D3.69 - Tissue-Specific Allergen Distribution in Blue Swimmer Crab (Portunus pelagicus): Implications for Shellfish Allergy Diagnostics

Shellfish allergy affects up to 3% of children and adults, often leading to severe allergic reactions. Current extract-based diagnostic tests depend on whole-shellfish protein extracts, which may fail to detect critical allergenic components due to losses occurring during the extraction process. This limitation can result in false-negative diagnoses, leaving allergic individuals at risk. Identifying tissue-specific allergens and their distribution is essential for improving diagnostic accuracy.

In this study, we investigated tissue-specific allergens in blue swimmer crab (Portunus pelagicus), dissecting crabs into three distinct tissue groups: body, claw, and leg muscle. Protein extracts from each tissue were analyzed using SDS-PAGE, immunoblotting, and LC–MS, while IgE reactivity was assessed in 40 crustacean-allergic individuals confirmed by clinical history, skin prick tests, ImmunoCAP, and ALEX assay.

ALEX assay analysis revealed that 40% (n=16) of individuals exhibited IgE reactivity exclusively to a single allergenic component, rather than the whole extract. Notably, 87.5% (n=14) of these individuals reacted to troponin C (TnC), a critical allergen that seems to be lost during protein extraction. Among these TnC-reactive individuals, tissue-specific IgE-binding immunoassays demonstrated significant differences in allergen distribution: 86% (n=12) reacted to claw muscle, 71.5% (n=10) to leg muscle, but only 36% (n=5) to body muscle. These findings indicate that body muscle contains lower levels of IgE-binding TnC, potentially contributing to false-negative results when whole-body extracts are used in diagnostics.

Furthermore, LC–MS analysis identified lower levels of other known crustacean allergens, such as tropomyosin, in body tissue compared to claws and leg tissue. Interestingly, heat-labile allergens (e.g., hemocyanin) exhibited partial heat stability depending on the tissue type, suggesting that cooking may alter allergen exposure in different crab parts.

These findings underscore the importance of tissue-specific allergens in shellfish allergy diagnostics. Standardized extracts incorporating allergen-rich tissues could improve diagnostic precision and reduce the risk of false-negative results, ultimately leading to more effective patient management and safer food allergy diagnostics.