Reactivation of temperature-sensitive and non-temperature-sensitive infectious bovine rhinotracheitis vaccine virus with dexamethasone

Latent infections by a temperature-sensitive (ts) infectious bovine rhinotracheitis virus vaccine was produced as frequently as by non-ts vaccine virus. Thus, virus could be reactivated in seven of eight ts vaccinates and six of eight non-ts vaccinates after dexamethasone treatment. Virus excretion could be detectable for 1 to 8 days at a level of 2 X 106 to 3 X 108 plaque-forming units per ml of nasal secretions. The reactivated virus was shown to be the same as the original virus used for vaccination by its inability to grow at the restrictive temperature (39°C) as well as by its restriction endonuclease cleavage pattern.