A blood test designed by researchers at the University of Toronto and Sinai Health's Lunenfeld-Tanenbaum Research Institute can accurately detect whether a person was previously infected with the virus that causes COVID-19 - and whether their immune response is functional.
The researchers found the test can detect the presence of antibodies to the SARS-CoV-2 virus and also evaluate whether these antibodies can block attachment of the viral spike protein to the human protein ACE2, a critical step in the infection process.
"This study goes well beyond the normal detection of antibodies and provides insight into the functionality of those antibodies," said Anne-Claude Gingras, a co-leader of the effort who is a professor of molecular genetics at U of T and senior investigator at LTRI. "It takes a village to make important scientific advances, and this project was no different."
The biology pre-print server bioRxiv published the study results.
Gingras and her lab worked with James Rini, a professor of biochemistry and molecular genetics at U of T, as well as the National Microbiology Lab in Winnipeg, Canadian Blood Services and the National Research Council of Canada, among others.
"Using this test, we are able to quantitate the levels of receptor-blocking antibodies found in a given patient's serum," Rini said. "Information of this sort provides insight into how we might develop therapeutics and vaccines to combat COVID-19."
Neutralizing antibodies hold great promise in the development of COVID-19 vaccines and other potential therapies, although that potential has not yet been realized.
Jim Woodgett, Koffler director of research at LTRI and a professor of medical biophysics at U of T, said the assay for neutralizing antibodies provides a deeper understanding of the immune response to COVID-19 infection.
"This is a bit like the difference between finding a bunch of batteries versus knowing which ones actually work," Woodgett said. "We don't just want to know whether a person has had a prior infection but whether they generated a degree of immunity. This is why a functional assay is much more useful than a detection test."
However, the researchers warn that it is still unclear how long those antibodies remain functional in fighting off reinfection.
Detecting neutralizing antibodies typically involves working with live virus, a requirement which greatly limits widespread screening. This form of testing does not use live virus, but instead uses purified fragments of the viral spike protein and ACE2, which means the assay can be performed in standard immunology and clinical laboratories.
In the coming months, the team hopes to test up to 1,000 volunteers as part of the next phase of their research into a mass-scale serology test for COVID-19.
Work in the Gingras lab was partially funded by a contribution from QuestCap through the Sinai Health Foundation.
