Latent tuberculosis infection--Revisiting and revising concepts

Biomarkers of cell-mediated immunity to bovine tuberculosis

Whole blood based assays, particularly interferon gamma (IFN-γ) release assays (IGRAs), are used for the diagnosis of both bovine and human tuberculosis (TB). The aim of the current study was to evaluate a panel of cytokines and chemokines for potential use as diagnostic readouts indicative of Mycobacterium bovis (M. bovis) infection in cattle. A gene expression assay was used to determine the kinetics of the response to M. bovis purified protein derivative and a fusion protein consisting of ESAT-6, CFP10, and Rv3615c upon aerosol infection with ∼10⁴ cfu of M. bovis. The panel of biomarkers included: IFN-γ, CXCL9, CXCL10, CCL2, CCL3, TNF-α, IL-1α, IL-1β, IL-1Ra, IL-22, IL-21 and IL-13. Protein levels of IFN-γ, CXCL9, and CXCL10 were determined by ELISA. Findings suggest that CXCL9, CXCL10, IL-21, IL-13, and several acute phase cytokines may be worth pursuing as diagnostic biomarkers of M. bovis infection in cattle.

Partitioning the risk of tuberculosis transmission in household contact studies

Household contact studies of tuberculosis (TB) are a common way to study disease transmission dynamics. However these studies lack a mechanism for accounting for community transmission, which is known to be significant, particularly in high burden settings. We illustrate a statistical approach for estimating both the correlates with transmission of TB in a household setting and the probability of community transmission using a modified Bayesian mixed-effects model. This is applied to two household contact studies in Vitória, Brazil from 2008-2013 and Kampala, Uganda from 1995-2004 that enrolled households with an individual that was recently diagnosed with pulmonary TB. We estimate the probability of community transmission to be higher in Uganda (ranging from 0.21 to 0.69, depending on HHC age and HIV status of the index case) than in Brazil (ranging from 0.13 for young children to 0.50 in adults). These estimates are consistent with a higher overall burden of disease in Uganda compared to Brazil. Our method also estimates an increasing risk of community-acquired TB with age of the household contact, consistent with existing literature. This approach is a useful way to integrate the role of the community in understanding TB disease transmission dynamics in household contact studies.

The Presence of Cough and Tuberculosis: Active Case Finding Outcomes in the Philippines

The results of a tuberculosis (TB) active case finding (ACF) program, implemented by International Care Ministries (ICM) in the Philippines, were examined to understand how the presence of physical symptoms might influence ACF outcomes among extreme low-income Filipinos. ICM health staff implemented symptom screening in villages and suspected cases were referred to the closest rural health unit (RHU) for TB testing. ACF was carried out in Mindanao and the Visayas, across 16 different provinces. All participants were interviewed pre/postprogram, and screening outcomes were collected. A multilevel regression model was constructed to explore the effect of factors on the likelihood of getting tested. A total of 4635 individuals were screened; 1290 (27.8%) were symptom positive and referred. From those referred, 336 (7.2%) were tested for TB and 53 (1.1%) were TB positive. “Cough for more than two weeks” was associated with a 1.09 (95% CI 1.01, 1.15) times increase in likelihood of getting tested. The finding that the presence of cough is associated with higher rate of testing suggests that individuals in these settings might not know or believe that the lack of cough does not equate to lack of TB infection. While technologies and screening algorithms give us the ability to refine the ‘supply' side of the TB screening, addressing the knowledge gap should improve ‘demand'.

Farmer and veterinarian attitudes towards the risk of zoonotic Mycobacterium bovis infection in Northern Ireland

Based on a qualitative social science research methodology using semi-structured interviews, this paper examines the attitudes of farmers and veterinarians in Northern Ireland around the risk of acquiring tuberculosis caused by Mycobacterium bovis from infected cattle and drinking raw milk. This region has traditionally had one of the highest rates of bovine tuberculosis in the United Kingdom and among the highest in Europe. The research finds that the risk is often downplayed and considered so rare that it is no longer a significant public health risk due to the pasteurisation of milk and intensive surveillance on farms through systematic testing and removal of positive animals, as evidenced by the low recorded human incidence. Although the incidence of tuberculosis in humans caused by M bovis is only around 1% of all annual human tuberculosis cases, this paper argues that M bovis may be underestimated as a human pathogen and makes the case for a renewed perspective. Discourses surrounding the disease may need to be re-orientated to remind relevant stakeholders that human infection with M bovis is a hazard that needs to be treated with more caution on the front line of control.

Conformational Switch Driven Membrane Pore Formation by Mycobacterium Secretory Protein MPT63 Induces Macrophage Cell Death

Virulent Mycobacterium tuberculosis (MTB) strains cause cell death of macrophages (Mϕ) inside TB granuloma using a mechanism which is not well understood. Many bacterial systems utilize toxins to induce host cell damage, which occurs along with immune evasion. These toxins often use chameleon sequences to generate an environment-sensitive conformational switch, facilitating the process of infection. The presence of toxins is not yet known for MTB. Here, we show that MTB-secreted immunogenic MPT63 protein undergoes a switch from β-sheet to helix in response to mutational and environmental stresses. MPT63 in its helical form creates pores in both synthetic and Mϕ membranes, while the native β-sheet protein remains inert toward membrane interactions. Using fluorescence correlation spectroscopy and atomic force microscopy, we show further that the helical form undergoes self-association to produce toxic oligomers of different morphology. Trypan blue and flow cytometry analyses reveal that the helical state can be utilized by MTB for killing Mϕ cells. Collectively, our study emphasizes for the first time a toxin-like behavior of MPT63 induced by an environment-dependent conformational switch, resulting in membrane pore formation by toxic oligomers and Mϕ cell death.

A rare case of multi-focal human TB after BCG instillation for non-muscle-invasive bladder cancer

OBJECTIVE

To describe a left epididymitis and para-aortical involvement caused by Mycobacterium tuberculosis hominis reactivation after bacillus Calmette-Guérin instillation for non-muscle-invasive bladder cancer.

PATIENT AND METHODS

A Caucasian male, aged 76 years, exposed to bacillus Calmette-Guérin for a high-grade non-muscle-invasive bladder cancer in 2015, reported painful and progressive left scrotal swelling with purulent discharge from a cutaneous fistulous track that yielded, on liquid culture, a pan-susceptible Mycobacterium tuberculosis hominis strain. Moreover, after 6 months of anti-tuberculosis treatment, an abdominal peri-aortic mass, sized 4 cm, was found and a surgical biopsy showed necrotizing granulomas; however, although smear microscopy and Xpert MTB/Rif™ performed on fresh biopsy sample were positive, liquid cultures resulted negative, indicating treatment efficacy.

RESULTS

Numerous peculiar and multi-organ involvement due to BCGitis after intravesical immunotherapy have been previously described, including 17 scientific articles about epididymitis, however, no reports so far showed reactivation of Mycobacterium tuberculosis hominis after bacillus Calmette-Guérin treatment.

CONCLUSION

Although BCGitis is more prevalent in patients undergoing bacillus Calmette-Guérin instillation for non-muscle-invasive bladder cancer, tuberculosis by other species of Mycobacterium tuberculosis should be always ruled out by molecular and conventional microbiology in patients with a history of Mycobacterium tuberculosis hominis exposure.

Updates on 18F-FDG-PET/CT as a clinical tool for tuberculosis evaluation and therapeutic monitoring

Tuberculosis (TB) is currently the world's leading cause of infectious mortality. The complex immune response of the human body to Mycobacterium tuberculosis (M.tb) results in a wide array of clinical manifestations, thus the clinical and radiological diagnosis can be challenging. ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG-PET) scan with/without computed tomography (CT) component images the whole body and provides a metabolic map of the infection, enabling clinicians to assess the disease burden. ¹⁸F-FDG-PET/CT scan is particularly useful in detecting the disease in previously unknown sites, and allows the most appropriate site of biopsy to be selected. ¹⁸F-FDG-PET/CT is also very valuable in assessing early disease response to therapy, and plays an important role in cases where conventional microbiological methods are unavailable and for monitoring response to therapy in cases of multidrug-resistant TB or extrapulmonary TB. ¹⁸F-FDG-PET/CT cannot reliably differentiate active TB lesion from malignant lesions and false positives can also be due to other infective or inflammatory conditions. ¹⁸F-FDG PET is also unable to distinguish tuberculous lymphadenitis from metastatic lymph node involvement. The lack of specificity is a limitation for ¹⁸F-FDG-PET/CT in TB management.

Further evidence of Mycobacterium tuberculosis in the sputum of culture-negative pulmonary tuberculosis suspects using an ultrasensitive molecular assay

BACKGROUND

Rapid diagnosis of pulmonary tuberculosis (TB) is critical to TB control. However, many patients with paucibacillary TB disease remain undiagnosed. Current TB elimination goals require new tools to diagnose early disease. We evaluated performance of the Totally Optimized PCR (TOP) TB assay, a novel ultrasensitive molecular test.

METHODS

We assessed analytical specificity against nontuberculous mycobacteria (NTM), and estimated the diagnostic accuracy of TOP in a pilot study in Brazil (n = 46) and a cross-sectional study in Boston (n = 60). We compared TOP results to culture and a composite reference standard (CRS).

RESULTS

TOP exhibited no cross-reactivity against NTM. We tested 132 respiratory specimens from 106 patients with suspected pulmonary TB. The pilot demonstrated feasibility and 100% (95% CI 85-100) sensitivity in predominantly smear-positive specimens; TOP's specificity against solid media culture was low (58%, 37-77) but improved against a CRS (93%, 68-100). Similarly, when using the CRS in the Boston study, TOP (88%, 1-99) had greater sensitivity than solid or liquid media culture (25%, 3-65) and similar specificity (both 100%, 93-100).

CONCLUSIONS

The TOP assay enables detection of M. tuberculosis in culture-negative paucibacillary disease. While the use of TOP for the diagnosis of paucibacillary disease will require further clinical validation, its high sensitivity indicate a more immediate utility as a rule out TB test.

Cat and Mouse: HIV Transcription in Latency, Immune Evasion and Cure/Remission Strategies

There is broad scientific and societal consensus that finding a cure for HIV infection must be pursued. The major barrier to achieving a cure for HIV/AIDS is the capacity of the HIV virus to avoid both immune surveillance and current antiretroviral therapy (ART) by rapidly establishing latently infected cell populations, termed latent reservoirs. Here, we provide an overview of the rapidly evolving field of HIV cure/remission research, highlighting recent progress and ongoing challenges in the understanding of HIV reservoirs, the role of HIV transcription in latency and immune evasion. We review the major approaches towards a cure that are currently being explored and further argue that small molecules that inhibit HIV transcription, and therefore uncouple HIV gene expression from signals sent by the host immune response, might be a particularly promising approach to attain a cure or remission. We emphasize that a better understanding of the game of "cat and mouse" between the host immune system and the HIV virus is a crucial knowledge gap to be filled in both cure and vaccine research.

Biomarkers for tuberculosis: the case for lipoarabinomannan

Tuberculosis (TB) is considered the most onerous of infectious diseases according to recent reports from the World Health Organization. Available tests for TB diagnosis present severe limitations, and a reliable point-of-care (POC) diagnostic test does not exist. Neither is there a test to discern between the different stages of TB, and in particular to predict which patients with Mycobacterium tuberculosis infection and no clinical signs are more at risk of advancing to overt disease. We here review the usefulness of mycobacterial lipoarabinomannan (LAM) as a diagnostic marker for active and latent TB and, also, aspects of the immune response to LAM relevant to such tests. There is a high potential for urinary LAM-based POC tests for the diagnosis of active TB. Some technical challenges to optimised sensitivity of the test will be detailed. A method to quantify LAM in urine or serum should be further explored as a test of treatment effect. Recent data on the immune response to LAM suggest that markers for host response to LAM should be investigated for a prognostic test to recognise individuals at the greatest risk of disease activation.

There is a high potential for a urinary LAM-based point-of-care test to diagnose TB. Markers for host response to LAM should be explored to identify those at highest risk of developing active TB.http://ow.ly/FyCs30n4uFE

The blood transcriptional signature for active and latent tuberculosis

BACKGROUND

Although the incidence of tuberculosis (TB) has dropped substantially, it still is a serious threat to human health. And in recent years, the emergence of resistant bacilli and inadequate disease control and prevention has led to a significant rise in the global TB epidemic. It is known that the cause of TB is Mycobacterium tuberculosis infection. But it is not clear why some infected patients are active while others are latent.

METHODS

We analyzed the blood gene expression profiles of 69 latent TB patients and 54 active pulmonary TB patients from GEO (Transcript Expression Omnibus) database.

RESULTS

By applying minimal redundancy maximal relevance and incremental feature selection, we identified 24 signature genes which can predict the TB activation. The support vector machine predictor based on these 24 genes had a sensitivity of 0.907, specificity of 0.913, and accuracy of 0.911, respectively. Although they need to be validated in a large independent dataset, the biological analysis of these 24 genes showed great promise.

CONCLUSION

We found that cytokine production was a key process during TB activation and genes like CYBB, TSPO, CD36, and STAT1 worth further investigation.

Tuberculosis preventive treatment: the next chapter of tuberculosis elimination in India

The End TB Strategy envisions a world free of tuberculosis—zero deaths, disease and suffering due to tuberculosis by 2035. This requires reducing the global tuberculosis incidence from >1250 cases per million people to <100 cases per million people within the next two decades. Expanding testing and treatment of tuberculosis infection is critical to achieving this goal. In high-burden countries, like India, the implementation of tuberculosis preventive treatment (TPT) remains a low priority. In this analysis article, we explore potential challenges and solutions of implementing TPT in India. The next chapter in tuberculosis elimination in India will require cost-effective and sustainable interventions aimed at tuberculosis infection. This will require constant innovation, locally driven solutions to address the diverse and dynamic tuberculosis epidemiology and persistent programme monitoring and evaluation. As new tools, regimens and approaches emerge, midcourse adjustments to policy and practice must be adopted. The development and implementation of new tools and strategies will call for close collaboration between local, national and international partners—both public and private—national health authorities, non-governmental organisations, research community and the diagnostic and pharmaceutical industry. Leading by example, India can contribute to global knowledge through operational research and programmatic implementation for combating tuberculosis infection.

Sex and age differences in Mycobacterium tuberculosis infection in Brazil

Globally, the prevalence of tuberculosis (TB) disease is higher in males. This study examined the effect of sex and age on Mycobacterium tuberculosis (Mtb) infection. Demographic and exposure data were collected on household contacts of sputum smear-positive pulmonary TB patients in Brazil. Contacts with tuberculin skin test induration ⩾10 mm at baseline or 12 weeks were considered Mtb infected. The study enrolled 917 household contacts from 160 households; 508 (55.4%) were female, median age was 21.0 years (range 0.30-87.0) and 609 (66.4%) had Mtb infection. The proportion infected increased with age from 63.3% in girls <5 years to 75.4% in women ⩾40 years and from 44.9% in boys <5 years to 73.6% in men ⩾40 years. Multivariable modelling showed the odds of infection increased between age 5 and 14 years among female contacts (OR 1.5 per 5-year age increase; 95% CI 1.1-2.2; P = 0.02) and between ages 0-4 and 15-39 years among male contacts (OR 2.7, 95% CI 0.83-8.9 and 1.1, 95% CI 0.99-1.3 per 5-year age increase; P = 0.10, 0.07, respectively). The study suggests that the age at which Mtb infection increases most is different in females compared with males. Studies are needed to explore whether these findings are due to differences in host susceptibility, exposure outside the household or other factors.

High dose dry powder inhalers to overcome the challenges of tuberculosis treatment

Tuberculosis (TB) is a major global health burden. The emergence of the human immunodeficiency virus (HIV) epidemic and drug resistance has complicated global TB control. Pulmonary delivery of drugs using dry powder inhalers (DPI) is an emerging approach to treat TB. In comparison with the conventional pulmonary delivery for asthma and chronic obstructive pulmonary disease (COPD), TB requires high dose delivery to the lung. However, high dose delivery depends on the successful design of the inhaler device and the formulation of highly aerosolizable powders. Particle engineering techniques play an important role in the development of high dose dry powder formulations. This review focuses on the development of high dose dry powder formulations for TB treatment with background information on the challenges of the current treatment of TB and the potential for pulmonary delivery. Particle engineering techniques with a particular focus on the spray drying and a summary of the developed dry powder formulations using different techniques are also discussed.

FDG-PET/CT activity leads to the diagnosis of unsuspected TB: a retrospective study

Objective

Mycobacterium tuberculosis infection leads to latent or active tuberculosis (TB). Increased uptake on ¹⁸F-fluoro-2-deoxy-glucose-positron emission tomography/computed tomography (FDG-PET/CT) has been reported in the lungs and lymph nodes of individuals with recent infection and active TB, but not in individuals without known recent exposure or suggestive symptoms. We describe five patients with lung nodules not suspected to be due to TB in whom abnormalities on FDG-PET/CT scans ultimately were attributed to TB infection.

Results

Patient records were searched using the words “positron emission tomography/computed tomography” and 24 codes for TB between 2004 and 2013. Patients with a diagnosis of TB and a PET/CT scan were included. Clinical and radiographic data were retrieved. PET/CT images were reviewed by an experienced radiologist. FDG-PET/CT scans revealed elevated FDG-uptake in lungs of five patients subsequently diagnosed with active (n = 3) or clinically inactive (n = 2) tuberculosis. Uptake magnitude was unrelated to disease activity. These findings suggest that tuberculosis latency may include periods of percolating inflammation of uncertain relationship to future disease risk.

"Tuberculosis in advanced HIV infection is associated with increased expression of IFNγ and its downstream targets"

BACKGROUND

Tuberculosis (TB) is the major cause of death in Human Immunodeficiency Virus (HIV)-infected individuals. However, diagnosis of TB in HIV remains challenging particularly when HIV infection is advanced. Several gene signatures and serum protein biomarkers have been identified that distinguish active TB from latent infection. Our study was designed to assess if gene expression signatures and cytokine levels would distinguish active TB in advanced HIV.

METHODS

We conducted a case-control study of whole blood RNA-Seq and plasma cytokine/chemokine analysis in HIV-infected with CD4+ T cell count of ≤ 100 cells/μl, with and without active TB. Next, the overlap of the differentially expressed genes (DEG) with the published signatures was performed and then receiver operator characteristic (ROC) analysis was done on small gene discriminators to determine their performance in distinguishing TB in advanced HIV. ELISA was performed on plasma to evaluate cytokine and chemokine levels.

RESULTS

Hierarchical clustering of the transcriptional profiles showed that, in general, HIV-infected individuals with TB (TB-HIV) clustered separately from those without TB. IPA indicated that the TB-HIV signature was characterized by an increase in inflammatory signaling pathways. Analysis of overlaps between DEG in our data set with published TB signatures revealed that significant overlap was seen with one TB signature and one TB-IRIS signature. ROC analysis revealed that transcript levels of FcGR1A (AUC = 0.85) and BATF2 (AUC = 0.82), previously reported as consistent single gene classifiers of active TB irrespective of HIV status, performed successfully even in advanced HIV. Plasma protein levels of IFNγ, a stimulator of FcGR1A and BATF2, and CXCL10, also up-regulated by IFNγ, accurately classified active TB (AUC = 0.98 and 0.91, respectively) in advanced HIV. Neither of these genes nor proteins distinguished between TB and TB-IRIS.

CONCLUSIONS

Gene expression of FcGR1A and BATF2, and plasma protein levels of IFNγ and CXCL10 have the potential to independently detect TB in advanced HIV. However, since other lung diseases were not included in this study, these final candidates need to be validated as specific to TB in the advanced HIV population with TB.

Assessment of Forces in Intradermal Injection Devices: Hydrodynamic Versus Human Factors

PURPOSE

The force that has to be exerted on the plunger for administering a given amount of fluid in a given time, has an important influence on comfort for the subject and usability for the administrator in intradermal drug delivery. The purpose of this study is to model those forces that are subject-independent, by linking needle and syringe geometry to the force required for ejecting a given fluid at a given ejection rate.

MATERIAL AND METHODS

We extend the well-known Hagen-Poiseuille formula to predict pressure drop induced by a fluid passing through a cylindrical body. The model investigates the relation between the pressure drop in needles and the theoretic Hagen-Poiseuille prediction and is validated in fifteen needles from 26G up to 33G suited for intradermal drug delivery. We also provide a method to assess forces exerted by operators in real world conditions.

RESULTS

The model is highly linear in each individual needle with R-square values ranging from 75% up to 99.9%. Ten out of fifteen needles exhibit R-square values above 99%. A proof-of-concept for force assessment is provided by logging forces in operators in real life conditions.

CONCLUSIONS

The force assessment method and the model can be used to pinpoint needle geometry for intradermal injection devices, tuning comfort for subjects and usability for operators.

Use of a leukocyte-targeted peptide probe as a potential tracer for imaging the tuberculosis granuloma

Granulomas are the histopathologic hallmark of tuberculosis (TB), both in latency and active disease. Diagnostic and therapeutic strategies that specifically target granulomas have not been developed. Our objective is to develop a probe for imaging relevant immune cell populations infiltrating the granuloma. We report the binding specificity of Cyanine 3 (Cy3)-labeled cFLFLFK-PEG₁₂ to human leukocytes and cellular constituents within a human in vitro granuloma model. We also report use of the probe in in vivo studies using a mouse model of lung granulomatous inflammation. We found that the probe preferentially binds human neutrophils and macrophages in human granuloma structures. Inhibition studies showed that peptide binding to human neutrophils is mediated by the receptor formyl peptide receptor 1 (FPR1). Imaging the distribution of intravenously administered cFLFLFK-PEG₁₂-Cy3 in the mouse model revealed probe accumulation within granulomatous inflammatory responses in the lung. Further characterization revealed that the probe preferentially associated with neutrophils and cells of the monocyte/macrophage lineage. As there is no current clinical diagnostic imaging tool that specifically targets granulomas, the use of this probe in the context of latent and active TB may provide a unique advantage over current clinical imaging probes. We anticipate that utilizing a FPR1-targeted radiopharmaceutical analog of cFLFLFK in preclinical imaging studies may greatly contribute to our understanding of granuloma influx patterns and the biological roles and consequences of FPR1-expressing cells in contributing to disease pathogenesis.

New concepts in understanding latent tuberculosis

PURPOSE OF REVIEW

Mycobacterium tuberculosis (M.tb), the etiologic agent of tuberculosis, is a prominent global health threat because of the enormous reservoir of subclinical latent tuberculosis infection (LTBI). Current diagnostic approaches are limited in their ability to predict reactivation risk and LTBI is recalcitrant to antibiotic treatment. The present review summarizes recent advances in our ability to detect, treat and model LTBI as well as our understanding of bacterial physiology during latency.

RECENT FINDINGS

T-cell subsets and circulating proteins have been identified which could serve as biomarkers for LTBI or indicators of reactivation risk. In addition, experimental and in-silico models have enabled discoveries regarding bacterial physiology during latency and the host immune response following infection with latent M.tb.

SUMMARY

Despite recent advances, much more research is needed to bolster our ability to detect, implement treatment and model LTBI. The present work is crucial for the eradication of this global problem.

Intensity of exposure to pulmonary tuberculosis determines risk of tuberculosis infection and disease

Household contacts of pulmonary tuberculosis (TB) patients are at increased risk of TB infection and disease. However, their risk in relation to the intensity of exposure remains unknown.We studied smear-positive TB cases and their household contacts in Vitória, Brazil. We collected clinical, demographic and radiographic information from TB cases, and obtained tuberculin skin test (TST) and QuantiFERON-TB Gold (QFT) results from household contacts. We measured intensity of exposure using a proximity score and sleep location in relation to the TB index case and defined infection by TST ≥10 mm or QFT ≥0.35 UI·mL-1 We ascertained secondary TB cases by reviewing local and nationwide case registries.We included 160 TB index cases and 894 household contacts. 464 (65%) had TB infection and 23 (2.6%) developed TB disease. Risk of TB infection and disease increased with more intense exposures. In an adjusted analysis, the proximity score was associated with TB disease (OR 1.61, 95% CI 1.25-2.08; p<0.000); however, its diagnostic performance was only moderate.Intensity of exposure increased risk of TB infection and disease among household contacts; however, its diagnostic performance was still suboptimal. A biomarker to target preventive therapy is urgently needed in this at-risk population.

Cost-effectiveness of Testing and Treatment for Latent Tuberculosis Infection in Residents Born Outside the United States With and Without Medical Comorbidities in a Simulation Model

IMPORTANCE

Testing for and treating latent tuberculosis infection (LTBI) is among the main strategies to achieve TB elimination in the United States. The best approach to testing among non-US born residents, particularly those with comorbid conditions, is uncertain.

OBJECTIVE

To estimate health outcomes, costs, and cost-effectiveness of LTBI testing and treatment among non-US born residents with and without medical comorbidities.

DESIGN, SETTING, AND PARTICIPANTS

Decision analytic tree and Markov cohort simulation model among non-US born residents with no comorbidities, with diabetes, with HIV infection, or with end-stage renal disease (ESRD) using a health care sector perspective with 3% annual discounting. Strategies compared included no testing, tuberculin skin test (TST), interferon gamma release assay (IGRA), confirm positive (initial TST, IGRA only for TST-positive results; both tests positive indicates LTBI), and confirm negative (initial IGRA, then TST for IGRA-negative; any test positive indicates LTBI). All strategies were coupled to treatment with 3 months of self-administered rifapentine and isoniazid.

MAIN OUTCOMES AND MEASURES

Number needed to test and treat to prevent 1 case of TB reactivation, discounted quality-adjusted life-years (QALYs), discounted lifetime medical costs, and incremental cost-effectiveness ratios (ICERs).

RESULTS

Improving health outcomes increased costs, with choice of test dependent on willingness to pay. Strategies ranked by ascending costs and benefits: no testing, confirm positive, TST, IGRA, and confirm negative. The ICERs varied by non-US born patient risk group: patients with no comorbidities, IGRA was likely cost-effective at $83 000/QALY; patients with diabetes, both confirm positive ($53 000/QALY) and IGRA ($120 000/QALY) were likely cost-effective; patients with HIV, confirm negative was clearly preferred ($63 000/QALY); and patients with ESRD, no testing was cost-effective. Increased LTBI prevalence and reduced return for TST reading improved IGRA's relative performance. In 10 000 probabilistic simulations among non-US born patients with no comorbidities, with diabetes, and with HIV, some form of testing was virtually always cost-effective. These simulations highlight the uncertainty of test choice for non-US born patients with no comorbidities and non-US born patients with diabetes, but strategies including IGRA were preferred in over 60% of simulations for all non-US born populations except those with ESRD.

CONCLUSIONS AND RELEVANCE

Testing for and treating LTBI among non-US born residents with and without selected comorbidities is likely cost-effective except among those with ESRD in whom competing risks of death limit benefits. Strategies including IGRA fell below a $100 000/QALY willingness-to-pay threshold for non-US born patients with no comorbidities, patients with diabetes, and patients with HIV.

Latent tuberculosis infection among patients with erectile dysfunction

No previous studies have investigated the prevalence of latent tuberculosis infection (LTBI) among patients with erectile dysfunction (ED) or its contribution to the development of high-grade ED through a process of chronic inflammation-induced atherosclerosis. The aim of this study was to determine the frequency of LTBI among patients with erectile dysfunction and to explore the contribution of LTBI to high-grade ED. For all the study sample, clinical evaluation, imaging studies, and laboratory investigations were provided. Evaluation included, but was not confined to, scrotal ultrasonography, tuberculin skin test, and QuantiFERON-TB Gold test. The study sample mean ± SD age was 47.9 ± 13.6 years. Approximately 30% of the patients had LTBI and 43% had high-grade ED. After a multivariate analysis, it was found that older age (≥40 years) (OR, 5.2; 95% CI, 1.9-54.6; p 0.004), metabolic syndrome (MS) (OR, 3.4; 95% CI, 1.3-48.2; p 0.016), and LTBI (OR, 4.1; 95% CI, 1.7-61.3; p 0.021) were significantly, independently associated with high-grade ED as opposed to low-grade ED. In conclusion, the prevalence of LTBI among patients with high-grade ED is higher than among those with low-grade ED. In addition to LTBI, older age and MS are associated with high-grade ED as opposed to low-grade ED.

New antituberculous drugs derived from natural products: current perspectives and issues in antituberculous drug development

Tuberculosis is one of the most common and challenging infectious diseases worldwide. Especially, the lack of effective chemotherapeutic drugs for tuberculosis/human immunodeficiency virus co-infection and prevalence of multidrug-resistant and extensively drug-resistant tuberculosis remain to be serious clinical problems. Development of new drugs is a potential solution to fight tuberculosis. In this decade, the development status of new antituberculous drugs has been greatly advanced by the leading role of international organizations such as the Global Alliance for Tuberculosis Drug Development, Stop Tuberculosis Partnership and Global Health Innovative Technology Fund. In this review, we introduce the development status of new drugs for tuberculosis, focusing on those derived from natural products.The Journal of Antibiotics advance online publication, 1 November 2017; doi:10.1038/ja.2017.126.

Incident Mycobacterium tuberculosis infection in household contacts of infectious tuberculosis patients in Brazil

BACKGROUND

In household contact investigations of tuberculosis (TB), a second tuberculin skin test (TST) obtained several weeks after a first negative result consistently identifies individuals that undergo TST conversion. It remains unclear whether this delay in M. tuberculosis infection is related to differences in the infectious exposure, TST boosting, partial host resistance, or some other factor.

METHODS

We conducted a household contact study Vitória, Brazil. Between 2008 and 2013, we identified culture-positive pulmonary TB patients and evaluated their household contacts with both a TST and interferon gamma release assay (IGRA), and identified TST converters at 8-12 weeks post study enrollment. Contacts were classified as TST-positive (≥10 mm) at baseline, TST converters, or persistently TST-negative. We compared TST converters to TST-positive and to TST-negative contacts separately, using generalized estimating equations.

RESULTS

We enrolled 160 index patients and 838 contacts; 523 (62.4%) were TST+, 62 (7.4%) TST converters, and 253 (30.2%) TST-. TST converters were frequently IGRA- at 8-12 weeks. In adjusted analyses, characteristics distinguishing TST converters from TST+ contacts (no contact with another TB patient and residence ownership) were different than those differentiating them from TST- contacts (stronger cough in index patient and contact BCG scar).

CONCLUSIONS

The individual risk and timing of M. tuberculosis infection within households is variable and dependent on index patient, contact and environmental factors within the household, and the surrounding community. Our findings suggest a threshold effect in the risk of infection in humans.

Late boosting phenomenon in TST conversion among health care workers

BACKGROUND

Available information is insufficient to guide determination of whether tuberculin skin test (TST) conversions of health care workers (HCWs) within 2 years of two-step testing are related to occupational exposures or to other causes, including late boosting.

AIMS

To describe the epidemiologic factors of TST conversion in HCWs, comparing early TST conversion (≤2 years after two-step testing) with late conversion to possibly distinguish late boosting phenomenon from occupational TST conversion.

METHODS

Retrospective analysis of a database of TSTs of HCWs from 1 January 1998, through 31 May 2014, in the United States Midwest.

RESULTS

In total, 40142 HCWs had 197932 tests over the 16 years, with 123 conversions (conversion rate: 0.3%; 95% CI 0.3-0.4%). Among 61 HCWs with a negative two-step TST, 30 (49%) were found to have early TST conversion within 2 years; 31 (51%) had late conversion, with likely occupational exposure but no identifiable community risks. Persons with early conversion were more likely to be born outside the USA (89% versus 57%; P < 0.05), had a higher rate of prior bacille Calmette-Guérin (BCG) vaccination (89% versus 52%; P < 0.05) and had no identifiable risk factors for conversion (63% versus 58%; P < 0.05).

CONCLUSIONS

Early conversions among HCWs after negative two-step TST are associated with various nonoccupational factors, including international birth and BCG vaccination history. Therefore, conversion is not a reliable indicator of recent tuberculosis contact in this population, and two-step TST is insufficient to discount a delayed boosting response for HCWs.

Lipoarabinomannan-Responsive Polycytotoxic T Cells Are Associated with Protection in Human Tuberculosis

RATIONALE

The development of host-targeted, prophylactic, and therapeutic interventions against tuberculosis requires a better understanding of the immune mechanisms that determine the outcome of infection with Mycobacterium tuberculosis.

OBJECTIVES

To identify T-cell-dependent mechanisms that are protective in tuberculosis.

METHODS

Multicolor flow cytometry, cell sorting and growth inhibition assays were employed to compare the frequency, phenotype and function of T lymphocytes from bronchoalveolar lavage or the peripheral blood.

MEASUREMENTS AND MAIN RESULTS

At two independent study sites, bronchoalveolar lavage cells from donors with latent tuberculosis infection limited the growth of virulent Mycobacterium tuberculosis more efficiently than those in patients who developed disease. Unconventional, glycolipid-responsive T cells contributed to reduced mycobacterial growth because antibodies to CD1b inhibited this effect by 55%. Lipoarabinomannan was the most potent mycobacterial lipid antigen (activation of 1.3% T lymphocytes) and activated CD1b-restricted T cells that limited bacterial growth. A subset of IFN-γ-producing lipoarabinomannan-responsive T cells coexpressed the cytotoxic molecules perforin, granulysin, and granzyme B, which we termed polycytotoxic T cells. Taking advantage of two well-defined cohorts of subjects latently infected with Mycobacterium tuberculosis or patients who developed active disease after infection, we found a correlation between the frequency of polycytotoxic T cells and the ability to control infection (latent tuberculosis infection, 62%; posttuberculosis patients, 26%).

CONCLUSIONS

Our data define an unconventional CD8(+) T-cell subset (polycytotoxic T cells) that is based on antigen recognition and function. The results link clinical and mechanistic evidence that glycolipid-responsive, polycytotoxic T cells contribute to protection against tuberculosis.

Mycobacterium tuberculosis Induction of Heme Oxygenase-1 Expression Is Dependent on Oxidative Stress and Reflects Treatment Outcomes

The antioxidant enzyme heme oxygenase-1 (HO-1) is implicated in the pathogenesis of tuberculosis (TB) and has been proposed as a biomarker of active disease. Nevertheless, the mechanisms by which Mycobacterium tuberculosis (Mtb) induces HO-1 as well as how its expression is affected by HIV-1 coinfection and successful antitubercular therapy (ATT) are poorly understood. We found that HO-1 expression is markedly increased in rabbits, mice, and non-human primates during experimental Mtb infection and gradually decreased during ATT. In addition, we examined circulating concentrations of HO-1 in a cohort of 130 HIV-1 coinfected and uninfected pulmonary TB patients undergoing ATT to investigate changes in expression of this biomarker in relation to HIV-1 status, radiological disease severity, and treatment outcome. We found that plasma levels of HO-1 were elevated in untreated HIV-1 coinfected TB patients and correlated positively with HIV-1 viral load and negatively with CD4⁺ T cell count. In both HIV-1 coinfected and Mtb monoinfected patients, HO-1 levels were substantially reduced during successful TB treatment but not in those who experienced treatment failure or subsequently relapsed. To further delineate the molecular mechanisms involved in induction of HO-1 by Mtb, we performed a series of in vitro experiments using mouse and human macrophages. We found that Mtb-induced HO-1 expression requires NADPH oxidase-dependent reactive oxygen species production induced by the early-secreted antigen ESAT-6, which in turn triggers nuclear translocation of the transcription factor NRF-2. These observations provide further insight into the utility of HO-1 as a biomarker of both disease and successful therapy in TB monoinfected and HIV-TB coinfected patients and reveal a previously undocumented pathway linking expression of the enzyme with oxidative stress.

From Latent Tuberculosis Infection to Tuberculosis. News in Diagnostics (QuantiFERON-Plus)

It is estimated that one third of the world's population have latent tuberculosis infection and that this is a significant reservoir for future tuberculosis cases. Most cases occur within two years following initial infection. The identification of individuals with latent tuberculosis infection is difficult due to the lack of an ideal diagnostic assay and incomplete understanding of latent infection. Currently, there are three tests: the oldest tuberculin skin test, T-SPOT.TB and the latest QuantiFERON-Plus for the detection of Mycobacterium tuberculosis infection. The interpretation of the test results must be used in the conjunction with a patient's epidemiological history, risk assessment, current clinical status, radiography and microbiological methods to ensure accurate diagnosis.

Prevalence and associated risk factors of latent tuberculosis infection among undergraduate and postgraduate dental students: A retrospective study

To estimate the prevalence of latent tuberculosis (TB) infection (LTBI) in Italian dental students exposed to the same occupational risks as dental health care personnel and to evaluate potential risk factors, a cross-sectional study was conducted on undergraduate and postgraduate students. After clinical evaluation, students were given a tuberculin skin test; in those found positive, an interferon-γ release assay (IGRA) was conducted. Of the 281 students enrolled, 10 were only TST positive; 8 were TST or/and IGRA positive. We found that participants testing positive at TST and/or IGRA, a group in which the risk of false LTBI positives is minimal, were older and had been studying longer. Although the prevalence of LTBI among dental students in our study was low, a risk of acquiring a work-related infection exists even in a country with a low incidence of TB. Thus, dental students should be screened to catch LTBI early on.

Tuberculosis: Is the landscape changing?

Robert Heinrich Herman Koch, a German physician and microbiologist, received Nobel Prize in 1905 for identifying the specific causative agent of tuberculosis (TB). During his time it was believed that TB was an inherited disease. However he was convinced that the disease was caused by a bacterium and was infectious, tested his postulates using guinea pigs, and found the causative agent to be slow growing mycobacterium tuberculosis. TB is the second most common cause of death from infectious diseases after HIV/AIDS. Drug-resistant TB poses serious challenge to effective management of TB worldwide. Multidrug-resistant TB accounted for about half a million new cases and over 200,000 deaths in 2013. Whole-genome sequencing (first done in 1998) technologies have provided new insight into the mechanism of drug resistance. For the first time in 50 y, new anti TB drugs have been developed. The World Health Organization (WHO) has recently revised their treatment guidelines based on 32 studies. In United States, latent TB affects between 10 and 15 million people, 10% of whom may develop active TB disease. QuantiFERON TB Gold and T-SPOT.TB test are used for diagnosis. Further research will look into the importance of newly discovered gene mutations in causing drug resistance.

Tuberculosis exposure, infection and disease in children: a systematic diagnostic approach

The accurate diagnosis of tuberculosis (TB) in children remains challenging. A myriad of common childhood diseases can present with similar symptoms and signs, and differentiating between exposure and infection, as well as infection and disease can be problematic. The paucibacillary nature of childhood TB complicates bacteriological confirmation and specimen collection is difficult. In most instances intrathoracic TB remains a clinical diagnosis. TB infection and disease represent a dynamic continuum from TB exposure with/without infection, to subclinical/incipient disease, to non-severe and severe disease. The clinical spectrum of intrathoracic TB in children is broad, and the classification of clinical, radiological, endoscopic, and laboratory findings into recognized clinical syndromes allows a more refined diagnostic approach in order to minimize both under- and over-diagnosis. Bacteriological confirmation can be improved significantly by collecting multiple, high-quality specimens from the most appropriate source. Mycobacterial testing should include traditional smear microscopy and culture, as well as nucleic acid amplification testing. A systematic approach to the child with recent exposure to TB, or with clinical and radiological findings compatible with this diagnosis, should allow pragmatic classification as TB exposure, infection, or disease to facilitate timely and appropriate management. It is important to also assess risk factors for TB disease progression and to undertake follow-up evaluations to monitor treatment response and ongoing evidence supporting a TB, or alternative, diagnosis.

Prevalence of latent tuberculosis infection in healthcare workers at a hospital in Naples, Italy, a low-incidence country

Background

Healthcare workers (HCWs) are at higher risk than the general population of contracting tuberculosis (TB). Moreover, although subjects with latent TB infection (LTBI) are asymptomatic and are not infectious, they may eventually develop active disease. Thus, a fundamental tool of TB control programs for HCWs is the screening and treatment of LTBI.

Methods

From January 2014 to January 2015, hospital personnel at Azienda Ospedaliera Universitaria, Naples, Italy, were screened for TB. To this end, a tuberculin skin test (TST) was administered as an initial examination, unless when contraindicated, in which case the QuantiFERON® TB-Gold (QFT) assay was performed. Moreover, QFT was carried out on all TST-positive cases to confirm the initial result.

Results

Of 628 personnel asked to participate, 28 (4.5%) denied consent, 533 were administered TST as the baseline examination, and 67 were tested only with QFT. In the TST group, 73 (13.2%) individuals were found positive, 418 (78.4%) were negative, and 42 (7.9%) were absent for the reading window; QFT confirmed the result in 39 (53.4%) TST-positive individuals. In the QFT-only group, 44 (65.7%) individuals were found positive. All TST- and/or QFT-positive subjects were referred for chest X-ray and examination by an infectious diseases specialist. None were found to have active TB, and were thus diagnosed with LTBI.

Conclusions

Although Italy is a low-incidence country regarding TB, our findings suggest that the prevalence of LTBI in HCWs may be relatively high. As a result, active screening for TB and LTBI is needed for these workers.

Electronic supplementary material

The online version of this article (doi:10.1186/s12995-016-0141-6) contains supplementary material, which is available to authorized users.

Infection control and tuberculosis among health care workers in Viet Nam, 2009-2013: a cross-sectional survey

Background

Data on tuberculosis (TB) among health care workers (HCW) and TB infection control (TBIC) indicators are rarely available at national level. We assessed multi-year trends in notification data of TB among HCW and explored possible associations with TBIC indicators.

Methods

Notified TB incidence among HCW and 3 other TBIC indicators were collected annually from all 64 provincial and 3 national TB facilities in Vietnam. Time trends in TB notification between 2009 and 2013 were assessed using linear regression analysis. Multivariate regression models were applied to assess associations between the facility-specific 5-year notification rate and TBIC indicators.

Results

Forty-seven (70 %) of 67 facilities contributed data annually over five years; 15 reported at least one HCW with TB in 2009 compared to six in 2013. The TB notification rate dropped from 593 to 197 per 100,000 HCW (p_trend = 0.02).

Among 104 TB cases reported, 30 were employed at TB wards, 24 at other clinical wards, ten in the microbiology laboratory, six at the MDR-TB ward, and 34 in other positions.

The proportion of facilities with a TBIC plan and focal person remained relatively stable between 70 % and 84 %. The proportion of facilities providing personal protective equipment (PPE) to their staff increased over time. Facilities with a TBIC focal person were 7.6 times more likely to report any TB cases than facilities without a focal person.

Conclusions

The TB notification rates among HCW seemed to decrease over time. Availability of PPE increased over the same period. Appointing a TBIC focal person was associated with reporting of TB cases among HCW. It remains unclear whether TBIC measures helped in reduction of the TB notification rates in HCW.

Diagnosis and management of latent tuberculosis

PURPOSE OF REVIEW

Latent tuberculosis infection (LTBI) may affect over two billion individuals and serves as a potential reservoir for future active tuberculosis. The identification and treatment of LTBI in those at highest risk for progression is an essential part of tuberculosis control.

RECENT FINDINGS

Interferon-γ release assays are increasingly used for targeted testing and diagnosis of latent disease. The performance of these immunodiagnostic tests has been studied in various groups and may be better than the tuberculin skin test in certain populations. Ongoing research is focused on new biomarkers that may diagnose LTBI or predict progression to active tuberculosis. Isoniazid preventive treatment is effective at reducing risk of active disease, but length of treatment and potential side-effects limit patient acceptance and compliance. Rifamycin-based regimens are increasingly studied as a shorter and perhaps less toxic alternative for preventive therapy.

SUMMARY

Identification of those with LTBI is important as it allows treatment of those at highest risk of progression to active disease and thus decreases the overall burden of tuberculosis. The development of new immunodiagnostics may further improve identification of those at risk and alternative medication regimens may increase compliance with and efficacy of preventive therapy.

Progression to tuberculosis disease increases with multiple exposures

During a single year, a Canadian village had 34 individuals with microbiologically confirmed tuberculosis (TB) among 169 people with a new infection (20%). A contact investigation revealed multiple exposures for each person. We investigated whether the intensity of exposure might contribute to this extraordinary risk of disease.We carried out a case-control study using a public health database. Among those with a new infection, 34 had culture-confirmed TB (cases) and 118 did not progress to disease (controls). 17 patients with probable disease were excluded. Contact investigation data were utilised to tabulate the number of potential sources (total exposures). Generalised estimating equations with a logit link were used to identify associations between exposures and progression, and to investigate other potential risk factors.The median (interquartile range) number of total exposures was 15 (3-23) for cases and 3 (2-12) for controls (p=0.001). The adjusted OR for disease was 1.11 (95% CI 1.06-1.16) per additional exposure, corresponding to an OR of 3.4 for disease when comparing the medians of 15 versus 3 total exposures. This association increased when restricting to tuberculin skin test conversions.Increased exposure could be a marker of greater risk of progression to TB disease. Therefore, this risk may not be transportable across epidemiologic settings with variable exposure intensities.

Helminth-Tuberculosis Co-infection: An Immunologic Perspective

Over 2 billion people worldwide are infected with helminths (worms). Similarly, infection with Mycobacterium tuberculosis (Mtb) occurs in over a third of the world's population, often with a great degree of geographical overlap with helminth infection. Interestingly, the responses induced by the extracellular helminths and those induced by the intracellular Mtb are often mutually antagonistic and, as a consequence, can result in impaired (or cross-regulated) host responses to either of the infecting pathogens. In this review, we outline the nature of the immune responses induced by infections with helminths and tuberculosis (TB) and then provide data from both experimental models and human studies that illustrate how the immune response engendered by helminth parasites modulates Mtb-specific responses in helminth-TB coinfection.

Detection and Quantification of Mycobacterium tuberculosis in the Sputum of Culture-Negative HIV-infected Pulmonary Tuberculosis Suspects: A Proof-of-Concept Study

RATIONALE

Rapid diagnosis of pulmonary tuberculosis (TB) is critical for timely initiation of treatment and interruption of transmission. Yet, despite recent advances, many patients remain undiagnosed. Culture, usually considered the most sensitive diagnostic method, is sub-optimal for paucibacillary disease.

METHODS

We evaluated the Totally Optimized PCR (TOP) TB assay, a new molecular test that we hypothesize is more sensitive than culture. After pre-clinical studies, we estimated TOP's per-patient sensitivity and specificity in a convenience sample of 261 HIV-infected pulmonary TB suspects enrolled into a TB diagnostic study in Mbarara, Uganda against MGIT culture, Xpert MTB/RIF and a composite reference standard. We validated results with a confirmatory PCR used for sequencing M. tuberculosis.

MEASUREMENTS AND RESULTS

Using culture as reference, TOP had 100% sensitivity but 35% specificity. Against a composite reference standard, the sensitivity of culture (27%) and Xpert MTB/RIF (27%) was lower than TOP (99%), with similar specificity (100%, 98% and 87%, respectively). In unadjusted analyses, culture-negative/TOP-positive patients were more likely to be older (P<0·001), female (P<0·001), have salivary sputum (P = 0·05), sputum smear-negative (P<0.001) and less advanced disease on chest radiograph (P = 0.05). M. tuberculosis genotypes identified in sputum by DNA sequencing exhibit differential growth in culture.

CONCLUSIONS

These findings suggest that the TOP TB assay is accurately detecting M. tuberculosis DNA in the sputum of culture-negative tuberculosis suspects. Our results require prospective validation with clinical outcomes. If the operating characteristics of the TOP assay are confirmed in future studies, it will be justified as a "TB rule out" test.

The emerging role of gasotransmitters in the pathogenesis of tuberculosis

Mycobacterium tuberculosis (Mtb) is a facultative intracellular pathogen and the second largest contributor to global mortality caused by an infectious agent after HIV. In infected host cells, Mtb is faced with a harsh intracellular environment including hypoxia and the release of nitric oxide (NO) and carbon monoxide (CO) by immune cells. Hypoxia, NO and CO induce a state of in vitro dormancy where Mtb senses these gases via the DosS and DosT heme sensor kinase proteins, which in turn induce a set of ∼47 genes, known as the Mtb Dos dormancy regulon. On the contrary, both iNOS and HO-1, which produce NO and CO, respectively, have been shown to be important against mycobacterial disease progression. In this review, we discuss the impact of O2, NO and CO on Mtb physiology and in host responses to Mtb infection as well as the potential role of another major endogenous gas, hydrogen sulfide (H2S), in Mtb pathogenesis.

Reactivation tuberculosis: role of surveillance

The incidence and death rates from tuberculosis (TB) have declined through concerted efforts in the diagnosis and treatment of active disease. Despite this, 9.6 million new cases and 1.1 million deaths in 2014 are unacceptably high. To decrease the rates of TB further, the huge number of persons with latent TB infection (LTBI) from whom new cases will arise has to be addressed with a sense of priority. Identifying the highest risk groups and providing effective treatment has been shown to decrease active TB. Further research to refine the predictors of reactivation and shorter effective treatments are urgently needed. Implementing intensified case finding, testing and treatment for LTBI will require continued investment in health care capacity at multiple levels.

Cough Aerosols of Mycobacterium tuberculosis in the Prediction of Incident Tuberculosis Disease in Household Contacts

BACKGROUND

Tuberculosis disease develops in only 5%-10% of humans infected with Mycobacterium tuberculosis The mechanisms underlying this variability remain poorly understood. We recently demonstrated that colony-forming units of M. tuberculosis in cough-generated aerosols are a better predictor of infection than the standard sputum acid-fast bacilli smear. We hypothesized that cough aerosol cultures may also predict progression to tuberculosis disease in contacts.

METHODS

We conducted a retrospective cohort study of 85 patients with smear-positive tuberculosis and their 369 household contacts in Kampala, Uganda. Index case patients underwent a standard evaluation, and we cultured M. tuberculosis from cough aerosols. Contacts underwent a standard evaluation at enrollment, and they were later traced to determine their tuberculosis status.

RESULTS

During a median follow-up of 3.9 years, 8 (2%) of the contacts developed tuberculosis disease. In unadjusted and adjusted analyses, incident tuberculosis disease in contacts was associated with sputum Mycobacterial Growth Indicator Tube culture (odds ratio, 8.2; 95% confidence interval, 1.1-59.2; P = .04), exposure to a high-aerosol tuberculosis case patient (6.0, 1.4-25.2; P = .01), and marginally, human immunodeficiency virus in the contact (6.11; 0.89-41.7; P = .07). We present data demonstrating that sputum and aerosol specimens measure 2 related but different phenomena.

CONCLUSIONS

We found an increased risk of tuberculosis progression among contacts of high-aerosol case patients. The hypothesis that a larger infectious inoculum, represented by high aerosol production, determines the risk of disease progression deserves evaluation in future prospective studies.

The role of Xpert MTB/RIF in diagnosing pulmonary tuberculosis in post-mortem tissues

The extent to which the Xpert MTB/RIF (Gene Xpert) contributes to tuberculosis (TB) diagnosis in samples other than sputum and cerebrospinal fluid remains uncertain. We aimed to assess the role of Xpert MTB/RIF for detecting M. tuberculosis in post-mortem tissues. We conducted a study among 30 complete diagnostic autopsies (CDA) performed at the Maputo Central Hospital (Mozambique). Lung tissues were screened for TB in all cases. In addition other tissues were tested when compatible lesions were identified in the histological exam. We used in-house real time PCR and LAMP assays to confirm the presence of M. tuberculosis DNA. The diagnosis of tuberculosis at death was established based on microbiological and histopathological results. Eight out of 30 cases (26.7%) were diagnosed of tuberculosis. Xpert had a sensitivity to detect TB in lung tissue of 87.5% (95% CI 47.3–99.7) and a specificity of 95.7% (95% CI: 78.1–99.9). In-house DNA amplification methods and Xpert showed 93.6% concordance for lung tissue and 100% concordance for brain and liver tissues. The final cause of death was attributable to tuberculosis in four cases. Xpert MTB/RIF may represent a valuable, easy-to perform technique for post-mortem TB diagnosis.

Interleukin-17A as a Biomarker for Bovine Tuberculosis

T helper 17 (Th17)-associated cytokines are integral to the immune responses to tuberculosis, initiating both protective and harmful inflammatory responses. The aim of the present study was to evaluate applied aspects of interleukin-17 (IL-17) biology in the context of Mycobacterium bovis infection of cattle. Using transcriptome sequencing (RNA-Seq), numerous Th17-associated cytokine genes (including IL-17A, IL-17F, IL-22, IL-19, and IL-27) were upregulated >9-fold in response to purified protein derivative stimulation of peripheral blood mononuclear cells from experimentally M. bovis-infected cattle. Protective vaccines elicited IL-17A, IL-17F, IL-22, and IL-27 responses. Reduced IL-17A responses by vaccine recipients, compared to nonvaccinated animals, at 2.5 weeks after M. bovis challenge correlated with reduced disease burdens. Additionally, IL-17A and interferon gamma (IFN-γ) responses were highly correlated and exhibited similar diagnostic capacities. The present findings support the use of Th17-associated cytokines as biomarkers of infection and protection in the immune responses to bovine tuberculosis.

Dynamics of the T cell response to Mycobacterium tuberculosis DosR and Rpf antigens in a Colombian population of household contacts of recently diagnosed pulmonary tuberculosis patients

Immune response to DosR and Rpf antigens from Mycobacterium tuberculosis (Mtb) seems to be important for latency maintenance. Little is known about the dynamics of the immune response to these antigens in an endemic community. Thus, the IFNγ response and cytokine production in response to PPD, Esat6-Cfp10 (E6-C10), DosR and Rpf antigens in healthy HHC of tuberculosis (TB) patients over a 12 (T12) months period (short-term, stLTBI) was investigated. This response was compared with a group of LTBI, who have remained healthy for 5-7 years (long-term, ltLTBI). According to the IFNγ response, two groups of HHCs were identified in stLTBI in response to E6-C10. At T12, E6-C10(+) HHCs displayed a decrease in the IFNγ levels and a generalized decrease in cytokines production. The E6-C10(-) HHC showed an increase in the IFNγ response and cytokine levels. In stLTBI, the responses to E6-C10, DosR, and Rpf may be interpreted as a protective immune response controlling Mtb infection and may be leading to a state of latent infection. Comparing the response of stLTBI and ltLTBI, we observed significant changes in the proportions of CD45RO(+)CD27(+) T cells to specific DosR and Rpf, which may indicate a persistent immune response to Mtb antigens in ltLTBI.

Tuberculosis as a three-act play: A new paradigm for the pathogenesis of pulmonary tuberculosis

Lack of access to human tissues with untreated tuberculosis (TB) has forced generations of researchers to use animal models and to adopt a paradigm that granulomas are the characteristic lesion of both primary and post primary TB. An extended search of studies of human lung tissues failed to find any reports that support this paradigm. We found scores of publications from gross pathology in 1804 through high resolution CT scans in 2015 that identify obstructive lobular pneumonia, not granulomas, as the characteristic lesion of developing post-primary TB. This paper reviews this literature together with other relevant observations to formulate a new paradigm of TB with three distinct stages: a three-act play. First, primary TB, a war of attrition, begins with infection that spreads via lymphatics and blood stream before inducing systemic immunity that contains and controls the organisms within granulomas. Second, post-primary TB, a sneak attack, develops during latent TB as an asymptomatic obstructive lobular pneumonia in persons with effective systemic immunity. It is a paucibacillary process with no granulomas that spreads via bronchi and accumulates mycobacterial antigens and host lipids for 1-2 years before suddenly undergoing caseous necrosis. Third, the fallout, is responsible for nearly all clinical post primary disease. It begins with caseous necrotic pneumonia that is either retained to become the focus of fibrocaseous disease or is coughed out to leave a cavity. This three-stage paradigm suggests testable hypotheses and plausible answers to long standing questions of immunity to TB.

Major Loci on Chromosomes 8q and 3q Control Interferon γ Production Triggered by Bacillus Calmette-Guerin and 6-kDa Early Secretory Antigen Target, Respectively, in Various Populations

Background. Interferon γ (IFN-γ) release assays (IGRAs) provide an in vitro measurement of antimycobacterial immunity that is widely used as a test for Mycobacterium tuberculosis infection. IGRA outcomes are highly heritable in various populations, but the nature of the involved genetic factors remains unknown.

Methods. We conducted a genome-wide linkage analysis of IGRA phenotypes in families from a tuberculosis household contact study in France and a replication study in families from South Africa to confirm the loci identified.

Results. We identified a major locus on chromosome 8q controlling IFN-γ production in response to stimulation with live bacillus Calmette-Guerin (BCG; LOD score, 3.81; P = 1.40 × 10⁻⁵). We also detected a second locus, on chromosome 3q, that controlled IFN-γ levels in response to stimulation with 6-kDa early secretory antigen target, when accounting for the IFN-γ production shared with that induced by BCG (LOD score, 3.72; P = 1.8 × 10⁻⁵). Both loci were replicated in South African families, where tuberculosis is hyperendemic. These loci differ from those previously identified as controlling the response to the tuberculin skin test (TST1 and TST2) and the production of TNF-α (TNF1).

Conclusions. The identification of 2 new linkage signals in populations of various ethnic origins living in different M. tuberculosis exposure settings provides new clues about the genetic control of human antimycobacterial immunity.