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 vaccines 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 10(6) to 3 x 10(8) 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 degrees C) as well as by its restriction endonuclease cleavage pattern.