A group of Canadian researchers, led by Andrés Finzi from the Université de Montréal, investigated the duration of antibodies against SARS-CoV-2 in people who were recovering from COVID-19. This has important implications for the use of plasma as a potential treatment for COVID-19.

In this study, blood samples were collected from 31 patients at different time points, in order to assess the capacity of their antibodies to eliminate SARS-CoV-2. Different types of antibodies were measured to determine for how long they could be detected as well as how they reacted to different variants of the virus.

The researchers found that between 6 to 10 weeks after the start of symptoms, there was a drop in the proportion of people who had antibodies that were able to prevent entry of SARS-CoV-2 in human cells in a pseudo-neutralization assay. Moreover, they found that a certain type of antibody, IgM, that recognizes the region on the virus responsible for binding to the human cellular receptor (called the receptor binding domain), declined faster than other types and was closely associated with the capacity to neutralize SARS-Co-V2.

They stipulated that if plasma from recovering patients depends on the capacity of antibodies to eliminate SARS-Co-V2 to be an effective therapy, it should be taken before this decline in IgM, within the short window of time they described.


Beaudoin-Bussières G, Laumaea A, Anand SP, Prévost J, Gasser R, Goyette G, Medjahed H, Perreault J, Tremblay T, Lewin A, Gokool L, Morrisseau C , Bégin P, Tremblay C, Martel-Laferrière V, Kaufmann D, Richard J, Bazin R, Finzi A. Decline of humoral responses against SARS-CoV-2 spike in convalescent individuals. MBio. 2020 Oct 27;11(5). doi: 10.1128/mBio.02590-20.


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