Partial characterization of allergens associated with hypersensitivity to the ‘green nimitti’ midge (Cladotanytarsus lewisi, Diptera: Chironomidae)

Abstract

Allergens in extracts of the green nimitti midge, C. lewisi Freeman (Diptera: Chironomidae), a cause of widespread hypersensitivity in the Sudan [Africa], were isolated and partially characterized by assays which depend on the binding of 125I-anti-IgE to allergen-IgE complexes. These methods included RAST [radioallergosorbent test] inhibition, crossed radioimmunoelectrophoresis (CRIE) and rocket radioimmunoelectrophoresis (RRIE). Following Sephadex G100 chromatography the major peak of allergenicity as determined by RAST inhibition. RRIE and SDS-PAGE [sodium dodecyl sulfate-polyacrylamide gel electrophoresis] was associated with molecules of .apprx. 17,000 daltons. The peak eluting at Vo contained material of MW 66,000 which also bound 125I-anti-IgE but had only 61% of the activity of the major peak by RAST inhibition. By isoelectric focusing and RRIE of fracitons obtained by chromatofocusing with polybuffer exchanger 94, the major peak was associated with multiple bands with a pI [isoelectric point] range of 3.5-5.5. Thus, the major allergens from C. lewisi are a group of closely related acidic peptides.