Identification of hazelnut major allergens in sensitive patients with positive double-blind, placebo-controlled food challenge results.
BACKGROUND
The hazelnut major allergens identified to date are an 18-kd protein homologous to Bet v 1 and a 14-kd allergen homologous to Bet v 2. No studies have reported hazelnut allergens recognized in patients with positive double-blind, placebo-controlled food challenge (DBPCFC) results or in patients allergic to hazelnut but not to birch.


OBJECTIVE
We characterized the hazelnut allergens by studying the IgE reactivity of 65 patients with positive DBPCFC results and 7 patients with severe anaphylaxis to hazelnut.


METHODS
Hazelnut allergens were identified by means of SDS-PAGE and IgE immunoblotting. Further characterization was done with amino acid sequencing, evaluation of the IgE-binding properties of raw and roasted hazelnut with enzyme allergosorbent test inhibition, assessment of cross-reactivity with different allergens by means of immunoblotting inhibition, and purification by means of HPLC.


RESULTS
All the sera from the patients with positive DBPCFC results recognized an 18- and a 47-kd allergen; other major allergens were at molecular weights of 32 and 35 kd. Binding to the 18-kd band was inhibited by birch extract, indicating its homology with the birch major allergen, and abolished in roasted hazelnut. The 47-kd allergen is a sucrose-binding protein, the 35-kd allergen is a legumin, and the 32-kd allergen is a 2S albumin. Patients with severe anaphylactic reactions to hazelnut showed specific IgE reactivity to a 9-kd allergen, totally inhibited by purified peach lipid-transfer protein (LTP), which was heat stable and, when purified, corresponded to an LTP.


CONCLUSIONS
The major allergen of hazelnut is an 18-kd protein homologous to Bet v 1, and the 9-kd allergen is presumably an LTP. Other major allergens have molecular weights of 47, 32, and 35 kd.
Pastorello
Elide A
EA
Allergy Center, 3rd Division of General Medicine, Ospedale Maggiore IRCCS, Milan, Italy.
Vieths
Stefan
S
Pravettoni
Valerio
V
Farioli
Laura
L
Trambaioli
Chiara
C
Fortunato
Donatella
D
Lüttkopf
Dirk
D
Calamari
Marianna
M
Ansaloni
Raffaella
R
Scibilia
Joseph
J
Ballmer-Weber
Barbara K
BK
Poulsen
Lars K
LK
Wütrich
Brunello
B
Hansen
Kirsten Skamstrup
KS
Robino
Anna Maria
AM
Ortolani
Claudio
C
Conti
Amedeo
A
D000485:Allergens / Q000009:adverse effects* / Q000737:chemistry* / Q000276:immunology; D000595:Amino Acid Sequence; D000707:Anaphylaxis / Q000175:diagnosis / Q000209:etiology; D003429:Cross Reactions; D004311:Double-Blind Method; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D015151:Immunoblotting; D007073:Immunoglobulin E / Q000097:blood; D008969:Molecular Sequence Data; D021184:Nut Hypersensitivity / Q000175:diagnosis / Q000209:etiology*; D009754:Nuts / Q000009:adverse effects* / Q000737:chemistry* / Q000276:immunology
D000485:Allergens; D007073:Immunoglobulin E