Treatment of Drug Susceptible Pulmonary Tuberculosis

Development of a population pharmacokinetic model of pyrazinamide to guide personalized therapy: impacts of geriatric and diabetes mellitus on clearance

Objectives: This study was performed to develop a population pharmacokinetic model of pyrazinamide for Korean tuberculosis (TB) patients and to explore and identify the influence of demographic and clinical factors, especially geriatric diabetes mellitus (DM), on the pharmacokinetics (PK) of pyrazinamide (PZA). Methods: PZA concentrations at random post-dose points, demographic characteristics, and clinical information were collected in a multicenter prospective TB cohort study from 18 hospitals in Korea. Data obtained from 610 TB patients were divided into training and test datasets at a 4:1 ratio. A population PK model was developed using a nonlinear mixed-effects method. Results: A one-compartment model with allometric scaling for body size effect adequately described the PK of PZA. Geriatric patients with DM (age >70 years) were identified as a significant covariate, increasing the apparent clearance of PZA by 30% (geriatric patients with DM: 5.73 L/h; others: 4.50 L/h), thereby decreasing the area under the concentration-time curve from 0 to 24 h by a similar degree compared with other patients (geriatric patients with DM: 99.87 μg h/mL; others: 132.3 μg h/mL). Our model was externally evaluated using the test set and provided better predictive performance compared with the previously published model. Conclusion: The established population PK model sufficiently described the PK of PZA in Korean TB patients. Our model will be useful in therapeutic drug monitoring to provide dose optimization of PZA, particularly for geriatric patients with DM and TB.

Using TBAg/PHA Ratio for Monitoring TB Treatment: A Prospective Multicenter Study

The way to monitor tuberculosis (TB) treatment is extremely lacking in clinical practice. The aim of the study is to assess the role of the TBAg/PHA ratio in the treatment monitoring of TB. TB patients were followed up for 6 months and serial T-SPOT.TB (T-SPOT) assays were performed. In patients with successful treatment outcomes, the ESAT-6 sfc, CFP-10 sfc, and TBAg/PHA ratio all showed a decreased trend after the initiation of treatment. Conversely, PHA sfc showed an increased trend after 2 months of treatment. However, these indicators had moderate performance in distinguishing between before and after 6 months of treatment, and the AUC ranged from 0.702 to 0.839. Notably, the TBAg/PHA ratio in patients without risk factors was of important value in differentiation between before and after treatment. The optimal AUC of TBAg/PHA ratio reached up to 0.890. Patients with unsuccessful treatment outcomes showed persistently high levels of TBAg/PHA ratio. The TBAg/PHA ratio in patients after 6 months of treatment showed a certain potential in distinguishing between patients with successful and unsuccessful treatment outcomes. A further calculation of the TBAg/PHA ratio in T-SPOT assay has potential value in the treatment monitoring of TB, but further confirmation is needed.

Population Pharmacokinetics Analyses of Rifampicin in Adult and Children Populations: A Systematic Review

AIMS

Rifampicin has become an essential component as the first-line therapy for pulmonary tuberculosis (PTB). Several population pharmacokinetic (PK) studies on rifampicin in the adult and children population have been studied previously. Therefore, the aims of the systematic review were (i) to summarize the relevant published studies and significant covariates that influence the PK of rifampicin across different populations, (ii) to identify any knowledge gap that requires additional research in the future.

METHODS

A total of 121 relevant population PK articles were systematically identified using PubMed and Scopus from inception to October 2021. Review articles, in-vitro, and physiological methods, animal studies, and noncompartmental analysis were excluded.

RESULTS

19 studies which 16 involved adults, two involved children, and one involved both adults and children were included in the review. The structural model of rifampicin can be described as one compartment with a transient compartment absorption model and first-order elimination in most of the studies. Pharmaceutical formulation, body weight, gender, pregnancy status, diabetes, and nutritional supplementation were found to be the significant covariates that affect the PK parameters. External validation of the developed PK model was only conducted in two studies.

CONCLUSIONS

The source of variability for PK parameters of rifampicin remains inconsistent and poorly understood even though there were many potential covariates investigated in the selected studies. Exploring other possible factors and implementation a strict sampling strategy by considering the induction effects might unravel precise and reliable information. Furthermore, external validation should be frequently conducted to produce better predictability of model performance.

Nitric Oxide-Dependent Electron Transport Chain Inhibition by the Cytochrome bc1 Inhibitor and Pretomanid Combination Kills Mycobacterium tuberculosis

Mycobacterium tuberculosis, the causative agent of human tuberculosis, harbors a branched electron transport chain, preventing the bactericidal action of cytochrome bc₁ inhibitors (e.g., TB47). Here, we investigated, using luminescent mycobacterial strains, the in vitro combination activity of cytochrome bc₁ inhibitors and nitric oxide (NO) donors including pretomanid (PMD) and explored the mechanisms of combination activity. The TB47 and PMD combination quickly abolished the light emission of luminescent bacilli, as was the case for the combination of TB47 and aurachin D, a putative cytochrome bd inhibitor. The TB47 and PMD combination inhibited M. tuberculosis oxygen consumption, decreased ATP levels, and had a delayed bactericidal effect. The NO scavenger carboxy-PTIO prevented the bactericidal activity of the drug combination, suggesting the requirement for NO. In addition, cytochrome bc₁ inhibitors were largely bactericidal when administered with DETA NONOate, another NO donor. Proteomic analysis revealed that the cotreated bacilli had a compromised expression of the dormancy regulon proteins, PE/PPE proteins, and proteins required for the biosynthesis of several cofactors, including mycofactocin. Some of these proteomic changes, e.g., the impaired dormancy regulon induction, were attributed to PMD. In conclusion, combination of cytochrome bc₁ inhibitors with PMD inhibited M. tuberculosis respiration and killed the bacilli. The activity of cytochrome bc₁ inhibitors can be greatly enhanced by NO donors. Monitoring of luminescence may be further exploited to screen cytochrome bd inhibitors.

Oral anti-tuberculosis drugs: An urgent medication reconciliation at hospitals in Indonesia

Background: Four oral anti-tuberculosis drugs are conceived to be the most effective ones to eradicate Mycobacterium tuberculosis bacteria and to obviate the resistant organisms. However, the patients’ adherence and medication discrepancies are obstacles to achieving the goal. This study aimed to define the anti-tuberculosis drugs used in the hospitals and to detect the discrepancies in the continuity of the tuberculosis treatment.

Design and Methods: This retrospective cross-sectional study was based on medical records of adult patients, and was conducted in two district tertiary care hospitals. Only 35 out of 136 patient records from Hospital A and 33 out of 85 records from Hospital B met the inclusion criteria.

Results: The most common systemic anti-infective drugs in the study were ceftriaxone (51.80 DDD/100 patient-days) used in Hospital A and isoniazid (59.53 DDD/100 patient-days) used in Hospital B. The number of rifampicin prescriptions was less than that of isoniazid. Each patient received an average of two DDD/100 patient-days, which is an under dosage for an effective treatment.

Conclusion: This study showed a medication discrepancy of tuberculosis therapy. Tuberculosis patients’ medical histories are not under the full attention of treating physicians wherever they are admitted. Thus, medication reconciliation is needed to accomplish the goal of a Tuberculosis-free world in 2050.

Changes in chest X-ray findings in 1- and 2-month group after treatment initiation for suspected pulmonary tuberculosis

BACKGROUND/AIMS

Although re-evaluation of radiographic follow-up after 2 to 3 months of therapy is recommended for patients administered anti-tuberculosis medication owing to suspected pulmonary tuberculosis, reported findings are limited. Therefore, this study aimed to investigate changes in 1- and 2-month chest X-ray (CXR) findings after the treatment initiation and compared them according to the final diagnosis of tuberculosis or non-tuberculosis.

METHODS

Patients who started anti-tuberculosis medication for suspected pulmonary tuberculosis were selected at a tertiary referral hospital in South Korea between January 2012 and December 2015. Changes in the 1- and 2-month CXR findings were classified as improved, unchanged, and aggravated.

RESULTS

Among the 120 patients enrolled in the 1-month CXR group, 76 (63.3%) had the final diagnosis of tuberculosis. Comparison between the 1-month CXR changes and diagnosis showed that the final diagnosis was tuberculosis in 81.8% (45/55), 50.0% (26/52), and 38.5% (5/13) of patients whose 1-month CXR was improved, unchanged, and aggravated, respectively. In the 2-month CXR group, 167 patients were enrolled, and 139 (83.2%) of them were diagnosed with tuberculosis. Tuberculosis was the final diagnosis in 92.6% (100/108), 70.0% (35/50), and 44.4% (4/9) patients with improved, unchanged, and aggravated 2-month CXR findings, respectively. In patients with the final diagnosis of non-tuberculosis, nontuberculous mycobacteria and malignancy were the most common causes of improved and aggravated 1- and 2-month CXR findings, respectively.

CONCLUSION

Two-month CXR findings were of limited value for deciding on whether to continue anti-tuberculosis treatment. One-month CXR findings could help determine the need for further work-up.

A population approach of rifampicin pharmacogenetics and pharmacokinetics in Mexican patients with tuberculosis

The aim of this study was to develop a population pharmacokinetic model of rifampicin (RMP) in Mexican patients with tuberculosis (TB) to evaluate the influence of anthropometric and clinical covariates, as well as genotypic variants associated with MDR1 and OATP1B1 transporters. A prospective study approved by Research Ethics Committee was performed at Hospital Central in San Luis Potosí, Mexico. TB patients under DOTS scheme and who signed informed consent were consecutively included. Anthropometric and clinical information was retrieved from medical records. Single nucleotide polymorphisms in MDR1 (C3435T) and SLCO1B1 (A388G and T521C) genes were evaluated. RMP plasma concentrations and time data were assessed with NONMEM software. A total of 71 Mexican TB patients from 18 to 72 years old were included for RMP quantification from 0.3 to 12 h after dose; 329 and 97 plasma concentrations were available for model development and validation, respectively. Sequential process includes a typical lag time of 0.25 h prior to absorption start with a Ka of 1.24 h^-1 and a zero-order absorption of 0.62 h to characterize the gradual increase in RMP plasma concentrations. Final model includes total body weight in volume of distribution (0.7 L/kg, CV = 26.8%) and a total clearance of 5.96 L/h (CV = 38.5%). Bioavailability was modified according to time under treatment and generic formulation administration. In conclusion, a population pharmacokinetic model was developed to describe the variability in RMP plasma concentrations in Mexican TB patients. Genetic variants evaluated did not showed significant influence on pharmacokinetic parameters. Final model will allow therapeutic drug monitoring at early stages.

The potassium transporter KdpA affects persister formation by regulating ATP levels in Mycobacterium marinum

Mycobacterial persistence mechanisms remain to be fully characterized. Screening a transposon insertion library of Mycobacterium marinum identified kdpA, whose inactivation reduced the fraction of persisters after exposure to rifampicin. kdpA encodes a transmembrane protein that is part of the Kdp-ATPase, an ATP-dependent high-affinity potassium (K⁺) transport system. We found that kdpA is induced under low K⁺ conditions and is required for pH homeostasis and growth in media with low concentrations of K⁺. The inactivation of the Kdp system in a kdpA insertion mutant caused hyperpolarization of the cross-membrane potential, increased proton motive force (PMF) and elevated levels of intracellular ATP. The KdpA mutant phenotype could be complemented with a functional kdpA gene or supplementation with high K⁺ concentrations. Taken together, our results suggest that the Kdp system is required for ATP homeostasis and persister formation. The results also confirm that ATP-mediated regulation of persister formation is a general mechanism in bacteria, and suggest that K⁺ transporters could play a role in the regulation of ATP levels and persistence. These findings could have implications for the development of new drugs that could either target persisters or reduce their presence.

Impact of the change in the antitubercular regimen from three to four drugs on cure and frequency of adverse reactions in tuberculosis patients from Brazil: A retrospective cohort study

BACKGROUND

The Ministry of Health in Brazil included ethambutol in the intensive phase of sensible tuberculosis (TB) treatment in March 2010, due to the increasing drug resistance, and implemented the fixed dose combination in the TB treatment guidelines.

METHODS

A retrospective cohort study was performed to determine the impact of change from three to four drugs schemes on the TB cure and frequency of adverse drug reactions (ADRs) in TB patients. To answer this question, we used data from 730 randomly selected patients who received anti-TB treatment between January 2007 and December 2014 in a reference center from Salvador, Brazil.

FINDINGS

TB patients who received the RHEZ regimen (n = 365) developed ADRs more frequently than those treated with the RHZ (n = 365) (86 [23.6%] vs. 55 [15.1%]; p = 0.01). This difference in ADR incidence was even higher in patients above 30 years-old (64 [74.4%] vs. 36 [65.5%]; p = 0.01). The overall number of ADR episodes was greater in patients from the RHEZ group than in the group that received RHZ (170 [61.4%] vs. 107 [38.6%]; p = 0.03). Multivariable logistic regression analysis adjusted for age, alcohol use and diabetes demonstrated that patients receiving the RHEZ regimen had increased odds of developing ADRs than those undertaking the RHZ scheme (odds ratio [OR]: 1.61, 95% confidence interval [CI]: 1.10-2.35; p = 0.015). The overall cure rate was similar between the distinct treatment groups.

CONCLUSION

The patients treated with the four-drug regimen exhibited increased risk of ADRs compared to those who received the three-drug regimen, and especially in patients older than 30 years of age.

Early discontinuation of ethambutol in pulmonary tuberculosis treatment based on results of the GenoType MTBDRplus assay: A prospective, multicenter, non-inferiority randomized trial in South Korea

No studies have investigated whether discontinuation of ethambutol (EMB) based on the susceptibility to isoniazid and rifampin as determined by the GenoType MTBDRplus assay would be appropriate. We aimed to determine the feasibility of discontinuing EMB before the end of intensive phase treatment based on the result of MTBDRplus assay in patients with pulmonary tuberculosis (PTB). This prospective, multicenter non-inferiority randomized trial was conducted at 12 referral centers in South Korea in drug-susceptible PTB patients who initiated the standard four-drug regimen for PTB. Based on the results of the assay, EMB was discontinued in the MTBDRplus group after the confirmation that M. tuberculosis isolate was susceptible to isoniazid and rifampin. The timepoint for EMB discontinuation in the Guideline group was determined using the results of the phenotypic drug susceptibility test based on the Korean National TB Guidelines. The primary outcome was treatment success. Secondary outcomes included the 1-year rates of recurrence and adverse events. Of 600 randomized patients, the treatment outcome analysis was performed for 493 patients (MTBDRplus group, 244; Guideline group, 249). Treatment success rates were 93.9% (229/224) in the MTBDRplus group and 93.6% (233/249) in the Guideline group and did not differ between groups; relative risk 1.00 (95% CI 0.95-1.06). The 1-year recurrence rate between the two groups (0.9% vs. 0.5%, respectively) and differences in adverse drug reactions did not differ between groups. In conclusion, early discontinuation of EMB based on the results of the MTBDRplus assay did not affect the treatment outcomes in PTB.

Association of FAM65B, AGBL4, and CUX2 genetic polymorphisms with susceptibility to antituberculosis drug-induced hepatotoxicity: validation study in a Chinese Han population

OBJECTIVE

Antituberculosis (anti-TB) drug-induced hepatotoxicity (ATDH) is a serious adverse drug reaction, and its pathogenic mechanism has not been elucidated thoroughly to date. A recent genome-wide association study reported that seven single-nucleotide polymorphisms (SNPs) in the family with sequence similarity 65, member B gene (FAM65B), ATP/GTP-binding protein-like 4 gene (AGBL4), and cut-like homeobox 2 gene (CUX2) were associated strongly with ATDH in Ethiopian patients. We validated this relationship in a Chinese Han anti-TB treatment population.

PATIENTS AND METHODS

A 1 : 2 matched case-control study was carried out of 235 ATDH cases and 470 controls. Multivariate conditional logistic regression analysis was used to estimate the association between genotypes and risk of ATDH by odds ratios with 95% confidence intervals, and weight and hepatoprotectant use were used as covariates.

RESULTS

Patients with a polymorphism at rs10946737 in the FAM65B gene were at an increased risk of moderate and severe liver injury under the dominant model (adjusted odds ratio=2.147, 95% confidence interval: 1.067-4.323, P=0.032). No other genotypes or genetic risk scores were found to be significantly related to ATDH.

CONCLUSION

This is the first study to explore and validate the relationships between seven SNPs in the FAM65B, AGBL4, and CUX2 genes and ATDH in a Chinese population. On the basis of this case-control study, SNP rs10946737 in FAM65B may be associated with susceptibility to ATDH in Chinese Han anti-TB treatment patients. Further research is warranted to explain the role of the FAM65B gene and its contribution toward individual differences in susceptibility to ATDH.

Inhibitors of energy metabolism interfere with antibiotic-induced death in mycobacteria

Energy metabolism has recently gained interest as a target space for antibiotic drug development in mycobacteria. Of particular importance is bedaquiline (Sirturo), which kills mycobacteria by inhibiting the F₁F₀ ATP synthase. Other components of the electron transport chain such as the NADH dehydrogenases (NDH-2 and NdhA) and the terminal respiratory oxidase bc₁:aa₃ are also susceptible to chemical inhibition. Because antituberculosis drugs are prescribed as part of combination therapies, the interaction between novel drugs targeting energy metabolism and classical first and second line antibiotics must be considered to maximize treatment efficiency. Here, we show that subinhibitory concentration of drugs targeting the F₁F₀ ATP synthase and the cytochrome bc₁:aa₃, as well as energy uncouplers, interfere with the bactericidal potency of isoniazid and moxifloxacin. Isoniazid- and moxifloxacin-induced mycobacterial death correlated with a transient increase in intracellular ATP that was dissipated by co-incubation with energy metabolism inhibitors. Although oxidative phosphorylation is a promising target space for drug development, a better understanding of the link between energy metabolism and antibiotic-induced mycobacterial death is essential to develop potent drug combinations for the treatment of tuberculosis.

New Players in Immunity to Tuberculosis: The Host Microbiome, Lung Epithelium, and Innate Immune Cells

Tuberculosis (TB) is a highly contagious infection and devastating chronic disease, causing 10.4 million new infections and 1.8 million deaths every year globally. Efforts to control and eradicate TB are hampered by the rapid emergence of drug resistance and limited efficacy of the only available vaccine, BCG. Immunological events in the airways and lungs are of major importance in determining whether exposure to Mycobacterium tuberculosis (Mtb) results in successful infection or protective immunity. Several studies have demonstrated that the host microbiota is in constant contact with the immune system, and thus continually directs the nature of immune responses occurring during new infections. However, little is known about its role in the eventual outcome of the mycobacterial infection. In this review, we highlight the changes in microbial composition in the respiratory tract and gut that have been linked to the alteration of immune responses, and to the risk, prevention, and treatment of TB. In addition, we summarize our current understanding of alveolar epithelial cells and the innate immune system, and their interaction with Mtb during early infection. Extensive studies are warranted to fully understand the all-inclusive role of the lung microbiota, its interaction with epithelium and innate immune responses and resulting adaptive immune responses, and in the pathogenesis and/or protection from Mtb infection. Novel interventions aimed at influencing the microbiota, the alveolar immune system and innate immunity will shape future strategies of prevention and treatment for TB.

Antimicrobial peptides as an alternative to anti-tuberculosis drugs

Tuberculosis (TB) presently accounts for high global mortality and morbidity rates, despite the introduction four decades ago of the affordable and efficient four-drugs (isoniazid, rifampicin, pyrazinamide and ethambutol). Thus, a strong need exists for new drugs with special structures and uncommon modes of action to effectively overcome M. tuberculosis. Within this scope, antimicrobial peptides (AMPs), which are small, cationic and amphipathic peptides that comprise a section of the innate immune system, are currently the leading potential agents for the treatment of TB. Many studies have recently illustrated the capability of anti-mycobacterial peptides to disrupt the normal mycobacterial cell wall function through various modes, thereby interacting with the intracellular targets, as well as encompassing nucleic acids, enzymes and organelles. This review presents a wide array of antimicrobial activities, alongside the associated properties of the AMPs that could be utilized as potential agents in therapeutic tactics for TB treatment.

Estimated rates of recurrence, cure, and treatment abandonment in patients with pulmonary tuberculosis treated with a -four-drug fixed-dose combination regimen at a tertiary health care facility in the city of Rio de Janeiro, Brazil

Objective:

To estimate the rates of recurrence, cure, and treatment abandonment in patients with pulmonary tuberculosis treated with a four-drug fixed-dose combination (FDC) regimen, as well as to evaluate possible associated factors.

Methods:

This was a retrospective observational study involving 208 patients with a confirmed diagnosis of pulmonary tuberculosis enrolled in the Hospital Tuberculosis Control Program at the Institute for Thoracic Diseases, located in the city of Rio de Janeiro, Brazil. Between January of 2007 and October of 2010, the patients were treated with the rifampin-isoniazid-pyrazinamide (RHZ) regimen, whereas, between November of 2010 and June of 2013, the patients were treated with the rifampin-isoniazid-pyrazinamide-ethambutol FDC (RHZE/FDC) regimen. Data regarding tuberculosis recurrence and mortality in the patients studied were retrieved from the Brazilian Case Registry Database and the Brazilian Mortality Database, respectively. The follow-up period comprised two years after treatment completion.

Results:

The rates of cure, treatment abandonment, and death were 90.4%, 4.8%, and 4.8%, respectively. There were 7 cases of recurrence during the follow-up period. No significant differences in the recurrence rate were found between the RHZ and RHZE/FDC regimen groups (p = 0.13). We identified no factors associated with the occurrence of recurrence; nor were there any statistically significant differences between the treatment groups regarding adverse effects or rates of cure, treatment abandonment, or death.

Conclusions:

The adoption of the RHZE/FDC regimen produced no statistically significant differences in the rates of recurrence, cure, or treatment abandonment; nor did it have any effect on the occurrence of adverse effects, in comparison with the use of the RHZ regimen.

Recommendations for Optimizing Tuberculosis Treatment: Therapeutic Drug Monitoring, Pharmacogenetics, and Nutritional Status Considerations

Although tuberculosis is largely a curable disease, it remains a major cause of morbidity and mortality worldwide. Although the standard 6-month treatment regimen is highly effective for drug-susceptible tuberculosis, the use of multiple drugs over long periods of time can cause frequent adverse drug reactions. In addition, some patients with drug-susceptible tuberculosis do not respond adequately to treatment and develop treatment failure and drug resistance. Response to tuberculosis treatment could be affected by multiple factors associated with the host-pathogen interaction including genetic factors and the nutritional status of the host. These factors should be considered for effective tuberculosis control. Therefore, therapeutic drug monitoring (TDM), which is individualized drug dosing guided by serum drug concentrations during treatment, and pharmacogenetics-based personalized dosing guidelines of anti-tuberculosis drugs could reduce the incidence of adverse drug reactions and increase the likelihood of successful treatment outcomes. Moreover, assessment and management of comorbid conditions including nutritional status could improve anti-tuberculosis treatment response.

Clinical significance of smear positivity for acid-fast bacilli after ≥5 months of treatment in patients with drug-susceptible pulmonary tuberculosis

Patients with pulmonary tuberculosis (TB) with acid-fast bacilli (AFB)-positive sputum smear at 5 months or later during treatment are considered to be cases of treatment failure according to World Health Organization guidelines. This study evaluated the proportion, clinical characteristics, and significance of positive sputum smears after ≥5 months of standard treatment in patients with drug-susceptible pulmonary TB.This was a retrospective cohort study of 1611 patients with culture-confirmed drug-susceptible pulmonary TB who received standard anti-TB treatment from January 2009 to February 2014. Forty-one patients (2.5%) who were smear-positive after ≥5 months of treatment and 123 age- and sex-matched control patients were evaluated.Among the 41 smear-positive patients, culture of the sputum specimens yielded Mycobacterium tuberculosis (MTB) in 1 patient (2.4%), nontuberculous mycobacteria (NTM) in 7 (17.1%), and no growth in the remaining 33 patients (80.5%). Treatment was successfully completed in 40 patients (97.6%) with prolongation of the continuation phase regimens without change to second-line anti-TB treatment. In patients with smear positivity after ≥5 months of treatment compared with controls, cavitation on chest radiographs (53.7% vs. 25.2%, P = 0.001), bilateral involvement (51.2% vs. 30.1%, P = 0.01) and combined pleural effusion (26.8% vs. 10.6%, P = 0.01) were found more frequently at the time of treatment initiation, and paradoxical response occurred more commonly (19.5% vs. 3.3%, P = 0.002) during treatment.Smear-positive sputum after ≥5 months of standard anti-TB treatment was mainly because of nonviable MTB bacilli or NTM in patients with drug-susceptible pulmonary TB. AFB smear alone should not be used to assess treatment failure and careful examination of microbiologic status, including culture and drug susceptibility testing, is needed before making changes to retreatment regimens or empirical second-line anti-TB regimens in these patients.

Active transforming growth factor-β is associated with phenotypic changes in granulomas after drug treatment in pulmonary tuberculosis

Background

Tuberculosis (TB) chemotherapy clears bacterial burden in the lungs of patients and allows the tuberculous lesions to heal through a fibrotic process. The healing process leaves pulmonary scar tissue that can impair lung function. The goal of this study was to identify fibrotic mediators as a stepping-stone to begin exploring mechanisms of tissue repair in TB.

Methods

Hematoxylin and eosin staining and Masson’s trichrome stain were utilized to determine levels of collagenization in tuberculous granulomas from non-human primates. Immunohistochemistry was then employed to further interrogate these granulomas for markers associated with fibrogenesis, including transforming growth factor-β (TGFβ), α-smooth muscle actin (αSMA), phosphorylated SMAD-2/3, and CD163. These markers were compared across states of drug treatment using one-way ANOVA, and Pearson’s test was used to determine the association of these markers with one another.

Results

TGFβ and αSMA were present in granulomas from primates with active TB disease. These molecules were reduced in abundance after TB chemotherapy. Phosphorylated SMAD-2/3, a signaling intermediate of TGFβ, was observed in greater amounts after 1 month of drug treatment than in active disease, suggesting that this particular pathway is blocked in active disease. Collagen production during tissue repair is strongly associated with TGFβ in this model, but not with CD163+ macrophages.

Conclusions

Tissue repair and fibrosis in TB that occurs during drug treatment is associated with active TGFβ that is produced during active disease. Further work will identify mechanisms of fibrosis and work towards mitigating lung impairment with treatments that target those mechanisms.

Electronic supplementary material

The online version of this article (doi:10.1186/s13069-016-0043-3) contains supplementary material, which is available to authorized users.