COVID-19 antibodies decline in three months
02/10/2020
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COVID-19 antibodies start to disappear after three months of the onset of symptoms, which means collecting plasma should be done as early as possible, a new Canadian study has claimed.
The findings could have implications for vaccine design and for prevalence studies in communities trying to gauge how many people have recovered from the virus, say the authors.
The small study, published in Blood, drew from 282 COVID-19 plasma donors in Quebec, and followed 11 men and four women who had been diagnosed with and subsequently recovered from the virus. None had been hospitalised.
They each donated their plasma between four and nine times, with the first donation occurring between 33 and 77 days after symptom onset and the last donation between 66 and 114 days.
All 15 donors showed decreases in antibodies at the same time, about 88 days, and half of the detectable antibodies decreased within 21 days afterward.
Study author Dr Renée Bazin, of the Héma-Québec blood centre, said it was one of the first longitudinal analyses to show that people who were seropositive become seronegative.
“The antibodies disappear rapidly, so people recovering from COVID-19 who want to donate blood plasma should not wait too long once they become eligible to donate,” she said.
The researchers focused on antibodies to the receptor binding domain (RBD), which binds to the ACE-2 receptor on the surface of cell and allows virus to enter and infect the cell.
The immune system can develop RBD antibodies that inhibit the protein's ability to fit into and open the door through the ACE-2 receptor, thereby preventing the virus from entering the cells.
Dr Bazin said: “Based on our findings, clinicians should ideally use plasma that is collected early on after a donor's onset of symptoms and check for the presence of antibodies before giving donor plasma to a patient.”
She added that nearly 7% of the original 282 donors did not have detectable antibodies at their first donation and this proportion doubled when considering donors who waited more than 11 to 12 weeks after symptom onset before donating.
• The UK convalescent plasma programme treated 220 people in September, it has been announced. In total 916 patients have received plasma as part of the project.
The project is a trial, but NHS Blood and Transplant reported cases of successful treatment.
It is seeking to recruit donors 21 days after they recover from infection – and yesterday repeated its appeal for donors, especially men, who tend to have higher antibody levels.
Blood 1 October 2020
https://ashpublications.org/blood/article-abstract/doi/10.1182/blood.2020008367/463996/Waning-of-SARS-CoV-2-RBD-antibodies-in
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