Performance Of Novel Infection Phase-dependent Antigens In Syphilis Serodiagnosis And Treatment Efficacy Determination

Objective The objective of this study is to screen new antigens for syphilis serodiagnosis.Methods Firstly to identify the Treponema pallidum proteins Tp0971,Tp0768 and Tp0462 whether be infection phase-dependent antigens or not by observing the serum reactivity differences of New Zealand rabbits infected with activated or inactivated Treponema pallidum,the non-infection phase-dependent antigenTp92 membrane protein was used as the negative control group simultaneously.Secondly,Tp0971,Tp0768 and Tp0462 based ELISA were performed on 2138 human serum samples and compared with those of TPPA and LiZhu? Tp-ELISA.In addition,another 60 paired follow up human serum samples were analyzed to evaluate the relationships between the RPR titer change and the A450 nm difference values of Tp0971,Tp0768,Tp0462 and Tp92 antibodies measured by ELISA.Results Tp0971,Tp0768 and Tp0462 were notarized as infection phase-dependent antigens compared with Tp92(negative control).Compared with TPPA,the sensitivities of Tp0971,Tp0768 and Tp0462 based ELISA were 96.4%,96.9% and 93.0%,and the specificities were 97.7%,95.4% and 98.9%,resulting in consistencies of 97.1%,96.2% and 95.9%,respectively.Compared with LiZhu ? Tp-ELISA,the consistencies were 95.1%,94.2% and 94.0% with kappa values of 0.902,0.884 and 0.880 for Tp0971,Tp0768 and Tp0462 based ELISA,respectively.Tp0971,Tp0768 and Tp0462 demonstrated high sensitivities and specifities,and high conformance with TPPA and LiZhu? Tp-ELISA.Moreover,a significant positive spearman rank correlation coefficient(0.82,*P?0.05)was found between the A450 nm difference value of Tp0971 antibody with RPR titer change.Conclusion The infection phase-dependent antigensTp0971,Tp0768 and Tp0462 are promising antigens for syphilis diagnosis and Tp0971 may also be utilized in monitoring the efficacy of syphilis treatment.