title: Mapping of the complement C9 binding domain on Trichinella spiralis paramyosin.
abstract: BACKGROUND
  Trichinellosis is an important foodborne zoonosis that is distributed worldwide. Trichinella spiralis may evade host complement-mediated attack by expressing complement inhibitory proteins, such as paramyosin (Pmy). Previous studies have shown that Trichinella spiralis paramyosin (Ts-Pmy) is able to bind to the human complement component C9 to inhibit the complement activation and protect the parasite from complement-mediated attack. Further determination of the complement-binding domain on Ts-pmy will enable us to better understand the Ts-Pmy's biofunction in the immune evasion and provide feasible approach to develop epitope-based subunit vaccine against trichinellosis.
  
  
  METHODS
  The complement C9 binding region on Ts-Pmy was determined by expression of overlapped fragments of Ts-Pmy and their binding activities to C9. The exact binding site was further narrowed-down to a 14-amino acid peptide at C-terminus using synthesized peptides with different size of amino acid sequence. The C9 complement-binding of the 14-amino acid peptide and its interference in the C9 polymerization and the complement-mediated lysis of rabbit erythrocytes was investigated.
  
  
  RESULTS
  The protein interaction between human C9 and native Ts-Pmy was further confirmed by immunoprecipitation with T. spiralis lysates. The fragmental expression and C9 binding assays identified that the binding region of Ts-Pmy to C9 is located within 831-885 of Ts-Pmy C-terminus. The exact binding site on Ts-Pmy to C9 was narrowed down to 14 amino acid residues (⁸⁶⁶Val-⁸⁷⁹Met) by using different sizes of synthesized peptides. In the presence of the synthesized 14-amino acid peptide, human C9 polymerization and the hemolytic activity of the human complement was inhibited.
  
  
  CONCLUSIONS
  Our results revealed the precise molecular basis for T. spiralis to produce Ts-Pmy as an immunomodulator to evade the attack of the host complement system as a survival mechanism.
authors.forename: Xi
authors.initials: X
authors.lastname: Zhao
authors.forename: Yuwan
authors.initials: Y
authors.lastname: Hao
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.forename: Yuan
authors.initials: Y
authors.lastname: Gu
authors.affiliation: Department of Parasitology, School of Basic Medical Sciences, Capital Medical University, Beijing, China. zhuxping@ccmu.edu.cn.
authors.forename: Xinping
authors.initials: X
authors.lastname: Zhu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000909:Antibodies, Helminth / Q000276:immunology*; D000947:Antigens, Helminth / Q000276:immunology*; D003167:Complement Activation; D003186:Complement C9 / Q000276:immunology*; D015870:Gene Expression; D006461:Hemolysis; D006801:Humans; D057131:Immune Evasion; D007155:Immunologic Factors; D010449:Peptide Mapping; D011485:Protein Binding; D017208:Rats, Wistar; D011994:Recombinant Proteins; D017160:Trichinella spiralis / Q000276:immunology*; D014235:Trichinellosis / Q000276:immunology* / Q000469:parasitology; D014335:Tropomyosin / Q000276:immunology*
chemical_list: D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D003186:Complement C9; D007155:Immunologic Factors; D011994:Recombinant Proteins; D014335:Tropomyosin