James E. Bina, PhD
443 Bridgeside Point II
450 Technology Dr.
Pittsburgh, PA 15219
Our research is centered on defining the molecular mechanisms used by bacteria to resist antibiotics and cause disease in humans. Our work currently focuses on two important gram negative human pathogens: Vibrio cholerae and Francisella tularensis.
V. cholerae is a highly motile gram-negative, facultative human pathogen that causes the potentially lethal diarrheal disease cholera. V. cholerae is a significant health threat in the developing world where this organism is responsible for an estimated 3-5 million cholera cases each year with a mortality rate of ~1.5%. Cholera is acquired by ingestion of food or water contaminated with V. cholerae. Upon ingestion, V. cholerae colonizes the small intestine where the organism produces a variety of virulence factors that lead to disease.
Virulence factor production in V. cholerae is induced in vivo in response to unknown stimuli. A key question in cholera research is to determine how these unknown stimuli effect gene expression in vivo. We recently showed that cFP, a cyclic dipeptide that is produced by V. cholerae, functioned as an inhibitor of virulence factor production. Since cFP is produced in a growth-dependent manner, and functions independently of the quorum sensing systems, we hypothesize that cFP functions as a novel cell density-dependent signaling molecule that regulates gene expression during pathogenesis. We are currently working to define the genes involved in cFP biosynthesis and to define the signal transduction pathway by which cFP inhibits virulence factor production. We are also exploring the possible use of cFP-like chemicals as novel anti-virulence therapeutics for cholera treatment.
In addition to the production of virulence factors, to cause disease V. cholerae must also protect itself from the antibacterial effects of toxic molecules that are present in the host gastrointestinal tract. V. cholerae does this by the expression of active efflux systems belonging to the RND family. The RND family efflux systems are ubiquitous transporters found among gram negative bacteria. The RND systems function to remove toxic molecules from within the cell and thus contribute to the evolution of antibiotic resistance. We have shown that the RND systems are also required for the production of virulence factors in V. cholerae. This suggested that there is a relationship between RND efflux activity and virulence gene expression and provided the first evidence that the RND efflux systems influence pathogenesis by a mechanism other than antimicrobial resistance. We are currently studying the genetic linkage between efflux and virulence factor production.
F. tularensis is a gram negative bacterium that causes the zoonotic disease tularemia. F. tularensis is one of the most infectious pathogens known with an LD50 of fewer than 10 bacteria. F. tularensis is most frequently transmitted to humans by insect vectors or the handling of contaminated material, but can also be transmitted by inhalation. Untreated, inhalation tularemia is associated with a 30-60% mortality rate. The high infectivity, high virulence, and easy of dissemination by aerosols have led to the development of F. tularensis as a bioweapon by several nations. These properties have also let to growing concerns about the potential use of F. tularensis in bioterrorism.
Very little is known about F. tularensis pathogenesis. During infection of mammalian hosts F. tularensis is believed to grow intracellularly in macrophages. Subsequently, F. tularensis inhibits both phagosome and lysosome fusion by an unknown mechanism. Recent findings suggest that F. tularensis, like Listeria monocytogenes, rapidly escapes the phagosome and resides and replicates within the cytoplasm of host cells. Following an initial growth lag, intracellular F. tularensis enters logarithmic growth by 12 hours post-infection and eventually induces apoptosis and cell death.
My laboratory is working on the development and application of Francisella-specific genetic tools to define potential virulence factors and vaccine targets in this organism. We employ multiple disciplinary approaches including genetics, genomics, biochemistry and immunology and are collaborating with investigators at Emory University and the University of Tennessee Health Science Center to characterize the function of F. tularensis genes in virulence and immune evasion.
Lab Member: Dillon Kunkle, Graduate Student