Citation
- Authors: Sokal A. et al.
- Year: 2022
- Journal: Immunity 55 1096-1104
- Applications: in vitro / DNA / FectoPRO
- Cell type: Expi293F
Description: Human embryonic kidney Fibroblast
Known as: Expi 293-F, Expi, HEK-293 Expi
Method
The plasmids coding for recombinant proteins were transiently transfected in Expi293F™ cells (Thermo Fischer) using FectoPRO® DNA transfection reagent (Polyplus), according to the manufacturer’s instructions. The cells were incubated at 37 °C for 5 days and then the culture was centrifuged and the supernatant was concentrated. The proteins were purified from the supernatant by affinity chromatography using His-Trap™ Excel columns (Cytiva) (SARS-CoV-2 RBD). A final step of size-exclusion chromatography (SEC) in PBS was also performed, using a Superdex200 10/300 (Cytiva) for the SARS-CoV-2 RBD.
Abstract
The SARS-CoV-2 Omicron variant can escape neutralization by vaccine-elicited and convalescent antibodies. Memory B cells (MBCs) represent another layer of protection against SARS-CoV-2, as they persist after infection and vaccination and improve their affinity. Whether MBCs elicited by mRNA vaccines can recognize the Omicron variant remains unclear. We assessed the affinity and neutralization potency against the Omicron variant of several hundred naturally expressed MBC-derived monoclonal IgG antibodies from vaccinated COVID-19-recovered and -naive individuals. Compared with other variants of concern, Omicron evaded recognition by a larger proportion of MBC-derived antibodies, with only 30% retaining high affinity against the Omicron RBD, and the reduction in neutralization potency was even more pronounced. Nonetheless, neutralizing MBC clones could be found in all the analyzed individuals. Therefore, despite the strong immune escape potential of the Omicron variant, these results suggest that the MBC repertoire generated by mRNA vaccines still provides some protection against the Omicron variant in vaccinated individuals.