Impacts of sonication and filtration on VLP immunogenicity. a C57BL/6 mice were vaccinated two times, with 3 weeks between vaccinations, as in Figure 4a. VLP were untreated, sonicated, or sonicated and passed through either a 0.45 µm or 0.8/0.2 µm filter (indicated on x-axis). The percent survival is shown. p-values determined using Fisher’s exact test to compare survival of each treatment group at the given dose level to control VLP (“untreated”). b Anti-glycoprotein antibody titers of vaccinated mice measured from serum collected 2 weeks after the final vaccination. VLP dose level (10 or 20 µg) is indicated on the x-axis. P values determined using one-tailed Student’s t test where *p < 0.05, **p < 0.005, ***p < 0.0005.