Identification and Characterization of Main Allergic Proteins in Cooked Wolf Herring Fish

Our aim in this study was to identify and characterize allergic proteins in cooked wolf herring fish. We heated the crude extract alternatively at 50, 60, 70, 80, 90, and 100°C for one hour and results were compared by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Also, proteins were immunoblotted with fish-sensitive patients' sera. The major allergenic proteins were identified via mass spectrometry. These allergenic proteins were then purified by anion exchange chromatography and the IgE-immunoreactivity of the fractions was compared with the crude extracts via disk enzyme-linked immunosorbent assay (ELISA). SDS-PAGE of the crude extract showed more than 15 distinct protein bands. Five of these proteins, with apparent molecular weights of 12, 18, 24, 38, and 51 kDa, were only observed in the 100°C heated extract. Immunoblotting of the heated extract revealed that the 12 and 51 kDa proteins were IgE-immunoreactive with 88 percent of fish-sensitive patient sera while the 24 and 38 kDa proteins reacted with 33.3 and 55.5 percent of fish-sensitive patient sera, respectively. Mass spectrometry of the 12, 38, and 51 kDa proteins revealed that all three were parvalbumin oligomers. Disk ELISA results showed that 20 of 25 and 14 of 25 fish-allergic patients' sera were IgE-reactive with purified oligomeric parvalbumin-coated and crude extract-coated disks, respectively. Parvalbumin and its oligomers are the main allergenic molecules in cooked fish. Therefore, an enriched or purified fraction containing this protein could be a useful source of allergen for applications in ELISA-based immunoassays and could discriminate fish-allergic patients who can tolerate cooked fish from those who cannot.