Humans have been battling against syphilis infections for hundreds, if not thousands, of years. And yet even today the numbers of those infected is continuing to rise. But that might not be for much longer, as scientists are homing in on the potential targets for a vaccine that could help up get rid of the bacteria once and for all.
One of the main issues in treating syphilis comes down to the fact that it is not only the patient who is diagnosed that needs to be put on medication, but also whoever they happen to be having sex with, and in turn any of their recent partners too.
In general, people are pretty terrible about talking about their sexual partners and proclivities, particularly when it comes to sexually transmitted infections, and so it is no wonder that sometimes it can be an uphill struggle in tracking down all of those who may have been exposed to the bacteria and treating them.
This means that most see prevention as a far better way to tackle the disease than a cure. But there are a number of problems that scientists have repeatedly come up against when trying to develop a vaccine for syphilis.
The first is that unlike many other bacteria, Treponema pallidum cannot be grown in the laboratory. This means it is exceedingly hard to study, and thus figuring out how to target it is massively complicated. Apart from humans, the only other common animal to be infected by the microorganism are rabbits, but they clear the infection naturally too quickly to be of much use.
Studying the outside of the bacteria – which is critical if we are to develop an antibody that can target it – is further compounded by just how delicate the organisms are. While you can readily fix and study many other bacteria under a microscope, T. pallidum is far more fragile and so is easily broken up. This means that it can be tricky figuring out what proteins are usually found on its surface.
To try and get around this, the team decided to delve into the genome of the bacteria, which is mercifully small. From this they were able to find the genes that they suspected coded for the surface proteins, then use a computer model to see if they folded into the right shapes, and amazingly they did.
This has been a long time coming, as since the bacteria was first identified in 1905 no one has been able to pinpoint these proteins. But here they came up against the third issue.
The reason that syphilis is so good at infecting people is down to its ability to evade the immune system by rapidly changing these surface proteins. This makes them not only a poor target for our body’s own defense system, but also for any potential vaccine as they are simply too variable.
The team went back into the genome of the bacteria, and hunted down the genes that never changed – hoping that they were coding for proteins on the surface that themselves stayed stable. Incredibly, this is exactly what they were able to find.
The next step is to use these proteins to develop an antibody that could then be turned into a vaccine, and to see if it will allow them to immunize rabbits. If this works, it would be an astonishing move towards fighting such an archaic disease.
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