Coronaviruses are a group of enveloped RNA viruses with a positive-sense single-stranded 24 RNA genome ranging from 26-32 kilobases, which can cause respiratory tract infections. In December 25 2019, a novel coronavirus known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) 26 was identified in China and has caused a global ongoing pandemic of coronavirus disease (COVID-27 19). To date, SARS-CoV-2 has spread to 188 countries (https://coronavirus.jhu.edu/). More than 29 28 million cases and 900,000 deaths have been reported at the time of this writing.
Enveloped viruses are known to efficiently package their core elements with heterologous 30 envelope glycoproteins, giving rise to the so called 'pseudotypes' or 'pseudoviruses ' 
Neutralization titers NT50 and NT80 were calculated using Prism 8 (GraphPad, US).
To generate pseudovirion particles, three plasmids were co-transfected into HEK293FT cells. The 
HIV-1 LAI gp160-pseudotyped virus is used as a negative control as it utilizes CD4 as a primary 89 receptor, which is present in SupT1 cells but absent in HEK293T.
Pseudotyped MLV viruses were tested on HEK293FT, HEK293T-ACE2, Huh7 and SupT1 cells.
HEK293FT cells were used as a control cell line, which is known to lack of susceptibility of 
To test for specificity of neutralization, we asked whether neutralizing antibodies from SARS-
CoV-2 patients would exhibit cross-reactivity against a pseudotype expressing SARS-CoV-1 ( Figure   112 4). We tested samples #1, 2 and 3, which had the highest NT50 and NT80. None of these sera had 