Reduction in IgE reactivity of fish parvalbumin through heat denaturation

Abstract Parvalbumin is a prominent fish allergen with notable heat stability in structural and allergenic properties. However, high temperatures reduce immunoglobulin E (IgE) reactivity, likely due to the destruction of IgE-binding epitopes via heat-induced protein denaturation. This study investigated how heat treatment affects parvalbumin denaturation and IgE reactivity. IgE reactivity of patient sera was examined using Pacific chub mackerel extracts and purified parvalbumin by western blotting and enzyme-linked immunosorbent assay (ELISA). Parvalbumin IgE reactivity remained largely unchanged after 10 min at 100 °C, but declined significantly after 60 min. At 120 °C, IgE reactivity decreased rapidly. Denaturation of purified parvalbumin was assessed using phenylalanine-derived intrinsic fluorescence, hydrophobic region exposure with 1-anilinonaphthalene−8-sulfonic acid, and calcium-binding ability using Quin 2. The purified parvalbumin showed partial denaturation at 100 °C and complete denaturation at 120 °C. Western blotting of extracts from 20 fish species using a conformation-sensitive anti-parvalbumin antibody revealed slight reactivity after 60 min at 100 °C but complete loss after 60 min at 120 °C. ELISA showed slight IgE reactivity in many species after 60 min at 100 °C; however, all reactivities disappeared after 60 min at 120 °C. Parvalbumin from diverse fish species shows marked thermal stability, but heating at 120 °C induces denaturation and abolishes detectable IgE reactivity under the conditions tested.