The nutritional status of TB patients plays a significant role in severity of disease, mortality rates and patient recovery after drug therapy, where malnourished patients are reported to have significantly poorer outcomes. Nutritional supplementation with nicotinamide, a water-soluble form of vitamin B3, has been linked to reductions in TB burden. Nicotinamide is a substrate or precursor to formation of NAD+ (nicotinamide adenine dinucleotide) and its reducing equivalent NADH, both of which are involved in redox reactions occurring during glycolysis. From a mechanistic perspective, nicotinamide lies at the crossroads between host immunometabolism and Mycobacterium tuberculosis’ (Mtb’s) ability to disrupt glycolytic flux (which provides ATP and NADH) in host immune cells such as macrophages. Nicotinamide has been shown to restore glycolytic activity to TB-infected macrophages in vitro and to reduce pulmonary TB burden in a mouse TB infection model (Pacl et al (2023), Nat. Comms. 14:5427) Given that Mtb subpopulations residing in macrophages are more difficult to eliminate, targeting these subpopulations with multiple orthogonal strategies could be a key component to treatment shortening. As such, nicotinamide could be positioned as a cheap, orally bioavailable, easy to implement option in LMIC settings, that at the appropriate dose could contribute significant added benefit to both current standard of care drug regimen as well as novel treatment shortening TB regimens being progressed by the TBDA. In order to provide supporting evidence to the latter hypothesis, this grant will use in vitro macrophage screening assay to test the potential for the added effect of nicotinamide to novel TB drug combinations that have a high likelihood of entering the clinic.

We propose using our new drug/drug combination, intra-macrophage assay for probing the interaction of nicotinamide and its analogs with anti-TB drugs to identify optimal drug/drug regimens.