Adjunct therapy with all-trans-retinoic acid improves therapeutic efficacy through immunomodulation while treating tuberculosis with antibiotics in a murine model.

Tuberculosis (TB) is the second leading infectious killer after COVID-19. Standard anti-tubercular drugs exhibit various limitations like toxicity, lengthy, and unresponsive to dormant and drug resistant organisms. Here, we report that all-trans-retinoic acid (ATRA) improves M.tb clearance in mice while treating with anti-tubercular drug isoniazid (INH). Interestingly, ATRA promoted activities of lysosomes, mitochondria, and production of various inflammatory mediators in macrophages. Furthermore, ATRA upregulated the expression of genes of lipid metabolic pathways in macrophages. Along this line, we registered that ATRA activated MEK/ERK pathway in macrophages in-vitro and MEK/ERK and p38 MAPK pathways in the mice. Finally, ATRA induced both Th1 and Th17 responses in lungs and spleens of M.tb-infected mice. Taken together, these data indicated that ATRA provides beneficial adjunct therapeutic value by modulating MEK/ERK and p38 MAPK pathways and thus warrants further testing for human use.

Biapenem, a Carbapenem Antibiotic, Elicits Mycobacteria Specific Immune Responses and Reduces the Recurrence of Tuberculosis.

Tuberculosis (TB) still tops the list of global health burdens even after COVID-19. However, it will sooner transcend the current pandemic due to the prevailing risk of reactivation of latent TB in immunocompromised individuals. The indiscriminate misuse and overuse of antibiotics have resulted in the emergence of deadly drug-resistant variants of Mycobacterium tuberculosis (M.tb). This study aims to characterize the functionality of the carbapenem antibiotic-Biapenem (BPM) in generating long-lasting immunity against TB. BPM treatment significantly boosted the activation status of the innate immune arm-macrophages by augmenting p38 signaling. Macrophages further primed and activated the adaptive immune cells CD4+ and CD8+ T-cells in the lung and spleen of the infected mice model. Furthermore, BPM treatment significantly amplified the polarization of T lymphocytes toward inflammatory subsets, such as Th1 and Th17. The treatment also helped generate a long-lived central memory T-cell subset. The generation of central memory T lymphocyte subset upon BPM treatment in the murine model led to a significant curtailing in the recurrence of TB due to reactivation and reinfection. These results suggest the potentiality of BPM as a potent adjunct immunomodulator to improve host defense against M.tb by enriching long-term protective memory cells. IMPORTANCE Tuberculosis (TB) caused by Mycobacterium tuberculosis (M.tb) tops the list of infectious killers around the globe. The emergence of drug-resistant variants of M.tb has been a major hindrance toward realizing the "END TB" goal. Drug resistance has amplified the global burden toward the quest for novel drug molecules targeting M.tb. Host-directed therapy (HDT) offers a lucrative alternative to tackle emerging drug resistance and disease relapse by strengthening the host's immunity. Through our present study, we have tried to characterize the functionality of the carbapenem antibiotic-Biapenem (BPM). BPM treatment significantly augmented long-lasting immunity against TB by boosting the innate and adaptive immune arms. The generation of long-lived central memory T lymphocyte subset significantly improved the disease outcome and provided sterilizing immunity in the murine model of TB. The present investigation's encouraging results have helped us depict BPM as a potent adjunct immunomodulator for treating TB.

Cotreatment With Clofazimine and Rapamycin Eliminates Drug-Resistant Tuberculosis by Inducing Polyfunctional Central Memory T-Cell Responses.

Mycobacterium tuberculosis, the causative agent of tuberculosis, is acquiring drug resistance at a faster rate than the discovery of new antibiotics. Therefore, alternate therapies that can limit the drug resistance and disease recurrence are urgently needed. Emerging evidence indicates that combined treatment with antibiotics and an immunomodulator provides superior treatment efficacy. Clofazimine (CFZ) enhances the generation of T central memory (TCM) cells by blocking the Kv1.3+ potassium channels. Rapamycin (RAPA) facilitates M. tuberculosis clearance by inducing autophagy. In this study, we observed that cotreatment with CFZ and RAPA potently eliminates both multiple and extensively drug-resistant (MDR and XDR) clinical isolates of M. tuberculosis in a mouse model by inducing robust T-cell memory and polyfunctional TCM responses. Furthermore, cotreatment reduces the expression of latency-associated genes of M. tuberculosis in human macrophages. Therefore, CFZ and RAPA cotherapy holds promise for treating patients infected with MDR and XDR strains of M. tuberculosis.