Title : Mycobacterium tuberculosis virulence factor ESAT-6 induces biphasic immunometabolic reprogramming to redirect macrophage polarization
Abstract:
Tuberculosis remains one of the world’s deadliest and most persistent infectious diseases, caused by Mycobacterium tuberculosis (M.tb). Among its key virulence determinants, ESAT-6 (Early Secreted Antigenic Target-6) is a secreted protein widely recognized for its potent immunomodulatory properties and its ability to influence host cell signalling and metabolism. Given the central role of macrophage plasticity in determining infection outcomes, we investigated how ESAT-6 reshapes macrophage metabolism and cytokine responses to alter cellular phenotype and potentially favour bacterial persistence. Our findings demonstrate that ESAT-6 induces a dynamic, time-dependent reprogramming of macrophage function rather than a static inflammatory response. In the early phase, ESAT-6 treated macrophages display hallmarks of classical M1 activation, including elevated oxidative and nitrosative stress, increased pro-inflammatory cytokine production, enhanced glycolysis, and accumulation of metabolites such as lactate and succinate. As the response progresses, the proinflammatory cytokines like IL-6 remains sustained followed by decline in IL-12 level. On the other side anti-inflammatory cytokine like IL-10 increases, indicating a gradual shift toward an alternative, M2-like phenotype. This phenotypic transition is closely associated with alterations in intracellular redox balance and modulation of the NAD⁺/NADH ratio, underscoring a coordinated immunometabolic shift. Collectively, these results support a biphasic model in which ESAT-6 initially triggers inflammatory activation and subsequently redirects macrophage polarization through metabolic rewiring. Such temporal skewing from an M1-like to an alternative phenotype may create a more permissive intracellular environment that supports long-term bacterial survival. Overall, our study highlights how M.tb strategically exploits host immunometabolism via ESAT-6 to reshape macrophage identity and promote persistence, providing insight into mechanisms of chronic infection and identifying potential avenues for host-directed therapeutic intervention.
