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Background: Tests that sensitively detect the presence of actively replicating SARS-CoV-2 may improve patient care by allowing the safe and timely discontinuation of isolation. Correlates of active replication include nucleocapsid antigen and virus minus-strand RNA.
Methods: Qualitative agreement of the DiaSorin LIAISON SARS-CoV-2 nucleocapsid antigen chemiluminescent immunoassay (CLIA) with minus-strand RNA was determined using 402 upper respiratory specimens from 323 patients previously tested using a laboratory-developed SARS-CoV-2 strand-specific RT-qPCR. Nucleocapsid antigen levels, minus-strand and plus-strand cycle threshold values, as well as virus culture, were used to evaluate discordant specimens. Receiver operating characteristic curves were also used to identify virus RNA thresholds for active replication, including values harmonized to the World Health Organization International Standard.
Results: Overall agreement was 92.0% [95% confidence interval (CI): 89.0 - 94.5], positive percent agreement was 90.6% (95% CI: 84.4 - 95.0), and negative percent agreement was 92.8% (95% CI: 89.0 - 95.6). The kappa coefficient was 0.83 (95% CI: 0.77 - 0.88). Discordant specimens contained low levels of nucleocapsid antigen and minus-strand RNA. 84.8% (28/33) were negative by culture. Sensitivity-optimized plus-strand RNA thresholds for active replication were 31.6 cycles or 3.64 log IU/mL; resulting in 100.0% sensitivity (95% CI: 97.6 to 100.0) and 55.9 specificity (95% CI: 49.7 to 62.0).
Conclusions: Detection of nucleocapsid antigen by CLIA performs equivalently to minus-strand detection via strand-specific RT-qPCR, though these methods may overestimate replication-competent virus compared to culture. Careful implementation of biomarkers for actively replicating SARS-CoV-2 has the potential to inform infection control decision-making and patient management.
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http://dx.doi.org/10.1016/j.jcv.2023.105468 | DOI Listing |
Biochem Soc Trans
September 2025
The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia.
Deep mutational scanning (DMS), a high-throughput method leveraging next-generation sequencing, has been crucial in mapping the functional landscapes of key severe acquired respiratory syndrome-coronavirus 2 (SARS-CoV-2) proteins. By systematically assessing thousands of amino acid changes, DMS provides a framework to understand Angiotensin-converting enzyme 2 (ACE2) binding and immune evasion by the spike protein, mechanisms and drug escape potential of the main and papain-like viral proteases and has highlighted areas of concern in the nucleocapsid protein that may affect most currently available rapid antigen testing kits. Each application has required the design of bespoke assays in eukaryotic (yeast and mammalian) cell models, providing an exemplar for the application of this technique to future pandemics.
View Article and Find Full Text PDFBioelectrochemistry
August 2025
Department of Physical Chemistry, Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, Naugarduko St. 24, LT-03225 Vilnius, Lithuania; Department of Nanotechnology, State Research Institute Center for Physical and Technological Sciences, Sauletekio Ave. 3, LT-10257 Vilni
The emergence of SARS-CoV-2 has posed significant global health challenges. The nucleocapsid protein (N-protein) is a structural part of the SARS-CoV-2 virus and an important immunogenic target of specific antibodies, which are developed in the organism during the infection by this virus. Artificially designed specific (monoclonal and polyclonal) antibodies are also used for therapeutic and bioanalytical purposes, therefore, the assessment and characterization of newly designed antibodies is an important analytical issue.
View Article and Find Full Text PDFImmunol Res
September 2025
Centre for Advanced Materials and Technologies, Warsaw University of Technology, Warsaw, Poland.
We present a series of preclinical studies focused on developing in vitro 2D and 3D models for assessing immunogenic factors in preventing infectious diseases. Human peripheral blood mononuclear cells (PBMC) and Calu-3 cell lines (bronchial epithelial cells) were used to develop 2D and 3D models. Peptides: Spike-S1-His (S-His), nucleocapsid-His and adjuvants: human adenovirus five serotype-based viral vector (AdV-D24-ICOSL-CD40L), armed with inducible co-stimulator (ICOSL) and CD40 ligand (CD40L), and a vector lacking these transgenes (AdV5/3) were used due to their effective initial interaction with antigen-presenting cells (APC).
View Article and Find Full Text PDFThe first generation of Spike-based COVID-19 vaccines has reduced the risk of hospitalization, serious illness, and death caused by SARS-CoV-2 infections. However, waning immunity induced by these vaccines has failed to prevent immune escape, resulting in the emergence of multiple variants of concern (VOCs) and the prolongation of the COVID-19 pandemic. We hypothesize that a next-generation Coronavirus (CoV) vaccine incorporating highly conserved SARS-CoV-2 T cell antigens would confer potent, broad, and long-lasting cross-protective immunity against multiple VOCs.
View Article and Find Full Text PDFBackground: Sotrovimab is a neutralising monoclonal antibody targeting the SARS-CoV-2 spike protein. We aimed to evaluate the efficacy and safety of sotrovimab in the RECOVERY trial, an investigator-initiated, individually randomised, controlled, open-label, adaptive platform trial testing treatments for patients admitted to hospital with COVID-19.
Methods: Patients admitted with COVID-19 pneumonia to 107 UK hospitals were randomly assigned (1:1) to either usual care alone or usual care plus a single 1 g infusion of sotrovimab, using web-based unstratified randomisation.