Journal
VIRUSES-BASEL
Volume 14, Issue 3, Pages -Publisher
MDPI
DOI: 10.3390/v14030532
Keywords
COVID-19; SARS-CoV-2; convalescent plasma; antibodies; avidity; receptor-binding domain
Categories
Funding
- Ministere de l'Economie et de l'Innovation du Quebec, Programme de soutien aux organismes de recherche et d'innovation
- Fondation du CHUM
- CIHR foundation [352417]
- CIHR operating Pandemic and Health Emergencies Research grant [177958]
- CIHR
- Canada Foundation for Innovation (CFI) [41027]
- CIHR PhD fellowship
- Canada Research Chair on Retroviral Entry [RCHS0235 950-232424]
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SARS-CoV-2 infection leads to a gradual decline in antibody levels, but an increase in antibody avidity, which is correlated with B cell class switch. Similar increase in antibody avidity is observed after SARS-CoV-2 mRNA vaccination. Avidity determination of anti-RBD IgG could serve as a surrogate assay for antibody affinity maturation in studying humoral responses elicited by natural infection and/or vaccination.
SARS-CoV-2 infection rapidly elicits anti-Spike antibodies whose quantity in plasma gradually declines upon resolution of symptoms. This decline is part of the evolution of an immune response leading to B cell differentiation into short-lived antibody-secreting cells or resting memory B cells. At the same time, the ongoing class switch and antibody maturation processes occurring in germinal centers lead to the selection of B cell clones secreting antibodies with higher affinity for their cognate antigen, thereby improving their functional activity. To determine whether the decline in SARS-CoV-2 antibodies is paralleled with an increase in avidity of the anti-viral antibodies produced, we developed a simple assay to measure the avidity of anti-receptor binding domain (RBD) IgG elicited by SARS-CoV-2 infection. We longitudinally followed a cohort of 29 convalescent donors with blood samples collected between 6- and 32-weeks post-symptoms onset. We observed that, while the level of antibodies declines over time, the anti-RBD avidity progressively increases and correlates with the B cell class switch. Additionally, we observed that anti-RBD avidity increased similarly after SARS-CoV-2 mRNA vaccination and after SARS-CoV-2 infection. Our results suggest that anti-RBD IgG avidity determination could be a surrogate assay for antibody affinity maturation and, thus, suitable for studying humoral responses elicited by natural infection and/or vaccination.
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