Tuberculosis (TB) causes disease worldwide and multi-drug resistance is rising. Matrix metalloproteinases (MMPs) cause immunopathological lung matrix destruction, which results in transmission, morbidity and mortality. Collagen is the primary structural fibril of the lung and I primarily studied two collagenases: secreted MMP-8, and membrane bound MMP-14, and also the stromelysin MMP-10, which activates not only MMP-8 but another collagenase MMP-1.

Human monocyte and macrophages were stimulated with Mtb H37Rv, BCG, ESAT-6 peptides or Conditioned Media from Mtb infected monocytes (CoMTb). MMP concentrations were measured by Luminex bead array and ELISA. Gene expression was quantified by RT-PCR. Immunohistochemistry was performed on biopsies. Flow cytometry quantified MMP-14 expression. Fluorescent microscopy detected MMP-14 and monocyte driven fluorescent collagen degradation. Monocyte migration was measured by the agarose spot assay.

MMP-8 was increased in the plasma in TB compared to both respiratory symptomatics and controls (both p<0.001). MMP-10 was increased in the respiratory secretions of patients with TB compared to controls (p<0.05). Mtb drove up to a 31.5 fold increase in MMP-10 secretion from macrophages (both p<0.001). Mtb caused 3.5 fold more MMP-10 secretion from macrophages than BCG (p<0.001) and a specific peptide from ESAT-6 drove MMP-10 secretion from macrophages. In induced sputum, MMP-14 mRNA was increased 3.3-fold in TB compared to controls and positively correlated with infiltration on chest radiograph (both p<0.05). Macrophages of TB granulomas in biopsies stained strongly positive for MMP-14. Mtb increased monocyte MMP-14 surface expression 31.7-fold (p<0.05) and CoMTb 17.5-fold (p<0.01). Mtb infected monocytes degraded collagen, with co-localised MMP-14 surface expression. Monocytes migrated to the edge of CoMTb impregnated agarose drops, expressing MMP-14 on migration. Inhibition of MMP-14 activity with a neutralising antibody, decreased Mtb driven collagen degradation by 73% (p< 0.001) and CoMTb driven monocyte migration by 44% (p<0.001).

These data shows that, MMP-1, -8, -10 and -14 cause immunopathology and regulate leukocyte migration in TB.