Rapid Testing for SARS-CoV-2 Antibodies with New Serological Assay

Detection of SARS-CoV-2 relies predominantly on nucleic acid testing and serological testing.

Instigators working at the University of California, Santa Cruz, have created a new serological assay that can detect Sars-CoV-2 antibodies that is less complex and can be performed much faster than current available testing, while being just as accurate. Accurate serological testing is a crucial component in developing countermeasures against the coronavirus disease 2019 (COVID-19), including helping to identify and evaluate donors for convalescent plasma therapy and developing a vaccine.

Current forms of serological testing involve a complex laboratory method called ELISA, which can potentially take 4 to 6 hours to run. The tests provide a quantitative result indicating the strength of the immune response.

There are simpler assays on the market that use test strips to provide rapid results, but they don’t quantify antibody levels and are much less reliable. The method created in the study is called biolayer interferometry immunosorbent assay (BLI-ISA). In less than 20 minutes, the novel form of testing provides a complete quantitative result.

"Our assay is as sensitive if not better than other assays in detecting low levels of antibodies, and the specificity [false-positive rate] is as good as the best antibody tests out there," Rebecca DuBois, an author on the study said. "It combines the advantages of the test strips that take 20 minutes with the quantitative results and higher performance of ELISA."

BLI-ISA uses an optical technique that measures interactions between molecules by detecting the binding of molecules to the tip of a fiber-optic biosensor, called biolayer interferometry. The instrument uses an automated "dip-and-read" format, where the biosensor tip is dipped into a solution containing the viral protein which binds to it. A signal is then generated that can be used for quality control to ensure consistency in the loading step. The biosensor is then dipped into the sample of blood plasma and generates a signal as antibodies bind to the antigen.

When someone is infected with SARS-CoV-2, their immune system produces an array of antigens. The BLI-ISA is able to detect these antigens by measuring the binding of anti-IgG antibodies. The test provides a complete quantitative measurement of both total antibodies and IgG antibodies.

"This method provides a standardized way to quantify antibody levels, which could be used to compare antibody responses to different vaccine candidates,” John Dzimianski, first author on the study said. “In addition, running the assay itself is straightforward, requiring little more than the push of a button. It's a simple but powerful tool."