Local and systemic inflammatory responses following bronchial instillation of house dust mite allergen (HDM) and HDM/lipopolysaccharide (LPS) in mild asthmatics

Rationale: Exposure to house dust, containing HDM and LPS, is associated with severity of allergic asthma. We hypothesized that adding LPS to bronchial provocation with HDM amplifies allergic inflammation in asthmatics on maintenance treatment with inhalation corticosteroids (ICS). Aim: To assess the allergic inflammatory response in blood and bronchoalveolar lavage (BAL) fluid induced by provocation with HDM +/- LPS. Methods: We included 39 mild asthmatic patients with HDM allergy. After 2 weeks run-in with fluticasone 100μg bid, blood was drawn and subjects underwent bronchoscopy for instillation of saline in one lung followed by instillation of HDM +/- LPS in the contralateral lung. Six hours later, blood was drawn and BAL was performed. Statistical comparisons were made by Univariate Analysis. Results: Additional instillation of LPS to HDM resulted in a significant increase in peripheral blood leukocytes and neutrophils, and a decrease of eosinophils. Provocation with HDM+LPS significantly increased total cell numbers, neutrophils, and Eosinophil Cationic Protein (ECP) in BAL fluid (p=0.04), and showed a trend towards an increase in eosinophils. Conclusion: Additional instillation of LPS to a provocation with HDM in mild asthma decreases circulating eosinophils and increases pulmonary eosinophil influx and ECP-release, despite treatment with ICS.