Allergies caused by mosquito bites may produce local or systemic reactions. The inhalation of mosquito allergens may also cause asthma and/or allergic rhinoconjunctivitis in sensitized individuals. The mechanisms implicated in the development of these immune responses involve IgE antibodies, different subtypes of IgG and proinflammatory cytokines as well as basophils, eosinophils and mast cells. Several allergenic components have been identified in the saliva and bodies of mosquitoes and some of these are present in different mosquito species. The most common species implicated in allergic reactions belong to the genera Aedes, Culex and Anopheles. Several Aedes aegypti allergens have been cloned and sequenced. The recombinant molecules show IgE reactivity similar to that of the native allergens, making them good candidates for the diagnosis of mosquito allergies. Allergen-specific immunotherapy with mosquito extracts induces a protective response characterized by a decreased production of IgE antibodies, increased IgG levels, a reduction in the severity of cutaneous and respiratory symptoms and the need for medication. The aims of this review are to summarize the progress made in the characterization of mosquito allergens and discuss the types of immune responses induced by mosquito bites and the inhalation of mosquito allergens in atopic individuals.

Background: The mosquito Aedes aegypti is a potential source of important clinically relevant allergens. However, the allergenicity and cross-reactivity of most of these has not been fully described. Methods: Natural wild-type mosquito tropomyosin was purified by size exclusion and anionic-exchange chromatography from an A. aegypti extract. Further characterization was accomplished by MALDI-TOF/TOF. Two recombinant variants of tropomyosin were obtained by expression in Escherichia coli. Specific IgE measurement by ELISA and skin tests for mosquito extract were performed in 12 patients with asthma or allergy rhinitis residing on the Caribbean island of Martinique. Cross-reactivity between natural A. aegypti tropomyosin and recombinant tropomyosins from A. aegypti, house dust mite, shrimp and Ascaris lumbricoides was analyzed by ELISA competition. Results: Four variants of natural tropomyosin were purified. A band of 32 kDa in SDS-PAGE representing 2 tropomyosin variants (Aed a 10.0101 and Aed a 10.0201) reacted with specific IgE of 4 of the 12 (33%) allergic patients and with rabbit polyclonal anti-shrimp tropomyosin. A high degree of cross-reactivity (60-70%) was detected between natural mosquito tropomyosin and Blo t 10, Der p 10 and Lit v 1, and a lower degree with Asc l 3 from A. lumbricoides (<30%). rAed a 10.0101 inhibited IgE binding to natural A. aegypti tropomyosin; however, rAed a 10.0201 showed a low inhibitory capacity. Conclusion: Tropomyosin is a new IgE-binding protein from A. aegypti. Two of the 4 variants identified showed different degree of cross-reactivity with tropomyosins from other arthropods. The potential allergenic role of each variant should be further investigated.

Summary: Background: Aedes aegypti and Dermatophagoides pteronyssinus contain important allergens including cross‐reactive tropomyosins. However, the functional and clinical relevance of their cross‐reactivity is still debated.Objective: To analyse the humoral and cellular cross‐reactivity of recombinant Aed a 10.01, Aed a 10.02 and Der p 10.Methods: Sera from 15 Austrian house dust mite‐allergic, Der p 10‐sensitized individuals were tested for IgE reactivity to recombinant tropomyosins in ELISA, inhibition ELISA and basophil activation tests. BALB/c mice were immunized with Aed a 10.01 or Aed a 10.02, and their sera were assessed for reactivity to all tropomyosins. Splenocytes were stimulated with all tropomyosins and synthetic peptides representing the amino acid sequence of Aed a 10.01.Results: IgE antibodies of Der p 10‐sensitized patients cross‐reacted with both tropomyosins from A. aegypti. Aed a 10.01 was a more potent inhibitor of IgE binding to Der p 10 and a stronger activator of basophils sensitized with Der p 10‐specific IgE than Aed a 10.02. Murine antibodies raised against Aed a 10.01 and Aed a 10.02 cross‐reacted with Der p 10. Aed a 10.01‐specific antibody showed stronger cross‐reactivity with Der p 10 than Aed a 10.02‐specific antibody. Splenocytes from both groups of mice proliferated similarly to all tropomyosins. Five cross‐reactive T cell‐activating regions were identified.Conclusion and Clinical relevance: Tropomyosins from D. pteronyssinus and A. aegypti show humoral and cellular cross‐reactivity, involving 5 potential T cell‐activating regions. The more pronounced cross‐reactivity of Aed a 10.01 and Der p 10 matched the higher sequence similarity of both proteins.