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

Background: Saltwater fish are associated with more allergic reactions compared to freshwater fish. However, the factors contributing to this difference remain unclear.

Objective: To compare the heat stability of freshwater and saltwater fish proteins, and assess their binding affinity to allergen-specific antibodies.

Methods: 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.

Results: 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.

Conclusions: 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.