Type-specific antibody prevents platelet aggregation induced by group B streptococci type III

Area of Science:

• Microbiology
• Immunology
• Hematology

Background:

• Group B streptococci (GBS) are a significant cause of neonatal infections.
• GBS type III is a prevalent serotype associated with invasive disease.
• The interaction between GBS and human platelets is not fully understood.

Purpose of the Study:

• To investigate the effect of GBS type III on human platelet function.
• To determine the role of specific antibodies in modulating GBS-induced platelet responses.

Main Methods:

• Human platelet-rich plasma (PRP) was incubated with GBS type III.
• Platelet aggregation and serotonin release were measured.
• The effects of type-specific antisera and monoclonal antibodies (IgG, IgM, IgA) were assessed.

Main Results:

• GBS type III readily induced platelet aggregation and serotonin release in PRP.
• Aggregation occurred within minutes, with significant serotonin release preceding it.
• Type-specific rabbit antisera against GBS type III inhibited these responses in a dose-dependent manner.
• Monoclonal antibodies of IgG, IgM, and IgA isotypes effectively blocked GBS-induced platelet activation.

Conclusions:

• GBS type III actively modulates human platelet function, inducing aggregation and serotonin release.
• Antibodies against GBS type III antigens can inhibit these platelet responses.
• This antibody-mediated inhibition may represent a novel protective mechanism beyond opsonization and phagocytosis.