The role of immunoglobulin E-binding epitopes in the characterization of food allergy

Investigating the Mechanism of Microwave-Assisted Enzymolysis Synergized with Magnetic Bead Adsorption for Reducing Ovalbumin Allergenicity through Biomass Spectrometry Analysis

This study found that, after microwave treatment at 560 W for 30 s, alkaline protease enzymolysis significantly reduced the allergenicity of ovalbumin (OVA). Furthermore, specific adsorption of allergenic anti-enzyme hydrolyzed peptides in the enzymatic products by immunoglobulin G (IgG) bound to magnetic bead further decreased the allergenicity of OVA. The results indicated that microwave treatment disrupts the structure of OVA, increasing the accessibility of OVA to the alkaline protease. A comparison between 17 IgG-binding epitopes identified through high-performance liquid chromatography-higher energy collisional dissociation-tandem mass spectrometry and previously reported immunoglobulin E (IgE)-binding epitopes revealed a complete overlap in binding epitopes at amino acids (AA)125-135, AA151-158, AA357-366, and AA373-381. Additionally, partial overlap was observed at positions AA41-59, AA243-252, and AA320-340. Consequently, these binding epitopes were likely pivotal in eliciting the allergic reaction to OVA, warranting specific attention in future studies. In conclusion, microwave-assisted enzymolysis synergized with magnetic bead adsorption provides an effective method to reduce the allergenicity of OVA.

Assessing and Comparing Potential Allergenicity of Two Partially Hydrolyzed Whey-Based Formulas for Infants: A Population-Based Study in China

SCOPE

In cases where breast milk is unavailable or inadequate, hydrolyzed infant formula is recommended as the primary alternative. The aim of this study is to assess and compare the allergenicity of two partially hydrolyzed whey-based formulas (PHF-Ws) using serum samples from patients with cow's milk allergy (CMA).

METHODS AND RESULTS

LC-MS/MS technology is used to investigate the peptide distribution in both samples. The immunoreactivity of two PHF-Ws in 27 serum samples from 50 Chinese infants (02 years) with CMA is analyzed. The results demonstrate that even with a similar a degree of hydrolysis (DH), primary protein sources, peptides with molecular weights <5 kDa, and differences in the number of residual allergenic epitopes in the hydrolyzed peptide segments can lead to varying immune responses.

CONCLUSION

The two PHF-Ws have notably high intolerance rates, exceeding 10% among infants with CMA. Therefore, suggesting that PHF-Ws may not be suitable for infants and children with CMA in China.

Lactic acid bacteria modulate the gastrointestinal digestive behavior of soy glycinin and correlation with its immunoreactivity: a peptidomic study

Lactic acid bacterial fermentation helps reduce the immunoreactivity of soy protein. Nevertheless, the effect of lactic acid bacterial fermentation on a particular soy allergen and the consequent dynamic change of epitopes during gastrointestinal digestion are unclear. In this study, soy glycinin was isolated and an in vitro dynamic gastrointestinal model was established to investigate the dynamic change in the immunoreactivity and peptide profile of unfermented (UG) and fermented glycinin (FG) digestates. The results demonstrated that the FG intestinal digestate had a lower antigenicity (0.08%-0.12%) and IgE-binding capacity (1.49%-3.61%) towards glycinin at the early (I-5) and middle (I-30) stages of gastrointestinal digestion, especially those prepared at 2% (w/v) protein concentration. Peptidomic analysis showed that the glycinin subunits G1 and G2 were the preferred ones to release the most abundant peptides, whereas G2, G4, and G5 had an elevated epitope-cleavage rate in FG at stages I-5 and I-30. Three-dimensional modeling revealed that fermentation-induced differential degradation epitopes in gastrointestinal digestion were predominantly located in the α-helix and β-sheet structures. They were closely correlated with the reduced immunoreactivity of soy glycinin.

Digestion-Resistant Linear Epitopes as Dominant Contributors to Strong Allergenicity of Tropomyosin in Antarctic Krill (Euphausia superba)

Although tropomyosin has been identified as a major allergen in Antarctic krill, the digestive fate of Antarctic krill tropomyosin and its relationship with allergenicity are unknown. In this study, Antarctic krill tropomyosin was administered to BALB/c mice via both gavage and intraperitoneal injection to explore its sensitizing and eliciting capacity, and its digestion products were analyzed for structural changes and digestion-resistant linear epitopes. Mice gavaged with tropomyosin exhibited lower levels of specific IgE and IgG1, mast cell degranulation, vascular permeability, and anaphylaxis symptoms than those in the intraperitoneal injection group. This may be due to the destruction of macromolecular aggregates, loose expansion of the tertiary structure, complete disappearance of α-helix, and significant changes in molecular force upon the digestion of tropomyosin. Nevertheless, the intragastric administration of Antarctic krill tropomyosin still triggered strong allergic reactions, which was attributed to the existence of seven digestion-resistant linear epitopes (Glu26-His44, Thr111-Arg125, Glu157-Glu164, Glu177-Gly186, Val209-Ile225, Arg244-Arg255, and Val261-Ile270).

Epitope Mapping of Lysozyme Using the Chinese Egg-Allergic Sera at Both Pooled and Individual Levels

To accurately map the B-cell linear epitopes of lysozyme (LYS) in eggs, five bioinformatics tools were first used to obtain the mimotopes. Afterward, based on the Chinese egg-allergic sera samples screened by the indirect enzyme-linked immunosorbent, the epitopes possessing the capability of binding to IgG/IgE were mapped at both pooled and individual levels by using overlapping peptides covering the complete amino acid sequence of LYS. Six B-cell linear epitopes and two dominant B-cell linear epitopes that could bind to LYS-sIgG were mapped for the first time. Seven IgE-binding epitopes and three dominant IgE-binding epitopes were also obtained. Furthermore, AA31-34 and AA88-91 were the shared dominant epitopes of LYS-sIgG and LYS-sIgE at pooled and individual levels. Overall, the mapped B-cell linear epitopes filled in the gaps in the study of LYS epitopes, and the results may provide theoretical support for the following immunotherapy of egg allergy.

Allergenicity of peanut allergens and its dependence on the structure

Food allergies are a global food safety problem. Peanut allergies are common due, in part, to their popular utilization in the food industry. Peanut allergy is typically an immunoglobulin E-mediated reaction, and peanuts contain 17 allergens belonging to different families in peanut. In this review, we first introduce the mechanisms and management of peanut allergy, followed by the basic structures of associated allergens. Subsequently, we summarize methods of epitope localization for peanut allergens. These methods can be instrumental in speeding up the discovery of allergenicity-dependent structures. Many attempts have been made to decrease the allergenicity of peanuts. The structures of hypoallergens, which are manufactured during processing, were analyzed to strengthen the desensitization process and allergen immunotherapy. The identification of conformational epitopes is the bottleneck in both peanut and food allergies. Further, the identification and modification of such epitopes will lead to improved strategies for managing and preventing peanut allergy. Combining traditional wet chemistry research with structure simulation studies will help in the epitopes' localization.

Bile Acid Profile Influences Digestion Resistance and Antigenicity of Soybean 7S Protein

Soybean 7S storage protein (β-conglycinin) is the most important allergen, exhibits resistance in gastrointestinal (GI) digestion, and causes allergies in humans and animals. A previous study has demonstrated that 7S proteins contained innate amyloid aggregates, but the fate of these specific protein aggregates in intestinal digestion and correlation to allergenicity are unclear. In this study, via a modified INFOGEST static in vitro digestion and IgE binding test, we illustrate that the survived amyloid aggregates of soybean 7S protein in GI digestion might be dominant IgE epitopes of soybean protein in humans. The impact of conjugated primary bile acid salt (BS) profile on digestion resistance and immunogenicity of soybean protein is assessed, regarding the binding affinity of BS to protein aggregates with consideration of the BS composition and the physiologically relevant colloidal structure. The results show that chenodeoxycholate-containing colloidal structures exhibit high affinity and unfolding capacity to protein amyloid aggregates, promoting proteolysis by pancreatic enzymes and thus mitigating the antigenicity of soybean protein. This study presents a novel understanding of bile acid profile and colloidal structure influence on the digestibility and antigenicity of dietary proteins. It should be helpful to design in vitro digestion protocol and accurately replicate physiologically relevant digestion conditions.

Epitope mapping and the effects of various factors on the immunoreactivity of main allergens in egg white

Egg white has high protein content and numerous biological/functional properties. However, reported allergenicity for some of the proteins in egg white is an issue that needs to be paid exclusive attention. A consideration of the structure of IgE epitopes and their sequences, as well as a comprehensive understanding of the effects of various processes on epitopes and the impact of the gastrointestinal tract on them, can help target such issues. The current study focuses on the identified IgE epitopes in egg white proteins and evaluation of the effects of the gastrointestinal digestion, carbohydrate moiety, food matrix, microbial fermentation, recombinant allergen, heat treatment, Maillard reaction and combination of various processes and gastrointestinal digestion on egg white allergenicity. Although the gastrointestinal tract reduces the immunoreactivity of native egg white proteins, some of the IgE epitope-containing fragments remain intact during the digestion process. It has been found that the gastrointestinal tract can have both positive and negative impacts on the IgE binding activities of egg white proteins. Elimination of the carbohydrate moiety leads to a reduction in the immunoreactivity of ovalbumin. But, such effects from the carbohydrate parts in the IgE binding activity need to be explored further. In addition, the interaction between the egg white proteins and the food matrix leads to various effects from the gastrointestinal tract on the digestion of egg white proteins and their subsequent immunoreactivity. Further on this matter, studies have shown that both microbial fermentation and Maillard reaction can reduce the IgE binding activities of egg white proteins. Also, as an alternate approach, the thermal process can be used to treat the egg white proteins, which may result in the reduction or increase in their IgE binding activities depending on the conditions used in the process. Overall, based on the reported data, the allergenicity levels of egg white proteins can be mitigated or escalated depending on the conditions applied in the processing of the food products containing egg white. So far, no practical solutions have been reported to eliminate such allergenicity.

Linear Epitopes Play an Important Role in the Immunoglobulin G (IgG)/Immunoglobulin E (IgE)-Binding Capacity of Scy p 4

Sarcoplasmic calcium-binding protein is a stable allergen in Scylla paramamosain and named Scy p 4. To explore the importance of linear epitopes in the immunoglobulin G (IgG)/immunoglobulin E (IgE)-binding capacity of Scy p 4, chemical denaturants were used to destroy the structure. Scy p 4 was reduced with dithiothreitol and subsequently alkylated with iodoacetamide (IAA). Furthermore, the structural analysis indicated that IAA-Scy p 4 was an unstructured protein. The inhibition enzyme-linked immunosorbent assay showed that IAA-Scy p 4 could inhibit the binding of Scy p 4 to sensitize serum, with inhibition rates reached 55%. Moreover, the linear mimotopes of Scy p 4 were predicted in silico. Three linear epitopes were verified by serological tests and named L-Scy p 4-1 (AA_76-91), L-Scy p 4-2 (AA_111-125), and L-Scy p 4-3 (AA_137-146). Overall, these data provide an understanding of the relationship between the structure and allergenicity about Scy p 4, and the identified linear epitopes can be used for diagnosis and food processing of shellfish allergy.

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.

Medicolegal Implications of Biphasic Anaphylaxis

ABSTRACT

Biphasic anaphylaxis is an uncommon IgE-mediated condition whose pathophysiological mechanisms, risk factors, and predictive signs are not properly understood. Fortunately, the lethality of biphasic anaphylaxis, although probably underestimated, is low. Preventive clinical measures for biphasic anaphylaxis are neither standardized nor commonly applied. Furthermore, there are no laboratory protocols or anaphylactic markers to help identify the onset of biphasic anaphylaxis in clinical settings. The aim of this review is to highlight the medicolegal difficulties facing coroners and forensic pathologists in terms of the diagnosis and assessment of harm for victims and survivors of biphasic anaphylaxis.

Improving Diagnostic Accuracy in Food Allergy

The diagnosis of food allergy can have a major impact on the lives of patients and families, imposing dietary restrictions and limitations on social activities. On the other hand, misdiagnosis can place the patient at risk of a potentially severe allergic reaction. Therefore, an accurate diagnosis of food allergy is of utmost importance. The diagnosis of food allergy is often established by the combination of the clinical history and allergen-specific IgE; however, without a clear history of an allergic reaction, the interpretation of IgE sensitization tests can be difficult. There are also rare cases of clinical food allergy in the absence of IgE sensitization. For that reason, testing for suspected food allergy ideally requires access to oral food challenges (OFCs), which are currently the gold standard tests to diagnose food allergy. As OFCs are time consuming and involve the risk of acute allergic reactions of unpredictable severity, the question remains: how can we improve the accuracy of diagnosis before referring the patient for an OFC? Herein, we review the predictive value of different tests used to support the diagnosis of food allergy, discuss implications for therapy and prognosis, and propose a diagnostic approach to be applied in clinical practice.

Profiling serum antibodies with a pan allergen phage library identifies key wheat allergy epitopes

Allergic reactions occur when IgE molecules become crosslinked by antigens such as food proteins. Here we create the 'AllerScan' programmable phage display system to characterize the binding specificities of anti-allergen IgG and IgE antibodies in serum against thousands of allergenic proteins from hundreds of organisms at peptide resolution. Using AllerScan, we identify robust anti-wheat IgE reactivities in wheat allergic individuals but not in wheat-sensitized individuals. Meanwhile, a key wheat epitope in alpha purothionin elicits dominant IgE responses among allergic patients, and frequent IgG responses among sensitized and non-allergic patients. A double-blind, placebo-controlled trial shows that alpha purothionin reactivity, among others, is strongly modulated by oral immunotherapy in tolerized individuals. AllerScan may thus serve as a high-throughput platform for unbiased analysis of anti-allergen antibody specificities.

Epitope Mapping of Food Allergens Using Noncontact Piezoelectric Microarray Printer

Peptide microarrays have been used to study protein-protein interaction, enzyme-substrate profiling, epitope mapping, vaccine development, and immuno-profiling. Unlike proteins, peptides are cheap to produce, and can be produced in a high-throughput manner, in a reliable and consistent procedure that reduces batch-to-batch variability. All this provides the peptide microarrays a great potential in the development of new diagnostic tools. Noncontact printing, such as piezoelectric systems, results in a considerable advance in protein and peptide microarray production. In particular, they improve drop deposition, sample distribution, quality control, and flexibility in substrate deposition and eliminate cross-contamination and carryover. These features contribute to creating reproducible assays and generating more reliable data. Here we describe the methods and materials for epitope mapping of food allergens using peptide microarrays produced with a noncontact piezoelectric microarray printer.

Mapping and IgE-binding capacity analysis of heat/digested stable epitopes of mud crab allergens

Mud crab (Scylla paramamosain) is widely consumed after thermal processing. It is necessary to comprehensively evaluate of the allergenic potential and epitopes of allergens in high temperature-pressure (HTP) treated S. paramamosain. Tropomyosin and arginine kinase presented higher prevalence (30.77% and 42.13%) than the other three important crab allergens by component-resolved diagnosis. The surface expression of basophils CD63 and CD203c were decreased in HTP treated crab, an effect that was even more evident after digestion and absorption by the intestinal Caco-2 cell model. Of the 35 stable epitope, six were for the first time identified in shellfish. Seven heat/digested stable peptides of tropomyosin retained IgE-binding capacity and were shown to interact with MHC-II. Five epitopes (amino acids 19-29, 99-109, 153-162, 170-188 and 211-221) were the first identified in crab. The study provides insight into prevention and therapy of crab allergy, as well as helps to reduce crab allergenicity during thermal processing.

Allergome-wide peptide microarrays enable epitope deconvolution in allergen-specific immunotherapy

BACKGROUND

The interaction of allergens and allergen-specific IgE initiates the allergic cascade after crosslinking of receptors on effector cells. Antibodies of other isotypes may modulate such a reaction. Receptor crosslinking requires binding of antibodies to multiple epitopes on the allergen. Limited information is available on the complexity of the epitope structure of most allergens.

OBJECTIVES

We sought to allow description of the complexity of IgE, IgG₄, and IgG epitope recognition at a global, allergome-wide level during allergen-specific immunotherapy (AIT).

METHODS

We generated an allergome-wide microarray comprising 731 allergens in the form of more than 172,000 overlapping 16-mer peptides. Allergen recognition by IgE, IgG₄, and IgG was examined in serum samples collected from subjects undergoing AIT against pollen allergy.

RESULTS

Extensive induction of linear peptide-specific Phl p 1- and Bet v 1-specific humoral immunity was demonstrated in subjects undergoing a 3-year-long AIT against grass and birch pollen allergy, respectively. Epitope profiles differed between subjects but were largely established already after 1 year of AIT, suggesting that dominant allergen-specific antibody clones remained as important contributors to humoral immunity following their initial establishment during the early phase of AIT. Complex, subject-specific patterns of allergen isoform and group cross-reactivities in the repertoires were observed, patterns that may indicate different levels of protection against different allergen sources.

CONCLUSIONS

The study highlights the complexity and subject-specific nature of allergen epitopes recognized following AIT. We envisage that epitope deconvolution will be an important aspect of future efforts to describe and analyze the outcomes of AIT in a personalized manner.

IgE and IgG4 responses to shrimp allergen tropomyosin and its epitopes in patients from coastal areas of northern China

Sensitization to allergens and their peptides varies among patients due to geographical or ethnic differences. The present study aimed to investigate immunoglobulin (Ig)E and IgG₄ responses to tropomyosin and its peptides in shrimp allergic patients from northern China. A total of 92 subjects were studied, including 35 shrimp allergic patients, 29 patients with house dust mite (HDM) and/or cockroach allergic patients and 28 healthy volunteers. Serum IgE and IgG₄ antibodies to recombinant shrimp tropomyosin (rPen a 1) and its peptides were measured by means of a light-initiated chemiluminescent assay. A total of 9 major sequential epitopes of Pen a 1 reported in the literature were synthesized. Of 35 shrimp allergic patients, 25 (71.4%) had positive Pen 1-specific IgE (sIgE) antibodies and 22 (62.9%) contained measurable rPen a 1-specific IgG₄ (sIgG₄) antibodies. A strong IgG₄ response accompanied the presence of IgE to Pen a 1. None of the patients with HDM and/or cockroach allergy demonstrated IgE reactivity to rPen a 1. The reaction frequency of IgE binding epitope was 20–48%, while that of IgG₄ binding epitope was 63.6–3.9%. The IgE and IgG₄ recognition patterns of the tropomyosin peptides demonstrated high interpatient heterogeneity. Diversity of IgE binding epitopes was positively correlated with Pen a 1 sIgE levels. In the study population, tropomyosin was a major allergen recognized by the majority of shrimp allergic patients, which is consistent with previous reports. However, none of the 9 epitopes are major (reaction frequency >50%) IgE-binding regions, indicating the epitopes profile may be different in other regions.

Clinical utility of microarray B-cell epitope mapping in food allergies: A systematic review

BACKGROUND

Peptide microarray technology has been proposed as a useful tool for diagnosing food allergy. However, there is considerable heterogeneity in the clinical methods and analytical procedures used to assess its diagnostic and prognostic performance. We performed a systematic review of studies that have used B-cell epitopes by peptide microarray in food allergies to identify the clinical utility of this immunologic technique.

METHODS

Studies were screened in PubMed, Web of Science, and Embase according to an established keyword algorithm. Data extraction was performed, and information was collected in an Excel database. Descriptive analysis was carried out using Stata software.

RESULTS

Thirty relevant studies were identified. Most articles were cross-sectional (n = 24), included epitope mapping (n = 9), and assessed diagnostic utility (n = 11). All studies recruited allergic patients, and some included additional patients (sensitized, persistent, and tolerant). The primary microarray variables studied were IgE intensity (n = 29), IgG4 intensity (n = 15), and number of peptides (n = 17). Statistical approaches differed significantly between studies, with the Wilcoxon test being the most frequently used (n = 10).

CONCLUSIONS

Sensitization to particular epitopes of milk, peanut, and shrimp allergens can be used to determine clinical reactivity, persistence, severity, or response to oral immunotherapy; however, important methodological questions need to be addressed before drawing definitive conclusions. More research is needed to address the accuracy and clinical benefits of microarray-based technology. Standards are required to improve consistency and reproducibility, and to allow for better understanding of research findings.

Mapping Mimotopes for House Dust Mite Allergen Der f 7 Using a Specific Monoclonal Antibody

BACKGROUND

The dust mite Dermatophagoides farinae is a common worldwide cause of indoor allergies induced by its proteins, including the mid-tier allergen Der f 7.

OBJECTIVE

To identify conformational epitopes in Der f 7 using mimotope mapping and computational modelling.

METHODS

Here, we used standard hybridoma technology to generate 3 new monoclonal antibodies against Der f 7 and performed mimotope mapping by probing a random peptide phage display library. Computational tools, including Minox and the DiscoTope-2.0 Server were used to assess the structure and potential position of antigenic residues within Der f 7.

RESULTS

Thirteen mimotopes sharing the common sequence --XX[LST]P[-E][LI]MLPLR[-S]- were identified. Further, computationally-predicted conformational epitopes were found at residues 1-7, 10, 27, 76-81, 92, and 130-133 of Der f 7, and the key amino acids for these epitopes were deduced to be 2P, 3I, 10E, 27E, 78E, 79E, 81I, 130S, and 132E based on the common mimotope sequence.

CONCLUSION

We identified Der f 7 peptide mimotopes that may model binding sites for blocking antibodies. These may guide the development of immunotherapy for individuals with hypersensitivity to Der f 7.

A Comprehensive Review on Kiwifruit Allergy: Pathogenesis, Diagnosis, Management, and Potential Modification of Allergens Through Processing

Kiwifruit is rich in bioactive components including dietary fibers, carbohydrates, natural sugars, vitamins, minerals, omega-3 fatty acids, and antioxidants. These components are beneficial to boost the human immune system and prevent cancer and heart diseases. However, kiwifruit is emerging as one of the most common elicitors of food allergies worldwide. Kiwifruit allergy results from an abnormal immune response to kiwifruit proteins and occur after consuming this fruit. Symptoms range from the oral allergy syndrome (OAS) to the life-threatening anaphylaxis. Thirteen different allergens have been identified in green kiwifruit and, among these allergens, Act d 1, Act d 2, Act d 8, Act d 11, and Act d 12 are defined as the "major allergens." Act d 1 and Act d 2 are ripening-related allergens and are found in abundance in fully ripe kiwifruit. Structures of several kiwifruit allergens may be altered under high temperatures or strong acidic conditions. This review discusses the pathogenesis, clinical features, and diagnosis of kiwifruit allergy and evaluates food processing methods including thermal, ultrasound, and chemical processing which may be used to reduce the allergenicity of kiwifruit. Management and medical treatments for kiwifruit allergy are also summarized.

Food Allergen Epitope Mapping

With the increased global awareness and rise in food allergies, a multifold interest in food allergens is evident. The presence of undeclared food allergens results in expensive food recalls and increased risks of anaphylaxis for the sensitive individuals. Regardless of the allergenic food, the immunogen needs to be identified and detected before making any efforts to inactivate/eliminate it. In type I food allergies, protein immunogen cross-links immunoglobulin E, leading to basophil/mast cell degranulation, resulting in the symptoms that range from mild irritation to anaphylaxis. A portion/part of the protein, known as the epitope, can interact with either antibodies to elicit allergic reactions or T-cell receptors to initiate allergic sensitization. Antibody-recognized epitopes can be either a linear sequence of amino acids (linear epitope) or a three-dimensional motif (conformational epitope), while T-cell-receptor-recognized epitopes are exclusively linear peptides. Identifying and characterizing human-allergy-relevant epitopes are important for allergy diagnosis/prognosis, immunotherapy, and developing food processing methods that can reduce/eliminate immunogencity/immunoreactivity of the allergen.

Overview of the Commonly Used Methods for Food Allergens

Food allergy has become a major public health problem worldwide. In the past two decades, development in molecular biology and immunology has led to many new techniques that had improved traditional methods in the food allergy field. These methods greatly facilitate identification, characterization, and quantification of food allergen and are certainly leading to better diagnostics and therapeutics for food allergic diseases. Here we review methods commonly used for food allergens.

Natural tolerance development in cow's milk allergic children: IgE and IgG4 epitope binding

BACKGROUND

Although most of cow's milk (CM) allergic children will outgrow their allergy, the pathomechanism of the natural development of tolerance remains poorly understood. It has been suggested that the balance between milk-specific IgE and IgG4 plays a major role.

OBJECTIVE

We aimed to investigate differences in IgE and IgG4 antibody binding to CM epitopes between patients with persistent CM allergy (CMA) and those that naturally became tolerant.

METHODS

Sera from 35 children with proven CMA (median age at inclusion of 10 months) were analyzed retrospectively; 22 patients have become tolerant (median age at tolerance acquisition of 51 months) during the study period as confirmed by a negative oral food challenge. IgE and IgG4 binding to sequential epitopes derived from five major CM proteins were measured with a peptide microarray-based immunoassay.

RESULTS

At baselines, greater intensity and broader diversity of IgE and IgG4 binding have been found in children with persistent CMA beyond 5 years of age compared to patients with transient CMA. Moreover, children with transient CMA had IgE and IgG4 antibodies that more often recognized the same epitopes, compared to those with persistent CMA. From baseline to the time of tolerance development, both IgE and IgG4 binding intensity decreased significantly, particularly in areas of α-s- and β-casein (P<.01, false discovery rate [FDR]<.1). Interestingly, differences between IgE and IgG4 binding intensity to CM peptides decreased when the patients became tolerant.

CONCLUSIONS

Our results suggest that the overlap between IgE and IgG4 might be important in natural tolerance acquisition. Further studies are needed to confirm our data and can eventually lead to development of more targeted treatment of food allergy.

Gastrointestinal digestion of hazelnut allergens on molecular level: Elucidation of degradation kinetics and resistant immunoactive peptides using mass spectrometry

SCOPE

Allergy to hazelnut seeds ranks among the most prevalent food allergies in Europe. The aim of this study was to elucidate the gastrointestinal digestion of hazelnut allergens on molecular level.

METHODS AND RESULTS

Hazelnut flour was digested in vitro following the Infogest consensus model. For six allergenic proteins, the time-dependent course of digestion was monitored by SDS-PAGE and HPLC-MS/MS, and degradation products were characterized by a bottom-up proteomics approach. Depending on the molecular structure, a specific biochemical fate was observed for each allergen, and degradation kinetics were traced back to the peptide level. 1183 peptides were characterized, including 130 peptides that carry known IgE-binding epitopes and may represent sensitizers for hazelnut allergy. The kinetics of peptide formation and degradation were determined by label-free quantification and follow a complex multi-stage mechanism.

CONCLUSION

We present a comprehensive survey on the gastrointestinal digestion of a relevant allergenic food on level of the peptidome, including the first systematic characterization and quantification of degradation products. This provides information on the differential resistance of plant food allergens and their structural elements undergoing digestion and forms the basis for a deeper understanding of the molecular principles responsible for sensitization to food allergy.

IgE Epitope Mapping Using Peptide Microarray Immunoassay

IgE epitope mapping has the potential to become an additional tool for food allergy diagnosis/prognosis and to lead to a better understanding of the pathogenesis and tolerance induction of food allergy. Due to its ability to screen thousands of targets in parallel using small volumes of sample, peptide microarray has greatly facilitated large-scale IgE epitope mapping. In the past 10 years, we have developed and optimized a reliable and sensitive peptide microarray immunoassay, which has been successfully applied for IgE epitope mapping of many food allergens in our lab. Here, we describe the method of performing the peptide microarray immunoassay for IgE epitope mapping. In addition, we have upgraded the microarray platform to measure antibody affinity by adding one additional competition step, which is also described in this chapter.

Phage display peptide libraries in molecular allergology: from epitope mapping to mimotope-based immunotherapy

Identification of allergen epitopes is a key component in proper understanding of the pathogenesis of type I allergies, for understanding cross-reactivity and for the development of mimotope immunotherapeutics. Phage particles have garnered recognition in the field of molecular allergology due to their value not only in competitive immunoscreening of peptide libraries but also as immunogenic carriers of allergen mimotopes. They integrate epitope discovery technology and immunization functions into a single platform. This article provides an overview of allergen mimotopes identified through the phage display technique. We discuss the contribution of phage display peptide libraries in determining dominant B-cell epitopes of allergens, in developing mimotope immunotherapy, in understanding cross-reactivity, and in determining IgE epitope profiles of individual patients to improve diagnostics and individualize immunotherapy. We also discuss the advantages and pitfalls of the methodology used to identify and validate the mimotopes.

Food Allergy

Food allergy is receiving increased attention in recent years. Because there is currently no known cure for food allergy, avoiding the offending food is the best defense for sensitive individuals. Type I food allergy is mediated by food proteins, and thus, theoretically, any food protein is a potential allergen. Variability of an individual's immune system further complicates attempts to understand allergen-antibody interaction. In this article, we briefly review food allergy occurrence, prevalence, mechanisms, and detection. Efforts aimed at reducing/eliminating allergens through food processing are discussed. Future research needs are addressed.

IgE Epitope Mapping Using Peptide Microarray Immunoassay

IgE epitope mapping of food allergens contributes to a better understanding of the pathogenesis of food allergy and may become an additional tool for food allergy diagnosis/prognosis. Microarray platforms which allow for simultaneous screening of a large number of peptides corresponding to the sequences of food allergens are ideally suited for large-scale IgE epitope mapping. Here we describe the method of performing a reliable and sensitive peptide microarray immunoassay, which was developed in our lab and results in the identification of candidate IgE epitope biomarkers useful in determining allergic disease severity and prognosis, as well as in the prediction of treatment outcomes. A gastric digestion model that can be applied to prescreen peptides and reduce costs in the peptide microarray is also described in this chapter.

Common food allergens and their IgE-binding epitopes

Food allergy is an adverse immune response to certain kinds of food. Although any food can cause allergic reactions, chicken egg, cow's milk, wheat, shellfish, fruit, and buckwheat account for 75% of food allergies in Japan. Allergen-specific immunoglobulin E (IgE) antibodies play a pivotal role in the development of food allergy. Recent advances in molecular biological techniques have enabled the efficient analysis of food allergens. As a result, many food allergens have been identified, and their molecular structure and IgE-binding epitopes have also been identified. Studies of allergens have demonstrated that IgE antibodies specific to allergen components and/or the peptide epitopes are good indicators for the identification of patients with food allergy, prediction of clinical severity and development of tolerance. In this review, we summarize our current knowledge regarding the allergens and IgE epitopes in the well-researched allergies to chicken egg, cow's milk, wheat, shrimp, and peanut.

Epitope analysis of Ara h 2 and Ara h 6: characteristic patterns of IgE-binding fingerprints among individuals with similar clinical histories

BACKGROUND

Ara h 2 and Ara h 6 are moderately homologous and highly potent peanut allergens.

OBJECTIVE

To identify IgE-binding linear epitopes of Ara h 6, compare them to those of Ara h 2, and to stratify binding based on clinical histories.

METHODS

Thirty highly peanut-allergic subjects were stratified by clinical history. Sera were diluted to contain the same amount of anti-peanut IgE. IgE binding to overlapping 20-mer peptides of Ara h 2 and Ara h 6 was assessed using microarrays.

RESULTS

Each subject had a unique IgE-binding fingerprint to peptides; these data were coalesced into epitope binding. IgE from subjects with a history of more severe reactions (n = 19) had a smaller frequency of binding events (BEs) for both Ara h 2 (52 BEs of 152 (19X8epitopes) possible BEs and Ara h 6 (13 BEs of 133 (19X7 epitopes) possible BEs) compared to IgE from those with milder histories (n = 11) (Ara h 2: 47 BEs of 88 (11X8 epitopes) possible BEs, P < 0.01; Ara h 6: 25 BEs of 77 (11X7 epitopes) possible BEs, P < 0.001). Using an unsupervised hierarchal cluster analysis, subjects with similar histories tended to cluster. We have tentatively identified a high-risk pattern of binding to peptides of Ara h 2 and Ara h 6, predominantly in subjects with a history of more severe reactions (OR = 12.6; 95% CI: 2.0-79.5; P < 0.01).

CONCLUSIONS AND CLINICAL RELEVANCE

IgE from patients with more severe clinical histories recognize fewer linear epitopes of Ara h 2 and Ara h 6 than do subjects with milder reactions and bind these epitopes in characteristic patterns. Close examination of IgE binding to epitopes of Ara h 2 and Ara h 6 may have prognostic value.

Position document: IgE-mediated cow's milk allergy

The present document offers an update on the recommendations for managing patients with cow's milk allergy - a disorder that manifests in the first year of life, with an estimated prevalence of 1.6-3% in this paediatric age group. The main causal allergens are the caseins and proteins in lactoserum (beta-lactoglobulin, alpha-lactoalbumin), and the clinical manifestations are highly variable in terms of their presentation and severity. Most allergic reactions affect the skin, followed by the gastrointestinal and respiratory systems, and severe anaphylaxis may occur. The diagnosis of cow's milk allergy is based on the existence of a suggestive clinical history, a positive allergy study and the subsequent application of controlled exposure testing, which constitutes the gold standard for confirming the diagnosis. The most efficient treatment for cow's milk allergy is an elimination diet and the use of adequate substitution formulas. The elimination diet must include milk from other mammals (e.g., sheep, goat, etc.) due to the risk of cross-reactivity with the proteins of cow's milk. Most infants with IgE-mediated cow's milk allergy become tolerant in the first few years of life. In those cases where cow's milk allergy persists, novel treatment options may include oral immunotherapy, although most authors do not currently recommend this technique in routine clinical practice. Enough evidence is not there to confirm the efficacy of elimination diets in the mother and infant for preventing the appearance of cow's milk allergy. Likewise, no benefits have been observed with prebiotic and probiotic dietetic supplements in infants for preventing food allergy.

Current trends and investigative developments in wheat allergy

The prevalence of gluten-related diseases is increasing in an alarming rate. The studies regarding wheat allergy in the Southeastern and Central Europe are few. The aim of our study was to discuss the effectiveness of serological tests in detecting the prevalence of specific allergens.

Immunoglobulin E-binding epitopes of mite allergens: from characterization to immunotherapy

House dust mites and storage mites produce a number of allergens that can induce hypersensitivity reactions in humans and result in allergic diseases like asthma, rhinitis, and dermatitis. Recent advances in identifying and characterizing these allergens--and, in particular, their immunoglobulin E (IgE)-binding epitopes--have produced a wealth of knowledge. Here, methods for identifying IgE-binding epitopes, from immunoassays to in silico approaches, are summarized and placed in context with the identification of epitopes of mite allergens, particularly from the Dermatophagoides spp. major allergen groups 1 and 2. Finally, the transfer of this information to the clinical development and application of new diagnostic and immunotherapeutic approaches is discussed. While progress in recent years has built on the specific immunotherapies established decades ago, much work remains to be done to mitigate mite allergic disease. Future studies should seek to identify epitopes for mite species beyond Dermatophagoides and for minor allergens. Efforts in translational medicine should use the current epitope data to develop modified allergens for immunotherapy.

Molecular Diagnosis of Shrimp Allergy: Efficiency of Several Allergens to Predict Clinical Reactivity

BACKGROUND

The diagnosis of shellfish allergy remains a challenge for clinicians. Several shellfish allergens have been characterized and their IgE epitopes identified. However, the clinical relevance of this sensitization is still not clear.

OBJECTIVE

The objective of this study was to identify allergens and epitopes associated with clinical reactivity to shrimp.

METHODS

Shrimp-sensitized subjects were recruited and grouped based on the history of shrimp-allergic reactions and challenge outcome. IgE reactivity to recombinant crustacean allergens, and IgE and IgG4 reactivity to peptides were determined. Subjects sensitized to dust mites and/or cockroach without shrimp sensitization or reported allergic reactions, as well as nonatopic individuals, were used as controls.

RESULTS

A total of 86 subjects were recruited with a skin prick test to shrimp; 74 reported shrimp-allergic reactions, 58 were allergic (38 positive double-blind placebo-controlled food challenge and 20 recent anaphylaxis), and 16 were tolerant. All subjects without a history of reactions had negative challenges. The individuals with a positive challenge more frequently recognized tropomyosin and sarcoplasmic calcium-binding proteins than those found tolerant by the challenge. Especially a sarcoplasmic-calcium-binding-protein positive test is very likely to result in a positive challenge, though the frequency of recognition is low. Subjects with dust mite and/or cockroach allergy not sensitized to shrimp recognized arginine kinase and hemocyanin. Several epitopes of these allergens may be important in predicting clinical reactivity.

CONCLUSION

Tropomyosin and sarcoplasmic-calcium-binding-protein sensitization is associated with clinical reactivity to shrimp. Myosin light chain testing may help in the diagnosis of clinical reactivity. Arginine kinase and hemocyanin appear to be cross-reacting allergens between shrimp and arthropods. Detection of IgE to these allergens and some of their epitopes may be better diagnostic tools in the routine workup of shrimp allergy.

BSACI guideline for the diagnosis and management of cow's milk allergy

This guideline advises on the management of patients with cow's milk allergy. Cow's milk allergy presents in the first year of life with estimated population prevalence between 2% and 3%. The clinical manifestations of cow's milk allergy are very variable in type and severity making it the most difficult food allergy to diagnose. A careful age- and disease-specific history with relevant allergy tests including detection of milk-specific IgE (by skin prick test or serum assay), diagnostic elimination diet, and oral challenge will aid in diagnosis in most cases. Treatment is advice on cow's milk avoidance and suitable substitute milks. Cow's milk allergy often resolves. Reintroduction can be achieved by the graded exposure, either at home or supervised in hospital depending on severity, using a milk ladder. Where cow's milk allergy persists, novel treatment options may include oral tolerance induction, although most authors do not currently recommend it for routine clinical practice. Cow's milk allergy must be distinguished from primary lactose intolerance. This guideline was prepared by the Standards of Care Committee (SOCC) of the British Society for Allergy and Clinical Immunology (BSACI) and is intended for clinicians in secondary and tertiary care. The recommendations are evidence based, but where evidence is lacking the panel of experts in the committee reached consensus. Grades of recommendation are shown throughout. The document encompasses epidemiology, natural history, clinical presentations, diagnosis, and treatment.

The impact of structural integrity and route of administration on the antibody specificity against three cow's milk allergens - a study in Brown Norway rats

Background

Characterisation of the specific antibody response, including the epitope binding pattern, is an essential task for understanding the molecular mechanisms of food allergy. Examination of antibody formation in a controlled environment requires animal models. The purpose of this study was to examine the amount and types of antibodies raised against three cow’s milk allergens; β-lactoglobulin (BLG), α-lactalbumin (ALA) and β-casein upon oral or intraperitoneal (i.p.) administration. A special focus was given to the relative amount of antibodies raised against linear versus conformational epitopes.

Methods

Specific antibodies were raised in Brown Norway (BN) rats. BN rats were dosed either (1) i.p. with the purified native cow’s milk allergens or (2) orally with skimmed milk powder (SMP) alone or together with gluten, without the use of adjuvants. The allergens were denatured by reduction and alkylation, resulting in unfolding of the primary structure and a consequential loss of conformational epitopes. The specific IgG1 and IgE responses were analysed against both the native and denatured form of the three cow’s milk allergens, thus allowing examination of the relative amount of linear versus conformational epitopes.

Results

The inherent capacity to induce specific IgG1 and IgE antibodies were rather similar upon i.p. administration for the three cow’s milk allergens, with BLG = ALA > β-casein. Larger differences were found between the allergens upon oral administration, with BLG > ALA > β-casein. Co-administration of SMP and gluten had a great impact on the specific antibody response, resulting in a significant reduced amount of antibodies. Together results indicated that most antibodies were raised against conformational epitopes irrespectively of the administration route, though the relative proportions between linear and conformational epitopes differed remarkably between the allergens.

Conclusions

This study showed that the three-dimensional (3D) structure has a significant impact on the antibodies raised for both systemic and orally administered allergens. A remarkable difference in the antibody binding patterns against linear and conformational epitope was seen between the allergens, indicating that the structural characteristics of proteins may heavily affect the induced antibody response.

Relationships between IgE/IgG4 epitopes, structure and function in Anisakis simplex Ani s 5, a member of the SXP/RAL-2 protein family

BACKGROUND

Anisakiasis is a re-emerging global disease caused by consumption of raw or lightly cooked fish contaminated with L3 Anisakis larvae. This zoonotic disease is characterized by severe gastrointestinal and/or allergic symptoms which may misdiagnosed as appendicitis, gastric ulcer or other food allergies. The Anisakis allergen Ani s 5 is a protein belonging to the SXP/RAL-2 family; it is detected exclusively in nematodes. Previous studies showed that SXP/RAL-2 proteins are active antigens; however, their structure and function remain unknown. The aim of this study was to elucidate the three-dimensional structure of Ani s 5 and its main IgE and IgG4 binding regions.

METHODOLOGY/PRINCIPAL FINDINGS

The tertiary structure of recombinant Ani s 5 in solution was solved by nuclear magnetic resonance. Mg2+, but not Ca2+, binding was determined by band shift using SDS-PAGE. IgE and IgG4 epitopes were elucidated by microarray immunoassay and SPOTs membranes using sera from nine Anisakis allergic patients. The tertiary structure of Ani s 5 is composed of six alpha helices (H), with a Calmodulin like fold. H3 is a long, central helix that organizes the structure, with H1 and H2 packing at its N-terminus and H4 and H5 packing at its C-terminus. The orientation of H6 is undefined. Regarding epitopes recognized by IgE and IgG4 immunoglobulins, the same eleven peptides derived from Ani s 5 were bound by both IgE and IgG4. Peptides 14 (L40-K59), 26 (A76-A95) and 35 (I103-D122) were recognized by three out of nine sera.

CONCLUSIONS/SIGNIFICANCE

This is the first reported 3D structure of an Anisakis allergen. Magnesium ion binding and structural resemblance to Calmodulin, suggest some putative functions for SXP/RAL-2 proteins. Furthermore, the IgE/IgG4 binding regions of Ani s 5 were identified as segments localized on its surface. These data will contribute towards a better understanding of the interactions that occur between immunoglobulins and allergens and, in turn, facilitate the design of novel diagnostic tests and immunotherapeutic strategies.

Identification of parvalbumin and two new thermolabile major allergens of Thunnus tonggol using a proteomics approach

BACKGROUND

The longtail tuna (Thunnus tonggol) is widely consumed in Asia. Parvalbumin, the main major allergen of fish, has been well identified in multiple fish species, yet little is known about the allergenic proteins in T. tonggol. Thus, the aim of this study was to characterize the major allergens of T. tonggol using a proteomics approach.

METHODS

Raw and boiled extracts of the fish were prepared. Fish proteins were separated by means of SDS-PAGE and two-dimensional (2-DE) electrophoresis. 1-DE immunoblotting of raw extract was performed with sera from fish-allergic patients. Ten sera were further analysed by 2-DE immunoblotting. Selected major allergenic protein spots were excised, trypsin digested and analysed by means of mass spectrometry.

RESULTS

SDS-PAGE of raw extract revealed 26 protein fractions, while boiled extract demonstrated fewer bands. The 2-DE gel profile of the raw extract further fractionated the protein bands to more than 100 distinct protein spots. 1-DE immunoblotting of raw extract exhibited two thermolabile protein fractions of 42 and 51 kDa as the major allergens, while the boiled extract only revealed a single IgE-binding band at 151 kDa. 2-DE immunoblotting of raw extract further detected numerous major IgE-reactive spots of 11-13, 42 and 51 kDa. Mass spectrometry analysis of the peptides generated from the 12, 42 and 51 kDa digested spots indicated that these spots were parvalbumin, creatine kinase and enolase, respectively.

CONCLUSIONS

In addition to parvalbumin, two new thermolabile allergens were identified as major allergenic proteins of T. tonggol. This study proved that both thermostable and thermolabile proteins are important in local tuna allergy and should be included in diagnostic strategies.

Food allergy diagnosis and therapy: where are we now?

Food allergy is a growing worldwide epidemic that adversely effects up to 10% of the population. Causes and risk factors remain unclear and diagnostic methods are imprecise. There is currently no accepted treatment for food allergy. Therefore, there is an imminent need for greater understanding of food allergies, revised diagnostics and development of safe, effective therapies. Oral immunotherapy provides a particularly promising avenue, but is still highly experimental and not ready for clinical use.

Cow's milk allergy: from allergens to new forms of diagnosis, therapy and prevention

The first adverse reactions to cow's milk were already described 2,000 years ago. However, it was only 50 years ago that several groups started with the analysis of cow's milk allergens. Meanwhile the spectrum of allergy eliciting proteins within cow's milk is identified and several cow's milk allergens have been characterized regarding their biochemical properties, fold and IgE binding epitopes. The diagnosis of cow's milk allergy is diverse ranging from fast and cheap in vitro assays to elaborate in vivo assays. Considerable effort was spent to improve the diagnosis from an extract-based into a component resolved concept. There is still no suitable therapy available against cow's milk allergy except avoidance. Therefore research needs to focus on the development of suitable and safe immunotherapies that do not elicit severe side effect.