Reduction in IgE reactivity of Pacific mackerel parvalbumin by heat treatment

Parvalbumin, a major fish allergen, has been reported to be highly thermostable. However, little is known as to whether parvalbumin is stable at more than 100°C. Thermostability of the Pacific mackerel parvalbumin was examined by subjecting heated (20-140°C) muscle extracts to SDS-PAGE, western blotting and ELISA. As judged by SDS-PAGE and western blotting with the anti-parvalbumin antiserum recognizing the primary structure, the parvalbumin was not degraded even under severe heating conditions. However, western blotting analysis with the monoclonal antibody recognizing the stereoscopic structure revealed that the parvalbumin undergoes conformational changes in a heating load-dependent manner. Importantly, the IgE reactivity of the parvalbumin determined by ELISA using patient sera was also reduced in a heating load-dependent manner; complete loss of IgE reactivity was induced by heating at 140°C. This study showed that the allergenicity of the Pacific mackerel parvalbumin is considerably less thermostable than assumed for other fish parvalbumins.