Pru p 3, the nonspecific lipid transfer protein from peach, dominates the immune response to its homolog in hazelnut

Understanding of lipid transfer protein sensitization patterns and its clinical significance in children

Background: Lipid transfer proteins (LTP) are the most common food allergens in the Mediterranean region. Objective: The study aimed to investigate co-sensitization patterns and cluster relationships between LTP allergen molecules across a broad range of allergen-specific sensitization patterns, and clinical outcomes in eastern Mediterranean children. Methods: Among 496 children evaluated for multiple sensitizations with multiplex testing, 105 children (21%) with 16 different LTP sensitizations were analyzed. Clinical reactivity was examined based on clear-cut history of immunoglobulin E mediated symptoms (oral allergy syndrome [OAS], systemic reactions, and anaphylaxis). Results: All children included were sensitive to food LTPs, but 56% were sensitive to pollen LTPs. The number of children with OAS and clinical reactivity was 12 and 59, respectively, and no cofactors were reported. The most common sensitizations were Pru p 3 (74%) and Cor a 8 (66%). Significant correlations were observed in the heatmap between the LTP molecules other than Par j 2 and Tri a 14. Overall, clinical reactivity was associated with increased age and number of LTP molecule positivity. Conclusion: In the eastern Mediterranean region, 21% of children with multiple food and/or pollen sensitizations were found to have LTP sensitization; however, almost half reported clinical reactivity. The hierarchical pathway highlights that distinct LTP allergen molecules can act as primary sensitizers. Clinical reactivity is linked to increasing numbers of LTP molecule positivity and increasing age.

Factors and co-factors influencing clinical manifestations in nsLTPs allergy: between the good and the bad

Non-specific lipid transfer proteins (nsLTPs) are a family of plant pan-allergens that represent the primary cause of food allergies in the Mediterranean area, characterized by a wide range of clinical manifestations, ranging from the total absence of symptoms up to anaphylaxis. This wide variety of symptoms is related to the intrinsic capacity of nsLTPs to cause an allergic reaction in a specific subject, but also to the presence of co-factors exacerbating (i.e., exercise, NSAIDs, PPIs, alcohol, cannabis, prolonged fasting, menstruation, acute infections, sleep deprivation, chronic urticaria) or protecting from (i.e., co-sensitization to PR10, profilin or polcalcin) severe reactions. In this picture, recognizing some nsLTPs-related peculiarities (i.e., route, type and number of sensitizations, concentration of the allergen, cross-reactions) and eventual co-factors may help the allergist to define the risk profile of the single patient, in order to promote the appropriate management of the allergy from dietary advices up to the prescription of life-saving epinephrine autoinjector.

T-cell epitope discovery and single-cell technologies to advance food allergy research

There is good evidence for a role of T cells in food allergy, but there is a lack of mechanistic understanding and phenotypic markers of the specific T cells contributing to pathology. Recent technologic advancements have allowed for a new experimental paradigm where we can find and pull out rare antigen-specific T cells and characterize them at the single-cell level. However, studies in infectious disease and broader allergy have shown that these techniques benefit greatly from precisely defined T-cell epitopes. Food allergens have fewer epitopes currently available, but it is growing and promises to overcome this gap. With growing use of this experimental design, it will be important to unbiasedly map T-cell phenotypes across food allergy and look for commonalities and contrasts to other allergic and infectious diseases. Once a pathologic phenotype for T cells has been established, the frequencies of these cells can be monitored with simpler techniques that could be applied to the clinic and used in diagnosis, prediction of treatment responsiveness, and discovery of targets for new treatments.

How Do Pollen Allergens Sensitize?

Plant pollen is one of the main sources of allergens causing allergic diseases such as allergic rhinitis and asthma. Several allergens in plant pollen are panallergens which are also present in other allergen sources. As a result, sensitized individuals may also experience food allergies. The mechanism of sensitization and development of allergic inflammation is a consequence of the interaction of allergens with a large number of molecular factors that often are acting in a complex with other compounds, for example low-molecular-mass ligands, which contribute to the induction a type 2-driven response of immune system. In this review, special attention is paid not only to properties of allergens but also to an important role of their interaction with lipids and other hydrophobic molecules in pollen sensitization. The reactions of epithelial cells lining the nasal and bronchial mucosa and of other immunocompetent cells will also be considered, in particular the mechanisms of the activation of B and T lymphocytes and the formation of allergen-specific antibody responses.

Tomato (Solanum lycopersicum L.) accumulation and allergenicity in response to nickel stress

Vegetables represent a major source of Ni exposure. Environmental contamination and cultural practices can increase Ni amount in tomato posing significant risk for human health. This work assesses the tomato (Solanum lycopersicum L.) response to Ni on the agronomic yield of fruits and the related production of allergens. Two cultivars were grown in pots amended with Ni 0, 30, 60, 120, and 300 mg kg⁻¹, respectively. XRF and ICP-MS analyses highlighted the direct increase of fruit Ni content compared to soil Ni, maintaining a stable biomass. Leaf water content increased at Ni 300 mg kg⁻¹. Total protein content and individual allergenic components were investigated using biochemical (RP-HPLC and N-terminal amino acid sequencing) and immunological (inhibition tests of IgE binding by SPHIAa assay on the FABER testing system) methodologies. Ni affected the fruit tissue concentration of pathogenesis-related proteins and relevant allergens (LTP, profilin, Bet v 1-like protein and TLP). This study elucidates for the first time that tomato reacts to exogenous Ni, uptaking the metal while changing its allergenic profiles, with potential double increasing of exposure risks for consumers. This evidence highlighted the importance of adequate choice of low-Ni tomato cultivars and practices to reduce Ni uptake by potentially contaminated matrices.

Detection of Allergenic Proteins in Foodstuffs: Advantages of the Innovative Multiplex Allergen Microarray-Based Immunoassay Compared to Conventional Methods

Several factors can affect the allergen content and profile of a specific food, including processing procedures often leading to a decrease in allergenicity, although no change, or even an increase, have also been reported. Evaluation of the effectiveness of a processing procedure requires the availability of reliable methodologies to assess the variation in molecules able to induce allergic reactions in the analyzed food. Conventional and innovative strategies and methodologies can be exploited to identify allergenic proteins in foodstuffs. However, depending on the specific purposes, different methods can be used. In this review, we have critically reviewed the advantages of an innovative method, the multiplex allergen microarray-based immunoassay, in the detection of allergens in foodstuffs. In particular, we have analyzed some studies reporting the exploitation of an IgE-binding inhibition assay on multiplex allergen biochips, which has not yet been reviewed in the available literature. Unlike the others, this methodology enables the identification of many allergenic proteins, some of which are still unknown, which are recognized by IgE from allergic patients, with a single test. The examined literature suggests that the inhibition test associated with the multiplex allergen immunoassay is a promising methodology exploitable for the detection of IgE-binding proteins in food samples.

Common Reference-Based Tandem Mass Tag Multiplexing for the Relative Quantification of Peptides: Design and Application to Degradome Analysis of Diphtheria Toxoid

Currently, animal tests are being used to confirm the potency and lack of toxicity of toxoid vaccines. In a consistency approach, animal tests could be replaced if production consistency (compared to known good products) can be proven in a panel of in vitro assays. By mimicking the in vivo antigen processing in a simplified in vitro approach, it may be possible to distinguish aberrant products from good products. To demonstrate this, heat-exposed diphtheria toxoid was subjected to partial digestion by cathepsin S (an endoprotease involved in antigen processing), and the peptide formation/degradation kinetics were mapped for various heated toxoids. To overcome the limitations associated with the very large number of samples, we used common reference-based tandem mass tag (TMT) labeling. Instead of using one label per condition with direct comparison between the set of labels, we compared multiple labeled samples to a common reference (a pooled sample containing an aliquot of each condition). In this method, the number of samples is not limited by the number of unique TMT labels. This TMT multiplexing strategy allows for a 15-fold reduction of analysis time while retaining the reliability advantage of TMT labeling over label-free quantification. The formation of the most important peptides could be followed over time and compared among several conditions. The changes in enzymatic degradation kinetics of diphtheria toxoid revealed several suitable candidate peptides for use in a quality control assay that can distinguish structurally aberrant diphtheria toxoid from compliant toxoids.

Non-specific lipid-transfer proteins: Allergen structure and function, cross-reactivity, sensitization, and epidemiology

Background

Discovered and described 40 years ago, non‐specific lipid transfer proteins (nsLTP) are present in many plant species and play an important role protecting plants from stressors such as heat or drought. In the last 20 years, sensitization to nsLTP and consequent reactions to plant foods has become an increasing concern.

Aim

The aim of this paper is to review the evidence for the structure and function of nsLTP allergens, and cross‐reactivity, sensitization, and epidemiology of nsLTP allergy.

Materials and Methods

A Task Force, supported by the European Academy of Allergy & Clinical Immunology (EAACI), reviewed current evidence and provide a signpost for future research. The search terms for this paper were “Non‐specific Lipid Transfer Proteins”, “LTP syndrome”, “Pru p 3”, “plant food allergy”, “pollen‐food syndrome”.

Results

Most nsLTP allergens have a highly conserved structure stabilised by 4‐disulphide bridges. Studies on the peach nsLTP, Pru p 3, demonstrate that nsLTPs are very cross‐reactive, with the four major IgE epitopes of Pru p 3 being shared by nsLTP from other botanically related fruits. These nsLTP allergens are to varying degrees resistant to heat and digestion, and sensitization may occur through the oral, inhaled or cutaneous routes. In some populations, Pru p 3 is the primary and sole sensitizing allergen, but many are poly‐sensitised both to botanically un‐related nsLTP in foods, and non‐food sources of nsLTP such as Cannabis sativa, Platanus acerifolia, (plane tree), Ambrosia artemisiifolia (ragweed) and Artemisia vulgaris (mugwort). Initially, nsLTP sensitization appeared to be limited to Mediterranean countries, however more recent studies suggest clinically relevant sensitization occurs in North Atlantic regions and also countries in Northern Europe, with nsLTP sensitisation profiles being broadly similar.

Discussion

These robust allergens have the potential to sensitize and provoke symptoms to a large number of plant foods, including those which are raw, cooked or processed. It is unknown why some sensitized individuals develop clinical symptoms to foods whereas others do not, or indeed what other allergens besides Pru p 3 may be primary sensitising allergens. It is clear that these allergens are also relevant in non‐Mediterranean populations and there needs to be more recognition of this.

Conclusion

Non‐specific LTP allergens, present in a wide variety of plant foods and pollens, are structurally robust and so may be present in both raw and cooked foods. More studies are needed to understand routes of sensitization and the world‐wide prevalence of clinical symptoms associated with sensitization to these complex allergens.

The Role of Lipid Transfer Proteins as Food and Pollen Allergens Outside the Mediterranean Area

PURPOSE OF REVIEW

To provide an overview of the prevalence and clinical manifestation of non-specific lipid transfer proteins (LTP)-mediated allergies outside the Mediterranean area and to address potential reasons for the different geographical significance of LTP-driven allergies.

RECENT FINDINGS

LTPs are major allergens in the Mediterranean area, which frequently can elicit severe reactions. Pru p 3 the LTP from peach is reported as genuine allergen and is considered a prototypic marker for LTP-mediated allergies. However, both food and pollen LTP allergies exist outside the Mediterranean area, but with lower clinical significance, different immunogenicity, and less clarified role. Evidence has been reported that in areas with high exposure to pollen, in particular to mugwort, pollen-derived LTPs can act as a primary sensitizer to trigger secondary food allergies. Co-sensitization to unrelated allergens might be causative for less severe reactions in response to LTPs. However, the reason for the geographical different sensitization patterns to LTPs remains unclear.

Structural Characterization of Act c 10.0101 and Pun g 1.0101-Allergens from the Non-Specific Lipid Transfer Protein Family

(1) Background: Non-specific lipid transfer proteins (nsLTPs), which belong to the prolamin superfamily, are potent allergens. While the biological role of LTPs is still not well understood, it is known that these proteins bind lipids. Allergen nsLTPs are characterized by significant stability and resistance to digestion. (2) Methods: nsLTPs from gold kiwifruit (Act c 10.0101) and pomegranate (Pun g 1.0101) were isolated from their natural sources and structurally characterized using X-ray crystallography (3) Results: Both proteins crystallized and their crystal structures were determined. The proteins have a very similar overall fold with characteristic compact, mainly α-helical structures. The C-terminal sequence of Act c 10.0101 was updated based on our structural and mass spectrometry analysis. Information on proteins’ sequences and structures was used to estimate the risk of cross-reactive reactions between Act c 10.0101 or Pun g 1.0101 and other allergens from this family of proteins. (4) Conclusions: Structural studies indicate a conformational flexibility of allergens from the nsLTP family and suggest that immunoglobulin E binding to some surface regions of these allergens may depend on ligand binding. Both Act c 10.0101 and Pun g 1.0101 are likely to be involved in cross-reactive reactions involving other proteins from the nsLTP family.

Linking cross-reactivity clusters of food and respiratory allergens in PAMD@ to asthma and duration of allergy

BACKGROUND

Component resolved diagnosis, recently redefined as precision allergy medicine diagnosis - PAMD@, may help understanding allergic cross-reactivity patterns among polysensitized patients and their clinical implication.

OBJECTIVE

We aimed to investigate similarities among allergens by empirically determining the occurrence of co-sensitization patterns and to relate them to clinical features, in particular to asthma.

METHODS

A retrospective cohort study in 1057 participants suspected to have allergic sensitization was performed in Vienna. To define cross-reactivity patterns, cluster analysis for 671 patients who showed reaction to at least one of the allergens in ISAC112 was performed and followed by multivariate logistic regression analysis to relate clusters and clinical symptoms, in particular current asthma.

RESULTS

We determined 18 cross-reactivity clusters, comprising of 6 food, 10 respiratory, and 2 other clusters of allergens. Overall, 14% of the cohort patients were positive for 1 cross-reactivity cluster and 23% to 2 or more clusters. Multisensitized patients who were sensitized to PR-10 allergen proteins in addition to Bermuda timothy grass pollen clusters showed the highest association with asthma (odds ratio, 4.22 and 95% CI: 2.32-7.68) and an increase of 10 years of the duration of allergy increased the odds for a combined sensitization to PR-10 cluster and Bermuda-timothy cluster by 1.27 (95% CI: 1.06-1.53).

CONCLUSION

Similarities among IgE positivity patterns determined by ISAC112 revealed 18 cross-reactivity clusters. This PAMD@ approach allowed prediction of clinical features and revealed that certain cross-reactivity patterns are related to duration of allergic symptoms.

Are Physicochemical Properties Shaping the Allergenic Potency of Plant Allergens?

This review searched for published evidence that could explain how different physicochemical properties impact on the allergenicity of food proteins and if their effects would follow specific patterns among distinct protein families. Owing to the amount and complexity of the collected information, this literature overview was divided in two articles, the current one dedicated to protein families of plant allergens and a second one focused on animal allergens. Our extensive analysis of the available literature revealed that physicochemical characteristics had consistent effects on protein allergenicity for allergens belonging to the same protein family. For example, protein aggregation contributes to increased allergenicity of 2S albumins, while for legumins and cereal prolamins, the same phenomenon leads to a reduction. Molecular stability, related to structural resistance to heat and proteolysis, was identified as the most common feature promoting plant protein allergenicity, although it fails to explain the potency of some unstable allergens (e.g. pollen-related food allergens). Furthermore, data on physicochemical characteristics translating into clinical effects are limited, mainly because most studies are focused on in vitro IgE binding. Clinical data assessing how these parameters affect the development and clinical manifestation of allergies is minimal, with only few reports evaluating the sensitising capacity of modified proteins (addressing different physicochemical properties) in murine allergy models. In vivo testing of modified pure proteins by SPT or DBPCFC is scarce. At this stage, a systematic approach to link the physicochemical properties with clinical plant allergenicity in real-life scenarios is still missing.

In vitro gastroduodenal and jejunal brush border membrane digestion of raw and roasted tree nuts

Heat treatments induce chemical/physical modifications, which may affect the stability to enzymatic digestion and consequently the allergenicity of food proteins to a varying extent, depending on the time/temperature regimen. Herein, we evaluated the stability to digestion of whole tree nut (walnuts, hazelnuts and almonds) allergens in a food digestion model reflecting the real one by, taking into consideration the allergen-containing processed (roasted) food. To this aim, whole raw and roasted tree nuts were subjected to in vitro digestion combining the harmonized oral-gastric-duodenal digestion models with brush border membrane enzymes (BBM) to simulate the jejunal degradation of peptides. The degradation of allergens was monitored by integrated proteomic/peptidomic and bio-informatic tools. Roasting increased digestibility of tree nuts, since very few peptides were detected in digested samples (<6.5 kDa fraction). After BBM digestion step, the degradation of peptides was enhanced in roasted walnuts and hazelnuts compared to the raw counterpart. Conversely, almond allergens showed a different behaviour, since the presence of resistant peptides was more evident for roasted almonds, probably because of the hydrolysis of high molecular weight aggregates generated during roasting. Our results provide new insight into the relationship between thermal processing and metabolic fate of tree nut allergens, highlighting the importance of investigating the digestion stability of whole allergenic food, rather than purified proteins.

Formaldehyde treatment of proteins enhances proteolytic degradation by the endo-lysosomal protease cathepsin S

Enzymatic degradation of protein antigens by endo-lysosomal proteases in antigen-presenting cells is crucial for achieving cellular immunity. Structural changes caused by vaccine production process steps, such as formaldehyde inactivation, could affect the sensitivity of the antigen to lysosomal proteases. The aim of this study was to assess the effect of the formaldehyde detoxification process on the enzymatic proteolysis of antigens by studying model proteins. Bovine serum albumin, β-lactoglobulin A and cytochrome c were treated with various concentrations of isotopically labelled formaldehyde and glycine, and subjected to proteolytic digestion by cathepsin S, an important endo-lysosomal endoprotease. Degradation products were analysed by mass spectrometry and size exclusion chromatography. The most abundant modification sites were identified by their characteristic MS doublets. Unexpectedly, all studied proteins showed faster proteolytic degradation upon treatment with higher formaldehyde concentrations. This effect was observed both in the absence and presence of glycine, an often-used excipient during inactivation to prevent intermolecular crosslinking. Overall, subjecting proteins to formaldehyde or formaldehyde/glycine treatment results in changes in proteolysis rates, leading to an enhanced degradation speed. This accelerated degradation could have consequences for the immunogenicity and the efficacy of vaccine products containing formaldehyde-inactivated antigens.

New insights into the sensitization to nonspecific lipid transfer proteins from pollen and food: New role of allergen Ole e 7

BACKGROUND

Ole e 7 is a nonspecific lipid transfer protein (nsLTP) from olive pollen, one of the main allergenic pollens worldwide. This allergenic nsLTP is responsible for severe symptoms in regions with high olive pollen exposure, where many Ole e 7-sensitized patients exhibit a co-sensitization to the peach nsLTP, Pru p 3. However, there is no evidence of cross-reactivity, which explains this observed co-sensitization. Therefore, the purpose of this study was to explore the relationship between Ole e 7 and Pru p 3.

METHODS

A total of 48 patients sensitized to Ole e 7 and/or Pru p 3 were included in the study. Specific IgE serum levels were measured by ImmunoCAP 250 and ELISA. Inhibition assays were performed to determine the existence of cross-reactivity between both nsLTPs. Allergic response was analyzed ex vivo (basophil activation test) and in vitro (RBL-2H3 mast cell model).

RESULTS

Common IgG and IgE epitopes were identified between both allergens. IgE-binding inhibition was detected in Ole e 7-monosensitized patients using rPru p 3 as inhibitor, reaching inhibition values of 25 and 100%. Ex vivo and in vitro assays revealed a response against rPru p 3 in four (31%) Ole e 7-monosensitized patients.

CONCLUSIONS

Our results suggest that Ole e 7 could play a new role as primary sensitizer in regions with high olive pollen exposure, leading to the peach nsLTP sensitization. This co-sensitization process would occur because of the cross-reactivity between Ole e 7 and Pru p 3 observed in some allergic patients.

Pollen food allergy syndrome (PFAS): A review of current available literature

OBJECTIVE

Pollen food allergy syndrome (PFAS) is a complex syndrome posing a diagnostic and therapeutic challenge. Our objective was to summarize the available literature regarding its prevalence, pathogenesis, diagnosis, and treatment.

DATA SOURCES

A PubMed search was performed to include English language articles with the following search terms: pollen food syndrome, pollen food allergy syndrome, PFAS, oral allergy syndrome, OAS, food anaphylaxis, food components.

STUDY SELECTIONS

Human articles discussing PFAS.

RESULTS

Varying reports have been made of the prevalence of PFAS, ranging from 4.7% to greater than 20% in children and 13% to 58% in adults. Prevalence varies widely by geographic region. PFAS is typically the results of class II food allergens (e.g. sensitized to anaeroallergen, but reaction occurs due to cross reactivity from a food allergen). Commonly these reactions are limited to the oropharynx due to the lability of the proteins causing the reaction. As multiple families of proteins with varying stability cause PFAS, severe systemic reactions are also possible, as anaphylactic shock has been documented in up to 1.7% of reactions.

CONCLUSION

Pollen food allergy syndrome therefore cannot be dismissed as a benign food allergy, but it needs to be approached individually based on known risk factors.

The relevance of a digestibility evaluation in the allergenicity risk assessment of novel proteins. Opinion of a joint initiative of COST action ImpARAS and COST action INFOGEST

The current allergenicity assessment of novel proteins is based on the EFSA GMO guidance. Recently, EFSA launched a new guidance document on allergenicity assessment of GM plants (2017). This document describes, amongst other topics, the new scientific and regulatory developments on in vitro protein digestibility tests. The EFSA GMO Panel stated that for in vitro protein digestibility tests, additional investigations are needed before any additional recommendation in the form of guidance can be provided. To this end, an interim phase is considered necessary to evaluate the revisions to the in vitro gastrointestinal digestion test, proposed by EFSA. This prompted the establishment of a joint workshop through two COST Action networks: COST Action ImpARAS and COST Acton INFOGEST. In 2017, a workshop was organised to discuss the relevance of digestion in allergenicity risk assessment and how to potentially improve the current methods and readouts. The outcome of the workshop is that there is no rationale for a clear readout that is predictive for allergenicity and we suggest to omit the digestion test from the allergenicity assessment strategy for now, and put an effort into filling the knowledge gaps as summarized in this paper first.

A robust method for the estimation and visualization of IgE cross-reactivity likelihood between allergens belonging to the same protein family

Among the vast number of identified protein families, allergens emanate from relatively few families which translates to only a small fraction of identified protein families. In allergy diagnostics and immunotherapy, interactions between immunoglobulin E and allergens are crucial because the formation of an allergen-antibody complex is necessary for triggering an allergic reaction. In allergic diseases, there is a phenomenon known as cross-reactivity. Cross-reactivity describes a situation where an individual has produced antibodies against a particular allergenic protein, but said antibodies fail to discriminate between the original sensitizer and other similar proteins that usually belong to the same family. To expound the concept of cross-reactivity, this study examines ten protein families that include allergens selected specifically for the analysis of cross-reactivity. The selected allergen families had at least 13 representative proteins, overall folds that differ significantly between families, and include relevant allergens with various potencies. The selected allergens were analyzed using information on sequence similarities and identities between members of the families as well as reports on clinically relevant cross-reactivities. Based on our analysis, we propose to introduce a new A-RISC index (Allergens’–Relative Identity, Similarity and Cross-reactivity) which describes homology between two allergens belonging to the same protein family and is used to predict the likelihood of cross-reactivity between them. Information on sequence similarities and identities, as well as on the values of the proposed A-RISC index is used to introduce four categories describing a risk of a cross-reactive reaction, namely: high, medium-high, medium-low and low. The proposed approach can facilitate analysis in component-resolved allergy diagnostics, generation of avoidance guidelines for allergic individuals, and help with the design of immunotherapy.

Cross-Reactive Aeroallergens: Which Need to Cross Our Mind in Food Allergy Diagnosis?

Secondary food allergies due to cross-reactivity between inhalant and food allergens are a significant and increasing global health issue. Cross-reactive food allergies predominantly involve plant-derived foods resulting from a prior sensitization to cross-reactive components present in pollen (grass, tree, weeds) and natural rubber latex. Also, primary sensitization to allergens present in fungi, insects, and both nonmammalian and mammalian meat might induce cross-reactive food allergic syndromes. Correct diagnosis of these associated food allergies is not always straightforward and can pose a difficult challenge. As a matter of fact, cross-reactive allergens might hamper food allergy diagnosis, as they can cause clinically irrelevant positive tests to cross-reacting foods that are safely consumed. This review summarizes the most relevant cross-reactivity syndromes between inhalant and food allergens. Particular focus is paid to the potential and limitations of confirmatory testing such as skin testing, specific IgE assays, molecular diagnosis, and basophil activation test.

Sensitization profiles to hazelnut allergens across the United States

BACKGROUND

Measurement of IgE antibody to hazelnut components can aid in the prediction of allergic responses to the food.

OBJECTIVE

To investigate the association between patient demographics (age, location) and patterns of allergic sensitization to hazelnut components across the United States and to investigate the degree of correlation between hazelnut sensitization with sensitization to other tree nuts, peanuts, and their components.

METHODS

Serum samples from 10,503 individuals with hazelnut extract specific IgE (sIgE) levels of 0.35 kU_A/L or higher were analyzed for IgE antibodies to Cor a 1, 8, 9, and 14 by ImmunoCAP. A subset of these patients were analyzed for IgE antibodies to peanut, walnut, and cashew nut IgE along with associated components.

RESULTS

Among hazelnut sensitized individuals, children (<3 years old) were predominantly sensitized to Cor a 9 and Cor a 14. Conversely, Cor a 1 sIgE sensitization was much higher in adults than children, especially in the Northeastern United States. Cor a 8 sensitization was relatively constant (near 10%) across all ages. Cosensitization of hazelnut with other tree nuts and peanuts was related to correlation of IgE concentrations of individual component families.

CONCLUSION

We conclude that sensitization to individual hazelnut components is highly dependent on age and/or geographic location. Component correlations suggest that cosensitization to hazelnut and walnut may be caused by their pathogenesis-related protein 10 allergens, nonspecific lipid transfer proteins, or seed storage proteins, whereas hazelnut and peanut cosensitization is more often caused by cross-reactivity of pathogenesis-related protein 10 (Cor a 1 and Ara h 8) and nonspecific lipid transfer proteins (Cor a 8 and Ara h 9).

Diagnosing allergic sensitizations in the third millennium: why clinicians should know allergen molecule structures

Diagnostic tests to detect allergic sensitization were introduced at the end of the nineteenth century but only in the late 1990s did the advent of molecular allergology revolutionize the approach to the allergic patient. Personalized Medicine, a medical procedure that separates patients into different groups with different medical decisions, practices and interventions has sanctioned this change. In fact, in the last few years molecular allergology and the observation that not every patient has the same allergic profile, even when allergic to the same allergenic source, has originated the concept "one size does not fit all". This new approach requires the identification of still unknown allergens, but also the more detailed investigation of those already known. In depth studies of the structure-function relationships in allergenic molecules can reveal the structural determinants involved in the IgE-binding. Then, the knowledge of the epitope profile of each allergen and of the environmental/experimental conditions affecting the exposure of IgE-binding epitopes can provide important contributions to the understanding of cross-reaction processes and to the improvement of diagnosis, immunotherapy and the overall patient treatment. The evolution of diagnostic systems cannot ignore these new needs in this field.

Asymptomatic LTP sensitisation is common in plant-food allergic children from the Northeast of Spain

BACKGROUND

The sensitisation profile at molecular level in plant-food allergy is complex. Several allergens may be involved, with different potential for severe reactions. lipid transfer proteins (LTP) are considered the most relevant plant-food allergens in adults in Mediterranean countries, but less is known in children.

AIM

To describe the clinical pattern and sensitisation profile of children with plant-food allergy and LTP sensitisation from Northeast Spain.

METHODS

Children with history of immediate reaction to plant-food(s), positive skin-prick-test to the culprit plant-food(s) and specific-IgE to plant-food LTPs were analysed.

RESULTS

130 children were included. 69.2% (90/130) had reacted to ≥2 taxonomically unrelated plant-foods. Peach, walnut, hazelnut and peanut were most frequently involved. Reactions severity ranged from anaphylaxis (45.4%, 59/130) to oral symptoms only. Sensitisation to a particular plant-food LTP not always caused clinical symptoms with that plant-food; 69% (40/58) and 63% (17/27) of peach- and walnut-tolerant subjects had positive rPru p 3 and nJug r 3 specific IgE, respectively. 65.4% (85/130) of children were also sensitised to storage proteins, which was associated to anaphylaxis and nut allergy. However, 60% of patients without nuts/seeds allergy were sensitised to storage proteins. Specific-IgE levels to LTPs and/or storage proteins were not useful to predict allergy (vs. tolerance) to peach, walnut, peanut or hazelnut.

CONCLUSIONS

Sensitisation to LTP and/or storage proteins without clear clinical significance is relatively common. Prospective longitudinal studies are required to evaluate the relevance of these silent sensitisations over time. Caution is required when interpreting the results of molecular-based diagnostic tools in clinical practice.

Structure, stability, and IgE binding of the peach allergen Peamaclein (Pru p 7)

Knowledge of the structural properties of allergenic proteins is a necessary prerequisite to better understand the molecular bases of their action, and also to design targeted structural/functional modifications. Peamaclein is a recently identified 7 kDa peach allergen that has been associated with severe allergic reactions in sensitive subjects. This protein represents the first component of a new allergen family, which has no 3D structure available yet. Here, we report the first experimental data on the 3D-structure of Peamaclein. Almost 75% of the backbone resonances, including two helical stretches in the N-terminal region, and four out of six cysteine pairs have been assigned by 2D-NMR using a natural protein sample. Simulated gastrointestinal digestion experiments have highlighted that Peamaclein is even more resistant to digestion than the peach major allergen Pru p 3. Only the heat-denatured protein becomes sensitive to intestinal proteases. Similar to Pru p 3, Peamaclein keeps its native 3D-structure up to 90°C, but it becomes unfolded at temperatures of 100-120°C. Heat denaturation affects the immunological properties of both peach allergens, which lose at least partially their IgE-binding epitopes. In conclusion, the data collected in this study provide a first set of information on the molecular properties of Peamaclein. Future studies could lead to the possible use of the denatured form of this protein as a vaccine, and of the inclusion of cooked peach in the diet of subjects allergic to Peamaclein.

IgE recognition patterns in peanut allergy are age dependent: perspectives of the EuroPrevall study

BACKGROUND

We tested the hypothesis that specific molecular sensitization patterns correlate with the clinical data/manifestation in a European peanut-allergic population characterized under a common protocol.

METHODS

Sixty-eight peanut-allergic subjects and 82 tolerant controls from 11 European countries were included. Allergy to peanut and lowest symptom-eliciting dose was established by double-blind placebo-controlled food challenge in all but anaphylactic subjects. Information of early or late (before or after 14 years of age) onset of peanut allergy was obtained from standardized questionnaires. IgE to peanut allergens rAra h 1-3, 6, 8-9, profilin and CCD was determined using ImmunoCAP.

RESULTS

Seventy-eight percent of peanut allergics were sensitized to peanut extract and 90% to at least one peanut component. rAra h 2 was the sole major allergen for the peanut-allergic population. Geographical differences were observed for rAra h 8 and rAra h 9, which were major allergens for central/western and southern Europeans, respectively. Sensitization to rAra h 1 and 2 was exclusively observed in early-onset peanut allergy. Peanut-tolerant subjects were frequently sensitized to rAra h 8 or 9 but not to storage proteins. Sensitization to Ara h 2 ≥ 1.0 kUA /l conferred a 97% probability for a systemic reaction (P = 0.0002). Logistic regression revealed a significant influence of peanut extract sensitization and region on the occurrence of systemic reactions (P = 0.0185 and P = 0.0436, respectively).

CONCLUSION

Sensitization to Ara h 1, 2 and 3 is usually acquired in childhood. IgE to Ara h 2 ≥ 1.0 kUA /l is significantly associated with the development of systemic reactions to peanut.

Molecular allergy diagnosis: status anno 2015

IgE antibodies play a key role in type I allergic reactions. Today, different in vitro immunoassays for allergen-specific IgE antibodies are available. However, some major issues should be taken into account for correct interpretation of specific IgE (sIgE) antibody results, as these assays do not demonstrate absolute positive and negative predictive values. Therefore, additional diagnostic tests are needed to make the correct diagnosis. During the last two decades significant progress in biochemistry and molecular biology enabled the detection and quantification of sIgE antibodies to allergen protein components and epitope-emulating peptides, also called molecular allergy diagnosis or component resolved diagnosis (CRD). In contrast to conventional sIgE antibody assays, molecular allergy diagnosis makes it possible to discriminate between genuine allergy and merely sensitisation, to establish personalized sensitization patterns and to assess the individual risk of severity of an allergic reaction and finally it helps us to predict the natural course. In this review the use of CRD in inhalant, food, latex and hymenoptera venom allergy will be discussed. The primary focus will be on the most relevant clinical applications of CRD rather than to describe all the currently available allergen components and epitopes. Appropriate experience of our own research group is provided.

Correlation of sensitizing capacity and T-cell recognition within the Bet v 1 family

Background

Bet v 1 is the main sensitizing allergen in birch pollen. Like many other major allergens, it contains an immunodominant T cell–activating region (Bet v 1_142-156). Api g 1, the Bet v 1 homolog in celery, lacks the ability to sensitize and is devoid of major T-cell epitopes.

Objective

We analyzed the T-cell epitopes of Mal d 1, the nonsensitizing Bet v 1 homolog in apple, and assessed possible differences in uptake and antigen processing of Bet v 1, Api g 1, and Mal d 1.

Methods

For epitope mapping, Mal d 1–specific T-cell lines were stimulated with overlapping synthetic 12-mer peptides. The surface binding, internalization, and intracellular degradation of Bet v 1, Api g 1, and Mal d 1 by antigen-presenting cells were compared by using flow cytometry. All proteins were digested with endolysosomal extracts, and the resulting peptides were identified by means of mass spectrometry. The binding of Bet v 1_142-156 and the homologous region in Mal d 1 by HLA class II molecules was analyzed in silico.

Results

Like Api g 1, Mal d 1 lacked dominant T-cell epitopes. The degree of surface binding and the kinetics of uptake and endolysosomal degradation of Bet v 1, Api g 1, and Mal d 1 were comparable. Endolysosomal degradation of Bet v 1 and Mal d 1 resulted in very similar fragments. The Bet v 1_142-156 and Mal d 1_141-155 regions showed no striking difference in their binding affinities to the most frequent HLA-DR alleles.

Conclusion

The sensitizing activity of different Bet v 1 homologs correlates with the presence of immunodominant T-cell epitopes. However, the presence of Bet v 1_142-156 is not conferred by differential antigen processing.

The biochemical basis and clinical evidence of food allergy due to lipid transfer proteins: a comprehensive review

Plant lipid transfer proteins (LTPs) are ubiquitous proteins that are found in divergent plant species. Although the exact function of LTPs is not fully understood, LTPs are conserved across a broad range of plant species. Because LTPs share structural features, there is an increased probability for significant allergic cross-reactivity. The molecular features of LTPs also decrease the probability of degradation due to cooking or digestion, thereby increasing the probability of systemic absorption and severe allergic reactions. LTP allergy, unlike other forms of anaphylaxis, tends to occur more frequently in areas of lower latitude. The geographic distribution of LTP allergy, along with evidence of increased sensitization after respiratory exposure, has led to the hypothesis that LTP-related food allergy may be secondary to sensitization via the respiratory route. Clinical reactions associated with LTPs have broad clinical phenotypes and can be severe in nature. Life-threatening clinical reactions have been associated with ingestion of a multitude of plant products. Component-resolved diagnosis has played a significant role in research applications for LTP allergy. In the future, component-resolved diagnosis may play a significant role in day-to-day clinical care. Also, quantitative analysis of LTPs in foodstuffs may allow for the identification and/or production of low-LTP foods, thereby decreasing the risk to patients with LTP allergy. Furthermore, sublingual immunotherapy may provide a therapeutic option for patients with LTP allergy.

Transport of Pru p 3 across gastrointestinal epithelium - an essential step towards the induction of food allergy?

BACKGROUND

Since intestinal absorption of food protein can trigger an allergic reaction, the effect of plant food allergen on intestinal epithelial cell permeability and its ability to cross the epithelial monolayer was evaluated.

OBJECTIVE

To study the interaction of Pru p 3 with intestinal epithelium, its natural entrance, analyzing transport kinetics and cellular responses that trigger.

METHODS

This was achieved using Pru p 3, the peach LTP, as a model. Enterocytic monolayers were established by culturing Caco 2 cells, as a model of enterocytes, on permeable supports that separate the apical and basal compartments. Pru p 3 was added to the apical compartment, the transepithelial resistance (TEER) was measured, and the transport was quantified.

RESULTS

The peach allergen that crossed the cell monolayer was detected in the cell fraction and in the basal medium by immunodetection with specific antibodies and the quantity was measured by ELISA assay. Pru p 3 was able to cross the monolayer without disturbing the integrity of the tight junctions. This transport was significantly higher than that of a non-allergenic peach LTP, LTP1, and occurred via lipid raft pathway. The incubation of Caco 2 cells with Pru p 3 and LTP1 produced the expression of epithelial-specific cytokines TSLP, IL33 and IL25.

CONCLUSION

These results suggest that Pru p 3 was able to cross the cell monolayer by the transcellular route and then induce the production of Th2 cytokines. The results of the present study represent a step towards clarifying the importance of Pru p 3 as a sensitizer.

CLINICAL RELEVANCE

The capacity of food allergens to cross the intestinal monolayer could explain their high allergenic capacity and its fast diffusion through the body associating to severe symptoms.

Anaphylaxis to plant-foods and pollen allergens in patients with lipid transfer protein syndrome

PURPOSE OF REVIEW

Nonspecific lipid transfer protein (LTP) is the main cause of primary food allergy in adults living in the Mediterranean area. The way allergic patients get sensitized to this protein is all but established, and the clinical expression of sensitization is extremely variable, ranging from long-lasting symptomless sensitization to severe anaphylaxis. Such variability is seemingly due to the presence/absence of a number of cofactors.

RECENT FINDINGS

The possibility that LTP sensitization occurs via the inhalation of LTP-containing pollen particles seems unlikely; in contrast, peach particles containing the protein seem able to sensitize both via the airways and the skin. Cosensitization to pollen allergens as well as to labile plant food allergens makes LTP allergy syndrome less severe. In some LTP sensitized subjects clinical food allergy occurs only in the presence of cofactors such as exercise, NSAIDs, or chronic urticaria.

SUMMARY

Lipid transfer protein allergy syndrome shows some peculiarities that are unique in the primary food allergy panorama: geographical distribution, frequent asymptomatic sensitization, frequent need for cofactors, and reduced severity when pollen allergy is present. Future studies will have to address these points as the results may have favorable effects on other, more severe, types of food allergy.

Oral treatment with β-lactoglobulin peptides prevents clinical symptoms in a mouse model for cow's milk allergy

BACKGROUND

Prior exposure to partial whey hydrolysates has been shown to reduce the allergic response to whey in mice. This effect was more pronounced in combination with a diet containing non-digestible oligosaccharides (scGOS/lcFOS/pAOS). It is unknown which fractions/epitopes are responsible for this effect. Therefore, the prophylactic ability of synthetic peptides of β-lactoglobulin with/without a scGOS/lcFOS/pAOS-containing diet to reduce the allergic response in a mouse model for cow's milk allergy was investigated.

METHODS

Of 31 peptides, nine peptides were selected based on human T cell data. Mice were pre-treated orally with three peptide mixtures or single peptides for six consecutive days. During this period, they received a control or scGOS/lcFOS/pAOS-containing diet. Subsequently, mice were orally sensitized to whey and received an intradermal and oral challenge. After sacrifice, serum and mesenteric lymph nodes (MLN) were collected for further analysis.

RESULTS

Prior exposure to peptide mixtures 1 and 3 significantly reduced the acute allergic skin response to whey. Mixture 2 showed no effect. An additive effect of the scGOS/lcFOS/pAOS-containing diet was only observed for mixture 1. Of the peptides in mixture 1, one peptide (LLDAQSAPLRVYVEELKP) showed the strongest effect on the acute allergic skin response. This peptide also tended to decrease whey-specific antibody levels and to increase the percentages of CD11b+CD103+ dendritic cells and CD25+Foxp3+ T cells in the MLN.

CONCLUSIONS

Prior exposure to specific peptides of β-lactoglobulin reduces the allergic response to whey, which may involve regulatory dendritic and T cells. Combining peptides with a sGOS/lcFOS/pAOS-containing diet enhances this effect.

Anaphylaxis and generalized urticaria from eating Chinese bayberry fruit

Chinese bayberry Myrica rubra is a very popular fruit in southeastern China. In spite of its wide consumption, no allergies to this fruit have been reported previously. Here we report on a 40-year-old woman suffering from anaphylaxis to Chinese bayberry fruit. Prick-prick skin tests revealed strong reactions to fresh Chinese bayberry fruits as well as to peach, and weaker reactions to some other fruits including apple, melon, and banana. ImmunoCAP analysis revealed identical titers of specific IgE (4.3 kU(A)/L) to peach extract and its lipid transfer protein (LTP, rPru p 3), which was confirmed by detection of a 9 kD band following immunoblotting. Immunoblot analysis with Chinese bayberry extract gave bands of 22, 45, and 90 kD, but no 9 kD band was recognized. There was also no evidence of LTP recognition for loquat (36 kD) or melon (24 kD). This first report of a severe allergic reaction to Chinese bayberry fruit in a patient with LTP-mediated peach allergy indicates that other as yet unidentified non-pollen related fruit allergens are involved in this new severe fruit allergy.

Sensitization prevalence, antibody cross-reactivity and immunogenic peptide profile of Api g 2, the non-specific lipid transfer protein 1 of celery

Background

Celery (Apium graveolens) represents a relevant allergen source that can elicit severe reactions in the adult population. To investigate the sensitization prevalence and cross-reactivity of Api g 2 from celery stalks in a Mediterranean population and in a mouse model.

Methodology

786 non-randomized subjects from Italy were screened for IgE reactivity to rApi g 2, rArt v 3 (mugwort pollen LTP) and nPru p 3 (peach LTP) using an allergen microarray. Clinical data of 32 selected patients with reactivity to LTP under investigation were evaluated. Specific IgE titers and cross-inhibitions were performed in ELISA and allergen microarray. Balb/c mice were immunized with purified LTPs; IgG titers were determined in ELISA and mediator release was examined using RBL-2H3 cells. Simulated endolysosomal digestion was performed using microsomes obtained from human DCs.

Results

IgE testing showed a sensitization prevalence of 25.6% to Api g 2, 18.6% to Art v 3, and 28.6% to Pru p 3 and frequent co-sensitization and correlating IgE-reactivity was observed. 10/32 patients suffering from LTP-related allergy reported symptoms upon consumption of celery stalks which mainly presented as OAS. Considerable IgE cross-reactivity was observed between Api g 2, Art v 3, and Pru p 3 with varying inhibition degrees of individual patients' sera. Simulating LTP mono-sensitization in a mouse model showed development of more congruent antibody specificities between Api g 2 and Art v 3. Notably, biologically relevant murine IgE cross-reactivity was restricted to the latter and diverse from Pru p 3 epitopes. Endolysosomal processing of LTP showed generation of similar clusters, which presumably represent T-cell peptides.

Conclusions

Api g 2 represents a relevant celery stalk allergen in the LTP-sensitized population. The molecule displays common B cell epitopes and endolysosomal peptides that encompass T cell epitopes with pollen and plant-food derived LTP.