Alternative methods to reduce the animal use in quality controls of inactivated BTV8 Bluetongue vaccines

The acceptance of serology data instead of challenge for market release of new batches of commercial vaccine is under evaluation by regulatory agencies in order to reduce the use of animals and costs for manufacturers. In this study two vaccines for Bluetongue virus serotype 8 were submitted to quality controls required by the European Pharmacopoeia and tested on sheep in comparison with a commercial inactivated vaccine. Body temperature, antibody titres and viraemia of vaccinated and controls sheep were recorded. In addition IL4 and IFNγ in sera and supernatant derived from in vitro stimulation of blood cells were also quantified using two commercial ELISA kit. The outer-capsid protein VP2 contained in vaccine formulations was quantified using a home-made capture-ELISA. Results obtained indicates that in-lab evaluation of cell-mediated and humoral immune response are useful parameters to predict the efficacy of BTV inactivated vaccines avoiding the challenge phase required to release new batches of vaccines with proven clinical efficacy and safety. The correlation observed between serology data and VP2 protein concentration of final product could be useful in-process control to predict if a new vaccine batch of BTV must be discarded or released to the market.