Research conducted by Kansas State University biochemists discovered that Stappholoccacus aureus secretes a family of proteins that prevent neutrophil serine proteases, or NSPs, from working properly an important finding for understanding how infections become rooted.


Image Credit: Kansas State University

 Where do the cells of your body turn when a fire bursts to life? Your body is much like a big city metropolis, and the cells of your body do just how any person might react in such an emergency, you call the Fire Department! Your body's response is to release extra neutrophils in the blood. These neutrophils rush to the scene, the first responders in a messy, disordered, chaotic scene, this all, in addition to the subtle burn of fever from the microbial infection.

Neutrophils respond first to the endotoxins emitted by pathogens. Endotoxins are in a family of proteins known to cause fever in infected individuals. The word endotoxin itself comes from the Greek word éndon, within, and Latin toxicum "poison" literally meaning 'poison within', or sometimes referred to as the 'fire within' to reference the symptoms of fever and inflammation common with bacterial infections.

Neutrophils work to recruit help before deploying their fire hose at the site of infection when they release neutrophil serine proteases (or NSPs) from intracellular granules, a kind of fire hydrant positioned along your city streets.

Because neutrophils are the first responders to the site of infection, researchers Brian Geisbrecht, a professor of biochemistry and molecular biophysics at the University of Kansas, and his research associate Kasra Ramyar, are studying Staphylococcus aureus, to understand what is preventing Neutrophils from completely dousing the infection as well as what is leading to an increase in the number of staph infections [1].

"To our knowledge, Staph is the first example of any bacterium that secretes protease inhibitors specifically to block an aspect of the host immune response that is essential for its removal from the body," Geisbrecht said.

In their research paper, Geisbrecht, Ramyar and collaborators discovered that S. aureus secretes a family of proteins similar to the endotoxin family -- called extracellular adherence proteins, or Eaps that prevents these neutrophil serine proteases (or NSPs) from working properly. Their discovery is an important finding to block staph and prevent other infections from starting.

While the Staphylococcus bacterium is typically considered a harmless organism most commonly found on the skin and in the nose, it becomes more serious, even deadly, if it invades the deeper tissues.

"Understanding this interaction can not only help us design better therapies in the future, but may help make current treatment regimens work better," Geisbrecht said.

"Our bodies respond vigorously to being invaded by S. aureus, and in order to prevent the infection from spreading, we have an arsenal of soluble molecules and white blood cells," Ramyar said. "That is our immune system, and neutrophils are a vital part of that."

This discovery puts a new twist on decades of research on how Staph infections begin. Currently Geisbrecht, Ramyar and colleagues are deciphering how their recent discoveries may affect certain interpretations based upon previous research.

"Bacterial pathogens like staph wouldn't be making these proteins if they weren't important to the context of infection," said Geisbrecht.

"The bacteria are trying to shut off the inflammatory response and we should be paying attention to how they're doing it."


Journal Sources/References

Some of the above materials have been provided courtesy of Kansas State University

[1] D. A. C. Stapels, K. X. Ramyar, M. Bischoff, M. von Kockritz-Blickwede, F. J. Milder, M. Ruyken, J. Eisenbeis, W. J. McWhorter, M. Herrmann, K. P. M. van Kessel, B. V. Geisbrecht, S. H. M. Rooijakkers. Staphylococcus aureus secretes a unique class of neutrophil serine protease inhibitors. Proceedings of the National Academy of Sciences, 2014; DOI: 10.1073/pnas.1407616111