Harnessing recombinase polymerase amplification for rapid multi-gene detection of SARS-CoV-2 in resource-limited settings

• Published in: Biosensors & bioelectronics 2021-10, Vol.189, p.113328-113328, Article 113328
• Main Authors: Cherkaoui, Dounia, Huang, Da, Miller, Benjamin S., Turbé, Valérian, McKendry, Rachel A.
• Format: Article
• Language: English
• Subjects: Biosensing Techniques; COVID-19; Dipstick; Humans; Isothermal amplification; Molecular Diagnostic Techniques; Multi-gene; Nucleic Acid Amplification Techniques; Nucleic acid testing; Pandemics; Real-time detection; Real-Time Polymerase Chain Reaction; Recombinase polymerase amplification; Recombinases - genetics; RNA, Viral - genetics; SARS-CoV-2; Sensitivity and Specificity
• ISSN: 0956-5663; 1873-4235
• DOI: 10.1016/j.bios.2021.113328

The COVID-19 pandemic is challenging diagnostic testing capacity worldwide. The mass testing needed to limit the spread of the virus requires new molecular diagnostic tests to dramatically widen access at the point-of-care in resource-limited settings. Isothermal molecular assays have emerged as a promising technology, given the faster turn-around time and minimal equipment compared to gold standard laboratory PCR methods. However, unlike PCR, they do not typically target multiple SARS-CoV-2 genes, risking sensitivity and specificity. Moreover, they often require multiple steps thus adding complexity and delays. Here we develop a multiplexed, 1–2 step, fast (20–30 min) SARS-CoV-2 molecular test using reverse transcription recombinase polymerase amplification to simultaneously detect two conserved targets - the E and RdRP genes. The agile multi-gene platform offers two complementary detection methods: real-time fluorescence or dipstick. The analytical sensitivity of the fluorescence test was 9.5 (95% CI: 7.0–18) RNA copies per reaction for the E gene and 17 (95% CI: 11–93) RNA copies per reaction for the RdRP gene. The analytical sensitivity for the dipstick method was 130 (95% CI: 82–500) RNA copies per reaction. High specificity was found against common seasonal coronaviruses, SARS-CoV and MERS-CoV model samples. The dipstick readout demonstrated potential for point-of-care testing in decentralised settings, with minimal or equipment-free incubation methods and a user-friendly prototype smartphone application. This rapid, simple, ultrasensitive and multiplexed molecular test offers valuable advantages over gold standard tests and in future could be configurated to detect emerging variants of concern. •Rapid nucleic acid testing of SARS-CoV-2 simultaneously targeting multiple genes.•Isothermal amplification by RT-RPA using two complementary readouts.•Simple and equipment-free incubation methods for point-of-care application.•Towards a smartphone-connected dipstick test for decentralised testing.