Immunomolecular Assay Based on Selective Virion Capture by Spike Antibody and Viral Nucleic Acid Amplification for Detecting Intact SARS-CoV-2 Particles

Abstract

Background: Effective therapeutics and vaccines for coronavirus disease 2019 (COVID-19) are currently lacking because of the mutation and immune escape of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Based on the propagation characteristics of SARS-CoV-2, rapid and accurate detection of complete virions from clinical samples and the environment is critical for assessing infection risk and containing further COVID-19 outbreaks. However, currently applicable methods cannot achieve large-scale clinical application because of factors such as the high viral load, cumbersome virus isolation steps, demanding environmental conditions, and long experimental periods. In this study, we developed an immunomolecular detection method combining capture of the viral spike glycoprotein with monoclonal antibodies and nucleic acid amplification via quantitative reverse transcription PCR to rapidly and accurately detect complete virions.Results: After constructing a novel pseudovirus, screening for specific antibodies, and optimizing the detection parameters, the assay achieved a limit of detection of 9 × 102 transduction units/mL of viral titer with high confidence (~95%) and excellent stability against human serum and common virus/pseudovirus. The coefficients of variation were 1.0–2.0% for intra-assay and inter-assay analyses, respectively. Compared with reverse transcription-PCR, the immunomolecular method more accurately quantified complete virions. SARS-CoV-2/pseudovirus was more stable on plastic and paper than on aluminum and copper in the detection of SARS-CoV-2 pseudovirus under different conditions, and complete virions were detected up to 96 h after they were applied to these surfaces (except for copper), although the titer of the virions was greatly reduced. Conclusions: Convenient, inexpensive, and accurate complete virus detection can be applied in many fields, such as monitoring the infectivity of convalescent and post-discharge patients and assessing high-risk environments (isolation rooms, operating rooms, patient living environments, and cold chain logistics). This method can also be used to detect intact virions such as those of hepatitis B and C viruses, human immunodeficiency virus, influenza, and the partial pulmonary virus, which may further improve the accuracy of diagnoses and facilitate individualized and precise treatments.