3.3 Murine specific anti-FMDV Abs and neutralizing Abs are increased when ISPA is used as adjuvant
Antibody responses elicited by VLPs, VLPs-ISPA, VLPs-CA, Commercial vaccine, CA, ISPA and PBS were evaluated at 15, 21 and 36 dpv. Total specific anti-FMDV Ab titers measured by sandwich ELISA were significantly higher in the VLPs-ISPA and VLPs-CA groups as compared to the VLPs group (p<0.01) (Figure 3A). Importantly, when the virus neutralization test (VNT) was applied (Table 1), neutralizing antibody titers at 36 dpv were significantly higher in groups vaccinated with VLPs-ISPA, VLPs-CA and Commercial vaccine, than in the VLPs group (p<0.05, p<0.05 and p<0.001 respectively). VNT in the VLPs-CA and Commercial vaccine groups were similar. No neutralizing Abs were detected in the CA, ISPA and PBS groups.
Analysis of isotype profiles at 36 dpv showed that the VLPs-ISPA group achieved higher IgG1 titers than all other groups (p<0.001). Moreover, IgG1 titers in the VLPs-CA and Commercial vaccine groups were similar (Figure 3B). IgG2a titers were also higher in: VLPs-ISPA, VLPs-CA and Commercial vaccine groups than in the VLPs group (p<0.001). Finally, IgG3 titers in the VLPs-ISPA group were significantly higher than IgG3 titers in the VLPs and VLPs-CA groups (p<0.001 and p<0.01 respectively) and similar to the titers elicited by the Commercial vaccine. Moreover, the IgG3 titer in VLPs-CA group was significantly higher than in the VLPs group.