title: Mapping the binding between the tetraspanin molecule (Sjc23) of Schistosoma japonicum and human non-immune IgG.
abstract: BACKGROUND
  Schistosomal parasites can establish parasitization in a human host for decades; evasion of host immunorecognition including surface masking by acquisition of host serum components is one of the strategies explored by the parasites. Parasite molecules anchored on the membrane are the main elements in the interaction. Sjc23, a member of the tetraspanin (TSP) family of Schistosoma japonicum, was previously found to be highly immunogenic and regarded as a vaccine candidate against schistosomiasis. However, studies indicated that immunization with Sjc23 generated rapid antibody responses which were less protective than that with other antigens. The biological function of this membrane-anchored molecule has not been defined after decades of vaccination studies.
  
  
  RESULTS
  In this study, we explored affinity pull-down and peptide competition assays to investigate the potential binding between Sjc23 molecule and human non-immune IgG. We determined that Sjc23 could bind human non-immune IgG and the binding was through the interaction of the large extra-cellular domain (LED) of Sjc23 (named Sjc23-LED) with the Fc domain of human IgG. Sjc23 had no affinity to other immunoglobulin types. Affinity precipitation (pull-down assay) in the presence of overlapping peptides further pinpointed to a 9-amino acid motif within Sjc23-LED that mediated the binding to human IgG.
  
  
  CONCLUSIONS
  S. japonicum parasites cloak themselves through interaction with human non-immune IgG, and a member of the tetraspanin family, Sjc23, mediated the acquisition of human IgG via the interaction of a motif of 9 amino acids with the Fc domain of the IgG molecule. The consequence of this interaction will likely benefit parasitism of S. japonicum by evasion of host immune recognition or immunoresponses. This is the first report that an epitope of schistosomal ligand and its immunoglobulin receptor are defined, which provides further evidence of immune evasion strategy adopted by S. japonicum.
authors.affiliation: Key Laboratory of Zoonosis, The Ministry of Education, Jilin University, Changchun, China.
authors.forename: Chuang
authors.initials: C
authors.lastname: Wu
authors.forename: Pengfei
authors.initials: P
authors.lastname: Cai
authors.forename: Qiaocheng
authors.initials: Q
authors.lastname: Chang
authors.forename: Lili
authors.initials: L
authors.lastname: Hao
authors.forename: Shuai
authors.initials: S
authors.lastname: Peng
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Sun
authors.forename: Huijun
authors.initials: H
authors.lastname: Lu
authors.forename: Jigang
authors.initials: J
authors.lastname: Yin
authors.forename: Ning
authors.initials: N
authors.lastname: Jiang
authors.forename: Qijun
authors.initials: Q
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012549:Schistosoma japonicum / Q000378:metabolism*
chemical_list: D007074:Immunoglobulin G; D008565:Membrane Proteins; D011994:Recombinant Proteins