Application of the 16-kDa buckwheat 2 S storage albumin protein for diagnosis of clinical reactivity.
BACKGROUND
The 16-kDa protein of buckwheat (BW) has been implicated as a major allergen in BW allergy.


OBJECTIVE
To characterize the 16-kDa allergen and evaluate its clinical significance as an indicator of BW allergy.


METHODS
Complementary DNA from the 16-kDa allergen was cloned and expressed in Escherichia coli. Allergenicity was confirmed with IgE immunoblotting or with an enzyme-linked immunosorbent assay. The clinical utility of the recombinant protein (r16 kDa) for diagnosis of BW reactivity was evaluated in 18 BW-allergic and in 20 asymptomatic BW-sensitized subjects.


RESULTS
The 16-kDa allergen, composed of 127 amino acids, has 50% homology to the reported 8-kDa BW allergen, which belongs to the 2 S storage albumin. The r16-kDa protein can inhibit specific IgE (sIgE) antibody binding to the native BW 16-kDa allergen but minimally inhibited sIgE binding to crude BW extract. Approximately 77.8% of patients with the BW allergy produced sIgE antibodies to the r16-kDa protein, compared with a complete lack of reactivity in the 20 asymptomatic BW-sensitized subjects. The areas of the receiver operating characteristic curves for the skin prick test (mean, 0.93; 95% confidence interval, 0.85 to approximately 1.01; P < .001) and the rl6-kDa enzyme-linked immunosorbent assay (mean, 0.93; 95% confidence interval, 0.84 to approximately 1.01; P < .001) were higher than the area of the BW IgE measurement curve determined by ImmunoCAP (a system for assaying serum IgE) (mean, 0.80; 95% confidence interval, 0.66 to approximately 0.94; P = .002).


CONCLUSIONS
The 16-kDa allergen belongs to the 2 S storage albumin. Measurement of rl6-kDa sIgE was more discriminating than measurement of ImmunoCAP sIgE in whole BW extracts for the diagnosis of clinical reactivity to BW.
Choi
Soo-Young
SY
Institute of Allergy, Yonsei University College of Medicine, Seoul, Korea.
Sohn
Jung-Ho
JH
Lee
Yong-Won
YW
Lee
Eun-Kyung
EK
Hong
Chein-Soo
CS
Park
Jung-Won
JW
D055516:2S Albumins, Plant; D000293:Adolescent; D000328:Adult; D000595:Amino Acid Sequence; D052179:Antigens, Plant / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D001667:Binding, Competitive; D002648:Child; D016001:Confidence Intervals; D004311:Double-Blind Method; D004797:Enzyme-Linked Immunosorbent Assay; D019612:Fagopyrum / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D005260:Female; D005512:Food Hypersensitivity / Q000175:diagnosis* / Q000276:immunology; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology; D008297:Male; D008969:Molecular Sequence Data; D010936:Plant Extracts / Q000276:immunology; D010940:Plant Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D012372:ROC Curve; D011994:Recombinant Proteins / Q000276:immunology / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012882:Skin Tests / Q000379:methods
D055516:2S Albumins, Plant; D052179:Antigens, Plant; D010936:Plant Extracts; D010940:Plant Proteins; D011994:Recombinant Proteins; D007073:Immunoglobulin E