Fig. 5.

Humoral protection from group 2 influenza virus challenge is afforded by antibodies that target the NA. Mice were vaccinated twice (4-wk intervals) ID with 5 µg of monovalent or quadrivalent mRNA-LNPs. Sera were collected from vaccinated animals 4 wk after the boost and the sera were assessed for antibody reactivity toward A/Singapore/INFIMH-16-0019/2016 (H3N2, IVR-186) influenza virus-infected cells by cell-based ELISA (A). Sera from vaccinated mice were then transferred into naïve mice. Two hours after the transfer, sera from passively transferred naïve mice were assessed for antibody reactivity toward A/Singapore/INFIMH-16-0019/2016 (H3N2, IVR-186) influenza virus-infected cells by ELISA (B). Each symbol represents one animal, sera from 5 to 10 animals were assessed. AUCs with a cutoff value of the average background plus three SDs are shown. Bars represent the geometric mean for each group and error bars depict SD. Naïve mice were then I.N. challenged with 5mLD₅₀ of A/Switzerland/9715293/2013 (H3N2) and weight loss (C) and survival (D) were monitored for 14 d. Survival is also represented in parentheses in panel D. Data are shown as mean and error bars represent SD (n = 4 or 5 per group). One mouse passively transferred NP sera was excluded due to a failed transfer.