Monokine induced by interferon gamma and IFN-gamma response to a fusion protein of Mycobacterium tuberculosis ESAT-6 and CFP-10 in Brazilian tuberculosis patients

Biomarkers of cell-mediated immunity to bovine tuberculosis

Whole blood based assays, particularly interferon gamma (IFN-γ) release assays (IGRAs), are used for the diagnosis of both bovine and human tuberculosis (TB). The aim of the current study was to evaluate a panel of cytokines and chemokines for potential use as diagnostic readouts indicative of Mycobacterium bovis (M. bovis) infection in cattle. A gene expression assay was used to determine the kinetics of the response to M. bovis purified protein derivative and a fusion protein consisting of ESAT-6, CFP10, and Rv3615c upon aerosol infection with ∼10⁴ cfu of M. bovis. The panel of biomarkers included: IFN-γ, CXCL9, CXCL10, CCL2, CCL3, TNF-α, IL-1α, IL-1β, IL-1Ra, IL-22, IL-21 and IL-13. Protein levels of IFN-γ, CXCL9, and CXCL10 were determined by ELISA. Findings suggest that CXCL9, CXCL10, IL-21, IL-13, and several acute phase cytokines may be worth pursuing as diagnostic biomarkers of M. bovis infection in cattle.

Mycobacterium avium subspecies paratuberculosis seroconversion in dairy cattle and its association with raised somatic cell count

This retrospective case-control study investigates the relationship between seroconversion to Mycobacterium avium subspecies paratuberculosis (MAP) and raised somatic cell count (SCC). The study consists of 112 case cows from three dairy farms in the UK; for each case cow with a positive antibody titre, there was a seronegative control cow for comparison. Seroconversion was monitored using milk ELISA antibody titres for MAP taken at quarterly intervals. SCCs were recorded at the time a positive antibody titre was first recorded as well as at the previous and subsequent milk recording in order to explore a temporal relationship between the two events. The previous and subsequent milk recordings were a month before and after seroconversion was identified. The results showed that cows that were infected with MAP had an increased SCC around the time that they first became seropositive, providing evidence for a temporal relationship between the two events; high SCCs were particularly prevalent before and at the time of first detecting seroconversion. The explanation is being discussed that potentially an underlying, currently not studied, factor may be predisposing both events, the progression of paratuberculosis is predisposing the host to mastitis, or indeed intramammary infections help initiate paratuberculosis progression.

Evaluation of the transcriptional immune biomarkers in peripheral blood from Warao indigenous associate with the infection by Mycobacterium tuberculosis

INTRODUCTION

Biomarkers are critical tools for finding new approaches for controlling the spread of tuberculosis (TB), including for predicting the development of TB therapeutics, vaccines, and diagnostic tools.

METHODS

Expression of immune biomarkers was analyzed in peripheral blood cells stimulated and non-stimulated with M. tuberculosis antigens ESAT-6, CFP10 and TB7.7. in Warao indigenous individuals. These biomarkers may be able to differentiate TB states, such as active tuberculosis (ATB) cases and latent tuberculosis infection (LTBI) from non-infected controls (NIC). A real-time reverse transcription polymerase chain reaction (RT-qPCR) assay was performed on 100 blood samples under non-stimulation or direct ex vivo conditions (NS=50) and stimulation conditions (S=50).

RESULTS

The findings are shown as the median and interquartile range (IQR) of relative gene expression levels of IFN-γ, CD14, MMP9, CCR5, CCL11, CXCL9/MIG, and uPAR/PLAUR immune biomarkers. MMP9 levels were significantly higher in the LTBI-NS and LTBI-S groups compared with the NIC-NS and NIC-S groups. However, CCR5 levels were significantly lower in the LTBI-S group compared with both NIC-NS and NIC-S groups. CCL11 levels were significantly lower in the LTBI-S group compared with the NIC-NS group.

CONCLUSIONS

Preliminary findings showed that MMP9 immune biomarkers separated LTBI indigenous individuals from NIC indigenous individuals, while CCR5, CCL11, CD14, and IFN-γ did not differentiate TB states from NIC. MMP9 may be useful as a potential biomarker for LTBI and new infected case detection among Warao indigenous individuals at high risk of developing the disease. It may also be used to halt the epidemic, which will require further validation in larger studies.

Immunological characterization of latent tuberculosis infection in a low endemic country

The diagnosis of a latent tuberculosis infection (LTBI) is based on detection of immunity against Mycobacterium tuberculosis (Mtb). The tuberculin skin test (TST), the Quantiferon (QFT) and a prolonged lymphocyte stimulation test using either ESAT-6/CFP-10 (LST-EC) or PPD (LST-PPD) were evaluated in a cohort of 495 individuals, suspected to have LTBI, in a low endemic country. While the TST and LST-PPD were both positive in the majority (75%) of individuals, only one third responded in the LST-EC and in the QFT. The choice for LTBI treatment was significantly associated with ESAT6/CFP10 recognition, however the LST-EC detected considerably more individuals (21%) with immunity against Mtb, who might also be at risk for development of active TB, although none of them did during follow up. Follow-up for 2 years showed 7% conversions and 32% reversions for the QFT. The LST-EC showed higher conversion rates (∼45%), although the percentage of individuals positive in the LST-EC did not change significantly within the follow-up period. LTBI treatment did not alter immune recognition of Mtb antigens. In conclusion, the sensitivity of tests for detection of cellular immunity to Mtb specific antigens depends on test methodology and may vary considerably over time in a low endemic region.

Cytokine and Antibody Based Diagnostic Algorithms for Sputum Culture-Positive Pulmonary Tuberculosis

Background

Tuberculosis (TB) is one of the most serious infectious diseases globally and has high mortality rates. A variety of diagnostic tests are available, yet none are wholly reliable. Serum cytokines, although significantly and frequently induced by different diseases and thus good biomarkers for disease diagnosis and prognosis, are not sufficiently disease-specific. TB-specific antibody detection, on the other hand, has been reported to be highly specific but not sufficiently sensitive. In this study, our aim was to improve the sensitivity and specificity of TB diagnosis by combining detection of TB-related cytokines and TB-specific antibodies in peripheral blood samples.

Methods

TB-related serum cytokines were screened using a human cytokine array. TB-related cytokines and TB-specific antibodies were detected in parallel with microarray technology. The diagnostic performance of the new protocol for active TB was systematically compared with other traditional methods.

Results

Here, we show that cytokines I-309, IL-8 and MIG are capable of distinguishing patients with active TB from healthy controls, patients with latent TB infection, and those with a range of other pulmonary diseases, and that these cytokines, and their presence alongside antibodies for TB-specific antigens Ag14-16kDa, Ag32kDa, Ag38kDa and Ag85B, are specific markers for active TB. The diagnostic protocol for active TB developed here, which combines the detection of three TB-related cytokines and TB-specific antibodies, is highly sensitive (91.03%), specific (90.77%) and accurate (90.87%).

Conclusions

Our results show that combining detection of TB-related cytokines and TB-specific antibodies significantly enhances diagnostic accuracy for active TB, providing greater accuracy than conventional diagnostic methods such as interferon gamma release assays (IGRAs), TB antibody Colloidal Gold Assays and microbiological culture, and suggest that this diagnostic protocol has potential for clinical application.

Mycobacterium tuberculosis Sonicate-Induced IFNγ, CXCL10 and IL10 can Differentiate Severity in Tuberculosis

Improved tools are required to study immunopathogenesis of tuberculosis (TB). Mycobacterium tuberculosis antigen-stimulated T cell-based assays can detect TB but are less effective when responses are compromised such as in severe disease. We investigated immune responses to M. tuberculosis whole sonicate (MTBs), recombinant antigens ESAT6 and CFP10 in whole blood cells of healthy endemic controls (EC, n = 42) and patients with pulmonary (PTB, n = 36) or extrapulmonary (ETB, n = 41) disease. Biomarkers of T cell activation (IFNγ) or modulation (IL10) and chemokines, CXCL9, CXCL10 and CCL2, secretion were measured. MTBs, ESAT6 and CFP10 all induced IFNγ responses in TB. ESAT6-induced IFNγ was elevated in TB as compared with EC. MTBs stimulated the highest IFNγ levels but did not differentiate between TB and EC. However, MTBs-induced CXCL10 (P = 0.004) was reduced, while IL10 (P < 0.001) was raised in TB as compared with EC. Between sites, MTBs-induced CCL2 (P = 0.001) and IL10 secretion was higher in PTB than ETB (P < 0.001). In comparison of disease severity, MTBs-induced IFNγ (P = 0.014) and CXCL10 (P = 0.022) levels were raised in moderate as compared with far advanced PTB. In ETB, MTBs-induced IL10 levels were greater in less-severe (L-ETB) than in severe disseminated (D-ETB) cases, P = 0.035. Within the L-ETB group, MTBs-induced IFNγ was greater in patients with tuberculous lymphadenitis than those with pleural TB (P = 0.002). As immune responses to MTBs were differentially activated in TB of different sites and severity, we propose the utility of MTBs-induced IFNγ, CXCL10 and IL10 as biomarkers in TB.

The evaluation of candidate biomarkers of cell-mediated immunity for the diagnosis of Mycobacterium bovis infection in African buffaloes (Syncerus caffer)

We evaluated commercially available bovine enzyme linked immunosorbent assays (ELISA) and a human IP-10 ELISA to measure IP-10, MIG, MCP-1, MCP-2, MCP-3 and IL1-RA in buffalo plasma in order to identify sensitive markers of the immune response to Mycobacterium bovis-specific peptides. Additionally, we found that all coding mRNA sequences of these cytokines showed very high homology with their homologues in domestic cattle (97-99%) as did the derived amino acid sequences (97-99%). This high sequence homology between cattle and buffaloes supports the use of bovine ELISAs for the detection these cytokines in buffaloes. MCP-1 concentration showed a positive correlation with that of IFN-γ (p=0.0077) and appears to occur in far greater abundance in buffaloes when compared to humans. Using a bovine IP-10 ELISA, levels of this cytokine were found to be significantly increased in antigen-stimulated blood samples from M. bovis test positive buffaloes (p<0.0001) and IP-10 was detected in far greater abundance than IFN-γ. Measurement of IP-10 with this ELISA may prove to be a sensitive marker of M. bovis infection in African buffaloes.

Comparison of Tuberculin Skin Test result and interferon gamma response to human PPD in BCG scar positive and negative children

BACKGROUND

The aim of this study is to compare Tuberculin Skin Test (TST) result and interferon gamma response to human PPD (purified protein derivative), in scar positive and scar negative BCG-vaccinated children.

METHODS

Between August 2007 and May 2008 a total of 236 children aged 1-168 months (mean 21 months) admitted to Mofid Children's Hospital, Tehran, Iran, were enrolled in a cross-sectional study. Each patient was examined for BCG vaccine scar and tested with TST and human PPD-based Interferon Gamma Release Assay (IGRA).

RESULTS

Two hundred and twenty one cases out of 236 (44% female, 1-168 months, mean age 21 months) were scar positive of whom 95% TST result was negative. Human PPD-based IGRA was positive in 110 (49.8%), negative in 85 (38.4 %) and indeterminate in 26 (11.8%) of scar positive patients. Fifteen children (40% female, 1-156 months; mean age 42 months) were scar negative. All the scar negative cases were TST negative. Human PPD-based IGRA was positive in 10 (66.7%), negative in 4 (26.7%) and indeterminate in 1 (6.7%) of scar negative patients.

CONCLUSIONS

Immune responsiveness to human PPD antigens in scar positive and negative children may not correspond with results of the Tuberculin Skin Test.

Measurement of ESAT6-induced IFNγ responses adjunct with CXCL9 increases the rate of diagnosis of active tuberculosis in an endemic region

Due to difficulties in direct diagnosis of Mycobacterium tuberculosis infection where site-specific specimens are not available, indirect methods of testing for infection are required. M. tuberculosis early secreted antigen target-6 (ESAT6) induced IFN-γ responses are specific, but do not differentiate between latent and active TB. The use of adjunct biomarkers for TB diagnosis has been proposed, such as the chemokines: CXCL9, CXCL10 and CCL2. ESAT6-induced IFN-γ CXCL9, CXCL10 and CCL2 was measured in whole blood cell supernatants of patients with pulmonary tuberculosis (PTB, n=36) and extrapulmonary TB (ETB, n=31) and compared with healthy endemic controls (EC, n=33). ESAT6-induced IFN-γ responses were positive in 32% of TB cases as compared with 15% of EC cases (p=0.048). ESAT6-induced CXCL9 responses were positive in 42% of TB cases and 15% of EC cases (p=0.006). ESAT6-induced-CXCL10 and -CCL2 responses did not discriminate between TB and EC groups. Measurement of IFN-γ or CXCL9 together diagnosed TB (53%) cases and was significant as compared with EC (p=0.014) cases. IFN-γ and CXCL10 together did not increase the number of TB cases diagnosed. Within TB groups, ESAT6-IFN-γ/CXCL9-based detection increased to 53% in PTB (p=0.031) and 54% in ETB (p=0.021), with comparable diagnosis in less severe extrapulmonary TB (L-ETB, 55%) and severe disseminated extrapulmonary TB (D-ETB, 50%). Given that 47% of TB cases remained undetected, this study shown that ESAT6-induced IFNγ and CXCL9 can support diagnosis, but must be supported by clinical correlation and other relevant investigations.

Ethnicity-tailored novel set of ESAT-6 peptides for differentiating active and latent tuberculosis

Differentiation between active and latent TB is a diagnostic challenge in TB-endemic regions. The commercially available IFN-γ-release assays are unsuitable for achieving this discrimination. We, therefore, screened ESAT-6 and CFP-10 proteins through population coverage analysis to identify minimal sets of peptides that can discriminate between these two forms of TB in a North Indian population. Comparing the diagnostic performance of a set of 2 ESAT-6 peptides (positions: 16-36; 59-79) to that of the QuantiFERON(®)-TB Gold IT (QFTGIT) assay, we observed significant difference in IFN-γ and TNF-α levels between patients (n = 15) and their age- and sex-matched healthy household contacts (n = 15). While the mean (±SD) IFNγ titer was 241.8 (±219.24) IU/ml for patients, the same in controls was 564.2 (±334.82) IU/ml (p = 0.039). Similarly the TNFα response was significantly higher in patients, compared to controls (796.47 ± 175.21 IU/ml vs. 481.81 ± 378.72 IU/ml; p = 0.047). IL-4 response to these peptides was non- discriminatory between the two groups. The QFTGIT Assay, however, elicited no significant difference in IFN-γ, TNF-α or IL-4 levels. Hence we conclude that IFN-γ or TNF-α response to these ESAT-6 peptides has the potential to differentiate between active and latent TB in our population.

Early diagnosis of tuberculous meningitis by an indirect ELISA protocol based on the detection of the antigen ESAT-6 in cerebrospinal fluid

Background

Early diagnosis of tuberculous meningitis (TBM) is still a challenge; the present study aimed to establish a method of detecting the antigen early secreted antigenic target 6 (ESAT-6) in cerebrospinal fluid (CSF) by an indirect enzyme-linked immunosorbance assay (ELISA) protocol and to study the value of detecting ESAT-6 in CSF in the early diagnosis of TBM.

Methods

An indirect ELISA protocol was used, employing a monoclonal antibody (mAb) against ESAT-6, which was used to demonstrate ESAT-6 in the CSF from TBM patients and non-TBM controls. CSF was obtained from 100 patients: confirmed TBM, clinically diagnosed TBM, disease controls, and healthy controls (n = 10). Pure recombinant ESAT-6 (standard product) was used in serial dilutions to detect the absorbance and to establish a standard curve from the data; the concentration was on the X axis vs. absorbance on the Y axis, and the standard curve was used to interpolate the concentration of ESAT-6 in samples.

Results

The indirect ELISA method provided 88 % sensitivity and 92 % specificity for the diagnosis of TBM using a mAb to ESAT-6. The mean concentration of ESAT-6 in TBM patients was significantly higher than that of the non-TBM groups. There was also a significant difference in the mean ESAT-6 expression between the confirmed TBM patients and the clinically diagnosed TBM patients (p < 0.01).

Conclusions

Detection of ESAT-6 in the CSF of TBM patients by indirect ELISA protocol gives a reliable early diagnosis and can be used to develop an immunodiagnostic assay with increased sensitivity and specificity.

Immunological profile of silent brain infarction and lacunar stroke

Neuroinflammation is believed to be involved in the pathophysiological mechanisms of silent brain infarcts (SBI). However, the immunological profile of SBI has been scarcely investigated. In the context of a national research project named SILENCE, aimed at investigating clinical, biochemical and pathogenic features of SBI, we have measured the plasma profile of some inflammatory-related molecules in SBI patients (n = 21), patients with recent lacunar infarcts (LI, n = 28) and healthy controls (n = 31), consecutively enrolled in four Italian centres. A panel of chemokines (MIG, CTACK, IL16, SDF1a, MCP1), growth factors (SCF, SCGFb, HGF, IL3), immunoglobulin-type adhesion molecules (ICAM1, VCAM1), proinflammatory cytokines (IL18, INFa2, MIF, IL12p40), cell surface receptors on T-cells (IL2Ra), and inductors of apoptosis (TRAIL) was assessed in plasma samples by Luminex xMAP™ technology. Immunological parameters were compared using non-parametric statistics and performance to distinguish SBI and LI was evaluated by receiver operating characteristic (ROC) analysis. Plasma levels of ICAM1 were significantly higher in both SBI and LI patients as compared to controls (SBI≥LI>Ctrl). A different trend was observed for IL16 (SBI<LI>Ctrl), SCF (LI<SBI>Ctrl) and SCGFb (SBI>LI<Ctrl). SBI subjects had significantly increased levels of MIG when compared to controls (LI≤SBI>Ctrl) and IL18 when compared to LI patients (Ctrl≤SBI>LI). All the other immunological markers did not significantly differ among groups. According to ROC analysis, the best predictor for SBI condition was the chemokine MIG (AUC = 0.84, sensitivity 86%, specificity 77%), while SCF had the best performance in distinguishing LI patients (AUC = 0.84, sensitivity 86%, specificity 68%). These results confirm the involvement of inflammatory processes in cerebrovascular disorders, particularly in SBI, a very common age-related condition. The differences in plasma profile of inflammatory molecules may underlie different pathological mechanisms in SBI and LI patients.

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.

MIGRAs: are they the new IGRAs? Development of monokine-amplified IFN-γ release assays

IFN-γ release by antigen-specific T cells can be used to track immune responses to infections and vaccines. In recent years, there have been substantial advances in the techniques available to measure IFN-γ release and a generation of such assays are now available for clinical use, as well as in a research setting. Interferon release leads to subsequent release of interferon-responsive chemokines such as MIG and IP-10, thus amplifying the original signal. A number of investigators have assessed whether measurement of these chemokines might provide a sensitive platform for detection of infection and antigen-specific T-cell responses. In this article, we assess the potential of these new approaches. We have termed the new antigen-specific T-cell assays monokine-amplified IFN-γ release assays (MIGRAs). Overall, it seems likely that improvements in the detection threshold could be made by analysis of antigen-triggered chemokines and potentially of other molecules in the future, although whether MIGRAs will provide additional clinical utility still remains to be determined.

Multicytokine detection improves latent tuberculosis diagnosis in health care workers

In a low-incidence setting, health care workers (HCW) are at a higher risk of tuberculosis than the general population. The suboptimal sensitivity of the QuantiFERON-TB Gold In-Tube (QFT) test remains a critical issue when identifying occupational latent tuberculosis infection (LTBI) in HCW. The aim of this study was to identify additional biomarkers in order to overcome the limits of gamma interferon (IFN-γ) release assays (IGRAs) and improve the performance of LTBI diagnosis within this population. Seventy Bacille Calmette-Guérin-vaccinated HCW regularly exposed to Mycobacterium tuberculosis were grouped according to QFT results into an LTBI-positive group (positive QFT, n = 8), an LTBI-negative group (normal QFT and negative tuberculin skin test [TST], n = 21), and an undetermined group (subpositive QFT and/or positive TST, n = 41). The secretion of 22 cytokines in response to QFT-specific stimulation was quantified using a multiparameter-based immunoassay. As a result, thresholds discriminating LTBI-positive from LTBI-negative HCW were established by comparing areas under the receiver operating characteristic curves for interleukin-2 (IL-2), IL-15, IFN-γ-induced protein 10 (IP-10), and the monokine induced by IFN-γ (MIG), which are biomarkers differentially secreted by the two groups. The combination of IL-15 and MIG provided a sensitivity of 100% and a specificity of 94.1% in distinguishing LTBI-positive from LTBI-negative HCW. When using IL-15 and MIG among the undetermined group, 6/45 HCW could be classified in the LTBI-positive group. The use of additional biomarkers after IGRA screening could improve the diagnosis of LTBI. The performance of these biomarkers and their use in combination with TST and/or QFT, as well as the cost-effectiveness of such a diagnostic strategy, should be evaluated in further larger clinical trials.

Redefining latent tuberculosis

TB remains a public health problem worldwide, in part due to latent TB infection that serves as a global reservoir of potential disease. In the 20th century, the natural history of TB was defined by clinical symptoms, the tuberculin skin test and chest x-ray. The last decade witnessed the invention and application of IFN-γ release assays and newer immunological tools that enabled a re-appraisal of the natural history of TB. Here, we review the conventional understanding of latent TB and recount how immunology has redefined latent TB as a spectrum of pathogen burden and host immune control. We discuss recent and future advances in the fields of TB immunology and diagnostics that will improve public health strategies to control TB.

Detection of immune cell response to M. tuberculosis-specific antigens by quantitative polymerase chain reaction

One third of the world's population is latently infected with Mycobacterium tuberculosis (Mtb) and up to 10% of infected individuals develop active tuberculosis (TB) in their lifetime. Among the major challenges in the control of TB is the implementation of sensitive methods for detection of latent tuberculosis infection (LTBI). Currently, in vitro interferon gamma release assays, yielding single value readout, are used as an alternative to the traditional tuberculin skin test for the diagnosis of LTBI. More complex characterization of immune status of LTBI individuals, however, is desirable for indication of LTBI subjects for preventative chemotherapy. Here we describe a quantitative polymerase chain reaction (qPCR) for determination of expression levels of 14 genes, additional to interferon gamma, which was applied for comparison of the specific Mtb-antigen immune response of blood cells from healthy, latently infected, and TB individuals. With the use of principal component analysis and discriminant analysis, a pattern of mRNA levels of 6 genes was identified, allowing discrimination of healthy individuals from active TB and LTBI subjects. These results open the way to development of multimarker qPCR for the detection of LTBI.

A molecular assay for sensitive detection of pathogen-specific T-cells

Here we describe the development and validation of a highly sensitive assay of antigen-specific IFN-γ production using real time quantitative PCR (qPCR) for two reporters - monokine-induced by IFN-γ (MIG) and the IFN-γ inducible protein-10 (IP10). We developed and validated the assay and applied it to the detection of CMV, HIV and Mycobacterium tuberculosis (MTB) specific responses, in a cohort of HIV co-infected patients. We compared the sensitivity of this assay to that of the ex vivo RD1 (ESAT-6 and CFP-10)-specific IFN-γ Elispot assay. We observed a clear quantitative correlation between the two assays (P<0.001). Our assay proved to be a sensitive assay for the detection of MTB-specific T cells, could be performed on whole blood samples of fingerprick (50 uL) volumes, and was not affected by HIV-mediated immunosuppression. This assay platform is potentially of utility in diagnosis of infection in this and other clinical settings.

ML1419c peptide immunization induces Mycobacterium leprae-specific HLA-A*0201-restricted CTL in vivo with potential to kill live mycobacteria

MHC class I-restricted CD8(+) T cells play an important role in protective immunity against mycobacteria. Previously, we showed that p113-121, derived from Mycobacterium leprae protein ML1419c, induced significant IFN-γ production by CD8(+) T cells in 90% of paucibacillary leprosy patients and in 80% of multibacillary patients' contacts, demonstrating induction of M. leprae-specific CD8(+) T cell immunity. In this work, we studied the in vivo role and functional profile of ML1419c p113-121-induced T cells in HLA-A*0201 transgenic mice. Immunization with 9mer or 30mer covering the p113-121 sequence combined with TLR9 agonist CpG induced HLA-A*0201-restricted, M. leprae-specific CD8(+) T cells as visualized by p113-121/HLA-A*0201 tetramers. Most CD8(+) T cells produced IFN-γ, but distinct IFN-γ(+)/TNF-α(+) populations were detected simultaneously with significant secretion of CXCL10/IFN-γ-induced protein 10, CXCL9/MIG, and VEGF. Strikingly, peptide immunization also induced high ML1419c-specific IgG levels, strongly suggesting that peptide-specific CD8(+) T cells provide help to B cells in vivo, as CD4(+) T cells were undetectable. An additional important characteristic of p113-121-specific CD8(+) T cells was their capacity for in vivo killing of p113-121-labeled, HLA-A*0201(+) splenocytes. The cytotoxic function of p113-121/HLA-A*0201-specific CD8(+) T cells extended into direct killing of splenocytes infected with live Mycobacterium smegmatis expressing ML1419c: both 9mer and 30mer induced CD8(+) T cells that reduced the number of ML1419c-expressing mycobacteria by 95%, whereas no reduction occurred using wild-type M. smegmatis. These data, combined with previous observations in Brazilian cohorts, show that ML1419c p113-121 induces potent CD8(+) T cells that provide protective immunity against M. leprae and B cell help for induction of specific IgG, suggesting its potential use in diagnostics and as a subunit (vaccine) for M. leprae infection.

MIG and the regulatory cytokines IL-10 and TGF-β1 correlate with malaria vaccine immunogenicity and efficacy

Malaria remains one of the world's greatest killers and a vaccine is urgently required. There are no established correlates of protection against malaria either for natural immunity to the disease or for immunity conferred by candidate malaria vaccines. The RTS,S/AS02A vaccine offers significant partial efficacy against malaria.

mRNA expression of five key cytokines interferon-gamma (IFN-γ), monokine induced by gamma (MIG), interleukin-10 (IL-10), transforming growth factor-β (TGF-β) and forkhead box P3 (FoxP3) in peripheral blood mononuclear cells were measured by real-time RT-PCR before and after vaccination with RTS,S/AS02A and Modified Vaccinia virus Ankara encoding the circumsporozoite protein (MVA-CS) in healthy malaria-naïve adult volunteers. The only significant change was in IFN-γ mRNA expression, which was increased seven days after vaccination (P = 0.04). Expression of MIG mRNA seven days after vaccination correlated inversely with time to detection of parasites by blood film in an experimental sporozoite challenge (r = 0.94 P = 0.005). An inverse relationship was seen between both TGF-β1 and IL-10 mRNA at baseline and the anti-circumsporozoite IgG antibody response (r = −0.644 P = 0.022 and r = −0.554 P = 0.031 respectively). This study demonstrates the potential for MIG expression as a correlate of protection against malaria. Baseline levels of the regulatory cytokines TGF-β and IL-10 inversely correlated with antibody levels post vaccination and warrant further studies to improve understanding of individual differences in response to vaccination.

Anti-mycobacterial treatment reduces high plasma levels of CXC-chemokines detected in active tuberculosis by cytometric bead array

Chemokines recruit and activate leukocytes, assisting granuloma formation. Herein, we evaluated plasma chemokines in patients with active tuberculosis (ATB) and after completing treatment (TTB) and compared them to BCG-vaccinated healthy controls (HC). Levels of chemokines were measured by cytometric bead array. Levels of CXCL8, CXCL9 and CXCL10 were higher in ATB patients compared to HC, but they decreased in TTB. Levels of CCL2 and CCL5 in ATB patients were similar to those observed in HC. Thus, the high levels of CXC-chemokines detected during ATB, which can modulate the trafficking of immune cells from the periphery to the site of infection, were reversed by anti-mycobacterial treatment.

Marek's disease virus VP22 enhances potentially the immune response of ESAT-6/CFP-10 against Mycobacterium bovis infection

Currently available vaccines against Mycobacterium bovis, the causative agent of tuberculosis, do not provide reliable efficacy and there is therefore a need for a novel vaccine with improved efficacy. Here, we use protein transduction technology to deliver DNA vaccines expressing mycobacterial antigens directly to target cells. We used various protein transduction domain (PTD) proteins including the VP22 conjugate from Marek's disease virus serotype 1 (MDV-1), as delivery systems for DNA constructs encoding the antigens early secretory antigenic target-6 kDa (ESAT-6) protein and culture filtrate protein 10 (CFP-10) of M. bovis. The eukaryotic expression plasmid pZ106, encoding antigens ESAT-6 and CFP-10, conjugated to various PTDs, was used to construct experimental preparations. Our findings demonstrated that VP22 alone or in combination with CFP-10:ESAT-6 fusion protein could spread into all the nuclei of the cell monolayer surrounding the transfected cells. Whereas trans-activating transcriptional PTD showed limited delivery of the fusion protein and 8R peptide was unable to deliver the fusion protein into any untransfected cells. We have demonstrated that immunization with a preparation fused to VP22 leads to a higher antibody and interferon-gamma titer (P<0.05). Taken together, our results demonstrated that MDV-1 VP22 serves as a potential immune enhancer in gene therapy and immunization using DNA vaccines, offering a novel approach for the prevention of M. bovis infection.

Cytotoxic effect of recombinant Mycobacterium tuberculosis CFP-10/ESAT-6 protein on the crucial pathways of WI-38 cells

To unravel the cytotoxic effect of the recombinant CFP-10/ESAT-6 protein (rCFES) on WI-38 cells, an integrative analysis approach, combining time-course microarray data and annotated pathway databases, was proposed with the emphasis on identifying the potentially crucial pathways. The potentially crucial pathways were selected based on a composite criterion characterizing the average significance and topological properties of important genes. The analysis results suggested that the regulatory effect of rCFES was at least involved in cell proliferation, cell motility, cell survival, and metabolisms of WI-38 cells. The survivability of WI-38 cells, in particular, was significantly decreased to 62% with 12.5 μM rCFES. Furthermore, the focal adhesion pathway was identified as the potentially most-crucial pathway and 58 of 65 important genes in this pathway were downregulated by rCFES treatment. Using qRT-PCR, we have confirmed the changes in the expression levels of LAMA4, PIK3R3, BIRC3, and NFKBIA, suggesting that these proteins may play an essential role in the cytotoxic process in the rCFES-treated WI-38 cells.

A robust correlation estimator and nonlinear recurrent model to infer genetic interactions in Saccharomyces cerevisiae and pathways of pulmonary disease in Homo sapiens

In order to identify genes involved in complex diseases, it is crucial to study the genetic interactions at the systems biology level. By utilizing modern high throughput microarray technology, it has become feasible to obtain gene expressions data and turn it into knowledge that explains the regulatory behavior of genes. In this study, an unsupervised nonlinear model was proposed to infer gene regulatory networks on a genome-wide scale. The proposed model consists of two components, a robust correlation estimator and a nonlinear recurrent model. The robust correlation estimator was used to initialize the parameters of the nonlinear recurrent curve-fitting model. Then the initialized model was used to fit the microarray data. The model was used to simulate the underlying nonlinear regulatory mechanisms in biological organisms. The proposed algorithm was applied to infer the regulatory mechanisms of the general network in Saccharomyces cerevisiae and the pulmonary disease pathways in Homo sapiens. The proposed algorithm requires no prior biological knowledge to predict linkages between genes. The prediction results were checked against true positive links obtained from the YEASTRACT database, the TRANSFAC database, and the KEGG database. By checking the results with known interactions, we showed that the proposed algorithm could determine some meaningful pathways, many of which are supported by the existing literature.

Differential live Mycobacterium tuberculosis-, M. bovis BCG-, recombinant ESAT6-, and culture filtrate protein 10-induced immunity in tuberculosis

The high prevalence of Mycobacterium tuberculosis makes it imperative that immune responses to evaluate could be predictive of infection. We investigated live Mycobacterium- and recombinant antigen-induced cytokine and chemokine responses in patients with active tuberculosis (TB) compared with those of healthy controls from an area where TB is endemic (ECs). M. tuberculosis-, M. bovis BCG-, ESAT6-, and culture filtrate protein 10 (CFP10)-induced responses were determined in peripheral blood mononuclear cells from patients with pulmonary TB (n = 38) and ECs (n = 39). The levels of the cytokines gamma interferon (IFN-gamma) and interleukin-10 (IL-10) and the chemokines CCL2, CCL3, and CXCL9 were measured. The levels of M. tuberculosis- and BCG-induced IFN-gamma secretion were significantly reduced (P = 0.002 and P < 0.01, respectively), while the amount of IL-10 induced by both virulent (P < 0.01) and avirulent (P = 0.002) mycobacteria was increased in patients with TB. The ESAT6-induced IFN-gamma responses were increased in the patients with TB (P = 0.013) compared with those in the EC group. When tuberculin skin test (TST)-negative (TST(-); induration, <10 mm) and TST-positive (TST(+)) donors were studied separately, both TST(-) and TST(+) individuals showed increased IFN-gamma responses to M. tuberculosis compared with the responses of the patients with TB (P = 0.037 and P = 0.006, respectively). However, only TST(+) ECs showed reduced IFN-gamma responses to ESAT6 (P = 0.008) compared with the responses of the patients with TB. The levels of M. tuberculosis-induced CCL2 (P = 0.006) and CXCL9 (P = 0.017) were greater in the patients with TB. The levels of CCL3 secretion in response to Mycobacterium and antigen stimulation were comparable between the two groups. While the levels of ESAT6-induced chemokines did not differ between the patients with TB and the ECs, the levels of CFP10-induced CCL2 (P = 0.01) and CXCL9 (P = 0.001) were increased in the patients. These data indicate differential host IFN-gamma, CXCL9, and CCL2 responses to live mycobacteria and mycobacterial antigens and have implications for the identification of potential biomarkers of infection which could be used for the diagnosis of TB.

Relationship between circulating levels of IFN-gamma, IL-10, CXCL9 and CCL2 in pulmonary and extrapulmonary tuberculosis is dependent on disease severity

Protection against Mycobacterium tuberculosis infection is dependent on T cell and macrophage activation regulated by cytokines. Cytokines and chemokines produced at disease sites may be released into circulation. Data available on circulating cytokines in tuberculosis (TB) is mostly on pulmonary TB (PTB) with limited information on extrapulmonary disease (EPul-TB). We measured interferon-gamma (IFN-gamma), interkeukin-10 (IL-10), CXCL9 and CCL2 in sera of patients (n = 80) including; PTB (n = 42), EPul-TB (n = 38) and BCG vaccinated healthy endemic controls (EC, n = 42). EPul-TB patients comprised those with less severe (LNTB) or severe (SevTB) disease. Serum IFN-gamma, IL-10 and CXCL9 levels were significantly greater while CCL2 was reduced in TB patients as compared with EC. IFN-gamma was significantly greater in PTB as compared with LNTB (P = 0.002) and SevTB (P = 0.029). CXCL9 was greater in PTB as compared with LNTB (P = 0.009). In contrast, CCL2 levels were reduced in PTB as compared with LNTB (P = 0.021) and SevTB (P = 0.024). A Spearman's rank correlation analysis determined a positive association between IFN-gamma and IL-10 (rho = 0.473, P = 0.002) and IFN-gamma and CXCL9 (rho = 0.403, P = 0.008) in the PTB group. However, in SevTB, only IFN-gamma and CXCL9 were positively associated (rho = 0.529, P = 0.016). Systemic levels of cytokines are reflective of local responses at disease sites. Therefore, our data suggests that in PTB increased IFN-gamma and CXCL9 balanced by IL-10 may result in a more effective cell mediated response in the host. However, elevated inflammatory chemokines CXCL9 and CCL2 in severe EPul-TB without concomitant down modulatory cytokines may exacerbate disease related pathology and hamper restriction of M. tuberculosis infection.

ESAT6-induced IFNgamma and CXCL9 can differentiate severity of tuberculosis

BACKGROUND

Protective responses against Mycobacterium tuberculosis are dependent on appropriate T cell and macrophage activation. Mycobacterial antigen six kDa early secreted antigenic target (ESAT6) and culture filtrate protein 10 (CFP10) can detect M. tuberculosis specific IFNgamma responses. However, most studies have been performed in non-endemic regions and to study pulmonary tuberculosis (PTB). We have studied ESAT6 and CFP10 induced cytokine and chemokines responses in PTB and extrapulmonary (EPul) TB.

METHODOLOGY

IFNgamma, IL10, CXCL9 and CCL2 responses were determined using an ex vivo whole blood assay system in PTB (n = 30) and EPulTB patients with limited (LNTB, n = 24) or severe (SevTB, n = 22) disease, and in healthy endemic controls (ECs). Responses to bacterial LPS were also determined.

PRINCIPAL FINDINGS

ESAT6- and CFP10-induced IFNgamma was comparable between ECs and TB patients. Both ESAT6- and CFP10-induced IFNgamma secretion was greater in LNTB than PTB. ESAT6-induced CXCL9 was greater in EPulTB as compared with PTB, with an increase in SevTB as compared with LNTB. CFP10-induced CCL2 was higher in PTB than LNTB patients. LPS-stimulated CXCL9 was greatest in SevTB and LPS-induced CCL2 was increased in PTB as compared with LNTB patients. A positive correlation between ESAT6-induced IFNgamma and CXCL9 was present in all TB patients, but IFNgamma and CCL2 was only correlated in LNTB. ESAT-induced CCL2 and CXCL9 were significantly associated in LNTB while correlation in response to LPS was only present in SevTB.

CONCLUSIONS

ESAT6 induced IFNgamma and CXCL9 can differentiate between limited and severe TB infections.

Interferon gamma, interferon-gamma-induced-protein 10, and tuberculin responses of children at high risk of tuberculosis infection

BACKGROUND

Children in contact with adults with pulmonary tuberculosis (TB) are at risk for infection and disease progression, and chemoprophylaxis may reduce this risk. The identification of infection is based on the tuberculin skin test (TST) and interferon-gamma (INF-gamma) release assays. Other biomarkers such as interferon-gamma-induced-protein 10 (IP-10) may have potential for the diagnosis of latent TB infections.

OBJECTIVES

To describe IP-10 concentrations and their association to TST and INF-gamma responses in children recently exposed to adults with smear-positive TB in Brazil and Nepal.

METHODS

: Two surveys using the same design were undertaken to describe TST, INF-gamma, and IP-10 responses in 146 children in Nepal and 113 children in Brazil.

RESULTS

The concordance of TST and QuantiFERON-TB gold in-tube (QFT-IT) was high (kappa 0.73 in Brazil and 0.80 in Nepal). IP-10 responses were higher in children with both positive TST and positive QFT-IT (medians 1434 pg/mL in Brazil and 1402 pg/mL in Nepal) and lowest in children with both negative TST and negative QFT-IT (medians 206 pg/mL in Brazil and 81 pg/mL in Nepal). Children with negative TST and positive QFT-IT had higher IP-10 concentrations than children with positive TST but negative QFT-IT.

CONCLUSIONS

IP-10 is a potential marker to identify latent TB infections that is expressed in large quantities and with good agreement with QFT-IT. The reasons for the discrepant results observed are discussed.

MIG (CXCL9) is a more sensitive measure than IFN-gamma of vaccine induced T-cell responses in volunteers receiving investigated malaria vaccines

For many years the IFN-γ ex vivo ELISPOT has been a major assay for assessing human T-cell responses generated by malaria vaccines. The ELISPOT assay is a sensitive assay, but an imperfect correlate of protection against malaria. Monokine induced by gamma (MIG), or CXCL9, is a chemokine induced by IFN-γ and has the potential to provide amplification of the IFN-γ signal. MIG secretion could provide a measure of bio-active IFN-γ and a functional IFN-γ signalling pathway. We report that detecting MIG by flow cytometry and by RT-PCR can be more sensitive than the detection of IFN-γ using these methods. We also find that there is little inter-individual variability in MIG secretion when detected by flow cytometry and that the MIG assay may be used to estimate the amount of bio-active IFN-γ present. Measurement of MIG alongside IFN-γ may provide a fuller picture of Th1 type responses post-vaccination.

Expression of CXC and CC type of chemokines and its receptors in tuberculous and non-tuberculous effusions

Chemokines mediate their biological functions by transmigration of various immune cells to the site of infection. Tuberculous pleurisy provides an effective model to study the role of chemokines in the recruitment of immune cells to the pleura. Our aim was to understand the cumulative effect of chemokines (IP-10, MIG, IL-8, MCP-1, MIP-1alpha and RANTES) and its receptors (CXCR2, CXCR3, CCR1, CCR2, CCR5 and CCR7) in the recruitment of CD4(+) T cells obtained from blood (BL) and pleural fluid (PF) of tuberculous (TB) and non-tuberculous (NTB) patients. We observed significant increase in CD4(+) T cells in TB PF indicating lymphocytic rich effusion. All chemokines except RANTES were significantly high in PF compared to BL in TB group, whereas IL-8 and MCP-1 showed significant increase only in NTB PF. The significantly high levels of IFN-gamma and TauNuF-alpha in TB PF and their positive correlation with IP-10 and MIP-1alpha indicated their synergistic action to elicit a strong protective Th1 response. In spite of high levels of Th1 cytokines and chemokines in TB PF, significantly lower levels of RANTES indicated its limited role at the site. The CXC receptors in PF of both the groups and CC receptors except CCR5 in TB PF were significantly high compared to BL. Only CXCR2, CCR5 and CCR7 showed significant increase in TB compared to NTB. Thus a selective concentration of chemokines, cytokines and abundant expression of chemokine receptors confirm the accumulation of activated and memory T cells at the site of infection and help in polarizing Th1 immune response.

Deficient in vitro anti-mycobacterial immunity despite successful long-term highly active antiretroviral therapy in HIV-infected patients with past history of tuberculosis infection or disease

We evaluated the anti-Mycobacterium tuberculosis (Mtb) immune responses of HIV patients after long-term successful HAART, presenting >500 TCD4+ cells/microl, undetectable viral load, and past history of tuberculosis infection (HIV+PPD+, n=14) or disease (HIV+CTB, n=17). Their lymphoproliferative and IFN-gamma responses were compared with those from HIV-uninfected controls either PPD+ (HIV-PPD+, n=17) or with past history of pulmonary tuberculosis (n=15). Most HIV-infected patients presented normal PHA responses while responses to the Mtb recombinant polypeptides ESAT-6 and Ag85B were markedly reduced. Responses to a whole Mtb lysate (S-Mtb) in HIV+PPD+ patients were lower than in HIV-PPD+ controls, while in HIV+CTB patients these responses were similar to that of past-tuberculosis controls. Comparison between the two HIV groups also suggested better S-Mtb responses in those cured from tuberculosis. Thus, while immune responses to single Mtb proteins are depressed even after successful HAART, reactivity to S-Mtb is high, specially in those cured from tuberculosis, possibly as a result of the survival of higher numbers of mycobacteria-specific T cell clones during the immunosuppression phase, which may afford sufficient protection against new Mtb challenges.

Diagnosis of tuberculosis by an enzyme-linked immunospot assay for interferon-gamma

*National Taiwan University Hospital, Taipei, Taiwan,

This assay for interferon-γ can rapidly and accurately diagnose active tuberculosis in a disease-endemic area.

We evaluated an enzyme-linked immunospot assay for interferon-γ (T SPOT-TB) for rapid diagnosis of active tuberculosis (TB) in a disease-endemic area. From January to June 2005, patients whose clinical symptoms and radiographic findings were compatible with TB were recruited, and a blood sample was obtained for T SPOT-TB assay within 7 days of microbiologic studies. Sixty-five patients were studied, including 39 (60%) with active TB. Thirty-five (53.8%) patients had underlying medical conditions. Thirty-seven patients had positive cultures for Mycobacterium tuberculosis, and 11 patients had positive cultures for nontuberculous mycobacteria. The sensitivity, specificity, positive predictive value, and negative predictive value of the T SPOT-TB assay were 87.2%, 88.5%, 91.9%, and 82.1%, respectively. The accuracy of this test in diagnosing active TB is >80%, even in an area with a high incidence of nontuberculous mycobacteria disease.

Diagnóstico imunológico da tuberculose: problemas e estratégias para o sucesso

A tuberculose continua sendo um grave problema social e de saúde, afetando milhões de pessoas anualmente. A vacina Bacille Calmette-Guerin (BCG), usada no controle profilático, é incapaz de conter a progressão da doença, que usualmente se manifesta através da queda da imunidade celular do indivíduo. O diagnóstico da tuberculose em seus estágios iniciais, aliado à poliquimioterapia, pode contribuir para o controle da disseminação da infecção. Os atuais métodos de diagnóstico apresentam problemas, como: baixa sensibilidade da baciloscopia; longo tempo de realização das culturas microbiológicas; e baixa especificidade do teste cutâneo com o derivado protéico purificado do M. tuberculosis. Novos métodos de diagnóstico que utilizam antígenos específicos (por exemplo, os conhecidos em inglês como o early secreted antigenic target 6-kDa e o culture filtrate protein 10-kDa), estão sendo testados. Os genes que codificam esses antígenos estão localizados na região de diferença 1 do M. tuberculosis, M. africanum e M. bovis, mas estão ausentes no M. bovis (BCG) e na maioria das micobactérias do meio ambiente. Métodos de diagnóstico baseados na produção de interferon-gama por linfócitos T, em resposta a esses antígenos, como o QuantiFERON-TB® e o T SPOT.TB®, estão sendo testados, e superam o teste cutâneo com o derivado protéico purificado nas seguintes características: maior sensibilidade; menor reatividade cruzada devido à vacinação com o BCG ou infecção por micobactérias do meio ambiente; e tempo de execução. A introdução de métodos de diagnóstico mais específicos e sensíveis, assim como um maior entendimento dos mecanismos moleculares e celulares que regulam a interação parasito-hospedeiro, pode contribuir para um eficiente combate à tuberculose.

CXCL10/IP-10 release is induced by incubation of whole blood from tuberculosis patients with ESAT-6, CFP10 and TB7.7

IFN-gamma responses to Mycobacterium tuberculosis specific antigens are used as in vitro diagnostic tests for tuberculosis infection. The tests are sensitive and specific for latent and active tuberculosis disease, but sensitivity may be reduced during immunosuppression. The objective of the study was to explore new ways to improve the diagnosis of tuberculosis infection using CXCL10 and IL-2 as alternative markers to IFN-gamma. CXCL10, IL-2, and IFN-gamma responses to stimulation with ESAT-6/CFP10/TB7.7 were assessed in 12 Quantiferon positive, 8 Quantiferon negative tuberculosis patients and 11 Quantiferon negative controls. CXCL10 and IL-2 were determined by multiplex and IFN-gamma by the Quantiferon ELISA. The median antigen specific CXCL10, IFN-gamma, and IL-2 responses in patients with tuberculosis were 870 pg/ml (range 261-1576 pg/ml), 217 pg/ml (81-1273 pg/ml), 59 pg/ml (14-276 pg/ml) respectively, and the CXCL10 responses were significantly higher than any of the other cytokines measured (p=0.001). In 4/7 individuals with a negative (n=6) or indeterminate (n=1) Quantiferon test, antigen specific CXCL10 responses were detectable at high levels ranging from 196-532 pg/ml. In conclusion CXCL10 was strongly induced after M. tuberculosis specific stimulation and sensitivity appeared superior to the Quantiferon test. Our findings suggest that CXCL10 may serve as an alternative or additional marker for the immunodiagnosis of tuberculosis.

Immune markers measured before treatment predict outcome of intensive phase tuberculosis therapy

The development of a statistical model based on simple immunological markers which could predict the response to tuberculosis treatment would facilitate clinical trials of new anti-tuberculosis drugs. We have examined the ability of immunological biomarkers, measured at diagnosis and after 4 weeks of treatment, to predict sputum smear status at week 8. Eighteen tuberculosis patients with positive Ziehl-Nielsen (ZN)-stained sputum smears 8 weeks after initiation of treatment (slow response) were matched for age, gender, sputum smear grade and extent of disease on chest radiograph to 18 patients with negative sputum smears at week 8 (fast response). In addition to total white blood cell (WBC) counts and absolute lymphocyte, monocyte and neutrophil numbers, concentrations of six serum markers were measured by enzyme-linked immunosorbent assay (ELISA) in all patients (soluble interleukin-2 receptor alpha (sIL-2Ralpha), granzyme B, soluble tumour necrosis factor alpha receptors 1 and 2 (sTNF-R1 and -2), nitrotyrosine and interferon-gamma (IFN-gamma). At diagnosis, 4 biomarkers (sTNF-R1, total WBC, absolute monocyte and absolute neutrophil numbers) were significantly higher in slow response patients. At week 4, total WBC count and absolute monocyte and neutrophil numbers remained significantly higher in slow responders. Discriminant analysis of the diagnosis and week 4 data provided models for classification of slow response patients with 67% and 83% predictive accuracy. We suggest that treatment response phenotypes can be determined before the start of treatment. Reliable predictive models would allow targeted interventions for patients at risk for slow treatment response to standard tuberculosis therapy.