Safety and efficacy of house dust mite allergen challenge in patients with allergic rhinitis using a novel technique for inhalation studies in the Fraunhofer environmental challenge chamber

RATIONALE: There is an increasing demand for studies on indoor allergens, particularly on house dust mite (HDM) allergens, in order to perform basic clinical research and to test anti-allergic drugs under well-controlled conditions. At Fraunhofer ITEM, a novel technique to universally create an atmosphere loaded with allergen particles was recently developed. In brief, aerosol particles of defined size are produced by spray-drying of a solution that contains a licenced allergen extract and lactose as a carrier. The particle size distribution is dependent on the initial droplet size and the solute lactose concentration aiming to have a particle size above 10µm. The aim of this study was to test the safety and efficacy with dose-range finding and reproducibility of this novel HDM challenge in patients with allergic rhinitis in the Fraunhofer Environmental Challenge Chamber (ECC). METHODS: In a monocenter, placebo-controlled, single-blind, pilot study 18 subjects with allergic rhinitis and sensitization to HDM were exposed in the Fraunhofer ECC for 4 hours to house dust mite allergen (ALK lyophilisiert SQ503 Der p, ALK-Abello, Wedel, Germany) at either 250 SQE/m3, 500 SQE/m3, 1000 SQE/m3, or lactose alone (0 SQE/m3) seven days apart. The dose of 500 SQE/m3 was repeated to investigate reproducibility. Total nasal symptom score (TNSS), anterior rhinomanometry, nasal secretions, exhaled NO, FEV1 and adverse events were assessed prior to and during the exposures. RESULTS: At a lactose concentration of 10% (w/v) the mass median aerodynamic diameter of allergen particles was 13.5 µm and only 11% of particles were