Abstract
We investigated feasibility and accuracy of an interferon-γ release assay (IGRA) for detection of T-cell responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Whole ...blood IGRA accurately distinguished between convalescent and uninfected healthy blood donors with a predominantly CD4+ T-cell response. SARS-CoV-2 IGRA may serve as a useful diagnostic tool in managing the coronavirus disease 2019 pandemic.
•The QuantiFERON SARS-CoV-2 research use only assay response is mediated by CD4+ and CD8+ T cells.•Immune response to the antigen (Ag)2 tube is more accurate than that to the Ag1 tube.•Responses to ...QuantiFERON SARS-CoV-2 tubes are lower compared with a homemade test.•The QuantiFERON SARS-CoV-2 difference in accuracy is likely because of the peptide composition.
Objectives: In this study, we aimed to characterize the SARS-CoV-2-specific T cell response detected by the QuantiFERON SARS-CoV-2 research use only assay in terms of accuracy and T cell subsets involved compared with a homemade interferon (IFN)-γ release assay (IGRA).
Methods: We evaluated T cell response by the standardized QuantiFERON SARS-CoV-2 tubes (antigen Ag1 and Ag2) and a homemade IGRA quantifying IFN-γ response to SARS-CoV-2 spike peptides (homemade-IGRA-SPIKE test). We evaluated the T cell subsets mediating the specific response using flow cytometry.
Results: We prospectively enrolled 66 individuals: COVID-19 or post-COVID-19 subjects and NO-COVID-19-vaccinated subjects, including healthy donors and immunocompromised subjects. The standardized kit detected 62.1% (41/66) of T cell responders. Ag2 tube showed a higher IFN-γ quantitative and qualitative response. Ag1 tube response was mainly mediated by CD4+ T cells; Ag2 tube response was mediated by CD4+ and CD8+ T cells. The homemade-IGRA-SPIKE test detected a higher number of responders (52/66, 78.8%) than the QuantiFERON SARS-CoV-2 assay (P = 0.056). The response was found in both T cell subsets, although a higher magnitude and response rate was observed in the CD4+ T cell subset.
Conclusion: The QuantiFERON SARS-CoV-2 response is mediated by CD4+ and CD8+ T cells. A lower number of responders is found compared with the homemade-IGRA-SPIKE test, likely because of the different peptide composition.
The global SARS-CoV-2 pandemic has highlighted the critical importance of evaluating adaptive immunological status in both infected individuals and those who have been vaccinated. While the humoral ...immune response has been extensively studied, the cellular immune component has not progressed as rapidly due to challenges in developing rapid diagnostic tests for activated T cells. This study introduces a rapid, user-friendly assay aimed at addressing this need by using the early expression of interferon-gamma (IFN-γ) transcripts for rapid and direct evaluation. Using a novel design, this assay measures IFN-γ mRNA rather than its protein levels, thereby significantly shortening the time to result compared to traditional methods. The process involves incubating whole blood with a mixture of Spike and Nucleocapsid peptides, followed by immunomagnetic separation of CD3+ T cells and subsequent double-tagging RT-PCR. A lateral flow assay (LFA) is then used for detection, allowing IFN-γ mRNA levels to be assessed rapidly. Non-stimulated samples are used as controls to establish baseline IFN-γ expression. The intensity of the LFA signals from the stimulated samples is then compared to these baseline values using a smartphone interface. Furthermore, the study includes a time course analysis to monitor the T cell response dynamics over time in infected individuals. This LFA-IFN-γ represents a significant progress in the field of rapid diagnostics, offering a one-day protocol that simplifies testing procedures and is especially suitable for low-resource settings.
•Novel LFA rapidly assesses T-cell responses.•LFA compares CNP and AuNP for IFN-γ detection.•Test suitable for low-resource environments.•Visual readout integrates with smartphones.
BACKGROUNDAn estimated one fourth of the world's population is infected with Mycobacterium tuberculosis, and 5-10% of those infected develop tuberculosis in their lifetime. Preventing tuberculosis is ...one of the most underutilized but essential components of curtailing the tuberculosis epidemic. Moreover, current evidence illustrates that tuberculosis manifestations occur along a dynamic spectrum from infection to disease rather than a binary state as historically conceptualized. Elucidating determinants of transition between these states is crucial to decreasing the tuberculosis burden and reaching the END-TB Strategy goals as defined by the WHO. Vaccination, detection of infection, and provision of preventive treatment are key elements of tuberculosis prevention.OBJECTIVESThis review provides a comprehensive summary of recent evidence and state-of-the-art updates on advancements to prevent tuberculosis in various settings and high-risk populations.SOURCESWe identified relevant studies in the literature and synthesized the findings to provide an overview of the current state of tuberculosis prevention strategies and latest research developments.CONTENTWe present the current knowledge and recommendations regarding tuberculosis prevention, with a focus on M. bovis Bacille-Calmette-Guérin vaccination and novel vaccine candidates, tests for latent infection with M. tuberculosis, regimens available for tuberculosis preventive treatment and recommendations in low- and high-burden settings.IMPLICATIONSEffective tuberculosis prevention worldwide requires a multipronged approach that addresses social determinants, and improves access to tuberculosis detection and to new short tuberculosis preventive treatment regimens. Robust collaboration and innovative research are needed to reduce the global burden of tuberculosis and develop new detection tools, vaccines, and preventive treatments that serve all populations and ages.
Despite current guidelines for tuberculosis (TB) control in health care settings, which focused on smear-positive cases, prevention of nosocomial TB transmission continues to be a challenge. Here, we ...report the results of the first hospital-wide prospective study applying interferon-gamma release assay to investigate the role of smear-negative, culture-positive index cases in nosocomial TB transmission.
We prospectively identified cases of culture-confirmed smear-negative pulmonary TB receiving aerosol-generating procedures (AGPs) and cases of culture-confirmed smear-positive pulmonary TB admitted at a medical center. Nosocomial transmission was evaluated by screening their close contacts for latent TB infection (LTBI) using an interferon-gamma release assay.
A total of 93 smear-negative index receiving AGP and 122 smear-positive index were enrolled. Among them, 13 (14.0%) and 43 (35.2%) index cases, respectively, had secondary cases of LTBI (P < .001). Sputum smear negativity (adjusted odds ratio: 0.20 0.08-0.48) and AGP (sputum suction; adjusted odds ratio: 3.48 1.34-9.05) are independent factors of transmission. A similar proportion in the close contacts of the 2 index groups had LTBI (17 15.3% and 63 16.0%, respectively), and the former index group contributed to 21.3% of the nosocomial transmission.
Smear-negative, culture-positive index cases receiving AGPs could be as infectious as smear-positive index cases. Hospital TB control policy should also focus on the former group.
•The role of smear-negative index cases in nosocomial transmission remains unknown.•Smear-negative cases receiving AGPs could be as infectious as smear-positive cases.•Smear-negative cases may be responsible for 21.3% nosocomial TB transmissions.•Ongoing physician education to optimize the utilization of TB-NAAT is imperative.•Hospital TB control should also focus on smear-negative index receiving AGPs.
The QuantiFERON-TB Gold Plus (QFT-Plus; Qiagen, Germantown, MD) interferon gamma release assay (IGRA) received FDA clearance in 2017 and will replace the prior version of the assay, the QFT-Gold ...In-Tube (QFT-GIT). Here, we compared performances of the QFT-Plus assay and the QFT-GIT version in a diverse patient population, including patients undergoing evaluation for or follow-up of latent tuberculosis infection (LTBI;
= 39) or active TB infection (
= 3), and in health care workers (HCWs;
= 119) at Mayo Clinic (Rochester, MN). Compared to the QFT-GIT, the QFT-Plus assay showed 91.2% (31/34) positive, 98.4% (124/126) negative, and 96.6% (156/161) overall qualitative agreement among the 161 enrolled subjects, with a Cohen's kappa value of 0.91 (excellent interrater agreement). Among the 28 patients diagnosed with LTBI at the time of enrollment, the QFT-GIT and QFT-Plus assays agreed in 24 (85.7%) patients; in all four discordant patients, the positivity of the QFT-GIT or QFT-Plus IGRA was associated with low-level interferon gamma (IFN-γ) reactivity, ranging from 0.36 IU/ml to 0.66 IU/ml. Additionally, we document a high degree of correlation between IFN-γ levels in the QFT-GIT TB antigen tube and each of the two QFT-Plus TB antigen tubes, as well as between the QFT-Plus TB1 and TB2 tubes (Pearson's correlation coefficients
> 0.95). Overall, we show comparable results between the QFT-GIT and QFT-Plus assays in our study population composed of subjects presenting with a diverse spectrum of TB infections. Our findings suggest that the necessary transition to the QFT-Plus assay will be associated with a minimal difference in assay performance characteristics.
Le diagnostic de tuberculose oculaire (TO) demeure difficile et la contribution du QuantiFERON® (QFT) reste à préciser malgré sa généralisation en France. L’objectif de cette étude est d’évaluer dans ...quelles situations d’inflammation oculaire (IO) le QFT doit être prescrit et l’intérêt du nouveau test QuantiFERON®-TB-Plus (QFT-Plus) dans la TO.
Étude monocentrique, observationnelle, effectuée en ophtalmologie sur une période de 5 mois. Les critères d’inclusion étaient l’existence d’une IO avec QFT-Plus demandé à visée étiologique. Sur 316 dossiers consécutifs, 72 ont été exclus (tests indéterminés, bilan préthérapeutique, données manquantes et mauvaise indication) et 244 retenus et répartis en deux groupes : groupe 1 (uvéite antérieure/épislérite, n=129), groupe 2 (uvéite intermédiaire/postérieure/névrite optique/myosite oculaire, n=115). Tous les patients QFT+ ont bénéficié d’un bilan étiologique avec imagerie thoracique.
Quarante-cinq patients, d’âge médian de 52±12 ans, avaient un QFT+ (18,5 %), incluant 18 patients dans le groupe 1 et 27 dans le groupe 2. Un voyage en pays d’endémie et un contage tuberculeux et des anomalies de l’imagerie thoracique étaient identifiés, respectivement dans 70 %, 27 % et 22 % des cas. L’IO était chronique chez 36 % des patients (groupe 1, n=4/18 ; groupe 2, n=12/27). Aucun des 18 patients du groupe 1, n’a reçu de quadrithérapie antituberculeuse, ni n’a présenté de rechute à 1 an de suivi. Un diagnostic alterne était retrouvé chez 15 % des patients du groupe 2. Parmi les 23 patients, sans étiologie identifiée, 13 (59 %) avaient au moins un élément sémiologique ophtalmologique prédictif de TO (synéchies postérieures, vascularite rétinienne, granulomes choroïdiens). Onze patients ont bénéficié d’un traitement antituberculeux (TAT) d’épreuve (rifampicine/isoniazide/pirilène/éthambutol) de six mois. La présence de granulomes à l’angiographie et d’anomalies radiologiques à l’imagerie thoracique était statistiquement plus fréquente parmi les patients ayant reçu un TAT (respectivement, p=0,001 et 0,03). Une guérison à 12 mois était observée pour 8 patients (73 %), considéré a posteriori comme TO. Neuf patients ont reçu trois mois de bithérapie (rifampicine/isoniazide) sans que l’on puisse déterminer l’impact sur l’IO. La comparaison des réponses lymphocytaires T entre la stimulation CD4 par peptides ESAT-6/CFP-10 ou la co-stimulation CD4/CD8 était similaire, ne retrouvant que 4 discordances sur 244 tests (1,5 %). Aucun de ces 4 patients n'avait de TO.
La fréquence de positivité du QFT est élevée parmi les patients consultant pour une IO postérieure. Les anomalies radiologiques et la présence de granulomes semblent être les éléments qui ont incités le clinicien à initier un TAT aux patients QFT+, avec guérison dans 73 % des cas. Le QFT-Plus ne semble pas plus pertinent que le QFT-TB-Gold dans l’exploration d’une IO. Des études prospectives restent nécessaires pour codifier l’utilisation du QFT dans le bilan étiologique des IO et définir les indications du TAT d’épreuve et de ses modalités.
Ocular tuberculosis (TB) diagnosisremains difficult and quantiferon (QFT) contribution needs still yet to be specified, despite its generalization in France. The purpose of this observational study is to assess in which ocular inflammation (OI) presentation QFT is prescribed and to evaluate the added value of new QuantiFERON®-TB Gold Plus (QFT-Plus) test for diagnosis ocular TB diagnosis.
Monocentric, observational study, carried out in an ophthalmology department over a period of 5 months. Inclusion criteria were defined as an existence of an OI for which a QFT-Plus test was part of the etiological investigations. Of the 316 consecutive files, 72 were excluded (indeterminate test, prescription before anti-TNFα or immunosuppressant initiation, missing data, wrong indication) and 244 were selected and divided into two groups: group one (anterior uveitis/episcleritis, n=129) and group two (intermediate/posterior uveitis/optic neuritis/ocular myositis, n=115). All positive QFT patients underwent an etiological investigation including thoracic imaging.
Forty-five patients, aged 52±12 years, had positive QFT (18.5%), including 18 patients for group 1 and 27 for group 2. Living in TB-endemic area, TB exposure and chest imaging abnormalities were identified in 70%, 27% and 22% of cases, respectively. OI was chronic in 36% of cases (group one, 4/18; group two, 12/27). None of the 18 patients, in group 1, received anti-tuberculosis treatment (ATT) or experienced a relapse during one-year follow-up. Four QFT+ patients, from group 2 (15%) had another associated disease explaining their uveitis. Among the 23 other patients without identified etiology, 13 had at least one relevant ophthalmological signs predictive of TB uveitis (posterior synechiae, retinal vasculitis and/or choroidal granuloma) (59%). Eleven patients received a 6-month ATT trial. Radiological abnormalities and granulomas at angiography were significantly more frequent among treated patients (p=0.03 and 0.001, respectively). A full OI recovery was observed for 8 patients (73%), considered ex-post as ocular TB. Nine patients in group 2 received rifampicin/isoniazid dual therapy for 3 months, but no conclusion could be drawn as to the benefit of such prescription on OI. QFT rate comparison, according to CD4 stimulation by ESAT-6/CFP-10 peptides or by CD4/CD8 co-stimulation, was comparable and found only 4 cases of discrepancy (1.6%). None of these 4 cases had ocular TB diagnosis.
Positive QFT frequency among patients consulting for posterior OI remains high. In this study, radiological abnormalities and granulomas at angiography seemed to be more closely related to clinician decision for starting ATT trial in QFT+ patients, which was effective in 73% of cases. QFT-Plus does not seem more relevant than QFT-TB in exploring an OI. Prospective studies are necessary to codify QFT management in the etiological assessment of OI and clearly define ATT trial indications as well as their modalities.
Background: Evidence on the comparative performance of purified protein derivative tuberculin skin tests (TST) and interferon-gamma release assays (IGRA) for predicting incident active tuberculosis ...(TB) remains conflicting. We conducted an individual participant data meta-analysis to directly compare the predictive performance for incident TB disease between TST and IGRA to inform policy. Methods: We searched Medline and Embase from 1 January 2002 to 4 September 2020, and studies that were included in previous systematic reviews. We included prospective longitudinal studies in which participants received both TST and IGRA and estimated performance as hazard ratios (HR) for the development of all diagnoses of TB in participants with dichotomised positive test results compared to negative results, using different thresholds of positivity for TST. Secondary analyses included an evaluation of the impact of background TB incidence. We also estimated the sensitivity and specificity for predicting TB. We explored heterogeneity through pre-defined sub-group analyses (e.g. country-level TB incidence). Publication bias was assessed using funnel plots and Egger's test. This review is registered with PROSPERO, CRD42020205667. Findings: We obtained data from 13 studies out of 40 that were considered eligible (N = 32,034 participants: 36% from countries with TB incidence rate ≥100 per 100,000 population). All reported data on TST and QuantiFERON Gold in-Tube (QFT-GIT). The point estimate for the TST was highest with higher cut-offs for positivity and particularly when stratified by bacillus Calmette–Guérin vaccine (BCG) status (15 mm if BCG vaccinated and 5 mm if not TST5/15 mm) at 2.88 (95% CI 1.69–4.90). The pooled HR for QFT-GIT was higher than for TST at 4.15 (95% CI 1.97–8.75). The difference was large in countries with TB incidence rate <100 per 100,000 population (HR 10.38, 95% CI 4.17–25.87 for QFT-GIT VS. HR 5.36, 95% CI 3.82–7.51 for TST5/15 mm) but much of this difference was driven by a single study (HR 5.13, 95% CI 3.58–7.35 for TST5/15 mm VS. 7.18, 95% CI 4.48–11.51 for QFT-GIT, when excluding the study, in which all 19 TB cases had positive QFT-GIT results). The comparative performance was similar in the higher burden countries (HR 1.61, 95% CI 1.23–2.10 for QFT-GIT VS. HR 1.72, 95% CI 0.98–3.01 for TST5/15 mm). The predictive performance of both tests was higher in countries with TB incidence rate <100 per 100,000 population. In the lower TB incidence countries, the specificity of TST (76% for TST5/15 mm) and QFT-GIT (74%) for predicting active TB approached the minimum World Health Organization target (≥75%), but the sensitivity was below the target of ≥75% (63% for TST5/15 mm and 65% for QFT-GIT). The absolute differences in positive and negative predictive values between TST15 mm and QFT-GIT were small (positive predictive values 2.74% VS. 2.46%; negative predictive values 99.42% VS. 99.52% in low-incidence countries). Egger's test did not show evidence of publication bias (0.74 for TST15 mm and p = 0.68 for QFT-GIT). Interpretation: IGRA appears to have higher predictive performance than the TST in low TB incidence countries, but the difference was driven by a single study. Any advantage in clinical performance may be small, given the numerically similar positive and negative predictive values. Both IGRA and TST had lower performance in countries with high TB incidence. Test choice should be contextual and made considering operational and likely clinical impact of test results. Funding: YH, IA, and MXR were supported by the National Institute for Health and Care Research (NIHR), United Kingdom (RP-PG-0217-20009). MQ was supported by the Medical Research Council MC_UU_00004/07.
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