Soybean allergy in patients allergic to birch pollen: clinical investigation and molecular characterization of allergens.
BACKGROUND
Allergic reactions to legumes are generally thought to be acquired by means of primary sensitization through the gastrointestinal tract. Recently, Gly m 4 (starvation-associated message 22), a Bet v 1-related pathogenesis-related protein 10 from soy, was suggested to be an allergen in patients with allergic reactions to a dietary product containing a soy protein isolate.


OBJECTIVE
We sought to evaluate the clinical relevance of Gly m 4 in subjects allergic to birch pollen with soy allergy and to assess the risk for subjects allergic to birch pollen to acquire soy allergy.


METHODS
Twenty-two patients allergic to birch pollen with soy allergy confirmed by means of positive double-blind, placebo-controlled food challenge results (n = 16) or a convincing history (n = 6) were investigated for IgE reactivity to birch pollen and soy allergens by using the Pharmacia CAP system and immunoblot analysis. Cross-reactivity was assessed by means of enzyme allergosorbent test inhibition. Ninety-four patients with birch pollen allergy were interviewed to assess soy tolerance and screened for IgE reactivity to Gly m 4 by means of immunoblotting. The Gly m 4 content in soy foods and soybean varieties was investigated by means of quantitative evaluation of immunoblots.


RESULTS
During double-blind, placebo-controlled food challenge, 10 patients experienced symptoms localized to the oral cavity, and 6 patients had a more severe reaction. CAP analysis revealed Gly m 4-specific IgE in 96% (21/22) of the patients. All patients had Bet v 1-specific IgE antibodies, and 23% (5/22) had positive Bet v 2 results. In IgE immunoblotting 25% (6/22) of the patients recognized soy profilin (Gly m 3), and 64% (14/22) recognized other soy proteins. IgE binding to soy was at least 80% inhibited by birch pollen and 60% inhibited by rGly m 4 in 9 of 11 sera tested. Seventy-one percent (67/94) of highly Bet v 1-sensitized patients with birch pollen allergy were sensitized to Gly m 4, and 9 (9.6%) of those patients reported soy allergy. The Gly m 4 content in soy products ranged between 0 and 70 ppm (milligrams per kilogram).


CONCLUSIONS
Our results confirm that soybean is another birch pollen-related allergenic food. Gly m 4 is the major soy allergen for patients allergic to birch pollen with soy allergy. The content of Gly m 4 in soy food products strongly depends on the degree of food processing.
Mittag
Diana
D
Department of Dermatology, University Hospital, Zurich, Switzerland.
Vieths
Stefan
S
Vogel
Lothar
L
Becker
Wolf-Meinhard
WM
Rihs
Hans-Peter
HP
Helbling
Arthur
A
Wüthrich
Brunello
B
Ballmer-Weber
Barbara K
BK
D000293:Adolescent; D000328:Adult; D000485:Allergens / Q000032:analysis / Q000276:immunology*; D029662:Betula / Q000276:immunology*; D003285:Contractile Proteins; D003429:Cross Reactions; D003625:Data Collection; D004311:Double-Blind Method; D005260:Female; D005512:Food Hypersensitivity / Q000097:blood / Q000175:diagnosis / Q000276:immunology*; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology; D008297:Male; D008840:Microfilament Proteins / Q000276:immunology; D008875:Middle Aged; D015990:Placebo Effect; D010940:Plant Proteins / Q000276:immunology; D011058:Pollen / Q000276:immunology; D051304:Profilins; D030262:Soybean Proteins / Q000097:blood / Q000276:immunology*; D013025:Glycine max / Q000276:immunology*
D000485:Allergens; D003285:Contractile Proteins; D008840:Microfilament Proteins; D010940:Plant Proteins; D051304:Profilins; D030262:Soybean Proteins; D007073:Immunoglobulin E