Allergenicity potential of protein extract from freshwater and saltwater fish based on heat stability and antibody-binding frequency

Saltwater fish are associated with more allergic reactions compared to freshwater fish. However, the factors contributing to this difference remain unclear. To compare the heat stability of freshwater and saltwater fish proteins, and assess their binding affinity to allergen-specific antibodies. Protein extracts were isolated from saltwater fish-Selar crumenophthalmus, Euthynnus affinis, Ambassis urotaenia, and freshwater fish i.e., Rasbora argyrotaenia, Monopterus albus, and Poecilia reticulata. Protein extract from Penaeus monodon served as a standard allergen source. Both raw and heat-treated protein extracts were subjected to SDS-PAGE analysis. The number of protein bands, their molecular sizes, and intensities were evaluated. Protein binding frequencies to anti-tropomyosin antibodies and IgE-containing serum from allergic patients were measured using ELISA. The P. monodon protein extract < 100 kDa demonstrated heat stability, while A. urotaenia proteins < 40 kDa were also heat-stable. Raw protein extracts from R. argyrotaenia and M. albus exhibited binding frequencies to anti-tropomyosin IgG of 28.18 ± 1.05% and 14.79 ± 0.91%, respectively. In saltwater fish, raw protein extracts from A. urotaenia and S. crumenophthalmus showed binding frequencies of 61.74 ± 1.87% and 34.68 ± 1.39%, respectively. Freshwater and saltwater fish heat-treated protein extracts displayed binding frequencies below 10%. All heat-treated protein samples exhibited higher binding frequencies to polyclonal IgE in patient sera compared to their raw counterparts. Proteins smaller than 20 kDa exhibit significant heat stability. Raw protein extracts show higher binding frequencies to monoclonal IgG against crustacean tropomyosin, while heat-treated samples have increased binding frequency to IgE-containing human serum.