Mustard allergy in children

Gene editing in allergic diseases: Identification of novel pathways and impact of deleting allergen genes

Gene editing technology has emerged as a powerful tool in all aspects of health research and continues to advance our understanding of critical and essential elements in disease pathophysiology. The clustered regularly interspaced short palindromic repeats (CRISPR) gene editing technology has been used with precision to generate gene knockouts, alter genes, and identify genes that cause disease. The full spectrum of allergic/atopic diseases, in part because of shared pathophysiology, is ripe for studies with this technology. In this way, novel culprit genes are being identified and allow for manipulation of triggering allergens to reduce allergenicity and disease. Notwithstanding current limitations on precision and potential off-target effects, newer approaches are rapidly being introduced to more fully understand specific gene functions as well as the consequences of genetic manipulation. In this review, we examine the impact of editing technologies of novel genes relevant to peanut allergy and asthma as well as how gene modification of common allergens may lead to the deletion of allergenic proteins.

Re-evaluation of behenic acid from mustard seeds to be used in the manufacturing of certain emulsifiers pursuant to Article 21(2) of Regulation (EU) No 1169/2011 - for permanent exemption from labelling

Following a request from the European Commission, the Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to review a scientific assessment related to a notification from DuPont Nutrition Biosciences Aps on behenic acid from mustard seeds to be used in the manufacturing of certain emulsifiers pursuant to Article 21(2) of Regulation (EU) No 1169/2011 - for permanent exemption from labelling. The EC requested EFSA to consider comments raised by the German authorities in relation to: (a) the maximum amount of mustard protein that could be consumed from the emulsifiers manufactured from behenic acid (E470a, E471 and E477) on a single occasion and (b) the minimal observed eliciting dose (MOED) triggering allergic reactions in mustard-allergic individuals. The maximum amount of mustard protein content in behenic acid was re-assessed in view of new analytical data provided by the applicant. Intake estimates by the EFSA ANS Panel for E471 (adults) were used as a proxy for the combined intake (E470a, E471 and E477). Food challenge data and systematic reviews thereof deriving population minimal observed eliciting dose distributions for mustard protein were used to calculate the MOED and estimate the risk. The margin of exposure between the MOED (0.26 mg mustard protein) and the maximum amount of mustard protein that could be consumed from the emulsifiers on a single occasion (0.00895475 mg) is 29. It is predicted that between 0.1% and 1% of the mustard allergic population would react with mild objective symptoms to that dose. Overall, the assessment is conservative, particularly in relation to the exposure. Based on the information and data available, the NDA Panel concludes that it is extremely unlikely (≤ 1% probability) that oral consumption of emulsifiers to be manufactured using behenic acid from mustard seeds (i.e. E470a, E471 and E477) will trigger an allergic reaction in mustard-allergic individuals under the proposed conditions of use.

Removing the major allergen Bra j I from brown mustard (Brassica juncea) by CRISPR/Cas9

Food allergies are a major health issue worldwide. Modern breeding techniques such as genome editing via CRISPR/Cas9 have the potential to mitigate this by targeting allergens in plants. This study addressed the major allergen Bra j I, a seed storage protein of the 2S albumin class, in the allotetraploid brown mustard (Brassica juncea). Cotyledon explants of an Indian gene bank accession (CR2664) and the German variety Terratop were transformed using Agrobacterium tumefaciens harboring binary vectors with multiple single guide RNAs to induce either large deletions or frameshift mutations in both Bra j I homoeologs. A total of 49 T₀ lines were obtained with up to 3.8% transformation efficiency. Four lines had large deletions of 566 up to 790 bp in the Bra j IB allele. Among 18 Terratop T₀  lines, nine carried indels in the targeted regions. From 16 analyzed CR2664 T₀  lines, 14 held indels and three had all four Bra j I alleles mutated. The majority of the CRISPR/Cas9-induced mutations were heritable to T₁ progenies. In some edited lines, seed formation and viability were reduced and seeds showed a precocious development of the embryo leading to a rupture of the testa already in the siliques. Immunoblotting using newly developed Bra j I-specific antibodies revealed the amount of Bra j I protein to be reduced or absent in seed extracts of selected lines. Removing an allergenic determinant from mustard is an important first step towards the development of safer food crops.

Biologically Active Compounds in Mustard Seeds: A Toxicological Perspective

Mustard plants have been widely cultivated and used as spice, medicine and as source of edible oils. Currently, the use of the seeds of the mustard species Sinapis alba (white mustard or yellow mustard), Brassica juncea (brown mustard) and Brassica nigra (black mustard) in the food and beverage industry is immensely growing due to their nutritional and functional properties. The seeds serve as a source for a wide range of biologically active components including isothiocyanates that are responsible for the specific flavor of mustard, and tend to reveal conflicting results regarding possible health effects. Other potentially undesirable or toxic compounds, such as bisphenol F, erucic acid or allergens, may also occur in the seeds and in mustard products intended for human consumption. The aim of this article is to provide comprehensive information about potentially harmful compounds in mustard seeds and to evaluate potential health risks as an increasing use of mustard seeds is expected in the upcoming years.

Shotgun proteomics of Brassica rapa seed proteins identifies vicilin as a major seed storage protein in the mature seed

Proteins make up a large percentage of the Brassica seed and are second only to the oil in economic importance with uses for both animal and human nutrition. The most abundant proteins reported in the seeds of Brassica are the seed storage proteins cruciferin and napin, belonging to the 12S globulin and 2S albumin families of proteins, respectively. To gain insight into the Brassica rapa seed proteome and to confirm the presence and relative quantity of proteins encoded by candidate seed storage genes in the mature seed, shotgun proteomics was carried out on protein extracts from seeds of B. rapa inbred line R-o-18. Following liquid chromatography tandem mass spectrometry, a total of 34016 spectra were mapped to 323 proteins, where 233 proteins were identified in 3 out of 4 biological replicates by at least 2 unique peptides. 2S albumin like napin seed storage proteins (SSPs), 11/12S globulin like cruciferin SSPs and 7S globulin like vicilin SSPs were identified in the samples, along with other notable proteins including oil body proteins, namely ten oleosins and two oil body-associated proteins. The identification of vicilin like proteins in the mature B. rapa seed represents the first account of these proteins in the Brassicaceae and analysis indicates high conservation of sequence motifs to other 7S vicilin-like allergenic proteins as well as conservation of major allergenic epitopes in the proteins. This study enriches our existing knowledge on rapeseed seed proteins and provides a robust foundation and rational basis for plant bioengineering of seed storage proteins.

A Comprehensive Review on Mustard-Induced Allergy and Implications for Human Health

Mustard is widely used in a variety of foods/food products to enhance the flavor and nutritional value that subsequently raise the risk of hypersensitivity reactions. Mustard allergy has been reported for many years and is increasing gradually especially in the areas where its consumption is comparatively higher, and it may be considered among the most important food allergies. A number of relevant clinical studies focused on mustard-induced allergic manifestations are summarized in the current review. In addition, the knowledge regarding the immunological as well as biochemical characteristics of mustard allergens that have been known till date and their cross-reactivity with other food allergens have also been discussed here. Notably, mustard may also be present as a hidden allergen in foods; therefore, it is important to recognize food products that may contain mustard as it may pose potential risk for the allergic individuals. Additionally, the better understanding of the underlying mechanism in mustard allergy is a prerequisite for the development of specific therapeutic procedures. Conclusively, mustard sensitivity should be routinely tested in patients with idiopathic anaphylaxis for the safety of the allergic patients.

Detection and identification of allergens from Canadian mustard varieties of Sinapis alba and Brassica juncea

Currently, information on the allergens profiles of different mustard varieties is rather scarce. Therefore, the objective of this study was to assess protein profiles and immunoglobulin E (IgE)-binding patterns of selected Canadian mustard varieties. Optimization of a non-denaturing protein extraction from the seeds of selected mustard varieties was first undertaken, and the various extracts were quantitatively and qualitatively analyzed by means of protein recovery determination and protein profiling. The IgE-binding patterns of selected mustard seeds extracts were assessed by immunoblotting using sera from mustard sensitized and allergic individuals. In addition to the known mustard allergens—Sin a 2 (11S globulins), Sin a 1, and Bra j 1 (2S albumins)—the presence of other new IgE-binding protein bands was revealed from both Sinapis alba and Brassica juncea varieties. Mass spectrometry (MS) analysis of the in-gel digested IgE-reactive bands identified the unknown ones as being oleosin, β-glucosidase, enolase, and glutathione-S transferase proteins. A bioinformatic comparison of the amino acid sequence of the new IgE-binding mustard proteins with those of know allergens revealed a number of strong homologies that are highly relevant for potential allergic cross-reactivity. Moreover, it was found that Sin a 1, Bra j 1, and cruciferin polypeptides exhibited a stronger IgE reactivity under non-reducing conditions in comparison to reducing conditions, demonstrating the recognition of conformational epitopes. These results further support the utilization of non-denaturing extraction and analysis conditions, as denaturing conditions may lead to failure in the detection of important immunoreactive epitopes.

Hypersensitivities to sesame and other common edible seeds

Several seeds have been increasingly incorporated in various food items, with consequent risk of hypersensitivity reactions that are often severe. Identification of the specific seed as the culprit is often not explored or is difficult to verify. In this article, we reviewed the English literature from January 1930 to March 2016 using PubMed and Google Scholar searching for publications relevant to hypersensitivity to common edible seeds, namely sesame, sunflower seed, poppy seed, pumpkin seed, flaxseed, and mustard seed. Considering the worldwide consumption of those seeds, the number of published articles on the subject was relatively small and was mainly as case reports rather than large series. Allergy to sesame was more reported than to other seeds, with an estimated prevalence of 0.1-0.2%. In this review, we summarize the information relevant to each of the six seeds and their oils regarding the manifestations, routes of exposure, identified major allergens, and cross-reactivity with other seeds or other foods. We also addressed the important role of a thorough history taking in suspecting seed allergy, the limited reliability of routine diagnostic procedures, and the importance of verification by appropriate challenge tests. At present, management is basically dietary avoidance and the use of symptomatic medications that may include epinephrine auto-injectors. We did not encounter any well-designed studies on immunotherapy for seed allergy, but it is hoped that such a gap be filled by the development of safe effective protocols in the near future.

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.

Similar prevalence, different spectrum: IgE-mediated food allergy among Turkish adolescents

BACKGROUND

Scarcity of reliable data on food allergy prevalence exists in Turkey. We aimed to assess reported and confirmed IgE-mediated food allergy prevalence, and define the spectrum of allergenic food.

METHODS

We prospectively evaluated the ISAAC Phase II study population for food allergy. Participants that reported experiencing food allergy symptom in the last year and/or were skin prick test positive for a predefined list of food allergens, were interviewed via telephone, and those considered as having food allergy were invited to undergo clinical investigation, including challenge tests.

RESULTS

A total of 6963 questionnaires were available. Parental reported food allergy prevalence and skin prick sensitisation rate were 20.2 ± 0.9% and 5.9 ± 0.6%. According to the above-defined criteria, 1162 children (symptom positive n=909, skin prick test positive n=301, both positive n=48) were selected and 813 (70.0%) were interviewed via telephone. Out of 152 adolescents reporting a current complaint, 87 accepted clinical investigation. There were 12 food allergies diagnosed in nine adolescents, with food allergy prevalence of 0.16 ± 0.11%. The most common foods involved in allergic reactions were walnut (n=3) and beef meat (n=2), followed by hen's egg (n=1), peanut (n=1), spinach (n=1), kiwi (n=1), cheese (n=1), hazelnut (n=1) and peach (n=1).

CONCLUSIONS

While parental reported food allergy prevalence was within the range reported previously, confirmed IgE-mediated food allergy prevalence among adolescents was at least 0.16%, and the spectrum of foods involved in allergy differed from Western countries, implying environmental factors may play a role.

Analysis of the structural and immunological stability of 2S albumin, nonspecific lipid transfer protein, and profilin allergens from mustard seeds

This work investigates the resistance to proteolysis and heating of the yellow mustard (Sinapis alba L.) allergens Sin a 1 (2S albumin), Sin a 3 (nonspecific lipid transfer protein, LTP), and Sin a 4 (profilin) to explain their potential capability to induce primary sensitization at the gastrointestinal level. Sin a 1 and Sin a 3 resisted gastric digestion showing no reduction of the IgE reactivity. Intestinal digestion of Sin a 1 and Sin a 3 produced a limited proteolysis but retained significant IgE-binding reactivity. Sin a 1 was stable after heating, and although Sin a 3 was modified, most of its structure was recovered after cooling back. These two allergens would be therefore able to sensitize by ingestion. Sin a 4 was completely digested by gastric treatment and its conformational structure markedly modified at 85 °C. Thus, this allergen can be described as a nonsensitizing mustard allergen.

Food production and processing considerations of allergenic food ingredients: a review

Although most consumers show no adverse symptoms to food allergens, health consequences for sensitized individuals can be very serious. As a result, the Codex General Standard for the Labelling of Prepackaged Foods has specified a series of allergenic ingredients/substances requiring mandatory declaration when present in processed prepackaged food products. Countries adhering to international standards are required to observe this minimum of eight substances, but additional priority allergens are included in the list in some countries. Enforcement agencies have traditionally focused their effort on surveillance of prepackaged goods, but there is a growing need to apply a bottom-up approach to allergen risk management in food manufacturing starting from primary food processing operations in order to minimize the possibility of allergen contamination in finished products. The present paper aims to review food production considerations that impact allergen risk management, and it is directed mainly to food manufacturers and policy makers. Furthermore, a series of food ingredients and the allergenic fractions identified from them, as well as the current methodology used for detection of these allergenic foods, is provided.

Sensitization and allergy to turnip rape: a comparison between the Finnish and French children with atopic dermatitis

AIM

Finnish children with atopic dermatitis (AD) are frequently sensitized and show positive food challenge to turnip rape. We examined whether French children are also allergic to this oilseed plant and whether mustard could be the cross-reacting allergen.

METHODS

Turnip rape and mustard challenge was performed to 14 Finnish and 14 French children with atopic dermatitis and positive skin prick test to turnip rape. Specific IgE antibodies were measured by ImmunoCAP and enzyme-linked immunosorbent assay (ELISA).

RESULTS

Open labial or oral challenge to turnip rape was positive in 14 (100%) Finnish and five (36%) French children and mustard challenge in five Finnish and five French children. IgE antibodies to oilseed rape and mustard were slightly more frequent in the Finnish (100% and 93%) than in the French (93% and 71%) children but rare (4%) in the 28 matched controls. The same findings were true for IgE antibodies to purified 2S albumin allergens, which showed similar cross-wise IgE inhibition patterns.

CONCLUSION

French children with atopic dermatitis show IgE antibodies to turnip rape, oilseed rape and mustard similarly to the Finnish children. 2S albumin allergens in the seeds of these plants are highly cross-reactive and therefore, they all could be important sensitizers in children with atopic dermatitis.

Sensitization to turnip rape and oilseed rape in children with atopic dermatitis: a case-control study

Turnip rape and oilseed rape 2S albumins are new allergens in children with atopic dermatitis suspected for food allergy. We recently found that 11% (206/1887) of these children had a positive skin prick test to seeds of oilseed rape (Brassica napus) and/or turnip rape (Brassica rapa). In the present case-control study we examined how the children with atopic dermatitis sensitized to turnip rape and oilseed rape had been breast-fed and whether they had some common sensitization pattern to certain foods or pollens. A total of 64 children with atopic dermatitis and a positive skin prick test to turnip rape and/or oilseed rape (>or=5 mm) were examined. Sixty-four age- and sex-matched children with atopic dermatitis but negative skin prick tests to turnip rape and oilseed rape served as case controls. The turnip rape and/or oilseed rape sensitized children with atopic dermatitis had significantly more often positive skin prick tests reactions and IgE antibodies to various foods (cow's milk, egg, wheat, mustard; p < 0.01) and pollens (birch, timothy, mugwort; p < 0.01) than the control children. They had been exclusively breast-fed for a longer period (median 4 months; p < 0.05) and had more often associated asthma (36%) and allergic rhinitis (44%). Children with atopic dermatitis sensitized to oilseed rape and turnip rape had high frequency of associated sensitizations to all foods and pollens tested showing that oilseed plant sensitization affects especially atopic children who have been sensitized to multiple allergens.

2S Albumin Storage Proteins: What Makes them Food Allergens?

2S albumin storage proteins are becoming of increasing interest in nutritional and clinical studies as they have been reported as major food allergens in seeds of many mono- and di-cotyledonous plants. This review describes the main biochemical, structural and functional properties of these proteins thought to play a role in determining their potential allergenicity. 2S albumins are considered to sensitize directly via the gastrointestinal tract (GIT). The high stability of their intrinsic protein structure, dominated by a well-conserved skeleton of cysteine residues, to the harsh conditions present in the GIT suggests that these proteins are able to cross the gut mucosal barrier to sensitize the mucosal immune system and/or elicit an allergic response. The flexible and solvent-exposed hypervariable region of these proteins is immunodominant and has the ability to bind IgE from allergic patients sera. Several linear IgE-binding epitopes of 2S albumins spanning this region have been described to play a major role in allergenicity; the role of conformational epitopes of these proteins in food allergy is far from being understood and need to be investigated. Finally, the interaction of these proteins with other components of the food matrix might influence the absorption rates of immunologically reactive 2S albumins but also in their immune response.

Turnip rape and oilseed rape are new potential food allergens in children with atopic dermatitis

BACKGROUND

When skin prick testing (SPT) young children with atopic dermatitis (AD) for suspected food allergy, we frequently found positive reactions with turnip rape (Brassica rapa) and oilseed rape (Brassica napus). We performed food challenge to examine whether these children react clinically to turnip rape.

METHODS

A total of 1887 children were screened with SPTs for sensitization to turnip rape and oilseed rape. Twenty-eight children with clearly positive SPT (> or =5 mm) were first subjected to labial challenge with turnip rape seeds followed, if negative, by open oral challenge for up to 7 days. Twenty-five children with AD but negative SPT to turnip rape and oilseed rape served as controls.

RESULTS

Two-hundred and six (10.9%) children had positive SPT to turnip rape and/or oilseed rape. Twenty-five (89%) of 28 children showed a positive challenge reaction to turnip rape. Seventeen reacted with labial whealing, and eight in oral challenge with facial urticaria, flare-up of AD or abdominal symptoms. All 25 control children remained negative in the labial challenge.

CONCLUSIONS

Turnip rape and oilseed rape seem to be new important food allergens in young children with AD. The modes of exposure to these allergens and the possible routes of sensitization remain to be established.

Isolation and identification of an 11S globulin as a new major allergen in mustard seeds

BACKGROUND

Although mustard seed allergy has been largely reported during the preceding 20 years, currently only 2 allergens, Sin a 1 and Bra j 1, have been identified.

OBJECTIVE

To improve the characterization of the allergenic profile of yellow mustard seeds by reporting the identification and biochemical characterization of an 11S globulin as a new major allergen.

METHODS

Mustard seed proteins were separated using size exclusion and ion-exchange chromatographic columns, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and 2-dimensional polyacrylamide gel electrophoresis. Separation of different polypeptide chains was achieved by reverse-phase high-performance liquid chromatography. Mass spectrometry after tryptic digestion and Edman degradation were used to determine amino acid sequences of peptides. IgE binding assays were performed with 13 serum samples from mustard allergic patients in immunoblotting and enzyme-linked immunosorbent inhibition assays.

RESULTS

A protein of 51 kDa was recognized as a major allergen by patients allergic to mustard and called Sin a 2. The allergen was dissociated in 2 chains of 36 and 23 kDa, which also bound IgE. N-terminal end and internal amino acid sequences allowed identification of the new allergen as a seed storage 11S globulin belonging to the Cupin super family. Purified allergen was able to inhibit the IgE binding of sera from allergic patients to mustard seeds extract in up to 55% of the responses.

CONCLUSIONS

An 11S globulin storage protein has been isolated and identified as a novel major allergen of mustard seeds.

A Recombinant Precursor of the Mustard Allergen Sin a 1 Retains the Biochemical and Immunological Features of the Heterodimeric Native Protein

BACKGROUND

Mustard has been an important cause of food allergy of increasing incidence in the last years. Sin a 1, a storage 2S albumin, is the most relevant allergen from this spice.

METHODS

Pichia pastoris has been used as host for the recombinant production of the precursor form of Sin a 1 (rproSin a 1). rproSin a 1 was purified to homogeneity by three chromatographic steps: gel filtration, anion exchange and reverse-phase HPLC. Molecular characterization was performed using Edman degradation, mass spectrometry, amino acid composition, and circular dichroism. Immunological properties were analyzed by immunoblotting, ELISA, and ELISA inhibition experiments.

RESULTS

We overexpressed rproSin a 1 as a single polypeptide with both large and small chains linked by an internal processed fragment at high yield. The purified rproSin a 1 (>95%) was obtained as a monomeric and soluble protein. rproSin a 1 showed equivalent structural and immunological properties to natural heterodimeric Sin a 1 allergen. rproSin a 1 was recognized by 75% of the patients allergic to mustard. The inhibitory capacity of rproSin a 1 to the total allergenicity of mustard extracts varied from 13 to 83% in different patients, with a mean value of 54%.

CONCLUSIONS

rproSin a 1 is a good candidate to replace natural allergen in diagnosis protocols of mustard allergy. P. pastoris has been demonstrated to be a suitable expression system for the production of allergenic derivates of Sin a 1 that could be used for immunotherapy purposes in future.

Mustard allergy confirmed by double-blind placebo-controlled food challenges: clinical features and cross-reactivity with mugwort pollen and plant-derived foods

BACKGROUND

Mustard IgE-mediated allergy is supposed to be a rare cause of food allergy, and its clinical features and cross-reactivities have not been fully elucidated.

METHODS

A prospective study was carried out, recruiting mustard allergic patients, and paired control subjects. A clinical questionnaire was administered, and skin-prick tests (SPT) with panels of aeroallergens and foods, serum extraction for in vitro tests and double-blind placebo-controlled food challenges (DBPCFC) were performed.

RESULTS

Thirty-eight mainly adult patients, with 10.5% reporting systemic anaphylaxis, were included in the study [age (mean +/- SD): 21.9 +/- 8.6 years]. DBPCFC were performed in 24 patients, being positive in 14 cases (58.3%). Patients with positive outcome showed significantly greater mustard SPT than those with negative outcome (8.2 +/- 3.7 vs 5.3 +/- 2.4 mm, P <0.05), and the receiver-operating characteristic (ROC) curve analysis yielded a cut-off value for mustard commercial SPT of 8 mm, with a specificity of 90% (95% CI, 55.5-98.3), and a sensitivity of 50% (95% CI, 23.1-76.9). A significant association between mustard hypersensitivity and mugwort pollen sensitization was found (97.4% of patients), with partial cross-reactivity demonstrated by UniCAP System inhibition assays. All patients showed sensitization to other members of Brassicaceae family, and cross-reactivity among them was also confirmed. Moreover, significant associations with nut (97.4%), leguminous (94.7%), corn (78.9%), and Rosaceae fruit (89.5%) sensitizations were also shown. Around 40% of these food sensitizations were symptomatic, including food-dependent exercise-induced anaphylaxis in six patients.

CONCLUSIONS

Mustard allergy is a not-uncommon disorder that can induce severe reactions. Significant associations with mugwort pollinosis and several plant-derived food allergies are demonstrated, suggesting a new mustard-mugwort allergy syndrome. A relationship between this syndrome and food-dependent exercise-induced anaphylaxis is also reported.

Allergenic potency of spices: hot, medium hot, or very hot

Spices are the most attractive ingredients to confer an authentic taste to food. As they are derived from plants, they harbour allergenic potency and can induce symptoms ranging from mild local to severe systemic reactions. Due to the content of pharmacologically active substances of spices, the diagnosis of allergy and the differentiation from intolerance reactions may be difficult. Association with inhalative allergies via IgE cross-reactivity, but also direct gastrointestinal sensitization plays a role. This article is a botanical and allergological overview of the most important spices and molecules responsible for eliciting IgE-mediated reactions or cross-reactions. As no curative treatments are known at present, strict avoidance is recommended and, therefore, accurate labelling of pre-packed food is necessary.

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.

Prospective study of mustard allergy: first study with double-blind placebo-controlled food challenge trials (24 cases)

BACKGROUND

Mustard allergy accounts for 1.1% of food allergies in children. However, double-blind placebo-controlled food challenge trials (DB PCFCs) have not yet been proposed.

OBJECTIVE

To carry out DB PCFCs to determine the real frequency of mustard allergy in patients sensitized to mustard.

METHODS

A prospective study was conducted in 30 subjects aged 3-20 years presenting positive prick tests to ground mustard seeds (Brassica nigra), mustard flour (B. juncea), metabisulfite-free strong mustard seasoning (B. juncea) and a commercialized allergenic extract (B. nigra). Twenty-seven subjects were screened for mustard-specific immunoglobulin E (IgE). PCFCs were carried out either DB or single blind (SB) with up to 1340 mg of metabisulfite-free seasoning.

RESULTS

The mean diameter of the wheal induced by prick tests with the allergenic extract was lower (n.s.) than that induced by the native mustard products: 5.8 mm (1.5-15) vs 6.9 mm (0.5-18) for B. nigra ground seeds, 7.8 mm (1-20) for B. juncea flour and 9.7 mm (3-20) for the strong mustard seasoning. The diameter of the wheal induced by the allergenic extract was significantly different from that induced by the mustard seasoning (P < 0.005). The mean of mustard specific-IgE values was 8.7 KU/l (0.35-72.4). Seven of 30 food challenges were considered positive. Mean prick test results in the positive and negative PCFC subgroups were 5.5 mm vs 5.9 mm for the commercialized extract, 10.9 mm vs 5.8 mm for B. nigra ground seeds (P < 0.01), 9.9 mm vs 7.1 mm for B. juncea flour (n.s. P > 0.25) and 11.5 mm vs 9.1 mm for the metabisulfite-free mustard seasoning (n.s. P > 0.1). Mean specific IgE values determined by CAP system radioallergosorbent test (Phadebas Pharmacia) were higher but not significantly so (P > 0.25) in the subgroup with mustard allergy (12.3 K/l vs 7.6 KU/l).

CONCLUSIONS

About 23.3% of the sensitized subjects were allergic to a routine dose of mustard. Positive prick tests and the presence of specific IgE were not predictive. SB PCFC or DB PCFC is required before recommending avoidance diets.

Food allergy in children

Food allergies are increasing in prevalence and as a disease burden throughout the world, however they seem to increasingly affect countries with a formerly low prevalence. Consideration and diagnosis of food allergies are important as it has ramifications that affect a child's diet, care at school and home and is recognised to be associated with anxiety of parents, family and care takers. Food allergies vary significantly between countries, however nut allergies appear to be widely associated with serious reactions and death. The value of specific food immunoglobulin E (IgE) and skin prick tests (SPT) has been extensively analysed in children in recent years and can provide very useful information in an appropriately selected population. Diagnosis may require formal challenges to confirm a genuine allergic reaction condition rather than an intolerance reaction due to other mechanisms. The medical care of a food allergic child requires concurrent dietary advice and management, risk avoidance and emergency management plans. Reintroduction of foods occurs when the risk profile is appropriate based mainly on the predictive information obtained by SPTs and specific IgE levels. Fortunately allergies to egg and milk resolve by 3-5 years in about 80% of children. There have been some recent advances in immunotherapeutic approaches to food allergy although this has not translated to success in human treatment to date.

Clinical implications of cross-reactive food allergens

As a consequence of the general increase in allergic sensitization, the prevalence of hypersensitivity reactions to multiple foods that share homologous proteins has become a significant clinical problem. A variety of these allergens conserved among plants (eg, profilin and lipid transfer proteins) and animals (eg, tropomyosin and caseins) have been characterized. Although studies with molecular biologic techniques have elucidated the nature of these ubiquitous allergens, clinical studies have lagged behind. The physician is called on to determine the risk of reaction to related foods among legumes, tree nuts, fish, shellfish, cereal grains, mammalian and avian food products, and a variety of other plant-derived foods that may share proteins with pollens, latex, and each other. Clinical evaluations require a careful history, laboratory evaluation, and in some cases oral food challenges. The pitfalls in the evaluation of food allergy-unreliable histories and limitations in laboratory assessment primarily caused by false-positive skin prick test responses/RAST results are magnified when dealing with cross-reactive proteins. This review focuses on the clinical data regarding cross-reacting food allergens with the goal of providing a background for improved risk assessment and a framework on which to approach these difficult clinical questions.

Allergy to Diplotaxis erucoides pollen: occupational sensitization and cross-reactivity with other common pollens

BACKGROUND

Diplotaxis erucoides is a common weed of the Brassicaceae family widespread in southern and central Europe.

METHODS

A total of 410 consecutive patients referred for allergy study of rhinoconjunctivitis and/or asthma were skin tested with D. erucoides pollen, 14 proving positive. A purified D. erucoides pollen extract was prepared to perform quantitative skin tests, provocation tests, immunoblotting, and EIA inhibition in the 14 sensitized patients.

RESULTS

Three patients, directly involved in viniculture, had rhinoconjunctivitis related to D. erucoides pollen. No D. erucoides-related symptoms were observed in most patients, who were also sensitized to Artemisia pollen. RAST was positive in 12/14 patients and nasal provocation tests in 9/12. The molecular masses of the most prevalent IgE-binding proteins ranged from 26 to 27.5 and from 31 to 34 kDa. D. erucoides pollen inhibited the IgE-binding of other sensitizing pollens in the three viniculture workers, whereas both Artemisia and D. erucoides pollen produced similar heterologous inhibition in the pooled serum of the remaining, nonclinically affected, D. erucoides-sensitized patients.

CONCLUSION

D. erucoides pollen may be an important prevalent aeroallergen, particularly in rural areas. It may act as an occupational allergen in vineyard workers, in whom it seems to be the primary sensitizing agent, playing a secondary cross-reactive role in other sensitized patients.