Immunotherapy for tuberculosis: wave of the future or tilting at windmills?

Clinical Efficacy of a Combination of Thymopentin and Antituberculosis Drugs in Treating Drug-Resistant Pulmonary Tuberculosis: Meta Analysis

Objective

To make a systematic evaluation of the clinical efficacy of thymopentin combined with antituberculous drugs in treating drug-resistant pulmonary TB (PTB).

Methods

Relevant studies were retrieved from PubMed, Embase, Cochrane Library, Chinese Biomedical Literature Database, CNKI, and Wanfang Database. STATA software was used to evaluate the differences in focal absorption rate, the time to cough symptom remission, sputum culture-negative rate, CD3⁺ T, CD4⁺ T, and CD8⁺ T cell levels after treatment.

Results

A total of 23 randomized controlled trials literature involving 2031 cases were included. Meta-analysis revealed that compared with conventional therapy, the sputum culture-negative rate was significantly increased after 2–3 months and 6–9 months of treatment and the whole course of combined thymopentin treatment. The risk ratio (RR, 95% CI) was 1.44 (1.26–1.64), 1.47 (1.21–1.78), and 1.27 (1.18–1.36), respectively. In the combined thymopentin treatment group, the focal absorption rate was higher, with RR (95% CI) = 1.36 (1.25–1.47), the time of cough remission was shortened, with WMD (95% CI) =−9.46d (−10.36,−8.57) and the differences were all statistically significant. Combined thymopentin therapy could effectively improve the levels of CD3⁺ T and CD4⁺ T lymphocytes in patients with drug-resistant PTB after 2–3 months, 6–9 months of treatment. The WMD (95% CI) were 9.96% (7.84, 12.08), 4.68% (2.90, 6.47) and 10.26% (7.81, 12.71), 7.21% (6.28, 8.15), respectively, and could also reduce the level of CD8⁺ T lymphocytes after 2–3 months and 6–9 months of treatment. The WMD (95% CI) were −4.06% (−4.96, −3.13), −3.52%, (−4.07,−2.98), respectively, and the differences were all statistically significant.

Conclusion

Thymopentin adjuvant treatment for drug-resistant PTB can promote the therapeutic effect and improve the immune indexes in patients with drug-resistant PTB.

Adjunctive Immunotherapeutic Efficacy of N-Formylated Internal Peptide of Mycobacterial Glutamine Synthetase in Mouse Model of Tuberculosis

BACKGROUND

Host-directed therapies are a comparatively new and promising method for the treatment of tuberculosis. A variety of host pathways, vaccines and drugs have the potential to provide novel adjunctive therapies for the treatment of tuberculosis. In this connection, we have earlier reported the immunotherapeutic potential of N-formylated N-terminal peptide of glutamine synthetase of Mycobacterim tuberculosis H37Rv (Mir SA and Sharma S, 2014). Now in the present study, we investigated the immunotherapeutic effect of N-terminally formylated internal-peptide 'f- MLLLPD' of mycobacterial glutamine synthetase (Rv2220) in mouse model of tuberculosis.

METHODS

The N-terminally formylated peptide, f-MLLLPD was tested for its potential to generate Reactive Oxygen Species (ROS) in murine neutrophils. Further, its therapeutic effect alone or in combination with anti-tubercular drugs was evaluated in mouse model of tuberculosis.

RESULTS

The f-MLLLPD peptide treatment alone and in combination with ATDs reduced the bacterial load (indicated as colony forming units) in lungs of infected mice by 0.58 (p<0.01) and 2.92 (p<0.001) log10 units respectively and in their spleens by 0.46 (p<0.05) and 2.46 (p<0.001) log10 units respectively. In addition, the observed histopathological results correlated well with the CFU data.

CONCLUSION

The results of the current study show that f-MLLLPD peptide confers an additional therapeutic efficacy to the anti-tuberculosis drugs.

Immunotherapeutic potential of an N-formylated peptide of Listeria monocytogenes in experimental tuberculosis

Objective: The current therapeutic regimens for tuberculosis (TB) are complex and involve the prolonged use of multiple antibiotics with diverse side effects that lead to therapeutic failure and bacterial resistance. The standard appliance of immunotherapy may aid as a powerful tool to combat the ensuing threat of TB. We have earlier reported the immunotherapeutic potential of N-formylated peptides of two secretory proteins of Mycobacterium tuberculosis H₃₇Rv. Here, we investigated the immunotherapeutic effect of an N-formylated peptide from Listeria monocytogenes in experimental TB. Methods: The N-terminally formylated listerial peptide with amino acid sequence 'f-MIGWII' was tested for its adjunctive therapeutic efficacy in combination with anti-tuberculosis drugs (ATDs) in the mouse model of TB. In addition, its potential to generate reactive oxygen species (ROS) in murine neutrophils was also evaluated. Results: The LemA peptide (f-MIGWII) induced a significant increase in the intracellular ROS levels of mouse neutrophils (p ≤ .05). The ATD treatment reduced the colony forming units (CFU) in lungs and spleen of infected mice by 2.39 and 1.67 log₁₀ units, respectively (p < .001). Treatment of the infected mice with combination of ATDs and LemA peptide elicited higher therapeutic efficacy over ATDs alone. The histopathological changes in the lungs of infected mice also correlated well with the CFU data. Conclusions: Our results clearly indicate that LemA peptide conferred an additional therapeutic effect when given in combination with the ATDss (p < .01) and hence can be used as adjunct to the conventional chemotherapy against TB.

Effectiveness of a novel cellular therapy to treat multidrug-resistant tuberculosis

Introduction

We urgently need novel treatments for multidrug-resistant tuberculosis (MDR-TB). Autologous mesenchymal stromal cell (MSC) infusion is one such possibility due to its potential to repair damaged lung tissue and boost immune responses. We aimed to assess the effectiveness of MSC to improve outcomes among MDR-TB patients.

Methods

We analyzed outcomes for 108 Belarussian MDR-TB patients receiving chemotherapy. Thirty-six patients (“cases”) also had MSCs extracted, cultured and re-infused (average time from chemotherapy start to infusion was 49 days); another 36 patients were “study controls”. We identified another control group: 36 patients from the Belarussian surveillance database (“surveillance controls”) 1:1 matched to cases.

Results

Of the cases, 81% had successful outcomes versus 42% of surveillance controls and 39% of study controls. Successful outcome odds were 6.5 (95% Confidence Interval: 1.2–36.2, p = 0.032) times greater for cases than surveillance controls (age-adjusted). Radiological improvement was more likely in cases than study controls. Culture analysis prior to infusion demonstrated a poorer initial prognosis in cases, yet despite this they had better outcomes than the control groups.

Conclusion

MSC treatment could vastly improve outcomes for MDR-TB patients. Our findings could revolutionize therapy options and have strong implications for future directions of MDR-TB therapy research.

Targeting Tuberculosis and HIV Infection-Specific Regulatory T Cells with MEK/ERK Signaling Pathway Inhibitors

Human regulatory T cells (Tregs) are essential in maintaining immunological tolerance and suppress effector T cells. Tregs are commonly up-regulated in chronic infectious diseases such as tuberculosis (TB) and human immunodeficiency virus (HIV) infection and thereby hamper disease-specific immune responses and eradication of pathogens. The MEK/ERK signaling pathway is involved in regulation of the FoxP3 transcription factor, which directs a lineage-specific transcriptional program to define Tregs and control their suppressive function. Here, we aimed to target activation of disease-specific Tregs by inhibition of the MEK/ERK signaling pathway based on the hypothesis that this would improve anti-HIV and anti-TB immunity. Stimulation of T cells from untreated TB (n = 12) and HIV (n = 8) patients with disease-specific antigens in vitro in the presence of the MEK inhibitor (MEKI) trametinib (GSK1120212) resulted in significant down-regulation of both FoxP3 levels (MFI) and fractions of resting (CD45RA⁺FoxP3⁺) and activated (CD45RA⁻FoxP3⁺⁺) Tregs. MEKI also reduced the levels of specific T effector cells expressing the pro-inflammatory cytokines (IFN-γ, TNF-α and IL-2) in both HIV and TB patients. In conclusion, MEKIs modulate disease antigen-specific Treg activation and may have potential application in new treatment strategies in chronic infectious diseases where reduction of Treg activity would be favorable. Whether MEKIs can be used in current HIV or TB therapy regimens needs to be further investigated.

The beneficial effects of adjunctive recombinant human interleukin-2 for multidrug resistant tuberculosis

INTRODUCTION

Multidrug-resistant tuberculosis (MDR-TB) is a hard-to-treat disease with a poor outcome of chemotherapy. In the present study, the efficacy and safety of recombinant human interleukin-2 (rhIL-2) were investigated in patients with MDR-TB.

MATERIAL AND METHODS

Fifty culture-confirmed patients with MDR-TB were included. Twenty-five patients were randomly assigned to the trial group (injection of 500 000 IU of rhIL-2 once every other day at the first, third, fifth and seventh months in addition to standard multidrug therapy) and another 25 patients to the control group with standard multidrug therapy. All patients were monitored clinically, and T-cell subsets were analyzed by flow cytometry.

RESULTS

The rates of sputum negative conversion and X-ray resolution in the trial group were higher than those of the control, and the improvements were significant by completion of treatment. In addition, CD4(+)CD25(+) T cells in the controls rose gradually during treatment. The levels at the end of the seventh month were significantly higher than before, which were also significantly different when compared with those from the trial group at the same time. However, there were no such changes associated with treatment in the trial group. No significant differences appeared in other T cell subsets.

CONCLUSIONS

Exogenous IL-2 in the present regimen improves immunity status. Adjunctive immunotherapy with a long period of rhIL-2 is a promising treatment modality for MDR-TB.

Inflammation and tuberculosis: host-directed therapies

Tuberculosis (TB) is an airborne infectious disease that kills almost two million individuals every year. Multidrug-resistant (MDR) TB is caused by strains of Mycobacterium tuberculosis (M. tb) resistant to isoniazid and rifampin, the backbone of first-line antitubercular treatment. MDR TB affects an estimated 500,000 new patients annually. Genetic analysis of drug-resistant MDR-TB showed that airborne transmission of undetected and untreated strains played a major role in disease outbreaks. The need for new TB vaccines and faster diagnostics, as well as the development of new drugs, has recently been highlighted. The major problem in terms of current TB research and clinical demands is the increasing number of cases of extensively drug-resistant and 'treatment-refractory' TB. An emerging scenario of adjunct host-directed therapies is intended to target pulmonary TB where inflammatory processes can be deleterious and lead to immune exhaustion. 'Target-organ-saving' strategies may be warranted to prevent damage to infected tissues and achieve focused, clinically relevant and long-lasting anti-M. tb cellular immune responses. Candidates for such interventions may be biological agents or already approved drugs that can be 're-purposed' to interfere with biologically relevant cellular checkpoints. Here, we review current concepts of inflammation in TB disease and discuss candidate pathways for host-directed therapies to achieve better clinical outcomes.

Improving outcomes for multidrug-resistant tuberculosis: aggressive regimens prevent treatment failure and death

BACKGROUND

Evidence is sparse regarding the optimal construction of regimens to treat multidrug-resistant (MDR) tuberculosis disease due to strains of Mycobacterium tuberculosis resistant to at least both isoniazid and rifampin. Given the low potency of many second-line antituberculous drugs, we hypothesized that an aggressive regimen of at least 5 likely effective drugs during the intensive phase, including a fluoroquinolone and a parenteral agent, would be associated with a reduced risk of death or treatment failure.

METHODS

We conducted a retrospective cohort study of patients initiating MDR tuberculosis treatment between 2000 and 2004 in Tomsk, Russian Federation. We used a multivariate Cox proportional hazards model to assess whether monthly exposure to an aggressive regimen was associated with the risk of death or treatment failure.

RESULTS

Six hundred fourteen individuals with confirmed MDR tuberculosis were eligible for analysis. On multivariable analysis that adjusted for extensively drug-resistant (XDR) tuberculosis-MDR tuberculosis isolates resistant to fluoroquinolones and parenteral agents-we found that monthly exposure to an aggressive regimen was significantly associated with a lower risk of death or treatment failure (hazard ratio, 0.52 [95% confidence interval, .29-.94]; P = .030).

CONCLUSIONS

Receipt of an aggressive treatment regimen was a robust predictor of decreased risk of death or failure during MDR tuberculosis treatment. These findings further support the use of this regimen definition as the benchmark for the standard of care of MDR tuberculosis patients and should be used as the basis for evaluating novel therapies.

Autologous mesenchymal stromal cell infusion as adjunct treatment in patients with multidrug and extensively drug-resistant tuberculosis: an open-label phase 1 safety trial

BACKGROUND

Novel treatment options are urgently needed for multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis, which are associated with immune dysfunction and poor treatment outcomes. Mesenchymal stromal cells (MSCs) are immunomodulatory and adjunct autologous treatment with bone marrow-derived MSCs might improve clinical outcome by transforming chronic inflammation into productive immune responses. Our aim was to assess the safety of infusion of autologous MSCs as an adjunct treatment in patients with tuberculosis.

METHODS

30 patients with microbiologically confirmed MDR or XDR tuberculosis were treated with single-dose autologous bone marrow-derived MSCs (aimed for 1×10(6) cells per kg), within 4 weeks of the start of antituberculosis-drug treatment in a specialist centre in Minsk, Belarus. Inclusion patients were those with pulmonary tuberculosis confirmed by sputum smear microscopy, culture, or both; MDR or XDR tuberculosis confirmed by drug-susceptibility testing to first-line and second-line drugs; age older than 21 years to 65 years or younger; and absence of lesion compatible with a malignant process or ongoing tuberculosis in organs other than the lungs and pleura. In addition to the inclusion criteria, patients were excluded if they were pregnant, coinfected with HIV, or infected with hepatitis B, C, or both. The primary endpoint was safety measured by MSC-infusion related events; any tuberculosis-related event within the 6 month observation period that related to a worsening of the underlying infectious disease, measured by conversion of Mycobacterium tuberculosis culture or microscopic examination; or any adverse event defined clinically or by changes in blood haematology and biochemistry variables, measured monthly for 6 months after MSC infusion per protocol. This study is registered with the German Clinical Trials Registry, number DRKS00000763.

FINDINGS

The most common (grade 1 or 2) adverse events were high cholesterol levels (14 of 30 patients), nausea (11 of 30 patients), and lymphopenia or diarrhoea (ten of 30 patients). There were no serious adverse events reported. We recorded two grade 3 events that were transitory-ie, increased plasma potassium ion concentrations in one patient and a transitory grade 3 γ-glutamyltransferase elevation in another patient.

INTERPRETATION

MSCs as an adjunct therapy are safe and can now be explored further for the treatment of patients with MDR or XDR tuberculosis in combination with standard drug regimens. Adjunct treatment with MSCs needs to be evaluated in controlled phase 2 trials to assess effects on immune responses and clinical and microbiological outcomes.

Shortening the 'short-course' therapy- insights into host immunity may contribute to new treatment strategies for tuberculosis

Achieving global control of tuberculosis (TB) is a great challenge considering the current increase in multidrug resistance and mortality rate. Considerable efforts are therefore being made to develop new effective vaccines, more effective and rapid diagnostic tools as well as new drugs. Shortening the duration of TB treatment with revised regimens and modes of delivery of existing drugs, as well as development of new antimicrobial agents and optimization of the host response with adjuvant immunotherapy could have a profound impact on TB cure rates. Recent data show that chronic worm infection and deficiencies in micronutrients such as vitamin D and arginine are potential areas of intervention to optimize host immunity. Nutritional supplementation to enhance nitric oxide production and vitamin D-mediated effector functions as well as the treatment of worm infection to reduce immunosuppressive effects of regulatory T (Treg) lymphocytes may be more suitable and accessible strategies for highly endemic areas than adjuvant cytokine therapy. In this review, we focus mainly on immune control of human TB, and discuss how current treatment strategies, including immunotherapy and nutritional supplementation, could be optimized to enhance the host response leading to more effective treatment.

Cytokine therapy of tuberculosis at the crossroads

Drug treatment is the key strategy in TB control. However, the treatment course lasts 6-9 months because the current anti-TB drugs are poorly effective against nondividing (i.e., persistent) bacilli. As a result, completion rates are unsatisfactory, leading to emergence and spread of multidrug-resistant infection. It would, therefore, be very desirable to design a form of complementary treatment that could speed up the recovery process for people afflicted with TB and reduce the relapse rates. With the advancement of our understanding of the immunopathogenesis of TB, it has become increasingly possible to develop novel adjunctive immunotherapies for both drug-susceptible and drug-resistant TB. Notably, cytokines probably offer the most promising prospect of such a therapy being introduced in routine clinical practice. However, in many ways, the cytokine therapy of TB has reached a crossroad, since, although the initial promise failed to live up to expectations, sufficient encouraging evidence exists to warrant further exploration. There are clear arguments in favor as well as against such treatments. This review aims to provide a rationale for cytokine treatment of TB, to describe the current status of several cytokines that have been considered for that purpose and, ultimately, to make a case for the need for further clinical trials.

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

BACKGROUND

The 9-month-long chemotherapy of tuberculosis often results in poor compliance and emergence of drug-resistant strains. So, improved therapeutic strategy is urgently needed. Immunotherapy could be beneficial for the effective management of the disease. Previously we showed the protective efficacy of Mycobacterium indicus pranii (MIP) when given as prophylactic vaccine in animal models of tuberculosis.

METHODS

We sought to investigate whether MIP can be used as an adjunct to the chemotherapy in guinea pig models of tuberculosis. Efficacy of MIP was evaluated when given subcutaneously or by aerosol.

RESULTS

MIP-therapy as an adjunct to the chemotherapy was found to be effective in accelerating bacterial killing and improving organ pathology. MIP-immunotherapy resulted in higher numbers of activated antigen-presenting cells and lymphocytes in the infected lungs and also modulated the granulomatous response. Early increase in protective Th1 immune response was observed in the immunotherapy group. Following subsequent doses of MIP, decrease in the inflammatory response and increase in the immunosuppressive response was observed, which resulted in the improvement of lung pathology.

CONCLUSION

MIP immunotherapy is a valuable adjunct to chemotherapy for tuberculosis. Aerosol route of immunotherapy can play a crucial role for inducing immediate local immune response in the lung.

Adjunct immune therapy of first-diagnosed TB, relapsed TB, treatment-failed TB, multidrug-resistant TB and TB/HIV

Aim: To evaluate the effect of an adjunct immunotherapy in randomized double-blind, placebo-controlled Phase IIb trial involving 123 TB patients. Methods: Patients were randomly allocated into two arms: one (n = 62) received a once-daily pill of V-5 Immunitor™ (V5) and the other (control; n= 61) received placebo for 30 days in addition to first- or second-line TB drugs administered under directly observed therapy. The subjects in V5 and placebo arms had first-diagnosed, relapsed, treatment-failed and multidrug-resistant TB at ratios of 17:21:11:13 and 20:19:14:8, respectively; among them, ten and seven had HIV coinfection, respectively. Results: After 1 month, 55 out of 62 patients (88.7%) became sputum smear-negative in the V5 arm (p < 0.0001), whereas in the placebo group, nine out of 61 (14.8%) had converted. The conversion rate among V5 recipients was similar, regardless of whether TB was drug-sensitive, drug-resistant or with HIV. V5 downregulated TB-associated inflammation, as shown by the normalization of elevated leukocyte counts (8.7 vs 6.3 × 10 9/l; p < 0.0001) and decreased erythrocyte sedimentation rate (22.8 vs 12.6 mm/h; p < 0.0001), whereas among placebo recipients, changes were smaller (8.9 vs 8.2 × 10 9/l and 25.1 vs 19.9 mm/h). Thirty three (54.1%) placebo patients gained on average 0.8 kg (p = 0.0002); by contrast, 57 (91.9%) out of 62 patients in the V5 group gained a mean weight of 2.9 kg (p < 0.0001). No adverse side effects or reactivation of TB were seen at any time. Conclusion: V5 is safe and effective as an immune adjunct to chemotherapy for TB and can potentially reduce the treatment duration down to 1 month.

IFN-γTherapy of Tuberculosis and Related Infections

It is firmly established that interferon-gamma (IFN-gamma) plays a mandatory role in acquired protective immunity to pathogenic mycobacteria and other intracellular pathogens. Therefore, it seems conceivable that application of recombinant IFN-gamma could be exploited for the treatment of tuberculosis. However, the results of experimental studies and clinical trials, conducted mostly in patients with multidrug resistant (MDR) disease, have thus far been only moderately encouraging. Further studies are now needed to determine if a greater clinical benefit from IFN-gamma could be obtained for the prophylactic treatment of latent tuberculosis infection and for shortening of the protracted standard chemotherapy regimen. Thus, aerosolized IFN-gamma treatment could be particularly beneficial to AIDS patients at high risk of developing mycobacterial infections, that is, those with significantly declined CD4(+) T cell counts. This review describes the current state of research on IFN-gamma interventions in tuberculosis and related infections and highlights some of the future opportunities.

A combination of a transforming growth factor-beta antagonist and an inhibitor of cyclooxygenase is an effective treatment for murine pulmonary tuberculosis

Transforming growth factor-beta (TGF-beta) and prostaglandins (PG) regulate the cell-mediated immune response, so it has been proposed that they affect the progression of pulmonary tuberculosis. Here we report that the administration of soluble betaglycan, a potent TGF-beta antagonist, and niflumic acid, a PG synthesis inhibitor, during the chronic phase of experimental murine tuberculosis enhanced Th1 and decreased Th2 cytokines, increased the expression of iNOS and reduced pulmonary inflammation, fibrosis and bacillary load. This immunotherapeutic approach resulted in significant control of the disease comparable to that achieved by anti-microbial treatment alone. Importantly, the combination of immunotherapy and anti-microbials resulted in an accelerated clearance of bacilli from the lung. These results confirm that TGF-beta and PG have a central pathophysiological role in the progression of pulmonary tuberculosis in the mouse and suggest that the addition of immunotherapy to conventional anti-microbial drugs might result in improved treatment of the disease.

Revised Guidelines for the Diagnosis and Control of Tuberculosis

Despite major progress in the development of new strategies for diagnosing and treating tuberculosis, the disease still remains a major challenge for healthcare workers throughout the world. A number of causes are responsible for this threat but, unfortunately, many of these cannot be resolved easily because of cultural and social factors. Furthermore, not all countries throughout the world have enough financial resources to support educational and therapeutic programmes. The major challenges with tuberculosis are 2-fold: (i) to deal with the growing epidemic around the world (and especially in 'low-income' [developing] countries), and; (ii) to ensure correct use of antituberculosis medications in order to protect these drugs for future use. In 'high-income' countries, a major decline in the incidence of tuberculosis has been observed. Nevertheless, tuberculosis remains an important challenge in some risk groups, particularly the elderly patient, in these countries. The clinical and radiological presentations are often nonspecific, leading to delayed diagnosis and appropriate treatment, which often results in a large proportion of cases being discovered at autopsy only. Considering tuberculosis in the differential diagnosis remains the cornerstone of a fast and accurate diagnosis of this condition. Management of active tuberculosis in the elderly does not differ fundamentally from that in younger patients with respect to outcomes or adverse effects of treatment. However, empirical treatment perhaps may be considered more readily in the elderly patient. Elderly persons infected with tuberculosis at the beginning of the 20th century constitute a large reservoir of latent tuberculosis infection. Furthermore, these individuals are at increased risk of reactivation of this remote infection as their immunological status declines with aging. Compared with the past, modern guidelines are less reluctant to recommend use of tuberculin skin testing, treatment of latent tuberculosis infection in elderly persons, and prevention of transmission of tuberculosis in nursing homes.