Ecto-5'-nucleotidase: a candidate virulence factor in Streptococcus sanguinis experimental endocarditis

Area of Science:

• Microbiology
• Immunology
• Cardiovascular Research

Background:

• Streptococcus sanguinis is a primary cause of infective endocarditis (IE).
• The molecular mechanisms underlying S. sanguinis virulence are not fully understood.
• Identifying novel virulence factors is crucial for understanding IE pathogenesis.

Purpose of the Study:

• To identify novel virulence factors in Streptococcus sanguinis.
• To investigate the role of cell surface ecto-5'-nucleotidase (Nt5e) in S. sanguinis virulence.
• To elucidate the mechanisms by which Nt5e contributes to infective endocarditis.

Main Methods:

• Genomic screening of S. sanguinis for potential virulence factors.
• Biochemical assays to confirm ecto-5'-nucleotidase activity.
• In vitro platelet aggregation assays using wild-type and nt5e deletion mutant strains.
• In vivo rabbit model of infective endocarditis.

Main Results:

• A cell surface ecto-5'-nucleotidase (Nt5e) was identified in S. sanguinis.
• S. sanguinis Nt5e hydrolyzes extracellular adenosine triphosphate (ATP) to produce adenosine.
• Deletion of nt5e significantly reduced platelet aggregation onset and decreased vegetation mass and bacterial load in a rabbit IE model.
• Platelet-bacterial adhesion was not affected by the absence of nt5e.

Conclusions:

• Streptococcal Nt5e is a novel virulence factor contributing to infective endocarditis.
• Nt5e promotes S. sanguinis virulence by modulating platelet aggregation and potentially inhibiting host immune responses.
• Nt5e-mediated adenosine production may suppress immune cells and delay platelet microbicidal protein delivery, enhancing bacterial survival.