Comparison of serological detection effects of ELISA using rTpN17 or rTpN47 of Treponema pallidum as antigen with that of TPHA and TRUST

Objective: To clone tpn17 and tpn47 genes of Treponema pallidum and then construct their prokaryotic expression systems,to establish ELISAs based on rTpN17 and rTpN47 as antigens and to evaluate the sensitivity and specificity of the ELISAs for detection of serological diagnosis of syphilis.Methods: The whole length of tpn17 and tpn47 genes was amplified by PCR and then their prokaryotic expression systems were constructed.SDS-PAGE was used to measure the expression of the target recombinant proteins rTpN17 and rTpN47.Ni-NTA affinity chromatography was applied to extract rTpN17 and rTpN47,while Western blot was performed to determine the specific immunoreactivity of rTpN17 and rTpN47.By using rTpN17 and rTpN47 as the coated antigen,respectively,ELISAs(rTpN17-ELISA and rTpN47-ELISA) were established to detect serum samples from 200 healthy individuals,25 RA patients,17 SLE patients and 211 syphilis patients.The detection effects of the ELISAs were compared to those of TRUST and TPHA.Results: The sequence similarity of the cloned tpn17 and tpn47 genes was 100% compared with the corresponding sequences in GenBank.The expression outputs of rTpN17 and rTpN47 were approximately 37.2% and 26.8% of the total bacterial proteins,respectively.Both the extracted rTpN17 and rTpN47 could take place remarkable conjugation reactions to the sera with positive antibody against Treponema pallidum.The positive detection rate of TPHA(99.1%) was the highest(P0.001).The positive detection rates of rTpN17-ELISA(85.3%) and rTpN47-ELISA(84.3%) were similar(P0.05).The positive detection rates of TRUST(72.5%) was lower than that of rTpN17-ELISA (P=0.001) but similar to that of rTpN47-ELISA(P=0.014).The detection results of all the serum samples from healthy individuals,RA patients and SLE patients were negative,whereas 7.1%(3/42) of the samples from RA or SLE patients were positive.Conclusions: rTpN17 and rTpN47 are still maintaining their original immunoreactivity.The ELISAs using rTpN17 or rTpN47 as the antigen are rapid,simple and convenient,higher sensitivity and specificity methods for serological screening and detection of syphilis.