The frequency of fish allergy has been increasing as seafood cuisine including raw fish has become popular. Parvalbumin is a well-known allergen for fish allergy, however, the details still remain to be determined. In this study, we explored immunoblotting analysis of IgE from five patients with fish allergy. Western blot analysis revealed that a fish extract protein with molecular weight at approximately 250kD, PI 6-7 was recognized by the serum IgE in five out of six patients with fish allergy but not in controls. The protein of interest separated on the two-dimensional gel electrophoresis was identified as myosin heavy chain (MYHC) using LS-MS/MS. The IgE immunoreactivity was confirmed with newly synthesized recombinant MYHC. In addition, the result that patients’ IgE pre-absorbed with fish extracts lost the reactivity to MYHC recombinant protein further confirmed the IgE specificity for MYHC. Also, the basophil activation test revealed rsMYHC- dependent IgE reactivity in patient’s peripheral blood. Previous studies demonstrated that fish collagen and parvalbumin were major allergens for fish allergy. The present study revealed that patients with fish allergy were heterogenous in that some show positive for parvalbumin but not for MYHC, and the others show vice versa. Since raw fish cuisine is popular not only in Japan but also outside of Japan, the risk of fish allergy may be increasing. All the patients harboring MYHC-specific IgE had atopic dermatitis, therefore, impaired permeability barrier of hands might contribute to the sensitization of this high molecular sized allergen MYHC.

Myosin heavy chain, a novel allergen for fish allergy in patients with atopic dermatitis.