Gastrointestinal digestion of Bet v 1-homologous food allergens destroys their mediator-releasing, but not T cell-activating, capacity.
BACKGROUND
Food allergy to apples, hazelnuts, and celery is frequent in individuals with birch pollen allergy because IgE antibodies specific for the major birch pollen allergen, Bet v 1, cross-react with structurally related allergens in these foods. In addition, T lymphocytes specific for Bet v 1 also cross-react with these dietary proteins.


OBJECTIVE
We sought to evaluate the effects of simulated gastrointestinal degradation of Bet v 1-related food allergens on their mediator-releasing and T cell-activating capacity.


METHODS
Recombinant Mal d 1, Cor a 1.04, and Api g 1 were incubated separately with pepsin and trypsin. Binding of IgE was tested in immunoblots. After successive incubation with both enzymes, allergens were tested in mast cell mediator release assays and used to stimulate PBMCs and Bet v 1-specific T-cell lines and clones. Proteolytic fragments of allergens were analyzed and sequenced by means of mass spectrometry.


RESULTS
Pepsin completely destroyed IgE binding of all allergens within 1 second, and trypsin completely destroyed IgE binding of all allergens within 15 minutes, except for the major hazelnut allergen, which remained intact for 2 hours of trypsinolysis. Allergens after gastrointestinal digestion did not induce basophil activation but induced proliferation in PBMCs from allergic and nonallergic individuals. Digested Mal d 1 and Cor a 1.04 still activated Bet v 1-specific T cells, whereas digested Api g 1 did not. Different proteolytic fragments of Mal d 1 and Cor a 1.04 matching relevant Bet v 1 T-cell epitopes were found.


CONCLUSIONS
Gastrointestinal degradation of Bet v 1-related food allergens destroys their histamine-releasing, but not T cell-activating, property. Our data emphasize that birch pollen-related foods are relevant activators of pollen-specific T cells.
Schimek
Eva Maria
EM
Department of Pathophysiology, Center for Physiology and Pathophysiology, Medical University of Vienna, Austria.
Zwölfer
Bettina
B
Briza
Peter
P
Jahn-Schmid
Beatrice
B
Vogel
Lothar
L
Vieths
Stefan
S
Ebner
Christof
C
Bohle
Barbara
B
D000485:Allergens / Q000276:immunology / Q000378:metabolism*; D000595:Amino Acid Sequence; D029662:Betula / Q000276:immunology*; D003429:Cross Reactions; D004063:Digestion; D005512:Food Hypersensitivity / Q000276:immunology*; D006636:Histamine Release; D006801:Humans; D007073:Immunoglobulin E / Q000378:metabolism; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D010434:Pepsin A / Q000494:pharmacology; D010940:Plant Proteins; D011058:Pollen / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D014357:Trypsin / Q000494:pharmacology
D000485:Allergens; D010940:Plant Proteins; C053376:pathogenesis-related proteins, plant; D007073:Immunoglobulin E; D014357:Trypsin; D010434:Pepsin A