Measurement and characterization of cockroach allergens detected during normal domestic activity

Background: Cockroach allergen is recognized as a causal factor for asthma. However, airborne cockroach allergen has not been detected in undisturbed conditions, and therefore the behavior and properties of airborne cockroach allergen have been poorly characterized. A new aeroallergen sampling metho d and sensitive system of immunoassay have been used to examine cockroach a llergen exposure. Objective: Our purpose was to measure and characterize airborne cockroach a llergens during normal domestic exposure in the homes of Sydney, Australia. Methods: Air sampling with Institute of Occupational Medicine, Edinburgh (I OM) samplers was performed in the living rooms of 10 houses during low- and no-disturbance environments, In addition, inhaled particles were collected by each home occupant during low domestic exposure with use of intra-nasal samplers that impact particles onto an adhesive surface. The particles col lected on the IOMs and the intranasal samplers were immunostained with Bla g 1 monoclonal antibodies. Particle size, morphologic characteristics, and the relative Bla g 1 content of particles were estimated. Reservoir dust sa mples from the kitchen, living room, and bedroom were assayed by an ELISA. Two forms of repeatability of IOM air sampling were examined, The first mea sure tested the repeatability of 2 IOM samples collected simultaneously in the same room during low- and no-disturbance activities. The second measure examined the repeatability of IOM;I sampling over time on 10 consecutive d ays. Results: Bla g 1 was detected in reservoir dust samples taken from all home s (geometric mean 1.5 U/g, range 0.2-9.4 U/g), Inhaled particles containing Bla g 1 were detected during 1 hour of intra-nasal sampling in 8 of 10 hom es during low disturbance. Cockroach particles were detected on all of the IOM samples collected for both 4-hour low-disturbance and overnight no-dist urbance sampling environments. Particles containing Bla g 1 collected with the IOM samplers during low disturbance ranged in size from 3 to 350 mu m. These particles are amorphous and irregular in shape, and a majority of the large particles were described as flakes (flat, transparent particles) and fibers (threadlike). A relationship was demonstrated between the allergen content of cockroach particles and their particle size. The larger particle s elute more Bla g 1, The coefficient of repeatability for measurements mad e during low and no disturbance was 3.62 and 2.09, respectively. For measur ements repeated over time at the same site, the coefficient of repeatabilit y was 2.61. This represents the fold range within which 95% of pairs of mea surements made at an interval of 1 day would be expected to lie. Conclusions: Airborne cockroach allergen is present in both undisturbed and low-disturbance environments in homes with relatively low reservoir levels of Bla g 1. In agreement with previous reports, airborne particles contain ing cockroach allergen (Bla g 1) are mainly associated with particles >10 m u m. These particles are amorphous and irregular in shape and can be descri bed as flakes and fibers.