Chlamydia vaccine research 'shows early progress'

“Could a nose spray prevent chlamydia?” asks the Daily Mail, one of several media outlets reporting on promising research to develop a vaccine for the sexually transmitted disease (STI).

Canadian researchers found mice treated with an experimental vaccine given as a nasal spray fought off infection with a mouse variant of chlamydia faster.

The laboratory mice also produced fewer bacteria that could pass on the disease, and were less likely to get damaged fallopian tubes as a result of the infection spreading.

Chlamydia trachomatis is one of the most common STIs in the UK, with more than 200,000 cases reported in 2015.

It can be treated with antibiotics, but the infection can spread around the body and lead to long-term health problems, including infertility, if left untreated.

People don’t always know they have chlamydia as it doesn’t always cause symptoms. This means they don’t get treated, and may pass the infection on to partners.

A vaccine that prevented infection or helped the body clear the bacteria quickly would help slow the spread of the disease, and could prevent infertility.

Numerous attempts to create a vaccine since 1957 have failed because of the rapid resistance of chlamydia to the vaccine, unwanted side effects, or even a worse response to chlamydia infection.

While research in animals is a necessary early stage in the development of many vaccines and medicines, what works in mice does not always work in humans.

We need to see more research before we know whether this vaccine will fulfil its promise.

Condom use and regular testing are the best protection against chlamydia.

Where did the story come from?

The study was carried out by researchers from MG DeGroote Institute for Infectious Disease Research, McMaster University and St Joseph’s Healthcare, all in Canada.

It was funded by the Canadian Institutes for Health Research. The study was published in the peer-reviewed journal, Vaccine.

The Daily Mail reported the study without mentioning the crucial fact that the research was carried out in mice, not humans.

BBC News did a better job, giving a clear overview of the study and the context of the research.

What kind of research was this?

This was a pre-clinical experimental study carried out with laboratory-bred mice. This type of study usually takes place in the early days of developing a vaccine or medicine.

Mice studies are usually followed by studies in other animals before the vaccine can be tested in a small number of humans to check for safety. Only then can a vaccine be tested in large-scale human trials to see how well it works.

What did the research involve?

Researchers tested a vaccine called BD584 on laboratory-bred mice – half had the vaccine and half a dummy vaccine. They tested the mice for production of anti-chlamydia antibodies.

They infected vaccinated mice with chlamydia bacteria, then tested them to monitor how quickly they fought off the virus and how many of them got a condition called hydrosalpinx, which is blockage of the fallopian tubes caused by infection.

The vaccine included three proteins from the membrane of the chlamydia bacteria thought to be important for enabling the bacteria to infect cells. It was administered as a nasal spray.

Five mice were given the vaccine and five others a dummy vaccine. The mice had blood tests afterwards to check for antibodies specific to chlamydia bacteria. These antibodies were tested in the laboratory to see whether they worked to neutralise bacteria.

Twenty mice (10 vaccinated and 10 controls) were infected with a mouse variant of chlamydia called Chlamydia muridarum.

They then had tests every couple of days to see how much bacteria they were shedding, and for how long.

The researchers compared the response of vaccinated and non-vaccinated mice.

At the end of the study, they checked to see how many mice in each group had signs of blocked fallopian tubes.

What were the basic results?

All mice given the vaccine produced antibodies to chlamydia, while no mice given the dummy vaccine did.

Vaccinated mice shed (produced and released) far less bacteria than unvaccinated mice, with a 95% reduction in bacterial shedding on days five and seven, compared with non-vaccinated mice.

No bacteria were detected in tests of vaccinated mice 32 days after infection, while control mice were still infected.

One of the 10 vaccinated mice showed signs of hydrosalpinx, compared with 8 out of 10 unvaccinated mice.

How did the researchers interpret the results?

The researchers said they showed the vaccine reduced bacterial shedding and the length of infection for mice infected with chlamydia, and that as a result “we speculate that immunisation with BD584 may decrease the transmissibility of chlamydia infections”.

They say it also “decreased the rate of hydrosalpinx from 80% to 10%, suggesting that BD584 may reduce infertility”.

Both of these factors, they say, show the vaccine “affords a significant degree of protection and could be an effective vaccine for human use”.

Conclusion

It’s easy to get carried away by headlines about vaccines for common and damaging diseases, but early-stage studies in mice don’t always translate into usable vaccines for humans.

People have been trying to find an effective vaccine against chlamydia since the bacteria was discovered in 1957, and research is still being carried out into several different vaccine candidates.

This vaccine may turn out to be effective, but it could become one of the many failed vaccine candidates seen over the years.

This is a small study in just 20 specially bred laboratory mice, and involved a type of chlamydia (Chlamydia muridarum) only mice get.

Much more work will be needed to see whether this experiment can be successfully repeated, and whether the vaccine is safe for use in humans, before we can even look at whether it is effective in preventing Chlamydia trachomatis in humans.

Read more about chlamydia prevention and sexual health.

Links To The Headlines

Could a NOSE SPRAY prevent chlamydia? World’s first vaccine for the STD ‘is showing promising results’. Mail Online, July 19 2016

Chlamydia vaccine ‘shows promise’. BBC News, July 20 2016

Links To Science

Bulira DC, Steven Lianga, S, Leec A, et al. Immunization with chlamydial type III secretion antigens reduces vaginal shedding and prevents fallopian tube pathology following live C. muridarum challenge. Published online June 17 2016