Lipid transfer proteins and 2S albumins as allergens

Worldwide Heterogeneity of Food Allergy: Focus on Peach Allergy in Southern Italy

Food allergy (FA) has shown an increasing prevalence in the last decades, becoming a major public health problem. However, data on the prevalence of FA across the world are heterogeneous because they are influenced by several factors. Among IgE-mediated FA, an important role is played by FA related to plant-derived food which can result from the sensitization to a single protein (specific FA) or to homologous proteins present in different foods (cross-reactive FA) including non-specific lipid transfer proteins (nsLTPs), profilins, and pathogenesis-related class 10 (PR-10). In addition, the clinical presentation of FA is widely heterogeneous ranging from mild symptoms to severe reactions up to anaphylaxis, most frequently associated with nsLTP-related FA (LTP syndrome). Considering the potential life-threatening nature of nsLTP-related FA, the patient's geographical setting should always be taken into account; thereby, it is highly recommended to build a personalized approach for managing FA across the world in the precision medicine era. For this reason, in this review, we aim to provide an overview of the prevalence of nsLTP-mediated allergies in the Mediterranean area and to point out the potential reasons for the different geographical significance of LTP-driven allergies with a particular focus on the allergenic properties of food allergens and their cross reactivity.

Herbivory-inducible lipid-transfer proteins (LTPs) of Cicer arietinum as potential human allergens

Lipid-transfer proteins (LTPs) are lipid-binding small proteins, ubiquitously distributed amongst plant kingdom. Apart from their involvement in plant defense, it has also been discovered that they induce allergic reactions in humans. A plethora of LTPs have been identified in vegetables, fruits, pollens, nuts, and latex, among which Pru p 3, a LTP allergen from peach fruit, is extensively studied and exhibits cross-reactivity with potential allergens from different species. In Cicer arietinum, a family of LTPs (CaLTPs) has been identified and their importance in plant defense during Helicoverpa armigera-infestation has been recognized. However, the determination of the allergenicity potential of CaLTPs has not been attempted. In this study, we aim to decipher the allergenicity potential of defense-related CaLTPs. The allergenicity potential prediction, and identification of B-cell epitope binding regions showed that the CaLTPs had conserved domains and B-cell epitopes in the same regions as Prup3 (a marker allergen for LTPs). Using molecular docking and simulations, we observed that the CaLTPs successfully interacted with the Immunoglobin E(IgE)with docking energies ranging from -315.5 to -268.4 and the structures were stabilized within 10 ns of simulation. Through this study, we intend to embellish our present knowledge and understanding of the sensitization and allergenicity potential of CaLTPs.Communicated by Ramaswamy H. Sarma.

Lipid Transfer Proteins (LTPs)-Structure, Diversity and Roles beyond Antimicrobial Activity

Lipid transfer proteins (LTPs) are among the most promising plant-exclusive antimicrobial peptides (AMPs). They figure among the most challenging AMPs from the point of view of their structural diversity, functions and biotechnological applications. This review presents a current picture of the LTP research, addressing not only their structural, evolutionary and further predicted functional aspects. Traditionally, LTPs have been identified by their direct isolation by biochemical techniques, whereas omics data and bioinformatics deserve special attention for their potential to bring new insights. In this context, new possible functions have been identified revealing that LTPs are actually multipurpose, with many additional predicted roles. Despite some challenges due to the toxicity and allergenicity of LTPs, a systematic review and search in patent databases, indicate promising perspectives for the biotechnological use of LTPs in human health and also plant defense.

Are Physicochemical Properties Shaping the Allergenic Potency of Plant Allergens?

This review searched for published evidence that could explain how different physicochemical properties impact on the allergenicity of food proteins and if their effects would follow specific patterns among distinct protein families. Owing to the amount and complexity of the collected information, this literature overview was divided in two articles, the current one dedicated to protein families of plant allergens and a second one focused on animal allergens. Our extensive analysis of the available literature revealed that physicochemical characteristics had consistent effects on protein allergenicity for allergens belonging to the same protein family. For example, protein aggregation contributes to increased allergenicity of 2S albumins, while for legumins and cereal prolamins, the same phenomenon leads to a reduction. Molecular stability, related to structural resistance to heat and proteolysis, was identified as the most common feature promoting plant protein allergenicity, although it fails to explain the potency of some unstable allergens (e.g. pollen-related food allergens). Furthermore, data on physicochemical characteristics translating into clinical effects are limited, mainly because most studies are focused on in vitro IgE binding. Clinical data assessing how these parameters affect the development and clinical manifestation of allergies is minimal, with only few reports evaluating the sensitising capacity of modified proteins (addressing different physicochemical properties) in murine allergy models. In vivo testing of modified pure proteins by SPT or DBPCFC is scarce. At this stage, a systematic approach to link the physicochemical properties with clinical plant allergenicity in real-life scenarios is still missing.

2S albumins and nsLTP are involved in anaphylaxis to pizza sauce: IgE recognition before and after allergen processing

Although pizza is one of the most popular foods in the world, allergic responses after ingesting pizza are relatively uncommon. However, precisely identifying the allergens responsible for these allergic reactions is challenging because of the high and diverse number of ingredients used in pizza preparation. In this report, we aim to identify the allergens responsible for systemic allergic reactions following ingestion of pizza in two patients. Using a skin prick by prick test (SPPT) and in vitro techniques, with natural and recombinant purified allergens from tomato and mustard seeds, we identified 2S albumin and non-specific lipid transfer proteins (nsLTP) as the proteins involved. However, IgE responses to the four nsLTPs differed before and after denaturation and reduction, thus suggesting additional complexity around nsLTP in food processing.

Assessment of Natural Variability of Maize Lipid Transfer Protein Using a Validated Sandwich ELISA

Lipid transfer protein (LTP) is the main causative agent for rare food allergic reactions to maize. This paper describes a new, validated ELISA that accurately measures maize LTP concentrations from 0.2 to 6.4 ng/mL. The levels of LTP ranged from 171 to 865 μg/g of grain, a 5.1-fold difference, across a set of 49 samples of maize B73 hybrids derived from the Nested Association Mapping (NAM) founder lines and a diverse collection of landrace accessions from North and South America. A second set of 107 unique samples from 18 commercial hybrids grown over two years across 10 U.S. states showed a comparable range of LTP level (212-751 μg/g of grain). Statistical analysis showed that genetic and environmental factors contributed 63 and 6%, respectively, to the variance in LTP levels. Therefore, the natural variation of maize LTP is up to 5-fold different across a diverse collection of varieties that have a history of safe cultivation and consumption.

Evidence for proteomic and metabolic adaptations associated with alterations of seed yield and quality in sulfur-limited Brassica napus L

In Brassica napus, seed yield and quality are related to sulfate availability, but the seed metabolic changes in response to sulfate limitation remain largely unknown. To address this question, proteomics and biochemical studies were carried out on mature seeds obtained from plants grown under low sulfate applied at the bolting (LS32), early flowering (LS53), or start of pod filling (LS70) stage. The protein quality of all low-sulfate seeds was reduced and associated with a reduction of S-rich seed storage protein accumulation (as Cruciferin Cru4) and an increase of S-poor seed storage protein (as Cruciferin BnC1). This compensation allowed the protein content to be maintained in LS70 and LS53 seeds but was not sufficient to maintain the protein content in LS32 seeds. The lipid content and quality of LS53 and LS32 seeds were also affected, and these effects were primarily associated with a reduction of C18-derivative accumulation. Proteomics changes related to lipid storage, carbohydrate metabolism, and energy (reduction of caleosins, phosphoglycerate kinase, malate synthase, ATP-synthase β-subunit, and thiazole biosynthetic enzyme THI1 and accumulation of β-glucosidase and citrate synthase) provide insights into processes that may contribute to decreased oil content and altered lipid composition (in favor of long-chain fatty acids in LS53 and LS32 seeds). These data indicate that metabolic changes associated with S limitation responses affect seed storage protein composition and lipid quality. Proteins involved in plant stress response, such as dehydroascorbate reductase and Cu/Zn-superoxide dismutase, were also accumulated in LS53 and LS32 seeds, and this might be a consequence of reduced glutathione content under low S availability. LS32 treatment also resulted in (i) reduced germination vigor, as evidenced by lower germination indexes, (ii) reduced seed germination capacity, related to a lower seed viability, and (iii) a strong decrease of glyoxysomal malate synthase, which is essential for the use of fatty acids during seedling establishment.

Proteomics-based allergen analysis in plants

Plants may trigger hypersensitivity reactions when individuals with allergies consume foods derived from plant materials or inhale plant pollen. As each plant food or pollen contains multiple allergens, proteomics is a powerful tool to detect the allergens present. Allergen-targeted proteomics, termed allergenomics, has been used for comprehensive identification and/or quantification of plant allergens, because it is a simple and inexpensive tool for rapid detection of proteins that bind to IgE. There are increasing numbers of reports on the applications of allergenomics. In this review, we outline some of the applications of proteomics, including: (i) identification of novel allergens, (ii) allergic diagnoses, (iii) quantification of allergens, and (iv) natural diversity of allergens, and finally discuss (v) the use of allergenomics for safety assessment of genetically modified (GM) plants.

BIOLOGICAL SIGNIFICANCE

Recently, the number of allergic patients is increasing. Therefore, a comprehensive analysis of allergens (allergenomics) in plants is highly important for not only risk assessment of food plants but also diagnosis of allergic symptoms. In this manuscript, we reviewed the recent progress of allergenomics for identification, quantification and profiling of allergens. This article is part of a Special Issue entitled: Translational Plant Proteomics.

Stability of sunflower 2S albumins and LTP to physiologically relevant in vitro gastrointestinal digestion

In order for a protein to elicit a systemic allergic response it must reach the circulatory system through the intestinal mucosa as a sufficiently large fragment with adequate structural integrity. Sunflower LTP and 2S albumins (SFA8 and three mixed fractions of Alb1 and Alb2) were digested in simulated gastric fluid (SGF) for 2h and the conditions were then changed to mimic the intestinal environment for a further 2h digestion. The effects of phosphatidylcholine (PC) and emulsification on the digestibility of the proteins were investigated. PC protected all of the proteins studied against both gastric and intestinal digestive enzymes but to different extents. Emulsification of SFA8 resulted in strong protection against digestion, which was further enhanced by the presence of PC in the SGF. These results highlight the importance of considering real food structures such as emulsified systems and also the gastrointestinal environment that proteins are exposed to once consumed when assessing allergenicity.

Almond allergens: molecular characterization, detection, and clinical relevance

Almond ( Prunus dulcis ) has been widely used in all sorts of food products (bakery, pastry, snacks), mostly due to its pleasant flavor and health benefits. However, it is also classified as a potential allergenic seed known to be responsible for triggering several mild to life-threatening immune reactions in sensitized and allergic individuals. Presently, eight groups of allergenic proteins have been identified and characterized in almond, namely, PR-10 (Pru du 1), TLP (Pru du 2), prolamins (Pru du 2S albumin, Pru du 3), profilins (Pru du 4), 60sRP (Pru du 5), and cupin (Pru du 6, Pru du γ-conglutin), although only a few of them have been tested for reactivity with almond-allergic sera. To protect sensitized individuals, labeling regulations have been implemented for foods containing potential allergenic ingredients, impelling the development of adequate analytical methods. This work aims to present an updated and critical overview of the molecular characterization and clinical relevance of almond allergens, as well as review the main methodologies used to detect and quantitate food allergens with special emphasis on almond.

Ara h 2: crystal structure and IgE binding distinguish two subpopulations of peanut allergic patients by epitope diversity

BACKGROUND

Peanut allergy affects 1% of the population and causes the most fatal food-related anaphylactic reactions. The protein Ara h 2 is the most potent peanut allergen recognized by 80-90% of peanut allergic patients.

METHODS

The crystal structure of the major peanut allergen Ara h 2 was determined for the first time at 2.7 Å resolution using a customized maltose-binding protein (MBP)-fusion system. IgE antibody binding to the MBP fusion construct vs the natural allergen was compared by ELISA using sera from peanut allergic patients.

RESULTS

The structure of Ara h 2 is a five-helix bundle held together by four disulfide bonds and related to the prolamin protein superfamily. The fold is most similar to other amylase and trypsin inhibitors. The MBP--Ara h 2 fusion construct was positively recognized by IgE from 76% of allergic patients (25/33). Two populations of patients could be identified. Subpopulation 1 (n = 14) showed an excellent correlation of IgE antibody binding to natural vs recombinant Ara h 2. Subpopulation 2 (n = 15) showed significantly reduced IgE binding to the MBP fusion protein. Interestingly, about 20% of the IgE binding in subpopulation 2 could be recovered by increasing the distance between MBP and Ara h 2 in a second construct.

DISCUSSION

The reduced IgE binding to the MBP--Ara h 2 of subpopulation 2 indicates that the MBP molecule protects an immunodominant epitope region near the first helix of Ara h 2. Residues involved in the epitope(s) are suggested by the crystal structure. The MBP--Ara h 2 fusion constructs will be useful to further elucidate the relevance of certain epitopes to peanut allergy.

Transcriptome analysis of the oil-rich seed of the bioenergy crop Jatropha curcas L

BACKGROUND

To date, oil-rich plants are the main source of biodiesel products. Because concerns have been voiced about the impact of oil-crop cultivation on the price of food commodities, the interest in oil plants not used for food production and amenable to cultivation on non-agricultural land has soared. As a non-food, drought-resistant and oil-rich crop, Jatropha curcas L. fulfils many of the requirements for biofuel production.

RESULTS

We have generated 13,249 expressed sequence tags (ESTs) from developing and germinating Jatropha seeds. This strategy allowed us to detect most known genes related to lipid synthesis and degradation. We have also identified ESTs coding for proteins that may be involved in the toxicity of Jatropha seeds. Another unexpected finding is the high number of ESTs containing transposable element-related sequences in the developing seed library (800) when contrasted with those found in the germinating seed library (80).

CONCLUSIONS

The sequences generated in this work represent a considerable increase in the number of sequences deposited in public databases. These results can be used to produce genetically improved varieties of Jatropha with increased oil yields, different oil compositions and better agronomic characteristics.

Molecular diagnosis in allergy

Development and progress made in the field of recombinant allergens have allowed for the development of a new concept in allergy diagnosis, molecular diagnosis (MD), which makes it possible to identify potential disease-eliciting molecules. Microarray-based testing performed with a small amount of serum sample enables clinicians to determine specific-IgE antibodies against multiple recombinants or purified natural allergen components. Performance characteristics of allergens so far tested are comparable with current diagnostic tests, but have to be confirmed in larger studies. The use of allergen components and the successful interpretation of test results in the clinic require some degree of knowledge about the basis of allergen components and their clinical implications. Allergen components can be classified by protein families based on their function and structure. This review provides a brief overview of basic information on allergen components, recombinants or purified, currently available or soon to become commercially available in ImmunoCAP or ISAC systems, including names, protein family and function. Special consideration is given to primary or species-specific sensitization and possible cross-reactivity, because one of the most important clinical utility of MD is its ability to reveal whether the sensitization is genuine in nature (primary, species-specific) or if it is due to cross-reactivity to proteins with similar protein structures, which may help to evaluate the risk of reaction on exposure to different allergen sources. MD can be a support tool for choosing the right treatment for the right patient with the right timing. Such information will eventually give clinicians the possibility to individualize the actions taken, including an advice on targeted allergen exposure reduction, selection of suitable allergens for specific immunotherapy, or the need to perform food challenges. Nevertheless, all in vitro tests should be evaluated together with the clinical history, because allergen sensitization does not necessarily imply clinical responsiveness.

Specific sublingual immunotherapy with peach LTP (Pru p 3). One year treatment: a case report

Introduction

Food allergy is an increasing problem with limited therapeutic approaches apart from to the eviction diet.

Case presentation

A 40-year-old female patient with food allergy symptoms was polysensitized to almost all vegetable food since the age of 36; the onset of symptoms was during pregnancy. The allergological study demonstrated positive skin prick tests (SPT) to nuts, legumes, cereals, spices, several fresh fruits including peach, and other groups of vegetable foods however, it was negative to common aeroallergens. Serum specific IgE levels were negative (<0.35 kU/L) to profilin and carbohydrate determinants, but positive to Pru p 3 (3.5 kU/L). Positive double-blind placebo-controlled food challenge to peach confirmed the allergic disease. She received specific sublingual immunotherapy with native Pru p 3 at a concentration of 40 μg/ml with 5 administrations per week and a cumulative dose of 200 μg of nPru p 3 per month. After an ultra-rush build-up phase concluded in one day she continued therapy during a year with 5 administrations per week. The clinical evolution and laboratory studies demonstrated an early reduction on SPT reactions with no relevant changes on serum specific IgE, IgG, IgG1 and IgG4 to Pru p 3 during the immunotherapy period. The challenge test was negative 4 months after the beginning of the SLIT. Regarding clinical response she markedly improved after the first month of treatment, and by the 3th month she had no major vegetable dietary restrictions, except for nuts and pepper.

Conclusion

These results demonstrate the excellent efficacy and safety of sublingual specific protein immunotherapy developed according to the patient specific sensitivity profile to Pru p3.

Specific sublingual immunotherapy with peach LTP (Pru p 3). One year treatment: a case report

Introduction

Food allergy is an increasing problem with limited therapeutic approaches apart from to the eviction diet.

Case presentation

A 40-year-old female patient with food allergy symptoms was polysensitized to almost all vegetable food since the age of 36; the onset of symptoms was during pregnancy. The allergological study demonstrated positive skin prick tests (SPT) to nuts, legumes, cereals, spices, several fresh fruits including peach, and other groups of vegetable foods however, it was negative to common aeroallergens. Serum specific IgE levels were negative (<0.35 kU/L) to profilin and carbohydrate determinants, but positive to Pru p 3 (3.5 kU/L). Positive double-blind placebo-controlled food challenge to peach confirmed the allergic disease. She received specific sublingual immunotherapy with native Pru p 3 at a concentration of 40 μg/ml with 5 administrations per week and a cumulative dose of 200 μg of nPru p 3 per month. After an ultra-rush build-up phase concluded in one day she continued therapy during a year with 5 administrations per week. The clinical evolution and laboratory studies demonstrated an early reduction on SPT reactions with no relevant changes on serum specific IgE, IgG, IgG₁ and IgG₄ to Pru p 3 during the immunotherapy period. The challenge test was negative 4 months after the beginning of the SLIT. Regarding clinical response she markedly improved after the first month of treatment, and by the 3th month she had no major vegetable dietary restrictions, except for nuts and pepper.

Conclusion

These results demonstrate the excellent efficacy and safety of sublingual specific protein immunotherapy developed according to the patient specific sensitivity profile to Pru p3.

Hazelnut allergy: from pollen-associated mild allergy to severe anaphylactic reactions

PURPOSE OF REVIEW

Hazelnut allergy can vary between mild oral symptoms and potentially dangerous anaphylaxis. There is a need to predict which subjects are at risk for severe reactions. In this study, possibilities for 'component-resolved diagnosis', based on sensitization to different allergens in hazelnut, are discussed.

RECENT FINDINGS

One type of hazelnut allergy can be associated with sensitization to homologues of pollen allergens, predominantly birch, in hazelnut: Cor a 1 (Bet v 1) and Cor a 2 (profilin). These allergens account for relatively mild symptoms. However, subjects can also be sensitized to several other allergens in hazelnut that are related to more severe symptoms. These allergens are homologues of allergens in other nuts and peanut: Cor a 8 (lipid transfer protein) and Cor a 9 (11S globulin) and perhaps Cor a 11 (7S globulin). The clinical relevance of these and other potential hazelnut allergens has to be further defined. The diagnosis of hazelnut has to be confirmed by oral double-blind placebo-controlled food challenge.

SUMMARY

Sensitization to hazelnut can either be associated with mild oral symptoms, depending on sensitization to pollen, or with more serious allergic symptoms, related to sensitization to homologues of nut and peanut allergens.

Identification of a new natural Ara h 6 isoform and of its proteolytic product as major allergens in peanut

Numerous food allergens of plant origin belong to the 2S albumin family, including peanut Ara h 2. In addition to Ara h 2, several other conglutins related to 2S albumins are present in peanut seeds. We evaluated the allergenicity of different peanut conglutins as compared with Ara h 2. Several conglutins were isolated from the kernel, i.e. Ara h 2, a new isoform of Ara h 6 and its derived product, which is likely to be naturally formed during seed processing. Enzyme allergosorbent tests performed on sera of peanut allergic patients showed that more than 94% of 47 analyzed patients had positive IgE responses to Ara h 6 isoform and to its degradation product. Skin prick tests with the new isoform of Ara h 6 led to a positive response in seven out of the eight tested patients. Both enzyme allergosorbent tests and skin prick tests showed that the reactivity of Ara h 6 was similar to, or even higher than, that of Ara h 2, suggesting that the present isoform of Ara h 6 is as allergenic as Ara h 2. In addition the IgE response to the plant processed (i.e., hydrolyzed) Ara h 6 new isoform is equivalent to the IgE response to the native isoform. The IgE immunoreactivity is mostly abrogated by chemical reduction and denaturation of Ara h 6 isoforms, which underlined the importance of tertiary structure in Ara h 6 immunoreactivity. These results, and particularly the high correlation between anti-Ara h 2 and anti-Ara h 6 IgE responses, emphasise the major role of 2S albumins in peanut allergenicity.

Ses i 6, the sesame 11S globulin, can activate basophils and shows cross-reactivity with walnut in vitro

BACKGROUND

Sesame allergy is increasingly being reported, and multi-sensitization to peanut and tree nuts has been described. The clinical relevance and cross-reactivity of many sesame proteins, such as Ses i 6, are unknown.

OBJECTIVE

The aims of this study were to perform a preliminary examination of the cross-reactivity of Ses i 6 in vitro, examine the ability of Ses i 6 to activate basophils in a modified basophil activation test (mBAT), and assess whether such an assay may help to distinguish between potentially relevant and irrelevant IgE reactivity towards 11S globulin proteins.

METHODS

Inhibition immunoblotting and chicken anti-rJug r 4 antibodies were used to determine the cross-reactivity of rSes i 6. Basophils from atopic donors were stripped of resident IgE before passive sensitization with food-allergic sera and challenged with protein extracts or recombinant protein. Basophil activation was measured using two activation markers, CD203c and CD63, via flow cytometry.

RESULTS

IgE immunoblotting showed cross-reactivity between rJug r 4 and rSes i 6 using sera from two human donors and chicken IgY. Additionally, rSes i 6 activated basophils passively sensitized with sesame-allergic sera. Cross-reactive serum from a sesame-allergic but walnut-tolerant donor was not able to activate basophils when challenged by walnut extract despite IgE reactivity to walnut determined by immunoblotting.

CONCLUSIONS

The sesame 11S globulin shows partial immunological cross-reactivity with walnut, and although it is classified as a minor allergen, activated basophils sensitized with serum from seven out of eleven sesame-allergic donors. Additionally, the mBAT may help distinguish between clinically relevant and irrelevant in vitro IgE cross-reactivity of seed storage proteins in nuts and seeds and thus warrants use in further studies.

Evolutionary biology of plant food allergens

The majority of plant food allergens can be grouped into just 4 protein families. This review summarizes the evolutionary relationships of allergenic and nonallergenic members of these families. Proteins from the prolamin superfamily have been described in vascular plants. This superfamily contains several allergenic (2S albumins, nonspecific lipid transfer proteins, and cereal amylase and protease inhibitors) and nonallergenic (hybrid proline-rich proteins, cereal indolines, and alpha-globulins) member families. The cupin superfamily comprises numerous functionally highly diverse protein families from all groups of organisms. However, allergenicity within the cupins is confined to the vicilin and legumin seed storage proteins. Profilins are ubiquitous eukaryotic proteins that are nonallergenic, with the exception of profilins from flowering plants. Finally, the Bet v 1 superfamily contains the pathogenesis-related proteins 10 family, the family of major latex proteins and ripening-related proteins, the norcoclaurine synthases, and the cytokinin-binding proteins, with pathogenesis-related proteins 10 family members from certain taxa being the only allergenic members. The study of the distribution of allergenic and nonallergenic members of protein families will provide new insights into the evolution of allergenicity and the factors that make proteins allergenic.

Children with peanut allergy recognize predominantly Ara h2 and Ara h6, which remains stable over time

BACKGROUND

In peanut-allergic adults, IgE is mainly directed to Ara h1 and Ara h2. More recently, a role for Ara h6 has been suggested. In contrast to adults, IgE in children can fluctuate over time. Therefore, children may have a more dynamic reactivity to peanut.

OBJECTIVE

To examine the IgE reactivity to major peanut allergens in peanut-allergic children at two subsequent time-points.

METHODS

Twenty children (3-15 years old) with peanut allergy, confirmed by a double-blind placebo-controlled food challenge (DBPCFC), were included. Just before and 20 months after DBPCFC, IgE reactivity to purified Ara h1, Ara h2, Ara h3 and Ara h6 was studied by immunoblots and skin prick tests (SPTs).

RESULTS

Before DBPCFC, all peanut-allergic children showed IgE reactivity to Ara h2; Ara h6 was recognized by 16 children, and Ara h1 and Ara h3 by 10 children. After 20 months, peanut-specific IgE levels (median 23 kU/L) and the individual recognition of major allergens were comparable with the levels and recognition before challenge (median 28.2 kU/L). SPT with Ara h2 and Ara h6 was positive in most children, whereas SPT with Ara h1 and Ara h3 was positive in approximately half of the children. Ara h6 induced the largest weals. None of the parameters were related to the severity of peanut allergy.

CONCLUSION

Ara h2 and Ara h6 are the most frequently recognized major peanut allergens in children. The individual reactivity to the major peanut allergens remained stable over time, despite DBPCFC.

Microarray analysis of apple gene expression engaged in early fruit development

To evaluate gene expressions mostly engaged in early development of apple fruit, we performed the identification of transcripts differentially expressed in young fruit by using microarrays spotted with 6,253 cDNAs collected from young and mature apple fruits of the cultivar Fuji (Malus domestica Borkh. cv. Fuji). A total of 3,484 cDNAs out of 6,253 were selected after quality control of microarray spots and analyzed for differential gene expression patterns between young fruit and other tissues (mature fruit, leaf and flower). Among them, 192 cDNAs displayed a signal value higher than twofold in young fruit compared with other tissues. Blast analysis of the 192 cDNA clones identified 88 non-redundant groups encoding proteins with known function and 50 non-redundant groups with unknown function. The putative protein products were classified into the following categories: photosynthesis (16.7%), protein synthesis (12.3%), cell proliferation and differentiation (10.9%), cell enlargement (5.8%), metabolism (8.0%), stress response (7.2%), others (2.9%), and unknown functions (32.2%). Furthermore, confirming the microarray data by reverse transcription-polymerase chain reaction revealed that the wide range of transcripts differentially expressed in young fruit was expressed in other organs but not in the mature fruit. The data presented suggested that apple fruit development depends on the tight regulation of the expression of a number of genes, which are also expressed in other organs.

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.

Anaphylaxis to lemon soap: citrus seed and peanut allergen cross-reactivity

BACKGROUND

Many individuals allergic to peanuts have multiple allergen sensitivity.

OBJECTIVE

To report the first case, to our knowledge, of a peanut allergic patient who exhibited cosensitivity to citrus seeds and who had experienced anaphylaxis to lemon soap.

METHODS

Extracts of peanut and seeds from different varieties of citrus fruit (orange, lemon, and mandarin) were prepared and resolved with 14% sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Direct and inhibition immunoblotting of the patient's serum on the extracts was used to examine the pattern of IgE reactivity and the presence of cross-reactive allergens.

RESULTS

Numerous IgE reactive proteins were demonstrated in each citrus seed extract and the peanut extract. Complete IgE cross-reactivity was demonstrated among the different citrus seed extracts. Partial cross-reactivity was demonstrated between the peanut and orange seed extracts.

CONCLUSIONS

Citrus seeds contain numerous IgE reactive proteins that are completely cross-reactive among orange, lemon, and mandarin. When peanut allergy coexists with citrus seed allergy, IgE cross-reactivity between peanut and citrus seed proteins can be demonstrated, suggesting a basis to this cosensitivity.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

How reliable is the structural prediction of IgE-binding epitopes of allergens? The case study of plant lipid transfer proteins

The linear IgE-binding epitopes of non-specific lipid transfer proteins (nsLTP) from plants were predicted using a combination of predictive tools including (1) the hydropathic profiles based on different scales of hydrophilicity, flexibility and exposure to the solvent, (2) the hydrophobic cluster analysis plots, (3) the occurrence of charged residues in the predicted amino acid sequence stretches and, (4) the exposition of the predicted linear IgE-binding epitopes checked on the three-dimensional models built for the nsLTP. A reliable prediction was obtained for nsLTP as compared with the previously characterized IgE-binding epitopes of various proteins. A consensual IgE-binding epitope occurring in other plant nsLTP and responsible for some IgE-binding cross-reactivity among fruit nsLTP has been identified and characterized. Despite some discrepancies, a fairly good prediction resulted in applying our combination of predictive methods to longer nsLTP or plant profilins.

Allergen-specific IgE testing in the diagnosis of food allergy and the event of a positive match in the bioinformatics search

Current documents on risk assessment of genetically modified foods recommend including IgE-binding tests on sera from allergic patients. However, there is no generally accepted recommendation on technical aspects of the testing procedures or on the interpretation of the results, despite that fact that both false positive and false-negative results may be caused by variability of the test procedures. The present article discusses the state-of-the-art of serological test procedures for qualitative and quantitative determination of specific IgE and interpretation of test results. It is emphasized that the use of sera from clinically well-characterized subjects is of high importance. In the case of a positive test result, the biological activity of the detected IgE antibodies, i. e., the potential to trigger mediator release from basophils or mast cells in an allergen-specific manner, should be taken into account. However, present data also indicate that validation of such mediator release tests is required, both in terms of experimental protocols and with respect to correlation of the test results with the clinical situation. Further studies are also required to prove the usefulness of targeted serum screening, i. e., the testing of gene products from organisms not known to be allergenic with sera from subjects allergic to related species.

Anaphylactic reaction to apple, banana and lychee: what is common between botanically disparate plant families?

We present the case of a 33-year-old nonatopic woman with multiple episodes of anaphylaxis after ingestion of different fruits. The fruits implicated were apple, banana and lychee: all of which belong to different and botanically disparate plant families. The reaction to apple and banana was confirmed by prick testing. There was no history of allergy to other agents that are known to have cross reactions with fruits, viz. latex or pollen. As such patients often do not present to dermatologists, we wish to highlight the rare but potentially fatal clinical entity of type I allergy to fruits without concomitant allergy to other common airborne/contact allergens. We also discuss the possible explanation of type I reaction to apparently unrelated fruits and the allergens involved in such reactions.

Homology modelling of the major peanut allergen Ara h 2 and surface mapping of IgE-binding epitopes

Three-dimensional models built for the peanut Ara h 2 allergen and other structurally-related 2S albumin allergens of dietary nuts exhibited an overall three-dimensional fold stabilized by disulphide bridges well conserved among all the members of the 2S albumin superfamily. Conformational analysis of the linear IgE-binding epitopes mapped on the molecular surface of Ara h 2 showed no structural homology with the corresponding regions of the walnut Jug r 1, the pecan nut Car i 1 or the Brazil nut Ber e 1 allergens. The absence of epitopic community does not support the allergenic cross-reactivity observed between peanut and walnut or Brazil nut, which presumably depends on other ubiquitous seed storage protein allergens, namely the vicilins. However, the major IgE-binding epitope identified on the molecular surface of the walnut Jug r 1 allergen shared a pronounced structural homology with the corresponding region of the pecan nut Car i 1 allergen. With the exception of peanut, 2S albumins could thus account for the IgE-binding cross-reactivity observed between some other dietary nuts, e.g. walnut and pecan nut.

Sesame allergy in Britain: a questionnaire survey of members of the Anaphylaxis Campaign

Sesame is a major allergen in countries where it is a common food. It was noted that an increasing number of members of the UK charity, the anaphylaxis campaign, were reporting allergy to sesame. This study, sought to examine features of sesame allergy among members of the Anaphylaxis Campaign (which supports those at potentially life-threatening risk from allergies) focusing on clinical symptoms and features of the foods implicated. A physician-designed questionnaire was sent by post to 400 members of the Anaphylaxis Campaign who reported avoidance of sesame. Two hundred and eighty replies were received (70%). Twenty-three replies (7%) were excluded and 96 replies (24%) came from subjects who avoided sesame but had never reacted to it. One hundred and fifty people (54%) reported 288 reactions to sesame. 89% of reactive subjects reported other atopic diseases and notably 84% were also nut/peanut allergic. One in six (17%) had suffered potentially life-threatening symptoms, with 65% of severe reactions happening on first known exposure. The age of first reaction ranged from 6 months to 65 yr. The majority of reactions reported (91%) involved foods or dishes which had sesame as a deliberate ingredient, rather than sesame as an accidental contaminant. Respondents represented a well-informed and highly selected group of people at risk from potentially life-threatening allergies. Sesame should be identified clearly as an ingredient and separately from nuts and peanuts when it may be an allergen contaminant. People at potential risk need clear allergy diagnosis and informed guidance to enable them to avoid this key allergen more easily.

Allergenic potency of spices: hot, medium hot, or very hot

Spices are the most attractive ingredients to confer an authentic taste to food. As they are derived from plants, they harbour allergenic potency and can induce symptoms ranging from mild local to severe systemic reactions. Due to the content of pharmacologically active substances of spices, the diagnosis of allergy and the differentiation from intolerance reactions may be difficult. Association with inhalative allergies via IgE cross-reactivity, but also direct gastrointestinal sensitization plays a role. This article is a botanical and allergological overview of the most important spices and molecules responsible for eliciting IgE-mediated reactions or cross-reactions. As no curative treatments are known at present, strict avoidance is recommended and, therefore, accurate labelling of pre-packed food is necessary.

Diversity of asparagus allergy: clinical and immunological features

BACKGROUND

Asparagus (Asparagus officinalis) is an extensively grown and consumed vegetable. To a lesser extent than other Liliaceae vegetables, allergic contact dermatitis (ACD) due to asparagus has been reported. However, only a few case reports of asparagus IgE-mediated allergy have been published. In a previous study, we demonstrated that two lipid transfer proteins (LTPs) (Aspa o 1.01 and Aspa o 1.02) were relevant allergens of asparagus.

OBJECTIVE

We retrospectively analysed the 27 patients diagnosed with asparagus allergy during the last 5 years. All of them reported adverse symptoms after either asparagus ingestion or handling. We describe their clinical features and evaluate whether they were associated to immunological findings (immunoblot pattern and skin reactivity to LTPs).

METHODS

Patients underwent skin prick and patch tests with standard panels of vegetables and aeroallergens. Besides crude asparagus extract, two purified LTPs were prick and patch tested. Total and specific IgE measurements and asparagus extract IgE immunoblotting were performed. Patients reporting asthma symptoms underwent specific inhalation challenge to asparagus.

RESULTS

Of the 27 subjects, eight had ACD, 17 had IgE-mediated allergy and two had both ACD- and IgE-mediated allergy. Positive patch tests with the crude asparagus extract but not with LTPs were observed in subjects with ACD (n=10). Of 19 patients with IgE-mediated disease, 10 had contact urticaria after asparagus handling. Of them, five subjects and five others without skin allergy showed respiratory symptoms; of them, eight were diagnosed with occupational asthma confirmed by positive asparagus inhalation challenge, whereas the remaining two had isolated rhinitis. Four patients suffered from immediate allergic reactions related to asparagus ingestion (food allergy); three of them reported anaphylaxis whereas the other had oral allergic syndrome. Positive IgE immunoblotting (bands of 15 and 45-70 kDa) was observed in 10 subjects. Of 10 subjects with positive prick test to LTPs, six showed bands at 15 kDa. Either IgE-binding bands or positive prick tests to LTPs were observed in asthma (62%) and anaphylaxis (67%).

CONCLUSION

Asparagus is a relevant source of occupational allergy inducing ACD and also IgE-mediated reactions. Severe disease (anaphylaxis or asthma) is common and LTPs seem to play a major role. The clinical relevance of LTP sensitization among patients with mild disease or symptom-free subjects should be addressed in prospective studies.

The eight-cysteine motif, a versatile structure in plant proteins

A number of protein sequences deduced from the molecular analysis of plant cDNA or genomic libraries can be grouped in relation to a defined number of cysteine residues located in distinct positions of their sequences. This is the case for a group of around 500 polypeptides from different species that contain a small domain (less than 100 amino acids residues) displaying a pattern of eight-cysteines in a specific order. The plant sequences containing this motif belong to proteins having different functions, ranging from storage, protection, enzyme inhibition and lipid transfer, to cell wall structure. The eight-cysteine motif (8CM) appears to be a structural scaffold of conserved helical regions connected by variable loops, as observed by three-dimensional structure analysis. It is proposed that the cysteine residues would form a network of disulfide bridges necessary, for the maintenance of the tertiary structure of the molecule together with the central helical core, while the variable loops would provide the sequences required for the specific functions of the proteins.

Lettuce anaphylaxis: identification of a lipid transfer protein as the major allergen

BACKGROUND

Allergy to plant-derived foods is associated with birch pollinosis in central and northern Europe. Symptoms elicited are usually limited to the oropharyngeal system. By contrast, in the Mediterranean area, allergy to the same foods manifests more frequently with systemic reactions caused by nonspecific lipid transfer proteins (nsLTP), independently of an associated pollinosis.

OBJECTIVE

We sought to investigate the pattern of immunoglobulin E (IgE) binding protein bands implicated in lettuce allergy, in particular the presence of an nsLTP.

METHODS

Consecutive lettuce allergic patients were selected. Determination of serum-specific IgE, immunoblot, and inhibition experiments were performed in order to study the pattern of IgE binding proteins and the potential cross-reactivity to pollens. Inhibition studies with recombinant allergens were conducted to identify the lettuce allergens. The major allergen was subjected to N-terminal amino acid sequencing.

RESULTS

Fourteen patients were diagnosed as being allergic to lettuce. All were sensitized to Platanus pollen. Ten of them showed specific IgE to a lettuce protein of 9-kDa. The IgE binding to this protein was completely inhibited by the cherry-LTP and peach extract. The N-terminal sequence of the 9-kDa protein showed a high degree of amino acid sequence identity to other nsLTPs. A clear partial cross-reactivity was observed between lettuce-LTP and Platanus-pollen extract.

CONCLUSIONS

An LTP has been demonstrated to be a major allergen in patients suffering from lettuce allergy.

Refined solution structure of a liganded type 2 wheat nonspecific lipid transfer protein

The refined structure of a wheat type 2 nonspecific lipid transfer protein (ns-LTP2) liganded with l-alpha-palmitoylphosphatidylglycerol has been determined by NMR. The (15)N-labeled protein was produced in Pichia pastoris. Physicochemical conditions and ligandation were intensively screened to obtain the best NMR spectra quality. This ns-LTP2 is a 67-residue globular protein with a diameter of about 30 A. The structure is composed of five helices forming a right superhelix. The protein presents an inner cavity, which has been measured at 341 A(3). All of the helices display hydrophobic side chains oriented toward the cavity. The phospholipid is found in this cavity. Its fatty acid chain is completely inserted in the protein, the l-alpha-palmitoylphosphatidylglycerol glycerol moiety being located on a positively charged pocket on the surface of the protein. The superhelix structure of the protein is coiled around the fatty acid chain. The overall structure shows similarities with ns-LTP1. Nevertheless, large three-dimensional structural discrepancies are observed for the H3 and H4 alpha-helices, the C-terminal region, and the last turn of the H2 helix. The lipid is orthogonal to the orientation observed in ns-LTP1. The volume of the hydrophobic cavity appears to be in the same range as the one of ns-LTP1, despite the fact that ns-LTP2 is shorter by 24 residues.

Prospective study of mustard allergy: first study with double-blind placebo-controlled food challenge trials (24 cases)

BACKGROUND

Mustard allergy accounts for 1.1% of food allergies in children. However, double-blind placebo-controlled food challenge trials (DB PCFCs) have not yet been proposed.

OBJECTIVE

To carry out DB PCFCs to determine the real frequency of mustard allergy in patients sensitized to mustard.

METHODS

A prospective study was conducted in 30 subjects aged 3-20 years presenting positive prick tests to ground mustard seeds (Brassica nigra), mustard flour (B. juncea), metabisulfite-free strong mustard seasoning (B. juncea) and a commercialized allergenic extract (B. nigra). Twenty-seven subjects were screened for mustard-specific immunoglobulin E (IgE). PCFCs were carried out either DB or single blind (SB) with up to 1340 mg of metabisulfite-free seasoning.

RESULTS

The mean diameter of the wheal induced by prick tests with the allergenic extract was lower (n.s.) than that induced by the native mustard products: 5.8 mm (1.5-15) vs 6.9 mm (0.5-18) for B. nigra ground seeds, 7.8 mm (1-20) for B. juncea flour and 9.7 mm (3-20) for the strong mustard seasoning. The diameter of the wheal induced by the allergenic extract was significantly different from that induced by the mustard seasoning (P < 0.005). The mean of mustard specific-IgE values was 8.7 KU/l (0.35-72.4). Seven of 30 food challenges were considered positive. Mean prick test results in the positive and negative PCFC subgroups were 5.5 mm vs 5.9 mm for the commercialized extract, 10.9 mm vs 5.8 mm for B. nigra ground seeds (P < 0.01), 9.9 mm vs 7.1 mm for B. juncea flour (n.s. P > 0.25) and 11.5 mm vs 9.1 mm for the metabisulfite-free mustard seasoning (n.s. P > 0.1). Mean specific IgE values determined by CAP system radioallergosorbent test (Phadebas Pharmacia) were higher but not significantly so (P > 0.25) in the subgroup with mustard allergy (12.3 K/l vs 7.6 KU/l).

CONCLUSIONS

About 23.3% of the sensitized subjects were allergic to a routine dose of mustard. Positive prick tests and the presence of specific IgE were not predictive. SB PCFC or DB PCFC is required before recommending avoidance diets.

Roasted hazelnuts--allergenic activity evaluated by double-blind, placebo-controlled food challenge

BACKGROUND

Allergy to hazelnuts is a common example of birch pollen related food allergy. Symptoms upon ingestion are often confined to the mouth and throat, but severe systemic reactions have been described in some patients. The aim of the study was to evaluate the reduction in allergenicity by roasting of the nuts.

METHODS

Double-blind, placebo-controlled food challenges (DBPCFC) with roasted hazelnuts (140 degrees C, 40 min) were performed in 17 birch pollen allergic patients with DBPCFC-confirmed food allergy to raw hazelnuts. The effect of roasting was further evaluated by skin prick test (SPT), histamine release (HR), measurement of specific IgE, and IgE-inhibition experiments.

RESULTS

In 5/17 patients the DBPCFC with the roasted nuts were positive. The symptoms were generally mild and included OAS (oral allergy syndrome) in all patients. Roasting of the nuts significantly reduced the allergenic activity evaluated by SPT, HR, specific IgE, and IgE-inhibition. Immunoblotting experiments with recombinant hazelnut allergens showed sensitization against Cor a 1.04 in 16/17 patients and against Cor a 2 in 7/17 patients. None of the patients were sensitized to Cor a 8. Challenge-positive patients did not differ from the rest in IgE-binding pattern.

CONCLUSIONS

All the applied methods indicated that roasting of hazelnuts reduces the allergenicity, but since 5/17 birch pollen allergic patients were DBPCFC-positive to the roasted nuts, ingestion of roasted hazelnuts or products containing roasted hazelnuts can not be considered safe for a number of hazelnut allergic consumers. For patients with a history of severe allergic symptoms upon ingestion of hazelnuts, thorough and conscientious food labelling of hazelnuts and hazelnut residues is essential.

[Cross-reactive allergen clusters in pollen-associated food allergy]

Immediate symptoms caused by allergens without previous primary sensitization are commonly based on cross-reactive IgE antibodies. They are responsible for pollen-associated food allergies, i.e., fruit allergy in cases of birch pollen allergy or allergy to celery and spices in cases of mugwort pollen allergy. Similar structures between the major allergen of birch pollen (Bet v 1) and a variety of pathogenesis-related proteins from the same family (PR-10), abundant in hazelnuts, fruits, and vegetables, have been well established. Other candidates are profilins, ubiquitous panallergens with little clinical relevance, and stable lipid transfer proteins, responsible for systemic reactions predominantly in Mediterranean countries. Depending on stability, dose, and resorption of these proteins, clinical symptoms are limited to the oro-pharyngeal cavity or develop systemically far from the site of allergen exposure. Clinical diagnosis is based on a positive case history with corresponding allergic sensitization to pollen allergens. Targeted skin testing with native products (i.e., prick to prick test with fresh fruits) appears to be superior for unstable allergens compared to commercial extracts. Individuals should be familiar with cross-reactive patterns; however, allergen avoidance is only recommended in cases of clinical symptoms.

Tree nut allergy

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

The disulphide mapping, folding and characterisation of recombinant Ber e 1, an allergenic protein, and SFA8, two sulphur-rich 2S plant albumins

We have cloned and expressed genes encoding the allergenic brazil nut 2S albumin (Ber e 1) and the sunflower albumin 8 (SFA8) in the methylotrophic yeast Pichia pastoris. We show that both proteins were secreted at high levels and that the purified proteins were properly folded. We also showed that Ber e 1 is glycosylated during secretion and that the glycan does not interfere with the folding or immunoreactivity. The disulphide map of the Ber e 1 protein was experimentally established and is in agreement with the conserved disulphide structure of other members of the 2S albumin family. A model three-dimensional structure of the allergen was generated. During the expression studies and through mutation we have also shown that alteration of the sequences around the Kex2 endoproteolytic processing site in the expressed fusion protein can compromise the secretion by targeting part of the protein for possible degradation. The secreted production of these properly folded sulphur-rich plant albumins presents an opportunity to delineate the attributes that make an allergen and to facilitate the diagnosis and therapy of type I allergy.