Binding of the periodontal pathogen Actinobacillus actinomycetemcomitans to extracellular matrix proteins

The interaction of Actinobacillus actinomycetemcomitans, an important patho gen implicated in juvenile and adult periodontitis, with collagenous and no ncollagenous proteins of the extracellular matrix was investigated. A. acti nomycetemcomitans SUNY 465 bound to immobilized type I, II, III and V but n ot type IV collagen. Binding to immobilized collagen was saturable and conc entration dependent. This interaction could not be inhibited by soluble col lagen. suggesting that binding was dependent on a specific collagen conform ation. Bacteria grown anaerobically exhibited decreased collagen-binding ac tivity as compared with organisms grown aerobically. Bacterial outer membra ne proteins were essential for binding to collagen, ii. actinomycetemcomita ns SUNY 465 also bound to immobilized fibronectin. In contrast, bacteria di d not bind to fibrinogen, bone sialoprotein, oz-I-Is glycoprotein or albumi n. The mechanism of the interaction with fibronectin was more complex, poss ibly involving both protein and nonproteinaceous components. The majority o f other A. actinomycetemcomitans strains tested bound to extracellular matr ix proteins in a manner similar to SUNY 465 but with minor variation. These results demonstrate that A, actinomycetemcomitans binds to proteins found in connective tissue. The interaction with extracellular matrix proteins ma y contribute to the virulence of this pathogen at oral and extraoral sites of infection.