Role of cell-mediated immunity in the recovery of cattle from primary and recurrent infections with infectious bovine rhinotracheitis virus.

When cattle infected with infectious bovine rhinotracheitis virus (IBRV) were treated 3 months later with a synthetic corticosteroid, consistent recrudescence of the infection was observed. Suppression of cell-mediated immunity, as measured by lymphocyte transformation responses, could be demonstrated at the time of recrudescence. Treatment with adrenocorticotropic hormone and trigeminal neurotomy also resulted in recrudescence of IBRV, but immunosuppression was not detected in these animals. The detection of specific, antigen-induced, lymphocyte transformation responses at the time of recovery from both primary and recurrent infections suggests that cell-mediated immunity may be important in determining the duration and severity of the recurrent infection. However, immunosuppression may not be the direct mechanism of recrudescence. Lesions were not observed in untreated animals, and virus could not be detected in either tissues or secretions. However, both lesions and virus were found consistently after corticosteroid treatment.