Seafood allergy: Allergen, epitope mapping and immunotherapy strategy

A Crystal Structure of Pro c 2 Provides Insights into Cross-Reactivity of Aquatic Allergens from the Phosphagen Kinase Family

Arginine kinase (AK) from the phosphagen kinase family is a cross-reactive shellfish allergen. Structurally related cross-reactive allergens are involved in the pathogenesis of allergic symptoms. This study aimed to unravel the cross-reactivity of AK from a structural perspective. The crystal structure of Procambarus clarkii AK (Pro c 2) was resolved at 1.57 Å resolution, which showed a well-conserved structure not only to shellfish AKs but also to fish creatine kinase (CK), another allergen from the phosphagen kinase family. In Western blot, the CK corresponding protein in fish muscles was found to be reactive with AK-specific immunoglobulin (Ig) G. Recombinant Pro c 2 (rPro c 2) and CKs from Lateolabrax japonicus (rCK-L) and Ctenopharyngodon idell (rCK-C) were then produced, and the IgE reactivity of rCK-L and rCK-C, as well as their IgG/IgE cross-reactivity with rPro c 2, was confirmed by immunological assays. This study demonstrated the cross-reactivity among aquatic allergens from the phosphagen kinase family due to their structural similarity.

Rapid Gluten Allergen Detection Using an Integrated Photoimaging Assay and Ionic Liquid Extraction Sensor

In recent years, food allergies and food sensitivities have remained critical public health problems that affect approximately 15% of the global population. Wheat is a major food source worldwide, but it is also a common food allergen. Celiac disease is chronic immune-mediated enteropathy triggered by exposure to dietary gluten in genetically predisposed individuals; it can be treated only through strict gluten avoidance. Therefore, rapid gluten detection is crucial for protecting the health of patients. Gluten contains two primary water-insoluble proteins: gliadin and glutenin. Gliadin is a key contributor to celiac disease and poses challenges for sample pretreatment owing to its insolubility, thereby reducing the accuracy and sensitivity of detection systems. Rapid sample processing is a critical problem in gliadin detection. In this report, we developed a gliadin sensor system called the integrated food allergy and microorganism sensor (iFAMs). The iFAMs comprises a gliadin lateral flow chip, a one-pot extraction solution, and an image assay app. The iFAMs enables gliadin extraction and detection in under 2 min with high sensitivity (0.04 mg/kg for gliadin, lower than the regulatory limit of 20 mg/kg). Users can easily measure gluten concentrations in samples and quantify gliadin levels using the smartphone-based image assay app. In samples collected from restaurants, the iFAMs successfully detected hidden gluten within "gluten-free" food items. The compact size and user-friendly design of the iFAMs render it suitable for not only consumers but also clinicians, food industries, and regulators to enhance food safety.

Antigenic epitopes and cross-reactivity analysis of tropomyosin from Oratosquilla oratorio

Tropomyosin (TM) has been determined as the major allergen in Oratosquilla oratoria. However, little information is available about its antigenic epitopes and cross-reactivity. In this study, recombinant TM was obtained through genetic engineering and its IgG-/IgE-binding activity was similar to native TM. Subsequently, four T-cell epitopes were identified by using bioinformatics technology combined with CD4+ T-cell proliferation assay, and seven B-cell epitopes were identified by bioinformatics technology combined with serological assay. Moreover, dot blot analysis showed that TM had cross-reactivity among O. oratoria and other shellfish by using IgE polycolonal antibody from sera of shrimp-sensitive individuals or O. oratoria TM-immunized mice. Interestingly, three T-cell epitopes (AA4-24, AA194-212, and AA221-243) and four B-cell epitopes (AA85-100, AA121-138, AA209-233, and AA242-259) of TM in O. oratoria were conserved between O. oratoria and other shellfish, which may be the main reason for the cross-reactivity between them. In summary, these findings could serve for the diagnosis and prevention of shrimp allergy.

Development of Hypoallergenic Derivatives of Cra a 1 with B Cell Epitope Deletion and T Cell Epitope Retention

Tropomyosin was reported as an important allergen in Crassostrea angulata and designated as Cra a 1. The localization of the T cell epitopes and the reduction of the immunoreactivity of Cra a 1 are still lacking. In this study, four T cell epitopes were identified by using wild-type Cra a 1 (wtCra a 1)-immunized mouse splenocytes cultured with synthetic peptides. The immunoreactivity was maintained after chemical denaturation treatment, indicating that the linear epitope is an immunodominant epitope of wtCra a 1. Furthermore, the hypoallergenic derivative (mCra a 1) was developed by the deletion of linear B cell epitopes and retention of T cell epitopes. mCra a 1 could stimulate CD4+T cell proliferation and upregulate interleukin-10 secretion. Overall, basophil activation by mCra a 1 was low, but its ability to induce T cell proliferation was retained, suggesting that mCra a 1 may serve as a viable candidate for treating oyster allergy.

A SILAC-based accurate quantification of shrimp allergen tropomyosin in complex food matrices using UPLC-MS/MS

The carryover of trace allergens in complex food matrices poses challenges for detection techniques. Here, we demonstrate an accurate UPLC-MS/MS quantification assay for the shrimp allergen tropomyosin with a full-length isotope-labelled recombinant tropomyosin (TM-I) internal standard in complex food matrices. The TM-I, expressed based on the SILAC technique, exhibited a high isotope labelling ratio (>99%), purity, and alignment with the natural sequence. This method determined the tropomyosin ranging from 0.2 to 100 ng/mL. Mean recoveries ranged from 89 to 116%, with intra- and inter-day RSDs below 12%, for three signature peptides across three types of commercially processed food matrices. The limits of quantitation were 1 μg/g in pop food and sauce, and 10 μg/g in surimi product, respectively. This study supports the use of recombinant full-length isotope-labelled proteins rather than stable-isotope labelling peptides as internal standards to achieve more accurate quantitation of food allergens as the digestion error is corrected.