Background

Egg white proteins are usually subjected to heating, making them edible for the majority of egg-allergic children.

Objective

We sought to investigate the underlying mechanisms responsible for the reduced allergenicity displayed by heat-treated egg white allergens.

Methods

C3H/HeJ mice were orally sensitized with ovalbumin (OVA) or ovomucoid (OM) and challenged with native or heated proteins to evaluate their allergenicity. Immunoreactivity was assessed by immunoblotting using sera from egg-allergic children. In vitro gastrointestinal digestion of native and heated OVA and OM was studied by SDS-PAGE and liquid chromatography. Intestinal uptake of intact native and heated OVA and OM by human intestinal epithelial (Caco-2) cells was investigated. Rat basophil leukemia (RBL) cells passively sensitized with mouse serum and human basophils passively sensitized with egg-allergic children’s serum were used to assess the effector cell activation by heated, digested and transported OVA and OM.

Results

Heated OVA and OM did not induce symptoms of anaphylaxis in sensitized mice when administered orally. Heating did not completely destroy IgE-binding capacity of OVA or OM but enhanced in vitro digestibility of OVA. Digestion of both OVA and OM diminished mediator release in RBL assay and basophil activation. Heating of allergens prevented transport across human intestinal epithelial cells in a form capable of triggering basophil activation or T cell activation.

Conclusions

Heat treatment reduces allergenicity of OVA and OM. This is partially due to the enhanced gastrointestinal digestibility of heated OVA and the inability of heated OVA or OM to be absorbed in a form capable of triggering basophils.

Clinical implications

Reduced allergenicity of heated egg white proteins partially resulting from altered digestion and absorption in the gastrointestinal tract may explain the clinical tolerance of extensively heated egg in the majority of egg-allergic children.

Capsule summary

The majority of egg-allergic children tolerate extensively heated egg. This study demonstrates that the decreased allergenicity of heated ovalbumin and ovomucoid in large part results from altered digestion and processing in the gastrointestinal tract.

Short summary

IgE-mediated food sensitization and allergy are common in inner city children, even in the absence of reported clinical reactivity. Clinicians caring for this population should maintain a high index of suspicion for food allergy.

Background

The majority (∼75%) of cow's milk-allergic children tolerate extensively heated-(baked-) milk products. Long-term effects of inclusion of dietary baked-milk have not been reported.

Objective

We report on the outcomes of children who incorporated baked-milk products into their diets.

Methods

Children evaluated for tolerance to baked-milk (muffin) underwent sequential food challenges to baked-cheese (pizza) followed by unheated-milk. Immunologic parameters were measured at challenge visits. The comparison group were matched to active subjects (using age, sex, and baseline milk-specific IgE) to evaluate the natural history of tolerance development.

Results

Over a median of 37 months (range 8-75 months), 88 children underwent challenges at varying intervals (range 6-54 months). Among 65 subjects initially tolerant to baked-milk, 39 (60%) now tolerate unheated-milk, 18 (28%) tolerate baked-milk/baked-cheese and 8 (12%) chose to avoid milk strictly. Among the baked-milk-reactive subgroup (n=23), 2 (9%) tolerate unheated-milk, 3 (13%) tolerate baked-milk/baked-cheese, while the majority (78%) avoid milk strictly. Subjects who were initially tolerant to baked-milk were 28 times more likely to become unheated-milk-tolerant compared to baked-milk-reactive subjects (P<.001). Subjects who incorporated dietary baked-milk were 16 times more likely than the comparison group to become unheated-milk-tolerant (P<.001). Median casein IgG4 levels in the baked-milk-tolerant group increased significantly (P<.001); median milk IgE values did not change significantly.

Conclusions

Tolerance of baked-milk is a marker of transient IgE-mediated cow's milk allergy whereas reactivity to baked-milk portends a more persistent phenotype. The addition of baked-milk to the diet of children tolerating such foods appears to accelerate development of unheated-milk tolerance compared to strict avoidance.

Clinical implications

Addition of dietary baked-milk is safe, convenient, and well-accepted by patients. Prescribing baked-milk products to milk-allergic children represents an important shift in the treatment paradigm for milk allergy.

Capsule summary

The majority of cow's milk-allergic children tolerate extensively baked-milk products, which is a marker of transient IgE-mediated cow's milk allergy. Dietary baked-milk appears to accelerate development of unheated-milk tolerance compared to strict avoidance.

Food allergy is an increasingly prevalent problem in westernized countries and there is an unmet medical need for an effective form of therapy . A number of therapeutic strategies are under investigation targeting foods that most frequently provoke severe IgE-mediated anaphylactic reactions (peanut, tree nuts, shellfish) or are most common in children, such as cow’s milk and hen’s egg. Approaches being pursued are both food allergen-specific and non-specific. Allergen-specific approaches include oral, sublingual and epicutaneous immunotherapy (desensitization) with native food allergens, and mutated recombinant proteins, which have decreased IgE-binding activity, co-administered within heat-killed E.coli to generate maximum immune response. Diets containing extensively heated (baked) milk and egg represent an alternative approach to food oral immunotherapy and are already changing the paradigm of strict dietary avoidance for food-allergic patients. Non-specific approaches include monoclonal anti-IgE antibodies, which may increase the threshold dose for food allergen in food-allergic patients, and a Chinese herbal formulation, which prevented peanut-induced anaphylaxis in a mouse model, and is currently being investigated in clinical trials. The variety of strategies for treating food allergy increases the likelihood of success and gives hope that accomplishing an effective therapy for food allergy is within reach.

Background

Results from large-scale epitope mapping using peptide microarray have been shown to correlate with clinical features of milk allergy.

Objectives

We sought to assess IgE and IgG4 epitope diversity and IgE affinity in different clinical phenotypes of milk allergy and identify informative epitopes that may be predictive of clinical outcomes of milk allergy.

Methods

Forty-one subjects were recruited from a larger study on the effects of ingesting heat-denatured milk proteins in milk-allergic individuals. Using food challenges, subjects were characterized as clinically reactive to all forms of milk (n = 17), tolerant to heated milk (HM) products (n = 16), or outgrown their milk allergy (n = 8). Eleven non-milk allergic, healthy volunteers served as controls. Peptide microarray was performed using the previously published protocol.

Results

Milk allergic subjects had increased epitope diversity as compared to those who outgrew their allergy. HM tolerant subjects had IgE binding patterns similar to those who had outgrown their allergy, but IgG4 binding patterns that were more similar to the allergic group. Binding to higher numbers of IgE peptides was associated with more severe allergic reactions during challenge. There was no association between IgG4 peptides and clinical features of milk allergy. Using a competitive peptide microarray assay, allergic patients demonstrated a combination of high and low affinity IgE binding whereas HM tolerant subjects and those who had outgrown their milk allergy had primarily low affinity binding.

Conclusions

Greater IgE epitope diversity and higher affinity as determined by peptide microarray were associated with clinical phenotypes and severity of milk allergy.

Background

Data about epinephrine utilization and biphasic reactions in childhood food-induced anaphylaxis during oral food challenges are scarce.

Objective

To determine the prevalence and risk factors of reactions requiring epinephrine and the rate of biphasic reactions during oral food challenges (OFCs) in children.

Methods

Reaction details of positive OFCs in children between 1999 and 2007 were collected using a computerized database. Selection of patients for OFCs was generally predicated on ≤50% likelihood of a positive challenge and a low likelihood of a severe reaction based on the clinical history, specific IgE levels, and skin prick tests (SPTs).

Results

A total of 436 of 1273 OFCs resulted in a reaction (34%). Epinephrine was administered in 50 challenges (11% of positive challenges, 3.9% overall); for egg (n=15, 16% of positive OFCs to egg), milk (n=14, 12%), peanut (n=10, 26%), tree nuts (n=4, 33%), soy (n=3, 7%), wheat (n=3, 9%), and fish (n=1, 9%). Reactions requiring epinephrine occurred in older children (median 7.9 vs. 5.8 years, P<0.001), and were more often caused by peanuts (P=0.006) when compared to reactions not treated with epinephrine. There was no difference in the gender, prevalence of asthma, history of anaphylaxis, specific IgE level, SPTs, or amount of food administered. Two doses of epinephrine were required in 3/50 patients (6%) reacting to wheat, cow’s milk, and pistachio. There was one (2%) biphasic reaction. No reaction resulted in life-threatening respiratory or cardiovascular compromise.

Conclusion

Older age and reactions to peanuts were risk factors for anaphylaxis during oral food challenges. Reactions requiring multiple doses of epinephrine and biphasic reactions were infrequent.