Detection of Soy Proteins in Processed Foods: Literature Overview and New Experimental Work

Several tests for the detection of soy proteins in foods have been described in the literature, and some are commercially available. This article gives an overview of these methods and discusses the advantages and disadvantages of each individual method. Based on the conclusions of this inventory, an experimental approach was designed to improve the sensitivity of measuring soy protein in processed foods. The aimed sensitivity is 10 ppm (10 μg soy protein in 1 g solid sample), which is over 100-fold lower than presently available tests. The aimed sensitivity is this low because levels of food allergens at 10 ppm and above may provoke reactions in food allergic persons. Native soybean meal, soy protein isolate, soy protein concentrate, and textured soy flakes were used as test materials. Several extraction procedures were compared and a new method using high pH was selected. Polyclonal antibodies were raised in rabbits and goats, and immunopurified antibodies were used in sandwich and inhibition enzyme-linked immunosorbent assay (ELISA). Extraction at pH 12 resulted in good yields for all tested samples, both quantitatively (Bradford) and qualitatively by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Immunopurified rabbit antibodies against this extract used in a competition ELISA format resulted in a sensitive test with a detection limit of 0.02 μg/mL, corresponding to 0.4 μg/g (0.4 ppm) in food samples. Cross-reactivity with some main food ingredients was measured and appeared to be negative in all cases. The presently developed test is applicable for soy ingredients and soy-containing foods that are processed in different ways. The limit of quantitation is 1 ppm, which is an enormous improvement over earlier described methods.

Clinical relevance of sensitization to lupine in peanut-sensitized adults

BACKGROUND

The use of lupine in food has been increasing during the last decade and allergic reactions to lupine have been reported, especially in peanut-allergic patients. The frequency and the degree of cross-reactivity to other legumes are not known. The aim of the study was to investigate the frequency of sensitization to lupine, and in addition to pea and soy, and its clinical relevance, in peanut-sensitized patients. Furthermore, to determine the eliciting dose (ED) for lupine using double-blind placebo-controlled food challenges (DBPCFC).

METHODS

Thirty-nine unselected peanut-sensitized patients were evaluated by skin prick tests (SPT) and ImmunoCAP to lupine, pea, and soy. Clinical reactivity was measured by DBPCFC for lupine, and by history for pea and soy.

RESULTS

Eighty-two percent of the study population was sensitized to lupine, 55% to pea, and 87% to soy. Clinically relevant sensitization to lupine, pea, or soy occurred in 35%, 29%, and 33% respectively of the study population. None of the patients was aware of the use of lupine in food. The lowest ED for lupine, inducing mild subjective symptoms, was 0.5 mg, and the no observed adverse effect level (NOAEL) was 0.1 mg. No predictive factors for lupine allergy were found.

CONCLUSION

In peanut-sensitized patients, clinically relevant sensitization to either lupine or to pea or soy occurs frequently. The ED for lupine is low (0.5 mg), which is only fivefold higher than for peanut. Patients are not aware of lupine allergy and the presence of lupine in food, indicating that education is important to build awareness.

Does skin prick test reactivity to purified allergens correlate with clinical severity of peanut allergy?

BACKGROUND

Recognition of specific peanut allergens or the diversity of IgE binding to peanut allergens may play a role in the elicitation of severe allergic reactions.

OBJECTIVE

To investigate whether sensitization to individual allergens Ara h 1, Ara h 2, Ara h 3 and Ara h 6 is correlated with clinical severity.

METHODS

The reactivity of purified peanut allergens was measured by skin prick test (SPT) and by IgE immunoblot in 30 patients. The results were related to the clinical reactivity by history, and in 25 of them to the eliciting dose (ED).

RESULTS

The majority of patients recognized Ara h 2 and Ara h 6. Patients with severe symptoms had a higher SPT response to Ara h 2 and Ara h 6 at low concentrations (0.1 micro g/mL) and to Ara h 1 and Ara h 3 at higher concentrations (100 micro g/mL), compared with patients with mild symptoms. They also recognized a greater number of allergens and showed a higher cumulative SPT response compared with patients with mild symptoms. No significant differences were observed between patients with a low or high ED.

CONCLUSIONS

Ara h 2 and Ara h 6 appeared to be more potent than Ara h 1 and Ara h 3. Both SPT reactivity to low concentrations of Ara h 2 and Ara h 6 and to higher concentrations of Ara h 1 and Ara h 3 were shown to be indicative of severe symptoms.

Consumer attitudes and risks associated with packaged foods having advisory labeling regarding the presence of peanuts

BACKGROUND

Foods with advisory labeling (eg, "may contain") are increasingly prevalent. Consumers with food allergies might ignore advisory labeling advice.

OBJECTIVE

We sought to determine whether consumers with food allergy heeded advisory labels and whether products with advisory labels contained detectable peanut allergen.

METHODS

Surveys (n = 625 in 2003 and n = 645 in 2006) were conducted at Food Allergy & Anaphylaxis Network patient conferences. Food products bearing advisory statements regarding peanuts were analyzed for the presence of peanut.

RESULTS

Consumers were less likely to heed advisory labeling in 2006 (75%) compared with in 2003 (85%, P < .01); behavior varied significantly according to the form of the statement. Peanut protein was detected in 10% (20/200) of total food products bearing advisory statements, although clinically significant levels of peanut (>1 mg of peanut or >0.25 mg of peanut protein) were detected in only 13 of 200 such products.

CONCLUSION

Consumers with food allergy are increasingly ignoring advisory labeling. Because food products with advisory labeling do contain detectable levels of peanuts, a risk exists to consumers choosing to eat such foods. The format of the labeling statement did not influence the likelihood of finding detectable peanut, except for products listing peanuts as a minor ingredient, but did influence the choices of consumers with food allergy.

CLINICAL IMPLICATIONS

Allergic patients are taking risks by increasingly disregarding advisory labeling.

Determination of no-observed-adverse-effect levels and eliciting doses in a representative group of peanut-sensitized children

BACKGROUND

Current labeling practices for allergenic foods like peanut can be inadequate. For future regulatory and industry guidelines, information on no-observed-adverse-effect levels (NOAELs) and eliciting doses (EDs) for allergenic foods is necessary.

OBJECTIVE

To determine NOAEL and ED in a representative group of peanut-sensitized children, relate these data to history and sensitization, and evaluate the outcome of dietary management.

METHODS

From an overall eligible group of 96 peanut-sensitized children, a representative group of 27 was evaluated by questionnaires, skin prick test, determination of specific IgE, and double-blind placebo-controlled food challenge (DBPCFC) with peanut according to the international consensus protocol, with 9 doses ranging from 10 microg to 3 g peanut flour. Dietary management was evaluated over a 12-month period.

RESULTS

Twenty-two children (81%) had a positive DBPCFC. The NOAEL in this group was 1 mg peanut flour, corresponding to 2 mg whole peanut. The ED for subjective symptoms (10 mg to 3 g) was significantly lower than for objective symptoms (100 mg to 3 g; P = .002). Severe reactions occurred only at high doses. EDs were not correlated to previous reactions by history, skin prick test, or specific IgE levels. All patients with a positive DBPCFC were advised to follow a strict diet. During the follow-up period, 10 patients had a less strict diet likely containing traces of peanut. In 3 cases, a mild reaction occurred with food products labeled "may contain peanut."

CONCLUSION

The NOAEL in a representative group of children with peanut allergy was 2 mg. Dietary compliance in half of this group was inadequate.

IgE Binding to Pepsin-Digested Food Extracts

BACKGROUND

Pepsin resistance of allergens like lipid transfer protein and 2S albumin has been suggested as explanation for the severity of symptoms often induced by these allergens. Component-resolved diagnosis with purified labile and stable allergens has therefore been proposed to better characterize the risk involved in a positive in vitro IgE test. However, for many foods, purified allergens are not (yet) available.

OBJECTIVE

It was the aim of this study to evaluate the potential of pepsin-digested whole-food extracts to distinguish between IgE responses to stable (potentially severe) and labile (mild) allergens.

METHODS

Sera (n = 143) from Italian, Spanish and Dutch patients with hazelnut and/or apple ingestion-related symptoms were analyzed for residual IgE binding to pepsin-resistant hazelnut and/or apple allergens. Control and pepsin-digested hazelnut and apple extracts were used for radioallergosorbent test analysis and immunoblot analysis.

RESULTS

Pepsin digestion of food extracts, like from hazelnut and apple used for in vitro diagnostic tests, provides a way to distinguish sensitization to pepsin-resistant allergens from that to pepsin-susceptible allergens. In this selected group of patients, IgE reactivity to pepsin-digested extracts correlated with sensitization to the stable allergen lipid transfer protein. The analysis further revealed that the use of soluble pepsin can result in false-positive in vitro tests (2/143).

CONCLUSION

Pepsin-digested food extracts are a convenient tool to identify patients with IgE antibodies against potentially dangerous stable allergens, in particular for those foods where the relevant stable allergens have not yet been identified. This can increase the clinical prognostic value of food allergy serology.

Proteolytic processing of the peanut allergen Ara h 3

The allergen Ara h 3 has been purified recently from peanuts. In contrast to recombinant Ara h 3, a 60 kDa single-chain polypeptide, the allergen isolated from its native source is extensively proteolytically processed. The characteristic proteolytic processing for 11S plant storage proteins of the glycinin family is observed for Ara h 3 yielding an acidic and a basic subunit, bound by a disulfide bridge. In addition to this, proteolytic truncation is observed for the acidic subunit but not for the basic subunit of Ara h 3. A series of Ara h 3 polypeptides ranging from 13-45 kDa was separated by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and each band was digested by trypsin. Peptides related to the bands were identified and a scheme positioning the different polypeptides in the Ara h 3 sequence has been constructed. Peptide analysis showed sequence heterogeneity at two positions indicating the presence of multiple genes encoding variant, but highly homologous Ara h 3 proteins. The pool of Ara h 3 polypeptides from its native source illustrated that allergen from the peanut is much more complex than the recombinant protein used for epitope mapping experiments. From several Ara h 3 truncation products one or more immunoglobulin E (IgE) binding sites had been removed. Characterization of the allergenicity of Ara h 3 should therefore also include IgE-binding studies with peanut-derived Ara h 3, providing the high degree of variation in the Ara h 3 protein structure, as this is what peanut-allergic individuals are confronted with.

Purification and immunoglobulin E-binding properties of peanut allergen Ara h 6: evidence for cross-reactivity with Ara h 2

BACKGROUND

IgE-binding peanut proteins smaller than 15 kDa were previously identified as potential allergens in the majority of our peanut allergic population.

OBJECTIVE

To characterize the novel allergen in order to determine whether it was similar to one of the thus far identified recombinant peanut allergens (Ara h 1-7).

METHODS

An IgE-binding protein of <15 kDa was purified and identified via N-terminal sequencing. Its IgE-binding properties were investigated using immunoblotting, basophil degranulation, and skin prick testing. Possible cross-reacting epitopes with other peanut allergens were studied using IgE-immunoblotting inhibition.

RESULTS

The purified protein is a monomeric protein with a molecular weight of 14,981 Da as determined using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectroscopy. The amino acid sequence of the first 39 N-terminal residues is identical to that of Ara h 6, indicating that the allergen is Ara h 6. It is recognized by 20 out of 29 peanut-allergic patients on IgE-immunoblot, and its potent biological functionality is demonstrated by the degranulation of basophils, even at concentrations below 10 pg/mL, and by positive skin prick reactions. Ara h 6 has homology to Ara h 2, especially in the middle part and at the C-terminal part of the protein. Almost complete inhibition of IgE-Ara h 6 interaction with Ara h 2 demonstrates that at least part of the epitopes of Ara h 6 are cross-reactive with epitopes on Ara h 2.

CONCLUSIONS

Peanut-derived Ara h 6 is a biologically active allergen recognized by the majority of our peanut-allergic patient population and can be considered a clinically relevant peanut allergen.

Assessing Genetically Modified Crops to Minimize the Risk of Increased Food Allergy: A Review

The first genetically modified (GM) crops approved for food use (tomato and soybean) were evaluated for safety by the United States Food and Drug Administration prior to commercial production. Among other factors, those products and all additional GM crops that have been grown commercially have been evaluated for potential increases in allergenic properties using methods that are consistent with the current understanding of food allergens and knowledge regarding the prediction of allergenic activity. Although there have been refinements, the key aspects of the evaluation have not changed. The allergenic properties of the gene donor and the host (recipient) organisms are considered in determining the appropriate testing strategy. The amino acid sequence of the encoded protein is compared to all known allergens to determine whether the protein is a known allergen or is sufficiently similar to any known allergen to indicate an increased probability of allergic cross-reactivity. Stability of the protein in the presence of acid with the stomach protease pepsin is tested as a risk factor for food allergenicity. In vitro or in vivo human IgE binding are tested when appropriate, if the gene donor is an allergen or the sequence of the protein is similar to an allergen. Serum donors and skin test subjects are selected based on their proven allergic responses to the gene donor or to material containing the allergen that was matched in sequence. While some scientists and regulators have suggested using animal models, performing broadly targeted serum IgE testing or extensive pre- or post-market clinical tests, current evidence does not support these tests as being predictive or practical. Based on the evidence to date, the current assessment process has worked well to prevent the unintended introduction of allergens in commercial GM crops.

Reversible denaturation of Brazil nut 2S albumin (Ber e1) and implication of structural destabilization on digestion by pepsin

The high resistance of Brazil nut 2S albumin, previously identified as an allergen, against proteolysis by pepsin was examined in this work. Although the denaturation temperature of this protein exceeds the 110 degrees C at neutral pH, at low pH a fully reversible thermal denaturation was observed at approximately 82 degrees C. The poor digestibility of the protein by pepsin illustrates the tight globular packing. Chemical processing (i.e., subsequent reduction and alkylation of the protein) was used to destabilize the globular fold. Far-UV circular dichroism and infrared spectroscopy showed that the reduced and alkylated form had lost its beta-structures, whereas the alpha-helix content was conserved. The free energy of stabilization of the globular fold of the processed protein as assessed by a guanidine titration study was only 30-40% of that of the native form. Size exclusion chromatography indicated that the heavy chain lost its globular character once separated from the native 2S albumin. The consequences of these changes in structural stability for degradation by pepsin were analyzed using gel electrophoresis and mass spectrometry. Whereas native 2S albumin was digested slowly in 1 h, the reduced and alkylated protein was digested completely within 30 s. These results are discussed in view of the potential allergenicity of Brazil nut 2S albumin.

A novel approach for the detection of potentially hazardous pepsin stable hazelnut proteins as contaminants in chocolate-based food

Contamination of food products with pepsin resistant allergens is generally believed to be a serious threat to patients with severe food allergy. A sandwich type enzyme-linked immunosorbent assay (ELISA) was developed to measure pepsin resistant hazelnut protein in food products. Capturing and detecting rabbit antibodies were raised against pepsin-digested hazelnut and untreated hazelnut protein, respectively. The assay showed a detection limit of 0.7 ng/mL hazelnut protein or <1 microg hazelnut in 1 g food matrix and a maximum of 0.034% cross-reactivity (peanut). Chocolate samples spiked with 0.5-100 microg hazelnut/g chocolate showed a mean recovery of 97.3%. In 9/12 food products labeled "may contain nuts", hazelnut was detected between 1.2 and 417 microg hazelnut/g food. It can be concluded that the application of antibodies directed to pepsin-digested food extracts in ELISA can facilitate specific detection of stable proteins that have the highest potential of inducing severe food anaphylaxis.

A randomized, double-blinded, placebo-controlled oral challenge study to evaluate the allergenicity of commercial, food-grade fish gelatin

BACKGROUND

Recent interest in the labeling of foods and food proteins derived from allergenic sources necessitates determination of the potential allergenicity of such food ingredients. Fish gelatin is extracted from the skin of fish species known to elicit allergic reactions in sensitized individuals.

OBJECTIVE

To determine the allergenicity of fish gelatin by double-blinded, placebo-controlled food challenges (DBPCFC) in clinically fish-allergic individuals.

METHODS

Thirty fish-allergic patients diagnosed according to the EAACI Guidelines were included (age 9-50 years). Skin prick tests (SPT) and Histamine Release tests (HR) were performed with fish gelatin and codfish, and codfish-specific IgE was measured. All patients underwent DBPCFC with a cumulative dose of 14.61 g fish gelatin.

RESULTS

In all 30 patients SPT, HR, and specific IgE to codfish were positive. SPT and HR with fish gelatin were positive in 3/30 and 7/30, respectively. One patient showed mild reaction to placebo and no reaction to the active challenge. Two patients reported mild subjective reactions to active challenge. Upon re-challenge one of them described subjective symptoms again to the active challenge (7.61 g cumulated dose of fish gelatin) with no reaction to placebo, while the other experienced very mild subjective symptoms to placebo and nothing to the active. The proportion of truly sensitive patients was estimated to 0.03 in the total study group.

CONCLUSION

None of 30 fish allergic patients reacted adversely to the ingestion of 3.61 g cumulative dose of fish gelatin. In this study fish gelatin presents no risk to fish-allergic patients at the doses typically used. Statistically, these results indicate that there is 95% certainty that 90% of fish-allergic consumers will not react to ingestion of a 3.61 g cumulative dose of fish gelatin.

Ara h 8, a Bet v 1–homologous allergen from peanut, is a major allergen in patients with combined birch pollen and peanut allergy

BACKGROUND

We recently described patients with soybean allergy mainly mediated by cross-reactivity to birch pollen allergens. A majority of those patients were reported to have peanut allergy.

OBJECTIVE

We sought to study the occurrence of peanut allergy in patients allergic to birch pollen and characterized the Bet v 1-homologous peanut allergen Ara h 8.

METHODS

Recombinant Ara h 8 was cloned with degenerated primers and expressed in Escherichia coli. Nine Swiss and 11 Dutch patients with peanut and birch pollen allergy and a positive double-blind, placebo-controlled food challenge result to peanut were investigated for IgE reactivity to birch pollen and purified peanut allergens and cross-reactivity between birch and peanut. Ara h 8 stability against digestion and roasting was assessed by means of RAST inhibition. The IgE cross-linking potency of Ara h 8 was tested on the basis of basophil histamine release.

RESULTS

During double-blind, placebo-controlled food challenge, all patients experienced symptoms in the oral cavity, progressing to more severe symptoms in 40% of patients. CAP-FEIA detected recombinant (r) Ara h 8-specific IgE in 85%. IgE binding to Ara h 8 was inhibited by Bet v 1 in peanut extract immunoblotting and in RAST inhibition. In EAST inhibition recombinant rAra h 8 inhibited IgE binding to peanut in 4 of 7 tested patient sera. Antipeanut response was dominated by Ara h 8 in 12 of 17 tested patients. Furthermore, our results demonstrate a low stability of Ara h 8 to roasting and no stability to gastric digestion. Basophil histamine release with rAra h 8 was more than 20% in 5 of 7 tested sera.

CONCLUSIONS

Peanut allergy might be mediated in a subgroup of our patients by means of cross-reaction of Bet v 1 with the homologous peanut allergen Ara h 8.

Detection of soy proteins in processed foods: literature overview and new experimental work

Several tests for the detection of soy proteins in foods have been described in the literature, and some are commercially available. This article gives an overview of these methods and discusses the advantages and disadvantages of each individual method. Based on the conclusions of this inventory, an experimental approach was designed to improve the sensitivity of measuring soy protein in processed foods. The aimed sensitivity is 10 ppm (10 microg soy protein in 1 g solid sample), which is over 100-fold lower than presently available tests. The aimed sensitivity is this low because levels of food allergens at 10 ppm and above may provoke reactions in food allergic persons. Native soybean meal, soy protein isolate, soy protein concentrate, and textured soy flakes were used as test materials. Several extraction procedures were compared and a new method using high pH was selected. Polyclonal antibodies were raised in rabbits and goats, and immunopurified antibodies were used in sandwich and inhibition enzyme-linked immunosorbent assay (ELISA). Extraction at pH 12 resulted in good yields for all tested samples, both quantitatively (Bradford) and qualitatively by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Immunopurified rabbit antibodies against this extract used in a competition ELISA format resulted in a sensitive test with a detection limit of 0.02 microg/mL, corresponding to 0.4 microg/g (0.4 ppm) in food samples. Cross-reactivity with some main food ingredients was measured and appeared to be negative in all cases. The presently developed test is applicable for soy ingredients and soy-containing foods that are processed in different ways. The limit of quantitation is 1 ppm, which is an enormous improvement over earlier described methods.

Validated sandwich enzyme-linked immunosorbent assay for casein and its application to retail and milk-allergic complaint foods

Cows' milk is a commonly allergenic food. Cross-contamination of milk proteins into nondairy, kosher-pareve foods prepared on shared processing equipment can cause severe, life-threatening reactions in milk-allergic individuals. A sandwich-type enzyme-linked immunosorbent assay (ELISA; 96-well plate format) was developed for the detection of undeclared casein in foods. Rabbit anti-casein antibodies were used as the capture reagent. Food samples and standards were ground, extracted in 0.01 M phosphate-buffered saline, clarified by centrifugation, and added to the wells. Goat anti-casein antibodies were employed as the detector antibody, and the amount of antibody bound was determined with a commercial rabbit anti-goat immunoglobulin conjugated to alkaline phosphatase, with subsequent substrate reaction. Antibodies developed were specific to casein, with no cross-reaction observed with 30 foods and food ingredients. Non-milk-containing products such as fruit juices, fruit juice bars, sorbets, and dark and pareve-labeled chocolate were purchased from June 2002 through June 2003. In addition, samples allegedly causing eight milk-allergic consumer complaints were analyzed. The ELISA had a detection limit of less than 0.5 ppm of casein. The casein content in the analyzed foods ranged from less than 0.5 ppm to more than 40,000 ppm casein; undeclared casein residues were found in all of the samples implicated in allergic reactions. The levels of milk contamination in some of the other surveyed products could also be hazardous for milk-allergic consumers. This ELISA method provides a useful quality control tool for the food industry and could also be used as a validation of kosher-pareve status.

A multi-laboratory evaluation of a common in vitro pepsin digestion assay protocol used in assessing the safety of novel proteins

Rationale. Evaluation of the potential allergenicity of proteins derived from genetically modified foods has involved a weight of evidence approach that incorporates an evaluation of protein digestibility in pepsin. Currently, there is no standardized protocol to assess the digestibility of proteins using simulated gastric fluid. Potential variations in assay parameters include: pH, pepsin purity, pepsin to target protein ratio, target protein purity, and method of detection. The objective was to assess the digestibility of a common set of proteins in nine independent laboratories to determine the reproducibility of the assay when performed using a common protocol. Methods. A single lot of each test protein and pepsin was obtained and distributed to each laboratory. The test proteins consisted of Ara h 2 (a peanut conglutin-like protein), beta-lactoglobulin, bovine serum albumin, concanavalin A, horseradish peroxidase, ovalbumin, ovomucoid, phosphinothricin acetyltransferase, ribulose diphosphate carboxylase, and soybean trypsin inhibitor. A ratio of 10U of pepsin activity/microg test protein was selected for all tests (3:1 pepsin to protein, w:w). Digestions were performed at pH 1.2 and 2.0, with sampling at 0.5, 2, 5, 10, 20, 30, and 60min. Protein digestibility was assessed from stained gels following SDS-PAGE of digestion samples and controls. Results. Results were relatively consistent across laboratories for the full-length proteins. The identification of proteolytic fragments was less consistent, being affected by different fixation and staining methods. Overall, assay pH did not influence the time to disappearance of the full-length protein or protein fragments, however, results across laboratories were more consistent at pH 1.2 (91% agreement) than pH 2.0 (77%). Conclusions. These data demonstrate that this common protocol for evaluating the in vitro digestibility of proteins is reproducible and yields consistent results when performed using the same proteins at different laboratories.

A consensus protocol for the determination of the threshold doses for allergenic foods: how much is too much?

BACKGROUND

While the ingestion of small amounts of an offending food can elicit adverse reactions in individuals with IgE-mediated food allergies, little information is known regarding these threshold doses for specific allergenic foods. While low-dose challenge trials have been conducted on an appreciable number of allergic individuals, a variety of different clinical protocols were used making the estimation of the threshold dose very difficult.

OBJECTIVE

A roundtable conference was convened to develop a consensus clinical protocol for low-dose challenge trials for the estimation of threshold doses for specific allergenic foods.

METHODS

In May 2002, 20 clinical allergists and other interested parties were invited to participate in a roundtable conference to develop consensus of the key elements of a clinical protocol for low-dose challenge trials.

RESULTS

A consensus protocol was developed. Patients with convincing histories of food allergies and supporting diagnostic evidence including past challenge trials or high CAP-RAST scores can be enrolled in low-dose challenge trials. Care must be taken with younger patients to assure that they have not outgrown their food allergy. An approach was developed for the medication status of patients entering such trials. Challenge materials must be standardized, for example, partially defatted peanut flour composed of equal amounts of the three major varieties of peanuts (Florunner, Virginia, Spanish). Challenge materials must be appropriately blinded with sensory evaluation used to confirm the adequacy of blinding. A double-blind, placebo-controlled design should be used for low-dose challenge trials. Low-dose challenge trials would begin at doses of 10 microg of the allergenic food and would continue with doses of 100 microg and 1 mg followed by specific higher doses up to 100 mg depending upon the expert judgement of the physician; even higher doses might be applied to assure that the patient is indeed reactive to the particular food. A 30-min time interval would be used between doses, and reactive doses would be expressed as both discrete and cumulative doses. The goal of each challenge would be to develop objective symptoms; trials should not be discontinued on the basis of subjective symptoms only. Statistically, a minimum of 29 patients would be enrolled in low-dose challenge trials for each allergenic food because 0 reactors out of 29 patients at a particular dose allow the conclusion that there is 95% certainty that 90% of allergic individuals will not react to that dose.

CONCLUSION

A consensus protocol was developed. Using this protocol, it will be possible to estimate threshold doses for allergenic foods, the lowest amount that elicits mild, objective symptoms in highly sensitive individuals.

Food allergy and the food industry

Although most food-allergic reactions occur after ingestion of nonpackaged food products, the food industry has been subjected to increasing scrutiny of their allergen controls; the resulting impact on the industry has been remarkable. Undeclared food allergens have been responsible for many food product recalls during the past 13 years, and the food industry has made significant investment, effort, and improvements in allergen control during this time. Recently, tests for some allergenic foods have been commercialized, and proven useful to the industry in controlling allergens and helpful for regulatory agencies investigating food-allergic consumer complaints. However, testing methods still do not exist for some of the common allergenic foods. Labeling initiatives have been pursued to make ingredient listings more easily understood by food-allergic consumers, but further improvements could still be made. Additional research to determine eliciting doses for allergenic foods is needed to enable science-based risk assessment and risk management.

Presentation of allergen in different food preparations affects the nature of the allergic reaction - a case series

BACKGROUND

Characterization of fatal and non-fatal reactions to food indicates that the majority of reactions are due to the ingestion of prepared foods rather than the non-processed allergen. In an ongoing study that used a double-blind placebo-controlled food challenge to investigate peanut allergy and clinical symptoms, the observed reaction severity in four of the first six subjects was greater than anticipated. We hypothesized that this was due to differences in the composition of the challenge vehicle.

OBJECTIVE

The aim was to investigate whether the severity of observed challenge reactions would be repeated on re-challenge with a lower fat challenge vehicle.

METHODS

Peanut-allergic subjects were re-challenged with a lower fat recipe after reacting more severely than was anticipated to an initial peanut challenge. Similar challenge vehicle recipes were used, the only difference being the lower fat content (22.9% compared with 31.5%). The peanut content of the two recipes was analysed using RAST inhibition studies and ELISA tests.

RESULTS

Three of four subjects reacted to much smaller doses of peanut protein on re-challenge (mean dose equivalence - 23 times less peanut) with the lower fat recipe. RAST inhibition showed that neither recipe altered epitope recognition. The higher fat recipe required twice as much peanut to cause 50% inhibition. ELISA detected far lower levels of peanut in the higher fat recipe (220 000 parts per million (p.p.m.)) than in the lower fat recipe (990 000 p.p.m.).

CONCLUSION

The fat content of a challenge vehicle has a profound effect on the reaction experienced after allergen ingestion. This is another factor to be considered in assessing the risk of certain foods to food-allergic consumers and adds another dimension to clinical, research and regulatory practice.

Peanut allergen Ara h 3: isolation from peanuts and biochemical characterization

BACKGROUND

Peanut allergen Ara h 3 has been the subject of investigation for the last few years. The reported data strongly depend on recombinant Ara h 3, since a purification protocol for Ara h 3 from peanuts was not available.

METHODS

Peanut allergen Ara h 3 (glycinin), was purified and its posttranslational processing was investigated. Its allergenic properties were determined by studying IgE binding characteristics of the purified protein.

RESULTS

Ara h 3 consists of a series of polypeptides ranging from approximately 14 to 45 kDa that can be classified as acidic and basic subunits, similar to the subunit organization of soy glycinin. N-terminal sequences of the individual polypeptides were determined, and using the cDNA deduced amino-acid sequence, the organization into subunits was explained by revealing posttranslational processing of the different polypeptides. IgE-binding properties of Ara h 3 were investigated using direct elisa and Western blotting with sera from peanut-allergic individuals. The basic subunits, and to a lesser extent the acidic subunits, bind IgE and may act as allergenic peptides.

CONCLUSIONS

We conclude that peanut-derived Ara h 3, in contrast to earlier reported recombinant Ara h 3, resembles, to a large extent, the molecular organization typical for proteins from the glycinin family. Furthermore, posttranslational processing of Ara h 3 affects the IgE-binding properties and is therefore an essential subject of study for research on the allergenicity of Ara h 3.

In vitro and in vivo characterization of hazelnut skin prick test extracts

RATIONALE

Hazelnut allergy ranks among the most frequently observed food allergies. Clinical symptoms range from the oral allergy syndrome to life threatening anaphylaxis. Diagnosis of hazelnut allergy partially relies on in vivo testing by means of skin prick testing (SPT). The aim of this study was to characterize hazelnut SPT extracts both in vitro and in vivo.

METHODS

Hazelnut SPT extracts were investigated for protein concentration and composition. The major hazelnut allergen Cor a 1, lipid transfer protein (LTP) and thaumatin-like-protein (TLP) were monitored by competitive RIA and immunoblotting. SPT extracts (n = 6) were analyzed for skin reactivity and the correlation between the SPT extract protein concentration and the mean skin reactivity (HEIC) was determined in a group of hazelnut-allergic patients (n = 30). For one SPT extract, the threshold level for Cor a 1 was determined in Cor a 1-monosensitized patients (n = 5).

RESULTS

Protein concentrations ranged from 0.2-14 mg/ml. Although some proteins were present in most extracts (bands at 10, 22-28, 32 and around 48 kDa), clear differences in composition were observed (both intra- and inter-variability). The concentration of the major hazelnut allergen Cor a 1 differed up to a factor 50 (0.6-32 micrograms/ml). LTP was virtually absent in 3/9 SPT extracts and variable quantities of TLP were detected by immunoblotting. Some patients (6/30) had a false-negative SPT with 3/6 SPT extracts. There was a clear correlation between the protein concentration and the mean HEIC (RPearson = 0.87). The threshold level for Cor a 1 was +/- 3.2 ng/ml as assessed with one of the products investigated.

CONCLUSIONS

Heterogeneous protein concentration/composition of SPT extracts results in variable skin test responses. The absence of potentially severe allergens like LTP may lead to false-negative SPT results that jeopardize a patient's safety. From these results it can be concluded that there is a strong need for standardization of products for SPT.

The distribution of individual threshold doses eliciting allergic reactions in a population with peanut allergy

BACKGROUND

Hidden peanut in consumer products can endanger patients with peanut allergy. Individual threshold doses for eliciting allergic reactions need to be elucidated to assess the risks for development of allergic reactions after accidental ingestion of peanut in a population with peanut allergy.

OBJECTIVE

We sought to determine the distribution of individual threshold doses in a population with peanut allergy and to correlate these thresholds to the severity of peanut-induced symptoms.

METHODS

Twenty-six adult patients with a convincing history of peanut-related symptoms, a specific IgE level of 0.7 kU/L or greater, or a positive skin prick test response of 2+ or greater to peanut were included. These patients underwent double-blind, placebo-controlled food challenges with increasing doses of peanut. A threshold dose could be established when objective or repetitive subjective reactions occurred after active doses.

RESULTS

All patients had subjective oral symptoms (n = 26), prior subjective gastrointestinal symptoms (n = 14), or objective symptoms (n = 5). Reactions started within 30 minutes after ingestion of peanut, but in 2 patients additional symptoms were delayed by 1 to 2 hours. Threshold doses for allergic reactions ranged from a dose as low as 100 microg up to 1 g of peanut protein. Fifty percent of the study population (95% CI, 30%-70%) already had an allergic reaction after ingestion of 3 mg of peanut protein. Patients with severe symptoms had lower threshold doses compared with those of patients with mild symptoms (P =.027).

CONCLUSIONS

A substantial part of a population with peanut allergy will react to very low amounts of peanut, requiring accurate declaration of peanut content in consumer products. This is even more important because patients with severe reactions react to lower doses than patients with mild symptoms.

The range of minimum provoking doses in hazelnut-allergic patients as determined by double-blind, placebo-controlled food challenges

BACKGROUND

The risk for allergic reactions depends on the sensitivity of individuals and the quantities of offending food ingested. The sensitivity varies among allergic individuals, as does the threshold dose of a food allergen capable of inducing an allergic reaction.

OBJECTIVE

This study aimed at determining the distribution of minimum provoking doses of hazelnut in a hazelnut-allergic population.

METHODS

Thirty-one patients with a history of hazelnut-related allergic symptoms, a positive skin prick test to hazelnut and/or an elevated specific IgE level, were included. Double-blind, placebo-controlled food challenges (DBPCFC) were performed with seven increasing doses of dried hazelnut (1 mg to 1 g hazelnut protein) randomly interspersed with seven placebo doses.

RESULTS

Twenty-nine patients had a positive challenge. Itching of the oral cavity and/or lips was the first symptom in all cases. Additional gastrointestinal symptoms were reported in five patients and difficulty in swallowing in one patient. Lip swelling was observed in two patients, followed by generalized urticaria in one of these. Threshold doses for eliciting subjective reactions varied from a dose of 1 mg up to 100 mg hazelnut protein (equivalent to 6.4-640 mg hazelnut meal). Extrapolation of the dose-response curve showed that 50% of our hazelnut-allergic population will suffer from an allergic reaction after ingestion of 6 mg (95% CI, 2-11 mg) of hazelnut protein. Objective symptoms were observed in two patients after 1 and 1,000 mg, respectively.

CONCLUSION

DBPCFCs demonstrated threshold doses in half of the hazelnut-allergic patients similar to doses previously described to be hidden in consumer products. This stresses the need for careful labelling and strategies to prevent and detect contamination of food products with hazelnut residues.

Bioinformatic methods for allergenicity assessment using a comprehensive allergen database

BACKGROUND

A principal aim of the safety assessment of genetically modified crops is to prevent the introduction of known or clinically cross-reactive allergens. Current bioinformatic tools and a database of allergens and gliadins were tested for the ability to identify potential allergens by analyzing 6 Bacillus thuringiensis insecticidal proteins, 3 common non-allergenic food proteins and 50 randomly selected corn (Zea mays) proteins.

METHODS

Protein sequences were compared to allergens using the FASTA algorithm and by searching for matches of 6, 7 or 8 contiguous identical amino acids.

RESULTS

No significant sequence similarities or matches of 8 contiguous amino acids were found with the B. thuringiensis or food proteins. Surprisingly, 41 of 50 corn proteins matched at least one allergen with 6 contiguous identical amino acids. Only 7 of 50 corn proteins matched an allergen with 8 contiguous identical amino acids. When assessed for overall structural similarity to allergens, these 7 plus 2 additional corn proteins shared >or=35% identity in an overlap of >or=80 amino acids, but only 6 of the 7 were similar across the length of the protein, or shared >50% identity to an allergen.

CONCLUSIONS

An evaluation of a protein by the FASTA algorithm is the most predictive of a clinically relevant cross-reactive allergen. An additional search for matches of 8 amino acids may provide an added margin of safety when assessing the potential allergenicity of a protein, but a search with a 6-amino-acid window produces many random, irrelevant matches.

Genetically engineered foods: implications for food allergy

The products of agricultural biotechnology, including such common foods as corn and soybeans, are already reaching the consumer marketplace. Consumer exposure to such foods is already fairly significant, particularly in the USA. Thus far, no reports exist regarding allergic reactions to the crops that have been approved for introduction into the food supply. These crops have been modified to only a minor extent by comparison with their traditional counterparts, and the level of expression of new and novel proteins is quite low. Thus, consumer exposure to these novel proteins is very low and unlikely to result in allergic sensitization. Nevertheless, foods produced through agricultural biotechnology must be assessed for safety, including their potential allergenicity, before they may be approved by worldwide regulatory agencies for entry into the food supply. However, the adequacy of the current approach to the assessment of the potential allergenicity of foods produced through agricultural biotechnology has been the subject of considerable scientific and regulatory debate.

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.

How much food is too much? Threshold doses for allergenic foods

This review summarizes recent findings and controversies in the area of threshold doses for allergenic foods. Over the years, there have been many clinical reports that ingestion of small amounts of food can elicit IgE-mediated allergic reactions. In exquisitely allergic individuals, the threshold dose for elicitation of such reactions is often considered to be zero. However, some food-allergic patients report that they can tolerate small quantities of allergenic food. Are very low quantities hazardous to food-allergic consumers? How much of the offending food is too much? Why is the concept of a threshold level important? There have been very few studies to date on threshold doses for allergenic foods, and more research is needed in this important area.

Development of a sandwich enzyme-linked immunosorbent assay for the detection of egg residues in processed foodst

Chicken eggs are used extensively as an excellent source of dietary proteins. These proteins have many functional properties, making them valuable food ingredients. However, eggs are a frequent cause of food hypersensitivity, especially in children. Of major concern to food processors is the inadvertent cross-contact of food products with allergenic residues, which could result in potentially life-threatening reactions in those with a food allergy. The aim of the present study was to develop an enzyme-linked immunosorbent assay (ELISA) for the detection of undeclared egg residues in foods. Commercially purified ovalbumin (OVA) and dehydrated egg white solids were used as antigens to induce antibodies in rabbits and goats. Reference pasta standards and various food samples were extracted, then clarified by centrifugation. Goat anti-egg white antibodies were used as the capture reagent, nonspecific sites were blocked with gelatin, then standard and sample extracts were added. Rabbit anti-OVA antibodies were used as detector antibodies, followed by addition of commercial goat anti-rabbit IgG antibody labeled with alkaline phosphatase and subsequent substrate addition. Twenty brands of egg-free pasta (two lots each) were analyzed using the ELISA. Fourteen common pasta ingredients were also evaluated for cross-reactivity problems in the method. The detection limit of the assay was 1 ppm spray-dried whole egg. Fifty-five percent (22 samples) of the egg-free pasta samples tested positive for the presence of undeclared egg residues, with values ranging from 1 to >100,000 ppm. Minimal cross-reactivity was encountered in general, but portobello mushrooms and basil caused some minor matrix effects. This sandwich-type ELISA method can be used to detect undeclared egg residues in processed foods and to evaluate industrial clean-up operations.

Ingredient and labeling issues associated with allergenic foods

Foods contain a wide range of food ingredients that serve numerous technical functions. Per capita consumer exposure to most of these food ingredients is rather low with a few notable exceptions such as sugar and starch. Some food ingredients including edible oils, hydrolyzed proteins, lecithin, starch, lactose, flavors and gelatin may, at least in some products, be derived from sources commonly involved in IgE-mediated food allergies. These ingredients should be avoided by consumers with allergies to the source material if the ingredient contains detectable protein residues. Other food ingredients, including starch, malt, alcohol and vinegar, may be derived in some cases from wheat, rye or barley, the grains that are implicated in the causation of celiac disease. If these ingredients contain gluten residues, then they should be avoided by celiac sufferers. A few food ingredients are capable of eliciting allergic sensitization, although these ingredients would be classified as rarely allergenic. These ingredients include carmine, cochineal extract, annatto, tragacanth gum and papain. Food manufacturers should declare the presence of allergenic food ingredients in the ingredient listings on product labels so that allergic consumers can know to avoid these potentially hazardous products.

Hidden food allergens

This review summarizes recent advances and findings in the area of 'hidden' food allergens, i.e. allergenic foods that can either contaminate other foods, or be 'disguised' as part of a food, and cause allergic reactions. Newly emerging allergenic foods of increasing importance, recently developed methods for the detection of allergenic residues, the potential allergenicity of genetically engineered foods, and some unexpected sources of food allergens are described.

Will genetically modified foods be allergenic?

Foods produced through agricultural biotechnology, including such staples as corn, soybeans, canola, and potatoes, are already reaching the consumer marketplace. Agricultural biotechnology offers the promise to produce crops with improved agronomic characteristics (eg, insect resistance, herbicide tolerance, disease resistance, and climatic tolerance) and enhanced consumer benefits (eg, better taste and texture, longer shelf life, and more nutritious). Certainly, the products of agricultural biotechnology should be subjected to a careful and complete safety assessment before commercialization. Because the genetic modification ultimately results in the introduction of new proteins into the food plant, the safety, including the potential allergenicity, of the newly introduced proteins must be assessed. Although most allergens are proteins, only a few of the many proteins found in foods are allergenic under the typical circumstances of exposure. The potential allergenicity of the introduced proteins can be evaluated by focusing on the source of the gene, the sequence homology of the newly introduced protein to known allergens, the expression level of the novel protein in the modified crop, the functional classification of the novel protein, the reactivity of the novel protein with IgE from the serum of individuals with known allergies to the source of the transferred genetic material, and various physicochemical properties of the newly introduced protein, such as heat stability and digestive stability. Few products of agricultural biotechnology (and none of the current products) will involve the transfer of genes from known allergenic sources. Applying such criteria provides reasonable assurance that the newly introduced protein has limited capability to become an allergen.

Effect of ICAM-1 blockade on lung inflammation and physiology during acute viral bronchiolitis in rats

Viral respiratory infections cause acute bronchiolitis and physiologic dysfunction in human infants and in animals. It is possible that the pulmonary dysfunction is a consequence of the inflammatory cells that are recruited during viral illness. We hypothesized that blockade of intercellular adhesion molecule-1 (ICAM-1), a major cell adhesion molecule, would impede the ingress of leukocytes during viral infection and attenuate virus-induced pulmonary dysfunction. Adult male rats were inoculated with parainfluenza type 1 (Sendai) virus or sterile vehicle, and treated with blocking or nonblocking MAb specific for rat ICAM-1. Respiratory system resistance, oxygenation (PaO2), methacholine responsiveness, and bronchoalveolar lavage (BAL) leukocyte counts were measured in anesthetized, paralyzed, ventilated rats. Treatment with the blocking ICAM-1 antibody reduced virus-induced increases in BAL neutrophils and lymphocytes by 70% (p < 0.001), but did not affect BAL monocytes/macrophages. Peripheral blood leukocyte counts were elevated in anti-ICAM-1 blocking antibody-treated rats (p = 0.0003). Although virus-induced increases in resistance and decreases in PaO2 were not affected by anti-ICAM-1 treatment, there was a small but significant attenuation of virus-induced methacholine hyperresponsiveness (p = 0.02). We conclude that ICAM-1 has an important role in neutrophil and lymphocyte infiltration during respiratory viral illness, and that virus-induced changes in pulmonary physiology are not related directly to the numbers of neutrophils and lymphocytes that migrate to the air spaces during infection.

2S methionine-rich protein (SSA) from sunflower seed is an IgE-binding protein

BACKGROUND

Sunflower seed contains 2S albumins that in other crops have been associated with allergenicity. The sunflower seed methionine-rich 2S albumin (SSA) may be an IgE-binding protein responsible for anaphylactic reactions in some sunflower seed-sensitive subjects. The objective was to demonstrate that SSA is an IgE-binding protein.

METHODS

SSA was purified and the amino-acid sequence determined. The degree of purity of SSA was evaluated by silver staining, and its IgE-binding capacity by immunoblotting with serum from a subject with a convincing clinical history of anaphylaxis to sunflower seed.

RESULTS

The amino-acid sequence confirmed that the purified protein was the mature form of the methionine-rich storage protein SSA from sunflower seed (Helianthus annuus). The SSA was specifically recognized by IgE from the serum of the sunflower seed-allergic subject.

CONCLUSIONS

SSA is an IgE-binding protein, and subjects allergic to sunflower seed whose IgE binds to SSA are at risk of developing allergic reactions if they consume SSA.

A sandwich enzyme-linked immunosorbent assay for the detection of almonds in foods

An enzyme-linked immunosorbent assay was developed to detect almonds as potential allergenic contaminants in food. Polyclonal antibodies directed against roasted almonds were partially purified from immunized sheep and rabbits and used as capture and secondary antibodies, respectively, in a sandwich-type, 96-well plate format. Food samples and almond-spiked samples were extracted 1:10 in phosphate-buffered saline at 60 degrees C for 2 h, centrifuged, and applied to wells coated with sheep anti-almond antibody. After incubation, washing, and the addition of rabbit anti-almond antibody, the amount of almond present was detected with the subsequent addition of goat anti-rabbit immunoglobulin G-alkaline phosphatase conjugate and p-nitrophenyl phosphate substrate. Plate absorbances were read at 410 nm, and standard curves were developed in all matrices to quantify unknowns. Antibodies developed were specific for almond; however, some cross-reactivity was observed with extracts of some tree nuts and sesame seeds. Sodium dodecylsulfate-polyacrylamide gel electrophoresis and Western immunoblotting indicated that sheep anti-almond antibody recognized proteins extracted from black walnuts, Brazil nuts, cashews, hazelnuts, macadamia nuts, pistachios, and sesame seeds in addition to those from almond. The assay was optimized to detect less than 1 ppm of almond and was used successfully to determine almond residues in cereal and chocolate without cross-reacting interferences. A retail survey of 20 brands of cereal demonstrated that the assay produced statistically consistent results. This assay provides a useful quality control tool for the food industry for the protection of consumers allergic to almonds.

Identification of sunflower seed IgE-binding proteins

BACKGROUND

Sunflower seed can cause severe anaphylactic reactions in some susceptible individuals. It is conceivable that the 2S sunflower seed protein is an allergen based on its high degree of homology (34%) with the allergenic mature 2S albumin protein of the Brazil nut. The first step in determining the allergenicity of sunflower seed proteins is to identify IgE-binding proteins.

METHODS

Sera from sunflower seed-sensitive individuals were evaluated by radioallergosorbent test (RAST), isoelectric focusing (IEF) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis immunoblotting with sunflower seed proteins.

RESULTS

Positive RAST scores (>2) were observed in 3 individuals and immunoblotting demonstrated IgE-binding to 2-7 distinct proteins ranging in size from 10 to 50 kD. Two out of 3 sera recognized two proteins between 16 and 17 kD. The lower molecular weight protein (16 kD) approximates to the prepo region of the precursor methionine-rich 2S albumin protein found in sunflower seed (SFA-8/SSA). IEF followed by immunoblotting demonstrated several IgE-binding proteins, including two proteins with isoelectric points of 5.97 and 5.3, respectively, which are consistent with the mature and immature forms of the SFA-8/SSA region.

CONCLUSIONS

Sunflower seed contains several IgE-binding proteins, including regions of the high-methionine 2S albumin SFA-8/SSA.

Impact of processing on food allergens

In general, allergenic foods are resistant to processes commonly used in food manufacturing. Nearly all the causative proteins (allergens) retain their allergenicity after treatment by heat and/or proteolysis. Notable exceptions exist; for example, the allergenicity of many fresh fruits and vegetables is decreased or removed by relatively mild processes such as gentle heating or mashing. The use of proteolytic enzymes to remove allergenicity is successfully used in the production of hypoallergenic infant formulas, but this approach with other allergenic foods has resulted in only limited success. Processing effects can result in decreased or complete removal of allergenic qualities of a food, such as the removal of proteins in oilseed processing, which renders the oils hypoallergenic and safe for consumption by allergic individuals. This discussion will address the different allergenic foods and processes which can affect or decrease their allergenicity.

Anaphylaxis in a milk-allergic child following ingestion of lemon sorbet containing trace quantities of milk

Although allergic persons can react to foods containing trace quantities of unlabeled or unintended food allergens, there are few data available on the quantities of these allergens required to evoke allergic symptoms. We report a milk-allergic 3-year-old boy who experienced throat itching, facial angioedema, and vomiting within 20 min of ingesting 4 to 6 oz (ca. 113.4 to 170.1 g) of lemon sorbet. Subsequent analysis of two sorbet samples provided by the parents and a third sample purchased locally by the investigators revealed trace quantities of milk allergens, whey protein (8.8 micrograms/ml), or lactose (200 ppm). The quantity of whey protein ingested was estimated to be 120 to 180 micrograms (equivalent to 23 to 24 microliters of milk). All three sorbet samples had been manufactured in the same plant within a 4-month period; the equipment used to produce and package the sorbet was also used to produce and package ice cream. No milk allergen or whey protein was detected in 38 other marketplace sorbet samples submitted by the manufacturer for testing. We concluded that trace quantities of whey proteins (< 200 micrograms) can elicit systemic reactions in exquisitely milk-allergic individuals. Such individuals should avoid eating frozen desserts prepared using equipment also used for producing or packaging ice cream, unless manufacturers can demonstrate unequivocally that their cleaning practices are sufficient to prevent milk contamination. Adequate tests are not currently available to food manufacturers but are under development.

An evaluation of the sensitivity of subjects with peanut allergy to very low doses of peanut protein: a randomized, double-blind, placebo-controlled food challenge study

BACKGROUND

The minimum dose of food protein to which subjects with food allergy have reacted in double-blind, placebo-controlled food challenges is between 50 and 100 mg. However, subjects with peanut allergy often report severe reactions after minimal contact with peanuts, even through intact skin.

OBJECTIVE

We sought to determine whether adults previously proven by challenge to be allergic to peanut react to very low doses of peanut protein.

METHODS

We used a randomized, double-blind, placebo-controlled food challenge of 14 subjects allergic to peanuts with doses of peanut ranging from 10 microg to 50 mg, administered in the form of a commercially available peanut flour.

RESULTS

One subject had a systemic reaction to 5 mg of peanut protein, and two subjects had mild objective reactions to 2 mg and 50 mg of peanut protein, respectively. Five subjects had mild subjective reactions (1 to 5 mg and 4 to 50 mg). All subjects with convincing objective reactions had short-lived subjective reactions to preceding doses, as low as 100 microg in two cases. Five subjects did not react to any dose up to 50 mg.

CONCLUSION

Even in a group of well-characterized, highly sensitive subjects with peanut allergy, the threshold dose of peanut protein varies. As little as 100 microg of peanut protein provokes symptoms in some subjects with peanut allergy.