Effect of specific immunotherapy with house dust mite extract on the bronchial responsiveness of paediatric asthma patients

Abstract

Allergic asthma is common in children, and house dust mite (HDM) is an important source of perennial allergens. Bronchial hyperresponsiveness is a functional hallmark of asthma. Specific immunotherapy (SIT) with HDM extracts were shown to decrease symptoms, but its effect on bronchial responsiveness, as measured by non-pharmacological challenges, has not been evaluated. Twenty-six paediatric asthma patients allergic to HDM participated in this study. Fourteen patients received SIT with a HDM extract (Alavac, Bencard) for 2 years, and 12 served as controls. Bronchial responsiveness was assessed non-pharmacologically by cold dry air challenge (CACh) before and 3, 6, 12 and 24 months after SIT, and 12 months after termination of SIT. After 24 months, the SIT group showed a statistically significant reduction of the mean CACh-induced changes of both forced expiratory volume in one second (−21.8 ± 2.7% vs −13.7 ± 2.4%; P = 0.03) and maximal expiratory flow at 25% remaining vital capacity (−48.9 ± 4.9% vs −27.9 ± 6.2%; P = 0.01). In contrast, no significant changes of bronchial responsiveness were observed in the control group. In the SIT group more patients lost their bronchial hyperresponsiveness than in the control group (6/14 vs 1/12; P < 0.05). One year after terminating SIT, the treatment group showed a tendency towards returning bronchial hyperresponsiveness. These results demonstrate that during 2 years of SIT there was a reduction of bronchial hyperresponsiveness in HDM-allergic paediatric asthma patients.