Identification of IgE- and IgG-binding epitopes on alpha(s1)-casein: differences in patients with persistent and transient cow's milk allergy

A composite enzyme derived from papain and chymotrypsin reduces the Allergenicity of Cow's Milk allergen casein by targeting T and B cell epitopes

Casein, the major allergen in cow's milk, presents a significant challenge in providing nutritional support for children with allergies. To address this issue, we investigated a composite enzyme, comprising papain and chymotrypsin, to reduce the allergenicity of casein. Enzymatic hydrolysis induced substantial structural changes in casein, diminishing its affinity for specific IgE and IgG antibodies. Additionally, in a BALB/c mouse model, casein hydrolysate alleviated allergic symptoms, evidenced by lower serum IgE and IgG levels, reduced plasma histamine, and decreased Th2 cytokine release during cell co-culture. Peptidomic analysis revealed a 52.38% and 60% reduction in peptides containing IgE epitopes in casein hydrolyzed by the composite enzyme compared to papain and chymotrypsin, respectively, along with a notable absence of previously reported T cell epitopes. These results demonstrate the potential of enzyme combinations to enhance the efficiency of epitope destruction in allergenic proteins, providing valuable insights into the development of hypoallergenic dairy products.

A rapid immunomagnetic beads-based sELISA method for the detection of bovine αs1-casein based on specific epitopes

Although αs1-casein poses significant health risks to individuals with milk allergies, the availability of quantification methods for this allergen remains limited. In this study, we developed an immunomagnetic beads-based immunoassay (IMBs-ELISA) for the precise quantitative detection of bovine αs1-CN, specifically targeting epitope AA173-194. No cross-reactivity was observed with the other 7 food allergens including milk allergen. The linear detection range of the established IMBs-ELISA method was 0.125 μg/mL-2.000 μg/mL, with a limit of detection of 0.099 μg/mL. The accuracy of this method was 1.048 %, and the intra-plate and inter-plate precision achieved 4.100 % and 6.777 %, respectively. Notably, the entire IMBs-ELISA process could be completed within 75 min, representing a substantial time-saving advantage over traditional ELISA methods. These results proved the reliability and rapidity of the IMBs-ELISA method for detecting αs1-CN in real food.

Allergenicity Modulation of Casein with the Modifications of Linearization, Cross-Linking, and Glycation via the Regulation of Th1/Th2 Homeostasis

Casein (CN) is the primary allergenic protein in cow's milk, contributing to the worldwide escalating prevalence of food allergies. However, there remains limited knowledge regarding the effect of structural modifications on CN allergenicity. Herein, we prepared three modified CNs (mCN), including sodium dodecyl sulfate and dithiothreitol-induced linear CN (LCN), transglutaminase-cross-linked CN (TCN), and glucose-glycated CN (GCN). The electrophoresis results indicated widespread protein aggregation among mCN, causing variations in their molecular weights. The unique internal and external structural characteristics of mCN were substantiated by disparities in surface microstructure, alterations in the secondary structure, variations in free amino acid contents, and modifications in functional molecular groups. Despite the lower digestibility of TCN and GCN compared to LCN, they significantly suppressed IL-8 production in Caco-2 cells without significantly promoting their proliferation. Moreover, GCN showed the weakest capacity to induce LAD2 cell degranulation. Despite the therapeutic effect of TCN, GCN-treated mice displayed the most prominent attenuation of allergic reactions and a remarkably restored Th1/Th2 imbalance, while LCN administration resulted in severe allergic phenotypes and endotypes in both cellular and murine models. This study highlighted the detrimental effect of linear modifications and underscored the significance of glycation in relation to CN allergenicity.

Effect of lactic acid bacteria fermentation on cow milk allergenicity and antigenicity: A review

Cow milk is a major allergenic food. The potential prevention and treatment effects of lactic acid bacteria (LAB)-fermented dairy products on allergic symptoms have garnered considerable attention. Cow milk allergy (CMA) is mainly attributed to extracellular and/or cell envelope proteolytic enzymes with hydrolysis specificity. Numerous studies have demonstrated that LAB prevents the risk of allergies by modulating the development and regulation of the host immune system. Specifically, LAB and its effectors can enhance intestinal barrier function and affect immune cells by interfering with humoral and cellular immunity. Fermentation hydrolysis of allergenic epitopes is considered the main mechanism of reducing CMA. This article reviews the linear epitopes of allergens in cow milk and the effect of LAB on these allergens and provides insight into the means of predicting allergenic epitopes by conventional laboratory analysis methods combined with molecular simulation. Although LAB can reduce CMA in several ways, the mechanism of action remains partially clarified. Therefore, this review additionally attempts to summarize the main mechanism of LAB fermentation to provide guidance for establishing an effective preventive and treatment method for CMA and serve as a reference for the screening, research, and application of LAB-based intervention.

The B Cell Response and Formation of Allergenic and Anti-Allergenic Antibodies in Food Allergy

Food allergies are a growing public health concern worldwide, especially in children and young adults. Allergen-specific IgE plays a central role in the pathogenesis of food allergies, but their titers poorly correlate with allergy development. Host immune systems yield allergen-specific immunoglobulin (Ig)A, IgE and IgG subclasses with low or high affinities and differential Fc N-glycosylation patterns that can affect the allergic reaction to food in multiple ways. High-affinity IgE is required to induce strong mast cell activation eventually leading to allergic anaphylaxis, while low-affinity IgE can even inhibit the development of clinically relevant allergic symptoms. IgA and IgG antibodies can inhibit IgE-mediated mast cell activation through various mechanisms, thereby protecting IgE-positive individuals from allergy development. The production of IgE and IgG with differential allergenic potential seems to be affected by the signaling strength of individual B cell receptors, and by cytokines from T cells. This review provides an overview of the diversity of the B cell response and the diverse roles of antibodies in food allergy.

Real-Life Use of Component-Specific IgE in IgE-Mediated Cow's Milk Protein Allergy in a Spanish Paediatric Allergy Centre

BACKGROUND

In Spain, IgE-mediated cow's milk protein allergy (CMPA) affects approximately 0.69% of infants. Molecular diagnosis may be useful for monitoring natural spontaneous tolerance development in CMPA. The aim of this study was to retrospectively analyse a cohort of paediatric patients with IgE-mediated CMPA who were avoiding milk products awaiting natural tolerance and determine the relationship between disease persistence and major cow's milk allergens.

METHODS

A retrospective chart review of 200 patients diagnosed with IgE-mediated CMPA between 2011 and 2020 was conducted. Patients strictly avoided milk products until an oral food challenge was performed. The main outcome was the introduction of liquid milk following a negative oral food challenge and its correlation with IgE and SPT measurements of milk components at diagnosis. Secondary outcomes included the rate of allergic reactions and anaphylaxis during the treatment period and its correlation with IgE and SPT measurements.

RESULTS

Of the 200 charts analysed, 122 patients had a negative oral food challenge to milk (61.0%) (95% confidence interval (CI): 54.1-67.5) following a period of strict avoidance of milk. Higher levels of component-specific IgE, especially casein, were associated with failure in the oral food challenge (p = 0.02). Allergic reactions were experienced by 106 children (53%), of which 34 (17%; 95% CI: 12.4-22.8) had anaphylactic reactions. The risk of anaphylaxis was not predicted by raised IgE levels.

CONCLUSIONS

While a large proportion of children acquired natural tolerance to cow's milk following a period of strict avoidance, IgE-mediated CMPA persisted in many children. Casein IgE levels at diagnosis were raised in those who failed to achieve natural tolerance. Allergic reactions to milk, including anaphylaxis, occurred commonly, but this was not predicted by raised IgE levels or SPT measurements.

Antibody responses to dietary antigens are accompanied by specific plasma cells in the infant thymus

BACKGROUND

Human infants develop IgG responses to dietary antigens during the first 2 years of life. Yet, the source of these antibodies is unclear. In previous studies we reported on the thymus as a unique functional niche for plasma cells (PCs) specific to environmental antigens.

OBJECTIVE

We sought to examine whether PCs specific to dietary antigens are detected in the infant thymus.

METHODS

We tested IgG reactivity to 112 food antigens and allergens in the serum of 20 neonates and infants using microarrays. The presence of PC-secreting IgG specific to the most prominent antigens was then assessed among thymocytes in the same cohort. Using an LC-MS proteomics approach, we looked for traces of these antigens in the thymus.

RESULTS

Our studies first confirmed that cow's milk proteins are prevalent targets of serum IgG in early life. Subjects with the highest serum IgG titers to cow's milk proteins also harbored IgG-producing PCs specific to the same antigens in the thymic niche. Furthermore, we detected multiple peptide fragments of cow's milk antigens in the thymus. Lastly, we verified that both serum IgG and IgG secreted by thymic PCs recognized the peptide epitopes found in the thymus.

CONCLUSIONS

Our studies reveal the presence of antibody-secreting PCs specific to common dietary antigens in the infant thymus. The presence of these antigens in the thymus suggested that activation and differentiation of specific PCs occurred in this organ. Further studies are now warranted to evaluate the possible implication of these cells in tolerance to dietary antigens.

Research progress on the allergic mechanism, molecular properties, and immune cross-reactivity of the egg allergen Gal d 5

Eggs and their products are commonly consumed in food products worldwide, and in addition to dietary consumption, egg components are widely used in the food industry for their antimicrobial, cooking, and other functional properties. Globally, eggs are the second most common allergenic food after milk. However, current research on egg allergy primarily focuses on egg white allergens, while research on egg yolk allergens is not comprehensive enough. Therefore, summarizing and analyzing the important allergen α-livetin in egg yolk is significant in elucidating the mechanism of egg allergy and exploring effective desensitization methods. This paper discusses the incidence, underlying mechanism, and clinical symptoms of egg allergy. This article provides a comprehensive summary and analysis of the current research status concerning the molecular structural properties, epitopes, and immune cross-reactivity of the egg yolk allergen, Gal d 5. Additionally, it examines the effects of various processing methods on egg allergens. The article also offers suggestions and outlines potential future research directions and ideas in this field.

‘Early Introduction’ of Cow’s Milk for Children with IgE-Mediated Cow’s Milk Protein Allergy: A Review of Current and Emerging Approaches for CMPA Management

IgE-mediated cow’s milk protein allergy (CMPA) is one of the most prevalent food allergies in early childhood. Though the cornerstone of management involves the strict avoidance of milk products while awaiting natural tolerance, research increasingly shows that the rates of resolution are slowing down. Therefore, there is a need to explore alternative pathways to promote tolerance to cow’s milk in pediatric populations. This review aims to combine and appraise the scientific literature regarding the three CMPA management methods: avoidance, the milk ladder, and oral immunotherapy (OIT) and their outcomes in terms of efficacy, safety, and immunological effects. Cow’s milk (CM) avoidance virtually protects against allergic reaction until natural tolerance occurs, with hypoallergenic substitutes available in the market, but accidental ingestion represents the main issue for this strategy. Introduction to baked milk using the milk ladder was designed, with most CMPA patients successfully completing the ladder. Similar to baked milk treatment, many OIT protocols also demonstrated decreased IgE and increased IgG4 levels post protocol, as well as a reduction in wheal size diameter. Though these strategies are shown to be safe and effective in CMPA, future clinical trials should compare the safety and effectiveness of these three management strategies.

EAACI Molecular Allergology User's Guide 2.0

Since the discovery of immunoglobulin E (IgE) as a mediator of allergic diseases in 1967, our knowledge about the immunological mechanisms of IgE-mediated allergies has remarkably increased. In addition to understanding the immune response and clinical symptoms, allergy diagnosis and management depend strongly on the precise identification of the elicitors of the IgE-mediated allergic reaction. In the past four decades, innovations in bioscience and technology have facilitated the identification and production of well-defined, highly pure molecules for component-resolved diagnosis (CRD), allowing a personalized diagnosis and management of the allergic disease for individual patients. The first edition of the "EAACI Molecular Allergology User's Guide" (MAUG) in 2016 rapidly became a key reference for clinicians, scientists, and interested readers with a background in allergology, immunology, biology, and medicine. Nevertheless, the field of molecular allergology is moving fast, and after 6 years, a new EAACI Taskforce was established to provide an updated document. The Molecular Allergology User's Guide 2.0 summarizes state-of-the-art information on allergen molecules, their clinical relevance, and their application in diagnostic algorithms for clinical practice. It is designed for both, clinicians and scientists, guiding health care professionals through the overwhelming list of different allergen molecules available for testing. Further, it provides diagnostic algorithms on the clinical relevance of allergenic molecules and gives an overview of their biology, the basic mechanisms of test formats, and the application of tests to measure allergen exposure.

Favourable Interfacial Characteristics of A2 Milk Protein Monolayer

Shielding of the specific body organ using the biocompatible material helps preventing direct exposure of that part to the foreign entities responsible for infections. Here we show the potential of the A2 milk protein recovered from the milk of cow from Indian origin for possible prevention of the direct exposure to other foreign molecules. We measured the surface pressure of the monolayers of different types of protein samples using Langmuir isotherm experiments. The surface pressure measurements for the monolayer of four types of protein macromolecules have been carried out using the Wilhelmy plate micro pressure sensor. We studied the self-organization of different protein macromolecules and their monolayer compression characteristics. The electrochemical behaviour is studied using electrochemical impedance spectroscopy. We found the highest surface pressure for the monolayer of A2 protein. Further, it is also found that A2 protein exhibited the highest surface activity amongst the other proteins. This property can be effectively used for making the envelope of the A2 protein surrounding the targeted entity.

Secrets behind Protein Sequences: Unveiling the Potential Reasons for Varying Allergenicity Caused by Caseins from Cows, Goats, Camels, and Mares Based on Bioinformatics Analyses

This study systematically investigated the differences in allergenicity of casein in cow milk (CM), goat milk (GM), camel milk (CAM), and mare milk (MM) from protein structures using bioinformatics. Primary structure sequence analysis reveals high sequence similarity between the α-casein of CM and GM, while all allergenic subtypes are likely to have good hydrophilicity and thermal stability. By analyzing linear B-cell epitope, T-cell epitope, and allergenic peptides, the strongest casein allergenicity is observed for CM, followed by GM, and the casein of MM has the weakest allergenicity. Meanwhile, 7, 9, and 16 similar or identical amino acid fragments in linear B-cell epitopes, T-cell epitopes, and allergenic peptides, respectively, were observed in different milks. Among these, the same T-cell epitope FLGAEVQNQ was shared by κ-CN in all four different species' milk. Epitope results may provide targets of allergenic fragments for reducing milk allergenicity through physical or/and chemical methods. This study explained the underlying secrets for the high allergenicity of CM to some extent from the perspective of casein and provided new insights for the dairy industry to reduce milk allergy. Furthermore, it provides a new idea and method for comparing the allergenicity of homologous proteins from different species.

Identification of peptides sequence and conformation contributed to potential allergenicity of main allergens in yogurts

Yogurts provide a good source of nutrition and may induce tolerance in people with cow's milk allergy (CMA). This study aimed to investigate the IgE-binding capacity of main allergens in the different yogurts which provide a reference for people with a high risk of CMA, and analyze the epitopes of major allergen peptides in yogurt. We assessed the degradation and the allergenic properties of major allergens in six commercial yogurts and fresh milk. The degradation of major allergens was analyzed by SDS-PAGE and RP-HPLC. Western blot and ELISA experiments detected allergenic characteristics by using specific sera. The results showed that β-lactoglobulin (Bos d 5) and α-lactalbumin (Bos d 4) were obviously degraded in yogurts but caseins were still present in abundance, which indicated that the proteases in yogurts were specific to whey proteins. IgE and IgG binding ability of major allergens were obviously reduced in yogurts, especially GuMi yogurt. In addition, 17 peptides of major allergens in GuMi yogurt were identified by LC-MS/MS and most of them were located in the interior of the spatial structure of proteins. Among them, 8 peptides had specific biological functions for health benefits, such as antibacterial, antioxidant, and ACE-inhibitory. We also found that 6 and 14 IgE epitopes of Bos d 5 and caseins were destroyed in GuMi yogurt, which could lead to the reduction of IgE-binding capacity. Meanwhile, peptides [Bos d 5 (AA15-40), Bos d 9 (AA120-151, AA125-151)] also preserved T cell epitopes, which might also induce the development of oral tolerance. Therefore, this study suggested that the sequence and conformation of peptides in yogurts contributed to hypoallergenicity.

IgE and IgG4 Epitope Mapping of Food Allergens with a Peptide Microarray Immunoassay

Peptide microarrays are a powerful tool to identify linear epitopes of food allergens in a high-throughput manner. The main advantages of the microarray-based immunoassay are as follows: the possibility to assay thousands of targets simultaneously, the requirement of a low volume of serum, the more robust statistical analysis, and the possibility to test simultaneously several immunoglobulin subclasses. Among them, the last one has a special interest in the field of food allergy, because the development of tolerance to food allergens has been associated with a decrease in IgE and an increase in IgG4 levels against linear epitopes. However, the main limitation to the clinical use of microarray is the automated analysis of the data. Recent studies mapping the linear epitopes of food allergens with peptide microarray immunoassays have identified peptide biomarkers that can be used for early diagnosis of food allergies and to predict their severity or the self-development of tolerance. Using this approach, we have worked on epitope mapping of the two most important food allergens in the Spanish population, cow's milk, and chicken eggs. The final aim of these studies is to define subsets of peptides that could be used as biomarkers to improve the diagnosis and prognosis of food allergies. This chapter describes the protocol to produce microarrays using a library of overlapping peptides corresponding to the primary sequences of food allergens and data acquisition and analysis of IgE and IgG4 binding epitopes.

Does a Little Difference Make a Big Difference? Bovine β-Casein A1 and A2 Variants and Human Health-An Update

For over 20 years, bovine beta-casein has been a subject of increasing scientific interest because its genetic A1 variant during gastrointestinal digestion releases opioid-like peptide β-casomorphin-7 (β-CM-7). Since β-CM-7 is involved in the dysregulation of many physiological processes, there is a growing discussion of whether the consumption of the β-casein A1 variant has an influence on human health. In the last decade, the number of papers dealing with this problem has substantially increased. The newest clinical studies on humans showed a negative effect of variant A1 on serum glutathione level, digestive well-being, cognitive performance score in children, and mood score in women. Scientific reports in this field can affect the policies of dairy cattle breeders and the milk industry, leading to the elimination of allele A1 in dairy cattle populations and promoting milk products based on milk from cows with the A2A2 genotype. More scientific proof, especially in well-designed clinical studies, is necessary to determine whether a little difference in the β-casein amino acid sequence negatively affects the health of milk consumers.

Study on the Correlation between the Protein Profile of Lupin Milk and Its Cheese Production Compared with Cow's Milk

Australian sweet lupin, the largest legume crop grown in Western Australia, is receiving global attention from the producers of new foods. To understand the effect of protein on cheese yield, lupin milk proteins were separated from the first, second, and third filtrations by cheesecloths. However, proteins from the first and second were analyzed using two-dimensional polyacrylamide gel electrophoresis; then, the isolated proteins associated with cheese production were identified. The research also focused on identifying the optimal method of cheese production based on the coagulation process, temperature, yield, and sensory evaluation. Lupin curds from the two cultivars, Mandelup and PBA Jurien, were produced using vinegar, lemon juice, starter culture, vegetable rennet enzyme as coagulant, as well as curd generated using starter culture and vegetable rennet enzyme. Cow's milk was used as a control. The results indicated that first-time filtration produced better extraction and higher yield of lupin proteins and cheese than the second filtration. A sensory analysis indicated that lupin cheese produced from PBA Jurien lupin milk using vinegar, 7.80% expressed as acetic acid, and ground in 45 °C water, was the most acceptable. The cheeses were examined for their protein, carbohydrates, fat, ash, and moisture contents. The concentration of protein was approximately 27.3% and 20.6%, respectively, in the cheese from PBA Jurien and Mandelup. These results suggest that lupin milk can adequately supply the proteins needed in human diets and, thus, could be used in the production of many existing products that require animal milk as an input.

Evaluation of cross-reactivity between casein components using inhibition assay and in silico analysis

BACKGROUND

We previously reported that the specific IgE levels to αs1-casein (CN) and β-CN in patients with cow's milk allergy decreased with similar dynamics during oral immunotherapy. Therefore, we hypothesized that αs1- and β-CN have strong cross-reactivity among CN components, despite the low similarity in the full-length amino acid sequences.

METHODS

The αs1-, β-, and κ-CN were purified from commercial cow's milk. We recruited 39 patients with cow's milk allergy, and the serum IgE levels for each CN component were measured by enzyme-linked immunosorbent assay (ELISA). Cross-reactivity between CN components was investigated by competitive ELISA against αs1-CN. Sequence homology between CN components at the peptide level was calculated using in silico analysis and quantified by the property distance (PD) value.

RESULTS

The αs1-CN-specific IgE levels exhibited a strong positive correlation with the β-CN-specific IgE (r = 0.945, P < .001). Complete competition was observed by β-CN against αs1-CN, suggesting the presence of common epitopes between them. In silico analysis detected 24 peptide sets with PD values lower than 10 between αs1- and β-CN, and 14 sets between αs1- and κ-CN. The amino acid sequences of αs1-CN (E61-E70) and β-CN (I12-E21) that showed the lowest PD value (5.30) were present in the characteristic sequence known as casein phosphopeptide (CPP).

CONCLUSION

We detected strong cross-reactivity between CN components. Furthermore, we found highly homologous sequences in the CPP region, which contains a core sequence of "SSSEE" with phosphorylated serine residues.

Two Faces of Milk Proteins Peptides with Both Allergenic and Multidimensional Health Beneficial Impact- Integrated In Vitro/In Silico Approach

The main food-origin antigens that the infant's body is in contact with are cow's milk proteins (CMP). Still, CMP are one of the main sources of beneficial biologically active peptides that play a role in treatment of non-communicable diseases. Safe methods to quickly predict the sensitizing potential of food proteins among their range of health-promoting properties are essential. The aim of study was to adapt an integrated approach combining several in silico (IS) studies and in vitro (IV) assays to screen the multifunctionality of CMP-derived peptides. Major histocompatability complex type II MHC II-binders, interleukin-4 and -10 inducers, interferon γ -inducers and immunobioactivity tools were used to predict the peptide-power of inducing allergies or tolerance. A comparison of the peptide profiless revealed the presence of one identical and one overlapping sequence in IS and IV hydrolysate. By IS analysis, four of 24 peptides were found to have high affinity and stimulate IL-4 expression, and by IV, one of seven peptides had this potential (Bos d9 peptide DIPNPIGSENSEK (195-208)). Three IV peptides may induce IL-10 expression. The IV/IS assessment seems promising agents for peptides' potential determination dedicated only to preliminary screening of peptides. The IV verification is still crucial in further steps of studies.

IgE-binding residues analysis of the house dust mite allergen Der p 23

House dust mites (HDMs) are one of the major causes of allergies in the world. The group 23 allergen, Der p 23, from Dermatophagoides pteronyssinus, is a major allergen amongst HDM-sensitized individuals. This study aims to determine the specific immunoglobulin E (sIgE) binding frequency and IgE-binding residues of recombinant Der p 23 (rDer p 23) allergen amongst a cohort of consecutive atopic individuals in a tropical region. We performed site-directed mutagenesis and carried out immuno-dot blot assays using 65 atopic sera. The immuno-dot blot assays results indicated that the two residues K44 and E46 which are located at the N-terminal region are the major IgE-binding residues. The rDerp-23 sIgE titers are strongly correlated to the number of IgE-binding residues for rDer p 23 (P < 0.001). Atopic individuals who were only sensitized to HDM have a significantly higher number of IgE-binding residues than the individuals who were polysensitized to HDM and other crude allergens (P < 0.05). Individuals with allergic multimorbidity and moderate-to-severe allergic rhinitis also have a higher number of IgE-binding residues compared to those with single allergic disease and mild allergic rhinitis. The results prompt us to hypothesize that the individuals who have a higher number of IgE-binding residues may face a bigger challenge to be treated through immunotherapy due to the complexity in designing an effective hypoallergen with a high number of IgE-binding residues. We propose that the development of a refined molecular diagnostic assay, which includes alanine substitution of surface-exposed residues could be a more precise diagnostic strategy to identify all the IgE-binding residues of a major allergen for an atopic individual and the development could be another new dimension in allergy diagnosis and allergen immunotherapy treatment.

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.

Digestomics of Cow's Milk: Short Digestion-Resistant Peptides of Casein Form Functional Complexes by Aggregation

The aim of this study was to identify short digestion-resistant peptides (SDRPs) released by pepsin digestion of the whole cow’s milk and examine their IgE reactivity and allergenicity. Raw milk was subjected to simulated gastric digestion. SDRPs were fractionated from the digests and identified by MS. Milk SDRPs were evaluated for aggregability, propensity to compete for IgE binding with individual milk allergens, and ability to bind IgG4 from allergic and milk-tolerant individuals. The majority of milk SDRPs originated from caseins (97% of peptides) and overlapped with the known IgE epitopes of cow’s milk allergens. SDRPs competed with milk proteins for binding to human IgE and readily formed aggregates. The average peptide length was 10.6 ± 3.5 amino acids. The ability to provoke allergenic in vivo responses was confirmed by skin-prick testing (SPT) in five milk-allergic subjects. This was attributed to the peptide ability to aggregate into non-covalent complexes. SDRPs are able to induce response in SPT, but only in 50% of the sera SDRPs were able to inhibit IgG4 binding to caseins. Hence, SDRPs corresponding to the mainly continuous epitopes of milk proteins induce allergenic in vivo responses in milk-allergic subjects due to aggregation.

The effect of atmospheric cold plasma treatment on the antigenic properties of bovine milk casein and whey proteins

Casein, β-lactoglobulin and α-lactalbumin are major milk protein allergens. In the present study, the structural modifications and antigenic response of these bovine milk allergens as induced by non-thermal treatment by atmospheric cold plasma were investigated. Spark discharge (SD) and glow discharge (GD), as previously characterized cold plasma systems, were used for protein treatments. Casein, β-lactoglobulin and α-lactalbumin were analyzed before and after plasma treatment using SDS-PAGE, FTIR, UPLC-MS/MS and ELISA. SDS-PAGE results revealed a reduction in the casein and α-lactalbumin intensity bands after SD or GD treatments; however, the β-lactoglobulin intensity band remained unchanged. FTIR studies revealed alterations in protein secondary structure induced by plasma, particularly contents of β-sheet and β-turn. The UPLC-MS/MS results showed that the amino acid compositions decreased after plasma treatments. ELISA of casein and α-lactalbumin showed a decrease in antigenicity post plasma treatment, whereas ELISA of β-lactoglobulin showed an increase in antigenicity. The study indicates that atmospheric cold plasma can be tailored to mitigate the risk of bovine milk allergens in the dairy processing and ingredients sectors.

Egg Allergy: Diagnosis and Immunotherapy

Hypersensitivity or an allergy to chicken egg proteins is a predominant symptomatic condition affecting 1 in 20 children in Australia; however, an effective form of therapy has not yet been found. This occurs as the immune system of the allergic individual overreacts when in contact with egg allergens (egg proteins), triggering a complex immune response. The subsequent instantaneous inflammatory immune response is characterized by the excessive production of immunoglobulin E (IgE) antibody against the allergen, T-cell mediators and inflammation. Current allergen-specific approaches to egg allergy diagnosis and treatment lack consistency and therefore pose safety concerns among anaphylactic patients. Immunotherapy has thus far been found to be the most efficient way to treat and relieve symptoms, this includes oral immunotherapy (OIT) and sublingual immunotherapy (SLIT). A major limitation in immunotherapy, however, is the difficulty in preparing effective and safe extracts from natural allergen sources. Advances in molecular techniques allow for the production of safe and standardized recombinant and hypoallergenic egg variants by targeting the IgE-binding epitopes responsible for clinical allergic symptoms. Site-directed mutagenesis can be performed to create such safe hypoallergens for their potential use in future methods of immunotherapy, providing a feasible standardized therapeutic approach to target egg allergies safely.

Changes in passively-sensitized basophil activation to αS1-casein after oral immunotherapy

INTRODUCTION

Immune response to cow's milk allergen (CMA) has been analyzed mostly using crude milk antigen or a mixture of various caseins. This study aimed to assess the changes in the immunological response against αS1-casein during oral immunotherapy (OIT) and to investigate the mechanism of tolerance.

METHODS

We have performed rush OIT to 39 patients with CMA and obtained the serum samples up to 3 years after OIT. Immunoglobulin E (IgE) and IgG4 antibodies specific to highly purified αS1-casein as well as passively-sensitized basophil activation were evaluated using the serial samples. Furthermore, we examined whether basophil activation led by the pre-OIT serum was suppressed by the post-OIT serum, or by the tolerant serum obtained from naturally outgrown patients.

RESULTS

Specific IgE to αS1-casein was significantly reduced after OIT. Specific IgG4 (sIgG4) to αS1-casein was also detected in most of the pre-OIT sera, which was not significantly increased after OIT. Activation of passively-sensitized basophils to αS1-casein was significantly reduced after 2 years (14% ± 19%) and 3 years (19% ± 18%) post-OIT compared with pre-OIT (%CD63^high basophils; 51% ± 27%). Furthermore, the addition of post-OIT or tolerant serum to pre-OIT serum significantly suppressed the basophil activation. This suppression was abrogated by washing the supernatant after passive sensitization, but not by depleting IgG antibodies from post-OIT or tolerant sera, nor by blocking FcγRIIb using an anti-FcγR antibody.

CONCLUSIONS

αS1-casein-sIgG4 plays a minor role in tolerance mechanisms in cases of CMA; humoral factors other than antigen-sIgG4 may be involved.

Mechanisms that define transient versus persistent food allergy

Currently, we have a poor understanding of why some food allergies are outgrown and others are not. Deciphering the immune basis of the natural resolution of food allergy will likely provide critical information for developing new therapies for the treatment of persistent food allergies. There are limited cohort studies that have followed children with food allergy over time, but information generated from such cohorts points to features of innate and adaptive immunity, as well as environmental differences (microbiome) that discriminate those with persistent versus transient food allergy. Studies from mouse models highlight the importance of novel subsets of memory B cells rather than plasma cells combined with antigen re-exposure and T-cell help in the maintenance of IgE. In this review we discuss these findings from human cohorts and experimental systems and discuss existing gaps in our knowledge.

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.

Management of Cow's Milk Allergy from an Immunological Perspective: What Are the Options?

The immunological mechanism underlying Immunoglobuline E (IgE)-mediated cow’s milk allergy has been subject to investigations for many years. Identification of the key immune cells (mast cells, B cells) and molecules (IgE) in the allergic process has led to the understanding that avoidance of IgE-crosslinking epitopes is effective in the reduction of allergic symptoms but it cannot be envisioned as a treatment. For the treatment and prevention of IgE-mediated cow’s milk allergy, it is thought that the induction of a sustained state of immunological tolerance is needed. In this review, we will discuss various approaches aimed at achieving immunological tolerance and their success. Furthermore, we will speculate on the involved immunological mechanism.

Individual Sensitization Pattern Recognition to Cow's Milk and Human Milk Differs for Various Clinical Manifestations of Milk Allergy

Cow’s milk allergy (CMA) belongs to one of the most common food allergies in early childhood affecting 2–3% of children under 3 years of age. However, approximately 1% of adults remain allergic to cow’s milk, often showing severe reactions even to traces of milk. In our study, we recruited patients with different clinical manifestations of CMA, including patients with anaphylaxis and less severe symptoms. We assessed the sensitization patterns and allergic responses of these subgroups through different immunological and cell-based methods. Sera of patients were investigated for IgE against whole cow’s milk and its single allergens by CAP- FEIA. In a newly developed in-house multiplex dot assay and a basophil activation test (BAT), cow’s milk allergens, in addition to human breast milk and single allergens from cow’s and human milk were analyzed for IgE recognition and severity of CMA in the included patients. Both the CAP-FEIA routine diagnostic and the multiplex dot test could differentiate CMA with severe from milder allergic reactions by means of the patients’ casein sensitization. The BAT, which mirrors the clinical response in vitro, confirmed that basophils from patients with severe reactions were more reactive to caseins in contrast to the basophils from more moderate CMA patients. By means of this improved component-resolved diagnosis of CMA, individual sensitization patterns could be assessed, also taking sensitization against human milk into consideration.

Crystal structure and epitope analysis of house dust mite allergen Der f 21

Group 21 and 5 allergens are homologous house dust mite proteins known as mid-tier allergens. To reveal the biological function of group 21 allergens and to understand better the allergenicity of the rDer f 21 allergen, we determined the 1.5 Å crystal structure of rDer f 21 allergen from Dermatophagoides farinae. The rDer f 21 protein consists of a three helical bundle, similar to available structures of group 21 and homologous group 5 allergens. The rDer f 21 dimer forms a hydrophobic binding pocket similar to the one in the Der p 5 allergen, which indicates that both of the homologous groups could share a similar function. By performing structure-guided mutagenesis, we mutated all 38 surface-exposed polar residues of the rDer f 21 allergen and carried out immuno-dot blot assays using 24 atopic sera. Six residues, K10, K26, K42, E43, K46, and K48, which are located in the region between the N-terminus and the loop 1 of rDer f 21 were identified as the major IgE epitopes of rDer f 21. Epitope mapping of all potential IgE epitopes on the surface of the rDer f 21 crystal structure revealed heterogeneity in the sIgE recognition of the allergen epitopes in atopic individuals. The higher the allergen-sIgE level of an individual, the higher the number of epitope residues that are found in the allergen. The results illustrate the clear correlation between the number of specific major epitope residues in an allergen and the sIgE level of the atopic population.

Hypoallergenic Proteins for the Treatment of Food Allergy

PURPOSE OF REVIEW

Food allergy is a growing health problem worldwide that impacts millions of individuals. Current treatment options are limited and strict dietary avoidance remains the standard of care. Immunotherapy using whole, native allergens is under active clinical investigation but harbors the risk of severe side effects including anaphylaxis. Newer food-specific therapies with hypoallergenic proteins may potentially offer safer treatment alternatives, and this review seeks to investigate the evidence supporting the use of these modalities.

RECENT FINDINGS

The utilization of different methods to alter allergen structure and IgE binding leads to reduced allergenicity and decreases the risk for systemic reactions, making the use of potential therapies including extensively heated egg/milk, peptide immunotherapy, recombinant allergen immunotherapy, and DNA vaccines safe and possibly efficacious forms of treatment in food allergy. However, for the majority of these treatment modalities, limited data currently exists looking at the safety and efficacy in human subjects with food allergy. This review provides a comprehensive overview of the current evidence examining the safety and efficacy of hypoallergenic proteins in the treatment of food allergies.

Der p 5 allergen from house dust mite: first epitope mapping of rabbit IgG blocking antibodies

Der p 5 is one of the important house dust mite allergens in Algeria; this allergen is frequently recognized by patients with allergic asthma. However, there is no information on its IgG-binding epitopes. In the present study, rabbits were immunized with recombinant Der p 5 allergen, and serum samples were obtained. Recognition of linear IgG epitopes of Der p 5 was determined using synthesized peptides derived from the allergen sequence. The results showed that serum from immunized rabbits recognized three linear epitopes from Der p 5 (28EDKKHDYQNEFDFLLMERIHEQIK43), (37IHEQIKKGELALFYLQEQ55) and (92LMQRKDLDIFEQYNLEMAKKS112). More interestingly, we observed that the 92L-S112 amino acid sequence is well recognized by both IgE and IgG antibodies. Der p 5 stimulates the synthesis of specific IgG antibodies which recognize common but also novel epitopes compared to IgE antibody binding. Indeed, the potential to induce IgG antibodies can be used to inhibit human IgE binding to allergens which may be part of the mechanism of action of specific immunotherapy.

Can alternative epitope mapping approaches increase the impact of B-cell epitopes in food allergy diagnostics?

In vitro allergy diagnostics are currently based on the detection of specific IgE binding on intact allergens or a mixture thereof. This approach has drawbacks as it may yield false‐negative and/or false‐positive results. Thus, we reviewed the impact of known B‐cell epitopes of food allergens to predict transience or persistence, tolerance or allergy and the severity of an allergic reaction and to examine new epitope mapping strategies meant to improve serum‐based allergy diagnostics. Recent epitope mapping approaches have been worthwhile in epitope identification and may increase the specificity of allergy diagnostics by using epitopes predominately recognized by allergic patients in some cases. However, these approaches did not lead to discrimination between clinically relevant and irrelevant epitopes so far, since the polyclonal serum IgE‐binding epitope spectrum seems to be too individual, independent of the disease status of the patients. New epitope mapping strategies are necessary to overcome these obstacles. The use of patient‐derived monoclonal antibodies instead of patient sera for functional characterization of clinically relevant and irrelevant epitope combinations, distinguished by their ability to induce degranulation, might be a promising approach to gain more insight into the allergic reaction and to improve serum‐based allergy diagnostics.

Apical-to-basolateral transepithelial transport of cow's milk caseins by intestinal Caco-2 cell monolayers: MS-based quantitation of cellularly degraded α- and β-casein fragments

Casein (CN) is the major milk protein to nourish infants but, in certain population, it causes cow's milk allergy, indicating the uptake of antigenic CN and their peptides through the intestinal epithelium. Using human intestinal Caco-2 cell monolayers, the apical-to-basal transepithelial transport of CN was investigated. Confocal microscopy using component-specific antibodies showed that αs1-CN antigens became detectable as punctate signals at the apical-side cytoplasm and reached to the cytoplasm at a tight-junction level within a few hours. Such intracellular CN signals were more remarkable than those of the other antigens, β-lactoglobulin and ovalbumin, colocalized in part with an early endosome marker protein (EEA1) and decreased in the presence of cytochalasin D or sodium azide and also at lowered temperature at 4°C. Liquid chromatography coupled with mass spectroscopy analysis of the protein fraction in the basal-side medium identified the αs1-CB fragment including the N-terminal region and the αs2-CN fragment containing the central part of polypeptide at 100-1,000 fmol per well levels. Moreover, β-CN C-terminal overlapping peptides were identified in the peptide fraction below 10 kDa of the basal medium. These results suggest that CNs are partially degraded by cellular proteases and/or peptidases and immunologically active CN fragments are transported to basal side of the cell monolayers.

Stability of allergens

For proteins to cause IgE-mediated allergic reactions, several common characteristics have to be defined, including small molecular size, solubility and stability to changing pH levels and enzymatic degradation. Nevertheless, these features are not unique for potent allergens, but are also observed in non-allergenic proteins. Due to the increasing awareness by regulatory authorities regarding the allergy pandemic, definition of characteristics unique to potent allergens would facilitate allergenicity assessment in the future. Despite major research efforts even to date the features unique for major allergens have not been elucidated so far. The route of allergen entry into the organism determines to a great extent these required characteristics. Especially orally ingested allergens are exposed to the harsh milieu of the gastrointestinal tract but might additionally be influenced by food processing. Depending on molecular properties such as disulphide bonds contributing to protein fold and formation of conformational IgE epitopes, posttranslational protein modification or protein food matrix interactions, enzymatic and thermal stability might differ between allergens. Moreover, also ligand binding influences structural stability. In the current review article, we aim at highlighting specific characteristics and molecular pattern contributing to a stabilized protein structure and overall allergenicity.

Proteomics: a tool to develop novel diagnostic methods and unravel molecular mechanisms of pediatric diseases

Proteomics is the study of the expression of changes and post-translational modifications (PTM) of proteins along a metabolic condition either normal or pathological. In the field of health, proteomics allows obtaining valuable data for treatment, diagnosis or pathophysiological mechanisms of different illnesses. To illustrate the aforementioned, we describe two projects currently being performed at the Instituto Nacional de Pediatría: The immuno-proteomic study of cow milk allergy and the Proteomic study of childhood cataract. Cow's milk proteins (CMP) are the first antigens to which infants are exposed and generate allergy in some of them. In Mexico, the incidence of CMP allergy has been estimated at 5-7%. Clinical manifestations include both gastrointestinal and extra-gastrointestinal symptoms, making its diagnosis extremely difficult. An inappropriate diagnosis affects the development and growth of children. The goals of the study are to identify the main immune-reactive CMP in Mexican pediatric population and to design more accurate diagnostic tools for this disease. Childhood cataract is a major ocular disease representing one of the main causes of blindness in infants; in developing countries, this disease promotes up to 27% of cases related to visual loss. From this group, it has been estimated that close to 60% of children do not survive beyond two years after vision lost. PTM have been pointed out as the main cause of protein precipitation at the crystalline and, consequently, clouding of this tissue. The study of childhood cataract represents an outstanding opportunity to identify the PTM associated to the cataract-genesis process.

Making the Most of In Vitro Tests to Diagnose Food Allergy

Various in vitro tests assess different aspects of the underlying immune mechanism of IgE-mediated food allergy. Some can be used for diagnostic purposes; specific IgE to allergen extracts is widely available; specific IgE to allergen components is used in most specialist centers, and the basophil activation test is becoming increasingly used clinically. IgE to allergen peptides, T-cell assays, allergen-specific/total IgE ratios, and allergen-specific IgG4/IgE ratios are currently reserved for research. Different factors can modulate the likelihood of IgE-mediated food allergy of a given allergy test result, namely, the patients' age, ethnicity, previous allergic reaction to the identified food, concomitant atopic conditions, and geographical location, and need to be taken into account when interpreting the allergy test results in the clinic. The importance of the specific food, the clinical resources available, and patient preferences are additional aspects that need to be considered when deciding whether an oral food challenge is required to reach an accurate diagnosis of IgE-mediated food allergy.

Contribution of Molecular Allergen Analysis in Diagnosis of Milk Allergy

PURPOSE OF REVIEW

We sought to describe the available evidence supporting the utilization of the molecular allergen analysis (MAA) for diagnosis and management of cow milk protein allergy (CMPA).

RECENT FINDINGS

Cow milk proteins are among the most common food allergens in IgE- and non-IgE-mediated food allergic disorders in children. Most individuals with CMPA are sensitized to both caseins and whey proteins. Caseins are more resistant to high temperatures compared to whey proteins. MAA is not superior to the conventional diagnostic tests based on the whole allergen extracts for diagnosis of CMPA. However, MAA can be useful in diagnosing tolerance to extensively heated milk proteins in baked foods. Children with CMPA and high levels of casein IgE are less likely to tolerate baked milk compared to children with low levels of casein IgE. Specific IgE-binding patterns to casein and betalactoglobulin peptides may predict the natural course of CMPA and differentiate subjects who are more likely to develop CMPA at a younger age versus those with a more persistent CMPA. Specific IgE-binding patterns to casein and beta-lactoglobulin peptides may also predict response to milk OITand identify patientsmost likely to benefit fromOIT.

Road map for the clinical application of the basophil activation test in food allergy

The diagnosis of IgE‐mediated food allergy based solely on the clinical history and the documentation of specific IgE to whole allergen extract or single allergens is often ambiguous, requiring oral food challenges (OFCs), with the attendant risk and inconvenience to the patient, to confirm the diagnosis of food allergy. This is a considerable proportion of patients assessed in allergy clinics. The basophil activation test (BAT) has emerged as having superior specificity and comparable sensitivity to diagnose food allergy, when compared with skin prick test and specific IgE. BAT, therefore, may reduce the number of OFC required for accurate diagnosis, particularly positive OFC. BAT can also be used to monitor resolution of food allergy and the clinical response to immunomodulatory treatments. Given the practicalities involved in the performance of BAT, we propose that it can be applied for selected cases where the history, skin prick test and/or specific IgE are not definitive for the diagnosis of food allergy. In the cases that the BAT is positive, food allergy is sufficiently confirmed without OFC; in the cases that BAT is negative or the patient has non‐responder basophils, OFC may still be indicated. However, broad clinical application of BAT demands further standardization of the laboratory procedure and of the flow cytometry data analyses, as well as clinical validation of BAT as a diagnostic test for multiple target allergens and confirmation of its feasibility and cost‐effectiveness in multiple settings.

Identification of cross-reactive B-cell epitopes between Bos d 9.0101(Bos Taurus) and Gly m 5.0101 (Glycine max) by epitope mapping MALDI-TOF MS

Exposure to cow's milk constitutes one of the most common causes of food allergy. In addition, exposure to soy proteins has become relevant in a restricted proportion of milk allergic pediatric patients treated with soy formulae as a dairy substitute, because of the cross-allergenicity described between soy and milk proteins. We have previously identified several cross-reactive allergens between milk and soy that may explain this intolerance. The purpose of the present work was to identify epitopes in the purified αS1-casein and the recombinant soy allergen Gly m 5.0101 (Gly m 5) using an α-casein-specific monoclonal antibody (1D5 mAb) through two different approaches for epitope mapping, to understand cross-reactivity between milk and soy. The 1D5 mAb was immobilized onto magnetic beads, incubated with the peptide mixture previously obtained by enzymatic digestion of the allergens, and the captured peptides were identified by MALDI-TOF MS analysis. On a second approach, the peptide mixture was resolved by RP-HPLC and immunodominant peptides were identified by dot blot with the mAb. Finally, recognized peptides were sequenced by MALDI-TOF MS. This novel MS based approach led us to identify and characterize four peptides on α-casein and three peptides on Gly m 5 with a common core motif. Information obtained from these cross-reactive epitopes allows us to gain valuable insight into the molecular mechanisms of cross-reactivity, to further develop new and more effective vaccines for food allergy.