A new oral sensitization model in rats to food proteins and the importanceof dietary control in oral sensitization with soy

Although several in vivo antigenicity assays using parental immunization ar e operational, no adequate sensitization models are available to study food allergy and allergenicity of food proteins. This paper describes the devel opment of a model for food allergy research in the rat and the influence of dietary pre-exposure to an allergen on oral sensitization. For model devel opment Brown Norway (BN) rats were exposed to ovalbumin either ad libitum c ontinuously via their drinking water or by gavage during for 6 weeks. No ad juvants were used during the sensitization studies. Daily intra-gastric dos ing with ovalbumin resulted in antigen-specific IgG as well as IgE response s in almost all test animals. With ad libitum exposure, ovalbumin-specific Ige but no ovalbumin-specific IgE was detected. Cellular response was exami ned by determination of delayed-type hypersensitivity (DTH) reactions in th e animals dosed by daily gavage and in the ad libitum exposed rats. Both se nsitization protocols sensitised for DTH but the response was most pronounc ed in ad libitum exposed rats after a 28 day exposure. 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) after exposure to ovalbumin without the use of adju vants. One of the major factors that may have negatively affected the resul ts of many oral sensitization studies in animals may have been unscheduled dietary pre-exposure of the test animal, or their parental generations, to the antigen under investigation. Therefore, the influence of dietary pre-ex posure to soy-protein on oral sensitization studies with soy-protein in Bro wn Norway (BN) rats was investigated. The studies showed that if the parental generation was bred and raised on a diet containing soy-protein and they were placed on a soy-protein free die t 6 months before mating the first generation of offspring still showed con tinued expression of anti soy-protein antibodies when bred and raised on a soy-protein free diet. This indicates that not only the test animals must b e bred and raised on a specified antigen-free diet but also their parental generations to be able to orally sensitize the animals for the specified an tigen.