Study of the safety and efficacy of a recombinant vaccine for bluetongue virus serotype 2.

A total of 7 cows, 10 sheep and 10 goats were vaccinated subcutaneously with 5 ml of a recombinant vaccine consisting of synthetic virions containing the four principal proteins (VP2, VP3, VP5 and VP7) of bluetongue virus serotype 2 (BTV-2). The same number of animals and species were vaccinated with 2.5 ml (the normal vaccination dose) and 2 cows, 2 sheep and 2 goats were inoculated with a placebo and the adjuvant added to the vaccine. Animals vaccinated with the normal dose received a booster 14 days after the first injection and 8 sheep a third vaccination 4 months after the second inoculation. One month after the third vaccination, the 8 sheep and another 4 that had never come into contact with the virus were challenged with 1 ml of 10(5.8) TCID(50) of a BTV-2 Italian field isolate. All animals showed competitive enzyme-linked immunosorbent assay (c-ELISA) antibodies starting 14 days following the first vaccination. Conversely, no animal demonstrated neutralising antibodies to BTV-2 after vaccination. Fever (>40 degrees C) was observed in 6 vaccinated animals and 2 controls between 8 and 13 days post challenge. The virus was isolated from all animals from the 7th day post challenge. There was no significant difference in the blood chemical parameters tested and no significant interaction was found in the trial group.