Clinical role of a lipid transfer protein that acts as a new apple-specific allergen.
BACKGROUND
Allergy to apple is commonly associated with birch pollinosis because the two share homologous allergens. However, some patients have apple allergy but no birch pollinosis, suggesting that there are allergens that do not cross-react with birch.


OBJECTIVE
The aim of the study was to evaluate the IgE reactivity pattern to an apple extract in subjects with allergic reactions to apple, with and without birch hay fever.


METHODS
Forty-three patients with oral allergy syndrome for apple and positive open food challenge, skin prick test, and serum specific IgE antibodies to apple were admitted to the study. Thirty-two had birch pollinosis (documented by specific IgE for birch) and 11 were not allergic to birch. The IgE reactivity pattern to apple extract was identified by SDS-PAGE and immunoblotting. The consistent allergen, a 9-kd protein, was then purified by HPLC and characterized by periodic acid-Schiff staining, isoelectric point, and N-terminal amino acid sequencing.


RESULTS
The sera from 28% of patients allergic to apple with birch pollinosis, but from all patients allergic only to apple, recognized the 9-kd protein. This protein has an isoelectric point of 7.5 and is not glycosylated. Determination of its partial amino acid sequence showed that it belongs to the family of lipid transfer proteins, which act as major allergens in Prunoideae fruits.


CONCLUSIONS
These results indicate that a lipid transfer protein is an important allergen in patients allergic to apple but not to birch pollen. The prevalent IgE reactivity to this allergen in subjects with no birch pollinosis and the physicochemical characteristics of this protein suggest that sensitization may occur through the oral route.
Pastorello
E A
EA
Allergy Center, Third Division of General Medicine, Ospedale Maggiore Istituto di Ricerca e Cura a Carattere Scientifico, Milan, Italy.
Pravettoni
V
V
Farioli
L
L
Ispano
M
M
Fortunato
D
D
Monza
M
M
Giuffrida
M G
MG
Rivolta
F
F
Scibola
E
E
Ansaloni
R
R
Incorvaia
C
C
Conti
A
A
Ortolani
C
C
D000293:Adolescent; D000328:Adult; D000485:Allergens / Q000276:immunology*; D000595:Amino Acid Sequence; D052179:Antigens, Plant; D002352:Carrier Proteins / Q000276:immunology*; D002850:Chromatography, Gel / Q000379:methods; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D002852:Chromatography, Ion Exchange / Q000379:methods; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D005260:Female; D005512:Food Hypersensitivity / Q000276:immunology*; D006801:Humans; D015151:Immunoblotting; D007525:Isoelectric Focusing; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D010503:Periodic Acid-Schiff Reaction; D010940:Plant Proteins; D019685:Rosales / Q000276:immunology*; D012967:Sodium Dodecyl Sulfate; D013194:Staining and Labeling / Q000379:methods
D000485:Allergens; D052179:Antigens, Plant; D002352:Carrier Proteins; D010940:Plant Proteins; C511920:lipid transfer proteins, plant; D012967:Sodium Dodecyl Sulfate