Immunochemical assay of airborne cat allergen: value in assessing variability of allergen shedding and evaluating human bronchial response

Abstract

Twelve cats were selected from the animal care facility to determine their individual rates of allergen shedding. Cats were placed in a lucite chamber with an air sampler attached. Radioallergosorbent (RAST) inhibition type and monoclonal two-site radioimmunosurveys (RIAs) were used to express air concentrations in allergy units (AU) orFel d 1 units), respectively. Inter-cat variability ranged from a factor of 6 (inFel d 1 units) to a factor of 100 (in AU). Production of individual cats over time varied by a factor of 10–20 (AU orFel d 1). Three of the highest shedders were placed in wire cages in a room-sized chamber with closed ventilation. Four cat-sensitive asthmatics were individually exposed to the cats in the chamber and had spiromatic and minute ventilation measurements performed while personal air sampling was performed. Allergen concentration in the chamber was higher than in homes we have measured. 11% (Fel d 1) or 17% (AU) of the allergen concentration was associated with respirable particles (<9 μm). The dose of allergen required to elicit a 20% drop in FEV1 from baseline was calculated from the measured air concentration, patients' ventilation, particle sizing data and estimated lung deposition. This dose was substantially less than that required by breathing nebulized cat extract for 3 of the 4 subjects.