c-Myc Inhibits Macrophage Antimycobacterial Response in Mycobacterium tuberculosis Infection

Mycobacterium tuberculosis (MTB) is a major global cause of mortality, responsible for over a million deaths each year. Despite this burden, natural immunity prevents disease in more than 90% of exposed individuals. Previous studies have identified interferon-gamma (IFN-γ) as a key regulator of innate immune defense against MTB. Here, we investigate the impact of IFN-γ timing on macrophage-mediated control of MTB infection. We demonstrate that IFN-γ exposure before infection enhances macrophage antibacterial activity, whereas post-infection exposure does not. Further analysis of this phenotype revealed a strong association between c-Myc signaling and macrophage function in MTB control, as identified through unbiased in vitro systems approaches. Given the difficulty of perturbing c-Myc in primary cells, we developed a lentiviral system for c-Myc inhibition and overexpression. We profiled both datasets (IFN-γ timing and c-Myc inhibition) to characterize the resulting transcriptional shifts. IFN-γ timing experiments: BMDMs were isolated and differentiated as described in the Methods section. BMDMs that differentiated for 6 days were stimulated with IFN-γ according to the following conditions and were infected with MTB: full treatment (C3), IFN-γ only before MTB infection (C1), IFN-γ only after MTB infection (C2) and no IFN-γ treatment (C4). RNA was extracted after 6 and 24 hours. c-Myc inhibition experiments: HSCs and immune progenitors were isolated, transduced and differentiated as described in the Methods section. Transduced and WT BMDMs received doxycycline to induce overexpression c-Myc or Omomyc (c-Myc inhibition protein). RNA was extracted after 24 hours.