Streptococcus agalactiae glycolipids promote virulence by thwarting immune cell clearance

Area of Science:

• Microbiology
• Molecular Biology
• Immunology

Background:

• Group B Streptococcus (GBS) causes neonatal meningitis, often after gut colonization.
• Bacterial glycolipids are vital for host-pathogen interactions, but their precise roles in GBS remain unclear.
• GBS produces three main glycolipids: Glc-DAG, Glc2-DAG, and Lys-Glc-DAG.

Purpose of the Study:

• To identify the enzyme responsible for Glc-DAG biosynthesis in GBS.
• To investigate the collective role of GBS glycolipids in bacterial virulence and host defense evasion.

Main Methods:

• Utilized a murine model of neonatal meningitis to simulate late-onset disease (LOD).
• Generated and analyzed a GBS mutant lacking the IagB enzyme (GBS∆iagB).
• Assessed bacterial survival, gut-epithelial barrier traversal, and susceptibility to host immune factors.

Main Results:

• Identified IagB as the enzyme essential for Glc-DAG synthesis, a precursor for other GBS glycolipids.
• The GBS∆iagB mutant exhibited attenuated bloodstream survival and reduced brain bacterial loads compared to wild-type GBS.
• GBS∆iagB showed increased susceptibility to neutrophil killing and antimicrobial peptides.

Conclusions:

• GBS glycolipids, synthesized via IagB, are critical for protecting bacteria from host antimicrobial killing.
• This study uncovers a novel function of GBS glycolipids in evading host immune responses, impacting GBS pathogenesis.