Immune response and protective efficacy in sheep immunised with hydroxylamine-inactivated bluetongue virus vaccine

Vero cell adapted bluetongue virus (BTV), serotype 18 (BTV-18) was inactivated with hydroxylamine and adjuvanted with aluminium hydroxide (Al[OH](3)) gel, saponin, or Al(OH)(3) gel/saponin prior to immunisation of sheep. Group-specific non-neutralising antibodies to BTV were detected in all vaccinated sheep as soon as seven days after vaccination. However, before challenge, serotype-specific neutralising antibodies were not detected in vaccinated sheep. Upon challenge with homologous live BTV, there was a reduction in delayed type of hypersensitivity response in control sheep but not in the vaccinated animals. All vaccinated sheep had significant (P<0.01) reductions in their clinical reaction index (CRI) and duration of viraemia.