Oral birch allergy syndrome

Oral birch allergy syndrome:

• patients with birch pollen allergy frequently develop hypersensitivity reactions to certain foods, e.g. apples, celery, carrots and hazelnuts
  
  
  • reactions are mainly caused by IgE-antibodies specific for the major birch pollen allergen, Bet v 1, which cross-react with homologous proteins in these foods
    
    
  • food allergy represents an important manifestation of atopic allergy
    • primary food allergy mainly affects young children whereas adults frequently develop food allergy as a consequence of an inhalant sensitization
      • pollen-related food allergy has become the most frequent form of food allergy in adolescent and adult individuals in Europe
        • a typical example is the 'birch-fruit-vegetable-syndrome'.
          • more than 70% of birch pollen-allergic individuals develop allergic reactions to stone-fruits, nuts or certain vegetables. In the majority of patients these reactions are confined to the oropharynx and summarized as 'oral allergy syndrome' (OAS)
          • nevertheless, systemic IgE-mediated reactions such as urticaria, asthma or anaphylactic shock occur occasionally
            
            
      • the major birch pollen allergen, Bet v 1, is the most relevant sensitizing protein causing this type of food allergy but minor allergens such as Bet v 2, Bet v 5 and Bet v 6 have also been shown to be involved
        • whereas these allergens are recognized by 10-32% of birch pollen-allergic patients, more than 95% display IgE against Bet v 1(4)

Notes:

• major birch pollen allergen belongs to the pathogenesis-related (PR) protein family
  • other members of this protein family are present in various foods, such as fruits of Rosaceae (e.g. Mal d 1 in apple, Pru a 1 in cherry, Pyr c 1 in pear), vegetables of Apiaceae (e.g. Api g 1 in celery, Dau c 1 in carrot), hazelnut (Cor a 1), soybean (Gly m 4), mungbean (Vig r 1) and peanut (Ara h 8)
    • these proteins share a high degree of amino acid sequence similarity with the major birch pollen allergen resulting in a similar tertiary structure
    • thus, Bet v 1-specific IgE antibodies can bind to these dietary proteins which may cause immediate hypersensitivity reactions upon consumption of the respective foods
    • IgE-cross-reactivity between Bet v 1 and food homologues correlates roughly with the similarity of their primary protein structures

Reference:

• 1) Amlot PL, Kemeny DM, Zachary C, Parkes P, Lessof MH. Oral allergy syndrome (OAS): symptoms of IgE-mediated hypersensitivity to foods. Clin Allergy 1987;17:33-42.
• 2) Kleine-Tebbe J, Vogel L, Crowell DN, Haustein UF, Vieths S. Severe oral allergy syndrome and anaphylactic reactions caused by a Bet v 1- related PR-10 protein in soybean, SAM22. J Allergy Clin Immunol 2002;110:797-804.
• 3) Wuthrich B. Birch pollen allergy in relation with hypersensitivity for various kinds of fruit. Hautarzt 1990;41:583-584.
• 4) Bohle B.The impact of pollen-related food allergens on pollen allergy. Allergy. 2007 Jan;62(1):3-10.