Dissertation
IDENTIFICATION OF GENETIC FACTORS AFFECTING HOST ADAPTATION AND INFECTIVITY BY THE LYME DISEASE SPIROCHETE
Doctor of Philosophy (PhD), Washington State University
01/2015
Handle:
https://hdl.handle.net/2376/111607
Abstract
Lyme disease caused by infection with the bacterial pathogen Borrelia burgdorferi, is the most prevalent vector-borne disease in North America. Persistent infection is due to the ability of B. burgdorferi to evade the host's adaptive immune responses, and can lead to severely debilitating clinical manifestations in humans including chronic arthritis and carditis. Identification of bacterial factors required for host-pathogen interactions involved in immune evasion, tissue colonization, and disease pathology could provide targets for novel therapeutics and vaccines. The published genome of B. burgdorferi revealed a relative absence of identifiable virulence factors based on sequence similarity to other known pathogens. As such, alternative methods of virulence factor identification are required. In this study, a combination of targeted genome modification and host-specific bacterial gene expression analysis were utilized in order to identify novel virulence determinants of B. burgdorferi.
Using targeted genomic modifications, results from Chapters Two and Three identified key regions of the B. burgdorferi linear plasmid lp17 that are required during persistent murine infection. A 317 bp region of lp17 was found to be required for adaptive immune avoidance, as the presence of this region was correlated with efficient peripheral tissue colonization and associated disease pathology in immunocompetent mice. Additionally, the lp17-encoded gene bbd18 was found to affect regulation of expression of the known virulence determinant OspC, and deletion of bbd18 and surrounding genes was correlated with decreased bladder tissue colonization.
In Chapter Four, an In Vivo Expression Technology (IVET) reporter system was developed in B. burgdorferi that allowed for identification of bacterial sequences that act as active promoters only during murine infection. IVET was demonstrated as an effective tool for the identification of in vivo-induced promoter elements of B. burgdorferi, and provided insights into the infection dynamics of this bacterium; however an inefficiency of recovery limited the utility of IVET for genome-wide promoter screening.
Collectively, this study utilized both established and novel techniques in order to successfully identify B. burgdorferi genetic elements that are important during mammalian infection. Future studies characterizing the mechanisms of action of these genetic elements could lead to improved strategies for combating this important human pathogen.
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Details
- Title
- IDENTIFICATION OF GENETIC FACTORS AFFECTING HOST ADAPTATION AND INFECTIVITY BY THE LYME DISEASE SPIROCHETE
- Creators
- Timothy Richard Casselli
- Contributors
- Troy Bankhead (Advisor)Kelly A Brayton (Committee Member)Viveka Vadyvaloo (Committee Member)Glen A Scoles (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Veterinary Medicine, College of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 147
- Identifiers
- 99900581732301842
- Language
- English
- Resource Type
- Dissertation