content of individual allergens, vary between manufacturers, and even between different batches. Since the presence of food allergen-specific IgE antibodies does not always correlate with clinical symptoms against the respective food, oral provocation tests (ideally double-blind placebo-controlled food challenges) have to be performed to validate serological diagnosis or skin tests. However, oral provocation tests are connected to several practical problems and include a specific risk for the allergic patient. Applying DNA technology, up to 40 food allergens have been produced in recombinant form, which implies standardized quality and unlimited quantity of the respective proteins. Hence, such molecules might be used to solve problems of clinical and molecular allergology in diagnosis, research, and therapy of class II food allergies. First experiments with recombinant food allergens in this respect appear very promising.

Diagnostic value of scratch-chamber test, skin prick test, histamine release and specific IgE in birch-allergic patients with oral allergy syndrome to apple

BACKGROUND

The aim of the study was to examine the diagnostic value of skin prick test (SPT), scratch-chamber test (SCT), histamine release (HR) and specific immunoglobulin E (IgE) in birch-allergic patients with oral allergy syndrome to apple.

METHODS

Ten birch-allergic patients with oral allergy syndrome to apple and 10 control subjects were included. All were tested with SPT, SCT, HR and specific IgE [CAP, Pharmacia, Sweden and Magic Lite (ML), ALK-ABELLO, Denmark].

RESULTS

The SPT with apple, acetone extract of apple (A72) and commercial apple extract showed sensitivities of 0.80, 0.90 and 0.10, respectively. The SCT with the same extracts showed sensitivities of 0.30, 0.50 and 0.20, respectively. The sensitivity of specific IgE to apple were 0.90 (CAP) and 0.10 (ML). The sensitivity of the HR test was 90% (A72), and 25% using the commercial extract.

CONCLUSION

The SPT and HR test with apple and A72 showed a good diagnostic value with a sensitivity of more than 70% and a specificity of 100%. The SCT showed a poor sensitivity to apple, A72 and commercial apple extract. The ML test was not suitable in detecting specific IgE to apple compared with the CAP test. In daily practice a detailed case history about symptoms of oral allergy syndrome combined with a SPT with fresh apple peel or A72 will be useful.

Isolation and biochemical characterization of a thaumatin-like kiwi allergen

BACKGROUND

Kiwi fruit allergy, as well as its association with hypersensitivity to other foods and to pollen, has been extensively reported in the last few years. Several IgE-binding components have been detected in kiwi extract, but only one 30- kd allergen has been isolated; it was identified as actinidin (Act c 1). Recently, we have reported a 24-kd kiwi protein to be a potential major allergen in a group of patients with oral allergy syndrome (OAS).

OBJECTIVE

The aim of this study was to purify and characterize the 24-kd kiwi allergen biochemically.

METHODS

Seven polysensitized patients with OAS to kiwi were used in this study. The kiwi allergen was isolated by using a combination of gel permeation, ion exchange, and immobilized metal ion affinity chromatography. Its biochemical characterization included determination of its isoelectric point, molecular weight, N-terminal sequencing, concanavalin A -binding ability, digestibility in simulated gastric fluid, and antifungal activity. Western blotting, 2-dimensional PAGE immunoblotting, and skin prick tests were performed to characterize the isolated protein immunochemically.

RESULTS

All 7 patients recognized the isolated 24-kd kiwi protein as an allergen. The isolated protein consisted of 2 isoforms with isoelectric points of 9.4 and 9.5 migrated as one protein band of 20 kd after SDS-PAGE under nonreducing conditions or at 24 kd under reducing conditions. The partial N-terminal sequence revealed that it is a thaumatin-like protein (TLP) with concanavalin A -binding ability. The protein showed antifungal activity toward Saccharomyces carlsbergensis, and Candida albicans. The protein was degraded by the simulated gastric fluid within 1 minute. Both isoforms bound IgE from a pool of sera in a 2-dimensional PAGE immunoblot. The TLP elicited positive skin prick test responses in 4 (80 %) of 5 patients with OAS.

CONCLUSION

This study reported isolation and full characterization of a new kiwi allergen, TLP (isoelectric points of 9.4 and 9.5 and molecular weight of 24 kd), which belongs to the family of pathogenesis-related proteins. The isolated protein expressed antifungal activity toward S carlsbergensis and C albicans.

Comparison between the native glycosylated and the recombinant Cup a1 allergen: role of carbohydrates in the histamine release from basophils

BACKGROUND

Cypress pollinosis is an important cause of respiratory allergies. Recently, the Cupressus arizonica major allergen, Cup a1, has been cloned and expressed. The native counterpart of this allergen has been purified and characterized by our group. It has been suggested that sugar moieties play a role in the in vitro IgE binding on Cupressus arizonica pollen extract.

OBJECTIVE

To characterize the immunoreactivity of the recombinant major allergen in comparison with its native counterpart. To evaluate the role of carbohydrate moieties in the IgE-mediated in vitro histamine release from basophils by using the native glycosylated Cup a1 as compared with the recombinant one.

METHODS

Recombinant Cup a1 was expressed in E. coli. IgE reactivity of Cupressaceae-allergic patients on the native as well as the recombinant molecule was investigated by immunoblotting, ELISA experiments and histamine release test from passively sensitized basophils.

RESULTS

Fourteen out of 17 Cup a1-positive sera had IgE antibodies reactive with the native molecule only and lost their reactivity-after periodate deglycosylation of the allergen. Moreover, only native molecule was capable of inducing histamine release by this group of sera. Both the recombinant and the native molecules were recognized by three out of the 17 sera and were equally capable of triggering degranulation.

CONCLUSION

A large number of sera reactive with the major allergen recognize carbohydrate epitopes only. IgE from these sera are able to induce histamine release from basophils and they might play a functional role in the clinical symptoms of allergy.