Figure 6.

Heterologous IM/IN prime-boost immunization induces robust virus-neutralizing antibody titers in 129S1 and K18-hACE mice

129S1 and K18-hACE2 mice were vaccinated twice 4 weeks apart. Mice were primed either IM with 0.4 μg of BNT162b2 mRNA or PBS, or IN with 15 μg full-length S protein with either NE or NE/IVT. Mice were then boosted 4 weeks later IM with 0.4 μg of BNT162b2 mRNA, or IN with 15 μg S with PBS, NE or NE/IVT as indicated. Groups receiving two immunizations with IM Advx/S or PBS were included for comparison. Serum (A) IgG titers against WT S-protein, and nAb titers against (B) WT, (C) B.1.351, (D) B.1.1.529 (BA.1), and (E) BA.4/5 variant PSVs were measured 2 weeks after the boost immunization (wk6). K18-hACE2 transgenic mice were similarly primed either IM with 0.4 μg of BNT162b2 mRNA, or PBS, or IN with 15 μg S with either NE or NE/IVT. Mice were boosted 4 weeks later IM with 0.4 μg of BNT162b2 mRNA or PBS, or IN with 15 μg S with PBS, NE or NE/IVT as indicated. Groups receiving two immunizations with IM Advx/S or IN PBS were included for comparison. Serum (F) IgG titers against WT S-protein, and nAb titers against (G) WT, (H) B.1.351, (I) B.1.1.529 (BA.1), and (J) BA.4/5 variant PSVs were measured 2 weeks after the boost immunization (wk6). (n = 4–5/group; ∗p < 0.05, ∗∗p < 0.01 by Mann-Whitney U test shown only for select groups (full statistical analysis is shown in Table S1).