Immunotherapy with mosquito (Culex quinquefasciatus) extract: a double-blind, placebo-controlled study Deepsikha Srivastava, MSc*†; Bhanu P. Singh, PhD*; V. Thangam Sudha, MSc*†; Naveen Arora, PhD*; and Shailendra N. Gaur, MD‡ 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 1 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 1 year of immunotherapy. Mosquito specific IgE and IgG subclass antibody responses were evaluated at the basal level and after 1 year. Results: Patients receiving allergen immunotherapy for 1 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 1 second. Provocation concentration of histamine that caused a decrease in forced expiratory volume in 1 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. Ann Allergy Asthma Immunol. 2007;99:273–280. INTRODUCTION Allergic reactions to insects is a global problem. Up to 3% of the population is at risk for anaphylaxis to insect stings, with approximately 40 documented deaths annually. 1 Mosquito is one of the most common insects, and its bite results in a variety of diseases. Infection, mild discomfort, and cutaneous reactions are extremely common, and severe inflammatory reactions are not unusual. 2 In addition, mosquito-derived par- ticles are important inhalant allergens for IgE-mediated re- spiratory allergic disorders. 3,4 There are more than 3,000 mosquito species worldwide, of which Aedes vexans, Aedes aegypti, and Culex quinquefasciatus are the most common distributed globally. 5 Allergic reactions are caused by interaction of IgE with allergen on mast cells or basophils, leading to release of an array of inflammatory mediators, resulting in inflammation of airway mucous membrane, leading to clinical symptoms in the target organ. 6 Pharmacotherapy controls symptoms, which recur once treatment is stopped, 7 and has adverse effects because it acts at the last stage of mediator release. In contrast, allergen immunotherapy modifies the underlying pathologic immune response in an antigen-specific manner. 8 Controlled studies have convincingly demonstrated the ben- eficial effects of immunotherapy for allergic rhinitis and asthma treatment. 9 Immunotherapy also restricts seasonal in- creases in bronchial hyperresponsiveness and prevents the onset of new sensitizations. 10 Immunologic events in immu- notherapy include formation of blocking antibodies IgG, re- duction in specific IgE antibody levels, and induction of suppressor T cells. 11 However, allergen immunotherapy has long been a controversial treatment for asthma. 12 In India, only a few studies 13–15 were performed to evaluate the effects of immunotherapy with Cocos nucifera pollen and mixed allergen preparations (vaccines). Both IgE- and T-lymphocyte–mediated hypersensitivities are involved in mosquito-induced allergy, and mosquito bite causes specific sensitization. 16,17 Immunotherapy with whole- body extracts has demonstrated efficacy in children and adults. 18 –20 Culex quinquefasicatus, a common mosquito spe- * Allergy and Immunology Sections, Institute of Genomics and Integrative Biology, Delhi, India. † Department of Biotechnology, University of Pune, Ganeskhind, Pune, India. ‡ Department of Respiratory Medicine, Vallabhbhai Patel Chest Institute, University of Delhi, Delhi, India. Authors have nothing to disclose. This study was supported by the Department of Science and Technology, New Delhi. Received for publication January 23, 2007. Received in revised form April 18, 2007. Accepted for publication May 6, 2007. VOLUME 99, SEPTEMBER, 2007 273