MAY 22, 2018 03:39 PM PDT

Deadly Bacterium can Hijack Neurons

WRITTEN BY: Carmen Leitch

Plenty of people get strep throat; it is caused by a common bacterium called Streptococcus pyogenes. That bacterium can also cause flesh-eating disease, which impacts up to 1,200 people every year in the United States alone. It’s tough to diagnose, and can be fatal. New work by scientists at Harvard Medical School has found that the microbe uses neurons to its advantage; it hijacks the signals that are normally sent between the immune and nervous systems after infection or injury. Reporting in Cell, the researchers also suggest new ways to treat the disease.

Photomicrograph of Streptococcus pyogenes bacteria / Credit: CDC

"Necrotizing fasciitis is a devastating condition that remains extremely challenging to treat and has a mortality rate that's unacceptably high," said study senior investigator Isaac Chiu, assistant professor of microbiology and immunobiology at Harvard Medical School. "Our findings reveal a surprising new role of neurons in the development of this disease and point to promising countermeasures that warrant further exploration."

A flesh-eating infection, necrotizing fasciitis, usually begins with pain that’s rapidly followed by death in the surrounding tissue.  It can kill thirty percent of those infected, and the survivors may need extensive surgery or even amputation.

"We hope our findings can lead to new treatments for a condition that remains rare but can inflict significant damage and even death," said first author Felipe Pinho Ribeiro, a post-doctoral fellow in the Chiu lab.

After an injury, the nervous system first alerts the brain, which then feels pain; it sends a second signal to the immune system, to tamp down the immune response. Overactive immunity can do major damage to healthy tissue, so neurons try to prevent that from occurring.

"We believe this is the body's way of ensuring the delicate balance between alerting the body of brewing trouble while at the same time keeping overzealous immune cells at bay," Pinho Ribeiro explained. The bacterium exploits the communication between these systems to evade destruction by the body’s defense systems.

Chiu and colleagues, whose work is outlined in the video, wanted to know more about the role of neurons in the development of flesh-eating disease. Researchers had taken notice of a symptom seen in patients: they experience intense pain before other signs of the illness were visible. Using an animal model, the scientists found that a toxin made by the bacterium, streptolysin S, causes pain.

Additional research revealed that streptolysin S causes neurons to signal pain to the brain while also stimulating the release of a neurotransmitter called CGRP (calcitonin gene-related peptide), which tamps down the immune system. "Effectively, this neuronal signal silences the alarm system that normally calls on the body's infection fighters to curb infection," Chiu explained.

Clean wounds don’t need the immune system to come in and kill invading bacteria. But in the case of flesh-eating disease, the bacterium is able to call the immune system off so it can grow unimpeded. 

The investigators were able to block the progression of the infection by stopping the suppression of the immune system with CGRP-blocking molecules. They were also able to halt the disease by using botulinum toxin, which stopped the nerves from sending signals. Both therapeutics are already FDA-approved.

"Our findings provide a striking example of how closely intertwined the nervous and immune systems are and how intricate their interaction can be in the setting of infection," Chiu said. "Our study also underscores the therapeutic potential of modulating one system to affect the other as a way to treat infection."

 

Sources: AAAS/Eurekalert! via Harvard Medical School, Cell

About the Author
  • Experienced research scientist and technical expert with authorships on 28 peer-reviewed publications, traveler to over 60 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
OCT 22, 2019
Genetics & Genomics
OCT 22, 2019
A Pathogen That Has Evolved to Spread in Hospitals
Clostridium difficile is the primary cause of infections that are acquired in hospital settings; it causes diarrhea and intestinal inflammation....
OCT 22, 2019
Genetics & Genomics
OCT 22, 2019
Should We Use Epigenetic Tests to Verify Age Claims by Refugees?
  Around 70.8 million people have been forcibly displaced worldwide, with 37,000 people forced to leave their homes due to conflict or persecution eac...
OCT 22, 2019
Earth & The Environment
OCT 22, 2019
The methane-eating microorganisms in the ocean
New research published in the journal Limnology and Oceanography reveals part of the mystery behind a one million square kilometer patch of ocean in the Pa...
OCT 22, 2019
Microbiology
OCT 22, 2019
Electric Bacteria Form Undersea Networks of Conductivity
A team of scientists has found that bacteria can act like power lines, and send electrical currents over long distances....
OCT 22, 2019
Genetics & Genomics
OCT 22, 2019
Antibiotic-Resistance Genes Can Move From Humans to Animals
Researchers at Clemson University have been investigating how antibiotic resistance can move from humans into animals....
OCT 22, 2019
Drug Discovery & Development
OCT 22, 2019
New Potential Early Stage Treatment for Parkinson's
Parkinson’s Disease is the second most common neurodegenerative condition, affecting 35 million people globally. Currently without a cure, researcher...
Loading Comments...