Oral sensitization to food proteins: A Brown Norway rat model

Background: Although several in vivo antigenicity assays using parenteral immunization are operational, no adequate enteral sensitization models are available to study food allergy and allergenicity of food proteins. Objective: This paper describes the development of an enteral model 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 20mg/mL) continuously for 6 weeks or by garage (1 mg/mL per rat). Garage dosing was performed either daily, twice a week, once a week or once every 2 weeks during a period of 6 weeks. No adjuvants were used during the sensitization studies. Results: After intra-gastric administration of ovalbumin once or twice a week or once every two weeks, no or only a very low frequency of ovalbumin-specific antibody responses were detected. Daily intra-gastric dosing with ovalbumin resulted in antigen-specific IgG as well as IgE responses in almost all animals tested. Upon ad libitum exposure, ovalbumin-specific IgG but no ovalbumin-specific IgE was detected. The cellular response was examined by determination of delayed-type hypersensitivity (DTH) reactions in the animals dosed by daily garage and in the ad libitum exposed rats. Both sensitization protocols sensitized for DTH The response was most pronounced in ad libitum exposed rats at day 28 of exposure. Conclusions: These studies show that the BN rat may provide a suitable animal model for inducing specific IgG and IgE responses as well as specific T-cell mediated hypersensitivity (DTH) to ovalbumin upon exposure via the enteral route without the use of adjuvants.