title: Identification of the major allergens of Charybdis feriatus (red crab) and its cross-reactivity with Portunus pelagicus (blue crab).
abstract: BACKGROUND
  Tropomyosin and arginine kinase have been identified as the major allergens in multiple species of crab. Charybdis feriatus is an important commercial crab in this country.
  
  
  OBJECTIVE
  To characterize the major allergens of C. feriatus using a proteomics approach and subsequently to identify the allergens involved in cross-reactivity with Portunus pelagicus.
  
  
  METHODS
  Raw and boiled extracts of the crabs were prepared from crab meat. The protein profile of the extracts was determined by SDS-PAGE and two-dimensional electrophoresis (2-DE). Major allergens were identified by the immunoblotting test using sera from 50 patients with crab allergy. The major allergens were further identified by 2-DE immunoblotting. The major allergenic spots were then excised, digested by trypsin and identified by mass spectrometry analysis. The immunoblotting inhibition test was performed to study the crossreactivity between red crab and blue crab allergens using sera from 20 patients with allergy to both red and blue crabs.
  
  
  RESULTS
  At least 20 protein bands between 13 to 250 kDa were detected in the SDS-PAGE gel of raw extract, while boiled extract procuced fewer protein bands. Proteins of 36 kDa and 41 kDa were recognized as the major allergens of the crab. The major allergenic spot sequences of the 36 and 41 kDa proteins were identified as crab tropomyosin and arginine kinase, respectively. All IgE-binding proteins, including both major allergens, were found to be cross-creative with P. pelagicus allergens.
  
  
  CONCLUSIONS
  In addition to tropomyosin, arginine kinase was also identified as the major allergen of C. feriatus among our local crab-allergic patients. Cross-reactivity of this crab with P. pelagicus was demonstrated in this study.
authors: Department of Biology, Faculty of Science and Mathematics, Sultan Idris Education University, 35900 Tanjong Malim, Perak, Malaysia. rosmilah@fsmt.upsi.edu.my
authors: Rosmilah
authors: R
authors: Misnan
authors: Shahnaz
authors: S
authors: Murad
authors: Zailatul Hani Mohd
authors: ZH
authors: Yadzir
authors: Noormalin
authors: N
authors: Abdullah
mesh_terms: D000485:Allergens / Q000737:chemistry / Q000276:immunology*; D000818:Animals; D001122:Arginine Kinase / Q000737:chemistry / Q000276:immunology*; D060829:Arthropod Proteins / Q000737:chemistry / Q000276:immunology*; D003386:Brachyura / Q000737:chemistry / Q000276:immunology*; D003429:Cross Reactions; D005260:Female; D005512:Food Hypersensitivity / Q000097:blood / Q000276:immunology*; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology*; D008297:Male; D014335:Tropomyosin / Q000737:chemistry / Q000276:immunology*
chemical_list: D000485:Allergens; D060829:Arthropod Proteins; D014335:Tropomyosin; D007073:Immunoglobulin E; D001122:Arginine Kinase