Development and validation of mass spectrometry-based method for detecting shrimp allergen tropomyosin

In vivo biological analysis of cold plasma on allergenicity reduction of tropomyosin in shrimp

In vivo biological regulations of the allergenicity of tropomyosin (TM) treated by cold plasma (CP) were investigated by in vivo mouse model. The sensitization models of Balb/c mice were successfully established. CP treatment reduced the allergic symptoms of mice and regulated the Th1/Th2 balance to prevent allergy by activating Treg cells, which was deduced by serum and cytokines analysis. For intestinal flora analysis, allergy occurrence was accompanied by the decreased species abundance and the increased species diversity of intestinal flora. The significant species composition difference between the TM group and the PBS group showed a possible connection between bacterial diversity and allergy. Furthermore, Firmicutes, Bacteroidetes, Parabacteroides, Alloprevotella, Bacteroides, and Lachnospiraceae could relate to allergy occurrence. Intestinal section analysis suggested that allergy occurrence was accompanied by the damaged intestinal structure, and CP treatment could relieve the damage caused by an allergy.

Ultrasensitive Quantification of Crustacean Tropomyosin by Immuno-PCR

Tropomyosin is the major and predominant allergen among shellfish. This study developed an ultrasensitive immuno-PCR method for the quantification of crustacean tropomyosin in foods. The method couples sandwich ELISA with the real-time PCR (rtPCR) amplification of marker DNAs. Monoclonal anti-TPM antibody was the capture antibody, polyclonal rabbit anti-shrimp tropomyosin antibody was the detection antibody, while natural shrimp tropomyosin served as the standard. A double-stranded amino-DNA was covalently conjugated to a secondary anti-rabbit antibody and subsequently amplified and quantified via rtPCR. The quantification sensitivity of immuno-PCR was 20-fold higher than analogous ELISA, with LOQ 19.8 pg/mL. The developed immuno-PCR method is highly specific for the detection of crustacean tropomyosin and is highly precise in a broad concentration range. Tropomyosin recovery in the spiked vegetable soup was 87.7-115.6%. Crustacean tropomyosin was also quantified in commercial food products. The reported immuno-PCR assay is the most sensitive method for the quantification of crustacean tropomyosin and is the first immuno-PCR-based assay for the quantification of food allergen and food protein in general. The described method could be easily adapted for the specific and ultrasensitive immuno-PCR-based detection of traces of any food allergen that is currently being quantified with ELISA, which is of critical importance for people with food allergies.

Understanding the Mechanism of Increased IgG/IgE Reactivity but Decreased Immunodetection Recovery in Thermally Induced Shrimp (Litopenaeus vannamei) Tropomyosin via Multispectroscopic and Molecular Dynamics Simulation Techniques

Despite the fact that tropomyosin (TM) has highly stable structural characteristics, thermal processing can adversely influence its immunodetection, and the mechanism involved has not been elucidated. Purified TM was heated at various temperatures, and then the IgG/IgE-binding capacity and immunodetection recovery were determined; meanwhile, the structural alterations were analyzed via spectroscopic and molecular dynamics simulation techniques. The obtained results demonstrated that heat-treated TM showed significantly increased IgG/IgE reactivity, confirmed by indirect ELISA and immunoblotting analysis, which might be attributed to the increased structural flexibility, and thus allowed TM to be recognized IgG/IgE easily. However, these structural alterations during thermal processing would contribute to the masking of some epitopes located in TM's surface due to the presence of curled or folded conformation with a considerable reduction of the solvent-accessible surface and radius of gyration, which primarily caused immunodetection recovery reduction in the sandwich ELISA (sELISA) test. The number of antigen binding sites might play a crucial role in a sandwich immunodetection system for sensitive and precise analysis in processed foods.

Crustacean shellfish allergens: influence of food processing and their detection strategies

Despite the increasing popularity of crustacean shellfish among consumers due to their rich nutrients, they can induce a serious allergic response, sometimes even life-threatening. In the past decades, a variety of crustacean allergens have been identified to facilitate the diagnosis and management of crustacean allergies. Although food processing techniques can ease the risk of crustacean shellfish allergy, no available processing methods to tackle crustacean allergies thoroughly. Strict dietary avoidance of crustacean shellfish and its component is the best option for the protection of sensitized individuals, which should rely on the compliance of food labeling and, as such, on their verification by sensitive, reliable, and accurate detection techniques. In this present review, the physiochemical properties, structure aspects, and immunological characteristics of the major crustacean allergens have been described and discussed. Subsequently, the current research progresses on how various processing techniques cause the alterations and modifications in crustacean allergens to produce hypoallergenic crustacean food products were summarized and discussed. Particularly, various analytical methodologies employed in crustacean shellfish allergen detection, and the effect of food processing and matrix on these techniques, are also herein emphasized for the appropriate selection of analytical detection tools to safeguard consumers 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.