How a potentially deadly bacterium that could be used as a bioterrorist tool eludes being killed by the human immune system is now better understood, University of Iowa researchers report in the December issue of the Journal of Leukocyte Biology.

This bacterium, Francisella tularensis, is found naturally in the Northern Hemisphere and can be contracted through certain insect bites, contact with infected rabbits or ingesting contaminated food, water or air.

Francisella tularensis rarely infects people. However, because the bacteria has the potential to be used as a bioterrorist tool there is increased interest in understanding how it functions, said Lee-Ann Allen, Ph.D., associate professor of internal medicine and microbiology at the UI Roy J. and Lucille A. Carver College of Medicine.

"The rate of tularemia or 'rabbit fever' infection has significantly declined since the 1940s. However, the bacteria would be very deadly as an aerosolized terrorist weapon -- inhaling as few as 10 bacteria could be potentially deadly," said Allen, who also is a staff researcher with the Veterans Affairs Iowa City Health Care System.

"We wanted to better understand how Francisella tularensis can overcome the body's innate immune response and cause disease. In addition, learning more about this bacterium can help us learn more about the overall human immune response to bacteria," she said.

The team focused on how Francisella tularensis evades being killed by a form of white blood cells called neutrophils. Normally, neutrophils can be quickly activated in response to infection, making them the equivalent of "first responders" for the human immune system, Allen said.

"We knew that Francisella could live inside other white blood cells called macrophages and not be killed by them," Allen said. "But little research had been done on the bacteria's survival in neutrophils.

"Early data indicated that neutrophils did no
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Contact: Becky Soglin
becky-soglin@uiowa.edu
319-335-6660
University of Iowa
19-Dec-2006