Avirulent ts and thymidine kinase-deficient mutant of Aujeszky's disease virus.

The temperature-sensitive (ts), thymidine kinase-deficient (TK-) mutant designated ZHtsTK- strain, of Aujeszky's disease virus (ADV) was isolated from a virulent strain with the treatments using 5-bromodeoxyuridine and arabinosylthymine. The ZHtsTK- strain was easily distinguished from the other virulent ADV strains by plaque size on HmLu-1 and chicken embryo fibroblast cells and by restriction endonuclease analyses using Bam HI, Sal I and Kpn I. The ZHtsTK- strain was avirulent for mice, guinea pigs and rabbits, and produced neutralizing antibodies to ADV in these animals. The rabbits inoculated with the ZHtsTK- strain did not shed detectable amounts of virus after dexamethasone treatment. The ZHtsTK- strain was also avirulent for 5-day-old piglets and did not cause disease. No virus was detected from the piglets inoculated intramuscularly in the nasal swabs or the tissues examined on postinoculation day 9. These findings presented here suggested that there is a significant correlation between pathogenicity and properties such as ts and TK-, and the combination of ts and TK- properties plays a much larger role in reducing virulence for animals.