Fig. 3: Neutralizing antibody responses in K18-hACE2 mice after boosting with clinically representative versions of mRNA-1273, mRNA-1273.214 and mRNA-1273.222.
Seven-week-old female K18-hACE2 mice were immunized with 0.25 μg of control mRNA or mRNA-1273 vaccine and then boosted 31 weeks later with PBS, 0.25 μg of control mRNA or 0.25 μg of clinically representative versions of mRNA-1273, mRNA-1273.214 or mRNA-1273.222 vaccines. a, Scheme of immunizations, blood draws and virus challenge. b,c, Serum neutralizing antibody responses immediately before (b, pre-boost) and 4 weeks after (c, post-boost) receiving the indicated mRNA boosters or PBS as judged by focus reduction neutralization test (FRNT) with authentic WA1/2020 D614G, B.1.617.2, BA.1 and BA.5 viruses (n = 9 for mRNA-1273 and n = 10 for other groups, two experiments; tops of boxes show GMT values, which are indicated above each column, and dotted lines show LOD based on a 1/60 (WA1/2020 D614G and B.1.617.2) or 1/30 serum dilution (BA.1 and BA.5)). d, Scheme of serum depletion of anti-RBD antibodies. e, Serum (1/150 dilution) from mice boosted with mRNA-1273, mRNA-1273.214 or mRNA-1273.222 was incubated with empty, Wuhan-1 RBD-loaded or BA.4/5 RBD-loaded magnetic beads. After separation of pre-clearing beads, supernatants were diluted serially and added to ELISA plates coated with Wuhan-1 or BA.4/5 RBD. Representative depletion curves performed in technical duplicate corresponding to individual mice are shown for the indicated vaccines. f, Bar graphs derived from AUC analysis of the data in e showing the relative proportions of Wuhan-1-specific, Wuhan-1/BA.4/5 cross-reactive and BA.4/5-specific RBD responses (n = 9 for mRNA-1273 and n = 10 for mRNA-1273.214 and mRNA1273.222, two experiments; right edge of boxes illustrate mean values, and error bars indicate standard deviations). Statistical analysis. c, One-way Kruskal–Wallis ANOVA with Dunn’s multiple comparisons post test; comparisons are between all groups except for the PBS control, which is shown for reference. Exact P values are indicated, and only significant comparisons are shown. Primary data are provided as a Source Data file. Abs, antibodies.
