Development of a method for the quantification of fish major allergen parvalbumin in food matrix via liquid chromatography-tandem mass spectrometry with multiple reaction monitoring

Electrochemical Magnetic Immunoassay for the Determination of the Fish Allergen β-Parvalbumin

β-parvalbumin (β-PV) is the primary fish allergen responsible for most allergic reactions in individuals sensitive to fish. To ensure food safety, a sandwich-based magnetic immunoassay was developed using maleimide-functionalized magnetic beads (NH-MBs). Specific anti-β-PV antibodies were immobilized on these MBs, and a screen-printed carbon electrode was employed as the electrochemical transducer. A linear concentration range from 10 to 1000 ng/mL, a limit of detection of 1.8 ng/mL, and a limit of quantification of 7.1 ng/mL were achieved. Nineteen commercial food samples were analyzed to assess the potential of the sensor for routine use in food quality control. Important factors such as protein source and food processing (e.g., boiling, grilling, and frying) and preservation (e.g., in oil, and vacuum) were evaluated. The validated results confer the usefulness of the assay for food quality control.

Quantifying allergenic proteins using antibody-based methods or liquid chromatography-mass spectrometry/mass spectrometry: A review about the influence of food matrix, extraction, and sample preparation

Accurate quantification of allergens in food is crucial for ensuring consumer safety. Pretreatment steps directly affect accuracy and efficiency of allergen quantification. We systematically reviewed the latest advances in pretreatment steps for antibody-based methods and liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) protein quantification methods in food. For antibody-based methods, the effects induced by food matrix like decreased allergen solubility, epitope masking, and nonspecific binding are of the upmost importance. To mitigate interference from the matrix, effective and proper extraction can be used to obtain the target allergens with a high protein concentration and necessary epitope exposure. Removal of interfering substances, extraction systems (buffers and additives), assistive technologies, and commercial kits were discussed. About LC-MS/MS quantification, the preparation of the target peptides is the crucial step that significantly affects the efficiency and results obtained from the MS detector. The advantages and limitations of each method for pre-purification, enzymatic digestion, and peptide desalting were compared. Additionally, the application characteristics of microfluidic-based pretreatment devices were illustrated to improve the convenience and efficiency of quantification. A promising research direction is the targeted development of pretreatment methods for complex food matrices, such as lipid-based and carbohydrate-based matrices.

Development of an indirect competitive ELISA based on the common epitope of fish parvalbumin for its detection

A common epitope (AGSFDHKKFFKACGLSGKST) of parvalbumin from 16 fish species was excavated using bioinformatics tools combined with the characterization of fish parvalbumin binding profile of anti-single epitope antibody in this study. A competitive enzyme-linked immunosorbent assay (ELISA) based on the common epitope was established with a limit of detection of 10.15 ng/mL and a limit of quantification of 49.29 ng/mL. The developed ELISA exhibited a narrow range (71% to 107%) of related cross-reactivity of 15 fish parvalbumin. Besides, the recovery, the coefficient of variations for the intra-assay and the inter-assay were 84.3% to 108.2%, 7.4% to 13.9% and 8.5% to 15.6%. Our findings provide a novel idea for the development of a broad detection method for fish allergens and a practical tool for the detection of parvalbumin of economic fish species in food samples.

Characterization, Epitope Confirmation, and Cross-Reactivity Analysis of Parvalbumin from Lateolabrax maculatus by Multiomics Technologies

Spotted seabass (Lateolabrax maculatus) is the second largest maricultural fish species in China and is the main trigger of food-related allergic reactions. Nevertheless, studies on the allergens of L. maculatus are limited. This study aimed to characterize pan-allergen parvalbumin from L. maculatus. Two proteins of about 11 kDa were purified and confirmed as parvalbumins by mass spectrometry. The IgG- and IgE-binding activities were evaluated through an immunoblotting assay. The molecular characteristics of β-parvalbumin were investigated by combining proteomics, genomics, and immunoinformatics approaches. The results indicated that β-parvalbumin consists of 109 amino acids with a molecular weight of 11.5 kDa and is the major allergen displaying strong IgE-binding capacity. In silico analysis and a dot blotting assay confirmed seven linear B cell epitopes distributed mainly on α-helixes and the calcium-binding loops. In addition, the cross-reactivity among 26 commonly consumed fish species was analyzed. The in-house generated anti-L. maculatus parvalbumin polyclonal antibody recognized 100% of the 26 fish species, demonstrating cross-reactivity and better binding capacity than the anticod parvalbumin antibody. Together, this study provides an efficient protocol to characterize allergens with multiomics methods and supports parvalbumin from L. maculatus as a candidate for fish allergen determination and allergy diagnosis.

3D bio-printing-based vascular-microtissue electrochemical biosensor for fish parvalbumin detection

A novel 3D bio-printing vascular microtissue biosensor was developed to detect fish parvalbumin quickly. The graphite rod electrode was modified with gold and copper organic framework (Cu-MOF) to improve the sensor properties. Polydopamine-modified multi-wall carbon nanotubes (PDA-MWCNT) were mixed with gelatin methacryloyl (GelMA) to prepare a conductive hydrogel. The conductive hydrogel was mixed with mast cells and endothelial cells to produce a bio-ink for 3D bioprinting. High throughput and standardized preparation of vascular microtissue was performed by stereolithography 3D bioprinting. The vascular microtissue was immobilized on the modified electrode to construct the microtissue sensor. The biosensor's peak current was positively correlated with the fish parvalbumin concentration, and the detection linear concentration range was 0.1 ∼ 2.5 μg/mL. The standard curve equation was IDPV(μA) = 31.30 + 5.46 CPV(μg/mL), the correlation coefficient R2 was 0.990 (n = 5), and the detection limit was 0.065 μg/mL. These indicated a biomimetic microtissue sensor detecting fish parvalbumin has been successfully constructed.

Quantification of Allergic Crustacean Tropomyosin Using Shared Signature Peptides in Processed Foods with a Mass Spectrometry-Based Proteomic Strategy

Crustacean shellfish are major allergens in East Asia. In the present study, a major allergic protein in crustaceans, tropomyosin, was detected accurately using multiple reaction monitoring mode-based mass spectrometry, with shared signature peptides identified through proteomic analysis. The peptides were deliberately screened through thermal stability and enzymatic digestion efficiency to improve the suitability and accuracy of the developed method. Finally, the proposed method demonstrated a linear range of 0.15 to 30 mgTM/kgfood (R2 > 0.99), with a limit of detection of 0.15 mgTM/kg food and a limit of quantification of 0.5mgTM/kgfood and successfully applied to commercially processed foods, such as potato chips, biscuits, surimi, and hot pot seasonings, which evidenced the applicability of proteomics-based methodology for food allergen analysis.

Effects of different ohmic heating treatments on parvalbumin structure and reduction of allergenicity in Japanese eel (Anguilla japonica)

We investigated the effects of ohmic heating (OH) on the structural properties and allergenicity of parvalbumin (PV). Compared to other heating methods (water bath heating (WH), OH combined with WH, and OH combined with air thermostatic heating (AH)), pure OH heating expended the least time and total energy. PV sensitization was reduced by approximately 65% by pure OH heating. SDS-PAGE, tricine-SDS-PAGE, and western blotting analyses revealed a molecular weight of sensitized β-PV of about 12 kDa. Band intensity decreased with increasing OH time, and significant changes were observed in amino acid content, secondary structure, microstructure, and dielectric properties. Reducing PV, allergenicity through protein unfolding and secondary structural changes, thereby possibly reducing the allergenicity of eel, provides a theoretical basis for developing hypoallergenic products.

Simultaneous Identification and Species Differentiation of Major Allergen Tropomyosin in Crustacean and Shellfish by Infrared Spectroscopic Chemometrics

To solve the lack of rapid and accurate methods for allergen identification and traceability, an infrared spectroscopic chemometric analytical model (IR-CAM) was established by combining infrared spectroscopy with principal component and cluster analysis. By comparing the second derivative infrared (SD-IR) spectra of 5 proteins and 14 crustaceans and shellfish tropomyosin (TM), 8 shared peaks and unique fingerprint peaks in the amide III region were found for crabs, shrimps, and shellfish. Based on the unique fingerprint peaks coexisting with shared peaks, allergen TM in crustaceans and shellfish could be identified within 10 min (cf. ELISA ∼ 4 h). Concurrently, the species differentiation of TM at the Class/Family level was achieved based on IR-CAM. Validation by fermented aquatic products TM (n = 60) demonstrated that the developed IR-CAM could simultaneously identify and differentiate TM in crustaceans and shellfish accurately. It could be applied for allergen detection and traceability of aquatic products on an antibody-free basis.

A comprehensive overview of emerging processing techniques and detection methods for seafood allergens

Seafood is rich in nutrients and plays a significant role in human health. However, seafood allergy is a worldwide health issue by inducing adverse reactions ranging from mild to life-threatening in seafood-allergic individuals. Seafood consists of fish and shellfish, with the major allergens such as parvalbumin and tropomyosin, respectively. In the food industry, effective processing techniques are applied to seafood allergens to lower the allergenicity of seafood products. Also, sensitive and rapid allergen-detection methods are developed to identify and assess allergenic ingredients at varying times. This review paper provides an overview of recent advances in processing techniques (thermal, nonthermal, combined [hybrid] treatments) and main allergen-detection methods for seafood products. The article starts with the seafood consumption and classification, proceeding with the prevalence and symptoms of seafood allergy, followed by a description of biochemical characteristics of the major seafood allergens. As the topic is multidisciplinary in scope, it is intended to provide information for further research essential for food security and safety.

Determination of Tropomyosin in Shrimp and Crab by Liquid Chromatography–Tandem Mass Spectrometry Based on Immunoaffinity Purification

A UPLC-MS/MS method was developed for the detection of tropomyosin (TM) in shrimp and crab. After simple extraction, the samples were purified by immunoaffinity column and then digested by trypsin. The obtained sample was separated by Easy-nLC 1000-Q Exactive. The obtained spectrums were analyzed by Thermo Proteome Discoverer 1.4 software and then ANIQLVEK with high sensitivity was selected as the quantitative signature peptide. Isotope-labeled internal standard was used in the quantitative analysis. The method showed good linearity in the range of 5–5,000 μg/L with a limit of quantification (LOQ) of 0.1 mg/kg. The average recoveries were 77.22–95.66% with RSDs ≤ 9.97%, and the matrix effects were between 88.53 and 112.60%. This method could be used for rapid screening and quantitative analysis of TM in shrimp and crab. Thus, it could provide technical support for self-testing of TM by food manufacturers and promote further improvement of allergen labeling in China.

The History, Present and Future of Allergen Standardization in the United States and Europe

The topic of standardization in relation to allergen products has been discussed by allergists, regulators, and manufacturers for a long time. In contrast to synthetic medicinal products, the natural origin of allergen products makes the necessary comparability difficult to achieve. This holds true for both aspects of standardization: Batch-to-batch consistency (or product-specific standardization) and comparability among products from different manufacturers (or cross-product comparability). In this review, we focus on how the United States and the European Union have tackled the topic of allergen product standardization in the past, covering the early joint standardization efforts in the 1970s and 1980s as well as the different paths taken by the two players thereafter until today. So far, these two paths have been based on rather classical immunological methods, including the corresponding benefits like simple feasability. New technologies such as mass spectrometry present an opportunity to redefine the field of allergen standardization in the future.

Quantification of crustacean tropomyosin in foods using high-performance liquid chromatography-tandem mass spectrometry method

BACKGROUND

Allergic reactions to crustacean products have been increasing owing to the rising consumption. Tropomyosin (TM) is the main crustacean allergen; it has a coiled-coil structure, which shows stability to various food processing methods. Crustacean processed products have been used in several food products, thereby causing greater difficulties in detecting TM in these products. We aimed to develop an assay based on high-performance liquid chromatography-tandem mass spectrometry for the accurate and reproducible quantification of crustacean TM in foods.

RESULTS

The three peptides IQLLEEDLER, LAEASQAADESER, and IVELEEELR were selected as peptide markers, and the peptide IVELEEELR was selected as the quantitative marker. Extraction conditions and enzymatic digestion conditions were completely optimized. The extraction solution of Tris-hydrochloric acid buffer (50 mmol L^-1 , pH 7.4) containing 1 mol L^-1 potassium chloride and the enzymatic treatment at 1:15 ratio (enzyme/protein, m/m) for 13 h showed excellent efficiency. The method exhibited a good linear relationship, with the qualified coefficient of determination (R²  = 0.9994) in the wide range of 1 to 1000 μg L^-1 . The accuracy was validated based on spiked recovery at three spiking levels (12.5, 25.0, and 50.0 μg kg^-1 , TM/matrix) in blank matrices that included chicken sausages, beef balls, and egg-milk biscuits. The recoveries ranged from 91% to 109% with qualified relative standard deviations <15% with the limit of quantification (of 1.6 mg kg^-1 , TM/matrix).

CONCLUSION

This new approach can be used for the qualitative and quantitative detection of crustacean TM in various food matrices. © 2021 Society of Chemical Industry.

DNA, protein and aptamer-based methods for seafood allergens detection: Principles, comparisons and updated applications

The increasing number of people with seafood allergy has caused a series of problems for practitioners and consumers in the seafood industry year by year. Thereby, development of efficient, convenient and low-cost allergen detection methods is urgently needed. This review introduces three important existing seafood allergen detection methods associated with DNA-based, protein-based and aptamer-based. Their principles and biological characteristics are firstly presented. The core of these three methods are DNA amplification techniques, specific binding of antigens and antibodies, and specific binding of aptamers and ligands, respectively. Among them, DNA-based detection method is an indirect analysis, which takes the gene of allergen as the detection object and is characterized by good stability and high sensitivity. Protein-based and aptamer-based, methods employ indirect analysis for allergen detection. The difference is that the latter uses an easily synthesized and highly efficient aptamer as the detection probe, showing great promising potentials. The advantages and disadvantages of the three mentioned detection methods are also discussed. In the future, as more efficient and reliable detection methods for seafood allergens come into practice, the possibility of seafood allergy patients eating seafood products by mistake will be greatly reduced, which will ensure the food safety and the health of allergy patients.

A novel method based on infrared spectroscopic inception-resnet networks for the detection of the major fish allergen parvalbumin

We have developed a novel approach that involves inception-resnet network (IRN) modeling based on infrared spectroscopy (IR) for rapid and specific detection of the fish allergen parvalbumin. SDS-PAGE and ELISA were used to validate the new method. Through training and learning with parvalbumin IR spectra from 16 fish species, IRN, support vector machine (SVM), and random forest (RF) models were successfully established and compared. The IRN model extracted highly representative features from the IR spectra, leading to high accuracy in recognizing parvalbumin (up to 97.3%) in a variety of seafood matrices. The proposed infrared spectroscopic IRN (IR-IRN) method was rapid (~20 min, cf. ELISA ~4 h) and required minimal expert knowledge for application. Thus, it could be extended for large-scale field screening and identification of parvalbumin or other potential allergens in complex food matrices.

Novel monoclonal antibody-sandwich immunochromatographic assay based on Fe3O4/Au nanoparticles for rapid detection of fish allergen parvalbumin

In this study, a rapid sandwich immunochromatographic assay (ICA) was developed to detect parvalbumin (PV). Firstly, two optimum primary monoclonal antibody (mAb) against PV had been screened out: mAb1 was used as the capture antibody, and mAb2 conjugated to Fe₃O₄/Au nanoparticles (Fe₃O₄/AuNPs) that served as a detection reagent. Using this pair of mAbs, a sandwich ICA strip based on Fe₃O₄/AuNPs was developed. The results showed that the color intensity of test line positively correlated with the PV concentration in the standard or spiked sample. The limit of detection for qualitative (LOD) and quantitative detection (LOQ) were 2 ng/mL and 0.691 ng/mL, respectively. Besides, the detection time of this ICA strip was within 15 min. The recovery rates ranged from 104.0% to 117.4%, within an acceptable level (80-120%). Moreover, the developed assay also showed high cross reaction in different fish species. These results demonstrated that the established test strip has the potential to be used as a rapid screening tool for large scale determination of PV in foodstuffs.

Peptide markers for distinguishing guinea fowl meat from that of other species using liquid chromatography-mass spectrometry

The inability to easily identify the animal species in highly processed meat products makes them highly susceptible to adulterations. Reliable methods for detecting the species origin of meat used in processed food are required to ensure adequate labelling and minimize food fraud and allergenic potential. Liquid chromatography high resolution mass spectrometry was employed to identify new heat-stable guinea-fowl-specific peptide markers that can differentiate guinea fowl meat from other commonly consumed animal species, including closely related poultry species, in highly processed food products. We identified 26 unique guinea-fowl-specific markers. The high stability of guinea-fowl-specific peptides was confirmed by analysing food products with guinea fowl meat content ranging from 4% to 100%. The findings indicate that sensitive and reliable LC-MS/MS methods can be developed for the targeted detection and quantification of guinea fowl meat in highly processed meat products.

Development of a liquid chromatography-tandem mass spectrometry method for simultaneous quantification of hen's egg white allergens Gal d 1-4 in fresh and processed eggs

Hen's egg white allergens, namely Gal d 1-4, cause food allergies worldwide and their intake must be strictly controlled by allergic individuals. However, an efficient method for quantifying these allergens is currently unavailable. We aimed to develop an LC-MS/MS method for simultaneous Gal d 1-4 quantification. Purified Gal d 1-4 proteins were trypsin-digested and the resulting peptides used in LC-MS/MS analysis. The limits of quantification were 9.77-39.1 ng/mL. The Gal d 1-4 recovery in fresh and processed eggs was 68.3-121.3%, and intra- and interassay coefficients of variation were 1.5-15.7% and 2.4-38.1%, respectively, indicating high sensitivity, accuracy, and reproducibility. In addition, the high specificity of this method was confirmed by testing 27 other foods. This newly developed method could provide reliable information to the industrial food and clinical fields, facilitating improved quality of life for individuals with egg allergies.

Proteomics-Based Methodologies for the Detection and Quantification of Seafood Allergens

Seafood is considered one of the main food allergen sources by the European Food Safety Authority (EFSA). It comprises several distinct groups of edible aquatic animals, including fish and shellfish, such as crustacean and mollusks. Recently, the EFSA recognized the high risk of food allergy over the world and established the necessity of developing new methodologies for its control. Consequently, accurate, sensitive, and fast detection methods for seafood allergy control and detection in food products are highly recommended. In this work, we present a comprehensive review of the applications of the proteomics methodologies for the detection and quantification of seafood allergens. For this purpose, two consecutive proteomics strategies (discovery and targeted proteomics) that are applied to the study and control of seafood allergies are reviewed in detail. In addition, future directions and new perspectives are also provided.

Proteomics for understanding pathogenesis, immune modulation and host pathogen interactions in aquaculture

Proteomic analyses techniques are considered strong tools for identifying and quantifying the protein contents in different organisms, organs and secretions. In fish biotechnology, the proteomic analyses have been used for wide range of applications such as identification of immune related proteins during infections and stresses. The proteomic approach has a significant role in understanding pathogen surviving strategies, host defence responses and subsequently, the fish pathogen interactions. Proteomic analyses were employed to highlight the virulence related proteins secreted by the pathogens to invade the fish host's defence barriers and to monitor the kinetics of protein contents of different fish organs in response to infections. The immune related proteins of fish and the virulence related proteins of pathogens are up or down regulated according to their functions in defence or pathogenesis. Therefore, the proteomic analyses are useful in understanding the virulence mechanisms of microorganisms and the fish pathogen interactions thereby supporting the development of new effective therapies. In this review, we focus and summarise the recent proteomic profiling studies exploring pathogen virulence activities and fish immune responses to stressors and infections.

Identification and comparison of allergenicity of native and recombinant fish major allergen parvalbumins from Japanese flounder (Paralichthys olivaceus)

Compared with native parvalbumin, recombinant β-parvalbumin based on the optimized DNA sequence can be used in fish allergen confirmation.