A new vaccine candidate appears effective against chlamydia infections, scientists have discovered. Though treatments against the sexually transmitted disease exist, the development of a vaccine is considered crucial to stop its spread.

Around the world, about 113 million people suffer from chlamydia. In most cases, the infection is asymptomatic, which means it does not impact people's daily life but makes it harder to know for sure who is infected and easier for the disease to be transmitted.

Furthermore, many women can become infertile if they are not diagnosed and treated in time. This has made chlamydia a challenging global health issue.

A chlamydia vaccine would thus be beneficial but over the past few years, many scientists have tried to come up with one, without much luck.

In a recent study published in the journal Vaccine, researchers from McMaster University have tested a new chlamydia antigen against the most common species of chlamydia known as C. trachomatis .

They may have found the best vaccine candidate to date, to fight against the disease's ability to cause infertility.

Chlamydial antigen BD584

The antigen tested in this study is known as BD584, a vaccine candidate which consists of three proteins from C. trachomatis – the T3SS proteins. In the disease, these proteins are an essential factor influencing the virulence of the infection and intracellular replication.

In vitro, the antigen elicited neutralising antibodies that inhibited C. trachomatis infections. Subsequent experiments in mice showed BD584 was also able to reduce various symptoms of C. trachomatis. For instance, hydrosalpinx – which involves the fallopian tubes being blocked with serous fluids, potentially leading to infertility – was reduced by 87.5%.

This is a positive first step, but further research will now have to focus on testing the safety and effectiveness of BD584 against different strains of Chlamydia, before human trials can be considered.

"Vaccine development efforts in the past three decades have been unproductive and there is no vaccine approved for use in humans," concludes co-author David Bulir. "Vaccination would be the best way to prevent a chlamydia infection, and this study has identified important new antigens which could be used as part of a vaccine to prevent or eliminate the damaging reproductive consequences of untreated infections."