In this study, we constructed particles applicable for oral immunotherapy of type I allergy by protecting allergens from digestion and supporting intestinal antigen uptake. Therefore, birch-pollen allergens were entrapped in poly(D,L-lactic-co-glycolic acid) microspheres by spray-drying rendering microspheres with a main population of 1-3 mum. Microspheres were further coated with wheat germ agglutinin (WGA) to target enterocytes. Coating with WGA did not alter the surface characteristics of the microspheres as demonstrated in scanning electron microscopy. Binding of WGA was specific and could be inhibited by chitotriose to 14.7 +/- 6.9%. Comparable amounts of allergen were released from both particle-types with 46.3 +/- 1.7% and 44.5 +/- 2.6% during 21 days. Simulating gastric digestion in vitro, antigenicity of allergens entrapped in WGA-microspheres was preserved to 59.8 +/- 1.5% even after 2 h. Feedings of BALB/c mice with WGA-microspheres induced higher levels of allergen-specific IgG-levels than gavages of uncoated microparticles or naked protein. Thus, we conclude that WGA-microspheres are suitable vehicles for oral delivery and mucosal targeting due to lectin-mediated bioadhesion. (C) 2004 Elsevier Inc. All rights reserved.