Sublingual immunotherapy with a standardized cat dander extract:: evaluation of efficacy in a double blind placebo controlled study

Background: Little information is available on the clinical efficacy of sublingual immunotherapy (SLIT) using extracts derived from mammalian epithelia. Objectives: To assess clinical efficacy of cat SLIT based on natural exposure challenge test (NCT). Material and methods: Fifty cat allergic patients with rhinoconjunctivitis with or without asthma were included in a randomized double blind placebo controlled clinical trial of cat SLIT during 1 year. Twenty-five patients received active treatment and 25 placebo. Sublingual immunotherapy efficacy was assessed by natural exposure challenge to a cat in a cat-room and by skin tests. Airborne Fel d 1 levels, symptom scores and peak expiratory flow (PEF) values were monitored. Results: Thirty-three (66%) out of 50 patients completed the treatment. Fel d 1 content of the maximum concentration was 0.51 mu g per ml. During the build up phase, the accumulated dose was 1.7 mu g of Fel d 1 and during the entire length of the study was 17.1. No adverse reports were reported. The active group showed a marked reduction (62%) in symptoms during the NCT (P < 0.001) with no changes in placebo group. Active group also showed a reduced PEF response to cat exposure (P < 0.05), and an improvement in skin test reactivity to a standardized cat extract (P < 0.05), without significant changes in placebo group. Mean Fel d I exposure during the NCT was 6.2 +/- 2.21 ng/m(3). Conclusions: The results suggest that the cat SLIT used in this study was able to improve cat allergy based on natural exposure challenge.