FIG 3.

Blockade activity of mouse polyclonal sera against homotypic and heterotypic VLPs. Mice were immunized with VRPs expressing the capsid genes of GII.4-2006b, GII.4-2009, P.D1, and P.D302, and sera collected from the mice were tested for blockade activity against GII.4-2006b, GII.4-2009, P.D1, and P.D302 VLPs. Shown is the blockade activity of sera from mice immunized against GII.4-2006b (A), GII.4-2009 (B), P.D1 (C), and P.D302 (D) with homotypic and heterotypic VLPs. The mean percent control binding (the percentage of the VLP bound to carbohydrate ligand in the presence of sera compared to the amount of VLP bound with no serum present) of each VLP was fitted with a sigmoidal curve, and the mean EC₅₀ (% sera) blockade titers for GII.4-2006b, GII.4-2009, P.D1, and P.D302 were calculated. The error bars represent 95% confidence intervals. *, the mean EC₅₀ blockade titer for the test VLP was significantly different from the mean EC₅₀ for the homotypic strain (P < 0.05). Sera that did not block a particular VLP were assigned an EC₅₀ of 10% sera for statistical analysis and are shown on the graph as data points above the upper limit of detection (dashed lines). Statistics were calculated by one-way ANOVA with a Bonferroni posttest.