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Haemolysin II is a Bacillus cereus virulence factor that induces apoptosis of macrophages

Seav-Ly Tran1, Elisabeth Guillemet, Maud Ngo-Camus

  • 1INRA, Unité MICALIS, UMR 1319, équipe GME, La Minière, 78285 Guyancourt, France.

Cellular Microbiology
|August 25, 2010
PubMed

Insights

Bacillus cereus uses Haemolysin II (HlyII) to induce apoptosis in immune cells, promoting bacterial infections. This discovery reveals HlyII as a key virulence factor in B. cereus pathogenesis.

Area of Science:

  • Microbiology
  • Immunology
  • Bacterial Pathogenesis

Background:

  • Bacillus cereus causes food poisoning and opportunistic infections.
  • B. cereus infections involve bacterial accumulation despite phagocyte presence.
  • Mechanisms of immune evasion by B. cereus are not fully understood.

Purpose of the Study:

  • Identify the toxic component in B. cereus supernatant responsible for macrophage cell death.
  • Elucidate the role of bacterial factors in circumventing host immune responses.

Main Methods:

  • Analysis of B. cereus supernatant to isolate toxic factors.
  • Investigating the mechanism of macrophage cell death induced by purified toxins.
  • Utilizing in vivo models (insects and mice) to assess bacterial virulence.
  • Employing genetic deletion of specific genes (hlyII) to study virulence reduction.

Main Results:

  • Haemolysin II (HlyII) was identified as the toxic component inducing macrophage apoptosis.
  • HlyII induces apoptosis via pore-forming activity, dependent on caspase 3 and 8.
  • Deletion of hlyII significantly reduced B. cereus virulence in vivo.
  • Apoptosis of immune cells was observed in Bombyx mori larvae infected with B. cereus.

Conclusions:

  • Haemolysin II (HlyII) is a novel virulence protein of Bacillus cereus.
  • HlyII induces apoptosis in phagocytic cells both in vitro and in vivo.
  • HlyII contributes significantly to B. cereus pathogenesis by targeting host immune cells.

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