Immunological Comparison of Native and Recombinant Hen's Egg Yolk Allergen, Chicken Serum Albumin (Gal d 5), Produced in Kluveromyces lactis.

Chicken serum albumin (CSA) is a hen's egg yolk allergen causing IgE-mediated allergy. The objective of this study was to produce a recombinant version of CSA and compare its IgE reactivity to natural CSA (nCSA). CSA was cloned and expressed as a soluble fraction in the yeast Kluyveromyces lactis (K. lactis) protein expression system. The gene encoding CSA was amplified with a C-terminal hemagglutinin epitope tag by polymerase chain reaction (PCR) and cloned into the pKLAC2 expression vector prior to transforming into K. lactis. Recombinant CSA (rCSA) was purified by immunoprecipitation. Twenty-one patients allergic to hen's egg white were examined for sensitisation against nCSA. 38% of patients were found to be sensitised to CSA based on Western immunoassay. Immunoglobulin E (IgE) binding capacity of rCSA and nCSA was analysed by ELISA using sera from patients sensitised to CSA. Levels of IgE-binding were similar for both the recombinant and the natural CSA, indicating the existence of similar epitopes. rCSA produced in this study is a potential candidate to be used in component-resolved diagnosis (CRD) of egg yolk allergy. The usefulness of rCSA in CRD of egg yolk allergy warrants further characterisation using sera from patients with allergy to hen's egg yolk in future studies.

Risk Factors for Graves' Orbitopathy; the Australian Thyroid-Associated Orbitopathy Research (ATOR) Study.

CONTEXT: Previous association studies suggest the development of Graves' orbitopathy (GO) is variably influenced by environmental risk factors. OBJECTIVE: To determine the risk factors and predict odds for developing GO in Graves' hyperthyroidism (GH). DESIGN: Case-control study. SETTING: Multi-centre Australian Thyroid-associated Orbitopathy Research group consisting of tertiary endocrinology and ophthalmology outpatients and related private practices. PATIENTS OR OTHER PARTICIPANTS: A total of 1042 participants with GH were designated as cases if they had GO (n = 604) and controls if they did not have GO (n = 438). MAIN OUTCOME MEASURES: Primary outcome was GO risk factors and secondary outcome was dysthyroid optic neuropathy (DON) with the effects of risk factors measured by odds ratio (OR) using multiple logistic regression, adjusted for known risk factors and exploratory variables. RESULTS: The odds of GO increased by 17% for each decade increase in the age of onset of GH (OR 1.17, confidence interval (CI): 1.06-1.29; P = .002) and by 7% for each year increase in the duration of GH (OR 1.07, CI: 1.05-1.10; P < .001). Smoking increased the odds for GO by 2.22 for current smoker and 2.07 for exsmoker (P < .001), compared with never smoking. The odds of GO are 86% less in Graves' patients using antithyroid medication than those not (OR 0.14, CI: 0.06-0.34; P < .001). Predictors for DON were older age, oculomotility restriction, strabismus, reduced palpebral aperture, and active GO. CONCLUSIONS: This study identified increase age of onset, duration of GH, and smoking as risk factors for GO. Usage of antithyroid medication was negatively related to GO. Older patients with restricted ocular motility, strabismus, and active GO are at higher risk of DON and may benefit from early medical intervention.

Molecular and immunological analysis of hen's egg yolk allergens with a focus on YGP42 (Gal d 6).

Allergy to hen's (Gallus domesticus) egg white is one of the most common forms of food allergy. Allergy to hen's yolk also exists however, to a lesser extent when compared to egg white allergy. Two minor allergens from the hen's egg yolk known as α-livetin (Gal d 5) and YGP42 (Gal d 6) were discovered recently. In this study, we investigated whether sensitization to egg white is associated with reactivity to egg yolk as well. Sera obtained from 25 patients with allergy to egg white were tested for specific IgE binding for egg yolk proteins through western immunoblotting. 36% of patients were found with true IgE-sensitization against egg yolk proteins. It was found that most of the IgE reactive yolk proteins were fragments of major precursor proteins of hen; vitellogenin-1 (VTG-1), vitellogenin-2 (VTG-2) and apolipoprotein B (Apo B). The egg yolk allergen Gal d 6 is the C-terminal part of VTG-1 and was found to be allergenic in significant percentage of egg white allergy patients. These results highlight the significance of Gal d 6 as an important allergen of egg yolk. Therefore, the secondary aim of this study involved developing a recombinant version of YGP42 in an Escherichia coli expression system. Recombinant Gal d 6 (rGal d6) was expressed as a fusion peptide with a 6 × His tag and purified using metal chelating resin. The inhibition ELISA results showed that rYGP42 was IgE reactive and was able to inhibit IgE binding to crude egg yolk (CEY) by up to 30%. Traditionally, it was thought that allergy to egg yolk occurred independently from sensitization to egg white. This study underlies the importance of concomitant sensitization to egg yolk proteins in patients allergic to egg white. Evidence reported in this study strongly suggests that egg yolk has potentially undiscovered allergens and therefore warrants further investigation. Furthermore, IgE reactive Gal d 6 presented in this study has the potential to be used in diagnosis and immunotherapy to treat egg allergy.

Cracking the egg: An insight into egg hypersensitivity.

Hypersensitivity to the chicken egg is a widespread disorder mainly affecting 1-2% of children worldwide. It is the second most common food allergy in children, next to cow's milk allergy. Egg allergy is mainly caused by hypersensitivity to four allergens found in the egg white; ovomucoid, ovalbumin, ovotransferrin and lysozyme. However, some research suggests the involvement of allergens exclusively found in the egg yolk such as chicken serum albumin and YGP42, which may play a crucial role in the overall reaction. In egg allergic individuals, these allergens cause conditions such as itching, atopic dermatitis, bronchial asthma, vomiting, rhinitis, conjunctivitis, laryngeal oedema and chronic urticaria, and anaphylaxis. Currently there is no permanent cure for egg allergy. Upon positive diagnosis for egg allergy, strict dietary avoidance of eggs and products containing traces of eggs is the most effective way of avoiding future hypersensitivity reactions. However, it is difficult to fully avoid eggs since they are found in a range of processed food products. An understanding of the mechanisms of allergic reactions, egg allergens and their prevalence, egg allergy diagnosis and current treatment strategies are important for future studies. This review addresses these topics and discusses both egg white and egg yolk allergy as a whole.