Fig. 5: RBD-specific humoral immunity induced in mice immunized with the BA.4/5-type or bivalent LNP-mRNA-RBD.

a Schematic diagram showing the experimental workflow. K18-hACE2 mice were immunized with LNP-mRNA-RBD derived from the ancestral strain or the BA.4/5 strain by intramuscular inoculation, followed by a second booster dose 21 days later (n = 15/group). The details of the groups are described in the table. b At 2 weeks after the second immunization, serum was collected from the immunized mice. The neutralizing titers (FRNT50 values) of the serum samples were determined in Vero E6-TMPRSS2-T2A-ACE2 cells. Each dot represents data from one mouse. The lower limit of detection (value = 20) is indicated by the horizontal dashed line. Samples under the detection limit (<20-fold dilution) were assigned an FRNT50 of 20. Geometric mean titers are shown. Data were analyzed with the Friedman test followed by Dunn’s test. Data are from one experiment.