Macrophage activation in the presence of Burkholderia pseudomallei

Melioidosis is a potentially fatal disease caused by the soil dwelling bacterium Burkholderia pseudomallei. The disease is endemic in tropical and subtropical regions of the world but is primarily located in southeast Asia and in northern Australia. Acute melioidosis is characterised by a fulminating septicaemia that can result in death within days of exposure. The generation of sepsis results from a prolonged and or exaggerated stimulation of host immune cells by pathogens which culminates in the hyperproduction of inflammatory mediators. Stimulation of host cells by pathogens is facilitated by pattern recognition receptors which bind to microbial structures and initiate downstream signalling cascades. The most well studied pattern recognition receptors are those in the Toll-like receptor family (TLRs). Over the past decade a tremendous amount of work has been conducted to identify TLR specific ligands, TLR structures, associated signalling proteins and the cytokines produced by TLR activation. Understanding the nature of TLR mediated signalling in host cells is fundamental to elucidating the pathogenesis of sepsis and the improvement of clinical management. Up until 2007, no extensive publications had surfaced regarding TLR recognition of B. pseudomallei and the role of TLRs still remains an area of intense study. Therefore, the major focus of the research outlined within this thesis was the characterisation of TLR activation by B. pseudomallei during acute infection. This was achieved using infection studies in murine and human cell lines as well as in primary cells isolated from a previously characterised murine model of acute melioidosis. Primary cells were also isolated from partially resistant murine hosts and used in infection studies. To ascertain the degree of TLR activation by 26 B. pseudomallei isolates with varying levels of virulence, standard antibiotic protection assays were performed on RAW 264.7 macrophages and peritoneal exudate cells (PEC) challenged with B. pseudomallei. Reverse ...