Despite anti-tuberculous treatment (ATT), central nervous system tuberculosis (CNS-TB) still cause permanent neurological deficits and death. To identify prognostic factors, we profiled a prospective cohort of tuberculous meningitis (TBM) and non-TBM patients. We determined significantly increased cerebrospinal fluid (CSF) matrix metalloproteinases (MMPs) and neutrophil extracellular traps (NETs) are up-regulated in TBM patients with neuroradiological abnormalities and poor outcomes. To dissect mechanisms, we created a CNS-TB murine model which show neutrophil-rich necrotizing pyogranulomas with MMP-9 and NETs colocalizing, resembling human CNS-TB. Spatial transcriptomic analysis of both human and murine CNS-TB demonstrates a highly-inflamed and neutrophil-rich microenvironment of inflammatory immune responses, extracellular matrix degradation and angiogenesis within CNS-TB granulomas. Murine CNS-TB treated with ATT and MMP inhibitors SB-3CT or doxycycline show significantly suppressed NETs with improved survival. MMP inhibition arms show attenuated inflammation and well-formed blood vessels within granulomas. Adjunctive doxycycline is highly promising to improve CNS-TB outcomes and survival.

Understanding the pathophysiology of central nervous system tuberculosis (CNS-TB) is hampered by the lack of a good pre-clinical model that mirrors the human CNS-TB infection. We developed a murine CNS-TB model that demonstrates neurobehavioral changes with similar immunopathology with human CNS-TB. We injected two Mycobacterium tuberculosis (M.tb) strains, H37Rv and CDC1551, respectively, into two mouse strains, C3HeB/FeJ and Nos2−/− mice, either into the third ventricle or intravenous. We compared the neurological symptoms, histopathological changes and levels of adhesion molecules, chemokines, and inflammatory cytokines in the brain induced by the infections through different routes in different strains. Intra-cerebroventricular infection of Nos2−/− mice with M.tb led to development of neurological signs and more severe brain granulomas compared to C3HeB/FeJ mice. Compared with CDC1551 M.tb, H37Rv M.tb infection resulted in a higher neurobehavioral score and earlier mortality. Intra-cerebroventricular infection caused necrotic neutrophil-dominated pyogranulomas in the brain relative to intravenous infection which resulted in disseminated granulomas and mycobacteraemia. Histologically, intra-cerebroventricular infection of Nos2−/− mice with M.tb resembled human CNS-TB brain biopsy specimens. H37Rv intra-cerebroventricular infected mice demonstrated higher brain concentrations of inflammatory cytokines, chemokines and adhesion molecule ICAM-1 than H37Rv intravenous-infected mice. Intra-cerebroventricular infection of Nos2−/− mice with H37Rv creates a murine CNS-TB model that resembled human CNS-TB immunopathology, exhibiting the worst neurobehavioral score with a high and early mortality reflecting disease severity and its associated neurological morbidity. Our murine CNS-TB model serves as a pre-clinical platform to dissect host–pathogen interactions and evaluate therapeutic agents for CNS-TB.

BACKGROUND. Matrix metalloproteinases (MMPs) are key regulators of tissue destruction in tuberculosis (TB) and may be targets for host-directed therapy. We conducted a phase II double-blind, randomized, controlled trial investigating doxycycline, a licensed broad-spectrum MMP inhibitor, in patients with pulmonary TB. METHODS. Thirty patients with pulmonary TB were enrolled within 7 days of initiating anti-TB treatment and randomly assigned to receive either 100 mg doxycycline or placebo twice a day for 14 days, in addition to standard care. RESULTS. Whole blood RNA-sequencing demonstrated that doxycycline accelerated restoration of dysregulated gene expression in TB towards normality, rapidly down-regulating type I and II interferon and innate immune response genes, and up-regulating B-cell modules relative to placebo. The effects persisted for 6 weeks after doxycycline discontinuation, concurrent with suppressed plasma MMP-1. Doxycycline significantly reduced sputum MMP-1,-8,-9,-12 and-13, suppressed type I collagen and elastin destruction, reduced pulmonary cavity volume without altering sputum mycobacterial loads, and was safe. CONCLUSION. Adjunctive doxycycline with standard anti-TB treatment suppressed pathological MMPs in PTB patients. Larger studies on adjunctive doxycycline to limit TB immunopathology are merited.