Rise of Ruppia in Chesapeake Bay: Climate change-driven turnover of foundation species creates new threats and management opportunities.

Global change has converted many structurally complex and ecologically and economically valuable coastlines to bare substrate. In the structural habitats that remain, climate-tolerant and opportunistic species are increasing in response to environmental extremes and variability. The shifting of dominant foundation species identity with climate change poses a unique conservation challenge because species vary in their responses to environmental stressors and to management. Here, we combine 35 y of watershed modeling and biogeochemical water quality data with species comprehensive aerial surveys to describe causes and consequences of turnover in seagrass foundation species across 26,000 ha of habitat in the Chesapeake Bay. Repeated marine heatwaves have caused 54% retraction of the formerly dominant eelgrass (Zostera marina) since 1991, allowing 171% expansion of the temperature-tolerant widgeongrass (Ruppia maritima) that has likewise benefited from large-scale nutrient reductions. However, this phase shift in dominant seagrass identity now presents two significant shifts for management: Widgeongrass meadows are not only responsible for rapid, extensive recoveries but also for the largest crashes over the last four decades; and, while adapted to high temperatures, are much more susceptible than eelgrass to nutrient pulses driven by springtime runoff. Thus, by selecting for rapid post-disturbance recolonization but low resistance to punctuated freshwater flow disturbance, climate change could threaten the Chesapeake Bay seagrass' ability to provide consistent fishery habitat and sustain functioning over time. We demonstrate that understanding the dynamics of the next generation of foundation species is a critical management priority, because shifts from relatively stable habitat to high interannual variability can have far-reaching consequences across marine and terrestrial ecosystems.

Defensive hypervariable regions confer superinfection exclusion in microviruses.

Single-stranded DNA phages of the family Microviridae have fundamentally different evolutionary origins and dynamics than the more frequently studied double-stranded DNA phages. Despite their small size (around 5 kb), which imposes extreme constraints on genomic innovation, they have adapted to become prominent members of viromes in numerous ecosystems and hold a dominant position among viruses in the human gut. We show that multiple, divergent lineages in the family Microviridae have independently become capable of lysogenizing hosts and have convergently developed hypervariable regions in their DNA pilot protein, which is responsible for injecting the phage genome into the host. By creating microviruses with combinations of genomic segments from different phages and infecting Escherichia coli as a model system, we demonstrate that this hypervariable region confers the ability of temperate Microviridae to prevent DNA injection and infection by other microviruses. The DNA pilot protein is present in most microviruses, but has been recruited repeatedly into this additional role as microviruses altered their lifestyle by evolving the ability to integrate in bacterial genomes, which linked their survival to that of their hosts. Our results emphasize that competition between viruses is a considerable and often overlooked source of selective pressure, and by producing similar evolutionary outcomes in distinct lineages, it underlies the prevalence of hypervariable regions in the genomes of microviruses and perhaps beyond.

Data synthesis for environmental management: A case study of Chesapeake Bay.

Synthesizing large, complex data sets to inform resource managers towards effective environmental stewardship is a universal challenge. In Chesapeake Bay, a well-studied and intensively monitored estuary in North America, the challenge of synthesizing data on water quality and land use as factors related to a key habitat, submerged aquatic vegetation, was tackled by a team of scientists and resource managers operating at multiple levels of governance (state, federal). The synthesis effort took place over a two-year period (2016-2018), and the results were communicated widely to a) scientists via peer review publications and conference presentations; b) resource managers via web materials and workshop presentations; and c) the public through newspaper articles, radio interviews, and podcasts. The synthesis effort was initiated by resource managers at the United States Environmental Protection Agencys' Chesapeake Bay Program and 16 scientist participants were recruited from a diversity of organizations. Multiple short, immersive workshops were conducted regularly to conceptualize the problem, followed by data analysis and interpretation that supported the preparation of the synthetic products that were communicated widely. Reflections on the process indicate that there are a variety of structural and functional requirements, as well as enabling conditions, that need to be considered to achieve successful outcomes from synthesis efforts.

Long-term nutrient reductions lead to the unprecedented recovery of a temperate coastal region.

Humans strongly impact the dynamics of coastal systems, yet surprisingly few studies mechanistically link management of anthropogenic stressors and successful restoration of nearshore habitats over large spatial and temporal scales. Such examples are sorely needed to ensure the success of ecosystem restoration efforts worldwide. Here, we unite 30 consecutive years of watershed modeling, biogeochemical data, and comprehensive aerial surveys of Chesapeake Bay, United States to quantify the cascading effects of anthropogenic impacts on submersed aquatic vegetation (SAV), an ecologically and economically valuable habitat. We employ structural equation models to link land use change to higher nutrient loads, which in turn reduce SAV cover through multiple, independent pathways. We also show through our models that high biodiversity of SAV consistently promotes cover, an unexpected finding that corroborates emerging evidence from other terrestrial and marine systems. Due to sustained management actions that have reduced nitrogen concentrations in Chesapeake Bay by 23% since 1984, SAV has regained 17,000 ha to achieve its highest cover in almost half a century. Our study empirically demonstrates that nutrient reductions and biodiversity conservation are effective strategies to aid the successful recovery of degraded systems at regional scales, a finding which is highly relevant to the utility of environmental management programs worldwide.

Evaluation of Anatomical and Functional Hip Joint Center Methods: The Effects of Activity Type, Gender, and Proximal Reference Segment.

Accurate hip joint center (HJC) location is critical when studying hip joint biomechanics. The HJC is often determined from anatomical methods, but functional methods are becoming increasingly popular. Several studies have examined these methods using simulations and in vivo gait data, but none has studied high-range of motion activities, such a chair rise, nor has HJC prediction been compared between males and females. Furthermore, anterior superior iliac spine (ASIS) marker visibility during chair rise can be problematic, requiring a sacral cluster as an alternative proximal segment; but functional HJC has not been explored using this approach. For this study, the quality of HJC measurement was based on the joint gap error (JGE), which is the difference in global HJC between proximal and distal reference segments. The aims of the present study were to: (1) determine if JGE varies between pelvic and sacral referenced HJC for functional and anatomical methods, (2) investigate which functional calibration motion results in the lowest JGE and if the JGE varies depending on movement type (gait versus chair rise) and gender, and (3) assess whether the functional HJC calibration results in lower JGE than commonly used anatomical approaches and if it varies with movement type and gender. Data were collected on 39 healthy adults (19 males and 20 females) aged 14-50 yr old. Participants performed four hip "calibration" tests (arc, cross, star, and star-arc), as well as gait and chair rise (activities of daily living (ADL)). Two common anatomical methods were used to estimate HJC and were compared to HJC computed using a published functional method with the calibration motions above, when using pelvis or sacral cluster as the proximal reference. For ADL trials, functional methods resulted in lower JGE (12-19 mm) compared to anatomical methods (13-34 mm). It was also found that women had significantly higher JGE compared to men and JGE was significantly higher for chair rise compared to gait, across all methods. JGE for sacrum referenced HJC was consistently higher than for the pelvis, but only by 2.5 mm. The results indicate that dynamic hip range of movement and gender are significant factors in HJC quality. The findings also suggest that a rigid sacral cluster for HJC estimation is an acceptable alternative for relying solely on traditional pelvis markers.

High-Throughput Dose-Response Measurement Using a Label-Free Microarray-in-Microplate Assay Platform.

Microarray-based binding assays facilitate the discovery of protein ligands from large collections of small molecules. Hundreds of ligands can be identified, yet only a small portion of them have interfering effects (competitive or noncompetitive) on a specific protein-receptor binding reaction. Further efficient screening of ligands for those with specific modifying effect is needed in order to take the full advantage of throughputs of microarray-based assays for drug discovery. We report a label-free "microarray-in-microplate" assay platform for simultaneous acquisition of at least 32 dose-response curves in a single experiment, each curve having 12 concentration points. When combined with ligand discovery, this makes the microarray-based platform a true high-throughout means of finding inhibitors to specific protein-receptor reactions starting from a large collection of small-molecule libraries.

Determinants of Bacillus Calmette-Guérin (BCG) vaccination among Québec children.

OBJECTIVES: To identify determinants of Bacillus Calmette-Guérin (BCG) vaccination among children born in Québec, Canada, in 1974, the last year of the systematic vaccination campaign. METHOD: A retrospective birth cohort was assembled in 2011 through probabilistic linkage of administrative databases (n=81,496). Potential determinants were documented from administrative databases and by interviewing a subset of subjects (n=1643) in 2012. Analyses were conducted among subjects with complete data, 71,658 (88%) birth cohort subjects and 1154 (70%) interviewed subjects, then redone using multiple imputation. Determinants of BCG vaccination during the organized vaccination program (in 1974), and after the program (1975 onwards) were assessed separately. Logistic regression with backward elimination was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: Overall, 46% of subjects were BCG vaccinated, 43% during the program and 4% after it ended. BCG vaccination during the program was associated with parents' birthplace and urban or rural residence. BCG vaccination after the organized program was only related to ethnocultural origin of the child's grandparents. CONCLUSION: Different factors were related to vaccination within and after the organized program. Determinants of BCG vaccination in Québec, Canada, have never been studied and will be useful for future research and vaccination campaigns.

The TGF-ß-Smad3 pathway inhibits CD28-dependent cell growth and proliferation of CD4 T cells.

Transforming growth factor-ß (TGF-ß) maintains self-tolerance through a constitutive inhibitory effect on T-cell reactivity. In most physiological situations, the tolerogenic effects of TGF-ß depend on the canonical signaling molecule Smad3. To characterize how TGF-ß/Smad3 signaling contributes to maintenance of T-cell tolerance, we characterized the transcriptional landscape downstream of TGF-ß/Smad3 signaling in resting or activated CD4 T cells. We report that in the presence of TGF-ß, Smad3 modulates the expression of >400 transcripts. Notably, we identified 40 transcripts whose expression showed Smad3 dependence in both resting and activated cells. This 'signature' confirmed the non-redundant role of Smad3 in TGF-ß biology and identified both known and putative immunoregulatory genes. Moreover, we provide genomic and functional evidence that the TGF-ß/Smad3 pathway regulates T-cell activation and metabolism. In particular, we show that TGF-ß/Smad3 signaling dampens the effect of CD28 stimulation on T-cell growth and proliferation. The impact of TGF-ß/Smad3 signals on T-cell activation was similar to that of the mTOR inhibitor Rapamycin. Considering the importance of co-stimulation on the outcome of T-cell activation, we propose that TGF-ß-Smad3 signaling may maintain T-cell tolerance by suppressing co-stimulation-dependent mobilization of anabolic pathways.

A study comparing insulin lispro mix 25 with glargine plus lispro therapy in patients with Type 2 diabetes who have inadequate glycaemic control on oral anti-hyperglycaemic medication: results of the PARADIGM study.

AIMS: To test the hypothesis that initiation and intensification with 25% insulin lispro, 75% insulin lispro protamine suspension (LM25), is non-inferior to initiation and intensification with glargine + insulin lispro therapy on change from baseline in HbA(1c). METHODS: In this randomized, non-inferiority (margin of 0.4%), parallel, prospective, multi-country, 48-week, open-label study, patients (n = 426) with Type 2 diabetes inadequately controlled with oral anti-hyperglycaemic medications were assigned to either initiating therapy with one daily LM25 injection, progressing up to three daily injections (full analysis set n = 211; per protocol set n = 177) or initiating therapy with one daily glargine injection and progressing up to three daily insulin lispro injections (full analysis set n = 212; per protocol set n = 184). RESULTS: LM25 therapy was found to be non-inferior to glargine + insulin lispro therapy by study end (upper limit of 95% CI < 0.4), with a least-squares mean difference (95% CI) in HbA(1c) (LM25 minus glargine + insulin lispro) of -0.4 mmol/mol (95% CI -2.7 to 1.9); -0.04% (95% CI -0.25 to 0.17). No statistically significant differences between treatment groups were found in the percentage of patients achieving HbA(1c) targets or postprandial blood glucose levels. The increase in insulin dose, number of injections and weight change during the course of the study were similar in both groups. Patients in both groups experienced similar hypoglycaemia rates and safety profile. CONCLUSIONS: For patients with Type 2 diabetes inadequately controlled with oral anti-hyperglycaemic medications, glycaemic control when initiating and intensifying with LM25 therapy was found to be non-inferior to treatment with glargine + insulin lispro therapy.

Endovascular management of uretero-Iliac artery fistula.

Uretero-Iliac artery fistula (UIAF) is a rare condition in vascular surgery, its prognosis remains poor with a high mortality, requires rapid multidisciplinary diagnosis and treatment. We report the case of an uretero-Iliac artery fistula in a 65-year-old patient who underwent total pelvectomy with trans-ileal cutaneous ureterostomy (Bricker), followed by pelvic radiotherapy, and placement of a single J ureteral stent, diagnosed by abdominal and pelvic CT, and treated by endovascular approach.

Combi-seq for multiplexed transcriptome-based profiling of drug combinations using deterministic barcoding in single-cell droplets.

Anti-cancer therapies often exhibit only short-term effects. Tumors typically develop drug resistance causing relapses that might be tackled with drug combinations. Identification of the right combination is challenging and would benefit from high-content, high-throughput combinatorial screens directly on patient biopsies. However, such screens require a large amount of material, normally not available from patients. To address these challenges, we present a scalable microfluidic workflow, called Combi-Seq, to screen hundreds of drug combinations in picoliter-size droplets using transcriptome changes as a readout for drug effects. We devise a deterministic combinatorial DNA barcoding approach to encode treatment conditions, enabling the gene expression-based readout of drug effects in a highly multiplexed fashion. We apply Combi-Seq to screen the effect of 420 drug combinations on the transcriptome of K562 cells using only ~250 single cell droplets per condition, to successfully predict synergistic and antagonistic drug pairs, as well as their pathway activities.

Room temperature laser power standard using a microfabricated, electrical substitution bolometer.

The design and performance of a room temperature electrical substitution radiometer for use as an absolute standard for measuring continuous-wave laser power over a wide range of wavelengths, beam diameters, and powers are described. The standard achieves an accuracy of 0.46% (k = 2) for powers from 10 mW to 100 mW and 0.83% (k = 2) for powers from 1 mW to 10 mW and can accommodate laser beam diameters (1/e2) up to 11 mm and wavelengths from 300 nm to 2 µm. At low power levels, the uncertainty is dominated by sensitivity to fluctuations in the thermal environment. The core of the instrument is a planar, silicon microfabricated bolometer with vertically aligned carbon nanotube absorbers, commercial surface mount thermistors, and an integrated heater. Where possible, commercial electronics and components were used. The performance was validated by comparing it to a National Institute of Standards and Technology primary standard through a transfer standard silicon trap detector and by comparing it to the legacy "C-series" standards in operation at the U.S. Air Force Metrology and Calibration Division (AFMETCAL).

An exploratory analysis of factors associated with weight change in a 16-week trial of oral vs. orally disintegrating olanzapine: the PLATYPUS study.

BACKGROUND: We conducted exploratory analyses of the data from a multinational, randomised study to identify factors associated with weight change after 16 weeks of treatment with standard olanzapine tablets (SOT) or sublingual orally disintegrating olanzapine (ODO). METHODS: One hundred and forty nine outpatients who gained weight during prior SOT therapy were enrolled into the study and treated with ODO (N = 84) or SOT (N = 65). Exploratory analyses were conducted with the subset of compliant patients (ODO: n = 60; SOT: n = 47). RESULTS: The decrease in the rate of weight gain at the end of study therapy (change from baseline) was greater in the ODO group than the SOT group (-0.59 kg/week vs. -0.38 kg/week, p = 0.0246). Age was negatively associated with weight change (p = 0.0203) in both treatment groups combined: patients gained 0.7 kg less for every 10 years of age. The least squares mean weight gain was lower with ODO than SOT in male patients (0.35 kg vs. 3.04 kg, p = 0.061), but not female patients and in American patients (0.55 kg vs. 6.21 kg, p < 0.0001), but not Canadian or Mexican patients. CONCLUSIONS: Although not conclusive, these data suggest that ODO may be a reasonable treatment option for some patients who gain weight with SOT. Further research is required to confirm these findings.

Macromolecular scaffolds for immobilizing small molecule microarrays in label-free detection of protein-ligand interactions on solid support.

We explored two macromolecular scaffolds, bovine serum albumin (BSA) and polyvinyl alcohol (PVA), as chemically complementary platforms for immobilizing small molecule compounds on functionalized glass slides. We conjugated biotin molecules to BSA and amine-derivatized PVA and subsequently immobilized the conjugates on epoxy-functionalized glass slides through reaction of free amine residues on BSA and PVA with surface-bound epoxy groups. We studied binding reactions of such immobilized small molecule targets with solution-phase protein probes using an oblique-incidence reflectivity difference scanning optical microscope. The results showed that both BSA and amine-derivatized PVA were effective and efficient as carriers of small molecules with NHS residues and fluoric residues and for immobilization on epoxy-coated solid surfaces. A significant fraction of the conjugated small molecules retain their innate chemical activity.

Spheroidal aggregate culture of rat liver cells: histotypic reorganization, biomatrix deposition, and maintenance of functional activities.

Liver cells isolated from newborn rats and seeded on a non-adherent plastic substratum were found to spontaneously re-aggregate and to form, within a few days, spheroidal aggregates that eventually reached a plateaued diameter of 150-175 micron. Analyses on frozen sections from these spheroids by immunofluorescence microscopy using antibodies to various cytoskeletal elements and extracellular matrix components revealed a sorting out and a histotypic reorganization of three major cell types. A first type consisted of cells that segregated out on the aggregate surface forming a monolayer cell lining; a second type was identified as hepatocytes that regrouped in small islands often defining a central lumen; and a third group of cells reorganized into bile duct-like structures. This intercellular organization in the aggregates was paralleled by the accumulation of extracellular matrix components (laminin, fibronectin, and collagen) and their deposition following a specific pattern around each cell population structure. Determinations of albumin secretion and tyrosine aminotransferase induction by dexamethasone and glucagon at various times after the initiation of the cultures revealed a maintenance of the hepatocyte-differentiated functions for at least up to 2 mo at the levels measured at 3-5 d. It is concluded that cells dispersed as single cells from newborn rat liver conserve in part the necessary information to reconstruct a proper three-dimensional cyto-architecture and that the microenvironment so generated most likely represents a basic requirement for the optimal functioning of these differentiated cells.

SAPK2/p38-dependent F-actin reorganization regulates early membrane blebbing during stress-induced apoptosis.

In endothelial cells, H2O2 induces the rapid formation of focal adhesion complexes at the ventral face of the cells and a major reorganization of the actin cytoskeleton into dense transcytoplasmic stress fibers. This change in actin dynamics results from the activation of the mitogen-activated protein (MAP) kinase stress-activated protein kinase-2/p38 (SAPK2/p38), which, via MAP kinase-activated protein (MAPKAP) kinase-2/3, leads to the phosphorylation of the actin polymerization modulator heat shock protein of 27 kD (HSP27). Here we show that the concomitant activation of the extracellular signal-regulated kinase (ERK) MAP kinase pathway by H2O2 accomplishes an essential survival function during this process. When the activation of ERK was blocked with PD098059, the focal adhesion complexes formed under the plasma membrane, and the actin polymerization activity led to a rapid and intense membrane blebbing. The blebs were delimited by a thin F-actin ring and contained enhanced levels of HSP27. Later, the cells displayed hallmarks of apoptosis, such as DEVD protease activities and internucleosomal DNA fragmentation. Bleb formation but not apoptosis was blocked by extremely low concentrations of the actin polymerization inhibitor cytochalasin D or by the SAPK2 inhibitor SB203580, indicating that the two processes are not in the same linear cascade. The role of HSP27 in mediating membrane blebbing was assessed in fibroblastic cells. In control fibroblasts expressing a low level of endogenous HSP27 or in fibroblasts expressing a high level of a nonphosphorylatable HSP27, H2O2 did not induce F-actin accumulation, nor did it generate membrane blebbing activity in the presence or absence of PD098059. In contrast, in fibroblasts that expressed wild-type HSP27 to a level similar to that found in endothelial cells, H2O2 induced accumulation of F-actin and caused bleb formation when the ERK pathway was inhibited. Cis-platinum, which activated SAPK2 but induced little ERK activity, also induced membrane blebbing that was dependent on the expression of HSP27. In these cells, membrane blebbing was not followed by caspase activation or DNA fragmentation. We conclude that the HSP27-dependent actin polymerization-generating activity of SAPK2 associated with a misassembly of the focal adhesions is responsible for induction of membrane blebbing by stressing agents.

Heat shock resistance conferred by expression of the human HSP27 gene in rodent cells.

Heat shock induces in cells the synthesis of specific proteins called heat shock proteins (HSPs) and a transient state of thermotolerance. The putative role of one of the HSPs, HSP27, as a protective molecule during thermal stress has been directly assessed by measuring the resistance to hyperthermia of Chinese hamster and mouse cells transfected with the human HSP27 gene contained in plasmid pHS2711. One- and two-dimensional gel electrophoresis of [3H]leucine- and [32P]orthophosphate-labeled proteins, coupled with immunological analysis using Ha27Ab and Hu27Ab, two rabbit antisera that specifically recognize the hamster and the human HSP27 protein respectively, were used to monitor expression and inducibility of the transfected and endogenous proteins. The human HSP27 gene cloned in pHS2711 is constitutively expressed in rodent cells, resulting in accumulation of the human HSP27 and all phosphorylated derivatives. No modification of the basal or heat-induced expression of endogenous HSPs is detected. The presence of additional HSP27 protein provides immediate protection against heat shock administered 48 h after transfection and confers a permanent thermoresistant phenotype to stable transfectant Chinese hamster and mouse cell lines. Mild heat treatment of the transfected cells results in an induction of the full complement of the endogenous heat shock proteins and a small increase in thermoresistance, but the level attained did not surpass that of heat-induced thermotolerant control cells. These results indicate that elevated levels of HSP27 is sufficient to give protection from thermal killing. It is concluded that HSP27 plays a major role in the increased thermal resistance acquired by cells after exposure to HSP inducers.

[A case of acute and necrotizing cutaneous Mycobacterium marinum infection in a patient treated with infliximab for Crohn's disease]. / Infection cutanée aiguë et nécrosante a Mycobacterium marinum chez un patient traité par infliximab pour une maladie de Crohn.

BACKGROUND: The increasing use of anti-TNFalpha exposes patients to emerging risks, particularly that of infection. We report a case of severe cutaneous Mycobacterium marinum infection in a patient treated with infliximab and we discuss therapeutic options. PATIENTS AND METHODS: A man treated with infliximab for Crohn's disease developed a severe cutaneous infection with M. marinum. Despite withdrawal of infliximab and the introduction of triple antibiotic therapy, the patient's lesions worsened and surgical treatment was required. DISCUSSION: The worsening experienced by our patient 1 week after the beginning of the treatment is comparable with the immune reconstitution syndrome occasionally observed in tuberculosis in immunocompromised hosts, thus raising the question of the potential value of continuing infliximab treatment. Recommendations are needed concerning the prevention and treatment of M. marinum infections in patients on anti-TNFalpha biotherapies.

[Chloroquine cardiotoxicity in long-term lupus therapy in two patients]. / Cardiotoxicité après un traitement au long cours par chloroquine chez deux patientes lupiques.

BACKGROUND: The antimalarial compounds chloroquine and hydroxychloroquine are widely used in the treatment of connective tissue diseases and are usually well tolerated. We report two cases of chloroquine cardiotoxicity. PATIENTS AND METHODS: Two women (aged 43 and 48 years) were treated for 5 years for lupus. They developed severe conduction disturbances requiring a pacemaker. Plasma chloroquine concentrations were abnormally high in both cases. In one case, a genetic polymorphism modulating the activity of a cytochrome involved in chloroquine metabolism (CYP2C8) was identified. DISCUSSION: Since 1965, 60 cases of occasionally severe cardiotoxicity have been reported following long-term treatment with chloroquine in most cases, but also with hydroxychloroquine. This toxicity must be detected early and close cardiac assessment is required.

Preventive chemotherapy. Where has it got us? Where to go next?

The World Health Organization estimates that a third of the world's population is infected with Mycobacterium tuberculosis. Every second, one person becomes newly infected with tuberculosis (TB). In the past two decades, the spread of human immunodeficiency virus infection, worsening poverty and deteriorating health services have resulted in a steady increase in the overall incidence of TB globally. With treatment of latent TB infection (LTBI), the number of infected persons who develop active TB can be significantly diminished. Prevention through treatment of LTBI should therefore be an integral part of the control of TB. Although only a minority of those with LTBI will develop active disease, the risk varies substantially according to the time since infection and medical risk factors. If persons at low risk for TB are selected for preventive chemotherapy, the individual and public health benefits are low, and a large number will have to be treated to prevent a single active case. It is therefore important to identify and treat patients who are at high risk of disease. Tools for rapid and reliable identification of persons with LTBI who are most likely to progress to active disease are urgently needed, as this will permit rational use of preventive treatment by restricting treatment to those patients with the most favourable risk/benefit ratio. The major challenges are efficient identification of those at highest risk of developing disease and ensuring treatment completion with a non-toxic regimen. If these can be overcome, preventive treatment holds the promise to substantially assist in the achievement of global control of TB.