A major goal of tuberculosis (TB) drug discovery programs is the development of compounds that will reduce the duration of therapy, simultaneously limiting the emergence of drug-resistant strains of the causative agent, Mycobacterium tuberculosis (Mtb). The current six-month regimen is thought to result from the inability of existing anti-tuberculars to eliminate a sub-population of Mtb bacilli that are refracory to killing despite retaining full genetic susceptibility to the applied drugs. The existence of thee Mtb persisters, together with the increasing emergence of drug-resistant clinical isolates, in turn raises a critical question: is there a functional link between (non-genetic) persistence and the development of genetic drug resistance? Here, we will test the hypothesis that, by controlling functions involved in DNA repair and damage tolerance, the mycobacterial SOS response plays a key role in the inherent heterogeneity of Mtb populations and, therefore, contributes to the ability of Mtb to persist in the face of lethal stresses including drug treatmen. We will also evaluate the notion that the SOS-regulated imuA'-imuB/dnaE2 mutasome, which was previously implicated in Mtb survival and drug-resistance in vivo, drives mutagenesis in antibiotic-exposed persister populations and so links persistence and genetic resistance. Finally, we will utilize biochemical and target-based whole-cell (TB-WCS) screens to identify novel chemical inhibitors which sensitize Mtb to genotoxic stress and eliminate the emergence of resistance under drug-selective pressure in vitro. This fully collaborative proposal will utilize biochemical, genetic, and microbiological techniques that will require both partners to develop and apply. Moreover, it is predicated on the open transfer of scientific insight and technical expertise as part of a new collaboration designed to create a long-term partnership around the investigation of fundamental aspects of mycobacterial DNA replication and repair as an underexplored target for novel anti-TB agents.
The six-months required for standard tuberculosis (TB) therapy is thought to stem from the inability of the existing anti-TB drugs to eliminate a sub-population of specialist Mycobacterium tuberculosis (Mtb) bacilli which, though not resistant in the classic (genetic) sense, are able to withstand exposure to lethal antibiotics. We will investigate the predicted role of a major Mtb stress response pathway, the so-called 'SOS response', in providing the functional link between the formation of these 'persister' cells and the subsequent emergence of genetically drug resistant Mtb mutants during extended antibiotic treatment. Our project will exploit the complementary expertise of the US and South African partners in developing a comprehensive understanding of the biochemical and microbiological mechanisms underpinning the activity of a core SOS-controlled DNA repair machine - the 'mutasome' - and its role in generating drug-resistance mutations. This knowledge will be utilized in laboratory screens designed to identify chemical compounds which inhibit SOS-dependent mutasome function, and could be developed as 'anti-resistance' drugs to protect current and future anti-TB antibiotics.
| Reiche, Michael A; Warner, Digby F; Mizrahi, Valerie (2017) Targeting DNA Replication and Repair for the Development of Novel Therapeutics against Tuberculosis. Front Mol Biosci 4:75 |
| Ditse, Zanele; Lamers, Meindert H; Warner, Digby F (2017) DNA Replication in Mycobacterium tuberculosis. Microbiol Spectr 5: |
| Warner, Digby F; Rock, Jeremy M; Fortune, Sarah M et al. (2017) DNA Replication Fidelity in the Mycobacterium tuberculosis Complex. Adv Exp Med Biol 1019:247-262 |
