Efficacy of Mycobacterium indicus pranii immunotherapy as an adjunct to chemotherapy for tuberculosis and underlying immune responses in the lung

Goals and strategies in vaccine development against tuberculosis

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), continues to be a major health problem globally. The emergence of multi-drug-resistant TB and extensively drug-resistant TB has become a severe threat to TB control programs. Currently, the Bacille Calmette-Guerin (BCG) vaccine protects a child from disease dissemination efficiently, but its efficiency wanes in adults. Despite all the limitations of BCG and accelerated TB vaccine research, BCG remains the only approved vaccine available for TB. Anti-TB drug treatment has been successful in combating the disease, but it has various side effects and requires an extended drug treatment period. So, vaccination is the finest outlook that can surpass the above-mentioned limitations. Several vaccine candidates are in the pipeline, and the hope for a potential candidate to either boost the BCG vaccine or replace BCG is underway. This review discusses different approaches to TB vaccine development. It summarizes all the challenges and limitations in vaccine development, and its preclinical and clinical trials. Additionally, DNA vaccines and their vaccination techniques are also discussed. Furthermore, the immunoinformatics approach and nanomaterial-based vaccine delivery with practical and productive endpoints are also discussed. Lastly, the potential prospects are also suggested for further studies, which would help bring positive outcomes.

Tuberculosis vaccines and therapeutic drug: challenges and future directions

Tuberculosis (TB) remains a prominent global health challenge, with the World Health Organization documenting over 1 million annual fatalities. Despite the deployment of the Bacille Calmette-Guérin (BCG) vaccine and available therapeutic agents, the escalation of drug-resistant Mycobacterium tuberculosis strains underscores the pressing need for more efficacious vaccines and treatments. This review meticulously maps out the contemporary landscape of TB vaccine development, with a focus on antigen identification, clinical trial progress, and the obstacles and future trajectories in vaccine research. We spotlight innovative approaches, such as multi-antigen vaccines and mRNA technology platforms. Furthermore, the review delves into current TB therapeutics, particularly for multidrug-resistant tuberculosis (MDR-TB), exploring promising agents like bedaquiline (BDQ) and delamanid (DLM), as well as the potential of host-directed therapies. The hurdles in TB vaccine and therapeutic development encompass overcoming antigen diversity, enhancing vaccine effectiveness across diverse populations, and advancing novel vaccine platforms. Future initiatives emphasize combinatorial strategies, the development of anti-TB compounds targeting novel pathways, and personalized medicine for TB treatment and prevention. Despite notable advances, persistent challenges such as diagnostic failures and protracted treatment regimens continue to impede progress. This work aims to steer future research endeavors toward groundbreaking TB vaccines and therapeutic agents, providing crucial insights for enhancing TB prevention and treatment strategies.

Synergistic role of Mycobacterium indicus pranii and human beta Defensin-2 as adjunctive therapy against Mycobacterium tuberculosis

Host-directed therapies (HDT) via modulation of specific host responses like inflammation can limit mycobacterial infection. HDTs could be included in current TB therapy as an adjunct to increase bacterial clearance and limit tissue damage to control spread. Individually, Mycobacterium indicus pranii (MIP) and human beta defensin-2 (hBD-2) are promising therapies for tuberculosis (TB). They can directly target the TB bacilli and enhance cell-mediated immune responses, which is limiting with conventional drugs. Therefore, our study investigated the combined application of MIP and hBD-2 to evaluate their efficacy in clearing infections caused by Mycobacterium smegmatis (M.smeg) and Mycobacterium tuberculosis (M.tb) (both avirulent; H37Ra and virulent strain; H37Rv) in THP-1 cells and human monocyte-derived macrophages (MDMs). A strong pro-inflammatory response was observed against the combination of MIP and hBD-2 which also correlated with a significant reduction in the bacterial load. This combination further showed protection against M.tb by enhancing pyroptosis in the infected cells. The study suggests the combined use of these potent immunomodulators, which could be employed as an effective mode of therapy as adjuvants against mycobacterial infections after validation in a suitable animal model.

Mycobacterium w - a promising immunotherapeutic intervention for diseases

Immunomodulating agents interact with the immune system and alter the outcome of specific immune processes. As our understanding of the immune system continues to evolve, there is a growing effort to identify agents with immunomodulating applications to use therapeutically to treat various diseases. Mycobacterium w (Mw), a heat-killed mycobacterium, is an atypical mycobacterial species that possesses strong immunomodulatory properties. Mw was initially evaluated as an immune-therapeutic against leprosy, but since then Mw has generated a lot of interest and been studied for therapeutic applications across a host of diseases, such as pulmonary tuberculosis, tuberculous pericarditis, sepsis, lung cancer, and more. This article summarizes a large body of work published in the past five decades, describing various aspects of Mw and its potential for further therapeutic development.

Therapeutic DNA Vaccine Targeting Mycobacterium tuberculosis Persisters Shortens Curative Tuberculosis Treatment

Mycobacterium tuberculosis ( Mtb) is one of the leading infectious causes of death worldwide. There is no available licensed therapeutic vaccine that shortens active tuberculosis (TB) disease drug treatment and prevents relapse, despite the World Health Organization's calls. Here, we show that an intranasal DNA vaccine containing a fusion of the stringent response rel Mtb gene with the gene encoding the immature dendritic cell-targeting chemokine, MIP-3α/CCL20, shortens the duration of curative TB treatment in immunocompetent mice. Compared to the first-line regimen for drug-susceptible TB alone, our novel adjunctive vaccine induced greater Rel Mtb -specific T-cell responses associated with optimal TB control in spleen, blood, lungs, mediastinal lymph nodes, and bronchoalveolar lavage (BAL) fluid. These responses were sustained, if not augmented, over time. It also triggered more effective dendritic cell recruitment, activation, and colocalization with T cells, implying enhanced crosstalk between innate and adaptive immunity. Moreover, it potentiated a 6-month TB drug-resistant regimen, rendering it effective across treatment regimens, and also showed promising results in CD4+ knockout mice, perhaps due to enhanced Rel-specific CD8+ T-cell responses. Notably, our novel fusion vaccine was also immunogenic in nonhuman primates, the gold standard animal model for TB vaccine studies, eliciting antigen-specific T-cell responses in blood and BAL fluid analogous to those observed in protected mice. Our findings have critical implications for therapeutic TB vaccine clinical development in immunocompetent and immunocompromised populations and may serve as a model for defining immunological correlates of therapeutic vaccine-induced protection.

One sentence summary

A TB vaccine shortens curative drug treatment in mice by eliciting strong TB-protective immune responses and induces similar responses in macaques.

PreVenTB trial: protocol for evaluation of efficacy and safety of two vaccines VPM1002 and Immuvac (Mw) in preventing tuberculosis (TB) in healthy household contacts of newly diagnosed sputum smear-positive pulmonary TB patients: phase III, randomised, double-blind, three-arm placebo-controlled trial

INTRODUCTION

Tuberculosis (TB) continues to be one of the deadliest infectious diseases over the centuries, killing more people worldwide than any other single infectious disease. There is an urgent need for additional strategies which can expedite efforts to combat TB including a preventive vaccine. In this endeavour, we have developed a protocol for a multisite, double-blind, placebo-controlled clinical trial in India that aims to evaluate the efficacy and safety of two TB vaccines; namely, VPM1002 and Immuvac (M.w) (Mycobacterium Indicus Pranii) (MIP) among healthy household contacts (HHCs) of sputum smear-positive pulmonary TB (PTB) patients.

METHODS AND ANALYSIS

In the three-arm randomised double-blind placebo-controlled trial study protocol, a total of 12 000 HHCs (aged 6-99 years) of sputum smear-positive PTB patients will be randomised to receive either of the two vaccine candidates VPM1002 and MIP or placebo. The primary efficacy endpoint is the prevention of microbiologically confirmed TB. Secondary endpoints will include (1) prevention against Latent TB infection, (2) incidence of adverse events and serious adverse events in study participants, (3) efficacy of vaccine in prevention of PTB/extra PTB in different age groups (6-18 years, 19-35 years, 36-60 years and above 60 years) and (4) immunogenicity of VPM1002 and MIP at month 2 and month 6 after first vaccination in terms of flow cytometric analysis of M.Tb specific CD4+ and CD8+ T cells secreting cytokines and Luminex assays for the presence of different cytokines in the sera and supernatants of peripheral blood mononuclear cells cultures stimulated with whole cell lysates of M.Tb and subsequently similar analysis for the cases who develop TB postvaccination during the follow-up period.

ETHICS AND DISSEMINATION

Ethics committees' approvals have been granted by the Institutional Human Ethics Committees of all participating centres in this study and the names of the ethics committees and approvals are as follows: (1) National Institute for Research in Tuberculosis (NIRT)-Chennai (including subsites): ECR/135/Inst/TN/2013/RR-19, Approval No. 390/NIRT-Institutional Ethics Committee (IEC)/2018 dated 5 December 2018 (NIRT-Madurai-ECR/1365/Inst/TN/2020; approval dated 8 June 2020; NIRT, Vellore: ECR/1215/Inst/TN/2019; approval dated 26 September 2020); (2) All India Institute of Medical Sciences (AIIMS), Delhi (including subsites)-Institute Ethics Committee, ECR/547/Inst/DL/2014/RR-17 ECR/538/Inst/DL/2014/RR-20; approval No.IEC-385/06-07-2018, approval OP-28/05.04.2019 and SFH- ECR/593/Inst/DL/2014/RR-20 IEC/VMMC/SJH/project/2019-05/25 ; 23 May 2019; (3) National Institute of Tuberculosis and Respiratory Diseases (NITRD), Delhi: ECR/315/Inst/DL/2013/RR-19; approval IEC-No-NITRD/EC/2019/9004; 8 January 2019; (4) Pune-National AIDS Research Institute (NARI) and subsite-ECR/23/Inst/MH/2013/RR-19; IEC-NARI/EC/approval/2018/196; 29 May 2018; (5) Regional Medical Research Centre-Bhubaneshwar-ECR/911/Inst/OR-2017/RR-21; approval, dated 25 April 2018; Subsites- AIIMS, Bhubaneshwar ECR/534/Inst/OD/2014/RR-17 and 20 approval No. T/EMF/Pulm. Med/19/01 dated 13 May 2019; SCB, Cuttack No. No.ECR/84/Inst/OR/2013/RR-20; approval no.186 dated 7 February 2020; (6) NTI-Bengaluru: Ethics Committee-No-ECR/1819/Inst/KA/2019; approval No NTI-IEC/1.2019/principal investigator, dated 31 January 2019; (7) BMMRC, Hyderabad- ECR/450/Inst/AP/2013/RR-16 approval No. 779/BMMRC/2018/IEC, dated 11 June 2018 (Subsite Share India- Mediciti Ethics Committee-ECR/283/Inst/AP/2013/RR-20; Approval no. EC/11/VII/2K20(1) dated 11 July 2020) and (8) SJMC-Bengaluru: ECR/238/Inst/KA/2013/RR-19; approval IEC/1/491/2020; 7 August 2020.The trial findings will be published in accordance with the Consolidated Standards of Reporting Trials guidance. The results of this clinical trial will be presented at scientific conferences and disseminated through publications in peer-reviewed journals, conference presentations and shared with Ministry of Health and Family Welfare, policy-makers and other stakeholders.

TRIAL REGISTRATION NUMBER

CTRI/2019/01/017026.

Assessing the hazard of death, cardiac tamponade, and pericardial constriction among HIV and tuberculosis pericarditis patients using the extended Cox-hazard model: Intervention study

Background and Aims

Tuberculous (TB) pericarditis (TBP), a TB of the heart, is linked to significant morbidity and mortality rates. Administering glucocorticoid therapy to individuals with TBP might enhance overall results and lower the likelihood of fatality. However, the actual clinical effectiveness of supplementary glucocorticoids remains uncertain. This study specifically evaluated the effects of prednisolone, prednisolone-antiretroviral therapy (ART) interaction, and other potential risk factors in reducing the hazard of the composite outcome, death, cardiac tamponade, and constriction, among TBP and human immunodeficiency virus (HIV) patients.

Methods

The data used in this study were obtained from the investigation of the Management of Pericarditis trial, a multicentre international randomized double-blind placebo-controlled 2 × 2 factorial study that investigated the effects of two TB treatments, prednisolone and Mycobacterium indicus pranii  immunotherapy in patients with TBP in Africa. This study used a sample size of 587 TBP and HIV-positive patients randomized into prednisolone and its corresponding placebo arm. We used the extended Cox-proportional hazard model to evaluate the effects of the covariates on the hazard of the survival outcomes. Models fitting and parameter estimation were carried out using R version 4.3.1.

Results

Prednisolone reduces the hazard of composite outcome (hazrad ratio [HR] = 0.32, 95% confidence interval [CI] = 0.19 , 0.54 , p < 0.001), cardiac tamponade (HR = 0.14, 95% CI = 0.05, 0.42, p < 0.001) and constriction (HR = 0.81, 95% CI = 0.41, 1.61, p = 0.55). However, prednisolone increases the hazard of death (HR = 1.58, 95% CI = 1.11, 2.24, p = 0.01). Consistent usage of ART reduces the hazard of composite outcome, death, and constriction but insignificantly increased the hazard of cardiac tamponade.

Conclusion

The study offers valuable insights into how prednisolone impact the hazard of different outcomes in patients with TBP and HIV. The findings hold potential clinical significance, particularly in guiding treatment decisions and devising strategies to enhance outcomes in this specific patient group. However, there are concerns about prednisolone potentially increasing the risk of death due to HIV-related death.

Mycobacterium tuberculosis: immune response, biomarkers, and therapeutic intervention

Although tuberculosis (TB) is an infectious disease, the progression of the disease following Mycobacterium tuberculosis (MTB) infection is closely associated with the host's immune response. In this review, a comprehensive analysis of TB prevention, diagnosis, and treatment was conducted from an immunological perspective. First, we delved into the host's immune response mechanisms against MTB infection as well as the immune evasion mechanisms of the bacteria. Addressing the challenges currently faced in TB diagnosis and treatment, we also emphasized the importance of protein, genetic, and immunological biomarkers, aiming to provide new insights for early and personalized diagnosis and treatment of TB. Building upon this foundation, we further discussed intervention strategies involving chemical and immunological treatments for the increasingly critical issue of drug-resistant TB and other forms of TB. Finally, we summarized TB prevention, diagnosis, and treatment challenges and put forward future perspectives. Overall, these findings provide valuable insights into the immunological aspects of TB and offer new directions toward achieving the WHO's goal of eradicating TB by 2035.

Recombinant BCG expressing the LTAK63 adjuvant improves a short-term chemotherapy schedule in the control of tuberculosis in mice

Tuberculosis (TB) is one of the deadliest infectious diseases around the world. Prevention is based on the prophylactic use of BCG vaccine, effective in infants but as protection wanes with time, adults are less protected. Additionally, chemotherapy requires the use of many antibiotics for several months to be effective. Immunotherapeutic approaches can activate the immune system, intending to assist chemotherapy of TB patients, improving its effectiveness, and reducing treatment time. In this work, the recombinant BCG expressing LTAK63 (rBCG-LTAK63) was evaluated for its immunotherapeutic potential against TB. Bacillary load, immune response, and lung inflammation were evaluated in mice infected with Mycobacterium tuberculosis (Mtb) and treated either with BCG or rBCG-LTAK63 using different routes of administration. Mice infected with Mtb and treated intranasally or intravenously with rBCG-LTAK63 showed a reduced bacillary load and lung inflammatory area when compared to the group treated with BCG. In the spleen, rBCG-LTAK63 administered intravenously induced a higher inflammatory response of CD4+ T cells. On the other hand, in the lungs there was an increased presence of CD4+IL-10+ and regulatory T cells. When combined with a short-term chemotherapy regimen, rBCG-LTAK63 administered subcutaneously or intravenously decreases the Mtb bacillary load, increases the anti-inflammatory response, and reduces tissue inflammation. These findings highlight the potential of rBCG-LTAK63 in assisting chemotherapy against Mtb.

T cell responses to Mycobacterium indicus pranii immunotherapy and adjunctive glucocorticoid therapy in tuberculous pericarditis

Background

In the Investigation of the Management of Pericarditis (IMPI) randomized control, 2x2 factorial trial, Mycobacterium indicus pranii (MIP) immunotherapy, adjunctive corticosteroids or MIP combined with corticosteroids was compared to standard tuberculosis (TB) therapy for tuberculous pericarditis (TBP). While MIP and/or the combination of MIP and corticosteroids had no impact on all-cause mortality or pericarditis related outcomes, corticosteroids reduced the incidence of constrictive pericarditis at 12 months. Data suggests that both adjunctive therapies modulate the immune and inflammatory responses to pulmonary TB. Whether they affect systemic antigen-specific T cell responses, key immune mediators of Mycobacterium tuberculosis control, in patients with TBP is unknown.

Methods

Participants with definite or probable TBP were randomly assigned to receive five injections of MIP or placebo at 2-week intervals and either 6 weeks of oral prednisolone or placebo. Frequencies of CD4 and CD8 T cells expressing IFN-γ, IL-2 or TNF in response to MIP or purified protein derivative stimulation were measured by intracellular cytokine staining and flow cytometry up to 24 weeks post treatment.

Results

Immunotherapy with MIP did not significantly modulate frequencies of Th1 CD4 and CD8 T cells compared to placebo. Adjunctive prednisolone also did not change mycobacteria-specific CD4 or CD8 T cell responses. By contrast, combinatorial therapy with MIP and prednisolone was associated with a modest increase in frequencies of multifunctional and single cytokine-expressing CD4 T cell responses at 6 and 24 weeks post treatment.

Conclusions

Consistent with the lack of a significant clinical effect in the IMPI trial, MIP immunotherapy did not significantly modulate mycobacteria-specific T cell responses. Despite the positive effect of prednisolone on hospitalizations and constrictive pericarditis in the IMPI trial, prednisolone did not significantly reduce pro-inflammatory T cell responses in this sub-study. The modest improvement of mycobacteria-specific T cell upon combinatorial therapy with MIP and prednisolone requires further investigation.

Pathological and protective roles of dendritic cells in Mycobacterium tuberculosis infection: Interaction between host immune responses and pathogen evasion

Dendritic cells (DCs) are principal defense components that play multifactorial roles in translating innate immune responses to adaptive immunity in Mycobacterium tuberculosis (Mtb) infections. The heterogeneous nature of DC subsets follows their altered functions by interacting with other immune cells, Mtb, and its products, enhancing host defense mechanisms or facilitating pathogen evasion. Thus, a better understanding of the immune responses initiated, promoted, and amplified or inhibited by DCs in Mtb infection is an essential step in developing anti-tuberculosis (TB) control measures, such as host-directed adjunctive therapy and anti-TB vaccines. This review summarizes the recent advances in salient DC subsets, including their phenotypic classification, cytokine profiles, functional alterations according to disease stages and environments, and consequent TB outcomes. A comprehensive overview of the role of DCs from various perspectives enables a deeper understanding of TB pathogenesis and could be useful in developing DC-based vaccines and immunotherapies.

Therapeutic Vaccines for Tuberculosis: An Overview

Tuberculosis (TB), caused by Mycobacterium tuberculosis is the world’s deadliest bacterial infection, resulting in more than 1.4 million deaths annually. The emergence of drug-resistance to first-line antibiotic therapy poses a threat to successful treatment, and novel therapeutic options are required, particularly for drug-resistant tuberculosis. One modality emerging for TB treatment is therapeutic vaccination. As opposed to preventative vaccination – the aim of which is to prevent getting infected by M. tuberculosis or developing active tuberculosis, the purpose of therapeutic vaccination is as adjunctive treatment of TB or to prevent relapse following cure. Several candidate therapeutic vaccines, using killed whole-cell or live attenuated mycobacteria, mycobacterial fragments and viral vectored vaccines are in current clinical trials. Other modes of passive immunization, including monoclonal antibodies directed against M. tuberculosis antigens are in various pre-clinical stages of development. Here, we will discuss these various therapeutics and their proposed mechanisms of action. Although the full clinical utility of therapeutic vaccination for the treatment of tuberculosis is yet to be established, they hold potential as useful adjunct therapies.

Impact of an Immune Modulator Mycobacterium-w on Adaptive Natural Killer Cells and Protection Against COVID-19

The kinetics of NKG2C+ adaptive natural killer (ANK) cells and NKG2A+inhibitory NK (iNK) cells with respect to the incidence of SARS-CoV-2 infection were studied for 6 months in a cohort of healthcare workers following the administration of the heat-killed Mycobacterium w (Mw group) in comparison to a control group. In both groups, corona virus disease 2019 (COVID-19) correlated with lower NKG2C+ANK cells at baseline. There was a significant upregulation of NKG2C expression and IFN-γ release in the Mw group (p=0.0009), particularly in those with a lower baseline NKG2C expression, along with the downregulation of iNK cells (p<0.0001). This translated to a significant reduction in the incidence and severity of COVID-19 in the Mw group (incidence risk ratio-0.15, p=0.0004). RNA-seq analysis at 6 months showed an upregulation of the ANK pathway genes and an enhanced ANK-mediated antibody-dependent cellular cytotoxicity (ADCC) signature. Thus, Mw was observed to have a salutary impact on the ANK cell profile and a long-term upregulation of ANK-ADCC pathways, which could have provided protection against COVID-19 in a non-immune high-risk population.

It Takes a Village: The Multifaceted Immune Response to Mycobacterium tuberculosis Infection and Vaccine-Induced Immunity

Despite co-evolving with humans for centuries and being intensely studied for decades, the immune correlates of protection against Mycobacterium tuberculosis (Mtb) have yet to be fully defined. This lapse in understanding is a major lag in the pipeline for evaluating and advancing efficacious vaccine candidates. While CD4+ T helper 1 (TH1) pro-inflammatory responses have a significant role in controlling Mtb infection, the historically narrow focus on this cell population may have eclipsed the characterization of other requisite arms of the immune system. Over the last decade, the tuberculosis (TB) research community has intentionally and intensely increased the breadth of investigation of other immune players. Here, we review mechanistic preclinical studies as well as clinical anecdotes that suggest the degree to which different cell types, such as NK cells, CD8+ T cells, γ δ T cells, and B cells, influence infection or disease prevention. Additionally, we categorically outline the observed role each major cell type plays in vaccine-induced immunity, including Mycobacterium bovis bacillus Calmette-Guérin (BCG). Novel vaccine candidates advancing through either the preclinical or clinical pipeline leverage different platforms (e.g., protein + adjuvant, vector-based, nucleic acid-based) to purposefully elicit complex immune responses, and we review those design rationales and results to date. The better we as a community understand the essential composition, magnitude, timing, and trafficking of immune responses against Mtb, the closer we are to reducing the severe disease burden and toll on human health inflicted by TB globally.

Repurposing of Mycobacterium indicus pranii for the severe form of COVID -19 patients in India: A cohort study

SARS-CoV-2 induces the production of proinflammatory cytokines, which results in cytokine storm, and immune-modulators like Mycobacterium indicus pranii (MIP) might ameliorate COVID -19 related cytokine storm. Therefore, the present study evaluates whether MIP offers an advantage in the treatment of severe COVID -19 patients infected with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Prospective MIP cohort Study was conducted in chest disease hospitals in Srinagar, Jammu and Kashmir, India. In the present prospective, randomized clinical study, critically severe COVID -19 patients were divided into two groups, the MIP group (n=105) and Best Standard Treatment group (n=210). Procalcitonin, Ferritin, Hs-CRP (High Sensitive C Reactive Protein), D-dimer levels and Interleukin levels on 5^th -day post-treatment were significantly reduced in the MIP group compared to the BST group. Compared to the BST group, 105 consecutive patients with severe COVID -19 in the MIP group reported early weaning off mechanical ventilation, resolution of chest architecture (CT scan), significant increase in SpO₂ levels and decreased mortality with hazard ratio-0.234 (95% CI-0.264-2.31) (p-value-0.001). MIP restored SpO₂ , immune/inflammatory response, normalized lung abnormalities (Chest CT scan), and reduced mortality without any serious complications. However, there is a need for placebo-controlled double-blind and controlled clinical trials to confirm the efficacy. This article is protected by copyright. All rights reserved.

Insights into the molecular determinants involved in Mycobacterium tuberculosis persistence and their therapeutic implications

The establishment of persistent infections and the reactivation of persistent bacteria to active bacilli are the two hurdles in effective tuberculosis treatment. Mycobacterium tuberculosis, an etiologic tuberculosis agent, adapts to numerous antibiotics and resists the host immune system causing a disease of public health concern. Extensive research has been employed to combat this disease due to its sheer ability to persist in the host system, undetected, waiting for the opportunity to declare itself. Persisters are a bacterial subpopulation that possesses transient tolerance to high doses of antibiotics. There are certain inherent mechanisms that facilitate the persister cell formation in Mycobacterium tuberculosis, some of those had been characterized in the past namely, stringent response, transcriptional regulators, energy production pathways, lipid metabolism, cell wall remodeling enzymes, phosphate metabolism, and proteasome protein degradation. This article reviews the recent advancements made in various in vitro persistence models that assist to unravel the mechanisms involved in the persister cell formation and to hunt for the possible preventive or treatment measures. To tackle the persister population the immunodominant proteins that express specifically at the latent phase of infection can be used for diagnosis to distinguish between the active and latent tuberculosis, as well as to select potential drug or vaccine candidates. In addition, we discuss the genes engaged in the persistence to get more insights into resuscitation and persister cell formation. The in-depth understanding of persistent cells of mycobacteria can certainly unravel novel ways to target the pathogen and tackle its persistence.

A review of the BCG vaccine and other approaches toward tuberculosis eradication

Despite aggressive eradication efforts, Tuberculosis (TB) remains a global health burden, one that disproportionally affects poorer, less developed nations. The only vaccine approved for TB, the Bacillus of Calmette and Guérin (BCG) vaccine remains controversial because it's stated efficacy has been cited as anywhere from 0 to 80%. Nevertheless, there have been exciting discoveries about the mechanism of action of the BCG vaccine that suggests it has a role in immunization schedules today. We review recent data suggesting the vaccine imparts protection against both tuberculosis and non-tuberculosis pathogens via a newly discovered immune system called trained immunity. BCG's efficacy also appears to be tied to its affect on granulocytes at the epigenetic and hematopoietic stem cell levels, which we discuss in this article at length. We also write about how the different strains of the BCG vaccine elicit different immune responses, suggesting that certain BCG strains are more immunogenic than others. Finally, our review delves into how the current vaccine is being reformulated to be more efficacious, and track the development of the next generation vaccines against TB.

Development of New Therapeutics to Meet the Current Challenge of Drug Resistant Tuberculosis

Tuberculosis (TB) is a prominent infective disease and a major reason of mortality/ morbidity globally. Mycobacterium tuberculosis causes a long-lasting latent infection in a significant proportion of human population. The increasing burden of tuberculosis is mainly caused due to multi drug-resistance. The failure of conventional treatment has been observed in large number of cases. Drugs that are used to treat extensively drug-resistant tuberculosis are expensive, have limited efficacy, and have more side effects for a longer duration of time and are often associated with poor prognosis. To regulate the emergence of multidrug resistant tuberculosis, extensively drug-resistant tuberculosis and totally drug resistant tuberculosis, efforts are being made to understand the genetic/molecular basis of target drug delivery and mechanisms of drug resistance. Understanding the molecular approaches and pathology of Mycobacterium tuberculosis through whole genome sequencing may further help in the improvement of new therapeutics to meet the current challenge of global health. Understanding cellular mechanisms that trigger resistance to Mycobacterium tuberculosis infection may expose immune associates of protection, which could be an important way for vaccine development, diagnostics, and novel host-directed therapeutic strategies. The recent development of new drugs and combinational therapies for drug-resistant tuberculosis through major collaboration between industry, donors, and academia gives an improved hope to overcome the challenges in tuberculosis treatment. In this review article, an attempt was made to highlight the new developments of drug resistance to the conventional drugs and the recent progress in the development of new therapeutics for the treatment of drugresistant and non-resistant cases.

A Randomized Trial of Mycobacterium w in Severe Presumed Gram-Negative Sepsis

BACKGROUND

Mycobacterium w, an immunomodulator, has been shown to resolve early organ failure in severe sepsis.

RESEARCH QUESTION

Does Mw improve survival in patients with severe presumed gram-negative sepsis?

STUDY DESIGN AND METHODS

This was a randomized, double-blind, placebo-controlled, parallel-group study conducted in ICUs of five tertiary care centers in India. We included consecutive patients (age ≥ 18 years) with presumed gram-negative sepsis in the study within 48 h of the first organ dysfunction. Patients in the treatment arm received 0.3 mL/d of Mw intradermally for 3 consecutive days, whereas the control arm received matching placebo. The primary outcome was 28-day all-cause mortality. The secondary outcomes were ventilator-free days, days receiving vasopressor therapy, ICU and hospital length of stay, nosocomial infection rate, antibiotic use duration, and delta Sequential Organ Failure Assessment (SOFA) score.

RESULTS

We included 202 patients with severe sepsis (101 Mw, 101 placebo). The use of Mw significantly reduced the mortality (9/101 vs 20/101; estimate difference, 0.11 [95% CI, 0.01-0.21]; P = .04). We found no difference in ventilator-free days, days receiving vasopressor drugs, ICU length of stay, and the hospital length of stay. The time to mortality (median, 13 days vs 8.5 days) was significantly longer in the Mw than in the placebo arm. The delta SOFA score, rate of nosocomial infections, and antibiotic use duration were similar in the two arms. We found Mw to reduce significantly the odds (OR, 0.37 [95% CI, 0.15-0.9]) of mortality after adjusting for culture-positive sepsis, baseline SOFA score, age, and sex.

INTERPRETATION

The use of Mw was associated with a significant reduction in mortality in patients with severe presumed gram-negative sepsis. Further studies are required to confirm our findings.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT02330432; URL: www.clinicaltrials.gov.

Targeting Autophagy as a Strategy for Developing New Vaccines and Host-Directed Therapeutics Against Mycobacteria

Mycobacterial disease is an immense burden worldwide. This disease group includes tuberculosis, leprosy (Hansen's disease), Buruli Ulcer, and non-tuberculous mycobacterial (NTM) disease. The burden of NTM disease, both pulmonary and ulcerative, is drastically escalating globally, especially in developed countries such as America and Australia. Mycobacteria's ability to inhibit or evade the host immune system has contributed significantly to its continued prevalence. Pre-clinical studies have highlighted promising candidates that enhance endogenous pathways and/or limit destructive host responses. Autophagy is a cell-autonomous host defense mechanism by which intracytoplasmic cargos can be delivered and then destroyed in lysosomes. Previous studies have reported that autophagy-activating agents, small molecules, and autophagy-activating vaccines may be beneficial in restricting intracellular mycobacterial infection, even with multidrug-resistant strains. This review will examine how mycobacteria evade autophagy and discusses how autophagy could be exploited to design novel TB treatment strategies, such as host-directed therapeutics and vaccines, against Mycobacterium tuberculosis and NTMs.

Vaccination Against Tuberculosis: Revamping BCG by Molecular Genetics Guided by Immunology

Tuberculosis (TB) remains a major health threat. Although a vaccine has been available for almost 100 years termed Bacille Calmette-Guérin (BCG), it is insufficient and better vaccines are urgently needed. This treatise describes first the basic immunology and pathology of TB with an emphasis on the role of T lymphocytes. Better understanding of the immune response to Mycobacterium tuberculosis (Mtb) serves as blueprint for rational design of TB vaccines. Then, disease epidemiology and the benefits and failures of BCG vaccination will be presented. Next, types of novel vaccine candidates are being discussed. These include: (i) antigen/adjuvant subunit vaccines; (ii) viral vectored vaccines; and (III) whole cell mycobacterial vaccines which come as live recombinant vaccines or as dead whole cell or multi-component vaccines. Subsequently, the major endpoints of clinical trials as well as administration schemes are being described. Major endpoints for clinical trials are prevention of infection (PoI), prevention of disease (PoD), and prevention of recurrence (PoR). Vaccines can be administered either pre-exposure or post-exposure with Mtb. A central part of this treatise is the description of the viable BCG-based vaccine, VPM1002, currently undergoing phase III clinical trial assessment. Finally, new approaches which could facilitate design of refined next generation TB vaccines will be discussed.

Mycobacterium indicus pranii Induced Memory T-Cells in Lung Airways Are Sentinels for Improved Protection Against M.tb Infection

The lungs are the most vulnerable site for air-borne infections. Immunologic compartmentalization of the lungs into airway lumen and interstitium has paved the way to determine the immune status of the site of pathogen entry, which is crucial for the outcome of any air-borne infections. Vaccination via the nasal route with Mycobacterium indicus pranii (MIP), a prospective candidate vaccine against tuberculosis (TB), has been reported to confer superior protection as compared to the subcutaneous (s.c.) route in small-animal models of TB. However, the immune mechanism remains only partly understood. Here, we showed that intranasal (i.n.) immunization of mice with MIP resulted in a significant recruitment of CD4⁺ and CD8⁺ T-cells expressing activation markers in the lung airway lumen. A strong memory T-cell response was observed in the lung airway lumen after i.n. MIP vaccination, compared with s.c. vaccination. The recruitment of these T-cells was regulated primarily by CXCR3–CXCL11 axis in “MIP i.n.” group. MIP-primed T-cells in the lung airway lumen effectively transferred protective immunity into naïve mice against Mycobacterium tuberculosis (M.tb) infection and helped reducing the pulmonary bacterial burden. These signatures of protective immune response were virtually absent or very low in unimmunized and subcutaneously immunized mice, respectively, before and after M.tb challenge. Our study provides mechanistic insights for MIP-elicited protective response against M.tb infection.

Tuberculosis Vaccine Development: Progress in Clinical Evaluation

Tuberculosis (TB) is the leading killer among all infectious diseases worldwide despite extensive use of the Mycobacterium bovis bacille Calmette-Guérin (BCG) vaccine. A safer and more effective vaccine than BCG is urgently required. More than a dozen TB vaccine candidates are under active evaluation in clinical trials aimed to prevent infection, disease, and recurrence. After decades of extensive research, renewed promise of an effective vaccine against this ancient airborne disease has recently emerged. In two innovative phase 2b vaccine clinical trials, one for the prevention of Mycobacterium tuberculosis infection in healthy adolescents and another for the prevention of TB disease in M. tuberculosis-infected adults, efficacy signals were observed. These breakthroughs, based on the greatly expanded knowledge of the M. tuberculosis infection spectrum, immunology of TB, and vaccine platforms, have reinvigorated the TB vaccine field. Here, we review our current understanding of natural immunity to TB, limitations in BCG immunity that are guiding vaccinologists to design novel TB vaccine candidates and concepts, and the desired attributes of a modern TB vaccine. We provide an overview of the progress of TB vaccine candidates in clinical evaluation, perspectives on the challenges faced by current vaccine concepts, and potential avenues to build on recent successes and accelerate the TB vaccine research-and-development trajectory.

Intranasal Mycobacterium vaccae administration prevents stress-induced aggravation of dextran sulfate sodium (DSS) colitis

An increasing body of evidence indicates that immunodysregulation and subsequent chronic low-grade inflammation can promote the development of stress-related somatic and psychiatric pathologies, including inflammatory bowel disease (IBD) and posttraumatic stress disorder (PTSD). Thus, immunoregulatory approaches counterbalancing basal and/or stress-induced immune activation should have stress-protective potential. In support of this hypothesis, we recently demonstrated that repeated s.c. preimmunization with a heat-killed preparation of the immunoregulatory bacterium Mycobacterium vaccae (M. vaccae; National Collection of Type Culture (NCTC) 11659), protects mice against stress-induced general anxiety, spontaneous colitis, and aggravation of dextran sulfate sodium (DSS)-induced colitis in the chronic subordinate colony housing (CSC) paradigm, a validated model for PTSD in male mice. In the current study, we repeatedly administered M. vaccae via the non-invasive intranasal (i.n.; 0.1 mg/mouse/administration) route, prior to or during CSC exposure or single housed control (SHC) conditions, and assessed the effects on general and social anxiety, and on parameters related to the severity of DSS-induced colitis. While administration of M. vaccae prior to the onset of CSC exposure only had minor stress-protective effects, administration of M. vaccae during CSC completely prevented CSC-induced aggravation of DSS colitis. As CSC in the current experimental setting did not reliably increase general anxiety-related behavior, potential stress-protective effects of M.vaccae are difficult to interpret. Taken together, these data broaden the framework for developing bioimmunoregulatory approaches, based on the administration of microorganisms with anti-inflammatory and immunoregulatory properties, for the prevention of stress-related disorders.

Kallikrein 12 Regulates Innate Resistance of Murine Macrophages against Mycobacterium bovis Infection by Modulating Autophagy and Apoptosis

Mycobacterium bovis (M. bovis) is a member of the Mycobacterium tuberculosis (Mtb) complex causing bovine tuberculosis (TB) and imposing a high zoonotic threat to human health. Kallikreins (KLKs) belong to a subgroup of secreted serine proteases. As their role is established in various physiological and pathological processes, it is likely that KLKs expression may mediate a host immune response against the M. bovis infection. In the current study, we report in vivo and in vitro upregulation of KLK12 in the M. bovis infection. To define the role of KLK12 in immune response regulation of murine macrophages, we produced KLK12 knockdown bone marrow derived macrophages (BMDMs) by using siRNA transfection. Interestingly, the knockdown of KLK12 resulted in a significant downregulation of autophagy and apoptosis in M. bovis infected BMDMs. Furthermore, we demonstrated that this KLK12 mediated regulation of autophagy and apoptosis involves mTOR/AMPK/TSC2 and BAX/Bcl-2/Cytochrome c/Caspase 3 pathways, respectively. Similarly, inflammatory cytokines IL-1β, IL-6, IL-12 and TNF-α were significantly downregulated in KLK12 knockdown macrophages but the difference in IL-10 and IFN-β expression was non-significant. Taken together, these findings suggest that upregulation of KLK12 in M. bovis infected murine macrophages plays a substantial role in the protective immune response regulation by modulating autophagy, apoptosis and pro-inflammatory pathways. To our knowledge, this is the first report on expression and the role of KLK12 in the M. bovis infection and the data may contribute to a new paradigm for diagnosis and treatment of bovine TB.

Enhanced delivery of Mycobacterium tuberculosis antigens to antigen presenting cells using RVG peptide

Among the various strategies to improve vaccines against infectious diseases, targeting of antigens to dendritic cells (DCs), which are professional antigen presenting cells (APCs), has received increased attention in recent years. Here, we investigated whether a synthetic peptide region named RVG, originated from Rabies Virus Glycoprotein that binds to the α-7 subunit of the nicotinic acetylcholine receptors (AchR-α7) of APCs, could be used for the delivery of Mycobacterium tuberculosis (Mtb) peptide antigens to DCs and macrophages. Mouse bone marrow derived DCs (BMDCs) and human THP-1 macrophages stimulated with RVG fused peptide epitopes 85B241 and 85B96 (represent Ag85B241-256 and Ag85B96-111, respectively) from antigen 85B (Ag85B) of Mtb showed enhanced antigen presentation as compared to unfused peptide epitopes and BCG. Further, BMDCs stimulated with RVG fused 85B241 showed higher levels of IL-12 positive cells. Consistent with in vitro data, splenocytes of mice immunized with RVG-85B241 showed increased number of antigen specific IFN-γ, IL-2, and TNF-α producing cells in relation to splenocytes from mice immunized with 85B241 alone. These results suggest that RVG may be a promising tool to develop effective alternate vaccines against tuberculosis (TB).

Cell wall fraction of Mycobacterium indicus pranii shows potential Th1 adjuvant activity

Very few adjuvants inducing Th1 immune response have been developed and are under clinical investigation. Hence, there is the need to find an adjuvant that elicits strong Th1 immune response which should be safe when injected in the host along with vaccines. Mycobacterium indicus pranii (MIP), a non-pathogenic vaccine candidate, has shown strong immunomodulatory activity in leprosy/tuberculosis/cancer and in genital warts patients where its administration shifted the host immune response towards Th1 type. These findings prompted us to study the components of MIP in detail for their Th1 inducing property. Since mycobacterial cell wall is very rich in immunostimulatory components and is known to play important role in immune modulation, we investigated the activity of MIP cell wall using Ovalbumin antigen (OVA) as model antigen. 'Whole cell wall' (CW) and 'aqueous soluble cell wall fractions' (ACW) induced significant Th1 immune response while 'cell wall skeleton' (CWS) induced strong Th2 type of immune response. Finally, functional activity of fractions having Th1 inducing activity was evaluated in mouse model of melanoma. CW demonstrated significant anti-tumor activity similar to whole MIP. Anti-tumor activity of CW could be correlated with enhanced tumor antigen specific Th1 immune response observed in tumor draining lymph nodes.

Modulation of Autophagy for Controlling Immunity

Autophagy is an essential process that maintains physiological homeostasis by promoting the transfer of cytoplasmic constituents to autophagolysosomes for degradation. In immune cells, the autophagy pathway plays an additional role in facilitating proper immunological functions. Specifically, the autophagy pathway can participate in controlling key steps in innate and adaptive immunity. Accordingly, alterations in autophagy have been linked to inflammatory diseases and defective immune responses against pathogens. In this review, we discuss the various roles of autophagy signaling in coordinating immune responses and how these activities are connected to pathological conditions. We highlight the therapeutic potential of autophagy modulators that can impact immune responses and the mechanisms of action responsible.

Does the Development of Vaccines Advance Solutions for Tuberculosis?

BACKGROUND

Mycobacterium tuberculosis (Mtb) is considered as one of the most efficacious human pathogens. The global mortality rate of TB stands at approximately 2 million, while about 8 to 10 million active new cases are documented yearly. It is, therefore, a priority to develop vaccines that will prevent active TB. The vaccines currently used for the management of TB can only proffer a certain level of protection against meningitis, TB, and other forms of disseminated TB in children; however, their effectiveness against pulmonary TB varies and cannot provide life-long protective immunity. Based on these reasons, more efforts are channeled towards the development of new TB vaccines. During the development of TB vaccines, a major challenge has always been the lack of diversity in both the antigens contained in TB vaccines and the immune responses of the TB sufferers. Current efforts are channeled on widening both the range of antigens selection and the range of immune response elicited by the vaccines. The past two decades witnessed a significant progress in the development of TB vaccines; some of the discovered TB vaccines have recently even completed the third phase (phase III) of a clinical trial.

OBJECTIVE

The objectives of this article are to discuss the recent progress in the development of new vaccines against TB; to provide an insight on the mechanism of vaccine-mediated specific immune response stimulation, and to debate on the interaction between vaccines and global interventions to end TB.

Development of tuberculosis vaccines in clinical trials: Current status

Tuberculosis (TB) is an important infectious disease worldwide. Currently, Bacillus Calmette-Guérin (BCG) remains the only TB vaccine licensed for human use. This TB vaccine is effective in protecting children against severe military TB but offers variable protective efficacy in adults. Therefore, new vaccines against TB are needed to overcome this serious disease. At present, around 14 TB vaccine candidates are in different phases of clinical trials. These TB vaccines in clinical evaluation can be classified into two groups including preventive pre- and post-exposure vaccines: subunit vaccines (attenuated viral vectors or adjuvanted fusion proteins), and whole-cell vaccines (genetically attenuated Mycobacterium tuberculosis (M. tb), recombinant BCG, killed M. tb or M. vaccae). Although, over the last two decades a great progress in the search for a more effective TB vaccine has been demonstrated there is still no replacement for the licensed BCG vaccine. This article summarizes the current status of TB vaccine development and identifies crucial gaps of research for the development of an effective TB vaccine in all age groups.

Potential of adjunctive Mycobacterium w (MIP) immunotherapy in reducing the duration of standard chemotherapy against tuberculosis

INTRODUCTION

The need to shorten the treatment duration in tuberculosis has always been felt. Immunotherapy in combination with chemotherapy has been considered a promising approach for this purpose into tuberculosis. We studied the adjuvant immunotherapeutic activity of Mycobacterium indicus pranii (MIP or Mw) in combination with conventional chemotherapy using guinea pig of pulmonary tuberculosis infected with Mycobacterium tuberculosis H37Rv via aerosol.

METHODS

Experimental animals treated with standard chemotherapy and immunotherapy (MIP) separately and in combination of both. Guinea pig lungs evaluated following infection and subsequent therapy at predefine time point. Various cytokine mRNA expressions levels were quantified by quantitative reverse transcriptase PCR at the 4th, 8th and 12th week post-infection of M. tuberculosis.

RESULTS

We determined the time required for bacterial clearance from guinea pig lungs. Standard chemotherapy (RvCh) compared to the animals where chemotherapy plus Mw immunotherpay (RvChMwT) was given. It took 12 weeks to achieve bacterial clearance in the RvCh group while this was achieved in 8 weeks in RvChMwT group. Pro-inflammatory cytokines (IFN-γ, IL-2, IL-12p35 and TNF-α) level were higher in RvCh, RvChMwT and RvMwT group, while the IL-10 and TGF-β were suppressed.

CONCLUSION

Cytokine expression level showed that Mw in conjunction with chemotherapy enhances the effect of pro-inflammatory cytokines (such as, IFN-γ, IL-2, IL-12 and TNF-α) and reduces the production and effect of anti-inflammatory cytokines (like IL-10 and TGF-β) thereby restoring the pro-inflammatory / anti-inflammatory cytokines balance. Thus, the present study indicates that subject to rigorous testing by other parameters, Mw (MIP) as adjunct immunotherapy has potential for reducing treatment duration.

Autophagy induction by Mycobacterium indicus pranii promotes Mycobacterium tuberculosis clearance from RAW 264.7 macrophages

Mycobacterium indicus pranii (MIP) is a potent vaccine candidate against tuberculosis (TB) as it has demonstrated significant protection in animal models of tuberculosis as well as in clinical trials. Higher protective efficacy of MIP against TB as compared to BCG provoked the efforts to gain insight into the molecular mechanisms underlying MIP mediated protection against Mycobacterium tuberculosis (M.tb). Autophagy, initially described as a cell survival mechanism during starvation, also plays a key role in host resistance to M.tb. Virulent mycobacteria like M.tb, suppresses host autophagy response to increase its survival in macrophages. Since mycobacterial species have been shown to vary widely in their autophagy-inducing properties, in the present study, we examined the autophagy inducing efficacy of MIP and its role in MIP-mediated protection against M.tb. MIP was found to be potent inducer of autophagy in macrophages. Induced autophagy was responsible for reversal of the phagosome maturation block and phagolysosome fusion inhibition in M.tb infected macrophages, which ultimately lead to significantly enhanced clearance of M.tb from the macrophages. This is an important study which further delineated the underlying mechanisms for significant immunotherapeutic activity observed in TB patients / animal models of tuberculosis, given MIP therapy along with chemotherapy.

Efficacy and Safety of Mycobacterium indicus pranii as an adjunct therapy in Category II pulmonary tuberculosis in a randomized trial

Prolonged treatment of tuberculosis (TB) often leads to poor compliance, default and relapse, converting primary TB patients into category II TB (Cat IITB) cases, many of whom may convert to multi-drug resistant TB (MDR-TB). We have evaluated the immunotherapeutic potential of Mycobacterium indicus pranii (MIP) as an adjunct to Anti-Tubercular Treatment (ATT) in Cat II pulmonary TB (PTB) patients in a prospective, randomized, double blind, placebo controlled, multicentric clinical trial. 890 sputum smear positive Cat II PTB patients were randomized to receive either six intra-dermal injections (2 + 4) of heat-killed MIP at a dose of 5 × 10⁸ bacilli or placebo once in 2 weeks for 2 months. Sputum smear and culture examinations were performed at different time points. MIP was safe with no adverse effects. While sputum smear conversion did not show any statistically significant difference, significantly higher number of patients (67.1%) in the MIP group achieved sputum culture conversion at fourth week compared to the placebo (57%) group (p = 0.0002), suggesting a role of MIP in clearance of the bacilli. Since live bacteria are the major contributors for sustained incidence of TB, the potential of MIP in clearance of the bacilli has far reaching implications in controlling the spread of the disease.

Global Efforts in the Development of Vaccines for Tuberculosis: Requirements for Improved Vaccines Against Mycobacterium tuberculosis

Currently, more than 9.0 million people develop acute pulmonary tuberculosis (TB) each year and about 1.5 million people worldwide die from this infection. Thus, developing vaccines to prevent active TB disease remains a priority. This article discusses recent progress in the development of new vaccines against TB and focusses on the main requirements for development of improved vaccines against Mycobacterium tuberculosis (M. tb). Over the last two decades, significant progress has been made in TB vaccine development, and some TB vaccine candidates have currently completed a phase III clinical trial. The potential public health benefits of these vaccines are possible, but it will need much more effort, including new global governance investment on this research. This investment would certainly be less than the annual global financial toll of TB treatment.

Mycobacterium indicus pranii as a booster vaccine enhances BCG induced immunity and confers higher protection in animal models of tuberculosis

BCG, the only approved vaccine protects against severe form of childhood tuberculosis but its protective efficacy wanes in adolescence. BCG has reduced the incidence of infant TB considerably in endemic areas; therefore prime-boost strategy is the most realistic measure for control of tuberculosis in near future. Mycobacterium indicus pranii (MIP) shares significant antigenic repertoire with Mtb and BCG and has been shown to impart significant protection in animal models of tuberculosis. In this study, MIP was given as a booster to BCG vaccine which enhanced the BCG mediated immune response, resulting in higher protection. MIP booster via aerosol route was found to be more effective in protection than subcutaneous route of booster immunization. Pro-inflammatory cytokines like IFN-γ, IL-12 and IL-17 were induced at higher level in infected lungs of 'BCG-MIP' group both at mRNA expression level and in secretory form when compared with 'only BCG' group. BCG-MIP groups had increased frequency of multifunctional T cells with high MFI for IFN-γ and TNF-α in Mtb infected mice. Our data demonstrate for the first time, potential application of MIP as a booster to BCG vaccine for efficient protection against tuberculosis. This could be very cost effective strategy for efficient control of tuberculosis.

Immunotherapy for tuberculosis: future prospects

Tuberculosis (TB) is still a major global health problem. A third of the world’s population is infected with Mycobacterium tuberculosis. Only ~10% of infected individuals develop TB but there are 9 million TB cases with 1.5 million deaths annually. The standard prophylactic treatment regimens for latent TB infection take 3–9 months, and new cases of TB require at least 6 months of treatment with multiple drugs. The management of latent TB infection and TB has become more challenging because of the spread of multidrug-resistant and extremely drug-resistant TB. Intensified efforts to find new TB drugs and immunotherapies are needed. Immunotherapies could modulate the immune system in patients with latent TB infection or active disease, enabling better control of M. tuberculosis replication. This review describes several types of potential immunotherapies with a focus on those which have been tested in humans.

Mycobacterium tuberculosis infection and vaccine development

Following HIV/AIDS, tuberculosis (TB) continues to be the second most deadly infectious disease in humans. The global TB prevalence has become worse in recent years due to the emergence of multi-drug resistant (MDR) and extensively-drug resistant (XDR) strains, as well as co-infection with HIV. Although Bacillus Calmette-Guérin (BCG) vaccine has nearly been used for a century in many countries, it does not protect adult pulmonary tuberculosis and even causes disseminated BCG disease in HIV-positive population. It is impossible to use BCG to eliminate the Mycobacterium tuberculosis (M. tb) infection or to prevent TB onset and reactivation. Consequently, novel vaccines are urgently needed for TB prevention and immunotherapy. In this review, we discuss the TB prevalence, interaction between M. tb and host immune system, as well as recent progress of TB vaccine research and development.

Emerging drugs and alternative possibilities in the treatment of tuberculosis

INTRODUCTION

Tuberculosis (TB) remains a global health problem. Drug resistance, treatment duration, complexity, and adverse drug reactions associated with anti-TB regimens are associated with treatment failure, prolonged infectiousness and relapse. With the current set of anti-TB drugs the goal to end TB has not been met. New drugs and new treatment regimens are needed to eradicate TB.

AREAS COVERED

Literature was explored to select publications on drugs currently in phase II and phase III trials. These include new chemical entities, immunotherapy, established drugs in new treatment regimens and vaccines for the prophylaxis of TB.

EXPERT OPINION

Well designed trials, with detailed pharmacokinetic/pharmacodynamic analysis, in which information on drug exposure and drug susceptibility of the entire anti-TB regimen is included, in combination with long-term follow-up will provide relevant data to optimize TB treatment. The new multi arm multistage trial design could be used to test new combinations of compounds, immunotherapy and therapeutic vaccines. This new approach will both reduce the number of patients exposed to inferior treatment and the financial burden. Moreover, it will speed up drug evaluation. Considering the investments involved in development of new drugs it is worthwhile to thoroughly investigate existing, non-TB drugs in new regimens.

Cytotoxic and apoptotic effects of heat killed Mycobacterium indicus pranii (MIP) on various human cancer cell lines

Mycobacterium indicus pranii (MIP) is a non-pathogenic mycobacterium, which has been tested on several cancer types like lung and bladder where tumour regression and complete recovery was observed. In discovering the potential cytotoxic elements, a preliminary test was carried out using four different fractions consisting of live bacteria, culture supernatant, heat killed bacteria and heat killed culture supernatant of MIP against two human cancer cells A549 and CaSki by 3-(4,5-dimethyl thiazol)-2,5-diphenyl tetrazolium bromide (MTT) assay. Apoptosis was investigated in MCF-7 and ORL-115 cancer cells by poly-(ADP-ribose) polymerase (PARP) and DNA fragmentation assays. Among four MIP fractions, only heat killed MIP fraction (HKB) showed significant cytotoxicity in various cancer cells with inhibitory concentration, IC50 in the range 5.6-35.0 μl/(1.0 × 10(6) MIP cells/ml), while cytotoxicity effects were not observed in the remaining fractions. HKB did not show cytotoxic effects on non-cancerous cells contrary to cancerous cells, suggesting its safe usage and ability to differentially recognize between these cells. Evaluation on PARP assay further suggested that cytotoxicity in cancer cells were potentially induced via caspase-mediated apoptosis. The cytotoxic and apoptotic effects of MIP HKB have indicated that this fraction can be a good candidate to further identify effective anti-cancer agents.

Molecular analysis of clinical isolates previously diagnosed as Mycobacterium intracellulare reveals incidental findings of "Mycobacterium indicus pranii" genotypes in human lung infection

Background

Mycobacterium intracellulare is a major cause of Mycobacterium avium complex lung disease in many countries. Molecular studies have revealed several new Mycobacteria species that are closely related to M. intracellulare. The aim of this study was to re-identify and characterize clinical isolates from patients previously diagnosed with M. intracellulare lung disease at the molecular level.

Methods

Mycobacterial isolates from 77 patients, initially diagnosed with M. intracellulare lung disease were re-analyzed by multi-locus sequencing and pattern of insertion sequences.

Results

Among the 77 isolates, 74 (96 %) isolates were designated as M. intracellulare based on multigene sequence-based analysis. Interestingly, the three remaining strains (4 %) were re-identified as “Mycobacterium indicus pranii” according to distinct molecular phylogenetic positions in rpoB and hsp65 sequence-based typing. In hsp65 sequevar analysis, code 13 was found in the majority of cases and three unreported codes were identified. In 16S–23S rRNA internal transcribed spacer (ITS) sequevar analysis, all isolates of both species were classified within the Min-A ITS sequevar. Interestingly, four of the M. intracellulare isolates harbored IS1311, a M. avium-specific element. Two of three patients infected with “M. indicus pranii” had persistent positive sputum cultures after antibiotic therapy, indicating the clinical relevance of this study.

Conclusions

This analysis highlights the importance of precise identification of clinical isolates genetically close to Mycobacterium species, and suggests that greater attention should be paid to nontuberculous mycobacteria lung disease caused by “M. indicus pranii”.

Prednisolone and Mycobacterium indicus pranii in tuberculous pericarditis

BACKGROUND

Tuberculous pericarditis is associated with high morbidity and mortality even if antituberculosis therapy is administered. We evaluated the effects of adjunctive glucocorticoid therapy and Mycobacterium indicus pranii immunotherapy in patients with tuberculous pericarditis.

METHODS

Using a 2-by-2 factorial design, we randomly assigned 1400 adults with definite or probable tuberculous pericarditis to either prednisolone or placebo for 6 weeks and to either M. indicus pranii or placebo, administered in five injections over the course of 3 months. Two thirds of the participants had concomitant human immunodeficiency virus (HIV) infection. The primary efficacy outcome was a composite of death, cardiac tamponade requiring pericardiocentesis, or constrictive pericarditis.

RESULTS

There was no significant difference in the primary outcome between patients who received prednisolone and those who received placebo (23.8% and 24.5%, respectively; hazard ratio, 0.95; 95% confidence interval [CI], 0.77 to 1.18; P=0.66) or between those who received M. indicus pranii immunotherapy and those who received placebo (25.0% and 24.3%, respectively; hazard ratio, 1.03; 95% CI, 0.82 to 1.29; P=0.81). Prednisolone therapy, as compared with placebo, was associated with significant reductions in the incidence of constrictive pericarditis (4.4% vs. 7.8%; hazard ratio, 0.56; 95% CI, 0.36 to 0.87; P=0.009) and hospitalization (20.7% vs. 25.2%; hazard ratio, 0.79; 95% CI, 0.63 to 0.99; P=0.04). Both prednisolone and M. indicus pranii, each as compared with placebo, were associated with a significant increase in the incidence of cancer (1.8% vs. 0.6%; hazard ratio, 3.27; 95% CI, 1.07 to 10.03; P=0.03, and 1.8% vs. 0.5%; hazard ratio, 3.69; 95% CI, 1.03 to 13.24; P=0.03, respectively), owing mainly to an increase in HIV-associated cancer.

CONCLUSIONS

In patients with tuberculous pericarditis, neither prednisolone nor M. indicus pranii had a significant effect on the composite of death, cardiac tamponade requiring pericardiocentesis, or constrictive pericarditis. (Funded by the Canadian Institutes of Health Research and others; IMPI ClinicalTrials.gov number, NCT00810849.).

Adjunctive immunotherapy with α-crystallin based DNA vaccination reduces Tuberculosis chemotherapy period in chronically infected mice

By employing modified Cornell model, we have evaluated the potential of adjunctive immunotherapy with DNA vaccines to shorten the tuberculosis chemotherapy period and reduce disease reactivation. We demonstrate that α-crystallin based DNA vaccine (DNAacr) significantly reduced the chemotherapy period from 12 weeks to 8 weeks when compared with the chemotherapy alone. Immunotherapy with SodA based DNA vaccine (DNAsod) reduced the pulmonary bacilli only as much as DNAvec. Both DNAacr and DNAsod, although significantly delayed the reactivation in comparison to the chemotherapy alone, this delay was associated with the immunostimulatory sequences present in the vector backbone and was not antigen specific. Both DNA vaccines resulted in the production of significantly higher number of T_EM cells than the chemotherapy alone, however, only in the case of DNAsod, this enhancement was significant over the DNAvec treatment. Overall, our findings emphasize the immunotherapeutic potential of DNAacr in shortening the duration of TB chemotherapy.

Novel vaccination strategies against tuberculosis

The tuberculosis (TB) pandemic continues to rampage despite widespread use of the BCG (Bacillus Calmette-Guérin) vaccine. Novel vaccination strategies are urgently needed to arrest global transmission and prevent the uncontrolled development of multidrug-resistant forms of Mycobacterium tuberculosis. Over the last two decades, considerable progress has been made in the field of vaccine development with numerous innovative preclinical candidates and more than a dozen vaccines in clinical trials. These vaccines are developed either as boosters of the current BCG vaccine or as novel prime vaccines to replace BCG. Given the enormous prevalence of latent TB infection, vaccines that are protective on top of an already established infection remain a high priority and a significant scientific challenge. Here we discuss the current state of TB vaccine research and development, our understanding of the underlying immunology, and the requirements for an efficient TB vaccine.

Progress in tuberculosis vaccine development and host-directed therapies--a state of the art review

Tuberculosis continues to kill 1·4 million people annually. During the past 5 years, an alarming increase in the number of patients with multidrug-resistant tuberculosis and extensively drug-resistant tuberculosis has been noted, particularly in eastern Europe, Asia, and southern Africa. Treatment outcomes with available treatment regimens for drug-resistant tuberculosis are poor. Although substantial progress in drug development for tuberculosis has been made, scientific progress towards development of interventions for prevention and improvement of drug treatment outcomes have lagged behind. Innovative interventions are therefore needed to combat the growing pandemic of multidrug-resistant and extensively drug-resistant tuberculosis. Novel adjunct treatments are needed to accomplish improved cure rates for multidrug-resistant and extensively drug-resistant tuberculosis. A novel, safe, widely applicable, and more effective vaccine against tuberculosis is also desperately sought to achieve disease control. The quest to develop a universally protective vaccine for tuberculosis continues. So far, research and development of tuberculosis vaccines has resulted in almost 20 candidates at different stages of the clinical trial pipeline. Host-directed therapies are now being developed to refocus the anti-Mycobacterium tuberculosis-directed immune responses towards the host; a strategy that could be especially beneficial for patients with multidrug-resistant tuberculosis or extensively drug-resistant tuberculosis. As we are running short of canonical tuberculosis drugs, more attention should be given to host-directed preventive and therapeutic intervention measures.

Mycobacterium marinum: a potential immunotherapy for Mycobacterium tuberculosis infection

Purpose

The aim of the present study was to investigate the immune response induced by Mycobacterium marinum infection in vitro and the potential of M. marinum as an immunotherapy for M. tuberculosis infection.

Methods

The potential human immune response to certain bacillus infections was investigated in an immune cell-bacillus coculture system in vitro. As a potential novel immunotherapy, M. marinum was studied and compared with two other bacilli, Bacillus Calmette-Guérin (BCG) and live attenuated M. tuberculosis. We examined the changes in both the bacilli and immune cells, especially the time course of the viability of mycobacteria in the coculture system and host immune responses including multinuclear giant cell formation by Wright-Giemsa modified staining, macrophage polarization by cell surface antigen expression, and cytokines/chemokine production by both mRNA expression and protein secretion.

Results

The M. marinum stimulated coculture group showed more expression of CD209, CD68, CD80, and CD86 than the BCG and M. tuberculosis (an attenuated strain, H37Ra) groups, although the differences were not statistically significant. Moreover, the M. marinum group expressed more interleukin (IL)-1B and IL-12p40 on day 3 (IL-1B: P = 0.003 and 0.004, respectively; IL-12p40: P = 0.001 and 0.011, respectively), a higher level of CXCL10 on day 1 (P = 0.006 and 0.026, respectively), and higher levels of chemokine (C-X-C motif) ligand (CXCL) 8 and chemokine (C motif) ligand (XCL) 1 on day 3 (CXCL8: P = 0.012 and 0.014, respectively; XCL1: P = 0.000 and 0.000, respectively). The M. marinum stimulated coculture group also secreted more tumor necrosis factor (TNF)-α, IL-1β, and IL-10 on day 1 (TNF-α: P = 0.000 and 0.000, respectively; IL-1β: P = 0.000 and 0.000, respectively; IL-10: P = 0.002 and 0.019, respectively) and day 3 (TNF-α: P = 0.000 and 0.000, respectively; IL-1β: P = 0.000 and 0.001, respectively; IL-10: P = 0.000 and 0.000, respectively). In addition, the colony-forming units (an index of viability) of M. marinum in the M. marinum stimulated coculture group was significantly less than that of BCG and H37Ra in their corresponding bacillus stimulated groups (P = 0.037 and 0.013, respectively).

Conclusion

Our results indicated that M. marinum could be a potentially safe and effective immunotherapy.

Vaccine development for tuberculosis: current progress

Very substantial efforts have been made over the past decade or more to develop vaccines against tuberculosis. Historically, this began with a view to replace the current vaccine, Bacillus Calmette Guérin (BCG), but more recently most candidates are either new forms of this bacillus, or are designed to boost immunity in children given BCG as infants. Good progress is being made, but very few have, as yet, progressed into clinical trials. The leading candidate has advanced to phase IIb efficacy testing, with disappointing results. This article discusses the various types of vaccines, including those designed to be used in a prophylactic setting, either alone or BCG-boosting, true therapeutic (post-exposure) vaccines, and therapeutic vaccines designed to augment chemotherapy. While there is no doubt that progress is still being made, we have a growing awareness of the limitations of our animal model screening processes, further amplified by the fact that we still do not have a clear picture of the immunological responses involved, and the precise type of long-lived immunity that effective new vaccines will need to induce.