Figure 1.

Neutralization of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pseudovirus bearing wild-type (WT) or Beta variant spike proteins by antisera of rats vaccinated with adjuvanted S-2P. Rats (n = 10 for each dose group) were immunized 3 times at 2 weeks apart with the indicated amounts of adjuvanted S-2P. A, The antisera were harvested 2 weeks after the second immunization (day 29) and 2 weeks after the third immunization (day 43) and subjected to neutralization assay with pseudovirus expressing WT or Beta variant SARS-CoV-2 spike protein to determine the 50% inhibition dilution (ID₅₀) and 90% inhibition dilution (ID₉₀) titers of neutralizing antibodies. B, Fold reductions in neutralizing titers (ID₅₀ and ID₉₀) were calculated by dividing WT neutralizing titers by Beta neutralizing titers. Results are presented in (A) as horizontal bars representing geometric mean titers (GMTs) with symbols representing individual titers, and (B) as horizontal bars representing means and symbols representing individual titer ratios. Dotted lines indicate the lower and upper limits of detection of the assay. Kruskal-Wallis with Dunnett multiple comparisons test was performed and statistical significance of neutralizing titers between day 29 and day 43 of the Beta variant and WT at different dose levels. *P < .05, **P < .01, ***P < .001.