Abstract:
Burkholderia pseudomallei, the causative agent of melioidosis, is a facultative intracellular
gram-negative bacterium that can survive and multiply inside the macrophages. The signaling
pathway by which B. pseudomallei activates macrophage has not been elucidated. This study
demonstrated that B. pseudomallei was able to induce gene expression through MyD88-
dependent pathway (e.g. iκbζ, il-6, tnf-α, socs3) but failed to activate MyD88-independent
pathway (e.g. inos, ifn-β, irg1, socs1). Moreover, in the presence of cytochalasin D, the gene
expression in B. pseudomallei-infected macrophages was not affected, indicating that the
activation of these genes was likely triggered via surface receptors of the macrophages.
Examination of signaling by interaction of LPS to TLR showing that neutralizing antibody of
TLR4 failed to block the macrophages activation by B. pseudomallei LPS, suggesting that B.
pseudomallei LPS might use different types of TLR rather than TLR4 to activate the signaling.
IFN-γ not only enhanced gene expression of MyD88-dependent pathway but also restored the
gene expression of the MyD88-independent pathway and inhibited intracellular survival of B.
pseudomallei in the infected macrophages. These results suggest that the MyD88-independent
pathway is an essential pathway controlling B. pseudomallei survival in macrophages