EVALUATION OF THE SAFETY AND EFFICACY OF A THYMIDINE KINASE, INVERTEDREPEAT, GI, AND GPX GENE-DELETED PSEUDORABIES VACCINE

A thymidine kinase (TK), inverted repeat, glycoprotein I (gI) and glyc oprotein X (gpX) gene-deleted modified live virus pseudorabies vaccine was evaluated for safety in swine and for efficacy in protecting swin e against challenge with pseudorabies virus (PRV). Safety was evaluate d by inoculating pregnant gilts intravenously and 3-day-old pigs intra cerebrally with the vaccine. Efficacy was evaluated by 1) vaccinating 3-day-old pigs with a minimal protective dose intranasally and then ch allenging with PRV 3 weeks postvaccination or 2) vaccinating weaned pi gs with a standard field dose intramuscularly and then challenging wit h PRV 4 weeks postvaccination. The pigs vaccinated intranasally remain ed clinically normal following vaccination and challenge with PRV. The pigs vaccinated intramuscularly remained clinically normal following vaccination, but mild respiratory sips were seen in some of the vaccin ated pigs following challenge with PRV. Humoral immune response was ev aluated with enzyme-linked immunosorbent assays (ELISAs) and a serum v irus neutralization test. All of the intramuscularly vaccinated pigs b ecame gI and gpX positive on differential ELISAs following challenge. All of the intranasally vaccinated pigs were seropositive on the indir ect gI ELISA following challenge, but not all of the pigs were seropos itive on the blocking gI ELISA or the gpX ELISA 3 weeks postchallenge.