October 19, 2020 -- Antibody levels in the blood of coronavirus patients drop quickly after the body clears the virus, according to a new study published in mBio, an open access journal of the American Society for Microbiology.
For convalescent plasma to help patients who currently have COVID-19, the donated blood needs to be collected soon after recovery. Under current guidelines, however, patients can’t donate blood until 14 days after symptoms have resolved, and most donations occur even later.
“We don’t want to transfuse the virus, just transfuse the antibodies. But at the same time, our work shows that the capacity of the plasma to neutralize viral particles is going down during those first weeks,” Andres Finzi, one of the study authors and a microbiologist at the University of Montreal in Canada, said in a statement.
The research team analyzed blood samples from 31 people recovering from COVID-19 and measured antibodies at one-month intervals. Overall, the immunoglobulins that neutralize the virus dropped about six to 10 weeks after symptoms began. The ability of the antibodies to neutralize the virus also fell during that time.
In previous studies, researchers found that antibodies peak around two to three weeks after symptoms begin and fall after that. Finzi and his colleagues have also found that the ability to neutralize the virus decreases after that — about three to six weeks after symptoms begin.
Antibodies block the “spike” protein on SARS-CoV-2 that allows the virus to invade a cell in the body. They neutralize the coronavirus by preventing it from locking into a host’s cells and replicating.
Scientists aren’t sure whether the neutralizing function drives the efficacy of convalescent plasma use in COVID-19 patients, Finzi and the research team wrote. If so, recovered patients should be allowed to donate as soon as possible, they said.
“Efforts should be made to ensure that convalescent plasma is collected as soon as possible after recovery of the donor from active infection,” they wrote.