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Aggregatibacter actinomycetemcomitans cytolethal distending toxin modulates host phagocytic function.

Taewan J Kim1,2, Bruce J Shenker1, Andrew S MacElory1

  • 1Department of Basic and Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, United States.

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Cytolethal distending toxin (Cdt) from Aggregatibacter actinomycetemcomitans impairs macrophage function by altering phosphoinositide signaling. This disruption compromises phagosome maturation and bacterial killing, potentially increasing infection susceptibility.

Keywords:
Aggregatibacter actinomycetemcomitansCytolethal distending toxinlocalized aggressive periodontitisphagocytosisphagosome maturationphosphoinositide

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Area of Science:

  • Microbiology
  • Immunology
  • Cell Biology

Background:

  • Cytolethal distending toxins (Cdt) are virulence factors produced by human pathogens.
  • Cdt induces inflammatory disease by activating inflammasomes in macrophages.
  • Cdt interferes with PI3K signaling by depleting PIP3 pools.

Purpose of the Study:

  • To investigate the effect of Aggregatibacter actinomycetemcomitans Cdt (Aa Cdt) on macrophage phosphoinositide metabolism and phagosome function.
  • To determine how Aa Cdt impacts phagosome maturation, lysosome fusion, and bacterial clearance.

Main Methods:

  • Macrophage exposure to Aa Cdt.
  • Analysis of phosphoinositide pools and Rab5 association on phagosomes.
  • Assessment of phagosome maturation, phago-lysosome formation, and bacterial survival.

Main Results:

  • Aa Cdt manipulates phosphoinositide pools and alters Rab5 association on phagosome membranes.
  • Macrophage exposure to Aa Cdt slowed phagosome maturation and decreased phago-lysosome fusion.
  • Cdt-exposed macrophages exhibited reduced bactericidal capacity, increasing Aa survival.

Conclusions:

  • Aa Cdt compromises macrophage phagocytic function by disrupting phosphoinositide signaling and phagosome trafficking.
  • Cdt's interference with host cell processes may contribute to increased susceptibility to bacterial infections.
  • This study reveals a novel mechanism of Cdt virulence in pathogenesis.