Background: The efficacy of allergen immunotherapy using depigmented and polymerized extracts has been previously shown for Olea europaea, Phleum pratense, and Parietaria judaica. The objective of this study was to evaluate the efficacy after 3 and 6 months of treatment of a depigmented, polymerized extract of a mixture of Dermatophagoides pteronyssinus and D. farinae.
Methods: A group of 22 patients suffering from asthma and monosensitized to mites was treated with the mixture of modified allergen extract. A group of 11 mite-sensitive, asthmatic patients receiving only pharmacological treatment was used as control. The study was open, parallel, controlled, and random-allocated. Objective and subjective criteria, such as changes in D. pteronyssinus-specific bronchial hyperreactivity, visual scale, and medication/symptom scores were used to evaluate efficacy. Each patient received a built-up phase of 6 injections in 5 weeks, followed by 5 injections of the maintenance dose, which consisted of 42.5 micrograms of depigmented, polymerized extract of D. pteronyssinus and 32.5 of D. farinae. The Friedman test was used to compare the results of the specific bronchial challenges at baseline and after 3 and 6 months of treatment.
Results: A significant difference in the amount of native extract of D. pteronyssinus needed to produce a drop of 20% in the FEV1 (p = 0.0029) in the immunotherapy-treated group was found. In this group, the median allergen potency needed at baseline was 0.6 HEP (35 micrograms) vs. 3.96 HEP (232 micrograms) at the end of the study, whereas no difference (median 0.6 vs. 0.57 HEP) was found in the control group. At the end of the study, 10 patients in the immunotherapy treated group vs. 1 in the control group needed more than twice the amount of allergen than at baseline to experience a 20% drop in FEV1 (p = 0.03). Symptom and medication scores and visual scale evaluation did also show a significant improvement after 3 and 6 months of treatment only in active group. A significant decrease in skin test reactivity was also detected in the active group after 6 months, which needed a median of 3 times more allergen to elicit the same reaction as histamine (10 HEP) (p = 0.028), whereas no changes were found in control group. No serious side effects were registered.
Conclusions: Depigmented polymerized extracts of D. pteronyssinus and D. farinae are safe and effective in the treatment of mite allergic asthmatic patients, and provide clinical benefit in the shock organ after 6 months of treatment. Skin test reactivity, symptom and medication scores were also improved. Depigmented polymerized extracts of D. pteronyssinus and D. farinae induce clinical protection against a native extract as verified by specific bronchial challenges.