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We Are One Step Closer To A Syphilis Vaccine

02/13/2017 09:15 EST | Updated 02/13/2017 09:15 EST
Bloomberg via Getty Images
AUSTRALIA - AUGUST 14: A syringe and vials of penicillin used in the treatment of syphilis are displayed in a lab at the Melbourne Sexual Health Centre in Melbourne, Australia, on Tuesday, August 14, 2007. Syphilis cases are rising among gay and bisexual men as new drugs reduce the threat of AIDS, and doctors warn the outbreak may spread to the wider community. (Photo by Carla Gottgens/Bloomberg via Getty Images)

As Valentine's Day approaches, most Canadians turn their thoughts to love and all that comes with it. However, for public health officials, this year is particularly worrisome in the love department. It's all due to the rather unwelcome realization sexually transmitted diseases are continuing to rise in this country and are showing no signs of slowing.

According to statistics from the Public Health Agency of Canada, the rate of these infections has been increasing since the beginning of the millennium. Worse, there appears to be no signs of slowing. Of the most notable agents, the most shocking re-emergence happens to be in the form of an old villain once thought to be controlled in this country. It's Treponema pallidum, or as we know it better, syphilis.

Before the year 2000, this bacterium was rarely seen in Canada with only a handful of cases per year. But over the next ten years, the rate increased almost five-fold. While this was concerning, public health officials didn't consider this to be a crisis.

Then last year, the perspective changed dramatically. The number of cases soared making headlines in every corner of the country. Making the situation even more troublesome was the combination of inappropriate antibiotic treatment as well as the development of resistance. Although this wasn't officially seen as a watershed moment, the early warning signal most definitely was sounded.

For years, public health officials have been calling for the development of a vaccine against this bacterium. In response, researchers have been attempting to figure out how to train the immune system to recognize and attack this microbial enemy. However, the challenge has been daunting and many attempts have failed. The lack of proper biological information has been a significant hurdle as has the issue of long lasting protection. Even if a vaccine is provided to an animal, it may not be able to fend off a real attack later on.

Although the situation may appear to be hopeless, a recent study from a group of researchers from the University of Victoria has given us reason to believe the tide may be changing. As they show in a publication released last week, there is a new vaccine candidate against this disease. Based on the results of trials in rabbits, we may be able once again to march forward.

The team focused on a particular protein found on the surface of the T. pallidum bacterium known only as Tp0751. It was discovered by a member of the team back in 2003, and held great potential for a vaccine as it led to an immune response in rabbits. If there was any chance a vaccine would work, this was the candidate to assess.

The first experiment was relatively straightforward. The team put Tp0751 into a vaccine formulation and then gave it to rabbits. After three weeks, the animals were tested for the development of antibodies against the protein. As expected, the immune system had reacted to the vaccine and had developed a response.

Next came the real test for the candidate. The rabbits first were either vaccinated with Tp0751 or given a control. Then, after three weeks, the skin was inoculated with an extremely high dose of the syphilis bacteria. Over the next two weeks, the animals were observed for any signs of infection on the skin. With any luck, the vaccinated animals would be able to stop the bacteria before they could do significant harm.

The results were promising. There were fewer lesions on the skin in the vaccinated animals and within those wounds, there were significantly fewer bacteria. This suggested at first glance the vaccine was working.

But this result alone didn't mean Tp0751 was going to be a successful candidate. It had to prove it could stop one of the hallmarks of syphilis infection: migration throughout the body. Thankfully, when Tp0751-vaccinated animals were examined, the bacteria for the most part did not leave the zone of infection. This meant the invaders were being kept from spreading outside of the original area of invasion.

The last test was designed to find out whether the immune system was the reason for the reduced burden of disease. Biopsies were taken from the animals and examined for the presence of the body's defensive troops, immunological cells. As the previous two results implied, the team found higher numbers of these soldiers in the lesions. This meant the vaccine had indeed prepared them for battle and they were going strong to control the area and protect the rest of the body.

Despite the good news of this work, the authors state the results of this study are preliminary. Yet there is renewed hope for the development of a vaccine against syphilis. The information gained will be used to conduct even more animal trials and eventually clinical work in humans.

In the meantime, those wishing to celebrate Valentine's Day in a certain special way should be aware of the risks. Unless you happen to know your partner is uninfected, be sure to keep yourself safe. While there may be several means to prevent pregnancy, when it comes to sexually transmitted diseases, the most effective means is barrier protection.

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