Fig. 6: Antiviral formulation of 4RBD-Fc provides superior and sustained protection against SARS-CoV-2 compared to vaccine formulation.

A Vaccine immunization protocol for K18-hACE2 mice challenged with SARS-CoV-2 Delta strain. Mice were primed i.n. or i.m. with 4RBD-Fc and adjuvant, boosted at days 14 and 42, and challenged with 4 × 10³ PFU at day 63. Mock groups received only adjuvant (n = 5). For antiviral formulations, mice were i.n. administered 1 mg 4RBD-Fc, then challenged with SARS-CoV-2 Delta strain (4 × 10³ PFU) on days 7 and 14 (single challenge) or on days 0 and 14 (twice challenges) (n = 3). B Relative weight was measured as a percent of the starting weight on day 5 after infection with SARS-CoV-2 Delta strain. The dashed line indicates the starting weight. C, D Viral loads in throat swabs (C) and lungs (D), assessed by qRT-PCR. The dashed line indicates the limit of detection (LOD). Undetectable values were set to LOD –0.2 log units to distinguish them. Data are presented as mean ± s.d., symbols denote individual data points collected from mice. Statistical significance was calculated by one-way ANOVA with Dunnett correction.