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Hugh A. Sampson - One of the best experts on this subject based on the ideXlab platform.
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dietary baked egg accelerates resolution of egg allergy in children
The Journal of Allergy and Clinical Immunology, 2012Co-Authors: Stephanie A Leonard, Hugh A. Sampson, Scott H. Sicherer, Sally Noone, Erin Moshier, James Godbold, Anna NowakwegrzynAbstract:Background Baked egg is tolerated by a majority of egg-allergic children. Objective To characterize immunologic changes associated with ingestion of baked egg and evaluate the role that baked egg diets play in the development of tolerance to regular egg. Methods Egg-allergic subjects who tolerated baked egg challenge incorporated baked egg into their diet. Immunologic parameters were measured at follow-up visits. A comparison group strictly avoiding egg was used to evaluate the natural history of the development of tolerance. Results Of the 79 subjects in the intent-to-treat group followed for a median of 37.8 months, 89% now tolerate baked egg and 53% now tolerate regular egg. Of 23 initially baked egg–reactive subjects, 14 (61%) subsequently tolerated baked egg and 6 (26%) now tolerate regular egg. Within the initially baked egg–reactive group, subjects with persistent reactivity to baked egg had higher median baseline egg white (EW)-specific IgE levels (13.5 kU A /L) than those who subsequently tolerated baked egg (4.4 kU A /L; P = .04) and regular egg (3.1 kU A /L; P = .05). In subjects ingesting baked egg, EW-induced skin prick test wheal diameter and EW-, ovalbumin-, and Ovomucoid-specific IgE levels decreased significantly, while ovalbumin- and Ovomucoid-specific IgG 4 levels increased significantly. Subjects in the per-protocol group were 14.6 times more likely than subjects in the comparison group ( P P Conclusion Initiation of a baked egg diet accelerates the development of regular egg tolerance compared with strict avoidance. Higher serum EW-specific IgE level is associated with persistent baked and regular egg reactivity, while initial baked egg reactivity is not.
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Immunologic changes in children with egg allergy ingesting extensively heated egg.
Journal of Allergy and Clinical Immunology, 2008Co-Authors: Heather Lemon-mulé, Hugh A. Sampson, Scott H. Sicherer, Wayne G. Shreffler, Sally Noone, Anna Nowak-wegrzynAbstract:Background Prior studies have suggested that heated egg might be tolerated by some children with egg allergy. Objective We sought to confirm tolerance of heated egg in a subset of children with egg allergy, to evaluate clinical and immunologic predictors of heated egg tolerance, to characterize immunologic changes associated with continued ingestion of heated egg, and to determine whether a diet incorporating heated egg is well tolerated. Methods Subjects with documented IgE-mediated egg allergy underwent physician-supervised oral food challenges to extensively heated egg (in the form of a muffin and a waffle), with tolerant subjects also undergoing regular egg challenges (in a form of scrambled egg or French toast). Heated egg–tolerant subjects incorporated heated egg into their diets. Skin prick test wheal diameters and egg white, ovalbumin, and Ovomucoid IgE levels, as well as ovalbumin and Ovomucoid IgG4 levels, were measured at baseline for all subjects and at 3, 6, and 12 months for those tolerant of heated egg. Results Sixty-four of 117 subjects tolerated heated egg, 23 tolerated regular egg, and 27 reacted to heated egg. Heated egg–reactive subjects had larger skin test wheals and greater egg white–specific, ovalbumin-specific, and Ovomucoid-specific IgE levels compared with heated egg– and egg-tolerant subjects. Continued ingestion of heated egg was associated with decreased skin test wheal diameters and ovalbumin-specific IgE levels and increased ovalbumin-specific and Ovomucoid-specific IgG4 levels. Conclusions The majority of subjects with egg allergy were tolerant of heated egg. Continued ingestion of heated egg was well tolerated and associated with immunologic changes that paralleled the changes observed with the development of clinical tolerance to regular egg.
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specificity of ige antibodies to sequential epitopes of hen s egg Ovomucoid as a marker for persistence of egg allergy
Allergy, 2007Co-Authors: Kirsi M Jarvinen, Kirsten Beyer, Leticia Vila, Ludmilla Bardina, Michelle Mishoe, Hugh A. SampsonAbstract:Background: Approximately two-thirds of egg-allergic infants become tolerant within the first 5 years of life. Objective: We sought (1) to compare the recognition of sequential (linear) and conformational binding sites of Ovomucoid, ovalbumin and ovotransferrin, by IgE antibodies of children with persistent and transient egg allergy, (2) to identify immunodominant IgE-and IgG-binding epitopes of Ovomucoid, and (3) to compare epitope-specificity of IgE antibodies between patients with differing natural histories of egg allergy. Methods: Using immunodot-blots or ImmunoCAPs, IgE-antibodies against conformational (native) and sequential (reduced and alkylated) egg proteins were determined at the time of clinical reactivity in patients who retained their allergy and in those who developed clinical tolerance. IgE- and IgG-binding epitopes were mapped for Ovomucoid using overlapping decapeptides on SPOTs membranes. Recognition of the major IgE-binding epitopes were compared between patients with differing natural histories of egg allergy. Results: The patients with long-lasting egg allergy had a higher concentrations of IgE antibodies against sequential and native Ovomucoid and ovalbumin than the children who subsequently gained tolerance (P < 0.01). Four major IgE-binding epitopes were identified in Ovomucoid at amino acid 1–10, 9–20, 47–56, and 113–124. IgE antibodies of all seven patients with persistent egg allergy recognized these epitopes whereas none of the 11 children who outgrew their egg allergy did so. Conclusions: Patients with persistent egg allergy develop IgE antibodies against more sequential and conformational epitopes of Ovomucoid and ovalbumin. The presence of serum IgE antibodies to specific sequential epitopes of Ovomucoid may be used as a screening instrument for persistent egg allergy.
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allergenic properties of Ovomucoid in man
Journal of Immunology, 1997Co-Authors: Sara K Cooke, Hugh A. SampsonAbstract:Ovomucoid, the dominant allergen in hen's egg, is a highly glycosylated protein comprising 186 amino acids arranged in three tandem domains (Gal d 1.1, 1.2, and 1.3). The purpose of this study was to evaluate the allergenic properties of Ovomucoid. The three Ovomucoid domains were isolated and evaluated with sera from egg allergic patients to determine B cell domain specificity, B cell epitopes, and the relative importance of linear and conformational structures and carbohydrate chains to B cell epitopes. Peripheral blood T cells from egg allergic patients were used to evaluate T-dominant domains and reactivity to reduced and oxidized Ovomucoid. There was significantly more IgE activity to the second Ovomucoid domain (median percentage of Ovomucoid-specific IgE: Gal d 1.2, 40%; Gal d 1.1, 23%; Gal d 1.3, 26%). Quantities of patient IgG Ab were comparable for all three domains. Five IgE and seven IgG binding regions were identified. IgE Ab binding to reduced Ovomucoid and IgG binding to oxidized Ovomucoid were significantly reduced compared with that to native Ovomucoid (28 and 69%, respectively). Peripheral blood T cells of 21 of 33 patients reacted to Gal d 1.3, 18 of 33 reacted to Gal d 1.2, and 18 of 33 reacted to Gal d 1.1. T cell proliferation in vitro in response to reduced and oxidized Ovomucoid were significantly greater than that in response to the native protein. These results indicate a dichotomy between T and B cell domain dominance, and the presence of both unique and common IgE and IgG epitopes. Furthermore, the results suggest that conformational B cell epitopes play a more significant role in Ovomucoid allergenicity than previously appreciated, and that carbohydrate moieties have a minor effect on allergenicity.
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characterization of Ovomucoid specific t cell lines and clones from egg allergic subjects
Pediatric Allergy and Immunology, 1996Co-Authors: Philippe Eigenmann, Shau Ku Huang, Hugh A. SampsonAbstract:In the pathogenesis of allergic reactions, T cells and cytokines play a major role. However, characterizations of food allergen-specific T cells are very limited. In this study, we screened the peripheral blood mononuclear cells (PBMC) of 14 patients for reactivity to Ovomucoid (Gal d I), the major hen's egg allergen, and ovalbumin (Gal d II). Cell lines and clones specific to Ovomucoid were generated from PBMC of four egg-allergic subjects, in order to study antigen domain specificity and cell cytokine production profiles. The results demonstrated, firstly, that egg-allergic patients respond to Ovomucoid rather than to ovalbumin, and secondly, that antigen specificity is predominantly directed toward the second and third domains of Ovomucoid. The T-cell cytokine message was characterized by reverse transcrip-tase polymerase chain reaction (RT-PCR). Cell lines and clones from all four patients consistently expressed interleukin (IL)-5. IL-4, IL-13. and in-terferon-gamma were found to be expressed only by certain lines or clones. This observation suggests a central pathogenic role for IL-5 in food allergy-related symptoms.
Yoshinori Mine - One of the best experts on this subject based on the ideXlab platform.
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genetically glycosylated Ovomucoid third domain can modulate immunoglobulin e antibody production and cytokine response in balb c mice
Clinical & Experimental Allergy, 2007Co-Authors: P Rupa, Soichiro Nakamura, Yoshinori MineAbstract:BACKGROUND Food allergies are on the rise and it is estimated that in North America, 8% of the children and 4% of the adults have food allergies. Food allergies tend to occur more often in children than in adults due to their immature digestive and immune systems. Hen's egg is among the most common cause of food-induced allergic reactions in North America. OBJECTIVE The present study was undertaken to investigate the role of N-glycans of the third domain of Ovomucoid in IgE binding and modulation of allergen-specific immune response in BALB/c mice. METHODS The cDNA encoding the third domain of Ovomucoid was inserted into the yeast genome and expressed in Pichia pastoris X-33 cells, under the control of the glyceraldehyde-3-phosphate (GAP) dehydrogenase promoter for constitutive expression to obtain a post-translationally modified and functionally active Ovomucoid third domain. Upon expression, the protein was secreted into the extracellular medium and was purified by size exclusion chromatography. The recombinant protein was produced at 10 mg/L of the culture supernatant. BALB/c mice were sensitized with the recombinant and native forms of glycosylated Ovomucoid third domain antigen. The allergic response of the native and the recombinant glycosylated forms of Ovomucoid third domain antigens were compared using antibody and cytokine measurements. RESULTS ELISA tests indicated a significant decrease in specific IgE antibodies to the recombinant N-linked glycosylated form (P-Gly), when compared with the native glycosylated form (DIII+) using mice sera. Immunization with P-Gly induced the production of IFN-gamma [T-helper type 1 (Th1) response] and lowered the production of IL-4 (Th2 response), and a skewed balance towards the Th1 cytokine demonstrated that P-Gly has a modulating ability on Th1/Th2 balance to down-regulate Th2 response. Furthermore, N-linked glycan (N28) in the third domain of Ovomucoid was shown to be associated with suppression of the allergic response. CONCLUSION Therefore, we can conclude that P-Gly facilitates and contributes to the discovery of new molecular target for the development of a safe and specific therapeutic vaccine for the treatment of egg allergy, and oligosaccharides do seem to play a major role in the suppression of IgE-binding activity.
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engineered recombinant Ovomucoid third domain can modulate allergenic response in balb c mice model
Biochemical and Biophysical Research Communications, 2006Co-Authors: P Rupa, Yoshinori MineAbstract:IgE-mediated allergic reactions to egg white are a serious health problem and Ovomucoid being the dominant egg white allergen has been on focus in the past decade. Engineered hypoallergens with reduced reactivity for IgE antibodies are being examined to modulate the allergic response and develop prophylactic allergen vaccines. In this study, we evaluated the immunomodulatory effect of a genetic variant of the third domain of Ovomucoid (GMFA) which showed reduced IgE binding with egg allergic patient's sera in comparison to the native form of the third domain of Ovomucoid (DIII) in a murine model system. Balb/c mice were injected intraperitoneally with DIII and GMFA antigens. Allergen-specific serum IgG, IgG1, IgG2a, and IgE responses were evaluated using enzyme-linked immunosorbent assay. Splenocyte cytokine levels in the medium of the cultured cells were examined by ELISA and levels of IL-4, INF-gamma, and IL-12 (p70) cytokines were quantified. Neutralization with anti-IL-12 monoclonal antibody was assayed and cytokine levels with respect to GMFA mutant antigen stimulation were measured. GMFA mutant form was found to have significantly reduced levels of specific IgE when compared to the DIII suggesting a mutation-induced abrogation of the IgE binding epitope in mice. The increase in IgG2a levels in GMFA together with the decline of IgE and IgG1 points to a shift from a Th2 response to a Th1 dominated response. The cytokine profile showed a modulation of anti-allergic Th1 phenotype in GMFA from a proallergic Th2 response observed with DIII. Low levels of IL-4 and increased levels of INF-gamma and IL-12 were observed and anti-IL-12 monoclonal antibody restored the levels of IL-4 and suppressed levels of INF-gamma and IL-12 in the GMFA sensitized group. These results indicate that GMFA has a marked suppressive effect on the allergic response of Ovomucoid and caused a shift towards a Th1 pathway, thereby modulating the Th1/Th2 cytokine balance and could be used as a potential hypoallergenic candidate for allergen-immunotherapy in the treatment of egg white allergy.
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reduction of antigenicity and allergenicity of genetically modified egg white allergen Ovomucoid third domain
Biochemical and Biophysical Research Communications, 2003Co-Authors: Yoshinori Mine, Erika Sasaki, Jie Wei ZhangAbstract:Abstract Ovomucoid (Gal d1) is a major allergen in hen egg white, consisting of three tandem domains. In this study, five genetically modified third domain (DIII) mutants, which were substituted single or double amino acids within its IgE and IgG epitopes were compared with those prepared and their antigenicity and allergenicity with native analogue using Western immunoblot and enzyme-linked immunosorbent assay. The replacement of phenylalanine at 37 (F37) position with methionine caused drastical loss of IgG and IgE binding activities of human sera derived from egg allergic patients as well as disruption of the α-helix structure which comprises a part of the IgG and IgE epitopes. Substituting glycine at 32 position in conjunction with F37 showed a synergistic effect of decreasing antigenicity. The present study indicated that glycine 32 and phenylalanine 37 have an important role on its antigenicity and allergenicity as well as structural integrity of Ovomucoid DIII.
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identification and fine mapping of igg and ige epitopes in Ovomucoid
Biochemical and Biophysical Research Communications, 2002Co-Authors: Yoshinori Mine, Jie Wei ZhangAbstract:Ovomucoid is a major allergen in hen egg white which causes a serious IgE-mediated food allergy reaction. This study determined eight IgG epitopes, 5-11 amino acids in length, and nine IgE epitopes, 5-16 amino acids in length, within the primary sequence in Ovomucoid using arrays of overlapping peptides synthesized on cellulose membranes. Pooled sera from eight egg-allergic patients were used to probe the membrane. We also analyzed the amino acids that are critical for antibody binding by substituting a single amino acid within each epitope. Mutational analysis of the epitopes indicated that charged amino acids (aspartic acid, glutamic acid, and lysine) and some hydrophobic (leucine, phenylalanine, and glycine) and polar (serine, threonine, tyrosine, and cystein) amino acids were important for antibody binding. These results provide useful information for the molecular design necessary to reduce the allergenicity of Ovomucoid, and a better understanding of structure-function relationships of allergic epitopes in food proteins.
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immunochemical and structural analysis of pepsin digested egg white Ovomucoid
Journal of Agricultural and Food Chemistry, 2000Co-Authors: Jennifer Kovacsnolan, Jie Wei Zhang, Shigeru Hayakawa, Yoshinori MineAbstract:Ovomucoid, an egg protein comprising ∼10% egg white, was digested using the enzyme pepsin, and fragments were isolated by anion-exchange and reverse phase HPLC. Four distinct fragments were identified by analysis with SDS−PAGE, including three large fragments with molecular weights of around 24, 18, and 14 kDa. N- and C-terminal and amino acid sequencing analyses identified the fragments as V134−C186 (domain 3), V21−A133, and A1−A133 (domain 1+2). Further separation and sequencing of the fraction composed of small peptides, to determine their exact makeup and location in the protein, remained to be carried out and identified a peptide G51−Y73. All four fragments showed IgE-binding activity, as measured by ELISA, using human sera from egg-allergic individuals. Little change in the digestibility of Ovomucoid by trypsin and chymotrypsin was observed following digestion with pepsin, indicating that pepsin-digested Ovomucoid retains its trypsin (protease) inhibitor activities. Reduced carboxymethylated ovomuco...
John L. Markley - One of the best experts on this subject based on the ideXlab platform.
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nmr chemical shift mapping of the binding site of a protein proteinase inhibitor changes in the 1h 13c and 15n nmr chemical shifts of turkey Ovomucoid third domain upon binding to bovine chymotrypsin aα
Journal of Molecular Recognition, 2001Co-Authors: Jikui Song, John L. MarkleyAbstract:The substrate-like inhibition of serine proteinases by avian Ovomucoid domains has provided an excellent model for protein inhibitor-proteinase interactions of the standard type. 1H,15N and 13C NMR studies have been undertaken on complexes formed between turkey Ovomucoid third domain (OMTKY3)2 and chymotrypsin Aα (Ctr) in order to characterize structural changes occurring in the Ctr binding site of OMTKY3. 15N and 13C were incorporated uniformly into OMTKY3, allowing backbone resonances to be assigned for OMTKY3 in both its free and complex states. Chemical shift perturbation mapping indicates that the two regions, K13-P22 and N33-A40, are the primary sites in OMTKY3 involved in Ctr binding, in full agreement with the 12 consensus proteinase-contact residues of OMTKY3 defined previously on the basis of X-ray crystallographic and mutational analysis. Smaller chemical shift perturbations in selected other regions may result from minor structural changes on binding. Through-bond 15N–13C correlations between P1-13C′ and P1′-15N in two-dimensional H(N)CO and HN(CO) NMR spectra of selectively labeled OMTKY3 complexed with Ctr indicate that the scissile peptide bond between L18 and E19 of the inhibitor is intact in the complex. The chemical shifts of the reactive site peptide bond indicate that it is predominantly trigonal, although the data are not inconsistent with a slight perturbation of the hybridization of the peptide bond toward the first tetrahedral state along the reaction coordinate. Copyright © 2001 John Wiley & Sons, Ltd. Abbreviations used: BPTI bovine pancreatic trypsin inhibitor, Swiss-Prot P00974 Ctr bovine chymotrypsin Aα Swiss-Prot P00766 OMTKY3 third domain of the proteinase inhibitor (Ovomucoid) from turkey (Meleagris gallopavo), Swiss-Prot P01004 SSI streptomyces subtilisin inhibitor, Swiss-Prot P01006 STI soybean trypsin inhibitor, Swiss-Prot P01071.
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nmr chemical shift mapping of the binding site of a protein proteinase inhibitor changes in the 1 h 13 c and 15 n nmr chemical shifts of turkey Ovomucoid third domain upon binding to bovine chymotrypsin a alpha
Journal of Molecular Recognition, 2001Co-Authors: Jikui Song, John L. MarkleyAbstract:The substrate-like inhibition of serine proteinases by avian Ovomucoid domains has provided an excellent model for protein inhibitor-proteinase interactions of the standard type. 1H,15N and 13C NMR studies have been undertaken on complexes formed between turkey Ovomucoid third domain (OMTKY3)2 and chymotrypsin A(alpha) (Ctr) in order to characterize structural changes occurring in the Ctr binding site of OMTKY3. 15N and 13C were incorporated uniformly into OMTKY3, allowing backbone resonances to be assigned for OMTKY3 in both its free and complex states. Chemical shift perturbation mapping indicates that the two regions, K13-P22 and N33-A40, are the primary sites in OMTKY3 involved in Ctr binding, in full agreement with the 12 consensus proteinase-contact residues of OMTKY3 defined previously on the basis of X-ray crystallographic and mutational analysis. Smaller chemical shift perturbations in selected other regions may result from minor structural changes on binding. Through-bond 15N-13C correlations between P1-13C' and P1'-15N in two-dimensional H(N)CO and HN(CO) NMR spectra of selectively labeled OMTKY3 complexed with Ctr indicate that the scissile peptide bond between L18 and E19 of the inhibitor is intact in the complex. The chemical shifts of the reactive site peptide bond indicate that it is predominantly trigonal, although the data are not inconsistent with a slight perturbation of the hybridization of the peptide bond toward the first tetrahedral state along the reaction coordinate.
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Protein binding chiral discrimination of HPLC stationary phases made with whole, fragmented, and third domain Turkey Ovomucoid
Analytical chemistry, 1995Co-Authors: Thomas C. Pinkerton, W. Jeffrey. Howe, Eldon L. Ulrich, Joseph P. Comiskey, Jun Haginaka, Tokiko Murashima, William F. Walkenhorst, William M. Westler, John L. MarkleyAbstract:Individual protein domains and two domains in combination were prepared by enzymatic and chemical cleavage of turkey Ovomucoid followed by isolation and purification by size-exclusion and ion-exchange chromatography. Silica bonded-phase HPLC columns were made from either whole or isolated domains of turkey Ovomucoid. The protein columns were tested for chiral recognition by their abilities to resolve enantiomers among a wide range of racemates. The columns made from whole turkey Ovomucoid displayed chiral activity toward many racemates, where as a combination of the first and second domain resolved only a selected number of aromatic weak bases. The first and second domains independently gave no appreciable chiral activity. The turkey Ovomucoid third domain exhibited enantioselective protein binding for fused-ring aromatic weak acids. Glycosylation of the third domain did not affect chiral recognition. Titration of the third domain with model compounds in conjunction with NMR measurements enabled the identification of the amino acids responsible for binding. Molecular modeling of the ligand-protein complexation provided insights into the ability of a protein surface to discriminate enantiomers on the basis of multiple intermolecular interactions.
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solution structure of turkey Ovomucoid third domain as determined from nuclear magnetic resonance data
Journal of Molecular Biology, 1994Co-Authors: Andrzej M Krezel, Prashanth Darba, Andrew D Robertson, Jasna Fejzo, Slobodan Macura, John L. MarkleyAbstract:The solution structure of the 56 amino acid residue turkey Ovomucoid third domain was determined by n.m.r. methods. Of the 661 distance constraints used in the calculations, 120 were determined by quadratic approximation of the cross-relaxation rates. The remaining constraints were crudely estimated from a more standard analysis of NOESY spectra. Additionally, 29 torsion angle constraints, 17 hydrogen bonds, and three disulfide bridges were used in the structure calculations. Stereospecific assignments were accomplished for 24 beta-methylene groups and six isopropyl methyl groups (43% chiral assignments). The addition of more accurate distance constraints to the distance geometry/simulated annealing approach resulted in a significant reduction in the dispersion of calculated backbone torsion angles and root-mean-square deviations between structures. Detailed comparisons have been made between the n.m.r. structures of OMTKY3 and published X-ray structures of the same protein and of closely related avian Ovomucoid third domains. The refinement with more accurate distance constraints reduced differences between families of the n.m.r. and the X-ray structures.
Wanda Phipatanakul - One of the best experts on this subject based on the ideXlab platform.
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Ovomucoid specific immunoglobulin e as a predictor of tolerance to cooked egg
Allergy�Rhinol (Providence), 2015Co-Authors: Lisa M Bartnikas, William J Sheehan, Carter R Petty, Lynda C Schneider, Wanda Phipatanakul, Katherine L TuttleAbstract:BackgroundOvomucoid is the dominant allergen in hen's egg. Although several studies evaluated the utility of Ovomucoid specific immunoglobulin E (sIgE) levels in predicting baked (e.g., muffin or c...
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turning up the heat on skin testing for baked egg allergy
Clinical & Experimental Allergy, 2013Co-Authors: Lisa M Bartnikas, Wanda PhipatanakulAbstract:Egg allergy is one of the most common causes of pediatric food allergy [1–3]. Egg is an important source of nutrition and commonly found in commercial food products such as baked goods. Strict avoidance of egg can impair quality of life by limiting the number of allowed foods and making social events involving food potentially dangerous, stressful and isolating. Although most children eventually tolerate egg, children are outgrowing their egg allergies later than previously reported [4]. Recent studies suggest that most egg-allergic children may tolerate baked egg products [5–9]. Identification of predictable markers to identify these patients has high potential to aid physicians in clinical management of egg allergy. The prospective study by Tan et al. [10] published in this issue of the Journal investigates the role of skin prick testing (SPT) to Ovomucoid and a baked egg muffin in predicting outcomes of baked egg challenges. The authors found that SPT measurements to egg white, Ovomucoid and baked egg were significantly larger in those who failed baked egg challenges, compared to those who passed. Their results regarding egg white SPT are in agreement with previously reported data [7–9, 11]. The findings that Ovomucoid and baked egg SPT may be useful in predicting baked egg challenge outcome are novel. Ovomucoid, the dominant allergen in egg white, is relatively stable to thermal processing and proteolysis, which may explain its importance as an allergen [12]. As such, several studies have also demonstrated the potential importance of immune response to Ovomucoid in predicting baked egg tolerance [8, 11, 13–15], but its true utility is controversial. We have recently shown that while Ovomucoid specific IgE (sIgE) predicts outcomes of baked egg challenges, it is not superior to egg white sIgE or SPT, which remain useful predictors of baked egg tolerance [9]. Baking exposes proteins to high temperatures, which may reduce allergenicity by destroying conformational epitopes. In addition, allergenicity may be decreased by blocking epitope access through interaction with other food proteins, such as in a wheat matrix in a baked muffin [16]. There is presently no diagnostic test available to assess immune response to the egg proteins in a wheat complex, which represents a significant knowledge gap in current clinical practice. The utility of SPT to baked egg has been investigated in a small retrospective study and a negative SPT to baked egg was found to predict passing a baked egg challenge, but predictive values of positive SPTs were not further explored [17]. SPT can be performed quickly and inexpensively, making this test available to many practicing allergists. Unfortunately, Ovomucoid SPT extract is not currently commercially available in certain countries such as the United States. SPT to fresh muffin may best reflect the degree of egg protein modification that a patient is exposed to in a baked egg challenge. Therefore, SPT to baked egg may prove to be an important predictor of baked egg challenge outcome. SPT to the fresh baked good may also be useful in identifying children who may be tolerant to heated but even less well-baked forms of egg. SPT to brownies, meatballs, pancakes or even gooey cookies may be on the horizon of allergy testing. This study is limited in several aspects that suggest the need for future studies. Egg allergy was defined based on history of reported reaction to egg and/or positive testing, rather than a formal physician-observed food challenge, and not all children had a history of reactions to egg. Food challenges to investigate whether the children who passed baked egg challenges could also consume unheated egg were not done. Since baked egg SPT was done by creating a homogenate of the muffin, it is possible that concentrations and modifications of egg proteins may vary depending on what portion of the muffin was sampled (e.g., crust versus inner layer). Direct comparisons between other existing SPT and sIgE tests were not done to analyse whether one test was superior. So, while potentially useful, Ovomucoid and baked egg SPT should not replace other existing testing methods. Nevertheless, this study adds to the growing body of literature aimed at identifying predictors of baked egg challenge outcomes. SPT to baked egg and Ovomucoid are novel and potentially useful ways to rapidly and inexpensively identify children who may pass a baked egg challenge. The utility of baked egg and Ovomucoid SPT needs to be evaluated further before recommending these tests for the diagnosis of baked egg allergy in clinical practice.
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Ovomucoid is not superior to egg white testing in predicting tolerance to baked egg
The Journal of Allergy and Clinical Immunology: In Practice, 2013Co-Authors: Lisa M Bartnikas, William J Sheehan, Katherine Larabee, Carter R Petty, Lynda C Schneider, Wanda PhipatanakulAbstract:Background Children with egg allergy may tolerate baked egg products. Ovomucoid specific IgE (sIgE) antibody levels have been suggested to predict outcomes of baked egg challenges. Objective We determined the relationship of Ovomucoid and egg white sIgE levels and egg white skin prick test (SPT) wheal size with baked egg challenge outcome. Methods Retrospective review of 1186 patients who underwent Ovomucoid sIgE blood testing. Subset analysis was of 169 patients who underwent baked egg food challenges. Results Egg white sIgE, Ovomucoid sIgE, and egg white SPT were different among those eating regular egg, eating baked egg only, or avoiding all egg ( P 90% predictive values for passing baked egg challenge for egg white sIgE, Ovomucoid sIgE, and egg white SPT. No patient with egg white SPT wheal P = .301). Conclusion Most children with egg allergy in this study passed baked egg challenges. Ovomucoid sIgE, although a useful clinical predictor of baked egg tolerance, was not superior to egg white SPT or sIgE in predicting outcome of baked egg challenge.
Michael Laskowski - One of the best experts on this subject based on the ideXlab platform.
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despite having a common p1 leu eglin c inhibits α lytic proteinase a million fold more strongly than does turkey Ovomucoid third domain
Biochemistry, 2006Co-Authors: M A Qasim, Robert L Van Etten, Tina Yeh, Charles W Saunders, Philip J Ganz, Sabiha Qasim, L Wang, Michael LaskowskiAbstract:Results of the inhibition of α-lytic proteinase by two standard mechanism serine proteinase inhibitors, turkey Ovomucoid third domain (OMTKY3) and eglin C, and many of their variants are presented....
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what can the structures of enzyme inhibitor complexes tell us about the structures of enzyme substrate complexes
Biochimica et Biophysica Acta, 2000Co-Authors: Michael Laskowski, Maram Al I. QasimAbstract:Proteinases perform many beneficial functions that are essential to life, but they are also dangerous and must be controlled. Here we focus on one of the control mechanisms: the ubiquitous presence of protein proteinase inhibitors. We deal only with a subset of these: the standard mechanism, canonical protein inhibitors of serine proteinases. Each of the inhibitory domains of such inhibitors has one reactive site peptide bond, which serves all the cognate enzymes as a substrate. The reactive site peptide bond is in a combining loop which has an identical conformation in all inhibitors and in all enzyme–inhibitor complexes. There are at least 18 families of such inhibitors. They all share the conformation of the combining loops but each has its own global three-dimensional structure. Many three-dimensional structures of enzyme–inhibitor complexes were determined. They are frequently used to predict the conformation of substrates in very short-lived enzyme–substrate transition state complexes. Turkey Ovomucoid third domain and eglin c have a Leu residue at P1. In complexes with chymotrypsin, these P1 Leu residues assume the same conformation. The relative free energies of binding of P1 Leu (relative to either P1 Gly or P1 Ala) are within experimental error, the same for complexes of turkey Ovomucoid third domain, eglin c, P1 Leu variant of bovine pancreatic trypsin inhibitor and of a substrate with chymotrypsin. Therefore, the P1 Leu conformation in transition state complexes is predictable. In contrast, the conformation of P1 Lys+ is strikingly different in the complexes of Lys18 turkey Ovomucoid third domain and of bovine pancreatic trypsin inhibitor with chymotrypsin. The relative free energies of binding are also quite different. Yet, the relative free energies of binding are nearly identical for Lys+ in turkey Ovomucoid third domain and in a substrate, thus allowing us to know the structure of the latter. Similar reasoning is applied to a few other systems.
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arg15 lys17 arg18 turkey Ovomucoid third domain inhibits human furin
Journal of Biological Chemistry, 1993Co-Authors: Wenlei Zhang, S S Molloy, G Thomas, K Ryan, Yiwen Chiang, S Anderson, Michael LaskowskiAbstract:Turkey Ovomucoid third domain with Leu18 in its reactive site is a potent inhibitor of many serine proteinases: subtilisins, chymotrypsins, and elastases. Previous studies showed that an L18K mutation made it a moderately strong inhibitor of trypsin, while an L18E mutation made it a strong inhibitor of Glu-specific Streptomyces griseus proteinase (GluSGP). For human furin substrates the consensus optimal sequence is RXKR decreases. Therefore the A15R, T17K, and L18R mutations were made in turkey Ovomucoid third domain. The mutant inhibits human furin with a Ka of 1.1 x 10(7) M-1. As human furin catalyzes an obligatory step in human immunodeficiency virus proliferation, this inhibitor, along with the others already available, deserves further study.
