Development of a saliva and aptamer based antigen test for variants of concerns of SARS-CoV-2
Several COVID‑19 variants of concern (VoCs) are resulting in both increased transmission rates and reduced vaccine efficacy, giving rise to a third wave of outbreaks. Current rapid tests show low sensitivity, and thus the potential for asymptomatic transmission of VoCs is high. To aid in a return to normalcy, it is critical to put in place rapid, simple and cheap tests that can detect all current and future VoCs. Using Rapid Response Funding from CIHR, our McMaster team has developed a simple saliva-based test using a proprietary DNA aptamer (a DNA sequence that binds proteins) that specifically recognizes the spike protein of the original Wuhan variant of the virus. This aptamer has been fully validated for SARS-CoV-2 virus binding in human saliva, including positive patient samples. Two rapid tests have been created with this aptamer: an electrochemical sensor (like a glucose meter) and a lateral flow device (like a home pregnancy test) for use at home or in congregate settings. An instrument-based assay has also been developed for testing of many people at centralized testing centres. The rapid tests can be completed within 10 minutes and are currently being validated with saliva samples from our local hospitals and assessment centre (currently ~50 positive and ~100 negative samples), with very high clinical sensitivity and specificity. For Phase 2 of test development we will pursue three goals: (1) evaluate >100 current aptamers for binding to UK, South Africa and Brazil variants, and develop new aptamers for any variants for which no current aptamers shows high binding affinity; (2) create an experimental method that allows for rapid generation of new aptamers for future VoCs; (3) work with our clinicians and Canadian industrial partners to fully validate a rapid saliva-based aptamer tests to detect all VoCs using patient samples and finalize the manufacturing and distribution of these tests.
