My research has focused on investigating the host-pathogen interactions of Salmonella typhimurium with macrophage host cells. My primary tool has been two-dimensional gel electrophoresis which allows examination of the overall pattern of proteins in order to determine which proteins are induced, repressed, and unaffected by a given physiological condition. I have catalogued the cellular response that a certain strain of S. typhimurium makes in response to conditions within macrophage host cells. This was done by comparing the proteins induced during intracellular life with those induced in vitro by a variety of stress conditions. The in vitro stress conditions chosen were based on what was known about conditions within macrophage phagolysosomes. This work revealed that at least 36 proteins were induced in the intracellular condition and that induction of several of these proteins may be unique to the intracellular environment. Additional results from these experiments suggested that intracellular Salmonella existed in two populations: a few cells were rapidly dividing while a large number remained alive but were not actively growing.
My current goals are to investigate several aspects of pathogen-host interactions. I want to identify a number of the Salmonella proteins that are induced in the intracellular condition. It is now possible to cut proteins spots out of 2D gels and have amino acid sequencing done which allows matching of the unknown proteins to known genes in the sequence databases. Once genes of interest are identified in this way, it should be possible to create mutant strains that could be tested to determine whether the ability to grow within the host cell has been lost. In addition, the work that has been completed concerned just one strain of Salmonella and one cell line of macrophages, so it may also be useful to look at a variety of Salmonella strains in combination with macrophages from different sources. I am also planning to work with Dr. Joseph Carlin in using the 2D gel approach to investigate the interaction of the obligate intracellular pathogen, Chlamydia trachomatis, with host cells. I hope to be able to develop a catalogue of proteins important for this pathogen's virulence.