IDEHU   05542
INSTITUTO DE ESTUDIOS DE LA INMUNIDAD HUMORAL PROF. RICARDO A. MARGNI
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
The Brucella suis autotransporter protein BmaC mediates bacterial adhesión to epithelial cells
Autor/es:
POSADAS D.M.; RUIZ-RANWEZ V.; BONOMI H.R.; MARTÍN F.A.; ZORREGUIETA A.
Lugar:
Buenos Aires
Reunión:
Conferencia; Brucellosis 2011, International Research Conference Including the 64th Brucellosis Research Conference; 2011
Resumen:
Brucella species are facultative intracellular bacterial pathogens. Bacteria of this genus are the causative agents of brucellosis, one of the major bacterial zoonotic diseases. Most pathogenic bacteria express adhesins on their surfaces that mediate interaction with host cell receptors or with soluble macromolecules. This interaction offers a way to colonize and circumvent clearance from host fluids. In addition, contact of bacterial adhesins with host cell ligands mediates signaling events that may trigger or affect bacterial invasion, and even induce rapid host inflammatory responses. Brucella spp. enters the host through mucosal surfaces and the initial interaction steps are most likely crucial for establishing infection and promoting bacterial spread to different host tissues. However, little is known about the bases of this interaction. In an attempt to identify bacterial genes encoding adhesins, a M13 phage-display library of fragmented genomic DNA from Brucella suis M1330 was constructed and panned against some key components of the host extracellular matrix. Three putative fibronectin-binding proteins of B. suis were identified by this procedure. One of these candidates, designated BmaC, belongs to the type I (monomeric) autotransporter family of proteins. Phages displaying the fibronectin-binding domain of BmaC were able to adhere to HeLa cells and impaired the attachment of brucellae to HeLa cells in a dose-dependent manner. Biochemical and microscopy studies indicated that BmaC is an outer membrane protein located at one pole on the bacterial surface. In order to investigate the contribution of BmaC in the adhesion of B. suis to host cells, a clean deletion mutant of the bmaC gene was constructed. The ∆bmaC deletion mutant showed a marked reduction in the binding to HeLa cells compared with wild type brucellae. Furthermore, the wild type strain out-competed the ∆bmaC mutant in co-infection experiments, confirming that BmaC contributes to adherence to the host cells. Intracellular replication was also evaluated and, although the initial number of intracellular bacteria (1 and 4 h.p.i.) decreased in the ∆bmaC mutant, no differences between the intracellular replication rates of the wild type and the mutant strain were found. To provide final phenotypic confirmation, a bmaC knock-in complemented strain was generated. Introduction of a wild type copy of bmaC gene fully complemented the ability of this strain to attach and invade HeLa cells. Taken together, our results highlight the role of a novel monomeric autotransporter protein from B. suis in the adhesion to host surfaces.