Shuffling of DNA in a single gene might be why the syphilis bacteria can evade the immune system. The change alters a protein on its cell surface to create a distraction. People can become re-infected several times with syphilis because they can’t develop immunity, Untreated syphilis can hide in the body for decades. Genomic findings on these evasive strategies may point to designs for vaccines to outwit syphilis’ defenses.

The finding may help explain how syphilis can hide in the body for decades, thereby frustrating the immune system’s attempts to eradicate it. It might also account for the bacterium’s ability to re-infect people who had been previously been infected and should have acquired some immunity to it.

Although syphilis remains easily treated with penicillin, infection rates in the United States have increased steadily over the past two decades. The count rose to more than 115,000 new U.S. cases of the infection in 2018.

Worldwide there are an estimated 6 million new cases of syphilis among adults. The infection is responsible for an estimated 300,000 fetal and neonatal deaths annually.

However, despite its importance as a cause of disease, relatively little is known about the biology of Treponema pallidum.

One reason for this is that until recently it was impossible to grow it in a laboratory dish. As a consequence, many of the laboratory tools used to study other bacteria had not been developed for syphilis specifically.

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Materials provided by University of Washington Health Sciences/UW Medicine. Note: Content may be edited for style and length.