FIG 1.

(A) A schematic drawing illustrating the immunization schedule for the A129 IFNAR^−/− mice used. Four groups of mice were compared: group A (three doses of CCHF-DNA-plasmids i.d. by Biojector administration), group B (two doses of CCHF-DNA-plasmids i.d. by Biojector administration and a final booster with CCHF-VLPs i.p.), group C (three doses of VLPs alone by i.p. injection), and group D (empty-DNA plasmids i.d. by Biojector administration). Immunizations were performed with 3-week intervals. Lethal CCHFV challenge was delivered by i.p. injection at 6 weeks post-final immunization. (B) Box plot representation of the total anti-CCHFV serum IgG titers after the second and third immunizations of the three groups of A129 IFNAR^−/− mice. The box encloses 50% of the data, with the median value indicated by a horizontal line; the limits of the box represent the upper and lower quartiles. Whiskers mark the maximum and minimum values, excluding outliers. Filled circles represent outliers, defined as values greater than the upper quartile or smaller than the lower quartile, +1.5× the interquartile distance. (C) Geometric mean of anti-CCHFV neutralizing serum titers/vaccine-receiving group. In each group the sera were pooled into two pools/subgroup based on the CCHFV ELISA IgG titers. In each subgroup the three mice with the highest serum IgG ELISA titers were pooled with equal volumes (serum pool A1, B1, and C1, respectively), and the mice with lowest serum IgG ELISA titers per group were pooled into pools indicated as A2, B2, and C2, respectively. OD, optical density.