We use cookies to enhance your experience. By continuing to browse this site you agree to our use of cookies. More info.
In a recent study published in the journal Nature Biotechnology, an international team of researchers developed and evaluated quantitative polymerase chain reaction (qPCR)-based assays to quantify severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific functional T cell immunity.
Study: Rapid, scalable assessment of SARS-CoV-2 cellular immunity by whole-blood PCR. Image Credit: Instituto de Salud Carlos III / Shutterstock
Measuring the magnitude and duration of cellular immunity to SARS-CoV-2 on a large scale using rapid, high-throughput methods could help anticipate the risk of breakthrough infections (BTIs) from new SARS-CoV-2 variants, as well as revaccinate those at higher risk of developing BTIs on priority.
Although studies have demonstrated how T cells protect against severe coronavirus disease 2019 (COVID-19) and reduce viral transmission, determining T cell function has remained associated with technical challenges. The traditional methods, including enzyme-linked immunosorbent spot (ELISpot) and flow cytometry, are not easy to scale up and are inherently complex. These assays involve freezing and thawing peripheral blood mononuclear cells (PBMCs), which often introduce high variability in the results. Moreover, most studies using these methods have not been able to screen more than a few hundred participants.
In their previous works, the authors have demonstrated that 15-mers long synthetic peptides could activate T cells in vitro following overnight incubation with whole blood samples. Basically, when stimulated with SARS-CoV-2 antigens, whole-blood cells secrete chemokines, including interferon-gamma (IFN-γ) and interleukin-2 (IL-2), that restimulates PBMCs to produce C-X-C motif chemokine ligand 10 (CXCL10).
In the present study, researchers tested three approaches with distinctive advantages and limitations to detect SARS-CoV-2-specific cellular immunity.
Only the direct qPCR-based rapid T cell activation (dqTACT) assay used whole blood samples directly. It quantified CXCL10 messenger ribonucleic acid (mRNA), a chemokine whose expression correlates with the activation of antigen-specific T cells. It required ex vivo stimulation of whole-blood samples with a pool of SARS-CoV-2 spike (S) or nucleoprotein (NP) peptides followed by direct amplification of CXCL10.
Since the dqTACT assay did not require red blood cell lysis and viral RNA purification, it had minimal operator-induced errors and labor time. Another advantage was its pliability to repeatedly test patient samples, requiring only one ml of blood and a faster turnaround time. Overall, it was the easiest-to-implement protocol with high accuracy and minimal technical errors. It is under clinical testing in response to recent guidelines from the United States Food and Drug Administration (US-FDA) and European Medicines Agency (EMA).
The other two assays, viz., probe-based qPCR (qTACT) or next-generation sequencing (TACTseq), required viral RNA extraction to detect SARS-CoV-2-specific T cell immunity. The TACTseq measured cytokines produced by myeloid and T cells in the blood and measured the expression of 15 to 20 genes. The qTACT assay used two or more fluorophores to measure the expression of two to four genes.
COVID-19 recovered individuals had a higher median IFN-γ gene expression before vaccination compared to COVID-19 naïve individuals. The findings of qTACT were similar to more traditional enzyme-linked lectin assay (ELLA) and ELISpot for the S-specific T cell response by both CXCL10 and IFN-γ, 10 and 20 days after the first and second vaccine doses.
On the other hand, the dqTACT assay consistently detected T cells above the threshold up to eight months post-vaccination. It also reliably detected CXCL10 expression in vaccinated individuals. The authors observed a significant increase in CXCL10 expression in individuals who received a second dose of BNT162b2 compared to those that received only a first dose of the ChAdOx1s vaccine.
The authors optimized qTACT and dqTACT assays on multiple qPCR machines, including the 7500 Fast System, CFX96, CFX384, and bCUBE 2.0. The results for all three assays were comparable and appeared widely applicable across several diagnostic laboratories worldwide. More importantly, all the TACT assays were technically easy to use and had high accuracy.
The researchers evaluated the qTACT and dqTACT assays in different cohorts of naïve, COVID-19 recovered and vaccinated individuals. All three assays provided rapid information about the magnitude and duration of SARS-CoV-2-specific cellular immunity.
Since they used different peptides based on SARS-CoV-2 S or NP proteins, they represented a flexible strategy that could help detect the presence of functional T cells in a time-sensitive manner. Furthermore, these tests could be adapted to detect the degree of cellular immunity needed to complement the currently used assays measuring SARS-CoV-2 presence or anti-SARS-CoV-2 antibody titers. Overall, the information derived from these assays could be relevant for evaluating future vaccination strategies based on the levels of immune protection in the population.
Posted in: Device / Technology News | Medical Research News | Disease/Infection News
Tags: Antibody, Antigen, Assay, Biotechnology, Blood, Cell, Cell Lysis, Chemokine, Chemokines, Clinical Testing, Coronavirus, Coronavirus Disease COVID-19, covid-19, CXCL10, Cytokines, Cytometry, Diagnostic, Enzyme, Ex Vivo, Flow Cytometry, Food, Gene, Gene Expression, Genes, immunity, in vitro, Interferon, Interferon-gamma, Interleukin, Interleukin-2, Labor, Ligand, Peptides, Polymerase, Polymerase Chain Reaction, Respiratory, Ribonucleic Acid, RNA, RNA Extraction, RNA Purification, SARS, SARS-CoV-2, Severe Acute Respiratory, Severe Acute Respiratory Syndrome, Syndrome, Vaccine
Neha is a digital marketing professional based in Gurugram, India. She has a Master’s degree from the University of Rajasthan with a specialization in Biotechnology in 2008. She has experience in pre-clinical research as part of her research project in The Department of Toxicology at the prestigious Central Drug Research Institute (CDRI), Lucknow, India. She also holds a certification in C++ programming.
Please use one of the following formats to cite this article in your essay, paper or report:
Mathur, Neha. (2022, June 15). New test can tell if you are immune to SARS-CoV-2. News-Medical. Retrieved on June 18, 2022 from https://www.news-medical.net/news/20220615/New-test-can-tell-if-you-are-immune-to-SARS-CoV-2.aspx.
Mathur, Neha. "New test can tell if you are immune to SARS-CoV-2". News-Medical. 18 June 2022. <https://www.news-medical.net/news/20220615/New-test-can-tell-if-you-are-immune-to-SARS-CoV-2.aspx>.
Mathur, Neha. "New test can tell if you are immune to SARS-CoV-2". News-Medical. https://www.news-medical.net/news/20220615/New-test-can-tell-if-you-are-immune-to-SARS-CoV-2.aspx. (accessed June 18, 2022).
Mathur, Neha. 2022. New test can tell if you are immune to SARS-CoV-2. News-Medical, viewed 18 June 2022, https://www.news-medical.net/news/20220615/New-test-can-tell-if-you-are-immune-to-SARS-CoV-2.aspx.
News-Medical speaks to Henry Fingerhut, Senior Policy Analyst for Science & Innovation at the Tony Blair Institute for Global Change, about genomic surveillance and its associated opportunities and challenges.
Dr. Chenqu Suo and Dr. Cecilia Domínguez Conde
In this interview, News-Medical speaks to two researchers each discussing their respective studies that have contributed to the Human Cell Atlas; Dr. Chenqu Suo and Dr. Cecilia Domínguez Conde from the Wellcome Sanger Institute.
Irene Walsh and Professor Claire Smith
In this interview, News Medical speak to Irene Walsh, the director of Product, Design & Content, and 3D4Medical at Elsevier, and Professor Claire Smith, Head of Anatomy at Brighton and Sussex Medical School, about the real-world applications of the Complete Anatomy female model, the most advanced full female anatomy model in the world.
News-Medical.Net provides this medical information service in accordance with these terms and conditions. Please note that medical information found on this website is designed to support, not to replace the relationship between patient and physician/doctor and the medical advice they may provide.
This site complies with the HONcode standard for trustworthy health information: verify here.
News-Medical.net - An AZoNetwork Site
Owned and operated by AZoNetwork, © 2000-2022