Background: Celery root is often consumed in a processed form as a cooked vegetable or as a spice. So far, however, there has been no information about the allergenicity of processed celery in celery-allergic patients.
Methods: In 12 patients with a history of allergic reactions to raw or raw and cooked celery, double-blind placebo-controlled food challenges (DBPCFCs) with raw celery (n = 10), cooked celery (110 degrees C/15 min; n = 11), and celery spice (n = 5) were performed. Nine patients underwent an open mucosal challenge with four samples of canned celery retorted at Co-values (cooking effect) of 7.45-76.07 (corresponding to the time periods in minutes at a thermal influence of 100 degrees C). IgE immunoblot analysis of celery extract was performed with sera of all challenged patients. The thermal stability of celery allergen was investigated by enzyme allergosorbent test (EAST) inhibition. Furthermore, intraperitoneal immunization of mice followed by a rat basophil leukemia (RBL) cell mediator release assay was used as a biological in vitro model to assess the allergenicity of processed celery.
Results: Six out of 11 patients showed a positive DBPCFC to cooked celery and five out of five patients to celery spice. Allergenicity of celery was preserved in four patients with a positive DBPCFC to cooked celery even if celery was treated at a Co-value of 76.07. Patients with positive DBPCFC to cooked celery reacted to known celery allergens (Api g 1, Api g 4, cross-reactive carbohydrate determinants CCD). EAST inhibition showed that heat resistance of celery allergens decreases in the following order: CCD > Api g 4 > Api g 1. Accordingly, five of six patients with a positive DBPCFC to cooked celery were sensitized to profilin and/or CCD. The murine model reflected the reactivity of patients sensitized to the major allergen Api g 1.
Conclusions: 1) In a subset of patients with a positive DBPCFC to cooked celery, celery remains allergenic even after extended thermal treatment (76.07 min/100 degrees C). 2) Celery spice is allergenic for patients with an allergy to raw celery. 3) RBL cells sensitized with mouse IgE to raw celery may serve as a useful tool for screening the potential allergenicity of heat-processed products containing celery.