Biomarkers for TB treatment response: Challenges and future strategies

Changes of C-reactive protein and Procalcitonin after four weeks of treatment in patients with pulmonary TB

Objective

Tuberculosis (TB) remains a public health concern worldwide, affecting millions of people every year. Detailed characterization of disease pathophysiology is key to proper diagnosis, disease progression, or treatment follow-up and evaluation. The present study investigated C-reactive protein and Procalcitonin (PCT) as candidate markers of early treatment response and disease activity.

Methods

From September to December 2019, 21 HIV-negative consecutive TB patients were recruited, within the setting of the Gabonese TB specialized hospital and the National Laboratory of Public Health, in a prospective study. CRP and PCT levels were measured by chemiluminescence at diagnosis and 4 weeks following the initiation of anti-TB treatment.

Results

The mean concentration of CRP in TB patients was 114.7 mg/L (95 % CI: [83.8-145.6]) at diagnosis and 20.2 mg/L (95 % CI: [14.1-26.4]) 4 weeks following anti-TB treatment. The drop in CRP concentrations between diagnosis, and week 4 following anti-TB treatment showed was significant (p < 0.0001). The average concentration of PCT at the time of diagnosis was 0.3 ng/mL (95 % CI: [0.19-0.41]). PCT Concentration dropped below 0.05 ng/mL 4 weeks following the start of anti-TB treatment (p < 0.01).

Conclusion

CRP and PCT are potential TB biomarkers, each, carrying important keys. If the drop in both proteins may indicate a significant reduction of the Mtb burden, the maintenance of CRP above the inflammation threshold could indicate the presence of residual bacilli. However, the clinical translation of the present finding will require more investigation.

Isolation and Purification of Mycobacterial Extracellular Vesicles (EVs)

Bacterial extracellular vesicles (EVs) contain numerous active substances that mediate bacterial interactions with their host and with other microbes. Best defined are the EVs from Gram-negative bacteria that have been shown to deliver virulence factors, modulate the immune responses, mediate antibiotic resistance, and also inhibit competitive microbes. Due to the complex cell wall structures of Gram-positive bacteria and mycobacteria, EVs from these bacteria were only recently reported. This protocol describes the isolation of EVs from mycobacteria.

The Changing Paradigm of Drug-Resistant Tuberculosis Treatment: Successes, Pitfalls, and Future Perspectives

Drug-resistant tuberculosis (DR-TB) remains a global crisis due to the increasing incidence of drug-resistant forms of the disease, gaps in detection and prevention, models of care, and limited treatment options. The DR-TB treatment landscape has evolved over the last 10 years. Recent developments include the remarkable activity demonstrated by the newly approved anti-TB drugs bedaquiline and pretomanid against Mycobacterium tuberculosis. Hence, treatment of DR-TB has drastically evolved with the introduction of the short-course regimen for multidrug-resistant TB (MDR-TB), transitioning to injection-free regimens and the approval of the 6-month short regimens for rifampin-resistant TB and MDR-TB. Moreover, numerous clinical trials are under way with the aim to reduce pill burden and shorten the DR-TB treatment duration. While there have been apparent successes in the field, some challenges remain. These include the ongoing inclusion of high-dose isoniazid in DR-TB regimens despite a lack of evidence for its efficacy and the inclusion of ethambutol and pyrazinamide in the standard short regimen despite known high levels of background resistance to both drugs. Furthermore, antimicrobial heteroresistance, extensive cavitary disease and intracavitary gradients, the emergence of bedaquiline resistance, and the lack of biomarkers to monitor DR-TB treatment response remain serious challenges to the sustained successes. In this review, we outline the impact of the new drugs and regimens on patient treatment outcomes, explore evidence underpinning current practices on regimen selection and duration, reflect on the disappointments and pitfalls in the field, and highlight key areas that require continued efforts toward improving treatment approaches and rapid biomarkers for monitoring treatment response.

Is analysis of inflammatory biomarkers and lymphocyte subpopulations useful in prediction of tuberculosis treatment outcomes?

Analysis of inflammatory biomarkers and lymphocytes during the treatment of tuberculosis (TB) could yield findings that influence the routine clinical practice and use of new anti-TB drugs. This study aimed to evaluate whether the selected biomarkers-soluble intercellular adhesion molecule type 1, soluble urokinase-type plasminogen activator receptor (suPAR), and C-reactive protein (CRP)-and T-cell subpopulations are useful for predicting culture conversion, treatment outcomes, and the extent of radiological lesions (calculated using X-ray score) in patients with drug-sensitive pulmonary TB. This study included 62 patients with drug-sensitive pulmonary TB. CRP and suPAR levels significantly decreased after 1 month of treatment. Before treatment initiation, CRP and suPAR levels were significantly higher in patients without culture conversion; however, none of the selected host biomarkers appeared to significantly influence the conversion status or treatment outcomes. Some lymphocyte subpopulations were correlated with X-ray scores before TB treatment initiation, but lung destruction, as determined using X-ray scores, showed the highest correlation with the baseline CRP value. We conclude that selected host biomarkers have a very limited role in predicting TB treatment outcomes and culture conversion and do not appear to be superior to CRP in monitoring TB treatment.

Mycobacterium tuberculosis-stimulated whole blood culture to detect host biosignatures for tuberculosis treatment response

Host markers to monitor the response to tuberculosis (TB) therapy hold some promise. We evaluated the changes in concentration of Mycobacterium tuberculosis (M.tb)-induced soluble biomarkers during early treatment for predicting short- and long-term treatment outcomes. Whole blood samples from 30 cured and 12 relapsed TB patients from diagnosis, week 1, 2, and 4 of treatment were cultured in the presence of live M.tb for seven days and patients followed up for 24 weeks after the end of treatment. 57 markers were measured in unstimulated and antigen-stimulated culture supernatants using Luminex assays. Top performing multi-variable models at diagnosis using unstimulated values predicted outcome at 24 months after treatment completion with a sensitivity of 75.0% (95% CI, 42.8-94.5%) and specificity of 72.4% (95% CI, 52.8-87.3%) in leave-one-out cross validation. Month two treatment responder classification was correctly predicted with a sensitivity of 79.2% (95% CI, 57.8-92.9%) and specificity of 92.3% (95% CI, 64.0-99.8%). This study provides evidence of the early M.tb-specific treatment response in TB patients but shows that the observed unstimulated marker models are not outperformed by stimulated marker models. Performance of unstimulated predictive host marker signatures is promising and requires validation in larger studies.

Simultaneous 18F-FDG PET/MRI in tuberculous spondylitis: an independent method for assessing therapeutic response - case series

BACKGROUND

¹⁸F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) shows great potential for diagnosis and assessing therapeutic response of tuberculous spondylitis. Tuberculous spondylitis required long-term anti-tuberculosis (TB) medication therapy, and the optimal duration of therapy is controversial. There is still no clear way to tell when the anti-TB therapy can safely be discontinued.

CASE PRESENTATION

Three patients with tuberculous spondylitis were evaluated for therapeutic response using 18F-FDG PET/magnetic resonance imaging (MRI). Clinical and hematological improvements were achieved after about 12 months of anti-TB medication therapy, and we considered whether to discontinue the therapy. There was no relapse during one year of follow-up after discontinuation of 12 months anti-TB medication based on the low maximum standardized uptake value (SUV_max) of 1.83 in one patient. However, the other two patients continued further anti-TB medication therapy based on the high SUVmax of 4.14 and 7.02, which were suspected to indicate active residual lesions in the abscess or granulation tissues. Continuous TB was confirmed by the bacterial and histological examinations.

CONCLUSIONS

18F-FDG PET/MRI has metabolic and anatomical advantages for assessing therapeutic response in TB spondylitis, and can be considered as a helpful independent and alternative method for determining the appropriate time to discontinue anti-TB medication.

Urine IP-10 as a biomarker of therapeutic response in patients with active pulmonary tuberculosis

Background

Prior to clinical trials of new TB drugs or therapeutic vaccines, it is necessary to develop monitoring tools to predict treatment outcomes in TB patients. Urine interferon gamma inducible protein 10 (IP-10) is a potential biomarker of treatment response in chronic hepatitis C virus infection and lung diseases, including tuberculosis. In this study, we assessed IP-10 levels in urine samples from patients with active TB at diagnosis, during treatment, and at completion, and compared these with levels in serum samples collected in parallel from matched patients to determine whether urine IP-10 can be used to monitor treatment response in patients with active TB.

Methods

IP-10 was measured using enzyme-linked immunosorbent assays in urine and serum samples collected concomitantly from 23 patients with active TB and 21 healthy adults (44 total individuals). The Mann-Whitney U test and Wilcoxon matched-pairs signed rank test were used for comparisons among healthy controls and patients at three time points, and LOESS regression was used for longitudinal data.

Results

The levels of IP-10 in urine increased significantly after 2 months of treatment (P = 0.0163), but decreased by the completion of treatment (P = 0.0035). Serum IP-10 levels exhibited a similar trend, but did not increase significantly after 2 months of treatment in patients with active TB.

Conclusions

Unstimulated IP-10 in urine can be used as a biomarker to monitor treatment response in patients with active pulmonary TB.

The role of metabolomics in tuberculosis treatment research

Despite the fact that tuberculosis (TB) is a curable disease, it still results in approximately 1.8 million deaths annually. Various inadequacies in the current TB treatment strategies are major contributors to this high disease prevalence, including the long duration of therapy, the severe side effects associated with TB drugs, treatment failure due to drug resistance, post-treatment disease relapse, and HIV co-infection. In this review, we describe how metabolomics has contributed toward better explaining/elucidating the mechanisms of drug action/metabolism, drug toxicity and microbial drug resistance, and how metabolite biomarkers may serve as prognostic indicators for predicting treatment outcome as well as for the development of new TB drugs. We also discuss possible future contributions that metabolomics can make toward more efficient, less toxic TB treatment strategies.

Total IgM and Anti-Phosphatidylcholine IgM Antibody Secretion Continue After Clearance of Mycobacterium bovis Bacillus Calmette-Guerin Pleural Infection

The cellular immune response to Mycobacterium tuberculosis infection has been well characterized, while the humoral antibody response remains underexplored. We aimed to examine the total and anti-phospholipid IgM levels in the pleural lavage from mice with Mycobacterium bovis BCG extrapulmonary infection. We found that the levels of total and anti-phosphatidylcholine IgM antibodies remained significantly higher in infected mice as compared to non-infected mice up to day 90 after BCG infection, while the anti-cardiolipin IgM antibody levels decreased with bacteria clearance. Our findings suggest that IgM antibodies are secreted and their composition vary during early and late immune response to BCG pleurisy.

Animal Models for Tuberculosis in Translational and Precision Medicine

Tuberculosis (TB) is a health threat to the global population. Anti-TB drugs and vaccines are key approaches for TB prevention and control. TB animal models are basic tools for developing biomarkers of diagnosis, drugs for therapy, vaccines for prevention and researching pathogenic mechanisms for identification of targets; thus, they serve as the cornerstone of comparative medicine, translational medicine, and precision medicine. In this review, we discuss the current use of TB animal models and their problems, as well as offering perspectives on the future of these models.

Cytokine Kinetics in the First Week of Tuberculosis Therapy as a Tool to Confirm a Clinical Diagnosis and Guide Therapy

BACKGROUND

Many patients treated for tuberculosis (TB) in low and middle income countries are treated based on clinical suspicion without bacteriological confirmation. This is often due to lack of rapid simple accurate diagnostics and low healthcare provider confidence in the predictive value of current tests. We previously reported in an animal TB model that levels of host markers rapidly change in response to treatment initiation.

METHODS

We assessed the potential of host biomarker kinetics of TB patients during the first two weeks of therapy to identify patients responding to treatment. Adult patients clinically diagnosed with and treated for TB, 29 in Nigeria and 24 in Nepal, were analyzed.

RESULTS

Changes in concentrations of non-specific host biomarkers, particularly IP-10, in response to the first week of anti-TB therapy were strongly associated with bacteriological confirmation of TB. A decrease in IP-10 level of >300pg/ml between 0 and 7 days of treatment identified 75% of both smear-positive and smear-negative culture positive patients and correctly excluded TB in all nine culture negative patients.

CONCLUSIONS

Monitoring of early IP-10 responses to treatment could form the basis of a simplified assay and could help identify patients who were erroneously clinically diagnosed with TB or those infected with drug resistant strains on inappropriate treatment. We believe this approach may be particularly appropriate for difficult to diagnose patients, e.g. smear-negative HIV-positive, or those with extra-pulmonary TB, often treated without bacterial confirmation.

Cytokine response to selected MTB antigens in Ghanaian TB patients, before and at 2 weeks of anti-TB therapy is characterized by high expression of IFN-γ and Granzyme B and inter- individual variation

BACKGROUND

There has been a long held belief that patients with drug-susceptible TB are non-infectious after two weeks of therapy. Recent microbiological and epidemiological evidence has challenged this dogma, however, the nature of the Mtb-specific cellular immune response during this period has not been adequately investigated. This knowledge could be exploited in the development of immunological biomarkers of early treatment response.

METHODS

Cellular response to four Mtb infection phase-dependent antigens, ESAT-6/CFP-10 fusion protein and three DosR encoded proteins (Rv1733c, Rv2029c, Rv2628) were evaluated in a Ghanaian TB cohort (n=20) before and after 2 weeks of anti TB therapy. After 6-days in vitro stimulation, Peripheral blood mononuclear cell (PBMC) culture supernatant was harvested and the concentration of IFN-γ, Granzyme B, IL-10, IL-17, sIL2Rα and TNF-α were determined in a 6-plex Luminex assay. Frequencies of IFN-γ + CD4 and CD8 T cells were also determined in an intracellular cytokine assay.

RESULTS

All antigens induced higher levels of IFN-γ, followed by Granzyme B, TNF-α and IL-17 and low levels of IL-10 and sIL-2R-α in PBMC before treatment and after 2 weeks of treatment. Median cytokine levels of IFN-γ, Granzyme B, IL-17 and sIL-2R-α increased during week two, but it was significant for only Rv1733-specific production of Granzyme B (P = 0. 013). The median frequency of antigen specific IFN-γ + CD4 T cells increased at week two; however, only the increase in the ESAT-6/CFP-10-specific response was significant (P = 0. 0008). In contrast, the median frequency of ESAT-6/CFP-10- specific IFN-γ + CD8 T cell responses declined during week two (P = 0. 0024). Additionally, wide inter-individual variation with three distinct patterns were observed; increase in all cytokine levels, decrease in all cytokine levels and fluctuating cytokine levels after 2 weeks of treatment.

CONCLUSION

The second week of effective chemotherapy was characterized by a general increase in cytokine response to Mtb-specific antigens suggestive of an improvement in cellular response with therapy. However, the wide inter-individual variation observed would limit the utility of cytokine biomarkers during this period.

A subset of circulating blood mycobacteria-specific CD4 T cells can predict the time to Mycobacterium tuberculosis sputum culture conversion

We investigated 18 HIV-negative patients with MDR-TB for M. tuberculosis (Mtb)- and PPD-specific CD4 T cell responses and followed them over 6 months of drug therapy. Twelve of these patients were sputum culture (SC) positive and six patients were SC negative upon enrollment. Our aim was to identify a subset of mycobacteria-specific CD4 T cells that would predict time to culture conversion. The total frequency of mycobacteria-specific CD4 T cells at baseline could not distinguish patients showing positive or negative SC. However, a greater proportion of late-differentiated (LD) Mtb- and PPD-specific memory CD4 T cells was found in SC positive patients than in those who were SC negative (p = 0.004 and p = 0.0012, respectively). Similarly, a higher co-expression of HLA-DR+ Ki67+ on Mtb- and PPD-specific CD4 T cells could also discriminate between sputum SC positive versus SC negative (p = 0.004 and p = 0.001, respectively). Receiver operating characteristic (ROC) analysis revealed that baseline levels of Ki67+ HLA-DR+ Mtb- and PPD-specific CD4 T cells were predictive of the time to sputum culture conversion, with area-under-the-curve of 0.8 (p = 0.027). Upon treatment, there was a significant decline of these Ki67+ HLA-DR+ T cell populations in the first 2 months, with a progressive increase in mycobacteria-specific polyfunctional IFNγ+ IL2+ TNFα+ CD4 T cells over 6 months. Thus, a subset of activated and proliferating mycobacterial-specific CD4 T cells (Ki67+ HLA-DR+) may provide a valuable marker in peripheral blood that predicts time to sputum culture conversion in TB patients at the start of treatment.

In vitro and in vivo studies of a rapid and selective breath test for tuberculosis based upon mycobacterial CO dehydrogenase

One of the major hurdles in treating tuberculosis (TB) is the time-consuming and difficult methodology for diagnosis. Stable-isotope breath tests hold great potential for rapidly diagnosing an infectious disease, monitoring therapy, and determining a bacterial phenotype in a rapid, point-of-care manner that does not require invasive sampling. Here we describe the preclinical development of a potentially highly selective TB diagnostic breath test based upon the organism’s CO dehydrogenase activity. After development of the test in vitro, we were able to use the breath test to discriminate between infected and control rabbits, demonstrating that a diagnosis can potentially be made and also that a complex bacterial phenotype can be noninvasively and rapidly studied in the host.

Tuberculosis (TB) remains a major infectious cause of disease and death worldwide, and effective diagnosis and then treatment are the tools with which we fight TB. The more quickly and more specific the diagnosis can be made, the better, and this is also true of diagnosis being as close to the patient (point of care) as possible. Here we report our preclinical development of breath tests based upon specific mycobacterial metabolism that could, with development, allow rapid point-of-care diagnosis through measuring the mycobacterial conversion of labeled CO to labeled CO₂.

A metabolic biosignature of early response to anti-tuberculosis treatment

Background

The successful treatment of tuberculosis (TB) requires long-term multidrug chemotherapy. Clinical trials to evaluate new drugs and regimens for TB treatment are protracted due to the slow clearance of Mycobacterium tuberculosis (Mtb) infection and the lack of early biomarkers to predict treatment outcome. Advancements in the field of metabolomics make it possible to identify metabolic profiles that correlate with disease states or successful chemotherapy. However, proof-of-concept of this approach has not been provided for a TB-early treatment response biosignature (TB-ETRB).

Methods

Urine samples collected at baseline and during treatment from 48 Ugandan and 39 South African HIV-seronegative adults with pulmonary TB were divided into discovery and qualification sets, normalized to creatinine concentration, and analyzed by liquid chromatography-mass spectrometry to identify small molecule molecular features (MFs) in individual patient samples. A biosignature that distinguished baseline and 1 month treatment samples was selected by pairwise t-test using data from two discovery sample sets. Hierarchical clustering and repeated measures analysis were applied to additional sample data to down select molecular features that behaved consistently between the two clinical sites and these were evaluated by logistic regression analysis.

Results

Analysis of discovery samples identified 45 MFs that significantly changed in abundance at one month of treatment. Down selection using an extended set of discovery samples and qualification samples confirmed 23 MFs that consistently changed in abundance between baseline and 1, 2 and 6 months of therapy, with 12 MFs achieving statistical significance (p < 0.05). Six MFs classified the baseline and 1 month samples with an error rate of 11.8%.

Conclusions

These results define a urine based TB-early treatment response biosignature (TB-ETRB) applicable to different parts of Africa, and provide proof-of-concept for further evaluation of this technology in monitoring clinical responses to TB therapy.

Mycobacterium tuberculosis specific CD8(+) T cells rapidly decline with antituberculosis treatment

Rationale

Biomarkers associated with response to therapy in tuberculosis could have broad clinical utility. We postulated that the frequency of Mycobacterium tuberculosis (Mtb) specific CD8⁺ T cells, by virtue of detecting intracellular infection, could be a surrogate marker of response to therapy and would decrease during effective antituberculosis treatment.

Objectives: We sought to determine the relationship of Mtb specific CD4⁺ T cells and CD8⁺ T cells with duration of antituberculosis treatment.

Materials and Methods

We performed a prospective cohort study, enrolling between June 2008 and August 2010, of HIV-uninfected Ugandan adults (n = 50) with acid-fast bacillus smear-positive, culture confirmed pulmonary TB at the onset of antituberculosis treatment and the Mtb specific CD4⁺ and CD8⁺ T cell responses to ESAT-6 and CFP-10 were measured by IFN-γ ELISPOT at enrollment, week 8 and 24.

Results

There was a significant difference in the Mtb specific CD8⁺ T response, but not the CD4⁺ T cell response, over 24 weeks of antituberculosis treatment (p<0.0001), with an early difference observed at 8 weeks of therapy (p = 0.023). At 24 weeks, the estimated Mtb specific CD8⁺ T cell response decreased by 58%. In contrast, there was no significant difference in the Mtb specific CD4⁺ T cell during the treatment. The Mtb specific CD4⁺ T cell response, but not the CD8⁺ response, was negatively impacted by the body mass index.

Conclusions

Our data provide evidence that the Mtb specific CD8⁺ T cell response declines with antituberculosis treatment and could be a surrogate marker of response to therapy. Additional research is needed to determine if the Mtb specific CD8⁺ T cell response can detect early treatment failure, relapse, or to predict disease progression.

Host targeted activity of pyrazinamide in Mycobacterium tuberculosis infection

Pyrazinamide (PZA) is one of the first line antibiotics used for the treatment of tuberculosis (TB). In the present study, we have used in vitro and in vivo systems to investigate whether PZA, in addition to its known anti-mycobacterial properties, modulate the host immune response during Mycobacterium tuberculosis (Mtb) infection. In vitro we have examined the effect of PZA on cytokine and chemokine release by Mtb-infected or Toll-like receptor (TLR) -stimulated primary human monocytes. In vivo, we have investigated at the transcriptional levels using genome-wide microarray gene expression analysis, whether PZA treatment of Mtb-infected mice alters the host immune response to Mtb infection in the lungs. Here, we report that PZA treatment of Mtb-infected human monocytes and mice significantly reduces the release of pro-inflammatory cytokines and chemokines, including IL-1β, IL-6, TNF-α and MCP-1 at the protein and at the gene transcription levels, respectively. Data from microarray analysis also reveal that PZA treatment of Mtb-infected mice significantly alters the expression level of genes involved in the regulation of the pro-inflammatory mediators, lung inflammatory response and TLR signaling networks. Specifically, genes coding for adenylate cyclase and Peroxisome-Proliferator Activated Receptor (PPAR), molecules known for their anti-inflammatory effect, were found to be up-regulated in the lungs of PZA-treated Mtb-infected mice. Based on the microarray findings, we propose that PZA treatment modulates the host immune response to Mtb infection by reducing pro-inflammatory cytokine production, probably through PPAR- and NF-kB- dependent pathways. In addition, our results suggest that inclusion or exclusion of PZA in the TB treatment regimen could potentially affect the biomarker signature detected in the circulation of TB patients.

Modulation of NKG2D expression in human CD8(+) T cells corresponding with tuberculosis drug cure

Background

Biomarkers predicting tuberculosis treatment response and cure would facilitate drug development. This study investigated expression patterns of the co-stimulation molecule NKG2D in human tuberculosis and treatment to determine its potential usefulness as a host biomarker of tuberculosis drug efficacy.

Methods

Tuberculosis patients (n = 26) were recruited in Lahore, Pakistan, at diagnosis and followed up during treatment. Household contacts (n = 24) were also recruited. NKG2D expression was measured by qRT-PCR in RNA samples both ex vivo and following overnight mycobacterial stimulation in vitro. Protein expression of NKG2D and granzyme B was measured by flow cytometry.

Results

NKG2D expression in newly diagnosed tuberculosis patients was similar to household contacts in ex vivo RNA, but was higher following in vitro stimulation. The NKG2D expression was dramatically reduced by intensive phase chemotherapy, in both ex vivo blood RNA and CD8⁺ T cell protein expression, but then reverted to higher levels after the continuation phase in successfully treated patients.

Conclusion

The changes in NKG2D expression through successful treatment reflect modulation of the peripheral cytotoxic T cell response. This likely reflects firstly in vivo stimulation by live Mycobacterium tuberculosis, followed by the response to dead bacilli, antigen-release and finally immunopathology resolution. Such changes in host peripheral gene expression, alongside clinical and microbiological indices, could be developed into a biosignature of tuberculosis drug-induced cure to be used in future clinical trials.

Detectable changes in the blood transcriptome are present after two weeks of antituberculosis therapy

Rationale

Globally there are approximately 9 million new active tuberculosis cases and 1.4 million deaths annually. Effective antituberculosis treatment monitoring is difficult as there are no existing biomarkers of poor adherence or inadequate treatment earlier than 2 months after treatment initiation. Inadequate treatment leads to worsening disease, disease transmission and drug resistance.

Objectives

To determine if blood transcriptional signatures change in response to antituberculosis treatment and could act as early biomarkers of a successful response.

Methods

Blood transcriptional profiles of untreated active tuberculosis patients in South Africa were analysed before, during (2 weeks and 2 months), at the end of (6 months) and after (12 months) antituberculosis treatment, and compared to individuals with latent tuberculosis. An active-tuberculosis transcriptional signature and a specific treatment-response transcriptional signature were derived. The specific treatment response transcriptional signature was tested in two independent cohorts. Two quantitative scoring algorithms were applied to measure the changes in the transcriptional response. The most significantly represented pathways were determined using Ingenuity Pathway Analysis.

Results

An active tuberculosis 664-transcript signature and a treatment specific 320-transcript signature significantly diminished after 2 weeks of treatment in all cohorts, and continued to diminish until 6 months. The transcriptional response to treatment could be individually measured in each patient.

Conclusions

Significant changes in the transcriptional signatures measured by blood tests were readily detectable just 2 weeks after treatment initiation. These findings suggest that blood transcriptional signatures could be used as early surrogate biomarkers of successful treatment response.

Biomarkers of latent TB infection

For the last 100 years, the tuberculin skin test (TST) has been the only diagnostic tool available for latent TB infection (LTBI) and no biomarker per se is available to diagnose the presence of LTBI. With the introduction of M. tuberculosis-specific IFN-gamma release assays (IGRAs), a new area of in vitro immunodiagnostic tests for LTBI based on biomarker readout has become a reality. In this review, we discuss existing evidence on the clinical usefulness of IGRAs and the indefinite number of potential new biomarkers that can be used to improve diagnosis of latent TB infection. We also present early data suggesting that the monocyte-derived chemokine inducible protein-10 may be useful as a novel biomarker for the immunodiagnosis of latent TB infection.

[Treatment of recurrent pulmonary tuberculosis]

INTRODUCTION

Tuberculosis (TB) is a greatest public health problem of the world. This work aims to study the antituberculous treatment and the evolution of the patients with recurrent tuberculosis.

PATIENTS AND METHOD

The study is a retrospective study on 64 patients with recidivant pulmonary TB: A1 group: at the first TB attack; A2 group: at the time of recidivant TB, and 105 controls patients with confirmed TB without recidive.

RESULTS

Multidrug-resistant TB is more frequent with recidivant TB (21.1% vs 3%, P<0.05) and also extensively drug-resistant. Antituberculous treatment duration in group A1, A2 and T was respectively 8.63 months, 9.79 months, and 7.08 months. Antituberculous drug complications were more frequent in group A2 compared to group T (76.1% vs 41.2%; P<0.001).

CONCLUSION

All tuberculous patients, specially recidivant TB, should benefit of particular care and drug protocol adaptation.

Effect of standard tuberculosis treatment on plasma cytokine levels in patients with active pulmonary tuberculosis

BACKGROUND

Sputum Mycobacterium tuberculosis (Mtb) culture is commonly used to assess response to antibiotic treatment in individuals with pulmonary tuberculosis (TB). Such techniques are constrained by the slow growth rate of Mtb, and more sensitive methods to monitor Mtb clearance are needed. The goal of this study was to evaluate changes in plasma cytokines in patients undergoing treatment for TB as a means of identifying candidate host markers associated with microbiologic response to therapy.

METHODS

Twenty-four plasma cytokines/chemokines were measured in 42 individuals diagnosed with active pulmonary TB, 52% were HIV co-infected. Individuals, undergoing a 26-week standard TB treatment, were followed longitudinally over 18 months and measurements were associated with HIV status and rates of sputum culture conversion.

RESULTS

Plasma concentrations of interferon-inducible protein-10 (IP-10) and vascular endothelial growth factor (VEGF) were significantly reduced upon TB treatment, regardless of HIV status. By the end of treatment, IP-10 concentrations were significantly lower in HIV negative individuals when compared to HIV-positive individuals (p = 0.02). Moreover, in HIV negative patients, plasma VEGF concentrations, measured as early as 2-weeks post TB treatment initiation, positively correlated with the time of sputum conversion (p = 0.0017). No significant changes were observed in other studied immune mediators.

CONCLUSIONS

These data suggest that VEGF plasma concentration, measured during early TB treatment, could represent a surrogate marker to monitor sputum culture conversion in HIV uninfected individuals.

CDC/NIH Workshop. Tuberculosis biomarker and surrogate endpoint research roadmap

The Centers for Disease Control and Prevention and National Institutes of Health convened a multidisciplinary meeting to discuss surrogate markers of treatment response in tuberculosis. The goals were to assess recent surrogate marker research and to provide specific recommendations for (1) the qualification and validation of biomarkers of treatment outcome; (2) the standardization of specimen and data collection for future clinical trials, including a minimum set of samples and collection time points; and (3) the creation ofa specimen repository to support biomarker testing. This article summarizes these recommendations and provides a roadmap for their implementation.

Advances and hurdles on the way toward a leprosy vaccine

Prevalence rates for leprosy have declined sharply over the past 20 y, with this decline generally attributed to the WHO multi-drug therapy (MDT) campaign to provide free-of-charge treatment to all diagnosed leprosy patients. The success of this program appears to have reached its nadir, however, as evidenced by the stalled decreases in both global prevalence and new case detection rates of leprosy. Mass BCG vaccination for the prevention of tuberculosis (TB) at national levels has had a positive effect on leprosy decline and is often overlooked as an important factor in current leprosy control programs. Because BCG provides incomplete protection against both TB and leprosy, newer more effective TB vaccines are being developed. The impact that application of these vaccines will have on current leprosy control programs is unclear. In this review, we assess the need for vaccines within leprosy control programs. We summarize and discuss leprosy vaccine strategies that have been deployed previously and discuss those strategies that are currently being developed to augment recent breakthroughs in leprosy control.

Surrogate markers of infection: interrogation of the immune system

Infectious diseases remain the greatest causes of morbidity and mortality in global terms. As much of the burden occurs in the developing world, limited access to diagnostic testing has hampered the diagnosis and treatment of these conditions, while, in the developed world, the cost of managing infectious diseases remains considerable. Despite the size of the problem there remains an ongoing need for tests that improve diagnostic sensitivity and specificity, provide more rapid diagnoses, are available for point-of-care testing in remote regions, and can help inform therapeutic decision-making by identifying resistance patterns or patient outcomes. This article discusses the background to biomarker development for infectious diseases, some current assays that are providing useful information regarding the host's response to infection (using examples such as Cytomegalovirus and Mycobacterium tuberculosis), as well as likely future technologies and their limitations.

T cell monitoring of chemotherapy in experimental rat tuberculosis

Mycobacterium tuberculosis is the causative agent of a pulmonary epidemic that is estimated to infect one-third of the world's population and that has an increased incidence of multidrug resistance. The evaluation of new chemical entities against M. tuberculosis is hampered by the lack of biological tools to help predict efficacy, from early drug development to clinical trials. As the rat is the animal species of choice in the pharmaceutical industry, we have developed a rat model of acute and chronic phases of M. tuberculosis infection for drug efficacy testing. In this model, we have evaluated the impact of tuberculosis drugs on T cell response using the enzyme-linked immunospot assay methodology. Infected rats treated with isoniazid (INH) or rifampin (RIF) responded to therapy, the potency of which was comparable to that seen in the mouse. Peripheral blood mononuclear cells from infected rats produced gamma interferon (IFN-γ) in response to RD-1 antigens, such as the 6-kDa early secretory antigen target (ESAT-6) and the 10-kDa culture filtrate protein (CFP-10). A decrease in IFN-γ spot-forming cells (SFCs) was consistently observed in response to drug treatment. In both the acute- and chronic-phase models, the T cell response was more sensitive to ESAT-6 than to CFP-10. The SFC count in response to ESAT-6 appears to be an indicator of bacterial killing in the rat. Collectively, our data suggest that the ESAT-6 response could be used as a potential surrogate of drug efficacy in the rat and that such a readout could help shorten drug testing during preclinical development.

T lymphocyte surface expression of exhaustion markers as biomarkers of the efficacy of chemotherapy for tuberculosis

Predictive biomarkers illustrating the effectiveness of chemotherapeutic regimens for tuberculosis still remain elusive. To date, most are predicated on assays using sputum or serum; as a result, if not predictive, treatment failure in patients may not be evident for some time. We report here the results of a simple screening study in which T cell surface markers were examined in mice infected with Mycobacterium tuberculosis and then treated with drugs. These studies identified certain markers, the exhaustion markers PD-1 and TIM-3, as well as the marker KLRG-1, particularly on CD8 T cells, that changed in concert with reduction of the bacterial load in the lungs. While there is no guarantee these changes would also be seen on T cells in the blood, this approach should be further investigated.

Humoural Immune Responses to a Recombinant 16-kDa–38-kDa—ESAT-6 Mycobacterial Antigen in Tuberculosis

The present study investigated the diagnostic value of a recombinant 38-kDa–16-kDa—early secreted antigenic target of 6 kDa (ESAT-6) Mycobacterium tuberculosis (MTB) fusion antigen in 105 patients with tuberculosis (TB), 25 non-TB pulmonary disease patients and 20 healthy individuals. Its diagnostic value was compared with the commercially available enzyme-linked immunosorbent assay kit, the TB-directly observed therapy (DOT) kit. In the controls, the rate of positive antibody response to the TB-DOT kit was significantly higher than that of the recombinant antigen. The area under the receiver operating characteristic curve was 0.751, and the optimum sensitivity and specificity for detecting antibody responses to the recombinant antigen were 65.4% and 84.8%, respectively. The recombinant 38-kDa–16-kDa—ESAT-6 MTB antigen was more effective than the TB-DOT kit in distinguishing between TB patients and controls, and may be an optimal combination of antigens to provide a useful tool for the sensitive and specific diagnosis of patients with TB.

13[C]-urea breath test as a novel point-of-care biomarker for tuberculosis treatment and diagnosis

Background

Pathogen-specific metabolic pathways may be detected by breath tests based on introduction of stable isotopically-labeled substrates and detection of labeled products in exhaled breath using portable infrared spectrometers.

Methodology/Principal Findings

We tested whether mycobacterial urease activity could be utilized in such a breath test format as the basis of a novel biomarker and diagnostic for pulmonary TB. Sensitized New-Zealand White Rabbits underwent bronchoscopic infection with either Mycobacterium bovis or Mycobacterium tuberculosis. Rabbits were treated with 25 mg/kg of isoniazid (INH) approximately 2 months after infection when significant cavitary lung pathology was present. [¹³C] urea was instilled directly into the lungs of intubated rabbits at selected time points, exhaled air samples analyzed, and the kinetics of δ¹³CO₂ formation were determined. Samples obtained prior to inoculation served as control samples for background ¹³CO₂ conversion in the rabbit model. ¹³CO₂, from metabolic conversion of [¹³C]-urea by mycobacterial urease activity, was readily detectable in the exhaled breath of infected rabbits within 15 minutes of administration. Analyses showed a rapid increase in the rate of ¹³CO₂ formation both early in disease and prior to treatment with INH. Following INH treatment, all evaluable rabbits showed a decrease in the rate of ¹³CO₂ formation.

Conclusions/Significance

Urea breath testing may provide a useful diagnostic and biomarker assay for tuberculosis and for treatment response. Future work will test specificity for M. tuberculosis using lung-targeted dry powder inhalation formulations, combined with co-administering oral urease inhibitors together with a saturating oral dose of unlabeled urea, which would prevent the δ¹³CO₂ signal from urease-positive gastrointestinal organisms.

Biomarkers and diagnostics for tuberculosis: progress, needs, and translation into practice

Human infection with Mycobacterium tuberculosis can progress to active disease, be contained as latent infection, or be eradicated by the host response. Tuberculosis diagnostics classify a patient into one of these categories. These are not fixed distinct states, but rather are continua along which patients can move, and are affected by HIV infection, immunosuppressive therapies, antituberculosis treatments, and other poorly understood factors. Tuberculosis biomarkers-host or pathogen-specific-provide prognostic information, either for individual patients or study cohorts, about these outcomes. Tuberculosis case detection remains difficult, partly because of inaccurate diagnostic methods. Investments have yielded some progress in development of new diagnostics, although the existing pipeline is limited for tests for sputum-smear-negative cases, childhood tuberculosis, and accurate prediction of reactivation of latent tuberculosis. Despite new, sensitive, automated molecular platforms for detection of tuberculosis and drug resistance, a simple, inexpensive point-of-care test is still not available. The effect of any new tests will depend on the method and extent of their introduction, the strength of the laboratories, and the degree to which access to appropriate therapy follows access to diagnosis. Translation of scientific progress in biomarkers and diagnostics into clinical and public health programmes is possible-with political commitment, increased funding, and engagement of all stakeholders.

High granulocyte/lymphocyte ratio and paucity of NKT cells defines TB disease in a TB-endemic setting

Most people infected with Mycobacterium tuberculosis, the causative agent of tuberculosis (TB) actually maintain a strong immune response and are able to control bacterial growth (deemed latently infected (LTBI)), while approximately 10% progress to disease resulting in almost 2 million deaths per year. Determining the immune 'footprint' at specific stages of infection and disease will allow for better diagnostics, treatments and ultimately development of new vaccine candidates. In this study we performed multi-factorial flow cytometry on fresh blood from 56 TB cases, 46 Tuberculin Skin Test (TST) positive (LTBI) and 39 TST negative household contacts. We found a highly significant increase in granulocytes and decrease in B cells and invariant (Valpha24+Vbeta11+) NKT cells in TB cases compared to TST+ contacts (p<0.0001, p=0.007 and p=0.01 respectively) which were restored to LTBI levels following 6 months of TB treatment. Using support vector analysis, we found a combination of granulocyte and lymphocyte and/or NKT cell proportions allowed almost 90% correct classification into M. tuberculosis infection or disease. This work has important public health benefits in regards to diagnosis and treatment of TB in sub-Saharan Africa and in furthering our understanding of the requirements for protective immunity to TB.

New diagnostic methods for tuberculosis

PURPOSE OF REVIEW

During the last decade, laboratory tests for the detection of Mycobacterium tuberculosis (Mtb) have improved dramatically. Improvements in the ability to detect latent infection with Mtb, disease associated with Mtb, and strains resistant to commonly used antibiotics are reviewed.

RECENT FINDINGS

Advances in the detection of Mtb include light-emitting diode fluorescence microscopy, nucleic acid amplification of Mtb and drug-resistant strains, and more rapid liquid culture with adjunct drug susceptibility testing. In the detection of latent tuberculosis infection, interferon [gamma] release assays offer improved accuracy over the tuberculin skin test.

SUMMARY

The past 10 years have seen the most rapid growth in new diagnostics for Mtb in over a century. Although these tests offer improvements in the ability to detect Mtb, drug-resistant isolates, and those with latent tuberculosis infection, these improvements are counter-balanced by the need to deploy these tests in areas where Mtb burden is highest.

In vitro levels of interleukin 10 (IL-10) and IL-12 in response to a recombinant 32-kilodalton antigen of Mycobacterium bovis BCG after treatment for tuberculosis

Cell-mediated immunity plays a major role in conferring protection against tuberculosis (TB) on an individual. It is not known whether the immune status correlates with the bacterial load or whether the immunity improves after treatment. Also, it may be important to monitor treatment by being able to discriminate between active disease and successfully treated TB. The main aim of this study was to investigate the usefulness of a recombinant 32-kDa antigen (r32-kDa Ag) of Mycobacterium bovis BCG (Ag85A-BCG) as a diagnostic marker in patients being treated for TB. Specifically, the in vitro T-cell assays and the release of interleukin-12 (IL-12) (Th1-type cytokine) and IL-10 (Th2-type cytokine) in response to the r32-kDa Ag of BCG were assayed in patients with either pulmonary (sputum positive/negative, n = 74) or extrapulmonary TB (n = 49) and healthy controls. The proliferative responses of stimulated cells at 0, 2 to 4, and 6 months of treatment increased and were highly significant (P < 0.000) compared to the responses in controls. The increase in IL-12 and decrease in IL-10 release suggest that there is cytokine expression modification during different stages of TB, and treatment seems to have an influence on the levels of these cytokines, suggesting an augmentation in the protective responses. The in vitro response to the M. bovis BCG r32-kDa Ag may be useful in monitoring treatment of TB.