Tuberculosis disease in immunocompromised children and adolescents: a pTBnet multi-centre case-control study.

BACKGROUND: In high-resource settings the survival of immunocompromised (IC) children has increased and immunosuppressive therapies are increasingly being used. This study aimed to determine the clinical characteristics, performance of diagnostic tools and outcome of IC children with TB in Europe. METHODS: Multicentre, matched case-control study within the Paediatric Tuberculosis Network European Trials Group (ptbnet), capturing TB cases <18 years diagnosed 2000-2020. RESULTS: 417 TB cases were included, comprising 139 children with IC (HIV, inborn errors of immunity, drug-induced immunosuppression and other immunocompromising conditions) and 278 non-IC children as controls. Non-respiratory TB was more frequent among cases than controls (32.4% vs. 21.2%; p = 0.013). IC patients had an increased likelihood of presenting with severe disease (57.6% vs. 38.5%; p < 0.001; OR [95% CI]: 2.073 [1.37-3.13]). Children with IC had higher rates of false-negative tuberculin skin test (31.9% vs. 6.0%; p < 0.001) and QuantiFERON-TB Gold assay (30.0% vs. 7.3%; p < 0.001) results at diagnosis. Overall, the microbiological confirmation rate was similar in IC and non-IC cases (58.3% vs. 49.3%; p = 0.083). Although the mortality in IC children was <1%, the rate of long-term sequelae was significantly higher than in non-IC cases (14.8% vs. 6.1%; p = 0.004). CONCLUSIONS: IC children with TB disease in Europe have increased rates of non-respiratory TB, severe disease, and long-term sequelae. Immune-based TB tests have poor sensitivity in those children. Future research should focus on developing improved immunological TB tests that perform better in IC patients, and determining the reasons for the increased risk of long-term sequelae, with the aim to design preventive management strategies.

Evaluation of serological assays for the diagnosis of childhood tuberculosis disease: a study protocol.

BACKGROUND: Tuberculosis (TB) poses a major public health challenge, particularly in children. A substantial proportion of children with TB disease remain undetected and unconfirmed. Therefore, there is an urgent need for a highly sensitive point-of-care test. This study aims to assess the performance of serological assays based on various antigen targets and antibody properties in distinguishing children (0-18 years) with TB disease (1) from healthy TB-exposed children, (2) children with non-TB lower respiratory tract infections, and (3) from children with TB infection. METHODS: The study will use biobanked plasma samples collected from three prospective multicentric diagnostic observational studies: the Childhood TB in Switzerland (CITRUS) study, the Pediatric TB Research Network in Spain (pTBred), and the Procalcitonin guidance to reduce antibiotic treatment of lower respiratory tract infections in children and adolescents (ProPAED) study. Included are children diagnosed with TB disease or infection, healthy TB-exposed children, and sick children with non-TB lower respiratory tract infection. Serological multiplex assays will be performed to identify M. tuberculosis antigen-specific antibody features, including isotypes, subclasses, Fc receptor (FcR) binding, and IgG glycosylation. DISCUSSION: The findings from this study will help to design serological assays for diagnosing TB disease in children. Importantly, those assays could easily be developed as low-cost point-of-care tests, thereby offering a potential solution for resource-constrained settings. GOV IDENTIFIER: NCT03044509.

Performance of QuantiFERON-TB Gold Plus assays in paediatric tuberculosis: a multicentre PTBNET study.

RATIONALE: In 2016, a new interferon-gamma release assay (IGRA) was introduced, QuantiFERON-TB Gold Plus (QFT-Plus), claimed to have improved sensitivity in active tuberculosis (TB). OBJECTIVES: This study aimed to determine the performance of QFT-Plus, compared with previous generation IGRAs and the tuberculin skin test (TST), in children with TB in Europe. METHODS: Multicentre, ambispective cohort study within the Paediatric Tuberculosis Network European Trials Group (ptbnet), a dedicated paediatric TB research network comprising >300 members, capturing TB cases <18 years-of-age diagnosed between January 2009 and December 2019. MEASUREMENTS AND MAIN RESULTS: 1001 TB cases from 16 countries were included (mean age (IQR) 5.6 (2.4-12.1) years). QFT-Plus was performed in 358, QFT Gold in-Tube (QFT-GIT) in 600, T-SPOT.TB in 58 and TST in 636 cases. The overall test sensitivities were: QFT-Plus 83.8% (95% CI 80.2% to 87.8%), QFT-GIT 85.5% (95% CI 82.7% to 88.3%), T-SPOT.TB 77.6% (95% CI 66.9% to 88.3%) and TST (cut-off ≥10 mm) 83.3% (95% CI 83.3% to 86.2%). There was a trend for tests to have lower sensitivity in patients with miliary and/or central nervous system (CNS) TB (73.1%, 70.9%, 63.6% and 43.5%, respectively), and in immunocompromised patients (75.0%, 59.6%, 45.5% and 59.1%, respectively). CONCLUSIONS: The results indicate that the latest generation IGRA assay, QFT-Plus, does not perform better than previous generation IGRAs or the TST in children with TB disease. Overall, tests performed worse in CNS and miliary TB, and in immunocompromised children. None of the tests evaluated had sufficiently high sensitivity to be used as a rule-out test in children with suspected TB.

Dual latent tuberculosis screening with tuberculin skin tests and QuantiFERON-TB assays before TNF-α inhibitor initiation in children in Spain.

Tumor-necrosis-factor-α inhibitors (anti-TNF-α) are associated with an increased risk of tuberculosis (TB) disease, primarily due to reactivation of latent TB infection (LTBI). We assessed the performance of parallel LTBI screening with tuberculin skin test (TST) and QuantiFERON-TB Gold In-Tube assays (QFT-GIT) before anti-TNF-α treatment in children with immune-mediated inflammatory disorders in a low TB-burden setting. We conducted a multicenter cohort study involving 17 pediatric tertiary centers in Spain. LTBI was defined as the presence of a positive TST and/or QFT-GIT result without clinical or radiological signs of TB disease. A total of 270 patients (median age:11.0 years) were included, mainly with rheumatological (55.9%) or inflammatory bowel disease (34.8%). Twelve patients (4.4%) were diagnosed with TB infection at screening (LTBI, n = 11; TB disease, n = 1). Concordance between TST and QFT-GIT results was moderate (TST+/QFT-GIT+, n = 4; TST-/QFT-GIT+, n = 3; TST+/QFT-GIT-, n = 5; kappa coefficient: 0.48, 95% CI: 0.36-0.60). Indeterminate QFT-GIT results occurred in 10 patients (3.7%) and were associated with young age and elevated C-reactive protein concentrations. Eleven of 12 patients with TB infection uneventfully completed standard LTBI or TB treatment. During a median follow-up period of 6.4 years, only 2 patients developed TB disease (incidence density: 130 (95% CI: 20-440) per 100,000 person-years), both probable de novo infections. CONCLUSION: A substantial number of patients were diagnosed with LTBI during screening. The dual strategy identified more cases than either of the tests alone, and test agreement was only moderate. Our data show that in children in a low TB prevalence setting, a dual screening strategy with TST and IGRA before anti-TNF-α treatment is effective. WHAT IS KNOWN: • The optimal screening strategy for latent tuberculosis in children with immune-mediated inflammatory disorders remains uncertain. • Children receiving anti-TNF-α drugs are at increased risk of developing severe tuberculosis disease. WHAT IS NEW: • A dual screening strategy, using TST and an IGRA assay, identified more children with latent tuberculosis than either of the tests alone. • Identification and treatment of latent tuberculosis before initiation of anti-TNF-α therapy averted incident tuberculosis cases.

Bacillus Calmette-Guérin Skin Reaction Predicts Enhanced Mycobacteria-Specific T-Cell Responses in Infants: A Post Hoc Analysis of a Randomized Controlled Trial.

Rationale: Scar formation following bacillus Calmette-Guérin (BCG) vaccination has been associated with lower all-cause mortality; the relation between scar and mycobacteria-specific protection against tuberculosis is debated. Objectives: To evaluate the association between BCG skin reaction and mycobacteria-specific immune responses. Methods: A post hoc analysis was done among 214 infants in Australia randomized to vaccination with one of three BCG vaccine strains (BCG-Denmark, BCG-Japan, or BCG-Russia) given at birth or BCG-Denmark given at 2 months of age. Measurements and Main Results: BCG skin reaction size and characteristics 10 weeks after vaccination were related to the in vitro mycobacteria-specific immune responses measured in stimulated whole blood. The size and characteristics of the skin reaction correlated positively with in vitro immune responses, even after adjusting for BCG vaccine strain and age at vaccination. Specifically, the reaction size and characteristics correlated with the proportion of mycobacteria-specific polyfunctional CD4+ T cells after stimulation with BCG and PPD and, to a lesser extent, after stimulation with Mycobacterium tuberculosis or Mycobacterium ulcerans. A similar correlation was observed with concentrations of IFN-γ, IL-2, tumor necrosis factor, and IL-13 in the supernatant after stimulation with BCG, PPD, and M. tuberculosis and to some degree for the proportions of mycobacteria-specific polyfunctional CD8+ T cells and CD107+ cytotoxic cells. Conclusions: BCG skin reaction correlated with the magnitude of mycobacteria-specific T-cell responses. As T-cell responses play a key role in defense against mycobacteria, the relationship between BCG scar formation and protection against tuberculosis should be revisited. This may also extend to the need for BCG revaccination in scar-negative individuals.Clinical trial registered with www.australianclinicaltrials.gov.au/clinical-trial-registries (ACTRN12608000227392).

Treatment and Outcome in Children With Tuberculous Meningitis: A Multicenter Pediatric Tuberculosis Network European Trials Group Study.

BACKGROUND: Currently, data on treatment, outcome, and prognostic factors in children with tuberculous meningitis (TBM) in Europe are limited. To date, most existing data on TBM originate from adult studies, or studies conducted in low-resource settings. METHODS: We designed a multicenter, retrospective study involving 27 pediatric healthcare institutions in 9 European countries via an established pediatric TB research network, before and after the 2014 revision of World Health Organization (WHO) dosing recommendations. RESULTS: Of 118 children, 39 (33.1%) had TBM grade 1, 68 (57.6%) grade 2, and 11 (9.3%) grade 3. Fifty-eight (49.1%) children received a standard 4-drug treatment regimen; other commonly used drugs included streptomycin, prothionamide, and amikacin. Almost half of the patients (48.3%; 56/116) were admitted to intensive care unit, with a median stay of 10 (interquartile range [IQR] 4.5-21.0) days. Of 104 children with complete outcome data, 9.6% (10/104) died, and only 47.1% (49/104) recovered fully. Main long-term sequelae included spasticity of 1 or more limbs and developmental delay both in 19.2% (20/104), and seizure disorder in 17.3% (18/104). Multivariate regression analyses identified microbiological confirmation of TBM, the need for neurosurgical intervention, and mechanical ventilation as risk factors for unfavorable outcome. CONCLUSIONS: There was considerable heterogeneity in the use of TB drugs in this cohort. Despite few children presenting with advanced disease and the study being conducted in a high-resource setting, morbidity and mortality were high. Several risk factors for poor outcome were identified, which may aid prognostic predictions in children with TBM in the future.

Performance of QuantiFERON-TB Gold Plus assays in children and adolescents at risk of tuberculosis: a cross-sectional multicentre study.

INTRODUCTION: The QuantiFERON-TB Gold Plus (QFT-Plus) assay, which features two antigen-stimulated tubes (TB1 and TB2) instead of a single tube used in previous-generation interferon-gamma release assays (IGRAs), was launched in 2016. Despite this, data regarding the assay's performance in the paediatric setting remain scarce. This study aimed to determine the performance of QFT-Plus in a large cohort of children and adolescents at risk of tuberculosis (TB) in a low-burden setting. METHODS: Cross-sectional, multicentre study at healthcare institutions participating in the Spanish Paediatric TB Research Network, including patients <18 years who had a QFT-Plus performed between September 2016 and June 2020. RESULTS: Of 1726 patients (52.8% male, median age: 8.4 years), 260 (15.1%) underwent testing during contact tracing, 288 (16.7%) on clinical/radiological suspicion of tuberculosis disease (TBD), 649 (37.6%) during new-entrant migrant screening and 529 (30.6%) prior to initiation of immunosuppressive treatment. Overall, the sensitivity of QFT-Plus for TBD (n=189) and for latent tuberculosis infection (LTBI, n=195) was 83.6% and 68.2%, respectively. The agreement between QFT-Plus TB1 and TB2 antigen tubes was excellent (98.9%, κ=0.961). Only five (2.5%) patients with TBD had discordance between TB1 and TB2 results (TB1+/TB2-, n=2; TB1-/TB2+, n=3). Indeterminate assay results (n=54, 3.1%) were associated with young age, lymphopenia and elevated C reactive protein concentrations. CONCLUSIONS: Our non-comparative study indicates that QFT-Plus does not have greater sensitivity than previous-generation IGRAs in children in both TBD and LTBI. In TBD, the addition of the second antigen tube, TB2, does not enhance the assay's performance substantially.

Accuracy of Xpert Ultra for the diagnosis of paediatric tuberculosis in a low TB burden country: a prospective multicentre study.

INTRODUCTION: Childhood pulmonary tuberculosis (TB) remains a diagnostic challenge. This study aimed to evaluate the performance of Xpert Ultra for the diagnosis of pulmonary TB in children in a low TB prevalence setting. METHODS: Prospective, multicentre, diagnostic accuracy study. Children with clinical or radiological suspicion of pulmonary TB were recruited at 11 paediatric units in Spain. Up to three gastric or sputum specimens were taken on 3 consecutive days, and analysed by Xpert MTB/RIF, Xpert Ultra and culture in parallel. RESULTS: 86 children were included (median age 4.9 years, IQR 2.0-10.0; 51.2% male). The final diagnosis was pulmonary TB in 75 patients (87.2%); 33 (44.0%) were microbiologically confirmed. A total of 219 specimens, comprising gastric aspirates (n=194; 88.6%) and sputum specimens (n=25; 11.4%), were analysed. Using culture as reference standard and comparing individual specimens, the sensitivity was 37.8% (14/37) for Xpert MTB/RIF and 81.1% (30/37) for Xpert Ultra (p<0.001); specificity was 98.4% (179/182) and 93.4% (170/182), respectively (p=0.02). In the per-patient analysis, considering positive results on any specimen, the sensitivity was 42.9% (9/21) for Xpert MTB/RIF and 81.0% for Xpert Ultra (17/21, p=0.01); specificity was 96.9% (63/65) and 87.7% (57/65, p=0.07), respectively. CONCLUSIONS: In children with pulmonary TB in a low burden setting, Xpert Ultra has significantly higher sensitivity than the previous generation of Xpert assay and only marginally lower specificity. Therefore, in children undergoing evaluation for suspected pulmonary TB, Xpert Ultra should be used in preference to Xpert MTB/RIF whenever possible.

Interferon-Gamma Release Assays Differentiate between Mycobacterium avium Complex and Tuberculous Lymphadenitis in Children.

OBJECTIVES: To assess the performance of interferon-gamma release assays (IGRAs) in the differential diagnosis between Mycobacterium avium complex (MAC) and tuberculosis (TB) in children affected with subacute/chronic submandibular/cervical lymphadenitis. STUDY DESIGN: Multicenter observational study comparing children with microbiologically confirmed MAC lymphadenitis from the European NontuberculouS MycoBacterial Lymphadenitis in childrEn study with children with TB lymphadenitis from the Spanish Network for the Study of Pediatric TB database. RESULTS: Overall, 78 patients with MAC and 34 with TB lymphadenitis were included. Among MAC cases, 44 out of 74 (59.5%) had positive tuberculin skin test (TST) results at the 5-mm cut-off, compared with 32 out of 33 (97%) TB cases (P < .001); at the 10-mm cut-off TST results were positive in 23 out of 74 (31.1%) vs 26 out of 31 (83.9%), respectively (P < .001). IGRA results were positive in only 1 out of 32 (3.1%) patients with MAC who had undergone IGRA testing, compared with 21 out of 23 (91.3%) TB cases (P < .001). Agreement between TST and IGRA results was poor in MAC (23.3%; κ = 0.017), but good in TB cases (95.6%; κ = 0.646). IGRAs had a specificity of 96.9% (95% CI 84.3%-99.8%), positive predictive value of 95.4% (95% CI 78.2%-99.8%), and negative predictive value of 93.9% (95% CI 80.4%-98.9%) for TB lymphadenitis. CONCLUSIONS: In contrast to TST, IGRAs have high specificity, negative predictive value, and positive predictive value for TB lymphadenitis in children with subacute/chronic lymphadenopathy, and consequently can help to discriminate between TB and MAC disease. Therefore, IGRAs are useful tools in the diagnostic work-up of children with lymphadenopathy, particularly when culture and polymerase chain reaction results are negative.

Preventing tuberculosis in paediatric kidney transplant recipients: is there a role for BCG immunisation pre-transplantation in low tuberculosis incidence countries?

The risk of tuberculosis (TB) disease is increased in children with chronic kidney disease (CKD), even higher in stage 5 CKD/kidney failure and especially high after kidney transplantation due to immunosuppression. TB disease may follow recent primary infection, or result from reactivation of latent infection. Reactivation is more common in adults, while progression following primary infection makes up a greater proportion of disease in children. Recommendations for preventing TB disease in some low TB incidence countries have previously included offering Bacillus Calmette-Guérin (BCG) vaccine to all children listed for kidney transplant if they had not received this as part of previous national immunisation programmes. Based on the available evidence, we recommend modifying this practice, focusing instead on awareness of risk factors for TB exposure, infection and disease and the use of appropriate testing strategies to identify and treat TB infection and disease.

Exploring the perspectives of members of international tuberculosis control and research networks on the impact of COVID-19 on tuberculosis services: a cross sectional survey.

BACKGROUND: The COVID-19 pandemic has caused major disruption to healthcare services globally and has impacted on tuberculosis (TB) patients and TB diagnosis and treatment services both in low- and high-income countries. We therefore explored the perspectives of members of regional and international TB control and research networks to further understand TB service disruptions and compared the experiences of members from West African and European countries. METHODS: This cross-sectional, explorative descriptive study was conducted from May to July 2020 using an open online survey with target respondents from both West African and European countries. The survey comprised discrete questions exploring challenges faced with TB screening, diagnosis, treatment, prevention, and changes implemented. Additionally, respondents were asked to provide recommendations for remedial actions. RESULTS: We analysed responses from 124 respondents based in 29 countries located in Europe and West Africa. About half of the respondents reported challenges in delivering routine TB services during the COVID-19 pandemic, with over one third reporting having some form of guidance issued regarding maintaining delivery of routine TB services. Respondents emphasised the need for strengthening TB services especially in light of COVID-19 pandemic. Considerable similarities were found between the challenges experienced by TB professionals in both West African and European settings. Responses also highlighted the hidden challenges faced in some countries prior to the COVID-19 pandemic, especially in some West African settings where staff shortages and laboratory issues predated COVID-19. CONCLUSIONS: TB control and research professionals in West African and European settings experienced similar challenges to the delivery of TB diagnosis and treatment services due to the COVID-19 pandemic, and highlighted the need for clear communication of guidelines, prioritisation of routine TB service delivery, ongoing health education, and possible integration of TB and COVID-19 services to ensure that TB services are more resilient against the impact of the pandemic.

Tuberculosis Disease in Children and Adolescents on Therapy With Antitumor Necrosis Factor-ɑ Agents: A Collaborative, Multicenter Paediatric Tuberculosis Network European Trials Group (ptbnet) Study.

BACKGROUND: In adults, anti-tumor necrosis factor-α (TNF-α) therapy is associated with progression of latent tuberculosis (TB) infection (LTBI) to TB disease, but pediatric data are limited. METHODS: Retrospective multicenter study within the Paediatric Tuberculosis Network European Trials Group, capturing patients <18 years who developed TB disease during anti-TNF-α therapy. RESULTS: Sixty-six tertiary healthcare institutions providing care for children with TB participated. Nineteen cases were identified: Crohn's disease (n = 8; 42%) and juvenile idiopathic arthritis (n = 6; 32%) were the commonest underlying conditions. Immune-based TB screening (tuberculin skin test and/or interferon-γ release assay) was performed in 15 patients before commencing anti-TNF-α therapy but only identified 1 LTBI case; 13 patients were already receiving immunosuppressants at the time of screening. The median interval between starting anti-TNF-α therapy and TB diagnosis was 13.1 (IQR, 7.1-20.3) months. All cases presented with severe disease, predominantly miliary TB (n = 14; 78%). One case was diagnosed postmortem. TB was microbiologically confirmed in 15 cases (79%). The median duration of anti-TB treatment was 50 (IQR, 46-66) weeks. Five of 15 (33%) cases who had completed TB treatment had long-term sequelae. CONCLUSIONS: LTBI screening is frequently false-negative in this patient population, likely due to immunosuppressants impairing test performance. Therefore, patients with immune-mediated diseases should be screened for LTBI at the point of diagnosis, before commencing immunosuppressive medication. Children on anti-TNF-α therapy are prone to severe TB disease and significant long-term morbidity. Those observations underscore the need for robust LTBI screening programs in this high-risk patient population, even in low-TB-prevalence settings.

Performance of immune-based and microbiological tests in children with tuberculosis meningitis in Europe: a multicentre Paediatric Tuberculosis Network European Trials Group (ptbnet) study.

INTRODUCTION: Tuberculous meningitis (TBM) is often diagnostically challenging. Only limited data exist on the performance of interferon-γ release assays (IGRA) and molecular assays in children with TBM in routine clinical practice, particularly in the European setting. METHODS: Multicentre, retrospective study involving 27 healthcare institutions providing care for children with tuberculosis (TB) in nine European countries. RESULTS: Of 118 children included, 54 (45.8%) had definite, 38 (32.2%) probable and 26 (22.0%) possible TBM; 39 (33.1%) had TBM grade 1, 68 (57.6%) grade 2 and 11 (9.3%) grade 3. Of 108 patients who underwent cranial imaging 90 (83.3%) had at least one abnormal finding consistent with TBM. At the 5-mm cut-off the tuberculin skin test had a sensitivity of 61.9% (95% CI 51.2-71.6%) and at the 10-mm cut-off 50.0% (95% CI 40.0-60.0%). The test sensitivities of QuantiFERON-TB and T-SPOT.TB assays were 71.7% (95% CI 58.4-82.1%) and 82.5% (95% CI 58.2-94.6%), respectively (p=0.53). Indeterminate results were common, occurring in 17.0% of QuantiFERON-TB assays performed. Cerebrospinal fluid (CSF) cultures were positive in 50.0% (95% CI 40.1-59.9%) of cases, and CSF PCR in 34.8% (95% CI 22.9-43.7%). In the subgroup of children who underwent tuberculin skin test, IGRA, CSF culture and CSF PCR simultaneously, 84.4% had at least one positive test result (95% CI 67.8%-93.6%). CONCLUSIONS: Existing immunological and microbiological TB tests have suboptimal sensitivity in children with TBM, with each test producing false-negative results in a substantial proportion of patients. Combining immune-based tests with CSF culture and CSF PCR results in considerably higher positive diagnostic yields, and should therefore be standard clinical practice in high-resource settings.

Diagnostic Accuracy of QuantiFERON-TB Gold Plus Assays in Children and Adolescents with Tuberculosis Disease.

In 2016, a new interferon-gamma release assay, QuantiFERON-TB Gold Plus, was introduced. We conducted a cross-sectional multicenter study, involving 158 children and adolescents with tuberculosis disease. The overall sensitivity of the assay was 82.9% (IQR 77.0%-88.8%), indicating that in children this test does not have higher sensitivity than previous generation interferon-gamma release assays.

CD1b-restricted GEM T cell responses are modulated by Mycobacterium tuberculosis mycolic acid meromycolate chains.

Tuberculosis (TB), caused by Mycobacterium tuberculosis, remains a major human pandemic. Germline-encoded mycolyl lipid-reactive (GEM) T cells are donor-unrestricted and recognize CD1b-presented mycobacterial mycolates. However, the molecular requirements governing mycolate antigenicity for the GEM T cell receptor (TCR) remain poorly understood. Here, we demonstrate CD1b expression in TB granulomas and reveal a central role for meromycolate chains in influencing GEM-TCR activity. Meromycolate fine structure influences T cell responses in TB-exposed individuals, and meromycolate alterations modulate functional responses by GEM-TCRs. Computational simulations suggest that meromycolate chain dynamics regulate mycolate head group movement, thereby modulating GEM-TCR activity. Our findings have significant implications for the design of future vaccines that target GEM T cells.

Tuberculosis: An Infection-Initiated Autoimmune Disease?

Tuberculosis (TB) is caused by Mycobacterium tuberculosis (Mtb) and provided original proof that an infectious agent can cause human disease. However, key steps in TB pathogenesis remain poorly understood. We propose that autoimmunity is a critical and overlooked process driving pathology in TB, and present clinical and experimental observations supporting this hypothesis.

Corticosteroids and infliximab impair the performance of interferon-γ release assays used for diagnosis of latent tuberculosis.

The impact of immunosuppression on interferon-γ release assays and novel cytokine biomarkers of TB infection, mycobacteria-specific IL-2, IP-10 and TNF-α responses was investigated in an ex vivo model. Cytokine responses in standard QuantiFERON-TB Gold in-Tube (QFT-GIT) assays were compared with duplicate assays containing dexamethasone or infliximab. Dexamethasone converted QFT-GIT results from positive to negative in 30% of participants. Antigen-stimulated interferon-γ, IL-2 and TNF-α responses were markedly reduced, but IP-10 responses were preserved. Infliximab caused QFT-GIT result conversion in up to 30% of participants and substantial reductions in all cytokine responses. Therefore, corticosteroids and anti-TNF-α agents significantly impair interferon-γ release assay performance. IP-10 may be a more robust TB biomarker than interferon-γ in patients receiving corticosteroids.

D-methionine interferes with non-typeable Haemophilus influenzae peptidoglycan synthesis during growth and biofilm formation.

Non-typeable Haemophilus influenzae (NTHi) is an opportunistic pathogen that plays a major role in a number of respiratory tract infections, including otitis media, cystic fibrosis and chronic obstructive pulmonary disease. Biofilm formation has been implicated in both NTHi colonization and disease, and is responsible for the increased tolerance of this pathogen towards antibiotic treatment. Targeting metabolic pathways that are important in NTHi biofilm formation represents a potential strategy to combat this antibiotic recalcitrance. A previous investigation demonstrated increased expression of a putative d-methionine uptake protein following exposure of NTHi biofilms to the ubiquitous signalling molecule, nitric oxide. We therefore hypothesized that treatment with exogenous d-methionine would impact on NTHi biofilm formation and increase antibiotic sensitivity. Treatment of NTHi during the process of biofilm formation resulted in a reduction in biofilm viability, increased biomass, changes in the overall biofilm architecture and the adoption of an amorphous cellular morphology. Quantitative proteomic analyses identified 124 proteins that were differentially expressed following d-methionine treatment, of which 51 (41 %) were involved in metabolic and transport processes. Nine proteins involved in peptidoglycan synthesis and cell division showed significantly increased expression. Furthermore, d-methionine treatment augmented the efficacy of azithromycin treatment and highlighted the potential of d-methionine as an adjunctive therapeutic approach for NTHi biofilm-associated infections.