Direct interaction of iron-regulated surface determinant IsdB of Staphylococcus aureus with the GPIIb/IIIa receptor on platelets

Abstract

The interaction of bacteria with platelets is implicated in the pathogenesis of endovascular infections, including infective endocarditis, of whichStaphylococcus aureusis the leading cause. SeveralS. aureussurface proteins mediate aggregation of platelets by fibrinogen- or fibronectin-dependent processes, which also requires specific antibodies. In this studyS. aureuswas grown in iron-limited medium to mimicin vivoconditions in which iron is unavailable to pathogens. Under such conditions, aS. aureusmutant lacking the known platelet-activating surface proteins adhered directly to platelets in the absence of plasma proteins and triggered aggregation. Platelet adhesion and aggregation was prevented by inhibiting expression of iron-regulated surface determinant (Isd) proteins. Mutants defective in IsdB, but not IsdA or IsdH, were unable to adhere to or aggregate platelets. Antibodies to the platelet integrin GPIIb/IIIa inhibited platelet adhesion by IsdB-expressing strains, as did antagonists of GPIIb/IIIa. Surface plasmon resonance demonstrated that recombinant IsdB interacts directly with GPIIb/IIIa.