Dual Immunization with Lipoprotein Tp0663 and Flagellin FlaB3 Offers Augmented Protection against Treponema pallidum in Mice.

Syphilis is a significant multistage sexually transmitted infection caused by the bacterium Treponema pallidum. The pathogenesis of this pathogen remains inadequately understood, impeding the progress of syphilis vaccine development. Our prior study has demonstrated the potential of the Tp0663 protein as a viable candidate for a vaccine against T. pallidum. In the present study, we sought to explore the protective response of dual immunization using two different antigenic entities (i.e., flagellin FlaB3 and lipoprotein Tp0663) against T. pallidum in a murine model. Our investigation revealed that FlaB3 + Tp0663 can elicit robust humoral and cellular immune responses. In addition, the FlaB3 + Tp0663 vaccine demonstrated a notable reduction in the Treponemal burden within various anatomical sites of infected mice, including the blood, brain, liver, lymph nodes, spleen, and testicles. It is worth noting that the FlaB3 + Tp0663 vaccine suppressed the dissemination of T. pallidum in C57BL/6 mice. The findings demonstrate that T. pallidum flagellin FlaB3 may augment the immunoprotection of Tp0663. This represents a valuable practical perspective and offers insights into developing a syphilis vaccine.