Mycobacterial escape from macrophage phagosomes to the cytoplasm represents an alternate adaptation mechanism

Sci Rep. 2016 Mar 16:6:23089. doi: 10.1038/srep23089.

Abstract

Survival of Mycobacterium tuberculosis (Mtb) within the host macrophage is mediated through pathogen-dependent inhibition of phagosome-lysosome fusion, which enables bacteria to persist within the immature phagosomal compartment. By employing ultrastructural examination of different field isolates supported by biochemical analysis, we found that some of the Mtb strains were in fact poorly adapted for subsistence within endocytic vesicles of infected macrophages. Instead, through a mechanism involving activation of host cytosolic phospholipase A2, these bacteria rapidly escaped from phagosomes, and established residence in the cytoplasm of the host cell. Interestingly, by facilitating an enhanced suppression of host cellular autophagy, this translocation served as an alternate virulence acquisition mechanism. Thus, our studies reveal plasticity in the adaptation strategies employed by Mtb, for survival in the host macrophage.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Physiological / immunology*
  • Autophagy / immunology
  • Cell Line, Tumor
  • Cells, Cultured
  • Cytoplasm / immunology*
  • Cytoplasm / microbiology
  • Cytoplasm / ultrastructure
  • Host-Pathogen Interactions / immunology
  • Humans
  • Immune Evasion / immunology
  • Macrophages / immunology*
  • Macrophages / microbiology
  • Macrophages / ultrastructure
  • Microscopy, Confocal
  • Microscopy, Electron, Transmission
  • Mycobacterium tuberculosis / immunology*
  • Mycobacterium tuberculosis / pathogenicity
  • Mycobacterium tuberculosis / physiology
  • Phagocytosis / immunology
  • Phagosomes / immunology*
  • Phagosomes / microbiology
  • Phagosomes / ultrastructure
  • Phospholipases A2, Cytosolic / immunology
  • Phospholipases A2, Cytosolic / metabolism
  • Transport Vesicles / immunology
  • Transport Vesicles / microbiology
  • Transport Vesicles / ultrastructure
  • Virulence / immunology

Substances

  • Phospholipases A2, Cytosolic