Figure 4.

Protection of immunized IFNAR(-/-) mice against a lethal challenge with BTV-8. Groups of mice (n = 5) were immunized with a single dose of 10⁸ IU per mouse of ChAdOx1-NS1 or following a heterologous prime-boost regimen consisting of an initial dose of 10⁸ IU per mouse of ChAdOx1-NS1 (prime) followed by a second dose of 10⁷ PFU per mouse of MVA-NS1 (boost), administered 28 days apart. Immunized and non-immunized mice were challenged with a lethal dose (10 PFU) of BTV-8 at day 30 post-immunization (prime-only) or at day 15 post-boost (prime-boost). (a) Survival rates after infection. Statistical differences between the curves were calculated using Log-rank test. (b) Detection of BTV-4M in blood of non-immunized and immunized IFNAR(-/-) mice after challenge by RT-qPCR. Expression of mRNA of segment 5 (encoding NS1 protein) was quantified at 3, 5, 7, 10 and 17 d.p.i. Results are expressed as Ct (left y-axis) and PFU equivalents (right y-axis and dotted horizontal lines). Cut-off Ct ≥ 38 (dotted pink line). Differences between groups were calculated by multiple t test analysis using the Sidak–Bonferroni method. *** p-value < 0.001.