Antibodies-COVID-19: Unbiased University Of Montreal Study Shows That Antibody Levels Drop Rapidly In Recovering COVID-19 Patients
: A new unbiased study by researchers from the University of Montreal has shown that antibody levels drop rapidly in recovering COVID-19 patients.
The study team performed repeated analyses at 1-month intervals on 31 convalescent individuals to evaluate how the humoral responses against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Spike glycoprotein, including neutralization, evolve over time.
The team observed that the levels of receptor-binding-domain (RBD)-specific IgG and IgA slightly decreased between 6 and 10 weeks after the onset of symptoms but that RBD-specific IgM levels decreased much more abruptly
They also observed a significant decrease in the capacity of convalescent plasma to neutralize pseudoparticles bearing wild-type SARS-CoV-2 S or its D614G variant.
If neutralization activity proves to be an important factor in the clinical efficacy of convalescent plasma transfer, the study results suggest that plasma from convalescent donors should be recovered rapidly after resolution of symptoms.
The study findings were published in the peer reviewed journal: mBio
, an open-access journal of the American Society for Microbiology. https://mbio.asm.org/content/11/5/e02590-20
Presently In the absence of any approved, effective treatments for COVID-19, some doctors and hospitals have been treating patients with severe COVID symptoms with blood plasma from recovering patients.
Although plasma hasn't yet shown a benefit in randomized trials, some small retrospective studies suggest it may reduce illness severity and reduce hospitalization time.
The Canadian study team report that antibody levels in the blood of COVID-19 patients drop rapidly during the weeks after their bodies have cleared the virus and symptoms have subsided.
Should convalescent plasma ultimately show to have a clear benefit, the study team concluded, then it needs to be collected during a specific window of time after recovery. However, recovering patients can't donate blood until at least 14 days after symptoms have subsided, to give the body time to clear viral particles
Co-researcher Dr Andrés Finzi, Ph.D from University of Montrealtodl Thaialdn Medical News, “We do not 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
It is already known that the spike protein of SARS-CoV-2 plays a crucial role in helping the virus grab and invade host cells. Antibodies produced by the body's immune system bind to a part of this protein and block the capacity of this "key" to engage with the host's cellular "lock", said Dr Finzi, preventing the viral particle from infecting a cell host.
Past studies suggest that antibodies against the SARS-CoV-2 spike protein peak 2 or 3 weeks after the onset of symptoms.
Study findings from an earlier cross-sectional research by Dr Finzi's group, involving more than 100 patients, suggested that the ability of plasma to neutralize the virus decreased significantly between 3 and 6 weeks after symptom onset.
For this new longitudinal study, Dr Finzi and his colleagues analyzed blood samples collected at one-month intervals from 31 individuals recovering from COVID-19. They measured levels of immunoglobulins that act against the coronavirus S protein and tested the ability of the antibodies to neutralize the virus.
The study team observed variation on the level of individual patients but identified a consistent overall signal, the levels of Immunoglobulins G, A, and M that target the binding site decreased between 6 and 10 weeks after symptoms began. During the same time period, the ability of the antibodies to neutralize the virus similarly fell.
Dr Finzi's group has continued to study blood samples from the patients. Understanding how the levels of antibodies change over time, he said, is critical not only for optimizing the use of convalescent plasma but also for understanding vaccine efficacy and whether or not previously infected people are at risk of re-infection.
Significantly he asked, "How long do SARS-CoV-2 antibodies protect you?"
Dr Finzi's other research focuses on the immune response to human immunodeficiency virus, or HIV, which differs dramatically from SARS-CoV-2.
In summary, the study team said, “Our results indicate that plasma neutralization activity continues decreasing past the sixth week of symptom onset. It is currently unknown whether neutralizing activity truly drives the efficacy of convalescent plasma in acute COVID-19. If this were to be found to be the case, our results suggest that efforts should be made to ensure that convalescent plasma is collected as soon as possible after recovery of the donor from active infection.”
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