Component-resolved in vitro diagnosis of carrot allergy in three different regions of Europe

IgE to cyclophilins in pollen-allergic children: Epidemiologic, clinical, and diagnostic relevance of a neglected panallergen

BACKGROUND

Cyclophilins are ubiquitous panallergens whose epidemiologic, diagnostic, and clinical relevance is largely unknown and whose sensitization is rarely examined in routine allergy practice.

OBJECTIVE

We investigated the epidemiologic, diagnostic, and clinical relevance of cyclophilins in seasonal allergic rhinitis and its comorbidities.

METHODS

We examined a random sample of 253 (25%) of 1263 Italian children with seasonal allergic rhinitis from the Panallergens in Pediatrics (PAN-PED) cohort with characterized disease phenotypes. Nested studies of sensitization prevalence, correlation, and allergen extract inhibition were performed in patients sensitized to birch pollen extract but lacking IgE to Bet v 1/2/4 (74/1263) or with highest serum level of IgE to Bet v 1 (26/1263); and in patients with sensitization to various extracts (ragweed, mugwort, pellitory, Plantago, and plane tree), but not to their respective major allergenic molecule, profilins, and polcalcins. IgE to cyclophilin was detected with recombinant Bet v 7, and extract inhibition tests were performed with the same rBet v 7.

RESULTS

IgE to rBet v 7 was detected in 43 (17%) of 253 patients. It was associated with asthma (P < .028) and oral allergy syndrome (P < .017) in univariate but not multivariate analysis adjusted for IgE to profilins (Phl p 12), PR-10s (Bet v 1), and lipid transfer proteins (Pru p 3). IgE to rBet v 7 was also highly prevalent (47/74, 63%) among patients with unexplained sensitization to birch pollen extract. In patients with unexplained sensitization to ragweed, mugwort, pellitory, Plantago and plane tree pollen, the levels of IgE to those extracts correlated with the levels of IgE to rBet v 7, and they were also significantly inhibited by rBet v 7 (inhibition range 45%-74%).

CONCLUSIONS

IgE sensitization to cyclophilin is frequent in pollen-allergic patients living in temperate areas and can produce "false" positive outcomes in skin prick and IgE tests to pollen extracts. Molecular diagnostic guidelines should include this panallergen family.

Inconsistent Skin Prick Tests for Allergy to Birch Homologous Trees May Result from Cross-Reacting Allergens or Technical Errors

INTRODUCTION

Skin prick tests (SPTs) are the gold standard for diagnosis of allergic rhinitis (AR). A decrease in the number of allergens included in standard SPT panels has recently been debated - particularly regarding the cross-reacting homologous pollen from birch, alder, and hazel trees - but has not yet been implemented in clinical guidelines.

METHODS

A subgroup of patients with AR (n = 69) who showed inconsistent SPT results among birch, alder, and hazel was investigated in detail. Beyond SPT, patient workup included assessment of clinical relevance and various serological parameters (total IgE, and specific IgE to birch, alder, and hazel and to Bet v 1, Bet v 2, and Bet v 4).

RESULTS

More than half the study group had negative SPT results for birch but positive results for alder and/or hazel, and 87% of the study group was polysensitized, showing at least one more positive SPT result for other plants. Whereas 30.4% of patients showed serological sensitization to birch pollen extract, only 18.8% displayed positive specific IgE to Bet v 1. Clinical assessment revealed that most patients with AR were polysensitized and had perennial symptoms or symptoms also occurring during times other than tree flowering times. If the SPT panel is limited to testing birch only, 52.2% of patients in this subgroup would have been overlooked.

CONCLUSION

Inconsistent SPT results in the birch homologous group may result from cross-reacting allergens or technical errors. If patients report convincing clinical symptoms despite negative results from a reduced SPT panel or inconsistent results for homologous allergens, SPT should be repeated, and molecular markers should be added to achieve a correct diagnosis.

EAACI Molecular Allergology User's Guide 2.0

Since the discovery of immunoglobulin E (IgE) as a mediator of allergic diseases in 1967, our knowledge about the immunological mechanisms of IgE-mediated allergies has remarkably increased. In addition to understanding the immune response and clinical symptoms, allergy diagnosis and management depend strongly on the precise identification of the elicitors of the IgE-mediated allergic reaction. In the past four decades, innovations in bioscience and technology have facilitated the identification and production of well-defined, highly pure molecules for component-resolved diagnosis (CRD), allowing a personalized diagnosis and management of the allergic disease for individual patients. The first edition of the "EAACI Molecular Allergology User's Guide" (MAUG) in 2016 rapidly became a key reference for clinicians, scientists, and interested readers with a background in allergology, immunology, biology, and medicine. Nevertheless, the field of molecular allergology is moving fast, and after 6 years, a new EAACI Taskforce was established to provide an updated document. The Molecular Allergology User's Guide 2.0 summarizes state-of-the-art information on allergen molecules, their clinical relevance, and their application in diagnostic algorithms for clinical practice. It is designed for both, clinicians and scientists, guiding health care professionals through the overwhelming list of different allergen molecules available for testing. Further, it provides diagnostic algorithms on the clinical relevance of allergenic molecules and gives an overview of their biology, the basic mechanisms of test formats, and the application of tests to measure allergen exposure.

Food-Dependent Exercise-Induced Anaphylaxis Caused by Carrots: A Case Report

Background: Most cases of food-dependent exercise-induced anaphylaxis (FDEIA) are caused by eating wheat or crustaceans. However, fruits or vegetables may rarely act as allergens for FDEIA. We report a rare case of FDEIA caused by eating carrots. Case Presentation: An 8-year-old boy developed an anaphylactic reaction while playing, after eating lunch that included cooked carrots. Serum carrot-specific immunoglobulin E level was 0.19 UA/mL. The prick-by-prick test for raw carrots was positive (wheal diameter: 4 mm). The patient developed urticaria after exercise provocation tests following ingestion of raw carrots. Carrot proteins were analyzed by 2-dimensional Western blotting to identify the causative allergens. Nine proteins were identified as candidate antigens at 21-66 kDa. Conclusions: Our patient presented with FDEIA symptoms after ingesting both raw and cooked carrots. Both raw and cooked carrots contain 9 proteins that may induce FDEIA.

BSACI guideline for the diagnosis and management of pollen food syndrome in the UK

Pollen food syndrome (PFS) is a highly prevalent food allergy affecting pollen-sensitized children and adults. Sufferers experience allergic symptoms when consuming raw plant foods, due to the homology between the pollen allergens and unstable proteins in these foods. The triggers involved can vary depending on the pollen sensitization, which in turn is affected by geographical location. The British Society of Allergy and Clinical Immunology (BSACI) Standards of Care Committee (SOCC) identified a need to develop a guideline for the diagnosis and management of PFS in the United Kingdom (UK). Guidelines produced by the BSACI use either the GRADE or SIGN methodology; due to a lack of high-quality evidence these recommendations were formulated using the SIGN guidelines, which is acknowledged to be less robust than the GRADE approach. The correct diagnosis of PFS ensures the avoidance of a misdiagnosis of a primary peanut or tree nut allergy or confusion with another plant food allergy to non-specific lipid transfer proteins. The characteristic foods involved, and rapid-onset oropharyngeal symptoms, mean PFS can often be diagnosed from the clinical history alone. However, reactions involving tree nuts, peanuts and soya milk or severe/atypical reactions to fruits and vegetables may require additional diagnostic tests. Management is through the exclusion of known trigger foods, which may appear to be simple, but is highly problematic if coupled with a pre-existing food allergy or for individuals following a vegetarian/vegan diet. Immunotherapy to pollens is not an effective treatment for PFS, and although oral or sublingual immunotherapy to foods seems more promising, large, controlled studies are needed. The typically mild symptoms of PFS can lead to an erroneous perception that this condition is always easily managed, but severe reactions can occur, and anxiety about the onset of symptoms to new foods can have a profound effect on quality of life.

Prevalence of sensitization to molecular food allergens in Europe: A systematic review

Background

Recent reports indicate that the prevalence of food allergy is increasing, but accurate estimates remain a challenge due to cross-reactivity and limited use of precise diagnostic methods. Molecular allergy diagnostics, in which sensitization to individual molecular allergens is measured, is emerging as a promising tool for evaluation of sensitization profiles. In this systematic review, we summarized estimates of prevalence of sensitization to molecular food allergens in the general population in Europe.

Methods

Following a protocol prospectively registered with the International Prospective Register of Systematic Reviews (PROSPERO; reference CRD42021266657), we searched seven databases with no restrictions on publication date or language. Two reviewers independently screened the literature, extracted data, and appraised the risk of bias in the included studies. The findings were synthesized narratively.

Results

From 4776 de-duplicated records, five studies, with low to moderate overall risk of bias, were included. Forty-six molecular allergens from 18 foods were investigated. Overall, the prevalence of sensitization was low, particularly for major allergens, and non-existent for 10 molecular allergens (0% [95% CI 0-0.8]). The highest prevalence was seen for PR-10 proteins, such as Cor a 1.04 (13.6% [95% CI 10.9-16.9]).

Conclusions

Available data, primarily from North-western Europe, indicate that sensitization to molecular food allergens is overall low. The highest estimates were found for cross-reactive PR-10 proteins. There were not enough studies to discern regional differences or perform meta-analysis, highlighting the need for more population-representative studies in order to elucidate patterns of sensitization to molecular food allergens in Europe.

Structural characterization of the Pet c 1.0201 PR-10 protein isolated from roots of Petroselinum crispum (Mill.) Fuss

The native dimeric Petroselinum crispum (Mill.) Fuss protein Pet c 1.0201 and a monomeric xyloglucan endotransglycosylase enzyme (Garajova et al., 2008) isolated from the root cells co-purify and share similar molecular masses and acidic isoelectric points. In this work, we determined the complete primary structure of the parsley Pet c 1.0201 protein, based on tryptic and chymotryptic peptides followed by the manual micro-gradient chromatographic separation coupled with offline MALDI-TOF/TOF mass spectrometry. The bioinformatics approach enabled us to include the parsley protein into the PR-10 family, as it exhibited the highest protein sequence identity with the Apium graveolens Api g 1.0201 allergen and the major Daucus carota allergen Dau c 1.0201. Hence, we designated the Petroselinum crispum protein as Pet c 1.0201 and deposited it in the UniProt Knowledgebase under the accession C0HKF5. 3D protein homology modelling and molecular dynamics simulations of the Pet c 1.0201 dimer confirmed the typical structure of the Bet v 1 family allergens, and the potential of the Pet c 1.0201 protein to dimerize in water. However, the behavioural properties of Pet c 1.0201 and the celery allergen Api g 1.0101 differed in the presence of salts due to transiently and stably formed dimeric forms of Pet c 1.0201 and Api g 1.0101, respectively.

Allergen Recognition Patterns in Walnut Allergy Are Age Dependent and Correlate with the Severity of Allergic Reactions

BACKGROUND

Walnut is an important elicitor of food allergy in children and adults with a high rate of severe reactions. Multicenter studies using a common clinical protocol and a comprehensive allergen are lacking.

OBJECTIVE

To investigate potential correlations between molecular sensitization patterns and clinical characteristics of walnut-allergic patients.

METHODS

A total of 91 walnut-allergic subjects and 24 tolerant controls from Switzerland, Germany, and Spain were included. Walnut allergy was established by food challenge in all but anaphylactic subjects. Specific IgE (sIgE) to walnut extract, rJug r 1 (2S albumin), rJug r 3 (nonspecific lipid transfer protein 1), nJug r 4 (11S globulin), rJug r 5 (PR-10 protein), 2 vicilin fractions, profiling, and cross-reactive carbohydrate determinant was determined by ImmunoCAP. A threshold of 0.10 kU_A/L was used for positivity.

RESULTS

Sensitivity of sIgE to walnut extract was 87% and increased to 96% for the sum of all walnut components. sIgE to walnut extract and all walnut components, except rJug r 5, was significantly higher in patients younger than 14 years at inclusion. Stratification by age at onset of walnut allergy led to similar results. All patients younger than 14 years had severe reactions, whereas 38% of patients 14 years or older were mild reactors. Severe reactors (n = 70) had higher sIgE levels than did mild reactors (n = 21) to walnut extract (P < .0001), rJug r 1 (P < .0001), nJug r 4 (P = .0003), and both vicilin fractions (P < .0001), but not to Jug r 3 and Jug r 5.

CONCLUSIONS

Sensitization to walnut storage proteins is acquired in childhood and correlates with severe reactions. sIgE levels to storage proteins Jug r 1 and Jug r 4 and vicilin fractions, but not to nonspecific lipid transfer protein and PR-10 proteins, correlate with systemic reactions to walnut.

Mass spectrometry to complement standardization of house dust mite and other complex allergenic extracts

In the United States, the Center for Biologics Evaluation and Research of the US Food and Drug Administration regulates biologics used for diagnosis and treatment of allergic diseases. The Code of Federal Regulations 21CFR680.3(e) states that when measured, the potency of an allergenic extract is assessed according to its allergenic activity. As of 2016, 19 allergenic extracts are standardized for potency in the United States. While these standardized extracts constitute a minority of those available, they treat the most prevalent allergies (e.g. grass and ragweed pollens, dust mites, and cat) and those that induce life-threatening anaphylaxis (e.g. Hymenoptera venom). Standardization for potency enhances safety and efficacy of immunotherapy by minimizing the risks of variations in allergen dosing when switching from one lot of manufactured extract to another, and by providing an objective measure of stability of each lot of allergenic extract over time. Allergenic extracts that have multiple immunodominant allergenic proteins are standardized with little or no information about compositional differences among extracts. Here, we propose application of mass spectrometry towards measurement of compositional differences among extracts that may affect the efficacy and safety of allergen immunotherapy. In addition, we discuss of house dust mite allergen extracts as a prototypical complex extract that may be standardized by mass spectrometry.

Molecular allergy diagnostic tests: development and relevance in clinical practice

Molecular allergy is based on identification, characterization and subsequent use of single allergens, being components of complex allergen sources like pollen, mites, furred animals, foods or insect venoms. Only few protein families contain relevant allergens of similar sequence and structure, carrying common IgE epitopes as the basis of cross reactivity. Used as purified or recombinant (glyco)proteins single allergens can potentially improve in-vitro diagnostics, particularly allergen-specific IgE assays through a) increased sensitivity, b) use of risk and marker allergens, c) component-resolved diagnostics (CRD). CRD can differentiate primary, species-specific from secondary, cross-reactive sensitizations to single allergens. Allergen components facilitate an increased analytical sensitivity, particularly if they are underrepresented or missing in conventional allergen extracts. They are mainly used in single assays (singleplex) for the detection of IgE, but also in a microarray format (multiplex) with 112 components from 50 allergen sources with slightly decreased analytical sensitivity. Concepts of molecular allergy can only be separately defined and utilized for each allergen source (pollen, mites, foods or insect venoms). As soon as essential singe allergens are available, their specific role in diagnostics should be defined. This requires well characterized patient cohorts from various countries, since exposure, allergic immune response and clinical relevance can vary substantially between individual subjects and geographical regions. The patient's clinical information is essential for proper interpretation of molecular allergology results. The history and/or challenge test results will finally provide evidence, in how far a sensitization to single allergens might be clinically relevant or not.

Characterization of the T-cell response to Dau c 1, the Bet v 1-homolog in carrot

BACKGROUND

In contrast to other Bet v 1-related food allergens, the major carrot allergen, Dau c 1, has been suggested to induce food allergy independently from Bet v 1. As T cells are crucial in the sensitization process, we sought to characterize the T-cell response to Dau c 1 and its cross-reactivity with Bet v 1.

METHODS

Dau c 1-specific T-cell lines (TCL) and clones (TCC) established from PBMC of birch pollen-allergic patients with carrot allergy were analyzed for reactivity to Bet v 1, epitope specificity, allergen-induced cytokine secretion, and expression of integrins α4β7 and α4β1, critical for gut and lung homing, respectively. mRNA expression of GATA3 and Tbet was analyzed in sorted CD3+ CD4+ CFSElow cells proliferating upon stimulation of PBMC with Dau c 1 or Bet v 1. Dau c 1 was incubated with endolysosomal proteases, and the resulting fragments were identified by mass spectrometry.

RESULTS

Among 14 distinct T-cell-activating regions, Dau c 1139-153 was recognized by 55% of the patients. Only 6 of 15 (40%) Dau c 1-specific TCL and 9 of 21 (43%) TCC reacted with Bet v 1. Bet v 1-nonreactive TCC were mainly Th1-like and showed a higher expression of the integrin β7 and a significantly lower expression of the integrin β1 than Bet v 1-positive TCC. A Th1-like response was also detected in Dau c 1-reactive CD3+ CD4+ CFSElow cells. Full-length Dau c 1 was still detectable after 48 h of endolysosomal degradation. Proteolytic fragments of Dau c 1 matched its T-cell-activating regions.

CONCLUSION

Dau c 1 displays several characteristics of sensitizing allergens, namely a major T-cell-activating region, low susceptibility to endolysosomal degradation, and induction of a Bet v 1-independent T-cell response. These cellular insights confirm that the major carrot allergen has a special status among Bet v 1-related food allergens.

The conformational IgE epitope profile of soya bean allergen Gly m 4

BACKGROUND

Birch pollen-related soya allergy is mediated by Gly m 4. Conformational IgE epitopes of Gly m 4 are unknown.

OBJECTIVE

To identify the IgE epitope profile of Gly m 4 in subjects with birch pollen-related soya allergy utilizing an epitope library presented by Gly m 4-type model proteins.

METHODS

Sera from patients with (n = 26) and without (n = 19) allergy to soya as determined by oral provocation tests were studied. Specific IgE (Bet v 1/Gly m 4) was determined by ImmunoCAP. A library of 59 non-allergenic Gly m 4-type model proteins harbouring individual and multiple putative epitopes for IgE was tested in IgE binding assays. Primary, secondary and tertiary protein structures were assessed by mass spectrometry, circular dichroism and nuclear magnetic resonance spectroscopy.

RESULTS

All subjects were sensitized to Gly m 4 and Bet v 1. Allergen-specific serum IgE levels ranged from 0.94 to > 100 kU_A /L. The avidities of serum IgE were 5.06 ng (allergic) and 1.8 ng (tolerant) as determined by EC₅₀ for IgE binding to Gly m 4. 96% (46/48) of the protein variants bound IgE. Model proteins had Gly m 4-type conformation and individual IgE binding clustered in six major surface areas. Gly m 4-specific IgE binding could be inhibited to up to 80% by model proteins harbouring individual IgE binding sites in an epitope-wise equimolar fashion. Receiver operating curve analysis revealed an area under fitted curve of up to 0.88 for model proteins and 0.66 for Gly m 4.

CONCLUSION AND CLINICAL RELEVANCE

Serum levels and avidity of Gly m 4-specific IgE do not correlate with clinical reactivity to soya. Six IgE-binding areas, represented by 23 amino acids, account for more than 80% of total IgE binding capacity of Gly m 4. Model proteins may be used for epitope-resolved diagnosis to differentiate birch-soya allergy from clinical tolerance.

EAACI Molecular Allergology User's Guide

The availability of allergen molecules ('components') from several protein families has advanced our understanding of immunoglobulin E (IgE)-mediated responses and enabled 'component-resolved diagnosis' (CRD). The European Academy of Allergy and Clinical Immunology (EAACI) Molecular Allergology User's Guide (MAUG) provides comprehensive information on important allergens and describes the diagnostic options using CRD. Part A of the EAACI MAUG introduces allergen molecules, families, composition of extracts, databases, and diagnostic IgE, skin, and basophil tests. Singleplex and multiplex IgE assays with components improve both sensitivity for low-abundance allergens and analytical specificity; IgE to individual allergens can yield information on clinical risks and distinguish cross-reactivity from true primary sensitization. Part B discusses the clinical and molecular aspects of IgE-mediated allergies to foods (including nuts, seeds, legumes, fruits, vegetables, cereal grains, milk, egg, meat, fish, and shellfish), inhalants (pollen, mold spores, mites, and animal dander), and Hymenoptera venom. Diagnostic algorithms and short case histories provide useful information for the clinical workup of allergic individuals targeted for CRD. Part C covers protein families containing ubiquitous, highly cross-reactive panallergens from plant (lipid transfer proteins, polcalcins, PR-10, profilins) and animal sources (lipocalins, parvalbumins, serum albumins, tropomyosins) and explains their diagnostic and clinical utility. Part D lists 100 important allergen molecules. In conclusion, IgE-mediated reactions and allergic diseases, including allergic rhinoconjunctivitis, asthma, food reactions, and insect sting reactions, are discussed from a novel molecular perspective. The EAACI MAUG documents the rapid progression of molecular allergology from basic research to its integration into clinical practice, a quantum leap in the management of allergic patients.

Comparison and clinical utility evaluation of four multiple allergen simultaneous tests including two newly introduced fully automated analyzers

Background

We compared the diagnostic performances of two newly introduced fully automated multiple allergen simultaneous tests (MAST) analyzers with two conventional MAST assays.

Methods

The serum samples from a total of 53 and 104 patients were tested for food panels and inhalant panels, respectively, in four analyzers including AdvanSure AlloScreen (LG Life Science, Korea), AdvanSure Allostation Smart II (LG Life Science), PROTIA Allergy-Q (ProteomeTech, Korea), and RIDA Allergy Screen (R-Biopharm, Germany). We compared not only the total agreement percentages but also positive propensities among four analyzers.

Results

Evaluation of AdvanSure Allostation Smart II as upgraded version of AdvanSure AlloScreen revealed good concordance with total agreement percentages of 93.0% and 92.2% in food and inhalant panel, respectively. Comparisons of AdvanSure Allostation Smart II or PROTIA Allergy-Q with RIDA Allergy Screen also showed good concordance performance with positive propensities of two new analyzers for common allergens (Dermatophagoides farina and Dermatophagoides pteronyssinus). The changes of cut-off level resulted in various total agreement percentage fluctuations among allergens by different analyzers, although current cut-off level of class 2 appeared to be generally suitable.

Conclusions

AdvanSure Allostation Smart II and PROTIA Allergy-Q presented favorable agreement performances with RIDA Allergy Screen, although positive propensities were noticed in common allergens.

•

Two new multiple allergen simultaneous tests (MAST) analyzers are evaluated.

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AdvanSure Smart II and PROTIA presented favorable agreement performance with RIDA.

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Positive propensity of new assays for D. farina and D. pteronyssinus was noticed.

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The changes of cut-off level resulted in total agreement percentage fluctuations.

Quality Control of Biomedicinal Allergen Products - Highly Complex Isoallergen Composition Challenges Standard MS Database Search and Requires Manual Data Analyses

Allergy against birch pollen is among the most common causes of spring pollinosis in Europe and is diagnosed and treated using extracts from natural sources. Quality control is crucial for safe and effective diagnosis and treatment. However, current methods are very difficult to standardize and do not address individual allergen or isoallergen composition. MS provides information regarding selected proteins or the entire proteome and could overcome the aforementioned limitations. We studied the proteome of birch pollen, focusing on allergens and isoallergens, to clarify which of the 93 published sequence variants of the major allergen, Bet v 1, are expressed as proteins within one source material in parallel. The unexpectedly complex Bet v 1 isoallergen composition required manual data interpretation and a specific design of databases, as current database search engines fail to unambiguously assign spectra to highly homologous, partially identical proteins. We identified 47 non-allergenic proteins and all 5 known birch pollen allergens, and unambiguously proved the existence of 18 Bet v 1 isoallergens and variants by manual data analysis. This highly complex isoallergen composition raises questions whether isoallergens can be ignored or must be included for the quality control of allergen products, and which data analysis strategies are to be applied.

Component-resolved diagnostics in vernal conjunctivitis

BACKGROUND

Conventional diagnostic tests in allergy are insufficient to clarify the origin of vernal conjunctivitis (VC).

OBJECTIVES

To evaluate IgE-mediated hypersensitivity by component-resolved diagnosis (CRD) in tears and serum from patients with VC and to evaluate how to treat patients with identified triggering allergens by specific immunotherapy.

METHODS

Patients were divided into 3 groups: (1) patients with VC (25 patients), (2) patients allergic to grass pollen with seasonal allergic conjunctivitis (AC) (50 patients), and (3) healthy blood donors (50 patients). If triggering allergens were detected, specific conventional immunotherapy was administered for 1 year.

RESULTS

Twenty-five patients with VC were evaluated. The identified triggering allergens were n Lol p 1 (11 patients), n Cyn d 1 (8 patients), group 4 and 6 grasses (6 patients), and group 5 grasses (5 patients). Prick test and pollen IgE test results were positive in one patient. Clinical improvement was observed in 13 of the 25 patients with VC after 1 year of specific immunotherapy.

CONCLUSION

CRD seems to be a more sensitive diagnostic tool compared with prick test and IgE detection. Specific CRD-led immunotherapy may achieve clinical improvements in patients with VC.

Applications of Molecular Diagnostic Testing in Food Allergy

IgE-mediated food allergy is a relevant health problem inducing symptoms ranging from mild local reactions up to severe life-threatening situations. Currently, no immunotherapy is available and avoidance of the incriminating food is the method of choice. Therefore, reliable diagnostic tools to formulate dietary recommendations and to avoid unnecessary exclusion diets for the individual patient are urgently needed. This review provides an update on the current knowledge on food allergens and their application in various diagnostic approaches such as skin prick test, basophil activation test, and serum IgE testing. Furthermore, these new approaches are discussed and compared to conventional extract-based assays and correlated to the gold standard of food allergy diagnosis, the double-blind placebo-controlled food challenge. Finally, the application of food allergens for preventive measurements such as allergen detection assays and the determination of threshold levels for allergen levels are discussed.

Hazelnut allergy across Europe dissected molecularly: A EuroPrevall outpatient clinic survey

BACKGROUND

Hazelnut allergy is birch pollen-driven in Northern/Western Europe and lipid transfer protein-driven in Spain and Italy. Little is known about other regions and other allergens.

OBJECTIVE

Establishing a molecular map of hazelnut allergy across Europe.

METHODS

In 12 European cities, subjects reporting reactions to hazelnut (n = 731) were evaluated and sensitization to 24 foods, 12 respiratory allergen sources, and latex was tested by using skin prick test and ImmunoCAP. A subset (124 of 731) underwent a double-blind placebo-controlled food challenge to hazelnut. Sera of 423 of 731 subjects were analyzed for IgE against 7 hazelnut allergens and cross-reactive carbohydrate determinants by ImmunoCAP.

RESULTS

Hazelnut allergy was confirmed in 70% of those undergoing double-blind placebo-controlled food challenges. Birch pollen-driven hazelnut sensitization (Cor a 1) dominated in most cities, except in Reykjavik, Sofia, Athens, and Madrid, where reporting of hazelnut allergy was less frequent anyhow. In Athens, IgE against Cor a 8 dominated and strongly correlated with IgE against walnut, peach, and apple and against Chenopodium, plane tree, and mugwort pollen. Sensitization to seed storage proteins was observed in less than 10%, mainly in children, and correlated with IgE to nuts, seeds, and legumes. IgE to Cor a 12, observed in all cities (10% to 25%), correlated with IgE to nuts, seeds, and pollen.

CONCLUSIONS

In adulthood, the importance of hazelnut sensitization to storage proteins, oleosin (Cor a 12), and Cor a 8 is diluted by the increased role of birch pollen cross-reactivity with Cor a 1. Cor a 8 sensitization in the Mediterranean is probably driven by diet in combination with pollen exposure. Hazelnut oleosin sensitization is prevalent across Europe; however, the clinical relevance remains to be established.

The contribution of biotechnology toward progress in diagnosis, management, and treatment of allergic diseases

'Biotechnology' has been intuitively used by humans since thousands of years for the production of foods, beverages, and drugs based on the experience without any scientific background. However, the golden era of this discipline emerged only during the second half of the last century. Incredible progresses have been achieved on all fields starting from the industrialization of the production of foods to the discovery of antibiotics, the decipherment of the genetic code, and rational approaches to understand and define the status we now call 'healthy'. The extremely complex interactions between genetic background, life style, and environmental factors influencing our continuously increasing life span have become more and more evident and steadily generate new questions which are only partly answered. Here, we try to summarize the contribution of biotechnology to our understanding, control, and cure of IgE-mediated allergic diseases. We are aware that a review of such a vast topic can never cover all aspects of the progress achieved in the different fields.

Anaphylaxis: opportunities of stratified medicine for diagnosis and risk assessment

The risk to develop anaphylaxis depends on the sensitization pattern, the proportion of the involved immunoglobulin classes, the avidity and affinity of immunoglobulins to bind an allergen, characteristics of the allergen, the route of allergen application, and, last but not least, the presence of cofactors of anaphylaxis. To be able to calculate the risk to develop anaphylaxis and to anticipate the severity of the reactions under certain conditions, it is necessary to understand how all these factors interact with each other. Important progress for risk assessment in anaphylaxis is based on component-resolved stratified diagnostics, which allow to (i) determine a patient's sensitization pattern on a molecular basis, (ii) correlate clinical responses to defined sensitization patterns, and (iii) better identify cross-reactive allergens. Together with the increasing knowledge regarding the role and mode of action of cofactors of anaphylaxis, these data pave the way to unscramble the complex interactions determining the clinical relevance of sensitizations, the risk of anaphylaxis, and the severity of reactions. As a consequence, this understanding allows to better determine the individual risk in response to an identified allergen and results in more specific advices and education for our patients to prevent further life-threatening anaphylactic reactions.

Overview of component resolved diagnostics

Component-resolved diagnostics (CRD) utilize purified native or recombinant allergens to detect IgE sensitivity to individual allergen molecules and have become of growing importance in clinical investigation of IgE-mediated allergies. This overview updates current developments of CRD, including multiarray test systems. Cross-reactions between allergens of known allergen families (i.e. to Bet v 1 homologues) are emphasised. In pollinosis as well as in allergy to hymenoptera venoms or to food, CRD allows to some extent discrimination between clinically significant and irrelevant sIgE results and the establishing of sensitisation patterns with particular prognostic outcomes (i.e. sensitisations to storage proteins which correlate with clinically severe reactions in peanut allergy). Further promising improvements in diagnostics are expected from additional, not yet commercially available, recombinant allergen diagnostics identifying particular molecules of risk. Overall, CRD may decrease the need for provocation testing and may also improve the specificity of allergen-specific immunotherapy.