Reactivity of shrimp allergy-related IgE antibodies to krill tropomyosin.
BACKGROUND
Krill, which morphologically resembles small shrimp, represents small ocean crustaceans and has been used for human consumption in Japan and some other countries. The major allergen in crustaceans has been reported to be tropomyosin, but the allergenicity of krill tropomyosin remains uncertain.


METHODS
Amino acid sequences of tropomyosin in two species of krill (Euphausia superba and E. pacifica) were deduced. Recombinant krill tropomyosins were produced in Escherichia coli using a pCold IV vector system, and the cross-reactivity of shrimp allergy-related IgE to the recombinant tropomyosins and several animal protein extracts was assessed by immunoblotting.


RESULTS
The deduced amino acid sequences of the E. superba and E. pacifica tropomyosins (designated as Eup s 1 and Eup p 1, respectively) were 284 residues and showed significant homology to those of shrimp, lobster and crab tropomyosins. Shrimp allergy-related IgE reacted to approximately 38-kDa protein bands in krill (E. superba), shrimp, lobster and crab protein extracts but did not react to protein extracts from either mollusks or vertebrates. Furthermore, the IgE recognized rEup s 1 and rEup p 1 as 38-kDa protein bands, and absorption of the IgE with rEup s 1 removed IgE reactivity to recombinant tropomyosins and protein extracts from krill and shrimp.


CONCLUSIONS
Krill tropomyosins included highly homologous sequences to previously reported IgE-binding epitopes in Pen a 1 (tropomyosin of Penaeus aztecus). The cross-reactivity in shrimp allergy-related IgE binding among krill, shrimp, lobster and crab tropomyosins was revealed. These observations suggest the potential allergenicity of krill tropomyosin.
Nakano
Shigeru
S
Food Safety Research Institute, Nissin Food Products, Kusatsu, Shiga, Japan. s-nakano@mb1.nissinfoods.co.jp
Yoshinuma
Toshio
T
Yamada
Toshihiro
T
D000485:Allergens / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D003429:Cross Reactions; D003445:Crustacea / Q000737:chemistry* / Q000276:immunology; D005512:Food Hypersensitivity / Q000097:blood / Q000276:immunology; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology*; D007564:Japan; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000276:immunology; D016415:Sequence Alignment; D017385:Sequence Homology; D012758:Shellfish; D014335:Tropomyosin / Q000737:chemistry / Q000235:genetics / Q000276:immunology*
D000485:Allergens; D011994:Recombinant Proteins; D014335:Tropomyosin; D007073:Immunoglobulin E