Serum was collected from Swiss Webster mice that received a prime and boost of the indicated nanoparticle formulation, naïve mice, or RSV immune mice that received 4.8 × 106 PFU RSV-A2 56 days or 6 months prior. (A) PreF or (B) postF-directed total IgG, IgG1, or IgG2a antibodies were measured by antibody ELISA. Statistical significance was determined by 2-way ANOVA with a Tukey’s post hoc test. Asterisks represent significance between RSVNanoVax and RSV immune. *p<0.05, **p<0.01, ***p<0.001. Data represent mean ± SEM of 2 independent experiments (n=8–10).