( was turned off in the M14 strain. This...)Solved: The mystery of flesh-eating bacteria's relentless attack

The mice receiving this peptide survived at a much higher rate than mice that did not receive it. The team also observed many white blood cells at the infection site in mice receiving the peptide.

Next, the team turned its attention to an important human immune system signaling molecule, interleukin-8. In healthy people, an infection triggers the production of interleukin-8, which acts as a distress call. "When the body senses an infection, it creates interleukin-8 to recruit white blood cells to the infection," said Hanski.

In a laboratory culture, the M14 strain of Streptococcus destroyed interleukin-8. But when the team added the SilCR protein to the growing bacteria, the interleukin-8 survived.

"The amount of interleukin-8 that survives is inversely related to how much SilCR there is in the culture," said Hanski. This may be one reason why some strains are less virulent than others; they might make more SilCR. "It would be interesting to study the amount of SilCR produced by the other strains and to determine their degree of tissue invasiveness." said Hanski.

The link between SilCR and a healthy immune response still did not explain the underlying mechanism. The team knew that SilCR itself did not degrade interleukin-8, so they began to search for the missing link in the chain of events. They expected to find an enzyme that degrades IL-8. Drawing on a database of enzymes and using advanced techniques that measure the levels of gene transcription products in a cell, they soon identified the culprit: an enzyme called ScpC.

The team then created a mutant variation of the M14 strain of Strep
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Source:Howard Hughes Medical Institute