TBK1 does not play a role in the control of in vitro Burkholderia pseudomallei growth

Abstract

Burkholderia pseudomallei, the causative agent of melioidosis, is an important intracellular pathogen in tropical regions. TANK-binding kinase (TBK1), part of the pathway that induces transcription of Type I interferon genes, has been demonstrated to play an important role in controlling intracellular bacterial infections. To investigate the role of tbk1 in protecting against B. pseudomallei we developed tbk1-deficient cell lines by using shRNA for transient knockdown of the tbk1 gene in HeLa and RAW 264.7 cells. In tbk1-deficient RAW cells, the replication of invasive and non-invasive Escherichia coli was significantly increased at 48 h after infection compared with wild-type cells. The result was confirmed using Brucella melitensis in tbk1-deficient HeLa cells, which demonstrated a >1.5-2.0 log higher bacterial count at 6-48 h after infection compared to wild-type cells. By contrast, the growth of Burkholderia pseudomallei expressing either typical (A2) or atypical (G207) lipopolysaccharide was not significantly different between the tbk1-deficient and control cells. These results suggest that the tbk1 gene and its activation may be able to control invasive E. coli, non-invasive E. coli and B. melitensis growth but may not be able to control B. pseudomallei infection. The role of the tbk1 gene in proinflammatory cytokine induction and bacterial intracellular infection needs further investigation to identify mechanistic differences among the life cycles of various intracellular bacteria.

Involvement of the MyD88-independent pathway in controlling the intracellular fate ofBurkholderia pseudomalleiinfection in a mouse macrophage cell line (RAW 264.7)

“…Our results are consistent with those reported previously by another group of investigators, who demonstrated that TBK1 knockdown macrophages do not interfere with intracellular survival of this bacterium (20). Moreover, inactivation of TRIF, another adaptor molecule in the MyD88‐independent pathway, does not affect survival of infected animals, suggesting that only the MyD88‐dependent pathway is needed to control wild type infection (21).…”

Antimicrobial agents and Burkholderia pseudomallei: perspectives from Thailand

“…The data showed the same bacterial counts in TBK1 deficient cells and control cells. Thus the Myd88-independent pathway is not able to control B. pseudomallei infection, but is able to control Escherichia coli and Brucella melitensis [7]. Type II interferon (IFN-γ) is produced within the first 24 hours of interaction between the host and B. pseudomallei and has an important role to play against B. pseudomallei.…”