Relative reactivity to egg white and yolk or change upon heating as markers for baked egg tolerance.

BACKGROUND: Hen's egg food allergy is frequent in childhood and phenotypically heterogeneous. Some children can tolerate extensively heated egg. We investigated whether individual relative responses could differentiate children who tolerate baked egg. METHODS: Reactivities to raw, pasteurized or hard-boiled egg (E), egg white (EW), and egg yolk (EY) fractions were tested by skin prick test (SPT) in 54 egg-allergic children. IgE-sensitization to EW and EY was determined by ImmunoCAP and IgE-binding to EW and 8 EW proteins and to EY and 4 EY sub-fractions by ELISA. Population heterogeneity was assessed by hierarchical ascending classification upon individual variations of reactivity and links between classifications and clinical features by analyzing the contingency tables. RESULTS: All children had positive SPT to raw E and raw EW and 72% to raw EY. Heating decreased SPT-reactivity for some children, pasteurization being less effective than hard-boiling. Children were classed into three classes from relative SPT-reactivity to raw fractions, two from variations of SPT-reactivity with each thermal processing or EW/EY ratio of sensitization, and four from their sensitization pattern. Classifications according to heating were found independent of each other. SPT variations with hard-boiling, IgE-sensitization (ratio or pattern) were linked to allowance by the physicians of egg in baked products. CONCLUSIONS: Egg-allergic children were often both sensitized to EY and EW, and heterogeneous patterns of relative responses were evidenced. Irrespective of age and level of sensitization, a low EW/EY ratio or SPT getting null with hard-boiling was found in children allowed to eat baked egg.

Diagnosis and Rationale for Action Against Cow's Milk Allergy (DRACMA): a summary report.

The 2nd Milan Meeting on Adverse Reactions to Bovine Proteins was the venue for the presentation of the first consensus-based approach to the management of cow's milk allergy. It was also the first time that the Grading of Recommendations, Assessments, Development, and Evaluation approach for formulating guidelines and recommendations was applied to the field of food allergy. In this report we present the contributions in allergen science, epidemiology, natural history, evidence-based diagnosis, and therapy synthesized in the World Allergy Organization Diagnosis and Rationale for Action against Cow's Milk Allergy guidelines and presented during the meeting. A consensus emerged between discussants that cow's milk allergy management should reflect not only basic research but also a newer and better appraisal of the literature in the light of the values and preferences shared by patients and their caregivers in partnership. In the field of diagnosis, atopy patch testing and microarray technology have not yet evolved for use outside the research setting. With foreseeable breakthroughs (eg, immunotherapy and molecular diagnosis) in the offing, the step ahead in leadership can only stem from a worldwide organization implementing consensus-based clinical practice guidelines to diffuse and share clinical knowledge.

Vicilin allergens of peanut and tree nuts (walnut, hazelnut and cashew nut) share structurally related IgE-binding epitopes.

Surface-exposed IgE-binding epitopes of close overall conformation were characterized on the molecular surface of three-dimensional models built for the vicilin allergens of peanut (Ara h 1), walnut (Jug r 2), hazelnut (Cor a 11) and cashew nut (Ana o 1). They correspond to linear stretches of conserved amino acid sequences mainly located along the C-terminus of the polypeptide chains. A glyco-epitope corresponding to an exposed N-glycosylation site could also interfere with the IgE-binding epitopes. All these epitopic regions should participate in the IgE-binding cross-reactivity commonly reported between tree nuts or between peanut and some tree nuts in sensitized individuals. Owing to this epitopic community which constitutes a risk of cross-sensitization, the avoidance or a restricted consumption of other tree nuts should be recommended to peanut-sensitized individuals.

Food allergy in children suffering from atopic eczema.

Whilst the association between eczema and food allergy is well established, the role of dietary manipulation in children with eczema remains controversial. These case histories highlight the differing outcomes that dietary manipulation may have in an infant with early onset, severe eczema and an older child with milder eczema. Management strategies and the evidence to support them are presented, followed by a review of clinical recommendations.

New visions for atopic eczema: an iPAC summary and future trends.

Atopic eczema (AE) is a chronic inflammatory skin disease characterized by pruritus, dry skin and an ongoing course of exacerbations and remissions. AE is a common disorder in children with a worldwide cumulative prevalence of 15-20% in this age group. AE has a strong familial predisposition. While AE is a complex disease with multiple gene involvement, recent interest has focused on genes involved in skin barrier/epidermal differentiation and in immune response/host defense. Recent developments and future directions on pathogenesis, diagnosis, natural course and prognosis are discussed.

Promising treatments in development for food allergies.

Up to 6% of young children and 2% of adults suffer from food allergy. Among them many have IgE-mediated food allergy, a condition with potentially fatal allergic reactions. The only proven treatment is avoidance of the offending food, which can be identified using standardised allergic tests. However, several studies have addressed possible definite treatment options for food allergy. Immunotherapy, administered orally or by systemic injections, shows promising preliminary results, but these therapeutics are based on studies with insufficient scientific support, or are associated with a high risk of severe side effects. At present, no studies can support pharmacotherapy. However, promising results were recently published with anti-IgE antibodies in a human trial, and various approaches in a mouse model of food allergy (chinese herbal medicine, specific modulation of the T-cell response). Rapidly evolving findings might provide hope for a cure for food allergy in the near future.

Point prevalence and risk factors for food allergy in a cohort of 386 children with atopic dermatitis attending a multidisciplinary dermatology/paediatric allergy clinic.

BACKGROUND: There is considerable debate about the prevalence and relevance of food allergy (FA) in atopic dermatitis (AD). The aim of this study was to investigate the prevalence of and risk factors for FA in a cohort of children with AD attending a multidisciplinary paediatric allergy clinic. METHODS: The analysis was performed on 386 children (50.8% boys, median age 4 years) consecutively evaluated for AD. A diagnosis of FA was established on positive skin tests and/or a specific IgE value or a positive oral food challenge. RESULTS: Point prevalence of FA was 17.8%. Egg, peanuts, milk, tree nut and mustard accounted for 93% of cases. 37.7% of children had ≥2 positive food reactions. Risk factors associated with FA were young age (OR=7.9 when ≤2 years compared with ≥5 years), moderate to severe AD (OR=7.8 for severe and 2.4 for moderate AD) and onset of AD before 3 months of age (OR=5.7). CONCLUSION: Point prevalence of FA in children with AD is lower than initially reported in patients recruited in a paediatric allergology setting. Children≤2 years of age with early-onset or severe AD are at higher risk of FA and may be candidates for FA evaluation.

Characterization of IgE-binding epitopes of peanut (Arachis hypogaea) PNA lectin allergen cross-reacting with other structurally related legume lectins.

Sera from peanut allergic patients contain IgE that specifically interact with the peanut lectin PNA and other closely related legume lectins like LcA from lentil, PsA from pea and PHA from kidney bean. The IgE-binding activity of PNA and legume lectins was assessed by immunoblotting, surface plasmon resonance (SPR) and ELISA measurements, using sera from peanut allergic patients as a IgE source. This IgE-binding cross-reactivity most probably depends on the occurrence of structurally related epitopes that have been identified on the molecular surface of PNA and other legume lectins. These epitopes definitely differ from those responsible for the allergenicity of the major allergens Ara h 1, Ara h 2 and Ara h 3, also recognized by the IgE-containing sera of peanut allergic patients. Peanut lectin PNA and other legume lectins have been characterized as potential allergens for patients allergic to edible legume seeds. However, the clinical significance of the lectin-IgE interaction has to be addressed.

Novel approaches in treating food allergy using allergens.

Food allergy may be life-threatening and its management continues to consist of avoiding relevant allergens and, in the case of accidental ingestion, initiation of appropriate emergency therapy. The purpose of this review is to highlight the most promising novel approaches for treating food allergy using allergens. The use of specific immunotherapy for food allergy treatment is described. Clinical trials of immunotherapy have been published in the past. However, randomized, placebo-controlled studies are needed, including the evaluation of immune mechanisms. Immunotherapy is mainly indicated for persistent food allergy after the usual age of recovery. Reactive dose and symptoms of food allergy are less defined to indicate immunotherapy. Several procedures have been described: subcutaneous with constant adverse effects; oral tolerance induction with efficacy in a third of the cases, and sublingual which seems promising. The significance of the immunotherapy effect, persistent or transitory, or increasing the tolerated dose need to be defined.

Mapping and conformational analysis of IgE-binding epitopic regions on the molecular surface of the major Ara h 3 legumin allergen of peanut (Arachis hypogaea).

Eight distinct sequential IgE-binding epitopes were identified along the amino acid sequence of Ara h 3 using the Spot technology. They essentially correspond to preferencially electropositive regions exposed on the molecular surface of the protein. A few IgE-binding epitopes are coalescent to create more extended IgE-binding regions exposed on the surface of the allergen. Ara h 3 contains a core region corresponding to the cupin motifs and predicted to be preserved upon the trypsin and chymotrypsin attack in the gastro-intestinal tract. Some of the identified IgE-binding epitopes should remain unaltered in the core region to subsequently interact with the local immune system. They most probably account for the strong allergenic potency of Ara h 3. Most of the identified IgE-binding epitopes of Ara h 3 readily differ from the corresponding regions of other legume and tree-nut legumin allergens except for epitope #1 and #7 which are rather conserved essentially in other allergens. These structurally related epitopes could account for some cross-reactions occurring between Ara h 3 and other legumin allergens.

Expression of Jug r 1, the 2S albumin allergen from walnut (Juglans regia), as a correctly folded and functional recombinant protein.

Jug r 1, the 2S albumin allergen from walnut, was isolated from ripe nuts as a native allergen and expressed in Escherichia coli using the Gateway technology as a recombinant allergen. The recombinant Jug r 1 (15 kDa) differs from the native allergen by the absence of cleavage of the polypeptide chain in two covalently associated light (3.5 kDa) and heavy (8 kDa) chains. Recombinant rJug r 1 adopts the canonical alpha-helical fold of plant 2S albumins as checked on CD spectra. Four IgE-binding epitopic stretches were identified along the amino acid sequence of Jug r 1 and localized on the molecular surface of the modeled allergen. Both native and recombinant allergens exhibit similar IgE-binding activity and similarly trigger the degranulation of a FcepsilonRI-expressing rat basophilic leukaemia cell line previously treated by IgE-containing sera. Native Jug r 1 resists to heat denaturation and to the proteolytic attack of trypsin and chymotrypsin but is readily hydrolyzed in the presence of pepsin at acidic pH after 1 h of incubation at 37 degrees C in vitro. Recombinant Jug r 1 could be used for a component-resolved diagnosis of food-allergy.

What is the optimal occlusion time for the atopy patch test in the diagnosis of food allergies in children with atopic dermatitis?

The atopy patch test (APT) is a valuable additional tool in the diagnosis of food allergies in children with atopic dermatitis (AD). Nevertheless, this technique needs to be standardized, and this is particularly true for the occlusion time. We compared the results obtained after a 24-h occlusion period with those obtained after a 48-h occlusion period, the usual occlusion time used in contact allergy. We performed 64 open oral food challenges in 48 children (30 boys and 18 girls), aged between 3 and 29 months (median 14 months). The sensitivity, positive predictive value and negative predictive value were all better for the 48-h occlusion time than for the 24-h occlusion time. Therefore, the recommended occlusion time for the APT with foods should be 48 h, as for contact allergens.

Improved screening for peanut allergy by the combined use of skin prick tests and specific IgE assays.

BACKGROUND: The diagnosis of peanut allergy must be based on reliable, safe criteria. Double-blind, placebo-controlled food challenges (DBPCFCs) are the gold standard but are costly and dangerous because they can trigger severe reactions. OBJECTIVE: The aim of this study was to develop a new strategy for diagnosing peanut allergy while reducing the need for DBPCFCs. METHODS: We studied 363 children referred for an evaluation of suspected food hypersensitivity. They all benefited from the same diagnostic strategy, which included, in order, clinical history, a skin prick test (SPT), and a specific IgE assay. DBPCFCs were performed on all the children by personnel who were unaware of the results of the other tests. To assess the performance characteristics of the SPT (comparing commercial and raw peanut extracts) and the specific IgE assay, we compared the results with those provided by the DBPCFCs. For SPTs and specific IgE assays, we sought to determine the cutoff values required to exclude false-positive and false-negative results. RESULTS: According to DBPCFC results, 177 children were allergic to peanut, and 186 were not. The performance characteristics of the SPTs were superior with the raw extract because the negative predictive value was 100% (95% confidence interval [CI], 97.5-100). If the skin reaction with the raw extract was less than 3 mm, we could be quite certain that the child was not allergic. On the other hand, if the SPT resulted in a wheal diameter of larger than 3 mm, we could only be 74% certain that the children were allergic. Furthermore, if the SPT resulted in a wheal diameter of 16 mm or larger, we could be quite certain that the child was allergic because the positive predictive value was 100% (95% CI, 86.8-100). Specific IgE concentrations of 57 kU(A)/L or greater were associated with a positive predictive value of 100% (95% CI, 87.2-100). The combined use of the tests resulting in a positive diagnosis if the SPT result was 16 mm or larger or specific IgE concentration was 57 kU(A)/L or greater and in a negative diagnosis if the SPT result was less than 3 mm and the specific IgE concentration was less than 57 kU(A)/L allowed us to classify subjects with almost complete certainty as being allergic or not because the predictive values were 100%. CONCLUSION: Commercial extracts could not be used to reliably predict tolerance of peanut. Peanut DBPCFCs can be avoided when SPTs with raw extracts resulted in wheals with a largest diameter of less than 3 mm and a specific IgE concentration of less than 57 kU(A)/L and also when wheal diameters were 16 mm or larger or specific IgE values were 57 kU(A)/L or greater. Otherwise, DBPCFCs were indispensable for the unequivocal diagnosis of peanut allergy.

Factors affecting the determination of threshold doses for allergenic foods: how much is too much?

BACKGROUND: Ingestion of small amounts of an offending food can elicit adverse reactions in individuals with IgE-mediated food allergies. The threshold dose for provocation of such reactions is often considered to be zero. However, because of various practical limitations in food production and processing, foods may occasionally contain trace residues of the offending food. Are these very low, residual quantities hazardous to allergic consumers? How much of the offending food is too much? Very little quantitative information exists to allow any risk assessments to be conducted by the food industry. OBJECTIVE: We sought to determine whether the quality and quantity of existing clinical data on threshold doses for commonly allergenic foods were sufficient to allow consensus to be reached on establishment of threshold doses for specific foods. METHODS: In September 1999, 12 clinical allergists and other interested parties were invited to participate in a roundtable conference to share existing data on threshold doses and to discuss clinical approaches that would allow the acquisition of that information. RESULTS: Considerable data were identified in clinical files relating to the threshold doses for peanut, cows' milk, and egg; limited data were available for other foods, such as fish and mustard. CONCLUSIONS: Because these data were often obtained by means of different protocols, the estimation of a threshold dose was very difficult. Development of a standardized protocol for clinical experiments to allow determination of the threshold dose is needed.