DOI
https://doi.org/10.25772/BGJT-CX53
Author ORCID Identifier
0000-0001-8248-7665
Defense Date
2017
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Microbiology & Immunology
First Advisor
Dr. Janina P. Lewis
Second Advisor
Dr. Todd Kitten
Third Advisor
Dr. Kimberly Jefferson
Fourth Advisor
Dr. Christina Moyer
Fifth Advisor
Dr. Dennis Ohman
Sixth Advisor
Dr. Darrell Peterson
Abstract
Periodontal diseases (PD) affect 46% of American adults over age 30. These diseases cause symptoms including bleeding and swelling of the gums, bone resorption, and tooth loss, that affect quality of life and have a high economic burden. Periodontal diseases are caused by an imbalance in the oral microbiome, from a healthy state that contains anti-inflammatory commensals like Streptococcus gordonii and mitis, to a diseased state that has pro-inflammatory anaerobic pathogens including Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, and Tannerella forsythia. The latter initiate disease progression in the oral cavity. However, it’s the host immune response that causes a majority of the symptoms. Ideally, treatment for PD would be approached from both sides to reduce the numbers of pro-inflammatory bacterial cells in the oral cavity but also reduce the host immune response. A novel therapeutic, amixicile, has been created, which specifically targets anaerobes through the pyruvate:ferredoxin oxidoreductase (PFOR) system, the mechanism of energy metabolism found in anaerobic organisms. Our studies show that amixicile inhibits in vitro growth of oral anaerobes in monospecies cultures at concentrations as low as 0.5 µg/mL in broth and 1 µg/mL in biofilms, without affecting the Gram-positive commensal species. In multispecies cultures, amixicile specifically inhibited anaerobes, even in biofilms, with the concentration as low as 5 µg/mL in broth and 10 µg/mL in biofilms. By not affecting the commensal bacteria, we think this treatment could restore a healthy oral microbiome. Aside from the bacterial presence, the host response, particularly the innate immune response is not well understood. Using a Drosophila melanogaster infection model, we elucidated the innate immune response to both mono- and multispecies infections. The 7-Species infection included bacteria mentioned above and Aggregatibacter actinomycetemcomitans in order to replicate in vivo-like disease conditions. We determined that both Drosophila Toll and Imd pathways, which mimic TLR/IL-1 and TNF signaling pathways of mammalian innate immunity respectively, respond to the 7-Species challenge. We also verified virulent bacteria in Drosophila, including P. gingivalis and P. intermedia. Future directions include RNA sequencing to determine the full scope of immune gene expression and using human immune cells to further clarify the response.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
12-15-2017