Potential Biologic Warfare Agent Disables Neutrophil Response

Researchers have learned how the causative agent of tularemia, Francisella tularensis, infects and survives in blood cells that normally destroy invading bacteria. While F tularensis rarely infects people, its potential to be used as a bio-terrorist tool has generated increased interest in understanding its life cycle.

Investigators at the University of Iowa (Iowa City, USA) were primarily interested in finding out why despite being able to ingest F tularensis, human blood neutrophils were unable to kill them.

Results published in the December 2006 issue of the Journal of Leukocyte Biology demonstrated that the bacteria's ability to disrupt the neutrophils' "respiratory burst” was largely responsible for their ability to survive. This evidence was provided by luminol-enhanced chemiluminescence and nitroblue tetrazolium staining, which showed that neutrophils infected with live F tularensis did not generate reactive oxygen species.

"We wanted to better understand how Francisella tularensis could 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,” explained senior author Dr. Lee-Ann Allen, associate professor of internal medicine and microbiology at the University of Iowa. "The rate of tularemia 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.”



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