Discovery of Neutralizing Sars-cov-2 Antibodies Enriched in a Unique Antigen Specific B Cell Cluster

Stine Sofie Frank Lende, Nanna Møller Barnkob, Randi Westh Hansen, Harsh Bansia, Mike Vestergaard, Frederik Holm Rothemejer, Anne Worsaae, Deijona Brown, Maria Lange Pedersen, Anna Halling Folkmar Rahimic, Anna Karina Juhl, Torben Gjetting, Lars Østergaard, Amédée Des Georges, Laurent-Michel Vuillard, Mariane Høgsbjerg Schleimann, Klaus Koefoed, Martin Tolstrup


Despite development of effective SARS-CoV-2 vaccines, a sub-group of vaccine non-responders depends on therapeutic antibodies or small-molecule drugs in cases of severe disease. However, perpetual viral evolution has required continuous efficacy monitoring as well as exploration of new therapeutic antibodies, to circumvent resistance mutations arising in the viral population. We performed SARS-CoV-2-specific B cell sorting and subsequent single-cell sequencing on material from 15 SARS-CoV-2 convalescent participants. Through screening of 455 monoclonal antibodies for SARS-CoV-2 variant binding and virus neutralization, we identified a cluster of activated B cells highly enriched for SARS-CoV-2 neutralizing antibodies.


Throughout the SARS-CoV-2 pandemic, immense efforts have resulted in the rapid development and administration of vaccinations successfully reducing COVID-19 mortality [1]. However, several studies show the presence of a small group of primarily immunocompromised patients displaying vaccine non -or hypo-responses [2–7].These individuals, already at increased risk of severe disease from SARS-CoV-2, are consequently additionally vulnerable in the event of SARS-CoV-2 exposure and infection [8, 9]. This underlines the need for availability of effective treatment options and potential alternative prophylaxis.

Materials and method

A cohort of 203 SARS-CoV-2 convalescent individuals were included at the Department of Infectious Diseases at Aarhus University Hospital in spring 2020, and have been previously described by Vibholm et al [22] and Nielsen et al. [17]. Participant selection was based on the three following principles, with five patients selected from each: Group 1 had the highest plasma neutralization NT50 values, which was highly correlated to plasma levels of SARS-CoV-2 specific antibodies, assuming high levels of SARS-CoV-2 specific B cells would be present in these individuals.


To obtain cell material for B cell receptor characterization and mAb cloning, a cohort of 194 SARS-CoV-2 recovered participants infected during the spring of 2020 was considered, for which the clinical and immunological characteristics have been previously described [17, 22]. From this data, PBMC’s from 15 participants with high plasma neutralization capacity were selected for B cell isolation and antibody discovery (Fig 1). An overview of the 15 participants’ demographics and clinical characteristics is listed in Table 1. Of the included participants, 40% were female, with a group median age of 52 years (range 31–67). Participants experienced COVID-19 symptoms for a median of 16 days (range 0–47), and more than half (53.3%) of the selected group had been hospitalized during their disease course.


We aimed to isolate SARS-CoV-2 neutralizing mAbs from 15 COVID-19 convalescent participants, utilizing LIBRA-seq and single cell mRNA sequencing. 455 mAbs were selected from the participant’s B cell population, for SARS-CoV-2 binding and neutralization screening. Overall, we found that while all mAbs were expressed and screened in IgG1 format, neutralizing mAbs that were originally expressed by the B cells as IgA1 (13 mAbs), IgA2 (2 mAbs) and IgG1 (18 mAbs) exhibited neutralizing activity. This indicated that the reformatting did not disrupt binding in all cases, although it cannot be ruled out that some IgA mAbs lost binding capacity.


We would like to thank all the individuals in the study for the kind donation of both their time and biological material.

Citation: Lende SSF, Barnkob NM, Hansen RW, Bansia H, Vestergaard M, Rothemejer FH, et al. (2023) Discovery of neutralizing SARS-CoV-2 antibodies enriched in a unique antigen specific B cell cluster. PLoS ONE 18(9): e0291131.

Editor: Nagarajan Raju, Emory University, UNITED STATES

Received: May 3, 2023; Accepted: August 22, 2023; Published: September 20, 2023

Copyright: © 2023 Lende et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the paper and its Supporting Information files.

Funding: This study was supported by a grant from the Danish Ministry for Research and Education (grant# 0238-00001B to MT) and The Danish Innovation Fund (grant# 0208-00018B to MT and KK). SSFL was supported by a scholarship from Aarhus University. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

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