Specific interaction between Group B Streptococcus CC17 hypervirulent clone and phagocytes.

Area of Science:

• Immunology
• Microbiology
• Infectious Diseases

Background:

• Group B Streptococcus (GBS) is a major cause of neonatal invasive infections.
• The capsular serotype III clonal complex 17 (CC17) of GBS is a hypervirulent clone strongly associated with neonatal meningitis.
• Macrophages serve as a permissive intracellular niche for GBS survival.

Purpose of the Study:

• To investigate the specific interactions between hypervirulent GBS CC17 strains and macrophages.
• To elucidate the mechanisms underlying the enhanced interaction of GBS CC17 with host immune cells.

Main Methods:

• Comparative analysis of GBS CC17 and non-CC17 strain phagocytosis by human monocytes and macrophages.
• Investigation of the role of the HvgA protein and PI-2b pilus (Spb1) in GBS CC17 adhesion.
• Assessment of scavenger receptor involvement using inhibitors (fucoidan, poly(I)).
• Analysis of intracellular bacterial survival and egress mechanisms.

Main Results:

• GBS CC17 strains exhibit significantly higher adhesion and phagocytosis rates by macrophages compared to non-CC17 strains.
• Enhanced CC17 phagocytosis is mediated by the surface protein HvgA and the PI-2b pilus (Spb1), interacting with scavenger receptors.
• Intracellular survival and egress mechanisms were similar for both CC17 and non-CC17 strains within macrophages.

Conclusions:

• The hypervirulent GBS CC17 clone possesses a unique capacity for enhanced adhesion and phagocytosis by macrophages.
• This enhanced interaction, driven by specific surface factors, may contribute to the persistence and dissemination of GBS CC17 within the host.
• Understanding these interactions provides insights into host immune subversion by pathogenic bacteria.