Macroautophagy is essential for killing of intracellular Burkholderia pseudomallei in human neutrophils

Here, we show that survival of intracellular B. pseudomallei was significantly increased in the presence of 3-methyladenine or lysosomal cathepsin inhibitors. The LC3-flux was increased in B. pseudomallei -infected neutrophils.

Concordant with this result, confocal microscopy analyses using anti-LC3 antibodies revealed that B. pseudomallei -containing phagosomes partially overlapped with LC3-positive signal at 3 and 6 h postinfection. Electron microscopic analyses of B. pseudomallei -infected neutrophils at 3 h revealed B. pseudomallei -containing phagosomes that occasionally fused with phagophores or autophagosomes. Following infection with a B. pseudomallei mutant lacking the Burkholderia secretion apparatus Bsa Type III secretion system, neither this characteristic structure nor bacterial escape into the cytosol were observed.