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Could an effective chlamydia vaccine be on the horizon, despite failed previous attempts?

Fears about the negative effects following a previous attempt at a chlamydia vaccine could soon dissipate with hopeful new research.

Chlamydia is a disease that affects a large number of people each year, and if not detected early, it is the most preventable cause for blindness and can cause infertility.

Most people who are infected recover without symptoms, although they can infect others without knowing. But the rates of infection are startling. In the U.S., 1 million infections were reported in 2013, 100 million worldwide, which led the Centers for Disease Control and Preventions to declare it as, “the most commonly reported notifiable disease in the United States.” And it affects other species greatly as well — it’s a real threat to Koalas.

In the 1960s, a vaccine was created, which ended up having a reverse affect, actually putting more people at risk. Since then, creating a new vaccine has been challenging and basically put on hold for fear of similarly negative results. But there appears to be a potential solution moving forward, according to new research published in Science magazine.

A team led by Harvard Professor Ulrich von Andrian has announced a vaccine against chlamydia in mice. “This is really a very surprising and exciting observation,” von Andrian reported. “We used this vaccine to try to really understand an immune response that was previously not that well worked out. Now our vaccine gives very good protection, even against different chlamydia strains.”

The ’60s chlamydia vaccine used killed versions of the infectious agent, which were no longer able to breed. The injected bacteria couldn’t create an infection, but the body’s immune system could learn to recognize the invaders and generate new cells that could deal with a live dose.

IFLScience explained why this method was problematic:

The problem with previous vaccines, von Andrian’s team argue, is that chlamydia infects mucosal surfaces, such as the eyes and inside of the mouth. When the dead bacteria are first encountered within muscle or skin, the immune system remembers this context along with the bacteria, and becomes confused when meeting the live version on a mucosal surface. Sometimes the out-of-context exposure even induces tolerance, so the immune system leaves the bacteria alone.

For this reason, it’s important to administer the vaccine through mucosal pathways.

Von Andrian’s vaccine is injected in conjunction with charge-switching synthetic adjuvant nanoparticles (cSAPs) which strengthen the immune system’s response. While the use of adjuvants is standard for vaccines, cSAPs have the capacity to stick with the vaccine on the journey from a mucosal surface to the lymph nodes where the immune system is trained to recognize invaders.

“Mice that were given the cSAP vaccine very quickly eliminated chlamydia and were even faster at completely clearing it than the animals that had developed natural immunity after a previous infection,” von Andrian said.

Because of the previously unsuccessful attempt at a vaccine, von Andrian admits that it will be difficult to provide a worthwhile explanation for how this is different. He said, “It will be very hard to convince anyone to try your vaccine unless you can explain why there might have been this paradoxical effect 50 years ago and why we are confident that this paradoxical effect will not be observed with the current formulation.”

Still, he is confident that this new solution could be effective. He and his team have licensed the technology to biotech startup Selecta Biosciences.

Photo: Flickr user VCU CNS