Ovalbumin aeroallergen exposure-response in Brown Norway rats

A major route of exposure to allergens is through the respiratory tract. Co mparatively few animal studies have used aerosolized high-molecular-weight allergens for sensitization, and in these studies, proper characterization of the aeroallergen exposure was usually missing. The purpose of this study was to profile the exposure-response relationship in Brown Norway rats (BN R) to well-characterized ovalbumin (OVA) aerosols. Rats were exposed 30 min /wk x 6 wk to respirable OVA aerosols from <1 mg/m(3) to 64 mg/ m(3) air. O valbumin-specific circulating immunoglobulin (Ig)E, IgC, and IgA were measu red throughout the study period. Rats were sacrificed 1 day after the last exposure. Pulmonary tissue was processed for histopathological and histoche mical analysis. Tracheas were isolated, perfused, and assessed for in vitro responsiveness to methacholine. Serum concentrations of OVA-specific antib odies increased with both exposure concentration and number of exposures. T he number of BNR with measurable titers also increased with both dose and t ime. Pulmonary inflammatory changes were noted only in BNR exposed to highe r OVA concentrations (15 and 64 mg/m(3) air). Increased tracheal reactivity to methacholine was not found in any of the sensitized BNR. In summary, su stained aeroallergen concentration-dependent changes in specific antibody r esponses and pulmonary inflammation have been demonstrated.