RelevanceThe 15 kDa lipoprotein of Treponema pallidum is a major immunogen during natural syphilis infection in humans and experimental infection in other hosts. The humoral and cellular immune responses to this molecule appear late in infection as resistance to reinfection is developing.
The complete genome sequence of Treponema pallidum has been determined and shown to be 1,138,006 base pairs containing 1041 predicted coding sequences (open reading frames). Systems for DNA replication, transcription, translation, and repair are intact, but catabolic and biosynthetic activities are minimized.
Treponema pallidum is a gram-negative spirochaete bacterium and there are at least four known subspecies: T. pallidum pallidum, which causes syphilis; T. pallidum pertenue, which causes yaws; T. pallidum carateum, which causes pinta; and T. pallidum endemicum, which causes bejel.
There is no vaccine for syphilis. The outer membrane of T. pallidum has too few surface proteins for an antibody to be effective. Efforts to develop a safe and effective syphilis vaccine have been hindered by uncertainty about the relative importance of humoral and cellular mechanisms to protective immunity and the fact that T. pallidum outer membrane proteins have not been unambiguously identified.