Figure 4.

Comparison of antibody neutralization titers obtained by PRNT and VLP-EV fusion assays

PRNT assay: Infectious SARS-CoV-2 viruses were incubated with COVID-19 convalescent patient sera in half-log dilutions at 37°C for 30 min, inoculated onto Vero cells, and plaques enumerated two days later. The sera dilution factors generating 50% reduction of enumerated plaques were stated as Plaque Reduction Neutralization Titer (PRNT) values. VLP-EV fusion assay: SARS-2 VLPs were incubated with COVID-19 convalescent patient sera in half-log dilutions at 37°C for 30 min. After incubation, a mix of ACE2-containing EVs, substrate, and trypsin (50 ng/μL) were added to each well. The reactions were incubated on ice for 30 min. The reactions were then brought to 37°C and readings were recorded with a luminometer. IC50 values were calculated in GraphPad prism using the 60 min timepoint values.