In the absence of approved and effective treatments for COVID-19, some hospitals have treated patients with severe COVID symptoms with blood plasma from the recovery of patients. The blood of recovered patients contains antibodies that act against the coronavirus. Although plasma has not yet shown a benefit in randomized trials, some small retrospective studies suggest it could reduce disease severity and shorten hospitalization times.
This week in mBio, an open-access journal of the American Society for Microbiology, researchers report that antibody levels in COVID-19 patients’ blood drop rapidly during the weeks after their bodies clear the virus and symptoms subside. If convalescent plasma is ultimately shown to have a clear benefit, the authors concluded, then it must be collected during a specific time window after recovery. However, convalescing patients cannot donate blood until at least 14 days after the symptoms disappear, to give the body time to clear the virus particles.
“We don’t want to transfuse the virus, we just want to transfuse the antibodies,” said Andres Finzi, Ph.D., from the University of Montreal, Canada. “But at the same time, our work shows that the plasma’s ability to neutralize viral particles is waning during those first few weeks.”
The spike protein of SARS-CoV-2 it plays a crucial role in helping the virus grab and invade host cells. Antibodies produced by the body’s immune system bind to part of this protein and block the ability of this “key” to interact with the host’s cellular “block”, Finzi said, preventing the viral particle from infecting a host cell. .
Previous studies suggest that antibodies to the SARS-CoV-2 peak protein peak 2 to 3 weeks after symptoms appear. Results from a previous cross-sectional study by Finzi’s group, involving more than 100 patients, suggested that plasma’s ability to neutralize the virus significantly decreased between 3 and 6 weeks after symptom onset.
In the new longitudinal study, Finzi and his colleagues analyzed blood samples collected at monthly intervals from 31 individuals recovering from COVID-19. They measured the levels of immunoglobulins that act against the coronavirus protein S and tested the antibodies’ ability to neutralize the virus.
The researchers observed variations at the individual patient level, but identified a consistent overall signal: levels of immunoglobulin G, A and M targeting the binding site decreased between 6 and 10 weeks after the onset of symptoms. Over the same period of time, the ability of antibodies to neutralize the virus also decreased.
Finzi’s team continued to study the patients’ blood samples. Understanding how antibody levels change over time, he said, is critical not only to optimizing the use of convalescent plasma, but also to understanding the vaccine’s effectiveness and whether previously infected people are at risk of reinfection.
“How long do antibodies protect you?” churches.
Finzi’s other research focuses on the immune response to the human immunodeficiency virus, or HIV, which differs greatly from SARS-CoV-2.
Reference: “Decline of Humoral Responses against SARS-CoV-2 Spike in Convalescent Individuals” by Guillaume Beaudoin-Bussières, Annemarie Laumaea, Sai Priya Anand, Jérémie Prévost, Romain Gasser, Guillaume Goyette, Halima Medjahed, Josée Perreault, Tony Tremblay, Antoine 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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