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.
An 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.
This 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.
We 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.
We 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.
Effective 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.
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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.
QuantiFERON-TB Gold Plus (QFT-Plus) is a new-generation QuantiFERON-TB Gold In-Tube (QFT-GIT) assay which has two antigen-coated tubes called TB1, which contains long peptides derived from ESAT-6 and ...CFP-10, and TB2, which contains the same components as TB1 and additional short peptides which potentially stimulate CD8
T cells through the presentation of major histocompatibility complex class I. This is the first study to compare QFT-Plus and QFT-GIT for use in the diagnosis of latent tuberculosis infection (LTBI) among immunocompromised patients in the Republic of Korea. Among 317 consecutive patients who underwent screening for LTBI before solid organ or hematopoietic stem cell transplantation and tumor necrosis factor alpha inhibitor treatment, LTBI was identified in 92 (29.0%) and 88 (27.8%) patients by QFT-GIT and QFT-Plus, respectively. The rate of concordance between QFT-GIT and QFT-Plus was 93.7% (κ value, 0.860), and the indeterminate rate (3.2%) was similar between QFT-GIT and QFT-Plus. Of 20 (6.3%) samples with discordant results, 11 (55.0%) and 7 (35.0%) were positive by QFT-GIT alone and QFT-Plus alone, respectively, and 2 (15.0%) were indeterminate by each assay. The interferon gamma level in samples with discordant results ranged from 0.39 to 1.10 IU/ml, except for one sample, in which the gamma interferon level was 2.97 IU/ml only in TB2. Conclusively, there was a high degree of agreement between the results of QFT-GIT and QFT-Plus for the screening of immunocompromised patients for LTBI. The reactivity in TB2 contributed substantially to the difference between QFT-GIT and QFT-Plus, particularly in solid organ transplant candidates. The significance of the discrete responses in TB1 and TB2 of QFT-Plus needs to be explored further by means of an immunological and clinical approach in different patient groups and clinical settings.
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.
•Some interferon-gamma release assay (IGRA)-negative contacts evade contact tracing and develop active tuberculosis.•0.3% of IGRA-negative contacts developed tuberculosis (TB), and 50% of these ...developed TB within 23 months of index patient diagnosis.•IGRA-negative contacts of a smear-positive index patient were more likely to develop TB.•Risk factors were older age, Malay ethnicity, diabetes, and kidney disease.•Other factors were family relationship with the index patient or exposure in a dormitory or nursing home.•Following up contacts with risk factors for 24 months may prevent progression to TB.
Contacts of patients with infectious tuberculosis (TB) testing positive on interferon-gamma release assay (IGRA) are followed up to exclude active disease. However, identifying factors that predispose IGRA-negative contacts to TB could improve screening and follow-up strategies in a medium TB burden country such as Singapore.
We conducted a retrospective study of IGRA-negative contacts aged ≥2 years identified during contact investigation between January 2014 and December 2022. We examined the risk factors associated with developing active TB among contacts previously testing IGRA-negative, using univariate and multivariable logistic regression and odds ratios with 95% confidence intervals.
Of 60,377 IGRA-negative contacts, 150 developed TB disease, and half were notified within 23 months of index patient diagnosis. IGRA-negative contacts of a smear-positive index patient were more likely to develop TB. Independent risk factors for TB were age >50 years, Malay ethnicity, having diabetes or end-stage renal failure, a “family” relationship with the index patient, or exposure in a dormitory or nursing home.
Identifying risk factors could help optimise follow-up strategies and preventive treatment in IGRA-negative individuals. The incidence rate of TB in this group was 150 per 100,000 population, substantially higher than in the community, with a median 92 weeks to develop disease. Findings suggest that follow-up should be extended to 24 months for contacts with these risk factors.
Latent tuberculosis infection (LTBI) is a subclinical mycobacterial infection defined on the basis of cellular immune response to mycobacterial antigens. The tuberculin skin test (TST) and the ...interferon gamma release assay (IGRA) are currently used to establish the diagnosis of LTB. However, neither TST nor IGRA is useful to discriminate between active and latent tuberculosis. Moreover, these tests cannot be used to predict whether an individual with LTBI will develop active tuberculosis (TB) or whether therapy for LTBI could be effective to decrease the risk of developing active TB. Therefore, in this article, we review current approaches and some efforts to identify an immunological marker that could be useful in distinguishing LTBI from TB and in evaluating the effectiveness of treatment of LTB on the risk of progression to active TB.