Fig. 4.

Nucleoside-modified HA mRNA-LNP immunization induces HA stalk-reactive antibodies in ferrets. Ferrets were immunized two times i.m. with 60 µg of A/California/07/2009 HA mRNA-LNPs or 60 µg of poly(C) RNA-LNPs at week 0 (prime) and 4 (boost). HAI titers against the A/California/07/2009 (a) and A/swine/Jiangsu/40/2011 (b) viruses were determined at week 4 (prime) and week 13 (boost). c IgG binding to full-length H1 HA (total) and cH6/1 HA (stalk) proteins from serum samples obtained 9 weeks after the second immunization was determined. n = 12 ferrets. a, b Each symbol represents one animal, horizontal lines show the mean, dotted line indicates the limit of detection. c error bars are SEM. Statistical analysis: a, b one-way ANOVA with Bonferroni correction on log-transformed data, *p < 0.05. c Two-way ANOVA with Bonferroni correction comparing A/California/07/2009 HA and poly(C) immunizations for different dilutions. *p < 0.05