Figure 3. Humoral responses induced in mice by immunization with chimeric RHDV-FCV VLPs.

Sera samples from groups of mice inoculated twice with the indicated VLPs were analyzed by ELISA (a,b), or a plaque-reduction neutralization assay specific for FCV virus (c). Serum IgG antibody titers were measured by ELISA using RHDV VLPs to detect anti-VP60 antibodies (a), or a synthetic peptide encompassing FCV B-cell epitope sequence, to detect anti-FCV antibodies (b). The GMT was calculated for each group of mice. Error bars show the standard error of the mean. The groups corresponding to chimeric VLPs harbouring one copy of the inserted epitope per VP60 monomer (N1FCV, L1FCV and C1FCV) are shown as hatched bars. In (a), statistically significant differences in anti-VP60 antibody titers, with respect to those corresponding to the VP60 group are shown as *p < 0.05, **p < 0.01, ***p < 0.001. In (b), statistically significant differences in anti-FCV antibody titters between groups N1FCV, L1FCV and C1FCV (hatched bars) are shown as *; differences between groups harbouring the inserted epitope at the N-terminus are shown as Δ; differences between groups harbouring the inserted epitope at loop L1 are shown as ◻; and differences with respect to the antibody titters corresponding to the FCV VP62 group are shown as ⦁.