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

Background and objective Allergic asthma is common in children, and house d ust mite (HDM) is an important source of perennial allergens. Bronchial hyp erresponsiveness 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, h as not been evaluated. Methods Twenty-six paediatric asthma patients allergic to HDM participated in this study. Fourteen patients received SIT with a HDM extract (Alavac, B encard) for 2 years, and 12 served as controls. Bronchial responsiveness wa s assessed non-pharmacologically by cold dry air challenge (CACh) before an d 3, 6, 12 and 24 months after SIT, and 12 months after termination of SIT. Results After 24 months, the SIT group showed a statistically significant r eduction 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 expi ratory 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 responsiven ess were observed in the control group. In the SIT group more patients lost their bronchial hyperresponsiveness than in the control group (6/14 vs 1/1 2; P < 0.05). One year after terminating SIT, the treatment group showed a tendency towards returning bronchial hyperresponsiveness. Conclusion These results demonstrate that during 2 years of SIT there was a reduction of bronchial hyperresponsiveness in HDM-allergic paediatric asth ma patients.