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Hamilton lab makes discovery behind flesh-eating syndrome
A group of Montana scientists at Rocky Mountain Laboratories in Hamilton has figured out how the bug behind flesh-eating syndrome and other infectious ailments survives the attack of the body’s immune system.
In a paper published this week in the online version of the Journal of Immunology, Frank De Leo and his team of Rocky Mountain Labs scientists shows that group A Streptococcus bacteria senses the body’s impending immune attack, readies itself for the battle and can survive even the most intense onslaught of the body’s innate defenses.
By JENNIFER McKEE
Gazette State Bureau
Group A Strep causes strep throat, rheumatic fever and the deadly, deep infections known as flesh-eating syndrome.
The paper comes less than a year after De Leo and his team showed that strep can defeat the body’s front-line immune cells by commanding them to kill themselves.
"For anything to cause infection, it has to evade the neutrophil," De Leo said.
Neutrophils are the body’s first line of defense against disease and they typically wipe out unwelcome pathogens with efficiency. Neutrophils kill by "swallowing" an individual pathogen and sequestering it in a sack, De Leo said. It then pumps microbe-killing agents into the sack – a process that almost always wipes out the pathogen. Afterward, the neutrophil slowly and neatly kills itself.
But strep does something different, De Leo found. The bug senses the immune system coming.
"There’s elements in the neutrophils that tell the pathogen to mount a resistance," he said. "If they can initially sense the first few (immune system) cells that come in, then the subsequent bacteria that are growing and dividing are ready."
Neutrophils swallow the strep, he said. They put the bug in its special sack and let loose with their arsenal. But even as the immune system attacks the bug’s cell wall, strep is building it back up again. All the while, the bug is somehow telling the neutrophil to blow itself up.
It works.
Strep doesn’t have to live very long while under attack, De Leo said, just long enough to convince the neutrophil to kill itself.
"It is able to prolong its survival," he said. "It kills the cells and escapes and proliferates."
De Leo is not in the business of making new medicines. But his work sheds new light on how strep infections happen and they can be stopped.
The researchers discovered this by knocking out two genes of normal strep. Then, they inoculated some mice with the mutant strep and others with a normal strain of the bug.
"It’s clear that the mutant strain was much less dangerous," he said.
Rocky Mountain Labs is an arm of the federal National Institutes of Health.
Copyright © The Billings Gazette, a division of Lee Enterprises.
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