Fig 5. Full-length SF protein with the melittin signal peptide (msp) at the amino terminus and VSV G protein transmembrane domain and cytoplasmic tail (Gtc) at the carboxyl terminus induce the highest IgG titers against the SARS-CoV-2 Spike(ΔTM) protein.
Mice were prime immunized with rVSVInd-SARS-CoV-2 and boost immunized with rVSVNJ-SARS-CoV-2 two weeks after prime-immunization. Serum was collected to determine SARS-CoV-2 S1 protein-specific antibody levels by ELISA on day 13, one day before boost-immunization, and on day 27, two weeks after boost-immunization. (A) Prime-boost vaccination schedule. (B) Spike(ΔTM)-specific IgG titer after the prime-boost vaccination with doses of 5X107 PFU/mouse (C) Spike(ΔTM)-specific IgG titer after the prime-boost vaccination with doses of 5X108 PFU/mouse. Statistical significance was determined by two-way ANOVA with Tukey’s correction (*, p < 0.05; **, p < 0.005; ***, p< 0.001; ns, not significant). The data were presented as means with error bars of standard deviation (n = 5 mice per group). Purple box: honeybee msp, red box: VSV Gtc. VSV-Mock denotes VSV vector alone without any gene insert.