PLASMIN-COATED LEPTOSPIRA INTERROGANS MEDIATES FIBRONECTIN DEGRADATION.

Mônica Larucci Vieira (IBu); Zenaide M. Morais (FMVZ-USP); Silvio A. Vasconcellos (FMVZ-USP); Ana Lúcia Tabet Oller Nascimento (IBu)

Leptospirosis is one of the most spread zoonosis worldwide, caused by spirochetes of genus Leptospira. Although the availability of genomic sequences, molecular aspects of pathogenesis, virulence and invasion processes by which these bacteria infect the hosts are poorly characterized. It is well documented that interaction of pathogens with the extracellular matrix (ECM) might play a primary role in the colonization of host tissues. Indeed, the ability of the leptospires to adhere to ECM has been recently shown. Proteolytic activity achieved by subversion of host proteases by pathogens, such as plasmin (PLA) - a broad-spectrum serine protease component of the fibrinolytic system, composed by the zymogen plasminogen (PLG) - has been demonstrated to be important during several bacterial infections. Based on these assertions, we decided to investigate the ability of Leptospira to bind PLG. By modified ELISA we show that leptospires are capable to capture purified or plasma PLG in vitro, and that the binding seems to occur via lysine residues. The surface-bound PLG is demonstrated by indirect immunofluorescence under confocal microscopy with living leptospires. The PLG-bound bacteria acquire proteolytic activity by addition of PLA activator, as evaluated by the degradation of specific PLA substrate. The activation of PLA was detected in several species of Leptospira but significant higher was observed with low-passage, infectious strain of L. interrogans serovar Copenhageni, suggesting the role of this interaction in virulence. PLA-coated virulent leptospires were capable to degrade purified ECM fibronectin, an activity that might be important for tissue penetration. Our data provide for the first time evidence for the generation of active PLA on the surface of Leptospira. These results give new insights toward the understanding of leptospiral infectious process and molecular pathogenesis of the disease.