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


CONCLUSIONS
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.
Saarne
T
T
Department of Medicine, Clinical Immunology and Allergy Unit, Karolinska Institutet and University Hospital, Stockholm, Sweden.
Kaiser
L
L
Grönlund
H
H
Rasool
O
O
Gafvelin
G
G
van Hage-Hamsten
M
M
D000485:Allergens / Q000235:genetics* / Q000276:immunology; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D001491:Basophils / Q000276:immunology; D002415:Cats; D002455:Cell Division / Q000276:immunology; D000939:Epitopes / Q000235:genetics / Q000276:immunology; D005818:Genetic Engineering / Q000379:methods; D006023:Glycoproteins / Q000235:genetics* / Q000276:immunology; D006801:Humans; D006967:Hypersensitivity / Q000276:immunology; D007073:Immunoglobulin E / Q000276:immunology; D016233:Immunotherapy, Active / Q000379:methods*; D017354:Point Mutation / Q000235:genetics; D011994:Recombinant Proteins / Q000276:immunology; D011995:Recombination, Genetic / Q000235:genetics / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology
D000485:Allergens; D000939:Epitopes; D006023:Glycoproteins; D011994:Recombinant Proteins; D007073:Immunoglobulin E; C059296:Fel d 1 protein, Felis domesticus