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Novel vaccination strategies are crucial to efficiently control tuberculosis, as proposed by the World Health Organization under its flagship program "End TB Strategy." However, the emergence of drug-resistant strains of Mycobacterium tuberculosis (Mtb), particularly in those coinfected with HIV-AIDS, constitutes a major impediment to achieving this goal. We report here a novel vaccination strategy that involves synthesizing a formulation of an immunodominant peptide derived from the Acr1 protein of Mtb. This nanoformulation in addition displayed on the surface a toll-like receptor-2 ligand to offer to target dendritic cells (DCs). Our results showed an efficient uptake of such a concoction by DCs in a predominantly toll-like receptor-2-dependent pathway. These DCs produced elevated levels of nitric oxide, proinflammatory cytokines interleukin-6, interleukin-12, and tumor necrosis factor-α, and upregulated the surface expression of major histocompatibility complex class II molecules as well as costimulatory molecules such as CD80 and CD86. Animals injected with such a vaccine mounted a significantly higher response of effector and memory Th1 cells and Th17 cells. Furthermore, we noticed a reduction in the bacterial load in the lungs of animals challenged with aerosolized live Mtb. Therefore, our findings indicated that the described vaccine triggered protective anti-Mtb immunity to control the tuberculosis infection., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Mycobacterium tuberculosis (Mtb) is a smart and successful pathogen since it can persist in the intimidating environment of the host by taming and tuning the immune system. Mtb releases MPT64 (Rv1980c) protein in high amounts in patients with active tuberculosis (TB). Consequently, we were curious to decipher the role of MPT64 on the differentiating dendritic cells (DCs) and its relation to evading the immune system. We observed that pre-exposure of differentiating DCs to MPT64 (DC MPT64 ) transformed them into a phenotype of myeloid-derived suppressor cells (MDSCs). DC MPT64 expressed a high level of immunosuppressive molecules PD-L1, TIM-3, nitric oxide (NO), arginase 1, IDO-1, IL-10 and TGF-β, but inhibited the production of pro-inflammatory cytokines TNF-α, IL-6 and IL-12. DC MPT64 chemotaxis function was diminished due to the reduced expression of CCR7. DC MPT64 promoted the generation of regulatory T cells (Tregs) but inhibited the differentiation of Th1 cells and Th17 cells. Further, high lipid and methylglyoxal content, and reduced glucose consumption by DC MPT64 , rendered them metabolically quiescent and consequently, reduced DC MPT64 ability to phagocytose Mtb and provided a safer shelter for the intracellular survival of the mycobacterium. The mechanism identified in impairing the function of DC MPT64 was through the increased production and accumulation of methylglyoxal. Hence, for the first time, we demonstrate the novel role of MPT64 in promoting the generation of MDSCs to favor Mtb survival and escape its destruction by the immune system., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Tuberculosis (TB) treatment is lengthy and inflicted with severe side-effects. Here, we attempted a novel strategy to reinforce host immunity through NOD-like receptor (NOD-2) and Toll-like receptor (TLR-4) signaling in the murine model of TB. Intriguingly, we noticed that it not only bolstered the immunity but also reduced the dose and duration of rifampicin and isoniazid therapy. Further, we observed expansion in the pool of effector (CD44 hi , CD62L lo , CD127 hi ) and central (CD44 hi , CD62L hi , CD127 hi ) memory CD4 T cells and CD8 T cells and increased the intracellular killing of Mycobacterium tuberculosis ( Mtb ) by activated dendritic cells [CD86 hi , CD40 hi , IL-6 hi , IL-12 hi , TNF-α hi , nitric oxide (NO) hi ] with significant reduction in Mtb load in the lungs and spleen of infected animals. We infer that the signaling through NOD-2 and TLR-4 may be an important approach to reduce the dose and duration of the drugs to treat TB.

For a long time, tuberculosis (TB) has been inflicting mankind with the highest morbidity and mortality. Although the current treatment is extremely potent, a few bacilli can still hide inside the host mesenchymal stem cells (MSC). The functional capabilities of MSCs are known to be modulated by TLRs, NOD-2, and RIG-1 signaling. Therefore, we hypothesize that modulating the MSC activity through TLR-4 and NOD-2 can be an attractive immunotherapeutic strategy to eliminate the Mtb hiding inside these cells. In our current study, we observed that MSC stimulated through TLR-4 and NOD-2 (N2.T4) i) activated MSC and augmented the secretion of pro-inflammatory cytokines; ii) co-localized Mtb in the lysosomes; iii) induced autophagy; iv) enhanced NF-κB activity via p38 MAPK signaling pathway; and v) significantly reduced the intracellular survival of Mtb in the MSC. Overall, the results suggest that the triggering through N2.T4 can be a future method of immunotherapy to eliminate the Mtb concealed inside the MSC., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Aqdas, Singh, Amir, Maurya, Pahari and Agrewala.)

The generation of enduring protective immunity by vaccines is of utmost importance. Intriguingly, there is considerable variation in the efficacy of vaccines amongst individuals. Various studies have shown that normal flora of gastrointestinal tract plays a vital role in maintaining host homeostasis and immunity. Since gut microbiome is also extremely variable between individuals, we speculate that it might impact individual's response to vaccines. Consequently, we administered broad spectrum antibiotics cocktail to induce gut dysbiosis and monitored its impact on the generation of long-lasting memory T cells and thereby BCG vaccine efficacy. Interestingly, gut dysbiosis significantly decreased the activation of CD4 + T cells and CD8 + T cells. Further, there was decline in the frequency of memory CD4 + T cells and CD8 + T cells in lungs and secondary lymphoid organs of the vaccinated animals. Moreover, it dampened the IFN-γ and TNF-α secretion and proliferation of Mtb -specific T cells. Most importantly, dysbiosis hampered Mtb clearance in vaccinated animals, as evidenced by increase in the colony forming units (CFUs) in lungs and spleen. Our findings indicate that gut dysbiosis can be one of the major factors responsible for variable efficacy of TB vaccines across the world., (Copyright © 2020 Nadeem, Maurya, Das, Khan and Agrewala.)

Background: The clinical trials conducted at Chingleput India suggest that BCG fails to protect against tuberculosis (TB) in TB-endemic population. Recent studies advocate that non-tuberculous mycobacteria and latent Mycobacterium tuberculosis (Mtb) infection interferes in the antigen processing and presentation of BCG in inducing protective immunity against Mtb. Thereby, indicating that any vaccine that require extensive antigen processing may not be efficacious in TB-endemic zones. Recently, we have demonstrated that the vaccine candidate L91, which is composed of lipidated promiscuous MHC-II binder epitope, derived from latency associated Acr1 antigen of Mtb is immunogenic in the murine and Guinea pig models of TB and conferred better protection than BCG against Mtb., Methods: In this study, we have used a multi-stage based bi-epitope vaccine, namely L4.8, comprising of MHC-I and MHC-II binding peptides of active (TB10.4) and latent (Acr1) stages of Mtb antigens, respectively. These peptides were conjugated to the TLR-2 agonist Pam2Cys., Results: L4.8 significantly elicited both CD8 T cells and CD4 T cells immunity, as evidenced by increase in the enduring polyfunctional CD8 T cells and CD4 T cells. L4.8 efficiently declined Mtb-burden and protected animals better than BCG and L91, even at the late stage of Mtb infection., Conclusions: The BCG-L4.8 prime boost strategy imparts a better protection against TB than the BCG alone. This study emphatically denotes that L4.8 can be a promising future vaccine candidate for controlling active and latent TB.

Background: The current BCG vaccine induces only short-term protection against Mycobacterium tuberculosis (Mtb), suggesting its failure to generate long-lasting memory T cells. Previously, we have demonstrated that a self-adjuvanting peptide of Mtb (L91), successfully generated enduring memory Th1 cells. Consequently, we investigated if L91 was able to recuperate BCG potency in perpetuating the generation of memory T cells and protection against Mtb infected mice., Methods: In the present study, we evaluated the potency of a self adjuvanting Mtb peptide vaccine L91 in invigorating BCG immune response against Mtb in mice. Female BALB/c mice were immunized with BCG. Later, they were boosted twice with L91 or an antigenically irrelevant lipidated influenza virus hemagglutinin peptide (LH). Further, PBMCs obtained from BCG vaccinated healthy subjects were cultured in vitro with L91. T cell responses were determined by surface markers and intracellular cytokine staining. Secretion of cytokines was estimated in the culture supernatants (SNs) by ELISA., Results: Compared to the BCG-vaccinated controls, L91 booster significantly enhanced the percentage of memory Th1 cells and Th17 cells and reduced the mycobacterial burden in BCG primed and L91-boosted (BCG-L91) group, even after 229 days of BCG vaccination. Further, substantial augmentation in the central (CD44 hi CD62L hi CD127 hi ) and effector memory (CD44 hi CD62L lo CD127 lo ) CD4 T cells was detected. Furthermore, greater frequency of polyfunctional Th1 cells (IFN-γ + TNF-α + ) and Th17 cells (IFN-γ + IL-17A + ) was observed. Importantly, BCG-L91 successfully prevented CD4 T cells from exhaustion by decreasing the expression of PD-1 and Tim-3. Additionally, augmentation in the frequency of Th1 cells, Th17 cells and memory CD4 T cells was observed in the PBMCs of the BCG-vaccinated healthy individuals following in vitro stimulation with L91., Conclusions: Our study demonstrated that L91 robustly reinvigorate BCG potency to invoke enduring protection against Mtb. This novel vaccination stratagem involving BCG-priming followed by L91-boosting can be a future prophylactic measure to control TB.

Regardless of the fact that potent drug-regimen is currently available, tuberculosis continues to kill 1.5 million people annually. Tuberculosis patients are not only inflicted by the trauma of disease but they also suffer from the harmful side-effects, immune suppression and drug resistance instigated by prolonged therapy. It is an exigency to introduce radical changes in the existing drug-regime and discover safer and better therapeutic measures. Hence, we designed a novel therapeutic strategy by reinforcing the efficacy of drugs to kill Mtb by concurrently boosting host immunity by L91. L91 is chimera of promiscuous epitope of Acr1 antigen of Mtb and TLR-2 agonist Pam2Cys. The adjunct therapy using drugs and L91 (D-L91) significantly declined the bacterial load in Mtb infected animals. The mechanism involved was through enhancement of IFN-γ(+)TNF-α(+) polyfunctional Th1 cells and IL-17A(+)IFN-γ(+) Th17 cells, enduring memory CD4 T cells and downregulation of PD-1. The down-regulation of PD-1 prevents CD4 T cells from undergoing exhaustion and improves their function against Mtb. Importantly, the immune response observed in animals could be replicated using T cells of tuberculosis patients on drug therapy. In future, D-L91 therapy can invigorate drugs potency to treat tuberculosis patients and reduce the dose and duration of drug-regime.