Expression, purification, cross-reactivity and homology modeling of peanut profilin

Legume Allergens Pea, Chickpea, Lentil, Lupine and Beyond

PURPOSE OF THE REVIEW

In the last decade, an increasing trend towards a supposedly healthier vegan diet could be observed. However, recently, more cases of allergic reactions to plants and plant-based products such as meat-substitution products, which are often prepared with legumes, were reported. Here, we provide the current knowledge on legume allergen sources and the respective single allergens. We answer the question of which legumes beside the well-known food allergen sources peanut and soybean should be considered for diagnostic and therapeutic measures.

RECENT FINDINGS

These "non-priority" legumes, including beans, pea, lentils, chickpea, lupine, cowpea, pigeon pea, and fenugreek, are potentially new important allergen sources, causing mild-to-severe allergic reactions. Severe reactions have been described particularly for peas and lupine. An interesting aspect is the connection between anaphylactic reactions and exercise (food-dependent exercise-induced anaphylaxis), which has only recently been highlighted for legumes such as soybean, lentils and chickpea. Most allergic reactions derive from IgE cross-reactions to homologous proteins, for example between peanut and lupine, which is of particular importance for peanut-allergic individuals ignorant to these cross-reactions. From our findings we conclude that there is a need for large-scale studies that are geographically distinctive because most studies are case reports, and geographic differences of allergic diseases towards these legumes have already been discovered for well-known "Big 9" allergen sources such as peanut and soybean. Furthermore, the review illustrates the need for a better molecular diagnostic for these emerging non-priority allergen sources to evaluate IgE cross-reactivities to known allergens and identify true allergic reactions.

Hydrogen peroxide oxidation modifies the structural properties and allergenicity of the bee pollen allergen profilin

Bee pollen is a byproduct of pollination, which is a necessary process to produce foods. However, bee pollen can induce significant food-borne allergies. We previously identified a bee pollen-derived pan-allergen in the profilin family, Bra c p. Herein, we aimed to reduce Bra c p allergenicity via protein oxidation with hydrogen peroxide and explore the changes induced. Ion-mobility mass spectrometry revealed aggregation of the oxidized product; we also found irreversible sulfonation of the free sulfhydryl group of the Bra c p Cys98 residue to a more stable cysteine derivative. A significant proportion of the α-helices in Bra c p were transformed into β-sheets after oxidation, masking the antigenic epitopes. An immunoassay demonstrated that the IgE-binding affinity of Bra c p was decreased in vitro after oxidation. To our knowledge, this is the first report describing the application of protein oxidation to reduce the allergenicity of profilin family member in foods.

From Allergen Molecules to Molecular Immunotherapy of Nut Allergy: A Hard Nut to Crack

Peanuts and tree nuts are two of the most common elicitors of immunoglobulin E (IgE)-mediated food allergy. Nut allergy is frequently associated with systemic reactions and can lead to potentially life-threatening respiratory and circulatory symptoms. Furthermore, nut allergy usually persists throughout life. Whether sensitized patients exhibit severe and life-threatening reactions (e.g., anaphylaxis), mild and/or local reactions (e.g., pollen-food allergy syndrome) or no relevant symptoms depends much on IgE recognition of digestion-resistant class I food allergens, IgE cross-reactivity of class II food allergens with respiratory allergens and clinically not relevant plant-derived carbohydrate epitopes, respectively. Accordingly, molecular allergy diagnosis based on the measurement of allergen-specific IgE levels to allergen molecules provides important information in addition to provocation testing in the diagnosis of food allergy. Molecular allergy diagnosis helps identifying the genuinely sensitizing nuts, it determines IgE sensitization to class I and II food allergen molecules and hence provides a basis for personalized forms of treatment such as precise prescription of diet and allergen-specific immunotherapy (AIT). Currently available forms of nut-specific AIT are based only on allergen extracts, have been mainly developed for peanut but not for other nuts and, unlike AIT for respiratory allergies which utilize often subcutaneous administration, are given preferentially by the oral route. Here we review prevalence of allergy to peanut and tree nuts in different populations of the world, summarize knowledge regarding the involved nut allergen molecules and current AIT approaches for nut allergy. We argue that nut-specific AIT may benefit from molecular subcutaneous AIT (SCIT) approaches but identify also possible hurdles for such an approach and explain why molecular SCIT may be a hard nut to crack.

Crosslinked Recombinant-Ara h 1 Catalyzed by Microbial Transglutaminase: Preparation, Structural Characterization and Allergic Assessment

As the one of the major allergens in peanut, the allergenicity of Ara h 1 is influenced by its intrinsic structure, which can be modified by different processing. However, molecular information in this modification has not been clarified to date. Here, we detected the influence of microbial transglutaminase (MTG) catalyzed cross-linking on the recombinant peanut protein Ara h 1 (rAra h 1). Electrophoresis and spectroscopic methods were used to analysis the structural changes. The immunoreactivity alterations were characterized by enzyme linked immunosorbent assay (ELISA), immunoblotting and degranulation test. Structural features of cross-linked rAra h 1 varied at different reaction stages. Hydrogen bonds and disulfide bonds were the main molecular forces in polymers induced by heating and reducing. In MTG-catalyzed cross-linking, ε-(γ-glutamyl) lysine isopeptide bonds were formed, thus inducing a relatively stable structure in polymers. MTG catalyzed cross-linking could modestly but significantly reduce the immunoreactivity of rAra h 1. Decreased content of conserved secondary structures led to a loss of protection of linear epitopes. Besides, the reduced surface hydrophobic index and increased steric hindrance of rAra h 1 made it more difficult to bind with antibodies, thus hindering the subsequent allergic reaction.

Peanut allergens: new consolidated findings on structure, characteristics, and allergome

Immunoglobulin E-mediated food allergy is the result of a complex pathomechanism. Factors contributing to the dysfunction of the immune system are the allergenic sources and the variable matrix effects arising from the processes involved in interaction with the gastrointestinal tract, the allergens themselves through their structural features, and the specific behavior of the individual immune system. The starting point for elucidating the pathomechanism of food allergy is the identification of allergens and the description of their structure. They are the basis for in vitro diagnostics as well as the development of immunotherapeutic drugs. With regard to Class I food allergy, peanut allergy affects by far the largest group of patients. 11 allergens have been identified in peanuts. Ara h 1, Ara h 3, and Ara h 4 belong to the cupin superfamily, Ara h 2, Ara h 6, and Ara h 7 to the prolamin superfamily; Ara h 5 (profilins) and Ara h 8 (superfamily of Bet v 1-homologous proteins) are associated with aeroallergens. Peanut lipid transfer proteins (LTP) and two peanut oleosins are listed as Ara h 9, Ara h 10, and Ara h 11 by the IUIS Allergen Nomenclature Subcommittee. Peanut agglutinin (PNA) and a third oleosin have been shown to possess allergenic properties. The effect of the above specified allergens has to be considered in the context of their matrix, which is influenced by processing factors.

Peanut allergens

Peanut allergens have the potential to negatively impact on the health and quality of life of millions of consumers worldwide. The seeds of the peanut plant Arachis hypogaea contain an array of allergens that are able to induce the production of specific IgE antibodies in predisposed individuals. A lot of effort has been focused on obtaining the sequences and structures of these allergens due to the high health risk they represent. At present, 16 proteins present in peanuts are officially recognized as allergens. Research has also focused on their in-depth immunological characterization as well as on the design of modified hypoallergenic derivatives for potential use in clinical studies and the formulation of strategies for immunotherapy. Detailed research protocols are available for the purification of natural allergens as well as their recombinant production in bacterial, yeast, insect, and algal cells. Purified allergen molecules are now routinely used in diagnostic multiplex protein arrays for the detection of the presence of allergen-specific IgE. This review gives an overview on the wealth of knowledge that is available on individual peanut allergens.

Distinguishing allergens from non-allergenic homologues using Physical-Chemical Property (PCP) motifs

Quantitative guidelines to distinguish allergenic proteins from related, but non-allergenic ones are urgently needed for regulatory agencies, biotech companies and physicians. In a previous study, we found that allergenic proteins populate a relatively small number of protein families, as characterized by the Pfam database. However, these families also contain non-allergenic proteins, meaning that allergenic determinants must lie within more discrete regions of the sequence. Thus, new methods are needed to discriminate allergenic proteins within those families. Physical-Chemical Properties (PCP)-motifs specific for allergens within a Pfam class were determined for 17 highly populated protein domains. A novel scoring method based on PCP-motifs that characterize known allergenic proteins within these families was developed, and validated for those domains. The motif scores distinguished sequences of allergens from a large selection of 80,000 randomly selected non-allergenic sequences. The motif scores for the birch pollen allergen (Bet v 1) family, which also contains related fruit and nut allergens, correlated better than global sequence similarities with clinically observed cross-reactivities among those allergens. Further, we demonstrated that the average scores of allergen specific motifs for allergenic profilins are significantly different from the scores of non-allergenic profilins. Several of the selective motifs coincide with experimentally determined IgE epitopes of allergenic profilins. The motifs also discriminated allergenic pectate lyases, including Jun a 1 from mountain cedar pollen, from similar proteins in the human microbiome, which can be assumed to be non-allergens. The latter lacked key motifs characteristic of the known allergens, some of which correlate with known IgE binding sites.

Structural insights into the IgE mediated responses induced by the allergens Hev b 8 and Zea m 12 in their dimeric forms

Oligomerization of allergens plays an important role in IgE-mediated reactions, as effective crosslinking of IgE- FcεRI complexes on the cell membrane is dependent on the number of exposed B-cell epitopes in a single allergen molecule or on the occurrence of identical epitopes in a symmetrical arrangement. Few studies have attempted to experimentally demonstrate the connection between allergen dimerization and the ability to trigger allergic reactions. Here we studied plant allergenic profilins rHev b 8 (rubber tree) and rZea m 12 (maize) because they represent an important example of cross-reactivity in the latex-pollen-food syndrome. Both allergens in their monomeric and dimeric states were isolated and characterized by exclusion chromatography and mass spectrometry and were used in immunological in vitro experiments. Their crystal structures were solved, and for Hev b 8 a disulfide-linked homodimer was found. Comparing the structures we established that the longest loop is relevant for recognition by IgE antibodies, whereas the conserved regions are important for cross-reactivity. We produced a novel monoclonal murine IgE (mAb 2F5), specific for rHev b 8, which was useful to provide evidence that profilin dimerization considerably increases the IgE-mediated degranulation in rat basophilic leukemia cells.

Utility of specific IgE to Ara h 6 in peanut allergy diagnosis

BACKGROUND

Specific IgE to Ara h 2 has been shown to be useful in the diagnosis of peanut allergy, whereas the peanut lipid transfer protein, Ara h 9, has been suggested to be responsible for peanut allergy in the Mediterranean population.

OBJECTIVE

To better characterize peanut allergy in children from a Mediterranean area and determine the value of specific IgE to Ara h 6 (conglutinin, 2S albumin) for the diagnosis of peanut allergy.

METHODS

Ninety-one children with suspected allergy to edible vegetables were included in the study. They were classified as allergic or tolerant to peanut. Specific IgE to peanut allergens was measured by a commercially available microarray (ImmunoCAP ISAC 112, ThermoFisher, Uppsala, Sweden).

RESULTS

Patients allergic to peanut showed positive specific IgE changes to peanut seed storage proteins (Ara h 1, Ara h 2, Ara h 3, and Ara h 6) more frequently than tolerant subjects. Ara h 9 showed a similar frequency of reactivity in the 2 groups. Ara h 6 was the allergen most frequently recognized by patients with allergy. Four patients with allergy were found to be mono-sensitized to Ara h 6. Ara h 2 and Ara h 6 showed similar diagnostic accuracy (areas under the curve 0.792 and 0.852). A combined cutoff point for Ara h 2 (≥0.1 ISU) and Ara h 6 (≥2 ISU) yielded the best diagnostic performance (sensitivity 0.77, specificity 0.97, positive predictive value 0.89, negative predictive value 0.93).

CONCLUSION

Peanut allergy cannot be ruled out without obtaining a negative determination of Ara h 6.

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.

Prevalence of allergic sensitization in the United States: results from the National Health and Nutrition Examination Survey (NHANES) 2005-2006

BACKGROUND

Allergic sensitization is an important risk factor for the development of atopic disease. The National Health and Nutrition Examination Survey (NHANES) 2005-2006 provides the most comprehensive information on IgE-mediated sensitization in the general US population.

OBJECTIVE

We investigated clustering, sociodemographic, and regional patterns of allergic sensitization and examined risk factors associated with IgE-mediated sensitization.

METHODS

Data for this cross-sectional analysis were obtained from NHANES 2005-2006. Participants aged 1 year or older (n = 9440) were tested for serum specific IgEs (sIgEs) to inhalant and food allergens; participants 6 years or older were tested for 19 sIgEs, and children aged 1 to 5 years were tested for 9 sIgEs. Serum samples were analyzed by using the ImmunoCAP System. Information on demographics and participants' characteristics was collected by means of questionnaire.

RESULTS

Of the study population aged 6 years and older, 44.6% had detectable sIgEs, whereas 36.2% of children aged 1 to 5 years were sensitized to 1 or more allergens. Allergen-specific IgEs clustered into 7 groups that might have largely reflected biological cross-reactivity. Although sensitization to individual allergens and allergen types showed regional variation, the overall prevalence of sensitization did not differ across census regions, except in early childhood. In multivariate modeling young age, male sex, non-Hispanic black race/ethnicity, geographic location (census region), and reported pet avoidance measures were most consistently associated with IgE-mediated sensitization.

CONCLUSIONS

The overall prevalence of allergic sensitization does not vary across US census regions, except in early life, although allergen-specific sensitization differs based on sociodemographic and regional factors. Biological cross-reactivity might be an important but not the sole contributor to the clustering of allergen-specific IgEs.

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.

Peanut Allergy, Allergen Composition, and Methods of Reducing Allergenicity: A Review

Peanut allergy affects 1-2% of the world's population. It is dangerous, and usually lifelong, and it greatly decreases the life quality of peanut-allergic individuals and their families. In a word, peanut allergy has become a major health concern worldwide. Thirteen peanut allergens are identified, and they are briefly introduced in this paper. Although there is no feasible solution to peanut allergy at present, many methods have shown great promise. This paper reviews methods of reducing peanut allergenicity, including physical methods (heat and pressure, PUV), chemical methods (tannic acid and magnetic beads), and biological methods (conventional breeding, irradiation breeding, genetic engineering, enzymatic treatment, and fermentation).

Moving from peanut extract to peanut components: towards validation of component-resolved IgE tests

BACKGROUND

Replacement of peanut extracts by recombinant peanut components is an important step in allergy serologic testing. Criteria are needed for the unbiased inclusion of patients into a study to validate such a replacement.

METHODS

Plasma samples from 64 peanut-positive children (42 reactors, 22 nonreactors in a double-blind, placebo-controlled food challenge) were used to compare IgE reactivity to six recombinant peanut allergens with reactivity to natural peanut proteins extracted at neutral or low pH. We tested the hypothesis that poor extractability of Ara h 9 and other basic allergens at neutral pH leads to under-representation of patients with such sensitization.

RESULTS

IgE reactivity to the components did not fully explain IgE reactivity to peanut extract in 5 of 32 reactors with IgE to peanut extract ≤100 kUA /l. IgE reactivity to components was stronger than to the extract in 11 plasma samples, which was largely due to a low Ara h 8 reactivity of the extract. IgE reactivity to Ara h 9 was much lower than reactivity to other basic proteins, some of which bound IgE well in the RAST, but lost IgE reactivity upon immunoblotting.

CONCLUSIONS

Conventional peanut extracts are deficient in significant IgE-binding components. The inclusion of patients for a validation study should be based on serology performed with improved peanut reagents to avoid a bias against these under-represented, potentially important allergens. To judge clinical relevance of an allergen, the reagent used for inclusion of patients needs to be efficient in detecting IgE to this component.

Comparative proteomic analysis and IgE binding properties of peanut seed and testa (skin)

To investigate the protein composition and potential allergenicity of peanut testae or skins, proteome analysis was conducted using nanoLC-MS/MS sequencing. Initial amino acid analysis suggested differences in protein compositions between the blanched seed (skins removed) and skin. Phenolic compounds hindered analysis of proteins in skins when the conventional extraction method was used; therefore, phenol extraction of proteins was necessary. A total of 123 proteins were identified in blanched seed and skins, and 83 of the proteins were common between the two structures. The skins contained all of the known peanut allergens in addition to 38 proteins not identified in the seed. Multiple defense proteins with antifungal activity were identified in the skins. Western blotting using sera from peanut-allergic patients revealed that proteins extracted from both the blanched seed and skin bound significant levels of IgE. However, when phenolic compounds were present in the skin protein extract, no IgE binding was observed. These findings indicate that peanut skins contain potentially allergenic proteins; however, the presence of phenolic compounds may attenuate this effect.

Crystal structure of peanut (Arachis hypogaea) allergen Ara h 5

Profilins from numerous species are known to be allergens, including food allergens, such as peanut ( Arachis hypogaea ) allergen Ara h 5, and pollen allergens, such as birch allergen Bet v 2. Patients with pollen allergy can also cross-react to peanut. Structural characterization of allergens will allow a better understanding of the allergenicity of food allergens and their cross-reactivities. The three-dimensional structures of most known food allergens remain to be elucidated. Here, we report the first crystallographic study of a food allergen in the profilin family. The structure of peanut allergen Ara h 5 was determined, and the resolution of the final refined structure was 1.1 Å. Structure alignment revealed that Ara h 5 is more similar to Bet v 2 than to Hev b 8, although sequence alignment suggested that Ara h 5 is more closely related to Hev b 8 than to Bet v 2, indicating that homology-model-based prediction of immunoglobulin E epitopes needs to be interpreted with caution.

Assessment of 3D models for allergen research

Allergenic proteins must crosslink specific IgE molecules, bound to the surface of mast cells and basophils, to stimulate an immune response. A structural understanding of the allergen-IgE interface is needed to predict cross-reactivities between allergens and to design hypoallergenic proteins. However, there are less than 90 experimentally determined structures available for the approximately 1500 sequences of allergens and isoallergens cataloged in the Structural Database of Allergenic Proteins. To provide reliable structural data for the remaining proteins, we previously produced more than 500 3D models using an automated procedure, with strict controls on template choice and model quality evaluation. Here, we assessed how well the fold and residue surface exposure of 10 of these models correlated with recently published experimental 3D structures determined by X-ray crystallography or NMR. We also discuss the impact of intrinsically disordered regions on the structural comparison and epitope prediction. Overall, for seven allergens with sequence identities to the original templates higher than 27%, the backbone root-mean square deviations were less than 2 Å between the models and the subsequently determined experimental structures for the ordered regions. Further, the surface exposure of the known IgE epitopes on the models of three major allergens, from peanut (Ara h 1), latex (Hev b 2), and soy (Gly m 4), was very similar to the experimentally determined structures. For the three remaining allergens with lower sequence identities to the modeling templates, the 3D folds were correctly identified. However, the accuracy of those models is not sufficient for a reliable epitope mapping.

Size-selective fractionation and visual mapping of allergen protein chemistry in Arachis hypogaea

Peanuts (Arachis hypogaea) in addition to milk, eggs, fish, crustaceans, wheat, tree nuts, and soybean are commonly referred to as the "big eight" foods that contribute to the majority of food allergies worldwide. Despite the severity of allergic reactions and growing prevalence in children and adults, there is no cure for peanut allergy, leaving avoidance as the primary mode of treatment. To improve analytical methods for peanut allergen detection, researchers must overcome obstacles involved in handling complex food matrices while attempting to decipher the chemistry that underlies allergen protein interactions. To address such challenges, we conducted a global proteome characterization of raw peanuts using a sophisticated GELFrEE-PAGE-LC-MS/MS platform consisting of gel-based protein fractionation followed by mass spectrometric identification. The in-solution mass-selective protein fractionation: (1) enhances the number of unique peptide identifications, (2) provides a visual map of protein isoforms, and (3) aids in the identification of disulfide-linked protein complexes. GELFrEE-PAGE-LC-MS/MS not only overcomes many of the challenges involved in the study of plant proteomics, but enriches the understanding of peanut protein chemistry, which is typically unattainable in a traditional bottom-up proteomic analysis. A global understanding of protein chemistry in Arachis hypogaea ultimately will aid the development of improved methods for allergen detection in food.

Measurement of Ara h 1-, 2-, and 3-specific IgE antibodies is useful in diagnosis of peanut allergy in Japanese children

BACKGROUND

Food challenges are time-consuming, expensive, and not always possible to perform. Therefore, new tools to diagnose food allergy are desired. The aim was to evaluate IgE antibodies to peanut allergens in the diagnosis of peanut allergy in Japanese children using ImmunoCAP(®) and IgE immunoblotting.

METHODS

The study included 2-13-yr-old consecutive patients (n = 57) referred to our specialist clinic for investigation of current peanut allergy using food challenge. All children had a previous doctor's diagnosis of peanut allergy and were on elimination diet. Serum samples were analyzed for IgE reactivity to peanut, recombinant (r) Ara h 1, 2, 3, 5, 8, and 9. IgE immunoblotting (n = 23) was performed using extracts from raw and roasted peanut.

RESULTS

Twenty-six of the children failed (allergic group), and 31 passed the peanut challenge (tolerant group). The rAra h 2 ImmunoCAP test was superior in its ability to differentiate between children in the allergic and tolerant groups with a sensitivity and specificity of 88% and 84%, respectively (cutoff, 0.35 kU(A)/l). The combination of rAra h 1, 2, and 3 resulted in a higher specificity (94%) when IgE to all of them was the criteria for positivity. ImmunoCAP generally showed a good agreement with immunoblotting using both raw and roasted peanut for IgE reactivity to Ara h 1, 2, and 3.

CONCLUSIONS

Measurement of IgE antibodies to rAra h 1, 2, and 3 is useful in the diagnosis of peanut allergy and in the investigation of reactions to raw and roasted peanut.

Molecular diagnosis of peanut and legume allergy

PURPOSE OF REVIEW

To review and discuss recent studies on molecular diagnosis of peanut and other legume allergy.

RECENT FINDINGS

Studies from the UK and France suggest that quantification of Ara h 2-specific IgE may accurately discriminate peanut allergy from tolerance. However, the pattern of allergenic component recognition in peanut-sensitized patients from different populations or geographical areas varies, reflecting different pollen and dietary exposures. In the USA, peanut-allergic patients are commonly sensitized to Ara h 1-3, in Spain to Ara h 9 and in Sweden to Ara h 8. Patients with soybean allergy sensitized to Gly m 5 or Gly m 6 allergens may be at greater risk of experiencing severe allergic reactions.

SUMMARY

Accurate diagnosis of peanut and legume allergy is challenging and essential. Measurement of IgE response to specific allergenic molecules may be more useful in predicting the presence and severity of clinical allergy than currently used skin or blood tests based on whole extracts. However, given the heterogeneity in component recognition patterns observed in different geographical areas, further studies are essential to identify and confirm potentially useful molecular diagnostic and prognostic markers. Until such markers are confirmed and replicated in different age groups, oral food challenge (OFC) remains the gold standard for accurate diagnosis.