Antibodies made by the body to fight COVID-19 — the transfusion of which is being trialled as a treatment for other, more severe patients — fade rapidly after recovery.
Experts from Canada studied the blood of recovering coronavirus patients, finding that the extent of the immune defences drop 6–10 weeks after their first symptoms.
Plasma transfusions have not been proven as a treatment yet in randomised trials, but small retrospective studies have hinted that they may reduce illness severity.
If so-called ‘convalescent plasma’ is proven to be beneficial, this means that there is only a short window of opportunity for it to be donated, the researchers warned.
Donors must wait two weeks after symptoms subside before giving blood — to ensure viral particles are gone — and symptoms typically last two weeks before that.
Given this, the time frame for plasma donation could be as short as just a fortnight.
Antibodies made by the body to fight COVID-19 — the transfusion of which is being trialled as a treatment for other, more severe patients — fade rapidly after recovery. Pictured, a recovering coronavirus patient donated blood plasma for transfusion into a patient with a severe case
‘We don’t want to transfuse the virus, just transfuse the antibodies,’ said paper author and virologist Andrés Finzi of the University of Montreal, Canada.
‘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.’
Key to the way in which SARS-CoV-2 attacks the body is the so-called spike proteins that cover the virus’ shell — and allow it to latch onto cells and invade them.
Antibodies made by the immune system, however, bind to the end of the spike proteins, preventing them from sticking to cells and rendering the virus ineffective.
Previous studies have suggested that antibodies that target the coronavirus spike protein peak in the blood at around 2–3 weeks after the onset of symptoms — and that the effectiveness of this defence may fade some 4–6 weeks after the same.
In their new study, Dr Finzi and colleagues monitored 31 recovering COVID-19 patients — analysing blood samples taken from each individual at monthly intervals.
For each sample, the researchers measured the levels of the antibodies — or ‘immunoglobulins’ — that act against the coronavirus spike protein, alongside testing the ability of these antibodies to neutralize the virus.
Key to the way in which SARS-CoV-2 attacks the body is the so-called spike proteins that cover the virus’ shell (pictured) — and allow it to latch onto cells and invade them. Antibodies made by the immune system, however, bind to the end of the spike proteins, preventing them from sticking to cells and rendering the virus ineffective
While the team observed variations among the patients, they found that in all cases the levels of three key immunoglobulins that target the binding site on the virus’ spike protein fell between 6–10 weeks after symptoms began.
As the levels of these antibodies fell, so did their capacity to neutralize the virus — and, by extension, their potential usefulness within a plasma transfusion.
The full findings of the study were published in the journal mBio.
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