The CovS/CovR acid response regulator is required for intracellular survival of group B Streptococcus in macrophages

Area of Science:

• Microbiology
• Immunology
• Pathogenesis

Background:

• Group B Streptococcus (GBS) is a primary cause of neonatal meningitis and septicemia.
• GBS intracellular survival within phagocytic cells is critical for disease but poorly understood.
• GBS pathogenesis relies on its ability to evade host immune defenses.

Purpose of the Study:

• To investigate the mechanisms of GBS intracellular survival within macrophages.
• To determine if GBS strain characteristics influence intracellular survival.
• To identify key GBS factors involved in surviving within phagocytic cells.

Main Methods:

• GBS survival assays in J774 macrophage cell lines.
• Immunofluorescence staining for lysosome-associated membrane protein (LAMP).
• Pharmacological inhibition of phagosome acidification.
• Analysis of the GBS CovS/CovR two-component system.

Main Results:

• GBS demonstrated prolonged survival within J774 macrophages.
• Intracellular GBS survival was consistent across diverse GBS strains (serotypes, MLST, clinical origins).
• Phagosome acidification was essential for GBS intracellular survival, and the CovS/CovR system regulated this process.

Conclusions:

• GBS possesses robust intracellular survival mechanisms within macrophages.
• Phagosome acidification is a critical environmental cue for GBS intracellular persistence.
• The CovS/CovR system is a key regulator of GBS survival in the hostile phagosomal environment.