title: Identification of a virulence-related surface protein XF in piscine Streptococcus agalactiae by pre-absorbed immunoproteomics.
abstract: BACKGROUND
  Since 2009, large-scale Streptococcus agalactiae infections have broken out in cultured tilapia farms in China, resulting in considerable economic losses. Screening of the surface proteins is required to identify virulence factors or protective antigens involved in piscine S.agalactiae infections in tilapia. Pre-absorbed immunoproteomics method (PAIM) is a useful method previously established in our laboratory for identifying bacterial surface proteins.
  
  
  RESULTS
  A serine-rich repeat protein family 1 (Srr-1), designated XF, was identified by PAIM in piscine S. agalactiae isolate GD201008-001. To investigate the role of XF in the pathogenesis of piscine S. agalactiae, an isogenic xf mutant strain (Δxf) and a complemented strain (CΔxf) were successfully constructed. The Δxf mutant and CΔxf showed no significant differences in growth characteristics and adherence to HEp-2 cells compared with the wild-type strain. However the 50% lethal dose of Δxf was increased (4-fold) compared with that of the parental strain in a zebrafish infection model.
  
  
  CONCLUSIONS
  The findings demonstrated that XF is a virulence-related, highly immunoreactive surface protein and is involved in the pathogenicity of S. agalactiae infections in fish.
authors.affiliation: Key Laboratory of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Weigang No.1, Nanjing, 210095, Jiangsu, China. liugj100@njau.edu.cn.
authors.forename: Guangjin
authors.initials: G
authors.lastname: Liu
authors.affiliation: Key Laboratory of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Weigang No.1, Nanjing, 210095, Jiangsu, China. vszw@njau.edu.cn.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Weigang No.1, Nanjing, 210095, Jiangsu, China. liuyongjie@njau.edu.cn.
authors.forename: Yongjie
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Key Laboratory of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Weigang No.1, Nanjing, 210095, Jiangsu, China. yaohch@njau.edu.cn.
authors.forename: Huochun
authors.initials: H
authors.lastname: Yao
authors.affiliation: Key Laboratory of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Weigang No.1, Nanjing, 210095, Jiangsu, China. lucp@njau.edu.cn.
authors.forename: Chengping
authors.initials: C
authors.lastname: Lu
authors.affiliation: Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, 214081, China. xup@ffrc.cn.
authors.forename: Pao
authors.initials: P
authors.lastname: Xu
mesh_terms: D018829:Adhesins, Bacterial / Q000235:genetics / Q000276:immunology / Q000502:physiology; D000818:Animals; D005393:Fish Diseases / Q000382:microbiology*; D056945:Hep G2 Cells / Q000382:microbiology; D006801:Humans; D015151:Immunoblotting / Q000662:veterinary; D040901:Proteomics; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary; D013290:Streptococcal Infections / Q000382:microbiology / Q000662:veterinary*; D013292:Streptococcus agalactiae / Q000472:pathogenicity / Q000502:physiology*; D037521:Virulence Factors / Q000235:genetics / Q000276:immunology* / Q000502:physiology; D015027:Zebrafish / Q000382:microbiology
chemical_list: D018829:Adhesins, Bacterial; C524542:Srr-1 protein, Streptococcus agalactiae; D037521:Virulence Factors