Extracellular mycobacterial DNA-binding protein 1 participates in mycobacterium-lung epithelial cell interaction through hyaluronic acid.

Mycobacterium tuberculosis infects not only host macrophages but also nonprofessional phagocytes, such as alveolar epithelial cells. Glycosaminoglycans (GAGs) are considered as the component of mycobacterial adherence to epithelial cells. Here we show that extracellularly occurring mycobacterial DNA-binding protein 1 (MDP1) promotes mycobacterial infection to A549 human lung epithelial cells through hyaluronic acid (HA). Both surface plasmon resonance analysis and enzyme-linked immunosorbent assay revealed that MDP1 bound to HA, heparin, and chondroitin sulfate. Utilizing synthetic peptides, we next defined heparin-binding site of 20 amino acids from 31 to 50 of MDP1, which is responsible for the specific DNA-binding site of MDP1. MDP1 bound to A549 cells, and exogenous DNA and HA interfered with the interaction. The binding was also abolished by treatment of A549 cells with hyaluronidase, suggesting that HA participates in the MDP1-A549 cell interaction. Adherence of bacillus Calmette-Guérin (BCG) and M. tuberculosis to A549 cells was inhibited by addition of HA, DNA, and anti-MDP1 antibody, showing that MDP1 participates in the interaction between mycobacteria-alveolar epithelial cells. Simultaneous treatment of intratracheal BCG-infected mice with HA reduced the growth of BCG in vivo. Taken together, theses results suggest that HA participates in Mycobacterium-lung epithelium interaction and has potential for therapeutic and prophylactic interventions in mycobacterial infection.