Wheat IgE-mediated food allergy in European patients: alpha-amylase inhibitors, lipid transfer proteins and low-molecular-weight glutenins. Allergenic molecules recognized by double-blind, placebo-controlled food challenge.
BACKGROUND
Three main problems hamper the identification of wheat food allergens: (1) lack of a standardized procedure for extracting all of the wheat protein fractions; (2) absence of double-blind, placebo-controlled food challenge studies that compare the allergenic profile of Osborne's three protein fractions in subjects with real wheat allergy, and (3) lack of data on the differences in IgE-binding capacity between raw and cooked wheat.


METHODS
Sera of 16 wheat-challenge-positive patients and 6 patients with wheat anaphylaxis, recruited from Italy, Denmark and Switzerland, were used for sodium dodecyl sulfate-polyacrylamide gel electrophoresis/immunoblotting of the three Osborne's protein fractions (albumin/globulin, gliadins and glutenins) of raw and cooked wheat. Thermal sensitivity of wheat lipid transfer protein (LTP) was investigated by spectroscopic approaches. IgE cross-reactivity between wheat and grass pollen was studied by blot inhibition.


RESULTS
The most important wheat allergens were the alpha-amylase/trypsin inhibitor subunits, which were present in all three protein fractions of raw and cooked wheat. Other important allergens were a 9-kDa LTP in the albumin/globulin fraction and several low-molecular-weight (LMW) glutenin subunits in the gluten fraction. All these allergens showed heat resistance and lack of cross-reactivity to grass pollen allergens. LTP was a major allergen only in Italian patients.


CONCLUSIONS
The alpha-amylase inhibitor was confirmed to be the most important wheat allergen in food allergy and to play a role in wheat-dependent exercise-induced anaphylaxis, too. Other important allergens were LTP and the LMW glutenin subunits.
Pastorello
Elide A
EA
Unit of Allergology and Clinical Immunology, Niguarda Cà Granda Hospital, Milan, Italy. elide.pastorello@unimi.it
Farioli
Laura
L
Conti
Amedeo
A
Pravettoni
Valerio
V
Bonomi
Simona
S
Iametti
Stefania
S
Fortunato
Donatella
D
Scibilia
Joseph
J
Bindslev-Jensen
Carsten
C
Ballmer-Weber
Barbara
B
Robino
Anna M
AM
Ortolani
Claudio
C
D000328:Adult; D000485:Allergens / Q000276:immunology / Q000378:metabolism*; D000595:Amino Acid Sequence; D052179:Antigens, Plant / Q000276:immunology* / Q000378:metabolism; D002352:Carrier Proteins / Q000276:immunology* / Q000378:metabolism; D002675:Child, Preschool; D004311:Double-Blind Method; D004791:Enzyme Inhibitors / Q000276:immunology / Q000378:metabolism*; D005060:Europe; D005260:Female; D005512:Food Hypersensitivity / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism; D005983:Glutens / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007073:Immunoglobulin E / Q000096:biosynthesis / Q000097:blood / Q000502:physiology*; D007223:Infant; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010919:Placebos; D010940:Plant Proteins / Q000276:immunology* / Q000378:metabolism; D014908:Triticum / Q000737:chemistry / Q000276:immunology*; D014361:Trypsin Inhibitors / Q000378:metabolism; D000516:alpha-Amylases / Q000037:antagonists & inhibitors*
D000485:Allergens; D052179:Antigens, Plant; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D010919:Placebos; D010940:Plant Proteins; D014361:Trypsin Inhibitors; C511920:lipid transfer proteins, plant; D007073:Immunoglobulin E; D005983:Glutens; D000516:alpha-Amylases; C037302:glutenin