Mite-antigen avoidance can reduce bronchial epithelial shedding in allergic asthmatic children

BACKGROUND: Asthma is characterized by bronchial hyperresponsiveness (BHR), bronchial mucosa inflammation and airway epithelial damage. OBJECTIVE: This study was designed to evaluate the effect of mite avoidance on bronchial epithelial shedding in asthmatic children sensitized to Dermatophagoides. METHODS: The percentages of airway epithelial cells and eosinophil have been counted in samples obtained by hypertonic saline-induced sputum before and after a period of antigen avoidance in an Alpine environment (1756 m). The degree of bronchial hyperresponsiveness to methacholine was also evaluated. RESULTS: After avoidance the median (lower, Q1, and upper, Q3, quartile) percentage of epithelial cells in the sputum decreased significantly from 3.50 [0.50;6.98] to 0 [0;0.5] (P=0.012) and eosinophil percentage decreased from 1 [0;5.25] to 0 [0,1.5] (P<0.05). Median (Q1,Q3) PC20 increased significantly from 2.75 [1.53;7.5] to 3.25 [1.65;15.25] mg/ mL (P=0.038). After 3 weeks of re-exposure to mite the epithelial median (Q1,Q3) percentage raised to 3.90 [1.5;6] (P = 0.027), eosinophils to 1.5 [0;3.00] (NS) and PC20 was 5.25 [1.68;14.50] (NS). CONCLUSION: Exposure to house dust mite antigen can induce airway epithelial shedding even in subjects with low eosinophil airway infiltration, thus supporting the idea that epithelial damage in asthmatics sensitized to Dermatophagoides may be due to a proteolytic activity of the mite major antigens.