Evaluation of a flow cytometry-based surrogate assay (FlowSA) for the detection of SARS-CoV-2 in clinical samples

Introduction: The current diagnostic methods for SARS-CoV-2 rely on quantitative RT-PCR. However, the presence of viral RNA in samples does not necessarily reflect the presence of an infectious virus. Therefore, the reliable detection of infectious SARS-CoV-2 in clinical samples is necessary to limi...

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Main Authors: Vinit Upasani, Marjolein Knoester, Daniele Pantano, Lili Gard, Jolanda M. Smit, Bernardina T.F. van der Gun, Adriana Tami, Izabela A. Rodenhuis-Zybert
Format: Article
Language:English
Published: Elsevier 2025-02-01
Series:Journal of Clinical Virology Plus
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Online Access:http://www.sciencedirect.com/science/article/pii/S2667038025000031
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Summary:Introduction: The current diagnostic methods for SARS-CoV-2 rely on quantitative RT-PCR. However, the presence of viral RNA in samples does not necessarily reflect the presence of an infectious virus. Therefore, the reliable detection of infectious SARS-CoV-2 in clinical samples is necessary to limit viral transmission. Methods: We developed a flow cytometry-based surrogate assay (FlowSA), wherein the presence of infectious SARS-CoV-2 was detected using virus nucleocapsid-specific antibodies. Results: We showed that FlowSA allows the detection of a wide range of viral titers of multiple SARS-CoV-2 variants. Furthermore, the assay was successfully used to detect infectious SARS-CoV-2 in nasopharyngeal swabs from SARS-CoV-2 positive individuals, including those with high Ct values. Notably, FlowSA identified the presence of infectious SARS-CoV-2 in biological specimens that scored negative for cytopathic effect (CPE) in cell culture and would otherwise be considered negative. Conclusion: We propose that FlowSA can be adopted as an alternative to conventional CPE methods for viral diagnostics.
ISSN:2667-0380