Research Shows Promise for Syphilis Vaccine

Research released on June 12, 2018 by mBio, a journal published by the American Society for Microbiology, has pinpointed exterior proteins on the syphilis-causing bacteria, Treponema pallidum (T. pallidum), that could serve as vaccine targets for syphilis.

University of Conneticut (UConn) Health microbiologists Justin Radolf and Melissa Caimano began analyzing the genetics of syphilis bacteria they collected from patients in Colombia, as well as the syphilis samples sent to them by collaborators in San Francisco, CA, and the Czech Republic. The pair began to notice that the strains from different places were very similar and that not many genes differed. 

According to UConn, in an organism with such a small genetic code, every gene must be essential; the genes would only mutate into a different form if it was a matter of life and death. 

The scientists were then posed with the question of what controls life and death for T. pallidum?

“They’re mutating to avoid the immune system,” Radolf said in a university press release.

Radolf and Caimano’s team suspected that these mutating genes coded for the proteins they were looking for, so they began testing them. They used a computer modeling program to model the proteins these genes would make and see if those proteins had the characteristic barrel shape that bacteria use for proteins on their outer membranes. The team concluded that this was the case.

The researchers then made the proteins and tested whether they folded into the barrel shape in real life. Then the team made antibodies for the proteins and showed that these antibodies did attach to the exteriors of intact T. pallidum bacteria, i.e., the antibodies found their mark, confirming the presence of the proteins. 

Proteins that mutate often to hide from the immune system are not good candidates for a vaccine, according to UConn. The next task for the research team was to go back through T. pallidum’s genetic code to find genes that coded for proteins in the outer membrane that never changed using the genes they had already found as clues.

“You want the best candidate outer membrane protein for a vaccine, the one that varies the least,” said Caimano.

The researchers plan to use the proteins they found to immunize rabbits. The team is also looking for more diverse types of syphilis to include in their work. According to the university, UConn researchers will be collaborating with researchers at the University of North Carolina to enroll patients in Guangzhou, China, and Lilongwe, Malawi, to ensure the syphilis they have been studying is representative of syphilis worldwide.

This research was funded by UConn Health, Connecticut Children’s Medical Center, and the National Institute of Allergy and Infectious Diseases.

Source: University of Connecticut