Fig. 4. Neutralizing antibody titers are higher in mice immunized with immunogens than WT RBD.
(A) Immunization and blood draw schedule for CD-1 mice. (B) Serum ELISA titers against trimeric FL-spike ectodomain. Dashed line indicates detection limit of assay, bars represent GMT, and error bars indicate geometric SD. (C) Titers of antibodies blocking Ace2/RBD interaction depicted as described in (B). (D) Pseudovirus neutralization titers depicted as described in (B). Statistical comparisons were made using a Kruskal-Wallis analysis of variance (ANOVA) followed by Dunn’s test corrected for multiple comparisons of immunogens and FL-spike with WT RBD. (E) Neutralization of WA-1 SARS-CoV-2 in a plaque assay. ID50 values are indicated in parentheses. Serum from each animal in a group was pooled, except for the animal with the lowest pseudovirus neutralization titers in the FL-group, which had insufficient volume. (F) Antibody quality measured by ratio of pseudovirus neutralization titers (D) and FL-spike ELISA titers (B), depicted as described in (B). Statistical test is identical to (D).