Single-Cell Sequencing of Plasma Cells from COVID-19 Patients Reveals Highly Expanded Clonal Lineages Produce Specific and Neutralizing Antibodies to SARS-CoV-2

Isolation and characterization of antibodies in COVID-19 patients has largely focused on memory B cells, however it is the antibody-secreting plasma cells that are directly responsible for the production of serum antibodies, which play a critical role in controlling and resolving SARS-CoV-2 infection. To date there is little known about the specificity of plasma cells in COVID-19 patients. This is largely because plasma cells lack surface antibody expression, which complicates their screening. Here, we describe a technology pipeline that integrates single-cell antibody repertoire sequencing and high-throughput mammalian display screening to interrogate the specificity of plasma cells from 16 convalescent COVID-19 patients. Single-cell sequencing allows us to profile antibody repertoire features in these patients and identify highly expanded clonal lineages. Mammalian display screening is employed to reveal that 37 antibodies (out of 132 candidates) derived from expanded plasma cell clonal lineages are specific for SARS-CoV-2 antigens, including antibodies that target the receptor binding domain (RBD) with high affinity and exhibit potent neutralization of SARS-CoV-2. Funding: This work was supported by the European Research Grant CoroNAb (to S.T.R. and B.M.), Personalized Health and Related Technologies (to S.T.R. and R.V-L.), Botnar Research Centre for Child Health (to S.T.R.). Conflict of Interest: The authors have no competing interests to declare. Ethical Approval: Ethics permission was granted by the ethics board “Ethikkommission Nordwest- und. Zentralschweiz (EKNZ)”. Every participant has signed a written informed consent as described previously (Kaltenbach et al., 2020).