Malaria and tuberculosis co-infection-a review.

Malaria and tuberculosis remain highly prevalent infectious diseases and continue to cause significant burden worldwide. Endemic regions largely overlap, and co-infections are expected to occur frequently. Surprisingly, malaria-tuberculosis co-infection is relatively understudied. Malaria has long been known to have immunomodulatory effects, for example resulting in reduced vaccination responses against some pathogens, and it is conceivable that this also plays a role if co-infection occurs. Data from animal studies indeed suggest clinically important effects of malaria-tuberculosis co-infection on the immune responses with potential consequences for the pathophysiology and clinical course of both infections. Specifically, rodent studies consistently show reduced control of mycobacteria during malaria infection. Although the underlying immunological mechanisms largely remain unclear, an altered balance between pro- and anti-inflammatory responses may play a role. Some observations in humans also support the hypothesis that malaria infection skews the immune responses against tuberculosis, but data are limited. Further research is needed to unravel the underlying immunological mechanisms and delineate possible implications of malaria-tuberculosis co-infection for clinical practice.

Mechanisms of lung damage in tuberculosis: implications for chronic obstructive pulmonary disease.

Pulmonary tuberculosis is increasingly recognized as a risk factor for COPD. Severe lung function impairment has been reported in post-TB patients. Despite increasing evidence to support the association between TB and COPD, only a few studies describe the immunological basis of COPD among TB patients following successful treatment completion. In this review, we draw on well-elaborated Mycobacterium tuberculosis-induced immune mechanisms in the lungs to highlight shared mechanisms for COPD pathogenesis in the setting of tuberculosis disease. We further examine how such mechanisms could be exploited to guide COPD therapeutics.

High resolution imaging and five-year tuberculosis contact outcomes.

Background: The evolution of tuberculosis (TB) disease during the clinical latency period remains incompletely understood. Methods: 250 HIV-uninfected, adult household contacts of rifampicin-resistant TB with a negative symptom screen underwent baseline 18F-Fluorodeoxyglucose positron emission and computed tomography (PET/CT), repeated in 112 after 5-15 months. Following South African and WHO guidelines, participants did not receive preventive therapy. All participants had intensive baseline screening with spontaneous, followed by induced, sputum sampling and were then observed for an average of 4.7 years for culture-positive disease. Baseline PET/CT abnormalities were evaluated in relation to culture-positive disease. Results: At baseline, 59 (23.6%) participants had lung PET/CT findings consistent with TB of which 29 (11.6%) were defined as Subclinical TB, and 30 (12%) Subclinical TB-inactive. A further 83 (33.2%) had other lung parenchymal abnormalities and 108 (43.2%) had normal lungs. Over 1107-person years of follow-up 14 cases of culture-positive TB were diagnosed. Six cases were detected by intensive baseline screening, all would have been missed by the South African symptom-based screening strategy and only one detected by a WHO-recommended chest X-Ray screening strategy. Those with baseline Subclinical TB lesions on PET/CT were significantly more likely to be diagnosed with culture-positive TB over the study period, compared to those with normal lung parenchyma (10/29 [34.5%] vs 2/108 [1.9%], Hazard Ratio 22.37 [4.89-102.47, p<0.001]). Conclusions: These findings challenge the latent/active TB paradigm demonstrating that subclinical disease exists up to 4 years prior to microbiological detection and/or symptom onset. There are important implications for screening and management of TB.

Effect of the relationship between anaemia and systemic inflammation on the risk of incident tuberculosis and death in people with advanced HIV: a sub-analysis of the REMEMBER trial.

Background: Tuberculosis (TB) is an infectious morbidity that commonly occurs in people living with HIV (PWH) and increases the progression of HIV disease, as well as the risk of death. Simple markers of progression are much needed to identify those at highest risk for poor outcome. This study aimed to assess how baseline severity of anaemia and associated inflammatory profiles impact death and the incidence of TB in a cohort of PWH who received TB preventive therapy (TPT). Methods: This study is a secondary posthoc analysis of the AIDS Clinical Trials Group A5274 REMEMBER clinical trial (NCT0138008), an open-label randomised clinical trial of antiretroviral-naïve PWH with CD4 <50 cells/µL, performed from October 31, 2011 to June 9, 2014, from 18 outpatient research clinics in 10 low- and middle-income countries (Malawi, South Africa, Haiti, Kenya, Zambia, India, Brazil, Zimbabwe, Peru, and Uganda) who initiated antiretroviral therapy and either isoniazid TPT or 4-drug empiric TB therapy. Plasma concentrations of several soluble inflammatory biomarkers were measured prior to the commencement of antiretroviral and anti-TB therapies, and participants were followed up for at least 48 weeks. Incident TB or death during this period were primary outcomes. We performed multidimensional analyses, logistic regression analyses, survival curves, and Bayesian network analyses to delineate associations between anaemia, laboratory parameters, and clinical outcomes. Findings: Of all 269 participants, 76.2% (n = 205) were anaemic, and 31.2% (n = 84) had severe anaemia. PWH with moderate/severe anaemia exhibited a pronounced systemic pro-inflammatory profile compared to those with mild or without anaemia, hallmarked by a substantial increase in IL-6 plasma concentrations. Moderate/severe anaemia was also associated with incident TB incidence (aOR: 3.59, 95% CI: 1.32-9.76, p = 0.012) and death (aOR: 3.63, 95% CI: 1.07-12.33, p = 0.039). Interpretation: Our findings suggest that PWH with moderate/severe anaemia display a distinct pro-inflammatory profile. The presence of moderate/severe anaemia pre-ART was independently associated with the development of TB and death. PWH with anaemia should be monitored closely to minimise the occurrence of unfavourable outcomes. Funding: National Institutes of Health.

The severity of SARS-CoV-2 infection in K18-hACE2 mice is attenuated by a novel steroid-derivative in a gender-specific manner.

BACKGROUND AND PURPOSE: COVID-19 infections caused by SARS-CoV-2 disseminated through human-to-human transmission can evoke severe inflammation. Treatments to reduce the SARS-CoV-2-associated inflammation are needed and are the focus of much research. In this study, we investigated the effect of N-ethyl-N'-[(3ß,5α)-17-oxoandrostan-3-yl] urea (NEOU), a novel 17α-ketosteroid derivative, on the severity of COVID-19 infections. EXPERIMENTAL APPROACH: Studies were conducted in SARS-CoV-2-infected K18-hACE2 mice. KEY RESULTS: SARS-CoV-2-infected K18-hACE2 mice developed severe inflammatory crises and immune responses along with up-regulation of genes in associated signalling pathways in male more than female mice. Notably, SARS-CoV-2 infection down-regulated genes encoding drug metabolizing cytochrome P450 enzymes in male but not female mice. Treatment with NEOU (1 mg·kg-1 ·day-1 ) 24 or 72 h post-viral infection alleviated lung injury by decreasing expression of genes encoding inflammatory cytokines and chemokines while increasing expression of genes encoding immunoglobins. In situ hybridization using RNA scope™ probes and immunohistochemical assays revealed that NEOU increased resident CD169+ immunoregulatory macrophages and IBA-1 immunoreactive macrophage-dendritic cells within alveolar spaces in the lungs of infected mice. Consequentially, NEOU reduced morbidity more prominently in male than female mice. However, NEOU increased median survival time and accelerated recovery from infection by 6 days in both males and females. CONCLUSIONS AND IMPLICATIONS: These findings demonstrate that SARS-CoV-2 exhibits gender bias by differentially regulating genes encoding inflammatory cytokines, immunogenic factors and drug-metabolizing enzymes, in male versus female mice. Most importantly, we identified a novel 17α-ketosteroid that reduces the severity of COVID-19 infection and could be beneficial for reducing impact of COVID-19.

Dynamin-like proteins mediate extracellular vesicle secretion in Mycobacterium tuberculosis.

Mycobacterium tuberculosis (Mtb) secretes extracellular vesicles (EVs) containing a variety of proteins, lipoproteins, and lipoglycans. While emerging evidence suggests that EVs contribute to tuberculosis pathogenesis, the factors and molecular mechanisms involved in mycobacterial EV production have not been identified. In this study, we use a genetic approach to identify Mtb proteins that mediate vesicle release in response to iron limitation and antibiotic exposure. We uncover a critical role for the isoniazid-induced, dynamin-like proteins, IniA and IniC, in mycobacterial EV biogenesis. Further characterization of a Mtb iniA mutant shows that the production of EVs enables intracellular Mtb to export bacterial components into the extracellular environment to communicate with host cells and potentially modulate the immune response. The findings advance our understanding of the biogenesis and functions of mycobacterial EVs and provide an avenue for targeting vesicle production in vivo.

B cells promote granulomatous inflammation during chronic Mycobacterium tuberculosis infection in mice.

The current study reveals that in chronic TB, the B cell-deficient µMT strain, relative to wild-type (WT) C57BL/6 mice, displays in the lungs lower levels of inflammation that are associated with decreased CD4+ T cell proliferation, diminished Th1 response, and enhanced levels of interleukin (IL)-10. The latter result raises the possibility that B cells may restrict lung expression of IL-10 in chronic TB. These observations are recapitulated in WT mice depleted for B cells using anti-CD20 antibodies. IL-10 receptor (IL-10R) blockade reverses the phenotypes of decreased inflammation and attenuated CD4+ T cell responses in B cell-depleted mice. Together, these results suggest that in chronic murine TB, B cells, by virtue of their capacity to restrict expression of the anti-inflammatory and immunosuppressive IL-10 in the lungs, promote the development of a robust protective Th1 response, thereby optimizing anti-TB immunity. This vigorous Th1 immunity and restricted IL-10 expression may, however, allow the development of inflammation to a level that can be detrimental to the host. Indeed, decreased lung inflammation observed in chronically infected B cell-deficient mice, which exhibit augmented lung IL-10 levels, is associated with a survival advantage relative to WT animals. Collectively, the results reveal that in chronic murine TB, B cells play a role in modulating the protective Th1 immunity and the anti-inflammatory IL-10 response, which results in augmentation of lung inflammation that can be host-detrimental. Intriguingly, in tuberculous human lungs, conspicuous B cell aggregates are present in close proximity to tissue-damaging lesions manifesting necrosis and cavitation, suggesting the possibility that in human TB, B cells may contribute to the development of exacerbated pathology that is known to promote transmission. Since transmission is a major hindrance to TB control, investigating into whether B cells can shape the development of severe pulmonic pathological responses in tuberculous individuals is warranted.

Comparison of IGRA and TST in the diagnosis of latent tuberculosis among women of reproductive age in South India.

BACKGROUND: Latent tuberculosis infection (LTBI) is a mycobacterial infection defined on the basis of cellular immune response to mycobacterial antigens. The tuberculin skin test (TST) and the Interferon-Gamma Release Assay (IGRA) are the two tests currently used to establish the diagnosis of LTB. Literature suggests that a study regarding tuberculosis (TB) infection among women of reproductive age group is limited. METHODS: Female household contact, married, aged 18-49 years underwent written consent form and are screened for LTBI using the TST and IGRA. Participants are injected with TST [5 tuberculin unit (TU), purified protein derivative (PPD)] and IGRA [QuantiFERON®-TB Gold Plus kit (QFT-Plus)]. All the household contacts were followed-up for one year for incident TB cases. Statistical analysis was done using STATA version 14 (StataCorp., Texas, USA). Cohen's kappa test was used to determine the agreement between two tests. RESULTS: The prevalence of LTBI was found to be 69% (either TST or IGRA positive). Positivity rate of IGRA was higher when compared to that of TST. Out of 139 participants, 68 (49%) tested positive for TST, 80 (57.6%) tested positive for IGRA and 52 (37.4%) tested positive for both. Discordant results were observed in about two fifth of the study population and there was poor agreement between the two tests. CONCLUSION: Longitudinal studies are required to detect incident TB cases to evaluate the usefulness of these tests. The study was found that IGRA is more consistent to diagnosis of latent tuberculosis infection than the TST. Such studies can also be performed in varied settings among different populations which would help us to improve the diagnosis of LTBI and consequently help in TB control.

Diets Differently Regulate Pulmonary Pathogenesis and Immune Signaling in Mice during Acute and Chronic Mycobacterium tuberculosis Infection.

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) infection persists as a leading cause of mortality and morbidity globally, especially in developing and underdeveloped countries. The prevalence of TB-DM (diabetes mellitus) is higher in low- and middle-income countries where TB and DM are most prevalent. Epidemiological data suggest that slight obesity reduces the risk of TB, whereas DM increases the risk of pulmonary TB. Diets can alter the levels of body fat mass and body mass index by regulating systemic adiposity. Earlier, using a transgenic Mtb-infected murine model, we demonstrated that loss of body fat increased the risk of pulmonary bacterial load and pathology. In the present study, we investigated whether increased adiposity alters pulmonary pathology and bacterial load using C57BL/6 mice infected with HN878 Mtb strain and fed a medium-fat diet (MFD). We analyzed the effects of MFD on the lung during acute and chronic infections by comparing the results to those obtained with infected mice fed a regular diet (RD). Histological and biochemical analyses demonstrated that MFD reduces bacterial burden by increasing the activation of immune cells in the lungs during acute infection and reduces necrosis in the lungs during chronic infection by decreasing lipid accumulation. Our data suggest that slight adiposity likely protects the host during active TB infection by regulating immune and metabolic conditions in the lungs.

Comparison of gene set scoring methods for reproducible evaluation of multiple tuberculosis gene signatures.

Rationale: Many blood-based transcriptional gene signatures for tuberculosis (TB) have been developed with potential use to diagnose disease, predict risk of progression from infection to disease, and monitor TB treatment outcomes. However, an unresolved issue is whether gene set enrichment analysis (GSEA) of the signature transcripts alone is sufficient for prediction and differentiation, or whether it is necessary to use the original statistical model created when the signature was derived. Intra-method comparison is complicated by the unavailability of original training data, missing details about the original trained model, and inadequate publicly-available software tools or source code implementing models. To facilitate these signatures' replicability and appropriate utilization in TB research, comprehensive comparisons between gene set scoring methods with cross-data validation of original model implementations are needed. Objectives: We compared the performance of 19 TB gene signatures across 24 transcriptomic datasets using both re-rebuilt original models and gene set scoring methods to evaluate whether gene set scoring is a reasonable proxy to the performance of the original trained model. We have provided an open-access software implementation of the original models for all 19 signatures for future use. Methods: We considered existing gene set scoring and machine learning methods, including ssGSEA, GSVA, PLAGE, Singscore, and Zscore, as alternative approaches to profile gene signature performance. The sample-size-weighted mean area under the curve (AUC) value was computed to measure each signature's performance across datasets. Correlation analysis and Wilcoxon paired tests were used to analyze the performance of enrichment methods with the original models. Measurement and Main Results: For many signatures, the predictions from gene set scoring methods were highly correlated and statistically equivalent to the results given by the original diagnostic models. PLAGE outperformed all other gene scoring methods. In some cases, PLAGE outperformed the original models when considering signatures' weighted mean AUC values and the AUC results within individual studies. Conclusion: Gene set enrichment scoring of existing blood-based biomarker gene sets can distinguish patients with active TB disease from latent TB infection and other clinical conditions with equivalent or improved accuracy compared to the original methods and models. These data justify using gene set scoring methods of published TB gene signatures for predicting TB risk and treatment outcomes, especially when original models are difficult to apply or implement.

Predictors of weight loss during the intensive phase of tuberculosis treatment in patients with drug-susceptible pulmonary tuberculosis in South India.

BACKGROUND: Tuberculosis (TB) is well-known for causing wasting. Patients on treatment gain weight and weight loss is associated with unfavorable treatment outcomes. There is limited description of weight loss and its predictors during intensive treatment phase. The objective of this study was to assess the predictors of weight loss during intensive phase and to see if there is any association exists with sputum conversion at the end of intensive phase of treatment. METHODS: Data collected as a part of the prospective TB cohort (Regional Prospective Observational Research for TB India Phase 1) conducted in Pondicherry, Cuddalore and Viluppuram districts of Tamil Nadu were used for this study. Sputum smear and body weight comparison were made in the baseline and at the end of second month of treatment. RESULTS: In all, 726 participants had weight measurements at the two time points and 18.7% had weight loss; mean weight lost being 2.3 kg (SD 3.05). Mean weight loss was more among males (2.4 kg, SD 3.2), diabetics (2.8 kg, SD 3.9) and alcoholics (2.1 kg, SD 2.4). Alcohol consumption was the only predictor of weight loss after adjusting for age, diabetes, marital status and BMI (aRR 1.52, P 0.02). Weight loss was not associated with sputum conversion at the end of second month. CONCLUSIONS: Alcohol use emerged as the major predictor for weight loss during intensive phase.

Impact of Undernutrition on Tuberculosis Treatment Outcomes in India: A Multicenter, Prospective, Cohort Analysis.

BACKGROUND: Undernutrition is the leading risk factor for tuberculosis (TB) globally. Its impact on treatment outcomes is poorly defined. METHODS: We conducted a prospective cohort analysis of adults with drug-sensitive pulmonary TB at 5 sites from 2015-2019. Using multivariable Poisson regression, we assessed associations between unfavorable outcomes and nutritional status based on body mass index (BMI) nutritional status at treatment initiation, BMI prior to TB disease, stunting, and stagnant or declining BMI after 2 months of TB treatment. Unfavorable outcome was defined as a composite of treatment failure, death, or relapse within 6 months of treatment completion. RESULTS: Severe undernutrition (BMI <16 kg/m2) at treatment initiation and severe undernutrition before the onset of TB disease were both associated with unfavorable outcomes (adjusted incidence rate ratio [aIRR], 2.05; 95% confidence interval [CI], 1.42-2.91 and aIRR, 2.20; 95% CI, 1.16-3.94, respectively). Additionally, lack of BMI increase after treatment initiation was associated with increased unfavorable outcomes (aIRR, 1.81; 95% CI, 1.27-2.61). Severe stunting (height-for-age z score <-3) was associated with unfavorable outcomes (aIRR, 1.52; 95% CI, 1.00-2.24). Severe undernutrition at treatment initiation and lack of BMI increase during treatment were associated with a 4- and 5-fold higher rate of death, respectively. CONCLUSIONS: Premorbid undernutrition, undernutrition at treatment initiation, lack of BMI increase after intensive therapy, and severe stunting are associated with unfavorable TB treatment outcomes. These data highlight the need to address this widely prevalent TB comorbidity. Nutritional assessment should be integrated into standard TB care.

Development of prognostic scoring system for predicting 1-year mortality among pulmonary tuberculosis patients in South India.

BACKGROUND: Development of a prediction model using baseline characteristics of tuberculosis (TB) patients at the time of diagnosis will aid us in early identification of the high-risk groups and devise pertinent strategies accordingly. Hence, we did this study to develop a prognostic-scoring model for predicting the death among newly diagnosed drug sensitive pulmonary TB patients in South India. METHODS: We undertook a longitudinal analysis of cohort data under the Regional Prospective Observational Research for Tuberculosis India consortium. Multivariable cox regression using the stepwise backward elimination procedure was used to select variables for the model building and the nomogram-scoring system was developed with the final selected model. RESULTS: In total, 54 (4.6%) out of the 1181 patients had died during the 1-year follow-up period. The TB mortality rate was 0.20 per 1000 person-days. Eight variables (age, gender, functional limitation, anemia, leukopenia, thrombocytopenia, diabetes, neutrophil-lymphocyte ratio) were selected and a nomogram was built using these variables. The discriminatory power was 0.81 (95% confidence interval: 0.75-0.86) and this model was well-calibrated. Decision curve analysis showed that the model is beneficial at a threshold probability ~15-65%. CONCLUSIONS: This scoring system could help the clinicians and policy makers to devise targeted interventions and in turn reduce the TB mortality in India.

Effect of treatment adherence on the association between sex and unfavourable treatment outcomes among tuberculosis patients in Puducherry, India: a mediation analysis.

BACKGROUND: A better understanding of the complex interplay between risk factors of tuberculosis (TB) is essential. This study was part of the Regional Prospective Observational Research for Tuberculosis (RePORT) India consortium and includes newly diagnosed TB patients in Puducherry between 2014 and 2018. We employed mediation analysis to identify the effect of treatment adherence on association between sex and unfavourable TB treatment outcomes. METHODS: Required demographic and treatment-related variables were extracted from the RePORT India consortium database and causal mediation analysis using parametric regression models was done. RESULTS: Of the 712 TB patients, ~87 (12.2%) had unfavourable TB treatment outcomes. Total effect of male sex was significantly associated with the unfavourable TB treatment outcomes [adjusted odds ratio (aOR) = 2.48; 95% confidence interval (CI): 1.11-5.55]. However, the overall association between male sex and TB treatment outcomes was dominated by the indirect pathway, as the direct pathway does not show significant association (aOR = 1.67; 95% CI: 0.75-3.75), while the indirect pathway shows significantly higher odds of TB treatment outcomes (aOR = 1.48; 95% CI:1.27-1.73), indicating complete mediation by the treatment adherence. CONCLUSIONS: The study has shown a complete mediation of sexes through TB treatment adherence for unfavourable treatment outcomes. Developing of treatment strategies require better understanding between the biological and social factors related to TB.

Accuracy of Timika X-ray scoring system to predict the treatment outcomes among tuberculosis patients in India.

BACKGROUND: Timika scoring system is a radiographic grading tool, widely employed for grading the severity of tuberculosis (TB). We evaluated the predictive accuracy of this tool for adverse treatment outcomes among TB patients in Indian setting. METHODS: We undertook a longitudinal analysis of cohort data under the RePORT-India consortium. Cohort having participants with active pulmonary TB were included. CXRs were independently scored by chest physicians. Timika scoring system had a total score of 140. The predictive nature of the tool was assessed using the ROC analysis. RESULTS: Around 364 laboratory confirmed TB patients were enrolled. The mean (SD) of overall Timika score was 62.3 (24.9). Sputum conversion was achieved among 218/260 (83.8%) patients available at end of intensive phase. AUC for Timika score was 0.53 (95% CI: 0.43-0.63) and for percent lung affected, was 0.56 (95% CI: 0.46-0.65). Unfavorable treatment outcome was observed among 67/287 (23.3%) at the end of continuation phase. AUC for percent lung affected was 0.62 (95% CI: 0.54-0.70) and for Timika score was 0.59 (95% CI: 0.51-0.67). CONCLUSION: Both Timika scoring system and percent lung affected had poor predictive accuracy, highlighting the inability of a single CXR scoring system to predict the treatment outcome in Indian setting.

Corrigendum: Malnutrition leads to increased inflammation and expression of tuberculosis risk signatures in recently exposed household contacts of pulmonary tuberculosis.

[This corrects the article DOI: 10.3389/fimmu.2022.1011166.].

Malnutrition leads to increased inflammation and expression of tuberculosis risk signatures in recently exposed household contacts of pulmonary tuberculosis.

Background: Most individuals exposed to Mycobacterium tuberculosis (Mtb) develop latent tuberculosis infection (LTBI) and remain at risk for progressing to active tuberculosis disease (TB). Malnutrition is an important risk factor driving progression from LTBI to TB. However, the performance of blood-based TB risk signatures in malnourished individuals with LTBI remains unexplored. The aim of this study was to determine if malnourished and control individuals had differences in gene expression, immune pathways and TB risk signatures. Methods: We utilized data from 50 tuberculin skin test positive household contacts of persons with TB - 18 malnourished participants (body mass index [BMI] < 18.5 kg/m2) and 32 controls (individuals with BMI ≥ 18.5 kg/m2). Whole blood RNA-sequencing was conducted to identify differentially expressed genes (DEGs). Ingenuity Pathway Analysis was applied to the DEGs to identify top canonical pathways and gene regulators. Gene enrichment methods were then employed to score the performance of published gene signatures associated with progression from LTBI to TB. Results: Malnourished individuals had increased activation of inflammatory pathways, including pathways involved in neutrophil activation, T-cell activation and proinflammatory IL-1 and IL-6 cytokine signaling. Consistent with known association of inflammatory pathway activation with progression to TB disease, we found significantly increased expression of the RISK4 (area under the curve [AUC] = 0.734) and PREDICT29 (AUC = 0.736) progression signatures in malnourished individuals. Conclusion: Malnourished individuals display a peripheral immune response profile reflective of increased inflammation and a concomitant increased expression of risk signatures predicting progression to TB. With validation in prospective clinical cohorts, TB risk biomarkers have the potential to identify malnourished LTBI for targeted therapy.

Diagnostic biomarkers for active tuberculosis: progress and challenges.

Tuberculosis (TB) is a leading cause of morbidity and mortality from a single infectious agent, despite being preventable and curable. Early and accurate diagnosis of active TB is critical to both enhance patient care, improve patient outcomes, and break Mycobacterium tuberculosis (Mtb) transmission cycles. In 2020 an estimated 9.9 million people fell ill from Mtb, but only a little over half (5.8 million) received an active TB diagnosis and treatment. The World Health Organization has proposed target product profiles for biomarker- or biosignature-based diagnostics using point-of-care tests from easily accessible specimens such as urine or blood. Here we review and summarize progress made in the development of pathogen- and host-based biomarkers for active TB diagnosis. We describe several unique patient populations that have posed challenges to development of a universal diagnostic TB biomarker, such as people living with HIV, extrapulmonary TB, and children. We also review additional limitations to widespread validation and utilization of published biomarkers. We conclude with proposed solutions to enhance TB diagnostic biomarker validation and uptake.

Immunologic Biomarkers in Peripheral Blood of Persons With Tuberculosis and Advanced HIV.

Introduction: Tuberculosis (TB) is a common opportunistic infection among people living with HIV. Diagnostic tests such as culture, Xpert-MTB-RIF, and ULTRA have low sensitivity in paucibacillary TB disease; a blood biomarker could improve TB diagnostic capabilities. We assessed soluble factors to identify biomarkers associated with TB among persons with advanced HIV. Methods: A case-control (1:1) study was conducted, with participants from Rio de Janeiro and Manaus, Brazil. People living with HIV presenting with CD4 count ≤100 cells/mm3 were eligible to participate. Cases had culture-confirmed TB (N=15) (positive for Mycobacterium tuberculosis [Mtb]); controls had HIV-infection only (N=15). Study visits included baseline, month 2 and end of TB therapy, during which samples of peripheral blood were obtained. A panel containing 29 biomarkers including cytokines, chemokines and growth factors was utilized to assess candidate biomarkers using Luminex technology in cryopreserved EDTA plasma samples. We used neural network analysis, based on machine learning, to identify biomarkers (single or in combination) that best distinguished cases from controls. Additional multi-dimensional analyses provided detailed profiling of the systemic inflammatory environment in cases and controls. Results: Median CD4 count and HIV-1 RNA load values were similar between groups at all timepoints. Persons with TB had lower body mass index (BMI) (median=19.6, Interquartile Range [IQR]=18.6-22.3) than controls (23.7; IQR: 21.8 = 25.5, p=0.004). TB coinfection was also associated with increased frequency of other comorbidities. The overall profile of plasma cytokines, chemokines and growth factors were distinct between the study groups at all timepoints. Plasma concentrations of IL-15 and IL-10 were on average lower in TB cases than in controls. When used in combination, such markers were able to discriminate between TB cases and controls with the highest degree of accuracy at each study timepoint. Conclusion: Among persons with advanced HIV, plasma concentrations of IL-15 and IL-10 can be used in combination to identify TB disease regardless of time on anti-TB treatment.

Early alveolar macrophage response and IL-1R-dependent T cell priming determine transmissibility of Mycobacterium tuberculosis strains.

Mechanisms underlying variability in transmission of Mycobacterium tuberculosis strains remain undefined. By characterizing high and low transmission strains of M.tuberculosis in mice, we show here that high transmission M.tuberculosis strain induce rapid IL-1R-dependent alveolar macrophage migration from the alveolar space into the interstitium and that this action is key to subsequent temporal events of early dissemination of bacteria to the lymph nodes, Th1 priming, granulomatous response and bacterial control. In contrast, IL-1R-dependent alveolar macrophage migration and early dissemination of bacteria to lymph nodes is significantly impeded in infection with low transmission M.tuberculosis strain; these events promote the development of Th17 immunity, fostering neutrophilic inflammation and increased bacterial replication. Our results suggest that by inducing granulomas with the potential to develop into cavitary lesions that aids bacterial escape into the airways, high transmission M.tuberculosis strain is poised for greater transmissibility. These findings implicate bacterial heterogeneity as an important modifier of TB disease manifestations and transmission.