Fig. 3.

Antibody titers in mice immunized with PRRSV VLPs. Mice in four groups were immunized with 0.5, 1.0, 2.0, and 4.0 μg of the VLPs. Mice in two groups were immunized with a commercial inactivated PRRSV vaccine and PBS as positive and negative controls, respectively. All mice were vaccinated three times at 2-week intervals. Blood samples were obtained from mice before the first, second, and third vaccinations and 2 weeks after the third vaccination (0, 2, 4, and 6 weeks as shown in the insert). Total IgG titers were determined by ELISA using GP5 as an antigen. The antibody titers in serum samples collected at 4 and 6 weeks from mice vaccinated with 0.5, 1, 2, and 4 μg of the VLPs were significantly higher at p<0.001 (***) than those determined in mice vaccinated with the inactivated PRRSV vaccine and PBS