Incipient and subclinical tuberculosis: defining early disease states in the context of host immune response

Incipient tuberculosis: a comprehensive overview

In the context of the evolving global health landscape shaped by the COVID-19 pandemic, tuberculosis (TB) is gaining renewed attention as a reemerging threat even in low-endemic countries. Immunological tests such as the tuberculin skin test (TST) and interferon-gamma release assay (IGRA) are pivotal in identifying tuberculosis infection (TBI). However, their inability to distinguish between past and ongoing infection poses a diagnostic challenge, possibly leading to the unnecessary treatment of a significant portion of the population with potential side effects. This review delves into the concept of incipient tuberculosis (ITB), a dynamic, presymptomatic stage characterized by heightened Mycobacterium tuberculosis complex (MTC) metabolic activity and replication that result in minimal radiological changes, signifying a transitional state between TBI and TB. Key focus areas include epidemiological factors, underlying pathogenesis, imaging findings, and the ongoing challenges in the identification of individuals with ITB through the development of new biomarkers and the use of whole-genome sequencing-based analyses to implement early treatment strategies.

Chest Radiograph Screening for Detecting Subclinical Tuberculosis in Asymptomatic Household Contacts, Peru

The World Health Organization's end TB strategy promotes the use of symptom and chest radiograph screening for tuberculosis (TB) disease. However, asymptomatic early states of TB beyond latent TB infection and active disease can go unrecognized using current screening criteria. We conducted a longitudinal cohort study enrolling household contacts initially free of TB disease and followed them for the occurrence of incident TB over 1 year. Among 1,747 screened contacts, 27 (52%) of the 52 persons in whom TB subsequently developed during follow-up had a baseline abnormal radiograph. Of contacts without TB symptoms, persons with an abnormal radiograph were at higher risk for subsequent TB than persons with an unremarkable radiograph (adjusted hazard ratio 15.62 [95% CI 7.74-31.54]). In young adults, we found a strong linear relationship between radiograph severity and time to TB diagnosis. Our findings suggest chest radiograph screening can extend to detecting early TB states, thereby enabling timely intervention.

Systems genetics uncover new loci containing functional gene candidates in Mycobacterium tuberculosis-infected Diversity Outbred mice

Mycobacterium tuberculosis infects two billion people across the globe, and results in 8-9 million new tuberculosis (TB) cases and 1-1.5 million deaths each year. Most patients have no known genetic basis that predisposes them to disease. Here, we investigate the complex genetic basis of pulmonary TB by modelling human genetic diversity with the Diversity Outbred mouse population. When infected with M. tuberculosis, one-third develop early onset, rapidly progressive, necrotizing granulomas and succumb within 60 days. The remaining develop non-necrotizing granulomas and survive longer than 60 days. Genetic mapping using immune and inflammatory mediators; and clinical, microbiological, and granuloma correlates of disease identified five new loci on mouse chromosomes 1, 2, 4, 16; and three known loci on chromosomes 3 and 17. Further, multiple positively correlated traits shared loci on chromosomes 1, 16, and 17 and had similar patterns of allele effects, suggesting these loci contain critical genetic regulators of inflammatory responses to M. tuberculosis. To narrow the list of candidate genes, we used a machine learning strategy that integrated gene expression signatures from lungs of M. tuberculosis-infected Diversity Outbred mice with gene interaction networks to generate scores representing functional relationships. The scores were used to rank candidates for each mapped trait, resulting in 11 candidate genes: Ncf2, Fam20b, S100a8, S100a9, Itgb5, Fstl1, Zbtb20, Ddr1, Ier3, Vegfa, and Zfp318. Although all candidates have roles in infection, inflammation, cell migration, extracellular matrix remodeling, or intracellular signaling, and all contain single nucleotide polymorphisms (SNPs), SNPs in only four genes (S100a8, Itgb5, Fstl1, Zfp318) are predicted to have deleterious effects on protein functions. We performed methodological and candidate validations to (i) assess biological relevance of predicted allele effects by showing that Diversity Outbred mice carrying PWK/PhJ alleles at the H-2 locus on chromosome 17 QTL have shorter survival; (ii) confirm accuracy of predicted allele effects by quantifying S100A8 protein in inbred founder strains; and (iii) infection of C57BL/6 mice deficient for the S100a8 gene. Overall, this body of work demonstrates that systems genetics using Diversity Outbred mice can identify new (and known) QTLs and functionally relevant gene candidates that may be major regulators of complex host-pathogens interactions contributing to granuloma necrosis and acute inflammation in pulmonary TB.

Sociodemographic factors associated with the success or failure of anti-tuberculosis treatment in the Chiapas Highlands, Mexico, 2019-2022

OBJECTIVE

To estimate the incidence rate of tuberculosis (TB) in the Highlands (Tsotsil-Tseltal) region of Chiapas and to analyze sociodemographic factors that might influence the success of anti-TB treatment from the period of January 2019 to June 2022.

METHODS

Retrospective study in which the TB databases of the National Epidemiological Surveillance System (SINAVE) were analyzed. TB incidence rates were calculated based on the number of registered TB cases and estimated annual populations. The success-failure of anti-TB treatment was analyzed according to sociodemographic indicators, degree of concentration of indigenous population of the municipality of residence and admission to SINAVE.

RESULTS

Two hundred thirty-three cases were analyzed. The variables associated to a lower success rate of treatment against TB were: living in a municipality with high-very high concentration of indigenous population, being indigenous, having a primary school education or lower, and agricultural occupation. The number of TB diagnosed from 2020-2022 and the incidence rates from 2020-2021 decreased significantly compared to 2019.

CONCLUSIONS

It is necessary to strengthen the follow-up of TB cases in the region, mainly in areas with high-very high indigenous concentration, in people with low levels of education and engaged in agricultural work.

Systems genetics uncover new loci containing functional gene candidates in Mycobacterium tuberculosis-infected Diversity Outbred mice

Mycobacterium tuberculosis, the bacillus that causes tuberculosis (TB), infects 2 billion people across the globe, and results in 8-9 million new TB cases and 1-1.5 million deaths each year. Most patients have no known genetic basis that predisposes them to disease. We investigated the complex genetic basis of pulmonary TB by modelling human genetic diversity with the Diversity Outbred mouse population. When infected with M. tuberculosis, one-third develop early onset, rapidly progressive, necrotizing granulomas and succumb within 60 days. The remaining develop non-necrotizing granulomas and survive longer than 60 days. Genetic mapping using clinical indicators of disease, granuloma histopathological features, and immune response traits identified five new loci on mouse chromosomes 1, 2, 4, 16 and three previously identified loci on chromosomes 3 and 17. Quantitative trait loci (QTLs) on chromosomes 1, 16, and 17, associated with multiple correlated traits and had similar patterns of allele effects, suggesting these QTLs contain important genetic regulators of responses to M. tuberculosis. To narrow the list of candidate genes in QTLs, we used a machine learning strategy that integrated gene expression signatures from lungs of M. tuberculosis-infected Diversity Outbred mice with gene interaction networks, generating functional scores. The scores were then used to rank candidates for each mapped trait in each locus, resulting in 11 candidates: Ncf2, Fam20b, S100a8, S100a9, Itgb5, Fstl1, Zbtb20, Ddr1, Ier3, Vegfa, and Zfp318. Importantly, all 11 candidates have roles in infection, inflammation, cell migration, extracellular matrix remodeling, or intracellular signaling. Further, all candidates contain single nucleotide polymorphisms (SNPs), and some but not all SNPs were predicted to have deleterious consequences on protein functions. Multiple methods were used for validation including (i) a statistical method that showed Diversity Outbred mice carrying PWH/PhJ alleles on chromosome 17 QTL have shorter survival; (ii) quantification of S100A8 protein levels, confirming predicted allele effects; and (iii) infection of C57BL/6 mice deficient for the S100a8 gene. Overall, this work demonstrates that systems genetics using Diversity Outbred mice can identify new (and known) QTLs and new functionally relevant gene candidates that may be major regulators of granuloma necrosis and acute inflammation in pulmonary TB.

Beyond latent and active tuberculosis: a scoping review of conceptual frameworks

There is growing recognition that tuberculosis (TB) infection and disease exists as a spectrum of states beyond the current binary classification of latent and active TB. Our aim was to systematically map and synthesize published conceptual frameworks for TB states. We searched MEDLINE, Embase and EMcare for review articles from 1946 to September 2023. We included 40 articles that explicitly described greater than two states for TB. We identified that terminology, definitions and diagnostic criteria for additional TB states within these articles were inconsistent. Eight broad conceptual themes were identified that were used to categorize TB states: State 0: Mycobacterium tuberculosis (Mtb) elimination with innate immune response (n = 25/40, 63%); State I: Mtb elimination by acquired immune response (n = 31/40, 78%); State II: Mtb infection not eliminated but controlled (n = 37/40, 93%); State III: Mtb infection not controlled (n = 24/40, 60%); State IV: bacteriologically positive without symptoms (n = 26/40, 65%); State V: signs or symptoms associated with TB (n = 39/40, 98%); State VI: severe or disseminated TB disease (n = 11/40, 28%); and State VII: previous history of TB (n = 5/40, 13%). Consensus on a non-binary framework that includes additional TB states is required to standardize scientific communication and to inform advancements in research, clinical and public health practice.

From immunology to artificial intelligence: revolutionizing latent tuberculosis infection diagnosis with machine learning

Latent tuberculosis infection (LTBI) has become a major source of active tuberculosis (ATB). Although the tuberculin skin test and interferon-gamma release assay can be used to diagnose LTBI, these methods can only differentiate infected individuals from healthy ones but cannot discriminate between LTBI and ATB. Thus, the diagnosis of LTBI faces many challenges, such as the lack of effective biomarkers from Mycobacterium tuberculosis (MTB) for distinguishing LTBI, the low diagnostic efficacy of biomarkers derived from the human host, and the absence of a gold standard to differentiate between LTBI and ATB. Sputum culture, as the gold standard for diagnosing tuberculosis, is time-consuming and cannot distinguish between ATB and LTBI. In this article, we review the pathogenesis of MTB and the immune mechanisms of the host in LTBI, including the innate and adaptive immune responses, multiple immune evasion mechanisms of MTB, and epigenetic regulation. Based on this knowledge, we summarize the current status and challenges in diagnosing LTBI and present the application of machine learning (ML) in LTBI diagnosis, as well as the advantages and limitations of ML in this context. Finally, we discuss the future development directions of ML applied to LTBI diagnosis.

Tuberculosis prevention: current strategies and future directions

BACKGROUND

An estimated one fourth of the world's population is infected with Mycobacterium tuberculosis, and 5-10% of those infected develop tuberculosis in their lifetime. Preventing tuberculosis is one of the most underutilized but essential components of curtailing the tuberculosis epidemic. Moreover, current evidence illustrates that tuberculosis manifestations occur along a dynamic spectrum from infection to disease rather than a binary state as historically conceptualized. Elucidating determinants of transition between these states is crucial to decreasing the tuberculosis burden and reaching the END-TB Strategy goals as defined by the WHO. Vaccination, detection of infection, and provision of preventive treatment are key elements of tuberculosis prevention.

OBJECTIVES

This review provides a comprehensive summary of recent evidence and state-of-the-art updates on advancements to prevent tuberculosis in various settings and high-risk populations.

SOURCES

We identified relevant studies in the literature and synthesized the findings to provide an overview of the current state of tuberculosis prevention strategies and latest research developments.

CONTENT

We present the current knowledge and recommendations regarding tuberculosis prevention, with a focus on M. bovis Bacille-Calmette-Guérin vaccination and novel vaccine candidates, tests for latent infection with M. tuberculosis, regimens available for tuberculosis preventive treatment and recommendations in low- and high-burden settings.

IMPLICATIONS

Effective tuberculosis prevention worldwide requires a multipronged approach that addresses social determinants, and improves access to tuberculosis detection and to new short tuberculosis preventive treatment regimens. Robust collaboration and innovative research are needed to reduce the global burden of tuberculosis and develop new detection tools, vaccines, and preventive treatments that serve all populations and ages.

Comparative immune responses to Mycobacterium tuberculosis in people with latent infection or sterilizing protection

There is great need for vaccines against tuberculosis (TB) more efficacious than the licensed BCG. Our goal was to identify new vaccine benchmarks by identifying immune responses that distinguish individuals able to eradicate the infection (TB-resisters) from individuals with latent infection (LTBI-participants). TB-resisters had higher frequencies of circulating CD8+ glucose monomycolate (GMM)+ Granzyme-B+ T cells than LTBI-participants and higher proportions of polyfunctional conventional and nonconventional T cells expressing Granzyme-B and/or PD-1 after ex vivo M. tuberculosis stimulation of blood mononuclear cells. LTBI-participants had higher expression of activation markers and cytokines, including IL10, and IFNγ. An exploratory analysis of BCG-recipients with minimal exposure to TB showed absence of CD8+GMM+Granzyme-B+ T cells, lower or equal proportions of Granzyme-B+PD-1+ polyfunctional T cells than TB-resisters and higher or equal than LTBI-participants. In conclusion, high Granzyme-B+PD-1+ T cell responses to M. tuberculosis and, possibly, of CD8+GMM+Granzyme-B+ T cells may be desirable for new TB vaccines.

Do private providers initiate anti-tuberculosis therapy on the basis of chest radiographs? A standardised patient study in urban India

Background

The initiation of anti-tuberculosis treatment (ATT) based on results of WHO-approved microbiological diagnostics is an important marker of quality tuberculosis (TB) care. Evidence suggests that other diagnostic processes leading to treatment initiation may be preferred in high TB incidence settings. This study examines whether private providers start anti-TB therapy on the basis of chest radiography (CXR) and clinical examinations.

Methods

This study uses the standardized patient (SP) methodology to generate accurate and unbiased estimates of private sector, primary care provider practice when a patient presents a standardized TB case scenario with an abnormal CXR. Using multivariate log-binomial and linear regressions with standard errors clustered at the provider level, we analyzed 795 SP visits conducted over three data collection waves from 2014 to 2020 in two Indian cities. Data were inverse-probability-weighted based on the study sampling strategy, resulting in city-wave-representative results.

Findings

Amongst SPs who presented to a provider with an abnormal CXR, 25% (95% CI: 21-28%) visits resulted in ideal management, defined as the provider prescribing a microbiological test and not offering a concurrent prescription for a corticosteroid or antibiotic (including anti-TB medications). In contrast, 23% (95% CI: 19-26%) of 795 visits were prescribed anti-TB medications. Of 795 visits, 13% (95% CI: 10-16%) resulted in anti-TB treatment prescriptions/dispensation and an order for confirmatory microbiological testing.

Interpretation

One in five SPs presenting with abnormal CXR were prescribed ATT by private providers. This study contributes novel insights to empiric treatment prevalence based on CXR abnormality. Further work is needed to understand how providers make trade-offs between existing diagnostic practices, new technologies, profits, clinical outcomes, and the market dynamics with laboratories.

Funding

This study was funded by the Bill & Melinda Gates Foundation (grant OPP1091843), and the Knowledge for Change Program at The World Bank.

Subclinical ankle joint tuberculous arthritis - The role of scintigraphy: A case series

BACKGROUND

Tuberculosis remains a complicated problem. A lack of awareness accompanied by difficulty in diagnosis hinders the management of tuberculosis. Delayed management, particularly in osteoarticular regions, results in unnecessary procedures, including joint-sacrificing surgery.

CASE SUMMARY

Three cases of subclinical ankle joint tuberculosis without clear signs of tuberculosis were presented. The efficacy of technetium-99m-ethambutol scintigraphy in diagnosing early-stage tuberculous arthritis is reported.

CONCLUSION

The reports suggested that scintigraphy is recommended to diagnose subclinical tuberculous arthritis, especially in tuberculosis endemic regions.

Management of Tuberculosis Infection: Current Situation, Recent Developments and Operational Challenges

Tuberculosis infection (TBI) is defined as a state of infection in which individuals host live Mycobacterium tuberculosis with or without clinical signs of active TB. It is now understood as a dynamic process covering a spectrum of responses to infection resulting from the interaction between the TB bacilli and the host immune system. The global burden of TBI is about one-quarter of the world’s population, representing a reservoir of approximately 2 billion people. On average, 5–10% of people who are infected will develop TB disease over the course of their lives, but this risk is enhanced in a series of conditions, such as co-infection with HIV. The End-TB strategy promotes the programmatic management of TBI as a crucial endeavor to achieving global targets to end the TB epidemic. The current development of new diagnostic tests capable of discriminating between simple TBI and active TB, combined with novel short-course preventive treatments, will help achieve this goal. In this paper, we present the current situation and recent developments of management of TBI and the operational challenges.

Epidemiology of recurrent pulmonary tuberculosis by bacteriological features of 100 million residents in China

Background

Recurrence continues to place significant burden on patients and tuberculosis programmes worldwide, and previous studies have rarely provided analysis in negative recurrence cases. We characterized the epidemiological features of recurrent pulmonary tuberculosis (PTB) patients, estimated its probability associated with different bacteriology results and risk factors.

Methods

Using 2005–2018 provincial surveillance data from Henan, China, where the permanent population approximately were 100 million, we described the epidemiological and bacteriological features of recurrent PTB. The Kaplan–Meier method and Cox proportional hazard models, respectively, were used to estimate probability of recurrent PTB and risk factors.

Results

A total of 7143 (1.5%) PTB patients had recurrence, and of 21.1% were bacteriological positive on both laboratory tests (positive–positive), and of 34.9% were negative–negative. Compared with bacteriological negative recurrent PTB at first episodes, the bacteriological positive cases were more male (81.70% vs 72.79%; P < 0.001), higher mortality risk (1.78% vs 0.92%; P = 0.003), lower proportion of cured or completed treatment (82.81% vs 84.97%; P = 0.022), and longer time from onset to end-of-treatment. The probability of recurrence was higher in bacteriological positive cases than those in bacteriological negative cases (0.5% vs 0.4% at 20 months; P < 0.05).

Conclusions

Based on patient’s epidemiological characteristics and bacteriological type, it was necessary to actively enact measures to control their recurrent.

The Contribution of Chest Radiography to the Clinical Management of Children Exposed to Tuberculosis

Rationale: Although World Health Organization guidelines emphasize contact investigation for tuberculosis (TB)-exposed children, data that support chest radiography as a useful tool are lacking. Objectives: We evaluated the diagnostic and prognostic information of chest radiography in children exposed to TB and measured the efficacy of isoniazid preventive therapy (IPT) in those with relevant radiographic abnormalities. Methods: Between September 2009 and August 2012, we enrolled 4,468 TB-exposed children who were screened by tuberculin skin testing, symptom assessment, and chest radiography. Those negative for TB disease were followed for 1 year for the occurrence of new TB diagnoses. We assessed the protective efficacy of IPT in children with and without abnormal chest radiographs. Measurements and Main Results: Compared with asymptomatic children with normal chest films, asymptomatic children with abnormal radiographs were 25.1-fold more likely to have coprevalent TB (95% confidence interval [CI], 1.02-613.76) and 26.7-fold more likely to be diagnosed with incident TB disease during follow-up (95% CI, 10.44-68.30). Among the 29 symptom-negative and CXR-abnormal child contacts, 20% (3/15) of the isoniazid recipients developed incident TB, compared with 57% (8/14) of those who did not receive IPT (82% IPT efficacy). Conclusions: Our results strongly support the use of chest radiography as a routine screening tool for the evaluation of child TB contacts, which is readily available. Radiographic abnormalities not usually considered suggestive of TB may indicate incipient or subclinical disease, although TB preventive treatment is adequate in most cases.

Feasibility of novel approaches to detect viable Mycobacterium tuberculosis within the spectrum of the tuberculosis disease

Tuberculosis (TB) is a global disease caused by Mycobacterium tuberculosis (Mtb) and is manifested as a continuum spectrum of infectious states. Both, the most common and clinically asymptomatic latent tuberculosis infection (LTBI), and the symptomatic disease, active tuberculosis (TB), are at opposite ends of the spectrum. Such binary classification is insufficient to describe the existing clinical heterogeneity, which includes incipient and subclinical TB. The absence of clinically TB-related symptoms and the extremely low bacterial burden are features shared by LTBI, incipient and subclinical TB states. In addition, diagnosis relies on cytokine release after antigenic T cell stimulation, yet several studies have shown that a high proportion of individuals with immunoreactivity never developed disease, suggesting that they were no longer infected. LTBI is estimated to affect to approximately one fourth of the human population and, according to WHO data, reactivation of LTBI is the main responsible of TB cases in developed countries. Assuming the drawbacks associated to the current diagnostic tests at this part of the disease spectrum, properly assessing individuals at real risk of developing TB is a major need. Further, it would help to efficiently design preventive treatment. This quest would be achievable if information about bacterial viability during human silent Mtb infection could be determined. Here, we have evaluated the feasibility of new approaches to detect viable bacilli across the full spectrum of TB disease. We focused on methods that specifically can measure host-independent parameters relying on the viability of Mtb either by its direct or indirect detection.

Inhibition of Mycobacterium tuberculosis InhA (Enoyl-acyl carrier protein reductase) by synthetic Chalcones: a molecular modelling analysis and in-vitro evidence

Tuberculosis (TB) is a serious infectious disease caused by the bacillus Mycobacterium tuberculosis (Mtb). The World Health Organization (WHO) estimates that 1.8 million people die each year from TB, with 10 million new cases being registered each year. In this study, 50 Chalcones were developed, five of which were synthesized, and their inhibitory effects against Mtb were studied. The discovery of new powerful inhibitors with IC₅₀ values in the sub-micro molar range resulted from the development of structure-activity relationships (SAR). The goal of the molecular modelling studies was to uncover the most important structural criteria underpinning the binding affinity and selectivity of this class of inhibitors as possible anti-TB drugs. Because of their great efficacy and selectivity, our developed nitro and benzyloxy substituted Chalcones compounds appear to be promising anti-TB therapies.Communicated by Ramaswamy H. Sarma.

Symptom- and chest-radiography screening for active pulmonary tuberculosis in HIV-negative adults and adults with unknown HIV status

BACKGROUND

Systematic screening in high-burden settings is recommended as a strategy for early detection of pulmonary tuberculosis disease, reducing mortality, morbidity and transmission, and improving equity in access to care. Questioning for symptoms and chest radiography (CXR) have historically been the most widely available tools to screen for tuberculosis disease. Their accuracy is important for the design of tuberculosis screening programmes and determines, in combination with the accuracy of confirmatory diagnostic tests, the yield of a screening programme and the burden on individuals and the health service.

OBJECTIVES

To assess the sensitivity and specificity of questioning for the presence of one or more tuberculosis symptoms or symptom combinations, CXR, and combinations of these as screening tools for detecting bacteriologically confirmed pulmonary tuberculosis disease in HIV-negative adults and adults with unknown HIV status who are considered eligible for systematic screening for tuberculosis disease. Second, to investigate sources of heterogeneity, especially in relation to regional, epidemiological, and demographic characteristics of the study populations.

SEARCH METHODS

We searched the MEDLINE, Embase, LILACS, and HTA (Health Technology Assessment) databases using pre-specified search terms and consulted experts for unpublished reports, for the period 1992 to 2018. The search date was 10 December 2018. This search was repeated on 2 July 2021.

SELECTION CRITERIA

Studies were eligible if participants were screened for tuberculosis disease using symptom questions, or abnormalities on CXR, or both, and were offered confirmatory testing with a reference standard. We included studies if diagnostic two-by-two tables could be generated for one or more index tests, even if not all participants were subjected to a microbacteriological reference standard. We excluded studies evaluating self-reporting of symptoms.

DATA COLLECTION AND ANALYSIS

We categorized symptom and CXR index tests according to commonly used definitions. We assessed the methodological quality of included studies using the QUADAS-2 instrument. We examined the forest plots and receiver operating characteristic plots visually for heterogeneity. We estimated summary sensitivities and specificities (and 95% confidence intervals (CI)) for each index test using bivariate random-effects methods. We analyzed potential sources of heterogeneity in a hierarchical mixed-model.

MAIN RESULTS

The electronic database search identified 9473 titles and abstracts. Through expert consultation, we identified 31 reports on national tuberculosis prevalence surveys as eligible (of which eight were already captured in the search of the electronic databases), and we identified 957 potentially relevant articles through reference checking. After removal of duplicates, we assessed 10,415 titles and abstracts, of which we identified 430 (4%) for full text review, whereafter we excluded 364 articles. In total, 66 articles provided data on 59 studies. We assessed the 2 July 2021 search results; seven studies were potentially eligible but would make no material difference to the review findings or grading of the evidence, and were not added in this edition of the review. We judged most studies at high risk of bias in one or more domains, most commonly because of incorporation bias and verification bias. We judged applicability concerns low in more than 80% of studies in all three domains. The three most common symptom index tests, cough for two or more weeks (41 studies), any cough (21 studies), and any tuberculosis symptom (29 studies), showed a summary sensitivity of 42.1% (95% CI 36.6% to 47.7%), 51.3% (95% CI 42.8% to 59.7%), and 70.6% (95% CI 61.7% to 78.2%, all very low-certainty evidence), and a specificity of 94.4% (95% CI 92.6% to 95.8%, high-certainty evidence), 87.6% (95% CI 81.6% to 91.8%, low-certainty evidence), and 65.1% (95% CI 53.3% to 75.4%, low-certainty evidence), respectively. The data on symptom index tests were more heterogenous than those for CXR. The studies on any tuberculosis symptom were the most heterogeneous, but had the lowest number of variables explaining this variation. Symptom index tests also showed regional variation. The summary sensitivity of any CXR abnormality (23 studies) was 94.7% (95% CI 92.2% to 96.4%, very low-certainty evidence) and 84.8% (95% CI 76.7% to 90.4%, low-certainty evidence) for CXR abnormalities suggestive of tuberculosis (19 studies), and specificity was 89.1% (95% CI 85.6% to 91.8%, low-certainty evidence) and 95.6% (95% CI 92.6% to 97.4%, high-certainty evidence), respectively. Sensitivity was more heterogenous than specificity, and could be explained by regional variation. The addition of cough for two or more weeks, whether to any (pulmonary) CXR abnormality or to CXR abnormalities suggestive of tuberculosis, resulted in a summary sensitivity and specificity of 99.2% (95% CI 96.8% to 99.8%) and 84.9% (95% CI 81.2% to 88.1%) (15 studies; certainty of evidence not assessed).

AUTHORS' CONCLUSIONS

The summary estimates of the symptom and CXR index tests may inform the choice of screening and diagnostic algorithms in any given setting or country where screening for tuberculosis is being implemented. The high sensitivity of CXR index tests, with or without symptom questions in parallel, suggests a high yield of persons with tuberculosis disease. However, additional considerations will determine the design of screening and diagnostic algorithms, such as the availability and accessibility of CXR facilities or the resources to fund them, and the need for more or fewer diagnostic tests to confirm the diagnosis (depending on screening test specificity), which also has resource implications. These review findings should be interpreted with caution due to methodological limitations in the included studies and regional variation in sensitivity and specificity. The sensitivity and specificity of an index test in a specific setting cannot be predicted with great precision due to heterogeneity. This should be borne in mind when planning for and implementing tuberculosis screening programmes.

Recurrent subclinical tuberculosis among ART accessing participants: Incidence, clinical course, and outcomes

BACKGROUND

Undiagnosed asymptomatic subclinical tuberculosis (TB) remains a significant threat to global TB control and accounts for a substantial proportion of cases among people living with HIV/AIDS (PLWHA). We determined the incidence, progression, and outcomes of subclinical TB in anti-retroviral therapy (ART) accessing PLWHA with known previous TB in South Africa.

METHODS

A total of 402 adult PLWHA previously treated for TB were enrolled in the prospective CAPRISA TRuTH (TB Recurrence Upon TB and HIV treatment) study. Participants were screened for TB with quarterly clinical and bacteriologic evaluation and bi-annual chest radiographs over 36 months. Those with suspected or confirmed TB were referred to the National TB Programme. Participants received HIV services, including ART. Incidence rate of TB was estimated by Poisson regression, and descriptive statistical analyses summarised data.

RESULTS

A total of 48/402 (11.9%) bacteriologically confirmed incident recurrent TB cases was identified, comprising 17/48 (35.4%) subclinical TB cases and 31/48 (64.5%) clinical TB cases. Age, sex, and body mass index (BMI) were similar among subclinical , clinical , and no TB groups. Incidence rates of recurrent TB overall; in clinical TB; and subclinical TB groups was 2.3 [95% CI: 1.7-3.0]; 1.5 [95% CI: 1.1-2.2]; and 0.9 [95% CI: 0.5-1.4] per 100 person-years, respectively. In the subclinical TB group, 14/17 (82.4%) was diagnosed by TB culture only, 11/17 (64.7%) received TB treatment, and 6/17 (35.3%) resolved TB spontaneously.

CONCLUSION

The high incidence rates of recurrent subclinical TB in PLWHA highlight inadequacies of symptom-based TB screening in high TB-HIV burden settings.

Framing the Detection of Incipient Tuberculosis Infection: a qualitative study of political prioritization

Objective

Incipient Tuberculosis (ITB) refers to Mycobacterium tuberculosis infection that is likely to progress to active disease in the absence of treatment, but without clinical signs, symptoms, radiographic or microbiological evidence of disease. Biomarker‐based tests to diagnose incipient TB hold promise for better prediction and, through TB preventive therapy, prevention of disease. This study explored current and future framing and prioritisation of ITB.

Methods

Twenty‐two interviews across eight countries were conducted. A modified Shiffman & Smith Framework, containing four categories—Ideas, Issue Characteristics, Actor Power, and Political Contexts—was used to analyse the current landscape and potential for prioritisation of diagnosis and treatment of ITB.

Results

Latent TB policy implementation has been slow due to technical, logistical and financial challenges, and because it has been framed in a manner non‐conducive to gaining political priority. Framing ITB testing as ‘early detection’ rather than ‘prediction’, and its management as ‘treatment’ rather than ‘preventive therapy’, may help raise its importance in policies, and its acceptance among actors.

Conclusion

Consensus surrounding the framing of ITB will be crucial for the successful adoption of ITB diagnostics and treatment. When designing ITB tools and policies, it will be important to address challenges that pertain to latent TB policies.

An Update on Tuberculosis Vaccines

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is a leading cause of mortality and morbidity due to a single infectious agent. Aerosol infection with Mtb can result in a range of responses from elimination, active, incipient, subclinical, and latent Mtb infections (LTBI), depending on the host's immune response and the dose and nature of infecting bacilli. Currently, BCG is the only vaccine approved to prevent TB. Although BCG confers protection against severe forms of childhood TB, its use in adults and those with comorbid conditions, such as HIV infection, is questionable. Novel vaccines, including recombinant BCG (rBCG), were developed to improve BCG's efficacy and use as an alternative to BCG in a vulnerable population. The first-generation rBCG vaccines had different Mtb antigens and were tested as a prime, prime-boost, or immunotherapeutic intervention. The novel vaccines target one or more of the following requirements, namely prevention of infection (POI), prevention of disease (POD), prevention of recurrence (POR), and therapeutic vaccines to treat a TB disease. Several vaccine candidates currently in development are classified into four primary categories: live attenuated whole-cell vaccine, inactivated whole-cell vaccine, adjuvanted protein subunit vaccine, and viral-vectored vaccine. Each vaccine's immunogenicity, safety, and efficacy are tested in preclinical animal models and further validated through various phases of clinical trials. This chapter summarizes the various TB vaccine candidates under different clinical trial stages and promises better protection against TB.

Plasma host protein biomarkers correlating with increasing Mycobacterium tuberculosis infection activity prior to tuberculosis diagnosis in people living with HIV

BACKGROUND

Biomarkers correlating with Mycobacterium tuberculosis infection activity/burden in asymptomatic individuals are urgently needed to identify and treat those at highest risk for developing active tuberculosis (TB). Our main objective was to identify plasma host protein biomarkers that change over time prior to developing TB in people living with HIV (PLHIV).

METHODS

Using multiplex MRM-MS, we investigated host protein expressions from 2 years before until time of TB diagnosis in longitudinally collected (every 3-6 months) and stored plasma from PLHIV with incident TB, identified within a South African (SA) and US cohort. We performed temporal trend and discriminant analyses for proteins, and, to assure clinical relevance, we further compared protein levels at TB diagnosis to interferon-gamma release assay (IGRA; SA) or tuberculin-skin test (TST; US) positive and negative cohort subjects without TB. SA and US exploratory data were analyzed separately.

FINDINGS

We identified 15 proteins in the SA (n=30) and 10 in the US (n=24) incident TB subjects which both changed from 2 years prior until time of TB diagnosis after controlling for 10% false discovery rate, and were significantly different at time of TB diagnosis compared to non-TB subjects (p<0.01). Five proteins, CD14, A2GL, NID1, SCTM1, and A1AG1, overlapped between both cohorts. Furthermore, after cross-validation, panels of 5 - 12 proteins were able to predict TB up to two years before diagnosis.

INTERPRETATION

Host proteins can be biomarkers for increasing Mycobacterium tuberculosis infection activity/burden, incipient TB, and predict TB development in PLHIV.

FUNDING

NIH/NIAID AI117927, AI146329, and AI127173 to JMA.

Host Immune-Metabolic Adaptations Upon Mycobacterial Infections and Associated Co-Morbidities

Mycobacterial diseases are a major public health challenge. Their causative agents include, in order of impact, members of the Mycobacterium tuberculosis complex (causing tuberculosis), Mycobacterium leprae (causing leprosy), and non-tuberculous mycobacterial pathogens including Mycobacterium ulcerans. Macrophages are mycobacterial targets and they play an essential role in the host immune response to mycobacteria. This review aims to provide a comprehensive understanding of the immune-metabolic adaptations of the macrophage to mycobacterial infections. This metabolic rewiring involves changes in glycolysis and oxidative metabolism, as well as in the use of fatty acids and that of metals such as iron, zinc and copper. The macrophage metabolic adaptations result in changes in intracellular metabolites, which can post-translationally modify proteins including histones, with potential for shaping the epigenetic landscape. This review will also cover how critical tuberculosis co-morbidities such as smoking, diabetes and HIV infection shape host metabolic responses and impact disease outcome. Finally, we will explore how the immune-metabolic knowledge gained in the last decades can be harnessed towards the design of novel diagnostic and therapeutic tools, as well as vaccines.

Pulmonary Tuberculosis Disease Among Immigrant Detainees: Rapid Disease Detection, High Prevalence of Asymptomatic Disease, and Implications for Tuberculosis Prevention

BACKGROUND

Rapid screening for tuberculosis (TB) disease at intake into immigrant detention facilities allows for early detection and treatment. Detention facilities with United States Immigration and Customs Enforcement (ICE) Health Service Corps (IHSC) medical staffing utilize chest radiography and symptom screening as the primary screening for pulmonary TB (PTB) disease. This analysis describes the demographic, clinical, and microbiological characteristics of individuals identified with TB disease at these facilities.

METHODS

We conducted a retrospective analysis to describe the population of immigrant detainees identified via chest radiography with PTB disease between 1 January 2014 and 31 December 2016 at facilities with IHSC medical staffing. We collected demographic variables, clinical presentation, diagnostic testing results, and microbiological findings. We generated descriptive statistics and examined univariate and multivariate associations between the variables collected and symptomatic status.

RESULTS

We identified 327 patients with confirmed PTB disease (incidence rate, 92.8 per 100 000); the majority of patients were asymptomatic (79.2%) at diagnosis. Adjusting for all other variables in the model, the presence of cavitary lesions, acid-fast bacillus smear positivity, and multilobar presentation were significantly associated with symptomatic status. Among all patients identified with TB disease who had a tuberculin skin test (TST) result recorded, 27.2% were both asymptomatic and TST negative, including those with smear-positive disease.

CONCLUSIONS

Asymptomatic PTB disease is a significant clinical entity among immigrant detainees and placement in a congregate setting calls for aggressive screening to prevent transmission. Early identification, isolation, and treatment of TB disease benefit not only the health of the patient, but also the surrounding community.

A Case of Crohn's Disease with Cardiac Tamponade Caused by Tuberculous Pericarditis: Assessment of a Rare Phenomenon

A 28-year-old woman was hospitalized for cardiac tamponade caused by tuberculous pericarditis. She was taking ustekinumab (UST) for Crohn’s disease. UST is not considered to significantly increase the risk of developing serious infections, including tuberculosis. However, there is still a risk of Mycobacterium tuberculosis reactivation. Therefore, for patients on concurrent UST and antituberculosis medication, a close collaboration among specialists in infectious diseases, cardiology, and gastroenterology is necessary.

Latent tuberculosis screening before kidney transplantation in the South of Brazil

Background:

Tuberculosis (TB) is a prevalent infection after kidney transplantation (KT) in high-burden countries. Latent tuberculosis infection (LTBI) screening includes previous TB history, chest radiograph findings, and tuberculin test (TST) and/or interferon-gamma release assays (IGRAs) results. We aimed to compare our routine LTBI screening of KT candidates and living donors (LD) with their IGRA results, and evaluate if this would improve isoniazid (INH) treatment referral.

Methods:

We evaluated adult KT candidates and LD with complete routine LTBI screening and QuantiFERON-TB® Gold In-Tube (QFT) testing. Blood samples were collected from April 4th, 2014 to October 31st, 2018, with follow-up until October 31st, 2019.

Results:

There were 116 KT recipients, with 30% QFT-positive results. Positive QFT was associated with past TB history (p=0.007), positive TST (p<0.0001), residual radiographic lesions (p=0.003), and diabetes (p=0.035). There were 25 LD, 40% had positive QFT. Positive QFT was associated with a positive TST (p=0.002). Positive QFT results increased INH referral in 80%. Post-transplant TB incidence was 2.6% in a median follow-up of 2 (1-33) months. No variables were associated with post-transplant TB. TB patients had inferior, although non-significant, 5-year graft survival (66.7% vs. 76.5%) (p = 0.402).

Conclusion:

In the present study, the association of QFT to our routine LTBI screening incremented INH treatment referral, but there was still a high incidence of post-transplant TB, possibly related to other forms of infection, such as new exposure and donor transmission.

Clinical Characteristics and Risk Factors of Early-Onset Tuberculosis After Liver Transplantation

BACKGROUND

We encountered some cases of early-onset tuberculosis (TB) after liver transplant (LT), leading to further transmission to other immunocompromised patients. Therefore, we investigated the clinical characteristics and risk factors of early-onset TB after LT.

METHODS

All adult patients with TB after LT from 1996 to 2019 were retrospectively enrolled. Our hospital did not screen for latent TB infection (LTBI) in LT recipients because of concerns regarding the potential hepatotoxicity of anti-TB medication. Patients were categorized into 2 groups based on the TB onset time after LT: early-onset TB (≤2 months) and late-onset TB (>2 months).

RESULTS

Of 4301 LT recipients, 91 patients developed TB after LT (2.1%). The median time from LT to TB development was 9.4 months. Of these 91 patients, 11 were classified as having early-onset TB (12.1%). Patients with early-onset TB had a greater pretransplant TB history than patients with late-onset TB (36.4% vs 11.3%, P = .048).

CONCLUSION

This unusual early-onset TB was more common in patients with a pretransplant TB history, suggesting the possibility of missed TB or full manifestation of the indolent course of TB after LT. Therefore, LT recipients with a pretransplant TB history should undergo thorough screening for active TB and consider prophylaxis.

Immune Subtyping in Latent Tuberculosis

Latent tuberculosis infection (LTBI) poses a major roadblock in the global effort to eradicate tuberculosis (TB). A deep understanding of the host responses involved in establishment and maintenance of TB latency is required to propel the development of sensitive methods to detect and treat LTBI. Given that LTBI individuals are typically asymptomatic, it is challenging to differentiate latently infected from uninfected individuals. A major contributor to this problem is that no clear pattern of host response is linked with LTBI, as molecular correlates of latent infection have been hard to identify. In this study, we have analyzed the global perturbations in host response in LTBI individuals as compared to uninfected individuals and particularly the heterogeneity in such response, across LTBI cohorts. For this, we constructed individualized genome-wide host response networks informed by blood transcriptomes for 136 LTBI cases and have used a sensitive network mining algorithm to identify top-ranked host response subnetworks in each case. Our analysis indicates that despite the high heterogeneity in the gene expression profiles among LTBI samples, clear patterns of perturbation are found in the immune response pathways, leading to grouping LTBI samples into 4 different immune-subtypes. Our results suggest that different subnetworks of molecular perturbations are associated with latent tuberculosis.

The paradigm shift in the approach to management of latent tuberculosis infection in high tuberculosis burden countries

Introduction: Addressing the reservoir of Latent Tuberculosis Infection (LTBI) is critical to TB elimination because if left untreated LTBI can progress to active TB disease. This additional burden can prevent achieving the global targets of TB elimination. Management of LTBI has been a low priority target for National TB Elimination Programs (NTEP) due to various challenges in the field settings.Areas covered: This article reviews the most recent advances in the field of LTBI management including newer diagnostics, treatments, vaccines, programmatic challenges, and gaps and suggests a way forward that can be adopted by NTEPs for LTBI. We searched the electronic databases of PubMed, Scopus, and Web of Science for studies published between 2010 to 2020 using MeSH terms: Latent TB Diagnosis, TB preventive therapy, Vaccines, LTBI, and HIV/ COVID.Expert opinion: NTEPs of developing countries should offer a better, point-of-care diagnostic, and effective treatment for LTBI to reduce the number of new TB cases arising from people infected with M.tb. Awareness about LTBI should be increased among the health system staff and the public. More funding is needed to advance research as well as implement the newer findings in the NTEP to achieve the End TB targets by 2035.

Automatic discovery of clinically interpretable imaging biomarkers for Mycobacterium tuberculosis supersusceptibility using deep learning

BACKGROUND

Identifying which individuals will develop tuberculosis (TB) remains an unresolved problem due to few animal models and computational approaches that effectively address its heterogeneity. To meet these shortcomings, we show that Diversity Outbred (DO) mice reflect human-like genetic diversity and develop human-like lung granulomas when infected with Mycobacterium tuberculosis (M.tb) .

METHODS

Following M.tb infection, a "supersusceptible" phenotype develops in approximately one-third of DO mice characterized by rapid morbidity and mortality within 8 weeks. These supersusceptible DO mice develop lung granulomas patterns akin to humans. This led us to utilize deep learning to identify supersusceptibility from hematoxylin & eosin (H&E) lung tissue sections utilizing only clinical outcomes (supersusceptible or not-supersusceptible) as labels.

FINDINGS

The proposed machine learning model diagnosed supersusceptibility with high accuracy (91.50 ± 4.68%) compared to two expert pathologists using H&E stained lung sections (94.95% and 94.58%). Two non-experts used the imaging biomarker to diagnose supersusceptibility with high accuracy (88.25% and 87.95%) and agreement (96.00%). A board-certified veterinary pathologist (GB) examined the imaging biomarker and determined the model was making diagnostic decisions using a form of granuloma necrosis (karyorrhectic and pyknotic nuclear debris). This was corroborated by one other board-certified veterinary pathologist. Finally, the imaging biomarker was quantified, providing a novel means to convert visual patterns within granulomas to data suitable for statistical analyses.

IMPLICATIONS

Overall, our results have translatable implication to improve our understanding of TB and also to the broader field of computational pathology in which clinical outcomes alone can drive automatic identification of interpretable imaging biomarkers, knowledge discovery, and validation of existing clinical biomarkers.

FUNDING

National Institutes of Health and American Lung Association.

Evaluation of the performance of clinical predictors in estimating the probability of pulmonary tuberculosis among smear-negative cases in Northern Ethiopia: a cross-sectional study

OBJECTIVES

To evaluate the performance of the predictors in estimating the probability of pulmonary tuberculosis (PTB) when all versus only significant variables are combined into a decision model (1) among all clinical suspects and (2) among smear-negative cases based on the results of culture tests.

DESIGN

A cross-sectional study.

SETTING

Two public referral hospitals in Tigray, Ethiopia.

PARTICIPANTS

A total of 426 consecutive adult patients admitted to the hospitals with clinical suspicion of PTB were screened by sputum smear microscopy and chest radiograph (chest X-ray (CXR)) in accordance with the Ethiopian guidelines of the National Tuberculosis and Leprosy Program. Discontinuation of antituberculosis therapy in the past 3 months, unproductive cough, HIV positivity and unwillingness to give written informed consent were the basis of exclusion from the study.

PRIMARY AND SECONDARY OUTCOME MEASURES

A total of 354 patients were included in the final analysis, while 72 patients were excluded because culture tests were not done.

RESULTS

The strongest predictive variables of culture-positive PTB among patients with clinical suspicion were a positive smear test (OR 172; 95% CI 23.23 to 1273.54) and having CXR lesions compatible with PTB (OR 10.401; 95% CI 5.862 to 18.454). The regression model had a good predictive performance for identifying culture-positive PTB among patients with clinical suspicion (area under the curve (AUC) 0.84), but it was rather poor in patients with a negative smear result (AUC 0.64). Combining all the predictors in the model compared with only the independent significant variables did not really improve its performance to identify culture-positive (AUC 0.84-0.87) and culture-negative (AUC 0.64-0.69) PTB.

CONCLUSIONS

Our finding suggests that predictive models based on clinical variables will not be useful to discriminate patients with culture-negative PTB from patients with culture-positive PTB among patients with smear-negative cases.

Epidemiology of tuberculosis in Sabah, Malaysia, 2012-2018

BACKGROUND

Tuberculosis (TB) is of high public health importance in Malaysia. Sabah State, located on the island of Borneo, has previously reported a particularly high burden of disease and faces unique contextual challenges compared with peninsular Malaysia. The aim of this study is to describe the epidemiology of TB in Sabah to identify risk groups and hotspots of TB transmission.

METHODS

We conducted a retrospective review of TB cases notified in Sabah, Malaysia, between 2012 and 2018. Using data from the state's 'myTB' notification database, we calculated the case notification rate and described trends in the epidemiology, diagnostic practices and treatment outcomes of TB in Sabah within this period. The Chi-squared test was used for determining the difference between two proportions.

RESULTS

Between 2012 and 2018 there were 33 193 cases of TB reported in Sabah (128 cases per 100 000 population). We identified several geographic hotspots, including districts with > 200 cases per 100 000 population per year. TB rates increased with age and were highest in older males. Children < 15 years accounted for only 4.6% of cases. Moderate or advanced disease on chest X-ray and sputum smear positivity was high (58 and 81% of cases respectively), suggesting frequent late diagnosis. Multi-drug resistant (MDR) TB prevalence was low (0.3% of TB cases), however, rapid diagnostic test coverage was low (1.2%) and only 18% of all cases had a positive culture result. Treatment success was 83% (range: 81-85%) in those with drug-sensitive TB and 36% (range: 25-45%) in cases of MDR-TB.

CONCLUSION

Between 2012 and 2018, TB notifications in Sabah State equated to 20% of Malaysia's total TB notifications, despite Sabah representing only 10% of Malaysia's population. We found hotspots of TB in urbanised population hubs and points of migration, as well as evidence of late presentation and diagnosis. Ensuring universal health coverage and expansion of GeneXpert® coverage is recommended to reduce barriers to care and early diagnosis and treatment for TB.

Effects of Pregnancy and Isoniazid Preventive Therapy on M. tuberculosis Interferon Gamma Response Assays in Women with HIV

BACKGROUND

Pregnancy is accompanied by immune suppression. We hypothesized that M. tuberculosis-specific inflammatory responses used to identify latent tuberculosis infection (LTBI) lose positivity during pregnancy. We also hypothesized that isoniazid preventive therapy (IPT) may revert LTBI diagnoses because of its sterilizing activity.

METHODS

944 women with HIV participating in a randomized, double-blind, placebo-controlled study comparing 28 weeks of IPT antepartum versus postpartum, were tested by QuantiFERON-gold-in-tube (QGIT) antepartum and by QGIT and tuberculin skin test (TST) at delivery and postpartum. Serial QGIT positivity was assessed by logistic regression using generalized estimating equations.

RESULTS

From entry to delivery, 68 (24%) of 284 QGIT-positive women (24%) reverted to QGIT-negative or indeterminate. Of these, 42 (62%) recovered QGIT positivity postpartum. The loss of QGIT positivity during pregnancy was explained by decreased IFNγ production in response to TB antigen and/or mitogen. At delivery, QGIT identified 205 and TST 113 women with LTBI. Corresponding numbers postpartum were 229 and 122 women. QGIT and TST kappa agreement coefficients were 0.4 and 0.5, respectively. Among QGIT-positive women antepartum or at delivery, 34 (12%) reverted to QGIT-negative after IPT. There were no differences between women who initiated IPT antepartum or postpartum.

CONCLUSIONS

Decreased IFNγ responses in pregnancy reduced QGIT positivity, suggesting that this test cannot reliably rule out LTBI during pregnancy. TST was less affected by pregnancy, but had lower positivity compared to QGIT at all time points. IPT was associated with loss of QGIT positivity, the potential clinical consequences of which need to be investigated.

Tuberculosis-HIV Co-Infection: Progress and Challenges After Two Decades of Global Antiretroviral Treatment Roll-Out

Despite wide antiretroviral scale-up during the past two decades resulting in declining new infections and mortality globally, HIV-associated tuberculosis remains as a major public health concern. Tuberculosis is the leading HIV-associated opportunistic infection and the main cause of death globally and, particularly, in resource-limited settings. Several challenges exist regarding diagnosis, global implementation of latent tuberculosis treatment, management of active tuberculosis, delivery of optimal patient-centered TB and HIV prevention and care in high burden countries. In this article we review the advances on pathogenesis, diagnosis, and treatment after nearly two decades of global roll-out of antiretroviral therapy and discuss the current challenges for the global control of tuberculosis-HIV co-infection.

Modeling Missing Cases and Transmission Links in Networks of Extensively Drug-Resistant Tuberculosis in KwaZulu-Natal, South Africa

Patterns of transmission of drug-resistant tuberculosis (TB) remain poorly understood, despite over half a million incident cases worldwide in 2017. Modeling TB transmission networks can provide insight into drivers of transmission, but incomplete sampling of TB cases can pose challenges for inference from individual epidemiologic and molecular data. We assessed the effect of missing cases on a transmission network inferred from Mycobacterium tuberculosis sequencing data on extensively drug-resistant TB cases in KwaZulu-Natal, South Africa, diagnosed in 2011-2014. We tested scenarios in which cases were missing at random, missing differentially by clinical characteristics, or missing differentially by transmission (i.e., cases with many links were under- or oversampled). Under the assumption that cases were missing randomly, the mean number of transmissions per case in the complete network needed to be larger than 20, far higher than expected, to reproduce the observed network. Instead, the most likely scenario involved undersampling of high-transmitting cases, and models provided evidence for super-spreading. To our knowledge, this is the first analysis to have assessed support for different mechanisms of missingness in a TB transmission study, but our results are subject to the distributional assumptions of the network models we used. Transmission studies should consider the potential biases introduced by incomplete sampling and identify host, pathogen, or environmental factors driving super-spreading.

Guidance for Studies Evaluating the Accuracy of Biomarker-Based Nonsputum Tests to Diagnose Tuberculosis

The World Health Organization's (WHO) "End TB" strategy calls for development and implementation of novel tuberculosis (TB) diagnostics. Sputum-based diagnostics are challenging to implement and often less sensitive in high-priority populations. Nonsputum, biomarker-based tests may facilitate TB testing at lower levels of the healthcare system, accelerate treatment initiation, and improve outcomes. We provide guidance on the design of diagnostic accuracy studies evaluating nonsputum, biomarker-based tests within the context of WHO's target product profile for such tests. Study designs should account for the intended use when choosing the study population, setting, and reference standards. Although adults with respiratory symptoms may be an initial target population, other high-priority populations regardless of symptoms-including people living with human immunodeficiency virus, those unable to produce sputum samples or with extrapulmonary TB, household contacts, and children-should be considered. Studies beyond diagnostic accuracy that evaluate feasibility and population-level impacts are also needed. A biomarker-based diagnostic may be critical to ending the TB epidemic, but requires appropriate validation before implementation.

Latent tuberculosis infection: recent progress and challenges in South Korea

Management of latent tuberculosis infection (LTBI) is a critical element in the elimination of tuberculosis (TB). However, the low positive predictive value of the current diagnostic tests and the low acceptance and completion rate of the isoniazid- based regimen are major barriers to the implementation and scale-up of programmatic management of LTBI. In the past decade, there has been some progress in the conception, diagnosis, and treatment of LTBI. LTBI is now understood as a dynamic spectrum rather than the traditional binary distinction between active and latent TB. New insight into LTBI has led to a renewed interest in incipient TB, which would be a potential target for developing new diagnostics and therapeutics of LTBI. Recent studies showed that host transcriptomic signatures could be a potential biomarker for incipient TB. The new shorter rifamycin-based regimens have shown comparable efficacy, but better completion rate and safety compared to the isoniazid-based regimen. In South Korea, LTBI management has been expanded and integrated into key elements of the National Tuberculosis Control Program. For the programmatic approach to LTBI management, the following challenges need to be addressed; target group selection, treatment-related interventions, monitoring and surveillance system, and extending the plan for vulnerable groups.

Strategies for ending tuberculosis in the South-East Asian Region: A modelling approach

Background & objectives:

To support recent political commitments to end tuberculosis (TB) in the World Health Organization South-East Asian Region (SEAR), there is a need to understand by what measures, and with what investment, these goals could be reached. These questions were addressed by using mathematical models of TB transmission by doing the analysis on a country-by-country basis in SEAR.

Methods:

A dynamical model of TB transmission was developed, in consultation with each of the 11 countries in the SEAR. Three intervention scenarios were examined: (i) strengthening basic TB services (including private sector engagement), (ii) accelerating TB case-finding and notification, and (iii) deployment of a prognostic biomarker test by 2025, to guide mass preventive therapy of latent TB infection. Each scenario was built on the preceding ones, in successive combination.

Results:

Comprehensive improvements in basic TB services by 2020, in combination with accelerated case-finding to increase TB detection by at least two-fold by 2020, could lead to a reduction in TB incidence rates in SEAR by 67.3 per cent [95% credible intervals (CrI) 65.3-69.8] and TB deaths by 80.9 per cent (95% CrI 77.9-84.7) in 2035, relative to 2015. These interventions alone would require an additional investment of at least US$ 25 billion. However, their combined effect is insufficient to reach the end TB targets of 80 per cent by 2030 and 90 per cent by 2035. Model projections show how additionally, deployment of a biomarker test by 2025 could end TB in the region by 2035. Targeting specific risk groups, such as slum dwellers, could mitigate the coverage needed in the general population, to end TB in the Region.

Interpretation & conclusions:

While the scale-up of currently available strategies may play an important role in averting TB cases and deaths in the Region, there will ultimately be a need for novel, mass preventive measures, to meet the end TB goals. Achieving these impacts will require a substantial escalation in funding for TB control in the Region.

Tuberculosis-HIV Co-Infection: Progress and Challenges After Two Decades of Global Antiretroviral Treatment Roll-Out

Despite wide antiretroviral scale-up during the past two decades resulting in declining new infections and mortality globally, HIV-associated tuberculosis remains as a major public health concern. Tuberculosis is the leading HIV-associated opportunistic infection and the main cause of death globally and, particularly, in resource-limited settings. Several challenges exist regarding diagnosis, global implementation of latent tuberculosis treatment, management of active tuberculosis, delivery of optimal patient-centered TB and HIV prevention and care in high burden countries. In this article we review the advances on pathogenesis, diagnosis, and treatment after nearly two decades of global roll-out of antiretroviral therapy and discuss the current challenges for the global control of tuberculosis-HIV co-infection.

An Inflammatory Story: Antibodies in Tuberculosis Comorbidities

Mycobacterium tuberculosis (Mtb) resides in a quarter of the world's population and is the causative agent for tuberculosis (TB), the most common infectious reason of death in humans today. Although cellular immunity has been firmly established in the control of Mtb, there is growing evidence that antibodies may also modulate the infection. More specifically, certain antibody features are associated with inflammation and are divergent in different states of human infection and disease. Importantly, TB impacts not just the healthy but also those with chronic conditions. While HIV represents the quintessential comorbid condition for TB, recent epidemiological evidence shows that additional chronic conditions such as diabetes and kidney disease are rising. In fact, the prevalence of diabetes as a comorbid TB condition is now higher than that of HIV. These chronic diseases are themselves independently associated with pro-inflammatory immune states that encompass antibody profiles. This review discusses isotypes, subclasses, post-translational modifications and Fc-mediated functions of antibodies in TB infection and in the comorbid chronic conditions of HIV, diabetes, and kidney diseases. We propose that inflammatory antibody profiles, which are a marker of active TB, may be an important biomarker for detection of TB disease progression within comorbid individuals. We highlight the need for future studies to determine which inflammatory antibody profiles are the consequences of comorbidities and which may potentially contribute to TB reactivation.

Diagnostic Accuracy of Interleukin-27 in Bronchoalveolar Lavage Fluids for Pulmonary Tuberculosis

Background

The World Health Organization states that China had 0.9 million cases of tuberculosis in 2017, accounting for 9% of cases globally. Despite a decrease in the incidence and mortality of tuberculosis in China over time, development in choosing the appropriate prevention and control of TB is required.

Purpose

The aim of this study was to evaluate the diagnostic significance of interleukin-27 in bronchoalveolar lavage fluids for pulmonary tuberculosis.

Materials and methods

Eventually, 107 bronchoalveolar lavage fluids from patients were included in this study. The concentrations of interleukin-27 and adenosine deaminase were determined in bronchoalveolar lavage fluids using enzyme-linked immunosorbent assay.

Results

It was found that the concentrations of interleukin-27 in bronchoalveolar lavage fluids of sputum-positive pulmonary tuberculosis group were significantly higher than those in sputum-negative pulmonary tuberculosis, lung cancer, and previous pulmonary tuberculosis groups, respectively (all P<0.001). Interleukin-27 levels in bronchoalveolar lavage fluids could be used for diagnostic purpose for pulmonary tuberculosis, with the cutoff value of 7.867 pg/mL; interleukin-27 had a sensitivity of 68.8% and specificity of 100% for the differential diagnosis of pulmonary tuberculosis (sputum-negative and sputum-positive PTB) from lung cancer. And with the cutoff value of 6.012 pg/mL, IL-27 had sensitivity and specificity of both 100% for the differential diagnosis of PTB from previous PTB. The risk of pulmonary tuberculosis was positively associated with the concentrations of interleukin-27 and adenosine deaminase in bronchoalveolar lavage fluids.

Conclusion

Interleukin-27 in bronchoalveolar lavage fluids is a sensitive and specific biomarker for the differential diagnosis of pulmonary tuberculosis from lung cancer and previous pulmonary tuberculosis.

Host Gene Expression Kinetics During Treatment of Tuberculosis in HIV-Coinfected Individuals Is Independent of Highly Active Antiretroviral Therapy

Background

Limitations in diagnostic tools to discriminate between active tuberculosis and latent Mycobacterium tuberculosis infection and for monitoring antituberculosis treatment responses are major challenges in tuberculosis control, especially in human immunodeficiency virus (HIV)-coinfected individuals.

Methods

Expression levels of 105 immune-related genes were determined in 131 HIV-infected patients with active tuberculosis (n = 48), patients with latent M. tuberculosis infection (LTBI; n = 37), and controls with no M. tuberculosis infection (n = 46) in Addis Ababa, Ethiopia, using focused gene expression profiling with a dual-color reverse-transcription multiplex ligation-dependent probe amplification assay.

Results

Within the cohort of HIV-positive subjects, the expression profiles of 7 genes at baseline (FCGR1A, RAB24, TLR1, TLR4, MMP9, NLRC4, and IL1B) could accurately discriminate between active tuberculosis and both latent and no M. tuberculosis infection, largely independently of (in)eligibility for highly active antiretroviral therapy (HAART). Six months after antituberculosis treatment, biomarker profiles of patients with tuberculosis became indistinguishable from those of patients with LTBI and controls. Importantly, host gene expression kinetics during antituberculosis treatment in HIV-coinfected individuals was found to be independent of HAART use.

Conclusions

Blood transcriptomic profiles can potentially be used as biomarkers to discriminate the different clinical stages of tuberculosis in HIV-coinfected individuals and to monitor tuberculosis treatment responses in both HAART recipients and untreated individuals.

The evolving research agenda for paediatric tuberculosis infection

Following exposure to tuberculosis and subsequent infection, children often progress to tuberculosis disease more rapidly than adults. And yet the natural history of tuberculosis in children, as a continuum from exposure to infection and then to disease, is poorly understood. Children are rarely diagnosed with tuberculosis infection in routine care in international settings and few receive tuberculosis infection treatment. In this Personal View, we review the most up-to-date knowledge in three areas of childhood tuberculosis infection-namely, pathophysiology, diagnosis, and treatment. We then outline what is missing in each of these three areas to generate a priority research agenda. Finally, we suggest potential study designs that might answer these questions. Understanding of pathophysiology could be improved through animal models, laboratory studies assessing the immunological responses of blood or respiratory samples to Mycobacterium spp in vitro, as well as investigating immune responses in children exposed to tuberculosis. Identification of children with sub-clinical disease and at high risk of progression to clinically overt disease, would allow treatment to be targeted at those most likely to benefit. Optimisation and discovery of novel treatments for tuberculosis infection in children should account for mechanisms of action of tuberculosis drugs, as well as child-specific factors including pharmacokinetics and appropriate formulations. To conduct these studies, a change in mindset is required, with a recognition that the diagnosis and treatment of tuberculosis infection in children is a necessary component in addressing the overall tuberculosis epidemic. Collaboration between stakeholders will be required and funding will need to increase, both for research and implementation. The consequences of inaction, however, will lead to further decades of children suffering from what should increasingly be recognised as a preventable disease.

Combining urine lipoarabinomannan with antibody detection as a simple non-sputum-based screening method for HIV-associated tuberculosis

Background

Simple methods for the accurate triaging and screening of HIV-associated tuberculosis (TB) are urgently needed. We hypothesized that combining serum antibody with urine lipoarabinomannan (U-LAM) detection can improve the detection of HIV-associated TB.

Methods

We performed a case-control study with sampling from a prospective study of South African HIV-infected subjects who were screened for TB prior to initiating antiretroviral therapy. Sera from all available TB cases (n = 74) and randomly selected non-TB controls (n = 30), all tested for U-LAM, sputum microscopy, GeneXpert, and cultures, were evaluated for antibodies to LAM and arabinomannan (AM). Diagnostic logistic regression models for TB were developed based on the primary test results and the additive effect of antibodies with leave-one-out cross-validation.

Results

Antibody responses to LAM and AM correlated strongly (p<0.0001), and IgG and IgM reactivities were significantly higher in TB than non-TB patients (p<0.0001). At 80% specificity, the target specificity for a non-sputum-based simple triage/screening test determined by major TB stakeholders, combining U-LAM with IgG detection significantly increased the sensitivity for HIV-associated TB to 92% compared to 30% for U-LAM alone (p<0.001). Sputum microscopy combined with IgG detection increased sensitivity to 88% compared to 31% for microscopy alone, and Xpert with IgG increased sensitivity to 96% and 99% compared to 57% for testing one, and 70% for testing two sputa with Xpert alone, respectively.

Conclusion

Combining U-LAM with serum antibody detection could provide a simple low-cost method that meets the requirements for a non-sputum-based test for the screening of HIV-associated TB.

Advances in Cardiovascular Disease Lipid Research Can Provide Novel Insights Into Mycobacterial Pathogenesis

Cardiovascular disease (CVD) is the leading cause of death in industrialized nations and an emerging health problem in the developing world. Systemic inflammatory processes associated with alterations in lipid metabolism are a major contributing factor that mediates the development of CVDs, especially atherosclerosis. Therefore, the pathways promoting alterations in lipid metabolism and the interplay between varying cellular types, signaling agents, and effector molecules have been well-studied. Mycobacterial species are the causative agents of various infectious diseases in both humans and animals. Modulation of host lipid metabolism by mycobacteria plays a prominent role in its survival strategy within the host as well as in disease pathogenesis. However, there are still several knowledge gaps in the mechanistic understanding of how mycobacteria can alter host lipid metabolism. Considering the in-depth research available in the area of cardiovascular research, this review presents an overview of the parallel areas of research in host lipid-mediated immunological changes that might be extrapolated and explored to understand the underlying basis of mycobacterial pathogenesis.

Designing tuberculosis vaccine efficacy trials - lessons from recent studies

INTRODUCTION

Tuberculosis (TB) is the leading infectious killer globally and new TB vaccines will be crucial to ending the epidemic. Since the introduction in 1921 of the only currently licensed TB vaccine, BCG, very few novel vaccine candidates or strategies have advanced into clinical efficacy trials. Areas covered: Recently, however, two TB vaccine efficacy trials with novel designs have reported positive results and are now driving new momentum in the field. They are the first Prevention of Infection trial, evaluating the H4:IC31 candidate or BCG revaccination in high-risk adolescents and a Prevention of Disease trial evaluating the M72/AS01_E candidate in M.tuberculosis-infected, healthy adults. These trials are briefly reviewed, and lessons learned are proposed to help inform the design of future efficacy trials. The references cited were chosen by the author based on PubMed searches to provide context for the opinions expressed in this Perspective article. Expert opinion: The opportunities created by these two trials for gaining critically important knowledge are game-changing for TB vaccine development. Their results clearly establish feasibility in the relatively near term of developing novel, effective vaccines that could be crucial to ending the TB epidemic.

Factors Associated With Sputum Culture-Negative vs Culture-Positive Diagnosis of Pulmonary Tuberculosis

IMPORTANCE

Recognition of active tuberculosis (TB) in its earliest stages could reduce morbidity and prevent advancement to transmissible disease. Little is published about the occurrence and presentation of sputum culture-negative pulmonary TB (PTB), an early paucibacillary but often underrecognized disease state.

OBJECTIVE

To assess differences between culture-negative and culture-positive PTB regarding occurrence, clinical presentation, radiographic findings, demographics, and comorbidities.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional study in which surveillance data of adult patients with PTB reported to the New York City Department of Health in New York, New York, from 2011 through 2013, ie, years for which demographic, clinical, and radiographic data were collected. Patients were aged 18 years or older, had signs of pulmonary disease, and had mycobacterial sputum culture results; those with HIV coinfection or a TB diagnosis within 2 years prior to presentation were excluded. Culture-negative PTB was defined as clinical and radiographic presentation consistent with TB, 3 negative results on sputum culture, and improvement with antituberculous treatment. The analyses were performed between 2015 and 2016; notably, the proportion of reported patients with culture-negative PTB has remained consistent during the past 2 decades.

MAIN OUTCOMES AND MEASURES

The occurrence of culture-negative PTB among all patients with PTB was calculated, and demographics, comorbidities, symptoms, and radiographic findings were compared between culture-negative and culture-positive PTB.

RESULTS

Of the 796 patients with PTB (median [interquartile range] age, 41 [29-54] years; 499 [63%] men) who met criteria for analysis, 116 (15%) had negative results on sputum culture. Patients with culture-negative PTB compared with culture-positive PTB were less frequently male (53% vs 64%; P = .03) and presented with a significantly lower frequency of cough (68% vs 89%; P < .001), weight loss (39% vs 51%; P = .03), and cavitation on both chest radiograph (7% vs 28%; P < .001) and chest computed tomographic scan (26% vs 59%; P < .001).

CONCLUSIONS AND RELEVANCE

Given the lack of criterion-standard test confirmation and the relative paucity of symptoms and radiological abnormalities, culture-negative PTB is likely underdiagnosed and its occurrence underestimated globally. Awareness of these findings, enhanced diagnostic approaches, and, ideally, better biomarkers could improve detection and treatment of this early disease and reduce the development of transmissible TB.

Subclinical tuberculosis among adults with HIV: clinical features and outcomes in a South African cohort

BACKGROUND

Subclinical tuberculosis is an asymptomatic disease phase with important relevance to persons living with HIV. We describe the prevalence, clinical characteristics, and risk of mortality for HIV-infected adults with subclinical tuberculosis.

METHODS

Untreated adults with HIV presenting for outpatient care in Durban, South Africa were screened for tuberculosis-related symptoms and had sputum tested by acid-fast bacilli smear and tuberculosis culture. Active tuberculosis and subclinical tuberculosis were defined as having any tuberculosis symptom or no tuberculosis symptoms with culture-positive sputum. We evaluated the association between tuberculosis disease category and 12-month survival using Cox regression, adjusting for age, sex, and CD4 count.

RESULTS

Among 654 participants, 96 were diagnosed with active tuberculosis disease and 28 with subclinical disease. The median CD4 count was 68 (interquartile range 39-161) cells/mm3 in patients with active tuberculosis, 136 (72-312) cells/mm3 in patients with subclinical disease, and 249 (125-394) cells/mm3 in those without tuberculosis disease (P < 0.001). The proportion of smear positive cases did not differ significantly between the subclinical (29%) and active tuberculosis groups (14%, P 0.08). Risk of mortality was not increased in individuals with subclinical tuberculosis relative to no tuberculosis (adjusted hazard ratio 0.84, 95% confidence interval 0.26-2.73).

CONCLUSIONS

Nearly one-quarter of tuberculosis cases among HIV-infected adults were subclinical, which was characterized by an intermediate degree of immunosuppression. Although there was no significant difference in survival, anti-tuberculous treatment of subclinical cases was common.

TRIAL REGISTRATION

Prospectively registered on ClinicalTrials.gov , NCT01188941 (August 26, 2010).