Characterization of buckwheat 19-kD allergen and its application for diagnosing clinical reactivity.
BACKGROUND
The 19-kD protein of buckwheat (BW) has been suggested to be a major allergen, but its characteristics and clinical significance are poorly defined.


METHODS
cDNA of the 19-kD BW allergen was cloned and expressed in Escherichia coli. Allergenicity and cross-allergenicity were confirmed by inhibition immunoblotting or by ELISA inhibition. The recombinant (r19-kD) protein was assessed for clinical utility in the diagnosis of BW reactivity in 18 BW-allergic and 19 BW-asymptomatic sensitized subjects using receiver operating characteristic analysis.


RESULTS
The 19-kD BW allergen, which is composed of 135 amino acids, has a weak homology to the vicilin-like allergens of cashew (Ana o 1), English walnut (Jug r 2) and 7 S globulin from Sesamum indicum. The r19-kD protein can inhibit sIgE binding to native 19-kD BW allergen. The maximum percentage inhibition of sIgE binding to crude BW extract was 56%. About 83.3% of the BW allergy patients had sIgE bound to r19-kD protein, compared to only 1 of the 19 BW-asymptomatic sensitized subjects. The areas under the receiver operating characteristic curves for the skin prick tests [0.925 (95% confidence interval: 0.839-1.012), p < 0.001] as well as r19-kD protein sIgE ELISAs [0.860 (95% confidence interval: 0.725-0.995), p <0.001] were higher than that of BW sIgE coated allergen particle test results [0.803 (95% confidence interval: 0.661-0.945), p = 0.002].


CONCLUSIONS
The 19-kD BW allergen may be the major allergen from BW. For the diagnosis of clinical reactivity to BW, the r19-kD protein sIgE ELISA test was more discriminative than the coated allergen particle sIgE measurement using whole BW extract.
Choi
Soo-Young
SY
Department of Internal Medicine and 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
D000293:Adolescent; D000328:Adult; D000485:Allergens / Q000009:adverse effects* / Q000235:genetics / Q000276:immunology; D000595:Amino Acid Sequence; D052179:Antigens, Plant / Q000009:adverse effects* / Q000235:genetics / Q000276:immunology; D002648:Child; D018076:DNA, Complementary; D004311:Double-Blind Method; D019612:Fagopyrum / Q000737:chemistry / Q000276:immunology*; 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 / Q000009:adverse effects / Q000276:immunology; D010940:Plant Proteins / Q000009:adverse effects* / Q000235:genetics / Q000276:immunology; D011994:Recombinant Proteins / Q000276:immunology; D012882:Skin Tests
D000485:Allergens; D052179:Antigens, Plant; D018076:DNA, Complementary; D010936:Plant Extracts; D010940:Plant Proteins; D011994:Recombinant Proteins; D007073:Immunoglobulin E