Allergen vaccination with a liposome-encapsulated extract of Dermatophagoides pteronyssinus:: A randomized, double-blind, placebo-controlled trial in asthmatic patients

Background: Liposomes are potent immunologic adjuvants and have been proposed as allergen carriers in allergy vaccination. Objective: We sought to investigate the efficacy and safety of vaccination with Dermatophagoides pteronyssinus encapsulated in liposomes. Methods: We conducted a double-blind, placebo-controlled study. Fifty-five asthmatic patients sensitized to mites were randomly assigned vaccination with D pteronyssinus extract encapsulated in liposomes or empty liposomes for a period of 12 months. The principal parameters were symptom and medication-consumption scores. The percentage of healthy days (ie, days without medication and with absent or mild symptoms) was calculated. Immediate and late skin test results, allergen bronchial challenge test results, and allergen-specific serum immunoglobulin levels were evaluated be ore and after treatment. Results: All clinical Scores were markedly lower in the active group than in the placebo group after vaccination. Nearly half (45.8%) of the patients actively treated reduced their symptom and medication scores by at least 60% versus only 12% of patients receiving placebo treatment (P = .0388). The percentage of healthy days in the active group rose from 10.5% before treatment to 64.5% afterward (P = .0008). Reduction in organ sensitivity was demonstrated by skin prick test responses (P < .01), late-phase response after intradermal testing (P = .009), and bronchial challenge test results (P = .026) in the active group. Serum levels of specific IgG increased throughout the treatment, whereas specific IgE levels showed only an initial transient increase. No change in these parameters was observed in the placebo group. Vaccination was well tolerated, and no subcutaneous nodules appeared. Conclusion: Vaccination with D pteronyssinus encapsulated in liposomes is an effective and safe treatment for allergy-induced asthma.