Suzanne Bolhaar

Efficacy of birch-pollen immunotherapy on cross-reactive food allergy confirmed by skin tests and double-blind food challenges

Background The effect of birch‐pollen immunotherapy (IT) on cross‐reactive food allergies is controversial.

Mutational Analysis of Amino Acid Positions Crucial for IgE-Binding Epitopes of the Major Apple (Malus domestica) Allergen, Mal d 1

Background: Individual amino acid residues of the major birch pollen allergen, Bet v 1, have been identified to be crucial for IgE recognition. The objective of the present study was to evaluate whether this concept was applicable for the Bet v 1-homologous apple allergen, Mal d 1. Methods: A Mal d 1 five-point mutant was produced by PCR techniques, cloned into pMW 172 and expressed in Escherichia coli BL21(DE3) cells. To evaluate the allergenic properties of the engineered protein compared to Mal d 1 wild-type IgE immunoblotting, ELISA, peripheral blood monocytes proliferation assays, and skin prick tests were performed. Results: The Mal d 1 mutant showed reduced capacity to bind specific IgE as compared to wild-ype Mal d 1 in in vitro assays in the majority of the sera tested. In ELISA, 10 out of 14 serum samples displayed an 88–30% decrease in IgE binding to Mal d 1 mutant compared to wild-type Mal d 1. Skin prick tests in apple-allergic patients (n = 2) confirmed the markedly decreased ability of the Mal d 1 mutant to induce allergic reactions in vivo. However, the relevant T cell epitopes were present in the mutated molecule according to peripheral blood mononuclear cell proliferation assays. Conclusions: Our findings suggest that it is possible to modulate the IgE-binding properties of allergens by single amino acid substitutions at crucial positions which might be useful for future immunotherapy of birch-pollen-associated food allergies which are not ameliorated by birch pollen immunotherapy.

A mutant of the major apple allergen, Mal d 1, demonstrating hypo-allergenicity in the target organ by double-blind placebo-controlled food challenge.

Background Allergen‐specific immunotherapy for food allergy has been hindered by severe side‐effects in the past. Well‐characterized hypo‐allergenic recombinant food allergens potentially offer a safe solution.

Allergy to jackfruit: a novel example of Bet v 1-related food allergy

Background:  Jackfruit allergy has been reported just once. It is unknown whether this food allergy is caused by direct sensitization or cross‐sensitization to pollen allergens.

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.

Assessment of allelic diversity in intron-containing Mal d 1 genes and their association to apple allergenicity

BackgroundMal d 1 is a major apple allergen causing food allergic symptoms of the oral allergy syndrome (OAS) in birch-pollen sensitised patients. The Mal d 1 gene family is known to have at least 7 intron-containing and 11 intronless members that have been mapped in clusters on three linkage groups. In this study, the allelic diversity of the seven intron-containing Mal d 1 genes was assessed among a set of apple cultivars by sequencing or indirectly through pedigree genotyping. Protein variant constitutions were subsequently compared with Skin Prick Test (SPT) responses to study the association of deduced protein variants with allergenicity in a set of 14 cultivars.ResultsFrom the seven intron-containing Mal d 1 genes investigated, Mal d 1.01 and Mal d 1.02 were highly conserved, as nine out of ten cultivars coded for the same protein variant, while only one cultivar coded for a second variant. Mal d 1.04, Mal d 1.05 and Mal d 1.06 A, B and C were more variable, coding for three to six different protein variants. Comparison of Mal d 1 allelic composition between the high-allergenic cultivar Golden Delicious and the low-allergenic cultivars Santana and Priscilla, which are linked in pedigree, showed an association between the protein variants coded by the Mal d 1.04 and -1.06A genes (both located on linkage group 16) with allergenicity. This association was confirmed in 10 other cultivars. In addition, Mal d 1.06A allele dosage effects associated with the degree of allergenicity based on prick to prick testing. Conversely, no associations were observed for the protein variants coded by the Mal d 1.01 (on linkage group 13), -1.02, -1.06B, -1.06C genes (all on linkage group 16), nor by the Mal d 1.05 gene (on linkage group 6).ConclusionProtein variant compositions of Mal d 1.04 and -1.06A and, in case of Mal d 1.06A, allele doses are associated with the differences in allergenicity among fourteen apple cultivars. This information indicates the involvement of qualitative as well as quantitative factors in allergenicity and warrants further research in the relative importance of quantitative and qualitative aspects of Mal d 1 gene expression on allergenicity. Results from this study have implications for medical diagnostics, immunotherapy, clinical research and breeding schemes for new hypo-allergenic cultivars.

Severe allergy to sharon fruit caused by birch pollen.

Background: Allergy to sharon fruit (persimmon) has been only rarely reported. Cross-reactivity with pollen (profilin and Bet v 6) appeared to be involved, but Bet v 1 has not been implicated previously. Objective: It is our aim to identify whether Bet v 1 sensitization is linked to sharon fruit allergy. Methods: Two patients with a reaction upon first exposure to sharon fruit were included in the study, as well as 7 patients with birch-pollen-related apple allergy. Sensitivity was assessed by skin prick testing (SPT), a radio-allergosorbent test (RAST) and immunoblotting. RAST analysis was performed for Bet v 1, Bet v 2 and Bet v 6. Cross-reactivity was evaluated by RAST and immunoblot inhibitions. Biological activity of IgE was measured by basophil histamine release. Sharon fruit allergy was evaluated by double-blind placebo-controlled food challenge (DBPCFC) or open challenge (OC). Results: Both sharon-fruit-allergic patients demonstrated positive reactions in the RAST (8.6 and 6.2 IU/ml, respectively) and SPT (wheal area 37 and 36 mm2). Sharon fruit allergy was confirmed by DBPCFC in 1 patient. The second patient refused a challenge because of the severe initial reaction. Sera from both patients were reactive to Bet v 1 and Bet v 6, which was cross-reactive with sharon fruit by inhibition assays. The patient with the severest reactions was reactive to profilin on immunoblotting. However, profilin did not induce significant histamine release, nor did Bet v 6. Bet v 1 induce approximately 60% histamine release. An OC with sharon fruit in 7 patients allergic to birch pollen and apple, who had not eaten sharon fruit previously, was positive in 6/7 cases. Conclusions: Birch-pollen-related allergy to sharon fruit is mediated by the known cross-reactive pollen allergens including Bet v 1 and may become more of a problem should sharon fruit consumption increase.

IgE Binding to Pepsin-Digested Food Extracts

Background: Pepsin resistance of allergens like lipid transfer protein and 2S albumin has been suggested as explanation for the severity of symptoms often induced by these allergens. Component-resolved diagnosis with purified labile and stable allergens has therefore been proposed to better characterize the risk involved in a positive in vitroIgE test. However, for many foods, purified allergens are not (yet) available. Objective: It was the aim of this study to evaluate the potential of pepsin-digested whole-food extracts to distinguish between IgE responses to stable (potentially severe) and labile (mild) allergens. Methods: Sera (n = 143) from Italian, Spanish and Dutch patients with hazelnut and/or apple ingestion-related symptoms were analyzed for residual IgE binding to pepsin-resistant hazelnut and/or apple allergens. Control and pepsin-digested hazelnut and apple extracts were used for radioallergosorbent test analysis and immunoblot analysis. Results: Pepsin digestion of food extracts, like from hazelnut and apple used for in vitro diagnostic tests, provides a way to distinguish sensitization to pepsin-resistant allergens from that to pepsin-susceptible allergens. In this selected group of patients, IgE reactivity to pepsin-digested extracts correlated with sensitization to the stable allergen lipid transfer protein. The analysis further revealed that the use of soluble pepsin can result in false-positive in vitro tests (2/143). Conclusion: Pepsin-digested food extracts are a convenient tool to identify patients with IgE antibodies against potentially dangerous stable allergens, in particular for those foods where the relevant stable allergens have not yet been identified. This can increase the clinical prognostic value of food allergy serology.

Attitudes towards low‐allergen food in food allergic consumers

Purpose – The aim was to look at food‐allergic consumers’ preferences concerning the development of low‐allergen food.Design/methodology/approach – A questionnaire was designed to measure attitudes towards low‐allergen food. Data were collected from 20 food‐allergic consumers in Austria, Spain and The Netherlands respectively between April and May 2002 using interviewer‐assisted questionnaire methodology.Findings – The results suggested that food‐allergic consumers are interested in having low‐allergen food available, with 70‐95 per cent wanting it produced. A total of 89 per cent identified a number of benefits to themselves, including being able to resume eating the food to which they were allergic, and being able to eat all food with no worries, no symptoms and no need to check labels. Fewer disadvantages were mentioned, with 53 per cent identifying no disadvantages. Factors that would encourage or discourage purchase of low‐allergen food were also identified with price, quality (particularly taste) an...

Attitudes Towards Genetically Modified Food with a Specific Consumer Benefit in Food Allergic Consumers and Non‐food Allergic Consumers

The aim of the reported study was to investigate attitudes towards genetically modified food with a specific consumer benefit. Fifty food allergic and one hundred non‐allergic consumers took part in a telephone interview study in each of Austria, Spain and the Netherlands. Participants were first asked about their purchase intentions for an unspecified genetically modified food. Next, participants were asked about their purchase intentions for a genetically modified food with a specific consumer benefit. Food allergic consumers were asked about ‘low‐allergen food’ produced using genetic modification and non‐allergic consumers were asked about ‘food that benefits your health’ produced using genetic modification. It was found that intention to purchase genetically modified food with these specific benefits was higher than intention to purchase an unspecified genetically modified food.