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Updated: Aug 19, 2026

Legionella pneumophila Outer Membrane Vesicles: Isolation and Analysis of Their Pro-inflammatory Potential on Macrophages
08:34

Legionella pneumophila Outer Membrane Vesicles: Isolation and Analysis of Their Pro-inflammatory Potential on Macrophages

Published on: February 22, 2017

IcmS-dependent translocation of SdeA into macrophages by the Legionella pneumophila type IV secretion system

J Patrick Bardill1, Jennifer L Miller, Joseph P Vogel

  • 1Department of Molecular Microbiology, Washington University, St. Louis, MO 63110, USA.

Molecular Microbiology
|March 19, 2005
PubMed

Insights

Legionella pneumophila uses the type IV secretion system (T4SS) to infect macrophages. A novel protein, SdeA, is secreted early, aiding in pathogen survival and virulence.

Area of Science:

  • Microbiology
  • Cell Biology
  • Infectious Diseases

Background:

  • Legionella pneumophila causes Legionnaires' disease, a severe pneumonia.
  • Bacterial replication within host macrophages relies on the dot/icm type IV secretion system (T4SS).
  • Dot/Icm substrates are thought to manipulate host endocytic pathways for bacterial survival.

Purpose of the Study:

  • Investigate the role of the SidE family of proteins in L. pneumophila virulence.
  • Determine the secretion mechanism and host cell interactions of SdeA.
  • Elucidate the function of SidE proteins in early macrophage infection.

Main Methods:

  • Immunofluorescence microscopy to visualize protein localization.
  • Adenylate cyclase fusions to study protein secretion.
  • Virulence assays in Acanthamoeba castellanii.

Main Results:

  • A SidE family member, SdeA, interacts with IcmS and is crucial for virulence.
  • SdeA is secreted into host cells by L. pneumophila in an IcmS-dependent manner.
  • SidE proteins localize to the replicative phagosome, suggesting a role in its formation and potential complex assembly.

Conclusions:

  • SidE proteins, particularly SdeA, are critical virulence factors secreted early during L. pneumophila infection.
  • IcmS is essential for the secretion of SdeA.
  • The localization of SidE proteins suggests they contribute to the assembly of a Dot/Icm effector complex on the phagosome.

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