Figure 2.

Humoral Immune Responses in Nanoparticles Vaccinated BALB/c Mice

(A) Schematic of BALB/c vaccination. Six mice from each group were prime/boost-vaccinated with different vaccines at week 0 and week 4. Serum was collected every two weeks. All mice were euthanized at week 10.

(B–E) SARS-CoV-2 RBD- and HR-specific IgG titers of immunized BALB/c mice at each time point were detected by ELISA. IgG antibody titers of serum which collected at week 6 were determined by serial dilution, and represented as the reciprocal of the endpoint serum dilution

(B and C) (n = 6). RBD and HR-specific IgG titers in each week were calculated and plotted as time-course curve (D and E).

(F) FRNT50 of nAbs of each vaccine group was determined by FRNT and represented as half-maximal inhibitory concentrations (IC50), which was the reciprocal of half-maximal neutralizing dilution (n = 3). The right panel of (F) showed the representatives of FRNTspot wells within 1:100 and 1:1000 dilution groups.

(G) FRNTspots of serum of each time point in 1:100 and 1:1000 dilutions.

(H and I) The percentages of RBD-specific IgG1⁺ and IgG2b⁺ MBCs (CD19⁺B220⁺CD38⁺) within spleen of each vaccine group (n = 4). Experiments were conducted independently in triplicates. Data represented as mean ± SEM. Adjusted p values were calculated by one-way ANOVA with Tukey’s multiple comparisons test. ^∗p < 0.05, ^∗∗p < 0.01, ^∗∗∗p < 0.001, ^∗∗∗∗p < 0.0001.

See also Figures S2 and S3.