Open Collections

Persistence of Burkholderia pseudomallei, B. multivorans and B. cenocepacia : differential analysis by proteomics and activation of phosphoinositide-3 kinase

University of British Columbia

Persistent infection in mammalian hosts is one intriguing aspect of the study of human diseases. In order to gain insight into the establishment of persistence, this thesis will evaluate the bacterial and host components associated with persistence of two groups within the Burkholderia genus: Burkholderia pseudomallei and Burkholderia cepacia complex. Burkholderia pseudomallei causes septicemic melioidosis with a high rate of relapse; however microbial determinants of relapse are unknown. Proteins were analyzed from sequential B. pseudomallei isolates from primary and relapsing melioidosis. Analysis by iTRAQ revealed that factors required for nitric oxide detoxification (HmpA) and necessary for anaerobic growth (ArcA, ArcC, and ArcB) were highly expressed in the relapse isolate. 2D-PAGE revealed up-regulation of a putative hcp-1 protein in the primary isolate, and flagellin and HSP20/alpha crystalline in the relapse isolate. These observations provide targets for further analysis of latency and virulence of B. pseudomallei in patients with relapsing melioidosis. The role of the host phosphoinositide3-kinase/Akt (PI3K/Akt) signaling pathway in the interaction of Burkholderia cepacia complex (Bcc) species with human immortalized macrophages was explored. B. cenocepacia and B. multivorans are the most clinically important and prevalent of the Bcc members and are serious opportunistic pathogens in cystic fibrosis (CF) patients. This study evaluated whether these pathogens can differentially induce PI3K/Akt signaling pathway, which is important in cell survival. B. cenocepacia activated PI3K/Akt in multiple cell types and this activation proceeded faster after exposure to B. multivorans than to B. cenocepacia in macrophages. Both species promoted cell survival by preventing caspase 9 cleavage, and bacteria internalization was necessary for this process. Unlike, B. cenocepacia, B. multivorans induced PI3K/Akt mediated anti-apoptotic effect, faster NF-κB activation, and IκBα phosphorylation that was PIK3/Akt dependent. Macrophages exposed to B. cenocepacia induced greater proinflammatory cytokines release compared to B. multivorans. Internalization into macrophages of both species was PI3K regulated. These findings provide novel insights into the pathogenic mechanism underlying Bcc infection in CF. Together; this thesis provides data for the identification of mechanisms leading to the persistence of these bacteria in melioidosis and CF and may inform the design of therapeutic approaches for treatment in these diseases.

Text

2013-10-31

Attribution 3.0 Unported

http://hdl.handle.net/2429/42169

Pathology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by/3.0/