COVID-19 antibodies in patients’ blood fade quickly after symptoms disappear, study shows – leaving about two weeks for plasma transfusions
- Immune systems make antibodies that keep SARS-CoV-2 from attacking cells
- Preliminary studies suggest these can be used to treat severe cases
- Experts from Canada studied antibody levels in recovering COVID-19 patients
- They found that these defenses decreased significantly 6 to 10 weeks after the first symptoms
- Patients cannot donate blood plasma until two weeks after their symptoms to fade
Antibodies produced by the body to fight COVID-19 – the transfusion of which is being tried as a treatment for other, more severe patients – quickly fade after recovery.
Experts from Canada studied the blood of recovering coronavirus patients and found that the size of the immune defenses diminishes 6 to 10 weeks after their first symptoms.
Plasma transfusions have not yet been proven as a treatment in randomized trials, but small retrospective studies have hinted that they may reduce the severity of the disease.
If so-called “ restorative plasma ” is proven to be beneficial, it means there is only a short period of time to donate it, the researchers warned.
Donors have to wait two weeks after the symptoms clear before they can give blood – to make sure the viral particles are gone – and the symptoms usually last two weeks before that.
Given this, the time frame for plasma donation could be as little as fourteen days.
Antibodies produced by the body to fight COVID-19 – the transfusion of which is being tried as a treatment for other, more severe patients – quickly fade after recovery. The photo shows a recovering coronavirus patient who donated blood plasma for transfusion to a patient with a severe case
“We don’t want to transfuse the virus, just transfuse the antibodies,” said author and virologist Andrés Finzi of the University of Montreal, Canada.
“But at the same time, our work shows that the plasma’s ability to neutralize viral particles decreases during those first weeks.”
The key to how SARS-CoV-2 attacks the body are the so-called spike proteins that cover the shell of the virus – allowing cells to hold onto and enter them.
However, antibodies made by the immune system bind to the tip of the spike proteins, preventing them from sticking to cells and rendering the virus ineffective.
Previous studies have suggested that antibodies targeting the peak coronavirus protein peak in the blood around 2 to 3 weeks after the onset of symptoms – and that the effectiveness of these defenses may fade about 4 to 6 weeks after that.
In their new study, Dr. Finzi and colleagues followed 31 recovering COVID-19 patients, analyzing blood samples from each individual at monthly intervals.
For each sample, the researchers measured the levels of the antibodies – or ‘immunoglobulins’ – that work against the coronavirus spike protein, in addition to testing the ability of these antibodies to neutralize the virus.
The key to how SARS-CoV-2 attacks the body are the so-called spike proteins that cover the shell of the virus (see photo) – and allow it to attach to and enter cells. However, antibodies made by the immune system bind to the tip of the spike proteins, preventing them from sticking to cells and rendering the virus ineffective.
Although the team observed variations between the patients, they found that in all cases, levels of three major immunoglobulins that target the binding site on the virus’s spike protein dropped between 6 and 10 weeks after symptoms started.
As levels of these antibodies decreased, so did their ability to neutralize the virus – and, by extension, their potential utility within a plasma transfusion.
The full findings of the study are published in the journal mBio.