FIG 4.

Antibody responses induced by glycosylated mutant SARS-CoV-2 RBD protein. C57BL/6 and hACE2-Tg mice were immunized with the prototypic WT-RBD or MU-RBD protein, or with PBS control as described above, and collected for sera 10 days after the second and third immunizations. ELISA for detection of IgG antibodies specific to the SARS-CoV-2 WT-RBD (A, E, I, and M), Delta-RBD (B, F, J, and N), Omicron BA.1-RBD (C, G, K, and O), and Omicron BA.2-RBD (D, H, L, and P) from sera of C57BL/6 mice (A to H) and hACE2-Tg (I to P) mice after the second (A to D, I to L) and third (E to H, M to P) immunizations. Data are presented as mean ± SEM of quadruple wells from pooled sera of five mice in each group. The experiments were repeated twice, resulting in similar results.