Strains of Group B streptococci from septic patients induce platelet activation via Toll-like Receptor 2

Area of Science:

• Microbiology
• Immunology
• Hematology

Background:

• Group B Streptococcus (GBS) is a major cause of neonatal sepsis and can lead to thrombocytopenia in septic patients due to platelet activation.
• Understanding the mechanisms by which GBS interacts with platelets is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the role of GBS strains from septic patients in platelet aggregation and activation.
• To elucidate the molecular mechanisms underlying GBS-induced platelet responses, focusing on Toll-like receptors (TLRs) and signaling pathways.

Main Methods:

• Platelet aggregation assays were performed using GBS strains isolated from septic patients.
• Expression of CD62P, GPIIb/IIIa activation, and Toll-like receptor 2 (TLR2) and Toll-like receptor 4 (TLR4) expression were analyzed.
• Monoclonal antibodies against TLR2 and TLR4, as well as a phosphoinositide 3-kinase (PI3-K) inhibitor, were used to investigate signaling pathways.

Main Results:

• Three of the six tested GBS strains induced significant platelet aggregation, CD62P secretion, and GPIIb/IIIa activation.
• GBS-induced platelet activation correlated with increased TLR2 expression on platelets.
• Inhibition of TLR2, but not TLR4, blocked GBS-induced platelet responses.
• TLR2 stimulation activated the PI3-K/Akt signaling pathway, and PI3-K inhibition reduced GBS-induced platelet activation.

Conclusions:

• Certain GBS strains isolated from septic patients can directly activate platelets.
• Platelet activation by GBS involves the engagement of TLR2 and subsequent activation of the PI3-K/Akt signaling pathway.
• These findings highlight a novel mechanism of GBS pathogenesis contributing to thrombocytopenia in sepsis.