Figure legend
Figure 1 . Growth enhancement of SARS-CoV-2 wild type and
Omicron BA.2 variant by an ACE2-blocking monoclonal antibody. Vero E6
cells were seeded in 24-well cell culture plates at a density of 2 x
105 cells per well and were infected with SARS-CoV-2
wild type and Omicron BA.2 variant at 0.001 multiplicity of infection.
After removing virus and washing with 1xPBS three times, the
virus-infected cells were incubated with 1 mL of DMEM containing 2.5%
fetal bovine serum (FBS) and varying amounts (indicated on the top of A)
of the ACE2-blocking antibody. At 48 hours post-infection, the
virus-infected cells were lysed in 100 μl RIPR buffer, which were used
for quantification of NP protein by a Western blot analysis
(A ). The supernatants were used for titration of infectious
virus (B ) by a plaque assay same as that in Fig.2. The
infectious virus titers are average of triplicates.
Figure. 2 . Anti-ACE2 antibody-induced promotion of plaque
formation of SARS-CoV-2 wild type and different variants. Wild type
SARS-CoV-2 was previously described (11). SARS-CoV-2 alpha variant
(NR-55461), delta variant (NR-55611), Omicron variants BA.1 (NR-56475),
BA.2 (NR-56520), BA.4 (NR-56803), BA.5 (NR-58616), and BF.5 (NR-58716)
were obtained from Bei Resources and were grown in Calu-3 cells. Vero E6
(NR-54970) was seeded to 6-well cell culture plates at a density of 5 x
105 cells per well and were infected with 200 μL of
virus diluted serially with 1x PBS containing 1% FBS. Virus dilution
factors are indicated beneath each 6-well plate. After 1-hour incubation
at 37oC, virus-infected cells were cultured in 2 mL
agarose overlay (equal volume of 2 x DMEM, DMEM containing 10% FBS, and
1.5% agarose) with (Anti-ACE2) or without (Control) 0.2 μg/mL of
anti-ACE2 monoclonal antibody. After 48 hours, cells were fixed with 2
mL/well of 7.5% paraformaldehyde for 30 minutes, followed by staining
with 0.1% crystal violet solution containing 1% paraformaldehyde.