Age-related sensitization profiles for hazelnut (Corylus avellana) in a birch-endemic region

Background: Symptoms of hazelnut allergy seem related to geographic and possibly age variations in allergen recognition. Objective: To investigate sensitization profiles of hazelnut allergy in different age groups in a birch-endemic region using component resolved diagnosis (CRD) by microarray. Methods: Sixty-five patients with hazelnut allergy, 27 healthy control individuals tolerant to hazelnut, and 34 birch pollen allergic but hazelnut tolerant individuals were included. All blood samples were analyzed using ISAC microarray. Results: Twenty-nine patients with hazelnut allergy suffered from a systemic reaction (17 preschool children with a median age of 2 years, six school children, and six adults), whereas 36 patients reported an oral allergy syndrome (OAS; three preschool and nine school children and 24 adults). In the hazelnut allergic preschool children with systemic reactions, 65% were sensitized to Cor a 9, 12% to Cor a 8, 18% to Cor a 1.04, 6% to Cor a 1.0101, and 29% to Bet v 1. Of the school-aged systemic reactors, 50% were sensitized to Cor a 9, 17% to Cor a 8, 50% to Cor a 1.04 and Cor a 1.0101, and 67% to Bet v 1. In adults with hazelnut allergy, 3.3% were sensitized to Cor a 9, 6.7% to Cor a 8, 90% to Cor a 1.04 and Bet v 1, and 87% to Cor a 1.0101. In regard to systemic reactors in this group, 17% were sensitized to Cor a 9, 33% to Cor a 8 and Cor a 1.0101, and 50% to Cor a 1.04 and Bet v 1. In the patients with OAS, irrespective the age group, all were sensitized to Bet v 1 and over 97% to Cor a 1.04 and Cor a 1.0101. No sensitization to Cor a 9 or Cor a 8 was found in patients with only an OAS. Of the patients with birch pollen allergy, tolerant to hazelnut, none were sensitized to Cor a 9 or Cor a 8, 56% to Cor a 1.0101, 82% to Cor a 1.04, and 92% to Bet v 1. In healthy controls, no sensitization to components of hazelnut, hazel pollen or birch pollen was demonstrable. Conclusion: Hazelnut allergy in a birch-endemic region exhibits age-related sensitization profiles with distinct clinical outcomes that can be identified using CRD. The majority of hazelnut allergic preschool and school children in a birch-endemic region show systemic reactions on consumption of processed hazelnut, mostly being sensitized to the hazelnut legumin-like allergen Cor a 9 but unrelated to birch pollen allergy. In contrast, adults generally suffer from an OAS apparently as a result of cross-reactivity between Cor a 1.04 from hazelnut and Bet v 1 from birch pollen.