Withaferin A Protects against Primary and Recurrent Tuberculosis by Modulating Mycobacterium-Specific Host Immune Responses.

Abstract

The fate of Mycobacterium tuberculosis infection is governed by immune signaling pathways that can either eliminate the pathogen or result in tuberculosis (TB). Anti-TB therapy (ATT) is extensive and is efficacious only against active, drug-sensitive strains of M. tuberculosis. Due to severe side effects, ATT often causes impairment of host immunity, making it imperative to use novel immunotherapeutics for better clinical outcomes. In this study, we have explored the immunomodulatory potential of withaferin A (WA) as an immunotherapeutic against TB. Here, we demonstrate that WA can constrain intracellular drug-sensitive and -resistant strains of M. tuberculosis by augmenting host immune responses. We also established the potential of WA treatment in conjunction with isoniazid. We show that WA directs the host macrophages toward defensive M1 polarization and enhances TH1 and TH17 immune responses against M. tuberculosis infection. The reduced bacterial burden upon T cell adoptive transfer further corroborated the augmented T cell responses. Interestingly, WA stimulated the generation of T cell memory populations by instigating STAT signaling, thereby reducing the rate of TB recurrence due to reactivation and reinfection. We substantiate the prospects of WA as a potent adjunct immunomodulator that enriches protective memory cells by prompting STAT signaling and improves host defense against M. tuberculosis. IMPORTANCE Despite being extensive, conventional antituberculosis therapy (ATT) is barely proficient in providing sterile immunity to tuberculosis (TB). Failure to constrain the escalating global TB burden due to the emergence of drug-resistant bacterial strains and immune dampening effects of ATT necessitates adjunct immunotherapeutics for better clinical outcomes. We evaluated the prospects of withaferin A (WA), an active constituent of Withania somnifera, as an adjunct immunomodulator against diverse M. tuberculosis strains. WA efficiently restricts the progression of TB by stimulating antimycobacterial host responses, protective immune signaling, and activation of diverse immune cell populations. Protective effects of WA can be attributed to the enrichment of memory T cells by induction of STAT signaling, thereby enhancing resistance to reinfections and reactivation of disease. We ascertained the immunotherapeutic potential of WA in boosting host immune responses against M. tuberculosis.