Development of an automated processing platform based on luciferase fused TPP17 to detect specific Treponema pallidum antibody in clinical serum with high sensitivity and rapidity.

Syphilis (T. pallidum) is a systemic and sexually transmitted disease. Over 80 % of syphilis infections are asymptomatic, and some patients tend to conceal high-risk sex histories. Therefore, fast and effective screening of syphilis is crucial to control its spread. In this study, a methodology, combining a luciferase immuno-magnetic separation system (LIMS) with an automated magnetic-processing machine, has been designed to detect syphilis-specific antibodies against TPP17 of T. pallidum. Protein A/G-immobilized magnetic particles captured the antibodies in serum and then were specifically labeled with a chimeric protein of TPP17 with a luciferase hGluc. The magnetic separation was automatically executed. It takes only 25 min from samples to results for 32 samples once. Further, for clinical samples, antibody-negative serum samples from pregnant women were unexpectedly found to have higher bioluminescence than regular sera. Innovatively, two cutoff values were determined. ROC (receiver operating characteristic) analyses showed both the sensitivity and the specificity of 100 % for the regular sera, and the sensitivity and the specificity of 96.5 % and 100 % for the sera during pregnancy. The methodology was 32 times more sensitive than ELISA. The automated platform can potentially be commercialized and would be of great significance in controlling the spread of syphilis.