Controlling the drug-resistant tuberculosis epidemic in India: challenges and implications

India has a higher tuberculosis (TB) burden than any other country, accounting for an estimated one-fourth of the global burden. Drug-resistant tuberculosis (DR-TB) presents a major public health problem in India. Patients with DR-TB often require profound changes in their drug regimens, which are invariably linked to poor treatment adherence and sub-optimal treatment outcomes compared to drug-sensitive TB. The challenge of addressing DR-TB is critical for India, as India contributes over 27% of global DR-TB cases. In recent decades, India has been proactive in its battle against TB, even implementing a revised National Strategic Plan to eliminate TB by 2025. However, to achieve this ambitious goal, the country will need to take a multifaceted approach with respect to its management of DR-TB. Despite concerted efforts made by the National TB Elimination Program, India faces substantial challenges with regard to DR-TB care, especially in peripheral and resource-limited endemic zones. This article describes some of the major challenges associated with mitigating the growing DR-TB epidemic in India and their implications

Investigation of Immune Biomarkers Using Subcutaneous Model of M. tuberculosis Infection in BALB/c Mice: A Preliminary Report

Evaluation and screening of vaccines against tuberculosis depends on development of proper cost effective disease models along with identification of different immune markers that can be used as surrogate endpoints of protection in preclinical and clinical studies. The objective of the present study was therefore evaluation of subcutaneous model of M.tuberculosis infection along with investigation of different immune biomarkers of tuberculosis infection in BALB/c mice. Groups of mice were infected subcutaneously with two different doses : high (2×106 CFU) and low doses (2×102 CFU) of M.tuberculosis and immune markers including humoral and cellular markers were evaluated 30 days post M.tuberculosis infections. Based on results, we found that high dose of subcutaneous infection produced chronic disease with significant (p<0.001) production of immune markers of infection like IFNγ, heat shock antigens (65, 71) and antibody titres against panel of M.tuberculosis antigens (ESAT-6, CFP-10, Ag85B, 45kDa, GroES, Hsp-16) all of which correlated with high bacterial burden in lungs and spleen. To conclude high dose of subcutaneous infection produces chronic TB infection in mice and can be used as convenient alternative to aerosol models in resource limited settings. Moreover assessment of immune markers namely mycobacterial antigens and antibodies can provide us valuable insights on modulation of immune response post infection. However further investigations along with optimization of study protocols are needed to justify the outcome of present study and establish such markers as surrogate endpoints of vaccine protection in preclinical and clinical studies in futur

Effect of repeat dose of BCG vaccination on humoral response in mice model

7-10BCG is the only vaccine presently available against tuberculosis but it is estimated to prevent only 5% of the all potentially vaccine-preventable deaths due to Tuberculosis. Keeping these in view the present study has been undertaken to evaluate the efficacy of BCG and the effect of repeat dose of BCG on antimycobacterial humoral response in mouse model. To improve BCG immunogenicity, specific anti-mycobacterial immune responses (anti-BCG titre and total IgG level) were evaluated in mouse model using boost immunization protocols with the BCG vaccine. Mice induced with a repeat dose of BCG showed an increased anti mycobacterial humoral response, which gradually declined few weeks after single dose of BCG administration. The results suggest improved efficacy of BCG vaccine by giving repeat dose of BCG that can enhance the level of immunoprotection against tuberculosis as opposed to a single BCG dose

Modelling of cerebral tuberculosis in BALB/c mice using clinical strain from patients with CNS tuberculosis infection

Background & objectives: Central nervous system (CNS) infection caused by Mycobacterium tuberculosis (MTB) is the most severe form of extrapulmonary tuberculosis (EPTB) due to a high level of mortality and morbidity. Limited studies are available on CNS-TB animal model development. The present study describes the development of a murine model of CNS-TB using a clinical strain (C3) isolated from the cerebrospinal fluid (CSF) of CNS-TB patients. Methods: Groups of mice were infected by the intravenous route with MTB C3 strain isolated from the CSF of CNS-TB patients. Brain and lung tissue were evaluated for bacterial burden, histopathology and surrogate markers of TB infection at 30 and 50 days post-infection. Results: Mice infected intravenously with MTB C3 strains showed progressive development of CNS disease with high bacillary burden in lungs at the initial stage (30 days), which eventually disseminated to the brain at a later stage (50 days). Similarly, high mortality (60%) was associated in mice infected with C3 strain compared to control. Interpretation & conclusions: The study showed development of a novel murine model of CNS-TB using the C3 strain of MTB that replicated events of extrapulmonary dissemination. The developed model would be helpful in understanding the pathogenesis of CNS-TB infection for the development of improved therapeutic interventions in future

The assessment of cytokines in Quantiferon supernatants for the diagnosis of latent TB infection in a tribal population of Melghat, India

Summary: The tuberculin skin test (TST) and interferon-gamma release assays (IGRA), namely, the QuantiFERON-TB Gold test (QFT), remain the standard immunological diagnostic tools for latent tuberculosis (TB) infection (LTBI). However, the sub-optimal detection rates of both of these tests are major impediments in recognizing the population at risk. This study was aimed at evaluating additional cytokines besides interferon-gamma (IFN-γ) as biomarkers for improving LTBI diagnosis in the tribal population of Melghat, India. Seventy-four close TB contacts were stratified by QFT and TST results into: (i) QFT+/TST+ (n = 26), (ii) QFT+/TST− (n = 12), (iii) QFT−/TST− (n = 35) and (iv) QFT−/TST+ (n = 1) groups. A panel of cytokines (IL-6, IL-10, TNF-α and IL-2R) was then evaluated in antigen-stimulated QFT cell-free culture supernatants using IMMULITE-1000, an automated immunoassay analyzer. Cytokine estimation showed significantly higher levels of IL-6 in the QFT+/TST+ group, while significantly higher levels of IL-10 were found in the QFT−/TST− group. Correlation analysis identified a positive correlation between IL-6 and the QFT response (r = 0.6723, P < 0.0001), while a negative correlation was seen between QFT and IL-10 expression (r = −0.3271, P = 0.0044). Similarly, IL-6 was positively correlated with TST levels (r = 0.6631, P < 0.0001), and conversely, a negative correlation was found between TST and IL-10 expression (r = −0.5698, P < 0.0001). The positive and negative predictive values of IL-6 were found to be 92.59 and 93.33%, respectively, and the positive and negative predictive values of IL-10 were 96.55 and 91.18%, respectively. No significant impact of the demographic characteristics on cytokine positivity was observed. Our preliminary results suggest that the evaluation of additional cytokines in QFT cell-free culture supernatants may be valuable for the identification of LTBI. Combining IL-6 and IL-10 with QFT and/or TST could markedly improve the detection accuracy of LTBI. Our observations require investigation in larger well-characterized cohorts along with follow-up studies to further confirm the study outcome. Keywords: Cytokines, LTBI, TST, QF

Mycobacterial Dormancy Regulon Protein Rv2623 as a Novel Biomarker for the Diagnosis of Latent and Active Tuberculous Meningitis

The present study was designed to investigate Rv2623 antigen, a major dormancy regulon protein of Mycobacterium tuberculosis (MTB) in CSF of suspected latent and active tuberculous meningitis (TBM) patients. A total of 100 CSF samples from TBM (n=31), suspected latent TBM (n=22), and suitable noninfectious control subjects (n=47) were collected and evaluated for Rv2623 antigen level using ELISA protocol. A significantly high (P<0.05) mean absorbance was observed in samples of suspected latent TBM and active TBM patients as compared to non-TBM control patients. However, no significant difference in Rv2623 level was observed between suspected latent TBM and TBM patients. Our preliminary findings suggest that Rv2623 may be useful as a potential biomarker for the diagnosis of the latent as well as active TBM infection. Futher evaluation of this biomarker in large number of samples is therefore needed to confirm the result

Impact of socioeconomic status and living condition on latent tuberculosis diagnosis among the tribal population of Melghat: A cohort study

Aims: To study socioeconomic status (SES) and living conditions (LC) as risk factors for latent tuberculosis infection (LTBI) and their impact on QuantiFERON-TB gold (QFT-G) and tuberculin skin test (TST) outcome for determining a better diagnostic test for LTBI in the malnourished tribal population of Melghat. Settings and Design: Six hundred sixty nine participants matching the inclusion criteria were recruited from 10 tribal villages of Melghat region, India. Subjects and Methods: Complete information related to various risk factors and test outcome was obtained on 398 participants, which was analyzed as per predefined conceptual framework. Factors were classified based on their relevance either at individual or household level, and subsequently based on the possibility of intervention. Data were partitioned into concordant and discordant sets depending on test agreement. Results: In concordant set, the two tests revealed that LTBI was significantly associated with smoking (adjusted odds ratio [aOR]: 2.64 [95% confidence interval [CI]: 1.03-6.79]), tobacco usage (aOR: 2.74 [95% CI: 1.50-4.99]), and malnourishment (aOR: 1.97 [95% CI: 1.12-3.48]) after basic adjustment. Inclusion of latent variable SES and LC in the model has mediating effect on the association of above factors with LTBI. Further, the association of SES and LC with LTBI in concordant set was unaltered in presence of other cofactors. From discordant set, results of QFT-G corroborated with that of concordant set. Conclusions: Poor SES and LC can be considered as strong risk factors linked with LTBI as compared to malnourishment, which is often targeted in such communities. Further, our study showed QFT-G test as a reliable tool in screening of LTBI in the tribal population of Melghat, India