Rapid and accurate detection of infectious SARS-CoV-2 by viral receptor capture combined with loop-mediated isothermal amplification.

Rapid and accurate detection of infectious virus particles, not just viral nucleic acid, is essential to avoid unnecessary quarantine and effectively control the spread of viral diseases such as coronavirus disease 2019 (COVID-19), severe acute respiratory syndrome (SARS), and Middle East respiratory syndrome (MERS). Real-time quantitative polymerase chain reaction (RT-qPCR) was the most widely used detection technique during the COVID-19 outbreak. However, it cannot discriminate between intact infectious viruses and surface-distorted, non-infectious virus particles or naked viral RNA. In this study, we present a strategy for the specific detection of infectious coronaviruses by combining viral receptor capture and reverse transcription loop-mediated isothermal amplification (RT-LAMP). We successfully applied this strategy to detect infectious virus particles of the SARS-CoV-2 surrogate virus and the human coronavirus NL63 (HCoV-NL63). Virus particles were first captured on ELISA plates coated with the recombinant human angiotensin-converting enzyme 2 (hACE2) receptor. Viral RNA was then extracted from the particles and detected by RT-LAMP using virus-specific primers. In our experimental setting, the proposed method had a minimum detection limit (LOD) of 90 PFU/mL, sensitivity of 96.2%, and specificity of 100%. Our study provides a proof-of-concept that viral receptor capture combined with RT-LAMP can differentiate infectious coronaviruses from non-infectious virions or naked viral RNA. This paves the way for this virus detection strategy to become a mainstream tool for the management, prevention and control of epidemic coronavirus diseases.