Identification of major and cross-reactive allergens of local freshwater snail (Pila polita) and the impact of thermal and non-thermal food processing on allergen stability

BACKGROUND: Snail allergy is rare but can be fatal. Pila polita, a freshwater snail, was considered as a popular exotic food, particularly in tropical countries, and consumed in processed forms. Thus, the purpose of this study was to identify the major and cross-reactive allergens of P. polita and to determine the impact of food processing on the allergen stability.

RESULTS: Sodium dodecyl sulfate-polyacrylamide gel electrophoresis fractionated raw snail extract to approximately 24 protein bands, between 9 and 245 kDa. The prominent band at 33 kDa was detected in all raw and processed snail extracts. Immunoblotting tests of the raw extract demonstrated 19 immunoglobulin E (IgE)-binding proteins, and four of them, at 30, 35, 42 and 49 kDa, were revealed as the major IgE-binding proteins of P. polita. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry identified the 49 and 42 kDa major allergens as actin, whereas the 30 and 35 kDa major allergens were identified as tropomyosin. Immunoblotting revealed that the raw snail had more allergenic proteins than the processed snail. The degree of allergenicity in decreasing order was raw > brine pickled> boiled > roasted > fried > vinegar pickled. The presence of cross-reactivity between P. polita and the shellfish tested was exhibited with either no, complete, or partial inhibitions.

CONCLUSION: Actin and tropomyosin were identified as the major and cross-reactive allergens of P. polita among local patients with snail allergy. Those major allergens are highly stable to high temperatures, acidic pH, and high salt, which might played a crucial role in snail allergy in Malaysia. © 2023 Society of Chemical Industry.