Influence of food processing on the allergenicity of celery: DBPCFC with celery spice and cooked celery in patients with celery allergy

Sensitization prevalence, antibody cross-reactivity and immunogenic peptide profile of Api g 2, the non-specific lipid transfer protein 1 of celery

Background

Celery (Apium graveolens) represents a relevant allergen source that can elicit severe reactions in the adult population. To investigate the sensitization prevalence and cross-reactivity of Api g 2 from celery stalks in a Mediterranean population and in a mouse model.

Methodology

786 non-randomized subjects from Italy were screened for IgE reactivity to rApi g 2, rArt v 3 (mugwort pollen LTP) and nPru p 3 (peach LTP) using an allergen microarray. Clinical data of 32 selected patients with reactivity to LTP under investigation were evaluated. Specific IgE titers and cross-inhibitions were performed in ELISA and allergen microarray. Balb/c mice were immunized with purified LTPs; IgG titers were determined in ELISA and mediator release was examined using RBL-2H3 cells. Simulated endolysosomal digestion was performed using microsomes obtained from human DCs.

Results

IgE testing showed a sensitization prevalence of 25.6% to Api g 2, 18.6% to Art v 3, and 28.6% to Pru p 3 and frequent co-sensitization and correlating IgE-reactivity was observed. 10/32 patients suffering from LTP-related allergy reported symptoms upon consumption of celery stalks which mainly presented as OAS. Considerable IgE cross-reactivity was observed between Api g 2, Art v 3, and Pru p 3 with varying inhibition degrees of individual patients' sera. Simulating LTP mono-sensitization in a mouse model showed development of more congruent antibody specificities between Api g 2 and Art v 3. Notably, biologically relevant murine IgE cross-reactivity was restricted to the latter and diverse from Pru p 3 epitopes. Endolysosomal processing of LTP showed generation of similar clusters, which presumably represent T-cell peptides.

Conclusions

Api g 2 represents a relevant celery stalk allergen in the LTP-sensitized population. The molecule displays common B cell epitopes and endolysosomal peptides that encompass T cell epitopes with pollen and plant-food derived LTP.

Spice allergy

OBJECTIVES

To provide a review on spice allergy and its implementation in clinical practice.

DATA SOURCES

PubMed searches were performed using spice allergy as the keyword for original and review articles. Selected references were also procured from the reviewed articles' references list.

STUDY SELECTION

Articles were selected based on their relevance to the topic.

RESULTS

Spices are available in a large variety and are widely used, often as blends. Spice allergy seems to be rare, reportedly affecting between 4 and 13 of 10,000 adults and occurring more often in women because of cosmetic use. No figures were available on children. Most spice allergens are degraded by digestion; therefore, IgE sensitization is mostly through inhalation of cross-reacting pollens, particularly mugwort and birch. The symptoms are more likely to be respiratory when exposure is by inhalation and cutaneous if by contact. Studies on skin testing and specific IgE assays are limited and showed low reliability. The diagnosis primarily depends on a good history taking and confirmation with oral challenge. The common use of spice blends makes identifying the particular offending component difficult, particularly because their components are inconsistent.

CONCLUSION

Spices are widely used and contain multiple allergens, yet spice allergy is probably markedly underdiagnosed. There is a need for reliable skin testing extracts and serum specific IgE assays. Currently, the diagnosis depends on a good history taking and well-designed titrated challenge testing. Until immunotherapy becomes developed, treatment is strict avoidance, which may be difficult because of incomplete or vague labeling.

Impact of arbuscular mycorrhizal fungi on the allergenic potential of tomato

Arbuscular mycorrhizal (AM) fungi influence the expression of defence-related genes in roots and can cause systemic resistance in plants probably due to the induced expression of specific defence proteins. Among the different groups of defence proteins, plant food allergens were identified. We hypothesized that tomato-allergic patients differently react to tomatoes derived from plants inoculated or not by mycorrhizal fungi. To test this, two tomato genotypes, wild-type 76R and a nearly isogenic mycorrhizal mutant RMC, were inoculated with the AM fungus Glomus mosseae or not under conditions similar to horticultural practice. Under such conditions, the AM fungus showed only a very low colonisation rate, but still was able to increase shoot growth of the wild-type 76R. Nearly no colonisation was observed in the mutant RMC, and shoot development was also not affected. Root fresh weights were diminished in AM-inoculated plants of both genotypes compared to the corresponding controls. No mycorrhizal effects were observed on the biomass and the concentration of phosphate and nitrogen in fruits. Real-time quantitative polymerase chain reaction analysis revealed that six among eight genes encoding for putative allergens showed a significant induced RNA accumulation in fruits of AM-colonised plants. However, human skin reactivity tests using mixed samples of tomato fruits from the AM-inoculated and control plants showed no differences. Our data indicate that AM colonisation under conditions close to horticultural practice can induce the expression of allergen-encoding genes in fruits, but this does not lead necessarily to a higher allergenic potential.

Sensitization profiles of a case of pollen-food allergy syndrome

A 13-year-old girl who had had pollinosis since the age of eight began to experience itching of the ears and vomiting after eating fresh fruits such as peach, apple and watermelon. This occurred at 10 years of age. The girl displayed positive reactions to six kinds of pollens, eleven kinds of fruits, numerous vegetables and to recombinant: rBet v2 present in specific IgE antibodies. She also reacted positively to several pollens, fruits and rBet v2 in the skin prick test. In the component-resolved diagnosis (CRD) using microarray technology, she also tested positive for profilin, a pan-allergen among plants. It is reported that profilin cross-reacts between pollen, fruits, vegetables and latex. From these results, we concluded that the allergic reactions to multiple kinds of foodstuff and pollens observed in this subject were due to cross-reactivity induced by profilin. Our results demonstrate that CRD by microarray is a reliable test in the diagnosis of PFAS.

Profilins: mimickers of allergy or relevant allergens?

Profilins are ubiquitous proteins, present in all eukaryotic cells and identified as allergens in pollen, latex and plant foods. The highly conserved structure justifies the cross-reactive nature of IgE antibodies against plant profilins and their designation as pan-allergens. Primary sensitization to profilin seems to arise from pollen sensitization with later development of cross-reactive IgE antibodies against plant food (and possibly latex) profilins. The role of profilin in inducing allergic symptoms needs to be evaluated and raises important issues in allergy diagnosis due to cross-reactivity. IgE cross-reactivity among profilins is associated with multiple pollen sensitization and with various pollen-food syndromes. In respiratory allergy, sensitization to pollen to which the patient has virtually no environmental exposure has been identified as a manifestation of profilin sensitization. As a food allergen, profilin usually elicits mild reactions, such as oral allergy syndrome, is not modified by processing and is especially important in allergy to some fruits, such as melon, watermelon, banana, tomato, citrus fruit and persimmon. Purified natural and recombinant profilins for in vitro and in vivo allergy tests are helpful in the diagnostic work-up. Herein we review the current state of knowledge about the allergen profilin and its implications in the diagnosis and treatment of allergic diseases. We conclude that, although its role in triggering allergic symptoms is still controversial, profilin is undoubtedly a relevant allergen. As a pan-allergen, profilin is associated with multiple pollen sensitization and pollen-food-latex syndromes that the allergist has to be aware of in order to accomplish an accurate diagnosis and successful treatment of allergic diseases.

Molecular characterization of Api g 2, a novel allergenic member of the lipid-transfer protein 1 family from celery stalks

SCOPE

Celery represents a relevant cross-reactive food allergen source in the adult population. As the currently known allergens are not typical elicitors of severe symptoms, we aimed to identify and characterize a non-specific lipid transfer protein (nsLTP).

METHODS AND RESULTS

MS and cDNA cloning were applied to obtain the full-length sequence of a novel allergenic nsLTP from celery stalks. The purified natural molecule consisted of a single isoallergen designated as Api g 2.0101, which was recombinantly produced in Escherichia coli Rosetta-gami. The natural and recombinant molecules displayed equivalent physicochemical and immunological properties. Circular dichroism revealed a typical α-helical fold and high thermal stability. Moreover, Api g 2 was highly resistant to simulated gastrointestinal digestion. As assessed by ELISA, thermal denaturation did not affect the IgE binding of Api g 2. Natural and recombinant Api g 2 showed similar allergenic activity in mediator release assays. Api g 2-specific IgE antibodies cross-reacted with peach and mugwort pollen nsLTPs.

CONCLUSION

Based on our results, it can be anticipated that inclusion of recombinant Api g 2 in the current panel of allergens for molecule-based diagnosis will facilitate the evaluation of the clinical relevance of nsLTP sensitization in celery allergy and help clinicians in the management of food allergic patients.

Impact of food processing on the structural and allergenic properties of food allergens

This article reviews recent studies that address one of the major unanswered questions in food allergy research: what attributes of food or food proteins contribute to or enhance food allergenicity?

Production and characterization of an allergen panel for component-resolved diagnosis of celery allergy

In celery a relevant food allergen source, three allergens have been identified so far: Api g 1 and Api g 4, and one glycosylated protein, Api g 5. For component-resolved food allergy diagnosis high amounts of well-defined allergens are needed. Depending on the individual celery allergen, protocols for heterologous production and purification from natural source, respectively, were established to obtain homogenous protein batches. Afterwards the purified recombinant allergens, Api g 1, Api g 4 and natural Api g 5 were characterized regarding their structural integrity and immunological activity. Therefore, several methods were applied. Proteins were identified by partial N-terminal sequencing, protein mass was verified by MS and sequence integrity by MALDI-TOF and N-terminal sequencing after tryptic digestion. Presence of isoforms in natural allergen preparations was identified by 2-DE. Secondary and tertiary structures were evaluated by circular dichroism (CD) spectroscopy and NMR analysis. Finally, IgE binding capacity was verified using selected sera from celery allergic patients in IgE immunoblots and IgE ELISA. These well-defined celery allergens will be used to prove the concept of component-resolved diagnosis and will contribute to improve food allergy diagnosis in the future.

Food contact hypersensitivity syndrome: the mucosal contact urticaria paradigm

Oral allergy syndrome (OAS) or pollen-fruit allergy syndrome represents a mucosal allergic contact urticaria in people sensitized to common pollens, due to IgE cross-reactivity between homologous pollen allergens and various plant foods. It is the most prevalent food allergy, affecting millions of people with respiratory allergies. Usually, symptoms are mild, self-limiting and localized to the oropharyngeal mucosa, although they may sometimes become generalized and life-threatening. Although patients usually recognize the offending foods, diagnosis may sometimes be complicated. Several clinical syndromes and association between pollens and plant-derived foods have been described. Crossreactivity on the basis of stringent immunological and allergological criteria can also occur in people without pollen sensitization or concomitant respiratory allergies, as in latex-fruit syndrome. The term 'food contact hypersensitivity syndrome' (FCHS) is proposed in this paper for the first time, to include all mucosal hypersensitivity reactions presenting with contact to food (both immunological and nonimmunological), whether due to crossreactivity with homologous plant-derived allergens or not. At this time, prophylaxis and treatment can only be attained by avoidance, even when symptoms are mild, with consequent impairment in quality of life. A better understanding of the pathophysiological mechanisms of FCHS and food allergy in general is essential for deeper insights and future emergence of effective therapies.

Characterization of recombinant Mal d 4 and its application for component-resolved diagnosis of apple allergy

BACKGROUND

Profilins are ubiquitous panallergens that have been extensively characterized; yet, their clinical relevance is still unclear.

OBJECTIVE

The aim of the present study was to produce recombinant apple profilin (rMal d 4) and to evaluate its allergenic activity and its potency for component-resolved allergy diagnosis.

METHODS

Complementary DNA-derived Mal d 4 was cloned, expressed in Escherichia coli and subsequently purified via poly (l-proline) sepharose. A total of 28 sera from apple-allergic patients were used for IgE-ELISA, immunoblot, RAST and basophil histamine release (BHR) test. In addition, skin prick tests (SPTs) were performed in five patients.

RESULTS

Four different complementary DNA coding for apple profilin, Mal d 4, each with an open reading frame of 393 nucleotides, were identified. One isoform Mal d 4.0101 was expressed in Escherichia coli and subsequently purified. Mass spectroscopy revealed the expected mass of 13.826 for rMal d 4.0101, and circular dichroism analysis data were typical for a folded protein and small-angle X-ray scattering measurement identified the protein as a monomer. All the serum samples displayed IgE binding to rMal d 4.0101 in IgE ELISA, immunoblot and RAST. In immunoblotting, IgE binding to natural Mal d 4 was partially/completely inhibited by preincubation with rMal d 4.0101, and RAST values to apple extract were significantly reduced upon serum pretreatment with rMal d 4.0101. SPTs and BHR assays using purified rMal d 4.0101 were positive. Purified rMal d 4.0101 was destroyed within seconds when subjected to pepsin digestion.

CONCLUSIONS

Apple profilin complementary DNAs were identified. The physicochemical and allergenic properties of purified recombinant Mal d 4.0101 were evaluated showing that the recombinant protein was equal to the natural protein as shown by inhibition assays. Thus, Mal d 4 represents another example suitable for component-resolved diagnosis of food allergy.

Mutational epitope analysis and cross-reactivity of two isoforms of Api g 1, the major celery allergen

For better understanding the cross-reactivity between the major birch pollen and celery allergens, Bet v 1 and Api g 1, respectively, putative epitope areas and structurally important positions for IgE-binding of the isoforms Api g 1.01 and Api g 1.02 were point mutated. The IgE binding capacities were measured in ELISA, the IgE cross-reactivity between the isoforms, mutants and Bet v 1 investigated by ELISA-inhibition experiments with serum pools from patients with confirmed celery allergy (DBPCFC). Api g 1.01 displayed a clearly higher frequency and capacity of IgE binding than Api g 1.02. In Api g 1.01, substitution of lysine against glutamic acid at amino acid position 44, a key residue of the Bet v 1 "P-loop", increased the IgE-binding properties. Structural instability due to proline insertion at position 111/112 resulted in loss of IgE binding of Api g 1.01, but not of Api g 1.02. Between Api g 1.01 and Api g 1.02 only partial cross-reactivity was seen. The data suggest that the IgE epitopes of the two isoforms are distinct and that in contrast to Api g 1.01, the "P-loop" region plays an important role for IgE binding of celery allergic subjects to Api g 1.02. Understanding and investigation of the molecular mechanisms in celery allergy is an important step to generate hypoallergenic proteins for safe and efficacious immunotherapy of food allergy.

The impact of pollen-related food allergens on pollen allergy

Patients with birch pollen allergy frequently develop hypersensitivity reactions to certain foods, e.g. apples, celery, carrots and hazelnuts. These reactions are mainly caused by IgE-antibodies specific for the major birch pollen allergen, Bet v 1, which cross-react with homologous proteins in these foods. Analyzing the T-cell response to Bet v 1-related food allergens revealed that these dietary proteins contain several distinct T-cell epitopes and activate Bet v 1-specific T cells to proliferate and produce cytokines. Several of these cross-reactive T-cell epitopes were not destroyed by simulated gastrointestinal digestion of food allergens and stimulated Bet v 1-specific T cells despite nonreactivity with IgE antibodies. Similarly, cooked food allergens did not elicit IgE-mediated symptoms (oral allergy syndromes) but caused T-cell-mediated late-phase reactions (deterioration of atopic eczema) in birch pollen-allergic patients with atopic dermatitis because thermal processing affected their conformational structure and not the primary amino acid sequence. Thus, T-cell cross-reactivity between Bet v 1 and related food allergens occurs independently of IgE-cross-reactivity in vitro and in vivo. We speculate that symptom-free consumption of pollen-related food allergens may have implications for the pollen-specific immune response of allergic individuals.

Food allergies: prevalence, molecular characterization, and treatment/prevention strategies

A significant proportion of the population is either affected by or concerned about food allergy. Our knowledge about food allergens and how they stimulate the immune system has increased dramatically over the past decade. However, reasons for the increased prevalence of food allergy are not clear. The diagnosis of food allergy requires that the patient and caregivers examine all foods for the presence of potential allergens in order to prevent inadvertent ingestion and further reactions. Fortunately, many children develop tolerance to allergenic foods after a period of dietary elimination. Various immunotherapy approaches are under investigation to alleviate or prevent food-induced reactions in those who have persistent food allergies.

Structural, immunological and functional properties of natural recombinant Pen a 1, the major allergen of Brown Shrimp, Penaeus aztecus

BACKGROUND

Recombinant allergens are considered the basis for new diagnostic approaches and development of novel strategies of allergen-specific immunotherapy. As Pen a 1 from brown shrimp Penaeus aztecus is the only major allergen of shrimp and binds up to 75% of all shrimp-specific IgE antibodies this molecule may be an excellent model for the usage of allergens with reduced IgE antibody-binding capacity for specific immunotherapy.

AIM

The aim was to clone, express and characterize a full-length recombinant Pen a 1 molecule and compare it with natural Pen a 1 in regard to structural and immunological parameters such as IgE antibody capacity and ability to induce IgE-mediated mediator release.

METHODS

Total RNA was isolated from P. aztecus and a rapid amplification of cDNA ends (5' RACE) was performed to obtain full-length cDNA coding for Pen a 1. Using a gene-specific primer, PCR was performed and full-length cDNA was cloned and sequenced. Recombinant His-tagged Pen a 1 was isolated from Escherichia coli under native conditions by immobilized metal affinity chromatography. Secondary structure of natural and recombinant Pen a 1 was compared by circular dichroism (CD) spectroscopy, and the IgE antibody-binding capacity evaluated by RAST. The allergenic potency was tested by the capability of natural and recombinant Pen a 1 to induce mediator release in a murine and human in vitro model of IgE-mediated type I allergy.

RESULTS

The deduced amino-acid sequence was 284 residues long and amino-acid sequence identities with allergenic and non-allergenic tropomyosins ranged from 80% to 99% and 51% to 58%, respectively. The analysis of the secondary structure of natural and recombinant Pen a 1 by CD spectroscopic analysis showed that both nPen a 1 and rPen a 1 had alpha-helical conformation that is typical for tropomyosin. The IgE antibody binding capacities of nPen a 1 and r Pen a1 were found to be essentially identical by RAST. The mediator release experiments using both wild-type and humanized rat basophilic leukaemia 30/25 cells showed that rPen a 1 and nPen a 1 induced a similar level of mast cell activation.

CONCLUSIONS

Recombinant Pen a 1 and natural Pen a 1 are structurally and immunologically identical and rPen a 1 may be used as the basis for component-resolved diagnosis and the generation of modified shrimp tropomyosin for allergen-specific immunotherapy. The results of the animal studies indicate that C3H/HeJ mice that were sensitized with shrimp extract in combination with cholera toxin as adjuvant may be a suitable model to study shrimp allergy.

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.

Food allergy and the introduction of solid foods to infants: a consensus document. Adverse Reactions to Foods Committee, American College of Allergy, Asthma and Immunology

OBJECTIVE

To make recommendations based on a critical review of the evidence for the timing of the introduction of solid foods and its possible role in the development of food allergy.

DATA SOURCES

MEDLINE searches using the following search algorithm: [weaning AND infant AND allergy]/[food allergy AND sensitization]/[dietary prevention AND food allergy OR allergens]/[Jan 1980-Feb 2006].

STUDY SELECTION

Using the authors' clinical experience and research expertise, 52 studies were retrieved that satisfied the following conditions: English language, journal impact factor above 1 or scientific society, expert, or institutional publication, and appraisable using the World Health Organization categories of evidence.

RESULTS

Available information suggests that early introduction can increase the risk of food allergy, that avoidance of solids can prevent the development of specific food allergies, that some foods are more allergenic than others, and that some food allergies are more persistent than others.

CONCLUSIONS

Pediatricians and allergists should cautiously individualize the introduction of solids into the infants' diet. With assessed risk of allergy, the optimal age for the introduction of selected supplemental foods should be 6 months, dairy products 12 months, hen's egg 24 months, and peanut, tree nuts, fish, and seafood at least 36 months. For all infants, complementary feeding can be introduced from the sixth month, and egg, peanut, tree nuts, fish, and seafood introduction require caution. Foods should be introduced one at a time in small amounts. Mixed foods containing various food allergens should not be given unless tolerance to every ingredient has been assessed.

Structure and stability of 2S albumin-type peanut allergens: implications for the severity of peanut allergic reactions

Resistance to proteolytic enzymes and heat is thought to be a prerequisite property of food allergens. Allergens from peanut (Arachis hypogaea) are the most frequent cause of fatal food allergic reactions. The allergenic 2S albumin Ara h 2 and the homologous minor allergen Ara h 6 were studied at the molecular level with regard to allergenic potency of native and protease-treated allergen. A high-resolution solution structure of the protease-resistant core of Ara h 6 was determined by NMR spectroscopy, and homology modelling was applied to generate an Ara h 2 structure. Ara h 2 appeared to be the more potent allergen, even though the two peanut allergens share substantial cross-reactivity. Both allergens contain cores that are highly resistant to proteolytic digestion and to temperatures of up to 100 degrees C. Even though IgE antibody-binding capacity was reduced by protease treatment, the mediator release from a functional equivalent of a mast cell or basophil, the humanized RBL (rat basophilic leukaemia) cell, demonstrated that this reduction in IgE antibody-binding capacity does not necessarily translate into reduced allergenic potency. Native Ara h 2 and Ara h 6 have virtually identical allergenic potency as compared with the allergens that were treated with digestive enzymes. The folds of the allergenic cores are virtually identical with each other and with the fold of the corresponding regions in the undigested proteins. The extreme immunological stability of the core structures of Ara h 2 and Ara h 6 provides an explanation for the persistence of the allergenic potency even after food processing.

Kutane Symptome nach Genuss pollenassoziierter Nahrungsmittel

The molecular basis of pollen-related food allergy is the marked similarity in sequence and structure of allergenic proteins in pollens and food plants. In affected patients, specific IgE antibodies are primarily directed against pollen allergens but then recognize homologous allergens in plant food. In Central and Northern Europe up to 80% of birch pollen allergic subjects suffer from a food allergy, in particular to stone- and pip fruits, nuts and vegetables. The main clinical manifestation of pollen-related food allergy is the oral allergy syndrome (OAS), a contact urticaria of the oral mucosa. Other features include contact urticaria of the hands in those handling the foods, as well as generalized urticaria and angioedema following ingestion. The impact of pollen-related food allergy on the severity and course of atopic eczema remain to be elucidated.

Crystal Structure of the Major Celery Allergen Api g 1: Molecular Analysis of Cross-reactivity

Many patients who have been sensitised to pollen, display allergic symptoms after ingestion of certain plant food such as fresh fruit, vegetables and nuts. The cause is the cross-reactivity between structurally very similar major plant allergens. In particular, allergy to celery is very frequently associated with birch and mugwort pollen sensitization, known as to the birch-mugwort-celery syndrome. The crystal structure of the major celery allergen Api g 1, a homologue of the major birch pollen allergen Bet v 1, has been determined to a resolution of 2.9 A. The structure of Api g 1 is very similar to that of Bet v 1 with major differences occurring in the segment comprised of residues 23-45, preceding the well conserved glycine-rich P-loop, as well as in loops beta3-beta4 and beta5-beta6. In particular, Api g 1 lacks E45, which has been shown to be a crucial residue for antibody recognition in the crystal complex of Bet v 1 with the Fab fragment of a murine monoclonal IgG (BV16) antibody. The absence of E45 and the structural differences in the preceding segment suggest that this region of the Api g 1 surface is probably not responsible for the observed cross-reactivity with Bet v 1. A detailed analysis of the molecular surface in combination with sequence alignment revealed three conserved surface patches which may account for cross-reactivity with Bet v 1. Several residues of Bet v 1 which have been shown by mutagenesis studies to be involved in IgE recognition belong to these conserved surface regions. The structure of Api g 1 and the related epitope analysis provides a molecular basis for a better understanding of allergen cross-reactivity and may lead to the development of hypoallergens which would allow a safer immunotherapy.

Plant food allergies: a suggested approach to allergen-resolved diagnosis in the clinical practice by identifying easily available sensitization markers

BACKGROUND

Molecular biology techniques have led to the identification of a number of allergens in vegetable foods, but due to the lack of purified food proteins for routine diagnostic use, the detection of sensitizing allergens remains a nearly impossible task in most clinical settings. The allergen-resolved diagnosis of food allergy is essential because each plant-derived food may contain a number of different allergens showing different physical/chemical characteristics that strongly influence the clinical expression of allergy; moreover, many allergens may cross-react with homologue proteins present in botanically unrelated vegetable foods.

OBJECTIVE

Through a review of the available literature, this study aimed to detect "markers" of sensitization to specific plant food allergens that are easily accessible in the clinical practice.

RESULTS

There are several "markers" of sensitization to different allergenic proteins in vegetable foods that can be helpful in the clinical practice. Specific algorithms for patients allergic to Rosaceae and to tree nuts were built.

CONCLUSION

Clinical allergologists lacking the assistance of an advanced molecular biology lab may take advantage of some specific clinical data as well as of some "markers" in the difficult task of correctly diagnosing patients with plant food allergy and to provide them the best preventive advice.

Clinical tolerance of processed foods

OBJECTIVE

To review the effects of technological processing on selected foods of relevance to childhood allergy from the viewpoints of reduced allergenicity, contamination of processed foods by allergens introduced during processing, and ad hoc technologies to produce reduced hypoallergenic products.

DATA SOURCES

We searched the literature (PubMed/MEDLINE) for articles published between January 1994 and April 2004 using the following keywords: food allergy AND process* OR heat* OR cooking OR toleran*.

STUDY SELECTION

We drew on our collective clinical and biological experience to restrict retrieved studies to those of more frequent relevance to a hospital allergy practice.

RESULTS

Comparatively few clinical studies address the modification of allergenicity of food through cooking or processing. Dairy foods are largely unaffected by processing and may be contaminated by, or themselves become, hidden allergens. Hypoallergenic formulas based on milk, soy, or rice and homogenized beef are successful applications of allergenicity reduction via technological processing. Egg, fish, condiments, and vegetables all carry heat-resistant allergens and should also be considered contaminants. Cereals and bakery products are generally well tolerated, but their allergenicity may be enhanced by processing; the case of rice is still open. Peanut allergens are stable, and the evidence is scant that thermal processing affects the allergenicity of soybean and soy hydrolysates. The debate is ongoing about the tolerance of vegetable oils.

CONCLUSIONS

It is too early to systematize clinical studies based on single procedures. Processing affects antigenicity, but this does not always translate into safety recommendations. Industrial processing is liable to contamination, and monitoring and labeling are industry priorities. Clinicians should evaluate foods by as complete a workup as possible before recommending processed foods.

Food processing: effects on allergenicity

PURPOSE OF REVIEW

There has been an increase in the prevalence of food allergy, asthma and severe reactions to foods in the past decade. The reason for this increase is unknown and despite the potential for a lethal outcome, no treatments or therapies are available. Many areas are being explored to understand the increase in food allergy and the role of modern processing techniques is one of them.

RECENT FINDINGS

The fact that processing influences allergenicity is not a new concept, but due to some definitive studies in the last few years the topic has been revitalized. Not only is the processed form of a particular allergen important in assessment of allergenicity, but the role of the food matrix in which an allergen is processed must also be evaluated. The issue of allergenicity of particular foods is therefore highly complex, and even with our existing knowledge we have just begun to understand some of the contributions of processing to allergenic properties of proteins and foods.

SUMMARY

Researchers and medical personnel have begun to weigh the benefits and potential disadvantages of assessing the allergenicity of foods in unprocessed forms. In this review, the known effects of processing on the allergenicity of various foods will be discussed along with the implications of the most recent studies on the future direction of research in this area.

Ara h 8, a Bet v 1–homologous allergen from peanut, is a major allergen in patients with combined birch pollen and peanut allergy

BACKGROUND

We recently described patients with soybean allergy mainly mediated by cross-reactivity to birch pollen allergens. A majority of those patients were reported to have peanut allergy.

OBJECTIVE

We sought to study the occurrence of peanut allergy in patients allergic to birch pollen and characterized the Bet v 1-homologous peanut allergen Ara h 8.

METHODS

Recombinant Ara h 8 was cloned with degenerated primers and expressed in Escherichia coli. Nine Swiss and 11 Dutch patients with peanut and birch pollen allergy and a positive double-blind, placebo-controlled food challenge result to peanut were investigated for IgE reactivity to birch pollen and purified peanut allergens and cross-reactivity between birch and peanut. Ara h 8 stability against digestion and roasting was assessed by means of RAST inhibition. The IgE cross-linking potency of Ara h 8 was tested on the basis of basophil histamine release.

RESULTS

During double-blind, placebo-controlled food challenge, all patients experienced symptoms in the oral cavity, progressing to more severe symptoms in 40% of patients. CAP-FEIA detected recombinant (r) Ara h 8-specific IgE in 85%. IgE binding to Ara h 8 was inhibited by Bet v 1 in peanut extract immunoblotting and in RAST inhibition. In EAST inhibition recombinant rAra h 8 inhibited IgE binding to peanut in 4 of 7 tested patient sera. Antipeanut response was dominated by Ara h 8 in 12 of 17 tested patients. Furthermore, our results demonstrate a low stability of Ara h 8 to roasting and no stability to gastric digestion. Basophil histamine release with rAra h 8 was more than 20% in 5 of 7 tested sera.

CONCLUSIONS

Peanut allergy might be mediated in a subgroup of our patients by means of cross-reaction of Bet v 1 with the homologous peanut allergen Ara h 8.

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.

Characterization of cross-reactive bell pepper allergens involved in the latex-fruit syndrome

BACKGROUND

Between 30% and 50% of individuals who are allergic to latex products are also allergic to specific plant foods, a fact that is well documented as the latex-fruit syndrome. Simultaneous sensitization to latex and bell pepper has been previously reported. Although bell pepper fruits are frequently consumed raw, cooked or as a spice, little is known about the cross-reactive allergens.

OBJECTIVE

In this study we wished to identify bell pepper allergens involved in the latex-fruit syndrome.

METHODS

Sera of four patients who displayed clinical symptoms to latex and bell pepper were used in immunoblot studies on protein extracts of three different cultivars of fresh bell pepper and fresh Hevea latex. Cross-reactive allergens were identified by inhibition experiments using recombinant Hev b 8 (latex profilin), and natural Hev b 2 (latex beta-1,3-glucanase) in addition to the protein extracts. A novel cross-reactive IgE-reactive 30 kDa protein was subjected to sequence analysis.

RESULTS

Three patients displayed IgE to profilins from bell pepper fruits and latex. Two patients possessed IgE to Hev b 2, a latex beta-1,3-glucanase, and a homologous protein in bell pepper. One patient possessed IgE reactive with a protein of 30 kDa identified by N-terminal sequencing as an l-ascorbate peroxidase and another patient to a protein of 38 kDa. Additionally, IgE binding proteins in two higher molecular weight ranges showed cross-reactive capacities.

CONCLUSION

Our findings show on the molecular level that bell pepper is part of the latex-fruit syndrome. For the first time we have identified the major latex allergen Hev b 2, a beta-1,3-glucanase, and the bell pepper l-ascorbate peroxidase as cross-reactive allergens. We were also able to show that profilins are responsible for some of the IgE cross-reactivity.

Birch pollen-related food as a provocation factor of allergic symptoms in children with atopic eczema/dermatitis syndrome

BACKGROUND

Food allergy to cow's milk or hen's egg is a common problem in children with atopic eczema/dermatitis syndrome (AEDS) but the role of birch pollen-related food for the induction of allergic symptoms is still not clear.

PATIENTS/METHODS

Twelve children (median age 5 years) with AEDS underwent an oral challenge with those birch pollen-related foods which were reported to induce no immediate symptoms, but were consumed on a regular basis. Total IgE and specific IgE to birch pollen, Bet v 1/2 and various birch pollen-related foods were determined.

RESULTS

Seven of 12 children showed immediate and/or late eczematous reactions upon ingestion of birch pollen-related foodstuff. Four children showed a worsening of eczema 24 h upon oral challenge with a significant difference in SCORAD before and after challenge. There were no differences in terms of total IgE or birch pollen-specific IgE between children with a late eczematous response and non-reacting children.

CONCLUSIONS

Birch pollen-related food may induce allergic symptoms in children with AEDS who exhibit a sensitization to birch pollen. Oral challenge tests should be performed in those children who suffer from severe AEDS and who are highly sensitized to birch pollen allergens even in the absence of a history suggestive of food allergy.

Allergic cross-reactivity: from gene to the clinic

A large number of allergenic proteins have now their complete cDNA sequences determined and in some cases also the 3D structures. It turned out that most allergens could be grouped into a small number of structural protein families, regardless of their biological source. Structural similarity among proteins from diverse sources is the molecular basis of allergic cross-reactivity. The clinical relevance of immunoglobulin E (IgE) cross-reactivity seems to be influenced by a number of factors including the immune response against the allergen, exposure and the allergen. As individuals are exposed to a variable number of allergenic sources bearing homologous molecules, the exact nature of the antigenic structure inducing the primary IgE immune response cannot be easily defined. In general, the 'cross-reactivity' term should be limited to defined clinical manifestations showing reactivity to a source without previous exposure. 'Co-recognition', including by definition 'cross-reactivity', could be used to describe the large majority of the IgE reactivity where co-exposure to a number of sources bearing homologous molecules do not allow unequivocal identification of the sensitizing molecule. The analysis of reactivity clusters in diagnosis allows the interpretation of the patient's reactivity profile as a result of the sensitization process, which often begins with exposure to a single allergenic molecule.

Detection of clinical markers of sensitization to profilin in patients allergic to plant-derived foods

BACKGROUND

A proper classification of patients allergic to plant-derived foods is of pivotal importance because the clinical features of allergic reactions to fruits and vegetables depend on the nature and characteristics of proteins responsible for sensitization. However, in normal clinical settings this is presently impossible.

OBJECTIVE

We sought to detect clinical markers of sensitization to profilin.

METHODS

Seventy-one patients allergic to fruits and vegetables but not sensitized to lipid transfer protein or natural rubber latex were studied. Food allergy was ascertained on the basis of clinical history and positive skin prick test responses with fresh foods, commercial extracts, or both. Allergies to foods that had caused less than 2 adverse reactions were confirmed by means of open oral challenge. IgE reactivity to rBet v 1/rBet v 2 and to natural Phleum species profilin were detected. Moreover, IgE to the 30- to 40-kd and 60- to 90-kd birch pollen-enriched fractions, which also can be involved in cross-reactivity phenomena, were measured in sera from 52 patients by means of ELISA.

RESULTS

On the basis of in vitro tests, 24, 18, and 25 patients turned out to be sensitized to Bet v 1, Bet v 2, or both, respectively. Four patients had negative test results for both allergens. Hypersensitivity to Bet v 2 was strongly associated with clinical allergy to citrus fruits (39% in patients monosensitized to Bet v 2 vs 4% in patients monosensitized to Bet v 1, P <.025), melon or watermelon (67% vs 0%, P <.001), banana (66% vs 8%, P <.001), and tomato (33% vs 0%, P <.05), whereas Bet v 1 sensitivity was associated with clinical allergy to apple (100% vs 39%, P <.001) and hazelnut (56% vs 0%, P <.001). The sensitivity of a history of allergy to gourd fruits, citrus fruits, tomato, banana, or a combination thereof as a means to detect profilin-hypersensitive patients was 85% (41/48). The specificity of an allergy to any of these fruits exceeded 85%, with positive predictive values ranging between 68% and 91%.

CONCLUSION

In clinical settings in which laboratory investigations are not easily accessible, allergy to melon, watermelon, citrus fruits, tomato, and banana can be used as a marker of profilin hypersensitivity once a sensitization to natural rubber latex and lipid transfer protein is ruled out.

IgE and non-IgE food allergy

BACKGROUND

Food allergy (FA) is characterized by an abnormal immunologic reactivity to food proteins. The gastro-intestinal tract serves not only a nutritive function but also is a major immunologic organ. Although previously thought to be triggered primarily by an IgE-mediated mechanism of injury, considerable evidence now suggests that non-IgE mechanisms may also be involved in the pathogenesis of FA.

OBJECTIVE

To review the immunologic disturbances that occur in FA and to correlate these with the clinical manifestations expressed in affected target organs based upon a classification of IgE and non-IgE mechanisms.

METHODS

Data collected from a computerized MEDLINE search were used for the analysis of the following topics: immediate GI hypersensitivity, oral allergy syndrome, acute urticaria and angioedema, acute bronchospasm, celiac disease, cow's milk enteropathy, dietary protein enterocolitis, breast milk colitis, proctolitis, proctitis, dermatitis herpetiformis, Heiner syndrome, eosinophilic gastroenteritis, atopic dermatitis, asthma, attention-deficit-hyperactivity disorder and behavioral disorders, as well as systems affected by mucosal associated lymphoid tissue-mediated injury of associated lymphoid tissues and the immunologic deviation to Th1 or Th2 mechanisms of FA.

CONCLUSIONS

The results of this review allow the construction of a central, unifying hypothesis for a new classification of FA as follows: the clinical manifestations of FA, expressed in affected target organs, may be the result of immunologic injury mediated by interaction of food antigens with contiguous elements of mucosal associated lymphoid tissue. These appear to be modulated by relative imbalances of the Th1/Th2 paradigm, which may be the ultimate determinant governing the expression of FA as IgE-mediated, non--IgE-mediated, or mixed forms of IgE/non-IgE mechanisms of FA.

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.

Current understanding of cross-reactivity of food allergens and pollen

Pollen-allergic patients frequently present allergic symptoms after ingestion of several kinds of plant-derived foods. The majority of these reactions is caused by four distinct cross-reactive structures that are present in birch pollen. Proteins that share common epitopes with Bet v 1, the major birch pollen allergen, occur in pollens of several tree species: apples, stone fruits, celery, carrot, nuts, and soybeans. Approximately 70% of our patients who are allergic to birch pollen may experience symptoms after consumption of foods from these groups. In contrast, two minor allergenic structures-profilins and cross-reactive carbohydrate determinants (CCD)-that sensitize approximately 10-20% of all pollen-allergic patients are also present in grass pollen and weed pollen. Moreover, IgE-binding proteins related to the birch pollen minor allergen Bet v 6 have been found in many vegetable foods such as apple, peach, orange, lychee fruit, strawberry, persimmon, zucchini, and carrot. Frequently, the occurrence of cross-reactive IgE antibodies is not correlated with the development of clinical food allergy. In particular, the clinical relevance of sensitization to CCD is doubtful. Generally, pollen-related allergens tend to be more labile during heating procedures and in the digestive tract compared to allergens from classical allergenic foods such as peanut. However, recent DBPCFC studies have shown that both cooked celery and roasted hazelnuts still pose an allergenic risk for pollen-sensitized subjects. Since pathogenesis-related proteins share several common features with allergens and both the Bet v 1 and the Bet v 6-related food allergens are defense-related proteins, approaches to introduce such proteins as a measure to protect plants against diseases should be performed with caution as they may increase the allergenicity of these crops.