Mayo Clinic and corporate partners on Thursday unveiled a new test that will help answer the critical question of whether people develop immunity to the coronavirus that causes this infectious disease.
The test is first in the world that will be broadly commercially available to identify neutralizing antibodies — the proteins produced after COVID-19 that will effectively fight off the coronavirus if it ever comes back. Existing tests developed amid the pandemic show whether people have produced any antibodies in response to COVID-19, but not these key proteins.
“This is more reassuring than just … a positive [antibody test] to show you have been previously exposed to the virus,” said Dr. Stephen Russell, chief of executive of Vyriad, the Rochester, Minn., company that created the test and provided it to Mayo via a licensing partnership with a second company, Regeneron. “This test is showing what level of protection you actually have.”
Vyriad and Mayo leaders cautioned that the test can’t yet give “immunity passports,” or suggest that people are no longer at risk of COVID-19 after recovering from initial infections. Nobody yet knows the amount or concentration of neutralizing antibodies that are needed in blood serum to fight off reinfection.
Research has shown highly variable levels of these antibodies in patients who have recovered from COVID-19, including as many as 5% who paradoxically have no antibodies in response to this coronavirus.
“There’s no need for that because we don’t know what levels are significant at this point,” said Elitza Theel, director of Mayo’s infectious diseases serology laboratory. However, the availability of that test will accelerate research on that question. The test is now available to Mayo clinicians and researchers and will be provided to others later in June.
Mayo and the University of Minnesota were among the first institutions in the U.S. to develop COVID-19 antibody tests, raising hopes among Minnesota health leaders that the tests could be used to identify people who have recovered and to declare them safe to return to work and move about in society without fear of infection. That hasn’t come to pass, yet, but the prospect remains.
International research in monkeys has shown signs of immunity after infection with the SARS-CoV-2 virus that causes COVID-19. Studies of the prior global SARS pandemic in 2003 showed two to three years of immunity for people who had been infected by the SARS-CoV-1 coronavirus.
Establishing the prevalence of COVID-19 in Minnesota will be critical given predictions that the virus will linger in the state and could produce a second wave of cases in the pandemic — as occurred in the Spanish flu epidemic in 1918-1919. As of Thursday, the Minnesota Department of Health reported another 453 lab-confirmed cases and 13 deaths, bringing the toll of the pandemic to 29,316 cases so far and 1,249 deaths — including 994 deaths of residents of long-term care and assisted living facilities.
While growth in COVID-19 cases has ebbed in recent days, it’s unclear what happens next, said Jan Malcolm, state health commissioner, speaking Thursday at the invitation of the U’s Center for the Study of Politics and Governance. “We frankly have no idea where it goes from here, whether it stays in this pattern.”
The Institute for Health Metrics and Evaluation in Washington offered its first modeling predictions over a second national wave of the pandemic, likely starting with an uptick in deaths in August and September. The institute now predicts 2,193 deaths from COVID-19 in Minnesota by Oct. 1.
A key biological feature of the COVID-19 virus is a “spike” protein on its surface that helps it bind with receptors and invade human cells. While other antibodies act as triggers to activate the immune system to fight infection, the neutralizing antibodies appear to bind to the virus on their own and block its ability to infect cells, Theel said.
“Because of this, they are thought to be really good markers of immunity,” Theel said.
For starters, Mayo will use the new test for neutralizing antibodies to assess people who have recovered from COVID-19 for donating plasma. Mayo is leading a national trial to see if this convalescent plasma has therapeutic benefits for patients with active and severe COVID-19 cases.
Plasma that is rich in neutralizing antibodies could be particularly effective, Russell said. On the other hand, plasma lacking these particular antibodies could have an opposite effect and result in an accelerated spread of the virus.
“You do not want to be giving people low concentrations of antibodies,” he said. “You thereby run a risk of making things worse. So having a test for neutralizing antibodies that can discriminate between low, intermediate and high [levels] is pretty important.”
The neutralizing antibody test also could help in the development and distribution of vaccines against COVID-19, once they are validated through research and made available. Theel said initial vaccine quantities could be limited, so antibody testing could assess who is most in need of protection.
Further uses will be proven with time, she added.
“It’s kind of been the story for antibody testing from day one,” Theel said. “There was a lot of excitement, as there should have been, but at the same time we didn’t really understand the role of antibody testing, and I think there was, to some extent, overexcitement. But with the neutralizing antibody test, I would view this as another step, another tool that we can use to better understand our immune response to [the virus]. Without these tools, we cannot move forward.”
