Tuberculosis is a global epidemic that annually accounts for more than 3 million deaths worldwide. Because of the capacity of M. tuberculosis to establish a latent infection, an estimated 1-2 billion people worldwide are infected with M. tuberculosis. Immunodeficiency caused by malnutrition, old age or HIV infection enhances development of active disease, either from a primary infection or more likely from reactivation of a latent infection. However, the environmental cues responsible for initiating latent infection in the host are not clearly understood. We previously showed that the gas carbon monoxide (CO) produced by host macrophages triggers a dormancy response in mycobacteria mediated by a bacterial two-component system. We also showed that carbon monoxide is well tolerated by mycobacteria, suggesting that mycobacteria can resist CO toxicity, and further have recently discovered a novel gene in M. tuberculosis that affords such resistance. We are currently characterizing the role of this gene in CO resistance, including its precise biochemical mechanism, interacting partners, metabolic effects and role in pathogenesis. Furthermore, we are identifying additional CO resistance genes and characterizing their functions and role in pathogenesis.
In addition to studying the role of carbon monoxide in M. tuberculosis pathogenesis, we are broadly interested in the metabolic and physiologic adaptations of M. tuberculosis during latency. Because successful M. tuberculosis infection occurs as a consequence of complex interactions with the host, we also are studying unique cellular and immunologic responses of the host that facilitate M. tuberculosis survival. Our hope is to identify novel microbial and host factors that can be inhibited or modulated to improve the treatment or prevention of tuberculosis.