More than one tandem repeat domain of Extracellular Adherence Protein (Eap) of Staphylococcus aureus is required for aggregation, adherence and host cell invasion, but not for leucocyte activation

Eap is a multifunctional Staphylococcus aureus protein and broad spectrum adhesin for several host matrix and plasma proteins. We investigated the interactions of full length Eap and five recombinant tandem repeat domains with host proteins using surface plasmon resonance (SPR; BIAcore®) and ligand overlay assays. In addition, agglutination and host cell interaction, namely 5 adherence, invasion, and stimulation of proliferation was determined. In plasmon resonance, interaction of full length Eap isoforms (from strains Newman and Wood 46) with fibrinogen, fibronectin, vitronectin and thrombospondin 1 was found to be specific but with different affinities for the ligands tested. In ligand overlay assay, interaction of five single tandem repeat domains (D1 to D5) of Eap-7 (from strain CI-7) to fibronectin, fibrinogen, 10 vitronectin, thrombospondin-1, and collagen I, differed substantially. Most prominently, D3 bound strongest to fibronectin and fibrinogen. Full-length Eap, but none of the single tandem repeat domains, agglutinated S. aureus and enhanced adherence to and invasion of host cells by S. aureus. D3-4 and D1-3 (in cis) increased adherence and invasiveness compared to single Eap tandem repeat domains. By contrast, single Eap tandem repeat domains and full-length Eap similarly modulated 15 proliferation of PBMCs: low concentrations stimulated, whereas high concentrations inhibited proliferation. Taken together, Eap tandem repeat domains appear to have distinct characteristics for binding of soluble ligands, despite a high degree of sequence similarity. In addition, more than one Eap tandem repeat domain is required for S. aureus agglutination, adherence and cellular invasion, 20 but not for stimulation of PBMC proliferation. AC CE PT ED on N ovem er 2, 2017 by gest http/iai.asm .rg/ D ow nladed fom