Identification of Tropomyosins as Major Allergens in Antarctic Krill and Mantis Shrimp and Their Amino Acid Sequence Characteristics

Abstract

Tropomyosin represents a major allergen of decapod crustaceans such as shrimps and crabs, and its highly conserved amino acid sequence (>90% identity) is a molecular basis of the immunoglobulin E (IgE) cross-reactivity among decapods. At present, however, little information is available about allergens in edible crustaceans other than decapods. In this study, the major allergen in two species of edible crustaceans, Antarctic krill Euphausia superba and mantis shrimp Oratosquilla oratoria that are taxonomically distinct from decapods, was demonstrated to be tropomyosin by IgE-immunoblotting using patient sera. The cross-reactivity of the tropomyosins from both species with decapod tropomyosins was also confirmed by inhibition IgE immunoblotting. Sequences of the tropomyosins from both species were determined by complementary deoxyribonucleic acid cloning. The mantis shrimp tropomyosin has high sequence identity (>90% identity) with decapod tropomyosins, especially with fast-type tropomyosins. On the other hand, the Antarctic krill tropomyosin is characterized by diverse alterations in region 13-42, the amino acid sequence of which is highly conserved for decapod tropomyosins, and hence, it shares somewhat lower sequence identity (82.4-89.8% identity) with decapod tropomyosins than the mantis shrimp tropomyosin. Quantification by enzyme-linked immunosorbent assay revealed that Antarctic krill contains tropomyosin at almost the same level as decapods, suggesting that its allergenicity is equivalent to decapods. However, mantis shrimp was assumed to be substantially not allergenic because of the extremely low content of tropomyosin.

Scientific Opinion on the evaluation of allergenic foods and food ingredients for labelling purposes

“…These tropomyosins show extensive IgE-binding cross-reactivity with shrimp, crab and lobster tropomyosins (Nakano et al, 2008). Krill tropomyosins and mantis shrimp tropomyosin have 82.3 to 89.8 % and > 90 % sequence identity with decapod tropomyosins, respectively (Motoyama et al, 2008). Tropomyosin is also the main allergen in acorn barnacle (Balanus rostratus) and goose barnacle (Capitulum (Pollicipes) mitella).…”

Pulsed Ultraviolet Light Reduces Immunoglobulin E Binding to Atlantic White Shrimp (Litopenaeus setiferus) Extract

“…Shrimp extract was prepared following the methods of Motoyama and others [30,31] with modification. Briefly, shrimp (25 g) was ground in a food processor at low speed for 10 s. A volume of 0.6 M KCl in 0.01 M phosphate buffer (200 mL, pH 7) was added to the processed tissue, and the mixture was homogenized at the high-speed setting (10,000 rpm) for 1 min using a BioSpec BioHomogenizer (Bartlesville, OK).…”

IgE reactivity to type I collagen and its subunits from tilapia (Tilapia zillii)

“…Western blotting was achieved by the method of Motoyama et al (2008), with some modification. Collagen (0.3 lg) was carried on SDS-PAGE, then transferred to the membrane.…”