A mycobacterial lectin promotes bacilli adhesion to macrophages and influences pathogen growth during infection (INM3P.409)

Abstract

Surface and secreted mycobacterial proteins play a major role on the infection process by mediating macrophage-bacteria interactions as well as the fate of cell’s death. We have previously described a secreted 13-kDa lectin (sMTL-13) in Mycobacterium tuberculosis (Mtb), encoded by Rv1419 gene, and although a possible importance for this protein as a major mycobacterial antigen was shown in tuberculosis patients, the importance of such lectin during infection has not been formally addressed. We have generated an Rv1419 knockout Mtb (ΔRv1419) to investigate a possible role of this gene during infection. In silico analysis of the protein as well as its detection on Mtb surface suggest that sMTL-13 may participate during bacteria entry in the host macrophage. This was confirmed by binding experiments performed in either murine or human derived macrophages. In addition, lower levels of TNF were detected in ΔRv1419-infected cells, indicating that this lectin may be important for pathogen recognition. Importantly, ΔRv1419 displays higher intracellular growth than the WT bacteria. Thus, although binding of Mtb to macrophages is decreased in the absence of Rv1419 gene, cells exposed to the knockout Mtb display higher bacterial replication rate and cell death. These data suggest that sMTL-13 expressed on Mtb regulates macrophage entry and perhaps cell fate, which could serve as a pathogen survival strategy, allowing bacterial growth without leading host cells to a premature death.