FIG 7.

Levels of viremia in immunized sheep after challenge with BTV-4M. Groups of sheep (n  =  4) were immunized with a single dose of (A) ChAdOx1-NS1, (B) ChAdOx1-NS2-Nt, (C) ChAdOx1-NS1-NS2-Nt, or (D) following a heterologous prime-boost regimen consisting of a prime dose of ChAdOx1-NS1-NS2-Nt followed by a boost of MVA-NS1-NS2-Nt. A group was left untreated (control). Immunized and nonimmunized sheep were challenged with BTV-4M. Detection of BTV-4M was performed by RT-qPCR in blood of nonimmunized and immunized sheep after viral challenge. Expression of mRNA of segment 5 (encoding NS1 protein) was quantified at 0, 1, 4, 6, 8, 11, 13, and 18 d.p.i. Results were expressed as Ct (left y axis) and PFU/mL equivalents (right y axis and dotted horizontal lines). The real-time RT-qPCR specific for BTV segment 5 was performed as described by Toussaint et al. (83) and sheep blood containing different concentrations of virus were titrated and used as standards. Cut-off Ct  ≥  38 (dotted pink line). Points represent individual Ct for each sheep and lines represent the mean values of each group. Differences between groups were calculated by multiple t test analysis using the Sidak–Bonferroni method. ** P value  <  0.002; *** P value  <  0.001.