Immune-mediated effects upon oral challenge of ovalbumin-sensitized Brown Norway rats: Further characterization of a rat food allergy model

Although several in vivo antigenicity assays using parenteral immunization are operational, no full validated enteral models are available to study fo od allergy and allergenicity of food proteins. To further validate a develo ped enteral Brown Norway (BN) rat food allergy model, systemic and local im mune-mediated reactions were studied upon oral challenges. The animals were exposed to ovalbumin (OVA) by daily gavage dosing (1 mg OVA/rat/day) for 6 weeks, without the use of an adjuvant, or by intraperitoneal injections wi th OVA together with AL(OH)(3). Subsequently, effects on breathing frequenc y, blood pressure, and gastrointestinal permeability were investigated upon an oral challenge with 10 to 100 mg OVA in vivo. In both parenterally and orally sensitized rats, an increase in gut permeability (increased passage of beta-lactoglobulin as bystander protein) was determined between 0.5 and 1 h after an oral OVA challenge was given. An oral challenge with OVA did n ot induce a clear effect on the respiratory system or blood pressure in the majority of the animals. However, some animals demonstrated a temporary de crease in breathing frequency or systolic blood pressure. Upon oral challen ge with OVA of orally and parenterally sensitized animals, local effects we re observed in all animals whereas systemic effects were observed at a low frequency, which reflects the situation in food allergic patients after an oral challenge. These studies show that the BN rat provides a suitable anim al model to study oral sensitization to food proteins as well as immune-med iated effects after oral challenge with food proteins. (C) 1999 Academic Pr ess.