Lipid transfer protein and vicilin are important walnut allergens in patients not allergic to pollen.
BACKGROUND
Walnut is the most common cause of allergic reactions to tree nuts, as reported by large population studies. Two major allergens of walnut have been identified up until now: a 2S albumin and a vicilin-like protein.


OBJECTIVE
This study was designed to identify the walnut major allergens in the Italian population and to compare the walnut IgE-binding profile in patients with or without pollen allergy.


METHODS
We selected 46 patients either with oral allergy syndrome confirmed by open oral challenge or with systemic symptoms after ingestion of walnut. These patients' sera were used for the immunoblotting of walnut extract; the identified allergens were purified by HPLC and sequenced. A peach-walnut cross-inhibition study was then performed.


RESULTS
The only major allergen recognized by our study population was a 9-kd lipid transfer protein (LTP), recognized by 37 patients. Two other minor allergens of approximately 9-kd molecular weight, both belonging to the vicilin family, were recognized by 10 patients. IgE binding to walnut LTP was completely inhibited by peach LTP.


CONCLUSIONS
In Italian patients with walnut allergy confirmed by documented history of severe systemic reactions or by open oral food challenge, the major allergen is an LTP. The sensitization to this protein seems to be secondary to the sensitization to peach LTP, which acts as the primary sensitizer. LTP and vicilins were able to sensitize patients not allergic to pollen.
Allergy Center, Department of Internal Medicine and Dermatology, Ospedale Maggiore Istituto di Ricovero e Cura a Carattere Scientifico, Milan, Italy. elide.pastorello@unimi.it
Elide A
EA
Pastorello
Laura
L
Farioli
Valerio
V
Pravettoni
Anna M
AM
Robino
Joseph
J
Scibilia
Donatella
D
Fortunato
Amedeo
A
Conti
Linda
L
Borgonovo
Anders
A
Bengtsson
Claudio
C
Ortolani
D000293:Adolescent; D000328:Adult; D000485:Allergens / Q000276:immunology*; D052179:Antigens, Plant; D002352:Carrier Proteins / Q000276:immunology*; D002648:Child; D005260:Female; D005512:Food Hypersensitivity / Q000276:immunology*; D006801:Humans; D031324:Juglans / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D010940:Plant Proteins / Q000276:immunology*; D011058:Pollen / Q000276:immunology; D012130:Respiratory Hypersensitivity / Q000276:immunology; D055314:Seed Storage Proteins
D000485:Allergens; D052179:Antigens, Plant; D002352:Carrier Proteins; D010940:Plant Proteins; D055314:Seed Storage Proteins; C511920:lipid transfer proteins, plant; C015575:vicilin protein, plant