Syphilis resurgence spurs global vaccine search

Researchers have gained new insights into the syphilis genome to aid in vaccine design.

Syphilis cases are the highest they have been in over 70 years, leading public health officials to seek new ways to halt the spread. Now, an international collaboration has used whole-genome sequencing to investigate the genomic diversity of the syphilis bacterium, finding universal proteins that could be used as vaccine targets.

Syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum subspecies pallidum (TPA). After appearing in Europe around 500 years ago, syphilis cases decreased once effective treatment with injectable penicillin became available in the 1950s. However, recently, syphilis has made an unwelcome comeback. According to the US Centers for Disease Control (GA, USA), there were 207,255 cases in the US in 2022, the highest since the 1950s.

As symptoms often go unnoticed, the disease can progress without treatment for years, making it easy to spread. Developing a vaccine for syphilis would be an effective way to control the spread; however, few studies have been carried out evaluating TPA for syphilis vaccine development.

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To address this, researchers at the University of North Carolina at Chapel Hill (NC, USA) carried out TPA whole-genome sequencing on samples from people with syphilis from four countries: Colombia, China, Malawi and the US.

The researchers analyzed the resulting data, compared it to publicly available data and mapped mutations to 3D models of the bacteria’s proteins. They found that although syphilis bacteria differed between continents, there were enough similarities to find targets for an effective global vaccine.

The team is now continuing their efforts to develop a syphilis vaccine. “This study highlights the power of collaboration,” said co-lead author Juan Salazar (University of Connecticut School of Medicine, CT, USA). “Our work here is not just about addressing a local health concern; it’s about contributing to a global solution for a disease that continues to affect millions worldwide.”