Rational design of hypoallergens applied to the major cat allergen Fel d 1

Summary Background Allergen‐specific immunotherapy is the only treatment for allergic disease providing long‐lasting symptom relief. Currently, it is mainly based on the use of crude allergen extracts. The treatment may be improved by the use of genetically engineered allergens, hypoallergens, aiming at a more effective and safer therapy. Objective The aim of this study was to provide a rational design of hypoallergen candidates for immunotherapy by using structural information and knowledge of B and T cell epitopes of an allergen. Methods The three‐dimensional structure of the major cat allergen Fel d 1 was systematically altered by duplication of selected T cell epitopes and disruption of disulphide bonds. Seven Fel d 1 derivatives were generated and screened for allergenic reactivity in comparison with recombinant Fel d 1 in competition‐ELISA. The allergenicity was further evaluated in basophil activation experiments and T cell reactivity was assessed in a lymphoproliferation assay. Results Three out of seven Fel d 1 derivatives, with two duplicated T cell epitopes and one or two disulphide bonds disrupted, were carefully evaluated. The three derivatives displayed a strong reduction in allergenicity with 400–900 times lower IgE‐binding capacity than recombinant Fel d 1. In addition, they induced a lower degree of basophil activation and similar or stronger T cell proliferation than recombinant Fel d 1. Conclusion By a rational approach, we have constructed three Fel d 1 hypoallergens with reduced IgE‐binding capacities and retained T cell reactivities. This strategy may be applied to any well‐characterized allergen to improve immunotherapy for allergic patients.