Cloning, expression, purification and characterization of Leptospira interrogans thermolysin: interactions with plasminogen / plasmin system and implications for infection

Abstract

The pathogenesis and virulence of Leptospira, the causal agent of leptospirosis, remain unknown. To date, proteases involved in the active penetration and dissemination of the bacteria within the hosts nave not been reported. During the last years, we have focused our studies on the leptospiral interaction with the fibrinolytic system. We described that leptospires capture plasminogen (PLG) on the outer surface, which is converted to active plasmin (PLA) by exogenous activators, endowing the bacteria with proteolytic activity. PLA favors the penetration and dissemination and confers immune evasion activity. We also showed that leptospires induce the expression of PLG activators and enhance the availability and activation of matrix metaloproteases in endothelial cells. These activities were shown to be more pronounced in serum of leptospirosis' patients when compared with normal sera. Thermolysins (TLs) expressed by microorganisms are usually involved in the pathogenesis of diseases, constituting essential virulence factors. Several studies reported the interaction of TLs with proteolytic systems, mainly fibrinolysis, which intensify the proteolysis within the hosts, commonly by pro-enzymes activation and inhibitors degradation. In the genome of L. interrogans, we found four coding sequences that were annotated as putative leptospiral TLs. This project aims the functional characterization of these TLs. The main purpose is to analyze their interaction with proteolytic systems, particularly fibrinolytic, and the possible outcome for the host-Leptospira interactions. It is possible that these TLs are virulence factors involved in the pathogenesis of the disease. (AU)