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

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

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

Molecular approach to a patient's tailored diagnosis of the oral allergy syndrome

Oral allergy syndrome (OAS) is one of the most common IgE-mediated allergic reactions. It is characterized by a number of symptoms induced by the exposure of the oral and pharyngeal mucosa to allergenic proteins belonging to class 1 or to class 2 food allergens. OAS occurring when patients sensitized to pollens are exposed to some fresh plant foods has been called pollen food allergy syndrome (PFAS). In the wake of PFAS, several different associations of allergenic sources have been progressively proposed and called syndromes. Molecular allergology has shown that these associations are based on IgE co-recognition taking place between homologous allergens present in different allergenic sources. In addition, the molecular approach reveals that some allergens involved in OAS are also responsible for systemic reactions, as in the case of some food Bet v 1-related proteins, lipid transfer proteins and gibberellin regulated proteins. Therefore, in the presence of a convincing history of OAS, it becomes crucial to perform a patient's tailored molecule-based diagnosis in order to identify the individual IgE sensitization profile. This information allows the prediction of possible cross-reactions with homologous molecules contained in other sources. In addition, it allows the assessment of the risk of developing more severe symptoms on the basis of the features of the allergenic proteins to which the patient is sensitized. In this context, we aimed to provide an overview of the features of relevant plant allergenic molecules and their involvement in the clinical onset of OAS. The value of a personalized molecule-based approach to OAS diagnosis is also analyzed and discussed.

Molecular sensitization patterns in birch pollen-sensitized Korean children according to the presence of oral allergy syndrome

The profiles of sensitization based on component-resolved diagnosis (CRD) differ from region to region in populations sensitized to birch pollen. We investigated the endotypes of birch pollen-sensitized Korean children with allergic diseases using CRD and distinguished the endotypes of oral allergy syndrome (OAS) among them.Thirty-one birch pollen-sensitized children with allergic diseases were enrolled. Specific immunoglobulin E (IgE) to birch pollen and fruit including apple, peach, and kiwi were evaluated via skin prick tests and ImmunoCAP in all subjects. Sensitization profiles based on CRD were evaluated with the Immuno-solid-phase Allergen Chip for birch pollen-sensitization using birch pollen components (Bet v 1, Bet v 2, and Bet v 4), and for OAS using the allergen families pathogenesis-related class 10 proteins (PR-10), lipid transfer proteins, and profilin.All patients (n = 13) with OAS were sensitive to Bet v 1. However, 61% (11/18) of patients without OAS were sensitized to Bet v 1. The level of specific IgE to Bet v 1 was higher in patients with OAS than in those without OAS. All birch pollen-sensitized Korean children with OAS were sensitized to PR-10, and 69% (9/13) of them were mono-sensitized to PR-10. Among patients without OAS, 33% (6/18) were not sensitized to any of the allergen families.Birch pollen-sensitized Korean children with allergic diseases showed unique patterns of sensitization to Bet v 1, Bet v 2, and Bet v 4, and the sensitization profiles based on CRD were totally different according to the presence of OAS.

Validation of PROTIA™ Allergy-Q 64 Atopy® as a Specific IgE Measurement Assay for 10 Major Allergen Components

PURPOSE

Component-resolved diagnostics (CRD) is expected to provide additional diagnostic information in allergic patients. PROTIA™ Allergy-Q 64 Atopy®, a recently developed CRD-based multiplex specific immunoglobulin E (sIgE) assay, can quantitatively measure sIgE to major allergen components.

METHODS

The sIgE detection by PROTIA™ Allergy-Q 64 Atopy® and ImmunoCAP® assays was compared using the sera of 125 Korean allergic patients. Group 1 and 2 allergens of house dust mites (HDMs; Dermatophagoides farinae (Der f) 1 and Der f 2 in PROTIA™ Allergy-Q 64 Atopy®, Dermatophagoides pteronyssinus (Der p) 1 and Der p 2 in ImmunoCAP®), Bet v 1, Fel d 1, Que a 1, ω-5 gliadin, α-lactalbumin, β-lactoglobulin, casein and α-Gal were measured by both assays.

RESULTS

Comparing the results from the 2 assays, the agreement rate for all the 10 allergens was > 88% (group 1 HDM allergen, 100%; group 2 HDM allergen, 94.6%; Bet v 1, 97.4%; Fel d 1, 90.5%; Que a 1, 89.2%; α-lactalbumin, 96%; β-lactoglobulin, 88%; casein, 88%; ω-5 gliadin, 96%; α-Gal, 100%). Correlation analysis indicated that, all the 10 allergen sIgEs showed more than moderate positive correlation (Pearson correlation coefficients > 0.640). Additionally, intra-class comparison showed more than high correlation for all the 10 allergens (Spearman's rank correlation coefficients > 0.743).

CONCLUSIONS

PROTIA™ Allergy-Q 64 Atopy® is reliable and comparable to the ImmunoCAP® assay for component-resolved diagnosis.

Molecular Recognition Profiles and Clinical Patterns of PR-10 Sensitization in a Birch-Free Mediterranean Area

BACKGROUND

The order Fagales represents an important cause of tree-pollen allergy in northern countries. We investigated the IgE recognition profiles, mutual relationships, and association with clinical symptoms of a panel of allergens belonging to the PR-10 family, the main proteins responsible for Fagales allergy (Act d 8, Aln g 1, Api g 1, Ara h 8, Bet v 1, Cor a 1.0101, Cor a 1.0401, Gly m 4, Mal d 1, and Pru p 1).

METHODS

A total of 526 PR-10-reactive subjects living in central and southern Italy were studied by ImmunoCAP-ISAC-112 microarray analysis.

RESULTS

Overall, Bet v 1 reactivity was the most commonly (74%) observed among PR-10 proteins, but Cor a 1.0101 was the most prevalent in participants aged <6 years, and between 15 and 65 years. Overall, 26% of the PR-10-reactive persons were Bet v 1 negative, whilst 93.6% of the PR-10 polyreactive individuals were Bet v 1 positive. Among the 10 PR-10s evaluated, 100 combinations were recorded. The strongest association was observed between molecules with the highest sequence identities (Bet v 1 and Cor a 1.0101, Cor a 1.0401 or Aln g 1; Mal d 1 and Pru p 1). Bet v 1-, Cor a 1.0101-, and Aln g 1-specific IgE recognition was associated with respiratory symptoms, whilst Ara h 8, Cor a 1.0401, Gly m 4, Mal d 1, and Pru p 1 were selectively linked to an oral allergic syndrome.

CONCLUSIONS

Testing IgE reactivity to a panel of PR-10s in a birch-free area discloses peculiar relationships between clinical phenotypes and sensitization profiles, allowing the identification of novel cluster patterns.

White-fruited strawberry genotypes are not per se hypoallergenic

The strawberry fruit Fra a 1-proteins are homologues of the major birch pollen allergen Bet v 1 and have essential biological functions in pigment formation during fruit ripening. Patients affected by allergy against birch pollen tolerated fruits of a naturally occurring white-fruited F.×ananassa genotype, which showed reduced levels of Fra a 1 proteins along with enzymes of the anthocyanin pigment pathway. We evaluated the cross-reactive allergenic potential of a number of naturally occurring white- and red-fruited strawberry varieties to detect genotypes with low allergenic reactivity, whose fruit might be tolerated by patients with mild allergy. Protein extracts of 51 different strawberry varieties (Fragaria×ananassa, F. vesca, and F. nilgerensis) were screened by Western blot analysis with a polyclonal Fra a 1.02 antibody. Besides, activation of basophils of eight atopic patients allergic to birch pollen were studied using Bet v 1a and different concentrations of 15 selected strawberry protein extracts out of the 51 strawberry genotypes. Median percentages of activated basophils stimulated by extracts from white- and red-fruited genotypes ranged from 36 to 84% and 44 to 76%, respectively indicating that white-fruited strawberry are not per se hypoallergenic. Protein extracts from white-fruited F. vesca cv. Yellow Wonder showed the lowest cross-reactivity but high biological variability. The knowledge about the allergenic potential of different strawberry genotypes may help to improve food safety and can serve as starting point for the development of red-fruited hypoallergenic strawberry cultivars.

Fra a 1.02 Is the Most Potent Isoform of the Bet v 1-like Allergen in Strawberry Fruit

The strawberry fruit proteins Fra a 1.01E-1.08 are homologues of the major birch pollen allergen Bet v 1. Three of the proteins are known to have essential biological functions in pigment formation during fruit ripening and seem to be responsible for allergic reactions to strawberry fruit. We evaluated the cross-reactive allergenic potential of these putative strawberry allergens in patients allergic to birch pollen. Activation of basophils of eight atopic patients was studied using different concentrations of Fra a 1 isoforms. Bet v 1a was used as control and as atopic patient selection criterion. Although Fra a 1.01E-1.08 have amino acid sequence identities of 74.5-97.5% with Fra a 1.02, the basophil activation mediated by the eight Fra a 1 proteins differed substantially. Fra a 1.03 and Fra a 1.02 showed the highest activation of basophils, 73 and 66% of total basophils, respectively. On the basis of the high relative expression of the gene Fra a 1.02 in ripe strawberry fruits of allergenic varieties, Fra a 1.02 was identified as the main strawberry allergen of the Bet v 1 superfamily. Knowledge of the allergenic potential of Fra a 1.02/1.03 will help to improve food safety and can serve as a valuable marker for the development of red-fruited hypoallergenic strawberry cultivars.

High correlation of specific IgE sensitization between birch pollen, soy and apple allergens indicates pollen-food allergy syndrome among birch pollen allergic patients in northern China

BACKGROUND

Birch pollen sensitization and associated pollen-food syndrome among Chinese allergic patients have not been investigated.

METHODS

Sera from 203 allergic patients from the northern part of China and collected during February to July 2014 were investigated. Specific immunoglobulin E (IgE) against birch pollen extract Bet v and major birch pollen allergen Bet v 1 were measured using the ADVIA Centaur. The presence of major apple allergen Mal d 1 and soy bean allergen Gly m 4 specific IgE was measured by ImmunoCAP 100.

RESULTS

Among the 203 sera, 34 sera (16.7%) had specific IgE to Bet v and of these, 28 sera (82.4%) contained Bet v 1-specific IgE. Among the 28 sera with Bet v 1-specific IgE, 27 sera (96.4%) contained Mal d 1-specific IgE and 22 sera (78.6%) contained Gly m 4-specific IgE. Of the 34 Bet v-positive sera, 6 sera (17.6%) contained no specific IgE for Bet v 1, Mal d 1, or Gly m 4. Almost all Bet v-positive sera were donated during the birch pollen season.

CONCLUSIONS

The prevalence of birch allergy among patients visiting health care during pollen season can be as high as 16.7% in Tangshan City. The majority of Chinese birch allergic patients are IgE-sensitized to the major birch pollen allergen Bet v 1 as well as to the major apple allergen Mal d 1 and soy bean allergen Gly m 4. A relatively high number of patients (17.6%) are IgE-sensitized to birch pollen allergen(s) other than Bet v 1. The high prevalence of specific IgE to Mal d 1 and Gly m 4 among Bet v 1-sensitized patients indicates that pollen-food allergy syndrome could be of clinical relevance in China.

Pollen food syndrome amongst children with seasonal allergic rhinitis attending allergy clinic

BACKGROUND

There is limited information regarding the onset and sensitization patterns of pollen food syndrome (PFS) in children. The aim was to explore this within children referred to a specialist allergy clinic at a London Tertiary Hospital.

METHODS

A total of 54 patients with seasonal allergic rhinitis (SAR) were enrolled in equal numbers in three age groups; 0-5, 6-10, 11-15 years. Families completed a questionnaire on rhinitis, food symptoms and quality of life. Children underwent skin prick testing (SPT) to fresh fruits, nuts and a blood test for microarray analysis.

RESULTS

Clinical diagnosis of PFS was made in 26/54 (48%), increasing with age (group 1 = 3 (17%), group 2 = 9 (50%), group 3 = 14 (78%) (p = 0.03)). Microarray demonstrates children aged 2.8 years sensitized to pan-allergens and 4.5 years symptomatic to pan-allergens. Peach, cherry, carrot and strawberry SPT had the highest sensitivity and NPV at 100%. The sensitivity of PR10 molecules on microarray was 92%, PPV 62% and NPV 87%. Microarray confirmed 69% of allergens on clinical history compared to 61% by SPT. Microarray and SPT had a 19% false-negative rate. The quality-of-life data showed moderate impact across all domains, and patients with PFS were significantly more likely to have increased anxiety over time spent preparing food (p = 0.029).

CONCLUSIONS

We demonstrate that SAR occurs in children from 1.4 years and PFS from 4.5 years with a changing pattern of pan-allergen sensitization. Microarray and SPT have moderate concordance in confirming allergens. PFS impacts negatively on quality of life and should be assessed in all paediatric allergy patients.

Cross-reactivity between aeroallergens and food allergens

In patients with respiratory allergy, cross-reactivity between aeroallergens and foods may induce food allergy, symptoms ranging from oral allergy syndrome to severe anaphylaxis. Clinical entities due to IgE sensitization to cross-reactive aeroallergen and food allergen components are described for many sources of plant origin (pollen-food syndromes and associations, such as birch-apple, cypress-peach and celery-mugwort-spice syndromes, and mugwort-peach, mugwort-chamomile, mugwort-mustard, ragweed-melon-banana, goosefoot-melon associations), fungal origin (Alternaria-spinach syndrome), and invertebrate, mammalian or avian origin (mite-shrimp, cat-pork, and bird-egg syndromes). Clinical cases of allergic reactions to ingestion of food products containing pollen grains of specific plants, in patients with respiratory allergy to Asteraceae pollen, especially mugwort and ragweed, are also mentioned, for honey, royal jelly and bee polen dietary supplements, along with allergic reactions to foods contaminated with mites or fungi in patients with respiratory allergy to these aeroallergens. Medical history and diagnosis approach may be guided by the knowledge about the diverse cross-reacting allergens involved, and by the understanding of these clinical entities which may vary significantly or may be overlapping. The association between primary IgE sensitization with respiratory symptoms to inhaled allergens and food allergy due to cross-reactive allergen components is important to assess in allergy practice. The use of molecular-based diagnosis improves the understanding of clinically relevant IgE sensitization to cross-reactive allergen components from aeroallergen sources and foods.

Early childhood IgE reactivity to pathogenesis-related class 10 proteins predicts allergic rhinitis in adolescence

BACKGROUND

Component-resolved diagnosis might improve the prediction of future allergy in young children.

OBJECTIVE

We sought to investigate the association between IgE reactivity to the pathogenesis-related class 10 (PR-10) protein family and allergic rhinitis to birch pollen (ARbp) from early childhood up to age 16 years.

METHOD

Questionnaire data and sera obtained at 4, 8, and 16 years of age from the Barn/Children Allergi/Allergy Milieu Stockholm Epidemiologic (BAMSE) study birth cohort were used. Sera from 764 children were analyzed for IgE reactivity to 9 PR-10 allergen proteins at the 3 time points by using an allergen chip based on ISAC technology. ARbp was defined as upper airway symptoms during birch pollen exposure.

RESULTS

IgE reactivity to Bet v 1 was found in 12%, 17%, and 25% of children at 4, 8, and 16 years of age. IgE reactivity of PR-10 proteins showed a hierarchic intrarelationship: Bet v 1 > Mal d 1 > Cor a 1.04 > Ara h 8 > Pru p 1 > Aln g 1 > Api g 1 > Act d 8 > Gly m 4. There was an increased risk of incidence and persistence of ARbp up to age 16 years with increasing levels of Bet v 1-specific IgE or increasing numbers of IgE-reactive PR-10 proteins at 4 years. Children with severe ARbp at age 16 years had higher levels of Bet v 1-specific IgE at age 4 years compared with children with mild symptoms.

CONCLUSION

ARbp at age 16 years can be predicted by analysis of IgE reactivity to PR-10 proteins in early childhood.

Differences in the intrinsic immunogenicity and allergenicity of Bet v 1 and related food allergens revealed by site-directed mutagenesis

Background

Birch 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.

Methods

As 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.

Results

The 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.

Conclusion

These 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

BACKGROUND

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.

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Molecular mechanisms of IgE mediated food allergy

The purpose of this review is to collate current knowledge and recent advances in molecular mechanism behind the immediate type hypersensitivity of foods. Food allergy is a growing concern of human health in developed as well as developing countries now days. Food allergic reactions are mostly IgE mediated and also known as immediate type hypersensitivity or type I reaction. This review encompasses a wide range of molecular events during IgE mediated reactions like primary exposure of allergens, processing of allergens by antigen presenting cells, role of transcription factors like GATA-3, STAT-6, NF-AT, c-maf, c-kit and NF-κB, Treg cells, toll like receptors, cytokines and chemokines, class switch to IgE, FcεR1 receptor, priming of IgE on mast cells or basophils, signaling events followed by secondary exposure of allergens, degranulation and release of mediators like leukotrienes, histamines, prostaglandins, β-hexosaminidase and ultimately anaphylaxis. This review may be helpful to beginners as well as experts working in the field of allergy and immunology because of the stepwise explanations of molecular mechanisms involved in IgE mediated reactions.