Figure 1.

LNP-adjuvanted HA mRNA and protein subunit vaccines induce durable, protective humoral responses

(A) BALB/c mice received a single IM immunization with 10 μg of rHA mixed with eLNP (an equal amount of LNP as in 30 μg mRNA-LNP), 30 μg Luc mRNA-LNP, or AddaVax. PR8 HAI titers were followed for 20 weeks. Data are pooled from two independent experiments. n = 10 mice/group. The horizontal dotted line represents the protective HAI value (1:40). Data are shown as mean + SEM.

(B–D) BALB/c mice were immunized ID with 10 μg of rHA, rHA + Addavax, or rHA + eLNP or 10 μg HA mRNA-LNP. Animals were terminally bled 9 months after injection, and immune sera were transferred into naive mice. Mice were challenged with PR8 virus, and survival and weight loss were followed daily. n = 7 mice/group in two independent experiments.

(B) Weight of serum-transferred mice as percentage of starting weight.

(C) Survival as percentage of total number of live animals per group.

(D) HAI titers of pre-transfer immune sera and sera of injected mice at the time of infection (2 h after transfer). The lowest body weight percentage reached during 14 days after infection is shown.

(E) Titers of HA-binding IgG, IgG1, IgG2a, IgG2b, and IgA were determined by endpoint dilution ELISA using sera of immunized mice collected 4 weeks after IM immunization. n = 10 animals per treatment group, n = 6 naive animals in two independent experiments.

Statistical analysis: In (A), two-way ANOVA with Bonferroni’s multiple comparisons test; comparisons of AddaVax and eLNP groups are shown for each time point; ^∗∗∗p ≤ 0.001, ^∗∗∗∗p ≤ 0.0001. In (E), one-way ANOVA with Bonferroni’s multiple comparisons test was performed on log transformed values; ^∗p ≤ 0.05, ^∗∗p ≤ 0.01, ^∗∗∗p ≤ 0.001, ^∗∗∗∗p ≤ 0.0001. See also Figure S1.