Fig 1.

Influenza A/PR8 virus-specific IgG responses. Groups of mice (n = 12) immunized with a single dose of VLPs. Mice (n = 12 per group) were immunized with microneedles coated with 4 μg of influenza VLPs. At weeks 1 and 2 (W1 and W2) and months 1, 2, 3, 7, 10, and 13 (M1, M2, M3, M7, M10, and M13) after a single-dose vaccination, blood samples were collected. At month 14, mice were challenged with a high lethal dose of A/PR8 virus (10× LD₅₀) and IgG levels were measured 4 days after challenge (AC). The groups of immunized mice were designated V (microneedle vaccine without trehalose), VT (microneedle vaccine with trehalose as a stabilizer), and Mock (placebo microneedles with coating buffer only). Significant differences were detected between W1 and W2 (*, P < 0.05), W2 and M1 (**, P < 0.01), and M13 and AC (**, P < 0.01). Three independent experiments have been performed, and the data shown in the figures consist of the averages of several independent experiments. Data show averages ± standard errors of the means from 6 mice.