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The fight against gonorrhea gets a potential new weapon: a vaccine

Shot that curbs meningitis also appears to reduce infections of the sexually transmitted disease

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6:30pm, July 10, 2017
Gonorrhea

TWO-FOR-ONE  Gonorrhea culprit Neisseria gonorrhoeae (left, in false color) is genetically similar to bacteria that can cause meningitis, Neisseria meningitidis (right, in false color). That close relationship might explain why a vaccine that curbed meningitis in New Zealand also seemed to reduce gonorrhea infections.

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A vaccine against meningitis has an unexpected side effect: It appears to target gonorrhea, too. If confirmed, the results represent the first instance of a vaccine reducing gonorrhea infections.

After receiving a vaccine aimed at a type of meningitis, people were less likely to contract gonorrhea, scientists report online June 10 in the Lancet. That’s a big deal because worldwide each year, an estimated 78 million people contract gonorrhea, a sexually transmitted disease that can cause pelvic inflammation, infertility and throat infections. Gonorrhea’s bacterial culprit, Neisseria gonorrhoeae, has developed resistance to many antibiotics, making treatment much more difficult. Some strains of gonorrhea can now resist all known antibiotics, the Word Health Organization announced July 7.

“We are in desperate need for new therapies,” says Christine Johnston, an infectious disease specialist at the University of Washington in Seattle. Attempts to make a gonorrhea vaccine have failed so far. The new results are “the first to show that vaccination against gonorrhea could be possible,” Johnston says.

Finding the link between the two diseases was partly “a story of serendipity,” says study coauthor Helen Petousis-Harris, a vaccinologist at the University of Auckland in New Zealand. She and others had noted curious declines in gonorrhea cases in New Zealand, Cuba and, to a lesser extent, Norway after people had been vaccinated against a group B meningococcal bacterium, a pathogen that can cause meningitis and blood infections.

Bacteria that cause meningitis and gonorrhea are actually close kin, sharing 80 to 90 percent of their DNA. “There was certainly biological plausibility, but we needed some proof” that the vaccine really did curb gonorrhea, Petousis-Harris says.

She and colleagues looked at data from the New Zealand national vaccine registry to see who received a meningococcal vaccine that was available from 2004 to 2008, called MeNZB. That vaccination information was combined with data on over 14,000 15- to 30-year-olds who had either gonorrhea, chlamydia or both in New Zealand between 2004 and 2016.

Compared with unvaccinated people, those who had received the vaccine were about a third less likely to contract gonorrhea, the researchers found. The researchers had no information about people’s exposure to gonorrhea, only whether people were treated for the infection at a clinic. No such link was found between the vaccine and chlamydia.

MeNZB is a type of vaccine called an outer membrane vesicle vaccine. By mimicking bacterial bits released as the bugs proliferate, the vaccine trains the immune system to recognize and attack the bacteria. That exact vaccine is no longer in use, but similar vaccines exist, including Bexsero, which was used to treat a meningitis B outbreak at Princeton University in 2013.

The researchers don’t yet know what part of the MeNZB vaccine may be protective against gonorrhea. “We need to understand what was magical about this vaccine,” Petousis-Harris says. That knowledge could help researchers design a more targeted gonorrhea vaccine. Other meningitis vaccines ought to be scrutinized, too, Petousis-Harris says. “It might be that we’ve got a vaccine out there that could make a significant difference.”

Novartis, the health care company that developed Bexsero, provided funds for the study, but had no input on the design or results, Petousis-Harris says. A different company, GlaxoSmithKline, has since bought Novartis’ vaccine division.

Any new treatment for gonorrhea will eventually spur the bacteria to develop resistance, says Teodora Wi, a medical officer at WHO’s Department of Reproductive Health and Research in Geneva. But a vaccine couldn’t be evaded so easily. The current result “provides a very important breakthrough in the development of gonorrhea vaccines,” she says.

Citations

H. Petousis-Harris et al. Effectiveness of a group B outer membrane vesicle meningococcal vaccine against gonorrhoea in New Zealand: a retrospective case-control study. Lancet. Published online July 10, 2017. doi: 10.1016/ S0140-6736(17)31449-6.

Further Reading

B. Vastag. Tenacious STD: Drug-resistant gonorrhea is spreading. Science News. Vol. 171, April 21, 2007, p. 245.

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