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Authors: Chi et al. Link to paper: https://www.biorxiv.org/content/10.1101/2020.04.14.042010v1

Journal/ Pre-Print: bioRxiv

Key Words: Single Domain Antibodies, Spike Receptor Binding Domain, Nanobodies, Neutralizing Antibodies

Research Highlights 

1. Isolated and characterised neutralising single domain antibodies (sdAbs) against SARS-CoV-2 using both pseudotyped and infectious viruses.

Summary 

This study describes the isolation and characterisation of neutralising sdAbs, or nanobodies, targeting the SARS-CoV-2 spike receptor binding domain (RBD), generated using a synthetic humanised sdAb phage display library. Selected clones could bind to spike protein (KD 0.7 – 34 nM, as measured by SPR) and inhibit viral infection in vitro (IC50 0.2-0.5 µg/mL). Furthermore, in a competitive assay with ACE2 some clones could completely prevent RBD binding. Fusion of IgG1 Fc region to the C-terminus of selected nanobodies further improved their neutralization capacity from 10- to almost 100-fold in some cases.

Impact for SARS-CoV2/COVID19 research efforts

· Treatment of SARS-CoV2/COVID19 positive individuals

Study Type

· In vitro study

Strengths and limitations of the paper

Novelty: They created a novel panel of sdAbs targeting the SARS-CoV-2 spike RBD.

Standing in the field: Other groups have also suggested the use of sdAbs as antibody-based drugs directed against COVID-19, and released similar work - https://www.biorxiv.org/content/10.1101/2020.03.26.010165v1.full.pdf ; https://www.biorxiv.org/content/10.1101/2020.03.30.015990v1.full.pdf ; https://www.biorxiv.org/content/10.1101/2020.04.16.045419v1.

To date, one nanobody has been FDA approved for human use – caplacizumab in 2019 for the treatment of thrombotic thrombocytopenic purpura and thrombosisin.

Appropriate statistics: Lacking information – e.g. only one representative result selected from independent experiments, no information on technical replicates.

Viral model used: SARS-CoV-2, SARS-CoV-2 S-pseudotyped particle, SARS-CoV.

Translatability: There is potential, but further in vitro and in vivo studies are required.

Main limitations: No in vivo studies and would requires more in vitro work. SARS-CoV-2 virus neutralization activity was only tested in Vero cell line (African green monkey kidney cell line), and both SPR data quality and the purity of RBD protein used for antibody selection by phage display could also be improved.