Comparison of genetically engineered hypoallergenic rBet v 1 derivatives with rBet v 1 wild-type by skin prick and intradermal testing: results obtained in a French population.
BACKGROUND
Bet v 1, the major allergen in birch pollen, is recognized by more than 90% of patients allergic to birch in northern and central Europe. Immunotherapy is commonly performed with birch pollen extracts. Recently, hypoallergenic derivatives of Bet v 1 (rBet v 1 fragments, rBet v 1 dimer and trimer) were constructed and purified.


OBJECTIVE
Our aim was to compare the allergenic activity of wild-type rBet v 1 with recombinant Bet v 1 derivatives (rBet v 1 fragments, dimer and trimer) with potentially reduced anaphylactic activity by skin testing in a French population.


METHODS
Among the 36 birch pollen allergic patients included in the study, 29 were tested by skin prick testing and 30 by intradermal injections with purified monosubstances: rBet v 1 fragments (F1: aa1-74 and F2: aa75-160), Bet v 1 dimer and trimer. Intradermal tests were performed by the end-point intradermal titration method. Eight of the intradermally-tested patients were previously hyposensitized. Tests were performed over a period of 6 months (before, during and after birch pollen season); Bet v 1-specific IgE and IgG4 subclass responses were measured by immunoblotting and ELISA.


RESULTS
All patients showed lower reactivity with the modified rBet v 1 allergens, both in skin prick and intradermal tests. In 25 and 23 out of 29 patients the lowest concentration of fragment 1 and 2, respectively, resulting in a positive prick test was 100-fold higher than the lowest concentration of monomer resulting in a positive prick test. For dimer it was 100-fold or more in 25 out of 29 patients, and for trimer it was 100-fold or superior in 26 out of 29 patients. By intradermal testing, the end-point concentration was 160-fold higher for trimer than for monomer in 24 patients and 40-fold higher in five patients. For the two fragments the end-point concentration was 160-fold higher in 20 out of 22 patients.


CONCLUSIONS
Genetically modified hypoallergenic derivatives of the major birch pollen allergen, Bet v 1 showed reduced capacity to induce immediate type skin reactions. They may represent candidate molecules for immunotherapy of birch pollen allergy with reduced risk of anaphylactic side-effects.
Pauli
G
G
Service de Pneumologie and INSERM U-425, Hôpitaux Universitaires de Strasbourg, France.
Purohit
A
A
Oster
J P
JP
De Blay
F
F
Vrtala
S
S
Niederberger
V
V
Kraft
D
D
Valenta
R
R
D000293:Adolescent; D000328:Adult; D000485:Allergens; D052179:Antigens, Plant; D004306:Dose-Response Relationship, Immunologic; D005260:Female; D005602:France; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000276:immunology*; D007073:Immunoglobulin E / Q000032:analysis; D007074:Immunoglobulin G / Q000032:analysis; D007428:Intradermal Tests; D008297:Male; D008875:Middle Aged; D010940:Plant Proteins / Q000235:genetics* / Q000276:immunology*; D011058:Pollen / Q000276:immunology; D020836:Protein Structure, Quaternary; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D012882:Skin Tests
D000485:Allergens; D052179:Antigens, Plant; D007074:Immunoglobulin G; D010940:Plant Proteins; D011994:Recombinant Proteins; C061312:Bet v 1 allergen, Betula; D007073:Immunoglobulin E