Table 2.
Studies reporting IDO activity or either kynurenine or tryptophan in human active TB disease.
| References | Participant demographics | Sample type |
Method of IDO
quantification |
Major conclusion (s) |
|---|---|---|---|---|
| Almeida et al. (2009) | TB cases (n = 30) HIV+, active TB disease (n = 4) Other lungs diseases (No-TB, HIV– n = 11), Healthcare workers (n = 16) |
Induced Sputum | RT-PCR | Active TB patients expressed significantly higher IDO compared with patients with other lung disease and health care workers. IDO expression declined over 500-fold change 15 days post-treatment with anti-TB medication. |
| Li et al. (2011) | TB cases (n = 31) Controls (n = 35) |
Pleural effusion | Cell culture | Inhibiting IDO reversed cytokine production and restored T cell functions in vitro. |
| Weiner 3rd et al. (2012) | Active TB cases (n = 44) LTBI (TST+) (n = 46) No-TB (TST-) (n = 46) |
Blood | UPLC/GC–MS/MS Cell culture | Metabolic profiles showed IDO activity increased in TB pathogenesis. |
| Suzuki et al. (2012) | TB case (n = 174) Controls (n = 85) |
Serum | LC-MS/MS | Patients with pulmonary TB has elevated serum IDO activity compared to controls. Higher IDO activity independently predicted death of TB patients. |
| Suzuki et al. (2013) | TB cases (n = 92) TB pleurisy (n = 34), Malignant pleuritis (n = 36) Parapneumonic effusion (n = 15) |
Pleural effusion | LC-MS/MS | IDO activity may be strongly involved in the pathogenesis of TB pleurisy. IDO activity holds diagnostic significance in TB pleurisy. |
| Feng et al. (2015) | TB cases (n = 120) Non-TB (n = 146) Healthy controls (n = 105) |
Blood | UPLC-MS | Kynurenine and quinolinic acid, which are products of IDO-mediated tryptophan metabolism were among 20 metabolic profiles that indicated active TB disease. |
| Adu-Gyamfi et al. (2017) | TB-HIV cases (n = 32) Controls (HIV+, No-TB) (n = 70) Pneumonia (HIV positive) (n = 37) |
Plasma | UPLC-MS/MS | IDO activity is a plausible diagnostic active TB in HIV infected patients. IDO activity predicted active TB disease months ahead of major TB symptoms, IDO activity declined in all patients after standard TB treatment. |
| Van Laarhoven et al. (2018) | Discovery cohort: TBM, HIV– patients (n = 33) Controls (n = 22) Validation cohort: TBM patients (n = 101) Controls (HIV-, no TBM) (n = 17) |
CSF and Serum | UPLC-MS/MS | Increased tryptophan metabolites were found among TB meningitis patients, and it correlated strongly with mortality. |
| Shi et al. (2019) | Drug susceptible TB cases (n = 16) MDR-TB cases (n = 16), Controls (No-TB n = 11, Lung cancer n = 6) No patient or control had HIV infection. |
Plasma | LC-MS/MS | Plasma IDO activity could distinguish multi-drug resistance—TB (MDR-TB) from drug-susceptible TB and lung cancer. Higher plasma IDO activity can indicate a higher risk of MDR-TB. |
Tuberculosis (TB), Tuberculous meningitis (TBM), Human Immunodeficiency virus (HIV), Indoleamine 2,3-dioxygenase (IDO), latent Tuberculosis infection (LTBI), Positive (+), Negative (–), High-performance liquid chromatography-mass spectrometry (HPLC-MS/MS), Ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS), Gas chromatography-mass spectrometry, Real-time polymerase chain reaction (RT-PCR).