Allergenicity suppression of tropomyosin from Exopalaemon modestus by glycation with saccharides of different molecular sizes

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 Ball-Milling Treatment Combined with Glycosylation on the Structure and Functional Properties of Litopenaeus vannamei Protein

Litopenaeus vannamei protein (LVP) is a high-quality protein. However, its functional properties do not fully meet the needs of food processing. In this study, LVP-xylose conjugates were prepared by conventional wet heat method (GLVP) and ball-milling-assisted wet heat method (GBLVP), respectively. The changes in structure and functional properties of the glycosylated LVP were explored. The findings revealed that ball-milling pretreatment increased the grafting degree to 35.21%. GBLVP had a sparser surface structure and lower particle size than GLVP. FTIR spectra showed that xylose was grafted onto LVP successfully and GBLVP had the lowest α-helix content. Compared with GLVP, GBLVP had a decrease in intrinsic fluorescence intensity and surface hydrophobicity, and an increase in UV absorption intensity. Moreover, GBLVP had higher foaming capacity, solubility and water-holding capacity, and lower allergenicity than GLVP. However, ball-milling pretreatment had a negative impact on the vitro digestibility and oil-holding capacity of GBLVP. In conclusion, ball-milling-assisted treatment of glycosylation could effectively improve the functional properties of LVP, benefiting the broader application of LVP in the food industry.

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.

Ultrasound-assisted glycation and the allergenicity of α-lactalbumin

BACKGROUND

Ultrasound-assisted glycation is a promising method for decreasing the allergenicity of α-lactalbumin (ALA). However, there is a lack of in vivo studies on the allergenicity of ultrasound-assisted glycated ALA. In this study, the effects of the ultrasound-assisted glycation of ALA on the allergenicity and intestinal microflora were characterized using a BALB/c mouse model.

RESULTS

Increased immunoglobulin -G/ immunoglobulin-E (IgG/IgE) and interleukin-4/6 (IL-4/6) secretions, and reduced interferon-γ (IFN-γ) secretions were found in the serum of ALA sensitized and challenged, mice in comparison with a control group. However, there was no significant difference between the mice fed with ultrasound-assisted glycated ALA and the control group. Mice that were sensitized and challenged with ALA showed disrupted intestinal microflora, manifesting in significantly decreased Firmicutes and significantly increased Proteobacteria. It was found that 100ALA-gal could maintain the intestinal microflora of mice in a normal state. Pearson's rank correlation showed that Proteobacteria and Spirochaetota were correlated positively with the IL-4/IL-6 level and were correlated negatively with the expression of IFN-γ. Proteobacteria were also significantly positively correlated with IL-6 and negatively correlated with IFN-γ (P < 0.05).

CONCLUSION

These results suggested that ultrasound-assisted glycation on ALA can maintain the intestinal microflora in a normal state thus balancing the proportion of Th1/Th2 to decrease allergic reaction. © 2022 Society of Chemical Industry.

Comprehensive Analysis of the Structure and Allergenicity Changes of Seafood Allergens Induced by Non-Thermal Processing: A Review

Seafood allergy, mainly induced by fish, shrimp, crab, and shellfish, is a food safety problem worldwide. The non-thermal processing technology provides a new method in reducing seafood allergenicity. Based on the structural and antigenic properties of allergenic proteins, this review introduces current methods for a comprehensive analysis of the allergenicity changes of seafood allergens induced by non-thermal processing. The IgE-binding capacities/immunoreactivity of seafood allergens are reduced by the loss of conformation during non-thermal processing. Concretely, the destruction of native structure includes degradation, aggregation, uncoiling, unfolding, folding, and exposure, leading to masking of the epitopes. Moreover, most studies rely on IgE-mediated assays to evaluate the allergenic potential of seafood protein. This is not convincing enough to assess the effect of novel food processing techniques. Thus, further studies must be conducted with functional assays, in vivo assays, animal trials, simulated digestion, and intestinal microflora to strengthen the evidence. It also enables us to better identify the effects of non-thermal processing treatment, which would help further analyze its mechanism.

Simulated in vitro digestion of α-lactalbumin modified by phosphorylation: Detection of digestive products and allergenicity

The effects of phosphorylation on the allergenicity of bovine α-lactalbumin (BLA) and digestive products were studied in vitro digestion. Two components with different molecular weight and conformation were obtained from natural and phosphorylated BLA. In vivo and in vitro assessment of allergenicity showed that phosphorylation prior to digestion significantly decreased the IgE/IgG binding capacity and allergic response in KU812 cells, and reduced the levels of IgG, IgE, IL-4 and histamine, with an increase in IFN-γ levels in mouse serum, depending on the changes in BLA structures, producing numerous small peptides. There were four phosphorylated sites (S22, T29, S47 and S70) in the high molecular weight components of phosphorylated BLA after digestion. These phosphorylated sites could mask the linear epitopes of digestive products, resulting in reduced allergic activity. Phosphorylation prior to digestion of dairy products can reduce the risk of anaphylaxis in patients with milk allergy to some extent.

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.

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.

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.

Cloning, expression and comparison of the properties of Scy p 9, a Scylla paramamosain allergen

This study investigated the properties of Scy p 9 in mud crab (Scylla paramamosain). The gene sequence of filamin C obtained from crabs, which was denoted as Scy p 9, contains a 2544 bp open reading frame and encodes 848 amino acid residues. Recombinant Scy p 9 (rScy p 9) is expressed in Escherichia coli, which exhibits tertiary structure changes, and the IgE binding activity of rScy p 9 is higher than that of native Scy p 9 (nScy p 9). Moreover, this study explored the possibility of the presence and cross-reactivity of filamin C in 8 shellfish. IgE-specific binding to nScy p 9 and rScy p 9 in patients allergic to shellfish revealed that rScy p 9 was more sensitive than nScy p 9. The gene sequence of filamin C fills in the blank in shellfish. This study contributes to the understanding of the properties of Scy p 9, and the results indicate that rScy p 9 can be used as a candidate for component-resolved diagnosis in shellfish.

Glycation by saccharides of different molecular sizes affected the allergenicity of shrimp tropomyosin via epitope loss and the generation of advanced glycation end products

Tropomyosin is the most potent allergen of shrimp that can cause severe food allergy. However, to date, an effective approach to eliminate this allergenicity is still lacking. Glycation is a promising approach that can reduce the allergenicity of shrimp tropomyosin by destroying the epitopes; however, advanced glycation end products (AGEs) are also generated during glycation, which can function as neoallergens to strengthen the allergenicity; therefore, it is hard to tell how the glycation of an allergen with different saccharides affects the allergenicity via epitope loss and neoallergen generation. This study was aimed at the elucidation of how the glycation of tropomyosin (TM) with saccharides of different molecular sizes (glucose, maltose, and maltotriose) affected the allergenicity through epitope loss and the generation of neoallergns that belonged to advanced glycation end products (AGEs). Saccharides of higher molecular sizes (maltotriose) could lead to higher glycated TM than saccharides of smaller molecular sizes (glucose and maltose). Compared with TM, the TM glycated by glucose (TM-G) and maltotriose (TM-MTS) had lower allergenicity and contributed to weaker mouse allergy symptoms; on the other hand, the TM glycated by maltose (TM-M) had no significant impact on the allergenicity due to the generation of AGE-related neoallergens, which might offset the glycation-induced epitope loss. The glycation of TM by maltotriose led to lower generation of AGE neoallergens (e.g. CML) than that in the cases of glucose and maltose; therefore, maltotriose could be applied to desensitize TM-induced food allergy through glycation, and this could be a potential immunotherapy for shrimp allergy patients.

IgE-binding epitope mapping of tropomyosin allergen (Exo m 1) from Exopalaemon modestus, the freshwater Siberian prawn

Exopalaemon modestus (EM) is a shrimp delicacy that could cause food allergy, the major allergen of EM is Exo m 1. The amino acid (AA) sequence, IgE-binding epitopes and allergenic peptides in gastrointestinal (GI) digests of Exo m 1, and their effects on basophil function were investigated. Exo m 1 has an AA-sequence of high similarity with other shrimp tropomyosins, while not 100% matching. The IgE-binding epitopes of Exo m 1 are epitope 1 (43-59, VHNLQKRMQQLENDLDS), epitope 2 (85-105, VAALNRRIQLLEEDLERSEER), epitope 3 (131-164, ENRSLSDEERMDALENQLKEARFLAEEADRKYDE), epitope 4 (187-201, ESKIVELEEELRVVG) and epitope 5 (243-280, ERSVQKLQKEVDRLEDELVNEKEKYKSITDELDQTFSE). Among the thirty-three peptides of Exo m 1 identified in GI digests, two were highly recognized by IgE, twenty-four moderately or weakly bound IgE, and seven had no IgE-reactivities. These IgE-binding epitopes and GI digestion induced-allergenic peptides could activate basophil degranulation, and CD63 and CD203c expression, they could be potential peptide-based immunotherapy for shrimp allergic individuals.