Quantification of SARS-CoV-2 neutralizing antibody by a pseudotyped virus-based assay

Pseudotyped viruses are useful virological tools because of their safety and versatility. On the basis of a vesicular stomatitis virus (VSV) pseudotyped virus production system, we developed a pseudotyped virus-based neutralization assay against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in biosafety level 2 facilities. Compared with the binding antibody test, the neutralization assay could discriminate the protective agents from the antibody family. This protocol includes production and titration of the SARS-CoV-2 S pseudotyped virus and the neutralization assay based on it. Various types of samples targeting virus attachment and entry could be evaluated for their potency, including serum samples derived from animals and humans, monoclonal antibodies and fusion inhibitors (peptides or small molecules). If the pseudotyped virus stock has been prepared in advance, it will take 2 days to get the potency data for the candidate samples. Experience in handling cells is needed before implementing this protocol. The production and titration of the SARS-CoV-2 S pseudotyped virus using a VSV-based pseudovirus production system in this protocol enable its use under biosafety level 2 conditions as well as in a neutralization assay to assess the level of neutralizing antibodies or molecular inhibitors in a sample.