Mechanisms underlying differential food allergy response to heated egg

Clinical management of food allergy

Food allergies are commonly seen by the practitioner, and managing these patients is often challenging. Recent epidemiologic studies report that as many as 1 in 13 children in the United States may have a food allergy, which makes this an important disease process to appropriately diagnose and manage for primary care physicians and specialists alike. Having a understanding of the basic immunologic processes that underlie varying presentations of food-induced allergic diseases will guide the clinician in the initial workup. This review will cover the basic approach to understanding the immune response of an individual with food allergy after ingestion and will guide the clinician in applying appropriate testing modalities when needed by conducting food challenges if indicated and by educating the patient and his or her guardian to minimize the risk of accidental ingestion.

Debates in allergy medicine: baked egg and milk do not accelerate tolerance to egg and milk

There is emerging evidence that children with egg and cow's milk allergy who can tolerate these allergens cooked in baked goods are more likely to develop tolerance. As a result a hypothesis has arisen that exposure to egg and milk in baked goods may hasten tolerance development; however, it is unclear whether children who develop tolerance do so because they have ingested low levels of egg or milk in baked products. An alternative explanation for the improved prognosis in those who can tolerate food allergens in the baked form is that tolerance to egg and milk in baked goods is simply an indicator of a phenotype that is less likely to be persistent. We discuss the role that the baked egg or milk allergy phenotype plays on predicting tolerance development and suggest that it is the phenotype of the disease rather than exposure to altered allergens that is the strongest predictor of tolerance development.

Oral immunotherapy for food allergy: mechanisms and role in management

With the emergence of food allergy as an important public health problem, it has become clear that there is an unmet need in regard to treatment. In particular, IgE-mediated food allergy that is associated with risk of fatal anaphylaxis has been the subject of multiple studies in the past decade. The growing body of evidence derived from multiple centres and various study designs indicates that for IgE-mediated food allergy, immunomodulation through food immunotherapy is possible; however, the extent of protection afforded by such treatment is highly variable. At this time, the capacity for food immunotherapy to restore permanent tolerance to food has not been demonstrated conclusively. This review will discuss these topics as they apply to the most important studies of food oral immunotherapy.

Diagnosis, management, and investigational therapies for food allergies

Food allergies have increased in prevalence over the past 20 years, now becoming an important public health concern. Although there are no therapies currently available for routine clinical care, recent reports have indicated that immunotherapies targeting the mucosal immune system may be effective. Oral immunotherapy is conducted by administering small, increasing amounts of food allergen; it has shown promise for desensitizing individuals with peanut, egg, or milk allergies. Sublingual immunotherapy also desensitizes allergic patients to foods-2 major studies have examined the effects of sublingual immunotherapy in subjects with peanut allergies. We review the complex nature of IgE-mediated food allergies and the therapies being evaluated in clinical trials. We focus on the diagnosis and management of food allergies and investigational therapies.

Allergenicity of pasteurized whole raw Hen's egg compared with fresh whole raw Hen's egg

BACKGROUND

Oral food challenges for diagnosis and management of egg allergy using fresh egg are common; however, to limit the risk of foodborne infection, many allergy units use pasteurized raw egg. Pasteurization and drying processes have the potential to affect the structure of egg proteins in egg powder and thus the allergenicity when compared to fresh egg. Our aim was to compare the binding of serum IgE from egg-allergic children to in vitro digested and undigested pasteurized whole raw egg powder with unpasteurized fresh whole raw egg.

METHODS

Egg proteins from in vitro digested or undigested pasteurized whole raw egg powder, fresh whole egg, egg white and egg yolk were separated by SDS-PAGE, transferred onto nitrocellulose membrane and incubated overnight with pooled sera from egg-allergic children.

RESULTS

In both the raw egg samples and the pasteurized whole egg powder, protein bands corresponding to known molecular weights of the major egg allergens were present. Pasteurized whole raw egg powder was bound by serum IgE in a similar manner to unpasteurized whole raw egg and was unaffected by in vitro digestion. Serum IgE also bound egg yolk, indicating sensitization to both egg yolk and egg white proteins.

CONCLUSIONS

The main egg allergens are present in pasteurized whole raw egg powder, and serum IgE of egg-allergic children binds to them in a similar pattern to those in fresh whole raw egg. Pasteurized whole raw egg powder is a suitable substitute for raw egg in clinical practice for oral food challenges.

Food processing and allergenicity

Food processing can have many beneficial effects. However, processing may also alter the allergenic properties of food proteins. A wide variety of processing methods is available and their use depends largely on the food to be processed. In this review the impact of processing (heat and non-heat treatment) on the allergenic potential of proteins, and on the antigenic (IgG-binding) and allergenic (IgE-binding) properties of proteins has been considered. A variety of allergenic foods (peanuts, tree nuts, cows' milk, hens' eggs, soy, wheat and mustard) have been reviewed. The overall conclusion drawn is that processing does not completely abolish the allergenic potential of allergens. Currently, only fermentation and hydrolysis may have potential to reduce allergenicity to such an extent that symptoms will not be elicited, while other methods might be promising but need more data. Literature on the effect of processing on allergenic potential and the ability to induce sensitisation is scarce. This is an important issue since processing may impact on the ability of proteins to cause the acquisition of allergic sensitisation, and the subject should be a focus of future research. Also, there remains a need to develop robust and integrated methods for the risk assessment of food allergenicity.

Anaphylaxis to food

This article provides a clinically focused review of food-induced anaphylaxis that includes epidemiology, risk factors, allergens, diagnosis, and management. Currently, there is no treatment for food allergy. Dietary avoidance and emergency preparedness are the cornerstones of management. Effective and safe therapies to reduce the risk of serious food-induced reactions are urgently needed, as are reliable biomarkers to predict severity.

Native and denatured egg white protein IgE tests discriminate hen's egg allergic from egg-tolerant children

BACKGROUND

Accurate diagnosis of egg allergy by IgE testing is challenged by a large number of atopic subjects sensitized, but clinically tolerant to eggs. In addition, discrimination between allergy to raw only, or raw and cooked egg allergy is important. In this study, we investigate the diagnostic performance of IgE tests to native and denatured egg proteins.

METHODS

According to food challenges and clinical tolerance, study subjects were randomized to the following groups: (Group A) sensitized but clinically tolerant to egg, (Group B) allergic to raw egg only, or (Group C) allergic to raw and cooked egg. Serum-specific IgE to native or reduced and oxidized egg white, ovomucoid, and ovalbumin were measured.

RESULTS

Increasing titers of specific IgE to the various proteins were found according to the degree of the egg allergy. Cut-off values for IgE testing to native egg could be determined to distinguish between raw egg allergic and egg-tolerant subjects (1.6 kU/l), as well as raw and cooked egg allergic and egg-tolerant subjects (4.1 kU/l). ROC curves analysis showed that native ovalbumin was the best test for the diagnosis of allergy to raw and cooked egg, and native ovomucoid was best to distinguish between allergy to raw only, and allergy to raw and cooked egg. Sequential testing improved the diagnosis, when in addition to IgE to native egg white, IgE to native ovalbumin was tested for the diagnosis of raw and cooked egg allergy, and IgE to native ovomucoid for the discrimination between allergy to raw only, or to raw and cooked eggs.

CONCLUSION

The diagnosis of egg allergy can be significantly improved using a panel of IgE tests to egg proteins in the native or denatured form. The accuracy can be improved using combined IgE testing.

A modified weight-of-evidence approach to evaluate the allergenic potential of food proteins

Schematic interpretation of a modified weight-of-evidence approach for evaluating the allergenic potential of food proteins.

Effects of dry heating on the progression of in vitro digestion of egg white proteins: contribution of multifactorial data analysis

In vitrodigestion of egg white powders: multiple factor analysis to follow the dry-heating effect.

Effect of heat treatment on milk and egg proteins allergenicity

BACKGROUND

Heating destroys many conformational epitopes and reduces allergenicity of some foods. IgE-epitope binding has been shown to be different among patients who outgrew their cow's milk or hen's egg allergy and those who did not. A significant proportion of milk- or egg-allergic children are tolerant to these foods in their baked forms. We sought to explore the effects of heating on milk and egg proteins and to evaluate for differences in immunolabeling among children with regard to reactivity to heated milk or egg.

METHODS

Sera from participants in clinical dietary intervention trials were utilized. Milk and egg samples were variably heated and prepared (at times within a wheat matrix). Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE), protein transfer, and Western blot were completed.

RESULTS

Sera from 20 milk-allergic and 24 egg-allergic children were utilized. Gel electrophoresis showed strongly staining casein bands that persisted for up to 60 min of heating. In contrast, β-lactoglobulin and α-lactalbumin bands became progressively weaker with increasing heating times, with no detectable β-lactoglobulin after 15-20 min of heating. The ovalbumin band became progressively weaker, whereas ovomucoid remained stable after 25 min of heating. Immunolabeling revealed that all heated milk-reactive children possessed IgE antibodies that bound the casein fraction regardless of heating time. Presence of wheat during heating resulted in decreased IgE antibody binding to milk and egg white proteins.

CONCLUSION

Heating has a different effect on whey and caseins in cow's milk and ovalbumin and ovomucoid in hen's egg white. The effect of heat on protein allergenicity is affected by the temperature and duration, along with the presence of wheat.

Skin testing with raw egg does not predict tolerance to baked egg in egg-allergic children

BACKGROUND

Most children with egg allergy tolerate egg in baked foods, such as cake, but tolerance cannot be predicted with conventional allergy testing. We hypothesized that the skin prick test (SPT) wheal to unprocessed raw egg might predict tolerance of baked egg at formal oral food challenge (OFC).

METHODS

We conducted a retrospective chart review to assess the utility of SPT wheal to egg extract (EE), raw egg (RE), and the ratio of EE:RE in predicting outcome of baked-egg OFC in children presenting to our tertiary referral centers with a physician diagnosis of egg allergy and following complete egg avoidance in their diet, between 2009 and 2013. OFC were performed following a standardized protocol using baked egg in cake, to a total dose equivalent to 3g egg protein.

RESULTS

Data were analyzed from 186 completed challenges: OFC was positive in 64 (34%) children and negative in 122 (66%). Six children experienced anaphylaxis at OFC. Children tolerant to baked egg were more likely to have a lower SPT to egg extract/raw egg and EE:RE (median 0.56) than their allergic counterparts (0.70, p < 0.05). However, ROC curve analysis demonstrated poor predictivity of challenge outcome, with AUC for SPT to egg extract, raw egg and EE:ER equal to 0.71, 0.63 and 0.60, respectively.

CONCLUSION

EE:RE was not helpful in predicting outcome of baked-egg OFC. Indeed, SPT to egg extract was slightly better at predicting outcome than either SPT to raw egg or EE:RE. Unfortunately, tolerance to baked egg can only be predicted from previous history or through controlled exposure.

Novel strategy to create hypoallergenic peanut protein-polyphenol edible matrices for oral immunotherapy

Peanut allergy is an IgE-mediated hypersensitivity. Upon peanut consumption by an allergic individual, epitopes on peanut proteins bind and cross-link peanut-specific IgE on mast cell and basophil surfaces triggering the cells to release inflammatory mediators responsible for allergic reactions. Polyphenolic phytochemicals have high affinity to bind proteins and form soluble and insoluble complexes with unique functionality. This study investigated the allergenicity of polyphenol-fortified peanut matrices prepared by complexing various polyphenol-rich plant juices and extracts with peanut flour. Polyphenol-fortified peanut matrices reduced IgE binding to one or more peanut allergens (Ara h 1, Ara h 2, Ara h 3, and Ara h 6). Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) suggested changes in secondary protein structure. Peanut protein-cranberry polyphenol fortified matrices triggered significantly less basophil degranulation than unmodified flour in an ex vivo assay using human blood and less mast cell degranulation when used to orally challenge peanut-allergic mice. Polyphenol fortification of peanut flour resulted in a hypoallergenic matrix with reduced IgE binding and degranulation capacity, likely due to changes in protein secondary structure or masking of epitopes, suggesting potential applications for oral immunotherapy.

Oral immunotherapy for food allergy, ready for prime time? Heated egg and milk

Cow's milk and hen's egg allergies are two of the most common food allergies that affect children, with an estimated prevalence of 2-3 % each. Persistence of food allergy into late teen years and adulthood is being increasingly recognized, possibly due to strict avoidance practices. Heating has been known to alter food allergenicity, and the majority of milk- and egg-allergic patients tolerate heated forms of those foods. Heated milk and heated egg have been increasingly studied as oral immunotherapy (OIT) for treatment of milk and egg allergy. While heated milk and heated egg have been shown to be safe in selected milk- and egg-allergic cohorts, larger studies are needed to predict which patients are optimal candidates for this strategy and to further clarify whether ingestion of heated milk or heated egg truly accelerates the onset of clinical tolerance to unheated forms of these foods.

Food allergy: Insights into etiology, prevention, and treatment provided by murine models

Food allergy is a rapidly growing public health concern because of its increasing prevalence and life-threatening potential. Animal models of food allergy have emerged as a tool for identifying mechanisms involved in the development of sensitization to normally harmless food allergens, as well as delineating the critical immune components of the effector phase of allergic reactions to food. However, the role animal models might play in understanding human diseases remains contentious. This review summarizes how animal models have provided insights into the etiology of human food allergy, experimental corroboration for epidemiologic findings that might facilitate prevention strategies, and validation for the utility of new therapies for food allergy. Improved understanding of food allergy from the study of animal models together with human studies is likely to contribute to the development of novel strategies to prevent and treat food allergy.

Mucosal immunology of food allergy

Food allergies are increasing in prevalence at a higher rate than can be explained by genetic factors, suggesting a role for as yet unidentified environmental factors. In this review, we summarize the state of knowledge about the healthy immune response to antigens in the diet and the basis of immune deviation that results in immunoglobulin E (IgE) sensitization and allergic reactivity to foods. The intestinal epithelium forms the interface between the external environment and the mucosal immune system, and emerging data suggest that the interaction between intestinal epithelial cells and mucosal dendritic cells is of particular importance in determining the outcome of immune responses to dietary antigens. Exposure to food allergens through non-oral routes, in particular through the skin, is increasingly recognized as a potentially important factor in the increasing rate of food allergy. There are many open questions on the role of environmental factors, such as dietary factors and microbiota, in the development of food allergy, but data suggest that both have an important modulatory effect on the mucosal immune system. Finally, we discuss recent developments in our understanding of immune mechanisms of clinical manifestations of food allergy. New experimental tools, particularly in the field of genomics and the microbiome, are likely to shed light on factors responsible for the growing clinical problem of food allergy.

Influence of the carbohydrate moieties on the immunoreactivity and digestibility of the egg allergen ovomucoid

BACKGROUND

Ovomucoid (OM) has two carbohydrate chains on each of the first and second domains and one in the third. The contribution of the covalently bound carbohydrate chains to the overall OM allergenicity is controversial. Another aspect directly related with the immunological properties of OM that has not been studied in depth is the importance of the carbohydrate chains on its digestibility.

OBJECTIVE

The aim of the study was to assess the involvement of the carbohydrate moieties of OM in its digestibility and allergenic properties.

METHODS

IgE-binding and basophil activation by glycosylated and enzymatically deglycosylated OM (dOM) were compared using blood from egg-allergic patients. The peptides obtained after digestion using a physiologically relevant model were identified by RP-HPLC-MS/MS and the IgE-binding of the resulting fragments was evaluated by DOT-Blot.

RESULTS

No structural changes were observed after deglycosylation of OM. 80% of the patients showed lower IgE binding to dOM as compared with OM and, in some patients, IgE reactivity could not be inhibited by pre-incubation with dOM. A subtle reduction in the percentage of activated basophils was observed when incubated with dOM as compared to OM. Following simulated digestion, dOM was more extensively degraded than OM, particularly during the gastric phase and both, OM and dOM, yielded, after the duodenal phase, immunoreactive fragments that were totally or partially coincident with previously described epitopes.

CONCLUSION & CLINICAL RELEVANCE

this work demonstrated an enhanced IgE reactivity towards carbohydrate containing OM in some egg-allergic patients that could be attributed to cross-sensitization or sensitization to the glycosylated components. The carbohydrate chains contributed to an increased resistance to proteolysis, and thus, to its allergenic potency. Evaluation of the products of digestion of OM and dOM revealed the presence of high-frequency IgE-binding epitopes that could remain linked by disulphide bonds.

Food allergen selective thermal processing regimens may change oral tolerance in infancy

Food allergy can be considered a failure in the induction of oral tolerance. Recently, great interest has been focused on understanding the mechanisms and the contributing factors of oral tolerance development, hoping for new definitive interventions in the prevention and treatment of food allergy. Given that food processing may modify the properties and the nature of dietary proteins, several food processing methods could affect the allergenicity of these proteins and consequently may favour oral tolerance induction to food allergic children. Indeed, effective thermal food processing regimens of altering food proteins to reduce allergenicity have been recently reported in the literature. This article is mainly focused on the effect of selective thermal processing regimens on the main infant allergenic foods, with a potential clinical relevance on their allergenicity and therefore on oral tolerance induction. In the light of recent findings, the acquisition of tolerance in younger age and consequently the ability of young children to "outgrow" food allergy could be achieved through the application of selective thermal processing regimens on certain allergenic foods. Therefore, the ability of processed foods to circumvent clinical disease and at the same time to have an impact on the immune system and facilitate tolerance induction could be invaluable as a component of a successful therapeutic strategy. The opening in the new avenues of research in the use of processed foods in clinical practice for the amelioration of the impact on the quality of life of patients and possibly in food allergy prevention is warranted.

Safety of food challenges to extensively heated egg in egg-allergic children: a prospective cohort study

BACKGROUND

Many children with IgE-mediated allergy to egg can tolerate egg in baked foods. However, the clinical characteristics and severity of reactions of egg-allergic children who react to baked egg at open food challenge (OFC) are not well defined.

METHODS

Children presenting to our tertiary referral clinic with a diagnosis of egg allergy and following complete egg avoidance in their diet were offered OFC to baked egg. Challenges were performed with incremental dosages to a total of one baked muffin containing 1/6 egg (equivalent to 1 g egg protein) following a standardized protocol. Data were collected prospectively from 2009-2012.

RESULTS

Open food challenge to baked egg were carried out on 236 egg-allergic children who had been strictly avoiding egg in their diet. A total of 150 children (64%) passed and successfully incorporated baked egg into their diet. Eighty-six children (36%) reacted to their challenge. Of these, 12 (14%) experienced anaphylaxis (according to WAO criteria), including four to <100 mg extensively heated egg protein. Intramuscular adrenaline was administered to 5 of the 12 children, one of whom required a second dose due to persistent hypotension. Skin prick testing, asthma, or prior egg anaphylaxis were not predictive of challenge outcome.

CONCLUSION

The majority of children with IgE-mediated allergy to egg were able to tolerate 1 g of baked egg protein, but the outcome of OFC remained unpredictable, and 14% of children who failed OFC reacted with anaphylaxis. We recommend that OFC to baked egg should take place under medical supervision.

Oral immunotherapy for food allergy: clinical and preclinical studies

Food allergies affect approximately 5% of the U.S. population and have increased in the last decade. In recent years, oral immunotherapy (OIT) has been tested in clinical trials for peanut, milk, and egg allergies in young children. OIT appears to be fairly well tolerated by most subjects and leads to desensitization with a greatly increased threshold of allergen required to induce reactions. Further approaches being investigated in preclinical studies in mouse models indicate the potential for using adjuvants, such as TLR9 agonists in combination with OIT; peptide OIT; and non-allergen specific applications such as herbal formulations. Further questions about OIT remain, including the optimal dosing and length of treatment; whether tolerance can be developed; and the exact cellular mechanisms resulting in protection following OIT. With many clinical trials underway across the United States and other countries, and a growing pipeline of preclinical research with translational potential, there is great hope for a widely applicable food allergy treatment.

Heated allergens and induction of tolerance in food allergic children

Food allergies are one of the first manifestations of allergic disease and have been shown to significantly impact on general health perception, parental emotional distress and family activities. It is estimated that in the Western world, almost one in ten children have an IgE-mediated allergy. Cow's milk and egg allergy are common childhood allergies. Until recently, children with food allergy were advised to avoid all dietary exposure to the allergen to which they were sensitive, in the thought that consumption would exacerbate their allergy. However, recent publications indicate that up to 70% of children with egg allergy can tolerate egg baked in a cake or muffin without apparent reaction. Likewise, up to 75% of children can tolerate baked goods containing cow's milk, and these children demonstrate IgE and IgG4 profiles indicative of tolerance development. This article will review the current literature regarding the use of heated food allergens as immunotherapy for children with cow's milk and egg allergy.

Frequent baked egg ingestion was not associated with change in rate of decline in egg skin prick test in children with challenge confirmed egg allergy

BACKGROUND

It is controversial whether egg-allergic children should strictly avoid all forms of egg, or if regular ingestion of baked egg will either delay or hasten the resolution of egg allergy.

OBJECTIVE

This is the first study to examine the relationship between frequency of baked egg ingestion and rate of decline in egg skin prick test size in egg-allergic children.

METHODOLOGY

This was a retrospective clinical cohort study. All children with challenge-proven egg allergy who attended the Royal Children's Hospital Allergy Department 1996-2005 and had at least two egg skin prick tests performed in this period were included (n = 125). Frequency of baked egg ingestion was assessed by telephone questionnaire as follows: (a) frequent (> once per week), (b) regular (> once every 3 months, up to ≤ once per week) or (c) strict avoidance (≤ once every 3 months). The relationship between frequency of baked egg ingestion and rate of decline in egg skin prick test size was examined by multiple linear regression, adjusting for potential confounders.

RESULTS

Mean rate of decline in egg skin prick test size in all children was 0.7 mm/year (95% CI 0.5-1.0 mm/year). There was no evidence (P = 0.57) that the rate of decline in egg skin prick test size differed between children who undertook frequent ingestion (n = 21, mean 0.4 mm/year, 95% CI -0.3-1.2 mm/year), regular ingestion (n = 37, mean 0.9 mm/year, 95% CI 0.4-1.4 mm/year) or strict avoidance (n = 67, mean 0.7 mm/year, 95% CI 0.4-1.1 mm/year) of baked egg.

CONCLUSIONS

Compared with strict dietary avoidance, frequent consumption of baked egg was not associated with a different rate of decline in egg skin prick test size in egg-allergic children.

CLINICAL RELEVANCE

Given that dietary restrictions can adversely impact on the family, it is reasonable to consider liberalizing baked egg in the diet of egg-allergic children.

Food allergy: an enigmatic epidemic

Food allergy is a common disease that is rapidly increasing in prevalence for reasons that remain unknown. Current research efforts are focused on understanding the immune basis of food allergy, identifying environmental factors that may contribute to its rising prevalence, and developing immunotherapeutic approaches to establish immune tolerance to foods. Technological advances such as peptide microarray and MHC class II tetramers have begun to provide a comprehensive profile of the immune response to foods. The burgeoning field of mucosal immunology has provided intriguing clues to the role of the diet and the microbiota as risk factors in the development of food allergy. The purpose of this review is to highlight significant gaps in our knowledge that need answers to stem the progression of this disorder that is reaching epidemic proportions.

Mucosal immunology of tolerance and allergy in the gastrointestinal tract

The mucosal immune system typically exists in a state of active tolerance to food antigens and commensal bacteria. Tolerance to food proteins is induced in part by dendritic cells residing in the intestinal mucosa and implemented by regulatory T cells. Food allergy occurs when immune tolerance is disrupted and a sensitizing immune response characterized by food-specific IgE production occurs instead. Experimental food allergy in mice requires use of adjuvant or exploitation of alternate routes of sensitization to induce allergic sensitization, and can aid in understanding the mechanisms of sensitization to food allergens and the pathophysiology of gastrointestinal manifestations of food allergy. Recent work in the understanding of mucosal immunology of tolerance and allergy in the gastrointestinal tract will be discussed.

Glutathione exposes sequential IgE-epitopes in ovomucoid relevant in persistent egg allergy

SCOPE

Patients with persistent egg allergy have more immunoglobulin E (IgE) against sequential than conformational epitopes of ovomucoid (OVO). Here, we aimed to identify compounds capable to render sequential epitopes in egg.

METHODS AND RESULTS

Glutathione was used for in vitro reduction of OVO and circular dichroism analyses were performed. Glutathione reduced OVO in a concentration-dependent manner. Egg white was analyzed for reduced proteins with a thiol probe and by MALDI-TOF/TOF. In unprocessed total egg white, several reduced proteins were detected by the thiol probe, among them reduced ovalbumin could be confirmed with MS analyses. Egg-allergics or sensitized controls were tested serologically (n = 19) for IgE against native and reduced OVO and in skin prick tests (n = 9). More patients had IgE against reduced than native OVO in Western blots. In skin prick test, five out of seven persistent egg-allergics and none of the controls reacted with reduced OVO.

CONCLUSION

Reduced egg proteins are present in natural egg white. Glutathione, which is present in egg and furthermore is used as texture-improving additive in processed food, is capable of reducing OVO. Patients with persistent egg allergy reacted rather to reduce the native OVO. Hence, our data indicate that reduction is a novel natural and processing-associated principle, which contributes to the allergenicity of food.

Extensively heated milk and egg as oral immunotherapy

PURPOSE OF REVIEW

The introduction of extensively heated milk and egg protein into the diet has been explored in recent years.

RECENT FINDINGS

Studies have suggested that a large subset of children who react to unheated milk or egg can tolerate extensively heated forms of these foods. Immunologic changes induced by a diet containing baked milk and egg are similar to changes that have been observed during oral immunotherapy trials. The baked milk and egg diet appears to accelerate the development of regular milk and egg tolerance when compared with strict avoidance.

SUMMARY

An oral challenge to extensively heated milk and egg into milk and egg allergic children's diets should be considered when appropriate. Oral food challenges are the most reliable means of establishing a diagnosis and should be undertaken under physician supervision.

Mucosal antibodies in the regulation of tolerance and allergy to foods

The intestinal mucosa is densely packed with antibody-secreting B cells, the majority of which produce IgA. Mucosal antibodies have traditionally been thought of as neutralizing antibodies that exclude antigens, but they also function in antigen sampling, allowing for selective transcytosis of antigens from the intestinal lumen. IgE-mediated antigen uptake can facilitate the development of allergic reactions to foods, but emerging evidence indicates that IgG-mediated antigen uptake may also play an important role in the development of immune tolerance to foods, particularly in the neonate. This review will focus on the role of intestinal immunoglobulins in the development of clinical tolerance and allergy to food antigens.

Association between human IL-10 gene polymorphisms and serum IL-10 level in patients with food allergy

BACKGROUND/PURPOSE

Single nucleotide polymorphisms (SNPs) of the interleukin-10 (IL-10) gene are associated with allergic diseases in different populations. This study aimed to determine the distribution of two SNPs at -1082A/G and -592A/C (rs1800896 and rs1800872, respectively) in the IL-10 gene promoter of Taiwanese food allergy (FA) patients, and also to compare the serum IL-10 levels between patients with (FA) and controls.

METHODS

Thirty-seven patients with FA and 52 controls were enrolled, and their peripheral blood was collected for IL-10 SNP genotyping and the corresponding serum IL-10 level of each genotype.

RESULTS

The thirty-seven FA patients had positive food-specific IgE (≥ 0.75kU/L) to more than one food, and the most frequent allergens wereshrimp and crab (56.8% and 35.1%, respectively). The genotype distributions in the FA patients compared to the control group were AA and AG at -1082A/G (86.5% and 13.5% vs. 86.6% and 13.4%, respectively), and AA, AC, and CC at -592A/C (45.9%, 43.3% and 10.8% vs. 38.5%, 48.1% and 13.4%, respectively). Serum IL-10 levels were significantly lower in the FA group than in the control group (p=0.0187), and the IL-10 level of -592A/C of genotype AA was significantly lower than that of the other genotypes (AC+CC) (p=0.007). Patients with AA/AA haplotype homozygotes (10 of 24) had significantly lower serum IL-10 levels than those with other haplotypes.

CONCLUSIONS

The two SNPs at -1082A/G and -592A/C of IL-10 were associated with FA in our Taiwanese population, and FA patients with the genotype AA/AA haplotype homozygotes had lower serum IL-10 levels. This suggests that IL-10 might play a critical role in the pathogenesis of FA. We suggest that it may be practicable to evaluate the serum IL-10 levels of FA patients and to predict the possibility of FA if genotypes and haplotypes are checked regularly.