ORAL SENSITIZATION TO FOOD PROTEINS - A BROWN-NORWAY RAT MODEL

Background Although several in vivo antigenicity assays using parenter al immunization are operational, no adequate enteral sensitization mod els are available to study food allergy and allergenicity of food prot eins. Objective This paper describes the development of an enteral mod el for food allergy research in the Brown Norway (BN) rat. Methods The animals were exposed to ovalbumin either ad libitum via the drinking water (0.002 to 20 mg/mL) continuously for 6 weeks or by gavage (1 mg/ mL per rat). Gavage dosing was performed either daily, twice a week, o nce a week or once every 2 weeks during a period of 6 weeks. No adjuva nts were used during the sensitization studies. Results After intra-ga stric administration of ovalbumin once or twice a week or once every t wo weeks, no or only a very low frequency of ovalbumin-specific antibo dy responses were detected. Daily intra-gastric dosing with ovalbumin resulted in antigen-specific IgG as well as IgE responses in almost al l animals tested. Upon ad libitum exposure, ovalbumin-specific IgG but no ovalbumin-spefific IgE was detected. The cellular response was exa mined by determination of delayed-type hypersensitivity (DTH) reaction s in the animals dosed by daily gavage and in the ad libitum exposed r ats. Both sensitization protocols sensitized for DTH. The response was most pronounced in ad libitum exposed rats at day 28 of exposure. Con clusions These studies show that the BN rat may provide a suitable ani mal model for inducing specific IgG and IgE responses as well as speci fic T-cell mediated hypersensitivity (DTH) to ovalbumin upon exposure via the enteral route without the use of adjuvants.