Pollen-food Syndrome Research Articles

Isolation of Mal d 1 and Api g 1 - specific recombinant antibodies from mouse IgG Fab fragment libraries - Mal d 1-specific antibody exhibits cross-reactivity against Bet v 1.

BackgroundAround 3–5% of the population suffer from IgE-mediated food allergies in Western countries and the number of food-allergenic people is increasing. Individuals with certain pollen allergies may also suffer from a sensitisation to proteins in the food products. As an example a person sensitised to the major birch pollen allergen, Bet v 1, is often sensitised to its homologues, such as the major allergens of apple, Mal d 1, and celery, Api g 1, as well. Development of tools for the reliable, sensitive and quick detection of allergens present in various food products is essential for allergic persons to prevent the consumption of substances causing mild and even life-threatening immune responses. The use of monoclonal antibodies would ensure the specific detection of the harmful food content for a sensitised person.MethodsMouse IgG antibody libraries were constructed from immunised mice and specific recombinant antibodies for Mal d 1 and Api g 1 were isolated from the libraries by phage display. More detailed characterisation of the resulting antibodies was carried out using ELISA, SPR experiments and immunoprecipitation assays.ResultsThe allergen-specific Fab fragments exhibited high affinity towards the target recombinant allergens. Furthermore, the Fab fragments also recognised native allergens from natural sources. Interestingly, isolated Mal d 1-specific antibody bound also to Bet v 1, the main allergen eliciting the cross-reactivity syndrome between the birch pollen and apple. Despite the similarities in Api g 1 and Bet v 1 tertiary structures, the isolated Api g 1-specific antibodies showed no cross-reactivity to Bet v 1.ConclusionsHere, high-affinity allergen-specific recombinant antibodies were isolated with interesting binding properties. With further development, these antibodies can be utilised as tools for the specific and reliable detection of allergens from different consumable products. This study gives new preliminary insights to elucidate the mechanism behind the pollen-food syndrome and to study the IgG epitope of the allergens.

Frequent episodes of adult soybean allergy during and following the pollen season

The pollen-food syndrome (PFS) is one of the most common forms of food allergy in adults and adolescents. Allergic reactions to foods are explained by primary respiratory sensitization to pollen and IgE cross-reactivity between the pollen allergen and its homologous allergens in foods. In clinical practice, increased food-triggered allergic symptoms during or after the pollen season are observed in some patients with PFS, thought to be due to seasonal boosting of pollen-IgE levels. We consider that whether there is indeed a seasonal variation in food allergic symptoms is an important issue for the long-term management of patients with PFS. However, clinical evidence that supports seasonal variation has been quite limited so far, although there is one study that reports an increased clinical reactivity to apples during the birch pollen season. The aim of the present study was to clarify seasonal variation in severe allergic episodes of pollen-related food allergy. Here, we focused on the association between Betulaceae and Fagaceae pollen counts and increased episodes of severe allergic symptoms after soybean ingestion. We performed a retrospective medical chart-based review on consecutive adult patients with soybean allergy who first visited the food allergy department of Sagamihara National Hospital between October 2008 and September 2013. Soybean allergy was defined as meeting two criteria: (1) positive case history of immediate allergic symptoms after ingestion of soy products and (2) positive skin prick test results to soybean extract (extract “edamame,” Torii, Tokyo, Japan) and/or the causative soy product. First, we screened 85 consecutive patients with soybean allergy after reviewing charts of all outpatients during the study period, and gathered detailed information on symptoms that occurred after soy intake, including the day, month, and year when they had symptoms. Although the most common symptoms of soy allergy are restricted to the oral cavity, the subjects studied here were limited to those who had experienced systemic allergic symptoms (n 1⁄4 26) after soybean ingestion. Of these, 4 were excluded because data on the day, month, and year when they had symptoms were missing. Thus, 22 patients were finally included. The Ethics Committee of Sagamihara National Hospital approved the study protocol. Levels of serum IgE antibodies specific for alder pollen, soybean extract, recombinant Bet v 1 (rBet v 1), rGly m 4, native Gly m 5 (nGly m 5), and nGly m 6 were determined using a commercially available ImmunoCAP system (Thermo Fisher Scientific, Uppsala, Sweden). A level of IgE antibody 0.35 kUA/L was regarded as positive according to the manufacturers recommendation. Counts of airborne Betulaceae and Fagaceae pollen were recorded using a Durham gravity sampler on the roof of the Sagamihara National Hospital during the study period. Demographic and clinical characteristics of the 22 patients studied are shown in Table I. Twenty-one (96%) of them reported nasal allergic symptoms during the Betulaceae and Fagaceae pollen season (data not shown). They experienced a total of 33 episodes of systemic allergic symptoms after soy intake. We identified the timing of these episodes from the medical records. The most frequent offending soy product was soymilk (n 1⁄4 21), followed by tofu (n 1⁄4 3), and bean sprouts (n 1⁄4 3), consistent with previous studies. Details of the 22 patients are shown in Table E1 of this article’s Online Repository at www.jaci-inpractice.org. All patients were found to be sensitized to alder, the birch pollen major allergen, Bet v 1, and its homologous allergen in soy, rGly m 4. This indicates that all the patients can be regarded as having pollen-related soybean allergy.

Fruit and vegetable allergy.

Fruit and vegetable allergies are the most prevalent food allergies in adolescents and adults. The identification of the allergens involved and the elucidation of their intrinsic properties and cross-reactivity patterns has helped in the understanding of the mechanisms of sensitisation and how the allergen profiles determine the different phenotypes. The most frequent yet contrasting fruit and vegetable allergies are pollen-food syndrome (PFS) and lipid transfer protein (LTP) syndrome. In PFS, fruit and vegetable allergies result from a primary sensitisation to labile pollen allergens, such as Bet v 1 or profilin, and the resulting phenotype is mainly mild, consisting of local oropharyngeal reactions. In contrast, LTP syndrome results from a primary sensitisation to LTPs, which are stable plant food allergens, inducing frequent systemic reactions and even anaphylaxis. Although much less prevalent, severe fruit allergies may be associated with latex (latex-fruit syndrome). Molecular diagnosis is essential in guiding the management and risk assessment of these patients. Current management strategies comprise avoidance and rescue medication, including adrenaline, for severe LTP allergies. Specific immunotherapy with pollen is not indicated to treat pollen-food syndrome, but sublingual immunotherapy with LTPs seems to be a promising therapy for LTP syndrome.

A systematic review of randomised controlled trials, non-randomised controlled trials and observational studies to ascertain the role of pollen-specific immunotherapy in improving clinical outcomes in pollen-food (ORAL ALLERGY) syndrome

Background Pollen Food(Oral allergy) Syndrome (PFS) is a food allergy which is caused by cross-reactivity between inhalant pollen allergens and food allergens, causing mild to severe symptoms upon ingestion of the cross-reacting foods. PFS has a high and increasing prevalence in pollen-allergic patients. The role of pollen-specific immunotherapy in improving clinical outcomes for patients with PFS has not been established. To date, there are no systematic reviews which have been identified in the background research in this field. Aim of the review was to evaluate the evidence and determine whether pollenspecific immunotherapy clinically improves symptoms of PFS in pollen-allergic patients.

Food allergens: molecular and immunological aspects, allergen databases and cross-reactivity.

The currently known food allergens are assigned to a relatively small number of protein families. Food allergens grouped into protein families share common functional and structural features that can be attributed to the allergenic potency and potential cross-reactivity of certain proteins. Molecular data, in terms of structural information, biochemical characteristics and clinical relevance for each known allergen, including isoforms and variants, are mainly compiled into four open-access databases. Allergens are designated according to defined criteria by the World Health Organization and the International Union of Immunological Societies Allergen Nomenclature Sub-committee. Food allergies are caused by primary sensitisation to the disease-eliciting food allergens (class I food allergen), or they can be elicited as a consequence of a primary sensitisation to inhalant allergens and subsequent IgE cross-reaction to homologous proteins in food (class II food allergens). Class I and class II allergens display different clinical significance in children and adults and are characterised by different molecular features. In line with this, high stability when exposed to gastrointestinal digestion and heat treatment is attributed to many class I food allergens that frequently induce severe reactions. The stability of a food allergen is determined by its molecular characteristics and can be influenced by structural (chemical) modifications due to thermal processing. Moreover, the immunogenicity and allergenicity of food allergens further depends on specific T cell and B cell epitopes. Although the T cell epitope pattern can be highly diverse for individual patients, several immuno-prominent T cell epitopes have been identified. Such conserved T cell epitopes and IgE cross-reactive B cell epitopes contribute to cross-reactivity between food allergens of the same family and to clinical cross-reactivity, similar to the birch pollen-food syndrome.

Food allergen sensitization pattern in adults in relation to severity of atopic dermatitis

BackgroundLimited data are available on the frequency of IgE mediated food sensitization and food allergy (FA) in adults with atopic dermatitis (AD).ObjectiveWe investigated the pattern of food sensitization in adults with AD in relation to AD severity using multiplexed allergen microarray.Methods211 adult patients referred between January 2010-July 2011 for evaluation of AD were unselectively included. Severity of AD was determined by therapy intensity, SASSAD-skin-score and sTARC levels. Allergen specific sIgE levels were measured by ImmunoCAP ISAC® microarray. FA was defined as convincing history taken by physician and sensitization to the corresponding allergen.ResultsSensitization to food was found in 74.4% of the AD patients, 54% had a positive history of FA and 20.4% asymptomatic sensitization. There was no association between severity of AD and frequency of food sensitization or history of FA.Sensitization to PR-10 related food allergens occurred most frequently (63.5%) and was independent from AD severity. Correspondingly, pollen-food syndrome accounted for most of the FA, being also independent from AD severity. Of all plant food allergens only sensitization to nAra h 1 was significantly more frequent in patients with severe AD. In the total group 75 (35.5%) patients with AD showed sensitization to any animal food allergen. The percentage was significantly higher in patients with severe AD (51.4%) compared to patients with mild/moderate AD (27.7%). Sensitization to cow’s milk allergens, in particular to nBos d lactoferrin, was more frequent in severe AD patients.ConclusionAD was frequently associated with food sensitization. The percentage of sensitization to animal food allergens was significantly higher in severe AD patients.

Differences in the intrinsic immunogenicity and allergenicity of B et v 1 and related food allergens revealed by site‐directed mutagenesis

BackgroundBirch pollen allergies are frequently associated with adverse reactions to various fruits, nuts, or vegetables, described as pollen–food syndrome (PFS) and caused by cross-reactive IgE antibodies primarily directed against Bet v 1. Specific immunotherapy (SIT) represents an effective treatment for inhalant allergies; however, successful birch pollen SIT does not correlate well with the amelioration of concomitant food allergies.MethodsAs vaccine candidates, apple Mal d 1 as well as hazelnut Cor a 1 derivatives were designed by in silico backbone analyses of the respective allergens. The proteins were produced by site-directed mutagenesis as fold variants of their parental allergens. Because Mal d 1 and Cor a 1 form cysteine-mediated aggregates, nonaggregative cysteine to serine mutants were also generated. The proteins were characterized physicochemically, immunologically, and in in vivo models with or without adjuvant.ResultsThe structurally modified proteins showed significantly decreased IgE binding capacity. Notably, both in vivo models revealed reduced immunogenicity of the hypoallergenic fold variants. When formulated with alum, the monomeric cysteine mutants induced a similar immune response as the aggregated parental allergens, which is in contrast with data published on Bet v 1.ConclusionThese findings lead to the suggestion that the Bet v 1 structure has unique intrinsic properties, which could account for its high allergenicity. Obviously, these characteristics are not entirely shared with its food homologues from apple and hazelnut. Thus, it is important to tackle pollen-related food allergies from different angles for the generation of effective vaccine candidates to treat birch PFS.

Clinical Characterization and IgE Profiling of Birch (Betula verrucosa)–Allergic Individuals Suffering from Allergic Reactions to Raw Fruits and Vegetables

Hypersensitivity to raw fruits and vegetables is often associated with respiratory allergy to birch (Betula verrucosa) pollen and is considered to be the most prevalent form of food allergy in adults sensitized to birch pollen. The aim of the study was to investigate the association of clinical allergy and IgE profiles in individuals with birch pollen allergy and hypersensitivity to raw fruits and vegetables. A total of 59 adults with clinical and skin prick test confirmed birch pollen allergy were included in the study. All the subjects were interviewed by using a structured questionnaire and were examined in vivo by the open test, with the appropriate fruits and vegetables. ImmunoCAP and ImmunoCAP ISAC were used as in vitro diagnostics to assess sensitization profiles for each individual, and principal components analysis was used to analyze the IgE data sets. Of 59 individuals, 54 (92%) had positive prick-prick test with raw potato, carrot, apple, and/or hazelnut, and the skin prick test was always positive when the corresponding skin challenge was defined as positive. Specific IgE in the ImmunoCAP and inhibition assays with rMal d 1 and rBet v 1 demonstrated that Bet v 1 is driving the sensitization against pathogenesis related-10 proteins. However, positive IgE in vitro results could not be used to predict clinical reactivity to raw fruits and vegetables. The present study showed that component-based IgE profiling does not enhance the diagnostic potential in case of pollen-food syndrome, which may be associated with other as yet unidentified components.

The prevalence of PFS and prevalence and characteristics of reported food allergy; a survey of UK adults aged 18–75 incorporating a validated PFS diagnostic questionnaire

Pollen-food syndrome (PFS), a food allergy affecting pollen-sensitized individuals, is likely to be the most prevalent food allergy in adults, estimated to affect 50-90% of people allergic to birch tree pollen. A validated PFS diagnostic questionnaire (PFSDQ2) was used to determine the prevalence of PFS and also to characterize those who report reactions to foods. Five UK General practices each sent the PFSDQ2 by post to 2000 patients aged 18-75 years randomly selected from their practice database. The validated questionnaire was accompanied by an additional set of questions to ascertain the demographic of the population, the foods involved and the age of onset. There were 3590 subjects who returned completed questionnaires, with an average return rate from each practice of 36% (range 22-47%). Of these, 73 were diagnosed with PFS according to the questionnaire (PFS+ve) giving a population prevalence of 2%. A further 482 subjects reported reactions to foods but did not fulfil the diagnostic criteria for PFS. The greatest prevalence of PFS was in the Croydon (SE England) urban practice (4.1%) and the lowest in the Aberdeen (Scotland) urban practice (0.8%) (P < 0.001).The most frequently reported trigger foods were apples, hazelnuts and kiwifruit and the majority of those with PFS first experienced symptoms below the age of 20 years. PFS+ve subjects were also more likely to be female and have a higher socio-economic status than those who did not report reactions to foods. The UK prevalence of PFS was 2%, although this varied according to the location of the practice population. The majority of PFS+ve subjects first reported symptoms in their teens. The reported age of onset has important implications for the diagnosis of primary and cross-reactive peanut and tree nut allergies in teenagers and young adults. The continuing rise in aeroallergen sensitization is likely to result in an increased frequency of PFS presenting in both primary and secondary care.

Imbalance of serum IL-10 and TGF-β in patients with pollen food syndrome

BackgroundPollen food syndrome is one of the main causes of food allergies in adults. However, the intrinsic immunological mechanisms remain unclear. MethodsForty pollinosis sufferers [23 with a food allergy (PSFA) and 17 without a food allergy (PS)] and 17 non-atopic healthy controls were included in this study. The PSFA group was subdivided into an oral allergy syndrome group, a systemic reaction group, and an anaphylactic reaction group according to their symptoms after eating the suspected foods. Serum IL-10 and TGF-β levels of all participants were determined by ELISA. Clinical characteristics of the patients were also evaluated. ResultsThere were no significant differences in age, sex, pollen-associated symptoms, duration of respiratory disease, and positive parental history of atopy between the PSFA and PS groups. Compared to healthy controls, serum IL-10 levels of both the PSFA group and PS group were significantly lower (p≤0.01), but TGF β levels were significantly higher in the PSFA group (35.3±5.6ng/ml vs. 31.2±6.6ng/ml, respectively; p=0.037). Within the PSFA group, IL-10 levels in the anaphylactic reaction subgroup were significantly lower compared to oral allergy syndrome subgroup (1.87±0.47pg/ml vs. 1.40±0.30pg/ml, respectively; p=0.027). More severe food allergy symptoms were associated with lower serum IL-10 levels. In contrast, the highest serum levels of TGF-β were found in patients from the anaphylactic reaction subgroup. ConclusionsWith the exception of a defect in regulatory cells represented by the reduction of IL-10, other potential immunological mechanisms (e.g., Th17 or IL-23 together with TGF-β) may be involved in the development of pollen food syndrome.

Perplexing cases of allergy to salami

Perplexing cases of allergy to salami

Allergy to fruit seeds presenting with anaphylaxis

Allergic reactions to fruits, particularly citrus, are relatively common, often presenting with symptoms of oral allergy syndrome (also known as pollen-food syndrome), with systemic allergic reactions occurring less frequently. Fruit allergy testing, including serum specific immunoglobulin E (IgE) and skin prick testing will identify the allergen in most cases, however these tests commonly use extract from the fruit and may fail to identify reactions to the seed, which may be more severe. We report three children with anaphylactic reactions to fruit seeds, who were able to tolerate the fruit pulp. Two children experienced anaphylaxis to orange seed, and both had evidence of sensitisation to multiple citrus seeds, peanut and tree nuts. The third child developed anaphylaxis to a commercially-produced baby food containing apple puree, and was found to be sensitised to a range of fruit and citrus seeds, as well as to sesame and nuts. These cases highlight the need to consider fruit seeds as a potential cause of severe allergic reactions to fruit.

Pattern of food allergy in adults

The pattern of food allergy in adults is different from that of children in various aspects. The typical foods involved in infants are milk, egg, peanut and probably tree nuts, whereas in older children and adults fruits and nuts are the most frequent allergenic foods. In addition, allergy to vegetables can occur. Allergy to milk and egg largely disappears at young age, but can still be present in adults, in part because of persistence from childhood, but also as de novo allergies developing in adolescents or adults. The high prevalence of fruit and nut allergy in adults and older children is for a large part due to the pollen-food syndrome: the result of cross-reactivity between allergens in tree (birch) pollen and in fruits, nuts and vegetables. The list of foods cross-reacting with birch pollen is steadily increasing and contains members of different plant food families. Also some less frequently eaten tropical fruits are on the list. In general reactions due to the pollen-food syndrome tend to be relatively mild, but (more) severe reactions have been reported especially for soy, celery and tropical fruits. Severe reactions on first exposure of cross-reactive foods were reported. Another important cross-reactive allergy is that between latex and foods and vice versa. The most frequently involved foods are kiwi, banana, avocado, chestnut and buckwheat. In clinical practice the most important problem is how to confirm which are the culprit foods and how to judge the severity of the food allergy. Studies from different geographical regions have show that there can be significant differences in the prevalence and severity of specific food allergies due a.o. to differences in pollen exposure and eating habits, which is also partly reflected in differences in patterns of allergen profiles. The increasing knowledge on relevant allergen recognition patterns, known as component resolved diagnostics, will help to improve our insight in the relevant allergens involved, the routes of sensitisation and, at least partially, to estimate the risk of severe reactions.

Pollen-food syndrome is related to Bet v 1/PR-10 protein sensitisation, but not all patients have spring rhinitis

Pollen-food syndrome is related to Bet v 1/PR-10 protein sensitisation, but not all patients have spring rhinitis

Development and validation of a structured questionnaire for the diagnosis of oral allergy syndrome in subjects with seasonal allergic rhinitis during the UK birch pollen season

Birch pollen-associated oral allergy syndrome, also known as pollen-food syndrome (PFS), is the most common food allergy in adults in the United Kingdom. Because of its characteristic rapid onset of oro-pharyngeal symptoms associated with specific plant foods, it was hypothesized that a history-based questionnaire could accurately diagnose PFS in subjects with rhino-conjunctivitis symptoms in the UK springtime. In this study of diagnostic accuracy, we aimed to validate a simple PFS diagnostic questionnaire and algorithm against a reference diagnostic test method (RTM) comprising diagnosis by expert evaluation of clinical history, skin prick tests and oral food challenge, in subjects reporting allergic rhinitis (AR) in the UK birch pollen season from March to May. Participants were UK adults reporting symptoms of spring time-AR (hayfever). They self-completed a diagnostic questionnaire in addition to undergoing an RTM comprising clinical history, skin prick testing to foods and pollens and oral food challenge. Subjects who reported anaphylaxis were excluded on the basis that they required specialist referral. One hundred and twenty three subjects took part in the study. Data from 110 participants were analysed; of the 13 exclusions, four provided insufficient data and nine reported anaphylaxis such that they warranted specialist assessment. Fifty-two participants (47%) were diagnosed with PFS by the RTM in comparison with 51 (46%) by a diagnostic questionnaire and algorithm (P=1.000, McNemar's test). The diagnostic questionnaire and algorithm had a sensitivity of 0.90 (0.78-0.96), a specificity of 0.93 (0.82-0.97), a positive predictive value of 0.92 (0.80-0.97) and a negative predictive value of 0.91 (0.80-0.96) when measured against the RTM. The diagnostic questionnaire and algorithm is a practical and robust tool, which enables rapid identification, and therefore management, of individuals with PFS who experience rhino-conjunctivitis symptoms in the UK birch pollen season. Registered with CinicalTrials.Gov. registration number NCT00854958.

Food allergy.

Food allergies affect up to 6% of young children and 3%-4% of adults. They encompass a range of disorders that may be IgE and/or non-IgE mediated, including anaphylaxis, pollen food syndrome, food-protein-induced enterocolitis syndrome, food-induced proctocolitis, eosinophilic gastroenteropathies, and atopic dermatitis. Many complex host factors and properties of foods are involved in the development of food allergy. With recent advances in the understanding of how these factors interact, the development of several novel diagnostic and therapeutic strategies is underway and showing promise.

Food allergy and oral allergy or pollen-food syndrome

This paper reviews current concepts in our understanding of oral allergy or pollen-food syndrome. As technology has improved, much more accurate profiling of food allergic individuals is now possible, resulting in more precise diagnosis, elucidation of cross reactivity patterns and more helpful prediction of risk of anaphylaxis. The identification and characterization of various ubiquitous plant proteins have led to greater understanding of food cross reactive reactions. Newer diagnostic techniques utilizing purified and recombinant allergens are available for more precise diagnosis and clinical profiling of patients presenting with food allergy. In-vitro screening of food allergic patients with large panels of allergens will change the accuracy of diagnosis resulting in better management. Allergens are now available for use in the allergist's office to improve diagnostic accuracy of skin tests in patients presenting with plant-food allergy. Knowledge of the specific sensitization of individual patients has consequences for both risk assessment and dietary management.

Work-Related Allergy and Asthma in Spice Mill Workers – The Impact of Processing Dried Spices on IgE Reactivity Patterns

Background: Three spice mill workers developed work-related allergy and asthma after prolonged exposure to high levels (>10 mg/m³) of inhalable spice dust. Patterns of sensitization to a variety of spices and putative allergens were identified. Methods: Work-related allergy and asthma were assessed on history, clinical evaluation, pulmonary function and fractional exhaled nitric oxide. Specific IgE reactivity to a range of common inhalant, food and spice allergens was evaluated using ImmunoCAP and allergen microarray. The presence of non-IgE-mediated reactions was determined by basophil stimulation (CAST-ELISA). Specific allergens were identified by immunoblotting to extracts of raw and dried processed garlic, onion and chili pepper. Results: Asthma was confirmed in all 3 subjects, with work-related patterns prominent in worker 1 and 3. Sensitization to multiple spices and pollen was observed in both atopic workers 1 and 2, whereas garlic and chili pepper sensitization featured in all 3 workers. Microarray analysis demonstrated prominent profilin reactivity in atopic worker 2. Immunoblotting demonstrated a 50-kDa cross-reactive allergen in garlic and onion, and allergens of approximately 40 and 52 kDa in chili pepper. Dry powdered garlic and onion demonstrated greater IgE binding. Conclusions: This study demonstrated IgE reactivity to multiple spice allergens in workers exposed to high levels of inhalable spice dust. Processed garlic and onion powder demonstrated stronger IgE reactivity than the raw plant. Atopy and polysensitization to various plant profilins, suggesting pollen-food syndrome, represent additional risk factors for sensitizer-induced work-related asthma in spice mill workers.

Prevalence of pollen-related Oral Allergy Syndrome (OAS) in a UK population

RATIONALE: The commonest type of OAS is pollen-food syndrome (PFS), a food allergy caused by cross-reactions to plant foods in pollen-sensitised individuals. PFS has been estimated to affect 50 to 90% of people allergic to birch tree pollen. There have been no studies assessing the prevalence of PFS in a general population; a validated PFS diagnostic questionnaire (PFSDQ2) was used to undertake a UK prevalence study.

Identification of B‐cell epitopes of Bet v 1 involved in cross‐reactivity with food allergens

The pollen-food syndrome (PFS) is an association of food allergies to fruits, nuts, and vegetables in patients with pollen allergy. Mal d 1, the major apple allergen, is one of the most commonly associated food allergens for birch pollen-allergic patients suffering from PFS. Although the reactions are due to cross-reactive IgE antibodies originally raised against pollen Bet v 1, not every Bet v 1-allergic patient develops clinical reactions towards apple. We speculate that distinct IgE epitopes are responsible for the clinical manifestation of PFS. To test this hypothesis we grafted five Mal d 1 stretches onto Bet v 1. The grafted regions were 7- or 8-amino acids long encompassing amino acids residues previously shown to be crucial for IgE recognition of Bet v 1. A Bet v 1-Mal d 1 chimeric protein designated BMC was expressed in Escherichia coli and purified to homogeneity. IgE reactivity of BMC was tested with patients' sera originating from (i) Bet v 1-allergic patients displaying no clinical symptoms upon ingestion of apples; and (ii) Bet v 1-allergic patients displaying allergic symptoms upon ingestion of apples and other Bet v 1-related foods. Compared to birch pollen-allergic individuals, patients suffering from PFS showed significantly higher IgE reactivity with BMC (chimeric protein). The results suggest that the Mal d 1 regions grafted onto the Bet v 1 sequence comprise important IgE epitopes recognized by Bet v 1-allergic patients suffering from allergy to apples.