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Stef J Koppelman - One of the best experts on this subject based on the ideXlab platform.
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Release of Major Peanut Allergens from Their Matrix under Various pH and Simulated Saliva Conditions-Ara h2 and Ara h6 Are Readily Bio-Accessible
Nutrients, 2018Co-Authors: Stef J Koppelman, Steve L. Taylor, Govardus A.h. De Jong, Mieke Smits, Monic M. M. Tomassen, Joseph L. Baumert, Renger F. Witkamp, Robert Jan Veldman, Raymond Pieters, Harry J. WichersAbstract:The oral mucosa is the first immune tissue that encounters allergens upon ingestion of food. We hypothesized that the bio-accessibility of allergens at this stage may be a key determinant for sensitization. Light roasted peanut flour was suspended at various pH in buffers mimicking saliva. Protein concentrations and allergens profiles were determined in the supernatants. Peanut protein solubility was poor in the pH range between 3 and 6, while at a low pH (1.5) and at moderately high pHs (>8), it increased. In the pH range of saliva, between 6.5 and 8.5, the allergens Ara h2 and Ara h6 were readily released, whereas Ara h1 and Ara h3 were poorly released. Increasing the pH from 6.5 to 8.5 slightly increased the release of Ara h1 and Ara h3, but the recovery remained low (approximately 20%) compared to that of Ara h2 and Ara h6 (approximately 100% and 65%, respectively). This remarkable difference in the extraction kinetics suggests that Ara h2 and Ara h6 are the first allergens an individual is exposed to upon ingestion of peanut-containing food. We conclude that the peanut allergens Ara h2 and Ara h6 are quickly bio-accessible in the mouth, potentially explaining their extraordinary allergenicity.
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Ara h 6 complements Ara h 2 as an important marker for IgE reactivity to peanut.
Journal of agricultural and food chemistry, 2013Co-Authors: Audrey Koid, Martin D. Chapman, Stephen C. Dreskin, Stef J Koppelman, Robert G. Hamilton, Ronald Van Ree, Serge A. Versteeg, Sabina WünschmannAbstract:The similarities of two major peanut allergens, Ara h 2 and Ara h 6, in molecular size, amino acid sequence, and structure have made it difficult to obtain natural Ara h 6 free of Ara h 2. The objectives of this study were to purify natural Ara h 6 that is essentially free of Ara h 2 and to compare its IgE reactivity and potency in histamine release assays to Ara h 2. SDS-PAGE of the highly purified allergen (
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Digestion of peanut allergens Ara h 1, Ara h 2, Ara h 3, and Ara h 6: a compArative in vitro study and partial chAracterization of digestion-resistant peptides.
Molecular nutrition & food research, 2010Co-Authors: Stef J Koppelman, Susan L Hefle, Steve L. Taylor, Govardus A.h. De JongAbstract:Scope: There are differences in stability to pepsin between the major allergens in peanut; however, data are from different reports using different digestion models. This study provides a comprehensive comparison of the digestibility of the major peanut allergens.Methods and results: Peanut allergens Ara h 1, Ara h 2, Ara h 3 and Ara h 6 were incubated with pepsin to mimic the effect of gastric digestion. Samples were analyzed using SDS-PAGE. To further investigate resistance to digestion, Ara h 2 was additionally subjected to digestion with trypsin and residual peptides were chAracterized. Ara h 1 and Ara h 3 were rapidly hydrolyzed by pepsin. On the contrary, Ara h 2 and Ara h 6 were resistant to pepsin digestion, even at very high concentrations of pepsin. In fact, limited proteolysis could only be demonstrated by SDS-PAGE performed under reducing conditions, indicating an important role for the disulfide bridges in maintaining the quaternary structure of Ara h 2 and Ara h 6. Trypsin digestion of Ara h 2 similarly resulted in large residual peptides and these were identified.Conclusion: Ara h 2 and Ara h 6 are considerably more stable towards digestion than Ara h 1 and Ara h 3. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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children with peanut allergy recognize predominantly Ara h2 and Ara h6 which remains stable over time
Clinical & Experimental Allergy, 2007Co-Authors: Annebeth E Flinterman, André C. Knulst, Stef J Koppelman, E Van Hoffen, C Den Hartog F Jager, Carla A F M Bruijnzeelkoomen, Suzanne G M A Pasmans, M O Hoekstra, Edward F. KnolAbstract:Background: In peanut-allergic adults, IgE is mainly directed to Ara h1 and Ara h2. More recently, a role for Ara h6 has been suggested. In contrast to adults, IgE in children can fluctuate over time. Therefore, children may have a more dynamic reactivity to peanut. Objective: To examine the IgE reactivity to major peanut allergens in peanut-allergic children at two subsequent time-points. Methods: Twenty children (3-15 years old) with peanut allergy, confirmed by a double-blind placebo-controlled food challenge (DBPCFC), were included. Just before and 20 months after DBPCFC, IgE reactivity to purified Ara h1, Ara h2, Ara h3 and Ara h6 was studied by immunoblots and skin prick tests (SPTs). Results: Before DBPCFC, all peanut-allergic children showed IgE reactivity to Ara h2; Ara h6 was recognized by 16 children, and Ara h1 and Ara h3 by 10 children. After 20 months, peanut-specific IgE levels (median 23 kU/L) and the individual recognition of major allergens were compArable with the levels and recognition before challenge (median 28.2 kU/L). SPT with Ara h2 and Ara h6 was positive in most children, whereas SPT with Ara h1 and Ara h3 was positive in approximately half of the children. Ara h6 induced the largest weals. None of the pArameters were related to the severity of peanut allergy. Conclusion: Ara h2 and Ara h6 are the most frequently recognized major peanut allergens in children. The individual reactivity to the major peanut allergens remained stable over time, despite DBPCFC. © 2007 Blackwell Publishing Ltd.
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does skin prick test reactivity to purified allergens correlate with clinical severity of peanut allergy
Clinical & Experimental Allergy, 2007Co-Authors: K A B M Peeters, Edward F. Knol, Stef J Koppelman, E Van Hoffen, C W H Van Der Tas, C Den Hartog F Jager, Andre Penninks, Susan L Hefle, Carla A F M Bruijnzeelkoomen, André C. KnulstAbstract:Background: Recognition of specific peanut allergens or the diversity of IgE binding to peanut allergens may play a role in the elicitation of severe allergic reactions. Objective: To investigate whether sensitization to individual allergens Ara h 1, Ara h 2, Ara h 3 and Ara h 6 is correlated with clinical severity. Methods: The reactivity of purified peanut allergens was measured by skin prick test (SPT) and by IgE immunoblot in 30 patients. The results were related to the clinical reactivity by history, and in 25 of them to the eliciting dose (ED). Results: The majority of patients recognized Ara h 2 and Ara h 6. Patients with severe symptoms had a higher SPT response to Ara h 2 and Ara h 6 at low concentrations (0.1 μg/mL) and to Ara h 1 and Ara h 3 at higher concentrations (100 μg/mL), compared with patients with mild symptoms. They also recognized a greater number of allergens and showed a higher cumulative SPT response compared with patients with mild symptoms. No significant differences were observed between patients with a low or high ED. Conclusions: Ara h 2 and Ara h 6 appeared to be more potent than Ara h 1 and Ara h 3. Both SPT reactivity to low concentrations of Ara h 2 and Ara h 6 and to higher concentrations of Ara h 1 and Ara h 3 were shown to be indicative of severe symptoms. © 2007 Blackwell Publishing Ltd.
Hyo-kyung Han - One of the best experts on this subject based on the ideXlab platform.
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Pharmacokinetic chAracteristics of L -valyl-Ara-C and its implication on the oral delivery of Ara-C
Acta pharmacologica Sinica, 2007Co-Authors: Eun-pa Cheon, Hyo-kyung HanAbstract:Aim: To evaluate the pharmacokinetic chAracteristics of L -valyl-Ara-C, a peptidomimetic prodrug of Ara-C. Methods: After the synthesis of L-valyl-Ara-C, the in vitro stability of L -valyl-Ara-C was examined in various biological media. Plasma pharmacokinetic profiles of Ara-C and L -valyl-Ara-C were also evaluated in rats. Results: The degradation of L -valyl-Ara-C was negligible in fresh plasma and also in the presence of plasmin over a 2 h incubation period. Furthermore, L -valyl-Ara-C appeared to be stable in the leukemia cell homogenates, and subsequently, it was far less cytotoxic than the parent, Ara-C in AML2 and L1210 cells. The chemical hydrolysis of L -valyl-Ara-C was rather accelerated in acidic pH. Following an oral administration of L -valyl-Ara-C, the appeArance of Ara-C was observed in plasma although the systemic exposure of the prodrug was much higher than that of Ara-C. The bioavailability of Ara-C was about 4% via prodrug administration. Conclusion: The amide bond of L -valyl-Ara-C was stable against the enzymatic hydrolysis, and the utility of L -valyl-Ara-C as an oral delivery system of Ara-C appeared to be limited by its low metabolic conversion to Ara-C in rats.
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Enhanced cellular uptake of Ara-C via a peptidomimetic prodrug, L-valyl-Ara-C in Caco-2 cells
The Journal of pharmacy and pharmacology, 2006Co-Authors: Eun-pa Cheon, Joon Hee Hong, Hyo-kyung HanAbstract:This study aimed to investigate the gastrointestinal stability and the cellular uptake chAracteristics of l-valyl-Ara-C, a peptidomimetic prodrug of Ara-C (cytArabine). After the synthesis of l-valyl-Ara-C via the incorporation of l-valine into the N4-amino group of the cytosine ring in Ara-C, the gastrointestinal stability of l-valyl-Ara-C was examined using artificial gastric juice and artificial intestinal fluids. The cellular uptake chAracteristics of l-valyl-Ara-C were also examined in Caco-2 cells. The disappeArance half-life of l-valyl-Ara-C was 2.2 h in artificial gastric juice, while the degradation of l-valyl-Ara-C was negligible in artificial intestinal fluid and also in the supernatant above the Caco-2 cell monolayer during the 2-h incubation. The cellular accumulation of l-valyl-Ara-C was 5-fold higher than that of Ara-C in Caco-2 cells. Furthermore, the cellular uptake of l-valyl-Ara-C did not increase proportionally to the increase in drug concentration. The cellular accumulation of l-valyl-Ara-C was significantly reduced in the presence of uridine, p-aminohippurate, tetraethylammonium and small dipeptides, while it was not changed in the presence of l-valine and benzoic acid, suggesting that l-valyl-Ara-C could interact with multiple uptake transporters, including peptide transporters, organic anion and cation transporters and nucleoside transporters, but might not interact with amino acid transporters. In conclusion, l-valyl-Ara-C could be effective to improve the oral absorption of Ara-C via the carrier-mediated transport pathway.
Stephen C. Dreskin - One of the best experts on this subject based on the ideXlab platform.
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Variable IgE cross-reactivity between peanut 2S-albumins: The case for measuring IgE to both Ara h 2 and Ara h 6.
Clinical and Experimental Allergy, 2019Co-Authors: Stéphane Hazebrouck, Stephen C. Dreskin, Karine Adel-patient, Blanche Guillon, Evelyne Paty, Hervé BernardAbstract:BACKGROUND: 2S-albumins Ara h 2 and Ara h 6 are the most potent peanut allergens and levels of specific immunoglobulin E (IgE) towards these proteins are good predictors of clinical reactivity. Because of structural homologies, Ara h 6 is generally considered to cross-react extensively with Ara h 2. OBJECTIVE: We aimed to quantify the IgE cross-reactivity between Ara h 2 and Ara h 6. METHODS: Peanut 2S-albumins were purified from raw peanuts. The IgE cross-reactivity between Ara h 2 and Ara h 6 was evaluated with 32 sera from French and US peanut-allergic patients by measuring the residual IgE-binding to one 2S-albumin after depletion of IgE antibodies recognizing the other 2S-albumin. The IgE cross-reactivity between Ara h 2 and Ara h 6 was further investigated by competitive inhibition of IgE-binding and by a model of mast cell degranulation. RESULTS: A highly variable level of IgE cross-reactivity was revealed among the patients. The mean fraction of cross-reactive IgE antibodies represented only 17.1% of 2S-albumins-specific IgE antibodies and was lower than the mean fraction of IgE specific to Ara h 2 (57.4%) or to Ara h 6 (25.5%). The higher level of Ara h 2-specific IgE was principally due to the IgE-binding capacity of an insertion containing the repeated immunodominant linear epitope DPYSPOH S. The impact of IgE cross-reactivity on diagnostic testing was illustrated with a serum displaying an Ara h 6-specific IgE response of 26 UI/mL that was not associated with the capacity of Ara h 6 to trigger mast cell degranulation. CONCLUSIONS & CLINICAL RELEVANCE: Immunoglobulin E antibodies specific to peanut 2S-albumins are mainly non-cross-reactive, but low-affinity cross-reactivity can affect diagnostic accuracy. Testing IgE-binding to a mixture of 2S-albumins rather than to each sepArately may enhance diagnostic performance.
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Conformational IgE epitopes of peanut allergens Ara h 2 and Ara h 6
Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology, 2016Co-Authors: Xueni Chen, Surendra S. Negi, Sumei Liao, Valerie Gao, Werner Braun, Stephen C. DreskinAbstract:SummaryBackground Cross-linking of IgE antibody by specific epitopes on the surface of mast cells is a prerequisite for triggering symptoms of peanut allergy. IgE epitopes are frequently categorized as linear or conformational epitopes. Although linear IgE-binding epitopes of peanut allergens have been defined, little is known about conformational IgE-binding epitopes. Objective To identify clinically relevant conformational IgE epitopes of the two most important peanut allergens, Ara h 2 and Ara h 6, using phage peptide library. Methods A phage 12mer peptide library was screened with allergen-specific IgE from 4 peanut-allergic patients. Binding of the mimotopes to IgE from a total of 29 peanut-allergic subjects was measured by ELISA. The mimotope sequences were mapped on the surface areas of Ara h 2 and Ara h 6 using EpiSearch. Results Forty-one individual mimotopes were identified that specifically bind anti- Ara h 2/Ara h 6 IgE as well as rabbit anti-Ara h 2 and anti-Ara h 6 IgG. Sequence alignment showed that none of the mimotope sequences match a linear segment of the Ara h 2 or Ara h 6 sequences. EpiSearch analysis showed that all the mimotopes mapped to surface patches of Ara h 2 and Ara h 6. Eight of the mimotopes were recognized by more than 90% of the patients, suggesting immunodominance. Each patient had distinct IgE recognition patterns but the recognition frequency was not correlated to the concentration of peanut specific IgE or to clinical history. Conclusions The mimotopes identified in this study represent conformational epitopes. Identification of similar surface patches on Ara h 2 and Ara h 6 further underscores the similarities between these two potent allergens.
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Epitope analysis of Ara h 2 and Ara h 6: chAracteristic patterns of IgE-binding fingerprints among individuals with similar clinical histories
Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology, 2015Co-Authors: Kanao Otsu, R. Guo, Stephen C. DreskinAbstract:SummaryBackground Ara h 2 and Ara h 6 are moderately homologous and highly potent peanut allergens. Objective To identify IgE-binding linear epitopes of Ara h 6, compare them to those of Ara h 2, and to stratify binding based on clinical histories. Methods Thirty highly peanut-allergic subjects were stratified by clinical history. Sera were diluted to contain the same amount of anti-peanut IgE. IgE binding to overlapping 20-mer peptides of Ara h 2 and Ara h 6 was assessed using microarrays. Results Each subject had a unique IgE-binding fingerprint to peptides; these data were coalesced into epitope binding. IgE from subjects with a history of more severe reactions (n = 19) had a smaller frequency of binding events (BEs) for both Ara h 2 (52 BEs of 152 (19X8epitopes) possible BEs and Ara h 6 (13 BEs of 133 (19X7 epitopes) possible BEs) compared to IgE from those with milder histories (n = 11) (Ara h 2: 47 BEs of 88 (11X8 epitopes) possible BEs, P
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Ara h 6 complements Ara h 2 as an important marker for IgE reactivity to peanut.
Journal of agricultural and food chemistry, 2013Co-Authors: Audrey Koid, Martin D. Chapman, Stephen C. Dreskin, Stef J Koppelman, Robert G. Hamilton, Ronald Van Ree, Serge A. Versteeg, Sabina WünschmannAbstract:The similarities of two major peanut allergens, Ara h 2 and Ara h 6, in molecular size, amino acid sequence, and structure have made it difficult to obtain natural Ara h 6 free of Ara h 2. The objectives of this study were to purify natural Ara h 6 that is essentially free of Ara h 2 and to compare its IgE reactivity and potency in histamine release assays to Ara h 2. SDS-PAGE of the highly purified allergen (
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Ara h 6 complements Ara h 2 as an important marker for IgE reactivity to peanut
Clinical and Translational Allergy, 2013Co-Authors: James P. Hindley, Stephen C. Dreskin, Audrey Koid, Robert G. Hamilton, Ronald Van Ree, Serge A. Versteeg, Chapman, Sabina WünschmannAbstract:The similarities of two major peanut allergens, Ara h 2 and Ara h 6, in molecular size, amino acid sequence, and structure have made it difficult to obtain natural Ara h 6 free of Ara h 2. The objectives of this study were to purify natural Ara h 6 that is essentially free of Ara h 2 and to compare its IgE reactivity and potency in histamine release assays to Ara h 2. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis of the highly purified allergen (
Eun-pa Cheon - One of the best experts on this subject based on the ideXlab platform.
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Pharmacokinetic chAracteristics of L -valyl-Ara-C and its implication on the oral delivery of Ara-C
Acta pharmacologica Sinica, 2007Co-Authors: Eun-pa Cheon, Hyo-kyung HanAbstract:Aim: To evaluate the pharmacokinetic chAracteristics of L -valyl-Ara-C, a peptidomimetic prodrug of Ara-C. Methods: After the synthesis of L-valyl-Ara-C, the in vitro stability of L -valyl-Ara-C was examined in various biological media. Plasma pharmacokinetic profiles of Ara-C and L -valyl-Ara-C were also evaluated in rats. Results: The degradation of L -valyl-Ara-C was negligible in fresh plasma and also in the presence of plasmin over a 2 h incubation period. Furthermore, L -valyl-Ara-C appeared to be stable in the leukemia cell homogenates, and subsequently, it was far less cytotoxic than the parent, Ara-C in AML2 and L1210 cells. The chemical hydrolysis of L -valyl-Ara-C was rather accelerated in acidic pH. Following an oral administration of L -valyl-Ara-C, the appeArance of Ara-C was observed in plasma although the systemic exposure of the prodrug was much higher than that of Ara-C. The bioavailability of Ara-C was about 4% via prodrug administration. Conclusion: The amide bond of L -valyl-Ara-C was stable against the enzymatic hydrolysis, and the utility of L -valyl-Ara-C as an oral delivery system of Ara-C appeared to be limited by its low metabolic conversion to Ara-C in rats.
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Enhanced cellular uptake of Ara-C via a peptidomimetic prodrug, L-valyl-Ara-C in Caco-2 cells
The Journal of pharmacy and pharmacology, 2006Co-Authors: Eun-pa Cheon, Joon Hee Hong, Hyo-kyung HanAbstract:This study aimed to investigate the gastrointestinal stability and the cellular uptake chAracteristics of l-valyl-Ara-C, a peptidomimetic prodrug of Ara-C (cytArabine). After the synthesis of l-valyl-Ara-C via the incorporation of l-valine into the N4-amino group of the cytosine ring in Ara-C, the gastrointestinal stability of l-valyl-Ara-C was examined using artificial gastric juice and artificial intestinal fluids. The cellular uptake chAracteristics of l-valyl-Ara-C were also examined in Caco-2 cells. The disappeArance half-life of l-valyl-Ara-C was 2.2 h in artificial gastric juice, while the degradation of l-valyl-Ara-C was negligible in artificial intestinal fluid and also in the supernatant above the Caco-2 cell monolayer during the 2-h incubation. The cellular accumulation of l-valyl-Ara-C was 5-fold higher than that of Ara-C in Caco-2 cells. Furthermore, the cellular uptake of l-valyl-Ara-C did not increase proportionally to the increase in drug concentration. The cellular accumulation of l-valyl-Ara-C was significantly reduced in the presence of uridine, p-aminohippurate, tetraethylammonium and small dipeptides, while it was not changed in the presence of l-valine and benzoic acid, suggesting that l-valyl-Ara-C could interact with multiple uptake transporters, including peptide transporters, organic anion and cation transporters and nucleoside transporters, but might not interact with amino acid transporters. In conclusion, l-valyl-Ara-C could be effective to improve the oral absorption of Ara-C via the carrier-mediated transport pathway.
Edward F. Knol - One of the best experts on this subject based on the ideXlab platform.
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2S protein Ara h 7.0201 has unique epitopes compared to other Ara h 7 isoforms and is compArable to 2S proteins Ara h 2 and 6 in basophil degranulation capacity.
Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology, 2018Co-Authors: Simone M Hayen, Waltraud Suer, Edward F. Knol, André C. Knulst, Anna M. Ehlers, C.f. Den Hartog Jager, Johan Garssen, Linette E.m. Willemsen, H. G. OttenAbstract:Background: Screening for specific IgE against 2S albumin proteins Ara h 2 and 6 has good positive predictive value in diagnosing peanut allergy. From the third 2S member Ara h 7, 3 isoforms have been identified. Their allergenicity has not been elucidated. Objective: This study investigated the allergenicity of Ara h 7 isoforms compared to Ara h 2 and 6. Methods: Sensitization of 15 DBPCFC-confirmed peanut-allergic patients to recombinant Ara h 2.0201, Ara h 6.01 and isoforms of recombinant Ara h 7 was determined by IgE immunoblotting strips. A basophil activation test (BAT) was performed in 9 patients to determine IgE-cross-linking capacities of the allergens. Sensitivity to the allergens was tested in 5 patients who were sensitized to at least 1 Ara h 7 isoform, by a concentration range in the BAT. 3D prediction models and sequence alignments were used to visualize differences between isoforms and to predict allergenic epitope regions. Results: Sensitization to Ara h 7.0201 was most frequent (80%) and showed to be equally potent as Ara h 2.0201 and 6.01 in inducing basophil degranulation. Sensitization to Ara h 7.0201 together with Ara h 2.0201 and/or 6.01 was observed, indicating the presence of unique epitopes compared to the other 2 isoforms. Differences between the 3 Ara h 7 isoforms were observed in C-terminal cysteine residues, pepsin and trypsin cleavage sites and 3 single amino acid substitutions. Conclusion & clinical relevance: The majority of peanut-allergic patients are sensitized to isoform Ara h 7.0201, which is functionally as active as Ara h 2.0201 and 6.01. Unique epitopes are most likely located in the C-terminus or an allergenic loop region which is a known allergenic epitope region for Ara h 2.0201 and 6.01. Due to its unique epitopes and allergenicity, it is an interesting candidate to improve the diagnostic accuracy for peanut allergy.
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Specific IgE to peanut 2S albumin Ara h 7 has a discriminative ability compArable to Ara h 2 and 6.
Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology, 2017Co-Authors: Mark A. Blankestijn, Henny G. Otten, Waltraud Suer, Alf Weimann, Edward F. Knol, André C. KnulstAbstract:Background Little is known on the clinical relevance of peanut 2S albumin Ara h 7. Objective To investigate the discriminative ability of Ara h 7 in peanut allergy and assess the role of cross-reactivity between Ara h 2, 6 and Ara h 7 isoforms. Methods Sensitization to recombinant peanut storage proteins Ara h 1, 2, 3, 6 and 7 was assessed using a line blot in sera from 40 peanut tolerant and 40 peanut allergic patients, based on food challenge outcome. A dose-dependent ELISA inhibition experiment was performed with recombinant Ara h 2, 6 and Ara h 7 isoforms. Results For Ara h 7.0201 an area under the ROC curve was found of 0.83, compArable to Ara h 2 (AUC 0.81) and Ara h 6 (AUC 0.85). Ara h 7 intensity values strongly correlated with those from Ara h 2 and 6 (rs=0.81). Of all patients sensitized to 2S albumins Ara h 2, 6 or 7, the majority was co-sensitized to all three (n=24, 68%), although mono-sensitization to either 2S albumin was also observed in selected patients (Ara h 2: n=6, 17%; Ara h 6: n=2, 6%; Ara h 7: n=2, 6%). Binding to Ara h 7.0101 could be strongly inhibited by Ara h 7.0201, but not the other way around. Conclusions & Clinical Relevance Specific IgE against Ara h 7.0201 has a predictive ability for peanut allergy similar to Ara h 2 and 6, and possesses unique IgE epitopes as well as epitopes shared between the other Ara h 7 isoform and Ara h 2 and 6. While co-sensitization to all three 2S albumins is most common, mono-sensitization to either Ara h 2, 6 or 7 occurs in selected patients, leading to a risk of misdiagnosis when testing for a single 2S albumin. This article is protected by copyright. All rights reserved.
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children with peanut allergy recognize predominantly Ara h2 and Ara h6 which remains stable over time
Clinical & Experimental Allergy, 2007Co-Authors: Annebeth E Flinterman, André C. Knulst, Stef J Koppelman, E Van Hoffen, C Den Hartog F Jager, Carla A F M Bruijnzeelkoomen, Suzanne G M A Pasmans, M O Hoekstra, Edward F. KnolAbstract:Background: In peanut-allergic adults, IgE is mainly directed to Ara h1 and Ara h2. More recently, a role for Ara h6 has been suggested. In contrast to adults, IgE in children can fluctuate over time. Therefore, children may have a more dynamic reactivity to peanut. Objective: To examine the IgE reactivity to major peanut allergens in peanut-allergic children at two subsequent time-points. Methods: Twenty children (3-15 years old) with peanut allergy, confirmed by a double-blind placebo-controlled food challenge (DBPCFC), were included. Just before and 20 months after DBPCFC, IgE reactivity to purified Ara h1, Ara h2, Ara h3 and Ara h6 was studied by immunoblots and skin prick tests (SPTs). Results: Before DBPCFC, all peanut-allergic children showed IgE reactivity to Ara h2; Ara h6 was recognized by 16 children, and Ara h1 and Ara h3 by 10 children. After 20 months, peanut-specific IgE levels (median 23 kU/L) and the individual recognition of major allergens were compArable with the levels and recognition before challenge (median 28.2 kU/L). SPT with Ara h2 and Ara h6 was positive in most children, whereas SPT with Ara h1 and Ara h3 was positive in approximately half of the children. Ara h6 induced the largest weals. None of the pArameters were related to the severity of peanut allergy. Conclusion: Ara h2 and Ara h6 are the most frequently recognized major peanut allergens in children. The individual reactivity to the major peanut allergens remained stable over time, despite DBPCFC. © 2007 Blackwell Publishing Ltd.
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does skin prick test reactivity to purified allergens correlate with clinical severity of peanut allergy
Clinical & Experimental Allergy, 2007Co-Authors: K A B M Peeters, Edward F. Knol, Stef J Koppelman, E Van Hoffen, C W H Van Der Tas, C Den Hartog F Jager, Andre Penninks, Susan L Hefle, Carla A F M Bruijnzeelkoomen, André C. KnulstAbstract:Background: Recognition of specific peanut allergens or the diversity of IgE binding to peanut allergens may play a role in the elicitation of severe allergic reactions. Objective: To investigate whether sensitization to individual allergens Ara h 1, Ara h 2, Ara h 3 and Ara h 6 is correlated with clinical severity. Methods: The reactivity of purified peanut allergens was measured by skin prick test (SPT) and by IgE immunoblot in 30 patients. The results were related to the clinical reactivity by history, and in 25 of them to the eliciting dose (ED). Results: The majority of patients recognized Ara h 2 and Ara h 6. Patients with severe symptoms had a higher SPT response to Ara h 2 and Ara h 6 at low concentrations (0.1 μg/mL) and to Ara h 1 and Ara h 3 at higher concentrations (100 μg/mL), compared with patients with mild symptoms. They also recognized a greater number of allergens and showed a higher cumulative SPT response compared with patients with mild symptoms. No significant differences were observed between patients with a low or high ED. Conclusions: Ara h 2 and Ara h 6 appeared to be more potent than Ara h 1 and Ara h 3. Both SPT reactivity to low concentrations of Ara h 2 and Ara h 6 and to higher concentrations of Ara h 1 and Ara h 3 were shown to be indicative of severe symptoms. © 2007 Blackwell Publishing Ltd.
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Purification and IgE-binding properties of peanut allergen Ara h 6: Evidence for cross-reactivity with Ara h2
Journal of Allergy and Clinical Immunology, 2004Co-Authors: Stef J Koppelman, André C. Knulst, Susan L Hefle, G.a.h. De Jong, M. Ertmann, M. Wensing, Edward F. KnolAbstract:Abstract Rationale IgE-binding peanut proteins smaller than 15 kDa were previously identified as potential allergens in the majority of a peanut allergic population. We chAracterized the novel allergen and determined whether it was similar to one of the thus far identified recombinant peanut allergens (Ara h1 -7). Methods The IgE-binding protein of Results The purified protein is a monomeric protein with a molecular weight of 14,981 Da as determined with MALDI-TOF mass-spectroscopy. The amino acid sequence of the first 39 N-terminal residues is identical to that of Ara h6, indicating that the allergen is Ara h6. It is recognized by 20 out of 30 peanut-allergic patients on IgE-immunoblot, and its potent biological functionality is demonstrated by the release of histamine from basophils, even at concentrationsbelow 10 pg/ml. Ara h6 has homology with Ara h2, especially in the mid part and the C-terminal part of the protein. Almost complete inhibition of IgE-Ara h6 interaction with Ara h2 demonstrates that at least part of the epitopes of Ara h6 is cross-reactive with epitopes on Ara h2. The partial inhibition of Ara h2-IgE interaction with Ara h6 indicates that next to shared epitopes, unique IgE-binding epitopes on Ara h2 exists. Conclusions Peanut-derived Ara h 6 is a biologically active allergen recognized by the majority of our patient population.