Ara h 8, a Bet v 1-homologous allergen from peanut, is a major allergen in patients with combined birch pollen and peanut allergy.
BACKGROUND
We recently described patients with soybean allergy mainly mediated by cross-reactivity to birch pollen allergens. A majority of those patients were reported to have peanut allergy.


OBJECTIVE
We sought to study the occurrence of peanut allergy in patients allergic to birch pollen and characterized the Bet v 1-homologous peanut allergen Ara h 8.


METHODS
Recombinant Ara h 8 was cloned with degenerated primers and expressed in Escherichia coli. Nine Swiss and 11 Dutch patients with peanut and birch pollen allergy and a positive double-blind, placebo-controlled food challenge result to peanut were investigated for IgE reactivity to birch pollen and purified peanut allergens and cross-reactivity between birch and peanut. Ara h 8 stability against digestion and roasting was assessed by means of RAST inhibition. The IgE cross-linking potency of Ara h 8 was tested on the basis of basophil histamine release.


RESULTS
During double-blind, placebo-controlled food challenge, all patients experienced symptoms in the oral cavity, progressing to more severe symptoms in 40% of patients. CAP-FEIA detected recombinant (r) Ara h 8-specific IgE in 85%. IgE binding to Ara h 8 was inhibited by Bet v 1 in peanut extract immunoblotting and in RAST inhibition. In EAST inhibition recombinant rAra h 8 inhibited IgE binding to peanut in 4 of 7 tested patient sera. Antipeanut response was dominated by Ara h 8 in 12 of 17 tested patients. Furthermore, our results demonstrate a low stability of Ara h 8 to roasting and no stability to gastric digestion. Basophil histamine release with rAra h 8 was more than 20% in 5 of 7 tested sera.


CONCLUSIONS
Peanut allergy might be mediated in a subgroup of our patients by means of cross-reaction of Bet v 1 with the homologous peanut allergen Ara h 8.
Mittag
Diana
D
Department of Dermatology, University Hospital, Zurich.
Akkerdaas
Jaap
J
Ballmer-Weber
Barbara K
BK
Vogel
Lothar
L
Wensing
Marjolein
M
Becker
Wolf-Meinhard
WM
Koppelman
Stef J
SJ
Knulst
André C
AC
Helbling
Arthur
A
Hefle
Susan L
SL
Van Ree
Ronald
R
Vieths
Stefan
S
D000293:Adolescent; D000328:Adult; D000485:Allergens / Q000276:immunology*; D000595:Amino Acid Sequence; D001491:Basophils / Q000378:metabolism; D029662:Betula / Q000276:immunology*; D003429:Cross Reactions; D004311:Double-Blind Method; D005260:Female; D006636:Histamine Release; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology; D008297:Male; D008969:Molecular Sequence Data; D021183:Peanut Hypersensitivity / Q000209:etiology*; D010434:Pepsin A / Q000494:pharmacology; D011058:Pollen / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology
D000485:Allergens; D011994:Recombinant Proteins; D007073:Immunoglobulin E; D010434:Pepsin A