Low Cost Pinprick COVID-19 Test Detects SARS-CoV-2 Antibodies in Drop of Blood in Under an Hour

Researchers at the University of Toronto (Toronto, ON, Canada) have developed a new method for measuring immunity to coronavirus in those who have recovered from COVID-19. They are now ready to reveal their creation: a pinprick test that accurately measures the concentration of coronavirus antibodies in blood in under one hour. And it’s cheap - costing about a tenth of the current tests based on ELISA (enzyme-linked immunosorbent assay)-based methods which are considered the gold standard when it comes to measuring antibody concentration as a strength of individual immune response.

Their new method is called SATiN, which stands for Serological Assay based on split Tripart Nanoluciferase. It is the first COVID-19 serology test that uses highly sensitive protein complementation chemistry in which a light-emitting luciferase protein is reconstituted from separate fragments as test readout. Luciferase is initially supplied in fragments that cannot glow on their own. One piece is attached on the viral spike protein, which antibodies bind to in order to neutralize the virus, while another is hooked to a bacterial protein that antibodies also interact with. By binding simultaneously to the coronavirus spike protein and the bacterial protein, the antibody helps lock luciferase pieces together into a whole molecule. The result is a flash of light that can be detected and converted into antibody concentration by a plate reader instrument. All reagents can be prepared from scratch and in bulk, helping to keep costs down.

“Our assay is as sensitive as, if not better than, any other currently available assay in detecting low levels of IgG antibodies and its specificity - also known as false-positive rate – is as good as the best antibody test on the market,” said Igor Stagljar, a professor of biochemistry and molecular genetics in the Donnelly Centre for Cellular and Biomolecular Research at the University of Toronto’s Temerty Faculty of Medicine.

“It’s really useful to have that quantitative ability to know what someone’s antibody status is – whether it’s from a past infection or a vaccination,” added Stagljar, who collaborated with public health agencies and blood banks from across Canada to have the test validated on blood samples taken from former COVID-19 patients. “This will be of crucial importance for the next stage of the pandemic, especially now when governments of all countries started with mass vaccinations with recently approved anti-COVID-19 vaccines.”

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