Reactivity of serum immunoglobulin E to bullfrog Rana catesbeiana parvalbumins in fish‐allergic patients

  Parvalbumin, a calcium‐binding sarcoplasmic protein of approximately 12 kDa, represents the cross‐reactive, major allergen in fish. In consideration of the fact that parvalbumin is contained at high levels not only in fish muscle but also in frog muscle, the present study was undertaken to clarify whether fish‐allergic patients react to two parvalbumins (α‐ and β‐parvalbumins) purified from the bullfrog Rana catesbeiana , which is sometimes consumed as a delicacy in Japan. In enzyme‐linked immunosorbent assays (ELISA), sera from 12 of the 14 patients tested reacted equally to both parvalbumins purified from the Pacific mackerel Scomber japonicus and the bigeye tuna Thunnus obesus . Of the 12 sera positive to fish parvalbumins, eight sera also reacted to α‐ and β‐parvalbumins of the bullfrog with different spectra: one serum reacted strongly to α‐parvalbumin, six sera reacted strongly to β‐parvalbumin and one serum reacted equally to both α‐ and β‐parvalbumins. In addition, inhibition ELISA experiments revealed cross‐reactivity between fish and bullfrog parvalbumins. Based on these results, it is proposed that fish‐allergic patients should avoid the consumption of frog meat unless they are accurately diagnosed as lacking immunoglobulin E against frog.