Visualizing the dynamics of tuberculosis pathology using molecular imaging.

Nearly 140 years after Robert Koch discovered Mycobacterium tuberculosis, tuberculosis (TB) remains a global threat and a deadly human pathogen. M. tuberculosis is notable for complex host-pathogen interactions that lead to poorly understood disease states ranging from latent infection to active disease. Additionally, multiple pathologies with a distinct local milieu (bacterial burden, antibiotic exposure, and host response) can coexist simultaneously within the same subject and change independently over time. Current tools cannot optimally measure these distinct pathologies or the spatiotemporal changes. Next-generation molecular imaging affords unparalleled opportunities to visualize infection by providing holistic, 3D spatial characterization and noninvasive, temporal monitoring within the same subject. This rapidly evolving technology could powerfully augment TB research by advancing fundamental knowledge and accelerating the development of novel diagnostics, biomarkers, and therapeutics.

Host-Directed Therapies for Tuberculosis.

Host-directed therapies are a relatively new and promising approach to treatment of tuberculosis. Modulation of specific host immune pathways, including those that impact inflammation and immunopathology, can limit mycobacterial infection and pathology, both in cell culture and in animal models. This review explores a range of host pathways and drugs, some already approved for clinical use that have the potential to provide new adjunctive therapies for tuberculosis. Drugs targeting host processes may largely avoid the development of bacterial antibiotic resistance, a major public health concern for tuberculosis. However, these drugs may also have generally increased risk for side effects on the host. Understanding the specific mechanisms by which these drugs act and the relationship of these mechanisms to Mycobacterium tuberculosis pathogenesis will be critical in selecting appropriate host-directed therapy. Overall, these host-directed compounds provide a novel strategy for antituberculosis therapy.

TB: the Yin and Yang of lipid mediators.

There is a growing appreciation of the diverse roles that lipid mediators play in modulating inflammatory responses during infection. In the case of tuberculosis, virulent mycobacteria induce host production of anti-inflammatory mediators, including lipoxins, which limit the host inflammatory response and lead to necrotic cell death of infected macrophages. Recent work using the zebrafish model suggests that, while excess anti-inflammatory lipoxins are host detrimental during mycobacterial infections, excess pro-inflammatory lipids also drive host susceptibility. The balance of these inflammatory states is influenced by common human genetic variation in Asia. Fuller understanding of the mechanisms of eicosanoid-mediated inflammatory imbalance during tuberculosis infection has important implications for the development of adjunctive therapies.