A randomized, controlled study of specific immunotherapy in monosensitized subjects with seasonal rhinitis: effect on bronchial hyperresponsiveness, sputum inflammatory markers and development of asthma symptoms.

Allergic rhinitis is often associated with bronchial hyperresponsiveness (BHR) and airway inflammation, and it seems to be an important risk factor for the development of asthma. Specific immunotherapy (SIT) reduces symptoms and medication requirements in subjects with allergic rhinitis, but the mechanisms by which SIT promotes these beneficial effects are less clear. We have investigated the effects of Parietaria-SIT on rhinitis symptoms, BHR to inhaled methacholine, eosinophilic inflammation and cytokine production (interferon gamma and interleukin-4) in the sputum. The effect on asthma progression was also examined. Thirty non-asthmatic subjects with seasonal rhinitis and monosensitized to Parietaria judaica participated in a randomized, double-blind, placebo-controlled, parallel group study. Participants were randomly assigned to receive injections of a Parietaria pollen vaccine (n = 15) or matched placebo injections (n = 15) in a rapid updosing cluster regimen for 7 weeks, followed by monthly injections for 34 months. Throughout the 3-year study we collected data on symptoms and medication score, airway responsiveness to methacholine, eosinophilia and soluble cytokines in sputum, followed by a complete evaluation of the clinical course of atopy. Hay fever symptom and medication scores were well controlled by SIT. By the end of the study, in the placebo group, symptom and medication scores significantly increased by a median (interquartile range) of 121% (15-280%) and 263% (0-4400%) respectively (p < 0.01), whereas no significant difference was observed in the SIT group. We found no significant changes in the sputum parameters and methacholine PC15 values in both groups throughout the study. By the end of the investigation, a total of 9 out of 29 participants developed asthma symptoms; of these, seven (47%) belonged to the placebo group, whereas only 2 (14%) to the SIT-treated group (p = 0.056). In conclusion, Parietaria-SIT is effective in controlling hay fever symptoms and rescue medications, but no changes in the BHR to methacholine or sputum eosinophilia were observed. Moreover, Parietaria-SIT appears to prevent the natural progression of allergic rhinitis to asthma, suggesting that SIT should be considered earlier in the management of this condition.