3B). The embryo mortality and observed hemorrhagic characteristics were attributed to BTV since BTV RNA was detected only in swabs from homogenized embryos that had been inoculated with blood from controls. In contrast, no dead or hemorhaggic embryos were observed following inoculation with blood from vaccinated calves and no BTV RNA was detected in these embryos (Fig. 3B). BTV-8-specific neutralizing antibodies were detected in the sera of 5/6 vaccinated calves 1 week after second vaccination and in all vaccinated calves 2 weeks later (mean: 4.5 ± 1.4 log2 titers) (Fig. 4A). These titers remained high 3 BGB324 weeks after challenge. In contrast, BTV-8 neutralizing antibodies were only detected

in the sera of controls after challenge. BTV-8 VP2-specific

serum antibodies were detected by ELISA in all vaccinated calves 1 week after second immunization, continued to increase through 1 week after challenge, and remained stable 2 weeks later (Fig. 4B). VP2-specific antibodies were detected in controls 2 weeks after challenge and had increased 1 week CP-673451 price later. Increases in NS1-specific and NS2-specific serum antibody titers were detected in vaccinated calves 3 weeks after first and second vaccinations. Antibody titers to NS2 were significantly higher than those detected in controls 3 weeks after first vaccination (p ≤ 0.01) and to NS1 and NS2 3 weeks after second vaccination (p ≤ 0.05 and p ≤ 0.01, respectively) ( Fig. 4C and D). Antibodies to NS1 and NS2 (BTV-2) were observed 3 weeks after BTV-8 challenge in the sera of controls and vaccinated calves, but did not differ significantly (p = 0.94 and p = 0.23, respectively). In vitro NS1-specific and NS2-specific lymphoproliferative responses were detected in PBMC of vaccinated calves (means: 0.04 ± 0.06 and 0.05 ± 0.02 COD, respectively)

3 weeks after second vaccination, at statistically higher levels than controls (means: 0.00 ± 0.01 and 0.02 ± 0.04 COD, respectively; p ≤ 0.05 for both) ( Fig. 5). Furthermore, BTV-8 specific lymphoproliferation was detected in vaccinated why calves (mean: 0.04 ± 0.04 COD) at this time point but not in any controls (mean: 0.00 ± 0.00 COD, p ≤ 0.01). No VP2-specific lymphoproliferatives responses were observed. VP7-specific serum antibodies were not detected in any calf before challenge, but were detected at high levels (≥75%) in 5/6 controls 2 weeks after challenge and in all controls 1 week later (mean: 92 ± 3%) (Fig. 6). Vaccinated calves also developed VP7-specific serum antibodies following challenge, but antibody levels remained significantly lower than those in controls (peak mean: 44 ± 22% at 2 weeks after challenge, p ≤ 0.01). In this study, we demonstrated that the experimental vaccine based on VP2 of BTV-8 combined with NS1 and NS2 of BTV-2 and an ISCOM–matrix adjuvant provided strong clinical and virological protection against virulent BTV-8 challenge in calves.