Diane St. Germain
[log in to unmask]" type="cite">
[log in to unmask]" type="cite">To:  The George Mason University Community

Anne B. Verhoeven
PhD Biosciences Candidate

Date:   Thursday June 17, 2010
Time:   10:30 a.m. 
Place:  George Mason University
 	     Room 256, Bull Run Hall
	     Prince William campus
Dissertation Chair: Dr. Monique van Hoek
Committee members: Dr. Emanuel Petricoin III, Dr. Yuntao Wu, Dr. Timothy Born

Title: "An Analysis of Early Signaling Pathways Activated by Francisella Tularensis Infection"

A copy of the dissertation is on reserve in the Johnson Center Library, Fairfax campus.  The doctoral project will not be read at the meeting, but should be read in advance.

All members of the George Mason University community are invited to attend.


Francisella tularensis is a zoonotic, gram negative pathogen that in recent years has become a pathogen of increasing interest because of its bioterrorism implications.  Francisella has been classified as a Type A pathogen by the CDC.  It is capable of producing severe infection with doses as low as 10 organisms.  The possible threat of Francisella as a biological weapon makes understanding its specific pathogenicity of utmost importance. 
Francisella is an intracellular pathogen that enters the cell through an unknown method.  Infection from Francisella occurs in many different cell types, including macrophages, hepatocytes, and endothelial cells.  Once in the cell, Francisella is encapsulated in a phagosome.  Between 2-4 hours after the initial infection Francisella escapes the phagosome and proceeds to replicate in the hosts cytosol.  Previous studies have demonstrated that Francisella inhibits the release of pro-inflammatory cytokines such as TNF-alpha, IL-1, IL-12, and IL-8, thus hampering the ability of the innate immune system to respond to infection.  Also, there is an increase of IL-10 seen during Francisella infection.  IL-10 is an anti-inflammatory cytokine that further decreases the innate immune system response.  The lack of proper cytokine production might be caused by Francisella’s ability to block the TLR pathways, CR3 pathways, and the apoptosis pathways, further impeding the innate immune response.  Interestingly, Francisella does not employ any known secretion systems, such as type III or type IV secretion systems that are commonly found in pathogenic bacteria.  Nor does it produce toxins that could explain its ability to block cell signaling pathways.  The mechanism used by Francisella to directly interact with host cell pathways is still unknown.
We hypothesize that by looking at specific pathways that are activated during infection of J774A.1 macrophages by Francisella tularensis LVS and Francisella novicida, we will be able to obtain a phosphorylation map of activated host cell responses which could lead to novel therapeutics. The steps that we will use to accomplish this task are: 1) the use of Reverse Phase Protein Microarray analysis to generate a phosphorylation map of Francisella LVS and Francisella novicida infection in J774A.1 cells, 2) validation of this map through western blots and analysis of previous reported data on specific signaling pathways, 3) comparison of different phosphorylation maps of Francisella novicida and Francisella LVS to determine differences between the strains, and 4) in a separate study, we will examing changes in gene expression in human lung epithelial cells through the use of microarrays to determine the difference in host cell gene transcription between uninfected A549 cells and Francisella LVS infected A549 cells.