Figure 4
The 5G2 mAb binds to the WT and SARS-CoV-2 variants. (a) Binding of 5G2 mAb to SARS-CoV-2 spike proteins was detected by western blot. CBB, CBB stain (left). In the western blot (right), 0.2 μg/mL of 5G2 mAb was used and it was detected by anti-mIgG-HRP. “(-)” represents the uninfected Vero cell lysate. “WT” represents the Vero cells infected with Wuhan SARS-CoV-2. Recombinant “S1 + S2”, “S1” and “S2” stand for the recombinant spike proteins of “S1 + S2”, “S1” and “S2”, respectively. S1 + S2 and S2 proteins are indicated by the solid and open arrows, respectively. Commercially obtained recombinant S1 + S2 and S2 proteins, which lacks the cytoplasmic domain, were expressed by the Baculovirous-Insect Cell system and could be less glycosylated to show smaller molecular sizes compared to those expressed in the Vero cells. The recombinant S1 proteins produced by HEK293 cells shows larger molecular size due to the high glycosylation. (b) Immunofluorescence staining of spike proteins on the SARS-CoV-2 infected cell surface as detected by 5G2 mAb (green). Blue: DAPI was used for nuclear staining. Mock: Vero cells without SARS-CoV-2 infection, CoV-2: Vero cells infected with SARS-CoV-2. The leftmost panels show the phase contrast images. Scale bar: 10 μm. (c) ELISA for 5G2 mAb reactivity to 1 × 105 of SASR-CoV-2 WT and its variants (α, β, γ, and ο of BQ1.1, and BA.5). PBS: no virus coating. The data represent mean ± standard error (SE). The statistical significance was determined by one-way analysis of variance (one-way ANOVA). *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.
