Just like antharax and small pox, rabbit fever, aka tularemia, which in endemic in the United States, may be a risk to biosecurity as it has already been weaponized in different regions of the world.
At the 58th Annual Biophysical Society Meeting, which takes place Feb. 15-19, 2014, in San Francisco, Calif., Geoffrey K. Feld, a Postdoctoral researcher in the Physical & Life Sciences Directorate at Lawrence Livermore National Laboratory (LLNL), will describe his work to uncover the secrets of the bacterium Francisella tularensis
, which causes tularemia.
"Despite its importance for both public health and biodefense, F. tularensis
pathogenesis isn't entirely understood, nor do we fully understand how the organism persists in the environment," explained Feld.
Previous efforts, funded by both the National Institutes of Health and LLNL, demonstrated that amoebae may serve as a potential reservoir for the bacteria in nature. "Specifically, we demonstrated that amoebae exposed to fully virulent F. tularensis
rapidly form cysts -- dormant, metabolically inactive cells -- that allow the amoebae to survive unfavorable conditions," said Amy Rasley, the research team leader.
This encystment phenotype was rapidly induced by F. tularensis
in the laboratory and was required for the long-term survival of the bacteria. Further exploration led to the identification of secreted F. tularensis
proteins, which are responsible for induction of the rapid encystment phenotype (REP) observed in amoebae.
In the new work, Feld and colleagues characterized two of these REP proteins -- called REP24 and REP34 -- and began to describe their functions based on their three-dimensional crystal structures.
A big surprise finding was that these proteins resembled "proteases," which are proteins that cut other proteins in a specific manner. "Our preliminary data indicate that F. tularensis
bacteria lacking these proteins are diminished in their ability to infect or survive in human immune cells, which indicates that these proteins may also contribute to F. tularensis
virulence," Feld said.
Rasley and colleagues believe that careful characterization of these two novel F. tularensis
proteins may shed light on how this organism persists in the environment and causes disease.
"Ultimately, this type of research could inform efforts to combat the disease, although there is much work to do. Currently, we don't know the protein targets in the host -- amoeba, human, etc. -- that the REP proteins act on, nor do we know the mechanism by which the proteins could help F. tularensis
survive in the environment or cause disease," Feld said.
"Once these questions are elucidated, a broader understanding of environmental persistence and pathogenesis might lead to better diagnostics and/or novel countermeasures to combat tularemia," he added.