IgG Binding Capacity Research Articles

Molecular and Immunological Characterization of Troponin C: An Allergen from Scylla paramamosain.

Scylla paramamosain, a crustacean of substantial importance, is a frequent trigger of food allergies. This study examined the molecular and immunological properties of troponin C from S. paramamosain (Scy p TnC) as an allergen. The findings indicated that thermal stability of Scy p TnC comprised 150 amino acids and facilitated the induction of CD63/CD203c in basophils from crab allergy patients. Furthermore, treatment of Scy p TnC with chemical denaturants caused structural degradation, which resulted in diminished IgG binding capacity. Subsequently, 6 linear epitopes and 4 conformational epitope regions of TnC were predicted, with epitopes at the C-terminal being conserved throughout 9 discovered TnCs. Concurrently, mice sensitized with Scy p TnC exhibited markedly increased levels of IgE and IL-4 release, provoking a Th2 immune response. The results reveal crab allergens and enhance existing knowledge regarding allergenic components in crabs, thereby facilitating the advancement of molecular diagnostics and targeted therapeutic strategies.

Restructuring Biologically Assembled Binding Protein-Biopolymer Conjugates toward Advanced Materials.

Bacterial cell factories have been successfully engineered to efficiently assemble spherical polyhydroxybutyrate inclusions coated with functional proteins of interest. In these submicrometer-sized core-shell assemblies, proteins are bioconjugated to the polymer core, enabling bioengineering for uses as bioseparation resins, enzyme carriers, diagnostic reagents, and particulate vaccines. Here, we explore whether these functional protein-polymer assemblies could be restructured via dissolution and subsequent precipitation while retaining the functionality of the conjugated protein. Polymer core-protein shell assemblies were completely dissolved in chloroform. Subsequent reconstitution into different formats such as hollow spheres, fibers, and films was achieved. Different proteins such as the green fluorescent protein or IgG binding domains GB1 or Z derived from protein G or protein A, respectively, were implemented to monitor the retention of protein function upon generation of reformatted materials. Materials were characterized and the retention of protein functionality was studied by assessing the fluorescence or IgG binding capacity. Since the Z domain protein functionality is retained, it suggests that protein refolding properties are critical parameters for restructuring these functional materials. This study shows that bioengineered biologically assembled protein-coated biopolymer particles can be completely dissolved and reformed into fibers, films, and hollow spheres retaining the original protein function.

Dielectric barrier discharge cold plasma alleviated the immunoreactivity of egg white proteins with improved digestibility and functional properties

With the increasing number of children allergic to egg worldwide, there is an urgent need to develop strategies for effectively utilizing egg protein. As a novel food processing that can effectively reduce allergenicity and enhance protein quality and functional properties, cold plasma (CP) is gaining attention. The study investigated the impacts of the dielectric barrier discharge CP on the immunoreactivity, in vitro digestibility, functional properties, and structural changes of egg white protein (EWP). The results showed that the EWP treated with CP for 30 min had a significant decrease in immunoglobulin (IgG)-binding capacity by approximately 20% and improved in vitro digestibility. Further studies demonstrated that the decrease in the IgG-binding capacity of EWP correlated well with the alterations in the secondary and tertiary structures. The content of α-helix was decreased by 6.5% and the surface hydrophobicity increased by 2.5 folds after the 30-min treatment, compared with the untreated samples. The oxidation of peptide amino groups induces structural changes, accompanied by the oxidation of amino acid residues. This phenomenon has been validated through surface hydrophobicity and multispectral analysis. Additionally, CP also improved the foaming and emulsifying capacity of EWP by 140% and 8.03%, respectively. These findings suggest that CP treatment could be served as a potential technology to reduce the immunoreactivity, and improve the in vitro digestibility and functionality of EWP.

Modulating allergenicity of prawn tropomyosin (penaeus chinensis) via pulsed electric field-induced conformational changes

The effect of electric field intensities (EFIs, 5–20 kV/cm) and treatment times (0.5–2 h) on allergenicity and spatial conformation of prawn tropomyosin was evaluated. The results demonstrated that the IgG and IgE binding capacity of tropomyosin maximally increased by 24.34 % and 29.16 % respectively, followed by a subsequent decrease after 20 kV/cm treatment for 1 h. Interestingly, 5–10 kV/cm treatments significantly decreased the α-helix content (P < 0.05) and fluorescence intensity, while 20 kV/cm treatment promoted extensive spiralization, resulting in a tightly packed structure. The increased flexibility further exposed the hydrolysis sites and strengthened the gastrointestinal digestibility of tropomyosin. Additionally, molecular dynamic simulation indicated that extended EFIs increased structural flexibility and depolymerized the tropomyosin dimers through destroying intermolecular hydrogen bonds (formed within arginine and glutamate), which allowed tropomyosin to be easily recognized by IgG/IgE. Whereas, decrease of solvent-accessibility surface area (SASA), hydrophobic surface area induced conformation folded and caused epitopes masked.

Characterization of high intensity ultrasound on structure, digestibility, and IgG binding capacity of Pacific oyster ( Crassostrea gigas) tropomyosin

Characterization of high intensity ultrasound on structure, digestibility, and IgG binding capacity of Pacific oyster ( <em>Crassostrea gigas</em>) tropomyosin

A comparison of the physicochemical properties, allergenicity, and stability of recombinant β-lactoglobulin: Development of standard bovine milk allergens

Bovine milk is one of the eight major allergenic foods identified by WHO/FAO, and β-lactoglobulin (BLG) is the primary allergen. Allergen standardization is very important for the diagnosis of milk allergy, and recombinant protein preparation is a promising method. In this study, BLG with high soluble expression was prepared by a method based on Escherichia coli. To verify the feasibility of recombinant BLG, the difference in physicochemical properties, allergenicity, and stability were investigated. Recombinant and natural BLG both had a size of approximately 230 nm with a zeta potential of −50 mV, indicating that they share the similar solubility and colloidal properties. Additionally, allergic mice model results confirmed that recombinant BLG showed comparable ability in stimulating antibody production, Th2 cytokine release, and cellular immunity compared with natural BLG. Then, the thermal stability of BLG was studied using spectrum analysis within the range of 25–85 °C. Recombinant BLG showed satisfactory thermal stability, the concentration, protein structure and IgG binding capacity changed obviously until temperature reached at 55 °C, although natural BLG is more heat resistant. After 28 days storage at 4 °C in the form of lyophilized powder, there was no significant change in the content of recombinant and natural BLG. In summary, the physicochemical properties, allergenicity, and stability of recombinant BLG were comparable to those of natural BLG. This study provides theoretical reference for the development of standard bovine allergen, and it is expected that recombinant allergen can be used in the research and diagnosis of bovine milk allergy.

Effects of the covalent conjugation between caffeic acid and peanut allergen protein Ara h1 on the antigenicity and structure of Ara h1.

Ara h1 was the highest content of peanut allergen protein, identified as a biomarker of peanut allergen. In this study, Ara h1 was covalently complexed with caffeic acid (CA) to research the effects of covalent conjugation on the antigenicity and protein structural properties of Ara h1. After the covalent complexing of Ara h1 and CA, the IgG-binding capacity of Ara h1 was reduced compared with that of control Ara h1. Moreover, the structure of Ara h1 changed from ordered to disordered, the number of intermolecular hydrogen bonds decreased, and some hydrophobic groups were exposed or hydrophobic peptides were released. The carboxyl group in CA reacted with the amino group in Ara h1. The digestibility of Ara h1-CA was increased. The antigenicity of Ara h1-CA was undetectable after 30min of digestion in vitro. These findings can serve as a reference for further research on hypoallergenic peanut products.

γ-Conglutin Immunoreactivity Is Differently Affected by Thermal Treatment and Gastrointestinal Digestion in Lupine Species.

Lupine is a legume commonly used in human diet as a functional food due to its high nutritional content and important technological properties. However, its consumption can lead to the manifestation of adverse immunological reactions, posing significant health issues in sensitized/allergic patients. This work aims to investigate the effect of food processing combined with simulated gastrointestinal (GI) digestion on the immunoreactivity of lupine γ-conglutin. Model foods of wheat pasta containing 35% of lupine flour (Lupinus albus, L. luteus, and L. angustifolius) were prepared and submitted to a boiling process. The proteins were extracted and their profiles characterized by SDS-PAGE. Simulated GI digestion was performed on thermally treated pasta using the INFOGEST harmonized digestion protocol 2.0. The IgG binding capacity of γ-conglutin was assessed by immunoblotting in non-reducing conditions and indirect ELISA with specific antibodies. Results demonstrate that the boiling treatment affected the immunoreactivity of the three lupine species differently. Simulated GI digestion led to extensive destruction of the protein structure, more significant in the intestinal phase, reducing but not abolishing the IgG affinity to γ-conglutin and its potential presentation to immunocompetent cells. This information can offer valuable insights to the food industry for developing food formulations with reduced allergenic properties.

Effects of polyphenols from walnut pellicle on the structure and allergenicity of walnut globulin

This study investigated the effects of polyphenols from walnut pellicle on the structure and allergenicity of walnut globulin (WG). The allergenicity-guided assay revealed walnut globulin (WG) from walnut defatted powder without pellicle was the most allergenic protein fraction of walnut. Complexes of phenolic extracts from walnut pellicle (PEWP) and WG were prepared in different ratio and pH conditions to further investigate the effect of PEWP on the protein structure and allergenicity of globulin. The covalent interaction between PEWP and WG in pH 7 was lower than pH 11, according to the free amino groups' content and SDS-PAGE analysis. Comprehensive methods characterized the complexes, including UV–Visible, fluorescence, Fourier transform infrared, and circular dichroism spectroscopy, and indicated that combination of polyphenols with protein altered the secondary and tertiary structure of the protein, leading to the unfolding of the protein structure. Meanwhile, the combination with PEWP reduced the IgG-binding capacity of WG in a dose-dependent manner, reaching a minimum of 26.90 ± 4.31% (at pH 7), which was significantly (P < 0.05) lower compared to that at pH 11 (41.79 ± 1.25%). Correlation analysis revealed a significant correlation between IgG-binding capacity and protein structure, as well as the addition concentration of PEWP (r = −0.85, P < 0.01), and pH conditions may indirectly influence the structure and allergenicity of the protein by affecting the interaction between WG and PEWP. The interaction between WG and PEWP was characterized through fluorescence-quenching mechanism analysis, indicating that polyphenols from PEWP mainly interact with WG through hydrogen bond and hydrophobic interaction.

Effects of unfolding treatment assisted glycation on the IgE/IgG binding capacity and antioxidant activity of ovomucoid.

Ovomucoid is the immune-dominant allergen in the egg white of hens. Due to its structure based on nine disulfide bonds as well as its resistance to heat and enzymatic hydrolysis, the allergenicity of this food protein is difficult to decrease by technological processes. We sought to reduce its allergenicity through the Maillard reaction. The unfolding of ovomucoid with L-cysteine-mediated reduction was used to increase accessibility to conformational and linear epitopes by modifying the secondary and tertiary structures of the allergen. Glycation with different saccharides revealed the beneficial effect of maltose glycation on the IgG-binding capacity reduction. By determining the better glycation conditions of unfolded ovomucoid, we produced ovomucoid with reduced IgE binding capacity due to the glycation sites (K17, K112, K129, and K164) on epitopes. Moreover, after simulated infant and adult gastrointestinal digestion, the unfolded plus glycated ovomucoid showed higher ABTS˙+ scavenging activity, O2˙- scavenging activity, ˙OH scavenging activity, Fe2+ chelating activity, and a FRAP value; in particular, for ˙OH scavenging activity, there was a sharp increase of more than 100%.

Evaluation of the immunoreactivity and quality characteristics of cow milk following combined fermentation and enzymatic hydrolysis

Cow milk (CM) allergy is one of the most common food allergies in infants and children, which causing serious health concern. To the best of our knowledge, there are few studies on the effects of Lactobacillus paracei (L. paracei) fermentation combined with Alcalase hydrolysis on the immunoreactivity and quality characteristics of CM. In this study, immunoreactivity, protein patterns, free amino acid (FAA) profiles, nutritional quality after L. paracei fermentation, and Alcalase hydrolysis were systematically evaluated. L. paracei fermentation assisted by Alcalase hydrolysis (CM-LpA) effectively decreased the intensity, antigenicity, and allergenicity of cow milk proteins in CM. The IgG-binding capacity was significantly reduced (P < 0.05), with a reduction rate ranging from 51.20 to 68.13%. The IgE-binding capacity was also markedly reduced, with a reduction rate of 59.46%. Additionally, most of the FAA profiles increased significantly (P < 0.05), particularly those of Met (354-fold), Phe (91-fold), and Leu (213-fold). The color of the CM further changed and gradually became light red and yellow. The taste also changed, with the levels of sourness and astringency increasing dramatically (P < 0.05). Our results will lay the foundation for the development of hypoallergenic dairy products.

Insight into the conformational and allergenicity alterations of shrimp tropomyosin induced by Sargassum fusiforme polyphenol

Tropomyosin (TM) is the main allergen in shrimp food. Algae polyphenol reportedly could affect the structures and allergenicity of shrimp TM. In this study, the alterations of conformational structures and allergenicity of TM induced by Sargassum fusiforme polyphenol (SFP) were investigated. Compared to TM, the conjugation of SFP to TM induced conformational structure instability, the IgG-binding capacity and IgE-binding capacity of TM gradually decreased with more conjugation of SFP to TM, and the conjugation of SFP to TM could significantly reduce degranulation, histamine secretion and release of IL-4 and IL-13 from RBL-2H3 mast cells. Therefore, the conjugation of SFP to TM led to conformational instability, significantly decreased the IgG-binding capacity and IgE-binding capacity, weakened the allergic responses of TM-stimulated mast cell, and performed in vivo anti-allergic properties in BALB/c mouse model. Therefore, SFP could serve as candidate natural anti-allergic substances to reduce shrimp TM-induced food allergy.

Structure and allergenicity of α-lactalbumin: effects of ultrasonic prior to glycation and subsequent phosphorylation

Bovine α-lactalbumin (BLA) induced severe cow's milk allergy. In this study, a novel strategy combining ultrasonication, performed before glycation, and phosphorylation was proposed to reduce BLA allergenicity. Result showed that IgE- and IgG-binding capacities and the release rates of histamine and interleukin-6 from RBL-2H3 were reduced. Moreover, intrinsic fluorescence intensity and surface hydrophobicity were decreased, whereas glycated sites (R10, N44, K79, K108, N102 and K114) and phosphorylated sites (Y36 and S112) of BLA were increased. Minimum allergenicity was detected during BLA treatment after ultrasonic prior to glycation and subsequent phosphorylation because of considerable increase in glycated and phosphorylated sites. Therefore, the decrease in allergenicity of BLA, the effect correlated well with the shielding effect of glycated sites combined with phosphorylated sites and the conformational changes. This study provides important theoretical foundations for improving and using the ultrasonic technology combined with protein modification in allergenic protein processing.

Effects of high hydrostatic pressure on conformation and IgG binding capacity of tropomyosin in Pacific oyster (Crassostrea gigas)

To investigate the effects of high hydrostatic pressure (HHP) on the conformation and IgG binding capacity, tropomyosin (TM) from Pacific oysters was subjected to high pressures of 300, 450 or 600 MPa. The results showed that the α-helix of TM with HHP-induced was decreased, while β-turn, β-sheet (predominantly) and random coil were increased. The surface hydrophobicity and sulfhydryl group content of TM were increased, while the fluorescence/UV intensity were decreased after HHP treatment. Atomic force microscopy (AFM) result exhibited that the morphology of TM was changed at 600 MPa and formed fibrous structures. The IgG binding capacity of TM and digested TM was markedly reduced when the pressure was increased, especially at 600 MPa. Overall, this study indicated that HHP-induced conformational changes in TM contributed to the reduction in IgG binding capacity. These findings suggested that HHP may be a promising non-thermal technology for producing hypoallergenic oyster products.

Novel Approaches for Inhibiting the Indoor Allergen Der f 2 Excreted from House Dust Mites by Todomatsu Oil Produced from Woodland Residues.

House dust mite (HDM) is a globally ubiquitous domestic cause of allergic diseases. There is a pressing demand to discover efficient, harmless, and eco-friendly natural extracts to inhibit HDM allergens that are more likely to trigger allergies and challenging to be prevented entirely. This study, therefore, is aimed at assessing the inhibition of the allergenicity of major HDM allergen Der f 2 by todomatsu oil extracted from residues of Abies Sachalinensis. The inhibition was investigated experimentally (using enzyme-linked immunosorbent assay (ELISA), surface plasmon resonance (SPR), and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)) and in silico using molecular docking. The results showed that todomatsu oil inhibits the allergenicity of Der f 2 by reducing its amount instead of the IgG binding capacity of a single protein. Moreover, the compounds in todomatsu oil bind to Der f 2 via alkyl hydrophobic interactions. Notably, most compounds interact with the hydrophobic amino acids of Der f 2, and seven substances interact with CYS27. Contrarily, the principal compounds fail to attach to the amino acids forming the IgG epitope in Der f 2. Interestingly, chemical components with the lowest relative percentages in todomatsu oil show high-affinity values on Der f 2, especially β-maaliene (−8.0 kcal/mol). In conclusion, todomatsu oil has been proven in vitro as a potential effective public health strategy to inhibit the allergenicity of Der f 2.

Effect of covalent conjugation with chlorogenic acid and luteolin on allergenicity and functional properties of wheat gliadin

In order to develop hypoallergenic wheat products, this study investigated the reduction in allergenicity and improvement in functional properties of wheat gliadin (Gli) through covalent conjugation with chlorogenic acid (CA) and luteolin (LU), as well as the mechanism of covalent conjugation. The upward shifted of the electrophoresis band and the decrease of retention time of chromatographic peak suggested the molecular weight of Gli became larger, and the covalent conjugation was confirmed. Gli was covalently conjugated with CA/LU via the free amino, thiol and tyrosine groups. The grafting rate results showed the degree of covalent interaction between Gli and CA was greater than that of Gli-LU. The structure of Gli was altered distinctly after covalently conjugated with CA/LU, transforming to a more ordered structure. Western blot and ELISA analysis indicated that Gli-CA/LU conjugates showed the lower IgG binding capacity. Further, the thermal stability, antioxidant activity and in vitro digestibility of conjugates were significantly improved (p < 0.05). This research provided theoretical basis and guidance for the production of hypoallergenic wheat products.

The Effects of High Intensity Ultrasound on Tropomyosin of Pacific Oyster (Crassostrea Gigas): Structure, Digestibility, and IgG Binding Capacity

The Effects of High Intensity Ultrasound on Tropomyosin of Pacific Oyster (Crassostrea Gigas): Structure, Digestibility, and IgG Binding Capacity

Influence of ohmic heating on the structural and immunoreactive properties of soybean proteins

Ohmic heating (OH) encompasses interesting benefits towards thermal processing. Envisaging an increasing relevance of soybean protein as an alternative non-animal protein, it is important to understand how OH can contribute to the quality and immunoreactivity of soybean-derived products. This study describes, for the first time, the impact of OH when applied at different electrical frequencies (50 Hz–20 kHz) and moderate electric field intensities (up to 20 V/cm), on the leakage of metals from the electrodes and immunoreactivity aspects of soybean protein isolate (SPI). This was achieved by monitoring the occurrence of electrochemical reactions and evaluating IgG-binding capacity. OH performed at 50 Hz and 95 °C induced significant alterations on the intrinsic fluorescence of SPI (p ≤ 0.05) and the release of detectable amounts of Fe/Ni, with a subsequent reduction of 36% in the immunoreactivity of Gly m TI. The occurrence of non-thermal effects, as well as the interaction between protein and trace metals, may result in a partial blockage of protein epitopes, thus impairing specific antibody binding. These findings present novel information about the importance of OH parameters, such as electrical frequency and occurrence of electrochemical reactions, which can affect the structure and immunoreactivity of SPI fractions.

Utilization of sonication-glycation to improve the functional properties of ovalbumin: A high-resolution mass spectrometry study

Ovalbumin (OVA) is a globular protein found in hen's eggs that has excellent nutritional and functional properties but is a major allergen. Previous studies have shown that ultrasound pretreatment combined with glycation (sonication-glycation) of OVA markedly reduced its IgG and IgE binding capacities and enhanced its antioxidant activity. In this study, the effects of sonication-glycation on a number of important functional attributes of OVA were studied: foaming, emulsifying, and digestibility. These processes significantly enhanced the foaming and emulsifying properties of OVA by increasing the exposure of hydrophobic residues at the protein surfaces. Moreover, reversed-phase chromatography indicated that sonication-glycation only caused a small decrease in OVA digestibility under simulated gastric and small intestine conditions, and that the level of IgG and IgE binding of OVA was exceedingly low after digestion. Furthermore, sonication promoted the glycation of OVA by increasing the number of exposed glycation sites, as determined by high-resolution mass spectrometry. These results imply that sonication-glycation is a promising method for improving the functional performance of food proteins, while also reducing their immunogenicity.

Increasing immunoglobulin G adsorption in dextran-grafted protein A gels.

The formation of a stable spatial arrangement of protein A ligands is a great challenge for the development of high‐capacity polymer‐grafted protein A adsorbents due to the complexity in interplay between coupled ligands and polymer chain. In this work, carboxymethyl dextrans (CMDs) with different molecular weight were introduced to provide stable spatial ligand arrangement in CMD‐grafted protein A gels to improve IgG adsorption. The result showed that coupling of protein A ligand in CMD‐grafted layer had no marked influence on pore size and dextran layers coupled with the ligands were stable in experimental range of salt concentrations. The result of IgG adsorption revealed that carboxymethyl dextran T10, a short CMD, was more suitable as a scaffold for the synthesis of high‐capacity protein A gels. Moreover, the maximal adsorption capacity for IgG was obtained to be 96.4 mg/g gel at ionic capacities of 300–350 mmol/L and a ligand density of 15.2 mg/g gel. Dynamic binding capacity for IgG exhibited a higher capacity utilization in CMD‐grafted protein A gels than non‐grafted protein A gel. The research presented a tactics to establish a stable dextran layer coupled with protein A ligands and demonstrated its importance to improve binding capacity for IgG.