Immunotherapy with mosquito (Culex quinquefasciatus) extract:: a double-blind, placebo-controlled study

Background: Mosquito allergy is well established, but mosquito immunotherapy requires validation using clinical and immunologic variables. Objective: To evaluate the tolerability and efficacy of specific immunotherapy with Culex quinquefasciatus (mosquito) extract. Methods: We performed a randomized, double-blind, placebo-controlled trial of immunotherapy for I year in 40 patients with asthma, rhinitis, or both. Patients were evaluated by means of intradermal testing, symptom and drug scores, and histamine provocation testing before and after I year of immunotherapy. Mosquito specific IgE and IgG subclass antibody responses were evaluated at the basal level and after I year. Results: Patients receiving allergen immunotherapy for I year showed a significant improvement compared with baseline and patients receiving placebo regarding skin reactions, symptom scores (rhinitis and asthma), and forced expiratory volume in I second. Provocation concentration of histamine that caused a decrease in forced expiratory volume in I second of 20% by inhalation was elevated in the group receiving immunotherapy. In the active group serologic analysis showed a slight reduction in IgE levels (P =.02) but a significant elevation in IgG4 levels (P =.001), with a significant decrease in the IgE/IgG4 ratio (P =.001). All these changes in the placebo group were nonsignificant. Conclusions: Allergen immunotherapy with mosquito extract was well tolerated, with improvement in symptoms and airway reactivity. Good clinical outcome was associated with increased IgG4 antibody levels.