Battling a silent menace

Medical Sciences

- Jessica Gillies

Sexually transmitted infections aren’t something most of us like to talk or even think about. But when we do, syphilis doesn’t immediately spring to mind. After all, it’s a disease of the past, right?

Wrong. Syphilis rates are rising in BC and in the rest of Canada. The latest statistics reveal that BC has the highest reported rate of syphilis in Canada, with 6.9 cases per 100,000 people—more than double the rate of 10 years ago.

Dr. Caroline Cameron, a University of Victoria microbiologist and holder of the Canada Research Chair in Molecular Pathogenesis since 2006, is one of a handful of researchers who study this disease and the only one in Canada examining it at a basic science level.

Cameron is trying to understand how the syphilis bacterium, Treponema pallidum, attaches to the tissues of its host, how it passes through the tissue barrier and how it spreads to distant tissue sites.

“The syphilis bacterium is one of the most invasive organisms there is, and that’s partially because it’s corkscrew-shaped,” says Cameron. “It bores into tissues and is able to spread through the bloodstream to virtually every tissue and organ.”

Research on the fragile T. pallidum bacterium can be difficult. “When you try to use normal lab techniques on it, it breaks apart,” says Cameron. “Because it’s so technically challenging, there are very few investigators worldwide who work on it.”

But for Cameron, the challenge is exciting. “Treponema pallidum is fascinating,” she says. “It has shaped the history of the world; it’s still a problem; and there’s hardly anyone looking at it.”

There are three stages of syphilis. The primary stage appears as painless open lesions at the site of infection. These lesions may go unnoticed, especially if they occur internally, and therefore the disease goes untreated. In the secondary stage, an infectious rash appears, possibly with other symptoms.

In the third, or latent, stage the primary and secondary symptoms disappear. For 70 per cent of those infected, the disease will stay latent for the rest of their lives. But for the other 30 per cent, the disease enters the late stage and can lead to tissue destruction, insanity and death. This stage can occur at anywhere between two to 50 years after infection.

The bacterium enters the body through a mucous membrane or a break in the skin. From there, it moves to the bloodstream and then to the rest of the body. It’s this movement into and out of the bloodstream that is the focus of one of Cameron’s projects.

The bacterium attaches to specialized tissue, called the “basement membrane,” that lines blood vessels. One of the key components of this basement membrane is a substance called laminin.

“I have identified a protein from the bacterium that binds to laminin, so we now know how it is attaching,” she says. “Our goal is to prevent that binding by coming up with inhibitors or even a vaccine to stop it from getting into the bloodstream.”

Cameron is also working on two other T. pallidum projects: she’s investigating the proteins that are important to the development of the disease, and she’s developing an improved diagnostic test for syphilis.

In its early stages, syphilis is easily treatable with antibiotics. “In theory, we should be able to eradicate this disease from the globe, but that’s not happening,” says Cameron. In the developing world, lack of access to antibiotics is a big factor. In developed nations, the continued prevalence of syphilis is more complex, she says.

“The fact that syphilis is still here demonstrates that current public health measures are not sufficient to eliminate this disease.”

And it clearly shows the need for new ways to combat the disease. “The best way to accomplish this is through a greater understanding of the mechanisms of infection,” she says. “Research will enable us to conquer this pathogen and develop new methods for diagnosis and prevention.”

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Keywords: Sexually transmitted infections, diseases, research

People: Caroline Cameron

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