In the absence of approved, effective treatments for COVID-19, some hospitals treat patients with severe symptoms of COVID with blood plasma from recovering patients. The blood of recovered patients contains antibodies that act against the coronavirus. Although plasma has not yet been shown to be useful in randomized trials, some small retrospective studies suggest that it may reduce the severity of the disease and reduce the time to hospitalization.
This week in mBio, an open-access journal of the American Society of Microbiology, the researchers reported that antibody levels in the blood of patients with COVID-19 dropped rapidly in the weeks after their bodies cleared the virus and symptoms subsided. If it is ultimately found that convalescent plasma has a clear benefit, the authors conclude, it should be collected within a certain period of time after recovery. However, recovering patients cannot donate blood for at least 14 days after the symptoms have subsided to give the body time to clear the virus particles.
“We don’t want to transfuse the virus, we just transfuse the antibodies,” said Andres Finzi, MD, University of Montreal, Canada. “But at the same time, our work shows that the plasma capacity to neutralize virus particles decreases in the first weeks.”
The adhesion protein of SARS-CoV-2 plays a crucial role in helping the virus to seize and invade host cells. Antibodies produced by the body’s immune system bind to part of this protein and block the capacity of this “key” to bind to the host’s cellular “lock,” Finzi said, preventing the virus particle from being infected by the host cell.
Previous studies have suggested that antibodies to the SARS-CoV-2 jump protein peak 2 or 3 weeks after the onset of symptoms. Findings from an earlier cross-sectional study of the Finzi group, involving more than 100 patients, suggest that the plasma’s ability to neutralize the virus decreases significantly between 3 and 6 weeks after the onset of symptoms.
In the new longitudinal study, Finzi and colleagues analyzed blood samples collected at one-month intervals from 31 individuals recovering from COVID-19. They measure the levels of immunoglobulins that act against coronavirus S protein and test the ability of antibodies to neutralize the virus.
The researchers observed variations in the level of individual patients, but identified a consistent overall signal: Immunoglobulin G, A, and M levels, which target the binding site, decreased between 6 and 10 weeks after the onset of symptoms. Over the same period, the ability of antibodies to neutralize the virus decreased in a similar manner.
Finzi’s group continues to test blood samples from patients. Understanding how antibody levels change over time, he said, is crucial not only for optimizing the use of convalescent plasma, but also for understanding the effectiveness of the vaccine and whether previously infected people are at risk of re-infection. .
“How long do antibodies protect you?” He asked.
Other Finzi studies have focused on the immune response to human immunodeficiency virus or HIV, which differs drastically from SARS-CoV-2.
Reference: “Reduction of humoral responses against SARS-CoV-2 Spike in recovering individuals” by Guillaume Baudouin-Bussier, Anemari Laumea, Sai Priya Anand, Jeremy Prevost, Romain Gasser, Guillaume Goyet, Halima Mejahed, Josemione Trejorom Lewin, Laurie Gokool, Chantal Morrisseau, Philippe Bégin, Cécile Tremblay, Valérie Martel-Laferrière, Daniel E. Kaufmann, Jonathan Richard, Renée Bazin and Andrés Finzi, 16 October 2020, mBio.
DOI: 10,1128 / mBio.02590-20
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