Surface characterization of virulent Treponema pallidum

Area of Science:

• Microbiology
• Immunology
• Cell Biology

Background:

• Treponema pallidum, the causative agent of syphilis, possesses surface proteins crucial for host cell interaction.
• Understanding the molecular composition and function of T. pallidum's outer envelope is vital for developing effective diagnostics and treatments.

Purpose of the Study:

• To characterize the surface proteins of Treponema pallidum.
• To investigate the role of these proteins in the attachment of T. pallidum to eukaryotic cells.

Main Methods:

• [(125)I]lactoperoxidase-catalyzed iodination of intact T. pallidum organisms.
• Radioimmunoprecipitation and gel electrophoresis for protein identification and molecular weight determination.
• Cross-linking studies using dithiobis(succinimidyl)-propionate to assess protein organization.
• Adherence assays using T. pallidum and various eukaryotic cell monolayers (rabbit testicular cells, HEp-2 cells, macrophages).

Main Results:

• At least 11 outer membrane proteins (89K to 20K) were identified, all eliciting high antibody titers.
• Proteins of 89.5K, 29.5K, and 25.5K, previously implicated in attachment, were confirmed on the treponemal surface.
• Hydrophobic interactions were suggested for lower-molecular-weight proteins (60K, 45K, 30K).
• Trypsin treatment of T. pallidum reduced adherence, confirming a proteinaceous nature of attachment ligands.
• Periodate treatment of host cells significantly reduced treponemal attachment, indicating host membrane molecules mediate this interaction.

Conclusions:

• The study elucidates the proteinaceous nature of Treponema pallidum surface ligands involved in host cell attachment.
• Findings suggest a fluid outer envelope and specific host membrane molecules mediating treponemal parasitism.
• This research provides insights into the molecular mechanisms of syphilis infection and potential targets for intervention.