First Advisor

Rahul Raghavan

Date of Award

2015

Document Type

Thesis

Degree Name

Bachelor of Science (B.S.) in Biology and University Honors

Department

Biology

Subjects

Superoxide dismutase -- Metabolism -- Research, Coxiella burnetii, Q fever, Infection -- Pathogenesis

DOI

10.15760/honors.168

Abstract

Coxiella burnetii is the etiological agent of acute Q fever and highly fatal chronic endocarditis in humans. It is an intracellular bacterial pathogen that initially invades macrophages and thrives within a lysosome-like parasitophorous vacuole by modifying host processes. Expression analyses of THP-1 cells (human monocyte/macrophage cell line) using RNA-seq show differential expression of several host genes in C. burnetii infected cells when compared to uninfected cells. Mitochondrial Superoxide Dismutase (SOD2) expression is highly upregulated (8x) during C. burnetii infection as opposed to uninfected cells, but it is unknown if this expression pattern is a host immune response to suppress Coxiella growth or whether Coxiella induces it to promote its own intracellular growth. To understand the function of SOD2 during Coxiella infection in human macrophages, a targeted RNA silencing approach (siRNA) was used to knock down SOD2 gene expression in HeLa and THP-1 cells. An increase in the levels of C. burnetii infection would have indicated that the increased expression of SOD2 is a host response to control intracellular bacteria. Conversely, a decrease in C. burnetii numbers would have suggested that SOD2 expression is beneficial to Coxiella and is induced by the bacterium to promote intracellular growth. A significant transfection was not completed in the HeLa cell line, due to cytotoxicity of liposome delivery system. The change in bacterial growth in THP-1 cells that were transfected with a siRNA targeting the SOD2 transcript was insignificant. A gene expression analysis indicated that the success of the transfection was at about 30%, and therefore did not significantly affect the bacterial growth rate. When a more successful transfection method is optimized, the question can be revisited.

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Persistent Identifier

http://archives.pdx.edu/ds/psu/15555

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