Ahmad S, Bhattacharya D, Gupta N, Rawat V, Tousif S, Van Kaer L, Das G. Clofazimine enhances the efficacy of BCG revaccination via stem cell-like memory T cells.
PLoS Pathog 2020;
16:e1008356. [PMID:
32437421 PMCID:
PMC7269335 DOI:
10.1371/journal.ppat.1008356]
[Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 06/03/2020] [Accepted: 01/27/2020] [Indexed: 12/11/2022] Open
Abstract
Tuberculosis (TB) is one of the deadliest diseases, claiming ~2 million deaths annually worldwide. The majority of people in TB endemic regions are vaccinated with Bacillus Calmette Guerin (BCG), which is the only usable vaccine available. BCG is efficacious against meningeal and disseminated TB in children, but protective responses are relatively short-lived and fail to protect against adult pulmonary TB. The longevity of vaccine efficacy critically depends on the magnitude of long-lasting central memory T (TCM) cells, a major source of which is stem cell-like memory T (TSM) cells. These TSM cells exhibit enhanced self-renewal capacity as well as to rapidly respond to antigen and generate protective poly-functional T cells producing IFN-γ, TNF-α, IL-2 and IL-17. It is now evident that T helper Th 1 and Th17 cells are essential for host protection against TB. Recent reports have indicated that Th17 cells preserve the molecular signature for TSM cells, which eventually differentiate into IFN-γ-producing effector cells. BCG is ineffective in inducing Th17 cell responses, which might explain its inadequate vaccine efficacy. Here, we show that revaccination with BCG along with clofazimine treatment promotes TSM differentiation, which continuously restores TCM and T effector memory (TEM) cells and drastically increases vaccine efficacy in BCG-primed animals. Analyses of these TSM cells revealed that they are predominantly precursors to host protective Th1 and Th17 cells. Taken together, these findings revealed that clofazimine treatment at the time of BCG revaccination provides superior host protection against TB by increasing long-lasting TSM cells.
Tuberculosis (TB) is one of the deadliest diseases, claiming ~2 million deaths annually worldwide. Bacillus Calmette Guerin (BCG) is the only usable vaccine available and exhibits efficacy against meningeal and disseminated TB in children. Consequently, the vast majority of people in TB endemic regions are vaccinated with BCG. However, host protective immune responses diminish over time due to gradual depletion of T central memory (TCM) cells, which are responsible for long-term host protection. Here, we provide evidence that revaccination with BCG along with the clofazimine, an approved drug for treatment of leprosy and drug-resistant TB, induces stem cell-like memory T (TSM) cells. TSM cells are precursors to TCM cells, and provide long-term host protection to TB by continuous supply of TCM cells. Interestingly, these TSM cells were generated from IL-17-producing T helper (Th)17 cells. These TSM cells differentiated into TCM and T effector memory (TEM) cells and maintained a stable pool of critically important Th1 and Th17 cells to provide optimal host protection against TB.
Collapse