Spotted fever group (SFG) Rickettsia are obligate intracellular bacteria that are carried by
ticks. One such tick, Dermacentor variabilis is a vector for the etiologic agent of Rocky
Mountain spotted fever, R. rickettsii. These ticks also carry a non-pathogenic R. montanensis,
the agent used in this study. Interestingly, field data collected from infected D. variabilis
throughout the United States revealed that the majority of Rickettsia in ticks are non-pathogenic
species such as R. montanensis. Although ticks serve as both vector and reservoir hosts for SFG
Rickettsia, many questions regarding tick-Rickettsia interaction remain unresolved. Therefore,
the overall goal of this research was to study the relationship between ticks and Rickettsia,
specifically examining the molecular mechanisms of rickettsial infection of tick host. As SFG
Rickettsia can move between vertebrate and invertebrate hosts, the hypothesis is that conserved
mechanisms are utilized for invasion of both types of host cell. Biochemical inhibition assays
revealed that the tick molecules, PI 3-kinase, protein tyrosine kinases, Src, FAK, Rho GTPase
Rac1, N-WASP, Arp2/3 complex, actin, and V-ATPase are important for R. montanensis
invasion. Further studies were executed to molecularly and functionally characterize the tick
molecules, Arp2/3 complex and V-ATPase, which are central to rickettsial internalization. Full
length cDNA of Arp2/3 complex subunits and V-ATPase from D. variabilis were isolated.
Transcriptional profiles of Arp2/3 complex subunits and V-ATPase showed greater expression of
the mRNA in tick ovaries compared to midgut and salivary glands. In addition, to gain insight
into rickettsial invasion in nature, Arp2/3 complex inhibition assays were performed in tick
tissues. The results demonstrated the involvement of Arp2/3 complex in rickettsial entry into
midgut, ovary, and salivary glands. The tick molecules identified in this study may provide
novel points of intervention in the transmission of tick-borne rickettsial diseases.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-04152013-162204 |
| Date | 28 April 2013 |
| Creators | Petchampai, Natthida |
| Contributors | Macaluso, Kevin R., Thune, Ronald L., Hawke, John P., Elzer, Philip H., Schowalter, Timothy D. |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-04152013-162204/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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