Identification of IgE binding to Api g 1-derived peptides.

Celery is a frequent cause of food allergy in pollen-sensitized patients and can induce severe allergic reactions. Clinical symptoms cannot be predicted by skin prick tests (SPTs) or by determining allergen-specific immunoglobulin E (IgE). Our aim was to identify specific IgE binding peptides by using an array technique. For our study, the sera of 21 patients with positive double-blind, placebo-controlled food challenge (DBPCFC) to celery, as well as the sera of 17 healthy patients were used. Additionally, all patients underwent skin tests along with determinations of specific IgE binding. The major allergen of celery Api g 1.0101 (Apium graveolens) was synthesized as an array of overlapping peptides and probed with the patients' sera. We developed an improved immunoassay protocol by investigating peptide lengths, peptide densities, incubation parameters, and readout systems, which could influence IgE binding. Sera of celery-allergic patients showed binding to three distinct regions of Api g 1.0101. The region including amino acids 100 to 126 of Api g 1.0101 is the most important region for IgE binding. This region caused a fivefold higher binding of IgE from the sera of celery-allergic patients compared to those of healthy individuals. In particular, one peptide (VLVPTADGGSIC) was recognized by all sera of celery-allergic patients. In contrast, no binding to this peptide was detected in sera of the healthy controls. Our improved assay strategy allows us to distinguish between celery-allergic and healthy individuals, but needs to be explored in a larger cohort of well-defined patients.