Fig 1: Intranasal vaccination with CS/CpG/RBD results in mucosal and systemic immunity. Mice (n=4 per group) were vaccinated twice i.n with RBD alone, CS/RBD or CS/CpG/RBD. For comparison, an additional cohort (n=3) was vaccinated twice s.c. with CS/CpG/RBD. RBD-specific IgA responses in sera (A) and nasal rinses (B) 14 days after booster immunizations were detected via ELISA. Binding of serum IgG to RBD (C) or RBD-L452R-T478K (D) was measured via ELISA. Neutralizing antibody responses were determined by inhibition of RBD (E) or RBD-L452R-T478K (F) binding to ACE2 by diluted serum samples. *p < 0.05 via one-way ANOVA with Tukey’s posttest. ns, not significant.