Characterization of the sensitization profile to lupin in peanut-allergic children and assessment of cross-reactivity risk

Protein Concentration Affects the Food Allergen γ-Conglutin Uptake and Bacteria-Induced Cytokine Production in Dendritic Cells

γ-Conglutin (γ-C) from lupin seeds has been identified as a potent allergen with cross reactivity to peanuts. Here, we investigated how γ-C affected the response in bone marrow-derived dendritic cells (DCs) to bacterial stimuli. γ-C enhanced L. acidophilus NCFM (LaNCFM)-induced IL-12, IL-10, and IL-23 dose-dependently. In contrast, together with E. coli Nissle or LPS, γ-C reduced the production of IL-12 but not of IL-23 and IL-10. Enzyme-hydrolyzed γ-C also enhanced LaNCFM-induced IL-12 and IL-23 production. All preparations induced ROS production in the DCs. The mannose receptor ligands mannan and dextran and the clathrin inhibitor monodansylcadaverine partly inhibited the endocytosis of γ-C. Kunitz trypsin inhibitor and the scavenger receptor ligand polyG also enhanced LaNCFM-induced IL-12, indicating the involvement of receptors other than C-type lectin receptors. The endocytosis of labeled γ-C increased dose-dependently by addition of unlabeled γ-C, which coincided with γ-C's tendency to aggregate. Taken together, γ-C aggregation affects endocytosis and affects the cytokine production induced by gram-positive and gram-negative bacteria differently. We suggest that γ-C is taken up by the same mechanism as other food proteins but due to aggregation is present in higher concentration in the DCs. This could influence the resulting T-cell response in a microbial stimuli-dependent way.

High prevalence of lupin allergy among patients with peanut allergy: Identification of γ-conglutin as major allergen

BACKGROUND

Lupin is a protein-rich legume with a growing presence in the food market worldwide. With increased consumption, lupin allergy (LA) reports are also rising. Uncertainties exist on the cross-reactivity between peanut and lupin, the allergenic potential of different lupin species, and sensitization patterns among different populations.

OBJECTIVE

To evaluate the molecular basis of LA and to determine lupin allergens from 3 different species that may be involved in peanut allergy (PA) cross-reactivity.

METHODS

A total of 43 subjects with PA, those with LA, or controls without food allergy were evaluated with skin prick tests (SPTs) and specific IgEs (sIgEs). Lupin-sensitized subjects were offered a lupin oral food challenge (OFC). Immunoblots and enzyme-linked immunosorbent assays were performed on sera from lupin-sensitized subjects.

RESULTS

In this study, 44% of the PA subjects were confirmed to have LA by OFC. Anaphylaxis was the most frequent manifestation after lupin consumption, with a minimal eliciting dosage of 1 g lupin flour. There was no difference in lupin sIgE or SPT wheal size between lupin-sensitized and confirmed LA subjects or in the severity of symptoms among confirmed LA subjects. Sera from lupin-sensitized subjects uniformly reacted to all 3 different lupin species. Immunoblotting and enzyme-linked immunosorbent assays revealed immunoglobulin E binding to α- and γ-conglutin in all analyzed sera, whereas α- and β-conglutin recognition was variable.

CONCLUSION

Our findings reveal a high prevalence of LA among PA subjects, emphasizing lupin must be labeled as an allergen in foods. Owing to high variability in lupin-sIgE and lupin-SPT results, LA diagnosis may require OFC. In our population, γ-conglutin is the major allergen of lupin.

Identification of a vicilin-like major allergen from Prosopis juliflora exhibiting cross- reactivity with legume food allergens

BACKGROUND

Prosopis juliflora is a clinically relevant allergic sensitizer worldwide and shares cross-reactivity with allergens from several tree pollen and food. The present study aims to purify and immunobiochemically characterize a major allergen from Prosopis pollen. The allergen was further investigated for its cross-reactivity with legume allergens.

METHODS

Prosopis extract was fractionated by Q Sepharose and Superdex 75 gel filtration column to purify the allergen. Specific IgE against purified protein was estimated via ELISA and immunoblot. The protein was subjected to mass spectrometric analysis. Glycan characterization was performed by Schiff staining and lectin binding assay followed by deglycosylation studies. The functional activity of the purified protein was evaluated by the basophil activation test. Cross-reactivity was assessed by inhibition studies with legume extracts.

RESULTS

A 35 kDa protein was purified and showed 75% IgE reactivity with the patients' sera by ELISA and immunoblot. Glycan characterization of protein demonstrated the presence of terminal glucose and mannose residues. A reduction of 40% and 27% in IgE binding was observed upon chemical and enzymatic deglycosylation of the protein, respectively. The glycoprotein allergen upregulates the expression of CD203c on basophils which was significantly reduced upon deglycosylation, signifying its biological ability to activate the effector cells. The identified protein shared significant homology with Lup an 1 from the lupine bean. Immunoblot inhibition studies of the purified allergen with legume extracts underlined high cross-reactive potential. Complete inhibition was observed with peanut and common bean, while up to 70% inhibition was demonstrated with soy, black gram, chickpea, and lima bean.

CONCLUSION

A 35 kDa vicilin-like major allergen was isolated from P. juliflora. The protein possesses glycan moieties crucial for IgE binding and basophil activation. Furthermore, the purified protein shows homology with Lup an 1 and exhibits cross-reactivity with common edible legume proteins.

Lupine allergens: Clinical relevance, molecular characterization, cross-reactivity, and detection strategies

Lupine is commonly utilized as a technological food and ingredient in a great variety of processed products (snacks, bakery, meat, and dairy products) principally owing to its nutritional value and technological properties. However, its ingestion, even at trace amounts (in the range of mg protein per kg of food), can lead to severe adverse reactions in allergic individuals. Lupine belongs to the Leguminosae family, having the conglutins (α-, β-, δ-, and γ-) as allergens, among other proteins. Cross-sensitization of lupine-sensitized individuals with other legume species, mainly peanut, can occur, but the associated clinical reactivity is still unclear. The protection of the sensitized individuals should depend on an avoidance diet, which should rely on the compliance of food labeling and, as such, on their verification by analytical methods. Food processing, such as heat treatments, has an important influence on the structural properties of lupine proteins, altering their detectability and allergenicity. In this review, different aspects related with lupine allergy are described, namely, the overall prevalence, clinical relevance, diagnosis, and treatment. The characterization of lupine allergens and their potential cross-reactivity with other legumes are critically discussed. The effects of food matrix, processing, and digestibility on lupine proteins, as well as the available analytical tools for detecting lupine at trace levels in foods, are also herein emphasized.

Enzymatic hydrolysis of lupin protein isolates-Changes in the molecular weight distribution, technofunctional characteristics, and sensory attributes

Enzymatic hydrolysis of lupin protein isolates (LPI; Lupinus angustifolius L.) was performed with nine different protease preparations to investigate their effect on technofunctionality, sensory properties, and the integrity of the proteins to estimate the reduction of the immunoreactivity. Alcalase 2.4 L, papain, and pepsin were most effective in the degradation of the α- and β-conglutin examined by SDS-PAGE analysis, although the degree of hydrolysis only slightly increased. The technofunctional properties of LPI-solubility, emulsifying, and foaming activity-were improved by most of the proteolytic enzymes with the most impressive increase from 980% foam activity for LPI up to 3,614% foam activity for pepsin hydrolysate. The formation of bitterness, most likely linked to generation of bitter peptides, was pronounced in the Alcalase hydrolysate, while the other hydrolysates did not show an extensive increase in bitterness compared to the LPI. Other sensory attributes of the hydrolysates-with the exception of Alcalase treatment-were also very similar to the LPI. The results of this study show the potential of enzymatic degradation of LPI to modify the IgE-reacting polypeptides and to improve the technofunctionality of the isolates and therefore their use as food ingredients.

Food-Induced Anaphylaxis: Role of Hidden Allergens and Cofactors

Food anaphylaxis is on the increase, with those who have an allergy to peanuts, tree nuts, milk, and seafood at the highest risk of developing such a reaction. However, the diet in many societies is increasingly varied, much of the food consumed is prepared outside the home, and meals are often composed of many different ingredients. Anaphylaxis may occur to a composite food, and it may be unclear whether the reaction is due to contamination or to a culprit allergen present in an added ingredient. Composite foods can contain many allergic proteins present in small amounts, which do not always have to be labeled, unless they feature in European or US labeling regulations. These “hidden” allergens include mustard, celery, spices, lupine, pea, natural food colourings, and preservatives, but can occasionally include allergenic material from contaminants such as cereal mites. Hidden allergens can provoke severe reactions to seemingly unconnected foods which might then lead to a diagnosis of idiopathic anaphylaxis. The same problem can arise with two well-known types of food allergy; wheat-dependant exercise induced anaphylaxis and allergy to non-specific Lipid Transfer Protein allergens, both of which might only manifest when linked to a cofactor such as exercise. Many of these risk factors for food anaphylaxis have a common link; the public's engagement with popular concepts of health and fitness. This includes the development of a food and exercise culture involving the promotion and marketing of foods for their health-giving properties i.e., meat substitutes, wheat substitutes, supplements and alternative, or “natural” remedies for common ailments. Some of these foods have been reported as the cause of severe allergic reactions, but because they are often viewed as benign unlikely causes of severe allergic reactions, could be considered to be hidden allergens. The best resource to elicit the likelihood of a hidden allergen provoking an allergic reaction is to take a detailed history of the allergic reaction, presence of co-factors, foods suspected, type of food and where it was consumed. A good knowledge of commonly used ingredients, and list of potential hidden allergen suspects are essential tools for the food allergy detective.

Allergy to Peanut, Soybean, and Other Legumes: Recent Advances in Allergen Characterization, Stability to Processing and IgE Cross-Reactivity

Peanut and soybean are members of the Leguminosae family. They are two of the eight foods that account for the most significant food allergies in the United States and Europe. Allergic reactions to other legume species can be of importance in other regions of the world. The major allergens from peanut and soybean have been extensively analyzed and members of new protein families identified as potential marker allergens for symptom severity. Important recent advances concerning their molecular properties or clinical relevance have been made. Therefore, there is increasing interest in the characterization of allergens from other legume species such as lupine, lentil, chickpea, green bean, or pea. As legumes are mainly consumed after thermal processing, knowledge about the effect of such processing on the allergenicity of legumes has increased during the last years. In the present review, recent advances in the identification of allergens from peanut, soybean, lupine, and other legume species are summarized and discussed. An overview of the most recently described effects of thermal processing on the allergenic properties of legumes is provided and the potential IgE cross-reactivity among members of the Leguminosae family is discussed.

Lupin and Other Potentially Cross-Reactive Allergens in Peanut Allergy

PURPOSE OF REVIEW

The presence of IgE cross-reactivity between peanut allergens and allergens from other legumes and tree nuts has been demonstrated, but the identification of the involved individual allergens is still limited. The aim of this review is to describe new allergenic findings, of potential relevance for cross-reactivity among peanut and lupin.

RECENT FINDINGS

Seventeen allergens of peanut have been included in the official allergen nomenclature database to date. Lupin sensitization has been observed in 15-20% of individuals with known peanut allergy, The majority of lupin seed proteins are comprised of α-conglutins (legumin-like) and β-conglutins (vicilin-like), and to a lesser extent γ-conglutins (vicilin-like) and δ-conglutins (2S albumins). Several molecules may fuel peanut-lupin cross-reactivity. Awareness among physicians and general public could avoid unexpected allergic reactions. However, these do not appear frequent and no data suggest a precautionary labelling of lupin in foods.

Molecular characterization of allergens in raw and processed kiwifruit

BACKGROUND

The prevalence of allergy to kiwifruit is increasing in Europe since the last two decades. Different proteins have been identified as kiwifruit allergens; even though with geographic differences, Act d 1, a cysteine protease protein of 30 kDa, and Act d 2, a thaumatin-like protein of 24 kDa, are normally considered the most important. The aim of this study was (i) to identify at molecular level the sensitization pattern in a group of well-characterized patients allergic to kiwifruit and (ii) to assess the role of technological treatments on kiwifruit allergenic potential.

METHODS

The differences in the pattern of antigenicity between fresh and processed kiwifruit were evaluated by both immunoelectrophoretic techniques and clinical tests.

RESULTS

In the group of patients included in this study, three proteins were identified as major allergens in fresh kiwifruit, as the specific sensitization was present in ≥50% of the subjects. These proteins corresponded to actinidin (Act d 1), pectin methyl aldolase (Act d 6), and thaumatin-like protein (Act d 2). Kiwellin (Act d 5) and proteins of Bet v 1 family (Act d 8/act d 11) were also recognized as minor allergens. Immunoreactivity was totally eliminated by industrial treatments used for the production of kiwifruit strained derivative.

CONCLUSIONS

In this group of allergic children, the technological treatments used in the production of kiwifruit strained product reduced drastically the allergenic potential of kiwifruit.

Diagnosis and treatment of pediatric food allergy: an update

The prevalence of pediatric food allergy and anaphylaxis has increased in the last decades, especially in westernized countries where this emerging phenomenon was marked as a "second wave" of the allergic epidemic. Over recent years great advances have been achieved in the field of in vitro allergy testing and component-resolved diagnosis has increasingly entered clinical practice. Testing for allergen components can contribute to a more precise diagnosis by discriminating primary from cross-reactive sensitizations and assessing the risk of severe allergic reactions.The basic concept of the management of food allergy in children is also changing. Avoidance of the offending food is still the mainstay for disease management, especially in primary health care settings, but it severely affects the patients' quality of life without reducing the risk of accidental allergic reactions. There is a growing body of evidence to show that specific oral tolerance induction can represent a promising treatment option for food allergic patients. In parallel, education of food allergic patients and their caregivers as well as physicians about anaphylaxis and its treatment is becoming recognized a fundamental need. International guidelines have recently integrated these new evidences and their broad application all over Europe represents the new challenge for food allergy specialists.

Detection of Lupine (Lupinus spp. L.) as a food allergen using three methods: end-point PCR, Real-Time PCR and Elisa

The aim of this work was to compare three methods for the detection and quantification of lupine as an allergen in food. The methods that were used in this work were the direct method: ELISA and the indirect methods: end-point PCR and real-time PCR. We examined the detection limit (the sensitivity with which we can detect the presence of the allergen in a sample) and the reliability for performing an analysis. We used 17 samples of plant species from a processing plant for dehydrated soups production and lupine samples from lupine processing companies. Its practical use is wide and it is used mainly in the bakery industry, in the manufacture of confectionery, pasta, sauces, as a substitute for soy and also in the production of gluten-free food, because it does not contain gluten. Lupine, however, is also included in the list of 14 allergenic substances, which in accordance with the EU legislation must be listed on food labels. The high risk group, which suffers from primary sensitization or cross-reaction with peanuts, are allergic patients. In the EU, people who are allergic to peanuts range from 0.7 to 1.5%. In experiment 1, we detected the presence of lupine using primers for the detection of α- and δ-conglutine in the samples, using the end-point PCR method and the detection limit of this reaction was at the level of 100 ppm. For the vizualization of the DNA fragments, we used a 2% agarose gel and UV visualizer. In experiment 2 we detected lupine using the TaqMan real-time PCR reaction and primers for the detection of α and δ-conglutine at the level of 10 ppm of lupine in sample. The CP values of lupine using primers for the detection of α-conglutine was 24.85 ± 0.12 and the reliability equation was R2 = 0.9767. The CP lupine values using primers for the detection of δ-conglutine was 22.52 ± 0.17 and the reliability equation was R2 = 0.9925. In experiment 3, we used a sandwich ELISA method for the detection of lupine and the detection limit was within the range of 2-30 ppm and the reliability of the method according to the reliability equation was R2 = 0.9975. The high sensitivity and equation of reliability justify the use of these methods for the detection and quantification of lupine in practice. The most sensitive indirect method for the detection of lupine in our study was the method of real-time TaqMan PCR with a detection limit  10 000-10 ppm of lupine. The most sensitive direct methot was ELISA with detection limit 2-30 ppm of lupine.

Cross-reactivity of peanut allergens

Peanut seeds are currently widely used as source of human food ingredients in the United States of America and in European countries due to their high quality protein and oil content. This article describes the classification and molecular biology of peanut seed allergens with particular reference to their cross-reactivities. Currently, the IUIS allergen nomenclature subcommittee accepts 12 peanut allergens. Two allergens belong to the cupin and four to the prolamin superfamily, and six are distributed among profilins, Bet v 1-like proteins, oleosins, and defensins. Clinical observations frequently report an association of peanut allergy with allergies to legumes, tree nuts, seeds, fruits and pollen. Molecular cross-reactivity has been described between members of the Bet v 1-like proteins, the non-specific lipid transfer proteins, and the profilins. This review also addresses the less well-studied cross-reactivity between cupin and prolamin allergens of peanuts and of other plant food sources and the recently discovered cross-reactivity between peanut allergens of unrelated protein families.

Component-resolved diagnostics for the evaluation of peanut allergy in a low-prevalence area

BACKGROUND

Major allergenic components of peanut from distinct geographical regions are widely dispersed. Most of the diagnostic studies are from countries with a high prevalence. There have been only few reports of allergen component sensitizations from countries with a low prevalence of peanut allergy. We aimed to investigate roles of component-resolved diagnostic (CRD) to differentiate peanut allergy and peanut tolerance in the Asian population from a country with low prevalence of peanut allergy.

METHODS

Participants with peanut sensitization were enrolled. Clinical reactions were determined. Skin prick test (SPT) and specific IgE (sIgE) to peanut and related allergen components were performed.

RESULTS

Forty subjects with peanut sensitization were included. The mean wheal sizes of SPT and peanut sIgE were not good predictors for differentiating peanut reactions. SIgE to rAra h 2 was more often found in patients with peanut allergy and anaphylaxis. sIgE to rAra h 9 was also more frequent in the peanut-allergic group but not related to severe reactions. In the peanut-tolerant group, despite positive SPT and/or sIgE to peanut, 90% had negative sIgE to rAha h 2 and rAra h 9. Combining rAra h 2 and rAra h 9 resulted in high performance of the test with sensitivity, specificity, positive predictive value, and negative predictive value of 84%, 90%, 0.89, and 0.86, respectively. The ratio between rAra h 2 sIgE to peanut sIgE of 0.6 can be helpful in predicting patients who will develop severe reaction. SIgE to cross-reactive carbohydrate determinants (CCD) was exclusively found in the peanut-tolerant group (33.3% vs. 0%, p = 0.012).

CONCLUSIONS

Our study identifies three allergen components: rAra h 2, rAra h 9, and CCD as important components in the diagnosis of peanut allergy in an Asian country with low prevalence. The ratio between rArah h 2 sIgE to peanut sIgE can be used for predicting patients who will develop anaphylaxis.