Research overview–

Understanding Mycobacterial persistence and drug tolerance:

A central question in tuberculosis (TB) research is to identify the mechanisms that allow Mycobacterium tuberculosis (Mtb) to persist for decades in humans. Host-generated redox signals such as nitric oxide (NO), reactive oxygen species (ROS), acidic pH, carbon-limitation, and oxygen (O₂) have been proposed to be main signals that induce a change in the metabolism of Mtb to facilitate its entry into a drug-tolerant persistent state. However, the precise contribution of these signals in manipulating Mtb’s internal redox state and identity of a sensor(s) that precisely monitors pathogen’sphysiology and persistence in response to O₂ and NO remains unknown.

To fulfill this knowledge gap, we are taking multiple approaches:

• Developing non-invasive genetic technologies to measure redox physiology of Mtb during infection: – We have re-engineered a redox-sensitive green fluorescent protein (Mrx1-roGFP2) that senses dynamic changes in the levels and reduction-oxidation state of mycobacteria-specific antioxidant, mycothiol. This biosensor is currently being exploited in multiple projects related to stress mechanisms in Mtb, drug screening against MDR/XDR strains, and understanding mechanisms of phenotypic heterogeneity and drug tolerance,
• Mechanisms underlying redox heterogeneity and persistence: – We identified multiple Fe-S cluster containing transcription factors in Mtb, which function as sophisticated sensors of O₂, NO, and low pH. Our interest to understand the role of these transcription factors in facilitating persistence and evolution of drug resistance in Mtbduring infection,
• Targeting drug –resistance via redox-based interventions: – Drug screening efforts are ongoing to target drug-resistant Mtb strains using redox-oriented small molecules, and
• HIV-TB and redox: -We found that the cellular and subcellular redox environment of human macrophages and T-lymphocytes are important to maintain HIV-TB co-infection. Mechanistic studies using cutting edge technologies such as Seahorse XF flux analyzer, redox proteome, redox biosensor, and nanostring will be utilized to understand the synegistic basis of HIV-TB co-infection.