Researchers learn more about tularemia structures

Researchers at the Lawrence Livermore National Laboratory are learning more about how tularemia, a bacteria considered a significant biosecurity risk, persists in the environment and causes disease, according to a presentation on Sunday.

Geoffrey Feld, a postdoctoral researchers at LLNL, described his work on Sunday during a presentation called "Structure and Function of Two Putative Virulence Factors from Francisella tularensis." The presentation took place during the 58th Annual Biophysical Society Meeting in San Francisco.

Tularemia, also known as rabbit fever, has been weaponized in various parts of the world. Feld and his colleagues examined proteins secreted by F. tularensis that may contribute to the virulence of the bacteria.

Previous research efforts funded by LLNL and the National Institutes of Health found that amoebae may serve as a potential reservoir for tularemia bacteria in nature. The bacteria form dormant cells called cysts that allow the amoebae to survive unfavorable conditions. Further research led to the identification of proteins secreted by F. tularensis which are responsible for induction of the rapid encystment phenotype in amoebae.

Feld and his colleagues characterized two of the REP proteins, called REP24 and REP34, and started to describe their functions based on three-dimensional crystal structures.

"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.

Amy Rasley, the research team leader, and her team said that careful characterization of REP24 and REP34 may show how the organism persists in nature and causes disease.

Feld said that while the research could inform efforts to combat tularemia, further study is required to determine the protein targets in the host that REP proteins act upon and the mechanism REP proteins use to help the bacteria survive or cause disease.

The U.S. Centers for Disease Control and Prevention classifies tularemia as a Category A bioterrorism agent.

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