Media Releases

Research on gonorrhea uncovers new immune system trigger

June 11, 2015

Discovery by University of Toronto scientists could lead to new therapies and treatments

TORONTO, ON — Researchers at the Uni­ver­si­ty of Toron­to have uncov­ered how Gram-neg­a­tive bac­te­ria — a broad class of bugs that cause dis­eases rang­ing from gon­or­rhea to diar­rhea and pneu­mo­nia — can trig­ger a reac­tion from our immune sys­tem. This dis­cov­ery could lead to new ther­a­pies and treat­ments that use the immune sys­tem to fight infec­tions instead of antibi­otics.

Grad­u­ate stu­dent Ryan Gaudet, who works in the lab of Pro­fes­sor Scott Gray-Owen, made the break­through while inves­ti­gat­ing gon­or­rhea.

“This is a great exam­ple of how basic sci­ence research can lead to an unex­pect­ed dis­cov­ery,” says Gray-Owen, who is a pro­fes­sor of mol­e­c­u­lar genet­ics. He inves­ti­gates how bac­te­ria are able to invade healthy tis­sue and evade our oth­er­wise effec­tive immune respons­es. Neis­se­ria gon­or­rhoeae, the bac­te­ria that caus­es gon­or­rhea, is espe­cial­ly crafty.

Gon­or­rhea is a re-emerg­ing prob­lem because antibi­ot­ic-resis­tant super­bugs have begun to appear, includ­ing in the USA and Cana­da. The World Health Orga­ni­za­tion esti­mates that there are near­ly half a mil­lion new cas­es of gon­or­rhea occur­ring each day. Many peo­ple infect­ed show no signs or symp­toms as these stealthy bac­te­ria avoid detec­tion by the immune sys­tem. How­ev­er, if it becomes exposed, the immune sys­tem kicks into high gear, some­times with dev­as­tat­ing results. In these cas­es, it can cause an over­whelm­ing immune response that attacks not only the bac­te­ria, but also sur­round­ing tis­sue. In fact, gon­or­rhea remains a lead­ing cause of uter­ine scar­ring and steril­i­ty in women, and it can blind infants who are born to infect­ed moth­ers.

Gon­or­rhea also has a com­plex rela­tion­ship with HIV. Peo­ple with gon­or­rhea are more sus­cep­ti­ble to HIV, and peo­ple with HIV become more infec­tious when they encounter gon­or­rhea. Pre­vi­ous research has shown that this was tied to the immune response gon­or­rhea can trig­ger, but no one was sure why.

Gaudet’s research found that a type of sug­ar pro­duced by Gram-neg­a­tive bac­te­ria — called hep­tose — could trig­ger an immune response. Hep­tose is not made by humans, so it rep­re­sents a clear sig­nal that bac­te­ria have invad­ed the tis­sues. Such trig­gers are called pathogen-asso­ci­at­ed mol­e­c­u­lar pat­terns — or PAMPs — that act like flares to alert the immune sys­tem of a harm­ful pres­ence.

So what does this mean for HIV? HIV infects T‑cells, which are part of the immune sys­tem. It stays dor­mant until an immune response is ini­ti­at­ed. Once it is, T‑cells are acti­vat­ed and HIV can rapid­ly infect oth­er cells. So gonorrhea’s “flares” help HIV spread quick­ly.

Know­ing how to trig­ger an immune response, with­out the threat of spread­ing harm­ful bac­te­ria, can lead to new ther­a­pies Gaudet explains.

“There are a range of appli­ca­tions where we can use PAMPs to direct a pro­duc­tive immune response instead of using tra­di­tion­al drugs, rang­ing from treat­ments for infec­tious dis­ease to autoim­mune dis­ease and can­cer,” he says. Gaudet plans to inves­ti­gate those options as he com­pletes his PhD.

“The curi­ous thing is that oth­er bac­te­ria try to hide their hep­tose, while gon­or­rhea seems to release it inten­tion­al­ly. What we don’t under­stand is why gon­or­rhea is send­ing out its’ flares. Why does it want to cause an immune response?” says Gray-Owen. Fur­ther research will be done to answer that ques­tion.

The find­ings were pub­lished in lat­est issue of Sci­ence.

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For more infor­ma­tion, please con­tact:

Liam Mitchell
Temer­ty Temer­ty Fac­ul­ty of Med­i­cine
Uni­ver­si­ty of Toron­to
T: 416–978-4672
C: 647–522-2513
E: liam.mitchell@utoronto.ca