Basophil activation tests for the diagnosis of food allergy in children.

BACKGROUND: Positive skin prick tests (SPT) for food allergens and specific IgE (sIgE) in serum indicate sensitization but do not enable distinction between sensitized but tolerant and clinically allergic patients. OBJECTIVE: Herein, we evaluate the clinical relevance of basophil activation tests (BATs) for peanut or egg allergy diagnosis. METHODS: Thirty-two peanut-allergic, 14 peanut-sensitized (sIgE(+) and/or SPT(+) to peanuts) but tolerant children and 29 controls with no history of an adverse reaction to peanuts were included. Similarly, 31 egg-allergic, 14 egg-sensitized children (sIgE(+) and/or SPT(+) to egg white) and 22 controls were studied. Flow cytometric analysis of CD63 expression or CD203c upregulation on basophils and the production of leukotrienes (LT) were performed in response to an in vitro crude peanut extract or ovalbumin (OVA) challenge. RESULTS: After in vitro peanut challenge, the basophils from peanut-allergic children showed significantly higher levels of activation than those from controls (P<0.001). After OVA challenge, a similar distinction (P<0.001) was observed between egg-allergics and controls. Interestingly, the majority of egg- or peanut-sensitized children failed to activate basophils, respectively, in response to OVA and peanut challenge. The sensitivity of the CD63, CD203c and LT assay was 86.7%, 89.5% and 76.0% with a specificity of 94.1%, 97.1% and 94.6% for peanut allergy diagnosis. The corresponding performances of BATs applied to egg allergy diagnosis were 88.9%, 62.5% and 77.8% for the sensitivity and 100%, 96.4% and 96.4% for the specificity. CONCLUSION: Neither conventional tests nor BATs are sensitive and specific enough to predict food allergy accurately. However, BATs may helpfully complete conventional tests, especially SPT, allowing improved discrimination between allergic and non-allergic individuals.

Which infants with eczema are at risk of food allergy? Results from a population-based cohort

BACKGROUND: The relationship between early onset eczema and food allergy among infants has never been examined in a population-based sample using the gold standard for diagnosis, oral food challenge. OBJECTIVE: We characterised the risk of challenge-proven food allergy among infants with eczema in the general population. METHODS: One-year-old infants (n = 4453 meeting criteria for this analysis) were assessed for history of eczema, received a nurse-administered eczema examination and underwent skin prick testing to peanut, egg and sesame. Those with a detectable wheal to one of the test foods underwent an oral food challenge irrespective of wheal size. The risk of food allergy, stratified by eczema severity and age of onset, was estimated using multivariate logistic regression with population sampling weights. RESULTS: One in five infants with eczema were allergic to peanut, egg white or sesame, compared to one in twenty-five infants without eczema (OR 6.2, 95% CI 4.9, 7.9, P < 0.001). The prevalence of peanut allergy was low in the absence of eczema (0.7% 95% CI 0.4, 1.1). Infants with eczema were 11.0 times more likely to develop peanut allergy (95% CI 6.6, 18.6) and 5.8 times more likely to develop egg allergy (95% CI 4.6, 7.4) by 12 months than infants without eczema. 50.8% of infants (95% CI 42.8, 58.9) with early eczema onset (<3 months) who required doctor-prescribed topical corticosteroid treatment developed challenge-proven food allergy. CONCLUSION AND CLINICAL RELEVANCE: Eczema, across the clinical severity spectrum in infancy, is a strong risk factor for IgE-mediated food allergy. Infants with eczema were six times more likely to have egg allergy and 11 times more likely to have peanut allergy by 12 months than infants without eczema. Our data suggest that a heightened awareness of food allergy risk among healthcare practitioners treating infants with eczema, especially if early onset and severe, is warranted.

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.

Production and immunological analysis of IgE reactive recombinant egg white allergens expressed in Escherichia coli.

IgE-mediated allergy to chicken egg affects a large number of children and adults worldwide. The current management strategy for egg allergy is strict avoidance, however this is impractical due to the presence of eggs in a range of foods and pharmaceutical products including vaccines. Strict avoidance also poses nutritional disadvantages due to high nutritional value of eggs. Allergen specific immunotherapy is being pursued as a curative treatment, in which an allergic individual is gradually exposed to the allergen to induce tolerance. Use of recombinant proteins for immunotherapy has been beneficial due to the purity of the recombinant proteins compared to natural proteins. In this study, we produced IgE reactive recombinant egg white proteins that can be used for future immunotherapy. Using E. coli as an expression system, we successfully produced recombinant versions of Gal d 1, 2 and 3, that were IgE reactive when tested against a pool of egg allergic patients' sera. The IgE reactivity indicates that these recombinant proteins are capable of eliciting an immune response, thus being potential candidates for immunotherapy. We have, for the first time, attempted to produce recombinant versions of all 4 major egg white allergens in E. coli, and successfully produced 3, with only Gal d 4 showing loss of IgE reactivity in the recombinant version. The results suggest that egg allergy in Australian populations may mainly be due to IgE reactivity to Gal d 3 and 4, while Gal d 1 shows higher IgE reactivity. This is the first report of a collective and comparative immunological analysis of all 4 egg white allergens. The significance of this study is the potential use of the IgE reactive recombinant egg white proteins in immunotherapy to treat egg allergic patients.

Hypoallergenic variant of the major egg white allergen Gal d 1 produced by disruption of cysteine bridges

Gal d 1 (Ovomucoid) is the most allergenic protein in the chicken egg white. Hypoallergenic variants of this allergen can be used in immunotherapy as an egg allergy treatment approach. We hypothesized that disruption of selected cysteine-cysteine disulfide bridges by mutagenesis will allow us the production of a hypoallergenic variant of the protein.

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.

Production and characterization of hypoallergenic chicken eggs

This project aimed to develop novel therapeutics and methods to tackle egg allergy. In this study, recombinant variants of egg allergens were produced that may be used in future immunotherapy. Genetic engineering was also used to develop new strategies to produce non-allergenic chicken eggs.

Vaccine components and constituents: Responding to consumer concerns

Vaccination remains a vital strategy in the prevention of infectious disease. Commercial vaccine formulations contain a range of additives or manufacturing residuals, which may contribute to patient concerns about vaccine safety. Primary health care professionals are well placed to address patient concerns about vaccine safety. We describe the key constituents present in vaccines, discuss issues related to safety and acceptability of these constituents, and provide a table highlighting constituents of commercially available vaccines in Australia.

Allergy - 5: Allergy and the skin: eczema and chronic urticaria

Eczema is common, occurring in 15%-20% of infants and young children. For some infants it can be a severe chronic illness with a major impact on the child's general health and on the family. A minority of children will continue to have eczema as adults. The exact cause of eczema is not clear, but precipitating or aggravating factors may include food allergens (most commonly, egg) or environmental allergens/irritants, climatic conditions, stress. and genetic predisposition. Management of eczema consists of education; avoidance of triggers and allergens; liberal use of emollients or topical steroids to control inflammation; use of antihistamines to reduce itch; and treatment of infection if present. Treatment with systemic agents may be required in severe cases, but must be supervised by an immunologist. Urticaria (hives) may affect up to a quarter of people at some time in their lives. Acute urticaria is more common in children, while chronic urticaria is more common in adults. Chronic urticaria is not life-threatening, but the associated pruritus and unsightly weals can cause patients much distress and significantly affect their daily lives. Angioedema coexists with urticaria in about 50% of patients. It typically affects the lips, eyelids, palms, soles and genitalia. Management of urticaria is through education; avoidance of triggers and allergens (where relevant); use of antihistamines to reduce itch; and short-term use of corticosteroids when antihistamine therapy is ineffective. Referral is indicated for patients with resistant disease.

Parental confidence in managing food allergy:development of the Food Allergy Self-Efficacy Scale for parents (FASE-P)

Background: Food allergy is often a life-long condition that requires constant vigilance in order to prevent accidental exposure and avoid potentially life-threatening symptoms. Parents’ confidence in managing their child’s food allergy may relate to the poor quality of life anxiety and worry reported by parents of food allergic children. Objective: The aim of the current study was to develop and validate the first scale to measure parental confidence (self-efficacy) in managing food allergy in their child. Methods: The Food Allergy Self-Efficacy Scale for Parents (FASE-P) was developed through interviews with 53 parents, consultation of the literature and experts in the area. The FASE-P was then completed by 434 parents of food allergic children from a general population sample in addition to the General Self-Efficacy Scale (GSES), the Food Allergy Quality of Life Parental Burden Scale (FAQL-PB), the General Health Questionnaire (GHQ12) and the Food Allergy Impact Measure (FAIM). A total of 250 parents completed the re-test of the FASE-P. Results: Factor and reliability analysis resulted in a 21 item scale with 5 sub-scales. The overall scale and sub-scales has good to excellent internal consistency (α’s of 0.63-0.89) and the scale is stable over time. There were low to moderate significant correlations with the GSES, FAIM and GHQ12 and strong correlations with the FAQL-PB, with better parental confidence relating to better general self-efficacy, better quality of life and better mental health in the parent. Poorer self-efficacy was related to egg and milk allergy; self-efficacy was not related to severity of allergy. Conclusions and clinical relevance: The FASE-P is a reliable and valid scale for use with parents from a general population. Its application within clinical settings could aid provision of advice and improve targeted interventions by identifying areas where parents have less confidence in managing their child’s food allergy.

Direct and indirect effects of egg parasitism by Neopolyscystus Girault sp. (Hymenoptera: Pteromalidae) on Paropsis atomaria Olivier (Coleoptera: Chrysomelidae)

Abstract Neopolycystus sp. is the only primary egg parasitoid associated with the pest beetle Paropsis atomaria in subtropical eucalypt plantations, but its impact on its host populations is unknown. The simplified ecosystem represented by the plantation habitat, lack of interspecific competition for host and parasitoid, and the multivoltinism of the host population makes this an ideal system for quantifying the direct and indirect effects of egg parasitism, and hence, effects on host population dynamics. Within-, between- and overall-egg-batch parasitism rates were determined at three field sites over two field seasons, and up to seven host generations. The effect of exposure time (egg batch age), host density proximity to native forest and water sources on egg parasitism rates was also tested. Neopolycystus sp. exerts a significant influence on P. atomaria populations in Eucalyptus cloeziana. plantations in south-eastern Queensland, causing the direct (13%) and indirect (15%) mortality of almost one-third of all eggs in the field. Across seasons and generations, 45% of egg batches were parasitised, with a within-batch parasitism rate of around 30%. Between-batch parasitism increased up to 5–6 days after oviposition in the field, although within-batch parasitism rates generally did not. However, there were few apparent patterns to egg parasitism, with rates often varying significantly between sites and seasons.

An egg apparatus-specific enhancer of Arabidopsis, identified by enhancer detection

Despite a central role in angiosperm reproduction, few gametophyte-specific genes and promoters have been isolated, particularly for the inaccessible female gametophyte (embryo sac). Using the Ds-based enhancer-detector line ET253, we have cloned an egg apparatus-specific enhancer (EASE) from Arabidopsis (Arabidopsis thaliana). The genomic region flanking the Ds insertion site was further analyzed by examining its capability to control gusA and GFP reporter gene expression in the embryo sac in a transgenic context. Through analysis of a 5' and 3' deletion series in transgenic Arabidopsis, the sequence responsible for egg apparatus-specific expression was delineated to 77 bp. Our data showed that this enhancer is unique in the Arabidopsis genome, is conserved among different accessions, and shows an unusual pattern of sequence variation. This EASE works independently of position and orientation in Arabidopsis but is probably not associated with any nearby gene, suggesting either that it acts over a large distance or that a cryptic element was detected. Embryo-specific ablation in Arabidopsis was achieved by transactivation of a diphtheria toxin gene under the control of the EASE. The potential application of the EASE element and similar control elements as part of an open-source biotechnology toolkit for apomixis is discussed.