Related Experiment Video
Updated: Jul 8, 2026
Procedures for In Vitro Cultivation of Treponema pallidum, the Syphilis Spirochete
Published on: January 24, 2025
A human epithelial co-culture system reveals distinct host cell interaction behaviours for Treponema pallidum
Katia Capuccini1, Divenita Govender1, David Goulding1
1Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, UK.
Abstract:
Treponema pallidum subsp. pallidum, the causative agent of syphilis, remains difficult to study owing to long-standing limitations in in vitro cultivation. Although a rabbit epithelial cell co-culture system (Sf1Ep) enabled major advances, the absence of human cell-based models limits clinical relevance and mechanistic understanding of host-pathogen interactions. Here, we established a co-culture system using human epithelial cell lines capable of supporting T. pallidum growth in vitro. Six epithelial or epithelial-like cell lines from diverse tissues were evaluated under microaerophilic conditions using standard cultivation medium. CAL-39 (vulva) and HepG2 (liver) supported T. pallidum survival, replication, characteristic growth behaviours, and long-term passage at levels comparable to Sf1Ep cells. Growth kinetics, attachment dynamics, and motility were quantified over extended culture. Using live-cell imaging, we defined two distinct host-cell interaction behaviours: surface-associated crawling and stable single-polar attachment. Both behaviours were observed across all tested cell lines but persisted only in those permissive for sustained growth. Together, our findings establish clinically relevant human epithelial co-culture models for T. pallidum, provide new insights into host-cell-dependent growth and motility, and create a platform for mechanistic studies of syphilis pathogenesis and vaccine target discovery.
Insights
Researchers developed new human cell models to study Treponema pallidum, the syphilis bacterium. These models enable better understanding of syphilis infection and host-pathogen interactions.
Area of Science:
- Microbiology
- Infectious Diseases
- Cell Biology
Background:
- Treponema pallidum subsp. pallidum causes syphilis but is difficult to culture in vitro.
- Existing rabbit cell models lack direct clinical relevance for human syphilis.
- Human cell-based models are needed for studying host-pathogen interactions.
Purpose of the Study:
- To establish and characterize human epithelial cell co-culture systems for T. pallidum growth.
- To investigate T. pallidum's in vitro growth, behavior, and host cell interactions in human cells.
- To create a platform for syphilis pathogenesis research.
Main Methods:
- Evaluated six human epithelial cell lines for T. pallidum co-culture under microaerophilic conditions.
- Quantified T. pallidum growth kinetics, attachment, and motility using live-cell imaging.
- Assessed long-term survival and replication of T. pallidum in permissive cell lines.
Main Results:
- CAL-39 (vulva) and HepG2 (liver) cell lines supported T. pallidum survival, replication, and growth comparable to rabbit cells.
- Identified two distinct T. pallidum host-cell interaction behaviors: crawling and stable polar attachment.
- Observed that persistent interactions correlated with sustained T. pallidum growth.
Conclusions:
- Established clinically relevant human epithelial co-culture models for T. pallidum.
- Provided novel insights into T. pallidum's host-cell-dependent growth and motility.
- Created a foundation for syphilis pathogenesis and vaccine target discovery studies.
