Artemisia vulgaris pollen allergoids digestibility in the simulated conditions of the gastrointestinal tract

Chemically modified allergens (allergoids) have found use in both traditional and novel forms of immunotherapy of allergic disorders. Novel forms of immu- notherapy include local allergen delivery, via the gastrointestinal tract. This study con- veys the gastrointestinal stability of three types of mugwort pollen allergoids under sim- ulated conditions of the gut. Allergoids of the pollen extract of Artemisia vulgaris were obtained by means of potassium cyanate, succinic and maleic anhydride. Gastrointesti- nal tract conditions (saliva, and gastric fluid) were simulated in accordance with the EU Pharmacopoeia. The biochemical and immunochemical properties of the derivatives following exposure to different conditions were monitored by determining the number of residual amino groups with 2,4,6-trinitrobenzenesulfonic acid, SDS PAGE, immuno- blotting and inhibition of mugwort-specific IgE. Exposure to saliva fluid for 2 min did not influence the biochemical and immunochemical properties of the derivatives. In the very acidic conditions of the simulated gastric fluid, the degree of demaleylation and desuccinylation, even after 4 h exposure, was low, ranging from 10 to 30 %. The diges- tion patterns with pepsin proceeded rapidly in both the unmodified and modified sam- ples. In all four cases, a highly resistant IgE-binding protein the Mw of which was about 28 - 35 kD, was present. Within the physiological conditions, no new IgE binding epitopes were revealed, as demonstrated by immunoblot and CAP inhibition of the mugwort specific IgE binding. An important conclusion of this study is the stability of the modified derivatives in the gastrointestinal tract of patients, within physiological conditions. The means that they are suitable for use in much higher concentrations in lo- cal forms of immunotherapy than unmodified ones.