Measurement of health-related quality of life in adult patients with birch pollen-associated food allergy

Food allergy - New risks through vegan diet? Overview of new allergen sources and current data on the potential risk of anaphylaxis

A vegan diet is increasingly en vogue, i.e., a diet based on plants, in which animal products are completely avoided, often for health and environmental reasons. The menu is supplemented with pulses (e.g., soy, lentils, peas), nuts (e.g., cashew, macadamia, almond, pecan, para, walnut) and seeds (e.g., chia, flaxseed) or pseudo-grains (quinoa, buckwheat). Indeed, the product range is expanding to include vegan foods such as milk alternatives (e.g., oat, almond, soy drinks) and cheese or meat substitutes (e.g., soy-based). Food allergies are also on the rise, with an increasing prevalence worldwide. It is worthy of note that the main allergens of anaphylactic reactions to food in adults are predominantly of plant origin, mainly pulses and nuts - the very foods that form the main source of protein in the vegan diet. In this context, allergies to storage proteins (e.g., Gly m 5 and Gly m 6 from soya beans) can lead to severe anaphylactic reactions, while highly processed substitute products containing plant protein isolates (e.g., pea flour) in concentrated form continue to be of particular concern and may therefore be allergologically problematic. In this article, we aim to provide an overview of allergens and emerging allergen sources in vegan foods and highlight the anaphylaxis risk of the vegan diet.

Nahrungsmittelallergie - Neue Risiken durch vegane Ernährung? Überblick zu neuen Allergenquellen und aktuelle Daten zum Anaphylaxierisiko: Food allergy - New risks through vegan diet? Overview of new allergen sources and current data on the potential risk of anaphylaxis

Zunehmend mehr Menschen ernähren sich aus gesundheitlichen und Umweltaspekten ausschließlich von pflanzlichen Nahrungsmitteln (vegan). Dabei werden vielfach Hülsenfrüchte (wie Soja, Linsen, Erbsen), Schalenfrüchte (Cashew, Macadamia, Mandel, Pekan‐, Para‐ und Walnuss), Samen und Saaten (wie Chia, Leinsamen) oder (Pseudo‐)Getreide (wie Quinoa, Buchweizen) verzehrt. Vegane Milchalternativen sind Hafer‐, Mandel‐ und Sojadrinks, auch Käse‐ sowie Fleischersatzprodukte basieren oft auf einer Sojagrundlage. Gleichzeitig nimmt die Prävalenz von Nahrungsmittelallergien weltweit zu. Pflanzenallergene aus Hülsen‐ und Schalenfrüchten, die in der veganen Ernährung die Hauptproteinquelle ausmachen, zählen zu den häufigsten Auslösern von Nahrungsmittelallergien bei Erwachsenen. Dabei kommt es bei Allergien auf Speicherproteine (wie Gly m 5 und Gly m 6 aus der Sojabohne) zu teils schweren anaphylaktischen Reaktionen. Besonderes Augenmerk liegt weiter auf hochverarbeiteten Ersatzprodukten, die Pflanzenproteinisolate (zum Beispiel Erbsenmehl) in konzentrierter Form enthalten und damit allergologisch problematisch werden können. In diesem Artikel geben wir einen Überblick über wichtige Allergene und neue Allergenquellen in ausgesuchten veganen Nahrungsmitteln und betrachten die vegane Ernährung unter allergologischen Aspekten.

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.

[What is the role of allergen immunotherapy in IgE-mediated food allergy?]

In food allergy, allergen avoidance and emergency treatment are still therapeutic hallmarks but, recently, allergen immunotherapy (AIT), with different application routes, has gained more attention. In primary food allergy, oral immunotherapy has been frequently used in clinical trials. This year, an oral immunotherapy preparation for treatment of peanut allergy was licensed in Europe. In secondary food allergy, sublingual and subcutaneous extracts have been used in clinical trials, mostly with cross-reactive pollen allergens. As there is no AIT preparation licensed for this indication, therapy should only be started when there also is a need for treating associated respiratory symptoms.

Update on Type-1 Allergy Diagnostics

Diagnostics in type-1 allergy rely on medical history and clinical examination. Extent and severity of signs and symptoms can be documented by standardized scores and questionnaires. Both skin prick test and intradermal test are useful for search of immunoglobulin E-mediated sensitizations but the availability of commercially available diagnostic extracts has been markedly reduced during the last years. Investigation of total and of specific serum IgE is the most important in vitro diagnostic analyte in type-1 allergy. Identification of the individual molecules to which patients are sensitized, known as molecular or component-resolved diagnostics (CRD), has recently markedly improved management of type-1 allergy to pollen, food and hymenoptera venoms. Main features of CRD are increased analytic sensitivity, detection of cross-reactivity and determination of individual sensitization profiles which allow for risk assessment and facilitate decisions for or against allergen immunotherapy. Basophil activation test as well as determination of selected biomarkers (e.g. tryptase) may also be helpful in some cases. If any allergy test is positive, one will have to distinguish reactions, which are clinically relevant, from those, which are not. In vivo provocation tests (e.g. nasal provocation, oral drug or food challenge) may help to clarify the relevance of a sensitization.

Birch Pollen Related Pear Allergy: A Single-Blind Oral Challenge TRIAL with 2 Pear Cultivars

Approximately 70% of birch pollen allergic patients in Europe experience hypersensitivity reactions to Immunoglobulin E (IgE) cross-reactive food sources. This so-called pollen-food syndrome (PFS) is defined by allergic symptoms elicited promptly by the ingestion of fruits, nuts, or vegetables in these patients. So far, in the literature, less attention has been given to Bet v 1 cross-reactive symptoms caused by pear (Pyrus communis). In the Netherlands, pears are widely consumed. The primary objective of this study was to measure the type and severity of allergic symptoms during pear challenges in birch pollen allergic patients, with a positive history of pear allergy, using two different pear varieties. Fifteen patients were included, skin prick test (SPT), prick-to-prick test (PTP), specific Immunoglobulin E (sIgE), and single-blind oral challenges were performed with two pear (Pyrus communis) varieties: the ‘Cepuna’ (brand name Migo^®) and the ‘Conference’ pears. All patients were sensitized to one or both pear varieties. A total of 12 out of 15 participants developed symptoms during the ‘Cepuna’ food challenge and 14/15 reacted during the ‘Conference’ challenge. Challenges with the ‘Cepuna’ pears resulted in less objective symptoms (n = 2) in comparison with challenges with ‘Conference’ pears (n = 7). Although we did not find significance between both varieties in our study, we found a high likelihood of fewer and less severe symptoms during the ‘Cepuna’ challenges. Consequently selected pear sensitized patients can try to consume small doses of the ‘Cepuna’ pear outside the birch pollen season.

Factors correlating with serum birch pollen IgE status in pregnant women in Hokkaido, Japan: The Japan Environment and Children's Study (JECS)

BACKGROUND

Birch pollen allergy affects pregnant women, and such allergy may affect the development of allergic diseases in their children. Using nationwide birth cohort data, this study aimed to investigate the prevalence of birch pollen IgE positivity and to identify correlating factors in pregnant women in Hokkaido, Japan, a high-latitude island.

METHODS

Participants included 6856 pregnant women. Participants responded to questionnaires regarding lifestyle factors and history of allergies. Data regarding parity, height, and pre-pregnancy weight were collected from medical records. Blood samples were obtained from participants during the first trimester of pregnancy, and serum allergen-specific IgE titers were determined.

RESULTS

The serum of 30.2% participants was positive for birch pollen IgE (≥0.35 UA/mL). Such positivity significantly correlated with a history of other allergic diseases, particularly food allergy and allergic rhinitis/hay fever. In multivariate logistic regression analysis, pre-pregnancy high body mass index (BMI ≥ 25) significantly correlated with birch pollen IgE positivity [odds ratio (OR), 1.24; 95% CI, 1.05-1.47; reference BMI, 18.5-24.9] and higher income (≥10 million yen per year; OR,0.55; 95% CI, 0.37-0.81; reference, household income < 2 million yen per year), and second quintile level physical activity (OR,0.75; 95% CI, 0.63-0.88; reference, the first quintile of physical activity) had significant protective effects.

CONCLUSIONS

Birch pollen IgE positivity in pregnant women was positively associated with food allergy, allergic rhinitis, pre-pregnant high BMI, and was negatively associated with light exercise and high household income in Hokkaido.

TRIAL REGISTRATION

UMIN000030786.

High-Yield Production of the Major Birch Pollen Allergen Bet v 1 With Allergen Immunogenicity in Nicotiana benthamiana

Type I allergy is an immunological disorder triggered by allergens and causes significant health problems. The major allergen of birch pollen is Bet v 1, which belongs to the pathogen-related protein 10 (PR-10) family. Here, we established a rapid and robust method for the production of Bet v 1 in Nicotiana benthamiana leaves, with binding activity to allergic patients' IgE. The Bet v 1 allergen was expressed in N. benthamiana using a strong agroinfiltration-based transient protein expression system, which consists of a deconstructed geminiviral vector system with a double terminator. Five days post-infiltration, the allergen concentration in N. benthamiana leaves was 1.2 mg/g of fresh mass, being this the maximum yield of Bet v 1 in plants reported up to now. A part of plant-derived Bet v 1 was glycosylated. Bet v 1 purified from N. benthamiana or Brevibacillus brevis was used to carry out enzyme-linked immunoassays; both recombinant allergens were found to have comparable binding properties to the IgE of allergic patients. These results suggest that our plant expression system allows rapid and robust production of the allergen, which keeps the immunogenicity.

Lipid Transfer Protein allergy in the United Kingdom: Characterization and comparison with a matched Italian cohort

BACKGROUND

Although pollen-related food allergy occurs in all European populations, lipid transfer protein (LTP) allergy is considered to manifest mainly in Mediterranean countries. We aimed to characterize adults presenting with LTP allergy in a northern European country.

METHOD

The clinical history and sensitization patterns of subjects born and residing in the United Kingdom (UK), with a prior diagnosis of LTP allergy and sensitization to the peach LTP allergen Pru p 3, were compared to UK subjects with pollen food syndrome (PFS). The sensitization patterns were also evaluated against a matched cohort of Italian subjects diagnosed with LTP allergy.

RESULTS

None of the 15 UK PFS subjects had a positive SPT to LTP-enriched peach reagent, compared to 91% of the 35 UK LTP subjects. The UK LTP cohort were also more likely to have positive skin prick tests to cabbage, lettuce and mustard and sensitization to the LTP allergens in peach, walnut, mugwort and plane tree These sensitization patterns to individual allergens were not significantly different to those obtained from the Italian LTP subjects, with significant correlations between Pru p 3 and the LTP allergens in peanuts, walnuts, plane tree and mugwort in both groups.

CONCLUSION

Native UK subjects with LTP allergy are not dissimilar to those with LTP allergy in southern Europe. Testing to LTP-enriched peach SPT reagent and/or LTP allergens in peach, walnut, mugwort and plane tree may enhance diagnostic accuracy.

Birch pollen allergy in Europe

Birch and other related trees of the families Betulaceae and Fagaceae (alder, hazel, oak, hornbeam, chestnut, and beech) constitute the birch homologous group. This grouping is primarily based on the extensive IgE cross-reactivity of allergen homologs to the major birch allergen Bet v 1. Birch pollen is the most dominant tree pollen in Northern and Central Europe and is a major cause of allergic rhinitis and, possibly, asthma symptoms. Over the last few decades, levels of birch pollen have risen and the period of exposure has increased due to climate changes. Subsequently, the prevalence of birch pollen sensitization has also increased. The cross-reactivity and sequential pollen seasons within the birch homologous group create a prolonged symptomatic allergy period beyond birch pollen alone. Furthermore, many plant food allergens contain homologs to Bet v 1, meaning that the majority of patients with birch pollen allergy suffer from secondary pollen food syndrome (PFS). As a result, the negative impact on health-related quality of life (HRQoL) in patients allergic to birch pollen is significant. The purpose of this manuscript was to narratively review topics of interest such as taxonomy, cross-reactivity, prevalence, clinical relevance, PFS, and HRQoL with regard to birch pollen allergy from a European perspective.

Standardization of double blind placebo controlled food challenge with soy within a multicentre trial

Background

Multicentre trials investigating food allergies by double blind placebo controlled food challenges (DBPCFC) need standardized procedures, challenge meals and evaluation criteria. We aimed at developing a standardized approach for identifying patients with birch related soy allergy by means of DBPCFC to soy, including determination of threshold levels, in a multicentre setting.

Methods

Microbiologically stable soy challenge meals were composed of protein isolate with consistent Gly m 4 levels. Patients sensitized to main birch allergen Bet v 1 and concomitant sensitization to its soy homologue Gly m 4 underwent DBPCFC. Outcome was defined according to presence and/or absence of ten objective signs and intensity of eight subjective symptoms as measured by visual analogue scale (VAS).

Results

138 adult subjects (63.8% female, mean age 38 years) underwent DBPCFC. Challenge meals and defined evaluation criteria showed good applicability in all centres involved. 45.7% presented with objective signs and 65.2% with subjective symptoms at soy challenge. Placebo challenge meals elicited non-cardiovascular objective signs in 11.6%. In 82 (59.4%) subjects DBPCFC was judged as positive. 70.7% of DPBCFC+ showed objective signs and 85.4% subjective symptoms at soy challenge. Subjective symptoms to soy challenge meal in DBPCFC+ subjects started at significantly lower dose levels than objective signs (p < 0.001). Median cumulative eliciting doses for first objective signs in DBPCFC+ subjects were 4.7 g [0.7–24.7] and 0.7 g [0.2–4.7] total soy protein for first subjective symptoms (p = 0.01).

Conclusions

We present the hitherto largest group of adults with Bet v 1 and Gly m 4 sensitization being investigated by DBPCFC. In this type of food allergy evaluation of DBPCFC outcome should not only include monitoring of objective signs but also scoring of subjective symptoms. Our data may contribute to standardize DBPCFC in pollen-related food allergy in multicentre settings.

Trial registration

EudraCT: 2009-011737-27.