Yersinia enterocolitica O:3 Outer Membrane Vesicles as a Platform for Complement Activation.

Area of Science:

• Microbiology
• Immunology
• Bacterial Pathogenesis

Background:

• Lipopolysaccharide (LPS) is a key component of Gram-negative bacterial outer membrane vesicles (OMVs).
• OMVs are implicated in bacterial pathogenesis and can trigger inflammatory responses.

Purpose of the Study:

• To investigate the role of OMVs from Yersinia enterocolitica (YeO3) in complement activation and systemic inflammatory response syndrome (SIRS).
• To determine how LPS chemotype and OMV characteristics influence virulence and host response.

Main Methods:

• Utilized YeO3 variants with different LPS chemotypes (S, Ra, Rd1, Re) to produce OMVs.
• Assessed complement activation by OMVs, LPS, and bacteria.
• Conducted in vivo experiments in mice with complement depletion.
• Analyzed OMV biodistribution, clearance, and secretion influenced by LPS structure and temperature.

Main Results:

• OMVs potently activated complement independently of LPS chemotype.
• A distinct polysaccharide fraction bound mannose-binding lectin (MBL).
• Complement depletion reduced SIRS severity in mice.
• LPS O-specific polysaccharide length influenced OMV biodistribution and clearance.
• Bacteria with truncated LPS (Rd1) secreted the most OMVs.
• Temperature shift increased secretion of smaller OMVs with less toxic lipid A.

Conclusions:

• OMVs contribute to Yersinia pathogenicity via complement activation.
• OMV potency as virulence factors depends on size, polysaccharide chain length, and lipid A structure.
• This study elucidates OMV-complement interactions in YeO3, expanding knowledge on Gram-negative bacterial virulence mechanisms.