Virion stripping: A new role for bacterial proteases

Area of Science:

• Microbiology
• Virology
• Immunology

Background:

• Oral bacteria like Porphyromonas gingivalis (Pg) can translocate to the upper airways.
• Microbial interactions with host cells are crucial for antiviral defense, often mediated by pattern recognition receptors and interferon signaling.

Purpose of the Study:

• To investigate the role of Porphyromonas gingivalis in respiratory viral infections.
• To elucidate the mechanism by which Pg affects viral burden and host responses during Respiratory Syncytial Virus (RSV) infection.

Main Methods:

• Infection of wild-type mice with RSV.
• Analysis of viral loads and lung damage.
• Assessment of interferon lambda (IFN-λ) signaling pathways.
• In vitro studies on the effect of Pg proteases (gingipains) on RSV and Sendai virus (SeV).

Main Results:

• Pg translocation to the lungs significantly reduced viral loads and attenuated lung damage during RSV infection.
• Gingipains degraded envelope glycoproteins on RSV and SeV, impairing viral infectivity.
• Pg actively suppressed IFN-λ signaling in airway epithelial cells.
• Absence of IFN-λ signaling led to increased inflammation despite reduced viral load.

Conclusions:

• Porphyromonas gingivalis proteases (gingipains) directly inhibit viral infectivity by degrading viral surface proteins.
• This protease-mediated reduction in viral load diminishes respiratory viral infection severity independently of host interferon responses.
• Pg's proteolytic activity represents a novel mechanism of microbial defense against viral pathogens.