Mycobacterium tuberculosis Rv1096, facilitates mycobacterial survival by modulating the NF-κB/MAPK pathway as peptidoglycan N-deacetylase

Abstract

Mycobacterium tuberculosis (Mtb) is an intracellular pathogen that can infect and replicate in macrophages. Peptidoglycan (PGN) is a major component of the mycobacterial cell wall and is recognized by host pattern recognition receptors (PRRs). Many bacteria modulate and evade the immune defenses of their hosts through PGN deacetylation. Rv1096 was previously characterized as a PGN N-deacetylase gene in Mtb. However, the underlying mechanism by which Rv1096 regulates host immune defenses during macrophage infection remains unclear. In the present study, we investigated the role of Rv1096 in evading host immunity using a recombinant M. smegmatis expressing exogenous Rv1096 and Rv1096-deleted Mtb strain H37Rv mutant. We found that Rv1096 promoted intracellular bacillary survival and inhibited the inflammatory response in M. smegmatis- or Mtb-infected macrophages. The inhibition of mycobacteria-induced inflammatory response in macrophages was at least partially due to NF-κB and MAPK activation downstream of TLR and NOD signaling pathways. Furthermore, we found that Rv1096 inhibitory effect on inflammatory response was associated with TLR2, TLR4 and NOD2. Finally, we demonstrated the PGN deacetylase activity of Rv1096 by Fourier transform IR and Rv1096 NODB deficient mutant. Our findings suggest that Rv1096 may deacetylate PGNs to evade PRRs recognition, thus protecting Mtb from host immune surveillance and clearance in macrophages.

Keywords: Inflammation; Macrophage; Mycobacteria; Peptidoglycan; Rv1096.