Identification and production of recombinant Culicoides obsoletus allergens for diagnosis and immunotherapy of insect bite hypersensitive horses

Insect Bite Hypersensitivity (IBH) is a common IgE mediated skin allergy in horses, caused by the bites of Culicoides species (midges) that seriously affects the welfare of these horses. Currently no effective treatment and no reliable diagnostic test is available for this allergic condition. We identified midges of the C. obsoletus complex as the dominant Culicoides species feeding on horses in the Netherlands. Its transcriptome was determined and sequence similarity searches with allergens previously described forother midges (C. sonorensis and C. nubeculosus) revealed 7 potential allergens of C. obsoletus , named Cul o 1 – Cul o 7.The sequences encoding these allergens were cloned and expressed as his6-tagged recombinant proteins in E. coli andpurified on Ni2+ sepharose beads. The purified recombinant proteins were able to induce an allergic reaction after injection into the skin of IBH affected horses, but not in healthy control horses. They all showed significant (p