title: Sensitive and specific ELISA coated by TpN15-TpN17-TpN47 fusion protein for detection of antibodies to Treponema pallidum.
abstract: BACKGROUND
  We constructed an artificial fusion gene tpN15-17-47 and then used the prokaryotic expression fusion protein rTpN15-17-47 as the coated antigen to establish a new enzyme-linked immunosorbent assay (ELISA) for serological diagnosis of syphilis.
  
  
  METHODS
  tpN15, tpN17, and tpN47 genes were amplified separately by polymerase chain reaction (PCR) and then assembled into a fusion gene coding a trigeminy protein antigen by primer linking PCR. The target recombinant protein antigens rTpN15, rTpN17, rTpN-47, and rTpN15-17-47 were expressed and then purified antigens were immobilized on the surface of microplate wells for detecting Treponema pallidum-specific antibodies by ELISAs.
  
  
  RESULTS
  The relative positive rate of rTpN15-17-47-ELISA in 965 serum specimens of syphilis patients was 99.5%, which was higher than that of the T. pallidum hemagglutination assay (TPHA) (98.3%) (p<0.05) and much higher than that of the rTpN15-ELISA (83.1%), the rTpN17-ELISA (84.4%), the rTpN47-ELISA (82.1%), and the toluidine red unheated serum test (TRUST) (72.2%) (p<0.01). All the ELISAs and the TPHA in detecting serum specimens from 62 cases with systemic lupus erythematosus (SLE), 86 cases with rheumatic arthritis (RA), and 250 healthy cases were negative, but the TRUST was positive in five cases with SLE, seven cases with RA, and two healthy cases.
  
  
  CONCLUSIONS
  The rTpN15-17-47-ELISA is a sensitive and specific serological screening or a diagnostic method for syphilis in the clinical setting.
authors.affiliation: Faculty of Basic Medicine, Zhejiang Medical College, Zhejiang Hangzhou, PR China.
authors.forename: Ai Hua
authors.initials: AH
authors.lastname: Sun
authors.forename: Ya Fei
authors.initials: YF
authors.lastname: Mao
authors.forename: Ye
authors.initials: Y
authors.lastname: Hu
authors.forename: Qi
authors.initials: Q
authors.lastname: Sun
authors.forename: Jie
authors.initials: J
authors.lastname: Yan
mesh_terms: D000906:Antibodies / Q000097:blood* / Q000276:immunology; D015153:Blotting, Western; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D006801:Humans; D016133:Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification; D012680:Sensitivity and Specificity; D013587:Syphilis / Q000175:diagnosis; D014210:Treponema pallidum / Q000276:immunology*
chemical_list: D000906:Antibodies; D011993:Recombinant Fusion Proteins