Binding of Bartonella henselae to extracellular molecules: identification of potential adhesins

Bartonella henselae, the etiologic agent of cat scratch disease, bacillary angiomatosis and other clinical syndromes initiates infection through a trauma or wound to the skin suggesting involvement of extracellular matrix molecules. We have demonstrated in this study that B. henselae bound strongly fibronectin, collagen IX and X, but comparatively less laminin and collagen IV. B. henselae bound primarily the N- and C-terminal heparin (Hep-1 and Hep-2, respectively) and the gelatin-binding domains of fibronectin (Fn) but not the cell-binding domain. Binding to the Hep-binding domain was significantly inhibited by Hep suggesting common binding sites on the Fn molecule. Furthermore, glycosaminoglycans-mediated binding of B. henselae to soluble Fn showed that Hep but not dextran sulfate inhibited the bacterium binding to Fn. Unlike Fn, B. henselae bound strongly vitronectin only in the presence of Hep or dextran sulfate. Also, the binding of B. henselae to host cells could be inhibited by anti-B. henselae surface-reactive antibodies, the exogenous Fn or the anti-Fn polyclonal antibodies. Ligand blots, batch affinity purification and MALDI-TOF peptide fingerprinting identified B. henselae Pap31, Omp43 and Omp89 as the three major putative Fn-binding proteins (FnBPs) in B. henselae outer membrane proteins. We hypothesized that B. henselae wound associated infections involved interactions with extracellular matrix molecules. Taken together, the above data suggest that interactions between B. henselae and ECM molecules such as Fn may play an important role in the bacterium adherence to and invasion of host cells.