Biomedical subjects

Marjolein Wensing

Publications and source records attributed to Marjolein Wensing.

8 recordsLinked to original sources

PubMed2005

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.

Allergens↗

PubMed2004

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.

Cacao↗

PubMed2004

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.

Adolescent↗

PubMed2003

Patients with anaphylaxis to pea can have peanut allergy caused by cross-reactive IgE to vicilin (Ara h 1).

BACKGROUND: Serologic cross-reactivity among legumes has been described; however, it is rarely clinically significant. In this study 3 patients with a history of anaphylaxis to pea are described who subsequently had symptoms after ingestion of peanut. OBJECTIVE: We investigated whether the peanut-related symptoms were due to cross-reactivity between pea and peanut proteins. METHODS: Peanut-related symptoms were documented according to case history or double-blind, placebo-controlled food challenge results. Skin prick tests were performed, and specific IgE levels were determined for pea and peanut with the CAP system FEIA. IgE-binding proteins in pea and peanut were identified by using immunoblot analysis. Cross-reactivity was studied by means of immunoblot and ELISA inhibition studies with whole extracts and purified allergens. RESULTS: Peanut-related symptoms consisted of oral symptoms in all patients, with additional urticaria and dyspnea or angioedema in 2 patients. All patients had a positive skin prick test response and an increased IgE level to pea and peanut. Immunoblotting revealed strong IgE binding to mainly vicilin in pea extract and exclusively to Ara h 1 in crude peanut extract. Immunoblot and ELISA inhibition studies with crude extracts, as well as purified proteins, showed that IgE binding to peanut could be inhibited by pea but not or only partially the other way around. CONCLUSION: Clinically relevant cross-reactivity between pea and peanut does occur. Vicilin homologues in pea and peanut (Ara h 1) are the molecular basis for this cross-reactivity.

Allergens↗

PubMed2003

How accurate and safe is the diagnosis of hazelnut allergy by means of commercial skin prick test reagents?

BACKGROUND: Allergy to tree nuts, like hazelnuts, ranks among the most frequently observed food allergies. These allergies can start at early childhood and are, in contrast to other food allergies, not always outgrown by the patient. Tree nut allergy is frequently associated with severe reactions. Diagnosis partially relies on in vivo testing by means of a skin prick test (SPT) using commercially available SPT reagents. METHODS: Protein and allergen composition of nine commercial SPT solutions was evaluated using standard protein detection methods and specific immunoassays for measurement of five individual allergens. Diagnostic performance was assessed by SPT in 30 hazelnut-allergic subjects, of which 15 were provocation proven. RESULTS: Protein concentrations ranged from 0.2-14 mg/ml. SDS-PAGE/silver staining revealed clear differences in protein composition. The major allergen Cor a 1 was present in all extracts but concentrations differed up to a factor 50. An allergen associated with severe symptoms, Cor a 8 (lipid transfer protein), was not detected on immunoblot in three products, and concentrations varied by more than a factor 100 as was shown by RAST inhibition. Similar observations were made for profilin, thaumatin-like protein and a not fully characterized 38-kD allergen. Ratios of individual allergens were variable among the nine extracts. SPT showed significant difference, and 6/30 patients displayed false-negative results using 3/9 products. CONCLUSION: Variability in the composition of products for the diagnosis of hazelnut allergy is extreme. Sometimes, allergens implicated in severe anaphylaxis are not detected by immunoblotting. These shortcomings in standardisation and quality control can potentially cause a false-negative diagnosis in subjects at risk of severe reactions to hazelnuts.

Adolescent↗

PubMed2003

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.

Humans↗

PubMed2002

IgE to Bet v 1 and profilin: cross-reactivity patterns and clinical relevance.

BACKGROUND: Individuals with pollen allergy often have IgE against plant-derived foods. This can be due to cross-reactive IgE against Bet v 1 and homologues, profilins, and/or cross-reactive carbohydrate determinants. OBJECTIVE: The aim of this study was to correlate sensitization to Bet v 1 and profilin with individual recognition patterns to plant foods and clinical relevance. METHODS: Fifty-two patients with pollen allergy and IgE against at least one plant-derived food were included in the study. Adverse reactions to plant-derived foods were documented by using standardized interviews. Skin prick tests were performed for pollen (grass, birch, and mugwort) and 14 plant-derived foods. In addition, recombinant (r) Bet v 1 and rBet v 2 (profilin) were tested intracutaneously. Specific IgE against the abovementioned allergens were determined by means of RAST. Cross-reactivity was studied by means of RAST inhibition. RESULTS: Eighty-five percent of patients were sensitized to Bet v 1, and 71% were sensitized to profilin. Profilin was associated with a higher number of positive RAST results to plant-derived foods than Bet v 1. In contrast, Bet v 1 was associated with more positive skin prick test responses and more food-related symptoms. Sensitization to Bet v 1 was associated with IgE against apple, hazelnut, and peach, whereas sensitization to profilin was associated with positive RAST results to all investigated plant-derived foods except apple, peach, and melon. CONCLUSIONS: IgE antibodies against Bet v 1 have a more limited spectrum of cross-reactivity than those against profilin, but they frequently give rise to clinically relevant cross-reactivities to food. In analogy to anticarbohydrate IgE, cross-reactive IgE against food profilins have no or very limited clinical relevance.

Adolescent↗

PubMed2002

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.

Adolescent↗