Fig. 7: CoVac501 induced humoral immune responses against SARS-CoV-2 variants.

a Positioning of K417N, N439K, L452R, Y453F, S477N, E484K, E484Q, F490S, S494P, and N501Y in RBD. b, c Cynomolgus monkeys (n = 2) were immunized with saline or CoVac501 for three doses at days 0, 14, and 28. Sera were collected from the monkeys 35 days after the first dose of vaccine and the levels of RBD single mutations (b) and combined mutations (c) binding antibodies were tested for different serum dilutions using ELISA. d, e The neutralization of sera from cynomolgus monkeys 63 days after the first dose of vaccine for SARS-CoV-2 original strain and variants (Alpha, Beta, and Delta) by the pseudovirus test. ID₅₀ reciprocal titers were compared to the saline group (d) or between variants (e). f The graph shows the amino acid sequences of mutation peptides. g Cynomolgus monkeys (n = 2) were immunized with saline or mutation peptides for two doses at days 0 and 14. Sera were collected from the monkeys 21 days after the first dose of vaccine and the levels of RBD mutations (E484K and N501Y) binding antibodies were tested for different serum dilutions using ELISA. h, i The neutralization of sera from cynomolgus monkeys 21 days after the first dose of mutation peptides for SARS-CoV-2 original strain and variants (Alpha, Beta, and Delta) by the pseudovirus test. ID₅₀ reciprocal titers were compared to the saline group (h) or to the CoVac501 group for Beta pseudovirus (i). **P < 0.01; *P < 0.05; ns, not significant as determined by unpaired t-test. All data are presented as the means ± SEM.