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Introduction and Objectives: It was urgent to explain the role of egg yolk allergen sensitization to the egg allergic population and we would evaluate the diagnostic value of allergen components in whole eggs, including egg white and egg yolk., Materials and Methods: Firstly, we collected 99 positive and 21 negative sera against egg allergy. Then we used modified enzyme linked immunosorbent assay (ELISA) to survey specific IgE (sIgE) to all-proven and single component in eggs, Ovomucoid (Gal d 1), Ovalbumin (Gal d 2), Ovotransferrin (Gal d 3), Lysozyme C (Gal d 4), Serum Albumin (Gal d 5), and YGP42(Gal d 6) in allergic and non-allergic populations. Last but not least, we studied the sIgE reactivities to egg allergen components by receiver operating characteristic (ROC) analysis., Results: Among egg-allergic individuals, nearly 10% were sensitized to five of six egg allergen components, and the cross-reaction frequency between two egg yolk allergens with Gal d 1 was about 30% in the groups diagnosed with egg allergy or non-allergy. The best component-combination diagnosis in egg allergy of Gal d 1+ Gal d 6 demonstrated the largest area under curve (AUC) of 0.994., Conclusions: Our results suggested that there were individual differences in allergenicity of different egg allergen components, especially in the samples negative to egg allergy diagnosed but sensitive to egg yolk components. It was indicated that component resolved diagnosis of egg yolk improved the value for egg allergy management indispensably.

Ovotransferrin (OVT) is one of the main egg allergens with 2 iron-binding sites. Several studies have demonstrated that iron-chelation decreased the allergenicity of milk allergen and birch pollen allergens. Therefore, we hypothesized that iron-chelation could also reduce the allergenicity of OVT. Apo-OVT (iron-free OVT, the natural state in egg white) and Holo-OVT (iron-chelated OVT) were prepared, and the allergenicity of them were assessed and compared using a BALB/c mouse model as well as dendritic cells (DCs) based on antigen uptake. Mice were orally sensitized with Apo-OVT or Holo-OVT using cholera toxin as adjuvant. Clinical signs of allergy, morphological structure of jejunum, specific antibody levels, mast cell protease-1 (mMCP-1) concentrations, cytokines and antigen uptake by DCs were determined after the mice were challenged with Apo-OVT or Holo-OVT. Results showed that both Apo-OVT and Holo-OVT induced intestinal allergy, but no systematic allergic symbols were observed. Serum levels of mouse mast cell protease-1 (mMCP-1) and specific IgE in Apo-OVT group were lower than in control group, and no significant difference between Apo-OVT group and Holo-OVT group (P>.05). The levels of OVT-specific IgG and IgG1, as well as the Th-1 cytokine interferon gamma and Th2-type cytokine interleukin-13 in Holo-OVT sensitized mice were significantly decreased compared to Apo-OVT group (P<.05), while no significant difference with control group (P>.05). However, DCs took in less Apo-OVT than Holo-OVT. Overall, iron-induced chelation could alleviate the potential allergenicity of OVT in vivo., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Dogs with cutaneous adverse food reactions (CAFR) often have specific IgE to food allergens. Egg white, which is majorly composed of ovomucoid, ovalbumin, ovotransferrin, and lysozyme, is a food allergen in dogs. Information of the IgE reactivity to purified egg white allergens supports accurate diagnosis and efficiency treatment in humans. However, to the best of our knowledge, there have been no studies on the IgE reactivity to purified egg white allergens in dogs. Here, we investigated the IgE reactivity to crude and purified allergens of hen egg white in dogs with CAFR. First, when we examined serum samples from 82 dogs with CAFR for specific IgE to crude egg white by ELISA, 9.8% (8/82) of the dogs with CAFR showed the IgE reactivity to crude egg white. We then used sera from the eight dogs with positive IgE reactivity to crude egg white to examine the IgE reactivity to four purified allergens, ovomucoid, ovalbumin, ovotransferrin, and lysozyme, by ELISA. We found that 75% (6/8) of the dogs showed IgE reactivity to both ovomucoid and ovalbumin, and that 37.5% (3/8) of the dogs showed IgE reactivity to ovotransferrin. None (0/8) showed IgE reactivity to lysozyme. Moreover, validating these results, the immunoblot analyses were performed using the sera of the three dogs showing the highest IgE reactivity to crude egg white. Both anti-ovomucoid and anti-ovalbumin IgE were detected in the sera of these dogs, while anti-ovotransferrin IgE was not detected. Considering these, ovomucoid and ovalbumin appears to be the major egg white allergens in dogs with CAFR., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Ovotransferrin (OT), a multifunctional glycoprotein with defensive and protective activities, accounts for approximately 13% of chicken egg white proteins and is known as a major egg-associated allergen along with ovomucoid (OM). In contrast to the well-characterized N-glycans of OM, the N-glycan structure of OT has not been reported. Here, using HPLC equipped with a fluorescence detector and mass spectrometric analysis in combination with exoglycosidase digestion, we investigated the N-glycan type and branched pattern of OT, and compared them with those of OM. The HPLC peak area was used to calculate the relative quantity (%) of each glycan. Seventeen N-glycans, including 11 glycans (1 core structure and 10 complex-type oligosaccharides), that commonly exist in ovotransferrin and ovomucoid were identified. Six characteristic glycans (2 truncated structures, 1 complex-type, and 3 hybrid-type oligosaccharides) in OT and eight characteristic glycans in OM were classified. OT contains the following branched complex-type structures: mono-(13.2%), bi-(23.9%), tri-(9.0%), tetra-(2.7%), and penta-(2.8%) antennary oligosaccharides. However, OM contained mostly tri-(33.5%) and penta-(31.2%) antennary oligosaccharides. The N-glycan-containing bisecting N-acetylglucosamine comprised 43.4% and 79.8% of the total glycans in OT and OM, respectively. Moreover, using circular dichroism analysis, we observed that the secondary structure of the deglycosylated OT is quite different from that of the intact protein. To our knowledge, this is the first study to analyze N-glycans in OT in comparison with those of OM.

Background: Egg is a common cause of food-allergic reactions, especially among young children. Some egg-allergic patients do, however, tolerate heated egg products and component-resolved diagnostics (CRD) may facilitate prediction of different disease manifestations. Commercially available preparations of the egg-white allergens, ovomucoid, ovalbumin, conalbumin and lysozyme, have been reported to contain impurities which interfere with accurate CRD., Methods: Commercial preparations of the 4 egg-white allergens were characterized using allergen-specific monoclonal chimeric human/mouse IgE antibodies in experimental ImmunoCAP® tests. Further purification of commercial ovomucoid, ovalbumin and conalbumin preparations was performed by chromatography based on affinity to monoclonal antibodies. Purity was monitored by size exclusion chromatography, SDS-PAGE, Western blotting and experimental ImmunoCAP tests using allergen-specific chimeric IgE antibodies. IgE reactivity to the highly purified egg components was analyzed in 83 samples from egg white-sensitized individuals., Results: Preparations of commercially available ovomucoid, ovalbumin and conalbumin were found to contain other egg allergens which were removed by chromatographic purification. No impurities were detected in the commercial lysozyme preparation. Previously unknown complexes between the target allergens and contaminating allergens were detected and removed by affinity chromatography. IgE reactivity to ovalbumin was most common in the analyzed samples (87%), followed by ovomucoid (72%), conalbumin (69%) and lysozyme (58%)., Conclusions: In this study we demonstrate the advantage of using monoclonal antibodies for purification, and monoclonal chimeric IgE antibodies for characterization, of egg allergens intended for CRD. Our study also established that ovalbumin, ovomucoid, conalbumin and lysozyme are all major allergens., (Copyright © 2010 S. Karger AG, Basel.)

The emu (Dromaius novaehollandiae) egg is considered promising as an alternative egg product. To obtain basic biochemical information on emu egg white, the major protein compositions in emu and chicken egg whites and the primary structures of potential allergenic proteins were compared. The dominant protein in emu egg white was ovotransferrin (OVT), followed by ovalbumin (OVA) and TENP protein. The OVA and ovomucoid (OVM) levels in emu egg white were estimated as significantly lower than those in chicken egg white by Western blotting and enzyme-linked immunosorbent assays using anti-chicken OVA or OVM antibodies. Lysozyme and its enzymatic activity were not detected in emu egg white. OVT, OVA, and OVM genes were also cloned, and their nucleotide and amino acid sequences were determined. The protein sequences of OVT, OVA, and OVM from emu showed lower similarities to those of chicken than other avian species, such as quail and turkey. These results emphasize the low allergenicity of emu egg white and its potential as an alternative to chicken egg white.

Egg proteins represent one of the most important sources evoking food allergic reactions. In order to improve allergy diagnosis, purified and well-characterized proteins are needed. Although the egg white allergens Gal d 1, 2, 3 and 4 (ovomucoid, ovalbumin, ovotransferrin, and lysozyme) are commercially available, these preparations contain impurities, which affect exact in vitro diagnosis. The aim of the present study was to set up further purification protocols and to extend the characterization of the physicochemical and immunological properties of the final batches. The egg white allergens Gal d 1-4 were purified from commercial preparations, whereas Gal d 5 (alpha-livetin) was purified from egg yolk. The final batches of Gal d 1-5 consisted of a range of isoforms with defined tertiary structure. In addition, the IgE binding capacity of the purified egg allergens was tested using allergic patients' sera. The allergen batches will be further used to set up allergen specific diagnostic assays and to screen a larger collection of patients' sera.

Background: There appears to be a lack of agreement in the literature on the allergenicity of hen egg proteins. This may be partly due to the use of impure proteins in some cases. Egg yolk proteins have also been largely ignored in such studies. We therefore set out to determine, using especially purified proteins, their relative allergenicity, and to observe whether there were any relationships between their potency and the sensitivity of patients to them., Methods and Results: The sera of 40 patients with clinically observed hen egg hypersensitivity were tested for specific IgE binding to purified egg white and egg yolk proteins using the radioallergosorbent test (RAST). Statistical treatment by correspondence analysis of the percent radioactive uptakes in the RAST to the 8 proteins demonstrated that there were four distinct groups of patients reacting in a similar way to four discrete sets of proteins., Conclusions: The first three sets of allergens consisted of egg white proteins as follows: firstly, lysozyme and ovalbumin; secondly, ovomucoid; and thirdly, ovomucin. The fourth set contained the egg white protein ovotransferrin and the egg yolk proteins apovitellenins I and VI and phosvitin. The existence of patient groups may explain why various workers have reported different allergens to be important in egg hypersensitivity. A sufficiently large number of patients must be examined so as to give a representative distribution across each group, otherwise the results may be biased towards one allergen.

Background: No egg white products have been clearly proven to be hypoallergenic. The role of egg white proteins in allergic reactions to eggs is still debatable., Objective: This study was designed to determine the importance of ovomucoid, an egg white protein, in the development of allergies to egg white., Methods: We performed a double-blind, placebo-controlled food challenge in subjects with high levels of IgE antibodies for egg white to compare the allergenicities of heated and ovomucoid-depleted egg white, freeze-dried egg white, and heated egg white. Levels of IgE antibodies for egg white, ovomucoid, ovalbumin, ovotransferrin, and lysozyme were measured in serum by RAST., Results: Twenty-one of 38 subjects with positive challenge responses to freeze-dried egg white had negative challenge responses to heated egg white, whereas 16 of 17 subjects (94.1%) with positive responses to heated egg white did not respond to the heated and ovomucoid-depleted egg white challenge. The subjects with positive challenge responses to freeze-dried egg white tended to have higher IgE antibody values to ovomucoid than those with negative responses. IgE antibody levels to ovomucoid were significantly higher in subjects with positive responses to a challenge with heated egg white than in those with no response. There were no significant differences in the levels of IgE antibodies to the other proteins, except ovomucoid, in the negative-response and positive-response groups in challenge tests with freeze-dried and heated egg white., Conclusion: The heated and ovomucoid-depleted egg white preparation was less allergenic than heated or freeze-dried preparations. Ovomucoid has a more important role in the pathogenesis of allergic reactions to egg white than other proteins in egg white.