title: Trichinella spiralis paramyosin binds to C8 and C9 and protects the tissue-dwelling nematode from being attacked by host complement.
abstract: BACKGROUND
  Paramyosin is a thick myofibrillar protein found exclusively in invertebrates. Evidence suggested that paramyosin from helminths serves not only as a structural protein but also as an immunomodulatory agent. We previously reported that recombinant Trichinella spiralis paramyosin (Ts-Pmy) elicited a partial protective immunity in mice. In this study, the ability of Ts-Pmy to bind host complement components and protect against host complement attack was investigated.
  
  
  RESULTS
  In this study, the transcriptional and protein expression levels of Ts-Pmy were determined in T. spiralis newborn larva (NBL), muscle larva (ML) and adult worm developmental stages by RT-PCR and western blot analysis. Expression of Ts-Pmy at the outer membrane was observed in NBL and adult worms using immunogold electron microscopy and immunofluorescence staining. Functional analysis revealed that recombinant Ts-Pmy(rTs-Pmy) strongly bound to complement components C8 and C9 and inhibited the polymerization of C9 during the formation of the membrane attack complex (MAC). rTs-Pmy also inhibited the lysis of rabbit erythrocytes (E(R)) elicited by an alternative pathway-activated complement from guinea pig serum. Inhibition of native Ts-Pmy on the surface of NBL with a specific antiserum reduced larvae viability when under the attack of complement in vitro. In vivo passive transfer of anti-Ts-Pmy antiserum and complement-treated larvae into mice also significantly reduced the number of larvae that developed to ML.
  
  
  CONCLUSIONS
  These studies suggest that the outer membrane form of T. spiralis paramyosin plays an important role in the evasion of the host complement attack.
authors.affiliation: Department of Parasitology, School of Basic Medical Sciences, Capital Medical University, Beijing, People's Republic of China.
authors.forename: Zhifei
authors.initials: Z
authors.lastname: Zhang
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.forename: Junfei
authors.initials: J
authors.lastname: Wei
authors.forename: Yaping
authors.initials: Y
authors.lastname: Yang
authors.forename: Xiaoqin
authors.initials: X
authors.lastname: Chen
authors.forename: Xi
authors.initials: X
authors.lastname: Zhao
authors.forename: Yuan
authors.initials: Y
authors.lastname: Gu
authors.forename: Shijuan
authors.initials: S
authors.lastname: Cui
authors.forename: Xinping
authors.initials: X
authors.lastname: Zhu
mesh_terms: D000818:Animals; D015153:Blotting, Western; D003185:Complement C8 / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D003186:Complement C9 / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D015938:Complement Membrane Attack Complex / Q000037:antagonists & inhibitors; D004912:Erythrocytes; D005260:Female; D005455:Fluorescent Antibody Technique; D020869:Gene Expression Profiling; D006461:Hemolysis; D057131:Immune Evasion; D051379:Mice; D008813:Mice, Inbred ICR; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D011485:Protein Binding; D018510:RNA, Helminth / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017160:Trichinella spiralis / Q000276:immunology*; D014335:Tropomyosin / Q000276:immunology / Q000378:metabolism*
chemical_list: D003185:Complement C8; D003186:Complement C9; D015938:Complement Membrane Attack Complex; D018510:RNA, Helminth; D012333:RNA, Messenger; D014335:Tropomyosin