VACCINATION OF PIGS WITH REPLICATION-DEFECTIVE ADENOVIRUS VECTORED VACCINES - THE EXAMPLE OF PSEUDORABIES

The efficacy of a recombinant human adenovirus type 5 expressing go, one of the immunogenic glycoprotein of pseudorabies virus, was tested in pigs. Due to the deletion of the E1a gene, the recombinant virus is unable to replicate in non transcomplementing cells but is capable of eliciting an immune response against gp50 after inoculation into animals. The virus was formulated in a water/oil/water emulsion, a strategy previously shown to enhance the immune response against the virus-induced gp50. Pigs of 18-25 kg were vaccinated twice and the recombinant virus was not isolated from nasal and rectal swabs taken after each injection of the vaccine. High levels of neutralizing antibodies were induced by the vaccination. Protection against a severe challenge was effective, as measured by growth performance (dG = 1.73), and reduction of the time of excretion of the challenge strain (mean time: 4.4 days for the vaccinated and 7.9 days for the control pigs). These results show that non replicating adenoviruses are able to induce a strong protective immune response against foreign genes in pigs, which may be of general interest for the design of pig vaccines.