Insight into the allergenicity of shrimp tropomyosin glycated by functional oligosaccharides containing advanced glycation end products

Intervention Efficacy of Slightly Processed Allergen/Meat in Oral Immunotherapy for Seafood Allergy: A Systematic Review, Meta-Analysis, and Meta-Regression Analysis in Mouse Models and Clinical Patients

Background: Seafood allergy is a significant global health concern that greatly impacts a patient's quality of life. The intervention efficacy of oral immunotherapy (OIT), an emerging intervention strategy, for seafood allergy remains controversial. This study aimed to perform a systematic review and meta-analysis to evaluate the efficacy of slightly processed allergen/meat from fish and crustacea in OIT, both in mouse models and clinical patients. Methods: A comprehensive literature search was performed in four mainstream databases and the EBSCOhost database to identify all relevant case-control and cohort studies. The aim was to elucidate the intervention efficacy, encompassing various processing methods and assessing the efficacy of multiple major allergens in OIT. Results: The meta-analysis included five case-control studies on crustacean allergens in mouse models and 11 cohort studies on meat from fish and crustacea in clinical patients for final quantitative assessments. In mouse models, crustacean allergen substantially decreased the anaphylactic score after OIT treatment (mean difference (MD) = -1.30, p < 0.01). Subgroup analyses with low-level heterogeneities provided more reliable results for crab species (MD = -0.63, p < 0.01, I2 = 0), arginine kinase allergen (MD = -0.83, p < 0.01, I2 = 0), and Maillard reaction processing method (MD = -0.65, p < 0.01, I2 = 29%), respectively. In clinical patients, the main meta-analysis showed that the slightly processed meat significantly increased the incidence rate of oral tolerance (OT, incidence rate ratio (IRR) = 2.90, p < 0.01). Subgroup analyses for fish meat (IRR = 2.79, p < 0.01) and a simple cooking treatment (IRR = 2.36, p = 0.01) also demonstrated a substantial increase in the incidence rate of OT. Sensitivity and meta-regression analyses successfully identified specific studies contributing to heterogeneity in mouse models and clinical patients, although these studies did not impact the overall significant pooled effects. Conclusions: This meta-analysis provides preliminary evidence for the high intervention efficacy of slightly processed allergen/meat from fish and crustacea in OIT, both in mouse models and clinical patients. The Maillard reaction and cooking processing methods may emerge as potentially effective approaches to treating allergen/meat in OIT for clinical patients, offering a promising and specific treatment strategy for seafood allergy. However, these findings should be interpreted cautiously, and further supporting evidence is necessary.

Investigation of the allergenicity alterations of shrimp tropomyosin as glycated by glucose and maltotriose containing advanced glycation end products

Tropomyosin (TM) is the major allergen in shrimp that is known to be the primary trigger for shrimp-induced food allergy. Our previous reports suggest that glycation could reduce the allergenicity of TM and the reduction of allergenicity is largely dependent on the sources of saccharides. This investigation aimed to investigate the glycation of TM by glucose and maltotriose as well as the effects of glycation on the allergenicity of TM. Compared to TM, the IgG-binding capacity and IgE-binding capacity of tropomyosin glycated by glucose (TM-G) was greatly reduced with a longer glycation time, the release of allergic mediators from RBL-2H3 mast cells was reduced in a time-dependent manner, and weaker allergic reactions were induced in BALB/c mice. Conversely, tropomyosin glycated by maltotriose (TM-MTS) exhibited a stronger allergenicity after 48 hours of glycation due to the generation of neoallergens that were derived from the advanced glycation end products (AGEs). In conclusion, glucose could be used to desensitize the shrimp TM-induced food allergy via glycation, which could significantly reduce the allergenicity and alleviate allergic symptoms. This work could provide a novel approach to reduce the allergenicity of shrimp tropomyosin and prevent the shrimp tropomyosin-induced food allergy.

Genomics of Shrimp Allergens and Beyond

Allergy to shellfishes, including mollusks and crustaceans, is a growing health concern worldwide. Crustacean shellfish is one of the "Big Eight" allergens designated by the U.S. Food and Drug Administration and is the major cause of food-induced anaphylaxis. Shrimp is one of the most consumed crustaceans triggering immunoglobulin E (IgE)-mediated allergic reactions. Over the past decades, the allergen repertoire of shrimp has been unveiled based on conventional immunodetection methods. With the availability of genomic data for penaeid shrimp and other technological advancements like transcriptomic approaches, new shrimp allergens have been identified and directed new insights into their expression levels, cross-reactivity, and functional impact. In this review paper, we summarize the current knowledge on shrimp allergens, as well as allergens from other crustaceans and mollusks. Specific emphasis is put on the genomic information of the shrimp allergens, their protein characteristics, and cross-reactivity among shrimp and other organisms.

A comprehensive review on glycation and its potential application to reduce food allergenicity

Food allergens are a major concern for individuals who are susceptible to food allergies and may experience various health issues due to allergens in their food. Most allergenic foods are subjected to heat treatment before being consumed. However, thermal processing and prolonged storage can cause glycation reactions to occur in food. The glycation reaction is a common processing method requiring no special chemicals or equipment. It may affect the allergenicity of proteins by altering the structure of the epitope, revealing hidden epitopes, concealing linear epitopes, or creating new ones. Changes in food allergenicity following glycation processing depend on several factors, including the allergen's characteristics, processing parameters, and matrix, and are therefore hard to predict. This review examines how glycation reactions affect the allergenicity of different allergen groups in allergenic foods.

Insights into the Mechanism Underlying the Influence of Glycation with Different Saccharides and Temperatures on the IgG/IgE Binding Ability, Immunodetection, In Vitro Digestibility of Shrimp (Litopenaeus vannamei) Tropomyosin

Tropomyosin (TM) is a heat-stable protein that plays a crucial role as a major pan-allergen in crustacean shellfish. Despite the high thermal stability of the TM structure, its IgG/IgE binding ability, immunodetection, and in vitro digestibility can be negatively influenced by glycation during food processing, and the underlying mechanism remains unclear. In this study, TM was subjected to glycosylation using various sugars and temperatures. The resulting effects on IgG/IgE-binding capacity, immunodetection, and in vitro digestibility were analyzed, meanwhile, the structural alterations and modifications using spectroscopic and LC-MS/MS analysis were determined. Obtained results suggested that the IgG/IgE binding capacity of glycosylated TM, immunodetection recovery, and in vitro digestibility were significantly reduced depending on the degree of glycosylation, with the greatest reduction occurring in Rib-TM. These changes may be attributable to structural alterations and modifications that occur during glycosylation processing, which could mask or shield antigenic epitopes of TM (E3: 61-81, E5b: 142-162, and E5c: 157-183), subsequently reducing the immunodetection recognition and digestive enzyme degradation. Overall, these findings shed light on the detrimental impact of glycation on TMs potential allergenicity and digestibility immunodetection and provide insights into the structural changes and modifications induced by thermal processing.

Application of Molecular Transformer approach for predicting the potential reactions to generate advanced glycation end products in infant formula

Advanced glycation end products (AGEs) are associated with the occurrence of human chronic diseases, and exist commonly in thermally processed foods, such as infant formula. Existing research mainly focuses on the discrete simulation system, which is time-consuming and challenging, but accumulates of a large amount of valuable data. This study aimed to propose a specific Molecular Transformer-based model trained on the data curated from literature to predict the chemical reaction of AGEs, and apply it to infant formula to observe which new reactions could generate AGEs. The model achieved top-3 accuracy of 76.0% on the total dataset. Based on the model prediction results, five reactions were selected for experimental verification, and four of them were consistent with the model prediction results. This prospective study might potentially revolutionize the discovery of AGEs reactions and provide theoretical guidelines for designing a safer infant formula.

Assessment of the effect of glycation on the allergenicity of sesame proteins

Sesame allergy is a growing concern worldwide. In this study, sesame proteins was glycated with glucose, galactose, lactose and sucrose respectively, and the allergenicity of different glycated sesame proteins were assessed by a comprehensive strategy, including simulated gastrointestinal digestion in vitro, a BALB/c mice model, a rat basophilic leukemia (RBL)-2H3 cell degranulation model and a serological experiment. Firstly, simulated gastrointestinal digestion in vitro showed that glycated sesame proteins were more easily to digest than raw sesame. Subsequently, the allergenicity of sesame proteins was assessed in vivo by detecting the allergic indexes of mice, and results showed that the levels of total immunoglobulin E (IgE) and histamine were reduced in glycated sesame proteins treated mice. Meanwhile, the Th2 cytokines (IL-4, IL-5, and IL-13) were downregulated significantly, demonstrating that sesame allergy was relieved in glycated sesame treated mice. Thirdly, the RBL-2H3 cell degranulation model results showed that the release of β-hexosaminidase and histamine were decreased to different degrees in glycated sesame proteins treated groups. Notably, the monosaccharide glycated sesame proteins exhibited lower allergenicity both in vivo and in vitro. Furthermore, the study also analyzed the structure alteration of sesame proteins, and the results showed that the secondary structure of glycated sesame proteins were changed (the content of α-helix and β-sheet were reduced), and the tertiary structure of sesame proteins after glycation modification was also changed (microenvironment around aromatic amino acids was altered). Besides, the surface hydrophobicity of glycated sesame proteins was also reduced except sucrose glycated sesame proteins. In conclusion, this study demonstrated that glycation reduced the allergenicity of sesame proteins effectively, especially glycation with monosaccharides, and the allergenicity reduction might be related to structural changes. The results will provide a new reference for developing hypoallergenic sesame products.

Effects of Allergen-Specific and Non-Specific AGEs on the Allergenicity of Ovalbumin in a Mouse Model of Food Allergy

SCOPE

Epidemiologic studies suggest a link between the incidence of food allergy and the consumption of dietary advanced glycation end-products (AGEs). However, the pathogenic role of dietary AGEs in food allergy is largely unknown. This study aims to investigate the effect of allergen-specific and non-specific AGEs on the allergenic manifestation of ovalbumin (OVA), a typical food allergen in vivo.

METHODS AND RESULTS

OVA is glycated by methylglyoxal to prepare allergen-specific AGEs (i.e., OVA-AGE), and a standard AIN-93G diet is heated to obtain allergen-non-specific AGEs. A BALB/c mouse model orally sensitizes to OVA with different forms of AGEs is established and the outcomes are measured as clinical signs, specific antibodies, type-2/type-2 cytokines, immune cell subpopulations, intestinal barrier function, and gut microbiota (GM) composition. The OVA-AGE which has a lower immunoglobulin E (IgE)-binding level in vitro does not reduce the allergenicity of OVA but promotes a stronger T helper 2 cells (Th2)-response than native OVA in vivo. Both forms of AGEs up-regulate the expression of splenic RAGE and aggravate the destruction of gut barrier and GM dysbiosis, especially when exposes to non-relevant AGEs.

CONCLUSION

This study highlights the role of dietary AGEs in food allergy and helps to understand the biological consequences of immune-toxic compounds in modern diet.

Comparative Analysis of Glycosylation Affecting Sensitization by Regulating the Cross-Reactivity of Parvalbumins in Turbot (Scophthalmus maximus), Conger Eel (Conger myriaster) and Sea Bass (Micropterus salmoides)

Parvalbumin (PV) is the most common allergen in fish. Some patients with fish allergy are allergic to only one species of fish but are tolerant to others; however, the underlying mechanism has not been identified. This study showed that three types of glycated fishes' PV showed a similar decrease in immunoglobulin E (IgE) binding. Glycosylation could improve the simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) digestion resistance of fishes' PV. We also discovered that the cross-reactivity between eel and turbot was weaker than that of bass; glycosylation can reduce cross-reactivity between eel/bass and turbot by downregulating Th2 cytokines and upregulating Th1 cytokines as well as downregulating the expression of G-T PV, G-E PV, G-B PV of IL-4 (94.31 ± 3.16, 73.26 ± 0.91, 94.95 ± 3.03 ng/mL), and IL-13 (38.84 ± 0.75, 33.77 ± 0.71, 36.51 ± 0.50 ng/mL) and upregulating the expression of IFN-γ (318.01 ± 3.46, 387.15 ± 3.30, 318.01 ± 4.21 ng/mL) compared with T PV, respectively. This study showed that glycosylation affected sensitization by regulating the cross-reactivity of parvalbumins.

Glycosylation reduces the allergenicity of turbot (Scophthalmus maximus) parvalbumin by regulating digestibility, cellular mediators release and Th1/Th2 immunobalance

With turbot being increasingly consumed, turbot parvalbumin (TPV) allergy has become a pressing problem requiring immediate resolution. Glycosylation treatment not only resulted in cross-link formation but also caused changes in the simulated gastric fluid and simulated intestinal fluid digestion stability of TPV. In addition, KU812 experimentation revealed lower levels of β-hexosaminidase, histamine, tryptase, interleukin 4 (IL-4)/IL-13 in glycated protein-treated mice compared with native PV-treated ones. Glycated TPV exhibited a weaker allergic reaction compared with native TPV. Systemic anaphylaxis resulted in mild anaphylactic responses and reduced temperature, along with significantly increased levels of immunoglobulin E and histamine. Furthermore, glycosylation treatment reduced the release of cellular mediators and cytokines (IL-4/IL-13). Glycation to T-PV decreased allergic responses by downregulating Th2 cytokines, regulated the Th1/Th2 balance and effectively reduce the allergenicity and sensitisation ability of T-PV.

Isolation and allergenicity evaluation of glycated α-lactalbumin digestive products and identification of allergenic peptides

This study aimed to isolate and evaluate the allergenicity of glycated α-lactalbumin (ALA) digestive products and identify its allergenic peptides. The digestive products of native-, alone glycated- and ultrasound-assisted glycated ALA (ALA-D, ALA-gal-D, 100ALA-gal-D) were isolated into three fractions (F1, F2 and F3). High-resolution mass spectrometry showed that the digestion-resistant peptides of F2 and F3 mainly distributed in amino acid sequence (AA) 25-31, AA32-53, AA40-53, AA54-60, AA80-90, AA94-104. The allergenicity of the three fractions of glycated ALA was lower than that in ALA-D, indicating glycation of ALA could indeed reduce its allergenicity after digestion. Furthermore, most fractions isolated from high glycation-degree ALA had the lowest allergenicity. The IgG/IgE binding abilities of synthesized peptides indicated that AA94-104 firstly identified by us embodied the strongest allergenicity and might be the potential allergenic peptide. This will provide a theory for preparing hypoallergenic products based on the identified allergenic peptides.

Myofibrillar Protein Interacting with Trehalose Elevated the Quality of Frozen Meat

This work studied the interactions between trehalose/chitooligosaccharide (COS) and myofibrillar protein (MP), and the effect of such interactions on the quality of meat after freezing was also evaluated. Fourier transform infrared spectroscopy showed that both trehalose and COS could enhance the content of hydrogen bonds of MP. Zeta potential measurement displayed trehalose/COS reduced the absolute value of the surface potential of MP. The results of Raman spectroscopy suggested that the hydrophobic residues of MP were more exposed after treatment with trehalose/COS. Thus, trehalose and COS could both interact with MP through non-covalent bonds. Subsequently, the evaluation of the effect of trehalose and COS on the physicochemical properties of frozen meat was conducted. Results showed that both trehalose and COS significantly reduced thawing loss of frozen meat, and sensory evaluation showed that trehalose had a better performance from the perspective of smell, texture, and overall consumer acceptance. In conclusion, trehalose/COS interacting with MP can reduce meat thawing loss, which might provide technical guidance in the quality control of frozen meat.

Maillard Reaction Induced Changes in Allergenicity of Food

Food allergy is increasing in prevalence, posing aheavier social and financial burden. At present, there is still no widely accepted treatment for it. Methods to reduce or eliminate the allergenicity of trigger foods are urgently needed. Technological processing contributes to producing some hypoallergenic foods. Among the processing methods, the Maillard reaction (MR) is popular because neither special chemical materials nor sophisticated equipment is needed. MR may affect the allergenicity of proteins by disrupting the conformational epitope, disclosing the hidden epitope, masking the linear epitope, and/or forming a new epitope. Changes in the allergenicity of foods after processing are affected by various factors, such as the characteristics of the allergen, the processing parameters, and the processing matrix, and they are therefore variable and difficult to predict. This paper reviews the effects of MR on the allergenicity of each allergen group from common allergenic foods.

Receptor Mediated Effects of Advanced Glycation End Products (AGEs) on Innate and Adaptative Immunity: Relevance for Food Allergy

As of late, evidence has been emerging that the Maillard reaction (MR, also referred to as glycation) affects the structure and function of food proteins. MR induces the conformational and chemical modification of food proteins, not only on the level of IgG/IgE recognition, but also by increasing the interaction and recognition of these modified proteins by antigen-presenting cells (APCs). This affects their biological properties, including digestibility, bioavailability, immunogenicity, and ultimately their allergenicity. APCs possess various receptors that recognize glycation structures, which include receptor for advanced glycation end products (RAGE), scavenger receptors (SRs), galectin-3 and CD36. Through these receptors, glycation structures may influence the recognition, uptake and antigen-processing of food allergens by dendritic cells (DCs) and monocytes. This may lead to enhanced cytokine production and maturation of DCs, and may also induce adaptive immune responses to the antigens/allergens as a result of antigen uptake, processing and presentation to T cells. Here, we aim to review the current literature on the immunogenicity of AGEs originating from food (exogenous or dietary AGEs) in relation to AGEs that are formed within the body (endogenous AGEs), their interactions with receptors present on immune cells, and their effects on the activation of the innate as well as the adaptive immune system. Finally, we review the clinical relevance of AGEs in food allergies.

Reducing the Allergenicity of Shrimp Tropomyosin and Allergy Desensitization Based on Glycation Modification

Shrimp is a major allergic food that could trigger severe food allergy, with the most significant and potent allergen of shrimp referred to as tropomyosin (TM). Glycation modification (Maillard reaction) could reportedly weaken the allergenicity of TM and generate hypoallergenic TM, while up to now, there is still a lack of investigations on the hypoallergenic glycated tropomyosin (GTM) as a candidate immunotherapy for desensitizing the shrimp TM-induced allergy. This study analyzed the effects of glycation modification on decreasing the allergenicity of TM and generated hypoallergenic GTM and how GTM absorbed to the Al(OH)₃ function as a candidate immunotherapy for desensitizing allergy. As the results, in comparison to TM, the saccharides of smaller molecular sizes could lead to more advanced glycation end products in GTMs than saccharides of greater molecular sizes, and TM glycated by saccharides of different molecular sizes (glucose, maltose, maltotriose, maltopentaose, and maltoheptaose) exhibited lower allergenicity as a hypoallergen upon activating the allergic reactions of the mast cell and mouse model, while TM glycated by maltose had insignificant allergenicity changes upon activating the allergic reactions of the mast cell and mouse model. In addition, the hypoallergenic GTM + Al(OH)₃ was efficient as a candidate immunotherapy; this work intended to offer preclinical data to promote GTM + Al(OH)₃ as a candidate allergen-specific immunotherapy for desensitizing the allergy reactions for patients allergic to shrimp food.

Effects of deglycosylation and the Maillard reaction on conformation and allergenicity of the egg ovomucoid

Ovomucoid (OVM), known as the major allergen in egg white, has gained increasing concerns in industrialized countries. Here, we found the deglycosylation and Maillard reaction with galactooligosaccharide (GOS) and fructooligosaccharide (FOS) can induce conformational transformation of OVM from other structures (β-turn, strang, and random coils) to α-helix. We also introduced an approach to reduce the allergenicity of Gallus domesticus OVM by Maillard reaction with GOS and FOS. However, the OVM glycated by mannosan (MOS) and deglycosylated OVM exhibited higher allergenicity than native OVM. Therefore, GOS and FOS, especially GOS, could be applied in the reduction of the potential allergenicity of OVM through glycation. Furthermore, these findings may provide new insights into the development of hypoallergenic egg products. PRACTICAL APPLICATION: In this study, the allergenicity and conformation of OVM treated with deglycosylation and glycation (GOS, FOS, and MOS) were investigated. The results would provide a better understanding of the effects of deglycosylation and Maillard reaction with different reducing sugars on the molecular characteristics of OVM and further provide new insights into the development of hypoallergenic egg products.

Mechanism of the Reduced IgG/IgE Binding Abilities of Glycated β-Lactoglobulin and Its Digests through High-Resolution Mass Spectrometry

Glycation between proteins and reducing sugars is the common chemical modification in food protein, and many studies have focused on the allergenicity of the glycated protein. However, a systemic study on the allergenicity change of its digests is lacking. In this work, we explored the change rule of the digestibility and allergenicity of glycated β-Lg during in vitro gastrointestinal digestion and interpreted the mechanism using high-resolution mass spectrometry. Glycation with arabinose increased the resistance of β-Lg to digestive enzyme, with a low hydrolysis value. Indirect competitive ELISA showed that the IgG/IgE binding rates of β-Lg were reduced after glycation and further reduced after digestion, in comparison with the digests of unglycated β-Lg. There are two reasons for this phenomenon. On the one hand, 11 glycated sites were determined in the lowest allergenicity arabinose-β-Lg conjugation (Ara-β-Lg), which was distributed in the IgG and IgE linear allergic epitopes of β-Lg. On the other hand, glycation masking linear allergenic epitopes had a more significant effect on reducing allergenicity in comparison to digestive enzyme hydrolysis. These results indicated that the allergenicity of Ara-β-Lg in the human body might be lower than that of unglycated β-Lg.

Investigation of glycated shrimp tropomyosin as a hypoallergen for potential immunotherapy

Tropomyosin (TM) is the most important allergen in shrimps that could cause food allergy. Glycation is reported to be effective in reducing TM allergenicity and produce hypoallergen; however, up to now, there are very few reports on the potential of hypoallergenic glycated TM (GTM) as allergen immunotherapy for shrimp TM-induced food allergy. This study investigated the glycation of TM-produced hypoallergen and the immunotherapeutic efficacy of GTM + Al(OH)₃ as potential allergen immunotherapy. Compared to TM, the TM glycated by glucose (TM-G), maltotriose (TM-MTS), maltopentaose (TM-MPS) and maltoheptaose (TM-MHS) had weaker allergy activation on mast cells and mouse model as a hypoallergen. However, the TM glycated by maltose (TM-M) insignificantly affected the allergenicity. In addition, the GTM absorbed into Al(OH)₃ could be efficacious as potential allergen immunotherapy, particularly for the TM glycated by the saccharides having larger molecular size (e.g., TM-MHS), which could provide preclinical data to develop GTM + Al(OH)₃ as a candidate immunotherapy for shrimp allergic patients.

Effects of the Maillard reaction on the epitopes and immunoreactivity of tropomyosin, a major allergen in Chlamys nobilis

Scallop (Chlamys nobilis) causes an IgE-mediated food allergy; however, studies of the allergens in its musculus are not sufficiently comprehensive. In this context, the target protein was purified from scallops and confirmed to be the major allergen tropomyosin (TM) using proteomic technology and serological testing. Subsequently, seven potential IgE epitopes of TM were obtained using phage display technology with IgE enrichment from the serum of scallop-sensitized patients and identified via inhibition enzyme-linked immunosorbent assays. A method for the Maillard reaction of TM and xylose was established, and Maillard-reacted TM (MR-TM) showed significantly decreased immunobinding activity and CD63 and CD203c expression in basophils compared with TM. Furthermore, shotgun proteomics analysis showed that eleven specific amino acids (K12, R15, K28, K76, R125, R127, K128, R133, R140, K146, and K189) of the six IgE epitopes of TM were modified after the Maillard reaction. Overall, the immunoactivity of MR-TM was reduced, which provides a theoretical reference for the development of hypoallergenic foods.