Involvement of the MyD88-independent pathway in controlling the intracellular fate of Burkholderia pseudomallei infection in the mouse macrophage cell line RAW 264.7
Article first published online: 22 JAN 2010
© 2010 The Societies and Blackwell Publishing Asia Pty Ltd
Microbiology and Immunology
Volume 54, Issue 5, pages 282–290, May 2010
How to Cite
Tangsudjai, S., Pudla, M., Limposuwan, K., Woods, D.E., Sirisinha, S. and Utaisincharoen, P. (2010), Involvement of the MyD88-independent pathway in controlling the intracellular fate of Burkholderia pseudomallei infection in the mouse macrophage cell line RAW 264.7. Microbiology and Immunology, 54: 282–290. doi: 10.1111/j.1348-0421.2010.00205.x
- Issue published online: 22 APR 2010
- Article first published online: 22 JAN 2010
- Received 26 August 2009; revised 22 December 2009; accepted 12 January 2010.
- Burkholderia pseudomallei;
- MyD88-independent pathway;
Burkholderia pseudomallei is a facultative intracellular Gram-negative bacterium which is capable of surviving and multiplying inside macrophages. B. pseudomallei strain SRM117, a LPS mutant which lacks the O-antigenic polysaccharide moiety, is more susceptible to macrophage killing during the early phase of infection than is its parental wild type strain (1026b). In this study, it was shown that the wild type is able to induce expression of genes downstream of the MyD88-dependent (iκbζ, il-6 and tnf-α), but not of the MyD88-independent (inos, ifn-β and irg-1), pathways in the mouse macrophage cell line RAW 264.7. In contrast, LPS mutant-infected macrophages were able to express genes downstream of both pathways. To elucidate the significance of activation of the MyD88-independent pathway in B. pseudomallei-infected macrophages, the expression of TBK1, an essential protein in the MyD88-independent pathway, was silenced prior to the infection. The results showed that silencing the tbk1 expression interferes with the gene expression profile in LPS mutant-infected macrophages and allows the bacteria to replicate intracellularly, thus suggesting that the MyD88-independent pathway plays an essential role in controlling intracellular survival of the LPS mutant. Moreover, exogenous IFN-γ upregulated gene expression downstream of the MyD88-independent pathway, and interfered with intracellular survival in both wild type and tbk1-knockdown macrophages infected with either the wild type or the LPS mutant. These results suggest that gene expression downstream of the MyD88-independent pathway is essential in regulating the intracellular fate of B. pseudomallei, and that IFN-γ regulates gene expression through the TBK1-independent pathway.