Fig. 3. PR8 hemagglutinin mRNA-LNP vaccine elicits protective antibody responses in the presence of matAbs.

(A) Mice (21 days old) were vaccinated intramuscularly with 1 μg of nucleoside-modified PR8 hemagglutinin (HA) mRNA-LNP vaccine, and influenza virus–specific serum antibody responses were measured by ELISA. *P < 0.05 after comparison of serum titers from mice vaccinated with PR8 HA mRNA-LNP vaccine versus PBS in the presence (blue *) or absence (orange *) of influenza virus–specific matAbs; one-way ANOVA with Tukey’s post hoc test at each time point. (B) Mice in (A) were challenged at 189 days after vaccination with 300 TCID₅₀ of PR8 influenza virus intranasally, and weight loss was measured over 14 days. Data are shown as percentage of baseline weight (current weight divided by prechallenge weight). *P < 0.05 after comparison of percentage of baseline weight on each day for mice vaccinated as infants with PR8 HA mRNA-LNP vaccine versus PBS in the presence (blue *) or absence (orange *) of influenza virus–specific matAbs; one-way ANOVA with Tukey’s post hoc test at each day. (A and B) n = 3 (+matAbs) or n = 4 (−matAbs) mice per group. (C) Serum was collected at 100+ days after vaccination with 1 μg of PR8 HA mRNA-LNP vaccine or PBS in the presence or absence of influenza virus–specific matAbs and was pooled. Pooled serum (500 μl) was intraperitoneally transferred to 6- to 8-week-old naïve mice, and 4 to 5 hours later, mice were intranasally challenged with 300 TCID₅₀ of PR8 influenza virus. Weight loss was measured over 14 days. n = 4 mice per group. *P < 0.05 after comparison of percentage of baseline weight on each day for mice that received sera from mice vaccinated with PR8 HA mRNA-LNP vaccine or PBS as infants in the presence of influenza virus–specific matAbs; one-way ANOVA with Tukey’s post hoc test at each day. (D) Sera from mice vaccinated with 1 μg of PR8 HA mRNA-LNP vaccine in the presence or absence of influenza virus–specific matAbs and from naïve mice were collected 189 days post-vaccination. Sera were analyzed for influenza virus–specific IgG1 (left) or IgG2a (right). n = 8 (blue), n = 9 (orange), or n = 4 (black) mice per group. Serum titers of mice vaccinated with PR8 HA mRNA-LNP vaccine in the presence or absence of influenza virus–specific matAbs were compared using an unpaired two-tailed t test. In (D), each point represents one mouse. Data are shown as means ± SD. Panels (A) to (D) show data from one experiment that is representative of two independent biological replicates.