Virulence factors perforate the pathogen-containing vacuole to signal efferocytosis

Area of Science:

• Microbiology
• Immunology
• Cell Biology

Background:

• Intracellular pathogens evade immune responses by residing within host cells, primarily macrophages.
• Host cell death poses a risk by exposing these pathogens to the extracellular environment.
• Pathogens must have strategies to survive or spread upon host cell lysis.

Purpose of the Study:

• To investigate how intracellular pathogens evade immune detection during host cell death.
• To identify pathogen-derived mechanisms that facilitate survival and dissemination upon macrophage lysis.
• To elucidate the role of host cell lysis in pathogen-host interactions.

Main Methods:

• Investigated Salmonella and Brucella interactions with macrophages during cell death.
• Utilized genetic manipulation of bacterial virulence factors, including type III and type IV secretion systems.
• Assessed complement deposition on bacteria within pore-induced intracellular traps (PITs).
• Analyzed the role of efferocytosis in pathogen survival and dissemination.

Main Results:

• Intracellular pathogens utilize virulence factors to perforate the pathogen-containing vacuole (PCV) membrane during host cell death.
• This perforation leads to complement deposition on bacteria, forming a "find-me" signal.
• Complement-mediated signaling triggers efferocytosis by new phagocytes, such as neutrophils.
• Efferocytosis by neutrophils shelters bacteria from the host's respiratory burst.

Conclusions:

• Intracellular pathogens have evolved a strategy to exploit host cell death for dissemination.
• Virulence factor-induced perforation of the PCV generates a complement-dependent signal for efferocytosis.
• This mechanism allows pathogens to transition to new host cells, ensuring their survival and propagation.