Mycobacterium tuberculosis Rv3194c efficiently facilitates mycobacterial-lung epithelial interaction through its HA-binding site

Mycobacterium tuberculosis adhesins are surface-exposed molecules that mediate pathogen-host interaction, a fundamental step towards host infection. Here we show that serine protease (Rv3194c) promotes mycobacterial infection to lung epithelial through its hyaluronic acid (HA)-binding site. Both enzyme-linked immunosorbent assay and surface plasmon resonance analysis revealed that Rv3194c bound to HA. Utilizing synthetic peptides, we next defined HA-binding site of 20 amino acids from 91 to 110 of Rv3194c (P91-110). Immunofluorescence assay and an FACScan showed that Rv3194c was interacted with A549 cells (human lung epithelial cells), and its interaction was abolished by the addition of hyaluronidase or P91-110. Experimental infection in Vitro revealed that Rv3194c participates in attachment of recombinant Mycobacterium smegmatis (Rv3194c/MS) to A549 cells, and P91-110 treatment of A549 cells almost inhibited Rv3194c/MS-A549 cells interaction. To provide in vivo evidence, we constructed a reporter strain of M. smegmatis expressed a derivative of the firefly luciferase that is shifted to red (FFlucRT) in combination with Rv3194c (Rv3194c+FFlucRT/MS) to infect the rodents and monitor the progression of the disease. Using bioluminescence imaging and bacterial counts in lung tissue confirmed that Rv3194c dramatically enhanced the persistence of M. smegmatis. In addition, treatment of intratracheal Rv3194c+FFlucRT/MS-infected mice with P91-110 significantly suppressed the growth of Rv3194c+FFlucRT/MS in vivo. Taken together, these results demonstrate that Rv3194c was identified as a HA-binding adhesin, and P91-110 as anti-adhesion agents has potential for therapeutic and prophylactic interventions in mycobacterial infection.