Molecular diagnosis of fruit and vegetable allergy

Fruitful or unfruitful: strawberry and tomato specific immunoglobulin E testing at a tertiary pediatric center

Background

Suspected strawberry and tomato (S/T) food allergy (FA) can be evaluated using specific immunoglobulin E (sIgE) testing despite its low specificity and positive predictive value.

Objective

This study aims to understand ordering patterns for S/T sIgE testing and identify relevant factors to clinical decision-making.

Methods

We retrospectively reviewed 814 patients with sIgE testing available for strawberries (651), tomatoes (276), or both (113) from January 2012 to May 2022 at a tertiary pediatric hospital. Patient demographics, provider specialty, and reasons for testing were collected. Student's t-test and multiple regression analyses were performed to test the association between the S/T sIgE level and clinically relevant outcome (CRO) status. Fisher's exact test and general linear models were used to evaluate and compare potential predictive factors for CRO status.

Results

Allergy and immunology, gastroenterology, and general pediatrics ordered most S/T sIgE testing. Testing was ordered most frequently for non-IgE-mediated gastrointestinal symptoms, mild possible IgE-mediated reactions, and eczema. Testing was most often ordered for infants and school-age children. Mean sIgE levels were higher for S/T tests resulting in a CRO when controlling for other predictor variables (p = 0.015; p = 0.002 for S/T, respectively). Only 2.2% and 5.4% of tests resulted in a CRO for S/T, and severe allergy was rare. Testing for non-IgE-mediated GI symptoms or eczema, or in non-atopic patients, yielded no CROs. Exposure and reaction history of present illness (ERH) was associated with CROs (p < 0.001; p = 0.04) with a high negative predictive value (99.5%; 100%) and low positive predictive value (11.5%; 15.0%). ERH (p < 0.001, η2 = 0.073; p = 0.009, η2 = 0.123) was a more significant predictor than the sIgE level (p = 0.002, η2 = 0.037; p = 0.212, η2 = 0.030) for CRO status.

Conclusion

The diagnosis of S/T food allergy is made primarily based on clinical history. S/T sIgE testing for children and adolescents should be avoided for patients without an ERH and in the workup of non-IgE-mediated GI symptoms. Testing for eczema and non-atopic patients is likely low-yield.

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.

Investigating phenotypic relationships in persimmon accessions through integrated proteomic and metabolomic analysis of corresponding fruits

Together with phenological and genomic approaches, gel-based and label-free proteomic as well metabolomic procedures were separately applied to plants to highlight differences between ecotypes, to estimate genetic variability within/between organism populations, or to characterize specific mutants/genetically modified lines at metabolic level. To investigate the possible use of tandem mass tag (TMT)-based quantitative proteomics in the above-mentioned contexts and based on the absence of combined proteo-metabolomic studies on Diospyros kaki cultivars, we here applied integrated proteomic and metabolomic approaches to fruits from Italian persimmon ecotypes with the aim to characterize plant phenotypic diversity at molecular level. We identified 2255 proteins in fruits, assigning 102 differentially represented components between cultivars, including some related to pomological, nutritional and allergenic characteristics. Thirty-three polyphenols were also identified and quantified, which belong to hydroxybenzoic acid, flavanol, hydroxycinnamic acid, flavonol, flavanone and dihydrochalcone sub-classes. Heat-map representation of quantitative proteomic and metabolomic results highlighted compound representation differences in various accessions, whose elaboration through Euclidean distance functions and other linkage methods defined dendrograms establishing phenotypic relationships between cultivars. Principal component analysis of proteomic and metabolomic data provided clear information on phenotypic differences/similarities between persimmon accessions. Coherent cultivar association results were observed between proteomic and metabolomic data, emphasizing the utility of integrating combined omic approaches to identify and validate phenotypic relationships between ecotypes, and to estimate corresponding variability and distance. Accordingly, this study describes an original, combined approach to outline phenotypic signatures in persimmon cultivars, which may be used for a further characterization of other ecotypes of the same species and an improved description of nutritional characteristics of corresponding fruits.

Cross-Reacting Carbohydrate Determinants Inhibitor Can Improve the Diagnostic Accuracy in Pollen and Food Allergy

Background

Cross-reacting carbohydrate determinants (CCD) exist in some pollen and food allergens, but they do not contribute to allergic symptoms. However, CCD can induce specific IgE (sIgE) production and may lead to incorrect allergen diagnosis and treatment. CCD inhibitor is a specific antibody adsorbent which can preclude CCD from binding to sIgE. Currently, the data of CCD inhibition in allergen sIgE test are limited.

Methods

The allergic patients with positive skin prick reactions to two or more pollen and/or food allergen extracts were included in our study. Their sera were obtained and sIgE was tested with an allergen panel that included 29 single and mixed allergens (MEDIWISS Analytic GmbH, China) before and after CCD inhibition. The changes of sIgE against these allergens and the correlations of sIgEs to clinical symptoms were analyzed.

Results

A total of 44 patients were included and 36 (81.82%) of those were multi-sensitized to house dust mites and pollen allergens based on skin prick tests. The sIgE levels and positive rates against most pollen and food allergens were significantly lower after CCD inhibition. The sIgE levels of pollen were positively correlated to those of food allergens before CCD inhibition. However, these correlations were weakened or no longer existed after CCD inhibition. The sIgE against pollen and food allergens showed significantly higher consistency with clinical symptoms after CCD inhibition.

Conclusion

Cross-sensitization caused by CCD is widespread in pollen and food. CCD inhibition test can improve the diagnostic accuracy of pollen and food allergy.

Tomato Allergy: The Characterization of the Selected Allergens and Antioxidants of Tomato (Solanum lycopersicum)-A Review

Tomatoes are one of the most broadly produced and consumed crop plants. They are the source of health-promoting nutrients such as antioxidants, including ascorbic acid, polyphenols, or carotenoids. Despite the beneficial role of tomatoes in the daily diet, they have been confirmed as one of the most prevalent allergenic vegetables. Food allergies can cause many clinical symptoms, e.g., in the gastrointestinal tract, skin, and lungs, as well as anaphylactic shock. A huge amount of clinical research has been carried out to improve the understanding of the immunological mechanisms that lead to the lack of tolerance of food antigens, which can result in either immunoglobulin E (IgE)-mediated reactions or non-IgE-mediated reactions. Lifestyle and diet play an important role in triggering food allergies. Allergy to tomatoes is also linked to other allergies, such as grass pollen and latex allergy. Numerous attempts have been made to identify and characterize tomato allergens; however, the data available on the subject are not sufficient.

Combining Anti-IgE Monoclonal Antibodies and Oral Immunotherapy for the Treatment of Food Allergy

Immunoglobulin E (IgE)-mediated food allergy is a real public health problem worldwide. The prevalence of food allergy is particularly high in children. Patients with food allergy experience high morbidity with a change in quality of life due to the risk of severe anaphylaxis. Current treatment options are poor. Allergen avoidance is widely recommended but exposes patients to accidental ingestion. Oral immunotherapy is also used in patients with food allergies to the most common allergens. Oral immunotherapy consists of a daily administration of small, gradually increasing amounts of allergens to induce desensitisation. This procedure aims at inducing immune tolerance to the ingested food allergens. However, some patients experience adverse reactions and discontinue oral immunotherapy.Given that IgE plays a crucial role in food allergy and anti-IgE are effective in allergic asthma, the use of anti-IgE therapeutic monoclonal antibodies (mAbs) such as omalizumab has been assessed in food allergy patients. The use of omalizumab as a monotherapy in food allergy has not been extensively studied but looks promising. There is more published evidence regarding the effect of omalizumab and oral immunotherapy in food allergy. Given the promising results of oral immunotherapy regarding sustained tolerance in clinical trials and the potential capacity of omalizumab to reduce symptoms in case of accidental exposure, a strategy combining oral immunotherapy with omalizumab pre-treatment has been suggested as a safer option in patients with severe food allergy compared to isolated therapy. Omalizumab seems useful in ensuring safer administration of oral immunotherapy with the oral immunotherapy maintenance dose being reached more rapidly. Quality-of-life improvement is greater with oral immunotherapy + omalizumab compared to oral immunotherapy alone. Moreover, sustained unresponsiveness is achieved more frequently with omalizumab. Considering that precision medicine and personalised therapy are major goals for allergic diseases, predictive biomarkers are crucial in order to identify food allergy patients more likely to benefit from anti-IgE therapies.

Update of the S2k guideline on the management of IgE-mediated food allergies

Not available.

IgE-Reactivity Pattern of Tomato Seed and Peel Nonspecific Lipid-Transfer Proteins after in Vitro Gastrointestinal Digestion

The influence of gastrointestinal digestion on the immunological properties of three different nonspecific lipid-transfer proteins (nsLTPs) described in tomato fruit has been assessed using an in vitro system mimicking the stomach and intestine digestion conditions. Tomato peel/pulp nsLTP, Sola l 3, was degraded after digestion, although the immunoglobulin E (IgE) recognition of intact protein and a 10 kDa band were still observed after 30 min of duodenal digestion in the presence of phosphatidylcholine. The tomato seed nsLTP, Sola l 7, showed a higher stability than the other seed allergen, Sola l 6, during digestion. Sola l 7 showed an IgE immunoreactive 6.5 kDa band in immunoblotting analysis, retaining up to 7% of its IgE-binding capacity in inhibition ELISA test after 60 min of duodenal digestion and keeping intact its ability to activate basophils after digestion. These results suggest that the tomato seed allergen Sola l 7 might be considered as an important allergen in the induction of allergic responses to tomato due to its high stability against gastrointestinal digestion.

Comparative Study of Food Allergies in Children from China, India, and Russia: The EuroPrevall-INCO Surveys

BACKGROUND

A clear understanding of the differences in the epidemiology of food allergy between rural and urban populations may provide insights into the causes of increasing prevalence of food allergy in the developed world.

OBJECTIVE

We used a standardized methodology to determine the prevalence and types of food-specific allergic sensitization and food allergies in schoolchildren from urban and rural regions of China, Russia, and India.

METHODS

The current study is a multicenter epidemiological survey of children recruited from 5 cities in China (Hong Kong and Guangzhou), Russia (Tomsk), and India (Bengaluru and Mysore) and 1 rural county in Southern China (Shaoguan). A total of 35,549 children aged 6 to 11 years from 3 countries participated in this survey. Random samples of children from 3 countries were first screened by the EuroPrevall screening questionnaire. Children with and without a history of adverse reactions to foods were then recruited for the subsequent case-control comparative studies. We determined the prevalence rates of food-specific IgE sensitization and food allergies using the predefined criteria.

RESULTS

The prevalence rates of food-specific IgE sensitization (≥0.7 kU/L) to at least 1 food were 16.6% in Hong Kong, 7.0% in Guangzhou, 16.8% in rural Shaoguan, 8.0% in Tomsk, and 19.1% in India. Using a definition of probable food allergy as reporting allergic symptoms within 2 hours of ingestion of a specific food plus the presence of allergic sensitization to the specific food (positive IgE and/or positive skin prick test result), the prevalence of food allergy was highest in Hong Kong (1.50%), intermediate in Russia (0.87%), and lowest in Guangzhou (0.21%), Shaoguan (0.69%), and India (0.14%). For children recruited from Hong Kong, both sensitization and food allergy were significantly higher in children who were born and raised in Hong Kong when compared with those who were born in mainland China and migrated to Hong Kong, highlighting the importance of early-life exposures in affecting the subsequent development of food sensitization and food allergy.

CONCLUSIONS

There are wide variations in the prevalence of food-specific IgE sensitization and food allergy in the 3 participating countries. Food allergy appears to be less common when compared with developed countries. The variations in the prevalence of food allergen sensitization cannot be explained by the differences in the degree of urbanization. Despite the high prevalence of food-specific IgE sensitization in India and rural China, food allergy is still extremely uncommon. In addition to IgE sensitization, other factors must play important roles resulting in the clinical manifestations of food allergies.

Component-Resolved Diagnosis in Food Allergies

Component-resolved diagnostics (CRD) in food allergies is an approach utilized to characterize the molecular components of each allergen involved in a specific IgE (sIgE)-mediated response. In the clinical practice, CRD can improve diagnostic accuracy and assist the physician in many aspects of the allergy work-up. CRD allows for discriminatory co-sensitization versus cross-sensitization phenomena and can be useful to stratify the clinical risk associated with a specific sensitization pattern, in addition to the oral food challenge (OFC). Despite this, there are still some unmet needs, such as the risk of over-prescribing unnecessary elimination diets and adrenaline auto-injectors. Moreover, up until now, none of the identified sIgE cutoff have shown a specificity and sensitivity profile as accurate as the OFC, which is the gold standard in diagnosing food allergies. In light of this, the aim of this review is to summarize the most relevant concepts in the field of CRD in food allergy and to provide a practical approach useful in clinical practice.

Detection of allergen coding sequences of kiwi, peach, and apple in processed food by qPCR

BACKGROUND

Food traceability becomes lifesaving for persons suffering severe allergy or intolerance, and therefore need a complete avoidance of the immune-trigger food. This paper describes how to fingerprint the presence of some allergenic species (kiwi, peach, and apple) in foods by quantitative real-time PCR (qPCR).

RESULTS

Five DNA extraction procedures were tested on fruits and foods. The results were statistically evaluated, and discussed. Analysis by qPCR with SYBR Green was developed to detect traces of these allergenic species in foods. Plasmids containing the target sequences of kiwi, peach and apple were employed as internal reference standard. Analysis of spiked food samples showed a limit of detection of 25 mg kg^-1 for kiwi, 20 mg kg^-1 for peach and 50 mg kg^-1 for apple.

CONCLUSION

The qPCR method here developed, combined with the use of internal plasmid reference standard, represents a specific system for the quick detection of allergenic species in complex food matrices, with a limit of detection comparable with those reported using more time-consuming methods. © 2017 Society of Chemical Industry.

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.

Development and Application of a Multiplex Real-Time PCR Assay as an Indicator of Potential Allergenicity in Citrus Fruits

The effects of tissue type, harvest maturity, and genetic factors on the expression of genes that related to citrus fruit allergies remain poorly understood. In the present study, a multiplex real-time PCR assay was developed to monitor the expression of citrus allergen genes individually with the advantages of much fewer sample requirements and simultaneously multiple target genes detection. Gene specific primer pairs and Taqman probes of three citrus allergen genes Cit s 1.01, Cit s 2.01, and Cit s 3.01 and the house-keeping gene β-actin were designed based on gene sequence differences. The PCR results showed that differential expression patterns were found during the ripening process. The expression levels of Cit s 3.01 were much higher than those of Cit s 1.01 and Cit s 2.01 in both peel and pulp tissues among 10 citrus cultivars. Data suggested that Kao Phuang Pummelo could be safely consumed with a potential low risk in allergenicity. Considering that assessing allergenicity is one of the tests in food safety, this assay might also facilitate the breeding and production of "allergy-friendly" citrus fruits.

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.

A case study of apple seed and grape allergy with sensitisation to nonspecific lipid transfer protein

Lipid transfer proteins can be an important cause of allergy given their stability and high degree of protein sequence homology. We describe the case of a child who developed two separate episodes of anaphylaxis after consuming apple seed and grape, with evidence that nonspecific lipid transfer proteins may have been responsible for these reactions. Lipid transfer protein allergy should be considered when anaphylaxis is inconsistent, such as in patients who can tolerate fruit pulp but react to fresh whole fruit juices.

Allergenic Potential of Tomatoes Cultivated in Organic and Conventional Systems

Tomatoes (Lycopersicon esculentum Mill.) are a widely consumed vegetables and contain many health beneficial micronutrients. Unfortunately, they may also cause adverse allergic reactions in sensitized people. Many studies, conducted in recent years, indicate that organically produced vegetables have higher nutritional value, improved sensory quality and contain more health-enhancing bioactive compounds than vegetables grown under the conventional system. However, the relation between organic methods of cultivation and allergenic potential of tomatoes has received little scientific attention. This study analyzed samples of five tomato cultivars taken from organic and conventional systems over three consecutive years. The content of profilin, Bet v 1 and lipid transfer protein (LTP) analogues in tomato samples was determined using an indirect ELISA assay. Substantial quantities of these proteins were found in certain cultivars across all three years of cultivation. On the basis of these findings, organically grown tomatoes appear to offer little advantage over conventionally cultivated plants in terms of reduced allergenic potential.

The importance of EN ISO 15189 accreditation of allergen-specific IgE determination for reliable in vitro allergy diagnosis

BACKGROUND

Allergen-specific serum immunoglobulin E detection and quantification have become an important step in allergy diagnosis and follow-up. In line with the current trend of laboratory test accreditation to international standards, we set out to design and assess an accreditation procedure for allergen-specific serum IgE.

METHODS

Method validation according to the accreditation procedure under the EN ISO 15189 standard was carried out for allergen-specific immunoglobulin E determination using the fluoroimmunoenzymatic method ImmunoCAP(®) (ThermoFisher). Data were produced by 25 hospital laboratories in France. A total of 29 allergen specificities including mixes, extracts, and molecular allergens were assayed. Allergen-specific serum immunoglobulin E concentrations ranged from 0.1 to 100 kUA /l.

RESULTS

Repeatability, reproducibility, and accuracy results fulfilled method validation criteria for automated laboratory tests and proved similar irrespective of the allergen specificity, allergen-specific serum immunoglobulin E concentration, or individual laboratory.

CONCLUSION

Allergen-specific serum immunoglobulin E determination with the fluoroimmunoenzymatic method ImmunoCAP(®) is a highly repeatable, reproducible, and accurate method which may be considered as a single analyte assay in view of the EN ISO 15189 accreditation procedure.

[Personalised medicine for the diagnosis and treatment of allergic diseases]

Immunoglobulin E (IgE) mediated allergic diseases are characterised by heterogeneous clinical phenotypes and a large variety of different sensitisation patterns. Apart from genetic predisposition several environmental factors play a role in sensitisation and elicitation of symptoms. Since the majority of clinically relevant allergens are now available as purified recombinant allergens component-resolved in vitro diagnosis allows the sensitization profile of allergic patients to be determined at the molecular level. Such data may allow physicians to draw conclusions on the severity and persistence of a given allergic disease and to predict the outcome of allergen-specific immunotherapy (SIT) However, the potential of this approach needs to be demonstrated in controlled clinical trials. Moreover, in the context of atopic dermatitis, allergic rhinitis, allergic bronchial asthma as well as the atopic march several screening-biomarkers, diagnostic and prognostic biomarkers, biomarkers of severity and predictive biomarkers are presented and discussed in this article. Traditionally a relevant proportion of allergen-specific immunotherapies is performed in a personalised manner using named patient products manufactured on the basis of an individual prescription. Such named patient products are often mixtures containing several allergen extracts from different sources. However, there is no proven evidence for the safety and efficacy of this approach. In Germany the Therapy Allergen Ordinance ("Therapieallergene-Verordnung", TAV) regulates that in the future allergen products for SIT of insect venom allergies, allergies to pollen of early flowering trees and grass pollen and house dust mite allergies cannot be marketed as named patient products, but always require a marketing authorisation. Thus personalised SIT with named patient products is restricted to the treatment of less prevalent allergies, for which the generation of state-of-the-art clinical data is more difficult. Several recombinant allergens are currently evaluated in phase III clinical trials. In contrast to allergen extracts recombinant allergens offer the possibility to treat patients with a precisely adjusted mixture of the disease-eliciting allergen molecules. However, the implementation of this personalised approach to SIT within the given regulatory framework represents a challenge to regulators.

Value of allergy tests for the diagnosis of food allergy

Eosinophilic esophagitis (EoE) is a chronic T helper 2-type inflammatory disorder. Concurrent allergic diseases have been observed in EoE cases at a high prevalence. The observation that EoE responds to dietary treatment suggests that EoE is an antigen-driven process. However, the pathogenesis by which allergens mediate the eosinophilic disease in the esophagus needs further clarification. In immediate-type food allergy, diagnosis is based on a careful case history followed by a search for food-specific IgE either by skin testing [skin prick test (SPT)] or in vitro (e.g. ImmunoCAP). In children with atopic dermatitis and a food allergy to milk, eggs, peanuts, fish or wheat, the SPT and in vitro determination of specific IgE show excellent sensitivity and negative predictive values, whereas the positive predictive values are low. In pollen-related secondary food allergy, sensitivity and negative predictive values of IgE testing is much lower. Consequently, oral food provocation is the gold standard for the diagnosis of food allergy. Similarly, in EoE patients, SPT, atopy patch test and in vitro determination of IgE to foods do not reliably predict food allergy, and the average positive predictive values of these allergy tests are below 50%. In conclusion, the value of allergy tests to identify triggering foods are limited, and triggering foods have to be identified by an elimination diet and consequent reintroduction of single foods under biopsy control. However, due to the high prevalence of concurrent allergic diseases among EoE patients, an allergy work-up is urgently indicated in each patient with EoE.

Identification and characterization of a basic thaumatin-like protein (TLP 2) as an allergen in sapodilla plum (Manilkara zapota)

SCOPE

Cases of oral allergy syndrome following the ingestion of sapodilla plum (Manilkara zapota) have been reported rarely. As the causative allergens are not known, the main objective of this study was to identify and characterize the important allergens in sapodilla.

METHODS AND RESULTS

Allergy to sapodilla was diagnosed by case history, skin prick test, and serum allergen-specific IgE. The allergen was detected by IgE immunoblotting, purified on SP-Sepharose and characterized by native/SDS-PAGE, IEF, MS, and amino acid composition. Several cases of allergy to sapodilla fruit were identified; majority of the sapodilla-allergic subjects (6/7) experienced typical oral allergy syndrome symptoms, and allergen-specific IgE to the purified protein was positive. The allergen has a pI ≥9.5 and high contents of arginine, threonine, glycine, and cysteine. Circular dichroism revealed a secondary structure rich in beta sheets/turns. Based on its N-terminal sequence of A-T-F-D-I-Q-N-N-C-X-Y-, the allergen (21 578 Da) was identified as a thaumatin-like protein by homology.

CONCLUSION

The causative allergen in sapodilla plum has been identified and characterized as a highly basic thaumatin-like protein belonging to the pathogenesis-related protein (PR-5) family, which has been recognized as a new family of conserved, cross-reactive plant allergens.

Characterization and gene cloning of an acidic thaumatin-like protein (TLP 1), an allergen from sapodilla fruit (Manilkara zapota)

BACKGROUND

Allergy to sapodilla (Manilkara zapota) fruit ingestion is rare. An independent study from our group has identified a basic thaumatin-like protein (TLP 2) as the major allergen. The present study was aimed at identifying and characterizing additional allergens from sapodilla.

METHODS

Allergic subjects were identified by case history, skin prick test (SPT) and allergen-specific IgE. Sapodilla extract was fractionated using SP-Sepharose into 3 components (SP1, SP2 and SP3) which were analyzed by native/SDS-PAGE, IgE-immunoblot, isoelectric focusing (IEF) and N-terminal sequencing. The conserved regions of plant TLPs and the N-terminal sequence were used to design primers for PCR.

RESULTS

SPT and ELISA confirmed a subject with oral allergy syndrome (OAS) to sapodilla and custard apple. Two proteins (26.9 and 24.5kDa; reducing conditions) were detected as allergens, of which the latter in SP2 has already been identified as basic TLP (TLP 2). The 26.9kDa protein present in SP1 was identified as an acidic TLP based on native PAGE, IEF and N-terminal sequencing. Presence of a basic β-1,3-glucanase in SP3 was inferred by zymography. Sequence analysis of the genomic clone of the acidic TLP gene revealed that it is intronless and non-glycosylated. Evolutionary relatedness to olive, grape and kiwi fruit allergenic TLPs were inferred by phylogenetic analysis.

CONCLUSIONS

An acidic TLP (TLP 1) was identified as a new allergen in sapodilla. TLP 1 is a single polypeptide (207 residues) belonging to the thaumatin family of the GH64-TLP-SF superfamily. Clinically, sapodilla should be considered in the list of fruits causing OAS.

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.

Characterization of the allergenic potential of proteins: an assessment of the kiwifruit allergen actinidin

Assessment of the potential allergenicity (IgE-inducing properties) of novel proteins is an important challenge in the overall safety assessment of foods. Resistance to digestion with pepsin is commonly measured to characterize allergenicity, although the association is not absolute. We have previously shown that specific IgE antibody production induced by systemic [intraperitoneal (i.p.)] exposure of BALB/c strain mice to a range of proteins correlates with allergenic potential for known allergens. The purpose of the present study was to explore further the utility of these approaches using the food allergen, actinidin. Recently, kiwifruit has become an important allergenic foodstuff, coincident with its increased consumption, particularly as a weaning food. The ability of the kiwifruit allergen actinidin to stimulate antibody responses has been compared with the reference allergen ovalbumin, and with the non-allergen bovine haemoglobin. Haemoglobin was rapidly digested by pepsin whereas actinidin was resistant unless subjected to prior chemical reduction (reflecting intracellular digestion conditions). Haemoglobin stimulated detectable IgG antibody production at relatively high doses (10%), but failed to provoke detectable IgE. In contrast, actinidin was both immunogenic and allergenic at relatively low doses (0.25% to 1%). Vigorous IgG and IgG1 antibody and high titre IgE antibody responses were recorded, similar to those provoked by ovalbumin. Thus, actinidin displays a marked ability to provoke IgE, consistent with allergenic potential. These data provide further encouragement that in tandem with analysis of pepsin stability, the induction of IgE after systemic exposure of BALB/c strain mice provides a useful approach for the prospective identification of protein allergens.

Novel birch pollen specific immunotherapy formulation based on contiguous overlapping peptides

Background

Synthetic contiguous overlapping peptides (COPs) may represent an alternative to allergen extracts or recombinant allergens for allergen specific immunotherapy. In combination, COPs encompass the entire allergen sequence, providing all potential T cell epitopes, while preventing IgE conformational epitopes of the native allergen.

Methods

Individual COPs were derived from the sequence of Bet v 1, the major allergen of birch pollen, and its known crystal structure, and designed to avoid IgE binding. Three sets of COPs were tested in vitro in competition ELISA and basophil degranulation assays. Their in vivo reactivity was determined by intraperitoneal challenge in rBet v 1 sensitized mice as well as by skin prick tests in volunteers with allergic rhinoconjunctivitis to birch pollen.

Results

The combination, named AllerT, of three COPs selected for undetectable IgE binding in competition assays and for the absence of basophil activation in vitro was unable to induce anaphylaxis in sensitized mice in contrast to rBet v 1. In addition no positive reactivity to AllerT was observed in skin prick tests in human volunteers allergic to birch pollen. In contrast, a second set of COPs, AllerT4-T5 displayed some residual IgE binding in competition ELISA and a weak subliminal reactivity to skin prick testing.

Conclusions

The hypoallergenicity of contiguous overlapping peptides was confirmed by low, if any, IgE binding activity in vitro, by the absence of basophil activation and the absence of in vivo induction of allergic reactions in mouse and human.

Trial registration

ClinicalTrials.gov NCT01719133

Relationship between protein digestibility and allergenicity: comparisons of pepsin and cathepsin

An association between protein allergenicity and resistance to pepsin digestion in the gastrointestinal tract has been proposed. However, although widely accepted, such an association is inconsistent with known labile allergens and resistant nonallergens. Given the central role of antigen presenting cells, and in particular dendritic cells (DC), in the development of allergic responses, the stability of allergens to intracellular processing may be more relevant than resistance to extracellular pepsin digestion. We have characterised the expression by DC of cathepsins (proteolytic enzymes), and compared the proteolytic activity of the most highly expressed cathepsin with pepsin for a range of 9 allergens and 4 putative nonallergens. Cathepsin expression in bone marrow-derived DC (BM-DC) derived from BALB/c strain mice was characterised by flow cytometry; cathepsins D, E and S were identified, with cathepsin D being the most highly expressed. Digestion studies revealed that the majority of allergens (5/9) were pepsin resistant, whereas non-allergens (3/4) were labile. If the generation of pepsin-resistant fragments was considered as a feature of allergenicity, this increased to 7/9 allergens and 4/4 nonallergens. In contrast, most of the proteins examined were resistant to cathepsin digestion, with significant digestion recorded for only 2/9 allergens and 2/4 non-allergens. Chemical reduction (to mimic intracellular reducing conditions) increased the susceptibility of proteins to digestion by cathepsins, but did not improve discrimination between allergens and nonallergens on this basis. These data confirm that there is a general relationship between resistance to digestion with pepsin and allergenicity. The relationship is not absolute, but the information gained from this characteristic does provide useful information in a weight of evidence approach for allergenicity assessment. The most abundant cathepsin detected in antigen processing BM-DC, cathepsin D, is not an appropriate substitute for pepsin. The hypothesis that pepsin stability may be a surrogate for stability to digestion within DC may still hold true, but consideration of a single enzyme in this context is possibly an oversimplification.

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.

A qRT-PCR assay for the expression of all Mal d 1 isoallergen genes

BACKGROUND

A considerable number of individuals suffer from oral allergy syndrome (OAS) to apple, resulting in the avoidance of apple consumption. Apple cultivars differ greatly in their allergenic properties, but knowledge of the causes for such differences is incomplete. Mal d 1 is considered the major apple allergen. For Mal d 1, a wide range of isoallergens and variants exist, and they are encoded by a large gene family. To identify the specific proteins/genes that are potentially involved in the allergy, we developed a PCR assay to monitor the expression of each individual Mal d 1 gene. Gene-specific primer pairs were designed for the exploitation of sequence differences among Mal d 1 genes. The specificity of these primers was validated using both in silico and in vitro techniques. Subsequently, this assay was applied to the peel and flesh of fruits from the two cultivars 'Florina' and 'Gala'.

RESULTS

We successfully developed gene-specific primer pairs for each of the 31 Mal d 1 genes and incorporated them into a qRT-PCR assay. The results from the application of the assay showed that 11 genes were not expressed in fruit. In addition, differential expression was observed among the Mal d 1 genes that were expressed in the fruit. Moreover, the expression levels were tissue and cultivar dependent.

CONCLUSION

The assay developed in this study facilitated the first characterisation of the expression levels of all known Mal d 1 genes in a gene-specific manner. Using this assay on different fruit tissues and cultivars, we obtained knowledge concerning gene relevance in allergenicity. This study provides new perspectives for research on both plant breeding and immunotherapy.

The added value of allergen microarray technique to the management of poly-sensitized allergic patients

PURPOSE OF REVIEW

To evaluate the relevance of results obtained using allergen microarray technique for the description of the IgE repertoire in allergic patients.

RECENT FINDINGS

Allergen microarray was introduced at the beginning of the last decade. Since then, an increasing number of allergens have been identified, correspondingly increasing the accuracy of the description of immunoglobulin (Ig)E repertoire. In the last 2 years, a large number of articles were published that accurately described not only the general features of this technique, but also the use of allergen microarray in specific situations.

SUMMARY

The recent availability of highly purified or recombinant allergen components has deeply modified the laboratory approach to allergy diagnosis that, now, it cannot be limited to the detection of IgE specific to extractive allergens. Indeed, these contain both specific components (i.e. molecules strictly associated to that allergen source) and pan-allergen or cross-reacting allergens (i.e. molecules that are present in different similar allergen sources or that are present in highly homologous structures in different species). Newer techniques such as recombinant allergen testing and allergen microarray allow a more detailed evaluation of IgE responses. Future research is needed to more clearly define their role in clinical practice.

Correlation of anti-Pru p 3 IgE levels with severity of peach allergy reactions in children

BACKGROUND

Peach allergy is regarded as one of the most important fresh fruit allergies. Data are available on the state-of-the-art diagnosis, including food challenges, and a component-resolved diagnosis. However, the roles played by different peach allergens with respect to symptom severity are not completely understood.

OBJECTIVE

To evaluate the role of serum specific IgE to peach and recombinant allergens in the diagnosis of peach allergies in Italian children.

METHODS

Forty-four children with peach allergy confirmed by a placebo-controlled food challenge were divided into 2 groups based on their symptom severity: patients with mild oral allergy syndrome (OAS) and patients with systemic symptoms (SS). The presence of specific IgE to peach and rPru p 1, rPru p 3, and rPru p 4 was determined.

RESULTS

The presence of specific IgE to Pru p 4 and Pru p 1 was found significantly more frequently in patients with OAS, whereas specific IgE to Pru p 3 was not found significantly more frequently in patients with SS. Only anti-rPru p 4 IgE levels were significantly higher in patients with OAS, whereas no significant differences were found in anti-rPru p 1 and anti-rPru p 3 IgE levels between patients with OAS compared with patients with SS.

CONCLUSION

In Italian children with peach allergies, the presence of specific IgE to Pru p 3 is not associated with SS, and the levels of specific IgE to Pru p 3 do not correlate with the severity of the reactions.

Update on in vitro allergy diagnostics

Component-resolved diagnostics (CRD) have become of growing importance in clinical investigation of IgE-mediated allergies. This review updates the current use of CRD in respiratory allergies (e. g. to pollen, animal dander, mites, latex), as well as in allergies to hymenoptera venom or in food allergies to plants (e. g. Bet v 1 homologues, lipid transfer proteins, storage proteins) or to animal-derived food allergens (e. g. milk, meat, fish). CRD may help to elucidate the clinical relevance of an allergic sensitization. In some cases, CRD may also be useful in predicting either severity of clinical reactions or the therapeutic effect of specific immunotherapy.