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Following in Real Time the Impact of Pneumococcal Virulence Factors in an Acute Mouse Pneumonia Model Using Bioluminescent Bacteria
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Pneumolysin: a double-edged sword during the host-pathogen interaction.

Helen M Marriott1, Timothy J Mitchell, David H Dockrell

  • 1Section of Infection, Inflammation and Immunity, University of Sheffield School of Medicine and Biomedical Sciences, Sheffield, UK.

Current Molecular Medicine
|September 11, 2008
PubMed
Summary
This summary is machine-generated.

Pneumolysin, a toxin from Streptococcus pneumoniae, forms pores and triggers immune responses. Its role in disease involves a complex balance between bacterial damage and host immunity.

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Area of Science:

  • Microbiology
  • Immunology
  • Toxicology

Background:

  • Pneumolysin is a key virulence factor produced by Streptococcus pneumoniae.
  • It is a cholesterol-dependent cytolysin, forming pores in cell membranes.
  • Pneumolysin also modulates host immune responses, including complement activation.

Purpose of the Study:

  • To explore the multifaceted roles of pneumolysin in bacterial pathogenesis.
  • To investigate its mechanisms of action, including cytolysis and immune modulation.
  • To understand the complex interplay between pneumolysin and host immune responses.

Main Methods:

  • Analysis of pneumolysin's protein structure and function.
  • Mutational analysis to identify critical domains and activities.
  • Investigation of host cellular responses, including gene activation and signal transduction.
  • Examination of immune cell interactions, such as Toll-like receptor 4 recognition and T-cell responses.

Main Results:

  • Pneumolysin binds cholesterol, oligomerizes, and forms membrane pores.
  • It activates the classical complement pathway and numerous host genes, some via epigenetic modification.
  • The toxin contributes to lung injury and neuronal damage through cytolytic and pro-inflammatory effects.
  • Host immune responses, including TLR4-mediated recognition and apoptosis induction, are crucial for bacterial clearance.

Conclusions:

  • Pneumolysin's pathogenesis involves both direct tissue damage and intricate modulation of host immunity.
  • Effective bacterial clearance depends on a balanced host response to pneumolysin.
  • Dysregulation of this balance, leading to excessive immunity or toxin-induced immune subversion, exacerbates disease.