Bio-weapon in the lettuce patch
The common cottontail rabbit — ubiquitous in forests, suburban woods and backyard gardens — seems an unlikely agent of bioterrorism. However, Jason Huntley in the Medical Microbiology and Immunology Department has rabbits on his radar; they’re the best-known reservoirs of the deadly pathogen and potential bio-weapon he‘s studying.
Francisella tularensis is a bacterium high on the U.S. government’s list of Category A Select Agents, a rogue’s gallery of molecular bad guys that also includes anthrax, botulism and plague. Capable of surviving in species that range from an amoeba in a freshwater stream to flies, ticks, mammals and humans, F. tularensis is the cause of tularemia, which can kill an adult in as little as five days.
Particularly worrisome, Huntley says, is how easily F. tularensis can be aerosolized. (Documented cases include those caused by inhaling the aftermath of sick or dead rabbits caught in lawn mowers.) “The bacteria could easily be dispersed by a small device,” he notes. “And all it takes is one Francisella bacterium to kill a human, whereas for anthrax it’s about ten thousand spores.”
Huntley and his group study aspects of proteins that exist on the bacteria’s surface. One such characteristic of these proteins is their role in virulence: How can F. tularensis cause life-threatening disease so quickly? “We now have evidence that these proteins are involved not only in the basic survival functions of the bacterium, but also in attaching to host cells, invading them and killing them,” he says.
“We also study the bacteria from a defensive standpoint, for vaccine development. Because Francisella kills so quickly, the body doesn’t have time to react, to create the antibodies and recruit immune cells necessary to kill the invader. Developing a vaccine would allow the human body to have those defense mechanisms already in place.”
Studying such deadly pathogens has profound implications for other diseases, he adds. “If you can understand how they cause disease, you can start to ask questions about how many other bacteria and viruses work: pneumonia, GI infections, skin infections. The list goes on and on.”
Funded by the National Institutes of Health, Huntley’s work is under consideration by the U.S. Department of Defense.