Stratification by interferon-γ release assay level predicts risk of incident TB

Effect of BCG vaccination against Mycobacterium tuberculosis infection in adult Brazilian health-care workers: a nested clinical trial

BACKGROUND

The effectiveness of BCG vaccine for adult pulmonary tuberculosis remains uncertain. In this study, we aimed to evaluate the effect of vaccination with BCG-Denmark to prevent initial and sustained interferon-γ release assay conversion in Brazilian health-care workers.

METHODS

This substudy is a nested randomised controlled trial embedded within the BRACE trial (NCT04327206). Specifically, this substudy enrolled Brazilian health-care workers (aged ≥18 years) from three sites in Brazil (Manaus, Campo Grande, and Rio de Janeiro) irrespective of previously receiving BCG vaccination. Participants were excluded if they had contraindications to BCG vaccination, more than 1 month of treatment with specific tuberculosis treatment drugs, previous adverse reactions to BCG, recent BCG vaccination, or non-compliance with assigned interventions. Those eligible were randomly assigned (1:1) to either the BCG group (0·1 mL intradermal injection of BCG-Denmark [Danish strain 1331; AJ Vaccines, Copenhagen]) or the placebo group (intradermal injection of 0·9% saline) using a web-based randomisation process in variable-length blocks (2, 4, or 6), and were stratified based on the study site, age (<40, ≥40 to <60, ≥60 years), and comorbidity presence (diabetes, chronic respiratory disease, cardiac condition, hypertension). Sealed syringes were used to prevent inadvertent disclosure of group assignments. The QuantiFERON-TB Gold (QFT) Plus test (Qiagen; Hilden, Germany) was used for baseline and 12-month tuberculosis infection assessments. The primary efficacy outcome was QFT Plus conversion (≥0·35 IU/mL) by 12 months following vaccination in participants who had a negative baseline result (<0·35 IU/mL).

FINDINGS

Between Oct 7, 2020, and April 12, 2021, 1985 (77·3%) of 2568 participants were eligible for QFT Plus assessment at 12 months and were included in this substudy; 996 (50·2%) of 1985 were in the BCG group and 989 (49·8%) were in the placebo group. Overall, 1475 (74·3%) of 1985 participants were women and 510 (25·7%) were men, and the median age was 39 years (IQR 32-47). During the first 12 months, QFT Plus conversion occurred in 66 (3·3%) of 1985 participants, with no significant differences by study site (p=0·897). Specifically, 34 (3·4%) of 996 participants had initial QFT conversion in the BCG group compared with 32 (3·2%) of 989 in the placebo group (risk ratio 1·09 [95% CI 0·67-1·77]; p=0·791).

INTERPRETATION

BCG-Denmark vaccination did not reduce initial QFT Plus conversion risk in Brazilian health-care workers. This finding underscores the need to better understand tuberculosis prevention in populations at high risk.

FUNDING

Bill & Melinda Gates Foundation, the Minderoo Foundation, Sarah and Lachlan Murdoch, the Royal Children's Hospital Foundation, Health Services Union NSW, the Peter Sowerby Foundation, SA Health, the Insurance Advisernet Foundation, the NAB Foundation, the Calvert-Jones Foundation, the Modara Pines Charitable Foundation, the United Health Group Foundation, Epworth Healthcare, and individual donors.

TRANSLATION

For the Portuguese translation of the abstract see Supplementary Materials section.

Quantitative Interferon-Gamma Releasing Assay in Predicting Tuberculosis in South Korean Military: A Retrospective Cohort Study

OBJECTIVES

The interferon-gamma releasing assay (IGRA) has been widely used to diagnose latent tuberculosis infection (TBI). However, there are limited data on the association between performance in the IGRA and risk of tuberculosis disease (TBD), as well as on the appropriate IGRA threshold for initiating TBI treatment.

METHODS

The analysis was performed using the IGRA results in the Korean Military Manpower Administration database (January 2017 - December 2021), and TBD cases reported to the Korean Military Medical Command (January 2017 - June 2023). All Korean candidates for 18-month military service underwent the IGRA in the pre-enlistment examination, and enlistees who tested positive (≥0.35 IU/mL) were advised to receive TBI treatment before enlistment.

RESULTS

From 2017 to 2021, 1,647,941 individuals were screened, with 29,574 testing positive for IGRA. Excluding non-enlistees, namely individuals with TBD before enlistment, 19,387 individuals were IGRA positive and 1,356,324 IGRA negative. Of the positives, 4,351 were excluded due to discontinued or ongoing TBI treatment at or after enlistment. During follow-up of 9,219 untreated and 5,818 treated positive individuals and 1,356,324 negatives, TBD occurred in 22 of the IGRA positive individuals (97.5/100,000 person-years [95% CI 61.1 - 147.7]), predominantly in the untreated group (18 cases, 130.1/100,000 person-years [95% CI 77.1 - 205.7]) compared to the treated group (4 cases, 45.9/100,000 person-years [95% CI 12.5 - 117.4]), while 57 cases occurred in the IGRA negative group (2.8/100,000 person-years [95% CI 2.2 - 3.6]). Elevating the cut-off of IGRA from 0.35 IU/mL to 1.33 IU/mL increased positive predictive value (0.2% vs. 0.4%, p=0.03), with insignificant loss of sensitivity (24% vs. 20%, p=0.69) and decreased numbers needing treatment from 790.5 to 415.3.

CONCLUSION

Elevated IGRA levels before enlistment are associated with risk of TBD during military service. It is worth considering raising the IGRA threshold for treatment of TBI in cohorts of healthy, young military individuals.

Incipient tuberculosis: a comprehensive overview

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

Comparison of Tuberculin Skin Testing and Interferon-γ Release Assays in Predicting Tuberculosis Disease

Importance

Elimination of tuberculosis (TB) disease in the US hinges on the ability of tests to detect individual risk of developing disease to inform prevention. The relative performance of 3 available TB tests-the tuberculin skin test (TST) and 2 interferon-γ release assays (IGRAs; QuantiFERON-TB Gold In-Tube [QFT-GIT] and SPOT.TB [TSPOT])-in predicting TB disease development in the US remains unknown.

Objective

To compare the performance of the TST with the QFT-GIT and TSPOT IGRAs in predicting TB disease in high-risk populations.

Design, Setting, and Participants

This prospective diagnostic study included participants at high risk of TB infection (TBI) or progression to TB disease at 10 US sites between 2012 and 2020. Participants of any age who had close contact with a case patient with infectious TB, were born in a country with medium or high TB incidence, had traveled recently to a high-incidence country, were living with HIV infection, or were from a population with a high local prevalence were enrolled from July 12, 2012, through May 5, 2017. Participants were assessed for 2 years after enrollment and through registry matches until the study end date (November 15, 2020). Data analysis was performed in June 2023.

Exposures

At enrollment, participants were concurrently tested with 2 IGRAs (QFT-GIT from Qiagen and TSPOT from Oxford Immunotec) and the TST. Participants were classified as case patients with incident TB disease when diagnosed more than 30 days from enrollment.

Main Outcomes and Measures

Estimated positive predictive value (PPV) ratios from generalized estimating equation models were used to compare test performance in predicting incident TB. Incremental changes in PPV were estimated to determine whether predictive performance significantly improved with the addition of a second test. Case patients with prevalent TB were examined in sensitivity analysis.

Results

A total of 22 020 eligible participants were included in this study. Their median age was 32 (range, 0-102) years, more than half (51.2%) were male, and the median follow-up was 6.4 (range, 0.2-8.3) years. Most participants (82.0%) were born outside the US, and 9.6% were close contacts. Tuberculosis disease was identified in 129 case patients (0.6%): 42 (0.2%) had incident TB and 87 (0.4%) had prevalent TB. The TSPOT and QFT-GIT assays performed significantly better than the TST (PPV ratio, 1.65 [95% CI, 1.35-2.02] and 1.47 [95% CI, 1.22-1.77], respectively). The incremental gain in PPV, given a positive TST result, was statistically significant for positive QFT-GIT and TSPOT results (1.64 [95% CI, 1.40-1.93] and 1.94 [95% CI, 1.65-2.27], respectively).

Conclusions and Relevance

In this diagnostic study assessing predictive value, IGRAs demonstrated superior performance for predicting incident TB compared with the TST. Interferon-γ release assays provided a statistically significant incremental improvement in PPV when a positive TST result was known. These findings suggest that IGRA performance may enhance decisions to treat TBI and prevent TB.

Screening for latent tuberculosis in migrants-status quo and future challenges

OBJECTIVES

To review the evidence that migrants from tuberculosis (TB) high-incidence countries migrating to TB low-incidence countries significantly contribute to active TB cases in the counties of destination, primarily through reactivation of latent TB.

METHODS

This is a narrative review. The different screening programs in the countries of destination are reviewed either based on screening and preventive treatment of latent TB pre or more commonly - post arrival.

RESULTS

Screening can be performed using interferon-gamma release assays (IGRA) or tuberculin skin tests (TST). Preventive treatment of latent TB is using either monotherapy with isoniazid, or in combination with rifampicin or rifapentine. We discuss the ethical issues of preventive treatment in asymptomatic individuals and how these are addressed in different screening programs.

CONCLUSION

Screening migrants from TB high endemic countries to TB low endemic countries is beneficial. There is a lack of standardization and agreement on screening protocols, follow up and treatment.

Is the new tuberculous antigen-based skin test ready for use as an alternative to tuberculin skin test/interferon-gamma release assay for tuberculous diagnosis? A narrative review

In recent years, novel specific Mycobacteria tuberculous (TB) antigen-based skin test (TBST) has become available for clinical use. The mechanism of TBST is similar to the interferon-gamma release assay (IGRA), making it a potential alternative for identifying latent tuberculous infection (LTBI), especially in subjects with history of bacille Calmette-Guérin vaccination. Three different commercial brands have been developed in Denmark, Russia, and China. Clinical studies in the respective countries have shown promising sensitivity, specificity, and safety profile. Some studies attempted to address the applicability of TBST in specific subject groups but the discrepancy in defining LTBI and problematic methodologies undermine the generalisation of the results to other communities across the world. Limited cost-effectiveness studies for TBST have been conducted without exploring the health economics for preventing development of LTBI into active TB. Unlike IGRA, no clinical studies have addressed the correlation of TBST results (magnitude of induration) with the likelihood of development of active TB. Moreover, the different TBSTs are not widely available for clinical use. While TBST is a promising test to overcome the shortcomings of tuberculin skin tests, more clinical data are needed to support its general application globally for the diagnosis of LTBI.

Tuberculosis infection and hypertension: prevalence estimates from the US National Health and Nutrition Examination Survey

OBJECTIVES

Tuberculosis infection (TBI) is marked by dynamic host-pathogen interactions with persistent low-grade inflammation and is associated with increased risk of cardiovascular diseases (CVD) including acute coronary syndrome, myocardial infarction and stroke. However, few studies assess the relationship between TBI and hypertension, an intermediate of CVD. We sought to determine the association between TBI and hypertension using data representative of the adult US population.

METHODS

We performed cross-sectional analyses using data from the 2011-2012 US National Health and Nutrition Examination Survey (NHANES). Eligible participants included adults with valid QuantiFERON-TB Gold In-Tube (QFT-GIT) test results who also had blood pressure measures and no history of TB disease. TBI was defined by a positive QFT-GIT. We defined hypertension by either elevated measured blood pressure levels (ie, systolic ≥130 mm Hg or diastolic ≥80 mm Hg) or known hypertension indications (ie, self-reported previous diagnosis or use of antihypertensive medications). Analyses were performed using robust quasi-Poisson regressions and accounted for the stratified probability sampling design of NHANES.

RESULTS

The overall prevalence of TBI was 5.7% (95% CI 4.7% to 6.7%) and hypertension was present among 48.9% (95% CI 45.2% to 52.7%) of participants. The prevalence of hypertension was higher among those with TBI (58.5%, 95% CI 52.4% to 64.5%) than those without TBI (48.3%, 95% CI 44.5% to 52.1%) (prevalence ratio (PR) 1.2, 95% CI 1.1 to 1.3). However, after adjusting for confounders, the prevalence of hypertension was similar for those with and without TBI (adjusted PR 1.0, 95% CI 1.0 to 1.1). The unadjusted prevalence of hypertension was higher among those with TBI versus no TBI, especially among individuals without CVD risk factors including those with normal body mass index (PR 1.6, 95% CI 1.2 to 2.0), euglycaemia (PR 1.3, 95% CI 1.1 to 1.5) or non-smokers (PR 1.2, 95% CI 1.1 to 1.4).

CONCLUSIONS

More than half of adults with TBI in the USA had hypertension. Importantly, we observed a relationship between TBI and hypertension among those without established CVD risk factors.

SUMMARY

The prevalence of hypertension was high (59%) among adults with TBI in the USA. In addition, we found that the prevalence of hypertension was significantly higher among adults with positive QFT without established hypertension risk factors.

Shift in Tissue-Specific Immune Niches and CD137 Expression in Tuberculoma of Pembrolizumab-Treated Nasopharyngeal Carcinoma Patients

The use of immune checkpoint inhibitors (ICIs) in cancer treatment has shown promise but can also have unintended consequences, such as reactivating latent tuberculosis (TB). To develop treatments that address ICIs-related adverse events, it is essential to understand cellular heterogeneity across healthy and pathological tissues. We performed cross-tissue multiplexed staining analysis on samples from two patients with TB reactivation during pembrolizumab treatment for metastatic nasopharyngeal carcinoma. CD8+ T cells, rather than CD4+ T cells, accumulated preferentially in the tuberculoma and were associated with increased production of IFNγ and expression of CD137. Additionally, CD137 enrichment played a role in the spatial organization of the tuberculoma, with specific interaction limited to spatial proximal cells between IFNγ+ CD137+ CD8+ T cells and IL12+ CD137+ type-1 macrophages. This unique feature was not observed in non-tumoral or tumoral tissues. Our analysis of public transcriptomic datasets supported the notion that this cellular interaction was more prominent in patients with durable ICI responses compared to those with non-ICI-related TB. We suggest that shifts towards CD137-rich immune niches are correlated with both off-target immune-related adverse events and anti-tumor efficacy. Targeting the tumor microenvironment through conditional activation of anti-CD137 signaling in combination with ICIs can modulate the reactivity of T cells and macrophages for localized tumor killing without the potential off-target immune-related risks associated with ICIs alone.

[Recommendations for Contact Tracing for Tuberculosis - Update 2023]

The aim of contact tracing for tuberculosis is in addition to active case finding the detection of chains of infection and the prevention of the further spread of the disease. In this context, a careful selection of contact persons is necessary, depending on the type and duration of contact, to identify persons who are recently infected and therefore to increase the benefit of a preventive therapy and to avoid unnecessary testing of persons who are not at risk of infection. Since the last update of the recommendations on contact tracing, data on the use of interferon-y release assays (IGRAs) in children has been improved markedly. These are the preferred test in contact tracing of adults. For children, both IGRAs and the tuberculin skin test can be used equivalently. Rifampicin for 4 months, rifampicin and isoniazid for 3 months, or isoniazid for 9 months are recommended as preventive therapy in cases of confirmed infection.The implementation of the contact tracing in different age groups as well as legal framework conditions and socio-medical aspects and challenges are dealt with in detail. In addition, special cases, such as environmental screening in day-care centers, schools, or other community facilities, are discussed separately.

[Recommendations for contact tracing for tuberculosis - update 2023]

The aim of contact tracing for tuberculosis is in addition to active case finding the detection of chains of infection and the prevention of the further spread of the disease. In this context, a careful selection of contact persons is necessary, depending on the type and duration of contact, to identify persons who are recently infected and therefore to increase the benefit of a preventive therapy and to avoid unnecessary testing of persons who are not at risk of infection. Since the last update of the recommendations on contact tracing, data on the use of interferon-y release assays (IGRAs) in children has been improved markedly. These are the preferred test in contact tracing of adults. For children, both IGRAs and the tuberculin skin test can be used equivalently. Rifampicin for 4 months, rifampicin and isoniazid for 3 months, or isoniazid for 9 months are recommended as preventive therapy in cases of confirmed infection.The implementation of the contact tracing in different age groups as well as legal framework conditions and socio-medical aspects and challenges are dealt with in detail. In addition, special cases, such as environmental screening in day-care centers, schools, or other community facilities, are discussed separately.

Tuberculosis infection and hypertension: Prevalence estimates from the US National Health and Nutrition Examination Survey

Objectives

Latent Tuberculosis infection (LTBI) is marked by dynamic host-pathogen interactions with persistent low-grade inflammation and is associated with increased risk of cardiovascular diseases (CVD) including acute coronary syndrome, myocardial infarction, and stroke. However, few studies assess the relationship between LTBI and hypertension, an intermediate of CVD. We sought to determine the association between LTBI and hypertension using data representative of the adult US population.

Methods

We performed cross-sectional analyses using data from the 2011-2012 US National Health and Nutrition Examination Survey (NHANES). Eligible participants included adults with valid QuantiFERON-TB Gold In-Tube (QFT-GIT) test results who also had blood pressure measures and no history of TB disease. LTBI was defined by a positive QFT-GIT. We defined hypertension by either elevated measured blood pressure levels (i.e., systolic ≥130mmHg or diastolic ≥80mmHg) or known hypertension indications (i.e., self-reported previous diagnosis or use of antihypertensive medications). Analyses were performed using robust quasi-Poisson regressions and accounted for the stratified probability sampling design of NHANES.

Results

The overall prevalence of LTBI was 5.7% (95%CI 4.7-6.7) and hypertension was present among 48.9% (95%CI 45.2-52.7) of participants. The prevalence of hypertension was higher among those with LTBI (58.5%, 95%CI 52.4-64.5) than those without LTBI (48.3%, 95%CI 44.5-52.1) (prevalence ratio [PR]=1.2, 95%CI 1.1-1.3). However, after adjusting for confounders, the prevalence of hypertension was similar for those with and without LTBI (adjusted PR=1.0, 95%CI 0.9 -1.1). Among individuals without CVD risk factors of elevated BMI (PRnormal BMI=1.6, 95%CI 1.2-2.0), hyperglycemia (PReuglycemia=1.3, 95%CI 1.1-1.5), or cigarette smoking (PRnon-smokers=1.2, 95%CI 1.1-1.4), the unadjusted prevalence of hypertension was higher among those with LTBI vs. no LTBI.

Conclusions

More than half of adults with LTBI in the US had hypertension. Importantly, we observed a relationship between LTBI and hypertension among those without established CVD risk factors.

What's Old and New in Tuberculosis Vaccines for Children

Tuberculosis (TB) is a leading cause of global child mortality. Until the turn of the 21st century, Mycobacterium bovis bacille Calmette-Guerin (BCG) was the only vaccine to prevent TB. The pediatric TB vaccine pipeline has advanced in the past decade to include the evaluation of novel whole cell vaccines to replace infant BCG and investigation of subunit and whole cell vaccines to boost TB immunity during adolescence. We describe the history of BCG, current TB vaccine candidates in clinical trials, and the challenges and opportunities for future TB vaccine research in children. Children are a critical target population for TB vaccines, and expansion of the pediatric TB vaccine pipeline is urgently needed to end the TB pandemic.

Evaluation of a transcriptomic signature of tuberculosis risk in combination with an interferon gamma release assay: A diagnostic test accuracy study

BACKGROUND

We evaluated the diagnostic and prognostic performance of a transcriptomic signature of tuberculosis (TB) risk (RISK11) and QuantiFERON-TB Gold-plus (QFTPlus) as combination biomarkers of TB risk.

METHODS

Healthy South Africans who were HIV-negative aged 18-60 years with baseline RISK11 and QFTPlus results were evaluated in a prospective cohort study conducted between Sept 20, 2016 and Dec 20, 2019. Prevalence and incidence-rate ratios were used to evaluate risk of TB. Positive (LR+) and negative (LR-) likelihood ratios were used to compare individual tests versus Both-Positive (RISK11+/QFTPlus+) and Either-Positive (RISK11+ or QFTPlus+) combinations.

FINDINGS

Among 2912 participants, prevalent TB in RISK11+/QFTPlus+ participants was 13·3-fold (95% CI 4·2-42·7) higher than RISK11-/QFTPlus-; 2·4-fold (95% CI 1·2-4·8) higher than RISK11+/QFTPlus-; and 4·5-fold (95% CI 2·5-8·0) higher than RISK11-/QFTPlus+ participants. Risk of incident TB in RISK11+/QFTPlus+ participants was 8·3-fold (95% CI 2·5-27·0) higher than RISK11-/QFTPlus-; 2·5-fold (95% CI 1·0-6·6) higher than RISK11+/QFTPlus-; and 2·1-fold (95% CI 1·2-3·4) higher than RISK11-/QFTPlus+ participants, respectively. Compared to QFTPlus, the Both-Positive test combination increased diagnostic LR+ from 1·3 (95% CI 1·2-1·5) to 4·7 (95% CI 3·2-7·0), and prognostic LR+ from 1·4 (95% CI 1·2-1·5) to 2·8 (95% CI 1·5-5·1), but did not improve upon RISK11 alone. Compared with RISK11, the Either-Positive test combination decreased diagnostic LR- from 0·7 (95% CI 0·6-0·9) to 0·3 (95% CI 0·2-0·6), and prognostic LR- from 0·9 (95% CI 0·8-1·0) to 0·3 (0·1-0·7), but did not improve upon QFTPlus alone.

INTERPRETATION

Combining two tests such as RISK11 and QFTPlus, with discordant individual performance characteristics does not improve overall discriminatory performance, relative to the individual tests.

FUNDING

Bill and Melinda Gates Foundation, South African Medical Research Council.

Predicting Airborne Infection Risk: Association Between Personal Ambient Carbon Dioxide Level Monitoring and Incidence of Tuberculosis Infection in South African Health Workers

BACKGROUND

High rates of tuberculosis (TB) transmission occur in hospitals in high-incidence countries, yet there is no validated way to evaluate the impact of hospital design and function on airborne infection risk. We hypothesized that personal ambient carbon dioxide (CO2) monitoring could serve as a surrogate measure of rebreathed air exposure associated with TB infection risk in health workers (HWs).

METHODS

We analyzed baseline and repeat (12-month) interferon-γ release assay (IGRA) results in 138 HWs in Cape Town, South Africa. A random subset of HWs with a baseline negative QuantiFERON Plus (QFT-Plus) underwent personal ambient CO2 monitoring.

RESULTS

Annual incidence of TB infection (IGRA conversion) was high (34%). Junior doctors were less likely to have a positive baseline IGRA than other HWs (OR, 0.26; P = .005) but had similar IGRA conversion risk. IGRA converters experienced higher median CO2 levels compared to IGRA nonconverters using quantitative QFT-Plus thresholds of ≥0.35 IU/mL (P < .02) or ≥1 IU/mL (P < .01). Median CO2 levels were predictive of IGRA conversion (odds ratio [OR], 2.04; P = .04, ≥1 IU/mL threshold). Ordinal logistic regression demonstrated that the odds of a higher repeat quantitative IGRA result increased by almost 2-fold (OR, 1.81; P = .01) per 100 ppm unit increase in median CO2 levels, suggesting a dose-dependent response.

CONCLUSIONS

HWs face high occupational TB risk. Increasing median CO2 levels (indicative of poor ventilation and/or high occupancy) were associated with higher likelihood of HW TB infection. Personal ambient CO2 monitoring may help target interventions to decrease TB transmission in healthcare facilities and help HWs self-monitor occupational risk, with implications for other airborne infections including coronavirus disease 2019.

Modeling the Cost-Effectiveness of Latent Tuberculosis Screening and Treatment Strategies in Recent Migrants to a Low-Incidence Setting

Many tuberculosis (TB) cases in low-incidence settings are attributed to reactivation of latent TB infection (LTBI) acquired overseas. We assessed the cost-effectiveness of community-based LTBI screening and treatment strategies in recent migrants to a low-incidence setting (Australia). A decision-analytical Markov model was developed that cycled 1 migrant cohort (≥11-year-olds) annually over a lifetime from 2020. Postmigration/onshore and offshore (screening during visa application) strategies were compared with existing policy (chest x-ray during visa application). Outcomes included TB cases averted and discounted cost per quality-adjusted life-year (QALY) gained from a health-sector perspective. Most recent migrants are young adults and cost-effectiveness is limited by their relatively low LTBI prevalence, low TB mortality risks, and high emigration probability. Onshore strategies cost at least $203,188 (Australian) per QALY gained, preventing approximately 2.3%-7.0% of TB cases in the cohort. Offshore strategies (screening costs incurred by migrants) cost at least $13,907 per QALY gained, preventing 5.5%-16.9% of cases. Findings were most sensitive to the LTBI treatment quality-of-life decrement (further to severe adverse events); with a minimal decrement, all strategies caused more ill health than they prevented. Additional LTBI strategies in recent migrants could only marginally contribute to TB elimination and are unlikely to be cost-effective unless screening costs are borne by migrants and potential LTBI treatment quality-of-life decrements are ignored.

Protection against tuberculosis by Bacillus Calmette-Guérin (BCG) vaccination: A historical perspective

Bacillus Calmette-Guérin (BCG) was developed exactly 100 years ago, and it is still the only licensed tuberculosis (TB) vaccine and the most frequently administered of all vaccines worldwide. Despite universal vaccination policies in TB-endemic settings, the burden of TB remains high. Although BCG protects against Mycobacterium tuberculosis infection and TB disease, the level of protection varies greatly between age groups and settings. In this review, we present a historical perspective and describe the evidence for BCG's ability to protect against TB as well as the factors that influence protection. We also present the immunological mechanisms through which BCG vaccination induces protection, focusing on T cell, B cell, and innate immunity. Finally, we discuss several possibilities to boost BCG's efficacy, including alternative vaccination routes, BCG revaccination, and use of recombinant BCG vaccines, and describe the knowledge gaps that exist with respect to BCG's protection against TB.

Protective efficacy of 6-week regimen for latent tuberculosis infection treatment in rural China: 5-year follow-up of a randomised controlled trial

Background

Enlarging tuberculosis (TB) preventive treatment among at-risk populations is a critical component of the End TB Strategy. There is an urgent need to develop suitable latent tuberculosis infection (LTBI) testing and treatment tools according to the local TB epidemic and available resources worldwide.

Methods

Based on an open-label randomised controlled trial conducted since 2015 in China among rural residents aged 50–70 years with LTBI, the protective efficacy of a 6-week twice-weekly regimen of rifapentine plus isoniazid was further evaluated in a 5-year follow-up survey.

Results

1298 treated participants and 1151 untreated controls were included in the 5-year protective efficacy analysis. In the per-protocol analysis, the incidence rate was 0.49 (95% CI 0.30–0.67) per 100 person-years in the untreated control group and 0.19 (95% CI 0.07–0.32) per 100 person-years in the treated group; the protection rate was 61.22%. Subgroup analysis showed that the protection rate was 76.82% in the per-protocol analysis among participants with baseline interferon (IFN)-γ levels in the highest quartile (≥3.25 IU·mL⁻¹). Multiple logistic regression analysis indicated that participants with baseline body mass index <18.5 kg·m⁻² and with pulmonary fibrotic lesions had increased hazard of developing active disease with an adjusted hazard ratio (aHR) of 3.64 (95% CI 1.20–11.00) and 5.99 (95% CI 2.20–16.27), respectively. In addition, individuals with higher baseline IFN-γ levels showed an increased risk of TB occurrence (aHR 2.27, 95% CI 1.13–4.58).

Conclusions

Our findings suggest the 6-week twice-weekly regimen of rifapentine plus isoniazid for LTBI treatment might be an optional tool for TB control in the Chinese population.

A 6-week twice-weekly rifapentine plus isoniazid regimen showed a protective efficacy of >60% in 5 years, which indicated that preventive treatment based on a short-course regimen might be an optional tool for TB control in China.https://bit.ly/2Yeey7i

Engaging frontline providers: an important key to eliminating tuberculosis in Canada, and other high-income countries

The greatest human cost of the rapidly moving pandemic of SARS-CoV-2 may be due to its impact on the response to other diseases. One such other disease is tuberculosis (TB). All indications suggest that COVID-19-related diversions of healthcare resources and disruptions to public health programming will exacerbate the slower moving pandemic of TB. This is expected to set back TB elimination efforts by years. This is a prediction that is especially relevant to Canada, which has repeatedly failed to meet pre-set targets for the elimination of TB even before the COVID-19 pandemic began. A collaborative approach to achieve TB elimination, one that engages all care providers, has recently been emphasized by the STOP-TB Partnership. Among TB elimination strategies, frontline providers (e.g., family physicians, emergency room physicians, and others) are well positioned to identify candidates for the treatment of latent TB infection, and make the diagnosis of infection-spreading cases of TB in a timely manner, thereby interrupting forward-moving chains of transmission. Electronic medical records offer the promise of automating these processes. In this commentary, we promote broader engagement of the workforce across multiple sectors of medicine to reduce TB associated morbidity and mortality, interrupt transmission, and shrink the reservoir of latent TB infection.

Latent Tuberculosis Infection Screening and Treatment in Congregate Settings (TB FREE COREA): Demographic Profiles of Interferon-Gamma Release Assay Cohort

In 2017, the Korean government launched an unprecedentedly large-scaled latent tuberculosis infection (LTBI) screening project which covered more than a million individuals in congregate settings. A total of 1,047,689 participants of source population (n = 2,336,157) underwent LTBI testing from 2017 to 2018. The overall LTBI test uptake rate during this project was 44.8%. Workers in daycare centers (83.5%) and kindergartens (78.9%) showed high participation rate. A total of 1,012,206 individuals with valid results of interferon-gamma release assay (IGRA) were selected to constitute the IGRA cohort. Most of the enrolled participants in the IGRA cohort were in their working age. Approximately, three-quarters of total enrolled population were female. Investigating the LTBI prevalence, stages of LTBI care cascade, natural history of LTBI, efficacy of LTBI treatment and cost-effectiveness of LTBI screening are feasible within this IGRA cohort.

Prevalence and risk factors for latent tuberculosis in polish healthcare workers: the comparison of tuberculin skin test and interferon-gamma release assay (IGRA) performance

Background

Tuberculosis (TB) is still one of the most common infectious diseases worldwide. Health care workers (HCW) are at particular risk of the disease due to their constant exposure to TB patients or their specimens, nevertheless no specific surveillance is widely recommended in this group of professionals. Both, tuberculin skin test (TST) and interferon-gamma-release-assays (IGRAs) are widely applied to detect latent tuberculosis infection (LTBI). The aim of the present study was to evaluate the prevalence and risks of LTBI in the population of Polish HCW, to identify factors associated with LTBI, as well as to determine the rate of the discordance between the results of the two applied tests in relation to various factors in a TB endemic setting. The study participants were recruited from several health care facilities (hospitals and outpatients clinics) all over the country. Laboratory personnel included 156 persons from both TB and non-TB laboratories (118 clinical pathologists, 38 laboratory technicians), 31 medical doctors, 29 nurses (from both TB and non-TB wards and from family practices), 6 other medical employees (patients assistants). Out of examined group 88 (40%) declared constant (everyday) occupational contact with TB patients and/or contagious biologic materials, 134 (60%) reported sporadic (incidental) contact (few times a year). Administrative HCWs who were not in direct contact with patients were not included in the study group.

Material and methods

LTBI status was prospectively evaluated in 222 HCW, 204 females, 18 males, aged 40.8 ± 9 years, with tuberculin skin test (TST) and interferon gamma release assay (QuantiFERON-TB-Gold in Tube – QFT GIT).

Results

TST ≥ 10 mm was found in 58% of HCW, QFT GIT ≥ 0.35 IU/ml in 23%. Nevertheless the relative number of positive QFT GIT in HCW above 45 years of age exceeded those obtained in general population (prevalence of positive QTF test in polish adult population is around 23%). The risk of obtaining positive QFT GIT was significantly increased in the participants older than 44 years (OR = 4.95, 95%CI:2.375–10.193), in those employed > 10 years (OR = 2.726, 95%CI:1.126–6.599), and in those who reported the direct contact with tuberculous patients or infected biological materials (OR = 8.135, 95%CI:1.297–51.016). The concordance between TST and IGRA was poor (kappa 0.23), especially in younger participants, possibly due to BCG vaccination in childhood.

Conclusion

The increased risk of LTBI in Polish HCW was related to age, duration of employment and contact with infectious patients or their biological specimens. TB infection control measures in health care facilities in Poland are still insufficient. It is crucial to increase awareness about the importance of detecting and treating LTBI of HCW.

Longitudinal Mycobacterium tuberculosis specific interferon-γ responses in Ethiopian HIV-negative women during pregnancy and post-partum

Pregnancy may influence cellular immune responses to Mycobacterium tuberculosis. We investigated M. tuberculosis-specific interferon-γ responses in women followed longitudinally during pregnancy and postpartum. Interferon-γ levels (stimulated by M. tuberculosis antigens [TB1 and TB2] and mitogen included in the QuantiFERON-TB Gold Plus assay) were measured in blood from pregnant HIV-negative women identified from a prospective cohort at Ethiopian antenatal care clinics. Longitudinal comparisons included women without active tuberculosis (TB) with M. tuberculosis-triggered interferon-γ responses of ≥ 0.20 IU/ml, sampled on two and/or three occasions (1st/2nd trimester, 3rd trimester, and 9 months postpartum). Among 2,093 women in the source cohort, 363 met inclusion criteria for longitudinal comparisons of M. tuberculosis-stimulated interferon-γ responses. Median M. tuberculosis-triggered interferon-γ concentrations were higher at 3rd than those at the 1st/2nd trimester (in 38 women with samples available from these time points; TB1: 2.8 versus 1.6 IU/ml, P = 0.005; TB2: 3.3 versus 2.8 IU/ml, P = 0.03) and postpartum (in 49 women with samples available from these time points; TB1: 3.1 versus 2.2 IU/ml, P = 0.01; TB2: 3.1 versus 2.3 IU/ml, P = 0.03). In contrast, mitogen-stimulated interferon-γ levels were lower at 3rd than those at 1st/2nd trimester (in 32 women with samples available from these time points: 21.0 versus 34.9 IU/ml, P = 0.02). Results were similar in 22 women sampled on all 3 occasions. In HIV-negative women, M. tuberculosis-stimulated interferon-γ responses were higher during the 3rd trimester than those at earlier stages of pregnancy and postpartum, despite decreased mitogen-triggered responses. These findings suggest increased M. tuberculosis-specific cellular responses due to dynamic changes of latent TB infection during pregnancy.

Interferon-gamma release assay levels and risk of progression to active tuberculosis: a systematic review and dose-response meta-regression analysis

Background

Identifying and treating individuals with high risk of progression from latent tuberculosis infection to active tuberculosis (TB) disease is critical for eliminating the disease. We aimed to conduct a systematic review and meta-regression analysis to quantify the dose-response relationship between interferon-gamma release assay (IGRA) levels and the risk of progression to active TB.

Methods

We searched PubMed and Embase from 1 January 2001 to 10 May 2020 for longitudinal studies that reported the risk of progression from latent to active TB as a function of baseline IGRA values. We used a novel Bayesian meta-regression method to pool effect sizes from included studies and generate a continuous dose-response risk curve. Our modeling framework enabled us to incorporate random effects across studies, and include data with different IGRA ranges across studies. The quality of included studies were assessed using the Newcastle-Ottawa scale (NOS).

Results

We included 34 studies representing 581,956 person-years of follow-up with a total of 788 incident cases of TB in the meta-regression analysis. Higher levels of interferon-gamma were associated with increased risk of progression to active tuberculosis. In the dose-response curve, the risk increased sharply between interferon-gamma levels 0 and 5 IU/ml, after which the risk continued to increase moderately but at a slower pace until reaching about 15 IU/ml where the risk levels off. Compared to 0 IU/ml, the relative risk of progression to active TB among those with interferon-gamma levels of 0.35, 1, 5, 10, 15, and 20 IU/ml were: 1.64 (1.28–2.08), 2.90 (2.02–3.88), 11.38 (6.64–16.38), 19.00 (13.08–26.90), 21.82 (14.65–32.57), and 22.31 (15.43–33.00), respectively. The dose-response relationship remains consistent when limiting the analysis to studies that scored highest in the NOS.

Conclusion

The current practice of dichotomizing IGRA test results simplifies the TB infection disease continuum. Evaluating IGRA test results over a continuous scale could enable the identification of individuals at greatest risk of progression to active TB.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06141-4.

Quantifying the rates of late reactivation tuberculosis: a systematic review

The risk of tuberculosis is greatest soon after infection, but Mycobacterium tuberculosis can remain in the body latently, and individuals can develop disease in the future, sometimes years later. However, there is uncertainty about how often reactivation of latent tuberculosis infection (LTBI) occurs. We searched eight databases (inception to June 25, 2019) to identify studies that quantified tuberculosis reactivation rates occurring more than 2 years after infection (late reactivation), with a focus on identifying untreated study cohorts with defined timing of LTBI acquisition (PROSPERO registered: CRD42017070594). We included 110 studies, divided into four methodological groups. Group 1 included studies that documented late reactivation rates from conversion (n=14) and group 2 documented late reactivation rates in LTBI cohorts from exposure (n=11). Group 3 included 86 studies in LTBI cohorts with an unknown exposure history, and group 4 included seven ecological studies. Since antibiotics have been used to treat tuberculosis, only 11 studies have documented late reactivation rates in infected, untreated cohorts from either conversion (group 1) or exposure (group 2); six of these studies lasted at least 4 years and none lasted longer than 10 years. These studies found that tuberculosis rates declined over time, reaching approximately 200 cases per 100 000 person-years or less by the fifth year, and possibly declining further after 5 years but interpretation was limited by decreasing or unspecified cohort sizes. In cohorts with latent tuberculosis and an unknown exposure history (group 3), tuberculosis rates were generally lower than those seen in groups 1 and 2, and beyond 10 years after screening, rates had declined to less than 100 per 100 000 person-years. Reinfection risks limit interpretation in all studies and the effect of age is unclear. Late reactivation rates are commonly estimated or modelled to prioritise tuberculosis control strategies towards tubuculosis elimination, but significant gaps remain in our understanding that must be acknowledged; the relative importance of late reactivation versus early progression to the global burden of tuberculosis remains unknown.

Tuberculosis endotypes to guide stratified host-directed therapy

There is hope that host-directed therapy (HDT) for Tuberculosis (TB) can either shorten treatment duration, help cure drug resistant disease or limit the immunopathology. Many candidate HDT drugs have been proposed, however solid evidence only exists for a few select patient groups. The clinical presentation of TB is variable, with differences in severity, tissue pathology, and bacillary burden. TB clinical phenotypes likely determine the potential benefit of HDT. Underlying TB clinical phenotypes, there are TB "endotypes," defined as distinct molecular profiles, with specific metabolic, epigenetic, transcriptional, and immune phenotypes. TB endotypes can be characterized by either immunodeficiency or pathologic excessive inflammation. Additional factors, like comorbidities (HIV, diabetes, helminth infection), structural lung disease or Mycobacterial virulence also drive TB endotypes. Precise disease phenotyping, combined with in-depth immunologic and molecular profiling and multimodal omics integration, can identify TB endotypes, guide endotype-specific HDT, and improve TB outcomes, similar to advances in cancer medicine.

Discovery and validation of a personalized risk predictor for incident tuberculosis in low transmission settings

The risk of tuberculosis (TB) is variable among individuals with latent Mycobacterium tuberculosis infection (LTBI), but validated estimates of personalized risk are lacking. In pooled data from 18 systematically identified cohort studies from 20 countries, including 80,468 individuals tested for LTBI, 5-year cumulative incident TB risk among people with untreated LTBI was 15.6% (95% confidence interval (CI), 8.0-29.2%) among child contacts, 4.8% (95% CI, 3.0-7.7%) among adult contacts, 5.0% (95% CI, 1.6-14.5%) among migrants and 4.8% (95% CI, 1.5-14.3%) among immunocompromised groups. We confirmed highly variable estimates within risk groups, necessitating an individualized approach to risk stratification. Therefore, we developed a personalized risk predictor for incident TB (PERISKOPE-TB) that combines a quantitative measure of T cell sensitization and clinical covariates. Internal-external cross-validation of the model demonstrated a random effects meta-analysis C-statistic of 0.88 (95% CI, 0.82-0.93) for incident TB. In decision curve analysis, the model demonstrated clinical utility for targeting preventative treatment, compared to treating all, or no, people with LTBI. We challenge the current crude approach to TB risk estimation among people with LTBI in favor of our evidence-based and patient-centered method, in settings aiming for pre-elimination worldwide.

Primary Prophylaxis to Prevent Tuberculosis Infection in Prison Inmates: A Randomized, Double-Blind, Placebo-Controlled Trial

In many low- and middle-income countries, tuberculosis (TB) incidence in prisons is high, exposing incarcerated populations to an elevated risk of TB infection. We conducted a randomized, double-blind, placebo-controlled trial among HIV-negative male inmates of a high TB burden prison to determine whether isoniazid given twice weekly (900 mg) for 12 months prevents TB infection. The primary outcome was QuantiFERON-TB Gold in Plus (QFT) conversion to ≥ 0.35 international units per milliliter (IU/mL) at 6 months; secondary outcomes included alternative QFT thresholds (≥ 0.7, ≥ 2.0, and ≥ 4.0 IU/mL). In total, 467 participants were randomly assigned to intervention (N = 258) or control (N = 209). In an interim analysis of participants who had completed 6 months of follow-up (N = 170), QFT conversion occurred in 20.8% (19/91) and 21.5% (17/79) of participants in intervention and control arms (efficacy: 2.9%, P = 0.91), respectively. The trial was then stopped according to the trial protocol, and the remaining participants prematurely discontinued. In an analysis of secondary outcomes, the intervention arm had significantly lower rates of conversion at a cutoff of ≥ 2.0 IU/mL (efficacy: 82.6%, P < 0.01). In conclusion, 900 mg of isoniazid, administered twice a week, did not effectively prevent QFT conversion at a cutoff point ≥ 0.35 IU/mL in a trial of QFT-negative inmates. Higher QFT cutoffs are associated with sustained conversion and greater protection. Future clinical trials that evaluate protection for latent infection should use the highest cutoff than that recommended by the manufacturer.

Quantitative IFN-γ Release Assay and Tuberculin Skin Test Results to Predict Incident Tuberculosis. A Prospective Cohort Study

Rationale: Development of diagnostic tools with improved predictive value for tuberculosis (TB) is a global research priority.Objectives: We evaluated whether implementing higher diagnostic thresholds than currently recommended for QuantiFERON Gold-in-Tube (QFT-GIT), T-SPOT.TB, and the tuberculin skin test (TST) might improve prediction of incident TB.Methods: Follow-up of a UK cohort of 9,610 adult TB contacts and recent migrants was extended by relinkage to national TB surveillance records (median follow-up 4.7 yr). Incidence rates and rate ratios, sensitivities, specificities, and predictive values for incident TB were calculated according to ordinal strata for quantitative results of QFT-GIT, T-SPOT.TB, and TST (with adjustment for prior bacillus Calmette-Guérin [BCG] vaccination).Measurements and Main Results: For all tests, incidence rates and rate ratios increased with the magnitude of the test result (P < 0.0001). Over 3 years' follow-up, there was a modest increase in positive predictive value with the higher thresholds (3.0% for QFT-GIT ≥0.35 IU/ml vs. 3.6% for ≥4.00 IU/ml; 3.4% for T-SPOT.TB ≥5 spots vs. 5.0% for ≥50 spots; and 3.1% for BCG-adjusted TST ≥5 mm vs. 4.3% for ≥15 mm). As thresholds increased, sensitivity to detect incident TB waned for all tests (61.0% for QFT-GIT ≥0.35 IU/ml vs. 23.2% for ≥4.00 IU/ml; 65.4% for T-SPOT.TB ≥5 spots vs. 27.2% for ≥50 spots; 69.7% for BCG-adjusted TST ≥5 mm vs. 28.1% for ≥15 mm).Conclusions: Implementation of higher thresholds for QFT-GIT, T-SPOT.TB, and TST modestly increases positive predictive value for incident TB, but markedly reduces sensitivity. Novel biomarkers or validated multivariable risk algorithms are required to improve prediction of incident TB.

The diagnosis of latent tuberculosis infection (LTBI): currently available tests, future developments, and perspectives to eliminate tuberculosis (TB)

INTRODUCTION

Despite great efforts, tuberculosis (TB) is still a major public health threat worldwide. For decades, TB control programs have focused almost exclusively on infectious TB active cases.  However, it is evident that this strategy alone cannot achieve TB elimination. To achieve this objective a comprehensive strategy directed toward integrated latent tuberculosis infection (LTBI) management is needed. Recently it has been recognized that LTBI is not a stable condition but rather a spectrum of infections (e.g., intermittent, transient or progressive) which may lead to incipient, then subclinical, and finally active TB disease.

AIM

Provide an overview of current available LTBI diagnostic test including updates, future developments and perspectives.

RESULTS

There is currently no test for the direct identification of live MT infection in humans. The diagnosis of LTBI is indirect and relies on the detection of an immune response against MT antigens, assuming that the immune response has developed after a contact with the biological agent. Tuberculin skin test (TST) and interferon gamma release assays (IGRAs) are the main diagnostic tools for LTBI, however, both present strengths and limitations. The most ancient diagnostic test (TST) can be associated with several technical errors, has limited positive predictive value, is being influenced by BCG vaccination and several conditions can reduce the skin reactivity. Notwithstanding these limitations, prompt identification of TST conversion, should orientate indications for preventive therapy of LTBI. IGRAs have superior specificity, are not affected by M. bovis, BCG vaccination and other environmental mycobacteria. However, they present some logistical and organisational constraints and are more expensive. Currently, the WHO guidelines recommend that either a TST or an IGRA can be used to detect LTBI in high-income and upper middle-income countries with estimated TB incidences less than 100 per 100,000 population. Two skin tests (C-TB and Diaskintest), using only two specific M. tuberculosis antigens (ESAT-6 and CFP-10) instead of the tuberculin solution, have recently been developed but, to date, none of these tests is available on the European market.

CONCLUSION

Early identification and treatment of individuals with LTBI is an important priority for TB control in specific groups at risk within the population: this is of crucial meaning in recently infected cases both at the community level and in some occupational settings. Currently there is no gold standard test for LTBI: an improved understanding of the available tests is needed to develop better tools for diagnosing LTBI and predicting progression to clinical active disease.

Screening migrants from tuberculosis high-endemic countries for latent tuberculosis in Oman: A cross sectional cohort analysis

To fulfil the World Health Organization (WHO) End TB strategy, screening for tuberculosis (TB) in immigrants is an important component of the strategy to reduce the TB burden in low-incidence countries. Oman has an annual TB incidence rate of 5.7 per 100000 and transmission from migrants with activated latent TB infection (LTBI) to nationals is a concern. The aim of this study was to determine the proportion of migrants to the Sultanate of Oman with LTBI. The study used an interferon-gamma release assay (IGRA) to assess previous exposure to TB, defining LTBI and a positive IGRA with a normal chest X-ray. 1049 subjects were surveyed. Six participants were excluded from the analysis as they had been recently vaccinated and 1 had an indeterminate result, thus 1042 subjects were included. The overall IGRA-positive rate was 22.4% (234/1042), 30.9% and 21.2% of African and Asian migrants, respectively, were IGRA-positive. Fifty-eight of the participants had a strong IGRA reactivity defined as more than 4 IU/ml. The study shows the proportion of migrants from Asia and Africa with LTBI and 24.7% (58/234) of IGRA-positive migrants had an IGRA of >4 IU/ml, defining a subpopulation with a high risk of developing active TB in the first two years of arrival to the country.

Tuberculosis among Patients Undergoing Solid Organ Transplantation or Dialysis in a Low-Endemic Country, 2004-2017

Background

The risk of active TB among solid organ transplant (SOT) recipients and patients initiating chronic dialysis in a country with low incidence of TB is not well elucidated.

Methods

Patients aged >18 years who were transplanted with a solid organ or initiated chronic dialysis at Copenhagen University Hospital in the period 2004-2017 were followed from date of transplantation or initiation of dialysis. Data on demographics and outcomes were obtained from nationwide registries.

Results

We included 1,989 SOT recipients and 1,305 patients initiating chronic dialysis, who were followed for a total of 9,785 and 4,196 person-years (PY), respectively. Only a minority of patients had been screened for latent TB prior to SOT or initiation of dialysis. The incidence rates (IRs)/100,000 PY of TB among patients from medium/high TB endemic areas were 358 (95% CI 115-1,110) and 1,266 (95% CI 681-2354) for SOT and dialysis patients, respectively, whereas IRs among patients of Danish origin were 11 (95% CI 2-81) and 31 (95% CI 4-218).

Conclusion

The incidence of TB among immunosuppressed immigrants from medium/high TB endemic countries was very high, while the risk of TB among patients from low-endemic countries was minimal.

New Concepts in Tuberculosis Host Defense

Tuberculosis (TB) host defense depends on cellular immunity, including macrophages and adaptively acquired CD4⁺ and CD8⁺ T cells. More recently, roles for new immune components, including neutrophils, innate T cells, and B cells, have been defined, and the understanding of the function of macrophages and adaptively acquired T cells has been advanced. Moreover, the understanding of TB immunology elucidates TB infection and disease as a spectrum. Finally, determinates of TB host defense, such as age and comorbidities, affect clinical expression of TB disease. Herein, the authors comprehensively review TB immunology with an emphasis on new advances.

Tools to implement the World Health Organization End TB Strategy: Addressing common challenges in high and low endemic countries

AIM

The purpose of this viewpoint is to summarize the advantages and constraints of the tools and strategies available for reducing the annual incidence of tuberculosis (TB) by implementing the World Health Organization (WHO) End TB Strategy and the linked WHO TB Elimination Framework, with special reference to Oman.

METHODS

The case-study was built based on the presentations and discussions at an international workshop on TB elimination in low incidence countries organized by the Ministry of Health, Oman, which took place from September 5 to September 7, 2019, and supported by the WHO and European Society of Clinical Microbiology and Infectious Diseases (ESCMID).

RESULTS

Existing tools were reviewed, including the screening of migrants for latent TB infection (LTBI) with interferon-gamma release assays, clinical examination for active pulmonary TB (APTB) including chest X-rays, organization of laboratory services, and the existing centres for mandatory health examination of pre-arrival or arriving migrants, including examination for APTB. The need for public-private partnerships to handle the burden of screening arriving migrants for active TB was discussed at length and different models for financing were reviewed.

CONCLUSIONS

In a country with a high proportion of migrants from high endemic countries, screening for LTBI is of high priority. Molecular typing and the development of public-private partnerships are needed.

Dynamic changes of interferon gamma release assay results with latent tuberculosis infection treatment

OBJECTIVES

Using QuantiFERON-TB Gold In-Tube (QFT-GIT) for monitoring tuberculosis (TB) and latent TB infection treatment effect is controversial. The present study aimed to evaluate the dynamic changes of interferon gamma (IFN-γ) levels along with latent TB infection treatment via a randomized controlled study.

METHODS

A total of 910 participants treated with 8 weeks of once-weekly rifapentine plus isoniazid (group A), 890 treated with 6 weeks of twice-weekly rifapentine plus isoniazid (group B) and 818 untreated controls (group C) were followed for 2 years to track active TB development. QFT-GIT tests were repeated three times for all groups: before treatment (T0), at completion of treatment (T1) and 3 months after completion of treatment (T2).

RESULTS

Similar rates of persistent QFT-GIT reversion were observed in groups A (19.0%, 173/910), B (18.5%, 165/890) and C (20.7%, 169/818) (p 0.512). The dynamic changes of IFN-γ levels were not statistically significant among the three groups. In treated participants, individuals with higher baseline IFN-γ levels showed increased TB occurrence (1.0%, 9/896) compared to those with lower baseline levels (0.2%, 2/904) (p 0.037). A similar but statistically insignificant trend was also observed in untreated controls (1.8% (7/400) vs. 0.5% (2/418), p 0.100). When TB cases were matched with non-TB cases on baseline IFN-γ levels, no significant differences were found with respect to the dynamic changes in IFN-γ levels with time, regardless of whether they received treatment.

CONCLUSIONS

QFT-GIT reversion or decreased IFN-γ levels should not be used for monitoring host response to latent TB infection treatment.

Clinical Development of New TB Vaccines: Recent Advances and Next Steps

Mycobacterium tuberculosis (Mtb) kills more people worldwide than any single infectious pathogen, yet the only vaccine licensed against tuberculosis, Bacille Calmette Guerin (BCG) is approaching its centenary. Two recent advances in clinical tuberculosis vaccine development have invigorated the field. BCG revaccination of interferon-gamma release assay (IGRA) negative adolescents provided 45% protection against sustained Mtb infection defined by IGRA conversion; and the protein-subunit vaccine M72/AS01_E provided 50% protection against progression from Mtb infection to tuberculosis disease in IGRA-positive adults. These findings provide encouraging evidence for pre-exposure and post-exposure approaches to vaccination against tuberculosis, both of which may be necessary to rapidly interrupt the cycle of Mtb transmission and sustain long-term impact on global tuberculosis control. New trials are needed to demonstrate efficacy of M72/AS01_E with greater precision, in a wider age range, in diverse epidemic settings, and in populations that include Mtb-uninfected and HIV-infected persons. Modeling the impact of mass campaigns with M72/AS01_E and other fast-follower vaccine candidates will be crucial to make the use case and demonstrate public health value for TB endemic countries. The size and scope of the next generation of efficacy trials, and the need to expand and accelerate the existing clinical development pipeline, will require public and private consortium funding and concerted political will.

Borderline-Positive Quantiferon in Children

We systematically retested children with borderline-positive quantiferon (0.35-0.99 IU/mL) during the period 2015-2019. Among 647 tests, 27 (4%) were positive (>0.35 IU/mL). Borderline-positive quantiferon accounted for 10 of 27 (37%) positive tests. When retested, 9 of 10 (90%) were negative. Children younger than 5 years had negative tuberculin skin tests. Thus, we found high test variability in the borderline range and, in some children, high suspicion of false positive tests.

Tuberculosis Vaccine Development: Progress in Clinical Evaluation

Tuberculosis (TB) is the leading killer among all infectious diseases worldwide despite extensive use of the Mycobacterium bovis bacille Calmette-Guérin (BCG) vaccine. A safer and more effective vaccine than BCG is urgently required. More than a dozen TB vaccine candidates are under active evaluation in clinical trials aimed to prevent infection, disease, and recurrence. After decades of extensive research, renewed promise of an effective vaccine against this ancient airborne disease has recently emerged. In two innovative phase 2b vaccine clinical trials, one for the prevention of Mycobacterium tuberculosis infection in healthy adolescents and another for the prevention of TB disease in M. tuberculosis-infected adults, efficacy signals were observed. These breakthroughs, based on the greatly expanded knowledge of the M. tuberculosis infection spectrum, immunology of TB, and vaccine platforms, have reinvigorated the TB vaccine field. Here, we review our current understanding of natural immunity to TB, limitations in BCG immunity that are guiding vaccinologists to design novel TB vaccine candidates and concepts, and the desired attributes of a modern TB vaccine. We provide an overview of the progress of TB vaccine candidates in clinical evaluation, perspectives on the challenges faced by current vaccine concepts, and potential avenues to build on recent successes and accelerate the TB vaccine research-and-development trajectory.

Comparison of the QuantiFERON-TB and tuberculin skin test for detection of latent tuberculosis infection in cancer patients in a developing country

Cancer patients have an increased risk of reactivation of latent tuberculosis infection. It is unknown which strategy on screening should be used in this population in developing countries. We aimed to determine the concordance between the tuberculin skin test (TST) and QuantiFERON^®-TB (QFT) assay in order to diagnose latent tuberculosis infection in cancer patients. We conducted a cross-sectional study of the agreement of diagnostic tests. Prevalence and agreement between tests were calculated. A logistic regression to assess predictors of discordance was performed. The accuracy of the TST to predict QFT results by a receiver operating characteristic (ROC) curve was evaluated. We included 149 adults with cancer without active tuberculosis. Prevalence of latent tuberculosis infection was 21.5% (n=32), defined as positive results on either test. Test agreement was moderate for the diagnosis of latent tuberculosis infection (κ=0.43, 90% CI 0.26-0.6). No predictor was associated with the chance of discordant results. Agreement improved slightly using a cut-off point ≥8 mm (κ=0.5, 90% CI 0.35-0.66). In a moderate-incidence setting, a moderate agreement was found between tests in cancer patients. Modification of the cut-off points of test results achieved marginally better agreement between the TST and QFT.

A new mathematical model to identify contacts with recent and remote latent tuberculosis

Tuberculosis (TB) elimination programmes need to target preventive treatment to groups with an increased risk of TB activation, such as individuals with a latent tuberculosis infection (LTBI) acquired recently. Current diagnostic tests for LTBI have poor predictive values for TB activation and there is, at present, no reference method to evaluate new LTBI diagnostic and prognostic tools. Thus, our objective was to develop a mathematical model, independent of currently available diagnostic tests, to estimate the individual probability of recent and/or remote LTBI. Estimations of recent LTBI were based on the contagiousness of index case, proximity and time of exposure, and environmental factors. Estimation of remote LTBI was based on country of origin, previous stays in high-risk environments or known exposure to TB. Individual probabilities were calculated and compared with tuberculin skin test (TST) and interferon-γ release assay results for 162 contacts of 42 index TB cases. Probabilities of remote LTBI were 16% for European/American contacts and 38% for African/Asian contacts. The probability of recent LTBI was 35% for close contacts to smear microscopy positive index cases. A higher probability of remote LTBI was seen among TST-positive contacts. This model may, with further validation, be used as an independent tool to evaluate new diagnostic markers for recent LTBI.

Immigrant screening for latent tuberculosis infection: numbers needed to test and treat, a Norwegian population-based cohort study

OBJECTIVES

To estimate the number needed to screen (NNS) and the number needed to treat (NNT) to prevent one tuberculosis (TB) case in the Norwegian immigrant latent tuberculosis infection (LTBI) screening programme and to explore the effect of delay of LTBI treatment initiation.

DESIGN

Population-based, prospective cohort study.

PARTICIPANTS

Immigrants to Norway.

OUTCOME

Incident TB.

METHODS

We obtained aggregated data on immigration to Norway in 2008-2011 and used data from the Norwegian Surveillance System for Infectious Diseases to assess the number of TB cases arising in this cohort within 5 years after arrival. We calculated the average NNS and NNT for immigrants from the top 10 source countries for TB in Norway and by estimated TB incidence rates in source countries. We explored the sensitivity of these estimates with regard to test performance, treatment efficacy and treatment adherence using an extreme value approach, and assessed the effects of emigration, time to TB diagnosis (to define incident TB) and intervention timing.

RESULTS

NNS and NNT were overall high, with substantial variation. NNT showed numerically stronger negative correlation with TB notification rate in Norway (-0.75 [95% CI -1.00 to -0.44]) than with the WHO incidence rate (IR) (-0.32 [95% CI -0.93 to 0.29]). NNT was affected substantially by emigration and the definition of incident TB. Estimates were lowest for Somali (NNS 99 [70-150], NNT 27 [19-41]) and highest for Thai immigrants (NNS 585 [413-887], NNT 111 [79-116]). Implementing LTBI treatment in immigrants sooner after arrival may improve the effectiveness of the programme.

CONCLUSION

Using TB notifications in Norway, rather than IR in source countries, would improve targeting of immigrants for LTBI management. However, the overall high NNT is a concern and challenges the scale-up of preventive LTBI treatment for significant public health impact. Better data are urgently needed to monitor and evaluate NNS and NNT in countries implementing LTBI screening.

Prevention of M. tuberculosis Infection with H4:IC31 Vaccine or BCG Revaccination

BACKGROUND

Recent Mycobacterium tuberculosis infection confers a predisposition to the development of tuberculosis disease, the leading killer among global infectious diseases. H4:IC31, a candidate subunit vaccine, has shown protection against tuberculosis disease in preclinical models, and observational studies have indicated that primary bacille Calmette-Guérin (BCG) vaccination may offer partial protection against infection.

METHODS

In this phase 2 trial, we randomly assigned 990 adolescents in a high-risk setting who had undergone neonatal BCG vaccination to receive the H4:IC31 vaccine, BCG revaccination, or placebo. All the participants had negative results on testing for M. tuberculosis infection on the QuantiFERON-TB Gold In-tube assay (QFT) and for the human immunodeficiency virus. The primary outcomes were safety and acquisition of M. tuberculosis infection, as defined by initial conversion on QFT that was performed every 6 months during a 2-year period. Secondary outcomes were immunogenicity and sustained QFT conversion to a positive test without reversion to negative status at 3 months and 6 months after conversion. Estimates of vaccine efficacy are based on hazard ratios from Cox regression models and compare each vaccine with placebo.

RESULTS

Both the BCG and H4:IC31 vaccines were immunogenic. QFT conversion occurred in 44 of 308 participants (14.3%) in the H4:IC31 group and in 41 of 312 participants (13.1%) in the BCG group, as compared with 49 of 310 participants (15.8%) in the placebo group; the rate of sustained conversion was 8.1% in the H4:IC31 group and 6.7% in the BCG group, as compared with 11.6% in the placebo group. Neither the H4:IC31 vaccine nor the BCG vaccine prevented initial QFT conversion, with efficacy point estimates of 9.4% (P=0.63) and 20.1% (P=0.29), respectively. However, the BCG vaccine reduced the rate of sustained QFT conversion, with an efficacy of 45.4% (P=0.03); the efficacy of the H4:IC31 vaccine was 30.5% (P=0.16). There were no clinically significant between-group differences in the rates of serious adverse events, although mild-to-moderate injection-site reactions were more common with BCG revaccination.

CONCLUSIONS

In this trial, the rate of sustained QFT conversion, which may reflect sustained M. tuberculosis infection, was reduced by vaccination in a high-transmission setting. This finding may inform clinical development of new vaccine candidates. (Funded by Aeras and others; C-040-404 ClinicalTrials.gov number, NCT02075203 .).