Interferon-gamma release assay conversion after M. tuberculosis exposure specifically associates with greater risk of progression to tuberculosis: a prospective cohort study in Leicester (UK)

ObjectivesWe investigated whether quantifying the serial QuantiFERON-TB Gold (QFT) response improves tuberculosis (TB) risk stratification in pulmonary TB (PTB) contacts.Methods297 untreated adult household PTB contacts, QFT tested at baseline and 3 months after index notification, were prospectively observed (median 1460 days). Normal variance of serial QFT responses was established in 46 extra-pulmonary TB contacts. This informed categorisation of the response in QFT-positive PTB contacts as: converters; persistently QFT-positive with significant increase (PPincrease); and without significant increase (PPno-increase).ResultsEight co-prevalent TB (disease ≤ 3 months after index notification) and 12 incident TB (>3 months after index notification) cases were diagnosed. Genetic linkage to the index strain was confirmed in all culture-positive progressors. Cumulative 2-year incident TB risk in QFT-positive contacts was 8.4% (95% CI, 3.0% - 13.6%); stratifying by serial QFT response, significantly higher risk was observed in QFT-converters (28%), compared with PPno-increase (4.8%) and PPincrease (3.7%). Converters were characterised by exposure to index cases with a shorter interval from symptom onset to diagnosis (median reduction 50.0 days, p=0.013).ConclusionQFT conversion rather than quantitative changes of a persistently positive serial QFT response, associates with greater TB risk and exposure to rapidly progressive TB

A novel high sensitivity bacteriophage based assay identifies low level M.tuberculosis bacteraemia in immunocompetent patients with active and incipient TB

Haematogenous dissemination of M. tuberculosis (Mtb) is critical to pathogenesis of progressive tuberculous infection in animal models. Using a novel phage-based blood assay, we report the first concordant evidence in well-characterised immunocompetent human cohorts, demonstrating associations of Mtb bacteraemia with progressive phenotypes of latent infection and active pulmonary TB respectively

A modular transcriptional signature identifies phenotypic heterogeneity of human tuberculosis infection

Whole blood transcriptional signatures distinguishing active tuberculosis patients from asymptomatic latently infected individuals exist. Consensus has not been achieved regarding the optimal reduced gene sets as diagnostic biomarkers that also achieve discrimination from other diseases. Here we show a blood transcriptional signature of active tuberculosis using RNA-Seq, confirming microarray results, that discriminates active tuberculosis from latently infected and healthy individuals, validating this signature in an independent cohort. Using an advanced modular approach, we utilise the information from the entire transcriptome, which includes overabundance of type I interferon-inducible genes and underabundance of IFNG and TBX21, to develop a signature that discriminates active tuberculosis patients from latently infected individuals or those with acute viral and bacterial infections. We suggest that methods targeting gene selection across multiple discriminant modules can improve the development of diagnostic biomarkers with improved performance. Finally, utilising the modular approach, we demonstrate dynamic heterogeneity in a longitudinal study of recent tuberculosis contacts

Socio-demographic heterogeneity in the prevalence of COVID-19 during lockdown is associated with ethnicity and household size: results from an observational cohort study

BackgroundAccumulating evidence indicates that COVID-19 causes adverse outcomes in Black, Asian and Minority Ethnic (BAME) groups. However, little is known about the impact of ethnicity and household size on acquiring infection with SARS-CoV-2.MethodsWe undertook a retrospective cohort study, in Leicester (UK), of all individuals assessed for COVID-19 with polymerase chain reaction (PCR) testing at University Hospitals of Leicester NHS Trust between 1st March and 28th April 2020. We used logistic regression to identify sociodemographic, clinical and temporal factors associated with SARS-CoV-2 PCR positivity before/after lockdown.Findings 971/4051 (24.0%) patients with suspected COVID-19 were found to be PCR positive for SARS-CoV-2. PCR positivity was more common amongst individuals from BAME backgrounds than their White counterparts (White 20.0%, South Asian 37.5%, Black 36.1%, Other 32.2%; pInterpretationIn individuals presenting with suspected COVID-19, those from BAME communities and larger households had an increased likelihood of SARS-CoV-2 PCR positivity. Pandemic control measures may have more rapid impact on slowing viral transmission amongst those of White ethnicity compared to BAME groups, Research is urgently required to understand the mechanisms underlying these disparities and whether public health interventions have differential effects on individuals from BAME groups.</div