IN-VITRO STUDY OF THE GASTROINTESTINAL STABILITY OF CELERY ALLERGENS

The gastrointestinal stability of proteins and allergens from native c elery roots was studied by a simple two-step in vitro procedure. Comme rcial enzyme tablets that contained peptic and pancreatic enzymes were used to simulate gastric and duodenal conditions respectively. The in fluence on the whole protein pattern was monitored by SDS-PAGE. The an tigenicity and allergenicity of the three known important allergenic s tructures of celery were investigated with Ige from two rabbit antiser a. IgE from sera of allergic patients with known specificity for indiv idual allergens, and by a mediator release assay utilizing allergen-sp ecific polyclonal murine IgE. The following allergens were studied: (i ) Api g I, a 16-kDa celery, protein which shares high sequence identit y with the major birch pollen allergen, Bet v I, (ii) celery profilin that belongs to a group of ubiquitous 'plant pan allergens' and (iii) ubiquitous carbohydrate determinants present in many glycans of plant proteins in the mass range of 35-90 kDa. SDS-PAGE indicated degradatio n of many proteins under gastric conditions, but immunoblotting showed only a weak influence on the antigenicity and IgE reactivity of the a llergens. The protein degradation was clearly enhanced after 45 min of pancreatic digestion. To a weaker degree, all allergens were again re cognized on immunoblots. The presence of G considerable residual aller genic activity which seems to resist even duodenal conditions was conf irmed by the determination of human IgE specific for the digests using an Enzyme Allergosorbent Test. In addition, competitive IgE inhibitio n assays and measuring the celery-induced mediator release of permanen tly growing RBL-2H3 cells that had been passively sensitized with cele ry-specific murine IgE showed similar results. The generation of small small IgE binding peptides (less than or equal to 3 kDa) was tested b y ultrafiltration experiments. The whole IgE binding capacity was pres ent in the retentates even after duodenal digestion. We concluded that , like many other allergens from foods and other sources, the allergen s of native celery are relatively stable under gastrointestinal condit ions and that the residual allergenic activity, is mainly due to undig ested allergens.