Surface antigens of the syphilis spirochete and their potential as virulence determinants

Emerg Infect Dis. Jan-Mar 1997;3(1):11-20. doi: 10.3201/eid0301.970102.

Abstract

A unique physical feature of Treponema pallidum, the venereally transmitted agent of human syphilis, is that its outer membrane contains 100-fold less membrane-spanning protein than the outer membranes of typical gram-negative bacteria, a property that has been related to the chronicity of syphilitic infection. These membrane-spanning T. pallidum rare outer membrane proteins, termed TROMPs, represent potential surface-exposed virulence determinants and targets of host immunity. Only recently has the outer membrane of T. pallidum been isolated and its constituent proteins identified. Five proteins of molecular mass 17-, 28-, 31-, 45-, and 65-kDa were outer membrane associated. The 17- and 45-kDa proteins, which are also present in greater amounts with the T. pallidum inner membrane protoplasmic cylinder complex, had been previously characterized lipoproteins and are, therefore, not membrane-spanning but rather membrane-anchored by their lipid moiety. In contrast, the 28-, 31-, and 65-kDa proteins are exclusively associated with the outer membrane. Both the purified native and an Escherichia coli recombinant outer membrane form of the 31-kDa protein, designated Tromp1, exhibit porin activity, thereby confirming the membrane-spanning outer membrane topology of Tromp1. The 28-kDa protein, designated Tromp2, has sequence characteristics in common with membrane-spanning outer membrane proteins and has also been recombinantly expressed in E. coli, where it targets exclusively to the E. coli outer membrane. The 65-kDa protein, designated Tromp3, is present in the least amount relative to Tromps1 and 2. Tromps 1, 2, and 3 were antigenic when tested with serum from infection and immune syphilitic rabbits and humans. These newly identified TROMPs provide a molecular foundation for the future study of syphilis pathogenesis and immunity.

Publication types

  • Review

MeSH terms

  • Animals
  • Antigens, Bacterial / genetics
  • Antigens, Bacterial / isolation & purification*
  • Antigens, Surface / genetics
  • Antigens, Surface / isolation & purification*
  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Outer Membrane Proteins / immunology
  • Bacterial Outer Membrane Proteins / isolation & purification
  • Bacterial Proteins / genetics
  • Bacterial Proteins / immunology
  • Bacterial Proteins / isolation & purification
  • Escherichia coli / genetics
  • Freeze Fracturing
  • Humans
  • Membrane Proteins / genetics
  • Membrane Proteins / immunology
  • Membrane Proteins / isolation & purification
  • Microscopy, Electron
  • Porins / genetics
  • Porins / immunology
  • Porins / isolation & purification
  • Rabbits
  • Recombinant Proteins / genetics
  • Recombinant Proteins / immunology
  • Recombinant Proteins / isolation & purification
  • Syphilis / etiology
  • Syphilis / immunology
  • Treponema pallidum / genetics
  • Treponema pallidum / immunology*
  • Treponema pallidum / pathogenicity*
  • Virulence / immunology

Substances

  • Antigens, Bacterial
  • Antigens, Surface
  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Membrane Proteins
  • Porins
  • Recombinant Proteins
  • Tromp1 protein, Treponema pallidum
  • Tromp2 protein, Treponema pallidum