Defense Date


Document Type


Degree Name

Master of Science



First Advisor

Janina Lewis


Periodontal disease is one of the most common human diseases. Bacteria trigger the onset and progression of the disease and among them Porphyromonas gingivalis has been demonstrated to be a major etiologic agent. Although the interaction of the bacterium with the host is of major importance for the understanding of the disease mechanisms, both the host as well as the pathogen components involved in the interaction remain poorly understood. One of the bacterial components capable of eliciting a host response is unmethylated CpG DNA motifs found in bacteria. Thus, the first aim was to determine the response of oral epithelial cell line, HN4, to challenge with genomic DNA derived from P. gingivalis. Microarray analysis revealed that at a level of 2-fold or more, 95 genes were regulated after 6 hrs, and 33 genes were regulated after 24 hrs post infection with P. gingivalis DNA when compared to unchallenged HN4 cells. Furthermore, since the Toll-like receptor 9 (TLR9) was demonstrated to be critical in generating the innate immune response to both bacterial and viral unmethylated CpG DNA in immune cells as well as some epithelial cell lines, investigation of the expression and localization of this receptor in HN4 cells was examined. In addition, changes in TLR9 expression and localization in response to HN4 cells challenged with P. gingivalis DNA was also investigated. Our flow cytometry results indicated that the receptor is present intracellularly but interestingly, is also detected on the cell surface. Last, shRNA technology was employed to down-regulate TLR9 expression in HN4 cells. This would provide a useful tool for future studies examining the role of TLR9 in mediating the host response to genomic DNA derived from P. gingivalis and other periodontopathogens.


© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

August 2008