Real-time PCR Detection Methods for Food Allergens (Wheat, Buckwheat, and Peanuts) Using Reference Plasmids

Specific and sensitive real-time qualitative polymerase chain reaction (PCR) methods for the detection of food allergens including wheat, buckwheat, and peanuts were developed that could cancel between instrument effects and avoid risks of false-positives and false-negatives. In these real-time PCR analysis, the cutoff for determination of positive samples was set in every PCR run by using reference plasmids containing known copies of the target sequences. The copy numbers of the plasmids were used to detect the allergenic ingredients corresponding to 10 ppm (w/w) protein in highly processed foods (cooked for more than 30 min at 122 °C). Reference plasmid analysis for each real-time PCR run helped to minimize variability between runs and instruments (7900HT Real-Time PCR systems and Light Cycler Nano). It also helped to avoid false positives due to trace levels of contaminants from the laboratory environment or agricultural products. The specificity of the real-time PCR method was verified using 79 commonly used food materials and some of their relatives. The method was sensitive enough to detect those allergenic ingredients corresponding to 10 ppm (w/w) in seven types of incurred samples. The current official Japanese method was not able to detect the allergens in some of the incurred samples. The developed method can avoid false negatives due to lack of sensitivity and is useful to confirm positive ELISA screening tests.

Specific IgE for Fag e 3 Predicts Oral Buckwheat Food Challenge Test Results and Anaphylaxis: A Pilot Study

BACKGROUND

Buckwheat (BW) is the source of a life-threatening allergen. Fag e 3-specific serum IgE (sIgE) is more useful than BW-sIgE for diagnosis; however, it is unknown whether Fag e 3-sIgE can predict oral food challenge (OFC) results and anaphylaxis. This study aimed to clarify the efficacy of Fag e 3-sIgE in predicting OFC results and anaphylaxis.

METHODS

We conducted a retrospective review of BW- and Fag e 3-sIgE data obtained using the ImmunoCAP® assay system and fluorescent enzyme-linked immunosorbent assay from children who underwent OFC using 3,072 mg of BW protein between July 2006 and March 2014 at Sagamihara National Hospital, Kanagawa, Japan.

RESULTS

We analyzed 60 patients aged 1.9-13.4 years (median 6.0 years); 20 (33%) showed objective symptoms upon BW OFC. The patients without symptoms had significantly lower Fag e 3-sIgE than those with non-anaphylactic (p < 0.001) and anaphylactic reactions to BW (p = 0.004). Fag e 3-sIgE was the only tested factor that significantly predicted positive OFC results (odds ratio 8.93, 95% confidence interval 3.10-25.73, p < 0.001) and OFC-induced anaphylaxis (2.67, 1.12-6.35, p = 0.027). We suggest that a threshold Fag e 3-sIgE level of 18.0 kUE/L has 95% probability of provoking a positive reaction to BW.

CONCLUSIONS

Fag e 3-sIgE predicted OFC results and OFC-induced anaphylaxis. We further emphasize paying careful attention to the risk of BW OFC-induced anaphylaxis.

[Allergic reaction after ingestion of pancakes]

Buckwheat is increasingly used in food and pillows in Europe and is a potent potential allergen when ingested or inhaled. A 74-year-old Danish woman experienced anaphylaxis after ingesting industrially manufactured pancakes. She was IgE-sensitized and was persistently asymptomatic after allergen elimination. A thorough medical history is pivotal to identify untraditional allergens that can evoke severe allergic reactions.

[Buckwheat allergy can cause live-threatening anaphylaxia]

Alongside with the globalization of the Danish kitchen and the introduction of a larger number of commercial food items containing buckwheat, buckwheat allergy no longer seems to be a rare disease in Denmark. Since buckwheat allergy can cause life-threathening reactions, it is important for medical doctors to be aware of this allergy. Reliable serological tests showing specific IgE to buckwheat protein 2S albumin (Fag e2) are available in most countries. Three patients with anaphylactic reactions due to buckwheat allergy are presented.

Ribonuclease activity of buckwheat plant (Fagopyrum esculentum) cultivars with different sensitivities to buckwheat burn virus

Ribonucleases (RNases) are present in base-level amounts in intact plants, but this level is able to increase greatly under stress conditions. The possible cause for such an increase is protection against plant RNA-virus attack. Buckwheat burn virus (BBV) is a highly virulent pathogen that belongs to Rhabdoviridae family. In our study, we have analyzed the correlation between RNase activity and resistance of different buckwheat cultivars to BBV infection. Two cultivars, Kara-Dag and Roksolana, with different sensitivities to BBV have been used. Kara-Dag is a cultivar with medium sensitivity to virus and Roksolana is a tolerant cultivar. It has been shown that the base level of RNase activity in Roksolana cultivar was in most cases higher than the corresponding parameter in Kara-Dag cultivar. Both infected and uninfected plants of Roksolana cultivar demonstrated high RNase activity during two weeks. Whereas infected plants of Kara-Dag cultivar demonstrated unstable levels of RNase activity. Significant decline in RNase activity was detected on the 7th day post infection with subsequent gradual increase in RNase activity. Decline of the RNase activity during the first week could promote the virus replication and therefore more successful infection of upper leaves of plants. Unstable levels of RNase activity in infected buckwheat plants may be explained by insufficiency of virus-resistant mechanisms that determines the medium sensitivity of the cultivar to BBV. Thus, plants of buckwheat cultivar having less sensitivity to virus, displayed in general higher RNase activity.

Effects of Maillard reaction on allergenicity of buckwheat allergen Fag t 3 during thermal processing

BACKGROUND

Fag t 3 is a major allergenic protein in tartary buckwheat. The Maillard reaction commonly occurs in food processing, but few studies have been conducted on the influence of thermal processing on the allergenic potential of buckwheat allergen. The aim of the present study was to investigate the effects of autologous plant polysaccharides on the immunoreactivity of buckwheat Fag t 3 (11S globulin) following the Maillard reaction.

RESULTS

Fag t 3 and crude polysaccharides were prepared from tartary buckwheat (Fagopyrum tataricum) flour. After heating, the polysaccharides were covalently linked to Fag t 3 via a Maillard reaction, and the IgE/IgG-binding properties of Fag t 3 decreased dramatically, with significant changes also being observed in the electrophoretic mobility, secondary structure and solubility of the glycated Fag t 3. The great influence of glycation on IgE/IgG binding to Fag t 3 was correlated with a significant change in the structure and epitopes of the allergenic protein. These data indicated that conjugation of polysaccharides to Fag t 3 markedly reduced the allergen's immunoreactivity.

CONCLUSION

Glycation that occurs via the Maillard reaction during the processing of buckwheat food may be an efficient method to reduce Fag t 3 allergenicity.

Epitope mapping and identification on a 3D model built for the tartary buckwheat allergic protein TBb

Allergic protein TBb, a major allergen in tartary buckwheat, was divided into four epitope-containing fragments and was named F1, F2, F3, and F4, respectively. Results of immunological assays revealed that F2 had the strongest IgE-binding activity to patient's sera, which indicated that it might contain the linear IgE-binding epitope of TBb. According to the results of sequence analysis and molecular modeling of tartary buckwheat allergen, three mutants of F2 gene (R139A, R141A, and D144A) were reconstructed using site-directed mutagenesis, and each mutant was expressed in Escherichia coli BL21 (DE3). Following purification by Ni(2+) affinity chromatography, enzyme-linked immunosorbent assay and dot blot were performed for wild-type F2 and its mutants using sera from buckwheat-allergic patients and a negative control (non-allergic patient). Results showed that mutants R139A and D144A had weaker IgE-binding activity to patient's sera than wild-type F2, implying that Arg(139) and Asp(144) might be involved in the allergic activity of TBb. However, R141A had the weakest IgE-binding activity, suggesting that Arg(141) may be the critical amino acid of TBb. This is the first report on the epitope mapping and identification of TBb. Our findings will contribute to the production of TBb hypoallergens and to allergen-specific immunotherapy for tartary buckwheat allergy.

Clinical manifestations, co-sensitizations, and immunoblotting profiles of buckwheat-allergic patients

BACKGROUND

  Buckwheat allergy is a rare food allergy in Europe and North America, whereas it is often described and studied in Asia. The aim of this study was to describe a series of patients with proven buckwheat allergy evaluated in an Italian allergy clinic. Co-sensitization to other food and inhalant allergens and immunoblotting profiles of buckwheat-allergic patients were studied.

METHODS

  Patients with suspected buckwheat allergy who attended the allergy clinic between January 1, 2006, and September 30, 2008, were evaluated. All patients underwent skin prick tests for a standard panel of inhalant and food allergens, prick-by-prick with buckwheat flour, buckwheat-specific IgE determinations, and double-blind placebo-controlled food challenge (DBPCFC) with buckwheat flour. Immunoblotting with buckwheat flour extract was performed on sera from buckwheat-allergic patients.

RESULTS

  Among 72 patients with suspected buckwheat allergy, 30 (41.7%) were sensitized to buckwheat and 24 had a positive DBPCFC. The mean buckwheat IgE level was 6.23 kUA/l (range, 0.16 to >100 kUA/l). Several IgE-binding proteins were identified and grouped into three patterns: a 16-kDa band in patients with predominantly gastrointestinal symptoms with grass and wheat flour co-sensitization, a 25-kDa band in patients with predominantly cutaneous symptoms and a low frequency of co-sensitization, and a 40-kDa band in patients with anaphylaxis and a low frequency of co-sensitization.

CONCLUSIONS

  Buckwheat allergy is an emerging food allergy in Italy. We identified three distinct patterns of clinical and laboratory characteristics, suggesting that specific allergens could be more frequently associated with clinical manifestations of different severity.

[Expression and immunological characterization of the epitopes in tartary buckwheat allergen]

AIM

To determine the most important region in tartary buckwheat allergen.

METHODS

The gene of epitopes was amplified by PCR using the primers designed according to TBa cDNA. Four expression vectors containing the gene of epitopes were constructed, and then transformed into the E.coli BL21(DE3) host cells. The expression products were purified by Ni(2+);-NTA agarose affinity chromatography column and indirect ELISA, inhibition ELISA and Dot blot was performed using sera from allergenic patients.

RESULTS

The purified proteins were obtained and the immunological results showed that E1 exhibite stronger IgE binding to patient's serum than the other epitopes.

CONCLUSION

E1 is probably the most important region in tartary buckwheat allergen binding to buckwheat allergic sera IgE.

Purification, crystallization and preliminary X-ray analysis of a deletion mutant of a major buckwheat allergen

A 16 kDa buckwheat protein (BWp16) is a major allergen responsible for immediate hypersensitivity reactions including anaphylaxis. A deletion mutant of BWp16 (rBWp16DeltaN) was overproduced and purified and was shown to be immunologically active. A three-wavelength MAD data set was collected from a crystal of selenomethionine-labelled rBWp16DeltaN. The crystal belonged to the triclinic space group P1, with unit-cell parameters a = 28.39, b = 31.54, c = 32.20 A, alpha = 111.92, beta = 108.91, gamma = 98.74 degrees . One monomer was expected to be present in the asymmetric unit based on the calculated Matthews coefficient of 1.76 A(3) Da(-1).

Modulation of immunoresponse in BALB/c mice by oral administration of Fag e 1-glucomannan conjugate

Maillard-type glycosylation was applied to preparation of hypoallergenic agents from a major buckwheat allergen, Fag e 1. Conjugation with arabinogalactan (AG), xyloglucan (XG), or yeast glucomannan (YGM) successfully decreased in vitro allergenicity of Fag e 1. Determination of IgE titer in the tested allergic mice revealed that YGM was the most effective for in vivo allergenicity of Fag e 1 among these water-soluble polysaccharides. Real-time PCR analysis using a set of primer for IL-4 (a typical Th2 cytokine) or IFN-gamma (a typical Th1 cytokine) showed that expressed mRNA for IL-4 in splenocytes drastically decreased with increasing with Fag e 1-YGM conjugate feeding. In addition, based on a flow-cytometric analysis of T cell subsets in the splenocytes, it was confirmed that the feeding led to an improvement of Th1/Th2 balance in the allergic mice where population of Th1 increased from 2.91% to 4.02%, while that of Th2 decreased from 3.75% to 2.72%. Furthermore, it was revealed that differentiation ratio of regulatory T cell (Treg) in the splenocytes increased from 14.5% to 18.7% by the oral administration. These results indicated that Fag e 1-YGM conjugate can be available for an immunomodulating agent for buckwheat allergy.

IgE-binding epitopic peptide mapping on a three-dimensional model built for the 13S globulin allergen of buckwheat (Fagopyrum esculentum)

The three-dimensional model built for the 13S globulin allergen of buckwheat (Fagopyrum esculentum) consists of three protomers exhibiting the cupin motif, arranged in a homotrimer around a three-fold symmetry axis. Using the SPOT technique, 11 continuous IgE-binding epitopic peptides were characterized on the molecular surface of the 13S globulin allergen of buckwheat. Except for one of them, they all correspond to well exposed regions containing electropositiveley and/or electronegatively charged residues, which cover up to 40% of the molecular surface of the allergen. Some of these epitopes come in close contact to probably create more extended discontinuous epitopes, especially those located on the edge of the 13S globulin homotrimer. Half of the identified epitope peptides remain unaltered in a core structure protected against hydrolysis by digestive proteases and are thus assumed to promote the allergenicity of the 13S globulin. In addition, a few of these epitopes coincide with sequential IgE-binding epitopes previously characterized in soybean 11S globulins, that could account for the IgE-binding cross-reactions observed between soybean and buckwheat in Western blot experiments.

Molecular cloning, recombinant expression, and immunological characterization of a novel allergen from tartary buckwheat

Buckwheat is generally regarded as a nutritionally rich food source. However, earlier studies prove that it also causes allergies to subjects. Allergenic proteins with a strong IgE-binding activity have been identified in common buckwheat (CB) and a 24 kDa allergen (rTBa) in tartary buckwheat (TB). The objective of this research was to clone and express a novel allergen in tartary buckwheat and to evaluate its structure and immunological activity. The 1773 bp full-length cDNA was amplified and cloned from the total RNA of TB by polymerase chain reaction (PCR) and rapid amplification of cDNA ends (RACE) methods. Its nucleotide sequence had high similarity with legume-like 13S storage protein mRNA in CB. The deduced amino acid sequence included a putative signal peptide and 18 fragments as its epitope sites. The predicted full-length TB allergen sequence was found to have two domains, and the recombinant protein reacted with sera from patients with positive IgE binding to buckwheat and had a lower binding ability than the recombinant TBa and recombinant TBb (C- and N-terminal amino acid sequence of TBt codes for protein). This fact suggests that full-length TB allergen may hydrolyze to two domains in vivo, decreasing the IgE-binding ability.

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.

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.

Buckwheat anaphylaxis: an unusual allergen in Taiwan

IgE-mediated hypersensitivity to buckwheat is common in Korea, Japan, and some other Asian countries. However, buckwheat is not a common allergen in Taiwan. We report a woman with asthma who had anaphylactic shock, generalized urticaria, and an acute exacerbation of asthma five minutes after ingesting buckwheat. The patient underwent skin prick and Pharmacia CAP testing (Uppsala, Sweden) for specific IgE to buckwheat, white sesame and soybean as well as other common allergens in Taiwan including Dermatophagoides pteronyssinus (Dp), D. farinae (Df), cat and dog dander, cockroach, egg white, cow milk and codfish. The patient had a strongly positive skin prick test response to buckwheat and positive reactions to Dp and latex. Specific IgE results were class 6 for buckwheat, class 4 for Dp and Df, and class 2 for dog dander, wheat, sesame and soybean. Results of an open food challenge with white sesame and soybean were negative. Although buckwheat is a rare allergen in Taiwan, it can cause extremely serious reactions and should be considered in patients presenting with anaphylaxis after exposure to buckwheat.

Molecular Cloning of cDNA, Recombinant Protein Expression and Characterization of a Buckwheat 16-kDa Major Allergen

BACKGROUND

Buckwheat is a common food in Japan, Korea and other countries. A candidate major buckwheat allergen, a 16-kDa protein (BWp16), was previously characterized as a pepsin-resistant protein associated with immediate-type allergies to buckwheat. However, whether recombinant BWp16 can react with a patient's IgE remains uncertain.

METHODS

The cDNA encoding BWp16 from Japanese buckwheat seeds was cloned based on the sequences obtained by the 5'-rapid amplification of cDNA ends (RACE) and 3'-RACE PCR. Recombinant BWp16 protein expressed in Escherichia coli was purified using affinity chromatography. Western blotting, ELISA and cross inhibition tests of the purified recombinant BWp16 were performed using sera from patients with positive IgE binding to buckwheat and controls. Pepsin digestion experiments were also performed.

RESULTS

The full-length cDNA encodes 149 amino acid residues with a calculated molecular mass of 16.9 kDa. The deduced amino acid sequence included a putative signal peptide sequence. BWp16 showed significant homologies to the buckwheat 8-kDa allergen and Ricinus communis (castor bean) 2S albumin. Sera from patients with positive IgE binding to buckwheat reacted with the purified BWp16. Cross inhibition tests revealed immunological equivalence of the purified recombinant and natural BWp16. The recombinant and natural BWp16 were comparably resistant to pepsin digestion.

CONCLUSIONS

BWp16 belongs to the 2S albumin family and is a buckwheat allergen. This purified recombinant BWp16 could be used in the diagnosis of buckwheat allergy.

Cross-sensitization between poppy seed and buckwheat in a food-allergic patient with poppy seed anaphylaxis

The opium poppy, Papaver somniferum L., is the source of both poppy seeds and opium. The commercially available seeds are widely used as ingredients for various kinds of food. IgE-mediated sensitization to poppy seeds is rare, but, if present, clinical symptoms are usually severe. Cross-sensitizations between poppy seeds and other food allergens have been described with sesame, hazelnut, rye grain and kiwi fruit. We report the case of a 17-year-old female with an apparently food-allergic reaction after ingestion of a poppy seed cake. Allergological workup revealed a poppy seed anaphylaxis and led to the identification of a novel cross-sensitization with buckwheat.

Murine model of buckwheat allergy by intragastric sensitization with fresh buckwheat flour extract

Food allergies affect about 4% of the Korean population, and buckwheat allergy is one of the most severe food allergies in Korea. The purpose of the present study was to develop a murine model of IgE-mediated buckwheat hypersensitivity induced by intragastric sensitization. Young female C3H/HeJ mice were sensitized and challenged intragastricly with fresh buckwheat flour (1, 5, 25 mg/dose of proteins) mixed in cholera toxin, followed by intragastric challenge. Anaphylactic reactions, antigen-specific antibodies, splenocytes proliferation assays and cytokine productions were evaluated. Oral buckwheat challenges of sensitized mice provoked anaphylactic reactions such as severe scratch, perioral/periorbital swellings, or decreased activity. Reactions were associated with elevated levels of buckwheatspecific IgE antibodies. Splenocytes from buckwheat allergic mice exhibited significantly greater proliferative responses to buckwheat than non-allergic mice. Buckwheat-stimulated IL-4, IL-5, and INF-gamma productions were associated with elevated levels of buckwheat-specific IgE in sensitized mice. In this model, 1 mg and 5 mg dose of sensitization produced almost the same degree of Th2-directed immune response, however, a 25 mg dose showed blunted antibody responses. In conclusion, we developed IgE-mediated buckwheat allergy by intragastric sensitization and challenge, and this model could provide a good tool for future studies.

[Anaphylactic shock due to French galette. Type I allergic reaction to buckwheat]

A 37-year-old woman twice developed a life-threatening anaphylactic reaction after eating galettes, a special French pancake from Brittany. She had tolerated ordinary pancakes and crepes for many years. The allergological work-up revealed a Type I allergic reaction to buckwheat contained in the galettes. A prick test to buckwheat was positive and specific IgE antibodies to buckwheat were found in her serum. In contrast to wheat, buckwheat is not a cereal but a gluten-free knot-grass, initially from Asia. Whenever a patient suffers from allergic reactions due to pastries, a buckwheat allergy should be considered.

Purification and characterization of a 24 kDa protein from tartary buckwheat seeds

A 24 kDa protein was isolated from tartary buckwheat seeds by using chromatography of Superdex 75 gel filtration and Resource Q ion-exchange column. SDS-PAGE and Sephacryl S-200 gel filtration were used to provide information about the molecular mass of the protein purified from tartary buckwheat. The protein was composed of 215 amino acid residues and showed strong IgE binding activity in an ELISA test to the sera colleted from two patients allergic to buckwheat. These results suggested that the purified 24 kDa protein from tartary buckwheat seeds was an important functional protein and was relatively specific for buckwheat-allergic patients. It should be a very useful tool in the diagnosis of buckwheat allergy in the future.

Molecular characterization of a 10-kDa buckwheat molecule reactive to allergic patients' IgE

BACKGROUND

Using the sera from buckwheat (BW)-allergic patients, several putative causative molecules were reported. However, few molecules were determined on the molecular structure. We demonstrated in 2000 that the major allergen with 24 kDa (BW24KD) is a legumin-like storage protein.

OBJECTIVE

The aim of this study was to isolate and characterize further a major allergen with 10 kDa by molecular cloning.

METHODS AND RESULTS

Buckwheat allergens were identified by immunoblotting analysis using sera from 14 allergic and two nonallergic individuals. We identified a protein with 10 kDa (BW10KD) that reacted with immunoglobulin E (IgE) more strongly than with IgG and IgA in 57% of the allergic patients but not with IgE in nonallergic individuals. Analyses were performed by N-terminal amino acid sequencing and molecular cloning. Physiological significance was assessed by an immunoblotting experiment showing that the reactivity of an allergic patient's serum IgE to BW10KD was competitively inhibited by natural BW extracts.

CONCLUSION

Molecular cloning experiments indicated that BW10KD as a BW allergen was a member of the 2S-albumin multigene family.

Prediction of buckwheat allergy using specific IgE concentrations in children

INTRODUCTION

Buckwheat (BW) is considered to be one of the most important food allergens, and positive skin tests are found in about 5% of Koreans. We investigated the positive and negative predictive values of BW-specific IgE in subjects with a BW allergy in order to reduce the need for buckwheat challenge, which can be more riskier than other causes of food allergies.

METHODS

Twenty-eight BW allergic subjects with symptoms after BW Open food challenge and 16 asymptomatic control subjects with positive skin test to BW were recruited. Serum samples from all patients were analyzed for BW-specific IgE antibodies using the Pharmacia CAP System.

RESULTS

According to the receiver operator characteristic (ROC) analysis, the optimal cutoff level of BW-specific IgE, as the definitions of serum BW-specific IgE positive, was 1.26 kUA/l. With this selected cutoff level, the sensitivity, specificity, positive and negative predictive values were 93.10, 93.33, 79.75 and 97.96%, respectively.

CONCLUSION

The use of the optimal cutoff level, 1.26 kUA/l, that simultaneously maximizes sensitivity and specificity, would be helpful for avoiding unnecessary risky challenge in children with a strong clinical history and skin test responses.

Pepsin-resistant 16-kD buckwheat protein is associated with immediate hypersensitivity reaction in patients with buckwheat allergy

BACKGROUND

Buckwheat is becoming popular in many countries as a health food and the incidence of buckwheat allergy is increasing in Asia. The ingestion of small amounts sometimes provokes an anaphylactic reaction. However, it remains controversial which is the major allergen responsible for such reactions.

METHODS

The patients whose sera are positive for buckwheat-specific IgE antibody measured by the CAP system fluorescein-enzyme immunoassay (CAP-FEIA) were classified into two subgroups depending on the history of immediate hypersensitivity reactions (IHR). Major buckwheat allergens were identified with immunoblotting, ELISA and N-terminal amino acid sequencing. Various treatments such as pepsin digestion were added to characterize the proteins.

RESULTS

We found that the 24-kD protein that had previously been reported to be a major allergen reacted to IgE antibodies present in sera from almost all subjects (19/20) regardless of symptoms. On the other hand, 16- and 19-kD proteins were bound with IgE antibodies present in sera from 9 of the 10 patients with IHR including 8 patients with anaphylaxis but not in sera from buckwheat-specific IgE-positive subjects without IHR. After pepsin treatment, the 16-kD protein but not the 19- and 24-kD proteins remained undigested and preserved the capacity of IgE binding. This pepsin-resistant 16-kD protein had no homology with the 24-kD protein by the N-terminal amino acid sequencing.

CONCLUSIONS

The 16-kD buckwheat protein was resistant to pepsin digestion and appeared to be responsible for IHR including anaphylaxis, while the pepsin-sensitive 24-kD protein was responsible for CAP-FEIA but not IHR.

[Sensitisation to 'poffertjes' as a result of sleeping on a pillow containing buckwheat]

A 19-year-old man suffered an anaphylactic reaction after eating 'poffertjes' (small Dutch pancakes). This reaction appeared to be the result of an IgE-mediated allergy to buckwheat, a principal ingredient of 'poffertjes'. It is highly likely that the patient was sensitised by sleeping on a pillow stuffed with buckwheat husk.

Screening and selection of hypoallergenic buckwheat species

Both common buckwheat (Fagopyrum esculentum) flour and meal cause an allergy in sensitive patients, and if unnoticed, it can be fatal. It has become a potential occupational hazard for some mill workers. The development of hypoallergenic buckwheat would be more efficient if natural mutants for allergenic protein are detected. A screening and selection method was developed using SDS-PAGE coupled with PCR techniques. SDS-PAGE analysis of 14 different species of buckwheat revealed that F. lineare and F. urophyllum lack the 22-kDa major allergenic protein. PCR-based screening with specific primers for sequences encoding the allergenic protein was also effective in distinguishing the allergen-deficient species.

The immunostimulatory effect of bio-active peptide from pollen on murine and human lymphocytes

The effects of bio-active peptide (BP) from buckwheat pollen and its synthetic analogues on murine and human lymphocytes and HL-60 cells were examined. Both natural and synthetic BP had the same effect in the lymphocyte blast transformation test. The proliferative response of HL-60 cells, co-cultured for 72 h with BP, was measured by the MTT method. BP had a stimulatory effect on HL-60 cell proliferation. The optical density (OD) value was 0.339+/-0.015, whereas, that of the control without BP was significantly lower (0.279+/-0.037; P < 0.05). The CD25 (IL-2Ralpha chain) positive cells of BP-stimulated human lymphocytes assessed by indirect immunofluorescence were 53.97+/-7.12% (1 microg/ml) and 42.53+/-4.4% (10 microg/ml), significantly higher than the control (11.77+/-1.88%; P < 0.001). The content of sIL-2R in the supernatant after culture with BP was determined by ELISA and was 1782.3+/-78.18 U/ml, lower than control 2381.2+/-99.9 U/ml. Taken together, our results showed that BP has an immunostimulatory effect on lymphocytes. The likely mode of BP action and the possibility of developing a novel immunomodulator are discussed.

[Buckwheat allergy in 90,000 school children in Yokohama]

Hypersensitivity to buckwheat allergen frequently causes anaphylactic type reactions including urticaria, wheezing, dyspnea and/or shock. Though the susceptible pupil would be recommended to be careful for school lunch and picnic meals, the prevalence of buckwheat allergy in school children has not yet been elucidated. In this study, data on the children allergic to buckwheat were collected by sending questionnaire to 341 nurses in elementary school in Yokohama. Among the total subjects of this investigation, 92,680 children, the incidence of buckwheat allergy was determined 0.22% (140 boys and 54 girls). This percentage was not so low level besides the prevalence of such allergic diseases as bronchial asthma, atopic dermatitis, allergic rhinitis, allergic conjunctivitis and food allergy was 5.6%, 4.2%, 3.1%, 1.6%, and 1.3%, respectively. Although a large majority of clinical symptoms of buckwheat allergy were urticaria (37.3%), skin itching (33.3%), and wheezing (26.5%). Four children (3.9%) experienced anaphylactic shock having a need of medical emergency treatment. The incidence of anaphylactic shock due to buckwheat was higher than those due to egg and milk allergy. Actually 7 pupil was provoked allergic reaction by buckwheat noodle served at school lunch, and 1 pupil at picnic meals. Thus, school children allergic to buckwheat is not rare, and it is important to withdraw buckwheat food from school lunch and picnic meals.

Purification of a yeast TATA box-binding protein that exhibits human transcription factor IID activity

By a series of conventional chromatographic procedures we have purified from whole-cell extracts of Saccharomyces cerevisiae yeast transcription factor IID (TFIID), which functionally substitutes for human TFIID in a complementation assay comprised of the adenovirus type 2 major late promoter and HeLa cell-derived RNA polymerase II, transcription factors IIA, IIB, and IIE. Similar to its human counterpart, yeast TFIID also exhibited specific binding to the adenovirus type 2 major late promoter TATA element, as shown by both DNase I footprinting and gel mobility shift assays. NaDodSO4/PAGE analyses showed that a 27-kDa polypeptide coeluted with TFIID complementing activity through each chromatographic step. In agreement with this result and also suggesting that the native protein is a monomer, gel-filtration experiments indicated a molecular mass of 28 kDa for TFIID under nondenaturing conditions. That the 27-kDa polypeptide represented TFIID was further demonstrated by the ability of an HPLC-purified protein to bind specifically after renaturation to the adenovirus type 2 major late promoter TATA sequence.