G1-4A, a Polysaccharide from Tinospora cordifolia Inhibits the Survival of Mycobacterium tuberculosis by Modulating Host Immune Responses in TLR4 Dependent Manner.

Pramod Kumar Gupta,Prafull Kumar Singh,Pampi Chakraborty,M G R Rajan,Savita Kulkarni,Krishna B Sainis,Santosh Kumar,Selvakumar Subbian

doi:10.1371/journal.pone.0154725

Abstract

Rapid emergence of drug resistance in Mycobacterium tuberculosis (MTB) is a major health concern and demands the development of novel adjunct immunotherapeutic agents capable of modulating the host immune responses in order to control the pathogen. In the present study, we sought to investigate the immunomodulatory effects of G1-4A, a polysaccharide derived from the Indian medicinal plant Tinospora cordifolia, in in-vitro and aerosol mouse models of MTB infection. G1-4A treatment of MTB infected RAW264.7 macrophages significantly induced the surface expression of MHC-II and CD-86 molecules, secretion of proinflammatory cytokines (TNF-α, IL-β, IL-6, IL-12, IFN-γ) and nitric oxide leading to reduced intracellular survival of both drug sensitive (H37Rv) as well as multi drug resistant strains (Beijing and LAM) of MTB, which was partially attributed to G1-4A induced NO production in TLR4-MyD88 dependent manner. Similarly, bacillary burden was significantly reduced in the lungs of MTB infected BALB/c mice treated with G1-4A, with simultaneous up-regulation of the expression of TNF-α, INF-γ and NOS2 in the mouse lung along with increased levels of Th1 cytokines like IFN-γ, IL-12 and decreased levels of Th2 cytokine like IL-4 in the serum. Furthermore, combination of G1-4A with Isoniazid (INH) exhibited better protection against MTB compared to that due to INH or G1-4A alone, suggesting its potential as adjunct therapy. Our results demonstrate that modulation of host immune responses by G1-4A might improve the therapeutic efficacy of existing anti-tubercular drugs and provide an attractive strategy for the development of alternative therapies to control tuberculosis.

Highlights

The ability of Mycobacterium tuberculosis (MTB) to successfully parasitize the macrophages is a result of its capacity to adapt to the changing host environment by utilizing the resources available to it within host and inhibiting the host responses directed against it [1]
Our results demonstrate that G1-4A inhibits the survival of drug-sensitive as well as multi-drug resistant (MDR) strains of MTB in in vitro and ex vivo macrophage model of MTB infection, by inducing nitric oxide (NO) in TLR4-MyD88 dependent manner with simultaneous induction of pro-inflammatory cytokines and surface expression of MHC-II and CD-86
Our cytokine data demonstrated that IFN-γ levels were very low in supernatants of cells infected with all the MTB strains in absence of G1-4A but increased significantly after treatment with G1-4A (Fig 1A)

Summary

Introduction

The ability of Mycobacterium tuberculosis (MTB) to successfully parasitize the macrophages is a result of its capacity to adapt to the changing host environment by utilizing the resources available to it within host and inhibiting the host responses directed against it [1]. Despite the availability of effective treatment of TB, rapid emergence and spread of drug resistant MTB strains, along with need for extended use of current drug regimens, are worsening the burden of disease [11] and making it compulsory to explore the novel strategies of anti-tubercular therapies. One such approach involves selective modulation of host immune responses to enhance the therapeutic potential of existing anti-tubercular drugs [12]. CpG DNA, a TLR9 agonist was shown to control the microbial infections by boosting the innate immune responses, indicating antimicrobial potential of such compounds [16]

Methods

Results

Conclusion